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Biology of the Seas
of theU.S.S.R.

Biology of the Seas
of the U.S.S.R.

PROFESSOR L. ZENKEVITCH

Professor at Moscow State University

Chairman of the National Oceanographical Committee of the U.S.S.R.

Vice-President of the Special Committee
on Oceanic Research (SCO R)

TRANSLATED BY S. BOTCHARSKAYA

ILLUSTRATED

'У \

о
о.

1930

London
GEORGE ALLEN & UNWIN LTD

RUSKIN HOUSE MUSEUM STREET

jJ^sRARY

j »c ~—^J

THIS TRANSLATION FIRST PUBLISHED IN 1963

This book is copyright under the Berne Convention.
Apart from any fair dealing for the purpose of private
study, research, criticism or review, as permitted
under the Copyright Act 1956, no portion may be
reproduced by any process without written permis-
sion. Enquiries should be addressed to the publisher.

This translation © George Allen and Unwin Ltd 1963

TRANSLATED FROM THE RUSSIAN
BY SOPHIA BOTCHARSKAYA

PRINTED IN GREAT BRITAIN

in 10 point Times Roman type

BY WESTERN PRINTING SERVICES LTD
BRISTOL

PREFACE

The present publication is a considerably amended and supplemented version
of the second edition of my book The Fauna and Biological Productivity of the
Sea, published in 1947. A large amount of new research has been gathered
during the last fourteen years. Some bodies of water have considerably
changed their hydrographical and biological aspect during that time.

I have found it necessary to add a section on 'The Far Eastern Seas', which
was not included in the Russian edition. An Introduction has also been added.
Since I did not wish to make any considerable increase in the size of the book
I have shortened the sections on the Northern and Southern seas. Some illus-
trations have also been omitted.

I set myself the task of collecting in this book the results of research carried
out in seas adjacent to the frontiers of the u.s.s.R., and only in the section 'The
Far Eastern Seas, have I gone beyond the boundaries of the u.s.s.R. in order
to give a summary of the results of Soviet deep-water explorations in the
Pacific Ocean.

In the Russian edition of my book many problems of marine biology are
included in the first volume and are not discussed in further detail in the
second. These problems include, for instance, the conception of the biosphere,
biological productivity, the problem of brackish-water environment, bio-
geographical zonation, the practical significance of marine organisms, the
problems of acclimatization, and others. All these problems had to be ex-
cluded, the more so because of the addition of the large new section.

Unfortunately I have also been unable to include in the book a more de-
tailed exposition of comprehensive and numerous monographic studies on
individual groups of marine organisms, or of the large number of works on
the ecology and biology of individual forms. These works form an abundant
literature in Russian.

I have thought it essential to give a short physico-geographical introduction
to the description of each sea. Although a zoologist, I have considered it
expedient to include some botanical data, in order to give a more complete
biological picture.

The land mass of Europe and Asia is distinguished from other land masses in
that its shores are almost entirely bordered by coastal seas. This is particularly
true of the Soviet Union ; the south eastern coast of Kamchatka and the Kuril
Islands alone being washed by ocean waters. It is not surprising that these
coastal seas have been the subject of many different and complex marine
research studies, and in particular the Azov, Caspian, Barents and Black
Seas have been systematically explored. Equal attention has been given to the
study of plankton, benthos and fish.

This book has a strongly quantitative approach. There are quantitative
studies of the feeding habits of fish ; similar investigations of the distribution
of flora and fauna throughout the seasons make it possible for general con-
clusions about biological productivity to be drawn.

The author has taken part in many expeditions to both the northern and
the southern seas and has devoted fourteen years to the study of the Far

PREFACE

Eastern seas. He is extremely pleased to see his book published in English.
Original scientific papers in Russian have had little publicity outside the
u.s.s.R. and quite often works on marine biology or biogeography have
appeared in other languages purporting to offer a new interpretation of cer-
tain problems, when in fact they had already been examined and interpreted
by Russian writers.

With this book a special effort has been made to make Russian work as
widely available as possible to the foreign reader. The author believes that his
treatise will be a reliable aid and guide to all who seek access to the rich
literature of Russian marine biology.

L. Zenkevitch

CONTENTS

PREFACE page 5

INTRODUCTION 1 1

THE NORTHERN SEAS OF THE U.S.S.R.

1. GENERAL CHARACTERISTICS OF THE
NORTHERN SEAS 27

I. Hydrological conditions 27
п. General characteristics of the fauna of the eastern

sector of the Arctic basin 39

in. Zoogeographical zonation of the Arctic region 64
iv. Typology of the bodies of water of the Arctic basin

and the northern Atlantic 68

2. THE BARENTS SEA 72

I. History of exploration 73
п. Physics, geography, hydrology, hydrochemistry

and geology 76

ш. Flora and fauna: general characteristics 9 1

3. THE WHITE SEA 179

I. General characteristics 179

и. History of exploration 1 80
in. Physical geography, hydrology, hydrochemistry

and geology 1 8 1

iv. Flora and fauna 193

4. THE KARA SEA 220

I. General characteristics 229

n. History of exploration 221
m. Physical geography, hydrology and hydrochemistry 222

IV. Flora and fauna 231

5. THE LAPTEV SEA 255

i. History of exploration 255

и. Physical geography 255

m. Flora and fauna 257

6. THE CHUKOTSK SEA 261

i. Situation and history of exploration 261

H. Physical geography 261

in. Flora and fauna 264

BIOLOGY OF THE SEAS OF THE U.S.S.R.

THE BALTIC SEA

270

I. General characteristics

270

и. History of exploration
in. Physical geography, hydrology, hydrochemistry

and geology
iv. The geological past

v. Flora and fauna

270

271
287
292

VI. Origin of the fauna

333

THE SOUTHERN SEAS OF THE U.S.S.R.

8. GENERAL CHARACTERISTICS AND
GEOLOGICAL HISTORY 353

I. General characteristics 353

и. The geological past 354
in. Some peculiarities of the development of fauna and

and flora 367

9. THE BLACK SEA 380

I. General characteristics 380

п. History of the study of the Black Sea 380

in. Physical geography and hydrology 382

iv. Flora and fauna 401

10. THE SEA OF AZOV 465

i. General characteristics 465

H. History of exploration 465
in. Physical geography, hydrology and hydrochemistry 466

iv. Flora and fauna 478

v. Conclusion 526

vi. The Sivash, or Putrid, Sea 528

11. THE CASPIAN SEA 538

I. General characteristics 538

n. History of exploration 538
Ш. Physical geography, hydrology, hydrochemistry

and geology 539

IV. Flora and fauna 562

v. Conclusions 645

12. THE ARAL SEA 647

I. General characteristics 647

n. History of exploration 647

in. Physical geography 648

iv. Flora and fauna 657

CONTENTS
THE FAR EASTERN SEAS OF THE U.S.S.R.

13. GENERAL CHARACTERISTICS OF FAR

EASTERN SEAS AND OF ADJACENT PARTS

OF PACIFIC OCEAN 675

I. General characteristics 675

ii. History of exploration 677
Ш. Physical geography of northwestern part of Pacific

Ocean ■ 681

iv. Composition of flora and fauna 700
v. Commercial importance of the Far Eastern Seas 738

vi. Zoogeography of the Far Eastern Seas 744

14. THE SEA OF JAPAN 750

I. Physical geography 750

II. Flora and fauna 756

15. THE SEA OF OKHOTSK 783

i. Physical geography 783

п. Flora and fauna 788

16. THE BERING SEA 818

I. Physical geography 818

n. Flora and fauna 827

REFERENCES 843

INDEXES 899

INTRODUCTION

No country in the world possesses such an abundance and variety of bodies
of water as the u.s.s.r. Its frontiers are about 60,000 km long. Only a small
part of the seas of the u.s.s.r. is directly connected with the open ocean, most
of its shores being encirled by the accessory seas of three oceans — the Arctic,
the Atlantic and the Pacific.

A comparison with other continents, which are usually almost devoid of
accessory seas, brings out clearly this characteristic of Eurasia.

Twelve of the seas of the u.s.s.r. have retained their link with the open
oceans ; two of its greatest lake-oceans — the Caspian and Aral Seas — are at
present isolated from them.

The total area of these 14 seas composes about 5 per cent of the surface of
the world-ocean; they astonish their investigators by the variety of their
physico-geographical conditions, by the abundance and variety of their flora
and fauna and by the complexity of their geological past, which has left its
ineffaceable imprint on their composition, their biological peculiarities and
their ranges of flora and fauna which provide huge resources of plant and
animal raw material. The population of the seas of the u.s.s.r. is a very rich
subject for scientific investigation.

The seas of the u.s.s.r. include such pygmies as the Sea of Azov, with
depths no greater than 13-5 m, and such giants as the Bering Sea, with depths
exceeding 5 km. Some of its seas have a full marine salinity, some are brackish,
with a salinity of 12-10-8 parts per thousand and less. The composition of the
salts of some sea-lakes, such as the Caspian and the Aral Seas, has changed
considerably, and at present they differ greatly from that of the oceans. Some
details are given in Table 1.

The Baltic and northern seas of the u.s.s.r. contain a most characteristic
brackish- water relict fauna, the result of a considerable and protracted loss of
salinity experienced during the Ice Age. Some representatives of this relict
fauna moved southwards, penetrated into river systems and reached the Cas-
pian Sea. The southern seas of the u.s.s.r. give shelter to a rich, brackish-
water relict fauna — a remainder of the Pontic lake-sea fauna, which has in a
large number of representatives penetrated into the river systems of the Black,
Azov and Caspian Seas. No other seas contain such rich, brackish-water
fauna of varied origin as those of the u.s.s.r. The penetration of representa-
tatives of the Mediterranean (Atlantic) fauna eastward into the Caspian and
even the Aral Seas is also most interesting.

During the recent millennia the Barents Sea and the adjacent Siberian seas
have formed a broad route for the penetration of Atlantic fauna eastward,
and of Pacific fauna westward. The great depths of the central depression of the
Arctic basin with their original bathypelagic fauna are adjacent to the northern
confines of the Siberian seas.

One of the greatest depths in the Pacific — the Kurile-Kamchatka Trench
— lies immediately adjacent to the eastern boundary of the u.s.s.r.

12 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 1. Areas, volumes and depths of seas of the U.S.S.R*

Area Volume Mean depth Greatest depth

Name 103 x m2 103 x m3 m m

Baltic Sea 386 33 86 459

White Sea 90 8 89 330

Barents Sea 1,405 322 229 600

Kara Sea 883 104 118 620

Laptev Sea 650 338 519 2,980

East Siberian Sea 901 53 58 155

ChukotskSea 582 51 88 160

Bering Sea 2,304 3,683 1,598 4,773

Sea of Okhotsk 1,590 1,365 859 3,657

Sea of Japan 978 1,713 1,752 4,036

Black Sea 423 537 1,271 2,245

Sea of Azov 38 0-3 9 13

Caspian Sea 370 77 197 980

Aral Sea 64 10 75 68

Total 10,644 8,285-3

* Except for the Caspian and Aral Seas the data are taken from the Nautical Atlas,
Volume II, 1953. The greatest depths of Far Eastern Seas are according to the latest
Vityaz data.

The Caspian, White and Barents Seas have been an area of Russian fishery
from ancient times. Fisheries were developed in the Azov and Black Seas
somewhat later. In the seas of the Far East they were developed most recently.
At present the u.s.s.r. occupies one of the leading places in marine fishery.

Hence the investigation of the flora and fauna of the seas of the u.s.s.r. is
of exceptional interest.

The Russian people, who for centuries had lived by agriculture, were drawn
to the sea at the time when antiquity changed into the Middle Ages. As early
as the fifth century military expeditions took the Slavs down to the Black
Sea. Two powerful states — Novgorod and Kiev — arose in the ninth century
on the Volkhov and Dnieper, along the great water route from Varangians to
the Greeks. Both states learned to use the water routes for trade and war alike.
A high nautical culture developed in Novgorod state through the centuries.
The Novgorod helmsmen ploughed, in their small boats, first the Baltic Sea,
and then, from the beginning of the twelfth century, the White Sea and the
Arctic Ocean. In the ninth and tenth centuries numerous Russian ships
sailed to Byzantium. In the sixteenth and seventeenth centuries men of Nov-
gorod and Kiev were good navigators. Marine communications with the west
became more lively under Ivan III : English trade ships 'opened' the northern
sea route to the White Sea in the middle of the sixteenth century. Venice led a
lively trade with the south of Russia through the Black Sea. At first Russia's
role was rather passive but, in the sixteenth century under Ivan the Terrible,
there awoke a new striving for marine frontiers and an active struggle for the

INTRODUCTION 13

Black, Baltic and Caspian Seas was begun, followed later by that for the coast-
line of the Pacific Ocean.

In the time of Peter the Great Russian science was enriched by the first
data on the fauna of the seas which wash the shores of Russia. The eighteenth
and the first quarter of the nineteenth century was a real epoch of great expedi-
tions to explore the Russian seas. Eighteenth-century discoveries were con-
nected with V. Bering's expedition and with the Great Northern expedition.
Kruzenshtern and Lisyansky (1803-05), Kozebou (1816-17), Bellingshausen
and Lazarev (1819-21) and Litke (1826-29) sailed round the world in the
first quarter of the nineteenth century, bringing back from their voyages, for
Russian and world science, the first geographical data on Russian seas and
the first information on their populations.

Basic data on the Russian flora and fauna were gathered mostly during the
second half of the last century. Marine expeditions left for every corner of
Russia, laboratories and museums were enriched with collections of different
groups of marine fauna, marine stations were opened, scientific conferences
were organized, remarkable embryological investigations of marine fauna
were carried out by E. Metchnikov and A. Kovalevksy. The first scientific and
commercial expedition comprehensive both in the tasks it undertook and in
the results obtained was that of Baer to the Caspian Sea, which lasted from
1853 to 1856.

Sevastopol Biological Station started its work in 1871-72, the Murman
Biological Station in 1881, and the Scientific Fishery Station at Astrakhan on
the Caspian Sea was opened in 1897. All these played an important role in the
development of marine biological research in Russia.

In relation to the beginning of the present century the following should be
noted: ten-year (1898-1910) research work done by the 'Expedition for
Scientific-Industrial Research off the Murman Coast' on the ship Andrei
Pervozvanniy, organized by the eminent Russian oceanographer N. M. Knipo-
vitch, which discovered huge accumulations of commercial fish in the Barents
Sea ; Toll's expedition on the Zarya along the northern shores of Asia in 1900-
1901, and P. Schmidt's (1900-01) expedition to Korea and Sakhalin.

Nordenskjold's remarkable Swedish expedition on the Vega, the first to sail
through the northeastern passage, in 1878-79, played a very important part in
the study of the fauna of the northern seas of Russia.

N. Andrussov's and A. Lebedintzev's well-known expedition, which dis-
covered the contamination of the deep waters of the Black Sea with hydrogen
sulphide, worked in the early eighteen-nineties.

The excellent work of K. Derjugin in the Kola Guba, on the Murman
Peninsula, and that of S. Zernov in the Black Sea, in the Sevastopol area, car-
ried out in the first decade of the present century, should also be noted.

Biological research of the seas which wash the shores of the u.s.s.r. has
progressed greatly during the last 35 years or so, owing to the organization of
a large number of permanent marine institutions, carrying out a comprehensive
survey throughout the seas of the u.s.s.r. {Table 2). These numerous institu-
tions were under the authority of the Academies of Sciences of the u.s.s.r. and
Ukrainian s.s.r., of the Fishery Administration, of the Chief Administration

BIOLOGY OF THE SEAS OF THE U.S.S.R.

of the Hydrometeorological Service, the Ministry of Marine, the Ministry of
Higher Education, Administration of Nature Reserve and some others. In
the northern seas the efforts of the Marine Scientific Institute and its 20-year
expeditions on the ship Persey and the work done by the Arctic Institute with
its numerous expeditions on the ships Chelyuskin, Sadko, Sedov, Rusanov and
others, were mostly responsible for this progress.

K. Derjugin's researches and the work of his expeditions on the ship
Rosinante and others, and the organization of the Pacific Ocean Institutes of
Fisheries and Oceanography at Vladivostok in 1925 were just as important
for research in the Far Eastern Seas.

Knipovitch's expeditions and the work done by the Azov-Black Seas
Institute of Fisheries and Oceanography (from 1921) have played an important
role in the investigations in that area, while in the Caspian Sea important
research was carried out by the three expeditions of Knipovitch (1904-15) and,
during the Soviet period, in the nineteen-thirties, by scientific and industrial
expeditions.

The Solovets Biological Station of the St Petersburg Society of Naturalists
was set up in 1881. In 1899 this station was transferred to the town Aleksan-
drovsk (Kola Guba, on the Barents Sea); it remained there until 1929, when
it was transferred to Murmansk. In 1933 it was reorganized together with the
State Institute of Oceanography and the Institute of Fisheries into the Polar
Institute of Fisheries and Oceanography. The Murman Marine Biological
Institute in Dal'naya Zelenetskaya Guba mentioned in Table 2 came into
being in 1936, with no direct connection with the old Murmansk Station, but
it is continuing the work of the latter.

Table 2. Institutions carrying on research on the marine flora and fauna of the U.S.S.R.

Department and name
of Institution

Place

Date of
foundation

Main expedi-
tion ships

(A) Academy

of Sciences of the

U.S.S.R.

1 . Zoological Institute

2. Botanical Institute

Leningrad
Leningrad

3. Murman Marine Biological

Dal'naya

1936

Professor

Institute

Zelenetskaya
Guba, Mur-
mansk

Derjugin

4. Institute of Oceanology

5. Black Sea Station of the

Moscow
Gelendzhik

1941

Vityaz
Academician S.

Institute of Oceanology

Vavilov

6. Acoustic Institute

Moscow

1951

P. Lebedev
S. Vavilov

7. Institute of Marine Hydro-

Moscow

Lomonosov

physics
8. Black Sea Hydrophysical
Station of the Institute of

Katsiveli,
Crimea

1929

Marine Hydrophysics

INTRODUCTION
Table 2—{contd.)

Department and name
of Institution

Place

Date of
foundation

Main expedi-
tion ships

(B) Academy of Sciences of the Ukrainian s.s.r.

9. Sevastopol Biological
Station

10. Odessa Biological Station

1 1 . Laboratory of the Odessa

Biological Station

12. Karadag Biological Station

Sevastopol

Odessa
Vilkovo, Odessa

Province
Karadag,

Crimea

1871-72

1954
1954

1914

Alexander
Kovalevsky

13. White Sea Biological Station

Cape Kartesh,
Chupa Guba,
White Sea

1949

(D) University Marine Stations

14. Novorossiysk Biological Sta-

tion of Rostov University

15. White Sea Biological Station

of Moscow University

16. Peterhof Biological Institute

of Leningrad University

Novorossiysk 1921

Velikaya Salma,
Kandalaksha
Gulf, White Sea

Petrodvorets

1938

1920

(E) Institutes of Fisheries

17.

All-Union Institute of

Moscow

1933 (1921

Fisheries and Oceanography

(v.n.i.r.o.)

18.

Pacific Ocean Institute of

Vladivostok

1929

(1925) Zhemchug

Fisheries and Oceano-

Almaz

graphy

Isumrud
Ogon

19.

Kamchatka branch of the

Petropavlovsk

1932

Ozlik

Pacific Ocean Institute of

on Kamchatka

and others

Fisheries

Sakhalin Branch of the Paci-
fic Institute of Fisheries

Antonovo,
Chekhov Dis-
trict, Sakhalin

1932

Amur Branch of the Pacific

Khabarovsk

1945

Ocean Institute of Fisheries

BIOLOGY OF THE SEAS OF THE U.S.S.R.
Table 2—(contd.)

Department and name
of Institution

22. Polar Institute of Fisheries
and Oceanography

23. Baltic Institute of Fisheries

and Oceanography

24. Azov-Black Seas Institute of

Fishery and Oceanography

25. Azov Institute of Marine

Fishery

26. Latvian Institute of Marine

Fishery

27. Latvian Laboratory of Com-

mercial Ichthyology

28. Estonian Laboratory of

Commercial Ichthyology

29. Caspian Institute of Fisheries

and Oceanography-j-

30. Azerbaijan Institute of Fish-

ery!

3 1 . Georgian Scientific Experi-

mental Laboratory

32. Aral Institute of Fisheries and

Oceanography

33. Scientific Research Labora-

tory for Seaweeds

34. Kura Experimental Sturgeon

Hatchery

35. Institute of Lake and River

Fisheries (vniorkh)

36. Ob'-Tazov Branch of the In-

stitute of Lake and River
Fisheries

37. Siberian Branch of the Insti-

tute of Lake and River
Fisheries

38. Scientific Research Institute

of Marine Fisheries of the
Ukrainian s.s.r.

Date of Main expedi-
Place foundation tion ships

Murmansk

1933

(1929) Sevastopol
Knipovich
Academician
Berg

Kaliningrad

1945

Persey II
Professor
Masyatzev
Alazan

Kerch

1921

Grot

Donetz and
others

Rostov-on-Don

1955

Professor
Vasnetzov

Riga

1945

Riga

1945

Tallin

1944

Astrakhan

1897

Baku

1912

Batumi

1932

Aralsk

1929

Archangel

1930

Baku

Leningrad

1914

Tobolsk

1932

Krasnoyarsk

1908

Odessa

1932

* Emerged in 1933 when the Central Institute of Fisheries was united with the State
Oceanographie Institute I.

t Up to 1917 the Astrakhan Ichthyological Laboratory.
X Up to 1917 the Baku Ichthyological Laboratory.

INTRODUCTION

Table 2 — (contd.)

Department and name
of Institution

Date of Main expedi-
Place foundation tion ships

Leningrad 1959 1919

39. State Oceanographic Institute Moscow 1942

of the Hydrometeorologi-
cal Administration* (GOI)

40. All-Union Arctic and Ant-

arctic Institute of the Mini-
stry of the Merchant Marine

41. Kandalaksha State Nature Kandalaksha 1939

Reserve (White Sea)

42. Astrakhan Nature Reserve Astrakhan 1919

43. 'Gassan-Kuli' Nature Re- Krasnovodsk 1933

serve

44. 'Kzil-Agach' Nature Re- Lenkoran' 1929

serve

Schokalsky
Voejkov

Table 3. Major Russian monographs in the field of oceanography

The Acclimatization of Nereis in the Caspian Sea. Symposium, 1952.

Andriashev, A. P.

Andriashev, A. P.
Arkhangelsky, A.

Berezkin, V. A.
Berg, L. S.
Berg, L. S.
Blinov, L. K.
Brodsky, K. A.
Brujevitch, S. B.
Datzke, V. G.

Derjavin, A. N.
Derjavin, A. N.

Derjugin, К. M.
Derjugin, К. M.
Derjugin, К. M.
Djakonov, A. M.

Essay on the Animal Geography and Origin of the Fish of the
Bering Sea and Adjacent Waters. 1933.

The Fish of the Northern Seas of the U.S.S.R. 1954.
D. and Strahov, N. M. Geological Structure and History
of the Development of the Black Sea. 1958.

The Dynamics of the Sea. 1938.

The Aral Sea. 1908.

Fresh-water Fish of the U.S.S.R. 1948-49.

Hydrochemistry of the Aral Sea. 1956.

Copepods. 1950.

Hydrochemistry of the Central and Southern Caspian. 1937.

Organic Substances in the Waters of the South Seas of the
U.S.S.R. 1959.

The Caspian Mysids. 1939.

A Survey of the History of the Caspian Fauna and of the
Bodies of Fresh Water of Azerbaijan and the Caspian
Aquatic Fauna, from the Symposium 'Azerbaijan Ani-
mal World'. 1951.

The Fauna of the Kola Guba and Its Environment. 1915.

The Fauna of the White Sea and Its Environment. 1929.

The MogiVnoye Relict Lake. 1926.

The Echinoderms of the Barents, Kara and White Seas. Pro-
ceedings of the Leningrad Society of Naturalists. 1926,
56,2.

* Was founded in 1 942 separately from the State Oceanographic Institute (GOI N) which
had been reorganized in 1933 into the All-Union Institue of Fisheries and Oceanography.

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Gaevskaya, N. S.
Grimm, O. A.

GURJANOVA, E. F.
GURJANOVA, E. F.

Djakonov, A. M. Brittle Stars [Ophiuroidea] of the Seas of the U.S.S.R-

Classification Keys to U.S.S.R. Fauna, No. 55, 1954-
Zoological Institute of the Academy of Sciences of the

U.S.S.R.

Esipov, V. K. The Fish of the Kara Sea. 1952.

Filatova, Z. A. Zoogeographical Zona t ion of the Northern Seas of the

U.S.S.R. according to the Distribution of the Bivalves.

1957.
(Editor). Classification Keys to the Fauna and Flora of the

Northern Seas of the U.S.S.R. 1937.
The Caspian Sea and Its Fauna. (Works of the Aral-Caspian

Expedition 1876-77.)
Gurjanova, E. F., Zachs, I. G. and Uschakow, P. V. Das Litoral des Kola-
Fjords. 1928-30.
Gammaridae of the Seas of the U.S.S.R. and Adjacent

Waters. 1951.
77?? Gammaridae of the Northern Part of the Pacific Ocean.

1962.
Issatchenko, B. L. Research on Arctic Ocean Micro-organisms. 1914.
Ivanov, A. V. Commercial Water Invertebrates. 1955.

Ivanov, A. V. The Pogonophora. 1959, 1960.

Jashnov, V. A. Plankton Productivity of the Northern Seas of the U.S.S.R.

1940.
Jouse, A. P. Stratigraphic and Geographical Investigations in the North-

western Part of the Pacific Ocean. 1962.
Klenova, M. V. The Geology of the Sea. 1948.

Klenova, M. V. (1960). Geology of the Barents Sea. Ac. Sci. U.S.S.R. (R.)
Kluge, G. A. (1962). Bryozoa of the Seas of the U.S.S.R. Ac. Sci. U.S.S.R. (R).
Knipovitch, N. M. The Basis ofthe Hydrology ofthe European Arctic Осеатг.1906.
Knipovitch, N. M. The Hydrology of the Sea of Azov. 1927.
Knipovitch, N. M. Hydrological Research in the Sea of Azov. 1932.
Knipovitch, N. M. Hydrological Research in the Black Sea. 1932.
Knipovitch, N. M. The Hydrology of Seas and Brackish Waters. 1938.
Lindberg, G. U. The Quaternary Period in the Light of the Biogeographical

Data. 1955.
Invertebrate Fauna in the Lower Stream of the Rivers in the

Ukraine, its Environmental Conditions and its Utilization.

1953-55.
Bottom-living Fish in the Fishery Industry in the Barents Sea.

Proceedings of the Polar Institute of Fisheries and

Oceanography, No. 8. 1944.
Meisner, V. I. Fisheries. 1933. (Ed. 'Snabtechisdat' L.)

Milashevitch, К. O. The Molluscs of the Black and Azov Seas. 1916.
Moiseev, P. A. Cod and Dab of the Far Eastern Seas. 1933.

Mordukhai-Boltovskoy, F. D. The Caspian Fauna in the Azov-Black Sea Basin.

1960.
Morosowa-Wodjanitzkaja, N. V. Phytoplankton of the Black Sea. 1940-57.
Naumov, D. V. (1960). Hydroids and Ну dromedusa in Seawater, Brackish Water and

Fresh-water Basins of the U.S.S.R. Ac. Sci. U.S.S.R. (R).
Nikitin, B. N. Vertical Distribution of Plankton in the Black Sea. 1926-

29 and 1938-45.
Nikolsky, G. V. Fish of the Aral Sea. 1940.

Markovsky, J. M.

Maslov, N. A.

INTRODUCTION

Saidova, Кн. M. (1962)

Samoilov, N. V.
Schimkevitch, V
Schmidt, P. J.
Schmidt, P. J.
Schmidt, P. J.
Schmidt, P. J.
Schokalsky, J.

SCHOKALSKY, J.
SCHORYGIN, A.
SCHULEIKIN, V.
SlNOVA, E. S.
SlNOVA, E. S.

The Ecology of the Foraminifera and Paleogeography of the
Far East Seas of U.S.S.R. and Northwestern part of the
Pacific Ocean. Ac. Sci. U.S.S.R. (R.)
River Mouths. 1952.
M. Pantopoda. U.S.S.R. Fauna, Parts 1 and 2, 1929, 1930.
Pisces marium orientalium Imperii Rossici. 1904.
Fish of the Pacific Ocean. 1948.
The Migration of Fish. 1947.
Fish of the Sea of Okhotsk. 1950.
M. Oceanography. 1917.
M. Physical Oceanography. 1933.

A. Nutritionand Nutrient Correlations of Caspian Sea Fish. 1952.

V. The Physics of the Sea. 1932, 1937, 1941.

The Algae of the Murman. 1912-14.

The Algae of the White, Black, Japan, Chukotsk Seas.
1928-54.
Snezhinsky, V. A. Practical Oceanography. 1954.
Soldatov, V. K. and Lindberg, G. U. A Survey of the Fish of Far Eastern Seas.

1930.
Soldatov, V. K. Commercial Ichthyology. Vol. I, 1934; Vol. II, 1938.

Sovinsky, V. K. An Introduction to the Study of the Fauna of Ponto-Caspian-

Aral Sea Basin. Notes of the Kiev Society of Naturalists.
1904, 18.
The Foundations of Ichthyology. 1948.
Gadi forms, Fauna of the U.S.S.R. Fishes, 1948, 9, 4.
Clupeidae, U.S.S.R. Fauna. Fishes, 1952, 11, 1.
(Editor). The Fauna and Flora of the Chukotsk Sea. 1952.
Okhotsk Sea Fauna and Its Environment. 1953.
Polychaetae Worms of the Far Eastern Seas of the U.S.S.R.

1955.
Chemical Composition of Marine Organisms. (Works of the
Biochemistry and Geochemistry Laboratory of the
Academy of Sciences, u.s.s.r. 3 — 1935, 4 — 1936, 6 —
1944).
The Chemical Composition of Marine Organisms. The
Foundation for Marine Research, New Haven, 1953.
Vize, V. Yu. The Seas of the Soviet Arctic. 1948.

Vorobieff, V. P. The Benthos of the Azov Sea. 1945.

Zenkevitch, L. A. Fauna and the Biological Productivity of the Sea. Vol. I,

1947; Vol. II, 1951.
Zenkevitch, L. A. The Seas of the U.S.S.R., Their Fauna and Flora. 1951 and

1955.
Zernov, S. A. Textbook on Hydrobiology. 1934 and 1949.

Zernov, S. A. The Problem of the Study of Life in the Black Sea. 1913.

Zinova, A. D. Classification Key for Brown Algae. 1953.

Zinova, A. D. Classification Key for Red Algae of the Northern Seas. 1955.

Zubov, N. N. Oceanographic tables. 1931 and 1940.

Zubov, N. N. Sea Waters and Ice. 1938.

Zubov, N. N. Arctic Ice. 1945.

Zubov, N. N. Dynamic Oceanography. 1947.

Zubov, N. N. The Bases of the Study of the World-Ocean Straits. 1950.

Zubov, N. N. In the Centre of the Arctic. 1948.

Suvorov, E. K.
Svetovidov, A. N.
Svetovidov, A. N.
Uschakov, P. V.
Uschakov, P. V.
Uschakov, P. V.

Vinogradov, A. P.

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 4. The main Russian serials and proceedings of scientific institutes containing
the results of research done in the field of marine biology

Number of Publications to which the
volumes present series are succes-
Contemporary Year or parts sors

Transactions of the Institute of
Oceanology of the Academy of
Sciences of the u.s.s.r.

Transactions of the Institute of
Marine Hydrophysics of the
Academy of Sciences of the

U.S.S.R.

Transactions of the All-Union
Institute of Marine Fisheries
and Oceanography

Transactions of the Sevastopol
Biological Station of the Aca-
demy of Sciences of the u.s.s.r.

Transactions of the Murman
Marine Biological Institute of
the Academy of Sciences of the

U.S.S.R.

Transactions of the Karadag
Biological Station of the Aca-
demy of Sciences of the Ukrai-
nian s.s.R. {Travaux de la Sta-
tion Biologique de Karadag de
l'Academie des Sciences de
1'u.r.s.s.)

1946-62 1-53

1948-58 1-24

1935-62 1-44

1936-62 1-14

1948-62 1-5

1930-57 1-14

Transactions of the Scienti-
fic Institute of Fisheries,
Vols. 1-4, 1924-30

Transactions of the Central
Institute of Fisheries,
Vols. 1-4, 1931-32

Transactions of the All-
Union Institute of Fish-
eries, Vols. 1-3, 1933-34

Transactions of the Float-
ing Marine Scientific Insti-
tute, Vols. 1-2, 1926-1927

Transactions of the Marine
Scientific Institute (Be-
richte des wissenschaft-
lichen Meeresinstituts),
Vols. 3-4, 1928-30

Transactions of the State
Oceanographical Insti-
tute (GOI N), Vols. 1-3,
1932-33

Works of the Murman
Biological Station of the
Academy of Sciences,
u.s.s.r., Vols. 1-3, 1925-
1929

{Travaux de la Station Bio-
logique de Murman)

INTRODUCTION
Table 4—{contd.)

Contemporary

Number of
volumes
Year or parts

Publications to which the
present series are succes-

sors

Transactions of the Novorossiysk
Biological Station

Transactions of the Aral Branch of
the All-Union Institute of Mar-
ine Fisheries and Oceanography

Transactions of the Azov-Black
Sea Institute of Fisheries and
Oceanography

Transactions of the Caspian In-
stitute of Fisheries and Oceano-
graphy

Transactions of the 'N. M.
Knipovitch' Polar Institute of
Sea Fisheries and Oceanography

Transactions of the Pacific Ocean
Institute of Fisheries and
Oceanography.

{Abhandhmgen der wissenschaft-
lichen Fischerei-Expedition im
Asowschen und Schwarzen
Meer)

Transactions of the State
Oceanographical Institute

Fauna of the U.S.S.R. (pub-
lished by the Zoological Insti-
tute of the Academy of Sciences
of the u.s.s.r.)

Research on the Seas of the
U.S.S.R. (published by the Zoo-
logical Institute of the Academy
of Sciences of the u.s.s.r.)

1937-38 1-3

1933-35 1-5

1940-62 1-19

1957

13-16

1938-62 1-13

1930-62 5-47

1947-62 1-65

1917-62

1925-37 1-25

Transactions of Kerch Ich-
thyological Laboratory,
Vol. 1, 1926-27

Transactions of the Azov-
Black Sea Scientific
Fishery Station, Vols. 1-
9, 1927-39

Transactions of the Azov-
Black Sea Scientific and
Commercial Expedition,
Vols. 1-16, 1926-55

{Bulletin of the Pacific Sci-
entific Institute of Fisher-
ies and Oceanography)

Transactions of the Ich-
thyological Laboratory
attached to the Admini-
stration of the Caspian-
Volga Fish and Seal In-
dustries, Vol. 1, 1909

Transactions of the Pacific
Ocean Scientific-Com-
mercial Station, Vols. 1-
4, 1928-29

Fauna of Russia and Adja-
cent Countries, Vols. 1-
26, 1911-17

22 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 4 — (contd.)

Number of Publications to which the
volumes present series are succes-
Contemporary Year or parts sors

Research on the Far Eastern Seas 1927 1-7

of the U.S.S.R. (published by
the Zoological Institute of the
Academy of Sciences of the

U.S.S.R.)

Key to the Classification of the 1933-62
Fauna of the U.S.S.R. (pub-
lished by the Zoological In-
stitute of the Academy of
Sciences of the u.s.s.r.)

Tableaux analytiques de la Fauna
de VU.R.S.S. (publies par l'ln-
stitut Zoologique de l'Acade-
mie de Sciences de Tu.r.s.s.)

Transactions of the Zoological 1-28

Institute of the Academy of
Sciences of the u.s.s.r.

Transactions of the AU-Union 1949-62 1-12
Hydrobiological Society

Russian Hydrobiological Journal 1921-28 1-7
(published by the Volga Bio-
logical Station, Saratov)

Zoological Journal (published by 191 6-62 1-40
the Academy of Sciences of
the u.s.s.r.)

Oceanology (published by the 1961 1-2

Academy of Sciences of the
u.s.s.r.)

Problems of Ichthyology (pub- 1961 1-2

lished by the Academy of Sci-
ences of the u.s.s.r.)

Transactions of the Arctic and 1959-62 226-56
Antarctic Institute

Transactions of the Arctic In- 1933-59 1-225
stitute

THE MAIN TRENDS OF RESEARCH ON THE BIOLOGY OF
THE SEAS IN THE U.S.S.R.

The study of the seas of the u.s.s.r. has developed widely during the last 40
years in practically all areas, but to a lesser degree in the Laptev and East-
Siberian Seas, which are hard of access. Marine research has been carried out
in all the basic departments of oceanography, and for the most part has been
of a comprehensive character.

INTRODUCTION 23

Biological research has also been systematic and all-embracing, covering
more or less uniformly both plant and animal populations throughout the sea
column from its tidal zone to its abyssal zones. This started as a systema-
tic study of the fauna and biogeographical characteristics of the seas, which
covered, however, some ecological problems, as well as the seasonal cycles of
development and the phenomena of biological productivity. The study of fish
feeding and their use of plankton and benthos forms a considerable section of
marine biological research. The results of biological research were used in
dealing with the problem of acclimatization in new places of marine fish and
the invertebrates used by them as food. The acclimatization of Mugil awatus.
M. saliens, Nereis diver sicolor, Syndesmya ovata, Leander longirostris and L.
squilla in the Caspian Sea and Clupea harengus membras and Leander squilla
in the Aral Sea were found most effective and interesting.

THE NORTHERN SEAS OF THE U.S.S.R.

General Characteristics of the Northern Seas

I. HYDROLOGICAL CONDITIONS
The link with the Atlantic and the Pacific Oceans

The Arctic Ocean is sometimes regarded as a kind of Inter- American-Eurasian
Mediterranean Sea (North Polar Sea) which forms a supplementary body of
water for the Atlantic Ocean. The Arctic Ocean is, however, so much a
separate body of water with its own characteristic and independent climatic
and hydrological conditions, that it can be considered as an independent
ocean.

Nevertheless, this is not to deny that the Arctic Ocean and its fauna are at
the present time exposed to the continuous and very powerful influence of the
waters of the Atlantic Ocean, and to the comparatively insignificant influence
of the waters of the Pacific Ocean.

The cross section of the Bering Strait is only 2-5 km2 while that of all the
straits between Greenland and the Scandinavian Peninsula is about 370 km2.
The maximum depth of the Bering Strait is 70 m but the minimum depth of the
submarine ridge between Greenland and Scandinavia is about 440 m.

Approximately 8,000 km3 of water (Kort, 1962) enter the Arctic Ocean
annually through the Bering Strait, but no less than 400,000 km3 of Atlantic
waters enter the Arctic Ocean from the south. No less than 436,300 km3 of
water are carried out by the Arctic currents into the Atlantic Ocean includ-
ing approximately 6,000 km3 in the form of floating ice. Thus the Arctic
Ocean exercises a great influence on the Atlantic Ocean and on the climate
of North America. The amount of heat brought into the Arctic basin*
with the warm Atlantic waters is enormous. The heat liberated by cooling
these waters merely by Г would be sufficient to raise the temperature of a
4 km layer of air over the whole of Europe by 10°.

The warm Atlantic waters, acting as a special kind of heating system, heat
the Arctic and bring warm- water fauna far to the northward.

The surface layer of water with a lower salinity and the great extent of
floating ice, which in winter is about 1 1 x 106 km2, and in summer about
8x 106 km2 (60 to 80 per cent of the total surface), cover the warm Atlantic
waters like an insulator, and the thermal action of these waters is felt at a
depth of 300 to 900 m.

As will be shown below, the nature of the interaction of the faunas of the
three oceans, the strong influence of the faunas of the Atlantic and Arctic
Oceans upon each other, and the slight interaction between the faunas of the
Arctic and Pacific Oceans, are completely in keeping with the systematic inter-
change of water between the Arctic and its two neighbouring oceans.

This, however, is only true, of course, for the position at the present time.

* The expression Arctic basin is commonly used, and we shall use it here in the same
sense as the North Polar Ocean.

BIOLOGY OF THE SEAS OF THE U.S.S.R.

The relationships differed to a considerable degree in the Quaternary Period,
and even more during the Tertiary Period, not to mention the Mesozoic
era.

The seas lying within the Soviet sector of the Arctic basin

More than half of the coastline of the Arctic basin (North Polar Ocean) be-
longs to the Soviet Union. From the chart (Fig. 1a) it will be seen that a wide
belt of shallow water, 500 to 1 ,000 km in width, adjoins the coast of the u.s.s.r.,
forming a system of separate, more or less open seas. Most of them could be

Fig. 1a. Arctic basin bottom topography according to data from Soviet drifting

observation stations.

called inlets of the Arctic Ocean, rather than individual seas.* The most
westerly of them, the Barents Sea, is limited to the north by Spitsbergen and
Franz Joseph Land, and to the east by Novaya Zemlya. On the west the natural
boundary of the Barents Sea is formed by the edge of the continental shelf at a
depth of 500 m. To the south the White Sea adjoins the Barents Sea. The Kara
Sea extends from Novaya Zemlya to the Severnaya Zemlya archipelago, and
between the Severnaya Zemlya and the Novosibirsk Islands lies the Laptev
Sea. Beyond as far as Wrangel Island there is the East Siberian Sea, and lastly
the Chukotsk Sea lies between Wrangel Island and the Bering Strait. All these
seas, except for the western half of the Barents Sea, and part of the Chukotsk
Sea adjoining America, lie within the boundaries of the u.s.s.r. Whereas the
eastern and western boundaries of these seas can be defined fairly accurately,

* The epicontinental bodies of water composing the Arctic Ocean form about 37 per
cent of its whole area, whereas the continental self of the world-ocean forms only 8 per
cent of its area.

GENERAL CHARACTERISTICS OF THE NORTHERN SEAS 29

and the edge of the continental

to the north precise boundaries do not exist,
shelf is taken to be the boundary.

Huge European and Siberian rivers — the
Yenisei, Khatanga, Lena, Yana, Indigirka,
basin large masses of river water (up to 3,000
of the adjoining areas of sea water, especially
Laptev and East Siberian Seas, and likewise
Arctic Basin.

Northern Dvina, Pechora, Ob,
Kolyma — bring into the Arctic
km3 a year) lowering the salinity
that of the White Sea and of the
the surface waters of the whole

ПЛ ./>

Fig. 1b. Course of Fram and Sedov and Soviet drifting observation stations NP-1

to NP-7.

Size

The total area of the Arctic Ocean is about 13 x 106 km2, while its central part
is 4-891 X 106 km2. This latter is in the main more than 2,000 m deep, i.e. it con-
sists of an abyssal zone (70 per cent), while only a third of it (30 per cent) is
composed by the continental shelf (200 to 2,000 m). The expedition on board
the Sedov in 1939 established that the greatest depth of the Arctic Ocean —
5,180 m — lies to the north of Franz Joseph Land.

Ice-floes

The climatic conditions of our northern seas, except for the southwestern half
of the Barents Sea and the southern half of the Chukotsk Sea, are very severe.
Even during the warmest season of the year — in August — a great part of the
sea surface is usually covered with ice-floes (Fig. 1в). Polar ice can, perhaps, be
considered the most characteristic feature of the Arctic basin, determining
many aspects of its hydrological and biological conditions.

30 BIOLOGY OF THE SEAS OF THE U.S.S.R.

History of exploration

The remarkable voyage of Dr F. Nansen's Fram (1896) marked the beginning
of the comprehensive exploration of the central part of the Arctic Ocean. The
honour of the discovery of the great oceanic depths of the central depression
belongs to Dr Nansen, and it was he who first put forward a theory about the
stratification of, and the forces exerted by, the waters of the Arctic basin and
the causes of these phenomena.

After an interval of 32 years the intensive exploration of the central areas of
the Arctic Ocean was begun and has been brilliantly expanded by a long series
of remarkable Soviet expeditions, starting with the voyage of the icebreaker
Krasin to the north of Spitsbergen in 1928.

Substantial results were obtained by the expedition on board the Sadko
(1935) which succeeded in navigating between Franz Joseph Land and Sever-
naya Zemlya into the central Arctic up to a latitude of 82° 42'.

The drift expedition of Papanin, Shirshov, Fedorov and Krenkel (1937-38)
and the voyage of the Sedov (1937-40), which was remarkably well equipped
for scientific purposes, confirmed in the main the data previously obtained by
Dr Nansen during his voyage on the Fram about the peculiar stratification of
the waters in the central part of the Arctic basin, and collected abundant new
material.

Observations were carried out for more than a year, during 1950-51, from
M. Somov's drifting station (NP-2), landed from the air in the region of the
'Ice Pole'. Two drifting stations were fitted out in 1954 — the Treshnikov one
near the North Pole (NP-3) and the Tolstikov one within the region of the
'Pole of Inaccessibility' (NP-4). The existence of a peculiar cyclonic rotation
of water masses was observed in the eastern part of the Arctic basin at the
Somov and Tolstikov stations. Lately new drifting stations have been set up
every year. Rich material (meteorological, hydrological, geological and bio-
logical) has been gathered by all these expeditions. In particular they have
shown that the central part of the polar basin is divided into two independent
depressions by a huge submarine range, which has been named the Lomono-
sov range. It stretches from the Novosibirsk Islands to Ellesmere Island, rising
from a depth of 4 km to within 1 ,000 m of the surface at its summit.

Stratification of waters

Throughout the central part of the Arctic basin (Fig. 2), underneath the shallow
surface layer (100 to 150 m) of water with low salinity* (30 to 32%0) and of
low temperature (from —1-5 to —1-7°) there is a second layer with normal
salinity (34%0) but of low temperature ( — 1 -0°) and beneath it lies a 600 m
deep layer of warm (up to 20 to 2-5°) Atlantic water with high salinity (34-7
to 34-9%,,). Deeper down and extending to the sea bottom the salinity remains
the same as that of the layer immediately above it, but its temperature is low.
In the higher levels of the eastern sector of the Arctic basin waters are ob-
served which have penetrated from the Bering Sea.

* Salinity, symbol S, will be quoted in grammes per kilogramme (denoted %0) through-
out this text.

GENERAL CHARACTERISTICS OF THE NORTHERN SEAS

The surface layer results from the lowering of salinity by river waters. The
saline, cold layer deeper down is produced by the mixing of the lower-lying
Atlantic waters with the cold surface waters.

The deep-lying masses of fully saline, cold waters are the cooled Atlantic
waters. Dr F. Nansen assumed that they were formed by the cooling and sink-
ing of surface water in winter time in the northern part of the Greenland Sea.
Most probably, however, they result from a local cooling and downward

-2-0t

2-0 'NORTH POLE' 'N— 169'

1000

2000-

3000

35%,

Fig. .2. A. Salinity and temperature curves (Shirshov).

1 Station 28 of 'North Pole' expedition;

2 near North Pole according to data of 'North Pole' expedition;

3 within region of 'Pole of Inaccessibility', according to data of Libin-
Cherevichny expedition aircraft 'N-169'.

B. Diagram of distribution of four layers (Stockmann).

1 according to data of ' North Pole ' expedition ;

2 according to data of Libin-Cherevichny expedition.

movement along the declivities of part of the cold, saline water, formed on the
surface in winter time as a result of freezing.

This singular stratification is best seen in the light of the comparison between
the waters of the central part of the Arctic basin and those of the northern
part of the Greenland Sea situated somewhat more to the south, where the
warm Atlantic waters still remain on the surface {Table 5).

Warm Atlantic waters, passing over the Nansen ridge, enter the Arctic
basin and spread northwards and eastwards and being heavier sink below the
less saline surface layer (Figs. 3 and 4). The comparative thickness of the four
layers changes gradually with their movement northward and eastward away
from the regions adjacent to the outlets to the Atlantic ; this can be seen in

BIOLOGY OF THE SEAS OF THE U.S.S.R.

1200

/400

1500

82c 83° 84" 85" 88"

Fig. 3. Temperature curves from Sever nay a Zemlya to North Pole (Shirshov).

Table 5

Depth
m

Greenland Sea 76° 20'

N lat. 2° 17' E long.

Sadko, 1935

Arctic basin northeast

of Franz Joseph Land

82° 41' N lat. 87° 03'

E. long. Sadko, 1935

Arctic basin northeast
from Severnaya Zem-
lya 78° 31' N lat.
118° 18' E long. Sedov,
1937

*J/oo

t°

^%o

■S/oo

3-90

34-97

-1-70

31-60

-1-46

30-32

3-93

3503

-1-70

32-43

-1-70

31-58

1-62

3503

-1-74

33-98

-1-77

33-68

1-40

35-03

-1-34

34-20

-1-74

33-95

100

1-30

3503

-0-34

34-33

-1-65

34-51

150

0-70

34-96

1-91

34-74

—

200

—

109

34-65

250

-0-5

35-08

2-12

34-83

— ■

—

300

—

1-34

34-70

500

-0-44

34-92

1-58

34-90

0-80

34-70

800

. — .

—

001

34-72

1,000

-0-67

34-94

-016

34-85

-0-30

34-72

2,000

-0-99

34-94

-0-67

34-85

— ■

—

GENERAL CHARACTERISTICS OF THE NORTHERN SEAS

Fig. 2. The two upper layers become thicker, while the warm Atlantic layer,
on the contrary, gradually loses its heat, mixes with the water layers above
and below, and becomes thinner.

A comparison of the changes of temperature with depth at three points in
the central part of the Arctic basin — north of the Greenland Sea, near the
North Pole and within the region of the 'Pole of Inaccessibility' (station No. 3
Libin-Cherevichny air expedition, 1941, 3) — is given in Fig. 2. It is perfectly
clear from that figure that as one moves farther up the basin and towards the

Fig. 4. Distribution of isotherms at depth of 300 m (isothermobaths). Penetration

of deep Atlantic waters into northern parts of Barents, Kara and Laptev Seas is

clearly shown (Dobrovolsky, after Shirshov).

Bering Strait the upper cold layer becomes somewhat warmer, the inter-
mediate Atlantic one loses some of its heat and the cold abyssal one becomes
somewhat warmer. This is the result of a gradual intermixing of the inter-
mediate warm layer with the adjacent colder lower and upper layers. Accord-
ing to A. Dobrovolsky's computation the course of the Atlantic waters from
Spitsbergen to Kara Sea takes two years ; in one year more they reach the
Laptev Sea and two years later they penetrate the Chukotsk Sea. It takes
the Atlantic waters three years to cover the distance from Lofoten to
Spitsbergen.

It is evident from Table 5 that the deep waters of the Arctic basin are
warmer than those of the Greenland Sea.

34 BIOLOGY OF THE SEAS OF THE U.S.S.R.

The drift of polar waters

The direction of the drift bringing masses of surface waters and ice-floes out
of the eastern sector of the Arctic basin was charted by the voyage of the Fram
and, with greater precision, by the later Soviet expeditions — that of Papanin
on drifting ice and by the icebreaker Sedov (1937-39). As was shown by
N. Zubov in 1937-39 (Nansen had noted it earlier) the movement of the Arctic
basin surface water and of the ice-floes on it is occasioned by the prevailing
winds ; the direction the Arctic Ocean's currents corresponds to the direction
of the isobars. The Libin-Cherevichny expedition worked in 1941 at 78° 27'
to 81° 32' N latitude and 176° 32' to 190° 10' E longitude.

From the shores of Siberia diluted waters are carried away beyond the zone
of the shallows, whence they are caught up by the general westward current to
pass between Greenland and Spitsbergen. Two main streams of polar waters
and the ice move along the eastern shores of Greenland and through the Davis
Strait.

Water balance

The attempt to find the main indices of the water balance of the Arctic basin
goes back to Nansen. These indices may be given with some approximation
as in Table 6.

Table 6

Inflow of fresh water into

Arctic basin km3

Fresh water brought by the
rivers 4,000 to 5,000

Surplus rainfall over evapora-
tion

about 2,000

On account of exchange
through the Bering Strait

about 2,000

Total about 8,000 to 9 ,000

The present Arctic basin water balance is probably most unstable. During
the Ice Age the Arctic basin waters became greatly diluted, and in the succeed-
ing millennia the reverse process of increase of salinity must have gone on. It is
clear that the salinity of the Arctic waters always largely depends on the inflow
of river water, the amount of ice carried out (two factors greatly affected by
seasonal changes) and the nature of the water exchange with the Atlantic
Ocean (depending on the bottom topography of the passages connecting the
Arctic basin with the Atlantic Ocean).

GENERAL CHARACTERISTICS OF THE NORTHERN SEAS 35

This undoubtedly points to the instability of the saline conditions of the
surface waters of the whole of the Arctic basin and of the seas included in it.
In addition, the climate of the Arctic does not remain unchanged.

Increase in temperature of the Arctic

A considerable rise of temperature has been observed in the Arctic and the
adjacent temperate latitudes during the last 40 years ; it was first noted by
N. Knipovitch for the Barents Sea in 1921. In Spitsbergen during the five
months November to March of the period 1916-20 the mean temperature was
-17-6°, whereas in 1931-34 it was -8-6°, i.e. 9° higher.

A graphic illustration of the increase in temperature of the Arctic is given
by K. Badigin. It is evident from a comparison of the mean monthly tempera-
ture readings taken on the voyage of the From (1895) with those taken on the
Sedov (1939-39) that during the coldest months the average temperature of the
air is now almost 10° higher than it was 43 years ago (Table 7).

Table 7

Fram

Sedov

Months

1895-96

1938-39

September
October

-9-6

-21-2

-4-1

-12-8

November

-30-9

-21-7

December

-32-7

-22-5

January
February

-34-7
-34-7

-31-1
-30-2

The mean annual temperature at Archangel between 1891 and 1915 was
0-2° and between 1931 and 1934, 1-6°. In the Yugorsky Shar the mean
annual air temperature was —8-4° between 1914 and 1919, whereas from 1920
to 1935 it was +2-2°. In Franz Joseph Land (Tikhaya inlet ) between 1873
and 1914 the temperature was -13-9° and from 1929 to 1936, +3-4°. In
Spitsbergen the annual mean temperature was 1-7 to 1-8° above normal during
the period from 1923 to 1933. The mean winter temperature in Spitsbergen
has gradually risen over the years, Table 8.

Table 8

Period 1916-20

Mean winter
temperature, °C -17-6

There are many other indications of a rise of temperature in the Arctic in
the course of recent decades :* the retreat of glaciers which covered the Arctic

* Willet (1950) thinks that the increase in the temperature of the Arctic began in 1885.

921-25

1926-30

1931-35

-12-5

-13-9

-8-6

36 BIOLOGY OF THE SEAS OF THE U.S.S.R.

islands, the warming up of the Polar waters, a decrease in icing and easier
navigation for shipping in high latitudes.

As early as 1921-26 (taking average annual data) a rise of almost Г degree,
as compared with 1900-01, was observed in the temperature of the bottom
layers of water along the meridian of Kola ; the rise in the temperature of the
upper 200 m layer was on the average almost 2°. During that time the ice in
the Barents Sea decreased considerably (by 13 per cent).

The waters of the Kara Sea have been affected by a no less sharp rise in
temperature. This made possible the voyage in 1939 of the Sibiryakov, when
she rounded Severnaya Zemlya from the north, reaching a latitude of 80° N
in one season. On her passage from Cape Zhelaniye to Wiese Island and on
to the Pioner Island in 1933 the Taimyr never encountered a surface tempera-
ture below zero, while in some places the temperature of the water reached
4-5°.

The sea fauna, that extremely sensitive indicator of changes of temperature,
reacts to climatic changes, by changes both qualitative and quantitative in its
composition. Many warmth-loving sea dwellers new to the Arctic penetrate
far into it, while, on the other hand, forms characteristic of cold waters move
deeper into it from the more southerly parts of the Arctic regions. This con-
cerns not only individual forms ; whole communities change their composition
both qualitatively and quantitatively. All aspects of the biology of Arctic flora
and fauna are influenced by this general change towards a warmer climate ;
the Arctic's outposts — the Barents and Kara Seas — are particularly affected by
it. Fisheries are also affected since the regions of the shoaling of commercial
fish — cod, haddock, herring, bass, cambala — have moved east and north. The
Danish scientist Ad. S. Jensen (1939) thinks that the great development of cod
fishing off the southwestern shores of Greenland is due to the mass arrival of
cod in this region as a result of the increase in temperature of the Arctic. The
annual catch of this industry has increased since the 1920s from 400 to 8,000
tons.

Moreover Ad. S. Jensen notes that fish which were either absent or rare
off the western shores of Greenland have now become common there. This
includes haddock (Gadus aeglefinus), brismak (Brosmius brosme), sea pike
(Molva vulgaris) and others. Cod, herring, coalfish, salmon and others have
become common and are even fished there. Halibut and caplin are widely
distributed and, finally, some fish, e.g. bass, have begun to spawn there.
Hence according to Ad. S. Jensen's data, the fish of the Davis Strait have
undergone a complete change owing to the warming up of its waters. Among
others the common asterid (Asterias rubens) is widely propagated there. On
the other hand many forms have moved from the south to the northern parts
of the Davis Strait and Baffin Bay. The main shoaling of Delphinapterus leucas
and such fish as the fjord cod {Gadus ogac) and Greenland flatfish {Reinhardt-
ius hippoglossoides) have moved.

All these far-reaching changes in the composition and distribution of the
fauna of Greenland's western shores are the result of the intensification of
the stream of Atlantic water entering the Davis Strait from the south and of the
general Г to 2° rise in the temperature of the waters. A comparison of water

GENERAL CHARACTERISTICS OF THE NORTHERN SEAS 37

temperatures at various depths in one of the fjords on the southern point of
Greenland is given in Table 9.

Table 9

n , Temperature of water in °C

22.8.'09

16.8.'34

3-85

5-20

1-45

3-65

0-62

1-36

100

0-07

1-09

200

0-61

1-50

Similar changes in the fauna and especially in the fish population have
taken place in the waters of Iceland.

Many fish, such as caplin, herring and cod, the great bulk of which have
hitherto inhabited the warmer southern and western shores of the island have
migrated to the northern shores and begun to spawn there. Fish formerly
rare in Icelandic waters have now become common. They include tuna,
mackerel, Selache maxima, Scombresox saurus, Orthogoriscus mola, Paralepis
kroyeri and many others. Such southern forms as, for instance, Notidanus
griseus, Xiphias gladius and Caranx trachurus, which have never before been
observed in Icelandic waters, have been found there in recent years.

The same can be said about the invertebrates. Formerly unknown off the
shores of Iceland, there have now appeared there Echinus esculentus, Aphrodite
aculedta, Lithodes maja, and the huge south boreal polychaetes {Nereis virens),
which, by the way, was found in the White Sea in recent years (Annenkova and
Palenichko, 1946) and was undoubtedly absent from those waters before.

Not only marine animals but birds are extending their habitats northwards
because the climate is becoming milder. Some North-European gulls {Larus
ridibundus, L. fuscus and L. argentatus), which used to be rare in these parts,
have in recent years appeared in great numbers in Iceland.

Ice has disappeared from the northwestern, northern and eastern shores of
Iceland in recent years, the winter has become very mild, the average air
temperature in February and March has risen by 4° to 7° above the former
average, while the temperature of the surface waters along the northern and
western shores has risen by 0-5° to 4°. This rise in temperature is felt to depths
of 200 to 400 m; hence the difference between the temperatures of the
northern and southern shores of Iceland has practically disappeared. The
same phenomena are observed at Jan Mayen I., Spitsbergen and in Arctic
bodies of water situated to the east of them. In the 1870s and 1880s there was a
fairly good catch of cod and haddock along the western shores of Spits-
bergen. Later this fishing stopped completely to begin again in the third decade
of the present century. About 200 small Norwegian trawlers fishing in these
waters in 1935 obtained a total catch of 4,500 tons offish. N. Tanassijcuk

38 BIOLOGY OF THE SEAS OF THE U.S.S.R.

(1929) notes that in recent years fish which had hitherto been very rare along
the Murman coast have begun to appear there, such as Lamna cornubica,
Microstomas microcephalus, as well as Gadus merlangus, Trachypterus arcticus
and others ; Yu. Boldovsky (1937) has noted the finding of Gadus esmarki and
G. poutassou in Murman waters.

Some boreal forms which formerly were never or very rarely found in the
plankton of the Barents Sea have become common there. Among them may
be mentioned the cephalopod Ommatostrephes todarus, the siphonophore
Physophora hydrostatica, the polychaete Tomopteris helgolandica and a
series of others. Sometimes the warm-water pteropod mollusc Limacina
retroversa drifts in great numbers into the southwestern part of the Barents
Sea.

Meganyctiphanes norvegica (Euphausiacea), rare in the Barents Sea at the
beginning of this century, has now become a common form there. Still more
examples could be given as regards benthos. The boreal sea urchin Schizaster
fragilis, which according to K. Derjugin (1915) was absent in the Kola Guba
in 1908-09, has in recent years become a mass form there. The mollusc
Cardium echinatum was also unknown there. Another boreal sea urchin
Echinus esculentus has become common on the western Murman coast. A
whole series of boreal molluscs has become common in the Kola Guba and the
adjacent area of the Barents Sea; as for example Cardium edule, C.fasciatum,
С elegantulum, Acera bullata, Doto coronata, Gibbula tumida ; of crustaceans
Eupagurus bernhardus, Munida rugosa and others may be mentioned. At the
same time Arctic forms are receding eastward. The cold-water mollusc Ser-
ripes groenlandicus which at the time of K. Derjugin's explorations (1910 to
1914) was a mass form in the Kola Guba has at present (V. Zatzepin, 1946)
become a rarity there, and the cold-loving pteropod mollusc Limacina heli-
cina has been driven out into the eastern part of the sea.

The appearance of a whole series of warm-water fish off the shores of
Novaya Zemlya and in the Kara and White Seas has been observed (L. Berg,
1939). In 1883 the warm- water fish Scombresox saurus was very rarely
caught off the North Cape, but in 1937 it was caught at Matochkin Shar.
Moreover, herring, mackerel, haddock and coalfish were found off the shores
of Novaya Zemlya. Cod and coalfish have apparently begun to multiply
there.

Haddock, coalfish and bass have appeared in the White Sea; Atlantic
herring and Barents Sea cod have penetrated into the Kara Sea.

The quantitative and qualitative composition of the population of the Arctic
basin has substantially changed as a result of the warming up of the water by
a few degrees. The changes are in three directions : first of all there is a change
in the composition of the population, that is in the structure of the biocoe-
noses ; then there is migration not only of separate forms, but of whole
groups (biocoenoses) from south to north — the Arctic communities recede,
the boreal advance; finally there is also a change in the quantitative indices
of the density of the population. This colossal process of the general change of
the Arctic basin fauna proceeding in a definite direction and taking whole
decades to develop deserves most careful investigation.

GENERAL CHARACTERISTICS OF THE NORTHERN SEAS 39

II. GENERAL CHARACTERISTICS OF THE FAUNA OF THE
EASTERN SECTOR OF THE ARCTIC BASIN

Impoverishment of the fauna towards the north and east

The farther one moves east from the southwestern parts of the Barents Sea,
the greater is the distance from the sphere of influence of the warm, saline
Atlantic waters and the poorer the quality of the flora and fauna. The flora
and fauna of the littoral and of the highest level of the sublittoral are parti-
cularly affected by this process of impoverishment.

In the northern and eastern parts of the Barents Sea the littoral population
has almost vanished already. Only three or four of its hardiest representatives
(Fucus vesiculosus, Littorina rudis and Ba/anus balanoides) are found on the
seashore at low tide, and some species {Mytilus edulus, Fabricia sabella,
Balanus balanoides and others) have moved from the littoral into the sub-
littoral. These last remains of the littoral fauna are hardly ever found east of
Novaya Zemlya. The extreme ice conditions during the eight to nine winter
months are particularly destructive of the littoral fauna.

Although the study of the bottom fauna of the Siberian seas has so far been
extremely inadequate, the quantitative and qualitative poverty of both flora
and fauna are beyond doubt. The impoverishment of the fauna is particularly
clearly marked as one travels eastward, comparing the Barents Sea with the
Laptev Sea. A comparison of the number of species of some basic groups is
given in Table 10.

Table 10

Approximate number of known species of fauna
Group groups in

Barents Sea Kara Sea Laptev Sea

Polychaeta

about 200

about 150

Echinodermata

Amphipoda
Decapoda
Lamellibranchiata
Gastropoda
Tunica ta

262
25
87)

150J
50

225
14

about 100

87
5
23
32
24

Pisces

144

Total bottom fauna about 1,300 about 1,200 about 500

A. P. Andriashev (1954) has recorded 204 species and sub-species offish
in the northern seas of the u.s.s.r. from the Barents Sea to the Chukotsk Sea.
As one moves eastwards, the number of species and their composition for the
six families with the greatest number of species undergoes characteristic
changes {Table 11).

Moreover, not only a qualitative impoverishment but also a considerable
admixture of brackish relict and fresh-water families, Salmonidae, Gadidae
and Cottidae, is characteristic of the Kara Sea and farther east.

40 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 11

East
Total No. Barents White Kara Laptev Siberian Chukotsk
Family of species Sea Sea Sea Sea Sea Sea

Gadidae

Ragidae
Salmonidae

7
17

7
7

0
8

Zoarcidae

Cottidae

Pleuronectidae

Total

Qualitatively rich fauna, in a series of groups almost as varied as Barents
Sea fauna, is found only at the northern boundary of the Siberian seas at the
edges of the continental shelf, washed at the depth of some hundreds of metres
by the warm intermediate layer of Atlantic water, and in the deep trenches
entering the Kara and Laptev Seas from the north.

The richest benthos as regards numbers is found in the southeastern,
shallower part of the Barents Sea, in its central shallows and on the southern
and eastern slopes of the Spitsbergen shallows. The southwestern half of the
Barents Sea has quantitatively the richest plankton. A sharp decrease of the
biomass and an impoverishment of the qualitative composition of benthos
and plankton can be observed as one moves into the northern part of the
Barents Sea and eastward beyond Novaya Zemlya.

The southeastern part of the Kara Sea, the Laptev and East Siberian Seas
are probably the poorest in benthos and plankton, and the biomass of plank-
ton and benthos increases again only in the eastern part of the Chukotsk Sea.

The high salinity and the strong vertical circulation of the Barents and
Chukotsk Seas ensure richness of pelagic and bottom life. In the seas situated
between Novaya Zemlya and Wrangel Island the aeration of the bottom
layer and of the whole water column is, at any rate in certain seasons of the
year, impeded by the considerable desalting of the surface layer ; this has an
adverse effect on the development of life. The latter perhaps suffers even
more from the extremely severe climatic conditions of these seas, which are
only free from their ice cover for a short period, from the almost complete
suspension of the growth of phytoplankton for ten months of the year, and
finally from the considerable lowering of salinity in the southern part of the
whole chain of Siberian epicontinental water bodies. Their productivity must
be many times lower than that of the Barents Sea. Since the biomass in these
seas in summer, when it is flowering, is three to five times, or perhaps even
eight to ten times smaller than that of the Barents Sea, its annual production
must be much less.

The process of growth can serve as an indicator of the comparatively slow
rate of the biological processes in the northern seas as compared to those
taking place in the southern ones. Thus, for example, the fouling process in

GENERAL CHARACTERISTICS OF THE NORTHERN SEAS 41

Kola Guba, thermally one of the most favourable regions of the Barents Sea,
attains appreciable intensity during two months — July and August — only at a
temperature of 9° to 12° С Even then growth hardly reaches 700 to 800 g/m2,
whereas in the Black Sea the fouling process is continuous almost throughout
the whole year, and as a result of it during the same two months an animal
fouling is obtained weighing 8 to 10 kg/m2.

Phytoplankton

P. Usachev (1947) in his reference work on the phytoplankton of the seas of
the u.s.s.r. notes, from data obtained for August and September, the im-
poverishment of the qualitative composition of the plankton seaweeds in all
their component groups, as one moves from the Barents Sea east and north-
ward into the central part of the Arctic Ocean (Table 12).

Table 12

Flagellates, silico-

Total number

flagellates and

Region of phytoplankton

Diatoms

Peridineans

green algae

Central part of

Arctic basin

40 (76%)

10 (19%)

3(5%)

Western part of

Barents Sea

179

92(51%)

69 (39%)

18(10%)

Eastern part of

Barents Sea

110

56(51%)

47 (43%)

7 (6%)

White Sea

106

61 (58%)

29 (28%)

16 (14%)

Kara Sea (central

part)

52 (67%)

20 (25-6%)

6(7-7%)

Laptev Sea (central

part)

61 (64%)

28 (30%)

6 (6%)

As shown in Table 12 the relative variety of species of the diatomaceous
algae increases from 51 to 76 per cent while that of peridineans decreases from
39 to 11 per cent. This shows the Arctic aspect of the diatoms and the boreal
character of the peridineans.

The character of the two main groups of phytoplankton appears even more
clearly in the biomass. The diatoms have a preponderant influence, while the
peridineans play a very modest part (Table 13).

The considerable increase of the role of the flagellates in the plankton bio-
mass of the Barents, and partly of the Kara, Sea is caused by a mass develop-
ment of Phaeocystis and Dinobryon, which is sometimes observed even in
the form of 'bloom' in the Barents Sea and to a lesser degree in the northern
part of the Kara Sea.

The development of the phytoplankton of the Arctic basin is closely bound
up with ice conditions. The mass development of the spring plankton (mainly
diatoms) coincides with melting of the ice and the penetration of light into the

BIOLOGY OF THE SEAS OF THE U.S.S.R
Table 13

Region

Percentage of total phytoplankton biomass

Diatoms Peridineans Flagellates Green algae

Eastern half of Barents Sea
Kara Sea (central part)
Laptev Sea (central part)
North Pole

79 8 10 3
87 6 5 2
94 4 1 1
98 2 — —

water column. The nearer the Pole, the weaker is the vernal outburst and the
sooner it passes. In the seas adjacent to the Pole this lasts no more than a
month (August), but farther south the vegetation period is longer: in the
central part of the Kara Sea it lasts nearly three months, while in the south-
west of the Barents Sea it continues for about eight months (Fig. 5).

Although in the circumpolar part of the Arctic basin there is only a 'spring'
in the development of phytoplankton, in the Kara and Laptev Seas there is
also a ' summer', while in the Barents Sea there is an ' autumn', and the vegeta-
tion period lasts from April till November.

However luxuriant the development of phytoplankton, if its vegetation
period is of short duration, its production will be small. The maximum phyto-
plankton biomass at any single time in our Arctic seas may sometimes be
expressed by very high rates — from 6 to 14 g/m3 even in the East Siberian and
Laptev Seas. Nevertheless this cannot in any way be considered as a measure
of the high productive capabilities of these bodies of water. The average values
for a layer thirty metres thick are more truly indicative. The true value of
annual production is well demonstrated by a conventional index (the product
of the average biomass during observations times the length of the vegetation
period in months, divided into 12 months — Table 14) introduced by P.
Usachev, especially in comparison with similar indices for the southern seas.

Table 14

Phytoplankton

biomass during

Length of vege-

vegetation period :

tation period,

average values for

Conventional

Region

months

0-30 m layer, g/m3

index

(A)

(B)

(AxB)/l2

Central part of Arctic

basin

0-12

001

Laptev Sea

4-5

0-6

0-20

Kara Sea

0-6

0-20

East Siberian Sea

4-5

0-6

0-20

Northeastern part of

Barents Sea

0-5

0-20

Sea of Azov

9-5

4-0

3-20

GENERAL CHARACTERISTICS OF THE NORTHERN SEAS 43

Phyto-plankton

Winter Spring Summer. Winter

уткет г о Autumn

Summer ШИШ Autumn

Fig. 5. Biological seasons of plankton. A General indices
(Bogorov). В Phyto-plankton development (Usachev). 1 Cir-
cumpolar part of Arctic Ocean, 2 Central region Of Kara Sea,
3 Laptev Sea, 4 Northern part of Barents Sea, 5 Southwestern
part of Barents Sea.

Zooplankton

According to V. Bogorov's estimate, the zooplankton of our northern seas
on the basis of existing data includes 321 species* of which 41 species are

* It must be borne in mind that the populations of separate seas and parts of them
have not been studied equally well, as regards the qualitative variety of the fauna and
flora. The Kara Sea plankton is probably as varied as that of the Barents Sea, but the
former has been the subject of a more comprehensive survey.

44 BIOLOGY OF THE SEAS OF THE U.S.S.R.

infusorians (Tintinnoides) and 21 are forms whose systematic position is not
clear ('problematic' forms).

Apart from these two groups above there are 259 species. The numbers of
species are distributed among the various seas as follows (including the species
encountered in several seas): Barents Sea 131, White Sea 62, Kara Sea 138,
Laptev Sea 78, East Siberian Sea 37, Chukotsk Sea 74.

The number of species of the basic groups of plankton present in various
seas is: Tab/e J5

(

Common

East

to all

Barents

White

Kara

Laptev

Siberian Chukotsk

Group

seas

Sea

Radiolaria

— ■

—

■ —

—

Coelenterata

Rotatoria

—

Copepoda
calanoida

Copepoda
hyclopoida

Copepoda
karnacticoida

15
16

3
1

9
10

2
3

5
6

Ostracoda

—

Euphausiacea

Amphipoda

Mysidacea

Appendicularia

Other

5
11

2
6

5
5
6
3
18

2
5
5
2
13

2
2
1
1
11

Total

259

131

138

In the plankton fauna the greatest variety is found in the Copepoda group
(81 species). Copepoda, and in the Barents Sea Euphausiacea also, are as
usual the predominant groups of the biomass, forming the basic components
of the food of fish and some mammals.

In the epicontinental parts of the eastern sector of the Arctic basin a
definite change in the qualitative composition of plankton can, according to
Jashnov (1940), be traced as one moves eastwards and approaches the shores
where the coastal waters have lost some of their salinity (Fig. 6). Throughout
the southern part of the Barents Sea, to the west and north of Spitsbergen,
i.e. in the regions most subject to the influence of the Atlantic waters, nine-
tenths of the plankton consists of Calanus finmarchieus (1)* and contains many
boreal forms of Copepoda : Metridia lucens, Euphausiacea : Limacina retro-
versa and others. The average plankton biomass of these regions is equal to
230 mg/m3. In the northern part of the Barents Sea besides Calanus finmarchi-

* V. A. Jaschnov (1957, 1958) distinguished and singled out Calanus finmarchieus s.l.
species C. glacialis. The area of the latter's dwelling covers the entire Arctic Basin, the
waters adjoining from the east and west and extending towards North America up to New-
foundland in the southern direction. This area included also the Bering and the Okhotsk
Seas. From the south its area links up with the areas in the Pacific Ocean C. pacificus
and in the Atlantic Ocean C. finmarchieus s.str.

GENERAL CHARACTERISTICS OF THE NORTHERN SEAS

cus there are large amounts of Metridia longa (II). These two species together
form 90 per cent of the total plankton biomass. The total biomass is about
90 mg/m3.

In the upper layers of the northern part of the Kara and Laptev Seas
Calanus finmarchicus (not exceeding 60 per cent of the total biomass) is still the
main constituent of the plankton, but С hyperboreus (III) is mixed with it to a
considerable extent and, what is of special interest, in the deeper layers there
is a considerable admixture of forms penetrating from the north along the
troughs from the warm intermediate layer of the Arctic basin, such as

Fig. 6. Distribution of main types of zooplankton in northern seas (Jashnov, with

certain alterations).
/, // Pronounced predominance of Calanus finmarchicus (90 per cent of biomass ;
many boreal forms present) ; /// Predominance of Calanus finmarchicus (not more than
60 per cent of total biomass) and C. hyperboreus ; a considerable admixture of Atlan-
tic forms from intermediate layer; /^Predominance of Pseudocalanus elongatus and
a selection of brackish- water forms ; V Same as IV but with an admixture of Pacific

Ocean forms.

Pareuchaeta norvegica and P. glacialis, Conchoecia elegans, Themisto abys-
sorum, Eukrohnia hamata, Diphyes arctica and others. The plankton of the less
saline littoral waters of the bordering seas is characterized by the great pre-
dominance of brackish forms. The sea form of Pseudocalanus and brackish-
water Limnocalanus ghmaldi, Drepanopus bungei and Derjuginia tolli (IV) are
predominant here. All these copepoda crustaceans comprise 60 per cent of
the plankton biomass. About 20 per cent of the plankton consists of Sagitta
elegans, mixed with a considerable quantity of fresh- water forms.

Finally in the southern part of the Chukotsk Sea, as a result of an increase
of salinity, the brackish-water forms are becoming rare. Pacific Ocean forms
are found here but, as has been noted by V. Jashnov (1940), they do not play
any substantial role in the biomass (V).

BIOLOGY OF THE SEAS OF THE U.S.S.R.

The general picture of the quantitative distribution of zooplankton in the
Arctic basin is similar to that of benthos. According to V. Jashnov's work
(1940) high indices of plankton biomass are obtained only within the boun-
daries of the Barents Sea, while for the other Seas of the northern coasts of
Siberia the indices are much lower (Fig. 7).

Fig. 7. Distribution of maxima of mean biomass of zooplankton of seas adjacent
to eastern sector of the Arctic basin in mg/m3 (Jashnov, 1940).

The qualitative and quantitative changes of plankton in the central part of
the Arctic basin are given in Tables 16 to 20.

Table 16. Maximum values of mean plankton biomass for various areas of the Arctic

basin (V. Jashnov), mg/m3

Depth of

layer, m

Area

0-25

25-50

50-100

100-300

500-2,500

Southwestern part of Barents Sea

1,000

400

170

110

—

Northern half of Barents Sea

140

110

100

—

Area southeast of Franz Joseph Land

—

Central part of Arctic basin in Spits-

bergen area

200

160

—

Same basin, area of Severnaya

Zemlya

100

120

—

White Sea

200

100

—

Kara Sea

—

Laptev and East Siberian Seas

—

— ■

—

Chukotsk Sea

—

■ —

—

Arctic basin, area of abyssal depths

—

— ■

10-30

4-7

GENERAL CHARACTERISTICS OF THE NORTHERN SEAS 47

Table 17. Percentage content of zooplankton biomass in the Greenland Sea, July

1935 (Jashnov)

Plankton content composition

Depth of layer, m

0-200 200-500 500-745

Calanus finmarchicus 67-1 \ 67-2 л 17-4\

Metridia longa \ Lg ?9.2 ( 3Q.4

Calanus hyperboreus I .~g [

Pareuchaeta norvegica ) 12-0 ) 13-0

Other Copepoda J

Amphipoda 9-4 9-9 —

Chaetognatha 110 7-6 21-8

Coelenterata — 2-2 34-8

Mollusca — — 4-3

Others 1-6 1-1 8-7

Table 18. Percentage content of zooplankton biomass within the area north of
Spitsbergen, August 1935 (Jashnov)

Plankton content composition

Depth of layer,

0-100

100-200

200-600

Calanus finmarchicus

Other Copepoda

Amphipoda

Chaetognatha

Coelenterata

Others

63 0

28-0

0-3

2-4
3-3

580

13-7

4-6

18-3

3-4

20-8
18-9
10-2
29-7
130
7-4

Table 19. Percentage content of zooplankton biomass between Franz Joseph Land
and Sever nay a Zemlya (Jashnov)

Depth of layer,

Plankton content composition

0-100

100-200

200-500

Calanus finmarchicus

57-3

350

30-8

Metridia longa
Other Copepoda

й}>"

2^1-

22'8 ] 33-1
10-3 j J

Amphipoda

0-9

4-4

12-5

Chaetognatha

15-7

7-8

11-8

Coelenterata

2-9

16-6

8-1

Others

5-5

1-7

3-7

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 20. Percentage content of zooplankton biomass in northwestern part of

Laptev Sea (Jashnov)

Plankton content
composition

Calanus finmarchicus

Metridia longa
Pareuchaeta glaeialis
Calanus hyperboreus

Depth of layer, m

0-50 50-150 150-250 250-300 300-800

70 50 Calanus finmarchicus disappears.

The Atlantic forms of Copepoda:
30 Scaphocalanus magnus, Gaigius te-

nuispinus, Heterorhabdus norvegicus,
Montonilla minor and others and the
Polychaeta : Thvphloscolex mullerri,
Pelagobia longicirrata become
sharply preponderant

From the above tables it can be seen that Calanus finmarchicus prepon-
derates in the 200 m surface layer (colder and less saline), whereas Chaeto-
gnatha and Coelenterata are more abundant in deeper layers. Sometimes
various Atlantic forms of crustaceans greatly preponderate in this deep layer
(200 to 800 m) which is warmer and more saline than the surface layer.

All the data given refer, however, to sections of the Arctic basin exposed to
the influence of coastal waters. It may be supposed that as one penetrates
farther into the depths of the central part of the basin there is a significant
decrease of zooplankton biomass, and in this connection the collections made
aboard the Sadko in September 1935, northeast of Franz Joseph Land at
depths up to 2 km, are of great interest. Only 12 mg/m3 of plankton biomass
was obtained by the first catch at a depth of up to 100 m (50 per cent of it
consisted of Calanus finmarchicus). In a lower layer (100 to 500 m) the biomass
content was found to be higher — 29mg/m3, but the amount of Calanus fin-
marchicus was limited to 20 per cent. Other Copepoda, namely Metridia longa,
Pareuchaeta norvegica, P. glaeialis (approximately 3 per cent), preponderate
here. Of the other forms Coelenterata (Aglantha digitate), Ostracoda, Amphi-
poda and Polychaeta are the most important. At the lowest level (500 to
2,350 m) most of which lies in the abyssal cold layer (below 800 m) the biomass
was 7 mg/m3.

The Sadko data on the plankton in the central regions of the Arctic were
supplemented in 1937-40 during the famous drift of the G. Sedov (B. Bogorov,
1946) and by the researches of the drifting polar stations North Pole 2, 3 and 4
(K. Brodsky, 1956). In all, 73 species of zooplankton were found in this plank-
ton ; this includes 40 Calanoida species, 5 Amphipoda and 3 Appendicularia.
In direct contrast with the benthos, the majority of zooplankton species are
common in the Greenland Sea and northern Atlantic. The comparison be-
tween the number of species and the number of plankton specimens for
different regions of the Pacific Ocean and Arctic Seas, drawn by K. Brodsky
(1956), is of great interest (Fig. 8). The diversity of forms continuously dimin-
ishes as one moves from the Pacific Ocean to the Chukotsk Sea and only rises

GENERAL CHARACTERISTICS OF THE NORTHERN SEAS

<o
о

<^?q

Ш Ш

Fig. 8. Change in number of species (7) and number of specimens (2) per m3 from
tropical part of Pacific Ocean (/) through northern part of the Pacific (//, ///),
Bering Sea (IV, V), Chukotsk Sea (VI, VII) and Arctic basin (VIII) (K. Brodsky,

1956).

again, on account of the Atlantic forms of the intermediate warm layer, in the
western sector of the polar basin. On the other hand the biomass increases up
to the Bering Sea, decreasing sharply in the polar basin. However, the zoo-
plankton of the polar basin contains some endemic forms and very few Pacific
ones (Table 21).

Table 21. Number of Atlantic, Pacific and endemic forms of Calanoida in the Arctic

basin (percentage)

Area

Atlantic species

Pacific species Endemic species

Nansen Ridge
Arctic basin

60
48-50

0
13

Most typical of the endemic forms are the deep-water ones described by
K. Brodsky (1956): Pseudagaptilus polaris, Pareuchaeta polarls, Lucicutia ano-
mala, L. polaris and others. The quantitative and qualitative vertical sequence
of plankton in the central parts of the Arctic basin, illustrated in the following
manner by V. Jashnov (1940) (Table 22), is most significant.

The greatest density of plankton is related to the less saline surface layer of
water, while the greatest quantitative variety is found in the deep layers in

50 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 22

Depth

Number of specimens

> Number of

per

cubic metre

zooplankton species

0-10

2,430

10-25

1,870

25-50

750

50-100

300

100-200

200

200-500

110

500-700

direct contact with the Atlantic waters. Thus owing to a more or less complete
ice cover pelagic life of the central parts of the Arctic basin is very poor ;
V. Jashnov thinks that its average biomass does not exceed 10 to 30 mg/m3.
It is richer in coastal waters, but here too it grows poorer gradually as one
moves eastward.

According to V. Jashnov the sum total of the plankton biomass of the
central part of the Arctic basin is equal to 50 to 70 million tons, in the seas
bordering Siberia together with the Barents and White Seas also approxi-
mately 50 million tons, while the whole Arctic Ocean including the Green-
land Sea contains about 150 million tons.

Exceedingly interesting observations on the seasonal changes in the com-
position of biomass and of the plankton of our Polar seas were carried out by
V. Bogorov during the remarkable cruise of the icebreaker Litke in 1934, when
all the Siberian seas beginning with the Chukotsk Sea and ending with the
Barents Sea were traversed in a single voyage (3 July to 18 September).

Biological seasons of plankton

As V. Bogorov has shown (1938, 1939) it is difficult to establish a direct con-
nection between the distribution of the plankton biomass in the seas on the
edge of the Arctic basin and the variations of temperature and salinity ob-
served in them. On the other hand at the ice fringe there can be observed
everywhere a very rich development of plankton and a huge preponderance
of phytoplankton (bloom) over zooplankton (Fig. 5). But in the region of
solid ice zooplankton always preponderates over phytoplankton. In open
water, sufficiently far from the ice fringe and from the mouths of rivers, the
animal and vegetable parts of the plankton biomasses are almost equal. At
the mouths of rivers where fresh and saline waters meet, a huge development
of plankton, with a preponderance of its vegetable part, is observed.

Leaving aside this last increase of plankton at the mouths of rivers, caused
by the outflow of a mass of plant food and detritus in the river waters, the
regularity of the quantitative development of plankton and its two main
parts in the Arctic seas is determined, according to V. Bogorov, by the change
of the three main seasonal phases in the annual cycle of plankton. During the
period of ' biological winter' plankton is poor (less than 200 mg/m3) and the

GENERAL CHARACTERISTICS OF THE NORTHERN SEAS 51

animal part preponderates over the vegetable one. With the advent of 'bio-
logical spring' phytoplankton begins rapidly to predominate over the zoo-
plankton, and the total amount of plankton rises to 2,000 mg/m3. 'Biological
summer' is characterized by a decrease of the plankton biomass (about
1,000 mg/m3) with an increase of zooplankton ; moreover the phyto- and zoo-
plankton components become almost equal. This change is illustrated by the
data given in Table 23.

Table 23. Plankton biomass

, mgjmz

Biological
season

Zooplankton Phytoplankton

Total

biomass

Ratio of vegetable
to animal mass

Winter
Spring
Summer

52 41
122 2,470
230 560

2,592

790

0-8
20-0

2-5

Thus the zooplankton biomass is doubled between 'winter' and 'spring',
and is increased almost five times by the 'summer', while phytoplankton
increases 60 times between 'winter' and 'spring', and decreases five times by
' summer '. The composition of plankton also changes. In ' winter ' zooplankton
consists mainly of adult wintering stages, in the spring the plankton teems with
eggs and larvae of the pelagic forms, infusoria, rotifers and fritillaries. More
adult stages of Copepoda and the larvae of bottom forms are predominant
in the 'summer'. Under Arctic conditions, 'biological spring' arrives at the
time of melting of the ice and the appearance of open water ; it develops at the
edge of floating ice where the abundant bloom of phytoplankton is always
encountered. ' Biological summer ' is observed in plankton in places which have
been free of ice for some time.

Thus different phases of plankton development may be observed at the
same time in different regions of the sea or, on the other hand, the very same
phases of its development at different times. The microclimate causing the
transition from one phase of plankton development to another is determined
by the ice conditions. It is possible that, depending upon the ice, an approach-
ing phase may be broken off and started again with the recurrence of better
conditions.

V. Wiese (1943) notes that as it were the 'continuous' temperature and
saline front of the Arctic waters gets broken near the fringe of polar ice and
certain special conditions set in there, determined in winter by the formation
of a mass of floating ice and in summer by its melting.

These special conditions created near the ice fringe are reflected in hydro-
logical, hydrochemical and biological phenomena. In summer a reduction of
salinity, an increase of specific alkalinity, a fall in carbon dioxide pressure and
a rise in the hydrogen ion concentration and in oxygen content are observed
at the ice fringe. The phosphate and nitrate contents of the surface layer de-
crease. Almost all these characteristics are connected with a vigorous develop-
ment of phytoplankton.

52 BIOLOGY OF THE SEAS OF THE U.S.S.R.

The existence of a single phytoplankton maximum, as Bogorov noted, is
characteristic of the normal cycle of plankton development in the seas of the
high Arctic sub-region. There is no autumn maximum there, as there is in the
seas of the lower Arctic region and in more southerly seas.

This led Bogorov (1938, 1939) to the idea of using the seasonal state of
plankton as an indicator of ice conditions and, in particular, for ice forecasts
for Arctic passages ; he has repeatedly done this with great success.

A number of investigators both at home and abroad have taken a keen
interest in luxuriant plankton development near the fringe of polar ice. The
names of Gran, V. Bogorov, P. Usachev, P. Shirshov and others may be
mentioned.

Usachev (1935) saw that the mass development of phytoplankton at the
fringe of melting ice was caused by the special concentrations of carbonates
formed as a result of melting. N. Zubov (1938) points out the possibility of the
influence on seaweed development of 'trihydric' molecules abundant in
melt water. Shirshov (1936, 1937) and Bogorov consider the mass develop-
ment of phytoplankton as a temporary, seasonal condition in the regions of
melting winter ice.

In the course of a year plankton passes through distinct successive stages.
'When light penetrates into water a rapid growth of algae begins. In polar
seas this occurs during the light period of the year, when the surface of the
sea is free of solid ice. This phase of biological spring is followed by the
summer phase, which in its turn passes first into the autumn and then the
winter phases. The succession of the biological seasons is a definite pheno-
menon' (V. Bogorov, 1939). 'The phytoplankton bloom among the ice is not
at all a direct function of its melting; it is the usual spring maximum'
(P. Shirshov, 1937).

Phytobenthos

Among the bottom macrophytes of the Arctic Ocean there is a certain pre-
dominance of the orders Laminariales (Laminaria and Alaria) and Fucales
(Fucus, Ascophyllum) among the brown algae and Ulvacea (Enteromorpha
and Monostroma) among the green ones. These algae attain their highest
growth in the warmest parts of the Arctic basin — the southern part of the
Barents Sea and the southeastern part of the Chukotsk Sea. In other parts of
the Arctic the bottom macrophytes are only slightly developed largely owing
to the weak development or even absence of the littoral population and of the
population of the upper level of the sublittoral.

Qualitatively the Arctic basin macrophytes lack individuality. They all
belong to the typical Atlantic flora which has penetrated into the cold regions
of the north. The same may be said about the fauna of the littoral and the
upper level of the sublittoral. The peculiar characteristics of the fauna in-
crease with the depth of its habitat.

This phenomenon can be explained by the fact that the deterioration of
climatic conditions in the Ice Age naturally had more effect on the popula-
tion of the shallows, all of which inevitably perished ; in deeper layers the
fauna could more easily endure harsh conditions and survive.

GENERAL CHARACTERISTICS OF THE NORTHERN SEAS 53

Zoobenthos and the history of its formation

The fauna of the Arctic basin, including the Greenland and Norwegian Seas,
can be divided into the following main groups (according to E. F. Gurjanova,
1939, with some alterations):

I. The Arctic autochthonous forms

1. Species endemic in the Arctic region

(a) Eurybiotic circumpolar species

(b) High Arctic epicontinental species

2. Brackish-water relicts

3. Arctic boreal species (partly)

II. Immigrants from the North Atlantic

1. Post-glacial and contemporary immigrants (part of the Arctic
boreal species)

(a) Littoral boreal species

(b) North Atlantic forms of the continental shelf

2. Relicts of the Littorina period

III. Immigrants from the Northern Pacific

1. Post-glacial and modern immigrants

2. Pliocene relicts

L. Berg (1934), as has been mentioned before, thinks that in the Pliocene
Period the Arctic basin was widely connected with the Atlantic and Pacific
Oceans, and that its climate was considerably warmer. At that time a large
exchange of fauna between the two oceans must have taken place via the
Arctic basin, and the fauna of these three water bodies was very similar. As
early as the Pliocene Period, before the closing up of the Bering Strait, the
fauna inhabiting the Arctic basin began to be pushed southwards into the
Atlantic and Pacific Oceans under the influence of the continuous cooling of
this basin. In the opinion of L. Berg the main stock of amphyboreal forms
were evolved at that time.

E. Gurjanova (1938, 1939) gives a somewhat different explanation for this
phase of the history of the Arctic fauna. In her opinion the endemic character
of the Arctic fauna is so clearly reflected not only in its species but also in its
genera (Acanthostepheia, Onisimus, Pseudalibrotus, Mesidothea) that the
formation of the main autochthonous stock of the Arctic basin should be
ascribed to a period earlier than the Pliocene. The warming up during the
Pliocene Period gave the Pacific fauna as a whole the opportunity to pene-
trate into the Arctic, but its autochthonous stock had already been formed.
Later during the Ice Age the Pacific fauna, which had penetrated into the
Arctic basin, ' was almost completely destroyed and replaced by a new high
Arctic fauna, which had developed mostly from the ancient autochthonous
fauna of the Arctic '.

A. M. Djakonov (1945) also thinks that the Pliocene fauna of the Arctic
basin perished in the Ice Age, except for the species which moved into
the depths and there survived the period of unfavourable climate. The

54 BIOLOGY OF THE SEAS OF THE U.S.S.R.

repopulation of the Arctic by Pacific forms took place as early as the post-
glacial period.

The genesis of the Arctic basin fauna is closely connected with its geological
past, which so far is insufficiently known.

Some geologists (Du Toit, 1939) assume the formation of the central part
of the Arctic basin in the Mesozoic and Tertiary periods.

Others (D. Panov, 1945) think that a depression (900 to 1,000 m deep) was
formed in the Tertiary Era and that this only became deeper in the Ice Age.

Finally, according to Wegener's theory (1922) the depression of the polar
basin as it exists now was formed in the Quaternary Era.

In spite of the obscurity surrounding the geological past of the Arctic basin
it can be assumed that some components of the modern Arctic fauna were
evolved in preglacial times. Considering the orographic, climatic and hydro-
logical changes of the Quaternary Era with its most unfavourable conditions
for the life of sea fauna, we can only accept the genetic descent of the modern
fauna from the Tertiary one on the assumption that the latter survived the
Ice Age only in certain parts of the North Atlantic. The formation of the
main autochthonous fauna community of the Arctic basin should probably
be connected with the fall in temperature characteristic of the Ice Age.

The high Arctic aspect of the present fauna is a result of it. So far it is not
known whether it was formed inside the polar basin or at the ' approaches ' to
the ice barriers of the Quaternary Arctic, but considerable geographical move-
ment of this fauna during the Ice Age must be accepted.

Among the most typical and ancient endemic genera of crustaceans of the
Arctic region it is possible to establish a most curious division into species,
adapted to specific conditions of life. First of all we could single out groups of
species adapted to various degrees of salinity. Changes in the salinity of the
Arctic basin during the glacial and post-glacial periods played the main part
in the formation of these groups. If at the end of the Tertiary and especially
during the Quaternary Era there were long intervals when the Arctic basin
was completely or partially enclosed, then under the conditions of a temperate
or cold climate its waters must have lost much of their salinity. If this was
accompanied by the formation of brackish or fresh-water seas, they may have
acquired the character of whole interconnected systems. In the complex
system of transgressions and regressions these systems of semi-closed bodies of
water may have been connected at some time with the Atlantic, at other times
with the Pacific, becoming more saline once more and receiving some sea
fauna communities and later again losing some of their salinity. The bottom
topography of the epicontinental water bodies of the Arctic basin is such that
even a slight rise of the floor would have led to the formation of closed or semi-
closed bodies of water (Figs. 9 and 10). What effect would these changes of
salinity^have had on the marine fauna? The original fauna had either to die
during the decrease of salinity or to adapt itself to the new environment.
Nearly all the original fauna died out, but a definite number of species, mostly
crustaceans and fish, two groups most resistant to a decrease in salinity,
adapted themselves to life in less saline water. During the subsequent phase of
increasing salinity these forms were concentrated in the areas of the river

GENERAL CHARACTERISTICS OF THE NORTHERN SEAS

mouths and their further penetration into continental waters is easy to imagine
From this angle we can easily understand the genesis of the so-called ice-
sea relicts: Mysis, Mesidothea, Pontoporeia, Limnocalanus, Eurythemora,
Gammaracanthus, Pallasea, Pseudalibrotus, Myoxophalus, Lota, and a
number of the species of the families Salmonidae, Coregonidae and Osmendae
in the areas of river mouths of the Arctic basin, forming the dominant group
both as regards number of species and biomass. The crustacean Mysis relicta
(Fig. 11) may be cited as an example. In a number of crustaceans which

Fig. 9. Limits of greatest sea-trans-
gression in Quaternary Era (Zachs,
1945, 1948).

Fig. 10. Limits of the greatest sea-regres-
sion in the Quaternary Era (Zachs, 1495,
1948).

completely migrated into fresh water (M. relicta) the original forms, inhabiting
the brackish waters of the river-mouth zones, are known (M. oculata).

From this point of view the biology and distribution of the above-mentioned
fish are of interest. In the high Arctic sub-region of the Arctic basin the Gadi-
dae, a typical marine family, has five representatives: burbot, Arctic cod,
navaga and two species of the genus Arctogadus (Fig. 12). The other 50
species are not inhabitants of the Arctic region. Of the five Arctic species of
Gadidae, one (burbot) has completely migrated into fresh waters, the others
are more or less connected with it during their spawning period. These five
species probably survived the Quaternary Era somewhere in the Arctic basin
itself and the phases of its loss of salinity are reflected in their biology.

The salmon family (including Coregonidae and Osmeridae), the most
typical of the Arctic basin and so closely connected with fresh water in its
distribution and biology, is still more significant (Fig. 13). There is no doubt
that most species of this family (which includes more than 80 species) sur-
vived the Ice Age in the Arctic basin itself. The specific richness of Salmonidae

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Fig. 1 1 . Distribution of Mysis oculata (dots) and My sis re-
licta (rings).

Fig. 12. Distribution of family Gadidae. Intensity of

shading corresponds to number of species inhabiting a

given area (Zenkevitch, 1933).

GENERAL CHARACTERISTICS OF THE NORTHERN SEAS

developed in the post-Pliocene period, while the original Pliocene forms were
few. When the salinity of the waters had increased again the main mass of
Salmonidae was pushed into the estuaries of the rivers and into river systems
and within this new habitat they went through the process of rapid formation
of species. If the pre-Quaternary ancestors of the Salmonidae had already
possessed the original type of anadromous migration, then the system of
migration, as we know it now, developed as a result of the above-mentioned
palaegeographic changes.

It is remarkable that all this relict ice-marine fauna has in its distribution a

Fig. 13. Distribution of family Salmonidae including the
Coregonidae and Osmeridae (Zenkevitch, 1933).

clearly manifest character of stages, linked with its adaptation to definite
salinity.

A. Svetovidov (1952, 1954) has expressed some very interesting ideas about
the distribution of Clupeidae and Salmonidae in the Arctic. It is known that
both groups in their origin are connected with the northern half of the Atlantic
Ocean. Svetovidov thinks that in the case of both families only a few repre-
sentatives of the northern ocean have penetrated into the Pacific Ocean from
the Arctic basin and are represented by cold-living forms. The endemic,
small herring with a few vertebrates which are representatives of the Arctic
herrings are Ciupea harengus pallasi n. maris albi (White Sea) and Cl.h.d.n.
suvorovi (Cheshsko-pechora). The origin of the Arctic sub-species of herring
is no doubt connected with the Atlantic sub-species CI. harengus harengus.
Having migrated to the Pacific Ocean herring has formed there a variety

BIOLOGY OF THE SEAS OF THE U.S.S.R.

with few vertebrates; it is apparently a large form of CI. harenguspallasi, which
later moved eastward again across the Arctic basin and reached the White
Sea.

The Pacific cod Gadus morhua macrocephalus, according to Svetovidov
(1948), is a descendant of the Greenland cod G.m. ogac which came through
the Arctic along the American side of the polar basin. The Pacific navaga (Ele-
ginus gracilis), a descendant of the Arctic E. navaga, but of a larger size, pene-
trated into the Pacific along the Siberian side of the polar basin. At present

Fig. 14. Distribution of genus Mesidothea (Gurjanova,
1934). 1 Mesidothea entomon; 2 M. sibirica; 3 M. sabini;
4 M. sabini v. robusta.

both the original forms G. morhua ogac and E. navaga live mostly in the White
and Kara Seas, in the Hudson Strait and Hudson's Bay. Svetovidov, noting
that the Arctic basin cod mentioned above and representatives of the genera
Boreogadus and Arctogadus favour greatly diluted waters of much lowered
salinity during their spawning, sees in this their longing for warmer river
waters. However, it now seems that desire for less saline waters and for spawn-
ing at the coldest time of the year is evidence of prolonged existence in waters
of much lower salinity of the polar basin during the Ice Age.

The genus Mesidothea (Fig. 14) can also serve as a good illustration of a
group of closely related species, adapted to various degrees of salinity (step-
by-step distribution). M. sabini sabini lives in waters of normal salinity.
Other forms, M. sabini robusta and M. sibirica, live mainly in the outer part

GENERAL CHARACTERISTICS OF THE NORTHERN SEAS

of the brackish zone. M. entomon is a typical inhabitant of this zone and of
the fresh waters of many closed bodies of water of the Arctic basin.

E. F. Gurjanova (1938) considers that in the Ice Age many forms acquired
the capacity for a wide vertical distribution, and thus deep-water species were
formed which inhabited the depressions of the Arctic basin and in this way
escaped the surface loss of salinity. Some of these series are given in Table 24.

Table 24. Series with capacity for wide vertical distribution {after E. F. Gurjanova)

Deep-water
species

Shallow-water species

Normal salinity

Lowered

Brackish

Fresh water

salinity

water

Mesidothea

M. sabini

M.s. robusta

M. entomon

megalura

sabini

M. sibirica

glacialis

M. entomon

entomon

vetterensis

Onisimus

O. brevicaudatus

O. ajfnis

O. botkini

sextoni

O. turgidus

O. caricus

O. dubius

O. leucopis

O. dubius
O. edwardsi
O. derjugini
O. sibiricus
O. plautus
O. normanni

O. sibiricus

Pseudolibrotus
glacialis

Ps. littoralis

Ps. caspius
birulai

Ps. caspius
Ps. platy-

Ps. nanseni

ceras

Pontoporeia

P. femorata

P. sinuata

femorata

P. sinuata
P. weltneri

P. affinis

P. affinis
affinis

This distribution indicates that the formation of species adapted to various
degrees of salinity proceeded through several stages, and that the process
of the salinity change had a step-by-step character. This suggestion is confirmed
(E. F. Gurjanova, 1939) by the fact that 'all the links of this chain of species
from the typical marine stenohaline species to the fresh-water ones exist
simultaneously in the same basin (Kara and Laptev Seas). This indicates
that the formation of the present Arctic fauna, accompanied by the division
of the autochthonous genera into shallow-water species of a different stage
of brackishness and into deep-water species, took place there and that, con-
sequently, the region of the Kara and Laptev Seas is not only the centre of the
development of the modern young (Ice Age) high Arctic fauna of the con-
tinental shelf but also its place of origin. ' The high Arctic endemic forms of
the Arctic show usually a characteristic break in their circumpolar habitat
in the region of the Greenland Sea, the Norwegian Sea and the western part
of the Barents Sea.

BIOLOGY OF THE SEAS OF THE U.S.S.R.

On the other hand, many species of this autochthonous fauna having
acquired a capacity for a wide vertical propagation, and being marked with
considerable eurybiotic capacities, have moved far beyond the boundaries of
the Arctic basin. Thus some species of the genus Onisimus along the slopes
of the Greenland Sea penetrate through the trenches far to the south to the
Skagerak and Kattegat, and travel along the Asian coast into the Bering and
Okhotsk Seas.

Most of the forms included in the group of Arctic boreal species are des-
cendants of the eurybiotic part of the autochthonous Arctic fauna. In the

Fig. 15. Routes of exchange between the faunas of the Arctic Basin and the northern
parts of the Atlantic and the Pacific (Gurjanova). 1 Atlantic fauna ; 2 Pacific fauna ;

3 Arctic deep-water fauna.

Atlantic Ocean they come southward to the North Sea, and in the Pacific to
the Sea of Japan. At the same time they go down into the depths and become
smaller in size. At present there is constant exchange between the Arctic basin
fauna and the Pacific and Atlantic ones via the straits. The main routes of this
exchange are given in Fig. 15.

The Arctic basin is now being rapidly populated by the more thermophilic
forms from the Atlantic Ocean. G. Gorbunov (1939) points out a very interest-
ing phenomenon of ' the presence, as a rule, of a particularly high Arctic fauna
along the continental shores of the Siberian Seas. As one moves northwards,
thermophilic forms are more and more mixed with it and gradually the high
Arctic forms disappear ; finally on the slopes of the continental shelf the high
Arctic forms are represented only by some single species, while the main
mass consists of the low Arctic and Arctic boreal forms, and even some near-
boreal forms make their appearance. This is explained by the Arctic basin at

GENERAL CHARACTERISTICS OF THE NORTHERN SEAS 61

certain depths being full of warm waters from the Atlantic which in part
reach the surface in the shallows of the Siberian Seas carrying their fauna with
them.'

The greatest variety of species was found here near the fringe of the shallow
plateau of the Siberian Seas. Gorbunov notes that one of the Sadko stations
obtained more than 200 species of different animal forms at the fringe of a
shallow bank of the Kara Sea, at a depth of 698 m.

A considerable number of more thermophilic forms penetrated into the
Arctic from the Atlantic Ocean during the warm phase of the Littorina
period, and a part of them survives in the Arctic as relicts, as for example the
sea grass Zostera in the White Sea.

Bathyal and abyssal fauna of the Arctic basin

The collections of the latest Soviet polar expeditions have made it possible for
us to look into the interesting and hitherto closed world of the bathyal and
abyssal fauna of the Arctic basin.

The bathyal fauna has risen so much at the shallow northern fringe of the
Siberian Seas that at depths of 100 to 200 m, as has been pointed out by
G. Gorbunov (1946), the fauna has a completely bathyal character.

In the Barents Sea there is pseudo-abyssal fauna at depths of more than
200 m, while in the Novosibirsk shallows it rises to 40 to 50 m.

The Novosibirsk shallows have a rich fauna of more than 800 species
mainly of the foraminifera, polychaetes, bryozoa, amphipoda and molluscs.
As has been noted by G. Gorbunov (1946) this fauna consists mainly of high
Arctic, Arctic and Arctic boreal forms. In this region it is very difficult to draw
the line between the abyssal and the bathyal, and between this latter and the
sublittoral, since for a variety of reasons that have been discussed, the sub-
littoral forms go down more easily into the bathyal and the abyssal and the
bathyal fauna rise easily to the sublittoral.

Collections made at 300 to 400 m and sometimes higher should (according
to G. Gorbunov, 1946) be included in the bathyal fauna of the Arctic Ocean,
owing to a general rise to higher levels.

In the bathyal fauna of the high-latitude collections made by the Sadko
and Sedov expeditions Gorbunov includes 528 species of bottom animals ;
hence, in general, it contains four times more forms than the abyssal one.
With the exception of some groups, this author gives the analysis of bathyal
fauna of the Siberian shallows set out in Table 25.

Hence the bathyal fauna contains 72 per cent of sublittoral forms ; 80 of
these are really bathyal forms and 59 are endemic forms of the Arctic Ocean.
Gorbunov includes the typical bathyal forms Leucon spinulosus among the
Porifera, Umbellula encrinus among the Octocorallia, Phascolosoma glaciale
among the Sipunculids. As regards Amphipoda these are represented by
Halirages elegans, Cleppides lomonosovi, Amathillopsus spinigera, Bythocaris
payed ; there are Poliometra prolixa from the Crinoidea, and as regards fish
Lycodes eudipleurosticus. On the whole the fauna of the bathyal part of the
Siberian sector of the Arctic can be considered as 81 per cent endemic and
genetically linked with the abyssal fauna of the Atlantic Ocean but, unlike

62 BIOLOGY OF

THE

SEAS

OF THE U.S.S.R

Table 25

No. of

Endemic forms of Arctic Ocean

species

Per cent

Deep-water species :

Abyssal
Bathyal

29
59

7
14

Sublittoral species

128

Species of wider distribution

Deep-water species :

Abyssal
Bathyal

8
21

2
5

Sublittoral species

184

Total

429

100

the sublittoral fauna, Pacific elements are absent from it. The bathyal fauna
of the central part of the polar basin consists mostly of the pan-Arctic and
Arctic boreal forms.

Collections made by the Sadko in 1935 and 1937-38 give some idea of the
abyssal fauna of the central part of the Arctic Ocean north of the Novosibirsk
Islands. Members of 98 species were obtained by nine deep-water casts of the
trawl at depths of 1,180 to 3,800 m, among them 26 Foraminifera, 4 Porifera,
4 Coelenterata, 13 Polychaeta, 1 Pogonophora, 1 Copepoda, 1 Cirripedia, 1
Cumacea, 6 Isopoda, 10 Amphipoda, 2 Decapoda, 1 Pantopoda, 19 Mollusca,
8 Echinodermata, 1 Pisces, and including also the typical abyssal species like
Astrorhiza crassatina and Ammodiscus incertus of the Foraminifera, Myrio-
chele danielsseni, Gorbunovia malmgreni of the Polychaeta, Pogonophora,
LameUisabella gorbunovi, among Cumacea — Diastylis polaris, among Isopoda
llyarachna derjugini, Eurycope ratmanovi, Mesidothea megalura v. polaris,
among Amphipoda — Halirages gorbunovi, Melitapallida,3.nd Dulichia cy clops,
among Decapoda — Hymenodora glacialis, Bythocaris leucopis, among Mol-
lusca— Ganesa bujnitzkii, Natica bathybia, Sipho danielsseni, Tindaria derjugini,
Neilonella kolthoffi, Ledella tamara, Propeamussium frigidum, Thyasira otto-
schmidti, Lyonsiella Jeffrey si, L. uschacovi, and among Echinodermata —
Kolga hyalina. Most of the above-mentioned species are endemic forms of the
Arctic Ocean. Besides these forms 20 abyssal species come into the bathyal,
and 28 abyssal species were found only in the bathyal. Thirty-seven species
caught in the abyssal are immigrants from the sublittoral. The vertical propa-
gation of the forms found in the abyssal is given in Table 26.

A complete absence of bryozoans is a characteristic feature of the Arctic
Ocean fauna. Sixty per cent of this fauna is endemic and, of the purely abyssal
species, 89 per cent is endemic.

In Gorbunov's opinion (1946) based on the presence of a number of endemic

GENERAL CHARACTERISTICS OF THE NORTHERN SEAS 63

Table 26

No. of species, except
Endemic forms of Arctic Ocean Foraminifera

Deep-water species :

Purely abyssal 24

Abyssal eurybathic 32

Bathyal 5

Shallow eurybathic 7

More widely propagated species

Deep-water species :

Purely abyssal 3

Abyssal eurybathic 8

Bathyal 0

Shallow- water eurybathic 15

Total 94

species and even endemic genera, the abyssal fauna of the Arctic Ocean is
ancient, going back at least to Tertiary genesis.

On the other hand, E. F. Gurjanova (1938) thinks that all this fauna ori-
ginated from the forms inhabiting the shallow zones of the Arctic in the post-
glacial period. This fauna consists partly of the same species which still live
in the shallows, and partly of species developed from these latter. On the basis
of her data Gurjanova considers the Arctic basin as very young,* but this is
difficult to accept. If the deep-water fauna did exist here during preglacial
times, it might have perished totally or partially during the Ice Age as a result
of a considerable loss of salinity of the surface layers of the sea or perhaps
throughout the whole basin as occurred in the Sea of Japan.

As regards the pelagic fauna of the Arctic basin V. Jashnov (1940) has also
come to the conclusion that specific abyssal pelagic fauna of the Arctic basin
does not exist. Of the 46 species of Copepoda found in the depths of the Arctic
basin, the Norwegian and Greenland Seas and Baffin Bay, 42 are known also
in the rest of the Atlantic. The same may be said about the coastal vegetation
(macrophytes) of the Arctic basin. It has no peculiar features, it is simply an
impoverished Atlantic flora.

A remarkable phenomenon was observed by the latest Soviet high-latitude
expeditions — many members of the abyssal fauna of the Arctic basin have
risen into the comparatively shallow zones along its fringes in seas with high
Arctic conditions. This is particularly evident in the northern part of the Kara
Sea and the northwestern part of the Laptev Sea, where great depths approach
closely and where there are trenches (200 to 400 m) running from them.

* It must, however, be borne in mind that the abyssal fauna of the central part of the
Arctic Ocean is as yet practically uninvestigated. So far explorers have only penetrated
along the continental slopes of the northern part of the Kara Sea and the Novosibirsk
shallows.

64 BIOLOGY OF THE SEAS OF THE U.S.S.R.

The rise of the mass of abyssal forms to depths unusual for them (80 to
100 m), which does not occur anywhere in the southern part of the Arctic
basin (at the outlet into the Atlantic) may be explained by the following four
causes : (/) low temperature of surface water of high Arctic; (2) small annual
temperature fluctuations ; (3) comparatively low transparency of water ; (4)
obscuration caused by the ice cover which lasts almost all the year round.

Hence the deep-water fauna with a sharply expressed cold-water steno-
thermy and a negative phototropism finds no obstacles here for expanding
into comparatively higher levels.

III. ZOOGEOGRAPHICAL ZONATION OF THE ARCTIC

REGION

All our Arctic seas, except for the most southwestern corner of the Barents
Sea, belong to the Arctic region, which is limited by about 70° N latitude and
only comes down to 60° N in the Norwegian and Greenland Seas. The
boundaries of the Arctic and boreal regions in the North Atlantic are not the
same for the bottom and the pelagic fauna.

Ortmann noted this general phenomenon as early as 1896. Pelagic organ-
isms, easily carried around by currents and with life cycles shorter than those of
the bottom organisms, form more mobile zoogeographical boundaries than
the slowly growing benthos organisms liked with the bottom. The boundaries
given in Fig. 16 refer mainly to benthos. Sea currents would widen these bound-
aries more for plankton than for benthos. The boundary between the Arctic and
boreal plankton along the shores of Norway and in the western part of the
Barents Sea would (in relation to the boundary for benthos) therefore lie con-
siderably farther north and east, possibly as far as the central parts of the
Barents Sea. Along the eastern coasts of Greenland, on the other hand, this
boundary would be found such farther south, towards Newfoundland. In
exactly the same way fresh river waters carry fresh-water plankton out into the
sea and, in spreading outwards, move the boundary between the sea and
brackish plankton away to the north. Conversely, in the near-bottom layers,
the saline waters together with the bottom population move towards the
shore, often entering the estuarial zones, so that the surface layer frequently
has a completely fresh-water fauna, and the near-bottom one a sea fauna.
This can be seen by comparing the boundaries in Figs. 13 and 14.

The littoral fauna provides another case of the boundaries for different
groups of the population of the northern seas not being coincident. Owing
to a number of conditions which have already been mentioned the boreal
littoral fauna has been moved far to the east, covering all the Murman coast
and White Sea, i.e. regions where the fauna of the sublittoral, and the plank-
ton too, have a true Arctic character.

The Arctic region may be divided into three sub-regions (Fig. 16). First of all
there is the abyssal Arctic sub-region, embracing the three depressions
(Norwegian, Greenland and Central Arctic) of the Arctic basin and separating
them from the abyssal of the Atlantic Ocean proper. Species of the genus
Themisto can serve as an excellent example of the sharp fauna distinction
between the Arctic and Atlantic abyssal forms.

GENERAL CHARACTERISTICS OF THE NORTHERN SEAS

The sublittoral fauna of the Arctic region, which differs fairly sharply from
the abyssal, may in its turn be divided into two sub-regions — the shallow,
lower Arctic one, including the Barents and White Seas (the White Sea-
Spitsbergen province of the Arctic region, according to Gurjanova), and the
shallow, high Arctic sub-region, including all the other seas of the Soviet
and American sectors (the Siberian province and the North American-
Greenland province of the Arctic region, according to E. Gurjanova). Again,

Fig. 16. Zoogeographical zonation of the Arctic region (according to various investi-
gators). / Abyssal Arctic sub-region ; // Lower-Arctic, shallow sub-region ; HI High
Arctic, shallow sub-region ; Ilia Shallow marine province ; Illb Shallow brackish-
water province ; Ilia1 Suberian region, Ilia2 North American Greenland region. The
propagation of the boreal littoral fauna northwards and eastwards is marked by a
dotted line (Zenkevitch, 1947).

as has been stated above, the littoral fauna and to a certain extent the fauna
of the upper level of the Murman sublittoral and that of the western part of
the White Sea has a distinctly boreal character. E. F. Gurjanova, I. Zachs and
P. Ushakov (1925) attributed a sub- Arctic nature to it; however, this littoral
fauna, changing but little, reaches the shores of Brittany. On the other hand
it is evident that in the Ice Age and the Yoldian stage the Murman and White
Sea littoral was in the same state as it is at present in the high Arctic regions,
i.e. it was practically absent and only later, with the rise of temperature, could
the littoral fauna move northward and eastward. The absence of littoral fauna
is, in fact, characteristic of the high Arctic.

Movement far to the north and to the east is made possible for the boreal

66 BIOLOGY OF THE SEAS OF THE U.S.S.R.

littoral fauna by specific conditions of the littoral microclimate. Some
authors divide the Arctic littoral region into two provinces— the high Arctic
one (Kara-Siberia) with its uninhabited littoral zone, and the Arctic one with
its traces of littoral fauna and flora (Matochkin Shar, Spitsbergen). But it is
impossible to accept either of these divisions. The separation of an unin-
habited littorial zone into a zoogeographical province is not justified since
animal life is absent from it. Again there are no grounds for placing 'traces
of littoral fauna' in a separate province, since these contain no original
features and are actually 'traces' of a boreal littoral fauna penetrating from
the south.

G. Madsen (1936) has approached this problem somewhat differently. He
divides the littoral of the northern part of the Atlantic into sub-Arctic (we
call it boreal) and Arctic.

The sub-Arctic littoral ends when the periwinkle, sea mussel, Balanus are
absent; the Arctic littoral is characterized by such groups as Oligochaeta,
Hydracarina, Turbellaria, Amphipoda and Harpacticidae.

This view too, however, cannot be accepted. All the groups noted by Madsen
live also on the littoral of the boreal region, and to separate the Arctic littoral
into a group it is necessary to establish the specific features of its faunal
species and the adaptability of its main forms to only one given zoogeo-
graphical category.

The high Arctic shallow-water sub-region in its turn is not homogeneous.
It is known that the shallowest parts of the epicontinental Arctic seas, especi-
ally the Siberian seas, shelter a rich relict brackish fauna, both of plankton
and benthos, which is rich both qualitatively and, especially, quantitatively.
The northern parts of the epicontinental bodies of water of the Arctic have a
typically marine fauna.

On these grounds G. Gorbunov suggested (1941) the division of the high
Arctic sub-region into two parts: 'the high Arctic or continental water dis-
charge and the high Arctic of the open sea'. However, it is better to designate
them differently and to divide the high Arctic shallow-water sub-region into
sea-water and brackish-water provinces, thus marking the most characteristic
difference in the fauna of both parts. The brackish-water province could
probably be further divided into several zones according to their degree of
salinity and the fauna corresponding to them. Evidently the outer circle of the
brackish-water province, adjacent to the sea province of the shallow high
Arctic sub-region, is the zone so clearly defined by G. Gorbunov (1941) as
that of the distribution of the bivalve, Portlandia arctica (Fig. 1 7), comparing
it with that of the distribution of another high Arctic mollusc, Propeamussium
(Pecten) groenlandicum major.

Unlike P. arctica this mollusc cannot endure a lowering of salinity and lives
outside the zones influenced by river waters.

The two molluscs exclude each other, as it were, and are very rarely found
in large quantities in the same place.

Although P. arctica can live under conditions of full sea-salinity, the zones
of its mass development are connected with regions exposed to a greater or
lesser extent to river discharge.

GENERAL CHARACTERISTICS OF THE NORTHERN SEAS

Fig. 17. 1 Northern boundary of propagation of the bivalve Portlandia arctica
(brackish-water province) ; 2 Southern boundary of propagation of the bivalve Pec-
ten (Propeamusium) groenlandicum (marine province, according to Gorbunov,
1941); 3 Northern boundary of propagation of brackish-water plankton Crustacea
Limnocalanus grimaldi and Dropanopus bungei (Bogorov, 1944).

Hence on the whole the following scheme of zoogeographical subdivision
is obtained for the Arctic region (Fig. 16):

Region

Sub-region

Province

Regions

Arctic

I. Abyssal
II. Shallow lower
Arctic

II. Shallow high

(7) Sea

(a) Siberian

Arctic

(2) Brackish-

(b) North American-

water

Greenland

The echinoderm group, as one of the best studied, may be cited as an
example of the zoogeographical analysis of the Arctic basin fauna. According
to A. M. Djakonov (1945) the following* groups can be distinguished among
the 121 species of Echinodermata known in the Arctic Ocean.

(i) Cosmopolitan species, 4 per cent
(ii) Boreal species, immigrants from the Atlantic, 23 per cent

* Species were not taken into account when the percentage (23, 28 and 45) were cal-
culated.

68 BIOLOGY OF THE SEAS OF THE U.S.S.R.

(iii) Autochthons of the Arctic region, 28 per cent

(iv) Species of Pacific Ocean origin, 45 per cent (including circumpolar,
amphi-boreal and amphi-arctic).

Fifty-nine species of echinoderms of the Arctic basin (48 per cent) are not
known in the Pacific and have no common roots there. The abyssal fauna of
the Polar basin has very little in common with the deep-water fauna of the
Pacific ; this is fully explained by the shallowness of the Bering Strait.

The 34 species of echinoderms (28 per cent) autochthonous for the Arctic
basin consist above all of stenobathic-abyssal species (6) and eurybathic-
abyssal ones (10). These two groups contain five endemic genera.

Of the 18 autochthons inhabiting the continental shelf 14 species are limited
to the Arctic and 4 are arctic-boreal ones.

Djakonov distinguishes among the species of Pacific origin (45 per cent)
some species (about half) identical with the Pacific ones and other forms
which are represented in the Pacific by closely-related species. He divides
this group into the :

Circumpolar, 13 species

Forms characteristic of the eastern Arctic, 10 species

Amphi-boreal, 31 species.

In Djakonov's opinion all these forms came from the Pacific Ocean as
early as the post-glacial period and populated the northern shores of North
America.

As an example Djakonov gives the distribution of species of the genus
Leptasterias :

Region No. of Leptasterias species

Northern part of Pacific 27

Off the northeastern shores of North America 5

Off Greenland 2

Off Scandinavia 3

Circumpolar 1

The way described here in which the Arctic was populated by Pacific Ocean
forms is considered by several authors as basic.

IV. TYPOLOGY OF THE BODIES OF WATER OF THE ARCTIC

BASIN AND THE NORTHERN ATLANTIC
A quantitative survey of the marine fauna leads to the problem of the typo-
logy of the bodies of water based on biological productivity.

Beside the fact of it belonging to one or another biogeographical region,
characterized by a certain specific population, the most important features
which condition the whole type of a body of water and that of the biological
productivity developed in it are :

(7) the nature of the connection between the body of water and the ocean
(open bodies of water on the one hand, and closed or semi-closed on
the other)

GENERAL CHARACTERISTICS OF THE NORTHERN SEAS 69

(2) the vertical characteristics of the body of water (deep-water and epi-
continental bodies of water) and

(5) the general character of the hydrological conditions, and in particular,
the formation of an ice cover in winter.

In fact the character of the hydrological conditions (salinity, temperature,
the presence of gas, etc.), water circulation, the supply of nutritive substances
and other factors influencing biological production differ greatly in each of
the above-mentioned types of bodies of water.

In high latitudes, in closed and semi-closed bodies of water, a loss of salinity
inevitably takes place, leading to the disappearance of a number of typical
sea forms, and sometimes of whole groups of organisms. In connection with
this either a lowering of the biomass is observed or, in the presence of favour-
able feeding conditions, quantitatively rich communities of either meso- or
oligo-mixed type are developed; whereas polymixed communities are char-
acteristic of the fully saline open sea.

It is likewise easily shown that the course of the hydrological processes and
also a whole series of factors directly determining the character of the biolo-
gical productivity — most important being the supply of nutritive substances —
differ greatly in near-bottom bodies of water on the one hand and epicon-
tinental ones on the other.

The pre-polar parts of the Arctic basin, approximately within the limits of
the high Arctic sub-region, with Novaya Zemlya, the northern part of the
Barents Sea and the shores of Spitsbergen and Greenland as its boundaries on
the Atlantic side, and to the east the parts of the Bering Sea adjacent to
the Bering Strait, have four main characteristic features : (J) lowered salinity
in their upper 200 m layer and a considerably greater salinity of the deep
waters (saline stratification), (2) a vertical circulation rendered difficult in
consequence, (3) a very low (usually below— 1° C) temperature, except for a
short and slight summer heating of the surface layer, and (4) a cover of float-
ing ice usually throughout most of the year and sometimes during the whole
of it. As regards its fauna and palaeoclimatic conditions this region has the
following characteristics : (a) a preceding much colder phase connected with
the Ice Age and post-glacial period, (b) a comparatively short phase of higher
temperature during the Atlantic period, (c) a notable increase now of pene-
tration of forms more adapted to warm waters, and (d) the saturation of the
region of lower salinity by brackish relict fauna.

All the factors mentioned explain the low indices of biomass usually ob-
tained for the high Arctic sub-region (less than 50 g/m2) while in the circum-
polar zone the productivity rate is low. The poor quality of the population
for an undoubtedly mesomixed community, and a tendency of passing over at
some points to the oligomixed one, are also characteristic.

In the summer season plankton biomass in the surface layer comprises 100
to 3,200 mg/m3, but the amount of zooplankton is usually about 50 to 230
mg/m3; zooplankton biomass rises to 400 mg/m3 only in inlets and river
mouths. Rotatoria, Cladocera and among the Copepoda, Pseudocalanus
elongatus become significant in the plankton as a result of a considerable loss

70 BIOLOGY OF THE SEAS OF THE U.S.S.R.

of salinity, especially near the river mouths. Only one period of phytoplankton
bloom is observed in the spring ; the autumn one is absent.

The circumpolar zone with its numerically rich fauna and its considerably
increased productivity forms a belt round this pre-polar zone of the northern
hemisphere which has an impoverished fauna and a lowered productivity;
this belt passes through the northern Atlantic and the northern Pacific. Hydro-
logically this zone has the following characteristics : (/) the most favourable
conditions for vertical circulation, approaching uniformity of temperature
and salinity, (2) a temperature of more than 0°, and (3) a normal sea salinity.
The main meeting place of the warm waters moving from the south with the
local cold ones is situated in this zone, hence the phenomenon of the 'polar
front' develops here with all its consequences. To this given combination of
hydrological factors which determine the best conditions for feeding and life
processes, there corresponds an increased biomass (for benthos more than
100 to 200 g/cm2), a considerable productivity and polymixed communities.
Zooplankton biomass, consisting mainly of Calanus finmarchicus, is subject
to great fluctuations (from 1-5 to 3,843 mg/m3) and for the southwestern part
of the Barents Sea it is, on the average, about 230 mg/m3 in August. Two
maxima of bloom — the spring and autumn ones — are observed in the develop-
ment of phytoplankton.

Moving farther south, beyond the influence of the polar front, we reach a
zone with different hydrological and biological characteristics. The hydro-
logical conditions of this zone are : (/) a considerably higher temperature of
the upper layer of water which creates a thermal stratification in the warm
parts of the ocean in such marked degree that the whole nature of the biolo-
gical processes is determined by it, and (2) restricted vertical circulation. These
regions are characterized by the rich qualitative composition of their popu-
lation and their decreased biomass. Conditions for increased biomass and
productivity are created only in places with favourable circulation and in the
shallows.

Table 27 gives a typological scheme for the zonation of the northern
Atlantic and the polar basin, for the upper layer of the sea (200 to 300 m) due
to M. J. Dunbar (1951, 1953). It is drawn up according to particular char-
acteristics, both biological (the composition of the population and the pecu-
liarities of biological productivity) and hydrological (temperature, mixing).
The northern boundary of Dunbar's boreal region coincides with that given
by most of the biologists, except that Finmark and the western part of the
Murman coast are usually included in the boreal region. Dunbar divides the
region to the north of this boundary into Arctic and sub- Arctic zones of life.
These two zones on the whole correspond to the division generally accepted
in the u.s.s.r. for the Arctic region: the high Arctic sub-region (Dunbar's
Arctic) and lower Arctic one (Dunbar's sub-Arctic). We think that there is
not sufficient ground to call these two sub-regions independent ecological
zones of life on the regional scale. Their population does not possess sufficiently
sharp distinctive characteristics allowing them to be separated into categories
of a higher order.

The boundary between the Arctic and sub-Arctic of Dunbar differs in some

GENERAL CHARACTERISTICS OF THE NORTHERN SEAS

Table 27. Scheme for typological division of the bodies of water of the Arctic,
sub- Arc tic and boreal regions

Arctic

Open

Semi-closed

Sub-Arctic Open

Boreal

Semi-closed 8.

Open

10.

Semi-closed 1 1 .

High Arctic epicontinental (Kara and Laptev Seas,
etc., up to Crown Prince Gustav Sea and the shal-
low parts of Baffin Bay)

High Arctic deep-water (Arctic basin, deep parts of
the Greenland Sea and Baffin Bay)
Lower Arctic epicontinental (Barents Sea, waters off
northern Iceland, and southern Greenland coastal
waters)

Lower Arctic deep-water (Davis Strait)
High Arctic epicontinental (White Sea and
Hudson's Bay)

Sub- Arctic epicontinental (north Norwegian coastal
waters, south Icelandic waters)
Sub-Arctic deep-water (Norwegian Sea)
Sub-Arctic epicontinental deep-water (deep part of
Baltic Sea)

Boreal epicontinental (Faroe waters, North Sea
waters around the British Isles, epicontinental parts
of the Bering and Okhotsk Seas and the Sea of
Japan)

Deep-water boreal (Bay of Biscay, the depths of the
northern Atlantic, deep parts of the Bering and
Okhotsk Seas and the Sea of Japan)
Boreal epicontinental (Kattegat, Sounds, Belts, the
surface layers of the Baltic Sea)

detail from that drawn by us between the lower Arctic and high Arctic sub-
regions, specially for the Kara Sea. The southern half of the Kara Sea
undoubtedly should be referred to the high Arctic sub-region (Dunbar's
Arctic). Moreover the White Sea could not, from Dunbar's point of view, be
included in the sub- Arctic, since it is not a zone of the mixed polar and non-
polar waters, neither is the southern half of the Kara Sea.

2
The Barents Sea

The Barents Sea is an open epicontinental fully saline body of water, mainly of
Arctic character, covered in its northern and eastern parts with floating ice
during the winter season. As the warm Atlantic waters flowing from the west
enter this sea they are cooled (from 8° to — 1-8° C) ; thus a complex system of
horizontal circulation is set up, consisting of several main cyclonic revolutions.
The Sea is well aerated.

On the slopes of the shallows warmer and more mobile masses of Atlantic
waters meet cold and stagnant 'local' waters ; this causes strong vertical cir-
culations and other phenomena covered by the term polar front. In these
regions — where plant food is accumulated — the amount of benthos biomass
is 150 to 600 g/m2 or more. In the regions of increased vertical circu-
lation, benthos biomass falls to 20 to 50 g/m2 or less. This occurs in
the most westerly and especially in the northern part of the Sea, where
brown mud is widely distributed and owing to the insufficiently brisk vertical
circulation large amounts of carbon dioxide may accumulate in the bottom
layers. Marine fauna and flora with a preponderance of bivalve molluscs,
echinoderms, polychaetes, crustaceans, sponges, hydroides, bryozoans and
sipunculids are characteristic of this Sea.

Bottom communities of the polymixed type belong, except for the littoral,
to the high and low Arctic sub-regions of the Arctic. The main mass of the
coastal vegetation is concentrated in the south of the Sea at zero depth, with
a biomass of up to 24 to 28 kg/m2 (Laminaria, Ascophyllum, Fucus). At lower
levels the mass of macrophytes decreases greatly. The typical boreal littoral,
well represented in the warmer part of the Sea, disappears in regions which
remain under ice for a long time.

As a rough calculation for the main groups the following ranges may be
taken as typical PI В coefficients:* for littoral and sublittoral vegetation
approximately 1 ; for zoobenthos about 0-25 to 0-2 ; for zooplankton approxi-
mately 1 ; for phytoplankton approximately 50 ; for fish on the average
not more than a sixth. The quantity of organic matter present on the sea
bottom is low and depends on its mechanical composition. In the north,
where soft bottoms predominate, there is 1 to 2 per cent carbon, 0T to
0-3 per cent nitrogen ; in the south (south of 72° N) there are 0-3 to 0-8
per cent carbon and 005 to 0T 5 per cent nitrogen. The C/'N ratio in the sea
bed is 5-5 to 80.

The trawling industry both Soviet and foreign is highly developed in the
Barents Sea, the main catch being cod, haddock and bass. In that part of the
sea adjacent to the Murman coast herring fishing has been greatly developed
in Soviet times.

* Ratio of annual production/average annual biomass.
72

THE BARENTS SEA 73

I. HISTORY OF EXPLORATION

The first period

The first observations on the fauna of the Barents and White Seas, mainly on
fish and marine mammals, were collected by the Russian inhabitants of the
White Sea coast and by the Novgorod merchants, beginning in the twelfth
century. Sea fisheries existed here in the sixteenth and seventeenth centuries.
The first data on the Barents Sea fauna to appear in the literature were given

Fig. 18. Professor N. M. Knipovitch.

by the academician K. Baer, after his famous voyage to Novaya Zemlya in
1837. He collected about 70 species of various animals from those shores.

The fauna of the Murman coast was first studied during the voyages of the
St Petersburg zoologist F. Jarzhinsky (1869-70), S. Herzenstein (1880-84),
Grigoriev (1887) and others.

In the open parts of the Barents Sea and in its northern parts zoological
data were collected in the last century by the expeditions of Peyr and Vaiprecht
(1872-74), Baron E. Nordenskjold (1875-76 and 1878-79) and others.

BIOLOGY OF THE SEAS OF THE U.S.S.R.

The second period

A comprehensive study of the Barents Sea fauna was begun during the pre-
sent century and is first of all connected with the work done by the expedition
for the Murman scientific fishery survey, organized in 1898 and operating for
ten years under the direction first of N. M. Knipovitch and later of L. Breit-
fuss. A year later the biological station of the St Petersburg Natural History
Society, named the Murman Biological Station, was transferred from the

Fig. 19. Professor I. I. Mesiacev.

Solovetsk Islands to the Ekaterininskaya Bay of the Kola Guba. This scienti-
fic and industrial expedition made a basic survey of the hydrological conditions
of the Barents Sea and of the commercial fish, and the Murman station car-
ried out a careful examination of the fauna of the Kola Guba. Like the Sevas-
topol station of the Academy of Sciences, the Murman station was the centre
of research by Russian and Soviet biologists into marine fauna and flora.
It was here that K. Derjugin collected the data for his large monograph on the
fauna of the Kola Guba.

It should be noted that N. M. Knipovitch had a special vessel the Andrey
Pervozvanniy built for his Murman expedition, equipped also as a fishing

THE BARENTS SEA 75

trawler. It was the first experiment of this sort and a most fruitful one for the
practice of sea exploration. N. M. Knipovitch proved the practicability of
trawling in the Barents Sea.

The third period

The third period in the study of the fauna of the northern seas belongs to the
Soviet epoch. There was no sea in which the survey work was developed over

Fig. 20. Professor К. M. Derjugin.

so wide an area and to such a depth as that carried out in the Barents Sea in
the twenties and thirties. Almost at the same time (1919-21) there came into
existence three central institutes which carried out the exploration of this
region: the Northern Scientific-Industrial Expedition (later the AU-Union
Arctic Institute), the State Hydrological Institute, and the State Oceano-
graphic Institute, organized by I. Mesiacev (now the АН-Union Institute of
Sea Fisheries and Oceanography, vniro). A little later the Chief Director-
ate of the Northern Sea Route was created and its expeditionary activity

BIOLOGY OF THE SEAS OF THE U.S.S.R.

placed the names of Russian explorers in the first rank of explorers of the
polar regions. As a result the Barents Sea may be considered one of the best
surveyed seas in the world. The research vessel Persei of the State Oceano-

Fig. 21. Persei, research vessel of State Oceanographic Institute (1923 to 1940).

graphic Institute (1923 to 1940) (Fig. 21) has played a particularly important
role in the exploration of the Barents Sea.

Continuous research work on the fauna of the Barents Sea is now being
carried out by the N. M. Knipovitch Polar Institute of Sea Fisheries and
Oceanography in Murmansk (mainly by way of scientific and commercial
researches) and by the Murman biological station which was organized in
1936 on the Dalne-Zelenetskaya Guba by the Soviet Academy of Sciences.

II. PHYSICS, GEOGRAPHY, HYDROLOGY, HYDRO-
CHEMISTRY AND GEOLOGY

Boundaries

The Barents Sea (Fig. 22) is the first of the system of boundary epicontinental
bodies of water of the Arctic basin, which we enter in our voyage round
northwest Europe. It is a kind of approach to the outposts of the Arctic,
which have been conquered by the warm Atlantic waters. The Barents Sea is
bounded on the north by the Archipelagoes of Spitsbergen and Franz Joseph
Land, to the east by Novaya Zemlya, while to the west a slope towards the
great depths of the Greenland Sea serves as a boundary.

Size

Within these boundaries the area of the Barents Sea is 1,405,000 km2, the
average depth of the Sea is 229 m, and its volume is 322,000 km3. Depths
below 400 m are rare ; they are found in the western and northeastern parts

THE BARENTS SEA

of the Sea lying adjacent to the great depths of the Greenland Sea and the
Arctic basin.

N. Zubov (1932) has calculated the distribution of depths in the Barents Sea
in percentages as given in Table 28.

Fig. 22. Chart of Barents Sea, showing depths (Zubov) and currents (Zaytsev).

1 100 m; 2 100 to 200 m; 3 200 to 300 m; 4 300 to 400 m; 5 400 to 500 m; 6 >500

m ; 7 Main directions of currents.

In the opinion of F. Nansen (1922) the floor of the Barents Sea is an ela-
borate system of river valleys sunk under the sea surface. In fact if the sea-
level were lowered 500 m the whole of the Barents Sea would become dry land.

Bottom topography

The bottom topography of the Barents Sea has the following features (Fig. 22).

In three places troughs below 400 m enter the sea, the first lying between the

78 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 28

Depth Depth as % Area

m of total sea km2

100

22-9

311,000

101-200

25-1

341,000

201-300

36-6

470,000

301-400

14-6

199,000

400

2-8

39,000

Total 100 1,360,000

continent and Bear Island where a deep trench enters from the west with
three branches leading off to the northeast, east and southeast. Secondly,
depths below 400 m project into the northern part of the Sea in two tongues :
the western between Queen Victoria Land and Franz Joseph Land, and the
eastern northwards from Novaya Zemlya. However, there is no communi-
cation between the three trenches and they are divided from each other by
depths of less than 300 m. Further in the centre of the Sea there is a wide
depression which extends between the 76° and 71° parallels and the 35° and
47° meridians and has depths of over 400 m. In the centre of the Sea there are
two large shallows which partly divide these depressions : one is the central
elevation of the Barents Sea with depths of 150 to 200 m, and the other to the
north of the Persei elevation with depths of 100 to 200 m. Southwest of the
Persei elevation lies the wide Bear Island-Cape Nadezhda shallow (or Spits-
bergen Bank) with depths of less than 100 m, which in the north becomes the
coastal shallows of Spitsbergen. In the east and southeast a wide shallow
encircles Novaya Zemlya and the Kolguev-Kanin region and extends north-
wards from the Murman coast (the Murman shallow). There is another shal-
low in the southeastern part of the Sea ; although small it has great commer-
cial importance — Gusinaya Bank (between the 71° and 72° parallels and the
44° and 48° meridians).

Although all these depths vary by no more than 300 m and the angle of the
slope of the floor is usually negligibly small (a fraction of one degree), never-
theless all aspects of the conditions of the Barents Sea are closely linked with
its bottom contour — the distribution of currents, the nature of its bed, the
course of the tidal stream, the polar front phenomena and through the system
of horizontal and vertical circulation of water the distribution of densities of
bottom population and the concentration of commercial fish; all this in the
final analysis is primarily determined by the bottom topography.

Currents

A powerful stream of Atlantic waters, skirting the North Cape, enters the
Barents Sea from the west through the broad passage (128 km across) be-
tween the North Cape and Bear Island (Fig. 22).

Warm Atlantic waters penetrate into the Barents Sea not only from the
west, to the south and north of Bear Island, but also from the north through
the straits off the eastern and western coasts of Franz Joseph Land.

THE BARENTS SEA 79

The North Cape current enters the Barents Sea in two streams a little to the
north and south of 72° N latitude. The southern stream is slightly less saline
owing to the coastal dilution of water (34-2 to 35-2%0), its speed being slightly
greater (about 4 to 4-5 cm/sec). The northern stream consists of fully saline
Atlantic waters (35-0 to 35-2%0) and travels slower than the southern one
(about 2 cm/sec).

The chart of the currents of the Barents Sea was first compiled by N. M.
Knipovitch at the very beginning of this century (1902-06). In his opinion
(later developed in detail by L. Breitfuss and Gebel), the North Cape current
entering between Bear Island and the continent breaks into four main
branches, corresponding, as Knipovitch supposed, to the four deeper trenches
in the floor. In this conception the Barents Sea appeared as a kind of flowing
water mass, the movement being from west to east and north, and with more
or less rectilinear currents. According to Knipovitch cold and slightly saline
polar water lies on the ridges and shallows between the warm branches of
the stream. L. Breitfuss even assumed the presence of cold countercurrents
moving to meet the warm water and dividing into separate branches.

A different point of view on the circulation of the Barents Sea waters was
expressed about the same time. As early as 1902 F. Nansen and later Helland-
Hansen (1912) represented the movement of water in the Barents Sea as one
huge cyclonic vortex breaking up into several smaller ones. Over shallows
and depressions, round which cyclonic eddies are formed, cold local polar
water becomes stagnant. Nansen and Helland-Hansen's theory was completely
confirmed by N. Zubov (1932) and A. Sokolov (1932), when they applied the
dynamic method in their treatment of the extensive new data on the hydrology
of the Barents Sea. In the western part of the Sea (30° to 35° W) the North
Cape current is broken up by the influence of the floor contour into separate
branches, of which the least saline (34-6%0) but warm (average annual tempera-
ture 4-3° C) branch moves along the north of Norway and the Murman coast.
This is the so-called Ruppinovsk branch, which is of great significance for the
distribution of the littoral fauna. The second branch flows along the meridian
of the Kola Guba between 71° 51' and 72° 45' N, the third at 73° 15' N and
the fourth at 75° 15' N. The North Cape streams become cooler and less
saline the farther north they move.

Thus the southwestern part of the Sea as far as the Kola meridian to the
east and as far as 73° N have, except for the section next to the coast, a salinity
of about 35%0, and a temperature of not less than 3° С in the main depth of the
water column and 2° С in the bottom layer. These conditions make it possible
for the warmer-water fauna to exist there.

Water balance

The following quantitative characteristics of the waters flowing into the Barent
Sea were given for the summer of 1931 by A. Sokolov and V. Lednev (1935) :
North Cape-Bear Island 163-3 km3/day

Spitsbergen-Franz Joseph Land 38 0

Franz Joseph Land-Novaya Zemlya 49-2

Total 250-5

80 BIOLOGY OF THE SEAS OF THE U.S.S.R.

The amount of water flowing in and out through the above-mentioned
straits can change and create sometimes a positive, sometimes a negative
balance. Thus for July 1927 A. Sokolov gives the following data:

Flowing into the Flowing out of
Barents Sea the Barents Sea

North Cape-Bear Island 127-7 km3/day 97-6 km3/day

Spitsbergen-Franz Joseph Land 38 0 68-3

Franz Joseph Land-Novaya Zemlya 49-2 43-2

Total 214-9 2091

So we may accept that in one year 40 to 70 thousand cubic kilometres of
water flows into the Barents Sea from the southwest between the North Cape
and Bear Island, i.e. a little more than one-third of the water which, accord-
ing to Helland-Hansen's calculations, flows into the Norwegian Sea from the
south. Thirty-five to 60 thousand cubic kilometres flows out towards the
south from Bear Island back into the Norwegian Sea. At the north tip of
Novaya Zemlya 5 to 1 5 thousand cubic kilometres of water flows out of the
Barents Sea. According to Sokolov, the total volume of water flowing annually
into the Barents Sea is 75 thousand cubic kilometres, i.e. about a quarter of
the volume of the Sea.

Vertical circulation and polar front

Atlantic waters with a temperature of 4° to 12° and a salinity of 34-8 to 35-2%0,
entering from the west, get gradually cooler as they move east and north,
and acquire the character of the local polar waters. Under the influence of the
floor contour, the Atlantic waters press against the shallows and, meeting the
local less saline and colder waters, are cooled and sink. Water from the depths
wells up in their place. Hence in precisely the same way as at the meeting point
of the warm saline Atlantic waters and the cold less saline East Greenland
waters in the Greenland Sea, the phenomena of intensified vertical circulation
occur in certain areas of the Barents Sea. As a whole these phenomena are
known as the polar front. It brings to the surface nutrient salts accumulated
in deep layers of the Sea and causes the ventilation of the bottom layers. As a
result the shallow Barents Sea is found to be very favourable for a
rich development of plankton and bottom life and for the feeding of a huge
amount of commercial fish (Fig. 23).

Tides

Widely open on the side of the Atlantic Ocean, the Barents Sea is greatly ex-
posed to the influence of tides. In the southern part of the Sea on the Murman
shores, the tidal range is more than 4 m, and when the tide goes out part of the
bottom populated by a very rich littoral fauna is laid bare. The tides become
weaker as we travel east and north (except for the eastern Murman coast
and the entrance to the White Sea) and are reduced to lm or less.

THE BARENTS SEA

Temperature and saline conditions

In the western part of the Barents Sea (Fig. 24) where the warm Atlantic
waters enter, the whole water column has a temperature above zero even in
winter time. Following the bottom contour the Atlantic waters penetrate into
the Barents Sea in four streams — the northern one at 80° N, the middle one
along the 75° parallel, the main and most powerful stream between the 71°
and 72° parallels while the fourth stream flows close to the Murman coast. In

Fig. 23. 1 Main directions of currents; 2 Zone of polar front;
3 Regions of increased biomass and feeding aggregations
(Zenkevitch).

the north, east and southeast of the Sea these waters are cooled and remain
below zero from surface to floor all the year round. This is clearly shown from
the annual averages of temperature ranges at different levels (Fig. 25).

Thus a considerable change of the warm Atlantic waters which have flowed
into the cold local ones takes place in the Barents Sea. In the middle of the
Sea in its northern and eastern regions only a thin surface layer is heated in
summer. At depths of 10 to 25 m the temperature is already below zero.
Only in the most northeasterly part, between Novaya Zemlya and Franz
Joseph Land, at depths of 200 to 250 m can a temperature above zero (+ 1° C)
be observed at a high salinity (35%0). These are Atlantic waters which

BIOLOGY OF THE SEAS OF THE U.S.S.R.

penetrate from the northeast along the trenches from the centre of the polar
basin (Fig. 4). In addition there is another very interesting phenomenon to
be observed throughout the Barents Sea. In summer the lowest temperature
remains at a depth of 50 to 75 m. This is considerably cooled and saline
'winter' water which has sunk down. It is called the intermediate cold layer.
In the coastal areas of the southern part of the Sea, in its more or less isolated
parts, the temperature of the surface layer in summer may be fairly high,
owing to local heating, but in the hollows and trenches and over the shallows
water may remain very cold all the year round. In the inlets and fjords of the

Fig. 24. Mean secular limit of ice in the Barents Sea in months

from April to August (data from Meteorological Institute of

Denmark).

northern part of the Sea, if they are separated from the open sea by shallow
ridges, cold, low-salinity surface water remains even in summer, as, for
example, in Stur-fjord in Spitsbergen. In winter, however, owing to formation
of ice in bays and fjords, homothermia and homohalinity may be observed at
a temperature below zero and in the presence of high salinity (35 to 37%0).

The Murman coastal area has a considerably higher temperature (Fig. 26)
in summer, but in winter its temperature is above zero.

The Atlantic waters with a salinity of about 35%0 at their entrance into the
Barents Sea retain the same salinity in the deep layers as they move north
and east, while in the surface layers this goes down to 32 to 34%0, and only
farther up the inlets do they get considerably diluted.

THE BARENTS SEA

Ice conditions

The thick pack ice formed on the Barents Sea in winter disappears each sum-
mer, only remaining in the northern part of the Sea after a more severe winter
(Fig. 24). The ice reaches its southerly extreme in April, and recedes farthest
to the north in August-September.

63°Ж70' 30

30' 72° 30' 73' 30' 74' 30' 75° 3(У 76 30'

63'30'70' 30' 71° 30' 72° 30' 73° 30' 74° 30' 75° 30' 76° 30'
5 4 6 Э 6 8 0 5 15 7 4 0 0 8 0

300

q63°30'70° 30' 71° 30' 72° 30

200
300t

Fig. 25. Vertical distribution of temperatures (/), phos-
phates (II), nitrates (III), and concentration of hydrogen
ions (IV) along the Kola meridian of the Barents Sea
(33° 30' — in August 1930) (Kxeps and Verzhbinskaya).

Data on the temperature conditions along the Kola meridian and on the
ice conditions of the Barents Sea accumulated through years of work have
been very successfully used by N. Zubov (1932) for a system of ice prediction
for the Barents Sea, and therefore, to a certain extent, for other seas lying to
the east of it. Zubov has found that the extension of the winter ice cover of the
Barents Sea is closely connected with the average temperature along the Kola
meridian during the preceding summer. This average temperature for three

BIOLOGY OF THE SEAS OF THE U.S.S.R.

1'30'70' 30' 71° 30' 72' 30' 73° 30' 74° 30' 75° 30' 76° 30'

100м

Пб9°30'70° 30' 71° 30' 72° 30' 73° 30' 74° 3gj 75° 30' 76' 30'

Q69'3ff70° 30' 71° 30' 72° 30' 73° 30 74' '30' 75° 30' 76° 30'

n6S°30'70' 30' 71° 30' 72° 30 73° 30' 74° 30' 75° SO' 76° 3C

25Ш

200м

300m

Fig. 26. Same as Fig. 25, in March and April 1930 (Kreps
and Verzhbinskaya, 1930, 1932).

decades (1920 to 1950) is about 2-62° С in May and 4-41° С in August; more-
over, here too we have an example of the gradual rise in temperature over
long periods {Table 29).

Table 29

Period

May

August

Average for 1900-06
Average for 1921-34

2-16°

2-84°

3-94°
4-64°

Difference

+0-68

+0-70

The waters of the western part of the Barents Sea have definitely been getting
warmer recently. This corresponds closely with the data on the ice condition
of the sea {Table 30).

THE BARENTS SEA 85

Table 30

Period

Ice cover, %

Average for 1901-06
Average for 1921-31

57
44

Difference

-13

Oxygen

The Barents Sea, as has already been mentioned, is on the whole well aerated.
In summer the oxygen content of the surface layer is usually slightly above
100 per cent of saturation, on the average 105 per cent. In summer the 10 to
25 m layer contains the maximum amount of oxygen where it sometimes
reaches 123 per cent of saturation, which corresponds to the maximum
development of phytoplankton. In the autumn when the photosynthesis pro-
cess becomes weaker, while the vertical circulation increases, the amount of
oxygen in the upper layer is somewhat below 100 per cent of saturation (90 to
100 per cent). The average minimum amount of oxygen is rarely below 85 per
cent of saturation. Smaller oxygen contents were recorded in the deep trough
south of Novaya Zemlya (down to 70 per cent). The amount of oxygen in the
bottom layer is usually about 90 per cent. These data, however, do not cover
the actual bottom layer, since during the so-called 'bottom' sampling the
bathymeter remains at some distance from the sea floor. We shall revert
to this problem later in connection with the quantitative distribution of
benthos.

Nutrient salts

The distribution of nutrient salts, most important for the development of
vegetable plankton, is correlated with the system of vertical circulation. A
very full picture of the annual cycle of the changes of nutrrient salts in the
Barents Sea is given by the excellent research carried out by E. Kreps and
N. Verzhbinskaya (1930, 1932). The Arctic waters are slightly richer in nutrient
salts than the Atlantic ones. Owing to the vigorous development of phyto-
plankton in the photosynthesis layer, the amount of phosphates present
gradually decreases in the spring and during the summer. An accumulation
of nutrient salts in the abyssal layers proceeds simultaneously and, by August,
a definite stratification (Fig. 27) which also coincides with the period of the
highest temperature is established. At that time the nitrates are absent from
the upper layer, while their amount increases with depth and in the bottom
layer reaches 200 mg/m3. The summer shortage of phosphates is particularly
marked in the upper layer, from which they are absent during that season, but
in the bottom layer the quantity reaches 60 mg/m3.

With the arrival of the autumn circulation and during the winter, when the
whole water column gets mixed, the nutrient salts are brought up from the
lower levels and a uniform distribution of them is established. The most uni-
form distribution is observed in March (Fig. 26) — a period of most marked

BIOLOGY OF THE SEAS OF THE U.S.S.R.

homothermic conditions. At that time the amount of nitrates in the water
varies from 1 50 to 250, and of phosphates from 40 to 60 mg/m3. The nitrate
and phosphate contents increase slightly from south to north and in the
northern parts of the Sea the amount of nitrates in bottom layers reaches 450
to 460 mg/m3. The off-shore waters are, on the contrary, appreciably poorer
in nutrient salts. Their nitrate content may fall to 100 mg (and below) and
that of phosphates to 14 to 15 mg/m3. The Arctic waters are on the whole
richer in nutrient salts than the Atlantic ones. Careful all the year round
observation has allowed Kreps and Verzhbinskaya not only to draw a full

picture of the annual cycle of nutrient salts
but to come to some interesting conclusions
on biological productivity.

First of all it was found possible to
determine the total amount of phosphorus
used up during the multiplication period
of 1930—31 in the region near the Kola
meridian. Knowing the amount of phos-
phorus contained in phytoplankton (0-15
per cent of the wet weight) it is possible to
calculate the amount of phytoplankton
which could develop at the expense of a
given amount of phosphates. It was estab-
lished that 3,000 to 5,000 tons of the wet
mass of phytoplankton could be formed
for each square kilometre of sea surface
at the expense of the phosphates present
through the whole depth of the Barents
Sea. This amount is about double that of
the annual phytoplankton production cal-
culated by Atkinson for the English Channel (1,400 tons) and for the Oslo-
fjord by Gran (1,600 tons/km2).

Interesting data on the distribution of nitrites in the Barents Sea are given
by S. P. Brujevitch (1931). In summer nitrites are absent from the photo-
synthesis layer; the largest amount is accumulated under it, at a depth of
50 m or more.

The amount of nitrites is rarely above 10 mg/m3. Usually it is a few milli-
grammes. Nitrites are present in such amounts usually only at the end of the
summer and in the autumn. They generally disappear after the period of
vertical circulation in winter. Hence accumulation of nitrites takes place under
the zone of the highest production of plankton by the end of the photo-
synthesis period. Brujevitch notes a decrease of oxygen content in the layer
of the highest concentration of nitrites. The concentration of nitrites and the
decrease of oxygen content are the results of oxidation processes accompany-
ing the disintegration of the organic substances of defunct plankton, which
decomposes to amino-acids and ammonia. The fact of the rapid summer and
autumn accumulation of nitrites followed by their oxidation to nitrates was
also noted by Harvey for the Atlantic Ocean. The nitrites are considered by

MONTHS
Fig. 27. Seasonal changes in
nitrite and nitrate content in 0
to 100 m layer in Barents Sea
in 1930, on the 72° to 72° 30'
latitude along the Kola meri-
dian (33° 30') (Verzhbinskaya,
1932).

THE BARENTS SEA 87

most investigators to be an intermediate phase of the process of ammonia
and amino-acid oxidation to nitrates. On the other hand, V. Butkevitch
considers that the nitrites accumulate under the photosynthesis layer as a
result of the reduction of nitrates, since no nitrifying bacteria have been found
in the surface layers of sea water.

Quantitative correlation between the nitrates and nitrites is evident from
Fig. 27, drawn by Verzhbinskaya (1932) for the Barents Sea. Ammonia is
formed during the decomposition of organic substances. Nitrogen content in
the form of ammonia is low in the upper layer of the Barents Sea — no more
than 10 to 20 mg/m3. Below the photosynthesis layer (50 m) the amount of
ammonia decreases with depth and at the bottom it is 3 to 5 mg/m3. Similar
results were obtained for the Danish Strait by the Meteor expedition.

There is no shortage of silica in the Barents Sea even in the period of the
highest increase of photosynthesis, and therefore it is not a limiting factor in
the development of phytoplankton. The silica content in the waters of the
western part of the Barents Sea reaches 1 ,000 mg/m3. Within the region of the
Kola meridian the amount of silica in the winter varies between 400 and 800
mg/m3. By the end of summer, as a result of phytoplankton development,
the silica content in the upper layers of water falls to 200 mg/m3, and in the
bottom layer rises to 600 to 800 mg/m3.

Sea soils

M. Klenova (1940, 1961), who has for many years investigated the sea-bed of
the Barents Sea, points out that its sediments consist of grains of greatly vary-
ing sizes, mostly of mineral origin, from a thin silt to large boulders (Fig. 28).
Sandy silt (10 to 30 per cent; about 21 per cent of the fine fraction*) is the
preponderant soil of the Barents Sea, occupying about 4 per cent of its bottom
area. Fifteen per cent of the bottom area is covered with sand or sandy silt,
the remaining 25 per cent with silts. Clayey mud forms only 1 per cent of the
bottom area. There is a great predominance of silica and alumina in the
chemical composition of typical Barents Sea soils (Table 31).

Table 31. Typical percentage compositions of floor of Barents Sea

Constituent

Sand

Silty sand

Sand and silt

Silty clay

Silica (Si02)

84-21

79-88

70-34

58-21

Titania (TiOa)

0-29

0-26

—

Alumina (A1203)

7-00

8-78

12-99

19-78

Iron oxide (Fe203)

1-32

216

3-84

4-97

Calcium oxide (CaO)

2-43

2-76

1-54

1-76

Magnesium oxide (MgO)

0-78

0-55

2-24

2-62

Sulphuric anhydride (SOa)

—

0-68

—

Losses in calcination

2-66

3-18

4-61

8-11

Water (hygroscopic)

0-65

0-95

2-55

3-67

* Bottom sediments formed of grains less than 001 mm in diameter are called the fine
fraction.

88 BIOLOGY OF THE SEAS OF THE U.S.S.R.

The brown colour of the surface layer of the sandy silt and silt is a well-
known and interesting phenomenon characteristic of the floor of various
oceans and seas, and widespread in the Barents Sea.

The northern part of the Barents Sea and the trough south to Novaya
Zemlya have brown mud bottoms. The floor of the whole White Sea depres-
sion, most of the Kara Sea and that of the Arctic basin are covered with

Fig. 28. Distribution of soils in the floor of the Barents Sea (Vinogradova).
1 Sand ; 2 Silty sand ; 3 Sandy silt ; 4 Mud ; 5 Clay-silt ; 6 Clay ; 7 Limit of

brown soils.

brown mud. A brown tint of the often very thin surface layer of the sea-bed is
commonly found on different kinds of bottom, even on sand. This brown
colour is due to the presence of ferric and manganic hydroxides ; and its pre-
sence leads to the suggestion that the bottom layer contains sufficient oxygen
for their oxidation. However, brown mud beds are undoubtedly situated
mainly either in depressions or within the regions of unfavourable aeration and
of considerable accumulation of free carbon dioxide in the bottom layer ;
brown mud is not formed under conditions specially favourable for aeration.
M. Klenova (1938, 1940) suggests that the brown colour of this soil may dis-
appear as a result of a plentiful benthos population which would create a

THE BARENTS SEA

reducing medium. The fauna of brown mud is usually very scarce, hence the
oxidizing medium is retained. The conditions under which the brown mud is
created are undoubtedly unfavourable for the growth of benthos ; Hessle has
also pointed this out in relation to the Gulf of Bothnia. The problems of
brown muds await further investigations.

Plant foods in the sea-bed

T. Gorshkova (1958) has analysed the organic matter present in the bot-
tom sediments of the Barents Sea. Their carbon content varies over all

Fig. 29. Organic carbon content (A) and carbonates (B) in soils of Barents
Sea bottom (Gorshkova).

A. 1 0-5%; 2 0-5 to 10%; 3 10 to 20%; 4 20 to 3-0%.

B. I 0-25% 2 0-25 to 0-5%; 3 0-5 to 10%; 4 10% and more.

from 0-15 to 3-12 per cent, that of nitrogen from 002 to 0-42 per cent, and the
ratio of the first to the second from 5 to 8-7 (average 7). These values are
close to those obtained for the shallow parts of the Atlantic Ocean. They
indicate the origin of the organic matter in sedimentation as mainly due to
plankton. The range of organic carbon in the upper layer of the Barents Sea
sediment is shown in Fig. 29. No simple relationship can be established be-
tween the bed's content of organic substances and some definite factor of the
media; it is found to be much too complex.

The most constant relationship has been observed between the organic
matter content and the mechanical properties of marine sedimentation. As a
rule the larger the amount of the fine sediment fraction, the richer its organic
matter content (Fig. 30). This is clearly shown by a comparison of the organic

BIOLOGY OF THE SEAS OF THE U.S.S.R.

carbon content of the brown silts of the northern part of the Barents Sea
(T. Gorshkova, 1957).

Clayey silt
Ooze
Sandy silt
Silty sand

1 -78 per cent carbon
1-31 per cent carbon
0-97 per cent carbon
0-59 per cent carbon

In other words, in regions with favourable conditions for deposition of the
fine-grained fraction, large amounts of detritus are also deposited, but on the
other hand these regions are usually unfavourable for the development of

Fig. 30. Comparison of amounts of organic carbon
(/), fine sediment fraction (//), and benthos biomass
(///) in bottom soils of Barents Sea along cross sec-
tion from 75° 50' N latitude and 25° 00' E longitude
approximately along 74° parallel towards coast of
Novaya Zemlya. (IV) Depth, m (Gorshkova, 1958).

bottom life. However, in the northern parts of the sea on soft brown sedi-
ments life is scarce and the amount of organic matter low. Finally, many
regions with sandy bottoms and a rich life may have a low content of organic
matter. Good vertical and horizontal water circulation prevents the accumula-
tion of organic matter on the bottom, sweeping it again and again into a
vortex.

Hence, although on one hand one may accept the rule that seas rich in life
have more organic matter in their soils, in some of them a reverse relationship
between the amount of bottom life and of organic matter in the sea-bed may
be created. The comparison of benthos biomass and carbon content in the
sea-bed, given in Fig. 30, may serve as an illustration of this. The picture of
the relationship between the biomass density and the carbon content of the
sediment may also be obscured by the quantitative distribution of plankton
and its role in the formation of organic matter in the sea-bed.

THE BARENTS SEA 91

Thus the accumulation of organic matter in the bed depends on the abund-
ance of plankton and benthos life, which is its source, and on the conditions
favouring its deposition on the sea-floor; the two factors, however, may act
in the reverse direction.

The C/N ratio for the Barents Sea, close to 7, characteristic for plankto-
genetic organic substance, indicates a sufficient aeration of the whole water
column and the very limited role of the littoral vegetation on the genesis of
organic matter. From this point of view the data of T. Gorshkova (1939) on
the Motovsky Gulf are most interesting. Although the shores are close to each
other the ratio of C/N is here also about 7. There is no increase of organic
carbon which remains constant at 0-15 to 2-76 per cent, so that even near the
shores the littoral vegetation does not affect the amount and nature of the
organic matter in the sea-bed. The closeness of the shores affects only the
chlorophyll content, which is higher here than in regions farther removed
from a shore.

III. FLORA AND FAUNA: GENERAL CHARACTERISTICS

The fauna of the Barents Sea, in spite of a complete or partial absence of a
number of groups which are characteristic of warmer seas (radiolarians,
Siphonophorae, corals, cephalopod molluscs, crabs, salpes, pyrosomes and
some others), is both varied and abundant and consists mainly of bivalves
and gastropods, polychaetes, echinoderms, lower and higher crustaceans,
Porifera, hydroids, bryozoans, ascidians and Foraminifera (Fig. 31).

The number of animal species living in the Barents Sea is, probably, not
less than 2,500. At present, however, owing to an insufficiently systematic
study of many groups of the Barents Sea population, only an approximate
estimate of the number of its species is possible.

Plankton

The composition ofphytoplankton. The Barents Sea phytoplankton has not yet
been adequately investigated, especially as regards its productivity. Accord-
ing to I. Kisselev (1937) the plankton of the Barents Sea includes:
Green algae 9 forms

Diatomaceous algae 92 forms

Peridinean algae 69 forms

Flagellatean algae 7 forms

Others 2 forms

Total 179 forms

The actual number of phytoplankton forms is probably above 200.

However, in this fairly rich stock only a few are of importance, among
the diatoms the following : Chaetoceras diadema, Coscinodiscus subbul liens,
Corethron criophilum, Sceletonema costatum, and two species of Rhizoselenia-
R. styliformis and R. semispina. Of the green algae only Halosphaera viridis is
very widely distributed ; of the peridineans Peridinium depressum, P. ovatum,
P. pallidum ; and the three species of Ceratium— C. longipes, C. arcticum and
С fusum, that is 13 forms in all.

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THE BARENTS SEA

In the spring the diatoms are most important, developing rapidly and giving
an appearance of ' bloom ' in some parts of the Sea. In the autumn diatoms
are superseded in importance by the peridinean
mass, then showing maximum development.

The course of phytoplankton development,
with its two maxima, which is characteristic of
the whole temperate zone of the oceans of the
world, is well defined in the southwest of the
Barents Sea (Fig. 32). The first maximum in the
coastal waters is in May and is connected with
the mass bloom of Phaeocystis (Crypto-
monidinae) and to a much lesser degree with
that of the diatomaceous Chaetoceras and
Sceletonema. The second, smaller maximum
(July to September) is conditioned by the mass
development of peridineans.

Composition of zooplankton. Zooplankton in
the Barents Sea (V. Bogorov, 1946) is fairly poor
in its numbers; of the groups composing it only
Infusoria, Copepoda and Coelenterata {Table
32) stand out.

The Barents Sea zooplankton contains the
oceanic and neritic forms and forms distributed
equally in the coastal areas in the open sea.
M. Virketis (1928) includes in the first category
the main forms of Copepoda genera — Calanus,
Pseudocalanus, Metridia, Oithona, Euchaeta,
Microsetella ; salps — Oikopleura medusa, Aglanta
digitalis: and in the second the Daphnidae
Evadne and Podon, the Copepod Temora longi-
cornis, and the salps Fritillaria borealis and F.
medusa Rathkea octopunctata.

On the other hand the permanent inhabitants of the Barents Sea may be
distinguished from the more or less temporary visitors. The latter forms of one
origin or another may often appear in large numbers carried in by the waters,
and rapidly disappear with a change of hydrological conditions. Thus it is
possible to observe the seasonal change of zooplankton composition, which
is not possible with benthos forms. Virketis includes Calanus finmarchicus,
Metridia longa, Oithona similis and others among the main permanent in-
habitants of the Barents Sea.

The more thermophilic forms of western origin keep mostly in the warm
streams of the North Cape current. They move eastward in summer and west-
ward in winter. Their numbers are higher in warmer years than in colder.

In contrast to the thermophilic forms, the arctic ones attain their highest
development in winter and spring. In summer they travel far to the north, or
keep to the cooler abyssal layers or the colder waters remaining over the

V VI VII VIII IX X

MONTHS

Fig. 32. Quantitative altera-
tion of phytoplankton from
May to October 1932, in one
of the Gubas of western
Murman Peninsula (Man-
teufel, 1939). The ordinate
gives the number of cells in
millions in a 40 m column
of water of 50 cm2 cross
section.

BIOLOGY OF THE SEAS OF THE U.S.S.R.
Table 32

Group

No. of species

Group

No. of species

Radiolaria

Infusoria

Rhizopoda

Coelenterata

Vermes

Rotatoria

Mollusca

Cladocera

Copepoda
Ostracoda

38
3

2
32

3
10

Euphausiacea

Amphipoda

Mysidacea

Decapoda

Appendicularia

5
5
6

1
3

Total 151

shallows. As a typically arctic component of plankton, one may mention
such forms as Appendiculariidae Oikopleura labradoriensis and O. vanhoeffeni.
As occurs in other seas, the main part of Barents Sea zooplankton consists of
Copepoda: in the southwest of the sea (V. Jashnov, 1940) they form almost
90 per cent of the biomass : moreover the most important of them is Calanus
finmarchicus which constitutes on average 30 per cent of the plankton bio-
mass. Of the other plankton components only Euphausiacea (5-3 per cent)
and Chaetognatha are prominent (3-2 per cent). All the others taken together
average not more than 3 per cent (by biomass). B. Manteufel (1941) thinks
that in the southwestern parts of the Sea at certain seasons of the year,
Euphausiacea may form about half of the whole plankton biomass.

In sea inlets the relative number of Copepoda is smaller, and there is a
considerable admixture of Cladocera and Cirripedia larvae {Table 33).
The large number of Pteropoda is more or less accidental; in 1931 they were
very numerous (25 per cent of the biomass), and in 1932 they were entirely
absent. It is of interest to note that during both years of investigation in
Motovsky Gulf Calanus finmarchicus constituted about the same percentage of

Table 33

Form

Average percentage composition
annual biomass

of plankton in

Southwestern part
of Barents Sea

Motovsky Gulf

Calanus finmarchicus
Other Copepoda
Euphausiacea

80-46
7-80
5-32

63-5
7-0
5-6

Chaetognatha
Coelenterata

3-22
1-51

1-4
2-0

Balanus nauplii

—

3-3

Limacina retroversa

—

120

Cladocera

—

3-3

Others

1-65

6-2

THE BARENTS SEA

И Ш Ш IX

ЕЭ5

Fig. 33 Quantitative and qualitative changes (mg/m3) of zooplankton in

the Motovsky Gulf in 1931 (Manteufel). 1 Calanus finmarchicus ; 2

Balanus larvae ; 3 Decapoda larvae ; 4 Thysanoessa biennis ; 5 Copepoda

(summer community) ; 6 Limacina retroversa ; 7 Varia.

plankton (64 and 63 per cent) and that the relative amounts of some other
groups present in the open sea and in the gulf were also constant (other
Copepoda, Euphausiacea and Coelenterata).

In large inlets and fjords widely open to the sea, the composition of plankton
is intermediate between that of the open sea and of the closed bays and in-
lets. Copepoda (and particularly Calanus finmarchicus) constitute, as men-
tioned above, the preponderant part of the plankton (Fig. 33). The June maxi-
mum of zooplankton is connected actually with the development of C. fin-
marchicus. For a biomass of almost up to 300 mg/m3 (1931) the zooplankton
consists of 92 per cent Calanus finmarchicus.

In small bays and inlets, more or less isolated form the open sea, the neritic
character of the plankton is most strongly marked (Fig. 34). The May maxi-
mum of the phytoplankton is controlled here also by the mass development

Fff

i C32 \EB3 M~ Ш\5 £36 Шу ШШ8 Шз Шт □//

Fig. 34. Changes of zooplankton biomass (mg/m3) in one small isolated Guba of the
western Murman Peninsula in a layer of 10 to 25 m (Manteufel). The area of the
circle corresponds to the biomass represented by the numerals. 1 Nauplii-Cirri-
pedia ; 2 Polychaeta larvae ; 3 Decapoda larvae ; 4 Calanus finmarchicus, 5 Fritillaria
borealis ; 6 Neritic Copepoda ; 7 Pseudoealanus elongatus ; 8 Cladocera ; 9 Euphau-
siacea larvae ; 10 Medusae ; 11 Varia.

96 BIOLOGY OF THE SEAS OF THE U.S.S.R.

of Phaeocystis and only partly by the diatoms ; these latter are preponderant
in July and the peridineans in August and September. The May maximum of
zooplankton is connected with the larval forms of the bottom animals,
mainly with Balanus, Calanus finmarchicus and Thysanoessa inermis ; it is
rather low and persists through June only. Starting from June the neritic
Copepoda and medusa become the preponderant groups. Moreover, an inter-
esting fact is noted by B. Manteufel — the population of the deeper layers of
water of these inlets, which is not affected by the surface loss of salinity,
approaches much nearer to the plankton composition of the open seas than
does the population of the upper, always somewhat saline, layer.

Vertical migrations and seasonal variations. As was shown by V. Bogorov
(1932) and V. Jashnov (1939) for a number of the highest mass forms of Cope-
poda during their young stages they keep to the surface layer of water (in the
south of the Sea mainly at a depth of 10 to 25 m and in the north at 25 to
75 m) ; the adult forms, however, descend into deeper layers (75 to 300 m).

It is most curious that under the conditions of a polar day the Copepoda
remain on the same level at different hours of the day and night (V. Bogorov,
(1938) ; they do not migrate vertically every 24 hours, as they do in other lati-
tudes with the change of day to night. However, as we have noted in our general
section, owing to the presence of the deep waves, the layers of water are sub-
ject to 24-hourly vertical oscillations, sometimes of several tens of metres.
Evidently, Copepoda, in order to keep their position within the same inten-
sity of light, are forced to travel in the opposite direction to the wave motion.
Hence the purpose of the known vertical semidiurnal migrations of Copepoda
is to remain at a constant level. V. Bogorov has observed the same pheno-
menon in other plankton. In the autumn with the alternation of day and night
Copepoda begin their daily vertical migration of the usual type. On the other
hand, some organisms change their position of greatest density twice daily,
i.e. they do not actually migrate but go upwards and downwards with the
wave motion of the water layers.

V. Jashnov's (1939) detailed analysis of the succession of generations and the
seasonal changes in the distribution of the stages of growth of Calanus
finmarchicus led him to conclude that its nature was monocyclic. According
to his data from the Barents Sea only one generation of Copepoda succeeds
in developing within a year (Fig. 35). This fact is especially interesting when
compared with data from other parts of the northern Atlantic. Thus, accord-
ing to V. Bogorov's data (1934), in the Plymouth region three generations of
Calanus finmarchicus manage to develop within one year — the spring, summer
and winter ones. As has been shown by a number of foreign biologists,
Calanus finmarchicus gives two generations in the northern Atlantic, bred in
the spring and by the end of the summer (Scotland, the western shores of
Norway, etc.). However, a very circumstantial survey by M. Kamshilov (1955),
carried out almost fifteen years later, has led him to the conclusion that in the
eastern part of the Barents Sea Calanus finmarchicus breeds twice a year. The
first breeding period begins in April, and at the end of June or the beginning
of July there appears the second brood, with considerably bigger females.

THE BARENTS SEA

These females breed another summer generation. Moreover, Kamshilov notes
the considerable variation in the size of Calanus finmarchicus in the Barents
Sea, depending on temperature conditions. Large forms develop at a low
temperature, small ones at a high temperature. The large size, high breeding
capacity and other characteristics of the Barents Sea Calanus, do not enable
us, according to Kamshilov, to regard it as a special race different from the
Atlantic one. This difference between the data obtained by Jashnov and by
Kamshilov, separated by an interval of almost twenty years, might, possibly,
be explained by the warming-up of the Barents Sea waters. B. Manteufel

1-Е-Ш

PREDOMINANT STAGE
N Y

ШШ8
]9

Fig. 35. Seasonal changes in number of specimens of certain age stages
of Calanus finmarchicus in southern part of Barents Sea (Jashnov).
1 Eggs; 2 Nauplius; 3 Copepodite stage /; 4 Stage II; 5 Stage III;
6 Stage IV; 7 Stage V; 8 Females; 9 Males.

(1939) recorded a second generation of Calanus finmarchicus brought into the
southwest of the Barents Sea from the west.

Calanus finmarchicus males never rise above the 75 m level, while the females
are more uniformly distributed. Late in the autumn and in the winter the grow-
ing Calanus finmarchicus go down to the deeper layers of the sea. 'Before the
coming of spring, ' writes V. Jashnov, ' Calanus finmarchicus begins to rise in a
mass into the upper layers, and the newly bred young stages begin to appear
then. ' Thus Calanus finmarchicus serves as a good example of a plankton
organism making seasonal vertical migrations during the year.

The large pelagic crustaceans — Meganyctiphanes, Themisto, Thysanoessa
—have a biennial life cycle. Some of them breed twice a year, in the spring and
summer, others only in the summer. The picture of the vertical propagation
of these crustaceans is similar to that of Calanus finmarchicus : the immature

98 BIOLOGY OF THE SEAS OF THE U.S.S.R.

forms keep mostly to the surface layer, the adults to the depths. They like-
wise prefer the deep layers in the summer and the surface ones in the winter ;
this is an example of a peculiar type of migration conditioned by photo-
tropism but adapted not to the daily change of light, but to the yearly alter-
nation of the polar day and night.

A certain change of the qualitative composition of plankton is observed
during the year and is particularly marked in inlets.

In the spring and early summer, the oceanic forms of plankton are domi-
nant, while in the second half of the summer and in the autumn there is a
considerable admixture of neritic forms. A considerable amount of the larval
stages of bottom fauna appears also in the plankton during the second half of
the summer.

B. Manteufel (1937) distinguishes for the Motovsky Gulf four groups of
forms, producing their greatest development at different seasons of the year
(Fig. 33).

In early spring (April to May) Copepoda are almost absent, while plankton,
consisting mainly of the larval forms which have risen from the bottom for
breeding, is concentrated in the uppermost layers of water. In this group the
larvae of Balanus, Fritillaria borealis and those of the polychaetes, decapods
and some medusa such as Sarsia and Cyanea are prominent. In June the notable
preponderance of three forms — Calamis finmarchicus, Thysanoessa inermis and
Sagitta elegans — has been observed. Calanus finmarchicus is found mainly in
the third stage which is vigorously fed upon by all its numerous predators.
It we take the amount of third stage Calanus finmarchicus as the unit, then only
9 per cent of it develops to the fifth stage and only 0-1 per cent to the sixth.
Thysanoessa and Sagitta as they grow depart into the depths and partly,
perhaps, move away from the shores.

In their place there appear in summer (August to September) different
Copepoda (Acartia, Centropages, Temora, Paracalanus and others), Clado-
cera (Evadne, Podon), sometimes some Pteropoda (Limacina) and the mollusc
larvae. These are mostly thermophilic forms. The warmest water forms (some
Copepoda) are, in the early stages of their development, brought from the
west with warm water; they disappear with the coming of cold weather.
Others (Cladocera) live through the winter in the stage of resting eggs.

Finally, in the late autumn and in the winter the fourth group develops
significantly.

This group contains a whole series of Copepoda (Metridia, Calanus hyper-
horeus, Euchaeta, Oithona and others), Euphausiacea (Thysanoessa, Meganyc-
tiphanes), Oikopleura labradoriensis and Aglantha digitale. In the spring their
number is greatly reduced and in summer they are met only in the deepest
parts of the inlet, and then only in small numbers.

In the open sea the seasonal changes of plankton are not so sharply defined,
Calanus finmarchicus and Euphausiacea are, however, sharply predominant
even in June, and different Copepoda and other Euphausiacea in December.

Quantitative distribution of plankton. It is possible to obtain an idea of plankton
productivity in the southwesterly half of the Barents Sea, southwest of a line

100

200

300

100

200

300

100

200

300

CZh

ш*

Гу7]2 ГУЛ14 R^|6 !■

Fig. 36. Distribution of the Plankton biomass : A — in June, B— in August, С — in

December. 1 Calanus finmarchicus ; 2 Other Copepoda; 3 Euphausiacea ;

4 Amphipoda ; 5 Chaetognatha ; 6 Coelenterata ; 7 Mollusca : 8 Varia.

100 BIOLOGY OF THE SEAS OF THE U.S.S.R.

connecting Vaigach Island with Stur-fjord in Spitsbergen, from the work of
V. Jashnov (1939), B. Manteufel (1939) and M. Kamshilov (1956, 1957).
The quantitative and qualitative distribution of plankton and its changes with
depth are given in Fig. 36 for the Kola meridian (33° 30') northwards to
76° 30' latitude in June, August and December of 1929 and 1930. A considera-
tion of these three cross sections leads to some very important conclusions.*

The marked preponderance of Calanus finmarchicus over all the other
forms is obvious. Secondly a comparison of the cross sections A and В reveals
that in the southern part of the Sea the mass development of Calanus fin-
marchicus occurs in the beginning of the summer, and to the north of 72° or
73° in the autumn. Also there stands out sharply the high density of popu-
lation in the upper levels in summer and in the lower levels in winter. The
middle layers of water are the most scantily populated.

Zooplankton biomass decreases as we move from the open parts of the
sea up into the inlets {Table 34).

Table 34

Large bays corn-
Area Open parts of municating freely Inlets more or less
Barents Sea with Sea isolated from Sea

Mean zooplankton
biomass, mg/m3 140 49 43

B. Manteufel gives a number of interesting data on the qualitative and
quantitative distribution of zooplankton in the southwestern part of the
Barents Sea. The amount of zooplankton sometimes reaches 8 to 9 g/m3 but
usually it varies from 200 to 2,000 mg/m3, increasing during the summer.

Generally speaking, the amount of zooplankton in this southwestern area
is only slightly below that of the northern parts of the Atlantic Ocean where
plankton is especially abundant. M. Kamshilov (1957) gives quantitative
data for zooplankton from the southern part of the Barents Sea for July 1953.
In the littoral zone of the Murman coast two centres of mass development
of plankton have been observed — the northwest one of Calanus and the
southeast one composed mainly of Cirripedia larvae. The shoaling of herring
in this region is conditioned apparently by the mass development of plankton
in the littoral.

A seasonal census of plankton in the Barents Sea carried out by V. Jashnov
(1940) permitted him to approximate to a solution of the problem of its
annual production capacity. Using A. Vinogradov's data on the chemical
composition of plankton consisting of Calanus finmarchicus (Table 35),
Jashnov gives an estimate of the chemical composition of the Barents Sea
plankton as a whole, in millions of tons (Table 36), expressing the total
production of the Sea by the amount of food required by the whole mass of

* Total plankton biomass is represented by the area of the circle, while the biomass of
different plankton components is shown by sectors.

THE 1

3ARENTS
Table 35

SEA

101

% wet weight

Loss of
weight

on
drying

Ash

% dry w

eight

Calories,

cal/g

dry

basis

Plankton
from

Dry

residue

Chitin Albumen

Fat

Total
Nitrogen

Motovsky

Gulf 1
Motovsky

Gulf 2
Barents Sea

13 3

14-3
15-2

86-7

85-7
84-8

1404

1610

14-64

3-72

2-99
3-48

62-56

64-38
6100

19-3

14-8
21-5

10-21

10-48
9-98

5,742
5,339

Average

14-3

85-7

14-93

3-4

62-65

18-5

10-22

5,540

Calanus finmarchicus. The amount of oxygen used by this crustacean in the
adult state is assessed on the basis that 1,000 specimens require 0-33 m3/hour
in the summer.

On the other hand, knowing the chemical composition of Calanus fin-
marchicus, it may be calculated that 222 g of oxygen is required for the oxida-
tion of 1 kg of its wet material. Using these data, V. Jashnov has calculated
that the amount of food needed for Calanus finmarchicus in the Barents Sea
must be 290 to 480 tons under every 1 km2 of the sea surface ; and since
Calanus finmarchicus feeds mainly on phytoplankton, it is possible to estimate
the minimum value of the production of phytoplankton in the Barents Sea,
although its true value must be considerably higher. Let us remember that the
estimation of the annual production of phytoplankton by the consumption of
phosphates, carried out by Kreps and Verzhbinskaya, gave a quantity of the
order of 3,000 to 5,000 tons of wet weight under every 1 km2 of the sea surface,
and that even this figure, as we have said, must be recognized as considerably
lower than the actual one.

On the other hand, since Calanus finmarchicus is a one-year animal, we can
assume that the PjB ratio for the Barents Sea is about 1 .

Nutritional value of plankton. As in other seas of the world ocean, Calanus
finmarchicus of the Barents Sea is, as a mass form of Copepoda, one of the
main links in the food chain of the pelagic region. Huge masses of herrings,
haddock and the fry of various fish are fed on this crustacean medusa and
ctenophores, which devour enormous numbers of Calanus finmarchicus and
are great rivals of theirs.
As stated above, Calanus finmarchicus breeds once a year in the Barents

Table 36. Average chemical composition of Barents Sea plankton in millions of tons

after V. Jashnov.

Wet weight
Dry weight
Protein

38-6
6-4
3-9

Fat

Chitin

Ash

11
0-2
1-2

102

BIOLOGY OF THE SEAS OF THE U.S.S.R.

25' 30° 35° 40° 45'

25° 30° 35° 40° 45'

Fig. 37. Sequence of occurrence of 'red Calanus' zones in
Barents Sea (Manteufel). Months of occurrence are shown
in Roman numerals and days of life in Arabic numerals.

Sea. A second generation appears only in the extreme southwestern part of
the Sea brought in from the west. The so-called 'red Calanus' (fourth to fifth
Copepoda stages) which acquires the red tint as a consequence of colouring
by some oil drops, has the highest nutritional value. In summer, as reported
by B. Manteufel (1941), a kind of wave of the red Calanus passes from the
west to the east and north. Calanus reaches sexual maturity in the western
part of the Sea in April (Fig. 37) and in the eastern part in August. Moreover
the life span of red Calanus decreases from 65 to 75 days in the west to 15 to 30
days in the east and its numbers also decrease from west. The herring's most
abundant Calanus feeding ground is in the 0 to 25 m layer in the south-
western part of the Sea.

In some years even with a slight rise of temperature and some decrease in
salinity of the upper layers of the southwestern part of the Barents Sea
Ctenophora, Bolinopsis infundibulum and some medusae (Cyanea, Aurelia,
Staurophora) develop in large numbers in July, August and September. If
their period of mass development coincides with that of the red Calanus it is
devoured in large numbers by Ctenophora and medusa, and its amount may
be decreased so much that the herring would not find enough food in such
feeding grounds. Coelenterata devour not only Copepoda and other plankton,
but they clear masses of water of all living matter. In some years (for instance
in 1938) the number of Ctenophora was so great that it is actually possible to
assume that all the water of the layer inhabited by the Ctenophora was
cleared of the main mass of zooplankton by them. The quantitative ratio of
Ctenophora and Calanus in various regions of the sea in 1938 is shown in
Table 37. Table 37

Regions

Bolinopsis infundibulum None Small number Large number Masses

Calanus finmarchicus Many Fair amount Small number Very few

25°

THE BARENTS SEA

30° 35" 40°

103

45°

200-

")500

200

LESS THAN'--:
1200 mg/m* £|

45°

73°

72°

71°
70°
69°

Fig. 38. Distribution of plankton wet weight in 0 to 25 m
layer of water, mg/m3. A — in second half of June 1937
(Manteufel). 1 Plankton biomass above 1,000 mg/m2;
2 Plankton biomass 500 to 1,000 mg/m2.

The mass destruction of Calanus by Ctenophora in 1938 becomes particu-
larly conspicuous from a comparison of the quantitative distribution of this
crustacean in 1937 and 1938 (Figs. 38 and 39) with the wet weight of plankton
in the 0 to 25 m layer of the southwestern part of the Barents Sea, expressed
in mg/m3 {Table 38).

M. Kamshilov (1957) has elucidated some most interesting details of the
role of Ctenophora in the development of plankton. Three species of Cteno-
phora, Bolinopsis infundibulum, Pleurobrachia pileus and Beroe cucumis

25° 30° 35° 40°

Fig. 39. In second half of June 1938— the same notation
as in Fig. 38.

104

BIOLOGY

OF THE SEAS OF THE U.S
Table 38

S.R.

Year

First half
of June

Second half
of June

First half
of July

1937
1938
1939

437
819

1,233

270

1,580

2,258
133
491

inhabit the southern part of the Barents Sea. Up to 123 specimens of Bolinop-
sis per cubic metre were observed in July. This most predatory form destroys
a huge amount of various plankton organisms, mainly Calanus finmarchicus.
Experimental investigations have led to the conclusion that the mass of
Ctenophora observed requires about 170 mg/m3 of food, and the annual pro-
duction of Ctenophora was, according to the 1950-54 data, 343 mg/m3.

In the second half of June 1938 the total amount of plankton in the south-
western part of the Barents Sea was 1-5 million tons less than in 1939 and
1-1 million tons less than in 1937. Evidently such considerable fluctuations in
plankton development and, in particular, in that of Calanus and Ctenophora
would cause considerable fluctuations in the quantitative distribution of
herring and other plankton-eating fish.

Previously, 1935 was an equally unfavourable year for the feeding of herring
and other plankton-eating fish. The distribution of herring in the Barents
Sea and the routes of their horizontal migration depend to a great extent on
the composition and distribution of plankton : in summer, herrings move to
the east with the mass of the growing plankton. Herring fattens up mainly
in the southwestern part of the Sea. By the end of the winter it moves in the
opposite direction.

As has been shown also for the seas off North Europe, water bloom (Phaeo-
cystis, Rhizosolenia) either changes the migration routes of herring or makes
them sink to great depth, below the bloom zone. In spring and summer the
main mass of herring is in the upper layers of the sea, where it is intensively
fattened on red Calanus and Euphausiacea {Thysanoessa inermis). In spring
and autumn herring migrates vertically, together with the plankton (Fig.
40) : in winter it keeps to the depths. Masses of plankton, primarily Calanus
finmarchicus and Euphausiacea, migrate from the depths into the upper
layers in March and April. This rise is connected with breeding, which takes
place in the upper layers of the sea. Shoals of herring rise from the bottom
layers at the same time.

The influence of herring, caplin and the fry of other fish which feed on
plankton, upon the latter, is very considerable. Manteufel (1941) gives the fol-
lowing approximate estimate: in 1934 about 200,000 tons of herring entered
one of the gubas of the western Murman Peninsula. In the course of a year
these herring must have eaten not less than 4 million tons of Calanus plankton.
If we assume that the shoal of herring which enters the guba forms only a
small part of the total amount of Barents Sea herring, and that about the same
amount of plankton is eaten by caplin and that the other plankton-eating

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106 BIOLOGY OF THE SEAS OF THE U.S.S.R.

fish consume another like amount, the total annual requirement in plankton
would be, probably, of the order of some thousands of millions of tons.
Hence the amount of animal plankton in the Barents Sea cannot be con-
sidered inexhaustible. On the contrary, Calanus and Euphausiacea in parti-
cular might greatly decrease in numbers over large areas of the sea, being
eaten by fish, Coelenterata and others.

Benthos

Qualitative composition of phytobenthos, The bottom macrophytes (phyto-
benthos) form a wide belt round the southern shores of the Barents Sea.
The qualitative composition of the macrophytes has been established mainly
by the survey of Kjellman (1877), E. S. Sinova (1914, 1923), B. Flerov and
Karsakova (1932) and at present it seems to be as given in Table 39.

Table 39

Algae

Off Murman coast
(Zinova)

Off the shores of Novaya Zem-
lya (Flerov and Karsakova)

Green
Brown
Red

69*

48
41

Total

172 species

115 species

* According to A. D. Zinova (1950) 177 species of brown and red algae inhabit the
Barents Sea.

The vertical quantitative distribution of algae off the Murman coast was
carefully investigated by M. Kireeva and T. Shchapova (1932) (Fig. 41). Of
the 172 forms not more than 20 have the significance of mass forms, the
others play a secondary role as regards numbers.

The littoral zone of the Barents Sea, owing to the predominance of craggy
steep shores, is usually narrow. Only in the depths of the gubas are there
some more or less considerable areas which dry out with a slight slope to the
bottom and are covered with silty sand. On the west of the Murman coast the
difference between high and low water is about 4T7 m. The tidal range de-
creases as one moves east and north. On the western side of Novaya Zemlya
and in the northern parts of the Barents Sea it is no more than 2 to 3 ft. On
the other hand, in the Voronka region and especially near the Gorlo of the
White Sea, the tidal range increases sharply: at Iokanga up to 6 m, at the
Gorlo to 8-5 m.

The zonal distribution of the littoral algae is given also in the tables below.
Among the macrophytes the most important, quantitatively, are Pelvetia,
three species of fuci (F. vesiculosus, F. inflatus, F. serratus), Ascophyllum,
Chorda ; two species of Laminaria (L. saccharina, L. digitata), Dictyosiphon,
Desmarestia and Pylaiella among the brown ones ; two species of Cladophora,
two species of Enterimorpha and two species of Monostroma among the

THE BARENTS SEA

107

green ones ; and among the red ones Rhodymenia palmata, Odonthalia dentata,
Ptilota plumosa, Delesseria sanguined, Phyllophora, Brodiaei and Litho-
thamnion.

Quantitative distribution of phytobenthos. On the littoral, among the species
cited, Ascophyllum nodosum, Fucus vesiculosus, F. inflatus, F. serratus and
on the upper level of the sublittoral both species of Laminaria are much in

GREEN

BROWN

1-Fucus uesiculosus
2-Ascophyllum nodo-
sum 3-F-serratus
4-F inflatus 5- Chor-
da filum 6-Lami-
naria 7-Pylaiella
8-£)lctyosiphon 9-
Mon astro ma fuscun
10-11 Enteromorpha
и С I adophora graci-
lis 12-Cladopho-
ra fracta

Fig. 41. Quantitative vertical distribution of main
forms of phytobenthos on rock and stone soils
off the western Murman coast, g/m3 (Zenkevitch).
(The vertical series of numerals denotes metres
from zero depth.)

evidence. Moreover, it is remarkable that the mean biomass indices of all
these forms are very stable not only for different regions of the western
Murman coast, but also for a much wider area (Table 40 and Fig. 41).

In the Ascophyllum bed (Fig. 42) a biomass of as much as 28 kg/m2 has
been observed, while fuci do not produce more than 12 kg/m2. According to
the estimates of the above-mentioned workers, 39 tons of wet algae can be
obtained from a portion of a craggy or rocky littoral of 1 to 1 5 m wide and 1km
in length, while from the whole Murman coast more than 500,000 tons can be
obtained.

108

BIOLOGY OF THE SEAS OF THE U.S.S.R.
Table 40

Average biomass, kg/m2

Species

Western Murman
Craggy cliffs Rocky shale

Gulmar fjord

(Sweden)
(Gislen, 1930)

Ascophyllum nodosum
Fucus vesiculosus

160 16-5
8-8 100

160
90

The distribution of macrophytes on the sands and mud of the Murman
littoral is quite different. One of the small bights of the Kola Inlet, 220 m
long and 100 to 120 m wide (Fig. 43), may serve as an example. The figures on
the map present the algal biomass in g/m2. In the outer part of the tidal range
the brown algae are preponderant, Dictyosiphon fimiculaceus, D. mesogloja,
Stictyosiphon torilis and a few species of Pilavella and Fucus. Nearer the shore
the green algae are preponderant, Monostroma fuscum, Cladophora fracta,
CI. gracilis and different species of Enteromorpha. The biomass decreases
sharply with the distance from the shore; moreover it is considerably in-
ferior to the algal biomass on craggy and rocky floors. At the inner part of
the beach at low tide it is usually no more than 500 g/m2, while at the outer
one it reaches 3 kg/m2. The whole biomass of the vegetative cover of this
littoral is about 4-5 tons and on the average about 200 g/m2.

M. Kireeva and T. Shchapova (1937) have noted an interesting relation-
ship between the algal growth and some animal organisms inhabiting the
same section of the littoral. Sections with a large algal biomass have a small
mussel biomass and vice versa {Table 41).

Fig. 42. A belt of brown algae Ascophyllum and Fucus

on the rock littoral of Murman coast (Gurjanova, Zachs

and Ushakov).

THE BARENTS SEA

109

The main bulk of the macrophyte growth of the sublittoral upper level
(0-5 to 15 m) of the Murman coast and the shores of Novaya Zemlya is
formed by two species of Laminaria, L. saccharina and L. digitata with their
numerous forms. A/aria esculenta and still more Chorda filum and Des-
marestia aculeata are considerably inferior to them in numbers. Among the

Fig. 43. Qualitative and quantitative distribution of
macrophytes on the silty-sand littoral of one of the
bays of Kola Guba (Kireeva and Shchapova). The
height of the columns and the associated numerals
represent the biomass in g/m2.

red algae the most common here are Ptilota plumosa, Odonthalia dentata,
Delesseria sinuosa and Phyllophora brodiaei, usually fastened to the Lami-
naria stalks and rhizoids.

The uppermost horizon of the sublittoral (1 to 2 m) is occupied by a belt of
Chorda filum with an average biomass of 1 to 3 kg/m3. The average Laminaria
biomass is about 10 kg/m3, and it sometimes attains 27 kg/m3. The admixture
of red algae is noticeable from the depth of 5 m ; however, on average it never

110 IHOLOGY OF

THE SEAS OF
Table 41

THE

U.S.S.

Total biomass

Algae biomass

Biomass

Nature of bed

kg/m2

Fucus serratus + Mytilus edulis
1 sector

11-25

2-75

8-5

2 Sector

7-5

2-5

Rhodimenia palmata+Mytilus edulis

1 sector 15 0

4-6

10-4

2 sector

8-8

7-8

exceeds 100 g/m2. The total stock of both Laminaria on the Murman coast is
reckoned as 500 to 600 thousand tons of wet weight.

Qualitative composition of zoobenthos. The composition of zoobenthos in the
Barents Sea has not been equally well investigated for all groups. Echinoder-
mata, Isopoda, Lamellibranchiata and Pisces are among those which have
been studied in detail. As yet work on Spongia, Hydrozoa, Bryozoa and some
forms of Protozoa is inadequate. Hence only an approximate composition,
including some forms of macroplankton, can be given for the bottom fauna
of the Barents Sea (see Table 42).

One hundred and sixty-four species of the parasitic forms (Yu. Poljansky,
1955) should be added to these 1,730 species. Among them 33 Protozoa forms,
68 species of nemerteans, 20 species of nematodes, 3 species of leeches, 21
species of crustaceans.

Littoral fauna. The Murman littoral fauna has been already described by
K. Derjugin in his Fauna of the Kola Inlet (1915). His pupils — E. F. Gur-
janova, I. Zachs and P. Ushakov — carried out specially detailed qualitative
biocoenotic and general ecological investigations of the littoral fauna during
the years 1925 to 1930. Finally, in 1933, a quantitative survey of the littoral

Table 42

Name

No. of
Species

Name

No. of
Species

No. of
Name Species

Foraminifera

Cornacuspongia

Hydrozoa

Anthozoa

Turbellaria

Nematoda

(Enopliidae)
Nemertini
Priapuloidea
Sipunculoidea

115
91

119
20

97
20

2
6

Echiuroidea

Oligochaeta

Polychaeta

Brachiopoda

Bryozoa

Cirripedia

Cumacea

Amphipoda

Isopoda

Decapoda

200

272

262

Pantopoda 24
Lamellibranchiata 87
Gastropoda 150
Amphineura 8
Scaphopoda 2
Cephalopoda 3
Echinodermata 62
Ascidia 50
Pogonophora 1

Total 1,738

THE BARENTS SEA 111

fauna of the western Murman Peninsula was made by the author and his
collaborators (1945), while the eastern Murman was surveyed in 1939 by
N. Sokolova (1940), T. Gurjeva (1948) and T. Matveeva (1948).

A difference in the length of its drying-out period, its temperature and
salinity oscillations, and finally, the variety of the littoral zone soils made it
possible for us to divide it fractionally into a system of horizons and zones.

E. F. Gurjanova et al. (1928) gave a system of subdivisions for the cliffs
and the rocks of the littoral of the western Murman coast {Table 43).

Table 43
Horizon Floor Form Depth, ft

I 1 Lichens 4-1

2 Pelvetta canaliculata 3-7

II 1 \ (Littorina rudis \ (Fucus vesiculosus 3-4

2 \ iBalamts balanoides\ I Ascophyllum nodosum 2-5

3 J \Mytilus edulis J I Fucus inflatus 20

\ Cladophora, Spangomor-
pha, Monostroma, Rho-
\dymenia 1 -3

HI 1 Halosaccion, Ectocarpus, Pylatella 0-5

2 Balanus crenatus crust-Lithothamnion 0

The littoral and its fauna change considerably with the distance from the
open sea and the nature of the connection with it. This enables us to dis-
tinguish the following six main bionomic types* for the Murman littoral.

(/) Open shore, exposed to heavy swell

(2) Quiet bays situated near the open sea, but protected against the buffeting
of the waves

(3) Narrow straits, protected against the swell, but washed by very strong
currents

(4) Deep-cut gubas at some distance from the open sea, without any swell
or currents and with a somewhat lowered salinity

(5) Gubas of greatly reduced salinity remote from the open sea, without
swell or current

(6) Estuaries of low salinity and an absence of currents.

Every bionomic type is characterized by its own peculiar composition and its
own distribution of organisms. Many littoral biocoenoses are found in all the
bionomic types, but they undergo definite changes in their vertical position,
in their composition and in the relative significance of their separate compo-
nents.

In the seas of the Arctic basin, where for the greater part of the year float-
ing ice is piled up at the shores, life is very scarce in the littoral and the upper

* A term introduced by de Beauchamp and Zachs in 1913 for a definite combination
of conditions of existence, determining the character of the biocoenoses.

112 BIOLOGY OF THE SEAS OF THE U.S.S.R.

level of the sublittoral, and part of the typical littoral forms sink down to the
sublittoral. On the western and southern shores of Novaya Zemlya and off
the shores of Spitsbergen, where the abrasive effect of ice and the winter cold
is not so severe as in the high Arctic region, a very much impoverished flora
and fauna can be observed on the littoral. The littoral fauna of the White
Sea is fairly varied, it is a somewhat impoverished version of the fauna of the
Murman coast littoral ; this latter, however, is very rich. Farther west, along
the shores of Norway and the North Sea, the main components of the littoral
fauna remain the same but become more varied still, and a number of forms
absent in the north are added to it.

In the Barents Sea the littoral fauna reaches its most luxuriant development
on the western Murman coast — on its cliffs, shale deposits, silty sand and
sandy mud, in the depth of well-protected fjords, on wide beaches, provided
only that their salinity is not too much reduced.

The littoral fauna is at its richest in the autumn. In winter, owing to the
sharp deterioration of climatic conditions, a considerable regrouping of the
population of the littoral takes place ; some of it migrates to the sublittoral,
some sinks into a quiescent condition. The abundance of light in the summer
(the polar day on the western Murman Peninsula lasts from 22 May to 23
July) and its absence in winter (the polar night lasts from 30 November to
13 January) and extremely sharp seasonal fluctuations of temperature and
salinity are characteristic of the Murman littoral.

For the cliff facies with their overgrowth of fucoids besides Mytilus edulis
and two species of Balanus — B. balanoides and B. crenatus — the following
animal organisms are likewise particularly characteristic; gastropods: Lit-
torina rudis, L. lit tor ea L.palliata, Acmaea testudinalis, Purpura (Nucella) lapil-
lus, Limapontia capita ta, Rissoa aculeus; crustaceans: Gammarus locusta, Ido-
thea granulosa, Jaera albifrons; Bryozoa: Flustrella hispida, Alcyonidium
hirsutum, Sertularia pumilla, and others. All these cliff fauna can be grouped
into five basic biocoenoses: (7) Balanus balanoides; (2) Mytilus edulis; (3)
Ascophyllum nodosum, Sertularia and Flustrella; (4) red algae and (5) Spha-
cellaria with the fauna of worms and small molluscs.

On the rocky shale, usually partly sunk into the soft sea-bed, among the
fucoids, on the sides and lower parts of the rocks and between them and on
the floor under them the fauna is usually abundant. Here the most character-
istic groups are actinians : Actinia equina ; the sponge : Halichondria tenui-
derma ; the nemerteans : Lineus gesserensis and Amphiporus lactijloreus ; the
molluscs : Cyamium minutum, and Lacuna ; the crustaceans : Gammarus
locusta, G. marinus, Jaera marina ; the fish : Pholis gunnellus and Enchcliopus
(Zoarces) viviparus.

Bryozoa: Flustrella hispida; hydroids: Dynamena pumilla, Gonothyrea loveni
and Obelia longissima, O. loveni; three types of Littorina (L. rudis, L. littorea
and L.palliata); Balanus balanoides; a large number of molluscs: Acanthodoris
pilosa, Dendronotus frondosus, Lamellidoris muzicata and L. bilamellata,
Coryphella rufibranchialis, Limapontia capitata; some species of polychaetes:
Spirorbis ; and the mollusc Chiton marmoreus settle on the algae. There are
some worms in the groups under the rocks, such as Priapulus caudatus,

THE BARENTS SEA

113

Halicryptus spinulosus, Scoloplos armiger, Capitella capitata, Ophelia limacina,
Travisia forbesi, Nephthys ciliata, Glycera capitata, Lineus gesserensis, and
Amphiporus lactifloreus.

In the rocky shale facies besides the above-mentioned the following biocoe-
noses can be distinguished : Fucus serratus, Spirorbis borealis and Lacuna
pallidula ; fauna : the polychaetes Amphitrites johnstoni, Phyllodoce maculata,
together with nemerteans and oligochaetes.

The biocoenoses of Balanus balanoides and Mytilus edulis are most import-
ant for the facies of cliff, boulders and large rocks. The first of these forms is
most developed at a level of 2-5 to 3-5 m above zero depth, within the zone of
the luxuriant fucoid development. A narrow band of Fucus vesiculosus (20 to
30 cm in width) extends over all; under it there is a one-metre band of
Ascophyllum nodosum. Below this there is a band of Fucus inflatus and F.
serratus. Numerous animals find excellent protection from drying out under
the large fronds of Ascophyllum when the tide is low.

Fucus vesiculosus gives a comparatively small biomass of 4 to 7 kg/m2.
Ascophyllum nodosum, which gives the largest biomass of all the fuci, may
yield 10 to 18 kg/m2. As a rule the population of Balanus balanoides is most
dense directly under the fucus border, where they form a solid white band
10 to 20 cm in width and clearly visible even from a distance. The number
of young balanus settled on the rocks may reach up to 100 to 200 thousand
per square metre, and their biomass up to 1 kg/m2. The total biomass of the
animal biocoenosis of Balanus on the Murman coast is as high as 3-2 kg/m2
and sometimes even higher (up to 10 kg/m2). The quantitative composition
of the given biocoenosis is set out in Table 44.

With the growth of the young recently-settled balanus, their number con-
siderably decreases : during the period from May to September, the loss in

Table 44

Mean biomass

Mean No.

Maximum

Biocoenosis composition

found

g/m2

of total

biomass

of B. balanoides

per 1 m2

biomass
per cent

g/m2

B. balanoides over 1

year

old

253

136-30

9 08

10,000

B. balanoides young-

■of-

the-year

12,493

1,049 00

69-93

—

Littorina rudis

2,413

223-30

14-90

—

L. palliata

253

86-90

5-79

—

Acmaea testudinalis

1-50

010

—

Gammarus spp.

162

1-60

012

—

Jaera marina

202

100

007

—

Idothea baltica

0-20

001

—

Total

15,799

1,499-80

10000

114 BIOLOGY OF THE SEAS OF THE U.S.S.R.

the number of specimens is no less than 85 to 90 per cent, whereas the total sum
of the biomass increases two to three times. The winter frosts are also destruc-
tive of the settled balanus ; their mortality during the winter may be 95 to 98
per cent.

Somewhat below the layer of highest balanus development in the second
and third zones of the middle horizon, 1-3 m above zero depth, lies the
Mytilus biocoenosis — Mytilus edulis. Mytilus attains its highest development
in places where there is little swell, on cliffs and rocks and on rising ground
on the silty sand beaches. On cliffs and rocks the amount of Mytilus reaches
7 to 10 thousand specimens with a biomass of 10 to 15 kg/m2, and sometimes
up to 13 thousand specimens with a biomass of 19 to 25 kg/m2. Among the
fuci the quantity of Mytilus is smaller (2-5 to 3 kg/m2) and they themselves
are smaller in size.

The Mytilus biocoenosis is characterized also by the presence of a large
amount of Nucella lapillus, Acmaea testudinalis, molluscs, hydroids and
bryozoans and, in the lowest levels in autumn, of asterids Asterias rubens and
gastropods Buccinum undatum {Table 45).

Table 45

Composition of Mytilus

Maximum/m2

Average/m2

biocoenosis on cliffs and
rocks of Murman coast

No. of

Biomass

No. of

Biomass

specimens

Mytilus edulis

13,000

25,000

8,200

4,806

Littorina rudis

800

170

360

95-4

L. palliata

900

385

240

L. littorea

300

130

Nucella lapillus

200

325

Acmaea testudinalis

200

7-2

Gammarus spp.

—

620

10-4

Jaera marina

—

360

1-9

Nemerteans (Lineus +

Amphiporus)

—

160

4-5

Total

10,120

5,127-4

On silty sand of the lower littoral zone dense Mytilus colonies are common
(the so-called Mytilus banks) ; they form a kind of defensive border to the
littoral. The total amount of Mytilus on such banks is somewhat smaller
than on the cliffs, but it also can reach 19 to 21-5 kg/m2 and may be more
than 10,000 specimens {Table 46). Thus here a considerable part of the
population is represented by the Macoma community.

The main gatherings of Mytilus, forming powerful biofilters, are situated
within the lower level of the littoral and in the upper (1 to 3 m) level of the
sublittoral.

THE BARENTS SEA

115

Table 46

Composition of Mytilus

biocoenosis on silty-
sand littoral of Murman

Average/m2

Maximum/m2

No. of Biomass

No. of

Biomass

coast

specimens g

specimens

Mytilus edulis
Macoma baltica

2,624 4,651-2
460 114-7

3,380

555

Littorina rudis

241 25-8

1,200

106

Arenicola marina

8-4 14-65

—

Gammarus sp. sp.

233 7-54

—

Priapulus caudatus

11-7 2-3

392

19-6

Halicryptus spinulosus
Lineus gesserensis
Amphiporus lacteus
Phyllodoce macidata
Actinia equina
Others

3-2 0-3
39 1-8

3 0-25
53 0-6

3-6 1-45
381 306

220

16-5

Total

3,718 4,823-65

The newly-born Mytilus settle in masses on conferva and green algae beds
right at the water's edge.

As has been shown by the quantitative estimate of the cliff and rock littoral
fauna of the great Kharlovsky Island (eastern Murman, Seven Islands) car-
ried out by N. Sokolova in 1941 (1957), the basic forms here are Balanus bah'
noides, Littorina rudis and Mytilus edulis which form 98-8 per cent of the total
biomass {Table 47).

The littoral fauna of Kharlovsky Island is considerably impoverished by
reason of the swell. This bionomic phylum lies between the first and the
second phyla of the classification given above.

Table 47. Mean biomasss in cross section of rock littoral off Kharlovsky Island, gjm

Form

No. of
specimens

Mean
biomass

Highest
biomass

Balanus balanoides

2,070

617-3

7,8000

Littorina rudis

896

94-63

4250

Mytilus edulis
Turbellaria

53
209

17-53
3-68

75-2
450

Acmaea testudinalis

312

320

Oligochaeta
Jaera albifrons

558
193

0-72
0131

7-84
0-98

Various

—

100

—

Total

3,983

73811

8,3860

116 BIOLOGY OF THE SEAS OF THE U.S.S.R.

The most dense population is found on the rocks and cliffs in the middle
horizons of the intertidal zone.

The succession of the maximum development of individual forms proceeds
in the order given in Table 48.

Table 48

Level above

zero depth

Form

Oligochaeta

2-68

Jaera albifrons

1*30

Littorina rudis

2-21

Acmaea testudinalis

010

Balanus balanoides

1-52

Membranipora sp.

010

Mytilus edulis

1-45

Nemertini g. sp.

010

Turbellaria

1-30

Like the western Murman coast the littoral is inhabited by a large number
of gammarids which serve as food to the numerous fish during low tide;
their numbers, however, have not been estimated so far, owing to the diffi-
culty of collecting them. When the stones under which they hide during
low tide are turned over they scatter with astonishing speed and agility.

The biomass is somewhat lower (647-34 g/m2) on the cliffs and rocks of
the littoral entirely exposed to the pounding of the waves on Kharlovsky
Island. As before, Mytilus edulis, Balanus balanoides and Littorina rudis are
preponderant, but the dominant role is transferred to Mytilus edulis (forming
about 67 per cent of the total biomass). In the inlets on the southern side
of this island which are protected from the action of the swell, the littoral
fauna biomass increases sharply from 1-3 to 9-3 kg/m2; this is contributed by
Mytilus edulis and Balanus balanoides.

Littorina rudis, which inhabits the upper horizon of the littoral, is found in
the supralittoral too. This is one of the most enduring forms of the intertidal
zone. It can exist for a long time without water and easily tolerates fresh
water. Littorina rudis prefers to inhabit cliffs and rocks. Balanus balanoides
also thrives in cliffs and rocks ; however, it does not rise beyond the limits
of the littoral. Downwards it extends farther than Littorina. The third and
most typical form of the intertidal zone sea mussel is usually found in the
shape of brushes or bunches and is adapted mainly to the lower part of the
littoral. The number of sea mussels decreases from west to east. According
to Wollenberg the amount of sea mussels on the mussel grounds of Helgo-
land reaches 75 kg/m2 ; in the western Murman coast it is only 30 to 40, and
in the eastern it does not exceed 8 to 9 kg/m2. The amount of it in the White
Sea is smaller.

Algal biomass increases in the littoral and the quantitative ratio of its
groups and forms changes as we move into the inlets of the eastern Murman
coast. T. Gurjeva (1948) provides demonstrative material derived from experi-
ments for the Dal'ne Zelentzkaya Guba {Table 49).

THE BARENTS SEA 117

Table 49

Location

In the depth
of the Guba

In the
Strait

At Cape
Vykhodnoy

Mean plant biomass
Mean animal biomass

18,818
1,702

14,672
778

7,029
2,604

Total biomass

21,520

14,450

9,633

T. Gurjeva notes that on sectors open to a heavy swell some forms of the
littoral fauna rise to higher levels, passing even into the supralittoral ; others,
on the contrary, disappear. Thus in places where the swell is violent, Asco-
phyllum nodosum disappears almost completely, and is replaced by Rhody-
menia palmata. It is interesting that the biomass is considerably increased by
sea mussel both in places of a strong swell and on protected sectors. T. Gur-
jeva assumes the existence of two biological races of sea mussel.

T. Matveeva gives some interesting data on the seasonal changes of the
population of the rock littoral. The growth of the young in the summer
months is first to be noted. It is natural that the highest fluctuations (two or
three times) are given by the algae. In autumn and winter the number of
Littorina decreases considerably ; only a few forms such as Asterias rubens
and Buccinum groenlandicum migrate into the sublittoral. According to
T. Matveeva's observations, by the end of the summer many gastropods,
Margarita helicina, Lacuna divaricata, Trophon truncatus, Natica clausa,
and the crab Hyas araneus migrate to the sublittoral. About the same time
Nudibranchiata (Doto coronata, Coryphella rufibranchialis, Dendronotus
frondbsus, Acatodoris pelosa) appear in large numbers. Many components of
the littoral fauna go under cover in winter, hiding under rocks or even bur-
rowing into the bottom, as for example Nucella lapillus, Rissoa aculeus and
others.

The winter weakening in the growth of laminaria and the change of condi-
tions bring about the migration of some inhabitants of the upper level of
the sublittoral into the deeper layers. For instance, the mollusc Lacuna vincta
(V. Kuznetzov, 1 948) is apt to perform such seasonal migrations.

In the soft soils of the intertidal zone of the western Murman, the burrow-
ing bivalves and annelid worms in various forms inhabit the sea-weeds cover-
ing the beach (Enteromorpha, Monostroma and others). Among the members
of onfauna* Iaera marina, Gammarus locusta, Littorina rudis, Skeneaplanorbis,
Hydrobia ulvae, Limapontia capitata, Mytilus edulis may always be found here.
The upper layer of the soil and the turf-like seaweed beds are inhabited by
innumerable minute Fabricia sabella and Manayunkia polaris and by large
Cardium edule. The polychaetes Pygospio elegans, Arenicola marina, Polydora
quadrilobata, Scoloplos armiger, Ophelia limacina, Travisiaforbesi, Terebellides
stromi, the hypherian Priapulus caudatus and Halicryptus spinulosus, and the

* Danish and English authors use the terms onfauna and infauna to distinguish the
fauna living on the bed and in the bed.

118

BIOLOGY OF THE SEAS OF THE U.S.S.R.

bivalves Macoma baltica, My a truncata and M. arenaria. The main biocoenosis
of the infauna Macoma, Arenicola, Phygospio, Polydora, Terebellides and
Scoloplos may form fairly individual biocoenotic groupings.

Large numbers of oligochaetes and especially enhytreides such as Pachy-
drillus lineatus, P. profudus, Enchytreus albidus and Marionina crassa some-
times swarm under the rocks and washed-up sea-weeds.

The sea mussel communities Fabricia, Manayunkia and Littorina rudis may
be distinguished among the onfauna.

The zonation in the distribution of the fauna of silty sand littoral on the
western Murman coast may be illustrated by Table 50 from the paper of
Gurjanova, Zachs and and Ushakov (1930).

Table 50

Horizon Zone

Form

Depth, m

I Masses of washed-up seaweed. A mass

larvae of fly and of Oligochaeta 14-1

II 1\ [Oligochaeta 2-4

2 Fabricia Oligochaeta, Macoma baltica, Entero-

morpha intestinalis, Urospora penicilli-
formis 2-1
Mytilus edulis, Halicryptus spimdosus,
Priapulus caudatits, Macoma baltica,
.Arenicola marina 1-3

1 „_._ (Macoma baltica, Scoloplos armiger,

| Pygospio elegans, Ophelia limacina,
{ Travisia for be si, Terebellides strbmi 0-5

Mya truncata, Axinus flexuosus, Macoma baltica, Chiri-

dota laevis, Echiurus pallasi 0

Fabricia
> sabella
+ Manayunkia

Pygospio
elegans

A census of the fauna of the soft bed soils of the Kola Inlet littoral reveals
a marked preponderance of a few forms (Tables 51 and 52).

The contamination of the littoral is easily endured by Macoma while
Littorina and Priapulus even increase their numbers in it.

Arenicola and Cardium have a negative reaction to contamination. The
qualitative distribution of the dominant forms of the littoral fauna is given
in Figs. 44 and 45. As shown by the isobenths given, the biomass increases
gradually towards the sea, and then falls again towards zero depth.

The total benthos biomass of this small section of the littoral, of about
25,000 m2, is about 13-6 tons, of which 4-5 tons is attributed to plants and 9T
tons to animals. The onfauna and infauna are represented about equally : 4-6
tons of onfauna and 4-5 tons of infauna. The average benthos biomass is
422 g/m2, that is approximately double that of the macrophytes.

During high tide a considerable amount of fish enters the littoral zone to
feed; this was pointed out by us for the Kola Tnlet as early as 1933. This

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120

BIOLOGY OF THE SEAS OF THE U.S.S.R.
Table 52

Microfauna

Mean no. of

Microfauna

Mean no. of

form

specimens

form

specimens

Fabricia sabella

116,950

Foraminifera

11,225

Manayunkia polar is
Pygospio elegans
Polychaeta varia

34,250

48,000

650

laera

Harpacticidae

Ostracoda

12,650

12,550

700

Oligochaeta
Nematoda

92,600
218,350

Hydracarina
Chironomidae

150
16,050

Turbellaria

1,250

Total 564,175

phenomenon was noted by H. Thamdrup (1935) and O. Linke (1939) for the
North Sea littoral.

The following method was used in our investigation of the importance of the
Murman littoral fauna as food. On a section of the littoral suitable by its con-
figuration and at high tide, the exit into the sea was completely closed by
seines. When the tide went down all the fish caught were counted, weighed
and the contents of their stomachs were analysed. These observations showed
that a fish is hungry when it enters the littoral and that it feeds there vigorously.
A large number of young cod, haddock, coalfish, flounder, goby and vivi-
parous blenny swims into the littoral. No less than 100 kg offish concentrated

200-300 g/m1
200-150 si™*
150-100 g/m2

'^3</00

-\>10000 Sim2 F={ <200 g/m2
ГГГП 10 00-10 000 g/m2 Г^~Л 0
ШП200-1000 g/m2

Fig. 44. Quantitative distribution of main components of fauna of
the littoral of one of the gubas of western Murman (g/m2). A Mytilus
edulis; В Macoma baltica (Zenkevitch, Zatzepin and Filatova, 1948).

THE BARENTS SEA

121

near high tide in the comparatively small section of the littoral investigated
(25,000 km2).

The most commonly consumed marine organisms (Fig. 46) on the littoral
were in order of declining significance: Gammaridae, Macoma baltica,
Littorina rudis, Mytilus edulis, Priapulus caudatus. Cod, coalfish, viviparous
blenny and goby feed there almost exclusively on gammarus with a small

MACOMA BALTICA DISTRIBUTION AT
LOW TIDE, ON WESTERN MURMAN PENINSULA

ARENICOLA MARINA DISTRIBUTION AT
LOW TIDE, ON WESTERN MURMAN PENINSULA

Fig. 45. Quantitative distribution of main components of

fauna of littoral of one of the gubas of western Murman

(g/m2) (Zenkevitch, Zatzepin and Filatova, 1948).

admixture of other animals ; haddock and dab retain here their true bentho-
phagous nature. Haddock eats a little of everything, even a fairly large amount
of seaweed. On the whole the flounder feeds on bivalves (see mussel and
Macoma) and on Gastropoda (Littorina) molluscs but seizes everything else
too, in passing. Its indices of repletion are fairly high (100 to 340).

A quantitative comparison of the mass of littoral organisms and the in-
testine contents (Fig. 46b) of the fish visiting the littoral shows that at every
flood-tide, i.e. twice a day, the fish consume about 003 per cent of the whole
fauna.

From corresponding investigations at low tide the amount of animal forms
eaten in a year is about 1-5 to 2-0 tons, i.e. about 17 per cent of the whole
population ; moreover, in the main, only certain groups are being eaten, so that

]22 BIOLOGY OF THE SEAS OF THE U.S.S.R.

the percentage of consumption for the groups consumed must be much

^Thl' littoral fauna grows poorer both in quality and numbers as we travel
east™ d along the Murman coast. This decline is accelerated by the detenora-
??on of the climatic conditions and the absence of deep bays and mlets well
protected against the tides on the eastern Murman coast. According to

109-3

□

COD
Gammarus

Mytilus

Littorina

Macoma

Polychaeta

Priapulus

Jaera

Chironomidae larvae

Seaweeds

Oth

PLEURONECTES
FLESUS

HERRING
1683

QUAB

Fig 46 A Food range of fish entering the littoral of the western Murman

forfeeding Mean repletion indices are shown by numerals above

drcles В ComparaJfood value between inhabitants of littoral and

fish entering the littoral (Zenkevitch, Zatzepin and Filatova, 1948).

THE BARENTS SEA 123

E. Gurjanova's data (1928) farther east in the Cheshskaya Guba, some littoral
forms such as Balanus balanoides, Mytilus edulis, Acmaeo testudinalis, Littorina
rudis, Arenicola marina and Macoma baltica are retained in places where there
are rocks sparsely covered by seaweed.

In the southern bays of Novaya Zemlya (E. Gurjanova and P. Ushakov,
1928) Mytilus edulis, Littorina rudis, Rissoa aculeus, Margarita helicina
v. major, Gammarus locusta and others may still be found on the littoral. At
the Matochkin Shar (P. Ushakov, 1931) and farther northwards the littoral
fauna dwindles almost to nothing. It is represented only by Gammarus locusta
Pseudalibrotus littoralis and by the rare and small-sized Mytilus edulis. In
some places on the eastern coast of Spitsbergen colonies of small-sized
Balanus balanoides have been found on the rocks.

Sublittoral fauna. A qualitative biocoenotic description of the sublittoral
fauna was given by K. Derjugin in his monograph on the Kola Inlet (1915),
and later by his pupil E. F. Gurjanova for Cheshskaya Guba (1929) and by
E. F. Gurjanova and P. Ushakov (1928, 1931) for the shores on Novaya
Zemlya (Chernaya Guba and Matochkin Shar). Finally the benthos along the
Kola meridian has been under constant, careful investigation (K. Derjugin,
N. Tanassijchuk and others). In 1924 large-scale quantitative fauna surveys
were begun by the State Institute of Oceanography (Zenkevitch, Brotzkaya,
Idelson, Leibson, Filatova and Zatzepin) (1924 to 1939).

As depth increases and biotopic variety correspondingly decreases, so also
the range of animal and vegetable groups is reduced. Thus E. F. Gurjanova,
I. Zachs and P. Ushakov (1925 to 1930) have distinguished on a comparatively
small area of the Murman coast littoral more than fifteen basic biocoenoses.
About the same amount of biocoenoses was found by K. Derjugin (1915) on
the Kola Inlet sublittoral, on an area of about 1 30 km2. Finally no more than
ten more basic benthic groups were noted by the quantitative surveys on the
huge bottom area of the open parts of the Barents Sea. The largest variety of
species is adapted to the middle and lower levels of the sublittoral. As has
been mentioned above, Derjugin introduced also a pseudo-abyssal zone, at
depths below 250 m, in his description of the Kola Inlet fauna. There are no
plants at all here, while a considerable number of forms with fairly sharply
expressed abyssal characteristics (loss of pigmentation, extended extremities,
adjustments for inhabiting very soft floors, etc.) are accumulated.

For several years (1903, 1908, 1909) K. Derjugin studied in great detail at
the Murman Biological Station (Fig. 47) the distribution of the Kola bottom
fauna. As a result of his investigation a fundamental work appeared, The Kola
Inlet Fauna and the Conditions of Its Existence (1915). It still retains its
scientific importance as one of the greatest surveys of this type in world
literature.

Kola Inlet (Fig. 48), the largest inlet on the Murman coast, extends from
north to south for about 55 km and has a mouth about 6 km wide. It is
a typical fjord in its contour; it has great depths (down to 380 m) and,
unlike the nearby Motovksy Bay, it is separated from the open sea by a sub-
marine barrier with depths not exceeding 1 50 m. As a result the conditions of

124 BIOLOGY OF THE SEAS OF THE U.S.S.R.

the Kola Inlet are on the whole more severe than those of the well-washed,
comparatively shallow Motovsky Bay.

The northern part of the Kola Inlet has depths down to 350 to 380 m, the
middle part down to 200 m and the southern part has depths mostly less than
50 m. The precipitous rocky, granite shores (to 150 m) frequently lead under
water into steep bottom slopes and the type of environment of submarine
cliffs is very prominent indeed.

Almost all the deep parts of the bay are filled with ooze, sandy bottoms
appear only in the southern and middle parts of it. Rocky floors strewn with
large boulders are widely distributed over the whole inlet.

Everywhere, especially in the north of the inlet, there are extensive beds of
several species of calcareous algae or of the Lithothamnion genus (red algae
group) which are found in individual patches. Branching Lithothamnion

Fig. 47. Murmansk Biological Station of the Petersburg Society of Naturalists

(1914).

grows only in places where there are rapid currents, on steep cliff slopes, on
the cliff barriers at the mouth of the bay, and in narrow channels.

The considerable north to south extent of the Kola Inlet, the inflow of two
large rivers — Kola and Tuloma — into its southern part, and additionally the
heating effect of the warm Atlantic waters (Ruppin branch) flowing along the
Murman coast make the Kola waters heterogeneous both in their salinity and
temperature.

In summer the temperature in the northern part of the inlet is 5° to 13-5°
on the surface, and at a depth of 300 m it is only 1-3° to 2-0°. The temperature
falls rapidly from the surface to a depth of 50 to 100 m (down to the thermo-
cline layer) ; at greater depths it changes but little.

A homothermic state (0° to Г) is established by the end of the coldest
season of the year. The ' hydrological summer' comes to the surface layers of
Kola Inlet waters in July and August and the winter in January and February.

In summer there is a characteristic fall of salinity in the surface layer of the
Kola Inlet waters. Even in the northern part of the inlet up to 8-3%0 salinity
has been observed. However, even at a depth of 5 m salinity is never below
30%0; it increases still more lower down (up to 30 to 34-5%0), and its seasonal
changes in the deep zones are negligible. In winter the surface waters also

THE BARENTS SEA

125

attain 30 to 34%0 salinity. In spring, during the melting of the large masses of
snow which have fallen through the winter, the amount of fresh water enter-
ing the inlet increases considerably and the surface layer is diluted even more.
In summer, in the middle of the southern part of the inlet, the salinity in the
upper surface layer fluctuates from zero to 16-5%0, at a depth of 3 m from
2 to 31%0, at 5 m from 5 to 33%0, and at greater depths fluctuation is still
further increased.

S] SANDY SILT
GZ3SAND. SILTY SAND
■■CLIFFS
E3LITHOTHAMNION

Fig. 48. Chart of Kola Inlet with (A) depths (fathoms) and (B) composition of sea-
bed (Derjugin).

126 BIOLOGY OF THE SEAS OF THE U.S.S.R.

' The general picture of the Kola Inlet obtained from topographical, hydro-
graphic and geological surveys, is very much of the same type as that obtained
for the neighbouring Norwegian fjords ', writes Derjugin. ' The side parts of the
main fjord are usually connected with the main straits, cut through the ancient
moraines. There is always a main deep channel with an ooze bed, with ravines
or shores at its sides ; the side pans are determined by submarine barriers.'

K. Derjugin has distinguished five main biotopes (facies) in the Kola Inlet
sublittoral, namely cliffs and rocks, sand, shell, ooze and the branching
Lithothamnion. The most luxuriant sublittoral fauna is adapted to the lower
horizons (below 60 to 70 m). In the upper horizons abundant and varied
fauna is found only in the weed bed of the branching Lithothamnion and in
the silty sand and mud at shallow depths.

As for the cliff and rock facies in the lower horizons of the sublittoral, there
is a luxuriant group of sponges, hydroids and acidian Ascidia obliqua on the
cliffs and a rich fauna on the rocks and pebbles.

The Porifera and hydroids biocoenoses (mainly at a depth of 90 to 180 m)
are first of all characterized by various representatives of Spongia, including
Geodia baretti, Stryhhanus fortis, Polymastia puberrima, Tethya lyncurium,
Tentorium semisuberites, Phavellia bowerbanki and others. Then follow the
numerous hydroids : Lafosea gracillima, L.grandis, L. f mucosa, Diphasia abie-
tina, D. fallax, Grammaria abietina, Thuiaria lonchitis, Halecium polytheca
and others. As for bryozoans, they include: Pseudoflustra hincksi, Smittia
minuscula, Crisia eburneo-denticulata, Cr. arctica, Cellepora nodulosa, Cel.
nordgaardi, Cel. ventricosa, Retepora cellulosa, R. elongata, Menipea tornata v.
gracilis, Caberea ellisi, Bugula murmanica, Hornera lichenoides, Flustra mem-
branaceo-truncata, Idmonea atlantica, and others. The four species of brachio-
pods known in the Barents Sea are found therein large numbers : Rhychonella
psittacea, Terebratulina caput serpentis, Terebratella spitzbergensis, Waldheimia
cranium; echinoderms are represented most abundantly by Heliometra
quadrata, Ophiocantha bidentata and Gorgonocephalus eucnemis, while the
crustaceans include Pandalus borealis and Hippolyte polaris, and the pycno-
gonids : Chaetonymphon spinosum, Nymphon stromi and Pycnogonum littorale.
The polychaetes, molluscs and salps are only poorly represented.

In the Phallusia obliqua community (mostly at 60 to 100 m) besides the mass
swarmings of ascidians {Asc. obliqua as well as Asc. prunum, Pyura arctica,
Tethium loveni, Amaroucium mutabile and others) a multitude of Porifera is
found, mainly Grantia arctica, Gr. pennigera, Tethya lyncurium, and some
species of Leucosolenia (L. nanseni, L. coriacea, L. blanca and others). The
various bryozoans are represented most abundantly (mainly the genera
Flustra, Bugula, Caberea, Defrancia, Porella). Among the hydroids stand out
Tubularia larynx, of the polychaetes Glycera capitata, Nereis pelagica, Thele-
pus cincinnatus, Leodice norvegica, Syllis fabricii, S. armillaris, Nephthys
ciliata and others ; among the Gephyrea, Phascolosoma margaritaceum, Ph.
eremita and Phascolium strombi, the echinoderms Asterias rubens, Cribrella
sanguinolenta, Ophipholis aculeata, Ophiocantha bidentata, Ophiura sarsi and
others. The crustaceans are represented by Pandalus borealis, some species of
Spirontocaris and some other Decapoda. The molluscs are also varied and

THE BARENTS SEA 127

numerous, first of all Onchidiopsis glacialis, Trochus occidentalis, some
species of Velutina ( V. haliotoides, V. lanigera, Undata g. expansa, Columella
rosacea, Marsenina micromphald) and others.

On sand fades a more or less abundant life on the sublittoral develops only
with silting. Life is very poor on large-grain sand and gravel. Only the so-called
Dentalium sand (40 to 69 m), consisting mainly of finely ground mollusc
shells, is abundantly populated by a rich fauna of molluscs (up to 60 species)
Dentalium entails and species of the genera Bela, Philine, Solariella, Cylichna,
Astarte, Cardium, Mactra and others. Other groups of animals are rather
scantily represented here.

An abundant fauna of polychaetes, echinoderms and molluscs grows on
silty sands at shallow depths (4 to 1 5 m). Among the first-mentioned the most
frequent here are Ophelia limacina, Nephthys ciliata, Harmothoe imbricata,
Nychia cirrosa and Travisia forbesi ; of secondary importance are Chiridota
laevis, Strongylocentrotus droebachiensis and Asterias rubens. The molluscs
most frequently found include Nucula tenuis, Cardium ciliatum, Leda pernula,
Astarte banksi, A. borealis and Pec ten islanidcus, and of the crustaceans
Ну as araneus v. hoeki, Eupagurus pubescens and others.

The fauna of the facies of large-size shell gravel at shallow depths (20 to
30 m) is not typical and on the whole very poor. Much deeper (50 to 140 m)
finer coquina accumulate, giving shelter to an extremely abundant fauna,
consisting mainly of sponges, polychaetes, bryozoans, echinoderms and crusta-
ceans (amphipods). The Porifera are especially well represented here (up to
26 species) : in the first place — Phavellia bowerbanki, Geodia baretti, Grayella
pyrula, Trichostemma hemisphaericum, Tentorium semisuberites, Tedania
suctoria, Tethya lyncurium, and others. Among the polychaetes Onuphis
conchylega, Glycera capitata, Maldane sarsi, Nicomache lumbricalis, Nereis
pelagica, Leodice norvegica, Protula media, Placostegus tridentatus, Flabelligera
affinis, Filigrana implexa, Lumbrinereis fragilis, Thelepus cincinnatus, Sabella
fabricii, Nephthis ciliata, Brada granulosa and others should be noted.

Of the Sipunculoidea there are many Phascolion strombi. The bryozoans are
represented here by Flustra membranaceo-truncata, Fl. securifrons, some
species of Retepora, Idmonea atlantica, Menipea ternata v. gracilis, Bugula
murrayana, and others.

Of the echinoderms the most frequent here are young Heliometra quadrata,
and Cribrella sanguinolenta, Pteraster pulvillus, Solaster endeca, Ophiocantha
bidentata, Ophiopholis aculeata, Ophiura sarsi, Strongylocentrotus droe-
bachiensis, and others. Haploops tubicola, Socarnes vahlii, Pardalisca cuspi-
data and others are the characteristic amphipods. Other groups are scarcer
on coquina.

The fauna of the facies is both peculiar and rich. The clayey-sandy mud of
shallow depths (12 to 60 m) is inhabited by numerous burrowing fauna of
polychaetes, holothurians, molluscs, Cumacea and amphipods. The main
polychaetes are Pectinaria hyperborea, Nephthys ciliata, Brada villosa and
Scoloplos armiger. There are huge numbers of Myriotrochus rinki and
Chiridota laevis among Holothuriae. As for the other echinoderms there are
many Ophiura sarsi and Strongylocentratus droebachiensis.

128 BIOLOGY OF THE SEAS OF THE U.S.S.R.

The most characteristic molluscs are Joldia hyperborea, Cardium groen-
landicum, C. ciliatum, Nucula tenuis, Axinus flexuosus, Leda pemula, Mya
truncata, Macoma calcarea. Diastylis rathkei and amphipod Byblis gaimardi
are very numerous here.

The fauna of the sublittoral sandy silt and of the pseudo-abyssal, middle
and great depths (60 to 360 m) is especially rich. The bottom fauna of the
so-called' trawling hole ' with its typical Forsimmitera. Hyperammina subnodosa,
polychaetes Onuphis conchylega, Nicomache lumbricalis, Maldane sarsi,
Pectinaria hyperborea, Polycirrus albicans, Gephyrea Phascolium strombi,
bryozoans Defrancia lucernaria, Alcyonidium gelatinosum, echinoderms
Ctenodiscus crispatus, Asterias lincki, Ophiura sarsi, crustaceans Calathura
carinata, has been thoroughly studied. Among the molluscs Astarte crenata
and Area glacialis are found here in large numbers.

At the greatest depths, down to 400 m (pseudo-abyssal), certain Porifera
are added to this community, as for instance Myxilla brunnea, brachiopods
Terebratulina and Rhynchonella, the deep-sea echinoderm Rhegaster tumidus,
the crustacean Pontophilus norvegicus, and the molluscs Buccinum hydrophanum
and Pecten groenlandicus.

There is an extremely original and rich life in the facies of the branched
Lithothamnion (calcareous algae of the Rhodophyta) forming abundant
clusters at places of strong water-circulation at depths of 10 to 40 m. Owing
to the large number of its branches and to the presence of voida (similar to
coral reefs) the Lithothamnion algae present exceptional facilities for the
multiplying of specific fauna, partly hidden inside the Lithothamnion, partly
connected with its surface. Inside the Lithothamnion thrive innumerable
Lucernaria (Lucernaria quadricornis), nemerteans (Amphiporus, Cerebratulus)
polychaetes (Nereis, Glycera and others), Gephyrea (Phascolosoma eremita,
Ph. margaritaceum), Ophiuroidea (Ophiopholis aculeata), holothurians
(Phyllophorus pellucidus), young sea urchins, asterids and molluscs (Saxicava
arctica, Modiola modiolus). Ascidians (Ciona intestinalis, Pyura aurantium, P.
arctica, Sarcobotriloides aureum and others), actinium (Metridia dianthus),
polychaetes (Chone infundibuliformis, Leaena abranchiata, Myxicola steen-
strupi and Sabella fabricii) are attached to the surface of Lithothamnion.
Numerous echinoderms (Ophiopholis aculeata, Cucumaria frondosa) and
molluscs (Acmaea virginea, Margarita groenlandica, Chiton ruber, Ch.
marmoreus, Ch. albus, Velutina haliotoides, Anomia squamula, Pecten islandi-
cus) crawl over the Lithothamnion. The crustaceans (especially some species
of Spirontocaris — S. turgida, S. gaimardi, S. spinus and S. polaris), Sclero-
crangon boreas, Eupagurus pubescens, Ну as araneus are also numerous on the
Lithothamnion.

Almost 30 years after K. Derjugin's explorations, V. Zatzepin (1962)
carried out careful investigations on the quantitative distribution of bottom
fauna (1934 to 1936). First of all this worker remarks that the species compo-
sition and the distribution of the bottom biocoenoses are on the whole the
same as those given by K. Derjugin. The change in the species composition
can be easily explained first of all by the rise of temperature, which therefore
affected mostly the cliffs, rocks and sandy floors of the northern part of the

THE BARENTS SEA 129

bay (in particular the mass population of the urchin Brisaster fragilis) and the
southern part of the bay, from which a number of cold-water forms (for
instance Serripes groenlandicus) have disappeared.

With a wide variation of species the Kola Inlet fauna has only 20 to 30
species of polychaetes, bivalves, echinoderms and Gephyrea composing the
basic mass of its population.

As in the open parts of the Barents Sea polychaetes are preponderant at
great depths and on softer bottoms and the bivalves at lesser depths and on
harder floors.

The communities of the deep ooze and sand-ooze bottoms are very similar
in their composition to those of the adjacent open parts of the Barents Sea
(group II, see below).

In the Motovsky Bay, owing to its wide and free connection with the open
sea, before it joins the bight of the Kola Inlet and in its northern part, the
communities Cyprina, Macoma and Mactra, which inhabit warmer water,
are strongly developed ; a large number of warm- water boreal species are
found here. The cold-water species are concentrated in the south of the Inlet.

Up to 80 per cent of the deep part of the Kola Inlet (Fig. 49) is occupied by
a typical Barents Sea biocoenosis with a preponderance of Spiochaetopterus,
Maldane, Astarte, Ctenodiscus, Phascolosoma and Strongylocentrotus (see
below).

Zatzepin has distinguished in the deep part of the Kola Inlet, from north
to south, five variations of the above-mentioned biocoenoses ; for four of them
data are given in Table 53, and their distribution is shown in Fig. 49. These
four variations are distinguished by the preponderance of individual forms in
the biocoenoses components, but the basic composition remains unaltered.
Towards the south the dominant forms change. At first we find Astarte
crenata and Maldane sarsi, then Onuphis conchilega, Strongylocentrotus droe-
bachiensis, Nicomache lumbricalis, and finally in the southern part of the Inlet
Cardium ciliatum and Cyprina islandica. In the shallow holes of the Kola
Inlet another variant with the leading forms of Cardium ciliatum, Macoma
calcarea and Maldane sarsi is formed on sandy silt. Moreover of the char-
acteristic forms widely distributed throughout the whole Barents Sea there
are worms Spiochaetopterus typicus, Myriochele oculata, Nephthys ciliata,
Lumbriconereis fragilis, Phascolosoma margaritaceum, Phascolion strombi,
Rhodine gracilior, molluscs Portlandia lenticula, P. intermedia, Area glacialis,
Pecten islandicus, Yoldia hyperborea, Nucula tenuis, echinoderms Ctenodiscus
crispatus, Ophiura sarsi, with Ophiopholis aculeata and Terebratulina septen-
trionalis among the branchiopods. The sandy bed of the southern part of the
bay is inhabited by the biocoenoses Cardium ciliatum and Cyprina islandica.
Among the characteristic forms the polychaetes Scoloplos armiger, Pecti-
naria hyperborea, Myriochele oculata and Lumbriconereis fragilis, the molluscs
Yoldia hyperborea, Macoma calcarea and Axinus flexuosus and the echino-
derms Ctenodiscus crispatus and Myriotrochus rincki should be mentioned.

With all its qualitative changes within the limits of the two communities
considered, the biomass is not large (Fig. 49a) ; it varies from 25 to 200 g/m3,
rarely reaching this upper limit.

Fig. 49. Chart of Kola Inlet showing distribution of total benthos biomass and
main bottom biocoenoses (Zatzepin): A Biomass: 7 25; 2 25 to 50; 5 50 to 100;

4 100 to 150; 5 150 g/m2 and over. В Bottom biocoenoses: / Astarte-Maldane ;
2 Porifera-Brachiopoda-Bryozoa ; 3 Ascidia obliqua ; 4 Maldane-Саг^шш ciliatum ;

5 Maldane-Astarte ; 6 Astarte-Onuphis ; 7 Strongylocentrotus-Nicomache ; 8

Cardium-Scolopolos-Pectinaria.

THE

BARENTS SEA
Table 53

131

Depth of

Mean

Biomass, per cent

No of

total

rence

species

biomass

Bottom

Seston

g/m3

Infauna

Epifauna feeders

feeders

(1) Variations of the basic

communities of the Kola

Guba depths on soft bed :

Astarte-Maldane

150

83-6

16 89

Maldane-Astarte

200

48-9

12 90

Astarte-Onuphis

80-200

101

79-7

29 76

Strongylocentrotus-

Astarte-Nicomache

20-50

112

162-3

55 75

(2) Cardium-Cyprina commu-

nity

25-60

77-2

13 89

V. Zatzepin (1939) compared the consecutive changes of the total biomass
of the epi- and in-fauna of the depths for a stretch of the Kola Inlet 50 km long
and 1£ to 4| km wide. On the two submarine bars of the outer part of the
Inlet the epifauna is fed on the dying plankton and the organic detritus, and
is developed abundantly. In the hollow between the bars the infauna is pre-
ponderant, mainly detritus-eaters, living on detritus settled on the floor.
Farther into the Inlet the infauna increases as well as the epifauna because of
the presence of partly suspended detritus brought out by the rivers.

Changes in the individual groups of the bottom population from north to
south are given in Table 53. The benthos of the cliff and rocky floor of the
sublittoral of the northern part of the Kola Inlet is different in its character.

Table 54

Community

Ratio of component groups

in biomass,

per cent

Lamelli-

Echino-

Sipuncu-

Brachio-

branchiata

Polychaeta dermata

loidea

poda

Astarte-Maldane

Variation 1

56-3

24-6 6-6

7-12

1-45

Variation 2

19-4

46-1 20-3

7-4

3-6

Variation 3

23-4

45-6 14-5

10-2

2-8

Variation 4

42-8

13-5 36-8

4-3

—

Cardium-Cyprina

67-0

14-6 160

—

Epifauna is preponderant and the total biomass is much higher. Several most
typical communities may be distinguished there (Fig. 49a and в).

First of all there is the Porifera-Brachiopoda-Bryozoa community very
similar to the one so widely distributed in the open southwestern parts of the
Barents Sea shores and with the same main organisms (see below).

In separate patches among the above community, and often on more
shallow sites, the peculiar communities of the Salpa Ascidia obliqua (50 to

132

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Fig. 50. Murman Biological Station of the Academy of Sciences of the u.s.s.r. in the
Dal'naya Zelenetskaya Guba on the Murman Peninsula coast (1938).

100 m) and the population of the branched Lithothamnion are found every-
where. Both these communities are peculiar to places with vigorous water
movement ; the polychaetes Thelepus cincinnatus, Eunice norvegica, the mol-
luscs Astarte elliptica, A. crenata, A. sulcata, Cardium fasciatum, C. elegantu-
lum, bryozoans of the genera Retepora, Flustra and Defrancia, Porifera of the
genera Tethya and Tenthorium, and Ophiopholis aculeata are peculiar to the
first one. This community includes quite a number of warm-water forms.

Among the population of the branched Lithothamnion the following are of
significance as regards their numbers — of the echinoderms Ophiopholis acu-
leata, Strongylocentrotus droebachiensis, Cucumaria frondosa, of the molluscs
Pecten islandicus, Saxicava arctica, Modiola modiolus, of the tunicates Cyona
intestinalis, Руша aurantium, of the crustaceans Balanus porcatus and Eupa-
gurus pubescens.

The basic quantitative indices for the three above-mentioned communities
are given in Tables 55 and 56.

When moving east along the Murman coast and north along the Novaya
Zemlya coast the fauna suffers considerable impoverishment ; a large number
of boreal and sub-Arctic forms disappear, and a series of high Arctic species are

Table 55

Biomass, per cent

Community

Depth of Mean

occur- No. of total •

rence species biomass Infauna Epifauna Bottom Seston

m g/m2 feeders feeders

Porifera-Brachiopoda-Bryozoa 1 00-200
Ascidia obliqua 50-100
Population of branched Litho-
thamnion 5-75

131
93

170

524

321

23-3
4-3

76-7
95-7

100

41-3

7-4

54-3
91-1

THE

BARENTS SEA

Table 56

Ratio of component groups

in biomass, per cent

Communities

i 03

га

3
E

СЗ

ГЗ

-о
о
о.

<я

<л

"О

_ JS

4> CJ

«2

с_

E c

>-.

о.

'С

>-,

« 2

J л

Он

Porifera-Brachipoda-Bryozoa

11-8

10-5

20-8

6-1

4-5

36-9

2-4

2-6

Ascidia obliqua

4-1

4-2

0-4

2-8

—

• —

85-1

Population of branched Lithothamnion

7-6

—

75-9

—

1-6

5-6

added instead. A good illustration of this can be found in the papers of
E. Gurjanova and P. Ushakov on the fauna of Chernaya Guba in the Novaya
Zemlya (1928), of E. Gurjanova on the fauna of the Cheshskaya Guba (1929)
and of P. Ushakov on the Matochkin Shar (1931).

The Chernaya Guba fauna has a sharply pronounced Arctic character, but
side by side with it a whole series of boreal and warm-water forms have been
discovered. These latter include Acmaea rubella, Hydrobia ulrae, Rissoa acu-
leus, Littorina rudis, Cuthona distans, Corophium conelli and some others. Of
the Arctic forms the most characteristic are: among the molluscs Venus
fluctuosa, Pandora glacialis, among the polychaetes Harmothoe impar,
Axionice flexuosa, Castalia arctica, among the crustaceans Acanthostepheia
ma/mgreni, Gammar acanthus loricatus, Orchomene tschernyschevi, Socarnes
bidenticulateus.

Table 57 (p. 145) gives the composition and distribution of the fauna of the
Chernaya Guba in its main sectors.

Some warmth-loving forms can find conditions suitable for their existence
in some other parts of the Barents Sea. Cheshskaya Guba, for instance, is one
of them. In winter, it is true, Cheshskaya Guba undergoes long and severe
spells of cold weather, but in the summer the whole column of water is heated,
sometimes to 14° at a depth of 10 to 15 m, and to 5° at a depth of 38 m.
Evidently a number of forms can endure severe winter conditions, if in
summer time a temperature high enough for breeding is attained at least
for a short period. Among them we may point out Buccinium undatum,
Neptunea despecta typica, Acmaea testudinalis, Lacuna divarivata, Littorina
palliata, Modiola modiolus, Mytilus edulis, Eumida sanguinea, Castalia
punctata, Syllis armillaris, Balanus crenatus Apherusa tridentata, and Erialus
gaimardi gaimardi.

Some of these forms have possibly already broken away from their basic
habitat and can be considered as warm-water relicts in the Cheshskaya Guba.

Similar phenomena are known for the inhabitants of the White Sea.

E. Gurjanova's indication (1929) of a whole series of high Arctic forms which
do not visit the Cheshskaya Guba (Acanthostepheia malmgreni, Synidothea
bicuspida, Anonyx nugax, Neptunea despecta v. borealis, Buccinium glaciate,

134 BIOLOGY OF THE SEAS OF THE U.S.S.R.

B. ciliatum, Bela morchi, Dendronotus frondosus v. dalli and some others) is
also of great interest.

Sharp seasonal fluctuations of temperature in the Cheshskaya Guba, its
severe winter, and comparatively warm summer have led to the development
mainly of a eurytopic stable fauna.

Some peculiarities of benthos distribution. With the changes of the Barents
Sea conditions from west to east, a vertical displacement of either the zones
or individual forms is observed in its fauna range. In the White Sea the
boundaries of the vertical zones rise upwards considerably as compared with
those of the Barents Sea.

A number of typical Murman littoral forms in the eastern part of the Barents
Sea and off the coast of Novaya Zemlya go down into the upper levels of the
sublittoral. This is caused by severe climatic conditions, and chiefly by the
grinding effect of ice in winter. This was noted by a series of workers, begin-
ning with Stuxberg (1882, 1887). Thus in the Cheshskaya Guba Mytilus edulis
and Balanus crenatus form thick growths at depths down to 30 m. The poly-
chaete Fabricia sabella, so typical for the littoral, sinks down to a depth of 5
to 10 m in Belushja Guba. On the other hand, many forms typical of the sub-
littoral lower horizons move upwards in the eastern parts of the Sea. Ushakov,
for instance, caught (1931) in Matochkin Shar at a depth of 3 to 7 m such
forms as Yoldia hyper borea, Leda pernula, Pec ten groenlandicus, Pandora
glacialis, different species of Astarte and other forms which thrive at great
depths in the western parts of the Sea. The asterid Asterias panopla and the
mollusc Cardium ciliatum become also comparatively shallow-water forms in
the east. According to Stuxberg Gammarus locusta lives in the Kara Sea at a
depth of 6 m and Ophiura sarsi, Ophiocten sericeum and Asterias panopla
which in the Kola Inlet live in deep water are here encountered at 10 to 20 m.
This sinking down of the littoral fauna in deep inlets is due not only to the
above-mentioned cause, but may also be the consequence of a considerable
loss of salinity in the surface waters. The rise of the boundaries of the other
zones is controlled in the east by the low temperature of the surface layers
of the Sea, which allows the rise of cold-water bathypelagic fauna to higher
levels. This explains the migration of the many Barents Sea forms into the
colder deeper layers as they travel towards the more southerly parts of the
Atlantic. But observers have also noted the withdrawal to considerable
depths of the sublittoral of a number of typical littoral forms of the north-
western European shores, as they travelled into the Barents Sea {Pycnogonum
littorale, some species of Chiton, Margarita helicina, M. groenlandica, Anomia
squamula and others). K. Derjugin was inclined to explain this, as yet incom-
prehensible, phenomenon by biocoenotic correlation.

The warm-water fauna travelling from the west differs from that of the cold
local waters of the Barents Sea. It has been shown by K. Derjugin his colla-
borators that the distribution of a number of forms in the warm and cold
waters can be established by collecting the bottom fauna along the Kola
meridian.

The dominant forms in the warm waters consist of the coral polyps

THE BARENTS SEA 135

Virgularia mirabilis and Planularia arctica, the polychaetes Placostegus tri-
dentatus and Potamilla neglecta, the urchins Echinus esculentus and Brisaster
fragilis, the asterids Psilaster andromeda, the cirripiedia Scalpellum strbmi,
the amphipods Menigrates obtusifrons, Harpinia antennaria, Erichthonius
brasiliensis, Pantopods Pycnogonum littorale, the molluscs Dentalium entale,
Poromya gramdata, Astarte sulcata, Scaphander punctostriatus, Triops laser,
and others. The following forms are just as characteristic of the cold waters ;
the bottom medusa Ptichogastria polaris, the polychaete Glurhanostomum
pallescens, the asterid Asterias lincki, the brittle star Stegophiura nodosa, the
amphipods Stegocephalopsis ampulla, Acanthostepheia malmgreni, Lepido-
pecrewn umbo, Rozinante fragilis, Socarnes bidenticulatus, Pseudalibrotes
nanseni, Aegina echinata, the mollusc Acanthodoris sibirica and others. Some-
what earlier N. M. Knipovitch (1906) established a similar distribution of
bottom-fish of the genera Lycodes and Lycenchelys ; some of them are adapted
to cold waters, some to warm. Linko (1907, 1913) gives a very similar picture
of some plankton forms Halosphaera, Rhizosolenia, Ceratium, Globigerina
and especially the amphipods Hyperia and Euphausiaceae.

Later M. Virketis (1928) and Kisselev (1928) have also shown that a
number of warm-water forms of the zoo- and phyto-plankton are adapted to
the streams of Atlantic waters. Among the vegetable forms the following
should be noted : Rluzosolenia styliformis, Rh. shrubsolei, Rh. faerocensis, Rh.
alata, Corethron criophilum, Ceratium tripos, Thalassiosira decipiens, Chaeto-
ceras constrictum, Ch. curvisetum, Coscinodiscus centralis, Nitzschia delicatis-
sima and others, and among animal forms : Euchaeta norvegica, Microcalanus
pusillus, Temora longicornicus, Metridia lucens, Oithona plumifera v. atlantica
and others.

General distribution of benthos biomass in the open parts of the Sea. The
bottom of the Barents Sea is not homogeneous as regards the benthos biomass,
both of the total benthos and of its separate component groups (molluscs,
worms, echinoderms) (Figs. 51 and 52).

Areas with particularly small biomass (10 to 25 g/m2) stretch in the Barents
Sea from the west to 30° E longitude, extending farther in two tongues —
one southeastern and one northeastern ; they also occupy a large area of the
depths between the northern part of Novaya Zemlya and Franz Joseph Land ;
furthermore the biomass here is still lower than in the western part of the Sea.
In contrast to these impoverished areas there are some areas with a most
abundant bottom fauna. Five such areas with accumulations of organic
matter as living organisms may be pointed out :

(1) The southeastern slope of the Spitsbergen bank— shallow with biomass
up to 1 kg/m2 or more.

(2) Separate patches with an increased biomass (300 to 500 g/m2 or more) on
the shores of the northern part of Norway (mostly epifauna).

(3) The central part of the Barents Sea with a biomass of up to 150 g/m2.
{4) The Kanin-Kolguev-Pechora shallow with an exceptionally dense patch

of benthos near Kanin Nos (up to 300 g/m2).

136

BIOLOGY OF THE SEAS OF THE U.S.S.R.

(5) Novaya Zemlya shallow with separate patches of biomass exceeding
500 g/m2.

In many parts of the shores of the Murman Peninsula, Novaya Zemlya and
the Arctic archipelagoes, in inlets, gubas and fjords patches with very much

Fig. 51. Distribution of benthos biomass of Barents Sea (g/m2) (Brotzkaya and
Zenkevitch with additions by Filatova).

increased biomass are found. Thus in the inner parts of Sturfjord the average
biomass reaches 500 g/m2, in Mashigina Guba it exceeds 3 kg/m2, and
on some patches in the Kola Inlet and Motovsky Bay it exceeds 200 g/m2.
In general a certain increase of the biomass is observed in shallow regions,
partly on the shores, partly at the edges of banks. Moreover the benthos biomass
of the large and deep bays like the Kola Inlet, Motovsky Bay and Cheshskaya
Inlet is smaller in their central parts when the aeration of the bottom layer is

THE BARENTS SEA

137

impeded. Thus in the main area of the Motovsky Bay and Kola Inlet the
biomass is 25 to 50 g/m2, whereas at their entrances it is 50 to 100 g/m2 or
more. On average, as shown by M. Idelson (1934) for the whole benthos of the
Barents Sea the change of biomass is as follows :

At depths of 0 to 100 m
At depths of 100 to 200 m
At depths of 200 to 300 m
At depths of 300 to 400 m

311 g/m2

168 g/m2

93 g/m2

48 g/m2

However, since as a rule any increase of depth is associated with a decrease
of food supplies and a progressive worsening of air conditions in the bottom
layer of water, it is difficult to say whether the fall of biomass can be explained
by the increase of depth alone. On the contrary it is possible to see from some
separate cross sections of the Barents Sea that the inverse dependence of the
change of biomass on depth is only partly valid. The degree of upwelling of
water is, as was pointed out above, a much more important factor in the dis-
tribution of the total benthos biomass. Moreover since in the Barents Sea the

Fig. 52. Distribution of benthos biomass (g/m2) in southwestern Barents Sea

(Filatova, 1938).

138 BIOLOGY OF THE SEAS OF THE U.S.S.R.

regions of the most active mixing of waters coincide with the coolest parts of
the sea, an erroneous idea of an inverse dependence between the benthos bio-
mass and temperature might be formed, since the line of the polar front
coincides with a bottom temperature of from 0° to 1 °. The cause of the fall
of biomass towards the west should be sought in the more and more
difficult upwelling and in the shortage of food, rather than in the rise of
temperature.

As has been noted above, the areas of abundant biomass lie on the lines of
the polar front. This is confirmed by a comparison of the charts of currents
and of the biomass. The main areas of low biomass (the western and northern
parts of the Sea and its central depression) are situated within the centre of the
three great zones of cyclonic rotation, but at the meeting place of the alien
warm waters and the local cold ones the biomass increases sharply. However,
some other interlinking factors are active here. The horizontal circulation is
conditioned by the bottom contour ; halistatic areas are formed over the de-
pressions and soft mud sediments are deposited there. Poor development of
life is the result of somewhat impeded upwelling, an accumulation of carbon
dioxide in the bottom layer and of the chemical and mechanical properties of
the bed.

An interesting analysis of the quantitative distribution of the bottom fauna
on the Spitsbergen bank has been given by M. Idelson (1930). On the middle
parts of the bank, where the bed is washed clean, the fauna is very scarce,
most frequently only 1 to 4 g/m2. At the edges of the shallow, however, the
biomass increases sharply to 1 to 3 kg/m2, from 95 to 99 per cent of it epi-
fauna. Farther on at the very slope of the bank the benthos biomass is again
reduced to 150 to 350 g/m2, and then on the mud beds encircling the bank it
rises again to 500 to 1,500 g/m2. The main factor conditioning this biomass
range is the distribution of foodstuffs, mainly organic detritus. The high bio-
mass at the edges of the shallow, consisting mostly of epifauna, is conditioned
by the presence of rich detritus washed out from the central parts of the bank
and brought by water as a solid suspension. Farther on the reduction of the bio-
mass is due to conditions unfavourable for the development of the epifauna
and infauna. The last increase of the biomass is not due to the infauna, which
receives here, in a comparatively calm zone, an abundant amount of sedi-
mentary detritus.

The sum total of the benthos biomass of the whole Sea must be no less than
150 million tons of wet weight, i.e. on average 100 g/m2. The richest infauna
grows on the sandy silts and the silty-sand floors. Epifauna is numerous on
hard floors in regions of strong currents. Areas rich in infauna are usually poor
in epifauna and vice versa. On the one hand this is explained by the properties
of the floor since infauna cannot develop on rocky or cliff floors. On the other
hand, in some areas the floor could have given refuge to infauna, but the
abundant epifauna has taken all the food supplies ; the bottom may contain
large amounts of Porifera spicules and owing to mechanical factors may be-
come unfit for benthos habitation. This occurs on the Kildin bank, where finely
cartilaginous and sufficiently silted floors give refuge to a rich epifauna, and
are almost devoid of infauna. The same picture is observed in the wide belt

THE BARENTS SEA

139

adjacent to Finmark. Porifera and Brachiopoda are predominant in these
regions.

The third region of greatly increased epifauna biomass lies on the south-
eastern slopes of the Spitsbergen shallow. The patch of increased biomass in
the north of the Barents Sea, southwest from Franz Joseph Land, corresponds
to a considerable rise of the bottom, and likewise consists mostly of epifauna.
In the central part of the Barents Sea considerable quantities of epifauna
extend in a wide meridional band along 37° and 38°, on the shallow crest
which separates the western depth of the Sea from its central depressions

Fig. 53. Quantitative distribution in Barents Sea: A Bivalves (full line) and

polychaetes (dotted line); В Echinoderms. Thicker lines denote greater biomass

(Brotzkaya and Zenkevitch, 1939).

passing at the north into the central shallow. In the east an abundant epi-
fauna thrives north of Kolguev Island and especially on the Gusinaya bank
and farther along the shallows ofTNovaya Zemlya. In these regions the echino-
derms are preponderant (Strongylocentrotus, Ophiopholis, Psolus) and some
molluscs (Saxicava, Pecten, Buccinidae), crustaceans (Balanus and Eupagurus)
and polychaetes (Thelepus). The biomass of the central depression with its
great depths is comparatively poor. Coarse sand and gravel floors are very
poorly populated. They are practically without life. Such regions are found in
the Voronka of the White Sea southwest of Kanin Nos.

The main groups of the benthos — echinoderms, bivalves, polychaetes and
sipunculids — play different roles in furnishing the common biomass in
different areas of the sea (Fig. 53).

Lamellibranchiata are adapted mainly to fairly shallow (<150 m) silty-
sand bottoms with a large detritus content. The largest accumulations of bi-
valves are found off the coast of Novaya Zemlya, in the Pechora region and,
mainly, between Kolguev Island and Novaya Zemlya where their biomass

140 BIOLOGY OF THE SEAS OF THE U.S.S.R.

reaches 600 g/m2, forming more than 75 per cent of the total benthos. The
Pechora region and the shallow off Novaya Zemlya must obtain large amounts
of detritus from the abundant sea-weed growths off the southern coast of
Novaya Zemlya, and from the outflow of the waters of the Pechora, the
Novaya Zemlya rivers and from the Gorlo of the White Sea.

The following thirteen species are preponderant among the biomass of bi-
valves of the open parts of the Barents Sea: Astarte crenata, A. borealis, A.
montagui, A. efliptica, Cardium ciliatum, C. groenlandicum, Macoma calcarea,
Area glacialis, Leda pernula, Yoldia hyperborea, Nucula tenuis, Portlandia
arctica and P. intermedia.

The qualitative distribution of the echinoderms is almost the reverse of that
of the molluscs. Only in the southwest of the Sea, off the shores of Novaya
Zemlya, the echinoderm biomass is about 50 g/m2. The Pechora region is
characterized by its extreme poverty in echinoderms (less than one per cent
of the total biomass). The small number of echinoderms in the Kanin region
— west from Kolguev Island to the Sviatoi Nos meridian — is particularly
striking. The main mass of echinoderms is adapted to the deep western and
central parts of the Sea (30 to 50 per cent of the total biomass), to the slopes
of the Bear Island shallow and farther north and northeast. The reason for the
shortage of echinoderm representatives in the Kanin and Pechora regions is
not clear ; it can hardly be explained only by some decrease of salinity (33-0 to
34-5%0 in the bottom layer) and the shallowness of the region. However, the
mass development of bivalves in this region is very characteristic. It is well
known that echinoderms are natural enemies of bivalves, since they devour
their young fry. As has been shown by Petersen (1913), this antagonism may
have a decisive influence on the distribution of bivalves. The following eleven
species are the main quantitative forms of echinoderms in the Barents Sea:
Ctenodiscus crispatus, Strongylocentrotus droebachiensis, Brisaster fragilis, Mol-
padia sp., Ophiura robusta, O. sarsi, Ophiopholis aculeata, Ophiopleura borealis,
Ophiocantha bidentata, Ophioeten sericeum and Stegophiura nodosa.

The picture of quantitative distribution of polychaetes is different from that
of the molluscs and echinoderms. The greatest gathering of polychaetes is
adapted mainly to the halistatic regions and the softer floors connected with
them. The deeper western part of the Sea, so rich in echinoderms, is particu-
larly poor in polychaetes. Its main polychaete forms are : Spiochaetopterus
typicus, Maldane sarsi, Pectinaria hyperborea, Onuphis conchylega, Thelepus
cincinnatus, Myriochele oculata, Owenia assimilis and Scoloplos armiger.

Of all the remaining fauna the large sipunculids Phascolosoma margari-
taceum should be distinguished ; in the central parts of the Sea and on the
slopes of the southern island of Novaya Zemlya it forms dense colonies (15
to 65 g/m2) and frequently forms more than 50 per cent of the total benthos
biomass.

The distribution in depth of the three main above-mentioned groups of
Barents Sea benthos shows substantial differences (Fig. 54). The bivalves are
considerably reduced with depth, the echinoderms, on the contrary, increase in
numbers, while the polychaetes remain essentially unchanged. The same rela-
tionship in the vertical distribution of the three main groups of benthos has

THE BARENTS SEA

141

been established by R. Leibson (1939) for the Motovsky Gulf and the general
character of the distribution of echinoderms, bivalves and polychaetes in the
whole of the Barents Sea may be explained partly by these relationships.

Distribution and composition of the main communities of the open sea. Intensive
quantitative investigations carried out for ten years make it possible to dis-
tinguish six basic communities in the bottom fauna of the Barents Sea and
about forty secondary variations of these communities (Figs. 55 and 56). It
must be kept in mind that these data, obtained by means of a bottom-grab,
do not give a sufficiently complete picture of the epifauna, and its actual bio-
coenosis range must be wider. For the Barents Sea, however, with its soft

Fig. 54. Quantitative distribution of total benthos biomass (A) with depth and (B)
bivalves, echinoderms and polychaetes on ooze soils of Barents Sea (Idelson). A:
Benthos biomass and bottom temperature at the Central Elevation of the Barents
Sea (along meridian 35° E). B: 1 Lamellibranchiata ; 2 Echinodermata ; 3 Poly-

chaeta ; 4 Other groups.

bottom, and therefore a preponderance of infauna, data of this type may be
considered sufficient.

In the most southwesterly part of the Sea, open to considerable influence of
thermophilic Atlantic fauna, a large biocoenosis diversity is observed on
shallows of the continent. As has been shown by Z. Filatova (1938) the popu-
lation of the littoral sand and rock floor at depths of 60 to 1 00 m along west and
east Finmark loses some of its boreal forms, and they are replaced by Arctic
ones as we move eastward. Epifauna consisting of different planktophages is
here luxuriantly developed. To the west of the North Cape a mass develop-
ment of warm-water forms is observed : bryozoans Hornera lichenoides, Id-
monea atlantica, Flustra foliacea, soft coral Eunephthya, and the polychaetes
Placostegus tridentatus, Hydroides norvegica, Eunice norvegica, Pista cristata
and Goniada maculata. The boreal forms of echinoderms and especially sea-
urchins Echinus esculentus, Spatangus raschi, Brisasterfragilis, Echinocyamus
pusillus, Echinocardium flavescens are very typical. Among the molluscs
Astarte sulcata, Pecten auratus, Modiola barbata, Mactra elliptica, Cardium

142

BIOLOGY OF THE SEAS OF THE U.S.S.R.

fasciatum, Gibbula tumida, Trichotropis conica and others may be pointed out
and among the Brachiopoda Waldheimia cranium.

To the east of the North Cape the boreal forms are considerably decreased
and replaced by representative forms of the colder-water fauna. Instead of the
above-mentioned sedentaria, Protula media, Filigrana implexa, Pseudopota-
milla reniformis, Potamilla neglecta begin to preponderate here ; Waldheimia
cranium is replaced mainly by Terebratulina septentrionalis and Rhynchonella
psittacea. Among the warm-water sea-urchins Brisaster fragilis and Echinus

— ^7 — /WiJk11 — 1 J-' '•-»*<

V tSP/7& >J „,"*-7 Sc

^M— ~-л ч \

X/v > \~^s

\ \ ^<

(jfi*^^ """^ ^*4 -***

f XT^'Jy \ /

/Х<Л y^\\vj) /*

~~йщШ / \g.

Ao^V^^VX /l / V \/ -X

W\<y\i

^^J§E> Vi\i ^

"y^w

/ 1 ^^^TV»»/ "•

Fig. 55. Distribution of six main benthos biocoenoses in
Barents Sea: / Southwestern; // Central; /// Eastern
shallows; IV Eastern (coastal); V Northern (deep);
VI Northern (shallows) (Brotzkaya and Zenkevitch with
Filatova's additions).

esculentus still remain and of the molluscs Astarte montagui and Saxicava
arctica begin to prevail here.

East of North Cape a number of boreal forms are found in large amounts
as mollusc shells.

The benthos biomass of the littoral sand and rock floors varies from 120 to
400 g/m2.

Of the shallow (not deeper than 80 to 100 m) benthic groups of the Murman
sublittoral the biocoenosis of the large bivalves Modiola modiolus, Pecten
islandicus and Mactra elliptica are of great interest ; they have a definite north-
boreal character and in the last few years they have developed greatly on the
Murman coast owing to a considerable rise in temperature.

They reach their highest development in Danish waters and off Iceland and
the Faroe Islands. These communities grow poorer in quality and quantity
as one proceeds northwards and eastwards. Off the Murman shores both

THE BARENTS SEA

143

communities reach the edge of their habitat; they are absent from the
eastern and northern parts of the Barents Sea.

In the biocoenosis Modiola modiolus-Pecten islandicus, the polychaetes
Thelepus cincinnatus, the Ophuroidea Ophiopholis aculeata, Balanus balanus,
the sea-urchin Strongylocentrotus droebachiensis and some Bryozoa are the

Fig. 56. Composition of main bottom bio-
coenoses of Barents Sea (Brotzkaya, Zenke-
vitch and Filatova). / Porifera; II Central;
III Eastern (medium depths) ; IV Eastern lit-
toral ; V Northern littoral ; VI Northern (deep
water) ; VII Waldheimia-Brisaster. I Lamelli-
branchiata ; 2 Gephyrea ; 3 Crustacea ; 4 Coe-
lenterata; 5 Polychaeta; 6 Echinodermata ;
7 Porifera; 8 Sipunculoidea; 9 Gastropoda; 10
Tunicata ; 11 Brachiopoda ; 12 Varia. Average
biomass is given in numerals (g/m2).

most important. This biocoenosis is distributed mainly over large-grain sand
and shale gravel, in zones of the constant ebb and flow of tidal streams.

V. Zatzepin and Z. Filatova (1945) have noted that in summer these com-
munities keep to waters of 6° to 10° and in winter to 0-5° to 2-5°; large
growths of macrophy tes are frequently met, among them the branched Litho-
thamnion (red algae). On the Murman coast the biomass of Modiola bio-
coenosis reached 1 to 1-5 kg/m2 (an average of 350 g/m2). Proceeding west-
ward and southward the biocoenosis changes its qualitative composition —
its cold-water forms such as the molluscs Saxicava arctica, Pecten islandicus

144 BIOLOGY OF THE SEAS OF THE U.S.S.R.

and Astarte elliptica, polychaetes Onuphis conchylega, Thelepus cincinnatus
and Nephthys ciliata, and the brittle stars Ophiocantha bidentata are reduced
in numbers. They are gradually replaced by the thermophilic forms of echino-
derms, molluscs and worms. At the same time the biocoenosis biomass in-
creases, reaching 10 kg/m2 in Danish waters, in Gulmarfjord (S. Sweden) up
to 7 kg/m2 and off the Faroe Islands up to 16-5 kg/m2 (up to 300 specimens/
m2).

The biocoenosis Mactra elliptica has similar ranges, and changes in the same
manner with its advance to the east (according to the data of V. Zatzepin and
Z. Filatova, 1946). This biocoenosis does not extend, as did the former one,
eastwards to Sviatoi Nos ; it is distributed only in the western and along part of
the central Murman coast, but it is also found on large-grain sand and fine
gravel.

Whereas the previous biocoenosis consisted in its basic mass of epifauna
seston-feeding forms, * the Mactra elliptica biocoenosis is mainly represented
by the infauna bottom-feeding forms.

Besides Mactra elliptica, the bivalves Astarte borealis, Cyprina islandica
and the polychaetes Onuphis conchylega and Thelepus cincinnatus and others
play an essential role in this biocoenosis.

The quoted biomass of this biocoenosis is considerably smaller than that
of the Modiola modiolus-Pecten islandicus community, both on coasts and
in the north Atlantic. The average biomass off the Murman coast is,
according to V. Zatzepin (1946), only 50 g/m2 and the largest hardly
reaches 100 g/m2.

On the shores of Northern Norway the biomass of the Mactra elliptica
biocoenosis sometimes reaches 200 g/m2 and in the waters of Iceland it
reaches 270 g/m2.

Zatzepin confirms R. Sparck's (1936) opinion that the M. elliptica bio-
coenosis of the Faroe and Iceland waters (and according to Zatzepin's data,
those of the Murman coast as well) should be considered as colder-water
north-boreal modifications of the south-boreal groups of the Venus sand bio-
coenosis.

Among the biocoenoses peculiar to Murman coastal waters, it is possible to
distinguish other north-boreal ones with ranges similar to the two previously
mentioned. Such are the biocoenoses Cyprina islandica, Pseudopotamilla reni-
formis, Brisaster fragilis, Waldheimia cranium and others.

At great depths (150 to 350 m), on slightly silty sand floors containing rocks,
the Brachiopoda Waldheimia cranium community is greatly developed; it
stretches east almost to the Rybachiy Peninsula. Waldheimia, a typical
planktophage, forms mass accumulations of some hundreds of grammes per
m2 in sectors with strong currents. In this community Waldheimia comprises,
on the average, more than 50 per cent of the whole population. Moreover,
there is an abundance of Porifera {Geodia baretti, Craniella cranium, Thakellia
and others), polychaetes Placostegus tridentatus and Eunice norvegica,
molluscs Astarte sulcata, Anomia squamula, sea-urchin Brisaster fragilis,
asterid Cribrella sanguinolenta, crab Ну as coarctatus and others. In the west

* Zatzepin's terms.

THE BARENTS SEA 145

this community passes over gradually into the communities Placostegus-
Modiola barbata, and farther on, at Lofoten, into the community of the madre-
porarian coral Lophophelia prolifera. The average biomass of the Waldheimia
cranium community is 133 g/m2 (from 60 to 400 m.) Epifauna is sharply pre-
dominant in this community forming about 94 per cent of the total biomass
{Table 57).

Table 57. Composition of the Waldheimia cranium
community according to groups

Biomass

Percentage of

Group

g/m2

total biomass

Brachiopoda
Porifera

78-2
25-5

58-3
19-2

Polychaeta

Bryozoa

Echinodermata

10-9
6-3

5-5

8-2
4-7
40

Bivalvia

3-2

2-4

Ascidia

2-3

Others

0-9

Total biomass

133-7

100

The above-mentioned community in various places passes to the west,
north and east into the Porifera community, which frequently forms 95 to
98 per cent of the total benthos biomass. Proceeding from west to east one
observes that the thermophilic forms of this community are replaced by the
less thermophilic ones. Only the three areas of the greatest accumulation of
Porifera are marked on the chart ; lesser gatherings are met everywhere off
Finmark and the Murman coast on mixed rock bottoms. On bottom sectors
occupied by this community the work of trawlers is made difficult since Pori-
fera fill the trawl sometimes up to many tons and spoil the fish. On the other
hand, hunge amounts of dead Porifera spicules mix with the bed deposits in
such quantities that it becomes almost completely unfit for infauna habitation ;
after a little washing it appears as a compact felt made of spicules (the silica—
Porifera floor). Here infauna forms usually 1 to 3 per cent of the total fauna
biomass.

The development of other representatives of epifauna is also restricted by
the mass growth of Porifera, since these latter, loose powerful filters, are the
first to take out of water all the nutrient substances (detritus and plankton
and, possibly, the dissolved organic substances). Manteufel (1938) has sug-
gested that the warm-water plankton brought from the west and destroyed at
the entrance to the Barents Sea may serve as a considerable source of food for
Porifera off the shores of Finmark and the western Murman coast, and cause
its luxuriant development.

The biomass of the Porifera community reaches 5 to 6 kg/m2, and on the
average on the huge patch opposite Nordkyn, 350 g/m2. The mass forms of

146

BIOLOGY OF THE SEAS OF THE U.S.S.R,
Table 58

Group

Biomass Percentage of
g/m2 total biomass

Porifera

336-9

Echinodermata

6-8

Polychaeta

Brachiopoda

Bivalvia

2ЛЛ

2-2

1-4

Bryozoa
Others

0-8
0-8J

Total biomass

351-3

100

Porifera are Geodia baretti, Craniella cranium and Thenea muricata. It is
interesting to note that these Porifera usually lie free on the bottom and there-
fore can develop in masses on a comparatively soft floor (sand and silty sand).
Many mass forms of the previous community are of secondary significance
here (Waldheimia, Retepora, Placostegus, Eunice, Asyches and others). More-
over among the characteristic forms here one may note Astarte crenata,
Nephthys coeca, Ophiocantha bidentata, Maldane sarsi, Lumbriconerbis fragilis,
Ophiura sarsi and a number of asterids Ceramaster, Leptychaster, Cribrella,
etc. This particular group has the following composition {Table 58).

Farther east, in the Rybachiy Peninsula shallow, the admixture of cold-water
forms, such typical inhabitants of the Barents Sea as Myriochele oculata,
Macoma calcarea, Spiochaetopterus typicus and others, is felt even more
strongly.

The Waldheimia and Porifera communities described above are gradually
replaced by the Brisaster fragilis community which inhabits silty sand bottoms
(200 to 300 m deep), with a mass Foraminifera Astrorhiza and Rhabdammina.
High salinity (35 to 35-5%0) and a temperature of 3° to 4° turn it into a
suitable habitat for a large number of warm-water forms. The average bio-
mass of this community is not high — 37 g/m2 (from 20 to 80 m deep). The in-
fauna there already accounts for a biomass of about 90 per cent of the whole
fauna with a sharp preponderance of echinoderms and polychaetes {Table 59).

Table 59

Group

Biomass

g/m2

Percentage of
total biomass

Echinodermata

26-2

Polychaeta

4-8

Bivalvia

2-3

Coelenterata

0-9

Others

2-4

71 6

13-5
6-4

2-5
60

Total biomass

36-6

100

THE BARENTS SEA 147

Brisaster fragilis (on the average 60 per cent of the total biomass) is the
dominant form of this community. Among the characteristic forms one may
point out the molluscs Astarte crenata ; of the echinoderms Ctenodiscus crispa-
tus, Leptychaster arcticus, Ophiura sarsi, Trochostoma boreale; among the
polychaetes Asychis biceps, Myriochele oculata, Owenia assimilis, Spiochaetop-
terus typicus, Praxilella praetermissa, crustaceans Pandalus borealis and Hyas
coarctatus, and the brachiopods Waldheimia cranium and Terebratulina caput-
serpentis.

The vast Spitsbergen shallow, extending southwards to 74° N latitude in its
central part and especially between Bear Island and Nadezhda Island, is less
than 50 m deep and has a hard floor. Sections of cleanly washed pebble and
deposits of broken shells and fragments of Balanus with a small admixture of
sand are extremely unfavourable for the development of life. The benthos
biomass is here calculated (M. Idelson, 1930) as a few grammes or even frac-
tions of a gramme per m2. The population consists of small bivalves and
gastropod molluscs, polychaetes and crustaceans. In areas where the sea-bed
has finer structure, the epifauna is fairly abundant, forming sometimes
hundreds and even thousands of grammes per m2 mainly consisting of Cucu-
maria frondosa, Strongylocentrotus droebachiensis, Balanus balanus and
Alcyonidium gelatinosum. Only Cyprina islandica is distinguished by its bio-
mass among the infauna. On the silty sand and sandy silt bottoms surround-
ing Spitsbergen shallow from the east and south dwells the fauna described
above in other communities.

Porifera and Brisaster communities extending from the northwest are re-
placed by communities peculiar to the western trough, which is 400 m deep
and more, and is filled with soft ooze with a huge number of Foraminifera
Rhabdammina abyssorum cases. The population of the western trough repre-
sents the change-over from Porifera and Brisaster communities to typical
central Barents Sea low Arctic communities. The total biomass here is only
13-4 g/m2. This is explained by a shortage of food {Table 60).

In the cold waters of the northern part of the trough off the Bear Island

Table 60

Group

Total biomass
g/m2

Percentage of
total biomass

Echinodermata

310

Polychaeta
Bivalvia

3-4
1-9

25-5
150

Porifera

Coelenterata

0-9

Crustacea

0-8

5-5

Bryozoa

5 0

Others

0-6

Total

13-4

100

Epifauna
Infauna

5-2
8-2

401
59-9

148 BIOLOGY OF THE SEAS OF THE U.S.S.R.

shoal, forms typical of the middle part of the Barents Sea are highly developed
— Spiochaetopterus typicus, Maldane sarsi, Ctenodiscus crispatus, Astarte
crenata, and Arc a glacialis. In the southern parts of the trough the waters are
warmer and the warm-water Asychis biceps, Area pectunculoides, Pecten im-
brifer, Dentalium striolatum and others are predominant. In the deepest parts
of the trough (400 m) the benthos biomass decreases to 5 to 8 g m2 and less,
consisting entirely of infauna forms feeding on ooze.

Thus in the northern part of the west trough (400 m) and to the east of the
Brisaster community, the middle Barents Sea benthic community comes into
full development ; it occurs mainly on sandy silt and to a lesser extent on silt
and silty sand, at depths of 100 to 350 m.

The dominant forms of this community are : the polychaete Spiochaetop-
terus typicus, the sipunculid PhascoJosoma margaritaceum, the molluscs
Astarte crenata and Area glacialis, the echinoderms Ctenodiscus crispatus and
Psolus phantapus. Besides this the characteristic forms of the first order are the
polychaetes Lumbriconereis fragilis, Nicomache lumbricalis, Myriochele ocu-
lata, Maldane sarsi, the molluscs Cardium ciliatum, Macoma calcarea, Saxicava
arctica, Axinus flexuosus, the echinoderms Ophioplwlis aculeata, Ophio-
cantha bidentata, Ophiura sarsi and Molpadia species. This multiform com-
munity, occupying a huge area, can be subdivided into ten variants, differing
in their combinations of the above-mentioned forms, and sometimes by the
absence of a series of forms, but retaining, nevertheless, an inherent unity.
The average biomass of this community is not large — 85-5 g/m2 — and has the
following group composition {Table 61).

Table 61

Biomass

Percentage of

Group

g/m2

total biomass

Bivalvia

21-2

24-8

Polychaeta
Echinodermata

21-4

21-7

25-9
25-3

Sipunculoidea
Porifera

110

4-3

12-8

5-3

Coelenterata

1-5

1-8

Others

4-5

Total

85-5

100

Epifauna
Infauna

17-8
67-7

20-8
79-2

To the east and southeast of the Novaya Zemlya shoal and in the Pechora
region, forming a wide belt round the previous community, there lies in the
silty sand at shallow depths (50 to 250 m) a community with a preponderance
of bivalves. The dominant forms in this belt are : among the molluscs,
Astarte borealis, A. montagui, Macoma calcarea, Cardium ciliata, Yoldia
hyperborea, Cardium groenlandicum, and among the echinoderms : Ophio-
plwlis aculeata and Strongylocentrotus droebachiensis. The characteristic forms

THE BARENTS SEA 149

include a number of the dominant forms of the middle Barents Sea community.
This community can also be divided into nine variations. Among them is the
grouping to the east of Kolguev Island, on the silty sand at shallow depths
(50 to 70 m) with a sharp preponderance of Pectinaria hyperborea and Yoldia
hyperborea, with a considerable deviation from the ordinary phylum ; so also
is the grouping in the Novaya Zemlya trough on silty sand and at depths of
50 to 200 m. This trough shelters a very large population of a relict mollusc
Portlandia arctica.

The composition of this community, the richest in its biomass, is given by
groups in Table 62.

Table 62

Group

Biomass
g/m2

Percentage of
total biomass

Bivalvia

133-65

60-6

Polychaeta
Echinodermata

25-41
25-52

11-4

11-5

Sipunculoidea

Gastropoda

Crustacea

9-64

2-73

11-60

4-4
1-2

5-2

Others

1214

5-7

Total

220-69

100

Epifauna
Infauna

40-30
180-39

18-2
81-8

On the coastal sands of the eastern and southeastern parts of the Sea and in
the shallows of the open sea (Gusinaya bank, Kanin shallow) there thrives at
depths of 9 to 100 m a hard-bed community mainly on various types of sand,
from the slightly silty to the coarse-grained. This community gives a consider-
able admixture of shallow-water high Arctic forms, and consists half of epi-
fauna. Its dominant forms include among the molluscs: Astarte borealis,
Macoma calcarea and Serripes groenlandicus; among the bryozoans: Pelo-
naja corrugata; the crustaceans: Eupagurus pubescens and Balanus; and among
the echinoderms, Strongylocentrotus.

Among these characteristic of the first order are Alcyonidium disciforme,
Travisia forbesi, Pectinaris hyperborea, Owenia assimilis, Sabellldes borealis,
Ampharete vega, Ophelia limaeina, Ophiura nodosa, Myriotrochus rincki,
Cucumaria calcigera, Cyprina islandica, Astarte elliptica, A. montagui, Saxi-
cava arctica, Mya truncata, Diastylis rathkei, Hyas araneus and Balanus
balanus.

The fauna of the hard sea-floor (13 to 45 m deep) in the Cheshskaya Inlet
have a special aspect.

The dominant forms here are Mytilus edulis and Balanus crenatus. The
mass descent into the sublittoral of such a typical littoral form as sea mussel
is of special interst. This community has the following group composition
{Table 63).

150 BIOLOGY OF THE SEAS OF THE U.S.S.R,

Table 63

Group

Biomass
g/m2

Percentage of
total biomass

Bivalvia

790

51-3

Gastropoda

Polychaeta

Crustacea

11-5

100

240

7-5

6-5

15-6

Echinodermata

100

6-5

Ascidia

5-2

Bryozoa
Porifera

40
40

2-7
2-7

Coelenterata

3 0

Others

0-3

—

Total

1538

100

Epifauna
Infauna

79-5
74-3

51-7
48-3

The northern part of the Barents Sea and the central parts of the Kara Sea,
with its soft brown silts and depths of 200 to 450 m, are occupied by a bio-
coenosis with a large admixture of high Arctic forms. The dominant ones are
Astarte crenata and Ophiopleura borealis, the characteristic members of the
first order being Ophiocantha bidentata and Molpadia sp. (a high Arctic species
different from Molpadia of the southwestern part of the Sea). The biomass
here is very small — inferior only to that of the Atlantic trench {Table 64).

The nine biocoenoses examined are, of course, not all the biocoenotic
variety of the open parts of the Barents Sea, especially as regards its epifauna.

Distribution and composition of bottom communities of certain inlets andgubas.
A quantitative investigation of the benthos of the Motovsky (R. Leibson, 1939)

Table 64

Group

Biomass
g/m2

Percentage of
total biomass

Echinodermata

11-5

38-3

Bivalvia

7-3

24-3

Polychaeta

Sipunculoidea

Crustacea

4-9
1-3
1-2

16 3

4-3
40

Coelenterata

3-7

Bryozoa

Total

300

3-3
100

Epifauna
Infauna

24-77
5-23

82-6
17-4

THE BARENTS SEA 151

and Kola (V. Zatzepin, 1939)* Inlets showed that the principal deep parts of
both inlets have a reduced benthos biomass as compared to the adjacent parts
of the Sea. In front of the entrance into both these inlets and in the seaward
part of the Kola Inlet a benthos biomass of 50 to 100 g/m2 is the rule, where-
as all the central and abyssal part of the Motovsky Gulf has a benthos bio-
mass of less than 25 g/m2, and the corresponding parts of the Kola Inlet
about 25 to 50 g/m2. This impoverishment should be attributed to the develop-
ment of the stagnation phenomena and to greater silting in the deeper parts
of the inlet than in the open sea. Considerable areas of the Barents Sea, as we
have seen, are occupied by a biomass of more than 300 g/m2, consisting chiefly
of infauna ; on the Spitsbergen bank the biomass frequently reaches several
kilogrammes per m2. Such biomass indices have not been observed either in
the Motovsky or Kola Inlets, except for the littoral zone. Even the Ascidia
obliqua beds, the richest in fauna, have an average biomass of 520 g/m2,
exceeding 1 kg/m2 only in a few individual cases.

R. Leibson (1939) examined the dependence of the infauna biomass on the
amount of organic matter, and gave the following average data (for silt sea
bottoms only), expressed in percentages of organic carbon content {Table 65).

Table 65

Carbon per cent 10 10-1-5 1-5-20 20-30

Infauna biomass 58-8 64 77 128

As usual, the quantitative distribution of the epifauna and infauna in the
inlets gives a contrasting picture (Fig. 57). The largest accumulation of infauna
is found in the depth of the Motovsky Gulf, and the epifauna is found in
the coastal waters and the interior part. The total biomass increases farther up
the inlet. As for the bottom fauna communities all the middle parts of both
inlets are inhabited by the same central Barents Sea community mentioned
above ; the whole composition of the dominant and characteristic forms is the
same, only in a somewhat different combination. In the inlets the polychaete
Maldane sarsi is the most significant (Fig. 58), whereas in the most southern
part of the Kola Inlet Maldane sarsi, Spiochaetopterus typicus, Ctenodiscus
crispatus and Phascolosoma margaritaceum disappear. The depths there are
20 to 60 m ; the floor consists of slightly silty sand and the salinity is somewhat
reduced. The interior part of the Kola Inlet forms a different ecological
ranges are encountered, comprising qualitatively and quantitatively a fairly
rich fauna. Among the echinoderms are Strongylocentrotus droebachiensis
and Brisaster fragi/is ; there are large colonies of Gorgoncephalus arcticus,
Asterias lincki, Ophiura sarsi, Ophiopholis aculeata ; the polychaetes include
Nicomache lumbricalis, Myriochele oculata, Nephthys ciliata, Lumbriconereis
fragilis, Trophonia plumosa and side by side with them Aphrodite aculeata ;

* The quantitative composition of the benthos of the Kola Inlet has been discussed
above.

Fig. 57. Distribution of bottom fauna in Motovsky Gulf (Leibson, 1939)
A Total biomass, g/m2; В Biomass of infauna; С Biomass of epifauna.

Mai dan e sarsi
Balanus porcatus
Cyprina-Dentalium

Fig. 58. Distribution of main benthos biocoenoses in
Motovsky Gulf (Leibson, 1939).

THE BARENTS SEA 153

also present are the molluscs Astarte crenata, Cardium ciliatum, C. groen-
landicum and Pecten islandicus. Still farther into the inlet this rich fauna
grows poorer, many forms are not found and a series of forms peculiar to
sandy shallows make their appearance — Scoloplos armiger, Cyprina islandica,
Yoldia hyperborea, Macoma calcarea and others.

On the cliffs and rock floors of the great depths of the outer parts of both
inlets, especially in the Kola Inlet, lives the community Porifera-Brachio-
poda-Bryozoa, and slightly above it lives the great community Ascidia
obliqua, often with a biomass of more than 1 kg/m2. Still higher is the Balanus
belt, with Balanus balanas, Ophiopholis acideata, Thelepus cincinnatus, Pseudo-
potamilla reniformis, Modiola modiolus, Pecten islandicus, Miynchonella psit-
tacea, and containing a mass of bryozoans and hydroids.

In the outer parts of the Motovsky and Kola Inlets and east of the Gavrilov
Islands, on the sandy beaches of the sublittoral of the upper horizon is re-
corded an original fauna, developed in large numbers, primarily the molluscs :
Cyprina islandica, Mactra elliptica, Dentalium entalis, Macoma calcarea,
Astarte crenata, A. montagui and others.

A large number of warm-water boreal species are encountered there, and
there is a considerable similarity with the sublittoral communities of the Nor-
wegian coast. As we have seen above, the littoral fauna there has a more
sharply pronounced warm-water character. On the other hand in the great
depths of the inlets, in the zones of a weak vertical circulation and cold
stagnant waters some cold-water Arctic forms have found shelter, and as one
moves farther up the inlet, the higher do the cold-water forms ascend. Hence
considerable summer heating of the surface waters of the enclosed parts of
the inlets, and the presence of cold stagnant waters at shallow depths, results
in a. sharp vertical zonation of the fauna. Many representatives of the shallow-
water, littoral and upper sublittoral boreal fauna find here their extreme limit
of propagation to the east, and the Arctic fauna their extreme westerly limit.
A vertical displacement of fauna of different thermophilic aspects at the
border-line of their habitats is a common phenomenon. As has been pointed
out by V. Zatzepin (1939), in some individual bights of the Motovsky Gulf
(Ara, Ura, Zap. Litza), as a sequence of the submarine barriers, the depths
are filled with cold stagnant waters, inhabited by cold-water species. By
contrast, in bights not separated from the sea by submarine barriers, and not
having a deep stagnant zone (as, for example, Teriberka, Yarnyshnaya), most
of the sublittoral is inhabited by warm-water communities represented by
such forms as Cyprina islandica, Mactra elliptica, Cardium fasciatum, C. ele-
gantulum, С echinatum and Modiola modiolus. The central parts of the inlets
are, however, inhabited by cold-water forms such as Pandora glacialis, Lyonsia
arenosa, Serripes groenlandicus, C. ciliatum, Pelonaia corrugata and others.

The bottom population of Sturfjord to the east of Spitsbergen is quite
peculiar (V. Brotzkaya, 1930). This very wide and shallow (25 to 100 m) inlet
with its negative bottom temperature is climatically one of the most inclement
corners of the Barents Sea. Sturfjord is free for only a very short time of the
sea ice and icebergs which usually block it. Numerous glaciers come right
down to the water so that even in the warmest season of the year, the waters

154 BIOLOGY OF THE SEAS OF THE U.S.S.R.

of the inlet are only slightly warmed. The floor of the fjord is covered by a
homogeneous bed — a very soft green-grey silt, with a few boulders. There
is no submarine barrier at the outlet of the gulf and the whole column of water
is very well aerated. Owing to the homegeneity of its bed and to the hydro-
logical conditions, the Sturfjord bottom fauna likewise is very varied. The
dominant forms are Astarte borealis, A. montagui, Macoma calcarea, Nucula
tenuis, Maldane sarsi, Ophioeten sericeum and Strongylocentrotus droebachien-
sis. Among the characteristic forms the following must be noted : Leda pernula,
Axinus fexuosus, Turitella reticulata, Amphiura sundevalli, Nephthys malm-
greni and Chaetozone setosa.

Off the shore of the inlet lives the mollusc Portlandia arctica, probably in
large numbers, as if emphasizing the high Arctic character of the fjord. The
high Arctic Stegophiura nodosa is also found there. The number of bivalves
and the general biomass increase considerably as one moves deeper into the
fjord, the latter increasing from 126 g/m2 (average for the outer part of the
fjord) to 468 g/m2 (in its inner part) ; epifauna is markedly preponderant.

At some individual stations a considerably higher biomass was encountered.
The presence of the community Onuphis conchylega, Pecten groenlandicus
and Area glacialis common in other parts of the Barents Sea is to be expected
here. It is difficult to say what factors condition the high benthos biomass in
Sturfjord and what are its main sources of nourishment under such severe
climatic conditions.

For the sake of comparison one might mention the exceptionally high bio-
mass recorded in 1926 in the Mashigina Guba in Novaya Zemlya. Its climatic
conditions are also very severe and glaciers come right down to the waters
of the guba. The benthos biomass on the soft silt bottom was found to be
3,394 g/m2, consisting mostly of infauna. This is, probably, the highest infauna
biomass ever registered in the sea. It consists mainly of Saxicava arctica,
which here is one of the infauna components, Mya truncata and Cardium
cilia turn.

Comparison of the Barents Sea bottom communities and those of other regions
of the North Atlantic. The Barents Sea biocoenoses are very similar in their
composition to those of Greenland waters. Almost identical groupings are
observed there.

The bottom biocoenoses of Icelandic waters, while retaining a great simi-
larity with those of the Barents Sea, present a transition from Arctic groupings
to north-boreal ones.

Although the bottom biocoenoses of the Faroe Islands produce a series
of typical forms like those of the Barents Sea, their general aspects are
different : Faroe waters are a place where the north-boreal species preponder-
ate markedly. Only littoral fauna retain their qualitative uniformity over all
the huge distance from the North Sea to the White Sea.

A comparison of a number of forms of the highest biomass of the Barents
Sea and of that of other bodies of water of the northern Atlantic (Greenland,
Iceland, Faroe Islands) is of interest.

As shown in this comparison (Table 66), the biomass indices of the Barents

THE BARENTS SEA
Table 66

155

Benthos biomass epifauna

Barents

Faroe

Icelandic

West

Danish

preponderant

Sea

Islands

waters

Greenlanc

1 waters

Biocoenosis Modiola modiolus

Mean biomass

400

6,380

625

—

2,380

Highest biomass

1,568

17,259

1,932

—

10,320

Benthos biomass infauna

preponderant

Biocoenosis Macoma baltica

Highest biomass

693

1,136

1,280

744

—

Biocoenosis Mactra elliptica

Mean biomass

105

—

Highest biomass of some individual

forms

Astarte boiealis

457

—

540

—

A. elliptica

173

—

307

—

Macoma calcarea

243

642

1,725

—

10,000

Cardium ciliatum

222

—

243

—

Modiola modiolus

1,080

165,000

1,725

—

10,000

Mactra elliptica

117

266

—

Mytilus edulis

25,000

—

— ■

49,500
(Giillmarfjord)

Ophiopholus aculeata

441

48-5

—

Ophiopleura borealis

—

Sea are lower than those in many other sectors of the northern Atlantic (the
data are given in g/m2).

Dominant and characteristic species. The quantitative, biocoenotic investi-
gations carried out in the Barents Sea have provided a possibility of distin-
guishing the total number of dominant and characteristic benthos forms
{Table 67).

Ecological characteristics of individual species. A. Schorygin (1928) has
worked out, on the basis of the Barents Sea echinoderms, an interesting
statistical method for studying the life conditions of organisms by comparing
the frequency of occurrence of a species with the indices of temperature
(thermopathy), salinity (halopathy), depth (bathopathy) and the bottom
constitution (edaphopathy). As a result of it he gives four curves for each
echinoderm species, characteristic for its degree of adaptation to the main
factors of its environment (Figs. 59 and 60). Schorygin's method was later
used by I. Mesiacev in his monograph on bivalves of the Barents Sea (1931).
Finally, V. Brotzkaya and L. Zenkevitch (1937) worked out, by analogy
with the Barents Sea fauna, a method of charting quantitative ecological
habitats which makes it possible to establish the optimum conditions for the
existence of a given form in the Sea. In order to construct his graph Schorygin

156

BIOLOGY OF THE SEAS OF THE U.S.S.R.

- v A

15%
5%

0 200 400 600 800 1000 ions

15%

5°o

sand,

sand

sT"i °°Ie

s?cn«

scenes

20%
10%

-2°-1° 0° 1° 2° 3° 4° 5° 6° 7° С

10%

— '

35,00 33,50 34,00 34,50 35, CO %,

Fig. 59. Distribution of starfish Asterias lincki in Barents Sea (A) and its adaptation

to different factors of the medium (B) (Schorygin, 1928). /Bathopathy; //Edapho-

pathy; /// Thermopathy; IV Halopathy.

used the frequency of occurrence while Brotzkaya and Zenkevitch used the
biomass (Fig. 61). Ecological habitats show a quantitative adaptability of a
form to a combination of two factors of the habitat, in this case to tempera-
ture and depth.

Table 67

Characteristic

Group

Predominant

forms of

forms

first order

second order

Total

Lamellibranchiata

Gastropoda
Scaphopoda
Amphineura
Echinodermata

1
8

1
1

Polychaeta

Gephyrea

Crustacea

5
1
3

14
3

3
3

30
4
9

Bryozoa

Brachiopoda

Tunicata

1
2

2
1

4
3
3

Total

108

THE BARENTS SEA

157

'/*

/"4

\
\

20%
10%

-2° -1° 0° 1° 2° 3° 4° 5° 6° 7°C
Fig. 60. Temperature conditions for the existence of certain
echinoderms in the Barents Sea (Schorygin, 1928). 1
Ophiopleura borealis; 2 Ophiura sarsi; 3 Leptychaster

arcticus.

It is interesting to note that some forms have a centre within the limits of
their ecological habitat and the biomass decreases with the distance from this
centre to the periphery (/, 2, 3, 4). Other forms are uniformly distributed

Temperature °C

8763432 10-1-2 87 65 4 32 1 0 -1-2

Va.15

N Vse \

*Sbi.\kn

L -

r-r— Ш V

100
?00

чпп

0Ш

3.7

1 0

2.0

0 3

102

401]
500

,.,

—— .

,.»

ел

056

QJ6

Fig. 61. Ecological habitats of some bottom animals of the Barents Sea (Zenkevitch
and Brotzky, 1939). 1 Astarte montagui; 2 Spiochaetopterus typicus; 3 Astarte
crenata; 4 Brisaster fragilis; 5 Serripes groenlandicus; 6 Average ecological habitat
for 60 mass benthos forms.

158

BIOLOGY OF THE SEAS OF THE U.S.S.R.

within the whole habitat. Some forms are adapted to low temperatures, others
to higher ones; some live in shallow waters and others in the deep.

Biomass, productivity, PI В coefficient. Quantitative study of the Barents Sea
fauna has made it possible to give an outline of the relationship between bio-
mass, productivity and PI В ratio for the main groups of organisms (Table 68).

Table 68

Group of
Organisms

Biomass
tons

Annual productivity,
tons

Mean PI В
ratio

Bacteria in water

column
Bacteria in sea-bed
Phytoplankton
Phytobenthos
Zooplankton
Zoobenthos
Fish

Sea animals

1 million

10 millions

Some millions

Some tens of millions

140-150 millions
Some hundreds of

millions
300-400 thousand

Hundreds of millions

100-200 millions
Some tens of millions

25-30 millions
Some millions

Above 100
?

About 50
About 1

J to*

The biomass of the total area of the Barents Sea must be about 250 million
tons, or on average about 1 80 g per square metre of sea surface.

Sea birds, which are of importance in the life of the sea in general and of
the Barents Sea in particular, should be included in Table 68. Unfortunately,
even rough data for the whole Barents Sea are not available at present. There
are only some data of G. Gorbunov (1925) and L. Portenko (1931) for the
western coasts of Novaya Zemlya, where there are large gatherings of birds.

Guillemot (Uria lomvia lomvia) is the basic predominant species numbering
about 4 million in Novaya Zemlya. There are at least 600,000 on Pukhovy
Island alone, according to L. Portenko's calculations.

The teeming waters of the Barents Sea off Novaya Zemlya offer abundant
food for all these birds, which consume small fish (caplin, pollack and others)
and large pelagic crustaceans (Euphausiacea and others) in amounts of over
a hundred thousand tons. These small fish and crustaceans likewise require
millions of tons of animal plankton, principally Euphausiacea, Calanus fin-
marchicus and its other planktons.

Fish

General composition. A. Andriashev (1954) distinguishes 144 species offish, of
52 families, in the Barents Sea. As one moves eastwards through the Barents
Sea the variety of fish species decreases rapidly and in the eastern part of the
Sea barely half this number is present. Some families of the Barents Sea fish
are represented by a variety of species such as the following: Gadidae (19
species), Pleuronectidae (9 species), Zoarcidae (14 species), Cottidae (12
species), Rajidae (7 species) and Salmonidae (7 species). Most families, how-
ever, are represented by one or two species. Herring and bass, so important
in fisheries, are among these latter.

THE BARENTS SEA 159

Fish of commercial importance. Not more than 20 species could be included
in a list of commercial fish in the Barents Sea, and among them only ten are
of essential importance to the trawling industry. In this industry cod {Gadus
callarias), haddock {Gadus aeglefinus) and bass {Sebastes narinus) are the most
prominent.

The commercial importance of these three groups of fish changes from year
to year, as is evident from Table 69.

Table 69. Percentage significance of individual races offish in the catch of Barents Sea

trawlers

Year

Cod

Haddock

Bass

Others

1923

740

220

0-6

3-4

1926

67-0

210

5 0

1930

47-5

20-7

24-2

7-6

1936

851

9-9

3 0

1938

56-7

37-0

3-5

2-8

Blue sea catfish and catfish {Anarrhichas minor and A. lupus), long rough
dab {Drepanopsetta platessoides), sea dab {Pleuronectes platessa), halibut
(Hippoglossus hippoglossus), coalfish {Gadus virens) and shark {Somniosus
microcephalus), are of a secondary commercial importance in the industry.

In the last few years herring {Clupea harengus harengus) has acquired great
importance in the Barents Sea fish industry.

It is remarkable that all the main commercial fish — cod, haddock, bass,
coalfish and herring — occur in the Barents Sea at the extreme limit of their
distribution while they breed mainly outside the Barents Sea in the coastal
waters of Norway, where even in the deep floor layers the temperature does
not fall below 5° to 6°. The Barents Sea, with its spawning-feeding migra-
tions, is basically a feeding place for all these fish; they breed here only
partially (mainly in the coastal waters) (Fig. 62).

The trawling yield is steadily increasing from year to year. In 1921 it was
39 thousand centners (1 centner=100 kg), in 1930—350 thousand, in 1934 —
772 thousand, in 1936—1-75 million, in 1950—2-3 million, and in 1956—
5-5 million centners.

The catch of herring {Clupea harengus harengus) is still subject to great
fluctuations, but in some years it reaches a million centners. In 1956 the
herring catch was only 100,000 centners.

In 1955 the catch of the trawling fleets of the u.s.s.r., Britain and the
German Federal Republic was 7-5 million centners in the south of the Barents
Sea, in the Bear Island-Spitsbergen region (mainly the catch of Britain and
the German Federal Republic) it was 1-6 million centners, while off the north-
western coast of Norway it was 1-2 million centners. Furthermore the coastal
catch of Norway and the u.s.s.r. (from Lofoten to the eastern Murman
coast) in 1955 was 2-1 million centners, and the total for the Barents Sea
was approximately 10 million centners.

160

BIOLOGY OF THE SEAS OF THE U.S.S.R.

70° 75° 20° 10° 0° 10°20°30°40° 50" 60° 70°

10° 20° 30°

Fig. 62a. Distribution and spawning places of Norwegian
and Murman herring (Tikhonov, 1939). 1 Murman herring;
2 Norwegian herring.

Fish feeding. The quantitative method of analysis offish feeding for the Barents
Sea was first worked out at the Oceanographic Institute, and later applied to
other bodies of water of the Union. Before this there had been only qualita-
tive evaluations of the diet of fish in the Barents Sea. At present we have a
fairly complete quantitative analysis of the feeding of cod, haddock, herring,
caplin, launce, long rough dab, catfish and a series of abundant, non-com-
mercial fish.

4 S Ц

Z — N \ j

С \

Fig. 62b. Chart of drift of larvae and distribution of herring young-
of-the-year in the Barents Sea (Marti, 1939). 1 Spawning sites; 2 Lar-
vae up to 20 mm; 3 Up to 30 mm; 4 Up to 40 mm; 5 Up to 50 mm;
6 Young-of-the-year.

THE BARENTS SEA

161

The diet of the different main breeds of fish varies from purely benthos-
feeding (sea dab, haddock) to typical plankton eaters (herring, bass) (Fig. 63).
Such fish as long rough dab and ray have a mixed diet, feeding almost equally
on pelagic and bottom organisms.

Fig. 63. Feeding habits of the chief commercial fish of the

Barents Sea in order : haddock, Anarhichas, sand dab, ray,

cod, sea bass (Zenkevitch, 1931).

The feeding of cod. The diet of cod has been investigated most fully. Exhaustive
information is given in the extensive study by V. Zatzepin and N. Petrova
(1939). The cod's diet consists basically of small pelagic fish — herring, caplin,
young cod, haddock and finally, in the northern and western parts of the Sea,
polar pollack {Boreogadus saida). Fish forms 60 per cent of the diet of the cod.
Next come other pelagic organisms (more than 20 per cent), mainly the crus-
taceans: Euphausiacea and Hyperiidae (14 per cent), and prawns: Pandalus
borealis, Sabinea septemcarinata (4-4 per cent), and other members of the
Crangonidae and Hippolytidae families. Sometimes, especially in the west of
the Sea, ctenophores, jellyfish, appendicularians and other plankton organisms
form a considerable admixture to this diet (up to 2 per cent). In the eastern

162 BIOLOGY OF THE SEAS OF THE U.S.S.R.

part of the Sea the bottom fauna plays a considerable role. This consists
mainly of bottom crustaceans (about 5 per cent), Hyas araneus, Eupagurus
pubescens and different Amphopoda, Isopoda and Cumacea. Among the
other invertebrates (about 5 per cent) the most important are the molluscs,
echinoderms and polychaetes. Cod feeds also, to a small extent, on bottom
fish (about 4 per cent), on long rough dab, goby, launce and others. In general
more than 200 species of different creatures have been found in the stomachs
of cod.

Although omnivorous, cod always prefers fish which is its main food.
Pelagic crustaceans act as a substitute diet, since in the presence of herring or
caplin cod would always feed on them. With that exception, the diet range of
cod reflects, to a considerable degree, the quantitative ratio of various groups
of organisms present in water.

The quantitative ratio of the different components of the cod's diet is
very stable, as is obvious from a comparison of annual data for several years
{Table 70).

Table 70

Food composition of cod in
groups, per cent

Group 1939 data 1934-38 data

Pelagic fish

Other plankton organisms
Bottom crustaceans
Remaining benthos

27
5
3

62-4
20-4

5-2
5-4

In the course of a year cod feeds differently in various parts of the Barents
Sea, so that a regular annual cycle is obtained (Fig. 65 and Table 71). In early
spring (February-April) after slowing up during the winter, cod begins to
move eastwards (Fig. 64), feeding intensively on pelagic fish — herring and
caplin. The cod which have spawned off Lofoten arrive rather later and like-
wise feed on fish. In summer in the central commercial fishery areas it feeds
on the higher crustaceans (Euphausiacea and Hyperiidae). In autumn cod
assembles in shoals in the eastern parts of the Sea, and in the absence of her-
ring and caplin, turns quite extensively to bottom food — large crustaceans
such as crabs and hermit crabs, and molluscs. While starting its westward
movement cod reverts to a diet of fish (the young of both cod and haddock,
herring, caplin). Those cod which travel westward to spawn in the Lofoten
region (January- April) stop eating, at first partially and then completely ; off
Lofoten they are always caught with empty stomachs. The young cod, which
winters in the southwestern part of the Sea, also eats considerably less. After
intensive spring feeding the cod may pass through a period of compulsory
starvation, when the pelagic fish (herring and caplin) migrate from the regions
where cod dwell.

THE BARENTS SEA

163

Fig. 64. Chart of eastward migration of cod (Maslov). 1

Wintering areas of immature cod ; 2 Migration of mature cod ;

3 Migration of immature cod.

The seasonal change of cod diet (according to V. Zatzepin and N. Petrova)
as a percentage of the index* of repletion is also given in Table 71.

Cod eats most intensively at depths of 50 to 100 m ; lower down its food
consumption declines sharply. Since the eastern part of the Sea is its main

Table 71. Autumn feeding of cod in eastern part {winter lull)

Food groups

Periods

Fish

Pelagic

Other

Benthos

Other

Index of

Empty

crustaceans

planktons

crustaceans

benthic
animals

repletion

stomachs,
per cent

Spring fishing in
central fishery
areas

175

Period of forced

starvation

Summer feeding
in central fish-

ery areas

When migrating
to the east

162

When migrating
to the west

171

Immature cod

Mature cod

—

* The index of repletion is the ratio of the contents of the intestines to the weight of
fish, expressed as 1/100 of the percentage (prodecimille). There is a difference between the
general index of repletion (for the whole contents of the intestines) and the particular in-
dices (for the separate component groups).

164

BIOLOGY OF THE SEAS OF THE U.S.S.R.

feeding place, the highest indices of repletion of its intestines coincide with
low temperatures (from -f 1° to — 1°) or almost zero.

The cod's characteristic range of feeding is already established when it is
25 cm long.

Western Fishery
Grounds

Central Fishery
Grounds

Eastern Fishery
Grounds

Fig. 65. Diagram of food cycle of Barents Sea cod (Zatzepin and Petrova, 1939). Con-
tinuous lines — immature cod ; broken lines — mature cod ; / Summer fattening ; //
Main autumn feeding ; Ilia Period of lesser feeding during spawning migrations ;
Illb During spawning; IV Spring fattening in (a) central and (b) western fishing
regions ; V Period of forced starvation. Areas of circles correspond to repletion
indices. 1 Plankton organisms; 2 Euphausiaceae ; 3 Prawns; 4 Bottom-living
crustaceans ; 5 Other bottom-living animals ; 6 Herring ; 7 Caplin ; 8 Cod and had-
dock young; 9 Arctic cod; 10 Other fish.

For some sea areas, where cod gathers in dense shoals, migrating from one
region to another, an inverse ratio has been recorded between the index of
repletion of its intestines and its likelihood of being caught. In other areas,
however, abundant cod yields were taken during its periods of intensive feed-
ing. The cod's daily feeding routine of the Barents Sea is not expressed pre-
cisely (E. Zadulskaya and K. Smirnov, 1939). The hours of greatest repletion

THE BARENTS SEA

165

of the stomach differ with the seasons : in the summer and autumn they are
from 8 a.m. to noon, in the spring from noon to 4 p.m., in winter from 4 to
8 p.m. The greatest repletion of the stomach seems to be linked with definite
tidal phases (half flood and half ebb). Since there is no coincidence between
the time of day and the tidal phase accurate dependence of the feeding rhythm
on these two factors is destroyed.

The feeding of haddock. In contrast to cod, haddock feeds mainly on benthos
(Fig. 67). Two hundred various forms of benthos have been found in haddock

Fig. 66. Chart of haddock migration in Barents Sea. 1 Areas
of pre-spawning migrations of mature haddock; 2 Winter
shoaling areas of haddock ; 3 Areas of summer and autumn
shoaling; 4 Migration of mature haddock; 5 Migration of
immature haddock (Maslov, 1944).

intestines, with a preponderance of brittle stars, bivalves, polychaetes and si-
punculids. Ordinarily a large amount of the material of the sea bottom is
found in the haddock's stomach. Off the Murman coast, in spring and at the
beginning of summer, haddock feeds intensively on caplin, which approaches
the shores for spawning, and on its spawn (Fig. 66).

The importance of the separate components of the haddock's food as a
percentage of the total repletion index is shown in Table 72 (according to
V. Zatzepin, 1939 and A. Dekhtereva, 1931.)

V. Zatzepin drew an interesting comparison for the western Murman be-
tween the quantity of food consumed by haddock and the amount of benthos.
This gives a definite estimate of the selective capacity of fish for its food
Table 73).

Haddock prefers echinoderms (brittle stars and little sea-urchins) and

166

BIOLOGY OF THE SEAS OF THE U.S.S.R,
1884

890

PELAGIC CRUSTACEANS
(EUPHAUSIACEA, HYPERIIDAE, PRAWNS)

Г\ BOTTOM CRUSTACEANS (EUPAGURUS.
HYAS, AMPHIPODA, CUMACEA)
FISH (MOSTLY MALLOTUS VILLOSUS)
CAPELIN ROE
SEA-BED
REMAINDER OF BENTHOS

Fig. 67. Average food ranges and significance of certain groups of benthos-eating
haddock (A) off Murman coast and (B) in open Sea (Zatzepin). Mean repletion
index given by numerals above circles.

sipunculids {Phascolosoma margaritacewri) and feeds to a much lesser extent
on molluscs (Leda, Portlandia, Macoma Yoldia, Nucula, Natica, Margarita)
and polychaetes (Onuphis, Myriochele, Nephthys, Lumbriconereis).

The same can be observed in different Murman coast areas for the Cyprina
islandica community {Table 74).

Here too the haddock's preference for some types of food is fairly evident.
It is not clear whether the sea-bottom material gets into the haddock's in-
testines from the animals on which it feeds and thrives (brittle stars and
Phascolosoma feed on the sea bottom), or is seized with the animals consumed,
or is swallowed as such. Echinoderms become less and less important in
haddocks' nutrition as they proceed to the east ; they are replaced by small
molluscs and polychaetes.

Table 72. Composition of haddock' 's diet

Food group Murman coast

Open sea

Pelagic crustaceans (Euphausiaceae)

Bottom crustaceans (Amphipoda)

Remaining benthos

Fish

Sea-bottom material

General repletion index

3-6

1-5

390

130

35-3

97-5

2-2

44-1

121

31-4

890

THE BARENTS SEA
Table 73. Selection of food by haddock

167

Intestine content

Food groups

Bottom fauna. Maldane-

Astarte biocoenosis.

Northern part of Kola Inlet

Percentage of Percentage of
total reple- benthos reple- Percentage of Percentage of
tion index tion index food benthos total benthos

Fish ova

Fish

—

Pelagic crustaceans

9-5

—

Bottom crustaceans

1-4

—

0-5

0-2

Remaining benthos
Echinodermata

540

58-7

9-3

6-6

Sipunculida
Lamelli branchiata

—

170
9-5

150
180

71
56-3

Polychaeta
Gastropoda and
others

7-7
5-7

520

1-9

24-6
0-9

Brachiopoda, Bryozoa,
etc.

1-2

3-3

3-6

Varia

—

0-2

—

0-7

Sea-bottom material

33-9

—

Table 74

Intestine content

Bottom fauna. Cyprina
islandica off western Mur-

man coast

Food groups —

Benthos con-
Percentage of tent index Percentage of
total index of of repletion nutrient Percentage of
repletion per cent benthos total benthos

Fish ova

17-5

Fish (caplin)
Pelagic crustaceans
Bottom crustaceans

15-4
01
10

—

0-9

0-4

Other benthos

27-0

—

Lamellibranchiata

—

49-7

710

77-9

Polychaeta
Gastropoda and
others

22-6
10-4

150

3-5

8-2
5-6

Echinodermata

—

9-5

2-5

1-3

Gephyrea
Tunica ta

■ — -

3-8
3-6

5 0

0-6

3-2

Varia

—

0-4

2-8

Sea-bottom material

390

—

168

BIOLOGY OF THE SEAS OF THE U.S.S.R.

There are two annual maxima in the feeding of the haddock (Fig. 68) :
the larger one in spring at the expense of caplin, which approach the coast
for spawning, and its ova (index of repletion 256), and the autumn one, at the
expense of benthos (the repletion index in the open sea is 180). In the intervals
between the two maxima the repletion index of the stomach decreases to 40
to 45. The 'infauna-bottom feeders' are the best food for haddock ; 'epifauna-
seston feeding' (Zatzepin's terms) biocoenoses are of secondary importance
in the haddock's nutrition (Fig. 69).

Fig. 68. Annual course of feeding of haddock in the Barents Sea

(Zatzepin, 1939). 1 Mean repletion index in coastal area of Murman

Peninsula. 2 Same for open Sea.

Nutrition of other benthophages. As regards the other benthos feeders the diet
of the long rough dab (Hippoglossoides platessoides) (V. Brotzkaya and I.
Komarova), the only flat-fish species, was examined most thoroughly. It is a
typical inhabitant of the lower Arctic sub-region, widely distributed in enorm-
ous numbers throughout the Sea. Hippoglossoides platessoides feeds mostly on
ophiura (Ophiura sarsi, O. robusta, Ophiocten sericeum, Ophiopholis aculeata)
and the mollusc Pecten groenlandicus. Fifty-three per cent of the contents of
the stomach of the dab consists of benthos (except crustaceans). Fish is also
very important in its diet (35-4 per cent); Triglops pingeli, cod, haddock,
Boreogadus saida, caplin and herring are most commonly found in its sto-
mach. Pelagic forms (7-5 per cent) Panda/us borealis and bottom crustaceans
(4 per cent) are of secondary importance in the diet of the dab. Benthos is
markedly preponderant in the diet of a young dab (under 25 cm), while with the
adult one fish and benthos are in the food in almost equal parts. The dab's
food may change considerably in different areas, thus, on the Gusinaya bank
it feeds almost exclusively on benthos, while in the Persey and Murman
shallows fish forms 75 to 80 per cent of its diet and in the central shallow 60
per cent of its food consists of pelagic crustaceans (Pandalus borealis).

THE BARENTS SEA

169

GULF OF
MOTOVSK

community

, Spongia-Bryozc
Bracniopoda "

Ш1Ш1 шш ищ

8 9 10 It 12

Fig. 69. Relationship of total (whole water
column) and feeding (lower part) benthos for had-
dock on some typical biocoenoses of Murman
coast (Zatzepin, 1939). 1 Porifera; 2 Coelenterata;
3 Bryozoa; 4 Brachiopoda; 5 Polychaeta;6 Sipun-
culoidea; 7 Bivalves; 8 Gastropoda; 9 Echino-
dermata ; 10 Tunicata ; 11 Barnacles ; 12 Others.

Definite seasonal cycles were observed in the feeding of long rough dab :
it is low in winter and spring, especially in March-May, when the fish reaches
its sexual maturity. The main feeding takes place in June-October. The annual
change in the repletion index is given in Table 75.

The long rough dab's selective capacity is clearly shown by a comparison
of its stomach-content with the fauna of the bottom areas inhabited by it.

The sea-dab {Pleuronectes platessa) differs greatly from the long rough dab.
It feeds mainly on molluscs and polychaetes and, to a much lesser extent, on
bottom crustaceans, sipunculids and brittle stars.

Table 75

Month

Feb

Mar Apr May Jun

Jul

Aug

Sep

Index of repletion
No. with empty
stomachs, per cent

410
38

10-25 4318 180 78-8
72 68 80 3

88-8
11

87-6
20

102-7
7

170

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Catfish {Anarrhichas minor and A. lupus) are also mainly benthos-eating;
the echinoderms {Stronyglocentrotus droebachiensis, Ophiura sarsi, Ophiopho-
lis aculeata) and the molluscs {Pecten islandicus, Cardium ciliatum) are pre-
ponderant in its diet. However, it devours large amounts of fish also, mainly
cod and long rough dab.

Although an inhabitant of the sea bottom, more than half the diet of the

Fig. 70. Food ranges of various fish of the Barents
Sea (Brotzky, Briskina, Bogorov, and others).

1 Ammodytes tobianus; II Careproctus reinhardti;
III Gadus poutassou ; IV Liparis major ; V Gymna-
canthus tricuspis; VI Myoxocephalus quadricornis;
VII Icelus bicornis ; VIII Lycodes pallidus ; IX Arted-
iellus europeus; X Aspidophoroides olrickii; XI Tri-
glops pingeli. Repletion indices given by numerals
under circles. White sectors inside circles denote per-
centages of empty stomachs. 1 Full stomachs;

2 Empty stomachs ; 3 Pelagic crustaceans ; 4 Bottom-
living crustaceans; 5 Benthos; 6 Fish; 7 Sea-bed

soil.

ray {Raja radiata) consists of pelagic organisms (60 per cent) with 20 per cen-
fish and 20 per cent crustaceans and, to a lesser extent, benthos. Ray does not
touch infauna at all, it chooses the mobile benthos forms such as bottom crust
taceans and worms. Hence ray can be compared with cod as regards its feed-
ing habits. Among fish it chooses caplin, cod, haddock and long rough dab,
among the pelagic crustaceans Pandalus borealis and Thysanoessa.

Various non-commercial Barents Sea fish (M. Briskina, 1939) are typical
benthophages (Fig. 70), which tear out the infauna from the bottom, as for
example Artediellus europeus; others fatten on infauna, onfauna and on

THE BARENTS SEA

171

bottom crustaceans, as for example Gymnacanthus tricuspis, Icelus bicornis,
Aspidophoroides olriki, Triglops pingeli and Lycodes pallidus. Still others
thrive almost exclusively on bottom crustaceans, as Myoxocephalus quadri-
comis, Lycodes seminudus and L. agnostus ; some feed equally on benthic and
pelagic organisms (crustaceans) like Careproctus reinhardti and Liparis major ;
and finally a fifth group lives exclusively on
pelagic crustaceans, as for example Gadus
poutassou and Ammodytes tobianus.

Diet of herring and some other plankton-eating
fish. Herring, caplin, Boreogadus saida and bass
are the most characteristic plankton-eating fish
of the Barents Sea. The southwestern parts of the
Sea are the best feeding grounds for pelagic fish,
and the eastern ones for benthos feeders. In the
western part of the Sea even cod feeds mainly on
pelagic organisms and in the eastern one on
benthos.

During the summer (as was shown by Yu.
Boldovsky, 1941) herring fattens on Calanus
finmarchicus, Thysanoessa inermis and 77г. raschi,
which form no less than 90 per cent of the zooplankton consumed by it.
Herring fry thrives on unicellular algae and on the larvae of various
animals, but when a year old it begins to feed first on Calanus and then on
Euphausiacea (Fig. 71).

The dependence of the rate of growth of a herring on the plankton (B.
Manteufel, 1941) can be shown by comparing the amount of plankton with
the growth of the herring during the first year of its life {Table 76).

Fig. 71. Mean annual
ranges of feeding of Mur-
man herring in gubas of
Murman Peninsula (Bold-
ovsky). 1 Calanus finmar-
chicus ; 2 Cirripedia larvae ;
3 Euphausiaceae ; 4 Poly-
chaete larvae ; 5 Others.

Table 76

Year

1934 1935 1936 1937 1938

Average plankton biomass, mg/m3

at the entrance to Motovsky

Gulf in June 350 100

Increase in length of herring in the

first year of life, mm 8-55 7-71

320 360 400

8-39 908 801

In the southwestern part of the Sea Ctenophora and Bolinopsis congregate
at times in huge numbers of more than 200 mg/m3 ; they may compete with
the herring for food in summer. In such cases Calanus may all be consumed
by ctenophores and herring would move into other areas. The feeding of
herring proceeds most intensively in June, after which it decreases and then
rises again in November. B. Manteufel (1941) has established a relationship
similar to the one noted for cod, between the repletion of the herring and the
ease with which it is caught. Herring are dispersed in places where Calanus

172 BIOLOGY OF THE SEAS OF THE U.S.S.R.

finmarchicus shoals, and are not found there in commercial concentrations. In
June and July the main mass of Calanus finmarchicus sinks down into the
depths, the herring concentration increases, and the herring catch is larger.
Once herring has eaten its fill it can thrive in shoals in zones of abundant
plankton.

As in the North Sea, Barents Sea herring avoids places where the algae
Phaeocystis and Chaetoceras bloom, but it may be present in commercial
numbers at the edges of such zones. Descending to a depth of 100 m the her-
ring may shoal in large numbers under the zone where these algae bloom.
The amount of plankton needed for herring's food in the southwestern parts of
the Sea is reckoned in millions of tons.

Herring has many enemies — cod, marine mammals, sea-gulls, which often
follow the schools, preying on this tasty fish. Caplin (Mallotus villosus) is the
herring's most dangerous rival as regards food ; it is a comparatively small
pelagic fish of the Osmeridae family, which thrives in the Barents Sea in huge
numbers and comes up to the Murman coast to spawn. Polar cod (Boreogadus
saida), a small pelagic fish also found in exceptionally large numbers in the
Barents Sea, is not so dangerous a rival.

Their rivalry is weakened by the fact that they live in different parts of the
Sea. Herring's main habitat lies in the southwestern part of the Sea, caplin's
in the northern and eastern ones, while polar cod keeps mostly near the ice,
thriving in cold water with a temperature below zero ; it is the only pelagic
fish closely connected with ice. On the other hand these three fishes are all
devoured in huge numbers by other fish, mammals and birds.

The links between the food of polar cod and that of the other inhabitants
of the sea are particularly curious. The distribution of this high Arctic fish
links it with many floating-ice animals. In S. Klumov's opinion (1935) polar
cod feeds on phytoplankton in the summer and zooplankton in the winter.

The predominant role of phytoplankton in the polar cod diet is, in Klumov's
opinion, illustrated and confirmed by its love of ice since diatoms typically
representative of the ice phytoplankton are predominant in its stomach. The
polar cod food links are illustrated graphically by Klumov in Fig. 72.

History of fishing and hunting trades. Fishing and hunting trades have existed
in the Barents Sea since the fifteenth century. They covered a large area from
Finmark to the Pechora River in the east and as far as Spitsbergen to the north.
In the sixteenth century some tens of thousands of fishermen, inhabiting the
White Sea region, came to the Murman coast in the summer. At the end of
the eighteenth century up to 270 craft would in some years appear off Spits-
bergen coming from the White Sea. Up till the end of the last century the
fishing industry of the Barents Sea was haphazard in character. It was run
mainly by small commercial guilds in off-shore waters, in shallow, hardly
seaworthy ships equipped with very primitive gear. N. Knipovitch, the head
of the scientific and industrial expedition off the Murman coast, discovered
that trawling is possible in the open Barents Sea. Foreign trawlers were the
first to make use of this discovery at the turn of the century. Only in the last
few years before 1914 did an Archangel tradesman, Spade, buy four trawlers

THE BARENTS SEA

abroad ; his venture proved to be a success. Under the Soviet government
trawling in the Barents Sea began to develop rapidly. The trawler fleet of the
u.s.s.r. in the Barents Sea comprised 300 craft by the beginning of 1958

IAR

HAIRY
SEAL

SEA
HARE

SMALL
RORQUAL

NARWHAL

GREENLAND
SEAL

COD SAND-
DAB & OTHERS

SEA
BIRDS

MARKED LINK
WEAK LINK

Fig. 72. Diagram of food correlations of Arctic cod (Klumov, 1935).

(counting only ships of more than 42 m length and including a powerful
fleet of refrigerated trawler factory ships with a stern trawl sweep). In Soviet
times the herring fishery has developed rapidly on the Murman coast. The
hunting of marine animals — the Greenland seal — is a trade which has
existed since time immemorial in the Gorlo of the White Sea.

Acclimatization prospects in the Barents Sea. The Barents Sea may turn out
to be the most suitable region for the acclimatization of commercial fish
and of the forms it feeds on, of all the northern parts of the Pacific Ocean.

There is no doubt that several members of the Pacific Ocean fauna of the
lower Arctic and north-boreal aspects, for which the way through the Arctic
Ocean is now closed, could thrive successfully in the Barents Sea, since its
salinity and temperature conditions (potentially amphiboreal forms) are the
same as those of their main habitats. Attempts have been made to bring into
the White Sea the far eastern salmon (Oncorhynchus gorbuscha); Kamchatka
crab was also prepared for transportation into the Barents Sea, but as yet no
further ventures have been undertaken. No comprehensive study of the Pacific
Ocean fauna as an acclimatization stock for the Barents Sea has so far been
carried out. Neither should the idea of collecting stock for acclimatization in

174 BIOLOGY OF THE SEAS OF THE U.S.S.R.

the Barents Sea among the low Arctic and sub-Arctic fauna (bipolar forms) be
abandoned. It can be maintained with confidence that the acclimatization possi-
bilities along these two lines merit further study.

Zoogeographical characteristics

Zoogeographical subdivision. Before the appearance of K. Derjugin's mono-
graph (1915) on the fauna of the Kola Guba, the question as to which zoo-
geographical region should include the Barents Sea had not been properly
studied. This question was touched on only in passing when establishing the
boundaries of different regions.

Simultaneously with Derjugin, N. Hofsten (1915, 1916) was working out a
scheme for the zoogeographical subdivision of the Barents Sea. The opinions
of G. Broch (1927), who worked on the zoogeography of the northern parts
of the Atlantic for several decades, are also interesting. The boundaries
drawn by Hofsten and those of Broch differ considerably (Fig. 73). Broch
(1927) starts the southern boundary (pan- Arctic in Hofsten's sense) of the
Arctic region from the North Cape, drawing it along the littoral shallow of
Norway.

On the contrary, Hofsten, following Appellof (1912), includes the northern,
eastern and southeastern parts of the Barents Sea in the Arctic region, assign-
ing all the southwestern half of the Sea to the transitional boreal Arctic zone.
The boreal region, in Appellof's opinion, stretches from the North Cape
southwards.

K. Derjugin (1927), who also studied Arctic fauna in detail, came to the
following conclusions on the basis of his own work. He limits the Arctic
region to the area with a deep floor temperature of 0° and below. Its southern
boundary begins at the eastern Murman Peninsula near the entrance to the
White Sea and extends to the northeast, north and northwest to Bear Island.
This boundary almost coincides with the limit of the greatest southward
movement of floating polar ice in winter. Derjugin considers the transitional
region of mixed waters and fauna as much more significant than Appellof and
Hofsten, ascribing to it the importance of a separate zoogeographical region
(the boreo-Arctic region of the two investigators mentioned). In Derjugin's
opinion 0° to 5° or 6° is the typical temperature of this region ; moreover, as a
rule, no ice cover is formed there. Hence Derjugin includes about one-third
of the whole of the Barents Sea in this region, which he calls the sub-Arctic.

Since Derjugin's investigations A. Schorygin (1928) was the first to survey
the problem of the zoogeographical subdivision of the Barents Sea for the
echinoderm group. This investigator has based his scheme on a statistical
count of the frequency of occurrence of certain individual forms. Derjugin's
boundaries between the Arctic and sub-Arctic benthos were corrected by this
indirect but quantitative method. The boundary had to be moved 200 to 300
km to the west. Schorygin also drew a more accurate boundary between the
low Arctic and high Arctic sub-regions in the northern and southeastern parts
of the Barents Sea. His conclusions were later confirmed by a comprehensive
quantitative analysis of the bottom fauna carried out by V. Brotzkaya and
L. Zenkevitch in 1939 for the whole Sea and by Z. Filatova (1938) for the

THE BARENTS SEA

175

southwestern part of it (Fig. 73). Derjugin had drawn the boundary between
the Arctic and sub-Arctic benthos so far to the east as a result of his obser-
vation of the occurrence of some individual boreal forms far to the east. How-
ever, this drift of the boreal forms, under continuous pressure of warm waters

Fig. 73. Zoogeographical boundaries of the Barents Sea. / Boundary be-
tween Arctic and Atlantic-boreal sub-regions (Ortmann); // Limit of
Arctic region (Broch) : a for plankton, b for benthos ; /// Boundary be-
tween Arctic and sub- Arctic regions (Derjugin); IV Boundary between
Arctic and boreo- Arctic regions (Hofsten) ; V Boundary between Arctic
and transitional Atlantic region (Hentschel) ; VI Boundary between high
Arctic and low Arctic sub-regions (Brotzky and Zenkevitch) identical with
Schorygin's boundary ; VII Boundary between Arctic and boreal benthos
(Filatova), almost the same line as corresponding boundaries of Schorygin,
Brotzky and Zenkevitch.

from the west, has little quantitative effect. The main mass of the fauna remains
the same. A sharp numerical change of the fauna from the Arctic to boreal
forms takes place much farther to the west. Z. Filatova's (1934) quantitative
zoogeographical analysis of the fauna of the southwestern parts of the Barents
Sea is very interesting. A count of the ratios of the boreal, Arctic and Arctic-
boreal forms of the bottom communities makes it possible to draw a fairly
clear boundary between the Arctic and boreal regions. (Fig. 74). This study

176

BIOLOGY OF THE SEAS OF THE U.S.S.R.

ACCORDING TO

TO NUMBER

OF SPECIES

100

ACCORDING TO
DENSITY INDICES

brought Filatova to the conclusion that the introduction of a transitional
region (boreo-Arctic according to Appellof and Hofsten, or sub-Arctic
according to K. Derjugin) is unnecessary. It is evident from Fig. 74 that the
clearest picture is given by the biomass. The northern parts of the Atlantic

trench should be included in the Arctic region,
the southern ones in the boreal. Qualitative
estimation should always be corrected by
quantitative analysis.

As has been mentioned in our general
section, Ortmann as early as 1896, and later
many other zoogeographers, have pointed
out the difficulty of drawing common zoo-
geographical boundaries for plankton and
benthos, for the shallow- and deep-water
fauna. This is particularly true of the southern
part of the Barents Sea since the warm-water
forms are continuously drifting into it from
the west. Vertically the Barents Sea is not
zoogeographically homogeneous. Under the
favourable conditions of the Barents Sea
littoral its fauna extends almost without
qualitative change from the North Sea to the
White Sea; the plant and animal forms
remain practically the same, individual forms
and complete fauna as a whole retaining very
similar relationships. Thus the Murman and
White Sea littoral is populated mainly by
boreal fauna and should therefore be included
in the boreal region (Fig. 75). The main mass
of organisms of the upper horizon of the
sublittoral is also boreal in its characteristics.
In the opinion of V. Zatzepin (1939), who
made a special study of the Murman coastal
fauna, the latter retains its boreal character
up to the Gavrilov Islands. As one goes
deeper, the boreal forms become less
important, while the Arctic ones become
predominant. However, owing to a warm, so-
called Ruppin, branch of the Atlantic current,
in the coastal region the boundary of the
Arctic fauna recedes along the coast far to the east. Finally, as has been
mentioned above, high Arctic fauna concentrate in the cold bottom water
of some stagnant hollows of some sections of inlets on the Murman coast,
even in its western parts. Thus a vertical change of the fauna from boreal to
high Arctic may be observed within the same region as we proceed from
the littoral to the depths.
The Barents Sea fauna thriving in an area where the warm Atlantic waters

700
80

BOREAL SPECIES

ARCTIC SPECIES

ARCTIC -BOREAL

SPECIES

Fig. 74. Relationship between
Arctic, boreal and Arctic-
boreal species per cent in bot-
tom fauna biocoenoses of
southwestern part of Barents
Sea from west to east (Fila-
tova, 1934).

THE BARENTS SEA

177

meet the local cold ones goes through continuous and fairly substantial
changes, with warm-water forms now advancing, now receding, and being
replaced by the cold-water ones. These migrations depend directly on the
climatic changes, primarily on the greater or smaller thrust of the warm
Atlantic waters.

History of fauna development. As yet the palaeogeographical changes of the
Barents Sea during the Tertiary and Quaternary periods have not been
sufficiently investigated. As has been said above, a rise in temperature of the

Fig. 75. Penetration of boreal forms into Barents Sea. 1 Littoral fauna; 2
Fauna of upper horizon of sublittoral ; 3 Boreal pelagic fauna (Derjugin's
boundary) ; 4 Boundary of boreal and Arctic faunas (Filatova) ; 5 Direction
of migration. Places where cold-loving bottom-living fish Ly codes agnostus
(6) and Lycodes vahli v. septentrionalis (8) and the thermophilic Lycodes
seminudus (7) (Knipovitch) are found.

178 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Arctic and a migration of numerous representatives of the boreal fauna into
the Barents Sea have been observed during recent decades. It may be assumed
that similar climatic ameliorations occurred in former times, when warm
periods alternated with the cold ones. In the post-glacial epoch the highest
rise of temperature occurred during the Littorina stage, that is 5,000 years ago.
This considerable climatic amelioration (a rise in temperature of a few degrees)
left a definite trace in the eastern part of the Barents Sea in the form of resi-
dual warm-water forms, which penetrated into the Barents Sea and the White
Sea. Part of them are still living in the White Sea ; in the eastern part of the
Barents Sea they have died out. However, the shells of such molluscs as
Cardium edule, C. echinatum, Mactra elliptica, Nucella lapillus, Neptunea
despecta, Buccinum undatum and others, which no longer inhabit these parts,
are still found in a sub-fossil state there.

By the end of the Tertiary period the bottom of the Barents Sea was 400 to
500 m higher than it is now, and the whole Sea was dry land. The Atlantic
waters penetrated into the Barents Sea at the beginning of the Ice Age. During
that period the bottom of the Barents Sea underwent a number of sinkings and
risings; numerous coastal terraces, some now below sea-level (70, 100, 180,
220 m), others considerably above it (up to 400 m), bear witness to these
changes. The Barents Sea at times grew shallow and dried up in considerable
areas, at times it became much deeper than it is at present. During the period
of the greatest glaciation (Riss stage) the Barents Sea was about 200 m
shallower than it is now and was blocked with ice. At that time the submarine
ridges between Scotland, Ireland and Greenland were near the surface and the
Atlantic waters could scarcely penetrate into the Arctic basin ; this must have
affected its climate considerably, causing a sharp drop of temperature. In the
opinion of some scientists this alone was sufficient to bring about a glacial
period. The lowering of Fenno-Scandia, which occurred at the height of the
Ice Age and which opened the Arctic basin to the Atlantic waters, caused the
melting of the ice. The boreal transition probably conditioned the mass pene-
tration of warm-water fauna into the Arctic basin and the Barents Sea ; how-
ever, it was soon exterminated by the arrival of a new glaciation phase (Wurm
stage). The coldest phase of the post-glacial period, which lasted for 20,000
years for the water bodies surrounding Fenno-Scandia, was the Yoldian
stage with Yoldia (Portlandia) arctica as its predominant form ; this latter
is still found in the coldest sections of the Barents Sea and elsewhere in
the Arctic. Several breeds of molluscs originating from Yoldia arctica
(C. Mosevitch, 1928) inhabit river estuaries and have maintained their relict
character, although they do not seem to prefer a cold-water environment.

The alternation of colder and warmer phases in the course of the post-
glacial epoch resulted in one of the most characteristic features of the fauna
of the Barents and White Seas. This is a combination of cold- and warm-
water relicts which is frequently encountered even within small habitat areas.
The White Sea fauna displays this most clearly.

The post-glacial cUmatic changes of the Arctic basin are due not only to the
fluctuations of its sea-level and its temperature. As has been mentioned above,
the changes of salinity must have been just as pronounced.

The White Sea

I. GENERAL CHARACTERISTICS

The White Sea is a comparatively small Arctic body of water communicating
with the Barents Sea by a broad rather shallow channel. Compared with the
Barents Sea, the White Sea has a more continental climate — a warmer sum-
mer, and a harsher winter in which, for not less than half the year, the Sea is
covered along its shores by a broad continuous unmoving belt of ice, and out
at sea by floating ice-floes.

A large inflow of river water and the restricted exchange of water with the
open sea are causes of the reduced salinity of the Sea and of the considerable
difference in salinity between the surface layer (25 to 40 m) and the deeper
masses of the water which in summer, in some areas, reach a salinity of almost
10%o (it is usually 4 to 5%0).

In winter, when huge masses of ice form on the surface of the Sea, of which
a considerable part is carried out into the Barents Sea, and the surface layer
of water becomes brackish, there may set in a vertical homohalinity and an
intermingling of the whole column of water. In summer, when there is sharply
differentiated saline and thermal stratification in two layers, the phenomena
of stagnation and accumulation of carbon dioxide must take place in the deep
layer of the bathymetric part of the Sea. The poverty of the bottom fauna
and the predominance of brown mud point to this fact; however, so far there
is no experimental evidence in favour of this view.

The instability of conditions of salinity, especially in the surface layer of
the White Sea, is characteristic also for different seasons of the year and for
different years.

The flora and fauna of the White Sea, in consequence of its low salinity
and of the harshness of its winter, present, in the main, an impoverished
Barents Sea population, with weakly expressed endemic features and a certain
number of relicts, both warm-water and cold-water.

The summer rise and winter fall in temperature, more considerable than
those in the Barents Sea, and the persistent low temperature in the bathymetric
part of the Sea cause a zoogeographic polarization of the Sea. In different parts
of it there exist simultaneously both warm- water and cold-water relicts, absent
from the adjacent parts of the Barents Sea. At the same time the White Sea is the
western limit of distribution of a series of Pacific Ocean forms. At great depths
high Arctic animal forms are predominant ; on the other hand low Arctic forms
are principally characteristic of the upper levels of the Sea (down to 30 or 40 m
and the littoral is inhabited by a north-boreal community of forms typical
also of the Murman coast and the shores of Norway and the North Sea.

Not only in qualitative variety, but also by all indices of its biological pro-
ductivity, the White Sea falls considerably below the Barents Sea (biomass,
number of specimens, size, time of growth).

179

180 BIOLOGY OF THE SEAS OF THE U.S.S.R.

The fact that the productive capacities of the White Sea are several times
lower than those of the Barents Sea is caused by its shorter period of vege-
tation and by a series of other physico-geographical factors and explains,
in its turn, the relatively small commercial productivity of the Sea.

The only commercial fish present in quantity in the open sea are herring
and pollack ; in the Gorlo area, the Greenland seal is abundant.

II. HISTORY OF EXPLORATION

The first period

Interest in the study of the fauna of the White Sea arose at first in connection
with the journey of K. Baer to Novaya Zemlya in 1837. Baer, who also visited
the White Sea, drew attention to the richness of its fauna, especially in the
Gulf of Kandalaksha. In 1864 the Moscow zoologist, A. Kroneberg, went to
the White Sea and brought back a rich collection of marine animals. After
that the initiative in the study of White Sea fauna passed to the Petersburg
Society of Naturalists, which sent to the White Sea the zoologists F. Jarzhin-
sky and L. Iversen in 1869, and N. Wagner, C. Mereschkowsky and S. Her-
zenstein in 1876, 1877 and 1880. In 1870 a large-scale expedition to the White
Sea and the Barents Sea was likewise carried out from Moscow by V. Uljanin.
We are indebted to all these persons for the earliest information about the
fauna of the White Sea.

The second period

A closer investigation of the fauna of the White Sea began, however, in 1881,
when the above Society opened a biological station on Great Solovetsky
Island, which existed there for 18 years and was transferred in 1899 to Aleks-
androvsk on the Murman Peninsula. Over a series of years the outstand-
ing Russian zoologists V. M. Schimkevitch, N. M. Knipovitch, A. Birula,
K. Saint-Hilaire and many others worked at the Solovetsky biological station.
During the first 20 years of this century the work of K. Saint-Hilaire in the
Kovda Guba region, and of N. Livanov in the Solovetsky Islands, was parti-
cularly notable.

The third period

From 1920 onwards there began a period of more intensive study of the White
Sea by workers from the Hydrological Institute, the Northern Scientific and
Fishery Expedition, and the State Oceanographic Institute. At the same time
K. Derjugin also began work on the White Sea ; he published a voluminous
monograph devoted to it in 1928. In addition, several permanent establish-
ments arose on the shores of the White Sea. The first of these, after the trans-
fer of the Solovetsky station to the Murman Peninsula, was the summer bio-
logical laboratory founded by Saint-Hilaire at Kovda in 1908. In 1931 the
Hydrological Institute set up its White Sea station at Piryu Guba (Umba)
and the State Oceanographic Institute opened its branches at Archangel
and Kandalaksha. Finally, in 1939, the White Sea Biological Station of
Moscow University started functioning on the southern shore of the Gulf of

THE WHITE SEA

181

Kandalaksha (Rugozerskaya Guba); since 1945 the Biological Station of the
Petrozavodsk University has been working at Gridin, and since 1957 the
Biological Station of the Karelian Associate Branch of the Academy of
Sciences of the u.s.s.r. at Chupa Guba.

III. PHYSICAL GEOGRAPHY, HYDROLOGY, HYDRO-
CHEMISTRY AND GEOLOGY

Situation and size

The White Sea (Fig. 76) is an accessory body of water of the Barents Sea, to
which it is connected by a broad sound, projecting far into the mainland. It is
bounded by the coordinates 63° 48' to 68° 40' of north latitude and 32° 00' to
44° 40' of east longitude. The northern limit of the Sea is taken as being a line
joining Sviatoi Nos and Cape Kanin.

Curren'i

Fig. 76. Chart of White Sea with depths and currents.

The White Sea is subdivided into: (7) the funnel-shaped broad (100 to
170 km) shallow (20 to 40 to 80 m) outer part of the sound (to the northward
of a line from Danilov Island to Voronov Island) ; (2) the Gorlo, the narrow
(45 to 60 km), deeper (40 to 100 m) inner part of the sound, running south-
ward as far as a line joining Cape Nicodiemsky and Cape Veprevsky ; and (3)
the White Sea proper (the basin), consisting of a central part, open sea, and
three inlets, the Kandalaksha, Dvina and Onega Gulfs. The area of the whole
sea is approximately 90,000 km2, with a mean depth of 89 m. On a
line from the Gulf of Kandalaksha to the Dvina Gulf the Sea extends for
480 km. The considerable freshness of the water of the White Sea is deter-
mined by its positive fresh- water balance (V. Timonov, 1950). The annual in-
flux from the land composes 185 km3, with 19 km3 of sediment ; evaporation

182 BIOLOGY OF THE SEAS OF THE U.S.S.R.

accounts for 13 km3. So that inflow exceeds discharge by 191 km3. If this
excess were distributed over the whole surface of the Sea, it would form a
2-2 m layer of fresh water, or one-fortieth part of the volume of the Sea.

Bottom topography

The greatest depth in the White Sea is about 330 m (off Cape Tury), and its
central part is occupied by depths greater than 100 km, separated by the wide
ridge of the Voronka and the Gorlo from the deep parts of the Barents Sea.
The average depth of the basin is 110 m.

The deep bottom of the Gulf of Kandalaksha, which represents what in the
Ice Age was the bed of a great glacier, is covered with moraine deposits and
forms a series of depressions, which are separated on the seaward side by
banks (end moraine). Along its shores are a great number of inlets and islands.
The character of the Dvina Gulf, which receives the waters of the great
Northern Dvina river, is, however, quite different. Sandy deposits are pre-
dominant here ; the bottom slopes evenly down to the bed of the Sea, and the
shores have few inlets and islands. No less peculiar is the Gulf of Onega,
relatively shallow (20 to 40 m) and situated on a rocky plateau. It is separated
from the Sea by the Solovetsky Islands and has innumerable islands and
underwater shoals scattered about it.

Climate

In spite of the fact that the climate of the White Sea is considerably more
continental in character and much more rigorous in winter than that of the
Barents Sea, yet it is completely marine in character. At the same time the
climate in the open parts of the Sea is milder than in the inlets and bights, as
may be seen from Table 77, giving the mean monthly temperature for the
Solovetsky Islands and for Archangel.

Table 77

Month

Jan Feb Mar Apr

May

Jun

Jul

Solovetsky
Archangel

- 9-6 -11-2 -8-7 -2-1
-13-5 -12-7 -7-8 -1-2

+3-7
+ 50

+ 7-7
+ 11-9

+ 12-2
+ 15-7

Month

Aug Sept Oct

Nov

Dec

Mean
Annual

Solovetsky
Archangel

+ 11-2 +8-0 +2-6
+ 13-5 +8-0 +5-7

+ 1-9

+ 5-7

- 6-3
-11-3

+0-5
+0-3

Ice cover

In consequence of its climate, which is harsher than that of the Barents Sea,
considerable masses of ice are formed in the White Sea in winter and persist
for about half the year, sometimes for seven months (in the region of Mudyug
Lighthouse) — from the second half, or from the end, of October till the middle

THE WHITE SEA

183

or end of May. Only at the shore does the ice form a continuous covering to
the water, the coast ice as it is called, which is sometimes several kilometres
wide. A continuous covering is also formed in the inlets and gubas and between
the islands, where the ice may be as much as a metre thick. The open parts of
the Sea are covered with floating ice of every kind.

Currents

The fresher surface waters of the White Sea flow out through the Gorlo into
the Barents Sea along its eastern shore (the 'Winter Shore'). Along the western
side (the Tersky Shore) more saline water flows into the Sea from the Barents
Sea, as may be clearly seen from the sketch (Fig. 77).

Fig. 77. Distribution of salinity on the cross section through the
Gorlo of the White Sea along the line Sosnovetz Island to Megry
village (Timonov, 1950).

Across the Gorlo (from Sosnovetz Island) very strong tidal streams in the
Voronka, and especially in the Gorlo, check the perpetual currents and create
a movement of the whole mass of water in the Gorlo first towards the Barents
Sea, and then towards the White Sea. While the speed of a permanent out-
flow current will hardly exceed 20 cm/sec, the speed of the tidal shift may
attain 7 to 8 km/h, or exceed 200 cm/sec. These streams and currents cause
the most violent, turbulent confusion of the whole column of water in the
Voronka and the Gorlo, and as a consequence their bed is covered with an
extremely hard sediment.

As was shown by V. Shulejkin (1925), these tidal oscillations do not bring
the waters of the Barents Sea into the White Sea, but only shift the masses of
water in the Gorlo first in one direction and then in the other, for no more
than ten miles on one flood tide. An excellent illustration of this system of cur-
rents and streams (Fig. 79) is given by Derjugin (1928, from the data of M. Vir-
ketis) from the pattern of the distribution of certain plankton organisms.
V. Timonov (1947) presents the system of certain cyclonic and anticyclonic
rotations of the surface waters of the White Sea (Fig. 78).

Calanus finmarchicus is not found in either the Voronka or the Gorlo, and
is abundantly represented in both the Barents and White Seas. The infusoria
Tintinnopsis campanula is carried into the Gorlo along with the outflow cur-
rent; contrariwise, the typical Barents Sea infusoria Cyttarocyllis denticulata
is carried along the Tersky shore into the White Sea.

184

BIOLOGY ОГ THE SF.AS OF THE U.S.S.R.

Fig. 78. Chart of circulation of surface waters of the
White Sea (Timonov).

The Dvina and Kandalaksha Gulfs are in free communication with the
central parts of the Sea, but the shallow Gulf of Onega is barred from the rest
of the Sea by the Solovetsky Islands. In consequence of its shallowness and of
the strong tidal streams the waters of the Gulf of Onega are generally well
mixed from top to bottom, and are homothermic and homohaline. The Gulf
of Onega is the part of the Sea which is best warmed in summer and best
aerated, by virtue of which animal forms find here for themselves the most
favourable conditions of existence.

Fig. 79. Distribution of the Crustacea
Calanus finmarchicus (7), plankton ciliates
Cyttarocyllis denticulata (2) and Tintin-
nopsis campanula (3) in the White Sea (Der-
jugin from Virketis, 1928).

THE WHITE SEA

185

Temperature and salinity

The vertical distribution of salinity and temperature in summertime in the
main basin of the White Sea is shown in Fig. 80. As may be seen, the tempera-
ture on the surface of the open sea at the warmest time of the year reaches 14°
to 16°. With depth the temperature falls quickly and at 35 to 44 m it already
equals zero. In the Dvina Gulf there is a dome-shaped rise of isotherms and
isohalines, and the 0° isotherm is found at a depth of only 12 m. Derjugin
suggests that this is the centre of the halistatic region formed by the circular
rotation of the waters, and calls it the 'cold pole' of the White Sea. Farther
down the temperature decreases still more, to —1-4° at approximately the

Fig. 80. Vertical ranges of salinity and temperature in the White Sea at the beginning
of August 1922 on the cross section from Kandalaksha Bay to the Bay of Dvina

(Derjugin, 1928).

150 m level, and in places drops even to — 1-5°. Such clearly expressed strati-
fication is characteristic for salinity in summer as well. At the surface it is
equal to 25 to 26%0 and in the depths it reaches 30 to 34%0.

In winter the picture is sharply changed. A condition is established very close
to homothermic and the salinity of the surface layer rises considerably, as
may be seen from Table 78, borrowed from Derjugin.

While in the open parts of the Sea (the Gulf of Kandalaksha) the summer
temperature reaches 15° (Fig. 81), along the shoreline far up the inlets and
bights this maximum is still higher and may exceed 20°. In this way the White
Sea, in consequence of its small size and of the depth of its extension into the
mainland, has much harsher winter climatic conditions than the Barents Sea.
On the other hand, opposite correlation is set up in summer, and the surface
layer of the White Sea, especially in the inlets, is much more strongly warmed
than that of the Barents Sea, and the deep layers maintain a very low tempera-
ture all the year round.

This explains a series of biological phenomena. The depths of the Sea main-
tain a high Arctic fauna, while in the surface layer both Arctic and boreal
forms may exist. Some of them are absent either in the Barents Sea or in those
parts of pit adjacent to the White Sea.

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THE WHITE SEA

187

On the other hand the lowered salinity of the White Sea hinders the pene-
tration of many forms, both Arctic and boreal, which are common in the
Barents Sea, and even in those parts of it immediately adjacent to the Gorlo of
the White Sea.

In spring and at the beginning of summer the surface water is less saline in

Fig. 81. Seasonal fluctuations of mean monthly surface salinity (3) and

temperature (1), and of the bottom salinity (4) and temperature (2) in

the open parts of the Kandalaksha Guba of the White Sea (Voronkov,

Uralov and Chernovskaya).

consequence of the melting of ice and of the inflow off the land of water from
melted ice. In winter it becomes more saline in consequence of the lessened
inflow off the land and of the formation of sea-ice, and the difference in
salinity at that season between the surface and the deep layers is only 2%0.
In places where there is formation of ice on a large scale the water may be-
come still more saline and may slide down submerged slopes into the depths.
It is most probable that this is the way that partial aeration of the deep layer
takes place in winter.

Щ In consequence of the big inflow of river water into the White Sea, and of
the difficulty of exchange of water with the Barents Sea, the salinity of the

188 BIOLOGY OF THE SEAS OF THE U.S.S.R.

White Sea is considerably less than that of the Barents Sea and, besides this,
it may experience considerable variation from year to year. Thus a comparison
of conditions of salinity in the central part of the Sea in 1922 and 1926 shows
that during these four years the salinity of the upper layer of water increased
considerably, while the lower layer maintained the same salinity {Table 79).

Table 79

Mean salinity

Station 11 of
Derjugin's expedition

3/8/22

Station 429 of

the Persey expedition

4/6/26

In a layer \ 0 to 75 m
of water J 75 to 274 m

26'34%0
28-84%0

27-74%0

28-74%0

Derjugin suggests that the ventilation of the deep floor layers of water is
accomplished in the main at the expense of the horizontal transference of
masses of water. The distribution of the bathymetric, cold and more saline
water masses in the White Sea is indicated in Fig. 82. As shown in the sketches,
the deep, saline water is isolated, and is not connected with the saline water
of the Barents Sea, since salinity is less in the southern part of the Gorlo.
In the Voronka and the Gorlo the salinity decreases from 34%0 on the side
towards the Barents Sea to 26%0 on the side towards the White Sea. But it is
possible that in winter an isohaline of 30%0 reaches the White Sea proper, and
that saline waters from the Barents Sea supplement the store of deep layer
water in the White Sea. Besides this one may conjecture a non-periodical
inflow of more saline deep waters from the Barents Sea into the White Sea.

Oxygen

The distribution of oxygen in the water column of the White Sea shows no lack
of it in the deep floor layers. It is true that observations are available only for
certain seasons of the year, and do not embrace the bottom layer itself.
Nevertheless one must suppose that the bathymetric layers of water of the
White Sea are sufficiently aerated. It has not yet been established how this is
ensured, if, as Derjugin suggests, the convectional currents affect only the
surface layers of water (not deeper than 50 to 60 m). Derjugin speaks of deep
horizontal currents ; but the nature of the latter remains uncertain, as well
as the extent to which they ensure the aeration of the water near the bottom.

Oxygen in the White Sea is present in fairly large quantity throughout the
water column. It has not been possible to establish stagnation phenomena,
although the oxygen conditions of the true near-bottom layer still remain
obscure. It is agreed that the White Sea presents a rare example of a body of
water with a deep basin, separated by a high ridge from the open sea, and
without the presence of pronounced stagnation.

The annual course of oxygen content in the Gulf of Kandalaksha has been
given by E. Sokolova (1939) (Fig. 83). Some decrease of oxygen in the deep
layer is observed in July and August. In the surface layer oxygen saturation is

THE WHITE SEA

189

observed in April to July, caused by the activity of phytoplankton. Sometimes
the saturation zone descends to a considerable depth. Thus at the end of June
1933 oxygen at one of the stations at the same cross section of the Gulf of
Kandalaksha was distributed in the manner shown in Table 80.

It is possible that the passage of oxygen into the depths of the White Sea
occurs together with the slipping of masses of water down slopes into the
depths at the time of the winter rise of salinity of the surface water as a result

Fig. 82. Diagrams of the positions of the cold and

saline deep waters of the White Sea in August 1922

(Derjugin, 1928): A — temperature, В — salinity.

190

BIOLOGY OF THE SEAS OF THE U.S.S.R.

JUNE JULY AUG SEPT OCT

, 11 U 105 , , 105

Fig. 83. Oxygen content of Kandalaksha Bay water. A Annual course

of oxygen content (percentage of saturation) in the open Sea off Umba ;

В Cross section from Umba to Keret (Sokolova, 1939).

of freezing ; but we cannot yet rule out the equal possibility of the onset of
the summer-autumn stagnation in the bottom layer itself. On the other hand

Table 80

100 150 200 250

101-5 1000 950 88-1

Depth, m

Percentage of

oxygen

113-9

115-3

101-8

the presence of red clay in the White Sea makes it possible to presume an accu-
mulation of carbon dioxide in the bottom layer,- which obstructs an abundant
development of bottom life in the deep part of the Sea.

A. Trofimov and Ya. Golubchik (1947) have produced some mean indices
{Table 81) of chemical conditions in the central part of the White Sea in
springtime.

Table 81

Depth

Percentage

of oxygen

Phosphates

Nitrates

961

8 03

140

960

8-03

14-3

94-5

8-05

14-6

91-8

803

19-9

100

87-0

8 03

—

200

820

8 03

220

THE WHITE SEA

191

The sea-bed

The soils of the White Sea floor present every stage from cliff- and rock-bed
along the shore and in the Gorlo to red clay in the central part (Fig. 84). In
the Voronka and the Gorlo of the White Sea the sea-bed is covered with sand,
shell gravel and stones, and in the Gorlo also with outcrops of cliff. The basin
of the White Sea is mainly covered with very soft soils. Sand and silty sand
run in a comparatively narrow strip along the shore.

Hard floors are widely distributed only in the Dvina Gulf, and especially
in the Gulf of Onega. In the Gulf of Kandalaksha a very large number of

Fig. 84. Distribution of the soils of the White Sea (Gorshkova, 1957): 1 Less

than 5 % fine-grain fraction ( <001 mm) ; 2 From 5 to 10 % fine-grain fraction;

5 10 to 30% ; 4 30 to 50% ; 5 Clayey mud ; 6 Mud ; 7 Sandy silt.

rocks is observed, obviously of moraine origin ; in the Gulf of Onega there is
much variegation of the soils, which is dependent on the complicated system
of currents. Outcrops of cliff are encountered here, and soft muds.

According to the data of T. Gorshkova (1957) the content of organic carbon
in the sediments of the open parts of the White Sea (Fig. 85a) varies from 009
to 2-2 per cent, and for the whole of the White Sea the average is 1-14 per
cent. In the enclosed parts of the inlets and gubas the highest percentage of
organic carbon reaches 4-37 at the expense of enrichment by vegetable re-
mains. These data are a good illustration of the direct interdependence of the
quantity of organic matter and the mechanical composition of the sea-bed
— chiefly of organic matter and muddy sediments (Fig. 85b).

0.3-0.5%

Fig 5a. Organic carbon content in the upper layer of the White Sea soils as a
percentage (Gorshkova, 1957).

Fig. 85b. Average amount
of organic carbon (I), and
the <0-01 mm. fraction of
the White Sea soils (II),
along a cross section from
Gulf of Kandalaksha to the
Dvina Guba (Gorshkova,
1957). The lowest curve (III)
is the bottom.

THE WHITE SEA
IV. FLORA AND FAUNA

193

Plankton

Qualitative composition. The plankton of the White Sea has up to now been
very insufficiently studied. Its qualitative composition is given in Table 82.

Table 82

. of species

. of species No. of species

Plankton

and

Plankton

and

Plankton and

groups

varieties

groups

varieties

groups varieties

Flagellata

Protozoa

Pteropoda 2

Silicoflagellata

Hydrozoa

Cladocera 2

Chlorophyceae

Scyphozoa

Copepoda 13

Diatomacea

Ctenophora

Amphipoda 5

Peridinea

Chaetognatha

Schizopoda 7

Rotatoria

Appendicularia 2

Polychaeta

Phytoplankton

Zooplankton

total

106*

total 84
Plankton total 190

The composition of phytoplankton according to P. Usachev.

In connection with the fact that the surface layers of the White Sea are
warmed more in summer than those of the Barents Sea, and the deeper ones
are warmed less, the thermophilic forms are concentrated in the surface layers
and the cold-living forms in the deeper layers.

Of the former one should distinguish the ciliates Amphorella subulata, the
peridineans Ceratiumfusus, Peridinium conicum, the copepods Calanus finmar-
chicus, Oithora similis, Microsetella atlantica, Centropages hamatus and Temora
longicornis, the Cladocera Evadne nordmanni, the appendicularian Fritillaria
borealis and some others. Correspondingly considerable predominance in
the deep layers pertains to, for instance, the cold-water crustaceans Metridia
longa, and the ciliates Tintinnopsis campanula and T. ventricosa. Finally, the
third group of forms is distributed evenly throughout the whole column. To
these should be related the medusa Aglantha digitalis, the rotifer Anuraea
cruciformis and the crustacean Pseudocalanus elongatus. In the plankton the
predominant forms are the Arctic and Arctic-boreal, but also in the plankton
there are true boreal elements which are partly relict already. Thus the Cado-
cera Oothrix bidentata, for instance, which is encountered in the northern
part of the Atlantic Ocean, is absent from the Barents Sea, but has been estab-
lished in the White Sea. The ciliate Tintinnopsis campanula, which is known
from the Mediterranean, Black and North Seas and from the Gulf of Fin-
land, has likewise been discovered in the White Sea. It has not been found in
the Barents Sea. In the parts of the Barents Sea adjacent to the White Sea
many plankton forms are not encountered which are common in the White
Sea. Of these one may name the ciliate Amphorella subulata, the crustaceans

194 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Centropages hamatus and Temora longicornis, and some species of diatom of
the genus Chaetoceros {Ch. danicum, common in the Baltic Sea, Ch. curvisetum,
Ch. constriction, Ch. scolopendra).

Negative characteristics of the plankton of the White Sea. On the other hand
more than 50 Barents Sea phytoplankton forms and about 50 zooplankton
forms are absent from the White Sea. As M. Virketis has shown (1926), a
series of boreal forms of copepods, Rhinocalanus nasutus, for instance, and
Metridia lucens, Oithona plumifera and Acartia clausi, and equally typical
Arctic forms Ptychogastria polaris, Tiara conifera, Calanus hyperboreus,
Euchaeta norvegica, Krohnia hamata, Oikopleura Jabradoriensis, common in
the Barents Sea, are absent from the White Sea. No less interesting also is the
fact that ' certain species, common with Barents Sea species, exist in the White
Sea in entirely different conditions'.

Quantitative distribution of zooplankton. As V. Jashnov has shown (1940), in
the White Sea zooplankton Calanus finmarchicus, Metridia longa and Pseu-
docalanus elongatus are predominant in the spring, and, in contrast with the
Barents Sea, only 38 per cent of the total biomass of zooplankton falls to the
share of Calanus finmarchicus, to Metridia longa 23 per cent, to Chaetognatha
13 per cent, and to Euphausiaceae 1-1 per cent. At the same time Calanus
finmarchicus (49-2 per cent) is dominant in the surface layer (down to 25 m),
and Metridia longa (42-2 m) in the depths.

Nevertheless in the more thoroughly warmed areas of the Sea, in the Gulf of
Onega, for example (L. Epstein, 1957), the main representatives of zooplank-
ton are species of the genus Acartia with an admixture in time of warmth
of Centropages hamatus, Temora longicornis, Cladocera and others, and in
time of cold of Calanus finmarchicus and Metridia longa.

The greatest average density of zooplankton in the 25 m surface layer is
200 mg/m3 (Fig. 86a). At a depth of 200 to 300 m the zooplankton biomass
amounts to 50 mg/m3. The mean spring biomass for the whole Sea is 100
mg/m3. Jashnov (1940) suggests that the maximum zooplankton biomass of
the White Sea must be approximately equal to the biomass of the southwestern
part of the Barents Sea, and notices likewise a very great poverty in numbers
of plankton in the Gulf of Onega and the Gorlo of the White Sea. V. Jashnov
(1940) takes the maximum total zooplankton biomass of the White Sea as
equal to 1^ to 2 million tons.

But L. Epstein (1957), for the more productive Gulf of Onega, points for
1951 to a mean plankton biomass in the open part of the Gulf of 157 mg/m3
in the summer period and 37 mg/m3 in the autumn ; and, in the gubas of the
White Sea coastline, to 210 mg/m3 in summer and 11 mg/m3 in winter.
Epstein's data and certain other material give reason for suggesting that the
biomass indicated by Jashnov is somewhat overestimated. Moreover, in the
White Sea the phytoplankton sometimes gives a very great density (V.
Khmisnikova, 1947) which in some areas is as high as 10 mg/m3. The quanti-
tative distribution of phyto- and zoo-plankton in August 1932 is shown in
Fig. 86, a and в.

THE WHITE SEA

195

Fig. 86a. Quantitative distribution of phyto- and zoo-
plankton in the 0 to 10 m layer of the White Sea (cm3/m3)
(Khmisnikova, 1947).

Benthos

Phytobenthos. The qualitative variety of the White Sea flora is only slightly
less than that of the Murman Peninsula. According to the data of E. S. Zinova
(1928), A. D. Zinova (1950), K. I. Meyer (1933), and A. Kalugina (1958) the
composition of the bottom algae in the White Sea is as set out in Table 83.
The flowering plants Zostera marina and Z. nana, the most interesting
warm-living relicts in the White Sea, have a very great importance for life in
this Sea. Zostera attains a specially large size in the White Sea (up to 2\ m),
and on the other hand forms, as in the North Sea, a littoral dwarf variety

Fig. 86b. Quantitative distribution of plankton in

the 50 to 100 m layer of the White Sea (cm3/m3)

(Khmisnikova)

196

BIOLOGY OF THE SEAS OF THE U.S.S.R,
Table 83

Diatomaceae

Cyanophyceae

Chlorophyceae

Schizophyceae

Phaeophyceae

Rhodophyceae

Total

212 species

3 species

41 species

2 species

80 species

67 species

405 species

Z. nana. Of the macrophytes the greatest mass forms are : Laminaha sacchar-
ina, L. digitata, Fucus vesiculosus, F. serratus, Ascophyllum nodosum, Alaria
esculenta, Desmarestia aculeus, D. viridis, Chorda filum, Ch. tomentosa,
Pilayella, Ectocarpus, Rhodymenia pa/mata, Ahnfeltia plicata. It is interesting
to note that the mass destruction of Zostera that has taken place in the nor-
thern Atlantic has occurred in the White Sea only in 1960-61.

The supply of algae in the White Sea exceeds that on the Murman Peninsula.
The supply of Laminaria is as much as 800,000 tons wet weight ; of Fucus,
250,000 tons, and of Zostera, which is absent from the Murman Peninsula,
400,000 tons. The total supply of algae in the White Sea — macrophytes and
Zostera — is as much as 1-5 million tons wet weight.

Zoobenthos. The White Sea zoobenthos, from data that are not yet complete,
comprises, according to Derjugin, more than 1,000 species {Table 84) :

Table 84

Foraminifera

Cumacea

Harpacticoida 48

Cornacuspongia

Isopoda

Isopoda 92

Hydroidea

Hirudinea

Decapoda 1 3

Anthozoa

Gephyrea

Pantopoda 18

Turbellaria

Bryozoa

132

Amphineura 4

Nemertini

Brachiopoda

Lamellibranchiata 38

Priapuloidea

Echinodermata 22

Gastropoda 86

Oligochaeta

Cirripedia

Tunicata 28

Polychaeta

135

Ostracoda

Enteropneusta 2

Sipunculoidea

Together

Total 948

with : Cyclostomata 1

Pisces 5 1

Mammalia 6

Total 1,007

Clearly even these 1,007 species are not a complete list of the components
of the fauna. Further study of the fauna of the White Sea will add several
hundreds of species.

Zoogeographical characteristics. As has been said above, the fauna of the
White Sea is not homogeneous from the zoogeographical standpoint. On the

THE WHITE SEA

197

Fig. 87. Near-bottom isotherms of the White Sea
and the distribution in it of the starfish Asterias lincki
and ophiure Ophiopholis aculeata (Schorygin, 1926).

littoral, boreal forms predominate markedly. With increase of depth the
number of Arctic forms becomes greater and greater, and finally the deep
parts of the Sea are inhabited by fauna of a pronounced high Arctic character
{Table 85).

As we have shown, the mass form of zooplankton in the surface layer is
Calanus finmarchicus, while Metridia longa lives in masses in the depths.
A comparison of the distribution of two echinoderms, the Arctic-boreal
Ophiopholis aculeata and the cold-living starfish Asterias lincki, is even more
significant (Fig. 87).

Table 85. Relationship of different zoogeographical groups in the bottom fauna of
the White Sea as percentages of the total fauna

Zoogeograph ical
groups

Littoral

Pseudo-abyssal

Total number of species

Boreal

23-25

Chiefly boreal
Arctic boreal

18-28
22-93

Chiefly Arctic
Arctic

13-95
6-97

High Arctic

Endemic

Cosmopolitan species
Bipolar

6-97
7-65

41-53

6-97

1000

15-3

13-3

250

29 0

5-7

7-7

540

1000

198 BIOLOGY OF THE SEAS OF THE U.S.S.R.

By K. Derjugin's reckoning (1928) the majority of the more substantial
groups of benthos are half composed of Arctic species ; but for individual groups
the proportion of Arctic forms rises to 69 per cent (Decapoda) and even to 86 per
cent (Echinodermata). Many of these Arctic forms are highly characteristic
of the Kara Sea and the coldest parts of the Barents Sea, and certain ones in the
White Sea have already acquired a relict aspect. Arctic-boreal forms compose,
on the average, 17 to 25 per cent. On the other hand, the proportion of boreal
forms is also large — 11-5 to 23 per cent, of which many represent, in the White
Sea, warm-water relicts. That is, they also have broken away from their main
habitat.

Endemic characteristics. Although the fauna of the White Sea is, geologically
speaking, young, it nevertheless possesses definite endemic characteristics.
Both in the plankton, in the benthos and among the fish we find more or less
pronounced endemic forms. The majority of these are sub-species and variants
but sometimes they are clearly individual species. Of these we indicate the
remarkably mobile lucernaria Lucernosa saint-hilairei, the mollusc Lyonsia
schimkevitchi, the fishes Lycodes maris-albi, Gadus callarias maris-albi, Clupea
harengus pallasi maris-albi and others. There is also a genus endemic in the
White Sea, namely the Porifera Crellomima imparidens. As regards this last
Derjugin suggests that either it is a fragment of a more ancient group, or its
related forms will be found somewhere in the neighbouring seas.

Link with Pacific Ocean fauna. There are likewise in the White Sea a series
of forms which establish a link between its fauna and the fauna of the seas of
the Far East. The White Sea is the extreme western outpost of this fauna. Of
this latter group one may point to one of the White Sea herring, Clupea
harengus pallasi maris-albi, the lamprey Lampetra japonica septentrionalis,
and the polychaete Scalibregma robusta which inhabits the Sea of Okhotsk
and the White Sea.

Link with Baltic Sea fauna. Finally, the last group characteristic of the White
Sea, which indicates the existence in the Yoldian stage of a link between the
White and Baltic Seas. A series of forms both plant and animal are common
to both Seas and are absent from the Barents Sea and even from the waters
of the Norwegian coast. Among them are forms of both thermophilic and
cold-living character. As indicated in the chapter devoted to the Baltic Sea,
some geologists and zoogeographers deny the existence of a bygone link be-
tween these Seas in the post-glacial period; but the majority recognize it.
The most interesting of the forms that inhabit both Seas is the marine grass
Zostera marina, which in the Barents Sea is encountered in the most western
part of the Murman Peninsula (beginning at Vayda Guba and farther to the
west. The peridinean Pyrophacus horologicum and the diatom Chaetoceros
danicum, which are common in the Baltic Sea, are likewise not encountered
in the Barents Sea. In 1944 Z. Palenichko (1947) discovered in the Gulf of
Onega a boreal polychaete which was new for the White Sea, Nereis virens.
This is one of the most numerous representatives of the polychaete worms.

Т НЕ WHITE SEA 199

In its chief habitats N. virens attains 1 m in length. White Sea specimens are
20 to 30 cm long. According to fishermen, in spring the heteronereis stages of
this polychaete, as big as snakes, sometimes appear in numbers on the sur-
face of the water. On the Murman Peninsula individual specimens of N. virens
have been found only in its most western part. They have not been caught
farther east. It is possible that N. virens in the White Sea is a thermophilic
relict ; but it is more probable that it has penetrated here recently in consequence
of the general rise in temperature of the Arctic. In late years N. virens has
appeared also on the coast of Iceland, and it apparently ought to have been
discovered throughout the Murman coast.

Other forms inhabit the White, Barents and Baltic Seas, but are wholly or
partly absent from the coast of Norway and the North Sea. Examples are the
Arctic littoral Priapuloidea Halicryptus spinuJosus, the polychaete Rhodine
gracilior and others.

The peculiar distribution of these forms might have been explained even
without a direct link between both Seas in the past. When the climate was
colder than it is today, many Arctic forms moved far to the south, and may
have penetrated into the Baltic Sea through the North Sea. In a later phase,
warmer than at present (the Littorina stage), the Arctic forms were shifted
far to the north, and more thermophilic forms moved up after them and pene-
trated into Cheshskaya Inlet and through the Gorlo into the White Sea. The
Baltic Sea, in consequence of the rigorous climatic conditions in its northern
and deeper part, preserved Arctic relicts; the White Sea, because of the pecu-
liarity of its thermal conditions, preserved both cold-water and warm- water re-
licts. But the existence of a direct link between the White and Baltic Seas is not
based solely upon zoogeographical data, but also on geological investigations
in regions lying between the two Seas. If the direct link has been established
then' the merging of the fauna of both may have occurred on a large scale.
Thus we find in the White Sea fauna the following elements :

(7) Forms which also inhabit adjacent parts of the Barents Sea

(2) Warm-water relicts

(3) Cold-water relicts

(4) Forms common to the Baltic Sea

(5) Forms common to Far Eastern seas

(6) Endemic forms.

Thus the White Sea, like the Baltic Sea, and to some extent like the Barents
Sea also, is not homogeneous from a zoogeographical point of view. The
littoral fauna, as in the Barents Sea, bears a pronounced boreal character,
the sublittoral has an Arctic character, and the pseudo-abyssal a pronounced
high Arctic aspect.

History of the fauna. As the result of a detailed analysis of the fauna of the
White Sea K. Derjugin (1928) came to the conclusion that ' the whole of it was
formed during the period after the last glaciation and the freezing of the
White Sea basin in the post-glacial epoch; that is, its age amounts to about
13,500 years'.

200 BIOLOGY OF THE SEAS OF THE U.S.S.R.

In the glacial period, as Derjugin suggests, the fauna of the White Sea
must have been destroyed, since the basin of the sea was blocked with glacier
ice. From the latest post-glacial phase to the present time a large number of
high Arctic forms have been preserved in the White Sea, the most typical of
them being the mollusc Portlandia arctica. Many of these forms possess a
definitely relict character ; they are not encountered in the adjacent parts of the
Barents Sea, and are common in the Kara Sea and farther east. Such, for
instance, besides P. arctica, are the polychaetes Harmothoe badia, Melaenis
loveni, the holothurian Cucumaria calcigera, the crustaceans Paroediceros
intermedins and Aeanthostepheia malmgreni, the molluscs Cylichna densistriata
and Bela novaja-zemljensis, the ascidians Eugyra pedunculata and Rhizomilguta
globidaris, the fishes Lycodes agnostus and Liparis major and others. At the
same time, possibly there was also a link with the Baltic Sea.

In the warm Littorina stage the Arctic elements were shifted far to the
eastward and remained in the shape of relicts in the coldest corners of the
White Sea. A mass of thermophilic forms settled in the White Sea. Most
probably in the period of this same post-glacial rise of temperature there also
penetrated into the White Sea some Pacific Ocean forms such as the herring,
the lamprey and others.

The colder temperature of modern times destroyed some of these forms, and
some it transformed in the White Sea into thermophilic relicts. Examples of
these forms we have already adduced. The period which has passed since the
Ice Age has been shown to be sufficient for the creation of a whole series of
endemic forms chiefly variants and sub-species and, only to a small extent, of
new species.

Negative features in the fauna of the White Sea. Derjugin likewise subjected to
analysis another interesting phenomenon in the fauna of the White Sea, which
he called the negative features of the White Sea fauna. A whole series of forms
which are most common in the Barents Sea are absent from the White Sea,
as has been pointed out above in the description of the plankton. Of these
common forms of benthos alone there may be reckoned no fewer than 125,
which includes 45 molluscs, more than 25 crustaceans, 8 echinoderms, 7 poly-
chaetes, 6 coelenterates, 5 poriferae and only 3 species of fish.

Derjugin explains this phenomenon by the entirely unfavourable hydrolo-
gical conditions of the Voronka and the Gorlo. The turbulent mixing of the
whole mass of water which takes place at flood-tide and ebb-tide, the consider-
able warming of the water in summer and its severe chilling in winter, the
absence of soft sea-bed — all this makes extremely hard the transfer of tender
pelagic forms and stages of development through the 200 to 300 km of the
Voronka and Gorlo. In addition, the whole base mass of water in the Voronka
and Gorlo is shifted by the tide alternately in one direction and then in the
other, and the forward motion of permanent currents here is relatively feeble.
Derjugin calls the conditions of the Gorlo 'a biological plug'. One cannot help
agreeing with the correctness of this explanation for certain forms ; but for the
majority it is more probable to conjecture the destructive influence of a con-
siderable fall in salinity — to 7 to 8%0 — within a comparatively short distance.

THE WHITE SEA 201

If we set side by side the poverty of the Barents Sea fauna, against its transit
into the White Sea, and the analogous impoverishment in the Baltic Sea, the
coincidence, quantitatively, is most graphic ; and in the flood-tides which lead
into the Baltic Sea, the hydrological factor is absent by which Derjugin ex-
plains the poverty of the fauna of the White Sea.

With the passage from the North Sea at flood-tide, and with a fall in
salinity from 35 to 27 or even 23%0, there occurs a sharp decrease in fauna from
1,500 species to nearly 1,000. Thus 'negative features' in the fauna of the
central part of the Skagerrak are defined as approximately 500 animal
species. A fall of salinity even to 32%0 causes a loss of 350 forms. It is likewise
possible that the qualitative impoverishment of the fauna, with the transit
from the open coasts of the ocean into a system of inlets and sounds jutting
deeply into the land has, besides the loss of salinity and the powerful circu-
latory currents, yet other causes which have not yet been taken into account.
It is known, for instance, that there is a general qualitative impoverishment of
flora and fauna in seas that are smaller in dimensions.

In any case, it is impossible to explain this complicated phenomenon simply
by the unfavourable hydrological conditions in the Gorlo. This is one of many
causes, and very likely the least important.

Vertical displacement of zones. Likewise far from being fully understood by
us are the phenomena of the vertical displacement ('the displacement of zones'
in the earlier terminology) of groups and of individual forms, which are so
pronounced in the fauna of the White Sea. On the one hand it is as if a general
tendency to rise to lesser depths occurs, which may be conditioned in the first
place by the low temperature of the depths and the lower transparency of the
water ; and on the other hand a series of littoral forms moves into the sub-
littoral and some forms from upper layers of the sublittoral into lower layers.
The only explanation so far for these displacements is seen in the unfavourable
influence of the piling up of ice on the shore in the course of a long harsh
winter. For a series of forms, a part is probably also played by the consider-
able warming up of the surface waters at the shores in summer, which drives
the cold-loving forms down into the depths.

Very significant data were produced by M. Gostilovskaya (1957) in a com-
parative study of the vertical distribution of bryozoans in the Barents and
White Seas {Table 86).

Population of the supralittoral. Everywhere in the supralittoral of the White
Sea, especially where there are accumulations of sea-weed cast up by the
breakers, an abundant supralittoral fauna is found.

On the supralittoral, partly moving into the littoral, and even mingling with
certain typically marine forms (Balanus balanoides, Littorina rudis and others),
usually on the more sloping shores that are not subject to considerable surf,
there settle in large numbers the flowering plants, Plantago maritima, Triglochin
maritimus, Aster trifolium and Salicornia herbacea, which descend lowest of
all on the littoral and mingle there with the fucoids.

202

BIOLOGY OF

THE SEAS OF
Table 86

THE U.S

S.R.

Species

Depth, m

White Sea

Barents Sea

Crista producta

0-20

9-288

Tegella nigrans
Cribralina spitzbergense

15-40
9-50

14-230
30-320

Escharella dymphnae

7-45

12-170

Smittina majuscula

2-78

27-315

Porella fragilis
Umbonula arctica

35-60
2-91

23-235
5-297

Escharopsis rosacea

4-80

12-324

One of the areas of the sublittoral where there are accumulations of sea-
wrack, along the northern shore of the Kandalaksha Bay, has been the
subject of minute analysis by G. Gurvich and T. Matveeva (1939). 'The fades
of this biotope ', they write, ' is sufficiently varied even at first glance. Numbers
of spiders run over the surface of the wrack, deeper down there crawl different
Apterygota and mites, more rarely quick-moving beetles (Carabidae) and
also myriapods can be seen. Still deeper Oligochaeta creep about in huge
numbers, sometimes huddling together in whole bunches. At the very bottom
of the layer of wrack amphipods are met with and in particles of cortex
saturated with moisture, and in humus, live little characteristic Harpacticoida.'
An account of the number of animals in the heaps of sea-wrack, which are
often several metres wide and as much as half a metre thick, is given in
Table 87 and Fig. 88.

As may be judged from the data of the table, Oligochaeta constitute
96-05 per cent of the whole population of the heaps of sea-weed. Arachnoidea
predominate in the top layer, Apterygota in the middle, and Oligochaeta in

Table 87

Quantity of

organisms

Groups

No. of

Biomass,

specimens

g/ma

per m2

Oligochaeta

480,400

237-60

Nematoda

5,200

—

Acarina

29,900

2-30

Araneina

1,300

0-72

Apterygota

72,900

1-46

Coleoptera larvae

3,700

4-78

Coleoptera imagines

1,400

5-52

Total

594,800

352-38

THE WHITE SEA

203

the lowest. The biomass also increases with depth. Among all this fauna there
are only two species of crustaceans living in the lowest layer of the wrack,
which are properly marine forms — the Amphipoda Gammarus obtusatus and
the Copepoda Itunella mii/leri. Newly formed heaps of sea-weed are soon

3rd Layer

2nd Layer

4836g

Fig. 88. Composition of the fauna population in the
debris of the White Sea sublittoral (Gurvich and
Matveeva). The biomass in g/m2 is given below the
circles. 1 Oligochaeta; 2 Apterygota; 3 Coleoptera
larvae ; 4 Coleoptera imagines ; 5 Acarina ; 6 Arach-
noidea.

populated by specific fauna from the bottom floor. By autumn the fauna in
the weed-heaps suffers a sharp impoverishment.

Among the Oligochaeta the highest significance pertains to the Enchytraei-
dae family {Lumbricillus lineatus, Enchitraeus albidus and others). Among the
Tubificidae, Clitellio arenaria and Tubifex costatus have the greatest develop-
ment. These are joined also by some species of the Naididae family (Amphic-
teis leydigi, Paranais lit oralis and others).

Population of the littoral. The amplitude of the tidal range in the main basin
of the White Sea usually reaches 1-5 to 2 m, and, as distinct from the Murman
coast, sand-mud beaches extend here along nearly the whole shoreline, being
only rarely interrupted by outcrops of cliff. Thus, although the foreshore in
the White Sea is not particularly broad (usually some tens and rarely some
hundreds of metres) yet on the whole its relative significance is much greater
than on the Murman Peninsula, since in the larger part of the Sea it girdles
the whole shore line. In the White Sea we find on the littoral all the same en-
vironment and biological phyla as on the Murman Peninsula, only somewhat
less pronounced, with a slightly smaller qualitative variety and lower quantita-
tive indices of flora and fauna. The whole basic selection of forms of the
western Murman littoral is included here almost in its entirety. Of the pre-
dominant forms only Nucella lapillus and Cardium edule are absent.

204 BIOLOGY OF THE SEAS OF THE U.S.S.R.

If in summer the temperature of the air and water is higher in the White
Sea than on the Murman coast, yet in winter the fauna of the littoral finds itself
in much less favourable conditions. For many months the top layer of the
littoral of the White Sea freezes, and is covered with a thick crust of ice. The
fauna of the littoral part moves for the winter into the sublittoral, and part of
it digs itself deeper and buries itself in a dormant state.

As on the Murman coast the predominant macrophytes are Fucus vesicu-
losa in the upper level and Ascophyllum nodosum in the lower. But in the
White Sea the biomass is considerably less than off the Murman Peninsula
{Table 88).

Table 88

Average

biomass, kg/m2

Macrophyte

Kola Inlet

Gulf of
Kandalaksha
(White Sea)

Fucus vesiculosus
Ascophyllum nodosum

8-9
15-16

2-4
8-9

The White Sea sea-weeds are also smaller in size than those of the Murman
Peninsula. In the Kola Inlet the length of individual strands of Ascophyllum
nodosum reaches 1 m, but in the Gulf of Kandalaksha only 05 m.

Of the other macrophytes on the littoral one may point out Pelvetia canali-
culata, Fucus inflatus and F. serratus. Great peculiarity is given to the White
Sea littoral by patches of dwarf Zostera nana which settle on the lowest and
moistest parts of the littoral, which are usually left covered with water even
at low tide.

The zonation of the main fucoids of the foreshore — F. vesiculosus, Asc.
nodosum and F. inflatus — is not so distinct in the White Sea as off the Mur-
man Peninsula : all three species are mingled to a considerable degree.

E. F. Gurjanova and P. Ushakov (1929) give the following scheme for the
vertical distribution of organisms in the littoral zone of the Terskiy coast :

Horizon I: Dead, owing to the grinding effect of ice.

Horizon II: Sandy beach Scattered boulders

Zone I — Sand with biocoenosis: Arenicola Littorina rudis, Balanus balanoides.

marina-Mya arenaria, Littorina rudis.
Zone II — Silty sand with biocoenosis: Zos- Fucoids with their biocoenosis: Gono-
tera marina, Eteonearctica,Ariciaquadri- thirea loveni, Membranipora piiosa,
cuspida, Pygospio elegans, Lineus gesse- Jaera marina, Gammarus spp., Litto-
rensis, Amphiporus lactifloreus, Macoma rina palliata, L. rudis, Hydrobia ulvae,
baltica, Littorina littorea, L. rudis. Mytilus edulis, Pholis gunellus, Enche-

liopus viviparus.
On bare patches Usually under stones

Arenicola marina, Fabricia sabella, Mya Lineus gesserensis, Cephalothrix linearis,
arenaria. Halicryptus spinulosus. Between stones :

Macoma baltica, Pygospio elegans,
Oligochaeta. Larvae Chironomidae.

THE WHITE SEA

205

Abrikosov Sokolova (1948) gives a subdivision of the littoral of the Gulf of
Kandalaksha somewhat different from the above:

Upper horizon

On rocks — Littinora rudis, Mytilus edulis

Between rocks, frequently, the flowering plant Aster trifolium

Under rocks — pupae Insecta, Oligochaeta, Nematoda

Middle horizon

Balanus balanoides, Littorina rudis, Hydrobia, Rissoa, Mytilus edulis

Lower horizon

Littorina littorea, L. palliata, Buccinum groenlandicum, Natica clausa,
Margarita helicina, Asterias rubens

Actinia equina is common on the undersides of rocks. Under the rocks
Gammarus spp. is found in masses. In the White Sea many of the most typical
littoral forms descend in considerable numbers into the sublittoral, as, for
instance, Mytilus edulis, Balanus balanoides, Gammarus obtusatus, the Lit-
torina species and others. On the other hand, as was established for the littoral
of the Solovetsky Islands (A. Fedorov, 1928), many sublittoral forms {Asterias
rubens, for instance) rise to the lower level of the littoral. But even on the very
littoral of the White Sea the forms that inhabit it avoid, as it were, getting into
the upper levels, and strain downwards, nearer the water. Sokolova has pro-
duced Table 89 showing the quantitative ratio of the different forms inhabiting

Table 89

Karlov Islands
(eastern Murman

Rugozerskaya Guba
(Gulf of Kandalaksha)

Form

coast) as a percent-
age of total biomass

as a percentage of total
biomass

Epifauna of scattered boulders

Balanus balanoides

58-7

19-4

Mytilus edulis

Littorina rudis, L. palliata

28-5
12-4

33-2
24-2

Oligochaeta
Remainder

006
0-34

16-6

6-6

Total biomass

692-7

313-5

Flora of scattered boulders

Fucus vesicuiosus

40-4

34-5

F. inflatus

40-3

—

F. serratus

—

0-91

Ascophyllum nodosum
Rhodymenia palmata
Ahnfeltia

13 9

4-5

59-5
2-2
0-91

Remainder

0-9

1-98

Total biomass

5,754

3,103

206 BIOLOGY OF THE SEAS OF THE U.S.S.R.

the rocky littoral of the Kharlov Islands (eastern Murman coast) and of the
southern shores of the Gulf of Kandalaksha.

On the sandy and silty-sand areas of the White Sea littoral among the
infauna forms, the predominant ones are Macoma baltica, Arenicola marina
and Mya arenaria. Quite characteristic, but of small significance in the bio-
mass, are Halicryptus spinulosus and Priapulus caudatus. Of epifauna forms
Mytilus edulis, Littorina rudis, Hydrobia ulvae, Rissoa aculeus are noted
in considerable quantity.

As may be judged from Table 90 (according to Z. Zavistovich and K. Vosk-
resenski — unpublished material), the quantitative ratios between individual
forms among the constituents of the littoral fauna are subject to considerable
variations.

A comparison of the quantitative indices of the Murman and White Sea
littoral fauna shows that the former is more plentiful in quantity, but that in
quality the difference is insignificant.

The less favourable conditions for the development of littoral fauna in the
White Sea, as compared with the Murman coast, are reflected not only in a
decrease in the total biomass of plant and animal forms, but also in a decrease
in the size of the body in a series of typical forms. Mytilus, Littorina, Balanus
and Macoma have, in the White Sea, considerably smaller average dimen-
sions. Thus Macoma baltica, for instance, has at one of the low tides in the
Kola Inlet an average weight of 240 mg, but in the Gulf of Kandalaksha
only 112 mg; the Kola Inlet Littorina rudis weighs 109 mg, but the White
Sea one weighs 70 mg. Sea mussel similarly gives an average weight of 1,711
and 719 mg, and so on. Moreover a smaller size is characteristic of many repre-
sentatives of the White Sea fauna. The White Sea cod and herring are consider-
ably smaller than those of the Barents Sea. Portlandia arctica of the deeper
parts of the White Sea is considerably smaller than the same form taken in
the Novya Zemlya trough of the Barents Sea.

Thorough study of the microbenthos of the White Sea littoral has been
carried out (1951) by V. Brotzkaya at the White Sea biological station of
Moscow University. On the sandy littoral there have been discovered no
fewer than 80 species of small invertebrates, mainly: Harpacticoida (24
species), Turbellaria (more than 20 species), Ciliata, Rotatoria, Nematoda, and
several other groups. Some forms give very high density of population. In
one cubic centimetre of bottom soil Nematoda yield up to 1,000 specimens,
Harpacticoida up to 200, and Ciliata more than 1,000. Brotzkaya shares
A. Remane's opinion (1933) that the microbenthos of the sandy sea-bed is the
basic source of nourishment for the remainder of the bottom-feeding fauna.

At the White Sea biological station there has likewise been produced most
useful work on the calculation of the relative sizes of body and the weight
of different invertebrates of the littoral (N. Pertsov, 1952). This material gives
easy means for the calculation of size from weight, which is essential in
research into the feeding offish, from the contents of their intestines.

Population of the sublittoral. As Derjugin indicates, the sublittoral zone,
which in the Kola Inlet extends to 200 to 250 m, extends in the White Sea

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208

BTOLOGY OF THE SEAS OF THE U.S.S.R.

only to 40 to 50 m. Accordingly the upper layer of this zone (the former
'litoral' of Derjugin) is also raised from 60 to 70 m to 12 to 16 m. Mytilus
edulis and Fucus serratus descend from the littoral into the upper layers of
the sublittoral; in the White Sea the holothurian Chiridota laevis descends
from the upper layer of the sublittoral to great depths ; and there rise upwards
from below the red sea-weeds, poriferae, the hydroids and bryozoans, so
characteristic on the Murman coast of the lower horizons of the sublittoral.
The vertical distribution of the bottom fauna of the White Sea makes it

Table 91. Comparison of littoral fauna of western Murman Peninsula and White Sea*

One of the big foreshore zones in

the Kola Inlet

Gulf of Kandalaksha

Form

No. of

As a per-

No. of

As a per-

specimens

centage

specimens

centage

per m2

Biomass

minus

per m2

Biomass

minus

g/m2

sea mussel

g/m2

sea mussel

Mytilus edulis

823

1,409-00

— .

126

90-57

—

Macoma baltica

750

167-86

81-4

610

68-04

50-5

Arenicola marina

16-10

7-8

29-71

22-0

Cardium edule

8-92

4-3

—

Mya arenaria

—

1-5

21-65

16-1

Littorina rudis

4-80

2-3

122

8-50

6-3

Gammarus spp.

1-50 \

—

- 1

Priapuhts caudatus

1-20

0-5

0-34

Halicryptus spinulosis

1-20 [

4-2

0-5

0-23 ,

Hydrobia, Rissoa

—

791

5-19

Varia

4-60 /

365

0-97 /

Total

1,755

1,61 5- 18

2,025-5

225-20

Minus sea mussel

932

206-18

1000

1,899-5

134-63

1000

* The absence from the table of Hydrobia ulvae and Rissoa aculeus from the Kola
Inlet and of the gammarids from the White Sea is explained by a deficiency in the col-
lection of material.

possible to distinguish here the same zones and horizons as in the Barents
Sea.

Derjugin takes as the lowest limit of the sublittoral a depth of 150 m,
although usually vegetation disappears by a depth of 40 to 56 m. The littoral
flora and fauna of the White Sea moves, without any sudden leap (as happens
on the Murman coast), into the sublittoral ; and most characteristic of the
upper horizon of the sublittoral are Fucus inflatus, and F. serratus on rocky
bottoms, and Chorda filum and Zostera marina on soft ones. Lower still there
extends a great belt oi Laminar ia sac char ina, L. digitata, Alaria, Ahnfeltia and
others.

The upper division of the sublittoral, extending to 40 to 45 m, begins on
soft bottoms with Zostera growths which here attain luxuriant bloom (in-
dividual stems are as much as 3 m long), or Chorda filum, which attracted to
itself partly littoral fauna {Mytilus edulis, Littorina rudis, L. palliata, Rissoa

THE WHITE SEA

209

aculeus, Hydrobia ulvae, Skenea planorbis, Macoma baltica, Priapulus caudatus,
Halicryptus spinulosus, Arenicola marina, Lineus gesserensis and others) and
partly sublittoral {Ophelia limacina, Asterias rubens, Polydora quadrilobata,
Chiridota laevis and others). Zostera extends as far as 5 to 6 m in depth. The
belt of Laminaria may, on scattered boulders, reach the lower edge of the
littoral, and at spring tides is partly exposed. Besides the Laminaria, which
compose the main mass of vegetation, there are here always many other
different brown and red algae, partly epiphytes. Corallina and cork Litho-
thamnion may likewise attain a high stage of development here. At a depth

Fig. 89. Bottom biocoenoses of the lower stage of the sublittoral
and pseudolittoral of the White Sea (Zenkevitch, 1927). Boxed
numerals refer to the isobaths; the other numerals denote bio-
mass (g/m2) (61, 21, 17, 5 and 18). Different shading indicates
the various bottom biocoenoses: 1 Leda pernula, Yoldia hyper-
borea, Astarte montagui; 2 Portlandia arctica, Leda pernula,
Asterias lincki; 3 Astarte montagui, Leda pernula, Ophiocantha
bidentata; 4 Astarte borealis, Yoldia hyperborea, Leda pernula;
5 Portlandia arctica, Yoldia hyperborea, Pectinaria hyperborea;
6 Mesidothea entomon, Macoma baltica.

of approximately 10 m the belt of Laminaria comes to an end (on the Mur-
man coast it goes down to 15 m and more, the biomass of sea- weeds falls
sharply, and the red algae become predominant: Prilota, Phyllophora,
Odonthalia and others).

As on the Murman coast, so here also thallus and rhizome Laminaria give
shelter to a luxuriant and quite analogous fauna. On the thallus Laminaria
there settle in quantities the gasteropod molluscs Margarita helicina and
Lacuna divaricata ; Lucernaria quadricomis, and Haliclystus octoradiatus which
give special peculiarity to the sublittoral of the White Sea ; the bryozoans

210 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Lichenopora verrucaria, Crisia eburnea, the polychaete Spirorbis borealis and
the crustacean Caprella septentionalis. Certain littoral forms come down from
above, such as Mytilus edulis, Littorina rudis, Rissoa aculeus and others. To
the dominant forms mentioned there are added numerous hydroids, bryozoans,
molluscs, nemertineans, the characteristic sucking-fish Cyclopterus lumpus
and others. Rhizoid Laminaria, which attach themselves to rocks, forming a
tent-like structure, give shelter to a rich fauna, and chiefly to the polychaetes
Nereis pelagica, Phyllodoce maculata, Castalia punctata, Harmothoe imbricata,
Pholoe minuta, and amphipods Amphitae rubricata and Jscheroceros anguipes,
the gastropod molluscs Margarita groenlandica, M. helicina and Rissoa
aculeus, the brittle stars Ophiopholis aculeata and Ophiura robusta ; the star-
fish Asterias rubens, and many other polychaetes and molluscs. On bare sandy
patches, among the Laminaria growths, there settles the fauna of animal forms,
of which some dig themselves into the sea-bed {Macoma calcarea) and some
crawl about on it {Asterias rubens, Cribrella sanguinolenta, Ophiura robusta,
various gastropod molluscs, and others).

The White Sea biological station of Moscow University has carried out
investigations of the bottom fauna of Rugozerskaya Inlet, in the southern
part of the Gulf of Kandalaksha (Fig. 90), and divided it into five basic bio-
coenoses. In the outer part of the Inlet, at a depth of 6 to 12 m, is located a
biocoenosis Styela rustica, Potamilla reniformis, Astarte, and Ophiura robusta.
Sea-bed : silty-sand ; average biomass : 243 g/m2. Farther up the Inlet, at a
depth of 4-5 to 14 m, and on sand and mud, is located a biocoenosis Serripes
groenlandicus, Terebellides stromi, Pectinaria koreni, Ophiura robusta; mean
biomass : 32 g/m2. In the central part of this area there may be distinguished
a biocoenosis Cyprina islandica-Stegophiura nodosa, with a biomass of 96
g/m2. In the shallow areas of this region, near the shore at a depth of 4 to 5 m
and on soft mud where there are dead Zostera, is located a biocoenosis with
a considerable intermingling of relict brackish-water forms : Pontoporeia
femorata, Nephthys paradoxa, Mysis oculata, and Cumacea. The mean bio-
mass of this is 25 g/m2. In that part of the Inlet, where there is soft mud with
dead Zostera at a depth of 3-5 to 6 m, is located a biocoenosis Macoma baltica-
Nephthys paradoxa-Scohplos armiger, with a biomass of 30 g/m2. In the
inner part of the Inlet salinity falls at ebb-tide to 3 to 4 per cent, and at flood-
tide it rises to 21 to 22 per cent in the surface layer and to 22-5 per cent in the
bottom layer.

G. Gurvich and I. Ivanov (1939) give a description of several benthic com-
munities in the upper level of the sublittoral on soft bottoms in the area of
Umba (Gulf of Kandalaksha). At a depth of 4 to 6 m they distinguish a com-
munity with the following predominant forms : polychaetes, Terebellides
stromi and Scoloplos armiger; echinoderms, Ophiura robusta and Asterias
rubens; the bivalve Astarte montagui; and the small Cumacea Brachydia-
stylis resime; the biomass of this community is 89 g/m2.

Below the Laminaria zone (10 to 45 m) extends the level of the red algae:
Phyllophora, Rhodophyllis, Delesseria, Polysiphonia and others.

As Derjugin points out (1928) : 'This level is rich in life, and in it one may
evidently distinguish certain groups which have not yet been studied in detail.

THE WHITE SEA

211

Here there are many different representatives of the poriferae, bryozoans, poly-
chaetes, crustaceans, echinoderms, ascidians and molluscs, some living on the
sea-weeds themselves, some on the rocks, some on the sea-bed which here is
usually mud. '

In the inner parts of the Inlet the red algae Phyllophora flourishes luxu-
riantly, at a depth of 6 to 22 m on the muddy sea-bed, and is accompanied
by its community of animal forms with average biomass of 29 g/m2. The pre-
dominant form is Ophiura robusta. Of the polychaetes Scoloplos armiger,
Nephthys minuta and Myriochele oculata predominate; sometimes ascidians

Fig. 90. Chart of Gulf of Kandalaksha

including Rugozerskaya Inlet. 1 Bab'e More;

2 Site of White Sea Biological Station of

Moscow University; 3 Velikiye Is.

are found in great numbers; most characteristic among the molluscs are
Astarte elliptica, Cardium ciliatum and Axinus flexuosus. Rather deeper (20
to 30 m) colonies of Portlandia arctica are encountered in combination with
Leda pernula, Myriochele oculata, Yoldia hyperborea, Pectinaria hyperborea
and Maldanidae. This community, which has a biomass of 25 g/m2, is in
composition very like the communities on mud bottoms of the lower level of
the sublittoral, but it is characteristic of it that Portlandia exists here for a
considerable period of the year at a temperature above zero, and is separated
from the population which inhabits the deep part of the White Sea.

The lower division of the sublittoral (45 to 150 m) is characterized by the
great predominance of spacious areas of mud bottom, with only an occasional
rock, which are inhabited by red algae of various forms (Ptilota, Odonthalia,
Delesseria, Ahnfeltia, Polysiphonia and others). On these last there develops

212 BIOLOGY OF THE SEAS OF THE U.S.S.R.

a luxuriant population of poriferae, hydroids and bryozoans (about 160 species,
according to Derjugin). On the chief areas of soft mud bottom a clear pre-
dominance pertains to infauna consisting of comparatively few forms of bi-
valves (Astarte boreal/ s, A. elliptica, Yoldia hyperborea, Leda pernula, Macoma
calcarea, Dacrydium vitreum, Cardium ciliatum), polychaetes (Pectinaria hyper-
borea, Maldane sarsi) and echinoderms (Asterias lincki, Ophiocantha bi~
dent at a).

The census of the bottom fauna, carried out with the help of the Petersen
bottom-dredge, makes it possible to note the exact limits of this soft-mud-
bottom community, which embraces the central deep depression (Fig. 89).
The biomass of this community increases from east to west ; in the eastern
part of the sea the average biomass is 16-78 g/m2, in the central part 26-86,
and in the western part 61-23 g/m2; that is, it increases 3-5 times. A consider-
able increase in the biomass of benthos is observed in the Gulf of Onega
(according to S. Ivanova, 1957), in the greater part of which the biomass of
benthos ranges from 100 to 500 g/m2, and in certain parts exceeds this range,
with a clear predominance of bivalves. The comparative significance of the
separate components of the community changes also, as is shown in Table 92,
from east to west.

Table 92. Change in the composition of predominant forms in the mud-bottom community of

the lower division of the sublittoral

Mean total biomass

Eastern part

Central

West

part

No. of

Biomass

No. of

Biomass

No. of

Biomass

specimens

g/m2
16,766

specimens

g/m2
26,862

specimens

g/m2
61,230

Dominant forms :

Astarte elliptica, A.
montagui

9-3

4-68

33-7

6-65

1601

Dacrydium vitreum

0-02

61-5

0-67

0-22

Yoldia hyperborea
Leda pernula

2-2
13-9

0-26
2-16

1-39

5-87

7-75

Macoma calcarea

003

—

5-12

Asterias lincki

—

0-38

0-02

—

Ophiocantha bidentata
Pectinaria hyperborea

1-8

0-23
0-58

7-3
1-15

1-86
0-55

0-78

Maldane sarsi

0-85

0-3

001

015

The basic role in this community belongs to the bivalves (34 to 64 per cent
of the biomass) ; the polychaetes are considerably less numerous (11 to 39 per
cent) and the echinoderms rank third (up to 20 per cent).

The population of the pseudo-abyssal. The pseudo-abyssal zone, which occupies
the bathymetric part of the Sea (150 m), is characterized by its small amount
of light, absence of vegetation and feeble fluctuations of temperature (about
— 1 -4°) and salinity (about 30 per cent) and finally by its brown soils formed
of soft silty clay. The average biomass of this community is 20-6 g/m2, and

THE WHITE SEA

213

its dominant forms are the two molluscs Portlandia arctica and Leda pernula
and the two echinoderms Asterias lincki and Ophiocantha bidentata.

Derjugin considers the crawling transparent jellyfish Lucemosa saint-
hilairei, the pink transparent actinian (not yet identified), the molluscs Modio-
laria nigra var. bullata, Chaetoderma nitidulum var. intermedia, the poly-
chaetes Myrioehele heeri and Maldane sarsi, the crustacean Acanthostepheia
malmgreni and Rozinante fragi/is, the asterid Poraniomorpha tumida, the
transparent ascidian Eugyra pedunculata, the small fish Liparis major, as
equally characteristic for this peculiar community.

The qualitative indices for this pseudo-abyssal community are given in
Table 93.

Table 93. Constituents of the pseudo-abyssal community according to the data
obtained by use of bottom-sampler

Biomass

Form

No. of specimens

Total biomass

per m2

g/m2

per cent

Astarte elliptica, A. montagui

1-314

Dacrydium vitreum

3-4

0039

Yoldia hyperborea

0-6

0-440

Leda pernula

210

5130

Portlandia arctica

460

4-373

Others

0-530

Total Lamellibranchiata

—

11-823

57-75

Pe dinar ia hyperborea

0-3

0070

Maldane sarsi

0085

Others

1-220

Total Polychaeta

1-375

6-35

Asterias lincki

4-350

Ophiocantha bidentata

2-0

0-531

Total Echinodermata

4-881

18-68

Crustacea

0-242

1-18

Coelenterata

0-995

4-83

Sipunculoidea

1-670

811

Others (Gastropoda and

Nemertini)

0-637

310

Average total biomass

21-632

1000

The population of the bays. The distribution and composition of the bio-
coenoses of the benthos of the Rugozerskaya Inlet (the southern side of the
Gulf of Kandalaksha, see Fig. 90) are given in Fig. 89. The Inlet is adequately
enclosed from the sea except for a narrow pass. The depth of its middle part
reaches 25 m. G. Gurvich (1934) has given a description of the bottom

214

BIOLOGY OF THE SEAS OF THE U.S.S.R

communities of the Bab'e Sea, which is separated from the rest of the Sea by
the western side of Velikiye Islands (Gulf of Kandalaksha). The fairly large
(9x13 km) and comparatively shallow (down to 39 m) Bab'e Sea is connected
with the White Sea by two narrow and very shallow passes (Fig. 90). Below
15 m the circulation is slack, the oxygen content is low (about 50 per cent),
low temperature is permanent (below 20 m it is below zero), while its salinity
is comparatively high (close to 27%0).

The whole of the shallow part of the Bab'e Sea down to 4 to 6 m is covered
with Zostera fields. Macoma baltica, Mya arenaria, Arenicola marina, Littorina
littorea, L. rudis and other typical inhabitants of the littoral come down here
from it. Asterias rubens grows here in huge numbers. Sublittoral forms like

Fig. 91. Bottom biocoenoses of Rugozerskaya Inlet and their dominant
forms (Brotzky and Zhdanova and Semenova): 1 Leda permtla, Yoldia
hyperborea, Astarte montagui; 2 Portlandia arctica, Leda permda, Asterias
lincki; 3 Astarte montagui, Leda permda, Ophiocantha bidentata; 4 Astarte
borealis, Yoldia hyperborea, Leda permda; 5 Portlandia arctica, Yoldia
hyperborea, Pectinaria hyperborea; 6 Mesidothea en to топ, Macoma

baltica.

Macoma calcarea, Ophiura robusta etc. become predominant in the lower
parts of this level.

From 7 m downwards Zostera is replaced by red algae, mainly Phyllo-
phora, with a small admixture of Laminaria. Like the Zostera, Phyllophora
encircles the whole of the Bab'e Sea, extending to a depth of 1 5 m. Ophiura
robusta is a dominant animal form in this Sea, among the rest the following
should be noted : the ascidian Boltenia echinata ; the molluscs : Astarte ellip-
tica, Saxicava arctica, Macoma calcarea ; the echinoderms : Ophiura nodosa,
Ophiopholis aculeata, Asterias rubens, Cribrella sanguinolenta etc. ; the
polychaetes : Harmothoe imbricata and H. nodosa ; and the crustaceans.

This zone is the feeding ground of large numbers of cod.

Below 1 5 m the growth of red algae is cut off abruptly and the algae are
replaced by a Portlandia arctica community; a definite impoverishment in
forms takes place. The population consists of the following forms : the mol-
luscs Macoma calcarea, Astarte elliptica, Saxicava arctica Pandora glacialis,

THE WHITE SEA 215

Cardium ciliatum, the echinoderms Stegophiura nodosa and Ophiura robusta,
many polychaetes and a considerable number of amphipoda. The Arctic
forms are predominant at this depth of the Bab'e Sea. Mysis oculata typica is
abundant throughout. The deepest part of the Sea (below 25 m) is almost
free of animal forms.

This impoverishment of fauna, common in such cases, and the rise of the
boundaries of the vertical zones observed when passing from the Barents Sea
to the White Sea is even more accentuated as one moves from the White Sea
to the more or less isolated gubas, lagoons and pools. We have here a case of
the changes repeating the zonalities characteristic for the whole of the White
Sea as if in miniature.

Some original bottom communities of the Gulf of Dvinak may also be
noted. Thus, for instance, large colonies of Mesidothea entomon and Macoma
baltica, with a biomass of 18 g/m2, consisting mostly (86 per cent) of Mesido-
thea, live at fairly high temperature in the fresh or almost fresh waters off the
Northern Dvina estuary, on sandy bottoms at a depth of 5 to 10 m. A little
farther down the Sea lives a community poor in numbers (about 5 g/m2),
but characterized by one of its constituents — Portlandia arctica. In some
places the Sea is abundantly populated by Mytilus colonies. Portlandia arctica,
a relict of the coldest phases of the post-glacial period, is characteristic of the
coldest parts of the Arctic basin. It lives in large numbers in the central depres-
sion of the White Sea, in the Novaya Zemlya trench, in Sturfjord in eastern
Spitsbergen, in the Kara Sea, etc. Special races of this mollusc, which can
stand considerable water-dilution and, probably, periodically, a rise of tem-
perature, inhabit the estuaries of the rivers flowing into the Arctic basin, such
as the Dvina, Pechora, Ob, Yenisey and others.

It is remarkable that a deep-floor fauna like that of the White Sea, and in
particular Portlandia arctica, has remained till this day in comparatively
shallow, stagnant gubas along the White Sea shores, and in the never-warmed
deep parts. One of these gubas — the Glubokaya Guba of the Great Solovest-
kiy Island — served as the object of N. Livanov's fundamental study (1912).
Derjugin thinks that the bathymetric fauna must have remained in these gubas
since the severe climate period, and that the cold-water fauna, which has now
migrated to the depths, at that time populated the whole sea. 'Glubokaya
Guba', says Derjugin, 'represents in miniature those properties which, on a
larger scale, are found throughout the White Sea, as the relicts of a vast
ancient basin. '

Productivity

The great poverty of White Sea bottom fauna is clearly shown by the quanti-
tative data given above. This quantitative impoverishment increases
gradually with depth, and in the lower sublittoral and the pseudo-abyssal
zone the benthos biomass becomes 5-10-15 times smaller than that of the
Barents Sea. The average benthos biomass of the White Sea is probably about
20 g/m2, whereas in the Barents Sea it is 100 g/m2. This quantitative impover-
ishment affects, as has been mentioned above, not only animal and vegetable
organisms, not only the biomass as a bulk, but also the average weight and

216

BIOLOGY OF THE SEAS OF THE U.S.S.R.

size of individual specimens of most of the characteristic forms. The popu-
lation of individual forms of the White Sea, so far as we could observe, never
reached a density characteristic of the other regions of the Arctic. This can
be shown by a comparison of the quantitative data for a number of forms
common to the Barents and White Seas {Table 94).

Table 94. The largest biomass determined for certain forms in the White and Barents
Seas and in some other regions of the Arctic

Other Arctic

White Sea

Barents Sea

regions

Form

No. of

Biomass

No. of

Biomass

specimens

g/m2

specimens

g/m2

Molluscs

Astarte elliptica

391

1730

3070

Astarte montagui

105

201

800

Axinus flexuosus
Cardium ciliatum

105
10

3-5
19-8

4-4
365-5

90
243-6

Serripes groenlandicus
Macoma calcarea

3
20

6-2
23-6

186

308 0
243 0

941-0

Portlandia arctica

160

130

Leda pernula
Yoldia hyperborea

200
30

21 -1

261

120
145

23-5
300

1340

Nucula tenuis

210

15-2

190

180

Saxicava arctica

1-2

6000

291-5

Polychaetes
Lumbriconereis fragilis
Maldane sarsi

35
400

5-2

7,710

130
950

140

Myriochele
Pectinaria hyperborea

750

20
60

1,000
500

70
63-7

Only a few forms in the White and Barents Seas give similar biomass in-
dices, although the living conditions in the White Sea are exceptionally
favourable for a number of forms, such as Zostera marina among the plants
and Portlandia arctica, Leda pernula, Yoldia hyperborea, Asterias lincki and
others among the animals. Moreover both as regards the inflow of river water
and the supply of vegetative detritus, the White Sea may be classed as a most
favourable environment. In this respect there is some similarity between
the White and Baltic Seas. The biomass indices of this latter are also compara-
tively very low. The scarcity of the Baltic Sea fauna is naturally related to the
bad aeration of deep-floor layer and to a considerable dilution of the waters
of the eastern and especially the northern parts of the Sea. In the White Sea
this last factor is not of much importance for the quantitative development
of its fauna; as regards the deep-floor layer aeration, most investigators
consider it quite sufficient for the development of bottom life.

We think that the lowering of the indices of biological productivity of the
White Sea is mainly due to two factors. For the littoral fauna and for that of

THE WHITE SEA 217

the upper sublittoral, the determining factors are the very long, severe winter,
the short vegetation period of the plant organisms and the ice conditions of
the off-shore zone which are adverse for this latter. Life has no time to attain
any great density during the four or five summer months, while the severe
winter destroys a large number of organisms. In the lower sublittoral and the
pseudo-abyssal the low temperature and the gas content constitute adverse
factors for full development of life. Deep-sea layers and especially the true
deep-floor layer have not yet been sufficiently studied, and the possibility
of the periodical occurrence of shortage of oxygen cannot be denied. On the
other hand, the wide distribution of brown muds in the White Sea depression,
as in other bodies of water, may be an indication of unfavourable conditions
of the vertical circulation, and probably of a considerable periodical con-
centration of carbon dioxide in the presence, apparently, of sufficient amounts
of oxygen. Brown mud with its very poor life, always characteristic of depres-
sions and hollows, and undoubtedly very badly aerated (for instance the deep
depression of the Polar basin), still remains an enigma. Brown mud is un-
doubtedly unsuitable for the development of life owing either to some specific
mechanical (considerable softness ; porosity) or chemical (presence of carbon
dioxide ; abundance of ferric or manganic oxides) properties. The productivity
of the flora and fauna is limited by the seven months of winter and the heavy
ice cover. The sharp summer stratification, restricting vertical circulation, is
also of great importance, since it causes the weak development of bottom
life frequently from a depth of 15 to 25 m. Low temperature, characteristic
of the whole depth of the White Sea, except for its thin uppermost layer,
has a considerable effect on the growth of living forms. M. Kamshilov (1957),
however, confirms V. Jashnov's (1940) opinion, by some data obtained much
later, that as regards the plankton biomass the White Sea could rank side by
sidewith the southwestern part of the Barents Sea {Table 95).

Table 95. Mean annual zooplankton biomass of the Barents and White Sea
(M. Kamshilov, 1957)

Biomass
Sea Regions investigated mg/m2

Barents Sea Coastal regions (B. Manteufel) 44-2
The regions of the Murman Biological Station in-
vestigation in 1952 61 -8
Open Sea (V. Jashnov's and B. Manteufel's data) 1000

White Sea Gulf of Kandalaksha (Murman Biological Station

survey in 1952) 198-8

Food correlations

The diet of White Sea fish has not been properly studied. Only the feeding
of herring has been comprehensively studied by L. Chayanova. Although in
the White Sea Calanus finmarchicus is the most common component of the
herring's food, its diet is most varied, however, consisting of Copepoda,

218

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Cladocera, Chaetognatha, Euphausiacea, Mysidacea, Amphipoda and the
eggs and larvae of different invertebrates and fish. Herring feeds also on
fry, mainly its own. Its food varies greatly with the season (Fig. 92). The White
Sea herring fattens up in May : during the rest of the year its feeding is not
intensive. From September onwards herring practically stops eating, and the
percentage of empty stomachs in October may reach 40. In the spring its main
food is Calanus finmarchicus, in summer and autumn other Copepoda.
Spawning herring do not stop eating, but eat less. The rapacity of herring is
demonstrated not only by the fact that it prefers to devour great numbers of

PORVYA INLET
MAY

304

PORVYA INLET

JUNE
216

NISHCHEVA

INLET

JULY

Fig. 92. Food ranges of the White Sea herring in different months
(Chayanova, 1939). Repletion indices denoted by associated
numerals. 1 Calanus finmarchicus; 2 Small Crustacea; 3 Euphau-
siaceae; 4 Mysidacea; 5 Amphipoda; 6 Sagitta; 7 Pteropoda;
8 Fish larvae.

its own young, but also by its obvious preference for the larger forms of
plankton.

The young navaga, like herring, feeds mostly on different small plankton
crustaceans. The food of the adult navaga is also greatly varied ; however,
contrary to that of the herring, its main food consists of benthos, chiefly worms
and crustaceans (up to 70 per cent of its food). One-fifth of navaga's food
consists of fish-smelt, caplin, launce, Boreogadus saida and others, including
navaga itself. Navaga grows more rapacious with age, often swallowing a
prey almost as big as itself.

While spawning in January, navaga eats very little ; once its spawning is
over it once more falls greedily upon its food.

Seals and porpoises are the navaga's chief enemies.

Pollack or Polar cod also form an essential link in the food-chain of the
White Sea. The Arctic seas conceal an inexhaustible store of the small Gadidae.

The young Polar cod, like navaga, feeds on crustaceans ; when growing in
size it changes to fish, and its predatory instincts and voracity are just as bad
as those of navaga, enormous numbers of which it devours, and for which it
itself also serves as food. The Greenland Sea, Phoca hispida and Delphinapterus
leucas devour countless masses of Polar cod, navaga and herring.

THE WHITE SEA 219

Fishing

The total catch of the White Sea fisheries reaches 15,000 tons, which in-
cludes 2,500 tons of herring.

N. Dmitriev has pointed out (1957) that in the White Sea the chief quarry
of fishery consists of herring, navaga, smelt, White Sea cod, dab, and white-
fish. Owing to its delicious flavour, salmon is particularly important for trade.
At times large shoals of the Arctic cod (Boreogadus saida) and caplin (Mallosus
villosus) enter the White Sea. The bulk of the Sea herring trade consists of
some endemic species of herring with few vertebra (Clupea harengus pallasi).
Besides these species large numbers of multi-vertebrate Murman herring
{Clupea harengus harengus) appear at times in the White Sea. Moreover the
White Sea is the extreme western limit of the distribution of the Pacific Ocean
herring (CI. har. pallasi) of a later origin. There are two small-sized endemic
forms of cod in the White Sea — Gadus morhua f. hiemalis Taliev and G.m.
maris albi Derjugin. Moreover the large Barents Sea cod appears in the White
Sea from time to time.

The hunting of marine animals, and primarily of the Greenland seal
(Histriophoca groenlandica) which has for many centuries been intensively
hunted by man, is of great importance in the White Sea. The Greenland seal,
of which the greater number spend the summer on the floating ice of the
Greenland, Barents and Kara Seas and northward of them, migrate far to the
south during the winter while the breeding season is on. There are three main
gatherings of breeding seals : Newfoundland, Jan Mayen and the White Sea.
At the end of November and the beginning of December the rookeries of seal
gather in the White Sea, in February and March the seals calve on the ice of
the White Sea Gorlo, and at the end of March and the beginning of April
rookeries of seal are carried out of the Gorlo with the ice northwards into the
open sea. The hunting season of the Soviet and Norwegian vessels is timed to
coincide with this period. Powerful icebreakers with slaughtering gangs set
out to hunt seals in the early spring just when the ice begins to move out of the
White Sea. They are escorted by reconnaissance aircraft and manned by
crews of up to 1,500 men. The size of the total White Sea herd of 'skins' has
been estimated at several million head with the help of aerial photographs
(S. Freiman and S. Dorofeev). The Soviet and Norwegian annual catch is
about 300,000 head. Small numbers of smaller seals, the 'nerpa' (Phoca his-
pida) and of the large bearded seals (Erignathus barbatus) are caught all along
the shores of the White Sea. Beluga (Delphinapterus leucus) is very common
in the White Sea, and is caught off some parts of the coast during the time
when it approaches land. Of the marine animals mentioned the Greenland
seal and beluga feed on navaga, herring and Boreogadus saida and the Erigna-
thus barbatus on molluscs and crustaceans.

In view of the vast natural resources the collection of varec and sea-weed
(Laminaria and Ahnfeltia) should be greatly developed in the White Sea.

E. Palenichko estimates the natural resources of sea mussels in the White
Sea at 20 to 30 thousand tons (it can be assumed that the actual amount is
considerably higher) so that its exploitation is still at an inconsiderable level.

The Kara Sea

I. GENERAL CHARACTERISTICS

The Kara Sea (Fig. 93) is the first of the series of high Arctic epicontinental
seas lying along the northern shores of Siberia. With its western boundary at
Novaya Zemlya and its eastern limit at the western shores of the Taimyr
Peninsula and at the Severnaya Zemlya Archipelago, the Kara Sea is wide
open to the waters of the central part of the Arctic basin through the sound
between Franz Joseph Land and Severnaya Zemlya. Like other Siberian seas,
the Kara Sea loses much of its salinity, especially in its upper layer, from the
inflow of large rivers, and this leads to a fall in the salinity of the upper layer
throughout the Arctic basin.

Favourable conditions for the penetration of fresh-water fauna, mainly
plankton and fish, into the southern parts of the Siberian seas are created by
their considerable dilution with river water. Abundant brackish areas at river
mouths and estuaries give shelter to a varied, most original fauna which, in its
aspect, is a high Arctic relict brackish-water fauna — a legacy of the Ice Age —
consisting mainly of fish and crustaceans.

The Kara Sea may have been the centre of the evolution of this remarkable
fauna which penetrated, as a set of forms, far to the south into the depth of
Eurasia as far as the Caspian Sea and westward to the basin of the Baltic
Sea.

Of all the Siberian seas the Kara Sea alone is exposed, in its western part,
to the influence of the warmer and more saline waters of the Barents Sea with
its characteristic flora and fauna. On the other hand, warmer and more saline
Atlantic waters, of the intermediate layer of the central part of the Arctic
basin, carrying a most original fauna rich in forms, penetrate from the north
through the troughs into the deeper layers of all the four seas, but principally
into the Kara Sea. The penetration of the boreal and abyssal fauna into the
Kara Sea from the north with the deep cold waters is also characteristic.

The Siberian seas are paradoxical in their aspect owing to the above-
mentioned hydrological characteristics: in their northern parts the deep-
water layers of all of them are much warmer and have a qualitatively richer
fauna. The endemic marine fauna of all the four Siberian seas, except perhaps
the southern part of the Chukotsk Sea adjacent to the Bering Strait, has a
definitely high-Arctic aspect.

The shallows off the shores of the Kara Sea differ greatly both in their
conditions and fauna from those of the deep central part. The first are well
aerated, better warmed, often considerably diluted, and populated by a
fauna rich in variety and at times in numbers. The second, characterized by
its low temperature and high salinity, has a thick brown mud floor and is
populated by a fauna poor both in its numbers and its variety. Its char-
acteristic features are a great preponderance of echinoderms, exceptionally

220

THE KARA SEA

221

Fig. 93. Chart of the Kara Sea with depths and currents (according to data
of Arctic Institute).

large sizes of invertebrates, very poor fish, and very low indices of biomass
and productivity.

The Kara Sea is a true outpost of the high Arctic, since all the characteristic
features of the endemic high Arctic conditions and all the attenuating influ-
ences of the foreign Atlantic waters are reflected in it with extreme clarity.

II. HISTORY OF EXPLORATION
First period

The first data on the Kara Sea were collected by the Swedish expeditions of O.
Nordenskjold in 1875 (in the Proven), in 1876 (in the Imer) and in 1878 (in the
Vega). In 1882 and 1883 biological work was carried out there by a Dutch
expedition in the Varna and by a Danish one in the Dymphna. In 1893 the

222 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Kara Sea was surveyed by Nansen's famous Fram, in 1900 by Toll's Russian
expedition in the Zarya, in 1907 by the expedition of the Duke of Orleans in
the Belgica and in 1918 by R. Amundsen in the Mod. All these expeditions
have contributed to the study of the Kara Sea fauna.

Second period

A comprehensive study of the Kara Sea and its fauna was begun as recently as
1921 by the expedition of the Oceanographic Institute in the Malygin and
by that of the Hydrographic Directorate in the Taimyr. In subsequent years
a number of Soviet expeditions of the Arctic Institute and the Committee
of the Northern Sea Route cruised in the Kara Sea. Among them the voyages
of the Sedov (1929, 1930 and 1934), Lomonosov (1931), Rusanov (1931 and
1932) and others, and particularly the expeditions of the Sadko (1935, 1936
and 1 937) which sailed to the north of the Kara Sea far into the Arctic basin
and which was the first to haul bottom fauna from depths of almost 4,000 m,
are of especial interest. The results of the expedition of the trawler Maxim
Gorky in 1945 were of importance. During the Soviet period the number of
expeditions working in the Kara Sea has been more than doubled in com-
parison with those of all previous years. Earlier opinions on the Kara Sea
population have been radically altered by the Soviet expeditions of the last
twenty-five years. Formerly it was supposed that the Kara Sea flora and fauna
were qualitatively extremely poor; this was due to the expeditions sailing
only through the southern parts of the Sea, where the fauna is in fact very poor
in number and variety.

The Soviet expeditions, which covered the whole Sea up to its entrance into
the open parts of the Arctic basin, have shown that the Kara Sea fauna is
almost as varied as that of the Barents sea and much more so than the fauna
of any other Siberian sea.

III. PHYSICAL GEOGRAPHY, HYDROLOGY AND HYDRO-
CHEMISTRY

Boundaries

The Kara Sea is bounded on the west by Novaya Zemlya and on the east by
Severnaya Zemlya (56° to 105° E longitude); it extends northwards from 68°
to about 81° N latitude.

Bottom topography and size

A deep trench, with depths down to 200 m in the south and to 600 m in the
north, stretches along the coast of Novaya Zemlya. East of this trench the
bottom begins to rise to the extensive shallows of the Yamal and Taimyr
peninsulas (Fig. 93), with depths of less than 50 m. The area of the Kara Sea is
883,000 km2, and its volume 104,000 km3. Its average depth is 118 m, and its
greatest depth 620 m.

Another deep trench enters the northern part of the Kara Sea from the
north to the west of Severnaya Zemlya ; it may be connected with the deep

THE KARA SEA 223

Schokalsky and Vilkitsky Straits, which separate the islands of Severnaya
Zemlya.

In the northern part of the Sea (north of 80° N latitude) towards the Arctic
basin there is an increase of depth. The middle zone of the sea, extending
from southwest to northeast and in the northern part due north, forms a
wide plateau, with depths of 50 to 200 m, which rises in two wide submarine
terraces from the Novaya Zemlya trough to the Yamal and Taimyr shallows.

Currents

The Kara Sea is connected with the Laptev Sea through the deep Vilkitsky
and Schokalsky Straits. Huge masses of river water, of the order of 1,500
km3 annually, flow into it, forming a layer of fresh water about 2 m deep over
the whole surface. The waters of the Ob and Yenisey rivers in their main
mass are carried to the northeast, along the western coast of Taimyr. Part of
these waters turn north and northwest to the northern end of Novaya Zemlya
and then, partly swerving west and southwest, they create a cyclonic rotation
of the waters of the southern part of the Sea between Yamal and Novaya
Zemlya (Fig. 93). Skirting Novaya Zemlya, and also penetrating in smaller
amounts through the straits of Novaya Zemlya, the 'Atlantic' waters of
higher salinity enter the Kara Sea, and flow from the west, out of the Barents
Sea, sinking down below the much less saline surface waters. Larger volumes
of more saline and less cooled 'Atlantic' waters enter the Kara Sea from the
north, in the depths, at some hundreds of metres, between Franz Joseph
Land and Severnaya Zemlya and from the northeast out of the Laptev Sea
through Vilkitsky and Schokalsky Straits.

Temperature and saline conditions

The surface waters of the Kara Sea in the region of the Ob- Yenisey shallows
have a salinity of 7 to 10%0 and, in the warmest season, a temperature of 5°
to 8°. As one moves westwards and northwards the salinity increases, reach-
ing 32 to 34%0. The deeper layers are considerably more saline and colder.
One of the Malygin's stations in September 1921 opposite the Ob estuary
(Table 96) may be given as an example. The ranges of temperature and salinity
for the central part of the southern half of the Sea in the centre of the cyclonic
rotation are given in Table 97 for August 1921.

Table 96

Depth
m

f Q

*5%o

02/cm3

4-32

5 07

7-62

419

4-33

7-62

7-5

1:17

15-48

7-31

016

24-30

6-83

- 1 45

30-55

6-73

- 1 54

31 04

6-76

224 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 97

Depth

"Zoo

02/cm3

2-70

29-42

2-40

29-88

—1-45

33-57

8-32

-1-65

34-49

—

120

-1-52

34-72

7-88

In the western part of the Sea, in the depths of the Novaya Zemlya trough,
the salinity is 34-5 to 34-7%0 and the temperature is —1-6° to —1-75°. For
example, the conditions at one of the Persey stations east of Matochkin
Shar (September 1927) may be given {Table 98). Throughout the Kara Sea

Table 98

Depth

f С

•S/oo

3-95

26-41

3-95

27-14

0-95

33-44

-0-80

3402

100

-1-53

34-40

200

-1-66

34-47

360

-1-64

34-70

at a depth of 10 to 20 m a sharp fall of temperature and an increase in salinity
are observed; at depths greater than 50 m salinity does not fall below 34%0,
while the temperature remains below zero all the year round. The currents
skirting Novaya Zemlya from the north have a salinity of 32 to 33%0 at the
surface and a temperature of 0-5° to 1-0°.

Dilution of the surface layer by the Ob-Yenisey waters can be detected
throughout hundreds of kilometres north of the river estuaries, even to the
east of Cape Zhelaniye up to 77° N latitude {Tables 97 and 99).

Table 99

Depth

f С

"/bo

0-4

27-65

0-36

30-36

009

32-78

-111

34-16

218

-1-49

34-79

The kara sea 225

Side by side with the surface layer, with its considerable loss of salinity and
its summer rise in temperature, and with the deep, highly saline waters of
practically constant low temperature, there is in the Kara Sea in the summer a
definite intermediate cold layer 50 to 100 m deep. This layer is formed by the
sinking of the cold surface waters, which in the previous winter had been
considerably cooled and have become much more saline as a result of the
formation of an ice cover (Figs. 94 and 95). The presence of a thick cold inter-
mediate layer is an indication of a comparatively weak vertical circulation.

Like all the marginal seas, more or less cut off from the open ocean, with
a large inflow of river water, the Kara Sea is characterized in its surface
layer by unstable saline conditions which depend on the amount of river
water. As an example of this one may mention the differences in the tempera-
ture and saline conditions of the sea in 1927 and 1945, given in Figs. 94 and
95. In 1945 the inflow of river water into the Kara Sea was only about two
thirds of the many years average amount and the salinity of the surface sea
waters was found to be considerably higher. However, as can be seen from
the cross sections, the deep water retained its salinity. A general warming
up was equally clearly perceptible. Low temperature ( — 1-6° to — 1-7°) was re-
tained only in the deepest layer. The surface layers were warmed most of all.
In the summer of 1945 the Kara Sea was completely free of ice for several
months.

In summer the dilution of the surface layer prevents vertical circulation ;
in winter, however, it causes a further increase of ice formation. As a result
salt water, formed on the surface, sinks into the depths. In winter the tempera-
ture of the surface layers of the Kara Sea is mostly — 1-6° to — 1-8°, while its
salinity is 34%0 and higher. This feature of the hydrological conditions in the
Kara Sea is similar to that of the White Sea.

Atlantic waters of the intermediate layer of the Arctic basin (salinity up to
35%0 ; temperature up to 2-5°) and the much colder waters of the same salinity
lying beneath them, enter the northern part of the Sea at depths of 1 50 to
300 m.

Ice frequently begins to form in the Kara Sea as early as September, while
proper melting only begins in June. The summer is short and cold. The central
part of the Sea is not covered with solid ice, even in winter time, but wide firm
ice belts and large stranded hummocks are formed at the shores.

The general character of the summer ranges of temperature and salinity
throughout the Kara Sea waters in 1945 is given in the hydrological cross
section in Fig. 96. As may be seen from the second diagram, the northern part
of the Sea is warmed more than the central part, while the southern one is
under the influence of the warmer waters entering it from the Barents Sea
and of the local coastal ones.

The hydrological conditions of the Kara Sea are most complicated owing
to the entrance of deep currents of warmer and more saline Atlantic waters
into it from the north, partly from the Barents Sea and partly directly from
the Arctic basin ; to the exchange of water through the Kara Gates with the
Pechora region of the Barents Sea, and with the Laptev Sea in the east ; to
the inflow of huge masses of river water from the south ; and finally to sharply

226

BIOLOGY OF THE SEAS OF THE U.S.S.R,

Fig. 94. Range of surface temperatures of the

Kara Sea: A In September 1927 (Vasnetzov);

В In September 1945 (Zenkevitch and Fila-

tova).

THE KARA SEA

227

Fig. 95. Surface salinity range in the Kara Sea :
A In September 1927 (Vasnetzov); В In
September 1945 (Zenkevitch and Filatova).

228

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Fig. 96a. Hydrological cross sections through
the southern part of the Kara Sea from Shubert
Bay to Yamal. A In September 1927 (Vasnetzov).

defined summer stratification, vigorous ice formation and the formation of
surface saline waters in the winter.

Thus the following water masses can be distinguished in the Kara Sea
according to their origin :

(/) Local Kara Sea waters of small or medium depths.

(2) Deep cold and saline waters of local origin (having become cold and

more saline on the surface of the sea in the winter, they have sunk

down).
(J) Ob-Yenisey waters with a low salinity and comparatively high summer

temperature.

Fig. 96b. As Fig. 96a but in September 1945 (Zenke-
vitch and Filatova).

THE KARA SEA 229

(4) Atlantic saline and relatively warmer waters which penetrate into the
Kara Sea by three ways :

(a) from the north from the central parts of the Arctic basin from its
intermediate 'warm' layer,

(b) from the northwest from the Barents Sea, between Franz Joseph
Land and Novaya Zemlya, and

(5) Cold and saline deep waters, which penetrate into the northern parts of
the Sea from the lower layers of the central part of the Arctic basin.

Soils

Silts and clayey ooze are preponderant in the central, northern and north-
eastern deep parts of the Sea (Fig. 97). In its eastern part, mainly in the shal-
lows opposite the Ob and the Yenisey estuaries, silty sand and sand floors are
preponderant. The finer-grained bottoms of the Kara Sea are usually coloured
brown in their upper layer ; this is explained, as in other cases, by the presence
of manganese and iron oxides. The boundaries of the brown mud distribution
are given in Fig. 98. Brown muds and the ferromanganate concretions so
characteristic of them are more widely distributed in the Kara Sea than in
any other body of water in our Arctic. In the Kara Sea the brown mud
attains a thickness of 18 cm, lying over the silts and grey-blue clays. In the
deeper parts of the Sea the brown mud is usually thicker (Fig. 98). The deep-
water troughs running out of the Arctic basin from the north are also covered
with brown mud.

Manganese is particularly active in this process. Getting into the deeper
layers of the silt (the reduction zone) manganic oxides are reduced to the
manganous state. These soluble compounds are dissolved in deep water, get
oxidized again and are precipitated on to the sea-bed, where reduction may
occur again. Hence there is an active consumption of oxygen in the deep layer
and brown mud is characterized by the presence of both managanese and
iron in an oxidized state.

There is much that is still not clear about the zones of formation of brown
muds, the chemical state of the overlying deep-water layer, and the effect of
such a sea-bed on organisms. One might suppose that an accumulation of
brown mud takes place where there is an inflow of river waters, which drain
the marshland and carry out into the sea large amounts of iron and man-
ganese. However, the northern part of the Barents Sea and the central part
of the Arctic basin are too far removed from river estuaries for this. The
brown muds are most widely developed in the deeper parts, more or less
stagnant, of the water bodies; at the same time oxygen is required in sufficient
amounts for the oxidation of the iron and manganese. A large number of
ferromanaganese concretions, frequently of large size, are characteristic of
the Kara Sea.

The intensity of the oxidation-reduction reactions in the deep-water layer
above the brown mud is indicated by a high oxidation-reduction potential ;
the index of the active reaction, however, is lower, probably as a consequence
of the presence of carbon dioxide. This is connected also with the small

230

BIOLOGY OF THE SEAS OF THE U.S.S.R,

Fig. 97. Kara Sea sea-bed soils. 1 Clay and mud ; 2 Silt ; 3 Sand-mud ; 4 Silty

sand ; 5 Sand ; 6 No data ; 7 Ferromanganate concretion ; 8 Rock ; 9 Gravel ;

10 Limit of distribution of underlying clay (Gorshkova).

amount, and sometimes complete absence, of bicarbonates in the brown
mud.

Life is always scarce in the brown mud, but it is not clear why this is so.
It may be caused by a lack of free oxygen (taken up from the deep-water layer
by manganese compounds), by an accumulation of carbon dioxide, or, as

THE KARA SEA

231

has been suggested by Hessle (1924) for the Baltic Sea, by the poisonous pro-
perties of manganese.

As has been pointed out by T. Gorshkova (1957), the percentage of organic
carbon in the upper layer of the Kara Sea floor is comparatively small, vary-
ing between 0-27 and 1-99.

None of these three reasons explains the fact that some animal forms thrive

Fig. 98. Temperature cross section along the Kara Sea from the Karskie Vorota

towards NNE to 81° N latitude in mid-September 1946 (Zenkevitch and Filatova).

The thickness of the brown mud layer is given below in cm.

on brown mud, notably all echinoderms (especially the brittle stars, asterids
and holothurians) ; some coelenterata (Metridium, Umbellula); some mol-
luscs (Pecten) and crustaceans (Mesidothea, Sclerocrangon).

Lack of oxygen and high concentration of carbon dioxide are specially
marked in the deep-water layer of the Ob-Yenisey region, where the difference
in the salinity of the surface and deep-water layers is considerable (P. Lobza,
1945).

IV. FLORA AND FAUNA
General characteristics

The pelagic and bottom life of our northern seas situated east of Novaya
Zemlya is several times poorer in numbers than that of the Barents Sea, but
as to the qualitative variety of its benthos the fauna of the Kara Sea is not
much inferior to that of the Barents Sea. This is all the more remarkable,
considering the much more severe climate of the Kara Sea, its smaller size
and its inferiority to the Barents Sea as regards the variety of its biotopes.
For instance, all littoral fauna is absent from the Kara Sea, and since it does
not contain the macrophyte growths so characteristic of the upper level of the
Barents Sea sublittoral, very many forms peculiar to this level in the Barents
Sea are absent from the Kara Sea.

232 BIOLOGY OF THE SEAS OF THE U.S.S.R.

The qualitative wealth of the Kara Sea fauna, and probably also of the
northwestern part of the Laptev Sea, is explained by its being the meeting
ground of fauna of different origins. This is connected with the different
sources of the water masses noted above.

Plankton

The phytoplankton of the Kara Sea has been quite fully studied. There is the
following to be added to what has already been said in our introduction to
northern seas : the total number of species of plankton algae found in the Kara
Sea is 78 (see Table 100).

Table 100. Qualitative composition of phytoplankton of the Kara Sea {data of

P. Usachev, 1947)

Percentage of the
Form No. of species total number

Flagellates 2 2

Silicoflagellates 2 2

Peridineans 20 27

Diatoms 52 67

Green algae 2 2

Total 78 100

According to P. Usachev (1947), two areas of increased phytoplankton bio-
mass can be distinguished in the Kara Sea: * a northern one near Wiese Island
with a biomass of 1 to 3 g/m3 and more, in the parts of the Sea warmed by the
warmer Atlantic waters and near the edge of the melting ice ; and a southern
one, influenced by the inflow from the Ob and Yenisey, with a biomass of
more than 1 g/m3 (Fig. 99). It is evident from the diagrams given that the
main mass of plankton is adapted to the upper 25 m layer (more than
500 mg/m3).

Typical spring diatoms are preponderant in the northern region; in the
southern one later forms and forms typical of the estuarial zones are found
side by side with the former. In Usachev's opinion (1946) the productivity of
Kara Sea phytoplankton is about equal to the indices for the northeast region
of the Barents, Laptev and East Siberian Seas. The phytoplankton mass in
some cases is as high as 6 to 8 g/m3.

Qualitative composition of zooplankton. V. Khmisnikova (1936) has recorded
169 forms of plankton for the whole Kara Sea, not counting larvae and

* It should be borne in mind that all data on Kara Sea phytoplankton refer to the short
summer period of one to two months and are valid for one area and for one time of the
year. No observations exist for different seasons of the year and for different parts of the
Sea simultaneously.

THE KARA SEA

233

Fig. 99a, b. Quantitative distribution of phytoplankton (g/m3) in the
Kara Sea, August-September 1934 (Usachev, 1946).

Fig. 99c. Distribution of biomass of phyto-
plankton in the Kara Sea according to the
materials of the expedition of the ice-
breaker Sedov of the Arctic Institute
(August-September, 1934. For the 0 to 25
m layer, g/m3) (Usachev, 1941).

234

BIOLOGY OF THE SEAS OF THE U.S.S.R.

unidentified forms, whereas with the larvae, parasitic crustaceans and the
unidentified forms the number is 223 {Table 101).

Table 101

Foraminifera

Rotatoria

(Globigerina bulloides.
the northern part)
Radiolaria

Only in

Pteropoda
Copepoda
Cladocera

(10 of them only in the northern
part)
Ciliates
Coelenterata

Ostracoda
Amphipoda
Schizopoda
Tunicata

(Ctenophora

(Siphonophora

Vermes

2)
1)

Total

3
4

169

Kara Sea zooplankton as an indicator of hydrological conditions
The sharp differences in the water masses of the Kara Sea, varying in their
origin and in the fauna they bring with them, have made it possible for differ-
ent investigators of this body of water to pose with particular precision the
problem of the biological indicators of the different waters that compose it.
(G. Gorbunov, 1934, 1937, 1941 ; E. Gurjanova, 1934, 1936; V. Khmisnikova,
1936, 1937; M. Virketis, 1945; B. Bogorov, 1945, and others). As has been
justly remarked by Gurjanova, 'One should search for biological indices
among forms which, owing to their stenobiotic nature, are restricted in their
distribution. The common forms widely distributed throughout the whole
Arctic cannot serve as indices. The indifferent forms are uniformly distri-
buted throughout the Sea, in places of suitable depths and soils ; they are the
indifferent forms of the Barents Sea. However, when these species get into
the Kara Sea, they are most unevenly distributed there and depend on the
range of the currents. In the conditions of the Kara Sea they become biological
indicators of the presence of Barents Sea waters, in which they are distributed
about the Kara Sea. On the other hand the most common high Arctic forms
— indifferent for the Kara Sea because widely distributed in it — are already
becoming rare in the conditions of the Barents Sea and become indicators for
Arctic waters, while indicators of the western Atlantic waters would be the
boreal species more or less widely distributed in the northern part of the
Atlantic Ocean.'

There is no other marine body of water where the distribution of the fauna
gives such clear and abundant illustrations for the understanding of the ori-
gin of its masses of water as the Kara Sea. A very large number of plankton
and benthos forms can serve as indicators of both fresh and brackish waters,
and of waters penetrating from the west from the Barents Sea, and from the
north from the central parts of the Arctic basin. Among these it is possible to
distinguish the forms belonging to the warm Atlantic intermediate layer and
those of the cold Arctic bathyal and abyssal waters.

THE KARA SEA

235

The following biogeographic groups are commonly distinguished in the
Kara Sea plankton :

(7) forms widely distributed throughout the Arctic

(2) forms of western origin (Atlantic-Barents Sea forms)

(3) forms belonging to the cold Arctic waters, which have come from the
north

(4) forms of the warm Atlantic intermediate layer of the central part of the
Arctic basin

(5) brackish-water forms

(6) fresh-water forms.

Khmisnikova distinguishes four main regions in the Kara Sea according to
the distribution of these groups (Fig. 100).

J X'/'WA

Fig. 100. Areas of the Kara Sea according to plankton distribution (Khmisnikova).
1 Area of penetration of Atlantic and Arctic forms from the north ; 2 Area of pene-
tration of Barents Sea forms from the south ; 3 Area of predominance of brackish-
water forms ; 4 Area of predominance of fresh-water forms.

236

BIOLOGY Of THE SEAS OF THE U.S.S.R,

Fig. 101. Distribution of Microcalanus pyg-
maeus in the Kara Sea (Virketis).

The first group of plankton organisms includes a large number of forms of
which the basic population of the Kara Sea is composed. Among them several
are widely distributed throughout the Arctic, while some are cosmopolitan
forms (Figs. 101, 102). This group includes many Tintinnoidea (Parafavella),
Siphonophora Diphyes arctica, the worm Sagitta elegans, many Copepoda

46 56 66 76 86 96 106 116

dL<* A9 » /

/ /v'V

l^^pJu:

— ^4r \ ff4

A *

и '% \

1 *

* » / / / J)

" <4 \ \

^=т4~-М-

conventional signs
э Rothkea octopunctata
a Qithona allantica

/v V

. Evadne nordmanni

66 76

Fig. 102. Distribution of some Atlantic-
Barents Sea forms in the Kara Sea (Virketis).

THE KARA SEA

237

{Calanus finmarchicus, С hyperboreus, Pseudocalanus elongatus, Microcalanus
parvus, Oithona similis) and some salps (Fritillaria borealis and Oikopleura
vanhoeffeni and others). The cold-water forms are characteristic of the deep
water of the Kara Sea (below the 50 to 100 m layer) — Calanus hyperboreus,
Euchaeta glacialis, Metridia longa, Conchaecia borealis, Parathemistq oblivia,
Euthemisto libellula, Diphyes arctica and Clione limacina.

Of the upper layer of water the following are characteristic : Pseudocalanus
elongatus, Oithona similis, Centropages hamatus, Thysanoessa neglecta, Temora
longicornis, Acartia longiremis, Oithona plumifera var. atlantica, Microsetella

Fig. 103. Distribution of plankton forms

which have penetrated from the north and

forms from inland discharge in the Kara Sea

(Virketis).

norvegica, Oikopleura labradoriensis ; among the sea- weeds Halosphaera viridis
is the most typical. Most of these forms have arrived from the west.

The quantittaively richest form, Calanus finmarchicus, in its mature state,
lives in the deepest layers of water, but while young is adapted to the upper
zones. The forms of western origin come into the Kara Sea from the Barents
Sea, either skirting Novaya Zemlya from the north or through the southern
passages. At times only a few penetrate into the Kara Sea (Fig. 103); some-
times, however, they go far to the eastward, as far as the passages into the
Laptev Sea.

The ciliates Salpingella acuminata, Acanthostomella norvegica, Evadne nord-
manni, Podon leuckarti, meduse — Rathkea octopunctata, Crustacea — Evadne
nordmanni, Podon leuckarti, Centropages hamatus, C. typicus, Temora longi-
cornis and Oithona atlantica are included in this group of forms.

The third group of cold-water Polar forms, penetrating from the north, is

238 BIOLOGY OF THE SEAS OF THE U.S.S.R.

similar in its distribution in the Kara Sea to the fourth, which comes also from
the north, but from the warm Atlantic intermediate layer.

The former may be said to include Amphimelissa setosa, Amallophora magna,
Chiridius obtusifrons, Euchaeta glacialis, Fritillaria polaris, the fourth group
— the radiolarian Pectacantha oikiskos, the jelly-fish Homoeonema platygonon,
the crustaceans Euchaeta norvegica, Heterorhabdus norvegicus, Thysanoessa
longicaudata, Themisto abyssorum and others (Fig. 103).

A comprehensive study of the zooplankton of the Vilkitsky Strait led
M. Virketis (1944) to the conclusion that members of the zooplankton penetrate
this region both from the west and from the east. Small numbers of brackish-
water forms reach it from the Kara Sea along the shores, while the Atlantic
forms arrive from the Barents Sea through the open parts of the Strait
{Salpingella acuminata and Oithona atlantica). The Arctic-basin forms
{Amphimelissa setosa, Euchaeta glacialis, Frittilaria polaris) and the Atlantic
forms {Sticholonche zanglea, Thysanoessa longicaudata, Euchaeta norvegica,
Aglantha digitalis and probably Themisto abyssorum enter from the east. In
the western part of the Strait the influence is more strongly felt of the brackish-
water forms chiefly carried in by surface currents from the west, and in the
eastern part of the Strait that of the Atlantic forms mainly brought in with
the deep waters from the northeast.

Quantitative distribution of plankton. In places where the influence of the Ob-
Yenisey waters is at its greatest, in the upper, fresher layers, plankton acquires
a completely fresh-water character (Cladocera, Rotatoria, Copepoda). In
the brackish waters there predominate the brackish forms Limnocalanus
grimaldii, Drepanopus bungei, Pseudocalanus major, Derjuginia tolli, Lenicellu
calanoides.

Quantitatively the richest forms of the Kara Sea plankton are the Cope-
poda, namely Calanus finmarchicus (four-fifths of the total biomass) and
Oithona similis and Pseudocalanus elongatus (one-fifth of the total biomass).
Appendicularia (Fritillaria and Oikopleura) and Chaetognatha {Sagitta ele-
gans) are also of great significance. At times they form the largest biomass.
Sometimes the polychaete larvae acquire a very important place in the plank-
ton biomass. In the most diluted southern parts of the Sea Copepoda biomass
is inferior to that of the Rotifera (mainly Synchaeta) and Cladocera.

The average quantitative significance of the separate groups of the Kara
Sea zooplankton is given in Table 102, due to V. Bogorov (1944, 1946).

Jashnov (1940) considers that the average plankton biomass of the western
half of the Sea is 4-5 tons/km2, and of the total Sea in summer it is 5 million tons.

Benthos

Bottom flora. The phytobenthos of the Kara Sea is represented by only 55
forms, which is less than a third of the specific composition of the Barents Sea
algae {Table 103).

Thus, in contrast to the Barents Sea, the bottom flora of the Kara Sea is
qualitatively much poorer than its bottom fauna. This results primarily from
the peculiar conditions of the Kara Sea.

THE KARA SEA
Table 102. Significance of Kara Sea zooplankton groups

239

Group

Eastern Ob- Yenisei South- Gulf of
part region western Yenisei

part

Phytoplankton biomass,

mg/m3

1,622

900

122

Zooplankton biomass, mg/m3

150

(34 according

to Jashnov)

The significance of individual groups

in relation to the total

zooplankton

biomass, per cent

Copepoda

760

53-5

740

40-0

Appendicularia

190

—

2-8

—

Chaetognatha

—

2-2

— ■

Polychaeta larvae

0-7

0-4

120

—

Rotatoria (Synchaeta)

3-3

410

0-5

47-4

Cladocera

—

11-1

Mollusca larvae

0-4

—

Others

0-5

5-1

0-5

1-5

Adapted mainly to the upper levels of the sea bottom — the littoral and sub-
littoral — the bottom algae do not find favourable conditions for existence in
the Kara Sea, especially during harsher climatic periods. The penetration of
the bottom algae into the Kara Sea from the north through the deep central
parts of the Arctic basin, as with zoobenthos, is impossible.

Some members of the Barents Sea flora are at times found off the eastern
shores of Novaya Zemlya, but these forms belong to the upper horizons of
the sublittoral and they are represented by dwarf specimens of the genus Fucus.
Farther east along the shores of the mainland and off the islands higher algae
are absent; they have been observed in small quantities in western Taimyr
only.

The problem of the origin of the Kara Sea bottom flora is easily solved ; this
cannot be said, however, of its fauna. The overwhelmingly predominant part of
the flora consists of Barents Sea forms, which penetrate into the Kara Sea from

Table 103

Number of species

Groups of

phytobenthos

Kara Sea Barents Sea

White Sea

Green

Brown

Red

Total

55*

172

134

* According to A. D. Zinova's (1950) data there are 59 species of brown and red algae
in the Kara Sea.

240 BIOLOGY OF THE SEAS OF THE U.S.S.R.

the west through the straits and round the northern island of Novaya Zemlya.
Of the 55 macrophytes inhabiting the Kara Sea, 49 species (89 per cent)
are common to the western shores of Novaya Zemlya, and 46 species (82 per
cent) to the Murman coast. However, the Kara Sea macroflora contains mostly
cold-water forms, while the warm-water ones decrease. The following Arctic
forms are characteristic of the Kara Sea : Laminaria agardhii, L. solidungula,
L. nigripes, Fucus evanescens, F. inflatus, Phyllaria dermatodea, Omphalophyl-
lum ulvaceum, Turner ell septentrionalis and Sarcophyllis arctica. Apart from
these the following are the most widely distributed forms in the Kara Sea:
Chaetomorpha melagonium, Pylaiella litoralis, Chaetopteris plumosa, Des-
marestia aculeata, Ptilota pectinata, Phyllophora brodiaei, Ph. interrupta,
Rhodimenia palmata, Delesseria sinuosa, Odonthalia dentata, Rhodomela
lycopodioides, Polysiphonia arctica and Eutora cristata.

Qualitative composition of bottom fauna. At the present time it is still impossible
to give a complete list of the Kara Sea bottom fauna since the identification
of individual groups is neither uniform nor complete.

Some groups of Kara Sea benthos are as varied as those of the Barents Sea.
According to G. Gorbunov's (1939) count 1 ,200 species of bottom-living animal
forms have now been identified in the Kara Sea {Table 104).

It has to be kept in mind when considering this list that 91 forms given in it
for the Kara Sea have so far been found only in the straits but not in the Sea
itself. On the other hand, some benthos groups have not yet been properly
studied. Taking this into account one may assume that the number of species
of the bottom animal forms actually living in the Kara Sea is no fewer than
1,500 (about 60 per cent of the Barents Sea fauna).

Within the limits of the Sea itself the highest specific variety of the bottom
fauna is found in two areas. First of all along the eastern shores of Novaya
Zemlya and partly in the Baydaratskaya Guba and off the coast of Yamal,
whither the Barents Sea waters carry its varied fauna. The fauna is brought
largely by waters skirting Novaya Zemlya to the north and through the Kara
Gates, and to a lesser extent through Matochkin Shar and Yugorsky Shar.
This fauna is adapted mainly to the shallows of the Sea outside the zone of
brown mud.

Secondly a varied fauna of the bathyal and abyssal layers of the north
Atlantic and the central parts of the Arctic basin penetrates the Kara Sea
from the north. This fauna is distributed mostly about the great depths of the
Sea since it is very tolerant of the conditions of life of the brown mud. How-
ever, some individual members of this fauna move to places outside the limits
of the brown mud, where the water is less deep.

G. Gorbunov (1946) notes that one of the Sadko stations recorded 200
species of different animal forms at 698 m near the northern end of the slope
tending towards the greater depths, between Franz Joseph Land and Sever-
nay a Zemlya.

As one moves from the northern parts of the Sea into the southern, and
from the shores of Novaya Zemlya into the central part of the Sea, the quali-
tative variety of the fauna decreases, while the quantitative predominance of

THE KARA SEA
Table 104*

241

Benthos groups

Number of

species in

Kara Sea

Barents Sea

White Sea

Laptev Sea

Foraminifera

135

190

(80?)

Porifera

61(37)

135

Coelenterata

86(62)

109

Nematoda

(41)

—

Polychaeta

148(151)

200

120

Gephyrea

8(8)

Bryozoa

172(151)

200

Brachiopoda

2(4)

Copepoda

(13)

—

Cirripedia

6(5)

Isopoda

49(46)

Cumacea

19(23)

Schizopoda

Tanaidacea

—

Amphipoda

225(221)

262

Decapoda

14(17)

Pantopoda

25(29)

Mollusca

138(157)

224

127

Echinodermata

47(55)

Tunicata

31(29)

Pisces

61(17)

174

Total

1,263(1,196)

—

* The numbers in parentheses are taken from the work of T. Pergament (1945).

some individual forms, so characteristic of the southern part of the Sea
(Stuxberg, the zoologist of the O. Nordenskjold expedition, drew attention to it
as early as 1 886), and of the central parts, with brown mud soils, becomes more
and more evident.

The basic fauna of the Kara Sea consists of the high Arctic endemic fauna
peculiar to the epicontinental seas of the Arctic basin. This high Arctic fauna
consists of two quite different generic groups : one, typically marine, inhabits
the more saline parts ; the other, living in brackish water, is adapted to river
mouths and estuaries, and to the inlets of the southern and southeastern parts
of the Sea.

One may add to this high Arctic marine fauna some pan-Arctic forms, i.e.
forms thriving in both the Arctic sub-regions — the low Arctic and the high
Arctic, and the Arctic-boreal forms, with an even wider distribution, which
are common to both the Arctic and the boreal regions. A few forms are dis-
tributed even more widely throughout the whole world ocean.

The following most common forms may be mentioned (G. Gorbunov,
1937) among this group of fauna typical of the Kara Sea: the molluscs
Portlandia lenticula, P. intermedia, P. fraterna, P. arctica, Leda pernula,
Astarte acuticosta, A. crenata, A. borealis, A. montagui, Pecten (Propeamussium)

242 BIOLOGY OF THE SEAS OF THE U.S.S.R.

groenlandicum, P. imbrifer, Lima hyperborea, Area glacialis, Axinus {Thyasira
flexuosus), Saxicava arctica, crustaceans Mesidothea sabini, M. sabini robusta,
M. sibirica, Calathura robusta, Munnopsis typica, Anonyx nugax, Acantho-
stepheia malmgreni, Hetairus polar is, Eualus gaimardi, Sabinea septemcarinata,
Hegocephalus infiatus, Haploops tubicola, Paroediceros lynceus, Arrhis phy-
lonyx, the worms Onuphis conchilega, Pista maculata, Pectinaria hyperborea,
Apomatus globifer, Nereis zonata, Nephthys malmgreni, Terebellides stromi,
and the pyenogenids Nymphon robustum, N. spinosum var. hirtipes, N. sluiteri
and N. stromi gracillipes, the echinoderms Ophioscoles glacialis, Ophiocantha
bidentata, Ophiocten sericeum, Ophiopleura borealis, Stegophiura nodosa,
Pontaster tenuispinus, Ctenodiscus crispatus, Myriotrochus rincki, Trocho-
stoma arctica and Trochoderma elegans, Gorgonocephalus arcticus, Helio-
metra glacialis and Poliometra prolixa.

Moreover in the off-shore, mainly southernly, more shallow part of the Sea
the following are preponderant : Portlandica arctica, P. fraterna, Macoma
calcarea, M. baltica and M. moesta, Astarte borealis and A. montagui, Mesi-
dothea sibirica, while in the depths Portlandia frigida, Astarte acuticosta and
A. crenata, Pecten groenlandicus, Ophiopleura borealis and Poliometra prolixa
are more significant.

The bays and inlets of the southern part of the Sea, which receive the inflow
of rivers from the mainland, give shelter to an abundant brackish- water fauna,
which here represents the basic part of the community. Marine and fresh-
water euryhaline forms are mingled with it. Thus, for example, according to
A. Probatov's data (1934) from the Kara Inlet (southwestern shore of Bay-
daratskaya Inlet) the proportions of the 25 species of fish present are as
given in Table 105.

Table 105

No. of
Group fish species Percentage

Typically fresh-water fishes 2 8

Of a brackish relict aspect (Salmoni-

dae, Coregonidae, Osmeridae, goby,

Gadidae, stickleback) 16 64

Marine euryhaline fishes 7 28

Among the invertebrates a whole community of the brackish-water relicts
is found here in large numbers, first of all the crustaceans Limnocalanus
grimaldi, Mysis oculata, M. relicta, Mesidothea entomon glacialis, Ponto-
poreia affinis, Pseudalibrotus birulai, Gammar acanthus loricatus lacustris,
Oediceros minor, Monoculodes minutus, Acanthostepheia incarinata and
Brandtia fasciatoides.

All these relict crustaceans provide abundant food for fish, which are also
relict. Whereas the Ob-Yenisey waters, spreading over the surface of the south
of the Kara Sea, at times carry members of fresh-water plankton far to the
north, and still farther north the brackish- water community (Fig. 100), so

THE KARA SEA 243

also the salty deep waters pulled by the undertow far up the estuarian zones
draw with them more euryhaline bottom dwellers such as, for example, the
polychaetes Ampharete vegae, Marenzelleria wireni, Laonice annenkovae,
the molluscs Portlandia arctica, P. aestuariorum, and Cyrtodaria kurriana
usually found only in fresh water, and with them the genuine marine forms :
Perigonimus yoldiae-arcticae, Nephthys malmgreni, Terebellides stromi, Mesi-
dothea sibirica, M. sabini robusta, Diastylis sulcata stuxbergi, Paroediceros
intermedins, Gammarus setosus, Lora novajya-zemlyensis, Rhizomolgula globu-
laris and others.

The last-mentioned marine bottom dwellers penetrate to the south of Cape
Drovyanoy in Obskaya Inlet, and in the Gulf of Yenisey as far as the Shiro-
kaya Bay.

There is a considerable quantitative preponderance of echinoderms in the
Kara Sea benthos, and, in fact, this Sea may quite rightly be called the sea of
echinoderms. In the deep western part of the sea no less than four-fifths of the
benthos biomass consists of echinoderms. However, the echinoderms here are
not as varied as in the Barents Sea. Gorbunov records only 47 species of
echinoderms for the Kara Sea itself. Apparently, the molluscs too are not so
strongly represented here as in the Barents Sea. Besides the echinoderms
species of the genera Portlandia, Mesidothea and Synidothea stand out
among the rest of the bottom fauna.

The zoobenthos of the Kara Sea as an indicator of its hydrological conditions.
Several mass benthos forms of the Barents Sea penetrate into the Kara Sea
either by skirting Novaya Zemlya or by entering through the southern pas-
sages, such as the Arctic-boreal, low Arctic, sub Arctic and to some extent
boreal ones. Here they become indicators of the warmer and more saline
Barents Sea waters (Fig. 1 04). This influence of the more warmth-loving Barents
Sea fauna is plainly felt in the region between the islands of Wiese and Uyedi-
neniye. Here in the region of Wiese Island, and to the east of it, approximately
up to 87° E longitude there are found Arctic-boreal species foreign to the
Kara Sea. All these forms are brought here by the terminal streams of the
Novaya Zemlya branch of the North Cape current which enters the northern
part of the Kara Sea from the west.

The heating of this part of the Kara Sea by the warm waters of the inter-
mediate layer, which enters it from the north, furthers the penetration of the
Barents Sea fauna into the central part of its northern half. The molluscs
Pecten islandicus, the crustaceans Epimeria loricata, Pleustes panoplus, Aristias
tumidus, Centromedon pumilus, Eurysteus melanops, Calathura brachiata,
Pandalus borealis, Spirontocaris turgida, S. spina, the echinoderms Ophiopholis
aculeata, Henricia sanguinolenta, Stephanasterias albula, Strongylocentrotus
droebachiensis, Psolus phantapus, and the brachiopod Rhynchonella psittacea
are most characteristic of this fauna. Some members of this fauna go down the
Novaya Zemlya trough as far as Blagopoluchiya Bay and Pakhtusov Island.

Gorbunov's survey has shown that Matochkin Shar is of little importance
for the immigration of the Barents Sea fauna to the east. The Kara Gates
play a much greater role in this movement, and the influence of the flow of the

244

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Barents Sea forms through that passage is felt even along the western shores
of Yamal. Such warm- water forms as Orchomenella nana, Tryphosa hoerringi,
Hyas araneus, Eupagurus pubescens, Mytilus edulis, Solaster endeca, Cucu-
maria frondosa, cod, haddock and others have been found on the Kara Sea

Fig. 104.£Main ways of penetration into the Kara Sea of benthos of
different biogeographical nature (according to different workers). 1
Forms of the intermediate warm layer and of the cold deep layers;
2 Northern boundary of forms brought down by the discharge from the
mainland ; 3 Sublittoral deep-water forms and those of the Barents Sea
(marked by circles).

side in immediate proximity to the Kara Gates. The latter have a purely
Barents Sea fauna.

Many typical members of the Kara Sea fauna such as Synidothea bicuspida,
S. nodulosa, Mesidothea sabini, M. sibirica, Lembos arcticus, Paramphithoe
polyacantha, Melita formosa and others penetrate through Yugor Shar from
east to west into the Pechora region of the Barents Sea. No immigration to the
west through the Kara Gates has been observed.

THE KARA SEA

245

A large number of original forms, characteristic of the warmer waters of the
northern Atlantic, immigrate from the great depths of the Arctic basin and
from the intermediate 'warm' layer of the Atlantic waters from the north
into the Kara Sea.

At the same time a strongly marked phenomenon 'of the displacement of
zones' occurs in the Kara Sea. The bathypelagic fauna of the Arctic basin
penetrating the Kara Sea from the north through the deep troughs, and the

Fig. 105. Alteration of habitat-level of members of the bottom fauna in
Kara Sea. / Barents Sea ; II Kara Sea ; /// Arctic basin and its slopes ;
I and 2 Main biocoenoses of the Barents Sea; 3 Echinoderm com-
munity; 4 Deep-water Atlantic fauna; 5 Abyssal fauna of the Arctic
basin (Filatova and Zenkevitch, 1957).

Barents Sea fauna immigrating to the Kara Sea, rise to some levels unusual
for them (Fig. 105). This is often observed when passing from the oceans to the
seas fringing them, and from the seas into their bays. Portlandia arctica,
which lives at depths of 1 50 to 200 m in the Pechora trough of the Barents
Sea and in the White Sea, is frequently found at depths of 17 to 35 m in the
Kara Sea. Shell gravel horizon (Illrd group in the Barents Sea communities),
which occupies depths of 100 to 200 m and even 250 m of the Barents Sea,
rises to 20 to 100 m in the Kara Sea. The echinoderm community including
Ophiopleura and Trochostoma lives in the Barents Sea at a depth of 300 to
400 m and in the Kara Sea at 50 to 100 m.
It is interesting that certain bathyal and abyssal forms reach the Kara Sea

246 BIOLOGY OF THE SEAS OF THE U.S.S.R.

after bypassing the Barents Sea altogether, and possibly do not meet in the
Kara Sea. Owing to the bottom topography the bathypelagic forms of the
Arctic basin can penetrate more easily into the Kara and Laptev Seas than
into the Barents Sea, except, perhaps, at its most northeasterly corner.

Among these forms penetrating from the north the following may be noted :
Virgularia glacialis and the huge Umbellula ancrinus, reaching 2-5 m in
length; the polychaetes Melinnexis arctica, Jasmineira schaudini and Hyalo-
pomatus claparedi ; the molluscs Area frdei, Periploma abyssorum, Mohnia
mohni; the crustaceans Haplomesus quadrispinosus, Amathillopsis spinigera,
Cleippides quadricuspis, Halirages quadridentatus, Rhachotropis lomonossovi,
Pardalisca abyssi, Nmmoniscoides ungulatus, Gnathia stygia, Gn. robusta,
Eurycope hanseni, Leucon spinulosis, Compylopsis intermedia ; and finally the
echinoderms Tylaster willei, Bathybiaster vexillifer, Ophiopus arcticus, Pourta-
lesia jeffreysi, Bathycrinus carpenteri, Poliometra prolixa, Elipidia glacialis
and others.

All the three groups range over the Kara Sea, chiefly in its deeper parts,
where they mix with the basic Arctic fauna.

This process occurs intensively along the western trench (St Anna's Trench),
which communicates with the Novaya Zemlya Trench at the south. Some of
the above-mentioned forms reach the latitude of the Kara Gates through this
trench, such as, for example, Ephesia peripatus, Laphania boecki, Amathillopsis
spirigera, Bythocaris payeri, while others go only as far as the latitude of
Matochkin Shar, as, for example, Jasmineira schaudini, Pardalisca abyssi,
Halirages quadridentatus, Poliometra prolixa and others. Moreover, Elpidia
glacialis even penetrates into the eastern part of Matochkin Shar. Some of
these organisms penetrate southward only up to the latitude of Cape Zhe-
laniye and sometimes enter the deep hollow off this Cape, as, for example,
Ophiopus arcticus. A large part of this fauna, as, for example, Melinnexis
arctica, Eurycope hanseni, Gnathia stygia, Rdiachotropis lomonossovi, Bathy-
biaster vexillifer, Pourtalesia jeffreysi and others, when moving south do not
go farther than the deep trench between Novaya Zemlya and Wiese Island.

Gorbunov records a more intensive penetration into the Kara Sea through
the western trench than through the eastern. As has been mentioned above,
the Kara Sea fauna acquires an original aspect owing to the rising of boreal
and abyssal forms — which penetrate the Kara Sea from the north — to shallow
depths which are unusual for them. Such deep-water dwellers as Eurycope
hanseni, Pardalisca abyssi, Paralibrotus setosus, Erichtonius brasiliensis,
Poliometra prolixa, Tylaster willei and others are found here at comparatively
shallow depths.

As we have pointed out, this phenomenon is observed not only with the
alien fauna, but also with typical Kara Sea forms which live here at lesser
depths than in the Barents Sea; as for example, Hymenaster pellucidus,
Ophiopleura borealis and others (Fig. 106).

The second route for the penetration of fauna from the central part of the
Arctic basin into the Kara Sea (the boreal and abyssal forms both of the
Arctic basin itself and of the north Atlantic, and the moderate bathymetric
Atlantic forms living at moderate depths), passes, as has been shown by

THE KARA SEA

247

Gorbunov, through the northern deep part of the Laptev Sea and through
the deep Schokalsky and Vilkitsky Straits. Such characteristics forms as
Melirmexis arctica, Eurycope hanseni, Gnathia stygia, Halirages quadridentatus,
Rhaehotropis lomonossovi, Poliometra prolixa Elipidia glacialis and others

Fig. 106. Examples of the distribution in the Kara Sea of forms of
different origin — lower Arctic {Ophiopleura borealis) from the west,
bathyal and abyssal from the north and forms brought by the mainland

discharge.

have likewise been found in these Straits (Fig. 106). It is not yet known
how far this propagation spreads into the Kara Sea.

Shallow-water sub-Arctic, Arctic-boreal and even boreal forms, unknown
in the other part of the Kara Sea and foreign to its endemic fauna, such as
Stylaroides hirsuta, Tryphosa hoerringi, Haliragoides inermis, Henricia san-
guinolenta, Ophiopholis aculeata, Strongylocentrotus droebachiensis, Psoitis
phantapus and others, penetrate through these Straits into the Kara Sea, by a
route which so far is unknown.

248 BIOLOGY OF THE SEAS OF THE U.S.S.R.

The medium and shallow depths of the Kara Sea are populated mainly by
a typical, sublittoral, Arctic circumpolar and east-Arctic fauna. In his analy-
sis of the propagation of the molluscs Portlandia arctica and Pecten groen-
landicus in the Siberian seas, G. Gorbunov (1941) suggests that the absence
of the first of these molluscs in the Vilkitsky and Schokalsky Straits is an
indication that these deep passages are filled at the lower levels with typical
sea waters, mainly from the Laptev Sea side. A mass development of the
second mollusc in Vilkitsky Strait, and its absence from the Schokalsky
Strait, bear witness to a considerable penetration (from the east) into the
Schokalsky Strait of the intermediate layer of warmer Atlantic waters, and
of the absence of them in Vilkitsky Strait.

The zone of brown muds is populated by a most original community of
bathypelagic animal forms. As has been mentioned above, the physico-
chemical conditions (constant low temperature and salinity, weak supply of
nutrient substances, an inadequate vertical circulation, and the unfavourable
mechanical and chemical properties of the soils) lead first of all to a marked
qualitative impoverishment of the fauna. Whereas the bathypelagic life off the
shores of Novaya Zemlya and Baydaratskaya Guba is varied, farther into the
depths, where the brown muds begin, the fauna becomes much more uniform
and the number of species decreases sharply. A comparatively small selection
of forms remains unaltered throughout the whole extent of the brown muds.
The diversity of the molluscs, polychaetes and crustaceans decreases especi-
ally markedly and the preponderance of the echinoderms comes out more
sharply.

There is a considerable preponderance of large echinoderms — Urasterias
lincki, Icasterias panopla, Pontaster tenuispinus, Heliometra glacialis, Gorgo-
nocephalus arcticus, Trochostoma sp., Ophiopleura borealis, and Ophiocten
sericeum in the deeper central part of the Sea.

The polychaetes are distributed more evenly, but they too show an increase
in the central part of the Sea in respect of the large Onuphis conchylega, Pecti-
naria hyperborea, Nephthys longisetosa, N. malmgreni, Ampharete arctica,
Owenia fusiformis and others. In shallower places Thelepus cincinnatus, Pista
maculata and Maldane sarsi are also found in large numbers. A reverse picture
to that of echinoderms is obtained for the quantitative distribution of bi-
valves— the large forms live in the shallows on grey sandy mud: Astarte
borealis placenta, Serripes groenlandicum, Astarte montagui, Macoma cal-
carea, M. moesta and Portlandia arctica. In the northern part of the Sea, the
biomass increases to 100 to 200 and even to 300 g/m2 in respect of Astarte
crenata crebricostata, in the southern part — of Cardium ciliatum. In the
area of the Novaya Zemlya Trench the bivalves form a biomass of about
1 g/m2, mainly in respect of Axinus orbiculatus, Thyasira ferruginosa, Dacri-
dium vitreum, Yoldiella frigida, Y.fraterna, Y. lenticula which are all of small
size. Foraminifera are highly developed in the Kara Sea (Z. Shchedrina,
1938) and adapted mainly to the bathymetric part of the sea; hence the num-
bers of Foraminifera increase with the increase of the brown mud areas and
decrease of benthos biomass. Sand Foraminifera are greatly predominant in
the deeper parts occupied by brown mud, while the lime Foraminifera are

THE KARA SEA 249

so in the southeastern shallow parts ; this stands in agreement with the sug-
gestion of the increased amounts of carbon dioxide in the regions of brown
mud. Z. Shchedrina (1938) and T. Gorshkova (1957) recorded Ammo-
baculites cassis, Verneulina polystropha, Spiroplectammina biformis, Elphi-
dium gorbunovi, Reophax curtus and others in the shallow areas. Shchedrina
relates Trochommina turbinate, Nonion labradoricum, N. orbicular e, N. stelliger,
Hormosina globulifera, H. ovicula, Saccoriza ramosa, Trochammina globuli-
formis, Elphidium incertum and others to the group of the brown mud forms.

On the brown muds the main forms are the Foraminifera Saccorhiza ra-
mosa and Harmosina globulifera, the sponge Polymastia uberrima, the coe-
lenterate Actinium metridium, members of the Eunephthya genera and the very
large coral Umbellula encrinus, the polychaetes Nephthys ciliata, Nicomache
lumbricalis, and Thelepus cincinnatus, the Sipunculidae Phascolosoma minuta,
the crustaceans Mesidothea sabini, M. sibirica, Sabinea septemcarinata and
Sclerocrangon ferox, the pantopoda Colossendeis proboscidea, the gastropod
mollusc Neptunea curta, the bivalves Pecten groenlandicus and Astarte
crebricostata and especially various echinoderms, also the asteroids Pon-
taster tenuispinus, brittle stars Ophiopleura borealis, Ophioscolex glacialis,
Ophiocantha bidentata, Asterias panopfa, A. lincki, Hymenaster pellucidus,
the holothurians Molpadia and Trochostoma, and the lilies Poliometra
prolixa.

A comparatively large number of forms which rise above the bottom, such
as Metridium, Umbellula, Eunephtya, Colossendeis, Poliometra are char-
acteristic of the whole of this fauna. The very large size of most of the above-
mentioned forms is remarkable ; on the other hand the predominance of the
'parachute' type of forms — Polymastia, Mesidothea, Pecten, Pontaster,
Hymenaster, Gorgonocephalus and others — is also interesting. These three
factors are evidently the ways of adaptation to soft-floor conditions.

It is difficult to understand how the echinoderms with their solid calcareous
skeletons can reach such a high level of well-being on the brown mud, since
the carbonates are not retained in the floor itself, and we have never found
any accumulation of shell gravel in the areas of the occurrence of brown mud ;
on the contrary a rapid process has been observed of the solution of the
shells of dead molluscs and an evident shortage of calcium carbonate in the
living ones.

The fish population of the brown mud, which is very small, is also remark-
able. It consists usually of small-sized members of the Cyclopteridae, Zoar-
cidae and Cottidae families (the most common ones are Liparis coefoedi,
Icelus bicornis and Triglops pingelii). However, even these small-sized fish
are extremely rarely found. None of the rich selection of commercial fish of
the Barents Sea are found on the brown mud. They are kept away also by the
low temperature of the bathymetric layer all the year round (below zero).
Only the long rough dab (Hippoglossoides platessoides) lives here in small
numbers, as immature specimens or mature dwarfs.

The biocoenotic groups of the Kara Sea benthos were thoroughly studied
by Z. Filatova and L. A. Zenkevtich (1957). These workers have distin-
guished seven basic biocoenoses (Fig. 107) which have been combined into

250

BIOLOGY OF THE SEAS OF THE U.S.S.R.

four groups: (1) high Arctic, bathypelagic with a preponderance of echino-
derms, Foraminifera, small-sized molluscs and polychaetes ; (2) high Arctic
shallow-water forms, also with a preponderance of echinoderms, mostly
small brittle stars ; (3) high Arctic forms from the littoral shallows with a pre-
ponderance of molluscs ; and (4) low Arctic Barents Sea forms.

g^5

Ш2 ГТТТТ14

Fig. 107. A chart of the distribution of the bottom biocoenoses of
the Kara Sea (Filatova and Zenkevitch, 1957). 1 Portlandia aestua-
riarum ; 2 Portlandia arctica ; 3 Astarte borealis placenta ; 4 Ophiocten
sericeum; 5 Ophiopleura borealis; 6 Ophiopleura-Elpidia; 7 Spio-
chaetopterus typicus.

Quantitative distribution of benthos. In spite of its great qualitative variety the
bathypelagic fauna of the Kara Sea is much inferior in numbers to the benthos
of the southern half of the Barents Sea (Fig. 109) ; however, in some regions
of the Kara Sea it is higher than the benthos biomass of its northern part.
The average benthos biomass of the western part of the Sea is 50 g/m2.

As can be seen from the chart, the benthos biomass of the central part of
the Sea, in the area of brown muds, is less than 5 g/m2, and at times is no more

252

BIOLOGY OF THE SEAS OF THE U.S.S.R,

than 1 to 3 g/m2. The biomass increases at lesser depths, and on the shallows
off the Yamal shores to 100 or 200 and at times even to 300 g/m2.

The quantitative characteristics of the main biocoenoses is given in Fig.
108.

Thus it is evident that the Kara Sea is really bioanisotropic. The almost

Fig. 109. Distribution of benthos biomass in Kara Sea (g/m3) (Filatova
and Zenkevitch).

complete absence of fish within the area of brown muds (which might
justifiably be called the Ashless sea) is explained by the general lower productive
properties of this body of water and by the brown mud possessing conditions
unfavourable to fish-life.

The benthos biomass of the Kara Sea brown mud is twenty times lower than
the average Barents Sea biomass ; the productivity difference, however, is still
more marked, since the processes of biological plankton production are almost
suspended for 8 to 9 months and as a consequence all the links of the food
chain are slackened. The lowering of productive properties of the Kara Sea

THE KARA SEA

253

becomes even more evident when benthos is estimated from the point of
view of its nutrient significance.

A very great predominance of echinoderms and above-mentioned excessive
size bring the amounts of edible benthos within the zone of brown muds to
practically nothing.

Quite another picture is observed in the shallow coastal zone of the Kara
Sea (on the average less than 50 m deep). Benthos is fairly abundant here and
there is quite a large number of fish.

Fish

Kara Sea fish (according
fisted in Table 106.

to A. P. Andriashev
Table 106

, 1954) include the 53

species

Petromyzonidae

Squalidae

Rajidae

Clupeidae

Salmonidae

Osmeridae

Anguillidae

Belonidae

2
1
2
5
2
1
1

Scombresocidae

Gadidae

Gasterosteidae

Lampridae

Anarhichaedidae

Lumpenidae

Pholidae

Zoarcidae

1
6
2
1
1
3
1
4

Ammodytidae

Scombridae

Scorpaenidae

Cottidae

Agonidae

Cyclopteridae

Liparidae

Pleuronectidae

Total

1
1

1
6
3

1
2
4

In respect of brackish-water forms, suitable conditions for developing local
fisheries exist in the southern part of the Sea, off the mainland and along the
coast of Novaya Zemlya. Raw material for this would come chiefly from Arctic
Sea whitefish (coregonoids), frostfish (Osmeridae), navaga and arctic cod
(Gadidae) and among the other families Polar dab and goby. Many other
fish are caught there of the coregonoids and certain salmon (beardie, Stenodus
leucicthus nelma, grayling and others) and herring. Cod is fairly frequently
caught off the Novaya Zemlya coast, especially within the regions of the Kara
Gates and Matochkin Shar.

The exceptional poverty of the fish population of the open parts of the Kara
Sea is obvious from the following fact. In 1945 a trawler expedition worked in
the Kara Sea. A commercial otter-trawl was in operation for 43 hours in
different parts of the Sea. The total amount offish caught was about 500 small-
sized specimens, of a total weight of a few dozen kilogrammes.

Zoogeographical composition of the fauna. The nine following benthos groups
may be distinguished in the Kara Sea fauna, according to the nature of their
geographical range : (7) Arctic (mostly high Arctic) circumpolar forms ; (2)
Forms of the eastern sector of the Arctic. To these two groups, forming the
nucleus of our Siberian Sea fauna, belong no less than 50 per cent of all the
Kara Sea benthos. In the group of the Arctic forms of the Arctic eastern sector,

254 BIOLOGY OF THE SEAS OF THE U.S.S.R.

the brackish-water community, living in large numbers in the diluted waters
of the off-shore zones and the river mouths, is of importance. These are the
relicts of former eras of more considerable water-dilution and of even more
severe climate ; (3) Arctic-boreal species ; (4) Sub-Arctic Barents Sea forms ;
(5) The bathypelagic fauna of the central parts of the Arctic basin, which
penetrates through the deep troughs on to the continental shelf of the mar-
ginal seas of the eastern part of the Arctic ; (6) Warm- water north Atlantic
forms, which penetrate into the Kara Sea either directly from the north from
the warm intermediate layer of the central part of the Arctic basin, or from
the west from the Barents Sea ; (7) Fresh-water forms ; (8) Endemic forms of
the Kara Sea ; (9) Cosmopolitan forms.

Except for the fourth group this division can be applied to the fauna of
other seas situated to the east of the Kara Sea. Gorbunov gives the following
zoogeographical characteristics for the 97 mass species of the Kara Sea in
percentages :

High Arctic 15 ) _ Arctic-boreal 46

Pan-Arctic 37 J Cosmopolitan 2

It should be noted that, among the mass benthos forms, the sub-Arctic
and warm-water Atlantic species are not represented.

5
The Laptev Sea

I. HISTORY OF EXPLORATION

Nordenskjold's expedition on the Vega (1878-79) marked the beginning of
the exploration of the fauna and flora of the Laptev Sea, which was continued
by the Russian expeditions of Toll on the Zarya (1900-03) and Vilkitsky on
the Taimyr and Vaigach (1913). In the Soviet era the Norwegian expeditions
on the ship Mod (1918-20 and 1921-24), and the Soviet expeditions of
Khmisnikov (1926) and of Yu. Tchirikhin (1927) on the icebreakers Lithke
(1934) and Sadko (1937), have worked in the Laptev Sea.

II. PHYSICAL GEOGRAPHY

Situation, bottom topography and size

The Laptev Sea lies to the east of the Taymyr Peninsula and Severnaya Zemlya,
extending to the Novosibirsk Islands. The Laptev and East Siberian Seas have
the most severe climate and the lowest salinity of all the seas off the northern
coast of Asia.

As in the Kara Sea, a deep gully enters the western part of the Sea from the
north ; saline and somewhat warmer waters flow into the Laptev Sea through
it. To the east of the northern end of Taymyr the great depths of the Arctic
basin approach nearest to the Asian coast, lying only 100 to 200 km off the
Severnaya Zemlya and Taymyr shores. The area of the Sea is 650,000 km2 ;
its volume is 338,000 km3, its average depth is 519 m and its greatest depth is
2,980 m.

Temperature and salinity

The eastern part of the Sea with depths no greater than 60 to 80 m is consider-
ably diluted, and in summer warmed by the abundant waters of the great
Siberian rivers : Khatanga, Lena, and Yana. At a distance of 100 km and more
to the northeast of the Lena estuary the salinity is 5 to 6%0 down to a depth of
20 to 25 m (Fig. 1 10). The fresh Lena waters, carried out far to the north, dilute
the surface layers of the Sea. In 1893 the Fram recorded a salinity of 14-9%0
in latitude 75° 32' and a salinity of 18%0 at 76° 21', northwest of the Novo-
sibirsk Islands, 500 km from the Lena estuary. The highest salinity is observed
in the northwestern part of the Sea, whence more saline waters enter from the
north ; a salinity of more than 28%0 was observed there even on the surface.

In the northwestern part the surface temperature, even in the summer, may
be about zero. Ranges of temperature and salinity taken north of the Khatanga
river near the Taymyr Peninsula (76° 04' N latitude) during the Vega voyage,
in August, are given in Table 107.

In the southeastern part of the Sea the highest surface salinity is 17-0%o
and the deep-water salinity is 30-5%o. The salinity is commonly much lower,

255

256

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Fig. 110. Temperature (A) and salinity (B) ranges in

the cross section of Laptev Sea from its southeastern

part (on right of graph) to northwest (Wiese).

decreasing more and more as one approaches the rivers. In the southeastern
part the temperature rises in the summer and on the surface it may reach
5° to 8°. The ranges of temperature and salinity observed by Yu. Tchirikhin

Table 107

Depth,
m

Voo

0
10
20
30
40
50
59

-0-5
-10

-1-1
-1-2
-1-3
-1-4
-1-4

27-4
28-2
29-8
31-9
33-5
33-6
34-4

THE LAPTEV SEA 257

northward from the Lena estuary in 71° 43' N latitude are given in
Table 108.

Table 108

Depth,
m

*5%o

8-12
-0-43
-0-75

Insignificant
1904

23-33

Evidently the fauna of the upper and lower layers of water would differ
greatly. The diluted surface layers of the western part of the Sea spread north-
wards for hundreds of miles from the river estuaries and the salinity at that
distance is at times 15— 18— 25%0. On the other hand the saline waters travel
southwards along the bottom troughs.

After a long, harsh winter, when the waters are almost at freezing tempera-
ture, there comes a short summer, and the surface waters of the parts of the
Sea freed from ice are warmed partly by the river waters, partly by the sun, to
a few degrees (up to 4°) above zero. But the polar ice limit is not far away
even in the summer.

III. FLORA AND FAUNA
According to the investigations of K. Derjugin (1932), M. Virketis (1932),
I. Kisselev (1932) and A. Popov (1932) the Laptev Sea plankton and benthos
have the composition given below.

Table 109

Flagellata 6 Conjugatae 4

Peridineae 28 Diatomaceae 61

Chlorophyceae 25 Cyanophyceae 24

Total 148

Qualitative composition of phytoplankton

According to Usachev, the species and forms which have been found in the
southern part of the Sea, which is exposed to the strong influence of the Lena
waters, are those listed in Table 109.

In this fairly large selection of forms Kisselev distinguishes first of all the
groups of brackish-fresh- water forms (23 per cent), most common within the
off-shore, highly diluted region : Aphanizomenon flos-aquae, the species Ana-
baena, Melosira italica, M. islandica, M. granulata, Asterionella gracillima
and some others.

The author includes a number of species Diploneis and Navicula in the
group of the brackish-water forms (4 per cent). And finally to the group of
marine forms (5 per cent) there belong : Thalassiosira baltica, Coscinodiscus,

258 BIOLOGY OF THE SEAS OF THE U.S.S.R.

marginatus, Chaetoceros gracile and Ch. Wighami, Caloneis brevis, Navicula
sp., Dinophysus arctica, Peridinium breve, P. pellucidum and others.

Qualitative composition of zooplankton

Virketis gives the composition (species and forms) for the zooplankton of the

same part of the Sea in the form shown in Table 110.

Table 110

Tintinnoidea 5 Rotatoria 27

Scyphomedusae 1 Cladocera 5

Ctenophora 1 Copepoda 10

Total 49

Seasonal phenomena in plankton development

Bogorov who collected plankton in the western part of the Laptev Sea in
1934 during the period of plankton 'spring' found in the surface layer (0 to
10 m) some algae in bloom (average 3,400 mg/m3) ; the zooplankton, however,
had not yet reached its maximum (the average biomass was 1 10 mg/m3). On
the other hand in the eastern part of the Sea the plankton development had
already reached its summer phase — phytoplankton decreased (average 500
mg/m3) while the amount of zooplankton had risen to 313 mg/m3. At places
of maximum bloom the phytoplankton biomass had in the western part of the
Sea reached 14,132 mg/m3.

Quantitative distribution of zooplankton

In his quantitative analysis of the plankton of the Laptev and East Siberian
Seas, V. Jashnov (1940) compares the data for: (7) the middle part of the
Laptev Sea (depth 50 to 80 m) ; (2) a number of stations to the north and
northeast of Novosibirsk Islands, and (3) the cross section from Kotelni
Island to the Gulf of Tiksi (Table 111).

In some cases Appendicularia, mollusc and polychaete larvae and the ptero-
poda molluscs are of importance in the plankton.

It is evident from Table 111 that Copepoda form not less than a third of the
total plankton, frequently reaching 98 to 99 per cent of the whole biomass in
the surface layer. Here the plankton still retains its Kara Sea character, chang-
ing its composition sharply as one moves eastward: Calanus finmarchicus
practically disappears and is replaced first by Pseudocalanus elongatus and
then by the inhabitants of brackish waters — Pseudocalanus major, Limno-
calanus grimaldi, and Drepanopus bungei.

'Thus', says Jashnov, 'three concentric zones running along the Siberian
coast may be distinguished. The first zone, situated in close proximity to the
shore, is inhabited by a typical brackish- water fauna ; the second, farther away
from the shore, is characterized by the presence of marine, mainly euryhaline,
species which penetrate here through the lower water layers ; the third zone is
a transitional one between the second and the true marine one. The width

THE LAPTEV SEA
Table 111

259

Section from Kotelni

Stations to north

Island to the Gulf of

Central part of
Laptev Sea

and northeast of
Novosibirsk Islands

Tiksi (eastern part
of the Laptev Sea)

per cent

Calanus finmarchicus
Pseudocalanus

52-3'

3-5"

1-7"

elongatus
Limnocalanus

grimaldi
Drepanopus bungei
Pseudocalanus major

111

2-6

■71-3

43-1
0-2

7-2

•58-2

27-7

23-3

210

7-3

■82-6

Other Copepoda
Mollusca (Pteropoda)
Chaetognatha
Coelenterata

5-3 j
12-3
13-7

0-7

4-2 j
3-1
21-8

7-2

1-6 j

100

6-6

Others

8-3

0-8

and distance from the shore of these zones depend primarily on the quantity
of fresh water brought in by the rivers.' Jashnov (1940) points out the very
interesting fact that the brackish-water community is the only endemic and
autochthonous community of plankton in the Arctic basin. The western limit
of its distribution is the Kara Sea. 'All the other plankton forms belong either
to the number of widely distributed species or to forms whose existence is
conditioned by the penetration of the Atlantic and Pacific waters into the
Arctic zone.' Jashnov adds Halitholus cirratus and Calycopsis birulai to the
few crustaceans of this community.

The mean biomass of the summer zooplankton of the Laptev and East
Siberian Seas, according to Jashnov (1940), is 72 mg/m3, with fluctuations
from 24 to 200 mg/m3 (about 3 tons beneath each 1 km2). The total biomass of
summer zooplankton in the Laptev Sea is about 3 million tons, and in the
East Siberian Sea about 2 million tons.

Qualitative composition of zoobenthos

So far 405 benthos forms are known for the Laptev Sea {Table 112).

Table 112

Foraminifera

Echinodermata

Pantopoda

Porifera

Cirripedia

Lamellibranchiata

Hydrozoa
Anthozoa
Polychaeta
Bryozoa

Isopoda
Amphipoda
Schizopoda
Decapoda

87
2
5

Gastropoda
Cephalopoda
Tunicata
Pisces

Total

405

260 BIOLOGY OF THE SEAS OF THE U.S.S.R.

In the diluted southeastern part of the Laptev Sea only 73 species of even this
meagre fauna have been encountered (Coelenterata 5, Porifera 4, Polychaeta
8, Bryozoa 7, Mollusca 19, Crustacea 17, Pantopoda 2, Echinodermata 2,
Tunicata 7, and Pisces 5).

The high Arctic forms are overwhelmingly predominant in this fauna.

Near the river estuaries either brackish-water or the most euryhaline marine
forms are predominant: the crustaceans Gammar acanthus loricatus, Gam-
marus wilkitzkii, Mesidothea entomon, Mysis oculata var. relicta, the poly-
chaetes Polydora quadrilobata and Euchone papillosa, the molluscs Portlandia
arctica, the fish Myoxocephalus quadricomis. Farther out to sea Mesidothea
sabini, M. sibirica, Acanthostepheia malmgreni and others become gradually
predominant.

Popov notes a remarkable similarity between the fauna of the south-
eastern part of the Laptev Sea and that of the Ob- Yenisei Bay of the Kara Sea :
in both cases the main part of the benthos consists of Mesidothea sibirica,
M. sabini var. robusta, Onisimus botkini, Portlandia arctica siliqua, Gammarus
wilkitzkii, and Pseudalibrotis birulai.

Qualitative composition of fish fauna

The composition offish according to their families also deserves our attention

{Table 113).

Table 113

No. of No. of

species Percentage species

Salmonidae 7 184 Agonidae 2

Cottidae 9 23 Osmeridae 2

Zoarcidae 7 18 > 77 Cyclopteridae 1

Liparidae 5 13 Pleuronectidae 1

Gadidae 2 5/ Clupeidae 1

Acipenseridae 1 Gasterosteidae 1

Total 39

The high Arctic and brackish-water forms are even more prevalent here
than in the Kara Sea.

The fauna of the deep-water northwestern part of the Laptev Sea and that
of the passages between the Severnaya Zemlya Islands must be even greater
in variety. As in the Kara Sea large numbers of Arctic deep-water and inter-
mediate warm-layer fauna of the deep trench rise to lesser depths. Some
Barents Sea forms in small numbers reach the western part of the Laptev Sea.

The Chukotsk Sea

I. SITUATION AND HISTORY OF EXPLORATION

The Chukotsk Sea lies to the east of Wrangel Island as far as Cape Barrow and
is connected with the Pacific Ocean by the shallow, narrow Bering Strait. For
this reason its fauna is of special interest.

The study of the fauna of the Chukotsk Sea began with the collections made
by A. Stuxberg, of the O. Nordenskjold expedition on the Vega (1878-79).
The Soviet period — especially the expedition of the icebreaker F. Lithke
(1929, 1934), the Pacific Ocean expedition of the State Hydrological Institute
(1932-33), the expeditions of the Chelyuskin (1933, 1934) and finally in 1935
that of the icebreaker Krassin* — has been most fruitful as regards the ex-
ploration of the Chukotsk Sea.

II. PHYSICAL GEOGRAPHY

Size and bottom topography

The Chukotsk Sea (Fig. Ill) is fairly large (582,000 km2), but very shallow,
being for the most part less than 50 m deep. Its volume is 51,000 km3, its
average depth 86 m, and its greatest depth 180 m.

A trench with depths of more than 50 m (the average depth of the Sea
being about 45 m) enters the Chukotsk Sea to the east of Wrangel Island. This
trench at first runs towards the Chukotsk Peninsula and then eastwards along
it. North of 73° 30' N latitude the bottom begins to slope down steeply into
the greater depths of the Arctic basin. The floor of the Bering Strait and of the
Herald Shoal is hard (sand, gravel, pebble, rock) ; the rest of the bottom con-
sists of silty sands and clayey mud.

Currents

A fairly warm, strong current (Fig. Ill) enters the Chukotsk Sea through the
Bering Strait, travelling north along the eastern boundaries of the Sea ; north
of Cape Hope it divides into two branches — a northeastern and a north-
western. A cold current leaving De Long Sound moves southeast along the
coast of the Chukotsk Peninsula, part of it entering the Bering Strait, but its
main mass turning back into the southern part of the Sea. In general the move-
ment through the Bering Strait is that of the Pacific Ocean waters into the
Chukotsk Sea, and only to a very small extent a flow of the Chukotsk waters
to the south.

Temperature and salinity

It is evident from the range of the bottom temperatures in August (Fig. 112)

that the Chukotsk Sea waters are only very slightly warmed. The sea conditions

* In our further exposition we shall use the detailed summary of P. Ushakov (1945).

261

262

BIOLOGY OF THE SEAS OF THE U.S.S.R.

are very severe. For seven months (November to May) the temperature of
even the surface waters remains below —1-5° (—1-6° to —1-8°); in June,
September and October it keeps at about 0°, and only in July and August,
off the coast, does it rise to 3°, 5° or 7° (monthly average). Only in the south-
western part of the Sea, in the region of the Bering Strait, does the temperature
at times rise to 12° to 14° in the summer. The deeper layers of water (except

Fig. 111. The Chukotsk Sea showing depths, direction of the warm (2) and cold
(3) currents and the summer boundary of the ice (/) (Ushakov).

for the eastern part of the Sea) have a temperature of almost 0° even in the
summer (Fig. 1 12). In the northern parts of the Sea, near the open, deep parts
of the Arctic basin, a curious temperature range is observed in the summer :
' the influence of the warm waters of the Bering Strait is still felt in the surface
layer down to 20 m. The temperature reaches 2° to 3° ; lower down, at a depth
of 100 m, there are Arctic waters with a temperature of up to —1-7°; still
lower a heating effect is observed and at a depth of 150 m the temperature is
0° ' (Ratmanov, 1939). This is as far as the influence of the intermediate warm
layer extends to the east.
The salinity range of the Chukotsk Sea shows a good many variations.

THE CHUKOTSK SEA

263

Waters flowing into it from the East Siberian Sea through De Long Sound
have, in their deeper part, a salinity of 31-7 to 32-6%0. To the north their
salinity increases, reaching 34-8%0. The salinity of the surface layers varies
greatly. In summer time in the parts adjacent to the Chukotsk Peninsula the

Fig. 112. Quantitative benthos distribution in the Chu-
kotsk Sea, g/m3 (Ushakov, 1952). Summer bottom iso-
therms are also marked.

surface layers have a salinity of only 3-5-8%0 and sometimes even less. In the
rest of the Sea it usually remains at 29 to 32-5%0 in the surface layers, but often
it decreases in the regions of the melting ice by a few parts per thousand. In
winter time the surface layers must acquire a considerably higher salinity
owing to freezing of the water. The ice content of the Chukotsk Sea changes
from year to year, and the mean ice limit in August and September, i.e. the
warmest season of the year, can be indicated only approximately (Fig. 110).

Oxygen content

It is of great interest that the oxygen content in the warmed deep layer of
'Atlantic' waters, entering the Chukotsk Sea from the north, is greatly re-
duced, in some cases down to 20-47 per cent of saturation. The 1935 data of
one of the Krassin stations for the northern part of the Chukotsk Sea are given
in Table 114.

Deep 'Atlantic' water lost 5 or 6 cm3 of its oxygen per litre, receiving no
fresh supply, since the time [in N. Zubov's opinion (1944) no less than four
or five years] of its sinking beneath the upper diluted layer of water in the
region of Spitsbergen. Such a small oxygen consumption (approximately

264 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 114
Depth, m 0 10 25 50 100 154

t°

-0-60

-1-25

-1-46

-1-70

-1-66

-004

"/00

613

27-18

30-97

32-56

32-95

34-47

02cm3

9-35

7-44

815

5-93

4-66

2-43

02 per cent

92-75

84-25

94-43

69-19

54-56

30-07

1 m3 per litre per year) points to a very poor development of life in the inter-
mediate warm layer of water in the Arctic basin.

III. FLORA AND FAUNA
Plankton

Phytoplankton. P. Shirshov gives data on the distribution of phytoplankton
in the Chukotsk Sea (1936). In this case also a powerful stimulus to a mass
development of phytoplankton is given by the melting of ice in spring. This
outbreak of spring flowering proceeds mainly in respect of diatoms such as
Thalassiosira gravida, Fragrillaria islandica, Fr. oceanica, Achnanthes taeniata,
Amphipora hyperborea, Bacteosira fragilis, Detonula confervacea and a few
species of Chaetoceros socialis and Ch.furcellatus.

Having developed a considerable biomass (18-8 to 115-1 mg of chlorophyll
per m3 in alcohol extracts) and used up all the nutrient salts, phytoplankton
rapidly begins to decrease and, when defunct, sinks down into the lower layers
of water. A considerable development of zooplankton and a great scarcity of
phytoplankton are characteristic of the summer period of plankton life in the
Chukotsk Sea. The amount of chlorophyll is usually expressed in fractions of
a milligramme and rarely a few milligrammes (up to 5 or 6) per m3. In better
heated sea waters the predominance of the peridineans and in the colder
water of the Chaetoceros diatom genus are characteristic of 'summer'
plankton.

Zooplankton. The Pacific Ocean forms have an influence on the Chukotsk Sea
zooplankton. Jashnov notes the presence here of such forms as Calanus
cristatus, C. tonsus, Eucalanus bungei, Acartia tumida and others, pointing out
the small role played by these foreign forms which are present in restricted
numbers.

According to M. Virketis (1952) the Chukotsk Sea zooplankton consists of
93 species (not counting the larvae and the doubtful forms), the Copepoda,
Protozoa and Coelenterata (74 species) forming the main mass of the species.
The Arctic-boreal species are the most important in respect of mass (17 per
cent). The Arctic and boreal forms are equally represented. The following
forms can serve as indicators of the presence of Pacific Ocean waters : among
the Protozoa : Acanthostemella norvegica, Tintinnopsis japonica, T. Kofoidi,
Tintinnus rectus; among the jellyfish: Rathkea octopunctata ; among the
Cladocera : Evadne nordmanni and Podon leuckarti ; and among the Copepoda
Calanus cristatus, С tonsus, Eucalanus bungei, Acartia clausi, Epilabidocera

THE CHUKOTSK SEA 265

amphitrites and others. The most typical Arctic forms are the Infusoria
Metacylis vitroides, the jellyfish : Euphysa flammea and Aeginopsis laurentis;
the Copepoda Calanus hyperboreus, Euchaeta glacialis and Metridia longa,
and the Appendicularia Oikopleura vanhoeffeni.

V. Bogorov (1939) and V. Jashnov (1940) give a quantitative percentage
ratio of various plankton groups of the Chukotsk Sea, set out in Table 115.

Table 115

Plankton composition in the second
half of July 1934 (Bogorov's data) Plankton corn-
Form position, August-

Throughout whole Surface layer September 1 929
water column (10 m deep) (Jashnov's data)

44-8
25-2
73-0
140
50

Calanus finmarchicus
Pseudocalanus elongatus
Other Copepoda
Chaetognatha
Coelenterata

15-5
13-6

Appendicularia
Larvae of Decapoda
Larvae of Polychaeta
Larvae of Mollusca

36-7

25-0

1-3

Larvae of Cirripedia
Others

1-3

6-6

27-6 Z. 32-6

The difference in the plankton composition as given by these two authors
depends on the fact that Jashnov collected his data in the western and north-
western parts of the Sea, often far removed from the coast, whereas Bogorov
collected his data close to the Siberian shores. The relative decrease of Cope-
poda near the shores and the large admixture of larval forms is striking.
Data on the phyto- and zoo-plankton biomass are given in Table 116.

The reduction of the open sea biomass to almost one-third (right-hand
column) must be attributed to the season : the collection was made in the
second half of July, when zooplankton had not yet reached its full develop-
ment. The low indices of both parts of plankton for the Cape Angueme region
(second column) are explained by the accumulation of solid ice. The eastern
and western parts of the Sea were already clear of ice and phytoplankton was
in a state of vigorous bloom. According to V. Jashnov's calculation the largest
total biomass is almost 1 million tons ; this is apparently a considerable under-
estimate.

Benthos

Qualitative composition. The qualitative composition of the flora and fauna
of the Chukotsk Sea reveals a complex mixture of an Arctic fauna of Pacific
and Atlantic origin. According to data compiled by A. D. Zinova (1952) 70
species of green, brown and red algae — 29 brown and 31 red — have been

266

BIOLOGY OF THE SEAS OF THE U.S.S.R.
Table 116

Characteristic

Biomass of zoo- and phyto-plankton in central

areas of Chukotsk Sea, mg/m3

(Bogorov's data)

Upper water layer down to 10 m

Eastern
part of Sea

to Cape
Angueme

Cape

Angueme

area among

heavy ice

Western
part of Sea

Through-
out water
column

Whole Sea

Zooplankton

biomass in

open parts of

Chukotsk Sea

(Jashnov's

data)

Throughout
water column

Northwestern
part of Sea

Zooplankton
Range

Phytoplankton
Total biomass

232-2
38 762

1,510-0

1,742-2

1000
10 304

379-1
4791

139-5
71 208

2,7600
2,899-5

1600
56 465

640

The greatest

177

found in the Chukotsk Sea. The following numbers of animal species and
variants found in the Chukotsk Sea {Table 117) have so far been published.

As yet this list is very incomplete. Many groups have not yet been examined
(Turbellaria, Nemertini, Nematoda) and others not sufficiently analysed.
However, the considerably greater poverty of the Chukotsk Sea fauna com-
pared with that of the varied fauna of the Barents Sea is revealed by a com-
parison of the wealth of species of its groups already studied in detail.

P. Ushakov (1952) supposes that the shallow depths, the preponderance of
hard bottoms, the lowered salinity and the severe temperature conditions of
the Chukotsk Sea should be considered the causes of this poverty.

Distribution. The littoral zone of the Chukotsk Sea is not populated. Only at a
depth of 5 to 8 m do macrophytes live {Entermorpha crinita, Dichyosiphon

Table 117

Foraminifera

Cumacea

Porifera

Hydrozoa

Alcyoniaria

Actiniaria

Polychaeta

Sipunculoidea

Priapuloidea

Echiuroidea

8 (no less than 25)

176

Mysidacea

Euphausiacea

Amphipoda

Isopoda

Decapoda

Pantopoda

MoUusca

Echinodermata

103

106

Bryozoa
Cirripedia

113

Enteropneusta

Tunicata

Pisces

Total

2
28
37

755

THE CHUKOTSK SEA 267

faeniculaceus, Desmarestia aculeata, Laminaria saccharina, L. bongardiana,
Antithamnion borealis and others).

The fauna populating the shallow sand floor (7 or 8 m) off Wrangel Island
is similar in its composition to that inhabiting similar floors and depths off
Novaya Zemlya. The benthos biomass in this zone is a few dozen grammes
per m3.

The population of the chief, mud-covered areas, 30 to 50 m deep, is very
similar to that of the southeastern parts of the Barents Sea, and apparently
to that of all the shallow Siberian seas. The basic forms here are Macoma
calcarea, Nucula tenuis and Terebellides stromi. Apart from them the most
usual among the polychaetes are : Lysippe labiata, Nephthys ciliata, Chaeto-
zone setosa, Scoloplos armiger, Capitella capitata, Scalibregma inflata and
Sc. robusta; among the molluscs : Yoldia sp. and Axinus flexuosus var. gouldi;
among the crustaceans : Ampelisca eschrichti, Amp. macrocephala, Acantho-
stepheia malmgreni, Byblis gaimordi ; and among the echinoderms : Ophiura
sarsi, Myriotrochus rinkii, Ctenodiscus crispatus and Ophiocten sericeum.
The ratio between the individual biomass groups is also similar to that of
the southeastern part of the Barents Sea {Table 118).

Table 118

Vermes 35-2 g/m2 Gastropoda 20 g/m2

Crustacea 31-8 g/m2 Lamellibranchiata 114-6 g/m2

Echinodermata 16-2 g/m2 Varia 14-4 g/m2

Mean biomass 214-2 g/m3

Cirripedia, hardly represented in the Kara Sea, and so far not discovered
in the Laptev Sea, appear again after a long break in the Chukotsk Sea.

Benthos biomass (Fig. 112) varies usually from a few dozen grammes to
100 to 200 g/m2, increasing only at the most southern part of the Sea and in
the Bering Strait, mainly in respect of the epifauna (up to 500 g/m2 and more).
The numerical distribution of the bottom fauna in the Bering Strait and the
Chukotsk Sea is given by groups in Fig. 1 12.

As has been pointed out by Ushakov, the main part of the bottom fauna of
the Chukotsk Sea consists of Arctic-boreal, eurybiotic, widely distributed
forms, as for instance, the amphipods Ampelisca macrocephala, A. eschrichti,
Pontoporeiafemorata, the polychaetes Chaetozone setosa and others. However,
a boundary can be drawn between the areas characterized by a preponderance
of typically Arctic forms, which are peculiar for all parts of the Arctic basin,
and those with a preponderance of Pacific Ocean boreal forms, which pene-
trate through the Bering Strait. The influence of the Pacific Ocean waters on
the local Arctic ones is clearly indicated by these two groups of forms (Fig.
113).

Ushakov specifies the following forms as the most characteristic Arctic
and high Arctic forms — Foraminifera : Elphidium gorbunovi ; hydroids : Peri-
gonimus yoldiae arcticae; polychaetes: Melaenis loveni, Gat ty ana amundseni ;
bryozoans : Eucratea loricata var. cornuta, Notoplites sibirica ; amphipods :

268

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Onisimus genus and also Haploops laevis, Ampelisca birulai, Priscillina
armata, Acanthostepheia malmgreni; isopods: Mesidothea sibirica, M. sabini
robusta ; decapods : Spirontocaris phippsti, Antinoella badia, Castalia aphro-
ditoides, Lumbriconereis algida, A. beringiensis, Arrhis phylonyx, Rozinante
fragilis, Sabinea septemcarinata, Eualus gaimardi belhcheri; echinoderms:
Urasterias linki, Heliometria glacialis, Ophiocten sericeum, Eupirgus scaber ;
molluscs : Portlandia arctica, Montacuta spitzbergensis, Periploma fragilis and
others.
In the southwestern part of the Chukotsk Sea the boreal Pacific Ocean

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forms are widely distributed ; 50 per cent of the species consist of these groups
of fauna, especially of the Decapoda, Echinodermata and Tunicata. Among
the hydroids the following should be mentioned : Halecium ochotense, Abieti-
naria variabilis, A. turgida, Sertularia similis; among the polychaetes: Eunoe
spinicirrus, E. barbata, E. depressa, Gattyana ciliata, Spinier vegae; among
the bryozoans: Eucratea loricata var. macrostoma, Dondrobeania pseudo-
levenseni, Leischara orientalis ; among the Cirripedia : Balanus hesperius, Meso-
stylis dalli, M. bidentata ; among the amphipods : Ampelisca derjugini, Har-
pinia gurjanovae, Pontharpinia nasuta, Metopa submajuscula, M. robusta;
the isopod Janiria alascensis; the decapods: Pandalus goniurus, Eualus
suckleyi, E. flexa, E. camtchatica, Crangon dalli, Pagurus rathbuni, Para-
lithodes platypus, My as coarctatus alutaceus, Chionoecetes opilio ; the molluscs :
Yoldia scissurata, Venericardia crebricostata, V. crassidens, V. paucicostata,

THE CHUKOTSK SEA 269

Cardium calif orniensis, Serripes laperousii; the echinoderms : Solaster daw-
sonia arcticus, Asterias rathbwri anomala, Ophiura maculata, Gorgonocephalus
caryi typ. et f. stimpsoni, Echinaraclmius parma, Psoitis peronii, and others.

The Chukotsk Sea fish fauna includes 37 species, distributed as shown in
Table 119.

Table 119

Cottidae
Salmonidae

Lumpenidae
Gasterosteidae

2
1

Zoarcidae

Sticheidae

Pleuronectidae
Osmeridae

4
3

Ammodytidae
Agonidae

Gadidae

Liparidae

Seventy-five per cent of all the fish of the Chukotsk Sea consists of the five
first-mentioned families. High Arctic forms of the Arctic Ocean occur mainly
in waters adjacent to the western side of Wrangel Island and to the north of
it along the northern coast of Chukotsk almost up to the Bering Strait. The
Pacific Ocean forms are found in masses in the Bering Strait, penetrating the
Chukotsk Sea in two prongs : a northwestern one towards Herald Island and
a northeastern one along the shores of Alaska (Fig. 111).

This distribution stands in complete agreement with the main currents of the
Chukotsk Sea (Fig. 111).

In the northern part of the Chukotsk Sea, at the edge of the continental
shelf, Ushakov has found some typical Atlantic forms (Portlandia lenticula,
P.fratema), which, along with Atlantic waters, have penetrated the regions of
the Arctic basin so far removed from the Atlantic.

The Baltic Sea

I. GENERAL CHARACTERISTICS

The Baltic is a shallow (usually with depths no greater than 100 m), semi-
enclosed, epicontinental sea of the temperate zone which is considerably
diluted with fresh water. Closely embraced by the mainland, it is connected
with the open sea by a complex system of shallow straits (Fig. 1 14).

The unstable salinity conditions of the surface layer and sharply defined
saline stratification which are features of the Baltic Sea stamp the whole set of
its conditions on the distribution of life in it. A relatively feeble exchange of
water with the North Sea, the formation of considerable stagnant biologically
poor zones in places where there are deep depressions, the distinctive set of
conditions of the Gulf of Bothnia and the general low level of biological
productivity are conditioned by these factors.

In the post-glacial era the Baltic Sea was changing shape, acquiring and
losing outlets to the open sea both to the west and to the northeast, its water
becoming first more and then less saline. This complex geological history has
also brought about the genetically complex composition of its population.
Ice relicts of the Yoldian period, true brackish-water fauna, and euryhaline
immigrants from the North Sea and from fresh waters, may be distinguished
in it. The first and second of these groups are fragments of the fauna now
populating the Arctic basin in its least saline waters.

The Baltic Sea and its least saline areas are the most southern part of the
habitat of these two groups, which now are in the main separated from their
habitat. The forms which had migrated from the North Sea in later periods
(the third group) inhabit mostly the upper, better heated, layers ; they include
in their number forms typical of the north European littoral.

Thus the Baltic Sea, as regards its zoological geography, is divided into
two : the shallower southern and southwestern parts of the Sea are populated
mainly by boreal fauna, while the deeper northern and northeastern parts of
the Sea are populated by a fauna of Arctic aspect. The Baltic Sea communities
are characterized by their oligomixed nature which is particularly marked
within the more dilute part of the sea.

The productivity of the Baltic Sea is low. Its benthos biomass decreases
rapidly as it passes from the Belts and Oresund to the farther parts of the
Baltic, from hundreds of grammes to a few dozen per m2, and even to a few
grammes in the eastern inlets. In the north of the Gulf of Bothnia the
benthos biomass is only a fraction of a gramme.

II. HISTORY OF EXPLORATION

The Baltic Sea, its fauna and its flora have been very fully studied by the com-
bined efforts of the scientists of Denmark, Sweden, Finland, Russia, Poland
and Germany.

270

THE BALTIC SEA

271

The Swedish zoologist S. Loven (1864) laid the foundation of the study of
the fauna of the western part of the Baltic Sea.

A number of comprehensive works on the fauna of the Baltic Sea appeared
in the second half of the last century, among which the following should be
noted: the researches of K. Mobius (1873) on invertebrates and, in colla-
boration with Fr. Heinke (1883), on fish; the work of K. Brandt on Kiel
Bay fauna (1897), and that of O. Nordquist on the fauna of the invertebrates
of the north of the Baltic Sea and of the Gulf of Bothnia. In the 'nineties
Danish and Finnish scientists began their study of the Baltic Sea. From 1913
onwards a whole series of papers was published by the Swedish zoologist
Sv. Ekman.

The first quantitative survey of this fauna was carried out by the Dane,
С G. Joh. Petersen (1913, 1914, etc.) and by the Swede, G. Thulin (1922).

The extensive series Die Tierwelt der Nord- und Ost-see, which first appeared
in 1927 is the most comprehensive summary of work on fauna of the Baltic
Sea. A number of significant studies have been carried out by K. Demel,
A. Remane, K. Shliper, Sv. Sagerstrale, I. Valinkangas and others during
recent decades.

III. PHYSICAL GEOGRAPHY, HYDROLOGY, HYDRO-
CHEMISTRY AND GEOLOGY

Size and subdivisions

A characteristic feature of the orography of the Baltic Sea is its considerable
extent from south to north (more than 1 ,200 km) ; from Copenhagen to the
end of the Gulf of Bothnia is about 1,500 km. This causes great climatic
differences between the southern and northern parts of the Sea.

In Spethmann's opinion (1912) the area of the Baltic Sea is equal to 385,000
km2 (Sagerstrale suggests that it is 420,000 km2), while its volume is 21,700
km3. The greatest width of the Sea is approximately 300 km.

The annual inflow of fresh water is 630 km3, or 1/34 of the total volume of
the Sea. Four hundred and sixty-five km3 of water is brought into the Baltic
Sea by the 250 rivers which flow into it.

The Baltic Sea, with its large number of islands and bays and its somewhat
varied bottom topography, is subdivided into several natural areas. The system
of subdivision accepted by Sv. Ekman (1931) is set out below, although other
investigators prefer other subdivisions :

A. Belts (transitional area)

B. Oresund (transitional area)

C. Baltic Sea proper

D. Gulf of Riga (marginal area)

E. Gulf of Finland (marginal area)

Called also West
Baltic Sea

I. South Swedish-
Pomeranian Baltic

II. Central part of
Baltic Sea

1. Danish belt

2. German belt

3. Arcona or Rugen
region

4. Bornholm region

5. West Baltic central
part

6. East Baltic central
part

272 BIOLOGY OF THE SEAS OF THE tf.S.S.R.

F. Aland Sea (transitional area)

G. Southwest Finnish Quarken Sea

(transitional area)

rill. Outer part of Gulf: Bothnia Sea (Bot-
H. Gulf of Bothnia (marginal area) | tensee)

(iV. Inner part of Gulf (Bottenwiek)

The Belts are also known as the West Baltic Sea. The southern strait of
Oresund and the Darss Ridge, i.e. the eastern boundary of the German Belt,
form the western boundary of the Baltic Sea proper. The most westerly part of
the Baltic Sea proper, the Arcona or Riigen region (Arcona or Riigen Sea), lies
to the west of Bornholm Island ; to the east is the Bornholm region with its
deep Bornholm depression. These two areas are sometimes called the South
Baltic Sea or the South Swedish-Pomeranian Baltic Sea. Farther east and
north is the central area of the Baltic Sea, divided into eastern and western
parts by the island of Gotland. The transitional area between the Baltic Sea
proper and the Gulf of Bothnia is occupied by the Aland Sea west of the
Aland Islands and by the Quarken Sea, or the Southwest Finnish Quarken
Sea, to the east of them.

Bottom topography

The southern part of the Kattegat is nowhere more than 40 m deep. The three
narrow straits which connect the Kattegat with the Baltic Sea — the Great
and Little Belts and Oresund — are even shallower. Oresund, in the latitude
of Copenhagen, is only 7 m deep. The Little Belt is a little deeper, and in its
shallowest part is 10-5 m deep. In the Great Belt and its continuation in the
direction of the Baltic — the Langeland Belt — there is a continuous trench with
a depth of at least 30 m. However, farther to the east and before entering the
Baltic proper this system of straits becomes even shallower. Still farther to the
east depths begin to increase. Before the island of Bornholm is reached there
is the Arcona depression with depths down to 53 m. The next significant
hollow is situated east of Bornholm Island (the Bornholm depression) with
a maximum depth of 105 m (see Fig. 1 14). Farther north the floor rises again
slightly and then north of Gotland it goes down sharply ; the 80 m contour
line encloses a large area between the Gulf of Riga and Stockholm, which
stretches southwards with a tongue each side of Gotland (Gotland depres-
sion) and contains some exceptionally deep areas. Among them is the greatest
depth in the Baltic Sea — the Lansort depression, 459 m. deep. The Gotland
depressions extend even to the Gulf of Finland, becoming progressively shal-
lower as one moves east (40 m and less).

The Gulf of Bothnia, on the contrary, is separated from the Gotland depres-
sion by shoals (30 to 50 m) off the Aland Islands (Aland Ridge). The Gulf of
Bothnia itself is also divided by a shallow ridge off the Quarken into two
deeper parts : the southern one, the Bothnian Sea (Bottensee) with a maxi-
mum depth of 294 m, and the northern one — Bottenwiek — with a maximum
depth of 140 m. Finally a closed hollow with depths down to 301 m lies to the
west of the Aland Islands.

Fig. 1 14a. Regions of the Baltic Sea (Ekman). 1 Oresund ; 2 Danish
Belt; 3 German Belt; 4 Arcona depression; 5 Bornholm de-
pression; 6 Eastern part of central depression; 7 Western part of
central depression; 8 Gulf of Riga; 9 S. Quarken; 10 Aland Sea;
11 Gulf of Bothnia ; 12 Gulf of Finland.

Fig. 1 14b. Depths of the Baltic Sea (Ekman).

274

BIOLOGY OF THE SEAS OF THE U.S.S.R.

The sea-bed

A preponderance of sand, gravel and at times a rocky floor, are the character-
istic features of the sea-bed in the shallow zone (down to 50 m) of the Baltic.
Ooze bottoms are found only in stagnant bottom hollows. The deeper parts
of the bottom (over 50 m in depth) are occupied for the most part by clayey
mud with sand, at times by black ooze, rich in organic detritus. The sea
bottom is usually brown-red, especially in the Gulf of Bothnia; this colour
is due to an admixture of ferric hydroxide. This kind of distribution of brown
mud deposits is very characteristic of the floor of the Kara Sea and to a

Fig. 115. Bottom deposits in southern part of Baltic Sea (Demel). Unhatched areas
are sand; vertically hatched are sandy silt; horizontally hatched, silts.

lesser extent of that of the White Sea. This kind of bottom contains a large
amount of concretions. Z. K. Demel and Z. Mulicki (1954) have given a map
showing the distribution of the different soils of the southern part of the Baltic
(Fig. 115). As is shown in Fig. 115, sand and sandy silts are preponderant here.
Soft ooze is concentrated in the deepest places (more than 80 to 100 m).

The Swedish research scientist B. Kullenberg (1952) studied the salinity of
the solutions of cores up to 15m long taken from several sites in the Baltic.
The core taken near Bornholm, from a depth of 86 m, is particularly demon-
strative.

Interstitial water taken from a layer 2 m below the sea-floor indicated
salinity of 15%0; salinity decreased with depth down to 6%0 at 12 to 15 m
(Fig. 1 16). In B. Kullenberg's opinion (1954) this corresponds to the early period

THE BALTIC SEA

275

of the ice lake-sea (12,000 to 13,000 years ago). The great variety and contrasts
displayed by the different parts of the Baltic Sea shores are connected with the
difference of its geological structure and with the history of its development
in the Quaternary Period. The boundary of the crystalline rocks of the Baltic
icefoot is adjacent to the top
end of the Gulf of Finland.
The coastline of the northern
and western parts of the Sea
is formed of granites and
gneisses (Finland and Swe-
den). The Quarken shapes of
the southern shores of Fin-
land, the Aland Archipelago
and Sweden were formed
when this area was sub-
merged. The shores of Swe-
den belong to the fjord type.
All these shores are rising
at a high rate, especially at
the head of the Gulf of
Bothnia (up to 1 -2 cm annu-
ally). Palaeozoic deposits of
the Russian shelf are laid
bare at the southern shores
of the Gulf of Finland ; far-
ther south they drop below
sea-level. The whole coast
from the Gulf of Riga to
Jutland consists mainly of loose Quaternary deposits exposed to considerable
destruction by the sea. Large masses of alluvium formed during this process
are transported from west to east, and then from south to north. As a result,
large sand wash forms are created — the characteristic peninsulas and shoal
heads of the southern coast. Wind action leading to the formation of powerful
dune belts, at times up to 60 m high, is a feature of the southern and eastern
shores of the Baltic Sea.

Fig. 1 1 6. Change of salinity with depth at the
seafloor of the Baltic Sea (Kiillenberg).

Temperature

The bottom topography described above, together with the contour of the
coastline, exerts a very strong influence on the hydrological conditions of the
Baltic Sea. It brings about a relatively small water-exchange with the North
Sea, the formation of considerable stagnant zones with poor development of
life in the deep hollows and, finally, the distinctive set of conditions in the
Gulf of Bothnia. In the first place temperature conditions are affected. During
the season of the year when the water column has its lowest temperatures
(February), the surface waters of the northern parts of the Baltic (Gulfs of
Bothnia and Finland) are below 0°. In the warmer southern parts, the tempera-
ture is slightly above 2°. The two northern gulfs have an ice cover over most

276

BIOLOGY OF THE SEAS OF THE U.S.S.R,

Fig. 117. Ice chart of the Baltic Sea (Bliitgen, 1938). 1 Fast ice; 2 Periodical
drift pack ice ; 3 Periodical floes ; 4 Periodical drift ice ; 5 Episodical fast ice ;
6 Episodical pack ice ; 7 Episodical drift ice.

of their surface : in the inner parts for 2 to 5 months and more, at the inner
end of the Gulf of Finland for 3 to 6 months and at the top of the Gulf of
Bothnia for as much as 5 to 7 months. The ice conditions of the Baltic Sea
are shown in Fig. 117.

Such temperatures are unknown in the North Sea, which lies alongside the
Baltic and in the same latitude (Fig. 118). During the warmest time of the
year (August) the surface temperatures of both Seas are practically the same.
The heat conditions of the deepest parts of the sea undergo slight variations
in temperature in the course of the year. Below 50 m and down to the bottom

THE BALTIC SEA

277

the temperature usually ranges between 3° and 5° in the southern parts of the
Sea, and between 1° and 5° in the northern ones (Aland depression).

The phenomenon of dichothermia is very common in the Baltic Sea ; the
coldest layer of water (intermediate cold layer) lies usually not at the bottom

Fig. 118. Surface isotherms of the North and Baltic Seas in February
(A) and August (B) (Schulz).

but at a depth of 60 to 100 m. At the bottom the temperature rises again from
3° to 5° (Gotland and Danzig depressions). In this respect the diagram in
Fig. 119 is most instructive; it gives the changes of temperature at different
depths in the depression situated at the entrance to Danzig Bay, which has a
maximum depth of 113 m. The range of July temperatures in the area of the
Island of Gotland is given in Fig. 120.

Salinity

The most characteristic features of the hydrology of the Baltic Sea comprise
the instability of its saline conditions, especially in its transitional areas, the
movement of the more saline near-bottom water from west to east along the
deep troughs with a simultaneous surface discharge current in the opposite
direction and, in consequence, a sharp division of salinity in two layers of the

!78

BIOLOGY OF THE SEAS OF THE U.S.S.R,

^TEMPERATURE <^

Fig. 119. Changes of temperature at different depths of Danzig depression
during the period from 1902 to 1907 (Schulz).

waters of the Baltic Sea which affects the entire set of conditions of the Sea
and the distribution of life in it.

As is shown in Fig. 121, the surface salinity falls off to the east and to the
north very sharply in the area of the straits and more gradually in the rest of
the Sea. The surface salinity of the main basin of the Sea is 2 to 8%0. The
salinity conditions of the deep layers of the Baltic Sea (Fig. 122) result pri-
marily from its bottom topography and from its water-exchange with the
North Sea through the straits. A great difference in the salinity of surface
water — discharge Baltic current — and that of the lower layers — the deep
compensating current from the North Sea to the Baltic — is observed all the
year round in the straits connecting these two Seas. The salinity changes are

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jjj^ai^vertss

т\Щ^-!:_:А:^Ш^У

BORNHOLM "
DEPRESSION'

BORNHOLM
DEPRESSION

~~^\^'''tT~ / — ~~~~~

— Z_~ ^r^^^T*

GOTLAND
DEPRESSION

TEMPERATURE 0°C

LANDSORT DEPRESSION

Fig. 120. Temperature range at different depths round Gotland Island in July 1922

(Schulz).

THE BALTIC SEA

279

Fig. 121. Surface salinity of the Northern and
Baltic Seas in August (Schulz).

especially abrupt in the straits, in relation to both space and time, depending
on the season, and above all on the direction and force of the wind. Thus at
one and the same spot, in Oresund, the fluctuations of salinity observed on
the surface ranged from 7-2 to 22-4%0 and at a depth of 17 m from 11-7 to
22-5%0. The magnitude of the variations in the area of the Darss ridge is
about the same.

At another point in Oresund, within a period of six months salinity on the
surface ranged from 6-8 to 25-7%0 and at a depth of 8 m from 8-2 to 25-7%0.

Fig. 122. Near-bottom November isohalines (%0) of the

Baltic Sea. Broken lines are May surface isohalines

(Ekman).

280

BIOLOGY OF THE SEAS OF THE U.S.S.R,

In Kiel Bay salinity was found to vary from 3-9 to 26-3%0 on the surface and
from 10-3 to 28-8%0 at a depth of 14 m. Moreover the change of salinity some-
times occurs very rapidly.

The occasional mass penetration of a more saline-loving fauna into the
Baltic Sea is caused by the periodical inflow through the straits of masses of
more saline water from the North Sea. Thus in the spring of 1923 Schulz
reported that huge masses of saline water (more than 34%0) had flowed into
the Kattegat bringing great numbers of spawning haddock (Gadus aeglefinus).
The haddock larvae were brought by the bottom current into the southern
straits and the western part of the Baltic Sea. As a result, the usually low yield

Fig. 123. Salinity range of the Danzig depression from
1902 to 1907 (Schulz).

of haddock rose in 1925 to 50,000 kg, and in January and February 1926 to
500,000 kg, but the catch fell off sharply in March as the haddock migrated
back to the Skagerrak to spawn.

Deep saline waters, penetrating periodically through the deep troughs into
the Bornholm depression, frequently form there a very complex system of
overlapping, accompanied by the usual phenomena of stagnation. The
highest salinity observed there was 18-93%0, the lowest — 14-87%0 (September
1921), with an oxygen content of 0-7 per cent. However, at other times and at
precisely the same depths an oxygen content of 80 per cent has been recorded.
It has been noted that a layer of water of the same thickness as that over the
shallows situated to the west — approximately 40 m — is homohaline; in
winter it is also homothermic and is well mixed.

The diagram of the Danzig depression in Fig. 123 is a clear illustration of
this. The deep waters of the Bornholm depression (105 m) may partly pene-
trate even farther into the deeper Gotland depression (249 m). The salinity

THE BALTIC SEA

281

of the Danzig depression (113 m) varies, however, from 10-01 to 13-5%0, that
of the Gotland one from 11-49 to 12-65%0, and that of the Landsort one
(427 m, north of Gotland Island) from 9-83 to ll-08%o. The amplitude of the
salinity fluctuations decreases from 4 (Bornholm depression) to 1 • 1 5%0 as one
moves east.

The instability of the saline conditions is very marked not only in the
western part of the Baltic Sea but also in the eastern. This is well illustrated by
Sv. Sagerstrale (1951 a) for the Gulf of Finland. In the western part of the
Gulf in 1927-49, at a depth of 5 m, the salinity varied from 4-29 to 6-80%0,
and in its eastern part from 007 to 4-96%0.

Salinity fluctuations affect the distribution and biology of organic life.
Sv. Sagerstrale (1951 a) gives a number of interesting examples, among them
the differences in the time taken by the medusa, Amelia aurita, to reach
maturity.

Gas conditions

Saline and gas conditions off Gotland Island, shown on the diagrams (Figs.
124, 125), are most significant. The deep saline water is poor in oxygen and

BORNHOLM
DEPRESSION

^^p^r^^^rmff&^^r^^~-: ■

fK^-

^1*

T-g-

Г7 ff^

BORNHOLM
DEPRESSION

GOTLAND
DEPRESSION

OXYGEN
ccm/L

■

LANDSORT DEPRESSION

Т77Л 8ccm/L

y?m

9ccm/L

■

Fig. 124. Oxygen distribution in waters round Gotland Island in June 1922 (Schulz).

rich in carbon dioxide. In the autumn there is a vigorous vertical circula-
tion which continues even in the winter ; but it embraces only the upper 60 or
70 m layer. The summer warming which follows penetrates deeper still but

Fig. 125. Distribution of carbon dioxide in waters round Gotland Island in July

1922 (Schulz).

does not last long enough to warm the whole layer cooled during the winter.
This is the reason for the existence of an intermediate cold layer, between the
two warmer layers, at a depth of 40 to 60 m. The hydrological and hydro-
chemical conditions of Baltic waters in summer time off Gotland Island may
be illustrated by the data given in Table 120 (15 July 1922, west of Gotland
Island).

282

BIOLOGY OF THE SEAS OF THE U.S.S.R.
Table 120

Depth
m

u
О
Q-

E
и

'B
13

<u
ад
о

п
и

ЬХ)

>-*

•3

с
о

6Л С

£3

и В
С о

^ Г)

ел °

х 2

ТЗ о

с с
U о,

рН

t°

5%o

cm3/l.

ст3/1.

12-4

7-0

13-8

7-4

0-4

21-6

1-8

8-08

8-8

14-8

8-2

0-4

23-4

1-7

8-05

2-3

7-3

16-8

8-6

0-7

26-2

2-6

7-76

3-5

8-68

16-3

4-3

2-8

23-4

12-0

7-27

4-3

9-52

15-9

2-1

4-5

22-5

20-0

6-95

4-3

9-85

15-9

1-6

5-7

23-2

25-0

6-87

Fig. 126. Distribution of oxygen (cm3/l.) in the depths of the
Baltic Sea in May 1922 (Schulz).

THE BALTIC SEA

283

It is interesting to note that the ratio of the amount of carbon dioxide
formed at this depth to the oxygen consumed is about 0-9, which corresponds
to the respiratory coefficient of the organisms inhabiting the depths of the
Baltic Sea ; this has been confirmed by experiments with fish.

The acid conditions of the deep Baltic waters have a characteristic effect
on the process of the decomposition of mollusc shells (Grippenberg, 1934).

Fig. 127. Distribution of carbon dioxide (cm3/l.) in
near-bottom waters of Baltic Sea, May to July 1922
(Schulz, 1935).

This process has also been observed to be strongly developed in the deep part
of the Kara Sea.

The summer distribution of oxygen and carbon dioxide, and the concen-
tration of hydrogen ions in the bottom layer of the Baltic Sea, are shown in
Figs. 126, 127 and 128.

The Gulf of Bothnia is separated from the rest of the Sea by a shallow
ridge, which does not let through the deep saline waters from the west ; this
affects its hydrological conditions.

As shown in the three figures given, the gas conditions in the deep layers
of both Bothnian depressions are much more favourable than in the southern

284

BIOLOGY OF THE SEAS OF THE U.S.S.R.

part of the Sea. Thus in the deep layers of the Aland depression at a much
lower temperature (1-18° to 3-81°) and a lesser salinity (6-8 to 702%o), the
deep-water salinity is only 1%0 higher than that of the surface water, the verti-
cal circulation reaches the bottom and the amount of oxygen at 300 m is still
6-5 to 8-7 cm3/l- at 73 to 93 per cent of saturation. In the southern depression
of the Gulf of Bothnia the deep-water salinity varies between 6 and 6-5%0,
while in the northern depression it is about 4%0.
As regards deep-water gas conditions, the area of the eastern part of the

Fig. 128. Concentration of hydrogen ions in near-
bottom waters of Baltic in May to July 1922 (Schulz).

deep trough, which extends from the Gotland depression to the entrance to
the Gulf of Finland, is most interesting. Deep saline waters from the Gotland
depression penetrate into this area, while the surface waters, by contrast, are
considerably diluted ; so that conditions are created which are extremely un-
favourable for vertical circulation. The following phenomena have been ob-
served in the area to the north of Dago Island at a depth of 180 m (Bogskar
depression): marked salinity fluctuations (9-20 to 10T4%o), increased tem-
perature (3-71° to 4-96°) and changes in oxygen content from 0 to 2-49 cm3/l.
(0 to 29 per cent of saturation).

The range of deep-water salinity of the Gulf of Finland is shown in Fig. 129,
while the hydrological conditions of the most eastern part of the Gulf up to
Neva Guba are given in Fig. 130.

THE BALTIC SEA

285

««^'QUARKEN 0л4Ш
?,, SEA . tj ^T

BALTIC. •;>-..SE A

Fig. 129. Range of near-bottom salinity (%0) in the Gulf of

Finland (Sagerstrale). The populated points at Twerminn

(T) and Pelling (P) are marked on the chart.

500 250

100

s. ^^ J

- ю

I
1-

Q-

WOO
2000

S%o FLUCTUATIONS WITHIN

THE INTERVAL 0-21-3-64 °/oo

Fig. 130. Hydrological cross section from the Neva

Guba westwards to the south from KotUn Island

(Derjugin). Chlorine content in mg/1. is shown by the

numerals.

Distribution of nutrient salts

We have not yet got a sufficiently full picture of the distribution of nitrogen
and phosphorus compounds in the Baltic (Fig. 131). The conditions of the
northern and eastern parts of the Sea and some points of the most western
part of it (Kiel Bay) have been best investigated. The amount of ammonia
varies from 0 to 50 mg/m3. Its content is somewhat higher in surface waters

Fig. 131. Mean content of ammonium (/), nitrates (II) and phos-
phates (///) in the Baltic Sea. Numerator corresponds to their
content in the surface layer, denominator in the depth. The
natural regions are divided by lines (Buch).

286

BIOLOGY OF THE SEAS OF THE U.S.S.R,

Fig. 132. Vertical distribution of phos-
phates and nitrates in the Gulfs of
Bothnia (A) and Finland (B), mg/m3
(Gessner and Buch).

at the head of the gulfs, especially the Gulf of Bothnia. Large amounts of
nitrogen, together with humus substances, are brought into the two large

gulfs of the northern part of the
Baltic Sea from the mainland. Con-
trary to the ammonia nitrogen the
amount of nitrogen in the form of
nitrates increases with depth, since
the latter are consumed in the surface
layer by phytoplankton. Only in the
inner part of the Gulf of Bothnia'is
there a fairly high content of nitrates
in the surface layer (Fig. 132). In this
part of the Sea the plankton develop-
ment is very poor and, clearly, its
growth is not limited by the nitrates.
Nitrate content increases sharply in
the deeper layers below the thermo-
cline layer, where they are produced
mainly as a result of the nitrification
of organic matter. The reduced content of nitrate in the deep parts of the
Gulf of Bothnia is due to a very restricted inflow of deep waters from the
main basin of the Sea, owing to a shallow ridge which bars their entrance.
In the Gulf of Finland, which has no such ridge at its entrance, nitrate content
is the same as in the open parts of the Sea. The data on plankton distribution
accord fully with such a distribution of nitrates.

The distribution of phosphates is somewhat similar to that of nitrates : they
are scarce on the surface, their number increases considerably in the depths.
Here too, however, the Gulf of Bothnia stands apart : its deep waters are poor
in phosphates ; this is, perhaps, the main factor limiting plankton develop-
ment. The difference between the two Gulfs is illustrated in Fig. 132.

There are some considerable annual variations in the content of nutrient
salts in the depths of the Baltic Sea {Table 121).

The hydrochemical conditions of the Baltic Sea are peculiar in that,
although it is connected with the ocean, there is no proper exchange of water
with the latter. As a result its whole biogenic cycle proceeds on account of its
own resources and of the inflow from the mainland.

K. Buch (1931) represents as follows the nature of the processes of plant
food substances in the Baltic Sea. The current bringing the surface waters from

Table 121

Depth, m

July 1928

14 July 1929

Nitrogen

Phosphorus

Nitrogen Phosphorus

0
70
198-220

0
65
70

0
13
87

0 8-7
300 8-7
175 98

THE BALTIC SEA

287

the inner parts of the Sea towards the straits carries with it the living matter
produced in those inner parts. As they die off, the organisms must sooner or
later sink into the depths; the organic matter oxidizes, turns into mineral
matter and is accumulated on the bottom. The deep current moving in the

P, N mg/m3
5 10 15

— i — г*

/t°

\ /

N » Syoo ^

r '1

i / l

: / l

j / i

; / 1

;

1 i

i i i • ■

i ■ i

•

0 2 4 6 8 10 12 14 16 18 20

t\Of,S°/oo

Fig. 133. Vertical distributions of phosphorus,
nitrogen, density, temperature and salinity in the
Arcona depression in August 1932 (Buch from
Gessner). at indicates density at any given
temperature.

opposite direction carries back into the inner parts of the Sea the decomposed
nutritive substances.

The Gulf of Bothnia, however, has its own independent hydrochemical life.
As a result of this isolation of the separate parts of the Sea, and the obstacles
to the movements of organic substances to the southwestern part of the Sea,
these areas are poorer in nutritive matter than the northern ones ; this is con-
firmed by the data given by Buch for the Arcona depression (Fig. 133).

IV. THE GEOLOGICAL PAST

The composition of the fauna of the Baltic Sea, its ecological characteristics
and its distribution — more so than in the case of any other sea — cannot be
properly understood without taking account of its geological past. In that
respect the Baltic Sea is undoubtedly the best-studied Sea in the world (Fig.
134). From its last glaciation period, i.e. for the last 15,000 years, the history
of the Baltic Sea has been thoroughly studied. A sufficiently complete and
reliable history of this period and even its chronology can be found in the
works of the geologists, botanists and zoologists of primarily Sweden, Nor-
way and Finland. The study of this history of the Baltic Sea is linked with the

THE BALTIC SEA

289

names of the zoologists S. Loven, M. Sars and S. Ekman, the botanists
Sernander and L. Post, the geologists G. De-Geer, A. Hogbom, G. Munthe,
V. Ramsay, M. Sauramo, N. Jakovlev and others. The first ideas on this sub-
ject were due to the Swedish zoologist S. Loven (1839 and 1864) and to the
Norwegian zoologist M. Sars (1865).

Evolution of the Baltic Sea

According to the latest data the history of the Baltic Sea can be set down in
the form of Table 122.

Table 122

Glacial

Stages of the

Climatic periods of

Chronology

periods

Baltic Sea

southern Sweden

-1,000

Modern stage

Sub-Atlantic
period

Beginning of New

Post-glacial

(Sea of Mya and

Era

period

Limnae)

(cold and wet)

1,000

2,000

Littorina Sea

Sub-Boreal period

3,000

(warm and dry)

4,000

5,000

Ancyl lake

Altantic period

6,000

(warm and wet)
Boreal period
(warm and dry)

7,000

Finnish

Sub- Arctic

glaciation

period

8,000

9,000

Yoldian Sea

10,000

11,000

Gothland
glaciation

12,000

Baltic ice lake
(Rybnoe Lake)

Arctic period

13,000

Danish
glaciation

Fluctuations of sea-level and alterations of climate

Marked climatic fluctuations correspond to considerable changes both in the
sea-level and in the location of the dry land. In southern Finland traces of the
level of the Baltic ice lake (also known as Rybnoe Lake) are found at 150 m,
and of the Yoldian Sea at 90 m above the present sea-level (Sauramo). The
curves for the eustatic fluctuations of the sea-level (according to Antew)
are given in Fig. 135 (these fluctuations are caused by the change in the
volume of water in the ocean, as a result, for instance, of the accumulation
or melting of ice on the mainland or islands during the Ice Age at the time of
climatic changes). It is apparent that the accumulation of continental ice in

190

BIOLOGY OF THE SEAS OF THE U.S.S.R.

the Polar regions may cause considerable fluctuations of the ocean's level
either by their melting or by their massing. During the last Glaciation Period
( Wechseleiszeit), the ice masses of the northern hemisphere exceeded those of
the present day by 32,800,000 km3 ; for the southern hemisphere the difference
is 4,100,000 km3. The level of the ocean must have been 93 m lower than it is

ANCYL TAPES-LITTORINA

PERIOD PERIOD

-7 -6 -5 -4 -3 -2 -1000

m00 +1900

__SEA

__su

KFACE

®k

(35)

—

гЩ

(5b

)

—

Фзо)

YOLDIAN

PERIOD
-13000 -12 -11 -10 -9 -8
+10
±0

-20
-40
-BO
-80
-WO
-120
-140
-WO
-180

Fig. 135. Eustatic and isostatic fluctuations of level of Baltic Sea in post-glacial

period at Lysekil (Antew).

now on account of the increase of the Polar ice (corresponding approxi-
mately to 34,000,000 km3 of water). Northern glaciation alone must have
resulted in a lowering of the sea-level by 88 m (Antew, 1928). It has been
established that some thousands of years ago the ocean level was 5 to 6 m
higher than it is at present ; this might be related to intensive melting of the
Polar ice during the warm phases of the post-glacial period (Boreal, Atlantic
and sub-Boreal periods 3,000 to 9,000 years ago) and to the isostatic* varia-
tions of the level of the mainland at some point of the Swedish coast of the
Skagerrak.

The Ice Lake Sea

As a result of the violent melting of ice, which took place fifteen or twenty
thousand years ago, the Baltic depression was filled with huge masses of
melted ice water. The level of the Ice Lake Sea which had formed in this way
and spread widely was considerably higher than that of the ocean. This body
of water had an outflow to the ocean in the west ; on the east it was connected
with Lake Ladoga; it existed 13,000 years ago.

The Yoldian Sea

As the masses of continental ice which had supported the level of the Baltic
Ice Lake receded, the level fell, until at last masses of cold saline ocean waters
rushed into the Baltic Sea through the broad passage which was formed
* Caused by the lowering or rising of land.

THE BALTIC SEA

291

linking it with the North Sea. The Yoldian Sea was created with its Yoldia
(Portlandia) arctica, Area borealis, Mya truncata and other members of cold-
water Arctic fauna.

So far it has not been finally determined whether the Yoldian Sea was con-
nected in the northeast with the White Sea through Lakes Ladoga and Onega.
Several authors (G. De-Geer, 1910 and more recently N. Jakovlev, 1926,
A. Arkhangelsky and others) considered that during the Yoldian Period there
was a wide connection between the Baltic and White Seas. Lately, however, a
number of authors (Munthe, Sauramo, Ekman and others) have denied such
a connection, considering that the Yoldian Sea did not extend eastwards be-
yond Lake Ladoga. The salinity of the Yoldian Sea fell far short of the salinity
of the ocean, and the Sea existed for a very short time (according to Munthe
for no more than 700 years, according to Sauramo for 500).

Ancylus Lake Sea

The rising of the dry land in the area of southern Sweden again separated the
Yoldian Sea from the ocean. For a second time the Baltic waters underwent a
loss of salinity, which turned the sea into the cold, strongly diluted Ancyl
Lake Sea (Fig. 1 34). This was populated by, among others, the fresh- water mol-
luscs Ancylus fluviatilis, Lymnaea, Unio and others, and had a strong outflow
to the west. G. De-Geer estimates the length of this phase to be 2,200 years.

The Littorina Sea

As a result of the subsidence of the bottom of the southwestern part of the
Baltic and a eustatic rise of the level of the ocean (Ramsay) a link was again
established with the ocean at the end of the Ancylus Period. Once more the
Baltic waters began to be more saline, and their salinity reached higher than
the present level (Fig. 136). This Littorina phase of increased salinity (Littorina

Fig. 136. Surface salinity of the contemporary Baltic Sea (A)
and of the Littorina Sea (B) (Petterson).

292 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Sea) and slightly higher temperature (the air temperature in southern Sweden
was 2° to 2-25° higher than at present) lasted for about 4,000 years. A new
fauna appeared, with Littorina littorea, Cardium edule, Mytilus edulis, etc.
Subsequently, as a result of the rising of the sea-floor in the region of the
straits during the last 4,000 years, the inflow of the ocean waters slackened
and the Baltic Sea acquired a salinity approaching that of today. In the fol-
lowing period further distinction has been made between the Limnae Sea
(Lymnaea peregra) and the Mya Sea (Mva arenarid) ; the difference between
these two phases and the present phase is small as regards hydrology, and
it consists mainly of a change of fauna.

V. FLORA AND FAUNA

The present population of the Baltic Sea was evolved during the post-glacial
period and is very varied in its composition. It consists of three main com-
ponents— marine, fresh-water and brackish-water (in the narrow sense of
this word). In so far as the Baltic Sea has a low salinity all its population can
be considered as brackish in the broad sense of the word ; however, brackish-
water fauna in the narrow sense — the population of the Ice Age and the Arctic
basin — are also included in its composition.

It is essential, therefore, to make a distinction between the population of a
brackish body of water and a brackish fauna, retaining this term only for the
fauna which is brackish in the narrow sense of the word, i.e. fauna which
is the result of a (geologically) prolonged development of a fauna which is
marine in origin and partly also fresh-water under conditions of consider-
ably lowered salinity. The population of the Baltic Sea consists of the follow-
ing groups (Fig. 137):

(7) Marine euryhaline forms. The main part of the present population of the
Baltic Sea.

(7) Taxonomic unseparable
(2) Taxonomic separable
(5) Marine relicts of former geological periods
(4) Immigrants from distant seas.
(//) Fresh-water euryhaline forms. These form a considerable part of the
population of the Baltic Sea.
(7) Taxonomic unseparable
(2) Taxonomic separable.
(777) True brackish-water forms. These also form a considerable part of the
population of the Baltic Sea.

(7) Ancient brackish-water Arctic relicts (pseudo-relicts — immigrants)
formed during the Ice Age in the less saline parts of the Arctic
basin. They penetrated into the Baltic Sea during the post-glacial
period from the northeast and the east, possibly, via fresh-water
systems.
(2) Brackish-water forms which had originated from the fresh-water
ones.

THE BALTIC SEA

293

As in other brackish-water bodies the qualitative variety of the flora and
fauna of the Baltic Sea is not large ;
nor are the indices of biological
productivity high. Some individual,
mostly euryhaline, members of the
fauna of the adjacent fully saline
sea basins frequently become very
numerous. Biocoenoses with a few
(mesomixed) or with very few
(oligomixed) species are character-
istic of such bodies.

Many of the forms of the Baltic
Sea sink to great depths, penetrat-
ing into the areas with a salinity
lower than that of the North Sea,
and the fresh-water forms move
into areas of higher salinity.
Sagerstrale has pointed out (1957)
that Macoma baltica and Scoloplos
armiger are encountered in the
Baltic Sea down to 100 to 140 m
(Hessle, 1924). Fucus vesiculosus,
which does not go more than 5 m
deep into the Kattegat, descends in
the Baltic Sea to 10 to 12 m (Waern,
1952). Idothea baltica in the Gulf of
Finland reaches a salinity of 3 to
4%0, but ceases at a salinity of 10 to
15%0 near the coast of Jutland (Jo-
hansen, 1918). Fresh- water forms,
on the contrary, enter much farther
into the saline waters of the Baltic
Sea. For example, Lymnaea peregra
goes up to 1 0 to 11%0, while in Jutland
it does not enter more than 5 to 7%0
(Jaeckel, 1950; Johansen, 1918).

Many marine groups do not
penetrate, or only penetrate in
small numbers, into the Baltic Sea :
Porifera, Actiniaria, Madreporaria,
Octocorallia, Solenogastres,
Scaphopoda, Pteropoda, Cephalopoda, Echinodermata and others.

Plankton

Qualitative changes of plankton from west to east. Plankton suffers a marked
qualitative change as one leaves the Belt and Oresund and enters the Baltic
Sea (Fig. 138).

Fig. 1 37. Composition of barckish-water
population. / Marine, euryhaline fauna;
IA Typical marine forms d veloping only
slightly in brackish waters; IB Marine
forms of greater mass development in
brackish water ; 1С Marine forms weakly
connected with marine habitats, living
mostly in brackish waters; HA Typical
fresh-water forms, which penetrate into
brackish water; IIB Fresh- water forms
of greater mass development in brackish
waters; IIC Fresh-water forms weakly
linked with fresh-water habitats, living
mostly in brackish water; /// Typical
brackish-water forms alien to marine
and fresh-water forms.

294

BIOLOGY OF THE SEAS OF THE U.S.S.R.

While plankton in the straits leading to the Baltic Sea does not differ much
from that of the North Sea, in the upper parts of the Gulfs of Bothnia and
Finland the plankton has a purely fresh-water character. Instead of the
numerous marine species Chaetoceros, Rhizosolenia, Ceratium tripos and С
fusus, a considerable number of hydro-medusae, Copepoda (Oithona nana,
Eurytemora hirundo, Paracalanus parvus, Acartia longiremis), the marine
species of Rotifera (species of the genus Synchaeta mastigocera), numerous

Fig. 138. Penetration of certain Copepoda into the depths of the
North Sea and into the Baltic Sea (Pesta). 1 Eurytemora
hirundoides typicus; 2 E. hirundo; 3 Oithona; 4 Southern
boundary of Oithona similis (northeastern in the Baltic Sea) ;
5 Northern boundary of Oithona rnana ; 6 Eastern boundary of
Centropages; 7 Metridia longa; 8 Northern boundary of
Paracalanus parvus ; 9 Northern boundary of Pseudocalanus
elongatus; 10 Northern boundary of Acartia bifilosa; J J
Southern boundary of Limnocalanus grimaldi.

Tintinnoidea (Parafavella, Tintinnopsis), a series of the species Sagita, the
pteropod mollusc Limacina retroversa and others, we have east of the Darss
ridge throughout the Baltic the blue-green algae Aphanizomenon flos-aquae ,
Nodularia spumigena and Anabaena baltica; the diatoms Chaetoceros wig-
hami, Thalassiosira baltica and Ch. danicum, which sometimes bring about a
summer and autumn flowering of the peridineans P. depressum and P. pellu-
cidum, Prorocentrum micans, Dinophysis baltica, Goniaulax catenata and
others, some Infusoria, for instance Tintinnopsis campanula, Helicostomella
subulata, among the Rotifera a preponderance of Brachionidae, and the
species Collotheca pelagica. Most of the Rotifera belong to euryhaline fresh-
water forms (Brachionus angularis, B. pala, B. bakeri, Anuraea aculeata,

THE BALTIC SEA 295

A. cochlearis, A. eichwaldi, A. tecta, A. quadrata, Collotheca pelagica, C. muta-
bilis, Notolca striata, Triarthra Iongiseta, Polyarthra trigla, Asplanchna
brightwellii) or the brackish-water ones (Arntrea cruciformis var. eichwaldi,
Synchaeta ba/tica, S. monopus, S.fennica and S. littoralis).

The copepod crustaceans are presented mainly by Eurytemora hirundoides,
E. affinis, E. hirundo, Acartia bifilosa (on some sites A. tonsa), Pseudocalanus
elongatus, Temora longicornis and Eurytemora hirundoides, and in the coldest
parts of the Sea Limnocalanus grimaldi (Fig. 138), among the daphnid Bos-
mina maritima, Evadne nordmanni and some species of Podon, and in the
parts of the Gulf with the lowest salinity Daphnia cucullata, Chidorus sphaeri-
cus, Leptodora kindti and other fresh-water forms. In the deeper layers of the
western part of the Sea Calanus finmarchicus, Oithona similis and Sagitta
elegans f. ba/tica are frequently encountered. The mysid M. oculata is
widely distributed throughout the Baltic Sea. The other mysids — Gastrosac-
cus spinifer, Praunus inermis and P.flexuosus — are found in the Baltic Sea in
smaller numbers. The larvae of the bottom-living animals and especially
Macoma, Hydrobia, Balanus, Membranipora and the polychaetes form a
considerable constituent of the plankton. Among the tunicates Oikopleura
dioica and Fritillaria are encountered. Among the large plankton forms the
medusa Aurelia aurita is found at times in large numbers throughout the Sea,
and in the southern part of the Sea Cyanea capillata, Pleurobrachia pileus,
Hyperia gal/a, Sagitta elegans baltica (I. Markovsky, 1950).

An interesting phenomenon was noted by J. Valikangas (1926) for the
Baltic Sea, namely that a large number of fresh-water forms develop most
rapidly not in fresh water but at a salinity of 3-45 to 5-4%0. Examples are
Tintinnidium fluviatile, Floscularia sp., Asplanchna brightwellii, Triarthra
Iongiseta, T. brachiata and others.

C. Brandes (1939) distinguishes three groups of forms in the plankton of the
Baltic Sea: the 'marine', the brackish-water and the fresh- water. Although
many of the marine forms penetrate deep into the Sea, they are fairly rare
there and do not have a mass development.

The Darss ridge forms a marked boundary as regards both hydrography
and biology. This is particularly clear in the case of plankton. Brandes has
noted that the 'marine' forms are preponderant to the west and the brackish-
water ones to the east. At a salinity of more than 9%0 the marine Ceratium tripos,
Melosira, Rhizosolenia and the ciliates Parafavella are markedly preponderant.
With further loss of salinity the brackish-water form Chaetoceros danicus and
the ciliates Helicostomella and Aphanizomenon are no less markedly pre-
ponderant. At a salinity below 6-5%0 the fresh-water forms Chlorophyceae,
Chroococcacea and some Rotifera (Brachionus, Ratulus and others) become
abundant. The change of some plankton in a cross section from the Fehmarn
Belt to deep inside the Baltic Sea is shown in Fig. 139.

Two biogeographical communities stand out clearly in the Baltic Sea
phytoplankton (I. Nikolaev, 1951): the Arctic and the Boreal Arctic of the
spring period {Table 123).

The two communities partly overlap one another, but broadly speaking
the Arctic community is more marked in the spring at a temperature of

296

BIOLOGY OF THE SEAS OF THE U.S.S.R,

Melasma

■ Chaetocero damcus

■ Chlorophyceae* C/iroocnccacea

• » » • •

Infusoria
Marine Parafnuella 8. Tintinnopsis
— Brackish Water

Fig. 139. Transition from 'marine' forms

of plankton to ' brackish- water ' forms as

one passes from the Belt into the Baltic.

A Seaweeds; В Infusora (Brandes, 1939).

2° to 5° and in the northern part of the Sea. The Boreal Arctic community
develops most at temperatures from 3° to 4° to 8° to 10°, both in the spring
and in the autumn. The two communities are characterized by their broad
euryhalinity. I. Nikolaev (1951) has pointed out that 'there is a break between
the Arctic region of distribution and the Baltic Sea in the case of these forms'.

Table 123

Arctic forms

Boreal Arctic forms

Melocira arctica
Achnanthes taeniata
Fragilaria cylindricus
Navicula grand
Navicula Vanhoffeni
Nitzschia frigida
Goniaidax catenata

Chaetoceras gracilis
Chaetoceras holsaticus
Chaetoceras wighami
Sceletonema costatum
Thalassiosira baltica
Nitzschia longissima
Paridinium achromaticum
Dinobryon pellucidum

Plankton development in various parts of the Sea. The Baltic Sea plankton is
poorer both qualitatively and quantitatively than that of the North Sea and
the parts of the Atlantic Ocean adjacent to it. As has been pointed out by
F. Gessner, this results in the greater transparency of the Baltic Sea waters
as compared with those of the North Sea. Organic matter is accumulated in
the deep depressions of the Baltic, which are poor in oxygen and rich in car-
bon dioxide. The occurrence of such deep depressions in a body of water
causes a more or less inadequate development of its plankton life, especially
as geologically the Baltic basin was fed by melt waters, poor in nutritive

THE BALTIC SEA 297

substances (Ice and Ancylus Lakes). At the same time in some sections of the
Baltic Sea, in bays and gulfs well supplied with organic matter from the main-
land, plankton development is vigorous.

I. Nikolaev (1957) notes that the seasonal changes in the qualitative com-
position of the plankton are very marked owing to the fact that what he terms
the ' marine cold-water (Arctic) communities ' and the ' fresh- water brackish
(warm- water) ones' change places during the cold and warm periods in the
year. The accumulation of nutritive matter in the upper layers of the Sea and
the arrival of the sunny period result in a springtime 'blacking' of diatomous
phytoplankton in April. Intensive flowering is at that time observed in the
inlets. During the blooming the following forms develop in specially large
masses : the diatoms Sceletonema costatum, Achnanthes taeniata, Thalassio-
sira baltica, Chaetoceras holsaticus, and Melosira arctica; and among the
peridineans : Dinobryon pellucidum. Among the zooplankton the following
take part in the spring blooming : the ciliates Mesodinium rubrum, 3 or 4
species of Strombidium, Tintinnopsis tubulosa, T. brandti, Cothurnia maritima
and others; the Rotifera Synchaeta monopus and S. baltica; the Copepoda
Pseudocalanus, Acartia longiremis, A. bifilosa, Temora longicomis, Eurytemora
hirundoides ; and in the inlets Limnocalanus grimaldi, Acartia bifilosa, Euryte-
mora hirundoides, Sagitta elegans baltica, Fritillaria borealis ; the mysids My sis
oculata var. relicta and M. mixta.

In summer these forms disappear gradually and the dominant position is
occupied by the blue-green algae Aphanizomenon Jlos-aquae and Nodularia
spigena ; the diatoms Chaetoceras wighami, Actinocyclus ehrenbergi, Thalassio-
sira nana, T. baltica ; and among the peridians Peridimum pellucumid, Dino-
physis baltica. In July and August the blue-green algae are in full bloom every-
where. By the end of the summer period the following animal forms reach
their maximum mass development : among the ciliates Helicostomella subu-
lata; the Rotifera Keratella cochlearis, K. aculeata; the Copepoda Acartis
bifilosa and Eurytemora hirundoides ; and in huge numbers the Cladocera Bos-
mina coregoni f. maritima and Evadne nordmanni. The fresh- water aspect of the
summer plankton is infringed only by the Medusa Cyanea capillata, Amelia
aurita, and the Ctenophore Pleurobrachius pileus. The larvae of the bottom-
dwelling invertebrates are also mixed with plankton in large masses at this
time of the year.

In autumn (November, December) the plankton loses its summer forms.
The diatom Coscinodiscus grani begins to grow in large masses : the seasonal
changes described are clearly shown in Fig. 140.

All plankton species are very poorly represented in the Gulf of Bothnia,
especially in the central parts of its northern half, which K. Levander called
in 1900 'practically sterile'. The plankton there does not bloom even at the
beginning of the summer when sunlight is abundant.

Indices of plankton productivity. In the Arcona depression the very small
possibility of plankton development is evident from the vertical distribution
of the basic factors of the medium. The marked differences in the temperature
and salinity of the surface and deep-water layers, which restrict vertical

298

BIOLOGY OF THE SEAS OF THE U.S.S.R.

circulation, and the poor supply of nutrient salts do not provide favourable
conditions for plankton growth. Feeble development of plankton leads to an
almost complete disappearance of phosphates and nitrates in the surface
layer. The course of this process is shown in Fig. 141. The phosphates and

Gonyaulax catenata
Melosira arctica
Dinobryon pellucidum
Thalassiosira baltica
Chaetoceras holseticus
Ch. wighami
Thalassiosira nana
Actinocyclus ehrenbergii
Peridinium pellucidum
Aphanizomenon flos-aquae
Nodularia spumigena
Chaetoceros danicus
Coscinodiscus grani

Tintinnopsis tubulosa
Mesodinium rubrum
Coturnia maritima
Helicostomella subulala
Synchaeta baltica
Keratella quadrata
Pseudocalanus elongatus
Temora longicornis
Eurytemora hirundoides
Acarlia bifilosa
A. tonsa

Evadne nordmanni
Podon polyphemoides
Bosmina coregoni maritima
Fritillaria borealis
Sagilta elegans
Pleurobrachia pileus
Mysis oculata relicta
Praunus flexuosus

III | IV | v

VI | VII

VIII

XII

YTOP

LANK

TON

—

200PLANKT0N

Fig. 140. Periods of intensive development of main plankton species in
Central Baltic (Nikolaev).

nitrates are removed in March and April by an increase in the growth of
plankton (diatom). In May the dying plankton carries them to great depths ;
thus the surface layer of water loses both its plankton and its nutrient salts.
A partial regeneration of the phosphates and nitrates in June, July and August
results in a small new increase of plankton, when Cladocera is predominant
in the zooplankton. Plankton does not develop in winter when the tem-
perature is low and sunlight scarce, although the nutrient salts are more

THE BALTIC SEA

299

concentrated as a result of winter vertical circulation. At that time Copepoda
is the dominant form. Phytoplankton begins to develop rapidly with the first

10000a:

5000

MONTHSW ШК1ЛШ1ПШП¥Ш

z
<

U-

D
Z

Fig. 141. Alterations in the quantity of plankton
and nutrient substances with the months in the sur-
face layer of the Arcona depression (Gessner, 1940).

rays of spring sunshine, using all the nutrient salts and thus killing off the
plankton. As early as 1908 C. Apstein, working on the quantitative data of

2000

WOO

500

Fig. 142. Plankton bio-
mass in the Northern
(//) and Baltic (III)
Seas and in the straits
(/), in cc in the water
column of 1 m2 section
(Apstein).

Baltic Sea plankton, noted its huge development in May in the Beltsee, the
straits between the North and Baltic Seas (Fig. 142). Moreover he had found
that plankton growth in the Baltic is considerably poorer than in the North
Sea. The quantitative indices of plankton even in the most productive

300

BIOLOGY OF THE SEAS OF THE U.S.S.R.

southern part of the Sea are much lower than those of the corresponding parts
of the Atlantic (Fig. 143).

R. Kolbe (1927) similarly noted the stimulating effect of the slightly brack-
ish water on the development of fresh-water diatoms. A high concentration

OCEAN

(Г-ЗРЗОЧР 4О'-5(Г50'-б(Г ёРЖ BALTIC
LATITUDE SEA

Fig. 143. Comparison of plankton biomass at
different latitudes in the Baltic Sea and the
Atlantic (Gessner).

of nutrient matter must be considered the main factor conditioning the mass
development of these forms in low-salinity water. N. Tchougounov has
observed a similar phenomenon in the Caspian Sea opposite the Volga delta.
Some Arctic species as, for example, Goniaulax catenata, Achnanthes
taeniata, Fragilaria cylindrus, Melosira hyperborea and others break out into
intensive flowering in the cold springtime waters of the eastern and northern
parts of the Baltic Sea.

Benthos

Bottom vegetation — qualitative composition. The distribution of flora in the
Baltic Sea is wholly similar to the qualitative distribution of its fauna. Among
the vegetable organisms marine, true brackish, and fresh-water forms may
also be distinguished, and each of these groups includes euryhaline and
stenohaline representatives.

The impoverishment of the flora owing to the lowering of salinity as one
moves from the North Sea to the Baltic is shown in Table 124, which is
copied from K. Hofmann (1940). A comparison of Tables 123 and 124 reveals
a much more intense qualitative impoverishment of the fauna than of the
flora. Many representatives of the green algae have an unusually luxuriant
group in the Baltic Sea. Among the brown algae some, like Pylaiella rupincola,
develop intensively there also. As a rule, however, sea algae do not grow pro-
perly in the Baltic Sea ; thus, for example, the large marine algae Laminaria
saccharina in the Arctic region grows to a size of only a few centimetres. The

THE BALTIC SEA
Table 124

301

Group

of
algae

Off Boguslen,
salinity of
27-33%0

Off Sud Halland

and Schonen,

salinity of

17-24%0

Baltic Sea proper

(according to

Svidelius)

Green
Brown
Red

102

29
45
56

15
20
16

Total

269

130

plants decrease in size the farther they penetrate into the diluted waters of the
Baltic, and this is accompanied, as in the case of the zooplankton, by sterility.
Thus, for example, the small forms Polysiphonia nigrescens and Rhodomela
subfusca, inhabiting the inner parts of the Baltic, multiply very rarely
(S. Sagerstrale, 1957).

Propagation to the east. Just as with the fauna the Darss ridge sets a definite
limit to the propagation of marine algae to the east. To the west of the ridge
there is an abundance of such forms as Chaetopteris plumosa, Stvlophora
tuberculosa, Spermatochnus paradoxus, Laminariajiexicaulis, Fueus eeranoides,
Ascophyllus nodosum among the Phaeophycae and different species of Por-
phyra, Chondrus crispus, Cvstoclonium purpurescens, Rhodimenia palmata,
Delesseria sanguinea, Polysiphonia urceolata and other red algae. None
of this luxuriant marine flora extends eastward of the Darss ridge, and
the flora of the Baltic Sea east of the ridge contains such brown algae as
Fucus vesiculosus, Chorda /ilium, Ch. tomentosum, Elachista fueicola, Dictyo-
siphon foeniculaceus, Gobia baltica, Strichtyosiphon (Phlocospora) tortilis,
Sphacelaria racemosa, Ectocarpus siliculosus, E. confervoides, Pylaiella
litoralis. Limnaria saccharina reaches the shores of Bornholm, and Fucus
serratus — Gotland ; among the red algae are Asterocystis ramosa, Phyllophora
brodiaei, Polysiphonia violacea, P. nigrescens, Rhodomela subfusca, Ceramium
diaphanum, Furcellaria fastigiata and others. As for the green algae, various
species of Ulva, Monostroma, Enteromorpha and Chaetomorpha may be
added.

This composition of the flora is typical for the areas with a surface summer
salinity of about 8%0. A sharp decrease of marine forms is encountered again
at the entrance to the Gulf of Bothnia and at the transition from its outer to
its inner part.

Floral plants occupy a significant place in the coastal vegetation of the
Baltic Sea; their distribution according to salinity is given in Fig. 144a.

The algae of the Baltic Sea extend to a depth of 25 m ; the number of species
according to Hessner is given in Table 125. The red and brown algae descend
deeper than the others.

Only the most hardy forms reach the northern parts of the Gulf of Both-
nia (Fig. 144), namely: Fucus vesiculosus, Chorda filum, Elachista fueicola,

302

BIOLOGY OF THE SEAS OF THE U.S.S.R.
Table 125

Depth, m

Red algae Brown algae Green algae Blue-green algae

0-2

2-4

4-8

8-12

12-18

18-25

—

Fig. 144a. Penetration of some marine and brackish-water plants far into the Baltic

Sea (Sagerstrale).

THE BALTIC SEA 303

Dictyosiphon foeniculaceus, Gobia baltica, Strichtyosiphon tort His, Ceramium
diaphanum and Asterocystis ramosa ; moreover, here they are greatly reduced
in size.

There are no tides in the Baltic Sea ; however, considerable changes in the
level of the Sea have been observed under the effect of the wind and of differ-
ences in pressure. These fluctuations are at times as large as 1 to 1-3 m. This

Polyhaline
35 30 25 18

Metohaline

SALINITY °/oo

15 10 5 2

Oligobkline

1 ' 0,5 0,1

,, tabernaemontani

Potarnogeton perjoliatus

,, jilifortnis

pectmatus

Fig. 144b. Correlation between salinity and the distribution of flowering marine

plants (Gessner).

is reflected in the zonal distribution of the coastal vegetation and can be
expressed in the following pattern (M. Waern, 1952; F. Du Rietz, 1950):

(7) The geolittoral or geo-amphibiotic belt. Covered with water either when
the sea-level rises, or by waves and the swell. The upper limit of summer
growth of algae.

(2) The hydrolittoral or hydro-amphibiotic belt. Exposed at a low level of
water, thickly covered by threadlike sea-weeds {Cladophora glomerata).
The lower limit of summer growth of algae.

(3) Sublittoral. Always covered with water.

Zoobenthos

Qualitative composition. One of the three main components of Baltic Sea fauna
is the greatly impoverished North Sea fauna (Atlantic fauna), which pene-
trates into the body of water through the straits and undergoes, with the fall
in salinity, a marked loss in the number of species (Fig. 145), and the degenera-
tion of individuals. K. Brandt was the first to estimate the Atlantic fauna in
the Baltic Sea (1897). Ekman revised Brandt's data in 1935 from data
published in the series Die Tierwelt der Nord- und Ostsee. We give below

304

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Ekman's table with some additions from Brandt's table, from Remane
(1940), and new additions (marked by asterisks in Table 126) according to
S. Sagerstrale (1957).

30-35 25-30

Fig. 145a. Alteration of salinity from the passage from the North Sea far into the
Baltic. A Surface salinity in February ; В Change of salinity along the vertical cross
section in August (Remane and Wattenberg). Numbers of animal species are

encircled in A.

There is an excellent summary of present knowledge concerning the distri-
bution of Baltic Sea fauna in the works of the Finnish investigators J. Vali-
kangas (1933) and S. Sagerstrale (1957), and the Swedish zoologist Ekman
(1933 and 1935).

Propagation to the east. The most common Baltic hydroids— Clava squamata,
Sertularia pumila, Obeliageniculata and Campanulariaflexuosa—are character-
istic only of the western part of the Sea. Of the two Medusa known to exist in

THE BALTIC SEA

305

the Baltic Sea — Cyanea capillata and Aurelia aurita — the second penetrates
farther to the east and north, reaching the shores of Finland ; it is encountered
in areas with 5-75 to 6-0%0 salinity at the surface and 7%0 at the bottom. Four
actinians penetrate as far as Kiel Bay — Helcampa duodecimcirrata, Urticina
felina, Metridium dianthus and Sagartia viduata ; but they do not go farther
east than Kiel Bay.

There is a marked decrease in the number of polychaete species in the Belt ;
even in the southern part of the Baltic Sea only 25 species of them are known
including: Travisiaforbesi, Syllis armillaris, Nereis pelagica, Fabricia sabella,
Arenicola marina, Nephthys ciliata, N. coeca, Scoloplos armiger, Terebellides

North Sea

SnagerracK

^ Kattegat

500
400
300^
200

^ Belt

1 r/,

Bornholm district

Finnish and Bothnia <jul[s

35 33 31 29 27 25 23 21 19 17 15 13 II 9 7 5 3 I 0%0

Salinity

Fig. 145c. Decrease in number of species from North

Sea to Baltic compared with the decrease in salinity

(Zenkevitch).

stromii, Pygospio elegans, Harmothoe sarsi and Nereis diver sicolor. In the Belt
and the Sound about 143 species of polychaetes have been identified (Elias-
son, 1920). Pygospio elegans and Terebellides reach the entrance of the Gulfs
of Finland and Bothnia (Fig. 146). Nereis diver sicolor and Harmothoe sarsi
penetrate into the Gulfs (a little farther into the Gulf of Finland) and there
survive a lowering of salinity in the surface layers to 5-25%0.

Among the Gephyrea only Priapulus caudatus penetrates into the Baltic
Sea, remaining in the most westerly parts of it, while Halicryptus spinulosus,
which thrives in great numbers at the bottom of the Baltic Sea, reaches half-
way up the Gulf of Finland and to the Aland Islands and the Quarken of
Finland (Fig. 146).

Bryozoa are represented in the Baltic Sea proper by only four forms ; among
these only Membranipora pilosa f. membranacea is still found at a salinity of
4%0 (Fig. 146).

According to the summary due to Haas (1926), only five of the 87 species

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THE BALTIC SEA

307

of bivalves found in the Kattegat exist in the central part of the Baltic Sea, and
each of these forms a dense population in separate areas of the Sea. These
forms are, in order of decreasing importance : Macoma baltica, My a arenaria,

Fig. 146. Penetration of some marine and brackish-water animals far into the Baltic

Sea (Sagerstrale, 1957).

Cardium edule, Mytilus edulus and Macoma calcarea. Macoma baltica, far
and away the most dominant form not only among the molluscs but among
the whole fauna, has found in the Baltic Sea exceptionally favourable condi-
tions for existence. In the Bornholm area two more bivalves — Astarte ellip-
tica (synonym: A. compressa) and A. borealis (a cold-water relict) — should
be added to the five given above. Farther to the west, within the transitional

308 BIOLOGY OF THE SEAS OF THE U.S.S.R.

region, the number of molluscs increases markedly, and such typical North
Sea forms as Nucula nucleus, Mya truncata, Corbula gibba, Saxicava rugosa,
Teredo navalis, the species Syndesmya and Venus appear, while the Kattegat
is the habitat of various species like Leda, Yoldia, Area, Ostrea and Pecten.
Macoma baltica (Fig. 137) penetrates farther than any other form into the
Gulfs of Bothnia and Finland, surviving a salinity of 3-5 to 4%0, and even
multiplying intensively in it. Next comes Mytilus edulis, with a salinity limit
of 4-5 to 5%0, then Mya arenaria with a limit of 5%0 and Cardium edule reach-
ing a limit of 5-25 to 5-50%0.

It is characteristic that in the Gulf of Bothnia along the shores of Finland
all forms penetrate farther to the north than along the coast of Sweden ; this
is linked with the prevailing currents, which skirt the isohalines of the Gulf
of Bothnia to the northwest.

Of the numerous Kattegat Opisthobranchia only five species penetrate into
the Baltic Sea proper : Retusa obtusa (as far as Gotland), Calvina exigua (as
far as the Stockholm Quarken), Embletonia pallida, Alderia modesta and
Limapontia capitata (the last three species as far as the southern shores of
Finland) (see Fig. 146).

The number of Prosobranchia species in the Kattegat is more than 80,
in the Baltic Sea itself only three. Hydrobia baltica is the only species to reach
the Finnish coast, and along the southern shores of Sweden Hydrobia palu-
destrina {jenkimi) reaches Stockholm (see Fig. 146).

Among the 1 1 species of marine Copepoda which penetrate into the Baltic
Sea proper, four forms common there should be noted : Acartia longiremis,
Centropages hamatus, Pseudocalanus elongatus and Temora longicornis.

Of the three Cirripedia species found in the Baltic Sea, Balanus balanus, B.
cretanus and B. improvisus, only the last moves far into the Sea; it is still
found in considerable numbers off the shores of Finland, at a salinity of
5%0 (Fig. 146).

Among the Amphipoda, of which there are 300 species in the North Sea
and 132 in the Kattegat, only 12 are found in the Baltic Sea, and only 9 marine
and brackish-water species in the waters of Finland. They are : Pontoporeia
femorata, P. affinis, P. sinuata (a very rare endemic species), Calliopius rathkei,
Gammarus locusta, G. duebeni, Corophium volutator, C. lacustrae and Pallasea
quadrispinosa. Pontoporeia affinis, both Gammarus and Corophium volutator
reach almost the innermost parts of the Gulfs of Bothnia and Finland (Fig.
146).

The distribution in the Baltic Sea of the two Pontoporeia shows character-
istic differences. P. femorata reaches only the Aland Islands and partly enters
the Gulf of Finland. P. affinis is an Arctic brackish-water form. The density
of its population increases gradually as one moves north and east, as also
happens with Pallasea quadrispinosa and Limnocalanus grimaldi (Fig. 146).
P. affinis lives in many lakes of Northern Europe and Northern America as a
relict. Pallasea quadrispinosa is found in water with a salinity of up to 5 to
6%0 off the Swedish shores of the Central Baltic and the Gulf of Bothnia and
in the Gulf of Finland.

Among the Isopoda, Mesidothea entomon and Iaera albifrons enter farther

THE BALTIC SEA 309

into the zones of lower salinity than the other forms ; Idothea baltica enters
both Gulfs, while Idothea granulosa and /. viridis do not go beyond the en-
trances of the two Gulfs.

Decapoda of marine origin are very poorly represented in the central area
of the Baltic Sea. There are 64 species of decapod crustaceans in the Swedish
waters of the Skaggerak and Kattegat ; in Oresund there are 24, and ir. Kiel
Bay 10. Only two species — Crangon crangon and Leander adspersusvar.fabricii
— inhabit the central basin.

Apart from Mysis oculata, which densely populates this Sea, Mysis vulgaris
and M.flexuosa among the Mysidacea penetrate far into the Sea.

Of the echinoderms only the most euryhaline, Asterias rubens and Ophiura
albida, are found in the Baltic Sea itself.

Finally the sea fish most common in the Baltic Sea are : the brackish-water
race of herring, which occupies first place in the fishing industry ; Clupea
harengus membras (the so-called Baltic herring), and then the following : CI.
sprattus, Gadus morrhua, Lumpenus lampetriformis, Cottus scorpius quadri-
cornis, Liparis liparis, Cyclopterus lumpus, Pholis gunellis, Zoarces viviparus,
Spinachia spinachia, Nerophis ophidion, Siphostoma typhle, Ammodytes lan-
ceolatus, A. tobianus, Pleuronectes flesus and Bothus maximus.

Decrease in size. Like many other groups of organisms with a calcareous
skeleton, the molluscs diminish in size with decreasing salinity as one moves
eastwards (Fig. 147). Mytilus edulis, which is up to 150 mm long off the shores
of Great Britain, is no more than 110 mm long in Kiel Bay, no more than
40 mm off the Finnish coast, and only 20 to 25 mm at the far end of the Gulfs
of Bothnia and Finland. Off the Aland Islands Mytilus is no more than
37-5^mm long, while off Liban it is 38-5 mm. West of Bornholm it reaches
55-5 mm. The fluctuations in the maximum size within the limits of the Baltic
Sea proper are small, and a marked increase occurs only in the transitional
region*of the Belts and Oresund, this being related to changes in salinity.
The same is observed with Cardium and Mya. The maximum size of Cardium
edule at the northern boundary of its distribution is 18-5 mm; northwest of
the Aland Islands it is 23-7 mm, while in the North Sea its average size is
45 mm. In the North Sea and Kiel Bay the largest Mya arenaria is about 100
mm long ; off Gotland it is 58 mm, and at the eastern boundary of its distri-
bution in the Gulf of Finland it is 36-5 mm. In the case of many forms the
decrease in their size at the limits of their habitat, in the less saline sectors of
the Baltic Sea, is linked with the loss of reproductive power. The adult forms
exist, but either multiply very rarely or not at all. At a salinity below 6%0 the
normal sexual cells are formed in Amelia aurita, but the scyphistomae are not
developed (Sagerstrale, 1951).

At the same time it is interesting to note that this rule of a decrease in size
associated with a fall in salinity does not hold good with certain forms.
Macoma baltica, for example, is 22 mm. long in the North Sea and retains this
length in the Baltic Sea. It is true there are some indications that at the extreme
limits of its distribution in the Gulfs of Bothnia and Finland the size of
M. baltica falls to 15 to 18 mm. According to K. Levander (1899), however,

310

BIOLOGY OF THE SEAS OF THE U.S.S.R.

65-Ъ

60-
55 ■

45 \
40

35
30
25-
20-

15-

10
5 1
0

t~"?*<A

■Пса \y.

Byth Lma tentacutata
Theo doius ftuwa h its

35 30 25

20 15 10
SALINITY

Fig. 147. Changes in the length of the body
of marine bivalves and fresh-water Gastro-
poda with change in the salinity of the
medium (Remane, 1934).

Macoma reaches 21 to 24 mm in the areas west of Helsingfors, which are most
favourable for its existence (as regards its feeding). For the rest, both Cardium
and Mytilus are larger in this area. Unlike Mytilus, Mya and Cardium men-
tioned above, the size of Macoma is clearly only slightly affected by changes
of salinity. Macoma baltica becomes smaller with the depth of its habitat
{Table 127).

According to H. Luther's data (1908) Macoma baltica from the inner bays
of the Gulf of Finland is larger in size than the samples from the Littorina
Sea deposits.

At the same time, marine forms without a calcareous skeleton often do not
undergo a decrease in size, as for example the amphipods Gammarus zad-
dachi oceanicus and Corophium volutator, and the shrimp Leander adspersus
fabricii, which are the same size in Danish waters as in the Gulf of Finland.

Table 127

Depth, m

Sedimentation

Longest shell, mm

1-5

1-2-2-5
35-36

Gyttja

Sand

Gyttja

21-24
16
15

THE BALTIC SEA 311

Many fresh-water forms decrease in size when they penetrate into brackish
water as, for example, Theodoxus fluviatilis or Bithynia tentaculata.

The change in the size of the body with the passage from one medium to
another is illustrated in Fig. 147.

A. Remane (1935) has observed that alongside the decrease in size there is
a reduction of the calcareous skeleton as one moves into less saline areas.

Brackish-water forms are also reduced in size as they move into fresh
water, but they do not become smaller when they move into more saline
waters ; examples are Gasterosteus aculeatus, Pleuronectes flesus, Hydrobia
ulvae, etc.

Preponderance of North Atlantic littoral species. One of the most remarkable
features of Baltic Sea fauna is the huge preponderance of typical littoral
forms belonging to the North Atlantic. Almost all the main forms of the
littoral of the North Sea, Scandinavia, the Murman Peninsula and the White
Sea are encountered here : among the polychaetes : Fabricia sabella, Arenicola
marina, Pygospio elegans, Nereis diversicolor, Nephthys coeca; among the
Gephyrea: Priapulus caudatus and Halicryptus spinulosus; among the mol-
luscs : Macoma baltica Mya arenaria, Cardium edule, Mytilus edulis and some
species of Hydrobia and Limapontia capitata ; among the Crustacea : Gam-
marus locusta, G. duebeni, Jaera albifrons, Balanus improvisus; among the
echinoderms : Asterias rubens ; and even the common littoral fishes : Pholis
gunellus and Zoarces viviparus. This phenomenon, wholly exceptional in its
scale, of almost all the littoral fauna migrating into the sublittoral, deserves
the closest attention of biologists.

Presumably the colonization of the sublittoral in the Baltic Sea by the
biocoenosis Macoma baltica could have taken place only in circumstances
under which this horizon was poorly colonized by other organisms. The
phenomenon of competition or, so to speak, the biological resistance offered
to the colonization of the sublittoral by the fauna already existing there, was
either very weak or non-existent.

Probably during the Littorina Period the littoral biocoenosis of Macoma —
highly eurybiotic as regards salinity, temperature and oxygen — penetrated
without difficulty into the Baltic Sea. Meeting no serious competitors, it
populated densely the upper levels of the sublittoral. Eurytopic to a high
degree, these littoral forms penetrated farther into the Baltic Sea to waters
which are less saline. The Baltic Sea is tideless and their allied biotope is
absent there but, owing to their euryhalinity and the absence of competition,
they took almost complete possession of the upper level of the sublittoral.
The Arctic relict cold-water community is predominant at the lower hori-
zon but it too moved to much lower levels : it is related to the zone of the
shore off Greenland, while in the Baltic Sea it is concentrated in the deep-
water zone.

Fresh-water forms. As one moves farther into the Sea the marine forms be-
come less numerous at the same time as the fresh-water forms come more and
more into evidence ; in the least saline parts of the Sea they form a considerable,

312 BIOLOGY OF THE SEAS OF THE U.S.S.R.

and at times the predominant, part of the population. They penetrate into
Baltic Sea waters with a salinity of 4 to 6%0, while some forms are found
even at a salinity of 7%0. Among the fresh-water plants which penetrate the
saline Baltic waters we can point out the water moss : Fontinalis dolecorlica,
Phragmites communis, several species of Scirpus, Potamogeton, Myriophyl-
lum, Ranunculus, Chara, Enteromorpha, Cladophora and Ulotrix.

The larvae of insects (chironomid, dragonflies, mayfly, etc.) form a highly
characteristic part of the population of the considerably diluted waters of the
Sea.

In the least saline parts of the Sea the following fresh-water molluscs are
strongly represented: Neritina (Neritella) fluviatilis, Bythinia tentaculata,
Physa fontinalis, Paludinacontecta, Limnaeastagnalisvar. livonica, L. ovatavar.
baltica, L. peregra, L. palustris var. litoralis, Planorbis vortex, Anodonta and
Unio. Among the fresh-water crustaceans, Asellus aquaticus is common in the
off-shore waters (up to 6T3%0). In the plankton, even in the open sea, such
forms of Rotifera as Anuraea cochlearis, Notholca longispina and Asplanchna
priodonta are common.

Among the fresh- water fish, Coregonus lavaretus, С albula, Abramis brama,
Esox lucius, Lota lota, Perca fluviatilis and Thymallus thymallus are widely
distributed and are of commercial importance.

A certain number of plant and animal forms — emigrants from fresh waters
and now living in the less saline parts of the Baltic Sea — are either very rare
or completely absent from the adjacent fresh-water lakes. Among the plants
one may name : Najas marina, Zannichella repens, Z. pedunculata, Potamo-
geton panormitonus, Myriophyllum spicatum and Utricularia neglecta; and
among the animals : the Porifera Ephydatia fluviatilis, the mollusc Theodoxus
fluviatilis, together with some species of water bugs and water beetles.

Penetration into the Baltic Sea of new species from the Atlantic. The Baltic
is a young sea, but it may be assumed that the relationships of the components
of its fauna are fairly stable, and that the population of it by marine forms, and
the distribution of different inhabitants throughout the Sea, are in the main
a complete process. Some forms, however, are still penetrating it, either actively
or passively, and migrating from west to east.

Among new, contemporary immigrants the following groups may be dis-
tinguished: (/) immigrants from distant seas; (2) new immigrants from the
North Sea ; (5) forms migrating from the western parts of the Sea to the central
and eastern parts.

To the first group belongs the diatom algae Biddulphia sinensis, the gastro-
pod mollusc Potamopygus jenkinisi, the copepod Acartia tonsa and the bryo-
zoan Alcyonidium palyonum, two crabs — Rhitzopanopeus harrisi spp. triden-
tata (Birstein, 1952) and Eriocheir sinensis, perhaps the most interesting
representative of this group, is also called the Chinese hairy-legged crab ; it has
rapidly populated the shores of the North and Baltic Seas, as if it had found its
second home there. Some earlier immigrants should be included in this group,
such as Mya arenaria, found off the shores of Europe since the sixteenth and
seventeenth centuries (I. Hessle, 1946), and some Caspian elements which

THE BALTIC SEA

313

have penetrated from the south through river systems : Cordylophora caspia,
Dreissena polymorpha and Corophium curvispinum. I. Nikolaev (1951) points
out that brackish-water forms are the most significant in this group. Evidently
they were chiefly transported across the oceans by ships which remained for a
long time in harbours, where the salinity of the water is usually low and vari-
ous brackish-water forms are numbered among the inhabitants.

The Chinese crab was first discovered in the lower waters of the Elbe and
Weser. It has been suggested that it was brought from China around 1912 by
ships, possibly in their water tanks or in the growths which covered the sides
of the ship. During the last twenty-five years the crab has migrated along the
southern shores of the North Sea, the straits and the shores of the Baltic Sea,

го intend of 1924
VZHfrom1925 to the

mm 1930-1932

E3 W33-1935

Fig. 148. Distribution of the Chinese crab Eriocheir

sinensis in the Baltic basin (Peters and Panning, 1933).

Penetration up the rivers is shown by О and #■

and up the river systems. Its migration in the last fifteen years is shown on the
chart (Fig. 148). The fact that in new places the crab appears first of all near
large ports is evidence of its being brought by ships. Now it has settled over
an area of no less than 1,000,000 km2. This crab is a small, very active animal
(the largest are 7 cm long) which in unfavourable conditions is capable of
coming out on land and traversing it for quite considerable distances. In
come areas, especially in Germany, the Chinese crab has multiplied greatly
and become a very serious pest. It damages fishing nets, but the greatest harm
it does is through the destruction of the shore by its innumerable burrows. A
persistent campaign is waged against it. In some places as many as 50,000
crabs are caught in a day. In the Elbe alone the catch (1935) was more than
500 tons a year, i.e. no less than ten million specimens. The crab cannot
breed in fresh water ; it comes down to the estuaries for this purpose.

I. Nikolaev has assembled the data on the second and third groups of forms

314 BIOLOGY OF THE SEAS OF THE U.S.S.R.

(1949). He points out that in the changes of Baltic Sea flora and fauna account
should be taken not only of the qualitative factors — the appearance of a
formerly unknown form, but also the quantitative ones — a rare form can be-
come predominant.

Among the species formerly unknown in the Baltic Nikolaev notes the
diatom algae Coscinodiscus granii and the mullet Mugil capito, and among the
forms which have migrated into the eastern and northern areas of the Sea :
Sagitta elegans baltica ; the amphipod Bathyporeia pilosa ; and among the
fish : anchovy (Engraulis encrassicholus), marine pike (Belone belone), mackerel
{Scomber scomber) and the marine turbot (Onos cimbrius).

Quantitative biocoenotic distribution of benthos. As one moves farther into
the Baltic Sea an impoverishment is observed, both in species and in the
variety of bottom communities.

Petersen established eight benthic biocoenoses in a small area of the
Skagerrak; in the German Belt there are only two of these, the 'Abra bio-
coenosis' and the ' Macoma baltica biocoenosis'. All the rest of the compara-
tively huge area of the Baltic Sea bottom is occupied by only one community,
the Macoma baltica.

Data for an estimate of the qualitative and quantitative distribution of
the bottom communities of the Baltic Sea are given in the works of A. Hag-
meier (1926, 1930), G. Thulin (1922), Chr. Hessle (1924), S. Sagerstrale (1923),
A. Remane (1933, 1940, 1955), F. Gessner (1933, 1940, 1957), and K.
Demel and his collaborators (1935, 1951, 1954). The quantitative biocoenotic
distribution of the bottom fauna of the Baltic Sea presents a fairly simple
picture in consequence of the qualitative impoverishment of the population
and the two important factors of the medium — lower oxygen content in the
deeper layers and the gradual fall of salinity from west to east ; this general
picture is fully brought out by the researches mentioned above. The distri-
bution of the main bottom communities throughout the Baltic Sea is given in
Fig. 149. The data refer to the average benthos biomass in g/m3.

In general, moving from west to east, we can distinguish in the Baltic Sea
four main biocoenoses : (7) Cyprina + Astarte (a modification of Petersen's
'Abra biocoenosis') in the German Belt (Kiel and Mecklenburg Bays and the
adjacent sea areas) ; (2) Macoma calcarea (Arcona and Bornholm depressions
and the adjacent sea areas) ; (5) Macoma baltica and Astarte borealis (most of
the Baltic Sea and the Gulfs of Bothnia and Finland) ; and (4) Pontoporeia+
Mesidothea (the northern part of the Gulf of Bothnia).

(1) Cyprina-\- Astarte biocoenosis. According to the results of Petersen's work
in the deeper parts of the southern Kattegat, the dominant forms are Abra
alba, Macoma calcarea, and Cyprina islandica, while in the shallower Kiel
and Mecklenburg Bays Cyprina islandica and Astarte borealis become markedly
preponderant ; they provide, at some stations, a biomass of up to 450 g/m2 in
the first of these bays, and 190 g/m2 in the second. The average biomass of the
whole of this area is 176-6 g/m2. 110-2 g of this consists of Cyprina islandica
and 32 g of Astarte borealis. All the rest provides only 34-4 g/m2 (see Fig. 150).

THE BALTIC SEA

315

In these areas west of the Darss ridge, a still considerable qualitative variety
of benthos is observed ; there are a large number of worms : Nephthys ciliata,
N. coeca, Terebellides stromi, Pectinaria koreni, Scoloplos armiger and

PONTOPOREIA AFFINIS

У:::: :\ mesidothea community

.0000
0000
0000

MACOMA BALTICA

COMMUNITY

IMPOVERISHEDCOMMUNITY
OF POLYCHAETA
CRUSTACEA SCOLOPLOS —
PONTOPOREIA FEMORATA
MESIDOTHEA
MACOMA CALCAREA

COMMUNITY

Fig. 149. Distribution of bottom communities in the Baltic Sea (various authors)

Rhodine loveni are especially frequent ; among the molluscs : Macoma calcarea
and M. baltica ; Syndesmya alba, which is already found in large numbers in
the western part of the Northern Belt ; Modiolaria nigra ; among the crusta-
ceans : Diastylis rathkei, Pontoporeia femorata ; and among the echinoderms :
Ophiura albida.

316

BIOLOGY OF THE SEAS OF THE U.S.S.R.

The region of the typical Baltic mesomixed and oligomixed communities
only begins, however, east of the Darss ridge (Fig. 151). This ridge may in fact
be called a distinct quantitative-biocoenotic boundary (I. Valikangas, 1933).
The quantitative researches of the Swedish investigator G. Thulin (1922), and
of the Polish workers under K. Demel (1935, 1951, 1954), covered the Arcona
and Bornholm depressions, and in addition Demel's investigations covered all

102-5

31-11

3-03 2 384

] 9
10
11
12

Fig. 150. Composition of typical bottom communities of the
Baltic Sea. Numerals above circles denote mean biomass in g/m2
(Zenkevitch). 1 Cyprina islandica; 2 Macoma calcarea; 3 M.
baltica; 4 Astarte borealis; 5 Cardium edule; 6 Polychaeta; 7
Mesidothea; 8 Mytilus edulis; 9 My a arenaria; 10 Crustacean,
1 1 Pontoporeia affinis ; 1 2 Others. / Cryprina- Astarte of Kiel Bay ;
// Macoma calcarea of Bornholm depression; /// Macoma-
Cardium on Oderbank (to the north of Pommern); IV Macoma
baltica community of southern half of Gulf of Bothnia ; V Deep-
water community of the same part (Pontoporeia-Mesidothea) ;
VI Community of northern part of the Gulf of Bothnia (Macoma-
Pontoporeia-Mesidothea).

the southern part of the Sea. A. Hagmeier (1923-30) surveyed the same areas
in part, and also the southern Baltic. Farther to the north and as far as
the end of the Gulf of Bothnia lies the area investigated by the Swedish scien-
tist Chr. Hessle (1924). Along the Finnish shores of the Gulf of Finland the
Finnish investigator S. Sagerstrale conducted research (1933). A. Schurin has
described the distribution of benthos in the Bay of Riga (1957). The researches
of these investigators make it possible to give a quantitative biocoenotic
estimate of the Baltic Sea benthos.

On the whole it can be assumed that to the east of the Darss ridge there is a
single bottom biocoenosis, Macoma baltica; this form, however, develops

THE BALTIC SEA

317

especially in the shallower parts of the Sea and, in general, as depth increases
it gradually disappears.

(2) Macoma calcarea-\-Astarte borealis biocoenosis. In the deeper northern
half of the southwestern part of the Baltic Sea (below 40 m) the benthos com-
position undergoes a change — Macoma baltica decreases markedly in num-
bers, or disappears altogether, and is replaced by Macoma calcarea and
Astarte borealis, the former being more abundant in the Bornholm depression
and the latter in the Arcona depression (Fig. 150).
In some places in the Arcona depression Astarte borealis forms very dense

Fig. 151. Graphs of density indices (Zenkevitch).
A For the mesomixed community of the Arcona depres-
sion ; В For the oligomixed community of the inside part
of the Gulf of Bothnia. For A : Macoma baltica, Tere-
bellides stromi, Halicryptus spinulosus, Astarte borealis,
etc. ; for В : Pontoporeia affinis, Macoma baltica, Mesi-
dothea entomon.

populations with a biomass of 177 g/m2 and 346 specimens per 1 m2. Besides
the two mollusc forms, crustaceans are represented there at depths of 100 to
150 m by Pontoporeia femorata, Diastylis rathkei and the worms by Harmothoe
sarsi, Scoloplos armiger, Aricidea suecica, Terebellides stromi, Priapulus cau-
datus and Halicryptus spinulosus. The Astarte borealis community occupied
the Arcona and Bornholm depressions, extending to the east right up to the
entrance of the Bay of Danzig. The average benthos biomass for the Bornholm
region is about 102-5 g/m2.

(3) Macoma baltica biocoenosis. A little to the east of Mecklenburg Bay the
typical Macoma baltica biocoenosis begins; it remains almost unchanged
right up to the Bay of Danzig through the southern, shallower parts of the
Sea. The average biomass of this whole area may be taken as about 48T5 g/m2
(see Fig. 150). Macoma baltica begins here to become the dominant benthos
form. Some other forms, however, are well represented still : Cardium edule,
Mytilus edulis and Mya arenaria, Macoma calcarea, Astarte borealis and

318

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Syndesmya alba are poorly represented here. Among the worms the following
may be noted : Nephthys ciliata, Scoloplos armiger, Nereis diversicolor, Pygos-
pio elegans, Terebellides stromi, Harmothoe sarsi, Halicryptus spinulosus;
among the crustaceans: Diastylis rathkei, Pontoporeia femorata, Bathyporeia
pilosa and, in altogether negligible numbers, Mesidothea entomon. The last
named, like Pontoporeia affinis, has its western limit of distribution east of
Mecklenburg Bay, becoming a mass form to the east and north. On the other

Fig. 152. Distribution of Macoma biocoenosis in southern Baltic Sea (Demel and

others, 1954).

hand such forms as Mya, Cardium and Mytilus gradually disappear as one
moves eastward.

K. Demel and his collaborators W. Mankowski and Z. Mulicki (1951,
1954) as a result of comprehensive investigations over a number of years/were
able to draw a very interesting picture of the qualitative and quantitative dis-
tribution of the bottom fauna of the southern part of the Baltic Sea (south of
56° 45'). Demel reports that the Macoma baltica biocoenosis covers the whole
of the shallow zone of the southern part of the Baltic Sea (Fig. 152). In deeper
places Macoma baltica gradually disappears and is replaced by the biocoenosis
of worms (Scoloplos armiger, Halicryptus spinulosus, Priapulus caudatus)
and crustaceans (Pontoporeia femorata and Diastylis rathkei) (Fig. 153).
Demel thinks that the propagation of Macoma baltica into the depths is limited
by the lack of oxygen. In the greatest depths of the Gotland depression colonies
of Scoloplos armiger alone have been discovered. The region inhabited by

THE BALTIC SEA

319

Astarte borealis extends through the Arcona depression and the Slypsk
trough and farther to the east; the Bornholm depression is inhabited by
Macome calcarea (Fig. 1 54). In the Slypsk trough Terebellides stromi appears
in great masses, and Demel thinks it possible to distinguish in this area an
Astarte-Terebellides biocoenosis.

At lesser depths in the southern part of the Baltic Sea Mytilus edulis is
numerically a markedly preponderant form (Fig. 155), accompanied by
Cardium edule, My a arenaria, Macoma baltica and others.

PONTOPOREIA FEMORATA

* ж. ■ on the a'

Fig. 153. Total biomass of Pontoporeia femorata (20,460 tons) and of Pontoporeia
affinis (29,533 tons) (Demel).

The mass forms of the fauna at times provide a great density of population
as regards number of specimens {Table 128).

In comparison with the middle and northern parts of the Baltic Sea, the
large number of Mytilus, Astarte and Macoma calcarea is conspicuous.
K. Demel and Z. Mulicki (1954) have also drawn a chart of the distribution
of the benthos biomass in the southern part of the Baltic Sea (Fig. 1 56) and
its contents by separate components {Table 129).

Thus 90 per cent of the total biomass of bottom fauna consists of bivalves.

Some visual outlines of the distribution of bottom fauna are also given by
Demel and Mulicki; the meridional cross section through the Bornholm
depression is given in Fig. 157.

The same picture, as for all the southern part of the Sea, is repeated on a

Fig. 154. Total biomass of Astarte borealis (without shells) in southern Baltic Sea

(176,463 tons) (Demel).

MYTILUS roUUb

Fig. 155. Total biomass of Mytilus edulis (without shells) in southern Baltic Sea

(3,407,263 tons) (Demel).

THE BALTIC SEA
Table 128

321

Max. no of specimens

Max. biomass,

Forms

per 1 m2

g/m2

Macoma baltica

2,455

Astarte borealis

2,065

126

Macoma calcarea

110

64-68

Terebellides stromii

333

3-38

Pontoporeia femorata

900

4-39

P. affxnis

1,779

18-55

Diastylis rathkei

115

Scoloplos armiger

515

7-5

Halicryptus spinulosus

92-4

6-4

Mytilus edulis

7,010

31-0

Mesidothea entomon

7-8

small scale in the Bay of Danzig. At a depth of less than 100 m Macoma
baltica biocoenosis is preponderant ; deeper down it gives way to Scoloplos
armiger, Mesidothea entomon and Pontoporeia femorata.

Demel distinguishes two main groups of bottom biocoenoses : the deeper
and colder-water biocoenosis consisting exclusively of stenothermic cold-
water species, and the biocoenoses of shallower and warmer coastal waters

Fig. 156. Zoobenthos total biomass in southern Baltic Sea without Mytilus edulis
(Demel and Mulicki, 1954).

322

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 129

Species

Average biomass,

g/m2

Total biomass for
southern part of
Baltic Sea, tons

Mytilus edulis
Macoma baltica
Astarte borealis
Mesidothea entomon
Macoma calcarea
Pontoporeia affinis
P. femorata
Diastylis rathkei
Others

0-03-3,104

3-1-23-9

10-100

0-7-28-6

6-2

1-5

0-5

0-5-2-0

Total

3,407,263*

837,008

176,463

48,560

46,614

29,533

20,460

6,756

190,740

4,763,397

All molluscs given in wet weight without shells.

VALUE UNOETIRMIHED
•mmik Ш шсопи милел ПГО|«<

STATION П0

DCPTH 16 П *»

OXYOCN t.t »2 70

PW)M«n0H Of SAIT7.» 7.8 10.»

TIMPIOATVRE 7.3 «.4 г.8

в» 70 6» »6 51 14 m .

i.jt l.l 1.4 j* 7.0 (.9 ml/l

i«.o 15.7 I«I4.7 as *•• %

».o 6.J *7 Ao 4.6" J* К

Fig. 157. Meridinial contour of the quantitative distribution of zoobenthos through
the Bornholm region of the Baltic Sea (Demel and Mulicki, 1954).

THE BALTIC SEA

323

comprising mainly eurythermic species. The first group is qualitatively poor
and uniform, consisting almost exclusively of such Arctic species as Mesido-
thea entomon, Polynoe cirrata, Mysis mixta, Halicryptus spinulosus, Ponto-
poreiafemorata. Demel likewise includes the relict forms Terebellides stromii,
Macoma baltica and Diastylis rathkei. The shallower zone is inhabited by a
fairly varied fauna ; its most characteristic forms are : Cardium edule, Mya
arenaria, Nereis diversicolor, Macoma baltica, Mytilus edulis, Gammarus
locusta and Balanus improvisus. The boundary of the two groups of fauna (the
surface and the bathypelagic) lies at a depth of 25 to 40 m.

As regards the fate of the Macoma baltica biocoenosis farther north, it should
be pointed out that the area of Gotland Island serves as a kind of boundary
dividing this biocoenosis into two parts. South of Gotland the benthos has not
yet the distinct oligomixed nature characteristic of the more northerly
regions. Mytilus, Mya and Cardium do not yet lose their importance com-
pletely ; on the other hand such forms as Pontoporeia affinis and Mesidothea
entomon are still not yet developed to a significant extent. Pontoporeia femo-
rata still supplants its kindred species P. affinis. These two characteristic
biocoenoses of the Baltic fauna are adapted to two different biotopes. P.
affinis inhabits the less saline, shallower parts of the Sea and is often pre-
ponderant on sand bottoms. P.femorata keeps to more saline, deeper layers
and is frequently found in large numbers on mud bottoms.

The benthos composition in the area of Gotland and the Aland Islands is
set out in Table 130.

Table 130

Mesidothea
entomon

Pontoporeia
femorata

Macoma
baltica

Chironomidae

Depth,
m

Total

weight,

No. of

speci-
mens

Wt,

speci-
mens

Wt,

speci-
mens

Wt,

speci-
mens

Wt,

g/m2

per m2

g/m2

per m2

g/m2

per m2

g/m2

per m2

g/m2

0-10

—

180

14-21

19-28

11-50

1-85

208

0-69

7-17

22-67

0-52

11-78

>50

2-80

0-40

005

—

11-96

Encircling Gotland Island at depths below 80 m lives an impoverished
benthic community. As the depth increases, firstly the molluscs disappear,
then the worms and finally the crustaceans. Only the polychaete Scoloplos
armiger can five on mud bottoms infected with hydrogen sulphide. The
last representatives of the remaining animal population — Pontoporeia femorata
and Terebellides stromii — disappear a little earlier.

Another very characteristic Baltic Sea form, Mesidothea entomon, which
is abundant in the western and northern parts of the Sea, gradually disappears
south of the latitude of Aland Island.

As one moves farther to the north into the Aland Islands area the selection
of saline-loving forms {Cardium edule, Nereis diversicolor, Terebellides stromii,

324

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Harmothoe sarsi, Halicryptus spinulosus, Pontoporeia femorata, Idothea
granulosa and /. viridis) becomes poorer still ; there is a further drop of salin-
ity to 1%0 ; this is the extreme northern limit of its distribution. It is practically
never found north of the Aland Islands, where Pontoporeia affinis, Mesidothea
and Chironomidae begin to appear in considerable numbers.

The quantitative relationship of the main forms of benthos given in Table
131 is characteristic of the area of the Aland Islands.

Table 131

Mesidothea

Pontoporeia

Macoma

Chironomidae

Depth,
m

No. of
speci-
mens

per m2

Wt,

g/m2

No. of

speci-
mens
per m2

Wt,
g/m2

No. of
speci-
mens

per m2

Wt,

g/m2

No. of
speci-
mens

per m2

Wt,

g/m2

Total
weight,

g/m2

0-10

11-50

>50

8-30
6-65

7-15

2-88
2-57
1-60

627
1,344
1,705

2-33
3-02
4-90

228
93

55-10
19-45

0-35

65-31

25-62
6-57

In the open sea to the west of the Aland Islands, at depths greater than 40 m,
the benthos biomass reaches 44-36 g/m2 and 91 per cent of the benthos con-
sists of Macoma baltica. Deeper down a picture typical of the whole of the
Gulf of Bothnia is established : the biomass is reduced to 10 g/m2 owing to the
decrease of M. baltica (23 per cent) ; Pontoporeia affinis becomes the dominant
form, comprising half of this fauna. Chr. Hessle (1924) suggests that these two
forms (M. baltica and P. affinis) are either competitors for food, or that cray-
fish destroys the Macoma larvae. Hessle tries in this way to find an explana-
tion for the peculiar bathymetric distribution of both forms and, chiefly, for
the fact that Macoma baltica disappears with increasing depth in the areas
north of Gotland Island, that is, in the areas of mass development of Ponto-
poreia affinis in the deeper layers. Off Aland Island, and to some extent off Got-
land, the populations of Macoma baltica are very abundant at depths of 100 to
140 m (i.e. in water which is very poor in oxygen) ; but Pontoporeia affinis does
not grow in large numbers there. Its place is taken by P. femorata, with which
M. baltica can exist without harm to itself. Mesidothea entomon chiefly
inhabits the deep waters of the Aland Sea and of the Gulfs of Bothnia and
Finland, existing at the expense of Pontoporeia affinis, which is its basic food.

On the soft soils of the northern part of the central area the polychaetes
Nereis diversicolor in shallower places, and Harmothoe sarsi in deeper ones
(down to 200 m), are added to the three main fauna forms — Mesidothea and
the two species of Pontoporeia, which form the basic food of fish in the area.

Towards the south Harmothoe sarsi increases in numbers at lesser depths,
limited by a salinity of about 7%0 ; simultaneously it becomes more important
as fish food. Pygospio elegans and Halicryptus spinulosus, though not as
important, are also significant on the sandy bottoms of the central area.

The same benthic biocoenoses which were already formed in the area of

THE BALTIC SEA

325

Gotland Island, Pontoporeia-Mesidothea-Macoma, is very clearly repre-
sented in the Gulf of Bothnia, with a tendency for the biomass to be consider-
ably less.

The benthos biomass decreases markedly as one moves northwards (except
along the very shores of the bays). In the south of the Gulf of Bothnia (Bot-
tensee) in the shallow zone of the open sea the biomass is 30 to 40 g/m2 down
to a depth of 40 m ; but with increasing depth it is reduced to a few grammes
on account of the decrease of the number of specimens and the reduced
size of Macoma baltica and Mesidothea entomon. The benthos composition
at depths above and below 40 m is given in Fig. 1 50. For the southern part
of the Gulf of Bothnia the same decrease with depth is given in Table 132.

Table 132

Depth
m

Mesidothea

entomon

Pontoporeia affinis

Macoma baltica

Total
weight,

No. of

Wt,

No. of

Wt,

No. of

Wt,

specimens

g/m2

specimens

g/m2

specimens

g/m2

0-10

2-99

466

1-43

211

35-67

40-24

11-50

6-35

1-15

617

1-24

13-90

16-70

>50

5-4

0-80

1,158

2-35

—

3-15

The northern part of the Gulf of Bothnia with a salinity of no more than
4%0, with the latter falling as one moves northwards, has an extremely im-
poverished benthos with an average yield of 2-384 g/m2. Pontoporeia affinis is
the dominant form here; it is followed by Mesidothea entomon, Macoma
baltica and finally by the oligochaetes (see Fig. 151). M. baltica moves north-
wards only up to a salinity of 3-5%0, disappearing when the water is less saline
than this. The graph of the indices of the community density is given in Fig.
151. Of the 22 stations surveyed by Hessle in the northern part of the Gulf of
Bothnia, Macoma was found at only two, Pontoporeia at 19. The highest
quantitative indices for the latter are 2,160 specimens per m2 at a weight of
4-3 g. The average for all the Bottenwiek stations is 505 specimens and 1-32
g/m2. The corresponding data for Mesidothea are 2-7 specimens and 0-32
g/m2, and for Macoma 15 specimens and 0-80 g/m2. The biomass decrasese
somewhat with depth. For depths of less than 10 m it equals, on an average,
3-32 g/m2, while at 1 1 to 50 m it is 2-44 g/m2. In the bays of the off-shore zone
of the Gulf of Bothnia the fauna is undoubtedly much richer in numbers,
primarily on account of Chironomidae and Oligochaete larvae.

However, there are so far no quantitative data on this part of the Gulf.
On the basis of his own researches Hessle comes to the conclusion that
Bottenwiek is very poor in benthos biomass, mainly as a result of a consider-
able admixture of iron oxides in the sea-bed. A considerable area of the floor
of the Gulf is covered with these non-productive red sands. As for the number
of specimens, here too it is at times high — up to 1,000 specimens of Ponto-
poreia affinis per 1 m2.

326 BIOLOGY OF THE SEAS OF THE U.S.S.R.

(4) Pontoporeia-\- Mesidothea biocoenosis. In the most northern part of the
Gulf of Bothnia, at a salinity of 3-5%0, Macoma disappears and is replaced
by the Pontoporeia-f- Mesidothea biocoenosis in its pure form. This in its
turn passes at the shore-line into a mixed biocoenosis of Chironomidae and
Oligochaeta.

In the Gulf of Finland we find a similar but somewhat different picture. As
has been mentioned above, this Gulf is not separated from the central part of
the Sea either by islands or a submarine ridge ; hence the way is open for
both more saline waters and their characteristic fauna to enter through the
deep channel.

We shall consider the bottom fauna of the Gulf of Finland in greater detail,
from east to west, beginning at the Nevskaya Guba.

Research organized by the State Hydrological Institute in 1923-24 and
1934-35 under the direction of Derjugin has shown that the so-called Nev-
skaya Guba, i.e. the area separated from the open sea by Kotlin Island and
the Oranienbaum shoal, has completely fresh-water conditions. A small
amount of salinity, evident in the western part of the Nevskaya Guba, has
no substantial influence on the fauna, which there has a true fresh-water
character with a preponderance of molluscs, oligochaetes and insect larvae.
To the west of the Oranienbaum shoal the typical Baltic relict community
mentioned above comes in full strength with a preponderance of Mesidothea
entomon, Pallasea quadrispinosa, Pontoporeia affinis, Mysis oculata and the
addition of some extremely euryhaline forms such as Gammarus zaddachi,
G. locusta f. reducta, G. duebeni, Neomysis vulgaris f. baltica, Zoarces viviparus,
and the fresh- water chironomids. In this area, to the south and west of Kotlin
Island, the deep-water layer has an unstable salinity with marked fluctuations.
Saline water frequently flows in at a lower layer from the west (the pheno-
menon of internal waves). Thus the distribution of salinity given in Table
133 was once observed in March 25 km west of Kotlin Island.

Table 133

Depth

Temperature

t°C

^/00

14-8

1-52

14-7

1-52

14-6

1-63

4-5

5-01

In February the saline stratification somewhat to the east of this station
was even more strongly marked (Table 134).

According to different observations, the deep-water salinity south of Kotlin
Island was at one time 3-44%0, at another 0-52%0. Without doubt the magni-
tude of these fluctuations may be even greater. If the surface salinity fluctua-
tions west of Kotlin Island can reach a magnitude of from 003 to l-28%0 and
probably more, then in the deep-water layer they may be from 0-5 to 5-00%0.

THE BALTIC SEA 327

Table 134

Depth

Temperature

t°C

^/00

003

007

0-49

0-8

3-56

1-1

3-96

It must be perfectly clear from the above why in winter this saline, deep
water has a higher temperature than the surface layers, and why it retains its
reduced amount of oxygen, thereby destroying its winter homohalinity and
homothermia. The arrival of this water in summer also destroys the summer
homothermia and homohalinity.

Moving from the Nevskaya Guba to the west, we observe a gradual change
in the composition of the mass forms. According to the researches of S. Sager-
strale (1923), in the Pellinge area (coast of Finland, marked approximately
centrally on the chart — Fig. 121 — of the Gulf of Finland) at a salinity of 5 to
6%0 the main components of the benthos are again Macoma baltica, Mesidothea
entomon, Pontoporeia affinis and Chironomidae, with the addition of Cardium
edule. In other words we already have here the Macoma baltica biocoenosis.

Farther to the west, where the Gulf of Finland opens into the Sea, in the
Twerminn area (see Fig. 129), with the deep-water salinity slightly above
6%0 and the annual variations of salinity of not more than l-7%0, the dominant
form is again Macoma baltica ; it is followed by Chironomidae, Pontoporeia
affinis, Cardium edule, Mesidothea entomon, with the addition of Halicryptus
spinulosus and Mytilus edulis. The biomass of the Gulf of Finland increases
considerably from 25-75 to 60-206 g/m2 (the average for Pellinge is 55 and
for Twerminn 1 19 g/m2) as one moves from the centre of it to its exit.

The first area of S. Sagerstr ale's work (Pellinge, 1932) has a soft mud bottom
rich in organic matter, the so-called gyttja or sapropel. The composition of the
bottom communities of this area are illustrated in Fig. 158. The first is at a

48-24 61-58

Ш з

Fig. 158. Composition of bottom communities of
shores of Finland (Pellinge) (Sagerstrale, 1932).
Mean biomass, g/m2, is shown above the circles.
1 Macoma baltica ; 2 Mesidothea entomon ; 3 Ponto-
poreia femorata ; 4 Chironomidae ; 5 Others.

328

BIOLOGY OF THE SEAS OF THE U.S.S.R.

depth of 14 to 17 m, the second at 9 to 10 m. To the west, in the Twerminn
area, there are at certain stations communities identical with these. At other
stations a number of new forms are found ; and if, off Pellinge, we find the
Macoma-Pontoporeia-Mesidothea biocoenosis, here at deeper places (25 to
37 m) on the same gyttja, we find Macoma-Pontoporeia-Halicryptus (Fig.
159). At lesser depths (10 to 25 m) there is an extreme paucity of forms;

86-и

81-0

111-0

Fig. 159. Composition of bottom communities off the shores of
Finland (Twerminn) (Sagerstrale, 1932). Mean biomass, g/m2, is
shown above the circles. 1 Macoma baltica ; 2 Pontoporeia affinis ;
3 Halicryptus spinulosus; 4 Mytilus edulis; 5 Chironomidae ; 6
Cardium edule; 1 Corophium volutator; 8 Mesidothea entomon;
9 Others.

Macoma baltica is predominant with a small admixture of Pontoporeia affinis,
Halicryptus spinulosus and Mytilus edulis (Fig. 159). Moreover at times the
whole population consists solely of Macoma baltica (Fig. 159, III). Examples
of such a degree of uniformity of benthic marine communities are found again
only in the Sea of Azov.

At depths of less than 10 m the variety of the fauna increases and several
forms are added : Corophium volutator, Cardium edule, Mesidothea entomon,
Nereis diversicolor ; Chironomidae appear in large numbers, while Halicryptus
spinulosus disappears (Fig. 159).

However, as had been shown by Sagerstrale, Chironomidae in the Baltic
Sea are adapted only to the shallows and disappear with increasing depth
{Table 135).

THE BALTIC SEA 329

Table 135

No. of Chironomid specimens per m2

Twerminn Pellinge

June-July September September

1926 1928 1922

Depth, m

1-3

200-487

942

9-11

408

—

18-84

14-20

Maximum numbers of specimens and biomass. In conclusion we give the data
for the maximum indices of the biomass, and the numbers of specimens of
various bottom forms off the Finnish shore of the Gulf of Finland according
to Sagerstrale (Table 136).

Table 136

Forms

No. of specimens
per m2

Weight,
g/m2

Tetrastemma obscurum

0-22

Nereis diversicolor

7-4

Harmothoe sarsi

145

0-79

Tubifex tubifex
Halicryptus spinulosus
Cardium edule

217
75
14

0-84

4-93

16-84

Macoma baltica

1,407

152-14

Mytilus edulis
Neritina jiuviatilis
Bythinia tentaculata

188
10

15-77
0-28
0-67

Hydrobia baltica
Pontoporeia affinis
Pontoporeia femorata
Gammarus locusta

120

7,006

128

110

0-43

27-68

0-73

1-39

Corophium volutator
Mesidothea entomon

2,433
44

5-70
20-69

Asellus aquaticus

0-64

Chironomidae

1,662

32-96

S. Sagerstrale (1944, 1957) distinguishes as an individual biocoenosis the
overgrowth of Fucus vesiculosus. It consists in a high proportion of the
crustaceans Gammarus (zaddachi) oceanicus, G. zaddachi salinus, G. zaddachi,
Idotea granulosa, I. baltica, I. viridis, Taera albifrons (marina), Praunus
flexuosus, P. inermis, Leander adspersus fabricii, Mytilus edulis, the Cardium
edule fry, Balanus improvious, Laomedea loveni, Membranipora crustulenta and
Pelmatohydra oligactis, which attach themselves to the algae. The fresh-
water elements are represented by Theodoxus fluviatilis, Limnaea peregra
(ovata) and by chironomid larvae. In more enclosed places there are also the

330 BIOLOGY OF THE SEAS OF THE U.S.S.R.

larvae of Tcrihoptera, Turbellaria, Planaria lacustria, Poly cells nigra, the oligo-
chaetes Stylaria lacustrls, Nais ellnguis, and the Porifera Ephydatia fluviatilis.

For the first time the microfauna of the coastal sands has been subjected to
examination on the model of the Baltic Sea (Remane, 1933, 1952). The
original interstitial fauna (Mesopsammon) was found to be abundant in the
following species: Turbellaria, Gastrotricha, Archiannelida, Tardigrada,
Ostracoda, Harpacticoida and Nematoda. Near Twerminn (southern Fin-
land) the number of microbenthos organisms in some cases is more than
100,000 specimens per 1 m2, mainly on account of nematodes and ostracodes.

A. Schurin has carried out a comprehensive survey of the bottom fauna of
the Gulf of Riga (1961). Three characteristic features may be noted for bottom
fauna of the Gulf of Riga : (7) a general qualitative impoverishment, (2) de-
crease in size of all the main components, probably as a result of lower salinity
which makes this fauna completely accessible to local fish as food, and (5) a
rise in the levels of vertical distribution of biocoenoses and of individual
forms. Whereas in the open parts of the Sea the replacement of the shallow-
water mollusc benthos by the deep-water one, with a preponderance of crus-
taceans, takes place at depths of 50 to 100 m, in the Gulf of Riga this change
occurs at 10 to 20 m (Fig. 160).

On the actual shores of the Gulf of Riga the biocoenosis of the macrophyte
overgrowth is well represented, with abundant settlements of small amphi-
pods (Leptocheirus pilosus, Gammarus locusta, and others) and mysids
(Praunus inermis and P.flexuosus). In the sublittoral zone (2 to 20 m) there is a
very marked preponderance of bivalves (over 95 per cent) and especi-
ally Macoma baltica, My a arenaria and Cardium edule, but at a depth of 10
to 20 m the molluscs are greatly reduced in numbers, while the crustaceans
and worms increase ; the latter, and above all Pontoporeia affinis, are markedly
dominant at 20 to 40 m. The number of Pontoporeia affinis may reach
7,000 specimens per 1 m2. Among the other organisms the most significant
are Mesidothea entomon, Pontoporeia femorata, Halicryptus spinulosus and
Mysis mixta. Macoma baltica is still found in small numbers. Below 40 m
(and down to 60 m) in the stagnant zone of the central depression five species
in all have been found: Pontoporeia femorata, Pont, affinis, Mesidothea entomon,
Mysis mixta and M. oculata f. relicta. The molluscs and worms are entirely
absent. Total biomass of benthos in the Bay of Riga is about 670,000 tons
(Shurin, 1961).

General characteristics of productivity. The data on the qualitative distribution
of the Baltic Sea (Fig. 161) can therefore be summarized as follows. At the
start there are the biocoenoses of the Danish Belt and Oresund which are
diversified and rich in biomass (200 to 300 g, sometimes kilogrammes, in the
case of Modiolaria and Mytilus). Then, as one moves to the east and north,
an ever greater impoverishment is observed, both in quality and quantity ;
this continues until it finds its extreme expression in the uniformity of the
inner parts of the Gulfs of Bothnia and Finland, where at every step one finds
almost pure populations of Macoma baltica on the gyttja in the bays. Starting
from the Darss ridge itself we find, in effect, only one biocoenosis — Macoma

Fig. 160. Biocoenoses of the benthos in the Bay of Riga (Shurin, 1961). 1 Cardiwn-

Mya-Macoma ; 2 Macoma baltica ; 3 Pontoporeia affinis ; 4 Pontoporeia femorata ;

5 Dreissena polimorpha ; 6 Mytilus-Balanus.

332

BIOLOGY OF THE SEAS OF THE U.S.S.R.

baltica, which is the largest mass form of the present-day Baltic Sea. In
various places, however, as a result of unfavourable saline, gaseous or bio-
coenotic environment, Macoma baltica disappears, or is replaced either partly
or completely by other forms. In the Arcona and Bornholm depressions such
forms are Astarte borealis and Macoma calcarea.

In the depths of the central area of the Baltic Sea benthos biomass falls
almost to zero ; Macoma does not penetrate there, its place being taken by
polychaetes {Scoloplos armiger and Terebellides stromii) and crustaceans
(Pontoporeia femorata and Mesidothea entomori). Farther into the Gulfs of
Bothnia and of Finland, except for the actual coastal strip, benthos biomass

Fig. 161. Zonal distribution of Baltic fauna (Zenkevitch). 1 Eriocheir sinensis;
2 Balanus improvisus ; 3 Fucus vesiculosus and Chorda /Hum ; 4 Mytilus edulis ;
5 Mesidothea entomon ; 6 Macoma baltica ; 7 Pontoporeia affinis and P. femorata ;
8 Nereis diver sicolor ; 9 Aurclia aurita ; 1 0 Priapidus caudatus ; 1 1 Pleuronectes flesus ;
12 Herring; 13 Sprat tits sprat t us balticus; 14 Cod.

decreases markedly and, finally, at a salinity of about 3-5%0, Macoma dis-
appears, while the Pontoporeia-Mesidothea community remains, acquiring a
considerable admixture of fresh-water forms and in the actual coastal zone
being replaced by oligochaetes and chironomid larvae.

Macoma baltica, with its comparatively thin shell and high nutrient indices,
is devoured in huge quantities by various Baltic fishes.

Like other bodies of water the Baltic Sea varies greatly in the numerical
content of individual benthos mass forms in different seasons of the year —
Nereis diversicolor, Cardium edule, Macoma baltica, Pontoporeia affinis,
Mesidothea entomon and Corophium volutator. The last-named, an original
member of the Amphipoda group which lives in U-shaped tubes in the bot-
tom, also provides an example of sharp fluctuations in numbers from year
to year. The observations of S. Siigerstrale of Twerminn (Finland), carried

THE BALTIC SEA

333

out during 1928-31, have shown that Corophium volutator lives for only one
year. Over this period the fluctuations in the number of specimens of this cray-
fish per 1 m2, all collected in the same place, are given in Table 137.

Table 137

1928

May Jul Sep Nov
244 184 5,429 4,210

1929

May Jun Jul
3,151 1,712 105

Nov
1,774

1930

Apr May Jun Oct Nov
338 188 4 81 124

1931

Apr Oct
56 1,992

Nov
1,834

The same type of fluctuations were observed by Sagerstrale in the case of
another amphipod, Pontoporei aaffinis. These fluctuations are of special
interest since both crayfish are important items in the diet of fish.

A very approximate estimate, probably with considerable errors, can be
made for the benthos biomass of the whole Baltic Sea and its separate regions
for the summer season {Table 138).

Table 138

Total benthos

Average benthos

Area

biomass, tons

biomass, g/m2

Northern part of the Gulf of Bothnia

with reduced biomass

9,000

0-2

Southern part of Gulf of Bothnia

1,200,000

12-4

Gulf of Finland

1,200,000

57-0

Gulf of Riga

658,000

38-5

Baltic, Sea proper (north of 56° N lati-

tude)

3,500,000

250

Southern part of Sea (south of 56° N

latitude)

4,763,000

600

Belts and Oresund

2,170,000

186-0

For the whole Sea

13,500,000

330

VI. ORIGIN OF THE FAUNA
The main components

Four main components can be distinguished in the Baltic Sea fauna : (7) marine
cold-water relicts of the post-glacial period ; (2) true brackish-water fauna,
consisting mainly of Arctic brackish- water relicts of the Ice Age ; (3) marine
fauna, representing a greatly impoverished Atlantic fauna ; and (4) fresh-water
fauna (its most euryhaline representatives). The first group, and to some extent
the second, form groups of relicts of cold-water European boreal and Arctic
fauna.

The marine cold-water relicts of the Ice Age

According to Ekman's determination, a form may be considered a relict for
a given area if its habitat is cut off from its main habitat and if it or its original

334 BIOLOGY OF THE SEAS OF THE U.S.S.R.

form evolved in an environment different from that in which the relict form
exists today. Ekman calls a relict form pseudorelict if it has penetrated by a
second stage into its present environment from some other body of water. As
regards the Baltic Sea fauna it is often difficult to decide whether some form is
a relict or a pseudorelict, especially if one takes account of the fact that during
the colder phases of the post-glacial period some of those forms may have had
a continuous habitat across the North Sea. Thus the mark of a relict is its isola-
tion from its main habitat either in space or in time. Many forms which are
abundant in the central and northern parts of the Baltic Sea (Figs. 162 and
163) are either entirely absent from, or rare off, the western and northern
coasts of Scandinavia (Figs. 164, 165 and 166), their main habitat being the
Arctic Ocean.

All these forms in the Baltic Sea may be considered as marine ice relicts of
the Yoldian stage, which in an earlier, colder period had a continuous habitat
including the Arctic basin. The following are such relicts : among Hydrozoa :
Halitholus cirratus', among molluscs: Astarte borealis (Fig. 167); among
worms: Halicryptus spinulosus (Fig. 166); among crustaceans: Mesidothea
entomon, Pontoporeia affinis and P.femorata (Fig. 163) ; Pallasea quadrispinosa,
My sis oculata, M. mixta, Limnocalanus grimaldi (Fig. 162); among fish:
Myoxocephalus quadricomis (Fig. 164) ; and among mammals : Phoca hispida
{Ph. foetida).

S. Ekman (1935) has subdivided all these Ice Age marine relicts into three
groups. In the first group he includes the forms which at the present time also
live in their main habitat, the Arctic basin, only in greatly diluted or fresh
water. They are usually called true brackish-water forms or, strictly speaking,
Arctic brackish-water relict fauna. This group includes : Mesidothea entomon,
Pontoporeia affinis, Limnocalanus grimaldi, Pallasea quadrispinosa* The
second group consists of the extremely euryhaline forms Phoca hispida,
Myoxocephalus quadricomis and Mysis oculata, which can thrive equally well
in sea and fresh water. Euryhaline marine and brackish forms, of less eury-
halinity than the previous group, belong to the third group, namely : Ponto-
poreia femorata, Mysis mixta, Halicryptus spinulosus, Astarte borealis and
the hydroid Halitholus cirratus.

It is clear from the charts that the representatives of this last group avoid
the least saline parts of the Baltic Sea. Ekman suggests that during the Ancylus
stage these forms must have disappeared from the Baltic Sea ; he admits that
they may have found a refuge in the western part of the Sea within the region
of the present-day straits. These forms populated the Baltic Sea again during
the Littorina period.

Some of these relicts are found in the Baltic Sea in greater numbers than
anywhere in the Arctic region. Moreover the fauna of the Baltic Sea contains
a number of forms which are, as it were, intermediate between relicts and the
forms with a continuous distribution. These latter are abundantly represented
in the Baltic and the Arctic basin but are not found in large amounts in the
intervening areas. Such forms include the polychaetes Artacama proboscidea
and Harmothoe sarsi, and the molluscs Macoma (Tellina) baltica amd others.

* S. Sagerstrale explains the genesis of P. quadrispinosa in a different manner (see later)

Fig. 162. Distribution of the cope-
pods Limnocalanus grimaldi in the
Sea (A) and L. macrurus in the lakes
of Sweden (B) (Ekman, 1937). The
hatched part of the territory of Swe-
den was submerged during the Yoldic
period (same on Figs. 148 and 149).

Fig. 163. Distribution of Aiimphipoda Pontoporeia affini 's
(A) and P. femorata (B) in Baltic Sea (Ekman, 1937).

THE BALTIC SEA

337

У -Г /

&Л

Fig. 1 64. Distribution of Myoxocephalus quadricomis (A) in the Sea
and the lakes (B) of* Sweden (Ekman).

Several such forms are found in the southeastern part of the North Sea.
The Baltic Sea, stretching far from south to north, and with a very severe
climate in the north, provides a most favourable environment for the pre-
servation of cold-water relicts. It is possible that low temperature, rather than
salinity, promotes the existence of Arctic brackish- water relicts in the northern
part of the Baltic.

The same can be seen in the case of polychaetes. It follows from the zoo-
geographical analysis of this group given by A. Friedrich (1938) that, whereas
for the North Sea and the Baltic together the boreal, Lusitanean and Lusi-
tanean-boreal species form 53-2 per cent, and the Arctic, Arctic-boreal and

Fig. 165. Distribution of Mysis oculata in the Sea (A) and
M. o. relicta in the lakes of Sweden (B) (Ekman).

338

BIOLOGY OF THE SEAS OF THE U.S.S.R.

50 40 30 20 '0 0 10 2J 3D 4J 50 30 70

"1 /

Fig. 166. Distribution of the worm Halicryptus spinulosis
(Ekman).

0 4 8 12 16 20 24 28 32 36

8 12 16 20 24 28

Fig. 167. Distribution of the mollusc
Astarte borealis (Ekman and Johansen).

THE BALTIC SEA

339

Arctic-Mediterranean 42 per cent, for the Baltic Sea alone the first group
comprises only 22 per cent and the second 70 per cent.

Comparing the Baltic Sea fauna with that of the east Greenland fjords
G.Torhson( 1934) makes a good appreciation of the Arctic nature of theformer.
He points out that the similarity between the Greenland biocoenosis Astarte
borealis and the corresponding one from the Belt and the Baltic Sea is re-
markable. In the latter we again find : Macoma calcarea, Astarte borealis, A.
banksi, A. elliptica, Modiolaria nigra, Priapulus caudatus, Scoloplos armiger

Fig. 168. Occurrence of fossil Greenland seal on the shores of the Baltic and
its contemporary habitat in the Arctic basin (Ekman, 1930). 1 Sites of feeding
migrations ; 2 Breeding areas ; 3 Routes of migration ; 4 Occurrence in fossil

state.

(in eastern Greenland Sc. cuvieri) and some other polychaetes. In the shal-
lower places of the Baltic Sea Macoma calcarea is replaced by M. baltica,
remaining, however, in deeper patches. Torhson thinks that the fauna of the
deep-water zone of the Baltic Sea and the Belt corresponds to that of the
coastal zone of the eastern shores of Greenland and represents the Arctic relict
biocoenosis in the Baltic.

Many Arctic forms have moved their habitat to the north, leaving only
their fossil remains in the Baltic Sea area (Fig. 168). Thus Phoca groenlandica
was common in the Baltic even during the Littorina period, and was abun-
dantly used in the food of primitive man. It is not clear how the Greenland seal
could survive the fresh-water phase of the Ancylus Lake and the warm Littorina
phase. Ekman considers this seal a Yoldian Sea relict in the Littorina Sea.

When and in what way did the Ice Age marine ancestors of the present-
day relicts penetrate into the Baltic Sea? The answer to this must be sought

340 BIOLOGY OF THE SEAS OF THE U.S.S.R.

first of all in the questions touched on above concerning the role of the Ice
Lake Sea and the joining of the Yoldian Lake and White Sea.

The so-called 'ribbon' clays are thought to be the characteristic type of
the deposits of the Ice Lake Sea. They have been discovered in a number of
places between the Baltic and White Seas at heights of up to 180 m (on the
shore of Lake Onega). The Baltic Ice Lake Sea covered a considerable area of
north and northwest Europe, leaving in the south large inlets which became
lakes. Some scientists connect with the waters of this Ice Lake Sea the appear-
ance of a number of cold-water relicts of marine origin (Hogbom-Thienemann
theory) in the lakes of northwest Europe of the Baltic Sea basin which lie
beyond the boundaries of subsequent phases of the Baltic Sea. When, where
and how the waters of this phase of the Baltic Sea came into contact with the
neighbouring seas has not yet been established, but the Baltic Ice Lake un-
doubtedly received a group of brackish-water forms from some neighbour-
ing semi-fresh or fresh body of water, distributed them after its regression
among individual remaining lakes of the Baltic basin, and transferred
them to the fauna of the Yoldian Sea. It may quite possibly have obtained its
relicts from the northeast; the well-known Mysis relicta, for instance, and
Pontoporeia affinis, Pallasea quadrispinosa, Limnocalanus grimaldi, Mesi-
dothea entomon, Myoxocephalus quadricornis and Osmerus eperlanus. This
theory of Hogbom-Thienemann is accepted by many scientists (Ekman and
others). E. Gams (1929) has spoken against this theory; he thinks that the
penetration of these organisms into the lakes of Denmark, northern Germany
and the northwestern part of the European u.s.s.r. should be connected with
the Yoldian transgression.

The occurrence of relicts in the bodies of water outside the coastal bound-
aries of the Yoldian Sea is explained by Gams by passive transfer or active
migration and quick adaptation to fresh-water life, so that in these bodies
of water they are not relicts but immigrants according to Ekman's termino-
logy (relicts for the areas into which they were transferred or penetrated
at a second stage). Gams rejects any link between the history of these relicts
and the Ice Lake Sea. Many hydrobiologists, however, do not admit the
possibility of passive transfer or active migration of these animals from one
body of water to another, or against the current of a river. The migration
capabilities of such crayfish as Limnocalanus, Mysis, Pontoporeia, and of
Pallasea almost to the same extent, are very weak. Thus among the large
number of Scandinavian bodies of water investigated there is not a single one
situated above the mean boundaries of the Yoldian Sea which contains even
one of the four crustaceans mentioned. Their occurrence as a result of transfer
by birds or flying insects is, obviously, quite impossible. Therefore the passive
or active penetration of these crayfish into lakes which do not belong to the
Baltic Sea basin, as for example the Seliger Lake, is thus even more improbable.

Hogbom's theory of ice lakes of large area and high level extending south
much farther than the boundaries of the Yoldian Sea, can be used to explain
problems of a biological nature which arise if the possibility of passive trans-
fer or active migration of relict crayfish from one body of water to another
is accepted.

THE BALTIC SEA 341

As for the glacial marine relicts inhabiting saline-brackish waters which
could not have populated the fresh-water ice lakes, Ekman, sharing the
point of view of Miinthe and Sauramo, thinks that they arrived in the Yoldian
basin from the west.

The climatic conditions of the North Sea and the adjacent parts of the
Atlantic at the time were so severe that the Arctic fauna may have migrated
far to the south and lived in the North Sea. However, this fauna may have
come from the northeast, if we assume that the Yoldian Sea was connected
with the White Sea, or if this connection existed at later periods.

Sagerstrale (1957) likewise accepts this route of the penetration into the
Baltic Sea of a part of the brackish-water Arctic relicts ; he divides them into
several groups according to the time and route of their penetration into the
Baltic Sea.

(7) Limnocalamis macrurus (according to Sagerstrale the Baltic form L.
grimaldii evolved from it), Pontoporeia affinis, Pallasea quadrispinosa and
Mysis relicta were the first immigrants from the fresh waters in the north to
the Baltic Sea. Sagerstrale thinks that the isopod Pallasea came from the
fresh waters of Siberia.

(2) The second group of relicts, Mesidothea entomon, Gammar acanthus
lacustris, Cottus quadricornis and Phoca hispida, penetrated into the Baltic Sea
during the period of ice-recession, when the Gulf of Finland was freed of ice.
They may have migrated from the northeast from an ice lake in the area of
the White Sea, perhaps during the Littorina period when the water was not
yet saline.

(5) During the Littorina stage all these relicts were pushed into the least
saline areas and the penetration of Atlantic fauna and flora from the south-
west began ; for example : Littorina J it tor ea, Pontoporeia femorata, Mysis
mixta, Halicryptus spinulosus, and other remains of the cold-water fauna of the
Ice Age. In the case of some forms — Pallasea quadrispinosa is given as an
example — S. Sagerstrale (1957) accepts the view of P. Pirozhnikov (1937) and
E. Gurjanova (1946, 1951) regarding the west Siberian (Kara Sea) centre of
the evolution of a number of forms, and of their migration south down to the
Caspian Sea west of the Ural mountains via the Ob basin ; this theory is based
on the fact that the Kara Sea is now inhabited by a community of brackish-
water forms nearest to the Caspian immigrants (Fig. 169). For the rest,
Sagerstrale is inclined to consider P. quadrispinosa as genetically related to the
Lake Baikal P. kessleri. The fresh-water bodies of water of the Ice Lake
period may have served as further routes of migration (Fig. 170). Following
the opinion of Soviet authors (N. Lomakin, 1952), Sagerstrale is inclined to
connect the migration of the Caspian Pontoporeia (P. affinis microphthalma),
Gammaracanthus (G. loricatus caspius) and Mesidothea entomon with the
fate of the Siberian ice lakes.

In whatever way these forms penetrated into the basin of the Baltic Sea, as
a result of a subsequent change in the coastal contour and the rise
of temperature in the adjacent areas of the Atlantic, a discontinuous habitat
was created, the conditions of the Baltic were altered, and forms became
partly extinct, partly relicts.

342

BIOLOGY OF THE SEAS OF THE U.S.S.R.

The cold-water mollusc Yoldia (Portlandia) arctica is the most char-
acteristic form of the Yoldian Sea fauna known to us. Some other forms are,
however, equally characteristic, for example the diatom Campylodiscus
clypeus. Yoldia arctica, however, could have lived only in the most saline
western parts of the Sea. Myoxocephalus quadricomis and Phoca foetida in
the large Finnish lakes are probably remnants of this fauna, since these lakes
had been cut off from the Baltic Sea as early as the Littorina stage. The Yoldian

Fig. 169. Conjectured role of Siberian Ice Lake at period of its greatest glaciation,
in evolution and distribution of glacial relicts. The lake is marked by cross-hatching :
1 and 2 : routes of exchange of glacial forms ; 3 and 5 : migration of forms of marine
origin ; 4 : migration of the ancestor of Pallasea quadrispinosa (possibly P. kessleri)
from Lake Baikal. Places of occurrence of P. quadrispinosa are marked by a circle :
a, in Nalim's Lake ; b, in river Lena estuary ; c, in Novaya Zemlya. Occurrence of
P. laevis (possibly descended from P. quadrispinosa) is indicated by a triangle. Occur-
rence of Mesidothea entomon in eastern Siberia is marked by crosses (Sagerstrale).

Lake phase did not last long (barely 700 years according to Miinthe ; only for
500 years according to Sauramo, 1953).

A rise of land in the western part of the Yoldian Lake cut it off from the
ocean ; it lost much of its salinity and turned into the low-salinity, closed
Ancylus Lake Sea with a powerful flow of water to the west into the North
Sea. This phase, according to De-Geer, lasted for 2,200 years. When this
body of water lost its salinity it became densely populated with fresh-water
forms, among them the molluscs Ancylus fiuviatilis and various species of
crustaceans and molluscs (Limnaea, Planorbis).

Penetration of Atlantic fauna

During the Littorina stage salinity off Gotland reached 12%0 (Fig. 136); now
this salinity is found only in the Belt. The Baltic Sea again became con-
nected with Lake Ladoga. For this phase the mollusc Tapes decussatus is
most characteristic. Mytilus edulis, Cardium edule, Hydrobia baltica, Neritella

THE BALTIC SEA

343

fluviatilis appeared, and also Littorina Uttorea and L. rudis, both now absent
from the Baltic Sea. At that time L. Uttorea reached 62° 20' N, while now it

Fig. 1 70. Ice Lake and its role in the distribution of relicts (Sagerstrale, 1 957).

1 Limit of ice cover (in the northern part, according to various authorities) ;

2 Tentative location of ice cover ; 3 Watershed ; 4 Onega Ice Lake ; 5 Lake
deposits ; 6 Distribution of relicts (associated numerals denote altitude above
sea-level, m); A Lake Kenozero; В Lake Pochozero; С Lake Terekhovo;
D Latsha Lake ; E Kubensk Lake ; 7 Route of migrations of relicts ; 8 Cross-
distribution impossible for ecological reasons.

does not go farther than Malmo, Warnemunde and Riigen. Rissoa mem-
branacea lived round the Aland Islands during the Littorina stage, while now it
does not east of Oresund. Phoca vitulina, which now does not go farther north
than Gotland, in the Littorina Sea reached 64° N in the Gulf of Bothnia.

344 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Besides Phoca groenlandica and Ph. vitulina other seals — Phoca hispida,
Ph. foetida, Halichaerus gryphes — lived in the Littorina Sea. In keeping with
the higher salinity during the Littorina stage Cardium edule and Mytilus
edulis were larger than they are now in the same places.

The last phases in the formation of the present-day fauna
Approximately 2,000 years B.C. the straits again became shallow ; the sea lost
much of its salinity, and entered its present phase. Part of the fauna dis-
appeared {Scrobicularia piperata, Rissoa species, both littorines, Phoca
groenlandica). The sea was populated by fresh-water species, first of all
Limnaea ovata baltica, after which the phase is named the Limnaean Sea
(Loven, 1864 and Munthe, 1931).

Still later, during the second half of the Iron Age, and possibly in historical
times, the mollusc Mya arenaria (Myan Sea) and the fresh-water Limnaea
palustris, L. stagnalis, and later Dreissena polymorpha, migrated to the Baltic
Sea and multiplied abundantly in it. Each of these phases lasted for about
4,000 years, differing from the Baltic Sea of today not in their hydrology, but
in their fauna. The present phase of the Baltic Sea might quite justifiably
be called the 'Macoma Sea' because of the huge predominance in it of the
mollusc Macoma baltica.

Zoogeographical classification of the Baltic Sea

Owing to the heterogeneity of its fauna components a biogeographical
classification of the Baltic Sea presents considerable difficulties. From the
Littorina stage the Atlantic fauna vigorously populated this body of water,
and as regards this fauna the Baltic Sea should be related to the boreal region.
The deep parts of the Baltic Sea, however, and its shallow northern parts are
populated by cold-water Arctic relicts of varied genesis : partly relicts of the
cold Yoldian Sea, partly members of the original brackish- water community,
which in the Baltic Sea found only a secondary centre of settlement, and which
probably arrived as early as the time of the Ice Lake, possibly from the far
northeast. Both have marked Arctic characteristics and cannot be related to
the boreal region. Thus the Baltic Sea has a double zoogeographical aspect :
the more shallow, the southern and the southwestern parts of the Sea are
populated mainly by boreal fauna, the deeper places, and the northern and
eastern parts, by fauna of an Arctic aspect.

Zonation

We have had to point out several times that it is impossible to create a single
system of division of marine and brackish-water fauna according to the
salinity of the water, and that the zonation of each low-salinity body of water
must have its own special features.

The first schemes for the classification of waters according to their salinity
were worked out for the Baltic Sea. The problems of brackish waters were
also first studied in the Baltic Sea. The scheme of the German hydrobiologist
H. Redeke (1922), worked out for the Zuyderzee, was used as the basis of
these classifications.

THE BALTIC SEA 345

Three investigators, I. Valikangas (1933), A. Remane (1935) and S. Sager-
strale (1957), have given a more detailed estimate of the brackish waters of the
Baltic Sea. The first of them has established three marked limits of qualitative
change of Baltic Sea fauna as we move from west to east : (7) the area lying
between the Kattegat on one side and the Belt and Oresund on the other, with
salinity fluctuations of 1 5 to 20%o ; (2) the outlets from these straits into the
Baltic Sea with a salinity of 8 to 10%o ; and (J) a zone of much reduced salinity,
which differs somewhat for various groups: 3 to 3-5%0 salinity for the brown
and red algae and a little higher for the molluscs.

Valikangas, on the basis of Redeke's scheme, divides the marine waters into
the oligohaline (0-2 to 2-0%o), mesohaline (2-0 to 16-5%0) and polyhaline
(>16-5%0)asin Table 139.

Table 139

Zone

Salinity %0

Fresh waters

Oligohaline brackish waters
Meiomesohaline waters
Pleiomesohaline waters
Polyhaline brackish waters
Sea-waters

<0-5
0-5 to 3
3 to 8 (10)
8 (10) to 16-5
16-5 to 30
>30

Remane approached this problem in a rather different way. He took as a
basis the natural distribution of organisms and counted the number of species
of different genesis in waters of varying salinity. Thus Remane was the first
to apply, in the classification of the brackish zone, an indirect quantitative
method. He established that in the Baltic Sea marine forms more than 50 per
cent were at a salinity of 30 to 17%0, while in the range 17 to 8%0 the propor-
tion fell from 50 to 30 per cent. As a result Remane gives the following sub-
divisions for the Baltic Sea according to its salinity :

I. Purely marine zone 35 to 15%0

II. Brackish- water zone 15 to 3%0
(7) Brackish-marine mixed zone with a preponderance of

marine forms 15 to 10%o

(2) True brackish-water zone with a maximum develop-
ment of specific brackish- water fauna 10 to 5%0

(3) Brackish-fresh-water mixed region with a preponder-
ance of fresh-water elements 5 to 3%0

///. Fresh- water zone <3%0

Moreover the limits for various groups of organisms may be different.
Remane's system is applicable to benthos; for plankton the fresh-water
elements are already dominant at a salinity of 5 to 7%0. Remane distinguished
the four following groups of organisms :

(7) Euryhaline fresh-water forms
(2) Euryhaline marine forms

346 BIOLOGY OF THE SEAS OF THE U.S.S.R.

(5) Steno- and eury-haline brackish-water forms

(4) Highly euryhaline organisms, the distribution of which does not depend
on water salinity.

Finally the following classification of brackish water was accepted by the
Venetian symposium in 1958 as the most suitable for the Baltic Sea :

Zone Salinity, %0

Hyperhaline >40

Euryhaline 40 to 30

Mixohaline 30 to 0-5

Mixoeuhaline >30 (less than

the adjacent
euhaline
waters)

(mixo) polyhaline 30 to 18

(mixo) mesohaline 18 to 5

(mixo) olyghohaline 5 to 0-5

Fresh water <0-5

and further subdivisions for the (mixo) mesohaline and (mixo) oligohaline
zones :

(mixo) mesohaline

a-meshohaline 18 to 10

p-mesohaline 10 to 5

(mixo) oligohaline
oc-oligohaline 5 to 3

(3-oligohaline 3 to 0-5

However, this scheme is too detailed and therefore difficult to apply in
practice. For that reason Remane's classification, given above, is preferable.

The brackish-water relicts in the Baltic Sea which have retained their
Arctic aspect most are : Mesidothea entomon, Limnocalanus grimaldii, Ponto-
poreia affinis, Myoxocephalus quadricomis and Phoca hispida.

However, Mysis mixta, M. relicta, Astarte borealis, Pontoporeia femorata
and Halitholus cirratus are very closely akin to them, although in the Arctic
regions they do not belong, as the others do, to the preponderant brackish-
water forms. The third group — steno- and eury-haline brackish-water
animals in the Baltic Sea — comprises a fairly considerable group.

S. Sagerstrale (1957) includes in the group of true brackish- water organisms
of the Baltic Sea (except for the Ice Age relicts and the immigrants from other
seas) 1 5 species of plants and 43 species of animals :

Cyanophyceae Anabaena baltica

Diatomaceae Thalassiosira baltica, Chaetoceros subtilis, Ch. wighami,

Synedra tabulata, S. pulchella
Rhodophyceae Ceramium tenuicorne
Phaeophyceae Ectocarpus confervoides fluviatilis, Portoeirema fluviatile

THE BALTIC SEA

347

Characeae

Phanerogamae
Ciliata
Cnidaria
Turbellaria

Rotatoria

Nemertini

Polychaeta

Ostracoda

Copepoda

Cladocera

Decapoda

Isopoda

Tanaidacea

Amphipoda

Coleoptera

Gastropoda
Bryozoa

Tolypella nidifica, Chara baltica, Ch. canescenes (Ch.

crinitd)

Scirpus parvulus, Zannichellia pedunculata, Najas marina

Tintinnopsis tubulosa, T. brandti, Leprotintinnus bottnicus

Protohydra leuckarti, Pelmatohydra oligactis

Promesostoma baltica, P. cochlearis, P. lugubra, Koino-

cystis twaerminnensis

Synchaeta fennica, S. monopus, Anuraea cruciformis

eichwaldi, A. quadrata platei, A. cochlearis recurvispina

Prostoma obscurum

Streblospio dekhuyzeni, Alkmaria romijni

Cytherura gibba, Cytheromorpha fuscata

Eurytemora affinis, E. hirundoides, Acartia bifilosa

Bosmina coregoni maritima

Palaemonetes varians

Sphaeroma hookeri, Cyathura carinata, Idothea viridis

Heterotanais oerstedi

Bathyporeia pilosa, Melita palmata, Gammarus zaddachi

zaddachi, G. z. salinus, G. duebeni, Leptocheirus pilosus,

Corophium lacustre

Ochtebius marinus, Laccobius decorus, Haemonia mutica,

H. pubipennis

Hydrobia ventrosa, Alderia modesta

Membranipora crustulenta, Victorella pavida.

However, this group can be considerably reduced since some of the animal
forms included (possibly as many as 15) are not endemic to the Baltic Sea.
Some of the forms enumerated have possibly not been adequately identified.

Even if these endemic forms exist, their endemism is evidently very recent
and probably not sufficient to relate them to true brackish-water organisms.
Relict forms of much more ancient origin, which penetrated into the Baltic
Sea at a second stage, are much more deserving of this name. Remane
increases this list considerably, including 68 denominations of animals alone
(adding the Ice Age relicts and immigrants from other bodies of water). The
following forms from his list are not included in that of Sagerstrale given
above :

Coelenterata
Turbellaria

Rotatoria

Polychaeta

Cordylophora caspia

Procerodes ulvae

Acrorhynchus robustus

Macrostomum hystrix

Proales similis, Linasia tecusa, Eucentrum evistes, E. rous-

seleti, Erignatha thienemanni, Aspelta baltica, Colurella

dicentra, Notholca striata, N. bipalium, Brachionus plica-

tilis, Euchlanis plicata, Synchaeta lavina, S. littoralis,

Testudinella clypeata, Pedalia fennica

Manayunkia aestuarina, Polydora redekei

348 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Copepoda Acartia tonsa, Eurytemora hirundo, Limnocalanus grimal-

dii, Nitocra lacustris, N. spinipes, Ectinosoma curticorne,
Mesochra rapiens, M. liljeborgi, Laophonte mohammedi,
Schizopera clandestina, Cletocamptus confluens, Horsiella
brevicornis, Idunella muelleri

Ostracoda Cyprideis littoralis, Loxoconcha gauthieri, Leptocytere

castanea, Cypridopsis aculeata, Heterocypris salina, Can-
dona angulata

lsopoda Tanaidacea, Mesidothea entomon, Sphaeroma rudicaudum

Mollusca Hydrobia Jenkins i, Conger ia cochleata.

A list of 1 5 plant and 87 animal forms is obtained from both investigators
taken together.

What prevents this fauna from leaving the limits of the brackish-water zone
and from becoming euryhaline forms in the broadest sense of the word? After
all they are all descendants of either marine or fresh-water forms. This is a
complex phenomenon, which cannot be explained by a single cause. First
one must point out that the brackish-water fauna of the Baltic Sea consists
basically of three groups — crustaceans, fish and Rotifera. Hence not all the
animal groups constitute equal parts in the population of the brackish-water
zones.

The origin of the local brackish- water fauna can most probably be ex-
plained by the centuries-long fluctuations of salinity suffered by a zone of
transitional salinity. The aquatoria, which contain the most typical brackish-
water community, are known to have passed through continuous changes of
salinity (named by L. Zenkevitch (1933) 'salinity pulsations') during previous
geological periods (the Quaternary and to some extent the Tertiary too), and
at the present day a typical instability of saline conditions is characteristic of
them. Salinity fluctuations in one direction or the other must inevitably have
attracted certain forms from both the marine and fresh-water fauna; and
after that, in the order of species formation, the salinity fluctuations must have
strengthened in a hereditary way the adaptation of an organism to varying
salinity. In this process the biocoenotic factor no doubt played a significant
role.

Remane accepts the possibility of specific action of brackish water on
organisms. However this is only a surmise ; there are no precise data about
it. For the rest, if the explanation given above is accepted, there is no need of
any further explanation. It is of interest to note that forms of marine origin
are preponderant in the brackish-water fauna, comprising about 60 per cent.

Other zonal classifications according to salinity have been used for parti-
cular areas of the Baltic Sea. Thus A. Wilier (1925), in his magnificent survey
of Frishhaff, used the generally accepted terminology of the classification of
bodies of water according to salinity (eury-poly-meso-oligo-steno-halinity),
but he attached to it a purely local meaning, as if Frishhaff had been a marine
body of water of full value as regards salinity.

He distinguishes inside Frishhaff, for example, stenohaline brackish- water
organisms, typical of a 'polyhaline' zone, and 'euryhaline brackish- water

THE BALTIC SEA 349

organisms', typical of a mesohaline zone. The 'euryhaline fresh-water
organisms', according to Wilier, are those which are met throughout Frish-
haff. In actual fact Willer's highest salinity, his ' polyhaline ' zone, corresponds
only to the lower part of Redek's mesohaline zone. The typical, widely dis-
tributed euryhaline Medusa, Aurelia aurita, becomes with Wilier a steno-
haline brackish-water form.

F. Riech (1926), also for Frishhaff, and L. Szidat (1926) for Kurishhaff
followed practically in the path of Wilier. It is entirely understandable that
the whole classification is confused by the introduction of such schemes. The
problem becomes more controversial in the case of an independent and even
enclosed sea like the Caspian. In his quantitative survey of benthos in the
northern part of the Caspian Sea N. Tchougounov (1923) distinguishes the
'marine', the 'brackish- water' and other zones. The maximum salinity of the
Caspian Sea, except the highly saline inlets of the eastern shores, is no more
than 14%0 ; hence Tchougounov's marine zone has a salinity which is in prac-
tice never found in seas. There are sufficient reasons to regard the Caspian
Sea as a whole as a brackish-water basin, but according to Tchougounov 'the
brackish- water zone' is a narrow band close to the Volga delta. Thus, when
drawing separate local schemes of zonation according to salinity, the sub-
divisions used must be introduced as small units, after the determination
of the place of a given body of water in the general scheme for the seas.

Fish

Among the fish population of the Baltic Sea (it is poor in species), Myoxoce-
phalus quadricomis, salmon {Salmo salar) and representatives of coregonids
{Coredonus laveretus and C. albula) can be ascribed to the brackish-water
Arctic relicts. The most important from the commercial aspect are Baltic
herring {Clupea harengus membras), sprat {Sprattus sprattus balticus), and cod
(G. morrhua). Flatfish (Pleuronectes platessa and P. limanna in the southern
part of the Sea and P.flesus in the eastern) are of some importance in fisheries.
Fresh-water fish which are of significance for the industry are pike (Esox
lucius), golden shiner {Abramis brama), perch (Perca fluviatihs) and some
others ; river eel (Anguilla vulgaris) should be added to these fish. The fisheries
of the Baltic Sea outside the straits have a yield of about 3 million centners
offish, which gives about 80 kg/hectare, while the Gulf of Riga has an annual
yield of 500 to 600 thousand centners, or 30 to 36 kg/hectare (1 hectare=
1,000 m2).

The following are most important as food : among the molluscs : Macoma,
Mytilus and Lymnaea; among the crustaceans: Pontoporeia, Mesidothea,
Corophium, Gammarus, Idothea and Mysis, and among the insect larvae:
Chironomidae and Trichoptera.

THE SOUTHERN SEAS OF THE U.S.S.R.

8
General Characteristics and Geological History

I. GENERAL CHARACTERISTICS

The Black, Azov, Caspian and Aral Seas, and to some extent the Mediter-
ranean and even the Red Sea, for all the differences in their physical geo-
graphy, have a number of important features in common. All these Seas
possess a salinity of their own, different from that of the ocean ; this was parti-
cularly so in the historical past, when at times it exceeded the normal salinity
of the ocean in areas with a negative balance of fresh-water inflow (through-
out the Mediterranean and Red Seas, in many gulfs, inlets and the Sivash of
the Black, Azov and Caspian Seas). At times it decreased below that of the
ocean (the Black, Azov, Caspian and Aral Seas).

Equally characteristic of all these bodies of water, which are isolated from
the open ocean, is the temperature of their deep layers ; excluding the Azov
and Aral Seas, this temperature is high in comparison with the open ocean
—about 9° in the Black Sea, 5° to 6° in the Caspian, 13-5° to 13-7° in the
Mediterranean and 21-5° in the Red Sea. Their temperatures correspond, to
some extent, to the lower average temperature of their upper layers in winter.

These common features of the system of seas from the Black Sea to the
Aral Sea are chiefly due to their common origin, which is linked with the geo-
logical past of the so-called South Russian geosyncline. This, it is assumed,
constitutes a remnant of the ancient Tethys geosyncline, which underwent a
complex process of the isolation of sea-basins during almost the whole Neo-
genic Period.

A considerably lower salinity (10 to 22-5%0), as compared with the normal
marine salinity, and a significant difference between the surface and deep-
layer salinities, are also very characteristic of the South Russian bodies of
water. The marked saline stratification is accentuated by an abrupt tempera-
ture stratification which appears in the warm season of the year, when surface
water is at times warmed to 27° to 30°. In winter, on the other hand, the sur-
face layer of water becomes very much cooled, and a larger or smaller ice-
cover is formed. Saline, and sometimes temperature, stratification causes the
formation of hydrogen sulphide on the bottom, when, either at certain seasons
or throughout the year, deep waters in the more or less thick layers are con-
taminated. A. Archangelsky (1938) thinks that the contamination of the
Black Sea with hydrogen sulphide is not peculiar to its present phase, but is a
characteristic phenomenon common to all the bodies of water of the South
Russian geosyncline of the Neogene system.

Lastly, the historical basis of the fauna of the Southern Seas of the u.s.s.r.
is a peculiar relict fauna which is itself, in the final analysis, a remnant of the
Tethys fauna (Sarmatian, Pontic and Caspian fauna) formed by a complicated
succession of lower and higher salinity phases. To this fauna are added in
greater or lesser numbers immigrants from fresh waters and far-travelled

z 353

354 BIOLOGY OF THE SEAS OF THE U.S.S.R.

immigrants (pseudorelicts) from the Arctic basin (chiefly in the Caspian).
Atlantic (Mediterranean) fauna comes in vigorously from the west, individual
forms penetrating as far as the Aral Sea.

The difference between all these seas in respect of their fauna is most
marked. The Red Sea is populated by the tropical fauna of the Indian Ocean.
The Mediterranean fauna is a descendant of the south boreal fauna of the
Atlantic Ocean ; the Caspian Sea preserves in its fullest form the remarkable
relict ' Caspian ' fauna ; the least saline parts of the Black and Azov Seas are
inhabited by the 'Caspian' fauna, while the Mediterranean (Atlantic) fauna
populates the main basin.

II. THE GEOLOGICAL PAST

Evolution of the Seas of the Neogene System

The geological history of our South Russian Seas has been traced in its main
features by the work of a number of investigators. Special credit in this field
is due to Andrussov and, lately, Archangelsky.

N. Andrussov (1918) writes: 'the main characteristic of the history of the
Neogene ... of the Ponto-Caspian regions is their continuous and ever
increasing isolation from the ocean, leading to a change in the salt content of
the inland water basins which were being formed there, mainly in the direction
of lesser salinity, although at times an increase of salinity has also been
observed. . . . Owing to this isolation and the change in the salinity of the
waters covering different parts of the regions, the history of the fauna of these
waters affords a series of most interesting and instructive phenomena. The
marine fauna which originally inhabited them during the middle Miocene era
underwent a number of changes under the influence of changes in the composi-
tion of the water. On the one hand it is simply a gradual disappearance of the
stenohaline forms ; on the other it is a survival of forms less sensitive to
fluctuations in salinity (euryhaline forms), which is accompanied by con-
siderable morphological and anatomical changes, by great mutability of
species and the evolution of numerous new species and even genera . . .'

Lower and Middle Miocene Periods

During the Lower and Middle Miocene Periods a fully saline sea, with a
typically marine fauna of Mediterranean type and wide connections with the
ocean, stretched throughout the south of the European part of the u.s.s.r.,
extending far to both the west and east (Fig. 171).* The process of the separa-
tion of this huge sea, part of the disappearing Tethys, from the ocean may
already have begun by the end of the Middle Miocene, individual parts of the
Sea losing some of their salinity. The rise of the mountains and the formation
of watersheds broke up the Middle Miocene Sea into more or less isolated
parts, which collected masses of river water and lost some of their salinity.

* B. Zhizhchenko (1940) thinks that in the southern part of the u.s.s.r. there was a
much diluted basin (Aral Stage) by the end of the Oligocene and the beginning of the
Miocene Period, after which normal oceanic conditions were restored.

GENERAL CHARACTERISTICS AND GEOLOGICAL HISTORY 35!

Fig. 171. Mitmiocene basin (Zhizhchenko, 1940).

Sannatian basin

During the Upper Miocene a Sarmatian basin, cut off from the open seas,
was formed in the place of the Middle Miocene basin (Fig. 172).

A number of the most typical members of the Mediterranean fauna dis-
appeared in the Sarmatian basin as, for example, the sea urchins, the bivalves
Area, Pectunculus, Leda and its most typical representatives Cardium,
Pecten, Venus, Corbula, Conus, Natica, Turitella and others. Pleurotoma,
Murex, Lucina, Loripes, Corbula and others continued to exist there for some
time. The hardiest forms survived : the gastropods Cerithium, Trochus, Buc-
cinum, Nassa and the bivalves Cardium (small size), Modiola, Tapes,
Mactra, Syndesmya, Donax, Ervilia. As has been pointed out by V. Boga-
chev (1933) a peculiar vertebrate fauna was also associated with the Sar-
matian basin: among fish: grey mullet, gadidae, Clupea, dolphins and
other Cetotheria, and seals (very similar to the present Caspian seal). Later
the Sarmatian basin lost much of its salinity, becoming possibly much less
saline than the present Black Sea. Conditions favourable for the development
of a hydrogen sulphide zone were created by the existence of a considerable
difference in the salinity of the surface and deep layers of the sea. Almost the
whole Sarmatian basin fauna rapidly died off under the effect of considerable
general loss of salinity and the contamination of the deep layers by hydrogen

Fig. 172. Sarmatian basin (Kolesnikov).

356

BIOLOGY OF THE SEAS OF THE U.S.S.R.

sulphide, while a new flourishing development of an original fauna took place
in the new environment.

Mae otic basin

The fauna of the new Maeotic basin (Fig. 173) — its deposits occurring between
the Sarmatian and the Pliocene — owing to the establishment of a link with the

Fig. 173. Maeotic basin (Kolesnikov).

ocean again received a number of typical Mediterranean forms alien to the
Sarmatian period (Ostrea, Venerupis, Lucina, Dosinia, Cerithium, Area),
retaining only a few of the Sarmatian ones. The composition of the fauna in
the upper deposits of the Maeotic basin changed sharply again and, dis-
placing the Mediterranean forms, species of the genus Congeria and the
gastropods Neritina, Hydrobia and Micromelania appeared.

The process of loss of salinity in the Maeotic basin in the vicinity of the
Kerch peninsula is well illustrated by Andrussov's table (1926) of the number
of species in the three overlapping layers of deposits {Table 140).

Table 140

Layers with :

Marine
species

Brackish-water
species

Fresh-water
species

Congeria novorossica
Congeria panticapaea
Modiola volhynica var. minor

17
10

6
1
0

Archangelsky thinks that the hydrological conditions of the eastern part
of the Maeotic Sea were very similar to those existing at present in the Black
Sea and that there was a deep part which was contaminated by hydrogen
sulphide.

Pontic Lake-Sea

The so-called Pontic Lake-Sea was formed during the Pliocene Period (Fig.
174), its fauna differing greatly from those of the Sarmatian and Mediter-
ranean. The huge inland brackish-water lake-sea (similar to the present-day

GENERAL CHARACTERISTICS AND GEOLOGICAL HISTORY

357

Caspian Sea) had a fauna characterized by a marked predominance of
Dreissensiidae and Cardidae which retained a certain successive link with
the Maeotic basin fauna.

'Any geosyncline,' writes A. Archangelsky (1927), 'situated between
two platforms, at certain stages of its development is bound to undergo a
stage of dismemberment into a system of basins similar to that of the Caspian-
Mediterranean Sea. . . . The rise of some parts of the geosyncline and the
lowering of others can break up the geosyncline basin into a complex system
of deep bodies of water, some connected with the open sea, some entirely cut
off from it.'

'The development of the Pontic basin', write M. Gerasimov and K.
Markov (1939), 'is closely connected with the considerable loss of salinity of

Fig. 174. Pontic Lake-Sea (Andrussov).

the Maeotic basin with the replacement of the "semi-marine" "Euxine"
conditions by those of a greatly diluted inland lake-sea of the "Caspian"
type. Only the Cardidae, some Gastropoda and Dreissensiidae of the Maeotic
fauna passed over into the Pontic basin ; the numerous forms of the Melanop-
sidae, Paludinidae and Limnaeidae families were added to it in great numbers
from the rivers and lakes. The true Cardium are no longer there, only the
Limnocardium ; but Didacna, Monodacna and Prosodacna are numerous.'
N. Andrussov (1918) assumes that this Pontic community was formed in the
west in the Middle-Danube lake-sea and was then propagated to the east.

According to A. Archangelsky (1934) the basin of the Caspian Sea was
separated, either at the end of the Pontic Period or after it, by the rise of its
floor from the Black Sea part of the Pontic Lake-Sea, and since then the
development of the fauna of both parts proceeded independently (Fig. 1 75).

The Black Sea basin during the Middle and Upper Pliocene

In the western half, in the Cimmerian basin, the Pontic type of the fauna was
further developed. The Pontic fauna became considerably impoverished in
the subsequently somewhat less saline and warm Kuyalnits basin.

The fauna of the last of the Pliocene basins, in the area of the present Black
Sea — the Chaudinsk Lake-Sea — differs greatly from that of the Kuyalnits one ;
according to Andrussov it is a derivative of the Pontic fauna, although it has
a great similarity with that of the present Caspian Sea.

The history of the fauna of the Caspian part of the Pontic basin is different.

358 BIOLOGY OF THE SEAS OF THE U.S.S.R.

The deposition of productive sediments

Thicks layers of productive formation covered with deposits lie in Azerbaijan
on the Pontic layers ; these layers are found on other parts of the Caspian
shores, being made up of sand, clayey sand and clay. Their fauna is very poor,
consisting of either purely fresh-water or land molluscs. During the period
of the accumulation of the productive deposits the body of water was con-
siderably reduced in size and, in the opinion of V. Baturin (1931), it was
limited to a southern basin with the waters of Volga, Samur, Kura, Uzboi

Fig. 175. Basins of Cimmerian era (Archangelsky, 1927),
and of the productive zone era (Baturin, 1931).

(from the east) and other rivers flowing into it, and its water then became
almost fresh (Fig. 175). The productive formation, apparently connected by
its deposits with the river deltas, contains in its layers huge accumulations
of petroleum, the origin of which may be due to vigorous delta growths,
whereas the North Caucasian petroleum beds, as has been pointed out by A.
Archangelsky (1927), belong to the deep-water environment of the Middle-
Maeotic basin in the depths of the Chokraksky and Karagatsky Seas con-
taminated with hydrogen sulphide.

Akchagyl basin

The next deposits of Precaspian marine sediments (after the Pontic ones)
were those of the Akchagyl basin, when the waters of the Caspian basin
moved north on a wide front and, to a lesser degree, spread east and west
(Fig. 176) as the result of the submersion of the Precaspian region.

The fauna of the Akchagyl basin, characterized by its considerable salinity,
differs fairly sharply from that of the Pontic basin. It includes numerous
species of Mactra, Cardium, calcareous sea-weed, Avicularia and other
marine forms, which suggests that the salinity of the Akchagyl basin was
quite high. No explanation has yet been put forward for the high salinity of
the Akchagyl waters and the marine aspect of its fauna, in spite of the fact

GENERAL CHARACTERISTICS AND GEOLOGICAL HISTORY 359

that the preceding basin had very small quantities of productive deposit and
its /waters were almost completely fresh. The Akchagyl basin must have re-
ceived, from somewhere, both the main mass of the saline water filling it
and the corresponding fauna, which had a clearly expressed Sarmatian
aspect* (Andrussov, 1902). Although the existence of a link in the west be-
tween the Akchagyl and Kuyalnits basins has lately been established, the
former could not have obtained its marine forms from the latter, which was

Fig. 176. Kuyalnits (/) and Akchagyl (2) basins
(Archangelsky).

at that time a brackish-water basin of the Caspian or Pontic type, and itself
could rather have obtained a part of its forms from the east, from the Akchagyl
basin. A. Archangelsky (1934) admits only 'one single possible route for the
fauna from the southeast, from Persia, perhaps from the region of the Persian
Gulf. The originally poor Akchagyl fauna became very rich in species at the
middle of the existence of this basin. During its last phase the Akchagyl Sea
was connected with the Black Sea region through the discharge of its waters
to the west, south of Manych. At that time a certain number of Ackhagyl
forms penetrated to the west. Later the Akchagyl Sea began to contract
rapidly, its waters lost their salinity, and the rich Akchagyl fauna died out
almost completely except for some gastropods — Cardidae. Many of the
Dreissensiidae appeared simultaneously.

The Apsheron and Baku basins

The size of the Caspian basin became greatly reduced during the Apsheron
period (Fig. 177). The Apsheron basin, and the Baku basin which followed it,

* V. Kolesnikov (1940), however, considers the similarity between the Akchagyl
and Sarmatian faunas as purely extraneous. In his opinion this fauna has no connection
with the south-Russian Miocene or Pliocene.

360 BIOLOGY OF THE SEAS OF THE U.S.S.R.

had a salinity similar to that of the present Caspian Sea. Their population,
consisting of numerous species of Didacna, Adacna, Dreissensia, Neritina
and Micromelania, was close to the present-day Caspian fauna. I. Gerasimov
and K. Markov (1939) suppose that 'as a result of the loss of salinity of the
Apsheron basin immigrants from the west, from the Black Sea (Kuyal'nik-
Chauda) appeared in it. In the Baku basin era the flow of immigrants (from
Chauda) had evidently increased still further. Forms of the Pontic fauna

Fig. 177. Chaudinsk and Apsheron basins (Archangelsky
and Kolesnikov).

which had evolved in the Black Sea began to immigrate into the Caspian
Sea.'

The closed brackish Apsheron lake-sea obtained its fauna from three
sources: (7) from Akchagyl (Clessinia, Apscheronia), (2) from some fresh-
water source (Neritina, Melania, Melanopsis), and (3) in great quantity from
the Euxine region of the Chauda basin, probably through its connection along
the Manych depression (Dreissensia, Didacna, Monodacna). The modern
Caspian fauna is the result of a further, but now independent, evolution of
this fauna in the basin of the Caspian Sea.

History of the Tertiary fauna of the Caspian Sea

Reviewing the history of the Caspian Sea fauna during the Tertiary period,
V. Bogachev (1932) lays stress on the numerous marked changes of fauna,
which seem to break the genetic link of the fauna of one era with that of the
subsequent one. He discerns such interruptions in the transition from the Sar-
matian fauna to the Maeotic, from the latter to the Pontic, and from the Pontic
to the Akchagyl. Bogachev explains these changes by assuming, in accordance
with the views of E. Suess (1888), the existence of 'refuge' bodies of water
(' caspians ' as Suess called them) in which one or other fauna could survive

GENERAL CHARACTERISTICS AND GEOLOGICAL HISTORY

361

Bogachev (1932) thinks that for the Middle-Miocene fauna such a ' refuge ' was
preserved in Asia (in Turkestan) and from it the fauna penetrated first into the
Maeotic basin and later into the Akchagyl. Other ' refuges ' may have existed
for the Sarmatian and Pontic faunas. Other investigators assume a repeated
penetration of Mediterranean forms from the west, from the Mediterranean
Sea. If one takes into account the fact, for example, that in the present-day
Gulf of Taganrog there exist side by side the completely different Mediter-
ranean and Caspian faunas which have occupied this body of water in turn
during the post-Tertiary changes of salinity, the Suess conception of a ' refuge '
becomes wholly realistic. Table 141 sets out the history, described above, of the
Black and Caspian Seas and their faunas.

Table 141

Middle

Miocene
Upper

Miocene

Pliocene

Middle Miocene basin of full salinity

(Remains of Tethys)
Brackish-water Sarmatian basin (to the east beyond the Aral Sea,

to the west up to the middle Danube lowland)
Towards the end a great reduction in size, then again an enlarge-
ment and transition
Maeotic basin; semi-marine 'Euxine' conditions [A. Derzhavin
(1928) thinks that the Black Sea was connected with the Sea of
Marmora]
Pontic basin, considerable loss of salinity of the Maeotic basin.

'Caspian' conditions with a lowered salinity
Towards the end the Black, Caspian and Aral Seas are separated

from each other
Cimmerian basin The basin of productive deposits.

Kuyalnits basin Akchagyl basin (was for a time

connected with the Kuyalnits
basin)
Apsheron basin (was temporarily
connected with the Chaudin
basin)
Baku stage

Chaudin basin (was con-
nected through the Bos-
phorus with the low-salinity
Sea of Marmora, had no
connection with the Medi-
terranean)

Ancient Euxine basin (Cas-
pian type of fauna)

A connection is established
with the Mediterranean
(Karangatsky Sea)

Ancient Caspian basin (with a tem-
porary link through a flow into
the Black Sea along the Kumo-
Manych depression)

Post-Tertiary
Period

Novo-Euxine basin
Contemporary phase

Post-glacial transgression,
temporary basin

Con-

The Black Sea during the Quaternary Period

During the Quaternary Period the salinity changes of the Black Sea were
caused, on the one hand, by the existence or the absence of a connection with

362 BIOLOGY OF THE SEAS OF THE U.S.S.R.

the Mediterranean, on the other by the general climatic conditions of the
glacial and post-glacial periods and, in the first place, by the inflow of river-
waters, mainly from melting ice.

At the beginning of the Quaternary Period the Black Sea had a low salinity
and was populated by a Pontic fauna differing but little from that of the
Pontic basin ; its boundaries, moreover, have hardly changed at all up to the
present. Only along the Kumo-Manych depression is the Black Sea fauna
found, in deposits lying far outside its present boundaries. However, the
Black Sea salinity and its fauna underwent several substantial changes as
time went on.

The so-called Ancient Euxine basin with a Caspian type of fauna was con-
nected with the Sea of Marmora ; the latter, however, had no link with the
Aegean Sea and the Mediterranean and had the same Caspian fauna. After
the formation of the Dardanelles, the Black Sea was filled with Mediterranean
water and the Mediterranean fauna, while the Caspian fauna was pushed far
into the corners of the sea, which had lost some of their salinity. Later the
entry of the Mediterranean waters into the Black Sea was interrupted by new
risings of the bottom, and the body of water again lost some of its salinity, its
Mediterranean fauna died out, and it was occupied by Caspian fauna. The
latest subsidences of the shores again caused an inflow of Mediterranean
waters and the arrival of its fauna, while the Caspian autochthonous forms
were pushed away into the river mouths and inlets. The salinity of the water
column increased from 7 to 22%0 from the time when a connection between
the Black Sea and the Mediterranean was established ; at present, however,
the salinity balance of the Black Sea is near the equilibrium point (S. P.
Brujevitch, 1952). The alternations of the south- Russian basins during the
Quaternary Period, according to A. Archangelsky (1932), are given in Table
142.

A. Archangelsky and N. Strahov (1938) suggest that the glaciation periods
correspond to the low-salinity phases, and the interglacial periods to the
phases of increasing salinity.

The Caspian Sea during the Quaternary Period

The history of the Caspian Sea in the Quaternary Period begins in the Baku
basin with a fauna similar in its general features to the present one. This fauna
passes over into the subsequent post-Baku basins. Adacna, Monodacna and
Dreissensia are the most characteristic among the molluscs. The fluctuations
of salinity during the Ice Age and post-glacial period are mainly reflected in
a greater or smaller admixture of brackish- and fresh-water forms (Neritina,
Corbicula, Clessinia, Micromelania, Paludina, Unio, Valvata, Anodonta and
others). In the Caspian Sea, however, salinity did not reach the high level of
the Karangat basin during its high-salinity periods, but instead its waters
became more fresh than those of the Black Sea basin during the periods of
decreasing salinity. As a result the marked changes of fauna characteristic
of the Black Sea are absent in the Quaternary history of the Caspian Sea.
The main difficulty in the Quaternary history of the Caspian Sea is the

GENERAL CHARACTERISTICS AND GEOLOGICAL HISTORY 363

Table 142

Conformity with the Ice

Basin

Salinity

Rise or subsidence

Age phases (Gerasimov

of littoral

and Markov, 1939)

Chaudin lake-

Greatly

Rise

sea

lowered

Ancient Euxine

Greatly

Mindel glaciation

lake-sea

lowered

Uzunlar basin

Low

Mindel-Riss interglacial

(connected with

era

Mediterranean)

■ Subsidence

Karangat Sea (by

Saline

Riss-Wurm interglacial

the end the link

era. Riss glaciation

with the Mediter-

ranean is broken)

Novo-Euxine

Semi-fresh

Rise

Wiirm glaciation

lake-sea

Ancient Black Sea

Slightly

Subsidence

basin (new con-

saline

nection with the

Mediterranean)

Contemporary

Black Sea

Saline

synchronization of its separate phases with the general climatic changes and
the explanation of the occurrence of changes of sea-level.

The Baku basin covered a larger area than the present Caspian Sea, and
large parts of the northern Precaspian lowland were covered with its waters.
Evidently at that time there was an outflow to the west into the Ancient
Euxine basin. The succeeding Khazara basin was less saline but was of the
same size. As time went on the size of the basin gradually decreased, its level
fell and its salinity increased somewhat. I. Gerasimov and K. Markov (1939)
consider that 'there are no indications of any considerable change in the
salinity conditions of the Caspian Sea during the Quaternary Period'. How-
ever it is difficult to agree with their opinion. The historical period covered
by them appears as Table 143.

The Kumo-Manych depression several times served as a channel linking
the two seas and making possible either one-way or two-way penetration
of the fauna. The two above-mentioned authors provide the following
scheme :

1. Pontic

2. Akchagyl

3. Kuyalnits-Chauda
Apsheron-Baku period

The Manych region is submerged by the

waters of the Pontic Sea
Ingression of the Akchagyl waters. Migration

of fauna from the east
Ingression of Chauda water
Migration of fauna from the west

364

BIOLOGY OF THE SEAS OF THE U.S.S.R.
Table 143

Era

Basin Salinity

Level

Connection

with with

Black Sea Turan basin

Comparison

Baku

Lower
Caspian

Upper
Caspian

Con-
temporary

Baku

Average

Khazar Very low

Khvalynsk Slight
salinity

Con-
temporary

Average, Linked with Outflow of Ice Age

more or less Ancient fresh

stable Euxine basin water

Fluctuating, Interrupted Outflow

rise and fall ceased

Rise Connected Outflow

with Novo- along Uzboi
Euxine basin

Interruption Outflow
stopped

Post-glacial
period

4. Ancient Euxine period, Sea strait. Free exchange of faunas
Lower Caspian era

(Khazar basin)

5. Upper Euxine period, Sea strait. Probable migration of fauna from
Upper Caspian era the east

(Khvalynsk basin)

6. Contemporary era Drying up. Erosion by river waters

History of the Aral Sea

Contrary to the earlier view regarding the expansion of the Sea during the
greatest Caspian transgression, in one of the interglacial eras (Khvalynsk
era) through the Uzboi into the Sarakamysh hollow and the Aral Sea, A.
Archangelsky considers (1915) that the body of water occupying this area
had no connection with the Caspian Sea and was a huge completely fresh-
water lake with an outflow through the Uzboi (thick deposits of clay and sand
with Dreissensia, Limnaea, Unio and others). Later on this lake became much
smaller in size, and subsequently it was again filled with water as a result of
the climate becoming damper ; a system of brackish lakes was formed in the
depressions of the Sarakamysh hollow and along the Uzboi, and at this time
Cardium edule penetrated into the Aral Sea. With the transition to the present
era the climate again became dry and the Aral Sea acquired its present out-
line.

A. Behning (1938) discovered a whole series of forms of the Caspian fauna
in the lakes of the old bed of the Uzboi (Yaskhan, Karatogelek, Topiatan).
Besides several fish, among which the later Mediterranean immigrant
Atherina mochon pontica caspia is of particular importance, he listed for
those bodies of water the molluscs Dreissensia polymorpha, Theodoxus
pal/asi, Th. danubialis, the crustaceans Dikerogammarus haemobaphes, Ponto-
gammarus crassus, Corophium curvispinum and the little fish Proterorhinus

GENERAL CHARACTERISTICS AND GEOLOGICAL HISTORY

365

marmoratus. Behning thinks that the Caspian transgression reached Lake
Yaskhan and there left all these relicts.

Archangelsky's opinion, that there was no direct link between the Caspian
and Aral Seas, and his assumption of a complete loss of salinity by the latter
at the beginning of the Quaternary era, does not explain its genetic link
with the Caspian, which is indubitable in spite of all the poverty of its fauna.
Taking this into consideration V. Beklemishev (1922) relates the penetration
of the Caspian elements into the Aral Sea to the Maeotic period, assuming,
as did L. Berg (1908), the possibility of the survival of the most euryhaline
Caspian forms in the Aral Sea in the post-Tertiary period. С Grimm (1877)
gave a different explanation for the impoverishment of the Aral fauna : he
thought that the salinity of the Aral Sea had at one time increased greatly,
causing the extinction of most forms of the Caspian fauna.

Differences in the history of the southern seas

Thus each of our four southern seas had a separate history in the late Tertiary
and Quaternary Periods. The Black Sea underwent the greatest fluctuations
in temperature, salinity and fauna and the smallest in its water-level. The
Caspian Sea underwent much greater fluctuations in its level, but its salinity
changes were much less.

The simplest history is that of the Aral Sea, which was only formed in the
middle or second half of the Quaternary Period.

In general (I. Gerasimov and K. Markov, 1939) the history of these seas
can be presented in the form of Table 144.

Table 144

Black Sea

Caspian Sea

Aral Sea

Comparison with
glaciation phases

Freshened
Chaudin basin

Freshened
Ancient Euxine
basin

Brackish Uzunlar
basin. Saline
Karangat Sea
(connected with
Mediterranean)

Slightly brackish
Novo-Euxine
basin

Brackish Ancient
Black Sea (con-
nected with
Mediterranean)

Brackish
Baku basin

Freshened
Khazar basin

Brackish water
Khavalyn basin

Gradual lowering
of its level

Aral-Sarakamysh
alluvium plain

Formation of Aral
Sea

Riss glaciation

Tirrene period

Outflow of part of

Amu-Darya waters Wurm glaciation

(through Uzboi)
Drying up of Monastyr

Uzboi period

366 BIOLOGY OF THE SEAS OF THE U.S.S.R.

As one moves eastward the waters of the Black, Caspian and Aral Seas
undergo a lowering of their saline composition relative to that of the ocean
(Table 145).

Table 145. Comparative saline composition of waters of ocean and Black, Caspian
and Aral Seas, expressed in percentages of the total (L. Berg from L. Blinov)

Salt

components

Ocean

Black Sea

Caspian Sea

Aral Sea

CaS04

3-94

2-58

6-92

14-98

MgS04

6-40

7-11

23-56

25-87

KCL

1-69

2-99

1-21

2-05

NaCl

78-32

79-72

62-15

56-07

MgCl2 MgBr2

9-44

9-07

4-54

0-82

СаСОз C02

0-21

1-59

1-24

0-21

Total salinity

34-30

18-60

12-86

10-61

The increase of sulphates from 10-34 to 40-85 per cent and the decrease of
chlorides from 8945 to 58-94 per cent are the most characteristic features of
these changes. The change of the salt content of the water of the south-Russian
seas is not a simple derivative of the river discharge, although it is controlled
by it. Whereas the saline composition of the Caspian Sea salt content can be
considered as the 'chemical legacy' of the ocean, exposed for some time to
the influence of river discharge and subjected to a complex conversion, the
Aral Sea water is by origin metamorphized water of the coastal drainage.
This can be shown by a comparison of the salt composition of the water of
the Caspian Sea and that of the Volga, in percentages (Table 146) (S. Bruje-
vitch, 1937, 1941).

Table 146

Salts Ocean Caspian Sea Volga, off Astrakhan

so4
co3

This fact comes out even more clearly in a comparison of the salt composition
of the Aral Sea water with the average ionic discharge over many years
of the rivers Amu-Darya and Syr-Darya (Table 147) (O. Alekin, 1947).

30-593

24-82

}б-67

1-106

0-66

1-197

2-70

23-34

3-725

5-70

4-47

55-292

41-73

5-46

0188

006

7-692

23-49

25-63

0-207

0-84

34-43

GENERAL CHARACTERISTICS AND GEOLOGICAL HISTORY 367

Table 147

River Ca2+ Mg2+ Na+ + K +

in% in% in%

Amu-Darya 83-1 17-6 11-12 2-4 43-4 9-2

Syr-Darya 87-6 16-1 20-6 3-8 43-8 80

River HC03- S042 CI- Sum of

in% in% in% ions

Amu-Darya 153-5 32-6 104-9 22-3 74-1 15-7 470-8

Syr-Darya 186-1 35-1 164-4 30-2 40-3 7-4 543-8

III. SOME PECULIARITIES OF THE DEVELOPMENT OF
FAUNA AND FLORA

General features

The palaeogeographic changes discussed above in the seas which covered the
southern part of Europe and Asia during the Tertiary and Quaternary Periods
influenced their fauna in a radical way, primarily through loss of salinity
which was at times very considerable.

The genetic heterogeneity of the fauna of our southern seas is the result
of their history.

Relict community

The so-called ancient autochthonous community — the originally marine
Tertiary fauna elaborated by the fresher-water phases — may perhaps have
had a variety of origins. The marine fauna had several opportunities of
breaking into the bodies of water which occupied the area of the Black and
Caspian Seas. Most characteristic of the Caspian autochthonous fauna are
the families and genera of the Porifera Mecznikowiidae, the hydroids Cordy-
lophora, the jelly-fish Caspionema and Ostroumovia, the molluscs Cardiidae
(Adacna, Monodacna, Didacna), Dreissensiidae, Hydrobiidae (Microme-
lania, Caspia, Clessiniola, Hydrobia, Theodoxus), the polychaetes Hypania,
Hypaniola, Parhypania, the crustaceans Pontogammarus, Corophium,
Gmelina, Amathillina, Pseudocuma, Mesomysis, Paramysis, Metamysis,
Astacus, the bryozoans Victorella, the fish Acipenseridae,* Caspialosa,
Clupeonella and Gobiidae. This autochthonous community in the main
evolved from the marine fauna of the Tethys, which had spread its relicts
throughout the brackish and fresh bodies of water of southeastern Europe
and central Asia (including the Baikal and Okhrida lakes, the fauna of which
is akin to that of the Caspian Sea). This autochthonous community, domin-
ant in the Caspian Sea, is concentrated in the least saline parts of the more
saline Black-Azov Sea basin in the firths, river-mouths and the eastern part of
the Gulf of Taganrog, while the open parts of the Black and Azov Seas are

* The weight of evidence, however, suggests the derivation of Acipenseridae from fresh
water.

368 BIOLOGY OF THE SEAS OF THE U.S.S.R.

populated by Mediterranean fauna which penetrated into it after breaking
through the Dardanelles.

Table 148, drawn from the data of A. Derzhavin (1925), F. Mordukhai-
Boltovskoy (1939) and M. Bacesko (1940), is a good illustration of this.

Table 148

Order

Mysidacea

Cumacea

Amphipoda

Total

Percentage

Black Sea :

Mediterranean

62-5

Caspian
Endemic

28
5

31-8
5-7

Total

100

Azov Sea :

Mediterranean

33-3

Caspian
Endemic

15
1

29
3

60-4
6-3

Total

100

Lower Volga :
Mediterranean

5-7

Caspian
Endemic

94-3

Total

100

When investigating the fauna of the Dnieper delta, F. Mordukhai-Boltov-
skoy (1948) found that on the sands and clayey-sand bottoms of the arms of
the delta ' the fauna has on the whole a clearly expressed Caspian character.
Fresh-water species are generally of secondary importance, and in the main
arms, where there is a bottom of pure sand . . . the predominance of the Cas-
pian crustaceans, especially the mysids, becomes even more evident. At some
stations Caspian species were found exclusively. ' On rock bottoms the Dreis-
sensia biomass may amount to 3-6 kg/m3, an amount which has not been
found even in the Caspian Sea (see below). On the contrary, in the macro-
phyte growths of the littoral zone and in the lakes of the delta typical fresh-
water fauna is markedly predominant, while the Caspian elements are either
secondary or absent. Subsequently more light has been thrown on this
phenomenon through research carried out by Yu. Markovsky (1953-55).

The fauna of the deltas of the Dnieper and Don are very similar:
in both cases ' the significance of the Caspian fauna decreases with a fall in
the speed of the current and with the transition to bodies of water of the
lake type'.

Distribution of relicts in the Azov and Caspian basins

Latterly J. Birstein (1946) and F. Mordukhai-Boltovskoy (1946, 1960) have

approached from a new standpoint the problem of the time of penetration

GENERAL CHARACTERISTICS AND GEOLOGICAL HISTORY 369

into the Azov-Black Sea basin of the forms of the Caspian fauna living there
at present.

The Azov-Black Sea basin is almost free of the endemic forms of the
Caspian fauna (except for Moerisia maeotica (Ostroumovia) among the coe-
lenterata, Corophium maeoticum, Hemimysis serrata, Astacus colchicus, Gam-
mar us shablensis, Niphargoides intermedins, Stenogammarus compresso-similis
among the crustaceans, Percarina among the fishes and Clupenella abrau and
Monodacna colorata and M. pontica among the molluscs) ; this is an indi-
cation, contrary to widespread opinion, of a very recent penetration of
Caspian fauna into the Sea of Azov followed by its settlement in the Black
Sea. In the opinion of these workers, this penetration through the Manych
Strait should be related to the post-glacial period. P. Dvoichenko (1925),
however, had earlier expressed the same point of view for the whole of the
Caspian fauna of the Azov-Black Sea basin (migration during the Novo-
Euxine period).

Mordukhai-Boltovskoy relates this migration to the period of the Khvalynsk
transgression. Both authors accept the possibility of the mass extinction of
Pontic fauna in the Azov-Black Sea basin during the period of greatly in-
creased salinity in the Karangat era.

Taking issue with the two above-mentioned authorities, A. Derzhavin
(1951) has noted that 95 species and 50 genera of Ponto-Caspian autoch-
thonous forms live in the lower reaches of rivers and in inlets in the northwest
part of the Black Sea (from the Danube to the Dnieper), correspondingly 54
species and 32 genera live in the rivers and inlets of the Sea of Azov, and 64
species (34 genera) in the northern Caspian river basins. Moreover, a large
number of autochthonous relict Pontic forms absent from the Volga are
found in the rivers and inlets of the Black and Azov Seas. Derzhavin reckons
among such forms five genera and seventeen species of fish, six genera and
fourteen species of molluscs, two genera and three species of mysids, one
genus and ten species of amphipods and one species of decapods. According
to Derzhavin in all 46 species (15 genera) absent from the basin of the river
Volga, and 43 species (18 genera) absent from the Sea of of Azov live in the
river basins of the northwest part of the Black Sea. Moreover, Derzhavin
points out the fact that these forms thrive in fresh water and their coloniza-
tion of saline water would inevitably have been difficult. If the colonization
of the Caspian fauna had proceeded through the Sea of Azov and in a com-
paratively recent period, the picture would have been just the opposite.

Thus, without denying that an exchange of fauna took place in a recent
geological period between the Black and Caspian Seas, Derzhavin consider?
that an autochthonous fauna of the Pontic type existed in the Black Sea in
the pre-Khvalyn period. V. Pauli (1957) supports Derzhavin's opinion on the
basis of his examination of the distribution of the mysids of the Black Sea
and the Sea of Azov. Seven species of mysids live in the Black Sea and only
five in the Sea of Azov. Yu. Markovsky (1953), who considers the 'Caspian'
fauna in the inlets of the northwest part of the Black Sea to be a legacy of the
Pontic period, is of the same opinion. The facts quoted by Mordukhai-
Boltovskoy himself (1958) to some extent contradict his own opinion on the

370 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Khvalyn age of the 'Caspian' fauna in the Azov-Black Sea basin. 'The
comparative richness of the Caspian fauna in the northern approaches to the
Black Sea', he writes, 'is apparent not only in its high biomass, but also in
the considerably greater number of its species (as compared with the Sea of
Azov basin — L.Z.). Whereas we used to reckon 49 species of (Caspian —
L.Z.) invertebrates for the river Don, and only 23 for the River Kuban, for
the rivers Dnieper and Bug we have no less than 69 (Markovsky), and 64 for
the Danube. '

A very curious phenomenon comes to light in a comparison of the distribu-
tion of the autochthonous relict community in the Azov and Caspian Seas
(V. Beklemishev, 1922; later developed by J. Birstein, 1946, F. Mordukhai-
Boltovskoy, 1953 and Yu. Markovksy, 1953—56). In the Sea of Azov basin
the relicts are in the main concentrated in the area of the river mouths in
fresh water. In the Caspian Sea, however, most of them live in the saline
waters of the Sea itself.

Mordukhai-Boltovskoy points out, for example, that the mollusc Caspia
gmelini, which he found in the delta of the Don, in the Caspian lives only in
the Sea itself. The Don delta is in fact the main place where the relicts in the
Sea of Azov accumulate ; some of them are found there in large numbers
(Mesomysis kowalewskyi up to a few g/m2, Hypania and Hypaniola at times
up to 10 g/m2, and large quantities of Monodacna and Dreissensia). Only
six or seven species of these relicts are found in the Sea of Azov itself, while
in the Gulf of Taganrog their number rises to 25 forms in the less saline parts
(counting not only the peracarids, but also the molluscs, polychaetes and
coelenterates) Table 149).

Table 149. Distribution of autochthonous relict forms in the Sea of Azov and the River Don

Open parts

of" Sea of

Azov

Middle part
of Gulf of
Taganrog

Estuary
(part)
of Don

Lower
Don

Don

upper
course

Voronezh
river

Total number of relict

forms
As percentage of total

fauna

14-3
11

About 12
24-5
5-7

51-0

0-2

46
93-9

9
16-3

3
6-1

$Ao

Fresh water

The fact that the main mass of the relicts is adapted to the Don delta is
particularly interesting, since the pre-delta zone of the Gulf of Taganrog is
abundantly populated by fresh-water forms, which are often accumulated
there in very considerable numbers. Thus the Caspian relicts in the basin of
the Sea of Azov cannot endure a rise of salinity as well as the fresh-water
forms ; in other words they are more ' fresh water ' than the fresh- water organ-
isms themselves.

It has been shown, by the research done in the lower reaches of the rivers
and in the inlets of the northwestern part of the Black Sea by Markovsky and

GENERAL CHARACTERISTICS AND GEOLOGICAL HISTORY 371

some Bulgarian investigators, that in this area the aspect of the 'Caspian'
Sea fauna is even more a ' fresh water' one than it is in the Sea of Azov.

The same fauna, or fauna very nearly the same from a taxonomic stand-
point, exists in the Caspian Sea at a much higher salinity (up to 12 or 13%0).
Some species, which in the conditions of the Caspian Sea must be considered
comparatively stenohaline and avoiding fresh water, enter the rivers in the
Azov-Black Sea basin (Table 150). Among such forms the following may be
mentioned : Pandorites podoceroides, Pontogammarus maeoticus, Caspia
gmelini, Clesissiola variabilis (Dnieper inlet), Dreissensia rostriformis (Bug
inlet) and others. M. Bacesko (1948) discovered the polychaete Manayimkis
caspia, which lives in saline water in the Caspian Sea, in the Danube. Lateo-
labrax has a fresh-water habitat in the Bug inlet and a marine one in the
Caspian Sea. Birstein pointed out that the Azov Monodacna colorata and
Dreissensia polymorpha perish very rapidly in the Azov and Caspian waters
at a salinity of 5%0 (by chlorine).

The following relicts, among others, live in the Don ; two species of coelen-
terates, two bivalves and one gastropod mollusc, two polychaetes, one species
of leech and 38 species of higher crustaceans. Only three species of relict
forms living in the Sea of Azov are absent from the Don delta.

Among relicts, apart from Malacostraca, only one polychaete was en-
countered in the Volga and Ural rivers. In addition, all the relict forms live
in the open parts of the Sea.

The most natural explanation of this remarkable difference in the distribu-
tion of the autochthonous fauna in two seas situated side by side seems to
lie in the difference of their historical past and their salinity, and finally in the
influence on the autochthonous fauna of a stronger rival — the Mediterranean
fauna. A stronger fauna displaces the weaker one from all regions where it
can live itself. This proposition can only have a most general character. Some
of the forms of Caspian fauna in other bodies of water are very powerful
competitors of the local fauna, as are, for example, the Caspian immigrants
into the Baltic Sea, and still more, into fresh water. According to Mordukhai-
Boltovskoy (1960) some Caspian forms attain greater numbers and biomass in
the Black and Azov Seas than in the Caspian Sea. Thus, for example, in the
Azov-Black Sea basin Dreissensia polymorpha yields a biomass of up to 4-7

Table 150. Distribution of autochthonous relict forms in the Caspian Sea, Vo Iga and Ural

Throughout

Northern

Volga

Middle

Upper

Caspian Sea

Caspian

Delta

Volga

Total number of

relict higher

crustaceans

38-8%

9-2%

4-0%

Ural

Up to

Delta

Libshchensk

Uralsk

(100%)

(63-3%)

13-3%

8-2%

2-0%

S%o

Up to 13

<10

Fresh water

372

kg/m2
90,000

BIOLOGY OF THE SEAS OF THE U.S.S.R.

with 92,000 specimens, Pontogammarus maeoticus — 1-38 kg/m2 with
specimens, Hypaniainvalida — 5, 500 and 15-4 g/m2, Monodacna color ata

—9,000 and 1-35 kg/m2, Corophium
maeoticum — 39,780 and 158-7 g/m2,
and so on. It is most characteristic
that in relation to salinity the
autochthonous and Mediterranean
forms are distinct from each other;
this is clearly seen even in the case
of the mysids (Fig. 178).

Penetration of the relict community
into fresh water

The autochthonous relict community
penetrated into fresh water during
the phases of greatest loss of salinity
and the subsequent increase of salin-
ity. The migration into fresh water
was easiest for the crustaceans and
fishes and for some individual species
of coelenterates, molluscs, bryozoans and polychaetes. Like the fresh waters
of the Arctic basin those of the basins of our southern seas give shelter to an
abundant relict fauna {Table 150).

C\) Nh tQ °0 C3 C\j xj- CO OO Сэ C\J 0°/

Fig. 178. Distribution of Black Sea my-
sids according to salinity: / Relicts
(endemic forms) ; and II Mediterranean
forms (Bacesko).

Fresh-water immigrants

The low salinity of the bodies of water situated where the Black and Caspian
Seas now lie opened them to immigrants from fresh water. In this case
too, fish yield the greatest number of species, mainly the cyprinoid and
Percidae families, and, to a lesser extent, next come the lower crustaceans,
molluscs, oligochaetes and insect larvae (Chironomidae).

The Arctic community

The Arctic relict (or rather pseudo-relict) community which penetrated into
the south-Russian bodies of water from the north in the post-glacial period,
consisting mainly of crustaceans, is most original. It includes also some
fish, seal and, possibly, the polychaete Manayunkia. The Arctic immigrants
are very scarce in the Black Sea and are absent from the Aral Sea.

The Mediterranean community

The Mediterranean flora and fauna which filled the Black and Azov Seas
penetrated as far as the Aral Sea, although the connection between the Black
and Caspian Seas through the Kuma-Manych system and farther east through
the Uzboi was poor. Some thousands of years ago the mollusc Cardium edule
penetrated in this manner into the Aral Sea and Lake Charkhal, the fish
Atherina and the sea-weed Zostera nana (the latter also into the Aral Sea)

GENERAL CHARACTERISTICS AND GEOLOGICAL HISTORY

373

also migrated there at some unknown time. In recent decades the eastward
penetration of Mediterranean immigrants has continued, either with the
passive participation of man (Rhizosolenia, Mytilaster and two species of
shrimps Leander and two species of Balanus), or through measures being
taken for acclimatization (two species of the grey mullet Mugil, the poly-
chaete Nereis and the mollusc Syndesmya and some others). This enormous
activity of some forms of Mediterranean fauna, and their indubitable advant-
ages over the Caspian and Aral forms in the struggle for existence, is a clear
indication of the wide possibilities of acclimatization farther east of the
euryhaline Mediterranean fauna, inhabiting the Black Sea and the Sea of
Azov. The migration of the two brackish-water forms — the medusa Black-
fordia and the crab Rithropanopeus harrisi tridentatus — from the northwestern
part of the Atlantic Ocean to the Caspian Sea is also most curious.

Impoverishment of the Mediterranean fauna

For the reasons enumerated above the qualitative differentiation of the
Mediterranean fauna decreases with its movement to the east (Fig. 179).

The Mediterranean flora and fauna become four times poorer by the time
they reach the Black Sea, while in the Sea of Azov only 2-5 per cent remains.

Fig. 179. Qualitative abundance of Mediterranean flora and fauna and its impover-
ishment with its movement eastward. Total number of animal species is denoted by
the numerals (Zenkevitch). 1 Mediterranean fauna; 2 Caspian fauna; 3 Fresh-
water fauna ; 4 Arctic immigrants ; 5 Direction of migration.

The qualitative impoverishment in the Black Sea affects primarily the
most stenohaline part of the population — Radiolaria, Siphonophora, Cteno-
phora, corals, many groups of crustaceans and especially decapods, all the
molluscs and especially cephalopods and gastropods, the echinoderms, the
tunicates and fish.

In the Sea of Azov, of the 200* Mediterranean coelenterates only three
species are found, of the 1,457 species of molluscs only 12, of the 51 species of
crabs only one, of the 300 species of pelagic copepods only 8, and so on.

Another characteristic factor in the qualitative impoverishment of the

* The number of species of Mediterranean animals, according to Gr. Antipa (1941).

374 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Black Sea fauna is the absence of deeper-water fauna or a fauna connected in
its development with great depths (below 125 to 150 m).

The ' Atlantization' of the Mediterranean fauna in the Black Sea
The characteristic differences between the fauna of the Black and Azov Seas
and that of the Mediterranean had already been observed by the first investi-
gators of the fauna of our southern seas. K. Kessler (1860) pointed out that
fish in the Black Sea are often smaller than in the Mediterranean, 'which is the
result, probably, of lower temperature and less salinity'. This was also noted
by H. Ratke as early as 1837. V. Sovinsky too dwelt on this phenomena (1902).
S. Zernov (1913) pointed to the fact that the Mediterranean crab Carcinus
maenas is considerably smaller in size than those in the Black Sea and off the
shores of Great Britain. Zernov expressed the opinion that 'once in the
Mediterranean the crab became smaller, and when passing into the colder
water of the Black Sea it grew again in size'.

A. Sadovsky (1934) approached this problem on a wider front. He estab-
lished for 14 species of Black Sea molluscs (including sea mussel, oysters,
Patella, Syndesmya and others) a closer relationship in the shell structure
(size, shape, thickness, sculpturing, colouring) with Atlantic species than with
Mediterranean. Sadovsky considers that once the Atlantic forms got into the
Mediterranean they underwent definite changes as a result of higher salinity
and temperature. In the Black Sea, under the influence of lower salinity
(from 37 to 18%0) and temperature (the minimum Mediterranean temperature
is 13°; that of the northern part of the Black Sea descends to zero) there
took place a 'reshaping' of the original Mediterranean aspect into the
Black Sea one, which developed autochthonously in the Black Sea, since in
the hydrological conditions described we have, as it were, a return from
Mediterranean conditions to those of the North Atlantic. This author thinks
that the rule noted by him for molluscs must also be applicable to other
groups of Black Sea fauna. The species of molluscs which have undergone
'Atlantization' form 11-4 per cent of all Black Sea malacofauna. Sadovsky
points to the fact that in the 'warmer part of the Sea, in the Batum region,
one observes a greater similarity between some of the molluscs and the Medi-
terranean ones than one sees in the northern part of the Sea'. Finally, Sadov-
sky observes another interesting phenomenon in the case of Patella and
Mytilus : when young they resemble the Mediterranean forms more closely,
in maturity this resemblance is lost.

The affinity between the Black Sea fauna and that of the northern parts of
the Atlantic Ocean lies first in the selection of genera and species, and
secondly in the above-mentioned morphological resemblance between the
Black Sea and the Atlantic Ocean forms. As regards the former feature of
resemblance, Sovinsky says that in the Black Sea a selection was made of the
northern forms which had remained there since the Ice Age, and which
had died out or were poorly represented in the Mediterranean. Thus the Black
Sea fauna is a selection of cold-water relict species. To what extent can the
morphological peculiarities mentions d above also be explained by their
relict character, i.e. did these forms get into the Black Sea as 'northern' forms

GENERAL CHARACTERISTICS AND GEOLOGICAL HISTORY 375

during the Ice Age, as suggested by Sadovsky, or did they go through the
process of ' Atlantization ' in the Black Sea for a second time under the effect
of more stringent conditions of life? It is quite evident that both possibilities
must be considered. If the appearance of some characteristics can be easily
explained by the effect of Black Sea climatic conditions (size of the body,
thickness of the shell), others are easier to understand from the standpoint
of their relict origin (shape of the shell, sculpturing).

Among the group variations through which different Black Sea species may
have gone besides the change of size, one may note, for example, the solidity
of the mollusc shells. G. Afanas'ev has shown (1938) that the Black Sea
molluscs have a lighter shell than those of the fully saline seas. The ratio of

Fig. 180. Changes in benthos biomass (g/m2) from west to east along the system of
southern bodies of water (Zenkevitch, 1947).

the weight of the shells to that of the body for the Black Sea bivalves varies
from 0-95 to 4-5 per cent (average 1-8 per cent), while for molluscs of fully
saline seas it varies from 1-25 to 10-8 per cent (average 3-5 per cent).

Changes of biomass from west to east

The regular change in the intensity of the processes of biological productivity
from west to east is closely linked with the hydrological and hydrochemical
conditions of the southern European seas. A marked decrease of benthos
biomass, from a few hundred g/m2 to some tens, is observed as we pass from
the Atlantic Ocean to the Mediterranean Sea through the Straits of Gibraltar ;
it reaches its minimum in the eastern part of the Mediterranean Sea (a few
g/m2). Only in some places off the coast and at the mouths of rivers does the
biomass increase. In the Sea of Marmora the biomass is already greater ; it
reaches fairly high indices in the Black Sea (100 to 200 g/m2 and more). In
the Sea of Azov the processes of biological production reach their maximum.
Farther east a decrease of productive capacities is again observed, less signifi-
cant in the Caspian Sea and more marked in the Aral Sea (Fig. 180).

The Mediterranean Sea can be cited as an example of the least biologically
productive sea in the world ; the Sea of Azov, on the contrary, is the most
productive.

The decrease of biomass in the Mediterranean Sea and its subsequent

376 BIOLOGY OF THE SEAS OF THE U.S.S.R.

increase in the Black and Azov Seas must be explained first by the changes
in the quantity of nutrient salts in the zone of photosynthesis. The subsequent
decrease in the Caspian and especially in the Aral Sea should be accounted
for by the qualitative changes in the flora and fauna composition and some
peculiarities of the hydrological conditions in these seas.

As a result of the absence until very recently of any data on the quantitative
distribution of life in the Black Sea, owing to the hydrogen sulphide con-
tamination of its depths and the shortage of information on its very rich
pelagic life, and owing to the proximity of the Sea of Azov which is excep-
tionally abundant in life, a false picture of the poverty of life in the Black Sea
was gradually built up, beginning with Ratke and Nordmann. This was
furthered by the qualitative impoverishment of fauna as one passes from the
Mediterranean to the Black Sea, which had long been well known.

In very recent years a quantitative investigation of phytobenthos (N.
Morozova-Wodjanitzkaja, 1936-41), and of zoobenthos (V. Nikitin, 1934,
1938 ; L. Arnoldi, 1941), of phytoplankton (S. Maljatzky, 1940 ; N. Morozova-
Wodjanitzkaja, 1940) and of zooplankton (E. Kosjakina, 1940; V. Nikitin,
1939; S. Maljatzky, 1940) and, finally, of the enormous wealth offish in the
pelagic life of the open seas led V. Wodjanitzky (1941) to carry out a thor-
ough revision of the data on the biological productivity of the Black Sea
(see below).

In his estimate of the total resources of plant and animal organisms in the
Black Sea (not counting fish), Wodjanitzky calculates that there are on the
average about 150 g of organisms per 1 m2 of sea surface, i.e. approximately
the same as in the Barents Sea. The productivity of the Black Sea, however,
must be several times higher than that of the Barents Sea owing to its much
higher temperature.

Thus as regards its biological productivity the Black Sea should almost
occupy the second place in the system of the Mediterranean-Black-Azov-
Caspian and Aral Seas.

Fish migrations

This gradual increase of biological productivity from west to east in the
Mediterranean-Sea of Azov system has produced a peculiar pattern of
spawning and feeding migrations of the fish population; it seems, as it
were, to consist of three main links, besides a series of secondary ones.
This pattern of migration was brought into being largely through the effect
of the temperature-salinity range within the limits of the whole basin — in
summer time the temperature of the upper layers of water remains almost the
same throughout the whole basin, but in the winter the amplitude of its
fluctuations is more than 15° ; moreover the eastern part of the basin remains
covered by ice for a long time.

The range of salinity, which is maintained naturally throughout the whole
year, is even more marked: from 37 to 38%0 in the Mediterranean Sea to
9 to 10%0 in the Sea of Azov.

All these spawning-feeding migrations have a single general direction —
eastward for feeding, westward for spawning (Fig. 181). It is possible to

GENERAL CHARACTERISTICS AND GEOLOGICAL HISTORY 377

distinguish among them two large groups, connected with the thermopathy
and halopathy of the corresponding race of fish. Some fish move between
zones of small salinity range, keeping always within zones of similar salinities
(stenohaline) and during their whole existence living within the boundaries
of one body of water ; others can survive during their travels considerable
changes of salinity (euryhaline) and can pass from one body of water to
another. The same can be said about temperature conditions — some can
only survive limited changes of temperature during the year (stenothermic) ;
others can live through considerable temperature fluctuations (eurythermic).
This is illustrated by the diagram in Fig. 182.

It is remarkable that Sarda, which populates the eastern part of the Mediter-
ranean, moves in the summer to the Black Sea for feeding and spawning.

Fig. 181. General character of feeding migrations offish (3) in eastern part of Medi-
terranean, Black and Azov Seas, contrasted with abundance of plankton (7) (see
explanation in text) and with commercial productivity (2) (kg/ha) (Zenkevitch, 1947).

This is possibly evidence that the past history of the eastern Mediterranean
shoal of Sarda was somewhat exceptional — maybe that its fate was linked
during some periods of the Quaternary Period with life in bodies of water
of low salinity. A series of most interesting regularities was established by
A. Svetovidov (1943, 1948, 1957) in his comparison of the taxonomic com-
position, distribution, biology and size of fish in the Azov-Black Sea and
Caspian basins. First of all, Caspian pelagic fish are larger than those in the
Black and Azov Seas. Caspiolosa brashnikovi, with a length of 20 to 35 cm
(C. br. brashnikovi) in the Caspian Sea and 16 to 20 cm (C. br. maeotica) in
the Black Sea, can be taken as an example. The longest specimens of these two
forms of herrings ever found were 49 and 31 cm ; C. caspia caspia is usually
18 to 22 cm long, its greatest length being 28 cm, while C. caspia tanaica
is 14 to 16 cm long, with a maximum length of 20 cm. This holds true for all
the members of the Caspialosa and Clupeonella genera. The same was
observed with grey mullet — the largest size of the Black Sea M. saliens is
34 cm, while that of the Caspian M. saliens is 39 cm ; M. auratus has corres-
ponding lengths of 42 and 54 cm; Atherina mochon pontica reaches a

378

BIOLOGY OF THE SEAS OF THE U.S.S.R.

length of 12-5 cm, while the Caspian A. m. p. form reaches 14-0 cm. The
Black Sea pipefish {Syngnatus nigrolineatus) reaches 21-5 cm in length, and
the Caspian (S. n. caspius) — 23-0 cm. The fact that the Baltic herring, acclima-
tized in the Aral Sea, is much larger in size than that in the Baltic Sea (more
than 20 cm) is most interesting. According to some data, Nereis and some

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10
WINTER

TEMPERATURE

Fig. 182. Two types offish migrations in the Mediterranean, Black and Azov Seas

(Zenkevitch).

prawns transplanted from the Sea of Azov into the Caspian are also larger
in size.

It is very curious that a reverse relationship is apparent in the case of bull-
heads (Gobiidae) — the majority of them are much smaller in the Caspian Sea.
Thus, for example, in the Sea of Azov the largest size of Gobius melanostomus
is 23-5 cm, and in the Caspian Sea {affinis form) only 19-6 cm; Proterorhinus
marmoratus in the Sea of Azov and Pr. m. nasalis in the Caspian Sea are
respectively 11-5 and 7-0 cm in length, etc. Svetovidov explains this difference

GENERAL CHARACTERISTICS AND GEOLOGICAL HISTORY 379

by the fact that pelagic fish in the Caspian Sea, in contrast to those of the
Black and Azov Seas, have no powerful competitors ; it might also be the effect
of higher temperature. The other peculiarity to which Svetovidov drew atten-
tion lies in the fact that in the Caspian Sea they form a larger number of
species and a considerably larger number of smaller taxonomic subdivisions.
Six species of herring and one species of the Clupeonella genera live in the
Black Sea; in the Caspian there are eight species and sixteen smaller sub-
divisions of herring of the genera Caspiolosa. This difference is also ex-
plained by Svetovidov by the absence from the Caspian Sea of competitive
members of pelagic herring and other genera (in the Black Sea there are
Spratella, Sardina, Sardinella and Alosa), which has furthered the evolution of
the species. However, this might be rather more due to changes of salinity which
repeatedly occurred in the Caspian basin during the Tertiary and Quaternary
periods, during which a part of the Clupeidae must have died out and the
remainder have gone through a period of vigorous development of forms.

Finally Svetovidov also notes a third very characteristic feature of the
Caspian Clupeidae — a large number of purely 'marine' species and forms
which do not enter fresh waters, but which migrate great distances within the
sea and multiply in sea water. This relates both to the three Caspian species
of the genus Clupeonella and to the species of the genus Caspialosa (C.
brashnikovi, C. saposhnikovi, С sphaerocephala). Svetovidov thinks that in
the Black Sea such forms were 'pushed into the least saline parts of the Black
and Azov Seas by more vitally active Mediterranean immigrants'. Both
Caspian Clupeidae forms, which make long migrations, and the purely
' marine ' forms are absent from the Black and Azov Seas. These most curious
facts and the explanations given for the phenomena discussed above require
further research and additional speculation.

Zoogeographical affinity

The marked differences between the fauna of the Mediterranean and Caspian
Seas makes it impossible to include both in the same zoogeographical unit.
The Black Sea and the Sea of Azov must be included, as the Black Sea-Azov
province, in the Mediterranean-Lusitanian subregion of the boreal region ;
as for the Caspian Sea it should not be included as part of a Pontic-Caspian-
Aral province of the Mediterranean subregion as was done by V. Sovinsky
(1902), neither should it be considered as the Caspian province, as was done
by A. Derzhavin (1925). The Caspian fauna is too original and has little in
common with the Mediterranean fauna. Therefore it is more correct to give
to the Caspian Sea a separate zoographical place of its own as the Caspian
relict region.

9
The Black Sea

I. GENERAL CHARACTERISTICS

The Black Sea may be considered as a tributary of the Mediterranean of a
markedly anomalous character which penetrates deep inland. It is connected
with the Mediterranean Sea through the Bosporus and the Dardanelles ; it
is 3,000 km away from the Atlantic Ocean. Its considerable depth, its great
reduction in salinity by the inflow of river water, and an influx of bathy-
metric saline waters from the Sea of Marmora create a sharp saline stratifica-
tion of the Black Sea waters into an upper layer, inhabited by a rich flora and
fauna, and deep masses of water contaminated by hydrogen sulphide. There
is very little exchange of water between the two layers. The fauna of the Black
Sea consists of three genetically different elements.

The sections of the Sea with the lowest salinity — inlets and river mouths
and the rivers themselves — are inhabited by Caspian relict fauna. Members
of the fresh-water fauna move into these parts of the Sea from the rivers and
at times become abundant there.

The Sea, however, is inhabited by the most euryhaline forms of the Mediter-
ranean flora and fauna ; the number of species is about four times smaller
than that in the Mediterranean. The Black Sea fauna is numerically inferior
to that of the Sea of Azov and considerably superior to that of the Mediter-
ranean.

A luxuriant development of the pelagic fauna, enormous growths of red
algae, phyllophora and a marked display of filter-feeders (Mytilus, Modiola
and others) : such are the biological characteristics of the Black Sea. It is a
feeding ground for many Mediterranean fish, while a number of Black Sea
fish leavit in summer time, moving to the Sea of A zcv to feed.

II. HISTORY OF THE STUDY OF THE BLACK SEA

First period

The exploration of the Black Sea was begun by the voyages of P. Pallas
(1793-94) who devoted the third volume of his work Zoographia Rosso-
Asiatica (1811) to the genetic link between the Black and Caspian Sea fauna.
In 1858 the Russian ichthyologist K. Kessler worked on the shores of the
Black Sea ; he expressed, with remarkable precision, a correct opinion on the
geological part of the Black Sea (1874). Kessler arrived at the following con-
clusions : (J) at one time the Black, Azov and Caspian Seas formed one single
body of brackish water ; (2) the Caspian Sea was separated from the Black
Sea before the latter was connected with the Mediterranean ; (3) the migra-
tion of Mediterranean fauna into the Black Sea is continuing ; (4) the last
phase of the rise in salinity of the Black Sea caused its original fauna to move
into the less saline parts of the Sea and into the Sea of Azov.

380

THE BLACK SEA 381

A more profound study of the invertebrate fauna of the Black Sea was
begun by the end of the 'sixties with the investigations of V. Tchernjavsky
(mainly of the crustaceans).

In 1868 V. Uljanin, who later became the first director of the Sevastopol
Biological Station founded in Odessa in 1871-72 and was transferred to
Sevastopol in 1879, began his investigations of the Black Sea. As a result of
his work Uljanin produced for the Black Sea a list containing 380 species of
animals and proceeded to a zoogeographical appraisal of the Black Sea fauna
which remains basically correct to this day. The Black Sea fauna is mainly a
greatly impoverished Mediterranean fauna which has acquired only a feebly
marked independent character, and which shares some unimportant features
with the Aral-Caspian fauna.

On the initiative of our greatest geologist, N. Andrussov, a composite
sounding expedition worked in the Black Sea, which included Andrussov and
O. Ostroumov, with the hydrologist I. Spindler as its director. During this
expedition the contamination of the deep layers of the Sea by hydrogen sul-
phide and the absence of life there was discovered for the first time. Later the
work of Ostroumov in 1892-94 in the Bosporus, the Sea of Marmora and
in some parts of the Black Sea and the Sea of Azov was of great importance.
Westward of the Bosporus were found shells of Caspian molluscs in a semi-
fossil state, an indication that the Sea of Marmora had formed part of the
Pontic basin. On the other hand, Ostroumov showed that the fauna of the
eastern part of the Sea of Azov and of the river mouths and inlets of the Black
Sea bore the greatest resemblance to that of the Caspian Sea.

Thus the main ideas on the Black Sea fauna, its relation to the Caspian
and Mediterranean faunas, the history of its origin and development, were
formed by the beginning of the present century. The work of V. Sovinsky
(1902) who summed up all the information collected earlier on the Black Sea,
is an excellent conclusion to this stage of the investigation of its fauna and
zoogeography.

Second period

In the year of the publication of Sovinsky's monograph, S. Zernov began his
work on the Black Sea as the Director of the Sevastopol Biological Station ;
the second period of the investigation of the Black Sea fauna is linked with
his name. This ecological qualitative biocoenotic stage is characterized by a
comprehensive investigation of the distribution of life in the coastal zone and
of the main factors determining it (sea-bed, temperature, swell, etc.). Zer-
nov's ten years of work were concluded by the writing of his widely known
monograph On the Study of Life in the Black Sea (1913).

Third period

The great development of oceanographic investigation during the Soviet
epoch has also had its effect on the study of the Black Sea. Several research
institutes have been created and a series of expeditions has worked in the Sea.
Among the expeditions the most important were : the Azov and Black Seas

382

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Scientific Industrial Expedition, under the leadership of N. M. Knipovitch,
which worked for six years (1922-28), the expedition of the Hydrographic
Directorate, of the Sevastopol Biological Station and the Hydrological
Institute, under the leadership of Yu. M. Schokalsky and, finally, the expedi-
tions of the Hydrographic Directorate in the ship Hydrograph in 1932 and
1935.

At present hydrological investigations of the Black Sea are being carried
out by the Sevastopol Biological Station of the Academy of Sciences of the
u.s.s.r., by the Karadag Biological Station of the Ukrainian Academy of
Sciences, by the Novorossiysk Biological Station of Rostov University, by
the Scientific Fisheries and Biological Station of Georgia, and by the
Azov-Black Sea Scientific Investigation Institute of Fisheries and Oceano-
graphy.

III. PHYSICAL GEOGRAPHY AND HYDROLOGY

Situation and size

The Black Sea is situated between 46° 32-5' and 40° 55-5' N latitude and
between 27° 27' and 41° 42' E longitude. To the northeast the Black Sea is
connected with the Sea of Azov by the Kerch Strait and to the southwest with
the Sea of Marmora through the Bosporus. The greatest length of the Sea is
1,149 km. Its greatest width is 611 km. The Black Sea is characterized by the

Fig. 183. Bottom topography of Black Sea (Archangelsky and
Strahov).

absence of coastal features, by its small number of bays and inlets, by the
almost complete absence of islands and by its very steep shores (Fig. 183),
except for the northwestern part of the Sea (Karkinitsk Bay). The surface
of the Black Sea is 423,488 km2, its volume 537,000 km3, its greatest depth
2,245 m, its average depth 1,271 m. The 100 m isobath approaches the coast
almost everywhere, moving away from it only in the western, northeastern
and mainly in the northwestern part of the Sea. The angle of the floor dip is
usually 4° to 6°, but it often reaches 12° and even 14°.

THE BLACK SEA 383

Water balance

The Black Sea total water balance comprises the following elements: the
annual river inflow of fresh water is 400 km3, most of this being Danube
water (203 km3) ; the Dnieper and Bug inflow is only 54-7 km3 and that of
the Dniester 8-4 km3. A surface current of Azov waters of lesser salinity runs
into the Black Sea through the Kerch Strait diluting the northeastern corner
of the Sea, while the more saline Black Sea waters (17 to 17-5%0) enter as a
deep current the area of the Sea of Azov off Kerch. Black Sea waters of about
13%0 salinity enter the Sea of Marmora as a surface current through the
Bosporus (348 km3 annually), while a deep reciprocal current of saline Sea
of Marmora water enters the Black Sea (202 km3 per year), running down the
slope of the floor off the Bosporus.

Currents

As in every other sea the main current of the Black Sea has a counter-
clockwise circular motion (Fig. 184). In the narrowest part of the Sea, be-
tween the Crimean Peninsula and a spit running out from the Anatolian coast,
part of the waters moving from the west go north and the Sea is thus divided
as it were into two parts, each with its own circular motion. In each of these
circular currents is formed its own halistatic area. In the course of the current
all the isolines go down while in the halistatic areas, in contrast, they rise in a
cupola-shaped pattern.

Important additions to this system were introduced by N. Knipovitch
(1932), E. Skvortzov (1929), V. Nikitin (1929), A. Dobrovolsky (1933)
and G. Neumann (1942). In the eastern part of the Sea there is not one
but two halistatic areas, divided by a current running approximately in the
direction Samsun-Tuapse. In the most eastern part of the Sea, in the Batum
area, there is another circular current, but here, contrary to the three previous
halistatic areas, the circulation of the water has an anticy clonic character, and
therefore the iso-surfaces are not cupola-shaped, but form cup-shaped depres-
sions. Moreover, the existence of certain more or less important anticyclonic
and cyclonic rotations of waters in different parts of the Sea has been estab-
lished. As will be shown below, the character of the movement of water masses
in the Black Sea is well reflected by the lower limit of plankton distribution.

The general course of the iso-surfaces is given in Fig. 185, which is a dia-
gram of a cross section of the halistatic area of the Black Sea from coast to
coast. It is evident from this diagram that the isoline goes down most steeply
not off the coast itself, but at some distance from it ; the current too usually
does not run near the coast itself. The upper limit of hydrogen sulphide in the
centre of the halistatic area rises to 100 m, while in the area of the current
itself it goes down to 155 m. As has been suggested by V. Nikitin and E. Skvor-
tzov (1926) the descent of the isolines off the coast may also be furthered by the
water being driven off and on by winds, which causes considerable vertical
mixing. The fact that the hydrological conditions of the Black Sea are under-
going substantial secular changes, as a result of the alterations of climate, of the
mainland run-off and of the water exchange through the Bosporus and the

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THE BLACK SEA

385

Kerch Strait, is noted in recent literature (S. P. Brujevitch, 1953; A. Bog-
danova, 1959). A certain rise in salinity in the upper layer and a fall in salinity
throughout the water-column have been observed in the Black Sea for a period
of 25 years (1924-51). The decrease of salt content through that period for the
whole Sea was determined as 2 milliards of tons (A. Bogdanova, 1959). This
is caused primarily by the loss of salts through the Bosporus being greater
than the supply, a fact which is linked in its turn with a 19%0 rise in salinity
in the upper layer of the sea as a result of a decrease of the mainland run-off.

In Bogdanova's opinion the decrease in
salinity of the deep layers is connected with
the slackening of the deep Bosporus current.
The change in salinity of the upper layer and
the main column of water should have im-
proved vertical circulation. In addition, cool-
ing of the intermediate layer (75 to 300 m)
and some warming up of the deeper layers
were recorded.

In the off-shore zone animals were found at
depths of a little more than 200 m; on the
other hand in the halistatic area patches were
found where plankton animals disappeared at
a depth of no more than 87-5 m. Hence the
length of the Black Sea water column populated
by animals varies greatly in different parts of
the Sea.

2 J o-o-oo-o^

Fluctuations of water level

The ' fluctuations in the amount of water

coming from the mainland, or from rainfall,

evaporated from the sea surface, entering the

Sea as a result of water exchange with the

neighbouring seas through the straits may

affect the volume of sea-water. During

recent decades changes in the Black Sea level, with an amplitude of about

32-5 cm, have been observed. Seasonal changes in the sea-level have been

observed with ranges of 15 to 27-5 cm. Finally, the changes of sea-level may

be due to the wind and tides. The latter during the spring tide reach an

amplitude of about 8 cm.

Fig. 185. Hydrological cross
section from southern coast
of Crimea southwards to
Anatolian shore in February
1925 (Nikitin, 1930). /Isoxy-
gen,% saturation ; 2Isohaline,
%0 ; 3 Lines of equal content of
hydrogen sulphide, cm3/l. (its
upper limit) ; 4 Lower limit of
plankton.

Salinity

As in any other inland sea having impeded water exchange with a fully
saline sea, the salinity of the upper layer may undergo considerable fluctua-
tions depending on climatic changes, which, as we shall see below, is of some
significance to the development of life. The upper layers of the Black Sea,
except for areas adjacent to the river mouths and some parts of the coast
subject to salinity fluctuations, have a salinity of 17 or 18%0 (Fig. 186). The

THE BLACK SEA

387

lowest salinity is found in the northern part of the western half of the Sea
and in the region adjacent to the Kerch Strait. The salinity of the deep layers
of water, except for the area near the Bosporus, reaches 22-5 to 22-6%0.

Temperature

At the coldest time of the year (January and February) the surface waters of
the northwestern, and at times of the northeastern, corners of the Sea are
considerably cooled, down to and below zero Centigrade (in some cases
down to — 1-4°), whereas the southern parts of the Sea maintain a temperature
of 8 or 9°, and at times higher. The river mouths and inlets of the northern part

Fig. 187. Largest distribution of ice in Black Sea: 1 In mild winters; 2 In normal

winters ; 3 In severe winters ; 4 Maximum distribution in exceptionally severe winters

(Velokurova and Starov, 1946).

of the Sea have an ice cover every year. The open northwestern regions of the
Sea are also covered with ice when the winter is severe. The Dzharylgatch and
Karkinitsk inlets are frequently covered with an ice sheet (Fig. 187). The same
phenomenon, but to a lesser extent, is observed in the northeastern corner of
the Sea : the formation of coastal ice off Anapa is of frequent occurrence.
Large masses of floating ice may be formed during an exceptionally severe
winter off the Crimea and along the northwestern coast of the Black Sea ;
bays and inlets may be covered with ice. At the hottest time of the year
(usually in August) the temperature of the surface waters off the shores is
27° to 28° and sometimes even 29° (or slightly higher) ; in contrast with the
winter season, its fluctuations in different parts of the Sea are comparatively
small (3° or 4°). The fluctuations of the average annual temperature of the
Black Sea surface waters off the shores are 11-0° to 11-4° near Odessa, and

388 BIOLOGY OF THE SEAS OF THE U.S.S.R.

16-5° to 17-9° near Batumi. The range of temperature changes in the open sea
is considerably less than off the shores : according to the data available the
winter minimum is 6-6°, while the summer maximum is 27° with an amplitude
of more than 20°, while the annual range off the shores is 31°, i.e. 11° more.

Transparency

In the open parts of the Black Sea, with depths over 200 m, the water trans-
parency (the depth for the disappearance of a white disc) varies usually
from 18 to 21 m. Transparency decreases near the coast. The highest trans-
parency observed in the Black Sea was 30 m.

Vertical stratification

The Black Sea stands sharply apart from all other seas in its physical and
chemical characteristics. Moreover, the main factor determining all the others
is the great difference between the water density of its topmost layer, of 100 to
150 m deep, and that of the deeper mass of water. This difference is so great
that the mixing of the two layers proceeds only to a very small extent, and is
completely overlapped by the processes of sharply pronounced stratification
and stagnation. The layers differ greatly in their temperature, salinity (density),
their gas and nutrient salt contents and in the distribution of life in them.
Because of this peculiarity, M. Egunov (1900) called the Black Sea the bio-
anisotropic sea and N. Knipovitch (1933) called it the most typically anoma-
lous body of water. The sharp difference in water density between the
two layers is permanently maintained by the fall in salinity of the surface
layer which is due to the coastal run-off and the discharge of the Azov cur-
rent, and by the rise of the deep-layer salinity as a result of the lower Bosporus
current. This difference is so considerable that however much the temperature
of the surface water goes down, its density remains higher than that of the
deeper layers. The absence of sufficient vertical circulation for the mixing of
water is the result of this.

A picture of the distribution of the surface salinity is given in Fig. 186,
and that of the vertical changes of salinity and temperature during the
warmest and coldest seasons of the year in the middle part of the Sea is given
in Table 151, taken from Nikitin's work.

Table 151

Depth, Temperature, °C Salinity %0

m Summer Winter Amplitude Summer Winter

22-11

7-15

20-1

18-24

17-44

14-07

6-76

16-25

—

17-97

8-40

7-70

5-04

19-80

18-40

100

8-55

8-14

114

20-63

20-28

150

8-67

0-48

2101

500

8-90

0-21

22-01

2,000

8-94

0-25

22-23

THE BLACK SEA 389

As is shown in Table 151, containing data at great depths taken at one of
the stations, the annual fluctuations of temperature and salinity affect only
the 150 m upper layer, while deeper down they remain practically constant
throughout the year, the temperature being between 8° and 9° and the salinity
a Kttle above 22%0. The difference in salinity between the surface and deep
waters reaches 4 or 5%0.

Oxygen and hydrogen sulphide

In the Black Sea the amount of oxygen decreases sharply with the depth,
while that of hydrogen sulphide increases starting at 150 m; this is shown in
Table 152.

Table 152

Observed fluctuations

Average content of

Depth,

of oxygen content,

hydrogen sulphide

cm3/l

4-57-7-62

2-51-8-64

—

1-05-7-76

—

100

0-12-7-16

—

125

0-00-3-16

—

150

0-00-2-71

0088

200

0-00-1-88

0-470

300

000-1-93

1-480

500

000

3-779

1,000

000

5-637

2,000

000

5-796

As in other seas, the maximum oxygen content is at a depth of 25 m (up
to 124-133 per cent). Moreover, its supersaturation is regularly observed ; this
is the result of phytoplankton activity.

One of the most striking peculiarities of the Black Sea is the very great
amount of hydrogen sulphide which contaminates its depths. As early as 1892
the chemist A. Lebedintzev, a member of Andrussov's expeditions, the first
to investigate the phenomenon of hydrogen sulphide fermentation in the
depths of the Black Sea, expressed an opinion on the existence of two sources
of hydrogen sulphide, in both cases formed as a result of intensive bacterial
activity.

B. Issatchenko, during his microbiological investigations of the Black Sea
(1924), discovered bacteria responsible for the formation of hydrogen sul-
phide in both ways. The bottom dwelling bacteria of the genus Microspira
(mainly M. aestuarii) are the main source of hydrogen sulphide ; as a result of
their vital activity sulphates are reduced, carbonates are formed, and hydro-
gen sulphide is liberated. According to P. Danilchenko and N. Chigirin
(1926) 99-4 to 99-6 per cent of the whole of the hydrogen sulphide in the

390 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Black Sea is the result of this process, which was first discovered for the open
seas by Murray.

The hydrogen sulphide formation proceeds in two phases : the sulphate is
first reduced to sulphide with the evolution of carbon dioxide, according to
the equation :

CaS04+2C->CaS+C02

During the second phase the sulphide is decomposed by carbon dioxide,
hydrogen sulphide is evolved and a carbonate is formed

CaS+2C02+2H2O^Ca(HC03)2+H2S
Ca(HC03)2->CaC03+C02+H20

Moreover, some intermediate products are also formed

R2-S203 and R2-S03

In other words, the whole process can be expressed as

so42--^so32-^s2o32-^s2-

As has been shown by P. Danilchenko and N. Chigirin (1929), in the Black
Sea the carbonate content increases while there is a certain decrease of sul-
phates with depth {Table 153).

Table 153

Relative

Carbonate

Sulphate

amounts

Depth,

content

g/1-

s2o3+so3

sulphates

200

01040

1-477

115

1-502

300

01052

1-486

1-44

1-498

500

01155

1-518

1-58

1-497

1,000

01259

1-515

1-77

1-485

2,000

01304

1-506

2-83

1-474

The intermediate products of the reduction of sulphates, the amounts of
which increase with depth, were also found.

Anaerobic bacteria, which take part in the putrefaction of albuminous
substances in the absence of oxygen, are the second source of the hydrogen
sulphide formed. Anaerobic sulphide is oxidized by oxygen penetrating from
above : these two gases are as it were antagonists, however, since both may
occur simultaneously (in small amounts) on the boundary of the oxidation-
reduction zones. Hydrogen sulphide can be oxidized by ozygen in the absence
of bacteria, but in the Black Sea hydrogen sulphide oxidizing bacteria were
recorded everywhere.

The upper limit of hydrogen sulphide gives a very clear picture of the hori-
zontal course of the iso-surfaces (G. Neumann, 1953). In the centres of anti-
cyclonic rotation the iso-surfaces are raised while in centres of cyclonic ones
they are lowered (Fig. 188). As we have seen before, the contamination of the

392 BIOLOGY OF THE SEAS OF THE U.S.S.R.

deep layers of the Sea by hydrogen sulphide cannot be considered as char-
acteristic only of the present phase of the Black Sea history. When first dis-
covered this phenomenon was attributed to a mass destruction of the brackish-
water Pontic fauna due to the rise of salinity after the breaking through of
the Dardanelles strait, and further maintained by a constant formation of more
hydrogen sulphide resulting from the putrefaction of dead animals sinking
from the upper layers of the Sea. Lately, however, this opinion has been
abandoned and various investigators (A. Archangelsky, V. Vernadsky,
N. Knipovitch) have come to the conclusion that hydrogen sulphide fer-
mentation in the deep layers is one of the characteristics in the history of
the south-Russian geo-synclinal bodies of water.

Water balance and the circulation of water masses

The nature of the circulation of the Black Sea water masses and of its water
balance through the Bosporus is of great significance for a wide range of
biological phenomena in this semi-closed sea basin.

These problems have arisen since the depth-gauge expedition of 1890-91,
when the contamination of the deep zones of the Black Sea with hydrogen
sulphide was discovered, and since S. Makarov's study of the Bosporus cur-
rents in 1881-82. Different views on the nature of the vertical mixing of the
Black Sea waters have existed from the beginning of these investigations.
Some workers maintained that the deep hydrogen sulphide zone was linked
with the upper layer only by diffusion and a gradual upwelling due to the
inflow of saline waters from the Sea of Marmora through the Bosporus.
In their opinion the upper aerated layer and the deep layer, containing hydro-
gen sulphide, are quite different in origin and structure. Other investigators
have considered it probable that the two main water masses are mixed by the
wind, a system of currents, by internal waves and by a process of turbulent
mixing of the deep layers. The peculiar curving of isolines in the middle parts
of two cyclonic vortices was noted; moreover, curves of the isoline were also
observed in the deep layers of the Sea.

The estimation of Black Sea biological productivity depends on the solu-
tion of this problem. The first point of view leads to the assumption of a
low productivity for the water column caused by its constant loss of organic
matter, which is carried into the depths in every stage of decomposition, by its
mineralization and by its continuous accumulation in the deep stagnant zone.
The constant return of plant food substances into the inhabited layer of water
from the zone of accumulation and the existence of a sufficient supply for the
productive biological processes in the upper zone are comprehensible from
the second point of view. Hence there was a considerable difference of opinion
as regards the scale of biological production.

A considerable change of opinion on the mixing of the Black Sea water was
introduced not long ago as a result of the work of V. Wodjanitzky (1941,
1948, 1954) and G. Neumann (1942, 1943). Both investigators recognize the
presence of an exchange between the inhabited and hydrogen sulphide layers.

The former proposed the following scheme of water circulation for the
Black Sea, based on the analysis of hydrological data (Table 154) and the

THE BLACK SEA

393

Table 154. Mean values of hydrological data for the deep waters of the Black Sea

( Wodjanitzky)

Depth,

Actual

Potential

Salinity

Specific

Stability

temp., °C

^/00

volume, V*

£xl08

200

8-60

8-67

21-33

0-98374

500

8-87

8-82

21-95

329

109

1,000

8-96

8-86

22-20

313

1,500

904

8-89

22-23

309

2,000

911

8-90

22-27

308

distribution of iso-surfaces, while taking into consideration the water balance
through the Bosporus.

According to Wodjanitzky the path of the water masses in a cyclonic cir-
cular current is not rectilinear, but spirals towards the outer sides of the cur-
rent, i.e. from the central halistatic zone to the periphery (Fig. 189). Moreover,
the vertical mixing of water between the separate zones proceeds differently
at various depths.

In Wodjanitzky's opinion: 'The moving forces causing vertical water
exchange are : (/) the wind creating a system of surface currents, (2) the earth's
rotation, throwing the currents to the right hand side and causing a spiral

Fig. 189. Operational diagram of vertical
water exchange in the Black Sea (Wod-
janitzky).

394 BIOLOGY OF THE SEAS OF THE U.S.S.R.

rotation of the current, (3) the cooling of the surface layers, (4) the warming
up of the deep layers, (5) the internal waves, (6) turbulence and diffusion.'
Wodjanitzky thinks it possible, as a first approximation, to divide the Black
Sea water vertically into five zones — three main and two intermediate ones
(Fig. 189). 'In the first zone,' he writes, 'the water rises in the centre, there is a
horizontal movement towards the periphery, and a sinking down there — a
thermal convection. A turbulent mixing (internal waves) takes place in the
second zone. In the third there is a rise in the centre, a horizontal movement
away from the centre and a sinking down at the periphery. There is some tur-
bulent mixing with internal waves in the fourth zone. There is some thermal
convection and a feeble movement away from the periphery in the fifth zone.'
This problem cannot be solved without taking into consideration the water
balance through the Bosporus, and Wodjanitzky makes the following com-
putation : if the annual inflow of Sea of Marmora waters is 200 km3 (S 36%0)
and the outflow is 360 km3 (S 12%0) and if the salinity is taken into considera-
tion in both cases (the salinity of the Sea before it became connected with the
Dardanelles being 12%0, and the period lasting 6,000 years), the salinity bal-
ance of the basin can be represented in the manner indicated in Table 155 and
Fig. 190.

Table 155

Time

Salinity and

Salinity at surface

years

its increase

and its increase

12+4-4

1,000

16-4+2-2

14-5+2-5

2,000

18-6 + 1-6

16-0 + 1-5

3,000

20-2 + 10

16-8+0-8

4,000

21-2+0-6

17-4+0-4

5,000

21-8+0-2

17-8+0-2

6,000

220

180

If this rate of change* in the water balance through the Bosporus is main-
tained, there is no salinity increase at present and a certain equilibrium has
been established. As a result of his computations Wodjanitzky (1948) draws
the conclusion that a vertical mixing of the Black Sea waters takes place at all
levels and that the deep waters may be lifted to the upper, inhabited layer of
the Sea in 100 to 130 years.

Nitrogen and phosphorus compounds

P. Danilchenko and N. Chigirin (1930) have shown that in the depth of the
Black Sea the nitrates, like the sulphates, go through ' a process of reduction
with the formation of ammonia and free nitrogen (denitrification.) 'The

* In \9A2-A6 there appeared a series of articles by F. Illyott and O. Ilgaz, attempting
to prove that the Bosporus discharge current takes with it the reverse current waters,
and that this current does not actually reach the Black Sea. The opinions of these authors
were not accepted.

THE BLACK SEA

395

amount of nitrogen in the photosynthetic zone of the ordinary sea is either
zero or very small ; it increases, however, with depth.

In the depths of the oceans the amount of nitrogen in the form of nitrates
usually does not exceed 006 to 0-07 mg/lb ; at the surface it may rise to 0-1 1 to
0-16 mg/lb. The amount of nitrate nitrogen in the seas is usually expressed in
microgrammes per pound.

The ammonia content of the upper layer of the Black Sea is also practically
the same as that of the open seas and oceans ; it increases, however, with depth,

1000 2000 3000 4000 5000 6000 YEARS

Fig. 190. Reconstructed course of the alteration of salinity in the Black Sea after
the break-through of the Bosporus waters (Wodjanitzky, 1948): A Salinity at sur-
face ; В Mean salinity.

and at 1,500 to 2,000 m the amount of ammonia nitrogen is 1-10 to 1-46
mg/lb.

The content and distribution of nitrates and phosphates in the Black Sea
were first investigated by Danilchenko and Chigirin in 1929 and 1930. Twenty
years later their work was repeated by V. Datzko, and considerable deviations
from the earlier data were found. Lately M. Dobrzanskaja (1958) has investi-
gated the distribution and changes of phosphates throughout the Black Sea
column of water. This author notes the frequent absence of phosphates from
the upper region of the water (50 to 60 m) in spring and summer, although in
some years phosphates are present throughout the year in the upper layer of
the whole Sea during the periods of marked deficiency of nitrates. In some
areas of the Sea there is a pronounced increase in phosphate content as a
result of the off- and on-shore winds and the phenomena resulting from them.
Within the halistatic areas the phosphate iso-surfaces rise, and off-shore they
sink, with fluctuations of 50 to 100 m {Table 156).

396 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 156. The mean content of phosphate phosphorus and of nitrates in Black Sea

Danilchenko and

Chigirin

Datzko (1950)

Dobrzanskaja

(1930)

(1958)

Depth,

Phosphate

phosphorus Nitrates

phosphorus

Nitrates

phosphorus

—

100

200

179

124

143

300

194

500

228

174

—

185

1,000

265

188

—

226

1,500

293

—

240

—

2,000

299

262

—

Phosphate and nitrate contents were much lower in Datzko's data, mainly
in the 0 to 100 m layer, where their amount is about half, and in deeper layers
it is only one-quarter to one-fifth. The nitrogen content is correspondingly
eight times lower, but at a depth of 300 m the data for both periods correspond.
The phosphate-nitrate cycle of the Black Sea is characterized by a frequent
shortage of nitrates in the summer, when the phosphates may remain unused.
The higher phosphate indices found by Danilchenko and Chigirin, as com-
pared with those of Datzko, can probably be explained by differences in the
methods used ; the first investigators included organic phosphorus, which is
scarcer in the deep-water layers than at the surface. Generally speaking the
amount of biogenic matter (phosphates and nitrates) in the inhabited deep
regions of the Black Sea ' is approximately of the same order as its content in
the waters of Central and Southern Caspian' (V. Datzko, 1954) and somewhat
lower than in the Sea of Azov.

Datzko has also determined the carbon content of the Black Sea water, both
in solution and in precipitate {Table 157) ; it was found to be of the same order
at various depths of the Sea and similar to that of other seas.

Thus the data given are lower than those for the Sea of Azov where the
average carbon content of dissolved substances was, according to the same
author in 1949-50, 5-44 mg/1; in suspension 0-82 mg/1; the total being
6-26 mg/1.

A. Kriss (1958), examining the data on the sulphate and hydrogen sulphide
contents of the depths of the Black Sea, does not see any inverse correlation
between them, and therefore throws some doubt on the ideas of previous
investigators as to the formation of hydrogen sulphide from decomposed sul-
phates ; he gives as an example one of the stations {Table 158) from the paper
of B. Skopintsev and F. Gubin (1955).

THE

BLACK
Table 151

SEA

Mean carbon content

Depth,

in solution

precipitated

Total

3-11

019

3-30

3-24

0-24

3-60

3-26

0-34

3-60

100

3-15

0-51

3-66

200

3-23

0-30

3-53

500

3-13

0-36

3-49

1,000

3-03

0-31

3-34

1,500

2-98

0-28

3-26

2,000

2-83

0-27

310

397

Kriss does not share the opinion of P. Danilchenko and N. Chigirin (1926)
that a reduction of sulphates by organic carbon is also indicated by a com-
parison of the distribution of calcium and carbonates with that of hydrogen
sulphide. Thus Kriss has reason to doubt Danilchenko and Chigirin's sug-
gestion that ' hydrogen sulphide in the Black Sea results from the reduction of
sulphates by the carbon of organic substances through the formation of inter-
mediate products down to sulphides, and the decomposition of the latter by
carbonic acid and bicarbonates with the evolution of hydrogen sulphide'.
Without questioning this idea Kriss agrees with the opinion of Andrussov,
expressed earlier, that the hydrogen sulphide in the Black Sea 'is the sum
total of hydrogen sulphide developed during the putrefaction of organic
matter . . . plus the hydrogen sulphide formed as a final result of the reduction
of sulphates'.

Moreover S. Brujevitch (1953), the authority on this question, says that an
examination of all the data on hydrogen sulphide fermentation in the Black
Sea 'leaves no doubt that in the main mass hydrogen sulphide is the result of
sulphate reduction, and not of the decomposition of albuminous compounds'.

Table 158. Vertical distribution of hydrogen sulphide
and of sulphates at Station 3 {1955)

Depth,

Hydrogen sulphide

Sulphates

mg/1

g/kg

146

0-32

1-6330

194

0-52

1-6521

285

1-74

1-6643

290

3-64

1-6812

729

5-50

1-6739

976

6-40

1-6759

1,226

703

1-6823

1,475

6-64

1-7088

1,725

7-34

1-6777

1,975

7-27

1-6793

398 BIOLOGY OF THE SEAS OF THE U.S.S.R.

N. Chigirin (1930), the first worker to investigate the distribution of phos-
phates in the Black Sea, came to a number of interesting conclusions : phos-
phorus of dead plants remains mostly in the oxidation zone, while that of most
dead animals is driven into the reduction zone and accumulates there. Sixty
per cent of the total plankton phosphorus may consist of the latter ; the annual
amount of phosphorus brought in with river water forms about 1 per cent of
the total amount of phosphates dissolved in the oxidation zone. Hence some
definite amounts of phosphorus compounds are brought in from the reduction
to the oxidation zone. An alkalinity two to three times higher than that of the
open seas and considerably greater fluctuations in hydrogen ion concentra-
tion are also most characteristic of the waters of the Black Sea.

Dynamics of organic matter

All life in the Black Sea is concentrated in the upper layer, owing to its oxygen
and hydrogen sulphide distribution ; this layer is 150 to 200 m thick, forming
only 10 to 15 per cent of the volume of the Sea. The immense volume of the
deeper layers (85 to 90 per cent) is inhabited only by anaerobic bacteria.
Organic substances which reach the depths from the upper layer return to a
small extent and accumulate at the bottom. The feeble vertical circulation,
resulting in the accumulation of large amounts of organic matter in the depths,
also decreases the productive capacity of the Sea. As has been shown by
Danilchenko and Chigirin, the oxidation of nitrogen, ammonia and nitrites
to nitric acid ; of sulphur, sulphides, bisulphites, sulphites and hydrogen sul-
phide to sulphuric acid ; and the oxidation of ferrous and manganous com-
pounds into the ferric and manganic ones, takes place in the oxidation zone ;
there are no nitrites or nitrates in the reduction zone, which contains com-
paratively large amounts of ammonia and nitrogen, a smaller amount of
sulphates, and a larger one of carbonates and bicarbonates. Since hydrogen
sulphide is formed by the reduction of sulphates, in the deep layers of the
reduction zone their content is greatly reduced. In the hydrogen sulphide zone of
the Black Sea carbon, hydrogen, sulphur, phosphorus and silicon accumulate,
as well as nitrogen compounds. The combination of these conditions with the
existence of the hydrogen sulphide zone leads to a comparatively low general and
industrial productivity of the Black Sea in comparison with the Sea of Azov.

Sediments

The sediments of the Black Sea can be divided into two groups : those of the
oxidation zone (continental shelf) and those of the reduction zone (continental
slope and central depression). The shallow-water sediments were compre-
hensively investigated by S. Zernov in the first decade of the present century.
Deep-water sediments were thoroughly studied in the Soviet era (1924-33)
mainly by A. Archangelsky* (Fig. 191). The floor topography of the Black

* In this work Archangelsky succeeded in obtaining, by means of so-called core tubes,
a bottom core in 4 m in length, and deep-water sediments of various parts of the Sea were
synchronized by them. On the other hand, the micro-lamination of these sediments,
which in Archangelsky's opinion is annual, gave him the possibility of expressing in
chronological order the duration of the deposition periods of each sediment.

THE BLACK SEA 399

Sea reflects the chart of water circulation : in the off-shore sand zone, shell
gravel and shallow- water muds are preponderant ; in the area of the currents
crossing the Sea in the direction of the Crimea and of the northern part of the
Caucasian coast the bottom becomes more coarse-grained; the halistatic
areas have the softest bottom. The amount of the fine fraction increases with
depth (up to 96-5 per cent) ; so does the amount of organic matter, and the

Fig. 191. Distribution of contemporary deposits of Black Sea (Archangelsky and
Strahov, 1938, with the addition of Phyllophora beds). 1 Sand ; 2 Shell gravel ; 3 Mus-
sel ground ; 4 Phaseolin mud ; 5 Grey deep-sea clay ; 6 Grey clay with calcareous mud
interlays ; 7 Transitory mud ; 8 Same with grey mud interlays ; 9 Same with grey
mud and sand interlays; 10 Same with several grey mud interlays; 11 Calcareous
mud ; 12 Calcareous mud with grey clay interlays ; 13 Site free of contemporary
deposits; 14 Phyllophora beds.

increase of its carbonate content with depth is, perhaps, the most character-
istic feature of the Black Sea. The mean values of these changes are given in
Table 159.

The remarkable fact that the content of organic carbon in the present-day
Black Sea sediments of the hydrogen sulphide zone is practically the same,
down to the greatest depths, as that in 'normal' water basins was recorded
by N. Strahov (1941). This can be explained by the energetic decomposition
processes of organic residues and the return of the decomposition products
into the water column. A considerable amount of calcium carbonate in the
shallow- water muds is due to the presence of shell gravel. The calcium carbon-
ate of the deep-water oozes of the Black Sea is also of organic origin, but both
in its structure (a fine powder) and in the mode of its formation it differs from
that of the oxidation zone. It is mainly the product of the vital activities of the
desulphating and denitrifying bacteria which take part in the reduction of
sulphates (with the formation of hydrogen sulphide) and nitrates.

400

BIOLOGY OF THE

SEAS OF THE U.S.S.R.

Table 159

Fine fraction

Calcium

(00 1) in in-

Organic car-

Organic non-

carbonate

Sediment

soluble (in

bon, dry

carbonate

as carbon

HC1) residue

weight of soil

substances

dioxide

(percentage)

Sands

21-13-46-94

0-73-1-20

—

2-63-11-49

Mussel ooze

55-77

2-60

4-92

17-69

Phaseolin ooze

82-53

1-61

3-20

20-59

Shell gravel
Deep-water grey
Limestone mud

clay

95-23
91-95

1-74
4-54

3-43
7-80

15-81

61-87

Black mud (beneath

upper layers of
bed)

sea-

—

8-65-20-32

—

The organic matter content of the phaseolin ooze is lower than that of the
mussel ooze, although the former lies deeper; this is apparently due to the
lesser density of its animal population. The accumulation of organic matter in
the still deeper oozes, already in the
reduction zone, is conditioned by the
absence of organisms which could
have used it and by the feeble vertical
circulation which would have brought
it up into the upper layers of the Sea.

The first to make a comparison of the
salinity of the bottom water with that
of the main masses of sea water in
former geological periods was S. P.
Brujevitch (1952). A sharp decrease in
salinity, down to 4%0 (in chlorine) at a
depth of 6 m, was recorded by the exam-
ination of cores from the deeper parts
of the Black Sea. This, according to
Brujevitch, is the salinity of the Novo-
Euxine basin of brackish water; he
points out that in the open sea there is
no change of salinity with depth (Fig.
192). The same method was later used
by B. Kullenberg (1954) in the Baltic
Sea with the same result.

Benthos remains are almost absent while plankton remains are predominant
on the floor of the reduction zone in the deep-water sediments of the Black
Sea. The predominant part played by plankton organisms in the formation of
organic matter on the deep floor of the Black Sea is also shown by the
carbon/nitrogen ratio. While on the shallow floor this ratio is about 4 to 4-5

22 20 18 16 /4 12 10%

♦—CALCIUM CARBONATE

Fig. 192. Alterations in chlorine and

calcium carbonate content with the

depth in the sea- bed (Brujevitch).

THE BLACK SEA 401

(below the plankton one), it is 6 to 8 in the deep-water grey clay, i.e. almost
a typical plankton ratio.

By calculating the number of thin layers in the grey clay cores, Archangel-
sky has determined that (assuming that the layers are annual) the 1 m sedi-
mentation of grey clay took 5,000 years to accumulate. From the organic
matter content of the grey clay it is possible to calculate that 6 tons of organic
carbon accumulated on 1 km2 in a year during the deposition period. In a
similar manner, Archangelsky has calculated that 4-2 tons of organic carbon
were accumulated per 1 km2 of the floor annually during the period of deposi-
tion of the Maikop Oligocene clays. The magnitude of these deposits of
organic matter, accumulated on the bottom of the Black Sea, can be assessed
by the fact that the amount of organic carbon contained in the column of
Oligocene and Miocene deposits in the Sulak and Yaryk-Su area (near the
Caspian Sea) over about 500 km2 is approximately equal to the total amount
of coal in the Donets basin (67,170x 106 tons).

IV. FLORA AND FAUNA
Plankton

The qualitative composition of phytoplankton. According to the latest data of
N. Morozova-Wodjanitzkaja (1954) the phytoplankton of the Black Sea
comprises 350 species {Table 160).

Table 160

No. of

Group

No. of
genera

No. of
species

species
(percentage)

Diatomeae

150

42-9

Peridineae

146

41-7

Coccolithineae

5-1

Cyanophyceae
Silicofiagellata

5
5

6
6

1-7
1-7

Pterospermaceae
Heterocontae

2
2

1-7
0-6

Cystoflagellatae
Volvocaceae

1
6

1
11

0-3
3-1

Euglenaceae

0-9

Chytysomonadineae

0-3

Total

102

350

100

N. Morozova-Wodjanitzkaja and E. Belogorskaya (1957) have recorded
1 8 species of coccolithophorides, which had been thought to be absent from
the Black Sea.* Some members of this group are abundantly developed in the
Black Sea. Morozova-Wodjanitzkaja found up to 850,000 specimens of
Pontosphaera huxleyi in the Bay of Sevastopol during her March and April

* P. Usachev (1947) was the first to record the coccolithophorides in the Black Sea.
2G

402 BIOLOGY OF THE SEAS OF THE U.S.S.R.

sampling in one litre of water with a biomass of about 300 mg/m3. Ponto-
sphaera is just as abundant in the plankton of other areas of the Black Sea,
especially just off-shore.

This author sees a similarity between the phytoplankton of the Black Sea
and that of the North Sea, the Norwegian fjords, and the bays of sub-Arctic
and Arctic seas, as well as that of the Caspian and Aral Seas.

Among the diatoms the following genera are richest in species : Chaeto-
ceros, Coscinodiscus, Rhizosolenia and Melosira, and among the Dino-
flagellata-Peridinium, Dinophysis, Gonyaulax and Ceratium.

Of the individual species the most significant among the diatoms are Skele-
tonema costatum, Chaetoceros radians, Cerataulina bergonii, Leptocylin-
drus danicus, Thalassionema nitzschioides, Rhizosolenia calcar-avis, Rh.
fragilissima. Among the Dinoflagellata the most important are Prorocentrum
micans, Gonyaulax cordata, the species Glenodinium, Exuviella cordata and
some species of Peridinium, Ceratium tripos, C. furca and C. fusus. The pre-
sence of a large number of fungi, at various stages of development, through-
out the upper (down to 300 m) layer of the Black Sea has been discovered
during the study of its phytoplankton by N. Morozova-Wodjanitzkaja (1957).

Qualitative composition of zooplankton. The zooplankton of the Black Sea
is poorer in species and has the composition given in Table 161.

Table 161

No. of

Group

species

Percentage

Tintinnoidea

16*

21-2

Hydromedusae
Scyphomedusae
Ctenophora
Rotatoria

7
2

1 (16)t
14$

9-2

2-8

1-4

18-6

Polychaeta
Cladocera

12(5)

1-4
160

Copepoda
Isopoda
Chaetognatha
Appendicularia

17 (304)
2

3(6)
1

22-6
1-4
40
1-4

Total

/ 100

[ * L. Rossolimo (1922) gives 25 species and varieties of Tintinnoidea for the Black Sea
t The data in brackets are the numbers of species in the Mediterranean fauna.
% For the open sea and its parts of lower salinity M. Galadzhiev (1948) records 22

species of Rotifera.

Apart from the forms mentioned, a large number of eggs and larvae of
various pelagic and bottom invertebrates and fish are found among the Black
Sea plankton during certain periods of the year. The difference between the
Mediterranean plankton and that of the Black Sea lies in the absence of

THE BLACK SEA 403

radiolarians, siphonophores, pteropods, molluscs and salps, and, of some
typical larvae of bottom-living organisms.

The researches of V. Nikitin (1926, 1928, 1929, 1930, 1939, 1941), A. Kus-
morskaya (1950, 1954, 1955) and I. Galadzhiev (1948) on the Karkinit Bay are
the most comprehensive investigations of the zooplankton of the open parts
of the Black Sea.

The main forms of zooplankton of the open parts of the Black Sea comprise
Noctiluca miliaris among the Cystoflagellata ; Cyttarocylis helix, C. ehrenbergi,
Tintinnopsis campanula. T. ventricosa, T. tubulosa, Tintinnus mediterranea
and T. subulatus among the Tintinnoidea ; Amelia aurita and Pilema pulmo
among the true Medusae; the ctenophore Pleurobrachia pileus; the following
Copepoda: Oithona nana, O. similus, Paracalanus parvus, Acartia clausi,
Calanus helgolandicus, Pseudocalanus elongatus, Centropages kroeyeri; the
Cladocerans Evadne nordmanni, E. spinifera, Podon polyphemoides ; Sa-
gitta euxina among the Chaetognatha and Oikopleura dioica among the Appen-
dicularia. Moreover, in the off-shore regions the Hydromedusae Rathkea
octopunctata and Sarsia tubulosa, the Copepoda Pontella mediterranea, Ano-
malocera patersoni, the Penilla avirostris and the Chaetognath Sagitta setosa
are just as abundant. The relatively large isopod crustacean Idothea algirica is
found everywhere in the plankton, at times in large numbers.

Apart from the above-mentioned forms, eggs and larvae of various pelagic
and botton invertebrates and fish are mixed with the coastal plankton,
especially in the summer. Among them the most abundant are anchovy ova,
the larvae of Lamellibranchiata and the eggs and larvae of various Copepoda.

Vertical distribution of plankton. Several groups can be distinguished in the
Black Sea plankton by the character of their vertical distribution.

S.ome forms are distributed alike in winter and summer. The greatest mass
of them is usually adapted to a depth of 15 to 50 m. Their vertical distribution
is only slightly affected by variations of temperature and light, observed
throughout the seasons. These forms include Oithona nana, the most abundant
Copepoda, Acartia clausi, Paracalanus parvus and Oikopleura dioica. Idothea
algirica and Noctiluca miliaris are similar in distribution but the numbers of
the latter fluctuate considerably during the year ; it is very scarce in the winter
and multiplies intensively in summer.

The next group is represented by cold water stenothermal forms found in
winter at all depths ; in summer they sink to the greater depths. This group
includes Calanus helgolandicus, Pseudocalanus elongatus, Oithona similis,
Sagitta euxina and Pleurobrachia pileus. Throughout the whole of the cold
period of the year (December to April) they are found from the surface to
the lower limit of plankton distribution. With the spring warming up of the
upper layer of water they sink down, disappearing gradually from the upper-
most 50 m layer. At the end of November, with the autumn fall in temperature,
they move into the upper waters, remaining there until the beginning of May. .
This migration takes place only in the uppermost 50 to 60 m layer, since
below this the hydrological conditions are comparatively constant and there
is little change in the distribution of the cold water forms throughout the year.

404 BIOLOGY OF THE SEAS OF THE U.S.S.R.

The upper temperature limit for Sagitta is 10° or 11°, for Pleurobrachia —
12° or 13°, for Calanus and Pseudocalanus — 13°, and for Oithona — 14°.

Finally, a third group develops only in summer, keeping to the upper, warm
layer of water. During the summer warming-up these forms occupy a greater
and greater depth of water. When cooling begins they become gradually
scarcer, disappearing completely from the plankton in the winter. This group
includes Centropages kroeyeri, Evadne nordmanni, Evadne spinifera and Podon
polyphaemoides.

The lower temperature limit for these species frequently coincides with the
upper temperature limit of the previous groups of forms.

Hence in different inhabited zones of the Black Sea both constant and tem-
porary plankton species can be observed, the temporary ones appearing
either as a result of migration from the deeper layers, or developing in the
upper, warm layer in summer only. This is shown by V. Nikitin (1929) in a
clear diagram reproduced by us in an abbreviated form {Table 162).

Vertical migrations. Thus some plankton species have seasonal vertical
migrations. V. Nikitin thinks (1929) that under Black Sea conditions the
main factor causing these migrations is temperature, which masks the effect
of light.

The plankton forms inhabiting layers below 50 m must have the capacity
to exist, under Black Sea conditions, with little oxygen. In the deepest in-
habited layers, where the amount of oxygen is no more than 4 per cent and
may be less, five or six species are still found, among them Calanus helgo-
landicus and Pseudocalanus elongatus. Their high eurybiotic form was proved
experimentally by V. Nikitin and E. Malm (1927).

Apart from the seasonal migrations, daily migrations have been observed
for a number of species, conditioned primarily by variations in light. The most
pronounced daily migrations are those of Calanus helgolandicus and Sagitta
euxina.

The lower limit of distribution. Owing to the hydrological and hydrochemical
conditions of the Black Sea, both plankton and benthos exist only in the upper
layer of the Sea. In the central parts the plankton is concentrated in the upper
layer at 100 to 150 m, and in the littoral areas and in those of the middle of
the Sea between the shores of the Crimea and Anatolia, in the 150 to 175 m
layer. In the littoral areas of the western part of the Sea the lower boundary
of the inhabited zone lies a little higher (125 to 150 m) and in the eastern area
a little lower ( 1 75 to 200 m) than the average position. Thus the lower boundary
of the Black Sea inhabited zone is not horizontal, but slopes from west to
east with about 50 m difference in level. This sloping of the lower boundary
of the inhabited zone is conditioned by the greater decrease in salinity in the
western part of the Sea, which hinders vertical circulation. We shall see below
that the same phenomenon is found for the lower boundary of benthos dis-
tribution.

As is shown by a closer examination of the distribution limit of the Black
Sea pelagic plankton (Fig. 193), this is mostly in accordance with the general

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410 BIOLOGY OF THE SEAS OF THE U.S.S.R.

3 4 5 6

2000

100
I

_1_

100

mg/m-

Fig. 194. Distribution of micro-organism population and its density in the water
column of the Black Sea (Kriss, 1958).

scheme for the horizontal circulation of the upper layer of water, determining
equally the position of the lower limit of oxygen and the upper limit of
hydrogen sulphide.

Black Sea micro-organisms and their quantitative distribution. In his mono-
graph A. Kriss (1958) gives some data on the total number and the biomass of
the Black Sea bacteria population, determined by the method of membrane
ultra-filters (Figs. 194 and 195).* The number of micro-organisms decreases
from one or two hundred thousand specimens per 1 ml of water to a few tens

THE BLACK SEA

411

of thousands as one moves away from the coast, and especially in zones with
strong influence of coastal run-off. The largest number of micro-organisms is
found at depths of 10 to 75 m.

Bacteria biomass changes with the same regularity. The minimum number
of micro-organisms is found at depths of 75 to 1 50 m, where the bacterial
population of the upper layer is replaced by the community of the hydrogen
sulphide zone (mainly by a particular group of filamentary micro-organisms).
The number of micro-organisms in the hydrogen sulphide zone is considerably

DISTANCE FROM THE COAST, MILES

Fig. 195. Distribution of micro-organism population in Black Sea and the alteration
of its density with the distance from the coast (Kriss).

higher than that of the surface oxygenated zone. Another sharp rise in the
number of micro-organisms is observed in the upper layer of the sea-bed,
where it reaches 1^ to 3 milliards per 1 g of the wet weight with a biomass of
3 to 6 g/mA The effect of river discharge on the number of micro-organisms
in the water is clearly shown by M. Lebedeva (Fig. 196). The quantitative
range of micro-organisms changes in winter, owing to a considerable fall in
temperature : their main mass is then concentrated in the 0 to 50 m layer. The
number of bacteria decreases sharply deeper down, only increasing again in
the hydrogen sulphide zone (Fig. 197). Kriss gives comparative values of
phyto- and zoo-plankton biomass as an illustration to his data {Table 163).
According to these data the biomass of bacteria is considerably higher than
the quantity of plant and animal plankton, and if we take into consideration
a much greater biological activity of the micro-organisms, their immense
importance will become evident both for the phytoplankton and zooplankton
of the surface zone and for the biochemical processes in the hydrogen sulphide
zone. In the oxygenated zone a direct connection can be observed between
the quantity of micro-organisms and the plant and animal population, both
in the main mass of water and in the sea-bed.

Kriss determined the rates of multiplication of micro-organisms by a direct

Fig. 196. Effect of river discharge on quantitative distribution of micro-organisms
in northwestern area of Black Sea (Lebedeva). Numbers of cells in thousands per

1 ml. of water shown on block.

FEBRUARY. 1951

200 100 0 WO 3ft?MILLIARDS/m3
1 I I I I

Fig. 197. Vertical distribution of micro-
organism population on the coastal and sea
stations in Black Sea in summer and winter
(Lebedeva).

THE BLACK SEA 413

Table 163. Biomass of micro-organisms, phytoplankton
and zooplankton in the eastern part of the Black Sea

Mean biomass
Location throughout the Sea, mg

Mean biomass per 1 m3 in the 0 to
200 m layer 20

Mean biomass per 1 m3 in the 200
to 2,000 m layer 40

Total biomass of micro-organisms

beneath 1 m2 of the sea surface 74,050

Same for phytoplankton 11,600

Same for zooplankton 36,800

method of lowering glass slides to different depths and counting the number
of bacterial cells at definite time intervals. The average daily PjB coefficient
(ratio of production to biomass daily) is determined on the basis of these
observations. For the daily exposure of slides in the open part of the Sea an
average PjB coefficient of 0-2 to 0-7 was obtained. Similar indices have been
found for the Caspian Sea and the Arctic Ocean. The highest average daily
PI В coefficients have been recorded in the Pacific Ocean (the daily gain in
weight being about 80 per cent). Kriss gives the annual PjB ratio for the active
photosynthetic layer (0 to 50 m) in the Black Sea as 58-4, and for the hydrogen
sulphide zone — 29-2.

A. Kriss (1958) has also attempted to determine the total mass of micro-
organisms in the water of the Black Sea and the order of magnitude for the
mineralization of the organic matter resulting from their activity. For the
active photosynthetic layer (0 to 50 m) this value is 6-5 mg/m3, approximately
0- 1 per cent of the average content of organic matter in the Black Sea waters.
Deeper down, at 50 to 125 m, the concentration of micro-organisms is more
or less constant and equal to about 7 mg/m3, while the value for organic
matter mineralization at this depth is about 1 mg/m3.

A. Kriss (1958) comes to the following conclusion as a result of his com-
prehensive analysis: 'The synthesis of organic matter in the form of micro-
bial cells proceeds on a large scale in the Black Sea at the price of carbon
dioxide assimilation ; the amount of organic matter formed as a result of
autotrophic nutrition of micro-organisms is greater than that produced
through photosynthesis by the organisms of the oxygen zone. If the amount
of organic matter produced by phytoplankton throughout the whole Black
Sea comprises 4,000,000 tons (59 mg/m3 x 67,594 km3 of the oxygenated zone),
then the total mass of organic matter in the form of autotrophic (filamentary)
micro-organisms is more than 15 million tons (33 mg/m3 x 462,360 km3 of
water in the hydrogen sulphide zone). Thus, the complete mineralization of
dead organic matter, the regeneration of biogenic compounds in the form
required for aquatic plant nutrition, the synthesis of organic matter from
inorganic compounds and direct participation in nutrient chains constitute
the manifold activities of micro-organisms in the creation of biological and
in particular commercial productivity of seas and oceans.'

414 BIOLOGY OF THE SEAS OF THE U.S.S.R.

But Y. Sorokin, criticizing Kriss' method of water sampling, has recently
argued against the supposedly huge productivity of autotrophic sulphur bac-
teria and protein origin of hydrogen sulphide. In his opinion nitrificators and
denitrificators, practically absent from the Black Sea depths, play only a minor
role, and autotrophic production does not exceed that of photosynthetic
activity.

Quantitative distribution of phytoplankton. P. Usatchev (1926, 1928) laid the
foundation of the quantitative study of the Black Sea phytoplankton in his
survey of the northwestern part of the Sea. Later some data were collected
by N. Morozova-Wodjanitzkaja for the shores of the Crimea (1940), by
G. Konoplev (1937-38) for the Bay of Odessa, by V. Nikitin (1939) for the
Batum area and by S. Maljatzky (1940) for the open part of the Sea.

The diatoms are of preponderant significance in the Black Sea phyto-
plankton, the second place is occupied by Dinoflagellata. The number of plant
specimens in the plankton is exceeded by that of the animals (Fig. 198a, b).
As in the open seas there are in the Black Sea two main bloom periods : the
autumn-winter-spring one linked mainly with a mass development of dia-
toms, and a much weaker summer one, controlled by the multiplication of
Dinoflagellata. An increase of the diatoms is again observed in the autumn
(Fig. 199). In the winter there is a sharp preponderance in the phytoplankton
of Skeletonema costatum (up to 4 million cells per litre), Chaetoceros radians
and Ch. socialis (up to 31 million cells), Thalassionema nitzschioides and
Thalassiosira nana (up to 30,000 specimens) and Cerataulina bergoni (up to
1-7 million specimens).

From May onwards, and especially in the hot months (July and August),
the development of Dinoflagellata proceeds vigorously : Exuviella cordata (up
to 18,000 per litre), Prorocentrum micans (up to 72,000 specimens), Goniaulax
polyedra (up to 66,000 specimens), some species of Glenodinium apiculata
(up to 39,000 specimens) and Peridinium triquetrum (up to 43,000 specimens).
Among the diatoms Thalassionema nitzschioides also grows in large numbers in
the summer. A second autumn maximum of diatoms is observed in November,
when the phytoplankton passes into its winter state {Table 164).

The spring outburst of phytoplankton is four or five times greater in its
number of cells than the winter maximum and 2,000 times greater than the
autumn maximum. A comprehensive picture of the quantitative sequence of
phytoplankton during the year in the circumlittoral parts of the Bay of
Sevastopol is given in Table 165 (according to Morozova-Wodjanitzkaja's
data in the year 1938-39).

Marked changes, not only seasonal but annual, are observed in the com-
position and quantity of phytoplankton in the Black Sea. The average annual
number of Dinoflagellata in the plankton of the Bay of Sevastopol was
31,000 specimens in 1938, and of diatoms 19,000 specimens per litre, with an
average annual total amount of phytoplankton 52,000 cells per litre ; while
in 1939 the corresponding data were: 14,000, 3,240,000 and 3,257,000 per
litre. Thus the average annual number of Dinoflagellata in 1939 was half that
in 1938, while the number of diatoms in 1939 was, on the contrary, so much

78 7%

r$7°/o

Diatomeae
Dinoflagellatae

Silicoflageilatae
Zooplankton

Fig. 198a. Quantitative correlation of main plankton

groups in Black Sea in Batumi area in September,

according to the number of specimens (Morozova-

Wodjanitzkaja, 1948).

8400

8100 \

7800

7500

7200

6900

6600

6300

6000

5700

5400

5/00

4800

4-600

4200

3900

3600

3300

3000

Z700

2400

2100

1800

/500

1200

900

600

300 •

TOTAL
PHYTOPLANKTOh
BIOMASS

DIATOM
BIOMASS

Feb. March Apr. May June Ju|y Aug
EARLY SPRING SUMMER
SPRING

Oct. Nov Dec. Jan.
LATE WINTER
AUTUMN
I938 " I939

Fig. 198b. Annual alterations in diatom and Dinoflagellata
biomass in Sevastopol area(Morozova-Wodjanitzkaja, 1948).

416 BIOLOGY OF THE SEAS OF THE U.S.S.R.

20000000л

щц/хшшшахшш! v ш a z и ш щ

1938 1939

Fig. 199. Seasonal alterations in the quantity of diatoms and

peridinean algae in the plankton of the Black Sea and Bay of

Sevastopol (Morozova-Wodjanitzkaja).

greater that it must be defined according to an entirely different order of
values. Apart from annual fluctuations in the number of plankton specimens
a pronounced variety is observed in the time of mass development and the
significance of individual forms. In April and May 1939 about 300 milliard
cells were recorded under 1 m2 in a column of water down to 15 m in the Bay
of Sevastopol. In the summer this amount was reduced to 0-8 to 1-5 milliard
cells, and in winter to 700 to 800 million cells. Phytoplankton biomass in the
Bay of Sevastopol under 1 m2 surface area reaches 1 33 g in the spring. In
June it was found to be 70 or 80 g, and in autumn and winter it dropped to

Table 164. The seasonal shift of the dominant forms of phytoplankton in Black Sea

(Coast of Crimea)

Groups
of

Summer

Autumn

Winter

Spring

phytoplankton

Prorocentrum

micans

Peridineae

Goniaulax
polyedra

Exuviella
cordata

Thalassionema

Skeletonema

Cerataulina

nitzschioides

costatum

bergonii

Diatomeae

Cerataulina

Chaetoceros

bergonii

radians

The black sea

Table 165

417

Group

August

November

January

March

May

July

Diatomeae
Dinoflagellata
Silicoflagellata
Others

8,665

45,405

583

1,667

77,077

16,325

1,340

1,110

93,235

3,213

465

1,550

2,141,783
332
130
600

20,204,560

8,440

100

500

27,000

25,800

100

2,600

Total

56,320

95,852

98,463

2,142,845

20,213,600

55,500

6 to 10 g (at a depth of 15 m). During its spring bloom the amount of phyto-
plankton increases as one moves from the open sea to the coast, bays and
inlets (according to Morozova-Wodjanitzkaja (1948), 250 to 300 times). Thus,
in July 1938, 25 miles away from the Crimean shore there were, at a depth of
0 to 25 m, on the average 1 1,000 cells per litre, and in the Bay of Sevastopol
37,000; the respective data for October were 17,000 and 107,000. During the
spring bloom up to 31 million cells per litre were recorded in the Bay of
Sevastopol.

Phytoplankton density decreases with depth, but it is still high at a depth
of 100 m ; in depths below 50 m phytoplankton cells probably sink down and
phytosynthesis is no longer possible.

Whereas in its open parts the Black Sea is considerably inferior to the Sea
of Azov as regards its quantity of phytoplankton, in its bays and inlets the
amount of phytoplankton approximates to that of the Sea of Azov.

A comparison of the quantitative data on the Black Sea phytoplankton
with those of different areas of the Atlantic Ocean (the off-shore zones) leads
Morozova-Wodjanitzkaja to the conclusion that 'as regards its quantitative
phytoplankton development the Black Sea is not inferior to the North Sea . . .
or the Atlantic Ocean near the North American coast. ... In the Antarctic the
amount of phytoplankton (number of cells) is ten times higher than in the
open parts of the Black Sea, but it is much lower than that of its bays and inlets.'

S. Maljatzky (1940) gives the quantitative data on the average content of
phytoplankton in the photosynthetic zone (a 75 m layer of water) in the open
parts of the northeastern half of the Sea. At the beginning of the summer
(Fig. 200a) phytoplankton is particularly abundant in the part of the Sea
adjacent to the Kerch Strait and in the circumlittoral zone south of Novoros-
siysk : in the second half of the summer high indices of phytoplankton bio-
mass were found also in the central parts of the Sea (Fig. 200b). In the first
case the biomass in some areas was more than 200 mg/m3; in the second
more than 400 mg/m3 : i.e. it was found to be close to the phytoplankton bio-
mass of the Central Caspian.

S. Maljatzky (1940) and N. Morozova-Wodjanitzkaja have given a descrip-
tion of the phytoplankton of the eastern half of the Sea. The phytoplankton
of the western half of the Black Sea and of the northwestern area was com-
prehensively studied by P. Usachev (1928) and G. Pitzik (1950, 1954).

Both investigators have recorded high productivity indices for this area
of the Sea. The number of phytoplankton in the Odessa area reaches 5 milliard

418

BIOLOGY OF THE SEAS OF THE U.S.S.R.

cells per 1 m3 (G. Pitzik, 1950), and in the Bay of Sevastopol 30 milliard
cells (up to 12 g/m3: N. Morozova-Wodjanitzkaja, 1940, 1948). These data
are commensurable with those for the Sea of Azov. In the open part of the
Black Sea, in summer, the amount of phytoplankton is estimated as 5-10-15
million cells per 1 m3, and its biomass in tens of mg/m3 ; however, it is many
times less than in the bays and inlets and in the shallows of the Sea, and hun-
dreds of thousands of times less than in the Sea of Azov, although in some
places in the open sea and in some samplings the amount of phytoplankton
was of the order of hundreds of milligrammes and even up to 1 ,700 g/m3.

Fig. 200. Distribution of phytoplankton biomass (in mg/m3) in the Black Sea
(Maljatzky, 1940). A 21 May to 5 June 1939; В 2 to 7 August 1939.

Phytoplankton biomass throughout the Black Sea was estimated by
G. Pitzik : (1954) in a number of years as about 2-8 to 6-2 million tons. N. Moro-
zova-Wodjanitzkaja (1957) has tried to compute some general indices of Black
Sea plankton productivity. She thought that the daily production of phyto-
plankton in the open part of the Sea was 9-5 g in autumn and winter, and at the
beginning of the summer about 11-3 g under 1 m2 of surface. The daily P/B
ratio (the ratio of the daily gain of production to biomass) was 1-7 in
February, 2-2 in June and 1-2 in September. Moreover, she has determined the
daily coefficient (the ratio of daily consumption to the original biomass,
CjB) as 1-2 to 1-7, and the daily coefficient (ratio of production to consump-
tion, Р/С) in the spring and early summer as 1 to 1-2, i.e. at that time of the
year consumption is completely compensated for by new growth (production).
By the end of the summer and in the autumn (September to November) this
last coefficient is equal to 0-9, i.e. consumption exceeds new growth.

Quantitative distribution of zooplankton in the open parts of the Sea. Nikitin
(1945) has given a general picture of the quantitative distribution of plankton

THE BLACK SEA

419

(both animal and plant) in the open part of the Sea. He has determined the
total plankton biomass as approximately 7 million tons (6,937,714 t), half of
the plankton being contained in the upper 50 m layer, while the lower 150 to
175 m layer contains only 1 per cent of its bulk (Fig. 201). The Sea of Azov is a
body of water attached to the Black Sea which is remarkable in many respects.

'ertical distrib

Jtion of

total

plankton biomass

0-25

2160690

31,

25-5L

1440000

20,7%

Ш5

1172880

17,0%

75-10L

774984

11,2%

868776

125%

453276

6,5%

67108

Fig. 201. Vertical distribution of total plankton bio-
mass in open parts of Black Sea, tons (Nikitin).

It is essentially a broad, very shallow inlet of the Don, with water only
slightly saline. Owing to a number of circumstances it is supplied with abun-
dant'mineral substances.

Investigations made in recent years have led to a situation where the Sea
of Azov can now perhaps be placed among those seas of the u.s.s.r. which
have been most comprehensively studied.

The average plankton biomass decreases steadily from top to bottom
(Table 166).

Table 166

Depth, m
Biomass, mg/m3

0-25
210

25-50
147

50-75
121

75-100
84

Depth, m 100-125

Biomass, mg/m3 90

125-150

150-175

(150-225)

The increase of biomass in the 100-125 m layer as compared to the layer
above it, is explained by the accumulation in it of such cold water forms as
Calanus helgolandicus and Pseudocalanus elongatus throughout the greater
part of the year.

420

BIOLOGY OF THE SEAS OF THE U.S.S.R.

The decrease in plankton numbers with depth is accompanied by its quali-
tative impoverishment (Fig. 202). Below 50 m there is a considerable decrease
in the amount of oxygen and in the pH value, indicating increasing amounts of
free carbon dioxide. The average plankton biomass throughout the inhabited
zone is 1 18 mg/m3 (according to Maljatzky, 100 to 130 mg/m3).

Qualitative
PH — Oxygen composition

Plankton
biomass

of zooplankton

Fig. 202. Vertical distribution of oxygen, of the course of the
active reaction, and of the qualitative and quantitative distri-
bution of plankton in Black Sea (Nikitin). Biomass and number
of plankton species of the upper horizon are taken as 100
per cent.

A. Kusmorskaya (1950, 1954, 1955) has carefully studied the zooplankton
of the Black Sea, chiefly as food for fish, and the life cycles of mass forms. She
notes among the fish-food organisms the preponderance of the following
forms: Calanus helgolandicus, Pseudocalanus elongatus, Acartia clausi,
Penilla avirostris, predatory and voracious forms of Medusa, Pilemo pulmo
and Amelia aurita, Pleurobrachia pileus and Sagitta setosa are usually larger
in mass than food plankton, which they devour in huge amounts. Among
them S. setosa only is eaten by some fish (sprat and hardtail).

THE BLACK SEA 421

С helgolandicus breeds throughout the year, apparently producing five or
six generations (N. Klucharev, 1948; L. Chayanova, 1950). Its average
amount, in all its stages, under 1 m2 of surface is about 1 ,000 specimens.

During the cold season of the year C. helgolandicus keeps mostly to the upper
layers of the Sea and in the summer to the lower ones, but in summer also
Calanus travels vertically to the depth each day. During daylight its mass is
concentrated at a depth of 75 to 100 m, and during darkness in the 0 to 10 m
layer {Table 167). Pseudocalanus elongatus behaves in a similar manner.

Table 167. Vertical distribution of edible zooplankton biomass in April 1949, percentage
of total biomass in open part of Sea. {A. Kusmorskaya)

6 a.m. to

10 a.m.

9 p.m. to 11

p.m.

2 a.m. to 3

a.m.

Level,

Total mass

of plankton

Calanus

of plankton

Calanus

of plankton

Calanus

0-10

4-3

80-7

91-5

18-5

13-4

10-25

360

15-0

17-3

6-5

29-0

40-3

25-50

11-4

100

1-6

1-8

38-0

37-3

50-75

0-4

4-0

75-100

45-3

700

0-5

100-150

In contrast to C. helgolandicus, the development of Acartia clausi proceeds
throughout the year in the upper layer (0 to 50 m), and in the warm period of
the year the upper maximum of plankton development depends on the growth
of A. clausi and Penilla avirostris. As regards numbers Penilla occupies the
first place, Acartia the second and Calanus the third {Table 168).

Table 168. The numbers of Calanus, Acartia and Penilla, April to August, in the
0 to 150 m layer of the open Sea under 1 m2 {A. Kusmorskaya)

Species

April

July

August

October

C. helgolandicus

4,330

3,760

3,920

127

1949

(1948)

A. clausi

7,950

12,210

39,980
(1948)

2,850

P. avirostris

56,250
(1951)

Acartia clausi (L. Chayanova, 1950) produces nine generations in one year.
The numbers of Noctiluca miliaris reach 2,000 to 6,000, sometimes even
9,000, specimens per 1 m3 (in one case 80,000 specimens/m3 were recorded)
and Pleurobrachia pileus gives in the 50 to 100 m layer 2-5-6 and up to 15,000
specimens per 1 m3. At times they form a fairly considerable supplement to
food-plankton {Table 169).

An approximate distribution of food-zooplankton for August 1950 is
given in Fig. 203 (except the Medusa, Pleurobrachia and Noctiluca). The total

THE BLACK SEA 423

Table 169. Role of inedible forms of zooplankton in the Black Sea,
according to 1948-49 data (A. Kusmorskaya)

Biomass,
mg/m3

Western half
April August

Eastern half
September

Plankton composition
Edible zooplankton
Noctiluca miliaris
Pleurobrachia pileus

68
68
46

200
200
144

100
168

Total

179

484

341

amount of zooplankton and its separate components may undergo consider-
able annual and seasonal fluctuations, like those mentioned above for phyto-
plankton, as is evident from a comparison of Figs. 199 and 201. In the north-
western part of the Sea, in bays and inlets, the amount of plankton is always
greater than in the open sea ; in all these fluctuations, however, it is on a fairly
high level in the open sea too, as compared with other seas. An increased
amount of plankton is always observed in the western part of the Sea, which
is due to the proximity of the highly productive, northwestern, shallow
area and to an abundant river-discharge. A second highly productive Sea
area lies off the southeastern coast of the Crimea, this peculiarity being due to
the outflow of highly productive waters from the Sea of Azov. Generally
speaking the fluctuations in Black Sea plankton productivity display a
definite dependence (Fig. 204) on the variations of river-discharge (A. Kus-
morskaya, 1955). The mean biomass of food plankton in the Black Sea varies
between the limits 175 and 930 mg/m3 (A. Kusmorskaya, 1955) {Table 170).
Pseudocalanus elongatus and Acartia clausi are the main zooplankton forms
of the shallows of the northwestern area of the Black Sea (0 to 10 m). Calanus
helgolandicus becomes a mass form in the deeper part. There is a considerable
admixture of Penilla, Evadne and Podon in the shallows in summer (Fig. 205).

The nature of the zooplankton biomass distribution in the lower level of
the inhabited zone is different, where it corresponds well with the general
character of the circulation of the Black Sea water masses (Fig. 206).

The changes in the biomass and composition of the summer food-zoo-
plankton of the northwestern area shallows are given in Table 171.

Similar data are obtained from a comparison of the Black and Caspian
Seas zooplankton biomass (A. Kusmorskaya, 1950) (Table 172).

However, substantial additions should be made to this table. The predatory
plankton forms (Medusa, Ctenophora, Sagittae, Flagellata, Noctiluca miliaris),
which probably devour zooplankton like the Ctenophora of the Barents Sea
and thus decrease its significance as nutrient for fish, are absent from the
Caspian Sea.

The shallow northwestern part of the Black Sea, distinguished by its high
indices of plankton and benthos biomass, serves in summer as feeding ground
for many fish and their young. In some years, however, the picture is quite

424

BIOLOGY OF THE SEAS OF THE U.S.S.R.

August 1948

1949 Aug Sept.1950 Aug. 1951
Western half

Sept 1948

1949 Aug Sept 1950 Aug. 1951
Eastern half

Fig. 204. Annual fluctuations in the volume of river-discharge and in the biomass of
nutrient zooplankton in the 0 to 25 m layer of the Black Sea. 1 Total discharge ; 2
Summer floods; 3 Nutrient zooplankton biomass; 4 Penilia avirostris biomass

(Kusmorskaya).

different. Thus in 1955 a sharp decrease of food zooplankton and a mass
development of the diatoms Rhizosolenia calcar-avis were observed. They
may be the link in an inverse relationship. The same picture was observed in
the Sea of Azov in the summer of 1955 (25 to 50 mg/m3 in July and August).
A considerable mass of fish, chiefly anchovy, moved away from the north-
western part of the Sea. The feeding conditions began to deteriorate in the
northwestern part of the Black Sea after 1952. In 1954 the amount of food-
plankton decreased by several times (E. Yablonskaya, 1957). In 1955 the

Table 170. Annual and seasonal fluctuations in the biomass of food zooplankton
in different parts of the Black Sea {A. Kusmorskaya, 1954)

Month

Open sea
western half,
1949

0-100 m layer

eastern half,

1951

Northwestern part

0-10 m layer,

1951

mg/m3

February
April
May
June

60(1951)
65

599

July
August
September
October

60
140

930
417

384
323

December

—

■430 mg/m3

, 3

126 mg/m

Fig. 205. Distribution of nutrient zooplankton biomass in the Black Sea in August
1951 in the 0 to 25 m layer (Kusmorskaya, 1950). 1 Biomass above 1,000 mg/m3;
2 Biomass between 500 and 1,000 mg/m3 ; 3 Between 300 and 500 mg/m3 ; 4 Between
200 and 300 mg/m3 ; 5 Between 100 and 200 mg/m3 ; 6 Between 50 and 100 mg/m3.

Fig. 206. Horizontal distribution of plankton biomass in Black Sea in the 150 to

175 m layer (Nikitin).

Table 171. Changes (mg/mz) in the food-zoop lank ton biomass in the 0 to 10 m layer

(A. Kusmorskaya, 1950)

Mean

Evadne

Pseudo-

Month

biomass,
mg/m3

Acartia

Penilla

podon

calanus

Sagitta

Remainder

July

175

101

—

August

852

330

188

—

256

October

385

—

237

426

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 172. Comparison of mean zooplankton biomass (g/m3) of the Black
and Caspian Seas according to seasons in the 0 to 100 m layer

Food-plankton in
Season Central Southern western part of

Caspian Caspian Black Sea

Spring

Summer

140

Autumn

—

Winter

—

zooplankton biomass in the Sea of Azov decreased by almost twelve times
and the ratio between the peridineans and the diatoms changed greatly and
became unfavourable for fish. Nikitin also tried to trace a seasonal change in
the plankton biomass. Table 173 indicates his method.

Table 173

Depth
m

Avera

*e plankton

biomass,

* mg/m3

May

June

July

Aug-Sep

Oct-Nov

Feb

0-25

120

266

278

298

200

25-50

120

162

202

125

140

133

50-75

130

136

159

110

113

75-100

109

100-125

193(?)

125-150

79(?)

150-175

0-175

116

125

130

101

* V. Nikitin thinks that the magnitudes of plankton biomass obtained by him are con-
siderably understated, since Nansen's net was used for the collection and it lets through
almost the whole of nannoplankton and also part of the micro-plankton.

In the upper layers of the Sea (0 to 25 m) the seasonal changes of plankton
biomass are marked, but they are already attenuated at depths of 25 to 50 m,
while below 50 m they are practically absent. This is in complete conformity
with the course of the annual fluctuations of various factors of the environ-
ment, primarily with temperature. Moreover, it is to be borne in mind that the
main mass of phytoplankton is concentrated in the upper 25 m layer

V. Wodjanitzky estimates the total Black Sea plankton biomass as 12 to
18 million tons (1941), and its annual productivity as no less than 225 million
tons.*

* In V. Nikitin's book The Feeding of Anchovy (Engraulis encrasicholus L.) in the
Black Sea off the Shores of Georgia the total plankton biomass is given as 7 million tons,
and the annual production as 105 million tons. All these data should at present be con-
sidered as provisional.

THE BLACK SEA 427

In our general estimation of the biomass and productivity of the Black
Sea plankton we have to accept that these data are high and of the same order
as those of the Caspian Sea, which is completely confirmed by V. Wodjanit-
zky's (1941) opinion on the high biological productivity of the Black Sea.

Pelagic community. Some regions of the Sea, remote from the shores and
mainly within the convergence zones, are inhabited by an original pelagic
biocoenosis described by B. Iljin (1933) and somewhat resembling the Sar-
gasso Sea fauna, since it consists of large gatherings of floating plants, but,
in contrast to the Sargasso Sea, these are dying eel-grass leaves brought
out by currents from the shores. As has been described by Iljin, among the
mass of floating material live many animal-forms, which have specially
adapted themselves to this environment. Among them the more common
ones are : pipefish (Syngnathus schmidti) ; stickleback (Gasterosteus aculeatus) ;
the isopod (Idothea algirica), and large crab megalops (probably Liocar-
cinus holsatus and Portunus arcuatus) ; and at times in large numbers grey
mullet larvae, young fry, and the young of the year; anchovy {Engraulis
encrasicholus), sprat {Spratella sprattus phalerica); pipefish (Syngnathus
schmidti) and the predators feeding on it; mackerel (Scomber scombrus);
Sarda (Pelamys sarda); Tuna (Thymus thymus), and dolphin (Delphinus
delphis). All these forms have typical characteristics of pelagic organisms ; it is,
however, unknown whether stickleback can spawn away from the shores,
while grey mullet forms part of this biocoenosis only when young. Among the
birds the stormy petrel is always present.

S. Maljatzky has established (1940) the existence of several areas of abun-
dant gatherings of living organisms in the northern part of the eastern half of
the Sea ; he thinks that these areas are connected with the areas of increased
vertical circulation.

Not only an increase in the amount of zooplankton but a huge shoaling
of pelagic fish — anchovy, sarda and also dolphins — is observed in these areas.
This is also the spawning ground of both these fish (Fig. 207). The fact that
the spawning grounds of anchovy and sarda are always separate may be
due, Maljatzky thinks, to a mass devouring of anchovy by sarda.

Benthos and Nekton

The qualitative composition of phytobenthos. The qualitative composition of
Black Sea macrophytes was investigated by N. Voronichin (1908) and
E. S. Zinova (1936); N. Morozova-Wodjanitzkaja (1927-41) has done much
comprehensive research on its ecology and chiefly on its quantitative distri-
bution.

At present there are 236 known species of green, brown and red algae. With
the passage from the Mediterranean Sea to the Black Sea the macroflora is
much less impoverished than the animal forms ; only with the passage into
the saline waters of the Sea of Azov does the number of species of the bottom-
living algae drop markedly, as is shown in Table 174.

Apart from the algae two species of flowering plants — Zostera marina and

428

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Fig. 20/. JJisinouuon of anchovy and Sarda roe in northeastern corner of Black
Sea in May 1939 (Maljatzky).

Z. nana (Z. minor) — are of importance in the vegetation of the Black Sea.
Among the Black Sea sea-weeds the dominant forms are : Phyllophora nervosa,
Cystoseira barbata and C.b. var. placida.

Among the green algae the most important are Chaetomorpha chlorotica,
Enteromorpha intestinalis, some species of Cladophora and Ulva lactuca;
among the brown ones Cystoseira barbata with its variant placida and Scyto-
siphon lamentarius (in winter); and among the red ones Phyllophora rubens
var. nervosa, Ceramium rubrum and С diaphanum, Polysiphonia subulifera, P.
variegata, P. elongata, P. opaca and Laurencia obtusa.

It is quite remarkable that in contrast to the animals, the bottom-living
algae of the Black Sea have not evolved a single endemic autochthonous form :

Table 174

Group

Mediterranean

Sea:

Bay of Naples

(Funck)

Black Sea

(Voronichin and Zinova, from

Morozova-Wodjanitzkaja)

Sea of Azov, excluding

the Kerch Strait

(L. Volkov)

No. of

species, per

cent of

No. of

species, per

cent of

No. of
genera

No. of
species

No. of
genera

No. of
species

Mediter-
ranean

No. of
genera

No. of
species

Mediter-
ranean

Green algae
Brown algae
Red algae

126

267

23
41
43

92
51

127

55
47-5

7
3
5

4
10

30
4
4

Total

209

423

107

270

THE BLACK SEA

429

they are simply an impoverished flora of the Mediterranean Sea. N. Morozova-
Wodjanitzkaja points out also the small size of the Black Sea algae — on the
average 10 to 30 cm. The largest, Cystozera, is not longer than 1.2 m.

Quantitative distribution ofphytobenthos. In examining the quantitative distri-
bution of macrophy tes in the Black Sea it is necessary first of all to distinguish
the marine flowering plant eel-grass which, as has been mentioned above, is
represented in the Black Sea by two species. The main mass of eel-grass is
found in the northeastern part of Karkinitsk Bay (Fig. 208), where it forms
wide submarine meadows at depths of 0-5 to 6 m on sandy mud, at times

ЕЭ PHYLLOPHORA
ШШ ZOSTERA

Fig. 208. Distribution of Phyllophora and

Zostera growths in northwestern corner of

Black Sea (Morozova-Wodjanitzkaja).

together with Ruppia and Potamogeton ; it is found even deeper (down to 15 or
20 m), but only in small amounts. It is found in small amounts along the whole
coast of the Black Sea in its inlets and bays. In the most favourable environ-
ment the eel-grass biomass reaches 5 kg/m2 (on the average 1-5 kg/m2). The
abundant growths of eel-grass are concentrated off the Black Sea shores ; in
the shallows of Karkinitsk Bay they form a mass of no less than 200,000 tons,
while V. Wodjanitzky has determined the total amount in the Black Sea as
1 million tons (1941). The epidemic caused by the fungus Labirintula, which
afflicted the north Atlantic Zostera in the 'thirties, spread to the Black Sea
and destroyed Zostera marina wholesale. Besides Zostera the eel-grass
Phyllophora rubens var. nervosa should also be discussed separately. Phyllo-
phora, probably a special ecological form, is found along the whole shore of
the Black Sea, but 95 per cent of its total mass is concentrated in the north-
western part of the Sea (Fig. 208). This accumulation of algae, reckoned as
not less than 5 to 6 million tons,* covers the mud-shell gravel floor in one
huge mass over an area of about 15,000 km2 in the region called 'Zernov's
Phyllophora Sea' in honour of Academician S. Zernov, who discovered it

* V. Wodjanitzky (1941) determines the bulk of Phyllophora in the northwestern part
of the Black Sea as 17 million tons, which is obviously an exaggeration.

430 BIOLOGY OF THE SEAS OF THE U.S.S.R.

in 1908. The magnitude of these accumulations is obvious from the fact that
they are of the same order as those of the Sargassum weed in the Sargasso Sea.
The accumulation of Phyllophora in the Black Sea is, possibly, the mightiest
accumulation of red algae throughout the whole world ocean. The bulk of
all the other macrophytes throughout the Black Sea is no more than 500,000
tons. Phyllophora occurs at a depth of 30 to 60 m, i.e. at places where macro-
phytes are not usually found in large numbers. On the average the density of
Phyllophora is 1-7 kg/m3, but in individual cases it reaches 13 kg/m2. K.Meyer
(1937) came to the conclusion 'that in the Phyllophora Sea we find a layer of
Phyllophora which appears to have been torn from its original habitat in the
littoral zone. Phyllophora was brought there by currents, and huge stocks of
it have been formed through long years'. Phyllophora, however, retains its
capacity for multiplication. N. Morozova-Wodjanitzkaja thinks that, like the
accumulation of Sargassum in the central parts of the Atlantic, the Phyllo-
phora accumulations of 'Zernov's Sea' have lost their genetic link with the
coastal Phyllophora— it has not been carried into it by currents throughout
the years, but has grown and increased its mass independently through
vegetation.

This analogy is particularly remarkable since this huge accumulation,
which has no equal anywhere in the world's ocean, is formed by the brown,
drifting algae (Sargassum), while the other one, lying on the sea-floor at a
considerable depth, is formed by the red algae (Phyllophora). Small accumu-
lations of Phyllophora are distributed in other parts of the northwest of the
Black Sea ; it is found along the whole coast in small quantities. The occur-
rence of Phyllophora in the depths of the northwestern part of the Sea dis-
turbs the general course of the decrease of macrophyte biomass with depth.
Without Phyllophora this general course of decrease has the aspect shown in
Table 175.

Table 175

Depth, m Mean biomass of

macrophytes in g/m2

0-10 (coastal cliffs)

> 1,000

10-20 (sand and shell gravel)

20-30

30-50

50-90

The algae biomass is usually no higher than 2-5 kg/m2, rising rarely to 8 to
13 kg/m2.

The specific composition of the predominant forms changes also with
depth ; however, the general order of the vertical change of algae remains :
green — brown — red {Table 176).

Owing to the steep slope of the shores of the Black Sea the width of the
littoral zone occupied by macrophytes is not great, usually 3 to 6 km, and at
times only 1 km. It extends to 150 km only in the Odessa and Kirkinitsk Bays.

THE BLACK SEA 431

Table 176

Most common associations of

Highest

Depth,

macrophytes

Mean biomass,

biomass,

(N. Morozova-Wodjanitzkaja)

kg/m2

0-2

Conferva (Cladophora and Chaeto-

morpha) in bays

—

0-15

Zostera marina and Z. minor

1-1-5

0-23

Cystoseira barbata

6-7

4-35

Gracillaria, Polysiphonia elongata,
Zanardinia

25-35

Phyllophora rubens

The macrophyte biomass of the littoral zone of the Black Sea (without the
Phyllophora Sea vegetation) is only 0-5 million tons; moreover, the second
place after Phyllophora is occupied by the brown alga Cystoseira barbata.
The Cystoseira association produces at depths of 0-5 to 23-28 m a biomass of
an average of 3 kg/m2 (at times up to 6 or 7 kg/m2).

If 90 per cent of the total mass of the Black Sea macrophytes consists of
Phyllophora, then about 9 per cent of it is Cystoseira, whereas all the other
macrophytes form not more than about 0-7 per cent. Thus only two species of
benthos bottom-living algae are markedly predominant in the Black Sea.

Whereas the littoral zone of the Black Sea is not as rich in macrophytes as
the northern part of the Atlantic, its annual productivity is very near to that
of the latter, and is even somewhat higher.

According to N. Morozova-Wodjanitzkaja (1941) the highest annual macro-
phyte productivity is observed in bays, inlets and lagoons (up to 17 kg/m2,
and 7 to 8 kg/m2 in the open sea) {Table 177).

The qualitative composition of zoobenthos and fish fauna. The Black Sea fauna
is on the average four or five times poorer than that of the Mediterranean ;
moreover, different groups vary in the degree of their impoverishment. Some
groups could not penetrate into the Black Sea at all : such were Siphonophora,
Gephyrea, Brachipoda, Scaphopoda and Cephalopoda, Enteropneusta and
Salpae. Other groups became much poorer in the Black Sea, as for example
Ctenophorae, corals, Amphineura, Echinodermata and Tunicata {Table 178).

The number of species of macrophytes and animals decreases greatly from
the Black Sea to the Sea of Azov ; this can be seen by the example of the poly-
chaetes (according to V. Vorobieff, 1932) {Table 179). Evidently in the case
of polychaetes the number of genera decreases more rapidly than that of the
families, and that of the species more rapidly than that of the genera.

Lowered salinity (to 19%0) and the compal-atively narrow habitable upper
layer were the main factors preventing the Mediterranean fauna from settling
in the Black Sea. V. Wodjanitzky (1936) has brought out this last factor as
affecting the life of fish when writing 'that members of the Mediterranean
ichthyofauna could settle in the Black Sea only when in all stages of their
development they kept to the upper layers of water (or off the shores) '. In

432 BIOLOGY OF

THE SEAS

OF THE U.S.S.R.

Table 177

Quantitative indices

of some i

nacrophytes

in Novorossiysk region

Ratio of

Mean

Annual

productivity

biomass

productivity

to biomass

Group

g/m2

(P/B)

Brown algae

Cystoseira barbata

2,348-9

4,605-0

1-96

Dilophus repens

39-7

201-5

5-08

Scytosiphon lamentarius

9-8

51-8

5-29

Cladostephus verticillatus

3-9

23-3

5-97

Green algae

Chaetomorpha chlorotica

167-8

1,041-3

6-21

Enteromorpha intestinalis

71-6

290-5

4-06

Cladophora spp.

69-7

275-1

3-95

Ulva lactuca

93-6

314-1

3-36

Red algae

Ceramium rubrum

34-8

197-0

5-66

Gelidum crinale

27-0

134-9

5 00

Polysiphonia subulifera

61-2

19-7

3-59

Flowering plants

Zostera marina

19-4

64-1

3-30

his opinion, in discussing the colonization of the Black Sea by the Medi-
terranean fauna its most characteristic feature — the development of hydro-
gen sulphide in its deeper layers — should be kept in mind. Lowered salinity,
however, is much more important as a limiting factor. As we have seen,
a considerable number of animal groups living in the Mediterranean are
either absent from the Black Sea, or represented there by some individual
species.

A. Valkanov published in 1957 a list of fauna of the Bulgarian shore of the
Black Sea. The list contains 343 species of four variants of Protozoa and 1,005
species and 23 variants of multicellular organisms. M. Bacesco's mentioning
of the occurrence of the polychaetes Monayunkia caspica ssp. fluviatilis
{danubicus), an evidently Pontic relic, in the lower reaches of river Danube is
most interesting.

The process of the formation of Black Sea fauna is, possibly, incomplete
as yet and new forms may continue to penetrate into the Black Sea from the
Mediterranean. Two species of acorn barnacle (Balanus amphitrite communis
and B. perforatus var. angustus), discovered by G. Zevina and N. Tarasov
(1954) in the fouling of ships, may be included among the new immigrants
from the Mediterranean to the Black Sea. Continuous migration of new flora
and fauna forms from the Mediterranean may be seen from the example of
phytoplankton. Some species of Mediterranean diatoms, recent arrivals from
the Mediterranean {Rhizosolenia calcar-avis, Cerataulina bergoni and Lepto-
cylindricus danicus), have now become mass forms in the Black Sea.

Table 173

Number of

species*

Black Sea species

Mediterranean

per cent of

Group

Sea

Black Sea

Mediterranean

Porifera

110

Coelenterata

208

including

Scyphozoa

8-3

Ctenophora

Anthozoa

10-6

Mesozoa

Plathelminthes

279

152

54-5

Nemertini

Nematoda

156

84
(15 parasites)

Kinorhyncha

Chaetognatha

3-3

Acantocephala

Gephyrea

3-4

Phoronoidea

100

Polychaeta

516

153

29-7

Pantopoda

Copepoda

304

25-3

Ostracoda

125

Cirripedia

9-3

Cladocera

120

Leptostraca

Amphipoda

223

31-4

Isopoda

159

Cumacea

Schizopoda

Decapoda

251

Amphineura

Lamellibranchiata

358

Gastropoda

965

7-7

Scaphopoda

Cephalopoda

Pteropoda

Bryozoa

306

Kamptozoa

Brachiopoda

Echinodermata

9.4

Tunicata

200

Enteropneusta

Branchiostomata

100

Pisces

549

180

(Mediterranean)

112)

Reptilia

Mammalia

Total

5,244

1,145

21-8

* The number of species of the Mediterranean fauna apart from protozoa are taken
from the book of Gr. Antipa (Marea Neagra), 1941.

434 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 179. Number of poly chaete families, genera and species

Sea

Families
Total Per

number cent

Genera
Total Per

number cent

Species
Total Per

number cent

Mediterranean 36

—

214

—

433

—

Black 24

66-6

360

123

28-4

Azov (except inlets

and Sivash) 7

19-4

3-2

2-1

The Bosporus region, the most saline sector of the Black Sea, gives shelter
to immigrants from the Mediterranean, which are not found anywhere else
in the Black Sea. Twenty forms of this type, including anthozoa echinoderms,
molluscs, polychaetes and others have been found there.

The heterogeneity of the Black Sea fauna is conditioned, like that of the
Caspian Sea, by its past history and its lowered salinity. Its fauna comprises
three main components: (7) relict autochthonous fauna (commonly called
Pontic or Caspian) ; (2) Mediterranean immigrants, and (3) fresh-water forms.
These three elements are partly territorially separated, partly mixed ; this pro-
vided N. Knipovitch (1933) with an opportunity of giving a more detailed
classification of the Black Sea fauna according to its habitat. Knipovitch dis-
tinguishes the following groups mostly from the instances of fish (see also
Table 180).

1. Pontic relicts, which have survived only in the parts of the Black Sea
with very much lowered salinity, especially in its inlets, and the fresh waters
of the lower reaches of its rivers.

2. Pontic relicts inhabiting the Black Sea generally, but not met in the
Sea of Azov ; for example, some herrings : Caspialosa nordmanni, С pontica
and others.

3. Pontic relicts inhabiting both the Black Sea and the Sea of Azov. To this
group belong the sturgeon family, some herrings, for example, the Azov
herring (Caspialosa maeotica), and C. tanaica etc.

4. Mediterranean immigrants forming part of the settled population of the
Black Sea. This includes the main mass of organisms living in the Black Sea.

5. Mediterranean immigrants, which appear in the Black Sea temporarily,
and do not multiply in it.

Table 180. Composition of the Black Sea fish

Total number Number of Number of Number of
of species and Pontic Mediterranean fresh-
sub-species relicts immigrants water forms

According to

Knipovitch (1932) 159

According to

Slastenenko (1938) 180

28
31

97
112

34
37

THE BLACK SEA 435

6. Mediterranean immigrants, which feed and spawn in the summer in the
Sea of Azov and come back to the Black Sea in winter ; such as, for instance,
the Azov form of anchovy.

7. Fresh-water forms.

As regards the wealth of species the following forms are notable: the
autochthonous Acipenseridae (6 species), the mixed Clupeidae (9 species), the
fresh-water Cyprinidae (23 species), the Mediterranean Mugilidae (5 species),
partly the fresh-water Percidae (8 species), the Mediterranean Sparidae (8
species), Labridae (8 species), the mixed Gobiidae (22 species), the Medi-
terranean Blenniidae (8 species) and Syngnathidae (7 species).

Moreover, some forms, which penetrated into the Black Sea even earlier
but do not multiply there, are growing acclimatized, forming some separate
Black Sea colonies. Lobster, mackerel, Sarda, tuna and others can be included
among these forms. Finally, there are some forms which used to spawn very
rarely in the Black Sea before, but which within recent years have multiplied
there annually in large numbers.

The Black Sea is supplemented also by occasional immigrants from more
distant countries. V. Makarov (1941) has lately found in the Bug and Dnieper
inlets a mass settlement of the crab Rithropanopeus, carried there on ships from
the Zuyder Zee (Holland), which had come even earlier to the European shores
from the coast of Northern America. The gastropod mollusc Rapana bezoar
which has done incalculable harm to the oyster and Mytilus colonies, mainly
off the Caucasian shores, came to the Black Sea from the Sea of Japan in a
similar manner. Some Mediterranean forms, settled in the Black Sea, have
found here particularly favourable conditions for development, and, although
small in size, they form a very dense population. Thus there are the algae
Phyllophora and Cystoseira; the molluscs Teredo navalis, Cardium edule
and Syndesmya ovata ; the polychaetes Nereis diversicolor, N. cultrifera, N.
sue cine a, Nephthys hombergii and Melinna palmata, and a number of others.

The fauna which penetrated into the Black Sea has not yet had time to
change much and to deviate from the original Mediterranean species. This
demonstrates the youth of this fauna. Thus E. Slastenenko records (1938,
a, b) only nine Black Sea endemic forms among 105 species and sub-species
of fish of Mediterranean origin living in the Black Sea.* As early as 1902
Sovinsky pointed out that among the 680 Mediterranean immigrants only
194 (28 per cent) had evolved taxonomically separate forms. Frequently this
evolution of the Black Sea forms into species and sub-species is temporary in
character. Thus, for example, until lately anchovy inhabiting the Black Sea
were divided into two sub-species : the Azov Engraulis encrasicholus maeoticus
(I. Puzanov, 1936) and the Black Sea E. e. ponticus (I. Aleksandrov, 1927);
moreover, it was proposed (A. Mayorova, 1934) to divide the latter into two
regions — an eastern and a western. Moreover, there was a tendency to consider
anchovy as a relict of the Tertiary Period. S. Maljatzky (1939), having recon-
sidered the whole of this problem, came to the conclusion that the anchovy

* A tenth — the pipefish Syngnathus phlegon longicephalus — described by V. Nikitin
{Transactions of the Zoological Institute of the Georgian Academy of Sciences, 1946),
may be added to them.

436 BIOLOGY OF THE SEAS OF THE U.S.S.R.

populations of the Mediterranean, Black and Azov Seas are not isolated from
each other, but to a certain extent are constantly mingling with each other,
forming only local ecological varieties. Maljatzky does not consider anchovy
as a relict in the Black Sea. In exactly the same manner V. Zalkin (1938) does
not consider the Black Sea dolphin Phocaena relicta as an individual species.
It is only a sub-species, and is likewise not a Tertiary relict but a form which
arrived in the Black Sea recently.

The characteristic features of the distribution of fauna in the Bosporus
and the Sea of Marmora, conditioned by a gradual general decrease of salinity
from the Dardanelles to the Bosporus and by the existence of two currents in
the Bosporus and the region round it — the upper Black Sea current and the
deep, much more saline one — were established by the researches of Ostroumov
in the nineties of the last century. The boundary between the two currents
sinks gradually as one approaches the Black Sea. Off Constantinople it lies
at a depth of 20 m, and at the entrance into the Bosporus at 50 m. As a result the
upper-layer fauna has a Black Sea character, and that of the deeper layer a
Mediterranean one. A. Ostroumov (1893-6) has recorded 60 forms, also
found in the Black Sea, in his collection of the coastal fauna in the Bosporus
area. On the other hand, in deeper layers the fauna has a markedly Medi-
terranean character. Already at a distance of 1 8 km from the entrance into the
Black Sea, 49 per cent of the molluscs and more than 50 per cent of the amphi-
pods were found to be extraneous to the Black Sea. Sea lilies, sea urchins, sea
stars, the Siphonophora Dimophyes, and eight-rayed corals were found
here. Off the Prinkipo Islands 70 per cent of molluscs did not belong to the
Black Sea.

The surface plankton of the Sea of Marmora is also under considerable
influence from the dominant Black Sea forms, but below 20 to 30 m it has a
typically Mediterranean character.

Qualitative-biocoenotic characteristics of zoobenthos. More than 50 years
ago S. Zernov, in his work 'On the study of the life of the Black Sea' (1912),
gave a very full picture of the qualitative-biocoenotic distribution of the Black
Sea bottom-living fauna. The scheme given by Zernov has been neither
changed nor substantially supplemented by further researches. It appear ass
Table 181, and Figs. 209, 210 and 211.

Biocoenoses of supralittoral and pseudolittoral. Having reconsidered the
question of the existence of a 'littoral' zone in the Black Sea, L. Arnoldi
(1948) came to the conclusion that 'from the biological point of view there is
no theoretical difference between the flood- and ebb-tide phenomena as such,
and the fluctuations of the sea-level, which depend equally on the flood-
tides of cosmic origin and on the seiche (wind-induced tides)'. Confirming the
existence of a littoral zone in the Black Sea, Arnoldi distinguishes a Black Sea
type of littoral, using the word 'pseudolittoral' for it. A supralittoral (a zone
washed only by the surf) lies above the pseudolittoral.

O. Mokievsky, having very carefully studied the littoral fauna of the western

THE BLACK SEA

437

shores of the Crimea (1949), within the zone of distribution of marine organ-
isms above sea-level, also distinguishes two separate zones of amphibiotic
life — the supralittoral and pseudolittoral. In his view the first 'corresponds
completely to the supralittoral of the open seas, the second — the overwash
zone or pseudolittoral — is analogous to the true littoral . . . the pseudolittoral,
like the true littoral, is subject to periodic drainage and flooding, since it is

Fig. 209. General picture of distribution of Black Sea bottom fauna (Zernov's data
slightly altered). 1 Crab Pachygrapsus ; 2 Barnacle Balanus; 3 Mollusc Patella;
4 Brown alga Cystoseira; 5 Green alga Ulva and Enteromorpha ; 6 Sea mussel
(Mytilus); 7 Actinia; 8 Sea-urchin; 9 Nemertines Lineus; 10 Lower worms Sac-
cocirrus; 11 Amphipoda (scuds); 12 Mollusc Venus; 13 Red mullet; 14 Flat fish
Rhombus; 15 Crab-hermet Diogenes; 16 Zostera; 17 Pipe fish; 18 Crenilabrus;
19 Sea-horse; 20 Shrimp Leander; 21 Oysters; 22 Sea-robin Pecten; 23 Mussel;
24 Red Porifera Phyllophora; 25 Red Porifera Suberites; 26 Ascidian Ciona;
27 Phaseolin mollusc (Modiola phaseolina) ; 28 Brittle star Amphiura ; 29 Mollusc
Throphonopsis ; 30 Medusa Pilema pulmo; 31 Ctenophora Pleurobrachia ; Hydrogen

sulphide.

situated within the limits of the fluctuation of deep-water waves'. In Mokiev-
sky's opinion the supralittoral lies above the limit of overwash, and the water
impregnating it enters the beach owing to its capillarity.

The bivalves Donacilla cornea and the polychaete Ophelia bicornia (Oph.
taurica ?) are the mass forms of the pseudolittoral of the Crimean coast.
In some cases Donacilla gives a biomass of up to 689 g/m2 and 3, 100 specimens
per m2, and Ophelia yields 394 g/m2 and 400 specimens per m2. Apart from
these two dominant forms the following are fairly common : the amphipod
Pontogammarus maeoticus, with a maximum biomass of 83 g/m2 and greatest
number of specimens of 1 1,800 per m2; Mytilus mysid, Gastrosaccus sanctus,
the isopod Euridice pulchra, and the polychaetes (Spionidae) Nerine cirratus
and Nerinides cantabra. Sphaeroma serratum and Idothea baltica are much

Fig. 210. Chart of distribution of bottom biocoenoses in Black Sea, Sebastopol
region (Zernov, 1912). 1 Biocoenosis populating cliffs overgrown with Cystoseira,
with some patches of sand ; 2 Biocoenosis populating cliff sand and gravel and very fine
shell gravel ; 3 Biocoenosis populating Zostera and water- weed beds ; 4 Biocoenosis
living on oyster banks ; 5 Mussel mud biocoenosis ; 6 Phaseolin ooze biocoenosis.

Fig. 211. Distribution of bottom biocoenoses in the northern part of Black Sea.
1 Coastal sand and cliff biocoenoses ; 2 Shell gravel biocoenoses ; 3 Biocoenosis of
Zostera growths ; 4 Mussel mud biocoenosis ; 5 Phyllophora growth biocoenosis ;
6 Biocoenosis of dead Zostera out by the Sea ; 7 Phaseolin ooze biocoenosis ; 8 Bio-
coenosis of Terebellide ooze; 9 Limit of life (Zernov, 1912).

THE BLACK SEA 439

rarer crustaceans of the pseudolittoral. In Mokievsky's opinion the population
of the supralittoral is characterized by the amphipod Talorchestia deshayesei
with a maximum biomass of 121 g/m2 and a maximum number of specimens
of up to 48,400 per m2, and by the isopod Tylos latrelei var. pontica with a high
population-density (up to 129 g/m2 and 11,800 specimens per m2) and also,
among specimens washed ashore, some insects, arachnids and oligochaetes,
and the amphipods Orchestia gamarellus and Orchestia montagui.

The biocoenosis of the inhabitants of the coastal cliffs and immobile rocks
sinks at times in the open parts of the Sea to a depth of 28 m ; more usually,
however, to 15 m, and inside inlets to a few metres only. Above sea-level a
true littoral fauna finds shelter on the cliffs, although there are no tides in
the Black Sea. 'Together with the algae (Scythosiphon, Ceramium, Entero-
morpha, Corallina) some molluscs, Littorina neritoides and Patella pontica ;
the barnacles Chthamalus stellatus; the crabs Pachygrapsus marmoratus and
Eriphia spinifrons ; the isopod Lygia brandtii (which lives only above sea-level),
and the land snail Aplexia myosothis (under the rocks) come out of the water,
sometimes to a height of two or three metres above it.

On the more sloping shores, at the very edge of the water and slightly
above it, dead eel-grass, Cystoseira, Phyllophora and other algae are com-
monly washed ashore. A specific refuse fauna washed up by the Sea settles
down on these heaps of dead plants, and especially under them, a mass of
oligochaetes, amphipods and isopods.

Just below sea-level thick growths of Cystoseira invest all the cliffs with a
dense covering ; there are also some Mytilus galloprovineialis. In more polluted
places Cystoseira is replaced by green algae, sea lettuce and sea grass. Apart
from Cystoseira the cliffs are overgrown, to a much lesser extent, by other sea-
weeds. These sea-weed beds are inhabited, besides the forms mentioned, by a
large number of gastropods: Rissoa, Nassa reticulata, Trochus; the cliff
oyster ; the crab Xantho rivulosus ; the shrimps Hippolyte varians and Leander
squilla ; many Porifera, hydroids, bryozoans (especially Membranipora) and
polychaetes, often with lime tubes, amphipods and isopods. Rock-burrow-
ing molluscs, commonly Petricola lithophaga, bore passages through the cliffs.

Sand and mud shore biocoenoses. These produce a whole number of modifi-
cations depending on the depth of their occurrence and on the structure of
the floor; they sometimes spread down to 18 to 27 m. The coarser sand
stretching directly from the water's edge, called by Zernov ' Saccocirrus sand ',
gives shelter to an original fauna of worms. It is inhabited by a number of
Turbelaria, Procerodes lobata and Cercyra papillosa ; by the archiannelides
Saccocirrus papillocercus and Protodrilus flavocapitatus ; the polychaetes
Nerine and Spio ornatus ; by nemerteans, Lineus lacteus, Eunemertes gracilis,
Borlasia vivipara ; various amphipods and nematodes ; the gastropods Nassa
reticulata and Rissoa; hermit crabs {Diogenes varians); decapod crayfish,
Gebia littoralis and Calianassa subterranea; and, under the rocks, a great
number of isopods, Sphaeroma and Idothea. Farther up the bays, on the
slightly silted saccocirrus sand, live a number of polychaetes : Arenicola,
Glycera and Nereis.

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THE BLACK SEA 441

The small bivalves Cardium, Syndesmya and Loripes live in deeper places
(22 to 25 m) on fine and dense sand ; while on the bottom live Gebia littoralis ;
the crab Portunus holsatus, and a number of fish : Gobius, Blennius, Urano-
scopus, Mullus and others.

At the same depths on coarser sand, with an admixture of shell gravel-
lives an abundant fauna of worms : a large number of Turbellaria and poly,
chaetes ; the interesting archiannelid Polygordius ponticus ; and a remarkable
inhabitant of the Black Sea Branchiostoma (Amphioxus) lanceolata. At times
the holothurians Synapta digitata and S. hispida and gerbil are found here in
large numbers.

Some molluscs also are likewise most characteristic of sand bottoms;
among the gastropods Nassa reticulata, and among the bivalves Venus gallina,
Gouldia minima, Divaricella divaricata, Merethrix rudis, Calyptraea chinensis,
Mactra subtruncata, Tapes proclivis, Mytilus galloprovincialis, Cardium exi-
guum and others.

As has been said above, at the head of the bays and inlets the facies of the
rocks is gradually more and more reduced, while the sands become covered
with mud. Inside all the bays and inlets, in quieter places protected from the
waves, growths of Zostera, sheltering a very typical bottom-living fauna, are
found everywhere at depths of 5-5 and even down to 9 m. Z. marina lives pre-
ferably on silt and silty sand floors, but Z. minor prefers pure sand. Zernov
gives the following characteristics of the fauna of Zostera growths : ' A large
number of mysids, amphipods, isopods, shrimps, different genera and species
of pipefish, Grenilabrus tinea and other fish, the Medusa Cladonema and
Sagitta (Spadella) swim among the Zostera leaves ; innumerable Rissoa with
Syllids planted on their shells crawl about their leaves, as well as many
Tergipes ; masses of various Rhabdocoela and Acoela ; Cerithiolum, which
are found there in immense masses, Trochus and other molluscs. At the
approach of autumn Zostera becomes covered with bryozoans: Lepralia,
Membranipora and the tunicates Didemnidae, which die off in the winter,
causing the Zostera to sink under the weight of these accretions. Among
the roots of Zostera there hide amphiurae, Stenelais, Lagis, Rhynchobolus,
Gebia, Calianassa, Syndesmya, Cardium, Gastrana and other molluscs
which live on sand, and in the more muddy places very numerous poly-
chaetes, chiefly the two species Nereis cultrifera and N. diversicolor, but
also Nephthys, Glycera, Arenicola, Lagis and others.

Somewhat higher than the Zostera growths, in the silts near sea-level, the
same polychaetes which hide under Zostera roots live in large numbers:
Arenicola, Nereis, Glycera and others.

Shell-gravel biocoenosis. At the lower limit of the zone of sand and Zostera
growths, where the slightly muddy sand gradually passes into silty sand and
sandy mud, there lies along the shore a fairly wide band of the so-called
shell gravel — an accumulation of living and dead molluscs, mostly bivalves.
Shell gravel is specially well displayed in places where, in Zernov's words, 'the
effect of the waves is already too weak to break and powder it to sand, but is
still strong enough to carry the main mass of silt particles over them and

442

BIOLOGY OF THE SEAS OF THE U.S.S.R,

farther and deeper out into the Sea'. Shell gravel usually occupies separate,
isolated areas on the shores of the Black Sea, not forming a continuous
band. Well up inside the bays it usually rises to a depth of a few metres,
while in the open sea it may be as deep as 55 to 65 m. Shell gravel consists
mainly of the molluscs which inhabit the sand lying above it ; it contains an
admixture of oysters, mussels and some other forms. An oyster form called
Ostrea sublame/losa (cliff oyster) lives on the cliffs, and the O. taurica variety
(bank oyster) lives on the oyster-beds (Fig. 212).

\ SAND

MUSSEL OOZE

PHASEOLIN OOZE

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Fig. 212. Oyster bank off eastern coast of Black Sea

(Nikitin, 1934). A in plan. В cross-section; 1 Sand with

Venus ; 2 Oyster bank ; 3 Phaseolin ooze.

Thus the oyster-bed is a variety of shell gravel. Shell gravel is separated
from the zone of sand lying above it by imperceptible stages, while the
biocoenosis of deeper-lying mussel- and phaseolin-oozes is separated from the
shell gravel much more sharply.

Apart from oyster the following molluscs are components of this biocoeno-
sis : Mytilus galloprovincialis, Pecten ponticus, Tapes rugatus, Venus gallina,
Cardium edule, С exiguum, Modiola adriatica, Merethrix rudis, Nassa reti-
culata, Gouldia minima and others ; it contains also the crustaceans Porcellana,
Athanas, Portunus arcuatus and P. marmoreus; the hermit crab Diogenes
varians ; Balanus improvisus ; a mass of polychaetes, sponges (especially the
small boring sponge Cliona stationis) and hydroids. The shell-gravel biocoe-
nosis is the Black Sea group which is richest in its composition.

THE BLACK SEA 443

H. Caspers supplements the picture of the biocoenosis range of the Black
Sea bottom-living fauna given by Zernov with data related to the Gulf of
Varna (Fig. 213). He distinguishes the following biocoenoses: a littoral one,
with Pachygrapsus zostera ; a sandy one with Corbula ; that of the cliffs with
Sabellaria and Pectinaria ; and that of the central part and shell gravel.

/• • *

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Zostera
Variation

Pectinaria
Variation

:j:;:;:;:::::::::::::::-:::::::-

Central region

i i i 4"V
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Variation

Sand community

= Corbula biocoenosis

Rocky ground community
= Saballaria biocoenosis

re community
Pachygrapsus biocoenosis

Mud community

= Upogebia — Mellina — biocoenosis

Fig. 213. Distribution of main bottom communities in Gulf of Varna

(Caspers, 1957).

M. Bacesko (1957) has given a detailed description of the Corbulomya maeo-
tica biocoenosis off the Rumanian coast of the Black Sea on littoral sand at
depths of 1 to 20 m. This biocoenosis provides the basic stock of food for ben-
thos-eating fish : Acipenseridae, flatfish, Mugilidae, bullhead, etc. The average
biomass of this biocoenosis is 360 g/m2 (with fluctuations from 280 to
1 ,034 g/m2), and the number of Corbulomya specimens reaches 1 45,000 per m2.
Besides Corbulomya, which sometimes furnishes up to 97 per cent by weight

444 BIOLOGY OF THE SEAS OF THE U.S.S.R.

of the biocoenosis, the following are the most common : Nassa neritea, Venus,
Angulus, Paramysis kroyeri, Cumopsis, Pseudocwna longicornis pontica,
Gastrosaccus, Pontogammarus maeoticus, Nerine, Aricidea, Spio filicornis
and others. Apart from macrobenthos the author gives the first comprehen-
sive description of the microbenthos of the Black Sea. One cubic centimetre
of sand was found to contain 250 to 900 Foraminifera, 50 to 120 nematodes,
1 to 9 Harpacticidae (mainly Canuella perplexa and Ectinosoma elongatum)
and 11 other species (0-5 to 2-5 polychaetes, 0-5 to 1 higher crustaceans and
1 to 4 specimens of the young fry of Corbulomya).

V. Nikitin has given a very detailed description of an oyster bank near
Gudaut (1934), lying at a depth of 10 to 30 m among sand and mussel-mud and
occupying an area of about four square miles (Fig. 212). It can be seen from
the figure that the oyster bank lies on a slanting, slightly muddy slope. De-
pending on the nature of the sea-floor and the swell, the oyster ground lies
lower or higher. Among the large number of forms found on the oyster bank
Nikitin distinguishes four dominant forms of molluscs: Ostrea taurica,
Mytilus galloprovineialis \ax.frequens, Pecten ponticus and Modiola adriatica,
and a number of growths which accompany them. The stock of oysters in the
Gudaut bank was found (V. Nikitin) to be, in 1930-32, 14 millions with a total
weigh of flesh of 300 centners. The Gudaut oyster bank remained up to 1949
in practically the same state as, according to Nikitin's data (1934), it had been
in 1930-32, but during the last ten years the bank has been attacked by the
mollusc Rapana, which exterminates large bivalves such as oysters and sea
mussels. At present 'the oyster industry ... is not at all profitable. ... If
the stay of Rapana on the Gudaut bank is only temporary, its stock of oysters
may be restored' (I. Stark, 1950).

Rapana bezoar (Muricidae family) was first found in the Black Sea off
Novorossiysk in 1947 (E. Drapkin, 1947); it probably appeared in the Black
Sea in the early forties. This mollusc, common in the Yellow Sea and the Sea of
Japan and in Peter the Great Gulf, was brought from the Far East. The mol-
lusc probably travelled this long distance in the form of egg masses in growths
on a ship's bottom. It is usually found when ships are cleaned.

On the lower horizon the oyster bank may be displaced by mussel-shell
gravel as a result of the floor becoming too muddy for oysters ; and somewhat
deeper, on still more mud, the community of mussel bed — the strongest benthic
group of the Black Sea, except for the still deeper-lying grouping of the
phaseolin ooze — comes into force. As has been pointed out by Zernov, the
fauna of the mussel-ooze 'is really, in most cases, the shell gravel fauna, except
for oysters and other forms which cannot tolerate the ooze, so that mussels
have taken up the dominant position'. Farther up, at the tops of the bays and
inlets, the upper boundary of the mussel-ooze community rises to 9 to 1 1 m
below the surface (off Odessa even to 1 m below the surface), while in the
open sea it occupies a zone 55 to 78 m deep. For the mussel-ooze besides the
dominant form — mussel — the following are most characteristic : among the
molluscs; Cardium simile, Meretrix rudis and Tapes; the huge colonies of
hydroids, Aglaophenia pluma and Serture/la polyzonias ; the tunicates :
Ascidiella aspersa, Ciona intestinalis, Botryllus schlosseri, Eugyra adriatica;

THE BLACK SEA 445

and frequently large numbers of the nemerteans Cerebratulus kowalevskyi ;
the ooze-polychaetes Melinna palmata and Terebellides stromii; and the
brittle star Amphiura florifera. Among the crustaceans the most typical is
Crangon crangon. Among the plants Phyllophora is very characteristic. The
most interesting feature of this group is the huge mass development of a
typical littoral form — the sea mussel at depths of 27 to 65 m. In many places
thesea mussel goes down in ocean and seas with tides to depths unusual to it
as a littoral form ; this occurs either in tideless seas with no littoral (the Baltic
and the Mediterranean Seas), or owing to unfavourable conditions prevailing
on the littoral (Cheskaya Guba). However, nowhere does the sea mussel accu-
mulate in such huge masses at such low levels as in the Black Sea. In the Medi-
terranean (in the vicinity of Naples) the sea mussel does not go lower than
10 m. The cause of this mass development of sea mussel at a considerable
depth must be sought in biocoenotic relationships. Apparently at higher levels
sea mussel encounters some restricting rivals, which are absent at depths
where the mussel bed occurs. The main species of mussel which inhabits the bed
evolved an independent variety — Mytilus galloprovincialis var. frequens;
this is also of interest.

The biocoenosis of the Phyllophora field. On some sectors of mussel bed, in
quiet depths, huge accumulations of live (Phyllophora) or dead (Zostera)
plants are formed and carried away by the currents. We have already men-
tioned the existence of a colossal accumulation of Phyllophora in the middle of
the Sevastopol-Danube-Odessa area at depths of 27 to 55 m (mostly at
35-45 m). 'The Phyllophora fauna is very poor', writes Zernov, 'almost all
the organisms living on Phyllophora are coloured brown-red — in full harmony
with the colour of Phyllophora itself.

' The crustaceans such as Amphipoda, Isopoda are the most numerous here ;
there are some crabs (Portunus arcuatus), a few polychaetes, molluscs and
small fish. Apparently the huge beds of Phyllophora prevent any considerable
development of animal life.'

The biocoenosis populating the dead plants on the sea-bottom is specially
well developed at depths of 35 to 45 m in Karkinitsk Bay, where Zostera,
brought out from inside the bay, which is entirely overgrown by this sea-weed,
is gathered in large masses. It is abundant also in the Bay of Taman and other
places on the Black Sea coast. Masses of Amphipoda, Mysidae, Decapoda,
molluscs, Turbellaria, and some small fish live in the accumulations of dead
plants.

The phaseolin-ooze biocoenosis. This is even more original than that of the
mussel. It is the deepest zone of benthic life in the Black Sea. Usually found
first at 55 to 65 m (at times at 40 to 45 m ; in some places at 80 m) with a sharp
transition from the mussel-mud, the phaseolin ooze reaches on the average a
depth of 1 80 to 1 85 m. Modiola phaseolina is the main component of this group.
Modiola phaseolina is an interesting example of the ecological aspect of
many representatives of the Mediterranean fauna in the Black Sea. Outside the
Black Sea M. phaseolina is widely distributed in the Atlantic Ocean, as far as

446 BIOLOGY OF THE SEAS OF THE U.S.S.R.

the shores of Norway to the north, and is particularly abundant off the shores
of England. It is comparatively rare in the Mediterranean Sea. M. phaseolina
has a very wide vertical range ; it is found from the littoral to shallow depths
in the Atlantic Ocean, mostly to 100 m, and on hard or rocky sea-floors.
In the Black Sea it is most abundantly developed at depths of 65 to 100 m,
living only on soft mud floors, not rising above 40 m and not sinking down
below 167 m (L. Yakubova, 1948). Almost everywhere in the Black Sea M.
phaseolina is a dominant form at depths below 60 m, with a few hundred
specimens per m2.

Of other organisms commonly thriving in phaseolin mud one can point to
the molluscs Cardium simile, Syndesmya alba and Trophonopsis breviatus;
the sponge Suberites domuncula; the actinia Cehanthus cestitus and Cyliste
vicuata ; the worms Terebellides stromi, Melinna palmata and Nephthys cir-
rosa ; the crustacean Crangon crangon ; a number of amphipods ; the echino-
derms Amphiura florifera and Cucumaria orientalis ; the tunicates Ctenicella
appendiculata, Eugyra adriatica, and Ciona intestinalis. Modiola phaseolina,
Melinna palmata, Cerianthus vestitus and Amphiura florifera are predominant
among all these forms.

Sea- weeds become rare at 80 to 90 m ; below this lies the pseudo-abyssal
and its only group is the fauna of the phaseolin ooze.

The filter-feeding phenomenon. The bottom-living population of the Black
Sea is characterized by a strong development of filter-feeding phenomena.
Accumulations of bivalves (typical filter-feeders) and among them the ones
of greatest mass — sea-mussel, oyster, Mytilaster and Modiola {Modiola
adriatica and M. phaseolina) — form a wide ring from the water's edge to the
limit of inhabited depth. The capacity of filter-feeders is huge, and the upper
column of sea water permanently exposed to their action is freed from micro-
sestonic suspension. The effect of the filter organisms on the bottom soils of
the Black Sea is just as important. Ooze deposits are a result of their fecal
pellets. In this way the apparently contradictory fact of large accumulations
of sea-mussels being adapted to soft-deposit zones can be reconciled. Soft soils
occur in quiet zones, and the sea-mussel usually inhabits well-washed areas of
the sea-bed. Evidently the mussel-shell deposit areas, and partly those of
phaseolin ooze, are by no means quiet zones ; moreover, the soft ooze here
may be formed by the molluscs themselves and may have a biogenic character.
Without the filter organisms the oozes would not have been deposited in
masses in these zones. However, this is so far only a hypothesis, which needs
to be proved.

Fauna zonation. L. Yakubova (1935) used the qualitative distribution of the
Black Sea benthos as a basis for the classification of the fauna according to
three coastal zones (Fig. 214).

I. The eastern half of the Sea, from the southern coast of the Crimea, along
the Caucasian coast and the eastern part of the coast of Anatolia. Yakubova
considers the fauna of this area as the most typical of the Black Sea at present.

II. The southwestern zone, open to the influence of the more saline waters

THE BLACK SEA

447

of the Bosporus, including the western part of the Anatolian coast and the
southern half of its eastern part. A number of species not found in other parts
of the Black Sea have been recorded here. Tuna, swordfish, lobster and a
number of invertebrates are fairly common here. An exchange of fauna pro-
ceeds continuously between the Black Sea and the Sea of Marmora
through the Bosporus. The waters of the Sea of Marmora, carrying its
characteristic fauna, penetrate into the Black Sea by the lower current. Such

Fig. 214. Zoogeographical regions of Black Sea (Yakubova)
(see text).

typical Mediterranean plankton as the Siphonophora Diphyes, the Radio-
laria Acanthometra, and the polychaete Tomopteris are found in the Bosporus
area of the Black Sea.

A number of the Mediterranean benthic forms have been discovered in the
Bosporus region of the Black Sea, within the sphere of the lower Bosporus
currents ; these forms, apparently, do not penetrate very far into the Black
Sea (Nikitin, 1927, Jakubova, 1948, Bacesko, 1959). They have been recorded
at depths of 38 to 94 m (more than 60 species) and include such forms as the
Coelenteratae Phellia elongata and Virgularia mirabilis; the echinoderms
Ostergrenia adriatica, Ophiura texturata, Ophiothrix echinata and Cucumaria
orientalis ; the molluscs Nucula sulcata, Turitella communis, Murex tareniinus,
Venus bragniarti, Nassa incrassata, Corbula gibba, Fissurella graeca, Natica
fusca, Gibbula de versa, Schismope stria tula, Cyclonassa brusinai, Pandocia
singularis; the worms Phascolosoma minuta, Paronais lira, Proclea graffi,
Drilonereis filum, Polidora antennata, Sternaspis scuttata; the crustaceans
Cymodoce erythrea euxinica, Elaphognathia monodi, Pontotanais borceai,
Colomastix pusillus, Harpinia della-vallei, Philomedes interpuncta, Citereis
jonesii ; 20 species of the Foraminifera and many others. They chiefly extend
to the north along the western shores of the Sea.

The Bosporus fauna forms a kind of intermediate link between the faunas
of the Black Sea and the Sea of Marmora.

O. Ostroumov (1894) gave an illustration of this fact, from the example of
bivalves, as set out in Table 182.

448

BIOLOGY OF THE SEAS OF THE U.S.S.R,
Table 182

No. of

Ratio of

Area

Mediterranean

Mediterranean to

genera

Archipelago
genera

Archipelago

Sea of Marmora near

157

100

Bosporus
Upper Bosporus
Black Sea

103
86
56

65-6
54-8
35-7

III. The northwestern zone embraces a vast shallow (less than 150 m deep)
part of the Sea between the Crimea and the western coast. This zone, in con-
trast to the previous one, is the least saline part of the Sea, as a result of dilu-
tion by river waters. It is also the coldest in the winter. Huge accumulations
of Leophora are concentrated here ; forms tolerant of considerable loss of
salinity are abundantly represented (the molluscs Corbulomya maeotica,
Solen marginatus, Bamea Candida var. pontica, and others) ; on the other hand
many common Black Sea forms are absent (Patella, Littorina and Pecten
among the molluscs ; Amphioxus, Phoronis, Lygia, Saccocirrus, etc.).

The lower limit of benthos. As mentioned above the lower limit of plankton
distribution in the Black Sea slopes from west to east. The same is observed
for benthos. V. Nikitin has shown (1938) that the lower limit of benthos runs
at different depths in different areas (Fig. 215) {Table 183).

Only in the Bosporus area does the lower limit of benthos go down to a
depth of 170 to 200 m. The area occupied by benthos is about 2,900 km2.
Hence in the areas of circular currents plankton penetrates deeper than ben-
thos by about 25 to 40 m. The total area occupied by benthos in the Black
Sea is 95,360 km2 or a little more than 23 per cent of the total Sea area. The
lower limit of bottom-life is related to a considerable decrease of oxygen-
content (2 to 5 per cent) and an increase of carbon dioxide (pH 7-7 to 7-6).

Fig. 215. Lower limit of zoobenthos in Black Sea (Nikitin, 1938).

THE BLACK SEA 449

Table 183. Depth of lower limit of benthos, m, and area of sea-bed occupied by benthos,

km2

Off In Off Off Off

western northwestern southern Crimean Caucasian
coast part coast coast coast

Depth 125-127 115-125 130-135 127-135 135-165

Sea-bed area 12,500 57,600 9,500 6,800 6,000

L. Yakubova pointed out (1935) that of the individual forms Modiola phaseo-
lina penetrates deepest (180 m); then came Amphiura stepanovi (165), Neph-
thys hombergii (162); Cerianthus vestitus and Melinna palmata do not quite
reach such depths. Terebellides stroemi, Syndesmya alba, Cardium simile,
Mytilus galloprovincialis and Phoronis go down as far as 130 m. Eugyra
adriatica (125 m) and Suberites domuncula live in rather shallower waters.

Quantitative distribution of zoobenthos. As distinct from all the other seas of
the European part of the u.s.s.r., we possess only scarce data on the quanti-
tative distribution of the Black Sea bottom-living fauna. For the purpose
mentioned we can use only certain indications from the works of V. Wod-
janitzky (1941), V. Nikitin (1938), V. P. Vorobieff (1938), L. Arnoldi (1941)
and O. Mokievsky (1949).

As has been mentioned in the introductory chapter, the high summer
temperature of the surface layer of the Black Sea brings about, especially in
the enclosed bays, a high intensity of biological productivity. In summer on
free surfaces, growths give a biomass of up to 30 or 40 kg/m2. A thick pile of
30 to 35 cm diameter may be destroyed almost completely by marine borers
in the three summer months (July to September). * The rock-burrowing molluscs
are represented in the Black Sea by four species : Petricola lithophaga, Barnea
Candida var. pontica, Pholas dactylus and Gastrochaena dubia (V. Nikitin,
1951). Uninterrupted colonies of Barnea Candida var. pontica and Pholas
dactilus with a population-density of up to 2,500 specimens/m2 have been
discovered on the bare marl shale off the Caucasian shores.

M. Dolgopol'skaya (1954) has given the results of her experimental research
on fouling in the Black Sea. The total annual weight of the fouling is up to
100 kg/m2; the main fouling organisms are: balanus, sea-mussels, bryozoa,
ascidians and oysters. V. Wodjanitzky has pointed out (1941) that on mussel-
shell gravel at 10 to 25 m deep the benthos biomass can reach 3-7 kg/m2 and
is often 1-5 to 2-0 kg/m2. A biomass of up to 60 g/m2 is obtained on the sand
floor off the coast, and on the mussel-mud up to 250 or even 500 g/m2.f
On phaseolin ooze the biomass varies from a few grammes to 800 g/m2.

* According to P. Ryabchikov (1957) three species of teredinids have been observed in
the Black Sea : T. navalis, T. utriculus and T. pedicillata.

t O. Mokievsky has observed (1945) along the western coast of the Crimean peninsula,
on the beach sand above sea-level, abundant colonies of crustaceans (Orchestia), mol-
luscs {Donacilla cornea) and polychaetes {Ophelia bicornis) with a biomass of over 0-5
kg/m2.

450

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Wodjanitzky gives the total biomass of the Black Sea zoobenthos as 1 5 to 30
million tons. This amount is possibly a little overestimated. L. Arnoldi (1941)*
{Table 184) gives more accurate data, but only for a small area of the southern
coast of the Crimea (from Cape Fiolent to Alupka).

Table 184

Environment

Biocoenosis

Census of the population per m2

Mean Mean Minimum Maximum

number of biomass biomass biomass
specimens g/m2 g/m2 g/m2

I. Coastal pure Venus gallina

sand

II. Silty sand

III. Mussel
mud

IV. Phaseolin
ooze

Divaricella divaricata

Mactra subtruncata

Donax venustus

Diogenes pugilator

Tellinafabula

Venus gallina

Mactra subtruncata

Divaricella divaricata

Tapes lineatus

Gouldia minima

Modiola adriatica

Meretrix rudis

Mytilus galloprovincialis var.

frequens
Meretrix rudis
Modiola adriatica
Cardium simile
Mactra subtruncata
Syndesmya alba
Modiola phaseolina
Modiola phaseolina
Molgula euprocta
Terebellides stromii
Syndesmya alba
Cardium simile
Melinna adriatica

1,926

1,844

108

388

8-7

140

262

767

825 667 135 2,076

2,258 138

0 . 654

Mean indices of biomass and the population-density per m2 of the four bio-
coenoses listed in Table 184 can be calculated from Arnoldi's data for a num-
ber of dominant and characteristic benthos species {Table 185).

Moreover, the Mytilaster lineatus biomass of 382 g/m2 at 2,900 specimens/
m2 and the maximum biomass for Modiola phaseolina of 119 g/m2 at 10,700
specimens/m2 recorded by Arnoldi should be noted. These data closely
approach V. Wodjanitzky's result.

Nikitin (1949) thinks that the mean benthos biomass for the Caucasian
coast (not counting the mussel and oyster banks) can be taken as 136 g/m2. If
we use this amount for the populated part of the whole Sea we shall obtain a

* L. Arnoldi writes (1941) that the Karkinitsky Bay zoobenthos is in its biomass poorer
than that of the open parts of the Sea, being on the average about 100 g/m2.

THE

BLACK SEA
Table 185

III

Biocoenosis

No. of Biomass No. of Biomass No. of Biomass No. of Biomass

specimens

g/m2

specimens g/m2

specimens

g/m2

specimens

g/m2

Venus gallina

126

248 131

0-5

0-02

Divaricella divaricata

595

858 5-8

—

002

Mactra subtruncata

473

22-3

127 34

—

Donax venustus

6-7

Diogenes pugilator

3-2

16 1-6

—

Tellina fabula

1-7

26 6-6

—

Tapes lineatus

29 52

—

Gouldia minima

116 9-7

2-5

0-5

0-2

Modiola adriatica

30 41

—

Meretrix rudis

43 18

—

Nassa reticulata

19 10

—

Mytilus galloprovincialis

6 32

185

464

Pecten ponticus

5 22

—

Cardium simile

3-3

Syndesmya alba

4-5

Modiola phaseolina

108

7-5

1,958

111

Molgula euprocta

—

Terebellides stromii

—

Melinna adriatica

—

1-4

total biomass for the Sea of approximately 12 million tons. This is also approxi-
mately the amount of total annual benthos production.

The change of benthos biomass with depth off the Caucasian coast shows
an increase at depths of 10 to 50 m, i.e. on the shell gravel and mussel-mud
{Table 186).

As shown by Table 186 the largest number of benthos specimens is observed
on mussel beds (50 to 100 m deep) and the largest biomass on the shell gravel
(10 to 50 m). The number of molluscs and crustaceans invariably decreases
with depth, while the number of worms increases.

Table 186

Mean

Percentage

ratio

of individual

groups

Depth
m

Soils

specimens

g/m2

Molluscs

Worms

Crustaceans

Others

0-10

500

128

82-5

4-8

4-2

8-5

Mostly sand

10-30

680

171

90-3

2-9

5-8

Silty sand and
shell gravel

30-50

884

176

88-3

7-5

0-8

3-4

Sandy silt and
silt

50-70

1,204

0-7

4-3

70-100

1,950

100

34-8

0-1

\ Ooze

100-130

582

21-5

72-5

0-02

130-160

1-5

5-5

)

Lower limit of

benthos

452 BIOLOGY OF THE SEAS OF THE U.S.S.R.

A similar picture of quantitative distribution of benthos (number of speci-
mens and biomass) is given by Nikitin for the Anatolian coast. The maximum
number of specimens was observed at 60 to 75 m (up to 1,500 specimens/m2),
and the greatest biomass at 35 to 50 m (up to 2,000 g/m2).

The Black Sea is inferior to the Sea of Azov and superior to the Caspian
Sea in the benthos biomass of the populated part of its floor. Comparing the
benthos of the Black and Azov Seas V. Wodjanitzky (1940) comes to the con-
clusion that only about 50 per cent of the benthos of the former can be used
by fish (food-benthos), whereas in the Sea of Azov it is almost entirely food-
benthos. Hence taking into consideration its feeding properties the Sea of
Azov benthos is four times more productive than that of the Black Sea, and
when calculated for the whole surface of the Sea it is sixteen times more pro-
ductive.

Quantitative estimate of microbenthos. In 1939-40 L. Arnoldi carried out the
first quantitative recording of the microbenthos of the upper layers of the
soil (1-5 to 2-5 m) in the northwestern part of the Black Sea. As numbers go,
the first place is occupied by worms (nematodes, nemerteans, archianellides)
ciliates, crustaceans and mollusc larvae.

The number of micro-zoobenthos specimens reaches 4-6 million per 1 m2
(on the average 1-6 million) and its biomass 30 g/m2.

The number of micro-phytobenthos (diatoms) reaches 30 to 50 million
specimens per 1 m2, giving a biomass of up to 10 g/m2.

Summarizing the as yet insufficient data on the numbers of the Black Sea
fauna one can draw up Table 187.

Table 187

Group

Biomass
103 tons

Annual production
103 tons

Plankton
Phyllophora
Other macrophytes
Zoobenthos
Dolphins

10,000 to 12,000

17,000

1,500

13,000 to 15,000

Up to 30

150,000 to 200,000
?

1,500

13,000 to 15,000

The presence of numerous inlets at all stages of their development (Fig. 216)
is the characteristic peculiarity of the northwestern part of the Black Sea.
N. Zagorovsky (1925-30), F. Mordukhai-Boltovskoy (1948, 1953) and Yu.
Markovsky (1955, 1959) have studied the inlets. A description of the Bulgarian
inlets is given by G. Paspalev, A. Volkanov and G. Caspers, and of the Ruman-
ian ones by P. Bujor.

The Dniester, Sukhoy, Khadzhibeysky, Kuyal'nitsky, Greater and Lesser
Adzhalitsky, Tiligulsky, Tuzlovsky solonetz, Berezansky and the Dnieper-
Bug inlets (Fig. 216) are river valleys flooded (possibly several times)
by the post-Pliocene sea when its level was much higher than at present.
In the later, drier periods, when river waters were not abundant, the inlets

THE BLACK SEA

453

would lose their connection with the Sea, being separated from it by a bar ;
their salinity would rise to saturation with lake salt, and black oily ooze rich
in iron compounds, used in modern times for medical purposes, would be
formed. Communication with the Sea might be established by an inrush of the
Sea through the bar and to a certain degree by the percolation of sea-water
through it. The suspension of river water supply to the inlets might, in the
final account, lead to a complete drying up and the formation of a solonetz.

Fig. 216. Inlets of the northwest part of the Black Sea (Markovsky). 1 Dniester inlet ;

2 Kutchurgansky inlet; 3 Khadzhibeysky inlet; 4 Kuyal'nitsky ; 5 Tiligulsky;

6 Berezanksy ; 7 Dnieprovsky ; 8 Bug inlet.

The population of the inlets gives a clear picture of a mixture of the euryhaline
marine (Mediterranean) fauna with a relict, Pontic, brackish-water fauna of
the Caspian type and with fresh- water immigrants. The marine fauna of the
inlets, qualitatively impoverished, and usually of a smaller size, does not,
however, form dense settlements. On the other hand, an abundance of relict
Pontic forms is observed in the inlets, which creates, in V. Sovinsky's expres-
sion (1902) 'a similarity between the fauna of the northwestern area (Gulf of
Odessa) and that of the Caspian Sea'. 'We can consider', wrote A. Ostroumov
(1897), 'the Bug inlet as a corner of the Pliocene basin, thrown up into the
mainland and slightly renovated.'

Mordukhai-Boltovskoy (1961) points out that about 120 species of the

454 BIOLOGY OF THE SEAS OF THE U.S.S.R.

animal' Caspian' fauna live in the Azov-Black Sea basin, which comprises 40
per cent of the autochthonous Caspian Sea fauna, taking it as 300 to 305
species (without the Protozoa). The main part of this fauna comprises the
amphipods (33 species), the mysids (8 species), Cumacea (10 species), mol-
luscs (11 species) and fish (30 species).

Only 1 8 representatives of the Caspian fauna five in the open parts of the
Black Sea, and in the Sea of Azov as many as 30, mostly fish.

Yu. Markovsky writes also (1954) that the 'Caspian' forms are the nucleus
of the Dnieper-Bug inlet fauna, and he points out the very important fact
(1954) that 'the Caspian fauna in the Dnieper-Bug basin has a greater ten-
dency towards saline water than the fauna of the Danube-Dniester basin ', i.e.
farther west. We have noted a similar phenomenon when comparing the dis-
tribution of the Caspian fauna in the Caspian Sea itself and in the Sea of Azov.
Consequently, as one moves to the west, beginning with the Caspian Sea,
through the Sea of Azov, through the eastern and western parts of the Black
Sea and even within the limits of the latter, the Caspian relicts acquire a more
and more fresh- water aspect. 'Although a considerable part of the "Caspian"
species', writes Markovsky, 'develops best in fresh water . . . many of these
forms (about 35 per cent) find the optimum conditions for their development
not in fresh but in slightly saline water (1-5 to 3%0) ... a considerable part of
the fresh-water "Caspian" forms of the inlet (33-4 per cent) belongs to the
fresh-water stenohaline species, which move away when the salinity rises
above 1%0.' Markovsky relates 59-2 per cent of the species to the forms which
can endure a salinity of up to 5%0 ; only a few species (7-4 per cent) move into
water of higher salinity.

On the other hand, the number of marine forms decreases rapidly at
salinities below 3-5 to 4%0 as one moves farther into the inlet. Markovsky
has come to the same conclusion as other workers who have studied the
fauna of the Gulf of Taganrog and of the Sea of Azov — that the main
habitats of the marine and 'Caspian' forms overlap very rarely and that, in
this case, there is little reason to speak of the displacement of Caspian by
Mediterranean species.

In the Dnieper and Don deltas the Caspian fauna comprises on rocky
bottoms 80 to 100 per cent, on sands 70 to 86 per cent, on silty-sands 30 to
58 per cent, on grey muds 15 to 28 per cent, on black ooze in stagnant bodies
of water 1 per cent (F. Mordukhai-Boltovskoy, 1948). This clearly shows the
adaptability of this relict fauna to well-aerated rapid currents. Markovsky
has identified 78 Caspian forms in the Dnieper inlet, among them two coelen-
terates, three polychaetes,* one leech, three gastropods, and six bivalves;
the rest are crustaceans. Markovsky has recorded 64 forms in the Bug inlet
(Manyunkia caspica should be added to them), among them two coelenterates,
four worms, six bivalves, three gastropods and 50 crustaceans.

In analysing the biocoenoses of the Dnieper-Bug inlet Markovsky dis-
tinguished 28 bottom ones, 3 bentho-nectic and 15 plankton ones. The domi-
nant forms comprise Dreissensia polymorpha, Monodacna colorata, Clessi-
niola variabilis, Cardium edule, Adacna laeviuscula sp.fragilis, Adacna plicata
* Manayunkia caspica must be added to them.

THE BLACK SEA

455

sp. relicta, Vivipara vivipara, Theodoxus danubialis, Unio tumidus, Ponto-
gammarus maeoticus, Corophium volutator, С nobile, Balanus improvisus,
Oligochaeta, Tendipedidae, Hypaniola invalida, Nereis spp., Mytilus gallo-
provincialis. Half of them are 'Caspian' and 2 or 3 fresh-water forms. The
average biomass of the bottom biocoenoses is from a few grammes to 1 kg
per m2.

The bentho-nectic biocoenoses are formed of 'Caspian' mysids; fresh-
water Rotifera and crustaceans are greatly preponderant in the plankton, the
Caspian fauna in them being represented only by Eurytemora velox.

The Dniester inlet is only slightly smaller in size than the Dnieper-Bug

Fig. 217. Distribution of isohalines (CI-, mg/1.)

in the Dniester inlet, 27 June to 1 July 1950:

1 Surface ; 2 Bottom layer (Markovsky).

inlet (377 km2 according to Markovsky) ; its salinity decreases gradually from
south to north (Fig. 217), undergoing considerable fluctuations under the
influence of the weather and the season of the year.

Yu. Markovsky writes (1953) that zooplankton of the inlet consists mainly
of 'Caspian' crustaceans . . . which are represented in the Dniester inlet by
fresh-water populations with a few purely fresh-water forms.

As in the Dnieper-Bug inlet, the plankton benthos of the Dniester inlet
has a pronounced preponderance of 'Caspian' mysids with some admixture of
'Caspian' Cumacea and amphipods.

The bottom population of the inlet consists mainly of 'Caspian' forms.
According to Yu. Markovsky (1953) their number decreases as one approaches
the sea. If the inlet is divided into fresh-water, transitional and brackish-
water parts, the fauna of the first two comprises 66 to 67 per cent of the

456

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Caspian species, while 63-8 per cent of the last one consists of marine forms.
A. Ostroumov had already pointed out in 1897 that the animal population
of the seaward area of the inlet consisted mainly of marine species, which
gave place to the ' Caspian ' and fresh- water species farther up the inlet (Figs.

Fig. 218. Distribution of
marine, relict and fresh-water
bottom biocoenoses in the
delta and the inlet of the
Dniester. Biocoenoses: 1
Fresh-water; 2 Relict; 3
Marine or relict depending on
salinity; 4 Marine (Markov-
sky).

70
65
60
55
50
45
40
35
30
25

го

/5
10

5
0

Fig. 219. Percentage relationship
of the number of 'Caspian'
fresh-water and marine species
of bottom animals in various
zones of the Dniester inlet (Mar-
kovsky). 1 Percentage, 'Caspian'
species; 2 Percentage, fresh-
water species; 3 Percentage,
marine species.

218 and 219). Markovsky distinguishes nine bottom biocoenoses in the Dnie-
ster inlet with the following dominant forms: {Pontogammarus maeoticus,
Corophium volutator, Nereis sp., Corophium nobile, Dikerogammarus, Dreis-
sensia polymorpha, Monodacna, Clessiniola variabilis, Micromelania lincta,
Lithogliphus naticoides, Syndemya ovata and Cardium), i.e. the 'Caspian'
species are again predominant. Markovsky records in all more than 100
species of bottom and benthopelagic animals. The 'Caspian' species comprise
54 per cent in the Kuchurgan inlet and the lower reaches of rivers, and their

THE BLACK SEA 457

number is greatly reduced as we pass into the more saline waters of the inlet.
' Caspian ' crustaceans settle down farther up the stream of a river, moving up
the Dniester to its middle and upper parts. Twenty-four species of Gam-
maridae have been discovered in the Dniester and its inlet, seven of Coro-
phiidae and nine of Cumacea. In the 17 biocoenoses distinguished, the 'Cas-
pian ' species are predominant in 13, and the first among them are : Monodacna
pontica, Dreissensia polymorpha, Clessiniola variabilis, Micromelania lincta,
Pontogammarus maeoticus, Dikerogammarus villosus, Hypania invalida and
others.

The Kuchurgan inlet of the same river system, but situated to the north
of the Dniester inlet and of a very low salinity (0-05 to 0-2%o by chlorine), has
a fauna characterized by the dominant role of its relict forms of Caspian
aspect (Markovsky, 1953) both in its plankton (Heterocope caspia), its
necto-benthos (Caspian mysids Paramysis, Mesomysis, Katamysis and
Limnomysis), and also in its benthos (Hypania, Hypaniola, Adacna, Mono-
dacna, Micromelania, Theodoxus, Dreissensia and others) (M. Yaroshenko,
1950).

Some data on the fauna of the Danube delta may form substantial additions
to what has been said above. At one time the lower reaches of the Danube and
the estuary zones of the rivers of the northwestern Black Sea were occupied
by a wide arm of the sea, along the northwest side of which numerous inlets
were formed (Figs. 220 and 22 1). Some excellent research was carried out on the
fauna of the lower reaches of the Danube by Rumanian and Russian investi-
gators, in particular by Yu. Markovsky (1955) on the Killisk delta. In the
Killisk delta he recorded 1 40 species of invertebrates (without Protozoa) out
of the total number of 412 species known for all the Danube delta (among
them 58 molluscs and 186 crustaceans), including 36 species of molluscs and
43 species of crustaceans. In most cases half of the fauna, or more, consists of
'Caspian' forms (in Katlabug 62-8 per cent). The fresh- water aspect of the
' Caspian ' species in the Danube and its delta is even more pronounced than
in the other inlets of the northwestern part of the Black Sea and the character-
istics of its plankton, plankton-benthos and benthos faunas are the same.
The aboriginal fresh-water species are greatly predominant in the plankton,
whereas in plankton-benthos the 'Caspian' species are just as predominant,
thanks to the mysids, and in the benthos half of the species are ' Caspian '
forms.

The fresh- water aspect of the Danube 'Caspian' forms which has been
acquired to a great degree has been used, and may be used later on a much
larger scale, for their acclimatization in bodies of fresh water of other river
systems and even in the Dnieper (F. Mordukhai-Boltovskoy, 1950, 1952;
Yu. Markovsky, 1952, 1954; P. Yuravel, 1950, 1952) where stable populations
increasing the valuable components of fish-food resources may be created.

The greater fresh- water tendency of the Black-Azov Sea ' Caspian ' species,
as compared with that of the same community in the Caspian, and the
strengthening of the ' fresh- water ' aspect in the Black and Azov Seas from
east to west is difficult to explain. The easiest way would have been to assume
that the Pontic fauna remained in the Black and Azov Seas throughout the

458

BIOLOGY OF THE SEAS OF THE U.S.S.R.

whole post-Pontic period, and altered here under the effect of the freshening
of the waters of the Caspian Sea. There are, however, several serious objections
to this. To explain this phenomenon by the salt composition of the Azov and

Fig. 220. Diagram of ancient estuary of river Danube
(Antipa, 1910).

Black Seas or by competition (in virtue of the above-mentioned facts) with the
Mediterranean fauna, which pushed the ' Caspian ' forms into fresh waters, is
even more difficult.

Fish and mammals

The Black Sea ichthyofauna, with its 122 species of marine fish and 34 of
fresh-water fish, is about twice as rich as the Caspian Sea (77) and 25 per cent
richer than the Barents Sea (114) in its variety of species. The characteristic
difference from the fish of the Barents Sea consists of a much greater variety
of commercial fish. In the Barents Sea only 10 per cent of the species are
commercial, while in the Black Sea no less than 20 per cent are so.

A. Krotov (1949) includes in the list of the Pontic relict species of fish:
Percarina demidoffi, Lucioperca marina, Clupeonella delicatula and six species

THE BLACK SEA

459

of bullheads (among them Mesogobius batrachocephalus, M. gymnotrachelus,
Neogobius rata, N. platyrostris, N. syrman). Krotov (1949) traces a connection
with later immigrants from the Caspian Sea : the Acipenseridae (Huso huso,
Acipenser guldenstradti, A. stellatus, A. nudiventris and A. ruthenus), Clupeidae
(Caspialosa kessleri pontica, С brashnikovi maeotica, С caspia nordmanni,
С. с. tanaica, С. с. paleostomi), salmon (Salmo trutta labrax), Benthophilus
Benthophilus macrocephali magistri and B. stellatus), Benthophiloides brauneri,

Fig. 221. Diagram of estuary of river Danube (Carausu, 1943). Localities where
biological samples were taken.

Caspiosoma caspium, some species of bullheads (Neogobius melanostomus,
N. cephalarges, N. kessleri, N. fluviatilis and Proterorhinus marmoratus) and
the stickleback Pungitius platygaster ; no fewer than 39 species in all. Most of
the Black and Azov Sea fish are immigrants from the Mediterranean after the
Dardanelles break-in. They comprise 60 per cent of the whole Black Sea and
Azov Sea ichthyofauna, including the fresh-water fish.

In the Black and Azov Seas the process of species evolution also involved
a number of fish of Mediterranean origin such as anchovy, with its Black Sea
and Sea of Azov sub-species, the brill, garfish, red mullet and others. A
number of fish which enter the Black Sea from the Mediterranean may also
breed there (mackerel, Sarda). It has been proved by Wodjanitzky (1940) that

460 BIOLOGY OF THE SEAS OF THE U.S.S.R.

many fish which need great depths for their development could not become
acclimatized in the Black Sea, and for this reason among the Mediterranean
communities fish with pelagic ova are predominant in the Black Sea.

Large numbers of anchovy, mackerel, Sarda, greenfish (Pemnodon saltator),
hardtail, tuna, Sprattus phalericus, sardines and others enter the Black Sea
in the spring through the Bosporus. Not long ago it was considered that neither
mackerel nor Sarda nor tuna multiply in the Black Sea, but only feed there.
However, it was shown by V. Wodjanitzky in 1936 that Sarda and tuna
multiply in the Black Sea. There are some data too on the multiplication of
mackerel in the Black Sea. Besides the large numbers of Mediterranean fish
entering the Black Sea, Black Sea fish migrate from the western half of the
Sea in large masses to feed in the northwestern part, and from the eastern
part into the Sea of Azov through the Kerch Strait. Most favourable fishing
conditions are created in the narrow Kerch strait, when a mass of fish
(anchovy, herring, Clupeonella, grey mullet, red mullet) are trying to enter
the Sea of Azov ; the catch then may amount to 200,000 centners. A large
mass of two- or three-year-old anchovy dies during the winter. Fish, mainly
the anchovy, which leave the Sea of Azov for the winter and play a very
important role in the food of predatory fish and dolphin, move in different
years either to the shores of the Crimea or to the Caucasian coast, thus creat-
ing a varying picture of the distribution of food resources. Moreover, dying-
off in some parts of the Sea (S. Maljatzky, 1934) may form a large accumu-
lation of organic substances in its deep layers.

Fish nutrition. V. Wodjanitzky (1941) has given a diagram of the nutrition
relationship among the Black Sea fish (Table 188).

The main mass of the pelagic Black Sea fish (anchovy, Sprattus, Clupeo-
nella, sardines, pelagic pipefish Syngnathus schmidti and the fry of many other
fish) feeds on plankton, fattening mostly in the northwestern part of the Sea.
Small herring and mackerel feed also mainly on plankton and small fish.
Sarda, tuna, greenfish, large herring and dolphins — the real pelagic carnivores
— also feed on small fish. One common dolphin (Delphinus delphis), the object
of a large fishery industry in the Black Sea, consumes during a year 1-5 to 3
million centners offish, i.e. two or three times more than the yield of the Black
Sea catch.

Moreover, Phocaena phocaena is common in the coastal areas of the Black
Sea and in the Sea of Azov. The third dolphin species in the Black Sea, Mona-
chus monachus, is the fourth mammal form of the Sea.

According to V. Moskvin's data (1940) the herrings of the northeastern
part of the Black Sea differ greatly in their feeding habits, whereas Caspialosa
pontica and C. maeotica are typical predators feeding mainly on small fish
(chiefly anchovy) and large crustaceans. C. tanaica feeds on lower crustaceans
(mainly Calanus helgolandicus) and sea-weeds (Table 189).

According to A. Makarov's data (1939) mackerel — also a typical pelagic
carnivore — feeds mainly on Sprattus, anchovy, smelt and copepods. The diet
of hardtail is very similar to that of mackerel ; however, since it is a bottom-
living fish, it feeds not on copepods but on mobile benthos organisms, mostly

THE BLACK SEA
Table 188

461

DETRITUS

MICRO-ORGANISMS

PHYTOPLANKTON

ZOOPLANKTON

Engraulis, Spratella, Clupeonetla, Syngnatus schmidti, Sanlinella
Pisces juvenes spp.

kk H

Caspialosa, Scomber, Belone

i ; ТЧ.ГТГ"

Pelamvs. Pan

tomato miis

Sadus, Trachitrus

Delphinus, Phocaena \

Tursiops

Scorpaena, Gobius,

Uranoscopus, Trachinus, Serranus,

Lophius

(passive carnivore)

Mullus, Pleuronectes, Sotea,

Corvina, Umbrina, Ammodhes, Gobius,

Smarts, Motella, Callionymus,

Ophidian, Syngnathus

A canthias, Acipenser,

Huso, Bothus, Raja, Trigon,

Trigla, Labrax

(active carnivore)

Mugil, Atherina,

Labridae, Blennius, Sargus,

Charax, Heliastes

ZOOBENTHOS

PHYTOBENTHOS

I u

SOILS, DETRITUS, PRODUCTS OF DECOMPOSITION, BACTERIA

crustaceans. The food of the hardtail, like that of the mackerel, consists of
approximately half fish and half crustaceans.

Apart from the pelagic carnivores one may distinguish a group of bottom-
living carnivores : flatfish, Acanthias and some beluga, sturgeon and others.
There is a large number of small fish among the benthophages, representative
of Grenilabrus, Ophidon and Mullus genera, partly sturgeon, beluga, and
starred sturgeon. Finally, some fish feed on detritus deposited on the bottom,
and on members of the microbenthos. Among them grey mullet may be
named.

V. Wodjanitzky (1941) notes that among the Black Sea fish there are fewer
benthophages than planktophages ; benthophages are richer in number of
species and are of secondary importance in fishing, except for sturgeon and

462 BIOLOGY OF THE SEAS OF THE U.S.S.R.

grey mullet. Some fish, for instance hardtail and Gadus (gaidropsarus) medi-
terraneus, have a mixed diet.

Table 189. Composition of the food of three species of Black Sea herrings as a

percentage

Higher Lower

Fish crustaceans crustaceans Sea-weeds

C.pontica 74-1 9-7 —

C. maeotica 95-4 3-4 — —

C. tanaica — — 49-7 50-3

The ratio of planktophages to benthophages in the Black Sea is the
exact reverse of that in the Sea of Azov. The pelagic carnivores are hardly
represented at all. Azov predatory fish feed mainly on small bottom-living
fish, as, for example, pike-perch. Marti's idea that considerable development
of pelagic carnivores is impossible in the Sea of Azov because of the low
transparency of its waters is very interesting. In the Black Sea, however,
large accumulations of pelagic carnivores shoal in the region near the Kerch
Straits in autumn, as if waiting for the anchovy to come out of the Sea of
Azov.

V. Wodjanitzky (1941) notes that the ratio of pelagic to benthic fish in the
commercial yields is 7:1. Actually this ratio of the two groups of fish is even
higher, since fishing in the open parts of the Black Sea is still undeveloped.

Since the Black Sea plankton biomass is two or three times smaller than
that of benthos, the cause of this sharp predominance of pelagic fish over the
benthophages should, in Wodjanitzky's opinion, be sought in the fact that
'with its small biomass plankton is highly productive throughout the year,
doubling its biomass several times . . . and in the food-chain plankton-fish
we have, undoubtedly, a more complete and direct utilization of substances
for the building up of commercially useful organisms than in the food-chain
benthos-fish, as in the complex chain of feeding on benthos and the feeding
of benthos we find a large number of dead ends which finish up in useless
organisms'. Many benthos-eating fish feed in the northwestern part of the
Black Sea.

L. Arnoldi and E. Fortunatova (1941) have carried out a comprehensive
investigation of the biology and physiology of the nutrition of small, bottom-
living coastal-water fish. They have elucidated the standards of the daily
consumption of food, the feeding intensity, the gain in weight for various
standards of feeding, the rate of digestion, the assimilation of food, etc., and
the changes in all these indices with the season and with temperature.

Fisheries. The situation and the prospects of development of the Black Sea
fisheries reflect in a most characteristic manner some peculiarities of the
distribution of fauna in it.

Before 1939 the yield of our fisheries in the Black Sea was about 500,000
centners. The yield of those of other countries was about 360,000 centners

THE BLACK SEA

463

(which corresponds to approximately 2-0 kg offish per hectare calculated for
the whole Sea surface).

General characteristics of Black Sea productivity

Our general idea of Black Sea productive peculiarities depends on the con-
ception described above of vertical circulation adopted by us. If the vertical
circulation goes down to the depth of the Sea, then the latter is not a bottom-
less well, absorbing large quantities of organic substances ; but a great part
of them is brought back into the inhabited zone. After his comprehensive
examination of the problem V. Wodjanitzky (1954) came to the conclusion
that the production processes are not weakened in the Black Sea as compared
with those in other seas. To confirm his point of view Wodjanitzky reproduces
V. Datzko's table, given here as Table 190.

Table 190

Biomass

Annual

Annual production,

Group of

103

tons

PIB

103

tons

Percentage

organisms

Wet

Dry

ratio

Wet

Dry

of dry

weight

substance

Phytoplankton in 0-50 m

layer

3,600

360

300

1,000,000

100,000

Micro-organisms in

0-200 m layer

13,500

2,700

250

3,375,000

675,000

Zooplankton in 0-10 m

layer

1 1 ,000

1,100

330,000

33,000

Zoobenthos

15,000

2,250

2-5

3,700

5,550

Phytobenthos*

20,000

2,400

20,000

2,400

Fish :

Plankton-eating

5,000

1,500

0-5

2,500

750

Benthos-eating

700

310

0-5

350

105

Dolphin

0-35

* The figure is undoubtedly double what it should be.

In elucidating Table 190 Wodjanitzky adduces the following considerations :
that the quantities of nutrient salts (nitrates and phosphates) in the inhabited
layer of the Sea are of the same order as in other seas (the nitrate content is
somewhat decreased and there is a certain saturation with phosphates and
ammonia) ; the salt ratio in the surface and in the depths is, moreover, the
same.

In its inhabited zone the Black Sea cannot be considered as impoverished
either in phyto- or zoo-plankton. In any case according to all these indices
it is not poorer but richer than the Caspian Sea. As regards its fisheries, the
Black Sea occupies a middle position between the Mediterranean and the
Sea of Azov. Wodjanitzky thinks that its resources of pelagic fish (anchovy,
sprat, Clupeonella, herring, mackerel, garfish, hardtail, Sarda, Pomatomus
saltatrix, tuna and others) are very rich, and that from them the fishing
industry can be greatly expanded.

464 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 191. Quantity of plankton in the Black Sea, summer 1939 (S. Maljatzky)

Group

May-June

August

Total annual plankton bio-

Mean

13-8

1018

mass mg/m3
Calanidae

Range
Mean

2-3 to 39-9

2,578

3-5 to 20

17-79

(No. of specimens)
Sagittae

Range
Mean

10 to 19,600
756

10 to 6,928
235

(No. of specimens)
Phytoplankton
(mg/m3)

Range
Mean
Range

1 to 3,524
850
34 to 6,620

2 to 1,560

1980
310 to 4,780

M. Dobrzanskaya (1954) gives the comparative data on phytoplankton
production, obtained from photosynthesis data for the different Seas {Table
192). It follows from them that (7) the Black Sea in this respect is not inferior

Table 192. Daily production of phytoplankton in the surface horizon of different Seas
(ml/litre of glucose) (M. Dobrzanskaya, 1954)

Coastal areas of Black Sea, March 1948 to November 1950

(M. Dobrzanskaya) 0-32-0-90

Depths of Black Sea, March 1948 to November 1950

(M. Dobrzanskaya) 0-11-0-39

Southern part of Caspian Sea, August 1932 to October 1934

(S. P. Brujevitch) 0-19-0-75

Bay of Naples, February 1907 to August 1908 (A. Rutter,

1924) 0-71-0-94

Coasts of Sea of Norway, March 1922 (G. Gran) 0-30-0-37

Shores of Atlantic Ocean, August 1947 (Rayleigh and

George) 0-68

Sargasso Sea, Atlantic Ocean, July to September 1947

(Rayleigh and George) 0-08-0-25

but superior to other Seas, and (2) that its surface waters are as productive
in phytoplankton as the deeper waters.

10
The Sea of Azov

I. GENERAL CHARACTERISTICS

The Sea of Azov is a body of water attached to the Black Sea which is remark-
able in many respects. It is essentially a broad, very shallow inlet of the Don,
with water only slightly saline. Owing to a number of circumstances it is
supplied with abundant mineral substances.

A rich bottom-population, an abundance of organic substances, great
warmth in summer, and a readily established saline stratification cause the
upper limit of the reduction zone to rise easily from the sea-floor into the
water of the deepest, central part, with the consequent phenomenon of suffo-
cation of the bottom-fauna.

The Sea of Azov is populated mainly by the most euryhaline forms of the
Mediterranean fauna, chiefly molluscs, which are exceptionally abundant
there. Relict Caspian Sea fauna lives only in the most eastern corner of the
Gulf of Taganrog.

For a large number of Black Sea fish and for some river fish the Sea of
Azov is a plentiful feeding ground in the warm season of the year.

The Sea of Azov is the most productive sea in the world, its fish catch being
80 kg/hectare in some years.

II. HISTORY OF EXPLORATION

First period

The first reliable information about the fauna of the Sea of Azov resulted
from the research of A. Ostroumov (1892, 1896, 1897) and V. Sovinsky
(1894, 1902). During the first fifteen years of the present century biological
collections were made in the Sea of Azov by N. Borodin (1901) and S. Zernov
(1901). All these investigations were concerned with classification of the fauna
and the Sea as such was hardly studied at all, either as regards its hydrological
conditions or its biology.

Second period

Investigations made in recent years have led to a situation where the Sea of
Azov can now perhaps be placed among those seas of the u.s.s.r. which have
been most comprehensively studied. From 1923 to 1927 the Azov and Black
Seas scientific-industrial expedition, under the leadership of N. M. Knipovitch,
worked in the Sea of Azov. N. Tchougounov (1926), a member of this expedi-
tion, has given in his work a general picture of the quantitative distribution
of the fauna and some general principles of this distribution. An elaborate
taxonomic-faunal investigation of the most interesting group of relict crus-
taceans of the basin of the Sea of Azov was carried out by A. Martynov
2g 465

466 BIOLOGY OF THE SEAS OF THE U.S.S.R.

(1924), A. Derzhavin (1925) and others, independently of the Azov-Black
Sea expedition.

Third period

Very valuable and thorough quantitative investigations of the fauna of the
Sea of Azov have been carried out in the last few years by the Azov-Black
Sea Institute of Fisheries and Oceanography and the Don-Kuban Fisheries
Station. Among these works the most important from our standpoint are those
of V. VorobiefT on the benthos of the Sea of Azov (1944) and on the Sivash
fauna (1940), of A. Okul (1940) on the plankton of the Sea of Azov, of F. Mor-
dukhai-Boltovskoy (1937) on the bottom-living fauna of the Gulf of Taganrog,
and of V. Maisky (1940) on fish census. The work of A. Zhukov (1938) on
the chemical conditions of the Sea, which hitherto had remained almost un-
examined, must also be noted. All these investigations have been carried out
in recent years.

In connection with the changes in the Caspian Sea conditions, as a result
of hydro-power construction on the river Don, detailed investigations of the
conditions and the biology of the Sea of Azov have been carried out by
(A. Karpevitch, 1955, 1957; M. Zheltenkova, 1955; T. Gorshkova, 1955;
V. Datzko, 1951; G. Pitzik, 1951; G. Pitzik and A. Novoshilova, 1951;
I. Stark, 1951, 1955, 1956; E. Yablonskaya, 1955, 1957; V. Maisky, 1955;
F. Mordukhai-Boltovskoy, 1948, 1953, 1960; A. Novoshilova, 1955, 1958).

III. PHYSICAL GEOGRAPHY, HYDROLOGY AND HYDRO-
CHEMISTRY

Situation and size

The Sea of Azov, extending to 45° 17' N latitude and from 34° 19' to
39° 18' 30" W longitude is a very shallow water body (Fig. 222), which is
greatly diluted in its eastern part by the rivers Don and Kuban and made
more saline in its western part on account of evaporation. The Sea of Azov
is connected with the Black Sea by the narrow Kerch Strait, and it can be
regarded as a broad inlet of the Don. On the northwest the Sea of Azov is
connected with the Sivash or Putrid Sea by the narrow Genichensk Strait
(120 m). The surface area of the Sea of Azov is 38,000 km2 (without Sivash) ;
of this total 5,640-6 km2 is the area of the Gulf of Taganrog. The surface area
of the Sivash is 2,630 km2.

Bottom topography

The greatest depth of the Sea of Azov is only 13^ m. The average depth of
the Gulf of Taganrog is 4-7 m, that of the Sea of Azov without the Gulf of
Taganrog — 7-2 m, and with it 6-8 m. The total volume of the Sea is 320 km3.
The Sivash is very shallow, its greatest depth being no more than 3-6 m. A
shallow zone of less than 5 m deep (Fig. 222) forms a narrow strip off the
coast. Depths of 5 to 10 m encircle the body of water, except for the southern
part of the Sea of Azov, occupying 42-7 per cent of its area. Depths of 10 m

THE SEA OF AZOV

467

and more form 50-2 per cent of the total area. Hence the shallows (less than
5 m) occupy only 7 per cent of the Sea.

As one moves farther into the Gulf of Taganrog its depth decreases from
9 to 8 m in the central part of its western half. The greatest part of this half of

ISOBATH 5m
■ ISOBATH 10m

Fig . 222. Chart of Sea of Azov with the 5 and 10 m isobaths (Knipovitch).

the Gulf is 5 to 7 m deep, and the 4 m isobath approaches close to the coast.
In the eastern part of the Sea, by contrast, large areas are occupied by shallow
banks 2 to 3 m deep or less. The most eastern sector of the Gulf is a sub-
marine delta of the river Don, with troughs — the continuation of the arms of
the delta — which are divided by shoals. 53-6 per cent of the total area of the
Gulf of Taganrog is 5 m deep or less.

Currents

Owing to the shallowness of the Sea, its water is in a state of perpetual hori-
zontal motion and under the effect of the winds ; various multiform systems
of irregular currents are thus created. N. M. Knipovitch (1932), however,
considers that there are many indications of the existence of some constant
system of circular cyclonic current along the shores, circling round the central,
deeper part of the Sea.

Fluctuations of water-level and water-balance

The water-level of the Sea of Azov and its various parts undergoes con-
siderable fluctuations as a result of spring floods, of rainfall, of summer

468

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Fig. 223a. Contemporary salinity distribution in the Sea of Azov, average secular
(mean annual) salinity (Voronkov and Svitashev from the data of Samoilenko).

evaporation and of the phenomena of on-shore and off-shore winds. The
phenomena of on-shore and off-shore winds are very powerful in the Sea of
Azov and the Gulf of Taganrog ; as a result the range of variations in the

OOZE SAND SHELL

GRAVEL

_„«— MEAN ISOHALINES IN
"* TERMS OF CHLORINE

Fig. 223b. Distribution of soils and salinity in Gulf of Taganrog (Mordukhai-

Boltovskoy).

THE SEA OF AZOV 469

sea-level reaches 4-44 m in the Gulf of Taganrog. The picture of the currents
is therefore confused. However, it may be concluded that waters are carried
out of the Gulf into the Sea mainly along the northern shore, while Azov
waters enter it along the southern one. This can be clearly seen from the
distribution of the isohalines (Fig. 223a, b) which also give a general picture
of the range of salinity in the Gulf of Taganrog.

The water-balance of the Sea of Azov is made up of the elements given in
Table 193 (V. Samoilenko, 1947).

Table 193

Influx km3 Consumption km3

River discharge 41 Evaporation 29

Precipitation 14 Loss through the Kerch

Inflow through the Kerch Strait 8 8 to 1 2 1

Strait 63 to 96 Loss through the Narrow

Inflow through the Narrow Strait (into the Sivash) 4

Strait (out of the 3

Sivash)

Total 121 to 154 Total 121 to 154

Since the inflow of fresh water into the Sea of Azov is not fully matched by
evaporation, the remaining surplus of water is distributed between the Geni-
chensk and Kerch Straits. In early spring a surplus of saline water flows from
the Sivash into the Utlyukski inlet through the Genichensk Strait, but for the
rest of the year there is a prevailing current from the Sea into the Sivash. The
exchange of waters through the Kerch Strait is irregular in character, being
greatly affected by winds. The currents of the Kerch Strait play an important
part in the hydrology and biology of the Sea of Azov : on the one hand, the
surplus masses of less saline waters are carried out of the Sea of Azov by this
current ; on the other, the more saline waters of the Black Sea are carried in.

The Tsymlyansk dam on the river Don was completed in 1952. This led to
the formation of the huge Tsymlyansk water reservoir above the dam, while
below it new conditions in the river and the Sea began to form (A. Karpe-
vitch, 1957). Twenty-three per cent of the average yearly discharge of the Don
was intended to be removed for irrigation purposes. In coming years, as a
result of hydro-power construction on the rivers Don and Kuban, the supply
of nutrient substances into the Sea of Azov will be reduced by about 50 per
cent, while the primary production of phytoplankton will decrease to about
40 per cent of the annual average (V. Datzko and M. Fedosov, 1955). More-
over, the salinity of the Sea of Azov will increase to 15%0. In 1952 the salinity
of the Sea of Azov increased on the average about 0-4 1%0 by comparison with
1951. In 1953 it increased again by 0-32%o (E. Vinogradova, 1955).

According to V. P. Vorobieff (1944) the average annual discharge of solid
matter from the land into the Sea of Azov is of the order of 8-3 million tons,
which gives on the average 12-9 cm3 per 1 m3 of water, whereas the discharge
of dissolved substances is more than 13 million tons.

470 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Transparency

The water of the Sea of Azov is only slightly transparent, owing to the large
amount of organic and inorganic matter suspended in it. The limits of the
fluctuations of transparency are ОТ to 5-0 m; in the overwhelming majority
of cases transparency does not extend farther than 2 m, and in 60 per cent of
them farther than 1 m. On the whole the water is more transparent in the
central and western parts of the Sea than in the east.

Temperature

Like the Black and Caspian Seas, the Sea of Azov, except for the Sivash,
belongs to the bodies of brackish water, in the sense used by N. M. Knipo-
vitch (1929), to which we referred earlier.

Some features of the hydrological conditions of the Sea of Azov are due to
this brackishness of its waters. In winter time, with the surface water at
freezing temperature and partly covered with ice, warmer and at the same time
heavier waters are concentrated in the depths. At a salinity of 6%0* (by
chlorine), the temperature at the surface at that time will be —0-58°, and at
the bottom 1-67°. When the circulation is vigorous and the whole column of
water has a temperature of about freezing point, then, in the spring, once the
surface layers are warmed to 1-67° they rapidly sink and quickly warm the
whole column of water to the temperature of the highest density, i.e. 1-67°.
Further heating is mainly concentrated in the upper layers of water and passed
over to the lower layers only gradually as a result of drifting circulations.

The summer rise in temperature of the waters of the Sea of Azov, and the
mean annual temperature, are fairly high. Thus the mean annual temperature
of the surface of the Sea for the four years 1924-27 was 11-28° for Taganrog
and 12-4° for Temryuk.

In the four summer months at Temryuk the water temperature is higher
than 20°, reaching 25° at times. The lowest average monthly temperature,
which sometimes occurs in January, but usually in February, is about 0°;
some lower temperatures have been recorded occasionally : —0-3° for Tagan-
rog, — 10 for Temryuk, — 1-3 for Genichensk. On the other hand the highest
average monthly temperature of water on the surface of the Sea, usually
occurring in July, reaches 25-9° at Taganrog, and the highest single observa-
tions were 29-6° at Taganrog, 31-2° at Eisk, and 29-3 at Temryuk.

In autumn and winter as a rule an almost homothermic state is observed ;
the temperature varies only slightly with depth. Only in the spring, during the
period of a quick rise of water temperature, is a considerable decrease of
temperature with depth commonly observed. A strong wind brings about
considerable changes in the range of temperature right down to the bottom.

* The salt ratio in the Sea of Azov, and especially in the Caspian, is somewhat different
from that of typical sea-water. Hence it is impossible to obtain an accurate expression of
its total salinity from the usual formula of the change in the chlorine content obtained by
titration (weight of chlorine in grammes per kilogramme of water). For the Sea of Azov
and still more for the Caspian Sea the so called ' chlorine numbers ' are commonly used
instead of salinity. The usual formula can be used to convert it into general salinity:

S<L = 0-030+ 1-8050 CI

THE SEA OF AZOV 471

Ice conditions

The considerable fall of temperature in December, January and February
leads to the formation of ice, which proceeds the more readily owing to the
shallow water and the low salinity of the Sea of Azov. Ice formation begins
at the Gulf of Taganrog, where it remains longer than anywhere else. Ice
formation is weakest off the southern shores.

In some years an almost continuous ice cover persists for 4 to A\ months.
In 1923-28 the period of ice varied in different parts of the Sea from 38 to
138 days, while the thickness of the cover ranged from 9 to 90 cm. Ice usually
appears in the first half of December and disappears in the second half of
March. 'Taking into consideration the considerable thickness of the ice
fields', wrote N. M. Knipovitch (1932), 'which are 80 or even 90 cm thick, the
masses of hummocks and the piling up of ice which sometimes reaches down
to the sea bottom, one cannot help seeing that the freezing of such great
masses of water with the separating out of large amounts of salts, would
increase to a considerable degree the salinity of the sea in winter, particularly
in so shallow a sea as the Sea of Azov.'

Salinity *

The mean salinity of the Sea of Azov may be taken as 1 1 -2%0 ; seasonal
fluctuations of salinity are observed with a maximum in winter and a mini-
mum in summer (Fig. 223a).

The salinity of the Sivash is unusual for the Sea of Azov. In the Northern
Sivash a salinity of 400%0 has been observed and it increases even more
farther south and west.

In the Sea of Azov itself maximum salinity (17-5%0) is found in the bottom
layers in the area of the Kerch Strait — this is Black Sea water which is only
slightly diluted.

The salinity of the Sea of Azov fluctuates considerably during the course of
the year. Maximum salinity is found in the winter months when its rise is
caused by the decrease in the river inflow and the freezing up of large masses
of fresh water. Salinity begins to decrease gradually with the melting of the
snows, and a period of minimum salinity is reached by the end of summer
(September). In the eastern part of the Gulf of Taganrog the water is often
almost fresh, while in the west, close to the entrance into the Sea of Azov,
salinity rises to 4 to 5%0 (chlorine).

Gas conditions

The surface layers of the Sea of Azov usually contain an adequate amount
of oxygen, owing to its shallow waters and its good aeration. Annual changes
of oxygen content in the water-column are shown in Fig. 224a where they
are compared with the course of phytoplankton development. Fluctuations
of oxygen content are small (92 to 1 14 per cent saturation). The deep-water
layers, however, owing to the abundant life in the Sea, the accumulation of
huge masses of decomposed organic substances and the high temperature,
may easily lose their oxygen and pass to a state of oxygen deficiency. This

/Ч OXYGEN

Д I / \

10000

/ VA / \ "

100

8000

^6000

, 1

/ \

/ 1

z
<

А ' '

£4000

/\ / \

1 \ II

/ *

I
а.

' * 77" 1 *

2000

■ I \ \

0
I/

кп

7/ К/// //Г /Г XI XII III V VI VIIй

MONTHS

к J V J

■V 1

1936 1937

Fig. 224а. Seasonal alterations of oxygen content and

the development of phytoplankton in the Sea of Azov

(Zhukov). I Oxygen ; // Phytoplankton.

Fig. 224b. Area of occurrence of oxygen deficiency in summer :
1 Isobaths ; 2 Main zone of possible oxygen deficiency (Fedosov).

THE SEA OF AZOV

473

occurs usually in May and continues until August. This state may develop with
a catastrophic rapidity when conditions make vertical circulation difficult
(calm weather, considerable warming up of the upper lower salinity layer)
(Fig. 224b).

This is assisted also by the saline stratification which is especially apparent
in the part of the Sea adjacent to the Kerch Strait : the more saline Black Sea
waters entering the Sea of Azov through the Strait lie in the bottom layer
where they are covered by the diluted waters of the Sea of Azov.

In June 1937 A. Zhukov observed a 40 to 80 per cent oxygen saturation in
the bottom layers throughout the Sea, and in July phenomena of a very in-
tense suffocation developed in the bottom layer, from which oxygen dis-
appeared throughout most of the Sea. In August the situation became less
acute and the September gales broke down the established stratification and
the amount of oxygen near the bottom increased. Similar intense suffocation
phenomena were observed in 1946.

Stormy weather mixes up the whole water-column and disturbs the strati-
fication. The table given by Knipovitch is a good illustration of this {Table
194).

Table 194

After calm weather

After stormy weather

Depth

Oxygen content

% of satu-

Oxygen
(

content
Ус of satu-

•S/bo

cm" ration

t°C

^/00

cm3

ration

24-96

10-72

6-945 120-09

21-76

10-46

4-34

73-43

24-96

10-72

6-55 114-91

21-75

10-50

4-32

73-10

22-56

10-72

1-09 18-41

—

— .

12-5

' 21-96

10-81

00185 0-31

21-76

10-50

4-32

73-10

Bottom zones exposed to frequent suffocation phenomena are the poorest
in benthos. Suffocation leads to a mass extinction of bentopelagic organisms ;
among fish some species of bullheads suffer most.

For some areas of the Sea of Azov the bacterium Microspira aestuarii is
very characteristic; it is sometimes found in huge amounts reaching 56
million specimens per 1 g of soil. The total amount of bacteria can rise to
776 million specimens per 1 g of soil (in the Kazantip area). Sulphates are
reduced by this bacterium, while carbonates are formed in the process and
hydrogen sulphide is evolved ; this can also contribute to a loss of oxygen
content, since it is bound to be used for the oxidation of the hydrogen sul-
phide formed. Bacteria decomposing cellular tissues with the formation of
marsh gas (methane), which requires for its further oxidation large amounts of
oxygen, are important among the bacteria of the bottom of the Sea of Azov.

Nutrient salts

As regards nitrates, in July 1936 these were everywhere absent. They began
to appear in August and by the beginning of the autumn (September-October)

474 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 195. Changes in the concentration of plant nutrients, mgjm%, in the Sea of Azov
{without the Gulf of Taganrog) in 1957 {by M. Fedosov and E. Vinogradova, 1955)

Month

Phosphorus

Silicon

Nitrogen + ammonia

March

240

198

April-May

159

June

11-6

188

July

233

100

August

318

155

September

(1,250)*

October

(1,335)*

November

(103)*

(2,190)*

* Bottom-samples in parentheses.

the nitrate content in the water had risen to 30 mg/m3. In November it in-
creased to 60 and even to 90 mg/m3. A specially large amount of nitrates was
observed in the Gulf of Taganrog (up to 150 to 200 mg/m3).

In 1937 the nitrates accumulated during the winter were exhausted in a
short time by the spring bloom of phytoplankton. In April-May the nitrates
disappeared completely, remaining only in the middle part of the Gulf of
Taganrog in amounts of 80 to 300 mg/m3. By June-July 1937 there was a
small accumulation of nitrates, but in August and September they had again
disappeared from the whole area of the Sea. Even in the Gulf of Taganrog the
amount of nitrates fell to 8 mg/m3 and only in the actual estuary of the Don
did it reach 100 mg/m3. The waters of the Don carry 500 to 700 mg/m3 nitro-
gen in the form of nitrates.

On the other hand the amount of ammonium nitrogen in the Sea of Azov is
exceedingly large, especially during the periods of the mass dying-off of plank-
ton; for instance, after spring bloom (up to 900 mg/m3). This is obviously
connected with the decomposition of a large bulk of organic matter. The
picture of ammonia distribution is the reverse of that of oxygen. The amount
of ammonia nitrogen in seas usually appears as a few tens of milligrammes
per cubic metre of water, and it rarely exceeds 100 (Baltic and Mediterranean
Seas). Only in the deep part of the Black Sea does the amount of ammonia
nitrogen reach 1,000 to 1,200 mg/m3.

Unlike the nitrates, the phosphates remain all the year round in the waters
of the Sea of Azov, although at times in small amounts ; only in the upper
layer may they be completely consumed {Table 195). In April to August
phosphorus in the upper layer is either absent or remains at a level of 4 to 12
mg/m3; in the bottom layer it may increase from 30 mg/m3 to 200 or 300
mg/m3 in June, and then fall to 40 or 50 mg/m3 in August. The usual phos-
phorus content in sea-water in winter is 20, 40, 60 and even 90 mg/m3. The
river Don contains from 50 to 150 mg/m3 of elementary phosphorus.

Silicic acid

Silicic acid content is as much as 2,050 to 3,500 mg/m3 in October and

November ; it falls, as spring approaches, to an average of only 250 mg/m3 in

THE SEA OF AZOV 475

March. In April and May its content falls to 50 mg/m3 in the surface layer and
to 100 mg/m3 in the bottom one. These sharp fluctuations in silicic acid
content should be attributed to its being consumed by plankton diatoms.
During the autumn dying-off of plankton some silicic acid appears in the
water again.

Thus the most typical features of the chemical conditions of the Sea of
Azov are due to an abundant discharge of detritus and plant food by the river
Don, which ensures an exceptionally intensive development of plankton and
benthos life.

Chemical characteristics

However, a good supply of oxygen is required for the development of life
on this scale and for the oxidation of huge amounts of organic substances.
Since in the Sea of Azov the process of aeration is at times, and in the region
of the Straits always, impeded by salinity and temperature stratification,
catastrophic suffocation of the benthopelagic fauna may occur, accompanied
by an accumulation of large amounts of ammonia in the bottom layer. Two
maxima of nitrate and phosphate accumulation are observed during the year,
with at times a complete consumption of nitrates in April-May and August-
September. Owing to the shallowness of the Sea of Azov, large amounts of
phosphates and silicic acid can accumulate on the bottom; they may also
be dissolved in the water.

All aspects of the chemical conditions of the Sea of Azov are to a great
extent determined by the course of phytoplankton development, both by its
increased multiplication and its dying off. The oxidation conditions, the
accumulation of ammonia, the phosphorus, nitrogen and silicon cycles all
reflect the various phases of plankton development, especially because of the
shallowness of the Sea.

The soils

A diagram of the distribution of soils appears in Fig. 225a. There are few
rocky shores in the Sea of Azov, and these are mainly situated on the southern
coast. A wide band of sands with a smaller or larger admixture of shell
gravel encircles the central part of the Sea and of the Gulf of Taganrog,
occupied by silty mud and shell-gravel mud. In the southern part of the Sea
this band of sands is narrower than on the other shores, and the mud bottom
approaches the coast more closely. The proportion of fines (less than 0-01 mm)
in these muds reaches 30 to 50 per cent ; in the silty muds of the central part
of the Sea it is always in excess of 50 per cent. The deepest parts of the Gulf
of Taganrog, beginning from a depth of 3-5 m, have a soft mud floor, with a
characteristically large number of Ostracoda shells. F. Mordukhai-Boltov-
skoy (1937) thinks that these muds might be called Ostracoda muds (up to
50,000 or 100,000 and more live Ostracoda per 1 m2). Sand stretches in a more
or less narrow band along the coast, entering deep into the Gulf only with
shoal heads. Vast areas of the bottom, especially in the part of the Gulf
farthest west, are occupied by mixed mud, sand and shell gravel.

476

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Fig. 225a. Diagram of distribution of soils in Sea of Azov
(Vorobieff, 1949). 1 Ooze-shell gravel ; 2 Clayish ooze ; 3 Shell
gravel on sand-ooze and ooze-sand.

The distribution of organic carbon in the upper layer of the sea-bed soils
corresponds closely with the change in the nature of the latter (T. Gorshkova,
1955). It is most remarkable that no special accumulation of organic carbon
is observed anywhere in the Sea of Azov, not even in its deep central part, as

Fig. 225b. Distribution of organic carbon, expressed as percentage of dry weight of
the substance in the upper layer of the Sea of Azov deposits (Gorshkova, 1955).
1 From 2-9 to 2-4%; 2 From 2-4 to 20%; i From 20 to 1-5%; 4 From 1-5 to 1%;

5 From 1 to 0-5%.

THE SEA OF AZOV 477

might have been expected from the high indices of plankton and benthos bio-
mass and from the abundant amounts of organic substances brought in by
the rivers {Table 196 and Fig. 225b).

Table 196. Mean percentage of organic carbon in the sediments of different seas
Region Maximum and minimum Mean

Sea of Azov 0-6 -2-9 1-63

Barents Sea 015-312 1-28

Northern Caspian 0-25-3-0 0-63

Since large areas of the sea-bed of the Barents Sea, and especially of the
Northern Caspian, are occupied by sand, and that of the Sea of Azov by
muds, the data of Table 196 may be considered very close to one another.

As has been revealed by the same author's examination of the salinity of
the soil solutions of the Sea of Azov, the salinity of this Sea and that of the
Gulf of Taganrog has increased during the last century.

M. Fedosov (1955) characterizes the genetic composition of the bottom-
deposits of the Sea of Azov in the manner given in Table 197.

Table 197

Constituent Percentage

Mineral river suspensions 45-5

Organic substances of river suspensions 1 -4

Precipitates of organic substances formed in the Sea 13-5

Mineral and organic precipitates 6-3

Eolian' deposits and products of the breakdown of the banks 33-3

1000

Nature of the shores

As V. Zenkovitch (1958) has pointed out, all the coastal waters of the Sea of
Azov are exceptionally shallow ; this is connected with the small depth of the
Sea itself. The basin of the Sea, which receives the turbid waters of the Don
and Kuban rivers and of the products of the wash-out of loess shores, is
filled with mud, which rises to unusually shallow depths (of about 3 m).

Quaternary loess and sand deposits stretch along the whole northern shore
of the Sea, the southern shore of the Gulf of Taganrog and the eastern shore
down to Primorsko-Akhtarsk. Shores made of such deposits are intensively
washed out and in some sectors this wash-out reaches a rate of 10 m/year. The
shores of the Kerch and Taman peninsulas are more resistant, since there are
some outcrops of hard Tertiary limestone. In the southeastern corner (Tem-
ryuk Bay) the wide delta of the Kuban river is cut off from the Sea by a long
sandy bar. The Kuban enters the Sea by three separate mouths. Along the
western coasts of the Sea stretches the shell-gravel sand bar — the Arabat

478 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Strelka, behind which is situated the estuarine lake of Sivash with its greatly
increased salinity. This lake is connected with the Sea by the Genichensk
Strait.

The coasts of the Sea of Azov have two exceptional characteristics. A series
of five narrow shoals, stretching out from the coast into the Sea at an angle
of about 45° in a south-southwesterly direction, is situated in the north. The
length of these shoals increases from east to west ; the biggest is more than
50 km (Fedotova shoal with Biryichy Island). Their unusual formation is
connected with the marked prevalence of easterly and northeasterly winds,
owing to which the resultant of the action of the waves is oriented almost
parallel to the present coast (A. Aksenov, 1955). The cause of this unusual
orientation of the shoals is due to the deposits being shifted at maximum
speed at an angle of about 45° to the direction of the waves.

The second characteristic of the shores of the Sea of Azov is that the basic
material of accumulated forms consists almost exclusively of shell gravel
brought out to the coast. The shoals on the eastern shore consist entirely of
marine shell gravel. This rare phenomenon is connected, first with the very
high productivity of the bottom-fauna, and secondly with the instability of the
coastal loess which, when broken down, is too fine to be deposited on the shore.

IV. FLORA AND FAUNA
General characteristics

We know of no other sea in the world which can be compared with the Sea
of Azov in the extreme intensity of its productive processes. This is the result
of a whole series of factors, although there are some which have a reverse
effect (for example, the occurrence at times of a pronounced oxygen deficiency
and the formation of hydrogen sulphide in the bottom layers). Knipovitch
rightly includes among the conditions contributing to the high productivity
of the Sea of Azov : its shallowness, which facilitates the return of nutrient
substances from the bottom into the water ; an adequate exposure to sunlight
of the whole water-column (in spite of its low transparency) ; favourable condi-
tions for mixing and aeration and, finally, the large amounts of inorganic and
organic matter brought in by the rivers, both in solution and in suspension.

Knipovitch also notes that the lowered salinity greatly affects the qualitative
composition of the flora and fauna but does not hinder its very rich quanti-
tative development.

The following should be added to these considerations. If the Sea of Azov
were widely connected with the Black Sea and formed a part of it, like for
instance the northwestern part of the Black Sea, its productivity would un-
doubtedly be less even though the amounts of nutrient salts carried from the
shore and detritus were the same. All nutrient substances are accumulated
in the Sea of Azov and, except for a comparatively negligible loss through the
Kerch Strait, they are not carried out of it. We see something quite different
in the area of the Black Sea mentioned above : nutrient substances and detritus
are carried away in large quantities from the shallow coastal regions into the
adjacent deeper parts, which considerably lowers the biological yield of those
shallows.

THE SEA OF AZOV 479

The second important factor leading to high productivity of the Sea of
Azov is the summer warming both of the whole water-column and of the sea-
bottom for a long period from April to October. The heating of the upper
layer of water of the Sea of Azov corresponds to approximately 3,800 degree-
days annually, and that of the bottom-layer to a little less.

The intensity of the productive processes of the Sea of Azov may possibly
be connected in some measure with the ice-formation process, or, more pre-
cisely, with the melting of ice. If this phenomenon has a wide impact in nature
then, given that the shallow depths of the Sea, and the fact that its ice-cover
composes one twentieth to one twenty-fifth of the whole volume of water,
the effect of melted water on the development of life in spring must be
particularly important.

Composition and heterogeneity of population

At present 226 species of invertebrates (Mordukhai-Boltovskoy, 1960) and 79
forms of fish have been shown to exist in the Sea of Azov. The list includes
among the invertebrates 35 species of polychaetes, 33 species of molluscs,
30 species of lower and 61 species of higher crustaceans. Of the total number
of 305 animal species, 165 belong to the Mediterranean and 75 species are
Caspian relicts.

In recent years, as a result of the increase in the salinity of the Sea of Azov,
a migration into it of Black Sea forms has begun. Thus a form of the genus
Teredo, which had not hitherto penetrated farther than the Kerch Strait,
has been found off Kazantip. On the other hand, the movement of more salt-
loving forms from the Utlyuksky inlet and the Sivash into the Sea of Azov
has also been observed. The qualitative composition of the population of the
Sea of Azov is a biological factor of exceptional interest. It includes several
heterogeneous groups.

The relicts of the Novo-Euxine Caspian fauna, now populating the least
saline parts of the Sea of Azov and the eastern part of the Gulf of Taganrog
(river mouths, inlets), provide some species which propagate throughout the
whole Sea. To these relicts belong, among the coelenterates : Ostroumovia
maeotica and Cordylophora caspia ; among the polychaetes : Hypania invalida,
Hypaniola kowalewskyi and Manayunkia caspica ; among the molluscs : Mono-
dacna colorata, Dreissena polymorpha and Theodoxus pallasi ; among the Cu-
macea : Pterocuma pectinata ; among the mysids : Mesomysis kowalewskyi ;
among the amphipods : Cordiophilus baeri, Gmelina kusnetzowi, Dikerogam-
marus villosus, D. haemobaphes, Chaetogammarus ischnus, Pontogammarus
robustoides, P. weidemanni, P. crassus, Amathillina cristata, Calanus curvispi-
num, C. maeoticus, Pontogammarus maeoticus, and others. The last named
evidently now finds the best conditions for its existence in the Sea of Azov.
Fresh-water fauna in considerable numbers are mixed with this relict fauna in
the least saline parts of the Sea.

The main mass of the fauna of the Sea of Azov consists, however, of Medi-
terranean immigrants ; some of them have found exceptionally good condi-
tions for mass development in the Sea of Azov. Among them the following
should be noted first of all: Balanus, Cardium, Mytilaster, Syndesmya,

480 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Nereis and others. All these forms are widely euryhaline, being found at a
salinity of 7 to 27%0. Some of them can endure a very considerable lack
of salinity (down to 2 to 3-6%0) ; others, on the contrary, prefer very high
salinity, being found even at a salinity of 50 to 70%o. Among the Mediter-
ranean immigrants the most important are the groups of polychaetes (32
species), molluscs (22 species) and amphipods (12 species). The considerable
qualitative poverty of the Mediterranean fauna in the Sea of Azov is appa-
rent if only from the fact that of the 137 species of coelenterates of the Medi-
terranean, only three species live in the Sea of Azov; of the 1,451 species of
molluscs, only 22; of the 300 species of pelagic copepods, only 8; of the 51
species of crabs, only one — Brachynotus lucasii ; of the 223 species of amphi-
pods only 12 species, etc.

The remains of the more salinity-loving fauna of the ancient Black Sea
period live as relicts in the western part of the Sea, in the Utlyuksk inlet and
in the Northern Sivash. As typical Black Sea relicts the polychaete Pectinaria
neopolitana and the mollusc Loripes lacteus may be named. The others have
disappeared from the fauna of the Sea of Azov ; but their shells are found
everywhere in large numbers, as, for instance, Venus gallina, Gastranafragilis,
Tapes and others.

The ultra-haline forms so marked in the Sivash and found in large numbers
at salinities higher than 30%o are a characteristic element of the fauna of the
Sea of Azov. The most typical of them are the crustaceans Artemia salina
and Chironomus salinarius.

Zoogeographical zonation

The Sea itself can be subdivided according to its fauna in the following
manner : the eastern part of the Gulf of Taganrog (relict, Novo-Euxine fauna
with an admixture of some fresh- water species), the Sea of Azov itself and the
western part of the Gulf of Taganrog (with the contemporary Azov-Black
Sea fauna of Mediterranean origin) ; the Utlyukskyi inlet and the northern part
of the Sivash (a mixture of the contemporary Azov-Black Sea fauna with
Novo-Euxine relicts of the ancient Black Sea basin) ; and the remainder of the
Sivash and the saline Kuban inlet (ultra-haline forms).

Immiscibility of the relict and Mediterranean faunas

B. Iljin (1930), F. Mordukhai-Boltovskoy (1937) and V. P. Vorobieff (1945),
examining the relationship between the brackish-water and Mediterranean
faunas, have noted that these two faunas rarely mix with one another. The
brackish- water (relict) fauna is concentrated to the east of a line connecting
the base of Krivaya shoal with the village of Porkaton, i.e. to the east of the
isohaline 3-6%0 (Fig. 226a, b). To the west of a line from Mariupol to the
base of Eisk shoal (7-2%0 salinity) the predominance of the Mediterranean
fauna is just as marked. Between these two limits (3-64 to 7-25%0 or 2 to 4%0
by chlorine) live the most euryhaline members of both faunas (Cyprideis
littoralis, Corophium volutator, Macropsis slabberi, Nereis diversicolor,
Hypaniola kowalewskyi and some others). The number of species and the
amount of biomass in this zone are much smaller than to the east or west.

THE SEA OF AZOV

481

Fig. 226a. Distribution of biomass (g/m3) of Monodacna and Syn-
desmya in the Gulf of Taganrog (Mordukhai-Boltovskoy).

The marked interchange of relict and marine faunas in the Gulf of Taganrog
affects not only the qualitative composition but also the quantitative ratio
of these two components. In the eastern part of the Gulf there is a huge pre-
dominance of relict species in the biomass, while in the western part the
marine forms are predominant (Fig. 227).

Thus not only do these two faunas not mix, but they are divided from each
other by a distinctive intermediate area. This fact, it corresponds to reality, is
of great theoretical interest, as we have said earlier.

Plankton

Qualitative composition of phytoplankton. As usually happens, the biomass of
the vegetable part of the plankton of the Sea of Azov is considerably larger

Fig. 226b. Distribution of Cardium and Dreissena biomass
(g/m3) in the Gulf Taganrog (Mordukhai-Boltovskoy).

482

BIOLOGY OF THE SEAS OF THE U.S.S.R.

180
/60
/40-
120-

loo-
se
60
40
20

Benthos 6iomass

Fig. 227. Alterations in benthos communities of the Gulf of
Taganrog from west to east (Mordukhai-Boltovskoy with some
changes). 7 Cardium complex ; 7/ Ostracoda-Nereis community ;
/// Ostracoda community; IV Monodacna-Dreissena com-
munity; V Monodacna-Unionidae community; 1 Mediter-
ranean forms ; 2 Fresh-water forms ; 3 Relict forms.

than that of the animal. The relationship of the two plankton groups and the
part played by separate phytoplankton components in different months is
shown in Figs. 228 and 229. In the Sea of Azov 188 species of phytoplankton
are known at present (see Table 198 by P. Usachev, 1927 and G. Pitzik, 1951).

Table 198

Group

No. of species

Percentage

Peridineans 52

Green algae and Heterocontae 48
Diatom 41

Green-blue algae 35

Flagellates 10

Silico-flagellates 2

Total

27-7
25-5
21-8
18-6
5-3
11

100

THE SEA OF AZOV

483

a£{ phytopfanxton

\Matomeae

PeiLdineae

Cyanophyceae

тиупгнуннххш iitwririiniixxuxii иимг/ютжхлт// iwwmi.nu'x.xxiin uwr.ri /// \nnixx xi xu
Fig. 228. Seasonal changes of certain groups of phytoplankton in the Sea of Azov

(Okul).

There are only 32 species of mass forms among them. Among the Blue-
green algae there are : Microcystis feruginosa, Aphanizomenon flos aquae,
Nodularia spumigena f. typica, var. lato-rea, Anabaena knipowitschi, A. hassalii
var. macrospora; among the Protozoa, Silico-flagellata : Ebria tripartita;
among the peridineans : Exuviella cordata, Proterocentrum micans and Gleno-
dinium danicum; among the diatoms: Skeletonema costatum, Thalassiosira
nana, Coscinodiscus biconicus, Leptocylindrus danicus, Rhizosolenia calcar-
avis, Rh. radiatus, Chaetoceros subtile, Biddulfia mobiliensis, Ditylium bright-
welli and Thalassionema nitzschioides.

Phytoplankton biomass. The relative significance of phytoplankton in the
productive processes is comparatively high, owing to the very weak develop-
ment of coastal vegetation. As regards mass the main role in the phyto-
plankton is played by the diatoms (about 55 per cent of all the phytoplankton
in the whole of the Sea), the peridineans (about 41-2 per cent of all the phyto-
plankton, chiefly in the open sea), and to a much lesser extent by the algae.

months /и ,y.v V! V// v//i iX x xi xil III IV i VI VI/ VIII IX X Я Ml

Fig. 229. Quantitative relationship between the phyto- and zoo-plankton of the Sea
of Azov in various seasons of the year (Okul).

|1^\\\^Ч\\ЧЧЧ^о

THE SEA OF AZOV 485

The blue-green algae (chiefly in the Gulf of Taganrog) constitute even at the
time of their maximum bloom (summer) barely 13 per cent of all the phyto-
plankton, and on the average only 4-2 per cent.

Diatoms have two maxima : a larger spring one (March-April) {Skeletonema
costatum and Coscinodiscus spp.), when the amount of diatoms reaches
7 g/m3, and a late autumn one (October-November) {Rhizosolenia calcar-avis,
Leptocylindrus danicus, Ditylium brightwelli, Skeletonema costatum, Thalas-
sionema nitzschioides, Thalassiosira nana and different species of Chaetoceros
and Coscinodiscus), with a maximum of up to 2 g/m3. During the rest of the
year the amount of diatoms decreases sharply (May, June, July, December,
January, February). During the bloom periods the diatoms form 90 to 98 per
cent of the total phytoplankton biomass. At times the biomass of the Sea of
Azov reaches a colossal amount, one which has been found in no other sea.
For August 1925 P. Usachev gives a plankton biomass of 270 g/m3 (385 g/m3
in other years) and for October 1924 — 106 g/m3; moreover, the plankton
consisted almost entirely of the diatom Rhizosolenia calcar-avis. As G. Pitzik
has shown (1951), such a huge phytoplankton biomass has not been found since
1934 owing to a great reduction of the number of diatoms of Rhizosolenia
calcar-avis during the periods of bloom, when it was no higher than 13 g/m3,
and usually about 2 to 4 g/m3.

The peridineans form an almost equally important component of the Sea
of Azov plankton. Their maximum multiplication takes place in the summer.
Their summer bloom is preceded by a small early-spring bloom in March
(about 0-85 g/m3). At its maximum development, in August, the peridinean
biomass is on the average about 3-5 g/m3, consisting mainly of Exuviella cor-
data, Goniaulax polyedra, G. triacantha, Proter о centrum micans, Peridineum
knipowitschi, and others; owing to their mass development the water is
coloured reddish-brown.

Among the Cyanophyceae mainly Nodularia spumigena and, to a lesser
extent, Aphanizomenon fios-aquae, Microcystis aeruginosa and some species of
Anabaena develop in large masses. Volvocales and the green algae are mostly
concentrated in the parts of the Sea with a lower salinity.

Blooming in patches is at times caused by a mass development of Flagellates
of the orders Chrysomonadina and Cryptomonadina. Among the Silico-
flagellates Ebria tripertita is predominant.

Phytoplankton development in the Gulf of Taganrog has some features
peculiar to itself (Fig. 230a and в). In the first place, phytoplankton is con-
siderably more developed here, and the blue-green algae (Microcystis and
Aphanizomenon) are predominant during the whole warm season (June to
November), reaching in the autumn a phytoplankton biomass of 85 to 93
per cent; the diatoms become markedly preponderant only in spring (Fig.
231).

The number of Aphanizomenon filaments may be more than 5-5 mil-
liards/m3, each of the filaments consisting of 100 to 150 cells. The number of
peridineans and diatoms at one station also reached 4-5 millions of
specimens/m3.

All these quantitative data, which are mainly taken from the work of

486

BIOLOGY OF THE SEAS OF THE U.S.S.R.

'AZOV

I.E2Z

З.ЕЭЗ

4. Egg

s.l 1

TEMRYUK

Fig. 230b. Distribution of phytoplankton in the Sea of Azov in July 1947 (mg):
1 Diatoms ; 2 Peridineans ; 3 Plus-green algae ; 4 Green algae ; 5 Others (Pitzik).

S4?

Ю0
SO

70
60
SO

v>v^X*X*vTv*

4Yvi:Yv>>>>"!

йЖ**-У:К*К**«

z
о

Щ <l jjffzziit

Ullllllllllllllllllllln,

JTHS

IV-V W W VJI IX X£

IV VII

YE/

\RS

/937

/9U7

Fig. 23 1 . Comparison of main groups
of phytoplankton in the Gulf of
Taganrog (Pitzik, 1951) : 1 Diatoms; 2
Peridineans; 3 Blue-green algae; 4
Green algae ; 5 Others.

Ш1 ШШ2 CZ]3 EZJ* (%3s

THE SEA OF AZOV 487

A. Okul and G. Pitzik, relate to 1937 and 1950; the picture may have been
different in other years. In particular P. Usachev (1927) notes that the blue-
green algae play an important part in the life of the Sea of Azov. This con-
tradiction may be explained by the erroneous picture obtained by the qualita-
tive method of investigation, since the blue-green algae accumulate mainly on
the surface of the sea. Apart from the spring, a mass development of the
Sea of Azov plankton is also observed in the summer and autumn up to
October. This course of plankton development, in the opinion of N. M. Kni-
povitch (1932), indicates that there is no shortage of nutrient salts in the water
of the Sea of Azov ; this is apparently due to the proximity of the bottom,
the rapidity of the processes of mineralization and regeneration, and generally
to a large amount of limiting nutrient salts.

The frequently observed saturation of the Azov Sea water with oxygen is
the result of a similar huge accumulation of algae in the water-column. A
case was mentioned above of the Sea of Azov phytoplankton reaching a
density of 300 to 400 g/m3, which approximately corresponds to the same
amount of grammes by weight. If the depth of that station was 8 m, up to
2 or 3 kg of phytoplankton alone could have been concentrated in a water-
column of 1 m2 cross section. Moreover, the plankton is often very unevenly
distributed — in patches and strips, carried about by currents and vertical
movements of the water. A particularly important development of plankton
can be observed in the western part of the Sea, sometimes in the middle part
of the Gulf of Taganrog.

Qualitative composition ofzooplankton. The qualitative composition of the Sea
of Azov zooplankton (G. Pitzik and A. Novoshilova, 1951) can be expressed
in the form of Table 199.

Table 199

Protozoa 14 species Copepoda 31 species

Coelenterata 6 species Mysidacea 1 1 species

Rotatoria 20 species Cumacea 6 species

Chaetognatha 1 species Amphipoda 2 species

Cladocera 17 species

Total 108 species

In addition the plankton usually contains a large number of the larvae
stages of polychaetes, brozoans, Cirripedia and decapod crustaceans which
live on the bottom. However, only 50 species in all are found in the main
basin of the Sea of Azov, and only a few of these develop in large masses.
Among the separate groups, divided according to their origin, those most
characteristic of the Sea of Azov are the following :

I. Novo-Euxine relicts (mainly in the Gulf of Taganrog) Evadne trigona,
Cercopagis pengoi, Heterocope caspia, Calanipeda aquae dulcis and
others.

488 BIOLOGY OF THE SEAS OF THE U.S.S.R.

II. Mediterranean immigrants. Mainly among the Copepoda : Acartia cluasi,
Paracartia latisetosa, Centropages kroyeri, Labidocera brunescens,
Oithona nana ; among the Tintinnoidae : Tintinnopsis minuta, T. meunieri,
T. tubulosa var. sub >acuta, T.relicta, Leptotintinnus pellucidus, L. botanicus;
among the Cladocera : Podon polyphemoides.
III. Fresh-water Cladocera and Rotatoria in the least saline sections (Lepto-
dora, Asplanchna and others).

Calanipeda aquae dulcis, Evadne trigona, Brachionus quadridentatus, B.
plicatilis and Pedalion oxyuris are particularly richly developed.

In the outer part of the Gulf of Taganrog Heterocope, Cercopagis and, in
the least saline parts, the fresh-water Rotatoria, Cladocera and Cyclopidae
are developed in large masses.

Zooplankton biomass. Quantitative investigations of the Azov Sea plankton
were carried out by F. Mordukhai-Boltovskoy (1938) and A. Okul (1940),
by G. Pitzik and A. Novoshilova (1951) and by A. Novoshilova (1955).

In the Sea of Azov the highest annual zooplankton biomass for the last
20 years was recorded in 1937 (Table 200). In recent years it has fluctuated

Table 200

Mean annual

Year

zooplankton biomass,

mg/m3,

in Sea of Azov

Year

zooplankton biomass,

mg/m3,

in Sea of Azov

1937

612

1941

502

1938

236

1947

388

1939

213

1948

132

1940

372

1949

386

considerably and was lowest in 1939 and 1948. Individual components of
plankton groups have also shown significant variations in particular years.
In the Gulf of Taganrog the zooplankton biomass has also fluctuated sub-
stantially from year to year. In 1937 it was very high (1,351-3 mg/m3) and still
higher (up to 2,082-7 mg/m3) in 1949. As has been shown by investigations
lasting for many years, before the flow of the river Don was controlled, the
total zooplankton of the Sea of Azov in early spring (March- April) consists
of 47 to 90 per cent Rotifera (Synchaeta). In May and June, side by side with
Copepoda and Rotatoria, the number of the larvae of bottom invertebrates
(Cirripedia, Vermes and Mollusca) increases greatly. In May 1949 and 1950
the biomass of the Cirripedia larvae formed 83 to 85 per cent of the total zoo-
plankton biomass in the northeastern part of the Sea (A. Novoshilova, 1958).
The number of Copepoda increases towards the beginning of the summer,
reaching 65 to 95 per cent of the total biomass (slightly less in the Gulf of
Taganrog), mostly on account of Acartia clausi and Centropages kroyeri, and
in the Gulf of Taganrog Calanipeda aquae dulcis and Heterocope caspia.

THE SEA OF AZOV 489

Table 201. Fluctuations of zooplankton biomass in the Sea of Azov in mg/m3
(A. Novoshilova, 1958)

Sea of Azov

Gulf of

Taganrog

Year

Feb

Apr

Jul

Aug

Oct

Apr

Jul

Aug

Oct

1938

463

367

272

175

1,835

240

747

1940

—

315

756

—

1941

—

942

—

— .

—

— .

—

1947

—

573

802

—

411

1,079

—

1948

—

263

—

180

— .

740

793

1949

—

833

319

—

2,728

1,914

—

1950

—

493

214

—

1951

—

189

483

509

596

213

1,134

1,506

—

1952

174

784

246

109

884

1953

—

104

517

232

—

129

449

1,105

1,110

1954

—

120

131

133

352

818

831

1955

338

534

254

517

562

1956

—

245

306

519

693

1,994

This was observed also in the autumn, when the 'marine' plankton moved
eastwards. In subsequent years the Sea of Azov zooplankton biomass decreased
owing to the change in the flow of the river Don {Table 201).

General quantitative characteristics of zooplankton and its seasonal
changes are given in Figs 232 and 233.

Fig. 232a. Alterations of zooplankton biomass in the Sea of Azov proper (Pitzik

and Novoshilova).

490

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Copepoda and Rotifera play a dominant part in the Sea of Azov zooplank-
ton. Their annual mean biomass, according to A. Okul's data, is 210 mg/m3,
i.e. more than 50 per cent of the total zooplankton biomass, with fluctuations

«n

E
<•>

3000
2800
2600

2400

2200
2000

1800

1600
1400

1200

1000

800

600

400

200

MONTHS

1^1**

>^ls*^

**!£

^Щ^

YEARS

/937

/938

/947

/948

/9*9

Fig. 232b. Alterations of zooplankton biomass in the Gulf of Taganrog (Pitzik and

Novoshilova).

from 10 to 600 mg/m3. Copepoda reach their greatest development in July
and August. Their main forms are Acartia clausia, A. latisetosa, Centropages
kroyeri and Calanipeda aquae dulcis (Figs. 233 and 234). The first and last
forms are found all the year round, the second and third reach their greatest
development during the warmest part of the year. In the Gulf of Taganrog

THE SEA OF AZOV

491

months E M (fi E w. Ш а К Ж ш

S. V

S Ш i HI С EJ I Ш

YEARS

/93 7

/947

f943

/949

\/ ШШ2 СЗз G34 CZ35

5ZD7 E3<5 888 э E^/i?

Fig. 233. Alterations of biomass of certain zooplankton species of the Sea of Azov
proper : 1 Copepoda ; 2 Rotatoria ; 3 Tintinnoidea ; 4 Mollusc larvae ; 5 Cirripedia ;
6 Cladocera; 7 Hydrozoa larvae; 8 Polychaeta larvae; 9 Mysidacea; 10 Others

(Okul, 1941).

Copepoda development is even greater than in the open part of the Sea of
Azov (on the average 70 per cent of all the zooplankton biomass ; in fact
1,500 mg/m3, chiefly consisting of Calanipeda aquae dulcis). The relict form
Heterocope caspia is very characteristic of the Gulf of Taganrog ; there is a
considerable admixture of fresh- water species in the most eastern part of the
Gulf. Cirripedia larvae play a substantial part in the Sea of Azov in June ;
42 per cent of zooplankton biomass consists of them, they yield up to 270
mg/m3. Their numbers are much smaller in the Gulf of Taganrog.

Among the other groups which go to form the Sea of Azov zooplankton,
that of the marine Infusoria Tintinnoidea should be mentioned first ; in spite
of its minute size, it gives a mean annual biomass of 39 mg/m3 (9-6 per cent
of the total zooplankton). During the period of its greatest development, in

SEA OF AZOV

GULF OF TAGANROG

too-

90-
80-

70-
60-

so-
но-
во-
го-

to ■
о ■

II III IV

m VIII IX X XI XII

Fig. 234. Composition and distribution of Copepoda in the plankton of the Sea of
Azov and the Gulf of Taganrog according to the months of the year (Okul, 1941).

492 BIOLOGY OF THE SEAS OF THE U.S.S.R.

July, Tintinnoidea forms 16-8 per cent of the total zooplankton. At times,
when the number of its specimens reaches 50 million per 1 m3, they yield a
biomass of more than 1 g/m3. In the Gulf of Taganrog the quantity of ciliates
is much smaller. Rotifera are also important in the Sea of Azov zooplankton,'
especially in the Gulf of Taganrog ; their annual biomass is about 25 per cent
of the total zooplankton, and in the spring even 80 or 90 per cent. Asplanchna
priodonta, Brachionus quadridentatus, B. plicatiles, Synchaeta baltica, S.
у or ax and Pedal ion oxyuris are the principal forms. There is a considerable
admixture of typical fresh-water forms, such as Keratella cochlearis, K.
quadrata, Triarthra longiseta and others, in the eastern part of the Gulf of
Taganrog. Mollusc larvae are found in the plankton of the Sea of Azov
almost all the year round, but they yield a considerable development in the
summer. In June they produce 94 mg/m3 (14-5 per cent of the total zooplankton
biomass). Finally, the Mysidacea, which rise from the bottom during the
hours of darkness, play a considerable part in the plankton. The main forms
here are Macropsis slabbed, Mesomysis helleri and also M. kowalewskyi in the
Gulf of Taganrog. The first of these forms produces at night in the Sea of
Azov 152 mg beneath 1 m2 of surface area, and in the Gulf of Taganrog even
185 mg; Mesomysis kowalewskyi in the Gulf of Taganrog produces 254 mg,
and M. helled in the Sea of Azov, 57 mg. A small part of the Sea of Azov
zooplankton consists of Cladocera (Evadne tdgona and Podon polyphemoides)
and polychaete larvae. G. Pitzik (1951) gave an interesting comparison of the
mass development of phyto- and zooplankton in the Sea of Azov and of the
significance of the first as food for the second : ' Early in the spring phyto-
plankton develops in such colossal quantities, that the scarce zooplankton
leaves much of it untouched. At that period for every gramme of zooplankton
there is 30 to 70 g of phytoplankton, including 27 to 66 g of diatoms and 2 to
4 g of peridineans. With such a ratio the main mass of phytoplankton,
dying off, is deposited on the sea-bottom ; together with the detritus which is
brought down in huge amounts by run-off from the land, it forms large de-
posits of organic matter. In late spring there are only 0-9 to 1-2 g of phyto-
plankton per 1 g of zooplankton . . . and the feeding conditions for zoo-
plankton, and through it for plankton-eating fish as well, may become un-
favourable. ... In the summer and at the beginning of autumn ... in the Sea
of Azov itself, there are 2 to 1 1 g of phytoplankton, among it 1 to 8 g of peri-
dineans per 1 g of zooplankton. ... In the Gulf of Taganrog during the warm
season . . . there are generally 2-5 to 7 g per 1 g of zooplankton ... the main
part of it consisting of blue-green algae. . . . ' The same relationship is retained
in winter in the Sea of Azov itself. 'Thus in the course of the year the most
favourable feeding conditions for zooplankton . . . are found in the summer
and at the beginning of the autumn, when the peridineans are preponderant
in the Sea of Azov itself . . . and the blue-green and green algae and flagellates
... in the Gulf of Taganrog.'

Reduction of the discharge of the river Don in 1950, caused by the regula-
tion of its flow, led to the salt-water fauna moving deeper up into the Gulf of
Taganrog and the fresh- water fauna receding. In 1951 the discharge of the
Don was considerably greater, and the Gulf fauna moved in the opposite

THE SEA OF AZOV

493

direction, but in 1952, when the Tsimlyansk reservoir was filled, the salinity
of the Gulf waters rose again and ' marine ' fauna again moved eastwards.
There were no marked changes in the zooplankton biomass during 1950-52
(A. Novoshilova, 1955). A clear illustration of this process of changes in

I 3 5 7 9 П S %„

5 7 9 I I 1 3 S %o

9 S°/c<

Г
О 1 00.

7 9 II 13 S%

Fig. 235. Relation between the quantitative development of the main zooplankton
species and the salinity of the waters (Yablonskaya, 1957). A Fresh-water Rotifera
{Brachionus annularis, Keratella cochlearis, Keratella quadrata, Polyarthra trigld);
В Synchaeta sp. (a spring form) ; С Asplanchna phodonta ; D Calanipeda aquae dulcis ;
E Acartia clausi; F Heterocope caspia; G Acanthocy clops vemalis; H Fresh- water
Cladocera (Daphnia longispina, Diaphanozoma brachyurum, Laptodora kindtii);
I Mysidacea (1 Macropsis slabbed; 2 Mesomysis kowalevskyi).

numbers with a change of salinity, as related to the Rotifera and Crustacea,
is given (Fig. 235) by Yablonskaya, who has also drawn a prognosis of
the distribution of the main zooplankton biocoenoses in the Sea of Azov
at different stages of the loss of river water due to irrigation measures
(Fig. 236).

494

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Fig. 236. Diagram of distribution of zooplankton communities (Yablonskaya, 1957) :
A At an average river discharge ; В At 15% of the river discharge ; С At 40% only
of river discharge; 1 Fresh-water community; 2 Brackish-water community;
3 Sea of Azov community ; 4 Black Sea community.

Benthos

Micro-organisms. Data on the bacterial population of the Sea of Azov were
also obtained by Knipovitch's expedition. Apart from the above-mentioned
micro-organisms, which give off hydrogen sulphide during the conversion
of sulphates into carbonates and produce this gas during the process of decom-
position of organic compounds, micro-organisms which oxidize hydrogen
sulphide, those which nitrify and denitrify, iron-depositing micro-organisms,
chitin-decomposing and other micro-organisms have been recorded in the
composition of the Sea of Azov micro-flora. B. Isatchenko (1924) carried out
a quantitative survey of the Sea of Azov bottom micro-organisms and obtained
for some coastal areas the sum of 274 to 776 million specimens per gramme
of the soil. If the average size of micro-organisms is 1 /x3, and their average
number 500 millions, than 1 g of the soil contains an approximate weight of
0-5 mg of micro-organisms. This, when converted to 1 m2, would give a huge
quantity for the mass of micro-organisms and gives some idea of the colossal
processes taking place in the sea-bed, especially if we keep in mind that the
annual production of micro-organisms in the Sea of Azov is hundreds and
maybe thousands of times greater than its biomass.

Only within the area of the Kerch Strait itself is the quantity of micro-
organisms greatly reduced.

THE SEA OF AZOV 495

The qualitative composition of the macrophytes of the Sea of Azov is consider-
ably impoverished as compared with the Black Sea. Instead of the 221 species
of green, red and brown algae of the Black Sea there are no more than 25 or
30 species in the Sea of Azov. The amount of algae decreases markedly as one
moves eastwards, and at the entrance to the Gulf of Taganrog red algae are
not found. In the Sea of Azov among the red algae the most widely distri-
buted are Ceramium diaphanum, Polysiphonia opaca and P. variegata ; among
the green species, Enteromorpha and Cladophora. The macrophytes populate
only a narrow band along the shore of the Sea of Azov. Apart from this
among the flowering plants Zostera marina, Z. nana (minor), Zannichelia
pedunculata and Potamogeton marinus are common in the Sea of Azov.

Continuous macrophyte beds are rare in the Sea of Azov, and only in the
Utlyuksk inlet and in the northern Sivash are there abundant growths of
Zostera, which are exploited commercially. According to V. Generalova the
maximum biomass of bottom-algae of the Utlyuksk inlet is 22-4 tons, and
that of calcareous plants 69-3 tons per hectare. According to the data of
M. Kireeva and T. Shchapova (1939) in those areas the amount of Zostera
occupying an area of 9,500 hectares is 25,000 tons dry weight.

According to V. Generalova (1951) Zostera forms about half of the total
mass of water macrophytes in the Sea of Azov, red algae form 35 per cent and
the green 1 5 per cent. Commercial stocks of macrophytes of the northwestern
part of the Sea of Azov are small (Table 202).

Table 202

Area

Biomass, tons

per hectare

Mini.

Algae

Max.

Zostera
Mini. Max.

Utlyuksk Inlet
Arabat Strelka

2,125
2,000

2,246

17,582 69,333
16,000 —

Qualitative composition of zoobenthos (Fig. 237). We do not possess sufficient
data for a complete list of species of the bottom-fauna of the Sea of Azov,
but we can make use of the incomplete list drawn up by F. Mordukhai-
Boltovskoy (1960). This list includes (with unimportant additions but without
Protozoa) 292 invertebrate species and sub-species (Table 203).

The crustaceans occupy the first place by the richness of their specific
composition and the number of specimens per unit area (about 3,670), but
as regards biomass the bivalves are considerably superior to the rest. The Sea
of Azov may be truly called the mollusc sea, or the Cardium-Syndesmya
sea, as the Baltic Sea can be called the Macoma sea; this may be illustrated
by the data given in Table 204.

The peculiar conditions of the Sea of Azov— its salinity lower than that of
the Black Sea, its marked seasonal fluctuations of temperature, its long
winter and shallow waters — lead to a definite selection of forms from the

496

BIOLOGY OF THE SEAS OF THE U.S.S.R.

9. SYNDESMYA OVATA
10. POLYCHAETA NEPHTHYS HOMBERGl"

II. MOLUSC HYDROBIA VENTROSA

1. PONTOGAMMARUS MOEOTICUS

2. BEDS OF ZOSTERA MARINA

3. MYTILASTER LINEATUS

4. NEREIS SUCCINEA

5. A STONE WITH BALANUS IMPROVISUS 12. BRACHINOTUS LUKASI

6. CARDIUM EDULE 13. OSTROUMOVIA

7. NEREIS DIVERSICOLOR M. BLACKFORDIA

15. GOLDEN SHINER

8. CARBULOMYA MAEOTICA

16. PIKE PERCH

17. ANCHOVY

18. CLUPEONELLA

19. STURGEON

20. STARRED STURGEON

Fig. 237. Character of the distribution of the main forms of the Sea of Azov fauna

(Zenkevitch).

considerably richer Black Sea fauna, which in its turn is a selected fauna
from the Mediterranean. In spite of this, a certain number of Mediterranean
forms find in the Sea of Azov conditions exceptionally favourable for their
development and form huge accumulations. As a result, the communities of
the Sea of Azov are often characterized by their large biomass and by their
high productivity indices and, at the same time, by the extreme poverty of
their qualitative composition (oligo-mixed communities). Of the 137 species
of benthos only 30 species are found more or less frequently.

Table 203

No. of

Group

species and
sub-species

Group

species and
sub-species

Porifera

Coelenterata

Turbellaria

7
4

Copepoda
Cirripedia
Ostracoda

2
3

Nemertini

Polychaeta

Oligochaeta

Hirudinea

Bryozoa

Rotatoria

Gastropoda

Lammellibranchiata

Amphipoda

Mysidacea

Cumacea

Isopoda

Decapoda

Chaetognatha

Tunicata

Pisces

29
11
10

3
8

Cladocera

Total

292

THE SEA OF AZOV 497

Table 204

Mean number Mean

Group of percentage biomass percentage

specimens/ 1 m2 g/m2

Bivalves

971

6-3

98-50

74-2

Crustaceans

11,345

74-0

15-26

11-6

Worms

1,939

12-6

7-50

5-8

Others

911

7-1

10-74

8-4

Total 15,166 100-0 1320 100-0

For its salinity the Sea of Azov should be included, according to Re-
mane's (1935) classification, in the mesohaline zone. The true relict brackish-
water fauna is concentrated in the inner part of the Gulf of Taganrog, living
there at a salinity below 3-6%0.

Zoobenthos biocoenoses. Bottom biocoenoses of the Sea of Azov, which were
comprehensively investigated by V. P. Vorobieff (1944), F. Mordukhai-
Boltovskoy (1939), and later by I. Stark (1951, 1955, 1958), can be divided
first of all into two large groups :

(1) Relict biocoenoses, with early Pontic relicts as dominant species —
Dreissena, Monodacna, Hypaniola and some species of Corophium and
Pontagammarus.

(2) Mediterranean or Azov-Black Sea biocoenoses, with Ostracoda as domi-
nant species as well as Corophium, Cardium, Syndesmya, Mytilaster,
Corbulomya, Hydrobia, Balanus, Nereis, Sphaeroma and Pectinaria.

However, both these groups, especially the first, are distinguished by a
strongly marked oligohalinity ; this, and the small difference in their living
conditions, leads to a great similarity in the type of biocoenosis, making easy
the transition of various combinations into each other.

The general picture of the autumn distribution of bottom biocoenoses and
of the biomass for 1934-35 is given in Fig. 238a, b. Let us consider the brief
characterization of individual biocoenoses marked on the chart, beginning
from the east.

Biocoenosis: Dreissena-Monodacna-Unionidae — In the most eastern corner
of the Gulf of Taganrog, in front of the Don delta on the estuarial shallows,
there are situated different variations of the Dreissena-Monodacna-Unionidae
biocoenosis. Nearer to the Don, in the least saline part, Dreissena is predomi-
nant. Only the most hardy forms can endure sharp fluctuations of salinity
and sometimes considerable drying-up caused by land winds. The mean bio-
mass here is 13 g/m2, of which Dreissena polymorpha forms 1 1 -6 g/m2. Among
the other forms the relict crustaceans Cumacea (Pterocuma sowinskyi, Steno-
cuma tenuicauda, species of the Schizorhynchus genus), Mysidacea (Metamy-
sis strauchi, Mesomysis kowalewskyi), Amphipoda {Corophium curvispinum,
Pontogammarus abbreviatus), the species of Gmelina genus, Oligochaeta

Fig. 238a. Distribution of bottom biocoenoses (see text) of the Sea of Azov in
autumn 1934-35 (g/m3) (Vorobieff, 1944). 1 Syndesmya-Hydrobia ; 2 Cardium;
3 Mytilaster ; 4 Balanus ; 5 Nereis-Ostracoda ; 6 Monodacna-Dreissena ; 7 Nereis ;

8 Corbulomya.

" ,i% ''"'

L Mess than 1 g.

^ШГгот! to 50 g.
Wmfrom50to200g.
ШШгот200 to 1000 g.
Wmfromt000to2000g.

Fig. 238b. Distribution of benthos biomass of the Sea of Azov in autumn 1934-35

(g/m3) (Vorobieff).

THE SEA OF AZOV 499

(Tubificidae) and Chironomidae, are of importance. 89-3 per cent of the total
biomass consists of molluscs, and 8-4 per cent of crustaceans. Marked varia-
tions of salinity, and its increase as one moves westwards, cause a decline in
the number of species.

In the most westerly part of the biocoenosis, on coastal sands and shell
gravel at depths of 1-5 to 3-5 m and around the Peschanye Islands, lives a
very much impoverished (2-6 g/m2) variant of this biocoenosis, with a pre-
dominance of the relict polychaete Hypaniola kowalevskyi, the crustacean
Corophium volutator and an oligochaete of the Tubificidae family. It is almost
free of fresh-water elements and molluscs (mainly Monodacna), and resem-
bles somewhat the following ostracode biocoenosis, but without the ostra-
codes or Tanypus. Apart from the above-mentioned forms, the presence of
the relict crustaceans Pterocuma pectinata and Gmelina ovata and the generally
pronounced relict aspect are characteristic of this group.

The Nereis diversicolor Ostracoda biocoenosis — In the western half of the
Gulf of Taganrog, on the soft dark so-called Ostracode muds, lives the Nereis
diversicolor Ostracoda biocoenosis, which also produces a number of vari-
ants. This biocoenosis penetrates far to the east along the deepest part of the
Gulf. In the westward direction the marine forms become gradually dominant
in it, although there is still a considerable admixture of Tubificidae and Tany-
pus. In the central, deeper part (below 4 m) of the Gulf of Taganrog Ostracoda
are markedly predominant in the benthos. With a very low average biomass
(9T2 g/m2) the biocoenosis has a strikingly large number of minute crustaceans,
whose shells, in innumerable numbers, compose the basis of the sea-bed (the
average number of live specimens of Ostracoda is 40,000 specimens per 1 m2,
at times up to 150,000, at a biomass of 3 to 6 g/m2, comprising more than half
the total biomass — 58 per cent).

In the Eisk inlet the Amphipoda Corophium volutator (more than 6,000
specimens per 1 m2 and 26 per cent of the total biomass) produces a large
biomass. Colonies of the relict polychaete Hypaniola kowalevskyi are just
as abundant here (up to 40,000 specimens per 1 m2). Among the other forms
the following should be noted: Nereis diversicolor, Tubificidae, Balanus
improvisus, Cardium edule and Monodacna color ata. In general 73-3 per cent
of the total biomass consists at times of crustaceans.

In the western half of the sector occupied by the Nereis-Ostracoda bio-
coenosis, at a depth of 4 to 8 m, Nereis diversicolor becomes more and more
significant. The biomass here is also low (an average of 23 g/m2) and 40 per
cent of it consists of Ostracoda (up to 230,000 specimens per 1 m2). Worms
(mainly Nereis diversicolor and Hypaniola kowalevskyi), comprising 47 per
cent by weight of the biomass, are almost as significant. Among the other
forms the molluscs Syndesmya ovata and Cardium edule and the crustacean
Corophium volutator should be noted.

The Nereis succinea biocoenosis — In the rest of the Sea of Azov, throughout
the coastal zone wherever there is a mud bottom, the biocoenosis Nereis suc-
cinea is found. The biocoenosis Nereis succinea is met in different biocoenotic
combinations, in the main with Ostracoda, Balanus, Cardium, Hydrobia,
Pterocuma, Mytilaster, Ampelisca and Corbulomya.

500 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Nereis diversicolor lives mainly in the Gulf of Taganrog, N. succinea in the
rest of the Sea. The variant N. diversicolor-Ostmcoda lives in the Gulf of
Taganrog all the year round. N. succinea possesses a more intensive faculty for
spawning than N. diversicolor ; it forms large numbers of eggs and it has some
pelagic larvae and heteroneroid forms. N. succinea probably pushes its rival
N. diversicolor out of the Sea of Azov into the Gulf of Taganrog, which is not
suitable for N. succinea owing to its low salinity. In the Black Sea, however,
with a salinity too high for N. succinea, N. diversicolor develops intensively,
forming powerful populations, and competes successfully with another
species — N. cultrifera.

Clamworms form excellent food for many fish of the Black and Azov Seas.
Ninety per cent of them are assimilated by fish, compared with only 77 per
cent of crustaceans, 85 per cent of fish and only 29 per cent of molluscs. The
high content of nitrogen (64 per cent) and fats (16 per cent) in clamworms
also increase their value as food.

As is known, Nereis of the Sea of Azov has been used for acclimati-
zation in the Caspian Sea in order to increase the feeding value of the
benthos for fish, primarily for the sturgeon. The results of this acclimatiza-
tion are given in Chapter II. Naturally, since Nereis has developed hugely in
the Caspian Sea, that system of competitive relationships with the local benthos
is of great interest. May Nereis do real harm to the benthos population of the
Caspian Sea? The system of synecological interconnection established for
Nereis in the Sea of Azov is of interest for the solution of this problem.
This has been comprehensively studied by I. Stark (1959). The latter confirms
the well known fact that Nereis succinea and N. diversicolor, like many other
nereides, thrive on ooze and vegetable detritus, and that they may take live
components of zoobenthos only accidentally and passively, together with their
main food, and that therefore they do no substantial harm to the rest of the
infauna, oligochaetes and chironomids included. Stark finds proof of this in
the frequency of the occurrence of dense nereides colonies within the areas
of high indices of the number of specimens and biomass of those more passive
forms of infauna which could have suffered from the nereides. Thus in the
Gulf of Taganrog, where the nereid biomass is highest, chironomids, oligo-
chaetes and Hypaniola reach their greatest development.

The Pontogammarus maeoticus biocoenosis — The only relict, and the most
oligo-mixed, biocoenosis found throughout the whole of the Sea of Azov,
apart from the Gulf of Taganrog, on sloping sandy beaches, right at the
water's edge and within the regularly washed zone, is Pontogammarus maeo-
ticus. The biomass and number of organisms in this biocoenosis varies greatly,
reaching occasionally (in places with broken sea-weeds and detritus) 80,000
specimens of P. maeoticus per 1 m2, with a biomass of 642 g/m2. P. maeoticus
does not tolerate an accumulation of rotting sea- weeds since it is a steno-oxy-
biotic form. P. maeoticus is also rare on pure sand. In unfavourable weather
(strong swell, gales) and in winter time the whole mass of P. maeoticus
migrates into deeper waters. This form is found up to 10 m deep as a com-
ponent of almost all biocoenoses of the Sea of Azov.

The Cardium edule biocoenosis — The Cardium edule biocoenosis begins

THE SEA OF AZOV 501

in the most westerly part of the Gulf of Taganrog ; it is very widely distri-
buted in the open parts of the Sea of Azov, and in 1934 occupied about one-
third of its bottom.

A bottom-area of 10,000 km2 of the Sea of Azov is occupied by this bio-
coenosis in the spring, and 12,000 km2 in the autumn. The widening of its
habitat is due to its pushing out other biocoenoses {Nereis succinea, Syn-
desmya, Mytilaster).

Cardium does not form such massive populations in the Black Sea as in
the Sea of Azov, where it has found exceptionally favourable conditions for its
mass development. Cardium edule is a typical filter-feeder since it lives on
plankton and detritus suspended in water; it competes with Mytilaster,
Balanus and Corbulomya in its feeding, forming with them a powerful filter.
Huge plankton development and the abundance of detritus in the Sea of Azov
create most favourable conditions for the existence of C. edule. This biocoeno-
sis reaches its highest development on silty sand bottoms. This species is also
widely distributed in the Atlantic Ocean, reaching the western part of the
Murman peninsula in the north. The Baltic Sea also is thickly populated by
it. In the northern part of the Atlantic C. edule is adapted mainly to the tidal
zone and is a typical littoral organism. Thus it is a very widely distributed
eurytopic species, with a great capacity for adapting itself to different condi-
tions of life : temperature, salinity, soils and depths. This mollusc is devoured
in large numbers by fish (in the Sea of Azov by bullhead, Acipenseridae, flat
fish, golden shiner, roach, Rutilus rutilus heckeli and others); for many
thousands of years it has also been used as food by man.

As a result of C. edule 's capacity for adapting itself to different conditions
of existence, numerous varieties have been evolved from it ; C. edule var.
maeotica lives in the Sea of Azov, while in the Utlyuksk inlet and the Sivash
С edule var. picta is also found.

In the Sea of Azov C. edule is found on various sea-bottoms, but it prefers
soft beds. A single biomass of this mollusc varies from a few grammes to 2 kg
and more per 1 m2. C. edule does not require a great amount of oxygen but it
cannot survive a considerable lowering of oxygen content. In the Sea of Azov
its greatest numbers are adapted to a depth of 6 to 10 m. At a greater depth
it is replaced by Syndesmya ovata. Since Cardium is fairly tolerant to consider-
able fluctuations of salinity it can compete successfully with all the forms of
benthos of the Sea of Azov ; Mytilaster alone pushes it out on the harder sea-
bed of the Zhelezinskaya Bank, while Corbulomya does so on sand, or silty
sand bottom at a depth of less than 4 m. C. edule begins to multiply during
the second summer of its life, but its breeding reaches its greatest intensity
only in its third or fourth summer. С edule may perhaps breed three times a
year, laying some tens of thousands of eggs.

A comparison of the rate of growth of C. edule off the English and German
coasts shows that in the Sea of Azov it is much slower and that C. edule does
not reach as advanced an age. As regards the rate of growth this can appa-
rently be explained by lowered salinity and by the unfavourable aeration
conditions of the Sea of Azov, and partly also by the higher temperature,
causing earlier sexual maturity ; the shorter life-span of the Azov C. edule

502

BIOLOGY OF THE SEAS OF THE U.S.S.R
Table 205

Sprir

Autumn

Name of form

No. of

specimens per
1 m2

Biomass

g/m2

specimens per
1 m2

Biomass
g/m2

Cardium edule

395

279-10

1,426

754-61

Syndesmya ovata
Nereis succinea

1,464
139

93-83
7-58

462
463

42-03

5-42

Balanus impr о visits

143

6-81

564

21-02

Hydrobia ventrosa
Mytilaster lineatus
Nephthys hombergi
Corbulomya maeotica
Ampelisca diadema

1,483

1,211

3-18
4-60
1-54
2-25
1-07

2,778

140

5-13
11-51
1-19
015
0-21

Ostracoda

913

010

2,000

010

Brachinotus lucasi

—

3-69

Others

5-81

154

0-66

Total

6,028

396-86

8,163

845-72

must be explained by the latter. In the Sea of Azov five-year-old C. edule are
23 to 26 mm long, while the English ones are 39 to 42 mm; moreover, off the
shores of England they live up to nine years, and off the shores of the Murman
peninsula to eleven years, and they attain an even bigger size. Cardium, like
Nereis, takes part in various biocoenotic groupings in different parts of the
Sea.

Cardium-Syndesmya is the most usual grouping found in the Sea of Azov,
mostly at depths of 8 to 16 m and on mud-floors. The quantitative ratio of
individual components for the whole C. edule biocoenosis is given in Tables
205, 206 and 207. Thus the gain in weight in C. edule biomass consists of the
settling of the young, the migration of the one-year-old from the deeper parts,
and the growth of all age groups. The loss of biomass is the result of the three
first age groups being devoured (fish do not feed on four- and five-year-olds) ;

Table 206

Spring

Autumn

Groups No. of
specimens
per 1 m2

Biomass
g/m2 %

No. of
specimens
per 1 m2

Biomass
g/m2 %

Lamellibranchiata 3,138
Gastropoda 1,483
Vermes 176
Crustacea 1 ,076
Balanus 143

375-78
3-18
9-40
1-64
6-81

94-76
0-80
2-37
0-41
1-71

2,033
2,778

598
2,190

564

803-30 95-58

513 0-60

6-99 0-82

4-16 0-49

2102 2-49

THE SEA OF AZOV 503

Table 207

Forms

No. of specimens
per 1 m2

Biomass
g/m2

Cardium edule

467

151-5

Syndesmya ovata
Hydrobia ventrosa
Nephthys hombergi
Nereis succinea

2,740

14,321

151-3
14-85
1-69
2-14

Balanus improvisus
Ostracoda

30
1,563

2-20
016

Corbulomya maeotica
Others

10
19

1-46
0-96

Total

19,249

326-26

it is, moreover, possible to show that the comparative percentage of the young
stages in the regions of intensive feeding of fish is very low as compared to
regions where fish do not feed. On the Zhelezinskaya and Eleninskya Banks,
where fish feed intensively, the young of Cardium forms only 12-4 per cent
in comparison with the adults, while along the Arabat Strelka, where there
are fewer fish, this percentage rises to 55-7.

Vorobieff (1944) has estimated the consumption by fish of young Cardium
at 3 1 to 77 per cent by comparing these data. Knowing the numbers of settled
young it can be calculated that the fish consume 644 specimens with a bio-
mass of 102-4 g/m2. Similar data were obtained by Vorobieff when he deter-
mined the amount of young Cardium eaten by fish from their intestinal con-
tent. I.t was calculated in the same way that the amount of one-year-olds
consumed by fish is 70 per cent as compared with those under one year, and
184 per cent of two-year-olds. The loss of Cardium due to consumption by
fish from May to November in the biocoenosis under consideration is given
in Table 208 (calculations were carried out for those under one year).

After making some corrections Vorobieff concludes that 661 g/m2 of
Cardium are consumed. The difference in the average biomass, from spring

Table 208

Consumption
Age group No. of specimens Biomass

per 1 m2 g/m2

Under one year

One-year-olds

Two-year-olds

Three-year-olds

Four-year-olds

644

102-40

450

179-55

238

31600

59-71

—

7-28

Total 1,354 664-94

504 BIOLOGY OF THE SEAS OF THE U.S.S.R.

to autumn, for the Cardium biocoenosis is 185 g/m2. Hence to a first apoprxi-
mation, the actual production of Cardium in this biocoenosis is 1,146 g/m2.
The P/B coefficient for the original spring biomass will be 1,146 :279 = 4: 1.

Balanus sometimes settles on mollusc shells in large numbers and take away
tieir food and oxygen. On the other hand, Mytilaster young also settle at
times on the Balanus cases and even on top of them, tightening up the cases
with their bysus threads. By taking away its food and oxygen and in a purely
mechanical manner Mytilaster young, when settling in masses, may destroy
B. improvisus. The destruction of one of the components of this close sym-
biosis may cause the destruction of another, especially when a mass of B.
improvisus settles on С edule. The mollusc dies and stops the aeration of the
water, and the Balanus settled there are deprived of their food.

In fish feeding-grounds masses of С edule and M. lineatus are devoured and
B. improvisus acquires a dominant position. Moreover, the last named grows
more vigorously than its rivals, but it multiplies less intensively. It produces
hundreds of eggs, while C. edule produces tens of thousands and Mytilaster
hundreds of thousands. Thus the changes in the groupings Balanus, Mytilaster
and Cardium, and their transition from one into another, are caused primarily
by their struggle for the site, food and oxygen, and by their being eaten by
fish. Large areas of sea-bed at depths of 6 to 8 m with hard soils, in cases when
Cardium, Mytilaster and Syndesmya are devoured in masses by fish, are
rapidly populated by the intensively developing Balanus, which has a very
long period of puberty. This might be the reason why the Balanus improvisus
biocoenosis is found in patches, mainly along the routes along which fish
travel. Moreover, the considerable washing out of the bed soil during a vio-
lent swell affects Cardium and Mytilaster very strongly, while a low oxygen
content kills off Balanus. That is why a biocoenosis with a marked pre-
dominance of Balanus is more often found in the autumn than in the spring,
Its total area in the spring is 607 km2, and in the autumn 2,200 km2. Apart
from on rocks and cliffs, which are rare in the Sea of Azov, Balanus develops
best on shell gravel, either pure or with an admixture of sand or mud, at a
depth of 4 to 6 m.

As with other bottom groupings of the Sea of Azov, so with the biocoeno-
sis in which Balanus is predominant one can readily establish its plasticity
and the most varied combinations with other mass benthos species, especially
Nereis succinea, Cardium edule, Mytilaster lineatus, Hydrobia ventrosa,
Syndesmya ovata and Brachynotus lucasi.

The P/B ratio of Balanus improvisus varies within the limits of 1 to 4-76
in different biocoenoses, depending on the density of the population of other
species present and primarily, of course, on that of Balanus itself (intra-
specific and inter-specific competition). Another variant of the Cardium bio-
coenosis, scattered in separate patches like the previous one, is the variant
with a marked predominance of Mytilaster lineatus. The main accumulations
of M. lineatus were adapted to the Zhelezinskaya Bank, off the craggy
southern shores of the Sea of Azov and also to the coast of the Arabat
Strelka. On the Zhelezinskaya Bank it had pushed out almost all the other bio-
coenoses. The total area occupied by this grouping — 1,470 km2 — is almost

THE SEA OF AZOV

505

one and a half times greater in autumn than in spring. The species invariably
accompanying M. Hneatus are, in order of decreasing importance, Balanus,
Cardium and Nereis succinea. In contrast to all the other biocoenoses of the
Sea of Azov, the M. Hneatus grouping is more stable and permanent. The
quantitative ratio of different species in this biocoenosis is given in Table
209.

In the spring M. hneatus is represented in the biocoenosis by two age-
stages; the one-year-olds (on the average 4,904 specimens per 1 m2) and the

Table 209

Spring

Autumn

Species

No. of

specimens per

Biomass

specimens per

Biomass

1 m2

g/m2

1 m2

g/m2

Mytilaster Hneatus

5,277

279-00

10,810

600-83

Balanus improvisus

1,282

61-28

1,609

62-30

Cardium edule

203

38-85

63-35

Nereis succinea

230

1602

915

9 06

Syndesmya ovata

11-20

0-53

Ampelisca maeotica

143

3-35

0-18

My til us galloprovincialis

511

—

Hydrobia ventrosa

358

1-40

146

0-23

Brachinotus lucasi

0-90

7-00

Microdeutopus gryllotalpa

0-21

686

0-50

Corbulomya maeotica

2-5

0-40

—

Others

117-5

100

305

1-80

Total

7,706

415-72

14,644

745-78

two-year-olds (374 specimens per 1 m2). It begins to multiply in April and
ceases to do so in August. The two-year-olds breed in April ; in May and June
the one-year-olds also begin to multiply. In the autumn those under one
year also begin to breed (7,812 specimens per 1 m2). During this time the
number of one-year-olds and two-year olds is reduced (2,890 and 108 speci-
mens per 1 m2) as a result of their being eaten by fish (bullheads, golden shiner,
roach and the Acipenseridae). Thus, the loss of one-year-olds from May to
November is 2,014 specimens, and that of the two-year-olds 266 specimens
per 1 m2.

It has been established that the losses suffered by the one-year-olds per
1 m2 are 160-32 g; of the two-year-olds, 81-66 g; and of those under one year
338-75 g. These data were obtained by examination of the variations of M.
Hneatus from different places, by the calculation of losses due mainly to their
being eaten by fish, by the analysis of stomach-content of fish and by making
use of the average weight of molluscs of a certain size. The total amount of
all three age groups of M. Hneatus eaten by fish from May to November is

506 BIOLOGY OF THE SEAS OF THE U.S.S.R.

about 579-73 g/m2. The autumn increment of biomass {Table 209), obtained
in spite of this loss, is the result of intensive increase of the molluscs remaining
in the population. The actual production of M. Meatus can be determined as
900 g/m2, while the average P/B ratio is 3-22. This high ratio for the Sea of
Azov is explained by its high temperature and the abundance of food.

The Syndesmya ovata biocoenosis — In the deepest part of the Sea, beyond
the Cardium edule biocoenosis, there lay in 1934-35 the Syndesmya ovata
biocoenosis, occupying an area of about 14,500 km2; this latter is somewhat
reduced in the autumn, since it is replaced by its contiguous C. edule bio-
coenosis. In the deepest part of the Sea (12 to 13 m), over an area of 4,500
km2, the number of Syndesmya is small, and the gastropod mollusc Hydrobia
ventrosa is predominant. In a wide zone surrounding this deepest part (10 to
11 m), over an area of 10,000 km2, Syndesmya ovata is greatly preponderant,
while at depths less than 9 m Syndesmya is replaced by Cardium.

S. ovata is one of the most numerous molluscs in the Sea of Azov. In the
Black Sea it is mostly found in fairly shallow low-salinity sectors, especially
under the roots of Zostera and the Chareal sea-weeds in lagoons and inlets.
This species is widely distributed in the Mediterranean Sea and in the Atlantic
Ocean off the coast of Europe. Specimens living on sand or shell gravel are
larger in size (up to 25 mm) and have a thicker shell, while on mud soils
they are smaller (up to 20 mm) and have a thin transparent shell. In the Sea
of Azov they live in largest numbers on silt or silty sand. S. ovata feeds on
detritus and dwells in the upper layer of the sea-bottom. It has extensible
siphon-tubes which help it to endure the unfavourable gas conditions of the
near-bottom layer. In general this species is hardier than C. edule and goes
to greater depths in the Sea of Azov than other molluscs, excepting only
Hydrobia ventrosa, and it is adapted to the zone of 'blackened shell gravel'
with an admixture of mud, in which the proportion of fines is 40 to 50 per cent.
In deep and less well-aerated sectors of the bottom Syndesmya displaces
Cardium; both molluscs are found in almost equal numbers at depths of
9 to 10 m ; in higher layers Syndesmya is replaced by Cardium. S. ovata is
found at all depths from 1 to 13 m in the Sea of Azov, but it reaches a maxi-
mum at 10 to 1 1 m. However, in shallower places (4 to 6 m) S. ovata produces
a second maximum on silty sand or shell gravel and mud, since it does not
find there its powerful rivals Cardium and Mytilaster, which displace it at
depths of 6 to 9 m.

This eurytopic capacity of S. ovata is also shown in its response to salinity.
In the Sea of Azov it survives salinity fluctuations of 5-5 to 7-0%0 in the Gulf
of Taganrog and up to 55%0 in the Sivash. Its optimum, however, is reached at
9 to 12%0. It can live in the presence of hydrogen sulphide and ammonia and
can even exist for some time (5 to 8 days) under anaerobic conditions.

S. ovata is one of the favourite foods of almost all the bathypelagic fish
of the Sea of Azov, especially sturgeon and golden shiner, and it has a high
food-value, partly due to its small size and thin shell.

S. ovata has a very high fecundity : the number of its eggs reaches some
hundreds of thousands. It breeds from the end of April to the end of Septem-
ber. 51. ovata reaches its sexual maturity in the third year of its life, rarely in

THE SEA

OF AZOV

507

Table 210

Spring

Autumn

Species

No. of

specimens per
1 m2

Biomass
g/m2

specimens per
1 m2

Biomass
g/m2

Syndesmya ovata
Cardium edule

2,143
49

181-40
15-72

3,765
62

285-15
48-75

Hydrobia ventrosa
Nereis succinea

3,663
93

5-00
4-83

2,893
142

4-66
5-26

Nephthys hombergi
Ostracoda

48
2,772

1-99
0-42

73
1,077

2-95
015

Corbulomya maeotica
Ampelisca diadema

28
17

0-57
0-26

2
0-4

010
000

Balanus improvisus

0-43

2-48

Mytilaster lineatus
Others

3-48

21
16-6

2-46
0-29

Total

8,838

214-10

8,083

352-25

the second. S. ovata has two mass larvae spat-falls, in June and in August-
September. The characteristic features of the S. ovata biocoenosis and its
separate components are shown in Tables 210 and 211.

The amount of S. ovata consumed by fish per 1 m2 (it is the prey also of the
small crab Brachynotus lucasi) was calculated by Vorobieff in a manner
similar to that used for Cardium edule and appears by components in Table
212. .

The processes of growth, however, prevail over losses, and by November
the biomass is 100-75 g/m2 greater than that of the spring. As for the preced-
ing species in the winter natural mortality must take place, thereby bringing
the autumn numbers down to the spring ones. The actual production of
S. ovata is 377 g/m2, and its P/B coefficient is equal to 2-05.

Table 211

Spring

Autumn

Groups

No. of

specimens per

Biomass

specimens per Biomass

1 m2

g/m2

lm2

g/m2

°/o

Bivalves

2,222

200-74

93-77

3,850

336-46

9500

Gastropods

3,663

506

2-36

2,893

4-66

1-32

Worms

155

6-87

3-21

222

8-70

2-43

Balanus

0-43

0-20

2-48

0-70

Other crustaceans

2,722

0-93

0-43

1,086

1-88

0-53

Others

—

006

003

—

008

002

508

BIOLOGY OF THE SEAS OF THE U.S.S.R.
Table 212

Age group

Under one year
One-year-olds
Two-year-olds
Three-year-olds

Total

No. of specimens

3,756

683

371

3,817

Weight, g

68-36

78-55

124-66

4-71

276-27

The central, deepest (11 to 13 m) part of the Sea, over an area of 4,500
km2, is inhabited by the variant Hydrobia-Nephthys-Syndesmya of this bio-
coenosis. It lives on grey liquid clay-mud with a small admixture of blackened
shell gravel, which smells of hydrogen sulphide. This biocoenosis consists of
about 16 species only; most of them, moreover, are temporary inhabitants,
while the permanent components of the biocoenosis are Hydrobia ventrosa,
Nephthys hombergi, Nereis succinea and Syndesmya ovata, which are the most
eury-oxybiotic species. Among the other species only Corbulomya maeotica
and Cardium edule are found more or less frequently. A remarkable feature of
this group, which is determined by the phenomenon of suffocation frequently
occurring there, is the marked uniformity of the age of the mollusc popu-
lations, which have settled after the suffocation and survive until the following
one. Considerable numbers of Cardium edule migrate, as a result of a shortage
of oxygen, into the neighbouring shallower sectors of the sea-bottom. The
density of the population fluctuates greatly from zero up to 38,400 speci-
mens per 1 m2, and its biomass up to 120 g/m2. The predominant biomass is,
however, 10 to 15 g/m2. The relationship between the components and the
fluctuations from spring to autumn are given in Table 213.

Among all the species found in this grouping a gain in biomass is observed
only with Syndesmya ; moreover its PjB ratio is only 0-99 here. For all the

Table 213

Spring

Autumn

Species

No. of

specimens per '.

1 m2

Biomass
g/m2

No. of
specimens per
1 m2

Biomass
g/m2

Hydrobia ventrosa
Nephthys hombergi
Nereis succinea
Syndesmya ovata
Corbulomya maeotica
Cardium edule
Others

2,736

213

6-43
2-94
2-25
2-65
0-59

005

3,131

1Л82

82
22
21
91

6-28
2-07
1-42
5-29
0-41
3-02
0-64

Total

3,104

14-91

4,579

1913

THE SEA OF AZOV

509

others an increase in the number of specimens with a decrease of biomass is
observed during the summer ; this is either caused by replacement of the older
age groups by the young, or is the result of a reduction of density and bio-
mass.

The Corbulomya maeotica biocoenosis — This biocoenosis is adapted mainly
to depths of 1 to 6 m off the coasts. It reaches its maximum at depths of
2 to 4 m on pure sand with shell gravel or on slightly silty sand. In the spring
it occupies an area of 1,270 km2, but in the autumn only 819 km2, being re-
placed by Cardium edule which comes up from the deeper sector. The most
usual components of this biocoenosis are Nereis succinea, Ampelisca diadema,

BOUNDARIES OF BIOCOENOSES /

//933 f /334-35 fl936

Fig. 239. Displacement from west to east of the boundaries of bottom biocoenoses
of the .Gulf of Taganrog under the effect of the rise of salinity in 1933-36 (Morduk-
hai-Boltovskoy, 1939). / Monodacna-Dreissena-Unionidae; II Monodacna; ///
Ostracoda-Hypaniola-Corophium-Tubificidae ; IV Nereis-Ostracoda ; V Cardium.

Cardium edule and Syndesmya ovata, which form different quantitative com-
binations with Corbulomya.

Many of the biocoenoses of the open parts of the Sea of Azov which have
been considered Hve also in the Utlyuksk inlet, where they undergo great
changes in their composition owing to a considerable admixture of Black
Seas relicts, which have survived there as a result of somewhat higher salinity,
and especially of such forms as Cerithiolium reticulatum, Pectinarianeapolitana,
Cardium exiguum, Rissoa euxinica, R. venusta and others.

Seasonal and annual migrations of biocoenoses. A noticeable migration of
marine benthic biocoenoses eastwards into the Gulf, brought about by the
fluctuation of the outflow from the Don, was observed by F. Mordukhai-
Boltovskoy (1939) when he compared quantitative-biocoenotic data on the
Gulf of Taganrog benthos in 1933 with those for 1934-36 (Fig. 239). A con-
siderable loss of salinity in the Gulf in 1932 was caused by the abundance of
the Don spring outflow, which in previous years had been much lower and

510 BIOLOGY Of THE SEAS OF THE U.S.S.R.

had caused a rise of salinity. As marine biocoenoses advance, the brackish
water and relict biocoenoses recede eastwards. This is particularly noticeable
in the case of the Monodacna biocoenosis in the east and those of Cardium
and Syndesmya in the west.

The benthos biomass of the Sea of Azov undergoes considerable changes
from spring to autumn. Generally it is doubled, but not in all sectors ; at times
it remains unchanged, at times it is reduced. The absence of changes in the
biomass may be the result either of poor productivity, or high mortality, or a
considerable consumption by fish. Throughout all the central part of the
Sea the biomass remains almost unchanged ; the cause of this must be sought
in the low productivity of the Hydrobia grouping as a result of unfavour-
able living conditions and suffocation. The absence of increase in biomass in
the coastal sectors of the eastern and northern part of the Sea, in the 5 to 6 m
zone, is attributable to considerable consumption by fish, since in the summer
bream, roach, starred sturgeon and bullheads are concentrated here, especially
in the eastern part of the Sea. In these areas benthos consumption by fish may
be so intensive that the biomass decreases. It is particularly intensive off the
Achuev and Akhtarsk inlets, on the Zhelezinskaya and Eleninskaya Banks,
at the entrance into the Gulf of Taganrog and in some other areas. Shoals of
commercial fish are most frequently found in these places. Vorobieff based the
organization of a commercial survey on these data which he had obtained,
and his expectations were to a great extent justified. In the Sea of Azov the
consumption of benthos by fish rarely takes on a catastrophic character.
Benthos left over in the autumn is represented, apart from the older age
groups, by the numerous young, and the biomass may not only be restored
later on account of its growth, but may even be increased. It may be assumed
that greater consumption corresponds to a greater concentration of fish. In
his calculations of the amount of benthos consumed by fish Vorobieff takes
50 g/m as unity. Vorobieff fixed the grounds where fish would probably shoal
for feeding in a similiar manner by examining the dynamics of benthos and
the transition of one community into another, as a result of fish eating the
benthos in spring time.

The distribution of benthos biomass in the Sea of Azov (see Fig. 238b) is
very irregular and is characterized by considerable patchiness. Areas of high
biomass alternate with sectors of very low biomass. In the open part of the
Sea of Azov, in spite of its considerable variegation, it is possible to trace a
concentric distribution of zones of increasing biomass from the centre of the
Sea to its periphery, followed by a fall in biomass as the coast approaches.
The outline of the biomass in a latitudinal cross section passing through the
central impoverished zone is shown in Fig. 240 ; the ring of high biomass en-
circling the central deeper part is very evident here. Given the phenomenon
occurring in the Sea of Azov of the suffocation of bottom fauna, and the
equally massive phenomenon of the consumption of the fauna by fish, the
huge spat-fall of larvae and the subsequent development of mollusc popu-
lations of uniform age can proceed over the areas — and in some years they
are very wide areas — which have been freed from living organisms. The dis-
tribution of the large number of larvae is controlled by the direction of the

THE SEA OF AZOV

511

currents. In this way the combination of currents and soils favourable to the
development of the large numbers of larvae carried in by the currents, i.e.
soils found red on their journey which either are slightly populated or have
been altogether deprived of organisms, creates conditions for the develop-
ment of the populations of uniform age which are so characteristic of the
benthos of the Sea of Azov. The theory of soil-currents is expounded by
the English investigator F. Davis (1924) for the North Sea and is more applic-
able to the Sea of Azov than to any other. The distribution of some patches

Fig. 240. Benthos biomass of the Sea of Azov in a cross section (meridional direction

from Arbat Banks to Achuev shoal head, which crosses the deep central part of the

Sea (data of Vorobieff and Mordukhai-Boltovskoy).

along a circular current in the Sea of Azov seems to confirm this point of
view. These patches will move from year to year according to the life-span of
the molluscs in the direction of the currents, depending on the distribution
of soils and the bottom topography, and then after an interval they will
occur again in their old places. Larvae will not be able to develop in places
occupied already by a powerful population of some other organism ; they
will perish there in masses. Such patches of molluscs will exist for 3 to 4 years
if the population neither dies nor is eaten by fish in a shorter time — which
may be almost an annual occurrence in the deeper parts of the Sea of Azov.

General assessment of zoobenthos productivity. A quantitative investigation of
benthos and its productivity carried out by Vorobieff and Mordukhai-
Boltovskoy enabled the former to calculate the indices of biomass and pro-
ductivity of the Sea of Azov benthos with the greatest accuracy possible at that
time, both in its total and for the different biocoenoses discussed above and
their variants for 1933-35 {Table 214).

A comparison of the biomass indices of the Sea of Azov with those of other
seas shows that the Sea of Azov is in a class by itself. The average benthos
biomass of the Sea of Azov was 418 g/m2 in the autumn, while the average for
the years 1934 and 1935 was 313 g/m2.

512

BIOLOGY OF THE SEAS OF THE U.S.S.R.
Table 214

Actual annual

Groups

Biomass

tons

production PjB

Spring

Autumn

tons

Dreissena

5,888

10,592

17,404

Monodacna

69,741

125,533

216,432

Ostracoda-Corophium

7,392

13,305

21,878

Ostracoda-Tubificidae

14,780

26,604

43,748

Hypaniola

1,074

1,933

3,178

Nereis

33,465

60,237

99,056

Cardium

41,106

73,990

121,670

For the Gulf of Taganrog

176,446

312,194

513,366 ca. 21

Groups proper to Sea of

Azov

Cardium

3,969,503

10,215,450

13,116,488

Syndesmya

2,337,950

2,693,940

1,352,762

Mytilaster

611,520

1,527,808

2,565,606

Corbulomya

425,785

398,749

—

Hydrobia

71,245

83,087

43,815

Balanus

60,093

473,000

1,527,755

Nereis

26,767

5,005

—

Pontogammarus

237

170

—

Pectinaria

325

—

Sphaeroma

—

For the Sea of Azov

proper

7,503,438

15,397,209

18,606,426 ca. 1-6

For the whole of the

Sea of Azov

7,676,884

15,709,403

19,119,792

Changes in the Sea of Azov benthos over a period of many years. I. Stark, con-
tinuing the researches of Vorobieff and Mordukhai-Boltovskoy, has prepared
a series of comprehensive studies (1951, 1955, 1958) of the benthos of the Sea
of Azov. She has brought greater precision into the picture of benthos distri-
bution in the northeastern part of the Sea and the Gulf of Taganrog up to
1952. In her survey of the general course of quantitative changes of benthos,
in the areas she investigated where Sea of Azov fish have their main feeding
grounds, Stark notes that the loss of benthos biomass in areas of large con-
centrations of fish as a result of suffocation, consumption by fish and natural
mortality, exceeds at some seasons of the year (summer and autumn) the.
gain by breeding and growth.

In other seasons (late autumn and spring) the picture is reversed, gain ex-
ceeding loss. The loss of benthos in winter time is due to natural mortality
and sometimes to suffocation of the fauna. After a huge extinction of fish
by suffocation in 1937 the quantity of benthos continued to decrease for

THE SEA OF AZOV

513

several years, and Mytilaster was almost completely replaced by Cardium.
The increase of benthos up to 1947 was mostly due to Cardium (Fig. 241).
The amount of benthos continued to decrease, and by the autumn of 1948
its mean biomass was reduced to 106 g/m2 in the northern part of the Sea of
Azov. In Stark's opinion these changes in the quantitative composition of the
benthos may have been partly the result of silting, linked with the abundance

kwto

Fig. 241. Bottom biocoenoses of the Sea of Azov (occurrence at the stations (Stark,
I960)). 1 Mytilaster; 2 Cardium; 3 Brachynotus; 4 Syndesmya; 5Balanus; 6 Hy-
drobia ; 7 Nereis ; 8 Corbulomya ; 9 Nephthys.

of flood waters in 1937-39, which had an unfavourable effect on fauna which
avoids soft mud bottoms (Mytilaster, Balanus and others).

Bottom-fauna of the Gulf of Taganrog varies considerably from year to
year; Stark (1955), as well as Mordukhai-Boltovskoy (1948), connects these
fluctuations with the changes in the spring floods of the river Don. During the
years 1933-35 Cardium, Balanus, Hydrobia and other more salt-loving species
were widely represented in the benthos. Those were years of low spring floods.
In 1948, when floods were high, the role of these forms became insignificant,
but after the exceptionally low floods of the Don in 1949 and 1950 a pro-
nounced increase of marine fauna, principally the inferior food forms Balanus

514 BIOLOGY OF THE SEAS OF THE U.S.S.R.

and Cardium, began to be observed. The exceptionally low floods of 1949
and 1950 evoked great changes in the benthos not only of the Gulf of Tagan-
rog, but also of the whole Sea of Azov. In the eastern part of the Sea the
Mytilaster biocoenosis almost completely disappeared, and, as I. Stark has
pointed out (1955), 'in 1951 more substantial changes occurred in the benthos
of the Sea of Azov than in the 15-year period since the work of Vorobieff and
the 25-year period since the observations of N. T. Tchougounov. The area
occupied by the Syndesmya biocoenosis (Syndesmya ovatd) was greatly
reduced, while that occupied by the Cardium . . . and Corbulomya (Corbu-
lomya maeotica) biocoenoses, situated hitherto mainly in the coastal zone, was
widened (Fig. 242) ... the Hydrobia (Hydrobia ventrosa) biocoenosis dis-
appeared and the new Nephthys (Nephthys hombergi and Actinia equina)
biocoenoses were formed.' The increase in the numbers of the polychaete
Nephthys hombergi is linked with a decrease in the numbers of Nereis and
vice versa ; this too can be considered the result of the silting of corresponding
areas of the sea-bed (Fig. 243). The total benthos biomass, however, did not
undergo any considerable changes, although in some individual areas the
changes might be considerable. All these changes depend on the volume of
the spring floods, on the variations and distribution of the soils of the sea-
bed, on the development of plankton, on the amount eaten by fish and on the
occurrence of suffocation. A change in these conditions can bring about a
suitable environment for the development at one time of filter-feeders, at
another of soil-eaters, in the latter case accompanied by an accumulation of
liquid mud soil.

In the open part of the Sea of Azov the changes in salinity observed do not
affect to any considerable extent its benthos distribution. In the Gulf of
Taganrog salinity fluctuations are much more pronounced; they have a
great influence on the distribution of the bottom-fauna and on its biomass.
Marine species gain possession of the Gulf of Taganrog in years when the water
is low. An inverse dependence on the distribution of the benthos biomass is
observed for the western and eastern parts of the Gulf of Taganrog — an in-
crease of the benthos biomass in its western part corresponds to a decrease in
the eastern one (Fig. 244) (I. Stark, 1955). Stark thinks that a fall in the in-
flow from the river Don will not have a bad effect on the benthophage feeding
grounds in the Sea of Azov proper, in spite of a pronounced decrease in the
number of Syndesmya and an increase in that of Corbulomya Cardium and
Mytilaster. The Gulf of Taganrog will be more densely populated by Cardium,
Hydrobia, Nephthys and Syndesmya, but conditions for the feeding of the
young would deteriorate, since the habitats of the small-sized forms of in-
fauna (chironomids and Hypaniola) will be reduced ; for adult fish the deterio-
ration would be marked by a reduction in the numbers of Monodacna and
Dreissena. Changes, however, were observed in the Sea of Azov also ; with the
increase of salinity, salt-loving forms such as Actinia equina, Cardium exiguum,
Cylista viduata, Pectinaria neapolitana, Glycera convoluta, Melinna palmata,
Nassa reticulata, Cyclonassa kamyschensis and several others penetrate into
the basin through the Kerch Strait and the Utlyuksk inlet. The Teredo navalis,
hitherto unknown in the Sea of Azov, has been recorded off Kazantip.

THE SEA OF AZOV

515

E. Yablonskaya has forecast the changes in the distribution of the benthos
of the Sea of Azov that might be brought about by a loss of 1 5 to 40 per cent

SPRING 1934-1935

10 11 12 13

•tV

Sir-

о «0

V Y V
У V

V V V

Fig. 242. Distribution of bottom biocoenoses in the Sea of Azov (Stark) : 1 Cardium ;
2 Mytilaster; 3 Balanus; 4 Hydrobia; 5 Nereis; 6 Syndesmya; 7 Corbulomya;
8 Monodacna; 9 Actinia; 10 Ampelisca; 11 Oligochaeta; 12 Ostracoda; 13 Neph-

thys.

of its river inflow on the basis of all earlier relevant research (Fig. 245). ТЫз
mainly consists of a strong development of the Cardium, Balanus and Myti-
laster biocoenoses and a reduction of the Hydrobia and Nereis biocoenoses,
and, in part, a considerable development of the last named in the Gulf of
Taganrog.

516

BIOLOGY OF THE SEAS OF THE U.S.S.R

Great changes have thus occurred in the distribution of the bottom-
biocoenoses of the Sea of Azov during the last ten years. In 1951 Syndesmya
and Hydrobia biocoenoses were being replaced by that of Corbulomya, but

/ 2 3 * 5 6

Fig. 243. Distribution of Nereis in the Sea of Azov, g/m3 (Stark). 1 Not less than 1 ;
2 From 1 to 5 ; 3 From 5 to 10 ; 4 From 10 to 25 ; 5 From 25 to 50 ; 6 From 50 to 100.

even in 1952 the latter was coming to be replaced by the biocoenosis of Car-
dium, Mytilaster, Balanus and others. In the southeastern part of the Sea the
Syndesmya and polychaete biocoenoses began to appear again in 1955 and
1956 owing, possibly, to an increase in the run-off from the land. The bio-
mass of the central part of the Sea increases considerably after years of low
floods and drops again when there are heavy floods ; the total average benthos
biomass also undergoes considerable fluctuations {Table 215).

650
600

550
500
НО

т ш

{ 350

$ зоо

1 250

* ZOO
150
100
50

HONTH
YEARS
PART

'ТъЛл''/

ал_и

_E2L

IV И VII IX Л/

VII

IV VI VII IX м

WYWWX

то

I95Z

1950

1951

1952

Fig. 244. Distribution of benthos biomass of the Gulf of Taganrog according to
seasons and regions (Stark).

Fig. 245. Diagram of the distribution of bottom biocoenoses in the Sea of Azov and
the Gulf of Taganrog (Yablonskaya, 1957). A At an average water discharge; В At
about 85% water discharge ; С At about 60% water discharge ; 1 Dreissena ; 2 Mono-
dacna ; 3 Hypaniola-Corophium ; 4 Ostracoda ; 5 Cardium ; 6 Nereis-Ostracoda ;
7 Corbulomya ; 8 Nereis ; 9Balanus ; 10 Mytilaster, mussel ; 11 Hydrobya-Nephthys ;

12 Syndesmya.

518 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 215. Changes in the Azov Sea benthos biomass in gjm2 {after V. P. Vorobieff

and I. Stark)

1934-35 1950 1951 1952

Spring Autumn July April July October April July October

Sea of Azov 241-7 496-0 183-3 199-2 391-2 267-0 252-3 292-2 448-1

Gulf of Taganrog 34-0 — 192-2 179-4 248-4 441-8 — 53-8 —

Yield of benthos-
eating fish (% of
the 1934-35
yield) 100 37-7 55-1 53-6

Fish

Qualitative composition. The fish population of the Sea of Azov proper
consists of 79 species. Among them 19 are migratory or semi-migratory forms
(Acipenseridae, Clupeidae, Percidae and Pleuronectidae) and 13 are fresh-
water ones. Cyprinidae, Gobiidae, Acipenseridae, Clupeidae, Percidae and
Pleuronectidae families are outstanding in respect of the number of their
forms. N. M. Knipovitch (1932) divides the fish of the Sea of Azov into
seven different groups.

(7) Representatives of the Mediterranean fauna which have become
naturalized in the Sea of Azov, where they form the main mass of settled
population and have sometimes evolved already into separate endemic
species, as for example the Azov brill (flatfish Bothus torosus).

(2) The Mediterranean immigrants which spend part of the year in the
Sea of Azov and then move back into the Black Sea or even the Sea of Mar-
mora (mullet, red mullet, anchovy).

(3) Representatives of the Mediterranean fauna, irregular visitors to the
Sea of Azov (mackerel, tuna).

(4) Autochthonous relicts of Pontic fauna which do not leave the Sea of
Azov (Percarina maeoticd).

(5) Autochthonous relicts of Pontic fauna which leave the Sea of Azov
periodically for spawning in the rivers (different migratory fish).

(6) Autochthonous relicts of Pontic fauna which spend part of their life in
the Black Sea, part in the Sea of Azov, and part in the rivers (herring —
Caspialosa pontica, Caspialosa tanaica, beluga).

(7) Fresh-water organisms.

Quantitative estimate offish. A most valuable and so far unique attempt at a
direct census of fish, suggested by Yu. Marti, was carried out by V. Maisky
(1940) in the Sea of Azov. In August and September of 1936 the whole of the
Sea of Azov was covered with about two hundred hauls using fine-meshed
lampara in the open parts of the Sea and scraper off the shores. Each series
of net hauls took 10 to 12 days. The shallowness of the Sea of Azov makes
the use of the lampara or similar equipment specially handy for a census of
fish throughout the Sea (Fig. 246).

THE SEA OF AZOV

519

As a result of his investigations Maisky produced a chart showing the quan-
titative distribution of every fish throughout the Sea. A tabular summary of
the raw material resources for separate breeds of fish in the Sea of Azov is
included here. These data are of exceptional interest, since this kind of in-
formation has not been obtained for any other sea ; moreover, it gives much
more accurate estimates of commercial resources of fish than those usually
obtained with the aid of biostatic analysis {Table 216).

In the following years (1936-52) according to V. Maisky's data (1955)

mmuptosoog

УЖ1 500-2 Hq

5-10 kg
more than lOkq

Fig. 246. Quantitative distribution of anchovy (yield of one catch of lampara) in

the Sea of Azov in different seasons of 1933 according to the data of the census

(Smirnov). I June-July; II September; III beginning of October.

' a great increase in the number of commercial shoals of migratory and semi-
migratory fish and the reduction of the habitat of bream and Pelecus ' were
recorded. There were also some changes in the numbers of anchovy, Clupeo-
nella, Percarina and Benthophilus. The quantities of other fish changed only
little.

Using the same data of direct census Maisky gives for some fish a diagram
of the movements of the whole Azov shoal : that of Azov Clupeonella (Clu-
peonella dehcatula delicatula) is given in Fig. 247.

Although these data may not be very accurate, this is the first attempt to
give a general quantitative picture according to age of fish in our Seas by
direct calculation with quantitative collection equipment. Thus the total
amount of fish, as determined by direct census, must be no less than 60,000 tons.
The amount of benthos eaten by fish, as determined by V. P. Vorobieff from
the data of his direct census, is of the order of 10 or 11 million tons; this

520

BIOLOGY OF THE SEAS OF THE U.S.S.R.
Table 216

Under one year

One to two
years old

Groups of marketable
age

Form

No. of No. of No. of

specimens Centners specimens Centners specimens Centners
x 10~6 x 10-3 x 10"6 x lO"3 x Ю-6 x 10-3

Don pike perch

2-3

— 10-21

200-400

Kuban pike perch

2-2

— 8^0

150-800

Bream

44-91

300-800

Acipenseridae

200

Kuban roach

300

Herring

800

50-200

50-150

Clupeonella

40,000

320

66,000

1,780

Anchovy

17,500

351

5,250

356 6,000

420

Friar

1,000

3,000

Percarina

3,000

8,000

200

Bullhead

1,000

400-3,000

150-900

600

100

Total approximately

1,000

6,000

MONTHS/y VI VIII X

MULTIPLICATION FROM

APRIL TO JULY
GAIN IN THE YOUNG BY
SEPT. 100 THOUS. CENTNERS

STOCKS OF CLUPEONELLA

thous.cen/P00 1700 1200 800 1100 1200 \/A-00\ /4-00
months./-//-/// IV V VI VII VIII IX X-XI-X/I

MORTALITY
?

DESTRUCTION BY PREDATORS

TH0US.CEN25 701201201207025
months IV V VI VII VIII IX X

commercial yield
thous. cen. /48 4-14 238-6 3 4
months iv v VI -IX X XI

Fig. 247. Diagram of population movements of Sea of
Azov Clupeonella in 1937 (Maisky).

THE SEA OF AZOV 521

would correspond approximately to 600 to 900 thousand tons of fish, i.e.
similar results are obtained by both methods.*

Feeding offish. The high benthos- and plankton-productivity of the Sea of
Azov determines the exceptional qualities of this body of water as a feeding
ground not only for the Azov fish, but also partly for those of the Black Sea
(herring, anchovy, red mullet, grey mullet, etc.). Herring, anchovy and
other pelagic fish prey on zooplankton; bullhead, Percarina, Benthophilus
and Atherinopsis feed on benthos. In their turn they serve as food for pike
perch. Some fish, like striped mullet (Mugil cephalus) and mullet {Mugil
auratus), live mostly on detritus.

So far there has been no general summary of fish nutrition in the Sea of
Azov like that made by A. Schorygin for the Caspian Sea. The fullest quan-
titative data exist on the nutrition of anchovy and some other plankton-eating
fish (A. Okul, 1939 and A. Smirnov, 1938). Of the benthos-eating fish the
bream alone has so far been thoroughly studied (V. P. Vorobieff, 1938).
Finally, for the predatory fish there are some data on the nutrition of pike
perch (N. Tchougounov, 1931; V. Maisky, 1939 and V. P. Vorobieff in
manuscript). In recent years comprehensive studies of the nutrition of Sea
of Azov fish have been made, and were published in 1955 (E. Bokova,
M. Zheltenkova, V. Kornilova, V. Kostyuchenko, E. Fesenko and M. Sheinin).

Plankton-eating fish. During periods of its multiplication the mass of plankton
in the Sea of Azov must be not less and very probably larger than the mass of
benthos. Taking into account the fact that the production of the Azov phyto-
plankton must considerably exceed that of benthos, it becomes clear that the
plankton of the Sea of Azov has a higher productivity than its benthos. The
intensively productive Azov plankton serves as a plentiful source of food for
the fish which gather there from the Caspian Sea and from the rivers to fatten.

The Azov anchovy {Engraulis encrassicholus maeoticus) — one of the main
commercial objectives of the Black and Azov Sea fisheries — enters the Sea
of Azov in the spring (April-June) for intensive feeding and spawning. The
anchovy leaves the Sea of Azov from the second half of August till the end
of November ; it hardly feeds at all during its stay in the Black Sea.

Coming into the Sea of Azov the anchovy begins to feed intensively (Fig.
248). A. Smirnov (1938) and A. Okul (1940) have shown that the western half
of the Sea serves as a specially rich feeding ground. Plankton forms the main
part of the anchovy's food ; when this is short, it feeds on benthos (poly-
chaetes, molluscs). The anchovy's feeding proceeds intensively and by June
its repletion index is 128; by July it is 117. In some individual areas of the
Sea its repletion index may be even higher (up to 210). In the coastal areas
in June it feeds mainly on worms (40 per cent), copepods (30 per cent), bar-
nacles (13 per cent) and molluscs (10 per cent). At that time phytoplankton
constitutes a small part (2 per cent) in the anchovy's diet. In some individual

* The census of anchovy carried out recently from the air (I. Golenchenko, 1947)
leads to the conclusion that the resources of anchovy in the Sea of Azov are considerably
larger.

522

BIOLOGY OF THE SEAS OF THE U.S.S.R.

cases anchovy stomachs were filled with polychaetes and small Hydrobia
only.

Copepoda form the main food of anchovy and Atherina and even more so
of Clupeonella (Fig. 248). The intestines of these three fish contain on the
average 60 to 70 per cent by weight of copepods (85-8 per cent in Clupeonella,

ADULT

APRIL-MAY JUNE

YOUNG

JULY

AUGUST

JUNE

SEPTEMBER OCTOBER NOVEMBER

[HUPhytoplankton
ISSS Rotatoria
dZlPolychaeta larvae
ESPolychaeta
DUCIadocera
■■Copepoda
'""ICirripedia larvae
HillMysidacea
SEPTEMBER OCTOBER :23Mollusca larvae
5SZ! Hydrobia
^H3Fish larvae

ANCHOVY

SEA OF AZOV

MARCH APRIL-
MAY

BAY OF TAGANROG

AUGUST

SEPTEMBER

APRIL-MAY

AUGUST

CLUPEONELLA

SEPTEMBER OCTOBER NOVEMBER DECEMBER
[■]•'] Phytoplankton
Щ Rotatoria
pq Polychaeta larvae
Ol Cladocera
IB Copepoda
рт] Cirripedia larvae
E3 Mysidacea
E*3 Amphipoda
LD Mollusca larvae
ШИ Fish larvae

SEPTEMBER

Fig. 248. Food spectra of (A) anchovy and (B) Clupeonella in the Sea of Azov and
their changes during the year. The area of the circle corresponds to the value of the
repletion index. White sector within the circle is the percentage of empty stomachs

(Okul, 1941).

40 per cent in anchovy, 56-5 per cent in Atherina). For herring, however,
Copepoda are not an important item of diet.

In spring Rotifera constitute a large part of the food of fish, ranging from
25 to 63 per cent for Clupeonella and up to 21 per cent for anchovy. For
a short period in June (at the time of their mass occurrence) Cirripedia larvae
may acquire an important place in the nutrition of plankton-eating fish;
anchovy food includes 33 to 37 per cent of them, that of Clupeonella 25 per
cent, of Atherina 10 to 14 per cent and of herring 4 per cent. In spring and
autumn Mysidacea (mainly Macropsis slabberi) plays an important role in
the nutrition of Atherina and herring, forming 31 to 47 per cent and 21 per
cent of the whole content of stomachs of herring and Atherina respectively.
Mollusc larvae have little feeding value for fish (1 to 4 per cent). Herring eat
large numbers of fish fry and young fish.

THE SEA OF AZOV

523

Taking into consideration the indices of repletion of the intestines and the
time of digestion, Okul has arrived at an index of daily food consumption
(the ratio of the weight of food consumed during a day to the weight of the
body of the fish). Taking into consideration the stock of food for plankton-

DAILY CONSUMPTION OF FOOD
BY THE FISH SHOAL

ANCHOVY

1000 -
900 -
800 ~
700 ~
Q 600 ~
500 -
400 -

300 -
200 -
/00 -

12000 -

/1000

/0000

9000

B000 -
7000 -
6000 -
5000 -
4000 -
3000 -
2000 -

1000

IV-V V/ VII

VIII IX

IIIIV-VVI VII VIII IX X

CLUPEONELLA

800-

o/\

700 -

0 / \

o/ \

TONS

DAILY CONSUMPTION OF FOOD

600-

0 /

г/

°/

6000 -

BY THE FISH SHOAL

500-

5000-

400-

о /

4-000-

300

°v

3000-

200-
100

x. /REPLETION INDE>

/stomach \
\ intestine/ ч

2000-
^^■^1000

III IV-V VI VII VIII IX X XI XI/ I///VYVIVIIVI///XXX/X/I

Fig. 249. Daily consumption of food by anchovy and Clupeonella in the Sea of
Azov. On the left-hand side consumption by individuals, on the right by the shoal

as a whole (Okul).

524

BIOLOGY OF THE SEAS OF THE U.S.S.R

eating fish in the Sea of Azov (Fig. 249), he calculated the total amount
of plankton consumed. In 1937 this quantity for the Sea of Azov was
1,700,000 tons, and for the Gulf of Taganrog 200,000 tons. This amount is

ANCHOVY

*esoUP££--^ ,

60 ui — """ У

4 PLANKTON

.1.1 dl

1931

1935

1936

1937

Fig. 250. Alterations from year to year in the development of plankton and
anchovy resources in the Sea of Azov (Okul).

considerably higher than the plankton biomass observed at any moment of
the year. Azov plankton-eating fish consume no less than 1,200,000 tons of
Copepoda alone, and for them the P/B coefficient is hardly less than 30. It is
interesting to note that Copepoda — the main food reserve of the plankton-
eating fish— is, like Cladocera and Cirripedia larvae, used only in small
quantities as food by benthos.

Finally, over a number of years Okul likewise established for the Sea of
Azov a certain direct dependence between the amount of plankton and the
fish preying on it for the Sea as a whole and for some points in it, by means
of individual catches (Fig. 250). The yield of fish is usually large when the
plankton they feed upon is abundant.

Benthos-eating fish. Some breeds of Azov Sea benthos-eating fish prefer a
definite quarry. Bullheads (Gobius melanostomus) feed preferably on clam-
worms, Mytilaster and Syndesmya. Bream chooses the same quarry, and adds
crustaceans and Hydrobia as well. Starred sturgeon feeds mainly on crabs,
worms and bullheads ; sturgeon on Syndesmya, Cardium and worms ; roach
on Mytilaster, Syndesmya, Hydrobia, crustaceans and worms. As has already
been shown by Tchougounov the Azov Sea benthos is suitable for fish to feed
on almost exclusively.

THE SEA OF AZOV 525

In the Gulf of Taganrog the western part is the most important feeding
ground ; the main mass of adult fish remains there temporarily on its way to
spawn in the river Don and on the way back again ; fish fry and immature
fish are fattened there to a great extent. Huge shoals of fish under one year
old, of one-, two- and three-year old pike perch, bream, carp, Pelecus, herring,
etc. gather in the Gulf of Taganrog, especially in summer and autumn. Only
the Clupeidae prey mainly on plankton ; the other fish feed on benthos. Of
the benthos only the large Unionidae, Monodacna and Dreissena are used
in small amounts by fish : all of the rest is consumed by fish.

As shown by V. P. VorobiefT(1938) bream is a real polyphage. In the course
of its life, however, bream changes its diet. Its fry feeds mainly on plankton,
then bream begins to prey on the larvae of insects, worms and crustaceans ;
large adult bream lives on worms, molluscs and large crayfish.

Predatory fish. The pike perch is the main commercial fish of the Sea of Azov;
in the amount of its yield it is inferior only to Clupeonella (721,000 centners
in 1937). As a predator pike perch preys mainly on fish; prawns form an
addition to its food. It is the main consumer of small fish in the Sea of Azov.
Together with other predators, such as herrings and bullheads (Mesogobius
melanostromus and Neogobius syrmari), beluga, catfish, Pelecus, Aspius aspius
and others, it destroys a huge amount of small fish ; it could in this respect
appear as a rival of man. As Maisky has noted (1939), pike perch fattens
mainly in the Gulf of Taganrog and the eastern part of the Sea of Azov. In the
course of a year it destroys 3 to 3-5 million centners of small fish, a quantity
much higher than that taken by man from the whole fishing industry in the
Sea of Azov. In addition bullhead comprises 55 to 60 per cent, Clupeonella
14 to 15 per cent and anchovy 11 to 12 per cent of the food eaten by the pike
perch;

In spring and summer pike perch feeds mostly on Clupeonella and anchovy,
and in the autumn almost exclusively on bullhead. The pike perch's annual
consumption of fish, according to Karpevitch's data, is about seven times its
own weight.

Fisheries. The fisheries of the Sea of Azov at present bring in about 1-5
million centners (IT 5 million centners in 1930, and 2-75 million centners in
1936); but the yield of the most valuable fish — pike perch, golden shiner,
herring and Acipenseridae — has decreased. The catch of Clupeonella, and
particularly of bullhead, has increased (L. Berdichevsky, 1957).

The catch in the Sea of Azov (without the Kerch Strait) was 1 -05 millon
centners in 1957, comprising 90 thousand centners of pike perch, 41 thousand
centners of golden shiner, 80 thousand centners of roach {Rutilus rutilus)
and 733 thousand centners of bullhead. In 1937 the catch of different breeds
offish was only the following : 81,900 tons of Clupeonella, 72,100 tons of pike
perch, 50,400 tons of anchovy, 34,100 tons of bream, 3,900 tons of roach,
1,200 tons of carp, 7,500 tons of Acipenseridae, 6,200 tons of herring, 4,400
tons of bullhead and 1 1 ,900 tons of other fish, totalling 277,500 tons.

The yield from the fisheries in the Sea of Azov constituted then some 90 per

526

BIOLOGY OF THE SEAS OF THE U.S.S.R.

cent of all the fish caught in the Azov-Black Sea basin; only 10 per cent of
this came from the Kerch Strait. In recent years the proportion has dropped
to 65 per cent or so. The yield from the whole area of the Sea of Azov is
73 kg per hectare (in some years up to 82 kg/hectare).

V. CONCLUSION

V. Pauli (1939) gives a very good description of the Sea of Azov as a eutrophic
sea: 'In the Sea of Azov not only do the reduction processes fall behind the
activity of the producers, but the production itself does not correspond to the
amount of biogenic compounds. According to the data for phosphorus pent-
oxide, and probably some other biogenic compounds as well, these are not
completely used up by the autotrophic population even at the time of maxi-
mum plankton development.'

The masses of organogenic compounds brought down by the rivers Don
and Kuban into the Sea of Azov are only partly consumed by fish. Consider-
able quantities of them are converted into the organic compounds of plankton
organisms and are not used by fish. An appreciable part of the biogenic
compounds is carried away into the Black Sea.

Datzko has given the biomass of the annual production of the main groups
of the Sea of Azov population {Table 217).

Table 217

Biomass, 103 tons

Annual
- production

Annual
P/B

Group

Percentage

103 tons

ratio

Wet

of total

Dry

weight

biomass

weight

Micro-

organisms

250

3-2

175,000

700

Phytoplankton

1,000

100

340,000

340

Zooplankton

200

2-7

600

Zoobenthos

4,800

63-5

720

12,000

2-5

Fish

1,300

17-4

390

800

0-6

Forecast of changes in the biological productivity of the Sea of Azov in con-
nection with reduction of river inflow. The hydrology and biology of the Sea of
Azov are bound to change as a result of hydrotechnical construction on the
river Don and the losses which it will involve in river inflow and in a certain
part of the dissolved or suspended substances brought down by the Don
into the Sea. A number of investigators have speculated on these possible
changes.

The salinity of the Sea of Azov would increase by 2%0 with an assumed loss
of 10 km3 of Don water, and by 5%0 with a loss of 20 km3. Taking into con-
sideration the fact that in the south Russian seas fisheries are concentrated
mainly in the less saline parts, V. Samoilenko (1955) supposes that a reduction

THE SEA OF AZOV 527

of the less saline parts and a decrease of the inflow of organic biogenic
subtances would lead to a drop in the level of biological productivity and
would have an unfavourable effect on the fisheries of the Sea of Azov. As
a result of the building of hydrological installations the feeding areas for
fish might be reduced and their passage into rivers for breeding might be
hindered.

F. Mordukhai-Boltovskoy (1953) approaches this problem from a different
angle. He starts from the assumption that as things are at present (before the
construction of the Volga-Don canal) the Don waters bring into the Sea of
Azov an excess amount of plant food, which causes a superfluous develop-
ment of plankton and an over-accumulation of organic substances in the
central parts of the Sea ; this led to a constant oxygen deficiency and to the
suffocation of fish and bottom-fauna over large areas of the sea-bed. In this
worker's opinion the loss of 10 km3 of river water and the freedom of reser-
voirs from suspended matter will have a favourable effect on the oxygen
conditions of the Sea and on the yield of fish, since it will free the Sea from
over-accumulation of organic matter. A loss of 20 km3 of Don waters must
lead to a shortage of food supply and to a lowering of productive yield,
both as a result of that shortage and as a result of the great reduction of
habitat areas (low-salinity water) for semi-migratory fish.

Later this problem was again considered by E. Yablonskaya (1955),
A. Karpevitch (1955) and a number of other investigators, and the results of
their work are given in a two-volume symposium Reorganization of Fisheries
in the Sea of Azov (1955). Yablonskaya does not share Mordukhai-Boltov-
skoy's view on the over-accumulation of organic substances on the bed of the
Sea of Azov. According to the data of T. Gorshkova (1955) such over-
accumulation has not been observed, and Yablonskaya therefore assumes that
the productive capacity of the Sea of Azov would not be improved by the
drop in the outflow from the river Don and by the settling down, as precipi-
tates in reservoirs, of the plant food substances which reached the Sea before
control of outflow from the river was fairly fully utilized. Yablonskaya there-
fore thinks that with a 15 per cent drop in the river outflow zooplankton
production, both in the Gulf of Taganrog and in the Sea proper, would be
somewhat lowered, while at a 50 per cent loss of river outflow Azov plankton
production might go down by about 40 per cent. Benthos biomass in the Gulf
of Taganrog might increase as a result of the immigration of larger-sized
components of fauna from the west, but its importance for feeding will be
reduced. In Yablonskaya's opinion (see also Stark) the benthos biomass of
the Sea of Azov proper would change little. Fish feeding on this mass of
organisms — the plankton eaters (mainly anchovy and Clupeonella) — will
be somewhat less in number. At present benthos-eating fish do not con-
sume all the benthos available, and when the river outflow is reduced they
will on the whole have enough food, although this will apply to a different
extent for different species offish.

E. Yablonskaya (1957) describes the changes in the conditions of the Sea of
Azov connected with the control of the flow of the river Don in the following
way: 'the first 4 years (1951-55) were characterized by a reduction of the

528 BIOLOGY OF THE SEAS OF THE U.S.S.R.

flow of the Don (in 1921-51 an average of 26-2 km3 a year; in 1952-55 an
average of 19-4 km3 a year), by a reduction in the biogenic discharge into the
Sea (Table 218) and by its transformation in the water reservoir and in the
river, as a consequence of which its primary food-value was lowered ; the
salinity of the Sea rose by almost 2%0, causing a marked reduction in the
provision of food for the plankton-eating fish, and as a result their producti-
vity became almost 2-5 times lower than the average before the control of the
river waters'.

Among the inhabitants of the Gulf of Taganrog, according to Yablon-
skaya's data, there is a series of forms the mass development of which is
adapted to a salinity of 4 to 9%0 (Fig. 235) ; they belong to brackish-water and
fresh-water types. Yablonskaya has made a diagram, based on all existing
data, of the future distribution of bottom biocoenoses corresponding to a
loss of 1 5 and of 40 per cent of the river water (Fig. 236) ; plankton and ben-
thos would react differently to a change in the salinity of the Gulf, which would
be occupied mainly by brackish-water plankton and Sea of Azov benthos.

Table 218. A comparison of some indices of the biological conditions of the Sea of

Azov before and after commencement of control of flow of the river Don

{E. Yablonskaya)

Characteristic Average before control 1955

Phosphorus compounds 2,016 650

Nitrogen (spring) compounds 179 97

Nitrogen (summer) compounds 327 58

Zooplankton biomass 475 40
Production of plankton-eating fish (anchovy

and Clupeonella) in thousands of centners 4,990 1,844

Peridinean, per cent 88-9 20-3

Diatoms, per cent 3-9 78-7

VI. THE SIVASH, OR PUTRID, SEA

Situation and area

The Sivash, or Putrid, Sea is a peculiar, large (2,700 km2), subsidiary body
of water of the Sea of Azov. Situated to the west of it, the Sivash is connected
with it by the shallow (2 to 3 m) and narrow (120 m in width) Tonky Strait. It
is separated from the Sea of Azov by the long and narrow Arabat Strelka,
and it comprises a complex system of inlets connected by straits and of numer-
ous islands.

The greatest depth of the Sivash hardly reaches 3-2 m in its southern part,
while its average depth changes from 0-63 m in its northern part to 0-86 m in
the south. With a volume of water of about 1 km3 the ratio of its volume to its
area is equal to 1/1,300, while the corresponding ratio for the Sea of Azov is
1/150.

THE SEA OF AZOV

529

Salinity

The salinity of the Sivash is greatly increased by a considerable preponder-
ance of evaporation over precipitation and inflow of water from rivers. The
gradual increase in salinity in the
Sivash is shown in Fig. 251. In the
southern part of the Sivash the
salinity rises to 124 to 166%0.

Salts dissolved in Sivash water
consist mainly of sodium chloride,
magnesium chloride, magnesium
sulphate, magnesium bromide,
potassium chloride, calcium
sulphate and calcium bicarbonate,
sodium chloride, magnesium
chloride and magnesium sulphate
being considerably preponderant;
the salt composition of Sivash
water differs little from that of the
ocean {Table 219).

There is a higher content of
sulphates and carbonates in the
water of the Sea of Azov as a
result of the considerable inflow
of river waters. The Azov waters
entering the Sivash are concentrated

and freed from excess of calcium carbonates and sulphates ; thus there occurs
a gradual return to the salt ratio common in the ocean. This process is
called' by Danilchenko and Ponizovsky 'normalization of Sivash brine'; to
illustrate this they give the data set out in Table 220.

Fig. 251. Gain in salinity (in chlorine)
in Sivash from north to south (Zhukov
from data of VorobierT).

Table 219. Salt composition of waters of the ocean, Black and Azov Seas, and the
Sivash (Percentage weight of the salt) (P. Danilchenko and A. Ponizovsky, 1954)

Western

Eastern

Sivash

Ocean

Sivash off

(Sergeev-

(after

Black

Sea of

Chongarsk

sky body

Salt

Ditmar)

Sea

Azov

Strait

of water)

Sodium chloride
Potassium chloride

77-68 \
2-10 I

79-40

76-90

79-00

/ 78-35
I 2-09

Magnesium chloride

9-21

8-92

9-81

9-87

9-39

Magnesium sulphate

6-39

6-33

6-80

6-51

6-95

Magnesium bromide

0-21

0-20

0-21

0-17

Calcium sulphate

3-70

3-64

3-79

3-65

2-82

Calcium bicarbonate

0-74

1-52

2-72

0-76

0-21

Overall salinity, per-

centage weight

3-53

1-83

1-03

4-08

12-89

530 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 220. Change in the chlorine coefficients of the waters of the ocean, Black and
Azov Seas, and the Sivash (P. Danilchenko and A. Ponizovsky, 1954)

Sea of Eastern
Coefficients Ocean Black Sea Azov Sivash

Ca2+

cFxW0

Mg2 +

(so4)2-
ci-

(НСОз)

xlOO
-xlOO
xlOO

ci-

CPXW0

Na+
_x,00

K +
-x,00

Sum of salts

MgS04

m^ci;

2-16

2-49

6-73

6-75

13-93

13-54

0-66

2-00

0-34

0-33

55-58

55-45

200

2-20

1-81

0-67

0-70

3 08

2-22

7-05

6-79

14-80

14-45

3-55

0-24

—

0-34

55-29

56-90

1-98

1-85

1-80

0-71

0-66

M. Bozhenko (1935) determines the sum total of the stock of salts in the
Sivash as 190 million tons, including 309,000 tons of elemental bromine and
7-1 million tons of magnesium.

Temperature

The shallow waters of Sivash become considerably warmed in the summer
(up to 30° to 35°). On the other hand in the winter their temperature falls to
— 1 ° or — 2° (and even to — 3 ° in the southern part), and the northern and some
of the central Sivash is covered with ice.

According to Vorobieff either a mass extinction or a migration of animals
into the deeper parts of the Sivash occurs as a result of the sharp seasonal
temperature fluctuations and of a partial freezing of the whole column of
water.

Oxygen

Oxygen content decreases sharply from north to south. A litre of water in the
north of the Sivash contains 5-51 cm3 of oxygen, in the central part 40 cm3,
and in the south 1-88 to 1 -75 cm3. The phenomenon of bottom-fauna suffo-
cation occurs more readily in calm summer weather in the Sivash than in the
Sea of Azov ; this is due to the shallow depth of water and to the large amounts
of oxygen used in the decay of organic substances.

THE SEA OF AZOV 531

Phosphorus and nitrogen

A further characteristic is the insignificant content of phosphates and nitrates
in Sivash waters which was noted by Vorobieff. Only in winter has an appre-
ciable accumulation of these substances been recorded.

Soils

According to Vorobieff the prevailing soils are ' muds of varying colour and
density, with an admixture of sand, shell gravel and organic remains. These
muds are mainly composed of huge amounts of plant remains, detritus and
plankton, which dies off in salt water, brought from the Sea of Azov and the
Utlyuksk inlet (autochthonous matter) and also of the plants of the Sivash
itself, which develop in huge masses. In the northern part the mud consists
of dead ditch-grass, Zostera, dog whelk and the green algae Cladophora ; in
the central and southern Sivash it consists of Cladophora and green-blue algae.
The small crustacean Artemia salina, which develops in enormous numbers in
the summer, must play an important role in mud formation of the southern
Sivash.' The processes of the decay of organic substancesare limited owing to
the high salinity and large amounts of organic matter deposited among the
bottom sediments.

'Organisms most tolerant of hydrogen sulphide, methane and other gases
liberated during the processes of decay, such as Sphaeroma, Idothea, Gam-
marus, the fly larvae, nemertines and others, are found in huge quantities
among decaying sea-weeds on the shores of the Sivash.'

Spionidae, Pectinaria, Syndesmya and Cardium are found in muddy sand,
and Clymene, Nereidae, Syndesmya, Cardium, Hydrobia, Chironomidae and
others in muds.

Distribution and composition of fauna '

Vorobieff (1940) has made a comprehensive study of the distribution of life in

the Sivash, and we shall be using his data below.

As one moves up into the bay there is a change in the qualitative compo-
sition of the fauna with the increase of salinity — the marine forms become less
numerous and the number of the typical ultrahaline forms increases (Figs. 252
and 253).

Huge amounts of plankton and larval forms of benthos are constantly
brought into the Sivash by the Azov Sea waters ; a kind of compulsory coloni-
zation of the Sivash is going on. Most of the larvae and adult organisms
which find themselves in the Sivash either perish, or live for only a short time,
or settle in the Northern Sivash. We have every reason to assume that if it
were not for this constant influx of Azov Sea forms the population of
the Sivash would be much poorer in variety and biomass, since most of the
species which survive in the Sivash have a very low productivity and a sharp
decrease in their biomass occurs throughout most of the year.

At the present time only the ultrahaline species five in the central and
southern Sivash. The Novo-Euxine and ancient Black Sea relicts are the first
to disappear as one moves into the Sivash, then the Azov-Black Sea species
and the fresh-water halophilic ones.

532

BIOLOGY OF THE SEAS OF THE U.S.S.R.

BOUNDARIES OF DISTRIBUTION
"PECTINARIA NEAPOLITANA

LORIPES RETUSA AND SPIONODAE

NEMERTINI AND SYNCESMA

CARDIUM EDULE 1DOTHEA
G. IOCUSTA AND
NEREIS DIVERSICOLOR

HYDROBIA
►-•-•- OSTRACODA

CHIRONOMIDAE

^^CLADOPHORA

EPHYDRA

ARTEMIA SALINA

Fig. 252. Limit of distribution in the

depth of the Sivash of some Azov-Black

Sea forms (Vorobieff).

Fig. 253. Northern boundary of distri-
bution of ultrahaline forms in the Sivash
(Vorobieff).

Vorobieff gives the number of animal and plant species inhabiting various
parts of the Sivash as in Table 221.

Of the 40 species of zoobenthos in the Sivash 18 (39-9 per cent) are Novo-
Euxine relicts, 5 (11-1 per cent) are ultrahaline forms, 19 (42-2 per cent) are
Azov-Black Sea forms and 3 (6-7 per cent) are ancient Euxine relicts.

Of the 75 species of zooplankton 6 (7-98 per cent) are Novo-Euxine relicts,
9 species (12-9 per cent) are ultrahaline forms, 59 (79-4 per cent) are Azov-
Black Sea forms and 1 (1-33 per cent) is a Novo-Euxine relict. The occasional
drying up by the wind of large areas of the bottom is a characteristic pheno-
menon of the Sivash ; one part of its fauna perishes, while another develops
the ability to survive the dry periods by burrowing into the sea-bed.

Plankton

Plankton distribution, according to Vorobieff, is as set out in Table 222.
Plankton biomass throughout the Sivash comprises 22,440 tons in February,

Table 221

Group

Sections of Sivash

1st northern 2nd northern

Central

Southern

Benthos
Zooplankton
Phytoplankton
Fish

40 38
56 55
43 70
53 9

5
23
34

THE SEA OF AZOV

Table 222

533

Group

Zooplankton

No. of Percentage
species

Group

Phytoplankton

No. of Percentage
species

Protozoa
Coelenterata
Vermes larvae
Rotatoria
Entomostraca
Mollusca larvae

24
1

30-24

1-26

2-53

11-34

42-02

2-53

Chlorophyceae

Cyanophycae

Diatomacaea

Peridineae

Flagellata

7
54
21

10-7

7-49

58-27

22-47

1-07

Total

100

Total

100

9,540 in May-June, 19,184 in July, 9,161 in August, 5,910 in September and
6,412 in November (an annual average of 26,063). Consequently there are
two maxima in plankton development : in spring and autumn.

Benthos

Summer suffocation of the Sivash bottom-fauna in calm weather is a common
occurrence; as a result, the deeper-lying mud beds are much more sparsely
populated. Summer, moreover, is the least favourable season for the develop-
ment of bottom-fauna ; winter and especially spring are the most favourable.
As a result, seasonal changes in benthos biomass in the Sivash are observed
on mud bottoms in the deeper parts : a decrease from summer to autumn as a
result of suffocation, further winter reduction, and an increase in the spring (a
further drop in the spring may in certain cases be caused through consump-
tion of it by fish). 'The fact that sand and a mixture of silty sand and shell
gravel are the most productive soils in the northern Sivash is explained by
the same reasons, i.e. in the last analysis by the aeration conditions at the
bottom.'

Among the large forms of the benthos only Chironomus salinarius and fly-
larvae are found on the muds in the central and southern parts of the Sivash.
Macrobenthos is absent from coarse-grained soils, while the fly larvae are
adapted best to silty sand with shell gravel ; the anaerobic conditions of mud
soils are not favourable to them. Here the biomass is very small, fluctuating
between 1 and 12 g/m2. In the most saline part (60%o) it drops to a few grammes
or fractions of a gramme.

Phytobenthos presents a different picture since the inner parts of the bay
are considerably overgrown with the ultrahaline Cladophora siwaschensis,
which is absent from the outer parts of the bay. The increase of the amount of
phytobenthos at a chlorine content of 20 to 40%o is explained by the intensive
development of Zostera and Ruppia under these conditions.

Of the nine bottom-communities established for the Sivash the following
are the most numerous: Cardium, Syndesmya, Hydrobia, Chironomus,
Artemia and Cladophora.

534 BIOLOGY OF THE SEAS OF THE U.S.S.R.

In the northern Sivash the mollusc Cardium edule is present in various
combinations as the dominant species, with a number of others. In the summer
it is associated with Chironomus, Syndesmya ovata and Gammarus locusta,
in the autumn with Hydrobia ventrosa, Chironomus, Syndesmya and Pecti-
naria, in the winter with Chironomus, Hydrobia and Syndesmya, in the spring
with Syndesmya and Hydrobia. Among the other forms Nephthys hombergi,
Mytilaster, Nereis diversicolor, N. zonata and Chironomus may be noted.

In the northern Sivash the mean biomass is 200 to 300 g/m2 {Table 223).

Table 223

Species

No. of specimens

Biomass

per 1 m2

g/m2

Cardium edule

1,172

145-2

Chironomus

10,680

25-6

Syndesmya ovata

343

18-3

Gammarus locusta

396

7-1

Nephthys hombergi

157

3-0

Mytilaster lineatus

2-6

Hydrobia ventrosa

920

2-3

Nereis zonata

146

1-7

In the summer other forms are present only in small numbers. In autumn
the numbers of Hydrobia may attain 17,230 specimens per 1 m2 with a bio-
mass of 44-54 g/m2. The numbers of Pectinaria (up to 13 g/m2) and of
Nereis diversicolor (up to 5-9 g/m2) are considerably increased. Lamelli-
branchiata composes from 66-7 to 93-9 per cent of the total biomass, Hydro-
bia in autumn up to 13 per cent, Vermes up to 11-5 per cent, Chironomidae
by the end of the winter up to 18 per cent.

In the outermost part of the bay the Syndesmya biocoenosis is preponder-
ant in benthos almost in the same combination of species, but with a biomass
of up to 400 to 500 g/m2.

The site occupied by the Syndesmya biocoenosis (1st northern Sivash) gives
shelter to a fairly abundant ichthyofauna. According to N. Tarasov's data
(1927) 53 species offish were recorded which feed there, but rarely penetrate
into the second part of the northern Sivash. Vorobieff suggests that 'all the
production of this biocoenosis is completely consumed by fish'.

In the autumn Hydrobia becomes the dominant form in the area formerly
occupied by the Cardium biocoenosis, and partly in the first northern Sivash
inhabited by the Syndesmya biocoenosis. The distribution of Loripes, Myti-
laster, Gammarus and Vermes (Nephthys and Nereis) communities is limited
in time and space.

More than two-thirds of the Sivash area is occupied by the Chironomus
salinarius biocoenosis. This biocoenosis inhabits some parts of the northern
Sivash and the whole of the central and southern Sivash. Chironomus is
found in the central Sivash in various combinations with the same Hydrobia,
Cardium, Gammarus, Ostracoda and Artemia; in the northern Sivash, with

THE SEA OF AZOV 535

Gammarus, Ostracoda and Artemia ; and in the southern only with Artemia,
which all dies out in the second half of the summer.

In the central and southern Sivash the biocoenoses acquire a sharply pro-
nounced oligo-mixed character and are really a combination of two species,
Chironomus and Artemia. In summer the mean biomass of these organisms
is 18-8 and 2-3 g/m2, in autumn 24-5 and 0-5 g/m2, in winter 2-7 and 00 g/m2,
and in spring 7-7 and 0-03 g/m2 respectively; Ostracoda and Ephydra are
mixed with these two forms in small numbers only.

Together with Artemia salina and Chironomus, Cladophora siwaschensis,
which inhabits the central and southern Sivash in vast numbers, gives this
area its particular character.

On the whole benthos biomass decreases gradually as one moves farther
into the Bay ; this can be seen on the charts in Fig. 254. On the other hand we
observe that sites of increased biomass as well as the main vegetation growths
lie close to the eastern shores.

In winter the benthos biomass of all the biocoenoses falls sharply.

The mean annual biomass of the outer half of the northern Sivash is equal
to 360 g/m2, that of the inner 140 g/m2. The mean annual biomass of the
central Sivash comprises 22 g/m2, and of the southern 4-26 g/m2.

The macrophytes play an important part in the phenomena of biological
production in the Sivash. In the first northern Sivash, where Cladophora
is weakly developed owing to low salinity, there are Zostera and Ruppia ; in
the rest of the Sivash Cladophora produces a very high biomass. Owing to
the large amounts of Cladophora in the central and southern Sivash, the mean
annual total biomass of the whole (zoo- and phyto-) benthos is found to be
approximately uniform throughout the area :

1st northern Sivash 564 g/m2

2nd northern Sivash 514 g/m2

Central Sivash 257 g/m2

Southern Sivash 515 g/m2

Fish

Of the 12 species of fish living permanently in the Sivash the flatfish Pleuro-
nectes flesus luscus, some bullheads, pipefish, sea horses and sticklebacks
may be noted. Of all these species only the flatfish and the bullhead (Zostricola
ophiocephalus) have some commercial significance.

Eight species of fish (all commercial) enter the Sivash to feed : two species
of grey mullet (Mugil auratus and M. cephalus), anchovy (Engrau/is encras-
sicholus maeoticus), herrmg(Caspiolosa maeotica), Atherina {Atherina pontica),
jackfish {Trachurus trachurus), garfish (Be/one acus) and bullhead (Gobius
fluviatilis).

Finally there are about 30 species of Azov Sea fish which occasionally visit
the Sivash.

The limits of the distribution of some fish are given in Fig. 255.

Fish fed in the Sivash grow faster and fatter. Grey mullet, which goes into
the Black Sea to spawn, is particularly fat.

BIOMASS <I0
0-100
■ 100-500
500-2000

SUMMER 1935

AUTUMN 1935

WINTER 1936

SPRING AND SUMMER 1936

Fig 254. Seasonal distribution of benthos biomass (g/m3) in the Sivash (Vorobieff,

1944).

Fig. 255. Limit of penetration of
some fish into the Sivash (Voro-
bieff). 1 Engraulis encrassicholus ;
2 Pleuronectes flesus luscus; 3
Young gobiidae; 4 Young
Mugil.

THE SEA OF AZOV 537

The average catch of grey mullet during the last 20 years constitutes 80 to
90 tons; in some years, however, it has risen to 550 tons (1923). The grey
mullet which feed in the Sivash are mostly young.

Some of the anchovy entering the Sea of Azov from the Black Sea in April
occasionally get into the Sivash and find excellent feeding there on plankton.
Some dozens of tons are caught. Up to 150 tons of other pelagic fish are caught
in the Sivash including Atherina pontica, which feeds on plankton and on
some small bottom-dwellers.

In addition it has been established that in spring considerable numbers of
flatfish migrate from the Sivash into the Utlyuksk inlet and the Sea of Azov.
Finally in some areas of the northern Sivash commercial production reaches
the very high rate of 100 kg/hectare. In the second (southern) part of the
northern Sivash the production is only 1 5 kg/hectare, while in the central and
southern Sivash it is insignificant.

A certain loss of salinity might have a favourable effect on the Sivash
fisheries. In Vorobieff's opinion this could be achieved by separating off the
western and southern Sivash from its main part by dams and by digging a
channel through the Arabat Strelka into the central Sivash.

A deepening of the channels connecting the Sivash with the Sea is desirable
in order to facilitate the entry and return of fish from the Sea of Azov. In
this way a wider area of the Sivash could be used for intensive fishery.

Vorobieff estimates in the following manner the size of the main groups of
organisms in the northern Sivash, by applying the methods used by I. Peter-
sen for Danish waters : 'The total amount offish in the northern Sivash, when
all food is used, may be estimated at 21,000 tons. When only two-thirds of the
food resources are used this quantity becomes 14,000 tons.' Vorobieff esti-
mates the annual resources of plant food for the zoobenthos as 628,000 tons :
'With. 10 as a coefficient, 62,800 tons of benthos could have developed from
these stocks. When only two-thirds of the food is used this amount becomes
41,900 tons, which approaches the data actually recorded.' Further calcula-
tions lead Vorobieff to the conclusion that of the 1,322,000 tons of phyto-
plankton and phytobenthos produced in the Sivash annually only a small
part is consumed by animals.

The Caspian Sea

I. GENERAL CHARACTERISTICS

The Caspian Lake-Sea is the largest enclosed body of water in the world, and
is exceptional in its peculiarity.

Salinity-stratification of its waters is much less pronounced than in those
of the Black Sea ; an oxygen supply, sufficient for the penetration of individual
numbers of its fauna to their limiting depths, is provided by water circulation.
However, the density of the population is high only in the upper horizon ;
below 100 m life is very much restricted owing to a shortage of oxygen.

The Sea has been apportioned to separate zoo-geographical provinces and
its fauna is composed mainly of remarkable, relict, genetically heterogeneous
forms — the remains of relict marine faunas, formerly much more widely dis-
tributed, which have survived in other marine and fresh bodies of water in
Eurasia and which are linked in origin with the Tethys fauna.

Immigrants from the Arctic basin, from the Black and Azov Seas (Medi-
terranean fauna) and from fresh waters are added to this nucleus of Caspian
fauna.

In the struggle for existence the Caspian fauna is inferior to the biologically
stronger fauna of the open seas ; this makes the Caspian Sea exceptionally
suitable for acclimatization.

Fisheries are very rich in the Sea, and its yield is original in its specific
composition.

II. HISTORY OF EXPLORATION

First period

The first data on the Caspian Sea biology are found in the works of P. Pallas
(1741-1811) and S. Gmelin (1745-74). Important biological data were
brought back by the expeditions of K. Baer (1853-56) and O. Grimm (1874
and 1876).

Second period

The next period, of a closer, more comprehensive study of the Sea, is con-
nected with the name of N. M. Knipovitch, who organised and carried out
three expeditions in it in twelve years (1904 to 1915) before the war, which
interrupted its further exploration for many years.

Knipovitch's first expedition worked in 1904, the second in 1912 and 1913
and the third in 1914-15. A general picture of the distribution of the depths of
the Caspian Sea, its currents, temperature, salinity, oxygen and hydrogen
sulphide content, as well as that of plankton, benthos and fish was obtained
by Knipovitch's expeditions. Seasonal changes in some of these phenomena
were also recorded. These expeditions provided the physico-geographical,

538

THE CASPIAN SEA 539

hydrological and biological foundation on which wider and profounder
researches were to be based in Soviet times.

Third period

Little was added to our knowledge of the Caspian Sea during the sixteen
years following Knipovitch's expedition. In this period the following should
be noted : N. Tchougounov's work on the census of the North Caspian ben-
thos (1923), on the feeding of the young of commercial fish (1918), and on the
North Caspian plankton (1921) ; and A. Derzhavin's thorough examination of
starred sturgeon, vobla and bream (1915, 1918 and 1922), and certain others.
The herring expedition (1930) and the All Caspian Fisheries Expedition
(1931-34) concentrated their attention almost exclusively on scientific-trade
problems.

Fourth period

In 1932 large-scale biological investigations were begun in the Caspian Sea
by the Oceanographic Institute and its branches which have eventually de-
veloped into a comprehensive study of all sections of oceanography within the
system of work of the All Union Institute of Marine Fisheries and Oceano-
graphy. During this fourth period the study of the hydrochemical conditions,
of the quantitative distribution of life and the phenomena of biological pro-
ductivity and of means of acclimatization have become particularly important
and widely developed.

The Astrakhan (1904) and Baku (1912) Scientific Fisheries Stations have
played an important part in the study of the Caspian Sea.

HI. PHYSICAL GEOGRAPHY, HYDROLOGY, HYDRO-
CHEMISTRY AND GEOLOGY

Situation and size

The Caspian Sea (see Fig. 256) extends in a north-south direction and is about
1,204 km long, with a width of from 204 km (opposite the Apsheron penin-
sula) to 566 km (in its widest part).

It lies between 47° 13' and 36° 34' 35" N latitude and between 46° 38' 39"
and 54° 44' 19" E longitude. The area of the Sea is 436,000 km2. Its volume is
about 77,000 km3, with an average depth of 180 m. The northern part of the
Caspian (north of a line Chechen Island to Tyub-Karagan Point) has an
average depth of only 6-2 m and its volume is less than 1/100 of that of the
whole Sea (0-94 per cent), whereas in area the Northern Caspian constitutes
about 27-73 per cent of the whole. The Central Caspian, if it is bounded on the
south by a line from Zhiloy Island to Kuuli Cape, forms a little more than one-
third of the volume (35-39 per cent), and about 36-63 per cent of the area of
the whole Sea, its average depth being 175-6 m and its greatest about 770 m.

The Southern Caspian, which is the deepest part of the Sea, has a greatest
depth of about 1,000 m and an average depth of 325 m. In volume this part
is a little less than two-thirds of the whole body of water (63-67 per cent);
and its surface area is 35-64 per cent. The depths of the Central and Southern

540

BIOLOGY OF THE SEAS OF THE U.S.S.R,

Caspian are divided by a comparatively shallow ridge running to the east
from the Apsheron peninsula at a depth of not more than 200 m.
The Northern Caspian is exceptionally shallow and is mostly not more than

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grained fraction ; // Coarse fraction.

10 m deep. There is a somewhat deeper part in its eastern region, the so-
called Gur'evskaya Furrow.

Sea-bed

The bottom topography is closely linked with the distribution of bottom-
deposits and detritus, as well as with that of the benthos biomass. Thick, soft

THE CASPIAN SEA 541

mud deposits {batkaki) are formed — frequently right at the shore and in
shallow water — under favourable conditions (bottom topography, slow cur-
rents) from the large accumulation of detritus brought down by river water
and retained by vegetation. Detritus and fine-grained soil fractions moved
away from the shores and were carried into the deep Central and Southern
Caspian depressions, which thus become encircled by a wide belt of the coarse
fraction, mainly huge beds of shell gravel (Fig. 256). This peculiarity — the
transfer of detritus from shallows to depths, and an abundance of pure shell-
gravel floors — is of cardinal importance for the phenomena of biological
productivity taking place in the Sea; it decreases considerably its potential
level, both as regards benthos and also, apparently, as regards plankton.

The organisms populating the Sea, the molluscs most of all, are of extreme
importance in the formation of the sea-bed. According to A. Kolokolov's
computations (1940) the ratio of plant nutrients to terrigenous substances in
the North Caspian sea-bed is about 1:1. Dead molluscs remain in those parts
of the Sea where they lived and sea-beds rich in shell gravel are formed, and
are thus most productive as regards benthos.

Sea level

The level of the Caspian Sea, averaged over the last century, has been 25-45 m
below the ocean level. Moreover, it is not constant from year to year, but
undergoes considerable seasonal variations and fluctuations which may last
for many years. The average level of the Caspian Sea (for the hundred years
1830 to 1929) is 327 cm from zero on the Baku sea-gauge (its level being 28-73 m
above sea-level). The highest level of the Sea, 363 cm above zero on the
Baku sea-gauge, was recorded in 1896, and the lowest in very recent years.
In 1945 the level of the Caspian Sea was only 134-26 cm, and it is continuing
to fall: Thus in the last 50 years the range of the fluctuations of the level of the
Caspian Sea has been 229 cm. In the last 17 years (1929-46) it has fallen by
almost 2 m (187 cm); the decrease is proceeding fairly uniformly. Only in
1942-44 was there some indication of a break in this uniformity, when the
level of the Sea rose by 1 1-5 cm as compared with 1941 ; by 1945, however, its
level had dropped again by 20-5 cm as compared to 1943.

There is reason to suppose that the catastrophic drop in the level of the
Caspian Sea, caused by the considerable decrease of river inflow (from 1930
to 1943) has now been stabilized at the level of about 130 cm above zero on
the Baku sea-gauge. A further insignificant drop of the level to 1 10 to 115 cm
above zero on the Baku sea-gauge may be expected in the coming years.

In the opinion of most investigators (L. Berg, S. P. Brujevitch and others)
these changes in the level of the Caspian Sea are the results of the fluctuations
in the amounts of fresh water received by the Sea from the rivers and from rain-
fall minus evaporation. According to a different view the changes are caused
by the movements of the earth's crust (I. Gubkin, P. Pravoslavlev and others).

A number of mountain ranges in the Southern Caspian, stretching from
north to south (Fig. 257), were discovered by recent investigations (V. Solov'evt
1958) with the use of an echo sounder. In Solov'ev's opinion they are of recen,
formation ; this indicates the continuance of structural processes, which could

542 BIOLOGY OF THE SEAS OF THE U.S.S.R.

naturally be linked with the change of sea-level. Similar mountain-forming
processes may probably be discovered also in the Central Caspian.

Although the second explanation may have some truth in it, it is possible to
show, as has been done in a graphic form by Brujevitch, that the fluctuations
in the level of the Caspian Sea are in close accord with the quantity of water
supplied by the rivers. The mightiest water-artery feeding the Caspian Sea,
the Volga, brings into it on the average about 270-8 km3 of water each year.
According to G. Bregman's calculations about 75-6 per cent of the whole
supply of fresh water is brought by the river Volga (the average annual in-
flow from rivers, measured over many years, has been 355 km3). The con-
formity between the fluctuations of sea-level and those of the inflow of the
Volga waters is so close that the direct influence of the latter on the level of
the Sea has been established (Fig. 258).

Zenkevitch considers that the greatest part of the shore of the Caspian Sea

Fig. 257. One of the latitude contours of the Caspian Sea bottom in its southern part
(Solov'ev, Kulakova and Agapova).

bears a definite imprint of the effect of a considerable lowering of its level,
characteristic of the whole Quaternary period. A huge lowland area was sub-
merged by the ancient Caspian in the north, and now its shores are moving
southwards along the completely flat surface of the ancient sea-bed. Only the
extensive delta of the Volga is under the influence of fluvial factors and is
growing as a result of alluvial accretion. All along the rest of the shore the
morphology is not clearly defined, and the water's edge may recede up to
20 km to the south, due to the effect of on-shore and off-shore winds.

The western (Caucasian) shore consists of relatively solid Neogene car-
bonate rock. Nevertheless alluvium-bearing currents may be formed along
this coast. Alluvium deposited by them is supplied by large rivers (Samur,
Sulak, etc.) and by the washed out sea-bed, from which a mass of shell gravel
is cast up on to the beach. South of the Apsheron peninsula the coast is more
irregular with a number of headlands and a whole archipelago of islands,
mud-volcanic and others, lying to seaward. Farther south, within the area of
the delta of the river Kura, the stretch of friable alluvial shore begins and
extends to within the boundaries of Iran.

The abundant shallows round the Apsheron peninsula have a peculiar
structure. Complex tectonic structures have been discovered on the bottom,
some of them oil-bearing, and marine petroleum works have been set up there.

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544 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Large areas of the sea-bed are covered with sand. The whole southern shore
of tne Sea is an alluvial plain, receiving a large number of rivers which flow
down from the El'burz range.

The structure of the eastern shore of the Sea is also peculiar. There is no
river inflow, and the deserts border immediately upon the Sea. The contour
of this shore is uneven. Abrasion ledges, formed of Neogene carbonate rock,
alternate here with low-lying areas with coastal bars and long shoal-heads. The
eastern coast alluvium consists mainly of shell gravel and oolitic grains (a
variety of granular calcite).

Large coastal bars and shoal-heads have been formed in many places on
this coast by marine sediments thrown up by the Sea. Among them the follow-
ing may be noted : the bar of the Kara-Kul lagoon, the bars and shoal-heads
of Krasnovodsk Bay and of Kara-Bogaz-Gol Bay, and likewise Ogurchinsky
Island and the submarine bank which continues it far to the south (V. Zen-
kevitch, 1957).

In the area of Krasnovodsk and Turkmensk Inlets, with its peculiar struc-
ture, the coast has retained its uneven outline. The estuary of the ancient Oxus
(Amu-Darya) was situated here. Farther south, and right up to the frontier
of Iran, the sand desert of southwestern Kara-Kum borders the Sea.

Water balance

The huge area — 3-7 million km2 — of the Caspian Sea basin receives annually
about 355 km3 of river water (Table 224) :

Table 224

Proportion of

River

Volume delivered

whole delivery

km3

°/

Volga

270-83

76-3

Kura

17-22

4-9

Ural

1317

3-7

Terek

11-31

3-2

Others

42-65

11-9

Total 355-18

100

This mass of river water flowing into the Caspian Sea, comprising about
1/250 of its whole volume, is increased by rainfall to 451 km3 or to 1/176 of
the whole volume. Without evaporation this quantity of water might have
raised the level of the Caspian Sea by 123 to 125 cm* in one year. The climatic
conditions determining the quantity of river inflow, of rainfall and evapora-
tion would, with such a water balance, evidently have a considerable effect
on the sea-level, and by influencing the salinity of the upper layers of the Sea

* V. Prishletzov (1940) determines the average annual evaporation from the whole
Caspian Sea as 86-6 cm.

THE CASPIAN SEA

545

cause, as we shall see below, considerable changes in the phenomena of bio-
logical productivity.

According to Brujevitch's computations (1938) the level of the Caspian Sea
would remain practically constant with an average Volga inflow of 257 km3.
The level would inevitably drop with a decrease in the inflow, and would rise
with an increase (Fig. 258).

Fluctuations of the level of the Caspian
Sea are complicated by seasonal changes ;
during the first half of the summer after
the floods, the level is at its highest, and
it is at its lowest at the beginning of
winter.

Currents

The movements of the water masses of
the Caspian Sea, like those of any other
sea, are expressed in a system of vertical
and horizontal displacements due to
different causes. The Caspian Sea is
encircled by a large cyclonic current,
forming two powerful halistatic areas in
the Southern and Central Caspian (Fig.
259). The speed of this current along the
western side of the Central Caspian may
reach, according to Stokman (1938), 20
cm/sec. On the approach to the shallows
of the Northern Caspian the main mass of
waters,' moving from the south along the eastern shore of the Sea, turns to
the west and, farther on, to the south, receiving the main mass of the dis-
charge waters of the Northern Caspian. Part of these waters passing the
Mangyshlak peninsula is diverted into the Northern Caspian.

There is a separate cyclonic current in the southern part of the Southern
Caspian with its own halistatic area in the centre. Part of the waters moving
southwards along the western side of the Central Caspian runs away from the
western shores, at the latitude of the Apsheron ridge, and passes to the eastern
side. The Volga waters move south partly along the western coast, partly
directly east, creating two anticyclonic gyrations : one to the northwest from
the northern end of Kulaly Island, the other to the northeast over the Ural
trench. The existence of a circular movement of waters over the Ural trench is
confirmed by the accumulation of soft silty deposits in the trench, by the
presence of hydrogen sulphide, and by the absence of hydrogen sulphide in the
sea-bed encircling the trench as a result of the washing-out effect of the cir-
cular current. In the Northern Caspian, however, especially in summer, the
picture of the permanent currents is changed by strong winds owing to the
shallowness of the Sea, and by on- and off-shore winds (A. Milkhalevsky, 1931).

According to N. Gorsky (1936) the system of the winter under-ice currents
of the Northern Caspian differs greatly from what has just been described.

2м

Fig. 259. Currents of the Caspian
Sea (A. Mikhalevsky, 1931).

546 BIOLOGY Of THE SEAS OF THE U.S.S.R.

Saline Central Caspian waters slowly fill the Ural trench, flowing in between
Kulaly Island and the Central-Zhemchuzhnaya Bank close to the Buzachi
peninsula. A compensating current of fresh water runs mostly along the
western shore of the Northern Caspian.

Vertical transferences of water masses

The vertical mixing of the Caspian Sea water masses is well assured, with
comparatively small differences in the density of the surface and deeper layers
of water owing to winter cooling, to the effect of on- and off-shore winds,
to the heating of deep waters owing to adiabatic processes, and as the result
of turbulence.

Temperature conditions

Temperature conditions in the Caspian Sea are very peculiar and are deter-
mined by a sharp difference in temperature between its southern and northern
parts in winter and a levelling-up of the temperature in summer. On the other
hand, strong annual fluctuations of temperature are characteristic in the
upper layer of the Sea, with uniform temperature in its deeper part. The fact
that the Caspian Sea extends for 1,200 km from north to south determines
also the climatic differences on land adjacent to the Sea. The average annual
air temperature at the mouth of the river Ural is 7-8° C, and at Pehlevi 15-6°.
However, in some years it may reach 19-5° (Inlet of Astrabad). In January the
average temperature at the mouth of the river Ural is — 10-5°, and at Pehlevi
+5-9°. In July the difference between the air temperatures of the shores of
the Northern and Southern Caspian is only 3° to 3-5°.

Since the Sea is heated mostly from its surface, the difference in the air
temperatures of areas adjacent to the northern and southern parts of the Sea
controls the difference in the surface temperature of the Sea. The nature of the
distribution of surface temperature and its seasonal changes are well illu-
strated by Fig. 260. Almost all the northern part of the Sea is commonly
(with variations in different years) covered with ice for four months a year
(December to March). The ice-cover attains a thickness of 40 to 50 cm, and
in the northeast even of 70 cm; the temperature of the water drops to —1°.
For the surface layer of the Sea January and February are the coldest months,
and July and August the warmest. The heating of the Sea in spring and its
cooling in autumn start at the coastal shallows, gradually spreading to the
centre and into the depths. In the hottest time of the year the surface tempera-
ture may rise to 30° and even 30-8°. The seasonal range of temperature fluctua-
tions is sharply pronounced in the upper layer and grows gradually less and
less with depth, and finally at 400 to 450 m it completely fades away ; below
this lies a layer of a practically constant temperature, with a somewhat
higher temperature in the Southern Caspian depression (a little below 6°) as
compared with that of the Central Caspian (slightly below 5°). As in any
other sea, time is required for the heating to be transferred into the depths
and with increasing depth this delay becomes greater. Knipovitch has shown
that in 1914-15 the maximum heating of surface water occurred at the end of

THE CASPIAN SEA

547

<±/~~*^£^

t ff, " /r~

\25 W%

JPv p

26 j>;

AUGUST i^^M^^

Fig. 260. Diagrammatic distribution of surface temperatures
of the Caspian Sea in (A) February and (B) August.

July and the beginning of August. At a depth of 50 m the highest temperature
was reached by the end of August, at that of 100 m in January, while deeper
still the greatest rise of temperature was in February ; that is, with a delay of
six months. At a time when it is winter on the surface of the Sea, at a
depth of 300 to 400 m there is a ' hydrological summer'. Below 400 m the
temperature remains constant. As an example the average annual data may
be given (Table 225); these allow a comparison to be made of the vertical

Table 225

Central Caspian

Southern Caspian

Mean temp.

Mean temp. Mean temp.

Depth

21 Feb to

25 Jul to

21 Feb to 25 Jul to

8 Mar 1934

12 Oct 1934

8 Mar 1934 12 Oct 1934

5-94

22-03

905

24-18

5-78

6-63

8-92

9-58

100

5-62

5-76

7-20

7-11

200

5-27

5-29

611

6-14

Mean annual temperat

Lire

Mean annual temperature

300

5-07 5-01

4-96

5-91

5-93 5-96

400

4-88

5-90

500

4-82

5-93

600

4-86

5-93

700

4-83

5-92

800

5-96

900

5-94

548

BIOLOGY OF THE SEAS OF THE U.S.S.R.

course of temperature in the Central and Southern Caspian as well as the
temperatures in the cross sections, longitudinal along the Sea and transverse
ones across the Central and Southern Caspian (Fig. 261a, в, c).

Fig. 261 . Isotherms of cross sections of the Caspian Sea in (A) winter, and (B) summer

(Brujevitch, 1937).

The temperature of the deep waters of the Caspian Sea varies but little and
in practice it may be considered constant. Over the last 20 years a difference
of only 0-05° has been recorded in the depths of the Sea (according to Bruje-
vitch, 1937).

It had already been established by the work of Knipovitch that there is a

THE CASPIAN SEA

549

rise of temperature of a few hundredths of a degree in the bottom layer of the
two Caspian Sea depressions.

N. Gorsky (1936) explains this by two causes: the heat radiated from the
earth's crust, and the rise of temperature obtained as a result of the com-
pression of water at great depths (adiabatic process).

The temperature conditions of the Northern Caspian differ considerably

1000 SOUTHERN CASPIAN

Fig. 261c. Isohalines (by chlorine) of the cross sections of the Caspian Sea

(Brujevitch).

from those of the Central and Southern. In consequence of its shallowness and
of the ease with which its water is displaced by wind and of the vigorous pheno-
mena of the on- and off-shore winds, stratification is hardly maintained at all
in the Northern Caspian. The isolines usually run vertically not horizontally,
i.e. changes of temperature, salinity, etc. run not from the surface of the Sea
to its bottom, but from the centre to the shores. Hence each of the three large
parts of the Caspian Sea has its own definite temperature characteristics (Fig.
262).

Ice conditions

Only the Northern Caspian has an ice-cover every winter. First of all, with
the onset of the frosts, huge 'young shore ice' is formed in the shallows where
the water is of low salinity. After two weeks the deeper part of the sea is
covered with ice. This delay is due to the higher salinity of the central part
of the Northern Caspian and to its greater swell which breaks the crust of the
congealing ice. Strong variable winds destroy the ice, even when the central

550

BIOLOGY OF THE SEAS OF THE U.S.S.R.

part of the Sea has been frozen, causing some clearings and the formation of
drifting ice fields. The fields drift at varying speeds and constantly collide
with each other : some get broken up, and at times one field is forced on top

Temperature
IO /5

Central Caspian
Southern Caspian

Fig. 262. Diagram of vertical distribution of tem-
perature in winter and summer from the three parts
of the Caspian Sea (Knipovitch, 1923).

of another. Thus there are formed embacles and lump ice, that is, big floes
which go aground and grow bigger on account of more drifting floes sliding
on top of them. The limit of solid ice is more or less permanent. It runs along
the 12 m isobath from the northern end of Kulaly Island to Tyuleni Island.

Salinity

The salinity of the Caspian Sea differs greatly from that of the ocean both in
the ratio of its components and in their sum. According to S. P. Brujevitch
(1937) the average composition of the waters of the Caspian Sea, the river
Volga and the ocean are determined by the data expressed in percentages
appearing in Table 226.

The chlorine coefficient of the Caspian Sea may be taken as 2-396 (by Lebe-
dintzev, 2-386) and its average salinity as 12-80 to 12-85%0. Alternatively the
salinity may be represented as in Table 227 (according to Knipovitch, 1923).

As shown by the tables, Caspian waters are poor in sodium and chlorine
and rich in calcium and sulphates by comparison with the ocean ; this differ-
ence in the salt ratio makes its water approximate more to river water.

The surface salinity of the Central and Southern Caspian is fairly uniform ;
it is contained between the isohalines of 12 and 13%0. Only in the far south-
eastern corner of the Sea (Krasnovodsk Bay) is the surface salinity above

THE

CASPIAN SEA

551

Table 226. Total salinity

Caspian

Sea

Salts of

Volga at

Earlier data

Brujevitch

Astrakhan

Ocean

12-63 to 12-89%0 i:

2-68 to 12-94%0

0-19856%0

jj/oo

24-69

24-82 \
0-66/

6-67

30-593

0-63

1106

2-59

2-70

23-34

1-197

5-66

5-70

4-47

3-725

41-67

41-73

5-46

55-292

008

006

—

0188

S04

23-82

23-49

25-63

7-692

CO3

0-86

0-84

34-43

0-207

13%0. To the north the 12%0 isohaline runs somewhat south of the boundary
between the Northern and Central Caspian. Farther north salinity falls fairly
sharply at the delta of the rivers Volga and Ural. A picture of the distribution
of the surface salinity is given by Figs. 263a and 263b.

In the open parts of the Sea salinity increases with depth, as shown in
Table 228 which gives the average annual salinities for August 1933.

Vertical salinity distribution is also given in the foregoing diagrams (Fig.
261a, в, c).

The quantity of river water and precipitation received by the eastern shores
is very low, since evaporation is considerable. As a result a greater or lesser
rise of salinity is observed in all the inlets of the eastern part of the Caspian
Sea. In Kaidak, which no longer exists, salinity reached 59-52%0 in 1934
(with. a chlorine number of 2501). In the inner parts of Krasnovodsk Bay
salinity is almost as high, but it reaches its maximum in Kara-Bogaz where
at times it goes up to 200%o. S. P. Brujevitch (1950) has pointed out that a
decrease of river inflow has caused a considerable rise of salinity in the
Northern Caspian. Thus in 1939 the average surface salinity reached 5-42%0 in
chlorine, i.e. a salinity observed in the depths of the Central and Lower
Caspian {Table 228).

Table 227

Salt

Caspian Sea

Ocean

NaCl

62-15

78-32

MgS04
MgCl2 \
MgBr2 J
CaC02

23-58
4-54
1-24

6-40
9.44

0-21

KC1

1-21

1-69

CaSQ4

6-92

3-94

99-64%

10000

552

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Fig. 263a. Distribution of surface Fig. 263b. Distribution of surface salinity of

salinity (%0) of the Caspian Sea in the northern Caspian Sea in June 1934 (%0)
February and March 1934 (Brujevitch, (Ivanov).

1950).

The difference in the salt ratio of Caspian and ocean waters {Table 227),
which appeared as a result of the separation of the Caspian Sea from the ocean
and which is gradually rising owing to the metamorphism by river discharge,
makes it possible to calculate the approximate period of time of the existence
of the 'lake' phase of the Caspian Sea. S. Brujevitch (1939) has calculated it in

Table 228

Salinity %c

Depth, m

100

200

300

Central Caspian
Southern Caspian

12-59
12-61

12-66
12-65

12-68
12-68

12-72
12-74

12-76

Depth, m

400

600

800

900

Central Caspian
Southern Caspian

12-76
12-82

12-78
12-84

12-84
12-87

12-90

THE CASPIAN SEA 553

relation to chlorine, magnesium and the sulphates. He considers the 'lake age'
of the Caspian to be about 1 5,000 years.

In the salt balance of the Caspian Sea the carrying away of the salts beyond
the limits of the Sea by the wind plays a definite role. L. Blinov (1950) deter-
mines by means of complex computations the amount of salts carried away
from the surface of the Caspian Sea beyond its limits as 62,400 tons per day
(at an average wind speed of 6 m/sec), which is about 30 per cent of the total
accession of salts from the river inflow (according to S. P. Brujevitch it is
195,000 tons per day).

Oxygen

The oxygen conditions of the Caspian Sea are the result of the following fac-
tors. In summer the oxygen content at the surface of the Sea is near saturation :
98 per cent in the Central Caspian and 94 per cent in the Southern. In the
Northern Caspian the picture is rather more varied, but on the average the
oxygen content is more than 90 per cent. There is a slight supersaturation in
the winter throughout the whole surface of the Sea (103 to 105 per cent).
Changes in oxygen content with depth are shown in Table 229 and in Fig. 264.

Table 229

Average amounts and seasonal differences in the content of

oxygen dissolved in water for various parts of the Caspian Sea

as percentage of saturation

Seasonal variations

Central
Caspian

Depth

Caspian

Central

Southern

' m

Feb-Mar 1934

Caspian

101

104

101

103

101

100

200

400

(32)

—

600

800

— ■

—

The decrease of oxygen content with depth in the Caspian Sea is not nearly
so pronounced as that of the Black Sea. As we have seen, the much weaker
saline stratification does not hinder the penetration of the vertical displace-
ment of water into the depths. It is evident from the comparison given that in
the Central Caspian the oxygen content is higher than in the Southern.

Substantial changes have taken place in oxygen distribution in the column
of Caspian waters in the 40 years since the last works of N. M. Knipovitch
(1914-15). Oxygen was then entirely absent near the bottom of the Central

554

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Caspian. In 1934 even at the greatest depths there was some 0-13 to 0-64 cm3/l.
of oxygen. According to N. M. Knipovitch's data (1914-15) for the Central
Caspian, at a depth of 700 m oxygen was disappearing and hydrogen sulphide
appearing (up to 0-3 to 0-4 cm3/l.). A smaller amount of hydrogen sulphide
was recorded in the Southern Caspian. In 1934 S. Brujevitch recorded some
small amounts of hydrogen sulphide (about 0-2 cm3/l.) in the Southern Cas-
pian at a depth of 700 m.
As in the Black Sea, the hydrogen sulphide is mainly the result of anaerobic

SOUTHERN CASPIAN

Fig. 264. Oxygen content (percentage saturation) of the Central Caspian in cross

section (Brujevitch, 1934).

reduction of sulphates due to the activities of bacteria of the Microspira type.
Moreover A. Pelsh (1936) discovered in the Caspian Sea a new group of
bacteria (Hydrogenthiobacteria) capable of synthesizing hydrogen sulphide
from solid sulphur and gaseous hydrogen. In contrast to that of the Black
Sea, animal life in the Caspian Sea penetrates to the greatest depths.

Suffocation phenomena of the type found in the Sea of Azov have not been
recorded in the Caspian Sea. If they do exist in the Northern Caspian they are
probably local and limited ; this is confirmed by the absence from the Caspian
of zones of blackened shell gravel, so typical of the Sea of Azov. This is ex-
plained by the wide distribution of sand and large-grain soils in the shallows
encircling the Caspian depths, which indicates a sufficient aeration of the
bottom layer in shallow areas. It is different in the shallows with mud-accu-
mulations, where a very marked shortage of oxygen (4 to 20 per cent of satu-
ration) has been recorded at times. A mass accumulation of soft mud-beds
in protected regions and bottom hollows, however small, is due to abundant

THE CASPIAN SEA

555

organic substances, either brought by the rivers (allochthonous), or gathered
in the Sea itself as the remains of dead animals and, still more, dead plants
(autochthonous). Such regions are most frequent in the Northern Caspian,
often in very shallow places. In the eastern part of the Northern Caucasus,
in the Kaidak and Mangishlak areas, and in Krasnovodsk Bay large areas of
the bottom are covered by muds many metres thick, the so-called batkaki,
rich in organic substances with a thick bacterial crust, evolving huge amounts
of methane and hydrogen sulphide. According to A. Sadovsky (1929) a 4 cm

SOUTHERN CASPIAN

Fig. 265. Distribution of nitrate nitrogen in the Caspian Sea waters (mg/m3) in
cross section (Brujevitch, 1934).

layer of mud is accumulated there annually. Throughout the northern shore of
the Northern Caspian, in Agrakhansk Bay and in Krasnovodsk Bay, we find
similar zones of huge deposits of decaying organic matter. They also fill the
central part of the Ural trench. Under certain conditions, when the water in
these shallows gets thoroughly mixed by a gale, the top layer of the soil may
be washed away and hydrogen sulphide may enter the water. These pheno-
mena may sometimes become acute and lead to suffocation. It is a purely
local phenomenon, linked with the occurrence of muds rich in hydrogen
sulphide in very shallow areas.

Let us now consider the content of nitrogen, phosphorus and silicon com-
pounds in the Caspian Sea waters (Figs. 265, 266 and 267).

Nitrogen

Ammonia nitrogen content in the Caspian is about the same as that of the
Baltic and North Seas, higher than in the ocean, but in deeper layers much
lower than that in the Black Sea. Its amount in the Caspian fluctuates within
a few tens (20 to 50, and in the Southern up to 70 mg/m3).

The nature of the distribution of nitrites is similar to that of other seas. In
winter the nitrites are found fairly uniformly distributed within a 50 to 100 m

556

BIOLOGY OF THE SEAS OF THE U.S.S.R.

SOUTHERN CASPIAN

Fig. 266. Distribution of phosphate phosphorus in the Caspian Sea (mg/m3) in
autumn in cross section (Brujevitch, 1934).

column of water. Deeper down the nitrites are absent. Nitrites are accumulated
in the summer at a depth of 50 to 100 m with the development of phyto-
plankton and the establishment of temperature stratification. Below 100 m the
content of nitrites gradually decreases, and below 400 m it falls to zero.

Unlike ammonia and nitrite nitrogen, nitrate nitrogen gives an original
picture of distribution different from that of other seas. Intensive accumu-
lation of nitrates proceeds at 100 to 600 m (mainly at 200 to 400 m). Above
100 m, within the zone of intense vertical circulation and the consumption
of plant nutrients, the nitrate content is either very low (in winter in the Central
Caspian 5-10-15 mg per 1 m3) or absent (in the summer). The lower limit of

SOUTHERN CASPIAN

Fig. 267. Distribution of silicon in the Caspian Sea (mg/m3) in autumn in cross
section (Brujevitch, 1934).

THE CASPIAN SEA

557

the layer rich in nitrates is linked with the horizon of the sharp fall of oxygen
content. Within the water column, at 200 to 400 m deep, nitrate nitrogen con-
tent fluctuates between 110 and 180 mg/m3; below 600 m nitrates disappear.

Fig. 268. The carrying out of nutrient substances by river waters in the northern

Caspian (mg/m3). A Phosphorus content by the end of August (Brujevitch and

Ivanov) ; В Nitrates in front of the Ural delta in February and March (Brujevitch

and Fedosov); С Silicon in September (Brujevitch and Ivanov).

This is similar to the distribution of nitrates in the Black Sea, only the upper
zone of impoverishment is thinner there (above 50 m) ; it frequently contains a
considerable amount of nitrates. The lower limit of this zone is at 200 m.
Both Seas have similar amounts of nitrates.

The Caspian waters are kept continuously enriched in nutrient salts by
river waters (Fig. 268).

Phosphorus

As in other seas the phosphates are completely absent from the upper layer
of the Caspian Sea in summer. In winter they are found in small amounts in the
upper layer, but not everywhere (up to 6 to 9 mg/m3). From 100 m downwards
the phosphorus content increases to 60 to 80 mg/m3 {Table 230 and Fig. 266).

Table 230. Average amounts of phosphate phosphorus in mg/m3 in the Caspian Sea

Depth, m

100

Central Caspian
Southern Caspian

Winter
Autumn
Winter
Autumn

4-2
01
10
0-3

4-2
0-2
1-2
01

4-8
0-4
1-3
01

3-8

1-6

9
11
11
11

Depth, m

200

400

600

800

900

Central Caspian
Southern Caspian

Winter
Autumn
Winter
Autumn

27
24
24
24

38
35
37
41

53
44
50
49

(75)

(52)

78
65

558

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Seasonal fluctuations in phosphorus content in the upper layer of the Cas-
pian Sea are very small — in the Southern Caspian about 1 mg/m3, in the Cen-
tral Caspian up to 4-5 mg/m3; these data are commonly much higher in other
seas : in the Barents Sea phosphorus is up to 22 mg/m3, in the Channel up to
18 mg/m3.

Silicon

As in other seas the quantity of silicon remains very high in the upper layers
of the Caspian all through the year {Table 231).

Table 231. Average amounts of silicon in mg\mz in the Caspian Sea

Depth, m

100

Central Caspian
Southern Caspian

Winter
Autumn
Winter
Autumn

426
346
321
226

426
306
305

212

428
371
246
245

443
517
317
331

496
594
486
547

Depth, m

200

400

600

800

900

Central Caspian
Southern Caspian

Winter
Autumn
Winter
Autumn

910

907
747
749

852
1,485
1,355
1,315

3,019
2,560
2,040
2,116

2,193

2,319

2,742

There is more silicon in the upper layer in winter, while in the summer the
largest quantity is found at a depth of 50 to 100 m; this is connected with
the development of plankton and its regeneration in a deeper layer from the
sinking dead plankton. Seasonal fluctuations in silicon content in the upper
layer are similar to those observed in the Barents Sea and the Channel (about
100 mg/m3).

Vertical zonation

S. P. Brujevitch has established a definite vertical zonation of the Caspian
Sea waters on the basis of his comprehensive study of the hydrochemistry
of the Sea; it is related mainly to the distribution of plant nutrients.
Brujevitch (1938) calls it structural zonation {Table 232).

Table 232

Zones

Depth, m

Subzones

Depth, m

I. Zone (impoverishment)

of consumption of plant

nutrients 0-100

II. Zone (aggregation) of

accumulation of plant

nutrients Below 100

IA Photosynthesis

IB Nitrites
IIA Nitrates
IIB Reduction

0-25 (50)
50-100
100^00 (600)
Below 400 (600)

THE CASPIAN SEA 559

The upper zone is the area of phy toplankton activity, with intensive photo-
synthesis proceeding mainly in the 25 to 50 m layer. Below 100 m there is
accumulation of organic matter and plant nutrients caused by the sinking
down of the remains of dying plankton, while vertical circulation is not
sufficiently strong to bring them up in any considerable quantities; thus
accumulation is greater than consumption. Within the zone of impoverish-
ment of plant nutrients only the 25 to 50 m layer (on the average 35 m) is
characterized by intensive photosynthesis (the subzone of photosynthesis).
Deeper down, sunlight does not penetrate in the amounts required for intensive
phytoplankton development. The nitrites are accumulated below the photo-
synthesis subzone as a result of the decomposition of plankton organisms,
which sink into this subzone (the nitrites subzone). The two subzones of the
upper zone are divided in summer time by a layer with a sharp temperature
drop and are hardly mixed at all. The upper zone is intensively mixed when
the surface water is cooled, and plant nutrients, which had disappeared from
the upper layer in the summer, are distributed throughout its whole column.
Within the accumulation zone the oxygen content decreases while the plant
nutrients increase with depth. A considerable accumulation of nitrates, mostly
at depths of 200 to 400 m, is characteristic of the upper part of this zone ;
at a greater depth (below 400 m) ammonia nitrification becomes impossible
owing to a shortage of oxygen and the process stops at the ammonia stage.
A sharp decrease of oxygen content is characteristic of the lower boundary
of the nitrate subzone.

Mean data along the cross section Kurinsky Kamen'-Ogurchinsky Island
for August 1933 are given in Table 233 and in Fig. 269. The letters and Roman
figures correspond to Brujevitch's zones and subzones in Table 232.

Table 233

Nitrate

Nitrite

Ammonia

Zones Sub-

Depth

t°C

CO/
*J/00

nitrogen

zones

°/

mg/m3

( °

25-03

12-61

8-42

1-1

194

24-81

12-62

8-41

1-3

197

I 25

24-57

12-63

8-41

1-5

193

—

(50
1 100

10-45

12-65

8-30

2-2

214

1-3

—

7-90

12-68

8-22

7-0

265

0-5

—

11 A

/200
\400

6-20

12-74

8 00

26-0

561

115

0-2

5-86

12-82

7-85

400

1,000

100

1-1

—

/600

5-87

12-84

7-74

560

1,637

—

800

5-87

12-87

8-72

67-0

1,855

—

1 900

5-88

12-90

7-74

700

2,000

—

Naturally none of these boundaries remains constant, especially in differ-
ent parts of the Caspian Sea, and some of them frequently do not coincide
with each other. Sharp changes in quantities of phosphates do not coincide
with the boundary of the accumulation of nitrates and silicic acid, etc. The

560

BIOLOGY OF THE SEAS OF THE U.S.S.R.

main zones of enrichment have the following sequence : silicic acid, nitrates,
phosphates.
L. A. Zenkevitch had suggested a little earlier (1932) a different vertical

0 200 400 BOO 800 1000 1200 1400 1600 1800 2000 Si mp/m 3
< i 1 1 1 ■ 1 1 1 ■ ■ o/

0.0 0K5 1,0 1,5 N(N02)mg/m3

0 10 20 30 40 50 60 70 80 90 100110 120 P, N(N03) mg/m 3

0
100
200
300
400
<^500

-to

^600
700
800
900

20 22 24 26
t° S%c,02 с cm

Fig. 269. Distribution of main elements of the medium in Caspian Sea
waters. / Subzone of photosynthesis ; // Nitrites subzone ; /// Nitrates
subzone; / V Reduction subzone (Zenkevitch, 1947).

division of the water column into zones for the Barents Sea based chiefly on
oxygen conditions (see Barents Sea). The two diagrams, however, can be
contrasted.

Chemical conditions of the Northern Caspian

Hydrochemical conditions of the Northern Caspian differ greatly from those
of the rest of this Sea because of its instability, its strong seasonal fluctuations,
and its greater dependence, owing to its shallowness, on winds and the
chemical properties of its soil. Slightly less than 300 km3 of fresh water are
brought into the Caspian Sea each year by the rivers; rainfall adds about
18 km3, and about 100 km3 is lost by evaporation, so that the annual gain in
fresh water is of the order of 200 km3, i.e. about one-fourth of the whole
volume of water of the Northern Caspian. The volume of winter ice in the

THE CASPIAN SEA 561

winter is about 10 per cent of the whole volume of water. Intensive'early
summer flooding, which freshens this part of the sea, considerable seasonal
fluctuations of water-exchange with the Central Caspian, sharp fluctuations
in the amounts of plant nutrients brought in with fresh waters, all these
factors make the Northern Caspian saline conditions unstable and change-
able. The large river-mouth areas of the Sea become almost completely
freshened under the effect of river water. Salinity increases in the south, and
on the boundary between the Northern and Central Caspian (along the line
Chechen' Island-Mangishlak peninsula) the average salinity is 5T%0 by
chlorine* (the general salinity being 12-1%0). Salinity decreases to the north
of this line. The Northern Caspian mainly has a salinity of 8 or 9%0 : only in
the estuaries of the rivers Volga and Ural does the salinity drop sharply.
Huge amounts of plant nutrients are brought into the Northern Caspian with
the fresh water ; they are found in amounts maximal for the whole of the
Caspian Sea just to seaward of the Volga and Ural delta : up to 40 mg phos-
phorus, up to 2,800 mg silicon, up to 250 mg nitrogen as nitrates per 1 m3.
The junction of the fresh waters rich in plant nutrients with the more saline
waters is a place of huge plankton development (up to 2,000 to 4,000 mg/m3).
A kind of powerful phytoplankton filter is created and only a very small
quantity of plant nutrients passes through it, so that outside it the quantity
of plankton diminishes sharply to a few or a few tenths of mm3 per 1 m3.
Hence, since the plant nutrients are almost completely used up by the great
gatherings of plankton just seaward of the deltas, the Sea is supplied with it
not directly from the river inflow, but only from detritus plant nutrients and
from the diluted organic, and probably colloidal, compounds. The bottom
deposits of the zone situated to seaward of the deltas play the role of a store-
house for a definite period. The distribution of huge silt deposits in the
Northern Caspian, forming wide bands in front of the Terek, Volga and Ural
estuaries, is in complete accord with this.

Changes in depth of vertical circulation

Being distributed throughout the whole Sea, plant nutrients drift finally into
the deep depressions of the Central and Southern Caspian ; return from there
is difficult and rare. However, there is another factor which influences the
return of plant food from the deep depressions, which act as huge store-
houses.

The upper layer of the Sea would get either more or less saline as a result
of an increase or decrease of river inflow, which would also cause either a
rise or a fall of the level of the Caspian. However small the salinity fluctua-
tions of the upper layer of the Sea they would affect the vertical mixing of
waters. With increase of salinity in the upper layer the lower limit of vertical
circulation goes deeper (possibly only by a few tens of metres), especially in
winter ; deeper layers of the sea rich in plant nutrients will then be drawn into

* The usual Knudsen formula for the determination of the total salinity of marine
water from the chlorine numbers cannot be applied to the Caspian Sea, and the co-
efficient 2-38, established by Lebedintzev, is used instead — S%0 = Clx2-38.

562 BIOLOGY OF THE SEAS OF THE U.S.S.R.

the circulation, and in spring the upper column of water will be better 'ferti-
lized' than in years when the upper layer becomes fresher and the lower limit
of circulation moves upwards. As a result there may be years more or less
favourable for the quantitative development of phytoplankton, and conse-
quently of zooplankton and all the succeeding links in the food chains.

During the last few years the level of the Caspian has gone down by 2 m.
At the same time these years were characterized by an extremely vigorous
plankton development. Brujevitch has pointed out that during a 22 cm fall
in the level of the Sea from 1933 to 1934 the salinity of the upper 100 m
column of water must have been raised by almost 0-1 %0. The quantity of
nutrient salts at a depth of 50 to 100 m in 1934 was higher than that in 1933 ;
this probably indicates their rise from great depths as a result of more intense
vertical circulation {Table 234).

Table 234

Depth
m

Phosphorus, rr

g/m3

Silicon, mg/m3

Nitrate

nitrogen,

mg/m3

Aug

Feb

Oct

Aug

Feb

Oct

Aug

Feb

Oct

1933

1934

1933

1934

1933

1934

0-8

194

392

253

1-3

0-7

197

351

266

1-5

1-3

193

262

267

2-2

4-0

214

346

391

100

110

265

469

612

IV. FLORA AND FAUNA

General characteristics

The Caspian Sea fauna (Fig. 270), qualitatively very poor, is very varied in its
origin ; its basic forms are descended from the Tertiary marine fauna, which
underwent considerable evolution as a result of changes in the orography and
in the whole hydrological conditions of the Sea. The remains of the fauna of
Tertiary seas of the Sarmatian and Pontic periods are represented by such
characteristic groups of the Caspian Sea as : herrings, bullheads, Bentho-
philus ; the molluscs by various forms of Cardae (except Cardium edule) ; and
by Dreissena, Bryozoa Victorella, the polychaetes Hypania, Hypaniola Parhy-
pania and perhaps Manayunkia caspica ; some of the Turbellaria ; all the Deca-
poda except prawns and Heteropanope ; Cumacea; most of the mysids;
Gammaridae ; Porifera ; the medusa Moerisia and the hydroid Cordylophora.
Later immigrants from the northern (Arctic community) and western (Medi-
terranean community) seas and from fresh waters are mixed in considerable
numbers with this basic part of the fauna.

This fourfold genesis of the Caspian Sea fauna is a striking peculiarity
of its biology. During the periods of its history when its salinity was
greatly reduced it became a body of almost fresh water (for example the
Glacial transgression) ; at least into some of its component parts, a fresh-
water fauna made its way there and partly adapted itself to the subsequent

THE CASPIAN SEA

563

rises in salinity. Such were the cyprinids and perch, the most important
among fish, all or almost all the gastropods, tubificid worms, some of the
Turbellaria, and a considerable number of animal and plant planktons. Two
main components of the modern Caspian population, the original marine
and fresh-water faunas, having lived together through the phases of its sub-
sequent history had become, in a remarkable manner, interlocked with each
other, acquiring similar biological characteristics and similar distribution
throughout the Sea. Both groups include some typical ' marine ' forms living
exclusively in the most saline parts of the Sea, some 'brackish- water'
ones, some tolerant to various degrees of salinity, and other forms which

AMPHIPODA PONTOGAMMARUS
ARALENSIS

2. BIVALVE DIDACNA TRIGONOIDES

3. WORM NEREIS SUCCINEA

4. COCKLE CARDIUM EDULE

5. DREISSENA CASPIA

6. MYTILASTER LINEATUS

7. SEAWEED ZOSTERA

8. AMPHIPODA DIKEROGAMMARUS

9. BULLHEAD GOBIUS FLUVIATILIS

10. BENTHPHILUS

11. MOLLUSC THEODOXUS SCHULTZI

12. M'ESIDOTHEA ENTOMON

13. PONTOPORFIA AFFINIS

14. PSEUDOLIBROTUS

15. PRAWN LEANDER

16. MYSIS

17. MEDUSA MOERISIA r;

18. PARAMYSIS

19. GOLDEN SHINER

20. HERRING CASPIALOSA

VOLGENSIS

21. PIKE PERCH

22. CASPIAN HERRING

23. VOBLA

24. SPRAT

25. STURGEON;;;;.

26. STARRED STURGEON ■

27. MICROMELANIA I

28. WORM HYPANIA INVAL

Fig. 270. General distribution of Caspian Sea fauna (Zenkevitch, 1951).

have migrated into fresh water. Recent immigrants from the Black and Azov
Seas and from the north, from the Arctic basin, have joined these basic
groups of the Caspian fauna. However these genetically heterogeneous com-
munities retain some of their biological and physiological peculiarities.

The present-day distribution of an organism throughout a sea often does
not provide us with a clue as to its genesis. This should be considered mainly
as the result of subsequent changes in sahnity. The time and means of
penetration of many groups and individual representatives of the Caspian
fauna into the Sea, their migration into fresh waters and their subsequent
life in the body of water remain obscure.

Derzhavin (1951) and Mordukhai-Boltovskoy (1960) revised the list of
the present-day fauna of the Caspian Sea. It now comprises 727 animal species
(374 genera) — 538 free-living specimens (301 genera) (see Table 235), 170 para-
site forms (67 genera) and 23 species (14 genera) which have penetrated into

564 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 235. Composition of the fauna of the Caspian Sea, except the parasites

Endemic forms

Animal group

Total number

of the Black,

Azov

of the

and

Caspiar

i Seas

Caspian Sea

Poriferae

Coelenterata

Turbellaria

Nematodes

Rotatoria

OHgochaeta

Polychaeta
Cladocera

4
19

2
16

Ostracoda

Copepoda

Cirripedia

Mysidacea

Isopoda

Amphipoda

Cumacea

2
20

2
72
19

1
72
19

Decapoda

Hydracarina

Insecta

5
2
9

1
2

—

Mollusca

Bryozoa
Pisces

4
78

W
54

Mammalia

Total

476

315

222

the Caspian from the Black and Azov Seas within the last thirty-forty years,
either with or without the help of man. The general composition of the Cas-
pian Sea fauna cannot be considered as finally established, since many groups
(among them Protozoa and Vermes) have not yet been sufficiently des-
cribed.

The data given in Table 235 shows that ' of the total number, 695, of the
Caspian species (excluding the parasites) 315 species are limited in their
distribution by the basins of the south Russian seas. The list of the Caspian
endemic forms, in the strict sense of this term, contains 222 species. Besides
this, the presence of 50 sub-species of Protozoa, polychaetes, crustaceans and
fish, found only in the Caspian Sea, stresses the endemic character of the
Caspian fauna.' (A. Derzhavin, 1951.)

It is also clear from this computation that the Caspian Sea is now the main
habitat of the ancient autochthonous fauna of the south Russian seas.
Derzhavin believes, however, that the considerable number of representatives
of the Caspian fauna peculiar to the Black and Azov Seas should not be under-
estimated.

THE CASPIAN SEA 565

According to his evaluation of the Caspian Sea fauna, Poriferae, Coelen-
terata, Turbellaria, annelides, higher crustaceans, hydrachnid molluscs and
fish comprise 308 species and 138 genera. Of these the endemic forms of
the Black, Azov, Caspian and Aral Seas comprise 263 species (89 per cent)
and 72 genera (52-2 per cent), among them 32 genera (23-2 per cent) and 174
species (58-9 per cent) of Caspian forms endemic in the strict sense. On the
other hand, among the 170 species of parasites 21 species are endemic forms
of the Caspian Sea. No endemic genera have been recorded among the
parasites. Among the separate groups of the autochthonous Caspian fauna,
Poriferae and Coelenterata are the first to attract attention. Four species of
Poriferae inhabit the Caspian Sea — two species of the genus Metschni-
kovia (M. intermedia and M. tuber culata) together with Protoschmidtia flava
and Amorphina caspia.

All the four species belong to the Renieridae family of the Cornacuspongia
order. The four species of Poriferae are Caspian endemics, while the species
of the genus Metschnikovia are related to the Baikal Baicalospongia and
Ochrid Ochridospongia.

One of the three autochthonous Caspian Coelenterata, Polypodium hydri-
forme, occupying an ambiguous place among the orders of the sub-class
Hydroidea, is a parasite on the ova of Acipenseridae inhabiting the basins
of the Caspian, Black and Aral Seas. The Medusa Caspionema (Moerisia)
pallasi, a strictly endemic form of the Caspian Sea, does not possess the hy-
droid stage ; it belongs to the Clavidae family (Leptolida order). The hydroid
Cordylophora caspia belongs to the same order ; in contrast to the Caspionema
it lacks the medusa stage. Cordylophora with some other forms probably
penetrated into the Caspian Sea when this was joined to the Baltic Sea by
canals in the last century ; it was widely propagated in the Caspian and has
migrated from it, by means of shipping, into different parts of the world ;
it has now become a cosmopolitan form (L. A. Zenkevitch, 1940). Cordy-
lophora is also known in the Kurun Lake (lower Egypt).

M. Tikhy has recorded as early as 1916 the existence of a plankton hydroid
in the Caspian Sea ; he did not give a detailed description of it and no one
else has recorded it since. The three closely related forms of polychaetes
inhabiting the Caspian Sea — Parhypania brevispinis, Hypania invalida and
Hypaniola kowalewskii — of the Ampharetidae family, are typical Caspian
autochthonous forms. The first is found only in the Caspian Sea, and the two
others are known in the inlets and rivers of the basins of the Black and Azov
Seas.

Manayunkia caspica (Sabellidae family), a Caspian endemic form, is
closely related to the Manayunkia of North America, Europe and Asia and
to those of Lake Baikal. Manayunkia possibly penetrated into the Caspian
Sea with the Arctic community forms in the post-glacial age; however it
does not have a cold-water aspect as other relict immigrants have, and its
occurrence (M. Bacesko, 1948) in the Danube is an indication of its earlier
(pre-Khvalyn) genesis and of its penetration into the Pontic basin from the
northeast by fresh-water routes.

Among the Caspian autochthonous forms one of the most prominent places

566 BIOLOGY OF THE SEAS OF THE U.S.S.R.

is occupied, side by side with molluscs and fish, by crustaceans, mainly Pera-
carida; 136 species of this last inhabit the Caspian Sea. All Caspian mysids
belong to the sub-family Mysini, the family Mysidae and the genera Hemi-
mysis (1 species), Mysis (4 species), Schistomysis (1 species), Paramysis (10
species), Caspiomysis (1 species), Katamysis (1 species), Diamysis (1 species),
and Limnomysis (1 species). Only Caspiomysis is strictly endemic to the
Caspian Sea. Katamysis and Limnomysis are endemic forms of the Pontic-
Caspian region. The others have a wider distribution in the oceans. The Mysis
genus stands apart. Most mysids are representatives of plankton-benthos,
but Paramysis loxolepis and the species of the genus Mysis (except M. caspia)
belong to plankton ; they make daily vertical migrations of some hundreds
of metres (up to 500 m). Representatives of the genus Mysis, evolved from
the Arctic immigrant Mysis oculata var. relicta, have retained their Arctic
aspect, living in depths of more than 50 m. A number of Caspian mysids
penetrate fresh waters and become adapted to them.

Among the Cumacea order representatives of 8 genera (Pseudocumatidae
family, Pseudocuma, Stenocuma, Pterocuma, Volgocuma, Caspiocuma,
Schizorhynchus, Chasarocuma) and 19 species live in the Caspian Sea.
Derzhavin has pointed out that they have probably all evolved from one
ancestral form of the genus Pseudocuma, and that they all converge (mor-
phologically and biologically) on the Cumacea community of the ocean fauna.
All the 19 species of Cumacea inhabit only the Pontic-Caspian region, and
10 species are strictly endemic to the Caspian. Some Caspian Cumacea have
also penetrated into fresh waters in the basins of the Caspian Sea (10 species),
of the Azov Sea (9 species), and of the Black Sea (9 species plus two doubtful
ones). Cumacea live at the bottom ; however they are involved in the diurnal
rhythm of vertical migrations.

The large order Isopoda is represented in the Caspian Sea by 3 species only
of varied genesis. laera sarsi is an endemic form of the Pontic-Caspian region.
Mesidothea entomon f. caspia is an immigrant from the Arctic. The third form,
Nannoniseus caspius, described by O. Grimm in 1875 from one specimen, has
not been recorded by any one else in the Caspian Sea. Iaera inhabits the
shallow littoral zone, while Mesidotea, in contrast, retaining its Arctic aspect,
does not rise into the upper warmed layers.

Among the higher crustaceans the order Amphipoda is the richest in species
and the most characteristic of the Caspian fauna. All Caspian amphipods (72
species) belong to the only sub-order — Gammarideae — and mostly to the
Gammaridae (60 species) and Corophiidae (8 species) families. Of the other
four species two Pseudalibrotus species and one of Pontoporeia are immi-
grants from the far north, while Caspicola knipovitschi, an original form
described by Derzhavin, forms a separate family — the Caspicolidae. Except
for these forms the Caspian Amphipoda belong to two families. The follow-
ing genera are particularly rich in species : Gmelina (5 species), Amathillina
(5 species), Niphargoides (11 species), Pontogammarus (10 species), Steno-
gammarus (6 species), Dikerogammarus (4 species), Chaetogammarus
(4 species), and Corophium (8 species). The other genera — Niphargus,
Boeckia, Gmelinopsis, Gammaracanthus (Arctic immigrant), Cardiophilus,

THE CASPIAN SEA 567

Derzhavinella, Zernovia, Behningiella and Sowinskya — have only one species
each, while Gammarus, Pandorites and Iphigenella have two each. The
endemic nature of the two main families of Caspian amphipoda is shown
in Table 236.

Table 236. Endemic nature of Amphipoda of the Caspian fauna (Gammaridae and
Corophiidae families) {A. Derzhavin)

Total number Pontic-Caspian endemics

Caspian

Genera Species Genera
No. %

Species
No. %

Genera Species

No. % No. %

Gammaridae
Corophiidae

19 60 16 84-2
18 0 0

60 100
8 100

6
0

31-6 30 50
0 4 50

This clear picture of specific endemism is broken only by Stennogammarus
ischnus and Corophium curvispinum, which have recently penetrated from the*
Baltic Sea through some water systems. Generic endemism is broken (if we
except the Arctic immigrants Pseudalibrotus, Pontoporeia and Gammara-
canthus) by the genera of the Corophiidae family, widely distributed outside
the limits of the Pontic-Caspian region. Thirty-five species of Caspian Amphi-
poda have adapted themselves to life in river systems. Of the order Decapoda
two species of the Astacidae family (river crayfish) are known in the Caspian
(Astacus leptodactylus and A. pachypus) and two species of the Palaemonidae
family, brought there by man, while the shrimps Leander rectirostris and L.
squilla are found.

The group of molluscs represented by the classes Gastropoda (according
to Lindholm, 37 species) and Lamellibranchiata (21 species) are no less char-
acteristic and significant in the fauna of the Caspian Sea.

Of the Neritidae family (Prosobranchia, Diotocardia) two species are known
for the Caspian Sea — Theodoxus pallasi and 77г. schultzii. The latter is strictly
endemic to the Caspian Sea, whereas the first has also been recorded in the
inlets of the northwestern part of the Black Sea, in Lake Top'yaton, and in the
Sea of Azov. The three families of the Monotocardia order — Valvatidae (1
species), Hydrobiidae (3 species) and Micromelaniidae (19 species) — are much
richer in species.*

Of the Hydrobiidae family Derzhavin points out 3 species — Lithoglyphus
exiguus, Hydrobia pusilla and H. grimmi — and representatives of the Micro-
melaniidae family — 19 species, belonging to 4 genera — Micromelania (6
species) Nematurella (3 species), Caspia (7 species), and Clessiniola (3 species).
All these 19 species are Pontic-Caspian endemic forms, only Gaspia gmelini
and Clessiniola variabilis live outside the Caspian in the inlets of the Black and
Azov Seas. Thus the strictly Caspian endemic nature of this group is well
emphasized.

* V. Lindholm did not publish a complete description of the gastropod molluscs of the
Caspian Sea, and, using the description of Derzhavin, 23 species are given here.

568 BIOLOGY OF THE SEAS OF THE U.S.S.R.

The taxonomic composition of the Caspian Lamellibranchiata has been
more thoroughly studied than that of the Gastropoda. Apart from Mytilaster
lineatus, a recent immigrant from the Black Sea, and Syndesmya ovata, trans-
ferred from the Sea of Azov, all the Caspian bivalves are endemic forms of the
Pontic-Caspian basin. They are represented by three tribes of the Hetero-
donta suborder, one species of the Corbiculidae family (C. fluminalis),
five species of the genus Dreissena (D. polymorpha, D. rostriformis, D. cas-
pica, D. grimmi, D. andrussovi), one species of Cardium (C. edule), two
species of Monodacna (M. caspia and M. edentula) and seven species of the
genus Adacna {A. trigonoides, A. crassa, A. pyramidata, A. longipes, A. bar-
bot-de marnyi, A. baeri and A. latens). Except for Cardium edule, which had
penetrated into the Caspian Sea through Manych in the Khvalyn period,
and Dreissena polymorpha and Corbicula fluminalis (an ancient fresh-water
immigrant), which have migrated far beyond the limits of the Caspian Sea,
the endemic nature of the bivalves is most pronounced; in Derzhavin's
opinion they are all autochthonous forms of the Pliocene Seas. Sixteen species
are endemic forms of the Caspian, while Didacna is an endemic genus of it
{Table 237) (A. Derzhavin, 1951).

Table 237

Number of endemic forms among them

Total amount of Caspian molluscs

Pontic-Aralo- Caspian

Caspian
Genera Species Genera Species Genera Species

Number 16 57 0 53 4 50

Percentage 100 100 62-5 93-0 25-0 87-7

The heterogeneous nature of the Caspian fauna is well illustrated in the
Turbellaria group. V. Beklemishev established (1915) the presence of 29
species of Turbellaria in the Caspian Sea (Triclada — 6 species, Acoela —
11, Alloeocoela — 5, Rhabdocoela — 7). Twenty-seven species of Turbellaria
are endemics ; in fact there are no less than two endemic genera. In Bekle-
mishev's opinion 18 species of Turbellaria are undoubtedly marine forms
(Acoela, part of Rhabdocoela and the majority of Alloeocoela) ; they originated
in the Tertiary period when the Caspian basin was still connected with the
ocean. The 7 species of Rhabdocoela are ancient (Tertiary) immigrants from
fresh water into the Caspian Sea. The other species have only recently come
from fresh waters.

The so-called negative features are more sharply pronounced in the popu-
lation of the Caspian Sea than in that of the open sea; many typically marine
groups are either completely absent from the Caspian or represented by very
few species. Strictly speaking only fish, crustaceans and, to a smaller extent,
the molluscs are varied here. The number of species of these three groups
constitutes about 60 per cent of all the species of the free-living animals of
the Caspian.

THE CASPIAN SEA 569

A very large number of endemic forms (about 60 per cent) are also char-
acteristic of the Caspian Sea.

The very vigorous development of new species brought in from the Azov
and Black Sea helps one to understand the biological properties and pro-
ductivity of the Caspian population. On the other hand, at different periods of
the Tertiary and Quaternary epochs some individual representatives of the
Caspian autochthonous fauna left the Caspian basin through the river systems,
rapidly settled in a vast territory, and in some cases acquired a cosmopolitan
nature. Caspian fauna, especially its fish and crustaceans, readily migrate
into the fluviatile systems, penetrating far upstream.

Brackish-water character of Caspian autochthonous fauna

The small salinity range tolerated by the brackish-water relict Caspian fauna
is its remarkable peculiarity. In contrast to the Sea of Azov immigrants this
fauna is incapable — as has been shown experimentally (A. Karpevitch,
G. Belyaev and Ya. Birstein, 1946; N. Romanova, 1956) — of enduring high
salinity (Fig. 271). Karpevitch has proved experimentally from forms of the
two faunas that in contrast to the immigrants from the west (euryhaline marine
forms) the brackish-water forms have a considerable stenohalinity. The dis-
tribution of these forms throughout the Caspian Sea is determined by these
characteristics. On the other hand, it has been shown by the experiments of
G. Belyaev and Ya. Birstein (1946) that a salinity of about 15%0 is lethal for
the Caspian brackish-water mysids, while for some species of Gammaridae
it becomes lethal at about 20 to 25%0. The most saline areas of the Caspian
Sea (20 to 25%0) are densely populated by euryhaline marine immigrants from
the west — Mugil auratus and M. saliens, Syngnathus nigrolineatus caspius,
Cardium edule, Pomatoschistus caucasicus. Among the Caspian relicts only
the herring Caspiolosa caspia salina, and the crustacean Dikerogammarus
aralensis are associated with them. The first is found only within the areas of
high salinity, the second throughout the whole Caspian Sea ; it is particularly
abundant in the Aral Sea.

N. Romanova (1956) has studied experimentally the survival, in various
conditions of salinity, of the highest mass species of crustaceans of the Caspian
Sea. She has divided them into three groups :

(/) Species distributed throughout the Caspian Sea which enter the rivers

of the Caspian basin (saline limits 0 to 13%0).
(II) Species distributed throughout the Caspian Sea, which do not enter

fresh water (salinity range 2 to 13%0).
(Ill) Species characteristic only of the Central and Southern Caspian (salinity

range 8 to 20%o).

The low tolerance of most brackish-water Caspian crustaceans of a
rise in salinity was confirmed by the experiments of Romanova and
Karpevitch. The majority of these crustaceans die at a salinity between 14
and 20%o.

570

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Dreissensia polymorpha
v. marina

Dreissensia polymorpha
v. fluviatilis

Dreissensia polymorpha
Dreissensia andrussovi

Dreissensia caspia

Adacna minima in the
Caspian Sea

Adacna minima in the
Aral Sea

Monodacna edentula
Didacna trigonoides
Didacna barbot-de-marni
Mytilaster lineatus
Cardium edule
Nereis diversicolor
Sindesmia ovata

35 %>

Fig. 271. Survival of certain species of bivalves and Nereis in the Caspian Sea

(Zenkevitch, 1959).

Negative features of the Caspian fauna

The negative features of the Caspian fauna, as compared to the fauna of the
open seas, consist of the complete depletion of such groups as Radiolaria, cal-
carean and horny Poriferae, Siphonophora, true medusae, Anthozoa, Cteno-
phorae, Polyclada, nemertinians, echiurids, sipunculids, priapulids, brachio-
pods, chaetognaths, pantopods, crabs, chitons, scaphopods, cephalopods,
echinoderms, Enteropneusta, tunicates, Acrania, skates, sharks and ceta-
ceans. Moreover, many typical marine groups are very poorly represented
here, such as, for example, Foraminifera, Poriferae, Hydrozoa, Polychaeta,
Bryozoa, Decapoda, Gastropoda and most of the order of bivalves.

There is a marked preponderance of crustaceans and fish in the fauna of
the Caspian Sea, while the majority of the marine groups are absent.

THE CASPIAN SEA 571

The free-living fauna of the Barents Sea comprises approximately 2,000
species, the Mediterranean 6,000, and the Caspian only 538 ; the last is about
27 per cent of that of the Barents Sea and 9 per cent of that of the Medi-
terranean. Moreover this low proportion differs greatly for various groups
{Table 238).

Table 238

Barents Sea

Mediterranean

Caspian Sea

Sea

Groups

%of

Barents

Mediter-

Caspian

No. of

total

No. of

total

No. of

Sea

ranean

Sea

species

fauna

species

fauna

species

fauna

Echinodermata

3-1

101

1-7

0-7

1-3

4-3

Bryozoa

Polychaeta

Bivalvia

272

200

140
100

3-2

138
433
366

2-3
7-2
61

4
6

1-6

36-0

3
1-4

6-4

Gastropoda
Higher Crustacea
Fish

150

152
121

7-5
7-6
60

937
620
529

15-6
10-3

8-7

32
118

21-0
78-0
640

3-4
190
15-0

22-0
12-6

Fish and higher
crustaceans

273

13-6

1,196

190

196

72-0

140

36-4

Evidently the migration into brackish waters is much easier for the higher
crustaceans and fish than for other animals, since they can endure the sub-
sequent changes of salinity of the water body much more readily. This is due
to their integuments which protect their body from osmotic processes.

Formation of species

The process of vigorous species formation undergone by its many forms is a
characteristic peculiarity of the Caspian Sea fauna; groups of numerous
species were evolved here and their transitions are often indistinct. Such are
herrings, bullheads, Benthophilus, Amphipoda, mysids, Cumacea, Dreissena,

and others. - .

K. Kiselevitch (1923) considers that all the numerous forms of Caspian
herrings have evolved from the one species Caspialosa caspia. G. Sars (1927)
came to the conclusion, as a result of his study of Caspian crustaceans, that
all the members of the Cumacea species have evolved from the same ancestral
form, an immigrant from the Mediterranean. This feature is even more pro-
nounced for the remarkable faunas of Lakes Baikal and Tanganaika.

A definite part of the autochthonous fauna of the Caspian Sea is a relict
of the Tertiary seas which had begun to evolve by the end of the middle Mio-
cene under the effect of the fall in salinity.

Sovinsky points out the huge preponderance (89-39 per cent) of forms
peculiar to the Pontic-Caspian-Aral area in the Caspian Sea fauna, among
which almost three-quarters of the forms are found in the Caspian Sea only.

572 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Cosmopolitan species

Foraminifera can be cited as an example of a widely cosmopolitan group.
Shokhina, who studed Foraminifera in the Mertviy Kultuk and Kaidak In-
lets, has distinguished six deep-water forms for that area belonging to the
genera Elphidium, Rotalia and Discorbis. Among them the most frequently
met are Rotalia beccarii, Elphidium polyanum and Discorbis vilardeboana.
All three forms are widely distributed in the Atlantic and Pacific oceans
and the seas connected with them. Nonion depressulum and Elphidium granu-
losum, pointed out by Behning, and Ammobaculites pseudospirale, mentioned
by Voloshinova, can be added to these six forms. Moreover, Shokhina has
discovered four species of plankton Foraminifera : Globigerina bulloides, Gl.
triloba, Globorotalia crassa and Globigerinella aegui/ateralis. Hence there are
indications that 1 3 forms of Foraminifera have been recorded in the Caspian
Sea. The most numerous form, Rotalia, gives on sandy beds up to 2,500
specimens and on silt up to 15,000 (in one case 60,000 specimens) per 5 g
of soil. The next most common form, Elphidium polyanum, reaches 5,000
specimens per 5 g of soil.

History of the fauna

Humboldt formulated a theory in the forties of the last century, according to
which the Aral-Caspian basin was widely connected with the Arctic Ocean
through the western Siberian lowlands by the end of the Miocene epoch. In
Suess's opinion a new northern fauna had penetrated into the Sarmatian Sea
through this so-called Humboldt Strait. However Suess's theory of the
northern genesis of the Sarmatian fauna had no further development and his
assumption of the existence of a direct link between the Caspian Sea and the
Arctic Ocean to both east and west of the Ural Mountains, at all events since
the Eocene period, has been refuted. Th. Fuchs (1887) denied the theory of
the northern genesis of the Sarmatian fauna. In his opinion it was an original
fauna, evolved in this body of water as a result of its isolation and of the rise
in salinity.

Since it was difficult to derive the Sarmatian fauna from the fauna of the
Middle Miocene basin Andrussov and Mushketov deduced that it was
evolved from the remains of the Oligocene fauna of the Turanian basin, which
had become adapted to less saline water and had migrated from the east into
the Sarmatian basin, then in a state of formation. Andrussov assumes that the
Sarmatian Sea was populated by (7) forms which arrived from the east, (2)
forms which had survived since the time of the Middle Miocene Sea, and (5)
forms evolved during the Sarmatian Era.

The origin of the Akchagyl fauna, which has much in common with the
Sarmatian, is just as difficult to trace. The Pontic Sea, which followed the
abundantly saline Sarmatian Sea, had lost much of its salinity and was popu-
lated by fresh- and brackish-water faunas. This in turn was replaced by a
saline Akchagyl Sea, and a rich fauna, similar to the Sarmatian one, appeared
in it again. N. Andrussov (1911), and after him I. Gubkin (1931) and A. Arch-
angelsky (1932), think that some shelter existed, where the Sarmatian fauna

THE CASPIAN SEA 573

survived the Pontic period, and that it returned to the Caspian Sea in the
Akchagyl period. In the opinion of V. Kolesnikov (1941) the cyclic changes of
Caspian mollusc faunas in the Tertiary epoch noted by Andrussov is ex-
plained not by the survival of one sheltered fauna, but by consecutive migra-
tions of Mediterranean species into the Caspian basin. Moreover, during some
definite eras fresh-water forms migrated into the Caspian Sea. Thus, for
example, Kolesnikov thinks that the fauna of the Apsheron period, which has
been studed in more detail, has three origins : (7) the greatly altered remains of
the former Akchagyl population ; (2) fresh- water immigrants, including among
others Dreissensia distincta, Dr. polymorpha, Dr. caspia and Nematurella, and
(J) the considerably changed immigrants from the Black Sea area. Among the
75 Apsheron molluscs 12 are very similar to, and four are identical with, the
present Caspian forms.

Fresh-water immigrants

The more or less ancient fresh-water immigrants constitute a considerable
part of the fauna of the Caspian Sea. Such colonization of the Caspian Sea
occurred several times during its history in its periods of greatest freshening.
Many of the origins of the fresh-water immigrants of the Caspian Sea are lost
in the distant past. It has been noted, for example (B. Dybovsky, 1933, V. Bo-
gachev, 1932), that the very original Caspian gastropods should be considered
as immigrants from the fresh waters of the Pliocene ; this would explain their
close relationship with the Baikal molluscs. Manayunkia caspia among the
polychaetes, Acipenseridae and some other fish, and possibly seal, are prob-
ably ancient immigrants from the fresh waters of the Pliocene. For some forms,
the cyprinids for example, a fresh-water genesis seems more evident, and many
of them have apparently migrated during the late post-glacial transgression,
when the Caspian Sea received its last large party of fresh-water immigrants.
It seems certain that the Caspian Sea, and especially the Aral, were ener-
getically colonized by fresh-water forms, and V. Beklemishev and V. Baskina-
Zakolodkina (1933) have shown that this movement was not only furthered
by the decrease of salinity of the water. They have proved for these Seas the
importance of the nature of the salinity of the Caspian and Anal Seas, i.e.
the ratio of the magnesium and calcium ion concentrations, which brings the
saline waters of our southern sea-lakes close to fresh water. The ratio Mg/Ca
= 1-34 in the Aral Sea makes it most suitable for the existence of the fresh-
water crustacean Daphnia. In Caspian waters this ratio (2-5) is higher but still
less than that in the Black Sea (3-12); the higher survival of Daphnia in the
Caspian rather than in the Black Sea waters might be explained in this way.

Mediterranean elements

After the final separation of the Caspian and Black Seas and the linking of the
latter with the Mediterranean and its colonization by Mediterranean fauna,
some of its species penetrated into the Caspian, and even the Aral, Sea. Three
periods can be distinguished in the history of the Neogene colonization of the
Caspian Sea by Mediterranean organisms. The first and most ancient of these
periods apparently belongs to Khvalyn times ; it is linked with the penetration

574 BIOLOGY OF THE SEAS OF THE U.S.S.R.

of some six species through the Kuma-Manych depression (Zostera nana,
Cardium edule, Fabricia sabella, Atherina mochon pontica caspia, Syngnathus
nigrolineatus caspius, Pomatoschistus caucasicus).

The second period, which started in the twenties of this century, is linked
with the accidental or purposeful bringing in of species by man ; nine Mediter-
ranean species have penetrated into the Caspian Sea during this period (Rhizo-
solenia calcar-avis, Mytilaster lineatus, Syndesmya ovata, Nereis diversicolor,
Leander squilla, L. rectirostris, Mugil auratus, M. saliens, Pleuronectes flesus) ;
the fish Gambusia affinis was also imported about this time.

The third period was the time of the establishment of a direct water route
between the Caspian and Azov Seas by the Volga-Don canal and the auto-
immigration into the Caspian Sea of nine new Mediterranean forms (Black-
fordia virginica, Membranipora {Electro) crustulenta, Balanus improvisus, B.
eburneus and Rlrithropanopues harrisii spp. tridentata, the polychaete Mercier-
ella enigmatica, Monodaena colorata, Corbulomya maeotica and Podon poly-
phemoides). This third period, which began a few years ago, will prob-
ably turn later on into a long, complex and extremely curious process of
the reconstruction of the Caspian Sea fauna, as a result of the free influx
of the most euryhaline members of the Mediterranean flora and fauna.

Apart from the above-mentioned 23 animal species, ten new sea-weed
species have been discovered in the Caspian Sea : first, Ceramium diaphanum
and C. tenuissimum (M. Kireeva and T. Shchapova, 1957); secondly, Ecto-
carpus confervoides f.fluviatilis and Polysiphonia variegata (G. Zevina, 1958).
Apparently none of these four forms was present in the Caspian in the
'thirties (Kireeva and Shchapova). A number of sea-weed forms, hitherto
unknown in the Caspian Sea (Acrochaeta parasitica, Ectochaete leptochete,
Enteromorpha tubulosa, E. salina, Entoneme salina, Acrochaetium daviesii)
were found by Zevina in the growths fouling hydrotechnical constructions.

Thus the 'Mediterranean' group in the Caspian Sea comprises only 28
species, including one diatom, ten bottom-living algae, one marine flowering
plant, one medusa, one bryozoan, two barnacles, two shrimps, one crab, two
polychaetes, three molluscs, one cladocer and three species of fish.

The process of the colonization of the Caspian Sea by new members of
flora and fauna and an exceptional mass development of some of them in
their new habitat (Mytilaster, Mugil, Rhizosolenia, Leander, Nereis, Syn-
desmya and Balanus) is linked with a number of curious ecological (syne-
cological) phenomena. First of all, with some of them an extremely intensive
development, similar to a kind of 'biological explosion', has been observed.
Thus Rhizosolenia calcar-avis, which penetrated into the Caspian Sea early
in the 'thirties, probably in small numbers, had by 1934 multiplied into several
million tons, forming two-thirds of the whole mass of plankton. The first
wave of exceptional mass development was followed by a drop in its numbers
and the biocoenosis, into which the new form entered and adapted itself,
limited its development. Immigrants from distant seas are of particular inter-
est among the new forms of the Caspian fauna. There are two of these in the
composition of the Caspian Sea fauna: the medusa Blackfordia virginica
(B. Logvinenko, 1959) and the crab Rhithropanopeus harrisii sp. tridentata

THE CASPIAN SEA 575

(T. Nebolsina, 1959). The original home of both forms is on the northeastern
shores of North America. The medusa has apparently come to the Sea of Azov
directly, while the crab arrived in the Black Sea via Dutch coastal waters
(Zuyder Zee). This latter brackish-water form had originally immigrated from
North America and was described in the Zuyder Zee as a new form, Hetero-
panope tridentata. Rh. harrisii found favourable conditions for its existence in
the Sea of Azov and the Don estuary ; in its further travel it proceeded by
canal into the Caspian Sea where it found a fourth home.

A. Karpevitch (1958) and E. Bokova (1958) have raised the problem of the
utilization of Caspian crustaceans as an acclimatization stock for the Aral
and Baltic Seas and for Lake Balkhash. The ecology and physiology of a
number of mass forms of Caspian crustaceans were carefully studied and the
following were recommended for the Aral Sea and Lake Balkhash : Meso-
mysis (Paramysis) kowalewskyi, M. baeri and M. intermedia (Karpevitch),
and for the Aral and Baltic Seas Schizorhynchus bilamellatus, Pterocuma pecti-
nata of the Cumacea, and Corophium nobile and C. curvispinum of the Amphi-
poda (Bokova). The three mysids were transported in the adult stage into the
Aral Sea in the summer of 1958. The results of this attempt at acclimatization
are so far unknown.

Bogachev was the first to record in 1928 the mollusc Mytilaster lineatus
in the Caspian Sea ; he thinks that it was brought from the Black Sea during
the civil war from Batum on small craft, the undersides of which are often
covered with clumps of Mytilaster. Closing its valves tightly the mollusc
can endure life in the air for a long time.

The history of the colonization of the Caspian Sea by this mollusc Myti-
laster and of the annual increase of its biomass was studied by V. Brotzky and
M. Netzengevitch (1940). As early as 1932, according to their data, Mytilaster
had already moved from the Baku area, following the main currents, along the
coast of the Southern Caspian, colonized the eastern shore of the Central
Caspian and penetrated into the southern part of the Northern Caspian.
In the following years it moved still father north and along the western coast
of the Central Caspian (Figs. 272 and 273) ; its biomass was growing rapidly.
In 1938 Mytilaster biomass in the Caspian constituted five million tons, and
if we include the growths on the cliffs this quantity will be at least doubled.

Besides actual growth of the Mytilaster biomass the increase of its relative
significance in the total biomass has also been observed. Thus, for example, in
1933 on the eastern shore of the Southern Caspian Mytilaster composed only
18 per cent of the total benthos biomass ; by 1935 it composed as much as 89
per cent, and in the following years more than 90 per cent. Moreover, it over-
whelmed the growth of other benthos components, as may be seen by com-
paring data for the western coast of the Southern Caspian {Table 239).

It is difficult to decide at the moment whether Mytilaster acclimatization in
the Caspian Sea is favourable or unfavourable for its fisheries. On the one
hand Mytilaster no doubt suppresses the development of some valuable food
forms, in particular Dreissensia ; on the other, it now forms part of the diet
of many commercial fish. In the Southern and to some extent also in the Central
Caspian sturgeon feed on this mollusc to a considerable extent; starred

576

BIOLOGY OF THE SEAS OF THE U.S.S.R.

sturgeon, marine pike-perch, the roach Rutilus frisii kutum and some other
fish are beginning to eat it. Ducks, wintering on the shore of the Caspian, feed
intensively on the Mytilaster of the neighbouring cliffs. They have begun to
winter in places colonized by it where they had never appeared before owing

Fig. 272. Distribution of Mytilaster lineatus bio-
mass in the Caspian Sea in 1938 (Brotzky and
Netzengevitch).

to the absence of food. Black Sea grey mullet (Mugil auratus and M. saliens)
were successfully acclimatized in the Caspian in 1930. The prawns Leander
rectirostris and L. squilla, brought in with the grey mullet, have multiplied as
prolifically as Mytilaster during the last thirty years.

According to Yu. Marti's data (1940, 1941) the fry chiefly of M. auratus,
and in considerably smaller numbers of M. cephalus and M. saliens, were
brought into the Caspian Sea. M. cephalus fry do not easily endure transport
and must have perished. M. auratus is now widely distributed throughout th-

THE CASPIAN SEA

577

SOUTHERN CASPIAN WESTERN COAST
SOUTHERN CASPIAN EASTERN COAST
CENTRAL CASPIAN EASTERN COAST
CENTRAL CASPIAN WESTERN COAST

— — %OCCUR«ENCE

MEAN BIOMASS

$8 \'9 ..

03 Жг~3>*

400

300

ZOO

100

u ats wi zj& i о

10 20 30 40 50 60 70 80™™ ">
В

Ш STATIONS WITH LIVE MYTIIASTW

| | STATIONS WITH OEAD MYTILASTE*
DEAD BIVALVES

£T 36

18 18

1
'■ 0-10 10-20 ZMO 3040 iuTo 5040 60To 70-80

Fig. 273. Mytilaster lineatus biomass (g/m2). / In Central and Southern Caspian

according to the years ; II Distribution with depth ; A Occurrence (% stations) and

mean biomass (g/m2); В Ratio between the living and the dead Mytilaster

(Brotzkaya and Netzengevitch).

Caspian Sea ; it has penetrated into the northern part and in particular into
Mertvyi Kultuk. M. saliens is adapted mainly to the western shore, where it
lives with M. auratus. On the Turkmen coast M. saliens is more numerous
than M. auratus.

Finally, in 1939 and 1940, Nereis and Syndesmya ovata were brought from
the Sea of Azov into the Caspian Sea for acclimatization in order to increase
food resources for commercial fish.* Sixty-one thousand specimens in all of
Nereis and 18,000 specimens of Syndesmya ovata were put overboard in
different places of the Caspian Sea (L. A. Zenkevitch, Ya. Birstein and A. Kar-
pevitch, 1945).

In the autumn of 1944 N. Spassky (1945) recorded for the first time

* In the course of the transplantation of Nereis into the Caspian Sea there was a
theory that the transplanted species was Nereis succinea.

Some time later this belief altered and doubts arose. The first one to express doubt
was Dr. Joel W. Hedgpeth (1957), who in his 'Treatise' published some critical notes
referring to my paper on the Caspian Sea. Presently material on the Nereis from the
Caspian Sea was forwarded to the prominent specialist working with the Polychaeta,
Olga Hartman. She classified this species as Nereis diversicolor (1960). The careful
examination of Nereis coming from the Caspian Sea (V. Chlebovitsch, 1962) has con-
firmed the wide-range distribution of this species throughout various seas, whereas
Nereis succinea was not discovered.

578

BIOLOGY

OF THE SEAS OF
Table 239

THE

U.S.S.R.

Year

Mean benthos
biomass

Biomass without
Mytilaster

1932
1937

1,129 g/m2
2,019 g/m2

45 g/m2
34 g/m2

Nereis in large quantities in the intestines of sturgeon caught off Chechen'
Island ; this result was later obtained in other places in the Caspian. These
findings were a proof of the success of the acclimatization of Nereis in the
Caspian Sea. Syndesmya ovata was not found in the Caspian until 1955
(A. Saenkova, 1959).

In a few years Nereis biomass in the Caspian Sea formed 100,000 tons. The
colonization of the Caspian Sea by shrimps was of about the same nature.
Barnacles had developed in exceptional numbers (G. Zevina, 1958). They have
spread all over the shallow parts of the Caspian Sea bottom, over hydro-
technical constructions and, in certain seasons of the year, on fishing gear,
which was covered by them. Undoubtedly their total mass is now an almost
solid layer of not less than some hundreds of tons. These factors indicate an
exclusive activity and vitality of many euryhaline and eurytopic members of
the Mediterranean fauna, which have also colonized the Sea of Azov. The
endemic fauna of the Caspian Sea is also probably wasting some of the life
resources of this Sea, and it may not be very powerful in its struggle with its
most active Mediterranean rivals. Such detritus-eating forms as the red mullet
and Nereis are certainly wasting some of the Sea resources. On the other hand,
Mytilaster is in close competition with the local Dreissensia as a filter feeder
and fouling organism; barnacles, which arrived later, are a closely related
biological form, and possibly also take part in the rivalry. Hence two accli-
matizations can be distinguished : that of intrusion, when the local forms
(Nereis, Mugil) remain undisturbed, and when they are dislodged (Myti-
laster, Rhizosolenia) (L. A. Zenkevitch, 1940). Shrimps, perhaps, have estab-
lished some relationship with local mysids. While some forms are undoubtedly
useful in the Caspian Sea (Nereis, Syndesmya, Mugil) the usefulness of others
is not clear (Leander, Mytilaster), and others still play a negative role (Rhizo-
solenia, Balanus and possibly Mytilaster).

The unusual fate of many new immigrants into the Caspian Sea has empha-
sized the conceptions of potential habitat and of the acclimatization stock
(L. A. Zenkevitch, 1940). For most of the land and marine forms their actual
habitat is probably far from occupying all that part of the biosphere in which
these forms could live, and into which, for some reason, they cannot penetrate.
All these parts of the biosphere form potential habitats for them. On the
other hand, many species could live in areas where they are absent if they
were brought into them. Such forms belong to the acclimatization stock for
these areas. The most successful acclimatization of the Baltic herring Clupea
harengus membras in the Aral Sea can, from this point of view, serve as a
good example for the Soviet Seas. It is quite probable that, for the Caspian

THE CASPIAN SEA 579

and Aral Seas on the one hand, and for the Baltic Sea on the other, many
members of their faunas could have been included in their reciprocal accli-
matization stocks, and some of them have already been used by Nature itself
(Dreissensia, Cordylophora and others in the Baltic Sea, and the Arctic immi-
grants in the Baltic and Caspian Seas). The utilization of acclimatization
stocks, especially in the Caspian and Aral Seas, offers man the prospect of
many possibilities for the reconstruction of the fauna of these Seas under
conditions of forthcoming changes in their salinity.

Arctic immigrants

The fourth component of the Caspian fauna — the Arctic immigrants from the
Arctic basin — is in all respects just as remarkable. At present the following
are included in this group of forms : (1) Limnocalanus grimaldi, (2) Mesidothea
entomon spp. glacialis, (3) Pseudalibrotus caspius, (4) Ps.platyceras, (5) Ponto-
poreia affinis microphthalma, (6) Gammarcanthus loricatus caspius, (7) My sis
caspia, (8) M. microphthalma, (9) M. macrolepsis, (10) M. amblyops, (1 1) Steno-
dus leucichthys, (12) Salmo trutta. The seal Phoca caspia, the polychaete
Manayunkia caspia and, according to Dogel and Bykhovsky, some fish para-
sites of the genera Corynosoma, Crepidostomum, Bunocotyle and others
should most probably be included in this group.

There is no doubt at present that these organisms penetrated into the Cas-
pian Sea from the north after the latter became isolated from the Black Sea.
These Arctic immigrants are very thinly represented in the Black Sea. They
have deviated very slightly from their original forms. The ten main Arctic
immigrants comprise two groups of animals — crustaceans and fish, i.e. the
two groups best able to endure the freshening of the water. As we shall see
below this indicates a fresh-water route for their migration from the north ;
this has already been suggested by O. Grimm (1888), K. Kessler (1877),
R. Gr'edner and, in a more definite form, by V. Sovinsky (1902).

As early as 1916 Sv. Ekman pointed out the closer family relationship of the
Caspian forms of the Arctic community with their relatives from the Arctic
Ocean, compared with those of the Baltic Sea. This led Ekman to assume the
probable former existence of a direct link between the Caspian Sea and the
Arctic Ocean ; therefore he does not accept the suggestion of the penetration
of some forms, for example Limnocalanus grimaldi, by a fresh-water route.
Ekman is inclined to relate the moment of the penetration of this crustacean
into the Caspian Sea either to the end of the Tertiary period or to one of the
inter-glacial eras. The former existence of a direct link between the Caspian Sea
and the Arctic Ocean had been suggested before by G. O. Sarz.

However, in spite of these difficulties the view that the Arctic community
penetrated into the Caspian Sea in the post-glacial era through river and lake
systems, as has been suggested by Kessler, must be accepted. Further support
for this opinion was given by the Swedish geologist A. Hogbom (1917).

Attempts to trace the route of the Arctic community into the Caspian Sea
through the Humboldt Strait have been abandoned. Hogbom thinks that
eastern Europe was flooded by water melting from receding ice, which, on
the other hand, prevented its escape to the north, and therefore this water

580 BIOLOGY OF THE SEAS OF THE U.S.S.R.

flowed southward, carrying with it Arctic organisms which populated the
freshened or fresh-water inlets which extended far to the south of the Arctic Sea.

E. F. Gurjanova in 1933 and P. Pirozhnikov in 1937 introduced a new
approach to this problem. Since the Caspian forms of crustaceans are closest
of all to those of the Kara Sea and are often almost indistinguishable from
them, Gurjanova suggested that this must be just where the Caspian immi-
grants came from. Pirozhnikov transferred the ideas expressed by Hogbom
on the elastic glacier effect to the Ob-Yenisei plain. The main argument
against this point of view rests in our ignorance of the distribution of the
original Caspian species in the Arctic basin in the post-glacial era. It is quite
possible that at that time they also inhabited the European part of the Arctic
basin and that later, when the temperature rose, they were pushed eastwards
beyond Novaya Zemlya.

L. Berg's hypothesis (1928) is just as plausible; according to it the pene-
tration of the northern organisms into the Caspian Sea from the Baltic took
place through the extensive Rybnoe Lake, which in the post-glacial era over-
flowed the shores of the Baltic Sea and of Lakes Ladoga and Onega (and
also Beloozero and Shesna which were connected with the Caspian Sea)
and deposited the striated clays discovered by S. Jakovlev on the watershed
between Lakes Onega and Beloozero.. In Pirozhnikov's opinion this hypo-
thesis is contradicted by the absence now of Stenodus and Pseudalibrotus in
the Baltic Sea; however, as was noted by A. Derzhavin (1939), Stenodus
leucichthys is found in the Baltic basin, and Pseudalibrotus could have lived
in the Baltic Sea under the severe conditions of the Ice Age and could have
disappeared with the rise in temperature.

Finally A. Podlesniy (1941) admits the possibility that Stenodus leucichthys
and salmon penetrated into the basin of the Caspian Sea from the Northern
Dvina through the Kol'sko-Vychegodsk confluence of the North and South
Kel'tma rivers. He suggests that both forms of the salmon family had pene-
trated to the south more than once even in the post-glacial era.

The intrusion of Caspian fauna into fresh waters

Apart from the fact of the original marine groups being, in the history of the
Caspian fauna, the forms best able to endure a considerable fall of salinity,
they evolved a number of new forms which could move even farther ; these,
pressed on by phases of increase of salinity which set in after phases of freshen-
ing, penetrated into fresh waters. Here again we see mainly the same two
groups — crustaceans and fish — best fitted, owing to their more or less im-
penetrable integuments, to retain the hypertony of their perivisceral fluid in
relation to environment.

Table 240
Isopoda 1 ; Amphipoda 35; Cumacea 10; Mysidacea 6; Decapoda 1. Total 53

Ya. Birstein (1935) has pointed out that 44 species — 53 according to A.
Derzhavin {Table 240) — of Caspian crustaceans have immigrated into the
river Volga.

THE CASPIAN SEA 581

No fewer than 1 8 species of Caspian fish of marine origin have penetrated
into rivers. Among the other groups only a few forms of the Caspian autoch-
thonous fauna succeeded in penetrating into fresh waters: Cordylophora
caspia and possibly Polypodium hydriforme among the coelenterates ; Dreissena
polymorpha among the bivalves; some species of Theodoxus and Melanopsis
among the gastropods ; and among the polychaetes Hypania invalida and Hypa-
niola kowalewskyi. Hence crustaceans and fish occupy the first place ; there are
only seven species of molluscs, three of coelenterates and two of polychaetes.

Two theories have been suggested to explain the occurrence of Caspian
crustaceans in the fresh water of the Pontic-Caspian basin. According to one
hypothesis they are typical relicts, i.e. they continue to live where they were
left by the receding sea (A. Derzhavin, 1912, 1924, 1939; A. Behning, 1924;
S. Zernov, 1934 and others); or they have migrated up the rivers beyond the
limits of Caspian transgressions. According to the second theory these forms
are active immigrants from the Caspian Sea into the rivers (A. Skorikov, 1903 ;
V. Zykov, 1903; L. Berg, 1908; V. Beklemishev, 1923; Ya. Birstein, 1935).

In principle there seems no difference between the two theories. The dis-
crepancy centres mainly on the problem of the place where the euryhalinity of
crustaceans living at different salinities was developed : whether it occurred
in the Sea itself or in its inlets, which covered the lower course of the present-
day Volga and other Caspian rivers. No objections were raised against the
capabiUty of Peracarida to move by some means or other against the current
and settle down. The freshening of a considerable part of the Sea and the
development of the euryhaline forms in the Sea itself seems to us more
plausible. This freshening may have occurred during the melting of the
ice when a considerable amount of melt-water flowed into the Caspian
Sea. In his last work A. Derzhavin (1939) also relates the appearance of
mysids. in the lower reaches of the Volga to the inter-glacial era, marked by
the Baku transgression of the Caspian Sea which was caused by the inflow
of glacier waters.

The migration of the marine animals from the Sea into the rivers proceeded
no doubt as a result of a subsequent increase of salinity in the Sea, i.e. in this
case the phenomenon known as 'saline pulsations' took place. When the
freshening of the Sea is followed by a rise in salinity, a definite part of its
fauna is unable to adapt itself to this greater salinity and therefore gathers in
places of lowest salinity — mouths and estuaries of rivers, for example. This
process consists both of extinction and of active and passive transference,
differing in degree for various biological forms. Into the complex, multiform
phenomenon of the change-over of marine organisms to life in fresh water
there are interwoven both moments of relict state and moments of passive
and active immigration. Furthermore the same species may be a relict in one
part of its habitat and an immigrant in another.

The marine Peracarida of the Volga (except for its very lowest reaches) are
probably immigrants from the Caspian, or a freshened inlet of it where they
had settled. Some species enlarged their habitat by passive immigration,
attaching themselves to boats and living ensconced in the encrustations on the
hulls. The absence from Caspian rivers of sedentary marine forms of molluscs

582 BIOLOGY OF THE SEAS OF THE U.S.S.R.

(except for the passive immigrant Dreissena polymorpha) and of polychaetes
underlines the importance of a capability for active migration in the coloni-
zation of rivers. According to A. Derzhavin (1939) these species do not live
in the rivers because their plankton larvae are carried away by the current.
However, the Caspian Ampharetidae (and the great majority of other members
of this family) do not have plankton larvae ; on the other hand the existence
of such larvae in the case of Dreissena polymorpha has not prevented the latter
from densely populating the whole of the Volga. Colonization by way of
passive immigration has been extremely effective for Caspian animals. Cordy-
lophora caspia, Victor ella parida, Dreissena polymorpha, Stenogammarus isch-
nus and Corophium curvispinum have moved farthest northward, as far as the
Baltic Sea. The four forms could easily have been propagated by river-craft.
Cordylophora caspia outdistanced the others and at present it is becoming
cosmopolitan. It has been found in North and South America, in Australia,
New Zealand and China, so far everywhere in large sea ports, where it is
brought by ships. However, the last rise in salinity of the Caspian basin
after the glacial transgression was not the sole cause of the colonization of
the river systems by a number of forms. Such 'waves' of immigration have
taken place many times in the history of the south Russian bodies of water.
Ya. Birstein and Vinogradov (1934) have noted, in the process of the im-
migration of river crayfish, three such ' waves ' even before the isolation of
the Caspian Sea from the Black Sea. The fresh-water medusa Craspedacusta
is, no doubt, also a very ancient immigrant from some bodies of water,
ancestors of the Sarmatian basin (L. A. Zenkevitch, 1940).

The correlation between the Caspian, Baikal and Okhrida faunas
The family ties between the Caspian fauna and those of some very remote
bodies of water, in particular those of Lakes Baikal and Okhrida, are evi-
dent. The Caspian Porifera Metschnikovia is akin to the Baikal Lubomir.
skiidae and the Okhrida Ochridospongia. The gastropod molluscs Micro-
melaniinae belong, together with the Baikal Baicaliinae, to one Microme-
laniidae family, members of which live elsewhere only in Lake Okhrida. The
polychaete genus Manayunkia has some of its forms in Lake Baikal and in
the Caspian Sea. Finally a whole number of the Caspian and Baikal sand-
hoppers are undoubtedly related ; this was proved not only morphologically
but also by the results of the precipitation reaction. In the opinion of A. Mar-
tynov (1924) and D. Taliev (1941) the links between the Caspian Sea and Lake
Baikal are explained by the migration of some Caspian forms into fresh water
in the Tertiary period; they then migrated extensively and reached Lake
Baikal, where they have maintained themselves to this day. G. Vereshchagin
(1941) thinks 'that the Caspian and Lake Baikal are two centres of the develop-
ment of marine fauna which had intruded into inland waters ; moreover the
ancestors of these forms, which lived in the pre-Sarmatian Seas on the one
hand, and in the east-Asiatic Seas on the other, were not identical, but were
similar in different groups in a different way'. Indeed, Vereshchagin thinks
that the marine organisms penetrated into the Caspian Sea much later than
into Lake Baikal.

THE CASPIAN SEA 583

Zoogeographical situation of the Caspian Sea

V. Sovinsky (1902) examined the typical Caspian fauna, which is fairly
markedly repeated in the Aral Sea and which abundantly populates, as we
have seen, the fresher parts of the Black and Azov Seas, and he had full reason
to distinguish a separate Pontic-Caspian-Aral marine zoogeographical pro-
vince consisting of two parts : ' The Black-Azov Seas part, which has retained
its Caspian fauna only in the freshened section ; and the Caspian-Aral one,
which kept its original fauna completely intact.' According to Sovinsky this
province is part of the Celtic-Boreal region.

However, V. Uljanin (1871) justly pointed out the great preponderance of
Mediterranean fauna in the Black and even the Azov Seas ; thus the inclusion
of these Seas in one single Pontic-Caspian-Aral province is artificial. Der-
zhavin considered this problem in 1925 and came to the correct conclusion of
the existence of a Caspian zoogeographical brackish-water and fresh-water
province, but not of a Pontic-Caspian-Aral marine one ; he thus brought in
an important correction of principle into the appellation given by Sovinsky.

Caspian fauna with its peculiar history of development and the complexity
of its origin from different sources could hardly be included in the Atlantic-
Boreal region. It seems more correct to consider it as a separate biogeogra-
phical unit, since we cannot relate it to any one marine zoogeographical region.
Thus we can assume that the Caspian fauna belongs to a separate brackish-
water region of partly marine, partly fresh-water origin.

The micro-organism population of the Caspian Sea

Micro-organisms probably play a much greater role in the Caspian Sea than
in many other bodies of water. Huge chemical processes take place here with
their assistance. Desulphurizing bacteria with a more or less strong reducing
effect are found in every bottom sample, as has been shown by A. Maliyants
(1933). They are as important here as in the Sea of Azov. Thick bacteria films
and whole coverings are formed in the upper layers of mud floors, in the more
or less enclosed shallows of the eastern shores and off the deltas of rivers with
deposits of organic matter carried there by the rivers.

The chemical role of Caspian Sea micro-organisms has not yet been pro-
perly investigated ; however, some valuable data for the understanding of the
main bacterial processes, and, in particular, for their quantitative estimation
are given in the works of Voroshilova and Dianova.

The decomposition of organic matter proceeds, especially in the accumula-
tion zones, by means of putrifying bacteria. In the middle part of the Kaidak,
for instance, their number rises to 1,000 to 2,500/cm3, whereas in the purer
waters of the Northern Caspian there are only 1 to 60 specimens/cm3. They
do not descend into the depths of the sea-bed. Ammonia and hydrogen
sulphide are the products of their (life) activity. Further decomposition of the
compounds (nitrification) proceeds under the action of the nitrate and nitrite
bacteria. Ammonium compounds are oxidized to nitrites in water, and to
nitrates in the soil, since the nitrate bacteria are absent from water. The
denitrifying bacteria, reducing nitrites and nitrates, are opposite in their

584 BIOLOGY OF THE SEAS OF THE U.S.S.R.

function to the previous nitrifying ones and are usually found in all the
samples. The nitrogen fixer, the anaerobic Clostridium pasterianum, which
sometimes goes down 80 cm into the sea-bed, performs the function of
nitrogen accumulation.

Anaerobic bacteria of methane and hydrogen fermentation of cellular
tissue, stimulating the process of carbohydrate decomposition, are of great
significance in the decomposition of organic residues in the soil. Large amounts
of methane and hydrogen are contained in the mud bottoms of the Caspian
shallows. At times these gases bubble up to the surface. A kind of 'boiling'
has at times been observed on the dump wrack lying off the Volga estuary,
formed by the mass of gas bubbles rising from the bottom. This process is
neutralized by micro-organisms which live in the uppermost layer of the
bottom ; they require a certain quantity of oxygen for their development and
have an oxidizing effect on the compounds of sulphur (sulphur micro-
organisms), methane (methane micro-organisms) and hydrogen (hydrogen
micro-organisms) formed at greater depths. The column of water is protected
from the entry of hydrogen, methane and hydrogen sulphide by the presence
of these three groups of micro-organisms in the uppermost layer of the bottom
soil. This film, as previously noted, can be destroyed by violent disturbances
of the water caused by wind, and the harmful gases may then enter the water
and poison it. The slight disturbances common in these shallows bring to the
surface of the floor the oxygen required for the development of thioneine,
methane and hydrogen micro-organisms, which, besides protecting the water
from poisonous gases, give a brown colour to the upper layer of the floor.
Deeper down, there usually lie thick layers of black, stinking mud.

This protective film in its turn serves, according to Voroshilova and
Dianova, as a substratum for the development of huge amounts of unicellular
algae, which synthesize organic matter. In Butkevitch's opinion life would
have completely disappeared from Caspian waters if this bacterial film, with
its reducing effect on hydrogen sulphide, methane and hydrogen, had been
removed.

The presence of a huge number of micro-organisms in the Northern Cas-
pian (100,000 to 400,000 and up to 17,000,000 specimens per one millilitre
of water) had already been recorded by V. Butkevitch (1938). The number of
micro-organisms is, as usual, related to the total amount of plant and animal
life, or to the amount of decaying organic remains (batkaks). Kriss points
out that the amount of micro-organisms in the waters of the middle parts of
the Northern, Central and Southern Caspian varies generally between 100,000
to 300,000 specimens per 1 ml of water. Below 100 m the amount of bacteria
drops to a few thousands (Figs. 274 and 275). According to V. Butkevitch's
calculations the biomass of the Northern Caspian micro-organisms is 50 to
250 mg/m3, and even 1 g/m3 off the Volga. Kriss, however, says that these
values are about twice too high. In the central and southern parts of the
Caspian Sea, according to Kriss, if the average biomass of micro-organisms
is taken as 36 mg/m3 (or 7-2 mg/m3 dry weight) within the layer of active
photosynthesis (0 to 50 m), the coefficient of its daily increase is 0-35. The
amount of decomposed organic matter will be 11-2 mg/m3. In Kriss's opinion

STATIONS из иг
,0

Fig. 274. Density of micro-
organism population and
its distribution in Southern
Caspian along the cross
section Kurinskiy Kamen'-
Ogurchinskiy Is. (Kriss).
Numbers of bacteria in
thousands per 1 ml of
water indicated by numerals
in diagram.

STATIONS 34-

2b 2221

Fig. 275. Distribution of micro-organism population density in Central Caspian

along the cross section Makhach-Kala-Sagunduk (Kriss). Numbers of bacteria in

thousands per 1 ml of water indicated by numerals in diagram.

586 BIOLOGY OF THE SEAS OF THE U.S.S.R.

the ratio of the production of micro-organisms to their biomass is 127-7 for
the Caspian Sea.

The number of micro-organisms in the bottom-soil of the Northern part
of the Caspian Sea reaches, according to A. Zhukova (1955), 12 milliards of
cells per one gramme of wet soil, in the Southern and Central parts 128 to
897 millions, and in the inlets, according to D. Evdokimov (1937), 105-7 to
1,627-6 millions per one gramme of wet soil.

A. Kriss (1958) considers that the total biomass of the micro-organisms
in the Caspian Sea is probably as much as 1,600,000 tons.

Plankton

Qualitative composition of phytoplankton. P. Usachev's comprehensive work
(1941) and I. Makarova's data (1957) on the diatoms are used by us for Cas-
pian Sea phytoplankton. The general composition of the plankton algae by
groups is given in Table 241.

Table 241

Species and

Dominant

Main

Group

Genera

subspecies

Percentage

species

Peridineae

10 +

28 +

Other Flagellata

Chlorophyceae

Diatomaceae

9 +
17
20

17
29
59

9
15
31

7
1

2
2
5

Cyanophyceae
Unclassified

Total

76 +

189 +

100

Blue-green algae constitute half the dominant and characteristic forms and
diatoms about 34 per cent. Thus, contrary to other seas, blue-green algae
acquire a predominant significance, while the Peridineae occupy third or
fourth place {Table 242).

Table 242

Group

Kara Sea
Total %

Barents Sea
Total %

Sea of Azov
Total %

Caspian
Total

Sea

Peridineae

Other Flagellata

( + Silicoflagellata)
Chlorophyceae
Diatomaceae

155

7
48
41

4
26
23

17
29
59

9
15
31

Cyanophyceae
Unidentified

29
1

Total

276

100

110

100

183

100

189

100

THE CASPIAN SEA 587

I. Makarova (1957) distinguished 59 species, subspecies and forms of dia-
tomaceous algae in the phytoplankton of the Central and Southern Caspian.
There are 17 species and varieties of Chaetoceros (Ch. wighami, Ch. paulsenii,
Ch. subtilis) ; 10 species of Coscinodiscus {C.jonesianus, C.j. var. commutatus) ;
and 6 species of Thalassiosira. Thus more than half the Caspian diatoms be-
long to these three genera. Among the other genera Sceletonema costatum,
Cyclotella caspia, Actinocyclus ehrenbergi, and among the immigrants Rhizo-
solenia calcar-avis are the dominant forms. The fact that, contrary to animal
groups, endemism among the diatoms is poorly marked, is most characteristic.
Makarova points out C. radiatus and C. perforatus as the only two endemic
species ; both belong to the widely distributed genus Thalassiosira (77г. cas-
pica and 77г. variabile). There is also one species of just as common a genus,
Actinocyclus paradoxus. On the other hand, there is a pronounced predomin-
ance of marine-brackish- water, brackish- water and cosmopolitan forms
among the plankton diatoms (about 62 per cent). The composition of the
Caspian Sea diatoms has a very great similarity with that of the north-
western part of the Black Sea and the Sea of Azov.

Thirty-five per cent of Caspian species are common with those of the lower
Volga and its delta ; 37 per cent of the species are common with those of the
Aral Sea, but the greatest similarity is observed with the Sea of Azov (114
common forms, or 63 per cent). The species common with the Black Sea
constitute 36 per cent, mainly among the diatoms and peridineans ; there are
no common species among the blue-green algae. Hence as regards its phyto-
plankton composition the Caspian Sea lies between the Sea of Azov and the
Aral Sea.

Phytoplankton biomass. Among the peridinean algae one species — Exuviella
cordata with two variants (typica and aralensis) — plays an exceptional role
in the biology of all parts of the Caspian Sea ; it forms the basic food of plank-
ton animals and plankton-eating fish, producing at times a biomass of 4-5 to
6-5 g/m3, mostly on the western side of the Northern and Central Caspian.
This is probably due to the presence of a powerful current, carrying plant
food and running along the western coast. The intensive development of
Rhizosolenia calcar-avis since 1934 has resulted in a pronounced decrease of
Exuviella. Among the other peridineans Prorocentrum micans var. scutellum
and Gonyaulax polyedra have most significance in the Caspian Sea.

As in the Sea of Azov, and contrary to the open seas, green algae play an
important part in the Caspian Sea phytoplankton, especially in its northern
part and still more in its freshest part. The majority are fresh-water forms.
Dictyosphaerium ehrenbergianum var. subsalsa, Oocystis socialis and Botryo-
coccus braunii are the most widely distributed green algae. Among the diatoms
the dominant species in the plankton up to 1934 were Skeletonema costatum,
Actinocyclus ehrenbergii, Coscinodiscus biconicus, Chaetoceros subtilis, Ch.
wighamii, Thalassionema nitzshioides. A new form, Rhizosolenia calcar-avis,
appeared in the Caspian Sea in 1934 and later became the dominant form of
the whole phytoplankton. The distribution of the diatoms in the northern
part of the Sea is given in Fig. 276.

588

BIOLOGY OF THE SEAS OF THE U.S.S.R.

The diatoms play a very important role in the Caspian Sea phytoplankton.
The diatom biomass in the Central Caspian constitutes 12 to 20 per cent of the
total phytoplankton ; their quantity is even higher in the Northern Caspian,
especially in its northwestern corner, where it has been known to reach 10
g/m3. Mass development of Rhizosolenia calcar-avis was first recorded in the
Caspian plankton in 1934 in its south- westernmost corner (more than 6
g/m3) ; by 1935 it had already spread through the whole of the Sea. Rh. calcar-
avis produces a biomass of 5 or 6 to 9 g/m3 in different places in the Sea

Fig. 276. Distribution of phytoplankton biomass (g/m3) in northern part of Caspian
Sea (Usachev). A August 1934; / Exuviella biomass 4-5 to 6-5 g/m3; // The main
zone of Exuviella gathering; III Isoplankta of diatoms 0-8; /^Isoplankta of dia-
toms 0-3; В September 1934; / Exuviella 01 to 0-2 g/m3; // Diatoms 0-3 to 0-8
g/m3; /// Blue-green algae 0-3 to 0-5 g/m3.

(Fig. 277). In some cases it constitutes 99 per cent of the total phytoplankton ;
it commonly exceeds 80 per cent. This is a completely unprecedented example
of a mass development of one single form and of the displacement by it of
20 to 25 per cent of another mass form, Exuviella cordata, which even in
1934 constituted 56 to 78 per cent of the whole mass of phytoplankton. Its
average number of specimens is 108 m3; that of Rhizosolenia is 2x 107. This
situation remained unchanged in 1936. In 1937 the Rhizosolenia biomass de-
creased* on the average to 0-06 to 2*16 g/m3.

Among the blue-green algae of the Caspian Sea the dominant species are
the following : Aphanizomenon flos-aquae, Nodularia spumigera, N. harveyana,
Anabaena bergii, A. bergii var. minor and Merismopedia tenuissima, Blue-

* High indices of the phytoplankton biomass were observed, however, only off the
coast; in the Central part of the Sea the amount of phytoplankton is measured in tens of
milligrammes per cubic metre (10 to 20 mg/m3).

THE CASPIAN SEA

589

green algae reach their highest development in the Northern Caspian, where
their summer and autumn bloom is observed and where their biomass rises to
0-4 to 0-7 g/m3, consisting mainly of Aphanizomenon flos-aquae. If the mean
biomass of the Caspian phytoplankton in the autumn of 1934 be taken as 1-2

#i\:

'"rS&i/1 :

^jXp^O^r

к I

• .^^ioiia /,

t/V М

/1/ Л / л '

И пз ¥

ЩЛу-г/////

га mis Ш

ЩШ

шпшю "Щ

^%0уйУ^

ЕЗ TL0.5

1 ^CiA'r'/

CD Ж0.1

Fig. 277. Quantitative development of Rhizosolenia
calcar-avis in 1934 (Usachev).

g/m3, then by 1935 it had increased to almost 2 g/m3 and in 1936 to 3 g/m3.
The whole of this increase is due to Rhizosolenia. The largest plankton
accumulations are adapted to the Northern, and partly to the Central,
Caspian— mainly on the western side, where a discharge current enriches the
water with plant food carried down by the Volga (Figs. 278 and 279).
The main mass of the Caspian phytoplankton is adapted to the upper

590

BIOLOGY OF THE SEAS OF THE U.S.S.R.

25 m layer of water. There is every reason to think that phytoplankton caught
in deeper layers is in a moribund state. As a result, in late autumn and winter,
with the decrease in production on the surface, the maximum phytoplankton
may move to deeper layers (Fig. 280). In the Central Caspian Rhizosolenia

Fig. 278. Total phytoplankton in autumn 1935
(Usachev).

was still absent in 1934, and Exuviella was the dominant form. With the
appearance and prompt domination of Rhizosolenia, Exuviella had to cede
its place (Fig. 281). Changes in the total phytoplankton biomass and in the
relationship between Exuviella and Rhizosolenia in 1934 to 1936 are given in
Table 243.
The general quantitative distribution of surface phytoplankton throughout

THE CASPIAN SEA

591

Fig. 279. Distribution of mean biomass of surface

phytoplankton (g/m3) from June to August 1936

(Usachev).

Table 243

Year

1934

1935

1936

Mean phytoplankton

biomass, g/m3

1-2

Exuviella only (%)

—

Rhizosolenia only (%)

1 -1

-С

f/l

СЗ

СЛ

■J

V©

<?'

го

-О

ел

•л

а,

/~v

о
J3

ь/

*■■

СЛ

-с

г/">

С
О

тз

>■,

1(Н

Чн

^т

,С

1-1

сС

-о

THE CASPIAN SEA

593

the Caspian Sea in 1935 is given in Fig. 278. It is evident that the plankton
biomass in the estuarian zone of the Caspian Sea had already reached the
huge amount of 100 g/m3 (in some individual cases 140 g/m3).

Fig. 281. Alterations of the mean phyto-plankton
biomass (g/m3) with depth (/) and of that of Exuviella
separately (//) in September 1934 in the coastal part of
the Northern Caspian. /// and IV: same for Central
Caspian; V and VI: same for Southern Caspian with
the appearance of Rhizosolenia; VI: same for Rhizo-
solenia separately (Usachev).

Usachev has compared the phytoplankton biomass of the Caspian and
Azov Seas. The mean phytoplankton biomass of the Sea of Azov during the
blootii of Rhizosolenia calcar-avis was found to be 2-0 to 5-2 g/m3 higher than
that of the Caspian Sea ; in 1925 it was 100 g/m3 higher.

Phytoplankton productivity. Valuable data on the characteristics of plankton
distribution in the Sea are obtained from the quantitative estimation of phyto-
plankton (productive part of plankton). The determination of productivity
on the basis of biomass data is most difficult and at present almost impossible.
As we have seen in Vorobieff ' s work on the Sea of Azov, such data can be
computed for the benthos since the indices of growth, multiplication, dying
off, and consumption by fish can be obtained. The problem, however,
generally becomes most difficult for plankton species. It can be solved in
part for zooplankton. Let us recall, for example, the Barents Sea plankton,
80 to 85 per cent of which is composed of a one-year-old population of
Calanus finmarchicus. The estimation of phytoplankton productivity cannot
be approached by means of population census. On the other hand, the exist-
ence of phytoplankton is closely linked with the chemistry of the water, with
the amounts of oxygen, carbon dioxide, phosphorus and nitrogen present,
and with its pH value.

S. P. Brujevitch (1937) has determined phytoplankton productivity in the

594 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Caspian Sea by the daily changes in oxygen content and pH in the sea itself,
that is by the difference between the afternoon maximum and the night
minimum of oxygen content. The average hourly consumption of oxygen was
determined by the difference between oxygen content after sunset and before
sunrise divided by the number of hours between the two determinations.

Brujevitch recorded the greatest phytoplankton production in the Mertvyi
Kultuk inlet in August 1934 (3-65 to 3-25 mg of glucose per litre). In the
Central Caspian the average phytoplankton production in August and
September 1934 was about 0-68 mg of glucose per litre, in the Southern part
about 0-75 mg/1. of glucose. Taking the plankton biomass for the Southern
Caspian as approximately 02 g/m3 of glucose, Brujevitch determines its daily
P/B ratio as 3-7, and for Mertvyi Kultuk as 2-8. If the distribution of
plankton in the upper 25 m column is more or less uniform, then the daily
plankton production is 17 to 19 g under 1 m2, or 170 to 190 kg of glucose
under 1 hectare.

Qualitative composition of zooplankton. We do not as yet possess sufficient
data on the Caspian Sea zooplankton similar to those on its phytoplankton.
According to V. Arnoldi and N. Tchougounov 92 species of zooplankton were
recorded for the whole of the Northern Caspian in the proportions shown in
Table 244. The fresh-water forms consist mainly of Rotatoria and Cladocera.

Table 244

Fresh-water forms 56-5% Rotatoria 45-2%

Brackish-water forms 7-5% Cladocera 28-6%

Marine 33-8% Copepoda 21-7%

Indifferent 2-2% Others 4-5%

According to these investigators 1 1 5 zooplankton forms have been dis-
tinguished in the Azov, Caspian and Aral Seas ; of these 60 per cent are fresh-
water and 40 per cent marine and brackish-water forms. The Northern Cas-
pian has the greatest similarity with the Aral Sea (25 per cent common
forms).

A. Kusmorskaya made a detailed study of the Northern Caspian zoo-
plankton in 1938 (Fig. 282). According to her data the qualitative composition
of Northern Caspian zooplankton does not differ from the characteristics
given in Table 244. Among the Protozoa, Tintinnoidea are the most numer-
ous and most widely distributed; they are represented by three species:
Tintinnus mitra, Codortella relicta and Tintinnopsis spp. ; moreover, the first
of them is not found in Mertvyi Kultuk and Kaidak, where C. relicta and
Tintinnopsis spp. reach their highest development. The Coelenterata are
represented by the medusa Caspionema pallasi, by its hydroid and by a hydroid
of a new form not yet described. The most numerous Rotifera are Asplanchna
priodonta, three species of Brachionus {B. bakeri, B. pala, and B. mulleri) and
a few species of Synchaeta and Ceratella aculeata var. tropica. The distribution
of many fresh-water species is limited to the estuarian zones of the rivers ;

THE CASPIAN SEA

595

they are not found at salinities above 4 to 5%0. On the other hand, a series of
forms characteristic of brackish waters Brachionus mulleri, Synchaeta vorax,
S. neapolitana, and others) have been successfully distinguished.

Cladocera are even more sharply divided into fresh- and brackish-water
forms. The first group includes the fairly numerous representatives of the
families Sididae, Daphnidae, Bosminidae and Chydoridae, which move far
out to sea only during the flooding of rivers. The second group consists of
genera of the Polyphemidae family (Polyphemus, Cercopagis, Apagis and
Evadne), which avoid places of considerably lowered salinity. Evadne trigona

Fig. 282. Distribution of zooplankton biomass of Northern Caspian and the iso-
halines in September 1935 (Kusmorskaya).

and Cercopagis gracillima are the most widely distributed and numerous
representatives of this group. Among the Copepoda the dominant form
for the whole Northern Caspian zooplankton is Calanipeda aquae dulcis —
an extremely eurybiotic and widely distributed species. From February to
November inclusive, Calanipeda comprises on the average 50 per cent of the
total zooplankton biomass. Halicyclops sarsi is also very numerous and widely
distributed. Heterocope caspia is much more stenohaline, avoiding both an
increase and decrease of salinity. The rest of the Copepoda are found much
less frequently and in smaller numbers. Among them too it is possible to dis-
tinguish a group of species connected with fresh water {Cyclops spp., Nitocra
incerta, Schizopera tenera, Nannopus palusths, Diaptomus gracilis, Eury femora
affinis and others) and the group of species connected with saline water
{Eurytemora grimmi, Idyaea brevicornis).

Kusmorskaya gives the composition of zooplankton in the western half of
the Northern Caspian and in the Mangishlaksk area of the Caspian Sea in the
form shown in Table 245.

596

BIOLOGY

OF THE SEAS OF THE U.S
Table 245

.S.R.

Groups

Number of

species

in the

western half of

Mangishlaksk

Northern Caspian

area

Tintinnoidea

—

Coelenterata

—

Rotatoria

Cladocera

Harpacticoida

Cyclopoida

Calanoida

7
10

5
3

Total

The biomass of North Caspian zooplankton. The seasonal changes in the
composition and numbers of North Caspian zooplankton are very marked.
In winter zooplankton is very poor in both numbers and variety, comprising
only four forms {Calanipeda aquae dulcis, Halicyclops sarsi, Ectinosoma sp.
and Synchaeta sp.). 99-7 per cent of its biomass consists of C. aquae dulcis
and is on the average only 9-5 mg/m3. There are 350 specimens per 1 m3. A
rapid qualitative and quantitative increase of zooplankton is observed in
April and May: its average biomass in April is 15 mg/m3 and in May 58
mg/m3. The number of species found rises to 30 in April and 40 in May. This
is connected primarily with its multiplication, which begins in the spring.
The main mass of zooplankton, as regards specimens, is composed of Hali-
cyclops sarsi, Harpacticoida and Lamellibranchiata in April ; there are then
few Rotatoria and Cladocera. At the end of May and the beginning of June
the flood waters move much farther south and therefore the number of fresh-
water Rotatoria and Cladocera increases considerably. Intensive multi-
plication of almost all plankton forms proceeds simultaneously, chiefly that
of Calanipeda, which by that time occupies first place in the biomass. Further
growth of zooplankton biomass takes place in the summer, and in the mouth
of the river Volga it increases by 70 per cent by August as compared with
April. The intensive multiplication of the majority of planktons continues,
and in this respect the August plankton does not differ much from that of May.
In August the mean biomass in the western half of the Northern Caspian
(less productive in zooplankton than the eastern half) constitutes 60 mg/m3,
the average number of specimens being 6,950 per 1 m3. An extinction of zoo-
plankton was observed in September 1934. It could not be considered a
consequence of strong changes in the hydrological conditions of the Sea,
since in this respect the difference between August and September is slight.
It may be that the food resources of the Sea were exhausted by September.
The zooplankton biomass dropped at that time to 15 mg/m3. In September
1925 zooplankton was found to be much richer than in the previous year.
The average zooplankton biomass then was 100 mg/m3. Some differences

THE CASPIAN SEA 597

were also observed in the relationship between individual groups : thus, for
example, in September 1934 Rotifera comprised 9 per cent, and in September
1 935 17 per cent, of the zooplankton biomass. A gradual drop of zooplankton
biomass takes place in October and November, accompanied by an increase
in the relative significance of Calanipeda. The average zooplankton biomass
for October 1935 was 92 mg/m3, 56 per cent of it being Calanipeda; for
November 1935 the average biomass was 35 mg/m3 with 65 per cent Calani-
peda.

This difference between the September data of 1934 and 1935 can be
explained by the hydrological conditions of the Northern Caspian in 1935.
In autumn 1935 the southern part of the Northern Caspian was exceptionally
enriched by plant food, brought, apparently, from great depths of the Central
Caspian and carried far to the north owing to the increased flow of Central
Caspian waters. This brought about an intensive Rhizosolenia bloom in the
southern and middle parts of the Northern Caspian and also, no doubt,
favoured zooplankton development.

Zooplankton distribution is not uniform in the Northern Caspian (see Fig.
282). As early as 1921 N. Tchugunov distinguished there three plankton zones
characterized by their specific composition and the extent of quantitative
development of zooplankton, controlled primarily by salinity : (7) the mouths
of the Volga and Ural rivers with their lowered salinity of 0-3 to O4%0 ; (2)
the zone of mixing of the saline and fresh waters, with a salinity of 8 to
9%0, approximately within the 12 to 18 ft bar of material carried down by the
rivers; (3) the saline zone, with a salinity of 10 to 12%0 exposed to the direct
influence of the Central Caspian, occupying the southern and central part
of the western half of the Northern Caspian. The boundaries between these
zones are naturally very unstable, change frequently, and can approach each
other depending on the amount of flood water, wind, etc.

The zooplankton of the first zone is poor, and consists only of fresh-water
species.

The next zone, richest in number and wealth of zooplankton, is populated
by typically brackish-water organisms. In early spring the average zooplank-
ton biomass of this zone is 16-5 mg/m3, say three times higher than in the
first zone ; by the end of May and the beginning of June it is 92 mg/m3, in
August 130 mg/m3, in September 160 mg/m3 and in October* 154 mg/m3. It
was in this zone that the maximum phytoplankton development was recorded.

The zooplankton of the third zone is considerably poorer both in numbers
and variety of species. Several species are not found here and the remaining
ones do not reach mass development. The average zooplankton biomass of
this zone in August 1935 was 20 mg/m3, in September 1935 27 mg/m3, and
in October 1935 only 13 mg/m3.

The difference in zooplankton biomass in these zones is controlled by other
factors as well as salinity, which limits the range of one or another species ;
as has been shown by Kusmorskaya, plant food content in various areas is of
great significance in this respect.

* The data for May, June, August, September and October are given only for the
western part of the Northern Caspian.

598

BIOLOGY OF THE SEAS OF THE U.S.S.R.

A remarkable coincidence between quantitative development of zoo-
plankton and of bacterial flora is evident from the data gathered by Kusmor-
skayr (1938). On the cross section Volga delta-Mangistau maximum numbers
of micro-organisms and zooplankton are found together, falling exactly within
the area of confluence of river and sea waters (Fig. 283). The same coin-
cidence was recorded for Mertvyi Kultuk and Kaidak. It might reflect both

MICRO-
ORGANISMS

160000-

140000-

120000-

WO 000

80000

60000

40000

20000
10000

ZOOPLANKTON

NUMBER OF MICRO-ORGANISMS (COLONIES)
ZOOPLANKTON BIOMASS mg/m

ч 0

Fig. 283. Quantitative distribution of bacteria and zooplankton along the cross
section Volga delta-Mangistau (Kusmorskaya).

an indirect and a direct dependence of zooplankton on micro-organisms.
Micro-organisms decompose organic matter and enrich the waters with
plant food. The development of phytoplankton biomass is due to it ; this in its
turn serves as food for zooplankton. Moreover plankton Copepoda feed
directly on micro-organisms, and bacterial flora is used to feed zooplankton.
Taking Knipovitch's value of 793 km3 as the volume of the Northern
Caspian, Kusmorskaya calculated the absolute amounts of zooplankton bio-
mass and has obtained indices for the whole Northern Caspian as given in
Table 246.

Zooplankton biomass of Central and Southern Caspian. Quantitative data on
Central and Southern Caspian zooplankton are contained in the works of
M. Idelson (1941) and V. Jashnov (1938, 1939). According to Idelson the
largest zooplankton biomass is found in the 0 to 100 m layer; below that it
decreases regularly with depth (Table 247).

The relationship between separate groups changes simultaneously (Fig.
284). Copepoda are the dominant groups in the 0 to 100 m layer, comprising
96 to 99 per cent of the total biomass in the Central Caspian and 71 to 95 per

Fig. 284. Vertical distribution of zooplankton along the cross section through the
central part of the Central Caspian, Divichi-Kenderli Bay, April (A) and August (B)

(Idelson).

600

BIOLOGY OF THE

SEAS OF THE U.S.S

Table 246

Total biomass in-

cluding plankto-

and nectobenthic

Total biomass for

crustaceans for

whole Northern

Mean biomass

Caspian

Months

mg/m3

tons

February-March

1935

9-5

7,500

—

April 1935

11-5

9,000

12,000

May-June 1935

58-0

46,000

92,000

August 1934

600

47,500

48,300

September 1935

1000

79,300

94,300

October 1935

920

73,000

77,000

November 1935

31-5

25,000

50,000

cent of that in the Southern Caspian. Limnocalanus grimaldi should be con-
sidered as the dominant form of Copepoda (92-6 to 36-4 per cent of the total
Central Caspian biomass and 49 per cent of the Southern Caspian). In the
100 to 200 m layer Mysidae become significant (15-8 to 31 per cent in the
Central Caspian, 25 per cent in the Southern Caspian) ; Copepoda, however,
remain the dominant form. Below 200 m Mysidae become the dominant form
in the Central Caspian (86 per cent); their specific weight increases in the
Southern Caspian (39-8 per cent). Mysis microphthalma, M. amblyops and
Par amy sis (Austromysis) loxolepsis are the most numerous deep-water Mysidae.

The horizontal distribution of zooplankton biomass within the 0 to 100 m
layer is not uniform. The deep middle part of the Central Caspian and the
Apsheron ridge are the richest zooplankton areas in the spring. The biomass
there may exceed 200 mg/m3. The poorest area is the northern part of the
Central Caspian (less than 25 mg/m3). As a rule the shallows are poorer in
zooplankton population than the deeper parts (Fig. 284).

Zooplankton composition in different areas of the Sea also varies. In the
middle parts of the Central and Southern Caspian Limnocalanus grimaldi is
predominant; next come, in lesser numbers, Mysidae and Cladocera. The
relationships of planktons are approximately the same as in the eastern
coastal zone. In the western coastal zone fairly considerable numbers of

Table 247

Depth
m

Biomass in April

1938, mg/m3

Central Caspian

Southern Caspian

0-100
100-200
200- sea bed

3620

1480

23-8

50-7
501
22-9

THE CASPIAN SEA

601

Rotatoria, Lamellibranchiata (larvae), Mysidae, Amphipoda and Cumacea,
as well as fish-fry, are found in addition to Copepoda, which remain the pre-
dominant group.

In the Central and Southern Caspian the total amount of zooplankton
biomass and its qualitative composition change considerably with the seasons.

Fig. 285a. Distribution of zooplankton biomass

of Central and Southern Caspian in autumn

1934 (Jashnov).

Unfortunately there is no material available for the assessment of this pheno-
menon. A comparison can only be drawn from the data (by Idelson) for
March-April and August, and for December for the Southern Caspian. This
comparison shows an increase of zooplankton concentration in the western
coastal zone of the Central Caspian by the autumn, which at that time becomes
richer in zooplankton (235 mg/m3) than the central (86-2 mg/m3) and
eastern coastal zones (39 mg/m3). According to Jashnov's data a similar
distribution of plankton population was recorded in the autumn of 1934-35
(Fig. 285a). The seasonal changes of the vertical distribution of zooplankton

602 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 248

Layer
m

0-100

100-200

Below 200

Biomass,

mg/m3

Apr

Aug

1938

238

120

in the middle part of the Central Caspian are well illustrated in Table 248.
As shown in this table zooplankton biomass decreases by the autumn in the
upper layers, and increases in the lower ones. The relationships between
different groups change also. In the middle part of the Central Caspian
Limnocalanus grimaldi is concentrated by the autumn in the lower layers (in
the 100 to 200 m layer it constitutes 67 per cent and at 200 m it is 54-2 per cent
of the total biomass) while in the upper layer, where in the spring the plankton
consists almost exclusively of Limnocalanus grimaldi, by the autumn it forms
only 9-7 per cent of the biomass. The migration of L. grimaldi to the lower
layers in the autumn is undoubtedly connected with the adaptation of this
species to relatively lower temperatures, and is caused by a considerable
warming of the surface layer. In the western coastal zone a large number of
Lamellibranchiata larvae appear by the autumn (90 mg/m3, comprising
42-2 per cent of the total biomass). Copepoda remain, however, the dominant
group (comprising 47-3 per cent of the total biomass, containing 11-6 per
cent Eurytemora, 10-6 per cent Calanipeda, 15-2 per cent Halicyclops and
9-2 per cent nauplii). Limnocalanus grimaldi, dominant in spring in the eastern
coastal zone, comprises only 6-8 per cent of the total biomass by the autumn,
nauplii (42-6 per cent), Eurytemora (28-5 per cent) and Lamellibranchiata
larvae (9-2 per cent) take precedence. Observations from the Southern Caspian
are shown in Table 249.

Zooplankton biomass and composition in the upper layer did not change
much. However, in the 100 to 200 m layer and from 200 m to the sea-floor a
considerable decrease of zooplankton biomass was recorded in March 1939;
moreover there were some natural alterations in the relationships between the
separate groups: Limnocalanus was the dominant form in April 1938 (68
and 56 per cent) while second place was occupied by the mysids (25 and
39-8 per cent); in December 1938 and in March 1939 in particular these

Table 249

Layer
m

Mar
1938

Biomass, mg/m3
Apr
1938

Dec

1938

0-100

100-200

Below 200

52
5
8

51
50
23

22
23

THE CASPIAN SEA

603

animals changed places, the mysids occupying the first place (54 to 98 per
cent), while the Limnocalanus biomass went down to 4-2 to 22-7 per cent.

The Central Caspian zooplankton biomass is subject to both seasonal
and annual fluctuations. The data for the spring of 1938 and 1939 showed an
increase of zooplankton biomass in 1939 (the average biomass for 1938 was 287

Fig. 285b. Distribution of zooplankton biomass of
Central and Southern Caspian in May 1939 (Idelson).

mg/m3, for 1939 — 362 mg/m3) while its qualitative composition remained
unchanged (Fig. 285b). The same fact was recorded for phytoplankton. In
autumn 1938 the zooplankton biomass was higher (86-2 mg/m3) than in the
autumn of 1934 (55 mg/m3). There are no similar observations for the
Southern Caspian. Similar indices were, however, obtained for this part of
the Sea in 1938 and 1939. Plankton biomass data from different parts of the
Sea (Jashnov) are given in Table 250 for the autumn of 1934; Rhizosolenia,
however, is not included.

604

BIOLOGY

OF THE

SEAS OF THE U

S.S.R.

Table 250

Zooplankton biomass in Caspian

Depth

Sea, mg/m3

Northern

Central

Southern

0-25

288

182

145

25-50

—

122

50-100

■ —

103

100-300

—

300-500

—

500-800

—

Plankton biomass in the Caspian Sea is inferior to that of many other
seas, in particular to the Barents Sea and Sea of Azov ; it is, no doubt, inferior
to the latter in productivity also.

Vertical migration of zooplankton. The phenomena of vertical migration
of plankton, some plankton-benthos and even benthic crustaceans (for ex-
ample Cumacea and Corophiidae) are extremely pronounced in the Caspian
Sea. While it is dark these organisms rise in huge masses to the surface, attracted
by its large food resources and oxygen. The water teems with them, and the
masses of animals present give it a milky appearance by electric light. This
process is most striking owing to its very size. No fewer than 4 to 5 millions
of crustaceans move hundreds of metres up and down twice a day.

N. M. Knipovitch (1921) has already pointed out the daily vertical migra-
tion of bathopelagic mysids with Mysis microphthalma, M. amblyops and
Austromysis loxolepis as specially characteristic. In daylight the maximum
numbers keep within the 250 to 350 m layer ; at night they are in the top layer
of the Sea. They may travel as much as 300 m. Their migration is accompanied
by a 30 atm pressure change. Twice a day the animals experience, without
harm to themselves, these great changes in pressure and correspondingly in
temperature. Limnocalanus grimaldi and the larvae of the Caspian sprat also
experience this kind of migration. Knipovitch has determined the rate of rise
of some mysids as 90 m in 75 minutes.

The number of the plankton forms in vertical migration given by Jashnov
for August 1934 {Table 251) is even more indicative.

V. Bogorov (1939) has given a comprehensive description of the vertical

Table 251

Depth
m

Amount of plankton, ton/km3

Central Caspian Southern Caspian

day night day night

0-50

50-100

100-400

1-1

3
16-8

9-7 0-7 7-7
1-9 0-9 3-4
60 6-3 1-5

THE CASPIAN SEA 605

migration of Eurytemora grimmi in the Caspian Sea. This crustacean never
forms a maximum in the surface layer. It starts its upward movement from
the depths in the afternoon. At midnight it begins to sink again. This is clearly
pronounced in the early morning hours, and by 8 o'clock in the morning
almost all the Eurytemora grimmi are already at a depth of 50 to 83 m, where
they remain till their next ascent. The nature of the changes is shown in
Table 252, which includes the data for all the stages (in number of specimens

Table 252

Depth

Hour of the day

6 p.m.

8 p.m.

ll-12p.m

2 a.m.

5 a.m.

8 a.m.

11 a.m.

2 p.m.

1-10

928

1,600

1,680

1,358

10-25

2,863

3,240

2,396

3,378

373

—

2,250

25-50

1,595

277

765

1,109

1,201

709

2,010

50-83

—

5,413

3,181

1,610

per 1 m3). No significant changes in the process of migration for different
ages have been recorded for E. grimmi, but such changes were noted for the
Northern Sea Calanus finmarchicus by A. Nicholls (1953). The rate of upward
movement of these small Copepoda is about 2 cm/sec (72 m/h) ; their descent
is almost as rapid.

Borgoov has given an interesting estimation of the biological significance
of the'vertical migration of E. grimmi. An average of 7 mg/m3 of living matter
is transferred during one day. It is understandable that the feeding significance
of plankton in different layers changes sharply in connection with these
movements. A certain layer can contain very different amounts of food-
forms at various times of the day. Bogorov has established the feeding value
of a given layer (the product of mean biomass by the number of hours, corres-
ponding to the given state of the biomass) and the feeding intensity of a given
layer (quotient of mean biomass divided by the number of hours for a given
biomass). For E. grimmi, one of the most important food-plankton of the
Caspian Sea, these values are given in Table 253.

Table 253

Depth Feeding Feeding

m value intensity

0-10

1-3

10-25

210

0-9

25-50

120

0-5

50-83

180

2-2

The 10 to 25 m and 50 to 83 m layers have the highest feeding value, while
the highest feeding intensity is found in the 0 to 10 m and 50 to 83 m layers,
since a huge number of organisms is gathered there for a short time. Using

606 BIOLOGY OF THE SEAS OF THE U.S.S.R.

the data obtained by S. Marshall and A. Orr (1955) and by A. Nicholls (1937)
for Calanusfinmarchicus, V. Bogorov (1939) calculated the volume of oxygen
consumed by the whole Eurytemora grimmi population and the carbon di-
oxide liberated by it in various layers of water in 24 hours. When it is dark the
main oxygen consumption takes place in the top layer (0 to 25 m) ; when light,
in the 50 to 83 m layer {Table 254).

Table 254

Horizon 0-10

10-25

25-50

50-83

Daily oxygen consumption, cm3/m3 30
Carbon dioxide increase, cm3/m3 24

80
64

50
40

The coefficient of daily vertical distribution of the highest mass of plankton
can be calculated from these data. From the data of a definite station, col-
lected at a definite hour, it is possible to calculate the distribution of plankton
at any moment of the day, using the previously established coefficients of daily
vertical distribution of organisms according to stage and sex.

For Eurytemora the coefficients of daily vertical distribution have been cal-
culated in the form given in Table 255.

Table 255

Time of catch

Coeffic
distrib

Depth

6 p.m.

8 p.m.

11-12
p.m.

2 a.m.

5 a.m. 8 a.m.

11 a.m.

2 p.m.

ution

Day

Night

0-10
10-50
25-50
50-85

20
50
30

30
50
18

20
60
18

5 1
20
70 11

5 88

1
39
30
30

2
15
28
55

The converse picture is obtained for the day and night distribution of E.
grimmi. A similar method of calculation is less reliable when the stations are
not complete or only one sample was taken.

Benthos

Qualitative composition of phytobenthos. Kireeva and Shchapova's interesting
and comprehensive research on macrophytes (1939, 1957) should not be
omitted from the list of oceanographic work done in the Northern Caspian
in the last 15 years. A very full picture of their distribution in number and
species is given for the eastern and northeastern coast of the Sea. Before all
else the specific composition of the Caspian Sea macrophytes is characteristic,
as compared to the flora of other seas {Table 256).

In the Mediterranean and Black Seas red algae predominate, then come the

THE CASPIAN SEA 607

Table 256

Mediterranean

Group of

Alboran

Black Sea

Sea of

Caspian

Baltic

bottom

coast

Azov

Sea

algae

No. of %

No. of

°/

No. of %

species

Blue-green

algae

67 13-6

—

28-0

55 15-1

Green algae

78 15-9

24-5

40-0

132 36-2

Red algae

258 52-5

103

46-6

42-5

25-0

78 21-4

Brown algae

89 18-0

28-9

11-5

7-0

100 27-3

Total

492 100

221

100

116

100

365 100

brown and finally the green. In the Caspian Sea there is a reverse relationship
between these species : the first place is occupied by the blue-green and green
algae, the percentage of brown and red is low, and their ratio to the first is
even lower. The Baltic Sea ratio is somewhat similar.

The qualitative poverty and the ratio between the separate groups of the
Caspian Sea macrophytes is related to the historical past of the Sea and to
its low salinity. Apart from the algae tabulated, on the eastern shores of the
Sea five species of flowering plants are widely distributed : Zostera nana,
Ruppia maritima, R. spiralis, Najas marina and Potamogeton pectinatus (63
forms in all).

T. Shchapova (1938) thinks that the majority of brown and red algae
belong to the transformed Sarmatian and later Pontic flora, and that owing
to the occurrence of numerous and considerable losses of salinity in the Cas-
pian basin a whole series of marine species has disappeared, while new forms
of fresh-water origin have settled in. Some marine forms could have pene-
trated here from the west very recently. It is probable that Zostera nana was
one of them. The evolution of a brackish-water flora was furthered by the
history of the Caspian Sea ; moreover the mass development of the charial
algae is of particular interest. Thus the complete analogy between the Caspian
flora and fauna becomes evident.

Distribution and biomass of phytobenthos. Shchapova distinguishes three main
groupings of bottom-living macrophytes according to the type of the sea-bed
soil.

On rocky soils, chiefly on the western and eastern coasts, green and red algae
with the highest percentage of marine forms are preponderant. The highest
horizon is inhabited by Cladophora glomerata flavescens, CI. nitida and
Enter omorpha intestinalis. At a depth of only 0-3 to 0-4 m green algae already
yield their place to red ones (Laurencia paniculata, Polysiphonia elongata
and P. vio/acea). Among brown algae Monosiphon caspius is common here.

On shallow sand-shell-gravel soils Zostera nana is the highest developed
form and, to a much lesser extent, Ruppia maritima and Polysiphonia sertula-
rioides. Exceptionally large growths of Zostera are found in the Mangishlak

608 BIOLOGY OF THE SEAS OF THE U.S.S.R.

area and, apparently, in the southeasternmost part of the Sea. Zostera is
easily detached from the bottom by the swell and, since it floats, it gets
scattered throughout the Sea, often forming heaps of wrack in places distant
from that of its original growth. The main accumulations of the second form
—Polysiphonia sertularioides—ате recorded in the southeastern parts of the
Sea.

Charial algae (Chara intermedia, Ch. polyacantha, Ch. aspera and Ch.
crinita) grow in huge amounts on the shallow (0-2 to 2 m) hydrogen sulphide
silt soils of the eastern coast, mostly in inlets and behind the islands, etc.
Macrophyte sea-weeds in the Caspian Sea do not sink deeper than 25 m
owing to the poor transparency of its waters. The biomass distribution of algae
is very patchy, rising at times almost to 30 kg/m3 with the growths of charial
algae and sometimes dropping to insignificant amounts ; it is adapted mainly
to within 2 m of the surface. Zostera nana biomass reaches 1 kg/m3 at some
places, but is commonly about 200 to 300 g/m3 (wet weight). Total raw re-
sources of this commercial plant constitute about 700,000 tons of wet weight
in the Caspian Sea. Its yield in the area of the Apsheron peninsula alone is
about 1-5 to 2 thousand tons. Red algae are especially abundant along the
western coast of the Caspian Sea. OffSvinoi Island they have a biomass of up
to 3-6 kg/m3, consisting mostly of Laurencia paniculata. In other areas the
red algae Ceramium diaphanum and Polysiphonia sertularioides predominate.
Among the green algae Enteromorpha ampressa and Cladophora spp. are
preponderant with their biomass of a few kilogrammes. Charial algae give
2 to 3 kg/m2 biomass in some areas. Brown algae do not form any consider-
able biomass in the Caspian Sea. The total biomass of Caspian macrophytes
is of the order of 3 million tons of wet weight, with an average PjB ratio
about unity. A chart of the macrophyte biomass of the eastern shores of the
Caspian Sea is given in Fig. 286.

The maximum macrophyte biomass is found in the Caspian Sea near soft-
soil shores, the minimum near rocky floors. This has led Kireeva and Shcha-
pova to assume that the Caspian is more of a lake than a sea by the distribution
of its phytobenthos biomass.

Qualitative composition of bottom-living fauna. As has been mentioned above,
the Caspian Sea fauna is considerably inferior in its variety to that of the open
sea, both in the total number of its species and in the relationship between its
separate component groups. Table 256 contains some plankton-benthos and
plankton groups.

The difference between the composition of the marine and Caspian Sea
fauna is shown in Table 257.

It is evident from this table that in full-salinity seas Porifera, Coelenterata,
Polychaeta and Bryozoa form groups as varied as those of the molluscs,
crustaceans and fish, while in the low-salinity waters of the Black, Caspian
and Baltic Seas the last three groups constitute only 50 to 65 per cent of the
groups mentioned. Moreover one of the greatest characteristics of the
Caspian Sea — the poverty of its qualitative composition — is shown graphic-
ally in Tables 257 and 258.

Table 257. Composition of Caspian Sea bottom living fauna

Groups

No. of species

Groups

of species

Foraminifera

Amphipoda

Porifera

Isopoda

Coelenterata

4(1)*

Cumacea

Turbellaria

Mysidacea

Nemertini

Decapoda

5(3)

Hirudinea

Chironomidae

Oligochaeta

Hydracarina

Polychaeta

6(1)

Bryozoa

4(1)

Ostracoda

Lamellibranchiata

23(4)

Cirripedia

2(2)

Gastropoda
Pisces

32
78(3)

Total number of free

-living

animals

336(15)

* The composition of the Caspian Sea fauna, especially the Protozoa which are not
listed here except for Foraminifera, has not been fully investigated yet. Data in paren-
theses give numbers of species which have recently penetrated into the Caspian Sea.

Fig. 286. Distribution of the
biomass of macrophytes of the
eastern coast of the Caspian
Sea (Kireeva and Shchapova).

610 BIOLOGY

OF THE

SEAS OF THE U

.S.S.R.

Table 258

Baltic Sea

Groups

Caspian

Barents

Black

including

Sea

Arcona area

Foraminifera

115

Porifera

Hydrozoa and Anthozoa

139

Turbellaria

Nemertini

Polychaeta

200

123

Gephyrea

—

Bryozoa

272

Brachiopoda

—

Higher crustaceans

118

361

214

Lamellibranchiata

Pantopoda

—

Gastropoda

150

Echinodermata

—

4(5)

Ascidia

—

Pisces

174

(E.

143
Slastenenko
1938)

Fish-parasite fauna. The list of the parasites of Caspian fish, not yet complete,
may be added to that of the free-living forms {Table 259). V. Dogel and B. By-
khovsky (1939) divide these species according to their origin into the groups
(except forms of uncertain origin) shown in Table 260.

Table 259

No. of

Groups

species

Flagellata (Trypanosoma,

Trypanoplasma)
Myxosporidia
Microsporidia
Coccidia

17
18

1
1

Infusoria

Trematoda monogenea
Trematoda digenea

45
29

Cestodes

Acanthocephala
Nematoda

5
19

Hirudinea

Copepoda
Branchiura

Total

170

THE CASPIAN SEA
Table 260

611

Groups according to
origin

Fresh water

Marine

Non- Non-

endemic Endemic endemic

Endemic

Total

Southeastern

—

Southern

Northern

European

2
36
14
93

Total

120

It follows from Table 259 that the parasite fauna of Caspian fish consists
mainly of fresh- water species (94-3 per cent). Parasites of marine origin com-
prise only 5-7 per cent of the total number of species and are chiefly peculiar
to the herring family, Acipenseridae and bullheads. Of the 22 endemic
Pontic-Caspian-Aral forms only 7 inhabit the Caspian Sea alone. Of special
interest among these two species of northern origin are the parasite of
the seal Carynosoma strumosum and the Caspian herring parasite, Bunocotyle
cingulata, neither of which has any genetic link with the north.

It is most characteristic that a large number (22) of the Caspian fish para-
sites live in fish in their larval stage and in birds when adults. This is no doubt
linked with the exceptional abundance of diving birds in the Caspian Sea.
Only eleven larvae of such species are recorded for Aral fish and only ten
for the Neva Inlet. The Caspian Sea is in general much richer in fish-parasites
than the Aral Sea. On one particular kind offish 1 19 species of parasites were
recorded in the Caspian Sea and only 70 in the Aral. The comparison of the
data on the Caspian and Aral sturgeon Acipenser nudiventris is particularly
indicative in this respect (before the appearance of Nitzschia sturionis in the
Aral Sea).

On this subject Dogel and Bykhovsky write as follows : ' We see that not
one of the (first eight) specific Acipenseridae parasites has survived in the Aral
Sea. All the Aral parasites of the sturgeon Acipenser nudiventris have either an
accidental character or (Asymphilodora, Macroseroides) have moved on to
it from fish of different kinds.' Dogel and Bykhovsky explain the greater abund-
ance of fish-parasites in the Caspian Sea as compared with the Aral Sea by
the greater variety of invertebrates in the Caspian fauna, since the latter serve
as intermediate hosts to parasitic worms ; and also by the historical past of the
Aral Sea. On the other hand Caspian fish and, in particular, Acipenseridae
are poorer in marine parasites and richer in endemic and fresh-water forms
than Black Sea fish.

Among the Caspian fish-parasites recorded a number of forms are harmful
to fisheries : Ligula, afflicting annually some millions of specimens of cypri-
noids ; Caligus, which causes the emaciation of carp ; Dioctophymidae larvae,
which form tumours in the intestines of Acipenseridae ; Eustrongylides larvae,
causing red boils in the muscles of pike perch, and others.

612 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Vertical distribution of zoo benthos. O. Grimm had already pointed out in 1877
the vertical zonality of the distribution of Caspian fauna and had estab-
lished three faunal zones covering the upper 300 m. A similar division of the
Sea was suggested by N. M. Knipovitch (1921), based on the distribution of a
series of hydrological and biological factors. He suggested four zones for the
Central Caspian and three for the Southern. The upper zone (100 to 200m), with
its seasonal temperature fluctuations and a larger oxygen content, was further
divided into sub-zones by Knipovitch. The second zone is characterized by a
lower oxygen content and a fairly constant temperature (down to 450 m).
According'to Knipovitch the third zone with a constant temperature and low
oxygen content extends in the Southern Caspian to the sea-bed and in
the Central to 750 m. Below it lies the fourth zone, characterized by the pre-
sence of hydrogen sulphide. According to Knipovitch the limit of bottom life
lies at 415 m in the Central Caspian and at 460 m in the Southern. The main
mass of benthos lives in the two upper zones. More recently S. P. Brujevitch
(1937) suggested a diagram for the vertical division of the Sea according to
chemical indices, of which mention has been made above.

As has been shown by recent research the maximum depths for bottom-
living organisms are greater than those suggested by Grimm and Knipovitch,
the 400 to 500 m deep water column was found to contain some benthos,
although here it is poor both in number and variety (Fig. 287). Hypania in-
xalida was discovered down to maximum depths (960 m) ; Pseudolibrotus was
caught in plankton nets below 600 m. Some mysids were found at almost the
same depth. They can all, apparently, exist on very small amounts of oxygen.

In the Central Caspian bottom fauna becomes very scarce at about 100 m.
Crustaceans of Arctic origin live here : Mesidothea entomon, Pseudolibrotus
platyceras, Ps. caspius, Pontoporeia affinis, Mysis caspia, M. microphthalma
and M. amblyops. AmathiUina spinosa, Pandorites podoceroides, Niphargoides
grimmi, Stenocuma diastvloides are found down to a depth of 150 m. An
almost complete absence of molluscs is characteristic ; only very rarely would
a grab bring up Dreissena grimmi, Dr. rostiformis, Micromelania spica, M.
caspia and M. elegantula. Deeper down (to 400 m) the Oligochaeta and
Hypania invalida are found. In the Southern Caspian, only Hypania invalida
and the Arctic mysids were found.

The specific deep-water fauna is absent from the great depths of the Caspian
Sea. These are inhabited first by the forms of Arctic origin, adapted to low
temperature ; secondly by Caspian autochthonous forms, descendants of the
shallower fauna, which acquired a deep-water aspect. The fauna is much
richer above 100 m. Bivalves begin to play a dominant role here by their bio-
mass (up to 90 per cent). However, at a depth of 50 to 100 m, the greatest
mass forms are absent : MytiJaster lineatus, Dreissena polymorpha, Dr. caspia,
Didacna trigonoides, D. barbot-de-marnyi, D. crassa, all the Adacna species,
Cardium edule, Theodoxus pallasi, Hydrobia, all the species of the Ponto-
gammarus genus, almost all of the Pterocuma, Turbellaria and Cordylo-
phora caspia. Instead the original fauna of the large, higher crustaceans are
most developed here : AmathiUina spinosa, Dikerogammarus caspius, D. grimmi,
D. macrocephalus, Gammarus placidus, Paramysis eurylepis, Metamysis infiata

THE CASPIAN SEA

613

and some gastropods: Micromelania elegantula, M. dimidiata, Theodoxus
schultzi.

At depths of less than 50 m the Arctic species disappear, the number of
large crustaceans decreases considerably, while Mytilaster lineatus, Dreissena
caspia and Dr. rostriformis appear in large numbers, and Dr. polymorpha.

Fig. 287. Diagram of vertical zonality of the Caspian
Sea (Zenkevitch, 1947).

Didacna baeri, D.protracta and species of the genera Pontogammarus, Dikero-
gammarus haemobaphes and others appear in smaller numbers. On sand silt
above 15 m Pontogammarus maeoticus, Dikerogammarus haemobaphes, Myti-
laster lineatus, Theodoxus pallasi and other Gastropoda are preponderant,
while the Cardidae, except Didacna trigonoides, are almost absent. Ponto-
gammarus maeoticus lives in huge numbers on sands right at the edge of the
water, forming a biocoenosis very similar to that of the Sea of Azov (the zone
of over wash).

614 BIOLOGY OF THE SEAS OF THE U.S.S.R.

The Caspian benthos is distributed into definite zones; moreover widely
eurybathic forms and groups such as, for example, Hypania invalida (0 to
900 m), Oligochaeta (0 to 400 m), Chironomidae (0 to 400 m), Dreissena
grimmi (5 to 300 m) and some others may be noted.

The vertical distribution of benthos agrees best with Brujevitch's ' structural
zones'. The best conditions for benthos development are found in the photo-
synthetic subzone with its rich plankton and good aeration ; and in fact at a
depth of 1 5 to 25 m the biomass is at its maximum (up to 1 ,200 g/m2). Feeding
conditions deteriorate in the nitrite zone and the biomass falls to 70 to 150
g/m2, and even less at the lower limit of this zone. Benthos biomass is very
low in the accumulation zone, with an increasing shortage of oxygen and
foodstuffs (often only a fraction of 1 g/m2) (Fig. 288).

Qualitative and quantitative distribution of benthos. The first survey of the
distribution of bottom-living biocoenoses in the Northern Caspian was given
by N. Tchugunov. He was the first worker in the U.S.S.R. to use a grab
for the study of marine fauna (1923). Ya. Birstein altered Tchugunov's data
and added some new ones. A more comprehensive picture was given by
L. Vinogradov (1955).

The biocoenosis of Dreissena polymorpha, Unio pichorum, Viviparus vivi-
parus, Pandorites platycheir, Metamysis strauchi and the much rarer Volgo-
cuma thelmatophora and Limnaea ovata is settled in the mouth of the Volga
and partly along the western coast of the Northern Caspian (Fig. 289). This
biocoenosis is adapted to low salinity (2 to 3%0), strong currents, a hard sea-
floor, small depths and an abundance of nutrient substances. The biomass of
this biocoenosis is sometimes as high as 200 g/m2 owing to the numerous
large fresh-water molluscs and Dreissena.

The biocoenosis Monodacna caspia, Dreissena polymorpha, Adacna plicata,
Chironomidae, Oligochaeta, Corophiwn nobile, С chelicorne, C. monodon,
Pterocuma sowinskyi, Pt. pectinata, Schizorhynchus bilamellatus, Gmelina
pusilla, Stenoganvnarus similis, S. compressus, Cordylophora caspia and some
others extends as a wide band from Agrakhansk Bay to the Ural River.
Fresh-water forms are not found here. This biocoenosis is settled on a soft
sea-floor, in areas with unstable saline (3 to 7%0) and gas conditions, and in
shallow depths (2 to 8 m). Although the biomass of this biocoenosis is fairly
low (12 g/m2) the area is the feeding ground of a number of commercial fish
(vobla, golden shiners and others).

The remaining part of the Northern Caspian, except for the Ural Trench
and the transition zone to the Central Caspian, is occupied by the hard-sea-
bed biocoenosis, adapted to depths of 8 to 12 m and a salinity of 5 to 9%0,
with Didacna trigonoides as a dominant species. Among the other forms
Monodacna caspia, Dreissena polymorpha, Dr. caspia, Adacna plicata, Theo-
doxus pallasi, Niphargoides caspius, N. corpulentus, Corophium chelicorne and
Dikerogammarus haemobaphes are most developed here. The average biomass
is 28 g/m2. Ninety-five per cent of the total biomass here is composed of mol-
luscs, whereas in the previous biocoenosis they formed only 86 per cent.

The soft soils filling the Ural Trench are inhabited by a small community

THE CASPIAN SEA

615

Gram per /m2-
~~ less thdn 1

from По 25
" 25 "WO
» 100 » 500

\» 500 "1000

v-f s'tig M

Fig. 288. Distribution of benthos biomass of the Caspian Sea in
1935 (Birstein, Briskina and Ryabchikov).

616

BIOLOGY OF THE SEAS OF THE U.S.S.R.

(average biomass— 11-28 g/m2) which differs from the preceding one by the
absence of some species (Dikerogammarus haemobaphes) and a poor develop-
ment of Corophidae and Cumacea. This community lives at a depth below
1 1 m at a comparatively high and constant salinity (more than 9%„). Pandorites
podoceroids is its dominant form.

The zone adjacent to the Central Caspian, with a salinity of 10 to 12%0,
a hard sea bed and depths of more than 1 1 m, is populated by a typical mid-
Caspian fauna rich in its composition and biomass (an average of 124 g/m2).
Its dominant forms are Didacna barbot-de-marnyi and Dreissena caspia, and

Fig. 289. Diagram of distribution of benthos biocoenoses in the
Northern Caspian according to spring surveys 1947 to 1951 (Vino-
gradov). Biocoenoses: 1 River Dreissena ; 2 V. viviparus and other
fresh-water forms, low salinity and coastal forms; 3 Ural-Caspian
Dreissena ; 4 Adacna minima ; 5 Adacna costata ; 6 Adacna plicata ;
7 Oligochaetes, chironomids and crustaceans: brackish water; 8
Marine Dreissena; 9 Monodacna; 10 Didacna trigonoides: salt-
loving relict; 11 Marine Didacna; 12 Dreissena caspia; Mediter-
ranean ; 13 Nereis ; 14 Carditim edule ; 15 Mytilaster.

some Monodacna sp., Mytilaster lineatus, Cardium edule and Didacna trigo-
noides are also found.

The biomass distribution in the Northern Caspian shows a pronounced
drop at 2 to 8%0 salinity (Fig. 290a) ; this is due to the fact that only a few
fresh-water species can endure a salinity above 1 to 2%0, while the Caspian
autochthonous species ready to Uve at a salinity below 8%0 are rare. Hence
within the zone of a salinity of 2 to 8%0 life is poor both in number and in
variety. The same phenomenon occurs in the zone where fresh- and sea-
waters mix in all seas.

Here, however, apart from salinity the gas conditions of the bottom layer
are also of great importance. Salinities of 2 to 8%0 are found within the zone
of the 12 to 18 ft heap of wrack. The soft soils here owe their origin to the
deposition of suspended particles under the effect of the coagulative action

THE CASPIAN SEA

617

S%„/ 2 3 4 5 В 7 8 9 10 11 12 13 14 2 4 6 8 10 12 14 16 18 20 22 24 26 28 m

SALINITY DEPTH

Fig. 290a. Distribution of benthos Fig. 290b. Distribution of benthos biomass

biomass of Northern Caspian accord- of Northern Caspian according to depth
ing to salinity (Birstein, 1939). (Birstein, 1939).

of sea-water. In calm weather a definite vertical stratification is observed in
this zone, since the fresh waters of the Volga and Ural flow over the saline
sea- water. When the processes of decomposition of the organic substances of
the sea-bed become intensive owing to conditions of vertical stratification,
oxygen is used for the oxidation of the soil and the bottom layer loses much
of its oxygen. This oppresses many benthic animals and the heap of wrack
becomes inhabited by euryoxybiotic forms which can live in water deficient
in oxygen. This problem was discussed above when dealing with brackish
water.

In the Northern Caspian the main benthos biomass is found at depths of
12 to 16 m, whereas its average depth is only 6 m (Fig. 290b). The relationship
between the benthos biomass and the nature of the sea-bed is just as indica-
tive. It has been shown for many seas that on mobile hard floor (gravel,
shell gravel, large-grain sands) the fauna becomes scarce and sometimes dis-
appears.

This, however, is not so in the Caspian Sea. Low biomass indices are found
on soft beds, situated chiefly along the 12 to 18 ft of wrack {Table 261). This is

Table 261

Sea-bed

Mean biomass,

g/m2

Shell-gravel

79-0

Sand-shell-gravel

32-2

Sand

23-9

Sand-shell-gravel-ooze

26-7

Ooze-shell-gravel

18-8

Ooze

8-8

Ooze with hydrogen sulphide

0-9

618 BIOLOGY OF THE SEAS OF THE U.S.S.R.

due, as we have seen, to unfavourable oxygen conditions (often 0-5 to 1 cm3
per litre) and under certain circumstances the appearance of hydrogen
sulphide from the bed, soft beds being very rich in hydrogen sulphide (for
instance the muds of the Ural Trench according to Fedosov).

Therefore such oligo-oxybiotic groups as Oligochaeta and Chironomidae
find favourable conditions here for their existence. Areas of the bottom open
to continuous currents and well aerated, and therefore practically free of
smelts which are easily washed away by the currents, are thickly populated by
benthos, feeding mainly on detritus carried over the sea-bed. Ivanov has
shown that the waters of the Central Caspian, rich in plant food, move into
the southern part of the Northern Caspian, causing a luxuriant development
of plankton and benthos. The filter-feeding phenomenon is not as strongly
manifest in the bottom-living fauna of the Caspian Sea as in that of the Black
Sea ; this may be due to the absence of such powerful filter-feeders as the sea
mussel, the oysters and phaseolin. Dreissena, however, is also a filter-feeder
and the presence of large patches of shell-gravel silts on the bottom of the
Caspian Sea leads to the conclusion that they have a biogenic origin.

Perhaps a certain deficiency in the representation in the Caspian of the
filter-feeding phenomena has conditioned such a luxuriant development in it
of a typical filter-feeder, the alien Mytilaster— a development which is not
characteristic of it in its native habitat, the Black and Azov Seas.

The process of the accumulation of silt soils may possibly increase in the
areas of the dense settlements of Mytilaster in the Caspian Sea.

During the last 25 years much qualitative and quantitative research has
been carried out on the bottom-living fauna of the Caspian Sea. The Northern
Caspian has been investigated in particular detail.

On the average the benthos biomass of the Northern Caspian has remained
unaltered, except for its catastrophic drop in 1937-38, which was followed by
fairly slow regeneration over many years. A second, less violent drop was
recorded in 1946 and 1947 (Table 262).

As shown by Table 262 the drop in biomass is in both cases controlled
mainly by the decrease in the number of molluscs and, to a lesser extent, by
that of the crustaceans in 1937 and 1938. Birstein suggests that at that time
some suffocation phenomena took place as a result of oxygen shortage.
Bivalves are markedly predominant in the Northern Caspian benthos ; among
other groups Nereis stands out sharply (Table 263).

These data on the state of benthos in the Northern Caspian can be supple-
mented by those given by V. Osadchikh (1958) for 1954 and 1956. The total
benthos biomass increased during this period by 30 per cent, mainly owing to
worms (by 98 per cent) and crustaceans (by 70 per cent). Oligochaete biomass
increased by 193 per cent and that of Nereis by 59 per cent. The chironomid
biomass increased very greatly (by 355 per cent). The food available for adult
fish rose by 25 per cent and for young fish by 46 per cent. Considerable
patches of Syndesmya were formed (Table 264).

It is evident from the data in Table 264 that the intrusion of Nereis has had
no harmful effect on local fauna ; neither the oligochaetes nor the chironomids
have been affected, as might first have been expected if this effect existed.

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620 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 263. Benthos composition in Northern Caspian, gjm2, in 1949

Groups

Biomass

Groups

Biomass

Oligochaeta

0-79

Monodacna

6-30

Ampharetidae

008

Adacna

1-62

Nereis

1-5

Didacna

4-63
0-89

Hirudinea

0008

Cardium

Dreissena

6-56

Total of Vermes

2-38

Mytilaster

5-61

Chironomidae

011

Gastropoda

0-40

Gammaridae

0-70

Total of Mollusca

2601

Corophiidae

0-82

Cumacea

0-35

Total of benthos

30-37

Total of crustaceans

1-87

Table 264. Benthos composition in Northern Caspian in 1954

and

1956, glm2

(V. Osadchikh, 1958)

1954

1956

Organism

Within the zone Within the zone

Throughout the

of commercial of commercial

zone

fish distribution fish distribution

investigated

Dreissena polymorpha

3-51

4-49

5-15

Adacna minima

2-25

1-22

116

Monodacna

4-89

5-41

5-93

Didacna trigonoides

1-84

3-03

3-77

Cardium edule

012

0-22

0-75

Mytilaster lineatus

006

0004

0-42

Syndesmya о vat a

—

00003

0-22

Total of molluscs

12-67

14-37

17-40

Corophiidae

0-91

1-61

1-40

Gammaridae

0-90

1-41

1-40

Cumacea

0-66

1-18

1-13

Total of Crustacea

2-47

4-20

3-93

Nereis

1-12

1-78

1-91

Oligochaeta

1-50

4-40

4-12

Ampharetidae

0-73

0-47

Total of worms

3-35

6-65

6-50

Chironomidae

009

0-40

0-37

Total biomass

18-64

25-62

28-20

THE CASPIAN SEA

621

The Nereis biocoenosis (L. Vinogradov, 1953) has not replaced, and could
not have replaced, the biocoenosis of small Adacna, higher crustacean and
chironomid larvae. Only in one place (Tyuleni Island), forming 1 -8 per cent of
the whole area, has the Nereis biocoenosis taken the place of an oligochaete
biocoenosis, but it formed a biomass there two to seven times (in different years)
greater than the oligochaete biocoenosis. The examination of benthos
throughout the whole Caspian Sea carried out in 1956, 18 years after the 1938

Fig. 291 . Quantitative distribution of benthos in Central
and part of the Southern Caspian in 1956 (g/m2)
(Romanova, 1960).

survey (N. Romanova, 1960), has revealed considerable changes in the nature
of the distribution of the bottom-living fauna (Fig. 291). The eastern shores
of the Northern and Central Caspian are richer in benthos than the western
ones. The main mass of benthos is formed by Mytilaster, with a pronounced
decrease in the amount of Dreissena, Didacna, Monodacna and Adacna (63
per cent of total biomass in the Central Caspian, and 94 per cent in the
Southern). The part played by Cardium is increased, and Nereis is strongly
developed (Fig. 292) on soils rich in organic matter (Fig. 293). In its central
parts the Sea is deeper than 200 m and the benthos biomass there falls below
1 g/m2. Total benthos biomass reaches its maximum at depths of 10 to 25 m.
In the Southern Caspian at depths of 200 to 300 m the biomass decreases to

622

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Fig. 292. Quantitative distribution of Nereis in Northern Caspian in

June 1948: above 50 (7); 50-25 (2); 25-10 (5); 10-5 (4); below 5 (5)

(Birstein and Spassky, 1952).

0-60 to 0-70 g/m2, while at 700 m it falls to 002 g/m2. In the Northern Caspian
the mean benthos biomass is 7-59 g/m2 even at 150 m. As in the Central
Caspian the Central and Southern Caspian benthos has a preponderance of
molluscs (90 per cent of the total biomass in the Central Caspian, 98 per cent

Fig. 293. Distribution of organic substances in the soils of the Northern
Caspian as percentages (Yastrebova, with data of Gorshkova added) :
above 3 (I); 3-2 (2); 2-1-5 (5); 1-5-1 (4); 1-0-5 (5); below 0-5 (6);

trace (7).

THE CASPIAN SEA

623

in the Southern). In the Central Caspian the higher crustaceans, Gammari-
dae and Corophiidae, which penetrate to great depths and give a biomass of
about 6 g/m2, develop in considerable numbers. The Nereis biomass reaches
0-6 to 0-8 g/m2, based on the whole Sea area, and 3-5 to 5-0 g/m2 for the areas
no deeper than 200 m. Its favourite habitats are Mytilaster concretions,
where it apparently uses the mollusc faeces and pseudofaeces rich in organic
matter. 'The vigorous development and the wide eurybiotic capacity of the
members of Mediterranean fauna which have penetrated into the Caspian
Sea have often been recorded', writes N. Romanova (1959). 'The consider-
able adaptability of the immigrants, their higher viability than that of the local
autochthonous fauna, is illustrated by the composition of the Southern
Caspian fauna. Exceptionally high biomass is always due to the development
of species of Mediterranean fauna : Mytilaster, Cardium and Nereis ', with this
difference between Mytilaster and Nereis, that the first crowds out other bi-
valves in its development, while the second does not crowd anything out
when growing in large numbers.

A detailed survey of Nereis colonies, of their utilization by fish and of the
change in the composition of the bottom biocoenosis, was again organized
in 1948 and 1949; a series of experimental researches was also carried out.
The results of this work were published in a special volume (1952).

Special attention was naturally paid to Nereis and Syndesmya in their new
habitat. As has been mentioned above, the worm was discovered in the Cas-
pian Sea in 1944, i.e. five years after its transplantation. By that time the

Table 265. Benthos composition of Central and Southern Caspian

Percentag

e of total

Organism

g/m2

Biomass

Thousands of tons

order

Central

Southern

Central

Southern

Central

Southern

Nereis

0-6

0-8

0-98

0-65

68-8

76-7

Oligochaeta

0-5

0-3

0-76

0-24

57-4

28-7

Polychaeta

0-2

0-3

008

22-9

9-6

Vermes

1-3

1-2

1-98

0-97

1491

1150

Chironomidae

0-21

007

0-33

004

24-1

6-7

Isopoda

0-8

008

1-22

007

91-8

7-6

Amphipoda:

(a) Gammaridae

2-1

0-4

3-2

0-3

240-9

38-4

(b) Corophiidae

2-4

0-5

3-64

0-4

275-3

47-9

Cumacea

0-5

0-3

0-76

0-24

57-4

28-7

Malacostraca

5-8

1-28

8-82

101

665-4

122-6

Balanus improvisus

0-22

0-3

0-34

0-25

25-2

28-7

Mytilaster lineatus

41-5

1141

62-9

94-38

4,761-4

10,942-2

Dreissena distincta

11-6

003

17-6

002

1,330-9

2-8

Cardium edule

4-1

1-51

3-4

114-7

393-2

Didacna

3-6

002

5-46

002

4130

1-9

Monodacna

0-3

0-45

001

34-4

9-6

Adacna

0-4

—

0-61

—

15-9

—

Molluscs

58-4

118-35

88-53

97-83

6,670-3

11,349-7

Total

65-93

1211

100

7,534-1

11,622-7

624

BIOLOGY OF THE SEAS OF THE U.S.S.R.

main sandy silt areas of the Northern Caspian, hitherto practically unin-
habited (Fig. 294), were already populated by Nereis. Nereis can endure a
scarcity of oxygen and can exist for a long time in its absence (A. Karpevitch,
1952). The habitat of Nereis was charted with greater precision during the
extensive investigations of the Northern Caspian bottom-living fauna carried
out in 1948-49 (Fig. 292). Its total biomass was found to be 1-4 to 1-7 million
centners. If we take into consideration the worms consumed by fish and their

Fig. 294. Distribution of Nereis in Northern and the

northern part of the Southern Caspian in summer 1 956

(Romanova, 1960).

mass mortality after spawning, the annual production of Nereis in the Northern
Caspian must be two or three times larger still.

According to the latest survey, carried out in 1954 and 1956 (V. Osadchikh,
1958), the habitat of Nereis and its numbers have remained unchanged in the
Northern Caspian.

The benthos survey of 1956 covered also the Central Caspian and part of
the Southern (N. Romanova, 1959); a picture of the quantitative distribution
of Nereis obtained showed quantitative indices similar to those for the
Northern Caspian (Fig. 294). Thus the total quantity of the Nereis biomass in
the Caspian Sea reaches one million tons, while its annual production is two
to three times greater. The fate of another immigrant into the Caspian Sea

THE CASPIAN SEA 625

— Syndesmya ovata — is quite different. It was discovered only in 1955 (A. Saen-
kova, 1956) and so far its propagation has been limited to individual patches
in the southern part of the Northern Caspian. On the average it gave in 1956
a biomass of 022 g/m2 in the area investigated (V. Osadchikh, 1958), and a
total of about 200,000 to 300,000 centners. Before 1956 Syndesmya ovata
was not recorded in either the Central or the Southern Caspian. There are
reasons to believe that the first transplantation of Syndesmya into the Caspian
Sea gave no results, while that of 1948 was successful.

A careful study of the biology of Nereis has shown (G. Belyaev, 1952) that
the worms can live in huge numbers (up to 8,900 specimens with a biomass
of up to 870 g/m2, and with some specimens growing to 14 cm in length and to
more than 2 g in weight) in shallow lagoons and inlets of the northwestern
part of the Caspian Sea on silty sand soils. The author notes that on these
sites Nereis evidently feeds exclusively on soil detritus rich in organic matter.
Young and adult worms can easily live through a fall of salinity down to
l%o or less; fertilization and egg development require a salinity of not less
than 5%0. Nereis mass multiplication takes place in shallows in the spring
and in greater depths in summer, moreover heteronereis stages are formed
which leave the burrows inhabited by immature worms. The worms die after
spawning; the whole cycle of their development is accomplished in one year,
or perhaps even in one summer. These observations are supplemented by a
comprehensive study of the feeding of Nereis (E. Yablonskaya, 1952) which
has shown that Nereis, which spends most of its life actually in the soil, 'has
developed a capacity for swallowing as food the upper layer of the soil with
all its components . . . using, instead of detritus, films at different stages of
destruction and plants and animals living in them when they are within
reach, without any special selection or hunting for them . . . moreover, the
natural conditions of the Nereis environment would make the latter impossible
in the majority of cases'. Owing to this manner of feeding, animal remains
are very rare in the worms' intestines. V. Beklemishev (1950) has studied in
detail the feeding of Nereis pelagica in the Barents Sea. The intestines of this
worm are always filled with algae, with a little admixture of animals which
were taken in with the algae. N. diversicolor and N. xirens, as well as N. suc-
cinea, have adopted the same manner of feeding. The jaws of all these species
of Nereis, arranged exactly alike, are not a weapon of attack on living
victims, but an instrument for raking algae and detritus into their mouths.

A. Zhukova (1954) has shown experimentally that Nereis, fed on micro-
organisms and yeast, develops and grows normally. She has thus proved the
detritus feeding of this worm and confirmed Yablonskaya's data. A survey
of the feeding of fish in the Northern Caspian (N. Sokolova, 1952; Ya.
Birstein, 1952) has shown that, since Nereis colonies appeared in the Caspian
Sea, starred sturgeon has almost exclusively passed over to a Nereis diet, and
sturgeon and a number of other fish have added a considerable amount of it
to their diet.

The nutrient qualities of Nereis, both as fat and as protein, and its calorific
value are certainly high {Table 266).
The calorific value of Northern Caspian benthos has increased greatly with

626 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 266. Nutrient value of Caspian invertebrates (E. Bokova, 1946; L. Vinogradov,
1948; M. Zheltenkova, 1939)

Foodstuff

Content,
Fats

percentage of dry weight
Proteins Ash

Calorific

value

к cal/g

Caspian molluscs {Dreissena

polymorpha)
Caspian crustaceans (Gammaridae

and Corophiidae)
Nereis diversicolor

1-23

6-47

7-73

1016

53-71
66-88

8306

25-59
13-82

0-63

3-13
5-58

its colonization by Nereis, and in 1946-49 21 to 30 per cent of its total calorific
value was due to Nereis.

Changes in benthos distribution (quantitative and qualitative) in the Cas-
pian Sea are controlled not only by the distribution of new immigrants, but
also by its rise in salinity, especially in the Northern Caspian.

Mytilaster, Cardium and Nereis have moved far northwards ; on the other
hand Dreissena polymorpha and Didacna trigonoides, much less tolerant of
salinity, have receded to the northwest and reduced the area of their habitat.

Zoobenthos biomass of the Caspian Sea. The following is a count of the
benthos biomass in the different areas of the Caspian Sea :

Southern 116,227 tons

Central 10,000,000 tons

Northern 6,100,000 tons

Total 27,622,700 tons

Thus almost four-fifths of all bottom fauna are concentrated in the Central
Caspian. Plankton does not form such accumulations there, especially along
the eastern shores ; the cause of the abundance of benthos is as yet unknown.

Food value of zoobenthos of Caspian Sea. Data on the qualities as food of
the main species of the Caspian and Azov-Black Sea fauna are of interest.
E. Bokova (1946) gives some interesting information on this aspect in her
work {Tables 267, 268, 269). It is evident from these data that species of the
genus Adacna have the highest food value among the Caspian molluscs.
Mytilaster and Syndesmya are close to them in their properties {Table 267).

The molluscs occupy first place in the Caspian benthos and in the diet of
Caspian fish.

Crustaceans are different in their nutrient qualities and it is evident from
Table 267 that crustaceans, which occupy second place in the diet of Caspian
fish, are much superior to the molluscs in their significance as food.

The average percentage of protein and fat content in crustaceans is more
than five times higher than that in molluscs, while the ash content is corres-
pondingly three times lower.

THE CASPIAN SEA 627

Table 267

Percentage dry weight
Form Protein Fat Ash

Caspian
Didacna trigonoides
D. barbot-de-marnyi
Adacna minima
A. laeviuscula
A. plicata
Dreissena polymorpha

Mediterranean
Cardium edide
Mytilaster lineatus
Syndesmya ovata

5-10

91 00

606

0-90

88-60

17-53

2-33

75-60

14-80

1-30

7210

12-56

—

9-93

0-68

86-81

5-62

0-95

92-90

14-41

1-72

72-80

13-00

1-24

71-54

Average for all the Caspian mol-
luscs (except Syndesmya) 1016 1-23 83-05

Food indices of worms (and insect larvae) are even higher than those of the
crustaceans. Nereis, acclimatized in the Caspian Sea, has the most favourable
food indices {Table 269).

Fish

The Caspian Sea fish, according to A. Derzhavin, include 78 species {Table

270).

The last four families in Table 270, which includes two species of grey

Table 268

Form

Protein

Percentage dry weight
Fat

Ash

Caspian
Paramysis baeri
Paramysis baquensis
Metamysis strauchi

73-10

51-25
70-25

600
500
8-30

1600
27 00
14-17

Average for mysids
Pontogammarus maeoticus
Dikerogammarus haemobaphes
Stenogammarus similis
Pandorites platycheir

63-37
54-77
50-31
49-18
46-49

6-87
9-40
8-50
3-80
9-37

19-18
25-00
24-10
33-50
35-29

Average for amphipods
Pterocuma pectinata \
Pterocuma sowinskyi]

48-83
29-20

7-21
3-17

29-68
40

Average for all crustaceans
Mediterranean
Leander nectirostius

53-71
71-85

6-47
4-44

25-59
13-98

628

BIOLOGY OF THE SEAS OF THE U.S.S.R.
Table 269

Species

Percentage dry weight
Proteins Fat Ash

Caspian
Chironomids
Oligochaetes

Mediterranean
Nereis

6612
63-70

66-88

7-60
5 00

7-73

10-40
5-85

13-82

mullet, flatfish and mosquito-fish, were introduced into the Caspian Sea fauna
by man. Of the 38 aboriginal genera of the Caspian fish, eleven — Caspiomy-
zon, Caspialosa, Neogobius, Mesogobius, Proterorhinus, Asra, Caspiosoma,
Hyrcanogobius, Benthophiloides, Benthophilus and Anatirostrum — are en-
demic forms of the Pontic-Caspian-Aral region ; of these Caspiomyzon, Asra,
Anatirostrum and 22 other species exist only in the Caspian Sea. The greatest
variety of species is given by the Gobiidae, Cyprinidae, Clupeidae and Aci-
penseridae families. The Clupeidae and Gobiidae families are exceptional in
their process of forming small taxonomic units. For example, Caspialosa
caspia has five forms and Caspialosa brashnikovi has seven forms (sub-
species).

Table 270. Composition of Caspian Sea ichthyofauna

Among these, number of endemic forms :

Total
number

of
species

Family

Pontic-
Caspian
species

Aral
Percentage Species

Caspian
Percentage Species

Petromyzonidae
Acipenseridae
Clupeidae
Salmonidae

5
9
2

3
9

100
60

100
50

1
0
4
1

100
0

55-5
50

Esocidae

Cyprinidae
Cobitidae

55
1

33
50

1
1

7
50

9
0

Siluridae

Gadidae

Gasterosteidae

100

Syngnatidae

100

Atherinidae

Percidae

Gobiidae

100

53 0

Mugilidae

Pleuronectidae

Poeciliidae

Total

69-3

32-0

THE CASPIAN SEA 629

A most characteristic feature of the Caspian Sea ichthyofauna is the wide
range of its species between those of fresh and saline waters, with most varied
forms of adaptation to water of different salinity — from fresh water (with the
development of settled breeds) to the high salinity of the eastern inlets of the
Caspian Sea. Thus Caspialosa caspia salina lives at a salinity of 35-8%0.
The western species Pomatoschistus caucasicus, Syngnathus nigrolineatus
caspius and Atherina mochon pontica caspia live and multiply at a salinity of
59-5%0. Derzhavin correctly remarks that: 'such a variation in the behaviour
of Caspian fish is a manifestation of a wide adaptation during the Quaternary
history of this body of water to the changing conditions of water, climate and
salinity in different parts of the Caspian Sea'. The formation of one single
fauna from marine and fresh-water forms through a complex history of
a fauna of diversified genesis is graphically shown from the example of Caspian
fish ; in individual biological groups of this fauna fresh- water and marine forms
are found side by side. A prolonged coexistence under changing conditions
had erased the features linked with the early diversified genesis of species
and a single fauna was evolved, bound together by its conditions of existence
in a given body of water and by the history of the latter.

Biological groups of fish. Among the fish of the Caspian Sea the group of
migratory fish inhabiting the Sea itself and moving up the rivers for spawning
is chiefly distinguishable. Vobla, Acipenseridae (except sterlet), Stenodus
leucichthys, salmon and some herrings may be included in this group. The
second group, of semi-migratory fish, includes primarily those which keep
to the less saline areas of the Sea and move up the rivers for spawning (pike
perch, golden shiner, carp and Pelecus), and secondly those which keep only
to the much more diluted waters of the river mouths and also move upstream
for spawning {Abramis bal/erus, Abramis sapa, Rutilus rutilus, Aspius aspius
and others). The third group consists of the native river fish. They are either
absent or rare even in the areas of the Sea with a reduced salinity (sterlet,Tinca,
Carassius auratus). Finally, the fourth group comprises fish which very rarely
enter waters of lowered salinity (marine pike perch, some varieties of the
South Caspian herrings such as Caspialosa braslmikovi grimmi, C.b. kissele-
vitschi, C. caspia knipovitschi, С braslmikovi autumnal is, Clupeonella and a
series of the species of bullheads and Benthophilus). Some of them move to
the shore for spawning, others make regular migrations from the Central
and Southern Caspian into the Northern. Marine pike perch and three breeds
of Southern Caspian herrings never enter the zones of lowered salinity at all.
Most of these groups include species of ancient autochthonous forms and
fresh-water immigrants.

The great differences in the manner of life of the Caspian fish attracted the
attention of workers long ago. K. Kessler (1887), the author of the first
biological classification offish, based his work on his observations of Caspian
fish.

Fish migration. The exceptional richness in migratory fish is the interesting
feature of the Caspian Sea (and also of the Sea of Azov). All the Acipenseridae

630 BIOLOGY OF THE SEAS OF THE U.S.S.R.

(except sterlet), Salmonidae and Cyprinidae of the Caspian Sea enter a river
for spawning and then return to the Sea. Among the herrings Caspialosa
volgensis and C. kessleri are migratory fish. The latter enters the Volga, with
its gonads still immature, from the beginning of April till the end of June,
moving upstream as far as Gorki, going up the Oka to Serpukhov and Kaluga,
and up the Kama to beyond Molotov. Caspialosa volgensis spawns mainly in
the lower Volga (up to Saratov) ; only a few of the fish go farther upstream.
Side by side with these there are semi-migratory herrings which spawn in the
pre-delta and delta of the Volga (C. caspia aestuarina, C. suvorovi) and herring
which enter fresher waters of the Sea for spawning but do not go upstream
(C. brashnikovi with its varieties and C. caspia with its sub-species). Thus an
examination of these herrings, so closely related to each other, reveals a series
of gradual transitions from the migratory to the marine fish.

The migrations of Caspian herring within the limits of the Sea are regular
and fairly complex. In winter they all gather in the southern and central parts
of the Caspian (Fig. 295a), mostly within the area open to the influence of the
warm current running from the shores of Iran along the eastern coast of the
Southern Caspian.

With the coming of warm spring weather, herrings approach the western
and part of the eastern shores of the Central and Southern Caspian, while
some breeds move into the Northern Caspian (Fig. 295b). The more cold-
loving herrings (C. brashnikovi, Alosa and the migrant herrings) are the first
to approach the shore. When the temperature of the coastal waters rises
above 12° С the herring move northward where the water is still much cooler.
They keep in the open sea away from the shore. Only some endemic Southern
Caspian herring can endure a comparatively high temperature, and they
spawn off the coast at a temperature of 12° and even higher.

In summer the main mass of herrings is gathered in the Northern Caspian.
The fry of migratory herrings (C. brashnikovi, C. sphaerocephala and C.
saposhnikovi) come down to this area from the rivers Volga and Ural, attract-
ing the predatory herring which have remained in the Northern Caspian
after spawning, feeding on the fry of migratory herring and on the sprat. In
the summer large numbers of migratory herrings and of the Central Caspian
Alosa are found in this region.

The entry of herrings into the warmer Central Caspian waters begins in the
autumn with the arrival of colder weather in the Northern Caspian. Herrings
and sprat young-of-the-year are the first to leave ; they are followed by adult
predatory herrings preying on them. With the drop in temperature herrings
move farther and farther south (Fig. 295c), lingering in shallow inlets and
bays, where they feed on plankton (C. caspia) and on the young fish (predatory
breeds). Moreover, they move much more slowly than in the spring, keeping
to the upper layer of water (15 to 25 m), since in the autumn only a shallow
layer is heated.

Apart from the two herring species above, Caspiomyzon wagneri, two
species of Salmonidae (Stenodus leucichthys and Salmo trutta caspius) and the
Acipenseridae should be included in the group of migratory fish of marine
origin. Usually these fish make long spawning journeys; moreover, there are

>— ► HERRING
MASS MOVE*
-MENT

-MOVEMENT

OF HERRING
TOWARDS
THE COAST

Ими-ТГШ01
^NUMEROUS
Ш SOME
Щ\ FEW

Fig. 295. Distribution of herring in the Caspian Sea (Tchugunov, with some
alterations) : A In winter and early spring; В In spring; С In autumn.

632 BIOLOGY OF THE SEAS OF THE U.S.S.R.

frequently two breeds of each species present — the 'winter' and 'spring' ones
(L. Berg, 1934), differing in the time of their entry into the river and in their
wintering place (either in the river or in the Sea).

The migrations of Salmonidae {Stenodus leucichthys and Caspian salmon)
are of special interest. Stenodus leucichthys moves from the Caspian into the
Volga, Kama, Belaya, and finally into the river Ufa, travelling about 3,000 km.
A certain number of Stenodus leucichthys also enters the river Ural; salmon,
on the contrary, mostly enter the rivers on the Caucasian shore, and only
single specimens of it enter the Volga.* Acipenseridae have been observed to
choose some individual rivers for spawning ; it has been known for centuries
that some rivers are preferred by the Acipenseridae (the rivers Volga, Samur,
Gyurgenchai and Sefidrud) and others (Kura, Terek, Sulak, Ural) by starred
sturgeon.

Among the migratory fish of fresh-water genesis the following should be
mentioned; Rutilus rutilus caspius, Rutilus frisii kutum, Abramis brama, Bar-
bus brachycephalus caspius, Cyprinus carpio, Pelecus cultratus and Lucioperca
lucioperca. They all spawn in fresh water (except for some shoals of carp) and
fatten in the Sea ; but they spawn in the deltas and lower reaches of the Caspian
rivers and therefore they do not make long migrations. Autumn migration
into rivers for wintering, apart from the spring spawning migration, is most
characteristic of this group of fish. All the above mentioned fish, except for
vobla and to some extent carp, winter in the lower reaches of the rivers in
deep places or 'pits', where they ' spend the winter either completely or almost
completely motionless, being covered by a thick layer of slime as if by a fur
coat' (V. Meisner, 1933). Vobla approaches the shores for wintering, bedding
down in the pits of the Volga delta ; but it does not enter the river. Carp
winter either in the pits or in the Sea. In the same way various shoals of carp,
apart from the carp which spawn in the river, also spawn in different places,
in brackish water, in inlets and in the bays and inlets of the Northern Caspian.

P. Schmidt (1938) believes that there is a great difference in principle
between the movements of migratory fish of marine and of fresh-water origin.
'Whereas the true marine fish acquire a new element in their biology in the
shape of spawning migration into fresh waters, the fresh-water, semi-migratory
fish are only extending their feeding migration, covering the neighbouring
parts of the Sea, in as much as they succeed in restoring their long-lost capacity
for enduring an increase of salinity in the water. In the first case it is an acquisi-
tion of new properties and instincts, a reconstruction of the whole process of
breeding and development ; in the second it is only the renewal of a capacity
they had possessed. . . . '

Semi-migratory fish like Abramis sapa, Abramis ballerus, Blicca bjornca,
Aspius aspius and Si/urus g/anis do not move farther than just outside the delta,
as they are strictly limited in their propagation by fresh water and can tolerate
only a very slight increase of salinity.

As for the marine fish listed above, almost nothing is known as yet about

* Judging by archival material collected by A. Derzhavin (1939), salmon were abundant
in the Volga in the seventeenth and eighteenth centuries; their numbers have greatly
decreased since then.

THE CASPIAN SEA 633

their migration (except for that of herrings). In the literature there are but
few indications of the approach to the shores of some bullheads and marine
pike perch for spawning (N. Tchugunov and F. Egerman, 1932). Fish of
Mediterranean origin (Atherina, Pomatoschistus and Syngnathus) move into
the saline southeastern corner of the Caspian Sea for spawning, which they
do at a salinity of 30%o.

The question of the causes which compel fish to accomplish long and com-
plicated migrations is an extraordinarily intricate one. To solve it we have to
turn to geological data. Some workers point to the extreme importance of the
post-glacial loss of salinity of the Caspian Sea and its effect on the working
out of the migrational rates of Caspian fish. Ya. Birstein writes (1935)
that ' the difference between a sea and a body of fresh water at that time had
probably become so negligible that for assimilated (formerly) marine fauna
the river was no longer an alien medium ; fresh-water fish also could readily
extend their habitat into the Sea, which was formerly closed to them owing to
us physicochemical conditions. The subsequent gradual increase in salinity
had apparently only slightly affected the habitats of fresh-water fish which
had mainly been formed in post-glacial time ; it may, however, have some-
what reduced their distribution in the Sea. It may have been this, in fact,
which assigned fish to the biological types — migratory, semi-migratory and
fresh-water non-migratory — which have already been established by Kessler.'
Schmidt thinks that ' the migratory routes of the herring now observed may
have begun to be developed at the end of the glacial period. When with the be-
ginning of the ice recession great torrents of fresh water began to flow towards
the Sea, some species of herring, probably already more adapted to fresh
water, used them for spawning, and the range of their migrations increased
more and more with the further withdrawal of ice and the lengthening of the
rivers.. Other herring species have remained marine or semi-migratory forms
up to our time.'

Numerous species of the Clupeidae are the main consumers of plankton ;
not all, however, for some of them are predators (Fig. 296). Among the plank-
ton-eating Clupeidae three pelagic species of the genus Clupeonella (Clupeo-
nella and Sprattus phalericus), which form large colonies in the Caspian Sea,
are distinguished by their small size. Volga and Caspian herrings are also
plankton eaters, whereas the Brashnikov and Saposhnikov herrings are typical
predators. Some forms have a mixed diet as, for example, Caspialosa kessleri.
A. Behning (1938) showed that plankton Copepoda {Ewytemora grimmi)
feed mostly on Flagellata and unicellular algae. Mysids feed also on these
forms, as well as on small crustaceans. Sprats and herring-fry feed mostly on
copepods, while Caspialosa caspia feeds on copepods and pericardians. The
seal feeds on sprats and on Caspialosa caspia. A general diagram of the food
chain of Caspian plankton-eaters can be drawn from the data available
(Fig. 297).

Feeding of benthos-eating fish. The problem of the nutrition and feeding correla-
tions of Northern Caspian benthos-eating fish has been carefully investigated by
Schorygin(1952). His research can be regarded as a model of this type of study.

у t — Т "

HARENGULA ATHERINA CASPIALOSA JUV.

T7ZT

I C. BRASCH SAPOS

С KESSLERI

CASPIALOSA CASPIA С. с VOLGENSIS

* t t

| juv |luciopercalu volgensTs]

RUTILUS RUTILUS V CASPICUS

I ♦

f t T t 1

VERMES

insecta| MOLLUSC
(freshwater)

MALACOSTRACA

Jac.guldenst

t t tt

ACSTELLATUS

H HUSO H )

DREISSENSIDAE

CHIRONOM
I (SEA>

Fig. 296. Diagram of the feeding of the main Caspian Sea fish (Tchugunov, 1928).

Fig. 297. Diagram of the feeding series of
Caspian planktophages (Behning, 1938, with
some additions). 1 Pike perch, starred sturgeon ;
2 Seal ; 3 Herring predators (C. braschnikovi) ;

4 'Peaceful' herring (C caspia, Clupeonella) ;

5 Large crustaceans (Pericardia); 6 Small
crustaceans (Calanipeda) ; 7 Small zooplank-

ton ; 8 Phytoplankton.

THE CASPIAN SEA

635

Benthos-eating fish of the Caspian Sea can be divided into four groups :
worm eaters in a wide sense (including chironomids), and those which live on
molluscs, crustaceans and fish (usually called predators) ; moreover, individual
fish are transitional types as regards their diet. As may be judged from Table
271 sturgeon and two species of bullheads — Pomatoschistus (Bubyr) causasicus
and Knipovitschia longicaudata — feed on worms ; vobla, Benthophilus stellatus
and B. macrocephalus and the bullheads Gobius melanostamus affinis and G.
kessleri feed on molluscs. Predators and crustacean eaters often have a mixed

Table 271. General character {percentage basis) of . fish diet in Northern Caspian

General nature of diet

RrppH

Main nutrient groups

Worms and

Crusta-

chironomids

Molluscs

ceans

Fish

Sturgeon

— .

—

Chironomidae

Pomatoschistus caucasicus

—

Chironomidae

Knipo vitschia longicaudata

—

Chironomidae, Gammaridae

Benthophilus stellatus

—

100

—

Adacna, Didacna, Monodacna

B. macrocephalus

Gastropoda, Monodacna

Vobla

Dreissena, Monodacna

Gobius melanostomus affinis

0-4

Gammaridae, Cardium, Dreissena

G. kessleri

—

Gammaridae, Cardium, Gobiidae

Hyrcanogobius bergi

—

Cumacea, Gammaridae

Gobius fiuviatilis pallasi

Gammaridae, Corophiidae

G. caspius

—

Gammaridae, Mysidae

Golden shiner

0-2

Cumacea, Corophiidae, Adacna

Carp

16-5

Gammaridae, Dreissena, Coro-
phiidae

Starred sturgeon

0-5

Mysidae, sprat

Caspialosa • saposh niko vi

Mysidae, sprat

Salmon

Gobiidae, sprat

Caspialosa sphaerocephala

—

Sprat

Pike perch

—

Gobiidae, sprat

Caspialosa brashnikovi

—

Sprat

Beluga

—

diet. The bullheads Hyrcanogobius bergi, Gobius fiuviatilus pallasi, G. caspius,
pike perch and carp may be considered typical crustacean eaters ; while the
typical predators are belugam pike perch, Caspialosa saposhnikovi, Caspialosa
brashnikovi and C. sphaerocephala. Starred sturgeon and sturgeon also have a
mixed diet.

Some less pronounced transitions also exist between the typical crustacean
and mollusc eaters. Gobius melanostomus affinis, G. kessleri, G. pallasi, G. cas-
pius, golden shiner and carp have a mixed diet of this type. However, in all
these cases except for the first two, the consumption of crustaceans is greatly
in excess of that of molluscs.

A comparison between the main nature of diet and the average index of
repletion brings out a definite dependence : the higher the calorific value of
food the lower the index of repletion. Moreover, the indices of repletion

636

BIOLOGY OF THE SEAS OF THE U.S.S.R.

vary greatly for different fish — from 26 for starred sturgeon to 368 for B.
stellatus. Mollusc-eating fish have the highest index of repletion (from 107 to
368) ; it varies from 75 to 21 1 for worm eaters. When fish is the basic diet the
repletion indices fall to 26 to 120 and, finally, with a diet of crustaceans the
indices range from 27 to 79. In general indices of repletion are inversely pro-
portional to the calorific value of food, as illustrated by the following data:

Gammaridae
Corophiidae
Chironomidae
Sprat

3-92 cal/g Vobla 1-00 cal/g

2-34 cal/g Bullheads 0-76 cal/g

2-34 cal/g Benthophilus 0-63 cal/g

1-47 cal/g Dreissena polymorpha 0-63 cal/g

This regularity is somewhat broken only by worm-eating fish, since for
food of high calorific value the indices of repletion are high.

Fig. 298. Vertical distribution of fish feeding grounds in the Caspian Sea (Schorygin,
1952). 1 Knipowitschia longicaudata; 2 Bubyr caucasicus; 3 Sturgeon; 4 Benthophilus
marmoratus ; 5 Golden shiner ; 6 Hyrcanogobius bergi ; 7 Carp ; 8 Gobius flimatilis pal-
lasi; 9 Gobius melanostomus affinis ; 10 Vobla ; 1 1 Benthophilus stellatus ; 12 Sturgeon ;
1 3 Casp. Alosa ; 1 4 Starred sturgeon ; 1 5 Pike perch ; 1 6 Casp. braschnikovi ; 1 7 Casp.
sphaerocephala {agrakhanskaya) .

A fish's choice of food is to a considerable degree correlated with its man-
ner of life : fish living in a definite horizon use mainly organisms adapted
to this horizon. If food organisms are divided into pelagic and benthonectic,
epifauna and infauna, we get a basic adaptation of each fish to a certain
horizon (Fig. 298). Typical predators, pike perch, and the dolginskaya and
agrakhanskaya herrings feed mainly on pelagic organisms. Morover, pike
perch feed mostly on bottom-living fish (bullheads and vobla), and herring
on pelagic fish (sprats). Starred sturgeon and Caspialosa saposhnikovi eat
benthos (both the epifauna and the infauna), although pelagic organisms are
predominant in their diet.

Carp, vobla and some bullheads feed mainly on epifauna, while sturgeon,
Pomatoschistus caucasicus and Knipovitschia longicaudata prey mainly on the
infauna.

The change of diet with age of the sturgeon is interesting (Fig. 299 IV).
When less than 50 cm long it feeds almost exclusively on Gammaridae, passing
first to Corophiidae as it grows and then to river crustaceans. Simultaneously
fish and Nereis acquire more and more significance in its diet, comprising
40 per cent of its food when the sturgeon is 60 cm long. However, with further
growth the sturgeon does not remain on a diet of fish ; it begins to eat more

THE CASPIAN SEA

637

and more molluscs (Cardidae, Mytilaster and Nereis). When a sturgeon reaches
170 to 180 cm it feeds exclusively on molluscs and Nereis. This change is

С 3 10 12 /4 16 Id 20

28 Cm. 30 50 70 90 110 130 /SO 170 190 210 230 Clll.

100
80
60
40
20
0

{Crust a

Cordylophora

30 50 10 90 110 130 150 ПО 190 200 gr.

%
/00

40
20\
0

\Crustacea

+*«.x'*"*"

Corophiidae

Gobijdae
Clupeidae Vi

5 10 IS 20 25 30 35 40 45 SO 55 60 С1П.

Fig. 299. Change of diet with age of some Caspian Sea fish (Schorygin). / Vobla ;
// Benthophilus macrocephalus ; /// Gobius kessleri; IV Sturgeon; V Caspialosa
saposhnikovi ; VI Pike perch.

connected with the approach of sexual maturity. Generally speaking sturgeon
is a typical euryphague.

Competition for food. The examination of the inter-relation in feeding among
the different species is one of the essential problems in the study of fish nutri-
tion ; moreover, as has been noted by Schorygin it is equally important ' to
establish between which species, where, when, and for which foodstuffs such
competition arises, and also, if possible, to determine the degree of competi-
tion. It is equally important to study the nature of the effect of the consumers

638

BIOLOGY OF THE SEAS OF THE U.S.S.R

we examine on food provision and to determine the strength of this effect
on individual food groups.'

The general scheme of inter-relation in feeding of the main breeds of fish
in the Northern Caspian is given in Fig. 300. It is clear that fish feed almost
equally on all groups of fauna. As has been mentioned before, molluscs and
crustaceans are the main groups fed upon. The crustaceans, except for Deca-
poda and Chironomidae (especially Cumacea), are relatively the most inten-
sively consumed. Among fish the sprat, a small, quickly growing fish living
in large masses throughout the Caspian Sea, is consumed in huge amounts.

AGRAKANSKAYA

HERRING

DOLGINSKAYA
ERRING

900?Q

Fig. 300. Diagram of food correlations between Northern Caspian fish. Only groups
constituting no less than 25 per cent of food are given in the diagram (Schorygin).

Schorygin was the first to evaluate the feeding inter-relation between
species. First of all a 'degree of coincidence ' in the diet of two species offish
can be determined. This index is obtained (as a percentage of the total amount
of food) when the percentage composition of the diets of two fish is compared,
as the sum of smaller percentages. The basis of this simple method of calcu-
lation can be illustrated by a graph (Fig. 301) where the area of the coin-
cidence of the diet of the two species is defined by the smaller ordinates,
independently of which kind of feeding the species belong to. This index
(food coincidence, denoted Fc) will decrease with the increase of the precision
of determination of the specific composition of food. It was found that the
nature of vobla diet is nearest to that of Benthophilus and the bullhead
Gobius melanostomus affinis (36 to 39 per cent) ; this similarity is much weaker
with carp and golden shiner (27 per cent) and with other fish it scarcely exists.
Golden shiner diet is much like that of some bullheads (32 to 61 per cent),
and least like that of carp (34 per cent). The diet of cyprinoids is usually
coincident with that of some bullheads (25-6 per cent) ; however, between

THE CASPIAN SEA

639

the members of this family this coincidence is even greater (29-3 per cent).
The diet of the Clupeidae examined has a high coincidence coefficient (75-9
per cent) ; with pike perch the coefficient is 26-2 per cent, with the Acipen-
seridae 24-8 per cent; it is low with cypri-
noids 6-7 per cent and with Gobiidae 7-5
per cent. The various Acipenseridae species
differ greatly in their diet (16 per cent), yet not
so much as do cyprinoids (14-3 per cent), but
more than Gobiidae (17T per cent) and Clupei-
dae (24-8 per cent) and so on.

The food-coincidence coefficient, while
giving an idea of the relative similarity between
the diets of rival species, does not express the
intensity of their competition. Schorygin dis-
tinguishes also the amount and intensity of it.
The amount of competition is the ratio of the
part of their diet for which they compete to
their total consumption. The intensity of the
competition is the ratio between the demand
made, in the shortest possible interval of time,
by the rival organisms on the food for which
they are competing and the availability of that
food. The product of the amount of com-
petition by its intensity expresses the force
of competition. Comparative food competi-
tion of fish in the Northern Caspian as given
by Schorygin is shown in Table 272 (in con-
ventional units).

It is clear from these data that intraspecific competition is, on the whole,
higher than intrageneric, and the competition between the genera is weaker
than between the forms of the same genus. Thus with cyprinoids the intra-
specific competition is on the average expressed by 170 conventional units, and
the intrageneric one by 121 ; with the Gobiidae it is only 41, with the

э Э

S S

9 § s I

.£_

Fig. 301. Extent of similarity
between nature of feeding of
Benthophilus macrosephalus
and Gobius JJuviatilis pallasi
(Schorygin).

Table 272

B. macro-

G. me I.

G.fluv.

Golden

Starred

Pike

Competitor

cephalus

affinis

pallasi

Vobla

shiner

sturgeon

Sturgeon

perch

Benthophilus

macrocephalus

0-5

0-8

Gobius melanostomus

affinis

0-6

G. fluviatilis pallasi

144

Vobla

0-6

Golden shiner

144

291

Starred sturgeon

0-5

100

Sturgeon

0-8

175

Pike perch

0-6

640

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Acipenseridae 7, and with pike perch 3-3. With Acipenseridae intraspecific
competition is on the average 133, intrageneric 101 ; with pike perch 44, with
cyprinoids 7, and with Gobiidae 5 (conventional units).

By May the competition between golden shiner and vobla becomes less
intensive and the two diets become more similar. In June the feeding of the
two fish becomes more intensive and the competition is more acute, while the
coincidence of the diet is much lessened. By August the intensity of the com-
petition continues to grow, and both the amount and the intensity are increased.

Schorygin gives (Fig. 302a) a general picture of the dynamics of the food
relationship between the two forms of fish. By the summer feeding and
intensity of competition increase, but the two diets become less similar, since

Fig. 302a. Diagram of food correlation of two

fish (Schorygin) : 1 Feeding ground coincidence ;

2 Competition intensity ; 3 Competition tension ;

4 Volume of competition.

the two fish have by then driven each other away to feed on different organ-
isms. The force of competition remains practically the same, with a decrease
in the coincidence of the diet and a corresponding growth of competition.
At the same time, although the two species begin to feed in different areas, the
force of the rivalry between them begins to grow. Then, if the intensity of com-
petition still increases its force begins to grow rapidly and a complete (forced)
divergence may take place both as regards food and feeding grounds;
following a decrease in intensity of competition the reverse process may take
place.

The degree of elasticity in the diet of different breeds of fish plays an
important part in the course of these changes. Schorygin has also tried to
evaluate this latter. The degree of stability of the diet of a definite fish in
different seasons and areas can be determined from the indices of food coin-
cidence (Fc), and the mean value of this can also be found. Taking the value
complementary to 100 of the mean thus obtained, we shall have the index of
variability of diet. The results obtained in this way for six fish are given in
Table 273. The elasticity of diet develops with increase of the regional and
seasonal variations in the composition of the food. This effect can be excluded

THE CASPIAN SEA 641

from our calculations by determining the extent of the variations in the pro-
vision of food, by the method used to determine changes in the nature of the
diet. The ratio of the second value to the first is the index of the extent of the
elasticity of the diet, regardless of the variations in provision of food. These
indices are given in Table 273.

Table 273

Sturgeon

Starred

Pike

Vobla

Gobius

Golden

Elasticity of diet

sturgeon

Perch

fiuviatilis
pallasi

shiner

Without corrections for

changes in available food 75

With a correction for

changes in available food

(ratio of degree of

change of nature of diet

to that of available food) 1 -9

1-7

1-4

1-2

The elasticity in the diet of sturgeon and starred sturgeon is high ; that of
golden shiner is the lowest. It should be noted also that in the Northern
Caspian the variability of the nature of the diet is greater than that of the
provision of food. Finally Schorygin has introduced one more new con-
ception— the feeding activity of fish, meaning the capacity of the organism
to maintain its peculiar type of nutrition. The feeding activity and elasticity
of the sturgeon, pike perch, and to some extent of the starred sturgeon, are
high. Pike perch has a high activity but a low elasticity and vobla, on the
contrary, a high elasticity with low activity. In his later work A. Schorygin
(1948) has compared the results of his observations in 1935 with those of
1941. During that time the edible fauna had decreased by 56 per cent and the
changes in benthos had brought about a change in the composition of fish
diet. However, the force of competition for food between the six fish chosen
(three species of bullheads, vobla, golden shiner and sturgeon) has remained
practically unchanged. This is explained by the high elasticity of fish diet and
is achieved by : (7) a separation of the feeding grounds of different species,
(2) the divergence in the nature of their diet, and (5) by a more even utiliza-
tion of food provided. The former strong competition was weakened, while
the weak food fink grew stronger (Fig. 302b). Seven or eight years after
Schorygin's observations his method of quantitative examination offish food
competition was repeated by Ya. Birstein (1952), and it was found that
competition for food in 1948-49 was considerably weaker than in 1941
(Fig. 302c). It was clear from his detailed examination of fish nutrition over
these years that the slackening of competititon for food between the fish-
benthophages is due to a huge development of Nereis which took place at
that time, and which provided the fish with some millions of centners of
supplementary foodstuffs of high calorific value.

642

BIOLOGY OF THE SEAS OF THE U.S.S.R.

/935 ~ffll

100 S00 300 Ш 500 600 700

Fig. 302b. Alterations of food correla-
tions of benthos-feeding fish of the
Caspian Sea from 1935 to 1941 (Schory-
gin). The intensity of food correlation
between rival pairs of species of fish
during the period examined is given in
circles as indices of magnitude. The
diagonal line corresponds to the posi-
tion of points when food correlations
remain permanent.

260 -
240

220-

/80 -

/4o -

too -

80 -

60 -

/®

<y7®

/1941 4

• (i

— ,

/949

о го <ta 6o во wo /го /4o /во /во гоо гго гйо гео гдо

Fig. 302с. Same as Fig 302в for the period 1941 to 1949
(Birstein).

THE CASPIAN SEA 643

Yield cf fish. Fish yield in the Northern Caspian in 1935 was about 31-6
kg/hectare (24 kg/hectare for benthophages), in the Sea of Azov 73 kg/hectare,
in the Aral Sea 4-5 kg/hectare, and in the North Sea about 17 kg/hectare (in
ponds 60 to 160 kg/hectare, and when fertilized up to 2,000). Thus the yield of
fish from the Caspian Sea is comparatively high. The FIB coefficient for these
Seas is also most significant. For the Northern Caspian it is about 1/12, for
the Sea of Azov 1/20, for the Aral Sea 1/50, for the North Sea 1/140. Hence
North Caspian benthos is utilized in the most efficient manner, and evidently
there is strong rivalry for food between its consumers. Partly in connection
with this, and partly owing to the existence of an abundant provision of
food in the form of nereids* in the Sea of Azov, fish grow in it much better
than in the Caspian Sea.

Schorygin's comprehensive examination of fish nutrition in the Northern
Caspian makes it possible to come to a most reliable prognosis of the state of
fish feeding under possible changes in the conditions and surface of the body
of water. On the other hand, the examination of Caspian fish nutrition and a
comparison of its results with data on the growth of commercial fish points
to the existence of competition between some fish and to a considerable
rivalry as regards provision of food. This in fact led to the idea that the Cas-
pian Sea could be widely used for the acclimatization of the Mediterranean
(Azov-Black Seas) fauna.

Commercial fish resources. The rough quantities of fish resources of the Cas-
pian Sea given by some authors are based mostly on data from commercial
statistics and on the examination for age of catch.

The Caspian Sea occupied the first place in our fisheries during the first
two decades of this century. Later, however, owing to vigorous development
of fisheries in the Barents Sea and in the Far Eastern Seas the Caspian trade
dropped to third place. Recent yields of the Caspian fisheries were only
65-4 per cent (4-3 million centners in 1954) of the 1913 catch (L. Berdichevsky,
1957). This reduction has affected the most valuable breeds offish — herring,
vobla and pike perch; the yield of Acipenseridae is about half that of 1913,
but it has remained on the same level since 1930. Sprat fishery has developed
greatly. The fisheries of the Caspian Sea have changed a great deal during the
last 30 years {Table 274).

Table 274.

Yields

offish

in the
(L.

Caspian Sea (in thousands
Berdichevsky, 1957)

of centners)

since 1930

Breed

1930

1940

1950

1954

Pike perch
Golden shiner
Acipenseridae

909
374
135-2

348
612
89-4

314
713
130-1

333
374
129

In 1956 the catch of fish in the Caspian Sea was 4-3 million centners
(Table 275).

* The data given refer to the period before the implantation of Nereis.

644 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 275. Yields offish in the Caspian Sea in 1956

Catch Catch

Breed 103 centners Breed 103 centners

Starred sturgeon 64 Catfish 128
Sturgeon 54 Pike 123
Beluga 10 Vobla 623
Herring 410

Total Acipenserida 128 ^ ,'8«

Pike perch 217 other fish 355

Golden shiner 270

Carp 161 Total catch 4,306

Avifauna

Much serious damage to the fisheries of the Caspian Sea is caused by fish-
eating birds, chiefly cormorants, herons, sea-gulls and pelicans (A. Pak-
hulsky, 1951). The stock of fish-eating birds in the Caspian is more than
six hundred thousand head and the quantity of fish consumed by them
(1948) is about a million centners a year, 70 per cent of which is taken by
cormorants. Moreover, the birds propagate a series of intestinal fish-worms;
sea-gulls are the cause of violent epidemics of ligulosis affecting a great
number of vobla.

Gulf of Karabugas

The Gulf of Karabugas is most remarkable ; it can be considered as the final
stage of the process of the eastern Caspian inlets turning saline ; these, with
their narrow finks with the Sea, run deep into a desert country with a hot and
dry climate. The ratio of the content of ions in the Caspian waters when they
are concentrated, which does not alter in the Mertvyi Kultuk and Kaidak
inlets (as S. Makarov and D. Enikeev (1937) have shown) does, in the Gulf of
Karabugas, alter in the direction of an increase in the content of sodium
sulphate.

The Gulf of Karabugas is the largest sodium sulphate body of water in the
world. The area of the Gulf of Karabugas (about 14,000 to 15,000 km2) as
well as its depth and salt content have changed considerably owing to fluctua-
tions in the level of the Caspian Sea (this has dropped by 193 cm between 1929
and 1945) and in its depth and the form of its connection with the Caspian Sea.

The greatest depth of the Gulf of Karabugas is now only 4-5 m, whereas
once it was 9 m. The level of the Caspian Sea is 3 m higher than that of the
Gulf of Karabugas.

In 1939 the inflow from the Caspian Sea to the Gulf of Karabugas de-
creased from 25 km3 to 6 km3; it rose again, however, in 1946 to 12 to 14 km3
owing to the deepening of the strait. The water of the Gulf of Karabugas has
become considerably more saline in the last 60 years :

in 1897 salinity comprised 16-4 per cent by weight
in 1929-30 salinity comprised 20-5 to 21-0 per cent
in 1938 salinity comprised 28-1 per cent.

THE CASPIAN SEA 645

The limit of saturation is reached at this last salinity.
If we take 26-24 per cent by weight as its present mean salinity, its com-
position will be the following :

SO2- ions represent 6-24 per cent by weight
Cl~ ions represent 11-89 per cent by weight
Mg2+ ions represent 2-76 per cent by weight
Na+ ions represent 5-35 per cent by weight

The ratio Cl-/Mg2+ is 4-31.

The waters of the inlet contain about 17-88 milliard tons of salts, among
them 9-3 milliard tons of sodium chloride, 5-33 of magnesium sulphate and
2-8 of magnesium chloride. More than 8 milliard tons of mirabilite and other
salts were precipitated on the bottom of the Gulf of Karabugas in the winter
of 1949-50.

In winter, when the temperature of the waters of the Gulf of Karabugas falls,
mirabilite (Glauber salt) is precipitated. The salinity of the Gulf of Karabugas
is now twenty times higher than that of the Caspian Sea.

In 1897 the A. Spindler and N. Andrussov expedition discovered a mass of
Artemia salina in the inlet ; now owing to the rise of salinity this crustacean
has disappeared from the inlet ; only its eggs are found in large numbers on
the shores. Animal organisms are absent from the inlet; its waters, however,
are teeming with various representatives of microflora — algae and micro-
organisms. The alga Aphanothece salina, forming huge, slimy colonies off the
shores, and the Flagellates Dunaliella viridis and D. salina, with their profuse
flowering during the precipitation of Glauber salt, are the two mass forms.
There are, according to A. Pel'sh (1936), about 530,000 cells of Dunaliella
to a gramme of solid salt mass, and on the average 2 1 ,000,000 micro-organisms
to 1 cm3 of the water of the Gulf of Karabugas.

V. CONCLUSIONS
S. P. Brujevitch tries to draw a comparison of total biomass and production
of the whole body of water from the data on the numbers of the main com-
ponents of the fauna and flora of the Caspian Sea. This table cannot be
considered as very accurate, but the orders of quantities given for most of the
groups can be taken as more or less valid {Table 276).

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12
The Aral Sea

I. GENERAL CHARACTERISTICS

The most easterly Sea in the system of large bodies of water of the south
Russian geosyncline is the Aral Sea, which is the fourth biggest enclosed sea
in the world.

For the most part well heated in the summer and well aerated, the Aral
Sea has practically the same salinity as that of the Caspian and Azov Seas ;
but the ratio of the different salts approaches that characteristic of fresh
water, even more than in the case of the Caspian Sea.

As result of a most complex geological history of alterations in its orography
and salinity the Aral Sea has qualitatively poor flora and fauna. However, a
small number of autochthonous Caspian forms still live in the Aral Sea, which
is the extreme point of the penetration eastwards of the most active immi-
grants of Mediterranean fauna.

The Aral Sea is considerably inferior to other south Russian Seas in its
biological productivity ; however, it seems to offer very wide possibilities for
ameliorative measures aimed at an increase in the yield of fish by means of
fertilization, fish-breeding and acclimatization.

II. HISTORY OF EXPLORATION

First period

The first data on the flora and fauna of the Aral Sea were collected in the
nineteenth century by several expeditions. Among them the following should
be noted : A. Butenev's expedition in 1841, in collaboration with the naturalist
A. Leman ; A. Butakov's expedition in 1848-49 and, finally, the Aral-Caspian
expedition of 1 874, with the participation of the zoologist V. Alenitzyn : the
materials obtained were worked up by I. Borshchov (1877), N. Andrussov
(1897), K. Kessler (1877) and others.

A most comprehensive investigation of the Aral Sea was carried out by
L. Berg's expeditions in 1900 to 1902 and 1906; the result was the first com-
prehensive monograph describing the Aral Sea, published in 1908.

Second period

The next stage in the closer investigation of the Aral Sea with particular
reference to its commercial wealth is linked with the activity of the Aral
Fishery Station, which was inaugurated in 1929 in the town of Aralsk.

A. Behning (1934, 1935), V. Nikitinsky (1933) and G. V. Nikolsky worked
at this station. The latter was responsible for a comprehensive monograph
(1940) which brought together all existing information on the Aral Sea,
particularly in regard to fish.

647

648 BIOLOGY OF THE SEAS OF THE U.S.S.R.

III. PHYSICAL GEOGRAPHY
Size and level

The greatest length of the Aral Sea is 428 km, and its greatest width 284 km
(Fig. 303). Its area is 64,500 km2 : i.e. in size it occupies fourth place among the

Fig. 303. Bathymetric chart of the Aral Sea

(Nikolsky, 1940). Currents indicated by arrows

(Kulichenko, 1944).

lakes of the world (after the Caspian Sea, Lake Superior and Lake Victoria).
The volume of the Aral Sea is 103 km3.

The level of the Aral Sea is 79-5 m higher than that of the Caspian and 52 m
higher than that of the ocean.

Water balance

The water balance of the Aral Sea was determined by V. Samoilenko (1947)

as given in Table 277.

Table 277

Gain

3/year

Loss

km3/year

River inflow
Rainfall

54
5-36

Evaporation

Leakage through sea-bed

5809

1-27

Total

59-36

THE ARAL SEA

649

Bottom topography

The greatest depth (67 m) occurs near the western shore of the Sea (Fig. 303) ;
the predominant depths are 10 to 30 m, with an average depth of 16-2 m.

The Aral Sea is divided into two basins by a submarine ridge with a system
of islands stretching from north to south : the smaller, but deeper, western
basin and the eastern one which does not exceed 30 m in depth.

The northern part, separated from the rest of the Sea by the Kuch-Aral
island, is called the Maloe More.

^r-~-j\ SANDY SILT
fc'VyVH^ COARSE SAND AVERAGE hZ-Z-ZH SILTY SAND OOZE

|:.::У:-У-.-;| FINE SAND | | CLAY AND MUD

НПППМЩ DEPOSITS WITH MORE
1111111111111 THAN 40% LIME

Fig. 304. Distribution of the soils of the Aral sea-bed
(Kulichenko, 1944).

Soils

Grey mud covered by a thin brown layer is the predominant bed of the Aral

Sea (Fig. 304). Black mud, owing its colour to the presence of a colloidal

ferrous hydroxide, is found in the western deeper part of the Sea and in some

inlets.

Freshly brought up black mud usually smells of hydrogen sulphide. Huge
masses of rotting filamentous algae, forming a complete felt-like cover over

650 BIOLOGY OF THE SEAS OF THE U.S.S.R.

the bottom, are concentrated in the western, deeper part of the Sea; the
formation of hydrogen sulphide is facilitated by their presence.

River mouths are characterized by brown clay mud.

Sand floors, passing over into mud beds at depths below 10 m, form a wide
band along the northern, eastern and southern coasts of the Aral Sea.

According to K. Gilzen's data (1908) the Aral Sea bed contains very little
organic matter. The carbon content recorded at 15 stations fluctuates from
0-07 to 0-43 per cent. Its nitrogen content was determined at two stations as
00 187 and 0-0068 per cent; the ratio C/N was 6-7 and 10-6 at these places.

The western and southern shores of the Aral Sea are flat and low (V. Zenko-
vitch, 1962). For the most part they consist of the deltas of great rivers over-
grown with bullrushes : the Amu-Dar'ya (to the south) and the Syr-Dar'ya.
In a wide area between them shores of a specific kind have developed, called
'Aral' type by L. Berg (1908). Owing to a slight rise in its level the Sea in
this area has entered some troughs between banks of the adjacent wind-
borne desert sand, thus creating a very broken coastline. This latter is being
slowly levelled out by the effect of the waves.

The western shore is almost straight and consists of the steep clunka
escarpment (up to 200 m high) of a faulted structure origin which has by now
been greatly broken up by landslides. Throughout its length this coast is
steep (V. Lymarev, 1957).

The northern coast has characteristic laminated contours, with a few large
islands and peninsulas. These shores are not high; they consist of loose
Quaternary deposits. They are intensely abraded, forming small local currents
of alluvium.

Transparency

The waters of the Aral Sea are for a lake exceptionally transparent : in the
western part of the Sea a white disc ceased to be visible at a depth of 24 m.

Currents

L. Berg was the first to note (1908) that the currents of the Aral Sea, in con-
trast to those of other inland bodies of water, move clockwise (Fig. 303) ;
thus the Amu-Dar'ya waters spread northwards throughout the western part
of the Sea, and the Syr-Dar'ya waters southwards throughout the eastern
part. The surface layer, however, is controlled in its movements by the pre-
vailing winds. Owing to the shallowness of the Sea and to its low coastline
the phenomena of strong on- and off-shore winds sometimes occur to a
marked degree.

In August, the warmest time of the year, the average temperature of the
surface waters of the open part of the Sea is 24° to 25°, while in the depths of
the western depression it is 2-3°. In June, however, the average temperature
near the bottom falls to 0-3° (Table 278). The layer of sudden change usually
occurs at a depth of 16 to 28 m, while in the shallow eastern part the water is
warmed down to the bottom and the layer of sudden change is not found
{Table 278).

THE ARAL SEA

651

Table 278.

Mean temperature of Aral Sea waters

Depth

Feb

Apr Jun

Aug

Oct

Dec

Deep western depression

4-2 18-8

24-2

16-3

3-3 160

21-3

16-9

2-7 12-0

201

16-5

4-9

1-5 4-3

13-4

16-3

— 2-4

6-4

9-8

4-6

—

— 0-4

3-5

4-5

—

— -0-2

2-7

4-2

—

— -0-3

2-3

3-7

—

Central part of the Sea

0-7

5-3 19-4

23-7

14-4

2-5

—

— 17-2

23-6

14-4

—

— 14-5

22-9

14-3

—

— 9-4

21-9

14-4

—

Surface waters are cooled in the autumn (October and November), while
in winter the whole column of water acquires a near-zero temperature. In
mid-winter conditions the temperature falls to freezing point and ice begins
to form on the surface.

Ice conditions

Water usually begins to freeze in the northern part of the Sea at the end of
November, and two or three weeks later in the southern part. At first ice
forms near the shores and the northern inlets freeze up ; then the whole of the
Maloe More and the eastern shores freeze. The open part of the Bolshoe More
is usually free of ice. Ice does not finally disappear until the second half of
April.

Salinity

As has been mentioned above, the salt composition of the Aral Sea differs from
that of ocean waters, even more than do those of the Caspian Sea, and as
regards the ratio of individual salts it approximates to fresh water {Table 279).

Sodium, magnesium and calcium, and among the compounds sodium
chloride (54 per cent), magnesium sulphate (26 per cent) and calcium sulphate
(15 per cent) are preponderant in the Aral waters.

The average salinity of the Aral Sea is about 10%o (Fig. 305). A fall of
salinity is observed in the mouths of the rivers, while in the inlets of the south-
eastern part of the Sea salinity rises to 14%0 as a result of intense evaporation.
A state approaching homohalinity is established in winter and spring ; in the
summer the surface waters lose some of their salinity.

A forecast of the change of salinity of the Aral Sea associated with a pos-
sible future decrease of incoming river water and a fall of sea-level has been
made by L. Blinov (1956). The relationship of average salinity to sea-level

Table 279

Percentage of salts in waters of:

Ocean

Caspian Sea

Aral Sea

Lake Superior

Sodium

30-593

24-82

21-30

Potassium

1106

0-66

0-79

5-52

Calcium

1-197

2-70

5-00

22-42

Magnesium

3-725

5-70

5-41

5-35

Chlorine

55-292

41-73

33-93

1-89

Bromine

0-188

006

003

—

Sulphates

7-692

23-49

31-29

3-62

Carbonates

0-207

0-86

1-75

47-42

Silicates

—

12-76

Nitrates

—

— ■

0-86

Iron + aluminium

— ■

—

0-50

016

Total

35 00

12-8

1019

006

58°IO' 30' 59° 30' 60° 30' 61° 30' 61°&

43 —
S^io' 30'

59°

30'

60c

— 4

30' 61* 30' 6Г5*

Fig. 305. Average distribution of salinity over many years in
the upper layer of the Aral Sea (Blinov, 1956).

THE ARAL SEA

653

is given in Fig. 306, and the distribution of surface salinity of the Aral Sea,
should its level drop by 5 m, is given in Fig. 307. If the sea-level dropped
10 m below what it is now, the salinity of the surface waters would increase
by another 7%0.
The essential elements of the balance of the saline mass of the waters of

h m

-1

-7

-3

-4
-5
-6

-7
-8
-9

-10

... - i

Fig. 306. Relationship of average salinity to sea-level
of the Aral Sea (Blinov).

the Aral Sea under certain geographical and climatic conditions of the area
are as follows (L. Blinov, 1956):

Salts deposited by rivers 12,850,000 tons

Salts carried away by winds 101,120 tons
Salts supplied from atmosphere 64,800 tons.

The total mass of salts in the Aral Sea is about 1 ,050,000,000 tons with an
average salinity of 10-3%o. L. Blinov also determined the volume of water
which leaks away through the soil as 1 -26 km3, and assumes that this loss of
salt compensates for the average annual salt supply by rivers.

As a result of a most detailed examination of the salinity of the waters of
the Aral Sea and of its balance L. Blinov (1958) has come to the important
conclusion that 'in relation to their saline (ionic) composition, the waters of
the Aral Sea must be regarded as the strongly metamorphosed waters of the
river discharge feeding the Sea. As a result of the processes of metamor-
phism the waters of the Aral Sea, and those of the Caspian Sea, became an

654

BIOLOGY OF THE SEAS OF THE U.S.S.R.

44o

58° 10' 30' 59° 30' 60е 30' 61° 30' 6le5S'

Fig. 307. Diagram of salinity distribution in the upper layer of the Aral

Sea.

THE ARAL SEA 655

intermediate type between the hydrocarbonate calcium waters of the land
and the sodium chloride waters of the ocean . . . although as regards their
salt-forming ions the waters of the Aral Sea are closer to typical mainland
waters than those of the Caspian. The salt system of the waters of the ocean
and of the Caspian Sea is Cl-Na-SO, and that of the Aral Sea is Na-Cl-Mg.'*

Oxygen content

In summer time the waters of the Aral Sea are, as a rule, supersaturated with
oxygen (at times up to 130 per cent saturation) even over the areas of black
mud smelling of hydrogen sulphide. The great transparency of the water at
comparatively shallow depths causes an abundant development of sea-weeds
on the bottom of the Aral Sea, even at considerable depths, and the peculiar
distribution of oxygen, which increases with depth, is also a direct result.
Oxygen content below 81 per cent has never been observed in the Aral Sea.
The presence of hydrogen sulphide has never been recorded, neither in the
deepest parts and near the sea-floor, nor even where the sea-bed was known to
contain hydrogen sulphide in its soil (mainly in the western basin).

The concentration of hydrogen ions

As regards the concentration of hydrogen ions the Aral waters differ from
those of other big lakes ; the pH index is comparatively small (7-2 to 7-8).

Plant nutrients

The distribution of plant nutrients in the waters of the Aral Sea has some
peculiar characteristics. There is a normal active reaction, which on the
average gives only small seasonal fluctuations (8-20 to 8-34) throughout the
whole Sea.

These waters are very poor in phosphates. Their average content (P mg/m3)
in certain years (L. Blinov, 1956) varied within the limits 10 to 4-2 mg/m3.
Over a period of years the largest amount of phosphates, recorded in August
1949, was 231 P mg/m3. In contrast with other Seas the quantity of phos-
phates here decreases with depth, often down to zero (10 to 20 m), and there
is no accumulation of phosphorus in the depths. In the near-bottom layer
phosphates are rapidly used up by vegetation. The average phosphate con-
tent in the upper layer of the Sea is given in Table 280 (L. Blinov).

The nitrate content is also very low; it was found to be no more than 5
mg/m3 in individual samples. Some increase was recorded only in the estuar-
ine zones. There is more nitrogen in ammonium salts in the Aral Sea waters,
its content reaching 80 mg/m3. However, ammonium nitrogen is apparently
of very little use. L. Blinov (1956) points out that it would hardly be possible
to find another place affording a more monotonous picture of an 'analytical
zero' of phosphorus and nitrogen than the Aral Sea. The content of silicic
acid in the Aral Sea is considerably lower than in other seas; however,

* L. Blinov (1956) has investigated the chlorine number of the Aral Sea waters and has
worked out the following formula for the determination of the salinity of total salts in
terms of chlorine:

5% = 0-264+2-791 d%0

656

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Ни STATION 23'

WZSMO.K

CROSS SECTION 6
STATION 23 STATION 22* STATION 22 STATION 22 <* STATION 21

98№?Q 98Ш24 91 №15 98ШЛ Ш15

SALINITY 0/00

PHOSPHORUS mg/m3

си .ты / 3 PHOSPHORUS mg/m3
SILICON mg/m'*

Fig. 308. Eastern meridional cross section through the central part of the
Bol'shoe More, 3 to 6 June 1950 (Blinov).

STATION 24

CROSS SECTION 5.

SALINITY %

PHOSPHORUS mg/m3

OXYGEN %
SILICON mg/rr?

SALINITY %

PHOSPHORUS mg/m3

CROSS SECTION 5. CENTRAL CROSS SECTION OF
BOL'SHOE MORE FROM THE WESTERN DEEP
DEPRESSION STATION 24 (45° OS N. LAT..580 27' E.
LONG) TO WESTERN COAST OF VOZROZHDENIE
IS. STATION 24 (45° OS' N. LAT.. 58° 50' E. LONG)
3rd JUNE, 1950

Fig. 309. Western meridional cross section through the central part of
Bol'shoe More. 3 June 1950 (Blinov).

THE ARAL SEA 657

Table 280. Mean content of phosphates {P mg/mz)

Northern Central Southern

Period section section section

May-June 0-7 0-8 1-8

August-September 0-8 3-1 2-5

October 0-8 0-8 —

it never decreases to zero. Whereas there are hundreds and thousands of mg/m3
of silicic acid in the surface waters of the Caspian Sea, there is only 1 50 to
250 mg/m3 in the Aral Sea.

The hydrophysical and hydrochemical characteristics of the Aral Sea are
given in Figs. 308 and 309.

IV. FLORA AND FAUNA
The general characteristics of the population of the Aral Sea and its' history
have been given above.

Composition of phytoplankton

The Aral Sea plankton is poor in numbers and in species.

A. Behning (1935) gives the following basic composition of phytoplankton :

Cyanophyceae 6 species

Flagellates 11 species

Conjugatae 2 species

Chlorophyceae 2 species

Diatomaceae 18 species

Among these 39 forms the most common blue-green algae are Chroococcus
turgidus, Merismopedia glauca and Anabaena bergi ; among flagellates — Exu-
viella cordata aralensis, Prorocentrum obtusum, Glenodinium trochoideum,
Gonyaulax levanderi, Peridinium achromaticum, P. subsalsum, Diplosalis cas-
pica and D. pillula ; among the conjugates — Spirogyra spp. and Mougeotia spp.
and among the green algae — Oocystis socialis, Botryococcus braunii ; among
the diatoms — Actinocyclus ehrenbergi, Chaetoceras wighanii, Ch. subtile,
some Campylodiscus spp., Coscinodiscus granii var. aralensis, Sceletonema
costatum, Melosira borreri, Thalassiosira dicipens, Bacillaria paradoxa and
others.

The flagellates are of essential significance in the Aral Sea nannoplankton,
forming the basic group in the food of Rotifera and Crustacea.

The diatoms dominate the plankton by their mass ; the principal form among
them is Actinocyclus ehrenbergi var. crasa, which sometimes produces over a
million specimens per 1 m3. Actinocyclus is the usual food of Diaptomus
salinus, the highest mass form of Aral Sea zooplankton, which in its turn is
the basic food of the young of most fish.

Botryococcus braunii is also of significance in the phytoplankton and in the
food of zooplankton.

658 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Thus the main supply of food for the zooplankton consists of flagellates,
diatoms and to a lesser degree of green algae.

Composition of zooplankton

There are 24 main zooplankton forms in the Aral Sea, including :

Tintinnoidea 2 species

Rotatoria 8 species

Cladocera 7 species

Copepoda 7 species

In addition, the plankton usually contains a great many Dreissena poly-
mer pha larvae (up to 10,000 specimens per 1 m3) and small-sized (and, in the
hours of darkness, also fully grown) Pontogammarus aralensis.

The most usual zooplankton forms are : Infusoria Codonella relicta (up to
40,000 specimens per 1 m3); the Rotifera Floscularia mutabilis, Synchaeta
vorax, S. neapolitana and Rattulus marinus; among the Cladocera Cerio-
daphnia reticulata, Moina microphthalma (up to 3,000 specimens per 1 m3),
Cercopagis pengoi, Evadne camptonyx (up to 12,000 specimens per 1 m3),
and E. anonyx. Among the Copepoda Diaptomus salinus (producing up to
8,500 specimens per 1 m3) is the most important in the Aral Sea. This form is
greatly predominant over all the other zooplankton forms ; it is the main food
offish-fry, and sometimes of adult fish (stickleback, Pelecus, Chalcalburnus).
According to V. Pankratova (1935) D. salinus forms 58 per cent of the food of
carp-fry, 32 per cent of that of Chalcalburnus, 20 per cent of that of bream,
and 10 per cent of that of vobla. In the open parts of the Sea Mesocy clops
leuckarti and M. hyalinus (up to 600 specimens per 1 m3) are the most common
of the Copepoda.

In August the total zooplankton biomass is on the average 0-5 g/m3.
Copepoda biomass sometimes yields up to 230 mg/m3, Cladocera up to 650
mg/m3 and the larvae of molluscs up to 160 to 170 g/m3.

In A. Behning's opinion (1935) no less than 95 per cent of the total biomass
of Aral zooplankton is composed of Dreissena larvae and of all stages of
Diaptomus salinus. Thus the Aral zooplankton is an example of the pronounced
predominance of a few forms (olygomixed).

Horizontal and vertical distribution of plankton

A. Behning (1935) has distinguished in the Aral Sea three areas differing from
each other in their qualitative and quantitative plankton composition: the
open Sea, the coastal areas and the estuarine reaches (Fig. 310).

The area of the open Sea is exposed to smaller fluctuations of temperature
and salinity (10-3 to 10-5%o), while in the depths the temperature remains low
(between 4-5° and 9-5°) all through the year. This area includes the central
part of the Bol'shoy More and the open parts of the northern inlets of the
Maloe More. There is 3-2 times more plankton (up to 1,200,000 specimens
per 1 m3) in the depths than there is in the surface layer (up to 370,000 speci-
mens per 1 m3) mainly owing to Actinocyclus ehrenbergi. The mean biomass in

THE ARAL SEA

659

the open Sea, according to G. V. Nikolsky (1940), is 3-23 cm3 per 1 m3.
Diaptomus salinus, Cladocera and Dreissena larvae make daily vertical migra-
tions ; in daytime they keep mainly at

a depth of 10 to 20 m (Fig. 311).

'These daily plankton migrations',
says A. Behning, ' have real significance
in the life of the Sea. They enable the
plankton animals to use all layers of
water in their search for food ; masses
of diatoms are found by them in day-
time in the depths — Actinocyclus,
Campylodiscus, Pleurosigma — and by
night in the upper layer they find
flagellates and other species of phyto-
plankton.'

In bays and inlets, which usually
have a somehat higher salinity and are
subject to greater temperature and
salinity fluctuations, the most common
forms among the plankton, accord-
ing to A. Behning, are the algae
Chroococcus turgidus, Oscillatoria
tenuis, Lyngbya aestuarii, two species
of peridinians Cyclotella and Melosira
Borreri, among the animals the Rotifera Brachionus bakeri, B. mulleri,
and Colurella adriatica, and among the Crustacea Halicyclops aequoreus,
Cyclops viridis and Alona rectangula. The mean plankton biomass is here
about 2-75 mg/m3. Near the mouth of the rivers Amu- and Sur-Daria,

SEA AREA
LITTORAL AREA
ШШ ESTUARINE AREA

Fig. 310. The region of the north-
western part of the Aral Sea according
to plankton composition (Behning).

ens

Fig. 311. Vertical migrations of plankton in the

Aral Sea in August 1933 according to the number

of specimens (Behning).

within the areas of the lower surface salinity, the plankton composition
changes, many forms of the saline Aral waters are not found, and there is a
considerable admixture of fresh-water forms. The most characteristic are the
following : Microcystis aeruginosa, Dinobryon sertularia, Ceratium hirundinella,
Eudorina elegans, Fragilaria crotonensis, Keratella aculeata and Diaphanosoma
brachyurum. At the confluence of fresh and saline waters there is an increase
of plankton biomass caused by the high content of plant nutrients in the
river waters. The average wet volume of plankton in the Syr-Dar'ya estuary
is 3 mg/m3.

660 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Seasonal changes of plankton

The Aral Sea plankton is more abundant in variety and numbers in summer
time (May to October) ; moreover, a number of forms (for example Brac-
hionus mulleri, Evadne camptonyx) have a maximum growth in the warmest
time of the year. G. V. Nikolsky has pointed out that a large number of
chironomid pupae are observed in the plankton, mainly in the autumn.

The significance of plankton as food

The Aral Sea plankton is most important as food for the bottom-fauna and
the fish-fry. As has been said above, among the adult fish of the Aral Sea only
stickleback can be considered as a typical plankton eater. As the investi-
gations of V. Pankratova (1935) and A. Behning (1935) have shown, plankton
constitutes 69 per cent of stickleback food, 16 per cent of that of Pelecus, 9 per
cent of that of Chalcalburnus and 3 per cent of that of bream. Diaptomus
salinus and to a much lesser extent other Copepoda and Cladocera form the
main food of these fish. The fry of most fish feeds on plankton.

The quantitative estimate of plankton

Quantitatively the plankton of the Aral Sea is somewhat inferior to that of the
Caspian and much poorer than that of the Sea of Azov (and other central
Asian lakes except Lake Balkhash) (Fig. 312). Its average biomass is about
3 cm3/m3 and the number of specimens of plankton organisms is of the order
of 8 to 9 millions, mainly flagellates and the diatoms Actinocyclus, Exuviella,
Proterocentrum, Glenodinium, Diplosalis and other nannoplankton forms.
The quantitative distribution of the plankton of the Aral is illustrated in
Fig. 312. The inadequacy of the nutrient salts is regarded by Nikolsky as the
cause of the poverty of plankton in the Aral Sea.

Benthos

Phytobenthos. According to A. Behning (1935) the phytobenthos of the Aral
Sea, except for the flowering plants of the coastal zone, comprises the follow-
ing groups :

Chlorophyceae 4 species

Diatomaceae 25 species

Rhodophyceae 1 species

Characeae 1 species

Phanerogamae 1 species

Among these 32 forms the flowering plant Zostera nana, the green algae
Vaucheha dichotoma and Cladophora gracilis, the red algae Polysiphonia vio-
lacea and Characea alga Tolypella aralica are the specially large mass forms.

Zostera mainly inhabits silty sand soils in the shallower areas of the bottom
of the eastern and northern parts of the Sea. Large accumulations of it are
found there. As in the Black and Caspian Seas, Zostera forms floating fields
in the Aral Sea and great masses of it are cast up on the shore. Bottom

THE ARAL SEA

661

sea-weeds go down much deeper than Zostera, and these sea-weeds (mainly
Vaucheria dichotoma) form a thick cover on grey mud down to depths of
26 m. The Charial sea-weed Tolypella aralica forms abundant beds on black

Е2Э < '"О re« litre

E^ 500-1300 »

W",\ 1300-2500 ■•

ВШ > 2500

Fig. 312. Quantitative distribution of plankton

in the Aral Sea in summer 1932-33, number of

specimens per litre (Behning).

ooze which smells of hydrogen sulphide, mainly in bays and inlets more or
less separated from the Sea. The thin brown film covering the mud soils
comprises a huge number of diatomaceous algae.

The qualitative composition and quantitative distribution of zoobenthos (Fig.
313). Qualitatively zoobenthos is as poor as plankton; it comprises only 48
forms :

Foraminifera

Nematoda (free-living)

Turbellaria

Oligochaeta

Bryozoa

Harpacticoida

Ostracoda

2 species
7 species

12 species

3 species
1 species
5 species
3 species

Amphipoda

Gastropoda

Lamellibranchiata

Trichoptera

Chironomidae

Hydracarina

1 species

2 species
4 species
2 species
6 species
1 species

662

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Fish-parasites. Seventy-one species of different fish-parasites should be added
to this list. According to V. Dogjel and B. Bykhovsky (1934) they are distri-
buted among the following groups :

Protozoa

Coelenterata

Trematoda

Cestoda

Nematoda

Hirudinea

Crustacea

14 species

1 species
30 species

9 species
10 species

2 species
5 species

Fig. 313. Zonal distribution of Aral fauna (Zenkevitch, 1951).

For the Sea itself only 33 species of parasites have been confirmed. All
the others are inhabitants of low-salinity areas. Among these parasites the
Coelenterata Poly podium hydriforme and the Trematoda Nitschia sturionis,
brought into the Aral Sea with starred sturgeon during its acclimatization, are
of great interest.* About a hundred specimens of starred sturgeon were
introduced into the Aral Sea from the Caspian Sea, without being dis-
infected against parasites.

The parasite of the gills of the starred sturgeon is the trematode Nitschia,
which is widely dispersed in the Caspian Sea and does little harm there. No
more than 40 specimens per fish have been recorded in that Sea. Once in the
Aral Sea, however, the trematode transferred to the local sturgeon Acipenser
and caused a serious epizootic epidemic which led to high mortality among
fish. Up to 600 trematodes have been counted on one sturgeon Acipenser.

Over a period of some years the number of Trematoda dropped sharply ;

* There is, however, an opinion that Nitschia sturionis existed in the Aral Sea before the
starred sturgeon was introduced.

THE ARAL SEA 663

however, the stock of sturgeon Acipenser was not restored to its former
numbers.

It was discovered in 1945 that the Aral sturgeon Acipenser was infected, in
addition to the trematode, by a parasite of the roe of Acipenseridae fish well
known in the Caspian Sea — the coelenterate Polypodium hydriforme. The poor
multiplication of Acipenser sturgeon when the epizootic epidemic caused by
Trematoda was over may have been due to its infection by Polypodium
hydriforme. V. Dogjel and B. Bykhovsky noted the general poverty of the
parasite-fauna of the Aral fish (two to three times poorer than the parasite-
fauna of Neva Inlet in the Gulf of Finland), caused by the properties of the
Aral waters and by the absence among the rest of the fauna of vector forms,
the intermediate hosts.

Mass zoobenthos forms. The most common benthos forms are the Oligo-
chaeta Paranais simplex and Nais elinguis; among Ostracoda Cyprideis
littoralis, widely distributed in the Azov and Caspian Seas ; only one repre-
sentative of higher Crustacea, Pontogammarus aralensis; among molluscs
Adacna minima, Dreissena polymorpha and, much more rarely, Cardium edule ;
and among the insects, the larvae of caddis flies and of chironomids. The
highest number of specimens recorded and the weight of these forms per
1 m3 are given in Table 281.

Table 281

No. of

Biomass

Form

specimens

g/m2

Oligochaeta

600

1-3

Ostracoda

920

0-2

Amphipoda
Adacna minima

750
700

6-8

32-8

Dreissena polymorpha
Cardium edule

2,000 (25,625)
80

6615 (955)
9-8

Trichoptera
Chironomidae

80
1,840

33-2

Hydrobia
Dikerogammarus aralensis

462
150

2-0

It is evident from Table 281 that even the highest mass forms, such as for
example Dreissena, which in the Caspian Sea frequently produces a few kilo-
grammes per 1 m3, do not produce more than a few dozen grammes in the Aral
Sea. The Dreissena genus is represented in the Aral Sea (according to N. Husai-
nova, 1958) by four species — Dr. polymorpha with two variants {obtusecari-
nata and aralensis), Dr. caspia, Dr. pallasi and Dr. rostriformis. Cyprideis
littoralis, at times found in the Sea of Azov in hundreds of thousands of
specimens per m3, is in the Aral Sea no higher than 1,000 with a biomass
of 0-2 g/m2. The same holds true of plants. The highest Zostera biomass
recorded is only 90 g/m2, Tolypella 9-5 g/m2, and Vaucheria 531 g/m2. The
total weight of all the plants rarely exceeds 0-5 kg/m2.

664

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Bivalves are usually preponderant in the benthos biomass, constituting at
times 94 per cent of its total. Chironomids occupy second place, Phryganidae
third, and Pontogammams aralensis fourth. Other benthos groups are of little
significance.

All the organisms of Aral benthos are consumed by fish, but only a certain
proportion of those of the Azov and Caspian benthos are taken. This fact

Fig. 314. Distribution of the total benthos biomass (g/m2)
of the Aral Sea in 1954-57 (Yablonskaya).

must be taken into consideration when estimating the food significance of
Aral benthos. The significance of benthos as food is thus relatively higher in
the Aral Sea.

Uniform distribution, within the limits of one biotope, and the absence of
areas of great concentration, are characteristic of Aral benthos. Even Drei-
ssena does not form extensive accumulations here. The phenomenon of
bottom-fauna suffocation has not been recorded in the Aral Sea.

The quantitative and qualitative distribution of the zoobenthos of the Aral
Sea has more than once been investigated by V. Nikitinsky (1933), A. Behning

THE ARAL SEA

665

(1935) and I. Kulichenko (1944). The most recent comprehensive study was
undertaken by E. Yablonskaya (1959), who has distinguished seven main
biocoenoses. Practically the whole Sea is encircled (Fig. 315, 1) at little
depth (2 to 10 m) by a zone of vegetation. Dreissena polymorpha is the pre-
dominant form. The mean mass of charial algae is 67T58 g/m2; among the
Zostera in the Maloe More— 22-255 g/m2; among the soft macrophytes

И r

Fig. 315. Main benthos biocoenoses of the Aral Sea in 1954 to
1957 (Yablonskaya). See text for interpretation.

(Potamogeton and others) — 10-874 g/m2. This zone is followed by the sandy
zone, which has a predominance of Adacna minima (Fig. 315,2) with a bio-
mass of 6-181 g/m2. Still deeper (10 to 24 m) on the silty sand (Fig. 315, 3)
the Dreissena and Adacna biocoenosis develops with a biomass of 15 to
14 g/m2. Chironomid larvae are the dominant form on the mud soil of
Adzhibai Inlet (Fig. 315, 4), producing a biomass of up to 16-2 g/m2. All
the central part of the Sea, with depths down to 27 m, on sand and grey mud
soils is populated by the Chironomus, Dreissena and Adacna biocoenosis

666

BIOLOGY OF THE SEAS OF THE U.S.S.R.

21. 8ф

SANDY SILT ZONE

(Fig. 315, 5) which forms a biomass of 20 g/m2 in the Bol'shoe More and of
58-8 g/m2 in the Maloe More. In the western depression on black mud with
Vaucheris at depths of 28 to 60 m, Dreissena is predominant with a biomass
of 12 to 18 g/m2 (Fig. 315, 6), but at depths of 40 to 60 m the biomass drops
to a few tens of milligrammes per 1 m2. In the Syr- and Amu-Daria estuarine
zones Adacna biocoenosis with an average biomass of 5-290 g/m2 develops
on brown soils at depths of 4 to 10 m. Dreissena polymorpha in combination
with chironomid larvae and to a lesser extent with Adacna is the main form of

the bottom-fauna of the Aral Sea.
27.6 z/m* _. . _ Pontogammarus aralensis lives in

large numbers on the sands of the
shore.

In reality the bottom of the Aral
Sea is populated by one biocoenosis,
the Dreissena (Fig. 316), with differ-
ent variations according to the type
of soil.

This biocoenosis is most clearly
marked on grey muds. At times 80
per cent of the whole population is
composed of Dreissena. Sometimes
chironomid larvae are predominant,
constituting 60 per cent of the total
benthos. On sands Dreissena and
Adacna (on the average more than
97 per cent) are predominant; the
Chironomus and Gammaridae larvae
are found only as single specimens.
Nearer to the coast and off it in the
vegetation beds of the bays and inlets
there is a particularly large number
of Pontogammarus aralensis. Behning points out that 'after a gale one can
frequently observe along the coast whole strips of wrack consisting entirely
of these small-sized crustaceans. They are always numerous too among the
sea grass cast up on the shore.'

Bottom-life is scarce in the deeper part with black muds and hydrogen
sulphide, and in some areas it may not be found at all.

In the shallower areas covered by black mud (40 to 50 m) benthos is poorly
developed and is represented mainly by Nematoda, Oligochaeta and Ostra-
coda.

Benthos is richest in shell-gravel areas where, according to Behning, it
reaches 40 g/m2. Bottom-life is scarce or even completely absent opposite
the mouths of both great rivers and, like that of the black muds, it is repre-
sented here by Nematoda, Oligochaeta, Ostracoda and chironomid larvae.

A survey of the distribution of bottom fauna in the Adzhibai inlet (south-
western corner of the Sea) was undertaken by P. Dengina in 1957. The
salinity of the Sea (measured by chlorine) varies from 4%0 at the end of the

GREY OOZE ZONE
OF BOL'SHOE SEA

Dreissena

fJdacna

Caidlum

VA/A/A Chnonomidae

III! Jam ma 1 1 dae

WW Phiyganldae

Fig. 316. Composition of bottom-living

population of Aral Sea (Nikitinsky) :

Left: On grey ooze zone; Right: On

sandy silt zone.

THE ARAL SEA 667

Amu-Darya delta to 6-0%0 at the entrance to the Sea. Most of the inlet floor is
occupied by a bed of Zostera nana ; in summer there are up to 3,000 stems per
1 m2. Dengina points out that Zostera 'is of great significance for the zoo-
benthos, since it serves as a substratum for the fixation of sessile forms
(Dreissena) and as a habitat for the not very mobile forms. Bacterial flora
developing on the stems and leaves of Zostera serves as food for cladocerans,
insect larvae and molluscs. Zostera is the food of almost all benthophagic
fish ; it offers good shelter for the young of commercial fish which float down
from the delta waters.'

Among the bivalves three forms of Dreissena (D. polymorpha, D.p. var.
aralensis and D. caspia), Adacna vitrea var. minima and Cardium edule — and
among the Gastropoda Hydrobia ventrosa and Theodxus pallasi belong to the
highest mass forms. Ostracoda (Cyprodeis littoralis, C. torosa and Hemicy-
thera sicula) play an important role in the benthos.

Among the crustaceans Dikerogammarus aralensis, and among the bryo-
zoans Vic tor el la bergi develop in large numbers. The larvae of insects are
found everywhere, sometimes in large numbers. The mean zoobenthos bio-
mass of the inlet has been determined by Dengina as 11-7 g/m2 in the spring
and 12-2 g/m2 in the summer.

The data for the mean benthos biomass of the Aral Sea given by different
investigators range from 16 to 18 g/m2 (Behning) to 21 g/m2 (Kulichenko)
and 23 g/m2 (V. Nikitinsky). Benthos is most abundant in the Maloe More
(owing to Dreissena) and in some areas of the central part of the Bol'shoe
More (due to chironomids). Benthos biomass is commonly 20 to 40 g/m2.
The benthos biomass of the Aral Sea undergoes considerable fluctuations
over a period of years (Table 282).

Table 282. Mean benthos biomass, g/m2

1936

1937

1938

1939

Soil

spr

sum

aut

spr

sum

aut

spr

sum

aut

spr

Mud

Clayey mud

Sandy mud

Silty sand

Sand

Making a general estimate on the basis of the quantitative data of Aral Sea
benthos, the three above-mentioned workers do not incline to the view that
its benthos is very poor. On the contrary Nikitinsky and Kulichenko believe
that the Aral benthos with its high quality as food forms a satisfactory stock
of food for the present fish population.

Thus, in contrast to the Caspian Sea and like our other seas, the Aral Sea
benthos biomass is greater on soft bottoms than on hard ones ; this can prob-
ably be explained by the peculiarities of both bodies of water and by the
conditions under which the different types of soil were formed in them.

668 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Benthos biomass is highest in the summer ; in the autumn it is somewhat
higher than in the spring.

The causes of this type of seasonal change lie mainly in the intensity of
the summer feeding of the fish.

Fish

Qualitative composition. The Aral Sea fish are represented by 1 1 families and
24 species; the family Cyprinidae alone comprises 12 species (50 per cent)
and the Percidae 3 species (13 per cent); the other 9 families (including Aci-
penseridae, Salmonidae, Siluridae, Esocidae and Gasterosteidae) are repre-
sented by only one species. Seven species were brought into the Sea by man
in recent years.

The transplantation of the Caspian Caspialosa caspia aestuarina and two
species of Mugil into the Aral Sea was apparently not successful ; the herring
and mullet died out, because of the low winter temperature of the Aral Sea.

G. V. Nikolsky (1940) notes that the fauna of the Aral Sea comprises three
genetic communities : (1) the remains of the upper-Tertiary fauna, (2) repre-
sentatives of Aral-Caspian fauna and (3) representatives of northern Siberian
fish. The Aral-Caspian forms constitute 45 per cent of the fish. They are
mainly members of the cyprinid family. The fish of the Aral Sea are much
poorer than those of the Caspian. Among the large lakes only Balkhash and
Issyk-КиГ are poorer in fish species. There are only nine endemic forms (38
per cent) among the fish of the Aral Sea ; moreover, the majority of them are
sub-species : there is only one endemic species (Aral barbel).

The complete disappearance from the original Aral fauna of the members
of the families Clupeidae and Gobiidae, which are so characteristic of the
Caspian Sea, is most remarkable. Among the 24 species of Aral fish 14 are
common to it and to the Caspian Sea and 10 belong to other different sub-
species. Thus the Aral Sea fish are closely related to those of the Caspian Sea.
'It is well known that a gradual decrease in the number of fish species is
observed', wrote Nikolsky, 'as one moves from west to east — from the Black
Sea through the Caspian and Aral Seas to Lake Balkhash. Thus the number
of species in the Black Sea (without the basin, Slastenenko's data) is more
than 170. In the Caspian Sea the number of species falls below 100, in the
Aral Sea to 20 and in Lake Balkhash to 8.' Nikolsky thinks that the 'fish of the
Aral Sea were evolved from those of the Amu-Daria and its ancient tributary
Syr-Daria.

Fish feeding. G. V. Nikolsky (1940) distinguishes two main biological group-
ings of Aral Sea fish — that of the open Sea and that of the coastal zones ; the
absence of small, benthos-feeding, comparatively immobile fish is highly
characteristic of the Aral Sea (also there are no fish which live permanently
away from the coast). The majority of Aral fish are good swimmers feeding on
pelagic and bottom fauna.

The main commercial fish — golden shiner, vobla, bream, Abramis sapa,
Pelecus and Chalcalburnus — feed in the open parts of the Sea from the middle
of May to October at depths of 1 5 to 30 m and on the grey mud ; nevertheless

THE ARAL SEA

669

none of the species multiplies there. According to G. Nikolsky, ' the main
items of fish diet in this part of the Sea, both in the epilimnion and in the
hypolimnion are amphipods {Pontogammarus aralensis). Bivalves and gastro-
pod molluscs play a much smaller role. Air insects, mainly caddis fly and
chironomids, are of significance in the diet of fish living in the epilimnion
(bream, Abramis sapa and vobla in the spring and autumn, and Pelecus and
Chalcalburnus throughout the year) ; thus the typical pelagic fish is absent
from the Aral Sea and the food which in the Caspian Sea is taken by Clupeo-
nella is not used here.' Since there are no small pelagic fish there are no pelagic
predators, which are so typical of the Black Sea and to a lesser extent of the

Cormorants)

/fSoy

plankton

Adacna Smother Chirono
Dreissena Molluscs midae

Phyto-
Benthos

Phryga-
nidae

Vermes

Fig. 317. Diagram of food correlation of fish in the open parts of the Aral Sea

(Nikolsky). 1 Pelecus oil tr at us; 2 Abramis sapa; 3 Lucioperca lucioperca; 4 Rutilus

rutilus; 5 Chalcalburnus chalcoides ; 6 Abramis brama ; 7 Pungitius platygaster.

Caspian. G. V. Nikolsky notes that the food chain of pike perch turned in
the Caspian Sea towards the pelagic forms : plankton — Mysidae — Caspialosa
— pike perch ; in the Aral Sea it consists mainly of benthos : plankton —
Pontogammarus — Pelecus — pike perch — Abramis sapa.

According to the nature of their diet the Aral fish can be distinguished into
zoobenthophages, planktophages, and predators; phytophages are poorly
represented here, and there are no mud-eaters.

Food correlations of fish of the open parts of the Aral Sea are given in
Fig. 317.

The coastal grouping of Aral Sea fish comprises a large number of species
of plant-eaters (rudd and some carp).

There is only one typical planktophage here, as well as in the open parts of
the Sea — stickleback.

670

BIOLOGY OF THE SEAS OF THE U.S.S.R.

The composition of food for the fish, which also inhabit the open parts of
the Sea, changes considerably near the shores, where gammarids become
less and molluscs more significant; Ostracoda is added to the diet. Some
shorter food chains make their appearance (for example: phytobenthos —
rudd — pike perch) ; plankton is even less important.

V. Pankratova (1935) has shown that fish feed more on vegetable food in
the winter than in the summer, and more on animal food in the summer than
in the winter. According to this worker (Fig. 318) Acipenser nudiventris feeds
exclusively on molluscs. The diets of vobla (Rutilus rutilus aralensis) and

2 3 4

Molluscs

Gammaridae
E2 Phryganidae

t^i High crustaceans
P??H Vaucheria

I — | Diaptomus
sal in us

ШВ Chironomidae
Fig. 318. Food composition for Aral Sea fish (Pankratova). 1 Acipenser nudiventris;
2 Rutilus rutilus ; 3 Barbus brachicephalus ; 4 Chalcalburnus chalcoides ; 5 Abramis
brama; 6 Abramis sapa; 7 Pelecus cultratus; 8 Cyprinus carpio; 9 Perca fluviatilis;

10 Pungitius platygaster.

bream {Abramis sapa) are the most varied, and the ratio of their components
is very similar. Vegetable food is most significant in both diets: for vobla
63-5 per cent of fish had some remains of vegetable food in their intestines,
and 49-5 per cent of them had only vegetable food in their intestines. Among
the animals molluscs and insect larvae are predominant in the vobla's diet.
Forty per cent of bream {Abramis sapa) had vegetable food (Vaucheria, and
other filamentous algae), and among the animals caddis and beach fleas are
predominant.

Barbus brachycephalus feeds mostly on molluscs, and to a much smaller
extent on gammarids and higher plants.

Chalcalburnus chalcoides aralensis feeds on gammarids and phriganids, and
Abramis brama eats all the benthos, but mostly gammarids and chironomid
larvae. Pelecus cultratus preys almost exclusively on animals and mainly on
beach fleas. It swallows also a number of land insects which fall into the water.

The main diet of Cyprinus carpio is chironomid larvae, and to a lesser extent

THE ARAL SEA 671

molluscs, pelagic crustaceans and plants. Perca fluviatilis feeds exclusively
on gammarus, and Pungitius platygaster aralensis is a typical planktophague.
Its main food is Diaptomus salimts, and a supplementary one is chironomid
pupae. Silirus glanis, Lucioperca lucioperca, Aspius aspius illiodes and Esox
lucius are predators which feed on fish and very rarely eat other animals and
plants.

Acclimatization measures. In recent years acclimatization measures in the
Aral Sea have acquired a systematic character. In this work the high food
value of the benthos, in spite of its small biomass, is taken into consideration
as well as the great poverty of plankton food and the presence of considerable
amounts of mostly vegetable organic detritus.

Adult Acipenser stellatus was brought from the Caspian Sea in 1933-34.
Acclimatization measures were again undertaken in 1948-56. Acipenser stella-
tus, however, was brought as roe from the delta of the Ural river. Both species
of grey mullet (Mugil auratus and M. saliens) and with them both species of
prawns {Leander adspersus and L. squilla) were also brought from the Caspian
Sea into the Aral Sea in 1954-56, while during the same years the roe of
Clupea harengus membras came from the Baltic Sea. The transplantation of
Baltic herring and its successful development in the Aral Sea is of special
interest, the more so since in its new habitat the fish grows quicker and larger
in size (two or three times larger). The severe temperature conditions of the
Aral Sea might cause some doubts about the acclimatization of grey mullet ;
but as a mud-eater it has plenty of food there. So far it has not been discovered
in the Aral Sea.

Two species of Caspian bullheads {Pomatoschistus caucasicus, and Gobius
melanostomus affinis) and three species of Caspian mysids {Mesomysis kowa-
lewskyi, Mesomysis intermedia and Par amy sis baeri) were brought into the
Aral Sea with the grey mullet (1958).

The fish Atherina mochon pontica caspia was brought in by accident. A
future possibility is the transplantation into the Aral Sea of forms successfully
acclimatized in the Caspian Sea — Nereis and Syndesmya and others. The
success of the transplantation of the Baltic herring into the Aral Sea is an
indication that other inhabitants of the Baltic might later be transplanted too.
Among the invertebrates the bivalve Macoma baltica seems to offer some
possibility of acclimatization in the Aral Sea.

Fishery. Carp, bream and vobla are the main items of commercial fishery in
the Aral Sea. Chalcalburnus, catfish, Abramis sapa, barbel pike, pike perch
and Aspius aspius are of less importance. The total catch in recent years
(1956) has reached 459 centners. In 1956 there was a total yield of 166,000
centners of bream, 100,000 centners of carp, 57,000 centners of vobla, 25,000
centners of pike, 23,000 centners of Chalcalburnus, and 9,000 centners of
pike perch. Fishing has so far been done mainly in the in-shore areas, chiefly
in the mouths of rivers.

THE FAR EASTERN SEAS OF THE U.S.S.R

General Characteristics of the Far Eastern Seas and of
Adjacent Parts of the Pacific Ocean

I. GENERAL CHARACTERISTICS

A quarter of the coast of the u.s.s.r. is washed by the Pacific Ocean and the
Seas of the Far East. Only a seventh of the whole coast is actually washed by
the waters of the Pacific, while six-sevenths of it consists of the shores of the
Seas of Japan and of Okhotsk and the Bering Sea. [The total area of the three
Seas (4,872,000 km2) is almost double the area of the European Seas of the
u.s.s.r. from the White and Barents Seas to the Aral Sea (2,842,500 km2).
The volume of the Far Eastern Seas (6,741,300 km3) is seven times greater
than that of the European Seas (978,300 km3)].

There is a free exchange of water through the numerous straits between
the three Seas and the Pacific. The whole mass of water of the Bering Sea has
free access to the Pacific through its many deep straits (down to 5,000 km),
and therefore it can be considered as a bay of the Ocean. This is true to a
lesser extent of the Sea of Okhotsk since, apart from its surface and modified
near-bottom layers, its waters have the same characteristics as those of the
neighbouring Pacific.

The Sea of Japan is the most isolated from the Pacific, owing to the shallow-
ness (not more than 130 m) of the four straits which connect them.

The Sea of Japan has not, however, a reduced salinity ; as a whole this
approximates to that of the Ocean ; its depths are well supplied with oxygen
as a re.sult of considerable mixing in winter.

A small shelf and great depths are characteristic of our Far Eastern Seas.
Only the northern and northeastern parts of the Bering Sea are occupied by
vast shallows, which constitute about half of its whole area. The shelf zone is
very narrow in the Sea of Okhotsk and narrower still in the Sea of Japan. This
influences the composition and especially the biological properties of its fauna.

The Seas of Japan and Okhotsk and the Bering Sea extend in a southwestern
and northeasterly direction for almost 5,000 km. Whereas the climate of the
northern parts of the Sea of Okhotsk and of the northwestern parts of the
Bering Sea is arctic and severe, and both contain large masses of ice for several
months, the small Kuril Bar and the southern part of the Sea of Japan closely
approach the tropical zone. In the northwesterly part of the Pacific, as also
in that of the Atlantic, the cold and warm water zones occur very close to
each other, and as a result masses of cold water move from the north and
masses of warm water move from the south (Gulf Stream, Kuroshio). This
is in contrast to the northeastern sides of the oceans, where the extent of these
zones is considerably greater, and the boundaries between the cold, temperate
and warm water zones are spread out and the sharpness of the division be-
tween them is less distinct (Fig. 319).

As a result of the convergence of the cold and warm waters on the western

675

676

BIOLOGY OF THE SEAS OF THE U.S.S.R.

side of the Ocean off the shores of Japan, the 0° and 16° isotherms are
separated in winter by only 10°, whereas off the American shores the zone of
eparation is more than 30°. In summer there is a 15° belt between the iso-
therms 10° and 26° on the western side of the Ocean and 40° on the eastern.
This influences not only the climate of the coastal regions of the mainland
but also the whole biological environment, and most of all the marked pheno-
mena of oceanic convergence on the western side of the Ocean.

These peculiarities create conditions in the northwestern part of the Pacific
Ocean for the existence of quantitatively very rich flora and fauna, and zones

Fig. 319. Diagram of the Arctic (/), boreal (2), tropical (5) and
mixed (4) zones on both sides of the Pacific Ocean.

of heterogeneity where Arctic boreal and subtropical meet. There are some
mixed tropical and subtropical zones. This is most apparent in the zone
where the waters of the Oyashio and Kuroshio meet in the pelagic region ;
we are therefore led to the conclusion that a mixed zone exists here rather
than a subtropical region, since the boreal and tropical fauna and flora
resemble each other very closely and are partly intermixed.

The qualitative variety of the population is increased also as a result of the
great vertical range (down to 1,100 km) and of the much greater biotopic
variety (a large number of archipelagos and the presence of coastal features).
The fauna of the northwestern part of the Pacific and its adjacent seas is at
least twice as rich as that of the seas of northwestern Europe. The deep-water
fauna of the Sea of Okhotsk, the Bering Sea and the adjacent part of the
Pacific (with the Aleutian, Kuril-Kamchatka and Japanese trenches) is ex-
tremely rich; its variety is probably considerably greater than that of any
other part of the world ocean.

GENERAL CHARACTERISTICS OF THE EASTERN SEAS 677

The flora and fauna, rich in variety and quantity, contain a number of
species which are, or could be, of great commercial value — some 200 of the
total of 800 species among fish alone. Oysters and scallops could first be added
to the list of organisms exploited commercially ; and then the huge variety of
molluscs and crustaceans (primarily the Kamchatka crab), the large stock of
marine algae (Laminaria and Alaria) and marine flowering plants (Zostera
and Phyllospadix). Whales, fur-seals, walruses, sea lions, sea otters and other
marine mammals could also be added to this list of the abundant and still
almost untapped resources.

The exceptional abundance of life in some regions of the northwestern part
of the Pacific is striking. The meeting zone of the Oyashio and Kuroshio
waters is the richest among them ; very many fish are attracted by the abund-
ance of plankton, the fish in their turn being followed by large shoals of
squids, whales and flocks of birds.

II. HISTORY OF EXPLORATION

Three hundred years ago (1648) the Cossack Semen Dezhnev rounded the
Chukotsk Peninsula and sailed through the straits (which should really have
been called after him), entering the Pacific Ocean from the north. The Rus-
sians, who at that time were settled on the far-distant northeastern border of
Asia hunting sea beasts, must have had some knowledge of sea fish and
mammals and of the geography of the regions in which they swam. V. Bering's
expedition (1725 to 1743), one of the greatest geographical undertakings in the
history of ocean exploration, marked the beginning of a more systematic
study of the flora and fauna of the Far Eastern Seas. Numerous documents
form the legacy of this expedition. The naturalists S. Steller and S. Krashenin-
nikov, who took part in the expedition, gave the first, very valuable obser-
vations on the flora and fauna of the Far Eastern Seas and their shores.

At the end of the eighteenth and the beginning of the nineteenth centuries
the ships of numerous Russian expeditions ploughed the northern part of the
Pacific Ocean. Descriptions of the coastline of northern Asia and America
were made by these expeditions. Biologists often participated. The expeditions
of I. Billings and G. Sarychev (1785 to 1793), I. Kruzenshtern and Yu.
Lisyansky (1803 to 1806), O. Kotzebu (1815 to 1818) and others are parti-
cularly well known.

The second period of the exploration of the Far Eastern Seas and the begin-
ning of the systematic study of their flora and fauna are linked with the names
of the members or collaborators of the St Petersburg Academy of Sciences —
I. Voznesensky, A. Middendorf, L. Shrenk, N. Grebnitzky and others. The
voyage of Admiral S. O. Makarov (1886 to 1889) in the corvette Vityaz was
of exceptional importance in the history of the exploration of the Pacific.

At the beginning of this century several large expeditions were sent out to
investigate the commercial wealth of the Far Eastern Seas. The most signi-
ficant among them were the researches of V. Brazhnikov (1899 to 1904),
P. Schmidt (1900 to 1901) and V. Soldatov (1907 to 1913).

The last and most fruitful period in the exploration of the Far Eastern
Seas, of their environment, flora and fauna, including the deep-water fauna,

678 BIOLOGY OF THE SEAS OF THE U.S.S.R.

and assessment of their commercial wealth, began in the 'twenties of the
present century with the works of K. Derjugin, P. Schmidt (since 1925) and
their collaborators (P. Ushakov, A. Ivanov, N. Tarasov, E. Gurjanova,
G. Lindberg, P. Moiseev, G. Ratmanov, A. Taranetz and many others).
The organization of the first Pacific Scientific-Industrial Station, and since
1929 of the Institute of Scientific Research on Marine Fisheries and Oceano-
graphy (t.i.n.r.o.) has been of great significance in the development of further
work. The exploration of the Far Eastern Seas was developed on a particu-
larly large scale in 1932 and 1933 under the leadership of K. Derjugin and
P. Schmidt in connection with the Second International Polar Year. The
State Hydrological Institute and the Pacific Institute of Fisheries and Oceano-
graphy sent out five research ships (including the Rossinanta, DaVnevostochnik
and Gagara) for a thorough survey of the Chukotsk and Bering Seas and the
Seas of Okhotsk and Japan. Trawlings down to 3,800 m were carried out and
a varied deep-floor fauna was found both in the Sea of Okhotsk and in the
Bering Sea as well as in the adjacent part of the Pacific. As a result of this
work many aspects of the conditions and biology of the Far Eastern Seas came
to light for the first time ; the huge amount of data collected was examined
and classified by many workers over a number of years. One of the most
important results of this survey was the creation of the Pacific Institute of
Fisheries and Oceanography and the further development of its activity in
the succeeding 25 years, when two branches were organized on Kamchatka
and Sakhalin. Research was done by the Institute, mostly along scientific-
industrial lines, but also in the field of general oceanography. Fifty volumes
of its Bulletin have since been published.

The State Hydrological Institute and the Zoological Institute of the
Academy of Sciences of the u.s.s.r. continued their research into the Far
Eastern Seas during the 27 years since Derjugin's expedition. The most signi-
ficant data were obtained by the Kuril-Sakhalin expedition, organized in
1947 to 1949 jointly by the Zoological Institute and the Pacific Institute of
Fisheries under the leadership of Lindberg.

Japanese explorers have done much important work on the Seas of Japan
and of Okhotsk. One of the biggest Japanese expeditions, headed by a pro-
fessor of the Tokyo Institute of Fisheries, X.Marukava, took place from 1915
to 1917. It carried out an extensive survey of the hydrology, biology and fish-
eries of the Seas of Japan and of Okhotsk. Four ships took part in the expedi-
tion.

The discovery of large feeding aggregations of Far Eastern salmon in the
northwestern part of the Pacific and to the southeast of Kamchatka may be
considered as a great achievement of Japanese biologists. An important part
in the success of this commercial prospecting expedition was the location of
areas of very abundant development of plankton, in a region where cold and
warm waters — rich feeding grounds for salmon — meet.

Research on a large scale by the Institute of Sea-weed Research of Hok-
kaido University has continued for many years under Professor Yamada,
studying commercial sea-weeds in the regions surrounding Hokkaido Island.

In 1949 the ship Vityaz (Fig. 320) was sent by the Institute of Oceanology

Fig. 320. Vityaz, the exploration vessel of the Institute of Oceanology of the
Academy of Sciences of the u.s.s.r.

Fig. 321. Vityaz survey in the Pacific Ocean in 1949-56.

680

BIOLOGY OF THE SEAS OF THE U.S.S.R.

of the Academy of Sciences for a broad, many-sided survey of the Far Eastern
Seas and of the northern part of the Pacific Ocean. During the International
Geophysical Year (1957-59) the work done by this expedition was further
extended to cover all the northern part of the Pacific Ocean (Figs. 321 and
322).
The old idea of Soviet oceanologists of a floating marine laboratory, which

Fig. 322. Vityaz survey in the Pacific Ocean during the period of 1957-59.

could survey simultaneously the sea waters from the surface to the great
depths of the ocean throughout all its regions, was fulfilled by the Vityaz.
In the early 'twenties the research ship Perseus was built for this purpose by
the State Oceanographic Institute, and for many years (1920 to 1943) she
worked in the northern seas of the u.s.s.R.

Throughout the 12 years of research by the Vityaz (30 separate expeditions)
rich new material was collected on all branches of oceanology and especially
on the geology and biology of the great depths of the Pacific Ocean, including

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS 681

the bottom topography and the depths of the greatest ocean trenches, the
composition and distribution of marine deposits, the composition and distri-
bution of deep-water fauna, etc. (Figs. 321 and 322).

Most of the papers on the survey of the Far Eastern Seas are published
in the Bulletin of the Pacific Institute of Fisheries and Oceanography, in the
Proceedings of the Institute of Oceanology of the Academy of Sciences of the
u.s.s.R. and in the series 'The Exploration of the Seas of the u.s.s.R. ', which
was first published by the State Hydrological Institute together with the
Pacific Institute of Fisheries and Oceanography. Since 1941 the papers have
been appearing under the title The Survey of the Far Eastern Seas of the
U.S.S.R., published by the Zoological Institute of the Academy of Sciences,
and in the periodicals The Survey of the Seas of the U.S.S.R., The Fauna of
the U.S.S.R., and The Proceedings of the Zoological Institute of the Academy
of Sciences of the U.S.S.R. published by the same institute.

III. PHYSICAL GEOGRAPHY OF NORTHWESTERN PART
OF PACIFIC OCEAN

Coastline and bottom topography

The coastline, bottom topography, circulation of the water masses and some
phenomena of their geological past are the most characteristic features of
these Far Eastern Seas.

The northwestern part of the Pacific Ocean is characterized by a rich
development of coastal features and by the presence of numerous islands
which form three great arcs — namely, the Japanese, Kuril and Aleutian, and
the Alaska and Kamchatka Peninsulas, which cut off the Seas of Japan and
of Okhotsk and the Bering Sea from the Ocean. The hydrology, chemistry and
biology of the three Seas bordering the northeast of Asia are greatly influenced
by the width and depth of the straits. The basin of the Sea of Japan is separated
from the Pacific by shallow straits (not deeper than 130 m) ; its depths, how-
ever, are well aerated, and its geological past has left a deep imprint on its
fauna. The straits connecting the Sea of Okhotsk with the Ocean are deep ;
they fall short of the greatest depth of the Sea by only 1,350 m (Table 283).
The huge masses of the deep waters of the Sea of Okhotsk suffer, however,
from a pronounced shortage of oxygen. The straits leading into the Bering
Sea offer little impediment to the exchange of its waters with those of the
Ocean, and therefore the Sea of Okhotsk, situated to the south of the Bering
Sea, has a much more severe climate.

The present bottom topography of the Far Eastern Seas is characterized
by a small shelf and a large zone of great depths. The areas of the three zones
(the shelf, the bathyal and the abyssal) are about equal (Fig. 323). The three
Seas, however, differ greatly in this respect. The Sea of Japan has a small
shelf, and the abyssal zone is predominant in its bottom topgraphy. The Sea
of Okhotsk has a fairly limited abyssal zone, and its bathyal zone is greatly
developed, whereas the Bering Sea has an extremely limited bathyal zone and
a large shelf in its northeastern part. Its shelf and the abyssal zone occupy
practically equal areas (forming about 90 per cent of the total area of the S ea)

682

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 283. Maximum depths of the deepest Pacific trenches of the Far Eastern Seas,
and of the straits which connect them with the Pacific Ocean

Depth

Location

Trenches

Straits

Mariana

11,034

Bering

Tonga

10,882

Kamchatka

4,420

Kuril-Kamchatka

10,382

Kruzenshtern

1,920

Philippine

10,265

Boussole

2,318

Kermadec

10,047

Nevel'

ca. 5

Far Eastern Seas

La Perouse

Sea of Japan

3,669

Sangar

130

Sea of Okhotsk

3,372

Korea

105

Bering Sea

4,420

This is of great significance for the development of the population of these
Seas.

The presence of one of the deepest oceanic trenches — the Kuril-Kamchatka
trench, which goes down to 10,382 m (according to G. Udintzev's latest cal-
culations, 10,542 m) — is a most important factor in the structure of the earth's
crust in the northwestern part of the Pacific.

The Kuril-Kamchatka trench (Fig. 324) is only one sector of the huge
Pacific Ocean ring of faults in the earth's crust, high mountainous forma-
tions and depths of more than 1 1 km (Mariana trench). Each trench is a

Fig. 323. Chart of the distribution of the continental shelf (1) continental

slope (2) and the deep floor (3) in the Seas of Japan and Okhotsk and

the Bering Sea (Ushakov, 1953).

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS

683

complex formation, some hundreds of kilometres wide (Fig. 325). It does not
consist merely of a mountainous range of islands (the Kuril bank is a double

Fig. 324. Sea-bed relief of the Sea of Okhotsk and the Kuril-Kamchatka
trench (Udintzev).

formation — the western range with summits above water and the submarine
eastern range, the ' Vityaz'). The southern hollow of the Sea of Okhotsk is
adjacent to the range of islands to the west; to the east of it lies the trench and
elevation of the plateau edge. This mountainous formation can be regarded

684

BIOLOGY OF THE SEAS OF THE U.S.S.R.

as a fault in the earth's crust and an advance of the mainland massif on the
ocean bed, leading to mountain formations.

Numerous volcanoes are situated on the outer side of the line of faults
(the Kuril Islands arc) ; on its inner side, towards the mainland, the earth-
quake epicentres descend deeper and deeper into the earth's crust, and under
the Sea of Okhotsk they reach a depth of 600 km.

The narrowness of the Kuril-Kamchatka trench is one of the most char-
acteristic features of the bottom topography thereabouts. The trench framed

by the 9,000 m isobath extends to
550 km ; its width, however, is no more
than 5 km. The 6,000 m isobath is
200 km long. The 5,000 m isobath
connects the northeastern part of
the Kuril-Kamchatka trench with the
northwestern end of the Aleutian
trench. The great development of
tectonic forms in its bottom topography
is also most characteristic of the
northern part of the Kuril-Kamchatka
trench. Faults (sometimes many
hundreds of metres long), submarine
landslides and the outcrop of ancient
main rocks sometimes lead to the
formation of a complex bottom profile.
The shores of Eastern Kamchatka,
except for their northern part, are made
of volcanic rock of different ages (V.
Zenkovitch, 1960). There are many
coastal features, such as the wide and fairly shallow inlets (Avachinsky,
Kronotsky and Kamchatsky Bays), and the peninsulas (Shipunsky, Kronot-
sky and Kamchatsky) which do not protrude far to the seaward. The shores
of Kamchatka, with its sandy beaches, are greatly affected by the swell.

The monotony of the coastline is broken by the wide Avachinsky Bay and
by the presence of coastal features of the fjord type. Wide areas of dry sand
or mud are often formed inside the bays and fjords. The regular, semi-
diurnal tides on the shores of Kamchatka reach a height of 2-5 m.

The slopes of the outer Kuril submarine range (the Vityaz range), the steep
slopes of the abyssal and submarine elevations on the edge of the ocean
bed are characterized by rocky outcrops (P. Bezrukov, 1955). Many of these
sites, especially in the Kuril Straits and on the slopes of the Kuril Islands, have
a gravel-pebble floor. At certain points there is in the deposits a considerable
admixture of the products of submarine eruptions — pumice, lapilli and vol-
canic slag.

Sand floors are greatly developed on the slopes of the coast of Kamchatka,
and in the region of the Kuril Islands (down to a depth of 3,000 m), while
diatomaceous oozes are accumulated in the trenches. In general the north-
western part of the Pacific, and the Sea of Okhotsk, are exceptionally rich in

Fig. 325. Block-diagram of the
Kuril-Kamchatka trench (Udintzev,
1955). 1 Sea of Okhotsk; 2 Kuril
Islands; 3 Pacific Ocean; 4 Sub-
marine Vityaz range; 5 Kuril-
Kamchatka trench; 6 Submarine
volcanoes ; 7 Earthquake epicentres.

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS

685

diatomaceous oozes (Fig. 326) ; this is the result of the intensive development
of diatoms in these regions.

Geological past of the Far Eastern Seas

The problem of the geological past and the palaeogeography of the Far Eastern
Seas is exceptionally important. The nature of the alterations endured and the
differences in the past of the Seas of Japan and of Okhotsk and the Bering

Fig. 326. Distribution of deposits of amorphous
silica produced by diatoms (as percentage of dry
weight of soil) (Bezrukov): 1 Less than 1%;
2 From 10 to 20% ; 3 From 20 to 30% ; 4 More than
30%.

Sea during the Tertiary and Quaternary Periods are two most important
problems.

In his work on the Quaternary geology of Hokkaido Island the Japan-
ese geologist Minato (1955) maintains the existence of a strong mainland
glaciation in the Ice Age, noting its traces on Hokkaido Island. Having
examined all the available data he considers there were two periods of con-
siderable fall of temperature (two Ice Ages, one much earlier than the other)
and great fluctuations of the sea-level, marked by a series of terraces at
different horizons up to a height of 200 m above sea-level. On the other side
Minato envisages considerable shifts of the coastline to seaward, during which
the Islands of Japan must have been joined to the mainland.

The Tertiary and Quaternary Periods of the history of the Far Eastern Seas
are characterized by the difference in the past of the Bering and Okhotsk
Seas on the one hand and that of the Sea of Japan on the other. The first two
basins retained their broad link with the Ocean ; the past of the Sea of Japan

686

BIOLOGY OF THE SEAS OF THE U.S.S.R.

was very complex, and it is still not sufficiently known. Was there a period of
complete isolation of the Sea of Japan from the Ocean, and were its waters
then fresh? Is H. Yabe's (1929) hypothesis true (Fig. 327)? Were the basins
of the Okhotsk and Bering Seas dry land at the beginning of the Quaternary

PRESENT-DAY DRY LAND

INCREMENT OF DRY LAND AT THE BE-
GINNING OF THE QUATERNARY EPOCH

INLAND BASINS ON SITES OF PRESENT- g|^=
DAY ADJACENT SEAS

PACIFIC OCEAN AT THE BEGINNING OF
QUATERNARY EPOCH

Fig. 327. Mainland relief of Far Eastern Seas at the beginning of the Quaternary

period (H. Yabe).

Period and to what period should the appearance of their deep trenches be
ascribed?

G. Lindberg's series of works on the palaeogeographic past of the north-
western part of the Pacific (1948, 1953, 1956) are most interesting. An
examination of the contemporary geographical distribution of fresh-water fish
has led this worker to the conclusion that in the recent geological past some
river systems now cut off from each other by the sea were then linked through
areas of the mainland which are now submerged. The examination of the
contemporary bottom topography of the Far Eastern Seas led Lindberg to the

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS 687

conclusion that these Seas were formerly dry land, either partly or even wholly ;
and that even during the Quaternary Period, when the single common river
systems did exist, the level of the Ocean underwent a considerable change (up
to 500 m). This worker suggests that during the Quaternary Period the Far
Eastern Seas underwent alteration of the phases of regression and trans-
gression no less than three times. In addition to such fluctuations of the sea-
level G. Lindberg also maintains that the formation of the Seas of Japan and
of Okhotsk and the Bering Sea trench was due to downwarping. He casts
doubts upon the permanent or even more or less prolonged existence of the
trenches and of the Pacific Ocean itself and of ' the existence in comparatively
recent times of a continental link joining the Islands of Melanesia, Micronesia
and Polynesia to the Hawaiian Islands and likewise to southeast Asia' (1948).

According to the latest opinion of Soviet geologists (P. Kropotkin, 1956,
I. Andreeva and G. Udintzev, 1958) the trench in the Sea of Japan is very
ancient (lower Palaeozoic). In its structure it closely resembles other trenches
on the western edge of the Pacific, and the bed of the Ocean ; it should there-
fore be regarded as a relict of this bed.

Bottom deposits of 1-5 km thick were found in the southern part of the Sea
of Japan by seismo-acoustic methods. Associated with this, many geologists
assume a raising of the edges of the Sea of Japan at the end of the Pliocene
Period, until the Sea was completely separated from the Pacific (P. Kropotkin,
1954, 1956).

The history of the existence of links between the Bering Sea and the Arctic
Ocean is equally obscure. The solutions of all these problems are most
important for the understanding of the history of the fauna and in particular
of such phenomena as amphi-boreal distribution.

The analysis of long cores from the sea-bed and the examination of their
content of the remains of diatomaceous Radiolaria, Foraminifera, spores
and plant pollen are exceptionally valuable for the understanding of the
palaeo-geographical past of the Far Eastern Seas and of the palaeo-climatic
changes.

T. Sechkina (1959) has analysed a 17 m long core obtained from the Vityaz
in 1957 from a depth of 3,504 m in the northern part of the trench in the Sea
of Japan, approximately on the latitude of the Strait of Sangara. The quanti-
tative and qualitative compositions of the diatoms were found to alter con-
siderably with the length of the core. Sechkina divided the core according to
its diatom content into five horizons (0 to 140 cm, 140 to 280 cm, 280 to
590 cm, 590 to 1,033 cm and 1,033 to 1,706 cm). The uppermost horizon
resembles the contemporary one in the composition of its diatoms ; the second
one differs from it greatly, reflecting a considerable decrease of temperature.
In contrast, the diatoms of the third horizon bear witness to a considerable
rise of temperature and there is in it a pronounced admixture of tropical
diatoms, while the Arctic ones are absent. The upper four metres of the fourth
horizon are, as it were, 'dumb', containing no diatoms. There is a thin (23 cm)
layer of cold-water Arctic flora of diatoms under it (the 'dumb' column cor-
responds to the beginning of a great fall in temperature). The 'dumb' layer
probably corresponds to the period of the greatest fall in temperature, to a

688 BIOLOGY OF THE SEAS OF THE U.S.S.R.

short period of diatom plankton vegetation, to a considerable loss of terri-
genous substances and to a dispersion of diatoms in its mass.

The 7 m long section of the core is characterized by the predominance in the
lower horizon of warm-water forms which, however, are not found at the
lower end of the core, and by the absence of Arctic species ; it resembles in its
composition the first and third horizons.

According to the data given there were two periods of glaciation (Ice Ages)
and two inter-glacial periods when the temperature was higher.

The 17 m long core may possibly have penetrated into the Quaternary
deposits ; during that period the Sea of Japan retained its marine nature. If
the Sea of Japan was ever isolated from the Ocean, this isolation cannot have
taken place in the second half of the Quaternary Period.

A. Zhuze (1954) examined in a similar way the remains of the diatoms in
the soils of the Okhotsk and Bering Sea beds, taking 27 m long cores from a
depth of 3,355 m in the Sea of Okhotsk and a 16-5 m core from 3,638 m in
the eastern trench of the Bering Sea. He distinguishes five main horizons and
establishes the synchronism of the alterations of the two Seas, which have the
same characteristics as the soils of the Sea of Japan. Zhuze has also estab-
lished the local sequence: in the upper 150 to 185 cm the composition of the
diatoms tallies with that of the present period. The second 3-5 m thick horizon
is characteristic of a period of lowered temperature ; while the third horizon,
lying inside the sediments at a depth of 5 to 1 1 m corresponds to the period
of the rise of temperature, the fourth again to a fall in temperature, and the
fifth to a rise.

Therefore this worker assumes also 'that the monoliths examined cover a
period of two Ice Ages and two inter-glacial epochs in the northeast of the
u.s.s.r.'. The Ice Ages are characterized by sediments with a weak qualitative
and quantitative development of diatoms, of predominantly Arctic forms, and
a considerable admixture of neritic and fresh-water forms ; the periods of
warming up by an increase of oceanic warm-water forms, and a great abund-
ance and rich variety of diatoms. The 27 m long core from the Sea of Okhotsk,
however, belongs entirely to Quaternary deposits.

Currents, salinity and temperature

Cold masses of water (Oyashio) move from the north along the whole of the
western coast of the Bering Sea, Kamchatka and the Kuril Islands, while the
strong warm current, Kuroshio — the Gulf Stream of the Pacific (Fig. 328) —
flows from the south along the shores of Japan to meet them. The warm
Pacific waters penetrate into all the three Seas. They enter the Sea of Japan
through the Korea Strait, the Sea of Okhotsk through the North Kuril
Straits and the Bering Sea through the Aleutian Straits.

In summer more abundant warm currents move farther north, penetrating
deeper into the Far Eastern Seas. In winter the main streams of Kuroshio
move northeastward and eastward much farther to the south, and the intensity
of the currents is greatly slackened in the northern part of the Ocean. This
can be seen even better from the distribution of surface isotherms (Fig. 329).
In summer the Aleutian Islands are skirted by the 10° isotherm and in winter

GENERAL CHARACTERISTICS OF THE EASTERN SEAS

689

by that for 2°; at that season the isotherm 12° lies close to 40° N latitude,
where in summer the 20° isotherm passes.

The southern limit of the cold layer is subject to substantial fluctuations
over many years (M. Uda, 1955), which have a pronounced effect on biological

Fig. 328a. Diagram of continuous surface currents (summer) (Dobro-

volsky, 1948).

phenomena. In 1933 this limit passed close to the Kuril Islands; in subse-
quent years it moved farther and farther southeast, and in 1953 it had moved
away between 200 and 500 miles from its position of twenty years earlier.

Fig. 328b. Diagram of continuous surface currents (winter) (Dobrovolsky).

The Ivasi catastrophe may have been connected, either directly or indirectly,
with these fluctuations.

A clear picture of the changes of temperature, salinity, oxygen, phosphorus
and silica content is given in Figs. 330, 331, 332 and 333.

The amplitude of temperature fluctuations becomes less with depth. In the
Kuroshio region the amplitude is 13-5° (10-5° to 24°) on the surface; at a
depth of 200 m it is 2-5° (9° to 11-5°); at 500 m barely one degree; while at

■Я
о

-С

о
й

Он
(14

-с

я
m

692

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Fig. 330. Distribution of (a) ten- and (в) fifty-metre isotherms in Bering Sea and
Sea of Okhotsk in July to September (Ushakov, 1953).

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS 693

140*

150° 160

Fig. 330c. Isotherms at a depth of 200 m (July to September) (Ushakov, 1953).

Fig. 331a. Isohalines at a depth of 10 m (July to September) (Ushakov, 1953).

694

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Fig. 331b. Isohalines at a depth of 50 m (July to September) (Ushakov, 1953).

tMW1

gP*- ■■ -55

170'

Fig. 331c. Isohalines at a depth of 200 m (July to September) (Ushakov, 1953).

H IS 1-е П 1-8 19 20 2-1 22 23 2-4 2-5 344 34-5 34-6 341

ml/l

2 3

1 ■

1 1 1

Ч'

Ч *

\$>

)"РЬ

/7777 1 j

и2

i /777772 , ,

01 0-2 0-3 ОЬ

mg-at/L

Fig. 332. Vertical distribution of temperature, salinity and oxygen content in

Kuril-Kamchatka trench and Philippine deep (Bogoyavlensky). Continuous line—

1 5 May ; dotted line— 30 June 1 953 in Kuril-Kamchatka trench ; chain-dotted line —

23 January 1948 in Philippine deep. Data from Albatross.

ml/l

12345 67 89

mg/m3

10 20 30 40 SO SO 70 80 90

mg/m3

1000 2000 3000 4000

\^j?

j?^

500

- ь

-1 '

1000

1 1
-V

\ 1

- I1

- 11
II

- u

1500

- ll

- ii
ii

Oxygen

- у

i i i i i

01 0-2 0-3 0-4 0-5 OS 0-7 08

mg-at/L

10 20 30

mg-at/m3

50 100 150

mg-ai/m3

Fig. 333. Distribution of oxygen, phosphorus and silicon in the waters of the
'shallows' of the Kuril-Kamchatka trench in May and June 1953 (Bogoyavlensky).
Continuous line — 1 5 May ; dashed line — 30 June.

696

BIOLOGY OF THE SEAS OF THE U.S.S.R.

depths of 1 km and below the temperature remains practically constant
throughout the year.

As is shown by the dynamic analysis of water masses (K. Bogoyavlensky
and V. Burkov, 1948) in the zone of the convergence of cold and warm waters
the currents lose their rectilinear course ; the main streams begin to meander
and several cyclonic and anticyclonic swirls are formed (Fig. 334).

Even during the warmest season of the year the temperature of the water
in the Bering and Okhotsk Seas does not rise to any extent. The upper layer
is warmed only to temperatures of between 6° and 10°. In deeper layers

Fig. 334. Chart of movements of surface waters within zone of contact of

Kuroshio and Oyashio currents, May 1955. Vityaz voyage shown by a

double line (Beklemishev and Burkov).

there is a considerable difference between the Okhotsk and the Bering
Seas (P. Ushakov, 1953). The Sea of Okhotsk has a thick intermediate layer
with a temperature below freezing point throughout. In the Bering Sea the
intermediate cold layer is not so strongly developed ; its temperature is above
freezing point and it is concentrated mainly in Anadyr and Olyutorsky Bays.
Deeper down the temperature of the water is somewhat higher, up to 3° in
the Bering Sea and up to Г in the Sea of Okhotsk.

As a result of the fall of temperature in the surface layers floating ice is
formed, thickest in the Sea of Okhotsk (Fig. 335) and thinnest in the north
and northeastern parts of the Sea of Japan. An intensive formation of ice
begins in the northern parts of the Bering and Okhotsk Seas as early as
December; it reaches its greatest development in March, when floating ice
covers all the Okhotsk Sea and the greater part of the Bering Sea. In the Sea
of Japan the ice may sometimes reach the Korean shores. Ice remains even
in June in the most northerly and westerly parts of the Sea of Okhotsk and
in the north of the Bering Sea, especially in the Bay of Anadyr. As late as May

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS

697

there is ice in the northern part of the Tartary Strait. The ice is carried out
into the Ocean through the Kuril Straits and along the Kamchatka coast.
Large areas of the Okhotsk and Bering Seas are covered with ice for almost
eight months. As for the other seas of the u.s.s.R., this phenomenon is found
only in those off the Siberian coast.

The salinity of the Far Eastern Seas (apart from on their littoral and in the
mouths of the rivers) does not exhibit pronounced fluctuations (P. Ushakov,
1953), but varies merely within the limits 31 to 33-5%0 (Fig. 331). The surface
waters of the northwestern part of the Sea of Okhotsk (the influence of the

Fig. 335. Mean limit of floe-ice from March to June: 1 March; 2 April; 3 May;

4 June (Ushakov, 1953).

Amur) and of the Bay of Anadyr (the Anadyr River) have lost some of their
salinity. At a depth of 50 m their salinity varies within the limits 32-5 to 33%0
and at a depth of 200 m within those of 33-25 to 33-50%0 (P. Ushakov, 1953).

The salinity of the Sea of Japan is somewhat higher ; along the western
coast the salinity of the surface waters is below 34%0, along the eastern coast
it is above 34%0. With depth this difference disappears and the salinity rises to
34-5%0.

Vertical changes of temperature, salinity, and the contents of oxygen,
phosphorus and silicon over the 'shallows' of the Kuril-Kamchatka trench
are shown in Figs. 332 and 333.

The oxygen conditions of the Okhotsk and Bering Seas are practically the
same as those of the adjacent parts of the Pacific. This is one of their most
characteristic peculiarities as 'inlets' of the Pacific. Their oxygen content
decreases gradually with depth, reaching only 10 per cent of saturation in the

698

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Sea of Okhotsk and only 7 per cent in the Bering Sea at depths of between
1,000 and 1,500 m. Farther down the amount of oxygen rises again to 20 to
25 per cent of saturation.

The satisfactory oxygen supply in the deeper waters of the Sea of Japan, in
spite of the isolation of its deep trench, is of special interest. The oxygen con-
tent of the deep waters of the Sea of Japan does not fall below 67 to 70 per
cent of saturation (P. Ushakov, 1953). This is due to strong processes of verti-
cal circulation in autumn and winter, caused by the cooling of the surface
waters.

Three main masses of water (Fig. 336) may be distinguished in vertical dis-

STATIONS

322S 3223 322S 3230 323f 12J2 3233

-b-

H 1000

Fig. 336. Boundaries of water masses and distribution of two species
of boreal Copepoda on the cross section southeast of Sangar Strait
(Beklemishev and Burkov). A — Boundary of water masses; В —
Front of Kuroshio current ; С — Upper boundary of the distribution
of Calanus cristatus (boreal cold-water species); D — Places of
occurrence of Calanus pacificus (south boreal thermophylic species).
la — Modified subtropical water mass in the zone of mixing ; lb
Subtropical water mass (proper); 2 — Cold intermediate layer; 3
— Zone of interaction of subtropical and sub-Arctic waters ; 4 — ■
Intermediate layer of lowered salinity ; 5 — -Warm intermediate layer ;
6 — Deep oceanic waters.

tribution over the Kuril-Kamchatka trench and in the Bering Sea (K. Morosh-
kin, 1955 ; A. Bogoyavlensky, 1955 and D. Smetanin, 1958 and 1959). These are:

(7) Upper sub-Arctic water masses (0 to 200 m), wherein all indices are
subject to most pronounced seasonal alterations. These are the waters modi-
fied by local conditions (in the Bering Sea and over the Kuril-Kamchatka
trench). In their turn they may be divided into the surface layer subject to
summer heating (0 to 50 m), and a deeper (down to 200 m), cold intermediate
layer. The salinity of these waters is slightly higher than 32%0.

During the period of spring bloom the amount of oxygen reaches 1 30 to
175 per cent of saturation ; the amount of phosphates in terms of phosphorus
decreases from 60 or 70 to between 20 and 10 mg/m3 or less ; that of nitrates

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS 699

from 350 to between 20 and 40 mg/m3, and of silicon from the range 1,000 to
1,300 down to 200 to 300 mg/m3. Phytoplankton production was calculated
from the amount of plant food as 75 g of carbon under 1 m2 (D. Smetanin,
1959). Moreover, if in the coastal waters off Kamchatka the 'yield' during
the spring reaches 125 g/m3 in terms of carbon, in the open regions of the
Ocean it falls to 5 or 6 g/m3, i.e. by about 25 times. Vertical changes in the
content of oxygen and plant food and in the ranges of temperature and
salinity in spring at various places in the central Kuril-Kamchatka trench
are given in Tables 284, 285 and 286.

Table 284

Depth Oxygen Phosphorus Silicon

m (percentage) (mg/m3) (mg/m3)

105-132

9-56

240-1,000

108-113

43-59

560-1,020

100-104

58-69

860-1,060

100

92-97

71-74

1,120-1,200

200

24-90

76-84

1,180-1,700

Table 285

Depth Temperature Salinity Oxygen

m °C %0 (percentage) pH

1-30

1-3

33-24

33-20

8-08

8-55

8-13

8-17

1-10

0-58

33-26

33-29

8-08

7-71

8-12

809

100

0-90

116

33-26

33-42

806

5-90

805

8-02

200

2-68

2-48

33-82

33-74

2-70

3 00

7-80

7-83

300

3-32

2-46

3402

33-84

0-85

2-54

7-71

7-79

500

3-14

301

34-20

34-10

0-50

104

7-61

7-64

1,000

2-60

2-40

34-45

34-42

0-61

0-80

7-61

7-71

1,500

2-20

2-17

34-59

34-55

1-05

102

7-78

Table 286

Oxygen Phosphate Ammonium

Depth Temperature (percentage) phosphorus nitrogen Silicon

m °C (mg/m3) (mg/m3) (mg/m3

1-60

122

375

1,400

100

0-80

390

1,400

200

3-15

590

2,740

500

3-10

6-5

615

3,700

1,000

2-45

600

4,260

2,000

1-72

560

4,560

4,000

1-44

480

4,160

8,000

1-92

—

3,900

700 BIOLOGY OF THE SEAS OF THE U.S.S.R.

(2) The lower sub-Arctic water mass may in its turn be divided into two
layers — a layer (200 to 1 ,400 m) with a much lowered oxygen content, an in-
creased amount of nutrient salts and a higher temperature; and a lower-
temperature layer with an oxygen content of 32 to 46 per cent of saturation.
This water mass likewise may be regarded as locally modified water, which
enters mainly from the Bering Sea in the winter and sinks down from the
Sea of Okhotsk. The rate of the movement of these waters southwards
reaches 10 to 13 cm/sec at a depth of 600 m.

(J) Deep Pacific Ocean water masses (below 1,400 m) and bottom water,
which is in constant reaction with bottom sediments. Deep water masses
are characterized by their great homogeneity and by their comparatively low
oxygen content (D. Smetanin, 1959) (3 to 4 ml of oxygen per litre as against
5 or more in the Atlantic Ocean) and by their increased content of plant food.
Smetanin considers that this phenomenon is linked with the greater age of
these waters as compared with those of the Atlantic.

In Smetanin's expression (1959) the waters of the ultra-abyssal of the Kuril-
Kamchatka trench are, as it were, deep water spread out vertically ; they are
in constant movement (probably from north to south) at the same speed as
the waters above them (A. Bogoyavlensky, 1955). The temperature of this
water falls to 1 -45°, but below 4,000 m it rises to 2- 1 5° at the bottom (adiabatic
process) ; its salinity increases to 34-75%0, its oxygen content to 3-6 ml per
litre and the amount of phosphates to 60 mg/m3 in terms of phosphorus.

IV. COMPOSITION OF FLORA AND FAUNA

The flora and fauna of the Pacific Ocean are in general richer than those of the
Atlantic, and similarly the population of its northwestern part is considerably
richer than that of the corresponding parts of the Atlantic.

The general taxonomic composition of the flora and fauna of the north-
western parts of the Pacific cannot be considered as well known ; some groups
have been studied in sufficient detail, others much less (Porifera, Coelenterata,
Gastropoda and others) ; the taxonomy of some groups — Turbellaria, Nema-
toda, Actinia, bottom nemertines, Harpacticoidea and others — has hardly
been established at all. The composition given in Table 287 should only be
taken as preliminary.

The complete list of the fauna of the northwestern part of the Pacific Ocean
contains no fewer than 6,000 animal species. It is apparently considerably
richer than that of the Atlantic Ocean fauna in the same latitudes.

The richness of the fauna of the Far Eastern Seas and the antiquity of its
origin is accentuated by its abundant parasite fauna, studied by V. Dogjel
and his pupils (A. Akhmerov, B. Bykhovsky and others).

About 900 parasite forms are known now, and one may assume that their
actual number is much greater. This number is composed of species of 1 30
Protozoa, 400 Trematoda, 20 Cestoidea, 120 Nematoda, 80 Crustacea, 10
Gastropoda and 120 others.

The richness of the flora and fauna of the northern part of the Pacific may
be demonstrated also from many other examples. Thus, for example, among

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS

701

Table 287. Composition of flora [A. Zinova, 1954, I960 and E. Zinova, J 940, J 954]
and fauna [P. Ushakov, 1953 and P. Ushakov and others 1955, with some additions]

Sea of Japan

Sea of

Bering Sea

Group

[northern part]

Okhotsk

[western part]

Total

Sea-weeds :

Diatoms [plankton]

—

Green algae

Brown algae

109

105

143

Red algae

214

136

246

Total

379

301

138

468

Invertebrates :

Foraminifera

>160

>400

>140

—600

Radiolaria

—

120

106

—200

Ciliata

—

—25

—

Porifera [Cornacuspongida

] 70

101

>150

Coelenterata [Hydroidea]

185

132

>200

Nemertini [pelagic]

—

Polychaeta

>300

244

220

420

Hirudinea

Echiuroidea

-20

Sipunculoidea

Bryozoa

—250

>200

—

—350

Copepoda [pelagic]

224

Cirripedia

—20

Isopoda

-175

Amphipoda

254

250

210

—500

Cumacea

Euphausiacea

—

Decapoda

125

—175

Pantopoda

—50

Bivalvia

—

—150

>200

—350

Gastropoda

—

154

—

-400

Cephalopoda

Amphineura

[all molluscs]

[-300]

[-262]

[-250]

[-750]

Brachiopoda

Echinodermata

—188

-160

186

>275

Ascidia

-80

Vertebrates :

Pisces ГТ. Rass]

615

276

315

—800

Mammalia

—

Total number of animals

>3,250

> 3,000

>2,500

-5,200

702 BIOLOGY OF THE SEAS OF THE U.S.S.R.

130 species (64-6 per cent) and 30 genera (90 per cent) of the family Lamina-
riales, 84 species and 27 genera are known in the northern part of the Pacific
Ocean (mainly along the Asian coast) ; in the northern part of the Atlantic 8
species and 5 genera are known. Thirty-five species of Laminariales are known
for the Bering Sea, 40 for the Sea of Okhotsk and 32 for the Sea of Japan
(4 species only are known for the Yellow Sea).

P. Ushakov (1953) points out 'that the occurrence in many groups of
"bunches" or "fans" of numerous very similar and, in most cases, not suffi-
ciently distinguished new subspecies and varieties is a distinctive feature of
the Far Eastern fauna. It bears incontestable witness to very violent contem-
porary processes of the formation of new species. These processes, moreover,
are most intensive in the Sea of Okhotsk.'

Indeed, this phenomenon of the specific richness of the flora and fauna of
the northwestern area of the Pacific Ocean (within the limits of the boreal
region) is observed not only in the Far Eastern Seas but also in the composi-
tion of the deep-water fauna of the adjacent part of the Pacific Ocean.
Echiuroidea, Cephalopoda, Amphipoda, Isopoda, and especially Pogono-
phora (A. Ivanov, 1959) and Pisces may serve as examples. This is possibly
due partly to the insufficient investigation of this region of the Ocean ; but
mainly it is the result of the considerable antiquity and great variety of the
physico-chemical conditions of the northwestern part of the Pacific and of
some specific geochemical peculiarity.

Some fauna groups of the northwestern part of the Pacific display an
abundance of species both in the shallow and deep-water fauna. Foramini-
fera, Radiolaria, Polychaeta, Amphipoda, Mollusca, Echinodermata, Pogo-
nophora, Pisces and Mammalia belong to these groups. Note that the last
three belong to these groups ; Pogonophora is particularly indicative in this
respect. Half of all the known species of this group have been recorded for the
northwestern part of the Pacific; not only the species but likewise the
genera, families and orders (Fig. 337). In contrast, as yet only one representa-
tive of the genus Siboglinum, out of 1 1 genera and a large number of species,
has been found in the Altantic Ocean.

Plankton

The group Calanoida occupies an exceptionally dominant position in the
oceanic plankton of the temperate zone (boreal region). Among the great
choice of species of this group the most significant in the Far Eastern Seas are
the following: Pseudocalanus elongatus, Calanus tonsus, Eucalanus bringii,
Calanus cristatus, Metridia pacifica, Scolecithricella minor and Pareuchaeta
japonica. C. cristatus, C. tonsus, E. bungii, P. japonica, M. pacifica, Sc. minor
var. orientalis and others are endemics of the Far Eastern Seas (K. Brodsky,
1955). The boreal aspect of this group of Calanoida is accentuated by the
close resemblance of many of the above-mentioned forms to the boreal
Atlantic forms.

The boreal Far Eastern plankton is replaced by the tropical plankton in the
zone where the waters of the currents of Kuroshio and Oyashio meet. This
group is predominant in the upper layer of the Bering and Okhotsk Seas ; a

GENERAL CHARACTERISTICS OF THE EASTERN SEAS

703

considerable admixture of cold water forms is observed only in the very
northern part of these Seas. Its distribution is limited in the Sea of Japan by
the warm waters of the Tsushima current, which brings warm-water plankton.
Bathypelagic Calanoida (400 to 3,000 m) are more widely distributed ; how-
ever, they disappear completely from the fauna of the Sea of Japan (except

Oligobrachia dooieli
BirsTelma viTjasi

Sibog

Stboq

S.bog
Sibog

ilteryi

num cincTuTum

num peMucidum
num minuTum
nam pus.Uum

Siboglmum fedofovi - ©

Siboglinum plumosum - «.

НерГаЬгасК'Э. abysiicota '- D

HepTabrachia gracilis - и

HepTabrachia subtilis - о

HeptabracWa bennqensis- в

Mybrachia annuUta в

Ро[ц.ЬгэсЫа barbafa

(ongiss
Larnetlisabella zachsl
Lamellisabella johan»!
Sp'robrachia grandis
5pirobra;hid ber.lemist
Diplobrachia japonic

Fig. 337. Distribution of Pogonophora in northwestern
part of the Pacific Ocean (Ivanov, 1959).

for certain upper bathypelagic forms) which are retained in the shallow
straits.

Two hundred and twenty-four species of Calanoida have been established
for the northern part of the Pacific Ocean, including 39 for the Sea of Japan,
71 for the Sea of Okhotsk and 49 for the Bering Sea.

Among the Calanoida of the Far Eastern Seas certain species are of excep-
tional significance for fish and cetaceans. Off the eastern coasts of Kamchatka
Eucalanus bungei and Calanus cristatus form the main food of the herring. In
the Sea of Japan the pilchard feeds mostly on Paracalanus parvus, Pseudo-
calanus elongatus and Calanus pacificus. The whales Balaenoptera physalis,
B. borealis, B. musculus and Megaptera nodosa feed on Copepoda, mainly
Calanus cristatus.

As has been mentioned above, the sub- Arctic waters of the Kuril current
(Oyashio) meet the warm waters of Kuroshio off Honshu Island in 40° to

704

BIOLOGY OF THE SEAS OF THE U.S.S.R.

42° N latitude and react on each other. The boundaries of these zones agree
closely with the distribution of certain mass forms of plankton (Fig. 338).
To the north of the zone of mixing of the waters plankton is typically boreal,
with a predominance of Calanus cristatus, C. plumchrus, Eucalanus bungii
bungii and Metridia ochotensis (K. Beklimishev and V. Burkov, 1953). To
the south of it Velella and Janthina become predominant, while large masses

Fig. 338. Distribution of zooplankton communities in
the surface waters of the northwestern Pacific in August
to October 1954. 1 Boreal complex; 2 Zone of mixing;
3 Tropical complex. Dashed line is an 18° isotherm on
the surface of the water (Bogorov and Vinogradov, 1955).

of Doliolum and Salpae, Lepas, Physalia, Porpita, Cestus and others make
their appearance.

This type of replacement of the population of certain waters is clearly seen
in the phytoplankton too (G. Semina, 1958) (Fig. 339). Bogorov has given an
exceptionally clear and complete picture of the distribution of zooplankton
within the zone of the meeting of the Kuroshio and Oyashio currents (the
Polar front). North of latitude 40° to 42° surface waters have a winter tem-
perature below 3° and a summer temperature of up to 14° or 15°. South of this
zone of sub-Arctic convergence (the Polar front) the temperature rises to
26° to 28° in summer, while in winter it is 18° to 20°. The convergence zone is
100 miles wide in summer and several times wider in winter. To the north of
it the boreal plants {Thalassiosire nordenskjoldii, Chaetoceras convolutus, Ch.
atlanticus, Ceratium longipes) and the animals {Calanus plumchrus, Eucalanus
bungii, Calanus cristatus, Sagitta elegans, Euphausia pacifica, Thysanoessa

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS

705

longipes) and other forms are predominant in the surface plankton ; they are
replaced in the south by the sea-weeds Rhizosolenia bergonii, Chaetoceras
lorenzianus, Climacodium biconcavum, coccolithines, and animals, Cestus
amphitrites, Velella, Physalia, Pteropoda and Heteropoda ; and from among
the Copepoda members of the genera Herocalanus, Undinula, Copilia, Sap-
phirina, Salpas, Halobates and many others.

Since the convergence zone has no population which is peculiar to itself

140° 145° 150° 155° 160° 165° 170*

140

145

150

155

160"

165"

170

Fig. 339. Distribution of phytoplankton (as percentage
of total number of species) in boreal waters, zone of
mixing and northern waters of Kuroshio. 1 Cold water
species ; 2 Temperate cold water species ; 3 Temperate
species; 4 Warm water species. August to October
1954 (Bogorov).

alone in this part of the Pacific, Bogorov thinks that it does not possess the
importance of a subtropical zone but only of a ' blending ' zone, of the meet-
ing of the tropical and boreal planktons. In the boreal waters north of the
convergence zone peridinean sea-weeds constitute about one-third of the
total number of plankton species, while south of it the number of diatom
species is three or four times greater than that of the peridineans. In the
northern part boreal phytoplankton species constitute 79 per cent (I. Smirnov,
1956), to the south 0-5 per cent; warm-water species, however, form 93-5 per
cent. In general phytoplankton and zooplankton are similar in distribution.
Many plankton sea- weeds, among them Rhizosolenia alata and Coscinodiscus

706

BIOLOGY OF THE SEAS OF THE U.S.S.R,

viridis as cold-water forms, and Planktoniella sol and Vultar sumatranum
as warm-water forms, may serve as good indicators of the warm (Kuroshio)
and cold (Oyashio) waters of the northwestern part of the Pacific Ocean
(G. Semina, 1958). Alterations in the plankton density (Fig 340) and in the
indices of its primary production (Fig. 341) are just as characteristic. Off the
Kamchatka coast primary production in the autumn of 1955 was 20 times
higher than in the tropical region. Plankton biomass in the waters adjacent to
the Kuril Islands is on the average 200 mg/m3 in autumn. Increasing gradually
to the southeast, it becomes more than 500 mg/m3 within the region of greatest

140'

145

160

165°

Fig. 340. Distribution of zooplankton biomass in
0 to 100 m layer of the northwestern Pacific, August to
October 1954. 1 Above 500 mg/m3; 2 From 250 to
500 mg/m3; 3 From 100 to 250 mg/m3; 4 Below 100
mg/m3 (Bogorov and Vinogradov).

vertical mixing (V. Bogorov and L. Vinogradov, 1955), reaching at times
2,000 to 3,000 mg/m3. Still farther to the southeast the plankton biomass falls
to 50 or even 20 mg/m3. However, it has to be taken into account that in the
warm tropical waters the number of plankton generations is considerably
higher and the period of multiplication much longer, thus compensating for
the small indices of isochronous biomass. In the Kuril-Kamchatka region,
for instance, Calanus plwnchrus has only two multiplication maxima, the
spring and autumn ones, and only two seasonal generations. The dominant
forms of the surface euphotic zone (0 to 200 m) in Kuril (boreal) waters have
been given above.

In May and June 1953 the 0 to 200 m layer contained 31-2 per cent of the
total zooplankton biomass of the whole huge water column of the Kuril-
Kamchatka trench. The transition zone immediately below it contained

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS

707

another 31-8 per cent. The 4 km layer of the deep waters of the trench held
only 2 per cent of the plankton biomass of the 8 km deep-water column. The
plankton biomass of the 0 to 50 m layer varies from 100 to 1,100 mg/m3 in
different places and at different hours of the day. A pronounced decrease of
plankton biomass, followed by a consecutive increase in the 200 to 300 m
layer, is characteristic of the cold intermediate layer of the Kuril region.
Farther down the biomass decreases rapidly to between 1,000 and 1,200 m,
after which its rate of fall decreases ; but at a depth of 6 to 8-5 km it falls to
0-5 mg/m3. Within the trench itself at this depth there is only 1-2 g/m2 of

Fig. 341. Average diurnal production of carbon,

mg/1, in the northwestern Pacific. August to

October 1954, determined by the oxygen method

(Bogorov and Beklemishev).

plankton biomass. Some species of Copepoda, Amphipoda and Ostracoda
are characteristic of the ultra-abyssal plankton. Many planktons there lose
their red colour, which is typical of the deep-water plankton, and acquire a
dirty grey colour. Apparently (V. Bogorov and L. Vinogradov, 1955) the
differences in the quantitative development of plankton in the boreal and
tropical regions of the northwestern part of the Pacific are retained even with a
transition to the deep floor (Fig. 342), hence the suggestion that the organic
substances of the production zone are carried away in the vertical direction
more than they are in the horizontal. Life phenomena which develop in the
surface zone of the Ocean influence bottom fauna and the organic components
of the sea-bed. The distribution of silica in the soils of the northwestern part
of the Pacific Ocean, corresponding to the abundant development of plankton
diatoms in the surface layer, is a good illustration of this correlation (Fig. 326).
M. Vinogradov (1954) has established some curious phenomena of the

708

BIOLOGY OF THE SEAS OF THE U.S.S.R.

vertical migrations of plankton. Diurnal vertical migrations of many plankton
species of the surface zone are either absent or only feebly developed, being
determined either by the season of the year or by the age of the organism,
the latter being much more important. On the contrary, species inhabiting

much greater depths (for instance
Metridia pacifica, M. ochotensis, Para-
themiato japonica) descend many
hundreds of metres and rise again.
There are reasons for thinking that
throughout the 5 km deep Ocean waters
plankton follows a steplike system of
vertical migrations.

Apart from the diurnal vertical
migrations, ranging between 300 and
5,000 m, numerous crustaceans have
seasonal migrations extending for
Calanus tonsus and C. cristatus to 2 or
3 km (K. Brodsky, 1956).

K. Brodsky (1956) in his attempt to
divide the pelagic zone into districts
correctly takes the quantitative signifi-
cance of certain plankton species
(number of specimens per m3) as the
basis of his work. He uses only one
dominant plankton group, the
Calanoida, for the zonation of the Far
Eastern Seas. Certain individual species
are characterized by several quantita-
tive indices — the frequency of their
occurrence, the number of specimens

1000

'l /2

3000

3500
4000

100

1000 mg/m3

Fig. 342. Vertical distribution of zoo-
plankton biomass in different layers
at the deep-water stations in the
northwestern Pacific. / Tropical
waters; 2 Boreal waters (Bogorov
and Vinogradov).

per m3, the percentage of the num-

ber of specimens to the total number
of Calanoida. The main forms of
Calanoida are: Pseudocalanus elongatus, Calanus tonsus, C. cristatus,
Eucalanus bungii, Metridia pacifica, Scolecithricella minor, Pareuchaeta
japonica and Microcalanus pygmaeus. Brodsky's proposal to include the
northwestern part of the Seas of Japan and of Okhotsk, and of the Bering
Sea, and the southeastern part of the Chukotsk Sea is based on the
distribution of Calanoida in the boreal regions. Moreover, he distinguishes
the northern Japanese, northern Okhotsk and northern Bering provinces, all
three with Calanus finmarchicus as a predominant form; this is widely distri-
buted in the boreal and Arctic waters of the Atlantic and Arctic Oceans.
Brodsky calls the fauna of these three provinces pan-Arctic: 'similar to the
Arctic, but not identical with it, i.e. analogous but not homologous'.

The vertical distribution of Calanoida in the northwestern part of the
Pacific Ocean is as follows : poor variety of species in the surface waters ; a
still smaller number of species in the cold intermediate layer; the greatest

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS 709

abundance of species in the bathypelagic zone, and a decrease in the number
of species in the abyssal. The same phenomenon has been noted by V. Dogjel
and V. Reschetnjak (1956) for the Radiolaria, when the greatest specific
abundance was at a depth of 200 to 2,000 m.

Benthos

The fauna of the littoral and sublittoral. The exceptionally rich flora and fauna
of the littoral and sublittoral of the Ocean coast of the Komandorski
Islands, of Kamchatka and the Kuril Islands have not so far been investi-
gated sufficiently. E. F. Gurjanova (1935) has given a colourful description of
the littoral fauna of the Komandorski Islands.

The littoral flora and fauna of the Komandorski Islands are very rich both
in numbers and variety. The sea surrounding the islands does not freeze ; its
water has an almost oceanic salinity. Even in winter only close inshore and
after a storm does the temperature of the surface water fall to —1-2° С ;
farther out into the sea it varies from 0-5° to 1-5°, and reaches 9° to 11° in
summer. At greater depths the temperature is still 2° to 2-5° even in winter
(Gurjanova). Littoral flora and fauna Jive within the 4 m layer, and some
individual organisms are considerably nearer to the surface. The tidal zone
of the Komandorski Islands is characterized by the irregularities of the tides,
as a result of which it may either remain submerged for several days or dry out.

'The Bering expedition', writes Gurjanova, 'cast up by a storm on the
shores of Komandor, found there herds of fur seals, millions strong, thou-
sands of sea lions, herds of sea cows and sea otters and thousands of polar
foxes. All these large animals fed off the shores of the islands on sea-weeds,
invertebrates and fish . . . the bottom of the sea round the islands is over-
grown with whole submarine forests of huge sea-weeds. These Macrocystis
and Nereocystis sea-weeds, sometimes attaining heights of some dozens of
metres (up to 300 m), Alariafistulosa, with a thallus 10 to 12 m long, Lami-
naria, Thalassiophyllum, and others, form dense submarine forests, which
rise to the surface from depths of 20 or 30 m.' This vegetation has a very rich
fauna of invertebrates. The Bering Island littoral is inhabited by 7 species of
chiton, 6 species of Anomura, 6 of crabs, 4 of starfish, 2 of sea urchins, 2 of
holothurians and a multitude of species of worms, molluscs crustaceans,
actinians, bryozoans and ascidians. This fauna is peculiar to the softer soils
of the littoral. 'However, the cliffs which rise above the water level', writes
Gurjanova, 'beaten by the swell, are also densely inhabited. Thick beds of
vigorous Laminaria Jongipes, L. dentigera, Thalassiophyllum clathrum, with
their powerful rhizoids, whole carpets of soft, ramified and cortical bryozoans,
Porifera and actinians, continuous settlements of the large acorn barnacles
Semibalanus cariosus, and complex ascidians, develop intensely on these cliffs,
constantly washed by the swell. Red algae, bright red sponges and large
chitons rise here from the sublittoral.' Quiet coves with sandy bottoms have
columns of the polychaetes Schizobranchus insignis, and large gastropods,
Argobuccinum, spp. and Natica clausa, while the sands are inhabited by a
multitude of large-sized Bivalvia — Spisula, Siliqua and Tellina. The Komandor
littoral fauna in general has a warm- water aspect, reflected by the variety of its

710 BIOLOGY OF THE SEAS OF THE U.S.S.R.

biocoenoses and a large number of warm-water forms of sea-weeds and
invertebrates (Thalassiophyllum, Amphiroa, Acmaea pelta, Strombella,
Pholas crispata, Pholedidea penita, Tapes stominea, and others) and by the
rich development of the sublittoral fauna.

The narrow shelf zone of the eastern shores of Kamchatka and the northern
Kuril Islands has also an exceptionally rich bottom fauna (Bivalvia, Poly-
chaeta, Crustacea, Echinodermata and others), which in the summer attracts
numerous shoals of commercial fish — pollack, cod, flatfish, sea bass and
Kamchatka crab. The intensive development of the fauna is the result of the
abundance of littoral vegetation and plankton. A. Kuznetzov carried out a
detailed investigation of these regions and established (1959) the presence of
16 biocoenoses; Modiolus modiolus, Mytilus edulis, Porifera, Hydroidea,
Echinarachnius parma, Astarte rollandi, A. alaskensis, Macoma calcarea, Car-
dium ciliatum, Ophiura sarsi, Ophiopholis aculeata, Pavonaria finmarchica (?),
Asteronyx loveni, Astarte icani, Ampelisca macrocephala, Brisaster townsendi,
Aci/a castrensis, Brisaster latifrons, Artacama proboscidea, Ammotrypane aulo-
gaster, Rhodine gracilior, Pista vinogradovi.

The predominance of Arctic and Arctic-boreal species (30 species or 48-3
per cent of the 64 dominant and characteristic species) in the fauna is evident
from this list of the composition of the main forms and a quantitative analysis
of their predominance. The eastern shores of Kamchatka and of the northern
Kuril Islands are washed by cold waters flowing from the Bering Sea. The
boreal species constitute 38-8 per cent of the main species, and the cosmo-
politan ones 9-7 per cent (6 species). The number of subtropical-boreal species
among the main species is very small — only 2, or 3-2 per cent. This is in
strong contrast with the composition of the shelf fauna of the southern Kuril
Islands. Many of the above mentioned forms (9 out of 20) are mass forms of
the lower Arctic seas including the Barents Sea. The somewhat original verti-
cal distribution of the cold- and warm-water zoogeographical communities
corresponds to the distribution of the water masses (A. Kuznetzov, 1959).
Arctic-boreal biocoenoses are developed most intensely at a depth of 100 to
200 m (at a temperature of about 0° C) and at 500 to 1 ,200 m (at a temperature
of 2° to 2-5°). The water mass at 0 to 100 m deep is considerably warmed up
in summer, while at 200 to 500 m the temperature remains between 3° and 4°.

The bottom fauna of these regions is characterized by high density indices
(Table 288).

The rich littoral population of the southernmost Kuril Island, Kunashir
(O. Kusakin, 1956), has much in common with the littoral population of the
southern part of the northern Japanese shore, some areas of southern Sakha-
lin and the shore of the southern Kuril Islands, and it can be included in the
south-boreal province of the boreal region, with considerable influence from
the subtropical littoral flora and fauna. Among the south-boreal and sub-
tropical species the following should be mentioned : the hydroids Campanu-
laria platycarpa ; the Porifera Grantessa nemurensis; the polychaetes Achisto-
comus sovieticus, Staurocephalus japonica, Audouinia tentaculata and Polymnia
trigonostoma ; the amphipod family Talitridae ; the isopods Ligia cinerescens,
Excirolana japonica, Dynoides denticinus, C/eantis isopus; the decapods

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS 711

Table 288. Biomass of bottom-living biocoenoses of eastern shores of Kamchatka and

northern Kuril Islands

Biomass

of biocoenoses, g/m3,

at depths of

Region

0-500 m

Lowest

Highest

Mean

Kamchatka Bay (0-500 m)

3-5

588

174

Kronotsky Bay (0-2,000 m)

0-9

1,182

206

South-eastern tip of Kamchatka

and eastern side of northern

Kuril Islands

25-8

10,536

495

Western side of northern Kuril

Islands

1,135

268

Pachycheles stevensii, Pandalus latirostris, Spirontocaris ochotensis mororani,
Puggetia quadridens, Cancer gibbosulus, Eriocheir japonicus; the molluscs
Turbo sangarensis, Pot amides aterrina, Purpura japonica, Pec ten jessoensis, P.
swiftii, Venerupia philippinarum, Ostrea gigas; the echinoderms Disto-
laterias elegans, Lysatrosoma anthosticta, Aphelasterias japonica, and many
others.

In the so-called Nemuoro Sea, which is situated between Kunashir Island
and the small Kuril Ridge, the two heterogenous faunas — the cold-water fauna
of the shallows of the Bering and Okhotsk Seas and the warm- water fauna of
subtropical origin common with that of the southeastern part of the Sea of
Japan — are, in view of their hydrological environment and the distribution of
water masses, exceptionally well mixed with each other. The north-Pacific
boreal fauna, which does not penetrate farther north than the Nemuoro Sea
(P. Ushakov, 1951), forms the basic stock of the whole fauna.

The fauna of the southeastern end of the Sea of Okhotsk is nearer in its
composition to that of the Sea of Japan than to that of the Sea of Okhotsk.

Whereas the exchange of fauna between the Seas of Okhotsk and Japan
through the Tartary Strait is greatly restricted, it proceeds on a large scale
through the Sengara Strait (P. Ushakov, 1955). Warm-water fauna of the
southern Kuril Islands penetrates there through the Sengara Strait with the
warm Tsushima waters (Soya current). Along the western side of the Sea this
fauna only reaches the Gulf of Peter the Great. On the other hand, some cold-
water species of the Sea of Okhotsk can penetrate south along the Sakhalin
coast into the Sea of Japan, mostly during the cold season.

The abyssal fauna of the Kuril-Kamchatka trench. For ten years (1949-59) the
Institute of Oceanology of the Academy of Sciences of the u.s.s.r. has carried
out a study of the Pacific Ocean deep-water fauna using the Vityaz. To start
with this work proceeded side by side with that done on the Danish vessel
Galathea. Both expeditions brought to light much new knowledge on the
fauna of the oceanic depths, of that living not only in the ocean bed, but also
in the trenches, down to their greatest depths.

712

BIOLOGY OF THE SEAS OF THE U.S.S.R.

The research done by the Galathea is particularly significant, since it
covered the deep waters of the whole tropical zone of the Ocean. This team
surveyed the greatest depth of the Ocean and their collections offish and other
bottom-living fauna are of great value. The Galathea collections have en-
riched our knowledge with the description of many new animal forms, of
which some (for instance Neopilina) are of exceptional importance. The
Vityaz survey was concentrated mainly in the northwestern part of the Pacific
Ocean. It was therefore carried out in a most detailed manner, attention
being directed chiefly to the changes of biological phenomena in a meridional

/■

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,/i~

Щ®

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V /

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500

Fig. 343. Vertical distribution of collection from Vityaz

gathered by trawling (7) and by bottom grab (2) through

the cross section of the Kuril-Kamchatka trench, 1949

to 1955. /to V— Vertical zones, see Table 289.

direction, and vertically — from the surface to the greatest depths. The Vityaz
and Ob explorations made it possible to draw a picture of the meridional
changes of phenomena (geographical zonation) from the Bering Strait to
Antarctic waters, and to obtain quantitative indices for pelagic and bottom
life, which is of particular importance. The Kuril-Kamchatka trench was
explored in great detail (Fig. 343).

Many new species and groups of deep-water animals were found in the
Vityaz collections, among them the large new group of Pogonophora (Fig.
337).

Quantitative indices for the trawling collection were also obtained by means
of the trawl-graph. Grab samples down to more than 7 km were obtained —
trawls reached the greatest depths of the trenches.

The vertical zonality of the distribution of life had to be reconsidered
owing to the intensive development of the investigation of the whole water

GENERAL CHARACTERISTICS OF THE EASTERN SEAS 713

column of the ocean. The works of Ya. Birstein, N. Vinogradova and Yu. Chin-
donova (1955, 1958) mark the beginning of this exploration. They have sub-
divided the pelagic area of the Pacific into zones. N. Vinogradova, moreover,
suggested a system of division for the bottom-living fauna (1955, 1956).
In later years all the Vityaz biologists were faced with this problem and it was
found that the same zonation scheme is applicable to the pelagic and bottom
life (Fig. 344) of the northwestern part of the Pacific Ocean.*

This scheme is fairly similar to that of Y. Hedgpeth (1957). For the equa-
torial zone and for the Antarctic waters this scheme might require some
alterations.

It is clear from this scheme that transitional horizons, where two neigh-
bouring faunas are intermingled, should be distinguished between the
sublittoral and bathyal as well as between the latter and the abyssal
(Table 289).

Such zones as the supralittoral (above sea-level), the littoral (the tidal zone),
the sublittoral (the photosynthesis zone), the zone of the propagation of plant
organisms, the bathyal (the zone of the continental shelf), and the abyssal
(the zone of the ocean bed) are definite and established conceptions. The two
transitional horizons, a separate ultra-abyssal zone (zones of oceanic trenches)
and the division of the abyssal into two sub-zones need further explanation.
The convenience of this scheme has been checked on a series of groups of
invertebrates, the Pogonophorae, undoubtedly one of the most remarkable
groups of the bottom-living fauna of the Okhotsk and Bering Seas and of the
adjacent part of the Pacific Ocean.

The first representative of this group (Siboglinum weberi) was described by
M. Caullerie (1914) from the collection of the Siboga expedition as a member
of a new family of a new group of animals. This first Pogonophora was found
in the waters of the Malayan Archipelago. The second specimen of the group
(LameilisabeUa zachsi) was found by Ushakov in the Bering Sea. A series of
new forms of this remarkable group of animals was found (A. Ivanov, 1949,
1952, 1955, 1957, 1959, 1960) at the beginning of the researches of the Vityaz,
when many new species of it were rapidly discovered. The place occupied by
Pogonophorae in the system of animal classification, as an independent group
of much taxonomic significance, was then determined (sub-phylum or even
phylum). Since the first research of Ivanov, the promoter of this remarkable
group, Pogonophorae were found in other places in the world ocean and in
the old collections of different expeditions, where they had been placed in jars
with polychaetes owing to the superficial resemblance of their tubes. Up to the
beginning of 1959 42 species of Pogonophorae have been recorded, but not
yet fully described, and assigned to 1 1 genera and a few families and orders.
The collections made by the Vityaz and other expeditions contain some dozens
of so far undescribed forms. New Pogonophorae forms are brought by every

* At first the following terms were suggested for depths below 6 to 7 km and for the
fauna populating them: super-oceanic depths and super deep fauna (L. Zenkevitch,
1953). Later, however, Ya. Birstein suggested better terms — ultra-abyssal zone and ultra-
abyssal fauna. In 1956 the term Hadal (from the name of the mythological god Hades,
the ruler of the underground kingdom and the dead souls) was introduced by A. Brunn.

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716 BIOLOGY OF THE SEAS OF THE U.S.S.R.

new expedition, and there is little doubt that soon this group will comprise
some hundreds of species.

Judging by the intensive researches of the Vityaz, it is possible so far to assume
to some extent that the main abundance of Pogonophorae species is concen-
trated in the Far Eastern seas and the northwestern part of the Pacific Ocean
(Fig. 337), as well as in the northern hemisphere. Only forms of the genus
Siboglinum, Oligobrachia and Polybrachia the richest in species, have so far
been found in the Atlantic Ocean. Only one species of this genus has been
recorded in Antarctic waters. Diplobranchia belajevi is the only species of
this group so far reported from the Indian Ocean. Soviet expeditions have
discovered in the Arctic basin Polybranchia gorbunovi in its eastern sector and
Siboglinum hyperboreum off the eastern coast of Greenland ; these have been
found also in the Bering Sea. The Pacific Ocean is generally much richer in
Pogonophorae, although they are unevenly distributed there. Only two
species, Krampolinum galatheae and Lamellisabella zachsi are known from the
eastern part of the Pacific, the Gulf of Panama. Galathea and Vityaz trawl-
ing in the Philippines and in the Mariana, Tonga and Kermadec trenches have
not produced any Pogonophorae. The seas of the Malayan Archipelago have a
more abundant Pogonophora fauna. However, so far only Siboglinum weberi,
S. pinnulatum, S. taeniaphorum and Galathealinum brunni are known there —
only four species of two genera. Four species of Siboglinum were found in the
northern part of the Coral Sea {S. microcephalum, S. buccelliferum, S. robus-
tum and S. frenigerum). The Vityaz found four species of Siboglinum (S.
vinculatum, S. variabilis, S. bogorovi and S. tenuis) in the waters of the
northern island of New Zealand.

Thus 20 species of Pogonophorae belonging to six genera are known out-
side the northwestern part of the Pacific, while in the latter 22 species belong-
ing to nine genera have been found. Twenty-five new species of Pogonophora
have been found in the Indian Ocean {Vityaz, 1959-60).

The Pogonophorae are typical deep-water organisms ; in three areas, how-
ever, they rise to depths which are unusual for them : in the Sea of Okhotsk,
{Siboglinum caulleryi to 22 m, S. plumosum to 119 m and Oligobrachia dogieli
to 142 m) ; in the seas of the Malayan Archipelago {Siboglinum pinnulatum and
S. taeniaphorum to 260 m) ; and in the Atlantic Ocean {Siboglinum ermani,
S. atlanticum, S. inermis Oligobrachia ivanovi, and Polybrachia capillaris to
300 to 340 m; and in the Barents Sea (Nereilinum, to 170 m) ). Many of
these species descend to great depths, some even to the ultra-abyssal (for
instance, Siboglinum caulleryi from 22 m to 8,164 m). As to their ascent to the
upper layers in the Sea of Okhotsk, we are dealing, apparently, with a case
similar to the rising of deep-water forms to the surface waters in the Arctic,
a phenomenon well known for the Atlantic sector of the Arctic basin,
the Sea of Okhotsk and the Antarctic. The ascent of deep-water forms
to shallow depths has neither been investigated in detail nor sufficiently
explained.

E. Vinogradova has recently studied this problem (1955). She points out
that the ascent of the deep-water fauna to shallow depths unusual for them
has been observed also in tropical latitudes. 'This kind of ascent is very

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS 717

pronounced in some areas of the West Indies and the seas of the Malayan
Archipelago . . . thus, for example, the sea urchin Pvgmaeoeidaris prioni-
gera, usually found at depths of 2,000 to 3,000 m in the Molo Strait of the
Malayan Archipelago, has been recovered from a depth of only 69 to 91 m.
The same has been observed of the deep-water family of sea urchins Echino-
thuriidae and Aspidodiadematidae, the Porifera Hyalonema and Farrea and
the crabs Ethusina and others. ... In that respect the region of the Banda Sea
and the Key Islands is particularly remarkable, since an apparent mass ascent
of the deep-water fauna to shallow depths is observed there. . . . The plateau
on which the Key Islands are situated lies in shallow water and the temperature
of the water falls below 10° to 13°. A mass ascent of deep-water fauna to the
shallows is observed within the area of this plateau, which falls sharply away
into the great depths of the Banda Sea. This deep-water fauna consists of
most varied species of sea urchins, holothurians, starfish, glass sponges and
others. '

Such a peculiarity in the vertical distribution of deep-water fauna may pos-
sibly be connected with the manner of its formation.

It is therefore even more astonishing that in the Bering Sea, where in general
several deep-water forms have a tendency to rise to the upper horizons
(E. F. Gurjanova, 1936), and in the neighbouring Sea of Okhotsk Pogono-
phorae were found only in a few cases at depths of less than 1 ,400 m (one
case) and 1,693 m (two cases), and that usually they do not rise in the sea
above 2,800 to 3,000 m.* Of the three Far Eastern Seas the highest number of
Pogonophorae species has been recorded in the Bering Sea (1 1), seven of which
appear, so far, to be endemic to it. Of the five species recorded in the Sea of
Okhotsk only Siboglinum plumosum can provisionally be regarded as endemic.
So far only one species has been discovered in the Sea of Japan, Oligobrachia
dogieli, which had obviously penetrated from the Sea of Okhotsk where it
lives at a depth of 119 to 572 m. Eight species of Pogonophorae have been
described for the Kuril-Kamchatka trench, four of them endemic to it. Three
endemic species have been found in the Japanese trench.

Echiuroidea (mainly of the family Bonelliidae) form a most original and
characteristic element of the abyssal and ultra-abyssal fauna of the north-
western part of the Pacific ; there are eleven species of them (L. Zenkevitch,
1957, 1958) belonging to seven genera. Such an abundance of Echiuroidea is
not known for any other region of the ocean. Echiuroidea are extremely
poorly represented in the Galathea collection ; there was only one specimen
each among the material gathered by Challenger and Ziboga. There were none
at all in the Valdivia collection. One of its species may be considered as a
bipolar form. Echiuroidea {Prometor benthophila) are very rarely found on the
eastern side of the Pacific Ocean. A group of ultra-abyssal forms can be clearly
distinguished among the Echiuroidea (Table 290).

As a result of the researches of the Vityaz into the deep-water fauna it was
found possible to widen considerably the limits of distribution in the depths of
many groups of fauna (Table 291).

* In the Antarctic also at a depth of 3,000 m.

718

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Table 290

Species

Depth of

occurrence, m

Jakobia birsteini

6,150-8,100

Vitjazema ultraabyssalis

5,560-9,735

V. aleutica

7,286

Alomasoma nordpacifica

520-7,820

A. chaetifera

7,286

Bonellia pacifica

3,800-4,130

B. achaeta

3,500-5,540

Tatjanellia gracilis

3,940-5,020

T. grandis

2,970-3,400

Eiibonellia valida

412-1,240

Listriolobus pelodes

1,580

Foraminifera, Hexacorallia, Nematoda, Polychaeta, Echiuroidae, Har-
pacticoida, Amphipoda, Isopoda, Gastropoda, Bivalvia and Holothurioidea
penetrate deepest of all. In contrast Bryozoa, Brachiopoda and Decapoda des-
cend least far into the depths. The deepest occurrence of fish — that of Care-
proctus amblystomopsis of the family Liparidae (A. P. Andriashev, 1955)
(Fig. 345) — was in the Kuril-Kamchatka trench at a depth of 7,230 m ; later,
however, this fish was recorded in the Japanese trench at a depth of 7,579 m.
This fish, according to Andriashev's terminology, is a secondary deep-water
dweller. The variety of species of the fauna decreases rapidly with increasing
depth, especially with the transition into the ultra-abyssal depths of the
trenches (Fig. 346).

In the Kuril-Kamchatka trench 45 benthos species were found at a depth
of 6,860 m, 41 at 7,210 to 7,230 m, 20 at 8,330 to 8,430 m, 9 at 8,610 to 8,660 m,
18 at 9,000 to 9,050 m, and 6 at 9,700 to 9,950 m.

The fact that the number of benthos species alone decreases with depth is of
special interest. Plankton behaves differently (Fig. 347). The highest qualita-
tive variety (calculated from Copepoda) is found not in the surface zone, but
at depths between 2,000 and 5,000 m. Unfortunately this phenomenon has not
yet been explained. It is best illustrated for Calanoidae in the Kuril-Kam-
chatka trench (Table 292). The same is noted in the case of pelagic Gammari-
dae {Table 293).

Fig. 345. Careproctus (Pseudoliparis) amblystomopsis andriashev; absolute
length 238 mm. Kuril-Kamchatka trench, depth 7,230 m.

2000

WOO 6000

DEPTH, no

8000 10000

Fig. 346. Decreases in numbers of species (percentage
basis) in certain groups of marine bottom-living inverte-
brates with increase of depth (Zenkevitch, Birstein and
Belyaev). A Polychaeta; В Pericardia; С Pogonophora;
D Asteroidea ; E Holothurioidea.

NUM8ER OF SPECI6S
I000

3000

Д000

I000

3000

5000

I0000-

BENTHOS

.* PLANKTON

Fig. 347. Diagram of change

in qualitative composition of

oceanic plankton and benthos

with depth (Zenkevitch).

Table 291. Greatest depths of distribution of various groups of bottom-living animals

Depth

Research

Group

Trench

ship

Year

Foraminifera

10,415-10,687*

Tonga

Vityaz

1957

Porifera

8.610-8,660

Kuril-Kamchatka

Vityaz

1953

Hydrozoa

8,210-8,300

Kermadec

Galathea

1952

Octocorallia

8,610-8,660

Kuril-Kamchatka

Vityaz

1953

Hexacorallia

10,630-10,710

Mariana

Vityaz

1958

Nemertini

7,210-7,230

Kuril-Kamchatka

Vityaz

1953

Nematoda

10,715-10,687

Tonga

Vityaz

1957

Polychaeta

10,630-10,710

Mariana

Vityaz

1958

Echiuroidea

10,190

Philippine

Galathea

1951

Priapuloidea

7,565-7,579

Japan

Vityaz

1957

Sipunculoidea

8,210-8,300

Kermadec

Galathea

1952

Bryozoa

5,850

Kermadec

Galathea

1952

Brachiopoda

5,730-5,458

Pacific Ocean

Vityaz

1957

Ostracoda

6,920-7,657

Bougainville

Vityaz

1957

Harpacticoida

9,995-10,002

Kermadec

Vityaz

1958

Cirripedia

6,960-7,000

Kermadec

Vityaz

1952

Tanaidacea

8,928-9,174

Kermadec

Vityaz

1958

Amphipoda

10,715-10,687

Tonga

Vityaz

1957

Isopoda

10,630-10,710

Mariana

Vityaz

1957

Cumacea

7,974-8,006

Bougainville

Vityaz

1957

Mysidacea

7,210-7,230

Kuril-Kamchatka

Vityaz

1953

Decapoda

5,300

Kermadec

Galathea

1952

Pantopoda

6,860

Kuril-Kamchatka

Vityaz

1953

Loricata

6,920-7,657

Bougainville

Vityaz

1957

Solenogastres

6,660-6,770

Kuril-Kamchatka

Vityaz

1953

Gastropoda

10,715-10,687

Tonga

Vityaz

1957

Scaphopoda

6,930-7,000

Javan

Galathea

1951

Bivalvia

10,715-10,687

Tonga

Vityaz

1957

Octopoda

8,100

Kuril-Kamchatka

Vityaz

1949

Asteroidea

7,587-7,614

Mariana

Vityaz

1955

Ophiuroidea

7,974-8,006

Bougainville

Vityaz

1957

Echinoidea

7,250-7,290

Banda Sea

Galathea

1951

Holothurioidea

10,630-10,710

Mariana

Vityaz

1958

Crinoidea

9,715-9735

Idzu-Bonin

Vityaz

1956

Pogonophora

9,700-9,950

Kuril-Kamchatka

Vityaz

1953

Enteropneustra

8,100

Kuril-Kamchatka

Vityaz

1949

Ascidiae

7,210-7,230

Kuril-Kamchatka

Vityaz

1953

Pisces

7,565-7,579

Japan

Vityaz

1957

* The depth at the beginning and end of the trawl.

Table 292. Number of Calanoidea species per mz at different depths of the Kuril-
Kamchatka trench (Brodsky, 1952)

Horizon, m 0-25 25-50 50-100 100-200

Number of species 7 7 9 10

Horizon, m 200-500

Number of species 28

500-1,000
30

,000-4,000
87

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS 721

Table 293. Number of species of pelagic Gam-
mar idae at different depths of Kuril- Kamchatka
trench ( Ya. Bir stein and M. Vinogradov, J 955).
The zones correspond to those in Fig. 338

No. of
Zones and sub-zones species

Surface 1

Transitional 1

Upper abyssal 1 3

Lower abyssal 1 2

Ultra-abyssal 6

Quantitative development of different groups varies greatly with the horizon
(Eig. 348). While Porifera (Hondrocladia, Hyalonema) are predominant at a
depth of 1 ,000 to 2,000 m, holothurians (Elpiidae) and starfish (Porcellana-
steridae) are the main groups between 2,500 and 7,000 m; still farther down
holothurians become predominant in terms of biomass. At times the number
of Pogonophorae specimens is remarkable. Thus, for example, about 3,000
specimens of Elpiidae, more than 4,000 tubes of Pogonophorae, mainly
Zenkevitchiana, and about 100 specimens of Echiuroidea vitjazema were
brought up from a depth of 9,000 m in one sweep at one of the stations in the
Kuril-Kamchatka trench.

The qualitative variety of plankton increases with depth, while its numbers
decrease steadily {Table 294) by no less than 1 ,000 times from the surface to the
great oceanic depths ; and probably, if we include the coastal areas and the
periods of the greatest development of surface plankton, by several thousand
times.

An interesting comparison of the vertical distribution of plankton biomass
in the Kuril-Kamchatka, Mariana and Bougainville trenches is given by
M. Vinogradov (1958) {Table 294).

Table 294. Vertical distribution of plankton biomass {mgjm3)

Depth, Kuril

-Kamchatka

Mariana

Bougainville

trench

0-50

508

24-0

127

50-100

376

14-9

107

100-200

288

10-9

32-8

200-500

59-3

2-1

9-4

1,000-2,000

21-8

2-4

4,000-6,000

2-64

—

009

4,000-8,000

1-84

0012

—

6,000-8,000

0-48

—

001

Benthos biomass fluctuations from the surface to great depths are even
more marked. Even within the limits of the abyssal the benthos biomass may
vary by some hundreds of times {Table 295).

a»

a»
5

1000

2000

3000

4000

5000

£000

7000

8000

9000

10000

Mcionarian
polyps

Fig. 348. Quantitative vertical distribution of the main benthos groups in Kuril-
Kamchatka trench (Zenkevitch).

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS

723

Table 295. Changes in benthos biomass with depth (Ya. Bir stein and G. Belyaev, 1955) in

northwestern part of Pacific Ocean

Depth, m

Coastal
zone

50-200

950^1,070

5,070-7,230 8,330-9,250
Kuril-Kamchatka

5,000-6,000
Central part
of ocean bed

Biomass

g/m2

1,000-5,000

200

6-94

1-22 0-32

0010

The considerable difference between the variations of the biomass of plank-
ton and of benthos, either in the direction from the coast to the open ocean
or from the surface into its depths, is due apparently to the multiplication of
benthos being more closely dependent on the shore than is that of zooplank-
ton. The latter depends much more on phytoplankton, the development of
which in its turn is determined by the nutrient salts, the system of vertical
mixing which brings them from the depths to the surface, and by the general
conditions of lighting.

Two diagrams may serve to illustrate this ; first the qualitative distribution of
life through a cross section of the Kuril-Kamchatka trench (Fig. 349).

The amount of plankton decreases from 400 to 30 mg/m3 from the neretic
zone to the oceanic (I). The increase (to 500 mg/m3) corresponds to the in-
crease of plankton biomass towards the zone of convergence of the cold and
warm waters. Throughout the same field the benthos biomass (II) decreases

Fig. 349. Diagram of quantitative changes in plankton and benthos south-east of
the Kuril chain (Zenkevitch). / Plankton; // Benthos; /// Bottom topography
(cross section of Kuril-Kamchatka trench).

724

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Fig. 350. Diagrammatic representation of quantitative dis-
tribution of (right) plankton and (left) benthos in the Ocean.

from 1,000 to 0-4 g/m2 with some further decrease in the depths of the Kuril-
Kamchatka trench. The curve of benthos biomass does not correspond to the
scale of depths given on the left. Bottom relief is represented by curve III.
Moreover, the decrease in the amount of plankton with depth for the trench
and for the ocean bed is also shown (I).

The second, more abstract diagram (Fig. 350) gives the concentric zonation
character of the quantitative distribution of benthos with an amplitude of a
million, and the combined zonation (concentric on the periphery and along
the latitude) of the qualitative distribution of the surface plankton with an
amplitude of 20-50-100.

A curious series of changes — an original abyssal growth to gigantic sizes —
has been established for certain groups of the deep-water fauna of the north-
western part of the Pacific Ocean. Birstein demonstrated this from several
species of mysids of the genus Amblyops {Table 296).

There are some more similar examples, but the causes of this gigantism are
not yet clear.

Some remarkable principles have come to light in the study of the vertical
distribution of animal organisms in the Ocean (Fig. 344). They must, however,
be further investigated and explained. These are the clearly discontinuous and
non-uniform changes in the faunal qualitative composition corresponding
with depth, a characteristic which is not repeated in its quantitative distri-
bution. The latter change proceeds, in general gradually and evenly, for both
plankton and benthos.

Table 296. Depth of habitat and size of body of various species
of the genus Amblyops (Birstein, 1958)

Species

Depth, m

Length, mm

A. kempi

700-1,463

A. tenuicauda

820-1,400

A. abbreviata

366-1,372

A. chlini

1,940-1,980

A. croze ti

2,930

A. magna

7,800

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS 725

The most complete and, graphic data on this phenomenon are provided
by N. Vinogradova (1958), who has examined the vertical distribution of
1,144 species of deep-water animals (below 2,000 m). The first horizon with
a pronounced change of bathyal and partly sub-abyssal species lies at a depth
of 2,500 to 3,500 m, the second at 4,000 to 5,000 m (Figs. 351a, в and 352a,
b). A large number of new species and even new groups appear in both hori-
zons, while those inhabiting higher ones disappear.

Z. Shchedrina (1958) notes also that 'the most luxuriant and varied Fora-
minifera fauna . . . was recorded on two zones or horizons ; at depths of about
3,000 m and at 4,850 to 5,570 m. Between these two zones of maximum Fora-
minifera variety two more transitional zones, characterized by scarcer Fora-
minifera fauna, can be distinguished.' With some groups a third horizon of a
more marked change can be distinguished at 6,000 to 7,000 m, the threshold
of the ultra-abyssal zone. This worker does not explain the cause of such
vertical distribution : 'the explanation of this phenomenon should be sought
both in the ecology of the animals inhabiting the deepest water, and in the
historical causes which promoted their existence'.

It is most interesting that similar kinds of principles in the alterations in the
qualitative composition according to depth have been observed also for the
pelagic fauna of the Gammaridae (Ya. Birstein and L. Vinogradov, 1955) in
the Kuril-Kamchatka trench (Table 297 and Fig. 353).

Table 297

Zones Sub-zones Gammaridae forms

Deep-water, Upper, л Cvphocaris challenged, Cyclocaris guilelmi,

500-6,000 m 500-2,000 m Korogam egalops, Paracalanus alberti, Paran-

Lower, [ dania boecki, Eusirella multicalceola, Rhach-

2,000-6,000 m ) otropis natator

Lower, Cyphocaris richardi, Astyra zenkevitchi, A.

2,000-6,000 m bogorovi, Halice aculeata, H. shoemakeri,

Cleonardo macrocephala

Ultra-abyssal, Tetronychia gigas, Hyperiopsis latiearpa, Anda-

6,000 m niexis subabyssi, Halice quarta, Vitjaziana

gurjanovae, Protohyperiopsos arquata

These workers note also that the number of new forms not found in the
higher horizons increases with depth — there are two (15-4 per cent) such
forms in the upper deep-water zone ; seven (52 per cent) in the lower, and six
(100 per cent) in the ultra-abyssal. These last are considered by them as ende-
mic to the Kuril-Kamchatka trench. Moreover, Birstein and Vinogradov
arrange their data according to their zoogeography. Among the deep-water
Gammaridae they distinguish four main groups : (1) Organisms with a pan-
oceanic type of distribution (6 species) ; (2) Atlantic-Pacific (amphi-boreal)
forms (7 species); (5) Arctic forms (1 species) and (4) North Pacific forms
(2 species).

It is to be noted that the endemic nature of the fauna increases with depth —

Number of species

20 30 40

Fig. 351a. Vertical distribution of Porifera species, found at a depth of more than

2,000 m (Vinogradova). 1 Total number of species; 2 Number of species appearing

at a given depth; 3 Number of species disappearing at a given depth.

NUMBER OF SPECIES
20 39

№

Ш0

Fig. 351b. Vertical distribution of Elasipoda species, found at a depth of
more than 2,000 m (Vinogradova). 1 Total number of species; 2 Number
of species appearing at a given depth ; 3 Number of species disappearing

at a given depth.

NUMBER OF SPECIES

20 30

i г

1U000-
WiOO

ttm

Fig. 352a. Vertical distribution of species Forcipulata,
found at a depth of more than 2,000 m (Vinogradova).
1 Total number of species ; 2 Number of species appear-
ing at a given depth ; 3 Number of species disappearing
at a given depth.

NUMBER OF SPECIES

10 Ю

Fig. 352b. Vertical distribution of species Phanero-
zonia found at a depth of more than 2,000 m (Vino-
gradova). / Total number of species; 2 Number of
species appearing at a given depth ; 3 Number of species
disappearing at a given depth.

728

BIOLOGY OF THE SEAS OF THE U.S.S.R.

50 00

6000

7000

8000

9000

Fig. 353. Vertical distribution of certain species of Gam-
maridae (Birstein and Vinogradova). 1 Cyphocaris chal-
lenged ; 2 Cyclocaris guilemi ; 3 Eusirella multicalceola ; 4
Rhaehotropis natator; 5 Koroga megalops; 6 Parandania
boeeki ; 7 Paracallisoma alberti ; 8 Cleonardo mawocephala ;
9 Astyra bogorovi; 10 Halyce shoemakeri', 11 Cyphocaris
richardi; 12 Ля/уга zenkevitchi; 13 Halyce aculeata;
14 Tetronychia gigas; 15 Vitjaziana gurjanovae. Zones
undoubtedly inhabited are coloured black, zones of pos-
sible habitat are cross-hatched.

endemic species are practically absent from the upper abyssal sub-zone; in
the abyssal they constitute 50 per cent, and in the ultra-abyssal 100 per cent.
To a certain extent, however, this is accounted for by the deep-water fauna
not having been sufficiently studied.

Abyssal plankton of the northern part of the Pacific Ocean contains not

GENERAL CHARACTERISTICS OF THE EASTERN SEAS 729

only endemic species, but even endemic genera (Lucicutia, Heterorhabdus,
Parenchaeta, Bathypontia, Bathycalanus, Spinocalanus, Pachyptilus, Hete-
roptilus) with a majority of endemic species. Some of these forms penetrate
into the Bering and Okhotsk Seas through the deep straits. 'Abyssal species',
writes Brodsky, ' are not widely distributed, certain species being endemic to
certain areas of the World Ocean'.

Developing his idea further K. Brodsky notes (1948) that a 'series of species
of Calanoida are wrongly said to be widely distributed'; this happened be-
cause different species were known under the same name. Thus Metridia
pacifica was classified with M. lucens, M. okhotensis with M. longa, Calanus
pacificus with C.fimnarchicus, etc. When these forms were distinguished from
one another their habitats naturally became more limited. As a result of the
revision of the taxonomic composition of the Far Eastern fauna of the species,
Calanoida was found to be 60 per cent, while its cosmopolitan species formed
only 1-8 per cent.

A similar vertical distribution of zooplankton in the column of water was
traced for other pelagic organisms by M. Vinogradov (1955) from the data
obtained from a series of vertical catches of plankton according to horizons,
during trawling down to 8,500 m in the region of the Kuril-Kamchatka
trench. In the 500 to 1,000 m layer the predominant zooplankton species were
Calanus cristatus, С tonsus, Eucalanus bungii and Sagitta elegans. Hymeno-
dora frontalis appears at a depth of 200 to 500 m, attaining its greatest numbers
within the 500 to 1 ,000 m horizon. Below 1 ,000 m it is replaced by H. gla-
cialis, and by Eukronia fowler i among the Chaetognatha. Among the mysids at
a depth of 500 to 2,000 m Eucopia grimaldi is predominant, while at 4,000 m
E. australis and Gnathophausia gigas assume this role. Among the Euphau-
siaceae Euphasia pacifica lives at depths down to 500 m, and Bentheuphausia
amblyops between 3,000 and 4,000 m. Similar pictures are observed with many
other species. In the trench itself, below 6,000 m, the usual abyssal species
disappear, and plankton comprises mainly the species Copepoda and Amphi-
poda.

Yet not all the plankton groups have this type of vertical distribution ; thus.
for example, among the Chaetognatha (Yu. Chinodonova, 1955) only one
group of abyssal forms (in the broad sense) can be distinguished {Sagitta
macrocephala, S. planctonis, Eukronia fowleri and Heterekronia mirabilis).

Qualitative changes with depth of the bottom-living fauna can be deter-
mined also by various other biotic and abiotic factors. Such alterations should
first be linked with the tropical factor (M. Sokolova, 1956, 1958, 1959).
Macro- and micro-zonal distribution of bottom-living fauna is readily ex-
plained when this method is applied, and when the properties of the soil
(mechanical and chemical), the rates of the movement of bottom-water
masses, their content of suspended substances and the general composition
of the fauna are taken into account. The detritus-eating group is markedly
predominant among the benthos of the abyssal. Sokolova distinguishes among
them those which consume the upper layer of the soil indiscriminately, those
which discriminate roughly the surface layer of the sea-bed, and those which
make a delicate choice of detritus on the surface layer of the sea-bed.

730 BIOLOGY OF THE SEAS OF THE U.S.S.R.

This type of analysis provides us with an interesting scheme of the changes
in feeding groups of the sestonophages, detritophages and carnivores. The
replacement of one such group by another takes place not once but many
times. Within the Kuril-Kamchatka trench it occurs at depths of 3,000,
5,000 and 8,500 to 9,000 m (Fig. 354 and Table 298). Moreover, during the
replacement the group of biological phyla (according to their feeding)
remains the same, but the species may be quite different.

Generally speaking detritus eaters are predominant, the plant-eating

Continental
slope

fl=/-5

Ocean bed
'Slope into trench

. 1
iverage depths
of trench КЛЛО| g

_ 3

I'-uiM/ Maximum cfep-fhs

200

3000

5000

7000

9000

- 10000

Fig. 354. Correlation between benthos groups and bottom topography of the Ocean.
1 Sestonophage zone ; 2 Zone of a considerable development of all three feeding
groups ; 3 Zone of development of detritus feeders, either only roughly sorting the
soil or swallowing it whole A — Ratio by weight of detritus feeders to carnivores

(Sokolova).

species are absent from the deep-water fauna, and the deeper the water the
more pronounced this becomes.

Among the crustaceans of the Far Eastern Seas the species Crangonidae
are carnivores (M. Sokolova, 1957). They feed on worms, crustaceans and
molluscs. Ophiuroidae form the main food of Sclerocrangon derugini. The
diet of the Crangonidae is most varied.

Only a rough picture of the distribution of the bottom biocoenoses of the
northwestern part of the Pacific Ocean adjacent to the Kuril Islands and Kam-
chatka has yet been given (L. Zenkevitch and Z. Filatova, 1958) (Fig. 355).
Owing to the steep descent into the Kuril-Kamchatka trench, populated by
the ultra-abyssal biocoenosis of holothurians (Elpiidae), Pogonophorae

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS

731

Table 298. Vertical changes in the main feeding groupings of bottom-living fauna in Kuril-
Kamchatka trench (M. Sokolova, 1959)

Ratio of de-

Ratio of car-

Dominant

Dominant groups of

tritophages to

nivores to ses-

types of

organisms

sestonophages

carnivores

tonophages by

feeding

Zones

by weight

weight

Porifera

004

0-77

005

Madreporaria, Antipa-

Sestonophages

taria, Sabellidae, Cri-

noidea

3-5

26-2

007

Pogonophora, Crinoidea

2-5

27-5

004

Molpadonia, Amphareti-
dae, Decapoda, Actini-

Sestonophages

aria

170

200

Detritophages

в,

Molpadonia, Porcella-

Carnivores

nasteridae, Amphareti-
dae, Isopoda, Malletii-

dae, Actiniaria

210

7-5

Gephyrothuriidae, Por-

cellanosteridae

450

1160

0-38

Detritophages

Elpidiidae, Gephyrothu-

riidae

—

Elpiidae

840

1620

0-80

(Zenkevitchiana and others) and different species of Foraminifera, the coastal
biocoenosis consists almost exclusively of agglutinating forms (Z. Shche-
drina, 1958), Echiuroidea (Vitjazema and Jakobia) and Polychaeta (Macelli-
cephala and Macellicephaloides). Farther to the southeast the Pacific Ocean
is characterized for large areas by the biocoenoses of deep-water holothurians
(Elpiidae and Psychropotidae), starfish (Porcellanasteridae and Brisingidae),
sea-urchins (family Pourtalesiidae, and Echinothuriidae), actinians, single
madreporian corals, lilies (Bathycrinus), Polychaeta (families Maldanidae and
Ampharetidae), Mollusca {Spinula oceanica), and some dozens of species of
Foraminifera. The density of the bottom population (Fig. 356) decreases to
10-5 and 1 g/m2 as one moves southeastwards away from the Kuril Islands.
All the huge area of the open parts of the Pacific Ocean is embraced by the
1 g/m2 isobenth, and by far the greater part of it by the 0T g/m2 isobenth.
The benthos biomass of the Ocean bottom in some parts is no higher than
0-01 g/m2 (Fig. 357).

Some comprehensive studies on the deep-water fish of the northwestern
part of the Pacific Ocean are due to P. Schmidt (1948, 1950), A. P. Andriashev
(1935) and T. Rass (1954). Andriashev suggested differentiating between an-
cient and secondary deep-water fish. The first (for instance Stomiatoidei,
Opisthoproctoidei and many others) are, as a rule, rare in the waters of the
continental shelf seas ; the second belong to families widely represented in
shallow seas (for instance the families Cottidae, Liparidae, Zoarcidae and
others). The boundary between these two groups is probably rather indistinct.

732

BIOLOGY OF THE SEAS OF THE U.S.S.R.

It is more probable that the deep-water fish took a geologically long time to
be formed and that the duration of their evolution varies. Rass pointed out
the existence of a series of transitional groups (for instance Brotulidae and
Moridae). The group of ancient deep-water fish of the Far Eastern Seas and

170

160

w\\\w\\

* ^\\\\\

www

\\\\\\\\\4

\ \ \ \ „ ,. ч ,, ,. ,.

\*-

■v \ \ \ \

W 4

bw\

\\\

s\\

\\\

VMP-

. .->

W \\\\\\л

•\\\\\\\\\.

■ www
\w\\\\\\\
v\\\\\\\\\

■\\\\\\\\\\

'^\ХЧЧХЧ44

\\\v\\\\\\

. W\~\\\\\

^\\\\\\\\ч

>W\\\\

W
\

\ \

170

/во

Fig. 355. Distribution of the biocoenoses of bottom-living fauna in northwestern
part of Pacific Ocean (Zenkevitch and Filatova). / Fouling fauna (Porifera, Bryozoa,
Hydroida and others); 2 Biocoenosis Echinarachnius parma; 3 Biocoenosis of small
bivalves ; 4 Biocoenosis Elpidiidae-Psychropotidea-Porcellanasteriidae and others ;
5 Biocoenosis Spinula; 6 Biocoenosis Elpidia-Macellicephalis-Thalassema and

others.

the adjacent part of the Pacific Ocean includes about 60 species, belonging to
25 families.

T. Rass (1955) gives a list of 46 species belonging to 31 genera of deep-water
fish of the Kuril-Kamchatka trench, pointing out that 25 of them are found
off the shores of America, 15 or 16 species are recorded in the waters of Japan,
12 in the Sea of Okhotsk, 14 in the Bering Sea and 5 in the Gulf of Panama.
Moreover, all the deep-water fish of the Sea of Okhotsk were found in the

Fig. 356. Quantitative distribution of biomass (g/m2) of bottom-living
fauna in northwestern part of Pacific Ocean (Zenkevitch and Filatova).

Fig. 357. Quantitative distribution of bottom-living fauna of the Oceans at depths

of more than 2,000 m (Belvaev and Zenkevitch). 1 Above 1,000; 2 From 100 to

1,000; 3 From 50 to 100; 4 From 10 to 50; 5 Less than 10 mg/m2.

734

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Kuril-Kamchatka trench, the fauna of this latter being closest of all to the
fauna of the American littoral in the composition of its deep-water fish.

Only 8 species (5 families) of deep-water fish are known in the Sea of Japan,
12 in the Sea of Okhotsk, 25 to 29 species in the Bering Sea and about 50
species in the Kuril-Kamchatka trench (Figs. 358 and 359). The greatest
number of species belongs to the families Gonostomidae (5 species), Scopeli-
dae (5 species), Moridae (5 species) and Macruridae (8 species). It is interest-
ing to note that all the five deep-water fish of the Sea of Japan live in the
waters adjacent to Japan, but are absent from the Okhotsk and Bering Seas
and from the Kuril-Kamchatka trench. These last two Seas and the trench

Fig. 358. Deep-water fish of the Sea of Japan (Rass). 1 Alepocephalus umbriceps;

2 Argentina semifasciata ; 3 Maurolicus japonicus ; 4 Physiculus japonicus ; 5 Lotella

maximowiczi; 6 L. phycis; 7 Halleutaea stellata; 8 Cryptopsaras couesil.

have many species in common. Their deep-water fish is an impoverished fauna
of the northern part of the Pacific Ocean (T. Rass, 1954).

Among the secondary deep-water fish of the Far Eastern Seas (the families
Zoarcidae, Scorpaenidae, Cottidae, Cyclopteridae and Liparidae) there are
44 species in the Sea of Okhotsk, 27 in the Bering Sea and 14 in the Sea of
Japan.

As has been shown by researches carried out by the Galathea, and especially
by the Vityaz, the old idea of geographical uniformity of the deep-water
fauna should be reconsidered, particularly as regards the bottom-living
organisms. Pelagic fauna is, in general, linked with the water masses which it
inhabits and with their distribution. First of all there are certain cases of deep-
water bottom fauna with most restricted habitats. Certain organisms, more-
over, keep strictly to the same horizon. Thus, for example, members of the
Monoplacophora were found only in the most easterly part of the Pacific
Ocean on a very small sector of the equatorial belt ; they occur, however, in

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS 735

Fig. 359. Deep-water fish of the Sea of Okhotsk and the Bering Sea (some species)
(Rass). 1, 8, 9, 11, 12, 13, 18, 19 — not found in the Okhotsk Sea. 1 Ericara salmonea;
2 Cyclothone micwdon; 3 Leuroglossus stilbius schmidti ; 4 Bathylagus pacificus ; 5 B.
miller i\ 6 Chaidiodus macouni; 1 Alepisaurus aesculapius; 8 Lampanyctus nanno-
chir; 9 L. leucopsarus; 10 L. nannochir laticauda; 11 Histiobranchus bathybius;
12 Polyacanthonotus challengeri; 13 Antimora microlepis; 14 Podonema longipes;
15 Coryphaenoides cinereus; 16 С pec t oralis; 17 С acrolepis; 18 Melamphaeus
nycterinus; 19 Coryphaenoides lepturus.

three different sites, all three at a depth of about 3,000 m. The Echiuroidea
Tatjanellia grandis, characterized by its bipolar distribution, is found on the
same horizon (about 3,000 m) in the northwestern part of the Pacific Ocean
and in Antarctic waters. The great variety of the species, genera, families and
orders of Pogonophora are found only in the northwestern part of the Pacific
Ocean. Every deep trench is characterized by different sub-species and species

736

BIOLOGY OF THE SEAS OF THE U.S.S.R.

of the same genera. Of course there are many examples among deep-water
fauna of a wide vertical and horizontal distribution of individual species, but
a relatively restricted area of habitat is characteristic of all the deep-water
fauna.

This is most evident from N. Vinogradova's examination of the distribution
of many forms of deep-water benthos (1955-58). The invariable increase of
endemic forms with depth is shown by this comparison both of the three

i.2000

>zooo

>3D00

>WD

Fig. 360. Extent of taxonomic
isolation of deep-water bottom-
living fauna of western and
eastern parts of the Pacific
Ocean at different depths (Vino-
gradova, 1955).

Oceans and of some individual parts of them. This is well illustrated by the
Figs. 360 and 361.

The deep-water fauna of the eastern and western parts of the Pacific Ocean
has in the surface zone (<2,000 m) about half of the total number of forms,
but at great depths (>4,000 m) less than 10 per cent of them. The same
phenomenon was observed from comparison between the northern and
southern parts of the oceans and between the oceans themselves. Further
research on the deep-water fauna will no doubt weaken the conception of its
endemic nature, but will hardly destroy it. The idea of the uniformity and
geographical homogeneity of the deep-water fauna was based on the con-
ception of the uniformity, constancy and slight changeability of the conditions
of its existence (t°, S%0, oxygen), and on the absence of any restriction on its

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS

737

Fig. 361. Extent of taxonomic isolation of deep-water bottom-living fauna of the

northern and southern halves of the Oceans. The lower chart for depths less than

2,000 m, upper chart for depths more than 4,000 m (Vinogradova).

horizontal distribution. It is most remarkable that the deep-water fauna is to a
great extent both bipolar (Fig. 362) and amphi-boreal in its distribution. The
circumtropical distribution of many members of the deep-water fauna also
needs some explanation. What factors restrict its distribution southwards
and northwards?
Change of pressure may restrict the upward and downward movements of

За

738

BIOLOGY OF THE SEAS OF THE U.S.S.R.

stenobathic forms. Horizontal movements are more difficult to explain. It
may only be suggested that their propagation is restricted by some chemical
characteristics of the medium. Moreover, it may be assumed that deep-water
animals have a much increased sensitivity to changes in the factors of en-
vironment, since they are not subject to daily, seasonal or secular variations.

Fig. 362. Bipolar distribution of deep-water animals of the Ocean (Vinogradova).
1 Phascolion eutense (Sipunculoidea) ; 2 Tatianellia grandis (Echiuroidea) ; 3 Scina
wcgleri var. abyssalis (Amphipoda) ; 4 Munidopsis antonii (Decapoda) ; 5 Glypho-
crangon rimapes (Decapoda) ; 6 Nymphon procerum (Pantopoda) ; 7 Hymen-
aster anomalus (Asteroidea) ; 8 Kolga nana (Holothurioidea) ; 9 Culeolus shumi;
10 C. murrai (Ascidia). (2,000-7,300 m.)

V. COMMERCIAL IMPORTANCE OF THE FAR EASTERN

SEAS
The Far Eastern Seas are commercially very rich. They contain about 800
species offish and approximately 200 of these are commercial or may become
so (P. Moiseev, 1953).

It is to be noted that 60 years ago fishing in Russian waters was confined to
river estuaries and the coastal zones. 'More than 96 per cent of the catch was
composed of salmon, Oncorhynchus keta, Oncorhynchus gorbusha and
others, which entered the river from the sea for spawning, and about 2-6 per
cent was herring, caught in the coastal, low-salinity areas ; the remaining yield
was composed mostly of Osmerus spenlanus dentex, navaga {Eleginus navaga
gracilis) and the Acipenseridae, also caught in the rivers' (T. Rass, 1955). Now
the Acipenseridae constitute no more than a third of the yield, and the fisheries
have mostly moved into the open sea. The Salmonidae trade, in particular,
has mostly moved into the northwestern part of the Pacific Ocean (Fig. 363a).

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS

739

Fig. 363a. Fishing regions abundant in commercial pelagic fish of the north-
western part of the Pacific Ocean (Rass). 1 Tuna and Cololabis (outlines);
2 Salmon ; 3 Herring ; 4 Scomber.

The catch of Kamchatka crab and marine mammals has increased consider-
ably in the last ten years {Table 299).

Three biological groups may be distinguished among the commercial fish :
transitional, marine pelagic (Salmonidae in their marine period) and the marine
bottom-living fish. Far Eastern salmon belongs to the first group; herring,

Table 299. Yield of Soviet marine industry in Far Eastern Seas, 10z centners (L. Berdi-

chevsky, 1957)

Year

1913

1930

1940

1950

1953

1954

Salmonidae

954

1,556

1,148

1,102

2,114

1,250

Herring

338

500

1,563

2,003

1,246

Gadidae

—

142

112

318

360

440

Pleuronectiformes

—

326

484

—

Crabs

—

242

158

223

290

393

Whales

—

114

530

768

755

Other marine mammals

—

Total

1,072

3,186

3,093

4,752

2,433

5,240

740

BIOLOGY OF THE SEAS OF THE U.S.S.R,

mackerel, tuna and Cololabis to the second. The catch of sardines in the Sea
of Japan, which reached 1,400,000 centners in 1937, ceased altogether in 1941.
Among the pelagic fish herring, with its huge shoals off eastern Sakhalin and
in the northern part of the Sea of Okhotsk, will no doubt become the main

Fig. 363b. Diagram of commercial aggregations of plaice (1) and pollack (2)

(Rass, 1955).

object of future fisheries. Mackerel approaches the Primor'e coast for spawn-
ing. The tuna Sajra {Cololabis sajra) fisheries are still undeveloped in the

U.S.S.R.

Among the bottom-living fish the most important are the flatfish (plaice
and halibut), the gadoids (cod, alaska-pollack (Teragra chalcogramma) and
navaga), rock fish (sebastodes) and atka-fish (Pleurogrammus) (Fig. 363b).
The shelf zone is poorly developed in the Far Eastern Seas and as a result there
is a considerable predominance, as compared with the Barents Sea, of pelagic
fish (salmon, herring, sardines, sajra) over the bottom-living fish (cod, flat-
fish). Owing to the abundance of food in those areas of the Far Eastern Seas
open to commercial fish, the latter grow rapidly and get very fat (Table 300).

The faunas of the northern parts of the Atlantic and Pacific Oceans have
much in common in their ampni-boreal characteristics, Many species of their
fish and invertebrates, however, while not showing any essential taxonomic

GENERAL CHARACTERISTICS OF THE EASTERN SEAS 741

Table 300. Pacific and Atlantic cod, annual gain in weight, kg (P. Moiseev, 1953)

Sea

Age in years

Fatness
(Clark)

6 7

Bering
Barents

1-60
0-42

2-62
0-86

3-45 5-30
1-40 204

6-80
3 06

8-65
4-53

112
0-85

differences, vary greatly in their ecology and mass development. Many mass
forms found developed in one basin occupy a secondary place in the other.
The cod is subject to long distance seasonal migrations in the North Atlantic,
but in the Pacific its movements are limited to local seasonal vertical trans-
positions which are characteristic also of certain other fish and of commercial
crabs (Fig. 364).

However, the new data from the results of tagging cod at different points
of the eastern coast (I. Polutov, 1952) have shown that cod may migrate from
the Avachinsky Bay not only into the Kronotsky Bay, but much farther north
to the Olyutor Inlet thousands of kilometres away. However, even such
journeys cannot be compared with the long migrations of cod in the Atlantic.

Among the distinguishing features of the seas of the northwestern Pacific
as compared with those of the eastern Atlantic P. Moiseev (1953) notes the
higher velocities of its currents, leading to the formation of a series of
biological peculiarities in the fish. Thus the Pacific cod has the ova of a

Fig. 364. Diagram of cod migrations within the area of Karagin Island and Olyutor
Inlet (Moiseev, 1953). 1 Shoaling of cod; 2 Months of shoaling; 3 Spawning region.

742

BIOLOGY OF THE SEAS OF THE U.S.S.R.

bottom-dweller, and the Atlantic cod the ova of a pelagic fish. Many fish of
the Far Eastern Seas move to calm waters for spawning.

P. Moiseev (1953) maintains that a series of biological and morphological
peculiarities, in particular an increase in fertility {Table 301), spontaneous
spawning, bottom ova, a shortening of the incubation period and a higher
rate of growth within the first years of life, have developed as a result of the
great variety of species of fish in the Far Eastern Seas, including the carni-
vores.

Moiseev opposes the point of view, formerly held by many ichthyologists,
on the poor prospects of the development of fisheries of the near-bottom and
bottom-living fish in the Far Eastern Seas; he considers that this industry
might yield an output as high as that of the Atlantic Ocean. If, at the moment,
the bottom and near-bottom living fish of the northern part of the Pacific

Table 301. Fertility {thousands of ova) of certain Pacific and Atlantic fish
{P. Moiseev, 1953)

Species

Pacific Ocean

Atlantic Ocean

Cod

Navaga

Limanda aspera
L. limanda
Capelin
Herring

411-763*

170-250

25-0-2100

6-2-63-0

6260-1,1330

—

80-0-1400

15-3-39-9

6-2-13-4

39-9-92-4

14-8-23-3

per 1 kg of fish by weight.

produce 8-7 million centners as against the 22-2 of the northern parts of the
Atlantic, this is due only to the poor development of the industry.

The northwestern part of the Pacific Ocean is also exceptionally rich in
marine animals. M. Sleptzov (1952) writes that this area is inhabited by ' seven
species of pinnipeds representing all the three families of the order Pinni-
pedia; eared seals (fur seal and sea-lions), earless or proper seals (marine,
and ribbon seals, and ringed seals), walrus, and 30 species of the order Cetacea
(22 species of toothed whales and 8 species of baleen whales) '. Sea otter may
also be added to this list of sea mammals. 'Huge herds of white dolphins and
dolphins, shoals of cachalots and rorquals feed in these waters from spring to
autumn, since these areas are very rich feeding grounds for pinnipeds and
Cetacea.' Cachalots come there from the tropical zones of the Pacific; fur
seals move there from Japanese waters. Among all the 35 species the cachalot
and two species of seals, Phoca hispida ochotensis and Hystriophoca fasciata,
are the most important for the industry. The annual yield of cachalots reaches
7,000 head with a total weight of about 1-5 to 1-7 million centners. The marine
seal from the Komandorski Islands and Tyuleny Island in the Okhotsk Sea
is the most valuable for its fur.

Kamchatka crab {Paralithodes camtschatica), the annual yield of which
has risen in recent years to 400,000 centners, occupies a special place among

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS

743

the resources of the Far Eastern Seas. Two other species of the genus {P. platy-
pus and P. brevipes) are taken (Fig. 365) in small numbers along with the
Kamchatka crab. The other two species of this genus are not found in Soviet
waters. Only some of the smaller sized true crabs (Chionoecetes opilio, Erima-
crus isenbecki and Telmessus cheiragonus) might become important commer-
cially. So far, however, their role in the catch is insignificant. Kamchatka crab
is taken almost throughout the whole area of its distribution (L. Vinogradov,

Fig. 365. Places of concentration of commercial crabs (Vinogradov). 1 Paralithodes
camschatica ; 2 P. platypus ; 3 P. brevipes.

1941, 1945). P. brevipes has a similar area of distribution. The other four
species are found from the Bering Sea to the Sea of Japan. The largest crabs
belong to the genus Paralithodes, which forms large aggregations of commer-
cial importance. Kamchatka crab assembles off the shores of the u.s.s.R.,
Japan and Alaska. The largest yield of this crab is taken off the western coast
of Kamchatka. Seasonal migrations of the Kamchatka crab consist of travel-
ling to the coast (at depths of 1 5 to 70 m) for feeding during the summer, and
a return to lower layers (1 10 to 200 m), and even down to 270 m in the Sea of
Japan, where the water is better heated (1-5° to 2-5°) during the cold months
when the surface waters are much cooled. The migration routes of the Kam-
chatka crab cover dozens of miles (up to 100). The average daily distance

744 BIOLOGY OF THE SEAS OF THE U.S.S.R.

traversed by the crab during his migration is up to 5 or even 7 miles (L. Vino-
gradov, 1941). This migration starts when the young begin to appear. New
mating takes place in the shallows. After mating crabs cast their shells and
for part of the summer and autumn feed intensively on small bivalves, worms,
crustaceans and echinoderms (mainly Echinarachnius parma). Commercial
aggregation of the Kamchatka crab is always repeated at precisely the same
places. The biology, migrations and formation of commercial aggregations of
the Kamchatka crab are being thoroughly investigated by the numerous and
intensive researches of Soviet and Japanese zoologists (L. Vinogradov,
1933, and 1941 ; I. Zachs, 1936, X. Marukava, 1933).

Among the other crustaceans such as prawns, chiefly the large forms
Pandalus latirostris and Cambaroides schrenckii have great commercial
importance. The prospect of the commercial exploitation of molluscs
too in the Far Eastern Seas is just as important. These include primarily
Ostrea, Pecten, Spisula, Mytilus, Cardium, Area and a few dozen more
bivalves, gastropods and cephalopods. Trepang {Stychopus japonicus) might
also play an important role in the future. Commerical sea- weed resources in
the Far Eastern Seas are very great.

Sea-birds, which nest on the shores and feed on invertebrates and fish,
usually form bird rocks ('loGmenes'). They spend all their non-nesting time
over the sea, and thus also play an important role in the total balance of
organic matter in the sea, mostly in the neritic zone. Among the most striking
and widely known examples of this behaviour are the birds of the coasts of
Chile and Peru, mainly guanay {Phalacrocorax bougainvillei) and to a less
extent the pelican (Pelecanus thagus) and the blue-footed booby (Sula
nebouxii), which consume yearly more than 20 million centners of fish,
mainly anchovy {Engraulis ringens).

Such great aggregations of sea-birds do not exist on the shores of the u.s.s.r. ;
they are, however, very large and some are even immense, on the Iona and
Tyuleny Islands for example, and on some of the Kuril Islands in the Sea of
Okhotsk. Guano is not commercially exploited on the shores of the u.s.s.r. ;
some of the sea-birds themselves and their eggs are, however, of commercial
importance (Uria species, fulmar, puffins, eiders).

The main breeds of sea-birds of the Soviet Far Eastern shores (S. Uspen-
sky, 1959) are, apart from albatrosses (Diomedea) and shearwaters (Puffinus)
which do not form colonies, guillemots {Uria lomvia and U. algae), puffin
{Fratercula cirrata, F. corniculata), pelagic shag {Phalacrocorax pelagicus),
kittiwake {Rissa tridactyla), petrel {Fulmarus glacialis) and others. In the
southwestern part of the Sea of Okhotsk and in the Sea of Japan the following
are added to this list: Cerorhinca monocerata, the black-tailed gull {Lams
crassirostris), the Ussu cormorant {Phalacrocorax filamentosus), the guillemot
{Cepphus carbo) and others. All this abundant bird population consumes an
immense number of small fish and crustaceans {Tables 302 and 303).

VI. ZOOGEOGRAPHY OF THE FAR EASTERN SEAS
In estimating the biogeography of the Far Eastern Seas and the adjacent
parts of the Pacific Ocean one should proceed from the following premises :

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS 745

Table 302. Number of colony nesters, in thousands of individuals, in the Far Eastern
Seas (S. Uspensky, 1959)

Sea

Group

of birds

Auks

Tubinares

Gulls

Cormorants

Bering

Okhotsk

Japan

2,188

3,854

2,505
2,106

193

517

71
345

Total

6,095

4,612

731

451

Total of Sea birds 11,889

(i) Most of the Sea of Japan, the Sea of Okhotsk and the Bering Sea belong
to the boreal Pacific sub-region of the boreal region ; (ii) In the north the boreal
sub-region lies next the Arctic region, and the boundary between them should
be established; (iii) To the south it borders the tropical region, and this
demarcation line should also be drawn; (iv) Is there reason to distinguish
sub-Arctic and subtropical regions or should they be included in a mixed
transition zone and, finally, (v) What biogeographical divisions should be
established for the boreal Pacific sub-region (provinces, regions, etc.)?

As yet there is no generally accepted scheme for the biogeographical zona-
tion of surface areas of the northwestern part of the Pacific Ocean.*

The separation of the southern and southeastern parts of the Sea of Japan
into a subtropical sub-region, or more correctly a South Japanese province
of the Indo-West-Pacific sub-region of the tropical region, is generally
accepted. Ushakov calls it the Tsushima province. The problem of the
boundary between the Arctic and boreal facies in the northern parts of the
Bering Sea is the most obscure. The whole southeastern part of the Chukotsk
Sea is sometimes included in the boreal region (K. Brodsky, 1955). The
northern boundary of the boreal region is at times drawn through the Bering
Strait (P. Ushakov, 1953). Most investigators, however, include the northern
part of the Bering Sea, to the north of St Lawrence Island, and the greater part

Table 303

Total annual consumption (thousands
Sea of tons)

Fish

Invertebrates

Bering

Okhotsk

Japan

255

299

247

258

Total

567

508

* Zoogeographical zonation of the abyssal is given above.

746

BIOLOGY OF THE SEAS OF THE U.S.S.R.

of the Anadyr Bay in the lower Arctic sub-region of the Arctic region
(E. F. Gurjanova, 1935; A. P. Andriashev, 1939; L. Vinogradov, 1948)
(Figs. 366 and 367).

N. Vinogradova (1949) characterizes Anadyr Bay and that part of the Bering
Sea adjacent to the Bering Strait with St Lawrence Island as its southern
boundary, as the low-Arctic region (the presence of ice in winter, near-
bottom temperature either below freezing point or just above). L. Vinogradov
(1948) includes the bathyal zone of the Bering, Okhotsk and Japan Seas in sub-
Arctic regions, and the northern part of the Sea of Okhotsk in the glacial

Fig. 366. Zoogeographical regions of the Far Eastern Seas
(Vinogradov, 1948). 1 High Arctic; 2 Low Arctic; 3 Gla-
cial; 4 Sub-Arctic; 5 North-boreal; 6 South-boreal; 7
Sub-tropical regions.

regions. A number of investigators recognize the peculiar biogeography of the
northern and northwestern parts of the Sea of Okhotsk, with their large
number of cold-water, Arctic and Arctic boreal species. Without including
these regions in the lower Arctic sub-region a number of investigators give
them special biogeographical names — co-arctic (K. Brodsky, 1952), glacial
(L. Vinogradov, 1948) and others. The Tartary Strait can to some extent be
included in those regions. This problem will be solved when a precise qualitative
method is laid down as the basis of the system of zonation, as has been done
for the southwestern part of the Barents Sea (Z. Filatova, 1938).

T. Shchapova (1948) uses the geographical distribution of sea- weeds in her
division of the north-boreal Pacific sub-region into north-boreal (all the
northern part of the Bering Sea and of the Sea of Okhotsk) upper-temperate
boreal (southern part of the Bering Sea, Aleutian Islands, central and southern
parts of the Sea of Okhotsk and the northern part of the Sea of Japan) ;

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS

747

lower-temperate boreal (central parts of the Sea of Japan and the small Kuril
Ridge) ; and south boreal (southern and southeastern parts of the Sea of Japan).
Apart from the larger biogeographical subdivisions of the northwestern
part of the Pacific, some further subdivisions are possible for each basin.
Thus K. Brodsky (1954) divides the Bering Sea into six main regions accord-
ing to the zooplankton — the oceanic, the Bering Sea, the north Bering Sea,
western neritic, eastern neritic and deep water regions. Brodsky characterizes
each of them by their physicogeographical peculiarities and by the list of their

Fig. 367. Zoogeographical division of the Bering Sea
(Andriashev). 1 Chukotsk (temperate- Arctic) province ;
2a North Bering (sub- Arctic) region, Anadyr area;
2b Same, Norton area; 3a Province of Eastern
Kamchatka (boreal), Avachinsk area; 3b Same,
Komandor area ; 3c Same, Koryatzk area ; 4 Aleutian
(temperate-boreal) province.

forms of zooplankton. Andriashev has distinguished within the Bering Sea
temperate boreal province six smaller biogeographical subdivisions.

In a similar manner Savilov divides the Sea of Okhotsk, according to the
environment of the habitat and the predominant species, into six ecological
zones, each of which in turn might be divided further into more detailed bio-
coenoses. Six main regions of macrobiocoenoses are distinguishable for the
Barents Sea according to its bottom-living fauna. Such microregions could
be equally considered as biogeographical and ecological biocoenotic sub-
divisions. One merges into another.

Amphi-Pacific habitats in the northern part of the Ocean are as character-
istic of the distribution of its population as the amphi- Atlantic ; Shchapova
gives the littoral sea-weeds of the genera Eisenia and Pelvetia as examples of
this kind of zonation. Of the five species of Eisenia one (E. bicyclis) is
distributed along the shores of Japan ; three (E. arborea, E. masonii and E.

748 BIOLOGY OF THE SEAS OF THE U.S.S.R.

desmarestioides) off the Californian coast ; and the fifth (E. cookeri) off the
coast of Peru. Four species of the genus Pelvetia are similarly distributed.
P. typica is found along both Asian and American coasts of the temperate
region. P. wrightii lives off the Japanese coast, while P. galapagensis is found
only in the Galapagos Islands, and P. canaliculata off the western and northern
coasts of Europe. The species mentioned are an example not only of amphi-
Pacific but also of amphi-boreal and bipolar distribution.

A. P. Andriashev (1939) gives a large number of examples of the amphi-
Pacific distribution of fish. Two different sub-species of sardines (Sardinops
sagax) live off the American and Asian coasts; the anchovy (Engraoulis)
members of the family Osmeridae Hypomesus and Spirinchus, Cololabis saira,
many flatfish, and others have the same distribution. From this point of view
the distribution of the Pacific endemic family Embiotocidaeis most interesting.
This family is represented by 19 species (of 18 genera) off the coast of America.
Only two species (Ditrema and Neoditrema) live on the western side of the
Ocean. Many examples are known among Porifera, Polychaeta, Crustacea,
Echinodermata and Mollusca.

Andriashev indicates identical species, closely related sub-species, and
among the amphi-Pacific forms species and even genera differing by the degree
of the discontinuity of their habitats in the north. Moreover, the habitats of
a series of amphi-Pacific organisms on the American coast do not extend
farther north than Oregon-Californian waters, and on the western coast no
farther north than the Sea of Japan. There can be only one explanation for
this distribution — both amphi-boreal and amphi- Atlantic : 'the geological
history of the northern part of the Pacific is comparatively short. Conditions
allowing a partial exchange of forms between the two different faunas —
American and Asian — occurred at many different times. At the site of the
contemporary fault in the region of the Bering Sea conditions were often, and
at different geological periods, very favourable, allowing some individual
elements of the two different faunas to spread northwards and to cross over
to the opposite sides' (A. P. Andriashev, 1939). Such openings no doubt
occurred periodically, beginning in the upper Miocene and especially during
the Pliocene, and later during the two inter glacial warm periods. Andriashev
rightly notes also that 'when the northern part of the Bering Sea was dry land,
the warm branches of the Kuroshio current had a more intense warming effect
[on its waters — L.Z.]'.

All groups of the flora and fauna of the northern part of the Pacific are char-
acterized by their great mass development and their marked amphi-boreal
distribution. However, as a whole, the flora and fauna of both oceans differ
greatly. Thus the amphi-boreal organisms of the population of both oceans
alien to its original population belong to a young and newly arrived element.
It becomes evident, moreover, that some amphi-boreal groups are of Atlantic
origin (among the fish the family Gadidae, among the marine mammals
Phocidae) while others, much more numerous, are of Pacific origin (pleuro-
nectiforms among fish, Laminaria among sea-weeds).

Amphi-boreal organisms are represented mostly either by identical or by
very similar sub-species and species ; this bears evidence of their comparatively

GENERAL CHARACTERISTICS OF FAR EASTERN SEAS 749

recent spread into the new habitat. It can, in general, be considered as an
immense experiment in acclimatization by Nature herself — a conquest of vast
new habitats, often more spacious than the original ones. This experiment is a
good illustration of the actual and potential habitats (L. Zenkevitch, 1940); a
comparison of these two concepts should be kept in mind when plans are
worked out and measures for trans-oceanic acclimatization are put into effect.
A. P. Andriashev ( 1 944) gives 50 cases of amphi-boreal distribution among fish
including cod, navaga, herring, several species of flatfish, halibut and others.

Amphi-boreal forms are even more frequent among the invertebrates
(crustaceans, polychaetes, echinoderms, molluscs). Among them the follow-
ing commonly known mass forms may be mentioned : prawn {Pandalus
borealis), crab (Lithodes), barnacle {Balanus balanoides), starfish {Asterias
rubens), brittle stars (Ophiura robusta), holothurians {Cucumaria frondosa),
molluscs (Modiola modiolus), Enteropneusta {Balanoglossus mereschkowskii)
and many others — more than 100 species in all. It is characteristic that many
amphi-boreal organisms, predominant in one ocean, play only a modest
role in the other. Thus, for example, the forms dominant in the Bering Sea
benthos such as the echinoderms Ctenodiscus crispatus and Strongylocentrotus
droebachiensis; the worms Phascolosotna margaritaceum, Spiochaetopterus
typicus and Maldane sarsi; the molluscs Cardium ciliatum and many others,
become of secondary importance in the Pacific Ocean. Calanus finmarchicus,
markedly predominant in the plankton of North America, is intensively
developed in only a few areas of the Far Eastern Seas. Andriashev is in-
clined to refer the formation of the amphi-boreal community mainly to
the pre-glacial period, when, apparently, the Bering Strait was deeper
and wider and the temperature of its waters was (judging by its fossil mol-
luscs) 5° to 10° higher than it is now, and when the whole Arctic basin was
considerably warmer. The exchange of faunas could also have taken place,
but apparently in a much more restricted form, within the warm inter-
glacial periods and the post-glacial Littorina era.

Whereas the appearance of disconnected habitats along the latitude is
linked with the periods of rise of temperature, the bipolar distribution is the
result of periods of colder climate, when the organisms of moderate latitudes
could penetrate through the somewhat cooled equatorial belt.

The phenomenon of bipolarity is just as marked in the Pacific Ocean as in
the Atlantic. Laminariales among sea-weeds and sardines among fish may
serve as excellent examples of it. Along the Asian coast Laminaria have only
reached the Yellow Sea. They disappear farther south, appearing on the
western coast of the ocean only in 30° S latitude. On the eastern side, however,
they reach the Galapagos Islands. Their spread so far north along the coast
of South America is the result of the cooling effect of the Humboldt current.
Laminaria and penguins move with this current to the equator and the Gala-
pagos Islands. The order Laminaria includes only 30 genera and 130 species.
In the northern part of the Pacific Ocean 27 genera (90 per cent) and 84
species (65 per cent) of them are found, and in the southern hemisphere only
6 genera (20 per cent) and 22 species (17 per cent). Four species only are
recorded for the Yellow Sea.

14
The Sea of Japan

I. PHYSICAL GEOGRAPHY

The area of the Sea of Japan is about 978,000 km2; its volume is 1,713,000
km3; its average depth is 1,752 m and its greatest depth 4,036 m.

Owing to the shallowness of the straits connecting it with the Ocean, the
Sea of Japan occupies a special position among the Far Eastern Seas which
wash the shores of the u.s.s.r. In spite of this shallowness the isolation of its
deep waters is only relative, since in winter, as a result of the sinking of
cooled surface waters along its slopes, the deep waters are well aerated ; they
differ from the adjacent parts of the Ocean and from the Okhotsk and Bering
Seas by their lower temperature and by the absence of oxygen deficiency in
the middle layers. The cold intermediate layer is also absent from the Sea of
Japan. The salinity of the Sea of Japan is practically the same as that of the
Ocean {Table 304).

Table 304. Vertical distribution of temperature, salinity and oxygen in the central parts of the

Seas of Japan and Okhotsk and of the Bering Sea

Depth

Temperature,

°C

Salinity %<

Oxygen, ml/

Japan

Okhotsk

Bering

Japan

Okhotsk

Bering

Japan

Okhotsk

Bering

18-13

10-72

8-40

34 13

32-57

3311

6-54

6-38

6-91

3-04

-0-62

4-53

34-04

32-97

33-21

6-81

805

7-52

100

1-23

-1-44

2 00

34-07

3311

33-32

6-63

7-58

7-35

150

0-84

-015

2-92

34-07

33-35

33-58

6-89

6-55

4-47

250

0-40

102

3-65

34-09

33-52

33-97

6-45

3-82

2-07

500

015

2-07

3-38

3409

33-95

34-21

5-78

1-95

1-38

1,000

008

2-35

2-75

34-13

34-42

5-69

0-95

—

3,000

—

■ — •

1-58

■ —

— -

34-72

—

2-65

Water exchange in the Sea of Japan is also different from that of the Sea
of Okhotsk and the Bering Sea. All the deep waters of the Sea of Japan are
isolated from the trenches of the Pacific Ocean and adjacent seas ; only the
surface waters flow into the Sea of Japan from the neighbouring basins.
Warmer deep oceanic waters penetrate freely into the Sea of Okhotsk and the
Bering Sea through the deep straits and fill their trenches (Fig. 368).

The Sea of Japan has a varied bottom topography (Fig. 369) (N. Zenkevitch,
1959). Its greatest depth is situated in the northern, deep-water part. The sea-
floor is mostly below 3,000 m. Its shelf zone is very narrow except for the Bay
of Peter the Great, the northern part of Tartary Bay and the northern coast of
Hokkaido Island. Its bathyal zone is comparatively large. The shelf zone
forms only about 20 per cent of the total area of the Sea, and the bathyal
zone some 40 per cent ; the area of the deep-sea floor is also about 40 percent.

750

THE SEA OF JAPAN

751

In the southeastern part of the Sea there lies a large submarine range,
some of its elevations rising to within 300 to 400 m of sea-level. Moreover, in
different parts of the deep-water trench some summits rise to a height' of
1 ,500 to 2,000 m from the sea-floor.

The bottom deposits of the Sea of Japan are mostly aleurites of varying
coarseness (Fig. 370). The complete absence of diatomaceous oozes from the
Sea of Japan is noteworthy, since they are exceptionally abundant in the Sea
of Okhotsk and the ocean adjacent to it.

Almost the whole of the mainland coast of the Sea extends parallel to the

Fig. 368. Characteristic peculiarities of the water
exchange of the Seas of Japan and of Okhotsk and
Bering with the Ocean.

peaks of the Sikhote-Alin range. The coast there is fairly sheer and coastal
features are rare. The character of the coast changes greatly to the south
beyond Cape Povorotniy, and it runs at right angles to the axis of the Sikhote-
Alin range; its coastal features then become numerous. There are several
small, tortuous inlets and two large bays, those of Amur and Ussuriisky.

The coast of Western Sakhalin differs greatly from the mainland coast. It
is composed of easily disintegrated chalk and Tertiary rock and has been
smoothed throughout most of its length by the process of abrasion. Former
river estuaries are filled with alluvium, and some estuaries jut out into the
Sea, forming small smooth, prominent deltas. Abrasion has markedly de-
creased now owing to the formation of a very wide beach along the coast.
Although the tide-range is small, the tidal zone is frequently wide.

The Sea of Japan may be divided into two distinct parts according to the

Fig. 369. Sea-bed relief of the Sea of Japan (Zenkevitch).

Fig 370 Bottom deposits of the Sea of Japan (Skornikova). 1 Rock bottom; 2
Shingle-gravel sediments ; 3 Scattered shingle-gravel bed ; 4, 5 Sands ; 6-8 Aleuntes ;
ь b 9 Ooze.

Зв

Fig. 371. Surface temperatures in summer and winter of waters of Sea
of Japan (Istoshin).

THE SEA OF JAPAN

755

course of its temperature changes {Table 304). The isotherm 0° can be taken
as their boundary. The temperature of the northwestern part falls sharply in
winter and in the Tartary Strait ice is formed from November till April,
sometimes reaching great thickness in the northern part.

126' ISO" 135* 140' I44-'

Fig. 372. Surface currents in summer of Sea of Japan (Sizova, 1961).

In the southern part of the Sea the seasonal temperature fluctuations are as
high as 14°, and in the northern up to 20° (Fig. 371).

The currents of the Sea of Japan (Fig. 372) have a cyclonic, counter clock-
wise character, as is usual in seas of the northern hemisphere.

The tidal ranges of the northern and southern parts of the Sea vary consider-
ably. In the most southerly part of the Sea, the Korea Strait, the tidal range
is 0-5 m. The tidal range gradually increases in the Tartary Strait, reaching
2-3 to 2-8 m. In the Korea and Tartary Straits the tides are semi-diurnal, in
the Primor'e either diurnal or varied. The level of the Sea is subject to fluctua-
tions as a result of the on- and off-shore winds.

756 BIOLOGY OF THE SEAS OF THE U.S.S.R.

II. FLORA AND FAUNA

Four hundred and fifty different plants have been identified in the plankton
of the Sea of Japan (Y. Kiselev, 1937, 1947), among them 306 diatoms and
133 peridinians. In contrast with the northern part of the Sea of Okhotsk
the phytoplankton of the Sea of Japan has two maximum blooms — a spring
(March- April) diatom bloom and an autumn (September-October) peridinean
bloom.

Primary production in the Sea of Japan and the adjacent part of the Pacific
was estimated in the spring of 1957 (Yu. Sorokin and O. Koblents-Mishke,
1958) by the carbon tracer method. In the area surveyed primary production
fluctuated within the limits of 2 to 5 g of organic carbon in a column of water
of 1 m2 cross section. Before the spring bloom carbon production was 2 to
6 mg of carbon under 1 m2 along the western side of the Sea of Japan, which
is subject to the effect of the cold Primor'e current, and in the central part of
the Sea between 41° and 42° N latitude. In the same area carbon production
during the greatest bloom was between 200 and 1 ,900 mg of carbon. The corres-
ponding values in the eastern part of the Sea were 50 and 115 mg under lm2.
The highest production was recorded in the Ocean east of Hokkaido Island
within the zone of the convergence of warm and cold waters, where 5,000 mg
of carbon was reached. South of 40° N latitude production did not rise above
100 to 150 mg of carbon under 1 m2. Naturally the size of the primary pro-
duction depends on the bloom phase and is governed by the presence of
phosphates and by conditions to the north.

Zooplankton in the Sea of Japan is fairly varied, including no fewer than
70 or 80 organisms, among them about 50 species of Copepoda (36 species of
Calanoida Cyclopoida, 9 species of Harpacticoida), 4 species of Euphau-
siaceae, and 9 species of Hyperiidae.

The main forms of surface plankton in the Sea of Japan are : Paracalanus
parvus, Pseudocalanus elongatus, Oithona similis, Calanus pacificus, Metridia
lucens, Calanus tonsus, C. cristatus, Microcalanus pygmaeus and Oncaea
borealis.

The plankton of the Sea of Japan changes considerably both qualitatively
and quantitatively with depth. Cold-water forms are predominant in the
upper horizons in winter ; plankton composition changes sharply in summer.
Only eurythermic forms (for example Oithona similis) are found here all the
year round. There are many Foraminifera and Radiolaria in the plankton of
the surface layer during the cold season of the year. Below 500 m Micro-
calanus pygmaeus (K. Brodsky, 1941), the radiolarian Challengeron spp. and
the ostracoda Conchoecia become the main forms {Table 305).

As is shown by the data of Table 305, deep-water plankton species are
extremely scarce in the Sea of Japan.

In contrast with the northwestern part of the Pacific Ocean (K. Brodsky,
1952) where the number of species of Copepoda increases more than ten
times with depth, their number in the Sea of Japan is barely doubled with
depth. As regards the number of specimens down to 1,000 m the decrease is
five times more rapid in the Pacific Ocean than in the Sea of Japan. This may

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758 BIOLOGY OF THE SEAS OF THE U.S.S.R.

be due to a sufficient oxygen supply in the deep waters of the latter Sea
(Table 306).

The plankton of the Sea of Japan is divided into definite biogeographical
zones (Fig. 373). Its most northern part, adjacent to the Tartary Strait, is
occupied by a cold-water biocoenosis with Calanus finmarchicus. Calanus
tonsus is the dominant species in its central part, while the warm-water species
Calanus pacificus, Oithona plumifera, Paracalanus parvus and Coryceus sp.
inhabit the southeastern part of the Sea (M. Kun and I. Meshcheryakova,
1954). A neritic biocoenosis of zooplankton (with Labidocera, Epilabidocera,
Centropages, Acartia, Evadne, Podon and the larval forms of bottom-
living animals) encircles the Sea.

In K. Brodsky's opinion (1941) the list of warm- water organisms should
include Cladocera sp., Paracalanus parvus, Oithona brevicornis and Calanus

Table 306. Change in number of species and specimens of Copepoda with depth

{K. Brodsky, 1952)

Pacific Ocean,

northwestern part

Sea of Japan,

northwestern part

Horizon
m

No. of

species

specimens

species

specimens

0-25

15,240

46,224

25-50

8,160

61,612

50-100

5,040

29,794

100-200

320

3,401

300-5,000

2,734

500-1,000

1,154

1,000-4,000

—

1,000-2,000

— ■

—

303

pacificus, and the list of the cold-water organisms — Calanus cristatus, C. fin-
marchicus, С tonsus, Pseudocalanus elongatus and in part Oithona similis.

Plankton is much more developed in the open sea, furnishing a biomass in
excess of 1 g/m3 (Figs. 374 and 375).

In winter (December to February) the zooplankton biomass in the 0 to 200 m
layer remains fairly well developed in the central part of the Sea throughout
the whole layer (30 to 500 mg/m3, Fig. 376) (I. Meshcheryakova, 1954).
Calanus cristatus, Thysanoessa raschii, Themisto abyssorum and Calanus
tonsus are the dominant forms in the southern part. There is also an admixture
of C. finmarchicus in the coastal areas, and in the southern parts are found also
the warm-water Oithona plumifera, Clausocalanus arcuicornis and others.
The boundary between the area of winter conditions and that of spring
conditions runs at that season approximately along the fortieth parallel.

Zooplankton distribution in the northern part of the Sea of Japan has some
unusual winter features (L. Ponomareva, 1954). The most abundant plankton
may be concentrated in the uppermost 25 m layer. Plankton biomass de-
creases rapidly within the 100 to 200 m layer, and deeper down it becomes

THE SEA OF JAPAN

759

considerably richer again (Fig. 377). The layer of decreased biomass coincides
with the layer of sudden change. It is of interest to note that the diurnal

Fig. 373. Distribution of main species of Copepoda in Sea of
Japan (Khun and Meshcheryakova, 1954).

vertical migrations of most of the main zooplankton species in the Sea are
only feebly developed.

The euphausiids, which at times display a mass development, form a very
important group of zooplankton. Members of four species of this group —
Thysanoessa longipes, Th. inermis, Th. raschii and Euphausia pacifica — are
found in the Sea of Japan. The euphausiids form the main food of many com-
mercial fish (herring, mackerel, alaska-pollack, pink salmon) and of whales.

□ LESS THAN kSSSNSM глл „ _„ , к

300 mg/m3 fcP S 50° TO 70° m«/m3

Fig. 374. Horizontal distribution of plankton in Sea of Japan (Kusmorskaya).

THE SEA OF JAPAN

761

They are particularly abundant in the 0 to 50 m layer in January and February
(L. Ponomareva, 1955) when their biomass is between 1 and 3 mg/m3 in large
areas of the Sea. Euphausiids feed on calanoids with an admixture of various
plankton. They are probably the greatest consumers of calanoids.

As a result of some alterations in the Kuroshio system a certain fall of
temperature was observed in 1939 in the Sea of Japan, which increased in
subsequent years. Sardine fisheries decreased markedly in 1941, and in

< WO mg

100-200 mg

200-500 mg

500- WOO mg

northern boundary
of the zone of bloom

Fig. 375. Distribution of zooplankton biomass (mg/m3) in northwestern
part of Sea of Japan between 50 and 200 m, summer 1 952 (Meshcherya-

kova, 1950).

1942 sardines did not enter the Sea of Japan. They were not caught off the
Soviet shores of the Sea of Japan for many years after this.

This fall of temperature necessarily affected the plankton, and in May 1941
phytoplankton was still predominant in the northwestern part of the Sea
(A. Kusmorskaya, 1950) — mainly the diatoms Coscinodiscus oculis iridis.
In the eastern part of the region species of the genus Chaetoceros were domi-
nant, and in the southern Thalassiothrix longissima. Calanus finmarchicus,
Pseudocalanus elongatus, Oithona similis, Metridia lucens and other cold-water
forms were among the most widely distributed zooplankton components in
the spring. The mean biomass of zooplankton in May was only 136 mg/m3

-to

-25

■100

1-200

115

J2S №Ъ 213 287

Distance from the coast , miles, along cross section.

310

]"< 50 mg
50-100 mg

100-200 mg
200-500 mg

> 1000 mg

Fig. 376. Vertical distribution of zooplankton biomass (mg/m3) in
Sea of Japan along the cross section of 38° 24' (Meshcheryakova).

700
WO

700

200

300

BIOMASS, mg/m3

Fig. 377. Vertical dis-
tribution of zooplankton
biomass (mean data) in
northern part of Sea of
Japan in January 1950
(Ponomareva).

THE SEA OF JAPAN

763

for the 0 to 100 m layer. Calanus tonsus was also greatly developed (45 per
cent of the total plankton biomass).

As early as June diatomaceous plankton was replaced by peridinians (some
species of the genera Peridiniwn and Ceratium); among the zooplankton
Paracalanus parvus was intensely developed. The amount of zooplankton
increased to 350 mg/m3, and with the warming of the surface water Calanus

for phytoplanKton
for zoopLanKton

3000

CO4

200 -

Fig. 378. Vertical distribution of plankton biomass (mg/m3) in Sea of

Japan from 31 March to 2 June 1939. 1 Phytoplankton (Coscinodiscus);

2 Zooplankton; 3 Calanus tonsus (Kusmorskaya, 1950).

tonsus became the main form. In 1937 the zooplankton biomass in the same
area, at the same season, was three times greater (1,300 g/m3) (K. Brodsky,
1939), and in 1936 it had even reached 1,640 mg/m3. The greatest concen-
tration of zooplankton is found at a depth of 24 m (Fig. 378). Phytoplankton
consists almost exclusively of Coscinodiscus oculis iridis, while half the zoo-
plankton consists of Calanus tonsus — the main food of sardines in the Sea of
Japan. In the opinion of many investigators the sardine catastrophe of 1939
was the result of an exceptional fall of temperature in the sardine spawning
area and also of the consequential scarcity of food for the newly-hatched
young.

764

BIOLOGY OF THE SEAS OF THE U.S.S.R

L. Kizevetter (1954) has recorded interesting observations on the chemical
composition and food value of the Sea of Japan plankton. He has found that
these indices, both of the zooplankton as a whole and of its separate com-
ponents, may be subject to considerable seasonal variations, their food value
being altered as a result {Tables 307, 308 and 309).

Table 307. Mean chemical composition of winter (January and February) zooplankton

in the Sea of Japan

Group

Moisture
content,
per cent

Composit

ion of

dry

substance, per cent

Fat

Protein

Carbohydrates Ash

Copepoda
Euphausiaceae
Chaetognatha
Hyperiidae

88-9
83-7
86-8
86-8

17-1
11-4

8-3
8-3

45-3
52-7
46-9
47-6

8-9 28-7
14-9 210
20-5 24-3
19-4 24-7

Table 308. Mean chemical composition of spring (April and May) zooplankton in the
northwestern part of the Pacific Ocean

Group

Composition, per cent

Fat

Proteins and
carbohydrates Ash

Copepoda
Euphausiaceae
Chaetognatha
Hyperiidae

24-1
4-3
6-7

7-5

61-3 14-6

77-8 17-9
73-1 20-2
66-5 260

Table 309. Mean chemical composition of autumn (August) zooplankton in the Sea of

Okhotsk

Group

Moisture
content,

Composition of dry substance, per cent

per cent

Fat Proteins Carbohydrates Ash

Copepoda

77-7

38-6 29-6 16-1 15-7

Euphausiaceae

70-2

28-2 54-4 5-6 11-8

Chaetognatha

68-9

190 52-5 11-6 16-9

Hyperiidae

69-8

43-9 35-5 8-7 10-9

Phytoplankton

90-86

1-48 29-40 37-52 31-60

Thus the calorific value of 100 g of zooplankton varies from 331-6 to 501-9.
The chemical composition of the phytoplankton of the Sea of Okhotsk in
August with its lower fat content and higher content of carbohydrates is
markedly different from that of the zooplankton.

THE SEA OF JAPAN 765

Copepoda and Euphausiaceae are very important in the diet of plankton-
eating fish, and in this respect herring has many rivals. In their turn Euphau-
siaceae and Chaetognatha consume very large numbers of Copepoda. It is
remarkable that the Pacific Ocean herring {Clupea harengus pallasi), which
lives in the northern part of the Sea of Japan, has the same diet as the Atlantic
herring of the Barents Sea (Thysanoessa inermis, Th. raschii and Calanus
finmarchicus), but in the Sea of Japan it adds Sagitta elegans as a further
component of its diet.

The flora of the bottom-living macrophytes of the Sea of Japan has been
investigated by the Soviet and Japanese workers E. Zinova (1928-54),
G. Gail (1930, 1936), T. Shchapova (1948, 1957), Miyabe (1908), K. Oka
(1907-34) and J. Tokida (1957). Three hundred and seventy-nine species of
bottom-living macrophytes of the Sea of Japan are listed in Table 310.

Table 310. Composition

littoral

sea- weeds
1958)

the Sea

of Japi

m (T Shchapova,

Group

No.

of species

Percentage of Primor'e
species

Cyanophyceae
Chlorophyceae
Phaeophyceae
Rhodophyceae

9
46
90

172

100
96
82
56

Total

317

68 (202 species)

T. Shchapova has investigated the littoral flora of the Soviet's Primor'e for
a number of years (from 1948). The exclusively littoral forms of the bottom
flora (including the uppermost horizon of the sublittoral up to 1 m) compose
only 25 per cent of the total, e.g. about 72 to 74 species. The marine flora of
the Primor'e does not contain Arctic or tropical organisms. Arctic-boreal
forms are predominant in the northern part and boreal ones in the southern.
Pylaiella littoralis and Dictyosiphonfoeniculaceus are most characteristic of the
first group ; Langsdorfii sp., Sargassum miyabei, Cystoseira crassipes, C. hako-
datensis, of the second. They are mainly endemic organisms of the northern
part of the Pacific. Apart from them the sea-weeds of the Sea of Japan con-
tain also some amphi-boreal species such as, for example, Halopteris scoparia,
Leathesia difformis, Ralfsia clavata, Colpomenia sinuosa, and some bipolar
ones — Scytosiphon lomentarius, Ilea fascia. Many organisms are distributed
on both sides of the Pacific ; on the other hand many of them are endemic
forms of the Asian coast — Nemacystus decipiens, Stschapovia flagellaris,
Cystoseira crassipes and others. The dominant species of the littoral and of the
upper horizon of the sublittoral are the following, which are endemic to the
northern part of the Pacific Ocean : Heterochordaria abietina, Pelvetia wrightii
f. babingtonii, Coccophora langsdorfii, Sargassum miyabei, Cystoseira crassipes,
C. hakodatensis. The most profusely developed Laminaria of the Primor'e
are Laminaria japonica, L. den tiger a, Alaria crassifolia, A. fistulosa, which
also are endemic to the Pacific Ocean.

766

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Unlike the brown sea-weeds, the red sea-weeds on the Soviet shores of the
Sea of Japan belong mostly to the boreal flora. Only Polysiphonia arctica
might be included among the Arctic forms. The comparative role of the red
sea-weeds in the Pacific Ocean is much greater than in the Atlantic.

Two of Shchapova's (1957) diagrams (Figs. 379 and 380) may be used for a

о»

с:
о

«о

Fig. 379. Distribution of macrophytes along littoral of De Castri Inlet. Alluvial
deposit in depth of bight ; 1 Gloiopeltis capillaris ; 2 Enteromorpha spp. ; 3 Fucus
evanescens, Pelvetia wrightii f. babingtonii; 5 Tichocarpus crinitus; 6 Corallina
officinalis ; 7 Cystoseira crassipes ; 8 Zostera marina ; 9 Biomass distribution curve ;
//, /// Littoral horizons (Vayan). Summer zero of depth is marked by a broken line ;
biomass in g/m2 (Shchapova, 1957).

comparison of the littoral macroflora of the northern (north of Peter the
Great Bay) and the southern regions.

The composition of the littoral macrophytes of the northern part of the
western shore of Sakhalin is very similar to that of the northern mainland
coast of the Primor'e ; that of the southern part, warmed by the warm cur-
rent, is similar to the southern and central Primor'e.

Vast fields of the commercial marine grass Phyllospadix occur at 0-5 to
15 m depth in some areas of the southern Primor'e (E. Kardakova, 1957); its
mean biomass is 2 to 5 kg/m2 wet weight (0-4 to 1-0 mg/m2 dry weight).

There is a great difference between the northern and southern parts of the
Primor'e, principally in temperature. Maximum temperatures of the two
parts differ by no less than 10° in certain months ; the tides and their char-
acter vary a great deal too.

THE SEA OF JAPAN

767

A predominance of perennial forms, with an all-year-round growth, is
characteristic of the northern part of the Primor'e (T. Shchapova, 1956). They
comprise two species of Fucus and Pelvetia babingtonii which, with a biomass
of the order of 5 to 7 kg/m3, form continuous homogeneous belts. 'The
littoral of the northern Primor'e', writes Shchapova, 'is similar in the

Fig. 380. Cross section through littoral of Olga
Inlet off Cape Linden. 1 Pelvetia wrightii f.
babingtonii; 2 Gloiopeltis capillaris; 3 Nemalion
helmintoides ; 4 Rhodomela latix; 5 Cora/Una
pillulifera ; 6 Plant mozaic ; 7 Iridea sp. ; 8 Chon-
drus pinnulatus; 9 Sargassum sp.; 11 Phyllo-
spadix scouleri; 11 Costaria costata. Biomass in
g/m2 (Shchapova).

development and thickness of its fucoid cover to the littoral of the northern
Atlantic, the Murman coast and the White Sea.'

As a result of unfavourable winter conditions in the northern Primor'e
'bottom vegetation is absent from the upper half of its littoral; the fucoids
frequently sink below zero depth (displacing the fringe of red algae) and there
is a general lowering of all the zones'. The formation of a layer of red algae
Gloiopeltis above the belts of Fucus and Pelevetia is very characteristic of the
Sea of Japan (and of the Bering and Okhotsk Seas). In the upper horizon of
the sublittoral brown algae, at times forming large beds, are mixed with the
sea-weeds of a northern aspect such as the fucoids, Myelophucus intestinalis
and Stictyosiphon tortilis. This mixture of northern and southern elements in

768 BIOLOGY OF THE SEAS OF THE U.S.S.R.

the flora may be considered a consequence of severe winter conditions and a
southern geographical situation.

The central and southern Primor'e are characterized by a predominance of
annual and seasonal species, by their patchy mosaic-like distribution, by
the reduction of the Fucii and Pelvetiae to secondary species, and by the
formation of a red sea-weed border of Iridophycus, Coralina pihdlifera sp.
Rhodomela larix, and Laurensia sp. in the lower littoral. 'Whereas 85 species
of sea-weeds have been recorded for the littoral of the northern Primor'e, in
the southern 108 species were found ; moreover, the number of red algae is one
and a half times greater. In the northern Primor'e the number of brown algae
species exceeds that of the red, while in the southern Primor'e there are twice
as many red algae as brown' (T. Shchapova, 1956).

In the very south of the Primor'e, Fucii disappear altogether, Pelvetiae
become scarce and Gloiopeltis is poorly developed, while the blue-green sea-
weeds become abundant. Similarity with the tropical littoral exists in the
general thinning of the algae cover, in the development of seasonal and
ephemeral forms and in an increase in specific variety. Secular macrophytes
migrate into the sublittoral. Changes in the vegetation of the coastal strip of
the Primor'e are accompanied by alterations in the animal population, the
latter acquiring a north-boreal character in the northern part of Tartary
Bay, and a warm-water, south-boreal aspect in the central and southern
Primor'e.

The first published results of the quantitative investigations of the bottom-
living fauna of the Far Eastern Seas are those of I. Zachs (1927), K. Derjugin
(1939) and K. Derjugin and N. Somova (1941), who studied the bottom-
living fauna in Peter the Great Bay in 1925 and 1931-33. Zachs was the first
to investigate the littoral fauna of the Far Eastern Seas.

Peter the Great Bay is a vast shallow which falls away steeply to the great
depths of the Sea of Japan. The bottom-living fauna of the Bay (Fig. 381)
is distributed according to definite zones. Derjugin distinguishes 41 biocoe-
noses from the supralittoral down to the greatest depths (Figs. 382 and 383).

The quantitative and qualitative development of the supralittoral and lit-
toral flora and fauna is limited by the small tidal range. The supralittoral
zone is characterized by the development of the sea-weeds Rivularia atra
and at times of Rhizoclonium riparium, and among the animals by Ligia
cinerascens and the small crabs Brachinotus sanguineus and Doclea bidentata.

In the upper horizon of the littoral zone the rock sea-floor is characterized
by growths of Gloiopeltis capillaris (funori algae), occasionally by Ulva and
Sargassum and frequently by Littorinae (L. sitchana and L. aqualida),
Patella sp. and Turbo sangarensis; by Chthamalus challenged of the genus
Ligia cinerascens and the crabs Brachinotus sanguineus and Doclea bidentata.

The lower horizon of rocky littoral is encircled by a fringe of Corallina
pellulifera and characterized by a much greater variety of both sea-weeds
{Leathesia difformis, Ralfsia, Chordaria) and animals (Hydroida, Actinia,
young Ostrea; the Amphipoda Allorchestres zivellinus and Orchestia ocho-
tensis ; the Gastropoda Thais limoi ; the starfish Patiria pectinifera and Aphe-
lasterias japonica and others).

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770

BIOLOGY OF THE SEAS OF THE U.S.S.R,

Life is much more abundant on the soft soils of the littoral ; the biocoenosis
Arenicola cristata, Mya arenaria, Laternula kamakurana is found everywhere
there. Throughout the littoral there is a large number of the jumping Amphi-
poda, Orchestia sp. ; they frequently travel far from the coast into the fields
and forests.

Four horizons may be distinguished in the sublittoral zone : (7) A transi-
tional horizon with its characteristic Corallina, Laurensia and Chordaria

Fig. 382. Distribution of main bottom-living biocoenoses in Peter the Great Bay
(Derjugin, 1939). 1 Harmothoe derjugini + Pecten randolphi; 2 Primnoa+Luidiaster
+Thaumantometra; 3 Heliometra + Ophiura sarsi; 4 Solariella + Eupyrgus +
Stegophiura; 5 Venus +Yoldiella + Plicifusus + Ampelisca; 6 Laminaria; 7 Mal-
dane + Scoloplos + Raeta+Theora; 8 Obelia + Ophiura + Philine ; 9 Echinarachnius
parma; 10 Turitella+ite/a erosa; 11 Solen + Pelonaja + Pareugyrioides; 12 Macro-
callista; 13 Echinocardium ; 14 Balanoglossus + Labidoplax ; 15 Zostera; 16 Cor-

bicula fluminea.

on the rocky bottom, and Arenicola pusilla, Echiurus pal 'lasi and Mya arenaria
(down to 0-5 to 1-0 m); (2) a Zostera horizon (down to 12 or 16 m); (5) a
Laminaria horizon mainly L. bullata (down to 30 to 50 m) and (4) the hori-
zon of the sand plateau (50 to 200 m).

Fields of the sea grass Zostera (Z. marina on silt sand, Z. pacifica on purer
sand) give shelter to abundant fauna. Phyllospadix scoulleri, closely akin to
Zostera, forms dense growths on cliffs and rocky sea-floors. Biocoenoses
inhabiting the leaves and those living in the sea-bed and roots can be dis-
tinguished for both Zostera and Phyllospadix. Each of these groups can, in
their turn, be divided into two — animals sessile on leaves and animals swim-

THE SEA OF JAPAN

771

ming among leaves in one case, and those crawling over the bottom and
living in the soils among Zostera roots in the other. For the Zostera leaves
the following are most characteristic: the Mollusca Lacuna divaricata,
Alaba vladivostokensis, Gibbula derjugini, Rissoa sp., Pandalus latirostris,
Botryllus sp., and Syngnathus soldatovi. A great variety of Polychaeta Crusta-
cea, Mollusca and Echinodermata live in the soil among the stems and
under the roots. A Zostera biocoenosis has some features in common with
that of Phyllospadix. Some other biocoenoses also inhabit this horizon (0 to
10 m) : a fine-grain sand biocoenosis with Mactra sachalinensis, M. sulcataria,
Dosinia japonica, Tellina lutea venulosa, Echinarachnius parma, E. griseus,

V W

Fig. 383. Composition of bottom biocoenoses in Peter
the Great Bay (Derjugin and Somova,) 1 Vermes; 2
Echinodermata; 3 Mollusca; 4 Ascidia; 5 Crustacea;
6 Varia. I Maldane sarsi+Ophiura sarsi vadicola +
Nucula tenuis + Philine japonica; II Turitella fortilirata
-\- Amphiodia craterodmeta + Magelona longicornis + Yol-
diajohanni+Axinopsis orbiculata; III Venus fluctuosa-\-
Ampelisca macrocephala+Haploarthron laeve+Yol-
diella derjugini ; IV Pareugyrioides japonica + Venus fluc-
tuosa + Yoldiella derjugini + Ampelisca macrocephala ;
V Solar iella varicosa+Solariella obscura+Myriotrochus
mitzucuri+Stegophiura nodosa +S. brachiactis; VI
Heliometra glacialis+Ophiura sarsi+ Verticordia nadina.

E. mirabilis ; the oyster biocoenosis (O. gigas, O. laperousi, O. posjetica) with
many accompanying organisms, among them at times Rapana bezoar; the
biocoenosis of Amphiroa cratacea+Mytilus sp. of the type giganteus ; the sea-
weed biocoenosis Sargassum, Cystophyllum, Coccophora, Rhodomela and
others on the cliff sectors washed by the surf; the biocoenosis Balanoglossus
proterogonius-\- Tellina incongrua-\-Lebidoplax variabilis on sectors heavily
covered with silt at a depth of 3 to 5 m, and a series of others. Somewhat
below these (12 to 50 m) lies the horizon of Laminaria (L. saccharina, L.

772 BIOLOGY OF THE SEAS OF THE U.S.S.R.

bullata and L. japonica) and red algae, together with a series of their
own biocoenoses. Derjugin distinguishes among them the biocoenosis of
Laminaria thallus, the rhizoid biocoenosis, and the biocoenosis of the soil with
a large number of Polychaeta {Maldane sarsi, Scoloplos armiger), brittle stars
(Ophiura sarsi var. vadicola, Amphiodia craterodmetd), Holothuria (Cucu-
maria japonica, Stichopus japonicus), starfish {Asterias amurensis, Distolasterias
nipon), Mollusca (Pecten swift, Modiola modiolus, Yoldiajohanni, Be/a erosa,
Philine japonica) and a series of other biocoenoses with a rich and varied fauna.
K. Derjugin and N. Somova (1941) have given a quantitative description of
some of these biocoenoses. In Peter the Great Bay the biocoenosis [Maldane
sarsi -{-Ophiura sarsi var. vadicola-\-Nucula tenuis-^- Philine japonica (Fig. 383)]
is widely distributed at a depth of 14 to 40 m on a sandy silt soil.

Among the Polychaeta, which make up more than half the biomass, the
most abundant, apart from M. sarsi, are Polydora coeca and Sosane gracilior.
The total biomass of this biocoenosis is from 50 to 262 g/m2. After the Poly-
chaeta the second and third places are occupied by Echinodermata and
Mollusca.

At a depth of 25 to 45 m, also on siltysand soil, the biocoenosis Turitella for-
tilirata-\- Amphiodia crater odmeta-{-Magelona longicornis-\-Yoldia johanni-\-
Axinopsis orbiculata is commonly found. The biomass of this biocoenosis is
100 to 200 g/m2 (Fig. 383).

On sandy floors, at depths of 50 to 80 m, one of the most widely distributed
biocoenoses in the Bay is that of Venus fluctuosa-\-Ampelisca macrocephala-\-
Haploarthron laeve-\- Yoldiella derjugini (Fig. 383).

On purer sand they become the dominant form. Crustaceans are pre-
dominant (70 to 95 per cent of the biomass) in this biocoenosis. Apart from
the four forms mentioned the following are characteristic for this biocoe-
nosis : the Ascidians Pelonaja corrugata and Pareugyrioides japonica ; the
Crustacea Byblis gaimardi; the Polychaeta Scoloplos armiger, Prionospio
steenstrupi, Euchone olegi; the Mollusca Macoma calcarea, Montacuta sp.,
Axinopsis sp., Crenella decussata and many others. The mean biomass of this
biocoenosis is about 1 50 g/m2, with the number of specimens per 1 m2 up
to 15,000, mainly Crustacea.

At greater depths (80 to 200 m) the biocoenosis Venus fluctuosa-Ampelisca
macrocephala is replaced by that of Salariella varicosa, S. obscura-{- Myriotro-
chus mitsukuri-\-Stegophiura nodosa, St. brachiactis (Fig. 383). The total bio-
mass is considerably less (80 to 85 g/m2) and there is qualitative impoverish-
ment. The following should be noted in this biocoenosis apart from the above
mentioned brittle stars : Amphiodia craterodmeta, the holothurian Eupyrgus
pacificus, the Mollusca Yoldiella derjugini, Venus fluctuosa, Verticordia nadina,
the Amphipoda Ampelisca macrocephala, the Polychaeta Scoloplos armiger,
Travisia forbesi, Asychis punctata and others.

On the uppermost horizon of the bathyal, on firm sand and boulders, a
biocoenosis of the Heliometra glacialis maxima -f Ophiura sarsi with the mol-
lusc Verticordia nadina is widely distributed (Fig. 383). It contains also the
peculiar Foraminifera Bathysiphon, the Polychaeta Travisia forbesi, Amage
anope, Lumbriconereis fragilis, L. japonica, Scalibregma robusta and others,

THE SEA OF JAPAN 773

the brittle star Amphioplus macraspis, the mollusc Yoldiella derjugini, the
Amphipoda Syrrhoe crenulata, Socarnes bidenticulatus, Anonyx nugax and
others. The mean biomass of this biocoenosis is 80 to 90 g/m2, with the
number of specimens about 1,000 per m2. The mean biomass throughout the
shelf of Peter the Great Bay is 170 to 200 g/m2.

In the lower horizon of the bathyal down to 2,000 m the following bio-
coenosis is equally widely distributed: the lily Thaumatometra tenuis, with
starfish Ctenodiscus crispatus and Luidiaster tuberculatus, the coral Primnoa
resedaeformis pacifica (Gorgonaria) (reaching 2 m in height), some single
madrepore corals Caryophyllia clavus, the hydroid Lafoeina maxima, the
brachiopods Terebratulina coreanica, the polychaetes Nephthys longisetosa,
Harmothoe impar and Jasmineira pacifica, the decapods Nectocrangon dentata,
Spirontocaris biunguis and Chionoecetes elongatus bathyalis, the Gephyrea
Phascolosoma spp., and the molluscs Leda sp., Buccinumsp., and Pectenrandolfi.

At depths below 2,000 m life becomes qualitatively and quantitatively poor.
Derjugin gives the benthos of the abyssal as comprising one single biocoenosis,
owing its composition not to the abyssal fauna, but to the bathyal or even the
sublittoral. It contains many species of Rhizopoda, Hyper ammina friabilis,
Haplophragmoides canariensis, and others; the hydroid Lafoeina maxima,
the polychaetes Harmothoe derjugini, H. impar, Scalibregma inflatum,
Chaetozone setosa, Nephthys malmgreni and others ; the brittle star Ophiura
leptoctenia ; the molluscs Pecten randolfi, Axinus fiexuosus gouldi (?), Cylichna
alba corticata; the amphipods Tmetonyx cicada, Anonyx ampulloides; the
isopods Eurycope spinifrons, Gnathia elongata ; and the ascidian Goniocarpa
coriacea.

A considerable admixture of cold-water species is characteristic of the
biocoenoses living even at depths of 50 to 80 m in Peter the Great Bay. Many
of these are well known as dominant mass forms in Arctic bodies of water :
Maldane sarsi, Harmothoe imbricata, Pelonaja corrugata, Byblis gaimardi,
Lembos arcticus, Hap/oops tubicola, Scoloplos armiger, Chaetozone setosa,
Lysippe labiata, Rhodine gracilior, Macoma calcarea, Crenella decussata,
Lacuna divaricata, Margarita helicina, Natica clausa, Venus fluctuosa and
Ophiopholis aculeata. All these species are present as dominant or characteristic
forms in the bottom-living biocoenoses of the Barents Sea.

At depths below 80 to 100 m a number of similar species such as Ophiura
sarsi, Ctenodiscus crispatus, Heliometra glacialis, Ophiocantha bidentata,
Stegophiura nodosa, Travisia forbesi, Lysippe labiata, Polycirrus medusa,
Myriochele oculata, Lumbriconereis fragilis and others are also included. On
the other hand, in the upper horizons, there is an admixture of tropical species
such as the crustaceans Blephariposajaponica, Calianassa sp. and Upogebia sp.,
Charybdis japonicus, the molluscs Alaba sp., Alectrion sp. and others.

K. Gordeeva (1949) added to Derjugin's description of biocoenoses some
supplementary data on the eastern part of Peter the Great Bay. A selection is
given in Table 311.

The bottom-living fauna of the Sea of Japan becomes markedly poorer in
species with increasing depth. Only fifty-three species of macrobenthos are
known for depths of 1,000 to 2,000 m, twenty-five for 2,000 to 3,000 m and
only five below 3,000 m (21 in the Sea of Okhotsk). Similarly the corresponding

774

BIOLOGY OF THE SEAS OF

THE U.S.S.R.

Table 311

Depth,

Mean

and

Dominant species of biocoenosis,

biomass,

soil

number of species/m2

g/m2

Remarks

15-35

Felaniella olivacea (438) + Scolo-

522-9

Molluscs constitute about three-

sand

plos armiger + Olivella falgu-

quarters of biomass, echino-

rata

derms about one-quarter

30-35

Echinarachnius parma+Amph-

343-4

Echinoderms constitute about

sand

iodia rossica + Scoloplos armi-

four-fifths of biomass, sipun-

ger

culids about one-fifth

51-58

Maldanidae sp. + Sen ipes groen-

398-5

Bivalves constitute four-fifths of

silty-

landicus + Lumbriconereis sp.

biomass. H2S present in soil

sand

55-64

Ampelisca macrocephala+ Lum-

182-4

More than half biomass com-

silty-

briconereis sp. + Amphioplus

posed of crustaceans, about

sand

macraspis + Plicifusus olivaceus

one-quarter of echinoderms

80-200

Macoma calcarea + Ceriantharia

212-6

Worms, Actinia, molluscs each

firm

+ Maldanidae sp . + Ophiura

form 28 per cent of biomass ;

sand

sarsi

the remainder are echino-

177-238 Ophiopenia tetracantha + Ophi-
fine ura sarsi + Verticordia nadina

sand —Amphioplus macraspis

and mud
340 Heliometra glacialis maxima +

Ophiura sarsi + Verticordia na-
dina

derms
158 Echinoderms form more than
half of biomass

242 Biomass formed almost
clusively of echinoderms

ex-

numbers of species of Foraminifera are fifty- two, nine and three (14 in the
Sea of Okhotsk). This is much less than in the neighbouring Okhotsk and
Bering Seas (O. Mokievsky, 1954). It is well known that the true deep-water
fauna is absent from the abyssal in the Sea of Japan. The most eurybathic
sublittoral organisms descend into it. The youth of this faunal group is re-
flected in the fact that it has not yet had time to acquire an endemic character.
Only very few deep-water forms can be called endemic (the polychaetes Har-
mothoe derjugini and Tharix pacifica ; the echinoderms Pedicillaster orientalis;
and the crab Chionoecetus angulatus bathyalis). At the same time a large
number of eurybathic species with a wide vertical habitat live in the depths
of the Sea of Japan (the polychaetes Capitella capitata, Maldane sarsi, Tere-
bellides stroemi, Artacama proboscidea, Harmothoe impar, Spiochaetopterus
typicus, Chaetozone setosa; the molluscs Thyasira flexuosa; and the echino-
derms Ctenodiscus crispatus and Ophiocantha bidentata). All these forms are
also widely distributed in the Arctic seas.

Boreal forms also live in the depths of the Sea of Japan (the polychaetes
Notoproctus oculatus, Aricidea succica; the crustaceans Nicippe tumida,
Urothoe denticulata, Nectocrangon dentata, Eualus biwiguis; the molluscs

THE SEA OF JAPAN
Table 312

775

Biomass, g/m2

Depth,

Mean

Maximum

Minimum

100-200

306

907

6-3

200-500

168

15-2

500-1,000

138

0-2

1,000-2,000

0-15

2,000-3,000

2-2

005

3,000-3,500

0-23

0-45

008

Yoldiella derjugini, Yoldia beringiana, Propeamussium randolphi, Ruccinum
bryani; the echinoderms Leptychaster anomalus, Synalactes nozamai and
others). In the Sea of Japan the biomass also decreases markedly as depth
increases (O. Mokievsky, 1954) {Table 312).

As can be seen from Table 312 the biomass decreases 1 ,300 times with depth
but the range of its fluctuations is considerably curtailed.

K. Derjugin (1933, 1935, 1939) has observed the following characteristics
of the fauna (both plankton and benthos) of the great depths of the Sea of
Japan: qualitative and quantitative impoverishment, absence of typically
abyssal elements, and the sinking to unusual depths of members of the sub-
littoral and bathyal fauna. The plankton of the depths of the Sea of Japan
(K. Brodsky, 1941; M. Vinogradov, 1953) includes: Radiolaria of the
families Challengeridae and Aulospheridae ; the Siphonophora Dymophies
arctica ; the Ctenophora Beroe sp. ; the Copepoda Gaetanus minor, Gaidius bre-
vispinus, Eucalanus bungii, Pareuchaeta japonica, Calanus cristatus, C. tonsus
(plumchrus), Scolecithricella minor, Microcalanus pigmaeus, Metridia lucens
{pacified), Oncaeaborealis, Microsatella rosea; the Ostracoda Conchaecia spp. ;
the Amphipoda Primno macropa, Parathemisto japonica ; the Mysidae Metery-
throps microphthalma, and the Euphausiidae Euphausia pacifica, Thysanoessa
longipes, Th. inermis. A comparison between the zooplankton biomass of the
Sea of Japan and of the adjacent regions of the Pacific Ocean shows the con-
siderable poverty of the former {Table 313).

M. Vinogradov had approached this problem differently (1959), following

Table 313. Plankton biomass {mg/mz) in the Sea of Japan {K. Brodsky, 1941) and in
the Kuril-Kamchatka trench {M. Vinogradov, 1954)

Depth

Sea of

Japan

Kuril-Kamchatka

Winter

Mean annual

trench, May-June

0-50

313

530

510

50-100

305

230

379

100-200

120

288

200-500

147

114

228

500-1,000

59-3

1,000-2,000

0-3

21-8

776 BIOLOGY OF THE SEAS OF THE U.S.S.R.

the analogy of the deep-water plankton of the Sea of Japan. While not deny-
ing the fact that the penetration of the deep-water plankton forms into the
Sea of Japan from the adjacent part of the Pacific Ocean is restricted by the
shallowness of the straits leading into it, Vinogradov draws attention also
to the contemporary physicochemical characteristics of the Sea of Japan as a
possible limiting factor. He confirms the conclusions of previous investigators
that only ' those species which, in the adjacent waters of the Pacific Ocean
and the Sea of Okhotsk, live at depths of less than 200 to 500 m are found in
the deep-water plankton of the Sea of Japan ; they rise during their daily
migrations at least to 50 to 100 m'. Many of the plankton and benthos species
sink down in the Sea of Japan to much greater depths than those which are
usual for them in the Pacific Ocean. Qualitatively and quantitatively, how-
ever, the deep-water fauna of the Sea of Japan is considerably impoverished.
Vinogradov has remarked on the large number of plankton species found in
the upper layers of the Ocean in the areas adjacent to the straits which do not
penetrate into the Sea of Japan.

The deep waters of the Sea of Japan have a lower temperature (0-12° to
0-22°) and somewhat lesser salinity (34-08 to 34T4%0) than the adjacent parts
of the Pacific Ocean and the Bering and Okhotsk Seas (-1-55° to 2-2°;
34-61 to 34-72%0). The main explanation of the absence of a specific deep-
water plankton in the Sea of Japan, in Vinogradov's opinion, is associated
with this difference in temperature and salinity conditions which might, he
thinks, possess the significance of a decisive factor, independently of the
geological past of the Sea.

In recent years the littoral fauna of the Sea of Japan has been investigated
by O. Mokievsky (1956, 1959), who has found much similarity between the
littoral fauna of the northern part of the Tartary Strait and the Sea of
Okhotsk, which are characterized by homogeneous colonies of comparatively
large-sized, mainly secular species. The rocks of the sublittoral and the
supralittoral here are inhabited by Littorina sitchana subtenebrosa. Differ-
ences are observed in the barnacles of the supralittoral : while mixed colonies
of Balanus balanoides and Chthamalus dalli, with a predominance of the
former, are characteristic of the Sea of Okhotsk, in the Sea of Japan the
supralittoral is populated almost exclusively by Chth. dalli. Lower down live
organisms which are also characteristic of the Sea of Okhotsk: Acmaea testu-
dinalis, Littorina squalida, Thais lima, large Gammaridae {Gammarus locu-
stoides, Echinogammarus spasskii and others), Idothea ochotensis; loosely
packed soil is inhabited by Nereis vexillosa, Eteone longa, Arenicola claparedi
and a few Maeoma baltica. It is to be noted that these last five species have not
been observed in the littoral of the central and southern Primor'e. The fauna
of fucii and other sea-weed growths, abundant in the northern part of the
Tartary Strait, is very poor both qualitatively and quantitatively. The number
of specimens is commonly not more than 100 to 2,000 per m2, the biomass
being from 25 to 150 g/m2.

In the central and southern Primor'e the fauna of the upper horizons of the
rocky littoral changes comparatively little. However, Mokievsky describes
some marked alterations in the sublittoral. Patchy growths of brown algae are

THE SEA OF JAPAN 777

populated by a varied and extremely numerous fauna of small crustaceans :
Amphipoda (Caprella spp., Jassa pulchella, Ischyrocerus spp., Parhyale zibel-
lina, Allorchestes spp., Pontogensia spp. and others) ; Isopoda (Dynamenella
glabra, Janiropsis kincaidi) ; Polychaeta of the families Syllidae and Nereidae ;
small Gastropoda (Cingula spp., and others), and a number of other groups.
Some of these species are altogether absent from the northern part of the
Tartary Inlet ; others are peculiar only to various biocoenoses of the sub-
littoral, others again are found only in insignificant numbers. South of the
Tartary Strait the number of these inhabitants of the brown sea-weed beds
of the sublittoral usually varies from 10,000 to 200,000 specimens per m2
with a small biomass (usually 50 to 150 g/m2, rising to 200 to 500 g/m2 only
in Corallina beds). The fauna of the loose soils of the Primor'e also changes
considerably.

Mokievsky explains these marked differences in the composition, and
especially in the distribution, of the littoral fauna of the two parts of the Sea
of Japan not only by the changes of temperature and climatic conditions, but
also by differences in its tidal ranges — the range of the tides in the northern
part of the Tartary Strait being over 2 m and in the central and southern
Primor'e, on the average, 1 m.

Mokievsky maintains that moisture conditions are basically different on
littorals with low and high tidal ranges, inasmuch as in the first case the tidal
effect on the sea-level is commonly moderated by the swell and by seasonal
and sporadic fluctuations of the level ; while in the second case there is a
precise tidal rhythm — semi-diurnal, diurnal or a mixture of the two. Pointing
out that the taxonomic composition of coastal flora and fauna is determined
first of all by the temperature factor, Mokievsky attaches very great import-
ance to the character of its moistening (in terms of the height of the tide) in
the formation of such features of the littoral as its zonality, the nature of its
biocoenoses and the quantitative indices and ratios. On this basis he distin-
guishes two types of littoral in the Soviet Far Eastern Seas. In his opinion the
littoral of the Sea of Okhotsk, of most of the Barents Sea, of the eastern coast
of Kamchatka and of almost the whole of the Kuril Range, and also of the
northern part of the Tartary Strait, belongs to the type of north-boreal littoral
with a long tidal range (from 1-15 m to 10 or even 13 m), while the central
and southern Primor'e and the southwestern coast of Sakhalin belong to the
south-boreal type with a short tidal range.

In contrast to other Far Eastern Seas the variety offish in the Sea of Japan
is exceptionally great [about 615 species; among them, in the northern part
from Peter the Great Bay to Sakhalin and the Tartary Strait, 245 have been
distinguished (T. Rass)]. This is a meeting place of cold-water fish and
subtropical and tropical fish which have penetrated into the Sea of Japan from
the south with the Tsushima current. The tropical and subtropical fish com-
prise members of the families Gobiidae (30 species), Chaetodontidae, Ser-
ranidae (15 species), Pharyngognathi, Balistidae, Monocanthidae, Ostra-
ciidae, Labridae (11 species), Carangidae (12 species) and Tetrodontidae
(12 species).

The number of tropical and subtropical fish decreases sharply as one moves

778 BIOLOGY OF THE SEAS OF THE U.S.S.R.

northward ; and in Peter the Great Bay the dominant forms are already such
cold-living families as Pleuronectidae (10 species), Cottidae (37 species),
Agonidae (14 species), Liparidae and Cyclopteridae (13 species), Pholidae
and Stichaeidae (21 species). However tuna fish, Trichiurus, Geriola, Auxis
and others have also been recorded in Peter the Great Bay in summer.

An even more cold-water aspect is acquired by fish in the Tartary Strait,
warm- water species being rare there ; in summer, however, the hammer-head
shark, the ray Trygon akjci, sayra, Trichiurus, and some others enter the
Strait. Warm-water fish penetrate much father northward along the eastern
side of the Sea of Japan and even through La Perouse Strait into the southern
part of the Sea of Okhotsk and to the southern Kuril Islands. Hence the
entire Sea of Japan, so far as its ichthyofauna is concerned, may be in-
cluded in the boreal region, with the possible exception of its most southerly
part. The remarkable similarity of the fish of the Sea of Japan and of the
Mediterranean Sea has often been noted (A. Gunther, 1880). G. Lindberg
(1947) gives a list of 90 families, 63 genera and 12 species common to these
two seas.

Until recently only eight oceanic deep-water fish had been recorded in the
Sea of Japan (T. Rass, 1954), but it has now been shown that their number is
greater, due to some additional species which inhabit the southeastern part.

There are apparently about twenty ' secondary ' deep-water fish (in Andria-
shev's terminology).

About 40 species of the fish in the Sea of Japan are of commercial value.
Until recently the Pacific sardine (Sardinops sagax melanostictus) was among
the most important. Soviet sardine fisheries were rapidly developed in the
'thirties, and by 1937 they were taking 1-4 million centners a year; but they
began to decrease in 1940 and during the 'forties ceased altogether. The sar-
dines disappeared from the Sea of Japan as a consequence of a considerable
fall in temperature. They ceased to enter their usual spawning-places and
abundant grazing groups in the Sea of Japan, and one may suppose that large
numbers of sardine fry perished owing to unfavourable temperature condi-
tions and a shortage of food. Pacific herring (Fig. 384) (Clupea harengus pallasi)
has for a long time occupied an important place in the fisheries there. Her-
ring aggregations are particularly large during their spawning migrations to
the coast of Hokkaido and the Primor'e and especially in the waters of
southern Sakhalin. The number of herrings approaching the shores is greater
than anywhere else in the world . . . ' the approach of the shoals of herring to
the shores of southern Sakhalin in April is sighted by the fishermen from far
away by the colour and movement of the water and by the behaviour of the
sea-birds : flocks of sea-gulls and kittiwakes start circling over the water,
filling the air with their cries' (P. Schmidt, 1948). 'The herring lay their eggs
on the coastal sea-weeds, in the shallowest patches on the shores. The male
herring discharges its milt in such amounts that the water frequently becomes
milky white for many hundreds of metres from the coast ; since milt is fatty,
the swell on the banks is calmed as if oil had been poured on to it, and the
surface of the Sea becomes smooth. So many ova are laid that, if there is a
storm and the ova are cast up on the shore, they form a regular bank which

THE SEA OF JAPAN

779

when it dries out, is turned into a soft carpet some few metres wide, stretching
for kilometres along the coast' (P. Schmidt, 1948).

Among the bottom-living fish of the Sea of Japan, the cod Gadus morrhua
macrocephalus and Theragra chalcogramma, and Soleidae, Cynoglossidae
and other flatfish except halibut are those usually fished for.

Some pelagic fish enter the Sea of Japan for feeding and reproduction,

Ca/anus

Euphausiacea

Fig. 384. Diagram of Feeding correlation be-
tween the herring and other organisms. 1 Fish
fry; 2 Caplin; 3 Starling; 4 Navaga; 5 Cod;
6 Shark; 7 Skumbria; 8 Pink salmon; 9 Jelly-
fish.

wintering, however, outside its boundaries (sardines, mackerel). In January
to March the main mackerel aggregations of the Sea of Japan are concen-
trated within the area of the Tsushima Strait, at a temperature of 12° to 15°.
As the temperature rises mackerel penetrates the Sea of Japan along its
eastern and western shores, reaching the Tartary Strait by August and the
beginning of September. With the cold autumn weather mackerel moves in
the reverse direction. Mackerel spawns in the coastal zone, in inlets and bays,
from April to the middle of June, and in Peter the Great Bay in June and July.

780 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Characteristically, mackerel feeds intensively during the period of its
spawning migration. After spawning, mackerel concentrates in the northern
part of the Sea in large numbers for feeding. It feeds mostly on large copepods
{Calanus tonsus, C. finmarchicus) and euphausiids (Thysanoessa raschii and
77?. sp.) and, as a predator, consumes also fish fry.

The study of the feeding habits of flatfish (Pleuronectidae family) of the
Far Eastern Seas (N. Gordeev, 1954; L. Mikulich, 1954) has shown that
halibut {Hippoglossus hippoglossus stenolepis, Reinhardtius hippoglossoides
matsurae, Atherestes evermanni) lives mostly on fish. Seventy-two per cent of
the diet of the first-named consists of fish (pollack, sand-eel and others). The

Fig. 385. Food correlation of plaice in the area of the southeastern coast of
Sakhalin (Mikulich, 1954). Thick lines — strong food correlations ; thin lines —
average, broken lines — weak food correlations. 1 Limanda aspera ; 2 Platessa
quadrituberculata ; 3 Pleuronectes stellatus ; 4 Limanda punctatissima probos-
cidea ; 5 L. p. punctatissima ; 6 Glyptocephalus stelleri ; 7 Pseudopleuronectes
yokohamae ; 8 Acanthopsetta nadeshnyi ; 9 Hippoglossoides elassodon dubius ;
10 Atheresthes evermanni; 11 Hippoglossus hippoglossus stenolepis.

second place in its diet is occupied by large crustaceans (crabs, hermit crabs,
amphipods, prawns) and large molluscs (Seripes groenlandicus and cephalo-
pods).

The majority of the Pacific Ocean flatfish, in contrast to halibut, are bentho-
pages (worms, polychaetes, molluscs, sometimes bottom-living crustaceans
and echinoderms). The diet of some flatfish is mixed, both fish and pelagic
crustaceans forming at times a considerable part of it (Figs. 385 and 386).
Stomach repletion indices of halibut and flatfish are 150 to 200, rising some-
times to 300 or even 600. The nature of the food of the Far Eastern Pleuro-
nectidae, both halibut and flat flounder, is very similar to that of those in the
Atlantic.

Owing to the peculiar temperature conditions of the surface water and the
narrowness of the shelf zone, the migrations of Pleuronectidae in the Sea of
Japan have a destructive character, similar to that of cod and Kamchatka
crab (Fig. 387). In summer they feed intensively in the off-shore areas which

Fig. 386. Feeding of flatfish of Far Eastern Seas (Mikulich, 1951).
I Hippoglosus hippoglossus stenolepis (Bering Sea); II Limanda
aspera (southwestern coast of Sakhalin) ; III Pseudoplewonectes
herzensteini (southwestern coast of Sakhalin); IV Pleuronectes
stellatus (western and eastern coast of Sakhalin) ; V Hippo-
glossoides elassodon dubius (Tartary Strait, Syurkum Cape).
1 Pisces; 2 Echinodermata ; 3 Mollusca; 4 Crustacea (bottom-
living) ; 5 Crustacea (pelagic) ; 6 Polychaeta ; 7 Varia ; 8 Sea-bed.

Fig. 387. Plaice migrations in Peter the Great Bay (Moiseev).
1 Winter shoalings ; 2 Summer shoalings.

782 BIOLOGY OF THE SEAS OF THE U.S.S.R.

are rich in benthos ; in winter they migrate into deeper parts, avoiding the
considerably cooled surface waters (P. Moiseev, 1955).

In 1955 about 1-6 million tons offish were taken from the Sea of Japan.
In 1936 the total catch was considerably higher, reaching 3 million tons
(T. Rass, 1948), mainly owing to a much greater catch than in 1955 of sar-
dines (Sardinops sagax melanosticta) and pollack (Theragra chalcogrammd).

The Primor'e is exceptionally rich, both qualitatively and quantitatively, in
commercial sea-weeds and in invertebrates. Among the bivalves the follow-
ing either are commercially significant or could become so : Ostrea gigas.
Mytilus grayanus, Pecten jessoensis, Mactra sachalinensis and Mya arenaria,
There are more than 20 species of bivalves of secondary significance. The
cephalopods Ommastrephes sloanei pacificus, Octopus dofleini, Paroctopus
conispadiceus and Octopus gilbertianus are of great commerical importance.
Trepang — Stichopus japonicus — has for a long time been an important item in
the fisheries of the Sea of Japan.

Apart from Kamchatka crab, the decapod crustaceans Pandalus latiro-
stris, Sclerocrangon selebrosa, Crangon septemspinosa and some others
are of great importance in the fisheries of the waters of the Primor'e and
southern Sakhalin. Stocks of all these invertebrates are very large in the Sea
of Japan, and the prospects of their commerical development are immense.

15
The Sea of Okhotsk

I. PHYSICAL GEOGRAPHY

The Sea of Okhotsk is separated from the Pacific Ocean by the Kuril
Islands. Numerous deep straits, but none deeper than 2,318 m (Boussole),
run between them. The great Kuril range, which rises above sea-level as a
chain of islands, forms a submarine barrier — the 'Vityaz ridge' — with its
eastern slopes sinking down to 10-3 km into the depths of the Kuril-Kam-
chatka trench. This geosyncline zone, of the Tertiary or pre-Tertiary Period,
runs from southwest to northeast comprising the south Okhotsk trench, the
two Kuril ranges divided by a trench, the deep-water Kuril-Kamchatka
trench and the bank which borders its southeastern side.

The process of the formation of the geosyncline zone of the Kuril-Kam-
chatka arch is not yet complete, and it is particularly active in its northern
part; it is connected with the phenomenon of the overthrust of the Con-
tinental block of Eastern Asia on to the bed of the Pacific Ocean (G. Udintzev,
1955).

The area of the Sea of Okhotsk is 1,590,000 km2, the volume of its waters
1,365,000 km3, its maximum depth 3,657 m, and its average depth 859 m. In
area the Sea of Okhotsk occupies second place after the Bering Sea among
the seas washing the shores of the u.s.s.r., while in volume it is fourth, after
the Bering, Japan and Black Seas. Its area is 42 times greater than that of the
Sea of Azov and its volume 4,500 times greater. The bottom topography
of the Sea of Okhotsk is rich in features (Fig. 388). To the south a deep
trench stretches in a latitudinal direction, south of 48° N, demarcated from
the northern part of the Sea by the 3,000 m isobath and a steep slope down to
the 15,000 m isobath. Its central part is 1,000 to 1,500 m. deep forming, how-
ever, some terraced elevations : two at a depth of approximately 1 ,000 m cut-
ting the central hollow of the Sea into two parts, and a northern ledge at a
depth of about 200 m bordering the northern shallows (the shelf proper) on the
southern side. The circulation of sea-water (Fig. 389) is greatly influenced
by the two terraced elevations, and the distribution of bottom deposits is
determined by them (Fig. 391).

Small streams of warm Pacific Ocean surface waters penetrate into the Sea
of Okhotsk through the northern Kuril Straits, warming the western shores of
Kamchatka, some even reaching Shelekhov Bay in small amounts. The main
masses of these warm waters, partly under the effect of the general system of
cyclonic rotation, turn westward and break up in a fanlike manner in the
central part of the Sea. Warm surface waters can be traced by the presence of
the crustacean Calanus tonsus (Fig. 390).

Deep Pacific Ocean waters, entering the Sea of Okhotsk mainly through the
Kruzenshtern Strait, fill the central hollow of the Sea and, moving north-
ward under the influence of the bottom topography, turn westward at each

783

Fig. 388. Sea-bed relief of the Sea of Okhotsk (Bezrukov).

(60' I64'*s-

Fig. 389. Currents of Sea of Okhotsk (diagram).

Fig. 390. Distribution of
Calanus tonsus. 1 Direc-
tions of current; 2
Calanus distribution
(Lubny-Gertzyk, 1955).

786 BIOLOGY OF THE SEAS OF THE U.S.S.R.

of the elevations mentioned, forming part of the total current through the
southern Kuril Straits (mainly through the Boussole Strait). Warm waters
divide in the north, following bottom topography, into a larger northwestern
branch which approaches Iona Island through the Derjugin trench, and a
smaller northeastern branch flowing towards Shelekhov Bay through the
Tinro trench.

The southern trench of the Sea of Okhotsk, with depths greater than the
maximum depth of the straits, is somewhat isolated both from the Sea itself
and from the adjacent parts of the Pacific Ocean. Hence the deep-water masses
of the Sea of Okhotsk may be divided into the deep Pacific Ocean waters and
the waters of the southern trench (Fig. 402). The wide Shelekhov Bay with
its two additional bays — the western Gizhiginskaya Inlet and the eastern
Penzhinskaya Inlet — lies in the northwest of the Sea of Okhotsk.

The northwestern part of the Sea or, more precisely, the western part of
the northern half of it, sometimes called the Shantar-More, is situated north-
west of the northern end of Sakhalin. The Shantar Islands (the Greater and the
Lesser) lie in the westernmost part of the Bay. The cone-shaped Iona Island
rises on the outer side of it. Two small islands (Safar'ev and Zav'yalov) are
situated at the northern end of the Sea at the entrance into the Tauisk Inlet.
The small Tyulenyi Island, with its important seal fishery, lies off the eastern
coast of Terpienya Bay, on the southeastern coast of Sakhalin.

The deposits of the Sea of Okhotsk bed are most varied (P. Bezrukov,
1955), sand, rock and cliff soils being found at all depths (Fig. 391). Cliffs
and gravel-shingle soils descending to depths of 3,000 m are strongly featured
on the slopes of the Kuril ridge and submarine range and off the coast of
Kamchatka. Cliff outcrop formations may be due to different causes such as
volcanic activity, the abruptness of the slopes, or the rapid currents. Even the
floor of the Kuril Straits and the marginal parts of the Ocean are frequently
covered by coarsely broken stones, When moving from north to south in the
Sea of Okhotsk, zones of hard soils are found occasionally, in conformity
with the bottom topography. The first zone is adjacent to the northern coast
(Fig. 402) ; the second lies at a depth of 100 to 1 50 m, the third at the Elevation
of the Institute of Oceanography, below 1 ,000 m. The fourth and fifth zones
lie on the elevation of the sea-bed along the northern and southern slopes of
the southern Okhotsk trench (the Elevation of the Academy of Sciences), in
Boussole Strait and elsewhere. The southern trench of the Sea of Okhotsk
is filled with soft ooze or oozy clay containing a large amount of amorphous
silica (diatoms and radiolarians) ; this latter forms a considerable part of all
the deposits throughout the Sea of Okhotsk (Fig. 392). Such an abundance of
silica as that found in the northwestern part of the Sea of Okhotsk is not
known in any other sea. Along the northwestern coast, in the region of Shantar
and Iona Islands, and in Shelekhov Bay with its inlets, boulder-gravel-
shingle floors are exceptionally abundant. Sands encircle the Sea, forming an
especially wide zone along the western coast of Kamchatka, the eastern and
northern shores of Sakhalin and along the ocean coast of the Kuril Islands.

On the mainland side the Sea of Okhotsk is surrounded by mountainous
formations, mostly of Mesozoic overthrust. Sakhalin, Kamchatka and the

Fig. 391. Bottom soils of Sea of Okhotsk (Bezru-
kov). 1 Boulder-shingle-gravel deposits ; 2 Sands ;
3 Aleurites ; 4 Aleurites-clay-diatomaceous oozes ;
6 Aleurites-clay oozes without silica; 7 Outcrops
of rock.

1Ж

П6 nS 150 !3г 15* 156 158 ISO 'б? 4* !Sl

Fig. 392. Distribution of amorphous silica in surface
layer of soils of Sea of Ohkotsk. 1 Less than 10 per cent;
2 From 10 to 20; 5 From 20 to 30; 4 From 30 to 40; 5
From 40 to 50; 6 More than 50 per cent (Bezrukov, 1955).

788

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Kuril Islands are formed by younger Mesozoic tectonic structures. Kam-
chatka and the Kurils are built of volcanic rock. Shelekhov Bay, especially in
its inner part, has very high tides (reaching 13 m), very strong tidal currents
and wide rock and sand beaches, and more rarely shores which dry out at low
tide. A series of broad lagoons, formed by alluvium from the rivers, stretches
along the northern shore of Sakhalin. The whole western shore of Kamchatka
is an alluvial plain.

The climate of the Sea of Okhotsk is more severe than that of any other
Far Eastern Sea. Its characteristics have been given above. Its cold inter-
mediate layer — a similar one is known only in the Kara Sea — is exceptionally
wide, especially in the north of the Sea.

The characteristic features of the distribution of temperature, salinity and
oxygen are given in Table 314.

Table 314

Oxygen

Depth

Temperature

Salinity

°C

°/

/00

cm3/l

Percentage of
complete
saturation

10-90

29-70

8-68

103-2

-1-58

32-88

8-10

95-0

-1-67

32-97

—

100

-1-51

33-04

7-58

89-2

150

010

33-33

4-87

600

200

0-78

33-46

4-10

51-4

500

1-88

33-82

216

28-6

1,000

2-32

—

0-77

100

1,500

2-32

34-29

0-70

9-2

The presence throughout the year of a substantial intermediate cold layer
in the Sea of Okhotsk has a decisive effect on the distribution of the zoo-
plankton and its vertical migration, since it cuts off the layers of water lying
above and below it. The benthos distribution is considerably affected by the
low content of oxygen in the depths of the central and southern trenches
(Fig. 393). The thick ice cover which forms in winter has an immense in-
fluence on the development of life in the coastal zone.

II. FLORA AND FAUNA

Micro-organisms

Fairly high indices are obtained for the quantitative distribution of micro-
organisms in the region of the Kuril Islands {Table 315).

Similar data were obtained later by A. Kriss (1958), who also gives the
mean biomass of micro-organisms for the Kuril-Kamchatka trench. It is
evident from the data of the two columns in Table 315 that the number of

THE SEA OF OKHOTSK

789

micro-organisms decreases with depth by some thousands of times (1,500
to 5,500).

Kriss also mentions the immense number (maybe thousands per 1 ml of
water) of suspended articles in the water, from a few to a hundred microns

140

150

160

Fig. 393. Isoxigenes of the near-bottom layer of Sea of Okhotsk

(Ushakov).

in size. The huge absorption surface of these small bodies is, according to this
investigator, most significant for an understanding of the biological and
physicochemical processes taking place in the water column.

Plankton

The list of the phytoplankton of the Sea of Okhotsk contains 290 species of

diatoms and 58 species of peridineans (P. Ushakov, 1953).

According to the data of A. Zhuze and G. Semina (1955) diatomaceous
sea-weeds are markedly predominant in the Sea of Okhotsk phytoplankton,
comprising from 70 to 100 per cent of its biomass. This latter may reach

790 BIOLOGY OF THE SEAS OF THE U.S.S.R.

20 g/m3 with 7 milliards of cells per 1 m3 ; this conforms with the abundance
of (amorphous) silica in the surface layers of the soil (up to 35 per cent and
in some parts of the Sea more than 50). Arctic and Arctic-boreal species
are predominant during the spring maximum (Thalassiosira nordenskioldii,
Th. gravida, Fragilaria oceanica, Chaetoceros furcellatus, Bacterosira fragilis).
More thermophilic species {Chaetoceros constrictus, Leptoclyindricus danicus)
are predominant during the autumn maximum. Only one maximum — the
spring-summer bloom — is recorded in the north of the Sea of Okhotsk
(P. Ushakov, 1953). This is a sign of very severe climatic conditions.

Table 315

No.

of micro-organisms

Depth,

(direct count)

No. of specimens/ml

Biomass, mg/m3

(E. Limbert-Ruban)

(A. Kriss)

29,603-8

33-3

37,484-9

40,259-3

18-800

8,699-7

11100

100

4,084-9

6- 100

500

3,421-4

0-300

1,000

3,856-9

0-400

1,500

2,363-9

0-300

3,000

234-3

0050

3,500

191

6,000-7,000

—

0010

7,000-8,000

—

0010

8,500-9,000

—

0006

Investigators have established the very interesting fact that the range of
diatoms in the water column corresponds exactly with those in the bottom
deposits. Only the thin-shelled diatoms may dissolve at considerable depth
when sinking to the bottom. It has been found experimentally on the basis of
the research mentioned, that the distance from the coast can be estimated by
the composition of the diatoms in the deposits. In coastal areas neritic dia-
toms form 78 per cent of the deposits ; in oceanic regions the same percentage
is composed of oceanic species.

The composition of the diatoms in cores of the soil (16 to 27 m) from great
depths of the Bering and Okhotsk Seas was examined by A. Zhuze (1954).
The whole thickness of the deposit, taken in the core, does not go beyond the
limits of the Quaternary Period ; moreover, the composition of the diatoms
according to horizons is exactly the same in both Seas. In the uppermost
layer (1-5 to 1-8 m) are found all the diatoms now living in the plankton,
mainly Coscinodiscus oculus iridis, С marginatus, Thalassiothrix longissima
and Rhizosolenia hebetata.

The composition of the diatoms in the 1-5 to 5 m layer of the soil is very

THE SEA OF OKHOTSK 791

mixed, with a predominance of neritic, re-deposited and fresh-water species.
At depths of 5 to 1 1 m below the surface of the soil oceanic diatoms again
become markedly predominant; there is, however, a considerable ad-
mixture of neritic forms. In the fourth horizon (10 to 16-5 m), as in the second,
diatoms become scarce, while the neritic (possible glacial) and fresh-water
forms are again predominant. Below about 16 m there is again a greater
abundance of oceanic species with some neritic ones and some bottom-living
diatoms of the Pliocene Age. Zhuze thinks it possible to synchronize the
layers rich in oceanic diatoms and those which are poor in them but have
an admixture of neritic and fresh-water forms with two periods of glaciation
and two inter-glacial periods. The contemporary period has the most 'oceanic'
aspect, and exchange between the Okhotsk and Bering Seas and the open
Ocean is on a greater scale now than ever. Changes in the Foraminifera in the
bottom deposits of the Sea of Okhotsk have also been comprehensively in-
vestigated (Kh. Saidova, 1953, 1955). About fifty such species were recorded,
including those in the Bering Sea, and almost all of them exist at present.
Examination of the successive layers of soil cores led Zhuze to the conclusion
that during the deposition of the layer of the sea-bed examined the Sea of
Okhotsk trenches underwent a submersion. The numbers of shallow-water
and cold-water Foraminifera increase with the depth.

Cold-water organisms are predominant in the summer zooplankton in the
north of the Sea of Okhotsk. The greatest plankton biomass (1,000 to 3,000
mg/m3) was recorded in 1949 in the east of the region at depths of more than
25 m (Fig. 394) at some distance (100 to 150 km) from the coast (M. Kuhn,
1951). There was a considerable predominance of Metridia sp., Oithona
similis, Pseudocalanus elongatus, Microcalanus pygmaeus, Acartia longiremis,
Sagitta sp. and Themisto libellula in the upper horizons (less than 25 m).
In the lower, most productive layers (below 25 m) and in addition to the
Metridia sp. (45 to 50 per cent of the biomass) and Themisto libellula men-
tioned above, there was a predominance of Calanus finmarchicus, C. tonsus,
С cristatus and Pareuchaeta japonica. The temperature of these lower horizons
is, however, below freezing point in summer. Some zooplankton species
{Metridia sp., Themisto libellula and Calanus finmarchicus), in spite of the
markedly cold intermediate layer, migrate freely through it.

A considerable admixture of warm-water and partly subtropical members
of the Calanoida group appears in two areas of the Sea of Okhotsk. They are
brought into the most southwesterly corner of the Sea through La Perouse
Strait with branches of the Tsushima current. Warm-water plankton forms
are also brought through the Kuril Straits by the warm Pacific waters into
the southeastern part of the Sea. Species of the genera Clytemnestra, Claudo-
calanus, and Pleuromamma can be mentioned among these warm-water
forms.

In the most northwesterly part of the Sea (Bay of Sakhalin) not only are
estuarine and brackish-water species (Eurytemora asymmetrica, E. herdmani,
E. americana, Acartia bifilosa, Totanus derjugini, Sinacalanus tenellus) greatly
developed under the effect of the fresh water of the river Amur, but also the
true fresh-water groups (Rotifera and Crustacea) are plentiful.

50-25 metres

: 1100- WOO mg/m
1000-500 mg/m

Fig. 394. Distribution of plankton biomass (mg/m3) in northern part
of Sea of Okhotsk in 1949, at the horizons 25 to 50 m and 50 to 100 m

(Kusmorskaya).

THE SEA OF OKHOTSK

793

Table 316. Vertical distribution of phytoplankton biomass and

temperature ranges in central part of Sea of Okhotsk during

the spring bloom

Depth, m

Biomass, mg/m3

1,200

1,600

110

Temperature, °C

10-90

—

1-58

The vertical distribution of Okhotsk plankton is greatly affected by the
presence of the cold intermediate layer. Plankton biomass decreases markedly
at depths of 40 to 50 m {Table 316), increasing again below the cold layer (at
100 to 150 m). This is clearly seen from specimens collected from the central
part of the Sea during the spring bloom (Fig. 395) (M. Vinogradov, 1954).

This vertical distribution of plankton is consistent with the changes of
temperature. The sinking of phytoplankton and the vertical migration of zoo-
plankton is restricted by the high range of temperature and density in the
upper and lower limits of the cold intermediate layer. Oithona similis and
Pseudocalanus elongatus are adapted to the surface zone (M. Vinogradov,
1954). Zooplankton organisms, which are capable of diurnal and seasonal
vertical migrations into the upper layer of the Sea, characterize the transi-
tional cold zone. They are composed mainly o\ Calanus tonsus (C.plumchrus),
С finmarchicus and C. cristatus, Eucalanus bungii, Metridia okhotensis and,
to a lesser extent, M. pacifica and Oncea borealis. The number of species in
the deep layers is much higher, and some of them do not penetrate at all into
the upper two horizons. These forms may be divided into two groups, those
which migrate, and those which do not. The first group includes species living

BIOMASS, g/m3

в to го зо

BIOMASS, g/m3
0 0,5 1,0 (5

гоо

a /ooo

гооо

Fig. 395. Vertical distribution of zooplankton

biomass (g/m2) in Sea of Okhotsk (left) and

Bering Sea (right) (Vinogradov).

794 BIOLOGY OF THE SEAS OF THE U.S.S.R.

above 1 ,000 m (Candacia columbiae, Racovitzanus antarcticus, Heterorhabdus
tonneri, Pareuchaeta japonica and others) and those adapted to greater depths
(from 2,000 to 3,000 m) (Pleuromamma scutulata, Scolecithricella ovata and
others). The species of the second group do not migrate and do not rise into
the upper layer {Halaptilus, pseudooxycephalus, Scaphocalanus magnus,
Pseudociphella spinifera and others).

The plankton of the Sea of Okhotsk is specially noted for its radiolarians ;
81 species have been recorded there.

Benthos (Fig. 396)

The coastal flora of the Sea of Okhotsk comprises about 162 species of sea-
weeds. The Kuril Islands flora is considerably richer {Table 317).

Table 317. Number of macrophyte species in the Sea of Okhotsk and Kuril Islands

Group

Sea of Okhotsk

Kuril Islands

Phaeophyceae

Rhodophyceae

Chlorophyceae

51
80
31

82
101

Total

162

227

The great wealth of species of the sea-weeds of the Kuril Islands is due to
the penetration of a series of oceanic and mainly warm-water forms. The
Kuril ridge may be divided, according to its coastal sea-weeds, into two
regions — a northeastern one embracing all the main ridge, and the southern
Islands of Urup, Iturup, Kunashir and all the islands of the small Kuril
ridge. Laminaria, Thalassiophyllum, Cymathere, Fucus evanescens, Mono-
stroma groenlandica, M. grevillei are predominant in the northern region, and
Pelvetia, Kjelmaniella, Cystoseira, Leathesia, Colpomenia, Chondrus and
Neodilsea in the southern. The range of the tides in the Okhotsk Sea is very
great : on southern Sakhalin and the Kuril Islands the range is no more than
50 cm, while in the Penzhinskaya Inlet it attains more than 13 m. Moreover,
the tides belong mostly to the mixed type — irregular semi-diurnal and irre-
gular diurnal (R. Ushakov, 1951). Most of the shore of the Sea of Okhotsk
is exposed to a strong swell, where the littoral fauna and flora are mostly
poorly developed ; a rich littoral population is concentrated in those coastal
sectors protected from the swell, in the inlets and bays of the northern coast of
the Sea of Okhotsk.

The littoral fauna of the Sea of Okhotsk, like that of the Barents and White
Seas, is typically boreal. It has much in common with the faunas of these Seas,
in the species it contains, in its general bionomic structure and in the structure
of its individual biocoenoses. The phenomena of amphi-boreal resemblance
is reflected in the littoral fauna, most of all in the mass development of its
representative species: Littorina rudis, L. sitchana, L. littores, L. squalida,
Arenicola marina, A. claparedii, Nucella lapillus, Thais lima and others. The

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796 BIOLOGY OF THE SEAS OF THE U.S.S.R.

Murman coast and the Sea of Okhotsk have a number of common littoral
inhabitants : Mytilus edulis, Balanus balanoides, Macoma calcarea, Mya
arenaria, Scoloplos armiger, Saccoglossus mereschkowskii, Travisia forbesi
and many others.

In the northern part of the Sea of Okhotsk a luxuriant development of life in
the littoral, especially in its upper horizons, is greatly restricted by the severe
ice conditions in winter. This is shown in Table 316. The first horizon, which
is flooded irregularly by the tides, is practically uninhabited. The first zone
of the second horizon is also very sparsely populated ; life becomes richer in
the lower zone of this horizon ; and only the third horizon, which lies below
the average neap low tide, has a rich population. Among the sea-weeds there
are Idothea ochotensis and a large number of Gammaridae and Polychaeta.
The lower zone of the third horizon, rarely exposed at low tide, is char-
acterized by various red algae ; apart from those given in the table there are :
Chondrus crispus, Tichocarpus crinitus, Rhodomela larix, and others. Sea-
weeds are populated by the molluscs Margarita helicina, Lacuna vincta,
Cingula marmorata and others ; apart from the crabs Paralithodes, there are
Telmessus cheirogonus and Haplogaster grebnitzkii. The ooze on the sea-
floor is inhabited by Echiurus echiurus, the Polychaeta Glycera capitata,
Nephthys longisetosa, Brada granulata, Travisia forbesi, Pectinaria granulata
and others; there is a large number of Porifera, Hydroidea, Bryozoa and
Ascidia on the rocks.

'The diagram of the vertical distribution of littoral organisms (in the Sea
of Okhotsk) is very similar to that drawn up previously for the Murman
coast ; this indicates that the facies of the two seas are similar, although the
nature of their tides differs. It is most indicative that the composition of the
main forms of species is practically the same in both cases. A complete
absence of Ascophyllum is the main difference between the Okhotsk littoral
and that of the Murman coast' (R. Ushakov, 1951).

The littoral fauna of the Shantar Islands, lying in the most western corner
of the northern part of the Sea of Okhotsk, mainly in Yakshina Inlet on the
Great Shantar Island, was comprehensively investigated as early as 1927 by
I. Zachs (1929). The tide range in the Yakshina Inlet is about 2 to 2\ m,
exposing large expanses of silty-sand littoral at low tide.

Zachs records wracks with the amphipoda Talitridae in the supralittoral
on the facies of cliffs and rocks. Below it, within the littoral, lies the
'dead' horizon; still lower are dense colonies of Fucus evanescens, Balanus
balanoides and Mytilus edulis. Red, green and brown algae flourish in the
lowest horizon.

The soft floor littoral is also encircled by banks of wrack with innumerable
Talitridae. Below the supralittoral lies a wide lifeless horizon (about two
metres according to the range of the tide), while in the lower horizon of the
littoral abundant life is developed with Arenicola, Echiurus, Macoma, Pecti-
naria, Venus and other worms and molluscs. The colonies on the Shantar
Island littoral are very dense, with adult Venus attaining 500 to 800 speci-
mens per 1 m2 (and even up to 1,375) ; Pectinaria from 500 to 900 specimens ;
small polychaetes and mollusc fry in thousands of specimens per 1 m2;

THE SEA OF OKHOTSK

797
with

Macoma baltica, 275 specimens ; Amphipoda, 625 specimens per 1 m
a mean biomass of no less than 1 kg/m2.

The upper horizons of the Sea of Okhotsk sublittoral are covered with
large sea-weed beds with their accompanying fauna. In the bays at depths of
0 to 5 m grow the Sargassum sea-weeds Cystophyllum and Zostera. Lami-
naria (L. agardti, L. bullata, L. saccharina, L. digitata, Alaria esculenta, A.

Fig. 397. Echinarachnius parma colonies in La Perouse Strait at a depth of 40 m
(photographed by Zenkevitch).

membranacea, A. ochotensis, Lessonia laminarioides) form dense growths
somewhat deeper (5 to 20 m).

All these vegetation beds are populated by a varied fauna of Bryozoa,
Hydroidea, Mollusca, Polychaeta and Crustacea. Still deeper (from 15 to
30 m) red sea-weeds become significant {Phycodrya simosa, Ph. fimbriata,
Odonthalia dentata, O. ochotensis, and various Polysiphonia sp. and Ptilota
sp.) with a fauna of Hydroida, Bryozoa, Polychaeta, Crustacea, Echinodermata
and Ascidia. At depths below 30 m the macrophytes gradually disappear, and
growths of Porifera, Hydroidea and Bryozoans become significant. The ori-
ginality of the bottom fauna of the Sea of Okhotsk is reflected in some details
of its composition and distribution.

The uncommon biocoenosis of Echinarachnius parma on pure fine-grain
sands at depths of 20 to 60 m (Fig. 397) occupies a special place in the fauna

798 BIOLOGY OF THE SEAS OF THE U.S.S.R.

groupings of the upper horizon of the sublittoral of the Far Eastern Seas.
The most characteristic among its accompanying species is Ampelisca macro-
cephala, with a population density of some thousands of specimens per m2.

Echinodermata form a continuous cover at the bottom, at times even with
two layers. They feed on vegetable detritus which is easily carried over the
compact sand and the aboral sides of the bodies of the Echinodermata.
Detritus rolls over the ambulacral grooves to the oral side, and is transported
into the mouth-opening.

On the soft soils of the lower horizons of the sublittoral large patches are
inhabited by the biocoenosis Ophiura sarsi.

A. Savilov has worked out a very interesting picture of the ecological dis-
tribution of the bottom fauna on the example of the Sea of Okhotsk (1961).
His work is based on the relationship between the character of feeding, the
nature of the sea-bed and the speed of the current, and comparing these
factors with the structure of the body, the organs of digestion and those used
for seizing food.

In his classification of animals according to their manner of feeding Savilov
(1961) follows S. Yong (1928), S. Zernov (1949), E. Turpaeva (1948, 1952),
J. Allen (1953) and others, distinguishing mobile and sessile sestonophages
(on hard and soft beds), mobile and sessile detritus-feeders, which swallow the
soil, carnivores and carrion-eaters. Savilov provides a distribution in space,
and a quantitative distribution for every ecological group, characterizing in
this manner the ecological structure of the bottom-living fauna throughout
the Sea of Okhotsk and its separate regions {Tables 318, 319 and 320 and Fig.
398).

Savilov has distinguished the following ecological zones of the benthic
fauna in the Sea of Okhotsk (Fig. 398) :

(1) Zone of predominance of the immobile sestonophages of the hard sub-
stratum (Porifera, Hydroidea, Alcionaria, Bryozoa, Cirripedia, Brachio-
poda, Ascidia).

(2) Zone of predominance of the mobile sestonophages of the soft sub-
stratum (Cardiidae, Astartidae, Mactridae, Veneridae, Ampeliscidae, Echina-
rachnius parmd).

(2a) Subzone of predominance of the uatsea-\irchm(Ecliinarachnius parma).

(3) Zone of predominance of the detritus-collecting forms (Tellinidae,
Nuculidae, Ledidae, Terebellidae, Ampharetidae, Ophiura spp.).

(Зв) Subzone of predominance of the detritus-collecting bivalves (Macoma
calcarea, Yoldia thraciaeformis, Y. limatula, Leda spp., Nucula spp.).

(4) Zone of predominance of the bottom feeders (Maldanidae, Capitellidae,
Brisaster, Ctenodiscus, Molpadiidae).

(5) Zone of predominance of the immobile sestonophages of the soft sub-
stratum (Pavonaria, Umbellula, Radiceps, Crinoidea, Potamilla symbiotica,
Sabellidae, Culeolus, Lamellisabella zachsi).

The quantitative distribution of the benthos in the Sea of Okhotsk is very
irregular (Fig. 399). The densest benthos colonies, with a predominance of
fouling fauna, are found off the northern and eastern shores of the Sea, where

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THE SEA OF OKHOTSK

803

the total biomass is frequently of the order of 1 kg/m2. In the deep trench in
the central part of the Sea the benthos biomass is extremely small, as low as
10 mg/m2.
The mean benthos biomass throughout the Sea of Okhotsk is about 200 g/m2,

Fig. 398. Ecological zones of bottom-living fauna of Sea of Okhotsk (Savilov,
1961). See page 800-802 for key.

while the general total biomass of bottom-living fauna is about 300 million
tons, molluscs occupying the first place among the individual groups.

In some cases biocoenoses acquire an oligomixed character, and under
markedly unfavourable life conditions only a few specifically adapted species
are able to multiply and develop. Thus, for example, on pure beach sands
there is a great and almost exclusive development of the Echinarachnius parma

804

BIOLOGY OF THE SEAS OF THE U.S.S.R,

population (with mean biomass of 356 g/m2, a maximum of 1 kg/m2, and
200 specimens per 1 m2) (Fig. 397) which can maintain itself there, feeding on
the detritus which is rolled to and fro on the flat, densely packed sand.
Each ecological group comprises a few biocoenoses with various dominant

Fig. 399. Distribution of the total benthos biomass in Sea of Okhotsk (Savilov).

forms ; this is the result of complex bottom topography, the variety of bottom
soils, the complicated system of water circulation and the changes in tempera-
ture. 'Bivalve filter-feeders (Cardium sp., Mactra sp. and others)', writes
Savilov, ' are predominant in some areas of development of the mobile sestono-
phages ; in others they are replaced by the sestonophage Echinarachnius sp.,
which in its turn gives place to species of Amphipoda of the family Ampelis-
cidae.

THE SEA OF OKHOTSK 805

' The predominant forms in the zone of detritus-collecting organisms are
either one or another species of bivalves (species of the genera Macoma,
Yoldia, Leda and Nucula replacing each other) or some mass species of Ophiura
(for example O. sarsi or O. leptoctenia), or detritus-collecting Holothuria or
Polychaeta.

'This change in the composition of species of the dominant ecological
group of animals within each zone is the result of an alteration in the mani-
festation of the factors in the environoment to which the ecological animal
group is adapted and of the inclusion of some new factors in it.

' A certain consequent replacement of one ecological zone by another in
proportion to the distance from the coast and the increase of depth is also
observed. Hence there arises the possibility of the occurrence of a certain
vertical zonation in the distribution of the ecological groups of bottom-living
animals. Rock soils in the coastal areas are commonly predominantly occupied
by a fouling fauna. . . . With increase in depth the zone of the predominance
of fouling fauna is replaced by that of the predominance of mobile sestono-
phages. The last is adjacent to the wide zone with a predominance of detritus-
collecting forms. . . . Mollusca are replaced by Ophiura, and finally, in the
lower horizons of the zone (mainly in the bathyal) where the finest detritus
fraction is deposited and the aeration of bottom-water layers becomes less
satisfactory, the Polychaeta, as the most eurybiotic forms, acquire a dominant
role in the biocoenoses. . . . The group of bottom feeders or sessile sestono-
phages of soft soils becomes intensely developed in the central deep-water
part of the Sea, on diatomaceous oozes rich in plant food.' Thus similar
ecological groupings, but having different compositions of species are found
in various parts of the Sea at different depths, on more or less common soils
and at currents of similar strength.

Quantitative distribution of sessile sestonophages (Fig. 400) and bottom
feeders (Fig. 401) could be used for the comparison of the nature of the distri-
bution of Savilov's ecological groups of benthos.

The distribution of Savilov's ecological groups and the total biomass and
its connection with bottom topography and currents is most graphically
shown in the longitudinal cross section of the Sea of Okhotsk (Fig. 402). This
picture is wholly comparable with the ecological profile due to Sokolova, con-
sidered above (page 730).

Mollusca occupy the first place (about 30 per cent) in the total benthos
biomass of the Sea of Okhotsk ; Echinodermata come second (about 25 per
cent) and the Polychaeta third (about 12 per cent) (Fig. 403).

Ushakov (1953) gives the simplest diagram of the distribution of bottom
biocoenoses in the Sea of Okhotsk on a chart of the Sea and on a latitudinal
cross section through the central part of the Sea (Figs. 404 and 405).

Colonies of luxuriant pink hydroid corals of the family Stylasteridae (St.
norvegicus f. pacifica, St. solidus, St. eximius, St. scabiosa, and Errinopora
staliferd) develop sporadically on rocky bottoms in the uppermost horizon
of the bathyal, especially in the area of Iona Island, at the entrance to Shelek-
hov Bay, at the northern end of Sakhalin and in the area of the Kuril Straits,
at depths of 100 to 200 m and somewhat deeper.

806

BIOLOGY OF THE SEAS OF THE U.S.S.R,

P. Ushakov (1953) divides the bathyal into two parts: an upper (200 to
750 m), and a lower (750 to 2,000 m), giving a colourful description of the
peculiar fauna of the upper zone of the Sea of Okhotsk bathyal (Fig. 406,

Fig. 400. Quantitative distribution (in g/m2) of sessile sestonophages of hard soils
of Sea of Okhotsk (Savilov).

1-5). 'The great Balanus evermanni forms large colonies on the steep rocky
slopes . . . many Octocorallia, and in particular the large sea-pen Pavonaria
finmarchica, forming an original biocoenosis with the long-armed ophiura
Aster onyx loveni. Immense arboreal colonies of Primnoa resedaeformis f.

THE SEA OF OKHOTSK

807

pacifica, reaching 1 m in height, and comparatively small but exquisite fan-
like colonies of Plumarella longispina, Caliptrophora ijimai and others are
adapted to the upper division of the continental shelf. On the soft soils of the

MORE THAN SO

25-50
10-25
| I LESS THAN 10

Fig. 401. Quantitative distribution (in g/m2) of soil-swallowing benthic forms of the

Sea of Okhotsk (Savilov).

upper horizon large patches are occupied by the Brisaster latifrons biocoe-
nosis.'

The fauna of the lower horizon of the bathyal zone (750 to 2,000 m) and
of the abyssal zone, considerably impoverished both qualitatively and quan-
titatively, are characterized also by a series of colourful forms (Fig. 406, 6-1 1) :
the Foraminifera Bathysiphon ; the Porifera Cryptospongia enigmatica pierced
by the long tube of the polychaete Potamilla symbiotica ; the single madre-
poric coral Caryophyllia clavus ; the sea- whip Radiceps verrillii ; the decapod

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Fig. 403. Total composition of
Sea of Okhotsk benthos accord-
ing to its biomass (Savilov). 1
Polychaeta ; 2 Crustacea ; 3 Mol-
lusca; 4 Echinodermata ; 5
Porifera, Hydroida, Bryozoa and
others.

Fig. 404. Chart of main bottom-living groups of Sea of Okhotsk.
1 Ophiura sarsi ; 2 Brisaster latifrons ; 3 Pot ami I la symbiotica ; 4 Lamel-
lisabella zachsi; 5 Temperature always below freezing point; 6 Near-
bottom isotherm 0° (winter) ; 7 Near-bottom isotherm 2° ; 8 Near-
bottom isoxine 15 per cent (Ushakov, 1953).

810

BIOLOGY OF THE SEAS OF THE U.S.S.R.

crab Munidopsis beringana ; the holothurian Psychropotes raripes ; Lamellisa-
bella zachsi, and the echiuride Tatjanellia grandis.

The vertical distribution of the characteristic faunal communities in the
sublittoral and bathyal zones of the southern part of the Sea of Okhotsk is
well illustrated in Figs. 404 and 405. The Ophiura sarsi biocoenosis is adapted
to the coldest layer of the Sea. Brisaster latifrons keeps to a deeper layer of
warmer water (1° to 2°), and Potamilla symbiotica lives at a temperature
above 2°.

Cold-water Arctic and Arctic-boreal forms are concentrated in the northern,
northwestern and western parts of the Sea on the shelf and in the areas where
water has been cooled most. Thermophilic forms are propagated in the eastern

Cape Terpemye

river Ozernaya
21 23 25

& Echmarachmus
Ophiura sarsi

Fig. 405. Distribution of bottom group and water masses on cross section from
southern part of Sea of Okhotsk, from Cape Terpeniye on Sakhalin to river Ozer-
naya in Kamchatka (according to data collected by the Gagara, 1932) (Ushakov).

and central parts of the Sea, in both surface and deep layers which are warmed
by the Pacific waters which enter through the Kuril Straits, spreading north-
wards, northwestwards and westwards in a fanlike movement. The increase
with depth of the percentage of thermophilic forms and the decrease of the
cold-water forms is also characteristic. This is in contrast with the Sea of
Japan ; there the cold intermediate layer is absent, and the surface waters are
warmed by the Tsushima current but the deep waters, isolated from the Pacific
Ocean, have a much lower temperature than those of the Sea of Okhotsk.

Gigantism is characteristic of many representatives of the fauna of the deep
waters of the Okhotsk Sea ; beginning with Balanus evermanni and ending with
Psychropotes raripes and Potamilla symbiotica, the main forms of the Sea of
Okhotsk are distinguished by their large size.

F. Pasternak (1957), using the same method of zonation as Savilov, fur-
nishes an even more detailed picture of the distribution of bottom-living
fauna in the northwestern corner of the Sea of Okhotsk (Bay of Sakhalin and
adjacent parts of the Sea). This region is characterized by a considerable
complexity in its hydrological conditions. A complex picture of benthos dis-
tribution is created by the collision of the lower-salinity and higher-tempera-

Fig. 406. Members of deep-water fauna of Sea of Okhotsk (Ushakov). Upper series
— upper part of the bathyal: 1 Asteronix loveni, on marine Pavonaria finmarchica;
2 Euplexaura (Octocorallia) ; 3 Octopus ochotensis; 4 Chondracladia gigantea;
5 Leanira areolata. Lower series — lower part of the bathyal and abyssal : 6 Radiceps
verrillii (Octocorallia); 7 Lamellisabella zachsi; 8 Potamilla symbiotica + Cripto-
spongia enigmatica; 9 Caryophyllaeus clavus; 10 Munidopsis beringana; 11 Psychro-

potes raripes.

812

BIOLOGY OF THE SEAS OF THE U.S.S.R.

ture waters of the Amur Inlet with the cold waters of the northern Sea of
Okhotsk current and the warmer waters entering from the southeast. The ben-
thos biomass is generally high (100 to 500 g/m2). The distribution of the main
biocoenoses is determined also by the nature of the bottom soils. There is a
belt of fine-grain, more or less silty sand round the whole area. Soft soils ex-
tend from the southeast to the northwest following the bottom topography.

Fig. 407. Distribution of biocoenoses of north-
western part of Sea of Okhotsk (Pasternak, 1957).

1 Area of predominance of fixed fouling fauna ;

2 Area of predominance of Echinarachnius par ma ;

3 Area of predominance of large detritus-eating
bivalves ; 4 Ophiura sarsi predominance ; 5 Bio-
coenoses with predominance of filter-feeders;
6 Amphipod predominance ; 7 Predominance of
forms swallowing detritus with the soil ; 8 Area
of predominance of small bivalves.

Zones of the predominance of fouling fauna in the northeastern part of the
region investigated could be singled out among the biocoenoses of the region
(Fig. 407). In the deeper parts of the trench and on its eastern slopes grass
Porifera with an admixture of Hydroidea are predominant — Cladocarpus,
Sertularia, Bonnevillea, Abiettinaria ; the Bryozoa, Smittina and Membrani-
pora ; Sabellidae and Actinia like Chondractinia, Ophiopholis aculeata, Coro-
phiidae and others.

Large spaces of this region are occupied by forms which collect detritus
from the surface of the bed. Hard fine-sand beaches are inhabited by large

THH SEA OF OKHOTSK 813

colonies of Echinarachnius parma ; silty sands are populated by large-sized
bivalves (Macoma calcarea, Tellina, Yoldia traciaeformis); still siltier sands
have an abundance of Ophiura sarsi with numerous small Mollusca (Nucula
tenuis, Yoldiella derjugini, Axinopsis and others) and Polychaeta (Spio-
chaetopterus typicus, Stylarioides plumosa, Sternaspis acutata, Ampharetidae
and others). Filter-feeder biocoenoses composed of large-sized Mollusca
{Astarte borealis, Sem'pes groenlandicus, Cardium ciliatum, Mya arenaria,
M. truncata, Liocyma fluctuosa, Modiolus modiolus and others) characterize
the region described. Amphipoda (Ampelisca eschrichti, A. macrocephala,

A. furcigera) with a biomass of 124-7 g/m2 and giving about 3,000 specimens
per 1 m2 have been found in large numbers in separate patches. The zone of
the predominance of organisms which swallow detritus with the soil should
also be noted. Pasternak includes in this group the Polychaeta (Maldanidae,
Capitellidae, Ariciidae, Scalibregmidae and Opheliidae), Gephyrea, the
Holothuria, the urchin Brisaster latifrons, the starfish Ctenodiscus crispatus
and others.

F. Pasternak (1957) describes the zoogeography of one of the most climatic-
ally severe regions of the Far Eastern Seas — the northwestern corner of the
Sea of Okhotsk. In this region the Arctic and Arctic-boreal species Ophiura
sarsi, Praxilella gracilis, Pr. praetermissa, Spiochaetopterus typicus, Scali-
bragma robusta, Chaetozone setosa, Terebellides stroemi, Myriochele heeri,
Astarte borealis, A. montagui, Serripes groenlandicus, Mya truncata, Macoma
moesta, M. calcarea, M. torelli, Liocyma fluctuosa, Thyasira gouldi and Yoldia
myalls play the dominant role in the fauna. Boreal forms are absent. The
northern part of the Sea of Okhotsk cannot be included in the boreal province.

N. Vinogradova (1954) has investigated in detail the bottom-living fauna of
the northeastern corner of the Sea.

Shelekhov Bay in the Sea of Okhotsk, thrusting far up into the Chukotsk
Peninsula, is the coldest sector of the Far Eastern Seas. It can be compared
only with the northwestern area of the Sea and the Gulf of Anadyr in the
Bering Sea. This extensive Bay has an area of about 140,000 km2. The distri-
bution and composition of its fauna, with its very cold water aspect and a
very high mean biomass (470 g/m2) with a predominance of Mollusca, is
controlled by the restricted connection of the Bay with the Sea, the feeble
penetration of warm waters from the south, its small depth, and the presence
of numerous coastal features.

N. Vinogradova (1954), judging by the composition and distribution of the
bottom-living fauna of Shelekhov Bay, distinguishes three main biocoenoses
disposed from south to north (Fig. 408): 1 — a biocoenosis of Balanidae-
Hydroidea-Bryozoa-Decapoda ; 2 — a biocoenosis of Ophiura sarsi-Macoma
calcarea and 3 — a biocoenosis of Leda (pernula type)-Ophiura sarsi-Poly-
chaeta. The dominant species of the first biocoenosis are Balanus evermanni,

B. rostratus dalli, Pagurus pubescens, Ну as coarctatus, and various Hydroidea
and Bryozoa. Moreover prawns (Pandalus, Sclerocrangon and others),
Echinodermata {Strongylocentrotus droebachiensis, Ophiopholis aculeata,
Ophiocantha bidentata, Gorgonocephalus cargi and various Asteroidea) and
numerous Porifera (Semisuberites arctica and others) are well represented in

814

BIOLOGY OF THE SEAS OF THE U.S.S.R.

this biocoenosis. Among the Polychaeta Nephthys coeca, N. ciliata, Onuphis
sp. and numerous Serpulidae are predominant. Various Buccinidae, Crepi-
dula, Pododesmus macroshisma, Astarte borealis, A. banksi, Nucula tenuis and
others are predominant among the Mollusca.
The biocoenosis Macoma calcarea-Ophiura sarsi is located in the central

Fig. 408. Distribution of biocoenoses in Penzhina In-
let (Vinogradova, 1954). / Balanidae-Hydroidae-Bry-
ozoa-Decapoda biocoenosis; // Ophiura sarsi bio-
coenosis ; /// Leda biocoenosis of the type pernula-
Ophiura ^/-jZ-Polychaeta. Mean biomass for each
biocoenosis indicated in circles, in g/m2 ; A — Crusta-
cea; В — Mollusca; С — Echinodermata ; D — Poly-
chaeta; E — Others.

part of the Bay. In this biocoenosis the most numerous among the Polychaeta
are Lumbriconereis impatiens, Myriochele oculata, Praxilella praetermissa,
Rhodine gracilior; among the Mollusca Leda (pernula?), Macoma moesta,
M. torelli, Musculus corrugatus, Yoldia traciaeformis, and Nucula tenuis;
there are numerous Crustacea (families Ampeliscidae). Among the Deca-
poda there are Chionoecetes opilio, Hyas coarctatus, Pagurus pubescens ; the
Polychaeta Nephthyidae, Aphroditidae ; and the starfish Crossaster papposus,
Pteraster and others.

THE SEA OF OKHOTSK

815

Table 321. Mean number of specimens and mean biomass of bottom-living fauna of
Shelekhov Bay (TV. Vinogradova, 1954)

Group

No. of specimens per 1 m2

Biomass, g/m2

Polychaeta

Mollusca

Crustacea

Echinodermata

Sipunculoidea

Others

324
127
516

28-3
210-3
940
55-8
660
15-1

Total

1,304

469-5

The northern part of the Bay and the Gizigina Inlet are occupied by a
biocoenosis in which Leda pernula{?), Ophiura sarsi, Amphiodia craterodmeta,
and Ophiura maculata are predominant. Among the Mollusca there
is an abundance of Leda minuta, Yoldia myalls, Y. llmatula, Y. traclaeformis,
Macoma calcarea, Saxicava arctlca and Cardium ciliatum. Among the Poly-
chaeta the most numerous are Maldane sarsi ; among the Crustacea Malda-
nidae, Myriochele occulata, Chaetozone setosa, Scoloplos armlger and Mage-
lone pacifica are distinguished by their numbers.

The benthos biomass increases considerably (Fig. 409 and Table 321) at
the entrance to the Inlet (500, 1,000 g/m3 and more) and in Gizigina Inlet
(up to 1,000 g/m2) ; moreover, Mollusca and Echinodermata are predominant
in the north of the Bay.

Fig. 409. Distribution of benthos biomass in

Penzhina Guba, Sea of Okhotsk, g/m2.

(Vinogradova).

816 BIOLOGY OF THE SEAS OF THE U.S.S.R.

As may be seen from the lists of the mass forms given, the fauna of Shelek-
hov Bay has on the whole an Arctic aspect (N. Vinogradova, 1954), boreal
forms being predominant in the southeastern part of the Bay (Venericardia
borealis ovata, V. crassidens, Crepidula sp. and others); and Arctic-boreal
and lower Arctic forms in the northwestern part of it (Macoma calcarea,
Leda pernula, L. minuta, Yoldia myalis, Mya truncata, Musculus substriatus,
Axinus gouldi and others). Arctic and high- Arctic forms are concentrated in
the central, deep-water part of the Bay {Macoma torelli, M. loveni, M. maesta,
Musculus corrugatus, Axinopsis orbiculata and others). Although this zoo-
geographical analysis is adduced only for the bivalves, it reflects the general
aspect of the Shelekhov Bay fauna well.

Abundant material on the qualitative and quantitative distribution of the
bottom fauna of the most important fishery region of the Sea of Okhotsk —
the western Kamchatka shelf — was studied by K. Gordeeva (1948). Spacious
feeding grouds of Kamchatka crab, flatfish, cod and others are situated within
this area, which is undoubtedly one of the richest regions of life in the Far
Eastern Seas. The mean biomass of the whole western Kamchatka shelf
is 482-7 g/m2 and the feeding part of the fauna is on the average 230 to
300 g/m2.

The surface zone of water heated up to 1 1° or 12° in summer lies at about
50 to 70 m. The cold intermediate layer is situated at a depth of 70 to 1 50 m
(temperature down to — 1-8°). The lower part of the shelf and the edge of the
bathyal (150 to 250 m) have a temperature above freezing point; crabs
migrate there for wintering.

The most characteristic forms on the sand soil are: the large Mollusca
Siliqua media, Tellina lutea, and at times Mya truncata and Spisula alascana ;
the worms Nephthys coeca, Travisia forbesi; the Echinodermata Echinarach-
nius parma ; the Crustacea Crangon dalli : below the sand on the gravel bed,
there are numerous epifauna organisms, such as the Actinia Halcampella;
the Mollusca Mytilus edulis; and the bed itself is inhabited by Mya spp.,
Serripes laperousi and Macoma middendorfi. The oozes (50 to 120 m) of the
southern part of the shelf contain many bivalves (Macoma, Nucula, Yoldia,
Liocyma and others); Gastropoda (Cylichna, Retusa and others); and an
abundance of the Maldanidae ; of Echinodermata Ophiura and Holothuria.
Still lower down, the zone of the cold intermediate layer is inhabited by bio-
coenoses of the most cold-water forms such as Macoma calcarea, Nucula
tenuis and Leda pernula.

Fish

The list of fish in the Sea of Okhotsk includes, according to Rass, about 300
species and subspecies (P. Schmidt, 1950, with T. Rass's corrections). Among
them 140 species are common with the Sea of Japan, and 112 species with the
Bering Sea. About 85 species, i.e. 28 to 30 per cent, are endemic.

Most of the species are cold-water ones ; however, only a few are properly
Arctic forms. The families Cottidae (53 species), Liparidae (43), Zoarcidae
(41), Pleuronectidae (21), Stichaeidae (17), Agonidae (15), Cyclopteridae (13)
and Salmonidae (10) are the most numerous.

THE SEA OF OKHOTSK 817

In the southwestern part of the Sea there are south-boreal and even sub-
tropical species of the families Gobiidae (5 species), Clupeidae (2 species),
Mugilidae, Carangidae, Oplegnathidae, Tetrodontidae and Pleuronectidae
(two species each), and Rhombidae, Engraulidae, Salangidae, Scombreso-
cidae, Syngnathidae, Scombridae, Trididae, Sparidae, Monacanthidae, Raji-
dae, Lamnidae, Embiotocidae (one species each). There are 29 or 30 such
species in all, about 10 per cent of the whole fish fauna.

There are 12 species of deep-water oceanic fish, among them 4 Macruridae,
3 Bathylagidae and one species each of Gonostomidae, Chauliodontidae,
Alepisauridae, Scopelidae, and Moridae (T. Rass, 1954). There are 44 second-
ary deep-water species, among them 27 Liparidae, 10 Zoarcidae, 5 Cottidae,
and 2 Scorpaenidae (P. Schmidt, 1950).

There are about 20 species of commercial fish in the Sea of Okhotsk:
Squalis acanthias, Clupea pallasi, Oncorhynchus keta, O.gorbuscha, O. kisutch,
O. nerka, Sahelinus malma, Osmerus eperlanus dentex, Cololabis sajra, Gadus
macrocephalus, Theragra chalcogramma, Eleginus gracilis, Sebastolobus
macrochir, Pleurogrammus azonus, Hippoglossoides elassodon, Lepidopsetta
bilineata, Limanda aspera, L. punctatissima, Platessa quadrituberculata,
Pleuronectes stellatus. The most important of them are herring, pink salmon,
keta, brook trout, pollack, rock trout and plaice.

About 870 thousand tons offish were caught in the Okhotsk Sea in 1955.
The catch in 1936 was estimated at 700 to 780 thousand tons (T. Rass, 1948) ;
it has increased mainly owing to the development of the herring, plaice,
pollack and rock trout fisheries.

In the northern part of the Sea of Okhotsk herring feeds on more orjess
large plankton (Themista libellula, Metridia and Calanus finmarchicus).

Commerical crabs (Paralithodes camtschatica, P. brevipes and P. platypus
and Chionoecetes opilio) feed in summer (M. Khun and L. Mikulich, 1954)
on various mass forms of benthos : Echinodermata (Strongylocentrotus and
Echinarachnius, various starfish and Ophiura), Mollusca, especially Serripes
groenlandicus, Cardium ciliatum and Macoma calcarea, various Polychaeta,
Ascidia, especially Pelonaia corrugata and Boltenia echinata, and various
Peracardia.

Using A. P. Andriashev's data (1939), L. Vinogradov (1948) distinguishes
three zoogeographical regions in the Sea of Okhotsk : the Glacial Okhotsk, the
western Kamchatka and the southeastern Sakhalin.

The Bering Sea

I. PHYSICAL GEOGRAPHY

The Bering Sea is the largest marine basin of all the seas surrounding the
u.s.s.R. Its surface is 2,304,000 km2 and its volume 3,683,000 km3. Its
greatest depth, in the region of Kamchatka Strait, is 4,420 m, its mean depth
1,598 m. The Bering Sea is divided by the 200 m isobath into two approxi-
mately equal parts : the northeastern shelf region, with depths of less than
200 m, and the southwestern part with depths of more than 3,500 m (Fig. 410) ;
this latter in its turn is subdivided by two trenches, a smaller, western one
and an eastern one, four times as big. The summits of Shirshov ridge rise to
depths of 1,000 to 2,000 m. It is a continuation of the Olyutorsky submarine
ridge. Another ridge stretching north of Semisopochny and Gorelov Islands,
part of the Aleutian arc, partitions off the southern part of the eastern basin.
The Bering Sea is enclosed on the south by the elevation of the Alaska Penin-
sula and the long Aleutian chain, composed of numerous islands and straits,
most of them shallow.

Shirshov ridge does not reach the base of the Aleutian chain, for there is a
rather narrow, deep (3,500 m) strait between them connecting (less than
50 km) both parts of the hollow. The bathyal zone in the Bering Sea is com-
paratively small {Table 322).

Table 322. Bottom topography of the Bering Sea (P. Ushakov, 1953)

Area
Zone

103 km2 Percentage

Shelf 1,000 44

Bathyal 289 13

Abyssal 992 43^

The Bering Sea is connected with the Pacific Ocean by the deep Kamchatka
Strait (4,420m). The trenches of the Strait are connected with each other, and
the western one with the Ocean, at all depths. A complete contact of sea and
ocean water masses and an identity of their water structure is secured by the
depth of certain of the Aleutian Straits. The Bering Sea can be considered as
an arm of the Pacific more than can any other sea.

In the north the Bering Sea is connected with the Chukotsk Sea through the
Bering Strait. The latter is very shallow (not more than 40 m), and with a width
of 85 km its cross section is only 2-5 km2.

With rare exceptions (in winter) the movement of water through the Bering
Strait is in one direction ; about 20,000 km3 of Bering Sea waters enter the
Chukotsk Sea through it.

818

820

BIOLOGY OF THE SEAS OF THE U.S.S.R.

The distribution of soils on the floor of the Sea gives a clear and simple
picture (Fig. 411). Large areas of the floor of the northeastern half of the
eastern shelf zone and the western half of the Bay of Anadyr are occupied
by sands. Sand forms a wide band stretching southwards to Cape Olyutorsky.
The rest of the shelf zone and the elevations of the Olyutorsky and Southern
ridges have a siltstone bed with a large patch of siltstone-clay ooze. Siltstone-
clay diatomaceous ooze with large patches of clay diatomaceous ooze in
each trench occupy the deep bed of the Sea.

The Soviet coast of the Bering Sea is more than 5,000 km long. Steep

Fig. 411. Bottom soils of Bering Sea (Lisitzin). 1 Boulders-shingle-gravel; 2 Sands;

3 Aleurites; 4 Aleurite-clay-diatomaceous oozes; 5 Clay-diatomaceous oozes;

6 Aleurite-clay oozes without silica ; 7 Outcrop of rock.

shores and the small tidal range limit the width of the beaches, and the
development of the littoral fauna is restricted by the severe winter conditions
and the presence of ice.

A diagram of the circulation of surface waters of the Bering Sea shows a
large cyclonic movement (Fig. 412).

The entry of surface and deep Pacific Ocean waters through the straits be-
tween the Aleutian Islands is the main feature of the system of Bering Sea
currents. The water masses move northward along the eastern side of the Sea
creating several anticyclonic and cyclonic rotations on the eastern side, and a
circular cyclonic current on the west. Skirting St Lawrence Island on the east,
Pacific waters enter the Chukotsk Sea through the Bering Strait, warming its

THE BERING SEA

821

eastern half and creating conditions allowing the penetration of boreal fauna
through the Strait. At times, especially in winter, cold waters can enter the
Bering Sea through the western side of the Strait and move along the Chukotsk
coast. Branches of a warm current, skirting St Lawrence Island, penetrate the
Bay of Anadyr from the south, somewhat warming its eastern part.

The anticyclonic movement of water in Anadyr Bay helps as a result of
the winter fall of temperature to form the so-called Anadyr cold patch. A
similar patch is formed in Olyutorsky Inlet. As a result of all these factors the

BO'

170'

175'

№'.'<■>

k\vW "'/

170'

160'

175*

160*

Fig. 412. Surface circulation of waters of Bering Sea (Dobrovolsky and Arsenev,

1959).

western side of the Sea is cooled considerably, so that in winter thick ice is at
times formed there.

Strong currents of cold western Bering Sea waters follow into the Pacific
Ocean through the Kamchatka Strait, forming the so-called Oyashio current.
Certain cold-water plankton organisms serve as good indicators of this cold
current, one of them being Calanus finmarchicus (Fig. 413).

The actual circulation of water masses in the western part of the Bering Sea
is probably much more complex than in the diagram given. The Bering Sea,
like the Sea of Okhotsk, is characterized, especially in its western and northern
parts, by the severity of conditions on the surface. Even in summer the surface
waters down to 30 or 40 m are never warmer than 9° to 10°.

Below the surface layers, especially on the western side of the Sea, there

822

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Fig. 413. Distribution of Calanus finmarchicus in Bering Sea : 1 Direc-
tion of currents; 2 Calanus distribution (Lubny-Gertzik, 1955).

lies a cold intermediate layer (at a depth of 100 to 200 m), and this is still
found at considerable distances from the exit from the Kamchatka Strait.
However, its character is not as pronounced in the Bering Sea as in the Sea
of Okhotsk, and its usual temperature is above freezing point {Table 323).

Changes of temperature, salinity and oxygen content can be seen in Fig.
414.

It is clear from the data given that the waters of the Bering Sea and of the
adjacent part of the Pacific Ocean have a very similar composition. The
amount of oxygen in the depths of the Bering Sea may be, as is shown in
Fig. 414, much less than the amounts given in Tables 323 and 324.

The cold conditions of the Anadyr and Olyutorsky regions are manifest

Table 323. Vertical distribution of temperature, salinity and oxygen in the eastern
trench of the Bering Sea in summer

Oxygen

Depth,

Temperature

Salinity

°C

/00

ml/1

Percentage of
saturation

8-90

32-52

—

1-41

33-40

5-94

75-30

100

0-80

33-40

5-31

66-40

200

0-68

33-40

—

300

3-55

33-82

609

81-90

500

3-44

34-05

1-25

16-80

1,000

2-80

34-42

0-45

16-90

2,000

1-91

34-01

1-44

2010

3,000

1-65

34-72

1-65

21-40

31.0

32.0

33. о

3S.o

M 0

500

1000

2000

3000

sx0

/500 1_Ь

/500

Fig. 414. Vertical distribution of temperature (con-
tinuous line), oxygen (short dashes) and salinity
(long dashes) in summer 1932 (Ratmanov).

Table 324. Oxygen and phosphorus in the Bering Sea and Pacific Ocean

Bering Sea

Pacific Ocean

Depth,

Kamchatka Strait

Central

part

of Sea

August, 1950

September,

1950

Oxygen

Phosphorus

Oxygen

Phosphorus

per cent

mg/m3

per cent

mg/m3

per cent

mg/m3

103

104

100

150

300

101

500

100

102

1,000

100

101

1,500

104

100

2,000

103

2,500

—

824

BIOLOGY OF THE SEAS OF THE U.S.S.R

even at the 25 m horizon (Fig. 415) and even more so in the temperature near
the bottom (Fig. 416). The salinity of the western and eastern parts of the Sea
is practically the same — about 32 or 33%0 ; it remains practically unchanged
from surface to bottom.

The phosphorus content of the Bering Sea waters is sufficient for the luxu-
riant development of phytoplankton (Fig. 417).

The changes of temperature of water layers from the surface to the 200 to

/60'

68T

60°-

50'

160-

. ъ*а

*4j:

50'

170<

180°

/70е

160е

Fig. 415. Isotherms of the Bering Sea in 1932 at a depth of 25 m (Ratmanov).

300 m level are clearly shown on the cross section from Cape Africa eastward.
Cold Kamchatka waters are pushed to the western side. At a depth of 300 to
400 m these differences are already indistinct (Fig. 418).

The water masses of the Bering Sea may be divided into four layers accord-
ing to their chemical properties (V. Mokievskaya, 1956): (7) the surface
layer, most exposed to seasonal fluctuations of temperature, salinity and
chemical properties ; (2) the transition zone, which becomes thicker in spring
and summer (50 to 200 m) while its boundaries become less pronounced;
(3) a third layer, characterized by a lower oxygen content, down to 10 to 15
per cent of saturation, and the highest phosphorus content (over 100 mg/m3)

THE BERING SEA

825

lying beneath the transition zone: this third layer extends down to 1,500 m;
(4) the fourth layer stretches from 1,500 m down to the sea-bed: its oxygen
content rises to 20 per cent of saturation and its phosphorus content decreases
to 90 mg/m3. The upper two layers, formed in the Bering Sea itself, are the
most characteristic. The lower two layers are similar to the Pacific waters, to
which they owe their origin, since they penetrate freely into the Bering Sea
through the straits.

Fig. 416. Isotherms near bottom of Bering Sea in 1932 (Ratmanov).

A comparison of the structures of the column of water of the Bering Sea
and of the adjacent Pacific Ocean is most significant (Table 324).

The amount of phosphorus in the Bering Sea is higher than that in the
Pacific Ocean, while its oxygen content is lower at depths of 1,000 to 2,000 m.

The Bay of Anadyr and the adjacent shallows have, as a result of the vigor-
ous autumn and winter vertical circulation, a uniform distribution of oxygen
and other elements. During the period of intense development of phyto-
plankton (June) the amount of oxygen increases, that of phosphorus de-
creases to 20 mg/m3, and that of silica may amount to 100 mg/m3.

A high concentration of plant food in the upper layer of the Sea is

SdJ}dfiJ

THE BERING SEA

827

characteristic of the Bering Sea, in contrast to the Seas of Okhotsk and
Japan. Their amounts are not reduced to a minimum by the development
of phytoplankton. However, a sharp decrease of nutrient salts is at times
observed in the surface waters {Table 325). The curves of phosphate

3346 3348 3349

Stations

3350 3351 3352 A1* 3353

33S4 3355 3356

i г

SO miles

Fig. 418. Distribution of temperature (a) and salinity (b) on the cross section Cape
Africa to Attu Island (Burkov, 1958).

distribution show a dome-like rise in the central part of the Sea ; this is the
result of the cyclonic movement of waters in the Bering Sea.

II. FLORA AND FAUNA
A biogeographical division into cold western and warm eastern zones
characterizes the surface horizons throughout the Bering Sea. This division
is particularly pronounced in the northern part of the Sea (Fig. 419).

828

BIOLOGY OF THE SEAS OF THE U.S.S.R

Table 325. Two types of distribution of nutrient salts in the northern shallows of the
Bering Sea (V. Mokievskaya, 1956)

First

type (Kamchatk

i coast)

Second type (Bay of Anady

r in summer)

Depth,

Phosphorus

Depth

Phosphorus

mg/m3

Si02, mg/m3

mg/m3

Si02, mg/m3

19-2

530

8-0

305

18-0

530

7-1

275

18-8

500

8-3

305

18-8

460

660

1,950

18-8

420

680

2,070

700

2,430

76-0

2,700

Plankton

One hundred and sixty-three phytoplankton forms have been recorded in the
northern part of the Bering Sea and in the Chukotsk Sea : Flagellata 2, Peri-
dinea 55, Diatomaceae 104, Chlorophyceae 2 (I. Kisselev, 1937). Boreal
peridineans are predominant even in the Bay of Anadyr in summer (Peri-
dinium thorianum, P. pallidum, P. depressum, P. ovatum, P. pellucidum, P.
granii, Dinophvsis acuta, Ceratium pentagonum and others). Only a few dia-
toms develop in large numbers {Chaetoceros concavicomis, Ch. debilis, Ch.
radicans, Rhizosolenia hebetata and others). At a depth of 20 to 30 m the

Fig. 419. Limit of zones of cold water (/) and thermophilic
fauna (//) in northern part of the Bering Sea.

THE BERING SEA 829

diatoms, however, become markedly predominant {Thalassiosira norden-
skioldi, Th. gravida, Fragillaria oceanica, Amphiprora hyperborea, Porosira
glacialis, Coscinosira polychorda and others.) Anadyr phytoplankton, how-
ever, is mainly Arctic or Arctic-boreal, the boreal forms being predominant
only in the surface layer in summer.

The same pronounced difference is observed between the phytoplankton
compositions in the western and eastern sides of the Bering Strait, Arctic and
Arctic-boreal forms being predominant in the first and boreal in the second.

The phytoplankton of the eastern side of the northern half of the Bering
Sea is characterized by the predominance of boreal forms with an admixture
of brackish-water and neritic species {Thalassiosira japonica, Coscinodiscus
granii, Actynoptychus undulatus, Rhizosolenia alata, Ditylum brightwellii,
Actinocyclus ehrenbergii, Bellerochea malleus, Asterionella japonica, Peri-
dinium excentricum). Arctic and Arctic-boreal species are just as character-
istic of the western side {Thalassiosira nordenskioldi, Th. gravida, Chaetoceros
socialis, Ch. radians, Porosira glacialis, Bacterosira fragilis, Eucampia groen-
landica proceeding from cold-water to warm-water forms) (I. Kisselev,
1937). Apart from these zoogeographical changes seasonal alterations are
observed in summer, especially in the surface layer of the western part of the
Sea.

The Bay of Anadyr phytoplankton is characterized by the predominance of
Arctic and Arctic-boreal species even in summer (except for its warmed sur-
face layer). It is possible, however, that small, terminal branches of warm
Pacific waters enter the Bay of Anadyr and currents stimulate a rich develop-
ment of boreal forms in summer.

Four main groupings of zooplankton may be distinguished in the Bering
Sea according to their distribution (K. Brodsky, 1954; M. Vinogradov, 1956)
(Fig. 420).

The southern Bering Sea oceanic group in the 200 m surface layer is char-
acterized by a selection of forms similar to those of the surface waters of the
northwestern part of the Pacific Ocean ; they penetrate into the Bering Sea
with the warm Pacific waters. Calanus cristatus, C. tonsus and Eucalanus
bungii are the mass forms of this group ; Racovitzanus antarcticus, Scolecith-
ricella minor, Parathemisto japonica, Oncaea borealis and others are added
to them in smaller numbers. This group penetrates far to the north and into
the Chukotsk Sea. The northern Bering Sea group lives on the shelf in the
northern part of the Sea, partly overlapping the first group. C. cristatus, С ton-
sus, Primno macropa and other warm-water forms are completely absent there,
while Calanus finmarchicus and Parathemisto libellula become abundant.
Certain cold-water species of this group move southwards with the cold
waters along the coast of the Chukotsk Peninsula and Kamchatka almost
to the southern end of the latter, forming the western neritic group together
with some neritic species ; this third group is very similar in its composition
to the eastern neritic group. Podon leuckarti, Centropages mamurrichi,
Acartia clausi and A. longiremis play an important role in the plankton of the
most shallow regions of low salinity. This group, with the Oceanic and
northern groups, penetrates into the Chukotsk Sea. A deep-water Bering Sea

830

BIOLOGY OF THE SEAS OF THE U.S.S.R.

group lives in the southern part of the Sea below 200 m ; it is an impoverished
deep-water plankton of the Pacific Ocean.

There are considerable seasonal changes in the vertical distribution of
plankton of the southern Bering oceanic group (Fig. 421). The cold intermedi-
ate layer of the Bering Sea is not so pronounced as that of the Sea of Okhotsk
(its temperature is usually above freezing point) ; it has less influence on the
vertical distribution of plankton and does not separate to the same extent

Fig. 420. Faunal grouping of zooplankton in Bering Sea in summer. 1 South
Bering Sea grouping ; 2 North Bering Sea oceanic grouping ; 3 West neritic grouping ;
4 East neritic grouping (Vinogradov, 1951).

the surface and subsurface plankton. The main mass of plankton is retained
below the 200 m surface layer by a considerable fall of temperature in winter.
In spring and summer, when the surface layer is warmed, zooplankton moves
upwards, concentrating mostly in the uppermost 100 m for feeding and multi-
plication (Eucalanus bungii, Calanus tonsus and C. cristatus), frequently form-
ing a biomass of from 1,500 to 2,500 mg/m3 in the 10 to 100 m layer ; the three
species of Copepoda mentioned constitute up to 90 per cent of the total bio-
mass in summer.

A very intensive development of phytoplankton (up to 1 5 or 20 g/m3) has
been recorded in the northern shallows in spring, while zooplankton is only

THE BERING SEA

831

feebly developed (M. Vinogradov, 1956). The Copepoda are concentrated in
the lower horizons (Fig. 422).

As in the Sea of Okhotsk, but to a lesser extent, the cold intermediate layer
influences the vertical migration of zooplankton, dividing it into three groups :
those migrating above the cold layer {Calanus tonsus, С cristatus, Eucalanus

Cape ChuKolsK

Fig. 421 . Distribution of zooplankton biomass (mg/m2) on cross section through the
Bering Sea, spring 1952). A Total zooplankton biomass; В Eucalanus bungii bio-
mass; С Calanus tonsus biomass; D C. cristatus biomass (Vinogradov).

bungii), forms migrating through it {Metridia pacifica, Pleuromamma scutu-
lata, Candacia columbiae and others), and those for which in their migrations
the cold layer serves as a 'ceiling'. When the boundaries of the cold inter-
mediate layer become less definite in summer the migration system becomes
complete. Calanus cristatus, and C. tonsus and later the cold-water Eucalanus
bungii sink down in autumn when the surface layer gets colder.

M. Vinogradov (1956) notes a characteristic peculiarity in the vertical

THE BERING SEA

833

distribution of the three dominant species of Copepoda : each species is pre-
dominant in a certain horizon, therefore, although they feed on the same
species of diatoms, their competition for food is less intense since their main
habitats belong to different horizons.

Eurythermic species — Oithonasimilis, Sagittaelegans, Calanus finmarchicus,
Parathemisto libellula — become predominant in winter as a result of the cool-
ing of the upper layer (down to 1,000 m) in the western part of the Sea and the
total zooplankton biomass is considerably reduced. It increases again by the
second half of the summer (Fig. 423), Eucalanus alone producing a biomass of
200 to 1,000 mg/m3. The amount of zooplankton decreases considerably

Fig. 423. Distribution of zooplankton biomass
(mg/m3) in the 0 to 100 m layer in June 1952
(Vinogradov).

again in autumn. In the Bay of Anadyr, however, zooplankton reaches its
highest development in autumn only, mainly on account of Eucalanus bungii.
In the north of the Bering Sea the biomass remains low throughout the year,
only at certain places does Calanus finmarchicus form great concentrations
with a density of up to 100 mg/m3, and 400 specimens per 1 m2.

The mass forms of the plankton Calanoida multiply at different times in the
Bering Sea, thus making the best use of the food resources available
(A. Geinrich, 1955). The multiplication of Calanus finmarchicus takes place
at the beginning of the greatest phytoplankton development; Eucalanus
bungii develops somewhat later, followed by Calanus tonsus (small race).
The multiplication of Calanus tonsus (large race) is not connected with phyto-
plankton vegetation. The multiplication of Metridia pacifica proceeds
throughout May to November, while Calanus cristatus spawns in December
to February. Most of the forms mentioned produce only one generation

834 BIOLOGY OF THE SEAS OF THE U.S.S.R.

annually (monocyclic), but in the southwestern part of the Sea the copepod
stages of the second generation appear in Calanus tonsus in the autumn.
Metridia pacifica produces several generations (up to four) during the summer.
A. Heinrich (1956) gives an estimate of the annual production of the main
species of Copepoda from data on the cycle of their development {Table 326).

Table 326. Annual production of Copepoda in the Bering Sea, g/m2, down to 500 m

Species

Western regions

Northern regions

Calanus finmarchicus
Calanus tonsus
Calanus cristatus
Eucalanus bungii
Metridia pacifica

220
26-5
510
160

5-2

1-6

3-3

Total

115-5

101

As shown by a comparison of these data with those on phytoplankton
production (A. Heinrich, 1960) the production of Copepoda is 1/12 to 1/19 of
phytoplankton production in the western regions of the Bering Sea, and only
1/200 of that in the northern regions.

Benthos

The species of coastal macrophytes of the Bering Sea are less varied than those
of the Sea of Okhotsk (301 species) and still less than those of the Sea of
Japan (379 species). A list of them contains only 138 species (25 green, 46
brown and 67 red). However if the Komandorski Islands are included the
variety of sea- weeds is greatly increased. One hundred and seventy-one species
of macrophytes have been recorded off the coast of these islands, especially
off their southern side. There are huge forests of immense Alaria (reaching to
10 to 15 m in length) and Nereocystis luetkeane in the deepest places. Sea-
weed growths give shelter to a rich fauna.

An elaborate investigation of the zoobenthos of the Bay of Anadyr was
carried out by N. Vinogradova (1954).

The Bay of Anadyr is the coldest place in the Bering Sea (the Anadyr cold
patch) ; only the waters of its western coast are somewhat warmed by small
branches of warm currents entering it. Like Shelekhov Bay, the Bay of Anadyr
has a quantitatively very rich fauna, on the average 426-5 g/m3, and is similar
to the former in number and variety of species. The bottom biocoenoses of
the Bay of Anadyr are more varied than those of Shelekhov Bay ; moreover,
they have a circular distribution (Fig. 424). The most characteristic biocoe-
noses are common to both bays. Fouling fauna (epifauna) develops intensely
on the rocks and cliffs along the shores. It is composed of Balanus balanus,
B. crenatus, B. rostratus dalli ; the Porifera Phakellia sp. ; the Bryozoa
Myriozown sp., Membranipora fiustra and others ; the Ascidia Boltenia ovifera,
B. echinata and Tethyum aurantium. Starfish (Leptasterias polar is and others),

THE BERING SEA

835

brittle stars (Gorgonocephalus sp., OphiophoHs aculeata), sea-urchins (Strongy-
locentrotus sp.), very numerous prawns {Nectocrangon lar, N. crassa, Hetairus
fasciata, Spirontocaris sp.), crabs {Chionoecetes opilio, Hyas coarctatus and

Fig. 424. Distribution of benthos biocoenoses in Bay of
Anadyr (Vinogradova). / Balanidae-Hydroida, Bryo-
zoa-Porifera biocoenosis; // Decapoda biocoenosis;
/// Ophiura sarsi-Macoma calcarea biocoenosis; IV
Yoldia limatula-Nucida tenuis biocoenosis ; V Ampelis-
cidae-Polychaeta biocoenosis; VI Echinarachnius parma
biocoenosis; VII Myrlotzochus-Ophiura sarsi-Voly-
chaeta biocoenosis; VIII Musculus discors-Potamilla
reniformis-Terebellides stroemi biocoenosis.

Encircled numerals denote average biomass (g/m3).

A— Crustacea ; В — Mollusca ; С — Echinodermata ; D —
Polychaeta; E— Others.

hermit crabs), Polychaeta (Polynoidae, Glyceridae, Nephthys), and Mollusca
(Saxicava arctica) all live among the strongly developed growths.

The southwestern corner of the Bay gives shelter to a number of thermo-
philic fish ; cod comes there in large numbers. On the sands of the western

836 BIOLOGY OF THE SEAS OF THE U.S.S.R.

side of the Bay Echinarachnius parma lives in huge numbers ; it is absent from
other parts of the Bay. Within the fouling and Echinarachnius parma biocoe-
noses there lies a wide belt with the biocoenosis Macoma calcarea — Ophiura
sarsi, with carnivores and carrion eating Buccinidae, Natica clausi, Leptas-
terias polaris, Crossaster papposus, Chionoecetes opilio, Hyas coarctatus, the
large-sized Polychaeta Polynoidae, Aphrodita, Nephthys and others. Numer-
ous Paguridae and prawns are added to these carnivores. All this huge num-
ber of carnivores and carrion eaters feeds on Macoma calcarea and other
bivalves and Polychaeta. Beds of empty shells of recently perished bivalves
are distributed in large patches.

The central part of the Bay is occupied by the biocoenosis Ophiura sarsi-
Macoma calcarea. Carnivores and carrion eaters do not penetrate into this
region. Apart from Macoma there is a large number of other bivalves here
(Yoldia limatula, Nucula tenuis, Leda pemula^l), Axinus gouldi, Astarte and
Periploma). Abundant polychaete colonies are composed of Maldane sarsi,
Axiothella catenata, Praxilella gracilis, Nicomache sp., Terebellides stroemi,
Scalibregma infiatum, Chaetozone setosa, Terebellidae sp., Ampharetidae sp.,
Lumbriconereis fragilis, L. impatiens, Onuphis parvastriata and others, i.e.
all forms devoured by carnivores in the surrounding biocoenoses. Other bio-
coenoses, shown in Fig. 424, are small in numbers {Table 327).

Table 327. Mean number of specimens and mean biomass of Anadyr Bay biocoenoses

according to groups

Group

Polychaeta

Mollusca

Crustacea

Echinodermata

Others

Total 710 426-6

The fauna of the Bay of Anadyr has an even greater tendency to gigantism
than that of Shelekhov Bay. The greatest benthos biomass is adapted to the
eastern and western coasts and to the region of the cold patch(500to 1 ,000 g/m2
and more).

The largest gatherings of Mollusca and Polychaetes have been recorded
in the central part of the Bay ; Echinodermata are most numerous in the
western and Crustacea in the eastern part. The whole central part of the Bay,
occupied by the biocoenosis Ophiura sarsi-Macoma calcarea, has a benthos
biomass of 100 to 200 g/m2 (Fig. 425). There is a sector in the middle of the
region with a considerably increased biomass, even exceeding 1,000 g/m2,
on account of carnivores gathered on the dense colonies of Macoma calcarea
(starfish, Gastropoda Mollusca, and crabs). The biomass is increased off the

Number of specimens

Biomass

per 1 m2

g/m2

168

33-6

101-1

382

55-7

188-6

47-6

THE BERING SEA 837

northeastern coast by the epifauna, and off the southwestern by Echinarach-
nius parma.

Data on the qualitative and quantitative distribution of benthos in the
eastern part of the Bering Sea are given in A. Neiman's paper (1960). This
investigator has drawn a picture of the biocoenotic distribution of bottom-
living fauna (Fig. 426).

There is a considerable difference in the composition and quantitative
distribution of the population between the northwestern shallow, the only

Fig. 425. Distribution of benthos biomass (g/m2) in
the Bay of Anadyr (Vinogradova, 1954).

large shallow in the Far Eastern Seas, and the southwestern and southern
deep parts of the Sea. The main bottom-living population of the Bering Sea
shelf is composed of bivalves, then come the Echinodermata (mainly Ophiura)
and Polychaeta. The oozes south and southwest of St Lawrence Island have
the richest population, reaching at times a biomass of 500 g/m2 at depths of
50 to 150 m. The population of the sands is scarce, furnishing a biomass of
less than 50 g/m2.

The eastern and western sides of the Bering Sea have a similar fauna. At a
temperature not higher than 3° the predominant forms are as follows : among
Mollusca Macoma calcarea, Leda pernula, Nucula tenuis, Serripes groen-
landicus, Yoldia hyperborea, Y. traciaeformis and Cardiwn cUiatum ; among
Echinodermata Ophiura sarsi, Echinarachnius parma, Brisaster sp., Cteno-
discus crispatus and Cucumaria calcigera.

It has been possible to draw a general chart of the quantitative distribution

180'

170'

160'

1E3 7E3 13CZ3

2F71 8;9le~e)l4;15l I
3-5(±±] 10ПТ71 16Г^"*7

6 G£3 11,12000 17 ■■
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60'

55°

180

170'

160'

50"

Fig. 426. Distribution of benthos biocoenosis in eastern part of Bering Sea (Neiman,
1960). 1 Macoma calcarea; 2 Leda permtla; 3, 4 Ophiura sarsi;6 Serripes groenlandi-
cus; 7 Cucumaria calcigera; 8, 9 Echinarachnius parma; 10 Chiridota sp. ; 11 Yoldia
traciaeformis + Ctenodiscus crispatus; 12 Ctenodiscus crispatus; 13 Cardium sp. ;
14, 15 Polychaeta; 16 Ophiura leptoctenia; 17 Fouling; 18 Glass Porifera.

THE BERING SEA 839

of the bottom-living fauna throughout the Bering Sea from all the data
collected on this problem (Fig. 427).

Fish

The Bering Sea contains about 315 species of fish (A. Andriashev, 1939,
with T. Rass's corrections) ; 1 12 of them are common with the Sea of Okhotsk.
Most of the species are cold-water boreal forms but certain true Arctic
species are recorded among them. Three main fauna elements can be dis-
tinguished (A. Andriashev, 1935); the Asian element: 122 species, genetic-
ally linked with the fauna of the other Far Eastern Seas; the American: 107
species, connected with the fauna of the American coast ; and the Polar ele-
ment : composed of 5 to 7 Arctic species (Ulcina olriki, Boreogadus saida and
others). South-boreal species, for example Sardinops sagax melanosticta and
Engraulis japonicus, enter the southwestern part of the Sea singly.

The following families, constituting about 70 per cent of all the fish, are
the richest in species : Cottidae (65 species), Liparidae (46), Zoarcidae (24),
Pleuronectidae (23), Stichaeidae (18), Agonidae (14), Salmonidae (12), and
Scorpaenidae (10).

The Bering Sea has about 30 deep-water oceanic spieces offish, among them
Macruridae (7), Gonostomidae (4), and Scopelidae (4) (T. Rass, 1954). There
are 48 secondary deep-water species, among them Liparidae (24), Zoarcidae
(8), Cottidae (5), and Scorpaenidae (4).

Approximately 25 species are of commerical value; among the most
important are herring (Clupea pallasi) and salmon (Oncorhynchus keta, O.
gorbuscha, O. nerka. O. tschawytscha, O. kisutch, and Salvelinus malma);
frostfish {Osmerus eperlanus dentex, Hypomesus olidus) ; cod (Gadus macro-
cephalus) ; navaga (Eleginus gracilis) ; halibut and flatfish (Hippoglossus steno-
lepis, Reinhardtius matsuurae, Hippoglossoides robustus, Limanda aspera,
Platessa quadrituberculata, Lepidopsetta bilineatd) ; sterling {Pleurogrammus
monopterygius) and others. So far the fisheries of the Bering Sea proper are
poorly developed, less than those in the adjacent waters of eastern Kamchatka
and southwestern Alaska. The fish stocks of this body of water should not be
estimated by the present fish yield. Much greater numbers of plaice, halibut,
sea bass (Sebastes), sterling, cod, frostfish and capelin could be taken in this
sea (T. Rass, 1955).

As a result of a zoogeographical analysis of the Bering Sea fauna Ya.
Birstein and M. Vinogradov (1952), taking Decapoda as an example, came
to the conclusion that the influence of the Arctic conditions is perceptible :
32-4 per cent of the species are found to be pan-Arctic, low-Arctic, Arctic-
boreal, low Arctic-boreal, sub-Arctic and sub-Arctic-boreal. This applies to
the decapod fauna (about a hundred species) throughout the Sea. The per-
centage rises to 38 T if the species recorded only off Unalashka Island are
excluded. The Arctic aspect of the fauna stands out even more sharply in the
northern part of the Sea. These two investigators have made an interesting
comparison of their data (obtained for the Bering Sea) with those for the Sea
of Okhotsk {Table 328).

The amphi-Pacific character of the fauna distribution is fairly pronounced

THE BERING SEA 841

Table 328. Comparison of percentage composition of fauna of decapod Crustacea in

Akhotsk and Bering Seas

Group Sea of Okhotsk BerTJ"g fea «eluding

r Unalashka Island

Pan-Arctic, low Arctic, Arctic-boreal

and low Arctic-boreal 36-4 33-7

Sub- Arctic and sub- Arctic-boreal 10-4 4-4

Pacific Ocean-glacial 7-8 3-4

Total 54-6 41-5
Boreal (including subtropic-boreal

for Sea of Okhotsk) 45-4 58-5

Total 100 100

in the Bering Sea. Decapod crustaceans and fish may be given as an example
{Table 329).

Many other groups have great qualitative variety in the eastern part of the
Ocean. The fact that not all of them do so is interesting. Certain deep-water
groups are greatly varied in the eastern part of the Ocean. Pogonophora and
Echiuroidea certainly belong to these groups, and possibly some others.

The great age and permanency of the Oceanic trenches, especially the
Pacific Ocean trenches, is proved, we think, by all the data given in this book,
particularly by the data on the Pacific Ocean fauna. Otherwise we would have
been unable to explain many phenomena which fully support this suggestion,
primarily the indubitable age of the geographical uniformities connected with
the temporary distribution of oceanic basins and of that of the oceanic flora
and fauna.

The greater richness of Pacific flora and fauna compared with those of the
Atlantic ; the ancient, primitive aspect of its deep-water fauna, amphiboreal
and bipolar phenomena ; the ancient aspect of the uniformity of the vertical
distribution of fauna ; the harmony of the whole system of geographical
zonation, in other words of the biological structure of the Ocean : all these
indicate the long existence of the main features of the contemporary geo-
graphical distribution of the water masses of this ocean.

Table 329. Distribution of decapod Crustacea and fish on eastern and western sides of

Bering Sea

Distribution Decapod Crustacea Fish

Common to western and eastern coast 52-5 46-1

Off western coast only 8-9 19-9

Off eastern coast only 38-6 34-0

REFERENCES

The reference list is composed along the following lines.

The names of the authors are given in transcription adopted by the authors.
In many instances the Russian authors spell their names in various ways : the
spelling varies in regard to the specific language in which the paper or the
summary is presented. For example, the same name may be spelled as:
Zinova and Sinova, Vodyanitzky and Wodianizky, Virketis and Wirkettiss,
Tchugunov and Tschugunoff, Stschapova, Scapova and Schapova, Ouchakoff
and Uschakov etc. Owing to this discrepancy the author places other versions
of spelling in brackets. These are followed by the translation of each paper's
title into English. To reduce the general size of the reference part the author
has made provisional abbreviation attached to the titles of journals, proceed-
ings, institutes, laboratories etc. which frequently appear in the text of the
book. The abbreviations are adopted in accordance with the initial letters
commonly referred to in Russian scientific papers. The next symbol introduced
into brackets is R — which shows that the paper is written only in Russian ;
E.s. — which indicates that an English summary is available ; F.s. — which
indicates that a French summary or G.s. — German summary is available.
Ed. stands for Edition.

A list of abbreviations in regard to institutions, journals, proceedings etc.
is given, and figures following the title of the journal, proceedings or symposia
reflect the volume and issue ; for example, Z.J. 18, 2 should be read as follows :
Zoological Journal, Vol. 18, Issue 2.

In the course of compiling the reference list the author was guided by the
fact that the Russian language is little known abroad and, hence, the papers
written in Russian are not widely read or used in the course of scientific
bibliographies ; in many cases papers in Russian are frequently not mentioned
at all. This fact should be ascribed partly to linguistic difficulties and partly to
the difficulty of finding the Russian papers scattered in various publications.

The author hopes that tins book and the reference list included will help
to disseminate knowledge about the advances of marine biology in Russia.

The reference list of Russian works is incomplete. An overwhelming num-
ber of papers devoted to classification, the faunistics and the biology of
marine fauna and flora, ichthyology and commercial fisheries, the physical
and chemical oceanography and marine geology are not included into the list.
The total coverage of the vast literature throughout the last forty years should
run as high as 10,000 titles.

A more complete, and in some cases a more exhaustive, list can be found
in a series of books and papers included in scientific periodicals. For informa-
tion it is advisable to refer to K. Derjugin's (1936) and L. Zenkevich's (1937)
works on the period covering the entire number of the water reservoirs of the
USSR; the southern seas are reviewed in N. Maximov's (1958) and V. Niki-
tina's (1934, 1939-40) reference list and also in N. Romanova's (1955) and

844 BIOLOGY OF THE SEAS OF THE U.S.S.R.

K. Vinogradov's (1958) reference list; the seas of the Soviet Far East are
mentioned in the work of E. F. Guryanova and G. Lindberg (1937) and in
N. Romanov's (1959) reference list. Above all, an extensive literature is
attached to the monographs devoted to the studies of separate seas or separate
groups of organisms. It is worth mentioning the Bibliographic Index for the
Study of the Barents Sea (1941), the Reference Book on the Hydrology of the
Seas of the USSR, the works of K. Derjugin devoted to the fauna of the Kola
Gulf (1915) and to the White Sea fauna (1928). Also worthy of note are
P. Ushakov's work on the fauna of the Okhotsk Sea (1953) and the fauna of
the Chukotsk Sea (1952); A. Sinova on the brown (1953) and red (1955)
algae; V. Vorobiev on the benthos of the Azov Sea (1949), S. Brujewicz on
the hydrochemistry of the mid and southern part of the Caspian Sea (1937);
V. Datzko devoted to the organic matter in the waters of the Southern Seas
of the USSR (1959); A. Andriashev on the fishes of the Northern Seas of the
USSR (1954); M. Klenova on marine geology (1948) and on the geology of
the Barents Sea (1960); N. Knipovich on marine hydrology (1932), brackish
waters (1938), the hydrology of the Black and Azov Seas (1932).

Literary references are also to be found in the numerous monographs of
N. Subov (1938, 1940, 1945, 1947, 1950); in P. Ushakov's works on the
Polychaetae; in L. Berg's work on the fresh-water fishes (1948-9); in P.
Schmidt's work on the fishes of the eastern seas (1904) and in the study
devoted to the fishes of the Okhotsk Sea (1950); in L. Zenkevich's work on
the fauna and the biological productivity of the sea (1947 and 1951); in J. H.
Segerstrale's study devoted to the Baltic Sea (1957); in H. Caspers' work
(1957) on the Black and Azov Seas and in many others.

Abrikosov, G. 1959. Bryozoa in the Caspian and Aral Seas. Z.J. 38, 5 (E.s.)
Abrikosov, G. and Sokolova, N. 1948. The study of the littoral in the White

Sea. Bull. Moscow Univ., Biology, 2 (R)
Acclimatization of the Nereis in the Caspian Sea. 1952. Ed. M.O.I. P. (R)
Acclimatization of fishes and feeding-organisms (for fish) in the seas of the

USSR. 1960. /. Tr. V.N.I.R.O. 43 (R)
Agenorov, V. 1946. On the dynamics of the waters in the Barents Sea.

Ed. G.O.I. (R)
Agenorov, V. 1947. On the water masses in the Barents Sea in summer.

Tr. G.O.I. 1 (3) (R)
Aksenov, A. 1955. Morphology and dynamic of the northern coast in the

Azov Sea. Tr. G.O.I. 29 (41) (R)
Alekin, O. 1947. On the problem of the origin of the salt composition in the

waters of the Aral Sea. Meteorologia and Hydrologia, 4 (R)
Alexandrov, A. 1927. The anchovy in the Azov-Black basin, their origin

and systematic position. Tr. kerch Sci. Fisheries Station, 1, 2-3 (R)
Andreeva, I. and Udintzev, G. 1958. The bottom structure of the Sea of

Japan, according to research done aboard Vityaz. Bull. Acad. Sci.

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Andriashev, A. 1935. Geographical distribution of the edible sea food of the

Bering Sea and the problems raised. Expl. des mers de VURSS, 22 (E.s.)

REFERENCES 845

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846 BIOLOGY OF THE SEAS OF THE U.S.S.R.

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848 BIOLOGY OF THE SEAS OF THE U.S.S.R.

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Trans. Arctic Inst. 9 (G.s.)
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Okhotsk Sea. DAN, USSR, 103, 3 (R)
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WAN, 12 (R)
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Geol. Congr. (XXI Session). Repts. Soviet geol. Problem 10 Marine

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submarine relief. DAN, USSR, 116, 5 (R)
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tieren der USSR (Zur Frage iiber die Herkunft der marinen Crustazeen

in den Fliissen des Ponto-Kaspischen Bassins). Z.J. 14, 4 (G.s.)
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Mertviy Kultuk and Kaidak in the Caspian Sea related to the salinity.

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REFERENCES 849

Birstein, J. 1952. The history of the crab. Priroda, 9 (R)

Birstein, J. 1952. Nourishment of Caspian benthos-feeding fish in 1948—

1949 and the use of Nereis as feeding material. Acclimatization of the

Nereis in the Caspian Sea. Bull. M.O.I. P., Moscow (R)
Birstein, J. 1956. Resultats de l'acclimatisation de Nereis succinea dans la

Mer Caspienne et leur critique. Bull. M.O.I. P., biol. 61, 1 (F.s.)
Birstein, J. and Beliaev, G. 1946. Action of the Balchash water on the

Caspian invertebrates. Z.J. 25, 3 (R)
Berstein, J. and Spassky, N. 1952. Bottom fauna of the Caspian Sea before

and after the introduction of Nereis in Caspian Sea. Acclimatization of

the Nereis in Caspian Sea. Bull. M.O.I. P., Moscow (R)
Birstein, J. and Tchindonova, J. 1958. Deep-sea mysids in the north-western

part of the Pacific ocean. Tr. 10 AN, 27 (R)
Birstein, J. and Tchindonova, J. 1958. Die Tiefsee-Mysiden des nord-

westlichen Teiles des Stillen Ozeans. Tr. WAN, 27 (R)
Birstein, J. and Vinogradov, L. 1934. Fresh- water Decapoda USSR and

their geographical distribution. Z.J. 13, 1 (R)
Birstein, J. and Vinogradov, M. 1955. The pelagic gammarids of the Kurile-

Kamchatka Trench. Tr. 10 AN, 12 (R)
Birstein, J. and Vinogradov, M. Pelagische Gammariden des nord- west-
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INDEX

Abrikosov, G., 205

Agapova, N., 542

Afanasiev, G., 375

Akhmerov, A., 700

Aksenov, A., 477, 478

Alekin, O., 366

Alenitzyn, V., 647

Alexandrov, A., 435

Allen, J., 798

Amundsen, R., 222

Andreeva, I., 687

Andriashev, A., 39, 253, 718, 731, 746, 817,

839
Andrussov, N.. 357, 359, 381, 389, 572,

645, 647
Annenkova, N., 37
Antews, E., 290
Antipa, G., 458
Appellof, A., 174
Apstein, C, 299
Archangelsky, A., 291, 357, 358, 359, 360,

362, 382, 392, 399, 572
Arnoldi, L., 37, 436, 449, 445, 452, 462, 594
Arseniev, M., 821
Atkinson, W., 86

Bacesko, M., 368, 371, 372, 443, 565

Badigin, K., 35

Baer, K., 72, 73, 180, 538

Baskina-Zakolodkina, V., 573

Baturin, V., 358

De Beauchamp, P., Ill

Behning, A., 364, 572, 581, 633, 634, 647,

657, 661
Beklemishev, C, 696, 698, 704, 707
Beklemishev, V., 370, 568, 573, 581, 625
Belogorskaya, E., 401
Belyaev, G., 569, 625, 719, 723, 733
Berdichevsky, L., 525, 643, 739
Berg, L., 38, 364, 366, 541, 580, 581, 632,

647, 650
Bering, V., 677

Bezrukov, P., 684, 685, 784, 786, 787
Birstein, Yu., 369, 370, 569, 577, 580, 581,

582, 614, 615, 617, 622, 633, 641, 642,

713, 721, 723, 727, 728, 839
Billing, 677

Blinov, L., 366, 651, 652, 655, 656
Bogachev, V., 355, 360, 573
Bogdanov, A., 385
Bogorov, V., 52, 93, 96, 170, 234, 265, 266,

606, 704
Bogorov, В., 43, 48, 50, 66, 604, 707
Bogyavlensky, A., 695, 696, 698, 700
Boichenko, L., 819
Bokova, E., 521, 515, 626
Boldovsky, G., 38, 171
Borodin, N., 465

Borshchov, I., 647

Bozhenko, M., 819

Brandes, C, 295

Brandt, K., 271

Brarhnikov, V., 677

Bregman, G., 542

Breitfuss, L., 74, 79

Briskina, M., 170, 615

Broch, H., 174

Brotskaya, V., 136, 142, 153, 155, 156, 157,

168
Brotsky, K., 48, 170, 175, 209, 575, 577,

708, 729, 745, 775, 829
Brujewich, S., 86, 385, 400, 463, 541, 542,

552, 557, 558, 559, 594, 614, 645
Brunn, A., 713
Buch, K., 285, 286
Bujor, P., 452

Burkov, W., 696, 698, 704, 827
Burula, A., 180
Butakov, A., 647
Butchev, A., 647
Butkevitch, V., 86, 584
Bykhovsky, В., 610, 611, 662, 663, 700

Caspers, H., 443, 452
Caullery, M., 713
Chayanova, L., 217, 421
Chigirin, N.. 389, 395, 396
Chindonova, Yu., 713, 729

Danilchenko, P., 389, 396, 530

Datzko, V., 395, 396, 463, 466, 469

Davis, F., 511

Dektereva, A., 165

Demel, K., 271, 274, 316, 306, 319, 320

Dengina, R., 666

Derjugin, K., 38, 74, 75, 110, 123, 125,

134, 175, 176, 177, 185, 200, 206, 215,

257, 369, 678, 775
Derzhavin, A., 361, 368, 563, 564, 567,

568, 580, 581, 583
Dezhnev, S., 677
Dianova, E., 583, 584
Djakonov, A., 53, 66, 716
Dmitriev, N., 219

Dobrovolsky, A., 33, 383, 689, 690, 821
Dobrzanskaya, M., 395, 396, 463, 464
Dogiel, V., 610, 611, 662, 663, 700
Dolgopol'skaya, M., 449
Dorofeev, S., 219
Drapkin, E., 444
Dunbar, M., 70
Du Toit, 54
Dvoichensko, P., 369
Dybovsky, В., 573

Egerman, F., 633

902

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Rass, Т., 731, 732, 734, 735, 736, 739, 740,

777, 778, 782, 816, 817, 839
Ratke, H., 374, 376
Ratmanoff, G., 678, 823, 824, 825
Redeke, H., 344, 345, 349
Reibisch, J., 312

Remane, A., 206, 271, 304, 314, 345
Reschetetnjak, V., 709
Riech, F., 349

Romanova, N., 569. 621, 623, 624
Rossolimo, L., 402

Sadowsky, A., 374

Saenkova, A., 578, 625

Sagerstrale, Sv., 271, 304, 314, 328, 329,

332, 341, 342, 343, 345
Saidova, Kh., 791
Saint Hilaire, 180

Samoilensko, В., 468, 469, 521, 648
Sars, G., 289, 579
Sarychev, G., 677
Sauramo, M., 287, 289, 341, 342
Savilov, A., 798, 803, 804, 805, 806, 807,

808, 809
Schimkevitch, V., 180
Schmidt, P., 632, 731, 778, 779, 816, 817
Schokalsky, Yu., 382
Schorygin, A., 155, 156, 175, 197, 521,

633, 637, 738, 629, 640, 641, 642
Schuleikin, V., 183
Schultz, Br., 277, 278
Schurin, A., 330
Sechkina, Т., 687
Semina, G., 706, 790
Sernander, 287
Setchkina, Т., 687

Shachapova, Т., 109, 495, 574, 606, 609
Shchedrina, Z., 249, 725, 731
Sheinin, M., 521
Shirshov, P., 31, 33, 52
Shirshov, Т., 30
Shliper, K., 271
Shrenk, L., 677
Sizova, N.. 755, 765, 766, 767
Skopintsed, В., 396
Skorikov, A., 581
Skornyakova, 754
Skvortzov, E., 383
Slastenenko, E., 434
Smetanin, D., 698, 700
Smirnoff, A., 164, 519, 521
Smirnov, L., 705
Sokolov, A., 79
Sokolova, E., 190
Sokolova, M., 729, 731, 805
Sokolova, N., Ill, 115, 625
Soldatov, V., 677
Solovev, V., 541, 542
Somova, N., 768
Sorokin, Yu., 756

Sovinsky, V., 374, 381, 453, 466, 579
Sparck, R., 144
Spassky, N., 577, 622
Spethmann, H., 271
Spindler, A., 381, 645

Stark, I., 466, 500, 514

Steller, S., 677

Strakhov, N„ 362, 382, 400

Stuxberg, A., 134, 241

Suess, E., 572

Svetovidov, A., 57, 374, 379

Szidat, L., 349

Taliev, D., 582

Tanasijchuk, N., 37, 123

Taranetz, A., 678

Tarasov, N., 432, 678

Tchernyavsky, V., 381

Tchirikhin, Y., 255

Tchougounov, N.. 465, 521, 594, 614, 631,

633, 634
Thamdrup, M., 120
Thienemann, A., 340
Thorson, G., 339
Thulin, G., 271, 314, 316
Tichonov, V., 160
Tikhy, M., 565
Timonov, V., 183
Tokida, J., 765
Toil, A., 222, 255
Troflmov, A., 190
Turpaeva, E., 798

Uda, N., 689

Udinzev, G., 682. 684, 687, 783

Ukjanin, V., 180, 381

Usachev, P., 42, 52, 133, 232, 482, 586,
588, 589, 590, 591, 592, 593

Ushakov, P., 65, 108, 110, 123, 204, 262,
678, 682, 696, 698, 701, 745, 789, 790,
794, 796, 805, 806, 810, 811, 818

Vaiprecht, V., 73

Valikangas, I., 271, 295, 304, 316, 345

Valkanov, A., 432

Vasnetzov, W., 226, 227, 228

Velokurov, N., 387

Verechshagin, G., 582

Vernadsky, V., 392

Verzhbinskaya, V., 87

Vinogradov, L., 582, 614, 616, 817

Vinogradov, M., 707, 708, 721, 746, 775,

776, 793, 829, 830, 831, 832, 833, 839
Vinogradova, E., 88, 474
Vinogradova, N., 713, 726, 728, 736, 737,

813, 814, 815, 816, 834, 835, 837
Virketis, M., 93, 135, 183, 184, 234, 236,

237, 257, 264
Vodyanitzky, E., 392, 394, 395
Volkov, L., 427
Vorobieff, V., 431, 449, 469, 498, 511,512,

521, 529, 531, 532, 536
Voronichin, N., 427
Voronkov, P., 187, 468
Voroshilova, A., 583, 584
Voskresenski, K.., 206

Waern, M., 303

Wagner, N.. 180

INDEX

903

Wegener, 54
Wiese, V., 51, 250
Wilier, A., 348, 349
Wollenberg, 116
Wright, W., 295

Yabe, H., 685, 686

Yablovskaya, E., 423, 493, 494, 527, 625,

664, 665
Yakovlev, N., 289
Yakubova, L., 444, 449, 517
Yamada, Т., 678
Yashnov, V., 44, 49, 97, 100, 101, 194, 217,

258, 259, 265, 266, 598, 601, 603
Yastrebova, M., 622
Young, S., 498

Zachs, I., 65, 108, 110, 123, 744, 768, 796
Zaduskaya, E., 164
Zagorovsky, N., 452
Zalkin, V., 436

143,
168,

, 122,
, 156,

, 252,
577,
723,

Zatsepin, V., 38, 120, 121, 122, 127
144, 151, 153, 163, 164, 165, 166
169, 176

Zavistovich, Z., 206

Zaytsev, G., 77

Zenger, N.. 270

Zenkevitch, L., 56, 81, 92, 120, 121
123, 136, 142, 143, 155, 174, 175
157, 161, 226, 227, 231, 249, 251
311, 332, 377, 378, 496, 560, 565
578, 582, 613, 662, 717, 719, 721
795

Zenkovitch, V., 477, 650

Zernov, S., 374, 381, 436, 443, 465, 581, 798

Zevina, G., 518

Zheltenkova, M., 466, 521

Zhizhchenko, В., 359

Zhukov, V., 472, 529, 581

Zhuze, A., 790, 791

Zinova, A., 106, 195, 427, 701

Zinova, E., 765, 801

Zubov, N., 377, 79, 83

902

BIOLOGY OF THE SEAS OF THE U.S.S.R.

Rass, Т., 731, 732, 734, 735, 736, 739, 740,

777, 778, 782, 816, 817, 839
Ratke, H., 374, 376
Ratmanoff, G., 678, 823, 824, 825
Redeke, H., 344, 345, 349
Reibisch, J., 312

Remane, A., 206, 271, 304, 314, 345
Reschetetnjak. V., 709
Riech, F., 349

Romanova, N., 569. 621, 623, 624
Rossolimo, L., 402

Sadowsky, A., 374

Saenkova, A., 578, 625

Sagerstrale, Sv., 271, 304, 314, 328, 329,

332, 341, 342, 343, 345
Saidova, Kh., 791
Saint Hilaire, 180

Samoilensko, В., 468, 469, 521, 648
Sars, G., 289, 579
Sarychev, G., 677
Sauramo, M., 287, 289, 341, 342
Savilov, A., 798, 803, 804, 805, 806, 807,

808, 809
Schimkevitch, V., 180
Schmidt, P., 632, 731, 778, 779, 816, 817
Schokalsky, Yu., 382
Schorygin, A., 155, 156, 175, 197, 521,

633, 637, 738, 629, 640, 641, 642
Schuleikin, V., 183
Schultz, Br., 277, 278
Schurin, A., 330
Sechkina, Т., 687
Semina, G., 706, 790
Sernander, 287
Setchkina, Т., 687

Shachapova, Т., 109, 495, 574, 606, 609
Shchedrina, Z., 249, 725, 731
Sheinin, M., 521
Shirshov, P., 31, 33, 52
Shirshov, Т., 30
Shliper, K., 271
Shrenk, L., 677
Sizova, N., 755, 765, 766, 767
Skopintsed, В., 396
Skorikov, A., 581
Skornyakova, 754
Skvortzov, E., 383
Slastenenko, E., 434
Smetanin, D., 698, 700
Smirnoff, A., 164, 519, 521
Smirnov, L., 705
Sokolov, A., 79
Sokolova, E., 190
Sokolova, M., 729, 731, 805
Sokolova, N., Ill, 115, 625
Soldatov, V., 677
Solovev, V., 541, 542
Somova, N., 768
Sorokin, Yu., 756

Sovinsky, V., 374, 381, 453, 466, 579
Sparck, R., 144
Spassky, N., 577, 622
Spethmann, H., 271
Spindler, A., 381, 645

Stark, I., 466, 500, 514

Steller, S., 677

Strakhov, R, 362, 382, 400

Stuxberg, A., 134, 241

Suess, E., 572

Svetovid'ov, A., 57, 374, 379

Szidat, L., 349

Taliev, D., 582

Tanasijchuk, N., 37, 123

Taranetz, A., 678

Tarasov, N., 432, 678

Tchernyavsky, V., 381

Tchirikhin, Y., 255

Tchougounov, N., 465, 521, 594, 614, 631,

633, 634
Thamdrup, M., 120
Thienemann, A., 340
Thorson, G., 339
Thulin, G., 271, 314, 316
Tichonov, V., 160
Tikhy, M., 565
Timonov, V., 183
Tokida, J., 765
Toil, A., 222, 255
Trofimov, A., 190
Turpaeva, E., 798

Uda, N., 689

Udinzev, G., 682. 684, 687, 783

Ukjanin, V., 180, 381

Usachev, P., 42, 52, 133, 232, 482, 586,
588, 589, 590, 591, 592, 593

Ushakov, P., 65, 108, 110, 123, 204, 262,
678, 682, 696, 698, 701, 745, 789, 790,
794, 796, 805, 806, 810, 811, 818

Vaiprecht, V., 73

Valikangas, I., 271, 295, 304, 316, 345

Valkanov, A., 432

Vasnetzov, W., 226, 227, 228

Velokurov, N.. 387

Verechshagin, G., 582

Vernadsky, V., 392

Verzhbinskaya, V., 87

Vinogradov, L., 582, 614, 616, 817

Vinogradov, M., 707, 708, 721, 746, 775,

776, 793, 829, 830, 831, 832, 833, 839
Vinogradova, E., 88, 474
Vinogradova, N., 713, 726, 728, 736, 737,

813, 814, 815, 816, 834, 835, 837
Virketis, M., 93, 135, 183, 184, 234, 236,

237, 257, 264
Vodyanitzky, E., 392, 394, 395
Volkov, L., 427
Vorobieff, V., 431, 449, 469, 498, 511, 512,

521, 529, 531, 532, 536
Voronichin, N., 427
Voronkov, P., 187, 468
Voroshilova, A., 583, 584
Voskresenski, K., 206

Waern, M., 303

Wagner, N.. 180

INDEX

903

Wegener, 54
Wiese, V., 51, 250
Wilier, A., 348, 349
Wollenberg, 116
Wright, W., 295

Yabe, H., 685, 686

Yablovskaya, E., 423, 493, 494, 527, 625,

664, 665
Yakovlev, N., 289
Yakubova, L., 444, 449, 517
Yamada, Т., 678
Yashnov, V., 44, 49, 97, 100, 101, 194, 217,

258, 259, 265, 266, 598, 601, 603
Yastrebova, M., 622
Young, S., 498

Zachs, I., 65, 108, 1 10, 123, 744, 768, 796
Zaduskaya, E., 164
Zagorovsky, N., 452
Zalkin, V., 436

Zatsepin, V., 38, 120, 121, 122, 127,
144, 151, 153, 163, 164, 165, 166,
169, 176

Zavistovich, Z., 206

Zaytsev, G., 77

Zenger, N., 270

Zenkevitch, L., 56, 81, 92, 120, 121,
123, 136, 142, 143, 155, 174, 175,
157, 161, 226, 227, 231, 249, 251,
311, 332, 377, 378, 496, 560, 565,
578, 582, 613, 662, 717, 719, 721,
795

Zenkovitch, V., 477, 650

Zernov, S., 374, 381, 436, 443, 465, 581, 798

Zevina, G., 518

Zheltenkova, M., 466, 521

Zhizhchenko, В., 359

Zhukov, V., 472, 529, 581

Zhuze, A., 790, 791

Zinova, A., 106, 195, 427, 701

Zinova, E., 765, 801

Zubov, N., 377, 79, 83

143,
168,

I, 122,
156,

252,
>, 577,
I, 723,

INDEX OF LATIN NAMES

Abra alba (Mollusca Lamellibranchiata),

314
Abramis ballerus (Pisces), 629

— brama (Pisces), 312, 349, 629, 632, 669

— sapa (Pisces), 629, 669, 670, 671
Acanthias, 461
Acanthocephala, 610
Acanthocyclops vernalis, 493
Acanthodoris pilosa (Mollusca Gastro-
poda), 112

— sibirica (Mollusca Gastropoda), 135
Acanthometra (Protozoa Radiolaria), 446
Acanthopsetta nadeshnyi, 780
Acanthostepheia (Crustacea Amphipoda),

— incarinata (Crustacea Amphipoda), 242

— malingreni (Crustacea Amphipoda),

133, 135, 200, 211, 242, 260, 268
Acanthostomella norvegica (Protozoa Cili-

ata), 237, 264, 267, 433
Acarina (Arachnoidea), 203
Acartia (Crustacea Copepoda), 98, 194, 264

— bifilosa (Crustacea Copepoda), 294,

295, 297, 298, 347

— clausia (Crustacea Copepoda), 194,

403-9, 420, 423, 490, 493, 488, 829

— latisetosa, 490

— longiremis (Crustacea Copepoda), 237,

295, 297, 305, 782, 829

— tonsa (Crustacea Copepoda), 295, 298,

312, 348

— tumida (Crustacea Copepoda), 264
Acera'bullata (Mollusca), 38

Aceros phyllonyx (Crustacea Amphipoda),

128
Achistocomus sovieticus, 710
Achnanthes taeniata (Algae Diatomeae),

264, 296, 297, 300
Acila castrensis, 710
Acipenser guldenstadti (Pisces), 459

— nudiventris (Pisces), 61 1, 670

— ruthenus, 459

— stellatus (Pisces), 459, 671
Acipenseridae (Pisces), 260, 359, 367, 435,

518, 611, 628, 629, 639, 644, 668
Acmaea rubelia (Mollusca Gastropoda),
133

— testudinalis (Mollusca Gastropoda),

133, 776

— virginea (Mollusca Gastropoda), 128
Acoella (Mollusca Gastropoda), 441, 568
Actinia equina (Coelenterata Anthozoa),

113, 115,437, 514, 515
Actiniaria (Coelenterata Anthozoa), 266,

293, 306
Actinocyclus (Algae Diatomeae), 559, 660

— ehrenbergii (Algae Diatomeae), 297,

298, 587, 657, 658, 829

var. crassa (Algae Diatomeae), 657

Adacna (Mollusca Lamellibranchiata),
362, 367, 568, 620, 665, 666

— baeri, 568

— barbot-de-marnyi, 568

— crassa, 568

— fragilis, 454

— laeviuscula, 454, 612, 621, 623, 627, 638

— latens, 568

— longipes, 568

— minima, 570, 620, 627, 633, 665, 667

— plicata, 454, 614, 627

— pyramidata, 568

— trigonoicles, 568

Aegina echinata (Crustacea Isopoda), 135

Aglantha digitalis (Coelenterata Hydrozoa),
48,93, 193,238

Aglaophenia pluma (Coelenterata Hydro-
zoa), 444

Ahnfeltia (Algae Rhodophyceae), 205, 208

— plicata, 196
Alaba, 773

Alaba vladivostokensis, 770
Alaria (Algae Phaeophyceae), 208

— crassifolia, 765

— esculenta, 109, 196, 797

— fistulosa, 709

— membranacea, 797

— ochotensis, 797

— tistulosa, 765

Alcyonaria (Coelenterata Anthozoa), 266
Alcyonidium disciforme (Bryozoa), 149

— gelatinosum, 128, 147

— hirsutum, 112

— palyonum, 312
Alderia modesta, 308
Alectrion, 773

Alepisaurus aesculapius, 735
Alepocephalus umbriceps, 734
Alexia myosothis, 435
Alkmaria romijni, 347
Allocoeola, 568

Allorchestres zivellinus, 768, 772
Alona rectangula, 659

Alosa, 630

Alteria modesta, 308, 348

Amage anope, 772

Amallophora magna, 238

Amaroucium mutabile, 126

Amathillina (Crustacea Amphipoda), 367

— cristata, 479

— spinosa, 612
Amathillopsis spinigera, 246
Ammobaculites pseudospirale, 572
Ammodytes, 461

— lanceolatus, 309

— tobianus, 171, 309
Ammotrypane aulogaster, 710

906

INDEX OF LATIN NAMES

Amorphina caspia, 565
Ampelisca, 499, 515

— diadema, 502, 507, 509

— eschrichti, 267, 313

— fureigera, 813

— macrocephala, 267, 710, 771, 813

— maeotica, 505
Ampharete vegae, 149, 243
Ampharetidae, 620, 813
Amphilina foliacea, 612
Amphimelissa setosa, 238
Amphineura, 156, 196, 306, 431, 433
Amphiodia eraterodmeta, 810

— rossica, 774
Amphioplus macraspis, 774
Amphioxus (Branchiostoma) lanceolatus,

440, 448

Amphipoda, 39, 44, 47, 48, 110, 162, 166,
193, 196, 203, 218, 234, 241, 259, 266,
306, 336, 347, 433, 487, 497, 580, 603

Amphipora hyperborea, 264, 829

Amphiporus, 114, 128

— lacteus, 115

— lactifloreus, 112
Amphiroa cratacea, 771
Amphithoe rubricata, 209
Amphitrite jonstoni, 113
Amphiura florifera, 445, 446

— stepanovi, 449

— sundevallii, 1 54
Amphorella subulata, 193
Anabaena, 257

— baltica, 294, 346, 485

— bergii, 588, 657
var. minor, 588

— hassalii var. macrospora, 483

— knipowitschi, 483
Anarrhichas lupus, 159, 170

— minor, 159, 170
Anatirostrum, 628
Ancylus fluviatilis, 281, 342
Andaniexis subabyssi, 725
Anguilla vulgaris, 349
Angulus, 444
Anodonta, 312, 362
Anomalocera petersoni, 403, 406, 407
Anomia squamula, 128, 134, 144
Anonyx nugax, 133, 242, 772

— ampulloides, 773
Antedon rosacea, 446
Anthozoa, 110, 196, 259, 433
Antithamnion borealis, 267, 295
Antimora mycrolepis, 735
Anurea cochlearis, 295, 312

— aculeata, 294, 347

— cruciformis, 193

— var. eichwaldi, 295, 347
tropica, 595

— quadrata, 295, 347
Apagis, 595
Aphanizomenon, 295, 485

— flos aquae, 257, 294, 297, 298, 483, 485,

588
Aphelasterias japonica, 711, 768
Apherusa tridentata, 133

Aphiodia eraterodmeta, 771

Aphrodite aculeata, 37, 151

Aplexia myosothis, 439

Apomotmus globifer, 242

Appendicularia, 44, 193, 239, 265, 402, 403

Apschoronia, 360

Apterygota, 202, 203

Arachnoidea, 203

Araneina, 203

Area, 308, 356, 359

— borealis, 291

— frilei, 246

— glacialis, 128, 129, 148, 149, 242

— pentunculoides, 148
Archaeobdella esmonti, 434
Archnanthes taeniata, 300
Arctogadus, 55
Arenicola, 118,439-41

— cristata, 770

— marina, 119, 123, 204-9, 305, 311, 794

— pusilla, 770

— claparedii, 776
Argentina semifasciata, 734
Argobuecinum, 709
Aricia quadricuspida, 204
Aricidea, 444

— suecica, 317, 774
Aristias tumidus, 243
Arrhis phylonyx, 242, 268
Artacama proboscidea, 334, 710
Artediellus europaeus, 1 70
Artemia, 533, 534, 535

— salina, 535
Ascidia, 306, 427, 610

— obliqua, 132, 133, 153

— prunum, 126
Ascidiella aspersa, 444
Ascophyllum, 52, 72, 106, 108

— nodosum, 111, 112, 196, 204, 205, 301
Asellus, 325

— aquaticus, 312, 329
Aspelta baltica, 347
Aspidophoroides olricki, 170, 171
Aspius aspius, 629, 671

— illioides, 671
Asplanchna brighwellii, 295

— priodonta, 312, 492, 493, 594
Asra, 628

Astacus, 367

— leptodactylis, 567

— pachypus, 567

Astarte, 127, 128-31, 134, 314, 316

— acuticosta, 241, 242

— alaskensis, 710

— banksii, 144, 339, 814

— borealis, 127, 140, 148, 149, 154, 155,

209, 211, 212, 241, 242, 248, 250, 253,
307, 314, 316-17, 319, 321, 322, 332,
334, 338, 339, 813, 814

— crebricostata, 249

— crenata, 129, 131. 140, 146-53, 157, 241,

242

— compressa, 307

— elliptica, 131, 140, 142, 144, 149, 155,

211-13, 307

INDEX OF LATIN NAMES

907

Astarte icani, 710

— montagui, 140, 148, 149, 154, 209-10,

213,241,242,248,813

— rollandi, 710

— sulcata, 135, 141, 144
Aster trifolium, 201
Asterias amurensis 772

— lincki, 128, 135, 151,197,209-12

— panopla, 134

— rubens, 748
Asterionella gracillima, 257

— japonica, 829
Asterocytis ramosa, 301, 303
Asteronyx loveni, 710, 806, 811
Astrorhiza, 146

Astyra logozovi, 725, 728

— zenkevitchi, 725, 728
Asychis, 146

— biceps, 146, 147, 148

— punctata, 772
Asymphilodora, 611

— tincae, 612
Athanas, 442

Atherestes evermanni, 780
Atherina, 461, 522, 535, 537, 629, 633

— mochon, 379, 629, 671

— pontica, 535, 671

— caspia, 364, 629, 671
Atherinidae, 628
Atherinopsis, 521
Atracama proboscidea, 774
Audouinia tentaculata, 710
Aurelia, 102

— aurita, 295, 297, 305, 306, 309, 332, 402,

420
Austromysis, 604
Avicula, 358
Avicularia, 358
Axinus flexuosus, 118, 127, 129, 148, 154,

211,216,242

— gouldi, 316, 336, 773
Axionice flexuosa, 133, 267
Axiothella catenata, 336
Axinopsis orbiculata, 771, 772, 816
Azra turkmenica, 628

Babingtonii, 765, 766
Bacillaria paradoxa, 657
Bacterosira fragillis, 264, 790, 829
Balaenoptera physalis, 703

— borealis, 703

— musculus, 703
Balanoglossus mereschkowski, 748

— proterogonius, 771

Balanus, 96, 98, 139, 149, 295, 497, 499,
502, 507, 578

— balanus, 143, 147, 148, 153, 169, 308,

437,479, 501, 512, 574, 834

— balanoides, 39, 111-13, 123, 201, 204,

205, 776, 796, 799

— crenatus, 133, 134, 308, 834

— evermanni, 806, 810, 813

— improvisus, 308, 311, 323, 329, 332, 442,

455, 499, 574

— porcatus, 132, 502-5, 507

— rostratus dalli, 813, 834
Barbus brachicephalus, 670

— caspius, 632

Barnea Candida var. pontica, 448, 449
Basmania coregoni maritima, 347
Bathybiaster vexillifer, 246
Bathycrinus carpenteri, 246
Bathylagus milleri, 735

— pacificus, 735

Bathyporeia pilosa, 314, 318, 347
Bela, 127

— erosa, 772

— nowaja-zemlensis, 200

— violacea var. morchi, 134
Bellerochea malleus, 829
Belone, 314

— acus, 461

Bentheuphausia amblyops, 729
Benthophiloides brauneri, 459, 628
Benthophilus. 459, 519, 521, 562, 571, 628,

635

— baeri, 628

— ctenolepidus, 628

— grimmi, 628

— kessleri, 628

— leptocephalus, 628

— leptorhynchus, 628

— macrocephalus, 459, 635, 637, 639

— spinosus, 628

— stellatus, 459, 635
Beroe, 103, 757

— cucumis, 102
Biddulphia sinensis, 312

— mobiliensis, 483
Bithynia tentaculata, 311
Blackfordia virginica, 574
Blenniidae, 435
Blennius, 441, 461
Blephariposa japonica, 773
Blicca bjoernka, 632
Bolinopsis infundibulum, 103
Boltenia echinata, 834, 817

— ovifera, 834

Boreogadus saida, 161, 219, 838
Borlasia vivipara, 439
Borreri, 659

Bosmina maritima, 297, 298
Bosminidae, 595
Bothus, 461

— maximus, 309

— torosus, 518
Botryllus, 771

— schlosseri, 444
Botryococcus braunii, 587, 657
Brachinotus sanguineus, 768
Brachionus, 296, 594

— angularis, 294, 493

— bakeri, 294, 295, 594, 659

— miilleri, 594, 595, 659, 660

— pala, 294, 594

— plicatiles, 492

— plicatilis, 488

— quadridentatus, 488, 492
Brachiopodus, 130, 131, 133, 143, 156, 167,

169, 196,241,431,433

908

INDEX OF LATIN NAMES

Brachydiastylis resime, 210
Brachynotus, 513

— fucasii, 480, 502-5, 507
Brada granulosa, 796

— villosa, 127
Branchiopoda, 294, 610
Branchiostoma lanceolatum, 441
Branchiostomata, 433
Branchiura, 610

Brandtia fasciatoides, 242
Brisaster, 142, 144, 146, 837

— fragilis, 124, 135, 140, 142, 144, 146,

147, 151, 159

— latifrons, 710, 713, 807, 809, 810

— townsendi, 710

Bryozoa, 110, 130, 131, 133, 150, 156, 167,
169, 196, 241, 253, 259, 260, 266, 306,
347, 433, 496, 562, 570, 571, 608, 610,
661

Buccinidae, 139

Buccinum ciliatum, 134, 355

— glaciale, 133

— groenlandicum, 205

— hydrophanum, 128

— undatum, 133, 178
Bugula, 126

— murmanica, 126

— murrayana, 127
Bubyr, 628
Bunocotyle, 579

— cingulata, 611

Byblis gaimardi, 127, 267, 772, 773
Bythinia tentaculata, 312, 329
Bythocaris payeri, 246

Caberea, 126

— ellisi, 126
Calanipeda, 595, 597

— aquae dulcis, 487, 488, 595
Calanoida, 44, 596, 720
Calanus, 93, 171

— cristatus, 264, 698, 702, 704, 708, 729,

756-8, 775, 791, 793, 829, 830, 831,
833, 834

— curvispinum, 479

— finmarchicus, 295, 593, 605, 708, 729,

748, 758, 761, 765, 780, 791, 793, 817,
821,822,829,833,834

— helgolandicus, 265, 403, 409, 420, 421,

423, 460

— hyperboreus, 45-8, 98, 194, 237, 265

— maeoticus, 479

— pacificus, 698, 703, 729, 756, 758

— plumeticus, 704, 706

— tonsus, 702, 708, 729, 756, 757, 758,

763, 775, 780, 783, 785, 791, 793, 829,
830,831, 833,834
Calathura branchiata, 128, 243

— robusta, 242
Calianassa, 441, 773

— subterranea, 439
Caligus, 61 1

Caliptrophora ijimai, 807
Calliopius rathkei, 308
Calloneis brevis, 258

Calvina exiqua, 308
Calycopsis birulai, 259
Calyptrea chinensis, 441
Cambaroides, schzenckii, 744
Campanularia flexuosa, 304

— platycarpa, 710
Campylodiscus, 657, 659

— clypeus, 342
Cancer gibbosulus, 711
Candacia columbiae, 794, 831
Candona angulata, 348
Canuella perplexa, 444
Caphalopoda, 293
Capillospirura ovotrichuria, 612
Capitella capitata, 113, 267, 774
Caprella, 777

— septentrionalis, 209
Carabidae, 202
Carcinus maenas, 374
Cardidae, 359, 367, 637
Cardiophilus baeri, 566

Cardium, 118, 127, 129, 131, 304, 309,
355-8, 440, 444, 456, 478, 481, 482,
495, 497, 499, 501, 518, 533, 534, 562,
620,621,623,635,638

— ciliatum, 127-9, 134, 140, 148, 153,

155, 170, 211, 216, 248, 710, 749, 813,
815, 817, 837, 838

— echinatum, 153, 178

— edule, 38, 117, 119, 178, 203, 208, 291,

307, 308, 309, 311, 316-17, 323-5,
327-32, 342, 344, 435, 442, 454, 499-
509, 534, 562, 568, 569, 570, 574,
612-16,620,623,630,633

var. maeotica, 501

picta, 501

— elegantulum, 38, 131, 153

— exiguum, 441, 442, 509, 514

— fasciatum, 38, 131, 141, 153

— groenlandicum, 38, 127, 140, 148, 153

— simile, 444, 446-51
Careproctus amblystomopsis, 718

— reinhardti, 171
Carynosoma strumosum, 611
Caryophyllia clavus, 773, 806
Caryophyllum, 446
Caspia, 367

— gmelini, 371

Caspialosa, 367, 377, 379, 461, 628, 669

— brashnikovi, 377, 379, 459, 628, 630,

635

autumnalis, 630, 629

grimmi, 629, 639

kisselewitschi, 459, 629, 630

nirchi, 628

orientalis, 628

sarensis, 628

— caspia, 459, 628, 629, 630, 633, 668
aestuarina, 630

— knipovitschi, 629

persica, 571

salina, 569, 623

typica, 635

— curensis, 629, 633

— kessleri, 459, 629, 630, 633, 135

INDEX OF LATIN NAMES

909

Caspialosa, maeotica, 434, 460, 461, 535

— nordmanni, 434, 459

— pontica, 434, 460, 461, 518

— saposhnikovi, 635, 637

— sphaerocephala, 379, 630, 635

— suvorovi, 379, 629, 630

— tanaica, 434, 459, 460, 461, 518

— volgensis, 629, 630
Caspiocuma campylaspoides, 566, 628
Caspiomysis, 566

Caspiomyzon wagneri, 628, 630
Caspionema, 367, 565

— pallasi, 565, 594

— sp., 598

Caspiosoma caspium, 628
Castalia arctica, 133

— punctata, 133, 209
Cellepora nodulosa, 126

— nordgaardi, 126

— ventricosa, 126
Centrocorona taurica, 442
Centromedon pumilis, 243
Centropages, 98

— hamatus, 193, 194, 237, 221, 308

— kroyeri, 403-7, 488, 490

— memuzziehi, 829

— typicus, 237, 431
Cephalopoda, 259, 433
Cephalothrix linearis, 204
Cepphus carbo, 744
Ceramaster, 145
Ceramium, 439

— diaphanum, 301, 303, 428, 574, 607

— rubrum, 428, 432

— tenuicorna, 346
Ceretaulina bergonii, 402, 414, 416
Ceratella aculeata var. tropica, 594
Ceratium, 91, 135, 355, 356, 402

— arcticus, 91, 763

— furca, 91

— fusus, 91, 193,294,402

— hirundinella, 659

— longipes, 91, 704

— pentagonum, 828

— tripos, 135, 294,402
Cercopagis, 488, 595

— gracillima, 595

— pengoi, 487, 658
Cercyra papillosa, 439
Cerebratulus, 128

— kovalevskyi, 445
Ceriantharia, 774
Cerianthus vestitus, 449
Ceriodaphnia reticulata, 658
Cerithiolum, 441, 446

— reticulatum, 503
Cerithium, 441
Cerorhinca monocerata, 744
Cestodes, 610, 662

Cestus amphitrites, 705
Cetotherium, 355

Chaetoceras, 91, 93, 172, 194, 294, 402,
485, 587, 761

— atlanticus, 704

— concavicornis, 828

— constrictum, 135, 194

— constrictus, 704

— convolutus, 704

— curvisetum, 194

— danicum, 194, 198, 294, 296, 298

— debilis, 828

— diadema, 91

— furcellatus, 264, 790

— gracile, 258, 296

— holsaticus, 297, 298

— lozenzianus, 705

— placidus, 369

— radians, 402, 414, 416, 828

— scolopendra, 194

— socialis, 264, 414, 829

— subtilis, 483, 587, 657

— wighamii, 258, 294, 296, 297, 298, 587

657
Chaetoderma nitidulum var. intermedia,

211
Chaetogammarus placidus, 479

— ischnus, 479

Chaetognatha, 47, 48, 193, 194, 218, 248,

259, 265, 402, 403, 433, 487, 496
Chaetomorpha, 301, 431

— chlorotica, 428, 432

— melagonium, 240
Chaetonymphon spinosum, 126
Chaetopteros plumosa, 240, 301
Chaetozone setosa, 154, 267, 773, 813, 815,

836
Chalcalburnus chalcoides aralensis, 658,

660, 669, 670, 671
Challengeron, 756, 757
Chara aspera, 312, 608

— baltica, 377

— canescenes, 347

— crinita, 347, 608

— cyclotella, 659

— intermedia, 608

— polyacantha, 608
Charax, 461
Characeae, 347, 660
Charybdis japonicus, 773
Chauliodus macouni, 735
Chiridius obtusifrons, 238
Chidorus sphaericus, 295
Chionoecetes opilio, 743, 814, 817, 835,

836

— angulatus bathyalis, 774

— elongatus bathyalis, 773
Chiridota laevis, 118, 127, 208, 209
Chiridothea, 340

Chironomidae, 120, 122, 204, 327, 349,
533, 609, 614, 618, 619, 620, 635, 638,

661, 663, 664, 669, 670
Chironomus, 533, 534

— salinarius, 480, 533, 534
Chiton, 134

— albus, 128

— marmoreus, 112

— ruber, 128

Chlorophyceae, 193, 196, 257, 296, 533,

586, 657, 660
Chondracladia gigantea, 811

910

INDEX OF LATIN NAMES

Chondrus crispus, 301, 796

— pinnulatus, 767

Chone infundibuliformis, 128
Chorda, 106

— filum, 109, 110, 196, 208, 301, 332

— tomentosa, 196, 301
Chordaria, 768
Chroococcus, 657

— turgidus, 659
Chrysomonadina, 485
Chthamalus, 799

— challenged, 768

— dalli, 776

— stellatus, 439
Chydoridae, 595
Ciliata, 206, 234, 294, 296
Cingula, 777

— marmorata, 796

Ciona intestinales, 128, 444, 446
Cirripedia, 94, 110, 133, 196, 259, 265, 266,

267, 308, 433, 487, 488, 491, 496, 529,

609
Cladocera, 98, 193, 194, 196, 218, 234, 238,

239, 258, 264, 297, 306, 347, 402, 403,

433, 487-93, 496, 594-6, 658, 659, 660
Cladonema, 441
Cladophora, 106, 111, 312, 428, 431, 533,

535, 608

— fracta, 108

— glomerata flavescens, 607

— gracilis, 108, 660

— nitida, 607

— siwaschensis, 533, 535
Cladostephus verticillatus, 432
Clausocalanus arcuicornis, 758
Clava squamata, 304
Cleantis isopus, 710
Cleippides quadricuspis, 246
Cleonardo macrocephala, 725, 728
Clessinia, 362, 366
Clessiniola, 367

— variabilis, 371, 454, 456, 457, 567
Cletocamptus confluens, 348
Climacodium biconcavum, 705
Cliona, 442

— strationis, 442
Clione limacina, 237
Clupea, 355

— harengus harengus, 159, 198, 219, 309
pallasi, 765, 778

membras, 349, 578, 671

— pallasi, 817

maris albi, 198, 219

— sprattus, 309

Clupeidae, 253, 260, 379, 435, 459, 518,

628, 633, 637
Clupeonella, 367, 377, 379, 461, 519, 522,

633

— delicatula caspia, 458, 5 1 9

— engrauliformis, 628

— grimmi, 628
Clymene, 531
Cobitidae, 628
Cobitis caspia, 628
Coccidia, 610

Coccolithineae, 401
Coccophora tangsdorfii, 765
Codonella relicta, 594, 658
Coelenterata, 44, 47-8, 98, 99, 143, 213,

234, 241, 251, 259, 260, 264, 265, 347,

433, 487, 497, 608, 662
Coleoptera imagines, 203

— larvae, 203, 533, 594, 596, 609
Collossendeis, 249

— proboscidea, 249
Collotheca, 294

— mutabilis, 294

— pelagica, 294
Columbella rosacea, 127
Cololabis safra, 740, 748, 817
Colpomenia sinuosa, 765
Colurella adriatica, 659

— dicentra, 347
Conchoecia, 757, 775

— borealis, 237

— elegans, 45
Congeria cochleata, 348

— novorossica, 357

— panticapea, 357
Conjugatae, 257, 657
Conus, 355

Copepoda, 44-8, 63, 91, 193, 218, 234-9,
241, 258, 259, 264, 265, 294, 295, 297,
300, 306, 308, 347, 348, 402, 403, 433,
487-91, 496, 595, 597, 601, 633, 658,
660

— colanoida — see Calanoida
Corallina, 208, 439

— officinalis, 766

— pillulifera, 767, 768
Corbicula, 362, 355, 443
Corbula, 308

— gibba, 308

Corbulomya, 443, 444, 497, 499, 501, 509,
512, 514, 517

— maeotica, 443, 448, 501-5, 507, 509, 514
Cordiophilus baeri, 479
Cordylophora, 367, 562, 565, 578, 637

— caspia, 313, 347, 479, 565, 581, 582, 612,

614
Coregonidae, 55
Coregonus albula, 312, 349

— lavaretus, 312, 349
Corethron criophilum, 91, 135
Corophiidae, 457, 566, 616, 620, 626, 635,

638
Corophium, 133, 349, 367, 497, 512, 517,
566

— bonnelli, 133

— chelicorne, 614

— curvispinum, 364, 497, 567, 575, 582

— lacustre, 308, 347
■ — maeoticus, 369

— monodon, 614

— nobile, 455, 456, 575, 614

— robustum, 369, 479, 614

— volutator, 308, 310, 328-32, 455, 456,

480, 499
Corvina, 461
Coryceus, 758

INDEX OF LATIN NAMES

Corynosoma, 579

— strumosum, 612
Coryphaenoides acrolepis, 735

— cinereus, 735

— lepturus, 735

— pectoralis, 735
Coryphella rufibranchialis, 112
Coscinodiscus, 402, 485, 587

— biconicus, 483

— centralis, 135

— granii, 829

var. aralensis, 297, 298, 314, 657

— marginatus, 258, 782

— oculis iridis, 761, 763, 782

— subbulliens, 91

— viridis, 705

Coscinosira polychorda, 829
Costaria costata, 767
Cothurnia maritima, 297, 298
Cottidae, 249, 253, 260, 269
Cottus quadricornis, 309, 341

— scorpius, 309

Crangon crangon, 219, 309, 446

— dalli, 816

— septemspinosa, 782
Crangonidae, 161
Craniella cranium, 144, 145
Craspedacusta, 111

— sowerbii, 580
Crellomina imparidens, 198
Crenella decussata, 772, 773
Crenilabrus, 582
Crepidostomum, 579
Crepidula, 816
Cribrella, 145

— sanguinolenta, 144, 126, 127, 210
Crisia arctica, 126

— eburnea, 209

— eburnea-denticulata, 126
Crossaster papposus, 814, 836
Crustacea, 143, 150, 156, 213, 218, 251,

260, 267, 502, 612, 637, 657, 659, 662,

663
Cryptomonadinae, 485
Cryptopsaras couesil, 734
Cryptospongia enigmatica, 807, 811
Ctenicella appendiculata, 446
Ctenodiscus, 129

— crispatus, 127, 129, 140, 147, 148, 151,

234, 242, 749, 773, 774, 813, 837, 838
Ctenophora, 110, 193, 234, 258, 267, 291,

423,431,433,580
Cucumaria calcigera, 149, 200, 837, 838

— frondosa, 128, 132, 147, 244, 749

— japonica, 772

— orientalis, 466
Culcolus shumi, 738

— murrai, 738

Cumacea, 110, 162, 166, 196,210,241,266,
433, 455, 457, 479, 487, 496, 497, 562,
566, 571, 575, 579, 601, 603, 616, 620,
623, 635

Cumopses, 446

— distans, 133
Cyamium minutum, 112

Cyanea, 98

— capillata, 295, 297, 305, 347
Cyanophyceae, 196, 257, 401, 485, 533,

586, 657
Cyathura, 347

Cyclocaris guilelmi, 725, 728
Cyclonassa kamyschensis, 514
Cyclopoida, 44, 596
Cyclops, 595

— viridis, 659

Cyclopteridae, 249, 253, 260
Cyclopterus lumpus, 209, 309
Cyclostomata, 196
Cyclotella, 659
Cyclothone microdon, 735
Cylichna, 127

— alba corticata, 773

— densistriata, 200
Cyliste viduata, 446, 514
Cyphocaris challenged, 725, 728

— richardi, 725, 728

Cyprideis littoralis, 348, 473, 663, 667
Cypridopsis aculeata, 348
Cyprina, 129-31, 314

— islandica, 129, 144-53, 210, 169, 314
Cyprinidae, 435, 518, 628

Cyprinus carpio, 632, 670
Cystoclonium purpurascens, 301
Cyrtodaria kurriana, 243
Cystoflagellata, 401, 404
Cystoseira, 435, 440

— barbata, 428, 431, 432, 439

— erassipes, 765, 766

— hakodatensis, 765
Cytheromorpha fuscata, 347
Cytherura gibba, 347
Cyttarocylis denticulata, 183

— helix, 403, 407, 408

— ehrenbergi, 403-8

Dacrydium vitreum, 209-13, 248

Daphnia longispina, 493

- — cuculata, 293

Daphnidae, 595

Decapoda, 39, 93, 110, 196, 198, 241, 259,

266, 268, 306, 347, 433, 445, 496, 562,

570, 580, 609
Defrancia, 128

— lucernaria, 128
Dellesseria, 210

— sanguinea, 301

— sinuosa, 109, 240
Delphinapterus leucas, 219
Delphinus delphus, 427
Dendronotus frondosus, 133

var. dalli, 133

Dentalium entalis, 127, 135, 153

— striolatum, 148
Derjuginia tolli, 45, 238
Desmarestia, 106

— aculeata, 109, 240, 267

— aculeus, 196
Detonula confervacea, 264
Diaphanosoma brachyurum, 493, 659
Diaptomus gracilis, 595

912

INDEX OF LATIN NAMES

Diaptomus salinus, 658-60, 670, 671
Diastylis rathkei, 127, 149, 315, 317, 318,
323

— stuxbergi, 243

— sulcata, 243

Diatomaceae, 196, 257, 533, 586, 657
Diatomeae, 193, 196, 346, 401, 415, 416
Dictyosiphon, 106

— foeniculaceus, 303

— foeniculacium, 108, 266, 301

— mesogloja, 108
Dictyosphaerium, 587

— ehrenbergianium var. subselsa, 434
Didacna, 357, 360, 367, 620, 621, 635

— baeri, 613

— barbot-de-marnyi, 570, 612, 616, 627

— crassa, 612

— protracta, 613

— trigonoides, 570, 612-16, 620, 627
Didemnidae, 441
Dikerogammarus caspius, 566, 612

— grimmi, 612

— haemobaphes, 364, 479, 613, 614, 616,

627

— macrocephalus, 612

— villosus, 457, 479
Dilophus repens, 432
Dimophyes arctica, 757, 775
Dinobryon pellucidum, 296, 297, 298

— sertularia, 659
Dinoflagellata, 402, 414, 415, 417
Dinophysis, 402

— acuta, 828

— arctica, 258

— baltica, 294, 297
Dioctophymidae, 611

Diogens pugilator, 439, 442, 450, 451

— varians, 439, 442
Diphasia abietina, 126

— faliax, 126

Diphyes = Dimophyes, 446

arctica, 45, 237

Diplobranchia gorbunoui, 716
Diploneis, 257
Diplopsalis, 660

— caspia, 657

— pallula, 657

Discorbis ( = Discorbiba), 572
Discorbis vilardeboana, 572
Distolaterias elegans, 71 1

— nipor, 772

Dityllum brightwelli, 483, 485
Divaricella divaricata, 441, 450, 451
Doclea bridentata, 768
Donacilla cornea, 437
Donax, 355

— venustus, 450, 45 1
Dosinia, 355

— japonica, 771
Dotocoronata, 38

Dreissena, 360, 362, 364, 370, 457, 497,
512, 514, 517, 562

— bugensis, 578, 614, 620, 621, 645, 659-

667, 669

— caspia, 568-70, 573, 612-16, 663, 667

— distincta, 573

— grimmi, 568

— polymorpha, 314, 344, 364-71, 454, 456,

457, 479, 497, 568, 570, 581, 582, 612,
613, 614, 620, 627, 658, 663, 665, 666,
667
caspia, 573, 371, 568

— rostriformis, 611, 612, 613, 663
Dreissensia — see Dreissena
Dreissensiidae, 357, 359, 367
Drepanopsetta platessoides, 159
Drepanopus bungei, 45, 67, 238, 258, 259
Dynoides denticinus, 710
Dynamenella glabra, 777

Ebria tripartita, 485, 486

Echinarachnius parma, 710, 732, 744, 774,

797, 798, 800, 802, 803, 804, 812, 813,

816, 835, 836, 837

— griseus, 771

— mirabilis, 771
Echinocardium flavescens, 141
Echinocyamus pusillus, 141
Echinodermata, 39, 110, 131, 133, 143,

150, 156, 167, 169, 198, 213, 241, 251,
259, 260, 266, 268, 293, 306, 431, 433,
571
Echinogammarus spasskii, 776
Echinus esculentus, 37, 135, 141, 142
Echiuroidea, 616

— vitjazema, 721
Echiurus pallasi, 118, 770

— echiurus, 796
Ectinomosoma, 595

— curvicorne, 348

— elongatus, 444
Ectocarpus, 111, 296, 346

— confervoides, 301, 574

— siliculosus, 301
Ectochaete leptochete, 574
Eisenia arborea, 747

— bicycles, 747

— cookeri, 748

— desmarcotioides, 747, 748

— mason ii, 747
Elachista fucicola, 301
Eleginus gracilis, 817, 839

— navaga gracilis, 738
Elpidia glacialis, 246, 247
Elpidium granulosum, 572

— polyanum, 572
Embletonia, 308
Enchelopus, 204

— viviparus, 1 1 2
Engraulis, 461

— encrassicholus, 314, 427, 521, 535, 536
maeoticus, 435, 521, 535

— japonicus, 839

— ponticus, 435

Enteromorpha, 52, 107, 108, 117, 301, 312,
439, 440, 766

— crinita, 266

— intestinalis, 428, 432, 607

— salina, 574

— tubulosa, 574

INDEX OF LATIN NAMES

913

Enteropneusta, 196, 266, 431, 433, 570

Entomostraca, 533

Entoneme salina, 574

Ephesia peripatus, 246

Ephydalia fluviatilis, 330, 312

Ephydra, 535

Epimeria loricata, 127, 243

Ericara salmonea, 735

Erichthonius brasiliensis, 135, 246

Erignathus barbatus, 219

— thienemanni, 347
Erimacrus isenbecki, 743
Eriocheir sinensis, 312
Eriphia spinifrons, 439
Errinopora stalifera, 805
Ervilia, 355
Esocidae, 628, 668

Esox lucius, 312, 349, 671
Eteone arctica, 204

— longa, 776

Eualus gaimardi gaimardi, 133, 242, 268
Eucalanus bungii, 264, 702, 703, 704, 708,
729, 775, 793, 829, 830, 831, 833, 834

— elongatus, 757
Eucampia groenlandica, 829
Eucentrum cristes, 347

— rousseleti, 347
Euchaeta, 93, 98

— japonica, 757

— gracilis, 237, 238, 265

— norvegica, 135, 194, 238
Euchlanis plicata, 347
Euchone olegi, 772

— papillosa, 260
Eudorina elegans, 659
Euglenaceae, 411

Eugyra adriatica, 44, 446, 449

— pedunculata, 200, 213
Eukrojinia, 45
Eukromia australia, 729

— fowled, 729

— grimaldi, 729
Eunemertes gracilis, 439
Eunephthya, 141
Eunice, 145

— norvegica, 131, 141, 144
Eunida sanguinea, 133
Eupagurus, 139, 166

— bernhardus, 38

— pubescens, 127, 132, 149, 162
Euphasia pacifica, 704, 729, 775, 759
Euphausiacea, 44, 158-61, 164, 166, 218,

266
Euphausiidae, 105
Euprimno macropus, 757
Eupyrgus pacificus, 772

— scaber, 128
Eurycope hanseni, 246, 247

— spinifrons, 773
Euridice pulchra, 437
Eurysteus melanops, 243
Eurytemora, 54

— affinis, 295, 347, 595

— americana, 79 1

— asymmetrica, 791

Зм

— grimmi, 595, 605, 633

— herdmani, 791

— hirundo, 294, 295, 348

— hirundoides, 294, 297, 298, 347
Eusirella multicalceola, 725, 728
Eustrongylides, 611
Euthemisto libellula, 237
Eutora cristata, 240

Evadne, 93, 98. 595

— anonyx, 658

— camptonyx, 658, 660

— nordmanni, 193, 237, 264, 295, 297,

298, 403-7

— spinifera, 403-6

— trigona, 487-92, 595
Evasterias rotifera, 794
Excirolana japonica, 710
Exuviella, 587-90, 660

— cordata, 402, 414, 416, 483, 485, 587-90
aralensis, 587

typica, 587

Fabricia, 207

— sabella, 39, 118, 120, 134, 305, 311, 574
Felamella olivacea, 774

Filigrana implexa, 142

Flabelligera affinis, 127

Flagellata, 193, 232, 257, 423, 485, 533,

586, 610, 657
Floscularia, 295

— mutabilis, 658
Flustra, 126, 133

— foliacea, 141

— membranaceo-truncata, 126, 127

— securifrons, 127
Flustrella, 112

— hispida, 112
Fontinalis dolecorlica, 312
Foraminifera, 120, 196, 234, 241, 248, 259,

266, 267, 570, 572, 609, 610, 661
Fragilaria crotonensis, 659

— cylindricus, 296, 300

— islandica, 264

— oceanica, 264, 790, 829
Fritillaria, 238

— borealis, 93, 98, 193, 237, 297, 298

— polaris, 238
Frutercula cirrata, 744

— cormiculata, 744
Fucaceae, 52, 72

— ceranoidea, 301

Fucus evanescens, 240, 768, 794, 796, 799

— inflatus, 106, 204, 205, 208, 240, 799

— serratus, 106, 113, 196, 204-8, 301, 329

— vesiculosus, 39, 106, 107, 108, 196, 204,

205, 293, 301, 322
Fulmarus glacialis, 744
Furcellaria fustigiata, 301

Gadidae, 253, 260, 269, 461, 628
Gadus aeglefinus, 36, 159

— callarias, 159, 198
maris, 98

— macrocephalus, 817, 839

914

INDEX OF LATIN NAMES

Gadus morrhua, 219, 309
macrocephalus, 779

— poutassou, 37, 170

— virens, 1 59
Gaetanus minor, 757, 775
Gadius brevispinus, 757, 775
Galathealinum brunni, 716
Gambusia affinis, 574
Gammaracanthus, 55, 341, 566

— lacustris, 579

— loricatus, 133, 242, 260, 341, 519
caspius, 579

Gammaridae, 119, 562, 566, 567, 620, 635
Gammarus, 308, 349, 534, 535

— duebeni, 308, 411, 326, 347

— f. reducta, 327

— locusta, 112-19, 122, 123, 134, 203-8,

308, 311, 323,326,329,330

— locustoides, 776

— marinus, 112

— placidus, 612

— setosa, 243

— wilkitzkii, 260

— zaddachi, 310
Gasterosteidae, 628, 668
Gasterosteus aculeatus, 253, 260, 269, 301,

347, 427
Gastrana, 441

— fragilis, 480
Gastrochaena dubia, 449
Gastropoda, 44, 110, 143, 156, 167, 169,

213, 251, 259, 267, 347, 357, 433, 496,
502, 567, 570, 571, 609, 610, 620, 635
Gastrosaccus, 444

— sanctus, 437

— spinifer, 295
Gastrotricha, 330
Gebia, 441

— littoralis, 439, 441
Gelidium crinale, 432

Geodia baretti, 126, 127, 144, 146
Gephyrea, 110, 131, 133, 143, 156, 167,

241,305,311,431,433,610
Gibbula tumida, 38, 142

— derjugini, 770
Gigas, 771

Glenodinium apiculatum, 414

— danicum, 483

— trochoideum, 657
Globigerina, 135

— bulloides, 234, 532

— triloba, 572

Globigerinella aequilateralis, 572
Globorotalia crassa, 572
Gloiopeltis capillaris, 766, 767, 768
Glycera, 128,439,441

— capitata, 113, 126, 796

— convoluta, 574
Glurhanostomum pallescens, 135
Glyphocrangon rimapes, 738
Glyptocephalus stelleri, 780
Gmelina, 497

— kusnetzowi, 479

— ovata, 499
Gnathia elongata, 773

— robusta, 246

— stygia, 246

Gobiidae, 367, 435, 518, 628, 635, 639
Gobio baltica, 301, 303
Gobius, 441,461

— caspius, 635

— fluviatilis, 535
pallasi, 635-9

— kessleri, 635, 637

— melanostomus, 378, 524, 635, 639
affinis, 671

Goniada maculata, 141
Goniocarpe coriacea, 773
Gonothyrea loveni, 112
Gonyaulax, 402

— catenata, 295, 296, 298, 300

— polyedra, 402, 411, 414, 485, 587

— triacantha, 485
Gorgonocephalus, 248, 835

— arcticus, 115, 242, 248

— cargi, 813

— eucnemis, 126
Gouldia, 446

— minima, 441, 442, 450, 451
Gracillaria, 431
Grammaria abietina, 126
Grantessa nemareusis, 710
Grantia arctica, 126

— penuigera, 126
Grayella pyrula, 127
Gremilabrous tinea, 441
Gruelinopsis, 566
Gymnacanthus tricuspis, 170, 171

Halaptilus pseudooxycephalus, 794
Halecium polytheca, 126
Halice aculeata, 725

— quarta, 725

— shoemakeri, 725
Halichoerus grypus, 344
Halichondria tenuiderma, 112
Haliclystis octoradiatus, 209
Halicryptus, 328

— spinulosis, 113, 115, 119, 199, 206-9,

305, 311, 317-23, 324, 327, 328, 329,
334, 338, 341
Halicyclops aequoreus, 659

— sarsi, 595, 596

Halirages quadridentalus, 246, 247
Haliragoides inermis, 247
Halitholus cirratus, 259, 334
Halleutaea stellata, 734
Halopteris seoparia, 765
Halosaccion, 1 1 1
Halosphaera, 135

— viridis, 237

Haploarthron laeve, 771, 772
Haplogaster grebnitzkii, 796
Haplomesus quadrispinosus, 246
Haploops tubicola, 127, 242, 773
Haplophragmoides canariensis, 773
Harmothoe badia, 200

— imbricata, 126, 214, 773

— impar, 127, 773, 774

— derjugini, 773, 774

INDEX OF LATIN NAMES

915

Harmothoe, nodosa, 214

— sarsi, 315, 317, 318, 324, 329, 334
Harpacticidae, 66, 120
Harpacticoida, 44, 206, 596, 661
Harpinia antennaria, 135
Helcampa duodecimcirrata, 305
Helicostomella, 294, 295

— subulata, 294, 297, 298
Heliastes, 461

Heliometra glacialis, 242, 248, 268, 771,

773
■ maxima, 774

— quadrata, 126, 127
Hemicythere sicula, 667
Henricia sanguinolenta, 243, 247
Hetairus fasciata, 835

— polaris, 242

Heterochordaria abictina, 765
Heterocontae, 401
Heterocope, 491

— caspia, 457, 487-91, 595
Heterocypris sabina, 348
Heteropanope tridentata, 575
Heterorhabdus norvegicus, 238

— tonneri, 794
Heterotanais oerstedi, 347
Hippoglossoides elassodon, 817
dubius, 780, 781

— platessoides, 168

— robustus, 839
Hippoglossus hippoglossus, 159
stenolepis, 780, 781

— stenolepis, 839
Hippolyte, 126

— gaimardi, 128

— polaris, 126

— spinus, 128

— turgida, 128

— varians, 439
Hippolytidae, 161

Hirudinea, 196, 496, 609, 610, 620, 662
Histiobranchius bathybius, 735
Histriophoca groenlandica, 219
Homoenata platygonom, 238
Hormosina globulifera, 249
Hornera lichenoides, 126, 141
Horsiella brevicornis, 348
Husa, 461, 459
Hyalopomatus claparedi, 246
Hyas araneus, 149, 162, 244
var. hoecki, 127

— coarctatus, 144, 147, 813, 814, 835, 836
Hydracarina, 609, 661

Hydrobia, 208, 295, 311, 356, 367, 497,
499, 512, 513, 515, 517, 522, 533, 534,
612, 663

— baltica, 308, 329, 342

— grimmi, 567

— jenkinsi, 308, 348

— pusilla, 567

— ulvae, 117, 133,206-9, 311

— ventrosa, 247, 502-8, 534, 667
Hydrobiidae, 367
Hydrogenthiobacteria, 554
Hydroidea, 19

Hydroides norvegica, 141
Hydromedusae, 402
Hydrozoa, 110, 193, 259, 266, 334
Hymenaster anomalus, 738

— pellucidus, 246
Hymendora frontalis, 729

— glacialis, 729
Hypania, 367, 370, 457, 562

— invalida, 457, 479, 565, 581, 612
Hypaniola, 367, 370, 455, 457, 497-505,

512-14,517

— kowalevskyi, 473, 480, 499, 565, 581
Hyperammina friabilis, 773

— subnodosa, 128
Hyperia, 135
—gala, 295
Hyperiidae, 166
Hyperiopsis laticarpa, 725
Hypomesus olidus, 839
Hyrcanogobius bergi, 627

Iaera, 120, 122

— albifrons, 112, 116, 308

— marina, 112, 117
Icelus bicornis, 170, 171
Icasterias panopla, 248
Idmonea atlantica, 126, 127, 141
Idothea, 324, 349, 439

— algirica, 403, 404, 407, 427

— baltica, 113, 293, 309, 329, 437

— granulosa, 112, 309, 324, 329

— ochotensis, 776, 796

— viridis, 309, 329
Idunella mulleri, 203, 348
Idyaea brevicornis, 595
Ilea fascia, 765
Insecta, 205

Iridea, 767
Ischyroceros, 777

— anguipes, 110, 196

Isopoda, 110, 196, 259, 266, 306, 348, 402,
406, 407, 433, 496, 580, 609

Jaera albifrons, 311
Janiropsis kincaldi, 777
Jasmineira pacifica, 773

— schaudini, 246

Kamptozoa, 433

Katamysis warpachowskyi, 457, 566

Keratella aculeata, 297

— cochlearis, 297, 492, 493

— eichwaldi, 347

— quadrata, 492, 493, 498
Kinorhyncha, 433
Knipowitschia, 434

— longicaudata, 635, 636
Koinocystis twaesmiuneusis, 347
Kolga nana, 738

Koroga megalops, 725, 728
Krampolinum galatheae, 716
Krohnia hamata, 194

Labidocera brunescens, 488
Labrax, 461

916

INDEX OF LATIN NAMES

Labridae, 435, 461

Laccobium decorus, 347

Lacuna divaricata, 133, 209, 770, 773

— pallida, 112

— vincta, 796
Lagis, 441

Lamellibranchiata, 39, 110, 131, 133, 143,
156, 259, 267, 306, 433, 496, 502, 567,
568, 595, 601, 609, 661

Lamellidoris billamellata, 112

— muricata, 112

Lamellisabella sachsi, 713, 716, 798, 809,

810, 811
Laminaria, 52, 72

— agardhii, 240, 797

— bongardiana, 267

— bullata, 770, 771, 747

— dentigera, 709, 765

— digitata, 106, 109, 196, 208, 797

— flexicaelis, 301

— japonica, 765, 771

— longipes, 709

— nigripes, 240

— saccharina, 106, 109, 196, 208, 267, 300,

771, 797

— solidungula, 240

— thallus, 772
Lampanyctus leucopsarus, 735

— nannochir, 735

laticauda, 735

Lampetra japonica, 198
Langsdorfii, 765
Laomedea loveni, 329
Laonice annenkovae, 243
Laophonte mohammedi, 348
Laperansi, 771

Laphania boecki, 246
Laphoea fruticosa, 126

— gracillima, 126

— grandis, 126
Laras crassirostris, 744
Laternula kamakurana, 770
Laurencia, 768

— obtusa, 428

— paniculata, 607
Laxolina maxima, 773
Leaena abranchiata, 128
Leander, 574

— adspersus, 310, 329, 671
var. fabricii, 308

— longirostris, 312

— squilla, 439, 567, 574, 570, 671
Leathesia difformis, 765, 768
Lebidoplax variabilis, 771

Leda, 166, 308, 355, 773, 798, 805, 814,
815

— minuta, 815, 816

— pernula, 127, 134, 140, 154, 209, 211-13,

241, 816, 837, 838
Lembos arcticus, 244, 773
Leodice norvegica, 126
Leoniza areolata, 811
Lepidopecreum lumbo, 135
Lepidopsetta bilineata, 817, 839
Lepralia, 441

— pallasiana, 442
Leprotintinnus botnicus 347, 488

— pellucides, 488
Leptasterias, 68

— polaris, 833, 836
Leptocheirus pilosus, 330, 347
Leptocylindrus danicus, 402, 432, 483, 485,

790
Leptodora kindti, 293, 493
Leptostraca, 433
Leptychaster, 146

— anomalus, 775

— arcticus, 147, 157
Lessonia laminarioides, 797
Leucon spinulosus, 61, 246
Leucosolenia, 126

— blanca, 1 26

— coriacea, 126

— nanseni, 126

Leuroglossus stibius schmidti, 735
Lichenopora verrucaria, 209
Ligia cinerescenes, 710, 768
Ligula, 611

Lima hyperborea, 242
Limacina, 98, 294

— halicina, 38

— retroversa, 38, 294

Limanda aspera, 742, 780, 871, 817, 839

— limanda, 742

— punctatissima, 780, 817

— punctatissima proboscidea, 780
Limapontia capitata, 112, 117, 308, 311
Limnaea, 291, 325, 342, 364

— ovata, 614

var. baltica, 312, 344

— palustris, 344

— peregra, 312, 329

— stagnalis, 344

— var. littoralis, 312
Limnaeidae, 357
Limnaria saccharina, 301
Limnocalanus, 55, 603

— grimaldii, 45, 238, 242, 258, 259, 294,

295, 297, 308, 334, 335, 339, 341, 579,
600, 602, 604

— macrurus, 335, 341
Limnocardium, 357
Limnomysis benedeni, 457, 566
Lindia tecusa, 347

Lineus, 112

— gesserensis, 67, 112, 114, 209

— lacteus, 439
Liocarcinus holsatus, 427
Liocyma fluctuosa, 813
Liparidae, 253, 260, 269
Liparis coefoedi, 249

— liparis, 309

— major, 170, 171, 200, 213
Lithogliphus naticoides, 456
Lithothamnion, 131, 209, 448
Littorina, littorea, 112, 114, 203-7, 341,

343

— neritoides, 439

— palliata, 112, 113, 133, 205-7

— rudis, 111, 112, 119-22, 133,201-7, 343

INDEX OF LATIN NAMES

917

Littorinae, 122

— aqualida, 768

— littores, 794

— rudis, 794

— sitchana, 768, 794, 799
subtenebrosa, 776

— squalida, 776, 794, 799
Lophophelia prolifera, 145
Lophinus, 461

Lora navaga-zemlenses, 243
Loripes, 355, 441, 534

— lacteus, 480
Lota, 55

— lota, 312

Lotella maximowiczi, 734

— phycis, 734
Loxoconcha gauthieri, 348
Lubomirskiidae, 582
Lucernaria quadricornis, 128, 209
Lucernosa sainthilairei, 198, 211
Lucina, 355, 351

Lucioperca lucioperca, 669, 671

— marina, 458
Luidiaster tuberculatus, 773
Lumbriconereis, 166, 268, 774

— fragilis, 146, 148, 151, 216

— japonica, 772

— impatiens, 814, 836
Lumpenus, 309

— medius, 170
Lycenchelys, 135
Lycodes, 135

Lycodes agnostus, 171, 177, 200

— maris albi, 198

— pallidus, 170

— seminudus, 171, 177
Lygia, 177, 448

— brandti, 439
Lymimaea peregra, 293
Lyngbya aestuarii, 659
Lyonsia aeronsa, 153

— schimkewitschi, 198
Lysatrosome anthostieta, 7 1 1
Lysippe labiata, 267, 773

Macoma, 118, 122, 129, 166, 295, 310, 318,
325 328 349

— baltica, 115, 118-22, 206, 210-14, 242,

293, 307, 308, 309, 314, 315-26, 327-
332, 334, 776, 797

— calcarea, 127, 129, 141, 146-58, 210-16,

242, 248, 267, 307, 314-17, 319, 332-9

— loveni, 816

— moesta, 242, 248, 813, 814, 816

— middendorfi, 816

— torelli, 813, 814, 816
Macropsis slabbed, 480, 492, 493, 522
Macrostomum hystrix, 347
Mactra, 127, 129,804

— elliptica, 141^1, 153-5, 178

— sachalimensis, 771, 782

— subtrancata, 441, 450, 451

— sulcatoria, 771
Madreporaria, 293
Magelona longicornis, 771, 772

— pacifica, 815
Malacostraca, 371
Maldane, 128

— sarsi, 128, 129, 140, 146-8, 151, 154,

169, 211-16, 248, 748, 771, 772, 773,

774, 815,836
Maldanidae, 211,774
Mallotus villosus, 166
Mammalia, 196, 433
Manayunkia, 371

— caspia, 454, 479, 562, 565, 573

— aestuarina, 347

— polaris, 117, 120
Marenzelleria wireni, 243
Margarita, 166

— groenlandica, 128, 134, 210

— helicina, 134, 205, 209, 773, 796
Marsenina macrocephala, 127
Mastigocerca, 294
Maurolicus japonicus, 734
Medusa, 297

Megaptera nodosa, 703
Meganyctiphanes, 97, 98
Melaenis loveni, 200, 267
Melamphaeus nycterinus, 735
Melania, 267, 300
Melanopsidae, 357
Melanopsis, 360, 581
Melinna adriatica, 451

— palmata, 435, 445, 446, 449, 514
Melinnexis arctica, 246, 247
Melita formosa, 244

— palmata, 347
Melonna palmata, 441
Melosira, 296, 659

— arctica, 297

— borreri, 657

— granulata, 257

— hyperborea, 300

— islandica, 257, 300

— italica, 257
Melostra arctica, 298
Membranipora, 116, 439, 441

— crustulenta, 329, 347, 574

— flustra, 834

— pilosa, 204, 365

var. membranacea, 305

Menigrates obtusifrons, 135
Menipea ternata var. gracilis, 126, 127
Meretrix, 440

— rudis, 442, 444, 450, 451
Merismopedia tenuissima, 588

— glauca, 657

Mesidothea, 55-7, 58, 59, 209, 212, 242,
249, 260, 325, 349, 560

— entomon, 58, 59, 21 5, 242, 260, 308, 315,
321, 323, 327, 334-40, 566, 579, 612

glacialis, 59

vetterensis, 59

— megalura, 59

— sabini, 58, 59, 242-9, 260, 268
robusta, 58, 59, 242

— sibirica, 58, 59, 242-9, 260, 268
Mesochra lilljeborgi, 348

— rapiens, 348

918

INDEX OF LATIN NAMES

Mesocyclops hyalinus, 658

— leuckarti, 658
Mesodinium rubrum, 297, 298
Mesogobius catrachocephalus, 459

— gymnotrachelus, 459

— nigronotatus, 628
Mesomysis, 367, 457

— helleri, 492

— intermedia, 575

— kowalewskyi, 370, 479, 493, 497, 575.

671, 492
Mesozoa, 433
Metamysis, 367

— inflata, 612

— strauchi, 93, 497, 614, 627
Meterythrops microphthalma, 775
Metridia, 93

— conga, 47-50, 193, 194, 196, 237, 265,

294, 729, 791

— lucens, 194, 756, 757, 761, 775

— odiotensis, 708, 729, 793

— pacifica, 702, 708, 729, 793, 831 , 833, 834
Metridium, 231,249

— dianthus, 128, 305
Metschnikovia, 565

— intermedia, 565

— tuberculata, 565
Microcalanus parvus, 237

— pusilus, 135

— pygmaeus, 708, 756, 757, 775, 791
Microcystis aeruginosa, 483-5, 659
Microdeutopus grillotalpa, 502-5
Micromelania, 356, 362, 367, 457

— caspia, 611

— dimidiata, 611, 613

— elegantula, 611, 613

— linota, 456, 457
Micromelaniidae, 582
Microsetella, 93

— atlantica, 193

— norvegica, 237

— rosea, 775
Microspira, 554

— aestuarii, 473
Microsporidia, 610
Modiola, 330, 355, 446

— adriatica, 442, 444, 446, 450, 451

— barbata, 141, 145

— modiolus, 128, 132, 133, 142, 143, 144,

153-5, 169, 710, 748, 772

— phaseolina, 437-51

— volhinica var. minor, 357
Modiolus modiolus, 813
Modiolaria nigra, 211, 315, 339

var. bullata, 21 1

Moerisia, 562, 565

Mohnia mohnii, 246

Moina microphthalma, 658

Molgula euprocta, 450, 451

Mollusca, 47, 239, 241, 259, 260, 265, 266,

348, 488, 533, 616, 623, 669, 670
Molpadia, 140, 148, 150
Monoculodes minutus, 242
Monodacna, 357, 358, 360-2, 367, 370,

456, 457, 497, 499, 512, 515, 517

— caspia, 568, 614

— colorata, 371, 454, 479, 620, 623, 635
Monosiphon caspius, 607
Monostroma, 52, 106, 111, 117, 501

— fuscum, 407

— grevillei, 794

— groenlandica, 794
Montacuta, 772
Motella, 461
Mougeotia, 657
Mugil,461,574, 578, 668

— auratus, 377, 521, 535, 569, 574, 576, 671

— cephalus, 314, 521, 535, 576

— saliens, 377, 569, 574, 576, 671
Mugilidae, 435, 628

Mullus, 441, 461
Munida rugosa, 38
Munidopsis antonii, 738

— beringana, 810, 811
Munnopsis typica, 128, 242
Murex, 355

Musculus corrugatus, 814, 816

— discus, 835

— substriatus, 816
Mya, 292, 309

— arenaria, 118, 205-7, 214, 219, 307, 308,

309,770,782,796,813

— truncata, 118, 127, 149, 308, 211, 317,

319, 344, 813,816
Myelophucus intestinalis, 767
Myocephalus, 55

— quadricornis, 171, 260, 334, 337, 340,

349
Myriochele, 161

— heeri, 211, 216, 813

— oculata, 129, 140, 146, 147, 148, 151,

210,211,773,814
Myriophyllum spicatum, 303, 312
Myriotrochus, 835

— mitzuenzi, 771

— rincki, 127, 131, 149, 218, 242, 267
Myriozoum, 834

Mysidacea, 44, 217, 218, 266, 309, 432,

497, 522, 580, 609, 669
Mysis, 55, 340, 349, 566

— amblyops, 573, 600, 602, 612

— caspia, 579, 612

— flexuosa, 309

— microphthalma, 579, 600, 602, 612

— mixta, 297, 333, 334

— oculata, 55, 210, 242, 260, 295, 297
typica, 210

var. relicta, 55, 242, 566

— relicta, 340, 341

— vulgaris, 309

Mytilaster, 446, 479, 497, 499, 501, 512-17,
534, 574, 575, 576, 578, 618, 620, 621,
623

— lineatus, 502-5, 534, 568, 574, 575, 576,

612,613,616,620,623,627
Mytilus, 206, 309, 319, 330, 374, 380, 512

— edulis, 39, 110, 111, 112, 114, 119, 133,

134, 149, 206-9, 244, 307, 308, 311,
317, 319, 323, 327, 328, 349, 374, 435,
710, 796, 816

INDEX OF LATIN NAMES

919

Mytilus, galloprovincialis, 439^4, 449-51

455, 505
var. frequens, 445

— giganteus, 771

— grayanus, 782
Myxicola steenstrupi, 128
Myxilla brunnea, 128
Myxosporidia, 610

Nais elinguis, 663
Najas marina, 303, 312, 349, 607
Nannoniscoides ungulatus, 246
Nannopus palustris, 595
Nassa, 355

— reticulata, 439, 441, 442

— meritea, 444
Natica, 166, 355,451,514

— clausa, 205, 709, 773, 836
Navicula, 257

— cylindricus, 296

— frigida, 296

— uranii, 296
Necina olriki, 839
Nectocrangon dentata, 773, 774

— crassa, 835

— laz, 835

Nemacystus, decipiens, 765
Nemalion helmintoides, 767
Nematoda, 110, 120, 202, 206, 241, 330,

433, 610, 661, 662,666
Nematurella, 573
Nemertini, 110, 116, 196, 213, 330, 433,

610, 661, 662, 666
Neogobius, 628

— cephalarges, 459

— fluviatilis, 459

— kessleri, 459

— melanostomus, 459

— pla.tyrostris, 459

— rata, 459

— syrman, 459
Neomysis vulgaris, 326
Nephthys, 16, 513-17

— ciliata, 115, 126, 127, 129, 144, 267, 814

— cirrosa, 146, 305, 315, 318, 446

— coeca, 145, 311, 315, 814, 816

— hombergii, 435, 499, 502, 503, 507, 508,

514, 534

— longisetosa, 773, 796

— malmgreni, 242, 243, 248, 773

— minuta, 210
Neptunea curta, 210

— despecta, 133, 178

typica, 133

var. borealis, 133

Nereidae, 128

Nereis, 126, 207, 439-41, 455, 456, 479,
497, 499, 512, 515, 517, 534, 574, 578,
618, 619, 620, 621, 623-6, 627, 628,
638

— cultrifera, 435, 441, 500

— diversicolor, 311, 315, 318-23, 329, 332,

435, 441, 480, 499-503, 534, 570, 574,
625, 626

— pelagica, 126, 127, 209, 305, 625

— succinea, 435, 499-508, 625

— vexillosa, 776

— virens, 37, 198, 625

— zonata, 242, 534
Nerine, 439, 444

— cirratus, 437
Nerinides cantabra, 437
Nereocystis luetkeane, 834
Neritella, 525

— fluviatilis, 349
Neritina, 356, 362

— fluviatilis, 311, 329
Nerophis ophidion, 309
Nicippe tumida, 774
Nicolea zostericola, 129
Nicomache, 836

— lumbricalis, 128, 148, 151
Niphargoides caspius, 614

— compressus, 614

— corpulentus, 614

— grimmi, 612
Nitocra incerta, 595

— lacustris, 348

— spinipes, 348
Nitzschia, 662

— delicatissima, 135

— longissima, 296

— sturionis, 611, 662
Noctiluca miliaris, 403
Nodularia harveyana, 588

— spumigera, 294, 297, 483, 485, 588
Nonion depressulum, 572
Notholca bipalium, 347

— longispina, 312

— striata, 295, 347
Notoproctus oculatus, 774
Nucella lapillus, 794

— tenuis, 816
Nucula, 166, 798, 805

— nucleus, 308

— tenuis, 771, 772, 813, 814, 836, 837

— tenuis biocoenosis, 835
Nychia cirrosa, 127
Nymphon procerum, 738

— robustun, 242

— sluiteri, 242

— spinosus, 242
var. hirtipes, 242

— stroemii gracillipes, 242

— stromi, 126

Obelia geniculata, 304

— longissima, 112
Ochridospongia, 565
Ochtelius marinus, 347
Octocorallia, 297
Octopus dofleini, 782

— gilbertianus, 782

— ochotensis, 811
Odonthalia, 209

— dentata, 106, 109. 240. 797

— ochotensis, 797
Oediceros minor, 242
Oikopleura, 93, 238

— dioica, 295, 403-9

920

INDEX OF LATIN NAMES

Oikopleura labradoriensis, 94, 237

— vanhoffeni, 94, 237, 265
Oithona, 93, 98, 294

— atlantica, 135,237,238

— brevicornis, 758

— nana, 294, 295, 403-9, 488

— plumifera, 135, 194, 758
var. atlantica, 237

— similis, 93, 193, 237, 294, 295, 403-9,

756,757, 758, 761, 791, 833
Oligochaeta, 66, 116, 118, 120, 196, 202-7,

455, 497, 515, 609, 614, 618-20, 628,

661,662, 666
Oligobrachia dogieli, 716, 717

— ivanovi, 716
Olivella falgurata, 774
Ommastrephes sloanei pacificus, 782
Omphalophyllum ulvaceum, 246
Oncaea borealis, 756, 775, 793, 829
Onchidiopsis glacialis, 126
Oncorhynchus gorvusha, 738, 817, 839

— keta, 738, 817, 839

— kisutch, 817, 839

— merka, 817, 839

— tschawytscha, 839
Onisimus, 53, 59

— affinis, 59

— botkini, 59, 260

— brevicaudatus, 59

— caricus, 59

— derjugini, 59

— dubius, 59

— edwardsi, 59

— normanni, 59

— plautus, 59

— sextoni, 59

— sibiricus, 59

— turgidus, 59
Onoscimbrius, 314
Onuphis 128, 166,814

— conchylega, 127, 129, 140, 144, 154,
248

— parvastriata, 836
Oocystis socialis, 587, 657
Oothrix bidentata, 193
Ophelia Hmacina, 126, 149, 209

— bicornia, 437

Ophiacantha bidentata, 126, 127, 140, 144,
146, 150, 209-11, 212, 213, 773, 774,
813

Ophidion, 461

Ophiocten sericeum, 134, 140, 154, 168,
242,248,250,251,267,268

Ophiopholis, 138

— aculeata, 126-9, 132, 140, 143, 148-55,

168, 170, 197, 210, 243, 247, 773, 812,

813, 835, 710
Ophiopenia tetracantha, 774
Ophiopleura borealis, 140, 150, 155, 157,

242, 246, 248, 250, 261
Ophiopus arcticus, 246
Ophiura albida, 309, 315

— leptoctenia, 713, 805, 838

— maculata, 815

— nodosa, 149

— robusta, 140, 168, 212, 749

— sarsi, 126, 127, 128, 129, 134, 140, 146,

147, 148, 151, 157, 168, 170, 267, 771,
772, 774, 805, 809, 810, 812, 813, 814,
815, 835, 836, 837, 838

vadicola, 771, 772, 773, 748

Opisthobranchia, 306

Orchestia, 770

— gamarellus, 439

— montagui, 439

— ochotensis, 768
Orchomene tschernyschevi, 133
Orchomenella nana, 244
Orientalis, 702
Oscillatoria tenuis, 659
Osmeridae, 55, 57, 260, 269
Osmerus eperlanus, 340
dentex, 817, 839

— spenlanus dentex, 638

Ostracoda, 44, 49, 120, 196, 234, 330, 347,
348, 433, 496-503, 512, 515, 517, 534,
535, 609, 661, 663, 667, 669, 670

Ostrea, 208, 356

— gigas, 711, 782

— sublamellosa, 442

— taurica, 442, 444
Ostroumovia, 367

— maeotica, 479

Owenia assimilis, 140, 147, 149

— fusiformis, 248

Pachygrapsus, 437

— marmoratus, 439, 443
Pachycheles stevensii, 711
Pagurus middendorffii, 749

— pubescens, 813, 814
Palaemonetes varians, 347
Pallasea, 55

— quadrispinosa, 308, 326, 334, 340
Paludestrina jenkinsi, 308
Paludina, 362

— contecta, 312
Paludinidae, 358

Pandalus borealis, 126, 147, 161, 168, 170,
243, 268, 749

— latirostris, 711, 744, 770, 782
Pandora glacialis, 133, 134, 153
Pandorites platycheir, 612, 637

— podoceroides, 371, 612
Pantopoda, 110, 196, 241, 259, 266, 433,

610
Paracalanus, 98

— alberti, 725

— parvus, 294, 403-9, 703, 758, 756
Paracalissoma alberti, 728
Paracartia latisetosa, 488
Parafavella, 236, 294, 295
Paralibrotus, setosus, 246
Paralithodes brevipes, 743, 799, 817

— camtschatica, 742, 817

— platypus, 743, 817
Paramphitoe polyacantha, 244
Paramysis, 367

— baeri, 627, 671

— banquensis, 627

INDEX OF LATIN NAMES

921

Paramysis kroyeri, 444

— loxolepis, 300, 566
Paranais simplex, 663
Parandania boecki, 725, 728
Parathemisto japonica, 757, 775, 829

— libellula, 829, 833

— olivii, 237
Parathemiato, 708
Pardalisca abyssii, 246
Pareuchaeta glacialis, 45-8

— japonica, 702, 708, 775, 791, 793
Pareugyzoides japonica, 771, 772
Parhyale zibellina, 777
Parhypania, 367, 565
Paroctopus conispadiceus, 782
Paroediceros intermedins, 200, 242, 243
Patella, 374, 437, 448, 768

— pontica, 439
Patiria pectinifera, 768
Pavonaria finmarchica, 710, 806, 81 1
Pecten, 140, 231, 249, 308, 355

— jessoensis, 711, 782

— auratus, 141

— groenlandicus, 67, 127, 134, 168, 241,

242, 448

— imbrifer, 148, 241

— randolfi, 773

— swiftii, 711, 772

— imbrifer, 148, 241

Pecten islandicus, 127, 128-9, 132, 142,
143, 144, 153, 169, 170,243

— ponticus, 442, 444, 45 1
Pectinaria, 128, 497, 512, 514, 534

— granulata, 796

— hyperborea, 127, 128, 140, 149,211-16,

242, 248, 315

— koreni, 210

— neopolitana, 509, 514
Pectunculus, 355
Pedalia fennica, 347
Pedalion oxyuris, 488, 492
Pedicillaster orientalis, 774
Pelamys, 461

— sarda, 425
Pelecus, 669

— cultratus, 519, 632, 669, 670
Pelicanus thagus, 744
Pelmatohydra oligactis, 329, 347
Pelonaia corrugata, 149, 153, 772, 773, 817
Pelvetia, 106

— canaliculata, 204, 748

— babingtonii, 767

— galapagensis, 748

— typica, 748

— wrightii, 748, 765, 766, 767
Pemnodon saltator, 460
Penilia schmackeri, 671
Penilla avirostris, 403

Perca fluviatilis, 312, 670, 671, 349
Percarina, 519, 521

— maeotica, 518
Percidae, 435. 518, 628

Peridineae, 193, 232, 257, 401, 402, 416,

586
Peridinium, 763

— achromaticum, 291, 657

— breve, 258

— conicum, 193

— depressum, 294, 828

— exentricum, 829

— granii, 828

— knipowitschi, 485

— ovatum, 91, 828

— pallidum, 91, 828

— pellucidum, 258

— polaris, 828

— thorianum, 828

— triquetrum, 414

Perigonimus yoldiae-arcticae, 243, 294
Periploma abyssorum, 246
Petricola lithophaga, 439, 449

— pholadiformis, 312
Petromyzonidae, 253, 628
Phakellia, 833

— bowerbankii, 127
Phaeocystis, 41, 93, 172
Phalacrocorax bougainvillei, 744

— filamentosus, 744

— pelagiens, 744
Phallusia obliqua, 126

— prunum, 126
Phaeophyceae, 196, 301, 346
Phanerogamae, 347, 660
Phascolion strombi, 127, 129, 426
— - lutense, 738
Phascolosoma, 128

— eremita, 126, 127

— margaritaceum, 126, 128, 129, 148, 749

— minuta, 249
Philine, 127

— japonica, 771, 772
Phoca caspia, 339, 344, 579

— foetida, 334, 342

— groenlandica, 339, 344

— hispida, 219, 334, 344

— — ochotensis, 742

— vitulina, 343, 344
Phocaena, 461

— phocaena, 466

— relicta, 438

■ — sardinella, 461

— sargus, 461

— scomber, 461

— scorpaena, 461

— serranus, 461

— solea, 461

— spratella, 461
Pholas crispata, 710
Pholedidea penita, 710
Pholis gunnellus, 112, 204, 311
Pholoe minuta, 209, 309
Phragmites communis, 303, 312
Phryganeidae, 664, 669, 670
Phycodrya simosa, 797

— fimbriata, 797
Phyllaria dermatodea, 246
Phyllodoce maculata, 112, 115, 209
Phyllophora, 209, 210, 429, 430, 435, 438

— brodiaei, 106, 109, 240, 301

— interrupta, 240

922

INDEX OF LATIN NAMES

Phyllophora rubens, 431

var. nervosa, 428, 429

Phyllophorus pellucidus, 128

Phyllopoda, 609

Phyllospadix scouleri, 767, 770

Physa fontinalis, 312

Physiculus japonicus, 734

Pilajella, 196

Pilema pulmo, 403, 420, 437

Pisces, 39, 110, 196,241,259,266,406,433,

461
Pista cristata, 141

— maculata, 248, 249

— vinogradovi, 710
Placorhynchus tvaerminnensis, 346
Placostegus, 145

— tridentatus, 125, 141, 144
Planaria lacustria, 330
Planktoniella sol, 706
Plantago maritima, 201
Planuralia arctica, 135

Platessa quadrituberculata, 780, 817, 839
Plathelminthes, 433
Plectacantha oikiskos, 238
Pleurobrachia pileus, 295, 297, 298, 403-9,

421
Pleuronectes flesus, 169, 309, 311, 461, 536

— platessa, 159

— stellatus, 780, 817
Pleurogrammus azonus, 816

— monopterygius, 839
Pleuromamma scutulata, 794, 831
Pleuronectidae, 253, 260, 269, 349, 518, 628
Pleurosigma, 659

Pleurotoma, 355
Pleustes panopleus, 243
Plicifusus olivaceus, 774
Plumaella longispina, 807
Pocciliidae, 628
Podon, 93, 98, 295

— leuckarti, 237, 264, 829

— polyphemoides, 298, 403-7, 488, 492
Pododesmus macroshima, 814
Poliometra prolixa, 242, 247
Polyacanthonotus challengeri, 735
Polyartha trigla, 295, 493
Polybranchia gorbunovi, 716
Polybrachia capillaris, 716
Polycellismigrea, 330

Polycharta, 39,49, 110, 118, 131, 133, 143,
156, 167, 169, 193, 196, 213, 239, 241,
251, 259, 265, 266, 291, 306, 347, 433,
496, 570, 608, 609, 610

Polycirrus albicans, 128

— medusa, 773
Polidora coeca, 772

— quadrilobata, 117, 260

— redekei, 347
Polygordius ponticus, 441
Polymastia, 249

— puberrima, 126
Polymnia trigonostoma, 710
Polynoe cirrata, 323
Polyphemidae, 515
Polvphemus, 595

Polypodium hydriforme, 565, 581, 662, 663
Polysiphonia, 210, 797

— arctica, 240

— elongata, 428, 431, 607

— nigrescens, 301

— opaca, 428, 495

— sertularioides, 607, 608

— spinosa, 494

— subulifera, 427, 432

— urceolata, 301

— variegata, 428, 495, 574

— violacea, 301, 607, 660
Pomatoneus, 461
Pomatoschistus, 629, 633

— caucasicus, 569, 574, 629, 631, 635, 671
Pontaster, 242, 248

Pontella mediterranea, 403
Pontogammarus, 367, 497, 500, 512, 566,
612, 613, 669

— abbreviatus, 497

— aralensis, 658, 663, 666, 669
crsssus 364 449

— maeoticus, 371, 437, 444, 455, 456, 457,

479, 500,613,627

— obesus, 367

— robustoides, 479

— weidemanni, 479
Pontogenea, 777
Pontophilus norvegicus, 128
Pontoporeia, 55, 308, 324, 328, 566

— affinis, 59, 242, 308, 317, 318-24, 327-

336, 340, 579, 612
var. microphthalma, 579

— femorata, 59, 308, 315-32, 334, 336

— sinuata, 59, 308

— weltneri, 59
Poraniomorpha tumida, 213
Porcellana, 367

Porella, 126

Porifera, 144, 241, 259, 266, 330, 367, 562

Poromya granulata, 135

Porphyra, 301

Portlandia ( = Joldia), 165, 243

arctica, 67, 140, 149, 179, 200, 209-

216, 241, 242, 243, 248, 250, 266, 268

aestuariorum, 243, 250

fraterna, 241, 242, 269

frigida, 242

intermedia, 127, 129, 140, 241

lenticula, 129, 241, 269

siliqua, 260

Portoeirema fluviatile, 346
Portunus arcuatus, 427, 442

— holsatus, 441

— marmoreus, 442
Potamides aterrina, 711
Potamilla neglecta, 135, 142

— reniformis, 835

— symbiotica, 798, 807, 809, 810, 811
Potamogeton, 312

— filiformis, 303

— marinus, 495

— panormitonus, 312

— pectinatus, 303, 607

— perfoliatus, 303

INDEX OF LATIN NAMES

923

Potamogeton vaginatus, 303
Potamopygus jenkinisi, 312
Pourtalesia jeffreysii, 246
Praunus inermis, 295, 330

— flexuosus, 295, 298, 329, 330
Praxillella gracilis, 813, 836

— praetermissa, 147, 813, 814
Priapuloidea, 196
Priapulus, 266

— caudatus, 112, 115, 117, 119,121,206-9,

305, 311, 317, 318, 332, 339, 799
Primnoa macrope, 775, 829

— resedaeformis, 806

pacifica, 773

Prionospio steenstrupi, 772
Proales similis, 347
Procerodes lobata, 439

— ulvae, 347
Promesostoma baltica, 347

— cochlearis, 347
— lugubra, 347
Prometor lenthophila, 717
Propeamusium ( = Pecten) groenlandicum

major, see Pecten

— randolphi, 775

Prorocentrum micans, 294, 402, 414, 587
var. scutellum, 586

— obtusum, 657

— subsalum, 657
Prosobranchia, 306
Prosodacna, 357
Prostoma obscurum, 347
Proterocentrum micans, 483, 485, 660
Proterorhinus marmoratus, 364, 378, 459,

628
Protodrilus flavocapitatus, 439
Protohydra leucarti, 347
Protohyperiopsos aquata, 725
Protoschmidtia flava, 565
Protozoa, 1 10, 193, 264, 483, 487, 533, 594,

662
Protula media, 127, 142
Pseudalibrotus, 53

— birulai, 59, 242, 260, 566

— caspius, 59, 579, 612

— glacialis, 59

— litoralis, 59

— nanseni, 59, 135

— platyceras, 59, 579, 612
Pseudocalanus, 93, 297

— elongatus, 45, 70, 193, 237, 238, 258,

259, 294, 708, 756, 757-8, 761, 791,
793

— major, 238, 258, 259, 298, 308, 403-9,

420, 423
Pseudociphella spinifera, 794
Pseudocuma, 367, 566

— longicornis, 444
Pseudoflustra hincksi, 126
Pseudopleuronectes yokohamae, 780

— herzensteini, 781
Pseudopotamilla reniformis, 142, 144
Psilaster andromeda, 135

Psolus, 139

— phantapus, 148, 243, 247

Psychropotes raripes, 810, 811
Pteraster pulvillus, 127
Pterocuma, 499, 566, 612

— pectinata, 367, 479, 499, 575, 614, 627

— sowinskyi, 497, 614, 627
Pterodina, 110, 143

Pteropoda, 110, 193, 218, 234, 293, 433
Ptilota, 797

— pectinata, 241

— plumosa, 106, 109
Ptychogastria polaris, 135, 194
Puggetia quadridens, 711

Pungitius platygaster aralensis, 459, 669.

670, 671
Purpura lapillus, 112, 178, 204

— japonica, 711

Pycnogonum litorale, 126, 134, 135
Pygospio, 207

— elegans, 117, 118, 204, 305, 311, 318,

324
Pylaiella rupincola, 300
Pylajella, 73

— litoralis, 240, 301, 765
Pyrophacus horologicum, 198
Pyura arctica, 126, 128

— aurantium, 128, 132

Rachotropis natator, 725, 728
Racovitzanus antarcticus, 794, 829
Radiceps verrillii, 807, 810, 811
Radiolaria, 44, 234
Raja radiata, 170
Ralfsia, 768

— clavata, 765
Ranunculus, 312

— bandotii, 303

Rapana beroar (bervar), 435, 771
Rathkea octopunctata, 237, 264, 403
Rattulus, 296

— marinus, 658

Reinhardtius hippoglossoides matsurae,
780

— matsuurae, 839
Reptilia, 433
Retepora, 126

— cellulosa, 126

— elongata, 126
Retusa obtusa, 308
Rhabdammina, 146

— abyssorum, 147
Rhabdocoela, 441, 568
Rhachotropis aculeata, 128

— lomonosovi, 246, 247
Rhegaster tumidus, 128
Rhinocalanus nasutus, 194
Rhizoclonium riparium, 768
Rhizomolgula globularis, 200, 243
Rhizosolenia, 91, 135, 294, 295, 574, 578,

589, 590-603

— alata, 135

— berganii, 705

— calcar-avis, 402, 432, 483, 485, 574,

587-93

— faerocensis, 135

— fragilissima, 402

924

INDEX OF LATIN NAMES

Rhizosolenia hebetata, 790, 828

— radiatus, 483

— semispina, 91

— shrubsolsi, 135

— styliformis, 91, 135
Rhodimenia, 1 1 1

— palmata, 106, 1 10, 205, 240, 301
Rhodine gracilior, 129, 199, 710, 773, 814

— loveni, 315

Rhodomela larix, 767, 768, 796

— lycopodioides, 240

— subfusca, 301
Rhodophyceae, 346
Rhodophyllis, 210
Rhynchobolus, 441
Rhynchonella, 126

— psittacea, 126, 142, 153, 243
Rissoa, 157, 344, 439-41, 770

— aculeus, 112, 133, 206-8, 211

— euxinica, 509

— membranacea, 343

— tridactyla, 744

— venusta, 509
Rivularia atra, 768

Rithropanopeus harrisi tridentatus, 373
Rotalia, 572

— beccarii, 512

Rotatoria, 44, 147, 206, 234, 239, 258,

345-7, 402, 487-93, 496, 533, 601
Rotifera, 488, 492, 594, 597, 657-8
Rozinante fragilis, 135, 213
Ruceinum bryani, 775
Ruppia, 533, 535

— maritima, 303, 607

— spiralis, 303, 607
Rutilus frisii kutum, 632

— rutilus aralensis, 501, 629, 669, 670
caspius, 629, 632

Sabella fabricii, 128
Sabellides borealis, 149
Sabinea 7-carinata, 128, 161, 242
Saccocirrus, 437, 439

— papillocercus, 437, 439
Saccoglossus meresehkowskii, 796, 799
Saccorhiza viduata, 305

Sagitta, 213, 218, 423, 441, 791

— elegans, 98, 237, 238, 295, 297, 298, 314,

729, 765, 833

— euxina, 403-8

— macrocephala, 729

— planctonis, 729

— setosa, 403-8, 420
Salicornia herbacea, 201
Salmo salor, 349

— trutta, 459, 579, 630
caspius, 630

Salmonidae, 55, 253, 260, 269, 628, 632,

668
Salpae, 431

Salpingella acuminata, 237, 238
Salvelinus malma, 817, 839
Sarcobotrilloides aureum, 128
Sarcophyllis arctica, 240
Sardinops sagax, 748

melanostictus, 778, 782, 839

Sargassum, 430

— miyabei, 765, 767
Sarsia tabulosa, 403
Saxicava, 139

— arctica, 128, 132, 142, 143, 148, 216, 242

— rugosa, 308
Scalibregma inflatum, 773, 836

— robusta, 198, 267, 772, 813
Scalpellum strdmi, 135
Scaphander puncto-striatus, 135
Scaphocalanus magnus, 794
Scaphopoda, 1 10, 156, 293, 431, 433
Scelerocrangon selebrose, 782
Sceletonema, 93

— costatum, 296, 297, 657
Scenea planorbis, 117, 208
Schizaster fragilis, 38
Schizobranchus insignis, 709
Schizopera clandestina, 348

— tenera, 595

Schizopoda, 193, 294, 241, 259, 433
Schizorhynchus, 497, 566

— bilamellatus, 575, 614
Scina wagleri, 738
Scirpus maritimus, 303

— parvulus, 330, 347

— tahernaemontani, 303
Sclerocrangon, 231

— boreas, 128

— ferox, 249

Scolecithricella minor, 702, 708, 757, 774,
829

— ovata, 794
Scoloplos, 130

— armiger, 127, 129, 140, 153, 206, 210,

267, 293, 305, 315-18, 321, 332, 339,
772,773,774,796,799,815

— cuvieri, 339

Scomber scomber, 314, 327
Scrobicularia piperata, 344
Scyphomedusae, 258, 291
Scyphozoa, 110, 193, 306, 433
Scytosiphon lamentarius, 428, 432, 765
Sebastes marinus, 159
Sebastolobus macrochir, 817
Semicalanus cariosus, 709
Semisuberites arctica, 813
Serripes groenlandicus, 774, 780, 813, 817,
837, 838

— laperousi, 816
Sertularella polyzonias, 444
Sertularia, 1 12

— pumilla, 304
Siboglinum, 716

— atlanticus, 716

— bogorovi, 716

— buecelliferum, 716

— caulleryi, 716

— ermani, 716

— frenigerum, 716

— hyperboreum, 716

— inermis, 716

— microcephalum, 716

— pinnulatum, 716

INDEX OF LATIN NAMES

925

Siboglinum plumosum, 716, 717

— robustum, 716

— tenuis, 716

— tueniapherum, 716

— variabilis, 716

— vinculatum, 716

— weberi, 716
Sididae, 595

Silicoflagellata, 193, 401 , 41 5, 41 7, 483, 485
Siliqua media, 816
Siluridae, 628, 668
Siluris glanis, 632, 671
Sinacalanus tenellus, 791
Siphonophora, 134, 431
Siphonostoma typhle, 309
Sipunculoidea, 167, 251, 266, 306
Skeletonema costatum, 402, 414, 416, 483,

485
Smittiia venuscula, 126
Socarnes bidenticulatus, 133, 135

— vahlii, 127
Solariella, 127

— obscura, 771
— varicosa, 771

Solaster endeca, 127, 244
Solen marginatus, 448
Somniosus microcephalus, 159
Sosane gracilior, 772
Spadella, 441
Spantangus raschi, 141
Sparidae, 435

Spermatchnus paradoxus, 301
Sphacelaria, 112

— racemosa, 301
Sphaeroma, 439, 497, 512

— rugicaudum, 348

— serratum, 348, 438
Sphaeronii hookeri, 347
Spinachia spinachia, 309
Spio filicornis, 444

— ornatus, 439
Spiochaetopterus, 129

— typicus, 129, 140, 146, 147-8, 151, 157,

250,437, 749,774, 801, 803
Spionidae, 437
Spirogyra, 657
Spirontocaris, 835

— biunguis, 773

— ochotensis mororani, 71 1

— spina, 128, 243

— turgida, 243
Spirorbis, 112

— borealis, 112,209
Spisula alascana, 816
Spongella elegans, 442

— porifera, 110, 126, 128, 133, 143, 146,

147, 153, 196, 313, 433, 439, 453, 496,

565, 570, 608, 610
Spongomorpha, 1 1 1
Spratella sprattus phalerica, 427, 633
Sprattus, 466

— baltica, 349

— phalericus, 460
Squalis acanthias, 817
Staurocephalus japonica, 710

Staurophora, 102
Stegocephalopsis ampulla, 135

— inflatus, 127, 242
Stegophiura brachiactis, 771, 772

— nodosa, 135, 140, 771, 772, 773
Stenelais, 154

Stenocuma diastyloides, 566, 612

— tenuicauda, 497
Stenodus, 579

— leucichthys, 253, 579, 580, 629, 630, 632
Stenogammarus, 566

— similis, 614, 627
Sternaspis scutata, 813
Sticholonche zanclea, 238
Stictyosiphon tortilis, 108, 303, 767
Streblospio shrubsoli, 347
Strongylocentrotus, 126-30, 139, 149, 835

— droebachiensis, 126, 127, 131, 132, 140,

143, 151, 154, 170, 243, 247, 749, 813
Stryphnus fortis, 126
Stschaporia flagellaris, 765
Stychopus japonicus, 744, 772, 782
Stylaria lacustris, 330
Stylarioides hirsuta, 247

— plumosa, 813
Stylasteridae, eximius, 805

— norvegicus, 805

— pacifica, 805

— scabiosa, 805

— solidus, 805
Stylophora tuberculata, 301
Suberites domuncula, 446, 449
Sula nebouxii, 744

Syllis armiHaris, 126, 133, 305

— fabricii, 126
Sympodium, 446
Synalactes nozamai, 774
Synapta, digitata, 441

— hispida, 441
Synchaeta, 238, 294, 493, 594

— baltica, 295, 297, 298, 492

— fennica, 295, 298

— littoralis, 295, 347

— monopus, 295, 297, 347

— neapolitana, 595, 658

— tavina, 347

— vorax, 595, 658

Syndesmya, 308, 355, 441-6, 449, 450, 45 1 ,
479, 495, 497, 499-509, 513-17, 533,
534,574,619

— alba, 315, 318,446

— ovata, 435, 456, 499-508, 509, 513, 543,

568, 570, 574, 577, 620, 627
Synedra pulchella, 346

— tabulata, 346
Syngnathidae,435, 628
Syngnathus, 633

— nigrolineatus caspius, 378, 569, 574, 629

— schmidti, 427, 461

— soldatovi, 771
Synidothea bicuspida, 244

— nodulosa, 133, 244
Syrrhoe cremulata, 772

Taera albifrons, 329

926

INDEX OF LATIN NAMES

Talorchestia deshayesi, 439
Tanaidacea, 241, 347
Tanypus, 499
Tapes, 355, 440, 444

— decussatus, 342

— lineatus, 450, 451

— proclivis, 441

— rugatus, 442

— stominae, 710
Tardigrada, 336

Tatjanellia grandis, 735, 738, 810
Tedania suctoria, 127
Tellina, 334

— fabula, 450, 451

— incongrua, 771

— lutea, 816

venulosa, 771

Telmessus cheragomus, 743, 796
Temora, 98

— longicornis, 93, 135, 194, 234, 295, 297,

298, 308
Tendipedidae, 455
Tenthorium, 131

— semisuberites, 126, 127
Teragra chalcogramma, 740
Terebellides, 319

— stromi, 118, 210, 242, 267, 305, 315, 317,

318, 319, 323, 332, 445, 446, 449, 450,
451, 774,813,835,836
Terebratulina, 127

— caput-serpentis, 126, 147

— coreanica, 773

— septentrionalis, 129, 142

— spitzbergensis, 126
Teredo navalis, 308, 435, 514
Tergipes, 441
Testudinella, 347

Tethya, 131

— lincurium, 126, 127
Tethyum aurantium, 833

— loveni, 162

Tetrastemma obscurum, 329
Tetronychia gigas, 725, 728
Thais lima, 776, 768, 796
Thalassionema nitzschiodes, 402, 416,483,

485
Thalassiophyllum elathrum, 709
Thalassiosira, 258, 294, 297, 298, 346, 704,

790, 829

— baltica, 258, 296, 587

— decipiens, 135, 651

— gravida, 264, 790, 826

— japonica, 829

— nana, 298, 414. 483

— nordenskjoldii, 704, 790, 829
Thallasiothrix longissima, 761, 790
Tharix pacifica, 774
Thaumatometra tenuis, 773
Thelepus, 139

— cincinnatus, 126, 127, 131, 140, 143,

144, 153, 248
Themisto, 65, 97

— abyssorum, 45, 238, 758

— libellula, 791, 817
Thenea muricata, 146

Theodoxus, 367, 457, 581

— danubialis, 364, 455

— fluviatilis, 312, 329

— pallasi, 364, 479, 567, 613, 614

— schultzi, 567, 612, 615

Theragra chalcogramma, 779, 782, 817
Throphonopsis, 437
Thuiaria lonchitis, 126
Thyasira flexuosa, 774

— gouldi, 813
Thymallus thymallus, 312
Thynnus thynnus, 427
Thysanoessa, 98, 170

— inermis, 96, 98, 104, 171, 759, 765, 775

— longicauda, 238

— longipes, 704, 759, 775

— raschii, 171, 758, 759, 765, 780
Tiara conifera, 194
Tichocarpus crinitus, 766, 796
Tintinnoidea, 43, 236, 258, 402, 403, 488,

491, 594
Tintinnopsis, 294, 594

— campanula, 294, 403

— meunier, 488

— minuta, 488

— nucula, 427

— parvula, 487
relictfl 488

— tubulosa, 297, 298, 347, 403-8, 488

— ventricoa, 403-8
Tintinnus mediterranea, 403-8

— mitra, 594

— subulatus, 403-8
Tmetonyx cicada, 773
Tolypella, 661, 664

— aralica, 661
Tomopteris, 446
Totanus derjugini, 791
Trachinus, 461
Trachurus, 461, 535

Travisia forbesii, 112, 118, 127, 149, 305,

773, 796, 816
Travista forbesi, 772
Trematoda, 662

— digenea, 610

— monogenea, 610
Triarthra brachiata, 295

— longiseta, 295, 492
Trichoptera, 330, 349, 661, 663
Trichoptropis conica, 142
Trichostemma haemisphaericum, 127
Triclada, 568

Trigea, 461

Triglochin maritimus, 201
Triglops pingeli, 170, 171
Triops laser, 135
Trochoderma elegans, 242
Trochostoma, 248

— arctica, 242

— boreale, 147
Trochus, 355, 439, 441

— occidentalis, 126
Trophonia breaviatus, 446
Trypanoplasma, 610
Trypanosoma, 610

INDEX OF LATIN NAMES

927

Tryphosa hoerringi, 244, 247
Tubifex albicola, 499

— tubifex, 329
Tubificidae, 512
Tubularia larynx, 126

Tunicata, 59, 110, 133, 143, 156, 167, 169,
196,234, 241,431,433,496

Turbellaria, 66, 110, 118, 196, 206, 259,
266, 336, 347, 439, 441, 496, 562, 565,
568, 609, 610, 612

Turbo sangarensis, 711, 768

Turitella, 355

— fortilirata, 771, 772

— reticulata, 154
Turnerella septentriolsi, 246
Tursiops, 461

Tylaster willei, 246
Tylos latrelei, 439

Ulva, 301,437, 440

— lactuca, 432
Ulvacea, 52
Umbellula, 231

— encrinus, 61, 246
Umbrina, 461
Unio, 291, 362, 364

— pictorum, 614

— tumidus, 455
Unionidae, 497, 509
Upogelia, 773
Uranoscopus, 441, 461, 497
Uria algae, 744

— lomvia, 158, 744
Urospora penicilliformis, 118
Urothoe denticulata, 774
Urticina felina, 305
Utricularia, 312

Valvata, 362
Vaucheria, 664, 670

— dichotoma, 660, 661
Velutina hallotoides, 127, 128

— lanigera, 127

— undata var. expansa, 127
Venerupia philippinarum, 711
Venerupis, 356
Venericardia borealis ovata, 816

— crassidens, 816
Venus, 144, 308, 355, 437

— fluctuosa, 135, 771, 772, 773

— gallina, 450,451,480

Vermes, 234, 440, 441, 488, 502, 533, 534,

619, 669
Verticordia nadina, 771, 772, 774
Victorella, 367

— pavida, 347
Virgularia glacialis, 246

— mirabilis, 135

Vitjaziana gurjanovoe, 725, 728
Viviparus viviparus, 455, 614
Volgocuma thelmatophora, 566, 614
Vultar sumatranum, 706

Waldheimia, 143, 146

— cranium, 126, 142, 144, 145

Xantho rivulosus, 147, 439

Yoldia, 165, 267, 308

— beringiana, 775

— hyperborea, 837

— johanni, 771, 772

— limatula, 797, 815, 835, 836

— myalis, 813, 815, 816

— thraciaeformis, 797, 813, 815, 837
Yoldia (Portlandia) arctica, 178, 342

— hyperborea, 127, 129, 134, 140, 148, 149,

153,209, 211
Yoldiella derjugini, 771, 772, 775, 813

— fraterna, 248

— frigida, 248

— lenticulla, 248

Zanardinia, 431

Zannichellia pendunculata, 312, 347

— repens, 312
Zoarces, 309, 326
Zoarcidae, 253

Zostera, 61, 249, 253, 266, 269, 429, 438,
440, 441, 495, 533, 535, 660, 661, 664,
665, 667

— marina, 95, 198, 204, 208, 303, 427, 429,

431,432,441,443,495, 770

— minor, 428, 431,441

— nana, 196, 303, 428, 495, 574, 607, 698,

660, 664, 667

— pacifica, 776
Zostericola ophiocephalus, 535

SUBJECT INDEX

Abramis callerus, 629, 632

Abyssal, 61, 65

acclimatization, 173, 373, 435, 500, 575.

577, 578, 625, 627, 643, 647, 662, 668,

671
accumulation: algae, 428, 608

— ammonia, 285, 394, 474, 475, 551

— bivalves, 446

— dead plants, 427, 439

— nitrates, 475

— nitrogen, 584

— phosphates, 475

— Phyllophora, 430, 445

— sea mussels, 445

— Zostera (eel grass), 429, 349, 608
Achuev inlet, 510

acid, carbonic, 390

— nitric, 398

— sulphuric, 398

actineans, 113, 128, 305, 651, 709, 722, 731

activity, feeding, 641

Aegean Sea — see sea

aeration of waters, 40, 88, 187, 188, 475

— bottom layers, 188

— water bodies, 471
Agrakhan Bay — see bay
air expeditions, 33
Akchagyl, 360, 361, 363
Akhtarsk inlet — see inlet
Aland Islands — see islands
Aland Sea — see sea
Alaska, 269, 618, 818
albatross, 744

Alboran coast, 607
Aleksandrovsk-on-Murman, 180
aleurites, 751, 753, 787, 820
Aleutian arc, 818

Algae, 52, 116, 239, 429-32, 677, 767, 768,
776, 799

— Alaria, 677

— blue-green, 294, 297, 372, 481, 482, 607

— bottom, 195, 607, 660-1

— brown, 52, 106, 108, 208, 239, 301, 302,

345,425,432,607,701,766

— calcareous, 124, 358

— charial, 607, 608, 661

— decaying, 649

— diatomous, 41, 91, 96, 194, 342, 414,

481, 586,587, 687

— filamentous, 114, 431, 649, 790

— flagellate, 41, 91, 232, 432, 495, 531, 657

— green, 52, 91, 106, 108, 115, 232, 239,

301, 302, 427, 432, 482, 587, 607, 701

— laminaria, 677

— littoral, 765

— macrocystis, 709

— nereocystis, 709

— peridinean, 91, 232, 297, 482, 586

— plankton, 41, 581

— red, 106, 110, 208, 209, 239, 285, 301,

302, 345, 395, 398, 475, 555, 556, 559,
583, 701, 766

— Sargassum, 430

— silicoflagellate, 91, 232, 482

— unicellular, 584
alkalinity — water, 398

alternating of colder and warmer phases,
178

Alupka, 450

amelioration, 178

ammonia, 286, 395, 475, 555

amphipods, 127, 135, 202, 268, 303, 439,
441, 454, 480, 497, 566, 567, 663, 669,
701,707,718,722,772,804

amphiurae, 441

amplitude fluctuations temperature, 185

— — tidal, 204
Amu-Darya — see river
Amur— see river
Anadyr — see river
anaerobic reduction, 554
analysis, biostatic, 519

— sea bed cores, 687, 688

— zoogeographical, 67, 337
Anapa, 387

Anatolian coast, 186, 388, 446

ancestors, pre-quaternary Salmonidae, 57

anchovy, 427, 460, 463, 520, 535

Andrey Pervozvanny, 74

Anguleme cape — see cape

Anomura, 709

Antarctic, 417

Anticyclonic gyrations, 545

Anzyl lake — see lake

appendicularians, 94, 193, 291

Apsheron peninsula — see peninsula

Apterygota, 202

Ara inlet — see inlet

Arabat bank — see Bank

— Strelka, 477, 504
Arachnoidea, 202
Aral Sea — see sea
Aral stage, 354
Aralsk, 647
Archangel, 35, 181
archiannelides, 439, 452
Archipelago, 448
Archipelagoes, Arctic, 136

— Franz-Joseph Land, 76, 220

— Malayan, 716, 717

— Severnaya Zemlaya, 220

— Spitzbergen, 76
Arctic, 25, 51-5, 65-8, 75

— passages, 52

— sea whitefish, 253
area, Batum, 383

930

SUBJECT INDEX

area, coastal, 805

— halistatic, 383, 385, 545

— Kaidak, 555, 596

— Mangishlak, 555, 595

— Sevastopol-Danube-Odessa, 445

— Sulak, 401

— Yaruk-Su, 401

ascidians, 91, 126, 150, 200, 709, 771, 772,

796, 797, 798
ash, 627, 628, 764, 796-8, 800
Asia, 361

asterida, 114, 128, 135,249
Astrabad inlet — see inlet
Astrakhan, 551
Atherina, 537, 555
Atka-fish, 740
Atlantic, 53, 60, 71,312, 341
Atlantic Ocean — see ocean
atlantization of Black Sea fauna, 374, 375
auks, 745
Australia, 582
autochthonous forms — see forms

— matter, 531
auto-immigrants, 340
autumn, biological, 42
Azerbaijan, 358
Azov Sea — see sea

Bab'e Sea — see sea

bacteria, 158, 389, 473, 493, 554, 583, 584,
598, 646, 788-90

— anaerobic, 390, 398, 584

— Black Sea, 410

— denitrification, 339, 493, 583

— desulphurization, 583

— film, 55, 583,584

— hydrogen sulphide, 389, 390

— iron-depositing, 494

— methane, 584

— nitrate, 583

— nitrification, 87, 493, 583

— nitrite, 583

— putrefaction, 583

— sulphur, 584

— thione, 584
Baffin Bay — see bay
Baikal — see lake
Baku, 575

Baku stage, 361

balance of waters, 34, 79, 383, 392, 467,
469, 544, 648

— salt content, 471

balanus, 66, 113, 147, 153, 295, 504, 514
Balkhash lake — see lake
Baltic Ice Lake — see lake
Baltic Sea — see sea
Bank, Arabat, 511

— Bear Is.-Spitzbergen, 81

— Central Zhemchuzhnaya, 546

— Eleninskaya, 503, 510

— Gudaut, 444

— Gusinaya, 78, 149

— Herald, 261

— Kil'din, 136

— Spitzbergen, 78, 151

— Zhelezinskaya, 501, 503, 504, 510
banks, Mytilus, 114

— oyster, 442, 444
barbel, Aral, 668

— pike, 671
Barents Sea — see sea
barnacles, 432, 439, 521, 709, 776
Barroy Cape — see cape

basic fish food, 324, 500, 506, 521-5, 633-8,

668-9
Basin, Akchagyl, 358, 359

— Ancient Caspian, 361

— Ancient Euxine, 361-5

— Apsheron, 359, 360

— Aral-Caspian, 572

— Arctic, 27, 38, 41, 42, 52-76, 178, 255,

259, 267, 334, 339, 354, 372, 579, 580

— Azov, 367, 369

— Azov-Black Sea, 187, 369

— Azov-Caspian, 360

— Baku, 359, 363-5

— Black Sea, 367, 369, 398

— Caspian, 357, 361, 369, 572

— Chaudinsk, 361-5

— Cimmerian, 357, 358

— Khazara, 363, 364

— Khvalynsk, 364, 365

— Kuyalnits, 359-61

— maeotic, 356, 357. 361

— Mediterranean, 355, 361, 572

— middle maeotic, 358

— miocene, 572

— 'Novo-Euxone, 361, 363-5
—'Ob', 342

— pliocene, 357

— polar, 54, 68

— Pontic, 361,362, 381,537

— Pontic-Caspian, 581

— Sarmatian, 355, 361, 572, 582

— Turan, 364

— Unzular, 363, 365

— White Sea, 181
bass, 36, 38, 92, 159
bathopathy, 155
batkaki, 584
Batumi, 388

Bay, Agrakhan, 555, 614

— Amur, 751

— Anadyr, 696, 746

— Avachinsky, 614

— Baffin, 36, 63, 71

— Biscay, 71

— Blagopoluchiya, 243

— Danzig, 277, 317

— Divichi-Kenderli, 599

— Hudson's, 71

— Kamchatka, 684, 711, 829

— Karabugas, 551, 544, 644-6

— Kiel, 271, 280, 285, 309, 314

— Kola, 38,41, 83, 118-23, 37, 151-3

— Krasnovodsk, 450, 551

— Kronobsky, 684, 711, 741

— Mecklenburg, 314, 317, 318

— Mertviy Kultuk, 572, 577, 594, 598, 644

SUBJECT INDEX

931

Bay, Motovsky, 90, 91, 123, 124, 129, 137,
151, 156, 171

— Ob'-Yenisey, 260

— Odessa, 414, 417, 430

— Olyutorsky, 698, 741

— Peter the Great, 768, 772, 773, 778

— Sakhalin, 810

— Sevastopol, 414

— Shelekhov, 783

— Shipusky, 681,684

— Taganrog, 360, 368, 370, 465, 466, 467,

468, 469, 479-92, 495, 497, 500, 501,
509, 510, 514-18, 524, 527, 528

— Taman, 445

— Temryuk, 470

— Tiksi, 258

— Ussuriisky, 751
beardie, 253

bed, Barents Sea, 77
bed of great glacier, 1 82
beds, calcareous algae, 124

— lithothamnion, 124

— phyllophora, 399
Belaya river — see river
Beloye lake — see lake

Belt, Great, 272, 293, 339, 342, 345

— Danish, 330

— Langeland, 106-10, 272

— Little, 272

— Fehmarn, 295

— German, 314

— Oresund, 272, 279, 293, 309, 330, 333,

343, 345
Belts, 272, 305, 309, 333, 339, 343, 345
Beluga, 219, 461, 518, 644
Belysh'ya inlet — see inlet
benthophages, 121, 461, 780
benthophilus, 371, 562
benthos, 38, 41, 46, 64, 129-33, 135-54,

204-15, 239-52, 259, 260, 300-33,

448-56, 494, 532, 533, 606, 620, 623,

660,709-11,797-803
Bering Sea — see sea
Bering Strait — see strait
bicarbonates, 398
bight, Ara, 153

— Litza, 153

— Teriberka, 153

— Ura, 153

— Yarnyshnaya, 153
biocoenosis, ascidian, 126

— Adacna, 665

— Arctic boreal, 710
relict, 339

— Azov-Black Seas, 497

— balanus, 113

— bivalves, 142

— bottom, 143, 498, 616, 732, 771

— cardium, 504

— coastal cliffs, 440

— corbulomya, 509

— dreissina, 665, 732

— facia of cliffs, 1 12, 350, 442

— foraminifera, 731

— holothurian, 430

— littoral, 111

— macoma, 310, 311, 323, 813

— Mediterranean, 497

— modiola, 142, 143

— mussel, 114

— mussel silt, 442, 450

— mytilus, 1 14, 504, 505

— nereis, 621

— oligo-mixed, 500, 535

— pelagic, 427

— phaseolin mud, 112, 350, 440, 442,

445

— phyllophora, 445

— pogonophorae, 730

— porifera-hydroids, 1 26

— relict, 497

— rocky shale, 440

— saccocirrus sand, 440

— sand shore, 440

— shell gravel, 440, 441, 442

— silty sand, 350, 440

— starfish, 731

— ultra-abyssal, 730

— urchin, 731
biofilter, 114
biological autumn, 51

— spring, 51

— summer, 5 1

— winter, 51

biological group of fish, 629

biomass, 41, 69, 72, 90, 118, 151, 155, 158,

203, 238, 264, 311, 329, 439, 502, 645,

646,663-671,775,815

— algae, 109, 110, 430, 432, 775

— ascidian, 149

— bacteria, 411, 412, 413

— benthos, 41, 72, 90, 130, 135, 147, 252,

267, 270, 314-24, 327-33, 463, 495-
505, 507-12, 517, 518, 533, 614-22,
663,664,803,804,813, 815

— bivalves, 145-50, 497

— brachiopods, 144, 145

— bryozoans, 146-50, 797

— cardium, 479, 501^4, 623

— ciliates, 492

— coelenterates, 147-50

— cumacea, 497

— cystoseira, 431

— diatoms, 426

— dresseina, 368, 562, 663

— echinoderma, 146-8

— epifauna, 129, 147-50

— fish, 643

— foulings, 449

— gastropod, 149

— gephyrea, 148-50

— goby, 643

— infauna, 129, 147-50

— littoral fauna, 115

— macrophytes, 430, 572

— microphytes, 452

— molluscs, 480, 498

— mussel, 109

— mussel mud, 449

— mytilaster, 574, 618

932

SUBJECT INDEX

biomass, phaseolin mud, 449

— phytobenthos, 107, 432, 607, 608

— phytoplankton, 41-3, 257, 264, 375,

413,416,419,420,587-94

— plankton, 41, 45-50, 69, 93, 98, 298,

376, 413-20, 452, 481, 483, 602, 660,
775

— polychaetes, 145-50

— porifera, 145-9

— rotifera, 488

— salps, 145

— syndesmya, 507

— vobla, 643

— zoobenthos, 449, 450, 511, 512, 517,

626, 661

— zooplankton, 47, 48, 194, 258, 488, 491,

596-604, 658
-zostera, 430, 608, 657, 771
bionomic type, 1 1
biostatic analysis, 519
biotopic variety, 676
bird gatherings, 158

— rocks, 744
bird, diving, 611

— fish-eating, 644

— sea, 158, 744
Biryuchiy Island — see island
Biscay Bay — see bay
bisulphates, 398

Black Sea — see sea
blenny viviparous, 120
bloom, phytoplankton, 50, 51, 70, 72, 93,
104,258,414,415,790

— spring-summer, 790
blue-footed booby, 744

bodies of water, epicontinental, 54, 66, 71,
72, 270

— refuge, 360

body of water — Arctic, 71

— anomalous, 388

— bioanisotropic, 388

— boreal, 71

— brackish, 54, 293, 470

— classified by salinity, 344, 345

— closed, 54, 69

— deep water, 69

— high-Arctic, 71

— open, 69-71

— Scandinavian, 340

— semi-closed, 69, 71

— sub-Arctic, 71
■ — sulphate, 644

— supplementary, 27
Bogyslan, 301
BoFshoe Sea — see sea

Bolshoy Karlov Island — see island
Bolshoy Solotvetsky Island — see island
Bornholm Island — see island
Bosporous, 361, 381, 392, 447
Bothnia Gulf — see gulf
Bothnia Sea — see sea
Bottenwick, 272
bottom topography, seas, 54, 681, 682

Aral Sea, 649

Baltic Sea, 274

Barents Sea, 77

Bering Sea, 681, 818, 819

Black Sea, 398

Caspian Sea, 539, 542

Chukotsk Sea, 261

Kara Sea, 222

Laptev Sea, 255

Far Eastern Seas, 681, 686, 723

Sea of Azov, 466

Sea of Japan, 68 1 , 725, 750, 753

Sea of Okhotsk, 681, 683, 783, 784

White Sea, 182

boundaries, ice, 83

— geographical, 64

brachiopods, 124, 125, 127, 243, 798, 800
brackishness of waters, 470
bream, 379, 520, 670
breed offish, spring, 632

winter, 632

breeds, fish, 638, 644
brill, 518

— Azov, 518
brismak, 36
Britain, 159
Brittany, 65

brown mud, 72, 88, 150, 217, 229, 249, 650,

660
bryozoans, 72, 91, 114, 126, 128, 131, 141,

143, 151, 210, 267, 268, 305, 367, 562,

571, 608, 701, 718, 796, 797, 798
Bug — see river
Bug liman — see liman
Bulgarian shore, 432
bullhead, 120, 242, 337, 459, 510, 524, 525,

562, 571, 611, 629, 635, 637, 638, 641
burbot, 55
Buzachi peninsula — see peninsula

cachalot, 742

caddis flies, 669

cadocera, 193

calanus, 96, 192, 103, 698, 708, 729

— red, 101, 102

calcium, 366, 397, 400, 551, 573, 652
calorific value of food, 635, 641
Cambala, 36, 38

— Greenland. 36
Canal, Volga-Don, 527
Cape Anguleme, 265

— Barrow, 261

— Drovyanoy, 246

— Fiolent, 450

— Hope, 261

— Kanin Nos = Cape Kanin Cape, 135,

139, 181

— Kuuli, 539

— Nikodimsky, 181

— Nordkyn, 145

— North, 38, 76, 80, 142

— Sviatoy Nos, 140, 144, 181

— Syurku, 781

— Terpen iye, 810

— Tyub-Karagan, 539

— Veprevsky, 131

— Zhelaniye, 246

SUBJECT INDEX

933

caplin, 36, 37, 104, 158, 161, 218, 742, 779

carassius auratus, 629

carbohydrates, 764

carbon, 89, 150, 191, 395, 398, 401, 650

— dioxide, 71, 88, 230, 281, 282, 283, 296,

390, 448
tracer method, 756

— organic, 171, 192, 397, 477
carbonates, 249, 389, 390, 397, 398
cardidae, 357, 359, 562

cardium, 479, 501, 502, 504, 513, 514, 571,

623
carp, 525, 611, 629, 632, 644, 671
Caspian Sea — see sea
catfish, 159, 170, 612, 633, 644, 671

— blue sea, 159
Caucasus, 446, 460

— coast, 435, 446

census, benthos, 215, 450, 539, 663

— — feeding fish, 466, 518

— fish, 518-20, 643

— plankton, 39, 47, 91, 100, 297

— population, 450, 451

— seasonal plankton, 100

— zooplankton, 27, 50, 93, 100
census from air, 521

Central Caspian, 451, 529, 545, 546, 548,

553, 604, 614, 621, 623, 629, 630
cestus, 704
cetaceans, 355
chaetognatha, 291
chalcalburnus, 658, 671
change, biological productivity, 326

— river discharge, 424

— salinity, eustatic, 290
isostatic, 290

sea, 54, 278, 348, 385, 391, 693, 695,

699

— in fish diet, 640

— phosphorus, 558

— phytoplankton, 472, 483

— seasonal, 58, 86, 96-8, 471, 485, 600,

666, 667

— seasonal indices, 698

— temperature, 185, 278, 304, 377, 388,

389, 691, 692, 695, 699
seasonal, 546

— tidal, 80, 385, 788

— water level, 385, 467, 545

change, biomass benthos, 375, 533, 557,

558, 561, 575

micro-organisms, 789

plankton, 419, 420, 421, 660, 775,

830

— climatic, 54, 289

— diatom, 415, 416

— diet with age, 637

— fauna, 38, 175,360,480

— fish diet, 162-4, 525
with age, 637

— fish feeding groups, 73 1

— oxygen content, 472, 553, 594, 689, 695,

699

— palaeographic, 57, 1 77

— plankton, 719

seasonal, 50,416,417,418, 660

Channel, English, 86, 558
Charkhal lake, 372
characteristics, endemic, 198

— fauna zoogeographical, 171, 197, 253,

254

— hydrochemical, 76, 222, 466, 539

— hydrological, 76, 222, 466, 539

— physico-geographical, 76, 222, 255, 261,

262, 263, 264, 271, 539, 648

— plankton, White Sea, 194

— seas, geological, 76
Chauda, 360

Chechen Island — see island
chemical characteristics, 475

— composition of zooplankton in autumn,

764

— spring, 764

winter, 764

Cheshskaya Gulf — see Gulf
Chief Directorate of Fisheries, 382

Hydrography, 382

Northern Sea route, 75

China, 582

chironomids, 326, 329, 330, 636, 663, 664,

669
chlorides, 366
chlorine, 366, 645

— number, 470, 550
chlorophyll, 91, 264
Chokraksky Sea— see sea
chrysomonadidae, 481
Chukotsk peninsula — see peninsula
Chukotsk Sea — see sea

ciliates, 44, 50, 193, 176, 237, 294, 295,

452, 658
circulation of waters, anticyclonic, 383,

821

drifting, 470

horizontal, 72, 90, 382, 392

— — surface, 184, 821

vertical, 39, 70, 72, 90, 138, 281, 559,

561
cirripedia, 62, 268
cladocera, 658
clamworms, 499, 500, 524
classification of bottom organisms, 800

— — fish, biological, 629

— — water bodies (by salinity), 344, 345
clays, 87, 229, 266, 399

— maikop oligocene, 401

— ribbon, 341

climate, 27, 54, 64, 179, 182

— continental, 179, 182

clupeonella, 375, 460, 463, 520, 521, 522,

523, 633
coalfish, 38, 159
coasts, American, 748

— Asian, 748, 765

— Bering Sea, 820

— Japanese, 748

cod, 36, 37, 72, 92, 159, 160, 161, 162, 206,
214, 219, 253, 740, 741, 742, 779, 835

— arctic, 55, 253

— polar, 218

934

SUBJECT INDEX

coefficient, biomass population density,
450

— chlorine, 550

— C/B consumption /biomass, 418

— daily highest mass plankton, 606

— F/B food biomass, 643

— F/C food coincidence, 638, 640

— P/B production/biomass, 72, 101, 158,

283, 413, 504, 506, 507, 508, 524, 593,
594, 608

— respiratory, 283

coelenterates, 62, 150, 197, 231, 249, 347,
371, 373, 479, 581, 608, 663, 701, 745
colonies, Arenicola, 799

— Balanus evermanni, 806

— Macoma, 799

— zooid, 800

colonization, 432, 573, 574, 575, 581, 627
column of productive water, 41, 63
commercial resources offish, 519
community, 36, 54, 69

— ascidian, 131

— arctic, 36, 39, 372, 562, 576

— arctic relict, 311, 339, 372

— autochthonous, 54, 367

— Azov Sea, 497, 498, 499, 500, 501

— Baltic relict, 326

— Barents Sea, 148

— bathypelagic, 248

— benthos, 142, 148, 210, 314, 329, 436,

445,497, 616

— bottom, 72, 154, 533

— brackish water, bottom, 242, 254, 259,

316, 344

— branched lithothamnium, 131

— carbulomia, 509

— cardium, 501, 502, 503, 504

— dead plants, 445

— dreissina, 497, 665

— endemic, 259

— hard ground, 149, 533

— infauna soil-eating forms, 1 68

— littoral, 122,213

— macoma, 114, 314, 328

— macrophyte, 431

— Mediterranean, 372

— mid-Barents Sea, 69

— mesomixed, 69

— north boreal, 179

— oligomixed, 69, 270, 316

— pelagic, 427

— polymixed type, 70

— porifera, 145, 146

— pseudo-abyssal, 213

— relicts, 379

— sand, 443

— shell gravel, 443

— silt bottom, 211
coast, 443

— soft grounds (beds), 131

— zostera, 443, 445

competition, habitat, 379, 504, 506, 578,
640

— amount of, 639
- feeding, 637, 641

— food, 171, 637, 639, 640, 643

— force of, 639, 640

— intensity of, 639, 640

— intrageneric, 639, 640

— intraspecific, 504, 639, 640
competitors, 379

composition of water, chemical, 551

bottom biocoenoses, 777

fauna, zoogeographical, 253, 701

flora, 70, 701, 702

invertebrates, 701, 702

phytoplankton, 265, 481

plankton, 265

population, 68, 70, 565

zoobenthos, 431, 661

zooplankton, 263, 487, 594

compounds, biogenic, 526

— organogenic, 526

concentration of hydrogen ions (pH), 51,
282, 284, 448, 594, 655

fish, 510

concretions, ferro manganate (iron-man-
ganese), 229

conditions, biological, 29

— chemical, 475

— geological, 539

— high arctic, 63

— hydrobiological, 29, 284, 375

— hydrochemical, 296, 375, 539, 560

— ice, 41, 51, 52, 83, 549, 550, 651

— oxygen, 188, 553, 655

— physico-chemical, 248

— saline, 34, 69, 81, 188, 223, 561

— thermal, 81, 228, 546
Constantinople, 436

consumption by fish of benthos, 122, 500,
505, 510, 633, 635

■ — cardium, 502, 503, 504

plankton, 104, 521

• syndesmia, 506

— of oxygen, 229, 593, 594, 606
contamination by H2S deep layers, 381,

392

littoral, 118, 119

Continental shelf, 40, 254, 398, 675, 682,

713

— slope, 398

cooling of sea waters, 70, 546, 650

in autumn, 546, 651

in winter, 651

copepoda — see crustaceans
corals, 91, 134, 141, 249, 373, 431

— hydroid, 805

— sea whip, 246, 249, 436

— soft, 141

cormorants, 644, 744, 745
corophiidae, 636
cosmopolites, 67, 235, 254
cosmopolitan, 572, 573

crab, 91, 162, 373, 374, 427, 441, 739, 740

— china, 312

— hermit, 162, 439

— Kamchatka, 173, 739, 742, 743, 744, 782

— lithodes maja, 37

Crimea, 383, 387, 416, 446, 447, 448

SUBJECT INDEX

935

Crimea, coast, 416, 437

crustaceans, 72, 91, 127, 128, 139, 147,
149, 150, 156, 200, 231, 249, 311, 315,
317, 349, 367, 371, 372, 373, 446, 450,
457, 479, 495, 570, 571, 579, 608, 612,
659,667,677,700,771,772

— Caspian, 571

— cirripidae, 135

— copepoda, 93, 100, 101, 294, 295, 348,

373,403,490,491, 697, 707

— daphnids, 295

— decapoda, 562, 718, 722

— eaters of, 635, 636

— fresh- water, 312

— higher, 371, 461, 525

— lower, 372,461, 525

— pelagic, 158

— relict, 242

ctenophores, 109 171, 373, 431
cumacea, 127, 479, 497, 566, 701
currents, 808

— alluvium-bearing, 542

— Atlantic, 176

— Azov Sea, 388

— Black Sea, 383, 384

— Bosporus, 385, 388

— Central Caspian, 545

— circular, 383, 467, 545

— cold, 262, 688, 696, 756

— compensating, 242, 278, 546

— convectional, 188

— convergent, 696

— cyclonic, 467, 543, 545

— deep, 278, 463

— Far Eastern Seas, 688

— Gulf Stream, 675

— horizontal, 545

— lower, 388, 447

— Kuril, 703

— Kuroshio, 675, 676, 688, 702, 703

— Ogashio, 675, 676, 688, 702, 704

— on-shore and off-shore winds, 468, 546

— reciprocal, 388

— sea, 63, 79, 176, 177, 183, 185, 221, 223,

233, 261, 383, 584, 785

— Soya, 711

— surface, 383, 384, 689, 755
discharge, 277, 278, 388

— Tsushima, 703, 711, 777, 810

— upwards, 436

— vertical, 545

— warm, 261, 688
cycle, biogenic, 286
cycles, change fauna, 572
food, 164

life, 460

cyprinids, 563
cystoseira, 429, 431, 439

dab, 171, 253
Dago Island — see island
Danilov Island — see island
Danube — see river
Danzig Bay — see bay
daphnids — see crustaceans

Dardanelles, 362, 368, 436

— breaking through of, 367, 392
Davis Strait — see strait

death of benthos, 510-11

phytoplankton, 590

population, 511

Pontic fauna, 392

decapods — see crustaceans

decaying algae, 531

decomposition of organic substances, 471,

475
decrease in size, 309, 310
decrease of forms with depth, 719
decrease of salinity in seas, 54, 225, 255,

284, 361, 363, 448, 561, 580, 581

surface, 57, 225, 255, 257

waters, 651

deep water, fish feeding in, 734
De Long strait — see strait
delta, Amu-Darya, 667

— Danube, 457

— Dnieper, 368

— Don, 368, 370, 497

— Killisk, 457

— Ural, 551

— Volga, 551, 561
denitrification, 394
density, of water, 388

— of bottom population, 499, 500, 614
deposits, moraine, 182

— oligocene, 401
Depression, Aland, 277, 284

— Arcona, 272, 287, 306, 316, 319

— Bogskar, 284

— Bornholm, 272, 281, 316, 319, 332

— Caspian, 541

— Central, 139

— Central Arctic, 64

— Danzig, 277, 280, 281

— Gotland, 272, 277, 281, 284

— Greenland, 64

— Kumo-Manych, 361, 362, 574

— Landsort, 272, 281

— Manych, 360

— Norwegian, 64

— Polar Basin, 30, 87

— White Sea, 215

depression of seas, 57, 64, 87, 88, 215
depth, decrease of forms with, 712
depths of seas, 27, 38, 45, 181, 217, 221,
256, 257, 273, 276, 310, 430, 649, 818
detritus, 50, 129,476, 531, 541

— eaters, 129,798-802,810
development of benthos, 796
fauna, 177

phytoplankton, 42, 52, 70, 483, 824

plankton, 42, 50, 52, 296, 297, 483

zooplankton, 298, 485-93

diatoms — see algae

dichothermia, 277

diet, anchovy, 305, 427, 521, 522

— bass, 161

— benthophilus, 521

— birds, 644

— bream, 524, 525, 668, 670

936

SUBJECT INDEX

diet, bullhead, 524, 535, 638

— caplan, 161, 171

— carp, 524, 635, 636, 638, 669

— catfish, 170, 522

— chalcalburnus, 668

— clupeonella, 522

— cod, 161-5

— ctenophores, 170

— dab, 168, 169

—fish, 160-73, 510, 521, 524, 537, 538,
635-68, 745

benthos-eating, 166, 168, 170, 523

fry, 526, 657, 658

-plankton-eating, 171, 172, 521-5

predators, 525

young, 161, 168, 521, 524

— friar, 520, 535-7

— goby, 535

— golden shiner, 638, 668

— haddock, 161, 165, 166, 167, 168

— herring, 161, 171, 218
— - — Caspian, 633

— mammals, 44

— pike-perch, 521, 524, 635, 636, 641,

669

— Polar cod, 218

— ray, 161, 170

— roach, 524

— saida, 172

— sand dab, 161

— starred sturgeon, 524, 641

— sturgeon, 524, 635, 636, 641

— vobla, 625, 666, 641, 668

— worms, 625

— zooplankton, 424, 598, 635, 657, 669
dinoflagellates, 402

discharge of biogenic substances, 557

coastal waters, 66

detritus, 475, 478

nutrient salts, 478

river waters, 469, 557

Don, 509

Volga, 545

displacement of fauna, 153, 204

— zones, 100, 201,245, 509
distribution: acartia, 421

— algae, 106, 705, 746

— amphi-boreal, 737

— amphipods, 336

— Azov-Sea fauna, 496

— bacteria, 410, 411, 412

— benthos, 133, 153, 252, 263, 267, 304,

317, 404, 441, 449, 722, 724, 798

— benthos biomass, 39, 46, 135, 136, 137,

138, 139, 140, 141, 151, 249, 252, 422,
426,449,536,804,815,837

— biocoenoses, 514, 812, 838

— bipolar, 735, 737, 738

— bivalves, 139

— bottom organisms, 720, 795, 809, 810

— calanus, 785

finmarchicus, 42, 822

tonsus, 785

— carbon, 476

— carbon dioxide, 281, 282

— Caspian fauna, 569

— copepods, 335

— crustaceans, 333, 334, 335, 336, 337

— depths, 126,719,720,757

— echinoderm, 138

— ecological groups, 805, 808
zones, 808

— fauna, 426, 733, 798, 799, 800, 801,

802

— fish, 332

— groups with depths, 451

— herring, 104, 160

— macrophytes, 108, 430

— molluscs, 138, 338

— mysids, 372

— nereis, 516, 621, 624

— oxygen, 188, 190, 281, 282, 420, 695,

820 823

— phytobenthos, 107, 301, 302, 428-30,

607, 608

— phytoplankton, 481, 484, 486, 658, 705,

793

— plankton, 724, 760, 793

— pogonophora, 703

— polychaetes, 1 39

— priapulides, 339

— relicts, 369-71

— salinity, 468, 552, 654, 822, 823, 827

— seals, 372, 695

— sestonophages, 805, 806

— soils, 84, 85, 86, 87, 88, 129, 229, 397,

467, 468, 476, 622

— vertical fauna, 310, 721, 725, 727, 728
nitrates, 83, 84

pH, 83, 84, 420

phosphates, 83, 84

plankton, 721

temperature, 83, 84, 822, 823, 827

— water-masses, 808, 810

— worms, 338

— zoobenthos, 431, 661

— zooplankton, 47, 100, 194, 195, 258,

463, 494, 704, 706, 708, 793, 831, 832,

833
ditch grass, 394

diurnal production of carbon, 707
Divichi, 599
Dnieper — see river
Dniester — see river
dog whelk — see red algae,
dolphins, 355, 427, 452, 460, 463

— white, 742
Don — see river

Dreissena, 357, 562, 751, 663, 665
drift of From, 30, 34

polar waters, 34

Sedov, 34, 35

drifting stations, 30
Drovyanoy Cape — see cape
drying up of sea bed, 532
ducks, 576

dump wrack, 584, 597
Dvina Gulf — see gulf
dynamics offish stocks, 518, 519
food relationship, 640

SUBJECT INDEX

937

dynamics of hydrological processes, 69

organic matter, 398

processes of organogenic substances,

286
Dzharylgatsk Gulf— see gulf

earthquake epicentres, 684

East Siberian Lowlands, 572

East Siberian Sea — see sea

echinoderma, 64,72,91, 126, 129, 139, 149,
150, 151, 156, 157, 166, 197, 231, 242,
248,264,268, 311, 315, 343,431, 571,
701, 702, 771, 774

ecological distribution, 798-802

— groups/biomass (percentage), 802
edaphopathy, 155, 156

eggs of copepods, 403

fish, 645

invertebrates, 403

Eisk, 470

Eisk shoal, 480

elasticity of diet (sturgeon), 641

Elba, 313

El'burz range, 544

elevation, Barents Sea, 78

elevation of Academy Sciences, 786, 808

Institute of Oceanography, 808

emigration from rivers, 568, 580, 581
end moraine, 182

endemic forms, 53, 199, 254, 308, 368, 435,
518, 611, 668

— — of Black Sea, 367
endemism, 53, 179, 198, 567
enemies of fishes, 218, 778
England, 446

English Channel, 86, 558

eocene 572

epifauna, 129, 131, 138, 141-7, 205, 636

epilimnion, 669

epizootic, 662

Era, Khvalynsk, 364

— Mindel-Riss, 363

— Riss-Wiirms, 363

— Sarmatian, 422, 572

estimate of quantitative benthos, 129, 216,

252,314,330,450,661

fish food, 633-7

littoral fauna, 113-18, 206-8

microbenthos, 452

micro-organisms, 494, 584

phytobenthos, 107-110, 196

phytoplankton, 414-17, 587-94

plankton, 39, 47, 91, 100, 238, 298,

660

pseudo-abyssal, 21 1

sublittoral, 123, 124, 131, 216

zooplankton, 47, 50, 93, 100, 194,

239, 419
Estonia, 349

estuaries, rivers, 260, 561
Eurasia, 220

Europe, 27, 76, 340, 367, 579
eurybiotic capacities, 60, 311
euryhalinity, 311, 348, 480, 581
euryphague, 637

eury topic capacity, 311, 506
evaporation, 468, 541, 651
evolution of fauna, 435

species, 459

exchange of fauna, 364, 447, 711
expedition, All-Caspian Scientific fishery,
539

— All-Union Arctic Institute on Sedov, 29,

222

— All-Union Institute of Marine Fishery

and Oceanography, 539

— Aral Caspian, 647

— Azov-Black Sea, 382

— Baer, 538

— Baltic, Grimm, 271

— Belgica, 222

— Berg, 647

— Bukatov, 647

— Butenev, 647

— Chelyuskin, 26 1

— Chirikhin, 255

— Drifting Ice, Papanin, 34

— Dymphna, 221

— Ekman, 271

— on From, 30, 35, 222
Galatea, 711,734

— Grimm, 538

— on Hydrograph, 382

— Hydrographic Administration, 382

— on Imer, 221

— Khmisnikov, 255

— Knipowitch, 538

— on Krasin, 30, 261, 263

— Libin-Cherevichnyi, 33, 34

— on Lith ke, 255,261

Lomonosov, 222

Malygin, 222

Mod, 222, 255

— Murmansk, for scientific fishery sur-

vey, 74

— North Pole, 731

— Papanin, Shirshov, Fedorov and Kren-

kel, 30

— Persei, 76, 227

— Peyr and Vaiprecht, 73

— on Pervenets, 22 1
Russanov, 222

Sadko, 30, 48, 62, 222, 240, 255

Sedov, 30, 31, 32, 33, 34, 35, 48,

222

— Sel'dyanaya, 541

— on Sibiryakov, 36

— Siloga, 713

— Spindler and Andrusov, 645

— State Hydrological Institute, 261
Taimyr, 255

— ТоГ on Zarya, 222, 255

— on Varna, 221

Vega, 221, 255, 261

Vityaz, 677, 678, 679, 680, 711, 712,

713, 716, 734
extinction of fauna, 257, 355, 369, 392, 460,

532

fish, 460, 473

organisms, 473

938

SUBJECT INDEX

facia branched Hthothamnium, 126, 128

— cliffs, 112-16, 799

— coquina, 126, 127

— rock, 112-16, 799

— rock-shale, 126

— sand, 126, 127

— silt, 126, 128

— soft soil, 799

Faroe Islands — see islands
fat, 627, 628, 764

fauna, abyssal, 61, 63, 220, 240, 478, 711,
773

— Akchagyl basin, 359, 572
Aral, 365

— Aral-Caspian, 569

— Arctic, 38, 61, 220, 268, 270, 333
basin, 53, 60

circumpolar, 248

cold water, 291

— Atlantic, 65, 141, 303, 333, 354
origin, 265

— autochthonous, 53, 59, 60, 370, 434

— Azov, 431

— Azov-Black Seas, 564

— Baikal, 573, 582

— Baltic, 198

— Barents Sea, 245

— bathyal, 61,240, 773

— bathyal-pelagic, 134,254

— Black Sea, 431

— boreal, 65, 220, 270, 333

— bottom, 39, 63, 110, 128, 162, 267, 608,

659, 710, 730, 739, 769, 773

— brackish relict, 66

— brackish- water, 66, 220, 270, 333, 453,

480, 497

— Caspian, 353, 354, 368, 465

— Caspian autochthonous, 366
relict, 380, 465

— Caspian type, 369

— clayey sand, 127

— cold-water, 134, 142, 333

— deep-water, 60, 64, 68, 254, 677, 735,

737, 776

— distinction of, 64

— Far Eastern Seas, 371, 700

— fresh-water, 64, 333, 380, 480

— high Arctic, 53, 59, 60, 241, 248

— Kola Bay, 74, 110

— Hthothamnium, 128

— littoral, 52, 64, 65, 74-123, 199, 206,

208, 709, 710, 779

— littoral-boreal, 64

— Mediterranean, 354, 362, 371, 373, 380,

465, 480, 518, 571, 643
euryhaline, 373

— meotic, 260

— middle miocene, 360

— mixed, 479

— northern, 572

— oligocene, 572

— Okhrida, 582

— Pacific, 198, 700
origin, 265

— pelagic, 63, 64, 388, 725

— phaseolin silt, 445

— pliocene, 54

— Pontic, 353, 357, 360, 453, 518

— Ponto-Caspian, 369

— pseudo-abyssal, 128

— refuse washed ashore, 439

— relict, 57, 65, 222, 333, 353, 372, 380,

453, 465
brackish, 66

— saline, 280

— Sarmatian, 353, 360, 572

— shell-gravel, 441

— silty sand, 128

— sublittoral, 64, 65, 125, 128, 709

— tethys, 353, 360

— tertiary, 668

— upward movement of, 134

— warm-water, 27, 134
of Barents Sea, 372

— White Sea, 193
fecal pellets, 446
fecundity, 501, 506
feeding of anchovy, 460, 521

arctic cod, 173

bass, 161

beluga, 525

bream, 524, 529, 660, 668

bullhead, 524, 525, 635

carp, 635, 636

catfish, 170, 525

— — chacalburnus, 668

clupeonella, 460, 522, 523, 633

cod, 161, 162, 172, 173

copepods, 633

crustaceans, 670, 730

ctenophores, 171

flatfish, 780, 781

friar (Atherina), 522, 633

haddock, 37, 165-69

hardtail, 461

herring, 171, 460, 522, 525, 633,

765

mackerel, 460, 780

mysids, 633

pelecus, 525

pike-perch, 462, 525, 635, 636, 641

ray, 170

rough dab, 168, 169

sarda, 460

sardines, 460

sea dab, 1 69

starred sturgeon, 461, 636

stickleback, 669

sturgeon, 461, 635

tuna, 460

vobla, 635, 666, 668

worms, 625, 634

— value, 605
feeding activity, 641

feeding ground, 45, 503, 521, 524, 641,

678
Fehmarn Belt, 295
Fenno-Scandia, 168
fermentation, hydrogen, 584
sulphide, 389, 392

SUBJECT INDEX

939

fermentation, methane, 584
ferrous compounds, 398, 649
fertility of cardium, 501

syndesmia, 506

fields of phyllospadix, 766, 770

fucoids, 767

pelvetia, 767

zostera, 770

filamentous algae — see algae
film, bacterial, 555, 584

— protective, 584

filter feeder, 380, 501, 618, 804

filters, 501

filters, plankton, 561

Finland, 275, 276, 289, 305, 327, 332

— Gulf — see gulf
Finmark, 70, 139, 141, 145
Finnish Coast, 308
fjord, Gulmar, 144

— Oslof jord, 86

— Sturfjord, 136, 154
fjords, Norwegian, 401

fish, 38, 54, 72, 106, 118, 158, 253, 260, 309,
311, 349, 369, 372, 458, 518, 532, 535,
570, 573, 579, 629, 633, 646, 677, 701,
741, 742, 745, 777-82, 816-19, 839-41

— Aral Sea, 668

— benthos-eating, 463, 524, 633

— Black Sea, 374

— bottom, 460, 731, 734

— commercial, 159, 173, 458, 535, 710

— eaters, 478

— enemies, 168, 218

— fresh-water, 242, 633

— of fresh-water genesis, 632

— fry, 522, 779, 780

— marine, 309, 633

— of marine genesis, 632

— Mediterranean, 633

— migratory, 629, 630, 632, 633

— pelagic, 462

— plankton-eating, 105, 463, 524, 633

— predatory, 525, 630

— relict, 242

— river, 628

— sub-tropical, 777

— tropical, 777

— young, 520, 522

fish families, Acipenseridae, 367, 611, 629,

738

Brotulidae, 732

Calanoidae, 703

Clupeidae, 57, 253, 611, 633, 817

Coregonidae, 55

Cottiidae, 40, 1 58, 253, 73 1 , 734, 8 1 6,

817 839

Cyclopteridae, 253, 734, 816

Cyprinidae, 573, 611

Gadidae, 55, 158, 253, 739

Gobiidae, 40, 367, 777, 817

Hyperiidae, 161

Liparidae, 731, 734

Lumpenidae, 253, 816, 839

Moridae, 732, 734, 817

Neritidae, 567

Osmeridae, 55, 253

Pereidae, 245

Pleuronectidae, 46, 157, 253, 816,

817
Rejidae, 40, 158,253

- Salmonidae, 40, 55, 57, 1 58, 253, 738,
816,839

Scorpaenidae, 734

— Zoarcidae, 253, 731, 734, 816, 817

— feeding activity, 139, 641

groupings, 73 1 , 778, 779

habits, 780

intensity, 605

fisheries, 172, 180, 219, 253, 349, 459, 462,
525, 534, 537, 643, 671

— Aral Sea, 525

— Baltic Sea, 349

— Barents Sea, 172, 173

— Black Sea, 459, 462

— Caspian Sea, 643

— cod, 219

— herring, 172, 253

— Kara Sea, 253

— Sea of Azov, 671

— seal, 219
fishing, 172, 219

— in narrow strait, 460

— trawling, 75

— regions, 739, 740
fish roe, 403, 428

— yield, 644
flagellates, 633, 658

flatfish, flounder, 120, 349, 501, 628, 710,
740, 780, 839

— polar, 253

— sea, 159, 169,219
floating marine laboratory, 680
floor, Barents Sea, 77

flora, 217

— Atlantic, 63

— bacterial, 598

— bottom, 238, 765

— brackish-water, 607

— littoral, 66, 112,765

— Mediterranean, 372

— Pontic, 667

— Sarmatian, 667

flowering plants, 204, 427, 432, 495, 660
fluctuations of benthos composition, 620,

721

biomass — see change

plankton — see change

population, 508, 658, 659, 707

salinity, 50, 349, 389, 471, 561, 659,

824

sea level, 289, 385, 467, 541, 755

temperature, 50, 64, 186, 387, 548,

651, 689, 755, 824

zooplankton biomass, 488, 489

food correlations, 164, 165, 173, 217, 522,

633, 634, 669, 779, 780
food coincidence, 638

— cycle, 164, 165

— range, 164, 165, 166, 170, 171, 218

— rivals, 172,643

940

SUBJECT INDEX

food, value (fish diet) of chironomidae,
670

crustaceans, 670

diatoms, 670

gammaridae, 670

molluscs, 670

phryganidae, 670

plankton, 605

foraminifera, 249, 267, 572, 701, 702, 718,

725, 755, 774
forecast, changes of productivity, 526
formation, Dardanelles, 362, 368-92
formation, fauna, 57, 432, 571, 629, 717,
772, 812

— species, 57, 702

— zone of geosyncline, 783
fouling, 41

— fauna, 449, 578, 798, 805

forms, abyssal, 63, 245, 246, 725, 729,
773

— amphiarctic, 68

— amphiboreal, 53, 68

— Arctic, 38, 133, 193, 265, 267, 323, 337,

612,710,725,765,810

— Arctic-boreal, 53, 60, 68, 193, 197, 247,

254, 337, 765, 810

— Arctic-Mediterranean, 338

— Atlantic, 48, 65, 246, 344

— autochthonous, 53, 59, 68, 362, 370,

371,435,612,616,629,647

— Azov-Black Seas, 480, 497, 531, 532

— Barents Sea, 244, 260

— benthic, 243

— bipolar, 174

— boreal, 34, 44, 68, 132, 133, 141, 197,

234, 246, 247, 710, 774
warm-water, 129, 141

— bottom, 63, 765

— brackish-water, 45, 235-8, 257, 258,

295, 296, 300, 308, 341, 348, 362, 563,
594, 791

— Caspian, 362, 456, 569

— Caspian origin, 368

— characteristic, 128, 150, 155, 354, 371,

586, 595

— circumpolar, 63, 68, 70, 253

— cold water, 128, 142, 150, 199, 234, 237,

773,791, 810

— cold-living, 193, 343, 420, 630

— commercial, 173

— cosmopolitan, 197, 154,236

— deep-water, 52, 244, 757

— dominant, 586, 587, 588, 598, 616, 765,

772

— endemic, 49, 53. 59, 197, 199, 254, 308,

369, 435, 518, 611, 668, 729, 765, 774

— epicontinental, 53

— epifauna — seston-eaters, 144

— estuarine, 791

— eurybathic, 68, 614

— eurybiotic, 53, 267, 311

— euryhaline, 293, 300, 326, 334, 345, 346,

349, 377, 453, 480, 581, 616, 757

— euryoxybiotic, 501, 617

— eurythermic, 377, 756

-eurytopic, 134, 501, 506

— fresh-water, 45, 235, 243, 254, 257, 258,

295-300, 311, 332, 344, 362, 434, 435,
480, 487, 491, 518, 587, 594, 611, 791

— high Arctic, 53, 132, 133, 197, 248, 254,

260

— high euryhaline, 346

— indifferent, 594

— infauna soil feeding, 144

— littoral, North Atlantic, 311

— lower Arctic, 243

— Lusitanian, 337

— mass, 37, 38, 146, 319, 663

— Mediterranean, 368, 434, 448
origin, 345, 434, 623

— migratory, 518

— neritic, 93, 98, 791

— North Atlantic, 254

— north boreal, 140

— oceanic, 93, 98

— Pacific, 45, 68, 264, 267, 269, 725

— pan-Arctic, 254

— pelagic, 63

— pliocene, 57

— potential-amphiboreal, 173

— predominant, 96, 129, 134, 147, 148,

149, 155, 212, 240, 307, 314, 444, 496,
497, 613, 614, 616, 663, 791

— relict, 200, 367, 372, 481, 487

— saline-loving, 323

— sessile, 770

— shallow-water, 134, 247, 757

— stenobathic-abyssal, 68

— stenohaline, 58, 300, 347, 354, 371, 595

— stenothermal, 403
cold, 403, 404

— sub-Arctic, 132, 243, 248, 253

— tolerant of varied range of salinity, 563

— tropical, 765

— ultra-abyssal, 717

— ultra-haline, 480, 531

— warm-water, 61, 69, 98, 133, 144, 193,

199, 254

phytoplankton, 135

zooplankton, 135

— western origin, 237
fossil, occurrence of, 339
Fram, ex/v., 30, 35, 222, 538
Franz-Joseph Land, 27, 45, 46, 78, 135,

220
freezing of water, 331, 411, 651
friar, 520
Frishhaff, 349
fritillaries, 51
frostfish, 218, 253, 839
fry, carp, 658

— fish, 101, 104, 427, 522, 601

— grey-mullet, 427

— herring, 630

— sprat, 630

fucoids, 106, 107, 110, 111,204,776

gadidae, 355

gammaridae, 121, 623, 635, 636, 670, 725,
796

SUBJECT INDEX

941

garfish, 460, 463, 535
gastropods — see molluscs
Gavrilovskiye Islands — see island
genesis of decapods, 309

bottom vegetation, 239

fauna, 54, 562-3

ice sea relicts, 54

Genichensk Strait — see strait
geological past, 287, 685
geosyncline. South Russian, 353

— Tethys, 353, 392

gephyrae, 118, 127, 128, 305, 311, 722
gerbil, 441
Germany, 159
Gibraltar, 375
gigantism, 221, 249, 810
glaciation, 288, 363, 365

— Danish, 289

— Finnish, 289

— Gotland, 289

— Mindel, 363

— Riss, 363, 365

— Wiirms, 363, 365
glauber salt, 645
Glubokaya Gulf — see gulf
glucose, 594

Gniloye Sea — see Sivash

goby, 253

golden shiner, 349, 501, 506, 525, 629, 635,

644
Gorlo, White Sea, 181, 188
Gotland — see island
grayling, 253

Great Britain. 71, 381,445
greenfish, 460
Greenland, 34, 36, 64, 69, 71, 154, 155, 178,

311
Greenland Sea — see sea
grey mullet — see mullet
groups of fauna, 433, 434, 435

biogeographical, 235

— biological, 629

zoogeographical, 197

growths, algae, 112, 427

— cardium, 501

— cystoseira, 439

— fucoids, 113

— lithothamnium, 124

— littoral, 666

— macrophytes, 335

— phyllophora, 430

— zostera, 208, 427, 444, 495
guanay, 744

Gudaut, 444

guillemots. 158, 744

Gulf, Baydaratsky, 242, 248

— Belyushya, 134

— Bothnia, 270-6, 284, 306, 308, 314, 316,

325-6, 343

— Chernaya, 123, 133

— Cheskaya, 123, 133, 134, 136, 199, 445

— Dvina, 181, 185,215

— Dzharylgatsk, 387

— Finland, 272, 276, 284, 286, 306, 307,

308, 309, 310, 314-26, 663

— Glubokaya, 215

— Kandalaksha, 181, 182, 185, 204, 205,

207, 214

— Kara, 242

— Konev, 207

— Mashigina, 136

— Neva, 285, 326, 611

— Ob', 243

— Onega, 181, 182, 184

— Panama, 732

— Persian, 359

— Piryu, 180

— Riga, 272, 275, 276, 349

— Rugozersky, 205, 209

— Tiksy, 258

— Vayda, 193

— Yenisei, 243
Gulmarfjord, 144
Gur'evskaya Furrow, 541
gyttja, 310, 327
Gyurgenchai river — see river

habitat, 37, 57, 157, 158, 245, 333, 341,

624
haddock, 36, 38, 72, 92, 101, 159
halibut, 37, 159, 839
halistatic areas, 138, 545

— zones, 185
halopathy, 155
halophilic forms, 531
hardtail, 460, 463

heat radiated from earth crust, 549

heating of bottom waters, 546

sea waters, 546-9

summer, 470, 479, 530

— — — surface, 546

Heligoland — see island

Helsingfors, 310

Herald Shoal, 261

herring,36, 37, 38, 72, 92, 101, 159, 162, 180,
198, 206, 217, 219, 253, 309, 377, 379,
460, 463, 518, 535, 562, 571, 629, 644,
739, 740, 742, 759, 778, 839

— agrakhanskaya, 636

— Atlantic, 38

— Azov, 434, 520

— Baltic, 309, 349

— Caspialasa brashnikovi, 630

— C. caspia, 439, 630, 633

— C. kessleri, 630

— C. sapozhnikovi, 630

— C. volgensis, 630

— dolginskaya, 636

— Murman, 219

— White Sea, 218

heteronereis stages of polychaetes, 199
history of seas, geological, 287, 292, 354-

365, 377, 685
exploration of seas, 180, 181, 221,

255, 262, 270, 363, 380, 465, 538, 572,

629, 677

fauna, 172, 177, 200, 572

Hogbom's theory, 340

holothurians, 200, 249, 441, 721, 722,

772

942

SUBJECT INDEX

homohalinity, 82, 179, 184, 327, 651
homothermia, 82, 184, 327, 470
horizon, littoral, 204, 205

— sublittoral, 204, 205
hosts, intermediate, 663
Hudson, 71
Humboldt — see strait
hummocks, 471
humus, 202, 283

hunting marine animals, 172, 219

— seal, 219
hydrobia, 524
hydrogen, 554, 555, 661

hydrogen sulphide, 353, 355, 356, 358, 376,
391, 396, 432, 494, 531, 612, 650

vertical distribution of, in Black Sea,

397

hydroids, 72, 91, 114, 126, 153, 211, 267,
268, 367, 444, 562, 637, 796-8

hydrological conditions, 28, 63, 70, 74, 275

hydro-medusa, 294

hypertonia, 580

hypolimnion, 669

Ice Age, 34, 52, 53, 63, 65, 69, 148, 178,

200, 334, 345, 363, 374, 685, 688
Icebreaker Sedov, 34

— Sibiryakov, 697

— Litke, 50,261
Ice chart, 276

— conditions, 39, 41, 51, 263, 471, 549, 651

— cover, 40, 50, 69, 182, 276, 387, 471,

546, 549

— field, drifting, 550

— floes, 29, 34, 696

— formation, 471, 549, 651

— fringe, 50-2

— melting, 264, 289, 479

— pole, 30

— prediction, 83

— recession, 633

— young shore, 549
Iceland, 37, 144, 178

ices, 24, 34, 38, 51, 72, 200, 219, 225, 254,

263, 579, 746
Ilmen lake — see lake
immigrants— 51, 312, 340, 353, 360, 544,

578, 584

— active, 581

— arctic, 342, 564, 579

— Azov-Black Sea, 563

— contemporary, 53, 54

— fresh-water, 353, 372, 573, 629

— North Atlantic, 531

— North Sea, 312, 518, 571

— Mediterranean, 373, 484, 485, 647

— passive, 581

— post-glacial, 53, 54

— pseudo-relict, 354

importance as food: benthos, 452, 511,
664-6

littoral fauna, 120-3

plankton, 101, 102, 605, 660

impoverishment of benthos, 40, 214, 431
Aral, 365

fauna, 39, 215, 330, 431

Mediterranean, 480

— in oxygen, 473, 612

— of zooplankton, 600

increase of salinity, 45, 263, 365, 581, 644-5
indicators, biological, 234, 269

— hydrological conditions, 243
indices, daily food consumption, 523

— density, 163,314,325

— food coincidence, 643

— productivity, 418

— repletion, 121, 163, 166, 218, 521-4,

635, 636, 780
Indigirka — see river
infauna, 118, 129, 139, 141-6, 206, 636
inflow of waters, fresh, 469

river, 529

— saline, 649

Volga, 545

ingression of waters, 363
Inlet, Adzibai, 665

— Akhtarsk, 510

— Amur, 812

— Astrabad, 546

— Belych'ya, 1 34

■ — Berezansky, 453

— Bug, 453

— Dnieper-Bug, 452, 455

— Dnieprovsky, 453

— Dniester, 453

— Dzharylgatsk, 387

— Gizhiginskaya, 786

— Kaidak, 551, 572, 583, 594, 598, 644

— Karkinitsk, 382, 387, 429, 430, 445

— Khadzhubey, 458

— Krasnovodsk, 544

— Kuban, 480

— Kutchurgan, 453, 456

— Kuyalnitzky, 453

— Penzhinskaya, 786

— Shirosky, 243

— Tiligolsky, 453

— Turkmensky, 542

— Utlyuk, 469, 495, 501, 509, 531, 534
Insects, 669, 670

Institute, All Union Fisheries and Oceano-
graphy, 75, 539

— Azov-Black Sea Fisheries and Oceano-

graphy, 382, 466

— Pacific Fisheries and Oceanography,

678

— Polar Marine Fisheries and Oceano-

graphy, 76

— State Hydrological, 75, 180, 326, 382,

678

— State Oceanographic, 222, 671, 711, 714

— State Oceanographic Archangel Kan-

dalaksha, 180

— Zoological Ac. Sc, 678, 681
intensity of food assimilation, 462
feeding, 462, 668

food competition, 639, 640

intensive fish feeding, 162, 462, 504, 521,

524, 537, 635, 668-9
interchanges, fauna, 481

SUBJECT INDEX

943

International Geophysical Year, 680

Second Year, 678

intrusion of fauna into fresh waters, 580,

581
invertebrates, 297, 403
Iokanga, 106
Iran, 630
Ireland, 148
Island, Aral, 649

— Bear, 48, 80, 147

— Bering, 709

— Bornholm, 709

— Chechen, 539, 561

— Dago, 284

— Danilov, 181

— Franz-Joseph Land, 28, 35, 44

— Gorelov, 818

— Gotland, 272, 277, 281, 309, 323, 342

— Great Solovetsky, 215

— Heligoland, 309

— Herald, 269

— Hokkaido, 678

— Honshu, 703
— Iona, 786

— Kamchatka, 678, 684, 688, 709, 730,

744, 780

— Kargin, 741

— Kolguev, 140, 149

— Komandorskiy, 709, 742

— Kotelniy, 258

— Kotlin, 326

— Kulali, 545, 548, 559

— Kunashir, 711

— Kuroshio, 703

— Novaya Zemlya, 28, 76, 80, 112, 123,

133, 135, 154

— Ogurchinskiy, 541, 559

— Peschany, 499

— Pioneer, 36

— Pukhovy, 158

— Queen Victoria Land, 78

— Riigen, 343

— Saint Lawrence, 745, 746, 826

— Sakhalin, 678, 766, 778, 805

— Semisopochny, 817

— Sosnovetz, 183

— Spitzbergen, 33

— Svinoi, 608

— Tyuleniy, 550, 621, 742, 781

— Uedineniye, 243

— Velikiy, 213

— Voronov, 181
Wiese, 243

— Wrangel, 28, 261, 264, 269

— Zhiloy, 539

Islands, Aland, 135, 272, 305, 309, 323

— Aleutian, 681, 746, 820

— Faroe, 144, 154, 155

— Gavrilovskiye, 146

— Hawaiian, 687

— Japanese, 681

— Kharlovskiye, 115,205

— Kuril, 684, 709, 711, 730, 756

— Lofoten, 33, 145, 162

— Melanesia, 687

— Novaya Zemlya, 28, 76, 80, 112, 123,

133, 135, 154

— Novosibirskiye, 28, 255, 258

— Pakhtusov, 243

— Polynesia, 687

— Prinkipo, 140, 436

— Seven, 115

— Severhaya Zemlya, 36, 47, 255, 260

— Solovetskiye, 182, 183, 184, 205, 213
isobaths, 467, 540, 684, 783
isohalines, 185, 188, 308, 385, 455, 469,

549, 693, 694
isolation of seas, 372
isopods, 268, 348, 427, 441, 566, 701, 702,

722
isotherms, 194, 274, 548, 688, 690, 755, 824
Issyk-Kul — see lake

Jan Meyen, 37
Jutland, 293

Kaidar inlet — see inlet

Kal'mius River — see river

Kama — see river

Kamchatka, 706

Kandalaksha, 181

Kandalaksha Bay — see bay

Kanin Cape — see cape

Kara Bogaz Bay — see bay

Kara Gates, 245, 253

Kara Gulf — see gulf

Kara Sea — see sea

Karkinitsk inlet — see inlet

Kattegat, 60, 272, 280, 293, 306, 308, 314,

345, 587
Kazantip, 473

Kel'tma northern and southern — see river
Kenderli Bay — see bay
Kerch Peninsula — see peninsula
Kerch Strait — see strait
Kharlovskiya Islands— see islands
Khatanga — see river
Kiel, 271

Kiel Bay — see bay
Kildinbank, 138
Kittiwake, 744, 778
Kola Bay — see bay
Kolguyev island — see island
Kolyma — see river
Konev inlet — see inlet
Kotelniy island — see island
Kotlin island — see island
Kovda, 180

Krasnovodsk Bay — see bay
Kuban — see river
Kulali Island — see island
Kulandy peninsula — see peninsula
Kura — see river
Kuril Bar, 675
Kurinsky Kamen, 559
Kurishhaff, 349
Kuuli — see cape
Kuyal'nik, 360

Ladoga lake — see lake

944

SUBJECT INDEX

lagoon Kara-Kul, 541

Lake, Baikal, 367, 565, 571, 582

— Balkhash, 575, 660, 668

— Baltic Ice, 288, 289

— Beloye, 580

— Charkal, 372

— Issyk-Kul, 668

— Karatogelek, 364

— Ladoga, 291, 342

— Okhrida, 367, 582

— Onega, 291, 340, 580

— Rybmoye, 289, 589

— Seliger, 340

— Superior, 648, 651

— Tanganyika, 571

— Topiatan, 364

— Victoria, 648

— Yashkan, 364

— Yoldian, 342
Lakes, Central Asia, 660

— Denmark, 340

— Finland, 342

— Ice, 341, 342,- 344

— North-western part of USSR, 346

— Northern Germany, 340

— Sweden, 337

Lake-seas, Ancient Euxine, 363

Aneylus, 288, 291, 342

Apsheron, 360

Chaudinsk, 357, 363

Ice, 290, 340

Middle Danube, 357

— — Novo-Euxine, 363

— — Pontic, 356, 357
lake age, Caspian, 414

laminaria, 106, 110, 208, 209, 214, 219,

400, 702
lamprey, 198, 200
lancelot, 441

Langeland belt — see belts
Laptev Sea — see sea
larvae, anchovy, 403

— of bottom animals, 295, 758
forms, 51

— bryozoans, 487

— caddis flies, 663

— chironomids, 330, 332, 665, 670

— cirripedia, 486, 491, 522

— copepods, 403

— decapods, 487

— Dreissena, 658

— fish, 402, 403, 427

— flies, 118, 531, 533

— gammaridae, 666

— haddock, 208

— insects, 372, 670

— invertebrates, 402, 403

— lamellibranchiata, 602

— molluscs, 452, 487, 492, 522

— oligochaetes, 325, 333

— parasites, 611

— pelagic forms, 51, 402
invertebrates, 402

— plankton, 582

— polychaetes, 238, 255, 295, 487, 491

— rotifers, 51

— sprats, 604

layer of sudden temperature drop, 559
layers of bottom water, 36, 64, 72

— decreased salinity, 49, 257

— intermediate water, 40, 45

— Pontic, 358
leech, 371, 434
Lena River — see river
Lepas, 704

level of the seas, 77, 541, 562, 648

Libau, 309

life, bottom, 40, 231

— cycle of zooplankton, 420
fish, 460

— pelagic, 40, 231
liman, Akhtar, 510

— Dnieper, 435

— Eisk, 499

— Kuban', 480

— Utlyuk, 469, 480, 509, 531, 535
Limnaean Sea, 344

lithothamnium, 126, 128, 131, 143, 209
Litke icebreaker, 50, 255

littoral, 38, 65, 71, 176

— Arctic, 66, 112

— boreal, 66

— cliffs, 107, 110, 112

— food significance, 120, 122

— Murman, 112, 123

— North Sea, 112

— Norway, 112

— population, 38

— rock, 107, 111, 112, 116

— shale, 112

— silty sands, 112, 114, 118

— White Sea, 140
Litza bight, 53
lobster, 435, 447

Lofoten Islands — see islands

loomeries, 744

loss of salinity of waters, 255

seas, 255

— ■ inhabitants, 122

lowland, Middle Danube, 361

— Pre-Caspian, 363

— Western Siberian, 572
low tides, 80
lucernariida, 128, 209

mackerel, 37, 39, 295, 424, 435, 440, 459,

460,463, 518, 759
macoma, 295, 424
macrophytes, 72, 106, 196, 204, 452, 495,

535, 606, 608, 766
macroplankton, 110
magnesium, 573, 645, 652
malacofauna, 374
Malmo, 343
Maloye Sea — see sea
mammals, marine, 44, 334, 458, 646, 739
marine animals, 158, 219, 645
manganese, 88, 229, 230, 398
Mangyshlak peninsula — see peninsula
Manych — see rivers

SUBJECT INDEX

945

marine borers, 449
Mariupol, 480
Marmora sea — see sea
Mashigina gulf — see gulf
Mecklenburg Bay — see bay
medusa, 96, 98, 101, 102, 135, 193, 304,
364, 562, 594

— fresh- water, 582
melting ice, 51, 264, 289

— snow, 471
Mendota lake — see lake
Mertvyi Kultuk — see strait
mesohalinity, 348
mesomixed community, 69, 509
methane, 473, 531, 555
microbenthos, 206, 452
microclimate, 51, 66
micro-organisms, 410
microphytobenthos, 452
microzoobenthos, 452
migration route, 633
migrations, active, 340, 582

— animals, 581

— annual, 509

— cardium, 502, 508

— fauna, 311, 341, 363, 364, 432, 573,

582,
deep water, 716

— fish, 163, 376, 378, 379, 460, 629, 782
anadromous, 57

feeding, 164, 165, 339, 630, 633, 779

spawning, 629, 630, 632, 740, 742,

744, 779, 780

-feeding, 159, 376, 521

wintering, 630

— flora, 432, 513

— herring, 104, 630

— plankton, 404, 659, 708

— plankton daily, 103, 404, 604, 605, 659,

776
seasonal, 509, 708, 793

— salmonidae, 630, 632
чся!ч 742

— vertical, 96, 404, 694, 659, 708, 759
diurnal, 708

herring, 103

plankton, 96, 98, 103, 404, 659, 708

zooplankton, 604-6, 793

mineralization, organic matter, 413

miocene, 354, 355, 361, 572, 748

mirabilite (Glauber salts), 645

mites, 202

mixing of waters, 145, 283, 336, 406, 412,
419, 559, 560

fauna, 446

zones, 473

modiola, 104, 143,446

molecules 'trihydchloric', 52

molluscs, 38, 99, 112, 124, 128, 131, 135,
141, 144, 149, 153, 200, 216, 231, 241,
243, 260, 264, 268, 311, 316, 334, 348,
367, 372, 375, 444, 446, 454, 465, 479,
480, 499, 568, 596, 663, 677, 701, 722,
771, 774

— amphineura, 112, 431

— bivalves, 66, 72, 91, 115, 129, 139, 142,

144, 150, 243, 355, 371, 375, 437, 441,
495, 774

— boreal, 38

— cephalopods, 38, 64, 91, 104, 702

— cold water, 37, 342

— fresh water, 291, 312, 358

— gastropods, 104, 112, 144,209,249,311,

418, 441, 562, 564, 573, 581, 582, 661,
667

— land, 358

— nudibranchiates, 114

— pteropod, 38, 95, 98, 258, 294

— rock-burrowing, 436

— warm-water, 38
mollusc-eating fish, 636
monocyclic distribution of growths, 96
moonfish, 37

Motovsky Bay — see bay
mouth, Ural, 597

— Volga, 597
mouths, river, 50, 254
Mudyug Lighthouse, 182
mullet, grey, 355, 427, 460, 535, 537

— red, 466, 516

Murman, 38, 64, 65, 72, 73, 136, 142, 172,
176, 311

— eastern, 115, 122

— western, 116, 118, 122, 145, 165, 208
mussels, 66, 114, 116, 149, 219, 374, 436,

443,444
mutability of species, 354
myriapods, 202
mysids, 114, 115, 295, 305, 341, 368, 441,

454, 479, 562
mytilaster, 446, 472, 524, 570, 574, 575,

576, 578, 616, 618, 620, 621, 623, 626
mytilus, 114, 437, 439, 445, 744

nannoplankton, 657

Naples, 428, 445

Navaga, 55, 218, 219, 253, 740, 742, 839

necton, 427-9

negative features of fauna, 194, 200, 201,

568
nematodes, 439, 452, 700
nemerteans, 209, 439, 452, 531
neogene, 354

nerpa (Phoca hispida), 219
Neva gulf — see gulf
Newfoundland, 64
New Zealand, 582, 711
nitrates, 51, 85, 86, 285, 286, 298, 339, 340,

395, 396, 398, 400, 474, 555, 556, 561,

655, 698
nitrification of organic substance, 286
nitrites, 51,86, 398, 555, 561
nitrogen, 72, 88, 285, 286, 394, 395, 474,

500,531,555,649,655
— fixer, 584
Nordkyn — see cape
North America, 27, 68, 308, 417, 582
NorthAtlantic,53,68,97, 142, 154, 155,431
North Cape — see cape
North Cape current — see current

946

SUBJECT INDEX

North Caucasian petroleum beds, 358

North Polar Sea, 27

North Pole, 33, 42

North Sea — see sea

Northern Caspian, 539, 545, 546, 555, 560,

575, 595, 596, 614, 616, 617, 618, 621,

624, 632, 638
Northern Dvina river — see river
Northern Europe, 308
Northern Norway, 142
Northern Pacific, 53
Novaya Zemlya, 69, 248, 253
Novorossiysk, 444
Novosibirskiye islands— see islands
Norway, 112, 134, 144, 159, 446
Norway Sea — see sea
nutrition of fish, 44, 160-72, 332, 460-2,

510, 521-5, 537, 538, 633, 669, 745

Aral, 668

benthos-eating, 168-70, 461, 524-

525

Caspian, 633

fry, 633, 636

■ plankton-eating, 171, 172, 460,

521-4, 660
predatory, 460, 525

— ■ young, 460, 657

mammals, 44, 173, 218

zooplankton, 634, 669

Ob' Gulf— see gulf
Ob' river— see river
Ob'-Yenisey Bay — see bay
Ocean, Antarctic, 716

— Arctic, 27, 41, 50, 334, 579, 708

— Atlantic, 300, 312, 425, 708, 716, 740,

741

— Pacific, 27, 268, 269, 685, 686, 687, 702,

709, 713, 740, 741, 744, 765

— world, 54
Okhrida Lake — see lake
Odessa, 387, 430, 444
Odessa Bay— see bay
Ogurchinsky Island — see island
Oka — see river

oligochaetes, 118, 202, 333, 372, 499, 663

oligohalinity, 348, 497

oligomixed nature, 70, 270, 497, 658

— of benthos, 328

biocoenoses, 497

zooplankton, 658

Onega bay — see bay

Onega lake — see lake

on fauna, 117, 118

ophiura, 127, 168, 249

Oranienbaum shoal, 326

Oresund, 272, 279, 303, 309, 343, 345

organic matter, 296

origin of fauna, 337, 700
orography of seas, 271
Oslofjord, 86
ostracoda silts — see silts
ostracode, 345, 499, 500, 663, 707
ostrea, 744
ova, 403, 428

overgrowth of algae, 112

cystoseira, 439

fucoids, 112

lithothamnum, 124

zostera, 441, 660, 667

oxidation, 86, 87, 396

— of ammonium compounds, 583
soil, 617

oxides, iron, 217, 229

— manganese, 217, 229

oxygen, 85, 88, 185-91, 281, 389, 390, 420,
473, 487, 530, 553-5, 559, 594, 606,
655

oxygen consumption, 229

— decrease, 553

— free, 230

— saturation, 473, 655

— supply, 698
oyster bank — see bank
oysters, 374,442, 618, 677

Pacific Ocean — see ocean
Pakhtosov Islands — see islands
palaeographic past of Pacific Ocean, 686
pantopods, 135, 249
parasites, Aral, 661, 700

— of Caspian fish, 565, 61 1

— of Far Eastern Seas, 700

— fish, 610, 662

— seal, 611

passive transfer of animals, 340

patella, 374

Pechora — see river

Pehlkevi, 546

pelagic carnivores, 462

pelecus, 658

pelicans, 744

Pellinge, 327, 329

penetration, active, 340

— of fauna, 307, 341, 342, 579, 647
flora, 341

fish, 536

— into fresh waters, 580
rivers, 580

— passive, 340

— of plants, 302

— of relicts, 341, 342
peninsula, Alaska, 681

— Apsheron, 542, 608

— Busachi, 546

— Chukotsk, 677

— Crimean, 383

— Kamchatka, 681, 684

— Kerch, 356

— Kropotsky, 684

— Mangishlak, 561

— Murman, 104, 203, 205

— Rybachy, 144, 146

— Scandinavian, 339, 340

— Shipusky, 684

— Taymyr, 220, 222

— Yamal, 222, 244, 252, 255
percarina, 518, 520

perch, 349
peridineans — see algae

SUBJECT INDEX

947

period, Akchagul, 573

— Ancylus, 291, 334

— Apsheron, 573

— Atlantic, 69, 219

— boreal, 290

— Danish, 289

— eocene, 572

— glaciation, 289

— gothian, 289, 369, 519, 581

— Finnish, 289, 573

— interglacial, 263

— littorine, 65, 177, 199, 200, 311, 334-41

— maeotic, 365

— mesozoic, 54

— pliocene, 53

— Pontic, 257, 562, 573

— post-glacial, 54, 63, 68, 200, 289

— post-pliocene, 57

— post-Pontic, 257

— preglacial, 63

— quaternary 28, 54, 177, 348, 365, 685,

686, 687, 688, 790

— Riss, 178

— Sarmatian, 422

— sub-boreal, 290

— tertiary, 28, 54, 177, 348, 365, 685

— Wiirm, 178

— Yoldian, 65, 178, 270, 334
periods, climatic, 54, 289

— feeding fish, 630

— flowering algae, 72

— glacial, 54, 200, 287, 288

— spawning, 630

— temperature drop, 178
rise, 177, 178

— vegetation, 42, 43

periwinkle (littorina rudis), 66, 114, 115,

' 344
Persey — see expedition
Persia, 359
Persian Bay — see bay
petrel, 744
petroleum, 348
pH, 448, 594
Phanerozonia, 727
phaseolin, 445, 618
phases, Caspian lake age, 553

— littorine stage, 342

— plankton development, 54

— salinity decrease, 67, 363
increase, 363

— temperature rise, 69

phosphates, 51, 85, 86, 286, 294, 395, 396,

398, 531, 557, 657, 698, 699
phosphorus, 86, 285, 286, 394, 396, 398,

474, 531, 556, 557, 561, 656, 689, 695,

698, 699, 823, 824, 826
photosynthesis, 86, 87, 376, 413, 559
phototropism, 64
phyllophora, 214, 380, 399, 430, 431, 436,

445, 452
phytobenthos, 52, 106, 195, 264, 300, 301,

463, 533, 605, 606, 607, 608, 646,

660
phytophanes, 669

phytoplankton, 42, 45, 50, 72, 85, 86, 87,
91, 92, 93, 94, 95, 96, 135, 193, 232,
233, 257, 258, 264, 401, 463, 471, 532,
559, 586, 587, 588, 589, 590, 591, 592,
593, 594, 646, 657, 697, 828, 829

pike, 349, 520, 644, 671

— marine, 36

— -perch, 462, 520, 525, 563, 576, 611, 629,

644, 671

perch, Don, 520

, Kuban, 520

pipefish, 427, 441, 535

Pir'yu gulf — see gulf

plain, Ob'-Yenisey, 579

plankton, 193, 232, 264, 452, 532, 702, 703,

704, 705, 706, 708, 709, 828

— abyssal, 728

— Aral Sea, 657-60

— Arctic, 64, 91

— Azov Sea, 481

— Baltic Sea, 294-9

— Black Sea, 401

— Barents Sea, 91-105

— boreal, 64

— brackish-water, 64

— Caspian Sea, 585

— Chukotsk Sea, 264, 265

— Far Eastern Seas, 702, 703, 704, 705,

706, 707, 708, 709

— fresh-water, 64

— Japan, 775

— Kara Sea, 232-79

— summer, 264

— tropical, 702

— White Sea, 193

planktonophages, 141, 145, 634, 669
plant eater, 669, 730

— food, 597, 618, 805, 825

— nutrients, 655, 659, 699
plants, flowering, 205, 427, 432, 607
pliocene, 53, 355, 361, 573
pogonophorae, 712, 713, 716, 717, 720,

730, 731, 735
polar year, international 1st, 678
2nd, 678

— basin, 54, 68

— front, 72, 80, 704
polarization, zoogeographical, 179
pole cold, White Sea, 185

— of inaccessibility, 33
pollack, 158, 180, 218, 780, 795

— Alaska, 140, 759

polychaetes, 37, 62, 72, 91, 98, 112, 117,
127, 128, 129, 131, 139, 140, 147, 150,
151, 162, 166, 198, 209, 243, 249, 267,
268, 305, 311, 324, 334, 339, 347, 367,
371, 373, 431, 445, 479, 480, 562, 571,
608, 701, 702, 718, 722, 771, 772, 774,
777, 805

polychaetes, boreal, 38

— relict, 499

— tubular, 128
polyhalinity, 348
polyps, coral, 134, 722
Pontic Sea, 363

948

SUBJECT INDEX

population, Baltic Sea, 292

— bacterial, 583, 585

— bays, 213, 267

— bottom, 64,455, 666, 731

— brackish-water, 293

— littoral, 38, 53

— pseudolittoral, 211, 212, 213

— specific, 68

— sublittoral, 206

— supralittoral, 202, 203

porifera, 72, 91, 92, 123, 131, 132, 145, 150,

306,608,701,721,722,726
Porkaton, 480
Porpita, 704
porpoises, 218
portlandia, 200

Poseidon, expedition vessel, 74, 75
post-glacial rise of temperature, 178
potential oxydation-reduction, 229
prawns, 161, 219, 440, 441, 525
predators, 460, 525, 635, 669, 730

— fish, 460, 744, 780

— pelagic, 460, 462
priapulides, 198, 199
Primor'e, 756, 777

— coast, 740

— current, 756

Princess Islands — see islands
processes, adiabatic, 546

— bacteriological, 583-4

— biological, 43, 72
production of bacteria, 413

— annual, 593

benthos, 450, 452

cardium, 504

fish, 646

fisheries, 537

macrophytes, 432

microphytes, 431

organic matter, 413

phytoplankton, 101, 593

in different seas, 464

plankton, annual, 100, 414

syndesmia, 508

productivity of benthos, 330-3

— biological, 68, 70, 398, 647

— of commercial fish, 180, 647

phytoplankton, 232, 593, 594

plankton, 98, 297, 427, 594, 699

zoobenthos, 51 1

productivity of sea, 40, 70, 158, 179, 215,
377, 604

Aral, 647

Azov, 465, 478

Baltic 330

Black, 462

Kara, 252

Southern Seas, 398

White Sea, 179, 215

prognosis, ice, 52, 83
protein, 627, 628, 764
province, Black-Azov Sea, 379

— brackish-water, 67

— Caspian Sea, 379

— marine, 66, 67

— Pontic-Caspian-Aral, 379, 583

— Tsushima, 745
provinces, zoogeographic, 583
protozoa, 432, 700

pseudo-abyssal, 128, 211, 213, 217, 446
pseudopoliparis, 718
pseudo-relicts, 354, 372

pteropods, 403

puffin, 744

Pukhovy Island — see island

pulsations, salinity, 348, 581

pupae, chironomid, 669, 671

pycnogonids, 121, 242

pyrosomes, 91

qualitative distribution of benthos phyto-
plankton, 417

— changes, fauna, 729, 730
quality nutrient of benthos, 626

— — — crustaceans, 626, 627

molluscs, 626

worms, 627

quantitative distribution of benthos, 250

phytoplankton, 233

plankton, 238

quantity, fish resources, 643
Quarken Sea — see seas
Queen Victoria Land, 78

radiation, earth's crust (thermal), 549
radiolaria, 91, 373,701, 709
rainfall, 467
range, Kuril, 684, 783

— Olyutorsky, 820

— Sikhote-Alin, 751

— Southern, 82

— Vityaz, 783

range of surface water salinity, 227, 256

temperatures, 226, 256

rate of digestion, fish, 462

— — currents, 183, 545, 741

growth, 501, 502,742

ray, 160, 161

reaction, oxydation-reduction, 229

— precipitation, 582
refuges, 360, 361
refuse fauna, 439

region, Arcona, 271, 306, 610

— Atlantic-boreal, 154, 241, 586

— Batumi, 383

— Bear Is.-Spitzbergen, 159

— Black Sea, 273, 360

— Bornholm, 271, 306

— Bosporus, 434

— Caspian relicts, 379

— Celtic, 381

— Celtic-boreal, 583

— euxine, 360

— Kanin, 140

— Ob'-Yenisey, 231

— pan-Arctic, 174

— Pechora, 140, 148

— Plymouth, 96

— Ponto-Caspian, 354

— Riigen, 271

SUBJECT INDEX

949

region, sub-Arctic, 70, 72
regions, Arctic, 55, 65, 68, 70, 76, 174, 241,
745, 746

— Baltic Sea, 306

— biogeographic, 70

— boreal, 64, 70, 174, 241, 344, 379, 745

— boreal- Arctic, 1 74

— halistatic, 138, 185, 383

— glacial, 746

— tropical, 707, 745

— zoogeographical, 174-6, 447, 586, 746
regressions, 54, 340, 687

— of glaciers, 633

relicts, 53, 54, 193, 200, 215, 308, 340, 341,
367, 369, 370, 374, 434, 450, 480

— ancient Euxine, 480, 497

— Arctic, 199, 292, 344

— Azov, 369

— Black Sea, 480, 496, 528

— brackish-water, 53, 337, 346

— Caspian, 369, 454, 479

— cold-water, 199

— Euxine, 532

— glacial, 333, 342

— littorine period, 53

— novo-Euxine, 479, 487

— pliocene, 53

— Pontic, 434

— post-glacial, 215

— tertiary, 435

— thermophilic, 200

— warm-water, 133, 195, 199

— Yoldian Sea, 339
reproduction, cardium, 501

— mytilaster, 504
resources, of algae, 219
crab, 742, 743

.fish, 519, 520, 524, 643

mussels, 219

phyllophora, 430

plant, 376

varec, 219

zostera, 429, 607, 608

rhizoids, 709
rhizopods, 128, 146, 249
Rhizosolenia, 588, 589, 590, 603
ridge, Aland, 272

— Apsheron, 545

— Darss, 272, 279, 301, 316, 330

— Elbruz, 544

— Nansen, 31

— Kurile, 711, 786, 794
ridges, submarine, 178
Riga Gulf — see gulf

rise of level of ocean, eustatic, 291
rising of Barents Sea bottom, 178

sea bottom, 178

River Amur, 697

— Amu-Darya, 366, 367, 650, 666, 668

— Anadyr, 697

— Belaya, 632

— Bug, 370, 383, 435

— Danube, 370, 383, 457

— Dnieper, 370, 383, 435

— Dniester, 383

— Don, 370, 466, 469

— Dvina, 215, 580

— Elba, 313

— Gyurgenchai, 362

— Indigirka, 29

— Kaluga, 630

— Kama, 630, 632

— Keltma, Northern and Southern, 580 -

— Khatanga, 29, 255

— Kolyma, 29

— Kuban, 370, 466

— Kura, 358, 542, 632

— Lena, 29, 255, 257

— Manych, 359

— Northern Dvina, 29, 182

— Ob', 29, 215

— Oka, 630

— Olyntorskaya, 818

— Ozernaya, 810

— Pechora, 215

— Samur, 358, 632

— Sefdrud, 632

— Sheksna, 579

— Shirshov, 818

— Sulak, 632

— Syr-Darya, 366, 367, 650, 659, 666,

668

— Terek, 632

— Ufa, 632

— Ural, 561, 596, 597, 632, 671

— Uzboi, 364

— Volga, 358, 366, 549, 596, 597, 630, 632

— Voronezh, 370

— Weser, 313

— Yana, 29, 255

— Yenisey, 29,215
river deltas, 632

— mouth, 54, 596

roach, 501, 520, 524, 525, 629

rorqual, 742

rotation, anticyclonic, 820, 821

— cyclonic, 821
rotatoria, 347

rotifera, 294, 297, 348, 488, 594, 597, 659

rudd, 669

Riigen Island — see island

Rugozerski Gulf — see gulf

Rumania, 413

Rupinovskaya branch, 176

Rybachy peninsula — see peninsula

Rybnoye lake — see lake

Sadko expedition/vessel, 48
sagitta, 441
saira, 740

salinity, 39, 54, 57, 66, 146, 277, 344, 354,
385,388,431,471,551

— of Aral Sea, 647, 651, 659
Azov Sea, 471

Baltic Sea, 277-81, 291, 305

Black Sea, 385-6

bottom, 82, 285

Caspian Sea, 550-3, 616, 644

Chukotsk Sea, 261, 263

deep water, 326

950

SUBJECT INDEX

salinity decreased, 54, 63, 274, 311, 361,
385,400, 561, 580, 616

— of Far Eastern Seas, 697

— increased, 45, 263, 291, 477, 479, 55 1,644

— of Laptev Sea, 261

— lowered, 51, 57, 69, 225

— normal, 59, 353
ocean, 291

• — pulsations, 348

— of surface, 278, 279, 280, 551, 552
Volga, 551

White Sea, 185

salmon, 36, 219, 459, 580, 629, 678, 739,
740, 833

— far eastern, 172

— pink, 759

salps, 91, 93, 237, 403, 446, 704, 705
salts, nutrient, 376, 388, 463, 473

— sulphates, 366, 389, 390, 525, 645
Samsun-Tuapse current, 383
Samur River — see river

sand, 88, 400, 440, 449, 451, 475, 554, 617,
665, 667

— dentalium, 127

— saccocirrus, 439

— silty, 88, 319, 440, 451, 665, 667

— with shell gravel, 441, 504, 617, 666
sand eel, 123, 165, 318,780
sandhopper (amphipod), 582
sapropel, 324

sarda, 427, 459, 463

sardines, 460, 470, 761, 778

Sargassum, 430, 771

Savilov's ecological zonation, 798

scallops, 677

Scandinavia, 27, 68, 311, 344

Scandinavian peninsula — see peninsula

Scombresox saurus, 37

Scotland, 178

sea, Aegean, 362

— Akchagyl, 360, 572

— Aland, 324

— Aral, 353, 361, 365, 366, 611, 647,

675

— Azov, 353, 368-70, 373, 378, 382, 419,

423, 431, 434, 452, 465 (cont.), 477,
577, 583-7, 593, 607, 613, 643, 660

— Bab'e, 213, 214

— Baltic, 216, 217, 445, 474, 579, 607,

610

— Banda, 717

— Barents, 28, 36, 38, 52, 59, 65, 72-104,

172, 239, 267, 458, 558, 579, 586,
675

— Bering, 69, 71, 42, 44, 173, 675, 682,

685, 701, 708, 711, 713, 734, 745,
776

— Black, 41, 360, 362, 368-3, 374-6, 380,

473, 474, 480, 500, 518, 554, 557, 582,
606, 607, 660

— Bolshoye, 651, 656, 666

— Bothnia, 271

— cardium-Syndesmia, 495

— Caspian, 360, 367, 371, 458, 539, 646,

668

— Chokraksky, 358

— Chukotsk, 28, 43, 48, 50, 52, 708, 818,

820, 829

— Coral, 711

— Crown Prince Gustav, 71

— Greenland, 27, 30, 33, 48, 59, 63, 76, 80
jce Lake 340

— Japan, 60, 63, 71, 675, 682, 686, 687,

701, 708, 745

— Kara, 28, 33, 36, 38, 39, 40, 43, 59, 215,

220-3, 579, 586

— Karagant, 358, 361, 363

— Laptev, 28, 33, 39, 40, 41, 43, 59, 246,

259

— Littorina, 288, 291, 343, 344

— Macoma, 344

— Maloe, 649, 651, 665, 666

— Marmora, 361, 362, 375, 380-1, 383,

436,447, 518

— Mediterranean, 361, 362, 374, 378, 380,

427, 433-6, 445, 480, 571 , 606, 607, 627

— Mollusc, 495

— Namuro, 711

— North, 60, 71, 112, 291, 300-6, 341, 417

— Norwegian, 59, 63, 80

— Okhotsk, 60, 76, 675, 682, 683, 684, 685,

701, 708, 711, 713, 724, 731, 734, 745,
774, 776

— Ostracoda, 499

— Phyllophora, 430, 431

— Pontic, 572

— post-Pliocene, 452

— Quarken, 272, 306, 308

— Sargasso, 430

— Sarmatian, 572

— Tethys, 361

— White, 28, 37, 41-2, 50, 52, 61, 65, 178,

181, 215, 291, 311, 675

— Yellow, 702
sea animals, 158

— beds, 191

— dab, 159

— gulls, 37, 172, 644, 745, 776
black-tailed, 744

grass, 439

sea horses, 535

— lettuce, 439

— level, 541

— lilies, 436

— lion, 742

— otter, 742

seal, 218, 219, 355, 372, 573, 677, 709

— bearded, 219

— eared, 742

— ribbon, 742

— ringed, 742

— occurrence of, 339
Seas, Arctic, 27, 46, 579

— bordering, 45, 50

— brackish-water, 62

— East Siberian, 28, 40, 42, 259, 263

— Far Eastern, 198, 643,675, 681, 685, 702,

730, 738, 744

— northern, 42

— open, 28

SUBJECT INDEX

951

Seas, Siberian, 39, 50, 60, 267
seasonal changes of zooplankton, chemi-
cal composition, 764
seasons, biological, in plankton, 50, 52, 258
sediments, 87, 398-401

— Akchagyl, 358

— deep-water, 398

— miocene, 401

— moraine, 182

— oligocene, 401

— shallow-water, 392

Sedov expedition/vessel, 34, 35

Seliger lake — see lake

sestonophages, 131, 132, 730, 731, 798,

800,801,802,808
Sevastopol, 445
Seven Islands, 115
Severnaya Zemlya, 28, 46, 47, 220, 225,

260
sexual maturity, 637
shallows, 27, 61,78, 675

— Barents Sea Central, 41

— Bear Island, 140, 147

— Behring Sea, 675

— Central, 139

— Kanin, 149

— Kanin-Kolguev-Pechora, 135

— Murman, 78, 168

— Norwegian, 174

— Novosibirsk, 60

— Novozemelsk, 139, 147

— Spitzbergen 40, 139, 147
shark, 37, 38, 159, 779

— hammer-head, 778
Shekshna, 580
shelf, 675

shell-gravel, 400, 440, 441-4, 451, 661

— mussel, 444
Shirokaya inlet — see inlet
shoal, Eisk, 480

— Krivaya, 480

shoaling of Caspian Sea, 541, 542, 544
shoaling, fish, 36
Shokal'sky strait — see strait
shrimps, 447, 578
silica, 87, 398, 685
silicilic acid, 474, 475, 560, 657
silicon, 398, 474, 556, 558, 699
silting, 127

silts, 87, 88, 451, 555, 618, 650, 661, 666,
667

— black, 400, 606, 649, 657, 661, 666

— calciferous, 400

— clayey, 88, 93, 229, 261, 457, 506, 649,

650, 666, 667

— cliff, 786

— diatomaceous ooze, 820

— grey, 400, 649, 661, 665, 666

— hydrogen sulphide, 608, 618, 649, 660,

661, 666

— mussel, 150, 220, 323, 400, 445, 449, 450

— ostracod, 449, 475

— phaseolin, 400, 445, 446, 450

— sandy, 87, 261, 441, 451, 649, 665, 666,

667

sinking down, of littoral fauna, 134, 293

— — and rising of Barents Sea bottom,

178

of Fenno-Scandia, 178

siphonophora, 38, 91, 236, 373, 403, 436,

446
sipunculids, 72, 141, 165
Sivash, 466, 470, 528-37
size, of Aral Sea, 648

Azov Sea, 466

Baltic Sea, 271

Barents Sea, 76

Bering Sea, 675, 818

Black Sea, 382

Caspian Sea, 539

Chukotsk Sea, 261

fish, 377, 378

Japan Sea, 750

Laptev Sea, 255

Okhotsk Sea, 675, 783

organisms, 724

decrease, 309, 330

Polar Ocean, 29

White Sea, 181

Skaggerak, 38, 91, 280, 306, 309, 314, 433
slopes, of continental shelf, 60
sodium, 366, 551,645, 652
soils, 191, 229, 230, 261, 475, 531, 540,

649, 665

— bottom, 787

— brown mud, 71, 88, 173, 217, 220, 229,

248, 249, 650, 666

— cartilaginous, finely, 138

— chemical composition, 87

— coarse-grained, 399, 533, 541, 551, 649

— hard, 261, 504, 614, 617, 786

— rock, 111, 191, 607, 608, 768, 786

— sandy, 90, 274, 267, 323, 393, 400, 415,

454, 499, 617, 665, 684, 771, 772, 774,
786, 820

— shell-gravel, 399, 451, 475, 499, 506,

607, 617, 666

— silica-porifera, 145

— silty (muds), 210, 267, 323, 499, 506,

554, 617, 665, 774, 812

— soft, 114, 142, 145, 191, 274, 399, 446,

608, 616, 617, 666, 709, 812
soil-swallowing forms, 801, 807
solonetz, 452, 453
Solovetskiye Islands — see islands
Sosnovets Island — see island
South America, 582

Southern Caspian, 539, 546, 548, 557, 558,
575, 587, 594, 600, 601, 603, 612, 623,
629, 630

spawnings, 36, 162, 435, 521, 630-3

species, Arctic-boreal, 53

— circumpolar, 53

— epicontinental, 53

— formation, 57, 571

— found below 2,000 m., 792
Elasipoda, 736

Focoropulata, 727

Phanerozonia, 727

spiders, 202

952

SUBJECT INDEX

Spitzbergen, 28, 37, 44, 47, 66, 69, 76, 82,
112, 123, 153, 172, 215, 263

sprat, 349, 427, 460, 463, 644

sprattus phalericus, 633

spring, biological. 51, 258

stagnation of water, 388

standards of food consumption, 462

starfish, 36, 114, 128, 135, 143, 145, 156,
249,436, 709, 721, 722

starred sturgeon, 575, 636, 639, 644, 662

station, biological, Belomorskaya of Mos-
cow University, 181

Karelian Associated Branch Ac. Sc,

181

Karadag Ukrainian Academy of

Science, 382

Murman, 74, 123, 124, 180

Northern Scientific Industrial, 75

Novorossiysk Rostov University,

382

Pacific Scientific Industrial, 678

Petrozavodsk University in Gridin,

181

St. Petersburg Natural History

Society, 74

Sevastopol, 74, 381, 382

Solovetsk islands, 180, 741

White Sea, 180

— fisheries, Aral, 647

Azov-Black Sea, 382

Astrakhan, 539

Baku, 539

Black Sea, 458, 462

Don-Kuban, 466

Georgia, 382

— Hydrometeorological in Piryu Gulf, 180
stenodus leucicthus nelma, 253
stenohalinity, 348

stenothermy, 64

sterlet 629

stickleback, 427, 535, 658, 671

Strait, Aleutian, 688

— belt — see belts

— Bering, 27, 261, 266, 682, 818

— Boussole, 682, 786

— Dardanelles, 362, 368

— Davis, 34, 36
-De Lon261,g, 263

— Genichesk, 478

— Gibraltar, 375

— Humboldt, 579

— Kaidak, 551, 594, 598, 644

— Kamchatka, 682, 818

— Kattegat, 60, 208, 306, 308, 309, 314,

345

— Kerch, 382, 385, 387, 460, 494, 466

— Korea, 682, 688, 755

— Kruzenshtern, 682, 783

— Kuril, 688, 786, 805, 810

— La-Perouse, 777, 761, 797

— Manych, 369

— Matochkin, Shar 38, 123, 133, 134, 224,

253

— Mertvyi Kultuk, 577, 594, 595, 644

— Nevel, 682

— North Kuril, 688

— Sangara, 682, 687, 688, 711

— Shokal'skiy, 223, 247, 248, 306, 309

— Skagerrak, 60, 280, 306, 314

— Taganrog, 314

— Tartary, 697, 711, 746, 756, 776, 777,

779

— Tonkiy, 528

— Velikaya Salma, 207

— Vilkitsky, 223, 247, 248

— Yugor Shar, 25, 240
stratification of waters, 30, 217, 617
saline, 326, 354, 473, 475

■ summer, 217

thermal, 70, 354, 475

vertical, 388, 698

striped mullet, 521
Stockholm, 308
structure of biocoenoses, 38
struggle for food, 504

oxygen, 504

site, 504

sturgeon, 501, 506, 520, 635, 644

— Aral, 611, 663
Sturfjord, 136, 154,215

sublittoral, 39, 53, 123-33, 142, 217, 311
sub-regional, abyssal, 65

— high Arctic, 51, 54, 65, 72, 174, 241, 746

— low Arctic, 51, 65, 174, 241, 746

— Mediterranean-Lusitanian, 379
substances, allochthonous, 555

— autochthonous, 431

— nutritive, 50, 297-99, 541, 557, 559, 561,

587, 597, 655
in sea-bed, 89-91

— organic, 327, 400, 460, 531, 555, 656

— organogenic, 475

— terrigenous, 541

sub-zone low oxygen consumption, 559

— nitrate, 558, 560

— nitrite, 558, 560

— photosynthesis, 558, 560, 614

— reduction, 558, 560
succession, 504

suffocation, 473, 475, 508, 530, 533, 554, 618
Sulak River — see river
sulphur, 398, 554, 584

— compounds, 396, 398, 400
summer, biological, 51
supralittoral, 201-3

survival under salinity ranges, 570
suspension, inorganic, 470

— microsestonic, 446

— organic, 476

Svyatoy Nos, 140, 144, 181

Sweden, 291, 337

swordfish (Xiphias gladius), 37, 447

syllids, 441

syndesmya, 374, 501, 504, 506, 514, 524,

623, 625
synthesis of organic matter, 413, 584
Syr-Darya — see river

Taganrog, 470

— Bay — see bay

SUBJECT INDEX

953

Taimyr, 220, 223, 239, 256

Taman' Bay — see bay

Tanganyika, 571

taxonomic isolation of fauna, 736, 737

temperature of bottom waters, 81, 82, 153,

229, 262, 547, 651, 821

column of water, 470, 651

deep waters, 276, 548, 822

freezing point of water, 470

surface waters, 37, 64, 262, 277, 470,

651, 821
waters, 36, 143, 146, 185-8, 223-9,

255, 256, 261-3, 275-7, 387, 470, 510,

546-9, 651, 821
Temryuk, 470

— gulf — see gulf
Terek — see river

— shores, 183
Teriberka — see bight
terraces, coastal, 178
Tethys, 36

theory, Hogbom, 340

— Wegener's, 54
thermopathy, 155
tidal zone, 501
tides, 80, 203
Tiksi — see gulf
Tinea, 629
tintinnoidea, 403
Tonkiy Strait — see strait
Topiatan — see lake

transfer, passive, of animals, 340
transference of water masses, 546
transgression, Baku, 581

— boreal, 178

— Caspian, 581

— glacial, 562

— post-glacial, 361, 573

— Yoldian, 340
transgressions, 54, 687
transition, boreal, 178
transparency of waters, 64, 388, 470
transplantation of herring, 671
trawling hole, 128

— industry, 72, 159
trematodes, 662, 770
trench, Aleutian, 676, 684

— Bougainville, 720, 721

— Idzu-Bonin, 720

— Japanese, 676

— Kermadec, 682, 716, 720

— Kuril-Kamchatka, 676, 682, 684, 695,

699, 706, 711, 718, 720, 721, 722, 723,
724, 729, 730, 731, 732, 734, 783

— Mariana, 682, 716, 720, 721

— Novozemelsky, 149, 215, 243, 246

— Okhotsk, 783

— Philippine, 683, 716, 720

— St. Ann, 246

— Tonga, 682, 716

— Ural, 545, 546, 555, 614, 618
trenches of seas, deep, 40, 60, 63, 78, 255,

260, 261

— Atlantic Ocean, 176

— Barents Sea, 147, 148

— Kara Sea, 222, 246

— Slypsk, 319
Tsymlyansk dam, 469
Tuapse, 383
Tubinares, 745

tuna, 37, 427, 431, 435, 447, 460, 463, 739,

740
turbellarians, 347, 445, 562, 563
Turkestan, 361
Twerminne, 327-30, 332
types of littoral, bionomic, 111
typology of marine water-bodies, 68
Tyub-Karagan Point, 539
Tyuleniy Island — see island

Ufa River — see river
Umba, 210
Ura Bight — see bight
Ural mountains, 572

— river, 614

— trench, 614

urchins, 38, 92, 128, 141, 355, 709, 798
Uzboi, 364

variations, climatic, 218

— of fish diet, 161, 162, 521, 522

seasonal fish diet, 169

phytoplankton, 51

— zooplankton, 51, 423

variety, biotopic, 676

— of population, 676

species, 60

Vayda Gulf — see gulf
vectors, 663
vegetation bed, 797

— bottom, 73

— coastal, 63, 73
Velikiy Island — see island
ventilation of water-masses, 546
Veprevsky Cape — see cape
Veser River — see river

vessel: Audrey Pervozvanny, 75

— Fram, 35

— Galatea, 712, 734

— Krasin, 30

— Litke, 255

— Lomonosov, 222

— Persey, 76

— Pervenetz, 221

— Sadko, 30

— Sedo v, 34, 35

— Sibiryakov, 36

— Taymyr, 223

— Vaigach, 250

— Varna, 221

— Vega, 221

— Vityaz, 679, 680, 713, 717, 734

— Zarya, 222
Victoria Lake — see lake
Vilkitsky Strait — see strait

vobla, 629, 635, 636, 644, 668, 670, 671
volcano, 684
Volga — see river
Volga-Don canal, 527
Voronezh River — see river

954

SUBJECT INDEX

Voronka, White Sea, 139, 182, 188
Voronov Island — see island

walrus, 677, 742

warming of waters, post-glacial, 178

Warnemiinde, 343

water balance, 34, 79, 384

— circulation, anticyclonic, 383, 545
cyclonic, 72, 545

— column, 42

— density, 388

— exchange, 34, 225, 393, 751

— transparency, 388
waters, abyssal, 33

— Antarctic, 713, 735

— Aral Sea, 651, 655

— Arctic, 30, 708

— Atlantic, 28-31, 39, 40, 44, 72, 76, 229,

259, 263, 269

— Azov Sea, 531

— Bering Sea, 241

— boreal, 471, 708

— brackish, 55, 238, 311, 471, 563

— Caspian, 653

— Chukotsk, 261

— coastal, 46

— cold, 228, 675

— continental, 54, 55

— Danish, 144, 155

— deep Arctic, 30

cold, 228

Kara Sea, 228

Pacific Ocean, 700

saline, 39, 64

stagnant, 72

— Faroe Islands, 71, 154, 155

— fresh, 311,471,473

— ice, 362, 581

— Iceland, 37, 71, 144, 155

— intermediate, 40, 44, 45

— less saline, 27, 30, 34, 45, 54, 362, 581

— Kuroshio, 677, 706

— Mediterranean, 352

— melt-, 581

— mesohaline, 345

— mid-Caspian, 545

— Murman, 38, 72

— Norway, 159

— Ob'-Yenisey, 179, 228

— ocean, 651

— oligohaline, 345

— Oregon-Californian, 748

— Oyashio, 677, 688, 706

— Pacific Ocean, 259, 262

— polar, 34

— polyhaline, 345

— river, 31, 362, 651

— Superior, Lake, 652

— surface, 27, 30, 34, 262, 284, 470

— tropical, 708

— Tsushima, 711

— upper layers, 470

— Ural, 617

— Volga, 546,717

— warm, 30, 39, 225, 675, 783

waters, meeting of cold and warm, 70, 675,

676, 810, 812
fresh and saline, 50, 597, 659, 677,

810,812
watershed, 354
Wegener's theory, 54
Weser River — see river
whale, 677, 739, 742, 759
white fish, 189,219,253
White Sea — see sea
Wiese Island — see island
winds, on- and off-shore, 383, 650, 755
winter, biological, 50
wintering, birds 493

— fish, 630, 632
winter shore, 183
world ocean, 54
worm-eaters, 635

worms, 144, 315, 318, 334, 451, 452, 499,
500, 620, 625, 709, 780

— parasitic, 61 1

wrack, algae, 202, 203, 617, 796

— zostera, 435, 607, 663

Yamal, 223, 244, 252
Yana, 29, 255

Yarnyshnaya Bight — see bight
Yaryk-Su, 401
Yaskhan Lake — see lake
Yenisey Gulf — see gulf
Yenisey River — see river
yield, of algae, 782

— biological, 478

— offish, 643,644,646,671,739,782
young cardium, 503

— of the year, 427

mytilaster, 504

young shore ice, 549
youth of fauna, 315
Yugor Shar, 246

Zhiloy Island — see island
zonality of fauna, 612, 713-16, 802

littoral forms, 799

water masses, 558, 715, 824

zonation, zoogeographical, 173, 480, 708,
713, 723, 813

— of fauna, 446-8

zone, abyssal, 681, 713, 714, 818

— accumulation, 558, 559, 614

— Arctic, 174, 676

— bathyal, 681, 713, 715, 746, 810, 818

— bathypelagic, 709, 715

— biogeographical, 758

— black mud, 666

— boreal, 174, 676

— brackish water, 345, 348

— circumpolar, 70

— coastal, 38, 253

— convergence, 704

— delta, 55, 64, 243, 667

— ecological, 798, 804

— enrichment, 560

— euryhaline, 345, 377

— fresh-water, 345

SUBJECT INDEX

955

zone, geosynclinic, 783

— grey mud, 665

— hard ground, 667

— hydrogen sulphide, 398

— impoverishment, 558, 559

— intertidal, 108, 116

— littoral, 66, 114, 116, 204, 266, 713

— marine, 345, 349

— meeting of saline and fresh waters.

597

— mesohalines, 345

— mixed waters, 354, 676, 698, 704

— nitrite, 614

— off-shore, 325, 430

— oxydation, 390-8, 559

— oxydation-reduction, 390, 559

— photosynthesis, 559

— plankton, 597, 598

— pre-polar, 70

— pseudo-abyssal, 123, 211

— red calanus, 102

— reduction, 229, 390, 400, 559, 560

— sand, 665

— seawards, of delta 561

— shallow-water, 63, 253

— shelf, 818

— shell-gravel, 666

— stenohaline, 377

— sub-littoral, 816

— sub-tropical, 705

— surface, 721

— transition, 705

— tropical, 676

— ultra-abyssal, 713-15, 721

— vegetation, 665
zoobenthophages, 669

zoobenthos, 196, 259, 431, 449, 452, 463,
612, 646, 661, 772, 773, 810, 835-8

zooplankton, 43, 50, 93, 96, 100, 232, 238,
243, 264, 303, 402, 646, 647, 706, 729,
758, 759, 761-3

— chemical composition of, 100, 101
zostera, 61, 196, 198, 208, 214, 219, 429,

436, 441, 445, 660, 663, 667, 771

— fields, 441,660, 663, 667
Zuyder Zee, 435

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H. BARNES

OCEANOGRAPHY AND MARINE BIOLOGY

A BOOK OF TECHNIQUES

The sea covers some seven-tenths of the earth's surface. It is not therefore
surprising that practically every science, zoology, chemistry, geology, physics,
etc., contributes to its study and yet many of the problems of technique are
peculiar to oceanography. Dr. Barnes describes comprehensively the ingenious
instruments and the careful methods by which we obtain our knowledge of
the sea. First, he deals with our methods of sampling the living organisms — the
free living plants and animals and those inhabiting the sea-bed. Methods of
taking bottom cores and of using nets, pumps, trawls, dredges and grabs are
all carefully set out. Then follows a section on the properties of the water itself
— temperature, salinity and currents. The older standard instruments are
described and particular attention is given to new techniques — the bathy-
thermograph, for instance.

The early explorers of the seas noticed underwater noise in 1807 — but only
recently has the noise originating from marine animals been investigated. Both
this and its converse — the use of sound waves — are dealt with, the latter including
an account of the construction and working of modern echo-sounders and their
use in biological problems.

The most spectacular of modern developments — underwater photography
and television — he has left for the last section. These techniques which allow
observations to be made on the natural conditions will certainly prove of
increasing importance. Aerial photography has a growing contribution to make
to oceanography and is included here.

Demy 8vo. 355. net

APPARATUS AND METHODS OF
OCEANOGRAPHY

The past few years have seen greatly increased activity in the fields of oceano-
graphy and marine biology. Not only have the personnel and existing institutions
been expanded but new centres of activity have been and still are being set up.
No compilation of the methods and techniques in these fields is available ; they
are scattered throughout the literature. It will be of considerable value to a large
number of people in the new centres of activity and in the older expanding
institutions to have an up-to-date and comprehensive handbook. This book,
which is being sponsored by the Union Geodesique et Geophysique Inter-
nationale, is intended to fill that gap.

It is intended as a working text and reference handbook for departments of
oceanography and marine biology. There are many new institutions with simple
equipment and also many established stations with only relatively limited
facilities; this has been borne in mind in writing the book. The simpler and
better-known methods have therefore been fully explained. Attention is also
drawn to the more complicated and involved methods, the use of which will
lead to more rapid progress.

Volume I consists of chemical methods and the author has had experience of
many of those described. In addition, critical comments have been included
from the leading specialists in this field in Europe and America.

Demy 8vo. Illustrated. 35s. net

OCEANOGRAPHY AND MARINE BIOLOGY

AN ANNUAL REVIEW

Edited by н. barnes

The very considerable increase in oceanographical and marine biological work
calls for a publication summarizing the results. The present series has the
following objects — to consider annually basic aspects of marine research return-
ing to each in future volumes at appropriate intervals, to deal with subjects of
special and topical importance, and to add new ones as they arise. Each article
endeavours to cover completely the literature. Physical, chemical, and biological
aspects of marine science are dealt with by experts still actively engaged in their
own field.

Volume 1 contains sixteen reviews ; the contents of Volume 2 are announced
at the same time and Volume 3 is currently being organized.

The series will become an essential reference text for research workers and
students and should find a place not only in the libraries of marine stations,
fisheries institutes, and the like, but also in those of universities and other
academic institutions.

Royal 8vo. About 40s. net

GALATHEA'S DEEP SEA EXPEDITION

1950-1952

Edited by dr. a. f. brunn, s. greve,

H. MIELCHE and DR. R. SPARCK

Translated by Reginald spinks

The sea covers three-quarters of the earth's surface reaching at the deepest
known point some 35,000 feet. Yet so far only four marine-biological world
expeditions have set out to study systematically oceanic fauna. The last expedi-
tion, that of the Danish Galathea, was made during 1950-52, and proved most
successful; partly because of the modern equipment, ship's radar and echo-
sounder, all well adapted for deep-sea research.

The very valuable work and results of this expedition are recorded here by
the scientists themselves. After a brief account of the background, origin and
objects of the expedition, there are chapters on the technique of deep-sea
research — the problems of trawling, echo-sounds, measuring the productivity
of the sea and animal density. Then follow chapters of absorbing interest,
dealing with he animal life found in the oceans. The Galathea sailed right
round the world and the editors have included descriptions of some of the
places visited — the Seychelles, islands of the giant palms ; the Nicobars ; Rennell,
an out-of-the-way coral island; and Campbell Island, home of elephant seals
and albatrosses.

Deep-sea research is a costly science and expeditions rare. The scientists on
the Galathea have made a very fine contribution to the study of the Seven Seas
and what they contain. The fascinating illustrations add to the interest and
value of this excellent account.

Small Royal 8vo. Profusely illustrated. 42s. net

ASTRONOMY FOR ALL

Entirely New Edition prepared under the direction of

Gabrielle Camille Flammarion and Andre Danjon

Translated from the French by Annabel and Bernard Paget

CAMILLE FLAMMARION

This great classic has now been completely recast and brought up to date by a
group of French astronomers led by Andre Danjon, Director of Paris Observa-
tory. While preserving the readable, pithy style of Camille Flammarion, and
avoiding mathematics completely, the book describes the discoveries of both
classical and modern astronomy in considerable detail — it gives a complete
picture of the vast and fascinating universe revealed by modern science and of
our small planet travelling in space.

Even the completely uninitiated reader is guided quite painlessly through the
eleven separate motions of the Earth in space ; the way time is kept ; the theory
of tides ; calculating the age of the Earth ; the motion and physical characteristics
of the Moon, planets and comets ; eclipses, the interior as well as the surface
layers of the Sun and its activity ; the properties of stars and their motion round
the centre of the Galaxy; star clusters; interstellar dust and gas; extragalactic
nebulae ; radio astronomy, and the construction and use of astronomical tele-
scopes, both large and small. Rockets and other space vehicles are fully dis-
cussed, together with the latest information they have revealed.

The coverage is complete, but the Flammarion-Danjon work is more than
an able popularization ; it is a classic with a tone and flavour of its own, and is
lavishly provided with exceptionally beautiful illustrations. If Camille Flam-
marion was one of the most celebrated pioneers of popular scientific writing
Andre Danjon is famous for many discoveries and inventions (including that
of the 'Impersonal Prism Astrolabe', at present probably the best instrument
for .determining the positions of stars on the celestial sphere). Dr. Bernard Pagel
is on the staff of the Astronomer Royal at Herstmonceux.

lOf X 8i inches. 917 plates. 2 coloured planispheres. 75s. net

THE WORLD OF MATHEMATICS

JAMES R. NEWMAN

This four-volume work presents the most extensive collection ever published for
layman and expert, of the great literature of mathematics from the Rhind
Papyrus of Egypt to Einstein's theories. With its publication, a magnificent
selection of writings by the world's foremost mathematicians is for the first time
presented as a unified library within the reach of the general reader.

From Archimedes on Poppies and the Universe to Lewis Carroll's Logical
Nonsense, from Rene Descartes' The Geometry to Lewis Fry Richardson's
The Statistics of Deadly Quarrels, from the early search for an accurate clock to
the latest attempts to chart infinity — here are more than 2,500 pages of selections
from a literature unparalleled for lucidity and imaginative splendour.

Small Royal Svo. 4 vols. Cloth 11. 7s.
Paper £4. 4s.

THE COLLECTED PAPERS OF LORD
RUTHERFORD OF NELSON, O.M., F.R.S.

VOLUME II

SIR JAMES CHADWICK, F.R.S.

Volume II takes the story into his Manchester period, during his time as
Professor of Physics, from 1907 to 1919. Here one of his main interests was the
atomic nucleus and the a particle. All aspects of his work in this field, which
was a lifelong preoccupation for him, are covered. There are papers he wrote
with Geiger, concerned with the method for mounting a particles, studies which
Geiger pursued further on his own. Other papers deal with the action of the
particles on different substances, the probability variations in their distribution,
the effects of their collision with light atoms.

Interrelated with this there is his research into the nature of the radioactive
elements, covering a great amount of work on the analysis of their decomposition
products and the radiation they emit.

This volume, like the first one, is a rich source for those who would wish to
follow the workings of a rare and lucid intellect. Like Volume I it is worthily
produced and illustrated with contemporary photographs and reproductions of
Rutherford's apparatus.

Small Royal 8vo. 512 pages. About 1055. net

THE COLLECTED PAPERS OF LORD
RUTHERFORD OF NELSON, O.M., F.R.S.

VOLUME I

'. . . this splendid monument to his scientific work. The publishers are also to
be complimented on the excellent production of this first volume. Succeeding
volumes will be awaited with the greatest interest.' — The Times Literary Supple-
ment.

'. . . admirably produced book. . . . Taken together, the four volumes should
provide young scientists with an almost matchless opportunity to follow the
developing ideas of a great experimental genius. ... no reader can fail to be
impressed by the vigour and directness of Rutherford's mind.' — Daily Telegraph.

\ . . provides a unique opportunity to study the evolution of a major scientist
and, at the same time, the evolution of a new branch of science.' — Time and Tide.

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