129 166
R. E. Coker
This great and wide
An Introduction tc
Oceanography and
Marine Biology
HARPER TOKCHBOOKS / The Science Library
HARPER & BROTHERS, NEW YORK
THIS GREAT AND WIDE SEA
Copyright 1947, 1949, 1954 by The University of North Carolina Press
Printed %n the United States of America
This book was originally published in 1947 by The University
of North Carolina Press, and is reprinted by arrangement.
First HARPER TORCHBOOK edition published 1962
IN UNDERTAKING TO DEAL WITH SO BROAD A SUBJECT AS THE SEAS IN
their physical, dynamic, and biological aspects, and to do this
in a single small volume, I realize only too well the difficulties
and the dangers. Yet three general purposes have urged me to the
task. First, and of least general significance, is the fact that, as a
teacher of biology, and of aquatic biology particularly, I have per-
sonally felt the need for a relatively brief, comprehensive, and not
too technical presentation of some of the basic phenomena of the
ocean as a place of life for plants and animals. For an even elemen-
tary understanding of the relations of temperature, light, gases, cir-
culation, and marine life, it was necessary to delve into many au-
thoritative treatises, some of which were not easily read, even so far
as one not highly trained in mathematics and physics could read
them at all. The results of a great deal of effort are here put into
print in the hope that others of like need may profit with less ex-
penditure of labor.
A second general motive was based on the belief that a more wide-
spread "sea-consciousness" must prevail in the future. There may
well be persons not specializing in the sciences who want to know
more about the seas over which so many will voyage by sea-ship or
by airship. It may be interesting to them it may even, on occasion,
be useful to them to understand a little of the conditions under-
lying some of the surprisingly anomalous states of temperature,
water-movement, and organic life so frequently encountered here
and there about the world. It is presumed, too, that there are those
V
vi Preface
who, out of mere intellectual curiosity, will want to gain a better
picture of that major portion of the earth's surface which is occu-
pied by salt water.
Finally, in respect to motivation, let it be said that, although the
book has, of necessity, its eclectic features, it is definitely not in-
tended to be a mere compilation of interesting facts about the seas.
The broader underlying and directive purpose may or may not have
been accomplished in some small measure. Personally, I have been
impressed with the unity of the seas; they form a single dynamic
mechanism, world-wide in operation and in influence. Yet it is not
an independent mechanism; on the contrary, it is obviously and
measurably affected by outside forces, particularly by the rotation
of the earth and by the celestial movements of sun and moon. It is
influenced also by direct income and outgo of radiant solar energy.
Furthermore, there are vital interchanges of energy between sea and
atmosphere and land: through radiation, through vapor formation,
along with its distribution and condensation, through the indirect
effects of geological processes, and through photosynthesis and other
biological phenomena. Perhaps this may sound complex and for-
bidding in the reading at this stage; there is the hope, however, that
it will seem to work out more simply as one passes from topic to
topic in the following pages. We may even need sometimes to guard
against thinking it all simpler and more fully comprehensible than
it is.
A very large volume would be necessary to do full justice to the
general idea, which, of course, is not new; yet either voluminous-
ness or a high degree of technicality in the presentation would de-
feat the major purpose. The justification for a small and non-
technical volume, if it has one, rests on the effort to assemble data
from many areas of oceanographic study, put them in as simple
terms as possible, and point out a good many of the linkages. Con-
nections between physical conditions and interrelations of biologi-
cal and physical phenomena will be emphasized. Obviously, repe-
titions are necessary; it is hoped that there may not seem to be ex-
cessive reiteration. The book attempts to enable the reader with
little or no technical training to grasp a good many of the inter-
relations. Certainly, the ordinary person does not want to give a life-
time to the study of the sea; but he may like to follow for at least a
few hours a short path leading to a point of vision of the sea as a
Preface vii
whole a point from which a glimpse may be had of physical,
chemical, dynamic, and biological phenomena as completely inter-
related. The relations are intricate, to be sure; let us not underrate
their complexity. Yet even to those who are barely initiated, the
general character of the relations can be grasped to an extent that
brings a definite measure of intellectual satisfaction.
The materials assembled and correlated in this volume have been
derived in small part from personal experience, in far greater part
from books and papers too numerous to mention. A selected bibli-
ography on page 301 to 303 lists a few publications to which the
writer is more particularly indebted, besides some popular or semi-
popular works that should be of interest to the general reader.
Sources to which only an occasional reference is made are cited in
footnotes. No apology need be offered for a fairly free use of quo-
tations. Direct quotations from writers of special experience and
knowledge may sometimes be reassuring to the reader who must
realize that no one can have full grasp of the whole field of oceanog-
raphy. Explicit credit is given for a good many unquoted state-
ments; but it may well be assumed that in such a work, unless the
whole text were littered with citations, the "debits" for facts and
ideas must greatly exceed the "credits" by acknowledgement.
A dozen friends have given help by reading chapters of the manu-
script, or the whole, and detecting some errors of fact or form al-
though, doubtless, not all. Professor Thurlow C Nelson of Rutgers
University gave valuable suggestions in connection with the earlier
chapters. These were read also by two graduate students, Misses
Catherine Henley and Carrie Ola Hughes, each of whom was gen-
uinely helpful. Another student, Miss Flossie Martin, contributed
materially to the historical chapters. Dr. Harden F. Taylor, recently
president of the Atlantic Coast Fisheries Company as well as a
competent biologist and technologist, has kindly read the entire
manuscript and offered many valuable criticisms and comments.
Professor W. C. Alice of the University of Chicago has made use-
ful comments in respect to the chapters dealing with marine biology.
I am grateful, indeed, to all of these and to several colleagues in the
University of North Carolina: Professors Karl Fussier, in the De-
partment of Physics, and R. W. Bost, Head of the Department of
Chemistry, have read several of the chapters on physical and chemi-
cal oceanography and have checked some slips; Captain E. E. Haz-
viii Preface
lett, U. S. N., Retired, Professor Samuel Emory of the Department
of Geology and Geography, and Professors C. D. Beers, D. P. Cos-
tello, C. S. Jones, and Nelson Marshall of the Department of Zo-
ology have been good enough to read large parts or all of the
manuscript and have given aid in the detection of errors. The author
alone is responsible for the ideas expressed and for such errors or
defects as remain.
R.E.C.
Page
Preface v
Introduction: Meaning of Oceanography ... 3
Part L HISTORY AND GEOGRAPHY
1. Discovery of the Seas n
2. Be farmings of Oceanography 17
3. Pioneers in Oceanography 19
Edward Forbes, 1815-1854 Matthew Fontaine Maury,
1806-1873 The "Challenger" and Sir Wyville Thomson,
1830-1882 Sir John Murray, 1841-1914 Palumbo and
the Closing Net Victor Hensen, Carl Chun, and the
Prince of Monaco Hans Lohmann and the Centrifuge
Recent European Oceanographic Expeditions Shore
Stations Across the Atlantic
4. Oceanography in America 4
Early American Oceanographic Research Alexander
Agassiz, 1835-1910 The "Albatross," 1882-1924, and
"The Fish Commission" Hydrographic Office, U. S.
Navy United States Coast and Geodetic Survey Re-
cent American Oceanographic Research Oceanography
Contents
Page
5. Sea and Land 57
Some Gross Features of the Ocean Some Interrelations
of the Oceans Continuity and Contrasts Depth and
Topography Interrelations of Sea and Land
Part II. CHEMISTRY AND PHYSICS
6. The Sea as a Solution 77
Chemical Nature of Sea Water Inorganic Substances in
Solution Collection of Samples and Analysis Distribu-
tion of Salinity Effect of Salt on Circulation Organic
Substances in Solution and Their Distribution Gases in
Solution Utilization of Materials in Solution
7. Some Physical Properties of Sea Water ... 94
Temperature How Temperature in the Deep is Taken
Temperature and Life in the Sea Viscosity Influence
of Viscosity on Organisms in the Sea Density Pressure
^ Deposits at the Bottom of the Sea . . . . 112
9. Sea Water m Motion: General Plans of Circulation . 1 20
Broad Features of Circulation and Methods of Observa-
tionThe Atlantic Ocean The Pacific Ocean The In-
dian Ocean The Antarctic Ocean The Arctic Ocean
Conclusion
0. Sea Water in Motion: Water Moved by the Winds . 138
Horizontal Currents Upwelling Waves
1. Sea Water in Motion: Tides and Other Movements . 146
The Tide Internal Waves "Tidal Waves" Biological
Relations of Waves, Tides, and Upwelling
2. The Sea and the Sun 160
The Sea a Dynamic Body The Sea as a Reservoir of
Heat How the Seas are Warmed and Cooled The
Penetration of Radiation
Contents xi
Page
Part HL LIFE IN THE SEA
13. Life in the Seas: General Conditions ... 177
Modes of Living and Habitats Some Relations to
Physical Conditions No Hiding Place Metabolism of
the Sea Summary
14. Pasturage of the Sea 197
Premium on Simplicity Kinds of Plants Summary
15. Drifting Life: The Plankton 208
Universality of Plankton Conditions Governing Distri-
bution by Regions and by Depth
1 6. Composition of the Plankton 219
Protozoa Sponges (Porif era) Coelenterata Comb
Jellies (Ctenophora) Flatworms (Platyhelminthes)
Round Worms (Nemathelminthes) Moss Animalicules
(Bryozoa) Brachiopoda Arrow-worms (Chaetog-
natha) Segmented Worms (Annelida) Echinodermata
Mollusca Arthropoda Summary for Chapters 15
and 16
17. Life on the Bottom: The Benthos .... 240
Stationary Life: The Edreobenthos Life near the
Shores: The Littoral Deep-Sea Life: Benthic How the
Bottom Fauna is Taken Benthonic Animals Useful to
Man Summary
1 8. Life at Large: The Nekton 255
Barriers to Distribution Zones of Life Kinds of Fishes
Useful Fishes Capture of Fish in the Depths Sum-
mary
19. More About Life at Large: The Nekton . . . 281
Some Features of the Natural History of Fishes Mol-
lusks: The Squid Some Lower Vertebrates Sea Fowl
Sea Otters, Sea Lions, and Sea Cows The Whales-
Summary
Selected Bibliography 301
Index 305
Figures
pt
1 Map of the world, showing all oceans ... 58
2 Map of northern and southern hemispheres . . 64
3 Distribution of the deeps 66
4 Map showing location of canyons and principal furrows
off the Mid-Atlantic states 68
5 Map of the Hudson canyon and vicinity ... 68
6 Schematic representation of the Continental Shelf, Edge,
and Slope 72
7 Schematic representation of the distribution of tempera-
tures by depth and latitude 97
8 The pelagic oozes 116
9 Ocean currents 121
10 Diagram showing the plan of the standard automatic
tide gage *47
1 1 Varieties of pelagic sargassum 200
12 A Dinoflagellate 203
13 Coccolithophores 204
14 The protozoan, Globigerina btdloides D'Orbigny . 220
15 Free-swimming pteropod mollusks . . . . 226
16 Giant ostracod "9
17 Copepods 2 3 X
mi
xiv Illustrations
Page
1 8 Old-type Blake trawl 249
19 Sea Robin 268
20 Bat fish 270
21 Oceanic fishes 271
22 Diagram of a purse seine 275
23 Diagram of steam-trawler with otter trawl . . 278
Plates
Between pages 30-31
1 Woods Hole Oceanographic Institution
2 Scnpps Institution of Oceanography
3 The research vessel ARGO
4 U.S. Fish and Wildlife Service Biological Station, North Carolina
5 ATLANTIS under sail
Between pages 142-143
6 Sandfall
7 Tide-predicting machine
8 Read-out Equipment
9 Standard automatic tide gage
10 Lowering of temperature probe
u Sea-mount
1 2 Nansen bottle
1 3 Six-tone crane for lowering heavy equipment in ocean
14 Underwater camera
15 Lowering chain dredge from research vessel HORIZON
Between pages 222-223
1 6 Clarke quantitative plankton sampler
1 7 Attaching meter net to towing cable for collecting plankton
1 8 Towing plankton net near the surf ace
19 Hauling in quantitative plankton net
20 Heavy catch in plankton net
2 1 Sea Spider, three brittle-stars and various tracks on sea floor
Plates xv
22 Living Coral
2 3 Cleaned skeleton of living coral
24 Plankton: diatoms
25 Plankton: copepod
26 Plankton: dmoglagellate
27 Plankton: radiolarian protozoan
28 Diver examining coral beds
29 Living sponge attached to a shell
30 Cleaned skeleton of sponge
31 Spider crab
32 Isaacs-Kidd midwater trawl
THIS GREAT AND WIDE SEA
The earth is full of Thy riches;
So is this great and wide sea,
Wherein are things creeping innumerable,
There go the ships:
There is that Leviathan,
(Psalm crv)
IN RECENT YEARS, AND ALMOST WITHOUT OUR AWARENESS, THE SEAS
have crept upon us; it might be said, they have crowded upon
us into our consciousness. Always we have known the
oceans were there, but for most of us they were remote. They were
places for recreation bathing, fishing, boating. They were high-
ways for travel and for commerce. They were protective walls about
our homelands, insuring us, we imagined, the opportunity to live
our lives without fear of molestation, though there could be dis-
tant peoples less sensible than we, and less devoted to peaceful and
constructive pursuits.
All the time, of course, but without our thinking much about it,
the seas significantly influenced every individual life; they were
mute but powerful forces acting on the whole structure of human
society. They affected climate and weather; and this was economi-
cally and socially significant. They yielded tasty and commercially
valuable foods, and oils, fertilizers, salt, pearls, and sponges; in so
doing, they often governed movements of populations and develop-
ment of cities. As avenues of trade between peoples of different
continents and islands, they facilitated the world-wide distribution
of a thousand comforts, conveniences, and luxuries, and the profit-
able disposal of farm and factory surpluses. Thus they had great
significance in the lives of all; yet for such as were not actually sea-
farers, there was little need for particular concern about those great
bodies of water. It was enough to know that the seas floated useful
ships, nourished marketable oysters, crabs, and fish, and kept po-
tentially hostile folks away.
4 This Great and Wide Sea
Almost suddenly, our conception of the oceans has undergone
drastic change. If we had thought of them as separating barriers, we
now see them as connecting links between all the continents and
islands. It is not only that the lands have become so interdependent
that whatever happens in one seriously to modify the fortunes of
life there, may quickly affect all others around the globe. The broad
waters are actual links. The protective walls, as we civilians once
saw them, now appear as wide avenues for invasion in either di-
rection. Ready and royal avenues they are too. Spatially, the Japa-
nese made by sea far greater and more rapid advances toward us
and our allies than ever the Germans did by land against France or
Russia. We, when we had regained our strength, proceeded east-
ward and westward at speeds, measured in miles per annum, far
greater over water than over land. This is definitely not a military
disquisition: no longer should a civilian have the temerity to meas-
ure the protective value of seas against thac of hills and valleys;
mentally, however, he notes that, not only for ships, as navy men
have always known, but also for armies and munitions, for planes
and rockets, the seas are not now "set as a bound that they may not
pass over."
In still other ways the seas have lost significance as barriers. They
no longer retard the passage of the spoken word. Every day vocal
language flies through the air, over and beyond the seas, to encircle
the globe with virtual instantaneity of passage. Human bodies are
transported from continent to continent, or even completely around
the world, with a time schedule of mere hours. Furthermore, planes
not only fly above the ocean; they make it their landing field.
Let us not think, either, that die "ships of the air" have no con-
cern with the seas except as something not to be collided with inop-
portunely. Nothing that moves through the air, whether it be over
sea or over land, is even halfway independent of oceanic phe-
nomena. Heat and cold, rains and snows, storms, hurricanes, up-
currents and down-currents all these anywhere may have greater
or less dependence upon the dynamics of die sea. To the air-minded
and who is not so now? one does not need to argue the impor-
tance of meteorology yet, meteorology and oceanography are in-
dissolufaly associated. In short, the seas are no longer what they
were when all rapid transport was by craft floating on water or by
vehicles with wheels demanding a solid substratum for traction.
Introduction $
More than ever, then, the seas have come into our lives in ways
that are appreciable. They are still avenues for pleasure and for
profit, but they are also highways for defensive and offensive lo-
gistics. Much more important for our thought in times of peace is
the fact that the basic conditions of our ordinary lives are governed
to no little extent by what takes place at and beneath the surface of
the sea. If we now begin to see the lands of our globe as "One
World," socially regarded, we might also come to sense more gen-
erally the fact that land and sea and atmosphere are one world.
We might then be interested in some of the facts and the princi-
ples of the relationships between the great components of an inte-
grated physical sphere. The interest has a sounder basis because the
integration does not stop with the physical or material structure. In
many ways, both simple and complex, die interrelations of sea, land,
and atmosphere have intimate ties with the world of organisms of
land and water; and they have impacts upon the economic and social
life of man.
WHAT IS OCEANOGRAPHY?
As the study of the sea in all its aspects, oceanography is not a
science in itself but is rather a correlation of various sciences
geographical, geological, physical, chemical, and biological, along
with some astronomy and with mathematics unlimited. The pursuit
and the correlation of such diversified studies are directed toward
learning what really goes on in a continuous, but varied, circulating,
and turbulent medium which covers some three-fourths of the
earth's surface. To some, oceanography embraces the physical
studies, leaving the biological phenomena involved to the special
field of hydrobiology. Others would make the former term more
inclusive and subdivide oceanography into hydrobiology and hy-
drography; yet the latter term seems inadequate to cover the neces-
sary geographical, physical, and chemical features. Why not just
say oceanography and distinguish, when necessary, its biological
and physical approaches? Everywhere it is becoming more difficult
to draw sharp lines between the different standard divisions of the
natural sciences, such as between chemistry and physics, between
biology and chemistry, or between biology and geology. If this
statement has validity in the broad field of science, it is particularly
true in respect to the oceans. Hardly any phenomenon of the sea is
6 This Great and Wide Sea
capable of satisfactory analysis without coordination of all the
fundamental natural sciences.
The geologist is concerned with topography and sediments; but
the sediments may be largely biological products, and topography
partly the effect of biological phenomena (coral islands, for ex-
ample) ; the nature of the bottom materials is governed in great part,
too, by physical and chemical phenomena. Physical and chemical
conditions are certainly dependent upon geological history and for-
mations. They depend also upon meteorological conditions; on the
other hand, the meteorologist cannot escape the consideration of
oceanographical and geological phenomena. Biological patterns in
the sea derive to a great extent from geographical, chemical, and
physical conditions, and these patterns contribute to an under-
standing of physical conditions as expressed in currents and drifts.
These are only suggestions of the close interlocking of the several
fields of science in the one great pattern presented to the ocean-
ographer. For our purpose it will suffice to regard oceanography as
the study of the sea in all of its aspects.
What has activated the study of the oceans? Perhaps the prob-
lems of navigation first played a leading part in directing ocean-
ographical studies, when it became apparent that knowledge of cur-
rents and drifts could shorten periods of sailing between ports, and
make navigation safer through facilitating avoidance of areas of
storm, calms, or icebergs. Certainly it required no special acumen to
recognize the practical value of accurate knowledge of depths and
shoals, reefs and rocks, in continental regions. Fairly recently
(1912) the tragic loss of the "Titanic," after collision with an ice-
berg, and the drowning of hundreds of its passengers and crew, led
to the establishment of the International Ice Patrol, with its pro-
gram of cooperative research, conducted in the North Atlantic
under the immediate direction of the U.S. Coast Guard. Problems
of empire, of naval efficiency, and of success in international wars
have come into the picture in various ways. The oceans loom large
in the visions of those who specialize in geopolitics.
A second and cogent motive for the study of the sea was afforded
by the needs of the fisheries, particularly in the northeast Atlantic
region, around Norway, in the North Sea, about the British Isles and
off the northeast coast of America. Centers of population have been
determined by the distribution of herring and other commercial
Introduction 7
fishes, the distribution of these fishes governed by populations of
copepods and other small organisms, and the distribution of the
microscopic life controlled, in turn, by currents and other physical
phenomena in the sea; hence, the inevitably close link between
oceanography and fisheries science.
Some of the most productive of the cruises in exploration of the
oceans have had as primary objectives the study of the biology of
the sea or other purely scientific objectives. Again, very significant
contributions to knowledge of the ocean have been made in con-
nection with the study of terrestrial magnetism by the Carnegie In-
stitution of Washington.
Often the possibility of contribution to a scientific understanding
of oceanographic phenomena has been regarded as secondary to
more practical basic purposes. A sentence from the intructions to
Lieutenant Wilkes commanding the United States Exploring Ex-
pedition, 1838-41, is illustrative. "Although the primary object of
the Expedition is the promotion of the great interests of commerce
and navigation, yet you will take all occasions, not incompatible
with the great purposes of your undertaking, to extend the bounds
of science and to promote the acquisition of knowledge." 1
Certainly there are oceanographic institutions and there have
been oceanic cruises whose first emphasis and "great purposes" are,
or were, the study of physical and biological oceanography in its
purely scientific aspects. Nevertheless, the financial support for such
expensive operations and they are always costly is generally
based on some faith that ultimately there will be substantial benefits
to navigation and commerce, to national safety or to empire.
i. Max Meisel, Bibliography of American Natural History. The Pioneer Century,
1769-186;, II, 652.
I
HISTORY AND GEOGRAPHY
CHAPTER i
Discovery of the Seas 2
EARLY MAN COULD NOT HAVE CONCEIVED, EVEN APPROXIMATELY,
of the oceans as we know them today. Lacking means and
implements for extended navigation, an individual or a com-
munity could see only a small part of the total area of sea or land.
As long as there were not effective means of communication, what
litde knowledge was gained in different coastal communities could
not be interchanged for synthesis and analysis, even if such habits of
mind had prevailed. Furthermore, most people of the ancient world
left no record of what they saw or knew. It happens, then, that our
knowledge of early concepts of world geography derives chiefly
from the Greeks and the Egyptians; we may well be impressed with
the capacity of the cultivated human mind of ancient times, armed
only with skill in mathematics and with curiosity concerning the
movements of visible celestial bodies, to picture the whole earth
even as little wrongly as they did (p. 13, below).
In the time of Homer, about 1000 B.C., the world was considered
to be a relatively flat disk of land around a part of the Mediterranean,
with some islands. An early concept, attributed to the Babylonians,
pictured an area of land surrounded by a broad ocean which in turn
was encircled by the Dawn. Even the early naturalistic observers
had some belief in the great breadth, endurance, and dominance of
the waters. An ancient poet and philosopher, one of whose writings
became a part of the Psalms of David and was considered by the
i. With substantial acknowledgements to Manner, The Sea; Herdman, Founders
of Oceanography; Murray and Hjoir, The Depths of the Ocean; and other
sources.
II
/ 2 This Great and Wide Sea
great naturalist Humboldt to be the finest poem of nature ever writ-
ten, pictured the earth as securely anchored in the sea: the waters
had even covered the whole earth but had been forced by an Al-
mighty power to recede from the lands and to remain at the boun-
daries fixed for them. 2
Going back to the Greeks, the poetry of Hesiod, ten centuries
B.C., contains references to lands out in the oceans, the Isles of the
Blessed, the Hesperides, and others. Pkto, in the fourth and third
centuries B.C., gives us the story of the great island of Atlantis, pre-
sumed to have been located in the Atlantic Ocean. The Greeks are
supposed to have learned of Atlantis 150 years earlier and to have
received through an Egyptian priest records dating back for nine
millennia. By their own prowess in batde, according to the story,
the Greeks saved European civilization from the might of the rulers
of Atlantis, which a great earthquake subsequently destroyed in a
day and night. It vanished beneath the sea, we are told, but the ques-
tions of its actual or fictitious existence, its location and the causes
of its disappearance lie in the field of speculation or imagination and
may always rest there.
The Atlantic Ocean was undoubtedly known to many early
mariners who voyaged some distance out from the Mediterranean to
reach England, probably Ireland, and possibly the Canaries. The
Phoenicians are believed to have sailed far out in the Atlantic and
into the Sargasso Sea, that great area of dark blue, translucent, and
highly saline water, with innumerable scattered patches of sea weed
(sargassum or "gulf weed*')? which is surrounded by the north equa-
torial current on the south, by the Gulf Stream on the west and
north, and by the Canaries current on the east and southeast. Herod-
otus tells us also of Phoenician mariners who, starting from the Red
Sea, worked their way around Africa to return through the Straits
of Gibraltar (the Pillars of Hercules) and the Mediterranean.
The conception of the world as a sphere, as improbable as that
idea must always seem to a casual observer, is not recent. No one
2. "Who layeth the beams of his chambers in the waters . . . who laid the
foundations of the earth that it should not be removed forever. Thou coveredst it
with the deep as with a garment: the Waters stood above the mountains. At Thy
rebuke they fled; at the voice of Thy thunder they hasted away. They go up by
the mountains; they go down by the valleys unto the place which Thou hast
founded for them. Thou hast set a bound that they may not pass over; that they
turn not again to cover the earth." Psalm ov.
Discovery of the Seas
had sailed around the globe when the historian Herodotus,
fifth century B.C., summarized knowledge of the earth as a s,
divided, somewhat as we now divide it, into five zones. The n
torrid zone and the outer cold zones were thought to be too ex
in temperature for human habitation.
Pytheas, navigator and geographer, a contemporary of A
der the Great, in the fourth century B.C., voyaged to the I
Isles, determined latitude and longitude, and related the tides
moon.
It is remarkable indeed that, even in the third century B.<
learned Eratosthenes gave the circumference of the earth '<
proximately what we know it to be today, about 25,000 mite
he drew lines for latitude and longitude corresponding in a g<
way to our parallels and meridians, and that he suggested the
bility of sailing around the globe were it not for the vast ext<
the Atlantic Sea. The geographer Strabo, at the beginning c
Christian Era, is said to have measured the depth of the Medi
nean near Sardinia to a depth of 1,000 fathoms, more than a mil
how did he do it? Widely traveled and steeped in the knowlec
Alexandria, Strabo accepted Eratosthenes* idea of the worlc
sphere with a circumference of 25,000 miles and the earlier co
of the five zones; he supposed that the inhabited land extended
one-third the way around the earth, and suggested that there i
be other continents as yet unknown.
In the second century, Ptolemy in Egypt, "last of the cfe
oceanographers," prepared his map of the world, which was
the standard geography for a very long rime. He exaggerated th
and west extent of the inhabited world and accepted a substar
reduced estimate of the circumference of the earth, some i
miles. Perhaps his errors were actually fortunate in that the
couraged the idea of reaching India by a westward voyag
shorter and simpler than it subsequently proved to be.
Unfortunately the early promising trend in understanding o
restrial relations soon went into reverse. The inhabitants of Ei
had to live through a millenium of non-scientific and suppo
scriptural interpretation of world geography by those who rem
ignorant of ancient learning. The earth again became flat i
minds of men who presumed to guide human thought.
Even during the long centuries of relative intellectual darl
14 This Great and Wide Sea
here were daring voyages on the Atlantic, particularly by the Vik-
ngs who discovered Iceland, Greenland, and North America. The
geographical knowledge gained by these bold sea-going tourists had
"datively little significance only because it never came to the atten-
ion of those who were writing the books or making geopolitical
)lans for the countries of Europe. Ancient knowledge, still pre-
:erved by the Arabians, had yet to come back to those who could
engage in great voyages of discovery and who, happily or unhap-
pily, cherished ambitions of empire. Modern knowledge of terres-
rial geography is rooted, then, not in those individually magnificent
voyages of the Vikings, but rather in the revival of the old ideas of
he Greeks and in the world-tours that they prompted. Most notable
)f these geographical expeditions were: the rounding of the Cape
)f Good Hope and return to Portugal by Bartholomeu Diaz in
487, the discovery of America by Columbus in i49z, the voyage of
/asco da Gama around the Cape of Good Hope and all the way to
ndia in 1499, the discovery of the eastern shore of the Pacific by
Jalboa in 1513, the first crossing of the Pacific by Magellan about
5 20-2 1 , and die completion in 1 5 2 2 of the first circumnavigation of
he earth. Magellan, himself, was killed in the Philippines, but Se-
>astian del Cano, commanding the "Victoria," continued westward
o Spain. John Fiske can be charged with little exaggeration in his
characterization (in a school history) of the voyages of Columbus
nd Magellan. That of Columbus was "the most (faring thing that
lad ever been done . . . Columbus was the first to bid good-bye to
he land and steer straight into the trackless ocean in reliance upon
, scientific theory"; "Magellan, in spite of mutiny, scurvy and
tarvation, crossed the vast Pacific in the most astonishing voyage
hat ever was made."
Even up to the present time there have been "astonishing" voy-
ges and travels in exploration of the remote and more difficult areas
>f the surface of the earth. Among such were the voyages in search
f the Northwest Passage by Martin Frobisher, heading westward in
576, '77, and '78, by Davis in 1585, '86, and '87, by Hudson and
toffin in the early part of the next century, by Bering and Cook
lore than a century later, and by Ross, Parry, and Franklin in the
ineteenth century. Presumably, from the records discovered,
ranklin completed the passage, but he never lived to obtain the
Discovery of the Seas
high monetary reward which went to McClure returning to
land after a search for the lost Franklin and his party; McClui
made the Northwest Passage, in 1853, although he had had to
partly over ice. It was only in the present century that the Is
west Passage was actually sailed by Roald Amundsen, starting
Norway in 1903 and arriving at Nome, Alaska, a litde over
years later. Meantime, in 1878-79 Baron Nordenskiold had
pleted the Northeast Passage from Sweden to the Pacific thj
the Bering Sea and Bering Strait.
Efforts of equal or greater daring and hardship were the pol
peditions. Let us mention, at least, those made in search of the 1
Pole: by the Scoresbys, father and son, in, respectively, 1801
1820; by Parry, 1819-25; by the British Markham and the Am(
Greeley fifty years later; by Fridtjof Nansen with "the drift <
Tram" 5 in 1893-96; and, finally, by Peary in voyages between
and 1909. Peary actually reached the North Pole on April 6,
dose approaches to the South Pole came much later; yet Ion
a valuable foundation of knowledge of that part of the earth'
face had been laid with the penetration of the Antarctic regio
circumnavigation of the South Sea by "that truly scientific ns
tor," Captain James Cook, in 1773, through the explorations o
linghausen and Wedell in the first quarter of the nineteenth cei
and of Sir James Ross about 1840, by the United States Exp]
Expedition (Wilkes Expedition, 1838-42), and by the cruise <
"Challenger" in 1874. About the "Challenger" more will b<
later. Of course, the South Pole is on land.
We have also the great voyages and treks of Scott, from 19
Shackleton in and after 1909, and of Roald Amundsen, wl
tained the South Pole on December 14, 1911. Four days mor<
a month after Amundsen had completed the primary quest, G
Scott and four of his party, approaching from another dire
reached the same position to find the markers and notes of Ac
sen. The record of the heroic, but uncompleted return jourr
Scott and his companions and the subsequent discovery of
frozen bodies and their well-kept records is already a classic <
tory. Truly the expeditions of those who sought the "passag
the poles, with the greatest possible display of endurance, exe
courage, and faith, whether they returned alive or perished
i 6 This Great and Wide Sea
effort, rank second to none in the almost superhuman achievements
of man in efforts to complete our knowledge of the globe on which
we live.
For the early mariners and explorers we have mentioned, the sea
served only as a highway. We are now concerned more with those
voyagers whose curiosity led them to look on the sea as in itself an
object of biological and physical study. Of such were many of the
Arctic and Antarctic explorers. To Scoresby, Wilkes, Nansen,
Amundsen, Peary, and Shackleton, we owe much scientific knowl-
edge. Captain Ross employed the dredge to obtain bottom-dwelling
animals in the Antarctic. Particularly notable, and the subject of
later reference, will be some of the studies of Nansen. Quite recently
we have had the extensive explorations in the Antarctic by Captain
Richard Byrd and his expedition, with its great collection of scien-
tific data and of materials for intensive studies by others. Not all the
grist that is brought to the mill of oceanography is ground in a single
day: the published or tabulated data and the specimens taken may be
the subject of thoughtful and meticulous consideration by various
specialists during a considerable period of time.
CHAPTER 2
of
THE TITLE "FOUNDER OF OCEANOGRAPHY" is SOMETIMES G
to Edward Forbes (1815-54), sometimes to our own M
( 1 806-7 3 ) , and sometimes to others. There is no one foui
but many. We have already said that oceanography is not a sci
in itself but rather a system of application of all the sciences
comprehensive and interrelated study of the seas in all their as]
and relationships.
For the beginnings of comprehensive knowledge of condi
within the sea we should perhaps go back to some who ar
thought of as oceanographers in any special sense. William Sc
by, to whom reference has previously been made as an early s<
of the North Pole, made soundings and also dipped "cole
waters in the Greenland Sea to find many diatoms, which se<
to have something to do with the movements of whales. A qu
of a century later, Ehrenberg found skeletons of diatoms and r
larian protozoa, both in the surface water and on the bottom
concluded with Alexander von Humboldt that the whole ses
filled with microscopic life. Neither Scoresby nor Ehrenberg ]
what diatoms were, nor did anyone, until the English bo
Hooker in 1847 recognized diatoms from Antarctic wate
microscopic plants, which he believed to play somewhat the
role in nutrition of animals in the sea as did the green plants oc
for terrestrial animals.
Hooker is said to have been the first to recognize the signifi*
of diatoms in the formation of bottom deposits beneath the
/ 8 This Great and Wide Sea
sea. The Danish naturalist Orstedt found great quantities of a blue-
green microscopic plant (Trichodesmium) giving color to the
waters of warmer regions and playing in the open water community
there a part like to that of the diatoms in colder waters. It is to Tri-
chodesmium erythraeum, actually red, that the color of the Red Ses
is attributed. Lohmann (1912) gives to Ehrenberg, Hooker, anc
Orstedt credit for two fundamental concepts of biological and geo-
logical oceanography: the significance of microscopic plants in the
organic community in the sea, and the notable part played by mi-
nute plants and radiolarian animals in the formation of bottoir
deposits.
The observations and reasoning of Charles Darwin on the voyage
of the "Beagle" (1831-36) deserve passing mention especially foi
his study of the origin of coral islands and reefs.
Strangely enough, early naturalists were generally slow to em-
ploy nets or other mechanical straining devices for exploration oi
the freely drifting organic communities of the sea. Some merely
dipped water to see what was afloat or adrift. Credit has commonly
been given to the great German physiologist and teacher, Johannes
Miiller, for discovering the possibilities in intensive collecting of the
drifting organisms, first by pouring dipped sea water through a net
of fine gauze and then by towing such a net from a moving boat
Actually, Miiller had been anticipated in this technique by Charles
Darwin, Vaughan Thompson, and, doubtless, several others. 1 Mullei
did, however, succeed in imparting to other naturalists generally his
great enthusiasm for the net, which soon revealed virtually a whole
new world of life. The inauguration of the townet as an instrument
for hydrobiology might almost be compared in significance with
the invention of the wheel or of the saU as implements for trans-
portation. Yet for a long time the townet remained chiefly a means
for the discovery of new species or of new stages in the life his-
tories of animals having pelagic eggs or larvae. We shall return
later to a consideration of the broader use of the net in expeditions
of the British "Challenger," the German "National" and "Valdivia/
the American "Albatross," and others.
i. Dr. Robert Gurney of Oxford, England, has kindly given me some early refer-
ences to the use of townets of bunting or muslin.
CHAPTER 3
\Jc
n \cea
noaraL
Edward Forbes, 1815-1854
THE NAMES MENTIONED SO FAR ARE THOSE OF MEN WHO
made observations, discoveries, or inventions forming ai
portant part of the foundation of modern oceanographi
search. They were naturalists, but not oceanographers in the sec
being among the pioneers who engaged in comprehensive st
of the sea as a whole, or of some substantial part of it, with the
pose of integrating oceanic observations and attempting gener;
tions respecting the oceans. Perhaps the real pioneer of ocea
raphy was the short-lived Manx naturalist, Edward Forbes
mixed descent, Scotch, English, and Manx, he had as a chil
markable precocity and as an adult exceptionally comprehe
knowledge, true originality, and notable capacity for achieve!
He is reported to have written at the age of twelve a manus
"Manual of British Natural History in All Its Departments." I
as a medical student in Edinburgh, he was rated an extreme
and he failed to report for his examination. He may have be<
idler as a medical student, but he could never have been inact
a naturalist. He went his own way and that proved to be a uni<
valuable one. He was later to be professor of botany in King's
lege, curator for the Geological Society, and paleontologist c
Geological Survey, all at one time. Still later he was to be appc
to the distinguished Chair of Natural History in the Univi
of Edinburgh (where he had declined to take his examinatic
20 This Great and Wide Sea
He occupied that chair only a few months before his untimely
death. 1
Forbes exerted a profound influence in the fields of botany, geol-
Dgy, zoology, paleontology, and oceanography. He seems to have
been a stimulating teacher, a jovial and witty companion, and a gen-
uine thinker. He was a pioneer in the systematic use of the scientific
dredge in shallow water, and in the study of zones of organic life
in the sea and on land. The dredge as an instrument of scientific col-
lection was not original with him; it had been invented, or modified
from the fishermen's oyster dredges, by Italian investigators about
1750, and modified again by the Dane, O. F. Miiller, about 1799.
Forbes used the dredge freely in waters adjacent to the British Isles
and also in the Aegean Sea where he collected from a depth of 200
fathoms, or about one quarter of a mile. As a result of the work in
die Aegean, he defined eight zones of depth, characterized by dis-
tinctive communities of animals. "About 1850 Forbes prepared his
remarkable map of distribution of marine life over the oceans of the
world, and of homoiozoic belts, which was probably the first at-
tempt to divide the oceans into provinces on scientific grounds." 2
Naturally the early hypotheses about zones were not all supported
by later evidence. We now know that Forbes's belief in a lifeless
deep was quite erroneous. Nevertheless, as Herdman has remarked,
his theories "have had a position and an influence in the history of
science, have been an inspiration to many both in his own generation
and since, and have led up to and guided the very researches which
have, in some cases, resulted in more correct views. His theory of
the 'azoic zone' in the sea, that no life existed below 300 fathoms,
based upon his observations in the Eastern Mediterranean, was justi-
fied by the facts known at the time, but required to be modified later
on when the deep-sea dredging expeditions, which Forbes's work
had stimulated, made known that an abundant living fauna ex-
tended down to the greatest depths of the abysses." 8
Matthew Fontaine Maury, 2806-1873
Oceanography as an organized study is generally and properly
dated from an American, Lieutenant Matthew Fontaine Maury,
1. Dr. Joel Hedgpeth includes a most interesting account of Forbes in "A Cen-
tury at the Seashore," The Scientific Monthly, LXI, 1945.
2. Herdman, op. ch., pp. 20-30.
Pioneers in Oceanography 2 1
"Pathfinder of the Sea," who published in 1855 what is frequently
called the first textbook on oceanography. He entitled it The Physi-
cal Geography of the Sea, adopting a characterization by Baron von
Humboldt of the system of research that Maury had already in-
augurated. As an officer of the U. S. Navy, Maury had voyaged
widely, even circumnavigating the globe, and had become "Officer
in Charge of Depot of Charts and Instruments," the Depot being
precursor to the Naval Hydrographic Office (cf. p. 45 below). It
was in this position that he began the accumulation and compila-
tion of data regarding winds and currents, enlisting the aid of mari-
ners of all types of ships and finally those of all nationalities. In ap-
praising the work of Maury, we must keep in mind that up to his
time there was little correlated knowledge of wind and weather,
tides and currents, such as every sailor needs. Each mariner learned
"the hard way." Trade secrets of sailing were sometimes cherished
to the disadvantage of all. 4 Much of the story is best told by quota-
tions from Maury's own book.
"By putting down on a chart the tracks of many vessels on the
same voyage, but at different times, in different years, and during all
seasons, and by projecting along each track the winds and currents
daily encountered, it was plain that navigators hereafter, by con-
sulting this chart, would have for their guide the results of the com-
bined experience of all whose tracks were thus pointed out." 5
"The results of the first chart, however, though meagre and un-
satisfactory, were brought to the notice of navigators; their atten-
tion was called to the blank spaces, and the importance of more and
better observations than the old sea-logs generally contained was
urged upon them.
"They were told that if each one would agree to cooperate in a
general plan of observations at sea, and would send regularly, at the
end of every cruise, an abstract log of their voyage to the National
Observatory at Washington, he should, for so doing, be furnished,
free of cost, with a copy of the charts and sailing directions that
might be founded upon those observations. . . .
"The quick, practical mind of the American ship-master took
hold of the proposition at once. . . .
4. Murray mentions a publication of James Rennell in 1832 summarizing the
knowledge of North Atlantic currents on the basis of sailors' observations.
5. M. F. Maury, The Physical Geography of the Sea, p. viL
22 This Great and Wide Sea
"So in a little while, there were more than a thousand navigators
engaged day and night, and in all parts of the ocean, in making and
recording observations according to a uniform plan, and in further-
ing this attempt to increase our knowledge as to the winds and cur-
rents of the sea, and other phenomena that relate to its safe naviga-
tion and physical geography." 6
Maury's work attracted international attention. The President of
the British Association, meeting in Liverpool in 1854, attempted a
calculation of the annual saving effected by those charts and sailing
directions to the commerce of the United States and the estimate ran
into millions, because "the sailing directions have shortened the pas-
sage to California 30 days, to Australia 20, and to Rio Janeiro 10."
Maury recognized the importance of the scientific study of the
sea, and he was, besides, a man of notable energy and enthusiasm
with a rare gift of expression to aid his practical persuasive powers.
The rhetorical aspect of his book, the text of which opens with the
short sentence, "There is a river in the ocean," 7 has been the occa-
sion of comment, and perhaps sometimes of disparagement. Al-
though it is now the fashion in scientific writings and textbooks to
be sparing of rhetoric (and sometimes, it would seem, to be wary
of clarity), it can hardly be questioned that Maury's style of expres-
sion, combining rhetoric, clarity, and piety, was one of his most ef-
fective implements of trade. He readily commanded the general co-
operation of shipmasters, who were no addicts of science or letters.
One of them wrote him: "For myself, I am free to confess that for
many years I commanded a ship, and, although never insensible to
the beauties of nature upon the sea or land, I yet feel that, until I
took up your work, I had been traversing the ocean blindfolded." 8
It was at Maury's instance that the government of the United
States invited "all the maritime states of Christendom" to a confer-
ence intended to promote a uniform system of observations at sea.
The representatives of ten nations, including all the leading states
6. Ibid^ p. it
7. "There is a river in the ocean. In the severest droughts it never fails, and in
the mightiest floods it never overflows. Its banks and its bottoms are of cold water,
while its current is of warm. The Gulf of Mexico is its fountain, and its mouth is
in the Arctic Sea. It is the Gulf Stream. There is in the world no other such ma-
jestic flow of waters. Its current is more rapid than the Mississippi or the Amazon,
and its volume more than a thousand times greater." Maury, op. ch. 3 p. 25.
8. Ibid^ p. xiH.
Pioneers in Oceanography 23
with maritime interests, met in Brussels in 1853 and recommended a
plan of observation to be followed on board the vessels of all
"friendly" nations. Nine other nations subsequently joined in, to
enter the circle of oceanographic friendship. "Thus," as Maury
comments with some enthusiasm, "the sea has been brought regu-
larly within the domains of philosophical research, and crowded
with observers." 9
Great as was Maury's achievement in enlisting the interest and
aid of thousands of observers and in making every ship at sea, and
every spot on the ocean passed over by each ship, a locus of oceanic
observation with respect to winds, currents, climates, etc., this was
not his best contribution to the germinating science of oceanog-
raphy. His greatest service was in what he did with the vast quantity
of assembled data, his work of integration and of deduction. His
book is still well worth reading as a whole with the understanding
that the facts and conclusions in many cases are not now acceptable
in the light of subsequent and more precise observations and of a far
better understanding of many oceanic phenomena. A glance at the
list of contents gives some indication of the comprehensive scope of
his work, as we see chapters upon the Gulf Stream, the atmosphere,
currents of the sea, the depths of the ocean, winds, climates, drifts,
storms, etc.
From data obtained by the use of a sounding apparatus with de-
tachable weight prepared by Midshipman Brooke, Maury prepared
the first bathymetrical map of the North Atlantic ocean, with con-
tour lines shown at the one, two, three, and four thousand fathom
lines. The bottom deposits obtained were examined by experts.
Maury's name is frequently associated with the Gulf Stream, first
mapped roughly by Benjamin Franklin. Of course, the great move-
ment of water long known as the Gulf Stream, has, in the light of
more comprehensive information, come to be known as being much
more complex than could have been suspected in Maury's time. As
we shall see later, it is now regarded as a system of movements, only
part of which is presently designated as the Gulf Stream. But
Maury's comprehension of the dynamics of the seas extended far
beyond the mapping of particular currents. He showed a profound
grasp of the fact that the sea is a single dynamic mechanism, with
"a system of oceanic circulation as complete, as perfect and as har-
9. Ibid., p. x.
24 This Great and Wide Sea
monious as is that of the atmosphere or the blood." "When, there-
fore, we take into consideration the fact that, as a general rule, sea
water is, with the exceptions above stated, everywhere and always
the same, and that it can only be made so by being well shaken to-
gether, we find grounds on which to base the conjecture that the
ocean has its system of circulation, which is probably as complete
and not less wonderful than is the circulation of blood through the
human system." 10
He finds the average water in the Pacific Ocean to have the same
analysis as the average water of the Atlantic. It is as if "the two
samples had been taken from the same bottle after having been well
shaken." "This fact, as to uniformity of components, appears to call
for the hypothesis that sea water which today is in one part of the
ocean will, in the process of time, be found in another part the most
remote. It must, therefore, be carried about by currents; and as these
currents have their offices to perform in the terrestrial economy,
they probably do not flow by chance, but in obedience to physical
laws. . . ." And, again: "Nay, having reached this threshold, and
taken a survey of the surrounding ocean, we are ready to assert,
with all the confidence of knowledge, that the sea has a system of
circulation for its waters." 11
The first intercontinental cable was laid down on lines suggested
by Maury and he was "the first scientist to foresee the possibility of
daily weather reports." 12 Maury's work for the Hydrographic
Office was interrupted when, at the outbreak of the Civil War in
1 86 1, he went with his state, Virginia, to join the Confederacy,
in which he served as commodore in the navy.
The "Challenger" and Sir Wyville Thomson, 1830-1882
It may be seen that, of the two great pioneers we have considered
so far, Forbes concerned himself primarily with what we would now
call hydrobiology and Maury with the beginnings of physical ocean-
ography. It was only a little before Forbes's death and the publica-
tion of Maury's text that the invention of the Midler net (p. 18,
above) introduced the possibility of adequate study of the micro-
10. Ibid^ p. 180.
11. Ibid., p. 181-82.
12. Naval Hydrographic Office. Special Notice to Mariners. One Hundredth
Anniversary Number, 1830-1930. Washington, 1930. Pp. 18. This is finely printed
Pioneers in Oceanography 25
scopic life of the sea as a highly important phase of oceanography.
The study of the small drifting organisms, which can be assembled
by a concentrating mechanism, such as the nets of fine-meshed
gauze, not only yields important biological knowledge, but it also
contributes to knowledge of the movements of masses of water, of
stratification of waters of different origins, and of other physical
phenomena.
The first world-wide use of the Midler net, and the most compre-
hensive exploration of the sea in its biological and physical features
that has ever been attempted by one agency, was that of the British
"Challenger Deep-Sea Exploring Expedition." Appropriately
enough it was from the "Challenger Expedition," as it is commonly
called, that the term "oceanography" was born. With the "Chal-
lenger" are associated a number of great names, more particularly
those of Thomson and Murray, later to be known as Sir Wyville
Thomson and Sir John Murray. There is a peculiar linkage be-
tween Forbes, Thomson, and Murray. Thomson, like Forbes,
studied in the Medical School at Edinburgh; also like Forbes, he left
without a degree but later became professor of natural history in the
University. In Thomson's case, ill health caused him to leave the
University just four years before Forbes returned to it. Doubtless
he derived inspiration from Forbes's distinguished work. At least he
had a somewhat similar interest and was an early and enthusiastic
addict to the use of the dredge in collection of animals from the bot-
tom. Murray, with the greatest name of all in the general field of
oceanography, was also a student of medicine in the University of
Edinburgh a few years after Forbes's death and, like the other two,
preferred to go his own way; he had no interest whatever in obtain-
ing a degree and, according to Herdman, expressed a contempt for
all examinations. He early became an associate and assistant to Wy-
ville Thomson and succeeded Thomson, not in the professorship of
natural history, but in the office of the Challenger Expedition Com-
mission located in Edinburgh and associated with the University.
The directorship of that commission had, by the time of Thomson's
death, become a full-time career.
Notwithstanding the lack of a doctorate, Wyville Thomson soon
won distinction as a naturalist, and came to occupy successively such
positions as lecturer on botany in the University at Aberdeen
(1851), professor of natural history in Queen's College, Cork
2 6 This Great and Wide Sea
(1853), professor of geology in Belfast (1854), and, a few years
later (1860), professor of zoology and botany in the same college.
As with Forbes, Thomson's interest and competence extended over
several fields of natural science.
With the aid of an older friend, Dr. W. B. Carpenter, and the
Council of the Royal Society, Thomson succeeded in inducing the
British admiralty to provide for exploration of eastern Atlantic
waters from the Faroes in the north to Gibraltar in the south. The
cruises of the "Lightning" in 1868 and the "Porcupine" in 1869 and
1870, although overshadowed by subsequent and more extensive ex-
plorations of the sea, were of great significance at the time. They
prepared the way for the "Challenger" and they led to the publica-
tion of Wyville Thomson's book, The Depths of the Sea (1873),
which is another claimant to the tide of "first textbook in ocea-
nography." Again, through Thomson, Carpenter, and the Royal So-
ciety, the British government was led to organize and equip a deep-
sea expedition on a unique scale. H.M.S. "Challenger," a spar-deck
corvette of a little over 2,000 tons displacement, propelled by sail
power and auxiliary engines, sailed in December, 1872, and re-
turned three and one-half years later, in May, 1876, after voyaging
69,000 miles in the Atlantic, Antarctic, and Pacific oceans. Thomson
was director of the scientific staff. He had a corps of assistants in-
cluding young John Murray (1841-1914), who, as was previously
mentioned, was to become his successor as director of the Challenger
Expedition Commission.
It is difficult now to form a clear conception of what the Chal-
lenger Expedition meant to knowledge of the sea in all its aspects
and to biological and geological sciences, because it is hard to realize
what was unknown before that expedition. The "Challenger,"
through its observations and records, furnished data for a general
map of the ocean basins with their main contour lines. It gave
knowledge of the low and constant bottom temperatures over the
Ejreat areas that exceed 2,000 fathoms in depth, where the tempera-
cure of the water stands always at but a little above the freezing
point, with some differences characteristic of different oceans. 13
The "Challenger" located the exact position of many islands and
13. Murray mentioned that the ooze dredged from the bottom in the tropics was
coo cold to be handled comfortably: and he is auoted a* tellino- frinufc rW t-h^
Pioneers in Oceanography 27
rocks. It determined currents at the surface and at various depths. It
showed that there was no great azoic area, but rather that animal life
existed at the greatest depths. It exploded the idea of an organic jelly,
"Bathybius," presumed to cover the bottom as a primitive proto-
plasmic slime. It defined the chief classes of strictly marine deep-sea
sediment, such as globigerina ooze, radiolarian ooze, diatom ooze,
and red clay. It obtained innumerable new kinds of animals including
a new protozoan radiolarian group, named in its honor the Chal-
lengerida, living at great depths but not on the bottom. It gathered
materials to show that the fauna of the deep sea is not, generally
speaking, a fossil survival but rather the derivative of shallow-water
fauna. Its scientific results were published during a period of fifteen
years in fifty large quarto volumes; these were edited under the di-
rection of the Challenger Office, headed first by Thomson and later
by Murray, but they were written by the leading biologists of the
world regardless of nationality. That great series of books, based
upon one cruise, will not go on a "five-foot book shelf'; it requires
several such shelves!
Sir John Murray, 1841-1914
In a certain sense John Murray, who might be described as a
Canadian-born Scotsman, may be designated as the "father of mod-
ern oceanography." He came to Scotland early in life to live with a
maternal grandfather and complete his education. He began with an
interest in electricity and the physical sciences in general but, to a
considerable extent, shifted into biology and geology. When he was
twenty-seven years old and an ex-medical student without a degree,
he managed to qualify as "surgeon" on board a whaler cruising in
Arctic waters. It happened that he was working in a laboratory at
the University of Edinburgh while Thomson was making up the
staff of the Challenger Expedition. At the last moment a vacancy
among the assistant naturalists had to be filled and Murray entered
upon a career which he was never to leave completely and in which
he was to become a leader. Chance plays a great part in the making
of careers and in the advancement of knowledge. Murray was most
active and productive in his work for the Challenger Expedition and
he published important works on deposits, plankton, and coral reefs.
In fact he was author or part author of five of the fifty large vol-
umes of Challenger Reports.
zS This Great and Wide Sea
It was fortunate for oceanographic science that Murray could
stay with the Challenger work long after the actual cruise to follow
through with publication of the results, that he lived a long life
without loss of interest in his first distinct calling, that he was canny
Scotsman enough to acquire considerable financial independence,
and, finally, that he was willing to apply his personal financial re-
sources to the advancement of oceanography. His acquirement of
financial independence makes a good story in itself and one pertinent
to the science of oceanography. Herdman, who enjoyed close asso-
ciation with Murray, tells us how Murray, in the examination of
materials from all sorts of sources for comparison with the sediments
obtained by the "Challenger," and, on the basis of a sample of rock
supplied him by a naval officer, became impressed with the possi-
bilities of mineral wealth in a neglected, uninhabited, and unclaimed
island in the Indian Ocean. He induced the British government to
annex "Christmas Island," organized a company to work its phos-
phate deposits, sent out scientific expeditions to study and report,
and laid out a model community which was occupied by about 1,500
colonists. He subsequently estimated that the share of the British
government in the returns from the mining operations more than
equalled the cost of the Challenger Expedition.
Murray's own share enabled him to do much for the promotion
of oceanographic research. We may cite a single but significant in-
stance of Murray's financial aid to oceanography. Over in Norway
was a comparatively young oceanographer, Dr. Johan Hjort, upon
whom was later to fall the mantle of oceanographic leadership. Sir
John Murray invited Hjort to visit him and proposed that, if the
Norwegian government would furnish a vessel and Dr. Hjort direct
the expedition, Sir John would pay the full scientific expenses. 14
This generous offer was promptly accepted by the Norwegian gov-
ernment and by Dr. Hjort. Thus was organized the cruise of the
"Michael Sars" in the North Atlantic in 1910. The scientific results
of that expedition were published in a series of volumes by the Ber-
gen Museum. One notable result was the general work, entitled
The Depths of the Ocean, by Murray and Hjort with distinguished
collaborators ( 19 1 2) . An authoritative and generally readable book,
covering the whole field of oceanography with reports on the latest
Pioneers in Oceanography 2$
discoveries up to the time of publication, this excellently printed
and beautifully illustrated work of over eight hundred pages has
long served for the general run of students of the ocean as a sort of
Bible of oceanography. A year later Murray published a small book
entitled The Ocean: A General Account of the Science of the Sea,
"undoubtedly the most concise and accurate and, so far as is pos-
sible within its small compass, complete account that has yet ap-
peared of all that pertains to the scientific investigation of the sea.
It is written in simple language for the general reader, and is prob-
ably the best introduction to oceanography that can be recom-
mended to the junior student or the intelligent non-specialist in-
quirer who desires information merely as a matter of general cul-
ture." 16
A notable instance of the interrelations of the different sciences
in the field of oceanography is afforded by the discovery, at first in-
direct and then direct, of the Wyville Thomson Ridge extending
from the northwest extremity of Scotland toward the Faroe Islands.
During the cruises of the "Lightning" and the "Porcupine" it was
found that, in crossing over this general line, the temperature in the
upper layers, something like a quarter of a mile in depth, remained
essentially unchanged; nearer the bottom, however, water to the
southeast was found to be warmer, by i2F. or more, than it was a
little northeastward, where it was actually 2 degrees colder than
fresh water at the freezing point. The inference was that, while the
upper waters of the relatively warm Atlantic moved freely to the
northeast, the deeper waters of that ocean were stopped by a bar-
rier that prevented their mixing with the deep Arctic water on the
northeast. A subsequent sounding expedition, originated by Thom-
son and participated in by Murray, revealed the actual existence of
such a ridge rising to within 300 fathoms of the surface. Still later, a
dredging expedition brought to light a striking difference in the
bottom fauna on the two sides of the ridge, with Arctic forms to the
north and Atlantic forms to the south. 16 Thus the study of tempera-
ture conditions (physical oceanography), zoological exploration
(hydrobiology), and deep-sea sounding (hydrography) proved
mutually supplementary.
15. Herdman, op. cit., p. 96.
16. Forbes, by the way, had long before suggested that dredgings in this region
would throw much light on marine biology. Murray and Hjort, The Depths of
the Ocean, p. 7.
30 This Great and Wide Sea
We are reminded of how effectively Alfred Russell Wallace, in
his study of animal life in the Malay Archipelago, made biology an
adjunct to geology. Here are innumerable islands disposed over an
area of truly continental dimensions. Many are small; some are only
tiny dots of land; others (Borneo, New Guinea, Sumatra) are im-
mense for islands. Hundreds of miles or only a few miles may sepa-
rate them; but it was not the distance between the islands, nor even
the physical features of the several land masses, that primarily de-
termined the nearness or remoteness of relationship between the
animals of all kinds which inhabited the islands. Consideration of
the animal life alone justified the division of the archipelago into
two great sub-archipelagos: the Indo-Malayan to the northwest,
related f aunally to Asia, and the Austro-Malayan to the southeast,
related to Australia, The two groups were presumed to have been
far longer separated from each other than had the several islands of
either group, regardless of present distances. The line between them
would pass through the Macassar Strait; in the southern chain of
islands, running in a long line from Java toward New Guinea, it
would cut through the tight fifteen-mile passage between Bali and
Lombock, just east of Java. Here there should be the deepest water;
subsequent soundings are understood to have shown that Wallace's
surmise, for which he had no adequate direct knowledge regarding
depths, was not too wide of the mark although not precisely correct.
Ydwnbo and the Closing Net
We have seen that Forbes's idea of a lifeless or azoic area of sea
bottom below 300 fathoms was shown, particularly by the Chal-
lenger Expedition, to be quite erroneous; but a new concept of an
azoic region developed, that of a great zone of open water beginning
at a level about 200 fathoms beneath the surface and ending a short
distance above the bottom. It was true that freely drifting organisms
bad been brought up in nets hauled at intermediate and great depths.
But it was claimed by champions of the doctrine of a watery desert
that this proved nothing: the organisms in the net were not neces-
sarily brought from the deep; they could have been captured as the
act was hauled up through the upper inhabited strata. Alexander
Agassiz in this country was a leading advocate of the idea of an
Above, PL 2. Aerial view of The University of California's Scripps Institu-
tion of Oceanography. The large budding at the lower left is a laboratory-
and-office building. Attached to it by an arcade is the wedge-shaped, 250-
seat auditorium. The largest building at the rear is Ritter Hall, completed
in 1931, and its two wings, one occupied in 1955, the other in I960.
Ritter Hall encloses the Library building on three sides. Near the head
of the pier is the Thomas Wayland Vaughn Aquarium-Museum. Below,
PL 3. The research vessel ARGO, 2 13-foot, 2,000 ton former Navy auxiliary
rescue and salvage vessel, part of the oceanographic research fleet of The
University of California's Scripps Institution of Oceanography. She carries
a crew of 3 1, and a scientific crew of 24.(The University of California, La
Jolla)
6-
II
II
jj
^3 A
" 5
^ .rt
-
Courtesy Woods Hole Oceanographic Institute
PL 5. ATLANTIS under sail.
Pioneers in Oceanography 3 1
the absence of life in the deeper off-shore waters, above the bottom-
most layers. 17
Obviously what was needed was a method of collecting that
would insure against the mixing of collections taken at different
levels and so would bring to the surface only such animals as were
actually taken into the net while it was at the depth being tested.
The first solution of the problem on the mechanical side was the
devising of what is now known as the "closing net." This was a net
that could be lowered in closed condition to any desired depth,
opened at will, hauled as long as was desired, and then closed be-
fore being raised. An Italian commander, Palumbo, has been cred-
ited with the first design of such a net, which was used during the
three-year cruise of the "Vettor Pisani" around the world. It was
first employed in 1884 in the Pacific Ocean, where one of the early
hauls was made between the Galapagos and the Hawaiian Islands at
a depth of 4,000 meters ( nearly two and one-half miles.) The Pal-
umbo net was much improved by the engineer Eugen von Peterson
and Professor Carl Chun of Breslau, and later by Victor Hensen and
by Fridtjof Nansen, the polar explorer.
There are now various types of "closing net." Opening and sub-
sequent closing are accomplished by sending metal "messengers"
down the line by which the net is hauled. The impact of the mes-
senger trips a catch which causes the net to open, or another to cause
the net to close. Closing may be effected by a weighted cord which
"purses" or constricts the net, or by a canvas cone which falls across
the mouth of the net, or in other ways.
The closing net has settled for all time the question of the occur-
rence of microscopic drifting life (plankton) at all depths: there is
no azoic zone on or above the bottom. This is not to say, however,
that there may not be regions where, because of paucity of materials
for subsistence, life is extremely scanty; there may be areas of bot-
tom sparsely inhabited and there are open waters remote from the
chief sources of food materials and virtually desert areas where the
water is bluest, for reasons that will be mentioned later in connection
with the subject of light and color.
17. Agassiz's observations in the Pacific, and especially his work with the Tan-
ner self-closing net, 'led him to believe that pelagic life did not extend to a depth
below 200 fathoms, and that the abyssal forms did not rise far above the bottom
thus leaving a relatively lifeless zone between." Charles A. Kofoid, "Contribu-
tions of Alexander Agassiz to Marine Biology," Internationale Revue der gesamten
Hydrobiologie und Hydrograpbie, IV. (1911), 42.
32 This Great and Wide Sea
Victor Hensen, Carl Chun, and the Prince of Monaco
For the progress of biological oceanography, much credit should
be given to Victor Hensen and Hans Lohmann, of Kiel, Germany.
Hensen proposed the collective term "plankton" for the small drift-
ing organisms, the basic lif e of the open sea. It is to him that we owe
distinct improvements in the Muller net and the introduction of
quantitative methods in the collection and study of plankton. What
is more important, we are indebted to Hensen for the concept of
systematic study of the plankton as a subject in itself and as neces-
sary for a general understanding of the biological productivity of
the sea. Perhaps Hensen exaggerated the simplicity of quantitative
studies, the uniformity of populations of plankton, and the possi-
bilities of quantitative appraisals of productivity. Nevertheless, his
studies, his methods, and his ideas have had a profound and benefi-
cent influence in the field of hydrobiology. The critics of his ideas,
among whom the great Ernst Haeckel was foremost, must in the
end rely upon quantitative methods such as were inaugurated by
Hensen if they are to prove the limitations (and incidentally the
utility) of quantitative appraisals. It was Haeckel, by the way, who
popularized the term "plankton' 7 while he added a number of new
terms differentiating the several types of relations between aquatic
animals and the environmental conditions.
Hensen is also known as the organizer and scientific director of
the German North Atlantic cruise of the S.S. "National" in 1889,
when collections of plankton by quantitative methods were first
extensively made; its published reports are designated as reports
of the "Plankton Expedition." Another notable voyage of ocea-
nographic exploration by the same nation was the German deep-sea
expedition of the "Valvivia" of 1898-99, directed by Carl Chun,
which has yielded a great series of scientific memoirs; investigations
were conducted in the Atlantic and Indian oceans and partly in
the Antarctic.
A most active participant in oceanographic research, and note-
worthy both for his own personal cruises and his unique benefac-
tions, was Albert Honore Charles (1848-1922), Prince of Monaco,
who pursued oceanographic studies in the Mediterranean and the
North Atlantic with his yachts "Hirondetle," "Hirondelle II,"
"Princesse Alice," and "Princesse Alice II." He was founder of the
Pioneers in Oceanography 55
great Oceanographic Museum and laboratory at Monaco and the
Oceanographic Institute in Paris, both of which institutions, with
several professorships in oceanography, were subsequently pre-
sented to the French nation.
Of the thousands of tourists who have visited the great aquarium
and museum on the rocks overlooking the Mediterranean at Mon-
aco, probably few have had any thought that the royal founder was
himself personally distinguished in scientific research. Besides pub-
lishing in scientific journals, the Prince of Monaco financed several
important series of elegantly printed memoirs of Oceanographic re-
sults issued from his own press: Resultats des Campagnes Scien-
tifiques, and Bulletins and Annales de f Institute Oceanographique.
The International Hydrographic Bureau, shared by various nations,
including the United States, was established at Monaco in 1919.
Among the important Oceanographic researches of the Prince of
Monaco, perhaps the following are most notable: his extensive in-
vestigations of the food of whales, in which he discovered parts of
hitherto unknown animals, such as the gigantic squid, a part of the
irm of which measured 27 feet in length; his discovery of the great
outflow of deep Mediterranean water into the Atlantic and of a par-
dally enclosed basin of relatively warm water, the "Monaco Deep,"
>n the floor of the Atlantic in the general vicinity of the Azores;
lis studies, by the use of drift bottles, of surface currents in the
Vorth Atlantic, making him at the time of his death in 1922, un-
doubtedly the leading authority on circulation of the Atlantic
.vater. 18
"By his researches the Prince of Monaco has won for himself a
Dlace in the foremost rank of men of science, and by enshrining the
esults in the monumental buildings at Monaco and Paris he has
nvested his labours with permanent value for all time." 19
4" ans Lobmann and the Centrifuge
The plankton nets of Muller, Hensen, and Palumbo led to the dis-
:overy of virtually a new world in biology while making possible
he exploration of the greatest in extent of all animal and plant habi-
ats, the open waters of seas and lakes. Nevertheless, the net still
1 8. Herdman, op. cit^ p. 126.
19. Ibid., p. 132.
54 This Great and Wide Sea
left undiscovered, or, at least, inadequately explored, a yet greater
world of life: the minute organisms, chiefly those classifiable as
plants, which will pass through the meshes of the finest devisable
net. It was Hans Lohmann who first made extensive use of the
centrifuge for separating out the finest forms of microscopic life;
for these, in 191 1, he introduced the term nannoplankton, meaning
dwarf plankton. With the old-time laboratory centrifuges, only a
few cubic centimeters of water could be tested at one time. Work-
ing on lakes in America, Birge and Juday of Wisconsin greatly
improved the efficiency of this method by introducing the use of
a continuously operating centrifuge, designed in their laboratories
by H. M. Foerst, and basically like a cream separator. The organ-
isms thrown out for study are mainly the most minute animals and
plants (protozoa, algae, and bacteria). It is enough to say now that
the nannoplankton, or "centrifuge plankton," greatly exceeds in
volume the "net plankton." These groups are discussed below
(p. 210).
Recent European Oceanographic Expeditions
Comparatively recent cruises, exclusive of American, are those
of the Norwegian "Michael Sars" (1910) directed by Murray and
Hjort; the German "Deutschland" (1911-12) partly in the At-
lantic and Antarctic; the Norwegian "Armauer Hansen" of Hel-
land-Hansen (from 1913); the Danish "Dana" (1921-22) in all
oceans and, again, in circumnavigation of the globe (1928-29); the
British "Discovery" and "Discovery II" (1925-39) in Atlantic,
Indian, and Antarctic; the German "Meteor" (1925-39); the British
"William Scoresby" (1926-31) in the Antarctic and South Pacific;
the Dutch "Willebrord Snellius" (1929-30)^1 the Indian Ocean and
East Indian Archipelago; and the British "Mabahis," better known
as the "John Murray Expedition" (1933-34) in the Indian Ocean.
Merely as suggestive of the part played in the advancement of
oceanography by other European countries than those mentioned,
there may be cited the dredgings by Michael Sars and his son, G. O.
Sars, off Norway in 1850 and afterward, studies by the Swedish
investigators Otto Pettersson and Gustav Ekman in 1890, and such
expeditions as the following: the French ships "Travailleur" and
"Talisman" in the eastern Atlantic from 1880 to 1883; the Italian
ship "Washington" working in the Mediterranean, and the "Vettor
Pioneers in Oceanography 3 f
Pisani" in its round-the-world cruise of 1881-85, when the closing
plankton net was first used; the Russian "Vitiaz" cruising around
the world in 1886-89; die investigations of the Austrian steamer
"Pola" in the Mediterranean and Red seas, 1890-98; the celebrated
drift of the Norwegian "Fram" with the ice in the North Polar Sea,
under the direction of Nansen, 1893-96; the Danish "Ingolf" in
the northern part of the North Atlantic, 1895-96; the Belgian Ant-
arctic Expedition of the "Belgic," the first vessel to winter in the
Antarctic region, 1887-88; the Dutch "Siboga" Expedition of 1899-
1900 in the Dutch East Indies under the leadership of Max Weber.
The Hydrographic Department of the Imperial Japanese Navy,
established in 1871, has been active in oceanographic research and,
especially since 1926, has employed several vessels in exploration
of the western Pacific. The Imperial Marine Observatory at Kobe
(1919) and the Institute of Physical Oceanography (1921) atKyoto
have engaged in oceanographic research.
China has had a Department of Oceanography in the Tsingtao
Observatory since 1936. Russia, as would be expected, has given
special attention to hydrobiologic and hydrographic surveys of the
Caspian, Black, and Azov seas and Arctic waters. Particularly to
be cited in this place are the Ail-Union Scientific Research Institu-
tion of Marine Fisheries and Oceanography (1933) and the Polar
Scientific Research Institute of Marine Fisheries and Oceanography,
which began in 1930 as the Murman Branch of the State Oceano-
graphic Institution.
Ships that have engaged in oceanographic exploration and institu-
tions of research on the ocean are listed extensively in the mono-
graph by Thomas Wayland Vaughan and others, International
Aspects of Oceanography, published by the National Academy of
Science, Washington, D. C, 1937.
Shore Stations Across the Atlantic
Little has been said of important European and British stations on
land, other than brief reference to the Oceanographic Museum at
Monaco (where also is located the International Hydrographic
Bureau), the Oceanographic Institute in Paris, and a few others.
Since the founding in 1872 of Dohrn's laboratory at Naples and the
establishment of Agassiz's highly significant but short-lived summer
station at Penekese in Massachusetts, laboratories by the sea have
3 6 This Great and Wide Sea
developed all around the world and have played a principal part in
the advancement of biological science. In direct or indirect ways,
many of these have contributed greatly to the development of
oceanography. Marine biological ^stations have been described as
seaside workshops in which are brought together the well-equipped
laboratory, competent specialists of diverse interests and qualifica-
tions, and the marine organisms in their native homes. Such a station
may have a small permanent staff of investigators, but usually the
greater part of the research is done by specialists from various uni-
versities who come for a few months during the year.
Perhaps most notable of all is the Stazioni Zoologica di Napoli of
which the great Anton Dohrn was "founder, benefactor, director
and center of activities." At Naples, as at Monte Carlo, one aspect
of the great scientific station is familiar to many tourists who visit
the popular aquarium associated with the laboratories. The first
building was completed in 1874, at a cost of 400,000 francs, three-
fourths of which was contributed by the founder himself. After-
wards, the institution was greatly enlarged as it received support
from many countries: until the beginning of the Second World
War, several institutions in America made annual contributions.
A continuing income from fees paid by visitors admitted to the
aquarium has aided substantially in maintenance of the station.
Indebted to the station are not only the specialists from all coun-
tries who have made use of the excellent facilities it affords, but also
all students of marine animals and plants, who find in libraries the
several series of scientific contributions and memoirs issued by the
station. Oceanographers anywhere value highly the thirty-nine
large, elegantly printed, and finely illustrated Fauna e Flora del
Golfo di Napoli. It is most fortunate that the "Naples Station," as
it is so widely known, passed through the bombardment of Naples
with little damage. This great laboratory has continued to be most
active under the successive leaderships of a son and a grandson of
the original founder, Drs. Richard and Peter Dohrn, respectively.
One of the most active and significant of all marine stations is
the laboratory of the Marine Biological Association of the United
Kingdom at Plymouth, England, begun in 1879 under the sponsor-
ship of T. H. Huxley and E. Ray Lankester. Supported by the
Association, the British government, private donations, entrance
fees to the aquarium, and the sales of specimens, it has been con-
Pioneers in Oceanography $ 7
cerned chiefly with hydrography, the chemistry of sea water, and
plankton. In various places in this volume we draw upon the dis-
tinguished work of Harvey, Russell, Atkins, and others associated
with the Plymouth station.
Great Britain has many other useful marine stations and agencies
for study of the seas. We can mention briefly only a few. The sta-
tion of the Liverpool Biological Committee at Port Erin on the Isle
of Man in the Irish Sea, founded in 1885 by Sir William Herdman,
is devoted particularly to fisheries research. The marine laboratory
of the Fishery Board for Scotland at Aberdeen was established in
1 882 and pursues fishery and oceanography research in the northern
area. On the Firth of Clyde is the Marine Biological Station at Mill-
port which was established in 1885 by Sir John Murray, to whom
oceanography owes so much in so many ways. The government-
operated Fisheries Laboratory at Lowestoft, Suffolk, founded in
1920, engages in the investigation of fisheries problems, both na-
tional and international. The Department of Zoology and Oceanog-
raphy at University College, Hull, with oceanographic laboratories,
opened in 1931, has been active in studies of the North Sea area.
Last to be mentioned for Great Britain, but first in origin and in
world-wide importance, is the Hydrographic Department of the
Admiralty, established in 1795, and maintaining, just before the war,
eight or nine surveying vessels. For a century and a half it has
engaged in hydrographic surveys, the preparation of charts, sailing
directions, and tide tables, and in many other services to mariners
and to science.
As might be expected, Germany long had prominence in studies
of the basic problems of oceanography. The great Naples Station
(1872) was born in great part from German initiative and support.
"The venerable Institution at Kiel (1871) has always been a leader
in marine exploration as related to the fundamental problems of
marine biology and the fisheries." 20 This station and the Royal
Prussian Biological Station on Helgoland in 1892 worked in co-
operation with each other and with the German Fisheries Society
and the International Commission for the Investigation of the Seas
20. Charles Atwood Kofoid, The Biological Stations of Europe, United States
Bureau of Education, Bulletin, 1910, No. 4. Whole number, 1940. The institution
referred to is the University of Kiel, with several laboratories and commissions
associated with it for the study of the seas.
3 8 This Great and Wide Sea
(1902). The laboratories at Kiel were the land base of the "Plankton
Expedition," whose importance we have already mentioned (p. 32,
above). From the laboratory came the quantitative methods of Hen-
sen and Lohmann's conception of the minute drifting life to be
taken by the use of centrifuges. No mention of agencies for marine
investigations would be complete without reference to the Institut
und Museum fur Meereskunde at Berlin, which was established in
1900, and which, before the war, pursued studies in oceanography
and economic geography in the widest sense. References will occur
on other pages to the work of Defant and Wust, of the staff of the
Institut.
France pioneered with seaside stations. Let us cite those at Con-
carneau (established in 1859), Arcachon (1863), Roscoff (1871),
Wimereau (1874), and the laboratory Arago at Banyuls sur Mer
(1881). Banyuls, attached to the University of Paris, engages in
marine biological studies and is a seat for oceanography conferences.
Russia was forehanded with a station at Sebastopol (1871), and
Italy with one at Catania (1870). Dohrn's temporary laboratory at
Messina (1867) was a forerunner of the great internationally sup-
ported station at Naples (1874).
The smaller countries of northern Europe have had great roles in
the theatre of oceanographic operations, as might be expected in
view of the importance to them of fisheries and navigation. Hardly
any country has ranked above Norway, with its University Bio-
logical Station at Dr0bak near Oslo, and the Geophysical Institute
at Bergen. The former is associated with the University of Oslo
and has been the base of operations for such leaders as Hjort and
Gran, whom we mention and quote several times on other pages.
The Geophysics Institute has operated the research vessel " Arrnauer
Hansen," previously mentioned; with it are associated the names
of such top specialists as B. Helland-Hansen in oceanography, J. A.
Bjerknes in meteorology, and H. Mosby in physics.
In Sweden, we have among other agencies the Hydrographic
Biological Commission, organized about fifty years ago by Otto
Pettersson, Gustav Ekman, and others. Associated with it is the
Borno Research Station, recently directed by Professor Hans
Pettersson.
The Danish Committee for Fisheries Investigations and the Study
Pioneers in Oceanography 39
of the Sea, with its laboratories in the old castle on Charlottenlund
Slot, near Copenhagen, deserves special mention if only because in
other pages of this volume mention must be made of contributions
to oceanographic science by the first chairman, Dr. C. G. J. Johannes
Petersen, and by Dr. Johannes Schmidt, who found die oceanic
spawning area of the fresh-water eels (cf. p. 263).
The same castle near Copenhagen is the home of the Permanent
International Council for the Exploration of the Sea (Conseil Perma-
nent International pour 1'Exploration de la Mer.), an organization
established in 1899 and participated in by twelve European coun-
tries and Great Britain and Iceland. With the Conseil have been
associated most of the leading oceanographers of Europe. Its work
is done through special committees, individuals, and cooperative
commissions in the several countries. Its publications, in half a
dozen series, comprise many more than a hundred volumes.
We could not begin to do justice to all such institutions. Dr.
Vaughan's volume entitled Imernational Aspects of Oceanography
and published in 1937 listed for the world 247 institutions engaged
in oceanographic work.
CHAPTER 4
in ^/vwienca
Early American Oceanographic Research other than that of Mawry
SO FAR WE HAVE CONCERNED OURSELVES CHIEFLY WITH OCEANO-
graphic developments on the eastern side of the Atlantic.
On the western side, the United States has not been inactive.
We have already alluded to the first map of the Gulf Stream pub-
lished by Benjamin Franklin in 1770, and we have considered the
pioneering work of Maury. As early as 1839 to 1842 the U. S.
Exploring Expedition under Captain Wilkes, with J. D. Dana as
naturalist, made deep-sea soundings and some dredgings. More
systematic research was undertaken by the U. S. Coast and Geodetic
Survey, beginning in 1844 when Director Bache arranged for the
taking of bottom samples in connection with soundings and for
competent study of the materials obtained. Soundings were also
made by the "Dolphin" and the "Arctic" in the North Atlantic
from 1851 to 1856; bottom samples were taken and studied.
Marine biology, particularly in America, owes much to the great
Swiss naturalist Louis Agassiz, who spent the latter and most pro-
ductive part of his life in the United States as a professor at Harvard.
Agassiz more than anyone else stimulated interest in marine biology.
He was not primarily an oceanographer but he took part in a cruise
arranged by the U. S. Coast and Geodetic Survey in 1867, along
with Louis Francois de Pourtales, who was another Swiss naturalist
adopted by America. Louis Agassiz concluded that the continental
area and the deep oceanic areas had undergone little change in posi-
tion since the earliest times.
40
Oceanography in America 4 1
Other oceanographic data was gained by the U. S. S. "Tuscarora"
(about 1875) under the direction of Rear Admiral G. E. Belknap
in the Pacific where piano wire was first used for sounding line
instead of the bulkier and heavier rope or cable. The U. S. S.
"Gettysburg" made deep-sea soundings in the North Atlantic in
1876. The U. S. Coast Survey steamer "Blake" explored the Carib-
bean and the Gulf of Mexico from 1877 to J 88o, making the Carib-
bean "one of the best mapped parts of the deep sea." The name of
Lieutenant Commander C. D. Sigsbee, commanding officer of the
"Blake," is associated with several kinds of oceanographic apparatus
the Sigsbee trawl, Sigsbee sounding machine, water bottle, etc.
It was the younger Agassiz, Alexander, son of Louis, who gave
scientific direction to the work of the "Blake" and also to that of
the U. S. Fish Commission steamer "Albatross," cruising along the
Atlantic coast of the United States, and a few years later exploring
the Pacific waters in the region of Panama. Agassiz directed a later
cruise of the "Albatross" in 1889-1900 in the tropical Pacific. The
results were published by the Museum of Comparative Zoology in
a notable series of volumes.
In 1885-86 the U. S. S. "Enterprise" cruised in all the great oceans,
making important collections of bottom samples. The U. S. S.
"Nero," surveying a cable route between the Hawaiian and Philip-
pine Islands in 1899, made the deepest soundings up to that time,
5,269 fathoms, in the vicinity of Guam.
Alexander Agassiz, 1 835- 1910
Alexander Agassiz has undoubtedly been overshadowed in repu-
tation by his great father; but the younger Agassiz was great in his
own name and rendered notable services in the fields of zoology,
geology, mining development, and particularly, in oceanography.
Lacking the buoyant spirit of his father, he was quiet and reserved
but exceptionally able. A capacity for organization, determination,
and clear judgment were qualities that he possessed in high degree.
As mining engineer and businessman he developed, against great
obstacles, the remarkable Calumet and Hecla copper mines and he
remained head of the operating system. He attained considerable
wealth, a substantial part of which he devoted to the advancement
of the Museum of Comparative Zoology at Harvard and to the
promotion of oceanographic research. He was, however, much
42 This Great and Wide Sea
more than a promoter of industry and science: while successful in
constructive business operations, he was an active and productive
zoologist and oceanographer. His personal achievements in the field
of oceanography were not of the kind that is easily pictured to the
general public; but oceanographers of the highest rank appreciated
his unique service. Perhaps, then, Alexander Agassiz's significance
may best be characterized by quotations from Kofoid, Herdman,
and Murray.
"He was the first to use steel cables for deep-sea dredging, on the
'Blake' in 1 877. This and all his subsequent expeditions on the 'Alba-
tross' and other vessels were noted for the foresight with which they
were planned with reference to all possible contingencies at sea, the
perfection with which the plan was carried out, and the success with
which the results were secured." 1
As the greatest explorer of the sea, says Kofoid, his explorations
in the Caribbean and in the Indian Ocean, and especially in the
tropical Pacific, carried him over 100,000 miles. "It is safe to say
that his expeditions mapped more lines across deep sea basins and
made more deep-sea soundings than all other scientific expeditions
combined." 2
"Agassiz's knowledge and experience as a mining engineer were
of the greatest value on board the 'Blake* in devising improvements
in the apparatus for deep-sea work. He substituted steel-wire rope
for dredging in place of hemp, and invented mechanical contrivances
for equalizing the strain and facilitating the hoisting-in of the appa-
ratus. He and Captain Sigsbee together devised a new form of
double-edged dredge, generally known as the 'Agassiz' or the 'Blake*
dredge or trawl, which will work equally well whichever way it
falls on the bottom; and also a very ingenious closing tow-net (called
the 'gravitating trap') , which could be lowered to any depth, opened
and towed, and then closed again, so that it was possible to strain
the plankton or minute organisms from a column of water of any
given length at a particular depth." 8
His explorations were made chiefly on the U. S. Coast Survey
steamer "Blake" (1877-80) and on the U. S. Fish Commission
1. Kofoid, "Contributions of Alexander Agassiz to Marine Biology," Inter-
nationale Rev. der gee>. Hydrobiologie u. Hydrographte t IV (1911), 40.
2. Ibid., p. 41.
3. Herdman, Founders of Oceanography r , pp. 107-8.
Oceanography in America 43
steamer "Albatross" in the South Seas (1899-1900), in the eastern
Pacific (1891), and in the eastern tropical Pacific (1904-1905); but
be often used smaller vessels.
The appraisal of Alexander Agassiz by Sir John Murray carries
particular weight:
"If we can say that we now know the physical and biological
conditions of the great ocean basins in their broad general outlines
and I believe we can do so the present state of our knowledge is
due to the combined work and observations of a great many men
belonging to many nationalities, but most probably more to the work
and inspiration of Alexander Agassiz than to any other single man." 4
The "Albatross," 1882-1924, and "The Fish Commission"
We have had more than one occasion to mention the "Albatross,"
which, it should be noted, was the first large vessel ever designed
particularly for oceanographic research; until her last years, at least,
she was employed exclusively in such work. She was a twin-screw
steamer of a little over 1,000 tons displacement, 200 feet long at
the twelve-foot water line and rigged with sail as a brigantine. Like
many other notable developments in the fields of fisheries, marine
biology, and oceanography, the "Albatross'* owed her origin to the
dsion and constructive imagination of Spencer F. Baird, who could
properly be called "founder" of the United States Commission of
Fish and Fisheries, and who was its first commissioner (without
pay), 187 1-87. In the early eighties Commissioner Baird called upon
I. L. Tanner, commanding officer of the Fish Commission vessel
"Fish Hawk," to outline general plans and estimates for the con-
struction and equipping of "a thoroughly sea-worthy steamer capa-
ble of making extensive cruises and working with dredge and trawls
in all depths to 3,000 fathoms." From Tanner's sketches the final
designs were made by Charles W. Copeland, marine architect and
engineer. Tanner superintended construction, became its first com-
manding officer, and served in such capacity for nearly twelve years.
Commissioned on November u, 1882, the "Albatross" was
manned and officered by the United States Navy while its scientific
work was guided by the Fish Commission under such distinguished
directors as Alexander Agassiz and Charles S. Townsend. Tanner's
4. Murray, quoted by Herdinan, op. cit., p, in.
44 This Great and Wide Sea
"Report on the Construction and Outfit of the United States
Steamer 'Albatross' " (1883) and his "Deep-sea Exploration: a Gen-
eral Description of the Steamer 'Albatross/ her Appliances and
Methods," with many illustrations as figures and plates, are highly
valuable for their details of description of the plan of the vessel and
of her technical apparatus. Tanner has also left his name signifi-
cantly in oceanographic literature by the invention of apparatus
for oceanographic research, such as the Tanner beam trawl, inter-
mediate tow net, sounding machine, etc.
The "Albatross" has a distinguished record of achievement giving
ample testimony to the care and planning which went into her con-
struction and which prompted Agassiz to write: "While of course
I knew in a general way the great facilities the ship afforded, I did
not fully realize the capacity of the equipment until I came to make
use of it myself." 5 It is interesting to note that in one haul of the
dredge, from 1,760 fathoms, the "Albatross" brought up more speci-
mens of deep-sea fishes than were collected by the famed "Chal-
lenger" throughout her service. Late in the second decade of this
century, the vessel became inactive, and in 1924 it was sold and
converted to other uses.
Townsend, in an epitaph for the "Albatross," 6 has well appraised
her service to oceanographic science:
"The 'Challenger' was a pioneer ship in oceanographic work and
must remain the leader in die literature of the science. The 'Alba-
tross' entered the field much later, but, thanks to her more modern
equipment and longer service, her collections were naturally much
more extensive and the bulk of her published results was perhaps also
greater."
"If ever the American people received the fullest possible value
from a government ship, they received it from this one. The benefits
to science, the fisheries, and commerce springing from her almost
continuous investigations the results of which have all been pub-
lished and widely distributed throughout the world are incalcu-
lable."
5. Quoted by C H. Townsend, "The Passing of the 'Albatross,' " Natural His-
tory, XXIV (1925).
6. Townsend, op. cit. p. 619-20. An excellent history of the "Albatross", with
listing of all its voyages has been given by Hedgpeth and Schmitt. Hedgpeth, Joel
W. and Waldo L. Schmitt. "The United States Fish Commission Steamer Alba-
tross." The American Neptune, 5(1), Salem, Massachusetts, 1945.
Oceanography in America 4;
In the broad field of biological oceanography the old United
States Fish Commission, the Smithsonian Institution (mainly through
the United States National Museum), and the Museum of Compara-
tive Zoology at Harvard have undoubtedly played leading parts.
The vision of Spencer F. Baird, Assistant Secretary of the Smith-
sonian and first Commissioner of Fish and Fisheries, put everything
connected with the knowledge of the sea and its organization in
possible relation to the development of fishery resources. The Com-
mission (and Bureau) acquired high distinction in oceanography,
not only through its unique contribution in the design of the "Alba-
tross" for oceanographic explorations and through its use of other
smaller vessels, such as the "Grampus" and the "Halcyon," but also
through its collaboration with other "sea-going" agencies of the
government (the Hydrographic Office, the Coast Survey, the Coast
Guard, and the International Ice Patrol), and with the National
Museum and the Museum of Comparative Zoology for care and
study of materials and publication of results. Among government
agencies, it was the Fisheries service and the National Museum
that were primarily qualified to deal with the biological aspects of
oceanography.
Hydrographic Office, United States Navy, 1830
No consideration of oceanography in the United States could
omit mention of the long and distinguished service of the Hydro-
graphic Office, United States Navy. Although it has borne that
name officially only since 1866, the Office appropriately celebrated
its one hundredth anniversary in 1930, dating from its establishment
in 1830 as the "Depot of Charts and Instruments." An excellent
resum6 of the history of the Depot and Office was published on the
occasion of the anniversary, 7 and I shall draw upon that paper in
this brief appraisal.
The Depot has already been mentioned in connection with the
pioneer work of Maury. It was established December 6, 1830, on
the suggestion of Lieutenant L. M. Goldsborough, who became its
first head, to be succeeded after two years by Lieutenant Charles
Wilkes, whose name has already been mentioned. It soon began the
7. Naval Hydrographic Office. Special Notice to Mariners, One Hundredth An-
niversary Number, 1830-1930* This is finely printed and illustrated with repro-
ductions of photographs, colored charts, etc.
46 This Great and Wide Sea
publication of lithographic charts, the first ones being based upon
surveys off the northeast coast. Then came the United States Ex-
ploring Expedition, 1838-42, our first great government scientific
expedition, carried on by a small fleet of five vessels, headed by
Wilkes on the sloop-of-war "Vincennes." The Act of Congress
in 1 83 6, which provided for this expedition, was explicitly prompted
by the very "important interests of our commerce, embarked in the
whale fisheries and other adventures in the great Southern Ocean."
Its explorations covered extensive areas in the Atlantic, Antarctic,
and Pacific, touching the regions of the Philippine, Samoan, Fiji,
and Hawaiian Islands, China, Japan, Alaska, the Columbia River,
etc. The charts that resulted from the surveys "have continued to
serve up to the present time as the basis of charts issued by all the
maritime nations." Wilkes, by the way, was the first to recognize
the Antarctic continent. More than 50,000 specimens were collected
during the five-year cruise and there were several published volumes
of scientific results. 8 The living land plants collected formed the
basis for the National Botanical Garden, 1852.
The Naval Observatory grew out of the Depot in the decade
of the 'forties to become a distinct agency in 1866. The historic
Perry Expedition to Japan with eleven vessels (1852-54) was pri-
marily diplomatic in purpose, but it engaged also in survey work
for the Office, especially in the Gulf of Yedo (Tokyo). There
were very limited biological collections, for which a bibliography
is given by Meisel. 9
Lieutenant Maury, the fourth head, assumed charge in 1842, but
we have already told how his creative imagination, personal energy
and enthusiasm, brought world fame to himself and to the Depot.
During his incumbency the North Pacific Exploring Expedition,
1853-59, was organized and conducted with five steam vessels under
the command first of Commander Ringgold and then of Lieutenant
Rodgers. Extensive surveys by this expedition led to the publication
of detailed coasting charts of the entire coast of Japan, the Bering
Sea and Straits, a part of the Atlantic Ocean, and other regions. We
8. A fpll bibliography of the United States Exploring Expedition is given by
Max Meisel in Bibliography of American Natural History. The Pioneer Century*
1769-1865, n (1926), 650-73. There are listed monographs and papers by Charles
Wilkes and such noted biologists and geologists as Louis Agassiz, S. F. Baird, James
Dwight Dana, Charles Girard, A. A. Gould, and Asa Gray.
9. Ibid^ m (1929), 145-48.
Oceanography in America 47
are grateful now for the work of both the Wilkes and the Ringgold-
Rodgers expeditions in mapping critical areas of the Pacific so long
ago. Rich biological collections were made by the North Pacific
Expedition and assigned to distinguished American scientists. Re-
ports upon them might have been forerunners to those of the "Chal-
lenger," but nearly all the collections, manuscripts, and drawings
were destroyed in the Chicago fire of 1 87 1 . 10
On suggestion of the Hydrographic Office, the patrol of iceberg-
ridden regions of the North Atlantic was started by the United
States Navy in the month following the loss of the "Titanic" in
1912, and the Office plays a major part in the International Ice
Patrol, which was organized cooperatively a couple of years later
and for which vessels and personnel have been supplied by the
United States Coast Guard. The Office shares in the direction of the
International Hydrographic Bureau at Monaco, or did so until
interrupted by the war. Under the guidance of the Hydrographic
Office, naval vessels have made surveys in virtually all seas and in the
Great Lakes, and such explorations by naval vessels, with auxiliary
aircraft for air-mapping, in which the Hydrographic Office
pioneered, were in progress up to the beginning of World War II.
Dynamic oceanographic surveys were then being carried out by
vessels of the Hydrographic Office in cooperation with the Woods
Hole Oceanographic Institution, the Scripps Institution of Ocea-
nography, and the Oceanographic Laboratories of the University of
Washington.
The Office has pioneered in many respects, but notably in im-
proved charting, in better methods of depth-finding, and in "air-
mapping." We can use the last term in two senses, referring to the
mapping of land and water by photographs from planes and to
actual mapping of air masses and air currents. A recent function is
the publication of monthly charts of the upper air for the North
Atlantic and the North Pacific Ocean.
We have already (p. 23) cited one of the most notable of early
improvements in sounding the apparatus devised by Midshipman
Brooke. The greatest recent contribution to oceanography was the
10. For neither the Wilkes nor the Ringgold-Rodgers expeditions was the pro-
gram of publication well handled, according to the best accounts. Otherwise, these
expeditions might have been more widely known and given greater stimulus to
oceanography. The limited bibliography of the latter expedition, is given by
Meisel, op. cit. r HI, 221-28.
48 This Great and Wide Sea
development by the United States Navy of sonic sounding, the
fruit of the researches of a number of persons. Credit is given,
however, to the Navy and to Professor H. C Hayes for developing
the first practical instrument for sonic sounding at all depths (see
p. 70 below). The early experiments of Dr. Hayes during the First
World War were directed not at depth-finding but at locating sub-
marines and other solid objects through the rebound of horizontal
sound waves. Somewhat accidentally, it was discovered that, with
appropriate adjustments, the method was equally applicable for
the determination of depth. By 1929 practically all Naval vessels
had been equipped with sonic sounding gear, the Fessenden type
having superseded the original Hayes apparatus. It was reported
by the Office in 1940" that it was receiving annually around 100,000
sonic soundings. In the realm of oceanography, the value of such
a contribution to the mapping of the bottom of the seas can hardly
be overrated.
United States Coast and Geodetic Survey, 1816
Much is due to the Coast Survey for knowledge of hydrographic
features of coastal waters and for an understanding of tides and
currents. On many pages of this volume are references to the
steamers "Blake" and "Bache" and to such Coast Survey leaders
and specialists as Bache, Sigsbee, Pillsbury, and Manner. Notwith-
standing that, by virtue of its official responsibilities, the work of
the Survey has been mostly in coastal waters, its charts, its researches
on theory of tides and its prediction of tides have high significance
to general oceanography, as well as to navigation, fisheries, and
safety of life at sea.
Recent American Oceanographic Research
We have seen that, in the last century and the early decades of
the twentieth century, the United States has contributed signifi-
cantly to the study of the oceans through Maury and Agassiz, and
through the explorations of the Naval Hydrographic Ofiice, the
Coast and Geodetic Survey (generally called "Coast Survey"), and
the Fish Commission, which later became the Bureau of Fisheries
in the Department of Commerce and is now a part of the Fish and
Wildlife Service in the Department of the Interior. The Naval
ii. Thomas H. Whitecroft, "Sonic Sounding," U. S. Naval Institute Proceed-
ings 69(2), No. 480: 216-23. Annapolis, 1943.
Oceanography in America 4$
Hydrographic Office and the Coast Survey have continued to be
somewhat active, but the pursuit of general oceanographic research
by agencies of the United States government undoubtedly declined
as the "Albatross" went out of commission. It may have been only
a coincidence, but diminishing governmental activity in general
oceanographic study, particularly in its biological phases, seems to
have gone along with the growth of a sentiment for isolationism and
a feeling among those who controlled public expenditures that the
United States could live independently of the rest of the world.
Doubtless, the most notable explorations of the seas conducted
or participated in by our government in the second and third decades
of this century were the explorations by the Coast Survey in co-
operation with the Bureau of Fisheries employing the Coast Survey
steamer "Bache" in West Indian waters in 1914 and after; the in-
tensive investigation of the Gulf of Maine by the Bureau of Fisheries
in cooperation with the Museum of Comparative Zoology of Har-
vard and under the direction of Professor Henry B. Bigelow (from
1912); and the International Ice Patrol in the North Atlantic, guided
by the United States Coast Guard. 12
Even more significant for oceanographic research in America in
recent times have been the studies made by institutions financed
primarily through private endowments.
Although the Scripps Institution of Oceanography at La Jolla,
California, assumed this name just twenty years ago, it has a long
and productive career in studies relating to the sea. The beginning
was a small seaside station at San Pedro, California, established in the
closing years of the past century by Dr. William E. Ritter of the
University of California. Professor C. A. Kofoid joined it in 1900.
Soon the laboratory was moved to the vicinity of San Diego, where
it settled at La Jolla in 1905 and was operated by the Marine Bio-
logical Association of San Diego. Drawing support from the Scripps
family, its laboratory studies were supplemented by extensive field
work. In 1912 it became the Scripps Institution for Biological Re-
search of the University of California, and began to receive aid
from the state as well as from private sources.
By 1924 when Dr. Ritter resigned and was succeeded by Dr.
12. The formation of this patrol was prompted by the loss of the British steamer
"Titanic" with its loss of more than 1,500 lives after collision with an iceberg, April
14, 1912.
jo This Great and Wide Sea
T. Wayland Vaughan, a research geologist, the Institution was
well embarked on a broad program with a full-time staff of scientists
qualified in diverse fields of oceanographic research. Its investiga-
tions, with specialist leaders in each field, embrace the physics of
the ocean and marine meteorology, the chemistry of sea water and
of marine organisms, marine biology and physiology of marine or-
ganisms, and the sea in relation to geology. More recently, on the
retirement of Dr. Vaughan in 1936, the Institution secured as its
director, Dr. H. U. Sverdrup, who had already in Norway attained
international distinction in theoretical meteorology and oceanog-
raphy.
At all seasons, but particularly in the summer, the productiveness
of the station is greatly extended through the use of its unique facil-
ities by many visiting investigators. Although the actual field opera-
tions are generally in waters at no great distance from the coast of
California, the contributions of the Scripps Institution to science
have world-wide significance to oceanography, because of their
bearing on basic principles of marine dynamics and biology, fisheries
science, and marine meteorology. Perhaps no other agency has
contributed more to an understanding of vertical movements of the
water off western coasts (cf. p. 140 below), the stratification of Pa-
cific waters, and the influence of such great streams as the Calif ornia
current of the northern Pacific and the Humboldt current of the
South Pacific.
The "Carnegie," a non-magnetic vessel of the Carnegie Institution
of Washington, cruising the Atlantic and Pacific oceans, has asso-
ciated physical and biological oceanography with its primary study
of terrestrial magnetism, particularly during the last years before
her tragic loss by fire at Apia, November 29, 1929.
The Bingham Oceanographic Laboratory was established at the
Peabody Museum of Natural History, Yale University, in 1928 by
Harry Payne Bingham. Under the direction of Professor Albert E.
Parr, the laboratory at first devoted itself chiefly to descriptive ma-
rine biology, preparing detailed reports of the invertebrate and
vertebrate material in the Bingham Oceanographic Collection which
had accumulated from a number of private expeditions preceding
1928. Within a few years its staff was increased and its activities
were expanded to include the dynamic aspects of oceanography,
with research on physical and chemical as well as biological prob-
Oceanography in America j /
lems. Cooperative investigations with the former U. S. Bureau oi
Fisheries and the Woods Hole Oceanographic Institution were also
undertaken. The results of this and subsequent work have been
published in the Bulletin of the Bingham Oceanographic Collection,
Volumes I to IX ( 1927 to the present), and other scientific journals.
In 1942 Professor Parr was succeeded in the directorship by Dr
Daniel Merriman. While continuing much of its previous work, the
laboratory in 1943 also undertook a program in which a large share
of its energies are directed toward the solution of practical problems
relating particularly to the conservation and development of the
food resources of the ocean and to the better utilization of waste
products of the fisheries and other unused organic resources.
Associated with the Bingham Laboratory is the Sears Foundation,
which publishes the Journal of Marine Research.
After exhaustive study of needs made by a committee of the Na-
tional Academy of Sciences, the Woods Hole Oceanographic Insti-
tution, at Woods Hole, Mass., was established in I930. 13 Its first
director was Professor Henry B. Bigelow, student of plankton and
general oceanographer, who was succeeded by Dr. Columbus Iselin
physical oceanographer, and professor of oceanography at Har-
vard. Its present director (1954) is Rear Admiral Edward H. Smith,
U.S.C.G. (ret.) . The Institution encourages and carries on the study
of oceanography in all its branches, having a large and modernly
equipped laboratory on the water front and several sea-going vessels,
The smaller vessels are intended for operations within the borders oi
the continental shelf and within a few days' run of Woods Hole
The larger vessel, the "Atlantis/ 1 a steel ketch, built to order ir
Copenhagen, was especially designed for Oceanographic work. Its
cruising radius of 3,000 miles under Diesel-engine power can be
indefinitely extended by the use of sail. With two laboratories or
the ship, living quarters for crew and scientists, and the mostmoderr
apparatus for Oceanographic studies, including 30,000 feet of dredg-
ing wire and a sonic sounding machine, the "Atlantis" is well-
equipped for hydrological, hydrographical, and meteorologica
observations, for chemical and physical analyses, and for biologica
13. Resulting in part from die survey made by this committee were the volume
by Bigelow entitled Oceanography, Its Scope, Problems and Economic Important
(1931), and the monograph of Vaughan and others, previously cited (pp. 35, 39)
International Aspects of Oceanography.
52 This Great and Wide Sea
collecting. So far its operations have been chiefly in the North
Atlantic.
Although independent in endowment and organization, the
Woods Hole Oceanographic Institution maintains, through its
trustees and its staff, close association with many educational insti-
tutions and government agencies. Originally, it had a small perma-
nent scientific staff, the greater part of its work being carried on
through visiting investigators, research associates and fellows, ap-
pointed from other research agencies for definite terms of service
on the staff of the institution. Now it has a very large staff and
more vessels. The results of research are published in various scien-
tific journals and bulletins, but reprints are collected and bound
into volumes issued periodically as Collected Reprints from the
Woods Hole Oceanographic Institution. The Institution also issues
a series of Papers in Physical Oceanography and Meteorology (with
the Massachusetts Institute of Technology). Most recently, a new
Laboratory of Oceanography has been founded at Woods Hole,
by the United States Office of Naval Research, to be operated in
conjunction with the Woods Hole Oceanographic Institution.
The University of Washington Oceanographic Laboratories were
organized in 1930 under the directorship of Dr. Thomas G. Thomp-
son, professor of chemistry in the University of Washington. 14 At
the present time, Professor Richard H. Fleming, oceanographer,
directs the laboratories. The base of operations and study is a large
and well equipped four-story laboratory building located on the Uni-
versity campus in Seattle, and facing on the Lake Washington Ship
Canal at its entrance to Portage Bay. Especially designed for ocean-
ographic research and built by aid of the Rockefeller Foundation,
it was completed in 1932. The field laboratories, where there is
most activity in summer, are those of the former Puget Sound Bio-
logical Station, known as the Friday Harbor Laboratories, on San
Juan Island. The principal vessel for Oceanographic explorations
is the "Catalyst," seventy feet long and of heavy construction with
a cruising range of 3,500 miles. Recently the "Catalyst" is in the
service of the United States.
Field operations have been conducted in waters off the coasts of
14. L. D. Phifer, "University of Washington Oceanographic Laboratories," The
Biologist, XIII (1932) 141-50; Thomas G. Thompson, "Oceanographic Laboratories
:> the University of Washington," The Collecting Net, X (1935) 281, 285-88.
Oceanography in America $3
Washington, British Columbia, and Alaska, in the Northeast Pacific
the Gulf of Alaska, and sometimes in the Bering Sea and the Arctic
Ocean, with research in the fields of physics, chemistry, biology
and geology. Special studies have been made of the physical anc
biological effects of upwelling off the continental shelf, where, be-
cause of upwelling, the surface waters are colder and much richej
in nutrient salts than waters of the same latitude beyond the conti-
nental shelf.
Oceanography in Canada
With its extended shores bathed by three of the five great ocean!
of the world, Atlantic, Arctic, and Pacific, the Dominion of Canads
has vital concern with the seas. The greater part of her peripherj
is deeply dissected by gulfs, bays and straits, semi-enclosed, bui
saline, and most of her principal ports are approached through tor-
tuous arms of the sea. As is natural in the conditions, much of the
Canadian research relating to the ocean has been applied to water:
in general proximity to the coasts, principally in the broad lowej
reaches of the St. Lawrence River and the Gulf of St. Lawrence
in the Bay of Fundy, in Hudson Bay, in waters, both semi-enclosec
and open, off the coast of British Columbia, and to a less extent ii
Arctic waters. Biological stations maintained by the Dominion 01
both Atlantic and Pacific coasts include the adjacent oceanic water
within the scope of their biological and physical studies. A recent!}
formed Committee on Oceanography, sponsored by the Fisherie
Research Board and the National Research Council of Canada ha:
been temporarily checked in activity by conditions of war.
More than a century ago, oceanographic exploration in the Gul
of St. Lawrence was undertaken with studies in the eighteen-thirtie
by Captain Bayfield and Dr. Kelly; the result appeared in scientifi<
journals, as well as in Sailing Directions for the Gzdf and River St
Lawrence. The reports of more recent studies are found in Repor
of Tides and Currents in Canadian Waters, published by the Depart
ment of Marine and Fisheries, in a series of Contributions to Cana
dim Biology , from the Biological Board of Canada, in the Journa
of the Fisheries Research Board of Canada, in the Canadian Arctit
Expedition, 1914-1% (the Stefansson Expedition), and elsewhere
In 1914 the Biological Board of Canada engaged the eminen
oceanographer, Dr. Johan Hjort of Norway, to whom reference
54 This Great and Wide Sea
have already been made, for a comprehensive investigation of At-
lantic waters off the outer coast of Nova Scotia. The results ap-
peared in 1919 as Report of the Canadian Fisheries Expedition of
1914-15. A general study of the same region, resumed in 1932, was
necessarily suspended at the outbreak of war. Investigation was
being extended over that broad continental shelf, or shoulder of the
continent, from which Newfoundland emerges and on which, far-
ther out, the Grand Bank approaches the surface. As is well known,
this is an area prolific in food fishes and the locus of important com-
mercial fisheries for several nations. That richness in organic life,
so significant to the food supply of the world, is not just accidental.
The general area is, indeed, one of the critical regions for the waters
of the world. It is where warm subtropical waters flowing north-
eastward as part of the Gulf Stream system meet cold Arctic waters
flowing southward As a region of convergence it is a place where
surface waters sink into the deep to be conveyed in leisurely drifts
to remote parts of the world. We "shall have occasion later (p. 61)
to cite this general locality as one of the chief sources of that vast
volume of water which passes across the Equator from North to
South Atlantic in compensation for the contributions at upper levels
from the southern ocean to the Gulf Stream system of the North
Atlantic. The phenomenal vertical circulations and mixing that
prevail are too complex for analysis here.
The results of investigations for the International Passamaquoddy
Fisheries Commission, sponsored by the North American Council
on Fisheries Investigations, as published in the Journal of the Bio-
logical Board, are notable "as a thorough attempt to relate oceanog-
raphy to fish production." 15 Indeed, no country has been more
effective than Canada in showing the applicability of oceanographic
research, in both its biological and physical phases, to the economic
pursuit of fisheries industries and to the conservation of fishery
resources.
Summary of Historical Review
It is to Forbes primarily that we owe the concept of organic com-
munities in the sea and their relations to the environment. Maury
conceived of the sea as a great dynamic system of waters in circula-
tion and saw it, with the atmosphere above and the bottom beneath,
15. Personal communication from Dr. A. G. Huntsman, Consulting Director,
Fisheries Research. Board of Canada,
Oceanography in America j j
as an object for diversified scientific study. Thomson had the imagi
nation and the initiative to plan and direct the greatest single world-
wide oceanographic exploration ever undertaken. Murray playec
a great part in Thomson's Challenger Expedition, and foUowec
through the publication of the greatest single series of publications
embodying the results of oceanography; as compared with any one
up to his time, he had probably the most complete grasp of th<
whole field of oceanography and doubtless he provided the greatesi
stimulus to general oceanographic research after Maury and Thorn
son. The expeditions guided by Alexander Agassiz covered th<
greatest number of miles and made the largest quantity of collec
tions: he was notable as an organizer, as a designer and stimulato]
of design for oceanographic apparatus, as a zoologist, and as a prac-
tical and theoretical oceanographer. Certainly, these names stanc
out among those of the pioneers in oceanography. Nevertheless
we should not overlook the special services rendered by Johanna
Miiller in popularization of the straining net, by Louis Agassiz ir
the stimulation of marine biology, by Victor Hensen in the organ
ization of planktology with the use of quantitative methods, bj
Carl Chun in the improvement of apparatus and in the organizatioi
and direction of a great oceanographic expedition, or by Hans Loh
mann, who, with the centrifuge, brought quantitative knowledge
of the bulk of marine life which the net cannot reveal. There ar<
many others, whose names we have barely mentioned or have en
tirely omitted in a survey altogether too brief to do general justice
but whose value may rank above some of those already cited. O
such are Bjorn Helland-Hansen of Bergen, Sven Ekman of the Uni-
versity of Upsala, A. Defant and Georg Wiist of Berlin, Ott(
Krummel, author of the classic handbook of oceanography, Gerharc
Schott, the oceanographic geographer, Fridtjof Nansen of Norway
Hans Pettersson of Sweden, Johan Hjort and H. H. Gran of Oslo
Johannes Schmitt of the Danish Commission for investigation of th<
sea, and others. There are equally notable oceanographers now i
harness, as it were, but it would be inappropriate and invidious t<
attempt here to appraise the special services of those whose work i
in active progress.
In this abbreviated review, it has not been the purpose to give ai
even measurably complete account of the history of oceanography
Rather, we have tried to suggest in rough outlines the great story o
5 6 This Great and Wide Sea
scientific endeavor, by many persons, agencies, and nations through-
out a long period of time. The cumulative results of so many and
such widely distributed efforts have led to the development of
oceanography as a coordinated and cooperative system of study
applied to the long-neglected but dominant part of the surface of
the earth. We say "dominant" part, having in mind two sets of
admissible facts: In the first place, the area of the sea is nearly three
times that of the land, and, as we shall see later, the volume of the
habitable zones for living organisms is many times greater in the
sea than on land; in the second place, and equally important, is the
basic fact that the solar energy, which is the source of all action
on the earth, must fall predominantly upon the face of the sea rather
than upon the face of the land.
It is appropriate, indeed, that the study of the continuous seas
covering three-fourths of the surface of the globe, bathing the
shores of almost every important nation, serving as the highway of
general commerce and offering a common field for fishery exploita-
tion, should have been an area of internationally cooperative, or,
at least, supplementary and harmonious, rather than competitive,
study. It is evident that no one country has monopolized the study
of the sea and that important oceanographic explorations have not
even been the private preserve of the larger nations. Norway,
Sweden, Denmark, and Holland have been in the front rank along
with Great Britain, the United States, Germany, Russia, and Japan.
It is natural, too, that the great expeditions and institutions men-
tioned have not ordinarily concentrated upon any one scientific
aspect of oceanography, but have usually concerned themselves
with the acquisition of physical and biological data by all practicable
methods consistent with the general purposes of the cruise.
Finally, it must be evident that the Atlantic, and particularly the
North Atlantic, has been much more thoroughly studied than the
other seas and that much jemains to be done, in all oceans, but
particularly in the Pacific.
CHAPTER 5
and
Some Gross Features of the Oceans
LIVING AS WE DO UPON LAND WE ARE INCLINED TO BE MORE
interested and concerned with areas of land than with areas
of water. It takes, however, only a moment's examination
of a globe to reveal the facts not only that much the greater part of
the surface of the earth is water (the proportion of land to water
being about 29 to 71) but also that the seas, taken together, form
one continuous body out of which emerge separately the small and
large land masses that we call islands or continents. The great conti-
nents and the larger groups of islands tend partially to divide a
continuous sea into more or less separate masses to which we assign
special names, such as the Pacific Ocean, the Atlantic Ocean, the
Mediterranean Sea, the South China Sea, the Gulf of Mexico, the
Bay of Bengal, etc. It is impossible to set more than arbitrary bound-
aries for most of these, and it is equally impossible to draw sharp
and inevitable lines between the great oceans, the Atlantic, the
Pacific, the Antarctic, the Indian, and the Arctic. Of these five
principal seas, the Arctic is the most nearly surrounded by natural
land barriers and the Antarctic the least well defined in its relations
to Atlantic, Pacific, and Indian oceans. (See Fig. 2, p. 64.)
Another glance at the globe shows that the emergent lands are
neither uniformly placed nor randomly distributed; consequently,
the oceans have distinctive sizes and forms. In the first place, the
surface of the earth is very conveniently divided, of course by
arbitrary lines, into eastern and western hemispheres. The eastern
57
Sea and Land $$
hemisphere has by far the greater bulk of land, including Europe,
Asia, Africa, Australia, and a large number of islands, many oi
which are of substantial size. The western hemisphere includes
North and South America, Greenland, and a much less extensive
body of islands. The Antarctic lands may be divided between the
two hemispheres, but its larger part would undoubtedly lie in the
hemisphere of the great land masses, the eastern hemisphere.
In the second place, if we divide the earth into northern anc
southern hemispheres, as we may do in a very natural way by fol-
lowing the line of the Equator, we find that the northern hemisphere
includes by far the greater part of the land. Eurasia and the greatej
part of Africa, North America, Greenland, and a small part of Soutf
America are all comprised within the northern hemisphere. In the
southern hemisphere we have the greater part of South America
but only a small part of Africa, with Australia and Antarctica anc
about half of the islands. It has been calculated that in the southerr
hemisphere something less than one-fifth of the total area is land
in the northern hemisphere there is more than twice as much land
but, even there, the proportions of land and sea are something lea
than two to three. Manner 1 has pointed out that if consideratior
is restricted to the temperate zones, which are best adapted for the
productive energies of man, we find in the northern hemisphere the
proportion of land and water to be approximately 50 to 50, whereai
in the southern hemisphere the proportions are approximately one
of land to eight of water. There is much more room for people ii
the north temperate than in the south temperate zone.
If we compare the several gresat oceans, as they are commonlj
delimited, esach is found to have its characteristic features. Th<
Atlantic and Indian oceans are not greatly different in sizes, eacl
being one-third or less the size of the Pacific; but their forms offe
marked contrasts. The Atlantic is long in the north-south directioi
and shows extreme irregularity of form; it is almost cut in two bj
the prominent bulges of South America and Africa which offer sucl
convenient termini for intercontinental airways. North Atlantic anc
South Atlantic are almost distinct oceans with characteristic forms
the South Atlantic has relatively smooth contours; the North At
lantic intrudes intricately into the land masses to form such partial!]
i. H. A. Manner, The Sea.
enclosed bodies of water as the Caribbean Sea, the Gulf of Mexico,
the Gulf of St. Lawrence, the Labrador Sea, the North and Baltic
seas, the Bay of Biscay, the Mediterranean, and many other bodies;
perhaps, we should include also the Gulf of Guinea and the Gulf
of Maine, to say nothing of such smaller indentations as Long Island
Sound and Chesapeake Bay. The Chesapeake Bay alone is said to
have, with "Tidewater" Virginia and Maryland, a shoreline of 5,000
miles, equal in mileage to one-fifth of the circumference of the
earth.
The Indian Ocean, which is at least as broad as it is long, has little
irregularity of form except on its northern and eastern boundaries.
The Pacific Ocean, too, has a relatively smooth outline except on
its western side. Contrast again the Atlantic, which extends into
the land masses in so many places and so deeply that, although it
has only about one-fifth the combined area of the Pacific and
Indian oceans, it has a longer coast line than those two oceans taken
together. 2 Furthermore, the coastal indentations of the Atlantic are
chiefly in the northern hemisphere and in the temperate zone, where
there are offered a far greater number of harbors and other condi-
tions favorable for the development of navigation and trade. It is
not by accident alone that the great populations and the great de-
velopments of agriculture, industry, navigation, and trade have been
realized in the north temperate zone, around the North Atlantic,
and, originally, on the western side of the North Pacific.
Some Interrelations of the Oceans
For our purposes it is important to keep in mind that the oceans
are interrelated, not merely spatially, but also functionally, or dy-
namically, in that more or less interchange of water occurs across
the imaginary lines of division. One ocean affects another and all
are organically connected. The phenomena of the Atlantic cannot
be understood without considering what takes place in the Ant-
arctic, nor those of the Antarctic without reference to its relations
with the Pacific and Indian oceans. Thus, the deep and bottom
water of all oceans is held to be derived chiefly from Arctic and
Antarctic regions. "From the Indian Ocean the Antarctic circum-
polar water with its components of Atlantic and Indian Ocean
2. /*&, p. 88.
Sea and Land 61
origin, enters the Pacific Ocean"; "The Pacific deep water is, there-
fore, Deep Water of Atlantic and Indian origin"; "the influence
of the Red Sea can probably be traced to the Antarctic." 8 These
few brief statements of fact by a leading oceanographer indicate
how definitely the five great seas are one.
Furthermore, South Atlantic water enters the Gulf of Mexicc
to continue on far into the North Atlantic and some of this watei
that crossed the Equator was of Antarctic origin. A corresponding
amount of North Atlantic water must, of course, flow into the
South Atlantic. The interchange between the North and the Souti
Atlantic is not insignificant; it has been calculated to be of the ordei
of six million cubic meters per second each way. The North At-
lantic water passing into the South Atlantic is supposed to have io
origin, in approximately equal quantities, in three general and wide!)
remote regions: in the Labrador Sea, off the southeast of Greenland
and off the straits of Gibraltar. North Atlantic deep water crossej
the Equator to flow south " 'sandwiched' between the Antarctic
Intermediate Water and the Antarctic Bottom Water, both oi
which are of low salinity." 4 The Mediterranean element of thi
water can be traced through the North and South Atlantic, crossing
the Equator beneath a mass of Antarctic water and continuing oi
around the southern extremity of Africa and to some extent througl
to the Antarctic. There is little interchange of water across th<
Equator in the Pacific; such interchange occurs chiefly in thi
Atlantic.
It is an interesting thought that a particular particle of wate
moistening one's toe on a Carolina or New Jersey beach may hav<
engaged in considerable global travel: it may have also dampenec
the toe of a South Sea Islander, and that of a penguin in Antarctica
that same particle, earlier in its travels, may even have contributec
to the drowning of Pharaoh's Army in its disastrous attempt t<
follow the Children of Israel across the Red Sea. We need no
forget either that the same water may sometimes engage in aeria
travel in the form of water vapor taken into the atmosphere b]
evaporation.
3. H. U. Sverdrup, Oceanography for Meteorologists, p. 215.
4. Ibld^ pp. 213, 214.
Sea and Land 6s
Duthern boundary can be fixed only by agreement among geogra-
hers. The Atlantic Ocean, as contrasted with the Pacific, has a
mch greater proportion of its area in temperate zones. It is note-
worthy, also, that by far the major portion of the fresh water drain-
ig the lands through great rivers finds its way into the Atlantic
)cean. The Atlantic and the Pacific are different oceans biolog-
:ally as well as geographically. Without going more into details,
is adequate for the present purpose to give warning, as it were,
lat the conditions of life and die compositions of the organic com-
iimities are different in the several oceans and in the several parts
f each ocean. In consequence of these and other conditions, the
Dnstitution of organic deposits on the bottom are distinctive of
iff erent regions.
The distinctiveness of different regions of the sea, whether viewed
orizontally or vertically, is well reflected in the fact that knowl-
Ige of currents and drifts is generally found, not so much by the
se of current meters as by study of the salinities, temperatures, dis-
>lved gas contents, or the drifting micro-organisms (the plankton).
Science comes the water of a particular place and time and whither
goes are often discoverable by chemical and biological analyses
idler than by direct physical observation of water movement,
'eep-lying Mediterranean water, for example, is traced for thou-
nds of miles westward and southward to round the Cape of Good
tope; and it is so traced, not by the use of current meters or drift
Dtties, but by precise observations of temperatures, salinity, and
sygen content.
\epth and Topography
The combined area of the oceans, as has been mentioned, is more
tan twice that of the lands (7 1 to 29) and their mean depth (about
800 meters or roughly 2 1/3 miles), 6 more than five times the
can elevation of the land (700 meters or 2,300 feet) ; hence, if all
te land were submerged in the sea, such a cataclysm would, after
I, cause the displacement of only a relatively small part, about
ic-eighth, of the total volume of the seas.
The greater part of the sea is below two thousand fathoms, or
ooo meters, roughly speaking, but only a very small part, some
per cent, is below three thousand fathoms (about 3 1/2 mfles, or
6. Manner, op. ch^ p. 95.
Sea and Land 67
some 6,000 meters). Areas of greater depth than three thousand
fathoms are known as "deeps." Greatest height of land (Mt. Everest,
29,002 feet) is more than a mile less than the greatest sounded depth
of the sea (35,400 feet, or about 6 1/2 miles) in the Emden Deep
off Mindanao in the Philippines. Deepest known in the Atlantic is
the "Milwaukee Depth" (30,246 feet, in the Puerto Rico trough,
95 miles northwest of Puerto Rico). Nearly sixty deeps have been
mapped (fig. 3). The bottom of the sea lying between two and
three thousand fathoms is described as generally an undulating plain
with slopes that are usually, but not invariably, gentle. There are
high cone-like elevations rising from the deep, with slopes of about
35 degrees comparable in inclination to a steep mountain side;
these, with narrow tops, which may be only some 50 meters below
the surface of the ocean, are thought to represent submarine
volcanic peaks. The Hawaiian Islands are good examples. If conti-
nents and islands are great solid masses rising above the level of the
sea, so are there other rock masses, in form like islands or ridges
hundreds or thousands of miles in length, which do not reach to
the surface and, therefore, constitute shoals, banks, plateaus, or
ridges more or less deep beneath the water. The "Mid-Atlantic
Swell," extending through North and South Atlantic, is some 2,000
fathoms down, but it still separates broad eastern and western basins.
Proceeding from the shores of the continents toward the central
parts of the oceans, there are commonly distinguishable (fig. 4): a
continental shelf, having generally very gentle inclination, but with
many deep and surprisingly precipitous gorges, and extending for
a greater or less distance to the continental edge at about one hun-
dred fathoms; beyond this, the much steeper continental slope,
notched by the mouths of the gorges and leading down to the floor
of the ocean. On some coasts the continental shelf is virtually want-
ing, as on the western coast of Peru, where the steep slope from the
high peaks of the Andes continues almost unbrokenly down to the
floor of the ocean below 20,000 feet, giving a roughly continuous
incline of some 40,000 feet from peak to deep.
Continental shelf and continental slope together constitute the
continental terrace, the flank of the continent. Its width may vary
between, say, zero and 800 miles, with an average of about 30 miles. 7
7. H. U. Sverdmp, Martin W. Johnson, and Richard H. Fleming, The Oceans,
Their Physics, Chemistry and General Biology.
68 This Great and Wide Sea
FIGURE 4. Map showing the location of canyons and principal furrows
off the Mid-Atlantic states; also the extent of the continental shelf and
the location of the continental slope. (After R. A. Daly, The Floor of
the Ocean)
FIGURE 5. Map of the Hudson canyon and vicinity. (After R. A. Daly,
The Floor of the Ocean)
Sea and Land 69
The slope, which begins at a depth of 50 to 100 fathoms, is actually
steep. Its average fall off the eastern United States is said to be about
one mile vertically in ten horizontal miles, but actually it is much
steeper toward the top. 8 Once thought to be a relatively smooth
bank, the shelf and the slope are now known to be extremely rugged
and deeply cut with gullies, gorges, and great canyons. The expla-
nation of the sharp sculpturing is not certain, but it is one view that
the cuts were made during certain stages of the glacial period by the
rush of heavy silt-laden submarine currents. If they are thus attrib-
utable to the action of moving water, they have an origin very sim-
ilar to that of terrestrial gullies and canyons. The Grand Canyon
of the Colorado River, pre-eminent example of a continental water-
worn gorge, has its measurable rivals on the continental terrace.
It may be asked: How have we learned about the great depths
in the ocean? The simplest sounding apparatus is, of course, a piece
of lead on the end of a line marked in f athoms or meters. The lower
end of the lead may be hollowed out and filled with soft soap to
bring up a slight sample of the bottom, whether sand, mud, or shell
fragments. For great depths, where the length of line must run into
thousands of fathoms, or miles, the bulk and weight of a line made
of rope is very great; furthermore, a heavy sinker is necessary to
carry the line to the bottom within a reasonable period of time and
at a rate such that the slackening of the line is apparent when the
lead reaches bottom.
Strabo is said to have sounded the Mediterranean to a depth of
more than a mile, but we do not know how he did it. Magellan is
said to have sounded to a depth of some thousands of fathoms, but
without reaching bottom. As early as 1840, Sir James Ross made
soundings at a depth of more than 3 miles, but not all of his sound-
ings were correct. The "Challenger" used a fine hemp line and
recorded accurately the time when each hundred-fathom mark went
over. When the rate at which the line ran out suddenly changed,
the bottom was presumed to have been reached.
It is a difficult and time-consuming task to haul in the line with
the heavy lead; many hours are required for a single sounding, and,
during the whole period, the ship must be kept as nearly as is possi-
ble in the same place. Another improvement, that of Midshipman
Brooke, working with Maury, was the use of a detachable weight
8. Daly, The floor of the Ocean: New Light on Old Mysteries, p. 101.
70 Ji Ms Lrreat and W ide bea
released when it touches the bottom. Twine could then be substi
tuted for the heavier and bulkier rope. When the sounding is mad<
at a great depth, the value of the lost weight is much less than th<
cost involved in raising it through miles of water. The vessel must
of course, be provided with at least as many heavy shot as the num
ber of deep soundings it proposes to make. The Sigsbee and the
Tanner sounding machine and necessary accessories are well de
scribed in Tanner's report of 1897, previously cited (p. 44).
It was a further improvement when Lord Kelvin in England anc
Belknap of the U. S. S. "Tuscarora" substituted piano wire for the
rope or twine. Not only does the fine wire, of a diameter of aboui
one-twentieth of an inch, require less space for storage, but, wher
properly protected, it is more durable and more economically manip-
ulated. The line, whether of rope or wire, may be coiled on a drum
from which it runs out over a revolving wheel; each turn of the
wheel corresponds to a known length of line. If the number oi
turns is automatically recorded, the amount of line paid out and the
depth of the sinker at any moment is readily determinable, provided
one can tell, by the slowing of the wheel, when the sinker has
stopped on the bottom some miles below.
It can readily be understood that deep-sea soundings taken by the
use of a line and weight are expensive in many ways. The miles oi
line required and the many heavy weights which must be discarded
represent considerable initial expenditure and occupy substantial
space on the vessel. The time, in hours, consumed in letting out and
hauling in miles of line while the boat is kept in one place means ex-
pensive delay. Even with the most modern motor-driven sounding
machines, a sounding in the greatest depths requires about three
hours. It is obvious that only a limited number of deep-sea observa-
tions requiring the use of long lines are practicable from a vessel
engaged in oceanographic exploration of general purpose.
An ideal sounding apparatus would be one that determined depth
in a few seconds or minutes and virtually continuously while the
boat was in motion. The answer to this need was the sonic depth-
finder developed in the early 1920*5 by Dr. Harvey C Hayes, a
research physicist in the United States Navy. 9 The apparatus con-
9. Harvey C. Hayes, "Measuring Ocean Depths by Acoustical Methods,"
Journal of the Franklin Institute, CXCVII (1924), 323-54. A very instructive and
interesting but concise account of the development of sonic sounding is given by
Thomas H. Whitecroft, "Sonic Sounding," he. cit., pp. 216, 223.
Sea and Land 7;
sists chiefly of a means of making a sound on the ship, with the
sound waves directed toward the bottom of the ocean, a delicate
receiving apparatus to catch the echo from the bottom, and a highly
accurate and delicate dock mechanism to measure the time interval
in small fractions of a second. Knowing the velocity of sound in
water, the depth can be calculated very closely. The "sound" is
not necessarily audible to the ears: supersonic waves may be more
effective.
Obviously "sonic sounding" presumes exact knowledge of the
velocity of sound in sea water and this has been found to vary with
temperature, salinity, and pressure, but to be generally a little over
800 fathoms per second. An intensive investigation of this subject
was made by the Coast Survey steamer "Guide," 10 cruising from
New London, Connecticut, by way of Porto Rico and Panama to
San Diego in 1923. The determinations of depth with the sonic
sounder were checked against repeated wire soundings while tem-
peratures were determined at several depths and water samples
taken for later determination of salinity; bottom samples were taken
also. The cruise extended over 6,500 miles, and the conditions
encountered covered wide ranges: the temperature range of the
water o to 28 G, the salinity 31 to 36.5 o/oo, the depth 185 to
4,617 fathoms. The computed velocities varied between 810 and 841
fathoms per second. The depths recorded by the sonic sounder,
with corrections for the several variables, seem to be accurate within
a very few fathoms and without appreciable error even where the
bottom is steeply sloping.
Given the necessary equipment, which occupies little space, and
a qualified operator, a practically unlimited number of soundings
can be made from any vessel on a continuous cruise. Consequently,
the sonic sounder has been of great significance to oceanography
and knowledge of the topography of tie bottom of the ocean has
been much advanced in Decent years. Curiously enough, we have
only recently begun to use "sound" in "sounding" the depths. In
another place (p. 279) we shall refer to the use of the echo-sounder
in locating schools of fish.
Now, although there is relatively little difference between the
greatest height of land and the greatest depth of the sea, there is a
10. N. H. Heck and Jerry H, Service, Velocity of Sound in Sea Wafer. U. S.
Coast and Geodetic Survey, Publication No. 108, 1924.
Sea and Land 75
vast difference between the thickness of the zones of life on land
and in the ocean, respectively. Terrestrial life everywhere occupies
a very thin stratum that follows roughly the contours of the knd,
except at the greatest elevations, while oceanic life extends through-
out the space from the surface of the ocean to the bottom, however
deep it may be (fig. 6). The thickness of the stratum of life on
land, which may roughly be said to extend from the tops of the
crowns of the trees to the greatest depths to which their roots pene-
trate, will not ordinarily exceed 100 feet, or some 30 meters, and
the mean thickness would certainly be much less; but if, with some
exaggeration, we assume this to be the mean and take the mean depth
of the habitable regions of the sea as about 12,000 feet (about 4,000
meters), and if we remember that the area of the sea is more than
twice the area of the land, we find the volume of space available for
organic life in the ocean to be some three hundred times the space
available over the continents and islands. This is a very rough sort
of calculation, but it indicates at least the order of relative magni-
tude of the terrestrial and the oceanic communities as a whole.
Interrelations of Sea and Land
Not only are the continents and islands completely surrounded
by the continuous sea, but almost all lands everywhere, as a result
of weathering processes, are being worn down and washed or blown
into the sea. It is estimated that nearly three billion metric tons of
material from the land are annually being dumped into the sea.
Indeed, were there no compensating returns to the knd, a few geo-
logic ages might have sufficed to cause the complete disappearance
of all dry land. There have been, however, and there must always
be such compensating movements, so long as the equilibrium of the
crust of the earth is maintained by the gradual elevation, in conti-
nental regions at least, of great areas of sea bottom to become dry
land. Enormous terrestrial areas, even the very tops of some of our
mountains, are known by their geologic formation and fossils to have
been former sea bottoms and, thus, to represent the repayment of
long-term loans from land to sea. The highest point of land, the
peak of Mount Everest, was once at the bottom of the sea. 11
In other ways than through geologic upheavals does the sea reg-
ii. Daly, op. cit* p. 93.
74 This Great and Wide Sea
ularly contribute to the land. The interrelations are too complex
to be analyzed briefly. It may only be suggested that the source of
our rain and snow and of rivers, lakes, springs, and ground waters
everywhere is, in part, the surface of the sea, where the heat energy
of the sun enables the atmosphere to pick up by evaporation the top-
most layer of water, some of which may fall later upon mountain or
plain. Then, too, the climates on land are regulated from the sea
in various ways. The winds from the sea are well-known tempering
influences, but it is not so generally understood that the great amount
of heat energy absorbed by evaporation of the sea water is, to a
notable extent, released by the precipitation that occurs when the
warm water-laden breezes are cooled over sea or land. It is hardly
relevant to our purpose to recall that the water powers which oper-
ate our lights and engines are giving us merely the energy of the
sun that was stored through evaporation and that this capture and
storage occurred in some part at the surface of the sea. In compar-
ison with these contributions from sea to land, the gift to man, bird,
and other terrestrial animals of a few billion pounds of food and
salt seems relatively insignificant, however important, and perhaps
absolutely essential, these materials are to man and to terrestrial lif e
in general.
n
CHEMISTRY AND PHYSICS
CHAPTER 6
a
Chemical Nature of Sea Water
ALLUSIONS TO "THE BRINY DEEP" NEVER NEED EXPLANATION;
everyone knows the sea is salty. What is not a matter of
such general information is the great array of other sub-
stances that go along with the common salt in solution: the minerals,
organic substances, and gases. It is easy to learn that sea water is an
elaborate chemical mixture; but without special study and consider-
ation one does not readily conceive what it means for plants and
animals, unlike those on land, to live completely immersed within a
nutrient chemical medium and what it means that this medium is
kept always in circulation. What is even less generally understood
is that the very saltiness of the sea has much to do with die mechanics
of world-wide circulation of ocean waters.
Without wishing to become too much concerned with the tech-
nicalities of ocean chemistry and physics, one has to recognize that
there can be no satisfactory understanding of conditions of life in
the sea without considering several special aspects of the sea as a
solution of so many substances. In this chapter the attempt is made
to treat in as simple language as is practicable the composition of sea
water, the distribution of the constituents by area and by depth
(geographic and bathymetric) , the changes that may occur here and
there, some features of utilization of the chemicals and the effect of
changes in concentration on movements of water masses. There
will be attempted also a brief exposition of the means by which
we learn about the composition of sea water at all depths. It is con-
77
j8 This Great and Wide Sea
venient to deal first with the inorganic constituents of sea water,
ignoring for a while, the organisms and their wastes in solution.
Inorganic Substances in Solution
Barring, of course, a few relatively small isolated basins, such as
those of the Great Salt Lake, the Caspian Sea, Lake Poopo in South
America, and the Dead Sea, all land drainage is toward the oceans.
The seas taken together, constitute a great catch-basin for all that
leaches from the land or is washed from its surface. To the surface
and soil drainage entering the sea, there are added the air-borne
materials originating on land or coming from interplanetary space.
Obviously the ocean water must be a great chemical potpourri:
doubtless it has in solution the salts of every one of the chemical
elements, although many occur in traces so slight as not to be de-
tected by ordinary methods of chemical analysis. Indeed, until re-
cently, elements that had never been detected in the water were,
nevertheless, found in marine organisms. 1 Since the animals or plants
could only have gotten the chemicals by extraction from the water,
it might be inferred that, at least in the extraction of some of the
rarest elements, the protoplasm of the organism was more efficient
than the most expert chemist. Chemical laboratory techniques have
undergone great refinements in recent years, but, as every chemist
and biologist recognizes, the protoplasm of plants and animals has
always led the field in organic chemistry. Only a limited number
of the materials in solution have presently known biological signifi-
cance; yet some of these, such as iodine, an important component of
some seaweeds, and copper in the blood of crabs, will show only as
traces in the records of chemical analyses. The cell membranes have
selective capacities, so that the concentration of substances in the
surrounding medium gives no indication of the concentration within
the plant or animal.
The accompanying Table I reproduces a rather old-fashioned
report of the analysis of sea water. It serves merely to give a rough
idea of the relative abundance of the several inorganic materials that
occur in greatest quantities. One notes the absence in this record
i. Vanadium in the blood of ascidians and holothurians, cobalt in lobsters and
mussels, nickel in mollusks, and lead in the ash of various marine organisms.
Henry B. Bigelow, Oceanography, pp. 100-10. Sverdrup, Johnson, and Fleming
(The Oceans, pp. 175 F.) list 49 elements now known to occur in sea water.
The Sea as a Solution
of such known essentials as phosphates and nitrates or of
iodine, copper, and other chemicals. It must not be under*
either, that the materials listed occur in just the combinations
cated, for the salts in sea water are largely in ionized form anc
sequently are susceptible of diverse and changing combinations
sodium ion, for example, may occur in combination with chl
TABLE I
ANALYSIS OF UNEVAPORATED RESIDUE OF SEA WATER*
(From Helland-Hensen in Murray and Hjort, after Dittm
in Challenger Reports)
gms.
percen
Sodium chloride
NaCl
27.213
77.76
Magnesium chloride
MgCl,
3.807
10. 8
Magnesium sulphate
Calcium sulphate
Potassium sulphate
Calcium carbonate
CaCO,
1.658
1.260
0.863
0.123
4-74
3-6c
2.4*
0.34
Magnesium bromide
MgBrj
0.076
0.22
Total.
35 ooo
IOO.OC
* For the expression of Dittmar's values in the units now in common u
Sverdrup, Johnson, and Fleming, The Oceans, Table 33, p. 166.
carbonate, sulf ate, or bromine ions or with organic negative
this has its advantages for the grasping organisms with their d
needs.
Collection of Samples and Analysis
It may be asked how the water for chemical or gas analys
be sampled at different depths. Given the proper equiprnec
can readily be done by the use of what is termed a "water-b
Water-bottles may be attached in series to a line lowered frc
ship to any depth, even to thousands of fathoms. Each bottle r
consists of a metal cylinder, open as it goes down so that the
passes freely through it, but capable of being closed at will v
small cylindrical weight or "messenger" is allowed to slide
the line and trip the catch of the uppermost bottle, as sho
pi. 25. The closing of this botde releases a similar messengc
viously suspended below the uppermost bottle, and this, i
8o This Great and Wide Sea
on down the line, effects the closing of the next bottle, and so on,
until the lowermost bottle is closed. The closing mechanism may
be a rotating valve, caused to rotate by the weight of the metal
bottle when it has been released, or it may be some form of top and
bottom "stoppers," so placed that the cylinder, which was previously
open at top and bottom, falls upon the bottom stopper while the
weighted upper stopper falls into the top of the bottle.
By whatever type of mechanism the water samples are taken, they
may be titrated in the ship's laboratory at once or they may be trans-
ferred to glass bottles which are then sealed for later precise analysis
of the contents. Needless to say, analyses for salinity or oxygen
content must be done with extreme precision where a particular
mass of water, distinguishable by a small difference in salinity or
oxygen content, is to be traced over considerable distances as it lies
above and below masses of different characteristics, and perhaps of
different directions of movement. Salinity can also be computed
from the accurate determination of density, from measurement of
the electrical conductivity or from the refractive index at a given
temperature. For determinations by measurements of electrical con-
ductivity it is not always necessary to take actual samples of water
and bring them to the surface.
Throughout the oceans there is general uniformity in the propor-
tions of the several inorganic salts with chloride ions constituting
about 55 per cent of the dissolved solids. Except, then, near conti-
nental shores, where land drainage affects the constitution of the
sea water or where special conditions may prevail, the differences
in the composition of sea water from place to place and from time
:o time are differences of concentration. Consequently, to ascertain
ite composition of any particular mass of sea water it is sufficient
:o determine only the amount of chlorine, or the chlorinity 9 which
s readily and accurately determined by titration with silver nitrate,
employing potassium chromate as the indicator. The salinity is then
ecorded by multiplying the chlorinity, stated in grams per kilo-
gram, by 1.805 and adding 0.03; it is expressed in parts per thousand
ising the symbol o/oo. Actually the determinations are not nearly
;o simple as this brief account may seem to imply: for one reason,
>ecause they involve the use of a standard "normal water" which
vas formerly prepared and distributed from the hydrographical
The Sea as a Solution
laboratories of the International Commission for the Explora
the Sea in Copenhagen, and now from the Woods Hole C
graphic Institution. 2
Since density, salinity, and chlorinity are closely interrelat
indirectly determinable from specific gravity, and since thesi
are sometimes confused, it is well to keep in mind their res
meanings. Density is the mass of matter per unit volume; we
say that its measure, with respect to gravity, is the weight of ,
volume, stated generally in grams per cubic centimeter at som<
fied temperature, which, in the case of water, is 4C. Pure
at either a higher or lower temperature than 4C, because of
sion, has a density somewhat less than one. Water with :
solution has greater density than pure water at the same tempe
The measure of density of a solution relative to that of c
water at 4C. is called specific gravity. When we speak of the
ties of different masses of sea water we are usually treating of s
gravities, which vary with salinity, with temperature, and, t
extent, with pressure. Now, although the specific gravity
water is proportionate to its salinity, or to the amount of
solution, the measures of the two qualities are not identical,
the presence of 35 parts of salts per 1,000 parts of sea wate
a salinity of 35 o/oo, but a specific gravity of only about i
little more or less, according to temperature. It will be son
higher under the conditions of great pressure in the depths
sea, and the pressure will, in turn, have some effect on temp
(cf. p. in, below). The relations of salinity and chlorinh
already been mentioned.
Distribution of Salinity
Generally the salinity in the oceans is between 34 and -
since the range in all oceans is small, the average salinity is
given as 3 5 ; actually it is a little less. In regions of high rainf a
dilution by rivers or melting ice the surface salinity may be <
erably less, as in certain semi-enclosed areas, such as the Baltic,
it may be less than 10, or, the Gulf of Bothnia, below 5. <
other hand, in isolated seas in intermediate latitudes where e^
tion is excessive, the Red Sea being an outstanding sample, &
2. See Sverdnip, Johnson, and Fleming, op. ch^ p. 51.
82 This Great and Wide Sea
may reach 40 or more, even up to 46.5.* There are oceanic areas of
relatively high surface salinity. Probably the greatest of these is the
central part of the great North Atlantic eddy, known as the Sargasso
Sea, with salinity as high as 38; a somewhat similar area is found in
the South Atlantic. The Indian Ocean has two such areas, one large
and extending southward from the Persian Gulf to the equator, and
another west of Australia with salinity of about 36. The North
Pacific presents no large area of surface waters with salinity above
36, but in the South Pacific there is found off the coast of Peru an
area with salinity of 36.5.*
On the average, the surface water of the sea as a whole is saltier
in the southern hemisphere (salinity about 35) than in the northern
(about 34). This is not surprising in view of the fact that there is
less sea water in the northern hemisphere (p. 59, above) to receive
the fresh water of rainfall upon land and sea.
In regions of low temperature and little evaporation, the surface
waters may be notably low in salinity, as in the Arctic where it is
30 or less. In general, the salinity is low in high latitudes and high
in low latitudes; yet the maximum mean salinity is found not just
at the Equator but, rather, approximately in the regions of the
Tropics of Cancer and Capricorn, or some 1,500 miles north and
south of the Equator. From causes that are not yet fully under-
stood the waters of the North Pacific are, in general, substantially
[ess saline than are those of the Atlantic, and this is surprising con-
sidering that "about half of the world drains into the Atlantic Ocean,
ind most of this into the North Atlantic." 5
The salinity of deep and bottom water varies within narrower
limits than does that of the surface water, which is more directly
iffected by rainfall and evaporation. 6 The range for deep water is
generally 34.5 to 35, but exceptions are found in the Mediterranean
ind Red seas, where waters of high salinity and high temperatures
ire found at great depths. The outflows into the great oceans from
hese nearly enclosed seas form distinctive deep waters of unexpect-
3. Richard Hesse, W. C. Alice, and Karl P. Schmidt, Ecological Anvmoi Geog-
>aphy, p. 164.
4. Manner, op. crt., p. 135.
5. Herdman, Founders of Oceanography, p. 182.
6. "It has been estimated that the surface waters of the sea have a salinity of
bout 34% while the waters of the sea as a whole have a salinity of about 34%."
farmer, op. ctt., p. 150.
1 he bea as a Solution
edly high salinity which can be traced for thousands of
It may be added finally that there is as yet no adequate e
tion for the great disproportion in which chlorine and sodiun
in the sea, as compared with other chemical substances cu
contributed by the rivers. The whole question of the dispai
tween relative abundance of the elements in sea water and
total drainage from lands into the ocean is too complex for
examination here. Living organisms undoubtedly play an-
long played a significant part in affecting concentrations
several elements in sea water and in contributing to the pen
removal of some materials through deposition on the boti
the sea.
Effect of Salt on Circulation ,_
As is often the case, the capacity to change is more imports
is the condition at any given time. The concentration of salt
water is subject to change almost anywhere, because of dilut
fresh water that comes from the lands, directly from the atmo!
or from the melting of drifting icebergs. Such changes occur
in continental regions; but everywhere over the whole exp;
the oceans, changes in concentration are regularly taking pL
cause of evaporation at the surface. The increased specific \
that goes along with increase in concentration leads to vertical
ments; that is to say, to the transport of surface waters to the
and the lifting of deeper and lighter waters toward the surf a
cause of various complicating factors horizontal movemei
superadded to vertical shifts. If the waters of the oceans we
a solution of many salts there would still be changes of derisi
to rising or falling temperatures, but one of the great factors
general scheme of oceanic circulation would be missing.
If, as the physical oceanographers tell us, water from the
terranean Sea, flowing out over the sill at the bottom of the
of Gibralter, can be traced through the South Atlantic and ;
the Cape of Good Hope (see p. 128 below), this great mo^s
could have originated only because the water exposed to the
terranean sun was salty to begin with and became more so tl
evaporation. The salts of the earth are important to plants ai
mals of land and fresh water, but nowhere else than in the
4 This Great and Wide Sea
ould they play such a great part in causing movements of environ-
ments.
The general scheme of circulation that makes the oceans one
;reat dynamic mechanism will be a subject for later discussion. Let
is keep in mind, now, as we consider the saltiness of the sea, only
hat one key to the dynamics of the sea is found in the fact that sea
vater is not pure water but a chemical mixture of evaporable water
nd heavier non-evaporable mineral substances. Furthermore, as we
hall see later, we may have in any region, between the surface and
he bottom, a series of identifiable strata of water distinguished in
>art by degrees of concentration of salts in the waters of the several
trata. Of course there is slow mixing along boundary surfaces, but,
vith the great masses of water involved, the recognizable stratifica-
ion is long persistent.
yrganic Substances in Solution and Their Distribution
The comparative uniformity in proportions of dissolved materials
n offshore waters is generally accepted. It is a near approximation
o the truth and one that may easily be overemphasized. Most sub-
tances in solution become, directly or indirectly, nutriment to
>rganisms that live in the waters, and the abundance of the plants
hat chiefly appropriate them is very variable with the season and
pith other conditions. It may well be, then, that materials which
>ccur in minimal quantities relative to demand are at times removed
rom solution, either entirely or to such an extent as to place a limit
n the development of the organisms that require such substances.
N. R. G. Atkins and H. W. Harvey, at the Plymouth Laboratory,
England, and some others, have investigated this subject extensively.
Nitrogenous compounds and phosphates, particularly, and perhaps
ilica, sometimes become so depleted as to check the growth of drif t-
ig microscopic plants and the animals that feed upon the plants.
Then, too, some of the dying plants and animals may sink into
eeper layers of water, there to become decomposed and dissolved,
ielding the chemical materials in a region where, for lack of light,
hey can not again be immediately utilized.
On land, leaves, twigs and other parts of plants, and the wastes of
nimals, fall a distance of a few feet to the ground to decay and
'ecome the nutrients of other plants or to furnish food for small
nimals or for bacteria of decomposition, which in turn are eaten
The Sea as a Solution
by animals. In ponds and lakes the organic wastes likewise ac
late on the bottom and there harbor a luxuriant commui
scavenger animals and bacteria. In the great open sea, howe\
fall extends through a long distance and, since the bodies of t
dominant populations of the sea are minute, the rate of sin
exceedingly slow. Even a large copepod falling at a rate of
one centimeter per second (or about 2 feet a minute) would j
a couple of days to reach a depth of a mile; protozoa, diator
coccolithophores must sink at vastly slower rates, except, p<
as the streamline form of some diatoms may facilitate sedimer
Meanwhile, the living animals of intermediate depths are al
supported, and what other source of food than the down-
bodies is available for such animals? There is also ample tib
the dissolution of the small bodies, so that in areas of great
even calcareous and silicious skeletons may be completely di
before the bottom is reached. It appears that, barring the ex
deposits of skeletons in regions of appropriate depth, ther<
great accumulation of solid organic wastes in the depths of t
On the other hand, there is a considerable accumulation
ganic matter in solution, which, although in dilute form,
stantial in amount. Krogh estimated that the dissolved c
substance was equivalent to some three hundred rimes the a
of living organic material in the sea at any one rime. He calc
that the Atlantic Ocean had dissolved organic matter equal to
times the world's wheat harvest for one year; he suggested tl
sibility that this material had "in the main gone out of c
circulation," that it was unrecoverable and was possibly accu
ing. There is, however, increasing knowledge of the capac
bacteria and other organisms of the depths of the sea to util
dissolved organic matter.
Clearly, with the slow but continuous subsidence of c
material from the upper into the deeper waters, questions '<
to its ultimate fate or the fate of its component substances
the drainage from surface to deep represent in considerab
an irretrievable loss to the organic world? Rates of diffusi
so slow, and the distance so great, that the return by diffu!
dissolved nutrient matter from the bottom to the upper wat
been thought to be insignificant. A quotation from Krog
suffice here:
?<f This Great and Wide Sea
"If no mixing took place the depletion would go on to exhaustion
ind life would die out except along the coasts, but in certain areas,
nainly at fairly high latitudes, but also for instance in the huge Gulf
)f Guinea, waters from the deep rise to the surface and become
he seat of a large outburst of planktonic life which imparts a distinct
int of green to the water. From these areas of fertility and abun-
lance the waters spread by the currents become progressively
>oorer in the salts necessary for plant growth, and the large areas of
he ocean where the water is of a pure blue can only be compared
o deserts supporting a minimum of life." T
Jases in Solution 9
There can be no life in water or on land without two simple sub-
itances which, almost invariably, at least, can be used only in the
jaseous form. Reference, of course, is to oxygen and carbon diox-
de. The production of organic matter of all kinds is based ulti-
nately on the synthesis of sugar from water and carbon dioxide in
funlight. To the best of our knowledge, the activities and functions
rf both plants and animals, including growth, reproduction, and the
various mental functions of such organisms as have them, are gen-
erally associated in some way with oxidation; the anaerobic bacteria
ind some other anaerobes may get their oxygen second hand.
The chief gases dissolved in the sea are nitrogen, oxygen, and
sarbon dioxide. Nitrogen occurs in sea water in a ratio to other
jases somewhat smaller (64 per cent) than in the air (78 per cent),
:>ut in approximately saturated solution. The elemental nitrogen in
he sea, so far as is now known, has little or no biological significance,
except in so far as nitrogen-fixing bacteria may use it for the pro-
iuction of ammonium salts and nitrates. Such are found to be active
:>n or near the bottom, and more abundant on some bottoms than on
others. There is now no reason to suppose that such bacteria play
my considerable part in the economy of the open ocean.
Oxygen is about one-fifth less soluble in sea water than in fresh
;vater, but it is absorbed in sea water in a proportion to other gases
7. Krogh, August. "Conditions of life in die ocean." Ecological Monographs, 4:
934 PP* 4^3~4
8. As they are found by plants and animals, the relations of these gases to water
s a physical rather than a chemical one, but we consider them in this chapter be-
muse we are concerned with them only as they play their parts in chemical reac-
ions involving die use of water and the chemicals in solution.
9. H. W. Harvey, 1928, p. 14 (quoting Krogh), and 1945, p. 112.
The Sea as a Solution
(34 per cent) substantially greater than in the air (21 per <
percentages applicable to sea water at the surface with sali
35 and temperature of roC. The figures indicating the i
oxygen relative to other gases in dissolved, as compared with
pheric, air are of less practical significance than are those inc
the volumes of oxygen in a liter of sea water at the point of
tion and this varies with the temperature, the pressure, t
salinity. At any given temperature and pressure, sea water c
in solution less oxygen (about one-fifth less) than can fresh
as is indicated by Table EL 10
TABLE II
SOLUBILITY OF OXYGEN IN FRESH AND SEA WATER AT DIF
TEMPERATURES UNDER CONDITIONS OF ATMOSPHERIC Mm
AND UNDER A PRESSURE OF ONE ATMOSPHERE
Temperature Fresh Water Sea Wa
(Salinity o per M.) (Salinity 35 ]
Oxygen in cc. per liter Oxygen in cc. j
o 10,29 8.03
10 8.02 6.40
20 6.57 5.35
30 5.57 4.50
The free oxygen in sea water is derived pardy from the
phere by absorption at the surface and partly from the ph<
theric activities of plants. The photosyntheric zone, as we s
later, is a superficial stratum some hundreds of meters in dej
it does not follow that the plants throughout all the depths ai
they may live are net contributors to the supply of free
available for animals. In the deeper zones inhabited by plar
may consume as much oxygen as they produce, or more, so
net contribution is nil or a minus quantity. The level at
oxygen consumed and oxygen produced are in balance is ca
compensation depth; in the Gulf of Maine in June, 1934, t
at 24-30 meters. 11
10. After Fox, from Murray and Hjort, The Depths of the Ocean, p. a
11. G. L. Clarke and R. H. Oster, "The Penetration of the Blue and I
ponents of Daylight into Atlantic Coastal Waters and its Relation to Plr
ton Metabolism," Biological Bulletm, LXVH (1934), 71.
8 This Great and Wide Sea
The solubility of carbon dioxide in sea water is such that it has
bout fifty times the ratio to other gases which it has in the atmos-
here, but even that is a very small proportion approximately 1.6
er cent of all gases by weight in sea water, as compared with 0.03
er cent in atmosphere. But carbon dioxide in the sea is present
i several forms: (i) as CO 2 in true solution, (2) as the undisso-
iated carbonic acid, H 2 CO 3 , in minute quantity; (3) as dissociated
arbonic acid, 'HCO~; (4) as the slightly soluble carbonates; and
5) as the more soluble bicarbonates. The carbonates and bicarbo-
ates are possible because the bases, calcium, magnesium, etc., in sea
rater are present in amounts greater than the equivalent of stable
cid radicals. This excess base constitutes the "alkali reserve" which,
i changing combination with carbonic acid, is of considerable sig-
ificance in maintaing a reserve of CO 2 for the use of plants. The
apacity of carbon dioxide to form loose or stable combinations
fith bases helps to maintain the acid-base equilibrium in sea water
nd to preserve a more favorable environment for all forms of life,
dthough the amount of carbon dioxide in true solution in a liter
f sea water must be measured in tenths of a cubic centimeter, there
; usually available, free or in combination, something like 45-50 cc.,
s compared with 5-10 cc. of free oxygen. About two-thirds of the
rcess base is present as the bicarbonate, which, being unstable,
sadily yields carbon dioxide to plants in rime of need. Conse-
uently, the changing combinations of CO 2 and the bases present in
sa water, act as a sort of bank-account for plants, the all-important
!O 2 being subject to regular "deposit" and "withdrawal."
Sea water is a little on the alkaline side of neutrality, but the de-
ree of alkalinity varies with hour of the day and season of the
ear. When the minute green (or yellow) plants are most active in
right sunlight, as at midday, and particularly in summer, the sup-
[y of CO 2 is diminished, the carbonic acid is less, and the shift is
>ward greater alkalinity. At night or in midwinter, when the re-
ase of CO 2 in respiration exceeds its withdrawal for photosynthe-
3, the supply of CO 2 and acid is greater and the water shows some-
hat less alkalinity. So far as animals and plants are concerned, the
nail changes in alkalinity or in hydrogen ion concentration, in off-
12. See Harvey, 1928, op. cit., pp. 64, 67.
The Sea as a Solution 8$
shore waters, probably have no significant effect on their move-
ments or welfare. More extreme changes of this kind, artificially
induced in the laboratory, may have decided effects. Changes such
as may occur in coastal waters, from the inflow of drainage waters
or from the extreme utilization of CO 2 in prolific plant growth, may
also have biological significance.
The relatively high solubility of carbon dioxide in sea water is of
great biological significance. After all, the synthesis involving union
of carbon dioxide and water in sunlight is the basis of all life. Ter-
estrial plants are surrounded by an atmosphere having only about
three one-hundredths of one percent of the essential carbon dioxide
and they must generally find their water through extensive root
systems. Pure water can hold in solution a somewhat greater
amount of carbon dioxide than is present in an equal volume of at-
mosphere. Sea water is not pure but alkaline, and the alkalinity en-
ables it to hold in true solution and in loose combination something
like one hundred times as much carbon dioxide as does an equal
volume of ordinary atmosphere. Consequently, where sunlight is
available, the minute marine plants have at hand a larger store of
this necessity along with an unlimited supply of water that does
not have to be "pulled up" from a soil through roots and stems.
Carbon dioxide moves very slowly from atmosphere to sea, and
vice versa, but it has been said 13 that the sea generally absorbs CO 2
from the atmosphere. If that is broadly true, the atmosphere is a
reservoir of CO 2 for the sea, and it might be presumed that photo-
synthesis in the sea exceeded that on land. To the speculative mind
this would tie in with the fact that the drift of raw materials for the
production of organic life is toward the sea. At any rate, the greater
the photosynthesis in the sea, the less is the permanent loss from the
organic cycle of materials caught in this great catch basin of ter-
restrial wastes.
The conditions of life of all animals and plants in the sea and in
other waters, as compared with those of terrestrial organisms, are
marked by this important distinction that the gaseous oxygen es-
sential for respiration, occurs in relatively extreme degree of dilu-
tion. A liter of air contains twenty-five or more times the amount of
oxygen that can be dissolved in a liter of sea water. The reverse
13. Ibid-, p. 64.
>o This Great and Wide Sea
with different proportions) is true of carbon dioxide, as we have
een.
Since the solubility of gases in water varies inversely with tem-
>erature, the cold waters of the Arctic are much richer than tropi-
al waters, in both dissolved carbon dioxide, necessary for photo-
ynthesis, and dissolved oxygen, required for respiration. Cold
waters, being heavier than warmer waters of like salinity, tend to
eek the bottom, and abyssal waters of all oceans are presumed to be
lerived in considerable part from the polar regions, particularly
rom the Antarctic, and to have been especially rich in oxygen at
he start. Surface waters generally have an overabundance of oxy-
gen. Deep waters might be supposed to be generally poor in oxygen,
ince the dissolved gas is used both in the respiration of abyssal ani-
nals and in the decomposition of organic materials which have set-
led to the bottom from the waters above, while, in the absence of
>hotosynthesis in the darkness, no free oxygen is being liberated
here. Mixing ("overturn") occurs in high latitudes, as we shall see
ater, and especially during the end of winter, when the colder
icavier waters of the surface, laden with oxygen, sink to a lower
evel to replace the somewhat lighter waters which rise to the top to
>ecome reoxygenated. Unfortunately for a happy answer to the
wroblem of the sources of oxygen in the depths, too many of the
mown vertical movements seem to affect only the relatively thin
ipper strata of sea water.
The actual conditions do not conform to any rules that may be
imply stated. Bottom waters, especially in the Atlantic, where they
nay be 75 per cent saturated, may contain more oxygen than
ayers far above them. Seiwell 14 observes that the minimum con-
'entration of oxygen in the western North Atlantic is generally be-
ween depths of 200 and 900 meters, with values ranging from 1.7 to
aore than 5.0 cc. per liter. Vaughan 16 says that there is in the east-
rn Pacific, usually between 600 and 1,200 meters, a layer where the
vater is only 5 per cent saturated with oxygen, while, below that,
he maximum saturation may range between 30 and 40 per cent.
14, H. R. Seiwell, "The Minimum Oxjrgen Concentration in the Western Basin
f the North Atlantic," "Papers in Physical Oceanography and Meteorology, V
1937)'
15. T. Wayland Vaughan, tc Present Trends in the Investigation of the Relation
f Marine Organisms to their Environment," Ecological Monographs, IV (1934),
The Sea as a Solution $ i
Carbon dioxide is certainly not consumed by green plants be-
low some 1,000 meters, and doubtless rarely at that depth, although
it must be produced there in quantity both by the respiration of
animals and by the decomposition of organic material. What then
becomes of that part of it in the depths which may not enter into
permanent chemical combination with dissolved minerals? Are the
vertical movements of water sufficient to maintain the proper equi-
librium of dissolved gases in the depths? We do not seem to have
the complete answers to these highly important questions.
Utilization of Material in Solution
At best sea water is a very dilute solution of many of the materials,
such as phosphates and compounds of nitrogen, required for the
growth and multiplication of plants; and, of course, the animals are
dependent upon plants for protein food, for the energy stored by
plants, and for a continuing supply of oxygen. Concentration of
some of the food substances in sea water is many times less than in
good soil. Correspondingly, marine plants must be adapted to de-
rive nutriment from an extremely weak solution, to tike oxygen
where it is relatively scant, and to absorb radiation where the light
is comparatively dim. Put in another way, they must have greatly
extended surfaces relative to size of body to permit of maximum
efficiency in absorption through the surface. In short, they must
generally be of minute size, since the smaller the body the greater
the ratio of surface to volume.
As Brooks pointed out long ago, it is advantageous for the new
plant cells formed by cell multiplication to separate from each
other as soon as possible in order to expose the whole of their sur-
face to the water. Cell aggregation and specialization in form have
not taken place among marine plants in any way comparable to
what has occurred with terrestrial vegetation. Hence we find in the
sea no direct counterparts to the grassy meadows and prairies or the
true forests and jungles of the land. The coastal "forests" and "gar-
dens" of dense populations of relatively simple seaweeds and the
so-called "floating islands" of sargassum are only apparent excep-
tions to the rule.
Of course, marine life requires no protection against desiccation,
such as is requisite for terrestrial animals, except where the home
92 This Great and Wide Sea
In further consequence of its chemical surroundings, the marine
>rganism, in comparison with its relatives in fresh water or on land,
las a much simpler task in preserving its own internal chemical
itability. Living continuously immersed in a solution not differing
videly in salt content from its body fluids, the minute plant, the
protozoan, the soft-bodied larva or the adult of higher groups re-
juires relatively little protection against unfavorable or fatal chemi-
:al interchanges between body and environment. Even for them,
lowever, the problem is not entirely wanting and protective devices
nay be needed. 16
Perhaps the most notable distinctive feature of the conditions of
ife in the sea (or life in a chemical medium) as contrasted with the
renditions of life on land is the promptness and completeness of the
Affects of fertilization of upper water by the upwelling of the rela-
ively rich deep-lying waters, wherever that may occur. This is
liscussed further in connection with "upwelling" (p. 140, below).
)nly certain features- of contrast need be mentioned now. When
oils are fertilized by man or by nature with the formation of
lumus, the growing plants have to search for the nutrients through
laborate root systems. In contrast, when surface waters are natu-
ally fertilized by upward movement of deeper waters, the bodies
>f one-celled plants are all in immediate contact with the pre-dis-
olved fertilizers. Ultimately the materials may be lost from upper
vater through the falling of solid wastes, but this occurs only after
tilization of nutrients in solution to form plant and animal bodies.
We have passed over an important group of organic products in
^lution. Living or decomposing organisms may give out into the
^ater "metabolites," wastes that may have diverse effects. They
ould be beneficial, as are vitamins, harmful to one or another spe-
ies as "antibiotics," or actually toxic. Mortalities of fishes and other
ndmals in the so-called "red tides" are attributed to wastes released
y dinoflagellates (pp. 172 and 204) when from unknown causes
icy develop extraordinary populations. On the other hand, animals
ften do better in company of others of their own or another kind.
. substance that helps one kind may be harmful to another. 18a
1 6. For an example, with respect to fish, see p. 182, below.
i6a. I need refer here only to W. C Alice, t( Recent Studies in Mass Physiology,"
ol. Rev. t 9, 1934, an< ^ C- E. Lucas, "The Biological Effects of External Meta-
>lites," ibid., 22, 1947.
The Sea as a Solution $3
Finally it is worth while to stress, not only the availability of the
nutrients in sea water, but also the completeness of the menu, so to
speak, for plants. The agriculturist now knows the importance of
what are called "trace elements" which are not necessarily found
in ordinary commercial fertilizers and are irregularly present in soils.
If deficient in the soils, they will be deficient in the plants growing
on the soils and in the animals that subsist on the plants. Accord-
ingly, the diet of whole communities of people may be sub-standard
in respect to this or that element essential for proper body functions.
Who does not know of goitre-ridden communities where soils are
deficient in iodine and sea food is not readily available? But iodine
is only one of the trace elements. The story has been told concisely
and vividly by Taylor. 17
"For ages die rains have been falling on the land, washing out the
soluble nutrients and carrying them down the rivers to enrich the
sea. By this process the sea has become an inexhaustible reservoir of
nearly all the soluble nutrients of the world not only of the famil-
iar fertilizers, fixed nitrogen, phosphorus and potash, but of the in-
dispensable array of trace elements such as iodine, fluorine, boron,
manganese, copper, zinc, and indeed whatever additional elements
may yet be found necessary to life; for they are all there, and in
such quantities that if the whole of mankind took all of its chemical
supply from the ocean, or dumped into it all of the chemicals it pos-
sesses, not the slightest detectable change would be made in the
composition of the sea. The plants and animals at sea are collectors
and concentrators of these elements, and when we bring them ashore
we return to the land a tiny fraction of what has been taken from
the land. The ocean is not only quantitatively the biggest, but quali-
tatively the most perfect source of nutriment in the world."
17. Harden F. Taylor, "Research in the Fisheries for the Betterment of the
South," in Research and Regional Welfare, Chapel Hill: The University of
North Carolina Press, 1946.
CHAPTER 7
f^hydical f^ropertied of J^ea lA/ater
Temperature
THE OCEANS CONSTITUTE AN ENORMOUS RESERVOIR OF HEAT.
This is not only because by far the greater part of the radia-
tion coming to the earth from the sun falls upon the surface
of the sea but also because, of all liquids and solids except ammonia,
water has the highest "specific heat," or the greatest capacity to ab-
sorb heat with minimum rise in temperature; to raise the tempera-
ture one degree requires the application of more heat for water than
for any other ordinary substance except ammonia. Raising the tem-
perature of the surface of the sea at any spot by only a few degrees
represents a tremendous storage of heat, which can be given off in
winter or at some distant place to which the water may be trans-
ported by currents, if the air above the water at the second place is
cooler than the sea. Obviously, too, great volumes of air can be
heated with little reduction in temperature of the water.
Furthermore, the sea contributes greatly to the reservoir of heat
in water vapor of the atmosphere. Water has by far the highest heat
of evaporation of all known substances that are liquid at ordinary
temperatures; in change from the liquid state to vapor it absorbs and
holds more heat than does any other such substance in making a cor-
responding change, and sea water is not essentially different from
pure water in this respect. Therefore, it is through evaporation of
the surface of the ocean that great quantities of heat are stored in the
form of water vapor, to be released again over other parts of the
ocean or over the land. Since, as it has been estimated, some 90 per
94
Some Physical Properties of Sea Water $5
cent of the heat surplus of the oceans is used for evaporation, "evap-
oration is of much greater importance to the heat balance of the
ocean than is the transfer of sensible heat." *
Water is peculiar also in the amount of heat absorbed in the melt-
ing of ice, and conversely, in the amount of heat that has to be re-
moved from water to permit freezing. 2 In this respect, again, it is
exceeded among common substances only by ammonia. It is not by
chance that we use water or water vapor (steam) for the distribu-
tion of heat throughout our buildings or that we use ice or ammonia
in refrigeration. So the seas serve in the great terrestrial heating and
cooling system, playing a leading part in the world-wide distribu-
tion of heat, and giving a sort of thermostaric control to regional
temperatures.
The source of heat is the sun, but the sunshine falls unevenly on
the earth, being greatest in tropical regions and least at the poles. The
absorption of solar radiation by the sea, its influence on movements
of sea water, and the part the sea plays in the general distribution of
heat over the earth are proper subjects for consideration in a later
chapter. At present we are concerned merely with the general con-
ditions of temperature in the seas as compared with temperatures on
land.
In the first place, it is to be noted that the range of temperature
in the sea is far less than that on land, and this is true whether we
consider daily or seasonal changes at a particular place, or the ex-
treme range over the whole world. Apparently, sea water is never
more than two or three degrees below the freezing point of fresh
water, the formation of ice checking a further fall; and it is rarely
higher than about 8oF. (27C). Evaporation serves as some check
on the rise. Air temperatures over the open sea are never far different
from those of the water. Over land, on the other hand, the air tem-
peratures may be 60 or 7oF. below zero or more than i2oF.
(about 50C.) above; they vary widely, not only with the season,
but also with the hours of the day. Nowhere in die sea, in contrast,
is the surface temperature likely to vary more than 10 with the
season or more than about one degree between day and night. 8 The
1. H. U. Sverdrup, Oceanography for Meteorologists, p. 6*2.
2. But see footnote 4,.p. 98, below.
3. There are, however, some geographic areas where at certain times warm cur-
rents displace cold water, and vice versa, so that seasonal differences as great as
40F. may be found. (See Manner, The Sea, p. 132, and below, p. 132.)
j?6 1 bis idreat and Widebea
highest temperatures in the oceans are found to come about two
o'clock in the afternoon and the lowest about five in the morning.
In the northern hemisphere surface waters are coolest in February
and warmest in August; in the southern hemisphere, the reverse is
the case. The temperature of the surface water in the ocean does
vary to some extent with season and with longitude, but much more
notably with latitude and with depth. At any given place deep water
is virtually unchanging in temperature, and it is always cold; bot-
tom water varies between 4C. and i.5C. Consequently, the
range of temperature between surface and bottom may be nearly as
great as between any two points on the surface.
Because of currents, to be discussed later, which convey great
masses of equatorial water toward the poles or bring waters from
Arctic and Antarctic regions toward the tropics, and, in part also,
because of sinking and upwelling movements of water in different
regions, the seas are generally warmest in their western parts.
At the most, the seasonal variations in temperature are rela-
tively small as compared with those that prevail on land in temperate
and subpolar regions and as compared with those of most fresh
waters in the same regions. Indeed, beyond a depth of about 200
meters, seasonal variations do not occur at all. Differences between
summer and winter temperatures of the surface of the Atlantic
Ocean are least in polar and in tropical regions, greatest in the north
temperate zone. Variations with latitude are notably modified by
ocean currents; so that, while comparatively warm water in the
course of the Gulf Stream prevails far up in the northern Atlantic,
surprisingly cold water is encountered in the path of the Humboldt,
or Peru, Current very close to the Equator in the eastern part of the
Pacific Ocean. The drift of icebergs also has observable effects on
the temperature of the North Atlantic, effects that vary with the
year and with the shifts of currents.
Sea water has no definite freezing point. There is a point on the
temperature scale for sea water of any given condition of salinity
when ice crystals begin to form; but the "freezing out" of pure
water leaves the remaining unfrozen water with higher salt content
and, therefore, with lower freezing point. Further cooling causes
formation of more ice crystals with still further increased salt con-
centration and lowered freezing point in the remaining water, until
finally there is formed a solid block of mixed ice and salt crystals.
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$8 This Great and Wide Sea
With rising temperatures the process is reversed: the first thawing
liquefies a part of the ice, and takes up heat; further heating is neces-
sary to cause further melting. It is a fact well known to polar ex-
plorers that, where sponge ice has been forced into heaps in such a
way that the concentrated salt water may seep out, the solid sea ice,
when melted, may give good drinking water. 4
Unlike fresh water, sea water becomes heavier as it is cooled until its
freezing point is reached, 5 so that the limitation of 4C. for tempera-
tures at the bottom of lakes does not apply in the sea, and bottom
temperatures of 1, or lower, may occur in polar currents; but,
although the temperature at which freezing begins ( i .9 for water
with salinity of 35 o/oo) is substantially lowered under high pres-
sure, bottom temperatures below the freezing point of fresh water
seem to be rare; nevertheless, they do prevail in some places, as in the
Norwegian Sea. Generally the temperature of abyssal waters is a
little above zero, owing no doubt in great part to what Helland-
Hansen has called "adiabatic warming" warming resulting from
the effect of pressure (see p. 1 1 1, below.) In the North Atlantic gen-
erally the bottom temperature is around 2C. The bottom water is
cold in equatorial as well as in polar regions; even at the Equator one
can find sea water close to the freezing point, if one only goes deep
enough. It may be recalled (p. 26, above, footnote 13) that ooze
from the bottom in tropical seas served well in lieu of ice for the
cooling of champagne! "Over 4/5 of the ocean floor exceeds one
mile in depth and has a temperature colder than 3C." 6 The barriers
of temperature and pressure that exist between the bottom and the
surface (separated by a distance of 4 or 5 miles) at the equator are
much more effective than those that exist between two points 10,000
miles apart on the bottom.
With respect to surface temperatures, latitude is the principal
4. Often sea ice contains air bubbles, since air may creep in where brine has
trickled out. Consequently the density of sea ice varies; it may be a little more or
a little less than that of pure ice. Sea ice is said to be highly transparent for visible
radiation. We speak of the beat of fusion of ice which is approximately 80 cal/g.
With sea ice, in contrast to ice from pure water, melting occurs whenever the
temperature rises, no matter how low it may be, so that no specific value for the
heat of fusion of sea ice can be stated. It does, however, require a substantial
amount of heat to melt a given amount of sea ice. See Sverdrup, 1942, pp. 33, 34.
5. This applies to water with a salinity of 24.7 o/oo or higher.
6. Claude E. ZoBell, "Microbiological Activities at Low Temperatures with Par-
ticular Reference to Marine Bacteria," Quarterly Review of Biology, IX (1934),
460-66.
Some Physical Properties of Sea Water 99
factor determining differences between different regions. There is
on the whole a decrease in average temperature from about 8iF.
(27C) near the Equator to about 29F., or 3 below the freezing
point of fresh water, in Arctic and Antarctic regions. As a rough
rule, it may be said that the average surface temperature decreases
about one-half a degree C. for each degree of increase in latitude. 7
The average surface temperature for the sea as a whole is about
63F., but it is higher in the northern hemisphere (67?.) and lower
in the southern (6iF.). For the Atlantic and the Indian oceans the
average temperatures of surface waters are not greatly different, but
for the Pacific it is some 4 higher (66 1 / 2 F.) . Obviously the princi-
pal reason for this difference is found in the forms of the two oceans.
The Pacific is roughly oval in shape, with great breadth in equatorial
regions where high temperatures prevail, but the Atlantic is some-
what hour-glass shaped, with a narrow waist in the low latitudes
crossing the Equator obliquely.
Evaporation tends, of course, to increase the density and weight
of surface water and might be expected to cause it always to sink,
but widespread vertical movements from this cause are believed to
be relatively insignificant because, where evaporation is consider-
able, as in warmer regions, its effect in raising specific gravity may
be more than counterbalanced by the decrease in density resulting
from the warming of the surface water. The cooling effect of evap-
Dration comes also into the picture. The lower salinity of surface
water over the continental shelf, where runoff from land is felt, and
the higher temperature of surface waters over the seas generally,
both tend to keep top water on top. Nevertheless, "overturn" occurs
in high latitudes, especially during or at the end of winter, whenever
iie surface-cooled waters become colder and heavier than those
Beneath them; but this overturn affects, perhaps, only the waters
ibove the thermocline or zone of most rapid change of temperature.
H ow Temperature in the Deep Is Taken
From what has been said about the continuity of the seas and the
:onstant movements of water masses, it may be understood that
generally there are neither sharp differences nor continously pro-
gressive changes in temperature of sea water from place to place or
rom depth to depth. If we are to trace movements of masses of
i oo This Great and Wide Sea
water on the partial basis of temperature differences, we must be
prepared to measure very small differences and to do so with a high
degree of accuracy. Surface thermometers should be accurate to
o.io of a degree centigrade and they must be repeatedly standard-
ized. For the depths, the thermometer must be accurate to a much
smaller fraction of a degree, say to one one-hundredth of a degree.
There is the further complication that precise recordings of deep
temperatures have to be made at a great distance, often thousands of
fathoms, from the observer.
At one time insulated water bottles were used to take samples of
water at desired depths, and the temperature would be read an hour
or several hours later when the bottle was hauled aboard ship. The
insulation prevented great change of temperature between time of
taking and time of observation. It is obvious that really accurate de-
terminations were not insured. What was needed was a thermometer
that would register the temperature at a particular depth and not
change as it was brought up through the warmer, upper waters to be
read later, perhaps hours later. This need was first met by the re-
versing thermometer, introduced by Negretti and Zambra of Eng-
land in 1874. Subsequently, the instrument was greatly improved
by the makers, and particularly, by a German instrument-maker
named Richter. The technician who can make such a thermometer is
rare indeed; it is only recently that they have been made in America.
The tube of a reversing thermometer is drawn exceedingly fine in
one section, which is coiled in a complex way. At a particular point
the fine bore is still more reduced to make a "breaking point" for
the column of mercury. In the position of the thermometer as it is
lowered, the bulb, or reservoir of mercury, is at the lower end, but
the scale, to be read after reversal, has the zero mark near the upper
end of the thermometer, which is quite empty of mercury. When
the instrument has been lowered to the level at which the record of
temperature is to be made, a metal "messenger," clasped around the
line, is released to slide down and trip a catch that has held the ther-
mometer in unbalanced position: the thermometer inverts itself im-
mediately. The scale, which was upside down, is now right side up.
In this process of violent upset, the column of mercury should part
at the "breaking point"; so that all the mercury that was above this
point at the time of inversion falls to the new bottom end, from
which its length can be read on the scale at any later time of obser-
Some Physical Properties of Sea Water 101
vation. It does not matter what happens later to the main mass of
mercury, since the reading will be taken f rom the mercury that 'was
beyond the breaking point at the moment of reversal It is only this
snapped-off mercury that counts. It is customary to have also a small
thermometer alongside the stem and within an outer protective case.
The reading of this "stem thermometer" gives the temperature at the
time of reading and makes possible certain small corrections for ex-
pansion or contraction of the snapped-off mercury between the time
of reversal and the time of record.
The reversing thermometer lowered to great depths is subjected
to high pressures and it must, therefore, be protected by an outer
closed tube of heavy glass with a lot of cushioning mercury around
the reservoir. The protection is in part against the effect of extreme
hydrostatic pressures on the mercury in the thermometer proper,
and, therefore, on the reading of the thermometer. Obviously a
thermometer mounted in an open glass tube would give a reading
that would be dependent both upon the temperature and the pres-
sure, and this would affect the apparent reading. Consequently, if an
unprotected reversing thermometer is paired with a protected re-
versing thermometer the difference between the readings of the two
thermometers will be an indication of the pressure and, therefore, of
the depth at which the thermometers were reversed. Such a determi-
nation of depth is particularly desirable where the line by which the
thermometers are suspended extends at an angle from the ship and
may even be curved.
By means of thermographs continuous records of temperatures
may be taken; but this type of instrument can be used only from
fixed stations or for records near the surface of the sea. The thermo-
graph is a mechanism by which a record of the temperature is made
on a revolving paper-covered drum. In other types of instruments
a pin moved by the thermometer draws a line on a smoked-glass
slide, the position of which changes with the pressure, that is to say
in this case, with the depth. One of the latest instruments is the
bathythermograph. This contains a bellows that contracts with in-
crease in pressure as the instrument descends and a Bourdon ele-
ment that responds to temperature changes. This torpedo-shaped
instrument at the end of a light cable can be lowered into the water
from a vessel in movement. During its descent a record of tempera-
ture is plotted against depth on a small glass plate.
/ 02 This Great and Wide Sea
Temperature and Life m the Sea
Temperature apparently exerts in many ways an influence on th
chemical activities in protoplasm that underlie growth, form, an<
multiplication. Rate of photosynthesis increases with temperature
while rates of most biological activities are more than doubled b;
a rise of ioC. Temperature governs, to some extent, the distnbu
tion of animals and plants and, where a particular species has a rang
extending through low and high latitudes, its form or the characte
of its shell may differ with the latitude. As will be mentioned agai
in connection with the consideration of density, the form of an ani
mal or plant in a given region may be notably different in summe
from that which it has in winter. It is not, however, easily deter
mined whether the differences that appear to go with temperatur
are governed actually by temperature or by other environmenta
conditions associated causally or incidentally with temperature. Ii
many instances, and perhaps as a general rule, the size that an ani
mal attains is greater when it is reared at a lower temperature.
It is true of some organisms, and perhaps generally true, tha
organisms grow faster, but attain smaller adult sizes in warme
waters; that they reproduce earlier and more frequently in warme
waters. If they grow more slowly and reproduce less frequently ir
colder waters, they may not only become larger but also live longer
so that colder waters may harbor much larger populations of som<
organisms, such as diatoms and copepods. Cold-bred organisms ma)
also differ in form from warm-bred members of the same species
the latter tending, sometimes, at least, to develop spinous or plumos<
extensions of the body surface.
Gran says: "Temperature, more perhaps than any other factor
determines the growth and decrease of the various species and th<
character of the communities dominating the plankton. But some
species are adapted even to the most extreme temperatures found ir
die sea, and a rich growth can take place as well at the lowesi
(1.5) as at the highest temperatures observed." 8 "Tempera-
ture," says Martin, 9 "is less directly important in the sea than or
land since there is no great danger of injurious extremes being
8. H. H. Gran, "Phytoplankton, Methods and Problems," Cons. Perm. Intern
Explor. Mer., Jour. Cowed. VII (1932), 348.
9. George W. Martin, "The Food Resources of the Sea," Scientific Monthly
XV (1922), 457. (Of course, fish in the sea, subject to a narrow range of tempera-
ture, may be highly sensitive to small changes.)
Some Physical Properties of Sea Water 1 03
reached. Indirectly, its importance lies in the fact that carbon di-
oxide is much more soluble in cold water than in warm, and it is
probably this, rather than the direct influence of temperature, which
accounts for the fact that the most luxuriant development of plant
life is in the colder waters of the earth.'* Allen, 10 on the other hand,
questions the certainty of a generally greater productivity of plank-
ton in high as compared with low latitudes.
Viscosity
Water is a liquid, but liquids vary in respect to their fluidity, al-
cohol being more and glycerine less fluid than water. The same
liquid is more or less fluid under different conditions: thus, as every-
one knows, warm water flows more readily, or is "wetter," so to
speak, than cold water. An animal expends more energy in moving
the same distance through cold than through warm water. We are
concerned, then, with the viscosity of sea water, meaning its re-
sistance to change of form or to movement, so far as that is due to
the combined effect of the qualities of adhesion and of cohesion
among particles of water. The viscosity of fresh water is an environ-
mental factor of substantial significance to both animals and plants.
The viscosity of sea water is a little greater than that of fresh water
and increases gradually with increasing salinity. It varies much more
with temperature, being nearly doubled by a decrease in tempera-
ture from 25C (77F.) to oC. (32F.). The change in viscosity
with falling temperature is not uniform, the increase per degree of
lowering temperature being greater at the lower temperatures.
Under actual conditions, simple Icmtmar viscosity is greatly com-
plicated by what is called eddy viscosity. A body moving through
a liquid sets in motion, through frictional stress, the liquid imme-
diately in contact with it, and that in turn sets in motion the next
adjacent layer of liquid and so on. Actually, however, we do not
have thin uniform layers gliding smoothly over one another (lami-
nar motion.) Not only does random movement of molecules cause
Interchange of molecules between adjacent layers, but also masses of
water pass from layer to layer, introducing turbulence phenomena
and dynamic eddy viscosity, which is effective in both horizontal
and vertical directions. The analysis of turbulence phenomena or
10. Winfred E. Allen, 'The Primary Food Supply of the Sea," Quarterly Re-
view of Biology, DC, 175.
/ 04 This Great and Wide Sea
eddy viscosity now taxes the skill of the most expert physicists and
mathematicians. We refer at all to these complex subjects only be-
cause it ought to be kept in mind that "coefficients of viscosity," as
expressed in ordinary tables, touch only a small part of the problem
of viscosity associated with the movements of animals and plants
through water. Eddy viscosity is many times greater than laminar
viscosity.
In consequence of the relation between viscosity and temperature,
an incompressible object may sink much more rapidly at the surface
than in the colder waters below; but any object will continue to
sink so long as its specific gravity is higher than that of the water it
meets. The old idea that sinking ships are arrested in their fall at
some level of intermediate depth is, of course, without foundation.
A wooden ship would, indeed, attain a greater sinking velocity as
the pressure reduced its displacement by squeezing out the air from
the wood cells. Contrary to what might be surmised, pressure does
not materially effect viscosity; for pure water viscosity is even
somewhat reduced by high pressure at temperatures below 32C.
Influence of Viscosity on Organisms in the Sea.
The viscosity of the medium offers two of the marked contrasts
between life in water and life in the atmosphere. As any swimmer or
any designer of automotive craft well knows, it requires a very
much greater expenditure of energy to propel a body through
water than it does to drive it through the atmosphere. One might
suppose, then, that aquatic animals were necessarily slow of move-
ment as compared with terrestrial animals; but again we find such
adaptations of form and of locomotive power that the swiftest
animals of the sea, such as the bonitos and related fishes, and even
bulky animals like porpoises and the larger whales, are capable of
velocities of movement that compare well with those of the swiftest
of terrestrial or aerial birds and mammals.
The viscosity of sea water has a further significance to organic
life in water in that it retards sinking; but sinking velocity is also a
function of form. Because of the inverse correlation of viscosity
with temperature, the viscosity of water, unlike its salinity, varies
materially with die season. A peculiar phenomenon that has en-
gaged the attention of many students of the drifting life of sea and
fresh waters is the seasonal change of form manifested by some
Some Physical Properties of Sea Water / o j
short-lived plants and animals, notably some diatoms, rotifers, clado-
cera, and copepods. The change occurs, not in the individual from
time to time, but in successive generations; thus at any given time the
animals (or the plants) may be quite different in appearance from
their ancestor or from their descendants living within the same
year but at other seasons. There seems clearly to be a variable adapta-
tion between form and viscosity, but it is not so evident whether the
changes in form observed in these phenomena of "cyclomorphosis"
are actually induced by changing viscosity or by changing tempera-
ture or by other conditions that vary concomitantly with tempera-
ture.
In the discussion of temperature and life (p. 102 above), we men-
tioned the fact that warm-bred organisms of the open waters often
attain less size than those bred (and grown) in colder waters. It is
obvious that small bodies have greater surface area than do larger
ones of the same form. The smaller size, with greater proportionate
surface exposure to the surrounding medium is, then, thought of as
an adaptation to the reduced viscosity of the medium. Less energy
is required to prevent sinking (in the "more liquid" medium) be-
low the favored or favoring level. We say more of this after con-
sidering density.
The "streamlining'* of the bodies of aquatic animals is governed
largely by the phenomena of viscosity and density in the medium
through which the organism moves. Its importance varies with the
speed of movement characteristic of the organism; for the faster the
movement, the greater is the stress exerted on the surface of the ani-
mal, and the greater the volume of water that must be displaced in a
given time. In this connection it should be added that the filling-in
of the space left behind the moving animal is a large part of the prob-
lem. Anyone who has felt the backward and downward "drag" on
the stern of a speed boat when the power is suddenly cut off can ap-
preciate the fact that replacement of water behind is as much a fea-
ture of movement as displacement of water ahead. As Welch has well
said, the results of experiments show that the closer is the approach
of body shape to the streamline form the greater is the reduction of
resistance to progress in water; so that, contrary to popular impres-
sion, an object or an animal with short, rounded, blunt forward
portion followed by a longer, tapering after-portion meets less re-
sistance to movement through water than does an object of the
/ o 6 1 ^his (dreat and Wide Sea
reverse form. The sperm whale is a notable example of good stream-
line form.
Density
The density of sea water, or, practically speaking, its specific
gravity, or weight relative to that of an equal volume of pure water
at 4C and at atmospheric pressure, is correlated with salinity.
Higher specific gravity, of course, reduces the effective weight of
animals or plants in the sea. The specific gravity of sea water of
salinity of 35 parts per 1,000 is close to 1.028 at oC, but it is
greater at lower temperatures and less at higher, and slightly greater
under high pressure (i % per cent greater at 400 atmospheres, as at
a depth of 4,000 meters) . n
The protoplasm of marine animals is not greatly different from
that of terrestrial animals, but the former live in a medium of ap-
proximately the same specific gravity as the living parts of their
bodies, while the latter are surrounded by a medium of far less dens-
ity. The support of the body against the pull of gravitation presents
a problem to the terrestrial animal that must be met by adaptation in
form, appendages, skeleton, and muscles. This problem is less acutely
felt by aquatic animals in fresh water, and much less so by those of
marine habit. Even when, on occasion, the problem of support is not
successfully met, the fall of an animal on the land is a much more
violent occurrence than the fall of an animal in the water within
die range of depth to which it is adapted. In the plant world as well,
the differences in form and structure of terrestrial and marine plants
are probably related in no little measure to the differences in dens-
ity of the respective media in which they have their being.
Doubtless all marine animals and most marine plants are some-
what heavier than the surrounding media except as they have special
buoyancy organs. But any one who has witnessed the effects of an
explosion of dynamite in the water knows that some of the dead
bodies of fish rise to the surface while others sink to the bottom. The
problem for marine animals that do not live on the bottom, and for
plants as well, is generally that of keeping above the bottom rather
than that of staying beneath the surface; falling to the bottom, it
may be understood, is a serious matter when the bottom is several
miles removed and marked by conditions of pressure, temperature,
ii. Welch, Paul S., Limnology, New York and London, 1935 (McGraw-Hill).
Some Physical Properties of Sea Water 1 07
and darkness that may not be tolerable to organisms of the upper
strata. Keeping within a zone of tolerable pressure represents for
animals in the sea a problem to which there is nothing comparable
for animals on land the problems of falling neither downward nor
upward to levels of extremely different conditions of pressure. Gas
bladders, accumulations of fat or oil droplets contribute to buoy-
ancy, while in both animals and plants notable extensions of the
body surface, the so-called "flotation processes" offer resistance to
sinking or serve as keels and rudders to facilitate movement in a
horizontal or upward direction.
The contrast in densities of sea water and fresh water is illustrated
by the fact that many marine fishes have eggs that are "emersal"
float at the surface or that remain suspended at intermediate
depths; the eggs of fresh-water fishes sink to the bottom, or are
"demersal." Floating eggs are almost unknown in fresh water, except
for some Amphibia, some Cladocera, and a very few insects.
In this connection, as in others, references may be made to the
minute size of the vast majority of organisms of the sea, a condi-
tion that seems not to prevail to the same degree with land and fresh-
water organisms. Doubtless, also, a great number of small organisms
quickly disintegrate after death into still smaller particles. Rate of
sinking is a function both of weight and of the frictional resistance
to movement through the water, and friction is a function both of
the viscosity of the medium and of the surface area in contact with
the medium. 12 The more viscous the medium and the greater the
surface in proportion to mass, the slower the rate of falling. It is a
12. By Stokes's law the rate of sinking is inversely proportional to the viscosity
but directly proportional to the difference in specific gravity between the body and
the medium. Sinking rate also depends upon size, varying with the square of the
radius, and upon form. Stokes's law holds only for a small sphere, whereas the
bodies of plankton organisms, which are generally of more or less irregular form,
offer special resistance derived from the increased area exposed to the medium.
As the dead body sinks there is also the possibility of its takmg up salts to change
its specific gravity and its sinking velocity. There enters in, moreover, the influence
of "eddy viscosity," previously alluded to, which retards sinking.
The formula for Stokes's law, expressing the velocity of fall of a spherical body
through a liquid, is
= ig(Pi - Pa)
911
Where V stands for velocity of fall, g is the acceleration due to gravity (32.1(5
feet per sec 2 ), PI and P* are the respective densities of sphere and liquid; r is the
radius of the sphere; and ji is the dynamic viscosity of the liquid.
i o8 This Great and Wide Sea
well-known law that the smaller the object the greater is the surface
relative to volume. As Krogh 13 has expressed it, "the rate of sinking
of the minute plankton organisms is so low that they can remain in
the upper strata of the water for the length of their natural lives."
Yet this does not fully answer the question of how non-motile or-
ganisms continue to live in the upper layers of water; for, unless
the rate of sinking were zero, each succeeding generation would
begin falling where the preceding generation had left off; and, after
a few generations, the bottom would be reached by all: the uppei
strata would have become entirely depopulated.
The rate of sinking can be zero only if the viscosity were infi-
nitely great that is to say, if the ocean were solid, which it is not;
or if the ratio of surface to volume were infinitely great, which is
impossible; or finally, if the organisms were of like weight with the
water in which they live. Should the last condition prevail, there
would be no need to invoke either viscosity of the medium or size
and form of the organism as factors of retardation, since there would
be no tendency to sink nothing to be retarded. We may assume
that sinking at a very slow rate does occur, but that either some
compensatory capacity for upward movement is inherent in the
smallest organisms, or upward currents in the water lift the organ-
isms as much as they sink.
In short, the mechanics of flotation of non-motile or weakly
motile organisms is not a fully solved problem. The phenomena of
viscosity to be encountered are by no means so simple as might at
first be thought. The sea is not static: there are movements of ani-
mals and of plants, even if only sinking movements, with accom-
panying disturbances of smaller or greater masses of water. Any-
where, too, there may be drifts or currents, as yet little known, but
producing correlative viscosity effects which can now be but im-
perfectly analyzed by the most expert mathematician.
As a final word in this brief consideration of the subject of spe-
cific gravity, it may be remarked that the dead bodies of marine ani-
mals and plants must generally sink to the bottom except as they
are devoured by scavengers or become dissolved in the water in the
course of their long descent. Since sinking velocity varies directly
with the size of the body, the smaller animals and plants are the mor
13. Op. cit. y p. 423.
borne Physical Properties of Sea W ater
likely to be dissolved or to be devoured on the way down; their com-
ponents may then reappear in part in new forms as the soluble meta-
bolic wastes of the "consumer." Bodies of larger organisms, sinking
much more rapidly and dissolving more slowly, have the greater
relative chance of reaching the bottom. Nevertheless, we shall see
later that the skeletons of myriads of minute plants and animals make
up a large part of the deposits on the floor of the ocean. The remains
of many large animals too are found at greater depths. Speaking of
whales, Krogh says: 14 "A sinking velocity of 100 meters per hour
will bring a body to the bottom in most places in less than two days.
At one station in the Southern Pacific the 'Challenger' got up in die
trawl from the red clay bottom at 4,300 meters (over 2% miles)
several thousand sharks' teeth and not less than fifty ear bones of
whales, but of course it is not known how many thousands of years
this accumulation required."
Pressure
Pressure in the ocean, increasing by one atmosphere for every 33
feet of depth, varies from one atmosphere (about 15 Ibs. per square
inch) at the surface to nearly 1,000 atmospheres at the greatest
depth. It is obvious, of course, that the greatest difference in pres-
sure to which a terrestrial animal may be subject in passing from the
lowest level of exposed land to the top of the loftiest mountain peak
or even to the greatest height to which a bird or a plane can soar,
must be considerably less than one atmosphere. In the sea so great
is the pressure even at the very moderate depth of 1,000 meters (a
litde over 100 atmospheres) that a block of ordinary wood, it is said,
would be reduced to half its volume, through the squeezing out of
air ordinarily imprisoned in the cell spaces; compressed to this ex-
tent, it would sink instead of float. A similar statement would apply
to cork.
It is an old but, as we now see, a very irrational assumption that
the conditions of pressure that prevail in the depths of the sea were
inconsistent with the existence of life. As was mentioned in con-
sideration of the pioneer work of Edward Forbes, an azoic area be-
yond the depth of some 1,800 feet (600 meters) was once con-
ceived to exist. Not only have explorations with deep-sea trawls,
14. Op. ctt^ p. 433.
; i o This Great and Wide Sea
dredges, and plankton nets revealed the falsity of such an assump-
tion, but obviously there was no a priori reason for it. It is a quality
of liquid, as of gas, that pressure at any level is uniformly distributed
in all directions. Consequently, for an organism adapted to the pres-
sure, it is no more to be supposed that the animal should suffer from
it than that we should be overwhelmed by an atmospheric pressure
of some fifteen pounds to the square inch let us say, some tens of
thousands of pounds of pressure per total area of body. Being
adapted to it we endure it, without even being aware of it except
under conditions of change of pressure.
Nevertheless, the change in pressure with depth does interpose
some barrier to the vertical migration of animals. If we suffer in
undergoing the relatively slight modification of pressure within the
limits of a single atmosphere when we ascend to an elevation of
1 0,000 or 1 5,000 feet or when we descend only a few meters into the
water, what must be expected to be the physiological effect upon a
marine organism that, in its daily or seasonal wanderings, may under-
go changes of pressure to the amount of several atmospheres? One of
the most noteworthy qualities of marine organisms is their capacity
for rapid adaptation to great differences in pressure. To take only
one conspicuous example, how does the whale escape damage from
compression when it "sounds" to pass in a few minutes through
ranges of pressure that would completely wreck a human system
even if it were allowed an indefinite period for the transition? And
why does it not suffer "caisson disease" from decompression when
it re-emerges? (One difference: air is not pumped to the whale! )
If the whale, according to the best records, may dive rapidly to a
depth of more than half a mile, not all marine animals are so adapt-
able. As Dr. Herdman has said, "If deep sea fishes accidentally get out
of their accustomed depth and pressure, the expansion of air in their
swim-bladders renders them so buoyant that they continue to tum-
ble upwards to the surface, helpless, and are eventually killed by the
distention of their bodies and the disorganization of their tissues due
to the diminished pressure. They die a violent death from falling
upwards." 15 Is death due sometimes to the extreme change of tem-
perature suffered in rising from the cold depths to the relatively
warm surface water?
15. Founders of Oceanography, p. 161.
Some Physical Properties of Sea Water in
Great pressures have certain secondary effects to which only al-
lusions may be made here. Curiously enough, high pressure reduces
slightly the viscosity of water, or what we might loosely describe as
the cohesiveness of its particles (cf. p. 104). Under the great pres-
sures prevailing in the depths the water is a little more fluid than is
water of the same temperature and salinity at the surface. Pre-
sumably, however, we can find no particular biological significance
in the slightly greater ease of movement for animals living in deep
water of slightly decreased viscosity, especially since, at the same
time that viscosity is reduced, density is increased.
Water is generally described as incompressible; but it is not en-
tirely so. We are told that, if the compression of water in the sea
under its own great weight could be miraculously eliminated, the
general sea level would rise about 27% meters, or nearly 93 feet. 16
It is only because of the compressibility of sea water, slight as it is,
that our eastern Atlantic coast line is where it is, instead of a hundred
or more miles to the west. Of some real significance, on the other
hand, is the effect of pressure on temperature. Deep water has ac-
tually a higher temperature than it would have except for the pres-
sure to which it is subjected. A sample of water having a tempera-
ture of 2 C. at 8,000 meters, when brought to the surface, will, with-
out addition or subtraction of heat, have a temperature nearly i
lower. 17 For an animal of the deep, there must be some biological
significance in such a difference, although, when we think of par-
ticular animals, the question is of theoretical interest alone: animals
of the deep are almost exclusively such as have experienced no
changes of conditions over great spaces and throughout their lives.
16. James Johnston, An Introduction to Oceanography.
17. Sverdrup, Oceanography for Meteorologies, p. 14.
CHAPTER 8
on
tke Dottom of tke
WE HAVE ALREADY CONSIDERED (P. 67, ABOVE) THE TOPOG-
raphy of the bottom, with its continental terrace (shelf
and slope) and rolling floor marked with hills, ridges, fur-
rows, and deeps. The continental shelf extends out some 100 miles, to
where the water is something like 100 fathoms. We have also al-
luded (p. 85, above) to the general absence from the floor of the
ocean of soft organic materials such as compose the familiar silt at
the bottoms of ponds and pools. Most falling organic material is dis-
solved or decomposed in the course of a lingering descent from the
prolific upper waters to the floor thousands of meters below. Where
the depth is great, only the hard parts or skeletal materials arrive at
the bottom. Even in the case of the skeleton of a minute organism,
the chance of arriving at the bottom depends upon its solubility and
the length of time required for the descent. The duration of the
period of falling is conditioned, in turn, upon the size and form of
the skeleton or skeletal part and upon the depth of the sea at the
place of sedimentation. Because of the density and viscosity of the
water, the tooth of a shark or the ear-bone of a whale will reach the
bottom in a fraction of the period of time required by the skeleton
of a protozoan and, because of this and of its size, it will be less af-
fected by processes of dissolution during the period of sinking. A
minute silicious skeleton of a radiolarian protozoan will arrive intact
at the bottom in deeper water than will the calcareous skeleton of a
foraminiferan of the same size, because it is more resistant to the
corrosive agents in sea water. Where the depth is very great, no fine
222
Deposits on the Bottom of the Sea 7/5
skeletal materials will reach the bottom and there one may find only
the original rock supplemented by skeletal remains of larger animals
and inorganic materials that have drifted into the sea through the
atmosphere. It is evident, then, that the floor of the deeper parts of
the sea is not padded with mire, or covered with a sludge, as may
be the bottoms of ponds and bays, but, rather, that it is covered with
a litter of hard remains of animals and plants and some inorganic
"dust."
The bottom may be sampled by the use of the deep-sea dredge
or of a bottom-sampling tube. Various forms of dredges are used.
The ordinary dredge consists of a bag hung behind a rectangular
or triangular frame of iron. Dredges are usually made so that they
function equally well, whichever long side lies on the bottom, and
the lips are beveled to scrape the upper layers. For special purposes,
dredges may have teeth to plough the bottom and stir out the bur-
rowing mollusks, worms, etc. There are also "bottom grabs" of the
clam-shell bucket type, the Ekman and the Petersen dredges, which
fall on the bottom in open positions; when a "messenger" of brass
tubing is sent down the line and releases a catch, powerful springs
close the mouth of the heavy bucket, causing it to bite into the bot-
tom, taking whatever in the upper layer is between its jaws. In
samples collected by such apparatus, the materials are mixed, and
there is no indication of their natural vertical disposition.
To gain information as to subsurface material or as to the natural
arrangement in layers, a steel tube may be driven into the bottom
to bring up a core sample. If the tube is lined with a smaller card-
board tube, the latter can be withdrawn and stored for later study
without disturbance of the original layering. The bottom-sampling
tube may be driven into the bottom by allowing a heavy weight to
drop automatically upon the head of the tube when its foot touches
the bottom. A more recent and eff ective method of applying force
to the tube is with the use of an explosive charge in a gun, such as the
"Piggott gun," which is attached at the top of the tube: the tube is
literally "shot" into the bottom.
For more than half a century cameras have been used for photo-
graphing the bottom, and this instrument has great possibilities in
the future; the shutter may be operated from the boat, or shutter
and flashlight may be set off automatically as the camera, or a
trigger-like extension from it, touches the bottom. 1
i. Science, C (Supplement), 10.
/ 14 This Great and Wide Sea
It was Sir John Murray who originally described the principal
marine deposits, after extensive studies of the "Challenger" (and
later) collections. His general classification is still followed. The
conditions of sedimentation beneath the shallower waters of the
continental shelf are naturally quite different from those below the
deep waters of the open seas. Because of the conditions just de-
scribed, deposits on the bottom of the ocean may be considered in
three chief groups: (i) terrigenous, with quartz and other mineral
matter brought from the land by rivers and wave action, and, on the
average, some two-thirds silica; (2) neritic, farther out, consisting of
materials from the land mixed with organic substances formed in the
shallow coastal waters, such as the remains of mollusks, Crustacea,
echinoderms, worm tubes, etc.; and (3), beyond the direct influence
of land, pelagic, comprising materials originating almost exclusively
in the sea or coming through the atmosphere, from land or inter-
planetary space.
Terrigenous and neritic deposits are, of course, found chiefly on
the continental shelf. The terrigenous deposits, mainly materials
from the land, are the shallow-water sands and muds, in which
quartz grains constitute a prominent part, and the deeper red, blue,
and green muds, with colors due to predominance of different min-
eral substances, such as oxides of iron and manganese and glauconite
(silicates of iron and potassium) ; volcanic muds and coral sands and
muds may form a part Terrigenous deposits shade into the neritic,
in which materials formed by organisms in the sea play a greater
part, along with the finer terrestrial materials.
The pelagic deposits comprise four chief "oozes" of organic
origin and "red clay." Oozes, in the oceanographic sense, are not to
be thought of as comparable in appearance or in character to the
oozy mud of ponds or coastal regions. We shall describe their com-
position in a moment. Named for the type of materials most con-
spicuous in them, these are: diatom ooze, globigerina ooze, radio-
larian ooze, and pteropod ooze.
Diatoms are minute plants, with outside coverings that are like
fine glass boxes in pairs, one box fitting over the other. Diatoms and
their sflicious shells were known from bottom samples and water
dippings long before anyone had an idea that the diatoms were
minute plants. They occur in great numbers in the sea constituting
a major source of food for the small animals, copepods, larvae, etc.,
Deposits on the Bottom of the Sea 125
which, in the ocean, play the same part in the organic cycle as do
the vegetarian grazers, browsers, and gnawers of the land. Diatoms,
with the still more minute coccolithophores, constitute the "grass*'
of the sea, but, unlike most of the land vegetation, they have indi-
gestable cases which pass through the alimentary tracts of the ani-
mals that feed upon them to sink to the bottom and form a part of
the permanent flooring of the sea. Diatoms are of microscopic size,
although some may be large enough to catch the eye of the close
observer. They occur all over the ocean but reach their greatest
numbers in cold waters. Sometimes, indeed, they are present in al-
most inconceivable abundance to make the water "soupy" and give
it a yellow tint. There are hundreds of different kinds. In form they
may be needle-like, boat-shaped, or disc-shaped, and they may have
slender extensions from the body of the shell.
Diatom ooze is found principally in cold regions of the Antarctic
and in the southern and far northern Pacific at 600-2,000 fathoms.
It is not that diatoms are restricted to waters above such areas or that
other skeleton-bearing organisms do not occur there, but rather
that in such regions the shells of diatoms are found on the bottom
in such extraordinary numbers as to obscure the other skeletal re-
mains.
Globigerina ooze is the designation for deposits where the cal-
careous shells of a particular kind of protozoan predominate. Glo-
bigerina is one of the divisions of Protozoa known as Foramini-
f era. Unlike many protozoa that paddle or scull themselves through
the water, a f oraminif eran effects its movement, such as it is, by the
flowing of its living protoplasm in changing lobes or rays, to which
are given the name pseudopodia, meaning "false feet." In this re-
spect they are like the amoebas, from which they differ in having
a calcareous shell with one or many chambers. The shell is porous
and has larger openings through all of which the pseudopodia
stream. When globigerina outgrows its tiny shell, it forms another
and larger shell which remains attached to the first shell. Succes-
sively larger shells are formed until the whole is a tapering linear
series of capsules or, more commonly, a chambered spiral suggestive
of the nautilus on a minute scale. In some cases the shells eventually
become large enough to be detectable by the unaided eye. Glo-
bigerina lives both on the bottom and freely in the open water as an
important element of the plankton. One is shown in Fig. 14, p. 220.
/ 6 This Great and Wide Sea
About two-thirds of the floor of the Atlantic, and more than one-
bird of the total area of all sea bottom, is covered by globigerina
>oze, composed in considerable part of the calcareous shells of
FIGURE 8. The pelagic oozes, (a) Diatom ooze (from Steuer, after
Chun), (b) Pteropod ooze (after Murray and Hjort). (c) Globigerina
ooze (after Murray), (d) Radiolarian ooze (from Steuer, after Krummel).
zlobigerina buttoides, mixed with coccoliths, or shell fragments of
he coccolithophores, to be mentioned later (cf. p. 205) ; this deposit
s about 65 per cent calcareous matter and is found at 1,000-2,500
athoms. Although it was once supposed that globigerina ooze was
he basis of chalk deposits, it is now believed that the chalk was
ormed in shallow seas and that such deposits do not, therefore,
epresent old deep-sea bottoms. Bigelow 2 refers to globigerina ooze
2. Oceanography , p. 35.
Deposits on the bottom of the Sea
as reported to be accumulating over submarine telegraph cables at
the apparent rate of a tenth of an inch a year, or a fathom in 720
years, but comments that the sea floor, over all the vast area occu-
pied by the globigerina ooze, is certainly not generally building up
at such a rate. Other estimates for deposition in the open seas ap-
proximate a millimeter, or one twenty-fifth of an inch, in a hundred
years!
In contrast to the calcareous ooze just mentioned is the silicious
radiolctrian ooze, consisting of a foundation of red clay in which are
mixed the remains of radiolarian shells; it occurs at 2,500-5,000
fathoms in isolated areas of the tropical Pacific and Indian Oceans.
The radiolaria, like the foraminifera, are protozoa with flowing
pseudopodia, but they differ from globigerina in that the shell is
usually silicious rather than calcareous and is, therefore, less soluble.
They differ also in the fact that the skeleton is internal: the body is
divided into two regions, one within the membraneous capsule and
one without, the capsule being elaborately perforated for continuity
between the two portions of the body. The animals may be fairly
large for protozoa, with a diameter of one-twelfth of an inch. The
pseudopodia are fine and raylike. Shells and bodies may be ex-
tremely complex and beautiful.
It is a distinctly higher type of animal that gives rise to the fourth
principal type of deep sea deposit of organic origin, pteropod ooze.
Usually we think of mollusks in terms of creeping snails, burrowing
clams, sedentary oysters or free-swimming squid; but there are small
mollusks whose whole individual lives are passed in the open water,
where they swim by means of fin-like structures on the head. The
pteropods have thin shells which in different species may be snail-
like in form, globular and spinous, or slender, conical, and straight
or curved. They are generally large enough to be plainly visible
to the eye, some of the slender ones having a length of approxi-
mately half an inch. (See Fig. 1 5, p. 226) Other free-swimming mol-
lusks, not closely related to pteropods, are the heteropods, which
may be described as minute conchs with transparent shells that are
conical or spiral and disc-like. The bodies may have delicate and
beautiful colors. Some of them are larger than the pteropods.
Like the organisms previously mentioned, pteropods, under
favorable conditions, become extremely abundant, dominating large
areas of the sea in such degree as to have attracted long ago the at-
/ / S 1 'his (Jreat and Wide Sea
tendon of whalers who call them "whale feed," and who know that
they offer promise of the proximity of "right whales" (whales that
bear whalebone). The whalebone whales, which include the largest
of all animals, follow the pteropods, as well as copepods and small
shrimplike Crustacea, to strain bushels of tiny organisms from the
sea through the whalebone sieves on their jaws. Calcareous pteropod
Doze, comprising the shells of pteropods, principally, and hetero-
pods, mixed with shells of Globigerina, occur principally in tropi-
cal regions at depths of 500 to 1,300 fathoms. 8 At greater depths
their delicate shells may be dissolved to leave only the more durable
remains of globigerina or other organisms.
Red clay is mostly inorganic material that has been deposited on
Jie bottom anywhere but is notable more particularly in the great
Jepths where it is not obscured by the organic deposits. Some of
iis is of volcanic origin and may originate from submarine erup-
ions or from terrestrial volcanoes. Terrestrial volcanic dust may
Joat through the air to settle to the sea over the deep areas; larger
)its of air-packed pumice may lodge on the surface waters nearer
jhore to float for a long rime, become waterlogged, and eventually
ank to the bottom remote from the place of its first contact with the
abater. Dust from the desert is carried long distances through the air
tnd is observable in deep-sea deposits. Floating icebergs may carry
ock fragments of considerable size. As Murray remarks, materials
)f extraterrestrial origin do not bulk large in marine deposits: they
ire rarities, but extremely interesting. Naturally, such matter is
loticed chiefly on the red clay areas, where other materials are so
ew. Interplanetary particles on the floor of the ocean are presumed
o be fragments of meteorites; they are chiefly black and brown
netallic spherules which, because of the iron in them, can be picked
)ut by the use of a magnet. There are also products formed in the
ea, concretions or nodules of manganese and barium, combinations
>f iron, potassium, and silica, and silicious and phosphatic con-
Tetions. The oxides of iron and manganese, especially noticeable in
leep sea deposits, give the color to the deep sea clays. Red clay con-
titutes more than half of the floor of the Pacific and is estimated to
ccupy about one-third of the combined area of the floor of all the
eas. Naturally, it is present in the greater depths to which the
3. Adolf Steuer, Lertfaden der Planktonkunde.
Deposits on the Bottom of the Sea 11$
organic materials cannot descend because of the depth and the sol-
vent agents in the water.
The red clay of the sea is not to be confused with the red day
of the land. There is no rock in the geological series that corresponds
to the red clay of the ocean floor; in other words, no present area of
land seems to comprise what has ever been the red clay of sea bot-
toms; this leads us to believe in the relative permanence of the deeper
parts of the seas. It may readily be understood that deposits of this
sort accumulate with exceeding slowness: Sir John Murray has esti-
mated that there has been an increment of about one foot since
Tertiary time! *
4. Although Murray's classification of marine deposits, as it has been outlined in
die text, retains its essential validity, it must undergo some revision in the light of
recent broader and more detailed observations. In die first place there can be no
sharp distinctions between the different types of deposits, which, necessarily are
mixtures. Revelle emphasizes a distinction in color between terrigenous and pelagic
bottoms. Terrigenous deposits build up relatively rapidly and are black, bluish,
green, or gray. The more slowly built pelagic deposits are red, brown, yellow, or
white. Revelle proposes a more derailed classification of die terrigenous muds and
the pelagic oozes. Calcium carbonate oozes have more than 30 per cent CaCOg and
are subdivided into various types of globigerraa, pteropod, and coccolith oozes.
Silicious oozes have remains of silicious organisms greater t-fian jo per cent and
CaCOs less than 30 per cent and are divided into several types of diatom and
radiolarian oozes. Red clay as contrasted with the oozes will have less than 30
per cent of organic skeletal remains and will be of one sob-type or another ac-
cording to its composition in detntal, volcanic, silicious, or calcareous materials.
The proposed classification is summarized on page 16 of Marine Bottom Samples
Collected in the Pacific Ocean by the Carnegie on Its Seventh Cruise (Carnegie
Institution of Washington, Publication 556 Washington, 1944, Pp. 180), by Roger
R. Revelle.
CHAPTER 9
iA/ater in I It lotion
\jenerai, f^ian6 or
3road Features of Circulation and Methods of Observation
THE BLASE TRAVELER LIKES TO REFER TO THE OCEAN HE HAS
crossed as "the pond," but no pond is so restless as any one of
the oceans. Besides waves, rides, and seiches, each ocean has
ts wide-reaching system of circulation. Furthermore, with even a
little knowledge of ocean currents and drifts, we begin to see how
ill the seas together constitute a single body with all its members
interconnected in a fairly orderly system of circulation; for in many
:ases the movements of great volumes of water from place to place,
'movements of translation," in contrast to "movements of oscilla-
ion" in waves and tides, are not confined by the boundaries of
>ceans as we may sketch them on the map. As with all circulating
ystems, the circulatory mechanism that interlocks the seas involves
ransf ormation of energy and, in this case, a notable amount of
energy. The ultimate source of the energy, as far as we can trace it,
nust concern us in another chapter, but it is well to have in mind
low that, with hardly any other mechanisms on earth, do we deal
vith so great regular income and outgo of energy.
By different means the oceanographer gathers data from many
observations about currents, and, when he has arranged and organ-
zed the data he can prepare generally reliable maps showing, with
ines and arrows, the broad eddies and great streams that move in
ome orderly fashion, although rarely with precise constancy of
120
122 This Great and Wide Sea
velocity or of direction. In some places the streaming movements
ire more rapid than are those of great rivers like the Mississippi or
he Amazon; sometimes they are nearly as constant in direction,
ilthough far larger in volume. In other places the motion is so slow
is scarcely to retard or accelerate the passage of a ship. The sea-
nan and the oceanographer speak of the slow movements as
'drifts," as for example, the great, eastward, circumpolar Antarctic
Drift. These currents of the ocean, except as they may be bounded
m one side by lands or shoals, are not confined in hard channels; so
hat the precise direction and the volume of flow may undergo
ninor changes. On occasion there may even be reversals of direc-
ion; while in a few cases, as in the Indian Ocean, reversal is seasonal.
The usual maps show the predominating or prevailing directions
>f surface currents and drifts; but it must be understood that there
ire deep flows, generally as slow drifts of immense masses of water,
ind that these are of equal significance with the superficial currents
n the whole system of mining and of interchanging of water masses
>etween different regions of the hydrosphere. 1
The surface currents have great influence on climates and on the
ictivities of man, and they have been studied from ancient days.
Various methods have been used to determine the direction and rate
jf movement of masses of water. The movements of water in sight
>f land may be observed with reference to some fixed object. Out
n the open sea there are no fixed objects, and indirect methods must
>e relied upon. Information may be obtained from floating objects,
'flotsam" in technical language, such as icebergs and wreckage;
>otdes may be deliberately set adrift, sealed and empty but for a
^rd which the finder may mail to obtain a small reward. In these
rases we cannot know just what course the drift has taken, how
oundabout may have been its journey, or, sometimes, what part
he wind, rather than the current, may have played in determining
he course followed. Of course, "drift bottles" are designed to
>ff er the least possible resistance to currents of air. To minimize the
lirect effect of wind on the bottle a "drift anchor" may be added
a the form of a cross of sheet metal suspended a few feet below
he bottle.
i. It is not only the lack of boundaries between oceans but also their general
ontmuity -with rivets and lakes, and the want of any definite break between all of
bese and the world-wide sheet of soil water, that gives basis for recognition of a
ontinuons watery envelope of the earth called the hydrosphere, which, with the
cospbere below and the atmosphere above, makes np the whole terrestrial globe.
General Plans of Circulation 223
Ships at sea can furnish much valuable information. A navigator
keeps regular records of his course and speed, but finds that, from
day to day, the position of the ship, as determined by astronomical
calculation based on observations of the heavenly bodies, is not what
should result from the recorded course and speed. The difference
is attributable to currents, whose direction and rate can then be
computed with some degree of approximation; but all allowance
must be made for wind drift and for errors arising from deviations
of the compass. A vessel at anchor in a current may determine the
direction and velocity of the current by the use of a chip log or by
setting loose drift buoys, whose direction and distance may be de-
termined after a given period of time. Sometimes a vessel may trail
a drifting buoy to determine its position at regular intervals. Such a
buoy, in order to be followed by the eye or the vessel, must have a
staff and flag that will give minimum resistance to the wind. The
submerged part in the form of a cross, "the current cross," is broad
enough in two directions to be carried by the water, no matter how
the buoy may turn.
Still other methods of determining rate of movement involve the
use of an instrument held in place and having a propeller which is
turned by the flowing water. Sometimes current meters are left
anchored to the bottom to be recovered after a certain period of
time. Such current meters are so devised as to make a record both
of the direction and of the rate of movement of the water. In the
Ekman current meter there is a propeller and a vane that orients the
instrument to keep the propeller always facing the current. There
is also a compass box rigidly connected to the vane of the meter; the
box is divided radially into a number of compartments, say thirty-
six, each corresponding to an angle of ten degrees. The magnets of
the compass, which adjust themselves in the magnetic meridian, are
attached to a frame that turns with the magnets and carries a bar 2
through which a small ball drops at intervals into one of the com-
partments of the box. The box, rigidly fixed in the instrument, turns
with the vane and is, therefore, oriented to the direction of the cur-
rent. One ball drops for each thirty-three revolutions of the pro-
peller, or more frequently, if desired. In consequence, the average
direction of the current can be determined by the distribution of
the balls in the compartments of the box, while the velocity is com-
2. The needle itself, if grooved to carry the ball, may serve in place of a special
bar.
224 This Great and Wide Sea
puted from the registered number of turns of the propeller. In the
possible event that the balls are too widely distributed in the several
compartments, the results may be considered invalid as to both the
direction and the velocity of the current.
When the movement of the water is very slow, say a fraction of
a centimeter per second, reliance must be upon the characteristics
of the water as determined by the thermometer and by analyses
made from samples; but see note, p. 137. This is particularly neces-
sary in the case of deep drifts. Precise determinations of salinity,
temperature, and dissolved oxygen identify different masses of
water and enable the oceanographer to map their distribution and
trace their movements.
Currents and other great movements of water have much to do
with the shaping of climates in all parts of the world. With its
strong component of hydrogen, water has the highest heat capacity
of all ordinary liquids except ammonia (NH 3 ) which has even more
hydrogen. This means that water has always exceptional capacity
both to absorb and store heat with relatively little change in temper-
ature and, when in motion, to transport heat from one place to an-
other. Accordingly, ocean currents are most important agents
for the transfer of heat from low to high latitudes. Winds blow-
ing from the sea, as everyone knows, have marked effects on
terrestrial climates, which indeed are determined to no little extent
by the winds. The climates of a region depend then not only on
latitude, but also on the direction from which the wind blows. Not
everywhere is the predominant drift of air over the land from the
cooler or warmer water of the sea, but in many regions this is the
case. Notable examples of the tempering effect of ocean currents
on the climate of the land are afforded by the Benguela Current,
bringing cold southern water up the west side of Africa and keeping
a long coastal strip relatively cool and foggy; the Peru Current,
conveying water of Antarctic origin almost to the Equator, so that
at Lima, only 12 degrees of latitude from the Equator, the highest
summer temperature is below 90 F. and winters are only continuous
fog; and the Gulf Stream with its tempering effect on the climate
of northwest Europe.
Ocean currents are caused by conditions existing in the water as
well as by outside forces. Of the internal causes, most prominent
are those due to differences in pressure; unequal pressure results
when one part of the ocean is heated to a higher temperature than
General Plans of Circulation 125
another or when the salinity is changed by evaporation or by inflow
of rivers, by melting icebergs or by rainfall. Of outside forces, the
winds are most readily observable; for strong winds obviously drive
the surface water. In respect to direction of flow, the influence of
the wind is easily seen; but the form of the coast line, the topography
of the bottom, and the rotation of the earth cause modification of
direction. Variation in atmospheric pressure causes rise and fall of
the level of the sea in particular regions, with resulting disturbance
of equilibrium to be corrected by subsequent shifts of masses of
water. The greatest of outside forces is the rotation of the earth,
which deflects currents to the right in regions north of the Equator
and to the left in areas south of it. (See p. 139, below.)
A rough outline of the general picture of oceanic circulation is
something Eke this. In each ocean that extends north-and-south
across the belt of the earth, there are, in equatorial regions, two
broad streams running from east to west and known as the North
Equatorial Current and the South Equatorial Current, Between
them is a narrow, equatorial Countercurrent directed toward the
east. The equatorial currents are deflected, partly by land masses and
partly by influences related to the earth's rotation, to the right in the
northern hemisphere and to the left in the southern. In the northern
hemisphere, the deflected streams move first in a northerly direction
turning gradually eastward and then southward to complete the
circle. In the southern hemisphere, the directions of drift follow in
reverse order, first southerly, then easterly in high southern latitudes,
and northerly; eventually they complete a great eddy in each part
of the Atlantic and Pacific oceans by entering in part again into the
equatorial currents. In the Indian Ocean this general scheme for
currents is changed somewhat by the monsoons, which are winds
that change direction with the seasons. In the southern hemisphere
the Antarctic Drift, influenced by the prevailing winds, the distri-
bution of land masses, and submarine topography, moves from west
to east around the Antarctic continent at a calculated rate of 4-4
cm/sec to 15 cm/sec; 8 that is to say, at a rate of about one-third of
a statute mile, or much less, per hour.
It may help to understand some of the very complex relations of
currents and drifts to be discussed in the following pages if we have
3. 50 cm/sec is equivalent, approximately, to one knot, or one nautical mile
of 6,000 feet per hour.
126 This Great and Wide Sea
in mind that the oceanographers distinguish several strata of water;
in order of vertical distribution, these are surface water, upper water,
intermediate water, deep water, and bottom water. These masses find
their relative levels according to their densities; water that is heavier,
because of low temperature, high salinity, or a combination of the
two, sinks below lighter water.
It must be observed that, when the density of surface water is
increased by cooling, by evaporation, or by the formation of ice
(leaving the water more saline), the water must sink until it meets
water of equal density while subsurface water rises to take its place.
The rising and falling currents are called convection currents. When
conditions effecting the increase of density continue, the densest
water accumulates at or near the bottom to flow out beneath the
lighter waters except as they may be within an enclosed basin. Con-
vection currents occur mainly in high latitudes but not usually to
such an extent that bottom 'water is formed. In any event, whenever
water of high salinity carried by currents is cooled in high latitudes,
or when water of relatively high salinity freezes, the water may
become of such density as to find its level only at the bottom.
The most striking examples of the formation of bottom water of
great density are found in Arctic and Antarctic regions or in the
Atlantic Ocean. "The deep and bottom water in all oceans is derived
mainly from these two sources, but is to some extent modified by
addition of high-salinity water flowing out across the sills of basins
in lower latitudes, particularly from the Mediterranean and the Red
Sea." 4
Circulation in the Atlantic Ocean
A prominent feature of the circulation in the North Atlantic is
the broad and warm northward flowing current off the east coast
of the United States, which is known generally as the Gulf Stream.
It was Maury of the United States Navy who first made a systematic
study of this stream, although it had been known to some of the
earliest explorers of America and had been roughly mapped by
Benjamin Franklin. It has been studied intensively by the Coast
and Geodetic Survey, with such leaders as Alexander Dallas Bache
(a grandson of Franklin), Alexander Agassiz, and J. E. Kllsbury.
4. Sverdrop, Johnson, and Fleming, The Oceans, p. 747.
General Plans of Circulation 127
The last-mentioned investigator anchored the "Blake" in the midst
of the swift stream, making observations and measurements at vari-
ous depths, which "are among the classical data of physical oceanog-
raphy." 5 The German physical oceanographer Wiist and the Amer-
ican Iselin have in recent years added much to knowledge of the
Gulf Stream. Whence comes this water, what is its volume and
where does it go? The answers to these questions are not ample;
for the stream itself is not simple, but really a system of currents, 6
including: Florida Current, Gulf Stream proper and North Atlantic
Current, to say nothing of secondary currents, eddies, and mean-
ders. (See "The Gulf Stream System," by C. O'D. Iselin, in Proc.
Am. Phil Soc., 96: 600-603.)
We must go back to the westerly flowing North Equatorial Cur-
rent, which, off the northeast coast of South America, is joined by
a great branch of the South Equatorial Current bringing water from
the South Atlantic. The combined waters move in part, through
the Caribbean Sea and the Yucatan Channel, gathering speed, to
pass on through the Straits of Florida; here, as the Florida Current,
it is a body 95 nautical miles wide and about 2 miles deep. The
velocity in the narrow part of the Straits is about 3 % knots, and
the transport of water here has been estimated, somewhat roughly
of course, at twenty-six million cubic meters per second. If this
is correct the stream here has something like the volume of a thou-
sand Mississippi Rivers at normal stages!
Past the Bahamas, the Florida Current is augmented by another
branch of the North Equatorial Current; this is the Antilles Current,
which has by-passed the landward seas and which carries water be-
lieved to be identical with that of the Sargasso Sea, to be mentioned
a little later. 7 Passing Cape Hatteras as the Gulf Stream, with re-
duced speed of about one nautical mile per hour and with its flow
deflected to the right, as is characteristic for all ocean currents in
the northern hemisphere, it leaves the continental slope to continue
in a more easterly direction and meet the southward flowing Labra-
dor Current in the vicinity of the Grand Banks of Newfoundland,
as we have mentioned above (page 54) . Now it divides into branches
to merge into the North Atlantic Current, which includes the east-
erly and northerly currents of the North Atlantic. Much of the
Gulf Stream water is diverted southward into the great central eddy
5. Ibid^ p. 673. 6. Sverdrup, op. ch^ p. 173. 7. Ibid^ p. 162.
128 This Great and Wide Sea
of the North Atlantic, the Sargasso Sea? Part of its water warms the
shores of Iceland and Norway, while some approaches the western
shores of Europe in southerly drift and even passes into the Medi-
terranean.
Whatever the origin of the water in the nearly-enclosed Mediter-
ranean, strong evaporation there increases salinity and density, so
that the. heavier upper waters sink to the depths, whence they flow
out through the Straits of Gibralter to form a mass of deep and bot-
tom water that can be traced far out into the Atlantic, southward
across the Equator, and even around the southern extremity of
Africa into the Indian Ocean.
To a considerable extent the winds over the eastern part of the
United States are from the northwest, so that the Gulf Stream has
a limited effect on our climate; but, through the agency of the pre-
vailing southwest winds of northwest Europe, the warm air from
waters traceable to the Gulf Stream moderates the climate of that
region in marked degree. As evidence, we have only to contrast the
habitability of Norway with that of Greenland or of Baffin Land
on the North American continent, far north of Labrador but in the
latitude of Norway. During recent years oceanographers of the
Scandinavian countries have been interested in the possibility of
long-time weather prediction for northwest Europe derived from
observations of variations of the Gulf Stream near its beginning,
across the ocean and far to the south.
Passing now to a consideration of the broad characteristics of the
Gulf Stream, we find that its waters are differentiated from those
of the open sea in some very definite ways. In general, the waters
of this stream are deep indigo blue and transparent; they are saline
and warm, relative to adjacent waters; the velocity of movements
is high as compared with average movements in the sea. The surface
velocity decreases from 3 1 / 2 knots in the Straits of Florida to 1 1 / 2 off
the coast of Georgia and one knot off Cape Hatteras. The average
temperature of surf ace waters is approximately 80 F. (27C.) in die
first 400 miles of the current, but subsurface temperatures decrease
rapidly toward the bottom; the water on the eastern side of the
current is warmer than that on the western side. The so-called "cold
wall" between the Gulf Stream and the United States coast is due
8. Ibid., p. 172.
General Plans of Circulation 12$
to several factors. Among these are: mixing, to some extent, with
water discharged from cold land streams; proximity to land having
low winter temperatures, with prevailing breezes from the land;
and cold waters from the Gulf of St. Lawrence, which are deflected
against the American coast by virtue of the earth's rotation.* For
the seas as a whole the salinity is hardly up to 35 o/oo, but the waters
of the Gulf Stream have a relatively high salinity, 35-36.5 o/oo,
although, as a whole they are distinctly less saline than the waters of
the Sargasso Sea.
The westward flowing North Equatorial Current, the northerly
and easterly Gulf Stream and North Atlantic currents, and the
southerly Canaries Drift on the east side of the Atlantic complete the
periphery of a great Central North Atlantic eddy. This is what
has long been known as the Sargasso Sea, an area of relatively still
or slowly turning water, where the floating "gulf weed," or sar-
gassum, accumulates; the weed propagates vegetatively to form in
some places floating islandlike clumps, but never, it appears, the
allegedly solid and impenetrable masses which only legend has
placed there. The water of this wide-stretched eddy, undiluted by
melting ice or the discharge from rivers, and subject to constant
evaporation, has relatively high salinity, as I have previously said
(p. 82). It is relatively poor in nutritive material and has the deep
blue characteristic of deep water with scant material in suspension.
We have seen that a great volume of upper water passes from the
South Atlantic into the Gulf Stream system of the northern ocean
and that the transport is estimated at something like six million cubic
meters per second. We shall see later that other South Atlantic or
Antarctic water enters the North Atlantic at intermediate levels.
Naturally, there must somewhere be an equivalent "pay back" from
northern to southern seas. The return of water from North to South
Atlantic is understood to occur at low levels; but tie sinking of
heavy surface water to form the lower return water is believed to
take place chiefly in three regions. As was mentioned before, surface
water becomes heavy and sinks, either through excess evaporation
or through lowering temperature, which may follow from the mix-
ing of cold and therefore heavy water with saline water of a mod-
erate temperature. The chief places of sinking in the North At-
9. Manner, The Sea, Chapter XVIII.
This Great and Wide Sea
lantic, as now known, are (i) outside the Straits of Gibraltar (saline
Mediterranean water); (2) in the region southwest of Greenland
(cold Arctic and North Atlantic water); and (3) in the region of
Labrador, where saline Gulf Stream waters are mixed with cold
Arctic waters. About two million cubic meters is presumed to sink
each second at each of these three places. 10 Of course these are
rough figures, but they are worth quoting as giving some idea of the
volumes of water involved in such shifts.
The conditions described in outline for the North Atlantic illus-
trate the complexity of the dynamics of the sea. It is not the purpose
here to give a systematic account of the circulation of the ocean.
For that one must refer to the more technical treatises, some of
which have been cited. It is hoped merely to give a rough picture
of the general nature and scope of the world-wide mechanism for
mixing ocean waters. A brief examination of outstanding features
of circulation in other oceans will complete the chapter.
In the South Atlantic there is a somewhat analogous but reverse
rotation in counterclockwise direction. The South Equatorial Cur-
rent forms the northern boundary of a central eddy. That part of
this current which does not join the Gulf stream turns south as the
warm Brazil Current on the west side of the eddy. On the southern
side is the easterly flowing Antarctic Current. The eastern side of
the eddy is formed by the Benguela Current, one of the more con-
spicuous ocean streams, bringing cold water northward along the
west coast of Africa and finally turning westward as the northern
cooler part of the South Equatorial Current. Upwelling of deep
waters (see page 140, below) along the African coast contributes
to maintenance of lower surface temperatures than would otherwise
be normal for the latitudes. In contrast to conditions in the North
Atlantic, it is the cold current of the east side of the South Atlantic
that is the most notable stream. The deeper waters of the South
Atlantic are pardy of Antarctic origin with northward drift and
partly of Arctic origin with southerly drift, as mentioned on page
128, above, and page 135, below.
Circulation in the Pacific Ocean
In the Pacific Ocean the conditions of circulation are less well
10. Sverdrup, op. cit^ p. 173.
General Plans of Circulation
known than are those of the Atlantic and they appear to be some-
what more complex. In the broad South Pacific there is a great
eddy in the eastern part, and there may be another with more erratic
conditions in the western region. As in the South Atlantic the best
defined current 'is on the east side. There we find the Humboldt
Current, or Peru Current, as it is sometimes called, which carries
a long way northward subantarctic water from the easterly drifting
Antarctic Current (West Wind Drift or Antarctic Drift), a belt of
easterly flowing water around the earth in high southern latitudes.
Again, as in the case of the Benguela Current of the South Atlantic,
the low surface temperatures maintained along the course of the
stream toward the Equator is due not solely to the coldness of the
subantarctic water received at the source, but, in considerable part,
to the fact that the winds tend to drive the surface water away from
the coast to be replaced by cold water upwelling from deeper
strata. 11
The Humboldt Current is not so well-defined as is the Gulf
Stream, but it is a definitely tangible current running almost to the
Equator and fairly close along shore. A voyager on a ship sailing
south from Panama, if the Equator is to be crossed during the night,
may be advised to put away his linen outers and don warm clothing
in the morning. Having lolled for several days under tropical sun-
shine over warm waters, he may not heed the advice at first; but,
if by morning the ship has entered the waters of the current, the
passenger will not be slow to seek warmer clothing. Even at seaside
points well within the tropical zone, the coastal water, in the sixties,
Fahrenheit, is distinctly cold for swimming. The Humboldt Cur-
ii. To quote Dr. Murphy, Oceanic Birds of Soicth ATnerica, (p. 95) :
"Significant features of the surface waters in the current are first, relatively low
temperatures in close proximity to the land, with rising temperatures offshore
along lines usually perpendicular to the trend of the coast; and second, extraordi-
nary uniformity of temperatures throughout the greater part of the length of the
current, a uniformity which is little affected either by latitude or season of the
year. Both of these facts would strongly suggest that the low temperatures close to
shore are due to upwelling from cooler intermediate layers, rather than to north-
ward transportation of subantarctic surface waters. The latter would, of course,
become gradually warmed during their progress into the tropics, and the Humboldt
Current would show appreciably rising temperatures from south to north, which is
not in accord with the facts. UpwelLng would, in any event, be inevitable in view
of the meteorological regime. An accelerated left-hand trend, and continuous verti-
cal circulation, is caused by the steady southerly winds parallel with the coast,
which tend to force the surface water offshore at an angle of 45 from their path."
About two-thirds of the floor of the Atlantic, and more than one-
hird of the total area of all sea bottom, is covered by globigerina
>oze, composed in considerable part of the calcareous shells of
FIGURE 8. The pelagic oozes, (a) Diatom ooze (from Steuer, after
Chun), (b) Pteropod ooze (after Murray and Hjort). (c) Globigerina
ooze (after Murray), (d) Radiolarian ooze (from Steuer, after Kriimmel).
jlobigerina bulloides, mixed with coccoliths, or shell fragments of
he coccolithophores, to be mentioned later (cf. p. 205) ; this deposit
s about 65 per cent calcareous matter and is found at 1,000-2,500
athoms. Although it was once supposed that globigerina ooze was
he basis of chalk deposits, it is now believed that the chalk was
ormed in shallow seas and that such deposits do not, therefore,
epresent old deep-sea bottoms. Bigelow 2 refers to globigerina ooze
2. Oceanography, p. 35.
General Plans of Circulation
rent, flows westward across the broad waist of the Pacific, gathering
increments of Central Pacific water on its northern side. Approach-
ing the Philippines on the west, a part is said to return as the
Countercurrent, but the larger part turns northward and then
northeastward, running eastward of Formosa and the Japanese
Archipelago as the Japan Current or Kuroshio ("black current")*
reminding us of the Gulf Stream in the North Atlantic. In the
region above Formosa, the rate of flow is something less than ^
nautical miles per hour. The salinity is lower than that of the Gulf
Stream, in keeping with the generally lower salinity of Pacific as
compared with Atlantic waters (p. 82, above). On leaving Japan
the Kuroshio divides into two branches: the larger southern branch
runs due east and is distinguishable as far as i6oE. longitude,
or nearly to the Hawaiian Islands; it merges into the easterly North
Pacific Current. The northern branch becomes mixed with the
southward flowing cold Oyashio, skirting the coast of upper Asia,
the mixture forming the masses of subarctic water found below the
Aleutians and Alaska. A certain degree of sinking seems to occur
at the convergence of warm Kuroshio and cold Oyashio. From
the easterly Aleutian Current, in the subarctic water, one branch
turns north into the Gulf of Alaska; another swings southward along
the coast of the United States to become the California Current
which moves strongly southeastward to merge finally with the
North Equatorial Current. The effect of the California Current
is to temper the climates of our western states; but, as with the Peru
Current, the relatively low temperature of the coastal water is attrib-
utable, not solely to its subarctic origin, but, in part and in some
regions, to the upwelling of deeper cooler waters.
In the North Pacific the "deep water," in the technical sense, is
reputed to be derived chiefly from the Indian Ocean, being Ant-
arctic water of Atlantic and Indian Ocean origins. Between northern
and southern Pacific there is believed to be little exchange of water
across the Equator.
Circulation in the Indian Ocean
The Indian Ocean has its own distinctive form, being roughly
circular in outline and with only a small part of its area north of
the Equator. Its currents, while comparable in some ways to those
This Great and Wide Sea
of the Atlantic, are much more variable, and this is due, in part at
least, to changes in the prevailing monsoon winds. In its southern
part a current flows from Africa toward Australia, approaching
close to that continent in southern winter. Interchanges of water
with the Pacific southward and northward of Australia seem to vary
with the season; but they need not concern us here.
As in other oceans, a South Equatorial Current flows toward the
west, its velocity varying with the season, being greatest in southern
winter. A part of this stream turns southward along the east coast
of Africa to form the Agulhas Current, which may feed partly into
the Atlantic around the Cape of Good Hope, but which mainly turns
eastward to contribute to the easterly flow first mentioned. Between
the eastward current and the westerly Equatorial Current there is
pictured a large eddy. In northern winter, when the northeast mon-
soon prevails, there is found a westward-flowing North Equatorial
Current north of an easterly Equatorial Countercurrent; but the
westerly current disappears under the influence of the southwest
monsoon, so that, in northern summer, the flow is all easterly.
An interesting feature of circulation in the Indian Ocean area is
the interchange between the ocean and the Red Sea, where great
evaporation produces water of notably high salinity. In winter the
winds drive top water into the Red Sea from the Gulf of Aden,
while highly saline and heavy Red Sea waters are flowing out in the
depths. In summer, with reversed winds, water flows out from the
Red Sea at the surface and, probably to some extent, at the depth of
"the sill" at the gateway between sea and ocean, while cold and less
saline waters are flowing into the Red Sea at intermediate levels. In
the depths of the Indian Ocean there are found, accordingly, some
waters of Red Sea origin, but also much of Atlantic origin. 13
Circulation in the Antarctic Ocean
The Antarctic, as a whole, presents a very different picture from
that of any of the other oceans. It surrounds a continent rather
than being partially surrounded by continents. It is, thus, a contin-
uous but ill-bounded circumpolar belt, northward on all sides of
the Antarctic continent. With a drift from west to east, the Ant-
arctic Current is irregular in width and in precise course, as its
13. Sverdrup, op. cit., p. 215.
General flans of Circulation 235
direction is affected by the distribution of land masses or of sub-
marine ridges. This unceasing tircumpolar drift of water is not
however, to be conceived of as a particular mass of water in con-
tinuous circulation: there are continual interchanges between it and
the oceans northward from it. Tongues of surface water are given
off, as in the Falkland Current, which flows along the eastern side
of the southern coast of South America, and contributions are re-
ceived, as in the case of a considerable part of the Agulhas Current
from the eastern side of South Africa.
We have already mentioned the masses of bottom water and inter-
mediate water of Antarctic origin both of which drift northward
in the South Atlantic below and above the southerly drift of North
Atlantic deep water. Antarctic bottom water has indeed been traced
as far as 35 degrees north latitude in the North Atlantic, or to the
approximate latitude of Cape Hatteras. Antarctic intermediate wa-
ters also move far up in the South Pacific and the Indian Oceans.
Presumably much of this Antarctic water becomes mixed with the
deep waters moving southward and returns to the Antarctic region
along with Indian and Atlantic and perhaps Red Sea water.
TTiere is also, as may already have been inferred, a distinct vertical
movement of water in the Antarctic region. The cold waters that
sink to form the great masses of intermediate water are rarely over
two degrees above the freezing point of fresh water and are heavily
charged with oxygen. This, of course, is true also of deeper waters
formed in Arctic regions.
The Arctic Ocean
In contrast to the Antarctic, which is hardly more than the south-
ern extension of Pacific, Atlantic, and Indian oceans to the borders
of a polar continent, the Arctic is a small polar sea hemmed in by
continental land masses. Broadly speaking, the Arctic is supposed
to include the oceanic waters north of latitude 6oN. and the Ant-
arctic those south of latitude 6oS. With less than one-fifth the area
of either the Atlantic or Indian Ocean, the Arctic is proportionately
much less in volume because its average depth is less than a third of
either of those oceans. Nevertheless, it has depths up to about three
and one-half miles with an average of some three quarters of a mile.
Its waters are low in salinity, less than 30. Throughout much of its
1 36 This Great and Wide Sea
extent, the surface temperatures are well below the freezing point
of fresh water. It is characteristically an area of sea ice, 5 to 9 feet
in thickness, but, as a result of the pressures of moving ice floes, the
ice may become piled up to a depth of 15 feet or more. Even in the
summer the Arctic is never half free of ice.
Largely enclosed by land, as it is, the significance of the Arctic
to general oceanic circulation arises chiefly from the sinking of its
cold waters when they come in contact with warm Gulf Stream
and North Atlantic waters to form Arctic "intermediate water"
which spreads out over a part of the North Atlantic. It also con-
tributes icebergs, which flow into the Atlantic with the southerly
current along the west shore of Baffin Bay, passing out through
Davis Strait, and entering the Labrador current to drift on to the
region of the Grand Banks off Newfoundland. The thawing of
these greafmasses of ice has noticeable effects on temperature and
salinities of waters in certain regions. The Arctic has litde relation to
the North Pacific, in which there are virtually no icebergs. The
Arctic Ocean is connected with Bering Sea only through the narrow
Bering Strait, some miles wide; and Bering Sea is to a great extent
shut off from the Pacific Ocean by the Alaska Peninsula, the long
loop-like chain of Aleutian Islands, and the Asiatic peninsula of
Kamchatka.
The Antarctic is a much more prolific producer of icebergs,
which are longer-lived than those from the Arctic, the upper
limits of life of individual icebergs being approximately two years
in the North Atlantic and ten years in the southern oceans. In each
region they may range to about 40 degrees in latitude. We need not
here concern ourselves particularly with the westerly drift of ice
in the Arctic, which has been the subject of a good deal of careful
study, notably by the Norwegian explorer Fridtjof Nansen in the
drift of the < Fram" in 1893. After being allowed to become frozen
in the ice near the New Siberian Islands, the vessel drifted with the
mass of ice northerly and westerly, to reach Norway, nearly a third
of the way around the earth, after almost three years in the ice.
Conclusion
In short, we find no sea independent of any of the others, and no
resting place for sea water anywhere, unless it is in some of the
General Plans of Circulation 1 3 7
semi-enclosed "deeps." If we may repeat what has been said or sug-
gested more than once, the seas, all together, constitute a great dy-
namic system with an intricate and world-wide mechanism for
mixing everything soluble that comes into it and a certain amount
of everything soluble on the face of the earth must some time drain
into the sea. This is the great concept of an integrated and world-
wide circulation of ocean water which Maury sensed a century ago,
not from much knowledge of the circulating mechanism, but from
the knowledge of the general uniformity of proportions of dissolved
matter in the sea.
NOTE. There is now an intriguing device for ascertaining direction and velocity
of surface flow of water while the vessel is in motion. Much more than a century
ago, the great English physicist Faraday suggested that "where water is flowing,
there electric currents should be formed," since the moving water is "cutting the
magnetic curves of the earth." It remained to perfect a device to measure electric
potentials developed by the movement of water through the earth's magnetic field.
This is now done with the Geomagnetic Electrokiwtograph ("G.E.K."), which is
towed behind a vessel under way. With a competent observer aboard and with
appropriate manipulation of the vessel, without stopping, direction and velocity
of flow are of continuous record. (William S. von Arx, "An Electromagnetic
Method for Measuring Velocities of Ocean Currents from a Ship Under Way,"
Papers in Physical Oceanography and Meteorology, MJ.T. and W.H.OJ., //
(3> I95
CHAPTER
10
lA/atef* in n lotion:
ater novea bit tke \AJina6
Horizontal currents
ANYONE OF EXPERIENCE ON LAKES OR ON COASTAL WATERS WELL
readily observe that, when there is a wind of sufficient force
and duration, the surface water is caused to flow in the gen-
eral direction of the wind, except as the direction may be modified
by coastal formations and bottom topography: water in movement
naturally follows the lines of least resistance. Wind blowing over
water exerts stress on the water, and it is this sheering stress which
initiates the flow at the surface. The surface water moving over
the next deeper water exerts a sheering stress to cause a movement
there; and so the translation of stresses and the consequent move-
ments proceed downward from level to level. A steadily blowing
wind may put into motion the whole mass of water from top to bot-
tom. The rate of movement would, of course, decrease with depth,
and physical studies have shown that the decrease is in direct geo-
metric proportion to distance below the surface.
There is nothing in these phenomena as they occur in confined
or coastal waters that would be contrary to the expectation of the
uninitiated. When, however, we consider the movements of wind
in the open ocean, where the depths are great, we find that the
current formed by the wind is not actually in the direction of the
wind. The effect of the rotation of the earth comes into play with
notable effects. Thus, it has been found (mathematically) that the
Water Moved by the Winds
direction of movement of the surface water caused by the stress of
the wind deviates from that of the wind to the amount of something
like 45 degrees, to the right of the wind direction in the northern
hemisphere, and to the left in the southern. The movement of the
surface water exerts a stress on the water beneath, which moves in
a direction deviating somewhat to the right (or to the left, accord-
ing to hemisphere) from the direction of movement of the surface
water. Since each layer exerts stress on the next layer below, and
at every level the deviation is always to the right (or to the left),
the surprising conclusion is reached that there will be a depth (de-
pending upon the strength of the wind and the viscosity of the
water) where the movement of the water is exactly the reverse of
the direction of the wind which exerts the original stress. But the
velocity of movement decreases with depth in geometric proportion,
so that, at the depth where the current is in a direction the reverse
of that of the wind, the velocity is very slight (about 4 per cent of
the surface rate), and it is virtually zero below that level. The total
transport of waters under the influence of wind is said to be at right
angles (normal) to the direction of the wind.
The conditions described in the last paragraph have theoretical
soundness, but there must be some modifications. The velocity of
movement of the surface of the earth is, of course, greatest in the
region of greatest diameter, which is at the Equator. In contrast, a
particle at either pole of rotation has, of course, no velocity of
translation about the axis: it revolves but is stationary with refer-
ence to the axis of the earth. Consequently, water that flows in the
general direction of either pole is moving from a region of greater
to regions of lesser velocity of the surface of the earth. If it carries
its momentum, as it must to some extent, it is moving to the eastward
more rapidly than a particle fixed at the latitude at which it is arriv-
ing. In other words, the motion relative to the axis of the earth is
eastward. This means that water flowing away from the Equator
necessarily turns eastward, which is to the right in the northern
hemisphere, to the left in the southern hemisphere. The general prin-
ciple of movement of water as influenced by the earth is broader
than is expressed by the illustration just given, which, however,
points to the basic fact that in the northern hemisphere currents tend
to have a clockwise rotary motion and in the southern a counter-
clockwise motion. This is in accord with statements in the preceding
7 40 This Great and Wide Sea
paragraph regarding the direction of wind-driven currents with
reference to the wind, with a deviation of 45 degrees, to the right in
the northern hemisphere and to the left in the southern hemisphere.
There must, however, be some qualifications in respect to latitude
and depth.
As Manner has so clearly stated: c< But it is to be noted that this
result is derived on the assumption of an ocean of infinite depth.
The sea, however, is not of infinite depth and this abrupt change of
90 degrees (at the Equator), in Ekman's words, 'has, of course, no
correspondence with reality.' Actually, the angle of deflection
would begin to decrease in the neighborhood of the equator and be
zero at die equator. In fact, for an ocean of finite depth Ekman's
equations show that the angle between the surface current and the
wind depends on the depth. In a very shallow ocean his calculations
make this angle very small, that is, the current sets nearly in the
direction of the wind; but as the depth of the ocean increases, the
angle increases and approximates to the value of 45 degrees.'* 1
Other qualifications with reference to wind-driven currents relate
to the directions of coast lines and to differences in density. The
effect of the wind in causing movement of water at some depth will
depend in part upon changes of density with depth. When the upper
waters are lighter because of reduced salinity or higher temperature,
the influence of the wind on the movement of the water may not
extend to as great a depth as in more homogeneous waters and we
may find a fairly homogeneous layer of water circulated by the
wind above the more stable water of the deeper zone. We are told,
however, that, in the sea generally, the changes in density with depth
are not great enough to cause direcdy any great modification of
the effects of wind action in a vertical direction, except as the vari-
ations in density influence eddy viscosity, with notable indirect
effect
Upwettmg
There are conditions when the influence of wind is such as to
cause the water to move continuously either toward or away from
the shore. This, of course, may result in secondary currents running
parallel to the shore and also in raising or lowering the level of the
coastal water. The resulting disturbance of equilibrium leads in
i. Manner, The Sea, p. 260.
Water Moved by the Winds 241
turn to vertical movements of the coastal waters upward or down-
word, according to whether the surface drift is toward or away
from the shore. When the lighter coastal water is carried away from
the coast, the water from below, which is generally colder and
heavier, rises to replace it. This "upwelling" of deeper, colder water
occurs most notably along the coasts of California, Peru, and West
Africa, where the conditions are most favorable in respect to direc-
tion of prevailing winds and pretipitateness of the coastal slope.
According to the more recent investigations (of McEwen partic-
ularly) the water drawn to the surface along the coast of southern
California comes from a depth of only 200 to 300 meters, so that
what actually occurs is an overturn of a relatively superficial layer.
The rate of rise on the coast of California has been estimated at
about a yard a day.
Rise of water from below must occur wherever there is divergence
of streams, attributable to winds or to other forces that move oceanic
currents. Such a divergence must occur, for example, in the region
of the Equator where, because of the rotation of the earth, there is
a trend to the right in the northern hemisphere and to the left in
the southern hemisphere. Obviously a deepening trough would
develop were it not for the rising of waters from a lower level. Con-
versely, in regions of convergence* of currents, piling up is obviated
by the subsidence of surface waters to flow away at a lower level
Principal convergences are the Antarctic convergence which is said
to be traceable all around the Antarctic continent, a subtropical con-
vergence farther northward and a tropical convergence.
Another form of vertical movement occurs when surface waters,
because of cooling or evaporation, become heavier than those be-
neath. A change of level takes place, the heavier surface waters sink-
ing to the level appropriate to their density. Such convection cur-
rents on a grand scale may result in an "overturn" in the fall; it is
thought to affect only a relatively thin upper stratum. Upwelling is
understood to occur all around the Antarctic continent, in compen-
sation for the sinking of heavy surface waters to form Antarctic
bottom water.
To the upwelling of a deeper water is attributed in large measure
the relative coldness of certain coastal waters. The upwelling wa-
ters seem also to bring into the surface zone of active photosynthesis
a good deal of dissolved nutritive matter to enrich the region and
/ 42 This Great and Wide Sea
promote the growth of plankton and fish. Accordingly, regions of
upwelling are likely to support extensive fisheries. The great guano
deposits on islands off the coast of Peru, formed by the innumerable
cormorants, gannets, and pelicans, are undoubtedly traceable in
considerable part to the abundant anchovies and other small fishes
upon which the birds feed; the anchovies are traceable to the plank-
ton and the plankton, in part, to the nutritive materials brought back
to the upper waters by upwelling.
Waves
To the ordinary observer nothing is more characteristic of the
ocean than the continual prevalence of wave motion. The waves
may be low and seemingly regular, or, in times of storm, high and
terrifying. They beat unceasingly on the shore and give zest to
bathing as they roll in and break in the shallowing water. Away
from shore they mark the continuing uneasiness of the surface and
give rise to seasickness or, perhaps, after some experience, to the
soothing cradle-roll or pitch of the vessel. They may be obviously
driven by the winds or, in times of calm, there may be only a long,
low heaving movement which we designate as "swell," but not
necessarily employing that term in its slang meaning of superb or
delightful. Even the swell, particularly in the broad Pacific, may
be marked by very great differences in elevation between crest and
trough and, on reaching the coast, cause tremendous damage as they
break on the exposed shores. Such is the case with the mar brava, or
"wild sea," occurring at times on the coast of Peru, which, in the
absence of local strong winds, drags ships at anchor in the ill-pro-
tected harbors, often beaching them or causing damaging collisions
and wreaking havoc upon docks and the strongest steel piers.
Everyone associates waves with winds, recognizing the persistence
of high waves for some time following wind storms and the spread
of waves from regions of storm to regions where only normal air
movement may have occurred. The mechanics of wave motion and
the relations of waves to winds are much too complex to be grasped
by the ordinary student. Yet there are a few facts about waves that
may be of interest to anyone. We know that waves have different
heights, lengths, periodicities, and velocities. We know that they
are not regular, but differ in size and form; that they do not always
run in the direction of the wind, that some are marked by breaking
The University of California, La Jolla
PL 6. "Sandfall" in the Cape San Lucas submarine canyon, Baja Cali-
fornia, during the Scripps Institution's Vermilion Sea Expedition. The
"fall" is about 30 feet high. Currents feed sand from the nearby beaches
on.
Above, PL 9- Standard automatic tide gage with transmitter for remote
recording. (Courtesy U.S. Coast and Geodetic Survey) Below, PL 10.
The amount of heat flowing through the crust of the earth into the ocean
waters varies considerably over the Pacific Ocean. The cause is unknown.
It may be that vast convection cells underlie the crust. Some of the first
such measurements made were taken on Capricorn Expedition, 1952-53.
Here scientists lower the temperature probe. The probe itself is the slender
steel rod; the larger section at the top houses recording instruments. (The
University of California, La Jolla)
DEPTH
IN
FATHOMS
t
x.
& r>i "^ ! s
C - -J
| too
VERTICAL EXAGGERATION 9 I
Above, PI. 1 1. Sea-mount-or underwater mountain, as tracked by Woods
Hole Oceanographic Institution echo sounder in the Caribbean area.
Depth is determined by the time it takes echo to go to bottom and return
to shop (Courtesy Woods Hole Oceanographic Institution) Below, PL
12. Marine Technician attaches a Nansen bottle to the hydrographic wire.
The Nansen bottle is one of the standard tools of oceanography through-
out the world Actuated by sliding weights called messengers, the bottles
on a line reverse and collect a sample of sea water at a specified depth.
Thermometers on the side of the bottle record temperature in situ. (The
University of California, La Jolla)
The University of Cabforma, La Jolla
PL 13. This six-ton crane aboard the Scripps Institution research vessel
ARGO enables oceanographers to lower heavy equipment to the deepest
parts of the ocean.
Above, PL 14. This underwater camera, designed by Carl J. Shipek of the
U.S. Navy Electronics Laboratory, was used on Capricorn Expedition to
the South Pacific in 1952-53. Below, PL 15. Lowering the chain dredge
from the stern of the research vessel HORIZON. The ship is one of the
oceanographic fleet of The University of California's Scripps Institution
of Oceanography. She was engaged in Northern Holiday Expedition to
the Gulf of Alaska at the time this photograph was taken. (The Univer-
sity of California, La Jolla)
Water Moved by the Winds
and foaming crests while others are not, that the "breaks" do not
occur uniformly along the crest of any particular wave, and that
the sloping surfaces are not necessarily smooth but may be marked
by various sorts of irregularities. Doubtless most of us understand,
too, that, despite the appearance of linear movement, there is no
substantial flow of water resulting from the waves. With wind
blowing across a field of wheat, each head of grain moves forward
and falls, rises and moves backward, but keeps its basic position. In
water, each particle in wave movement rises and moves forward,
falls and moves backward; its path is nearly circular, if the water is
deep, or elliptical if the bottom is nearer; but there is some slight
advance. The floating log, passed by succeeding waves and appear-
ing now at the crest and now in the trough and seemingly stationary
does make some progress, independently of the effect of direct wind
action on the log. Waves caused by wind, in contrast to currents,
are "movements of oscillation," not "movements of transport." 2
One fact about the relation between winds and waves that is easily
grasped, once our attention is called to it, is that, so long as the wind
blows faster in the direction of the wave movement than the waves
are moving, each wave acts as an obstacle to the movement of the
air, so that an eddy must form on the leeward side; consequently, the
pressure of the wind is greater on the windward slope than on the
other side of the crest and this pressure tends to increase the velocity
and the height of the waves.
The friction between air and water, the relative densities of air
and water, the surface tension and the viscosity of the water, and
the rate of movement of the air are all factors in the formation of
waves. It is said that wind velocities below about 2 miles per hour
will not cause disturbances of a smooth water surface but, as Sverd-
rup says, "as yet the problem of the generation of surface waves is
not satisfactorily solved." 8
In general the height, profile, and velocity of progress of waves
depend not only upon wind velocity at the time, but also upon the
length of time the wind has blown, the state of the sea when the
wind started blowing, and the dimensions of the area over which
2. There are, however, (t waves of translation," representing the progressive
forward movement of water, as when, by the breaking of a dam, a mass of water
is added to that below to move on over die smooth water or when, along shore,
"the crest of a breaking wave topples over and crashes down on the water surface
in front." Sverdrup, op. cit^ p. 147. See also Bigelow and Edmondson, 1047.
3. /<*, p. 134.
7 44 This Great and Wide Sea
the wind has blown. Practically all winds are variable in strength,
marked, as we say, by gusts. This inconstancy of the wind has much
to do with the irregularities of wave surfaces. The greatest wave
heights observed in most oceans are about 12 meters, although
heights up to 30 meters (98.4 feet) have been reported. Fifty feet
is thought to be "the extreme height of the waves of the sea due
to wind." 4 Of course a great wave breaking over a ship or on a
steep shore may throw water to a much greater height, even up to
100 feet. A particular series of high waves had a length between
crests of 3 10 meters (about one-fifth mile), a period of 13.5 seconds
(the time interval between crests passing a given point), and a
velocity of the order of 40 knots (about 48 miles per hour) . Heights,
lengths, periods, and velocities may be increased on approach to
shores, and all of these characteristics of waves vary greatly with
many conditions.
The length of a wave may be 15 to 30 times its height. For wind
waves it may be given as a general rule that the velocity is 2 % times
the square root of the length. In other words, if the distance be-
tween crests is zoo feet (the length), the rate of advance (velocity),
measured in feet per second, would be about 2 % x 10, or 22.5 feet
per second. The period, which is the interval of time elapsing be-
tween passages of successive crests at a given place, would, of course,
depend upon length and velocity. It is usually about one-half the
square root of the length, or, in the instance mentioned, about five
seconds. These remarks refer to waves caused by the wind. Waves
resulting from earthquakes or other seismic disturbances may have
very great velocities, even approximating the velocities of present
day airplanes.
Wave motion is largely a surface phenomenon, the wave motion
decreasing rapidly with increasing depth. A descending submarine
vessel easily gets below the level of disturbance from ordinary sur-
face wave action; 5 yet we know that, after great storms, bits of coral,
Baltic amber, or other material from the bottom at some depth,
may be dislodged and cast up on the beach. Murray in The Ocean 11
tells of the disturbance of sand on the bottom at nearly 200 fathoms
4. Manner, op. cit., p. 181. Wave height is the vertical distance from trough to
crest.
5. This is "by the book": a former submarine officer in the U. S. Navy assures
me that wive action is felt far down.
6. Pp. 105, 106.
Water Moved by the Winds
(almost one-fourth of a mile) during heavy gales. We are speaking
now of the subsurface effects of wind waves: it will be seen a litde
later that there are also disturbances in the depths which are inde-
pendent of surface waves.
The irregularities of wave motion on the ocean are attributable
in part to the fact that two or more patterns of wave movements
may prevail at the same place and time, superimposed upon one
another. Waves with different periodicities and lengths will, at
different points and moments, combine to cause a higher lift of the
water or, at another place, partially cancel each other to form a
shallower trough. For example, a long, low, swell running con-
currently with a series of waves may not be directly observable at
all, but will have the effect of causing noticeable irregularity by
raising some crests and lowering others, by malting troughs between
waves deeper or shallower, and by slightly advancing or retarding
crests, and thus producing observable irregularities in periodicities,
as well as in heights of waves and depths of troughs. 7
As waves approach the shore, their velocity is retarded in the
shallow water, the lower part being retarded more than the upper,
so that the crest "breaks" over, as is characteristic of the condition
of "surf." Another effect of the slowing down in shallow water is
to cause waves that were originally oblique to the shore to become
roughly parallel to it. The first part of an oblique wave to approach
the shallow water is slowed down while the free outer part continues
with undiminished velocity, so that the front of the wave is steadily
turned toward the shore. Such a change in direction of a wave as
occurs on approaching the shore may also occur as the wave ad-
vances over the relatively shallow water of an isolated shoal. Con-
sequently, pictures taken from an airplane may reveal the presence
of a shoal that has not been located by actual soundings.
7. See Sverdrup, op. #fc, p. 140, F^j. 38.
CHAPTER ii
cder in, n lotion:
and \Jtner tvlouement&
The Tide
WE HAVE DEALT WITH THE WAVES, THE SWELLS, THE CUR-
rents, and drifts. If by some miraculous intervention we
could stay any of these significant features of dynamic
action in the sea, the waters would still not be at rest. "The sea
moves also in a slower tempo. Twice each day, in rhythmic fashion,
it rises and falls in response to the mighty pulse of the tide-producing
forces. These stir the sea to its depths and bring about the phe-
nomena which for short are called the tide." 1 The tides are "the
largest waves in the ocean." 2
The relation of the tide to the moon is apparent when we observe
that generally the tide, like the moon, comes approximately fifty
minutes later each day. Its relation to the sun becomes evident when
our observations cover a longer period and we find that the tide
varies in height from day to day. It is a general rule that the tide
on the flood is highest, and on the ebb is lowest, when the moon is
"full" or when it is "new" that is to say when sun, moon, and
earth are in line; and the tide is least high at flood, and least low
at ebb, in the first and third quarters of the moon, when the three
bodies are farthest out of line. The extreme tides of the full and
new moon we call the spring tides; the moderate tides on the quar-
ters of the moon are called the neap tides. Spring and neap tides
i. Manner, The Sca> p. 203.
z. Sverdrup, Johnson, and Fleming, The Oceans, p. 545.
Tides and Other Movements z 47
are said to have the general rektive quantitative rektion of 13 to 5.
Actually, there is usually a lag, the spring and neap tides following
a little after the alignment of sun and moon. So also the semidaily
tides fall behind the primary tide-producing forces of the moon and
the sun as someone has said, like a dog pulled by a chain but fol-
FIGURE 10. Diagram show-
ing the plan of the standard
automatic tide gage. (Cour-
tesy XL S. Coast and Geo-
detic Survey)
lowing behind, rather than closely accompanying, the agent that
pulls the flJhflin.
The tides are not, of course, entirely regular. They vary from day
to day in the same place, they manifest themselves differently in dif-
ferent places in the same general area, and they have characteristic
features in particular regions. The partial inconstancy and the
diversity of tides are attributable to the fact that there are many
variables to which the tide is responsive. Among these are: the
elliptical orbits of earth about sun and of moon about earth, giving
changing distances between earth and sun, and between moon and
earth; the declinations (see p. 150, below) of sun and of moon,
/ 4% 1 to* Ureat and Wide bea
which have slow rhythms; the latitude of the place; the changes in
barometric pressure; the prevalence of off-shore or on-shore winds;
the width and the depth of the water on which the tidal forces act;
and the contours of shores.
Considering tides the world over, we can distinguish three types
or "species." A semidaily (semidiurnal) tide is the common form
of tide in the Atlantic, where the successive high rides of a day are
of nearly the same height, and the two low tides are about equally
low. A mixed ride is more common in the Pacific and Indian oceans,
where alternate highs may be nearly equal and the lows very une-
qual, or vice versa. One low is very low, while, at the next low, the
waters scarcely fall to mean sea level; or the lows may be nearly the
same, while alternate floods bring the water barely, if at all, to mean
sea level, as at Honolulu. A dally (diurnal) ride prevails in places
on the Gulf of Mexico, where alternate lows or highs are more or
less completely effaced and flood and ebb tide seem to follow one
another at about twenty-five-hour intervals, as at Pensacola and
sometimes at Galveston.
The mixed tides are actually combinations of daily and semidaily
tides, with different combinations at different places. The funda-
mental question, then, is: Why should there be daily and semidaily
tides? Without going too far into explanations that would lead us
considerably into the realm of the mathematician and the physicist,
the chief types of causes responsible for the two tides may perhaps
be suggested. Let us forget the diurnal tide for a moment and con-
sider only the semidiurnal tide.
The gravitational attraction between sun and earth and between
moon and earth supplies the force inducing the mass movements
that we know as the tide. The seas are upon the surface of the
earth and the differential "pull" of gravitation on parts of a whole
depends upon distances of the several parts from the center of
mass. Obviously, the sun pulls more strongly on water of the sur-
face that is toward the sun than on the center of the earth, while its
pull on the center of the earth is stronger than its pull on water
of the more distant surface. If the surface of the earth were en-
tirely water, 3 the pull of the sun would change the sphere into an
3. The surface of the earth is not all water, but we are not concerned here with
tidal strain over terrestrial areas. These are to some extent measurable, but the
Tides and Other Move?nents
oblate spheroid with increased diameter in a line running directly
from the sun through the earth and 'with decreased diameter in a
plane perpendicular to this long axis.
Let us imagine for a moment that the sun is directly over the
Equator: then, along the equator, two conditions of high ride will
prevail at one time, one at each extreme of the long axis that is to
say, on the face toward the sun and on the face away from the sun.
Halfway between, on each side, low tides prevail; thus there are two
lows at intermediate points. The four tides, two high and two low,
must prevail somewhere around the circumference of the earth at all
times. This is true, not only at the Equator, but, to a less extent, at
any latitude, although the effectiveness of the tide-producing force
will be somewhat reduced as we proceed away from the Equator
toward the poles.
But the earth makes a complete rotation about its axis in a day; so
that the two states of high solar tide and the two states of low solar
tide must pass completely around the earth in the course of a twenty-
four-hour period. This means that, at any place on the earth, there
must be two high solar tides, generally one in the day and one in the
night, and two low tides in between. Of course, this is not exactly
what we seem to find. Our failure, so far, to arrive at any close
approximation to the actual conditions is due to the fact that we
have not yet considered the influence of the moon which, as a tide-
producing force, is definitely stronger than that of the sun.
The moon revolves around the earth relatively slowly, but at such
a rate that the lunar day, resulting from the rotation of the earth
on its axis, is about fifty minutes longer than the solar day of twenty-
four hours. Just as, with the sun alone, we should have at any place
four solar tides in a period of twenty-four hours, so, with the moon
alone, there must be four lunar tides, two high and two low, during
a period of about twenty-four hours and fifty minutes. The tides
caused by the sun and those caused by the moon run with slightly
different periods; so that they are sometimes partially cancelling and
sometimes supplementing each other; lunar and solar tides will co-
incide and be fully cumulative only twice each lunar month, when,
solid earth yields too little to tidal forces to make the changes ordinarily observ-
able to man. It may be, however, that these strains set off some earthquakes, and
that something is felt by the catfishes whose movements are said to presage by
many hours the occurrence of earthquakes on Asiatic shores. Tidal effects in the
air mass around the earth are also too slight for ordinary attention.
'1 'his (jreat and Wide Sea
as previously mentioned, sun, moon, and earth are in line at full or
new moon; at other times lunar and solar tides will partly cancel one
another or be only pardy in summation.
We see, then, in a general way, why there should be semi-diurnal
high and low tides and why the tides should vary in degree of high-
ness or lowness in a somewhat regularly rhythmic fashion. But, it
may be asked, why should the general rhythm of the semidaily tide,
as we see it, follow the lunar period rather than the solar period.
The answer takes us back to two basic laws: the tide-producing
force of a celestial body varies directly 'with the mass and inversely
e with the cube of the distance* The sun has twenty-six million times
the mass of the moon, but it is 389 times farther from the earth than
is the moon, and the cube of 389 is nearly fifty-nine million. Con-
sequently, the relative tide-producing powers of moon and sun are
as 59 is to 26; the influence of the moon in this respect is about ^ %
times that of the sun. Naturally, then, the tides display a lunar
rather than a solar period. What we see of the solar tide is little
more than the changes it effects in the highness and lowness of the
tides on successive days. Consequently, die tides are most marked
in January, when the sun is nearest the earth and exerts the most
force with or against the moon.
What is known as the declination* of the moon is also a factor
in the height and rhythm of tides. In an earlier paragraph we as-
sumed that the moon and the sun stood directly over the equator.
As everyone knows, the sun is in this position only twice each year
and the moon only twice in approximately 27 1/3 days. Let us
imagine for a moment the moon at its maximum declination to the
north. That point on the surface of the earth which at a given min-
ute is nearest to the moon may be expected then to have its highest
lunar tide; at the same time, a point on the other side of the earth an
equal distance below the equator, and, therefore, farthest from the
moon, has also approximately its highest lunar tide. As the earth
revolves on its axis, each of these points comes, half a day later, to
a position where it is as far out of line with the moon and the center
of the earth as it can get on that day: in this position it is subject to
greatly reduced tidal force. It is time for "high ride," but this high
4. Meaning die angular distance with reference to the celestial equator. We are
concerned here with the angle of the moon with reference to the axis of the earth.
Tides and Other Movements
will not compare with the last high. Consequently, there is only
one very high ride in the course of the day, and one that is mod-
erately high. For this and other reasons, there is a dli&rnd rhythm
as weU as a semidiurnal rhythm.
Various sorts of mixtures of the diurnal and semi-diurnal lunar
and solar rides give us various types of tidal manif estarion in different
regions. "To a very large degree, the various oceans may be said
to show preferences for one or other of the three types of ride. In
the Atlantic Ocean the semidaily tide is the prevailing type, while
in the Pacific and Indian oceans die mixed tide is the prevailing type*
The daily tide is found in certain parts of the Gulf of Mexico, the
China Sea and in other like bodies of water." 5
From what has been said so far it may be assumed that, generally
speaking, and theoretically at least, the semidaily tides will be great-
est in equatorial regions and least as we approach the poles, while
the diurnal tide will be nearly zero around die equator and greatest
toward the poles.
Still another important set of conditions, as yet unmentioned, has
much to do with die form and rhythm of die tide. Every container
of water has, for the contained water, a natural period of oscillation,
depending on its length and depth, assuming that the water is made
to swing back and forth. A number of different basins of different
sizes and depths will offer an equal number of periods of oscillation.
If we apply a certain force to all of these containers we can expect
the greatest rise and fall of the water when the period of the applied
force is the same as the natural period of oscillation, so that the two
factors reinforce each other; and we shall have the least rise and fall
when the period of the applied force differs most from the natural
period of oscillation, so that one factor of oscillation tends to cancel
the other. We have various combinations of "free" oscillations com-
parable to seiches in enclosed bodies of water, with periods de-
pendent upon the geometric shape of the lake, bay, or ocean, and
"forced" oscillations, with periods dependent upon the outside
forces producing them. The seiche (pronounced sache), it may be
explained, is a sort of "see-saw" or back-and-forth swing of water
such as one causes in a long pan by suddenly raising one end.
We have seen, although in a very general way, that both daily
5. Manner, op. cit^ p. 215.
and semidaily rhythms characterize the chief ride-producing fore
**Now it happens that the lengths and depths of the various parts
the Atlantic Ocean are such as to make their natural periods
oscillation much more nearly half a day than a day. Hence, in tl
ocean there is little daily tide. In the Pacific and Indian oceai
depths and lengths are such as to permit oscillations of both the dai
and semidaily periods. In these oceans, therefore, both daily ai
semidaily tides are brought about, the combination of the two givi
rise to the mixed type of tide characteristic of these oceans. Final]
in the Gulf of Mexico the natural period of oscillation more near
approximates the daily rather than the semidaily tide, so that he
we find the daily tide well developed." 6
We have said nothing of tidal modifications resulting from vaj
ables such as the changing distances between moon and earth ai
between earth and sun, the varying barometric pressure, the chan
ing direction of the wind and the diversity of bottom and sho
forms. There are, indeed, so many complicating factors affectii
the tides that a full explanation of them taxes the most compete
mathematician equipped with the best mechanical devices. To for
cast the tide at any particular place and time, the U. S. Coast ai
Geodetic Survey employs an extremely complex and ingenious
devised machine which automatically summates the effects of mo
than a score of variables. We will do well now to emphasize ti
fact that this cursory account is not intended to offer an explanatk
of tides but merely to be suggestive of the principal forces behii
them, and behind their variable manifestations*
At this point we may distinguish three types of manifestations <
tidal phenomena. The "progressive wave" type, the real tide, pr<
ceeds around the whole earth; it reflects the external tidal fore
and in some places is essentially what is observed. There is also
"standing wave" type where the rhythmic rise and fall is strong
modified by the swing of water, or seiche, caused within a near
enclosed basin, such as a bay or harbor; the seiche reflects the for
of the container. As already indicated, even the great oceans funi
tion as basins whose seiches modify the progressive wave form <
tide: in bays there may be, over considerable areas, synchronoi
rather than successive rises.
6. Ibid., p. 218.
Tides and Other Movements
The "standing wave" is best illustrated by picturing a tub of water
in which, by tilting, the water is caused to swing back and forth.
It rises on one side and then on the other with no wave running
across the surface. If a similar tub of water is not tilted but the sur-
face is disturbed at one place, the "progressive wave" moves across.
In the first case, the rises at all points on one side come nearly syn-
chronously; in the other case, the crest of the wave proceeds suc-
cessively from point to point. In our terrestrial containers, which
may be bays, harbors, semi-enclosed seas, or even a great ocean, the
mighty tide-producing forces, together with the forms of the sev-
eral bodies of water, give rise to both standing and progressive
waves, with one or the other, or mixtures of the two, playing in each
case the greater part in determining what may be observed at a
particular place.
If, now, we add to our tub a shallow spout near the surface, then
either type of wave may cause a flow of water through the spout
and this flow is suggestive of the third type of tidal phenomena, "the
tidal current" through inlets and in the mouths of rivers and narrow
bays. The shape of the spout, as well as the type of wave, will have
much to do with determining the rate and height of flow. Where
the entering tidal current is cooped within a narrow estuary, or
under some other conditions, it may be transformed into a high and
powerful advancing wave or bore. Probably the tide in the ocean
offshore will rarely exceed 2 or 3 feet, but in the tidal current of
the Amazon we may have a rise and fall of 10 and 15 feet. In the
Bay of St. Malo, on the northwest coast of France, there are "tides"
of 39 feet; in Noel Bay, a part of the Bay of Fundy, the spring tides
may cause the water to rise more than 50 feet (ij^m.); there are
even records of a vertical tidal range of 66 feet for the Bay of
Fundy. The exact causes for the extreme tides in the Bay of St. Malo
are said to be different from those causing the still greater extremes
in the Bay of Fundy, but we can not go into an analysis of these con-
ditions. A famous "bore" is that in the Tsientang River in China,
south of Shanghai, where a towering, rushing and roaring wall some-
times offers great danger to those who do not know enough to an-
ticipate its coming and to be out of the path; although, with
properly constructed sampans, the bore can be utilized for rapid
advance up the river.
Internal Waves
We think of waves as surface phenomena, because it is only't
top that we see. Even the surface waves extend below, although wi
greatly diminishing degree of action with increasing depth: th
are not felt very far down. There can, however, be independe
subsurface waves, or, perhaps we should say, waves at surfaces ott
than that between sea and atmosphere. Actually, the waves that ^
see and call surface waves are not at the true surface of the eari
which is the outer limit of the atmosphere; they are at the bounda
between water and atmosphere, that is to say, between two me<
of very unequal density. There can be waves at any bounda
between layers of unequal density. Thus, we can have waves
the surface of a layer of heavy liquid overlaid by a thick layer
water, waves that are scarcely if at all apparent on the surface c
posed to the atmosphere: this is easily demonstrated in the laboj
tory. 7 So in the ocean, where there are, perhaps far down, bounda
lines between layers of water of unequal densities, waves can occ
at any boundary without being obvious at the surface of the sea, a]
quite independently of surface phenomena. Actually the deep wa
will have an effect extending upward to the surface, but with amp
tude diminishing so rapidly toward the surface that the resulri
wave motion there will be much too slight for ordinary observati
or consideration. That such internal waves occur, although,
course, they are not directly observable, seems now an establish
fact; their origins or causes remain to be discovered.
Although the greater number of observations and analyses
data concerning internal waves seem to have been made within t
past fifteen years, the occurrence of such phenomena was divin
by Hellaijd-Hansen and Nansen as long ago as 1909. The latter,
7. An experiment with relatively immiscible liquids of unequal density, such
carbon tetrachloride colored with crystals of iodine, overlaid by plain water,
simple and convincing as to the possibility of internal waves. There should
warning, however, that conditions are not precisely the same where the t
liquids of unequal density are miscible, as in the case of sea waters of differ
densities. In the latter case it would seem to be natural for eddy effects to lead
some slight degree of mixing, yet, speaking of the transition zone (halicline) 1
tween upper and less saline water and the deeper and more salty water, Profesj
Thurlow C. Nelson of Rutger's University has made the following interest
comment (by personal communication) : "Our studies of the halicline in Barne
Bay show it to be remarkably stable, broken only by fairly heavy waves. Even i
dead calm, however, the surface of the hahcline rises and falls about 2m
rhythmic fashion due to submarine waves."
Tides and Other Movements
his chapter on "Physical Oceanography" in Murray and Hjort,
The Depths of the Ocean, gave vivid suggestions of the phenomena
of deep turbulence.
"We arrived at the conclusion that there must be many forms of
motion of great and far-reaching importance, though hitherto hardly
known at all, among them vertical oscillations of the water-layers
and vortex movements. Many things go to prove that these are phe-
nomena of general occurrence. We must picture to ourselves great
submarine waves moving through the water-masses, alterations of
depth in the layers according to changes in the velocity of the cur-
rents, standing waves, and great vortices. We must further conceive
of constant fluctuations in the velocity, partly also in the direction,
of the great ocean currents, not only by reason of the tides and as
the effect of the wind, but also because the currents are subject to
a sort of pulsation, the nature and origin of which are as yet un-
known. There is an interplay of many different forces, producing
an extremely variegated picture; the sea in motion is a far more com-
plex thing than has hitherto been supposed. Physical oceanography
is confronted with a host of new problems, the solution of which
will be a matter of the highest interest." 8
Much remains to be learned about the nature, extent, and general
prevalence of internal waves, as well as concerning their causes.
There are "short" internal waves; in the open ocean there are also
long waves of low velocity, although these may be short in compar-
ison with tidal waves. They may have considerable amplitude, per-
haps much greater than that of surface waves. Seiwell (1937) found
evidence of vertical displacement of as much as 80 meters, with a
primary twenty-four-hour period, but with complicating oscillations
of twelve and eight hour periods. Sverdrup has found evidence of
internal waves with periods of about seven and fourteen days. 9
It may be asked how knowledge of such invisible and, to the ob-
server, impalpable, waves can be gained. In partial answer it can
be said that, where an oceanographic vessel, remaining approximately
in one place, discovers at given depths periodic changes in tempera-
ture, density, and oxygen content, it is reasonable to infer that at
a particular depth, different strata of water are being sampled at
different hours, in rhythmic alternation; the instruments of collection
8. Pp. 283-85.
9. See Sverdrup, et /., op. cit^ pp. 585-502.
i $6 This Great and Wide Sea
at a fixed depth are at certain hours in one layer and at another in
the next lower layer: rise and fall, or wave action, is indicated. If
on a dark night an object suspended from a pier were found to be
in the air and in the water in periodic alternation, the existence of
waves would hardly be questioned; so our sampling device in the
depths may yield alternating results that can be accounted for only
by the assumption of deep wave motion.
Between the top of the ocean and the bottom there may be a
number of different boundary surfaces between layers of different
densities associated with different conditions of salinity or of tem-
perature. Consequently, there may be internal waves at several dif-
ferent levels, and each series of waves may have some effect on those
above and below. The whole subject of internal waves is too com-
plex for our further consideration in this place; but, in the words of
Sverdrup, Johnson, and Fleming "The internal waves probably are
important to the process of mixing," 10 and they "greatly complicate
the actual movement of water masses and lead to the existence of
extremely intricate patterns of currents and vertical displace-
ments." 11
"Tidal Waves"
The term "tidal wave" is applied loosely to destructive advances
of the sea upon the coasts, and these have at least two distinct origins:
earthquakes and storms. Neither type is related to the tide and
those of the latter type are not actually waves.
The waves resulting from earthquakes arise in different ways:
They may occur through mere oscillations, or through liberations
of gas that rise to "lift the surface up like a great dome and produce
a transverse wave" which spreads in all directions. Again there are
waves resulting from submarine landslides. Earthquake waves may
be enormously high and may travel long distances. The wave ac-
companying the Lisbon earthquake of 1755 and causing most of
the damage there is said to have reached across the Atlantic to the
West Indies as a tidal wave 4 to 6 meters high. The wave resulting
from the eruption of the volcano Krakatao in 1883 caused great
damage and the loss of thousands of lives in the East Indies and, in
10. Ibid^ p. 601.
ir. Ibid^ p. S9<5, 597.
Tides and Other Movements 1 57
a round-about way, even reached England with a small but measur-
able height. Such waves are now called "tsunamis."
The great "tidal waves" that caused so much loss of life in Gal-
veston, Texas, in 1900 and in the Buzzard's Bay, Massachusetts, re-
gion in 1938, were much more than actual waves. The flooding of
the coastal regions in these cases was in considerable part the result
of direct transportation of water under the influence of exception-
ally strong winds. True "wave" motions are not transport but peri-
odic oscillation, of water particles within a limited space. It is not
unnatural that confusion of thought and language should occur,
especially since great waves and seiches usually accompany the
movements of masses of water before the wind. In some cases,
indeed, high waves break upon the shores with destructive effect
even before the strong winds are felt at the coast. The base level
of water along shore may also have been raised. The following flow
of water in the tidal wave (which is neither wave nor tide) only
increases the destruction.
Biological Relations of Waves, Tides and U fuelling
A whole book could be written on the subject of the significance
of waves and tides to life in the sea. Some of the relations will be
discussed in later chapters on biology. It is appropriate here only
to suggest some of the bearings of tidal and wave movements on
plant and animal life. That the rise and the fall of the tide and the
tidal currents are of significance to the living world must be appar-
ent to anyone who wanders even casually along the shores of bays
and harbors. There are great numbers of organisms, plant and ani-
mal, whose preferred home is above extreme low water, "between
the tide lines," where, for part of the time, they are washed by flood-
ing and ebbing water, with almost constant renewal of supplies of
food and oxygen. This is only a small part of the story. Because of
special conditions, commercial fishermen in harbors, employing
seines, seek the fish as they follow the rising tide over the shoals,
while sport fishermen know the advantages of fishing at the slack
of the tide.
Conditions of turbulence associated -with waves promote inter-
change between sea and atmosphere, as well as circulation and dis-
tribution of oxygen, heat, etc. within the upper layers. The proc-
/ 58 This Great and Wide Sea
esses of diffusion and conduction, by which oxygen and heat are
carried downward from the surface are extremely slow and of little
effect on distribution. That part of the sea which profits by inter-
change of temperature and gases between sea and atmosphere would
be restricted to a thin surface layer, were it not for the mixing effects
of waves and for certain density changes. The tides are responsible
for some coastwise currents and, in coastal regions, for much mxing;
but, well out in the open sea, waves are probably most significant in
mixing the upper waters and in preventing sharp superficial stratifi-
cation.
For animals such as oysters that have locally fixed stations on the
bottom or for those like clams that are relatively immobile, tidal
currents and wave movements circulate the supplies of food and
oxygen. Were it not that the sea water is virtually always in motion
we could not have in salt or brackish waters the great populations
of oysters, corals, sea anemones, barnacles, and other sedentary ani-
mals, for which there are no corresponding populations in fresh
water (p. 240, below.)
Animals of fixed habit and others that are mobile but sluggish
have larvae that live freely in the water for a while and then, when
properly developed, settle to the bottom wherever they happen to
be. For such the tidal and other currents permit limited migration
and, in great part, determine distribution.
As early as 1911, Otto Pettersson had found a relationship be-
tween the occurrence of herring in certain Swedish fiords and the
deep internal waves that one never sees at the surface. When great
submarine waves enter those fiords, they force out the less salty
upper waters; the herring go in with the deep waves or are drawn in
by them. These phenomena of the deep, although unseen by man,
may be of notable practical significance to those who "live by the
sea."
In certain regions upwelling of deeper water brings back in circu-
lation nutrient substances that had sunk and been lost. They had
been lost to the organic world, because, while they were in the deep,
they had been out of reach of the green and yellowish plants that
grow and multiply only in sunlight. These conditions must be
treated in more detail when consideration is given to the cycles of
life (see p. 190, below). A particular region may be cited here. The
Tides and Other Movements
region off die coast of Peru has been mentioned as a place where
upwelling of deeper cold waters is most notable. At another time 12
I wrote regarding that region:
"In contrast to the barrenness of the coast there is a peculiar
wealth of certain forms in the open ocean. The great red seas,
formed, sometimes at least, of myriads of microscopic dinoflagel-
lates, are of common occurrence Sometimes, too, great areas of
the surface of the sea are reddened by the vast numbers of small
Crustacea (Munida), which then play a part of great importance as
food for the fishes and for the guano-producing birds. More strik-
ing still are the immense schools of small fishes, the 'anchobetas'
(Engraulis ringem Jenyns), which are followed by numbers of
bonitos and other fishes and by sea lions, while at the same time they
are preyed upon by the flocks of cormorants, pelicans, gannets, and
other abundant sea birds. It is these birds, however, that offer the
most impressive sight The long files of pelicans, the low-moving
black clouds of cormorants, or the rainstorms of phriging gannets
probably can not be equaled in any other part of the v/orld. These
birds feed chiefly, almost exclusively, upon the anchobetas. The
anchobeta, then, is not only an article of diet to a large number of
Peruvians, and the food of the larger fishes, but, as the food of the
birds, it is the source from which is derived each year probably
a score of thousands of tons of high-grade bird guano. It is there-
fore to be regarded as the most valuable resource of the waters of
Peru. No more forcible testimony to its abundance could be offered
than the estimate, made roughly, but with not wide inaccuracy, that
a single flock of cormorants observed at the Chincha Islands would
consume each year a weight of these fish equal to one-fourth of the
entire catch of the fisheries of the United States."
12. 'The Fisheries and the Goano Industry of Peru," Bulletin C7. 5. Bureau of
Fisheries, Vol. XXVffl (1908). See also "Pern's Wealth-Producing Birds, 7 * National
Geographic Magazine (June, 1920), and "Habits and Economic Relations of the
Guano Birds of Peru," 7. 5. Notional Museum Proceedings, Vol. LVI (1919).
IAPTER
I 2
ana tke
9 Sea a Dynamo Body
VE HAVE HAD REPEATED OCCASION TO EMPHASIZE THE FACT
that the great mass of water covering most of the globe is
not a static body. However it may seem to those on a be-
ned ship, and however smooth may be the action of its internal
nbers, it is everywhere and at all times a dynamic mechanism,
ingine in restless action. There are surface waves and tides and
D movements of the same nature. In the upper waters there are
it currents, swift and relentless, or slow and fluctuating. There
eddies of oceanic dimensions and small ones as well. In the deep,
*e are slow and almost impalpable, but never insignificant, drifts,
are are vertical movements, the sinking of heavy and the rising
ighter waters. There are, indeed, all sorts and manner of shifts
Iting from the rotation of the earth, and from the rays of the
that effect changes in temperature and concentration and, there-
i, in density. Put in another way, there are everywhere con-
al disturbances of equilibrium which require compensatory
Cements, and the sea, as a continuous fluid, has widespread free-
i of movement.
^ater moves easily, but not without energy: it has mass and it has
osity, or internal resistance to circulation; so that, where move-
its of such great volumes are involved, there must be immense
formations of energy. There must also be one or more sources
he energy that is subject to world-wide change in the sea. The
tional movements of earth and moon and the movements of
The Sea and the Sun 1 6 1
these planetary bodies relative to the sun constitute one source or
set of related sources. It is for the astronomer or the physicist to
trace this energy to a more remote origin; but, undoubtedly, so far
as the sea absorbs the energies of movement of celestial bodies, there
must be a proportionate slowing down of the movement of those
bodies. The energy concerned directly in the movements of water
is probably not nearly so great as that involved in bringing about
the changes (heating, evaporation, etc.) that lead to disturbances
of equilibrium and the resulting movements.
The chief source of energy for the sea is the sun, and the means
of transfer of energy from the sun to the sea or land is what we
know as solar radiation, some of which is reflected, some absorbed.
The smaller part that is reflected can have no direct effect on the
sea. What is absorbed is converted into other forms of energy, for
that is the meaning of "absorption" of radiation. A most significant
feature of the energy relations for us is that the absorbed radiation
is not just retained within the sea. Not all the> energy received by
the sea is manifested in movements of water probably only a small
part. There are interchanges of a high order of magnitude between
sea and atmosphere, between sea and land, giving the oceans great
significance to weather, to terrestrial climates, and to the lives of
plants and animals everywhere. We are interested in many of these
relations, but let us consider first the reception and distribution of
the energy of radiation.
The Sea as a Reservoir of Heat 1
Energy is received in the form of radiation, which, whatever it
may actually be, is generally described as wave motion. The differ-
ent forms of radiation have different wave lengths, but an object
may receive energy of one wave length, transform it into another,
and radiate it again in the changed form. Thus energy may be
received in the short-wave form, the range of visible light, and be
radiated again in the long wave form that we recognize as heat
Speaking very roughly, let us say: the earth receives light and emits
chiefly heat. Transformations may give what we call work. It is
the transformation of energy, always without loss, that is significant.
i. The interested reader who is qualified in physics or mathematics is referred
to the authoritative discussion of radiation and heat budgets in Sverdrnp, Ocean-
ography for Meteorologists, Chapters I-IV. We draw freely upon that source for
some of the data in this chapter.
2 This Great and Wide Sea
[ the work we know of, including the growth and reproduction
living things, represents transformation of energy. The trend is
/ays toward heat; this is the well known law of the degradation
energy.
[f we consider all forms of radiation, the wave lengths have a
y wide range; but we are now concerned only with radiation
it has importance to the energy changes in the sea and this comes
thin a relatively narrow range. Wave lengths may be given in
s unit \L (micron), which is i/iooo of a millimeter, or it may be
asured by the smaller Angstrom unit (A), which is i/ 10,000 of
licron or 1/10,000,000 of a millimeter. The wave lengths visible
man that is to say, the wave lengths of light fall between about
00 and 7,600 A, or 0.39 to 0.76 \i. Wave lengths important to
5 heat budget of the earth are between 0.15 \L (1500 A) and 120 \i
,200,000 A), but the radiation from the sun with which we are
istly concerned is chiefly short-wave radiation, with little of wave
gths greater than 2.6 ^ (26,000 A), and with maximum intensity
>se to 0.5 [i (5,000 A), or at about the lengths of the longer blue
1 the green rays in the visible spectrum. On the side of the short
rs, the energy of radiation falls off very rapidly to the shortest
raviolet, but very much more gradually on the other side through
j infrared. In this connection it may be mentioned again that the
srgy radiated from the earth is largely in the long wave. The
th receives short-wave (chiefly visible light) but emits long-wave
liation (heat.)
Energy from the sun is constantly coming into the earth directly
indirectly; part (about 57 per cent) is absorbed and part (about
per cent) reflected. 2 That part of the radiation from the sun
it is reflected from the surface of the earth or from the upper sur-
'e of the clouds, and is not absorbed by the earth or the atmos-
ere, makes no contribution to the heat budget of the earth. It may
said that about 40 per cent of the energy reaching the outer
dts of the earth is reflected back into space, while some 60 per
it is absorbed by the earth or its atmosphere. On the other hand,
5 earth is constantly losing energy to space by radiation from the
. The "solar constant" is stated as approximately 1.94 g cal/cn^/min. The
rage solar radiation reaching the limit of the earth's atmosphere is found to be
-fourth of that, or o 485 g cal/crn 2 /min, of which 0.209 5s lost by reflection and
>f no concern to life on earth. The remainder o 276 is ultimately lost by back
The Sea and the Sun i 63
earth's surface or from the atmosphere, and, unless the earth is
constantly becoming warmer or colder, the outgoing energy must
be in approximate balance with the incoming energy.
Considering now the 60 per cent that is absorbed and then lost
by back radiation to space, we have loss by radiation from water
in the atmosphere and loss by radiation from the earth's surface, so
far as the latter escapes being absorbed by the water vapor and
carbon dioxide in the atmosphere. Water vapor is particularly
mentioned because at prevailing temperatures, it is the chief compo-
nent of the atmosphere that absorbs or emits amounts of radiation,
and water vapor absorbs only certain wave lengths, being trans-
parent to others (between 8.5 and 1 1 u), where the outgoing radi-
ation is nearly at a maximum. The radiation lost from the earth and
its atmosphere to space is, as previously mentioned, long-wave radia-
tion (which gives heat) with maximum intensity at ro to 15 p.
It is important for us to keep in mind that the oceans, the land
areas, and the atmosphere are not to be regarded separately, but are
really parts of one great system. Since most of us are not skilled
physicists, let us itemize here a few basic facts that we can accept
from the physicists and oceanograuhers and that we need to keep
in the backgrounds of our minds if \ve are to understand the prin-
cipal oceanographic phenomena.
(i) We must first recall some of the peculiar qualities of water
itself. The same amount of heat that would raise the temperature
of a given quantity (by weight) of water by iC. would raise the
temperature of the same quantity of chloroform more than 4C or
that of the same weight of iron about ioC. Water then, has high
"specific heat" or heat capacity; that is to say, capacity for storage
of heat relative to rise in temperature. This is true of other sub-
stances having much hydrogen in the molecule, such as liquid am-
monia (NH 3 ), which has even higher specific heat than water but
much less than pure hydrogen. Putting the idea in another way,
water, because it has high heat capacity, can absorb a great deal of
heat without getting particularly "hot," as temperature is measured
by the thermometer or by other common standards. Conversely, it
can lose much heat without being brought to a very low tempera-
ture. Other notable features of water are associated with changes
from the liquid to the solid state and the reverse. The formation of
a small amount of ice goes with the loss of a great ddal of heat, and,
/ 64 This Great and Wide Sea
conversely, a large amount of heat is required to melt a small amount
of ice. Incidentally, water freezes at a temperature that is relatively
high in relation to temperatures that occur on land. A mixture of
water and ice forms a fairly accurate thermostat. In short, liquid
water is one of the best possible media for use in absorption, storage,
and transport of heat. 3
(2) Perhaps even more significant characteristics of water are
related to its change from the liquid to the gaseous state. Water
evaporates at all ordinary temperatures (with a wide range), but
evaporation always requires the absorption of heat. No other sub-
stance has such a high heat of evaporation as does water. It re-
quires approximately as much heat to vaporize one gram of water
at its normal boiling point as it does to raise the temperature of 539
grams of water by i C. Evaporation, therefore, involves prodigious
storage of heat. It has been estimated that in the region of the equa-
tor something like one million horsepower per square kilometer is
used each year in evaporation. Computations by various methods
have indicated that over the whole ocean evaporation averages some-
thing like a meter each year. At any particular place and time the
amount of evaporation depends upon the humidity of the atmos-
phere, the temperatures of sea and air, and the velocity of the wind.
Not only does evaporation result in great initial storage of heat
in the atmosphere, but also it is the water vapor in the atmosphere
that intercepts and absorbs direct radiation from the sun, which,
otherwise, would pass through the mostly transparent atmosphere.
Hence water vaporized at the surface of the sea serves a double func-
tion: as it goes into the atmosphere it carries heat from the sea; in
the atmosphere it continues to accumulate heat. Furthermore, water
vapor is even more mobile than liquid water; so that heat absorbed
at one place and carried in the vapor, is easily transported by the
wind to other and distant places. Condensation of the water, wher-
ever its occurs, releases the latent heat stored. It is easy to see, then,
how the evaporation of water plays such a great part in the distribu-
tion of heat over the surface of the earth and why the sea and the
water vapor of the atmosphere may be regarded as great reservoirs
of heat.
3. Hence we use it in our domestic heating systems, although ammonia, at least,
has advantages over water in respect to specific heat and latent heat of fusion
but not in some other respects.
The Sea and the Sun 1 65
(3) Since in the atmosphere it is the water vapor, principally,
which absorbs, holds, and emits radiation, we want to know how
this vapor gains heat. This is only in very small part by conduction
from the earth's surface, where air and earth are in contact. (Where
any two bodies of unequal temperature are in contact, the warmer
tends to give heat to the cooler by conduction.) Atmospheric wa-
ter vapor acquires much more heat by direct absorption of both
short-wave radiation coming from the sun and long-wave radiation
given off from the earth, so far as it is not "transparent" to such
rays. But, as has already been suggested, there is another source of
heat for the atmosphere: and that is by condensation, since the con-
densation of water vapor releases the energy that was stored when
and where evaporation originally took place. Probably the atmos-
phere gains as much heat through condensation of water vapor as
through direct absorption of passing radiation.
What the atmosphere gains, year in and year out, it also loses.
This must be true because the atmosphere does not get progressively
warmer from year to year. It is said, by the way, that the gam of
heat by the atmosphere through absorption of long-wave radiation
from the earth and through condensation occurs at relatively low
altitudes. Loss of heat from the atmosphere to space is said to take
place chiefly at high altitudes by radiation from the water vapor
and from the upper surfaces of clouds. In short, heating of the
atmosphere takes place below and cooling above.
(4) For the earth as a whole, evaporation, which, to repeat, is
(in one aspect) the storage of heat in water vapor, takes place pre-
dominantly at the surface of the sea simply because the greater part
of the face of the earth is sea. This much is obvious, but the point
of special interest to us here, is that evaporation does not necessarily
occur where the heat is absorbed: Heat absorbed in one locality at
a given time may be used for evaporation later and in another -place.
By currents in the sea and by winds in the atmosphere, heat is trans-
ferred from regions of surplus receipt in low latitudes (from the
Equator to about 35N. and S.) to regions of deficiency in high lati-
tudes. Movements of masses of water transport heat slowly; move-
ments of water vapor by the winds transport it more rapidly. Hence,
movements of air masses and of water masses influenced by winds
or other conditions have much to do with determining when and
where evaporation will take place. Evaporation depends on differ-
/ 66 This Great and Wide Sea
ence in vapor pressure, between the water and the air in contact
with it. In general, water evaporates more rapidly when it is warmer
than the air mass above it and warms the air immediately at its sur-
face. "It must, therefore, be expected that the greatest evaporation
occurs when cold air flows over warm water." 4 In middle and high
latitudes, this condition on the sea occurs more generally in winter
than in summer. More heat is absorbed in summer than in winter;
but the transfer of heat to the atmosphere may be much greater in
winter! Even though the surface water is cooler in winter than it
is in summer, it may evaporate more rapidly in the cool season,
simply because the air above it is still colder and is capable of being
warmed by the water with corresponding decrease in vapor pressure.
(5) On the other hand, warm air holds more water vapor than
does cold air and, as everyone knows, the cooling of warm moisture-
laden air to below the dewpoint causes condensation. If the air
over water is decidedly colder than the water and takes up vapor
to the point of saturation, there may be some condensation, giving
rise to a particular sort of fog, called steam -fog or "smoke." It occurs
chiefly over small bodies of water, where the air mass is not in con-
tact with the water long enough to be brought generally to the same
temperature as the water; over the open ocean where the air, even
though in movement, has prolonged exposure to sea water, the dif-
ferences of temperature leading to smoke fog are less common.
Some fogs are caused by cooling of the air over a calm sea or land
whose temperature is being lowered by radiation. The usual heavy
fogs that hamper navigation are of another type called advection
fog. Such a fog occurs when warm moisture-laden air from sea or
land drifts over cool water, or land, and has its temperature lowered
to the point of condensation.
(6) The biologist will not want to lose sight of the fact that a
certain amount of short-wave radiation is absorbed by green plants, 6
particularly on land, to be stored through photosynthesis in the form
of food materials that will supply the energy of living organisms.
Eventually this energy employed in photosynthesis is changed to
heat through the metabolic activities of both animals and plants. The
4. Sverdrup, op. ch^ p. 64.
5. "About [0.15] per cent of that part of the son's energy which falls on die earth
is caught annually and stored by plants." W. J. Robbins, "The Importance of
Hants," Science, C. 1944, 440. (By typographical error in the publication a larger
figure is given. Correction is based on personal communication from the author.)
The Sea and the Sun 1 67
heat returns chiefly to the waters of the earth or to the water vapor
of the atmosphere. The biologist will remember also that a good
deal of the water vapor in the atmosphere is derived from the soils
through the transpiration of plants and, much less significantly,
through evaporation from animals. The heat liberated through evap-
oration from lungs, mouths, and skins of animals is, of course, prin-
cipally a product of metabolism and is thus a part of that originally
stored by the green plants. As will be seen later (p. 169) the amount
of energy stored and released by organic life in the sea is computed
to be a relatively minute part of the energy transformation in the
sea, although it is of the greatest importance to marine life.
(7) Conduction is the transmission of heat without motion of the
body as a whole; convection is the conveyance of heat by motion of
particles. In water heat is conveyed upward by convection, but, be-
cause solar radiation, the main source of heat for the sea, is applied
at the surface, convection, as a means of distribution of heat, is al-
most negligible. Conduction from the surface downward is like-
wise relatively insignificant, although water conducts heat more ef-
fectively than most liquids (much more slowly than most solids).
But a feature of the sea, as compared to the land, is its mobility in
both vertical and horizontal directions. The waves that stir the sur-
face distribute heat downward to a significant extent. And there are
other movements to promote circulation of heat.
Even though warm water is lighter than cold water having the
same concentration of salts, yet, if through evaporation the surface
water becomes sufficiently dense, it may sink to replace colder and
less dense water: in this way, some heat is carried below the surface,
although not ordinarily to any great depth. Horizontal movements
play a great part in distribution. We have seen that heated sea water
may be conveyed long distances from warm to cold regions, to re-
lease the transported heat either by radiation or evaporation in re-
gions that receive less direct radiation.
Let us make a rough summary of this section. The energy that
makes possible the circulation and the turbulence of the sea is de-
rived directly or indirectly from the sun through radiation. The in-
coming energy received is chiefly short-wave radiation (in and
around the wave lengths of visible light). An equal amount is lost
by reflection or, after transformation, as long-wave radiation
(roughly characterizable as heat). Because the sea occupies the
/ 68 This Great and Wide Sea
greater part of the surface of the earth, the predominant share of
energy available to the earth comes directly or indirectly to the
surface of the sea. As compared with nearly all ordinary substances,
water, in liquid, gaseous, or solid form, has exceptional qualities for
the absorption, storage, transport, and release of heat. It stores much
heat without relative rise of temperature. It absorbs heat at one
place and rime to release it later at another place, which may be a
little deeper in the water, higher in the atmosphere, or at distant-
places on the surface of the earth. Its mobility as liquid or vapor
facilitates this transfer in all directions, vertically in sea or atmos-
phere, and horizontally over the surface of the earth. All this is true
of fresh or salt water; but the liquid sea water has the further quality
of undergoing change of density with loss by evaporation. The
changes in density play no little part in the setting of conditions for
both vertical and horizontal movements.
Water goes back and forth between sea and atmosphere. With a
virtually unlimited amount of water for evaporation and storage of
heat, and with its mobility, the sea, like the atmosphere, is a great
reservoir of heat and a means of its 'wide distribution.
How the Seas are Warmed and Cooled
We are concerned with what might be called the "heat budget"
of the ocean, the income and outgo of radiation. As a basic fact, we
recognize that the oceans as a whole seem to be neither warming up
nor cooling down from year to year. This means that income and
outgo are approximately in balance: in respect to heat, the oceans
lose each year approximately what they gain. There are three chief
sources of heat for the sea. The water gains some heat from the at-
mosphere where two media are in contact. It gains more by absorp-
tion of radiation, coming directly from the sun or indirectly from the
sun by reflection from the sky. It is heated to some extent by the con-
densation of water vapor. We can think of other sources of heat,
such as conduction from the interior of the earth through the ocean
bottom, transformation into heat of the kinetic energy of currents
through friction, and heat released through chemical and biological
processes within the sea. The effects of these last-mentioned agencies
Df conversion of energy are considered practically negligible. Con-
versely, there are three chief ways in which the seas suffer loss of
beat: back radiation from the sea surface to the atmosphere and to
1 he bea and tbe bun
space, loss to the atmosphere by conduction, and loss by evapora-
tion through storage of heat in water vapor transferred to the atmos-
phere. Of course, a certain amount of radiation is used by plants in
photosynthesis; but the amount so used in the sea is estimated at only
a fraction of one per cent of the energy transformation in the sea. 6
Furthermore, most of the energy used in photosynthesis must be re-
turned to the sea through the metabolism of plants and animals, and
so, either directly or indirectly, as heat.
Now, although for the seas as a whole gains and losses in heat are
in approximate balance, yet for a particular locality or a given depth
at any one time, the conditions are quite different income and
outgo are not in balance locally and seasonally. The temperature of
the water at a particular place, level and time may be changing one
way or the other, and these changes might be cumulative to a more
notable degree were it not that, as the waters are being warmed or
cooled, they are also being regularly transferred by currents to other
localities or depths. In short, as we may seem to emphasize repeat-
edly, the circulatory mechanisms are significantly interrelated with
the heat budget, as with every other feature of ocean economy.
So far as the incoming short-wave radiation, chiefly in the range
of visible light, comes directly from the sun to the surface of the
sea, the amount must vary with place and time that is to say, with
latitude, season, and hour; and, we might add, with condition of the
atmosphere. When the sun is at a low altitude with reference to a
particular place, the rays must, of course, pass a greater distance
through the air and be subjected to more scattering against the
larger molecules in the air, chiefly the water molecules and carbon
dioxide: but, regardless of the altitude of the sun, the amount of
water vapor in the atmosphere affects the amount of scattering.
Much of the short-wave radiation "scattered" in the sky still reaches
the sea, 7 and much of that coming from the sun to the clouds, rather
than directly to the sea, may be reflected from the clouds to the sur-
face of the sea. Reflection from sparse clouds may, indeed, be so
much that even more radiation reaches the sea on an overcast day
6. The comments of Sverdrup (op. cit., p. 50) indicate that less than one-tenth
of one per cent of incoming radiation is utilized by plants in the sea for photo-
synthesis.
7. The reflection of diffused radiation reaching the sea as scattered or reflected
radiation is estimated at 8 to 28 per cent. Such estimates are approximate, and dif-
ferent figures have been given by different investigators.
This Great and Wide Sea
than on one which is clear and cloudless. Most of us have experi-
enced the severe sunburns gained on slighdy cloudy days. On a
really dark and rainy day, however, there is great reduction in radia-
tion at sea level, even to less than one-tenth of what is received on a
clear day.
The altitude of the sun varies, of course, not only with latitude
and season, but also with the time of day. We shall see a litde later,
however, that the effect of the altitude of the sun and the obliquity
of the rays is minimized in considerable degree by the refraction or
bending of light rays entering the sea at an angle to the surface. On
the other hand, not all of the radiation coming to the surface of the
sea enters the water to be transformed into heat. Waves increase
reflection, but, by and large, the greater part of incoming radiation
is absorbed. The proportion reflected changes significantly with the
altitude of the sun, increasing greatly as the altitude is diminished.
Thus, it is calculated that, while only 2 per cent of solar radiation
is lost by reflection when the sun is at the zenith, and only about
one-tenth of one per cent more when the sun is at <5o, three times
as much (6 per cent) is lost by reflection with the sun at 30 degrees,
and more than seventeen times as much (34.8 per cent) with the sun
at 10 degrees above the horizon. If water existed near the poles much
of the small amount of radiation coming to the sea would be reflected
even at the most favorable times of day; but the sea near the poles
is frozen and sea ice, especially if covered by snow, reflects much
more strongly than water even up to 50 or 80 per cent of all the
radiation received. It may be mentioned in this connection, too, that
snow also radiates more strongly than water; the actual loss by back
radiation so lowers the temperature of the ice as greatly to increase
its thickness; furthermore, the cooling of air over ice and its spread-
ing leads to further extension of the ice field.
When we consider the loss by back radiation, we find a basic dif-
ference between conditions on sea and on land in that the diurnal
and annual variations of sea surface temperatures and of the hu-
midity of the air over the surface are relatively small. Consequently,
the effective back radiation changes little with the hour of the day
or the season, notwithstanding that incoming radiation shows the
same wide diurnal variations over sea and over land. Of course,
clouds, which radiate heat to the sea, do cut down the effective back
radiation. 8
8. See Sverdrup, op. crt^ pp. 59-^0.
1 be bea and the bun
Finally, it has been found that, for the sea itself and in any latitude,
the incoming radiation is decidedly more than the outgoing back
radiation. The surplus received does not, however, serve to heat the
sea indefinitely. It is the exchange of heat and water vapor with the
atmosphere and with the land that plays such a great part in main-
taining the balance and in regulating ocean temperature and salinity.
As we shall see in consideration of the penetration of radiation,
most of it is absorbed in the first meter, so that only the uppermost
layers are directly heated. Even in the clearest ocean water, only
about one-sixtieth as much heat is absorbed at the ten-meter level
and something like 1/4,000 at the hundred-meter level. Were the
water absolutely at rest, the temperature changes from the surface
downward might correspond to this gradation in absorption; but, in
any body of water of substantial size, mixing takes place as the result
of the winds, and, in the sea, evaporation increases the density of the
warmer surface water, causing it to sink. For lakes, most of the sum-
mer rise in temperature of the lake, as a whole, is described as "wind-
distributed" heat. In the sea, we may refer not only to wind-distrib-
uted heat but also to gravity-distributed heat, while recognizing also
that much of the distribution of heat is attributable to the rotation
of the earth as it affects the movements of masses of water*
The Penetration of Radiation
Most of the energy that reaches the sea is in the visible arc of the
spectrum. That is to say, it is in the form of visible light (0.39 to
0.76 \i) without much ultra violet or infra-red. The energy taken in
is greatest at about 0.5 u, the region of blue to green; it declines
rapidly on the short-wave side being very slight in the region of the
violet and zero at about 0.35 ]i. On the other, or long-wave side, the
energy is considerable, but it declines somewhat steadily to about
2.5 |i
The radiation that enters the water decreases in passage down-
ward, partly because it is absorbed (converted into another form of
energy) and partly because it is scattered laterally by impact against
suspended particles or color substances or even against the mole-
cules of the water. Because the materials in the water effect scatter-
ing, the amount of scatter varies in different waters. Everywhere
sea water contains suspended matter, living or non-living, to scatter
9. Sverdrup, op. cit., fig. 8, p. 54.
This Great and Wide Sea
radiation; and, therefore, there is greater absorption and rise of
temperature within the same thickness of water than there would
be in pure water. Actually it is not yet altogether clear why there is
so much increase of absorption in oceanic water as contrasted with
pure water. Presumably, there is a certain amount of finely sus-
pended matter which is not yet definitely identified. There seem to
be minute suspended particles, which, in our ignorance of their
structure, are called "yellow substances" and which are perhaps
stable metabolic products of phytoplankton.
We are now concerned with the rate at which downward travel-
ing light decreases with depths: its mathematical expression is called
the "extinction coefficient" and, of course, it is different in different
waters and in the same water at different times. Penetration of light
has been determined by means of the Secchi disc, a white disc 20
centimeters (8 inches), or more, up to 2 meters in diameter, or by
lowering photographic plates. Helland-Hansen exposed panchro-
matic plates in the region of the Azores at noon, June 6: at 500
meters, with forty minutes exposure, there was some blackening; at
1,700 meters with two hours exposure, there was no blackening.
When color filters were used with such plates it was found that the
red was absorbed more rapidly, the green and blue less so.
Spectrophotometers have been used, but have not proved practi-
cable. Photoelectric cells with suitable color filters and with readings
from a galvanometer on the boat, are now most widely used and
most effective.
Much of the radiation that passes through the surface of the sea
is absorbed quickly, some 62 per cent in the first meter in clearest
water and much more in coastal or turbid waters. The absorption
is, however, highly selective. Roughly speaking, sea water is trans-
lucent for visible radiation only, and most penetrable for just the
wave lengths that are useful to plants. Even in clear oceanic water
there is no infrared at 10 meters and scarcely any ultraviolet. Wave
lengths in the blue-green range may penetrate well beyond 100
meters. Chlorophyll is capable of using in photosynthesis just the
wave lengths that penetrate farthest in clear water. In the average
coastal water nearly all radiation is absorbed in the first ten meters.
Generally speaking, the less clear the water, the more the shifting of
"surviving" wave lengths toward the longer waves, the green and
yellow.
The Sea and the Sun 1 75
In general, then, blue penetrates deepest in clear water, green or
yellow in turbid water. There are fresh waters, at least, in which
even the red goes deepest, not because the water itself is more trans-
parent to red, but because its content of dissolved and suspended
matter of particular sorts makes it much less transparent to the
shorter rays.
The familiar blue color of the deep sea is due to scattering among
water molecules, and it is, therefore, comparable to the blue of the
sky. The less of other material there is in the water the bluer it ap-
pears. Hence, blueness in the ocean is indicative of poverty; the
bluest parts of the blue sea are the "desert" areas. The green color
of great coastal areas of sea water has been attributed to the pres-
ence of the water-soluble yellow substances or to combinations of
yellow and the natural blue. Conspicuous greenness seems sometimes
to be associated with abundance of calcareous matter, as in some
coastal waters and in regions where corals are abundant,
It should, perhaps, be noted here, parenthetically, that apparent
discoloration, resulting from the presence of colored bodies in the
water is quite another condition from the color of sea water. Lakes
and ponds are often colored by chemicals in solution or by "blooms"
of algae or protozoa in suspension. For the sea, reference in this con-
nection is to the sometimes widely extended areas of conspicuous
color attributable to parriculate matter. "Red seas*' of great extent
may be encountered where, from a slight distance, the water appears
like a sea of blood; on closer examination, the color is to be found
only in the bodies of millions of red shrimp. "Red" or brown seas
result, here and there, from the luxuriant reproduction of copepods
or of dinoflagellates. Diatoms in enormous numbers give a yellowish
color.
Since the extinction coefficient is the measure of reduction of
radiation in a vertical direction, the angles at which the rays enter
the surface must be considered. This depends upon the altitude of
the sun which, of course, varies with the latitude and the season, and
even more with the time of day. The obliquity of the entering rays
is greatly reduced by refraction, or the bending of light rays in pass-
ing from air into water; scattering of light rays by particles within
the water also changes colors and affects penetration. When the sun
is at the zenith over still water there is no refraction: the angle of re-
fraction is zero. (But the sea is never quite still.) The lower the sun
This Great and Wide Sea
the greater the refraction until, with the sun at the horizon, the
angle is as much as 48.5 degrees. Consequently, the most oblique
rays that penetrate the water never form an extreme angle with the
vertical: no matter how low the sun, as long as they enter at all the
rays turn toward the vertical. This means that the altitude of the
sun has relatively little effect on the depth of penetration of non-
reflected light of given intensity; yet the amount reflected must in-
crease with diminishing altitude of the sun, especially on still water.
m
LIFE IN THE SEA
CHAPTER 13
in tke ^>ea: Ljeneral L^onaitlot
Modes of Living and Habitats
UNDER MANY CONDITIONS THE CASUAL OBSERVER MAY DERIVE
impressions of the richness and diversity of plant and animal
life in the sea. He may have observed the mats and streamers
on wave-beaten rocky shores of Maine or California or Peru.
Through a glass-bottom boat he may have glimpsed the luxuriant
"marine gardens" of some tropical islands. Perhaps he has made
just a slight exploration of the fauna of sand and mud flats of a
coastal bay, such as that of Beaufort, North Carolina. Anyone fortu-
nate enough to have the opportunity to see in dry-dock a lightship
from Hatteras, or other such region, must be amazed at the dense
and heavy mat of barnacles, hydroids, Bryozoa (moss animals), and
dozens of other sorts of organic life covering every inch of bottom.
On occasion, while voyaging at sea, one may look upon enormous
areas where the surface is broken by a spatter of small fish, sardines,
anchovies, or young herring, leaping into the air to escape larger
fish predators below and diving down to avoid the birds that
threaten from above. Certainly no one can fail to be thrilled at the
abundance and variety of small organisms caught in a fine-meshed
net drawn through the coastal surface waters on a calm dark night.
Nevertheless, the sea is not everywhere crowded with life: nor is
there any uniformity in distribution. There are, indeed, areas of
"desert," so far as marine life is concerned: and these, in the waters
above, are the areas of purest blue, where there is the least of matter
'77
/ 7 8 This Great and Wide Sea
other than water to scatter the entering rays of light; on the bottom,
red clay is an indication of barrenness.
Obviously, life in the sea cannot be treated adequately in a few
chapters: volumes are required. Discussion in this place must, then,
be restricted to a brief consideration of ways of life in the sea and of
how the living world has responded to the special physical condi-
tions that have been outlined in the preceding chapters. We may
want to know, too, something of the types of life characteristic par-
ticularly of oceanic rather than of interior or of coastal waters. 1
From the pictures of marine life suggested in the first paragraph,
it is apparent that marine life falls naturally into several fairly dis-
tinct categories in respect to capacity for exercise of control over
positions and movements. There are animals and plants that cruise
with the currents for a very brief period in early life, but, once they
have landed in a particular spot, are parked in the same place for the
remainder of their lives. Such are barnacles, oysters, hydroids, and
ascidians, attached to rocks, wharf piles, or buoys, and kelps, an-
chored to rocks while streaming out in the water. Worms and clams
that burrow into mud and sand or even into rocks may be nearly as
localized in space as are the barnacles. Other animals that are not
held back by solid barriers, yet continue to live within restricted
areas, are conchs and starfishes, creeping slowly over the bottom,
and crabs, running here and there at will over more or less wide
ranges, but not, in respect to location, at the mercy of the moving
waters. All of these are in the category called benthos? a term pro-
posed by the great naturalist, Ernst Haeckel, to include organisms
that live on or in the bottom of other fixed objects in the water. We
shall later (p. 242, below) propose a logical and seemingly neces-
sary subdivision of the benthos, to distinguish the attached and ac-
tually fixed organisms from the creepers and crawlers.
There are other marine animals with such powers of locomotion
as enable them either to roam widely by swimming against the cur-
1. The chapters by Hjort, Gran, and Appellof in Murray and Hjort's Depths of
the Ocean, although" published more than thirty years ago still constitute a mine of
exact information considered in a most discriminating manner. Of a more general
and readable nature is The Seas by Russell and Yonge. Most recent and valuable
is The Oceans by Sverdrap, Johnson, and Fleming, Chapters VII-X and XVI-XX
deal most directly with biology.
2. Greek for depth of the sea. The adjective form is benthoTuc, to be distin-
guished from the term "benthic," or "benthal," applicable to zone occupied.
Life in the Sea: General Conditions 17$
rents, or to remain relatively localized in spite of the movements of
the water in which they find food. Without being entirely inde-
pendent of currents, they are yet able to move with or against the
drifts; their location at any time is, to a considerable extent, gover-
ened by their own internal energies. In this group, which Haeckel
distinguished as nekton, 3 are found higher animals, mainly fish,
whales, seals, and sea turtles, and a very few invertebrate types, such
as squid and sometimes shrimp.
Although benthos and nekton include virtually all the animals
that catch the eye of the casual observer, yet by far the greater bulk
of life in the sea falls in a third category, which comprises the in-
numerable and generally small organisms that are free in the water
and at the mercy of the currents. These plants and animals, because
of their small size or feeble powers of locomotion, are carried hither
and yon by the currents. They constitute the plankton f a designa-
tion given by Victor Hensen of Kiel nearly sixty years ago (1887).
In general the plankters are to be seen only when strained from the
water by a fine-meshed net or when separated out by the use of a
centrifuge. In great part these drifters vary in size from the bac-
teria and the minute yellowish microscopic plants called coccolitho-
phores to copepods several millemeters in length. Yet some are quite
large; for drifters also are organisms, such as the sargassum weed
and jellyfishes that may be one or two meters in diameter; Salpa,
too, an ascidian, fairly high in the scale of animal life and only a
little below the vertebrates in bodily organization, occurs in chains
several meters in length. On the whole, however, those members
of the plankton that, individually, are large enough to catch the eye
constitute a very small proportion of the mass. In a later chapter
we shall give subdivisions of the plankton on the basis of size.
The classification of marine animals and plants by mode of life, as
benthos, nekton, and plankton, is not all inclusive, and there are
not absolute lines of division between the several groups so desig-
nated; but the classification has convenience and the term plank-
ton is indispensable. For life in fresh water a fourth category is
found necessary the neuston* comprising animals and plants that
live in connection with the surface film, either on it or just beneath
3. Neuter of Greek nektos, swimming.
4. Neuter of Greek plemktos, wandering.
5. From nous, Tieus, a boat or ship; proposed by Naumann in 1917.
/ 8o This Great and Wide Sea
it. Of these are some insects and Cladocera, the duckweeds, and, at
times, great numbers of bacteria, algae, and protozoa. The surface
film of the wave-ruffled sea offers no such favorable home for neus-
ton as does that of quiet ponds; the classification neuston might,
however, include the one seafaring insect, the water strider Halo-
bates, and, too, the Portuguese man-of-war and a few other floaters
at the surface.
Although sharp lines cannot be drawn between benthos, nekton,
and plankton, it will doubtless appear clearly enough in later pages
that the differentiation of sitters (and creepers), swimmers, and
drifters is not arbitrary or technical: it is, indeed, essential for any
consideration of the relations of organisms to the physical conditions
of the common environment the sea water. This much, at least,
should be obvious: the currents of the sea mean one thing to an ani-
mal fixed in position and dependent upon water movement for con-
tinued feeding and breathing; the same currents mean something
else to an active swimmer that may move freely through the moving
water; they have still another significance to the drifters that are
carried along from place to place in relative helplessness.
Again, we cannot well consider marine life without noting the
diversity in conditions of life as related to proximity or remoteness
from the lands. The homes or habitats of marine organisms present
almost infinite diversity; but we have to recognize, in the first order
of classification, several ecological domains, one of which occurs
wherever sea water reaches.
The great division of the homes or habitats of marine organisms,
although not sharply bounded, are yet marked by certain distinctive
conditions of living and by generally characteristic associations of
organisms. There is the extensive littoral region, bordering con-
tinents and islands and extending from the line of high tide out to
the edge of the continental shelf at about zoo meters. 6 According
to the very different conditions presented for living things, the bot-
6. Because of the extreme diversity of conditions along shore, in respect to
gradualness or abruptness of slopes of the bottom, and, no doubt, partly because of
the diversity of human minds and purposes, there is no general precise agreement
in die use of the term "littoral" and its subdivisions. Some restrict "littoral" to the
region in close proximity to the shore, others use it, more broadly, as stated in the
text above. Sumner, AUee, and others employ the term adlhtoral, "as designating the
zone of shallow water immediately adjacent to the shore," without setting a defi-
nite Blower limit of depth. Varying, doubtless, with local conditions and with
species, the adlittoral would probably not extend beyond two fathoms in depth.
Life in the Sea: General Conditions 1 8 1
torn of the littoral region can be subdivided into an mtertidal zone,
above the low-water mark, a eulittoral zone, reaching from the line
of low tide as far out as aquatic plants may grow on the bottom,
or to a depth of some 50 meters, and a sublittoral, extending to the
limits of the littoral. Beyond the littoral the bottom benthic 7 re-
gion divides itself naturally into the archibenthic, on the continental
slope and the abyssal benthic, beyond a depth of some 1,000 meters;
the last is, of course, a region of darkness and low temperature,
without seasonal changes such as must play so great a role in the lives
of terrestrial and coastal animals and of upper plankton. For water
above the bottom, the pelagic region is conveniently divided into
neritic and oceanic zones. The former embraces the open water
affected by continental influences and extending out to the edge of
the continental shelf; we may say that it includes all open water
within a depth of 200 meters or less and extends shoreward over
most of the littoral. The oceanic zone is the vastly greater region of
"blue sea," into which comes little of the nutritive drainage from
land. When, in the broad oceanic region, we wish to distinguish
zones in vertical series, there is, of course, an uppermost and rela-
tively thin illuminated zone (epip elagic), some 200 meters in depth.
Beneath this one may recognize a twilight zone (mesopelttgic) and
a deeper zone (bathy pelagic) of far greater volume into which no
solar light may ever penetrate. Finally, and below some 2,000
fathoms, is the abyssal pelagic zone. It will be evident that littoral
and neritic zones, receiving so much drainage from the lands, must
offer conditions of nutrition very different from those of benthic
and true oceanic regions.
Some Relations to Physical Conditions
In a general way the necessities of life are the same in the sea as CHI
land: water, sunlight, heat, oxygen, carbon dioxide, food (in the
forms both of the building materials of protoplasm and the fuel to
supply energy), anchorage or support, and protection from enemies.
We might add, among the necessities, enemies themselves or some
means of keeping a particular population, with its inherent urge to
reproduce, in equilibrium with the available supply of food.
Although the securing and conserving of water may be a very
/ 82 This Great and Wide Sea
practical problem for some terrestrial animals and plants, particularly
those of arid regions, the very condition of life in the sea insures an
unlimited water supply. Accordingly, marine animals and plants
have no need for special adaptations against desiccation, except in
the cases of those that live in the extreme littoral (intertidal) region
and are periodically subject to conditions of water loss.
With respect to the chemical nature of the environment, marine
invertebrates (and elasmobranch fishes) have an advantage over
invertebrates of fresh water in that their body fluids have very
nearly the same osmotic pressure as the external medium. They do
not, therefore, require such protective coverings or such expendi-
tures of energy as are necessary to maintain the normal internal con-
ditions against osmotic pressure from without that is to say,
against the physical tendency to equalize concentrations within and
without. 8 Sea water varies in concentration from place to place and
in many places, from time to time. Some physiological adjustments
are necessary; and marine animals and plants differ greatly in ca-
pacity to adjust themselves to changing salinities. The Virginia
oyster thrives in brackish waters where very considerable; changes
of salinity may occur in course of a day, or from season to season.
Corals will endure only small changes and are, therefore, wanting
from the vicinity of the mouths of great rivers. A few animals seem
to have extremely wide ranges of tolerance they are euryhalme;
so that they may pass from salt to fresh water and back at will.
Some, like the salmon, the shad, and the eel, are at home in salt
water for certain periods of their lives and equally at home in fresh
water for other periods. Most marine organisms, and particularly
8. The cell membranes of organisms are selectively permeable: they permit the
passage of water with relative freedom, but are more selective with reference to dis-
solved substances. The permeability depends in part upon the physical and chemi-
cal nature of the particular membrane, the material in solution, and the solvent,
which, in this case, is water. The flow through the membrane is governed also by
the difference in concentration of dissolved substances within and without the
cell, upon which depends osmotic pressure. The bony fishes of fresh water and
those of sea water differ in osmotic pressure but not nearly so much as do fresh
water and sea water. The body fluids of fresh-water fishes are bypcrtomc (having
higher osmotic pressure) as compared with the water around them. Were there
no protective effort of some kind, water would move into the body until the body
fluids became isotomc (of like osmotic pressure) with the outside water. The
fluids of bony fishes of salt water are bypotomc, and, but for protection, water
would pass out from them into the external medium until body fluids and sea
water were isotonic.
Life in the Sea: General Conditions 1 83
those of the open sea, have very narrow tolerances with respect to
salinity; they are stenohalme.
Between marine organisms and the sea water around them there
are many other chemical relations, some of which will be pointed
out in appropriate places. 9 Water is the universal solvent and may
carry in solution any chemical substance required for the mainte-
nance and multiplication of plants and animals. So far as the sub-
stances are used, they are taken out of solution in the water for the
time. It may be remarked, then, that plants and animals, themselves,
have some effect on the composition of sea water at a particular
place and time. It is quite possible that with prolific growth and
multiplication of some plankters, certain elements, such as silica,
used in diatom shells, or phosphorus, become depleted regionally
and seasonally, to a critical degree. Reproduction must then cease
for a period, and a whole population largely disappear, until such
time, as, by the slow processes of decomposition, the abstracted
chemicals are returned to solution and made available for new use.
For the utilization of sunlight and carbon dioxide, animals in gen-
eral are entirely dependent on green or yellowish plants which,
through the process known as photosynthesis, form carbohydrate
by combination of water and carbon dioxide with storage of the
radiant energy of the sun. Virtually all the energies of animals and
plants represent transformation of the energy stored by green plants;
and energy is involved, not only in movement but also in growth,
reproduction, and in every form of vital activity. Energy from
the sun may be stored in the form of fat as well as carbohydrates
(sugars and starch) and proteins, to say nothing of body warmth.
Physiologically, the energy of fats is less readily available than is
that of carbohydrates; but, for marine organisms, the fats, or oils,
have an advantage in their relatively low specific gravity, as well as
in their insolubility in water; fats favor flotation, obviating the need
for excessive expenditure of energy in maintenance of level in the
water. Animals are dependent upon plants, not only for the sources
of energy, but also for syntheses of vitamins and of amino acids, the
nitrogenous substances that are basic to the formation of proteins.
We have dealt in previous chapters with the sources and means of
9. Chapters VII, VHI, and XVII of Sverdrup, Johnson, and Fleming's The
Oceans, and the references there cited, will be particularly helpful to those inter-
ested more particularly in the chemical relations of life in die sea.
i 84 This Great and Wide Sea
distribution of sunlight, heat, oxygen, and carbon dioxide. Since sun-
light is the ultimate source of all organic energy, including that in-
volved in the synthesis of organic substance, it follows that original
production in the sea can take place only in the superficial layers of
water through which light penetrates. There are animals that spend
their entire lives in the darkness of the deep, but they can live only
at the expense of plants that enjoy sunlight at higher levels. Ob-
viously, since by far the greater area of the surface of the earth is
ocean, most of the radiation coming to the earth through or from
the atmosphere falls upon the sea. Much of what comes to the sur-
face of the water is reflected back and most of what is absorbed is
transformed into heat. A minuscular part is used in photosynthesis
(p. 169, above.) Whether the utilization of radiation for synthesis
of organic substance is greater on land than in the sea is at least
open to question. Terrestrial vegetation is exposed to relatively
brilliant illumination, as the rays of the sun pass through the highly
transparent atmosphere with relatively small scatter and absorption,
and that principally by the water vapor. Yet, because of structural
and other conditions, the plants on land seem to capture no more
and perhaps much less of die solar radiation falling on a given area.
The minute size and the unicellular form of the vast majority of
plants in the sea does give them the advantage of more complete
absorption and utilization of what sunlight there is to be used.
We do know that water and carbon dioxide with sunlight are the
basis of all organic substance. It is obvious too that organic wastes
from the land are continually carried into the sea by surface drain-
age. Whatever may have been the condition at the commencement
of life on earth, the populations of the sea in littoral and neritic re-
gions are now in part dependent upon the productivity of plants
that live on land. If, as is supposed, life began in the ocean and later
migrated out of water to reach its highest development on land, the
original discovery of the land and its "colonization" must have
proved in the end a stimulus to organic industry in the original
briny home. In the course of geological ages the members of the ter-
restrial colonies attained a higher state of development than did the
stay-at-homes; and now society in "the homeland" (the home-water,
we should rather say), lives in some part at the expense of the
colonies.
Temperature has much to do with the rate of chemical reactions
Life in the Sea: General Conditions 1 8$
which increases with rising temperature. Within limits, the chem-
ical processes associated with life in plants and ?mmg]$ may be more
than doubled by a rise of ioC Temperature, therefore, affects "rate
of living," including growth, reproduction, maturing, and duration
of life. Yet a notable phenomenon of distribution is the richness of
life in the cold and turbid seas of the north, when these are com-
pared with the warm and translucent waters of the tropics, where,
at first thought, the conditions of temperature and light might be
expected to support the richest fauna and flora. The anomaly is
probably related to the difference in content of dissolved gases in
cold and warm waters.
Oxygen and carbon dioxide are essential to life as we know it.
Nearly all living phenomena seem to involve oxidation and the trans^
formation of energy originally derived from the sun. But the solar
energy is made available for the processes of animal life only through
the use by plants of carbon dioxide and water. Cold water absorbs
and carries more oxygen and carbon dioxide than does warm water.
It seems a reasonable expectation then that, on the whole, there
should be more prolific life in cold than in warm waters. Most of the
evidence seems to point that way; but perhaps we should ask for yet
more comparative data of an exact quantitative nature. 10
It should be remarked, however, that waters may lie within the
tropics, geographically, and yet not be "tropical" in respect to tem-
perature: cool waters at low latitudes, such as those of the Hum-
boldt Current off the west coast of Peru, may rival the waters of
higher latitudes in luxuriance of animal and plant life. The warm
and light waters of truly "tropical" regions may hold less oxygen
and, remaining at the surface because of their relative lightness, be
drained of their nutrient materials which are not replaced by as-
cending currents from the depths. 11 Clear blue waters are com-
monly associated in our minds with warm regions; but, 'Tore blue
is the color of desolation of the high seas." u
10. Allen, at least, has questioned the certainty of a generally greater produc-
tivity of plankton in high as compared with low latitudes. Winfred E. Alien, The
Primary Food Supply of the Sea," Quarterly Review of Biology, IX: 161-80. Refer-
ence is to p. 175. It is possible, as Murray suggested long ago, that die turnover in
tropical waters is relatively^ higher in warm as compared with cold waters, be-
cause of faster growth, earlier breeding, shorter lives, and more rapid decomposi-
tion, at higher temperatures.
IT. See p. 86, above.
12. Schutt, quoted by Johnstone, 1908.
/ 8 6 This Great and Wide Sea
Thus the colder seas are richer in life than the wanner ones; or, at
the very least, the amount of life in polar seas is not less than in the
tropics. We are so accustomed to think of bright sunlight and high
temperature as favorable to terrestrial plant life that such statements
astonish us at first. "One stands," says Kjellman, "as before an in-
soluble problem when he makes a haul with a tow-net in the Arctic
and obtains abundant and strong vegetation, and this at a time when
the sea is covered with ice, the temperature is extremely low, and
nocturnal gloom predominates even at noon." 13
The density and the viscosity of sea water are conditions of real
influence on life in the sea. The viscosity is not markedly different
from that of fresh water, but the density is relatively high. In re-
spect to these qualities, the atmosphere in which the higher animals
live and move is hardly comparable at all. As to density, we are
particularly concerned with specific gravity, which is the ratio of
density to that of distilled water at a given temperature and pres-
sure. Now, the specific gravity of the sea is not markedly different
from that of the organisms that live in it. For the latter, then, there
is less general need for supporting structures. Plants characteristic
of the sea are without stiff trunks and stems. Relatively few of the
animals have legs for walking. The four-legged amphibian frogs and
salamanders do not occur in salt water. Birds, reptiles, and mammals
are not at home there, except for a few that have acquired secondary
modifications for excursions into the water or have become more
permanently adapted, with reduction of limbs (whales for example)
as means of bodily support. Of all the four-limbed animals, the fish
are the only ones primarily marine in habit, and their limbs are not de-
signed for support." Of the great phylum Arthropoda, animals with
externally jointed limbs, the myriapods (centipedes and millipedes)
are not found in the sea, and the hexapods (insects) and arachnids
(spiders and their relatives) are there represented by few species. In
this division of the animal kingdom, which includes many more spe-
cies of animals than all other phyla combined, only the Crustacea
have developed in the sea in substantial diversity of form, and with
great numbers of individuals, but the majority of these (in num-
bers) have legs for swimming rather than for walking.
13. James Johnstone, Condition of Life in the Sea, p. 205. If we should not now
say that the problem is "insoluble," it can not be denied that adequate solution
is yet to come.
14. Even these, or the bony fish at least, probably arose in fresh water.
Life in the Sea: General Conditions 2 87
Viscosity of the medium has important influences on life in water
in two important respects. It impedes movement and it retards sink-
ing. As an impediment to movement, viscosity, with density, has
led to the development of streamlined bodies. Reference to this was
made in an earlier chapter in connection with the consideration of
viscosity, and, especially, of eddy-viscosity (p. 103). The prob-
lem of streamlining is not so much to facilitate the pushing aside of
dense medium ahead as to reduce the "drag" resulting from the
filling in behind with all the complex phenomena of turbulence.
Streamlining expresses itself very differently in active swimmers of
plankton and nekton, in relatively inactive plankton, and in at-
tached animals; yet probably no animal or plant in the water is
without some touch of streamline. The more sluggish animals in the
stillness of abyssal depths, probably have least need for adaptation
of form to minimize friction and turbulence.
Viscosity also retards sinking under the influence of gravity and
thus facilitates maintenance of appropriate level. Both size and form
affect sinking velocity. It is only as we ignore friction that we can
say that a small body falls as rapidly as a large one of the same com-
position. Friction is on the surface and it is a recognized physical
and mathematical principle that the smaller the body is, the greater
the surface in proportion to weight, assuming, always, the same
composition of body. Irregularities or extensions of surface also in-
crease the area exposed to frictional "drag." Now viscosity varies
little with salinity but greatly with temperature of the water. We
may expect, then, in consideration of plankton and nekton, to find
that bodies of organisms tend to be larger in colder waters and smal-
ler in warmer and also that in other ways the plants and animals
of warm water often show increased extent of surface, as through
spinous or plumose appendages. We may find also that, where
upper waters are warm and, therefore, less viscous and deeper
waters are cold and more viscous, there will sometimes be found
a stratification of organisms of a species by size, the larger and older
living more deeply than the smaller and younger, which have
greater surfaces in proportion to bulk.
The significance of another basic condition of the environment
of organisms in the sea is easily overlooked or underestimated. The
fact that the water of the oceans is in continual circulation, that it is
everywhere a restless dynamic medium, is in the first rank of im-
/ 88 This Great and Wide Sea.
portance to marine life. The rhythmic and the progressive move-
ments of water affect the several types of organisms quite differ-
ently; but consideration of this aspect of the conditions of lif e in the
sea will best be deferred to the several later chapters.
Finally, in respect to the environmental conditions, let us con-
sider in the following section the notable absence of places of con-
cealment in the open sea.
No Hiding Place
As regards enemies and protection, there is need to emphasize in
the first line the fact that a reasonable number of enemies must gen-
erally be useful to a species. Without some control upon the in-
crease of a species, such as is afforded by predators, multiplication
in numbers must inevitably outrun the food supply and lead to
starvation. At any rate, we know nothing of the existence of organ-
isms without effective enemies and parasites. It is a recognized prin-
ciple of fish culture in ponds that numbers must be controlled if one
is to obtain the desired harvest of fishes of table size. Consequently,
it is a practice to have mixed populations, including a small propor-
tion of notably predatory species, such as the black bass or the pike.
Of course, the same result may be obtained by annual drainage of
the pond and removal of any surplus stock; just as in animal hus-
bandry, there is at least annual removal of the surplus of pigs, cattle,
or poultry. The last-mentioned practice is fully consistent with the
principle of the need for enemies; only, in this case, man himself
functions as the requisite "enemy" of his fish, cattle, or fowl.
On the other hand, protection or refuge from enemies, or some
other means of salvation, is equally essential both for the prey
and for the enemy. The predators may serve a useful purpose to
themselves and to their prey as they keep the multiplication of the
prey within bounds; but, in the interest of both parties to the con-
tract, the prey must have some means of regulating the extent, or the
effect, of the depredations made upon them.
On land and in marginal and bottom waters of lakes and seas,
there usually exists for animal life what is called "shelter," in the
substratum or in thickets of vegetation. Such havens of retreat play
a significant part in maintenance of an enduring state of equilibrium
between predators and prey. In short, shelter helps greatly to pre-
serve a balance between production and consumption or, if we
Life in the Sea: General Conditions
may carry over into biology a formula of economics, between
"supply and demand." In the picture that has been given of the open
sea, that is to say, of what is by far the greater part of the oceans,
we must have been impressed with the entire lack of refuge. Where
the vegetation is composed exclusively of plants of microscopic size,
scattered and free floating in this sort of diffuse and open pasture,
there is no place of hiding. Survival or death for plants and for the
animals of feeble powers of locomotion, which includes the vast ma-
jority of plankton animals, depends mainly upon the accidents of
the presence and the state of hunger of the potential consumer. Pro-
tective coloration is undoubtedly of some help, and for many
plankters transparency of body is a chief resort for concealment.
Transparency is associated with high water-content and, as Ostwald
remarked long ago, no organisms are so rich in water, and, generally
so transparent, as the inhabitants of the open waters of lake or
ocean. Fecundity offers for all species the strongest hope of sur-
vival (see also pp. 288-89, below).
Wherever shelter occurs in the sea it is availed of. dams, worms*
and Crustacea burrow in the bottom, and even in rock, or find con-
cealment among the shells of the bottom. The discarded shells of
conchs become the houses of hermit crabs. Oyster beds and thickets
of eelgrass harbor a rich and varied population of snail plants and
animals. The sargassum weed, which occurs in large floating gar-
dens in the Gulf Stream and in the central North Atlantic, offers
one of the rare refuges of the ocean proper, and the extensive masses
of weed are true zoological gardens: they afford shelter to an as-
tonishing community of fish, mollusks, Crustacea, and other animals.
Often these manifest the most bizarre forms, in correspondence with
their peculiar habitat. Among such are the sargassum fish, and a shell-
less snail, both of which have colors like the weed and leaflike pro-
jections from the skin. The several kinds of animal life associated
with sargassum in its diverse forms depend, according to Parr (p.
201, below), not upon place or season, but rather upon the form of
the plant. Still other animals find refuge within the bells of jelly-
fishes, in the empty tests of salpa or in shells of dead conchs. Many
instances of the intrusion of animals into every available form of
refuge could be cited; but all these will account for but a small part
of the life in the sea.
The ocean generally is a place without tangible refuge. Of course
This Great and Wide Sea
we know little of the conditions of life on the abyssal bottoms; but,
above the bottom, protection for the small organisms that pre-
dominate must depend upon translucency, upon other means of
making their bodies inconspicuous, or upon ability to live in the
darkness below the upper illuminated zones. We know of no con-
siderable habitat on land where want of refuge prevails in a way at
all comparable to that which marks the greater part of the surface
of the earth, occupied, as it is, by the open sea. Perhaps the nearest
approach to a shelterless area on land will be found in the open
grassland prairies as a home for the great populations of hoofed ani-
mals which, however, may resort to protective aggregation and to
speed of flight. We are so accustomed to the idea that the victim of
pursuit has some chance of sequestering itself that it is difficult to
realize that, for the animal world as a whole, places of refuge are for
the few not for the vast majority. The copepod, the pteropod, the
anchovy, and the larvae of any marine organism are almost as help-
less against depredation as is the grass in the meadow.
Metabolism of the Sea
In the sea, as on land, we have a great "organic cycle" in which
all organisms feed and, sooner or later, in one way or another, serve
as food. The food cycle might be said to begin with the inorganic
substances as utilized by green or yellow or brown plants, to run
through the chain of vegetarian animals and carnivores, and to con-
tinue with the activities of bacteria and other agents of decomposi-
tion in reduction of organic wastes to inorganic substances, which
are again ready for use by plants f or a new swing around the
circle.
Whatever may be the actual relative productivity of land and
sea, there is everywhere on land a drift of organic and inorganic ma-
terials toward the ocean, the great earthly catch basin. Much of the
organic material washed into the sea from the land is utilized by the
plants and animals of littoral and neritic zones, from which floating
and swimming organisms, at least in some measure, pass outward into
the open ocean, either traveling under their own power or conveyed
by streams and eddies. Consequently, the marine organic world is
not a closed system, but is continually receiving contributions of
organic substance from without. To what extent some of the organic
substance carried into the sea, or synthesized there, is ultimatelv lost
Life in the Sea: General Conditions
to the organic cycle by sinking irretrievably into the depths remains
an open question.
It may be well to look for a moment, at certain special aspects of
this cycle in the sea. Plants not only need water and carbon dioxide,
of which there are rich supplies (see p. 89, above) and sunlight,
but they also require nutrient salts of which phosphates and nitrates
are critical ones. The distribution of such salts in the sea is of inter-
est. Certain amounts are free and available in solution; but, in times
of active reproduction of diatoms or other small marine plants, the
stores may be depleted to a minimal amount; growth and reproduc-
tion must cease. Always a substantial but variable proportion of the
necessary nutrients is locked in the bodies of living plants and
those of the animals that have been nourished by the plants. Ob-
viously, the components of living organisms are not again available
for new plant growth, at the base of the ladder of life, until the death
and decay of bodies or wastes returns them to solution: only disso-
lution of such bodies can bring the material into circulation again.
The bodies of living plants and animals hold, then, a significant re-
serve of nutrients for later use in new production of microscopic
plants. It is well known that there may be more or less regular suc-
cessions of abundant diatoms giving place to a rich animal plankton
followed by great numbers of small fishes.
It is also obvious that many of the bodies and wastes holding the
reserve of nutrients will sink below the upper zone of photosyn-
thesis and thus be lost from the zone where any possible original
production can occur. Such bodies can be consumed by animals of
the intermediate depths, but the bodies and waste of these latter will
sink deeper before decomposition. Hence there must be a gradual
drainage of nutrient substance from the upper 'water mto the deep!
The downward drift of phosphorus and nitrates is well illustrated
from the tables given by Harvey 15 showing the results of analyses
for phosphates and nitrates at different depths. With none found
either at the surface or at 50 meters, at a particular place in the At-
lantic, there were 8 mg. of P 2 O 5 per cu. m. at 100 meters, 74 at 1000,
78 at 2,000, and 88 at 3,000 meters. For nitrate nitrogen and am-
monia nitrogen the mean value of samples taken by the 'TPIanet" in
15. Harvey, Biological Chemistry and Physics of Sea Water, pp. 41, 43. See also
Redfield, Alfred C., Homer P. Smith, and Bostwick Ketchnm, "The Cycle of
Organic Phosphorus in the Gulf of Maine," Biological Bulletin, 72, p. 421, 1937.
1 92 This Great and Wide Sea
the open ocean was 49 at the surface, 30 at 1,000, 47 at 2,000, and
107 at 3,000.
Apparently, the salts inevitably accumulating in the deep are lost
to the organic world for the time and must remain out of circula-
tion until, through vertical movements of water masses, they are
brought back into the photosynthetic zone, which is the illuminated
upper water. It is a fact anyway, as is emphasized more than once
in this volume, that, when deeper waters are brought up to the sur-
face through upwelling or other upward drifts, there is notable pro-
duction of microscopic plants, the small animals that feed upon
them, and the fishes. Fortunately, the nutrients brought back to the
surface can be used quickly and fully by the little plants, since they
have bodies made of single cells exposed on every side to the fer-
tilized medium and to the light. To illustrate how diatoms may
multiply in sea water enriched with nitrate and phosphate, Harvey
mentions 16 that roughly one gram of P 2 O 5 will suffice for the pro-
duction of nine hundred billion diatoms!
In reference to the nutrition of animals, there have been different
views as to the chief basic organic food supply. It was maintained
for a time, at least, that marine animals generally were able to utilize,
by absorption through the integument, the abundant organic sub-
stance in solution. Neither experiment nor reason has tended to sub-
stantiate this hypothesis in any significant degree. It was another
view that the chief basic food supply for animals in the sea was the
detritus, or finely-divided organic matter, resulting from the partial
decay and mechanical comminution of littoral plants, especially the
eelgrass which grows so luxuriantly along many coasts. This theory,
like the other, probably has only a small measure of truth as an an-
swer to the problem of the source of food for animals of the plank-
ton, nekton and benthos throughout the oceans.
In seeking the principal basic harvest in the open sea, there is, in-
deed, no need to look farther than the tiny photosynthetic organisms
of the plankton in the upper illuminated strata. Most of the organ-
isms taken in a fine-meshed net drawn through the water are animals;
but far more numerous are the minute algae, protozoa and bacteria,
the greater number of which are small enough to pass through the
meshes of the net. These are best secured by killing and allowing a
considerable period of time for settling, after which the water can
Life in the Sea: General Conditions
be drawn off, or by centrifuging at speeds that will throw down
even many bacteria. Another method of sampling for bacteria is by
making plate cultures from droplets of water. By whatever method
the small organisms are separated out, the number of each kind can
be counted, the dimensions of individuals measured under the micro-
scope, and their volumes calculated. Further computations and ob-
servations of reproduction give results to show that the synthesizing
plants of the nannoplankton, the "producers," they are called, gen-
erally exceed the net-plankton in total volume and greatly surpass
them in rate of multiplication, and, therefore, in crop production.
The photosynthetic algae undoubtedly afford the basic food supply
for the plankton animals, which, in turn, constitute the source of
nutrition for the larger swimming animals. Nothing has been learned
in recent years to cause essential modification of the statement made
fifty years ago by Professor W. K. Brooks: l7 "This is the funda-
mental conception of marine biology: the basis of all the life in the
modern ocean is to be sought in the microorganisms of the surface";
by "surface" we must, of course, understand the upper illuminated
zone, which may be one or two hundred metiers in depth.
Presumably, animals living below the illuminated zone near the
surface must depend for food largely on material falling from above.
But, to utilize the food, they also need oxygen. It is not remarkable
that the idea once held sway that the floor of the sea beyond the
continental shelf was without life, a great desert, an azoic area: in
this pitch-blackness, whence could come the supply of free oxygen
to support animal life? In temperate and Arctic regions, wherever the
surface water may at times be brought to a temperature at which it is
heavier than the waters below, it will, of course, sink toward the
bottom to be replaced at the surface by lighter waters from the
depths. By this "overturn," the oxygen supply of abyssal waters of
the region is renewed; but, over a great part of the Atlantic, Pa-
cific, and Indian oceans, such a condition cannot occur. Animals
yet thrive at the bottom; presumably they utilize oxygen brought
by the slow drifts of cold and richly oxygenated waters from polar
regions; cold water absorbs and carries the greatest amount of oxy-
gen. Probably the abyssal animals are not very abundant and lead
sluggish lives, involving a minimum oxygen demand.
17. W. K. Brooks, The GeTuts Stdpa. Memoirs from the Biological Laboratory
of the Johns Hopkins University, Baltimore, 1893.
This Great and Wide Sea
Summary
1. In coastal regions one easily obtains an impression of luxuriant
marine organic life, and this notwithstanding the dilution of nutritive
material in the sea and the reduced amount of light available to pho-
tosynthetic organisms beneath the surface. Often even far out at
sea, animal life may be found in profusion in the forms of fish,
shrimp like Crustacea, copepods or pteropods that are easily or barely
visible to the unaided eye; or, if fine nets or centrifuges are used, a
lush pasturage of minute plants may be revealed by the microscope.
Great areas of relative desert can also be found the regions of
really "blue sea" above or those of red clay at the bottom. There is
no uniformity in distribution of marine organisms throughout the
oceans, either horizontally or bathymetrically.
2. According to mode of life, the plants and animals of the seas
(and of lakes as well) fall into three great categories: the benthos
comprising those dependent upon a substratum; the nekton, includ-
ing the larger swimmers which can move somewhat independently
of water movements; and the plankton, embracing the drifters or
those organisms without or with relatively feeble powers of locomo-
tion, whose movements from place to place are determined chiefly
by the currents. A fourth category, the neuston, living against the
surface film, is scarcely represented in the wave-rufHed ocean, al-
though often prominent in lakes and ponds.
3. The habitats of marine organisms may be classified in a broad
way. The littoral, for the shallow coastal regions, is subdivided into
an mtenidal, above low-water mark; the euHttoral, or zone of pho-
tosynthetic plants on the bottom; and the sublittoral, extending out
to the edge of the continental shelf, the rim of the ocean basin.
Beyond is the benthic bottom region and the pelagic region of the
open waters above. The benthic region is conveniently subdivided
into the archibenthic on the continental slope and the deep, dark,
and cold abyssal zone. In the pelagic region of open water, we dis-
tinguish the neritic zone, which extends over the littoral, and the
oceanic for the open sea beyond the direct influence of continental
or insular drainage. The last mentioned zone has a superficial illumi-
nated, epipelagic, subzone above and deeper bathypelagic and
abyssal subzones of perpetual darkness and relative coldness.
4. Marine organisms beyond the intertidal zone are spared the
requirement of coverings to protect against desiccation. They live
Life in the Sea: General Conditions 2 5?
surrounded by a chemical medium containing in solution the mat<
rials requisite for production of organic substance. They var
widely in capacity to make adjustments to differences of salinin
In areas and times of extremely prolific multiplication, they ma
effect significant changes in the composition of the water with n
spect to some substances present in relatively minimal amounts.
5. Because of the density of sea water the need for supporrin
structures is diminished. Plants develop no trunks or stiff stem
Animals, other than some of the benthonts, have no need for legs t
support their bodies above a substratum.
6. In adaptation to the viscosity of water the streamlining c
bodies is highly but variously developed in aquatic organisms, fres
water and marine. This and the cycles of form in possible relation t
viscosity were discussed in an earlier chapter. Specific gravity c
many pelagic organisms is lessened by a high percentage of wate
in the body, giving translucency, and by the storage of food reserve
in the form of light oils rather than the heavier starches. Some organ
isms have larger and trimmer bodies in colder waters, smaller an
more elaborately formed bodies in warmer waters.
7. An indispensable basis of life is solar radiation, and most of th
radiation coming to the earth falls upon the sea. The greater pai
of it is reflected or converted into heat and only a minute part use<
directly by marine photosynthetic plants. The life in the sea, par
ticularly in the regions near the coasts, seems to depend in part upoi
organic production upon land. On the other hand, when the se
is compared with the land as a place of living for green plants, th
much greater availability of carbon dioxide and water (basic sub
stances for all life) and the one-celled bodies must give marine plant
a distinct advantage for the use of what sunlight there is.
8. Doubtless, in part, because of the greater content of dissolve*
gases in colder waters, cold seas are notably rich in organic life.
9. A distinctive feature of the neritic and pelagic zones is th
nearly complete lack of shelter or refuge. Survival depends upa
chance more than upon individual initiative; protective coloration
and translucency of body play some part with different specie
Fecundity is the salvation of most species. Shelter of many sorts pre
vails in the smaller littoral region, but rarely in the open sea.
10. Various theorists have assumed, severally, that the basic an<
immediate food supply of animals in the sea is: (a) the dissolve*
1 96 This Great and Wide Sea
organic matter in solution, (b) the detritus of littoral plants, or (c)
the self-reproducing organisms of the plankton. Unquestionably,
for the open ocean, the last-mentioned source of food is paramount.
The plankters utilize the dissolved matter resulting from decay of
organic bodies and wastes in the sea or washed into the seas from the
lands.
11. There is no depth of water without life. Food for abyssal ani-
mals must fall from above. The requisite oxygen is presumed to
have been brought chiefly through slow drifts, over the bottom, of
originally oxygen-rich water from the surface in cold regions.
1 2. There must be continual drainage of nutrients from the upper
water into the deep. So far as they go into solution they are lost to
the world of life except as in particular regions deep water is re-
turned to the surface through towelling or other vertical move-
ments. Regions of upwelling are regions of richness.
CHAPTER 14
or the
Premium on Simplicity
A\ COMPARED WITH SOIL WATER IN FERTILE AREAS, SEA WATER IS
a dilute solution of the nutritive materials necessary for plant
life. But whereas land grasses and trees have only roots in
the soil, sea plants are totally immersed in the nutritive water of the
sea. Food, oxygen, and carbon dioxide do not have to be reached
out for by branching roots or spreading leaves. The premium is oc
surface exposure. The smaller the body the greater is the surface;
consequently, in the oceans, there has been little tendency toward
the development of complex plant bodies. In the formation of a
new plant or animal body, the first step is the division of a single
reproductive cell. With higher organisms the two "daughter" cell*
remain attached, while each divides again. With repeated division*
there is formed a mass of cells in which differentiation of form anc
specialization of function begin. Eventually the complex bodj
results. But two cells, if joined together, have less surface exposun
to the surrounding medium than do the same two cells when sep
arated from each other. Capacities to absorb nutrients from th<
medium and the energy of sunlight are greater for each cell if it i
completely separate from the other. Only under special condition:
is it true that "in union there is strength." So it is found that, fo
most, but not quite all marine plants, union is foregone: the vas
bulk of the vegetation is in the form of single cells the diatoms
the coccolithophores, the dinofl agellates, and other small-bodied or
ganisms. Some of these minute organisms are so clearly on the bor
i $8 This Great and Wide Sea
derline between plants and animals that they are claimed both by
botanists and by zoologists. Certainly, so far as they synthesize
organic matter with the use of sunlight, they serve as original "pro-
ducers," and are comparable to the grasses of the pasture.
In treating of plant life in the sea, it should be remembered that
we deal with the greater part of the organic world: after all, vege-
tation is the broad base of the "pyramid of life" in the sea, as on land.
Through numbers and fecundity, plants must both maintain their
own populations and support the innumerable herbivores, which, in
turn, support the carnivores. If we remember that always each ani-
mal, in the course of a year, must eat many times its own weight we
get some glimmer of a concept of what the annual crop of vegeta-
tion must be.
We should recall, too, that, although the whole volume of the
oceans, from shore to shore and from surface to bottom, is the home
of animals, constituting the "consumer" group, yet the original pro-
duction through photosynthesis can occur only in the upper illumi-
nated zone. The microscopic plants of a relatively thin stratum have
to support not only the animals of their own level, but also those
scavengers and predators that live in the greater volume of dark
waters below. Apparently this is accomplished, not so much by
maintenance of excess of numbers and bulk at all times, as by rapid
n:u!tipl:caricn, insuring continual replacement of those being de-
voured each day and hour.
The depths to which living algae penetrate differ greatly in differ-
ent waters. Gran 1 found them restricted to a very thin surface layer
in Christiana Fjord, overlying a deeper infertile layer of more saline
water. Out in the open sea they extended deeper, being abundant at
50 meters, and in considerable numbers at 100 meters. Others have
reported algae in the open sea to be most abundant at 10 to 50 meters,
with hardly a tenth as many at 100 meters. The algae are, however,
much less abundant in the open sea than in coastal waters. Gran be-
lieved that the proportions of algae in coastal and typical open-sea
areas would be nearer one hundred to one than two to one. The
great disproportion he attributes to the fact that it is the drainage
from the land that brings essential nutritive substances. Naturally
the admixture of fresh water from rivers with the sea water produces
i. The references here are to H. H. Gran, Chapter VI in Murray and Hjort's
Depths of tbe Qcem.
Pasturage of the Sea
water that, as compared with the general mass of ocean water, is
both more fertile and less saline. This water, lighter because it is
lower in salinity, must override near the coast the more saline and
less fertile oceanic water. This would account also for the relative
thinness of the stratum of alga-rich waters close to the continents.
Kinds of Plants*
From the point of view of animal life, the producing plants of
land and sea have the same basic functions to perform to synthesize
carbohydrates (sugars and starches), proteins, vitamins, and fats
from inorganic salts, carbon dioxide, water, and the energy of the
sun, and to liberate more oxygen than they consume. Nevertheless,
as we have said, the contrast in character of vegetation in the two
types of homes is marked. None of the higher plants occurs in the
ocean remote from the shores. Seed plants are totally wanting there;
ferns and mosses, the next lower groups, occur nowhere in the sea.
Even along the coasts, the larger algae are chiefly of groups that are
represented hardly at all in fresh waters. The great group of primi-
tive blue-green algae, abundant in lakes and rivers, are prominent in
the ocean only near the mouths of large rivers or in tropical regions.
On an earlier page (p. 18) we have mentioned Trichodesmus, a
"blue-green" in classification, but colored red by an accessory pig-
ment, which often gives color to the Red Sea.
The green algae (Chlorophyceae), predominant in fresh waters,
are sparsely represented in salt waters, and then chiefly where there
is some admixture of fresh water. Codium, Enteromorpha, and the
familiar sheets of Ulva ("sea lettuce") are restricted narrowly to
coastal regions and do not occur below a depth of about 10 meters.
Some of these have actively swimming reproductive bodies (zo-
ospores), which may be so abundant as to give a distinct green
color to the water. The relatively simple filamentous algae that so
commonly form "blankets" on the surface of fresh-water ponds are
missing from the open sea, where, as previously mentioned, the con-
ditions have not favored cell aggregations.
On the other hand, the brown algae (Phaeophyceae) and the red
algae (Rhodophyceae), richly present in the benthonic life of the
ocean along and near the coast, are most sparingly represented in
2. The reader wishing more detail is referred particularly to Chapter DC of
Sverdrup, Johnson, and Fleming, The Oceans^ and to Chapter VI by Gran in
Murray and Hjort, op. cit.
200 This Great and Wide Sea
FIGURE n. Varieties of pelagic sargassum. (After Albert Eide Parr,
in Bulletin of the B'mgham Oceanographic Collection, Vol. VI, Art. 7)
Pasturage of the Sea 201
fresh water. Brown algae, including rockweeds, sargassum, and
kelps, are the largest and most conspicuous of marine algae. The
inherent green color is masked by yellow and brown pigments. The
rockweeds are conspicuous, attached to wharf piles, jetties, and shells
on the bottom. The kelps occur more commonly a little distance
from shore with long "stems" (stipes) and fronds waving in the
water from a base of attachment to rocks at the bottom. They may
have a total length of 100 feet and be anchored at corresponding
depths; usually they are in water of less depth, and some stream out
from the rocks of wave-beaten shores. Many are valuable for food
and for the extraction of drugs, iodine, algin, potash, and other
commercial products. 3 Sargassum is the only large seaweed that
finds a prominent place in the high seas. This is a fairly large "leafy"
weed. The long, branching stems bear leaflike extensions and little
stalked bladders, to which it owes its name, derived from the Portu-
guese word for grape, sarga. This marine grape-weed, or "gulf
weed," has been known to seafarers since the first voyage of Colum-
bus. Originally it grows attached along tropical shores. Breaking
loose, it drifts in the currents, multiplying vegetatively as it does,
and accumulates in the great eddy in the Atlantic Ocean known as
the Sargasso Sea. 4 Here it continues to grow. Before it dies to sink
and decompose, it forms an extensive shelter for a remarkable special
community of animals, many of which can live nowhere else than
in the clumps of sargassum.
The more delicate red algae (Rhodophyceae) on the bottom ex-
tend farther out into the sea, living not only in harbors and along the
shores but also in the deeper waters of the continental shelf beyond
the depths of penetration of the shorter rays of sunlight necessary
for the growth of truly green plants. The red algae are, therefore,
presumably of special significance as "producers" or photosynthetic
agents on the continental shelf. It is the red algae that are commer-
cially valuable for the production of agar. Some have a special ca-
pacity for the precipitation of calcium carbonate, with which they
3. See "Utilization of Seaweeds," by Cheng-Kwai Tseng in The Scientific
Monthly, LVm, (1944) 37-46. See also "Introduction to Agar and its Uses" by
Harold J. Humm and Frederich A. Wolf, Bulletin No. 3, Duke University Marine
Station, 1946.
4. Perhaps some species of sargassum lire permanently adrift. For much infor-
mation regarding the habits of sargassum, its several species and diversity of forms,
reference is made to the intensive study by A- E. Parr: "Pelagic Sargassum Vegeta-
tion of the North Atlantic," Bulletin, Bingham Oceanograpmc Collection, VI, 1939.
2 02 This Great and Wide Sea
encrust themselves. They are, therefore, important geological
agents.
The algae so far mentioned, being chiefly dependent upon the
bottom and narrowly restricted in distribution, can not serve as
principal photosyntheric agents for the oceans at large. The para-
mount producers, as we have already mentioned, are the single-
celled chlorophyll-bearing organisms of the plankton. Some of these
are indisputably plants; others have such a mixture of plant and ani-
mal qualities that both botanists and zoologists lay claim to them.
Let us mention briefly the more prominent kinds: the Heterococ-
cales (Halosphaera), the diatoms, the dinoflagellates, and the coc-
colithophores.
Halosphaera and a near relative are the only important algae of
the open ocean that are bright green in color. Once grouped by
botanists among the Chlorophyceae or true "green algae" (grass-
green), they are now placed in a distinct order, and related to the
yellow-greens (coccolithophores and others). Halospbaera viridis
sometimes occurs in great numbers, particularly in the Atlantic, the
Antarctic, and the Mediterranean. Although minute in size, the
single-celled bodies long ago caught the eyes of Mediterranean fish-
ermen who called them "punti verdi," or "green points."
Much more important as food for small vegetarian animals are the
diatoms, whose shells of silica we have previously mentioned as the
basis of a principal bottom deposit diatomaceous ooze (see p. 1 14) .
Diatoms occur abundantly in both fresh and salt waters, free living
or on the bottom where there is light, but they reach their fullest
flower, so to speak, in the marine plankton. They appear in great
diversity of form and size, the largest being barely visible to the
naked eye. Some, Rhizosolenia at least, show notable "cyclomor-
phosis," or change of form with season. In winter the pointed ends
of the long narrow shells (frustules) are short and blunt. Later gen-
erations in summer have long slender points, presumably in adapta-
tion to the changed viscosity of the water; the increased surface is
supposed to offer greater resistance to sinking in the wanner and
"more liquid" water. Diatoms store food in the form of fine oil
droplets, which lighten their bodies and facilitate floating. There is
some reason to believe that they form the basic substances of vita-
mins which are passed on to the copepods that eat them, and, in
turn, as vitamins, to the fish that eat the copepods, and so to those
Pasturage of the Sea 203
development of rich populations of diatoms. Not infrequently the
surface water, through areas miles in extent, may be discolored by
FIGURE 12. One of the mi-
nute plants of the plankton, a
dinoflagellate, Csrathtm bvr-
undinella. (From Kudo, after
Stein) Such plants, brownish
in color, may occur in vast
numbers causing the so-called
"red seas," many square miles
in extent. (See text, p. 204.)
them and actually "soupy" in character. The part diatoms play in
the nutrition of animals will be mentioned in a later chapter.
2 04 This Great and Wide Sea
The dinoflagellate algae (or protozoa to the zoologist), with shells
of cellulose, or sometimes without shells, are tiny free-swimming
FIGURE 13. Coccolithophores. (a) Rhabdosphaera
claviger (after Murray and Hjort). (b) Coccolithus
pela&cus (from Fntsch, after Lebour). These very
minute plants, whose name means "little stone bearers,"
constitute an important part of the pasturage of the
sea, and their skeletal parts, coccoliths, form a substan-
tial element in deposits on the bottom.
organisms with two flagella for locomotion. They occur in great
diversity of species. They may, on occasion, be so numerous as to
give the sea a muddy appearance, being one of the causes of the f re-
quently mentioned "red seas" in the ocean. They attain greatest
Pasturage of the Sea 205
numbers in the warmer waters. Some kinds are highly luminescent.
Because the organic shells of dinoflagellates decompose readily, they
do not appear as an element in bottom deposits.
Yet smaller than the diatoms and dinoflagellates are the Cocco-
lithophoridae, which are said to constitute a large proportion of the
marine plankton, but which pass through the finest silk nets and
must be sought by centrifuging. The name means "bearers of cocco-
liths," for the minute bodies are protected by calcareous plates or
spicules of the order of size of bacteria. As substantial components
of deep-sea calcareous deposits, especially the globigerina ooze, coc-
coliths (seed stones) were known to geologists long before it was
understood that they are fragments of the shells of living organisms.
These algae (or protozoa) are of the group of yellow flagellates,
called chrysomonads, to which belong also Dinobryon, a fresh-water
alga that sometimes occurs in such abundance as to discolor the water
of lakes and ponds and give a bad flavor and odor to municipal
drinking water. The coccolithophores seem to be universally dis-
tributed in the oceans except in the colder waters of polar seas.
All of the plankton algae are of course restricted to the upper few
hundred meters, where sunlight is available except, as their falling
bodies may invade the regions of darkness below.
We have passed over the bacteria, once thought to be not notably
abundant in the sea. There is nothing in the conditions of tempera-
ture and pressure at the bottom to prevent the growth of bacteria
(ZoBell), and they are now known to be enormously abundant in
superficial layers of the bottom. More knowledge is needed con-
cerning the bacteria of the deep, where much waste organic material
accumulates. In recent years, Waksman at Woods Hole and ZoBell
at Scripps have been adding much to knowledge of marine bacteria.
Experiments of Clarke and Gellis (1935) "indicate that bacteria and
other constituents of the nannoplankton may be an important food
for copepods in the sea." Bacteria may serve to some extent as syn-
thetic agents in regions of the sea where green plants can not func-
tion, but we still have too little information concerning the signifi-
cance of bacteria in the ocean. In areas occupied by plankton, they
are most abundant in the upper zone of water, are mostly attached
to plankton or other objects and perhaps are not truly planktonic. 5
5. Sverdrop, Johnson, and Fleming, The Oceans, p. 910.
2 06 This Great and Wide Sea
Such small pasturage organisms as have been mentioned have
much greater significance to man than is revealed by any considera-
tion of their use as food for higher animals. Whence came a great
part of the reservoirs of oil in the earth from which we derive the
fuel that drives our ships and trucks and heats our homes? The
bodies of organisms that settled on the sea bottom in ages past, and
the action upon them of various lands of bacteria, gave us in the end
the means of transportation and of light and warmth.
Although the higher plants are completely wanting in the open
sea, we should refer to a seed plant that is of considerable significance
in coastal waters. The common "eelgrass," Zostera, a flowering
plant of the pond-weed family, occurs on almost all ocean shores
where wave action is not severe. Its abundance and general distribu-
tion are indicated by the windrows of it seen on beaches of harbor
and ocean. As the annual crops of eelgrass die and the plants are
broken to pieces, the fine detritus to which they are ultimately re-
duced may be carried well out to sea to constitute a basic food sup-
ply for many kinds of animals. Indeed, some biologists, considering
the nutritive support of animal life in the ocean, have attached
greater importance to the detritus formed from eelgrass grown in
shallow waters than to the phytoplankton multiplying in the off-
shore waters. A remarkable phenomenon, and one not yet ade-
quately accounted for, was the comparatively recent and rather sud-
den disappearance of eelgrass on both sides of the Atlantic and on
some Pacific shores, apparently as the result, or with the accompani-
ment, of some sort of disease. It has been returning, to the great ad-
vantage of the scallops and other animals that find refuge in it. Ap-
parently that disaster to eelgrass and, of course, to many of the ani-
mals associated with it, was not entirely without precedent, but why
did the disease appear so suddenly and in such widespread fashion?
i. In oceanic areas the equivalent of our abundant land vegetation
is to be found in the microscopic plants of the upper illuminated
zone. The dilute state in sea water of many of the dissolved sub-
stances required to support life and the limited amount of light avail-
able beneath the surface have put a premium on high surface ex-
posure in relation to volume. Increased surface is attained by reduc-
Pasturage of the Sea 207
tion in size and multiplication in number. Accordingly, photosyn-
thetic organisms in the open sea have no large and complex bodies.
Marine vegetation is extremely low in the general scheme of plant
classification. The higher plants with elaborate bodies and special-
ized parts have all developed on land.
2. Some macroscopic algae of "bushy" or platelike form and
others (kelps) with long streaming fronds may be conspicuous in
coastal waters; the "sargassum weed," drifts widely at sea. All these
are mostly brown and red algae, low in the plant scale and charac-
teristic of the sea. A very few seed plants have invaded the marginal
waters. Undoubtedly all of these are important regioTially as original
"producers" of organic substance; but, the plants that are visible to
the naked eye play a minor part in the whole "metabolism of the
sea."
3. In the open sea the minute living algae are largely restricted to
the upper 100 meters, where the light is sufficient for photosynthesis.
Observations indicate that in coastal waters they are generally far
more abundant, but more superficial, than in the open sea.
4. Bacteria are abundant in the bottom muds and oozes, and, to
a lesser extent, in the upper waters.
5. The vegetation of the sea offers marked contrast to that on
the land, where, with the green hills, vales, and prairie, such obvious
plants as grass, weeds, shrubs, trees, and farm crops form the basic
support of animal life including man. To discover in the sea the
equivalent of these ultimate "producers" of organic matter, resort
must be had to the centrifuge and the microscope, particularly for
diatoms, dinoflagellates, and coccolithophores. The micro-pasturage
of the sea is nonetheless abundant and effective in support of animal
life.
CHAPTER 15
Junrtina <JLife: ^Jke
Universality of Plankton
DRIFTING ORGANISMS OCCUR IN ALL HABITABLE NATURAL
waters except shallow swift streams. On land and on the
bottoms of waters the organic world constitutes a relatively
thin layer, a sort of surface, whose extent is measured in two direc-
tions. In the sea and in lakes organisms adrift are to be found at all
levels; the territory of occupancy is to be measured not only north-
south and east-west, but also in the significant third dimension of
depth. When we recall that the average depth of the seas is about
two and one-third miles, the depth of terrestrial life, measured in
feet or in tens of feet seems insignificant. Even in superficial extent,
the waters of the earth are more than twice as great as the land. It is
obvious, then, that, measured in volume, the space inhabitated by
planktdn is incomparably greater than that occupied by terrestrial
and benthonic organisms. The swimming animak, termed nekton,
range through the plankton world, but they comprise only a small
part of the free life in waters. Consequently, we deal in this chapter
with the major part of the organic world: the great majority of
plants and animals are "drifters." We have already dealt with a
substantial part of the plankton in the discussion of "pasturage in the
sea"; hence, in this place, we shall refer to that part of the plankton
world only as incidental to the consideration of the animal plankton,
orzooplankton.
It now seems somewhat curious that the great world of the plank-
ton was hardly discovered a century ago. Ancient Greek writers
208
Drifting Life: The Plankton
are said to have made some allusions to the drifting life; Mediter-
ranean fishermen are known to have recognized the green alga,
Halosphaera, as "green points"; and whale fishermen have long seen
"whale feed" (copepods, pteropods, and euphausiids) as auguries
of good hunting. That great pioneer microscopist of the late seven-
teenth and early eighteenth centuries, Antoni van Leeuwenhoek,
who so often anticipated later scientists, saw and described a num-
ber of plankters. Yet, to the scientists, and to others generally, the
greatest of all living worlds waited for some great man to think of
using an extremely simple device the fine-meshed net, drawn
through the water. Diatoms and some other plankters of the ocean
had been discovered by examination of small quantities of water
dipped from the surface, or by observation of skeletal remains in
samples of the bottom; but virtually nothing was known about them
and there was no real conception of the wealth of diversified popu-
lations of microorganisms living permanently or temporarily in the
water. It now seems almost incredible that, for so long, it occurred
to so few to employ a fine-straining apparatus. Charles Darwin,
sailing on the "Beagle" (183 1-36) and adding immensely to biologi-
cal knowledge, dragged nets of bunting, but failed to give the
method effective advertisement.
Johannes Miiller, one of the great biologists of all times, (see
p. 1 8, above) made use of the net in 1845. Yet he did not at once
think of towing a net. He wanted to find larval stages of echino-
derms, between the easily obtainable fertilized egg and the creeping
young starfish. It occurred to him to dip water and pour it through
a fine-meshed net. Then he dipped 'with the net on the end of a pole.
Finally he thought of towing the net with a line from a boat. 1
Amazed at what he obtained, he wrote to Ernst Haeckel, advising
him to try the net, and added that once Haeckel had glimpsed this
world of drifting life, he would never be able to leave it. Apparently
he was right, and we owe much to Haeckel for his ecological classi-
fication of marine life. Biologists everywhere began towing "Miil-
ler nets" and examining the pelagic strainings (pelagische mulde).
Life histories of benthonic organisms that were hitherto unknown
were being completed by hundreds of students. Great numbers of
new animals and plants, whose existence had not previously been
i. Lohraann, 1912.
210 This Great and Wide Sea
suspected, were being described. But the concept of the plankton
as a coherent community of interrelated organisms was yet to come.
The tow-net was one of those rare devices that, like the micro-
scope, opened new worlds for biological exploration. Although a
real introduction to the drifting life dates from the use of the net,
the word "plankton" and its definition came only some thirty years
later, when Victor Hensen proposed the term, in 1887, with a some-
what broader meaning than it has today. Meantime, the first great
exploration of marine plankton was made by the "Challenger" in
the 'seventies. In the beginning certain misconceptions developed,
and the explorations prompted by these did much to stimulate inter-
est in plankton and to add to knowledge about it.
There were those who thought that free drifting life could exist
only in the upper few hundred meters of water. The closing nets
of Palumbo, von Peterson, Chun, and others (see p. 30, above)
made possible the certain knowledge that plankton lived at all
depths. It was supposed by some that plankton occurred f airly uni-
formly at all levels in the upper waters. The quantitative net, first
devised by Hensen at Kiel, helped to disprove his own theory of
generally uniform distribution. Quantitative studies yielded more
precise knowledge of the uneven distribution of plankton and led to
recognition of the significance of that basic fact in an understanding
of many broad problems of oceanography.
By size, the plankton is conveniently divisible into the net plank-
ton and the more minute organisms which pass through a net of
finest silk and are best taken by centrifuging small samples of water
at fairly high speeds. It was Hans Lohmann, at Kiel, who first used
the centrifuge in the study of plankton; for the smaller organisms
taken by the centrifuge he proposed (1911) the term nannoplank-
ton, meaning "dwarf plankton." There can be no sharp distinction
between net-plankton and nannoplankton, but the finest nets em-
ployed have meshes with diameter of about 0.05 mm. (1/500"). It
may be remarked in passing that Lohmann's attention to the nanno-
plankton was elicited by the discovery that some marine animals
that feed by filtering tiny organisms out of the water have a straining
apparatus of much finer mesh than our most expensive silk nets.
As the net plankton greatly exceeds the nekton in aggregate volume,
so the nannoplankton often exceeds the net plankton, not only in
numbers, but also in total volume and weight. This is particularly
Drifting Life: The Plankton 2 1 1
true in fresh water. It seems to be a rough general rule that, in the
aquatic organic world, the aggregate volume of living material is in
inverse proportion to size, if the rule is applied, not to particular
species, but only to sizes.
Obviously the plankton embraces organisms of a wide range of
sizes calling for various methods of capture. It is sometimes con-
venient to distinguish the macroplankton, comprising the larger or-
ganisms, like jellyfishes, small fish, salpas, and sargassum, which are
easily seen, the ml croplankton, or net plankton, and the ncttmoplmk-
ton (dwarf plankton) , or "centrifuge plankton"; perhaps we should
add, also, the idtraplankton of still more minute organisms that even
the centrifuge will not separate from the water. It is all one world,
however, and we will not stress these subdivisions.
In the comparison of marine and fresh water plankton, two dif-
ferences are noteworthy. In both there are plankters whose whole
lives are spent adrift; but the diversity of these holoplankters is far
greater in the sea than in fresh water. It is true that rotifers are
prominent in fresh water and not in the sea, but this is the one ex-
ception favoring fresh water. In the denser waters of the ocean,
several divisions of the animal kingdom have developed strictly
planktonic kinds such as the worms, the mollusks, and the lower
chordates that never touch the bottom; these groups are not repre-
sented at all in the fresh water zooplankton.
Yet the most striking difference between fresh water and marine
plankton is the presence in the latter of an almost limitless variety of
larval stages of benthonic and nektonic animals. The high specific
gravity of sea water, together, doubtless, with other conditions, has
been favorable to the assumption of a free-swimming habit at some
stage of life. Virtually all marine animals have such free larvae;
practically none of the fresh water animals that are not exclusively
planktonic have them. In lakes and ponds, newly-hatched snails,
worms, and insect larvae crawl out of their egg shells, clams creep
from the parental brood pouches to begin life on the bottom, 01
let fish carry them as parasites until they are prepared to burrow
into the bottom. 2 On the contrary, the eggs of marine snails, oysters
and worms develop into microscopic larval bodies, quite unlike the
2. The only strictly planktonic insect larvae are the "phantom larvae** of th<
midge commonly known as Corethra or Chaoboras. The familiar mosquito-
wiggleis live partly free, as planktonic, partly at rest on the bottom or at die sur-
face, as benthonic or nenstonic.
212 This Great and Wide Sea
adult and provided with numbers of delicate paddles which ro]
them around in the water until they can undergo metamorphosi
into the form of the sedentary adults. It is such free-swimmin
larval stages, constituting the meroplankton (part-plankton), tha
make the most conspicuous contrast between catches of marine an
fresh-water plankton.
Conditions Governing Distribution by Regions and by Depth
In respect to distribution, as we must emphasize for each of th
three types of major ecological communities in the sea, it is the pres
ence of nutritive substances that chiefly determines abundance c
plankton at any place. The foundation of any community is th
proper assemblage of inorganic substances in conjunction with sur
light and photosynthetic organisms. The starting places for th
organic cycle are the upper illuminated waters wherever they ma
be, and the sunlit land. Naturally, then, it is the upper waters, ger
erally, that are most richly populated and densities of populatio
must also show some sort of gradation with respect to distance f roi
land. If it were all quite as simple as this sounds, the problems i
the study of distribution would be easily solved. But there are man
complicating factors. Currents or drifts, universally present, can
nutritive substances, algae and the animal plankton, from place 1
place. Nutritive materials sink into the depths for temporary los
and much of this is brought back into illuminated waters along shoj
or somewhere out at sea. Among the basic nutritive substances, i
a broad sense, are carbon dioxide and oxygen; and cold water al
sorbs more of these gases, to make them available for aquatic plant
than does warm water, while the oxygen, at least, is used more raj
idly in wanner waters. This is not the whole story, but it is enoug
to show that the pattern of distribution is very complex.
The zone of production in the open sea is in the high upper watej
above a depth of 200 meters; yet it is not chiefly at the very surfac
Various observers have found the maxima of minute plants (alga<
at about 50 meters. 3 Since the basis of the pyramid of numbers
the sea is the community of photosynthetic organisms in the upp
waters, it might be expected that the algae in these waters wou
vastly exceed in number and volume the animal plankton. Th<
3. See Chapter XIV, p. 198.
Drifting Life: The Plankton 2 1 5
have the heavy task of maintaining themselves, the animals that live
with them and feed upon them, and, in addition, all the animal life
in the deeper waters below, where no original production can take
place. 4 It appears, however, that generally no such conspicuous
excess of plants over animals is found. The task of the algae in sup-
port both of themselves and of the animals is met, not so much by
continual maintenance of a greatly predominating population, as
by rapidity of reproduction. In die sea, as in the barnyard, the
livestock live and grow fat, not from the food in the trough in one
day, but from the regular replenishment of the manger. It is the
''turnover" that counts.
For various reasons, littoral and neritic waters are generally rich-
est in plankton. Organic and inorganic nutritive materials drain
from the land; photosynthetic algae may grow on the bottom in
littoral regions; and the only marine seed plants thrive on upper lit-
toral bottoms. These die, are broken up by wave action, and form
detritus that is carried by the water as food for animals of benthos
and plankton. Little of this gets out into the open sea. 5 Along the
coasts, and away from them as well, abundant development of
plankton may be expected where ascending currents faring up nu-
tritive material from below. 6 Where water descends from the sur-
face into the depth, plankton in the upper depleted waters will
usually be scarce. Sinking of surface water must occur where pre-
vailing on-shore winds cause the piling up of water, or where con-
vergence of oceanic currents occurs to produce the same effect. In
the relatively dead centers of oceanic eddies, increase of specific
gravity of the surface water through evaporation leads to subsidence.
Thus the upper plankton of the Sargasso Sea is reported to be no-
tably scant; 7 yet the sargassum weed decomposes to become detritus
and afford nourishment for deeper-living animals, 8 so that Hjort
found the waters in that sea at depths of 1,000-1,500 meters to be
notably richer in deep-living plankton and fish than those east of it.
4. It has been estimated that copepods and other small animals eonsnrr.e seirethir.g
like their own weight of food in ten days (cf. Murray and H-cr; op. j;r, p. -2- ,
varying, of course, with many conditions. According to other ccT.-;""ar?zs, T3.ar.i-
ton animals consume food materials equivalent :o rnelr own we:^hs jr. two cavs
(cf. Sverdrup, et. ed^ op. cit^ p. 901). The latter figure is probably applicable rrore
generally to Protozoa.
5. Hjort, in Murray and Hjort, op. cit., p. 386.
6. Ibid^ p. 368.
7. Ibid* p. 371-
8. Ibid^ p. 718.
2 1 4 This Great and Wide Sea
When warm and cold currents come together and mix, the rising
temperature may promote the growth and reproduction of algae,
and of their predators, to utilize more rapidly the materials carried
in the cold waters: it is like the coming of spring to the previously
colder waters. The mixture of Arctic currents, coastal waters carry-
ing detritus, and the warm Atlantic Gulf Stream leads to the rich-
ness of life in the Barents Sea, the waters north and east of Iceland
and those of the fishing banks off Labrador and Newfoundland. 9
The physical conditions of temperature and viscosity have much
to do with the geographic and depth distribution of particular kinds
of plankton organisms, as we shall see more particularly in our brief
consideration of the several groups of animals. There are species
tolerant only of cold and others only of warm waters. Such animals
as can endure only a narrow range in either the upper or lower part
of the temperature scale are called ttenothermal. Others are eury-
thermal, with apparent indifference to changes of temperature. It
is to be remembered, too, that cold waters are found, not only in
high northern and southern latitudes, but in all latitudes, even be-
neath the Equator, at sufficient depths. Pressure, which increases so
rapidly with depth, probably plays some part in determining the tol-
erable ranges of depth for particular species; but apparently of great-
est significance are temperature, which changes with depth, and
viscosity, which changes with temperature and, very little, with
salinity.
In respect to the depths at which plankton lives, we have seen that,
generally speaking, the algae are most abundant somewhat below
die very top water, and live hardly at all below 200 meters. The
plankton Crustacea, which are the most important of all animal
plankton, live mostly below 200 meters. Referring to the Atlantic,
Hjort said that "the greatest volume of pelagic Crustacea has never
been found in the upper 100 or 200 meters, where the production
of minute plants takes place, the great majority of small pelagic crus-
tacea live everywhere in the deeper intermediate layers." 10 There
is no depth at which some plankton does not occur, but, since the
zone of production is in the upper 200 meters, the deeper living ani-
mals can subsist only upon each other or upon what falls from above,
and those of each layer take their toll. Again, however, there are
9. Ibid^ p. 728.
10. Ibid^ p. 725.
Drifting Life: The Plankton 2 1 5
many complicating factors. If the waters are in movement, as is
the rule, the fall of material will be, not in a direct vertical direction,
but obliquely; the place of consumption is not immediately below
the place of production.
Falling matter may pass from a current flowing in one direction
into another having a different, even an opposite course. It may pass
from water of low salinity to water so much higher in salinity and,
in specific gravity as to cause a retardation, or even a stoppage of
descent. There will be, as Hjort suggests, a sort of "bottom" in
mid-water, when food accumulates to support a relatively dense
population of small pelagic animals. Such a region seems to prevail
in the Sargasso Sea at 500-1,000 meters, where many more small
Crustacea were found than in the uppermost waters.
It is elementary knowledge now that there is great diversity in
the composition of plankton, not only in different regions and at
different depths, but also at different seasons, and at different hours
at the same place and depth, and probably even in different years.
The conditions that lead to maxima and minima, as well as to minor
fluctuations of abundance of any particular plant or animal, are com-
plex indeed in their physical, chemical and biological aspects. Just
one of these conditions is the migratory habit of many plankters.
The powers of locomotion of such small orgarJszis are slight as com-
pared with those of larger animals in respect to horizontal move-
ments over broad areas. That is to say, a microscopic animal, how-
ever rapid may be its.movement in proportion to its size, will, never-
theless, in the course of a day, travel no considerable distance under
its own power. Changes in geographic location are to be accounted
for chiefly by the action of currents. On the other hand, locomo-
tion of individuals may result locally in the formation of dense
schools or in scattering. Most notable are the vertical migrations,
which are generally toward the surface when the light is dim and
away from it when the light increases. Consequently, surface hauls
taken at night will yield many times the numbers of plankters found
in surface hauls in the same place taken by day. The qualitative
composition of day and night collections will be different, since
different species, or even different ages or sizes of the same species,
may differ in migratory habit. Hjort obtained large catches of
copepods in surface hauls at night, although during the day, they
were taken only at 70 meters. Much greater vertical movements are
2 / 6 This Great and Wide Sea
eported. It is noteworthy that plankters that engage in extensive
liurnal vertical migrations, undergo in a period of ten or twelve
lours changes of pressure equivalent to several atmospheres.
Whether or not we deal in any particular case with plankton pop-
ilations that have some powers of locomotion, we do find every-
where that communities are always in process of change. At any
jpot changes may occur in the kinds of plants or animals that are
present and in the relative and absolute numbers of the several spe-
aes. There are seasonal changes, as the spawn of crabs, worms,
tarfishes, mollusks, and other benthonic animals rise to constitute
or a time prominent elements of the drifting populations. Finally,
imong the biological conditions causing changes in plankton popula-
ions, is the work of predators. Increase of algae promotes the
growth and reproduction of small animal plankters, which, in turn,
ire devoured by larger predators. Whole populations of particular
)rganisms may be greatly depleted or nearly wiped out in succession,
rlence there are notable cyclical changes in the plankton picture in
my one region.
A distinctive feature of the conditions of life for marine plankton
ierives from the dynamic nature of the environment. Marine plank-
ers live generally in a moving home, whether the movements are
he rhythmic and reversible tidal currents of harbors or the pro-
gressive currents, drifts, and eddies of the wide ocean. The imme-
liate home environment is without fixed geographic location: the
:everal populations are "on the move" but without ability in them-
lelves to govern their geographic distribution. Only at first glance
:an this difference seem insignificant. Assuming that a copepod
vere carried all the way across Lake Superior, it would have trav-
elled several hundred miles, but it would have encountered no nota-
>le change of conditions of life. Imagine, on the other hand, a cope-
x)d in die Gulf Stream, making 24 miles, more or less, each day,
:ome 700 miles a month, and perhaps several thousand miles in the
:ourse of its whole life. If not devoured on the way, it could have
Dassed from one set of conditions of light, temperature, and salinity
o another and significantly different environment. It might, of
:ourse, have been thrown out into an eddy, or it might have lived
>nly so long as conditions were not greatly changed; but at least,
he hazards of change were there.
Since not only the copepod, but also nearly everything surround-
urr]img Lije: JL toe
ing the copepod would be traveling at the same rate, the change ir
geographic location could not be perceived if the copepod had per-
ception. We do not feel the daily movement of rotation of our
selves, our homes, and our animal and plant associates around th*
axis of the earth at a rate something less than 1,000 miles per hour oj
our even more rapid movement in the orbit of the earth around the
sun. As we go on our diurnal and annual pilgrimages we encountei
changes in conditions of light and temperature, if not of chemica
environment, but we are regularly returned to the old position!
relative to the sun. This brings up the question, to what extent doe
the return occur with ccpepods, diatoms, pteropods, and worms
and, if it does, by what paths are the circuits completed?
Let us trace our touring copepod a little farther, with the cleaj
understanding that the story is hypothetical, although having a logi
cal basis, and that we follow it only for the purpose of raising '<
question. If, after 3,000 miles of travel, this copepod had offspring
the members of the next generation, fortunate enough to complete
a life span of six months might well, at the end, be over 7,000 mile
from the parental natal spot. So, from generation to generation, th<
log of travel would grow in mileage at various rates but mounting
eventually to astronomical figures, under any assumption as to rat<
of movement. Conceivably, there might be a return to the origina
home; yet, if this were the case, the successive generations wouk
have endured gradual but presumably significant changes in th<
conditions of life as regards temperature, light, and salinity. If ther<
should be no return, then the question arises: How is the origina
stock of a Gulf Stream or a Peru Current maintained? If everyon<
in Florida moved to the Carolinas, then on to Virginia, New Jersey
etc., who would start the new migrant populations in Florida?
Exactly the same problem arises if we assume a drift of only j
fraction of a mile an hour. There seems to be nothing seriouslj
wrong with our assumptions, except that they lead to questions tha
may not now be definitely answerable. A hypothetical answe
would be that at least a "nest egg" of all such planktonic species oc
curs practically universally and has only to encounter the right se
of conditions to propagate actively enough to make the large popu
lations that are observed in particular regions. 11 Another possibl
ii. But Schiitt, from the Plankton Expedition, concluded that different oceai
currents are inhabited by different types of floating plants (Sverdrup, et. /., op. cit
p. 701).
2 1 8 This Great and Wide Sea
answer, and a more likely one, would put the enduring brood stock,
for plankton species of oceanic currents, in lateral eddies relatively
fixed geographically. The populations conveyed to other regions in
far-reaching streams would then represent loss by drainage from the
original brood stock in a relatively fixed home, upon which always
the perpetuation of the species would depend. It is well known in-
deed that eddies adjacent to oceanic currents receive animate contri-
butions from the currents, some of which are incapable of contin-
uing life indefinitely under the new conditions, while others repro-
duce an endemic stock. The reverse may be equally true that the
populations of currents are dependent upon the eddies, some of
which are small and some of oceanic proportions. There are many
significant unsolved problems of plankton geography, and many of
these have to do with the fact that marine plankters inhabit a mov-
ing rather than a stationary medium that the sea is a dynamic
body of water, not a static one.
CHAPTER 16
Lsompo6itlon, of tke
SINCE ALL OF THE GENERAL TYPES OF LIFE ARE REPRESENTED IN
the ocean and some only there, and since virtually all ani-
mals in the sea enter into the composition of the plankton
at some stage of life, any complete account of the plankton 1 could
only be compassed in a shelf of volumes. Some suggestion of the
diversity and nature of plankters and of their significance to the
larger animals may be gained from a brief review of the several
groups of animals.
Many representatives of the Protozoa have already been men-
tioned in the consideration of algae. The microorganisms that form
a bridge between plant and animal kingdoms make impossible any
sharp line of division. The Foraminifera, typified by Globigerina
bulloides with external shells composed chiefly of carbonate of lime,
have already been mentioned as agents in the formation of globi-
gerina ooze. This occupies a large part of the bottom of the ocean
and, in places, at least, forms a rich feeding ground for benthonic
animals. In a calm sea globigerina may be found at the surface, the
larger ones barely visible to the naked eye. Since the calcareous
shells are relatively soluble, the deposits in which they predominate
are found only at moderate depths. The richest and most diverse
populations are said to be found in warmer waters; the number of
individuals and of species diminishes as one goes away from the
tropics. This is in partial contrast to the distribution of some other
i. Those particularly interested should read such books as Steuer's Plankton-
ktmde or Ekman's Tiergeographie des Meeres or the pertinent chapters in Murray
and Hjort, Sverdrup, Johnson, and Fleming, and other general works on oceanog-
raphy.
219
22 o This Great and Wide Sea
organisms, for the more general rule is: many more kinds in tropical
regions, but denser populations in colder waters.
Silicious shells of the Radiolaria (internal shells it may be recalled,
FIGURE 14. The protozoan, Globigerma bulloides D'Orbigny.
(from Murray and Hjort). This minute animal with house of cal-
careous and organic matter and fine spicules is important in the plank-
ton, and its skeleton gives the name to the type of bottom deposits
called globigerina ooze.
p. 1 1 7) are less soluble than those of Foraminifera and are therefore
characteristic of oozes that underlie deeper waters. Among the
Radiolaria, with their strikingly beautiful shells, there is great diver-
sity of form and of distribution by depth and latitude. Some species
have been found only in abyssal depths under the equator, others
only in the Antarctic. Those taken by the "Valdivia" expedition,
were found to fall into groups distinguished by the depths at which
the species lived. There were species of the uppermost layer of
water, species of a higher intermediate layer, 50-400 meters, and
others of a lower intermediate layer, 400-1,000 meters; there were
also abyssal species living chiefly at 1,500-5,000 meters.
The flagellate Peridineae, with shells of organic material, have
been mentioned before as occurring sometimes in such enormous
numbers as to cause "red seas." They are most important as food of
salpas and other plankters that feed by filtering water. Their shells
decompose too readily to figure in the formation of bottom deposits*
The cttiate protozoa are sometimes represented abundantly in the
plankton, particularly in coastal waters, by the tintinnoids, which
also have shells secreted about their bodies and often carry, attached
to the shells, minute solid objects such as parts of the shells of other
protozoa and algae. The highly important flagellate coccolitho-
phores have already been discussed (p. 205).
The large cystoflagellate Noctiluca of coastal waters should be
mentioned, if only for its brilliant luminescence. In certain inshore
waters, as at Beaufort, North Carolina, Noctiluca may at times
occur in such density of population that any moving body in
the water, whether fish, boat, or human bather, is brilliantly out-
lined in light by the flashes of the protozoa with which all parts of
the body-surface are making continuous contact. Most impressive
testimony to the capacity of some organisms for multiplication and
concentration in the sea is that of Allen 2 , who found Noctiluca
scmtillans in a concentration of three million to a liter in water as
dipped from the surface in the Gulf of California. Since this well-
named "scintillating night light" is macroscopic rather than micro-
scopic in size (it may attain a diameter of one millimeter), three mil-
lion of them in one million cubic millimeters would seem to leave
little room for water!
2. Winfred E. Allen "The Primary Food Supply of the Sea," Quarterly Review
of Biology, 7X, 161-180.
222 This Great and Wide Sea
The sponges (Porifera) are not significant in the plankton. The
colonial masses live attached on the bottom or other solid objects and
grow vegetatively. Yet they do form eggs that, when fertilized,
develop into free-swimming planktonic larvae.
The Coelenterata, on the other hand, are very prominent and
some are among the largest animals of the macroplankton. In this
group of jellyfishes, polyps, corals, sea anemones, and siphonophores,
there is remarkable diversity of form and habit. Typically, a coelen-
terate is a small elongate sack with a single opening surrounded by a
circlet of slender tentacles provided with minute stingers. This is
the polyp form. Attached to solid objects, they grow vegetatively
by budding and also sexually by fertilized eggs that develop into
free-swimming ciliated larvae. Commonly the eggs and sperm are
not produced by a polyp itself but by a medusa, or jelly fish, which
has arisen as a specialized bud that becomes free to swim in the water.
The bulk of the body of the jellyfish has the form of a bell margined
by the tentacles; suspended from the center of the bell is a clapper-
like portion having the mouth at its free end. Nearly the whole of
the body, bell and clapper, is a non-living, translucent, gelatinous
supporting material, sandwiched between very thin layers of living
cells covering the outside and lining the internal chambers. Swim-
ming with apparent aimlessness by rhythmic contractions of the
bell, the medusa makes a prominent part of the plankton. Some are
of immense size as much as 2 meters in diameter, and with ten-
tacles 35 meters or more in length (much more than 100 feet.)
We have, then, in many coelenterates, an "alternation of genera-
tions," with a sedentary polyp form, reproducing by budding, and a
free-swimming medusa form, originating as a particular sort of bud,
and reproducing through fertilized eggs that grow into new polyps.
In different groups there are various modifications of this cycle: in
some the medusa never separates from the attached colony, but
simply liberates the fertilized eggs; in others the eggs set free from
the free-living medusa develop directly into medusae, and there is no
sedentary asexual stage; and there are other modifications. Hence we
have medusae that are temporary members of the plankton mero-
plankters; (see p. 212) appearing seasonally as stages in the life his-
tory of benthonic hydroids, and medusae whose immediate ances-
tors and descendants live always adrift holoplankters. Not only
G L Clarke
PL 16. The Clarke quantitative plankton sampler ready to be hauled.
CoitM Coker
CoitM Coker
H7pp^r ///, PL 17. Attaching a meter net to the towing cable for collecting
plankton. Upper right, PL 18. Towing a plankton net near the surface.
Lower left, PL 19. Hauling in the quantitative plankton net. Lower rtgbt,
PL 20. A heavy catch in the plankton net.
US Fish and Wild lafe Service
Carnegie Institution of Washington
Courtesy Woods Hole Oceaaographic Insatuaoa
PL 21. Sea Spider, three britde-stars and various trades on sea floor. Photo
by D. M. Owen, south of Cape Cod in 1,000 fathoms.
Above, PI. 22. Living coral, Acropora muricata L. Below, PL 23. Its
cleaned skeleton.
Dr Waldo Schmitt and U S. National Museum
vi&-!f^i!
' V i* W *
Varieties of plankton catch. Upper left, PL 24. Chiefly diatoms. Upper
right, PL 25. Almost exclusively one species of copepod, Calanus fin-
marchtcits. Lower left, PL 26. Chiefly a dmoflagellate, Ceratium trtpos.
Lower rtght, PL 27. Chiefly a radiolarian protozoan.
U S Fish and Wild Life Service
The University of California, La Jolk
PL 28. The development of self-contained underwater breathing appara-
tus (SCUBA) has opened up a new world to the marine scientists. A diver
on Capricorn Expedition examines coral beds of the tropical Pacific. The
two-ship expedition was earned out by The University of California's
Scripps Institution of Oceanography in 1952-53-
'**"
** . *.
Waldo Schmit
Waldo Schmit
Left, PL 29. Living sponge attached to a shell. *M PL 30. The cleaned
skeleton of same.
PL 31. Spider crab, Perditbodes camtsckica (Tilesins).
U S. National Museum
V
~
Composition of the Plankton 223
in waters along the coasts, but also in the central areas of the great
oceans, medusae often display themselves in such numbers as to
arrest the attention of the most casual observer.
In some coelenterates the colonial polyps secrete about their bod-
ies a calcareous exoskeleton to form the elaborate coral masses, a
few of which are beautifully colored and commercially valuable.
Certain kinds of coral grow vegetatively to such an extent that
whole islands and reefs are built by them. Thus the tiny living
polyps of coral are actually geologic agents of no little significance.
Corals, too, liberate fertilized eggs which swim freely for a period of
days or even weeks; hence corals also enter into the plankton, be-
fore settling to the bottom to make the beginnings of new colonies.
The same is true of the sea anemones which, likewise, have no me-
dusa stage. Hence we have, as important elements in the plankton,
not only the large and small jellyfishes, but also the minute larvae of
all kinds of coelenterates.
There is yet another type of coelenterate in which the polypoid
forms are attached, not to foreign objects, but to large gas-filled
floats of their own manufacture. These are the siphonophores, of
which the "Portuguese man-of-war," Physalia, and the "by-the-
wind sailor," Velella, are representatives. The large floats of
Physalia, several inches in length, and half as high, display beautiful
translucent iridescent tints, but they are to be dreaded by the swim-
mer, because the long dangling streamers, which may be 30 or 40
feet in length, carry quantities of the pernicious stinging organs.
Both Physalia and Velella are surface animals and restricted, except
for strays, to the warmer waters. Other and deep-sea kinds, of
which Physophora is an example, are provided with numerous swim-
ming-bells.
The comb jellies or sea walnuts, Ctenophora, with jellylike bodies
and no sessile stage, were once classed with the Coelenterates, but
they are fundamentally distinct. They may be quite prominent in
the plankton of both the surface and the deep water. Their young
are also free swimming, of course.
The flatworms, or Platyhelminthes, are not generally planktonic
as adults; yet, if the nemerteans, or ribbon worms, are to be classed
with them, they have many planktonic species. One of the ribbon
worms (not planktonic) has the distinction of being the longest of
This Great and Wide Sea
all invertebrate animals about 75 feet, nearly equalling in length
the longest of all animals (a whale), but only a thread in diameter.
A nemertean of leaflike form and pelagic habit has been found at
i, 800 fathoms.
Although the round worms, or Nemathebninthes, are predomi-
nantly parasitic or benthonic, there are planktonic species. The
wheelworms or rotifers (wheel-bearers), or Trochelminthes, as
we have said, are almost exclusively inhabitants of fresh water, yet
a few marine species may appear in great numbers in neritic plank-
ton. The moss animalicules, Bryozoa, chiefly conspicuous as brushy
tufts on solid objects, have larvae in the plankton, as do the peculiar
"worms" of the small phylum Phoronidea, and the Brachiopoda,
those now fairly rare or localized, sedentary, shelled animals, which,
paleontologists tell us, were in ancient times the dominant animals of
the bottom communities.
The Chaetognatha (seta-jaws) make another very small phylum,
comprising the arrow- worms or glass-worms, which are highly im-
portant elements in the plankton. They are peculiarly dainty, trans-
lucent, swift-moving animals of slender arrow form. Sagitta is found
in all oceans: some species are widely distributed, some occur only in
warm waters, others in cold Arctic and boreal waters. They are most
conspicuous in surface catches, but certain species are taken only in
deep hauls, and are bright red in color. Generally rather small, the
maximum length is about 3 inches. The distribution of sagittae has
been the subject of a good deal of study, since they serve some-
times as indicators of the origin of water masses, where mixing
occurs.
The segmented worms, Annelida, are mostly of bottom-living
habit, some free, some in burrows, and some in calcareous or fibrous
tubes of various forms. The pear-shaped larval stages, or trocho-
phores, may be very prominent in the plankton of coastal waters at
the breeding rimes of the several abundant species. Remarkable
among all zoological phenomena is the breeding behavior of the
palolo worm. The adults live on the bottom, until the time of breed-
ing approaches; then a part of the body, carrying the reproductive
cells, is thrown off from the remainder. These breeding segments
of the body rise to the surface in countless numbers to swim while
the eggs are in process of liberation. Most remarkable of all is the
Composition of the Plankton 225
fact that the appearance of the palolos occurs each year with almost
clock-like regularity. The very day may be anticipated and the
natives of the Samoan, Fiji, and other islands, go out to net them in
quantities, for they are highly esteemed as food. The genus Tomop-
teris comprises annelids of general planktonic habit, including some
beautiful species of the warm surface waters, others of cold surface
waters and some from deep water. Examples taken in deep water
6f the Antarctic are described as being "as long as the finger, trans-
parent and with rose-colored feet" (platelike appendages on the
sides of the body).
In the phylum Echinodermata are the starfishes, sea urchins, brit-
tle stars, sea cucumbers, and sea lilies. All are benthonic as adults,
creeping, burrowing, or anchored in the bottom; but their larval
stages are often prominent in the coastal plankton, and very differ-
ent in appearance from the adults. To the student of the plankton,
the group has this special interest: it was the search for possible
Free-swimming stages of echinoderms that led to the use of the
plankton net and to the real discovery of the plankton world.
The Mollusca command special attention whether we deal with
Denthos, nekton, or plankton. Most prominent in the bottom fauna
are oysters, clams, scallops, limpets, conchs, snails, tusk shells, devil-
fishes, and others. In the division of swimming animals, we find the
jquids playing a great part in surface and deep waters. In the plank-
ton we have the larvae of all of these, and, in addition, the pteropods
md heteropods, which are relatives of the snails (gastropods). The
solid fleshy or muscular part of a mollusk, the so-called "foot," is
capable of most diverse modifications for crawling, seizing, or swim-
ning. In the snails it is a serviceable foot for creeping; in most bi-
valves it has become a hatchet-shaped blade for burrowing; in the
quid and devilfish, the nautilus and the argonaut, it has the form
)f a head with eight or ten long sucker-equipped arms used for seiz-
ng prey or for walking; in the pteropods and heteropods it is hardly
nore than a pair of light paddles for swimming.
The free-swimming mollusca may have light, small, spiral shells
)f pinhead size or long, slender, conical shells. They live more gen-
erally in warmer waters and, therefore, at no great depth. Pteropod
>oze, characterized by the abundance of pteropod shells, is "limited
o the tropical and subtropical regions." Certain kinds, however,
22 6 This Great and Wide Sea
occur in vast numbers in Arctic waters, even around Greenland and
Spitsbergen. Some species are reported from the Atlantic, Pacific,
and Indian oceans. Of chief interest is one known as whale's feed,
Clione limacina, which is found in polar waters, "swimming among
the ice floes." Individually quite small (or something over an inch
in length) , they occur in such numbers, that, strained from the water
by the whalebone sieves of the right whales, they afford rich
nourishment for these largest of all animals.
FIGURE 15. Free-swimming pteropod mollusks. (a) Clione limacina
Phipps (from Murray and Hjort, after Vanhoffen). (b) Cicuierina col-
vnmella Rang (from Cambridge Natural History, after Souleyet). (c)
Cresis wrgula Rang (from Cambridge Natural History, after Souleyet).
Among the mollusks we have also the largest of the animals with-
out backbones, The class Cephalopoda* comprises devilfishes, paper
nautilus, squid, and pearly nautilus. Except for the squid, these live
mainly on the bottom. The eight-armed "devilfishes" may attain a
length of 1 6 feet. Lurking in grottoes or other retreats, the mouths
of which may be littered with the skeletons of their victims, these
animals have excited the imagination of several writers, notably
Victor Hugo. The thrill of the titanic struggles between man and
octopus narrated in "Toilers of the Sea" need not be greatly lessened
by knowledge that the story is fiction and not well-founded natural
history. Nevertheless, a sizable octopus does not offer a pleasant en-
counter for a diver. The female argonaut, paper-sailor or paper-
3. Cephalopoda, head-foot, that is to say, the "foot" (of other mollusks) forms
die head of these.
Composition of the Plankton 227
autilus, has a beautiful, delicate shell which is f ormed as an "egg-
test" by two of its eight arms, and is not at all comparable to the
tails of other mollusks. They come to the surface at spawning time,
ut, contrary to old beliefs, they do not use the shell as a sail. They
wim, like other cephalopods by pumping water out of the mantle
avity (see p. 290, below). Thus they are benthonic and, at times,
ektonic or planktonic. The males are tiny "about an inch in length,
eing sometimes scarce a tenth of the size of a female." 4
Far more numerous than any other cephalopods are the ten-armed
quids, which include the largest of invertebrates up to 50 feet or
lore in length. These will best be considered in a following chapter
n nekton.
The pearly nautilus or chambered nautilus, which creeps over
tie bottom in relatively shallow water, and also swims by jet propul-
on, is generally best known for its beautiful chambered shells and
tie novelties made from it and for its established place in literature.
Tie "tentacles" of the pearly nautilus are without suckers and are
umerous about ninety.
Finally among the invertebrates, we have the most important of
11 plankters in the phylum Arthropoda, or animals with externally-
ointed limbs. The joints of limbs and body are external because the
/hole body is encased in a continuous outside skeleton to which the
luscles of movement have their attachments. This integument is
ot interrupted for joints, which occur only where, in rings around
be body or limbs, the skeletal armor remains flexible enough to
lermit freedom of movement. In this great 'branch of the animal
ingdom are the insects, spiders, and centipedes, which, together,
provide many more kinds of animals than are found in all the other
ranches of the animal kingdom combined. The insects are almost
vanting in the sea, although some midge and caddis larvae occur on
he bottom in coastal waters, and a single kind of water strider,
-lalobates, runs over the surface in tropical regions of the Atlantic
nd the Pacific, ranging even far from land. The spider and mites
:eep to land and fresh water, but some mites are marine, and distant
elatives, such as the long crab, or horse shoe crab (Limulus), and
he small lanky pycnogonids, live on the bottom or among the
gardens of plants or animals in waters near the shores.
4. Riverside Natural Htstorv* I. sec. 2. 370.
228 This Great and Wide Sea
The jointed-limbed animals of the class Crustacea, on the other
hand, are primarily marine. A good many (crayfish, copepods,
cladocera, and others) have become adapted to life in fresh waters,
and a very few to life on land (land crabs and pill bugs) . The great
majority live only in the sea. "No class of multiceMar animals in
the ocean," says Hjort, "is represented by anything like such count-
less forms and individuals as that of the Crustaceans." Haeckel com-
pared the part played by Crustacea in the sea to that of the insects on
land. We may conveniently distinguish the smaller Entomostraca,
mostly holoplanktonic, and the generally larger Malacostraca. Most
of the latter subclass live on the bottom as adults, but a few kinds are
important permanently free-swimming Crustacea. Of the Mala-
costraca we are concerned particularly with the Mysida, the
euphausiids, the amphipods, and the decapods.
Everyone is familiar with some of the larger decapods (ten-
legged) crabs, lobsters, crayfish, and shrimp. Most of these crawl
on the bottom, but the shrimp are active swimmers, especially the
larger ones, and will call for some attention in the chapter on nekton.
The larvae of all, which may be entirely unlike the parent form, ap-
pear abundantly, but seasonally and briefly, in the neritic plankton.
Some pelagic amphipods may occur abundantly in the upper waters
of warm regions, but others are found in deep water and at least two
species are important in very cold, even icy, waters. A particularly
interesting group of species taken in plankton catches makes homes
in the translucent empty barrellike coats of salpas (see p. 235, be-
low.) The primitive mysids live in cold water near or on the bottom.
Most noteworthy for us are the somewhat shrimp like euphau-
siids, 5 the "kril" of fishermen, which are highly important in the
plankton of colder northern and southern waters; they sometimes
constitute nearly the whole catch in the plankton nets. They may be
an inch or two in length. Generally they are colorless and trans-
parent, but some are conspicuously red in color. Brilliant light or-
gans are characteristic. TTiey may live near the bottom but rise to
the surface for spawning in great swarms. Sometimes one may see
the surface of the ocean blood-red with the dense shoals of small
shrimp, affording rich nourishment for fish and birds. They are a
favorite food of whalebone whales. It was found that in the cold
5. Once grouped with some other families in the order Schizopoda, but now
M^M.JoJ ^ 1 1 T_^_J ! T*. J-
Composition of the Plankton 229
vaters of Davis Strait, the maximum number of whales occured in
list the regions where the greatest number of euphausiid Crustacea
vere found.
The Entomostraca comprises the cladocera, the copepods, the
>stracods and the cirripedes or barnacles. The cladocera are nearly
Iways prominent in fresh-water plankton but only a very few
genera occur in the sea, being important in neritic waters. The
stracods have a comparatively small number of species in fresh
vater, chiefly along the bottom, but are highly developed in the
>ceans, where they rank next to the copepods, and occur from the
urface to great depths. Some are highly luminescent. There are
\xcric and Antarctic species, and at least one that occurs in upper
vaters "all the way from the Norwegian Sea to the Antarctic." A
totable abyssal species is the giant ostracod that may have a length
>f one centimeter and is found in the Atlantic, Pacific, and Indian
>ceans.
FIGURE 16. Giant ostracod, Gi-
gantocypris agassizii G. W. Mul-
ler (from Murray and Hjort).
Barnacles are the only Crustacea (other than parasitic species)
hat, as adults, give up all freedom of movement from place to place
nd live attached to solid objects. 6 The immobility of a "barnacle"
s proverbial. Barnacles are, of course, well known as pests on the
6. The burrowing isopods, Limnoria and others, so destructive to unprotected
/ood structures, live relatively sedentary lives m the narrow self-made homes; but
tiey are not attached or incapable of some locomotion.
23 o This Great and Wide Sea
bottoms of ships. In development they go through a remarkable
metamorphosis from the fertilized egg to the sedentary adult, and
mostly while drifting or swimming aimlessly in the plankton. When
liberated from the eggshell, they have minute triangular bodies with
a long "tail" and three pairs of limbs: this is the nauplms. With suc-
cessive molts they acquire more appendages through several stages
of nauplius and metanauplius. At the same time they undergo
change of form until they appear like small ostracods with body
enclosed in a bivalved shell. After swimming in this form for a short
while, they attach "head-to" on some favorable object, cement them-
selves firmly, and undergo further metamorphosis into the adult
barnacle. Some have long flexible "necks," bearing at the free end
the body enclosed in a white shell; these are the well-known "goose
barnacles." Others, the "acorn barnacles," are strictly sessile, the
body enclosed in a cup-shaped shell, with its flat base cemented to
the substratum. Barnacles are among the most numerous of ben-
thonic animals. Prominence of larval stages in the plankton depends
upon breeding seasons, since the duration of free-swimming life is
short. Some species of warm-water barnacles are widely distributed
in the several oceans.
It is the copepods, that almost everywhere and all the time, are im-
porta 
