DEEP-SEA RESEARCH Supplement toVolume 3
Papers in Marine Biology and Oceanography
Dedicated to
HENRY BRYANT B I G E L O W
By His Former Students and Associates
on the occasion of
The Twenty-fifth Anniversary of the Founding
of The Woods Hole Oceanographic Institution
1955
Distributed with the compliments of
the Woods Hole Oceanographic Institution
PERGAMON PRESS
London & New York I 955
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DEEP-SEA RESEARCH ^
Supplement to Volume 3
Papers in Marine Biology
/
and Oceanography
Dedicated to HENRY BRYANT B I G E L O W
By His Former Students and Associates
on the occasion of
The Twenty-fifth Anniversary of the Founding
of The Woods Hole Oceanographic Institution
1955
PERGAMON PRESS
London & New York 1955
Published by Pergamon Press Ltd., 4 & 5 Fitzroy Square, London, W.L and Pergamon Press Inc., 122 East 55th Street, New York 22, N. Y.
Printed in Great Britain by Page Bros. (Norwich) Ltd., Norwich
Publication of this volume has been aided by a gram tVom the Woods Hole Oceano- GRAPHic Institution. Individual papers have been supported by the Johannes Schmidt Foundation for Marine Research, by the Agnes Anderson Fund of the University of Washington, by Rutgers University and by the University of Florida. Contributions have been received from the following individuals who wish to honour
HENRY BRYANT BIGELOW
Charles Francis Adams Jr.
Mabel B. Agassiz
W. R. G. Atkins
Eric G. Ball
Charlotte H. Bartol
Robert P. Bellows
Margaret D. Bigelow
Trygve Braarud
Mary and Lewis Bremer
Anton Fr. Bruun
W. Sohier Bryant
Dean F. Bumpus
Nancy and Samuel Cabot
Cornelia L. Carey
J. N. Carruthers
Fenner a. Chace Jr.
Ruth and Richard Chute
George L. Clarke
Stanley Cobb
L. O. Colbert
John W. Condon
Charles A. Coolidge
Leslie H. N. Cooper
Elisabeth Deichmann
Tilly Edinger
Gardner Emmons
Marie and Charles J. Fish
Alexander Forbes
Horace S. Ford
Michael Graham
H. B. Hachey
Jan Hahn
Julia A. Hallowell
Alistair C. Hardy
Frank A. Howard
Georgina and Llewellyn Howland
A. G. Huntsman
Columbus O'D. Iselin
Bostwick H. Ketchum
Mary and Alfred Kidder II
Ellen Knudsen Poul M. Kramp Milford R. Lawrence Benjamin B. Leavitt Lois C. Lillick Charles P. Lyman Elizabeth C. Lyman Jessie Bell Mackenzie Arnaud C. Marts Shefna M. Marshall Ernst Mayr Dorothea F. Merriman William Jason Mixter A. W. H. Needler Margaret S. Nicodemus A. P. Orr Frances L. Parker Louisa B. Parker Hans Pettersson Helen F. Phillips John E. G. Raymont Alfred C. Redfield
LaWRASON RlGGS
Gordon A. Riley
Alfred S. Romer
Johan T. Ruud
Barbara and William E. Schevill
Ingeborg Schmidt
Waldo L. Schmitt
William C. Schroedfr
Mary Sears
O. E. Sette
Harlow Shapley
Virginia and George C. Shattuck
Henry L. Shattuck
Edward H. Smith
Virginia Walker Smith
Floyd M. Soule
Ragner Sparck
Athelstan F. Spilhaus
EiNAR Steemann Nielsen
Henry C. Stetson
Raymond Stevens
GuDRUN and Harald U. Sverdrup
A. Vedel Taning Thomas G. Thompson Alice Thorndike
GUNNAR THORSON
A. Knyvett Totton Theodor Von Brand George Wald Lionel A. Walford
Talbot H. Waterman Edmond E. Watson Francis C. Welch George C. Whiteley Jr. Florence H. Whitman H. B. Whittington Susan J. Williams R. S. Wimpenny
0. WiNGE
Mary A. Winsor Alfred H. Woodcock Donald J. Zinn
VI
CONTENTS
page FOREWORD xi
BIBLIOGRAPHY OF HENRY BRYANT BIGELOW xviii
Michael Graham: Effect of trawling on animals of the sea bed I
A. C. Hardy: A further example of the patchiness of plankton distribution 7
Mary Alys Plunkett and Norris W. Rakestraw: Dissolved organic matter
in the sea - 12
Selman a. Waksman: Marine bacteria: recollections and problems 15
Thomas G. Thompson and Tsaihwa J. Chow : The strontium-calcium atom ratio in carbonate-secreting marine organisms 20
Jean Brouardel and Louis Fage: Variation, en mer, de la teneur en oxygene dissous au proche voisinage des sediments 40
Fred B Phleger: Foraminiferal faunas in cores offshore from the Mississippi Delta 45
Pamela G. Jenkins: Seasonal changes in the phytoplankton as indicated by spectrophotometric chlorophyll estimations 1952-53 58
H. B. Hachey: Water replacements and their significance to a fishery 68
Daniel and Mary Merriman: Sir C. Wyville Thomson's correspondence on
the " Challenger " fishes 74
Dean F. Bumpus and E. Lowe Pierce: Hydrography and the distribution o^ chaetognaths over the continental shelf off North Carolina 92
S. M. Marshall and A. P. Orr: Experimental feeding of the copepod Ca/fl«w.sy7/;mfl/-c/7/rw5 (Gunner) on phytoplankton cultures labelled with radio- active carbon (^^C) ' •*-'
Alfred C. Redfield: The hydrography of the Gulf of Venezuela 115
H. Boschma: The specific characters of the coral Stylaster roseus 134
vii
Contents {com.) Page
C. E. Lucas: External metabolites in the sea 139
P. L. Kramp: a revision of Ernst Haeckel's determinations of a collection
of Medusae belonging to the Zoological Museum of Copenhagen 149
J. N. Carruthers: Some very simple devices for various oceanographical uses 169
J. E. G. Raymont: The fauna of an inter-tidal mud flat 178
Frances L. Parker: Distribution of planktonic Foraminifera in some Mediter- ranean sediments 204
L. H. N. Cooper: Hypotheses connecting fluctuations in Arctic climate with
biological productivity of the English Channel . 212
Gordon A. Riley: Review of the oceanography of Long Island Sound 224
A. K. Totton: Development and metamorphosis of the larva of Agalma
elegans (Sars) (Siphonophora Physonectae) 239
Charles J. Fish: Observations on the biology of Microsetella norvegica 242
R. S. Wimpenny: The production of Lisa ramada (Risso) in Lake Mariut, Egypt 250
JoHAN T. Ruud: The mortality rates of Antarctic fin whale stocks 257
Alfred Sherwood Romer: Fish origins — fresh or salt water? 261
E. Steemann Nielsen: The production of antibiotics by plankton algae and
its effect upon bacterial activities in the sea 281
John H. Welsh : On the nature and action of coelenterate toxins 287
Henry C. Stetson: Patterns of deposition at the continental margin 298
Ruth D. Turner : Scaphopods of the Atlantis dredgings in the Western Atlantic with a catalogue of the Scaphopod types in the Museum of Com- parative Zoology 309
A. G. Huntsman: Effect of freshets on Passamoquoddy plankton 321
R. B. Montgomery: Characteristics of surface water at Weather Ship J. 331
Hans Pettersson: Manganese nodules and oceanic radium 335
BosTWiCK H. Ketchum and D. Jean Keen: The accumulation of river water
over the continental shelf between Cape Cod and Chesapeake Bay 346
viii
Contents (cont.) Page
William C. Schroeder: Report on ihe results of exploratory otter-trawling along the continental shelf and slope between Nova Scotia and Virginia during the summers of 1952 and 1953 358
Georg WiJST : Stromgeschwindigkeiten im Tiefen- und Bodenwasser des Atlantischen Ozeans auf Grund dynamischer der Meteor- Profile der Deutschen Atlantischen Expedition 1925 27 373
Wm. C. Herrington : U.S. participation in conservation of international fishery resources 398
Donald R. Griffin; Hearing and acoustic orientation in marine animals 406
Anton Fr. Bruun and A. Kiilerich: Characteristics of the water-masses of
the Philippine, Kermadec, and Tonga Trenches 413
Talbot H. Waterman: Polarization of scattered sunlight in deep water 426
Walter Hansen : Elevation of sea level caused by wind in a rectangular channel 435
A. Vedel Taning: On the breeding areas of the Swordfish {Xiphias) 438
W. T. Edmonson: Factors effecting productivity in fertilized salt water 451
A. Defant: Die Ausbreitung des Mittelmeerwassers in Nordatlantischen Ozean 465
Lionel A. Walford: New directions in fishery research 471
C. O'D. Iselin: Coastal currents and the fisheries 474
Trygve Braarud: Electron microscopy in oceanographic research 479
John B. Tait: Long-term trends and changes in the hydrography oi the Faroe-Shetland Channel region . 48-
IX
XI
FOREWORD
The papers collected in this volume have been prepared by the students, disciples and friends of Henry Bryant Bigelow, as a testimonial not only of our personal affection but to honor him for his many contributions to the advancement of oceano- graphy.
A half century ago when Alexander Agassiz set sail for the Maldive Islands with Henry Bigelow as his assistant, oceanography in America was an interest promoted from time to time through individual initiative and, when in hne with their primary duties, by appropriate governmental agencies. Today, as his latest monograph on fishes comes off the press, oceanography is a fully recognized division of science, complete with standard textbook and special journals. Its work is instru- mented by half a dozen full-scale laboratories and research vessels operated by university departments or independently, and distributed equably along our coast. More important, it is a science in which a new viewpoint has developed and new vistas have opened. Of course, this has been the work of many men, but in the United States Henry Bigelovv' more than any other has provided the wise leadership which has insured success.
In the preface to his book, " Wind Waves at Sea, Breakers and Surf" (written with W. T. Edmondson as a contribution to the World War II effort), it is stated: " We wish it expressly understood that we have made no contributions to the theory of waves. But we would not have dared to undertake the task, if we had not observed the behavior of waves at sea, from large craft and from small, in various parts of the world, under various conditions of wind and weather; or if we had not had an opportunity to watch the development of breakers — and cope with the smaller sizes — off beaches of various shapes, off rocky coastlines, and over submerged ledges ". This insistence on personal experience as a necessary prerequisite of scientific judg- ment (or any other judgment for that matter) is characteristic.
By good fortune Henry Bigelow was born into a segment of New England society in which the tradition of plain living and high thinking was graced by the fruits of Yankee enterprise. Young men were expected to receive the best of educa- tion, any natural taste for outdoor life was encouraged and intellectual ambitions were not frowned upon. Summers at Cohasset, on Massachusetts Bay, gave him an instinctive knowledge of seamanship and the things of the sea. Hunting in autumn took him to all parts of the coast and the uplands as well. In winter the mountains were explored on snowshoes, and in later life on ski; the mountains are, in fact, the true love of this oceanographcr. And in the spring there are trout in the New England brooks.
Thus he became the best-informed naturalist that one could hope to go afield with. His outdoor life is a routine, fixed by the seasons, and followed with the same insistence on knowing all that is to be known of the matter, which marks his more professional effort. Students of the " Physical Oceanography of the Gulf of Maine " note that the only period not covered by observations at sea coincide with the
xii Foreword
partridge season. One would no more expect him to be " at work " at that time than to find him missing on the day his course began at Harvard.
Henry Bigelow graduated from Harvard College, cum laude, in 1901. As a graduate student in zoology his doctoral dissertation, prepared under Professor E. L. Mark's guidance, was on the nuclear cycle of Gonionemus murbachi. Although he did not pursue cytological studies further, this was a valued experience, for from Mark he first learned the exacting requirements of scientific work. Students among us will find here the source of the discipline to which Henry Bigelow subjected us to our immediate chagrin but ultimate profit.
It was inevitable that Henry Bigelow should become a naturaHst of some sort but it was not at all clear during his student days that he would become an oceano- grapher or even a marine biologist. His first publication was on the birds of the northeast coast of Labrador, where he had gone in company with Reginald A. Daly and Merritt L. Fernald on the Brown-Harvard Expedition in the summer before his graduation. A later one was on hybrid ducks. A study of hearing in gold- fish under the guidance of Professor G. H. Parker gave him acquaintance with experimental procedures. The die was cast, however, by the opportunity to accom- pany Alexander Agassiz on the voyage to the Maldive Islands, and, later on expedi- tions to the Eastern Tropical Pacific and to the West Indies. His duty was to care for the medusae and siphonophores collected on these voyages; and thus he gained a first-hand experience and competence in the classical disciplines of taxonomy and zoogeography which occupied the first decades of his mature career. Perhaps more important, he was introduced to the universal problems of oceanography and met first-hand the detailed tasks of scientific research at sea.
In 1912 the United States' Bureau of Fisheries and the Museum of Comparative Zoology jointly undertook a general oceanographic exploration of the Gulf of Maine which continued under Henry Bigelow's direction through 1924 when the field work was terminated. These explorations resulted in the publication of three superb monographs; on the fishes, the plankton, and the hydrography of the Gulf. The preparation of the first of these, on the fishes, was far advanced when interrupted by the untimely death of W. W. Welsh who had given special attention to this phase of the work, and was completed by Bigelow at the request of the Bureau. The others are entirely his own work not only in planning and direction but in the execution at sea, in fair weather and foul, in spite of seasickness and with ships and gear far from adequate.
It is difficult to appreciate today how primitive were the resources available for this work. Thus during 1912 and 1913 reversing thermometers were accurate only to ± 0.15° C; the shortage of water bottles required repeated casts for all but the shoalest stations. Limited means were, however, more than compensated by the challenge of the unknown. He wrote:
*' Few hving zoologists have been as fortunate as were we on setting sail on the Grampus from Gloucester on our first oceanographic cruise in the Gulf of Maine on July 9, 1912, for a veritable mare incognitum lay before us, so far as its floating Ufe was concerned, though the bottom fauna can be described as fairly well-known. Not but what an extensive list of pelagic crustaceans, coelenterates and other plank- tonic animals had been recorded thence, but everything was yet to be learned as to what groups or species would prove predominant in the pelagic fauna; their relative
Foreword xiii
importance in the natural economy of the Gulf, their geographic and bathymetric variations; their seasonal successions, migrations, and annual fluctuations; their temperature affinities, whether arctic, boreal, or tropic; and whether they were oceanic or creatures of the coastal zone. We even had no idea (incredible though it may seem at this place and day) what we should probably catch when wc first lowered our tow nets into deeper strata of Massachusetts Bay, for, so far as we could learn, tows had never previously been tried more than a few fathoms below its surface."
The outcome is that the Gulf of Maine is perhaps the best-known body of water of comparable size in the world; certainly the region most thoroughly explored by individual effort. Except for certain aspects which he did not examine deeply, i.e., submarine geology and sea-water chemistry, a quarter century of subsequent study added only trivial details to the picture.
During this period Henry Bigelow was the trusted advisor of the government on fisheries, a trust well earned by his first-hand knowledge of fish and fishermen, and by his incisive, direct, and ever-practical approach to human problems and his understanding of the role which science can play in their solution. A number of men later to hold important posts in the fisheries service, Herrington, Nesbit, Schroeder. Sette, and Walford, were among his students at Harvard.
In 1917-19 Henry Bigelow served as Special Expert to the U.S. Shipping Board and during 1918 the work on the Gulf of Maine was interrupted while he did his trick as navigation officer on the U.S. Army transport Amphion.
Of more interest in connection with scientific developments were his connections with the International Ice Patrol, established in 1913 as a result of tragic loss of life and property due to the collision of the steamship Titanic with an iceberg. Operation of the patrol became the duty of the U.S. Coast Guard, while the scientific studies necessary for its intelhgent prosecution were directed by an interdepartmental board composed of the heads of the interested agencies. Henry Bigelow was the special consultant to the Commandant of the Coast Guard for the work of this board. During the early years of the patrol observations on plankton as well as surface tem- peratures and salinities, were used to trace the drift of water carrying icebergs into the shipping lanes; later the techniques of dynamic oceanography were introduced to estimate, on the spot, the velocity of the movement. As in the case of the fishery experts a succession of officers of the Coast Guard, Smith, Ricketts, Hoyle, and Graves, came to Cambridge to receive indoctrination in oceanography from Pro- fessor Bigelow. Largely as the result of his wisdom in guiding the scientific studies on which the work of the ice patrol is based, the hydrography of the northern seas is well understood and the patrol has been enabled to discharge its duties with intelli- gence and success.
The study of the Gulf of Maine naturally led to intimate contact with Canadians working in adjacent, and often overlapping waters. One fruit of this was a close and continuing friendship with Professor A. G. Huntsman, for many years chairman of the Biological Board of Canada; another was Bigelow's association with the North American Committee on Fishery Investigations, in which Canada, Newfound- land, France, and the United States were associated. He attended the meetings of the committee regularly between 1921 and 1933 and served as chairman at all but a few of them.
During this period Henry Bigelow formed associations with the European
xiv Foreword
leaders in oceanography, marine biology, and fisheries; such men as Johannes Schmidt, Johan Hjort, D'Arcy Thompson, Martin Knudsen, Henry Maurice and many others still living. The esteem and affection which he won from these colleagues is nicely shown by the records of the meeting of the International Council for the Exploration of the Sea, which he attended in March 1931, as a representative of the North American Committee on Fishery Investigations and where he reported on the newly-founded Woods Hole Oceanographic Institution.
" The president . . . wished to take opportunity of his being actually present to express to him the satisfaction which his visit had caused to the Council. Dr. Bige- Low . . . had attended many council meetings and had so impressed his personality on the members and experts that the Consultative Committee had passed a recom- mendation ... so important that it ought to be specially treated. In effect it contained a standing invitation to the representatives of the Woods Hole Oceanographic Institution and the North American Council on Fisheries Investigations and he might add to Dr. Bigelow personally, whatever his future might be, to attend all meetings of the Council. The Council hoped in future to have many opportunities to consult them, to learn from them and to link up its own investigations with the work done on the western side of the Atlantic."
When in 1927 a committee of the National Academy of Sciences engaged Henry Bigelow as its secretary to prepare a report on the share of the United States in a world-wide program of oceanographic research, no one could have been found so well equipped by personal experience or general ability for the task. The greater part of this report, reviewing the scope, problems, and applications of oceanography, has been made public in a book entitled " Oceanography " pubHshed under his name in 1931. It is in the unpublished sections of this report, however, in which are set forth the principles that should determine the type of organization which would best remedy the then-present handicaps to the development of oceanography, that his genius for striking directly at the heart of any question and his power of exposition are superbly displayed. It is no wonder that this report was received with confidence, or that it led to the establishment of a new institution at Woods Hole and to sub- stantial benefits to oceanography and marine biology through gifts to the Scripps Institution, the University of Washington, and the Bermuda Biological Station, And it was inevitable that the author of this report should have been asked to direct the newly-established Woods Hole Oceanographic Institution.
The principle of the ripeness of time, as applied to the appearance of prophets, is well illustrated by the history of oceanography at this period. Not only did a man emerge who had prepared himself, perhaps unwittingly, for leadership at a time when men of influence had sensed that something should be done to improve the status of marine science in America, but new ideas were in the air wafted across the ocean from a multitude of general scientific advances. Henry Bigelow, though trained in the classical tradition, was sensitive to these breezes, bold enough to grasp their implication, and wise enough to act on their meaning.
The following paragraphs, excerpted from a paper pubhshed in Science in 1930, entitled " A developing viewpoint in Oceanography ", express in Bigelow's own words the creed which was to guide his thinking.
" Oceanography has of late entered a new intellectual phase, to explain which a word of retrospect is necessary . . . Students of the history of science may well date
Foreword
XV
the birth of modern oceanography from December 21, 1872. the day when the Challenger set sail from Plymouth, England, on her memorable voyage. . . . One great deep-sea expedition led to another, and more was learned about the sea during the last thirty years of the nineteenth century than had been during the preceding three thousand. But after a time, as so often happens when some scientific discipline takes a sudden spurt, this fact-finding began to lose something of its freshness.
" Students began, in short, to feel that the mere accumulation of facts from the sea, when there is an inexhaustible supply, may actually become a bit sterile, just as
catching fish is to a sportsman where fish are too plentiful. So it was natural that
when persistence in the old methods no longer yielded startling discoveries, signs
could be seen of the approach of a period of stagnation . And oceanography
would probably be in a moribund state in America today, just as the art of sailing a square-rigger is, but for the birth of the new idea that what is really interesting in sea science is the fitting of these facts to gether, and that enough facts had accumu- lated to make the time ripe for an attempt to lift the veil that had obscured (and still obscures) any real understanding of the marvelously complex and equally marvel- ously regulated cycle of events that take place within the sea.
" The foundation for this conscious alteration in view-point, from the descriptive to the explanatory, was a growing realization . . . that the further development of sea science the keynote must be physical, chemical and biological unity. . . .
" When one picks up a fish one may be said, allegorically, to hold one of the knots in an endless web of netting of which the countless other knots represent other facts, whether of marine chemistry, physics or geology, or other animals and plants. And just as one cannot make a fish-net until one has tied all the knots in their proper positions, so one cannot hope to comprehend this web until one can see its internodes in their true relationship. This is today the conscious aim of oceanographers."
Newcomers may feel surprise that this viewpoint had novelty, for it is still our guiding principle. But therein lies meaning.
The task of assembling a staff for the new Oceanographic Institution at Woods Hole was not an easy one for there was little raw material with which to work. There were a few young men with some experience at sea, and by combing the museums of the country doubtlessly he could have assembled a respectable group of experts on special groups of marine organisms. A primary objective, however, was to give impetus to oceanographic studies in the universities, and there was the " developing viewpoint " to be fostered. He chose the bolder course of educating a new generation drawn from the universities; physical chemists, meteorologists, physiologists, bac- teriologists, whoever could be persuaded that scope for their skills could be found in studies at sea. And so the practice grew that each should make at least one short voyage at sea each season. Daily the director made his rounds, instilling little by little something of his viewpoint and wisdom on the opportunities that lay beyond the tide fine. Boldness was encouraged for we were told that an oceanographer, like a turtle, made progress only by sticking his neck out.
After ten years as Director of the Woods Hole Oceanographic Institution. Henry Bigelow asked to be relieved. The painstaking labour of creating and guiding the development of the Institution had been a sacrifice to the general welfare, made at the expense of his own natural preference for first-hand scientific investigation. He continued to guide the Institution, at first as President of the Corporation and.
xvi Foreword
now, as Chairman of the Board of Trustees, but was thereafter able to devote full time to his interests at Harvard University.
Harvard University appears to have been a bit slow in recognizing the merits of Henry Bigelow. Tradition has it that, during his first year of service as assistant in the invertebrate zoology laboratory, he discovered a student who had depicted a tunicate embellished with a complete set of neatly labelled mammalian viscera, based rather on " natural logic " than on direct observation. This intellectual dis- honesty, or stupidity, so enraged him that the unfortunate student was told off in words so monosyllabic and unambiguous that the young assistant was never again to be permitted to have contact with the students in Harvard College. While the inference is perhaps apocryphal there is no doubt that the incident is authentic.
However this may be, so far as Harvard College was concerned Henry Bigelow remained relatively obscure, serving as curator and lecturer in the Museum of Comparative Zoology up to the time of the events leading to the establishment of the Oceanographic Institution. This may have resulted from the almost complete lack of intercourse between the Museum and the Department of Zoology during the period when these institutions existed under the same roof. At all events, it was a most fortunate state of affairs, for had he been burdened with the ordinary academic routine his achievements during this period would have been impossible. It is a tribute to the liberal policies of the University at that time that such great talent was enabled to fruit without distraction.
In 1931 Henry Bigelow became a full professor at Harvard and inaugurated a course in biological oceanography. Some years later this course passed into the hands of one of his disciples. Dr. George L. Clarke, and Bigelow took over instruc- tion in invertebrate zoology. This was a task he could put his heart into for he felt that nowhere else is the wonderful diversity of form with which organisms are en- dowed so well displayed as among the invertebrates. His obligation as a professor to the students in Harvard College was to him most sacred. It is too bad they could not have had more of him. Those who benefitted most from his talents as a teacher (and taskmaster) were the succession of graduate students, both men and women, who had the privilege of working at his side in the Museum, and those whom he in- fluenced by indirection at the Oceanographic Institution or wherever else he came in contact with thinking people.
As the years passed the counsel of Henry Bigelow, early recognized for its worth in the Museum of Comparative Zoology, became more and more influential in the Department of Biology and in Harvard University at large. On reaching the ordinary age of retirement the University asked him to continue in service, a very real honour, until the mandatory age of seventy was reached. In 1946 he was granted an honorary degree by Harvard and in the same year by the University of Oslo, similar recognition having been made by Yale University some years earlier.
Among other formal honours he is the recipient of the Johannes Schmidt Medal, the Agassiz Medal awarded by the National Academy of Sciences for contributions to Oceanography, and the Bowie Medal of the American Geophysical Union in recognition of accomplishment through cooperative effort in the advancement of the geophysical sciences. He has also been elected to membership in the National Academy, the American Academy of Arts and Sciences, and the Philosophical Society, and is affiUated with the Norske Videnskaps Academy, the Royal
Foreword xvii
Geographical Society of London, the Zoological Society of London, and the Marine Biological Society of the United Kingdom.
The crowning glory of these later years is not, however, the honours which come his way. It is the stream of publications which flowed from his pen, always in association with William C. Schroeder, about fishes. This flow shows no attenua- tion with time; it reached, in fact, its spate after retirement from academic duty, as a glance at the appended bibliography will show. The handsome monographs on the Fishes of the North-western Atlantic show where his heart really lies, for he was free to follow its guidance once he had played his part in putting American Oceano- graphy on its feet.
Henry Bryant Bigelow, we greet you on this the twenty-fifth anniversary of the opening of the laboratory of the Woods Hole Oceanographic Institution. " We '" are the authors of the papers appended hereto. If they are diverse in subject matter it is because you are catholic in the interests we share in common. If they appear disconnected it is because we have individually failed to achieve the physical, chemical, and biological unity to which you have encouraged us to aspire. " We " are also many others who have been unable to contribute a paper, for reasons which you can comprehend, but who none the less wish to join in this testimonial.
You have broadened the vision, sharpened the perception, fortified the deter- mination, simplified the outlook, improved the standards, and corrected the folly of each of us. We continue to come to you for counsel. You have always been your own excuse for being, and to all of us it is a joy to be with you.
We hope that what is written will not offend your Yankee reticence. We know it will not inflate your pride, for that is built of something tough. You are an "* indivi- dual " and we have hailed you as something of a prophet. That is a combination from which legends grow. Your legend can afford to be correct; it is not necessary to exaggerate the truth. We have followed your precepts in setting down what can be learned about you from the written word and the observed fact. In the inferences drawn and the judgments passed we hope we have not stuck the neck out too far. We will be happy if this volume pleases you.
BIBLIOGRAPHY OF HENRY BRYANT BIGELOW
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Birds of the northeastern coast of Labrador. The Auk, 19, 24-3 1 .
Medusae from the Maldive Islands. Bull. Mus. Comp. ZooL, Harvard Coll., 39 (9), 245-269, 9 pis.
The sense of hearing in the goldfish, Carassius auratus L. Amer. Natur., 38 (448), 275-284. The shoal-water deposits of the Bermuda Banks. Proc. Amer. Acad. Arts and Sci., 40 (15), 559-592.
On hybrids between the mallard (Anas boschas) and certain other ducks. The Auk, 24 (4), 382-388.
Studies on the nuclear cycle of Gonionenms murbachii A. G. Mayer. Bull. Mus. Comp. ZooL, Harvard Coll., 48 (4), 287-399, 8 pis.
Coelenterates from Labrador and Newfoundland, collected by Mr. Owen Bryant from July to October, 1908. Proc. U.S. Nat. Mus., 37 (1706), 301-320, Pis. 30-32. Cruise of the U.S. Fisheries Schooner Grampus in the Gulf Stream during July, 1908, with description of a new Medusa (Bythotiaridae). Bull. Mus. Comp. ZooL, Harvard Coll., 52 (12), 195-210, 1 pi.
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xviii
\l\
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U.S. Bureau of Fisheries. Harvard .Alumni Bull.. 31, 433 434. (1930), A developing view-point in oceanography. Sc/V/jfr. 71 (1830), 84 89. ( 1 930), The Woods Hole Oceanographic Institution. Harvard Alumni Bull.. 32, 749-750. (1930). The Woods Hole Oceanographic Institution. Science. 71, 277 278. (1930). The Woods Hole Oceanographic Institution. J. du Cons.. 5 (2). 226-228.
(1931), Siphonophorae from the Arcturus Oceanographic Expedition. Zoolo^ica. N.Y. Zool. Soc, 8(11), 525-592, text figs. 185-220.
(1931). Oceanography; its scope, pioblems and economic importance. Houghton Mifflin Co., N.Y., and Boston, 263 pp.
(1933), Studies of the waters on the continental shelf, Cape Cod to Chesapeake Bay. 1. The cycle of temperature. Pap. Phys. Oceanoi;r. Meteorol.. 2 (4). \ 1 35. 66 text figs.
( 1938). Plankton of the Bermuda Oceanographic Expeditions. VIII. Medusae taken durinu the years 1929 and 1930. Zooloma. N. Y. Zool. Soc, 23 (2), 99-189, 23 text tigs.
(1940), Eastern Pacific Expeditions of the New York Zoological Society. XX. Medusae of the Templeton Crocker and Eastern Pacific " Zaca " Expeditions. 19.^6 1938. Zoolovica. S.Y. Zool. Soc. 25 (3). 281 321, text tigs 1 20.
(1952). Thomas Barbour. Biof^n: Mem.. Nat. .had. Sci.. 21, \} 45.
BroELow. H. B. and Edmondson, W. T. (1947), Wind waves at sea, breakers and surf. U.S. Nt;vy
Hydro^r. Office Puh. 602, xii plus 177 pp.. 57 text figs.. 24 pis. (Also translated into Russian
in 1951 by B. B. SHTOKCiANA.)
BiGKLOW, H. B. and Farfante, I. P. (1948), Fishes of the Western North Atlantic. Chap. I. Lance- lets. Mem.. Sears Found. Mar. Res.. 1, 1-28. 3 text figs.
BiGELow, H. B. and Isflin, C. (1927). Oceanographic reconnaissance o\' the northern sector of ihc Labrador current. Science. 65 ( 1 69 1 ), 55 1 552.
BiciFLOW, H. B. and Lfslii , Maurinf ( 1930). Reconnaissance of the waters and plankton of Monterev
Bay, July 1928. Bull. Mus. Comp. Zool.. Harvard Coll.. 70 (5). 429 481, 43 text tigs. BiGFLOW, H. B., LiLLiCK, LoFS C. and Sears. Mary (1940). Phytoplankton and planktonic protozoa
of the offshore waters of the (iulf of Maine. I. Numerical distribution. Trans. Amer. ^/7.
Soc, n.s., 31 (3). 149 191, 10 text tigs. ^
BiGELOW, H. B. and Schroedfr, W. C. (1927), Notes on northwest Atlantic sharks and skates. Bull.
Mus. Comp. Zool.. Harvard Coll.. 68 (5). 239-251. BiGtLow, H. B. and Schrcfijfr. W. C. ( 1929), A rare Braniid fish (Taractes princeps Johnson) in the
northwestern Atlantic. Bull. Mus. Comp. Zool., Harvard Coll., 69 (2), 41-50. ! pi. BiGELOW. H. B. and Schrofdfr, W. C. (19.34), Canadian Atlantic Fauna. 12. Chordata. I2d.
Marsipobranchii (Lampreys). 12e. Elasmobranchii (Sharks and rays). 121". Holocephali
(Chimaeroids). Univ. Toronto Press for Biol. Bd., Canada. 38 pp., 35 text figs.
,\\
BiGtLOW, H. B. and ScHRotDbR, W. C. ( 1935), Two rare fishes, Notacanthus phas^anorus Goode and
Lvcichthvs latifrons (Steenstrup and Hallgrimsson), from the Nova Scotian banks. Proc.
Boston Soc. Nat. Hist.. 41 (2). 13-18, PI. 3. BiGELOW, H. B. and Schroeder, W. C. (1936), Supplemental notes on fishes of the Gulf of Maine.
Bull. U.S. Bur. Fish., 48 {Bull No. 20), 319-343. BiGELOW, H. B. and Schroeder, W. C. (1937), A record of Centrolophus ni^er (Gmelin) from the
western Atlantic. Copeia. 1937 (1). 61. BiGELOW, H. B. and Schroeder, W. C. (1939), Notes on the fauna above mud bottoms in deep
water in the Gulf of Maine. Biol. Bull., 46 (3). 305-324, 8 text figs. BiGELOW, H. B. and Schroeder, W. C. (1940), Notes on New England fishes — Carcharodon carcharias
(Linnaci:,)- Copeia, 1940(2), 139. BiGELOW, H. B. and Schroeder, W. C. (1940), Some deep sea fishes from the North Atlantic.
Copeia, 1940(4), 231-238. BiGELOW, H. B. and Schroeder, W. C. (1940), Sharks of the genus Mustelus in the western Atlantic.
Proc. Bo.ston Soc. Nat. Hist., 41 (8), 417^38, Pis. 14-19. BiGELOW, H. B. and Schroeder, W. C. (1941), Cephalurus, a new genus of Scyliorhinid shark with
redescription of the genotype Catulus cephalus Gilbert. Copeia, 1941 (2), Ti-16, 4 figs. BiG£LOW, H. B. and Schroeder, W. C. (1944), New sharks from the western North Atlantic. Proc.
New England Zool. Club, 23, 21-36, Pis. 7 10. BiGELOW, H. B. and Schroeder, W. C. (1945), Guide to commercial shark fishing in the Caribbean
area. Anglo-American Caribbean Commission, Washington, D.C., 149 pp., 56 figs. (Also,
Fishery Leaflet, U.S. Fish and Wildlife Service No. 135.) BiGELOW, H. B. and Schroeder, W. C. (1948), New genera and species of Batoid fishes. J. Mar.
Res., 7 (3), 543-566, Figs. 1-9. BiGELOW, H. B. and Schroeder. W. C. (1948), Fishes of the Western North Atlantic. Ch. 2. Cyclo-
stomes. Ch. 3. Sharks. Mem., Sears Found. Mar. Res.. 1(1). 29-546. 103 text figs. BiGELOW, H. B. and Schroeder, W. C. (1950), New and little known cartilaginous fishes from the
Atlantic. Bull. Mus. Comp. Zool., Harvard Coll., 103 (7). 385^08, 7 pis. BiGELOW. H. B. and Schroeder, W. C. ( 195 1 ). A new genus and species of Acanthobatid skate from
the Gulf of Mexico. J. Washington Acad. Sci., 41 (3). 1 10-113, 1 text fig. BiGELOW. H. B. and Schroeder. W. C. (1951), Three new skates and a new chimaerid fish from the
Gulf of Mexico. J. Washington Acad. Sci.. 41 (12), 383-392. 4 text figs. BiGELOW, H. B. and Schroeder, W. C. (1952), A new species of the cyclostome genus Paramyxine
from the Gulf of Mexico. Breviora. No. 8, 10 pp., 6 text figs. BiGELOW, H. B. and Schroeder, W. C. (1953), Fishes of the Gulf of Maine. First Revision. Fi.sh
and Wildlife Service, Fish. Bull.. 53 (F/.s/). Bidl. 74), 1-577, 288 text figs. BiGELOW, H. B. and Schroeder, W. C. (1953), Fishes of the Western North Atlantic. Ch. 1. Saw- fishes, Guitarfishes, Skates and Rays. Ch. 2. Chimaeroids. Mem., Sears Found. Mar. Res.,
1 (2). 588 pp.. 127 text figs. BiGELOW, H. B. and Schroeder, W. C. ( 1954), Deep water elasmobranchs and chimaeroids from the
northwestern Atlantic slope. Bull. Mus. Cotnp. Zool., Harvard Coll., 1 12 (2), 37-87, 7 text figs. BiGELOW, H. B. and Schroeder. W. C. (1954). A new family, a new genus and two new species of
Batoid fishes from the Gulf of Mexico. Breviora. No. 24. 1 6 pp., 4 text figs. BiGELOW, H. B. and Schroeder. W. C. ( 1955). Occurrence off the Middle and North Atlantic United
States of the offshore hake Merluccius alhidus (Mitchill) 1818. and of the blue whiting Gadus
{Micromesistius) Poutas.sou (Risso) 1826. Bull. Mus. Comp. Zool.. Harvard Coll., 113 (2).
205-226. 3 text figs. BiGELOW. H. B.. Schroeder. W. C. and Springer. Stewart (1943), A new species of Carcharinus
from the western Atlantic. Proc. New England Zool. Club. 11, 69-74. BiGELOW. H. B., Schroeder, W. C. and Springer. Stewart (1953). New and little known sharks
from the Atlantic and from the Gulf of Mexico. Bull. Mus. Comp. Zool.. Harvard Coll.,
109(3), 213 276, 10 text figs. BiGELOW. H. B. and Sears, Mary (1935), Studies of the waters of the continental shelf. Cape Cod to
Chesapeake Bay. II. Salinity. Pap. Phys. Oceanogr. Meteorol., 4(1), 1-94, 55 text figs. BiGELOW, H. B. and Sears, Mary (1937), H 2. Siphonophorae. Rept. Danish Oceanogr. Exped.,
1908-10, to the Mediterranean and Adjacent Seas, 2 (Biol.), 144 pp., 83 text figs. BiGELOW, H. B. and Sears, Mary (1939), Studies of the waters of the continental shelf. Cape Cod to
Cape Hatteras. HI. A volumetric study of the zooplankton. Mem. Mus. Comp. Zool.,
Harvard Coll., 54 (4), 183-378, 42 text figs. BiGELOW, H. B. and Welsh, W. W. (1925), Fishes of the Gulf of Maine. Bull. U.S. Bur. Fish., 40 ( 1 ),
1-567, 278 text figs. Barbour, Thomas and Bigelow, H. B. (1944), A new giant Ceriatid fish. Proc. New England Zool.
C/m6.23, 9-15, Pis. 4-6.
Papers in Marine Biology and Oceanography. Suppl. to vol. 3 of Deep-Sea Research, pp. 1-6.
Effect of trawling on animals of the sea bed
By Michael Graham Fisheries Laboratory, Lowestoft, England
Summary — Damage to fish food species trawled over in the main area of the North Sea plaice, cannot be serious; otherwise there would be a noticeable diflFcrence where trawling is impossible, as close to light vessels or among the under-water sand dunes.
Direct attack, covering the ground some five or six times over on the average, did break full-grown Heart Urchins, Echinocardium cordatum, and possibly swimming or paddlcr crabs (Portunus dcpuraior), but appeared not to damage Ophiura albida, nor any of the fragile-shelled plaice food animals: razor shells, Mactra or Tellina. Those forms were not very abundant, but all the 15 specimens taken of fragile animals (other than urchins and paddlers) were undamaged. Such large urchins as were damaged were not plaice food.
Doubtless Sabellaria habitations (ross) would be broken and laid low, but they would probably soon be reconstructed.
Trawling, even with a tickler chain, seems again to escape the so viable indictment.
INTRODUCTION
Many trawlermen are sure that their work alters the bed of the sea. Some say that it improves it, increasing the growth of animal forms growing up from the sea bed by clearing out old structures. Others say that trawling, especially with tickler chains, harms the food of fishes by breaking protective shells and structures.
The complaint of damage is an old one. In 1376 the Commons petitioned the King of England " that the great and long iron of the wondyrchoun runs so heavily and hardly over the ground when fishing that it destroys the flowers of the land below water there ". In the 19th century the beam trawl came in for similar criticism, which Dr. W, C. Macintosh, acting for the Royal Commission of 1863, disposed of. However, trawls have become heavier and tickler chains more common, in certain fisheries almost universal. One such fishery is the English one for plaice in the southern North Sea; and in 1938 it seemed worth while to devote a little research- vessel time to finding out whether tickler chains had any marked effect.
Doubtless trawling with heavy tickler chains breaks up and flattens structures made of sand-tubes by Sabellaria, and similar comparatively fragile highly projecting structures, when these are not so strong as to prevent trawling because of the frequency of tearing. But Sabellaria tenements seem to be annual growths, run up fairly quickly, so that it may not be assumed that much permanent damage is done.
The fishing skipper of the George Bligh advised that it would be foolish and not really relevant to experiment on Sabellaria grounds, which he thought to be limited compared with the whole plaice area; so the decision was made to confine the enquiry to the usual clean, sandy ground frequented by plaice.
METHODS The first line of approach was to assume that there exists a small sanctuary about three-quarters of a mile in radius centred on each light vessel, within which trawling would be very rare, for fear of fouling the lightship's moorings. If trawling had made
B
1
2 Michael Graham
an appreciable effect on the benthos of the plaice area, the community within that sanctuary should be appreciably different from the community outside. The sanctuaries of two light vessels, the Haaks and the Terschelling, were examined with the following gear : Petersen's grab ; Naturalist's dredge ; Agassiz trawl ; otter trawl with shrimp-
Table I. — Dredging before and after trawling
BEFORE
George Bligh, Cruise K (1938), Sta. 16, 10th July, 1938, Naturalist's dredge (6 foot) lined shrimp-netting, Egmont SE'ly 15 miles, Dhan on 90 fms. wire in Lat. 52° 44i' N. Long. 4° 16' E., 13 fathoms, sand, 1015 to 2010 hours, tides various, sea 4, wind SW'ly 4, sky cloudy, 14 hauls driving with wind and tide except where otherwise noted.
Dhan bearing and distance
N to NxW \ mile (magnetic variation 9° W)
S to SJE \ mile
S 1} miles
E to SE^E * mile
W to SWxW * mile
NE 200 yds. to \ mile (? direction reversed)
NE X E to SxWiW i mile
NExE i mile to ESE i mile
NExE i mile to 200 yards
NExE i mile '* tide getting less "
NExE i mile to ENE i mile
NExE to SW i mile
NExE to SW \ mile " with help of engines "
buoy to NE'ward no distance
AFTER
42 traverses with the trawl as nearly as possible to the tracks of Sta. 16, Hauls 7-13; Cruise K 1938, Sta. 20, 13th July, 1938, otherwise as for Sta. 16 but time 1415 to 1920 hours, tide " 1400, BuflFs and Dhan NNW, so pro- ceeded to buoy ", sea 2, wind variable 2, sky cloudy, 7 hauls driving with wind and tide.
Haul Time Dhan bearing and distance
(assumed 10 mins. duration)
1 1418-1428 NExN to ESE i mile
2 1447-1505 NNE to Simile
3 1524-1538 NExE to S i mile
4 1599-1612 NExE to SiE i mile 6 no record — " foul haul "
6 1 704- 1712 ENE 300 yards to SSW 200 yards
7 1730-1745 NExE to SxE i mile
8 1810-1826 ENE i mile to SSE 200 yards
9 1 842-1900 " ? washed it all out "
net cover on the codend. Control hauls were made 5 miles away from the Haaks only. That work was done on the 6th, 7th, 8th and 9th of July, 1938. {George Bligh K 1938, Stas. 2-10, 11-12, 13-14).
Another sanctuary is provided by the under-water sand dunes of the extreme south-eastern North Sea. These are dangerous to otter trawls, because of the trawl doors getting down into the small valleys between the ridges and the net then fouling
|
iaul |
Time |
|
(assumed 10 |
|
|
mins. duration) |
|
|
1 |
1038-1048 |
|
2 |
1110-1120 |
|
3 |
1145-1155 |
|
4 |
1235-1245 |
|
5 |
1314-1324 |
|
6 |
1356-1406 |
|
7 |
1440-1450 |
|
8 |
1519-1529 |
|
9 |
1551-1601 |
|
10 |
1623-1633 |
|
11 |
1654-1704 |
|
12 |
1725-1755 |
|
13 |
10 minutes |
|
14 |
10 minutes |
Effect of trawling on animals of the sea bed 3
the intervening crest. The beam trawls formerly used could generally get along safely, presumably because the beam took the blow of the sand-crest. By 1939, beam trawls were almost extinct, so the " bank " area provided another sanctuary. Had trawling had an appreciable effect, the benthos should be different as one left the bank area. On July 23rd and 24th, 1939, this was investigated near the northern boundary, as located by echo-sounding, using Petersen's grab and the Naturalists' dredge. Two lines of stations were completed {George B/igh L 1939, Sta. 14, Hauls 0-9, Sta. 15, Hauls 0-6).
Another line of approach was to try to damage animals of the sea-bed with a trawl armed with a heavy tickler-chain. The idea was to choose a bed of some animal with a fragile shell, as fragile as possible, and then tow over it as precisely as possible.
Fig. I. Dredge hauls before and after trawling
Tracks of hauls before using trawl and tickler chain are shown as whole arrows with the serial number in a circle; hauls after, as broken arrows with unringed serial numbers, related to the position of a buoy's anchor. " Before " hauls 7 to 10 showed a bed of Heart Urchins, which was also sampled by " after " hauls 2 to 8 with moderate success, the wind having changed. The swinging positions of the buoy have been taken into account. Its area of 180 yards radius limited trawling, probably to something like the shaped area indicated. In the waist, the area would be trawled over on, the average, about 5 times. Heart Urchins were broken, but not Mactra.
Range judged visually was perhaps accurate to within 20 per cent; but the buoy's position (on 90 fms. wire in 13 fms.) would alter with the tide. A trawl, which probably fished at something over 20 yards width, was furnished with half-inch chain extending for 100 feet between the otter-boards, shorter and therefore mostly ahead of the 120 foot ground-rope. This was towed up and down on the 11th, 12th, and 13th July, 1938, crossing the ground 42 times; but owing to the error in the buoy's position due to tide and the imprecision of trawling, these cannot be thought of as 42 exactly super- imposed hauls 20 yards wide. Instead we must think of an area like that shown in Fig. 1, representing fishing as close to the buoy's moorings as the ship dare go. The waist of the constricted area is 1 50 yards wide, which allows for 7 to 8 strips side by
4 Michael Graham
side; so, on the average, the ground would be swept about 5-6 times. It was possible to be more precise about the examination of the benthos bed before and after the trawling, by choosing the same phase of the tide. The animal tested was Echinocardium cordatum, the Heart Urchin, which was the most vulnerable animal we encountered — certainly not a plaice food at the size (from memory, about an inch and one-half in diameter), but no better animal was found. It had the further disadvantage that dredge catches would fall from 39 in a 10 minute haul to 3 when the tide slackened. This leads to an investigation of where exactly the dredge hauls lay (Table I).
The dredging ground (52° 44|' N., 4° 16' E.) was some 13 miles southerly of the Haaks Light Vessel, and because many of the hauls were made while the George Bligh was driving with wind and tide it is possible to plot the approximate tidal pattern (Sta. 16, Hauls 1-13, but discarding No. 6, for which the record is suspect). Assuming as a first approximation that the Dhan buoy did not swing during a 10 minute dredge haul, the course of the haul can be plotted out from the bearing and distance at the beginning and end of the haul, taking an arbitrary position for the buoy. Then, as a second approximation, the buoy is assumed to be on that bearing and at a distance of 180 yards (90 fms of wire in 13 fms of depth) from its anchor. The position of dredge haul is then replotted from the assumed true position of the buoy. Most positions of the buoy were found to lie near a N.E. and S.W. zone (magnetic), not very different from that derived from tidal information on admiralty chart 2 182 A for a position 52° 36' N., 4° 10' E.
The information given in Table I has been plotted on Fig, 1, from which it is seen that there is reasonable overlap of Sta. 16, Hauls 7-13 with Sta. 20, Hauls 2-8. Neither set lay perfectly in the trawlable area; but both lay partly within it. Sta. 16, Hauls 7-13, and Sta. 20, Hauls 1-8, may be said to do so.
Some benthos material was preserved from these investigations ; but none is to be found 17 years later. It is thought that the jars were buried for safety of staff in 1940, and discarded as not in good order in 1945. Data are therefore in the form of incom- plete identifications written in the log-books at the time. They are so given here=
During the attempt to break Echinocardium it was found possible to distinguish whole, broken or even fragmentary specimens, as " dead ", meaning " long dead " (having no spines), " recently dead " (having lost some spines), and " broken " (having all the proper spines). By counting fragments containing apical pores, it was possible to estimate the number of whole urchins.
RESULTS The sanctuaries from trawling showed no marked difference in benthos from outside, so there seems no reason to burden this paper with details of the results. The only point of interest was a bed of Echinocardium within three-quarters of a mile of the Haaks Light Vessel, but because this did not extend around the Light Vessel, we can hardly attribute significance to it, especially because later on we found a localized bed 13 miles away in the fishing area. The fauna also included " flat stars " (Astropecten), Asterias rubens, Portunus depurator, Eupagurus, and a few Mactra, Venus, and razor-shells. These showed no marked differences three-quarters of a mile and 5 miles from the Haaks Light Vessel, and the species and quantities three- quarters of a mile from the Terschelling Light Vessel seemed similar to those close to the Haaks.
Effect of trawling on animals of the sea bed 5
Similarly, there was no appreciable change in fauna taken in grab and dredge on stations 3 miles apart running out of the protected " banks " area and in to it again. The fauna was similar to that noted above.
On the other approach — the direct attack with the tickler chain and trawl — the results are shown in Table II. It will be remembered that Hauls 7-13 of the first
Table II. — Dredi^e catches before and after traw/ing
|
Heart Urchins |
* |
Paddlerst |
Other fragile forms |
|||||||||
|
Live |
Recently Dead |
Dead |
Live |
Recently Dead |
Dead |
Mactra, Razor-shells. Tel- lina. or Ophiura alhida. |
||||||
|
) |
unbroken exccp* where |
|||||||||||
|
_o |
JD |
c ' c <u <u u |
_u |
c |
c If u |
noted. Other forms un- |
||||||
|
"o |
9 .c 2 |
o |
-^ "o -^ |
o |
o |
1 ' I |
damaged included As- |
|||||
|
s: |
ill i |
^ |
J2 |
^ 1 .5 |
1 i |
1 i |
terias ruhens, Aslropeclen, |
|||||
|
++ |
++ |
++ |
j |
Venus and Hermit Crabs |
||||||||
|
Sta. 16 |
1 1 Preliminary hauls |
|||||||||||
|
Haul |
. |
|||||||||||
|
1 |
1 |
! |
1 Ophiura |
|||||||||
|
2 |
1 |
|||||||||||
|
3 |
2 |
|||||||||||
|
4 |
6° |
3 |
4 Ophiura, 2 Tellina |
|||||||||
|
5 |
3 |
3 |
1 Tellina |
|||||||||
|
6 |
4 |
3 |
3 Ophiura |
|||||||||
|
Before trawling |
||||||||||||
|
7 |
17 24 |
3 |
3 Ophiura, 2 Mactra |
|||||||||
|
8 |
10 27 i |
4 |
i |
2 Ophiura, 1 Razor. 2 Mactra (1 broken) |
||||||||
|
9 |
17° |
21 |
4 |
, |
2 Ophiura, ** 2 Mactra, 2 Tellina |
|||||||
|
10 |
12 |
27 |
2 |
1 Mactra, 2 Tellina |
||||||||
|
11 |
1 |
1 |
1 Razor |
|||||||||
|
12 |
3 |
9 |
2 |
4 Ophiura, 1 Mactra |
||||||||
|
13 |
1 |
3 |
2 Ophiura |
|||||||||
|
14 |
1 |
|||||||||||
|
Sta. 20 |
1 After trawling |
1 |
||||||||||
|
Haul |
||||||||||||
|
1 |
4 |
5 |
1 |
3 |
i |
2 Ophiura, 1 Mactra. 1 Razor, 1 Tellina |
||||||
|
2 |
1 1 I 1 |
7 |
5 |
1 Ophiura, 1 Razor |
||||||||
|
3 |
Foul haul |
|||||||||||
|
4 |
2 |
3 |
4 Ophiura |
|||||||||
|
5 |
Foul haul |
|||||||||||
|
6 |
1 |
1 3 |
4 |
1 |
1 Ophiura |
|||||||
|
7 |
1 |
1 |
1 |
3 |
1 |
|||||||
|
8 |
4 |
3 |
2 |
2 |
2 Ophiura, 1 Mactra |
|||||||
|
9 |
ni |
\, possibly washed o |
lit |
|||||||||
|
* Ecfi |
'nocarcUum cordatum |
anc |
1 1 very small |
|||||||||
|
t incl |
tiding fragments equiv |
ilent to one, by apic |
al pores |
f Poi |
tunus depurutor |
|||||||
|
** 5 c |
ms. |
station and Hauls 1-8 of the second, were more or less in the trawled area. It is clear that after trawUng there was a new phenomenon in the catches, namely Heart Urchins recently dead and broken. Possibly there is a similar phenomenon in Paddlers {Portunus depurator); but in no other form is there any sign of damage.
It may be noted that the 9 dead whole urchins taken in Haul 12 of Station 16 constitute one of those observations that one so frequently wishes one had not made.
6 Michael Graham
They do not upset the remainder of the results (not being broken), but they are intrinsically difficult to account for. In the cruise report I noted them as " presumably thrown overboard after previous hauls ". I can do no better now; but only regret the long chance that delivered them on board again, if indeed that is the explanation.
REFERENCES
Dalhousie Commission (1885), Report of the Dalhousie Commission: Trawl Net and Beam Trawl
Fishing, XXXV. Moore, S. A. and Moore, H. S. (1903), The History and Law of Fisheries, 175. Van Veen, Joh. (1935), Sand waves in the North Sea. Hydrogr. Rev., 12 (1), 21.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 7-11.
A further example of the patchiness of plankton distribution
By A. C. Hardy Department of Zoology and Comparative Anatomy, Oxford
Summary. — 32 consecutive plankton samples were taken by identical tow-nets in a straight line covering a total distance of nearly 11 miles. A marked patchiness was demonstrated for all animals occurring in sufficient numbers. The results are considered in relation to those of some other such samplings already published.
In JANUARY 1927, when the Royal Research Ships Discovery and William Scoreshv were making a survey of the plankton of the sub-antarctic whaling grounds round the island of South Georgia, two series of consecutive net hauls were taken to find out how patchy in distribution were the main elements in the macroplankton. One series consisted of 23 samples and the other of 48. The results, showing a marked patchiness, particularly in the distribution of Euphausia superba and the amphipod Parathemisto gaudichaudi, were published by Hardy and Gunther (1935, pp. 255- 263). A similar series of 32 consecutive samples were taken further to the south in the Bransfield Strait off Graham Land by the Discovery in April of the same year. As this series lay far outside the region of the South Georgia survey the results were not included in the former report and have not hitherto been published. Knowing that Professor Bigelow was much interested in the matter of uneven plankton distribution I have thought that, small as it is, this additional evidence of patchiness might not be an inappropriate contribution to this volume in his honour; I wish it could have been a larger study, but it is the only piece of marine work that I have at the moment ready for immediate publication.
The series of samples now to be described was taken by the Discovery on April 7ih, 1927, at Station 207 which lay some fifteen miles south of Livingstone Island; the exact positions at the beginning and end of the observations were respectively 62° 54' 00" S., 59° 50' 30" W. and 62° 49' 30" S., 60° 10' 30" W. The procedure adopted was the same as that on the two earlier occasions except that the nets used were of 70 cm diameter instead of the larger 100 cm diameter nets used formerly; a detailed descrip- tion of these nets (N70H and NIOOH) will be found in Kemp and Hardy (1929. pp. 183-185). Two nets, exactly similar to each other in every particular, were used. The first net was lowered away from the starboard quarter and towed just below the surface for exactly 10 minutes at a speed of 2 knots and then hauled in; as this net was coming in, the second net was lowered away from the port quarter and towed for a similar period. Whilst this net was being towed the first net was washed down, the bucket emptied and replaced and the net got ready for reshooting; then as the second net came in at the end of its ten minutes the first net went out again. In this manner the sampling was continued to give a series of 32 consecutive hauls each beginning just as the one before it ended so that a continuous line of observation (except for one four- minute gap) was made over a distance of nearly 11 miles. The sampling began at 0300 hrs and ended at 0824 hrs; there was a loss of 4 minutes between sample 30 and 31 due to one of the nets being torn and having to be replaced by a new one. At the
7
8
A. C. Hardy
speed of 2 knots each sample represented a haul covering a distance of one-third of a mile.
It might perhaps be thought that there was little need for further studies of patchi- ness of the kind here described since the automatic plankton recorder is always taking
Fig. 1 . Histograms showing the varying numbers of some plankton animals in thirty-two consecu- tive net hauls taken just below the surface at the Discovery station 207; each haul was of 10 minutes duration and covered a distance of one-third of a mile. For further details see text.
A further example of the patchiness of plankton distribution 9
series of continuous samples and often revealing marked unevenness in distribution. The plankton recorder, however, because it samples continuously on an ever-moving banding, cannot show the real degree of patchiness; each section of the banding
Young Copepoda other than Colonus
30 32
Fig. 2. Histograms showing the varying numbers of the more important copepods in ihe same series of consecutive net hauls in Fig. 1. The first sample was unfortunately lost by a tube breakage
before the analysis had been made.
10 A. C. Hardy
represents the passage of several miles of sea, so that any marked variation in numbers appearing from the analysis of the records is really showing itself through a consider- able " smoothing of results " effected by the very nature of the sampling (Hardy, 1936 A, p. 495). The recorder was, of course, in part designed to overcome the errors due to patchiness which may falsify the results of an ordinary net survey. As far as I am aware no other experiments of the kind here described have been made except those in the South Georgia survey already referred to, and two series taken to test the validity of the plankton recorder method: one in the open South Atlantic midway between Gough Island and Cape Town (Hardy, 1936 b, p. 535) and the other in the North Sea (Hardy and Ennis, in an appendix to Hardy, 1936 a). I believe more such experiments might be valuable in the understanding of planktonic ecology.
The results of the series here published may be shown most easily in graphical form by the use of histograms and so save much description in the text. They are shown in Figs. 1 and 2, and include only those animals of which over 50 have occurred in a single sample; the remainder, including ctenophores, several kinds of amphipod, other species of copepods, and Euphausia frigida were present in only insignificant numbers. Instead of giving the data in tabular form as well as graphically, the actual numbers are inserted against the appropriate histograms. Apart from the marked unevenness of distribution, the effect of vertical migration is clearly seen in the case of the Euphausia superba adults and the copepods. The series began in darkness and ended in daylight, sunrise being at 0645, i.e. in the middle of sample 23 ; we see the animals just mentioned gradually withdrawing from the surface as dawn approaches. It would be valuable, but difficult, to operate such a series of consecutive nets at lower levels, for they would have to be opened and closed at the end of each haul. Regarding the many possible causes of patchiness I still believe that some of the factors suggested in the section on the dynamics of distribution in Hardy and Gunther {he. cit., pp. 343-356) are likely to be important. More observations in the field are required and particularly more experiments specially designed to test the different hypotheses; further discussion must await the results of such work.
Apart from a consideration of causes, not much comment is necessary; the degree of patchiness is obvious. What moral can be drawn from it ? Let us suppose we had been carrying out a survey in this region using similar nets towed for 10 minutes at points say 10 miles apart ; it is clear that we should arrive at very different conclusions as to the distribution of the macroplankton according to exactly where our stations were placed within a circle having a radius of only half a mile. In the consecutive series here described a mile covers three adjacent samples; we see what a contrast there is within any such three we may select. On the evidence provided by this and the only available similar experiments it appears that much of the quantitative plankton distribution work of the past cannot have the degree of validity often attributed to it. Ecological experiments in the field call for a control just as much as those in the laboratory. Each tow-net survey is really in the nature of an experiment; in the case just imagined the experiment was to sample the water at 10 mile intervals to find out the distribution of the more important plankton animals over the area. Before accepting the results as valid a control experiment is necessary to see, if such samples are repeated at several points near the same place, that they give a reasonably con- sistent result : to see in fact if one such net towed at one place can be said to give a fair measure of the plankton lying to five miles on either side of it.
A further example of the patchiness of plankton distribution 1 1
I once heard quite a well known planktologist say that it did not do to arrange your stations in a survey too close together because it made it almost impossible to use contour methods when charting the results; 1 don't think he realized the significance of what he was saying.
I gratefully acknowledge the assistance of Dr. C. Cheng in the identification and estimation of the copepods in these samples.
REFERENCES
Hardy, A. C. (1936 a), The Continuous Plankton Recorder. Discovery Reports, 11, 457-510. Hardy, A. C. (1936 b). Observations on the Uneven Distribution of Oceanic Plankton. Discovery
Reports, 11, 513-538. Hardy, A. C. and Gunther, E. R. (1935), The Plankton of the South Georgia Whaling Grounds and
Adjacent Waters. Discovery Reports, 11, 1-456. Kemp, S. and Hardy, A. C. (1929), The Discovery Investigations, Objects, Equipment and Methods.
Part II. Discovery Reports, 1, 151-222.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 12-14.
Dissolved organic matter in the sea*
By Mary Alys PLUNKEXTf and Norris W. Rakestraw Scripps Institution of Oceanography, La Jolla
We havb little real information about the nature and amount of dissolved organic matter in the sea, especially in deep water. Among the few recorded determinations of dissolved organic carbon the limited number made by Krogh (1934) have seemed to us to be perhaps the most reliable. We are but slightly better off in our knowledge about dissolved organic nitrogen. In addition to a few determinations made by Krogh (1934), some results reported by von Brand and Rakestraw (1941), using the same methods, may perhaps be regarded with confidence. On the basis of these limited data it would appear that the concentration of dissolved organic matter in the open sea is fairly constant at about 5 mg per litre.
Krogh's work, just referred to, was carried out with the extreme care and attention to detail which was characteristic of all his microchemical analyses, but because of its limited extent (his carbon results were obtained from six samples collected from a single station) it has long seemed to us highly necessary to corroborate and extend it. His methods have never been used again until very recently, when Kay (1954) used a modification to obtain results in the shallow waters of the Kielerbucht.
Accordingly, in the spring of 1953, we assembled apparatus essentially similar to Krogh's and carried out the analyses shown in Table I, on samples from three stations off the coast of Southern and Lower California. The results are shown graphically in Figure 1, along with curves for temperature and for oxygen at Station 1 10.70. Two important conclusions emerge:
The general level of concentration of dissolved organic carbon which Krogh reported (two to three milligrams per litre) was confirmed at these stations. However, instead of being homogeneously distributed it is definitely less at intermediate depths. The significance of this fact is not clear; the data are too limited to conclude that it is related to the location of the oxygen-poor layer. In any event, it throws some doubt upon certain of Krogh's conclusions.
In the fall of 1953, samples were obtained from two stations on the " Transpac " expedition in the north-western Pacific. The results from these are tabulated in Table II and graphically shown in Fig. 1. It will be seen that these are rather more irregular in the upper layers and that the general level of concentration is distinctly lower than at the earlier stations. All samples except that from 506 m at Station T-P 99 were analyzed in duplicate. The samples from these two stations were frozen immediately and kept in this condition until analyzed several months later. While this introduces some uncertainty it nevertheless seems unlikely that significant oxidation took place in the meantime. Deep-sea water has been preserved for much longer times and at higher temperatures without appreciable consumption of oxygen (Rakestraw 1947). Keys, Christensen and Krogh (1935) have also shown that the dissolved organic
* Contribution of the Scripps Institution of Oceanography, New Series No. 802. t Present address: Vassar College, Poughkeepsie, New York.
12
Dissolved organic matter in the sea
13
o lo 20
O 5
o 10 20
O S O
O 10 20 T
OM
500
1000
I500
2000-
2500
3000-
3500
Fig. 1 . Vertical distribution of dissolved organic carbon at two stations off the California coast
(1 10.70 and 93.61) and two in the north-western Pacific (T-P 54 and T-P 99). Curves show carbon in
mg/L (C), temperature ° C (T) and dissolved oxygen ml/L (O).
Table I. — Vertical distribution of dissolved organic carbon
|
Dissolved |
||||||
|
Station |
Location |
Date |
Depth |
Carbon |
Temp. |
oxygen |
|
(m) |
(ingiD |
°C |
{ml ID |
|||
|
110.70 |
28= 40' N |
6/15 53 |
0 |
2-68 |
1614 |
|
|
118° 20' W |
99 195 317 665 1043 |
2-30 2-20 1-50 1-49 1-11 |
13-51 9-65 8-16 5-55 3-93 |
|||
|
110.70 |
3/22/53 |
0 |
214 |
15-62 |
5-53 |
|
|
104 |
2-58 |
13-96 |
5-17 |
|||
|
381 |
2-73 |
7-78 |
0-72 |
|||
|
470 |
2-59 |
6-90 |
0-43 |
|||
|
566 |
1-92 |
6-22 |
0-33 |
|||
|
759 |
1-41 |
5 09 |
0-32 |
|||
|
955 |
1-71 |
4-23 |
0-52 |
|||
|
1147 |
2-58 |
3-66 |
0-74 |
|||
|
1487 |
2-73 |
2-96 |
1 10 |
|||
|
93.61 |
32 50' N |
5/27 '53 |
0 |
2-67 |
14-36 |
|
|
119 45'W |
32 235 446 767 1092 2077 2690 |
2-48 2-43 2-49 1-52 2-76 2-31 2-82 |
12-94 7-73 6-12 4-59 3-69 2-02 1-73 |
|||
|
100.90 |
29° 45' N 120" 50'W |
4 28 53 |
3000 |
2-50 |
— |
14
Mary Alys Plunkett and Norris W. Rakestraw
matter is very resistant to bacterial action and does not change significantly during storage of water.
We are unable to find any other systematic analytical error which would account for such a large difference in the average concentration in the deep water. On the other hand, it is difficult to explain such a difference, since the phosphate concentra- tion, for example, is approximately the same in the regions concerned. The dissolved organic carbon, although in lower concentration at all depths, is not uniformly distributed vertically, being less in the intermediate zone, as it was in the eastern Pacific. In this case, however, the zone of lower carbon concentration seems to be somewhat above the steep oxygen gradient.
It is important that we learn more about the dissolved organic matter, since it is the largest fraction of the total organic matter in the sea. Although for the most part it seems to be resistant and unreactive we do not know what relation it has to the " oxidizable organic matter " which plays an important part in the distribution of dissolved oxygen. The work reported here will be continued and extended.
Table II. — Vertical distribution of dissolved organic carbon
|
1 I |
Dissolved |
|||||
|
Station |
Location Date |
Depth |
Carbon |
Temp. |
oxygen |
|
|
(w) |
(niglL) |
C C) |
imllL) |
|||
|
T-P 54 40° 34' N |
9/8/53 |
0 |
1-29 |
19-2 |
5-67 |
|
|
170° 2'E |
10 |
1-66 |
190 |
5-34 |
||
|
273 |
2-72 |
8-9 |
4-94 |
|||
|
366 |
1-42 |
7 0 |
4-56 |
|||
|
371 |
1-87 |
7 0 |
4-54 |
|||
|
464 |
1-47 |
5-8 |
3-70 |
|||
|
469 |
1-34 |
5-7 |
3-68 |
|||
|
753 |
1-37 |
4-3 |
1-35 |
|||
|
758 |
1-37 |
4-3 |
1-37 |
|||
|
2020 |
1-78 |
2-4 |
1-87 |
|||
|
3340 |
1-80 |
1-9 |
3-40 |
|||
|
3345 |
1-48 |
1-9 |
3-40 |
|||
|
T-P99 3r55'N |
10/26/53 |
0 |
1-57 |
25-4 |
4-58 |
|
|
142° 12' E |
24 |
1-72 |
25 0 |
4-56 |
||
|
153 |
1-57 |
19-2 |
4-41 |
|||
|
257 |
103 |
17-1 |
4-61 |
|||
|
406 |
0-78 |
15-3 |
4-21 |
|||
|
506 |
0-59 |
12-9 |
3-96 |
|||
|
607 |
118 |
10-3 |
3-65 |
|||
|
803 |
0-88 |
6-3 |
2-24 |
|||
|
1190 |
1-27 |
3-7 |
0-94 |
|||
|
1995 |
1-27 |
2-3 |
1-76 |
|||
|
2504 |
1-27 |
21 |
2-34 |
|||
|
3220 |
112 |
1-9 |
3 03 |
|||
|
4177 |
108 |
1-9 |
3-44 |
|||
|
5254 |
0-98 |
1-9 |
3-67 |
|||
|
6290 |
M8 |
1-9 |
3-71 |
REFERENCES
Kay, H. (1954), Untersuchungen zur Menge und Verteilung der organischen Substanz im Meer-
wasser. Kieler Meeresforschungen, 10, 202-214. Keys, A., Christensen, E. H. and Krogh, A. (1935), The organic metabolism of sea water with
special reference to the ultimate food cycle in the sea. /. Mar. Biol. Assn. U.K., 20, 181-196. Krogh, A. (1934), Conditions of Hfe at great depths in the ocean. Ecol. Mongr., 4, 430^39. Rakestraw, N. W. (1947), Oxygen consumption in sea water over long periods. /. Mar. Res., 6
(3), 259-263. Von Brand, T. and Rakestraw, N. W. (1941), The determination of dissolved organic nitrogen in
sea water. /. Mar. Res., 4 (1), 76-80.
Papers in Marine Biology and Oceanography, Suppl. lo vol. .1 of" Deep-Sea Research, pp. I.'i-I9.
Marine bacteria
Recollections and problems
By Selman a. Waksman Institute of Microbiology, Rutgers University
Early in the spring of 1931 I received a telephone call from the venerable biologist, Professor Edwin Conklin of Princeton University, to the effect that Professor Henry BiGELOW of Harvard was visiting him that day. They were discussing organizational plans for the newly established Oceanographic Institution at Woods Hole, Mass. The question had come up as to whether it would be desirable to establish a project in marine bacteriology at the Institution. Would I care to come to Princeton and present my ideas concerning the potentialities in this field of research?
I could lay claim to only very limited knowledge of marine bacteria. What little knowledge I had was based on a certain familiarity with a few problems in which marine bacteria were involved. One of these was concerned with precipitation of lime in sea-water. Just prior to World War I, a British bacteriologist. Dr. G. H. Drew, made a study of the precipitation of lime in tropical and subtropical water, notably in the region of the Bahamas. Drew reported this process to be a result of bacterial action. Certain groups of bacteria concerned with the reduction of nitrate to atmo- spheric nitrogen, or the so-called " denitrifying " types, were said to be primarily involved in the process. The untimely death of Dr. Drew in 1913 brought an end to these investigations.
Seven or eight years later. Professor Charles Lipman of the University of California became interested in this problem. Together with an assistant, he spent two or three summers in the laboratory of the Dry Tortugas, in an attempt to confirm Drews' results. Prof. Lipman visited me on several occasions and we had an opportunity to discuss this problem in detail. It appeared to me that the final answer had not been reached, certainly not as regards the role of bacteria in the process.
In 1929, a group of geologists from Princeton, headed by Professor Richard M. Field, organized an expedition to the Bahamas, particularly Andros Island, for the purpose of studying in detail this precipitation problem. Since " drewite ", the name given to the lime formation, was believed to be of bacteriological origin, it was felt that it would be desirable to have a bacteriologist participate. I was invited, but declined, because neither my available time nor my scientific interests, I felt, would permit me to do justice to the study. I was at that time on the point of developing a comprehensive study of " organic matter decomposition by micro-organisms and of humus formation ", and could not, therefore, afford to undertake a new problem that would require at least several months of my time. The Princeton group decided to invite a qualified bacteriologist interested in this problem. On my part, I promised to make facilities available in my laboratory for this study.
In 1930, Dr. W. Bavendamm, a German bacteriologist, came to this country to spend six months working on this problem. He was immediately placed in our
15
15 Selman a. Waksman
laboratory, where he was supplied with the necessary glassware and chemicals. We also helped to equip him with all the other materials required for the bacteriological phase of the expedition and discussed various aspects of the problem and the methods of approach. It was decided to limit the field expedition to the collection of samples and to carry out the studies themselves in our laboratory. Upon his return from the expedition. Dr. Bavendamm began to examine bacteriologically the samples of sea- water and sea bottom material.
Upon studying the data, I was struck by the frequent occurrence of a certain kind of bacterium which brought about rapid liquefaction of the agar in the medium. Each colony of this bacterium was surrounded by a clear, saucer-like circle of the liquefied agar. Because of my interest in organic matter disintegration, including such compounds as hemicelluloses and polyuronides, of which agar was a type, I suggested to Bavendamm that we both undertake a detailed study of this bacterium and its mode of action upon the agar. He agreed, and the remaining months of his stay in my laboratory were devoted to this investigation. Our results were incorporated in a joint paper, which was submitted to the Journal of Bacteriology, and Bavendamm himself published a paper on the question of calcium precipitation.
It was just about this time that the Oceanographic Institution was being organized. The director, Dr. Henry Bigelow, was approached by Dr. Field, who was requesting support for another expedition to the Bahamas. When asked about the accomplish- ments of the first expedition. Dr. Field cited the above two papers. When Dr. Conklin's opinion was asked about this matter, he suggested that I be consulted. Hence the telephone call to which I have referred.
There was another reason for consulting me on this matter. Since any comprehen- sive survey of the field of marine bacteriology would involve an understanding not only of bacteriological processes but of complex bacterial or even microbial popula- tions, a prior knowledge of other complex populations would be helpful. Inasmuch as my own field of study, that of soil microbiology, involved populations and relationships, there was a parallelism between the two. This could be contrasted to medical and industrial microbiology, where single cultures of organisms are concerned. Further, the cycles of life in both the soil and the sea are similar, both as regards the activities of various specific groups of micro-organisms, such as nitrifying, denitrifying, and cellulose-decomposing types, and the bacterial population of the natural substrate as a whole.
We spent several hours that beautiful spring afternoon in Princeton, in 1931, discussing various problems bearing upon marine bacteriology. All three of us reached the conclusion that neither oceanography nor marine bacteriology would gain much from another expedition to the Bahamas. However, we all felt strongly that a definite place on the research program of the Oceanographic Institution should be given to bacteriological investigators. Dr. Bigelow then suggested that I present a tentative plan for such a program. Within a few weeks I submitted a plan based on the idea that one or two investigators interested in complex microbiological activities be invited to spend two or more months every summer at the Oceanographic Institution. A laboratory was to be set aside for this purpose, and several assistants assigned to the project. Further, the senior investigator would continue during the rest of the year to work on one of the problems in his own laboratory, assisted by one or more graduate students provided by the Oceanographic Institution.
Marine bacteria 17
My plan was accepted by the Trustees of the Institution, and I was invited to spend a month that summer at Woods Hole to study the situation a little more closely. Subsequently, I was appointed investigator to organize the work in marine bacteriology.
The next 10 years found me busy every summer for about two months at the Oceanographic Institution, searching for bacteria in the sea. There were always several collaborators, assistants, and graduate students to help in the research program. It is of particular interest to mention among the associates Dr. Cornelia Carey, Professor of Bacteriology at Barnard, Dr. Margaret Hotchkiss of New York Medical College, and, later. Dr. Austin Phelps of Yale University. Among the assistants who should be mentioned are, first, Herbert W. Reuszer, Charles Renn, J. Stokes, and D. Q. Anderson, and, later, Charles Weiss, Donald Reynolds, and Don Johnstone. There were also various visiting investigators concerned with microbiological problems, principally Prof. H. Gran of Oslo, Norway, who has left his mark in bacteriology with his classical study of the agar-liquefying bacteria; Dr. Frederick K. Sparrow, who made a study of the fungi in the sea, especially those pathogenic to marine algae; and Prof. U. Vartiovaara of Finland. A number of summer laboratory assistants, especially Eric Warbasse, contributed much in collecting equipment, for both inside and outside (or boat) work, and helping to organize the laboratory at the Institution.
By the time I started the first investigation in 1931, the laboratories were fully equipped and ready to operate, thanks to the efforts of Reuszer, who did a great deal of the preparatory work, especially prior to my arrival at Woods Hole. He also continued some of the experimental studies in New Brunswick during the rest of the year. It was not until 1932, however, that our program of marine research was fully developed. During the preparatory period I had full opportunity to familiarize myself with the literature on the subject. We decided to approach the study of marine bacteria along four distinct lines :
1. The nature of the bacterial population as a whole, both in sea-water and in the sea bottom. Special attention was given to the influence of distance from land, depth of water, and nature of bottom material. A comparative study was also undertaken of the methods to be used, including suitable media, and of the changes in the popula- tion after the samples were taken, especially upon standing in the laboratory. Although most of these studies were quantitative in nature, others were also qualitative, since they involved a study of the specific nature of marine bacteria, such as aerobic v^. anaerobic, and spore-forming v^. non-spore-forming types.
2. The specific nature of some of the marine bacteria. Particular attention was paid to those responsible for the formation of nitrite and nitrate by oxidation of ammonia, the reduction of nitrate, the fixation of nitrogen, the decomposition of cellulose, and the nature and decomposition of marine algal constituents.
3. Transformation of organic matter in the water and in the bottom material. This included a variety of reactions, such as oxygen consumption, carbon dioxide liberation, and nitrogen transformation. The water from warm regions showed, for example a higher bacterial population with much less oxygen consumption than did the water from cold regions, when samples of water were kept under identical con- ditions for equal periods of time. This pointed to a greater concentration of available organic matter in the colder waters.
18 Selman a. Waksman
4. Various other problems came up for consideration during these years. The most important were the following:
(a) A study of the agents responsible for the disappearance of eel-grass along the Atlantic shore. Renn, who was appointed the senior assistant in marine bacteriology after the resignation of Reuszer, undertook this task and made a notable scientific contribution to it.
(b) A study of the presence or development in the sea of bacteria antagonistic or destructive to other bacteria. These particular investigations came toward the end of my stay in Woods Hole, in 1941 and 1942, and were influenced largely by my major interests at Rutgers on the antagonistic interrelations among micro-organisms and the production of antibiotic substances.
(c) The role of bacteria in the fouling of ship bottoms. This problem also came toward the end of my work at Woods Hole and on the eve of World War II. Since the chemists and biologists of the Institution soon took over this problem, it will no doubt be reported in this volume in further detail.
In addition to my work in the laboratory at the Oceanographic Institute, limited periods were spent elsewhere in connection with some of the marine microbiological problems. It is sufficient to mention two brief stays at the Bermuda Biological Station, and various trips on the ocean-going laboratory vessels, such as the Atlantis. The first were successful, since I had a first-hand opportunity to compare the bacterial population and the bacteriological changes in the waters in a warm region with those of cold regions. The ocean trips, however, were a complete failure, so far as I was concerned. Under the threefold movements of the ship, I immediately became sea- sick and had to leave the work largely to one of the assistants who always accompanied me. After two valiant efforts to carry out studies on the moving boat, I made no further attempts. Dr. Bigelow's comment, " Food was wasted on him ", was fully justified, and I gave up further sea voyages for bacteriological exploration. Fortunately, some of the assistants, especially Renn, Reynolds, and Johnstone, were excellent sailors, and could take good care of the problems under consideration.
Thus came to an end a decade of exploration of the sea for marine bacteria. The following list of papers published from the Oceanographic Institution bears evidence of the scope of the subject, the variety of problems involved, and some of the results attained. It affords proof of the vision and far-sightedness of the founder of the Oceanographic Institution and its first Director, Dr. Henry Bigelow, to whom this note is gratefully dedicated.
REFERENCES
Preliminary papers:
Bavendamm, W. (1931), The possible role of micro-organisms in the precipitation of calcium
carbonate in tropical seas. Science, 73, 597-598. Bavendamm, W. (1932), Die mikrobiologische Kalkfallung in der tropischen See. Bericht iiber die
mikrobiologischen Ergebnisse einer in Jahre 1930 von der Universitaten Princeton und Rutgers
(U.S.A.) untemommenen Forschungsreise nach den Bahama-Inseln. Arch. MikrobioL, 3, 205-276. Waksman, S. A. and Bavendamm, W. (1931), On the decomposition of agar-agar by an aerobic
bacterium. /. Bacteriol., 22, 91-102.
Published papers from the Woods Hole Oceanographic Institution:
Anderson, D. Q. (1940), Distribution of organic matter in marine sediments and its availability to
further decomposition. J. Mar. Res., 2, 225-235. Carey, C. L. (1938), The occurrence and distribution of nitrifying bacteria in the sea. /. Mar. Res.,
1. 291-304.
Marine bacteria 19
Carey, C. L. and Waksman, S. A. (1934), The presence of nitrifying bacteria in deep seas. Science,
79,349-350. Hock, C. W. (1940), Decomposition of chitin by marine bacteria. Biol. Bull., 79, 199-206. Hock, C. W. (1941), Marine chitin-dccomposing bacteria. J. Mar. Res., 4, 99-106. HoTCHKiss, M. and Waksman, S. A. (1936), Correlative studies of microscopic and plate methods
for evaluating the bacterial population of the sea. J. Bacterial., 32, 423-432. Renn, C. E. (1934), Wasting disease of Zostera in American waters. Nature, 134, 416-417. Renn, C. E. (1935), A mycetozoan parasite of Zo.sfera marina. Nature, 134, 544-545. Renn, C. E. (1936), The wasting disease of Zostera marina. 1. A phytological investigation of the
diseased plant. Biol. Bull., 70, 148-158. Reuszer, H. W. (1933). Marine bacteria and their role in the cycle of life in the sea. III. The distri- bution of bacteria in the ocean water and muds about Cape Cod. Biol. Bull., 65, 480 497. Waksman, S. A. (1933), On the distribution of organic matter in the sea bottom and the chemical
nature and origin of marine humus. Soil Sci., 36, 125-147. Waksman, S. A. (1934), The role of bacteria in the cycle of life in the sea. Sci. Monthly, 38, 35^9. Waksman, S. A. (1934), The distribution and conditions of existence of bacteria in the sea. Ecol.
Monogr., 4, 523-529. Waksman, S. A. (1941), Aquatic bacteria in relation to the cycle of organic matter in lakes. A
Symposium on Hydrobiology, Madison, Wisconsin, 86-105. Waksman, S. A. and Carey, C. L. (1933), Role of bacteria in decomposition of plant and animal
residues in the ocean. Proc. Sac. Exp. Biol. Med., 30, 526-527. Waksman, S. A. and Carey, C. L. (1935), Decomposition of organic matter in sea water by bacteria.
I. Bacteria multiplication in stored sea water. J. BacterioL, 29, 531-543. Waksman, S. A., Carey, C. L. and Allen, M. C. (1934), Bacteria decomposing alginic acid. J.
BacterioL, 28, 213-220. Waksman, S. A., Carey, C. L. and Reuszer, H. W. (1933), Marine bacteria and their role in the
cycle of life in the sea. Biol. Bull., 65, 57-79. Waksman, S. A. and Hotchkiss, M. (1937), Viability of bacteria in sea water. J. Bacterial.. 33,
389-400. Waksman, S. A. and Hotchkiss, M. (1938), On the oxidation of organic matter in marine sediments
by bacteria. J. Mar. Res., 1, 101-118. Waksman, S. A. Hotchkiss, M. and Carey, C. L. (1933), Marine bacteria and their role in the cycle
of life in the sea. II. Bacteria concerned in the cycle of nitrogen in the sea. Biol. Bull., 65, 137-167. Waksman, S. A., Hotchkiss, M., Carey, C. L. and Hardman, Yvette (1938), Decomposition of
nitrogenous substances in sea water by bacteria. J. Bacterial., 35, 477^86. Waksman, S. A., and Renn, C. E. (1936), Decomposition of organic matter in sea water by bacteria.
III. Factors influencing the rate of decomposition. Biol. Bull., 70, 472-483. Waksman, S. A., Reuszer, H. W., Carey, C. L., Hotchkiss, M. and Renn, C. E. (1933). Studies
on the biology and chemistry of the Gulf of Maine. III. Bacteriological investigations of the sea
water and marine bottoms. Biol. Bull., 65, 183-205. Waksman, S. A., Stokes, J. L. and Butler, M. R. (1937), Relation of bacteria to diatoms in sea
water. J. Mar. Biol. Assoc, U.K., n.s., 22, 359-373. Waksman, S. A. and Vartiovaara, Unto (1938), The adsorption of bacteria by marine bottom.
Biol. Bull., 74, 56-63.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 20-. 39
The strontium-calcium atom ratio in carbonate-secreting marine
organisms
By Thomas G. Thompson and Tsaihwa J. Chow Department of Oceanography, University of Washington
Summary — The purpose of the present investigation was to study the distribution of strontium and calcium in the biosphere. The contents of strontium and calcium in 250 species of carbonate-secreting marine organisms were determined. The strontium-calcium atom ratio in calcareous portions of marine organisms ranged from 1-0 to 11 x 10"^. With the exception of Nudibranchia and Madre- poraria, the atom ratio in marine organisms was less than that of sea water, 8 -9 x 10"*. The strontium- calcium atom ratios in marine organisms appeared to be constant in accordance with their phylo- genetic classification. Specimens of different species collected from a common ecological community showed diverse strontium-calcium atom ratios. On the other hand, the similar types of marine organisms living under different environmental conditions from arctic to tropical oceans, showed constant strontium-calcium atom ratios. Variations in salinity and temperature of sea water were apparently not the factors which influenced the strontium-calcium atom ratio in calcareous shells.
The mineralogical properties of calcium carbonate in marine organisms demonstrated a definite correlation with the occurrence of strontium. The marine organisms containing calcium carbonate as aragonite had strontium-calcium atom ratios greater than those as calcite. Samples of deep-sea sediments and Clobigerina ooze showed strontium-calcium atom ratios of 1 -94 x 10~* and 1 -49 x 10~*, respectively. The limestone deposits, which originated from marine organisms, had the smallest strontium-calcium atom ratio, 0-63 x 10"*, of all materials examined. Apparently, the matrix of calcareous deposits of marine origin has lost strontium during geological time.
INTRODUCTION
The present investigation was undertaken in order to study (1) the distribution of strontium in the carbonate-secreting marine organisms, (2) to ascertain possible correlations between the strontium and calcium contents of the calcareous skeletons, (3) to observe variations of the strontium-calcium atom ratio in accordance with the phylogeny of the marine organisms, (4) to note the extent of change in the atom ratio of marine organisms living in different natural environments, and (5) to determine the strontium content in relation to the mineralogical character of the calcium carbonate in the organisms.
The determination of small quantities of strontium in the presence of large amounts of calcium has been rather a laborious process. However, both of these elements can be determined readily by flame photometric methods recently described by Chow and Thompson (1955 a and b).
REVIEW OF LITERATURE
The occurrence of calcium in marine organisms has been studied extensively, as it is the major constituent of many skeletal remains in calcareous marine sediments. An authoritative summary and discussion on the distribution of calcium in marine organisms has been presented by Vinogradov (1953). The investigations of Lowen-
Contribution from the Department of Oceanography, University of Washington. Publication
No. 184.
20
The strontium-calcium atom ratio in carbonate-secreting marine organisms 21
STAM (1954 A and b) dealt with the effect of environmental factors upon the mineral- ogical character of the calcium carbonate in certain marine organisms.
Strontium has been detected in all phases of the biosphere. Due to the difficulty in analyzing trace quantities of strontium in the presence of calcium., only a few scattered analyses were reported in the early literature showing the existence of strontium in marine organisms (MoRETTi, 1813; Vogel, 1814; Forchhammer, 1852; DiEULAFAiT, 1877; ScHMELCK, 1901). More recently, the role of strontium in the carbonate-secreting marine organisms has been the object of investigation, and several quantitative determinations were made on the distribution of strontium in various biological materials (Fox and Ramage, 1931; Noll, 1934; McCance and Masters, 1937; Webb, 1937; Trueman, 1944; Tsuchiya, 1944, 1948; Vinogradov and Borovik-Romanova, 1945; Asari, 1950; Odum, 1951 a). The relationship between the strontium content of fossils and that of recent marine organisms has also been studied (Odum. 1951 b; Kulp, et ah, 1952).
In summarizing the work of previous investigators, it may be said that strontium was found not only in the calcareous shells, but also in the tissues of marine organisms. It was also stated by some that the primary factor which determines the strontium- calcium atom ratio in the calcareous skeletons is the atom ratio of these elements occurring in the water in which the organisms lived. Experiments showed that large quantities of strontium could be taken into the calcareous shells of marine organisms grown under controlled conditions and that the relationship between the strontium- calcium atom ratio in the shells is almost directly proportional to the atom ratio of the environment. Since the strontium-calcium atom ratio in the calcareous skeletons reflects the chemical composition of the water, the analysis of the strontium-calcium atom ratio in unaltered fossils could be used as a valid method of measuring the strontium-calcium ratio of the ancient oceans. Such findings presented strong evidence that the strontium-calcium atom ratio of ocean waters has been of about the same order of magnitude since Palaeozoic times at least, because this atom ratio of the fossils resembles that of the modern counterparts.
In marine organisms the strontium-calcium atom ratio of the growing shells is apparently independent of the age of the organisms. No evidence was found that would indicate any seasonal fluctuations in the strontium-calcium atom ratio of marine organisms. It was also concluded that the temperature of the ocean waters is a relatively insignificant factor in aff'ecting the strontium content of marine organisms.
Besides the chemical composition and the ecological environment, the mineralogical character, such as crystal lattice, of the calcareous skeletons was of some significance. It was found that there is always more strontium present when the calcium carbonate exists as aragonite rather than as calcite.
METHODS OF ANALYSIS
All chemicals used in the present investigation were of analytical grade and tested for traces of strontium and calcium. A stock solution of strontium, 6 00 mg-atoms per litre, was prepared by dissolving 0-886 gram of strontium carbonate in a limited volume of hydrochloric acid and then diluting to one litre; and that of calcium. 200 mg-atoms per litre, was prepared by d.ssolvmg 2 002 grams of calcium carbonate in hydrochloric acid and diluting to one litre. From such stock solutions, suitable aliquots were taken and diluted for the comparison standards. Polyethylene containers were used for storage of standard solutions in order to avoid possible contamination from the glassware.
The calcareous skeletons of the marine organisms were carefully cleaned and air-dried. Duplicate
22 Thomas G. Thompson and Tsaihwa J. Chow
weighed samples (0-5 to 1 -0 gram) of the dried materials were heated in an oven to a temperature of 350° C and then cooled. The loss in weight was designated as the organic matter. The samples were then further ignited at 1,100° C until all carbonates were decomposed. Upon cooling and weighing, the difference in weight was considered as carbon dioxide. The residues were treated with 10 ml of water, and 12 N hydrochloric acid was added dropwise until solution was complete. The solutions were then diluted to one litre, thoroughly mixed, and analyzed for strontium and calcium using the "internal standards" technique of flame photometry by Chow and Thompson (1955 a and b).
RESULTS OF ANALYSIS
All analyses were made on the fresh calcareous skeletons (unless otherwise stated) which had been carefully cleaned and air-dried for several weeks. In order to obtain a general idea of the distribution of strontium in the biosphere, a large variety of species of carbonate-secreting marine organisms was analyzed, rather than concentrating on possible variations in just a few particular species.
In tables the calcium, strontium, carbon dioxide and organic matter content of the organisms are reported as percent of constituents in air-dried samples. To demonstrate more clearly the relation of the strontium to the calcium, it was deemed desirable to report this relationship as the atom ratio of strontium to calcium. For example, the calcareous alga, Bossea orbigniana, contains 01 99% of strontium and 29-2% of calcium. The strontium-calcium atom ratio would be:
0-199/87-63
= 312 X 10-3
29 -2/40 08
and indicates that for every 1 ,000 atoms of calcium there are present approximately three atoms of strontium.
The mineralogical data cited in this paper were taken from the publications of Boggild (1930), Vinogradov (1953) and Chave (1954). However, the mineralogical properties of the specimens, which were analyzed chemically by the authors, will be studied further by Dr. R. G. Bader.
DISCUSSION
Phylogenetic Aspects:
1. Marine Algae: In most of the previous studies on calcareous algae, determina- tions of calcium and magnesium were given, the calcium carbonate in the skeletons being reported as calcite. Only one analysis of strontium was reported, which showed 0-26% of strontium in the ash of Lithothamnion polymorphum (Noll, 1934).
The results of analysis of calcareous algae, Corallinaceae, are shown in Table 1(A). The average strontium-calcium atom ratio was 3-20 x 10-'. The diatoms, Coscino- discus, were also analyzed. As they are primarily of a silicious nature, only traces of calcium were found in the skeletons.
2. Phylum Protozoa: The calcium content of Foraminifera has been investigated extensively, especially its relation to the origin of calcareous marine sediments, but no strontium determinations appeared in the literature.
Analyses of calcareous Foraminifera (Table I (B)) by the authors showed an average strontium-calcium atom ratio of 3-07 x 10-'. The presence of magnesium in the skeletons was detected qualitatively. It has long been known that radiolarian skeletons are rich in strontium, but the authors were unable to collect sufficient material for a quantitative study.
3. Phylum Porifera: The classification of sponges is based on the chemical com- position of the skeletons such as the Calcarea containing calcite spicules. Fox and Ramage (1931) noted the presence of strontium in Porifera when they examined the ash of Clathrina spectroscopically.
The strontium-calcium atom ratio in carbonate-secreting marine organisms 23
The average strontium-calcium atom ratio of calcareous sponges, Caicarea, containing measurable quantities of strontium, was 2-99 x 10 * (Table 1 (C)). The calcium content in silicious sponges, Demospongiae, was minute; only traces of strontium were detected.
4. Coelenterata: The high strontium content in corals was observed by Noll ( 1 934). He reported the following results as percentage of strontium in their ash: hydrozoan Millepora alcicornis, 0-43%; alcyonarian Cora/Hum ruhrum, 0-17%; and madrepor- arian Porites clavaria, 0-42%. Odum (1951 b) reported an average strontium-calcium atom ratio of 10-6 X 10^^ for corals. The calcium carbonate of Hydrozoa and Madreporaria was reported as aragonite, whereas that of Alcyonaria was calcite.
In Table I (D) are the results of analysis on calcareous portions of Coelenterata. In Hydrozoa, the Hydrocorallina possess calcareous skeletons. Except Errinopora zarhyncha, all the analyses yielded high strontium-calcium atom ratios which averaged 9-49 X 10-'.
The soft corals, Alcyonaria, contained less strontium than other corals, and magnesium was present in the skeletons. However, Heliopora coerulea, which has the calcium carbonate in the form of aragonite, showed a much higher atom ratio than other Alcyonaria. The Heliopora with their external tube-like skeletons differ morphologically from all other Alcyonaria. With the high content of organic matter and their strontium-calcium atom ratios comparable to Porifera (Caicarea), it is interesting to note that the skeletons of Alcyonaria also have much in common morphologically with those of Porifera.
The solitary corals, Madreporaria, were found to have consistently high strontium- calcium atom ratios with an average of 9-86 x 10'. This is one of the orders of marine organisms to show the atom ratio equal to or greater than that of sea water, 8-9 x 10-3.
5. Minor Phyla: Specimens of these skeletonless marine organisms were analyzed. They were Bolinopsis microptera (Ctenophora), 7Vo/o/7/fl«a ac/Zco/a (Platyhelminthes), Micrura verrilli (Nemertea), Urechis caupo (Echiuroidea), Phascolosoma agassizii (Sipunculoidea), and Phoronopsis viridis (Phoronidea). Being non-carbonate secreting, these organisms contained 85 to 99 % of organic matter which varied considerably among specimens. Calcium was always present in the ash of the organisms, and only traces of strontium could be detected.
6. Phylum Annelida: Many members of Annelida such as Polychaeta possess calcareous tubes which serve to shelter them. Lowenstam (1954 a) reported from 0-2 to 0-9% of strontium in the calcareous tubes of Serpulidae. Chave (1954) showed that the°calcium carbonate in Polychaeta varies from pure calcite in specimens collected in the north Pacific and Behring Sea to almost pure aragonite in specimens collected
in tropic areas.
Analyses of calcareous annelid tubes given in Table I (E) showed strontium-calcium atom ratios ranging from 3-86 to 8-22 X lO-^ This is the only group of marine organisms that demonstrated a wide range for the strontium-calcium atom ratio.
7. Phylum Arthropoda: The Arthropoda are represented in the ocean mainly by species of Crustacea. The majority of Crustacea possesses chitinous exoskeletons. The Cirripedia is the only group in this phylum which possesses calcareous skeletons
24 Thomas G. Thompson and Tsaihwa J, Chow
of calcite structure. Besides the Cirripedia, the Decapoda also contain calcite as well as an appreciable amount of phosphorite. Vinogradov and Borovik-Romanova (1945) found 0-2% of strontium in the ash of Balanus balanoides. Webb (1937) also reported 0-1% of strontium in the ash of the hermit crab Eupagums {=Pagurus) bernhardus.
The results of analysis of calcareous portions of Arthropoda are given in Table I (F). The strontium-calcium atom ratios of Cirripedia averaged 4-45 x 10 -^ which is the highest value for the organisms containing calcite.
The canapace of Decapoda was found to contain more organic matter than Cirri- pedia, but their strontium contents were of the same order of magnitude, although the calcium content of Decapoda was much lower. Appreciable amounts of magnesium and phosphate were detected qualitatively. The strontium-calcium atom ratio was rather uniform with an average of 6-17 X 10-^ The claws of Cancer antennarius were also analyzed, and showed no difference in chemical composition as compared to the carapace. The soft carapace of C. productus in its moulting stage was found to consist mainly of organic matter and only 0-44% of calcium. This may be cited as an illustration of the change in chemical composition of the exoskeletons during moulting.
8. Phylum Mollusca: The molluscs are widely distributed in the ocean and con- stitute the largest invertebrate group which possesses calcareous protective shells. The chemical composition, mainly calcium, of Pelecypoda and Gastropoda was studied by Clarke and Wheeler (1922), Fox and Ramage (1931), Noll (1934), McCance and Masters (1937), Webb (1937), Asari (1951), Odum (1951 b), Kulp, et al. (1952) and Vinogradov (1953). The majority of Pelecypoda and Gastropoda possesses shells consisting chiefly of a calcite-aragonite mixture. Only three families (Anomiidae, Ostreidae and Pectinidae) were reported to have calcite shells. Aragonite was reported in calcareous portions of Amphineura, Scaphopoda, Cephalopoda and Nudibranchia.
Class Amphineura: The chitons are considered morphologically to constitute the most primitive class of living shell-bearing molluscs. Only a few calcium analyses on these organisms were reported and none on strontium.
The results of analysis of chiton plates are given in Table I (G). They were composed mainly of calcium carbonate with relatively high percentage of strontium. The strontium-calcium atom ratios averaged 8-06 X 10-^ which was much higher than those in other classes of molluscs.
Class Pelecypoda: The results of analysis of 44 species of Pelecypoda are shown in Table I (H). Nine families (Myidae, Clinocardium, Saxicavidae, Tellinidae, Lyonsiidae, Mactridae, Periplomatidae, Pholadidae and Solenidae) had strontium- calcium atom ratios greater than 2-0 X 10-^ The lowest strontium-calcium atom ratio was found in the families which were reported as having calcite shells, and that of the highest was Myidae.
Class Gastropoda: Forty-six species of subclass Prosobranchia shown in Table I (I) were analyzed. The strontium-calcium atom ratios among all families ranged from 1-31 to 2-14 X 10-^ and were less than that for Pelecypoda.
The Nudibranchia of subclass Opisthobranchia do not possess any calcareous protective shells. The body wall of Anisodoris and Archidoris, which contains cal- careous materials, was analyzed (Table I (I)). The organisms were high in organic
The strontium-calcium atom ratio in carbonate-secreting marine organisms 25
matter and gave an average strontium-calcium atom ratio of 10 / 10 ^ This appears to be in agreement with the finding of McCance and Masters (1937) that ArchiJoris britannica has a high strontium-calcium atom ratio. However, the strontium and calcium content occurs in such low concentrations that a slight experimental error in the determination of either one of the elements markedly affects the atom ratio.
Class Scaphopoda: The analysis of Scaphopoda was performed on Dentalium which was reported to have a strontium-calcium atom ratio of 2-34 X 10" (Odum, 1951 b). The specimen of Dentalium entale (Table I (J)) analyzed by the authors showed an atom ratio of 2-35 x 10-^
Class Cephalopoda: Modern Cephalopoda, except Nautilus, usually possess an inner shell. In general, the calcareous inner shells contain more organic matter than the shells of Pelecypoda and Gastropoda. Odum (195 1 b) reported a strontium-calcium atom ratio of 3-87 x 10-^ for a species of Nautilus. The inner shell of Sepia (Table I (J)) was found by the authors to have an atom ratio of 3-74 x 10-^ The chitinous plate of Loligo opalescens was found to contain chiefly organic matter and traces of calcium.
9. Phylum Bryozoa: The calcium content of Bryozoa studied by previous investi- gators was reported as calcite, but there was little information on the occurrence of other elements. In Table I (K) are the results of analysis of Bryozoa. The strontium- calcium atom ratios averaged 3-41 x 10-^. An appreciable amount of magnesium was present.
10. Phylum Brachiopoda: The calcareous shells of Class Articulata were reported as containing calcite. Odum (1951 b) found a strontium-calcium atom ratio of 1 -75 x 10-* for a species of Terebratula. The other class of Brachiopoda, Inarticulata, consists of apatite, and an atom ratio of 3-60 X 10-* was reported for a species of Crania (Odum, 1951 b). Analyses by the authors showed that Articulata shells (Table I (L)) had strontium-calcium atom ratios ranging from 1 -20 to 1 -57 x 10 *.
11. Phylum Echinodermata: With the exception of Holothuroidea, the Echino- dermata possess calcium-magnesium skeletons. The body wall of Psolus possesses calcareous plates. The calcium carbonate in skeletons was reported as calcite. Previous investigators reported the following results expressed as percentage of strontium in the ash: Asterias rubens, 0-^%; Marthasterias glacialis, 0-6%; and Ophiocomina nigra, 1% (Webb, 1937); Aster ias rubens, 0-15%; Gorgonocephalus eucnemis, 0-2%; Ophiopholis aculeata, 0-2%; and Strongylocentrotus drobachiensis, 0-15% (Vino- gradov and BoROViK-RoMANOVA, 1945).
The results of analysis of calcareous portions of Echinodermata are shown in Table I (M). All five classes of Echinodermata showed remarkable uniformity in the strontium-calcium atom ratio which could be considered as a constant.
12. Phylum Chordata: The results of analysis are given in Table I (N). The organ- isms contained an undetermined amount of sand particles and only traces of strontium.
In Table II are the results of analysis of calcareous materials other than marine invertebrates. The relationship between the strontium-calcium atom ratios of marine Arthropoda and Mollusca and those of fresh water organisms, from the meagre data available for the latter, indicated an analogy: the fresh-water organisms having lower atom ratios.
26 Thomas G. Thompson and Tsaihwa J. Chow
A summary of all analytical results is presented phylogeneticaily in Table III. The data given for each column represent the average values obtained on various carbonate- secreting marine organisms as listed in foregoing tables. The strontium-calcium atom ratios are very constant in accordance with the phylogenetic classification. With the exception of Zoantharia (Madreporaria) and Opisthobranchia (Nudibranchia), the atom ratios in calcareous portions of marine organisms are less than that of sea-water, 8-9 X 10-'. In these instances and in that of radiolaria (Odum, 1951 a), it is apparent that strontium does play a physiological role in the development of calcareous shells of carbonate-secreting marine organisms. The mechanism of this selectivity presents an interesting physiological problem. Controlled laboratory experiments of growing marine organisms in artificial sea-water free of strontium, and further elaborating Odum's work with waters of varying strontium-calcium atom ratios, would probably yield fundamental information for explaining the role of strontium in marine organisms.
Ecological Aspects
1. Habitat: Organisms of various species are found associated together in an ecological niche. All species that have not adjusted themselves physiologically to the existing conditions will be eliminated from a given community. Since the environ- mental conditions influence the life of marine organisms, it is of interest to observe any variations of chemical composition of marine organisms which live in such a community. Various species were collected from two rocky shores near the Hopkins Marine Station, California, at the mid and the low inter-tidal levels. The results of analyses of calcareous portions of these organisms are listed in Table IV.
The strontium-calcium atom ratios of the organisms collected at the mid-tidal level varied from 1-01 x 10-* (Mytilus califomianus) to 7-91 X 10* (Nuttallina calif ornica). The Mytilus-Mitella-Pisaster which were closely associated in the habitat, showed striking differences in the strontium-calcium atom ratio. The organisms collected at the low inter-tidal level had strontium-calcium atom ratios ranging from 1-35 X 10* (Diodora aspera) to 11 X 10-* {Anisodohs nobilis). It appears that the marine organisms which live in the same ecological niche accumulate calcium and strontium in their calcareous shells in decidedly different proportions. On the other hand, a very definite relationship between the atom ratio and the phylogenetic classification of the organisms is indicated.
Another series of studies was carried out on the specimens of Echinodermata. Species of Echinodermata which lived in different habitats varying from inter-tidal rocky shore to deep-water, muddy substratum were collected near the Carmel- Monterey-Pacific Grove area. All Echinodermata given in Table V showed a remark- able constancy in their strontium-calcium atom ratios ranging from 2-56 to 2-89 X 10*. Allowing for the individual variation and for experimental error, the atom ratios can be considered as identical for the whole phylum. Thus it may be concluded that some types of marine organisms will have a constant strontium-calcium atom ratio in their calcareous skeletons regardless of their habitats.
2. Water temperature: The water temperature as well as the salinity affect the solubility of the calcium and strontium carbonates in sea water. Wattenberg and TiMMERMANN (1936) demonstrated that the solubility of calcium carbonate in sea water increased with increasing salinity and with decreasing temperature. The
The strontium-calcium atom ratio in carbonate-secreting marine organisms 27
Strontium and calcium carbonates had identical solubility products of 5x10 ' in sea water at a temperature of 20" C and a salinity of 35 .^ (Wattenberg and
TiMMERMANN, 1938).
BoGGiLD (1930) Stated that ecological variations are not effective on the form of calcium carbonate in marine organisms. Odum (1951 b) and Kulp, et a/. (1952) have also concluded that the sea water temperature is not an important factor in determining the chemical composition of calcareous skeletons. However, Lowen- STAM (1954 b) demonstrated that the environmental factors, principally temperature, greatly influence the mineralogical properties of calcium carbonate in some marine organisms.
The data obtained by the authors (see Table 1) showed that some types of marine organisms collected from arctic to tropical oceans always consisted of a nearly constant strontium-calcium atom ratio in their calcareous shells regardless of the water temperature of the environment.
3. Salinity: In their studies of strontium in fossils and limestones, Kulp, et al. (1952) stated that " the primary factor which determines strontium-calcium ratio in the shell or limestone is the strontium-calcium ratio of the water from which these are deposited. The strontium-calcium ratio of the water in turn is related to the salinity and the source." Odum (1951 b), who used artificial sea waters of varying strontium- calcium atom ratios, demonstrated that this ratio in the calcareous shell of Physa is directly proportional to that of artificial sea water. He also reported an atom ratio of 9-23 X 10-^ for the Atlantic Ocean water. Later investigations by Chow and Thompson (1955 a and b) showed that samples of sea water collected from various oceans have a constant ratio between strontium and chlorinity, and calcium and chlorinity. Thus, the strontium-calcium atom ratio would be a constant (8-9 x 10^') regardless of the salinity of ocean waters. From these findings and the experiments of Odum (1951 b), it may be concluded that dilution or concentration of sea water within the tolerance of marine organisms would not be an influential factor on the strontium-calcium atom ratio of calcareous skeletons.
Mineralogical Aspects
Noll (1934) concluded from his investigations that there is always more strontium associated with aragonite limestones than with calcite limestones. Kulp, et al. (1952) substantiated this by stating that calcite has a crystal lattice which is less amenable to strontium than the aragonite lattice. Vinogradov (1953) implied that Noll's rule cannot be applied strictly to calcareous shells of marine organisms, but that the rule is valid, in general, for many of them.
The analytical results obtained by the present authors together with the mineral- ogical data secured by previous investigators are summarized in Table VI. The majority of the specimens studied apparently had calcium carbonate existing as calcite- The calcite group includes Algae (Corallinaceae), Protozoa (Foraminifera), Porifera (Calcarea), Coelenterata (Alcyonaria), Arthropoda(Cirripedia), Mollusca (Anomiidae, Ostreidae and Pectinidae of Pelecypoda), Bryozoa, Brachiopoda (Articulata) and Echinodermata. The average strontium-calcium atom ratio of this group ranged from 1-22 to 4-45 X 10-^ In phylum Mollusca, the Pelecypoda (except three families mentioned above) and the Gastropoda (Prosobranchia) had a calcite-aragonitc
28 Thomas G. Thompson and Tsaihwa J. Chow '
mixture in their shells. The strontium-calcium atom ratios of this group were 1-94 x 10-3 and 1-49 X 10-^ respectively.
Aragonite was reported only in the calcareous portions of Coelenterata (Hydrozoa and Madreporaria) and Mollusca (Amphineura, Scaphopoda, Cephalopoda and Nudibranchia). The strontium-calcium atom ratios of the aragonite group ranged from 2-35 to 10 X 10-^. Scaphopoda and Cephalopoda which contain aragonite had atom ratios of 2-35 X 10-^ and 3-74 x 10 -^ respectively. When comparisons are made mineralogically among molluscs, there is demonstrated a very definite trend for the occurrence of strontium, that is, aragonite Mollusca (10, 8-06, 3-74 and 2-35 X 10-3), aragonite-calcite mixture Mollusca (1-94 and 1-68 x 10-^) and calcite Mollusca (1 -31 and 1 •2^''x lO-^). It appears logical to conclude, therefore, that marine skeletons consisting of aragonite contain more strontium than those of calcite.
The mineralogical structure of calcium carbonate in Polychaeta (Annelida) is not certain. It was reported (Chave, 1954) that species of Serpula contained calcium carbonate that varies from pure calcite in one specimen to pure aragonite in another. The Polychaeta shown in Table I (E) had an average strontium-calcium atom ratio of 5-86 X 10-3, 2^_nd thus it may be concluded that for most specimens examined, the calcium carbonate is predominantly aragonite.
The Decapoda (Arthropoda), which were found to contain an appreciable amount of phosphorite as well as calcite, showed an average strontium-calcium atom ratio of 6-17 X 10-3. jj^jg jg jjj agreement with Odum's findings (1951 b) on the phosphate in Brachiopoda, and with the statement of Kulp, et al. (1952) that the presence of phosphate in the shells tends to yield a high strontium-calcium atom ratio.
Analyses (Table II) on Globigerina ooze of the Pacific Ocean which consists mainly of calcium carbonate, showed a strontium-calcium atom ratio of 1-49 X 10-3. jj^g calcareous deep-sea sediments from the Indian Ocean showed an atom ratio of 1-94 X 10-3. xhese values are in marked contrast to those obtained by Kulp, et al. (1952) but are in excellent agreement with an average value of 1-86 x 10-3 given by Odum(1951 b).
The matrix of Permian limestone deposits from Roche Harbour, Washington, showed the lowest strontium-calcium atom ratio, 0-63 X 10-3, Qf ^jj materials examined. This finding is comparable to the average atom ratio of 0-71 X 10-3 q^ a number of limestone samples obtained by Kulp, et al. (1952) and to the value cited by Rankama and Sahama (1949). The matrix of strontionite deposits from Anacortes, Washington, contained 3-56% of calcium and 52-5% of strontium respectively, equivalent to an atom ratio of 6,750 X 10-3.
Most of the analyses of calcareous portions of living marine organisms showed strontium-calcium atom ratios greater than those obtained on marine sediments. The strontium-calcium atom ratio for these marine sediments in turn was greater than those for the matrix of geologically older limestone deposits of marine origin. Furthermore, calcium carbonate deposited originally as aragonite should contain more strontium than that of calcite, as evidenced by analyses given above. Aragonite limestones are metastable and, in geological time, eventually change into calcite limestones which have a strontium-calcium atom ratio much less than that of marine organisms. Thus it seems logical to conclude that the strontium content of calcareous deposits decreases as the result of geological aging.
To explain the elimination of strontium from calcareous deposits, the following is
The strontium-calcium atom ratio in carbonate-secreting marine organisms
29
postulated: the solubility products of calcium and strontium carbonates are about the same order of magnitude, 5 x 10-', in sea water at a temperature of 20" C and a salinity of 35%„ (Wattenberg and Timmermann, 1938). When marine organisms die and disintegrate, there is a tendency for calcareous materials to halmyrolyze and go into solution. Should strontianite (SrCOj) be present, it would dissolve slowly because sea water is not saturated with respect to strontium carbonate. On the other hand, the ionic strength of calcium in sea water is such that the re-solution of calcium carbonate is exceedingly limited. Should celestite (SrSOJ be present in such marine organisms which have a high strontium-calcium atom ratio, it would leach much more readily from the calcareous matrix, as strontium sulphate is about ten times more soluble than strontium and calcium carbonates. To partially substantiate this hypo- thesis, the experiments of Odum (1951 a) are cited. He demonstrated that strontium existed as celestite and not strontianite as previously assumed in radiolaria. It is the intention of the authors to investigate this problem further and to determine the actual chemical composition of the strontium compound in such marine organisms as Madreporaria.
ACKNOWLEDGEMENT The authors wish to express their appreciation for assistance received from the National Science Foundation. They are indebted to Professors Lawrence R. Blinks, Rolf L. Bolin and Donald P. Abbott of the Hopkins Marine Station of Stanford University, for co-operation with the junior author in collection and identification of the California specimens; and to Professor Emery F. Swan of the University of New Hampshire, for contributing the Atlantic coast specimens. They also gratefully acknowledge the many invaluable suggestions received from Dr. Dlxy Lee Ray, and from their colleagues of the Department of Oceanography, University of Washington.
Table I. — Chemical composition of calcareous portions of carbonate-secreting
marine organisms
|
Carbon |
Organic |
Atom ratio |
||||
|
Locality |
Calcium |
Strontium |
dioxide |
matter |
^'^ X 1000 |
|
|
/o |
/o |
O ' /o |
% |
Ca |
||
|
(A) MARINE ALGAE |
' |
|||||
|
DIVISION RHODOPL |
lYTA |
|||||
|
FAMILY CORALLI |
NACEAE |
|||||
|
Bossea orbigniana |
Calif.* |
29-2 |
0199 |
36-5 |
14-6 |
3-12 |
|
Bos sea sp. |
Calif. |
27 0 |
0-201 |
34-7 |
18-0 |
3-41 |
|
Calliarthron cheilosporioides |
Calif. |
23-6 |
0151 |
30-8 |
- 29-8 |
2-93 |
|
Corallina chilensis |
Calif. |
26-8 |
0180 |
34-7 |
19-1 |
3 06 |
|
C. gracilis |
Calif. |
26-2 |
01 95 |
34-2 |
19-5 |
3-39 |
|
C. officinalis |
N. H. |
29-2 |
0196 |
35-1 |
14-0 |
3-07 |
|
Corallina sp. |
N. H. |
26-6 |
0186 |
33-1 |
19-1 |
3-19 |
|
Lithophyllum sp. |
Calif. |
29-2 |
0-203 |
34-5 |
16-3 |
3-18 |
|
Lithothamnion conchatum |
Calif. |
29 0 |
0-219 |
34-2 |
164 |
3-45 |
|
DIVISION CHRYSOP |
HYTA |
|||||
|
Coscinodisciis sp. |
Wash. |
trace |
trace |
41 |
18-9 |
|
|
(B) PHYLUM PROTOZOA, |
CLASS SARCC |
)DINA, |
ORDER FORAMINIFERA |
|||
|
Calcarina sp. |
Ifaliic Atoll + |
31-6 |
0193 |
40-8 |
6-72 |
2-78 |
|
Baculogypsina sp. |
Ifalik AtolK |
31-4 |
0-217 |
40-8 |
9 40 |
316 |
|
Foraminifera (unidentified) |
Bermuda |
33-3 |
0-239 |
40-1 |
519 |
3-28 |
* The California specimens of algae were identified by Dr. G. J. Hollenberc. t The Foraminifera specimens were collected by Professor Donald Abbott and were identified y Mr. Frank Sullivan.
30
Thomas G. Thompson and Tsaihwa J. Chow
|
Table I (cont.) |
||||||
|
1 |
Carbon |
Organic |
Atom ratio |
|||
|
Localitv Calcium Strontium |
dioxide |
matter \ |
^- X 1000 |
|||
|
> % |
% |
% |
% |
Ca |
||
|
(C) PHYLUM PORIFERA |
||||||
|
CLASS CALCAREA |
||||||
|
ORDER HOMOCOELA |
||||||
|
Leucosolenia eleanor |
Calif. |
1-29 |
trace |
3-24 |
20-2 |
— |
|
Leucosolenia sp. |
Maine |
13-6 |
0 099 |
23-3 |
25 0 ; |
3-33 |
|
Sponge (unidentified) |
Beaufort Sea 1 3 -5 |
0098 |
34-4 |
22-8 |
3-34 |
|
|
ORDER HETEROCOELA |
||||||
|
Leuconia heathi |
Calif. |
100 |
trace |
2-28 |
30-3 |
— |
|
Rhabdodermella nuttingi |
Calif. |
29-6 |
0149 |
35-8 |
12-7 |
2-30 |
|
CLASS DEMOSPONGIAE |
||||||
|
SUBCLASS TETRAXONIDA, ORDER EPIPOLASIDA |
||||||
|
Tethya aurantia |
Calif. |
0 06 |
trace |
6-30 |
42-3 |
— |
|
SUBCLASS CORNACUSPONGIDA |
||||||
|
ORDER POECILOSCLERINA |
||||||
|
Esperiopsis originalis |
Calif. |
0 08 |
trace |
2-12 |
38-2 |
— |
|
Ophlitaspogia pennata |
Calif. |
005 |
trace |
1-97 |
40-8 |
— |
|
ORDER HAPLOSCLERINA |
||||||
|
Haliclona permolUs Calif. |
0 07 |
trace |
6-57 |
42-2 |
— |
|
|
ORDER KERATOSA |
||||||
|
Euspongia sp. |
Unknown |
005 |
trace |
12-6 |
85-0 |
— |
|
(D) PHYLUM COELENTERATA* |
||||||
|
CLASS HYDROZOA, ORDER MILLEPORINA |
||||||
|
Millepora tenera |
Ifalik Atoll |
381 |
0-686 |
41-4 |
3-15 |
8-22 |
|
ORDER STYLAS' |
ERINA |
|||||
|
Allopora calif ornica |
Calif. |
36-5 |
0-778 |
38-5 |
8-46 |
9-74 |
|
A. campyleca paragea |
Gulf of Alaska |
35-7 |
0-768 |
40-6 |
4-47 |
9-83 |
|
A. porphyra |
Calif. |
38-8 |
0-580 |
41-1 |
2-91 |
6-83 |
|
A. venusta |
Calif. |
370 |
0-808 |
40-4 |
5-38 |
9-97 |
|
Cryptohelia trophostega |
Bering Sea |
37-8 |
0-930 |
411 |
3-42 |
11-2 |
|
Distichopora violacea |
Marshall Is. |
37-6 |
0-640 |
41-2 |
3-54 |
7-77 |
|
Errinopora zarhyncha |
Aleutian Is. |
37-5 |
0-224 |
43-1 |
2-50 |
2-73 |
|
Stylaster elegans |
Marshall Is. |
37-4 |
0-852 |
41-3 |
3-84 |
10-4 |
|
S. sanguineus |
Hawaii |
37-7 |
0-843 |
41-2 |
3-88 |
10-2 |
|
CLASS ANTHOZOA, SUBCLASS AL |
CYONAR |
lA |
||||
|
ORDER STOLONIFERA |
||||||
|
Tubipora sp. |
Unknown |
311 |
0-225 |
41-8 |
2-38 |
3-30 |
|
ORDER ALCYNACEA |
||||||
|
Eunephthya rubiformis |
Beaufort Sea |
4-72 |
0-039 |
12-4 |
30-4 |
3-78 |
|
ORDER PENNATULACEA |
||||||
|
Stylatula elongata |
Calif. |
22-7 |
0-128 |
28-5 |
33 0 |
2-64 |
|
ORDER GORGO |
NACEA |
|||||
|
Psammogorgia arbuscuLa |
: Calif. |
21-4 |
0-136 |
30-0 |
37-5 |
2-90 |
ORDER COENOTHECALIA
Heliopora coerulea I Ifalik Atoll
37-3
0-618
40 0
660
7-57
* Some of the specimens were contributed by the Hopkins Marine Station from the collection of the late Professor W. K. Fisher.
The strontium-calcium atom ratio in carbonate-secreting marine organisms
31
Table I (cont.)
|
Locality |
Carbon Calcium Strontium dioxide o / 0/ 0 /o / 0 /cj |
Organic matter
/o
Atom ratio
^ y 1000 Ca
SUBCLASS ZOANTHARIA, ORDER MADREPORARIA
Acropora sp. Astrangia sp. Balanophyllia elegans Caryophyllia sp. Meandrina sinuosa PociUopora sp. Porites sp.
Ifalik Atoll
Calif.
Calif.
Calif.
Bermuda
Ifalik Atoll
Ifalik Atoll
37-3 370 32-3 37-4 36-5 37-9 37-3
(E) PHYLUM ANNELIDA, CLASS POLYCHAETA FAMILY CIRRATULIDAE
Dodecaceria pacifica B.C., Canada* 32-5
D.fistulicola Calif. 35 4
FAMILY SERPULIDAE
Salmacina tribranchiata \ Calif.
Serpula vermicu/aris B.C., Canada
S. vermicularis Calif.
Spirorbis sp. N. H.
33-2 32-4 321 29-2
0-810 0-868 0-666 0-850 0-802 0-735 0-790
0-574 0-530
0-596 0-288 0-289 0-247
41 41 37 41 41 41 40
40-6 40-3
36-5 40-7
42-5 34-2
3-85 3-43 8-84 2-90 3-25 3-13 5-38
5-38 5-20
6-35 4-51 4-60 15-0
ORDER THORACICA
Floridaf
N. H.
N. H.
Wash.
Beaufort Sea
Florida
Florida
Wash.
Calif.
Calif.
Wash.
Wash.
B.C., Canada
Calif.
N. C.
Calif.
Calif.
370 37-6 34-1 39-1 36-1 36-7 36-6 37-0 37-4 35-6 34-2 37-4 36-1 37-2 32-4 36-8 35-6
0-428 0-382 0-336 0-324 0-337 0-381 0-345 0-358 0-371 0-334 0-282 0-364 0-337 0-38! 0-328 0-344 0-381
41 41 39 42 41 41 41 41 41 39 36 41 41 41 37 40 41
5 3
7 1 3 4 2 3 2 7
12 2
3 1 8 4 4
•00
•27
-76
-80
-24
-80
-39
-12
-88
-18
-3
-72
-80
-88
-33
-48
-07
(F) PHYLUM ARTHROPODA, SUBPHYLUM MANDIBULATA, SUPERCLASS CRUSTACEA CLASS CIRRIPEDIA,
Balanus amphitrite
B. balanoides
B. balanoides
B. cariosus
B. crenatus
B. eburneus
B. eburneus
B. glandula
B. glandula
B. nubilis
B. nubilis
Balanus sp.
Balanus sp.
B. tintinnabulum
Chthamalus fragilis
Mitella polymerus
Tetraclita squamosa
9-92 10-7
9-41 10-4 10-1
8-85
9-67
8-07 6-84
8-24 4-06 4-12 3-86
5-28 4-64
CLASS MALACOSTRACA, SUBCLASS EUCARIDA, ORDER
Cancer antennarius C. antennariust C. borealis C. magister C. productus C. productus ** Hemigrapsus nudus Pugettia producta
Calif.
Calif.
N. H.
Wash.
Calif.
Calif.
Wash.
Calif.
(G) PHYLUM MOLLUSCA
CLASS AMPHINEURA, ORDER PO
27-2 28-0 24 0 24-0 23-3 0-44 26-0 21-2
0-363 0-371 0-322 0-351 0-308 trace 0-349 0-278
30-2 32-5 29 3 281 30-2 8-6 29-3 25-7
I
DECAPODA
32-7 20 0 27-2 28-1 30-0 85-5 28-7 33-3
LYPLACOPHORA
Cryptochiton stelleri C. stelleri
Cyanoplax hartwegii Nuttallina californica Tonicella lineata
Calif.
Wash.
Calif.
Calif.
Calif.
38-2 37-1 38-3 38-2 37-6
0-736 0-751 0-716 0-662 0-640
40-3 41-4 41-3 41 2 41 4
6-10 3-66 5-70 4-69 4-83
50
78 27 74 32 42 53 29 3-77 4-45 4-27 4-67 4-62 4-27 4-88
612 6 05 613 669 604
6-13 600
8-80
9-25 8-55 7-91
7-79
* The specimens from British Columbia were provided by Mr. Cyril Berkeley of the Pacihc
Biological Station. /^ c v
t The Florida specimens were provided by Mr. C. b. Yent.sch. t Claw ** Moulting
32
Thomas G. Thompson and Tsaihwa J. Chow
Table I (cont.)
Carbon Organic ' Atom ratio Calcium Strontium dioxide matter Sr
7o
/o
Ca
X 1000
(G) PHYLUM MOLLUSCA (continued) CLASS AMPHINEURA, ORDER
POLYPLACOPHORA
Ischnochiton heathiana
I. mertensii
Ischnochiton sp.
Katharina tunicata
Mopah'a ciliata
M. lignosa
M.muscosa
M. muscosa
M. wosnessenskii
Chiton (unidentified)
Calif.
Calif.
Wash.
CaUf.
Calif.
Calif.
Calif.
Wash.
Calif.
Beaufort Sea
38-7 38-6 38-8 38-7 37-2 37-9 37-9 37-8 37-6 37-0
(H) PHYLUM MOLLUSCA, CLASS PELECYPODA ORDER FILIBRANCHIA FAMILY ANOMIIDAE
Pododesmus macroschisma Calif.
FAMILY MYTILIDAE
Botula falcata Modiolus capax M. modiolus M. modiolus M. modiolus M. modiolus Modiolus sp. Mytilus edulis M. edulis M. edulis M. edulis M. edulis M. edulis M. edulis M. edulis M. californianus M. californianus
FAMILY
Pecten hindsii P. hericius
Calif.
Calif.
N. H.
N. H.
N. H.
N. H.
Wash.
N. H.
N. H.
Maine
Maine
Wash.
B.C., Canada
Beaufort Sea
Calif.
Calif.
Calif.
PECTINIDAE
Wash. Wash.
ORDER EULAMELLIBRANCHIA FAMILY OSTREIDAE
Crassostrea virginica C. virginica Ostrea gigas O. gigas O. lurida
N. H.
N. C.
B.C., Canada B.C., Canada Calif.
FAMILY SPONDYLIDAE
Spondylus sp. I unknown
FAMILY CHAMIDAE
Chama pellucida Calif.
FAMILY TELLINIDAE
Macoma irus Calif.
M. nasuta Calif.
M. secta Calif.
Tellina sp. B.C., Canada
38-6
38-6
37-5 37-8 38-8 37-5 37-8
38
37
37
38
37
38
38
36
36
390
38-5
38-2 37-8
33-7 37-8 34-6 36-2 38-6
38 0
36-8
0-636 0-636 0-680 0-687 0-626 0-664 0-608 0-709 0-606 0-680
0-103
0196 0-103 0125 0-116 0-112 0-132 0-099 0-176 110 128 116 106 154 117 118 0-086 0086
0111 0107
0 092 0-107 0-097 0100 0-085
0-128
0-142
•4 •3 •8 ■6 -1 -2
41'
41
41-
39-
41'
41-
41 0
42-2
41-4
41-5
42-6
38-9 41-1 41-8 42-7 41-3 4M 42-1 42-5 42-0 42-1 42-4 42-2 41-4 41-2 42-2 43-1 43-1
41-8 42-1
42-4 41-8 37-6 42-5 42-5
41-6
42-3
3-63 3-95 3-06 3-91
•83 -26 -74 -31
4-
4-
4-
3'
3-88
4 00
1-75
•67 10 ■97 39 •58 20 96 10 32 30 52 24 42 53 87 54 70
1-91
1-75
216 2-34 13-3 1-71 1-68
1-67
2-47
|
38-7 |
0153 |
40-8 |
2-42 |
1-81 |
|
38-0 |
.0-215 |
38-9 |
2-27 |
2-59 |
|
38-9 |
0-248 |
42-5 |
2-17 |
2-91 |
|
37-1 |
0173 |
42-1 |
2-50 |
214 |
7-52 7-55 8-02 8-12 7-69 801 7-32 8-57 7-37 8-41
1-22
2-32 1-25 1-52 1-37 1-37 1-60
119 216 1-33 1-53 1-43 1-26 1-82 1-46 1-48 101 102
1-33 1-29
1-25 1-29 1-28 1-26 101
1-54
1-76
The strontium-calcium atom ratio in carbonate-secreting marine organisms
33
Table I (conf.)
|
Carbon |
Organic |
Atom ratio |
||||
|
Locality |
Calcium |
Strontium |
dioxide |
matter |
^~ ' 1000 |
|
|
Vo |
o - o |
o / o |
o/ |
Co |
||
|
FAMILY SOLENIDAE |
||||||
|
Ensis directiis |
N. H. |
370 |
01 64 |
41-9 |
3-47 |
2 03 |
|
Siliqua costata |
N. H. |
38-4 |
0182 |
42-4 |
2-46 |
217 |
|
S. patula |
Wash. |
38-4 |
0-207 |
42-0 |
2-88 |
2-46 |
|
Solen sicarius |
CaHf. |
38-1 |
0116 |
42-9 |
1-66 |
1-39 |
|
FAMILY MACTRIDAE |
||||||
|
Mesodesma deauratum |
N. H. |
37-6 |
0164 |
42-0 |
3-31 |
2 00 |
|
Schizothaerus nuttallii |
Wash. |
37-8 |
0195 |
41-6 |
4-00 |
2-36 |
|
S. nuttallii |
Calif. |
391 |
0177 |
42-6 |
1-79 |
207 |
|
Spisida solidissima |
N. H. |
38-2 |
0-216 |
42-0 |
2-58 |
2-58 |
FAMILY PLEUROPHORIDAE
Cyprina islandica \ N. H.
FAMILY CLINOCARDIIDAE
Clinocardium nuttallii C. nuttallii C. nuttallii
Wash. Wash. Calif.
FAMILY VENERIDAE
Compsomyax subdiaphcma Irus lamellifer Protothaca staminea P. staminea P. tenerrima Saxidomus giganteus S. muttallii Tivela stultorum Venus mercenaria
Wash. Calif. Wash. Calif. Wash. Wash. Calif. Calif. Canadian Atlantic
FAMILY
Per ip lama sp.
PERIPLOMATIDAE
I B.C., Canada
FAMILY LYONSIIDAE
Mvtilimeria nuttallii Calif.
FAMILY MYIDAE
Mya arenaria M. arenaria M. arenaria M. arenaria
Maine Wash. Oregon
Wash.
FAMILY
Panope generosa Saxicava sp.
SAXICAVIDAE
Wash.
Beaufort Sea
FAMILY PHOLADIDAE
Pholadidea penita Calif.
P. ovoidea Calif.
Zirfaea crispata Z. pilsbryi
N. H.
Calif.
39-2
37-6 38-5 38-0
38-6 37-6 39-4 38-2 37-3 38-6 37-8 38-8
38-6
37-9
36-6
38-6 38-7 38-8 38-3
38-2 37-9
37-0 38-7 38-3 39-0
0135
0-245 0-188 0-185
0-180 0134 0-179 0-149 0-175 0-192 0-125 0-120
0148
0-183
0-188
0-246 0-238 0-181 0181
0-207 0-196
0-147 0-192 0-148 0-230
42-7
41-9 41-8 41-8
42-2 41-6 41-8 42-0 42-0 42-3 42-2 42-0
42-5
42-0
39-8
42-2 42-3 42-3 42-2
42-3 40-5
41-2
42-2 4I-2 42-5
(I) PHYLUM MOLLUSCA, CLASS GASTROPODA SUBCLASS PROSOBRANCHIA ORDER ASPIDOBRANCHIA, FAMILY FISSURELLIDAE
Diodora aspera i Calif.
Fissurella volcano j Calif.
Megathura crenulata ' Calif.
Megatebennus bimaculatus \ Calif. C
SUBORDER ZYGOBRANCHIA
38-5 39-5 38-0 390
0-114 0-108 0-104 0-117
41-5 42-6 42-8 42-1
1-93
2-98 3-68 3-55
07 20 30
45 94 23 63 ■34
2-38
2-60
7-63
2-44 2-28 2-48 2-22
2 03 4-98
3-63 2-36 3-63 2-30
3-54 1-86 2-03
2-74
1-57
2-98 2-23 2-22
2-13 1-63 2-08 1-78 214 2-27 1-52 1-41
1-75
2 20
2-35
2-91 2-81 2-12 216
2-48 2-36
1-82 2-27 1-77 2-70
1-35 1-25 1-25 1-38
34
Thomas. G. Thompson and Tsaihwa J. Chow
Table I (cont.)
Calcium Strontium
Carbon dioxide
Organic matter
%
Atom ratio Sr
Ca
1000
|
FAMILY HALIOTIDAE |
|
|
Haliotis cracherodii |
Calif. |
|
H. rufescens |
Calif. |
|
SUBORDER PATEL |
.lace; |
|
FAMILY ACMAEIDAE |
|
|
Acmaea digitalis |
Calif. |
|
A. digitalis |
Calif. |
|
A. insessa |
Calif. |
|
A. limatula |
Calif. |
|
A. mitra |
Calif. |
|
A. mitra |
Wash. |
|
A. pelt a |
Calif. |
|
A. persona |
Calif. |
|
A. scabra |
Calif. |
|
A. t. scutum |
N. H. |
|
A. t. scutum |
Calif. |
|
Lottia gigantea |
Calif. |
SUBORDER TROCHACEA FAMILY TROCHIDAE
Calliostoma canaliculatum ' Calif. C. costatum Calif.
C. gloriosum Tegula brunnea T. funebralis T. montereyi
Wash. Calif. Calif. Calif.
FAMILY TURBINIDAE
Astraea inaequalis I Calif.
ORDER PECTINIBRANCHIA SUBORDER TAENIOGLOSSA FAMILY EPITONIIDAE
Epitonium groenlandicum \ Atlantic
Epitonium sp. | Calif.
FAMILY VERMETIDAE
Petaloconchus montereyensis i CaUf.
FAMILY LITTORINIDAE
|
Littorina litorea |
Maine |
|
L. litorea |
N. H. |
|
L. palliata ( = L. obtusata) |
N. H. |
|
L. planaxis |
Calif. |
|
L. rudis (= L. saxatilis) |
N. H. |
|
L. rudis |
N. H. |
|
L. scutulata |
Calif. |
FAMILY CALYPTRAEIDAE
Crepidula adunca ' Calif.
C.fornicata | Mass.
C. nummaria ] Calif.
FAMILY Polinices Heros P. draconis Natica sp.
NATICIDAE
Mass. ' Wash. Beaufort Sea
SUBORDER STENOGLOSSA FAMILY OLIVIDAE Oliva litterata \ Florida
Olivella biplicata \ Calif.
37-1 38-8
38-5 37-6 37-8
38 37 38 37 37 37 38 37 37
37-2 370 36-3
37-5 37-4 38-2
36-7
370 36-8
35-6
38-4 38-7 37-2 37-8 38-6 37-5 38-4
37-7 38 0 38-5
37-7 38-8 37-8
39-6 38-9
0123 0130
0199 0-204 0183 01 68 0161 01 62 0151 0-201 0-180 0180 01 64 0-170
0-129 0-122 0-131 0-124 0-113 0-121
0-120
0-118 0-120
0144
0107 0107 0-142 0-155 0-140 0-125 0-121
0140 0-149 0-153
0-121 0-137 0-108
0145 0113
42-2 41-7
41-0
41-2 41-7 40-6 41-9 41-5
41 0
41-9 41-2
40-2
42-5 42-8 41-0 42-4 41-8 41-7 42-5
42 0 42-3 42-3
42-2 42-5 41-8
42-8 42-4
3-87 3-82
|
42-6 |
2-51 |
|
42-1 |
2-79 |
|
42-4 |
2-84 |
|
42-0 |
3 03 |
|
42-4 |
2-61 |
|
42-3 |
2-48 |
|
40-4 |
3-39 |
|
42-0 |
3-16 |
|
42-5 |
1-97 |
|
41-8 |
3-28 |
|
41-7 |
3-65 |
|
42-2 |
2-71 |
4-95 2-96 4-73 4-06 3-64 3-99
5-37
3 07 4-80
710
27 84 72 62 50 39 77
3-22 2-37 2-36
2-96 2-28 3-54
1-61 1-84
1-52 1-54
2-37 2-48 2-21 201 1-98 1-94 1-84 2-45 2-21 2-14 2 00 2-08
1-59 1-51
-65 -51 •38
1-45
1-50
1-46 1-49
1-85
1-27 1-26 74 87 66 53
1-44
1-70 1-79 1-82
1-47 1-61 1-31
1-67 1-33
The strontium-calcium atom ratio in carbonate-secreting marine organisms
Table I (cont.)
35
Locality
Calcium Strontium % %
Carbon dioxide
/a
Orf^anic matter
%
Atom ratio Sr
Ca
^ 1000
FAMILY FUSINIDAE
Fusinus monksae i Calif.
FAMILY NASSARIIDAE Nassa obsoleta ' N. H.
FAMILY MURICIDAE
Acanthina spirata Calif.
Murex pume Florida
M. triolatus Calif.
Thais canaliculata Calif.
T. emarginata Calif.
T. lamellosa Wash.
T. lapillus N. H.
T. lapillus N. H.
35-5
36-4
38-6 39-9 380
38-1 37-6 38-8 38-5 36-5
ons
0151
0131 0172 0131 0128 0138 0129 0126 0128
40- 1
40-9
42-3 41-7 42-6 42-8 42-3 42-8 42-7 39-4
4-27
6-46
2-66 2-30 1-68 2-26 3 03 1-45 113 3-68
1-48
1-89
55
97
58
54
68
1-52
1-50
1-60
SUBCLASS OPISTHOBRANCHIA, ORDER NUDIBRANCHIA
Anisodoris nobilis Calif.
Archidoris montereyensis I Calif.
Triopha grandis I Calif.
(J) PHYLUM MOLLUSCA CLASS SCAPHOPODA
Dentalium entale i Wash.
2-60 316 0-25
38-2
0 063 0 062
trace
0196
3-25 4-68
67-2 78 0
-91-3-
-)
42-3
1-81
11 9
2-35
CLASS CEPHALOPODA, SUBCLASS DIBRANCHIATA, ORDER DECAPODA
Loligo opalescens Calif. I trace trace trace 99 5
Sepia sp.
unknown
35-8
(K) PHYLUM BRYOZOA, CLASS ECTOPROCTA ORDER CYCLOSTOMATA
Idmonea sp.
Crista sp.
Bryozoa (unidentified)
Bryozoa (unidentified)
Bryozoa (unidentified)
f Calif Calif.
Beaufort Sea Beaufort Sea Beaufort Sea
ORDER CHEILOSTOMATA Bugula californica , Calif.
Hippodiplosia insculpta Phidolopora pacifica
Calif. Calif.
35-6
35-7 34-3 30-6 25-3
18-2 29-4 33-7
0-293
0-307 0-282 0-256 0-209 0181
0-124 0-247 0-221
401
38-1 38-2 40-2 35 0
31-8
23-7 35-8 400
7-35
7-90 6-28 7-30 16-5 23-2
36-0 13-8 6-37
3-74
3-94 3-61 3-41 3-12 3-27
312 3-84 3 00
(L) PHYLUM BRACHIOPODA, CLASS ARTICULATA, ORDER TESTICARDINES
Hemithyris psittacea Beaufort Sea 37-7 0113 42-2 3 02 1
H. psittacea* Beaufort Sea
Terebratalia transversa Wash.
Terebratulina unguicala Calif.
Brachiopoda (unidentified) Calif.
37-7 38-9 38 0 37-8 38-7
0113 0102 0130 0113 0108
42-2 42-8 41-3 42-5 42-7
3 02 1-94 2 02 1-8! 1-79
1-37 I 20 1-57 1-37 1-28
(M) PHYLUM ECHINODERMATA
CLASS CRINOIDEA I Antedon sp. ! Calif.
i CLASS ASTEROIDEA ORDER FORCIPULATA
25-8
0-145
38-
13-3
2-56
Asterias forbesi A. vulgaris A. vulgaris Leptasterias aequalis L. pusilla Mediaster aequalis
Mass. N. H.
Mass. Calif. Calif. Calif.
|
18-6 |
0113 |
24-9 |
39-4 |
2-78 |
|
22-5 |
0141 |
27-9 |
33-6 |
2-86 |
|
20-2 |
0-128 |
28-6 |
34-4 |
2-89 |
|
20-9 |
0-127 |
32-7 |
31-0 |
2-78 |
|
25-5 |
0146 |
37-7 |
204 |
2-61 |
|
27-3 |
01 58 |
36-1 |
190 |
2-60 |
* Remains.
36
Thomas G. Thompson and Tsaihwa J. Chow
Table I (cont.)
|
Carbon |
Organic |
Atom ratio |
||||
|
Locality |
Calcium |
Strontium |
dioxide |
matter |
— 1000 |
|
|
% |
% |
/o |
% |
Ca |
||
|
CLASS ASTEROIDEA (continued) |
||||||
|
ORDER FORCIPULATA |
||||||
|
Pisaster brevispinus |
Calif. |
22-7 |
0-131 |
33-6 |
28-5 |
2-64 |
|
P. giganteus |
Calif. |
17-2 |
0101 |
31-9 |
37-2 |
2-69 |
|
P. ochraceiis |
Calif. |
24-6 |
0148 |
34-0 |
24-4 |
2-76 |
|
Pycnopodia helianthoides |
Calif. |
200 |
0114 |
31-8 |
33-5 |
2-60 |
|
ORDER SPINULOSA |
||||||
|
Henricia leviuscula |
Wash. |
23-1 |
0136 |
30-3 |
28-6 |
2-69 |
|
H. leviuscula |
Calif. |
25-2 |
0-155 |
33-3 |
25-8 |
2-81 |
|
H. sanguinolenta |
N. H. |
18-4 |
0112 |
28-6 |
38-2 |
2-78 |
|
Henricia sp. |
Beaufort Sea |
20-6 |
0125 |
29-0 |
34-0 |
2-78 |
|
Solaster papposus |
Beaufort Sea |
23-2 |
0-131 |
31-0 |
28-8 |
2-60 |
|
Patiria miniata |
Calif. |
26-8 |
0162 |
36-1 |
21-2 |
2-77 |
|
ORDER PHANERO |
ZONIA |
|||||
|
Hippasteria spinosa |
Wash. |
22-7 |
0-137 |
30-8 |
29-6 |
2-76 |
|
Luidia sp. |
Calif. |
24-1 |
0-142 |
34-1 |
19-3 |
2-69 |
|
CLASS OPHIUROIDE |
A |
|||||
|
ORDER EURYALAE |
||||||
|
Gorgonocephalus sp. |
Beaufort Sea |
26-6 |
0158 |
33-4 |
21-8 |
2-72 |
|
ORDER OPHIURA] |
^ |
|||||
|
Amphipholis squamata |
^ Calif. |
24-7 |
0-146 |
33-2 |
23-5 |
2-70 |
|
Ophiopholis aculeata |
Maine |
24-5 |
0146 |
32-6 |
24-4 |
2-72 |
|
O. aculeata |
N. H. |
25-9 |
0-149 |
34-5 |
19-7 |
2-63 |
|
Ophiothrix spiculata |
Calif. |
20-4 |
0-118 |
28-9 |
33-4 |
2-64 |
|
Ophioplocus esmarki |
Calif. |
27-1 |
0-165 |
36-9 |
17-0 |
2-79 |
|
Ophiura sarsii |
Wash. |
31-2 |
0185 |
39-2 |
11-0 |
2-71 |
|
0. sarsii |
Beaufort Sea |
30-2 |
0-175 |
38-0 |
13-5 |
2-65 |
|
CLASS ECHINOIDE/i |
k. |
|||||
|
ORDER CENTRECHINOIDA |
||||||
|
Strongylocentrotus |
||||||
|
drobachiensis |
N. H. |
34-8 |
0-214 |
41 0 |
5-68 |
2-81 |
|
S. drobachiensis |
Wash. |
35-5 |
0-214 |
42 0 |
3-33 |
2-76 |
|
S. drobachiensis |
Wash. |
35-6 |
0-210 |
42-0 |
3-05 |
2-70 |
|
S. fragilis |
Calif. |
32-7 |
0-188 |
39-6 |
9-28 |
2-63 |
|
S. franciscanus |
Wash. |
36-4 |
0-218 |
42-8 |
2-97 |
2-74 |
|
S. pallidus |
Beaufort Sea |
32-2 |
0-191 |
40-0 |
810 |
2-71 |
|
S. purpuratus |
Wash. |
35-4 |
0-215 |
43-8 |
2-18 |
2-78 |
|
S. purpuratus |
Calif. |
33-2 |
0-210 |
41-4 |
6-96 |
2-89 |
|
Heterocentrotus trigonarius |
Ifalik Atoll |
31-6 |
0180 |
43-9 |
1-20 |
2-60 |
|
ORDER CLYPEAST |
ROIDA |
|||||
|
Dendraster excentricus |
Calif. |
33-5 |
0-205 |
43-5 |
2-85 |
2-79 |
|
Echinarachnius parma |
N. H. |
31-8 |
0-178 |
41-4 |
5-62 |
2-56 |
|
ORDER SPATANGi |
DIDEA |
|||||
|
Brisaster sp. |
Wash. |
30-5 |
0164 |
40-1 |
8-77 |
2-46 |
|
CLASS HOLOTHURC |
>IDEA |
|||||
|
ORDER DENDROCHIROTIDA |
||||||
|
Cucumaria curata |
Calif. |
0-8 |
trace |
7-5 |
84-0 |
— |
|
Psolus chitonoides |
Wash. |
29-1 |
0-173 |
38-3 |
12-2 |
2-72 |
|
P. peroni |
Beaufort Sea |
25-2 |
0-153 |
32-1 |
25-8 |
2-78 |
|
P. sp. |
Calif |
28-6 |
0-170 |
34-5 |
18-0 |
2-72 |
|
(N) PHYLUM CHORDATA |
CLASS ASCII |
)IACEA |
||||
|
Polyclinum planum \ Calif. |
0-30 |
trace |
13-8 |
70-0 |
— |
|
|
Synoicum par-fustis |
Calif. |
0-38 |
trace |
13-5 |
69-1 |
— |
The strontium-calcium atom ratio in carbonate-secreting marine organisms
37
Table II. — The occurrence of calcium and strontium in substances other than
marine organisms
Localilv
Carbon Organic Atom ratio Calcium Strontium dioxide matter ' Sr
Ca
X 1000
|
Walrus (Odobenus rosmarus) |
||||||
|
ivory |
Alaska |
21 0 |
trace |
2-96 |
36-8 |
|
|
Fresh water clam (unidentified) |
Wash. |
380 |
0 085 |
41-4 |
5-53 |
102 |
|
Fresh water clam (unidentified) |
Wash. |
36-4 |
0072 |
41-3 |
6 02 |
0-90 |
|
Potamobius sp. |
Wash. |
19-8 |
0077 |
21-7 |
45-5 |
1-78 |
|
Deep sea sediments* |
Indian Ocean (Swedish Deep |
|||||
|
Sea Expedi- |
29-4 |
0125 |
37-7 |
2-95 |
1-94 |
|
|
tion 1948- |
||||||
|
1949) |
||||||
|
Globigerina oozet |
Pacific Ocean |
37-5 |
0122 |
41-8 |
1-46 |
1-49 |
|
Coquina rock (cemented shells) |
Florida |
37-8 |
0153 |
41-7 |
1-57 |
1-85 |
|
Limestone deposits |
Wash. |
38-1 |
0052 |
42-5 |
0-68 |
0-63 |
|
Strontianite deposits |
Wash. |
3-56 |
52-5 |
31-5 |
0-26 |
6,750 |
|
Sea water |
Over-all |
8-90 |
* Specimen was provided by Mr. Taivo Laevastu. t Specimen was provided by Dr. Howard R. Gould.
Table III. — Summary of results arranged in accordance with the phylogenetic
classification of marine organisms
|
Carbon |
Organic |
Mean atom ratio |
|||
|
Classification |
Calcium |
Strontium |
dioxide |
matter |
^'' 1000 |
|
mean % |
mean % |
mean "„ |
mean % |
Ca |
|
|
Marine Algae, Corallinaceae |
27-4 |
0193 |
34-2 |
18-5 |
3-20 |
|
Protozoa, Foraminifera |
32-1 |
0-216 |
40-6 |
7-10 |
3-07 |
|
Porifera, Calcarea |
11-8 |
0 069 |
19-8 |
22-2 |
2-99 |
|
Demosponiae |
0 06 |
trace |
5-91 |
49-7 |
— |
|
Coelenterata, Hydrozoa |
37-4 |
0-711 |
41-0 |
4-16 |
S-69 |
|
Anthozoa |
|||||
|
Alcyonaria |
23-2 |
0-229 |
30-5 |
22-0 |
4-04 |
|
Zoantharia |
36-5 |
0-789 |
40-7 |
4-40 |
9-86 |
|
Annelida, Polychaeta |
32-5 |
0-421 |
39-1 |
6-84 |
5-87 |
|
Arthropoda. Cirripedia |
36-3 |
0-354 |
40-8 |
4-65 |
4-45 |
|
Decapoda |
24-6 |
0-328 |
29-3 |
27-8 |
6-17 |
|
Mollusca. Amphineura |
38 0 |
0-669 |
41-2 |
4-30 |
8 06 |
|
Pelecypoda |
37-9 |
0-154 |
41-8 |
3-18 |
1-85 |
|
Gastropoda |
|||||
|
Prosobranchia |
37-8 |
0-139 |
41-8 |
314 |
1-68 |
|
Opisthobranchia |
2-38 |
0-062 |
3-97 |
72-6 |
10 |
|
Scaphopoda |
38-2 |
0-196 |
42-3 |
1-81 |
2-35 |
|
Cephalopoda |
35-8 |
0-293 |
40-1 |
7-35 |
3-74 |
|
Bryozoa, Ectoprocta |
30-4 |
0-228 |
35-4 |
14-7 |
3-41 |
|
Brachiopoda. Articulata |
38-4 |
0-113 |
42-3 |
212 |
1-36 |
|
Echinodermata. Crinoidea |
25-8 |
0145 |
38-2 |
13-3 |
2-56 |
|
Asteroidea |
22-4 |
01 34 |
31-8 |
29-3 |
2-73 |
|
Ophiuroidea |
26-3 |
0153 |
34-6 |
20-5 |
2-69 |
|
Echinoidea |
33-6 |
0-199 |
41-8 |
5 00 |
2-70 |
|
Holothuroidea |
27-8 |
0-166 |
35-0 |
18-3 |
2-74 |
|
Chordata, Ascidiacea |
0-34 |
trace |
13-7 |
69-6 |
' |
38
Thomas G. Thompson and Tsaihwa J. Chow
Table IV. — Strontium-calcium atom ratio of marine invertebrates coltectea at
different tide levels
|
Mid-tidal Level |
Low Inter-tidal Level |
|
|
Atom ratio |
Atom ratio |
|
|
^^ X 1000 Ca |
Sr Ca |
X 1000 |
|
Mytilus calif ornianus 101 Littorina scutalata 1 -44 Pisaster ochraceus 2-76 |
Diodora aspera Rhabdodermella nuttingi Henricia leviscula |
1-35 2-30 2-81 |
|
Mitella polymerus 4-27 Balam4s glandula 5 06 Cancer ant ennarius 6-12 Nuttallina calif arnica 7-91 |
Tetraclita squamosa Pugettia producta Cryptochiton stelleri Balanophyllia elegans Anisodoris nobilis |
4-88 6 00 8-80 9-41 11 |
Table V. — Strontium-calcium atom ratio of Echinodermata in relation to their
habitats
|
Atom ratio |
|||
|
Habitat |
Specimen |
Sr Ca |
X 1000 |
|
Wharf Piling |
Pisaster giganteus |
2-69 |
|
|
Mid-tidal Level Rocky Shore |
P. ochraceus |
2-76 |
|
|
Low Inter-tidal Rocky Reef |
Henricia leviscula |
2-81 |
|
|
Burrowing |
Strongylocentrotus purpuratus |
2-89 |
|
|
Sandy Flat |
Dendraster excentricus |
2-79 |
|
|
Sandy-mud Substratum |
Ophioplocus esmarki |
2-79 |
|
|
Inter-tidal Zone |
P solus sp. |
2-72 |
|
|
Deep water |
Strongylocentrotus fragilis |
2-63 |
Table VI. — Strontium-calcium atom ratio in relation to the mineralogical character of calcium carbonate in marine organisms
|
Atom ratio |
Atom ratio |
Atom ratio |
|||
|
Calcite |
^'' X 1000 Ca |
Calcite-Aragonite Mixture |
J'' X 1000 Ca |
Aragonite |
4f- X 1000 Ca |
|
Algae, Corallinaceae |
3-20 |
Mollusca, |
Coelenterata, |
||
|
Protozoa, |
Pelecypoda |
l-94t |
Hydrozoa |
9-491 |
|
|
Foraminifera |
3-07 |
Gastropoda |
Zoantharia |
9-86 |
|
|
Porifera, Calcarea |
2-99 |
Prosobranchia |
1-68 |
Mollusca, |
|
|
Coelenterata, |
Amphineura |
8 06 |
|||
|
Alcyonaria |
316* |
Gastropoda |
|||
|
Arthropoda, |
Nudibranchia |
10 |
|||
|
Cirripedia |
4-45 |
Scaphopoda |
2-35 |
||
|
Mollusca, |
Cephalopoda |
3-74 |
|||
|
Pelecypoda |
|||||
|
Anomiidae |
1-22 |
||||
|
Ostreidae |
1-22 |
||||
|
Pectinidae |
1-31 |
||||
|
Bryozoa, Ectoprocta |
3-41 |
||||
|
Brachiopoda, |
|||||
|
Articulata |
1-36 |
||||
|
Echinodermata |
2-71 |
* Does not include the aragonite Heliopora.
t Does not include the calcite Anomiidae, Ostreidae and Pectinidae.
t Does not include the calcite Errinopora.
The strontium-calcium atom ratio in carbonate-secreting marine organisms 39
REFERENCES
AsARi, Tamiya (1950), Geochemical distribution of strontium. VII. Strontium contents of shells
/. Chem. Soc, Japan, 71, 156-158. B0GGILD, O. B. (1930), The shell structure of the molluscs. Kl. Danske Videnskab. Selskab, Skrifter,
Naturvidenskab. math. Afdel., (9) 2, 231-326. Chave, E. K. (1954), Aspects of the biogeochemistry of magnesium. I. Calcareous marine organisms.
J. GeoL, 62, 266-283. Chow, T. J. and Thompson, T. G. (1955 a). Flame photometric determination of strontium in sea
water. Anal. Chem., 27, 18-21. Chow, T. J. and Thompson, T. G. (1955 b). Flame photometric determination of calcium in sea water
and marine organisms. Anal. Chem. 11, 910-913. Clarke, F. W. and Wheeler, W. C. (1922), Inorganic constituents of marine invertebrates. Prof.
pap. U.S. Geol. Sur., No. 124, 1-62. DiEULAFAiT, L. (1877), La strontiane, sa diffusion dans la nature minerale. C.R. Acad. Sci., Paris,
84, 1303-1305. Forchhammer, G. (1852), Beitrage zur Bildungsgeschichte des Dolomits. N. Jb. Min. Geol. Paldont.,
p. 854. Fox, H. M. and Ramage, H. (1931), A spectrograph ic analysis of animal tissues. Proc. Rov. Soc,
London, B, 108, 157-173. KuLP, J. L., Truekain, Karl and Boyd, D. N. (1952), Strontium content of limestones and fossils,
Bull. Geol. Soc. Amer., 63, 701-716. Lowenstam, H. a. (1954 a), Environmental relations of modification compositions of certain
carbonate secreting marine invertebrates. Proc. Nat. Acad. Sci., U.S.A., 40, 39^8. Lowenstam, H. A. (1954 b). Factors affecting the aragonite-calcite ratios in carbonate secreting
marine organisms. J. Geol., 62, 284-321. McCance, R. a. and Masters, M. (1937), The chemical composition and the acid base balance of
Archidoris britannica. J. Mar. Biol. Ass., U.K., 22, 273-279. MoRETTi, Giuseppe (1813), Sur le sulfate de strontiane trouve dans le corps marins petrifes, et sur
deverses combinaisons de cette terre avec quelques acides. Ann. Chem., Paris, (1) 86, 262-273. Noll, W. (1934), Geochemie des Strontiums. Chem. Erde, 8, 507-600. Odum, H. T. (1951 a). Note on the strontium content of sea water, celestite Radiolaria, and stron-
tianite snail shells. Science, 114, 211-213. Odum, H. T. (1951 b). The stability of the world strontium cycle. Science, 114, 407-41 1. Rankama, K. and Sahama, T. G. (1949). Geochemistry, p. 226, The University of Chicago Press,
Chicago. SCHMELCK, L. (1901), Chemical examination of shells of Mollusca and dried Echinodermata. Norweg.
N. Atl. Exper., 1876-1878, Zoo/ogv, 7: (28), 129. Trueman, E. R. (1944), Strontium in molluscan shells. Nature, 135, 142. TsucHiYA, Yasuhiko (1944), Distribution of strontium in calcareous organisms. I. Strontium content
of reef-forming corals. J. Agr. Chem. Soc, Japan, 20, 653-654. TsucHiYA, Yasuhiko (1948), Studies on the method for the preparation of strontium from corals
and calcareous algae. /. Fac. Agric, Kyushu Univ., Japan, 9, 65-68. Vinogradov, A. P. (1953), The Elementary Chemical Composition of Marine Organisms. Sears
Foundation for Marine Research, Memoir IT. Yale University, New Haven. Vinogradov, A. P. and Borovik-Romanova, T. F. (1945), Geochemistry of strontium. C.R. .Acad.
Sci., U.S.S.R., 46, 193-196. VoGEL, H. August von (1814), Researches analytiques sur le corail rouge. Ann. Chim., Pans. (I)
89, 113-134. Wattenberg, H. and Timmermann, E. (1936), Uber die siittigung des Seewasser an CaCOj, und die
anorganogene Bildung von Kalksedimenten. Ann. d. Hydrogr. u. Mar. Meteor., pp. 23-31. Wattenberg, H. and Timmermann, E. (1938), Die Loslichkeit von Magnesiumkarbonate und
Strontiumkarbonate in Seewasser. Kieler Meeresforchungen, 2, 81-94. Webb, D. A. (1937), Studies on the ultimate composition of biological material. II. Spectrographic
analysis of marine invertebrates with special reference to the chemical composition of their environ- ment. Sci. Proc. Roy. Dublin Soc, 21, 505-539.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 40-44.
Variation, en mer, de la teneur en oxygene dissous au proche voisinage
des sediments
Par Jean Brouardel et Louis Face Institut Oceanographique, Paris
Sununary — The experiments reported in this paper show that the oxygen content of the water under- goes a rapid decrease in the immediate vicinity of the bottom. This decrease is related to the very rapid oxidation of the sediment and the very slow diffusion of the dissolved gas.
A LA SUITE d'une serie de dosages executes au large de Monaco en 1952 (Brouardel et Fage, 1954), sur des echantillons d'eau preleves a I'aide de carottiers de divers modeles, par des fonds de 200 a 1000 m, nous avions conclu que la teneur en Og dissous decroit brusquement au proche voisinage des sediments et nous emettions alors I'hypothese que cette diminution de la teneur en O2 pourrait etre plus importante encore au ras meme du sediment.
De nouvelles recherches poursuivies en 1953-54 a I'aide d'appareils construits en consequence ont eu pour but de preciser ce point.
Trois appareils differents ont servi aux prelevements destines a ces recherches, tous trois ont le caractere commun d'etre entierement en matiere plastique. Le tube preleveur est constitue par un cylindre de plexiglas completement ouvert a ses extrem- ites; ainsi, d'une part, il ne peut se produire aucune oxydation, d'autre part, il n'y a pas de perte de charge et done de melange d'eau du a des etranglements ou des soupapes.
Carottier. Simple tube en plexiglas (fig. 1) de 1 m de long sur 5 cm de diametre. A I'extremite superieure un clapet en matiere plastique est maintenu completement eclipse a la descente de I'appareil par un ergot auquel est fixe le cable du treuil. Lorsque le tube touche le fond, le cable en prenant du mou libere le clapet qui, sous Taction de deux ressorts en acier inoxydable, maintient hermetiquement fermee I'extremite superieure du tube. L'extremite inferieure etant bouchee par la carotte, lorsque le tube rencontre le sediment il se trouve simultanement ferme a ses deux extremites et emprisonne une veritable carotte d'eau.
Le fonctionnement du carottier, facilement controle au cours de plongees grace a la parfaite transparence du plexiglas, montre que, convenablement leste, il decoupe le sediment exactement " a I'emporte piece ", sans mettre en suspension de particules de vase au-dessus de la carotte.
Bouteille de prelevement . Cette bouteille (fig. 2) est destinee a faire des prelevements non plus au ras du sediment, mais a une hauteur determinee au-dessus de celui-ci (5 m dans nos experiences). Le corps de I'appareil est ici encore forme d'un simple tube en plexiglas a chacune des extremites duquel un clapet, en meme matiere, est maintenu a la descente totalement eclipse par un ergot. Le systeme de declenchement des clapets est base sur un principe analogue a celui d'une arbal^te dont la corde est constituee par le cable du treuil. Le carotier, fixe a I'extremite du cable, maintient bandee cette arbalete par la tension qu'il exerce sur celui-ci. Des que le carottier touche le fond, le cable detendu libere les ergots des clapets qui se ferment simultanement sous Faction de deux ressorts.
Preleveur de la surface du sediment (fig. 3). Le principe de cet appareil est celui du "Jenkins surface mud sampler " qui est employe en Limnologie. Mais, ici encore, cet appareil est entierement realise en matiere plastique ce qui lui procure une remarquable souplesse de fonctionnement indispensable a la mer. La bouteille elle-meme est un tube de plexiglas de 60 cm de long et de 7 cm de diametre supportee par un bati. Deux clapets, sortes de paupieres, eclipses a la descente, sont liberes des que
40
Fig. I. Carotticr a la descente. clapct ouvert.
Fig. 2. Boutcillc dc preIo\cmcnt.
Fig. 3. Preleveur de sLirface, clapets ouverts.
Variation, en mer, de la teneur en oxygene au proche voisinage des sediments
41
I'appareil louche le fond, puis soumis a Taction de deux jcux dc quatre ressorts qui les entraincnt avec puissance, mais aussi avec ienteur grace a Taction d"un frcin hydraulique. Le clapet situc a la partie inferieure decoupe la pellicule superficiellc du sediment (2 a 3 cm d'epaisseur) ainsi retenue dans le tube. A le remontee les deux clapets ferment hermetiquement les extremites de la bouteille.
Contrairement au carottier qui est descendu tres rapidement afin de faire une carotte sufTisamment importante pour boucher Textremite inferieure du tube, eel appareil est descendu exircmcment lentemenl des Tapproche du fond el verilablemenl " pose " sur celui-ci.
L'expose suivant a trait aux resultats obtcnus avec ces appareils simultanement employes au cours des sorties effectuees en Juin-Juillet 1954 avec VEider, bateau du Musee Oceanographique.
Distinguant parfaitement dans le carottier, grace a la transparence du plexiglas, la limite de la carotte et de I'eau limpide emprisonnee au-dessus d'elle, il est possible de faire des prelevements par siphonage, grace a un fin tube de verre. Les niveaux choisis pour ces prelevements ont ete les suivants: au ras du sediment, toutefois sans atteindre la carotte, puis a 5 — 10 — ^25 — 40 — 55 cm de celui-ci.
En outre, comme lors des experiences anterieures (Brouardel et Page, 1953), la bouteille-arbalete, suspendue au meme cable, etait disposee a 5 m au-dessus du carot- tier faisant done un prelevement d'eau a environ 6 m au-dessus du sediment.
Les teneurs en O2 de I'eau des divers echaniillons obtenus dans ces conditions figurent au tableau L Ces teneurs y sont exprimees en milligrammes par litre.
Tableau I Teneur en O2 de Veau prelevee a Vaide des appareils {Figs.
sediment
et 2) au-dessus du
|
Profondeur: |
100 m |
140 m |
210 m |
220 //; |
240 m |
245 m |
290 m |
305 m |
Moyennes |
|
5 m |
7,89 |
7,33 |
1,Q1 |
6,95 |
6,94 |
6,37 |
6,41 |
6,34 |
6.92 mc 1 |
|
55 cm |
7,88 |
7,23 |
6,84 |
7,20 |
6,86 |
6,81 |
6,27 |
6,21 |
6.91 |
|
40 |
7,76 |
7,23 |
6,93 |
6,80 |
6,58 |
6,79 |
6,50 |
6,48 |
6,88 |
|
25 |
7,83 |
7,23 |
7,13 |
6,78 |
6,60 |
6,40 |
6,42 |
6,36 |
6,84 |
|
10 |
7,71 |
7,56 |
7,11 |
6,76 |
6,39 |
6,46 |
6,47 |
6,22 |
6,83 |
|
5 |
7,83 |
7,13 |
6,67 |
6,58 |
6,75 |
6,47 |
6,37 |
6,42 |
6,78 |
|
au ras du |
|||||||||
|
sediment |
7,66 |
6,92 |
6,59 |
6,65 |
6,67 |
5,61 |
6,31 |
6,35 |
6.59 |
Sur la Figure 4, nous avons reporte en abscisses les teneurs moyennes en O2 des prises aux differentes hauteurs (ordonnees) au-dessus du sediment. Cette courbe fait apparaitre, avec plus de nettete que celles obtenues lors des experiences anterieures, la diminution rapide de taux d'C, au proche voisinage du sediment. L'amelioraiion due au remplacement de I'afcodur du carottier par le plexiglas transparent permet, en effet, de faire les prelevements plus pres de la carotte, a des hauteurs mieux detcr- minees, et d'avoir ainsi Failure de la courbe dans les premiers centimetres.
On voit qu'entre la teneur en O2 de I'echantiilon d'eau preleve par la bouteille a 5 m au-dessus du sediment et celle de I'eau prelevee a la partie superieure du carottier on n'observe pratiquement aucune difference. Par contre, la teneur en O. de I'eau renfermee dans le carottier diminue rapidement, et cela d'autant plus que Ton se rapproche de la carotte. Dans les experiences anterieures (carottier a clapet, puis carottier en afcodur) les differences entre les moyennes des taux d'Oj observes entre
42
Jean Brouardel et Louis Face
les deux etages extremes etaient de 3,7 et 3,5 %. Ici, la difference moyenne entre les prelevements extremes faits dans le carottier, a 55 cm I'un de I'autre, est de 0,32 mg soil 5 %.
Si le carottier employe ici presentait une amelioration sur les precedents il restait, dans son usage, un point sur lequel aucun calcul ne pouvait donner d'appreciation mais qui pouvait, pensions-nous, presenter de I'importance.
En effet, pour que la colonne d'eau reste emprisonnee dans le tube il fallait a son extremite inferieure une carotte relativement importante. Pour cela une assez grande Vitesse de descente etait necessaire et nous ne savions dans quelle mesure cette vitesse ne risquait pas de perturber la position des couches d'eau lors de la rencontre du
6 -
4 -
UJ
|
050 O 25 |
- |
^- |
|
|
'///sgdiment////^ |
1 |
1 1 1 |
|
|
66 |
67 68 69 |
Fig. 4. Teneurs en O2 de I'eau dans une couche de 6 m d'epaisseur au dessus du sediment (Carottier
et Bouteille de prelevement).
carottier avec le sediment. D'autre part, a la remontee la carotte risque toujours de glisser legerement le long du tube et de modifier peut-etre, la position de I'eau. C'est pour eliminer ces causes possibles de perturbation que nous nous sommes servis d'un appareil de principe different, c'est-a-dire du preleveur de surface dont nous avons donne plus haut une sommaire description.
Cette bouteille " carottier d'eau " et le carottier en plexiglas ont ete utilises simul- tanement au cours des sorties de X Eider en Juin-Juillet 1954, puis elle a ete utilisee avec la bouteille-arbalete, par de plus grandes profondeurs, en Octobre 1954 a bord de la Calypso.
Les prelevements, comme dans le cas du carottier, se faisaient par siphonage dont la technique etait d'ailleurs amelioree ici par I'emploi d'une " pige " qui guidait le fin tube de verre dans le carottier bouteille.
Lors des sorties de Juin-Juillet, les prelevements faits a des hauteurs de 1, 5, 10, 25 et 40 centimetres, au-dessus de la pellicule decoupee par le clapet inferieur de la bouteille, ont donne les resultats qui figurent au tableau II et qui permettent de construire la courbe figure 5.
Variation, en mer, de la teneur en oxygene au proche voisinage des sediments
43
6 -
X
m
I -
O 50 - 0 25 k
SEDIMENT
6-5 66
X
6 7
6-8 6 9
O, mq/ 1
71
7-2
Fig. 5. Teneurs en Og de Teau dans une couche de 40 cm d'epaisseur au-dessus du sediment (Preleveur
de surface).
Tableau II Teneur en O2 de Veau prelevee a Taide de Vappareil (Fig. 3), au-dessus du sediment
|
Profondeur: |
85 ni |
95 m |
130 m |
150 m |
150 m |
180 m |
220 m |
230 m |
235 m |
245 m |
250 m |
255 m |
275 m |
285 m |
430 m |
Moyennei |
|
40 cm |
7,89 |
7,95 |
7,53 |
7,83 |
7,44 |
7,36 |
7,08 |
7,44 |
7,07 |
6,90 |
6,65 |
7,08 |
6,73 |
7 |
6,17 |
7,21 mg 1 |
|
25 cm |
7,89 |
7,89 |
7,53 |
7,64 |
7,34 |
7,24 |
6,94 |
6,93 |
7,09 |
6,74 |
6,27 |
6,96 |
6,63 |
6.77 |
6,91 |
7.05 |
|
10 cm |
7,68 |
7,51 |
7.45 |
7,42 |
7,31 |
7,07 |
6,90 |
6,60 |
6,89 |
5,92 |
6,14 |
7,07 |
6,54 |
6,46 |
5,88 |
6,86 |
|
5 cm |
7,57 |
7,59 |
7,25 |
7,38 |
6,68 |
6,54 |
6,79 |
6,16 |
6,64 |
6,68 |
6,24 |
6,82 |
6,39 |
6,37 |
5.82 |
6.73 |
|
au ras du |
||||||||||||||||
|
sediment |
7,36 |
7,27 |
7,04 |
7,05 |
6,50 |
6,39 |
6,47 |
6,21 |
6,57 |
5,54 |
6,05 |
6,35 |
6,36 |
6,48 |
5.74 |
6,49 |
La courbe figure 6, deduite du tableau III a trait aux resultats obtenus en Octobre. Elle confirme, a une autre epoque et pour d'autres profondeurs, Failure de la courbe precedente.
Si Ton compare maintenant cette diminution du taux d'Oj avec celle due normale- ment a I'augmentation de la profondeur, mais en operant alors largement au-dessus du sediment, on constate que celle-ci est seulement de I'ordre de 0,15 mg 1 par 100 m ce qui represente sur 10 cm une variation de — 0,00015 mg 1, et cela dans la region ou nous operions, a la meme epoque et a la meme profondeur moyenne. Or dans les 10 cm d'eau au-dessus du sediment cette variation est (tableau II) de — 0,37 mg 1, soil
Tableau III Teneur en O^ de Peau prelevee a Taide des appareils (Figs. 2 et 3) au-dessus du sediment
Profondeur:
WO m
\60 m
870 m
950 m
1 740 ///
A/('it7;/;t-.v
|
5 m |
7,36 |
7,01 |
6,97 |
7,36 |
6,45 |
7.03 mgl |
|
40 cm |
7,21 |
7,02 |
6,86 |
7,46 |
6,33 |
6,96 |
|
25 cm |
7,18 |
6.98 |
6,85 |
7,04 |
6.24 |
6.86 |
|
10 cm |
7,10 |
6,53 |
6,59 |
7,21 |
6.17 |
6.72 |
|
5 |
7,14 |
6,60 |
6,45 |
6,75 |
6,04 |
6.6 |
|
au ras du |
||||||
|
sediment |
7,06 |
6.30 |
5.87 |
6,69 |
5.83 |
6.35 |
44
Jean Brouardel et Louis Fage
4 X 10* fois plus. On peut done veritablement parler d'une chute du taux d'oxygene au ras du sediment.
Ces dernieres experiences ont done permis de preciser I'allure de la variation du taux d'Oa au tres proche voisinage du sediment et ont montre qu'au fur et a mesuxe que les techniques de prelevements s'ameliorent cette variation apparait encore plus nettement sur les courbes. Le sediment constitue done une couche puissamment reductrice, cause du phenomene que nous analysons.
Nous avons alors essaye de determiner a quelle vitesse se fait cette oxydation. Avec les precautions necessaires, nous avons etale sur 5 cm d'epaisseur, au fond d'un bac, d'une contenance de 380 litres, 30 litres de sediment preleve au large et dont la couche superieure avait ete dessechee a I'etuve a 110° C. Le bac, haut de 55 cm,
I
^.3
^■•-
I -
0-50 O 25 -
SEDIMENT /^■^[^
_L
6-3
64
b 5
6-6 6-7
OjmyL
6-6
6-9
71
7-2
Fig. 6. Teneurs en O2 de I'eau dans une couche de 6 m d'epaisseur au-dessus du sediment (Preleveur
de surface et Bouteille de prelevement).
etant rempli d'eau de mer de teneur en O2 connue, nous avons, chaque jour, dose les variations de cette teneur a diflferents niveaux. II a ete constate que, dans la couche d'eau de 1 cm d'epaisseur au contact du sediment, la teneur en O2 s'abaisse si rapide- ment qu'au bout de 30 heures elle a diminue de moitie; au bout de trois jours, elle n'est plus que de I'ordre du milHgramme et, au bout de neuf jours, elle est si faible qu'elle ne peut plus etre mise en evidence par des methodes sensibles au 2/lOOe de milligramme : cette couche d'eau ne contient pratiquement plus d'oxygene. Pendant le meme temps, la couche situee seulement a 10 cm au-dessus n'a perdu que 0,5 mg/1, Ainsi sont mises en evidence, d'une part, la tres grande rapidite d'oxydation du sediment et, d' autre part, I'extreme lenteur de diffusion du gaz dissous. Ce qui est de nature a expliquer que la chute rapide de la teneur en O2 observee in situ, ne se produit qu'au proche voisinage du sediment.
REFERENCES
Brouardel, J. et Fage, L. (1953), Variation, en mer, de la teneur en oxygfene dissous au proche
voisinage des sediments. C.R. Acad. Sci., Paris, 237, 1605-1606. Brouardel, J. et Fage, L. (1954), Variation de la teneur en oxygdne de I'eau au proche
voisinage des sediments. Deep-Sea Res., 1 (2), 86-94.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sca Research, pp. 45-57.
Foraminiferal faunas in cores offshore from the Mississippi Delta*
By Fred B Phleger Scripps Institution of Oceanography, La Jolla
Summary — Study of Foraminifera from fifteen cores shows presence of cold-water faunas interpreted as representing glacial stages and/or substages, and of warm-water faunas interpreted as post-glacial and interglacial stages and/or substages. These sequences are similar to those previously reported from the northwestern Gulf of Mexico.
The amount of post-glacial deposition is greater on the lower continental shelf and upper continental slope than on the lower slope and basin. Variations in amount of post-glacial sedimentation within these topographic provinces are demonstrated.
Two cores located in the bottom of Mississippi Canyon contain faunas and sediments which have been displaced downslope, presumably by turbidity currents. It is suggested that the turbidity current was confined to Mississippi Canyon, and that submarine canyons generally tend to localize many turbidity currents.
INTRODUCTION
Members of the Woods Hole Oceanographic Institution have pioneered in studies of the offshore sediments in the northern Gulf of Mexico. Extensive collections of surface sediments and longer cores were taken along 2,500 miles of traverses in the north- western Gulf of Mexico in 1947, using the research vessel Atlantis. The physical parameters of these sediments were reported and interpreted by Stetson (1953), chemical studies of the materials are discussed by Trask (1953), and the foraminiferal faunas are described and interpreted by Phleger (1951) and Phleger and Parker (1951). In 1951 Stetson made extensive collections aboard the Atlantis in the north- eastern area, from the Mississippi Delta to Florida, collecting surface sediment samples and long cores along several hundred miles of traverses. The foraminiferal facies in the surface sediments along these traverses have been interpreted by Parker (1954), and study of the sediments is being undertaken by Stetson.
The present paper is a study of the vertical sequences of foraminiferal faunas in fifteen of these cores in a traverse extending southward from the Mississippi Delta. The purposes of this study are :
(1) To discover whether there is a vertical sequence of cold- and warm-water faunas as reported from the western Gulf of Mexico and elsewhere;
(2) To attempt to discover relative rates of deposition off a large delta;
(3) To evaluate the role of turbidity currents in deposition in the area covered by
the cores. The cores were studied at the suggestion of Henry C. Stetson of the Woods Hole Oceanographic Institution, who furnished them to the writer. The assistance of Jean F. Peirson in this study is gratefully acknowledged. Dr. Rufus J. LeBlanc, of the Shell Development Company, kindly arranged to have several of the cores sampled. The laboratory work was supported by the Office of Naval Research (Project NR 081-050, Contract Nonr-233, Task 1).
* Contribution No. 21, Marine Foraminifera Laboratory; Contribution from the Scripps Institu- tion of Oceanography, New Series, No. 804.
45
46
Fred B Phleger
LOCATIONS OF STATIONS AND DESCRIPTION OF THE AREA
The cores were collected along a traverse (Table I, Fig, 1) extending from the deep Gulf of Mexico basin at 3,017 m to the lower continental shelf at 88 m. The near-shore, shallow end of the traverse is only a short distance off Southwest Pass, one of the main distributaries of the Mississippi Delta.
.i? o
^ «5 ■S '-^ ■?: 5 o t: o o ^ c/: OS
Foraminiferal faunas in cores offshore from the Mississippi Delta 47
Table I— Locations and depths of cores
|
Core |
Depth in m |
.V. Lat. |
W. Long. |
|
3 |
3017 |
26^01' |
88=03' |
|
4 |
2972 |
26= 07' |
89= 09' |
|
5 |
2788 |
26' 31' |
89=09-5' |
|
6 |
2468 |
26 ' 58-5' |
89 12' |
|
7 |
1875 |
27 26' |
89 14' |
|
8 |
1417 |
27=37-5' |
89= 14-5' |
|
9 |
1372 |
27=51' |
89= 15' |
|
10 |
1298 |
28=01-5' |
89= 19' |
|
II |
914 |
28= 12' |
89= 20' |
|
12 |
732 |
28= 18' |
89 20' |
|
13 |
631 |
28=23-5' |
89 20' |
|
14 |
471 |
28= 29' |
89 22' |
|
15 |
298 |
28=33-5' |
89= 22' |
|
21 |
142 |
28= 39' |
89=25' |
|
18 |
88 |
28M5-5' |
89= 27' |
The topographic charts of the northwestern Gulf of Mexico, constructed by Gealy (1955), end at the approximate position of the Mississippi Delta, and all of the present core stations are off her chart except cores 7-12 (Fig. 2). Core 18 was taken at a depth of 88 m on the lower part of the narrow continental shelf Most of the other cores came from the continental slope, except those at the outer end of the traverse which are in or on the edge of the Gulf of Mexico basin. The continental slope in this area appears to be quite rugged, and is cut by the Mississippi Canyon. The Sigsbee Deep Scarp described by Gealy may not be present in the area traversed by the cores.
This is an area of high runoff from the Mississippi River and is presumed to have a rather high rate of sedimentation. It has been shown by Scruton (MS.) that the highest sedimentation rate is close to the delta distributaries and decreases rapidly offshore. There appears to be rather rapid sedimentation for approximately 60 miles offshore, according to analyses by Phleger (MS.). It seems likely that sedimentation is more rapid farther offshore in this area than in any other part of the northern Gulf of Mexico.
The physical oceanography of the area is not well-known. Offshore surface temperatures vary from a mean minimum of 20° C in February to a mean maximum of 29° C in August, according to Fuglister (1947). It thus has the surface-water temperatures of North Atlantic mid-latitudes in winter and of low latitudes in summer. A considerable amount of low-latitude water enters the Strait of Yucatan, and while much or most of this flows out the Florida Strait, its effect may be pronounced in the area of the outer part of the present traverse. Offshore salinities in the Gulf of Mexico are approximately 36"/^ 3. A near-shore wedge of lower-salinity water is expected in this high runoff area. Parr (1935) shows salinities of approximately 24°/^^ in the upper 50 m a few miles to the east of the present traverse.
METHOD OF STUDY
The cores were collected with a coring tube described by Hvorslev and Stetson (1946). The samples used in the present study were one-fourth of each core cut into sections approximately 5 cm in length, so that the entire core was sampled. Each sample was trimmed oi approximately I 8 inch of sediment to prevent contamination between samples and was washed free of tine sediment over a brass sieve having an average opening of 0 074 mm.
48
Fred B Phleger
84«»00'
Fig. 2. Locations of cores 7-12 in relation to topography. Topography modified after Gealy (1955).
Depths in fathoms
The foraminiferal faunas were analyzed quantitatively. Only a fraction of the population was counted in samples having very large populations; quartering was done by a method described previously (Phleger, 1951,7). Occurrences of species are listed in percent of the total ; benthonic and
Foraminiferal faunas in cores offshore from the Mississippi Dcha
49
Table II— Occurrences of Foraminifera in cores 3-6, in percent of total population. Plank tonic and hent/ionic populations computed separately
|
«. |
_ |
___ |
|||||||||||||||||||||||||||
|
CORE |
6 |
5 |
4 |
J, |
|||||||||||||||||||||||||
|
DEPTH IN METERS |
2468 |
278e |
2972 |
,,-,; ,. |
|||||||||||||||||||||||||
|
DEPTH IN CORE IN CM. FROM TOP |
-i to o • -D OC (J |
^ (J |
C |
It |
(J |
* |
3^ CD u; o w |
g C |
5 |
7 ? ? f w ut -^ a m w ut t> |
- O O (0 ro ~j O U> U> ~ — ro ro T 10 O - Ul .->) .UJ oi ui _ |
(r x» ^ c Ui ^ - .z - i^ ^ - A u) <j» ■- in * |
t>J 01 ^ ID r\> |
O ui ui — |
rvj w ui In |
V Ol UI |
Ol m bi |
a; |
0 |
ry 0 M 01 |
09 01 |
01 9 UI |
UI -J 0 |
- « ^5 "■ |
Ol 01 |
i> 01 - IB I* -. l^ UI .>* C Ui A 01 a [B UI fy - tn & u |
0 i _ e rj p ov 01 I* 1^ -^ ID — - . 0 0 Ui ^ .--* l^ ry |
||
|
TOTAL PLANKTONIC POPULATION G'obigerina bulloides G, digitoto G eggeri G inflota G pochydermo |
Ui W fV) OI CO o o o o 4 .6 712 |
- |
- |
- |
b c c H |
~ |
-.J o o 2 ~ 4 ~ |
C c c ic |
"en o o "4 2 |
o o 2 8 4 2 4 |
c - C ru c 8 5 8 ; |
p y ~ > b b w V o o o c o o o c 2 5 1 .s 7 9 12 1 |
b ^ O OOO OOO 4.9 8 1 11 11 10 |
<£> O O 7 3 |
CD O O o_ 1" |
Ol b o o Is rr |
Ui "oi o O ~ "7 |
l£ C "4 |
fi. 0 |
JT |
X |
"x |
7 |
b « 0 -J c . 8 6 |
o> 0 0 0 2 7 |
01 Ui 0 b Q 0 00 0 00 2 5 7 8 10 1 .2 |
- t\i ■* - IS 0 0 01 000 10 5 9 R 11 910 3 3 |
||
|
Globtgennella oeguiloterolis G lobigennito glutinota Globigennoides congloboto G- f u b f 0 G sacculifera Gioborotalio hirsuta G menofdii |
5 4 3 1 5 .3 5 23 ^31 |
_ |
_ |
- |
- |
4 ; 75 23 «C "3 |
~ |
1 2 7 9 ±_ 5 ~ |
2 "6 .6 5 |
.6 3 .8 43 27 |
4 1 8 6 5 49 4 26 |
12 42 4< 25 7 8 ^ |
2 4 3 2 17 15 II e .4.3.3.3 55 27 34 57 91622 a: |
4 4 5 ?4I7 9 1 52 44 56 9 7 9 |
3 0 3 57 6 |
7 ~ 0 7 11 8_ |
.8 10 |
3 8 2 5« 8 |
"4 3 36 5( |
i i .e 4 IC |
X X |
X X |
X x_ |
X X |
3 4 13 .2 3< « i S |
6 5 2 6 5 4 12 8 .9 .4 .9 42 90 3E 44 15 >e 16 7 .2 2.2 |
6 3 1 7 13 8 A 1 7 2 M 11 43 A 9 17 6 A 1 .4.3 |
||
|
G puncTulato |
1 4 |
|
|
|
1 |
|
T~ |
~7 |
~3" |
3 2 |
8 ,5 |
.7 1 |
2 5.2 |
6 |
"2 |
7 |
is |
"7 |
7 |
X |
IT |
x" |
8 .1 |
.3 |
fi-. |
8.7 4 |
|||
|
G tr uncatutinoides G tumida |
3 4 1 ^ |
_ |
_ |
— |
T I |
|
3~ |
3' |
8 2 |
2 |
4 3 2 2 |
2 2 2 |
7 |
2 2 |
[6 |
1 |
J |
"5 |
X |
X |
- |
- |
3 8 2 |
.6 2 |
2 1 8 2 1 |
2 .3 1 7 R |
|||
|
Or bulino universa |
3 "3 |
— |
— |
T |
— |
6 ~ |
2 |
is' |
3 |
t |
7 3 3 9 |
3 3 5 |
4 |
5 |
4 |
"4 |
"8 |
1 |
X |
X |
- |
- |
1 |
6 |
3 3.2 3 4 6 |
.6 R 3 4 4 |
|||
|
PuHeniotina o bliquiloculoto Sphoeroidinello dehiscens |
3 b |
- |
- |
i 3 |
-- |
4 |
6 |
2. 3 |
8 3 |
2 |
2 4 4 3 7 6 3 |
3 4 3 2 |
5 |
4 |
2 |
2 |
6 |
.4 |
|
X |
, |
|
1 |
2 |
3 2 1 |
5 3 .9 |
|||
|
TOTAL BENTHONIC POPULATION |
Ji o D O |
'--J O o |
o o |
In O o |
o o |
O o |
^ |
O |
c |
ro no Ji |
o -J u> O |
- b w — o o x» o o o o o |
u' w t» O (7) — OOO |
-J O |
0 m D o -) o |
o o |
0 |
01 0 |
0 |
0 |
ro (vj 0 OJ 0 |
b < 0 < |
Ji Ui 01 rs> :> ~ i^ - D 0 0 0 |
^ ^ ru 0 0 w |
|||||
|
Amphistegino (juvenile) |
"~ |
^ |
.5 |
.6 |
.6 |
||||||||||||||||||||||||
|
Angulogenno be Ma |
7 |
||||||||||||||||||||||||||||
|
Bohvjno olota |
.6.9 |
.7.8 1 |
4 .3 .8 |
.3 |
.3 |
7 |
|||||||||||||||||||||||
|
6 olbotrossi |
.5 |
.4 |
2 |
.3 |
.3 |
||||||||||||||||||||||||
|
B low mam |
.8 |
.5 |
r |
2 |
2 |
.2 |
2 |
3 5 6 2 |
2.8 .4 |
1 |
1 1 |
.2 |
4 |
2 |
2 3 1 .5 |
1 |
|||||||||||||
|
B poula |
.8 |
2 |
2 1 |
1 .4 |
1 . |
8.3 |
1 |
1 . |
7 1 .6 |
||||||||||||||||||||
|
B pulchella pnmiTivo |
4 |
.6 |
6 |
.5 .4 |
4 |
2 |
.5 |
1 |
|||||||||||||||||||||
|
B striatulo spmoto |
2 |
.4.4 |
|||||||||||||||||||||||||||
|
B subaenonensis mexicono |
4 |
u4 |
.4 .8 |
.6 |
4 1 |
.5. |
7 1 |
||||||||||||||||||||||
|
B subspinescens |
4 |
.3 |
.8 |
1 |
1 |
1 1 1 |
2.3 1 |
8 |
1 |
.5 . |
7 |
||||||||||||||||||
|
Buhmino spicato |
.2 |
.5 |
4 |
6 |
|||||||||||||||||||||||||
|
B sfrioto meKicana |
1 .8 |
1 |
.9 |
.6 |
2 |
.6 |
.3 |
.5 |
.3 |
||||||||||||||||||||
|
Bulimineiio cf bossendorfensis |
5 |
1 |
.4 .4 1 |
.3.5 |
.3 |
5 |
.7 |
.3 |
|||||||||||||||||||||
|
Concns oblonga |
7 |
||||||||||||||||||||||||||||
|
Cassidulina subglobosa |
5 5 |
4 |
5 |
2 |
2 |
1 .5 |
4 |
4 .4.8 2 |
2 2 3 |
2 |
3 .7 |
.5 |
.7 |
.7 |
.5 |
2 |
9 2 |
2 |
5 5 2 1 |
.6.6 l£ |
|||||||||
|
Cossidu hnoides tenuis |
4 |
1 |
.4 |
5 7 |
.4.8 _^ |
.5 |
1 |
» |
53 .i |
.5 |
.3 |
||||||||||||||||||
|
Cibicides hultenberqp |
1 |
1 |
1 |
3 |
2 |
2 |
2 |
1 1 |
.3 .4 |
.7 . |
B |
.2 |
1 |
||||||||||||||||
|
C fobef tsonionus |
4 8 |
7 |
3 |
3 |
4 |
2 |
2 |
6 |
7 |
.5 |
3 |
4 3.4 1 |
3.5 6 |
3 |
2 1 |
1 |
.7 |
1 |
7 |
7 .6 .9 .5 |
£ |
||||||||
|
C wueiiersroffi i |
8 12 |
18 |
13 |
10 |
12 |
13 |
1 1 |
6 |
2 |
4 13 7 |
14 20 3 |
5 12 2 8 |
10 7 20 |
24 1 |
3 24 |
21 |
21 |
5 |
10 |
20 |
4 13 |
2C 1 |
6 23 2121 |
iZ*X |
|||||
|
Eggerello brodyi |
1 .4 |
' |
.5 |
2 |
1 |
2 |
6 |
2 |
"2.4 1 |
.3 1 |
.7 . |
3 .3 |
r2 |
3 |
J |
.5 |
1 1 .3 1 |
2 .6 |
|||||||||||
|
Elphidium spp |
.7 |
,3. |
4 |
.6.6 |
1 |
||||||||||||||||||||||||
|
Epistominello decorate |
i 4 |
2 |
2 |
1 |
4 |
3 |
4 |
1 1 |
19 |
.5 |
ac |
9 8 2 |
1411 8 |
8 |
4 10 |
2 |
6 |
.7 |
.5 |
2 |
21 |
30 |
3 4 14 3 |
L 5 2 5 |
|||||
|
E eitguo |
4 .4 |
.2 |
.8 |
2 |
1 .8 |
73 1 |
.3 |
1 |
1 |
||||||||||||||||||||
|
E ponides pol'us |
3 1 |
2 |
.5 |
4 |
1 |
,5 |
8 |
6 2.4 |
.8 4 |
9 |
i 4 |
.2 |
6 |
4 |
.6 1 |
^.6 |
|||||||||||||
|
E tumdulus |
1 .8 |
1 |
19 |
.9 |
3 |
3 |
5 2.8 |
2.8 6 |
5 |
5 3 |
3 |
1 |
4 |
2 |
3 |
1 21 |
5 7 9 2 |
.6 5 9 |
|||||||||||
|
E turgidus |
4 2 |
3 |
1 |
2 |
.9 |
2 |
4 |
13 |
f 27 |
12 |
8 7 918 |
9 14 4 |
9 |
3 18 |
36 |
3e |
2e |
7 |
7 |
4 6 |
7 |
: 4 1331 |
3e le 9 |
||||||
|
Globobulimina offims 8 vors |
5 12 |
8 |
1 1 |
14 |
5 |
5 |
9 |
6 |
18 |
4 |
344 7 |
1 |
4 45C 5 |
95« |
10 |
5 .7 |
12 |
5 |
5C |
55 |
36 |
9 |
2 |
^411 |
i2€ S |
||||
|
Gyrotdino neosoldami |
2 |
.9 |
.6 |
.9 |
1 |
4 .4 |
.3 |
.3 . |
4 |
.i |
1 |
.7 |
.5 |
.5 |
3 .9 1 |
1 |
|||||||||||||
|
G orbicularis |
3 |
5 |
.5 |
I |
1 |
1 |
.5 |
I |
2 |
.3 |
.i |
1 |
.5 |
||||||||||||||||
|
Haplophrogmoides brodyi |
5 |
2 |
2 |
2 |
2 |
.5 . |
7 |
||||||||||||||||||||||
|
Hoglundino elegons |
4 14 |
14 |
VI |
?R |
?^ |
4 |
?8 |
1 1 |
10 |
1 |
.6 |
4 13 631 |
4 6 2 |
4 |
5 IC |
2 |
1 |
3 |
8 |
5 9 5 3 |
2 |
||||||||
|
Korrer lella brodyi |
|||||||||||||||||||||||||||||
|
Logenidoe ( |
5 8 |
5 |
6 |
7 |
7 |
4 |
4 |
6 |
2 |
3 1 |
10 |
11 12 915 |
2 4 2 |
7 7 |
6 |
2 |
4 |
2 |
3 |
5 |
7 |
7 114 5 |
4 ■ |
||||||
|
Miholidoe |
? 2 |
2 |
2 |
.6 |
2 |
.8 |
1 |
.4 2 |
.5 1 .8 |
1 |
.3 |
.6 |
1 1 2 |
t |
|||||||||||||||
|
Nonion pompiliordes i |
1 |
2 |
3 |
3 |
2 |
2 |
2 |
2 |
S.5 |
.6 |
2 5.8 3 |
2 3 2 |
i ' |
) 4 |
2 |
1 |
i |
5 |
1 |
2 |
7 7 6 1 |
2 4 |
|||||||
|
Nonionella o t loniico |
.4 |
.7 |
.3 |
||||||||||||||||||||||||||
|
N opima |
2 |
||||||||||||||||||||||||||||
|
Plec lino opicu Ions |
? |
? |
3 |
||||||||||||||||||||||||||
|
Pseudoeponides urn bona tus |
*> 3 |
3 |
3 |
3 |
3 |
3 |
2 |
1 1 |
1 |
f |
J 2 5C |
1 |
2.4,4 |
2 3 .4 |
2 .6 |
2 |
5 |
9 |
3 |
1 |
2 . |
r.6 2 7 |
2 |
||||||
|
Pu llenio spp <■ |
* 3 |
f> |
? |
? |
f. |
7 |
8 |
3 |
1 |
4 |
7 2 11 |
3 2 2 |
2 : |
3 |
2 |
3 |
.7 |
.5 |
.6 |
4 |
5 4 2 2 |
5 3 |
|||||||
|
Pyrgo murrhino |
.4 |
.5 |
9 |
6 |
3 |
8 |
3 |
i 1 |
1 |
.3 |
J |
5 |
.7 |
2 |
.3 |
1 |
2 .9 2 |
6 .6 |
|||||||||||
|
Qu inqueloculino sp |
R |
.5 |
1 |
9 |
8 |
2 |
.9 |
.6 |
.8 |
1 .5 |
3 |
5 |
£ .9.5 |
||||||||||||||||
|
Robutus spp |
? |
4 |
B |
2 |
.* |
> |
■« |
||||||||||||||||||||||
|
' RoTolio beccor n vors |
|
? |
4 |
5 |
|||||||||||||||||||||||||
|
"R" tronslucens |
? |
— |
— |
? |
.5 |
3 .8 |
.3 |
1 |
.5 |
||||||||||||||||||||
|
Sig moilina distorto |
"" |
■6 |
|||||||||||||||||||||||||||
|
S schlumbergen |
» ? |
1 |
? |
3 |
1 |
2 |
2 |
.5 |
29 |
7 .8 |
3,3 |
.7 ; |
2 |
1 |
7 |
4 1 |
.6 .3 |
1 |
|||||||||||
|
Siphonino brodyono |
.4 |
||||||||||||||||||||||||||||
|
S pulchro |
"" |
~ |
_ |
_ |
_ |
_ J |
|||||||||||||||||||||||
|
Siphoteitulono rolshouseni |
.4 .4 |
1 .5 1 |
5 |
7 |
_ |
_ |
1 |
.5 |
.S |
||||||||||||||||||||
|
Tr iloculino tncorinoto |
|
6 |
? |
1 |
4 1 |
2 .4 |
■* J |
.6 .6 |
|||||||||||||||||||||
|
fi |
3 |
? |
3 |
7 |
9 |
fi |
1 |
.5 |
20 |
1 |
3 1 |
2 |
|||||||||||||||||
|
> I |
7 |
? |
? |
4 |
3 |
e |
2 29 |
57 4C 2 |
1 2.4 |
4 1 .4 |
.6 |
2 |
5 |
3 |
3 |
_ |
_ |
4 .7 |
.6 |
« 4 U |
|||||||||
|
Virquhno odvena |
.4 |
_9 |
__ |
._ |
_ |
|
.6 |
2 |
5 .4 |
.7 |
^ |
± |
J |
- |
- |
- |
5 |
.8 1 .6 5 |
1 2 |
||||||||||
|
V complanota / V mexicono |
- |
_i |
- |
|
- |
.6 |
— |
- |
- |
.7 |
1 |
.3 |
|||||||||||||||||
|
V pontoni Loticonnino pouperoto OTher species i |
i 1 5 |
1 8 |
"5 _5 |
3 it |
T 2 |
? I |
2 6| |
3. |
6 |
.6 15 |
4.4 0 7 4 6 |
5 2 26 |
.4 4 f |
J3 |
i |
2 |
^ |
1 |
_ |
- |
_ |
.5 16 |
.5 7 f |
.3 5 7 3 |
1 • 2 |
50
Fred B Phleger
Table III — Occurrences of Foraminifera in cores 7-11, in percent of total population. Planktonic and benthonic populations computed separately
|
CORE |
1 1 |
10 |
9 |
8 |
7 |
||||||||||||||||||||||||||||||||||||
|
DEPTH IN METERS |
914 |
1298 |
1372 |
1417 |
1875 |
||||||||||||||||||||||||||||||||||||
|
DEPTH IN CORE IN CM. FROM TOP |
H O |
o (J) |
(Ti |
w |
o |
o io |
ro O o |
ro IN) -.J |
H O ■0 |
r\) At |
OD |
01 U1 |
O o |
o |
o* OD |
? ID |
(JI .^ ui ui (D Ul |
f OD C/i |
to ro |
(B 01 OI |
H O ■D |
(0 |
OJ o |
(j> o |
a> |
OD |
O OJ Ul o OD Ui |
ui CJl CJl |
ui Oi |
OJ OD OI |
o |
9 |
Oi |
_ bi OI |
OJ 9 OI Oi |
yi OI |
(D Ul o o |
ro 9 ro |
|||
|
TOTAL PLANKTONIC POPULATION |
o o |
8 |
"b o o |
to 8 |
O o |
o o |
o o |
ro OJ 8 |
8 |
o o |
m o o |
O o |
o o |
01 -J o o |
OJ ro o o |
>£l |
OI |
b o |
O |
OD o |
ro O |
ro O |
ro 01 O O |
O o b o o |
yi b o o |
rj b o o |
OJ O o |
01 OI |
ID "ro o o |
||||||||||||
|
Globigermo buHoides |
4 |
4 |
8 |
4 |
6 |
6 |
2 |
,4 |
.9 |
2 |
9 |
1 |
.5 |
2 |
1 |
13 |
6 |
2 |
.8 |
2 |
3 |
1 |
4 |
3 |
3 |
5 |
|||||||||||||||
|
G eggeri |
14 |
8 |
19 |
16 |
19 |
1 1 |
14 |
13 |
14 |
8 |
16 |
10 |
12 |
14 |
II |
4 |
6 |
18 |
10 |
10 |
8 |
14 |
BC |
8 |
10 |
II |
9 |
15 |
9 |
||||||||||||
|
G pochyderma |
1 |
||||||||||||||||||||||||||||||||||||||||
|
Globigerineilo aequHoteralis |
1 |
2 |
.7 |
4 |
.3 |
■8 |
1 |
6 |
2 |
.7 |
3 |
3 |
2 |
3 |
.8 |
2 |
1 |
7 |
2 |
4 |
5 |
6 |
1 |
||||||||||||||||||
|
Qlobigerinita glutmata |
3 |
6 |
7 |
5 |
2 |
7 |
3 |
4 |
4 |
6 |
3 |
5 |
3 |
4 |
5 |
10 |
10 |
1 |
.6 |
3 |
6 |
2 |
2 |
2 |
6 |
6 |
8 |
8 |
|||||||||||||
|
Globigermoides congloboto |
A |
.3 |
.5 |
.6 |
2 |
.3 |
2 |
.4 |
3 |
2 |
.2 |
3 |
.6 |
.5 |
.3 |
.3 |
|||||||||||||||||||||||||
|
G rubro |
33 |
37 |
35 |
45 |
4S |
41 |
25 |
25 |
27 |
39 |
31 |
32 |
27 |
33 |
35 |
51 |
33 |
2! |
29 |
22 |
43 |
35 |
33 |
32 |
41 |
3d |
38 |
24 |
36 |
||||||||||||
|
G socculifero |
17 |
12 |
13 |
8 |
8 |
8 |
6 |
10 |
14 |
13 |
19 |
5 |
13 |
12 |
12 |
8 |
10 |
6 |
36 |
35 |
25 |
6 |
14 |
15 |
17 |
II |
2C |
24 |
17 |
||||||||||||
|
Globorotolio menordii |
II |
8 |
.6 |
X |
X |
X |
9 |
13 |
13 |
8 |
8 |
3 |
13 |
9 |
II |
7 |
6 |
9 |
7 |
9 |
3 |
7 |
.3 |
II |
8 |
9 |
4 |
2 |
.3 |
||||||||||||
|
G punctulota |
2 |
5 |
4 |
6 |
II |
10 |
1 |
2 |
.4 |
.6 |
2 |
2 |
1 |
3 |
.7 |
13 |
.4 |
1 |
1 |
.3 |
14 |
||||||||||||||||||||
|
G scitulo |
.3 |
.6 |
2 |
2 |
.2 |
.5 |
.8 |
||||||||||||||||||||||||||||||||||
|
G truncatulinoides |
6 |
8 |
4 |
2 |
4 |
5 |
13 |
II |
12 |
9 |
7 |
7 |
12 |
9 |
10 |
6 |
3 |
12 |
5 |
5 |
4 |
4 |
3 |
5 |
5 |
7 |
2 |
6 |
3 |
||||||||||||
|
G tumido |
2 |
1 |
2 |
3 |
.5 |
4 |
3 |
3 |
3 |
5 |
2 |
2 |
4 |
2 |
1 |
1 |
4 |
.6 |
1 |
3 |
3 |
2 |
2 |
2 |
.9 |
5 |
2 |
||||||||||||||
|
Orbulino universo |
.9 |
■9 |
3 |
1 |
1 |
2 |
3 |
4 |
.8 |
3 |
2 |
8 |
2 |
1 |
3 |
7 |
2 |
7 |
5 |
5 |
10 |
3 |
8 |
4 |
5 |
6 |
2 |
2 |
|||||||||||||
|
PuMeniatino obliquiloculQto |
10 |
8 |
5 |
5 |
2 |
4 |
9 |
12 |
9 |
7 |
8 |
IC |
8 |
II |
7 |
4 |
13 |
12 |
2 |
5 |
7 |
II |
5 |
4 |
7 |
4 |
5 |
2 |
2 |
||||||||||||
|
Sphoeroidinello dehiscens |
.4 |
.3 |
.8 |
2 |
.2 |
.3 |
3 |
||||||||||||||||||||||||||||||||||
|
TOTAL BENTHONIC POPULATION |
01 o |
O o |
o o |
O O |
o o |
o o |
tJI O |
ro O |
o |
a> ot O |
OD O |
ro o |
a> o |
O |
OI o |
-.J o |
00 o> o |
OI O |
o |
OJ O |
01 o |
OJ O |
OD ro |
O |
rj O O |
o |
01 o |
rj oi O |
o o |
ro to O |
Ol o |
rj O O |
ro |
ro (9 O |
|||||||
|
Angulogerino bello |
.6 |
||||||||||||||||||||||||||||||||||||||||
|
Anomolinoides mexicono |
.3 |
.1 |
.3 |
.1 |
.2 |
.7 |
.3 |
.5 |
.1 |
.2 |
1 |
.6 |
.4 |
.2 |
|||||||||||||||||||||||||||
|
Bolivtno alota |
. 1 |
4 |
.4 |
.9 |
.7 |
2 |
.1 |
3 |
17 |
3 |
2 |
50 |
S3 |
12 |
17 |
42 |
3C |
33 |
45 |
32 |
46 |
||||||||||||||||||||
|
B albotrossi |
3 |
12 |
10 |
.7 |
1 |
1 |
8 |
II |
10 |
7 |
,9 |
.8 |
4 |
8 |
2 |
5 |
5 |
6 |
3 |
1 |
3 |
2 |
1 |
1 |
2 |
7 |
.3 |
4 |
1 |
2 |
2 |
||||||||||
|
e borbota |
3 |
4 |
|||||||||||||||||||||||||||||||||||||||
|
B lowmani |
1 |
2 |
2 |
.1 |
.1 |
2 |
2 |
3 |
.7 |
7 |
1 |
1 |
2 |
2 |
1 |
.9 |
1 |
2 |
.2 |
1 |
1 |
.4 |
.7 |
||||||||||||||||||
|
B ordinorio |
2 |
2 |
7 |
6 |
12 |
5 |
.5 |
.7 |
.2 |
.2 |
1 |
1 |
.5 |
.6 |
.4 |
||||||||||||||||||||||||||
|
B pulchello primitivQ |
.9 |
.3 |
|||||||||||||||||||||||||||||||||||||||
|
B stnatulo spinoto |
5 |
.4 |
.3 |
.5 |
4 |
.2 |
|||||||||||||||||||||||||||||||||||
|
B suboenoriensis mexicana |
.2 |
2 |
/» |
2 |
4 |
.2 |
6 |
.6 |
1 |
.6 |
.2 |
.7 |
2 |
2 |
|||||||||||||||||||||||||||
|
Bulimino oculeato |
4 |
3 |
1 |
6 |
21 |
16 |
8 |
II |
15 |
18 |
10 |
13 |
21 |
15 |
10 |
21 |
23 |
16 |
14 |
1 |
2 |
1 |
1 |
1 |
7 |
9 |
|||||||||||||||
|
B. olozonensis |
6 |
5 |
1 |
2 |
3 |
5 |
4 |
3 |
3 |
1 |
1 |
1 |
2 |
2 |
3 |
2 |
2 |
1 |
2 |
3 |
.5 |
||||||||||||||||||||
|
B morginoto |
5 |
2 |
|||||||||||||||||||||||||||||||||||||||
|
B spicoto |
2 |
2 |
.9 |
4 |
.8 |
2 |
3 |
1 |
.7 |
.3 |
.4 |
.9 |
.3 |
2 |
3 |
.6 |
2 |
.5 |
2 |
||||||||||||||||||||||
|
B strjota mexicono |
.2 |
.5 |
2 |
2 |
3 |
.6 |
2 |
.4 |
.7 |
.8 |
.9 |
1 |
.9 |
1 |
4 |
4 |
.8 |
2 |
.3 |
.6 |
1 |
.7 |
|||||||||||||||||||
|
Buliminello cf. bossendorfensis |
1 |
2 |
13 |
.2 |
.3 |
1 |
7 |
5 |
1 |
.5 |
,4 |
||||||||||||||||||||||||||||||
|
Cossidulino corincto |
.6 |
.3 |
1 |
4 |
2C |
73 |
.9 |
.2 |
.3 |
,2 |
.5 |
10 |
2C |
2 |
.5 |
1 |
1 |
1 |
.7 |
2 |
1 |
||||||||||||||||||||
|
C subgloboSQ |
9 |
4 |
10 |
5 |
5 |
2 |
9 |
II |
13 |
4 |
5 |
4 |
6 |
5 |
6 |
4 |
3 |
4 |
1 |
.6 |
1 |
.6 |
2 |
3 |
7 |
1 |
II |
3 |
.4 |
||||||||||||
|
ChMostomello oolino |
.2 |
.r |
.1 |
.9 |
.3 |
.4 |
1 |
7 |
1 |
22 |
.5 |
4 |
1 |
.5 |
16 |
.4 |
|||||||||||||||||||||||||
|
Cibicides off floridonus |
.6 |
2 |
5 |
4 |
3 |
.8 |
.2 |
4 |
5 |
5 |
5 |
3 |
3 |
2 |
2 |
3 |
3 |
1 |
3 |
4 |
.4 |
||||||||||||||||||||
|
C fobertsomonus |
2 |
.1 |
.1 |
2 |
.5 |
1 |
2 |
.8 |
1 |
2 |
2 |
3 |
.6 |
1 |
.2 |
.5 |
.6 |
2 |
3 |
5 |
3 |
||||||||||||||||||||
|
C- wuellerstorf 1 |
.2 |
2 |
. 1 |
.3 |
.9 |
1 |
2 |
1 |
.8 |
5 |
4 |
2 |
2 |
4 |
3 |
2 |
1 |
1 |
3 |
2 |
2 |
.7 |
3 |
7 |
|||||||||||||||||
|
Cibicidino strottont |
2 |
||||||||||||||||||||||||||||||||||||||||
|
Elphidi um spp |
4 |
1 |
.3 |
||||||||||||||||||||||||||||||||||||||
|
Epistominello decorofo |
.3 |
3 |
1 |
2 |
3 |
1 |
.6 |
2 |
4 |
1 |
4 |
2 |
8 |
5 |
3 |
18 |
1 |
10 |
|||||||||||||||||||||||
|
E exiguo |
4 |
5 |
12 |
II |
3 |
.2 |
4 |
2 |
4 |
4 |
2 |
1 |
1 |
3 |
2 |
3 |
2 |
2 |
7 |
.5 |
2 |
.6 |
3 |
1 |
6 |
.8 |
.2 |
2 |
3 |
.5 |
1 |
||||||||||
|
E rugoso |
2 |
.8 |
.9 |
1 |
.5 |
.4 |
.5 |
.1 |
.6 |
.5 |
|||||||||||||||||||||||||||||||
|
E vitrec |
27 |
19 |
|||||||||||||||||||||||||||||||||||||||
|
Eponides polius |
.4 |
.2 |
.7 |
.8 |
1 |
1 |
.9 |
.3 |
2 |
.5 |
1 |
.3 |
1 |
.6 |
.8 |
.2 |
|||||||||||||||||||||||||
|
E tumidulus |
.8 |
.3 |
.9 |
.3 |
2 |
.2 |
.2 |
.6 |
2 |
1 |
|||||||||||||||||||||||||||||||
|
E furgrdus |
8 |
5 |
4 |
2 |
5 |
.6 |
3 |
5 |
3 |
6 |
7 |
8 |
10 |
21 |
12 |
3 |
.9 |
1 |
2 |
.6 |
3 |
1 |
.7 |
.6 |
3 |
10 |
5 |
||||||||||||||
|
Globobulimino offlnis 8 vors |
.6 |
.6 |
2 |
.4 |
.9 |
.5 |
3 |
2 |
.5 |
1 |
2 |
4 |
.8 |
.1 |
1 |
2 |
2 |
23 |
2 |
3C |
35 |
II |
10 |
8 |
2 |
2 |
15 |
34 |
14 |
||||||||||||
|
G mississippiensis |
2 |
||||||||||||||||||||||||||||||||||||||||
|
Gyfoidino orbicularis |
3 |
.8 |
.6 |
1 |
1 |
2 |
1 |
2 |
4 |
2 |
3 |
4 |
5 |
4 |
2 |
3 |
4 |
2 |
.6 |
1 |
1 |
,7 |
5 |
3 |
|||||||||||||||||
|
Hoplophrogmoides brodyi |
7 |
1 |
.3 |
.5 |
2 |
2 |
.9 |
3 |
.5 |
||||||||||||||||||||||||||||||||
|
Hoglundino elegons |
.7 |
.2 |
.3 |
.2 |
.1 |
.8 |
.7 |
.4 |
3 |
4 |
2 |
1 |
2 |
.7 |
4 |
2 |
6 |
II |
5 |
||||||||||||||||||||||
|
Logenidoe |
2 |
2 |
4 |
3 |
.3 |
1 |
.3 |
5 |
4 |
9 |
3 |
4 |
4 |
6 |
4 |
5 |
6 |
7 |
.7 |
2 |
4 |
1 |
4 |
3 |
2 |
3 |
3 |
4 |
3 |
||||||||||||
|
Loticorinino pouperoto |
2 |
.6 |
1 |
1 |
.3 |
.9 |
2 |
2 |
2 |
1 |
2 |
2 |
2 |
1 |
2 |
2 |
.9 |
2 |
3 |
1 |
2 |
2 |
|||||||||||||||||||
|
Mi liolidoe |
.8 |
2 |
.6 |
.5 |
.2 |
2 |
.9 |
2 |
.4 |
5 |
1 |
1 |
1 |
1 |
.4 |
1 |
1 |
3 |
1 |
.9 |
.6 |
1 |
2 |
4 |
3 |
1 |
.4 |
||||||||||||||
|
Nonionello otlontico |
.6 |
||||||||||||||||||||||||||||||||||||||||
|
N opimo |
6 |
.2 |
1 |
.7 |
|||||||||||||||||||||||||||||||||||||
|
Osongulorio cultur |
.6 |
7 |
13 |
.7 |
2 |
3 |
2 |
6 |
S |
3 |
1 |
2 |
3 |
2 |
3 |
3 |
I |
1 |
5 |
4 |
3 |
1 |
2 |
.3 |
2 |
3 |
2 |
.7 |
|||||||||||||
|
Pseudoeponides umbonotus |
.5 |
.1 |
•3 |
.1 |
.3 |
.5 |
.2 |
.4 |
.5 |
1 |
1 |
.3 |
.5 |
.3 |
.5 |
3 |
4 |
1 |
.4 |
.7 |
£ |
1 |
.4 |
||||||||||||||||||
|
Pullenio spp. |
.6 |
2 |
1 |
1 |
1 |
.2 |
4 |
2 |
3 |
2 |
I |
3 |
5 |
3 |
4 |
5 |
2 |
.9 |
2 |
3 |
.6 |
2 |
1 |
.3 |
1 |
4 |
.4 |
||||||||||||||
|
Rectoboltvino odveno |
.6 |
||||||||||||||||||||||||||||||||||||||||
|
Robulus spp |
.2 |
.3 |
.3 |
.6 |
2 |
.2 |
1 |
.5 |
.9 |
.2 |
2 |
.7 |
1 |
2 |
1 |
.4 |
.2 |
.7 |
.6 |
.5 |
|||||||||||||||||||||
|
"Rotolio" beccoril vors. |
4 |
4 |
|||||||||||||||||||||||||||||||||||||||
|
"R", tronslucens |
1 |
3 |
3 |
13 |
12 |
.2 |
.3 |
5 |
1 |
5 |
.3 |
.9 |
2 |
.6 |
.2 |
2 |
3 |
3 |
.6 |
1 |
.6 |
||||||||||||||||||||
|
Uvigerino porvulo |
3 |
8 |
|||||||||||||||||||||||||||||||||||||||
|
U peregrino |
1 |
14 |
21 |
22 |
10 |
5 |
.2 |
6 |
7 |
8 |
5 |
6 |
8 |
8 |
4 |
5 |
4 |
6 |
15 |
2 |
17 |
8 |
5 |
5 |
6 |
3 |
5 |
15 |
,2 |
6 |
|||||||||||
|
Virgulino mexicano |
.1 |
.5 |
7 |
.2 |
3 |
2C |
3 |
2 |
.5 |
1 |
.4 |
.7 |
6 |
,4 |
|||||||||||||||||||||||||||
|
V pontoni |
2 |
2 |
|||||||||||||||||||||||||||||||||||||||
|
V tesselioto |
.2 |
.6 |
.1 |
.3 |
3 |
.5 |
.4 |
.7 |
.2 |
.3 |
.2 |
,3 |
.2 |
||||||||||||||||||||||||||||
|
Other species |
82 |
3 |
8 |
16, |
la |
I |
9 |
2 |
2S |
8 |
6 |
8 |
—1 |
2 |
4« |
10 |
9 |
24 |
4 |
10 |
4 |
8 |
«7 |
3 |
5 |
7 |
4 |
5 |
12 |
10 |
7 |
12 |
10 |
7 |
5 |
Foraminiferal faunas in cores offshore from the Mississippi Delta
51
Table IV— Occurrences of Foraminifera in cores 12-15, 1<S and 21, /// percent oj total population. Plank tonic and henthonic populations computed separately
|
CORE |
18 |
21 |
15 |
1 4 |
13 |
12 |
||||||||||||||||||||||||||||||||||
|
DEPTH IN METERS |
88 |
142 |
298 |
471 |
631 |
732 |
||||||||||||||||||||||||||||||||||
|
DEPTH IN CORE IN CM FROM TOP |
o |
U3 O |
ro -^ ID |
CD ro |
H O |
ro O |
JO |
in a o It. |
_ 9 rv |
ro m In |
H O |
o* 3 |
ro ik |
en o |
00 |
r (V ro In |
In 0 |
■D ro ■ |
0 |
5 |
(X) In at OJ In |
10 0 |
ro Xk U3 In |
00 0 |
0 |
ui OJ |
0 |
(S Ol (0 |
r OJ OJ |
0 |
-1 0 |
en 0 |
(T. fO |
0 |
0 <D |
OJ en en |
? en |
z 0 0 rj 0 |
||
|
TOTAL PLANKTONIC POPULATION |
W |
0^ |
O) |
m |
o |
O |
ID |
O O |
O |
ro o |
ro ■o O O |
8 |
8 |
_ro 8 |
rvj 'O o o |
O o |
0 |
t\i |
>o |
ro 3 |
'o 8 |
(71 8 0 |
3 b 8 |
~J |
tn 0 |
ro 0 0 |
OS en 0 |
0 10 |
JJl 0 0 |
01 |
ro |
eji 0 Si |
0 0 |
rj 'm 0 0 |
_rei |
o« ■<Ti 0 0 |
"en 0 0 |
|||
|
Globigenna bulloides |
'ii |
8 |
4 |
6 |
1 |
1 |
3 |
4 |
3 |
4 |
3 |
3 |
13 |
6 |
3 |
6 |
6 |
16 |
.7 |
2 |
5 |
4 |
7 |
4 |
5 |
1 |
3 |
1 |
6 |
2 |
7 |
|||||||||
|
G eggen |
22 |
12 |
14 |
15 |
13 |
II |
10 |
27 |
10 |
12 |
12 |
12 |
12 |
4 |
II |
15 |
II |
12 |
1 1 |
13 |
7 |
7 |
14 |
9 |
ao |
14 |
II |
9 |
13 |
14 |
17 |
2C |
||||||||
|
G pGchyderna |
2 |
2 |
||||||||||||||||||||||||||||||||||||||
|
Globigennello aequiloterolis |
10 |
1 |
2 |
2 |
.4 |
1 |
1 |
.4 |
2 |
I |
3 |
.6 |
.6 |
.8 |
1 |
.5 |
1 |
.7 |
2 |
.4 |
.4 |
.4 |
.7 |
1 |
.6 |
|||||||||||||||
|
Globigennito glutmota |
1 1 |
la |
6 |
3 |
2 |
7 |
6 |
5 |
2 |
3 |
1 |
3 |
1 |
2 |
2 |
8 |
7 |
5 |
3 |
1 |
4 |
6 |
3 |
.8 |
2 |
3 |
3 |
5 |
.9 |
2 |
||||||||||
|
Globigennoides conglobolo |
3 |
2 |
.7 |
.6 |
.7 |
2 |
1 |
.9 |
.3 |
2 |
2 |
3 |
.8 |
1 |
.5 |
2 |
.4 |
1 |
1 |
.6 |
.4 |
.4 |
.4 |
|||||||||||||||||
|
G fubro |
53 |
5C |
27 |
40 |
2C |
M |
28 |
43 |
55 |
42 |
12 |
38 |
42 |
5140 |
54 |
62 |
CD |
44 |
28 |
39 |
57 |
48 |
27 |
30 |
34 |
?5 |
3€ |
3€ |
3S |
30 |
?fl |
41 |
38 |
3? |
||||||
|
G saccuhtero |
33 |
6 |
12 |
10 |
4 |
10 |
8 |
12 |
6 |
4 |
16 |
13 |
13 |
18 |
16 |
13 |
8 |
5 |
9 |
17 |
3 |
9 |
12 |
II |
r? |
10 |
6 |
4 |
10 |
II |
14 |
21 |
9 |
|||||||
|
Globorotolio hirsuTo |
.4 |
3 |
2 |
3 |
.7 |
2 |
.4 |
|||||||||||||||||||||||||||||||||
|
G menardit |
17 |
12 |
1 |
7 |
3 |
14 |
IC |
13 |
3 |
2 |
4 |
5 |
3 |
6 |
9 |
B |
6 |
14 |
II |
12 |
16 |
12 |
9 |
5 |
3 |
1 1 |
14 |
4 |
5 |
.3 |
||||||||||
|
G punctutota |
1 |
.7 |
.7 |
.7 |
1 |
4 |
.6 |
.7 |
.7 |
.6 |
.3 |
5 |
14 |
3 |
.3 |
3 |
.4 |
5 |
.2 |
10 |
||||||||||||||||||||
|
G scitulo |
.3 |
2 |
||||||||||||||||||||||||||||||||||||||
|
G Ir uncotu hnoides |
22 |
50 |
9 |
8 |
3 |
4 |
7 |
12 |
10 |
II |
3 |
6 |
3 |
10 |
II |
7 |
4 |
.5 |
2S |
15 |
IB |
9 |
9 |
7 |
43 |
9 |
7 |
8 |
E |
4 |
4 |
4 |
||||||||
|
G tumida |
3 |
2 |
1 |
1 |
6 |
6 |
4 |
1 |
1 |
1 |
3 |
4 |
2 |
1 |
.7 |
4 |
3 |
7 |
3 |
4 |
3 |
6 |
5 |
5 |
2 |
6 |
||||||||||||||
|
Orbulina universo |
6 |
12 |
3 |
5 |
5 |
3 |
3 |
1 |
.4 |
.7 |
2 |
4 |
2 |
7 |
3 |
1 |
3 |
1 |
1 |
.7 |
4 |
.6 |
3 |
3 |
5 |
7 |
2 |
3 |
2 |
1 |
||||||||||
|
PuMeniotino obliquMoculato |
6 |
12 |
5C |
6 |
14 |
13 |
1 1 |
II |
14 |
5 |
7 |
4 |
8 |
2 |
4 |
6 |
10 |
12 |
3 |
1 |
43 |
12 |
10 |
10 |
13 |
6 |
K. |
14 |
19 |
17 |
9 |
6 |
6 |
6 |
||||||
|
Sphoefordinello dehiscens |
.4 |
.6 |
4 |
.4 |
.2 |
2, |
||||||||||||||||||||||||||||||||||
|
TOTAL BENTHONIC POPU LATION |
ro O |
O O |
'CD o o |
o o |
o o |
(0 o |
o |
a. o o |
O |
s o |
O o |
tn O 8 |
O O |
J-** en O o |
8 |
O o |
0 0 |
6i 0 0 |
0 0 |
OJ |
m ro 0 0 |
03 0 0 |
'^ 0 0 |
01 0 0 |
6 0 8 |
ro tn 0 |
0 |
0) 0 0 |
0 9 |
'tD 0 0 |
8 |
i^ 0 |
'o 0 0 |
"0 |
OJ 0 0 |
0 0 |
||||
|
Ammoscolano pseudospirolis |
.4 |
3 |
.6 |
2 |
r |
2 |
8 |
|||||||||||||||||||||||||||||||||
|
Bolivi na Qlbotrosst |
.4 |
.6 |
1 |
9 |
1 1 |
14 |
12 |
2 |
6 |
2 |
4 |
9 |
II |
3 |
5 |
4 |
7 |
7 |
8 |
6 |
5 |
10 |
10 |
1 |
||||||||||||||||
|
B borbota |
13 |
3 |
3 |
3 |
3 |
15 |
12 |
15 |
8 |
.9 |
1 |
2 |
.9 |
.6 |
4 |
2 |
6 |
.5 |
||||||||||||||||||||||
|
B lowmani |
.4 |
.3 |
.3 |
.3 |
.4 |
1 |
2 |
8 |
2 |
1 |
.7 |
1 |
2 |
.6 |
.5 |
.4 |
.9 |
.5 |
1 |
.3 |
2 |
.5 |
.6 |
1 |
2 |
1 |
.8 |
4 |
,9 |
|||||||||||
|
B ordinoriQ |
2 |
1 |
3 |
3 |
3 |
3 |
3 |
5 |
4 |
1 |
2 |
.7 |
13 |
14 |
8 |
9 |
1 1 |
1 1 |
10 |
6 |
13 |
IB |
15 |
7 |
3 |
4 |
10 |
14 |
||||||||||||
|
B stnatulQ spinato |
4 |
2 |
.4 |
2 |
.3 |
.3 |
.6 |
|||||||||||||||||||||||||||||||||
|
B suboenoriensis menrcana |
I |
.9 |
.6 |
1 |
2 |
40 |
21 |
15 |
13 |
6 |
.7 |
II |
5 |
9 |
13 |
13 |
9 |
.6 |
1 |
1 |
5 |
1 |
.5 |
.2 |
.8 |
.3 |
||||||||||||||
|
B subspinescens |
.8 |
.4 |
J |
1 |
1 |
.3 |
.3 |
.6 |
1 |
3 |
,41 |
1 |
1 |
.8 |
.9 |
1 |
.4 |
.2 |
.6 |
.6 |
||||||||||||||||||||
|
Bulimino oculeota |
.6 |
14 |
5 |
2 |
.6 |
a |
4 |
.4 |
.5 |
12 |
||||||||||||||||||||||||||||||
|
B alazanensis |
3 |
.9 |
2 |
3 |
1 |
4 |
3 |
4 |
4 |
5 |
9 |
3 |
||||||||||||||||||||||||||||
|
B marginofa |
15 |
8 |
4 |
9 |
5 |
20 |
15 |
6 |
8 |
12 |
13 |
3 |
4 |
10 |
23 |
22 |
31 |
.6 |
2 |
2 |
1 |
|||||||||||||||||||
|
B sprcota |
1 |
( |
.3 |
.3 |
4 |
.7 |
1 |
1 |
1 |
.1 |
||||||||||||||||||||||||||||||
|
B stnota mcicano |
1 |
.3 |
.4 |
.4 |
12 |
5 |
4 |
2 |
1 |
1 |
.7 |
5 |
6 |
4 |
.5 |
.3 |
13 |
4 |
5 |
4 |
2 |
2 |
5 |
6 |
3 |
1 |
.7 |
|||||||||||||
|
Butiminelta cf bossendor fensis |
32 |
17 |
30 |
22 |
54 |
.2 |
3 |
1 |
||||||||||||||||||||||||||||||||
|
Cossidulino connata |
.2 |
1 |
3 |
3 |
3 |
1 |
.7 |
4 |
30 |
10 |
5 |
2 |
17 |
49 |
6 |
3 |
2 |
13 |
2 |
.9 |
9 |
|||||||||||||||||||
|
C c u r V 0 to |
.5 |
2 |
3 |
2 |
2 |
2 |
2 |
2 |
3 |
.5 |
2 |
7 |
2 |
1 |
2 |
.4 |
.4 |
|||||||||||||||||||||||
|
C neoconnoto |
,5 |
1 |
4 |
6 |
6 |
.7 |
3 |
4 |
2 |
1 |
2 |
3 |
1 |
2 |
2 |
.8 |
.5 |
.4 |
.2 |
1 |
||||||||||||||||||||
|
C subglobosa |
.6 |
.3 |
.4 |
3 |
3 |
1 |
3 |
1 |
.9 |
.3 |
1 |
.4 |
2 |
.4 |
5 |
1 |
1 |
e |
3 |
6 |
9 |
8 |
.2 |
4 |
b |
_ |
II |
if |
||||||||||||
|
Ctbtcides off flondonus |
.3 |
2 |
15 |
9 |
16 |
9 |
4 |
II |
9 |
1 1 |
3 |
.6 |
3 |
2 |
1 |
2 |
4 |
2 |
1 |
3 |
i |
4 |
A |
5 |
B |
b |
2 |
|||||||||||||
|
Elphidium spp |
.3 |
.7 |
.3 |
J |
"2 |
|||||||||||||||||||||||||||||||||||
|
E pistominello exiguo |
.2 |
1 |
1 |
J |
/ |
7 |
4 |
12 |
iv |
19 |
4 |
5 |
5 |
_^ |
6 |
_ |
||||||||||||||||||||||||
|
£ rjgoSQ |
.2 |
.3 |
.4 |
2 |
3 |
? |
.9 |
2 |
1 |
_^ |
.9 |
.5 |
||||||||||||||||||||||||||||
|
E VI t reo |
.4 |
16 |
Jl |
30 |
42 |
23 |
.3 |
.4 |
3 |
1 |
.3 |
.6 |
-A |
|||||||||||||||||||||||||||
|
Eponides regutons |
6 |
8 |
6 |
6 |
1 |
2 |
4 |
.9 |
7 |
37 |
34I |
56 |
.6 |
.9 |
1 |
.7 |
' |
2 |
.1 |
|||||||||||||||||||||
|
E Turgidus |
2 |
.5 |
4 |
3 |
2 |
6 |
2 |
.9 |
.b |
.6 |
5 |
S |
e |
|||||||||||||||||||||||||||
|
Globobulirnino offtnis |
3 |
.4 |
.2 |
^ |
.4 |
.5 |
2 |
2 |
1 |
1 |
1 |
-A |
.2 |
|||||||||||||||||||||||||||
|
G mississippiensis |
.7 |
.3 |
1 |
2 |
.4 |
2 |
1 |
.3 |
_^ |
^ |
||||||||||||||||||||||||||||||
|
GyfOidino of biculons |
.2 |
.3 |
.6 |
2 |
3 |
2 |
.5 |
.4 |
2 |
_ |
i |
-J |
.6 |
|||||||||||||||||||||||||||
|
Gyroidinoides alt if or mis |
.6 |
.8 |
.5 |
.9 |
.3 |
2 |
2 |
.6 |
.9 |
.5 |
.5 |
2 |
.5 |
.6 |
TS |
.9 |
.2 |
.4 |
.2 |
- |
1 |
|||||||||||||||||||
|
GoesellQ mississippiensis |
3 |
53 |
3 |
_ |
1 |
1 |
_ |
|||||||||||||||||||||||||||||||||
|
Logenidae |
2 |
.3 |
1 |
1 |
2 |
2 |
2 |
1 |
.9 |
.9 |
2 |
2 |
2 |
1 |
1 |
2 |
2 |
.4 |
2 |
2 |
1 |
~r |
3 |
1 |
1 |
1 |
1 |
— |
— |
1 |
||||||||||
|
1 |
fi |
,9 |
.4 |
1 |
2 |
1 |
1 |
2 |
.9 |
.5 |
.8 |
.5 |
.2 |
^ |
.2 |
|||||||||||||||||||||||||
|
7 |
.3 |
.4 |
_ |
_, |
|
_ |
__ |
, |
_ |
|||||||||||||||||||||||||||||||
|
N, opima |
_ |
.2_ |
.i_ |
,4 |
, |
_ |
1 |
1 |
£ |
— |
^ |
— |
— |
-J |
.6 |
— |
— |
— |
— |
"4 |
T |
— |
"4 |
"? |
— |
"? |
"fi |
"fi |
- |
"3 |
- |
- |
- |
|||||||
|
Planulina anminensis |
— |
— |
— |
— |
— |
— |
— ' |
— ' |
— ' |
— |
3 |
— ' |
~ |
1 |
~ |
"3 |
1 |
3 |
2^ |
^ |
^ |
.6 |
||||||||||||||||||
|
P foveolato |
1 |
.6 |
3 |
3 |
.2 |
.5 |
2 |
2 |
.6 |
1 |
_ |
_ |
_ |
_ |
_ |
|||||||||||||||||||||||||
|
Pullenio spp |
.6 |
1 |
■ 4 |
.7 |
1 |
.9 |
1 |
.2 |
3 |
1 |
2 |
1 |
.6 |
.4 |
2 |
.6 |
1 |
1 |
.2 |
.4 |
.3 |
.a |
||||||||||||||||||
|
.5 |
.5 |
|
_ |
_ |
, 1 |
_ |
||||||||||||||||||||||||||||||||||
|
Robulus spp |
4 |
.6 |
8 |
,4 |
.3 |
1 |
1 |
3 |
3 |
3 |
3 |
4 |
3 |
.6 |
1 |
1 |
1 |
.9 |
_ |
|
.5 |
.b |
_ |
, |
|
.2 |
__ |
J^ |
, |
|
J |
|||||||||
|
.2 |
3 |
4 |
2 |
5 |
II |
7 |
14 |
1/ |
14 |
21 |
2/ |
B |
4 |
10 |
8 |
7 |
10 |
II |
|
__ |
, |
12 |
||||||||||||||||||
|
Rotamorphino loevigoto |
.2 |
2 |
.b |
.4 |
1 |
2 |
.9 |
.2 |
1 |
.8 |
1 |
_ |
_ |
|||||||||||||||||||||||||||
|
~~ |
.7 |
.8 |
.3 |
.8 |
2 |
.2 |
.b |
.3 |
_ |
_ |
|
|
__ |
|
_ |
|||||||||||||||||||||||||
|
' |
~ |
.2 |
.3 |
3 |
.3 |
r |
1 |
_ |
_ |
, |
_ |
|||||||||||||||||||||||||||||
|
.2 |
1 |
.6 |
1 |
2 |
8 |
4 |
3 |
2 |
.3 |
.9 |
1 |
6 |
4 |
5 |
7 |
3 |
8 |
2 |
2 |
3 |
b |
2 |
8 |
_b |
_4 |
, |
_5 |
_ |
__ |
•1 |
||||||||||
|
Bl |
~~" |
~ |
.9 |
M |
2 |
_ |
_ |
9 |
|
_ |
— |
, |
_ |
|||||||||||||||||||||||||||
|
Trttonna brodyi |
_ |
|
|
, |
|
_ |
— |
^ |
— |
"fi |
"9 |
- |
£ |
— |
1 |
.7 |
"9 |
- |
— |
- |
.4 |
- |
- |
• b |
- |
.J^ |
- |
- |
||||||||||||
|
Uvigerino laevis U pofvulo |
"e |
B |
27 |
is |
?6 |
I |
_2_ |
_4 |
^ |
_8 |
7 |
^ |
I |
12 5 |
T 3 |
3 |
— |
rf |
T |
75 |
TT |
T |
"fi |
~7 |
T |
■fl |
T |
"« |
i? |
i? |
13 |
- |
16 |
- |
- |
4 |
||||
|
U peregnno Volvuhnerio mexicono VirguliPO mexicono V tesselloto Other species |
M |
3 |
_ |
« |
2 |
3 |
]9 |
"7 1 |
4 [3 |
^ ^ T |
.6 3 |
— |
"4 |
2 |
■;4 3 |
E |
J |
2 T |
12 |
T |
2 .4 il |
^5 |
1 "4 |
]6 |
[I |
^5 J9 _7 |
.2 X |
.2 1 |
.4 .2 .2 5 |
E |
- |
- |
3 6 |
52 Fred B Phleger
/
planktonic forms are treated as separate populations, with each constituting 100%. Total populations are estimated for each sample, since they all contained approximately the same amount of sediment, with a few exceptions. Results of the faunal analyses are on Tables II-IV. Only the more common and/or important species are included in these lists; detailed analyses are on file at the Marine Foraminifera Laboratory.
Detailed faunal analyses were made on only a few samples from each core, but each sample was examined to ascertain whether or not there was a faunal change. Faunas in surface sediment samples from the stations along this traverse, collected with a small coring tube, have been analyzed by Parker (1954). Population data from some of these samples are included for comparative purposes, since the top sample from a long core may not represent the actual surface sediment due to methods of collecting and processing.
The following should be consulted for illustrations, descriptions, and additional distributions of the species listed in the present report: Phleger and Parker (1951), Parker (1954), Phleger, Parker and Peirson (1953), and Phleger (1954).
CORE FAUNAS
In a previous study of core faunas from the northwestern Gulf of Mexico (Phleger, 1951) it was possible to differentiate an "upper" and "lower" core fauna based on the assemblages of planktonic Foraminifera. The upper planktonic fauna is the modern one and has the following general composition :
30-70%
Globigerinoides rubra (d'Orbigny)
10-20%
Globigerina buUoides d'Orbigny
G. eggeri Rhumbler
Globorotalia truncatulinoides (d'Orbigny)
PuUeniatina obliquiloculata (Parker and Jones)
5-10%
Globigerinoides sacculifera (H. B. Brady) Globorotalia menardii (d'Orbigny)
<l-5%
Globigerinella aequilateralis (H. B. Brady) Globigerinoides conglobata (H. B. Brady) Globorotalia tumida (H. B. Brady) Orbulina universa d'Orbigny
The planktonic fauna which is widespread in lower sections of most northwestern Gulf of Mexico cores differs in having many or all of the following species absent or lower in frequency:
Globigerina eggeri Rhumbler
Globigerinella aequilateralis (H. B. Brady)
Globigerinoides conglobata (H. B. Brady)
Globorotalia menardii (d'Orbigny)
G. truncatulinoides (d'Orbigny)
G. tumida (H. B. Brady)
Orbulina universa d'Orbigny
PuUeniatina obliquiloculata (Parker and Jones)
Foraminiferal faunas in cores offshore from the Mississippi Delta In addition, the following occur in the lower fauna:
53
Globigerina inflata d'Orbigny G. pachyderma (Ehrenberg) Globorotalia punctulata (d'Orbigny) G. scitula (H. B. Brady)
CORE DEPTH
rO
5 o
X
I- a.
UJ Q
50
-100
■150
200
18 88 m.
w c
21
142m W C
15
298 m W C
14
471 m W C
I
13
631 m W C
12 732 m W C
n
914 m W C
10 1298 m W C
■
I-
DISPLACED SEDIMENT
CORE DEPTH
Z
o
I-
UJ
o
50
9 1372 m
W C
■100
DISPLACED SEDIMENT
150
8 1417 m
W C
W I
1-200
Fig. 3. Relative temperatures indicated by Foraminifera in the cores. W, relatively warm surface
water. C, relatively cold surface water
54 Fred B Phleger
The present cores contain " upper " and " lower " faunas which are comparable in species composition to those previously reported, with the following exceptions: in the upper, modern assemblage Globigerinoides sacculifera generally is more abund- ant especially in the area farthest off shore, Globorotalia truncatulinoides may be less abundant, and Globigehna eggeri may be more abundant; in the lower fauna, G. inflata and G. pachyderma are less common, being recorded in very low frequencies from only occasional samples.
The " upper " planktonic core fauna contains the modern assemblage and is assumed to represent conditions similar to those obtaining today, and may be con- sidered to represent relatively warm surface water. The " lower " fauna contains fewer North Atlantic low-latitude planktonic specimens and consequently more mid-latitude forms, and is considered to represent a time of cooler surface water. Interpretation of these distributions may be clarified by examination of the data and discussion in Phleger et al. (1953) on distributions of North Atlantic planktonic Foraminifera.
Lower, colder-water faunas were present in eight of the fifteen cores examined. The interpretations of the faunas are summarized in Fig. 3, and the faunas on which these interpretations are based are listed in Tables II-IV. Cores 3, 4 and 6 contain two cold-water faunas separated by a warm-water fauna and their lower sections contain an additional warm-water fauna. Cores 5, 7, 8, 11 and 14 contain a cold- water fauna in their lowermost sections. The other cores contain the modern Gulf of Mexico planktonic fauna throughout their entire lengths. Core 18, on the lower continental shelf at a depth of 88 m, contains few planktonic specimens.
The benthonic Foraminifera in most of the core samples are normal for the water depths at which the cores were collected (see Phleger, 1951, Figs. 22-25; Parker, 1954, Figs. 3-9). Striking exceptions occur in cores 9 and 10. In core 9, from 1372 m depth, the bottom sample at 158-163 cm contains the following shallow-water (continental shelf) species in significant frequencies:
Angulogerina be I la Phleger and Parker
Bolivina barbata Phleger and Parker
B. striatula spinata Cushman
Bulimina marginata d'Orbigny
Buliminella cf. bassendorfensis Cushman and Parker
Elphidium spp.
Globobulimina mississippiensis F. L. Parker
Nonionella opima Cushman
Rectobolivina advena (Cushman)
" Rotalia " beccarii (Linne) variants
Virgulina pontoni Cushman
A few of these species occur in lower frequencies from 145-158 cm, and single specimens of Bolivina striatula spinata, Buliminella cf. bassendorfensis and Liebusella sp. occur at 3-8 cm in the core. Most of the benthonic Foraminifera in this core are normal for the depth at which the core was collected. Quartz grains of fine sand size and wood fibres which are coloured dark brown occur from 85 cm to the bottom of the core.
Foraminiferal faunas in cores offshore from the Mississippi Delta 55
In core 10 from a depth of 1,298 m the following shallow-water species are important constituents of the bottom core section at 144-155 cm:
Bolivina pulchella primitiva Cushman
B. striatula spinata Cushman
Bulimina marginata d'Orbigny
Buliminella cf. bassendorfensis Cushman and Parker
Cibicidina strattoni (Applin)
Elphidium spp.
Nonionella opima Cushman
" Rotalia " beccarii (Linne) variants
Virgulina pontoni Cushman
A few specimens of Buliminella cf. bassendorfensis also occur at 56-5-61 -5 cm and 2-5-7 cm. Plant fibres and fine quartz sand occur in the samples from 75 cm to 155 cm. The major part of the benthonic fauna consists of species normal for the depth of the core.
Twenty-six specimens of Giimbelina are recorded from the lowermost section of core 10.
Occasional shallow-water benthonic Foraminifera are recorded from the following additional deep-water cores of this series: 3, 4, 5, 6, 7, 8, 13 and 14. These are single specimens and no sample contains more than four specimens, while many contain none. No other evidence of displacement of sediment was observed.
DISCUSSION
Interpretations of the core planktonic Foraminifera in terms of " warm " (like the present) and " cold " (colder than present) surface water temperatures are given on Fig. 3. In this figure, " W 1 " refers to the modern warm-water fauna, *' C 1 " to the last cold-water fauna, " W 2 " to the preceding warm-water fauna, etc. It is suggested that these stages can be correlated in the present cores, as shown on Fig. 3, especially where a succession of such faunal variations occurs and where there is no indication of displaced sediment. This is especially striking in comparing cores 3, 4 and 6. These cores came from the same relatively small area and from similar depths in the eastern Gulf of Mexico basin. Each of them has three warm-water faunas separated by two cold-water ones, and these occur within approximately the same thickness of sediment.
It is suggested that these warm and cold faunas also are to be correlated with similar successions described previously from northwestern Gulf of Mexico cores (Phleger, 1951, Figs. 29-33). The cold-water faunas have been interpreted elsewhere as representing Pleistocene glacial stages and/or substages and the warm-water faunas are thus possible interglacial stages and/or substages. The widespread occurrence of a cold-water fauna beneath the modern fauna in this region suggests a general coohng of Gulf of Mexico surface water during the last glacial or stadial stage.
Correlation of the planktonic faunas makes it possible to estimate the amount of post-glacial sedimentation along this traverse. This is based on the assumption that the upper, warm-water fauna represents post-glacial deposition. The amounts of deposition appear to be approximately as follows :
56 Fred B Phleger
|
Estimated post-glacial |
||
|
Core |
Water depth in m |
deposition in cm |
|
3 |
3017 |
65 |
|
4 |
2972 |
40 |
|
5 |
2788 |
170 |
|
6 |
2468 |
90 |
|
7 |
1875 |
120 |
|
8 |
1417 |
115 |
|
9 |
1372 |
>150 |
|
10 |
1298 |
>150 |
|
11 |
914 |
>210 |
|
12 |
732 |
>205 |
|
13 |
631 |
>180 |
|
14 |
471 |
155 |
|
15 |
298 |
>195 |
|
21 |
142 |
>195 |
|
18 |
88 |
>165 |
Some useful generalizations may be made from these data. The amount of post- glacial deposition is smallest away from the major source of supply, the Mississippi River, and near the centre of the basin ; there is a general increase in amount of deposition closer to the source, as expected. In all but one core shoaler than 1,400 m the coring tube did not penetrate through post-glacial sediment. There is considerable local variation in the amount of post-glacial deposition. For example, in core 5 in the basin there is two to four times as much post-glacial deposition as in nearby cores from similar depths. Core 14 on the upper part of the continental slope has consider- ably less post-glacial sedimentation than nearby cores at similar depths and position. The amount of post-glacial deposition in the cores from the basin and lower continental slope in the present cores is comparable to that shown in cores from the basin and lower slope reported previously from the northwestern area (see Phleger, 1951, Figs. 29-33). The amount of such deposition on the upper slope appears to be larger than in the western area, although there are exceptions.
Cores 9 and 10 contain sediments and faunas in their lower sections which appear to have been displaced downslope from shoaler depths, presumably in the form of turbidity currents. The presence of abundant sand, wood fibres and abundant shallow- water benthonic Foraminifera at water depths of 1,298 m and 1,372 m appears to be conclusive evidence for such displacement. Most of the benthonic Foraminifera are species normal for the depth at which the core was taken ; this demonstrates that the displaced material was deposited at the present water depths at those stations. The age of the displacement is post-glacial (W 1), as shown on Fig. 3.
Cores 9 and 10 occur in the bottom of Mississippi Canyon (Fig. 2). Other cores in this traverse do not have displaced sediment, at least in significant amounts, and these are located on topography other than the canyon floor. This suggests that the turbidity flow was localized in the canyon. Studies by Shepard (1951) and Ludwick (1950) in the San Diego area have shown that displacement of sediment from shallow to deep water appears to be funnelled down the canyons in that area, and it seems probable that much displaced sediment flows down the channels of submarine canyons in other areas of the world. The restriction of displaced sediment to the Mississippi Canyon floor in the present cores is evidence in this connection.
The lower section of core 15, below approximately 165 cm, contains abundant sand grains and plant fibres; this sediment contains no benthonic Foraminifera which are
Foraminiferal faunas in cores offshore from the Mississippi Delta 57
characteristic of water shoaler than that at which the core was collected (298 m). It is possible that this sediment was displaced from shallow water, but the absence of displaced Foraminifera suggests that a turbidity current was not the mechanism of deposition. It appears more likely that this material may be river sediment which was carried offshore (approximately 20 miles) during flood stages of the Mississippi River. Shallow-water Foraminifera would not be expected under these conditions.
It is suggested that the occasional specimens of shallow-water Foraminifera found in cores 3-8 and 13-14 do not indicate the presence of appreciable amounts of dis- placed sediment in these cores. These specimens may have been deposited by one or more of the following mechanisms :
(1) They may have been carried somewhat beyond the limit of turbidity flows because of slow settling velocity or low effective specific gravity. If the specimens contained protoplasm this mechanism would be aided.
(2) They may have been put in suspension by wave action when they contained protoplasm, and were carried to their present positions by currents. A few specimens of living, shallow-water benthonic Foraminifera have been reported in offshore plankton tows in the northwestern Gulf of Mexico (Phleger, 1951, p. 36).
(3) They may have been deposited by several very small-scale turbidity currents which transported small amounts of sedimentary materials.
The presence of specimens of Gumbelina in core 10 is diflicult to explain. These may have been carried out by the river and deposited at their present position, or they may possibly be contaminated by a salt plug bringing early Tertiary or Cretaceous sediments to the surface.
REFERENCES
FuGLiSTER, F. C. (1947), Average monthly sea surface temperatures of the western North Atlantic
Ocean. Papers in Phys. Oceanogr. and MeteoroL, Mass. Inst. Tech. and Woods Hole Oceanogr.
Inst., 10 (2), 5-25. Gealy, B. L. (1955), Topography of the continental slope in northwest Gulf of Mexico. Bull. Geol.
Sac. Amer., 66, 203-228. HvoRSLEV, M. J. and Stetson, H. C. (1946), Free-fall coring tube: a new type of gravity bottom
sampler. Bidl. Geol. Soc. Amer., 57, 935-950. LuDWiCK, J. C. (1950), Deep water sand layers off San Diego. Univ. of Calif, at Los Angeles, Doctor's
Thesis. Parker, F. L. (1954), Distribution of the Foraminifera in the northeastern Gulf of Mexico. Bull.
Mus. Comp. Zool., Ill (10), 453-588. Parr, A. E. (1935), Report on the hydrographic observations in the Gulf of Mexico and the adjacent
straits made during the Yale Oceanographic Expedition on the Mabel Taylor in 1932. Bull. Bingham
Oceanogr. Coll., 5, 1-88. Phleger, F. B (1951), Ecology of Foraminifera, northwest Gulf of Mexico. Part I, Forammitcra
distribution. Mem., Geol. Soc. Amer., 46, 1-88. Phleger, F. B (1954), Foraminifera and deep-sea research. Deep-Sea Research, 2, 1-23. Phleger, F. B and Parker, F. L. (1951), Ecology of Foraminifera, northwest Gulf ol Mexico.
Part II, Foraminifera species. Mem., Geol. Soc. .Amer., 46, 1-64. Phleger, F. B, Parker, F. L. and Peirson, J. F. (1953), Sediment cores from the Nort^h Atlantic
Ocean. No. 1, North Atlantic Foraminifera. Repts. Swedish Deep-Sea E.xped., 7, 3-122. Shepard, F. p. (1951), Sand and gravel in deep-water deposits. World Oil, 61-68. Stetson, H. C. (1953), The sediments of the western Gulf of Mexico. Part I. The contmental terrace
of the western Gulf of Mexico: its surface sediments, origin and development. Papers m Phys.
Oceanogr. and MeteoroL, 12 {4), 1^5. ^. • . j- r
Trask, p. D. (1953), The sediments of the western Gulf of Mexico. Part II, Chemical studies ot
sediments of the western Gulf of Mexico. Papers in Phys. Oceanog. and Metrorol., 12 (4), 49-120.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 58-67.
Seasonal changes in the phytoplankton as indicated by spectrophotometric chlorophyll estimations 1952-53
By Pamela G. Jenkins
(Introduction by W. R. G. Atkins)
Summary — Estimations of the chlorophyll content of the phytoplankton in the English Channel at station El were continued from September 1952 until August 1953 at ten depths from 0 to 70 m. As before, the species of the phytoplankton were identified by a culture method.
Minima of about 2 mg/m^ occur in winter and in June. Maxima at particular depths can occur in March, April or May, thus in 1952 the maximum was in a March surface sample, 34-2 mg/m^, whereas in 1953 sinking of the cells gave, in May, 78-8 mg/m*. The quantity found can be much influenced by the date of sampling. An autumn maximum late in September 1952 gave 21-1 mg/m^ at the surface.
The collodion filter disks varied in colour from dark grey or chocolate to a light sandy colour and examination with a low-power microscope shows phytoplankton, stray fibres and sometimes copepods and other animals. Copepods were counted in spring and summer, a maximum of 24 on one disk being found at 25 m on April 27, got from two litres of water. The figures for the column indicate about 300,000 per square metre down to 70 m.
The botanical composition of the phytoplankton was studied by the repeated examination, from first signs of growth onwards, of the chemically enriched samples placed in diffuse daylight. Fifty- four species of Bacillariphyceae were recorded. As before Skeletonema costatum, a Navicula sp. and Nitzschia closterium were the most common. Many species of Chaetoceros were identified in the autumn of 1952.
Six species of the Chlorophyceae, five of the Chrysophyceae, one of the Cyanophyceae and three of the Cryptophyceae were recorded. The most common species of the first class was a Chlorella, and of the second a species of Coccolithophora grew in each sample. Phaeocystis globosa grew from January to May. The member of the Cyanophyceae was an Oscillatoria. Neither this nor Phaeocystis was recorded for El in the previous year. Hemiselmis rufescens appeared once more.
INTRODUCTION
In this " Festschrift " number it may well be pointed out that the roots of the science of the sea are sunk deep in time. The adequate study of the sea involves all the exact sciences, including even astronomy, and all the biological sciences.
It is not, as often considered, a preserve for zoologists. The early devotees of the study of marine life were just biologists, mainly systematists, for of necessity one must follow Adam and name things. The beautifully illustrated papers of the early workers are highly educational, and remind one that it is not for us to misquote and say, " Surely we are the people and wisdom shall die with us ". I recall with sadness a morning in April 1941 when, in smoking Plymouth, I picked up one page of an old biological work — all that remained of our Athenaeum Library, which had housed so much of the older literature.
Perhaps Dr. Bigelow may be considered as having begun at about the end of the old era of amateur biologists. He was studying the phytoplankton of the Gulf of Maine in 1913. He found the entire basin occupied by a peridinian plankton, but never found diatoms in abundance in July or August except close along the coast and on Georges Bank.
58
Changes in phytoplankton as indicated by spectrophotometric chlorophyll estimations 1952-53 59
So when, largely by his efforts, the Woods Hole Oceanographic Institution was founded, they could begin with a basic knowledge of the phytoplankton which is still lacking in Plymouth. But quantitative work on the production of phytoplankton in the English Channel has been carried out since 1921, first by calculation from the changes in hydrogen ion concentration brought about by photosynthesis (1922) and since 1922 from the consumption of phosphate (1923). The arrival of a modern spectrophotometer however made it possible to estimate the phytoplankton crop by extracting the chlorophyll from collodion filter membranes on which even the smallest green flagellates had been retained. This was done in the year 1951-52, and by a culture method, similar to that of bacteriology, the organisms were grown and multiplied so that even those originally very sparsely distributed were not missed (Atkins and Jenkins, 1953).
The chlorophyll method of course gives the phytoplankton content of the water when sampled, whereas the phosphate calculations give the amount produced over a period. The two may be very different. A beginning was thus made in obtaining a better knowledge of what plants were present — and of when they flourished — also such work provides a basis for the study of the movement of water masses tagged by a known algal flora.
I therefore asked my collaborator Miss P. G. Jenkins to continue this research
and to give her results, which she has done as follows.
W. R. G. A.
ORIGIN OF SAMPLES AND THEIR EXAMINATION
Water was collected with a Nansen-Pettersson water bottle at the international hydrographic station England No. 1 (El), twenty miles S.W. from Plymouth, at a series of depths from 0 m to 70 m bottom. Two htres of each sample were filtered through a collodion (Gradocol) membrane of average pore diameter one micron.
The phytoplankton cells and the suspended matter which remained on the disks were examined under the low-power microscope. Then 10 ml of an 80 per cent aqueous acetone solution was used to extract the plant pigments from each membrane.
A " Unicam " spectrophotometer with 4 0 cm cuvettes served to measure the minimum percentage transmission in the red between 640 and 670 my.. These values were converted into concentrations of chlorophyll in mg 1 read off from a graph of the transmissions of 80% aqueous acetone solutions of a dry commercial chlorophyll plotted against their concentrations. This graph and the absorption spectrum of the chlorophyll may be seen in the 1953 paper. Using 10 ml of the aqueous acetone 10 extract the plankton from a litre of water, it is obvious that the chlorophyll has been concentrated one hundred times, so 1 mg/l as read oflFis equivalent to 001 mg, 1 or to 10 mg, m^. An allowance was of course made for the actual volume extracted.
In winter, i.e. November to February, the colour of the extracts was slightly yellow and the green was almost imperceptible. The colour deepened with the spring growth to a deep olive green, and lightened in the summer samples.
EXAMINATION OF THE PLANKTON ON THE DISKS
The disks varied in their intensity from a dark grey or chocolate to a very light sandy colour. It was impossible to deduce the amount of chlorophyll in the extracts from these shades. That deduction could only be made when the disks were a uniform faint green. They were often covered with diatoms of various species, and at times had green spots due to the presence of some species of the Chloro- phyceae. The Dinoflagellate Ceratium tripos occurred at every depth on Aug. 10. 1953. Fibres were frequently seen. Many copepods were found on the disks and as they were so numerous in the spring of 1953 their numbers were counted and set out in Table I. The totals in the second line from the
bottom'(S means) are based on the sum of the means for 2-5, 7-5, 12-5 67-5 m for 14 depths.
This sum is then multiplied by 5 (for 5 m intervals) and the totals in the bottom line are expressed as
60
Pamela G. Jenkins
the number of copepods in the column per square metre of surface, namely in 70 m^. (The amounts of chlorophyll in the water column (Fig. 5) to be considered later were conducted in the same way.) These totals were included because the phytoplankton and zooplankton crops are obviously related. In 1951-52 some medusae were found but none could be seen in the following year. Nudi- branch veligers were found from June to August, though not previously seen on the disks.
Table I — Numbers of Copepods found on collodion membrances from April until August
1953, in 2 litres of water at station E\
|
Depth |
April |
May |
June |
July |
August |
|
|
(m) |
nth |
11th |
nth |
22nd |
20th |
lOth |
|
0 |
0 |
4 |
16 |
4 |
11 |
0 |
|
5 10 15 |
4 |
6 |
14 |
5 |
4 |
0 3 2 |
|
3 |
10 |
22 |
6 |
15 |
||
|
20 |
10 |
7 |
14 |
7 |
15 |
9 |
|
25 |
7 |
24 |
3 |
12 |
18 |
8 |
|
30 |
10 |
6 |
10 |
1 |
14 |
6 |
|
40 |
6 |
9 |
5 |
— |
12 |
0 |
|
50 |
3 |
7 |
4 |
6 |
4 |
3 |
|
70 |
5 |
9 |
14 |
0 |
3 |
0 |
|
S means* |
70 |
124 |
148 |
62 |
130 |
45 |
|
thousands per m^ in column |
175 |
310 |
370 |
155 |
325 |
112 |
* See text, p. 59.
Table II — Diatoms identified in enriched cultures exposed to light Signs : — Not found A present B more frequent
C plentiful D very plentiful O not found in one of the two cruises
Where two letters occur for one month, two cruises were undertaken
Bacillariophyceae
Years
J
M
M
O N
D
COSCINODISCACEAE
Coscinodiscus sp.
C. concinnus C. excentricus C. radiatus Melosira moniliformis
Paralia sulcata
Skeletonema costatum
Thalassiosira sp.
T. condensata T. decipiens
T. gravida
T. nordenskioldii T. subtilis
Biddulphiaceae Biddulphia sp. B. regia B. sinensis Ditylum brightwellii
Eucampia zoodiacus
1952 1953 1952 1952 1952 1952 1953 1952 1953 1952 1953 1952 1953 1953 1952 1953 1952 1953 1953 1952 1953
1952 1952 1952 1952 1953 1953
B
— A
B
B
B D
CO AO
AO AO
B —
DO BO
BO — BO —
— — — — A —
— — — C — —
— — — A — — B — A B — —
OB
B
A
C B
B — C
D — BO —
— — — DO
— — AO AO
B — — —
D D
B D
A D D D B
B D
DD D C D
DD D
B
B D
D D
D D
__________A —
__________A —
— — — — — — — — B D C A
A — — — — — — — — OD— —
A ___________
Changes in phytoplankton as indicated by spectrophotometric chlorophyll estimations 1952-53 61
{Table II cont.)
|
Bacillariophyceae |
Years |
|
Chaetoceraceae |
|
|
Chaetoceros sp. |
1952 |
|
1953 |
|
|
C. affine |
1952 |
|
1953 |
|
|
C. ceratosporum |
1952 |
|
1953 |
|
|
C. compressum |
1952 |
|
C. convexicorne |
1952 |
|
1953 |
|
|
C. convoliituin |
1952 |
|
C. cur vise tuni |
1953 |
|
C. danicum |
1952 |
|
1953 |
|
|
C. debile |
1952 |
|
1953 |
|
|
C. decipiens |
1952 |
|
1953 |
|
|
C. densuin |
1952 |
|
C. did V mum |
1952 |
|
1953 |
|
|
C. gracile |
1952 |
|
C. laciniosum |
1953 |
|
C. lorenziamim |
1953 |
|
C. pseudocrinitum |
1952 |
|
1953 |
|
|
C. scolopendra |
1952 |
|
C. septentrionale |
1952 |
|
C. simplex |
1952 |
|
1953 |
|
|
C. sociale |
1952 |
|
1953 |
|
|
C. teres |
1952 |
|
Leptocylindraceae |
|
|
Lauderia borealis |
1952 |
|
1953 |
|
|
Leptocylindricus |
1952 |
|
danicus |
1953 |
|
Rhizosoleniaceae |
|
|
Rhizosolenia sp. |
1953 |
|
R. alata var. indica |
1952 |
|
1953 |
|
|
R. fragilissima |
1952 |
|
R. hebetata |
1952 |
|
1953 |
|
|
R. setigera |
1953 |
|
R. shrub solei |
1952 |
|
1953 |
|
|
R. styliformis |
1953 |
|
Fragilariaceae |
|
|
Asterionella japonica |
1952 1953 1952 |
|
Fragilaria sp. |
|
|
F. oceanica «[ |
1953 1952 |
|
F. striatula |
1953 |
|
Tabellariaceae |
|
|
Thalassionema |
1952 |
|
nitzschioides |
1953 |
F M
M J
S
O N
D
B— — — — — — D C — A C
A ABO — — OBB C DOD— —
— — — — — — — — A A A —
A __ — — __D — — — —
— — — — — — — — A — — A
— — _ — _OA— — — — — D
— — — — — — — — C D C H
A ______ — — — — —
A A A
— — AO— — OA— — — ODD — _-______ — A _ — —
______ — — — A D —
B — — — — — — — — — — —
__ — ___ — — B __ —
— — — — — — A _ — — — — _____ — — — — A — A
— — — — — — — A _ — — —
____ — — — — A A — —
____ — — — — A — — —
____ — _ — — A _ — —
A _— DO— — A _ — — — —
zE^zzz = = = = I =
___ — — — — — — — — B
C _ DO BO — — — A — — — —
____ — — C B A A— —
______ _ C DDD— —
B _ — — C— — — — — — —
___ — — -A C A A--
___ — — OBD D — — — —
ZZZZZZa — DDD— —
___--OA----D D
______ — — A A — —
_ — OA — — OD D — - — -
A —
|
B |
R |
|
|
\i |
C |
D |
|
|
|
|
— |
— |
l)D |
|||
|
B |
A |
— |
A |
— |
C |
D |
|
|
DA |
AO |
|
OD |
— |
A |
A |
— |
|
|
|
— |
B |
B |
— |
— AO
BO
D
A D C D _ D OD D
D
62
Pamela G. Jenkins
{Table II cont.)
|
Bacillariophyceae |
Years |
J |
F |
M |
A |
M |
J |
J |
A |
5 |
O |
N |
D |
|
Naviculaceae |
|||||||||||||
|
Navicula sp. |
1952 |
— |
B |
C |
D |
D |
D |
C |
B |
C |
D |
D |
B |
|
1953 |
A |
A |
AA |
AB |
C |
DC |
— |
A |
C |
DD |
|
|
|
|
N. membranacea |
1952 |
— |
— |
— |
— |
— |
— |
— |
— |
— |
A |
|
|
|
N. vanhoffeni |
1952 |
— |
— |
— |
— |
— |
— |
— |
— |
— |
B |
— |
|
|
1953 |
A |
— |
DD |
AO |
— |
OA |
c |
— |
— |
— |
D |
|
|
|
Pleurosigma sp. |
1952 1953 |
B |
A |
AO |
— |
— |
— |
— |
— |
A |
C |
D |
D |
|
Bacillariaceae |
|||||||||||||
|
Bacillaria paxillifer |
1952 |
— |
— |
— |
— |
— |
— |
— |
— |
B |
— |
— |
— |
|
Nitzschia closterium |
1952 |
D |
C |
C |
D |
A |
C |
D |
C |
B |
D |
D |
D |
|
1953 |
D |
D |
DB |
DD |
D |
|
C |
D |
D |
DD |
D |
D |
|
|
N. delicatissima |
1952 |
— |
— |
— |
— |
— |
|
— |
D |
C |
A |
D |
B |
|
1953 |
D |
— |
— |
DB |
B |
AO |
D |
D |
— |
— |
— |
— |
|
|
N. seriata |
1952 |
— |
— |
— |
— |
— |
— |
— |
B |
D |
D |
— |
A |
|
1953 |
— |
— |
— |
AO |
— |
— |
— |
— |
D |
DD |
D |
D |
SEASONAL VARIATIONS IN CHLOROPHYLL AND THEIR CONVERSION INTO WET
WEIGHT OF PHYTOPLANKTON
Water samples were taken at intermediate depths from the surface down to 50 m from August to October 1952, then down to 70 m from November 1952 to August 1953.
It was decided to extend sampling down to the lowest depth possible, 70 m to give a more accurate survey at El, so that the chlorophyll content for 70 m was known and
mq/m'
Fig. I. Variation in chlorophyll from August-December 1952, at Station El. Ordinates show depth of samphng in metres. Abscissae show concentration of chlorophyll in milligrams per cubic metre.
Changes in phytoplankton as indicated by spectrophotometric chlorophyll estimations 1952-53 63
need not be assumed to be the same as at 50 m, which was done in the 1953 paper. Fig. 1 illustrates the autumn growth from August 1952 (linking up with Atkins and Jenkins, 1953, Fig. 7) to October, with a surface outburst in September. Growth fell to a value almost uniform with depth during November and December in an almost isothermal water column.
Table III — Algae identified in enriched cultures exposed to light
Signs : — not found
A present
B more frequent
C plentiful
D very plentiful
O not found in one of the two cruises
Where two letters occur for one month, two cruises were under- taken
Chlorophyceae
Years
F M A M J
O N
D
Chlamydo-
monadaceae Chlamydomonas sp.
POLYBLEPHARIDACEAE
Pyramimonas sp.
Chlorellaceae Chlorella sp.
Ulotrichaceae Stichococciis sp.
Ulothrix subflaccida
Chaetophoraceae Ectochaete sp.
Chrysophyceae Chrysomonad sp.
Coccolithophora sp.
ISOCHRYSIDACEAE
Dicrateria sp. OCHROMONADACEAE
Ochromonas sp.
Chrysoca psaceae Phaeocystis globosa
Cyanophyceae
Oscillatoriaceae Oscillatoria sp.
Cryptophyceae Cryptomonad sp.
Cryptomonas sp.
Hemiselmis rufescens
1952 1953
1952 1953
1952 1953
1952 1953 1952 1953
1952 1953
1952 1953 1952 1953
— — B — C C BB OA
D
B
D
1953 1953 1953 i A
1953
1952 1953 1952 1953 I B
1952 ! D
1953 —
DA
C B
D D — A
A
C — B— — — — — — B
A — OC— — A _____
_DDDCBAADCD BBB— ADB— — — — — —
— C DC C B— — — — —
— OB OA — DO — — — — D — A _____ — — — — — AAOAO— — — — — — — —
— C D A C — — B A A A
— AO— — OC— — — — — —
_____B ___ — —
C---------B
D D D D D D D CD DC D DD B D D DD D D
__OC — BC — — — — — —
A — — — — — — — — — —
AOCDBD — — — — — — —
_— OA— — — — — — — —
___--B----B
_ _ BA - - -• - - 1^^ ^ A
£3ZZZZZ — — D D
_ OC - _ — B OD —
64
Pamela G. Jenkins
nt 30
Fig. 2. Variation in chlorophyll, January-April 1953 at El, in mg/m^.
The two winter months showed no appreciable change (Fig. 2), but from March onwards the samples gave a high value of chlorophyll at the surface and even at 70 m, giving a bottom maximum at 70 m of 78 -8 mg/ra^ on March 25th. These high readings for the lower depths showed that the cells must have sunk. Riley (1941 b) observed this high concentration of chlorophyll from 40-70 m at Georges Bank during March and April. Marshall and Orr long ago (1928) reported that " during the spring
m 30
"O " lO "^ ^O 30 3 40 SO 60 7C
mq/m
Fig. 3. Variation in chlorophyll, May to August 1953 at El, in mg/m^.
Changes in phytoplankton as indicated by spectrophotometric chlorophyll estimations 1952-53 65
months it was not uncommon in shallow water to find more plankton near the bottom than anywhere else ". They also found that during the spring outburst the phyto- plankton caused such a great reduction in submarine illumination that the compensa- tion point (or depth) was at times raised to 5 m or less.
The sudden drop from spring growth, May 1 1th to the summer minimum, June 8th, is seen in Fig. 3. The May readings were very high due to the abundance o^ Phaeocystis globosa. Two filtrations were necessary because the disks became clogged, so ordinary filter paper was first used and then the special membrane. Each of these was extracted twice. The later cruises show the gradual growth near the thermoclinc, building up to the autumn maximum, with a peculiar outburst at 25 mon August 10th of 31 -5 mg m\ This outburst must have occurred in a region where light intensity allows photosyn- thesis to take place and its occurrence at only this depth is probably due to the absence of sufficient nutrient salts in the upper 15 m.
The results for surface and bottom chlorophyll throughout the year are seen in Fig. 4 with a surface maximum in September and April and a bottom maximum in
SEPT
1952
APL I MAY 1953
rnmg^.rf ' The\?a «mp™tuT«\ surface, above, and for .he bo..on, ,70 n„ ,us, below ,hc
° ■ top line or the trame.
D
66
Pamela G. Jenkins
March, due to sinking. The thermoclines for the year were found on September 22nd, 1952, 15 m, 14-6° C; April 27th, 1953, 15 m, 12-5" C; June 22nd, 20 m, 13-0° C; August 10th, 15 m, 17-2° C.
In both 1951 and 1952 the autumn maximum (Fig. 5) was in September, the amounts being respectively 0-59 and 1 -02 g/m^ The spring minimum was in Novem- ber 1951, but was three months later the following winter when it was reached in February 1953. But the values were identical, 0-25 g/m^. The spring maximum in April 1952 was 1-33 g/m^ but this value was obtained on the assumption that the amount of chlorophyll was uniform beyond the last depth examined, 50 m to 70 m, bottom. Later work showed that, on account of sinking of the cells, this was probably an underestimate. The maximum was in May in 1953, 3-68 g/m^ (very much higher) with much Phaeocystis present. Both the summer minima fell in June, 0-15 g/m^ for 1952 and 0-35 g/m^ for 1953.
40
3 O
2 O
g/r
lO
|
- |
A |
- |
|||||||||
|
- |
A |
\\ |
- |
||||||||
|
- |
f |
- |
|||||||||
|
- |
19 |
i2-5: |
1 |
— |
|||||||
|
( |
^ |
\ 951-5 |
2 |
- |
|||||||
|
\ \ |
/ |
\ |
1 |
>A, |
— |
||||||
|
- o |
\ |
/ i |
\ |
. |
/ > |
V - |
|||||
|
^ |
*J |
^;r=t9=- |
»<y&^ |
£j |
^\ |
V |
-'0-- |
b _ --0 |
|||
|
SEPT |
OCT |
NOV |
DEC |
JAN |
FEB |
MAPx |
APL |
MAY |
JUNE |
JULY |
AUG |
oo
Fig. 5. Variation of chlorophyll in water column, 0-70 m, in grams per square metre for 1951-52
(broken line) and 1952-53 (full line). See text, p. 66.
These chlorophyll quantities may be converted into wet weights of phytoplankton as in the paper of 1953. Taking Riley's value 2-9 % of chlorophyll (1941 a), calculated on the dry weight, and taking the dry weight as 20 % of the wet weight, we arrive at a factor 1 72 by which one can multiply the weight of chlorophyll to convert it to wet weights of phytoplankton. It is recognized that these factors are somewhat arbitrary.
THE BOTANICAL COMPOSITION OF THE PHYTOPLANKTON AT STATION El
Samples of water, 100 ml, from each depth were poured into conical flasks and enriched with Miquel's solution, 0-2 cc of solution A and OT cc of solution B.
They were placed in a south window during winter and from spring to autumn were illuminated by a diffuse north light. The enrichment of the culture solution gave a better chance for species originally very sparsely represented to multiply and be detected. This amounts, in fact, to the common bacteriological technique.
Tables II and III are an attempt to indicate the relative amounts found in the earlier
Changes in phytoplankton as indicated by spectrophotometric chlorophyll estimations 1952-53 67
Stages of the cultures, the comparison being between the same species, so different growth rates are not involved.
Table II shows the Bacillariphyceae, identified as named and classified in Hendey's list (1954). Fifty-four species were found, as compared with twenty species found in 1951-52, but the autumn growths cannot be compared with 1951-52 since the samples were not enriched and exposed until February 1952.
Skeletonema costatum, Navicu/a sp., and Nitzschia closterium were again the most regular in occurrence. Species absent from our lists before 1953 were Thalassiosira condensata found in February, Eucampia zoodiacus in January, Rhizosolenia setigera in June, November and December, R. styliformis in July, also Fragilaria striatula in April.
The Algae listed in Table III are as named and classified in Parke's list (1953). The most regular occurrence of the Chlorophyceae were the Chlorella sp. and Chlamydomonas sp. The three others listed grew well in the spring, Ulothrix sub- flaccida which was found once in February, 1952, was present from February to early April in 1953.
Of the Chrysophyceae, the CoccoUthophora sp. were always in the cultures. Phaeo- cystis globosa, which was absent from the 1952 cultures, grew in 1953, increasing to a great mass in May. This caused the blocking of the sea water filtration.
One member of the Cyanophyceae was present in January and late April in 1953, an Oscillatoria sp. The growth of such sessile forms as this and the Ectochaete sp., Ulothrix subflaccida, and Stichococcus sp., though not truly planktonic showed that some must have been present in the water at the time of sampling.
Hemiselmis mfescens, a species of the Cryptophyceae, which grew in January 1952, was very plentiful in November and December 1952, also in April and the early autumn of 1953.
I would like to express my thanks to Dr. M. V. Lebour, Dr. M. Parke, Dr. T. J. Hart and Mr. T. R. Tozer for much help in the identifications, also Mr. F. A. J. Armstrong for the temperature observations. Finally for the collection of the sea water I have pleasure in thanking the captains and the crews of the R.V. Sula and the R.V. Sarsia.
REFERENCES
Atkins, W. R. G. (1922), The hydrogen ion concentration of sea water in its biological relations.
/. Mar. Biol. Assoc, 12, 717-771. Atkins, W. R. G. (1923), The phosphate content of fresh and salt waters in its relationship to the
growth of the algal plankton. /. Mar. Biol. Assoc, 13, 1 19-150. Atkins, W. R. G. and Jenkins, Pamela G. (1953), Seasonal changes in the phytoplankton during the
year 1951-52 as indicated by spectrophotometric chlorophyll determinations. J. Mar. Biol. .-Usoc,
31, 495-508. ^ . _, ^^
BiGELOW, Henry B. (1915), Exploration of the Coast Water between Nova Scotia and Chesapeake
Bay, July and August, 1913, by the U.S. Fisheries schooner Grampus. Oceanography and Plankton.
Bull. Mus. Comp. Zool., 59 (A), \5\-Z59. r u ^ >r r x-, o // ,. e o
BiGELOw, Henry B. (1926), Plankton of the Offshore Waters of the Gulf of Maine. Bull. L.6. Bur.
Fish., 40 (2), Document No. 968, 1-509. ^. , ,^ „. , ^
Hendey, N. Ingram (1954), A preliminary check-list of British marine diatoms. J. Mar. Biol. Assoc,
33,537-559. ^ ^. , . , , .,
Marshall, S. M. and Orr, A. P. (1928), The photosynthesis of diatom cultures in the sea. J. Mar
Biol. Assoc... \5,7>2\-60. . d- ; « it
Parke, Mary W. (1953), A preliminary check list of British marine algae. J. Mar. Bu>t. .Assoc. JZ,
497-520 Riley, G. A. (1941 a). Plankton studies 3. Long Island Sound. Bull. Bingham Oceanogr. Coll., 7 (3),
1-93 Riley, G. A. (1941 b), Plankton studies 4. Georges Bank. Bull. Bingham Oceanogr. Coll., 7 (4), 1-73.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 68-73.
Water replacements and their significance to a fishery
By H. B. Hachey Chief Oceanographer, Canadian Joint Committee on Oceanography
Summary — Attention has been directed to some of the major and more apparent effects that water replacements may have on various fisheries. It has been indicated that such interchanges may be responsible for the destruction of a fish population or the extension of others. The loss of larvae to scallop and haddock areas has been considered as the result of movements of a water mass, and it is suggested that the availability and catchability of certain species is effected by certain water replace- ment phenomena. When consideration is given to the cycle of life in the sea, it will be quite evident that many indirect effects may follow from these water replacements. While the processes of long- term replacements are not too well understood, wind action is one of the more apparent major casual factors in short-term replacements.
INTRODUCTION While the changing characteristics of a water mass, such as temperature and salinity, are followed in detail in the study of a fishery, the replacement of one body of water by another is a process which, generally, only attracts attention when the characteristics of the water bodies concerned are in considerable contrast.
Whether it be of the estuary, a coastal area, or the open ocean, the particles of a water mass are never at rest, being subjected to the internal and external forces of gravity, pressure, wind, tide and the Coriolis force. The resultant movements of the water particles under these forces bring about the flushing of estuaries, the replacement of water masses in a bay or coastal area, the removal of water masses from a fishing bank, and the transportation of large masses of ocean water from one location to another.
The flushing of estuaries has been given considerable attention during recent years, due to the need of considering the many problems of pollution. The principles derived from such studies furnish an insight into the mechanism involved in the replacement of waters in a comparatively small area, almost completely land-bound. In contrast, and on an ocean-wide scale. Cooper (1954, 127), has called attention to the large variations in the phosphate content and biological productivity of the English Channel in the last thirty years. He seeks an explanation in the replacement processes involving the replenishing of deep Atlantic water by potentially rich northern waters, these deep Atlantic waters eventually upwelling to determine the nutrient supply of the coastal waters of north-eastern Europe.
Attention is directed herein to many of the direct consequences to a fishery of the various processes of replacement.
THE DESTRUCTION OF A FISHERY BiGELOw and Welsh (1925) describe the disaster to the tilefish, which first came to light in March, 1882, when multitudes of dead fish were observed floating on the surface between the latitudes of Nantucket and Delaware Bay on the Atlantic coast. The area of destruction was at least 170 miles long by 25 miles broad, and covered the entire zone inhabited by the tilefish north of Delaware Bay. It is estimated that
68
Water replacements and their significance to a fishery 69
at least a billion and a half dead tilefish were sighted. There is evidence to indicate that the destruction of this fishery was caused by a sudden temporary flooding of the bottom by abnormally cold water. It has been shown that the tilefish of the Atlantic coast occupies a very definite environment, for it lives only along the upper part of the continental slope where the water temperatures are approximately 10" C, and never ventures into the lower temperatures on the shoaling bottom nearer land. We have in BiGELOW and Welsh's account of the disaster to the tilefish, a well-documented record of the significance of a temporary incursion of waters of contrasting tempera- ture, which in this case brought disaster to a fishery.
On the basis of present knowledge, the source of the abnormally cold water responsible for such a flooding is to be found to the eastward. A study of the slope water off the Scotian Shelf (McLellan, et al, 1953), has shown that, between the northern boundary of the slope water and the continental slope, there is found in varying quantities a body of cold water, less than 0-0° C off" the Grand Banks, and less than 4-0'' C east of Sable Island. The quantity of such water, acting as a cushion between the slope water and the continental slope, decreases with westward progression until the slope water generally makes contact with the continental slope to the west- ward of Emerald Bank. Northerly and southerly migrations of the northern edge of the slope water regime, and westerly progressions and easterly withdrawals of the colder waters along the continental slope, provide the mechanism for producing sharp and sudden changes in the water temperatures on the continental slope and over the outer areas of the continental shelf. While the disaster to the tilefish was of major import, and the westerly progression of cold water must have been greater than normal, similar phenomena on a less spectacular scale have been noted in recent years.
THE EXPANSION OF A FISHERY
In contrast, both as to time and extent, to the temporary incursion of colder waters, bringing about the destruction of a fishery over a limited area, is the historical record of the expansion of the Greenland fishery in recent years with the strengthening of the Atlantic influence in northern latitudes.
Passing over earlier history, about 1820, cod were known to be present in enormous quantities in West Greenland waters, as far north as Disko Bay (Jensen and Hansen, 1931). Thereafter, they were absent for a long period of years. Between 1845 and 1849, cod were again plentiful in the Greenland area and then entirely disappeared. From 1917 there was a marked upward tendency in the fishery. The catch increased from approximately 1,000 tons in 1925 to greater than 12,000 tons by 1945, and this fishery has persisted to the present. In dealing with the state of the West Greenland Current up to 1944, Dunbar (1946) points out that, by 1928, the waters for the west coast of Greenland were considerably warmer than in the preceding period, and that the peak warm year was reached within the period 1930-40. The increasing Atlantic influence however was clearly evident in Latitude 72 N in 1942. A comparison of oceano- graphic conditions in Hudson Bay and Hudson Strait, as observed in 1930, with those of 1948 (Bailey and Hachey, 1951) has shown that the observed higher temperatures and salinities of 1948 are indicative of the increasing Atlantic influence in northern waters generally. A meteorological study of Sherbog (Dunbar, 1946), has suggested that the warming of the Arctic and sub-Arctic regions from Greenland to Siberia, which has taken place in recent years, is one manifestation of a large scale climatic
70 H. B. Hachey
cycle of a period of about 225 years, which has presumably passed its maximum. It must be stressed here that the expansion of the Greenland cod fishery is associated with the extension of warmer Atlantic waters into more northerly latitudes, although such an extension is probably associated with the climatic cycle.
THE LOSS OF LARVAE
Studies on the replacement of Bay of Fundy waters were initiated some years ago (Hachey, 1934), and it became evident that the main factors involved in the replace- ment of these waters were land drainage, wind, and tide. Other things being equal, an excess of south-westerly winds favoured the retention of surface waters within the Bay and thus nullified the normal dynamic tendency for surface outflow and renewal of the waters at greater depths. Under such conditions a type of " closed circulation " is set up within the Bay, as opposed to an " open circulation " when surface waters are carried out of the Bay to be replaced by inflowing deeper waters. During the summer months the " closed circulation " favours higher surface water temperatures, and the surface temperatures, as well as the temperature gradient in the upper layer, can be used as an indication of the type of circulation prevailing. Dickie (1955) has made use of the temperature data for the Bay of Fundy to show that successful year classes of scallop are produced in those years when the " closed circulation " prevails. Not only do the warmer surface waters hasten development of the scallop larvae to the setting stage, but the " closed circulation " favours the retention of the larvae within the Bay where they settle and grow on suitable scallop bottom. Under the " open circulation " system, as indicated by lowered surface temperatures, the larvae are carried out of the Bay and are lost to the Bay of Fundy scallop fishery.
The replacement of Bay of Fundy waters is not necessarily a regular progressive process, even when the " open circulation " system prevails. Ketchum and Keen (1953) have worked out various mean flushing times and exchange ratios for various parts of the Bay of Fundy, and they point out that although their conclusions were based upon the distribution of river water, the same exchanges may be expected for any material or organism transported by the water. Ketchum and Keen calculated an average flushing time of 74 days for that part of the Bay of Fundy between Cape Chignecto and a line south of Grand Manan. Bailey (1953) has shown that within the period October 6th, 1952, and November 2lst, 1952, the waters of the Bay of Fundy were almost completely replaced, a replacement that only became apparent when it was found that the salinity throughout a section had increased by more than 0'5%o within the period. It might be emphasized that within this period of forty- six days (or less), practically all free-moving larvae in the surface layers would have been carried out of the Bay of Fundy. So too would all free-swimming forms which were feeding at random. The higher salinities as found on November 21st indicate that the replacement involved the inward movement of waters originating from sub-surface depths, and these waters would necessarily carry into the Bay non-swimming forms, and free swimming forms which were feeding at random.
According to Walford (1938) the survival of the eggs and larvae of the haddock on Georges Bank is dependent on the variations in the current system in this area, these variations being controlled to a large extent by winds (Bigelow, 1927, 857). He suggests that the loss of the eggs and larval population in 1932, which occurred some time after the first week of March, was due to the removal by currents. Similarly
Water replacements and their significance to a fishery 71
BiGELOW (1926, 77) wrote: " at the time of our March and April visits (to the north- eastern part of Georges Bank) in 1920, the presence of newly spawned eggs in abund- ance right out to the 1,000 metre contour proved that a drift out to sea was then taking place from the southern point of the Bank." Walford (1938, 49) states: " there was a very important difference between the circulatory picture in the season of 1932 and that of the corresponding period in 1931. While in 1931 the water movements were such as to permit the bulk of the eggs to remain on the bank and hatch there, in 1932 there were currents carrying eggs off the northern and southern edges into deep water where they were probably lost to Georges Bank." In summary, Walford (1938, 55) points out that a change in the circulatory system on Georges Bank may be disastrous to the haddock brood, and consequently, may be an important cause of fluctuations in abundance.
Carruthers, et a/. (1951) have directed attention to the variations in brood strength in the North Sea haddock in the light of relevant wind conditions, and the results of these studies have directed considerable effort to the analysis of wind systems as related to other North Sea Fisheries.
AVAILABILITY OF THE FISH
The displacement of surface waters on a grand scale by wind is amply demonstrated by the great ocean currents of the North Atlantic, and the fundamental principles have been thoroughly outlined in the classical work of Ekman (Sverdrup, et al., 1942, 492). Ekman has shown on a theoretical basis that a surface current set up by wind is directed 45° to the right of the wind direction in the northern hemisphere, and this has been shown by observation to be a satisfactory approximation in deep water. In shallow water the deflection of the surface wind current is smaller. A wind blowing parallel to a coast is thus effective in transporting surface waters towards the coast, when the coast is to the right of the wind (cum sole from the wind direction) in the northern hemisphere, and away from the coast when the coast is to the left of the wind.
The capture of young herring along the open coasts of the Bay of Fundy and the Gulf of Maine is chiefly dependent upon fixed shore weirs. Huntsman (1934) states: " that the herring are to a considerable extent quite near the surface during the twenty-four hours of the day is not only a matter of direct observation, but a requisite for successful operation of the weirs." Huntsman also states (1934, 96) that '* the herring may be treated as a planktonic form ". It then becomes evident that herring in the surface waters, and considered as a planktonic form, will be moved on or ofl the shore with the varying direction of the wind. This is particularly pertinent on an open coast, such as that of Maine, and the south coast of New Brunswick, where the availability of the herring to the shore-fixed weirs must be determined in part by the varying strength of the prevailing south-west winds during the summer months.
TEMPORARY ADJUSTMENTS IN A FISHERY Large scale water replacements of a temporary nature sometimes bring about sharp and sudden changes in water temperature, the changes in environment being sufficient to cause a body offish to either:
(a) move away from a fishing ground, or
(b) cease feeding and thus fail to be attracted to the bait.
72 H. B. Hachey
The water replacements in the Halifax area associated with the formation and subsequent movement of a tropical cyclone have been described (Hachey, 1934), and it has been shown that bottom water temperatures in some of the inshore areas increased from 2-0" C to greater than 15-0° C in less than one week. Under these circumstances, in these areas, all fishing for cod and haddock ceases, and does not resume until temperatures return to more normal values (Hachey, 1934; McKenzie, 1934; Vladykov, 1933).
Incursions of warmer slope water over the Scotian Shelf have been observed (Hachey, 1953), when bottom temperatures reached values as high as 12-0° C, about five degrees above normal seasonal temperatures. While no records of fishing effort are available for periods in which such incursions have been observed, it is well known that such bottom water temperatures are unfavourable to cod and haddock, the groundfish probably moving out of the areas subjected to the incursions of waters of such temperatures.
BARREN SEA FLOOR In the Gulf of St. Lawrence comparatively extreme variations in temperature and salinity have been observed at depth during the summer months (Lauzier, 1952) brought about by oscillations of the various water layers of contrasting characteristics on a gradually shoaling sea floor. It has been pointed out by Lauzier that organisms which cannot tolerate these sudden changes in temperature and salinity will not form important populations along the margins of the Magdalen Shallows, and Hunttsman (1918) has shown that there are bands of the sea floor between Cape Breton and the Magdalen Shallows which are comparatively barren. The oscillation of these water layers of contrasting temperatures is probably responsible for the periodic complete destruction of scallop beds which become temporarily established and fishable under marginally satisfactory conditions in the Magdalen Shallows (Annual Report for 1953, Fisheries Research Board of Canada, 34).
MARGINAL FISHERIES
In Canadian Atlantic waters, which are contained in the area of confluence of three current systems with waters of contrasting characteristics, extreme contrasts in water characteristics, chiefly temperature, are to be observed. Very sharp boundaries, both vertically and horizontally, are thus encountered, and various marine organisms suitable to one environment (frigid) or another (temperate) exist on a marginal basis. A small vertical or horizontal change in the margin sometimes exerts a very pronounced effect on a fishery.
With progressive warming of the waters during recent years we have witnessed the northerly expansion of successful oyster production in the Gulf of St. Lawrence, and the northerly extension of the green crab to the Bay of Fundy (Annual Report for 1953, Fisheries Research Board of Canada, 25). As mentioned earlier in this paper, the expansion of the west Greenland cod fishery is probably the most outstand- ing result of the increased Atlantic influence in northern waters. It is to be expected that a downward trend of temperatures would bring about a recession of these extensions.
In some cases, man is responsible for changes in environmental conditions, and this is particularly true in estuaries where pollution problems arise with present-day
Water replacements and their significance to a fishery 73
industrial developments. Of a different nature are the possible changes in ihc environment of Georges Bay, between Cape Breton and the Nova Scotia mainland, which may follow from the completion of the Canso Causeway. By cutting off the interchange between Gulf waters and those of the open Atlantic through Canso Strait, the strong possibility exists that the waters of Georges Bay will be warmer than heretofore. Slight upward changes in the water temperatures in this area may be sufficient to exert some influence on the lobster populations, and to bring about a southward extension of the oyster populations of neighbouring areas.
REFERENCES
Bailey, W. B. and Hachey, H. B (1951), An increasing Atlantic influence in Hudson Bay. Proc.
Nova Scot. Inst. Set., 12 (4), 17-34. Bailey, W. B. (1953), Seasonal variations in the Bay of Fundy. Fish. Res. Bd., Canada, Manuscript
Kept., No. 551. BiGELOW, H. B. (1926), Plankton of the offshore waters of the Gulf of Maine. Bull. U.S. Bur. Fish..
40 (2), 1-509. BiGELOW, H. B. (1927), Physical oceanography of the Gulf of Maine. Bull. U.S. Bur. Fish., 40 (2),
511-1027. BiGELOW, H. B. and Welsh, W. W. (1925), Fishes of the Gulf of Maine. Bull. U.S. Bur. Fish.. 40 ( 1 ),
1-566. Canada, Fisheries Research Board (1953), Annual Report, Ottawa, 185 pp. Carruthers, J. N., Lawford, A. L., Veley, V. F. C. and Parrish, B. B. ( 1951), Variations in brood- strength in the North Sea haddock in the light of relevant wind conditions. Nature, 168, 317-319. Cooper, L. H. N. (1954), Deep sea oceanography and biological productivity of shallow seas. Repts.
and Abstr. of Communications, Assoc. Ocean. Phvs., Union Geod. Geophys. Int., General Assembly,
Rome, Sept. 1954, 148 pp. Dickie, L. M. (1955), Fluctuations in abundance of the giant scallop, Placopecten magellanicus
(Gmelin) in the Digby area of the Bay of Fundy. J. Fish. Res. Bd., Canada (in press). Dunbar, M. J. (1946), The state of the West Greenland Current up to 1944. J. Fish. Res. Bd., Canada,
6(7), 460-471. Hachey, H. B. (1934), The replacement of Bay of Fundy waters. J. Biol. Bd., Canada, 1 (2), 121-131. Hachey, H. B. (1934), The weather man and coastal fisheries. Trans. Amer. Fish. Soc, 64, 382-389. Hachey, H. B. (1935), The effect of a storm on an inshore area of markedly stratified waters. J. Biol.
Bd., Canada, 1 (4). Hachey, H. B. (1953), A winter incursion of slope water on the Scotian Shelf J. Fish. Res. Bd.,
Canada, 10 (3), 148-153. Huntsman, A. G. (1918), The vertical distribution of certain intertidal animals. Trans. Roy. Soc,
Canada, Ser. Ill, 12 (4), 53-60. Huntsman, A. G. (1934), Herring and water movements. James Johnstone Memorial Volume, 81-
96, Univ. Press of Liverpool, 348 pp. Jensen, A. S. and Hansen, P. M. (1931), Investigations on the Greenland Cod (Gadus callarias L.)
with an introduction on the history of the Greenland cod fisheries. Cons. Perm. Int. Expl. Mer.
Rapp. Proc. Verb., 52, 3-41. Ketchum, B. K. and Keen, D. J. (1953), The exchange of fresh and salt waters m the Bay of Fundy
and in Passamaquoddy Bay. J. Fish. Res. Bd., Canada, 10 (3), 97-124. Lauzier, L. (1952), Effect of storms on the water conditions m the Magdalen Shallows. J. Fish. Res.
Bd., Canada, 8 (5), 332-339. , ^ .
McKenzie, R. a. (1934), Cod and water temperatures. Fish. Res. Bd., Canada, Atlantic Stas.,
Prog. Repts., No. 12, 3-6. , , ,-r ■ ^ ■ ou .r
McLellan, H. J., Lauzier, L., and Bailey, W. B. (1953), The slope water off the Scotian Shelf
J. Fish. Res. Bd., Canada, 10 (4), 155-176. ^ ^, ^ „ ,,„,
SvERDRUP, H. U., Johnson, M. W. and Fleming, R. H. (1942). The Oceans, Preniicc-Hall Inc.,
New York, 1087 pp. ^,. ^,„ „.^ y., •
Vladykov, V. D. (1933), High temperature stops haddock fishmg. Fi.sh. Res. Bd., Canada, Atlantic
Stas., Prog. Repts., No. 7, \0-\l. , . ^ • , ru ^i c
Walford, L. a. (1938), The effect of currents on distribuUon and survival of the eggs and larvae of the haddock (Melanogrammiis aeglifinis) on Georges Bank. Bull. U.S. Bur. Fish., 49, 1-73.
Papyers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 74-91.
Sir C. Wyville Thomson's correspondence on the "Challenger"
fishes
By Daniel and Mary Merriman Bingham Oceanographic Laboratory, Yale University
HISTORICAL ACCOUNT
Wyville Thomson's correspondence with Albert Gunther, Keeper of the Depart- ment of Zoology in the British Museum, about the disposition and study of the fishes taken on the H.M.S. Challenger expedition, 1872-1876, and about the publication of results, extended from 1877-1881. In a sense this correspondence centred around the year 1879 — the year in which Henry Bryant Bigelow was born on October 3rd in Boston, Massachusetts.*
Now-a-days it is common practice to call oceanography a " new " science. The speed with which it has advanced and, accordingly, with which our knowledge of the oceans has increased, is generally recognized. None the less, it is not altogether easy to maintain perspective and to reahze that "... the famous ' Challenger ' reports, which may be said to form the solid base upon which the superstructure of the science of oceanography has since been built " (Russell and Yonge, 1928), began first to be published only three-quarters of a century ago — in short, during the life-time of the man whom this volume honours. For this reason, it is perhaps worth looking with some care at the year 1879, both in its broad and special aspects, before turning to the hitherto unpublished correspondence which is the subject of this paper.
The second half of the 19th century in Europe was marked by many political and economic changes stemming from the Industrial Revolution. As a result of the Franco- Prussian war (1870-1871) there emerged a united Germany and a unification, too, of the Italian States. Russia had effectively pushed the Turks back into Asia, but the western powers resisted her attempts to obtain Constantinople and a command of the eastern Mediterranean. With the Congress of Berlin in 1878 the independence of the Balkan countries, Montenegro, Servia, and Roumania, was established. And the alliance of Germany and Austria-Hungary in 1879 proved most aggravating to Italy, who feared it would block her potential control of the Adriatic ; to France, who saw it as a blow to her ambition to regain Alsace-Lorraine; and to Russia, who still wanted a foothold in the Balkans and the Mediterranean. China posed problems in the Far East, as the western powers and Russia both tried to gain concessions to her great natural resources.
In the United States, 1879 was a singularly happy and prosperous year. Crops flourished, manufacturing and trade were stimulated, and the railroads were expanding to meet these demands. We were at peace with the world, except for Indian skirmishes in the west where Sitting Bull had been forced to retreat across the Canadian border.
* The October 3rd, 1879, edition of the London Times carried an admonition that there were 12 different Bostons in the U.S.A., and that the name of the state on the envelope address would facilitate accurate delivery.
74
Sir C. Wyville Thomson's correspondence on the "Challenger" fishes 75
England, it is said, was not so happily situated that year. There were wide crop failures and a continuing depression. Ireland, with the loss of her potatoes due to adverse weather, was agitating for Home Rule and land rent reforms; the situation was so acute that the American Irish were sending 510,000 a week towards relief in the homeland. England was fighting in Afghanistan to protect her affairs in India. She was also engaged in military operations in South Africa to keep this portion of her Empire. And she was even sending warships to the west coast of South America, where Chile and Peru were fighting, in order to guard her "... interests in guano for the fields of Yorkshire ". However, England's firm policy of colonization was to stand her in good stead. In addition to India and South Africa, she had acquired control of the Suez Canal, and had long since colonized Australia, New Zealand, Tasmania, and Canada — this, as other countries, notably Spain, had tended to lose their colonial domains. In a different context, Charles Darwin at the age of 70 in 1879,* just twenty years after the publication of The Origin, was doing the experi- mental work at Down which led to the publication in 1881 of The Formation of Vegetable Mould through the Action of Worms, to be received "... with what struck Darw^in as 'laughable enthusiasm'" (Moore, 1955). And the " episco- phagous " Huxley had turned to more peaceful pursuits and was preparing to publish The Crayfish (1880). It was not, after all, such a bad year for England.
Perusal of the London Times in the year 1879 yields amusing coincidence with today. The New York Herald was sponsoring a naval vessel's exploration of the North Pole.f The Macon (Georgia) Telegraph reported, and got space in the London Times on January 1, 1879, that there was a remarkable phenomenon on the Florida coast where "... dark, reddish water " was killing fish and creating "... a pestilential stench "; the account went on to state, " We have no other explanation of the poisoning " (reported to have extended as far as 150 miles into the Gulf) " than that it comes from inland waters — the everglades predominantly. ..." Panama had a revolutionary outbreak. The stevedores on the piers of New York were striking. A large underground cave in Algeria was found to contain blind fish.ij: Even the book titles have a familiar ring : we read reviews of " The Sea, its Stirring Story of Adventure, Peril, and Heroism " by F. Whymper. " The Broad, Broad, Ocean ", " Notable Voyages ", and " Episodes of the Sea " are a few others of the spate. And another Mr. Whymper** was bringing out " The Ascent of Matterhorn ".
We are also struck by many changes. In 1879 Woolworth opened his first store in Utica, New York (in 1955 the Woolworth Company reported its sales for the previous year at an all time high of $721,312,990). In 1879 Harvard College offered 112 scholarships varying from $40 to $350— today it offers over 1,000 scholarships at an average worth of nearly $700 each. In 1879 the Shah of Persia was planning to undertake a pilgrimage to Meshhed with 10,000 troops, while this year the Shah's
* " It was on . . . February 12, 1809 that the other man who along with Charles Darwin was most profoundly to influence their time, and perhaps the future, was born— Abraham Lincoln "' (Moore, 1955).
t See for comparison, Walter Sullivan's articles about the Atka expedition to Antarctica in preparation for International Geophysical Year, 1957, in the New York Times. January-March. 1955.
± Some 37 years after the discovery of the famous Kentucky Blind-fish. Amhyhpsis xpclaeus, whose origin the National Geographic Society states in 1955 " . . . is a mystery to naturalists ".
** Edward Whymper, 1840-191 1, English Alpinist and wood engraver, who found a route up the Matterhorn in 1865.
76 Daniel and Mary Merriman
travels have carried him to Sun Valley and Florida. In 1955 the production of syn- thetic diamonds has been achieved, finally bearing out the statement in 1879 by Nevil Story Maskelyne of the Mineral Department of the British Museum, "... that (this problem) will be solved, no scientific mind can doubt ". In Boston on December 3, 1879, the Atlantic Monthly gave a party for the seventieth birthday of the " Autocrat of the Breakfast Table " ; today it would be hard to rival the distinction of the gathering which included beside O. W. Holmes these others : H. B. Stowe, J. G. Whittier, H. W. Longfellow, R. W. Emerson, Mark Twain, W. D. How^lls, and J. W. Howe. The February 11th issue of the 1879 London Times carried the statement that, " Arrangements are being settled with the Societe Generale d'Elec- tricite for an experimental lighting of the reading-room of the Museum with the electric light ". And the April 10th issue reported that communication by telephone was established between the Royal Institution and Burlington House, "... with Professor Tyndall at one extremity of the wire and Professor Huxley at the other "; there was apparently much amusement among those present, and, " The feasibility of telephonic communication was clearly demonstrated, the voice being distinctly audible over the whole of a large room ".
The London Times for 1 879 also contains numerous articles on science and natural history and makes reference to many familiar names. Thus Frank Buckland* and Spencer Walpole published a report on the Sea Fisheries of England and Wales about which it was written:!
On these very surfaces and in these very depths there rages, has ever raged, and ever will to the end of time, a warfare compared with which historical battles sink to the dimensions of street rows or family jars. It is an incessant and universal war carried on between greater numbers than can be told, more species than can be well distinguished one from another, and every order of existence, from the scarcely visible and scarcely animated fibre or molecule up to the lords of creation. . . . Fish engaged in a universal internecine war devour many times more than we can do.
Francis Day:]: read a paper to the Linnean Society on the instincts and emotions of fish. Edwin Ray Lankester, founder of the Marine Biological Association five years later, was Public Examiner in Natural Science at Oxford. Edward Cope was appointed head of the department of organic material of the Permanent International Exhibition of Philadelphia. Alexander Agassiz was chief of the scientific staff on the cruise of the George S. Blake through the West Indies. William B. Carpenter resigned as Registrar of London University; this was the man who had helped to induce the Admiralty, through the Council of the Royal Society, to place at his and Wyville Thomson's disposal first H.M.S. Lightning (1868) and then H.M.S. Porcupine (1869 and 1870) for deep-sea exploration (Thomson, 1873), and who was a prime mover with the Government for the Challenger expedition "... to explore and make known the conditions of life in the great oceans " (Herdman, 1923). Huxley received an honorary LL.D. from Cambridge in company with Robert Browning. And at younger levels, William Herdman received his B.Sc. and the
* Author of The Natural History of British Fishes, London, 1880.
t London Times, December 6, 1879, p. 9.
X Author of The Fishes of Great Britain and Ireland, two volumes, London, 1880-1884, and of British and Irish Salmonidae, London, 1887.
Sir C. Wyville Thomson's correspondence on the "Challenger" fishes 77
Senior Bursary in anatomy and physiology from Edinburgh, while the Junior Macken- zie Bursary went to one D'Arcy Wentworth Thompson for "... the greatest industry and skill in the particular anatomy work during the winter session ". Francis Maitland Balfour, 1851-1882, had just published his monograph on the Develop- ment of Elasmobranch Fishes* German carp were introduced in southern United States waters, and the previous year the U.S. Fishery Commissioners had "... made a present of a million ova of the California salmon ... to the Government of New Zealand ", about 95% of which were reported to have produced " healthy fish ".f Over 100,000 individuals were employed directly or indirectly in the Scottish fisheries, and the Herring Board stated that:
With the exception of the occasional and uncontrollable influences of the weather which cause temporary fluctuations in the catch, the sea fisheries of Scotland and the herring fisheries in particular, are beyond the reach of any power to impair their abundance.
The British Association Meetings for 1879 opened in Sheffield on August 20th, and Professor G. J. Allman chose for the subject of his presidential address, " An Account of the Most Generalized Expression of Living Matter ". He made particular reference to the grey gelatinous material which appeared in preserved samples of the deep-sea dredgings made from the Porcupine at depths of 5,000-25,000 feet, and of the fact that it had appeared to be " . , . obviously endowed with life '". He recounted how it had been examined by Huxley, who declared it to consist of protoplasm and envisaged this living slime as extending over wide areas of the sea bottom as a sort of pabulum on which the animals living at these depths fed in the absence of plant life. Huxley had named the material Bathybius haeckelii, and Haeckel had fully supported Huxley's conclusions. Allman went on to state that the reality of Bathybius had not been universally accepted and that the Challenger did not find it. It remained for J. Y. Buchanan, Challenger chemist, to prove that the material was an inorganic precipitate owing to the action of the preserving fluid, alcohol. Huxley, in thanking Allman at the conclusion of his address, admitted that he had christened Bathybius. " He had hoped, indeed, that his young friend Bathybius would turn out a credit to him, but he was sorry to say as time had gone on Bathybius had not verified the promise of his youth " (London Times, August 21, 1879).
This was the great early period of oceanography. Wyville Thomson's cruises on the Porcupine and the Lightning in the North Atlantic had destroyed Edward Forbes' conception of the azoic zone. In 1870 Thomson, now forty, and having spent seven- teen years teaching in Ireland, succeeded Allman in the Chair of Natural History at Edinburgh. The Challenger expedition followed, with Thomson as director of the civilian scientific staff on board. As Murray (1895) reports, " After circumnavigating
* Macmillan and Co., London, 1878; reprint of papers in \hQ Journal of Anatomy ami Physiology, 1876-1878. The present-day classics on Elasmobranchs are by Bicelow and ScHROEDtR (1948 and 1953).
t At the same time the question of introducing California salmon into British waters was the subject of much debate in England. One writer, Sir Rose Price, emphasized the "... extremely risks nature of the experiment ", and claimed these fish would not take a fly and had no flavour. He concluded by stating, "The mortality among salmon in California is simply incredible" (London Times, April 16, 1879).
78 Daniel and Mary Merriman
i
the globe, and carrying on deep-sea and other investigations in many regions of the ocean, the Challenger returned to England in May 1876, and the crew was paid off after the ship had been in commission for over three years and seven months ". Then came the question of how best to work up and publish the results. Quantities of data in all branches of oceanography had been recorded, and the collections, which had been sent back to England from the expedition's different ports of call or brought back on ship-board, were wonderful in their extent and variety. There was extensive correspondence, in which members of the Royal Society, the Admiralty, the British Museum, and the Treasury all had a hand. Murray {he. cit.) again writes, " It was further determined that the records of the various observations and marine collections should remain in the meantime in the hands of those who had taken part in the Expedition, and that a temporary Government department, with a small annual grant, should be created, the duty of which should be to direct the discussion of the physical and biological observations, the examination of the collections, and the publication of the scientific results, so far as these had a bearing on the science o Oceanography ". Her Majesty's Stationery Office was to publish the results, and the " typical collections " were eventually to be deposited in the British Museum. In 1877 Wyville Thomson was appointed Director of the Challenger Expedition Com- mission, with headquarters in Edinburgh and John Murray as first assistant. Wyville Thomson fell into ill health shortly thereafter, and he lived only five more years — to the age of 52. In that time he settled the style of the publications and sent " a consider- able part " of the collections to the specialists* who were to examine and describe them. In fact, by 1882, the year of his death, 22 of the Challenger Memoirs were in print, the first having appeared in 1880. It remained for Murray to see the job through; the last of the " Fifty large Royal Quarto Volumes " appeared in 1895.
Thomson's letters to GuNXHERf resulted in three memoirs: on the shore fishes (1880), on the deep-sea fishes (1887), and on the pelagic fishes (1889). The corre- spondence, not all included here and in a most unhappy long-hand, provides fair evidence of the tremendous pains to which Sir Wyville went, of his attention to detail, of his ability to prod the contributors to the Challenger Reports when occasion demanded, and of his insatiable desire to see the whole series done to the highest degree of perfection.
University — Edinburgh March 17, 1877 Dear Dr. Giinther:
We have now gone over the greater part of the " Challenger " spirit collections and the Fishes are nearly ready to be handed over to you if you are inclined to take them up.
There are two distinct sets — those from the shallow water and from the marshes. This col- lection is not large as such a collection might easily be made with more time but I have no doubt there are many undescribed forms from the more remote places.
The other set is from deep water and many consist of a couple of hundred specimens (more or less) of forty or fifty species of which a large proportion are undescribed. They are mostly allied to the deep-water things which have come home from about Madeira.
* The completed Challenger Reports contain contributions from 76 authors.
t Published with the permission of the Trustees of the British Museum. We here express our best thanks to the several persons who helped us with the original letters of C. Wyville Thomson in the B.M.N. H., particularly Mr. Mugford of the Mineralogical Department Library.
Sir C. Wyville Thomson's correspondence on the "Challenger" fishes 79
If you undertake the Fishes the arrangement approved by the Treasury and by the Trustees of the British Museum is the following.
" That the fishes be sent to Dr. Giinther for determination and description and that Dr. Gunther be requested to select a complete set for the British Museum including all unique specimens and two specimens of all species of which there arc more than three; the remaining duplicates to be returned to me for distribution with the sanction of their Lordships."
There is one point with regard to the deep-sea fishes especially which I must mention. Mr. Murray has had charge of these and has devoted special attention to the circumstances under which they have occurred making careful notes in each case. No description would be complete particularly in its bearings on physical geography without such information and 1 think it would be very desirable that Mr. Murray should be associated with you in the description of this section; this is a matter, however, which I must leave in your hands.
I should wish all new species and all species which have not already been well figured in readily accessible publications to be fully illustrated with any necessary anatomical details. Of course I am prepared to defray the expense of illustration. I should like, if possible, to have some at all events of the plates done during the next financial year and I would be greatly obliged to you if you would, when you see the specimens, give me a rough estimate of the number of plates which will be required and of the approximate costs.
In the meantime, will you kindly let me know your views generally on the matter and when you would wish the Fishes sent.
I enclose a proof of a list of observing Stations and will send a corrected copy with the chart shortly.
I send a rough proof of one of the plates to give the size.
Yours faithfully,
C. Wyville Thomson
Bonsyde
Linlithgow, N.B*
July 10, 1877
Dear Sir:
I do not think that there is the slightest objection to your publishing the Kerguelen Fishes in
either way you prefer — Annals or Phil. Trans. The deep-sea series I should think of course to
form a part — or volume if need be — of the official report. Would you be good enough to give
me so far as you can a rough estimate of the amount which you expect to be able to undertake —
plates and letter-press, during the current financial year, and the total expense for this year—
the plates on the stone and the letter-press ready to go into the printer's hands.
I am glad that you are finding so many new and interesting forms. I think you may depend
upon the condition of the specimens being good, for certainly no care has been spared either in
that or any other group of marine forms.
1 am yrs faithfully,
C. WvviLLE Thomson
University of Edinburgh
18 October, 1877
Dear Sir:
I now enclose a plate as a sample of size and style that we may have the whole series as nearly uniform as possible. The tinting, the additional expense for which has been sanctioned by the Stationery Office, gives a great advantage in brightening of the figures by the use of white.
The exact size of the tinted portion of the plates, well within which the figures must be kept, is 10 X 8 inches. It would be well to keep the lettering the same as on the sample plate, altering
* Thomson's ancestral country home, where he was born and where he died The centre window of the aose of the parish church of St. Michael of Linlithgow was done m 1SS5 in memor>^of Sir WYvfLL? the ubject s a representation of the 104th Psalm. God's mamtcstation ot Hiniself mthe Works of Creation, and in the lower parts of the window are illustrated the great and wide sea .
80 Daniel and Mary Merriman
the legend on the right hand upper comer as required, e.g., Foraminifera PI. Ill Ostracoda PI. IV.
I should like that two proofs of each plate should be sent to me before the requisite number of impressions, which will probably be 525 are printed off.
The paper will be supplied by the Stationery Office. I am, sir.
Yours faithfully,
C. Wyville Thomson*
Edinburgh November n, 1877 Dear Dr. Giinther:
I have written to Spence Bate, t Under all the circumstances it may perhaps be as well to allow the Brachyura to stand over for the present.
Will you kindly let me know for the information of the Stationery Office how you propose to have your plates lithographed — through what firm, and at what cost — the plates to be of the same size as the pattern plate sent and the number of copies probably about 730. The Stationery Office supplies the paper, so it is merely the use of the stones and the printing.
Thank you for your interesting account of our Japan species. What a number of new forms there seems to be. Believe me.
Yrs. faithfully,
C. Wyville Thomson
Edinburgh May A, 1878 Dear Dr. Giinther:
I should think that there cannot be the least doubt of the advantage of the course you propose. The abstract of the description in the Annals should be " published with the permission of the Lords Commissioners of the Treasury ". I have heard nothing about fishes from Agassiz. He has got a fine haul of invertebrates.
Let me know what arrangement you make when you begin the plates so that we may be all square with the Stationery Office.
Yours faithfully,
C. Wyville Thomson
University Edinburgh
July 5, 1878 Dear Dr. Giinther:
Thank you for the signed list. It keeps things all square.
I am very glad to know that the illustrations of the Fishes are going on.
I am glad also that the condition of the Fishes pleases you. Murray took a great deal of
trouble.
Yrs. faithfully,
C. Wyville Thomson
*
This letter is not in Thomson's own hand, though the signature is clearly his. t See Challenger Report on the Crustacea Macrura, Vol. 24 (Zool.), Pt. Lll, 1
Sir C. Wyville Thomson's correspondence on the "Challenger" fishes 81
EdinhtiiKh
^ r^ ^. .u Octubcr 12, 1878
Dear Dr. Gunther:
1 am delighted to see the plates. They seem to be excellent. We have a contract with Minlcrn's so all you have to do is to order from him is to order {sic) 750 copies of each plate on the terms of his contract for the Challenger work. 1 think the best plan would be to leave all the plates at Mintern's except 20 copies of each which are allowed for editorial purposes, and which I should like to have sent to me. I do not care to have all the plates stored in one place. It concentrates the risk too much. I suppose Mintern's people have a Hre-proof store. The faster the plates come in now the better. I fear it will be impossible to complete the whole work within the time I gave* — but — we are doing our best.
1 send a copy of Lyman's synopsis of the first division of the Ophiuroids so you see what you have to expect in the way of new forms. 1 have not yet got the type specimens of the Echinids but most of the plates are done so you will get them soon.
Believe me
Yrs. faithfully,
C. Wyville Thomson
Edin.
Decembers], IS78 Dear Dr. Gunther:
Of the enclosed documents those marked I and II were returned to me from the Treasury on the grounds that Plates 3 and 6 had been charged twice.
I had signed both accounts supposing that the double marks referred to the two series — shore and deep-water fishes. Mintern's people seem to be careless in these matters. If this is the second time a mistake has occurred, would you mind asking them to send their accounts to you and initialing them if you find them correct?
Yrs. in this
C. Wyville Thomson
Edinburgh January 25, 1879 Dear Dr. Giinther:
Will you very kindly try and fill up the accompanying sheet. 1 am anxious to make out as
clearly as possible where I am and what I may expect.
Yrs. faithfully,
C. Wyville Thomson
Bonsyde
Linlithgow, N.B. Nov. 12, 1879
Dear Dr. Giinther:
I am now going on with your report and I will send you some proofs in a few days. It is somewhat different in form from the others. I thought the plates had been printed oflT. I suppose Mintern had better send to me a demand for the paper they require and I will send it up to the Stationery Office.
Will you kindly let me know to what the numbers attached to the species of shore-fishes refer.
* Murray (1895) writes, " In the year 1889 Her Majesty's Treasury declined to ask Parliament to renew the annual grant for the continuation of the work relating to the scientific results of the Expedition the time estimated for the completion of the publications havmg expired. However, after some correspondence, in which I offered to finish the Report at my own expense, the Govern- ment agreed to set apart the sum of sixteen hundred pounds for the completion ot the ofiicial publica- tions in the same style as that in which they had hitherto appeared. This sum has been the only pay- ment from Government funds in connection with the Challenger Expedition during the past six years. . . "
32 Daniel and Mary Merriman
As to the pelagic fishes if you think they would be better on woodcuts I have no objection. If you can employ Mr. Cooper 188 Strand to cut the blocks it would be convenient as we shall have an account with him at all events.
I shall be very glad to see the deep-sea fishes. Of course in this report the interest centres on the distribution and the bathymetrical range of the forms, and I should like it to be as complete in this respect as possible so as to form a basis for future work.
I would be glad if you would kindly give very full lists of the deep-sea fishes which have been described hitherto, and if you would cause to be figured anew any species taken by us, which have been only described and not figured, which have been badly figured, or which have been figured in not easily accessible books. You are no doubt aware that Agassiz's deep-sea fishes are in Steindachner's hands and now well advanced. As the abyssal fauna is very uniform many of our species are in that series.
I have heard from several of your London acquaintances that you are in some way dissatisfied
with the form in which you are receiving the British Museum Series of specimens. I do not
know what the cause of complaint is, but if there be any it would be better perhaps to refer it
to myself. I send a proof which happens to be lying before me to show you the form which the
reports are taking.
Yrs. faithfully,
C. Wyville Thomson
Bonsyde Linlithgow, N.B. Nov. 17, 1879 Dear Dr. Giinther:
Thank you so much for your note. You have not however told me to what the nos. attached to the Shore-fishes in your list refer. Please let me have a post-card as soon as you can.
I assure you if I had only heard of your supposed dissatisfaction casually or from one source I should have said nothing about it. Since, however, there seems to have been some mistake there is no use in taking further notice of the matter.
I consider it perhaps the principal part of my duty in connection with the working up of the " Challenger " collection to place the type specimens and whatever else seems necessary for full illustration, of every species, in the British Museum. And this 1 will carry out to the best of my power. As I told you at the time the specimens which you got from Agassiz belong to known species, and to a few new species of which many samples were found — possibly some of them are unnamed, and I sent them to you just as they came as I am aware that each transfer however carefully managed does some little damage, and I did so mainly that some pretty things such as Coelopleurus, Salenia, Asthenosoma, etc., might be seen at once.* You will get the type speci- mens whenever they are figured and described.
Thank you for your kind reference to my late illness. I fairly broke down with over-work,
but I am now nearly as well as ever.
Believe me
Yrs. faithfully,
C. Wyville Thomson
Bonsyde
Linlithgow, N.B. Feby \3th, 1880 Dear Dr. Giinther:
I send you at last a proof of your report on the Shore-fishes. I thought you would have had it long ago but some other things occupied us very fully for a time. As it turns out however this delay has been of no consequence for it will be a month yet it seems before your plates are
printed off. '"^ ^
What I send you, then, is a first-proof, corrected as far as we could manage it, but still needing
* See Challenger Report by A. Agassiz, Vol. 3 (Zool.), Pt. IX, 1881.
Sir C. Wyville Thomson's correspondence on the "Challenger" fishes 83
to be put into shape in certain respects. The Geographical list* I propose should come first— as an elaborate Table of contents. Then the descriptions and the systematic list at the end. There are several mistakes and among them a few which ought to be corrected. For example the fresh- water fishes from the Mary river were not presented to us but caught with some labour by a little party consisting of Murray, Lieut. Aldrich, and myself, who squatted on the bank of the river for a fortnight in the hopes of getting young Ceratoclus. We took two of the mature Cera- todus however and it should have been in your list. The specimens were not sent to you as ihey were not put up with the rest of the fishes. I know you had plates of it so I suppose you do not wish them. If you do you can have one. I should like to keep the other here as a memento of a pleasant holiday trip.
To save you trouble it would be better perhaps that I should add when necessary a note indicating anything special about the fishes— such as the mode of preserving them at different places. The account is rather bald without a few such details, t
Would it not be as well to substitute some other specific name for Sancii pauli.% The French are just describing the fauna of the other St. Pauls which is so much better known.
In the introduction of your preliminary notes on the Deep-sea fishes you make some remarks as to the extent and condition of the collection of fishes. I suppose you have no objection to these remarks being repeated here.
I send you two copies of the proof. If you want additional copies please send me a line- also if it is necessary to send the Mss. I retain a copy and will add such additional notes as I think are necessary, and then, when I get your corrected copy, 1 will have a clean proof drawn and send it to you before printing off, in case you have any further alterations.
I will be glad of the deep-sea fishes whenever I can get them. The first spurt is about over and we shall need as much material as we can get to go on with.
You will get the type collection of the Echini very shortly now. I hear from Agassiz that he is very nearly done. I hope to be able to be in London in March but I am not quite strong yet and am shirking the journey as long as possible.
Yrs. faithfully, C. Wyville Thomson
Bonsyde
Linlithgow, N.B.
February lA, 1880 Dear Dr. Giinther:
I am afraid it was trespassing altogether too much upon your time to ask you to take charge of the Report on the Challenger Fishes, but I followed the principles I tried to work on as far as I could, and applied to the most distinguished Ichthyologist I knew. I must ask you however to allow me to bring your list as nearly into the form which has been adopted after much consideration for the report, as its nature will allow.
I am taking the utmost care that the type collection of everything goes to the British Museum in its thorough completeness but I do not mean to make the Challenger Report a Museum Cata- logue in any sense. The data I mean to publish are those which have reference to the Expedition. No doubt all the letters and references to specimens in and out of the Museum will appear in your own catalogues when these Fishes are added to them. Such a list as you send me should be published by the Museum if it is required.
I suppose that the Shore-Fishes are not of much importance but I do not wish to publish matter which from my point of view is wholly irrelevant, and I must ;idd a few notes about the
* No geographical list as such appears in the printed version; the descriptions arc made under broad geographic headings, Atlantic, Temperate Zone of the South Pacific, etc.
t To make the account of Ceratodus less " bald ", Sir Wvvilli , who evidently felt strongly about these fish, wrote what must surely be one of the longer footnotes in ichthyology— almost a thousand words (GiJNTHER, 1880).
X GUNTHER apparently disregarded Thomson's suggestion, for Holoccnirum sancti pauli. n.sp. appears on page 4 of his Report on the Shore Fishes (1880).
84 Damel and Mary Merriman
Ceratodus and means by which the fishes were procured — to do my duty fairly as Editor. I have not time for many, but what are added you will see before they are printed off. The report on the Shore-Fishes might be as good as that on the birds which will give all the information we have. I will send you tomorrow the Mss. — and you will see that we have taken no little trouble correcting spelling, adding authorities, etc., etc. I would have certainly left out that long Geographical list altogether. It seems little more than a repetition of the main list. I will leave it out yet if you have no objection for I do not think it improves the appearance of the paper.
I have not the proof at hand — it is at the Office in Town but I will see it tomorrow and write again what I think had best be done.
Yrs faithfully,
C. Wyville Thomson
Bonsyde
Linlithgow, N.B.
March 10, 1880 Dear Dr. Giinther:
I daresay your plates are now nearly finished and the rest of the volume is ready. All you
need to do is to correct any errors in spelling and so on in the text, and I would like to have it
as soon as convenient.
Yrs. faithfully,
C. Wyville Thomson
Bonsyde
Linlithgow, N.B.
March 22, 1880 Dear Dr. Giinther:
I must apologize for having entirely forgotten to send Ceratodus. I suppose you have been waiting for it before sending the corrected proof. I will be glad of the proof whenever you are ready for we are anxious to set the type free.
There is another little matter which I ought to mention. I see you have communicated a paper to the Linnaean Society on some of the deep-sea fishes. If any report or abstract of that paper is published I would be greatly obliged if you would add to the heading " Published by permission of the Lord Commissioners of the Treasury ".
Of course in making this request I am only obeying my own instructions from the Treasury.
Yrs faithfully,
C. Wyville Thomson
29 March 1880 Dear Sir Wyville:*
The specimen of Ceratodus arrived safely on Saturday last, and I return it today with the proof sheets.
The proofs are corrected with the exception of 1 . The Geographical List which you propose to leave out. I see no objection to it and only regret that it was set up in type, time and expense being thereby saved. 2. Of the enumeration of the specimens of each species which I have left as you have had it set up.
With regard to my discourse at the Linnean Society, it referred to results of examinations made by myself long ago or others more recently independently of the Challenger Collections.
* This unsigned letter, much emended, appears to be the first draft of Gunther's answer to Thomson's of March 22, 1880.
Sir C. Wyville Thomson's correspondence on the "Challenger" fishes 85
Bonsydc
Linlithi^'OM, N.B.
April 1. IS SO Dear Dr. Gunther:
Many thanks for the corrected proofs. They will be put in hand in"rmcdiately and I uill send you a second proof before the paper is printed off. I see most of your corrections refer to matters oi form rather than Ichthyology. I do not suppose you attach much importance to the relative positions of n and sp! Our way of putting it was adopted after an amount of consideration sufficient for the subject, I think. It means either " new species " or " nova species " as you choose. On what ground it should be inverted, unless it came in as part of a Latin sentence, I am not aware. The single i terminating proper specific names ending in a consonant is in accord- ance with the " Strickland Code " and is I believe correct.
The first Zoological volume will now be out at once. I have not yet got your plates from Mintern's however — but I suppose they are ready.
I suppose you will have no ditficulty in arranging the account of the deep-sea fishes zoologically and putting the report into the same form as the others. It will save a deal of trouble. The sooner I can get the reports, the materials for which have been long in the hands of the authors, into print the better — for there will be a great accumulation towards the end.
Yrs faithfully,
C. Wyville Thomson
Bonsyde
Linlithgow. S.B. May A, 1880 Dear Dr. GUnther:
I hope this will answer now. I have, as you suggested, taken out the reference to the B.M. Catalogue, and have made the Report more comparable in shape of the rest.
I trust you will not find it to require much more correction— and that you will be able to let us have this Mss. proof at once, for the succeeding volume is almost finished and (we) are greatly
pressed to put the first out of hand. r ..r n
^ Yrs faithfully,
C. Wyville Thomson
Bonsyde Linlithgow, N.B. May 6. 1 880
Dear Dr. Gunther:
I think the addition of the paging to the systematic list would be a great improvement. I would
have had it done here but our hands are very full.
Delighted to hear that we shall soon see some deep-sea fishes. ^^ fai,h,-u||y
C. Wyville Thomson
Bonsyde
Linlithgow. S.B. July 5, 1880
Dear Dr. Gunther:
I was unlucky in missing you the last time I was in London. ^r .u. „, , ..
You wrote me some time ago that I might expect w.thm a very short fmc some of the pLtes of the deep-sea fishes. Could you drop me a line when you thmk these will be ready. I wish to arrange for the next set of volumes and I want to know when your memoir will come m-as
'"h^^^u u::^ci:^dr;ncorporaced or done anything with the set of Echinodern. . sent you^ I find that they were sent in a certain sense by mistake, and I could select your full set much
86 • Daniel and Mary Merriman
more satisfactorily if I had them back again. I have had no official receipt for them. They were only meant in a provisional lot in case anyone wished to see them and if they are not exhibited or entered if you wish to send them back to me I will send you the type lot complete.
Yours faithfully,
C. Wyville Thomson
*I am sorry that there has been any mistake about the preliminary set of Echinids; but, re- reading from letters, I must acquit myself of any share in the error.
The specimens have not only been put into different bottles, but have been registered, incorporated and reported to the Trustees; and by them to the House of Commons.
It is now, therefore, impossible for me to acquiesce in your request that they should be returned. It seems to me that the best thing to do will be to send me the type-series, when I will have them compared with what have been already sent, and, if I find that it is possible to return any of the freshly sent specimens, or finding that the characters and distribution of the species collected is already well enough represented by the previous series, I will certainly do so, in order that they may form a part of a good set for the museum, which has the second claim on this National collection.
So far as the specimens already sent are concerned, I may add that the assistant in my Depart- ment who is especially charged with the care of this group has engaged himself to remain in London until the end of August, and I may safely promise for him that he will spare no trouble in giving all assistance in his power to the artist (2) or the describer (1), if they are desirous of having another examination of the specimens already in the British Museum.
Bonsyde
Linlithgow, N.B.
July 10, 1880 Dear Dr. Giinther :
I am greatly obliged to you for the proofs which are already in the printer's hands.
Yrs faithfully,
C. Wyville Thomson
Bonsyde
Linlithgow, N.B. July 15, 1880 Dear Dr. Giinther:
Thank you so much for your note and for the first deep-sea fish plates. I suppose in these plates you will simply put the name of the Fish beneath as we have done in the other groups without locality or anything further. Either the generic name only or the generic and specific as you think proper.
It is all right about the Echinoderms. I thought it very possible you had incorporated them. I daresay you could without much trouble send me a list of the species already sent. I think I kept a duplicate list but I have changed my Secretary since, and I cannot at this moment lay my hands on it. I want to be sure that you get every species the old as well as the (sic) those not previously described.
Yrs faithfully
C. Wyville Thomson
P.S. Can you readily send me by return the date when you got the shore-fishes and the date when you returned me the Mss ? It has been suggested to me that these should be published in all cases and I did not think of it at the time.
C.W.T.
* This letter, unsigned and undated, but in the same hand as that of March 29, 1880, is apparently a first draft, Gunther to Thomson.
Sir C. Wyville Thomson's correspondence on the "Challenger"' fishes ' 87
Bonsyde Linlithgow, N.B. October 1, 1880 Dear Sir:
I have forwarded your note to Dr. Sclater* and see no reason why you should not enter the birds in your forthcoming volumes.
The Pteropods are not even commenced. They are not so numerous as might be expected in the Collection and, as they are greatly scattered on slides and in bottles of tow-net matter, it will be some time before they are ready. We must get through with the hii^ger things first.
You will get probably tomorrow or next day, a lot of fishes from the deep water off the Faroes ( ?) some of the spoils of the Knight-Errant.] 1 will be greatly obliged to you if you will simply add them to the Challenger things ...(?) That is look them over keep what you require for the Brit: Mus: and return us the remainder named. Only it would be a great favour if you would keep this lot separate, send us a specimen of all of those of which there are two in the same condition, and let me have a separate short report on them for a paper on the Faroe Channel which I am going to read at the R.S.E.
You will get lots of things in other departments by degrees from the same cruise, but I am having them all named and worked up with the Challenger things in the mean time.
Yrs faithfully,
C. Wyville Thomson
Bonsyde
Linlithgow, \'.B. October 25, ISm Dear Dr. Giinther:
Dr. Sclater promises to send you the birds as soon as possible after his return home. I am looking out most anxiously for the plates of the deep-sea fishes. They are now pressing me to finish my work on the Collections and leaving such a crush of printing for the end that I hardly see how I can manage it.
I would prefer having, as in other Memoirs, the name of the Fish only on the plate. 1 would especially rather not have the depth— for although of course the depth of the sounding is given in the station for the Fish, we can seldom be absolutely sure that the fish actually came from that depth— particularly in the case of using the trawl. faithfull
C. Wyville Thomson
±The bathybial Fish-fauna which surrounds the British Islands was hitherto almost unknoNsn. Beside the stray specimens which now and then were found thrown ashore or floatmg on the surface no further evidence of the existence of this fauna was obtained, except on two occasions, viz on a dredging-excursion of Dr. Gwyn-Jeffreys in 1867 from a depth of from SO to W fathoms;* and during the cruise of H.M.S. Porcupine in 1869 from a depth ot from 200 to 500 fathoms, t
*See Ann. & Mag. Nat. Hist. 1867, xx, p. 287. t/W.. 1874. XML p. 138.
* See Challenger Report by P. L. Sclater, Vol. 2 (Zool.), Pt. VIII. 1881.
t The cruise which led to the deliniation of Wyville Thomson ridge: see Herdman. p. 5!^. 1923.
J A^*^A or>H miirh emended is in the same hand as that of March 29 and .he^T.eiJjSw^col'-o-e t P. itZt aTpTremiy ano.her fi., draf. GO,.„h« .o THO^■so^.
88 Daniel and Mary Merriman
Neither of these two contributions can compare as regards interest and number of specimens with the series obtained during the cruise of the " Knight-errant " ; and it would seem as if now only the rich spoil which I ventured to indicate in 1 867 as resulting from an exploration of the Deep Sea round the British Islands, were being gathered. Six out of the ten species obtained^ are new to the British Fauna ; and of course represent but a small fraction of the actual number of Brit, deep-sea fishes. Much, therefore, remains to be done. The laws which govern the bathymetrical distribution of Fishes, are still obscure ; and it is evident that a series of continued methodical observations, such as can be made in a limited oceanic district like that round the Brit. Islds., whose hydrographic conditions with its surface and coast fauna are so well known, is most likely to reveal a chain of facts which cannot be recognized in disjointed observations made at distant localities. Besides, there are not a few obscure points in the life-history of our food- fishes which may be well expected to be cleared up by the deep-sea-dredge, such as the unaccount- able disappearance from certain parts of the coast of fishes like the Haddock, the change of habitat of many fishes according to the season, a change which evidently much more frequently takes place in a vertical than horizontal direction, etc. It is therefore to be hoped that the present successful expedition will be followed by equally well conducted efforts.
The collection submitted to my examination contains a much greater proportion of arctic forms, than of southern; and in this respect differs entirely from that made by Mr. Gwynn" Jeffreys at a less depth. The only southern form is Haloporphynus lepidion which we knew previously from the Mediterranean and Japan. Singularly, again, no trace of a Trachypterus or Regalecus was obtained; and we can account for their absence only by the supposition that it is difficult to enclose these long snake-like fishes in the dredge, and that young specimens from their extreme delicacy of structure are probably torn into fragments or lost long before the net reaches the surface. Some of the species have been previously obtained by the Scandinavian Expeditions in similar latitudes. As all the species will be fully referred to or described in my Report on the *' Challenger " Deep-sea-fishes, only a few notes on them are appended here.
Bonsyde Linlithgow, N.B. Oct. 26, 1880 Dear Dr. Giinther:
I had written you a note just the post before I got yrs. I am very much obliged to you for the report and greatly pleased that the fishes have interested you so much. I have been long looking forward to a careful overhaul of the Faroe Channel, and I have every hope that we may have another investigation this next summer under more favourable conditions.
So far as this years work is concerned I am at liberty to ask you to make what use you choose of the duplicity which I have much pleasure in doing ( ?) — only send me back what you can spare
Yrs faithfully,
C. Wyville Thomson
Nov. \st (?) — no address Dear Dr. Giinther:
I have just received a list signed by you from Mr. Moseley. You will exercise your own discretion in selecting the Brit : Mus : set. Of course my prime object is to make that as complete as possible, but, that done, it would be a convenience for (me) to have as many species here for comparison as I can get.
I have a note from Dr. Sclater that he has handed over or is about to do so, the birds. I suppose you will send me a list. I expect to send off the Pennatulida the end of the week.
For some whale bones and seal bones you will have to wait till the part on the bottom deposit
is finished. I am anxiously looking for the deep-sea fishes.
This is a most laborious job !
Yours faithfully
C. Wyville Thomson
Sir C. Wyville Thomson's correspondence on the "Challenger" fishes
89
Bonsydi'
Linlithgow
^ ^ ^.. ^ Nov. 2, 1880
Dear Dr. Gunther:
From having heard nothing from you with regard to the Corals of the Challenger Expedition I suppose I am right in concluding that you have not received them yet from Mr. Moselcy. As some difficulties have arisen in this department I have asked Mr. Moseley, to avoid any further complications, to send the whole collection, the type specimens, the second selected set. and the duplicates to you. I will be very much obliged to you if you will kindly select the first set accord- ing to the instructions sanctioned by the Treasury— and return the rest to me.
I am sorry to give you this trouble— but this is I think the only case. I will send you in the course of a few days the Ostracoda and the Pennatulida. I mean in all cases to send the specimens to the Museum as soon as possible after the Memoirs arc published. It would be scarcelv fair to do so much before.
I have been reading your book on Fishes with much pleasure, and I think I know more about them then I did before. It is a resume which was much wanted.
Yrs. faithfully
C. Wyville Thomson
Bonsycle
Linlithgow. N.B. December 17. 1880 Dear Dr. GiJnther:
I know pretty well all about the advantages of complete collections for reference. I am only very glad that so much attention is now being paid to these minute ( ?) groups in the B.M.
My great object has been to make the collection from the " Challenger " in all branches in the National Collection as perfect as possible. Beyond a certain point I cannot force this but I will do the best I can. Believe me yrs faithfully
C. Wyville Thomson
P.S. I will send you today the whole of the remaining material returned by Dr. Brady as duplicates. I forwarded your letter and list to Dr. Brady.*
Bonsyde
Linlithgow, N.B. January 16. 1881 Dear Dr. Giinther:
It has been suggested to me that perhaps I ought to have let you know that it was in my power to offer a moderate honorarium for literary work in connection with the Challenger Report. To tell the truth I had some delicacy in doing so remembering the strong representation which the Brit. Mus. officers made on that matter to government. I do not see howe\cr that preparing such a report, especially as I distinctly objected to its being in the form of a Brit. Mus. catalogue, could be considered a part of your regular work.
If you desire it I will send in an account for the sum to which you are entitled under my
instructions. Will you very kindly let me know how the Deep-sea Fishes stand.
Yours sincerel>
C. WVVILLK THOMSt)N
* Either G Stewardson Brady on the Copepoda (Challenger Report Vol. « (Zool.»- P' \\' • 1884) or Henry BOWMAN Brady on the Foraminifera (Challen.^er Report. Vol 9 (Zool.). Pt. WII.
1884).
90 Daniel and Mary Merriman
Bonsyde
Linlithgow, N.B.
February 11, 1881 Dear Dr. Gunther:
I am extremely sorry to hear that you are still on the sick list. I hope you will shortly be in condition to resume your work with comfort again. As to future arrangements I will be glad to meet your wishes in every way, as far as I can.
Yrs faithfully
C. Wyville Thomson
Bonsyde
Linlithgow, N.B.
March 1, 1881 Dear Dr. Gunther :
Let me introduce to you my Secretary Dr. W. A. Herdman, F.Z.S. — from whom I think you have heard from time to time.
I will be very much obliged to you if you will let him overhaul your Ascidians. He is doing ours and I know that he is thoroughly up to them. If you can help him in any way you will do me a great favour. Also on all " Challenger " matters talk to him as to myself.
I sincerely hope that you are now all right again. I hope to be in Town in about a fortnight
or so.
Yrs faithfully
C. Wyville Thomson
Bonsyde
Linlithgow
December A, 1881 Dear Dr. Giinther:
I am getting very anxious about your paper on the deep-sea Fishes and would be very glad
to see some of the work. Both the Royal Society and the Treasury are expressing some impatience
and I may be landed in difficulties if some of the promised memoirs are much longer delayed.
I would be greatly obliged to you also if you would send me a receipt for the Echinoidea sent
by Agassiz according to his Memoir.
There are several other Memoirs which will be ready for delivery shortly.
Believe me
Yrs faithfully
C. Wyville Thomson
Murray (1895) speaks of the fact that the Challenger Reports cover "... about twenty-nine thousand five hundred pages, illustrated by over three thousand litho- graphic plates, copper plates, charts, maps, and diagrams, together with a very large number of wood-cuts ". He goes on to say, " From beginning to end the history of the Challenger Expedition is simply a record of continuous and diUgent work ". In a sense it is just that. But who, most of all, had the perspective and pertinacity to initiate this first real study in deep-sea research ? If Thomson were alive today, it is fair to speculate that he would be astounded at the developments in oceanography since 1879. His was an unusually broad, inquiring mind — to which his writings and editing testify abundantly; his was the imagination that resulted in the Challenger Expedition; and his was the guiding hand that led to the foundation of the modern science of oceanography. In mute testimony, his name appears on the title page of
Sir C. Wyville Thomson's correspondence on the "Challenger" fishes 91
all Challenger volumes— whether produced before or after his death -" Prepared under the Superintendence of (the late) Sir C. Wyville Thomson, Knt., F.R.S., &c. Regius Professor of Natural History in the University of Edinburgh, Director of the Civilian Scientific Staff on Board".
REFERENCES
BiGELOW, H. B. and Schroeder, W. C. (1948), Fishes of the Western North Atlantic. Pt. I. Sharks.
Sears Foundation for Mar. Res., Mem. I, 59-576. BiGELOW, H. B. and Schroeder, W. C. (1953), Fishes of the Western North Atlantic. Pt. 2. Saw- fishes, Guitarfishes, Skates and Rays. Chimaeroids. Sears Foundation for .Mar. Res., Mem. I,
1-588. GiJNTHER, Albert (1880), Report on the Shore Fishes procured during the Voyage of H.M.S.
Challenger in the Years 1873-1876. Report on the Scientific Results of the Vovage of H.M.S.
Challenger, etc., Zool., I, 1-82. GiJNTHER, Albert (1887), Report on the Deep-Sea Fishes collected by H.M.S. Challenger during
the Years 1873-1876. Report on the Scientific Results of the Vovage of H.M.S. Challem^er. etc..
Zool., XXII, I-LXV and 1-335. GiJNTHER, Albert (1889), Report on the Pelagic Fishes collected by H.M.S. Challenger during the
Years 1873-1876. Report on the Scientific Results of the Vovage of H.M.S. Challenger, etc., Zool.,
XXXI, 1-^7. Herdman, W. a. (1923), Founders of Oceanography and their Work. Edward .Arnold & Co., London,
340 pp. Moore, Ruth (1955), Charles Darwin. Alfred A. Knopf, New York, 206 pp. Murray, John (1895), A Summary of the Scientific Results. Editorial Notes. Report on the Scientific
Results of the Vovage of H.M.S. Challenger, etc., VII-XII. Russell, F. S. and Yonge, C. M. (1928), The Seas. Frederick Warne & Co. Ltd., London and
New York, 379 pp. Thomson, C. W. (1873), The Depths of the Sea. Macmillan and Co., London. 527 pp.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 92-109.
The hydrography and the distribution of chaetognaths over the continental shelf off North Carolina
By Dean F. BuMPUs*t
Woods Hole Oceanographic Institution
and
E. Lowe Pierce
Department of Biology, University of Florida
Summary — Temperature, salinity and quantitative plankton data have been obtained from the continental shelf area and Florida Current off North Carolina in May and June 1953 and January 1954.
Two water types, Virginian Coastal water and Carolinian Coastal water, and one water mass, Florida Current water, are identified.
A breaching of the barrier at Hatteras between the two coastal water types was witnessed, and Virginian Coastal water was driven south-westerly across Diamond Shoals into Raleigh Bay by a north-east storm. The import of such an hydrographic event on the distribution of plankton is discussed.
The distribution of the chaetognaths in the area was investigated and their association with the water type and water mass tabulated. Twelve species representing three genera were collected. All of these are found in tropical and sub-tropical waters. Chaetognaths fail as satisfactory indicators of the Virginian Coastal water intrusion into Raleigh Bay because of the absence, in our collection, of characteristically Virginian types in the southern limits of that faunal subprovince.
INTRODUCTION
Prior to the efforts of Pierce (1953), who described the distribution of the chaetog- naths over the continental shelf off North Carolina in relation to the hydrography of the area, and Bumpus (1955), who considered the circulation of these waters, little was known about the effect of the circulation system on the distribution of planktonic elements of the flora and fauna in the Hatteras area. Parr (1933) noted in winter a temperature barrier at Cape Hatteras corroborated by Bigelow (1933) and a fairly large cold-water temperature zone southwest of Cape Hatteras. This temperature barrier is well illustrated in the surface temperature charts of Fuglister (1947). Bigelow and Sears (1935) pointed out the abrupt transition in salinity which occurs at Cape Hatteras, occasioned by the wedge of pure oceanic water (>35*5%o) which presses in close across the shelf in Raleigh Bay and entirely separates the shelf and slope water bands to the north from the low coastal salinities farther south. The data available at that time suggested that the situation exists throughout the year.
The existence of a barrier at Cape Hatteras has been postulated in defining the Carolinian and Virginian faunal subprovinces (Johnson, 1934). Many other zoologists have separated the cold-water and warm- water fauna on the continental shelf at this cape. Williams (1948, 1949), Sutcliffe (1950) and Pearse and Williams (1951)
* Contribution No. 760 from the Woods Hole Oceanographic Institution.
t Part of this research was sponsored by the Office of Naval Research under contract No. 27701.
92
Hydrography and distribution of chaetognaths over the continental shelf off North Carolina 93
found bottom living fauna, algae and plankton in Onslow Bay having in general tropical affinities. However, they noted in their winter and spring collections, in addition to the usual populations, a few individuals from a small number of species with northern affinities.
Our recent collections provide material for a better understanding of the hydro- graphic influence on the distribution of the chaetognaths in the area than has been available heretofore and indicate how the hydrographic barrier at Cape Hatteras is occasionally breached, thus permitting the temporary establishment of the anomalous communities noted by Williams, Pearse and Sutcliffe.
ACKNOWLEDGEMENT While the many outstanding investigations of Henry B. Bigelow do not strictly pertain to the area under discussion, the authors are especially grateful for his studies of the waters of the Gulf of Maine and the continental shelf from Cape Cod to Chesapeake Bay. His efforts have been a constant influence as we have attempted to extend the knowledge of shelf waters slightly beyond the area he so carefully and completely considered.
THE DATA
The data comprise a series of hydrographic sections together with plankton col- lections made in May and June 1953 (Caryn Cruise 64) and January 1954 (Atlantis Cruise 196) (Fig. 1).
At each station serial temperature-salinity depth determinations were made to the bottom or to nearly 500 metres, whichever was less. At most stations quantitative oblique plankton tows, using Plankton Samplers (Clarke and Bumpus, 1950) fitted with #2 silk nets, were made from near the bottom or 100 metres. When feasible two Plankton Sampler tows were made dividing the water column in two. The chaetog- naths were picked out of the plankton samples and identified (Tables I and II, Fig. 12). These plankton data are more nearly quantitative and extend closer to the shore than those of Pierce (1953).
HYDROGRAPHY
Bumpus (1955) has shown that, south of Cape Hatteras, a southerly flowing coastal current, such as is common north of Cape Hatteras, is a transient afi"air. Such a current, when present, is restricted to a very narrow portion of the continental shelf. The dynamic pressure gradient resulting from the combined effect of the runolf and the cross-shelf thermal gradient together with the prevailing wind and the frictional drag of the Florida Current provide for a northeasterly drift over a broad pari o\' the Carolina continental shelf.
In addition to the water of the Florida Current there arc two types of water in this region which we have named Virginian Coastal water and Carolinian Coastal water.* There are also mixtures of each of these with the Florida Current water. Virginian refers to the shelf water from Cape Cod to Cape Hatteras. Carolinian refers \o the
* We have used here two names apparently new to oceanography inasmuch as we have been unable to find names concisely describing the separate continental shelf regions north and south of Cape Hatteras. Because the terms Virginian and Carolinian are used to describe the faunal subprovinces of the continental shelf, we shall introduce these terms to identify the water types on the shelf.
94
Dean F. Bumpus and E. Lowe Pierce
|
36° |
9^^^^^^ |
78° 77° 76° 75° |
74. 1 |
|
|
{^^■■^■KlMP^iv' |
36' |
|||
|
^^H^^^BM|^^^^^B' -'HV |
||||
|
^^^^^BB^^I^H^BHi^r^ |
||||
|
^^^^^^^^^^^^^^^^^^^^^S .^^ ^■■- "^-o |
||||
|
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^B^^^^^^^^^^^r ^r^ |
||||
|
35' |
^^^^^^^ O' ••91 |
OlS8 169 O qITO I |
35' |
|
|
34° |
W^ml r- ^79 C ■• 176 / -186 X. I77T'»I75 ^185 ■■■•■-"■■■■■•••3-\ /' •'" /' •l74 _I8J lY |
34' |
||
|
33* |
ill 1 1 1 1 |
33° |
||
|
7 |
-^ |
1 1 1 1 |
4» |
|
|
9* |
78» 77* 76» 75' |
7 |
Fig. 1 (A). Location of stations, on Caryn Cruise 64, May and June 1953. Open circles indicate
no plankton tows were made.
shelf water from Cape Hatteras southwards. UnpubUshed data indicate that Caro- linian Coastal water, as described below, extends to the offing of Daytona Beach and possibly at certain times to the offing of Cape Canaveral.
The Virginian Coastal water is freshened by river water entering close to the surface inshore and salted by indrafts of slope water over the bottom from offshore (Bigelow and Sears, 1935). There is no widespread contribution to this coastal water from the south, nor flooding of the surface water with pure oceanic water of high temperature, nor upwelling onto the shelf of cold abyssal water (Bigelow, 1933).
The Carolinian Coastal water is composed of Florida Current water and river effluent. This mixture is in general more saline than most coastal waters because the river runoff is less than for other sections of the coast ; the effluent from the sounds is more saline than from river mouths ; and the highly saline Florida Current frequently makes broad invasions over the continental shelf.
There is no regular communication between the Virginian and Carolinian Coastal waters, although the frequent northeast storms from November to May (Miller,
Hydrography and distribution of chaetognaths over the continental shelf off North Carol
ina 95
1 — 7
5130
.5131
/^SISS
5140
.5154.
..-.y Yiii
o
5(32
Y
35*
34*
33'
79°
78'
75*
Fig. 1 (B). Locations of stations on Atlantis Cruise 196, January 1954. Open circles indicate no
plankton tows were made.
1946; New York University, 1954) provide the energy for transient indrafts of Vir- ginian Coastal water into Raleigh Bay. Three events may take place following such an indraft:
A. If the storm lasts for only a short period, one or two days, this water will eventually become absorbed within the Carolinian Coastal water, modifying it in proportion to the mixture.
B. A violent meander of the Florida Current may completely sweep the indrafted Virginian Coastal water out of Raleigh Bay toward the northeast. Such an event would be aided by a southeast storm.
C. If the northeast storm lasts for a period longer than two days or if another northeast storm follows within a few days, the indrafted water may eventually be driven around Cape Lookout into Onslow Bay. Such an occurrence could account for the presence there of the winter-spring species with northern atlinitics described by Williams (1948, 1949), Sutcliffe (1950), and Pearse and Williams (1951). Should this occur at a time of substantial runoff when a southerly flowing coastal
96 Dean F. Bumpus and E. Lowe Pierce
current is being maintained in Onslow Bay and southward, such water movements may distribute planktonic elements of Virginian fauna for some distance along the coast.
We have postulated here a sporadic occurrence which may contribute appreciably to the finding of anomalous species in the inshore waters of the northern part of the Carolinian subprovince. These species will find themselves in waters compatible to their existence until vernal warming traps them. Vernal warming or reduction in runoff with a consequent increase in salinity w^ill kill those species least resistant to higher temperatures and salinities.
THE DISTRIBUTION OF TEMPERATURE, SALINITY AND DENSITY IN MAY AND
JUNE, 1953, AND JANUARY, 1954
Typical spring conditions were encountered on the May and June cruises (Figs. 1, 2, 3, 4 and 5). These are the weak cross-shelf temperature gradient, moderate vertical temperature gradient, and the penetration across the shelf of highly saline Florida Current water along the bottom into Raleigh and Onslow Bays. In contrast the temperature and salinity in the Wimble Section are lower with weaker vertical tempera- ture gradients and stronger salinity gradients.
Typical winter conditions for the Wimble, Onslow and Long Bay sections were observed in January 1954 (Figs. 1 , 6 to 10). Note the cold coastal water in the Wimble section and the nearly as cold, highly saline water in Onslow Bay and Long Bay. But Raleigh Bay was filled in its inner part with coastal water from north of Cape Hatteras, in contrast to the typical winter conditions of January and February 1950 (Bumpus, 1955) and February 1931 (Bigelow and Sears, 1935), when the 36°/oo isohaline (Florida Current water) was pressed well in across the continental shelf. This anomalous condition was due to a north-east storm several days earlier.
This intrusion of Virginian Coastal water into Raleigh Bay is further discerned in the temperature-salinity relation (Fig. 11). The water at Stations 5141, 5142 and 5143 is clearly Virginian Coastal water.
The temperature-salinity relations also provide a clue to the sources in the Florida Current contributing to the composition of Carolinian Coastal water. The water over the inner middle part of Long Bay (Stations 5149, 5150, 5151), Onslow Bay (Stations 5134, 5135, 5136, 5146) and the southern part of Raleigh Bay (Station 5145) in January appears to be from depths in the Florida Current, i.e. from depths perhaps as great as 150 metres. This water has been forced up onto the shelf in the course of current meanders and chilled by the colder air temperatures encountered there. Stations 5133 in Onslow Bay and 5147 and 5148 in Long Bay, the closest inshore stations, indicate appreciable dilution of this Florida Current water with river effluent and greater chilling as a result of the colder air temperatures near the coast. In contrast, the water over the outer parts of the shelf (Stations 5144 in Raleigh Bay, 5137, 5138 and 5139 in Onslow Bay and 5152, 5153, 5154 in Long Bay) is Florida Current water which has moved in over the shelf with no change in depth and has mixed only slightly with the water inshore of it.
The intrusion of Florida Current water along the bottom in Onslow and Raleigh Bays in May and June (Figs. 3, 4, 5 and 1 1) was probably along surfaces of equal density. It has been forced onto the shelf by the meanders of the current as it passes
Hydrography and distribution of chaetognaths over the continental shelf olT North Carolina 97
■3- >%
ca
o
j:
E
c g
D >.
c v
g
C
c
'E
■r.
3
u a.
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o
c
3 t/1
Q
so
o
E
98
Dean F. Bumpus and E. Lowe Pierce
196 STA NBR 197
5 10 15 20 25
NAUT MILES
Fig. 3. (A) Distribution of temperature in ^ C, (B) salinity in °/^^ and (C) density (at), in Section II,
Raleigh Bay, June 1953.
162
5 10 15 20 25
NAUT MILES
ZOO
Fig. 4. (A) Distribution of temperature in " C, (B) salinity in "/^^ and (C) density (at), in Section III,
Onslow Bay, May 1953.
Hydrography and distribution of chaetognaths over the continental shelf ofT North Carolina 99
A
190 STA Nan
188 18 7
Fig. 5. (A) Distribution of temperature in "' C, (B) salinity in ""[^^ and (C) density (at), in Section IV.
Onslow Bay, June 1953.
SI29 STA MBR SIV>
Fig 6 (A) Distribution of temperature in C, (B) salmily in ,, and (C) density (at), in Section V.
Wimble Shoals. January I "^54.
100
Dean F. Bumpus and E. Lowe Pierce
5142 STA.NBR 5143
I
7^
5144
Fig. 7. (A) Distribution of temperature in "' C, (B) salinity in °l^^ and (C) density (ot), in Section VI,
Raleigh Bay, January 1954.
O 5 K) 15 20 25 NAUT MILES
Fig. 8, (A) Distribution of temperature in ° C, (B) salinity in °/oo and (C) density (at) in Section VII,
Onslow Bay, January 1954.
Hydrography and distribution of chaetognaths over the continental shelf off North Carolina 1 0 1
5148 5149 5150 5151
' ^ I I
5152 515 3 STA NBR 5154
Fig. 9. (A) Distribution of temperature in ° C, (B) salinity in ''/^^ and (C) density (o,), in Section VIII,
Long Bay, January 1954.
along the continental slope. During other parts of Caryn Cruise 64, the position of maximum current was observed to shift as much as 14 miles either side of the mean axis of flow (which off Onslow Bay normally lies about 18 miles south-east of the 100 fathom line. Associated with these shifts of position were onshore and offshore deflections in the direction of the current (von Arx, Bumpus and Richardson, 1955). This provides the energy to push water up the slope across the shelf. It also appears from salinity measurements that as the meanders move offshore they draw low salinity water (from the surface over the shelf) into the current.
The proximity of the Florida Current to the continental shelf precludes the occur- rence (between the Current and the Carolinian coastal water) of slope water such as is found north-east of Cape Hatteras between the continental shelf and the Gulf Stream.
DISTRIBUTION OF THE CHAETOGNATHS The chaetognaths collected in this area include 12 species representing three genera: Sagitta bipunctata, S. enflata, S. helenae, S. hexaptera, S. hispida, S. lyra, S. minima, S. serratodentata, S. tenuis, Krohnitta pacifica, K. subtilis, and Pterosagitta draco.
The quantitative composition of the plankton tows is recorded (Tables 1 and ID. The species are listed in the order of their association with water of low or high salinity from left to right. The stations are arranged in the order of distance from the coa^.t. The ranges of individual species overlap others considerably and in many cases completely. Nevertheless the tables show that there is a general correlation between salinity tolerance and the distance from the coast at which various species were found. The most euryhaline-^urythermal species was 5". enflata (Pierce, 1953), although it is doubtful if it can tolerate for long periods salinities as low as those in which 5. hispida are usually found. S. hispida, S. helenae, and S. tenuis are species which are largely restricted to water of the continental shelf below Hatteras. The remainder o^
102
Dean F. Bumpus and E. Lowe Pierce
Fig. 10. Distribution of surface temperature in ° C (upper), salinity in ^/oo (middle) and density (m) (lower) on North Carolina Shelf, January 1954. Dash-dot line indicates track of ship.
the species were found principally in the Florida Current. The increase in number of species is evident as one proceeds offshore over the shelf into Florida Current water.
Sagitta bipunctata. The distribution and abundance of this species was similar in the area covered by spring {Caryn 64) and winter {Atlantis 196) cruises. S. bipunctata was collected in small numbers at several of the stations beyond the continental shelf and in a few instances they ranged shoreward about midway over the shelf (Tables I and II). With one exception (Station 5143) it was taken only in water where salinity was greater than 35 -5° j^^. It therefore appears to be restricted in this region to Florida Current water or water recently mixed with such water. Bigelow and Sears (1939) did not find this species between Cape Cod and Chesapeake Bay.
Sagitta enflata was taken in almost every plankton sample on both cruises (Fig. 12). It was the most abundant chaetognath as well as the most widely distributed. The greatest concentrations were found near the edge of the shelf where as many as 160 per ten cubic metres were recorded. That they are sensitive to extreme conditions which are occasionally encountered in this area is borne out by their absence in the winter cruise from the three inshore stations north of Cape Hatteras. Here in water of less than 10° C and 32°/oo not a specimen was found. Moreover only one specimen was present at the two inshore stations south of Hatteras, where the water had been derived from Virginian Coastal water driven around the cape.
Hydrography and distribution of chaetognaths over the
continental shelf olV North Carolina |()3
1 r
WIMBLE
J L
WIMBLE
SAUNITY y„
"1 1 r
y
lee-
-^•.
;
RALEIGH
■^ ^
I9S-I95 " V ■.
L_Li
-I 1 I L
J L
« II
-J 1 1 L_
_J4
~i r
ONSLOW
JlM- rr7
/ . -
J.
,.« "-<
-^
ONSLOW J,,j_
' ». * • •
. I
-
Ill
J I I
IV
' I 1 1 r
RALEIGH
5l44f
!
1 r
ONSLOW
VI
5IJ7-fc i SI59 » ■
/».
SlJt
146
LONG
J4
~i r
SI55 *
VII
J L
►Sl»4
9191 •
X1I9I *>ISO "♦''^ ••9.49
9146 I
vm
J I
Fig. 11. Temperature-salinity diagrams, upper for Caryn Cruise 64, May and June 1953; lower for Atlantis Cruise 196, January 1954. The stippled line in the diagrams is the left side of an envelope describing the T-S characteristics of the Florida Current, Parr's (1937) stations in the Straits of
Florida.
Sagitta helenae was found all over the continental shelf south of Cape Hatteras but it disappeared at the stations beyond the edge (Fig. 12). The greatest concentrations were found in the middle of the shelf where as many as 94 specimens per ten cubic metres were collected. This species is able to tolerate a rather wide range of salinity, varying from approximately 32 to 36^o,. Although present in the edge of the Florida Current at times, it was never found far inside the current proper, and it does not appear from these data that it is a true inhabitant of such water.
This species has been closely associated with continental shelf water from the Gulf of Mexico (Ritter-Zahony, 1910; Pierce, 1951, 1953) to Cape Hatteras. Apparently it disappears jusi north of the cape where the colder, less saline water is encountered over the shelf. Only a few specimens were taken near the edge of the shelf above Hatteras in the spring and winter cruises. Bigelow and Sears (1939) do not record this species in their plankton studies from Chesapeake Bay to Cape Cod. Because of its close relation to continental shelf waters from North Carolina southward, this species appears to be of special interest in its relation to the hydrography of this area. 1 he movement of Virginian Coastal water around Hatteras in January displaced this species from the inshore stations jn Raleigh Bay where it usually occurs (Fig. 12).
104
Dean F. Bumpus and E. Lowe Pierce
Table I
The distribution of chaetognaths by station during Caryn Cruise 64. Species arranged in approximate series with respect to saUnity, those which normally occur in coastal water on the left. Figures indicate number per 10 cubic metres of water strained
|
4: |
■^ |
||||||||||||
|
«i |
|||||||||||||
|
i 1 |
c^2 |
<5 ^ ^ -s: |
S |
■4. |
.5 5 S |
^5 |
3 .§. |
i 1 1 |
|||||
|
^ |
Q |
^ ^ |
^ |
oj |
'>j |
^ |
^ |
c/j ^ |
k |
i< |
a^ |
t2.s |
:x |
|
SECTION I— |
-WIMBLE |
SHOALS |
|||||||||||
|
165* |
014 |
82 |
48 |
51 |
8 |
134 |
71 |
||||||
|
166 |
019 |
23 |
14 |
19 |
3 |
1 1 |
60 |
98 |
|||||
|
0-40 |
111 |
6 |
44 |
3 |
3 |
120 |
72 |
||||||
|
SECTION II |
—RALEIGH BAY |
||||||||||||
|
193 |
0-20 |
18 |
47 |
56 |
140 |
113 |
|||||||
|
194 |
010 |
72 |
2 |
16 |
98 |
111 |
|||||||
|
195 |
015 |
7 |
2 |
8 |
8 |
6 |
3 |
1 |
39 |
114 |
|||
|
15-30 |
83 |
3 |
79 |
11 |
5 |
1 |
1 |
1 |
163 |
89 |
|||
|
196* |
0-30 |
10 |
1 |
1 |
11 |
90 |
|||||||
|
30-60 |
38 |
4 |
35 |
4 |
1 |
1 |
3 |
1 |
244 |
270 |
|||
|
197 |
0-80 |
46 |
2 |
8 |
18 |
3 |
100 |
131 |
|||||
|
80-160 |
11 |
6 |
1 |
1 |
30 |
158 |
|||||||
|
SECTION III — ONSLOW BAY |
|||||||||||||
|
182 |
012 |
9 |
1 |
7 |
73 |
||||||||
|
181 |
0-20 |
4 |
5 |
27 |
84 |
152 |
|||||||
|
180 |
0-15 15-30 |
35 40 |
1 1 |
10 46 |
65 140 |
141 161 |
|||||||
|
179 |
0-31 |
94 |
4 |
52 |
23 |
314 |
180 |
||||||
|
178 |
015 |
52 |
1 |
13 |
41 |
3 |
172 |
158 |
|||||
|
15-30 |
54 |
2 |
32 |
10 |
164 |
168 |
|||||||
|
177* |
0-50 |
67 |
1 |
6 |
62 |
1 |
1 |
11 |
208 |
138 |
|||
|
50-100 |
29 |
1 |
29 |
5 |
1 |
2 |
184 |
287 |
|||||
|
176 |
0-30 |
4 |
2 |
54 |
2 |
2 |
2 |
110 |
163 |
||||
|
30-62 |
43 |
15 |
8 |
41 |
5 |
138 |
122 |
||||||
|
175 |
0-90 |
137 |
3 |
12 |
121 |
3 |
16 |
150 |
51 |
||||
|
90-180 |
11 |
3 |
7 |
2 |
1 |
31 |
122 |
||||||
|
174 |
0-80 |
30 |
39 |
4 |
2 |
3 |
18 |
198 |
206 |
||||
|
80-160 |
3 |
2 |
5 |
1 |
1 |
2 |
7 |
44 |
278 |
||||
|
173 |
0-80 |
21 |
1 |
25 |
1 |
1 |
7 |
136 |
244 |
||||
|
80-160 |
1 |
1 |
4 |
1 |
1 |
17 |
300 |
||||||
|
172 |
0-75 |
3 |
1 |
5 |
4 1 |
1 |
1 |
24 |
207 |
||||
|
75-150 |
3 |
3 |
6 |
1 |
2 |
3 |
59 |
318 |
|||||
|
SECTION IV — ONSLOW BAY |
|||||||||||||
|
192 |
0-10 10-20 |
2 |
5 |
0 11 |
130 140 |
||||||||
|
191 |
0-13 |
54 |
1 |
25 |
65 |
81 |
|||||||
|
13-26 |
29 |
2 |
38 |
1 |
93 |
135 |
|||||||
|
190 |
016 |
23 |
30 |
3 |
39 |
70 |
|||||||
|
16-37 |
23 |
41 |
70 |
20 |
98 |
98 |
|||||||
|
189 |
0-20 |
102 |
6 |
10 |
16 |
2 |
114 |
84 |
|||||
|
20-40 |
48 |
8 |
94 |
7 |
194 |
124 |
|||||||
|
188* |
0-20 |
35 |
4 |
1 |
2 |
35 |
83 |
||||||
|
20-40 |
25 |
18 |
3 |
3 |
4 |
53 |
98 |
||||||
|
186 |
0-50 |
9 |
19 |
4 |
106 |
337 |
|||||||
|
50-100 |
1 |
1 |
1 |
2 |
1 |
1 |
23 |
385 |
|||||
|
185 |
0-65 |
30 |
24 |
2 |
2 |
3 |
184 |
297 |
|||||
|
65-130 |
5 |
10 |
8 |
1 |
5 |
111 |
332 |
||||||
|
184 |
0-70 |
10 |
16 |
1 |
3 |
8 |
90 |
235 |
|||||
|
80- 140 |
5 |
6 |
1 |
1 1 |
1 |
1 |
2 |
60 |
297 |
||||
|
183 |
0-80 |
9 |
19 |
2 |
1 |
7 |
89 |
231 |
|||||
|
80- 100 |
1 |
2 |
3 |
1 1 |
3 |
1 |
26 |
297 |
* One hundred fathom contour lies between this station and the next.
Hydrography and distribution of chaetognaths over the continental shelf off North Carolina 1 05
Table II The distribution of chaetognaths by station during Atlantis Cruise 1 96 Species arranged m approximate series with respect to salinity, those which normally occur in coastal water on the left. Figures indicate number per 10 cubic metres of water strained
|
"g. |
--, |
||||||||||||
|
i .2 |
^cpth of sai (metres) |
5; |
1 |
s |
i 5! |
3 1 |
1. |
.2 |
lal No. sample |
1. |
|||
|
^ |
Q |
^ |
^ |
^ |
^ |
^ |
^ |
^ |
^ |
< |
■< ^ |
^.s |
— |
|
SECTION V— |
-WIMBLE |
SHOALS |
|||||||||||
|
5126 |
0-30 |
47 |
72 |
1 S4 |
|||||||||
|
5127 |
0-20 |
21 |
2 |
1 |
34 |
1 _'*T 141 |
|||||||
|
5128 |
0-28 |
1 |
1 |
3 47 |
1^1 159 167 |
||||||||
|
5129 |
0-45 |
1 |
7 |
1 |
19 |
||||||||
|
5130* |
0-25 |
34 |
5 |
2 |
45 |
2 |
14*^ |
165 |
|||||
|
5131 |
0 100 |
7 |
3 |
43 |
|||||||||
|
SECTION VI |
—RALEIGH BAY |
||||||||||||
|
5141 |
015 |
1 |
98 |
• |
113 |
115 |
|||||||
|
5142 |
016 |
13 |
1 |
4 |
19 |
108 |
|||||||
|
12-24 |
1 |
8 |
1 |
8 |
29 |
169 |
|||||||
|
5143 |
020 |
78 |
16 |
14 |
2 |
30 |
6 |
3 |
241 |
161 |
|||
|
20-40 |
49 |
15 |
4 |
2 |
10 |
1 |
2 |
1 |
2 |
152 |
178 |
||
|
5144 |
0-50 |
9 |
3 |
1 |
1 |
17 |
1 |
1 |
2 |
64 |
193 |
||
|
50-100 |
8 |
3 |
1 |
21 |
1 |
1 |
4 |
79 |
208 |
||||
|
5145 |
015 15-30 |
33 2 |
1 1 |
11 |
4 1 |
13 |
5 |
3 |
3 |
95 5 |
142 120 |
||
|
5146 |
015 |
16 |
1 |
4 |
1 |
8 |
4 |
1 |
40 |
111 |
|||
|
15-30 |
11 |
3 |
7 |
1 |
4 |
26 |
97 |
||||||
|
SECTION VII — ONSLOW BAY |
|||||||||||||
|
5133 |
0 13 |
21 |
14 |
183 |
8 |
267 |
118 |
||||||
|
5134 |
019 |
59 |
30 |
66 |
7 |
2 |
401 |
185 |
|||||
|
5135 |
0-25 |
56 |
2 |
5 |
11 |
6 |
1 |
1 |
124 |
152 |
|||
|
5136 |
0-28 |
3 |
2 |
2 |
2 |
2 |
1 |
14 |
120 |
||||
|
5137 |
0-39 |
27 |
5 |
12 |
6 |
21 |
1 |
4 |
156 |
204 |
|||
|
5138* |
0-20 |
50 |
5 |
38 |
13 |
2 |
3 |
145 |
132 |
||||
|
20-40 |
9 |
1 |
3 |
1 |
TV |
147 |
|||||||
|
5139 |
0-50 |
166 |
3 |
6 |
2 |
31 |
1 |
3 |
6 |
174 |
156 |
||
|
50-100 |
25 |
6 |
23 |
3 |
3 |
78 |
129 |
||||||
|
5140 |
0-50 |
9 |
12 |
1 |
2 |
1 3 |
50 |
181 |
|||||
|
50-100 |
6 |
4 |
6 |
1 5 |
40 |
192 |
|||||||
|
SECTION VIII — LONG BAY |
|||||||||||||
|
5147 |
015 |
5 1 |
minute unidentified chaetognaths in ; |
sample |
5 |
167 |
|||||||
|
5149 |
015 |
83 |
10 |
68 |
3 |
97 |
59 |
||||||
|
5150 |
0-20 |
17 |
4 |
20 |
1 |
48 |
113 |
||||||
|
5151 |
0-24 |
13 |
3 |
50 |
2 |
89 |
133 |
||||||
|
5152 |
0-30 |
122 |
13 |
44 |
T |
9 |
1 |
1 |
265 |
137 |
|||
|
5153 |
5-30 |
89 |
1 |
22 |
1 |
5 |
19S |
168 |
|||||
|
5154 |
0-50 50-100 |
39 29 |
2 I |
1 1 |
13 5 |
1 1 |
3 1 |
69 S4 |
155 226 |
* One hundred fathom contour lies between this station and the nc\t.
Sagitio hispida is an inshore species which was taken at Stations 182. 5133, 5141 in water with a salinity of 31 to 35°/oo- No specimens were collected as far offshore as the ten-fathom lino. Other records (Pierce, 1951) indicate that this species is present in bays and at points close to shore south of Cape Hatteras.
Sagitta minima was taken many miles on either side of the continental slope (Fig. 12). It was not taken at the stations within the ten-fathom curve or at the stations farthest in the Florida Current.
106
Dean F. Bumpus and E. Lowe Pierce
- NUMBER PER 10 CUBIC METERS = 0 • = <I0 \
10-50
>50
. NUMBER PER 10 CUBIC METERS 0=0 • = <I0
• = 10-50
Fig. 12. Distribution of 5. enflata, S. helenae, S. minima, S. serratodentata, S. tenuis and P. draco, upper in May and June 1953, Caryn Cruise 64, lower in January 1954, Atlantis Cruise 196.
It was a common chaetognath over the shelf but seldom appeared in numbers as large as S. enflata, S. helenae, or S. serratodentata. It was somewhat more abundant in the spring than in the winter and was usually associated with water close to 36°/oo in salinity.
Sagitta serratodentata was one of the most abundant and widely distributed species found in these collections (Fig. 12). It covered the continental shelf in Carolinian and Virginian Coastal water from the ten-fathom line into the Florida Current as far as the stations extended. This species occurred commonly in numbers of 10 to 40 per ten cubic metres in both spring and winter and was noticeably more abundant near the edge of the continental shelf. Its distribution was similar to that of S. minima
Hydrography and distribution of chaetognaths over the continental shelf off North Carolina |07
except that it was almost invariably more numerous in samples taken near the surface than in the deeper samples at any given station. This was true for samples taken during the day as well as at night.
Sagitta tenuis was restricted to the continental shelf waters both north and south of Cape Hatteras (Fig. 12). It extended from within a few miles of shore to the edge of the shelf. Many more specimens were caught and their range from shore was greater in the winter than in the spring. This species is one of the more euryhaline forms in this area, having been found in water ranging from less than 31 to 36-6°/eo- It does not appear beyond the shelf where the Florida Current proper is encountered. Specimens were commonly found in greatest abundance at the less inshore stations. Like many other species in this area it was collected in water ranging in temperature from 9° to 25^ C and little can be said about its optimum temperature.
Krohnitta pacifica and K. subtilis were never very abundant in any of the tows. They ranged from midway over the shelf outward as far as the stations extended. K. subtilis was noticeably rarer than K. pacifica. No significant difference could be seen between shallow and deep hauls in terms of either species or abundance. These species were almost always found in water whose salinity was 36'';oo or above. They were therefore directly associated with the Florida Current water. In the winter when a large incursion of Florida Current water moved into Onslow Bay a number of specimens of A. pacifica were taken in this water about as far inshore as it extended.
Pterosagitta draco was always identified in these catches with the warm saline water of the Florida Current (Fig. 12). Although one of the less abundant species it was widely distributed and found at almost all stations from midway over the shelf seaward. This species was closely associated with K. pacifica in these samples.
Sagitta hexaptera and S. lyra were also represented in some of the samples taken well inside the Florida Current. They were markedly more abundant in the spring than in the winter. Only a few hexaptera were found in the winter cruise and no lyra. Because they were present in small numbers their affinities are not obvious.
DISCUSSION
Chaetognaths were common and important members of the plankton community in all parts of the area studied. As a general rule those stations closest inshore and farthest offshore had fewer species than those near the edge of the shelf. The increase in number of species is the result of some of the typically shelf forms such as S. tenuis and S. helenae being present with species normally found in the Florida Current proper. This probably is the result of mixing which augments the total number of
species in this area.
A comparison of the total number of chaetognaths collected at each station together with the abundance of each species shows surprisingly little difference between the spring and winter collections. The more abundant species such as S. enfiata and 5. senatodentata were abundant in spring as well as winter. S. tenuis was more abundant and widespread during the winter than in the spring. S. hexaptera was less numerous in winter, and S. lyra, an uncommon form in these collections was not found ai all
during the winter cruise.
Certain species of chaetognaths have been observed to exhibit diurnal vortical migration (Michael, 1911; Russell, 1933). In these cruises samples were taken at all hours. Position of the ship dictated when a sample would be taken rather than hour of the day or night. An inspection of these samples shows no consistent evidence for vertical migration or pronounced abundance of individuals in the shallow samples as compared with the deeper samples (Tables I and 11). S. tninuna in the spring samples is an exception and does appear to be significantly more abundant in ihc deeper
samples. ^ ,
All species of chaetognaths collected in the area surveyed are known to occur in tropical and subtropical waters. None were typically Virginian (Table HI). Published
108 Dean F. Bumpus and E. Lowe Pierce
records do not show that S. helenae, S. hispida and S. tenuis are found over the con- tinental shelf much farther north than Cape Hatteras. 5'. minima was found in the slope water over Block Canyon off Long Island in October 1952.* S. serratodentata in addition to being found in Florida Current, Carolinian and Virginian Coastal water, is found in Virginian and Boreal Slope waters (Bigelow and Sears, 1939; Clarke, Pierce and Bumpus, 1943; Redfield and Beale, 1940; Huntsman, 1919).
Table III Distribution of chaetognaths with respect to water types*
Florida Current Carolinian Virginian
S. bipunctata
S. enflata S. enflata
S. helenae
S. hispida S. minima S. minima S. minima
S. serratodentata S. serratodentata S. serratodentata
S. tenuis S. tenuis
K. pacifica K. subtilis P. draco S. hexaptera S. lyra
* No inference is made that these chaetognaths are indicators of the above water types, see text.
The Virginian Coastal water in the area just north of Cape Hatteras had relatively few chaetognaths present and none which could be selected as indicators of that water type. S. elegans, which occurs in abundance farther north in coastal water was observed by Bigelow and Sears (1939) to diminish in numbers in the offing of Chesa- peake Bay. None were found in either of the Wimble Shoal sections in the present study. The higher temperature found in the southern portion of its range may be a limiting factor. Cowles (1930) reports it in Chesapeake Bay in salinities as low as
137oo.
The presence of a barrier to the southward movement of plankton in the Hatteras area is not as clearly demonstrated by the chaetognath distribution as one would expect in comparison with the hydrographic evidence. This is due to the lack of Virginian indicator species. f Evidence of the breaching of the barrier as far as Raleigh Bay in January 1954 is provided by the absence of the truly Carolinian species of chaetognaths, Sagitta enflata and S. helenae, at the inshore stations. Their distribution is compatible with the hydrographic evidence.
The occurrence and distribution of chaetognaths described in this study is in substantial agreement with the earlier investigation (Pierce, 1953). Pierce's Zones I and II have been labelled Carolinian Coastal water. The difference between Zones I and II is a matter of dilution with river effluent. Zone III remains as unmodified Florida Current water. As was found to be the case in the earlier collections, the largest number of species was taken near the outer part of the continental shelf.
* Personal communication from Dr. Richard Backus.
t The distribution of other elements of the plankton communities sampled in these collections is being examined by Philip St. John, a student at Harvard College.
Hydrography and distribution of chaetognaths over the continental shelf off North Carohna 1 09
The sources of Carolinian Coastal water are now better understood than heretofore. Mixing of Florida Current water with Carolinian Coastal water may be confined to the outer shelf zone or may occur over broad parts of the shelf. This is occasioned by the intrusion of the Florida Current up the slope along the bottom and across the shelf, penetrating more deeply into one bay than another. Occasional winter storm- driven indrafts of Virginian Coastal water may temporarily convert the inner part of Raleigh Bay from a warm, highly saline environment, to a cold, less saline one.
REFERENCES
BiGELOW, H B. (1933), Studies of the waters on the continental shelf, Cape Cod to Chesapeake Bay
I. The cycle of temperature. Pap. Phvs. Oceanogr. Meteor., 2 (4), 135 pp BiGELOw, H. B. and Sears, M. (1935), Studies of the waters on the continental shelf, Cape Cod to
Chesapeake Bay. II. Sahnity. Pap. Phvs. Oceanogr. Meteor., 4 {\),9A^p BiGELOW, H. B. and Sears, M. (1939), Studies of the waters on the continental shelf. Cape Cod to
Chesapeake Bay. III. A volumetric study of the zooplankton. Mem. Mus. Comp. Zool. Harvard
Co//.. 54 (4), 183-378. BuMPus, D. F. (1955), The circulation over the continental shelf south of Cape Hatteras. Trans.
Amer. Geophys. Un., 36 (4), (In press). Clarke, G. L. and Bumpus, D. F. (1950), The plankton sampler— an instrument for quantitative
plankton investigations. Amer. Soc. Limn. Oceanogr., Spec Pub., No. 5, 1-8. Clarke, G. L., Pierce, E. L. and Bumpus, D. F. (1943), The distribution and reproduction o^ Sagitta
elegans on Georges Bank in relation to the hydrographic conditions. Biol. Bull.. 85 (3). 201-226. CowLES, R. F. (1930), A biological study of the offshore waters of Chesapeake Bay. Bull. U.S. Bur.
Fish., 46, 2n-3Sl. FuGLiSTER, F. C. (1949), Average monthly sea surface temperatures of the Western North Atlantic
Ocean. Pap. Phys. Oceanogr. Meteor., 10 (2), 25 pp. Huntsman, A. G. (1919), Biology of Atlantic water of Canada. Some quantitative and qualitative
plankton studies of earlier Canadian plankton. III. A special study of Canadian chaetognaths.
their distribution, etc., in the waters of the eastern coast. Canad. Fish. Exped., 1914-15, Dcpt. Saval
Sci., 421-485. Johnson, C. W. (1934), List of marine molluscs of the Atlantic coast from Labrador to Texas. Proc.
Boston Soc. Nat. Hist., 40 (1), 1-203. Michael, E. L. (1911), Classification and vertical distribution of the chaetognaths of the San Diego
region including some re-descriptions of some doubtful species of the group. Uniw Calif. Pub.
Zool., 8 (3), 21-86. Miller, J. E. (1946), Cyclogenesis in the Atlantic coastal region of the United States. J. Meteor., 3,
31^14. New York University (1954), Monthly frequencies of cyclogenesis in the east coastal region of the
United States. In: Notes on cyclonic developments in the United States. Tech. Pap. No. 2,
Project SCUD, College of Engineering, Research Division. (Unpublished manuscript). Parr, A. E. (1933), A geographical-ecological analysis of the seasonal changes in temperature con- ditions in shallow water along the Atlantic coast of the United States. Bull., Bingham Oceanogr.
Coll., 4 (3), 1-90. Parr, A. E. (1937), Report on hydrographic observations at a series of anchor stations across the
Straits of Florida. Bull., Bingham Oceanogr. Coll., 6 (3), 1-62. Pearse, a. S. and Williams, L. G. (1951), The biota of the reefs off the Carolinas. Elisha Mitchell
Sci. Soc, 67, 133-161. Pierce, E. L. (1951), The chaetognaths of the west coast of Florida. Biol. Bull., 100 (3), 206-228. Pierce, E. L. (1953), The chaetognaths over the continental shelf of North Carolina with attention
to their relation to the hydrography of the area. J. Mar. Res., 12(1), 75-92. Redfield, a. C. and Beale, A. (1940), Factors determining the distribution of populations of chaeto- gnaths in the Gulf of Maine. Biol. Bull., 79, 459-487. Ritter-Zahony, R. von (1910), Westindische Chaetognathcn. Zool. Jb., Suppl. 11.2. 133 143. Russell, F. S. (1933), On the biology of Sagitta IV. Observations on the natural history of Sagitia
elegans Verrill and Sagitta setosa J. Mullcr in the Plymouth area. J. .Mar. Bud. .Lisoc. U.K..
N.S., 18 (2), 559-574. _, ^ , , n r . v. .w
Sutcliffe, W. H., Jr. (1950), Qualitative and quantitative study of zooplankton at Bcautort. North
Carolina. Thesis submitted to Duke University. .- u ^- .r
VON Arx, W. S., Bumpus, D. F. and Richardson, W. S. (1955). On the fine structure ot the Gulf
Stream hont, Deep-Sea Res., 3 (\), 46-65. ^ , , i., u .- r
Williams, L. G. (1948), Seasonal alternation of marine floras at Cape Lookout, North Carolina.
Amer. Jour. Bot., 35 {\0),6S2-695. v, u r- r d // r
Williams, L. G. (1949), Marine algal ecology at Cape Lookout, North Carolina. Bull.. Furman
C/mv., 31 (5), i-21.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 1 10-114.
Experimental feeding of the copepod Calanus finmarchicus (Gunner) on phytoplankton cultures labelled with radioactive carbon (^*C)
By S. M. Marshall and A, P. Orr The Marine Station, Millport
Summary — A small number of experiments were made on phytoplankton cultures labelled with ^*C; they confirmed earlier results obtained when using ^^P. With female Calanus the volume filtered varied from about 1 -40 ml per day, and the digestion of a diatom and two flagellates lay between 50 and 80 %. Since both carbon and phosphorus are important constituents of the algal cell, it is fair to assume that the major part of the organic material is digested. It may be concluded therefore that, during a period of diatom abundance in the sea, most of the food ingested is utihzed.
Qualitative WORK on the feeding of Ca/a«M5 (Dakin, 1908; Esterly, 1916; Lebour, 1922; Marshall, 1924) has shown that it can ingest most of the small organisms present in the marine plankton, but that its diet consists predominantly of diatoms. It is possible that small naked flagellates are also important as food, but, since they have no indigestible skeleton, they can rarely be recognized in the gut, and not at all in the faecal pellets.
It has been possible to measure the quantity of different food organisms consumed by counting the numbers of these in a known volume of culture before and after a known period of feeding (Clarke and Gellis, 1935; Fuller and Clarke, 1936; Fuller, 1937; Clarke and Bonnet, 1939; Gauld, 1951). The earlier workers obtained values for the volume of water filtered of a few ml per day, but Gauld obtained an average of about 70 ml per day, using cultures of Dunaliella sp. (Chlamy- domonas).
Recently some experiments have been carried out by Marshall and Orr (1955) on feeding Calanus with cultures of diatoms and flagellates labelled with radioactive phosphorus (*^P). These cultures were grown with a limiting quantity of phosphorus present, and were in most cases used after the phosphorus had been almost entirely taken up by the organisms. The initial concentration of ^^P in the culture was measured as well as that present at the end of the experiment in the body, faeces and eggs laid (if any). It was then possible to calculate the volume swept clear by the Calanus in 24 hours. This varied from less than 1 ml up to about 40 ml with a maxi- mum in a single instance of a little over 80 ml.
The digestion of most of the food organisms was unexpectedly complete, the figures being usually over 60 % and often over 90 %. With a few organisms only was it appar- ently very low. It was high even when the Calanus were feeding rapidly in rich concentrations of food cells. These experiments show therefore that the phosphorus- containing portion of the algal cell is readily assimilated.
It seemed possible that the high digestion figures might be misleading, since various workers have shown that the phosphorus in algal cells is partly labile, and that this fraction may be either adsorbed on the cell surface or present in inorganic solution within the cell (Gest and Kamen, 1948; Kamen and Spiegelman, 1948; Goldberg,
110
experimental feeding of copepod Calanus finmarchicus (Gunner) on phytoplankton cultures 1 1 I
Walker and Whisenand, 1951; Rice, 1953). The error is not likelv to be large for Rice has shown that in cultures a week old with a low phosphorus concentration only about 2 % is exchangeable. Most of our cultures were used when more than a week old, and when the phosphorus in solution had fallen to a low value.
It was, however, thought advisable to measure the digestion of some of the same organisms labelled with other radioactive isotopes. One of the most important elements in the plant cell is carbon, and by growing cultures using ^^C it was possible to measure the uptake and digestion in a way similar to that used with phosphorus.
There are certain disadvantages in the use of "C which are not met when using ^^p. Carbon is present in sea water as carbonate, bicarbonate and CO^, and it is never limiting so that the plant cells cannot be expected to remove all the carbon present. The cells have therefore to be removed and re-suspended in non-radioactive water before use. Again carbon is liberated as CO2 in respiration while the culture is growing, and also during the experiments, and although the value of this second figure may be small it will reduce the amount apparently used.
METHODS
The method adopted was in general similar to that used in the earlier experiments with radioactive phosphorus. The cultures were grown in sterile 250 ml conical flasks, to which were added 100 ml Erdschreiber culture medium and 50 ml of algal culture. The radioactive carbon was added in the form of bicarbonate, and 50 i^c was found to be a convenient quantity for this volume of culture medium. The flasks were kept airtight by means of rubber stoppers to avoid possible loss of '^C to the air as COj. The cultures were allowed to grow either in diff'use daylight or close to a fluorescent tube. They grew rapidly and well, and took up an unexpectedly high proportion (over 50",,) of the added ^^C in a fev,' days. For use in an experiment the culture was centrifuged at about 2500 r.p.m. for five minutes, the supernatant liquid decanted, membrane-filtered sea water added, and the organisms dispersed. This process was repeated twice more, and the cells finally suspended in mem- brane-filtered sea water in a dilution suitable for the experiment. For filtering the sea water a Gradocol membrane was used with an average pore diameter of about Q-9\j..
Since the (3-radiation of ^^C is relatively weak and readily absorbed, it is necessary either to correct for absorption or to make all the samples tested strictly comparable.
The second procedure was adopted. The methods used are discussed by Calvin, Heidelbergpr, Reid, Tolbert and Yankwich (1949). For sea water samples, uniform flat-bottomed dishes (plan- chettes) of 25 mm diameter were used. With a 0-2 ml delivery pipette the sample was put in the middle of the planchette and one drop of N/10 NaOH added. A circle of lens tissue of a diameter slightly less than the bottom of the planchette was then laid on the sample to spread the drop evenly so that, on drying, a layer of uniform thickness would be obtained. Drying was carried out on a hot plate. An attempt was made to increase the accuracy by using 0-5 ml instead of 0-2 ml, but it was unsuccess- ful because the self-absorption was relatively greater than with 0-2 ml, and the samples dried less uniformly.
The object of adding the NaOH was to avoid the exchange of CO.> between the air and the bicar- bonate of the sea water. If this procedure is not adopted, there may be a serious loss, and variable results will be obtained (Calvin, et ai, p. 123). The lens tissue should not be silicone treated, since this type tends to curl up on drying. There was no tendency to curl with the photographic Ions tissue used, so that the addition of collodion was unnecessary.
To ensure that no change in absorption of the radiation was caused by variations in salinii\. the same sample of sea water was used throughout the experiments.
The activity of each sample was measured by exposing it in a holder at a constant distance from the mica end-window of a G.-M. counter, and the counts were recorded on a scaling unit. The results are expressed as counts per minute, but since we know the concentration of cells in the culture and the activity of both whole culture and filtrate, we can also express them as cell equivalents.
The bodies and faecal pellets of the Calanus have an appreciable self-absorption, and even after they had been torn up by needles the losses were considerable. Good duplicates were obtained by
1 ] 2 S. M. Marshall and A. P. Orr
the use of a small disintegrator. This consisted of a narrow tube (diameter 9 mm) about 7 cm long, into which was fitted a perspex piston of almost the same diameter as the tube, and shaped at the foot to fit the bottom of the tube. The Calanus or the faecal pellets were put in the tube in about 0-5 ml of sea water, and the piston rotated by a small motor. By raising and lowering the tube the water and the Calanus or faecal pellets were forced past the rotating piston and thus disintegrated. After washing down the piston and tube and making the volume up to 3 ml, five aliquot samples were taken for measurement of activity. Microscopical examination showed that disintegration was almost complete. No fragments of a Calanus body could be recognized, and there were very few recognizable bits of faecal pellet. The disadvantage of the disintegration method is the dilution of the activity, since only 0-2 ml samples were used from the 3 ml of fluid. This can be countered by taking more sub-samples, or by making much longer counts.
In a feeding experiment a number of bottles of about 70 ml capacity were filled with the diluted culture prepared as described, and sampled for a count of cell number and activity. Into each bottle was introduced a single Calanus. Since females feed better than either Stage V or male Calanus they were always used. Each bottle was then tied in a black cloth bag (because Calanus feeds better in the dark than in the light), and attached to a wheel revolving about once every three minutes in a vertical plane. This keeps the culture cells from sinking to the bottom and so giving the Calanus an accumula- tion to feed on. Control bottles containing filtrate from the culture used were also set up to measure any uptake of ^*C from solution. Other control bottles, containing culture but no Calanus, were used to measure the^*C returned to solution by the respiration of the plant cells.
After leaving them to feed for a suitable time, usually 15 to 18 hours, each Calanus was removed, washed three times to free it from radioactive water, disintegrated and sampled. The contents of the bottle were then poured into a flat-bottomed perspex dish with the inside angles bevelled, and the faecal pellets picked out under a binocular microscope. These too were washed, disintegrated, and sampled and their activity was measured.
The activity of the Calanus body added to that of the faecal pellets gives a measure of the total i*C removed from the culture. From these and the culture reading can be calculated the number of cells ingested, the percentage digested and the volume of water swept clear. The results can be expressed either as counts per minute or as cell equivalents. The cell equivalent is a useful figure when consider- ing the total amount taken up, but if we express the activity of the faecal pellets as cell equivalents, it must be remembered that each " cell equivalent " really represents several cells, the number varying according to the percentage digested.
EXPERIMENTAL WORK
Feeding experiments with female Calanus were made, using cultures of the diatom Skeletonema costatum, one of the more important spring diatoms in the sea, and the flagellates Cryptomonas sp. (Plymouth strain 23) and Syracosphaera carterae. The cultures when used were only a few days old, and were probably in the exponential growth phase. It was thought that some of the "C might be present in the inorganic form, either adsorbed on the cells or in solution inside. This was tested with Skele- tonema by exposing samples on planchettes to the fumes of hydrochloric acid (Steemann Nielsen, 1952), and comparing the activity before and after exposure. About 7 % of the total disappeared with this treatment. With Syracosphaera, which possesses large numbers of calcareous coccoliths, the loss seemed to be greater but accurate measurements were not made.
The control bottle containing culture but no Calanus showed that, as a result of the respiration of the plant cells, the i*C content of the filtrate had risen by 2-5%. This will cause a slight underestimate of the amount taken up by the Calanus.
A preliminary experiment was done with a culture of Skeletonema costatum in two different concentrations. It was thought that the activity of the faecal pellets and, in the lower concentrations, of the bodies also, would be too weak for the disintegra- tion method, so they were torn up as finely as possible with needles and put in 0-2 ml
Experimental feeding of copepod Calanus finmarchicus (Gunner) on phytoplankton cultures 1 ] 3
Of sea water on a planchette. Owing to self-absorption, this was not a satisfactory method, giving results which were too low, and it was therefore impossible to calculate the percentage digested. If we assume that this is the same as in a later experiment (see Table I), a figure can be obtained for the volume filtered which will be approximately correct for the richer concentration but minimal for the weaker. The estimated volume filtered in 24 hours in a concentration of 106,000 Skeletonema cells per ml varied from 1-6 to 40 ml in 24 hours, and in a concentration of 10,600 cells per ml from 5-7^2-5 ml. It is usual to find that in high concentrations of food cells filtration falls off, and the figures obtained compare well with our earlier experiments using '^?.
Table I Feeding experiments with Calanus using cultures grown with "C
Species
Concentratiuns
Cal- anus
o
Time of
expt. in
hours
iFaecal pellets
I No
Skeletonema
costatum Culture
Filtrate
Cryptomonas Culture
Filtrate
1615 counts ml min 144000 cells ml 001 counts cell
35 counts/ml /min
1
T
3 4 5 A B
I7i 17-1 \1\ Ml 17*
1275 counts /ml /min 12600 cells ml 010 counts cell
60 counts/ml/min
1
2 3 4 5 A B
in in
in
in
21i
m in
54
17
47
0
10
4
0
Syracosphaera
carterae Culture Filtrate
840 counts/ml/min 1
13500 cells/ml 2
0 06 counts 'cell 3
8 counts ml min A
|
17 |
65 |
|
17 |
38 |
|
17 |
45 |
|
17 |
0 |
38 51 80 56
57 2
Lost
Body Total I less removed Countsfiltrate, c min | Imin cimin '
ml °o filtered used in 24 hr
lis
192 301
59 36
170
465 449 220 516
817 283 673 0 119
}«.
1095
475
974
0
178
74-6 59-6 69- 1
090 0-38 0-81
66-9 0 14
289
86
392
|
585 |
755 |
77-5 |
0-66 |
|
780 |
1245 |
62-7 |
110 |
|
811 |
1260 |
64-4 |
113 |
|
454 |
674 |
67-4 |
0-58 |
|
589 |
1105 |
53-3 |
0-98 |
|
0 |
|||
|
0 |
1 |
||
|
930 |
I2I9 |
76-3 |
2 07 |
|
180 |
266 |
67-7 . |
0-45 |
|
885 |
1277 |
69-3 |
216 |
|
30 |
The results of a second experiment with Skeletonema are shown in Table I. In this and subsequent experiments all the bodies and faecal pellets were disintegrated. As is usual in feeding experiments, individual variation was considerable; the number of faecal pellets varied from 10-54, and one Calanus did not feed at all. The amount digested varied from 60-75%, a figure very similar to that obtained with cultures labelled with ^^P. Unfortunately the Calanus v/ere in poor condition and the volume filtered, less than 1 ml in 24 hours, was low. The activity of the culture was not high enough to give very accurate results. In both experiments with Skeletonema, the cell concentration was high compared with what is found in the sea.
In an experiment with Cryptomonas, which has cells about 20ix long, all the females fed well, although they filtered on an average only about I ml in 24 hours (Table 1). The digestion ranged from 53-78%, as compared with 51-89% in cultures labelled with 3 2p.
Finally, the experiment with Syracosphaera was carried out using three Calanus in a concentration of 13,500 cells/ml. Judging by faecal pellet production, they fed
114 S. M. Marshall and A. P. Orr
well, but the maximum volume filtered was just over 2 mi in 24 hours (Table I). The digestion (68-76%), was decidedly lower than that found using Syracosphaera labelled with ^'^p^ in which it was usually over 90%. This may be due to the presence on its surface of a layer of coccoliths which would contain "C in the form of calcium carbonate.
The rate of production of faecal pellets was not high in any of the experiments with ^*C, the most rapid being found in a Calanus in Skeletonema culture, which produced an average of one every twelve minutes. It has been found that even with a much more rapid production, digestion of the phosphorus-containing fraction remains high.
ACKNOWLEDGEMENTS
The experiments with ^*C labelled cultures were carried out at The Laboratory, Plymouth, and we are very grateful to the Director and staff for their help. More especially we wish to thank Dr. H. W. Harvey and Dr. B. C. Abbott for their advice and assistance, and Dr. M. W. Parke and Miss D. Ballantine for supplying us with cultures.
REFERENCES
Calvin, M., Heidelberger, C, Reid, J. C, Tolbert, E. M. and Yankwich, P. F. (1949), Isotopic
carbon. New York and London, 376 pp. Clarke, G. L. and Bonnet, D. D. (1939), The influence of temperature on survival, growth and
respiration of Calanus finmarchicits. Biol. Bull., 76, 371-383. Clarke, G. L. and Gellis, S. S. (1935), The nutrition of copepods in relation to the food cycle of the
sea. Biol. Bull., 6S, 231-246. Dakin, W. J. (1908), Notes on the alimentary canal and food of the Copepoda. Int. Rev. HydrobioL,
1, 772-782. EsTERLY, C. O. (1916), The feeding habits and food of pelagic copepods and the question of nutrition
by organic substances in solution in the water. Univ. Calif. Pubi, Zool., 16, 171-184. Fuller, J. L. (1937), Feeding rate of Calanus finmarchicus in relation to environmental conditions.
Biol. Bull, 72, 233-246. Fuller, J. L. and Clarke, G. L. (1936), Further experiments on the feeding of Calanus finmarchicus.
Biol. Bull., 70, 308-320. Gauld, D. T. (1951), The grazing rate of planktonic copepods. /. Mar. Biol. Assoc, U.K., 29, 695-
706. Gest, H. and Kamen, M. D. (1948), Studies on the phosphorus metabolism of green algae and purple
bacteria in relation to photosynthesis. J. Biol. Chem., 176, 299-318. Goldberg, E. D., Walker, T. J. and WmsENAND, A. (1951), Phosphate utilization by diatoms.
Biol. Bull., 101, 274-284. Kamen, M. D. and Spiegelman, S. (1948), Studies on the phosphate metabolism of some unicellular
organisms. Svmp. Quant. Biol., Cold Spring Harb., 13, 151-163. Lebour, M. V. (1922), The food of plankton organisms. /. Mar. Biol. Assoc, U.K., 12, 644-677. Marshall, S. M. (1924), The food of Calanus finmarchicus during 1923. /. Mar. Biol. Assoc, U.K.,
13, 473-479. Marshall, S. M. and Orr, A. P. (1955), Studies on the biology of Calanus finmarchicus. VIIL Food
uptake, assimilation and excretion in adult and Stage V Calanus. J. Mar. Biol. Assoc, U.K., 34,
495-529. Nielsen, E. Steemann (1952), The use of radio-active carbon (C") for measuring organic production
in the sea. /. du Cons., 18, 117-140. Rice, T. R. (1953), Phosphorus exchange in marine phytoplankton. U.S. Fish and Wildlife Serv.,
Fish. Bull., 54 (80), 75-89.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 115-133.
The hydrography of the Gulf of Venezuela
By Alfred C. Redfield
Woods Hole Oceanographic Institution
and
Department of Biology
Harvard University
One of the very distinguished contributions of Henry B. Bigelow to the subject of oceanography is his study of the hydrography, plankton, and and fishes of the Gulf of Maine. It is the most complete description and analysis which exists of any circumscribed body of coastal water. Because of its breadth of outlook and high technical standard, this work is a model for studies in marine ecology. It is appropriate to contribute to this volume in Professor Bigelow's honour a sketch of the hydrographic conditions which are found in another gulf of somewhat similar pro- portions, but under far different influences than those which dominate the Gulf of Maine.
Summary — The distribution of salinity, temperature, oxygen, and total phosphorus in the Gulf of Venezuela is described.
The physical circulation appears to consist of two estuarine cells. The first is generated by the outflow from Lake Maracaibo, which terminates in a mixing zone over the sill off Calabozo Bay. where the water which occupies the deeper basin of the Bay is formed. The second is fed by water formed in this mixing zone which escapes seaward after mingling with more saline water drawn in from subsurface layers of the Caribbean.
The semi-diurnal components of the tide are augmented by resonance in the Gulf of Venezuela, and with the wind account for the vertical mixing which occurs over the sill of Calabozo Bay.
The trade winds, which predominate in winter, produce large seasonal differences in mean sea level across the Gulf, and control the distribution of the brackish water as it moves seaward from the outlet of Lake Maracaibo. Upwelling, which occurs in the lee of the Peninsula of Paraguana. is accompanied by an accumulation of phosphorus and a depletion of oxygen in the deep water near the coast. Similar conditions are found in the basin of Calabozo Bay.
The influence of countercurrents on the biochemical circulation is discussed.
The Gulf of Venezuela lies in the seaward extension of the syncline which fornix the Maracaibo Basin. It opens directly on the deep water of the Caribbean Sea, and carries into it the entire outflow from Lake Maracaibo. This is the most substantial accession of fresh water along the Venezuelan coast of the Caribbean, and is estimated at 21 billion cubic metres per year. The northeast trades blow steadily along the axis of the Gulf from December through April. The annual range in temperature is small, being about 2° C at Maracaibo. Being situated in 12^ N latitude the Corioli parameter is weak. Differences in salinity and the winds thus dominate the hydrography ol' the Gulf.
* Contribution No. 776 of the Woods Hole Oceanographic Institution
115
116
Alfred C. Redfield
The Gulf may be divided into two parts: the Outer Gulf and Calabozo Bay. These regions are separated by a sill with depths of 18 metres, extending along the 71st meridian. West of the sill a basin 28 metres in depth occupies the northern half of Calabozo Bay. East of the sill the bottom of the Outer Gulf slopes downward to provide depths of 40 to 80 metres over a considerable area. Access to the Gulf is probably limited to Caribbean water from depths not greater than 100 metres (Fig. 1).
The only earlier observations on the Gulf of which I am aware are measurements of
72° 71° 70"
Fig. 1. Bathymetric chart of Gulf of Venezuela. Based on H.O. No. 5520 — Depths in metres
surface salinities across the Gulf in December 1953 by Gessner (1953 b, 1955), and a few records of chlorinity off the entrance to Lake Maracaibo by the Corps of Engineers, U.S. Army (1938). Undocumented statements relative to the water of Lake Maracaibo and its approaches, and on tide levels in the Gulf, are based on information secured by the Woods Hole Oceanographic Institution in the course of studies which it is expected to publish subsequently. These studies were made for the Creole Petroleum Corporation, which has graciously consented to the use of this information. The outflow of Lake Maracaibo was estimated from climatological data by Douglas B. Carter of the Johns Hopkins University Laboratory of Climatology (Carter, 1954). The greater part of the data to be discussed was secured by the Atlantis between December 7 and 9, 1954. Three sections across the Gulf and two extending seaward from the adjacent capes provide information on the distribution of temperature,
The hydrography of the Gulf of Venezuela
117
salinity, oxygen, and total phosphorus content (Fig. 2). I am greatly indebted to L. V. WoRTHiNGTON and W. G. Metcalf who secured this data and to Nathaniel CoRWiN who analyzed the samples for total phosphorus, using the method of Harvey (1948).
The data secured by the Atlantis are presented in Figs. 3 to 6, which show the distribution of the variables in the five sections occupied. Fig. 7 shows their distribu- tion in a section along the axis of the Gulf.
ir 71" 70"
Fig. 2. Position of hydrographic stations, sections and tide stations
THE PHYSICAL CIRCULATION The Axial Circulation
The more general features of the circulation are shown by the distribution of properties along the axis of the Gulf (Fig. 7). The distribution of salinity is especially informative, since the fresh-water outflow from Lake Maracaibo serves as an indicator of the water movements.
In Calabozo Bay the circulation is estuarine. Along the western shore the outflow from the Lake produces a thin layer of brackish water of salinity less than 15\,^. As this water moves seaward the salinity of the surface layer increases gradually to about 30°/„^ over the sill. A rather sharp halocline at about 15 metres separates the surface layer from water having salinities greater than 307oo which occupies the deeper basin.
118
Alfred C. Redfield
Over the sill, and on its seaward slope, there appears to be a zone of eflfective mixing, in which the surface water from the Bay mingles with the Caribbean water from the Outer Gulf. In this zone the salinity increases from 30 to >35°J^^ and does not vary greatly with depth. On one side this mixing zone produces the bottom water of
SW 5238 5237 5236 NE
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SALINITY , 7oo
Fig. 3. Distribution of salinity in Sections 1-V, Gulf of Venezuela. See Fig. 2 for positions
The hydrography of the Gulf of Venezuela
19
Calabozo Bay which, flowing westward as a countercurrent, suppHes the salt consumed in diluting the outflow from the Lake. On the other side it produces a mixture so similar to the superficial layers of the Caribbean that its identity can be recognized only with difliculty.
SW 5238 5237 5236 NE
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Fig. 4. Distribution of temperature in Sections I-V, Gulf of Venezuela. See Fig. 2 for positions
120
Alfred C. Redfield
The distribution of temperature supports the above interpretation. The coolest surface water is found in the brackish outflow from the Lake. The surface water of Calabozo Bay warms as it moves toward the sill, where the warmest water and an almost uniform vertical distribution of temperature is found. The water of Calabozo
SW 5238 5237 5236 NE
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OXYGEN , mVl
Fig. 5. Distribution of oxygen in Sections I-V, Gulf of Venezuela. See Fig. 2 for positions
The hydrography of the Gulf of Venezuela
121
Bay below the halocline is warmer (>28° C) than any other water in the region. This water cannot have arisen by direct advection from the deeper water of the Outer Gulf, which is colder and more saline.
Data from the files of the U.S. Hydrographic Office show that the mean monthly
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TOTAL PHOSPHORUS , xo^/l
Fig. 6. Distribution of total phosphorus in Sections I-V, Gulf of Venezuela. See Fig. 2 for positions
122 Alfred C. Redfield
temperature of the surface water of the Outer Gulf is at a maximum of 28-2° C in October, and falls to a minimum of 25-3° C in February. In December the mean value is 27-0° C, corresponding closely to the present observations. The high tempera- ture of the deeper water of Calabozo Bay may be considered to have been acquired some months previously, when this water was formed in the mixing zone over the sill. The distribution of phosphorus and oxygen also shows the stratification arising from the estuarine circulation of Calabozo Bay, the similarity of the water in the Outer Gulf to that in the Caribbean, and the independence of the deeper water of Calabozo Bay from that east of the sill. These properties are dependent on biological processes as well as on the physical circulation, and will be considered in more detail below.
The Horizontal Circulation
The distribution of properties in the several sections across the Gulf (Figs. 3-6) and in the surface diagrams (Figs. 8-11) shows no evidence that the brackish outflow from Lake Maracaibo is deflected to the right by the Corioli force, as is so frequently the case in the estuaries of higher latitudes. The water of low salinity formed at the outlet of Lake Maracaibo occupies a crescentic band along the western margin of Calabozo Bay (Fig. 8). The eastward extent of this band along the southern shore of the Gulf is not defined by the data. Along the northern shore it terminates abruptly in a convergence at 71° 30' W. The Secchi disk showed an abrupt change in the transparency of the water across this convergence. This general distribution is reflected by the temperature and phosphorus content of the surface water.
Observations by the Corps of Engineers, U.S. Army (1938) show a northwesterly set of the alongshore currents off" the outlet of the Lake, supporting the view that surface water is being transported at that point toward the western end of the Bay. The Saihng Directions for the West Indies (U.S. Navy Hydrographic Office, 1949) on the other hand state that a current, which sets south-westerly along the coast of the Peninsula of Guajira, turns eastward to flow along the southern coast of Calabozo Bay as far as Punta Penas (70° 30' W), where it turns northward and is dissipated in the middle of the Gulf. A south-westerly set is described along the eastern shore of the Outer Gulf. This account indicates a convergence on the side of the Gulf opposite to that inferred from the Atlantis observations.
It seems probable that the north-east trade winds drive the brackish water formed at the outlet of Lake Maracaibo into the western end of the Bay, and tend to hold it against the shore. Escape is affected by alongshore currents, as discussed by Living- stone (1954). These currents appear to follow the coast of the Peninsula of Guajira until it turns northward, where they meet water moving into the Gulf along that shore, and both currents are deflected toward the middle of the Bay. Doubtless complex eddies exist throughout the Bay, but no pattern is revealed by the observations, nor any special path by which the fresh water works its way seaward. It may be that, as the trade winds slacken in summer, the brackish outflow from the Lake turns eastward under the Corioli influence, and sets up the pattern described in the Sailing Directions.
Although the water in the Outer Gulf resembles that in the Caribbean closely, small differences in temperature and salinity reveal the final steps in the escape of lake water to the Sea. Upwelling appears to occur along the Paraguana coast, as shown by the slope of the isohalines in Sections I and III, Fig. 3. This gives rise to a band of surface water having salinities higher than that found off'shore, which extends north-
The hydrography of the Gulf of Venezuela
123
|
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276
TEMPERATURE , *C
45
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Fig. 7. Distribution of salinity, temperature, oxygen,[and total phosphorus in Section A-A along
axis of Gulf of Venezuela. See Fig. 2 tor positions
124
Alfred C. Redfield
westward from the Peninsula of Paraguana. It provides a component which, when mixed with water from Calabozo Bay, forms a mass of water slightly colder and less saline than the water of the Caribbean. This mass may be traced as it flows west- wards close to shore around the Peninsula of Guajira (Fig. 8). The Sailing Directions report a westerly set of 1 -75 knots off this headland during the greater part of the year. In summary, the physical circulation of the Gulf of Venezuela appears to consist of two estuarine cells, separated by a transition zone of vertical mixing. The surface outflow of the inner cell is fed by water escaping from Lake Maracaibo, and is con- sumed in the mixing zone over the sill. This zone is the source of the deep counter-
72" 7r 70"
Fig. 8. Salinity at 1 metre depth in Gulf of Venezuela
current which provides salt to the surface outflow. The outer cell, less clearly defined, is fed by the water formed in the mixing zone, which escapes seaward at the surface after mingling with water from a countercurrent drawn in from the subsurface layers of the Caribbean. In both cells the surface drift is displaced to the left, under the influence of the wind.
The estuarine cell of Calabozo Bay finds its counterpart in many bays of the eastern coast of North America. Aside from the quantitative effects of the controlling topography, the more general difference in the circulation arises from the dominant effect of the prevailing wind on the horizontal flow in Calabozo Bay, as compared to the Corioli effect in the estuaries of higher latitudes.
The hydrography of the Gulf of Venezuela
125
Along the Atlantic coast the bays and estuaries discharge into, and lose their identity in producing, a broad band of coastal water of reduced salinity which separates the coast from the full sea water of the ocean. Along the Venezuelan shore a distinct band of coastal water is lacking, and Caribbean water in full strength penetrates the Gulf of Venezuela. The front separating the bay water from the full sea water is the mixing zone over the sill of Calabozo Bay. The water in this zone may be considered to be the rudimentary counterpart of the coastal water of the Atlantic coast.
If this view be accepted, the outer cell of the circulation of the Gulf of Venezuela finds its counterpart in those processes taking place along the margin of the Gulf
ir 7r
Fig. 9. Temperature at 1 metre depth in Gulf of Venezuela
Stream and in the slope water, by which the coastal water of the Atlantic coast becomes incorporated and lost in the general circulation of the ocean.
Tides
The tides at Aruba, like those of the Caribbean in general, are of the mixed type in which the diurnal constituents predominate. The diurnal range of tide is 0-8 feet. In contrast, at Zaparita Island, off the mouth of Tablazo Bay, the tide is predominantly semi-diurnal and the mean range is 3 feet. The dimensions of the Gulf of Venezuela are such that the semi-diurnal constituents are augmented by resonance to a high degree, while the diurnal constituents are relatively unaltered.
126
Alfred C. Redfield
A comparison of the harmonic contents of the tides (Table I) shows that the M2 component at Aruba precedes that at Zapara Island by 123° or more than one-quarter period. High water occurs at Las Piedras only one-half hour earlier than at Zaparita Island, and 1 -3 hours earlier than at Zapara Island. These relations place the antinode
72" 71" 70"
Fig. 10. Total phosphorus at 1 metre depth in Gulf of Venezuela
Table I Tidal harmonic constants, U.S. Coast and Geodetic Survey (1951)
|
Constituent |
Greenwich Epoch {G) Aruba Zapara I |
Amplitude {H)feet Aruba Zapara I |
|||
|
Diurnal |
Oi Pi Qi |
241° 228° 241° |
247° 246 243° 244" |
0-3 0-2 01 |
0-24 015 0 08 0 02 |
|
Semi-diurnal |
M2 S2 K2 |
161° 84° 282° |
284 217" 248 268" |
013 0 07 0 03 |
104 Oil 0-32 003 |
|
Sum — Diurnal amplitudes Semi-diurnal amplitudes |
0-6 0-23 |
0-49 1-50 |
|||
|
Ratio of sums |
2-7 |
0-33 |
The hydrography of the Gulf of Venezuela
127
for the semi-diurnal tides across the entrance to the Gulf at a longitude intermediate between Aruba and Las Piedras. The amplitude of the M, component is increased eightfold, and the sums of the semi-diurnal components sixfold as the result of the resonance.
72" 71° l(f
Fig. 11. Oxygen under saturation at 1 metre depth in Gulf of Venezuela
Since enough water must cross the sill of Calabozo Bay, having a depth of 18 metres, to raise and lower the level of the Bay nearly one metre twice daily, it is evident that strong tidal currents are to be expected over the sill. These currents, combined with the wind, account for the mixing which appears to occur in this region.
Water Levels
The monthly mean tide levels at Las Piedras change by as much as 0-8 feet in the course of the year (Fig. 12, A). The pattern is similar to that observed at positions on the Atlantic coast south of Chesapeake Bay and in the Gulf of Mexico (Marmer, 1951), and evidently is part of widespread phenomena. The monthly mean tide levels at Zaparita Island follow a similar pattern, but the annual variation in level is only 0-4 feet.
The mean annual difference in water level across the Gulf of Venezuela, between Las Piedras and Zaparita Island, is 0-92 feet in a distance of 93 nautical miles. The
128
Alfred C. Redfield
difference in level varies with the season, being highest (1-1 ft.) in January, and lowest (0-6 ft.) in October (Fig. 12, B).
The seasonal difference in levels across the Gulf is clearly related to the prevalence of north-easterly winds, as shown by wind data from Maracaibo (Fig. 12, D). The difference in levels may be explained in part by the reduced density of the water at the head of the Gulf. The magnitude of the difference is, however, so great as to raise a question as to the precision of the levelling between Las Piedras and Zaparita Island. There can be little doubt, however, that the mean tide level at Zaparita is one-half foot greater, relative to the level at Las Piedras when the north-east trades are at a maxi- mum, than it is when their influence is reduced. Clearly winds which affect the slope of the sea surface so greatly are adequate to produce the effects on the circulation which have been deduced from the hydrographic observations.
3.0
2 5
2 0
"I — I — r
"1 — I — r
ZAPARITA
- LAS PlEOPAS
-A MEAN TIDE LEVEL
J I I i I I \ I I L
J I L
I 2
10
0.8
06
04
I I I I r
1 — I — r
1 I 1 r
B DIFFERENCE IN LEVEL J I I I I I I I I I I [ I L
-4
T — r
2 —
- C WATER BALANCE l. maracaibo - J I I I l__l I I I I I I I L
"I — I — I — I — I — r
100 —
80 —
1 — I — r
• D WIND AT MARACAIBO
I I I I I I I I I I I L
J L
M A M J
S 0 N 0
M A M J
A S
N 0
Fig. 12. A. Monthly mean tide levels. Average at Las Piedras for 1942-49 and at Zaparita Island for 1940-53. Data from Bar Survey, Maracaibo
B. Difference in average monthly mean tide level at Las Piedras and Zaparita Island
C. Average monthly net water balance of Lake Maracaibo. Estimated by Carter (1954)
D. Per cent of time wind blew from N through ENE at Maracaibo, 1952. Data from Bulletin Bimensureal, Servicio de Meteorologia y Communicaciones, Ministerio de la Defensa , Fuerzas aereas, Maracay
The hydrography of the Gulf of Venezuela 1 29
Seasonal Influences on the Hydrography
The available data on the waters of the Gulf were collected in December. While there is no information on the conditions at other seasons, the annual variation in the two factors which control the circulation is known, and may be used to indicate the direction, if not the degree, in which the pattern will change with the season.
The rainy season in the Maracaibo Basin extends from April to December. The observations were consequently made at a time when the quantity of fresh water in the Gulf is maximal. During the following four months the outflow from the Lake is reduced and may come to an end (Fig. 12, C). The salinity of Calabozo Bay may consequently be expected to increase, and the hydraulic forces which drive its estuarine circulation to weaken. These tendencies should be reversed beginning in April. A rough estimate indicates that the quantity of fresh water present in Calabozo Bay in December is equivalent to about two years' outflow from the Lake. It is probable consequently that in the four months of the dry season the change in the mean salinity will be limited.
The effect of the north-east trade winds in maintaining the anticyclonic circulation in Calabozo Bay should continue through the winter. With the reduction in outflow from the Lake, the continued wind-induced motion will mix the water, and reduce the vertical and horizontal differences in salinity.
After April the winds become more variable and slacken in intensity. As the summer progresses, increasing outflow from the Lake should restore the salinity stratification. With the weakened effect of wind, the brackish water should spread more diffusely across the Bay. Possibly the Corioli force overcomes the wind influence and causes the escaping water to follow the southern shore to the eastward in the latter part of summer.
THE BIOCHEMICAL CIRCULATION The distribution of the major elements in sea water, which determine the salinity, is the result of purely physical processes of advection and mixing. It may be used, consequently, to trace the general circulation of the water. In contrast, the distribution of those elements which are present in limited quantity, and which enter into the composition of organisms, may be profoundly influenced by biological activity. In particular, elements such as phosphorus and nitrogen, which become incorporated into the substance of the phytoplankton growing in the surface layers of the sea, tend to be carried downvvards by the sinking of organisms, and are liberated at depth by the ultimate oxidation of the organic matter. There is thus a circulation of elements of biochemical importance which is different from that of the water itself, and of its biologically inert components.
In the case of the Gulf of Venezuela, data on the total phosphorus and oxygen content are available for an examination of the biochemical circulation.
Total Phosphorus
The total phosphorus content of water includes the phosphorus present as inorganic phosphate ions, as organic compounds present in solution, and as components of suspended organisms.
The total phosphorus content of the Gulf is higher than that of the source waters from the Caribbean. This is due primarily to the high phosphorus content of the
F
130 Alfred C. Redfield
water from Lake Maracaibo, which is on the average about 1 -4 [agA per litre, whereas the Caribbean water contains about one-quarter this amount. The general pattern of distribution of salinity and phosphorus in the surface waters (Figs. 8 and 10), and in the axial section (Fig. 7), are so similar as to suggest that both properties vary as the result of the system of circulation which mixes waters derived from the Lake and Sea.
In the deeper parts of Calabozo Bay and the eastern side of the Outer Gulf, con- centrations of phosphorus occur which are too great to be accounted for by the physical circulation (Figs. 6 and 7). In the former case the high salinity excludes an origin from lake water; in the latter the high phosphorus content precludes Caribbean water as the source. It is concluded that organisms and particulate matter have sunk into these basins, carrying down from the surface layers the phosphorus which has accumulated at depth.
Oxygen
In the Gulf of Venezuela the surface water, as well as that at greater depths, was everywhere under-saturated, in amount varying from 1-4 to 9-6 per cent. Physically this implies that the oxygen pressure was positive across the surface, and that oxygen was diffusing downward into the water. This condition cannot be explained by the cooling and consequent under-saturation of the surface, as is the case in higher latitudes in winter (Redfield, 1948), because the annual range in temperature is too small. It must be attributed to biochemical effects, arising from the excess of respiration over photosynthesis in the water.
The consumption of oxygen by respiration, in excess of its production by photo- synthesis, can only persist if there is available some external source of organic matter, as is the case in waters polluted by sewage. The undersaturation of the surface waters of the Gulf of Venezuela may be the result of the high organic content of the outflow from Lake Maracaibo. In the lake water two-thirds of the phosphorus (1 [J.gA/1) is present in organic form, and while in the Lake much of this is probably present in living organisms capable of photosynthesis. On introduction into the Gulf, however, these organisms, which are fresh water or brackish species (Gessner, 1953 a), may be killed by the higher salinity, and thus contribute to the quantity of organic matter immediately available for oxidation.
In support of this suggestion are the observations that the greatest under-saturation of surface water occurs in the immediate offing of Tablazo Bay (Fig. 1 1), and that the water of that bay is generally under-saturated with oxygen.
In the deeper parts of Calabozo Bay and the eastern parts of the Outer Gulf, where the total phosphorus was found to be anomalously high, the oxygen concentration is reduced to less than 3 ml per litre. (Compare Figs. 5 and 6). The deficiency in oxygen increases with the phosphorus content, and is about that to be expected from the increase in phosphorus if it arises from the oxidation of planktonic material (see Fig. 13). It may be concluded that the deficiency of oxygen in the deeper parts of the Gulf is due to the accumulation of organic matter as the results of the sinking of organisms and particulate matter from the surface layers of water, and that the greater part of this material has undergone oxidation.
At no place was the deeper water found to be completely devoid of oxygen. The deep circulation appears to be sufficiently rapid to prevent the accumulation of enough
The hydrography of" the Gull" of Venezuela
131
organic matter to exhaust the oxygen dissolved in the water. In the Strait of Maracaibo the water is flushed out each season by escaping lake water, to be replaced again with more saline water when the outflow slackens in the dry season. The oxygen content of the deeper water of the Strait is reduced to values comparable to those in the Gulf in the course of two or three months. Thus it is needless to assume that much more time is required to produce the conditions observed in the deeper parts of the Gulf.
>- 3
X
o
\
\ \
\
\_ O GO °
\
\
\ •
\ \ \ \
• \
\
\
\
\
\
\
\
\
\ •
\ \
\
\
\
\
\
\
\
\
\
\
\
\
\
\
\ • \
\
\
\
\
\
\
\
\
\
\
\
\
o •
- • SECTION III
- o SECTION V
\
\
\
\
\
\
\
J_
\
0.2 04 06 0.8
TOTAL PHOSPHORUS , /^^A/ \
\2
Fig. 13. Relation of oxygen and total phosphorus content of samples collected in Sections ill and V. The slope of the envelopes is that required by the complete oxidation of organic matter from plankton of average composition; i.e., 2-35 ml Oo is consumed in oxidizing organic matter containing 1 ;x gA
phosphorus
COUNTERCURRENT SYSTEMS AND BIOGENETIC PROPERTIES
The major ions of sea water exist in all parts of the ocean in very nearly equal proportions. It is a remarkable fact that, in contrast, most of those components which enter into the structure and chemical activity of living organisms are distributed in very different proportions in different parts of the oceans. Phosphate and nitrate, for example, are more than twice as abundant in the deep water of the Pacific and Indian Oceans than in the North Atlantic, although the concentrations of the major ions are approximately the same.
132 Alfred C. Redfield
The concentrations of the organic derivative of sea water (phosphate, nitrate, and carbonate), and of oxygen, have been shown to vary from place to place in proportions related to the statistical composition of the plankton (Redfield, 1934). It is evident that some broad-scale process of biological origin is responsible for the distribution of these biogenetic properties in ways which are anomalous in respect to the purely physical character of the circulation.
The obvious mechanism for separating the organic derivative from the dissolved materials in one mass of sea water, and transferring it to another, is the sinking and subsequent decomposition of organisms into a deeper layer. Redistribution leading to accumulation or attenuation is then dependent on the horizontal movement of the respective layers. If such movements are consistently in opposite directions, great differences in concentrations may be developed. The counter-current principle is commonly employed in such physical mechanisms as heat exchangers. Its applications in physiology have been discussed by Scholander (1954).
The Gulf of Venezuela affords examples of two somewhat different types of counter- current system which lead to the local accumulation of phosphorus, with attendant depletion of oxygen in the deeper water.
In the Outer Gulf the winds appear to produce an offshore movement of the surface water, which is compensated for by an onshore counter-current at depth. This is referred to as upwelling. Organic matter sinking from the surface layer is carried landwards in the deep counter-current. The process leads to an attenuation of phosphorus content of the surface layer with distance from shore, and its augmenta- tion in the deeper water which increases as the coast is approached. The degree of accumulation finally developed depends, of course, on a balance between this process and the dissipating effects of the circulation, which mixes the water vertically or trans- ports it horizontally across the region of upwelling.
The situation in the Outer Gulf provides a small-scale example of the mechanism of enrichment of ocean water which occurs wherever trade winds give rise to upwelling along the continental coasts.
In Calabozo Bay the counter-current system of the estuarine circulation is engendered by the inflow of fresh water from Lake Maracaibo rather than by the wind. Otherwise the process leading to the attenuation of phosphorus in the surface water and its accumulation at depth is the same as in the upwelling system of the Outer Gulf. The degree of accumulation attained is limited by the rate of circulation of the deep water, which appears to move toward the head of the Bay, where it is most actively incorporated into the surface outflow. The highest phosphorus and lowest oxygen concentrations were found immediately off the outlet of the Lake,
The estuarine circulation of Calabozo Bay provides an example of a mechanism which must operate to varied degrees in many coastal embayments, fjords, and estu- aries, and which may account in part for the greater fertility common to such enclosed waters, when compared to the off-lying sea.
REFERENCES
Carter, Douglas B. (1954), Report on water balance of the Maracaibo Basin. Unpublished manu- script on file, Woods Hole Oceanographic Institution.
Corps of Engineers, U.S. Army (1938), Model study of channel improvements at outer bar, Lake Maracaibo, Venezuela. U.S. Waterways Experiment Station, Corps of Engineers, U.S. Army, Tech. Memo. No. 106-1, 3 vols, December 1, 1938.
The hydrography of the Gulf of Venezuela I 33
Gessner, Fritz (1953 a), Aufdcn Spuren Alexander von Humboldts in Venezuela. Sciiur u. Wissen-
schaft, 138 neue Zeitung, 20, 13, 14, Juni 1953. Gessner, Fritz (1953 b), Investigaciones hidrograficas en el Lago de Maracaibo. Acta Cientifica
Venezolona, 4 (5), 173-177, 4 figs., 4 tables. Gessner, Fritz (1955), Die limnologischen Verhiiltnissc in den Seen und Fliissen von Venezuela.
Verhandl. lutcnuit. Verein.Jiir theoret. unci atii^ewandle LimnoL, 12. 284-295, 12 Hgs. Harvey, H. W. (1948), The estimation of phosphate and of total phosphorus in sea water. J. Mar.
Biol. Assoc, U.K., 27 (2), 337-359, 11 figs., 3 tables. Livingstone, D. A. ( 1954), On the orientation of lake basins. Amcr. J. Sci., 252 (9), 547-554. Marmer, H. a. (1951), Tidal datum planes. U.S. Coast ami Geodetic Survey, Spec. Pun. 135,, 142 pp. Redfield, Alfred C. (1934), On the proportions of organic derivatives in sea water and their relation
to the composition of plankton. In: James Johnstone Memorial Volume, Univ. Press, Liverpool,
176-192, 5 figs., 2 tables. Redfield, Alfred C. (1948), The exchange of oxygen across the sea surface. J. Mar. Res., 7 (3),
347-361, 4 figs., 3 tables. Scholander, p. F. (1954), Secretion of gases against high pressures in the swimbladder of deep-sea
fishes. II. The rete mirabile. Biol. Bull., 107 (2), 260-277, 5 figs., 4 tables. U.S. Coast and Geodetic Survey (1951), Tidal harmonic constants — Atlantic Ocean including Arctic
and Antarctic Regions, 137 pp. U.S. Navy Hydrographic Office (1949), Sailing directions for West Indies, Vol. II, The Lesser .Antilles
and the coast of Venezuela. H.O. Pub. 129 (6th ed.), 335 pp.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 134-138.
The specific characters of the coral Sty/aster roseus
By H. BoscHMA Rijksmuseum van Natuurlijke Historic, Leiden
In the collections brought together by Dr. P. Wagenaar Hummelinck in the Leeward Islands and other parts of the West Indian region there are a few small colonies of a stylasterine coral with the following data: Curasao, Plaja Djerimi, North corner, December 11, 1948 (rock, sand; tidal and lower zone). Examination of these corals showed that in all their salient characters they prove to correspond with Stylaster roseus (Pallas) as far as the eighteenth-century data on the species are concerned, while differing from the specimens identified with this name in recent literature.
The corals from Curasao are four or five colonies of a more or less fan-shaped growth, occurring together on a fragment of dead coral rock. The colonies are up to 3 cm high and not over 3 cm broad. Each colony consists of a few stems of a breadth of about 5 mm, rapidly tapering upwards while giving off side branchlets which in their topmost parts have a thickness of about 1 mm. The stems and the thicker branches are slightly compressed in the flabellar plane of the colony. On the upper parts of the branchlets the cyclosystems occur alternately on the two lateral surfaces, whilst on the thicker branches the cyclosystems are distributed without apparent order; they are more numerous on the anterior than on the posterior surface. The number of dactylopores in the cyclosystems varies from 7 to 12; this number was counted in 100 cyclosystems with the following result: 5 cyclosystems with 7 dactylopores; 12 with 8; 28 with 9; 37 with 10; 14 with 1 1 ; 4 with 12; yielding an average of 9-55.
Except on the tops of the smaller branchlets the cyclosystems extend very little above the surface of the coral; their diameter varies from 0-5 to 0-7 mm. The gastro- pores have a depth of about 1 mm, and the gastrostyles have a length of 0-4 mm and a thickness of 0-15 mm, so that they are rather slender, occupying about one-third to one-half of the lower part of the gastropore (Fig. lb). The gastrostyles are covered with small spines on the whole of their surface (Fig. la). Feebly developed dactylo- styles (not drawn in Fig. lb) are present in the dactylopores.
The colonies bear numerous ampullae of a hemispherical shape, scattered among the cyclosystems on the larger branches, or occurring in clusters densely covering large parts of the surface; as a rule the ampullae are numerous, especially on the posterior surface of the colonies. The ampullae have a smooth surface, without warts or spines, and their diameter varies from 0-6 to 0-8 mm, the size indicating that probably they are female ampullae.
The colour of the corals from Curasao is yellowish with an irregular admixture of pink, occasionally turning to a light purplish tint in the topmost parts of some branch- lets or on and around some cyclosystems on the larger branches.
Pallas (1766) gave a description of the coral named by him Madrepora rosea, mentioning some characters which at present still may be regarded as typical of the
134
The specific characters of the coral Stylaster roseus
135
species; this description was based on an examination of specimens in Dutch collec- tions. In Houttuyn's (1772) account of the coral, the salient data are mentioned as noted by Pallas; Houttuyn's work is here cited because it contains the first figure of the species (1772, PI. 129, Fig. 4, copied in Fig. 2 of the present paper). This figure
r\
Fig. 1. Stylaster roseus (Pallas) from Curasao, (a) gastrostyle,
cyclosystem, 60
250; (b) longitudinal section of a
Fig 2. Copy of the figure of Madrepora rosea
Pallas in houttuyn (1772, PI. 129, Fig. 4).
Original size
again appeared in a treatise by Muller (1775, PI. 23, Fig. 4), which practically is a translation of Houttuyn's work with a few additional remarks. Esper (1794) gave an elaborate description of the species, based on a specimen from a German collection, his figures (1794, Madrep., PI. 36) represent a coral of a shape similar to that of
136 H. BOSCHMA
HouTTUYN. The data noted here contain the original contributions towards a know- ledge of the species ; remarks in other eighteenth-century publications were copied from the cited works.
According to Pallas, the colonies of his Madrepora rosea •are " semi-palmares " (half a hand high, about 5 cm); Esper records the height of large specimens as " zwey bis drey Zollen " (about 5 to 1\ cm). The two authors further state that the basal parts of the stems are comparatively thick, and that they gradually taper to very thin terminal branchlets while giving off numerous side branchlets. At that time the only known locality of occurrence of the species was " Mare circa Insulam St. Domingo " (Pallas), " an den Kiisten der Insel Domingo " (Esper), the quoted passages referring to the eighteenth-century name of the island Haiti in the West Indies. It stands to reason that the corals which were collected nearly two hundred years ago came from shallow water.
It is interesting to note that the corals from Curasao, on account of their small size and of their gradually tapering branches, closely correspond with the specimens described and figured by Pallas, Houttuyn, and Esper, thereby differing from the other species of Stylaster known to occur in the West Indian region, which attain a larger size and have branches of a much slenderer growth.
Lamarck (1816) placed the species Madrepora roseus in the genus Oculina ; Gray (1831) erected the genus Stylaster, in which he placed the two species Oculina rosea and O. flabeUiformis \ in 1850 Milne Edwards and Haime (1850-1854) selected Stylaster roseus as the type of the genus Stylaster. In another paper (Milne Edwards and Haime, 1850) there is a rather elaborate description of Stylaster roseus, in which the authors state that they have never seen colonies of a larger size than a few centi- metres, the thicker branches of which have a thickness at the base of 5 to 6 millimetres. These data correspond with those of the corals from Curagao; in other details, however, there are slight differences: Milne Edwards and Haime remark that the number of dactylopores in the cyclosystems is from 10 to 14, most commonly 12, while the diameter of the cyclosystems is nearly 1 mm, these figures being somewhat higher than in the specimens from Curagao. The measurements of the ampullae in the specimens of Milne Edwards and Haime (not over \ millimetre) perhaps indicate that these were male ampullae.
PouRTALES (1871, p. 83) remarks that Stylaster roseus is " abundant on the under surface of blocks of coral rock, on the reef at Cruz del Padre, north coast of Cuba, a couple of feet below low-water mark ". Moseley (1880, p. 79) refers to this occur- rence of the species in almost the same words, and on another page {loc. cit., p. 77) remarks that " ampullae are especially well developed in the shallow water Stylaster roseus; those in the female stocks being very large and prominent ".
A coral of rather common occurrence in depths of 120 to 324 fathoms (220 to 592 metres) off the Florida Reef was described by Pourtales (1868) as Stylaster erubescens; with some slight changes this description again appeared in a later paper (Pourtales, 1871); the following details are taken from the latter, the terminology partly being altered to a more modern wording: younger branchlets slender, with rather close-set alternate cyclosystems, these slightly prominent, 1-2 to 1-5 mm in diameter, deep; nine to twelve, most frequently eleven dactylopores in a cyclosystem; gastrostyle deeply sunk, rounded and hirsute; dimensions, height and breadth of flabellum, 10 cm. On Plate 4 of the cited work is figured a colony of Stylaster erubescens in
The specific characters of the coral Stylaster roseus \ 37
natural size (Fig. 10), and the terminal part of a branch, 4 times enlarged (Fig. 11). The figures show that the tendency for a lateral arrangement of the cyclosystems on the branches is much more obvious than in the specimens from Curasao, that the branches are much less pronouncedly tapering, and that the cyclosystems definitely extend over the surface of the branchlets, the smaller branchlets thereby becoming distinctly zigzag-shaped, in contradistinction to the corresponding parts of the specimens from Curasao. The cyclosystems of Stylaster erubescens (diameter 1 -2- 1 -5 mm) are about twice as wide as those of the specimens from Curasao (diameter 0-5-0-7 mm), and distinctly wider than in the specimens of Stylaster roseus examined by Milne Edwards and Haime (diameter nearly I mm). The most important difference of the two forms is that of the entirely different shape of the gastroslyle, which in Stylaster erubescens is rounded (almost spherical), in the specimens from Curasao conical, more than twice as high as broad (Fig. I).
The Stylasteridae of the North Atlantic region remained imperfectly known till 1914, when Broch's important paper appeared dealing with the specific characters of Pliobothrus symmetricus Pourtales, Allopora norvegica (Gunnerus), Stylaster gem- mascens (Esper), and a species named by broch Stylaster roseus (Pallas). The material of the last named came from depths between 263 and 1,400 metres; Broch notes that the colonies display a marked difference between small branches, main branches, and stem, that the cyclosystems are placed laterally and alternately on the small branches, that the cyclosystems show from 8 to 17, generally 9 to 1 1 dactylopores, and that the gastrostyle is almost spherical, with equal height and breadth. The characters here cited from Broch's description are almost exactly those of the species Stylaster erubescens as described and figured by Pourtales (1871). Broch's figures of colonies in natural size (1914, PI. 1, Figs. 8 and 9, PI. 2, Figs. 10 and 1 1) represent corals with an entirely similar form of growth as the specimen of Stylaster erubescens of Pourtales (1871, PL 4, Fig. 10); moreover, the figures of enlarged terminal branches (Pourtales, 1871, PI. 4, Fig. 11 ; Broch, 1914, PI. 2, Fig. 17) are strikingly similar.
Unfortunately Broch gave the name Stylaster roseus to the corals here dealt with, while placing the name Stylaster erubescens in the synonymy of the species. In Broch's paper there is an instructive figure of a longitudinal section (1914, PI. 3, Fig. 22) showing in two of the cyclosystems the spherical gastrostyles, which, judging by this figure, have a height and a breadth of about 0-3 mm. This figure has been copied in other publications (Broch, 1924; Kuhn, 1939) as a longitudinal section of a branchlel of Stylaster roseus (Pallas).
Broch (1914, p. 15) remarks " As the species is the commonest Stylasterid in the Atlantic north of the equator, it is probably the same form that served as a basis for Pallas' description of Madrepora rosea "; this is right as far as the specific identity of the North Atlantic corals with Stylaster erubescens is concerned, but it was an error to identify this species with Stylaster roseus. Pourtales (1868, p. 136, footnote; 1871, p. 83) examined the two forms and referred to them as separate species, the one from shallow water, the other from deeper water only; it is to be regretted that he did not give a description of the specific characters of Stylaster roseus.
The conclusion of the data dealt with above is that Stylaster roseus (Pallas), the type species of its genus, has a rather complicated history. The descriptions and figures of the various eighteenth-century authors contain some characters which may be considered typical of the species. In later years these older data were overlooked
138 H. BOSCHMA
and the name S. roseus was given to corals which in reaUty belong to the species Sty/aster erubescens Pourtales. An examination of specimens from shallow water of the island Curagao could lead to additional characters, especially those of the gastro- style, proving that the species Stylaster roseus is distinct from all the later described species of the genus.
REFERENCES
Broch, Hj. (1914), Stylasteridae. Danish Ingolf Exped., Copenhagen, 5 (5), 1-25.
Broch, Hj. (1924), Hydroida. In: Handbuch der Zoologie (Kiikenthal-Krumbach), Berlin &
Leipzig, 1, 422-458. EsPER, E. J. C. (1794-1797), Fortsetzungen der Pflanzenthiere in Abbildungen nach der Natur mit
Farben erleuchtet nebst Beschreibungen. Niirnberg, 1, 1-230. Gray, J. E. (1831), Description of a new genus of star-bearing corals. The Zoological Miscellany,
London, 1-80. HouTTUYN, M. (1772), De Zee-Gewassen. Natuurlyke Historic . . . volgens het Samenstel van den
Heer Linnaeus. Amsterdam, 1 (17), 1-613. KuHN, O. (1939), Hydrozoa. In: Handbuch der Pal aozoologie (Schindewolf). Berlin, 2A, 3-68. Lamarck, J. B. P. A. de (1816), Histoire naturelle des animaux sans Vertebres. Paris, 2, 1-568. Milne Edwards, H. and Haime, J. (1850), Recherches sur les Polypiers; 5me mem. Monographic
des Oculinides. Ann. Sci. Nat., (3), ZooL, 13, 63-110. Milne Edwards, H. (1850-1854), A monograph of the British fossil corals. London, i-lxxxv, 1-322. Moseley, H. N. (1880), Report on certain Hydroid, Alcyonarian, and Madreporarian Corals pro- cured during the voyage of H.M.S. Challenger, in the years 1873-1876. Rept. Sci. Res., Challenger,
ZooL, 2 (1), 1-248. MiJLLER, P. L. S. (1775), Von den Corallen. Des Ritters Carl von Linne . . . voilstandiges Natur-
system. Nurnberg, 6 (2), 641-960. Pallas, P. S. (1766), Elenchus Zoophytorum. Hagae-Comitum, i-xxviii, 1^51. Pourtales, L. F. de (1868), Contributions to the fauna of the Gulf Stream at great depths (2nd series).
Bull. Mus. Comp. ZooL, Harvard Coll., 1 (7), 121-141. Pourtales, L. F. de (1871), Illustrated catalogue of the Museum of Comparative Zoology at Harvard
College, No. 4. Deep-sea Corals. Cambridge, 1-93.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp, 1.19-148.
External metabolites in the sea
By C. E. Lucas Marine Laboratory, Aberdeen
With the exception of a hint or two before the turn of the century, by such prophets as Brandt and Nathansohn, it was not until the inter-war period tiiat marine workers began to turn their minds to the possible existence of more subtle ecological relation- ships than those imposed on organisms by their inanimate environment and by predators. It is relevant that Knorrich and Putter had postulated the direct food value of dissolved organic food substances in the sea, although this view appeared to be finally rejected by Krogh (1931); however, such possibilities are not the main subject of this paper, although they may once again demand investigation. But those who drew our attention once more to the other possible significance of dissolved organic matter deserve our gratitude. Quite the most senior of those now living was Henry Bigelow who said in his famous book Oceanography, among many other stimulating things, " as yet we know little of the inter-relationships of different species or groups of animals in the sea beyond the obvious fact that some prey on others, but we may be certain that in many cases inter-relationships of less obvious sorts are vital links in the animal economy " (Bigelow, 1931, p. 131, quoted by Russell, 1936). Before many years elapsed, it seemed clear that he was right and we now know that he was! For the volume in his honour, it is fitting to pay tribute to his foresight.
It would not be proper on this occasion, however, to ignore the others: from Johnstone, Scott and Chadwick (1924)* to Allee (193l)t and Hardy (1935):}:. All were feeling towards the certainty of a new type of relationship in ecology, and particularly marine ecology, for which there was then all too little evidence (although it may now seem striking that it was around this very time, in 1929, that the late Sir Alexander Fleming was making his first observations on the antibiotic influence o'i Penicillium). It was the stimulus of such hints, and particularly that of working with Hardy when he was evolving his idea of " animal exclusion ", that led Lucas to gather an odd collection of references in support of a speculative theory of " non- predatory " relationships — based on the release and biological influence of metabolites ranging from " toxins to vitamins and hormones " (Lucas, 1938).
This evidence ranged from the effects of external metabolites in the field of bacterio- logy, through some of the " mass physiology " experiments of Allee's school, to the
* " Also, we are pretty sure that the plankton communities influence each other — that there are what we may call group symbioses on the great scale so that the kind of plankton which we may expect to be present in a certain sea-area must depend, to some extent, on the kind o{ plankton which was previously present."
t " Once formed, aggregations of aquatic organisms condition the medium surrounding them by the addition of secretions and excretions, the nature and biological effect of which form one of the important problems of mass physiology."
X Hardy postulated a " presumably chemical " basis for his theory of " animal exclusion ", and also speculated upon the '" biological history " of waters, e.g. the changes which may occur in water passing from regions of predominantly "free" phyto-plankton to regions of "■ imprisoned" phyto- plankton.
139
140 C. E. Lucas
speculations of Akehurst (1931) about the temporal alternation of oil-producing and starch-producing algae in ponds, and some tentative experiments (Lucas, 1936) regarding " animal exclusion ". With these were coupled Allen and Nelson's pioneer demonstrations (1910) of the need for some accessory substances in diatom culture; the use of " soil solution " for more effective growth; and Gran's observa- tions (1931) on the relatively intensive growth of phytoplankton at the junction of two bodies of water. But more evidence was needed.
More evidence did in fact exist, scattered widely through the field of biological research, and work during the war brought even more, particularly that associated with antibiotics. It thus became possible to review a wider field and to formulate the concept more precisely (Lucas, 1947, and from a more general ecological viewpoint, 1949). In the aquatic field reference was made, among others, to the very different growth-rates of diatoms cultured in different natural sea waters (Matsudiara, 1939; Harvey, 1939), and Harvey's associated investigations of the effects of various accessory substances on growth; to other examples of the influence of waters pre- viously containing living organisms (or their by-products) upon different organisms in culture (e.g. Levring, 1945); and to Fox's demonstrations of the occurrence of carotenoids free in natural waters and their deposits (e.g. 1944). When supported by the rapidly increasing knowledge from the various fields of microbiology, together with a wide range of other biological references, it seemed not unreasonable to come to conclusions along the following lines:
" (1) It is characteristic of cells to liberate certain metabolites, and these are known in a variety of instances to have great influence as endocrines.
" (2) It is now well known that a number of these potent metabolites are eliminated as secretions or excretions by the organisms themselves, and many other chemicals are eliminated which are not yet known to have any specific effects within the body.
"(3) Particularly insofar as any of these metabolites are . . . parts of the environ- ment of other organisms, they may be expected to have immediate potency for many of them. . . . The term ' ectocrines ' has been suggested for such metabolites.
"(4) More generally, however, . . . the capacity for adaptation of most organisms suggests that further differentiation between beneficial and antagonistic relationships would be likely to have developed between the producers and those affected. In the extreme instances escape, exclusion, or death must be expected on the one hand, and obligatory association (parasitism, symbiosis) on the other.
" (5) Such processes are believed to be important in evolution, and they are con- sidered to mediate communal relationships in ecology, which is the contemporary aspect of evolution. They should be seen as part of the nexus which also includes physical and chemical relationships as well as those of prey and predator " (Lucas, 1949, pp. 353-354).
If these seemed then to be rather premature speculations, they now have much more specific support. It is not possible to review the whole field here and this note is simply intended to bring together a few references indicating some of the lines along which progress is now being made. However, the suggestions could properly be regarded as stemming from, and partly supported by, the theory of " animal exclusion ", and evidence (Bainbridge, 1952) has recently been brought to bear against the only laboratory experiments (Lucas, 1936) specifically made to investigate that theory. It seems necessary, therefore, to mention Bainbridge's experiments first,
External metabolites in the sea 141
and it is particularly appropriate that they were made by one who has worked with both Hardy and Lucas. Lucas concluded that his very preliminary experiments were not inconsistent with Hardy's theory and, indeed, appeared to offer support for it. The work had to cease and they went no further than that. Bainbridge's work was not only more detailed but much more precisely executed, and it represents a real contribution to our knowledge of the prey-predator relationship. His criticism of Lucas's " light and dark " experiments is that they simply reflected the tropism of the animals — a possibility discussed by Lucas. It is and always was relevant. For all that, the very weaknesses in Lucas's work and the greatly improved techniques in Bainbridge's are very relevant, and they may still mean that Bainbridge's results are not necessarily so critical of the theory of animal exclusion as they seemed at first sight.
Bainbridge was careful to use only algal cultures aged not more than " a week or so " (his p. 391) after inoculation, whereas Lucas probably seldom used such fresh cultures in his work. Indeed, Lucas's cultures may, in the light of modern ideas (many of his experiments were made in 1934), have been approaching senescence at times and, whatever may be their potency during the early phase of a culture, we can now see that metabolites released during the later stages (e.g. Pratt, 1943) may well have been harmful and have acted more as deterrents than as attractions. This is, of course, far from certain and exploratory experiments on these lines would be useful. In any event, it is also relevant that, whilst Bainbridge found that most of his plankton animals were attracted by, or at least did not appear to avoid, the majority of the denser phytoplankton cultures, several were either neutral or were markedly avoided or even lethal. Two of the more " harmful " were flagellates. It is also significant that not only did most of his cultures influence the animals but, in several experiments, so did the culture fluids in the absence of the plant cells. The main conclusion is that his experiments demonstrated the release by plant cells of substances which were frequently attractive and occasionally repellent to many of his animals (Bainbridge, 1952, p. 429). Like Lucas, also, he found evidence of an optimum density of plant cells below and above which the animals were presumably either
starved or poisoned.
However, other evidence was accumulating. In the first place, there was the work of Lwoff's school (1943), which demonstrated convincingly the release of vitamins " into their environment by some micro-organisms, and the vital need for such vitamins by some other forms which are unable to synthesize them. Lwoff saw this as evidence of a progressive loss of physiological function during evolution, but it provided also a mass of evidence of mainly beneficial inter-relationships, mediated by the release ot metabolites potentially of communal significance.
Next there is the work of Lefevre and his school (1952) which, while collectively reviewed under the title of " Auto, et heteroantagonisme chez les algues d'eau douce ", demonstrates also quite clearly the very real influence, both favourable as well as unfavourable, which one micro-organism may exert upon others through the mediation of its secretions or excretions. In brief, these workers concluded that the three groups of bacteria, algae and fungi, all have " Faculte d'elaborer des substances actives autoantagonistes, heteroantagonistes ou favorisantes. Specific.te des substances actives produites . . . Decharge rapide des substances accumulees par les cellules quand on les replace dans un milieu neuf Solubilite des substances actives dans
142 C. E. Lucas
I'eau ou dans certains solvants organiques. . . . D'autre part, il n'est pas impossible que les substances actives produites par des Aigues se developpant massivement dans une collection d'eau aient une influence directe sur la multiplication et le developpe- ment des animaux aquatiques: Entomostraces, Insectes, Mollusques, Vermes et peut- etre meme Poissons " (Lefevre, Jakob and Nisbet, 1952).
The limitations implied by the title of their paper and the wider relevance of the text (summarized on their pages 173-181) are not without interest, for there seems to have been a strong tendency on the part of various workers to anticipate unfavourable reactions rather than favourable ones in given circumstances; e.g. the review by McCoMBiE, 1953, mentions only the possibility of harmful effects of free metabolites,* while one or two workers, in referring to Lucas' papers, have noticed only his ref- erences to harmful effects. The fact is that one organism's " meat " may be another's " poison " in the ecological nexus, and terms such as " harmful " and " beneficial " can only be used in an immediate and limited sense. In this sense, much of the evidence de- monstrates the development of " favourable " relationships, although admittedly some of the most striking are unfavourable. One of the latter is instanced by the phenomenon of" red tide ", with its harmful effects on marine animals and unfortunate repercussions on man. Lucas instanced such effects of the secretions of plants or animals, and much more evidence has been accumulated since (e.g. Br0ngersma-Saunders, 1948). There is now no doubt that, even though in their more striking forms such phenomena can be regarded as abnormal, they are, in fact, far from unusual in a lesser degree and, further, they are mediated by the release of " toxic " substances, frequently by flagellates. Their nature and the more precise conditions which lead to their production in a mild or extreme form, are being intensively investigated in several laboratories.
The major task now is to determine the nature and effects of some of the more significant metabolites in aquatic ecology, to trace their probably variable distribution in some natural waters, and to determine the conditions leading to their production. Several lines of work have recently been developed. In the United States, Pratt (1943) has produced clear evidence that Chlorella cells in culture release a growth inhibiting substance, whilst Rice (1954) has grown Chlorella vulgaris and Nitzschia frustulum (both fresh water algae) together, and demonstrated clearly that neither grows so satisfactorily in the company of the other as it does in pure culture (depending upon the size of the populations used). Each was similarly inhibited when grown in the culture medium of the other, after its cells had been removed by filtration, and both were also inhibited when grown in a culture medium prepared with pond water which had supported a dense growth of Pandorina before filtration. Again, the metabolites in solution could be absorbed in charcoal and removed by autoclaving, suggesting volatile substances.
Harvey, at Plymouth, following on his pioneer culture experiments with growth substances, is now attempting to review all the evidence available so as to define more
* Lucas drew attention to this tendency (1944 and later) in respect of the term " antibiotic ". He pointed out that not only were antibiotics necessarily favourable to those organisms, such as man, which are preyed upon by the object of antibiosis, but that the antibiotic might well prove beneficial to those organisms succeeding its producer in the ecological chain (just as Akehurst, 1931, had suggested the autotoxic secretions of one algae may be beneficial for its successors). Indeed, the ecological successors of the producers of antibiotics can only succeed by virtue of being adapted to the presence of the antibiotics or their degradation products, and there is already some evidence that this may be true even for a potent substance such as penicillin. Here is a possible theoretical basis for ecological succession.
i
External metabolites in the sea 143
rigorously than has previously been possible the precise requirements of phytoplankton organisms in nature and in culture. Meanwhile, Provasoli, Hutner, and their colleagues at the Haskins Laboratories, have also very rightly undertaken fundamental and precise experiments on the basic requirements for the growth of marine and fresh water micro-organisms. Provasoli and Pintner ( 1 953), in their review of the ecological implications of the nutritional requirements of algal flagellates, have brought together a large number of references to the need of various micro-organisms for growth factors and trace elements. To these they have added the striking results obtained in their own laboratory. The evidence ranges from the early demonstration by Hutchin- son (1943) of the actual existence of thiamin in natural waters, to the significant requirement of various forms for cobalamin (vitamin Bio) in pure culture within chemically defined media. Of particular importance is the rigorous technique, necessary and adopted, in their work. All the results to date demonstrate aspects of " non-predatory " relationships. As they say:
" It is a reasonable assumption that if an organism requires a growth factor in vitro, then this metabolite or its physiological equivalent should be found in significant amount in the environment " (p. 845).
" The water environment is the one in which metabolites are interchanged most efficiently. It is to be expected that the interdependent growth of the different groups of water organisms should sensitively reflect the excretion and consumption of metabolites. Undaunted by new intricacies, we should envisage all the possibilities in these relationships, and not hesitate to follow Lucas's lead in constructing theoretical frameworks upon which to hang data. In the present paper, only a few aspects of the nutrition of phytosynthetic forms are considered. It is possible, nevertheless, to state more definitely some of the interdependencies based upon ' external meta- bolites ': (1) the interchange of growth factors; (2) the lowering of inhibitory con- centrations of several major mineral nutrients, especially PO4; and (3) the preferential utilization of minerals, including trace metals, may condition waters, bringing their concentrations into the optimal zones for succeeding forms. The practical aim — to predict algal successions and blooms— may be achieved through a comprehensive knowledge of vitamin cycles as well as mineral cycles. An immediate problem is to trace the thiamine and cobalamin cycles " (p. 849).
Droop (for example, 1954) is pursuing a similar course at Millport, in Scotland, and has shown the need of several marine flagellates* for vitamin Bj... LEW'iN,in Canada, has also found B12 essential for the growth of the alga Stichococcus in sea water (1954). The presence of free B12 in natural sea water has been demonstrated, and its distribu- tion is being examined in more than one laboratory. Droop is now developing an assay for it in sea water. Along a rather diff'erent line Fogg (1952) has suggested that some at least of the external metabolites (for instance, the polypeptides of blue-green algae) may further communal growth, via chemical linkage, by making relatively insoluble nutrients available in a form more suitable for assimilation.
Turning now to the animal field, several workers have followed Allee in linking aggregations with the release of metabolites (for example. Cole and Knight-Jones, 1949, and Knight- Jones, 1950). Again, there was the demonstration by Allison and Cole (1935) that the feeding movements of barnacles can be correlated with the
* Droop has now demonstrated this need in the diatom Skeletonema costattim (Droop 1955).
144 C. E. Lucas
abundance of dinoflagellates in the water (with the postulate that this is mediated by a by-product) and the subsequent hint (Miazaki, 1938) of the effect of an alga upon the spawning of the male oyster. Now, Collier and his colleagues, at Galveston, Texas, have moved into this field from a rather different angle. Whilst studying the effects of industrial wastes on oysters, they deduced a generalized influence upon their pumping rates, which was found in due course to be correlated with the presence or absence in the water of a carbohydrate-like substance; this is either truly soluble or colloidal, and may attain densities in neritic waters of up to 25 mg/1 (Collier, Ray, Magnitski and Bell, 1953). During further work (Collier, 1953) they found that, along with tyrosine-tryptophane, these carbohydrates have a marked diurnal variation in abundance, and their production is associated with light and aeration — so that they are probably the by-products of plant growth. In addition, a rhamnoside (Wangersky, 1952) has been isolated from oceanic water, and particularly from " red tide " water up to quantities of 50 mg/l, whilst minute quantities of ascorbic acid and some other carbohydrates of very low molecular weight are being isolated for identification. The significance of such substances to the oyster may be two-fold, but it is at least clear that one of the substances in question is both widespread and very variable in quantity, and that it acts as a remarkably effective (and almost instantaneous) pumping stimulus. It would appear that the substance is also absorbed by the oysters (up to 50 mg per hour), although it remains to be seen whether such substances are of positive and substantial food value (see, for example, Korringa, 1949, and Jorgenson, 1952) — a possibility which would greatly have interested both PiJTTER and Krogh — or whether their role is limited to providing sensory stimuli and perhaps growth factors. At the moment, the chief point is that they " found a biologically active compound (or group of compounds) to which an organism would respond quantitatively ", and drew attention to the link between this work and the probable significance of external metabolites or " ectocrines ".
Work being undertaken by Wilson, at Plymouth, is also relevant. For many years he has been concerned with the problems of breeding and growing planktonic larvae, particularly polychaetes. On the one hand he noticed that sands from some areas were more suitable for the settlement of polychaete larvae than others (e.g. Wilson, 1948 and 1953) whilst, on the other hand, he found that, with the passage of years, his success with rearing these and other larvae was tending to decrease (Wilson, 1951). Continued and painstaking investigations in various directions now seem to make it clear, however, that the suitability of sands for larval settlement must be determined by the existence on them of other forms of life, probably micro- organisms— " Organic material, living or dead, on the sand grains plays an important role in rendering a sand attractive or repellent to the larvae " (Wilson, 1954). Whilst we may not be so obviously concerned here with a free metabolite (although that is quite possible), we have to deal once again with the significance for living larvae of organic remains, and with their detection by these larvae.
The other instance is of even more direct interest. Wilson associated his decreasing success with the now familiar change known to have taken place whereby the waters of the English Channel have been much less productive since 1930 than in the 1920s. Superficially, this was due to reduced phosphate content, but the possibility of more subtle factors remained, and comparative experiments were made by rearing poly- chaete and echinoderm larvae in (a) " local " Channel water collected in the Plymouth
External metabolites in the sea 1 45
neighbourhood (as had been usual) and (b) water collected from the Celtic Sea, in which the typical plankton community is normally similar to that of the " local " water before 1931. The results were striking; good growth of polychaete and echinoderm larvae was obtained in the latter and only poor or deformed growth in the former. Appropriate combinations of experiments suggested the presence of a " beneficial " substance in the Celtic water, and its lack in the local water, rather than the existence of a harmful substance in the latter. More recent work has shown that Clyde water also tends to be more suitable than " local " Channel water and, although there are variations, the inferences seem to be unambiguous. In association, Wilson and Armstrong (1954) have shown that heating the waters for shorter or longer periods generally had an adverse effect on the larvae bred in them, thus suggesting the existence of a beneficial substance of a more or less volatile nature. Their analyses have not yet been carried to the stage of demonstrating any particular component or fraction which is responsible for the biological difference.
Recently, at Aberdeen, Johnston has extracted various fractions of the organic matter in natural sea waters, and made some preliminary biochemical analyses. Certain of these were tested in bio-assay on a number of phytoplankton diatoms and flagellates (with results summarized by Johnston in his Table I, 1955, from a paper read to the International Council for the Exploration of the Sea in 1954). It was found that the growth of many was favoured and of some others hindered relative to controls, although, " since the tests were limited to one concentration, further (and perhaps different) instances of these effects would probably have been observed by testing a range of concentrations. One particular fraction was found to promote greater growth in 9 of the 1 1 species tested." The initial information so gained is providing a basis for the bio-assay of sea water samples from different areas, with a view to a preliminary labelling of such waters according to their physiological effects. Then, further attention will be given as far as possible to identifying some of the substances thus found to be of biological significance. Johnston tentatively discusses the possible value of such information to the fisheries worker.
In all such experimental work, tribute should be paid to the surveys made by Russell (e.g., 1939) and Fraser (e.g., 1952). By distinguishing on biological evidence between water masses, which have often been indistinguishable on familiar hydro- graphical criteria, they are providing the experimenter and biochemist with invaluable clues.
In conclusion, it can be said that, before the war, a few people were moving towards a conception of ecological inter-relationships which seemed likely to be an important complement to the already familiar relationships existing between the organism and its physical environment, and those between prey and predator. Limited observations in diverse fields suggested that these non-predatory relationships would be mediated by the release of metabolites of varying potency for other members of the community. Further work during the war made it possible to gather much more support for the suggestion, and it is now quite clear that dissolved or colloidal organic matter may be present in natural fresh and marine waters in greater quantities than was originally envisaged. Indeed, it is still uncertain whether these may not in themselves provide, for some forms, nutrients in the ordinary sense of the word*. It is also clear that within
*See, for example, Morris, 1955.
146 C. E. Lucas
this general heading of organic matter are included, sometimes in very minute quantities, substances whose effects within the community may not unreasonably be compared with those of endocrine metabolites within the body. It now seems necessary to believe that such substances play a considerable part in the growth of aquatic communities of bacteria, algae and fungi (we still have much to learn of the activities of the last in natural waters), so that the success of various organisms, and consequently their ecological succession, may be largely determined in this way. The next point is that we now have a number of instances in which such free metabolites affect not only the lives of protozoans (whose communal life may be expected to be very similar to that of the micro-plants, except in so far as their need for external metabolites can be expected to be much greater), but also those of higher animals such as worms, echinoderms and molluscs and probably crustaceans. We can confidently expect this list to be extended, probably even to include fish.
For example, Hasler and Wisby (1951) have obtained most interesting evidence of the influence of different natural waters upon the movements of fish. They found that minnows were able to discriminate between the waters of two Wisconsin creeks after as little as two months conditioning, while cautery of their olfactory epithelia rendered them unresponsive to conditioning. It appeared, therefore, that olfaction was the principal, if not the sole, means of discrimination. They further demonstrated that the chemical response was not to carbon-dioxide in the creek waters, for example, but that the significant fraction was probably organic, in the usual sense, in that the minnows reacted to the distillate rather than the residue (vacuum distillation at 25° C), so that the existence of a volatile substance in the water can be anticipated. Here then is the essence of one reaction system on which " homing ", and perhaps other aspects of migration, might reasonably be based. Indeed, Hasler's preliminary tests suggest that salmon can detect such " odours " of streams and discriminate between them. In that instance, it would be necessary to imagine the salmon being conditioned during its early fresh water life to the " odours " of the " home " tributary. Hasler has also been able to demonstrate that minnows could respond to such odours after " forgetting periods " which were longer in fishes trained when young than in old ones. It may not therefore be so unreasonable to think of such reactions as even applying to the move- ments of other and wholly marine fish.
Lastly, when mentioning this particular possibility as one of the possible uses to which such fundamental research might ultimately be put in a fisheries laboratory, Johnston (1955) also referred to the possibility that " fertilization " of natural waters, normally by enrichment with phosphates and nitrates, might come to include the addition of minute amounts of critical metabolites. Ideally, at least, these would be selected as those likely to mediate the succession of '' desirable " algae in relation to the favoured crop. For example, it has seemed at times that the risks of fertilization being followed by blooms of " undesirable " algae are considerable, but it does not seem unreasonable to imagine that such a succession could, to some extent, be con- trolled if the fertilizer included not only normal manures but a specific metabolite antagonistic to these algae and preferably favouring other forms. Indeed, it may not be too speculative to suggest that some natural waters, normally producing little in the way of a desirable crop, might be induced to undergo a complete ecological change by the addition of a critical metabolite alone. The apparent scarcity of nutrients in some of these waters may not be so significant as it may seem. Not only may there
External metabolites in the sea I47
be great reserves of nutrient in the bottom deposits but, as the Haskins Laboratories have demonstrated, many algae can tolerate only quite dilute nutrient solutions, and can thrive on them, so long as the necessary free metabolites are present. Perhaps particularly in some " barren " fresh waters, it may be that certain types of ecological development are blocked, just as in some laboratory experiments, by the natural absence of a specific metabolite essential to the life of an essential organism in fish management.
Such possibilities as these various lines of work indicate may make this field an attractive one to fisheries worker and biologist alike. Certainly, considerable develop- ment can be expected during the next few years. A number of those working in the various fields, however, may possibly have missed something of the community of interest they share with many others. With a few striking exceptions, what now seem to be very relevant cross references are frequently missing from bibliographies. Perhaps this paper may serve to emphasize, where necessary, some of the fundamental features thought to be common to the various investigations.
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Proc Roy. Soc, (B), 139, 372-397. Fox, D. L. (1944), Fossil pigments. Sci. Mon., 59, 394-396. Eraser, J. H. (1952), The Chaetognatha and other zooplankton of the Scottish area and their value
as biological indicators of hydrographical conditions. Scottish Home Dept., Mar. Res., 1952 (2),
1-52. Gran, H. H. (1931), On the conditions for the production of plankton in the sea. Rapp. Proc. Verb..
Cons. Perm. Int. E.xpl. Mer, 75, 37-46. Hardy, A. C. (1935), Part V. The plankton community, the whale fisheries, and the h\pothesis of
animal exclusion. In: Hardy, A. C. and Gunther, E. R. (1935), The plankton of the South
Georgia Whaling Grounds and adjacent waters, 1926-1927. Di.scovery Repis., 11, 1-456. Harvey, H. W. (1939), Substances controlling the growth of a diatom. J. Mar. Biol. Assoc, U.K..
23, 499-520. Hasler, a. D. and Wisby, W. J. (1951), Discrimination of stream odors by fishes and its relation
to parent stream behavior. Amer. Nat., 85, 223-238. Hutchinson, G. E. (1943), Thiamin in lake waters. Arch. Biochem., 2, 143-150. Johnston R (1955), Biologically active compounds in the sea. J. Mar. Biol. Assoc, U.K.M, 1S>-195. Johnstone, J., Scott, A. and Chadwick, H. C. (1924), Marine Plankton. Liverpool Univ. Press.
194 pp. ' ' J r . •■
JoRGENSEN, C. B. (1952), On the relation between water transport and food requirements m some
marine filter feeding invertebrates. Biol. Bull.. 103, 346-363. Knight-Jones, E. W. and Stevenson, J. P. (1950), Gregariousness dunng settlement in the barnacle
Elminius modestus Darwin. J. Mar. Biol. AS.SOC, U.K., 29, 28\-297. ,o-,-.-7
KoRRiNGA, p. (1949), More light upon the problem of the oyster s nutrition. BIjdr. Dierk., 28, 237-
248.
148 C. E. Lucas
Krogh, a. (1931), Dissolved substances as food of aquatic organisms. Biol. Rev., 6, 412-442. Lefevre, M., Jakob, H. and Nisbet, M. (1952), Auto, et heterochez les algues d'eau douce. Ann.
Sta. Cent. Hydrobiol. AppL, 4, 5-198. Levring, T. (1945), Some culture experiments with marine plankton diatoms. (Medd. Oceanogr..
Inst., Goteborg, 9.) Goteborgs Kiingl. Vetenskaps- och Vitterhets-Samhdlles Handi, 3 (12), 1-18. Lewin, R. a. (1954), A marine Stichococcus sp. which requires vitamin Bio (Cobaiamin). J. Gen.
Microbiol., 10(1), 93-96. Lucas, C. E. (1936), On certain interrelations between phytoplankton and zooplankton under
experimental conditions. J. du Cons., 11, 343-362. Lucas, C. E. (1938), Some aspects of integration in plankton communities. /. du Cons., 13, 309-322. Lucas, C. E. (1944), Excretions, ecology and evolution. Nature. 153, 378. Lucas, C. E. (1947), The ecological effects of external metabolites. Biol. Rev., 22, 270-295. Lucas, C. E. (1949), External metabolites and ecological adaptations. Svmp. Sac. Exp. Biol., 3,
336-356. LwoFF, A. (1943), L'evolution physiologique. Actualites Sci. Industr., 970, H. Hermann, Paris. McCoMBiE, A. M. (1953), Factors influencing the growth of phytoplankton. /. Fish. Res. Bd., Canada,
10 (5), 253-282. Matsudiara, T. (1939), The physiological property of sea water considered from the effect upon the
growth of diatoms, with special reference to its vertical and seasonal change. Bull. Japan. Soc.,
Sci. Fish., 8, 187-193. MiYAZAKi, I. (1938), On a substance which is contained in green algae and induces spawning action
of the male oyster. (Preliminary note.) Bull. Japan. Soc, Sci. Fish., 7, 137-138. Morris, R. W. (1955), Some considerations regarding the nutrition of marine fish larvae. J. du Cons.
20 (3), 255-265. Pratt, R. (1943), Studies on Chlorella vulgaris. VL Retardation of photosynthesis by a growth- inhibiting substance from Chlorella vulgaris. Amer. J. Bot., 30, 32-33. Provasoli, L. and Pintner, L J. (1953), Ecological implications of w vitro nutritional requirements of
algal flagellates. Ann. N. Y. Acad. Sci., 56, 839-851. Rice, T. R. (1954), Biotic influences aflfecting population growth of planktonic algae. U.S. Fish and
midlife Serv., Fish. Bull., 54 (87), 227-245. Russell, F. S. (1936), A review of some aspects of zooplankton research. Rapp. Proc. Verb., Cons.
Perm. Int. Expl. Mer, 95, 5-30. Russell, F. S. (1939), Hydrographical and biological conditions in the North Sea as indicated by
plankton organisms. J. du Cons., 14 (2), 171-192. Wangersky, p. J. (1952), Isolation of ascorbic acid and rhamnosides from sea water. Science, 115,
685. Wilson, D. P. (1948), The relation of the substratum to the metamorphosis of Ophelia larvae. /. Mar.
Biol. Assoc, U.K., 27, 723-760. Wilson, D. P. (1951), A biological difference between natural sea waters. J. Mar. Biol. Assoc, U.K.,
30, 1-20. Wilson, D. P. (1953), The settlement of Ophelia bicornis Savigny larvae. J. Mar. Biol. Assoc, U.K.,
31,413-438. Wilson, D. P. (1954), The attractive factor in the settlement of Ophelia bicornis Savigny. J. Mar. Biol.
Assoc, U.K., 33, 361-380. Wilson, D. P. and Armstrong, F. A. J. (1954), Biological differences between sea waters: experi- ments in 1953. J. Mar. Biol. Assoc, U.K., 33, 347-360.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Researcli. pp. 149-168.
A revision of Ernst Haeckel's determinations of a collection of Medusae belonging to the Zoological Museum of Copenhagen
By P. L. Kramp Zoological Museum, Copenhagen
Summary— The collection of medusae sent from the Zoological Museum of the University of Copen- hagen to Ernst Haeckel for identification comprised 231 numbers; from 166 of these the specimens are still in our collection and are the subject of this revision.
Specimens from 12 localities were not identified with certainty by Haeckel; they belong to 9 different species, 6 of which are described in previous literature, whereas 3 species have been described after the publication of Haeckel's monograph.
In the collection and the accompanying list 54 species are provided with generic and specific name in Haeckel's hand-writing. After the revision the actual number of species is reduced to 37.
26 species are designated as new and are represented by their type-specimens or cotypes; 5 of these may be retained as valid species, 3 of them with unaltered generic name; the remaining 21 of Haeckel's new species belong to 15 species previously described.
Among the 28 species, which are not marked as new, 10 are synonyms, and 8 are erroneously identified.
While Ernst Haeckel prepared his famous monograph, " Das System der Medusen ", which was published in 1879-80, he borrowed the whole collection of medusae belonging to the Zoological Museum of the University of Copenhagen. The Danish zoologist Japetus Steenstrup had organized a fruitful collecting of marine animals, particularly pelagic ones, by officials in Greenland (inspector Olrik and others) and captains and physicians on Danish merchant vessels (Andrea, Bang, Holboll, Hygom, etc.) on their journeys to Greenland, the West Indies, South America, India and China. The result was that, until the far-going oceanographical expeditions began with the cruise of the Challenger in 1873-76, the museum in Copenhagen possessed one of the greatest collections of marine animals in the world.
The collection of medusae was sent to Haeckel in Jena accompanied by a detailed list written by Chr. Lutken with (1) provisional determinations by Steenstrup and LiJTKEN, (2) localities, (3) names of collectors, (4) an empty column, in which Haeckel wrote his own determinations of the species. The list, which contains 231 numbers, is still in our museum and is a document of great value, giving us the names of all the species in Haeckel's own hand-writing (see Fig. 1). The majority of specimens are also still in our collection. Many of them are in a fairly good condition, though they must be handled with care, because they are more or less brittle in consequence of their being preserved in alcohol.
Many of the species described or recorded by Haeckel have been the subject of much discussion, and it has often been desirable to re-examine the original specimens. It is not to be denied that Haeckel's artistic temperament and fertile imagination sometimes led him to construct a detailed description and beautiful drawings from an ugly and mutilated specimen. But he also had excellent powers of observation, and when his descriptions and figures are based on living or tolerably well-preserved
149
150 P- L- Kramp
Specimens, they are usually reliable, though sometimes one must wonder at what he has overlooked (e.g. in " Hippocrene platygaster " and " Thaumantias eschscholtzii ", see below).
Occasionally some of the specimens in the Copenhagen collection have been re- examined, partly by me (Kramp, 1919; 1926; 1947, specimens from the northern Atlantic), partly by Cl. Hartlaub (1913, northern Pandeidae) and by G. Stiasny (1922 a, some East- Asiatic Scyphomedusae). Remarks on some tropical Atlantic forms will also be published by me in the near future {Atlantide Reports and Discovery Reports, in press).
A revision of the whole collection may, however, be useful to future workers on medusae, and in the present paper I shall give a complete list of that part of the old collection which is still in existence. Fortunately, as seen from the list, none of the specimens, which have disappeared, belonged to species which are not represented in the preserved collection. The succession of the species follows the order in which they are mentioned in Haeckel's monograph and with Haeckel's generic and specific names as head-lines, with the exception of the Narcomedusae, none of which were finally determined by him. In square brackets [ ] is added the correct name of each species as found by the revision, in so far as it differs from the name given by Haeckel or in cases where this latter turned out to comprise two or more species. The figures in common brackets ( ) refer to the numbers in the list.
It is very understandable that Haeckel, in his worship of beauty, was attracted by these pretty animals. His " System der Medusen ", followed immediately by his work on deep-sea medusae in the Challenger Reports (1881), is a mile-stone in the progress of our knowledge of the medusae, and this progress soon became rapid, especially when one great expedition after another was sent out to explore the oceans and their inhabitants. No wonder that the knowledge contained in Haeckel's works was soon considerably augmented, and the reliability of his apprehension of the observations, or even of the observations themselves, were considered open to doubt. In the present paper I hope to contribute to the removal of some of these cases of doubt.
When the next monograph of medusae appeared in A. G. Mayer's " The Medusae of the World " (1910), H. B. Bigelow^ had just published his outstanding work on the medusae of the eastern tropical Pacific (1909) to be followed {provisionally until 1940) by many other papers, to which the student of medusae must continually refer for valuable information.
ANTHOMEDUSAE Codonium princeps Haeckel. 1879, p. 13, PI. I, figs. 1, 2. [Sarsia princeps (Haeckel).] The description is based entirely on specimens in the Zoological Museum, Copen- hagen. Specimens are still retained from the following localities: (8 and 13) Greenland? Mus. zootom. Hafn. 3 specimens.
(9) Davis Strait and Baffin Bay; Borch, 1859. 2 specimens.
(10) Greenland; 1865. 7 specimens.
(12) Umanak, Greenland; Fleischer, 1865 (Neotype). 1 specimen.
(137) Godhavn, Greenland; Olrik, 1860. 12 specimens.
(138) Greenland. 4 specimens.
A revision of Ernst Haeckel's determinations of a collection of Medusae 1 5 1
No. 22 in the list, Greenland, H. P. C. Molllr, is determined by Haeckel as Sarsia g/acialis; this specimen really belongs to S. princeps. Haeckel's statement of the colour of the species was based on sketches made by H. P. C. Moller. These sketches are in our museum and they were drawn partly at Frederikshaab in 1839, partly at Godthaab in 1840; they evidently represent Sarsia tuhulosa and noi princeps, showing no trace of an apical canal.
No. 11 in the list, taken north of the Faroe Islands by Steincke and identified by Haeckel as Codonium princeps, is unfortunately not in the collection. It is very improbable that this species should have been found in this southern locality.
Since no type-specimen was pointed out by Haeckel, I designate No. 12, Umanak, Fleischer, 1865, as Neotype.
Sarsia tubulosa 1879, p. 16. Specimens identified by Haeckel as Sarsia tubulosa are retained from the following localities:
(15) Iceland; Steincke.
(16) Bordeyri, northern Iceland; Steincke. 2 specimens.
(17) Isafjord, Iceland; Mariboe, 1865. 2 specimens.
(18) Faroe Islands; Steenstrup, 1844. 2 specimens.
Steenstrupia galanthus
1879, p. 31.
[Steenstrupia nutans (M. Sars)]
No. 118 in the list, 49' N. 7" W., off the mouth of the English Channel, Hygom,
1857, is labelled by Haeckel Steenstrupia {rubra Forbes?). There are two specimens,
belonging to S. nutans.
Stomotoca pterophylla Haeckel. 1879, p. 52, PL IV, fig. 10. (168) 20' 36' N. 76" W., north of Cuba; Andrea, 1867. 3 specimens, one of which I designate as Neotype. Mayer (1910, p. 113) gives a new description of this species, slightly differing from that of Haeckel. Mayer presumes that certain errors in Haeckel's description are due to the state of preservation of the specimens. It is true that this may account for the absence of an apical projection and the finely serrate inner margin of the ring- canal. The so-called " Ocellarkolben " are rudimentary tentacle bulbs, and they have no ocelli; their number is as stated by Haeckel, and on the whole the description is in good accordance with the structure of the specimens.
Pandea saltatoria
1879, p. 54.
In the text of his monograph Haeckel only mentions the original specimen from
Norway described by M. Sars (1835) as Oceania saltatoria {Pandea saltatoria Lesson
1843), a species which has never been identified with certainty, though Hartlaub
(1913, p. 336) is inclined to think that it was an Aglantha.
152 P- L- Kramp
In our collection is a specimen (No. 112 in the list) labelled by Haeckel Pandea saltatoria, 14° N. 25° W., west of the Cape Verde Islands, collected by Hygom in 1858. It belongs to Pandea conica Lesson. The number of exumbral nematocyst tracks corresponds to the number of tentacles.
Conis cyclophthalma Haeckel. 1879, p. 55, PI. IV, fig. 1. [Oceania armata KoUiker.] (1 14) 36° 29' N. 2° 28' W., Mediterranean, near Gibraltar; Branner. (Haeckel as the result of misprints gives the longitude as 2° 23' W. and the name of the collector as Bramer.) This is the type specimen of C cyclophthalma, and we are fortunate to have it in the collection. Mayer (1910, p. 130) retains the species within the genus Conis beside C. mitrata Brandt. Hartlaub (1913, p. 342) has examined the type-specimen, and I can confirm his statement that it belongs to Oceania armata Kolliker. Thus Conis cyclophthalma is an obsolete name.
Oceania sp. Haeckel (1879, p. 56) declares that the generic name Oceania is obsolete, but in the list some medusae are mentioned as Oceania sp. ? One of them, 28-33° N. 60-64° W., Hedemann, 1867, has disappeared, the others are in the collection and may be identified as follows:
(88) 21° S. 57° E., east of Madagascar; Andrea, 1864, 2 specimens, 5 mm in
height, with 8 tentacles ; they belong to Neoturris papua (Lesson). (126) 49° N. 7° W., off the mouth of the EngHsh Channel; Hygom, 1857. 1 specimen, belonging to Leuckartiara nobilis Hartlaub.
Tiara pileata. 1879, p. 58. (Ill) 36° 17' N. 3° 27' W. Mediterranean near Gibraltar; Branner, 1869. 4 specimens, labelled by Haeckel: Tiara pileata = Oceania (coccinea). They belong to Pandea conica Lesson.
Tiara conifer a Haeckel. 1879, p. 59. (142 and 143) Greenland; Olrik. 2 specimens. Haeckel's description is entirely based on these specimens; they belong to Catablema vesicarium (A. Agassiz) as already presumed by Hartlaub (1913, p. 315).
Tiara reticulata Haeckel. 1879, p. 60, PI. Ill, fig. 11. [Pandea conica Lesson.] (104) 35° 31' S. 0° 51' W. Atlantic Ocean near Tristan da Cunha; Andrea, 1862. 2 specimens. These are the only specimens known, and they belong to Pandea conica Lesson, as already stated by Hartlaub (1913, p. 340).
I MVI 1;M1 1 ! K|S , ^. , . ^ ^ a/ ^ -^V Z(IOl,(MW^M Ml ^i-.l M --^7^ y^-^ r *^* ' ^
KJ0BENHAVN.
u.
•J£l- ^-^ • /^^.A^ j^./i^r. '^^'-«-- u.<^^J..^^^ /^-^ .■ ■ f^.j
Fig 1 Fascimile of one of the pages of the lisl ol medusae sent from the Zoological Museum of Copenhagen to Eknst Halckil. The right hall of the sheet contains the names of the species m Haeckkl s hand-wntmg.
A revision of Ernst Haeckel's determinations of a collection of Medusae I 53
Turris digitalis. 1879, p.61.
(44) 59° 20' N. 15"^ 47' W., between Scotland and Iceland; Rink, 1852. 7
specimens. (47) 58-59° N., between Iceland and Greenland; Rink, 1852. 1 specimen. (147) 59° 09' N. 16^ W., west of Scotland; Olrik, 1861. I specimen. These specimens were re-examined by Hartlaub (191 3. p. 329) and Kramp (1926, p. 94). They belong to Neoturris pHeata (Forskal).
Catablema campanula.
1879, p. 63, PI. IV, figs. 4, 5.
[Catablema vesicarium (A. Agassiz).^
Haeckel described this as a " nova species? ", indicating that it might be identical
with Medusa campanula Fabricius, 1780. The description was based on the following
specimens, which are still in our collection:
(43) Greenland; Zimmer, 1856. 2 specimens. (144) Umanak, Greenland; Olrik, 1853. 7 specimens. Haeckel also referred to a coloured sketch by H. P. C. Moller; the sketch is in our museum, and it was drawn after a specimen taken near Frederikshaab in Green- land in 1839; like the preserved specimens it undoubtedly belongs to C. vesicarium.
Catablema vesicarium. 1879, p. 64. In his book Haeckel only quotes the description of this species as given by A. Agassiz (1865) and says nothing about a specimen, which is in the collection, labelled by himself Catablema vesicarium :
(45) Greenland; Moberg, 1857.
Catablema eurystoma Haeckel. 1879, p. 64, PI. IV, figs. 6, 7. The description of this species was based on specimens in the museum of Copen- hagen and a coloured sketch by H. P. C. Moller, drawn at Qajartalik in Arsuk Fjord in southern Greenland. The species is undoubtedly identical with C. vesicarium (A. Agassiz), but the specimens are lost. They were taken in the following locality: (146) 67^ 35' N. 54' 10' W., in South Stromfjord, Greenland; Olrik, 1866.
Cytaeis nigritina Haeckel.
1879, p. 74, PI. VI, figs. 2-5.
[Cytaeis tetrastyla Eschscholtz."
On a previous occasion (Kramp, 1953, p. 263) I have discussed the name o( this
species. Haeckel applies the specific name tetrastyla only to the original form described
by Eschscholtz, but refers the numerous specimens from the museum of Copenhagen
to a new species,'c. nigritina. Mayer (1910, p. 133) tried to revive the name atlantica
Steenstrup, 1837, but, as stated by me, this name was only found in Steenstrup's
hand-written catalogue of the collection in our museum and was never published.
]54 P- L. Kramp
The specimens in our collection are derived from the following localities: (72, 73) 14° N. 20° W., near Cape Verde Islands; Prosch. 15 specimens, type specimens of Cytaeis nigritina.
(74) 8°30'N. 24° W., south of Cape Verde Islands; Andrea, 1872. 2 specimens,
labelled Nigritina atlantica.
(75) 31° 28' N. 29° 39' W., south of the Azores; Andrea, 1860. 5 specimens,
labelled Nigritina sp.
(76) 5° S, 28° W., off Cape San Roque, east coast of Brazil; Hygom. 2 speci-
mens, labelled Nigritina sp. {polyblasta ?).
(77) 23° 03' N. 31° 48' W., N.W. of Cape Verde Islands; Mathiesen, 1848.
2 specimens, labelled Nigritina atlantica.
(78) 5° 31' N. 23° 15' W., south of Cape Verde Islands; Reinhardt. 1 specimen,
labelled Nigritina atlantica ( ?).
(80) 34° N. 34° W., S.W. of the Azores; Hygom. 1 specimen, labelled Nigritina
{polyblasta'}).
(81) 6° N. 22° W., south of Cape Verde Islands; Hygom. 3 specimens, labelled
Nigritina (polyblastal). (89) Atlantic Ocean; Hygom, 1863. 1 specimen, labelled Cytaeis nigritina. Before the publication of his book Haeckel had evidently been much in doubt of the most convenient name of this species. The specific name polyblasta, applied to some of the specimens in the list, is found nowhere in the monograph; he may have thought about attaching this name to specimens carrying medusa buds.
Cytaeis macrogaster Haeckel. 1879, p. 74, PI. VI, fig. 1. [Cytaeis tetrastyla Eschscholtz.] It is generally acknowledged that C. macrogaster is merely a synonym of C. tetra- styla, and an examination of the present specimens confirms this view.
(83) 0° S. 29° W., Andrea, 1866. 2 specimens, designated as the types.
(84) 1° 20' S. 26° 20' W. Andrea, 1863. 1 specimen.
(85) 2°30'N. 24°W. Andrea, 1863. 4 specimens. (87) 1° 30' N. 24° W. Andrea, 1863. 3 specimens.
All these localities are at a considerable distance N.E. of Cape San Roque on the east coast of Brazil.
Margelis principis Steenstrup. 1879, p. 88, PI. VI, figs. 14-16. The specimens labelled Margelis principis belong to two different species: Bougain- villia principis Steenstrup, and B. superciliaris L. Agassiz.
(3) Sandvaag, Faroe Islands; Steenstrup, 1844. The type-specimen of Margelis principis.
(5) Davis Strait off Holsteinsborg; Olrik, 1859. 7 specimens.
(6) Godhavn, Greenland; Olrik, 1860. 1 specimen.
The specimens from the two last mentioned localities are Bougainvillia superciliaris.
No. 50 in the list, north of Orkney Islands, collected by Olrik, 1859, is likewise
identified by Haeckel as Margelis principis, but the specimens are not in the collection.
A revision of Ernst Haeckel's determinations of a collection of Medusae 1 55
Haeckel's figures of Marge/is principis are said to be based on specimens from Iceland, but no Icelandic locality is mentioned in the list.
Hippocrene platygaster Hacckel. 1879, p. 91. [Bougainvil/ia platygaster Haeckel.] (107) 25= 04' S. 27° 26' W., S.W. of the islands of Trinidad; Andrea, 1869. 2 specimens, one of which 1 have designated as the type; by Haeckel himself named H. platygaster n.sp. (1 10) 24° N. 33° W., about 700 miles N.W. of Cape Verde Islands; Iversen, 1871. 1 specimen, labelled Marge/is (platygasterl). In my report on the Hydromedusae of the Discovery expedition (in press), I have dealt with this species at some length. Numerous specimens were collected by the Discovery in the tropical parts of the Atlantic and off the east coast of Africa, and it was also taken by the Dana in some localities in West-Indian waters. In my opinion BougainviUia platygaster is a valid species, distinct from B. carolinensis (McCrady), B.fulva Agassiz and Mayer, and B. niobe Mayer. I found that B. platygaster exhibits a most peculiar form of asexual propagation and, as a matter of fact, this same form of propagation is also observed in one of Haeckel's own specimens (No. 107), but it seems to have escaped his attention; at any rate, he does not mention it in his description.
Hippocrene superciliaris. 1879, p. 92. [BougainviUia superciliaris L. Agassiz.] (1, 2 and 4) 66° 13' N. 55 05' W., off South Stromfjord, Greenland; Moberg. 12 specimens. These specimens really belong to B. superciliaris, as also some of the specimens erroneously identified as B. principis (see above).
Nemopsis heteronema Haeckel. 1879, p. 93, PI. V, figs. 6-9. [BougainviUia principis Steenstrup. , (7) Iceland; Steenstrup, 1839. 2 specimens. Haeckel described these specimens together with some others from Norway collected by himself. As previously pointed out by me (Kramp, 1926, p. 48; 1939. p. 6) the specimens from Iceland belong to BougainviUia principis (Steenstrup).
Rathkea fasciculata. 1879, p. 97. [Kollikerina fasciculata (Peron & Lesueur).] (151) Mediterranean; Keferstein and Ehlers. In the list as well as on the label this specimen is named Lizzia kollikeri Gegenbaur, but in the monograph the name is altered to Rathkea fasciculata.
[56 PL. Kramp
LEPTOMEDUSAE
Thaumantias eschscholtzii Haeckel.
1879, p. 129, PI. VIII, fig. 4. [Tiaropsis multicirrata (M. Sars).] (56) Greenland; Holboll, 1841. 1 specimen. (58) Greenland, 1865. 2 specimens. The description of this species was one of Haeckel's great mistakes. The beautiful figure is reproduced in several handbooks as a typical " Thaumantias ", a leptomedusa, without any kind of marginal sense organs. As a matter of fact, it has eight large, black ocelli adjacent to eight large, open marginal vesicles.
When as a young man, in 1915, I commenced my work at the Zoological Museum of Copenhagen, I found the specimens mentioned above, and of course I was very interested to see the type specimens of the famous Thaumantias eschscholtzii, but while looking at them through an ordinary hand lens I saw eight black spots on their umbrella margin, and a closer examination revealed the fact that they belonged to the common and well-known Tiaropsis multicirrata. This surprising discovery was published by me in the reports of the Danish Ingolf-Expedition (Kramp, 1919, p. 78; see also my revision of the Mitrocomidae, 1932, p. 364). To my regret " Thaumantias eschscholtzii " with a reproduction of the usual figure reappeared in Kukenthal's " Handbuch der Zoologie ", Bd. I, 1924. The author of the article on Hydroida, my friend Hj. Broch, Oslo, told me that his manuscript was delivered before 1914, and when the printing of the " Handbuch " was resumed after the war, he was not allowed to alter anything in his original text. Since then, however, I think that " Thaumantias eschscholtzii " has been regarded as an obsolete name.
Staurostoma laciniata.
1879, p. 130.
[Staurophora mertensi Brandt.]
(164) 43' N. 61° 30' W., near Nova Scotia, Canada; Hedemann. Fragments
of about 5 specimens. The specimens were labelled Staurostoma laciniata Agassiz, and in the monograph it is placed among the Thaumantidae, whereas Staurophora mertensi Brandt, which is the same species, is mentioned (p. 149) under the Cannotidae.
Laodice cruciata. 1879, p. 132. [Laodicea undulata Forbes & Goodsir.] (53, 54) 59' 07' N. 13° 32' W., north of Rockall; Moberg. 5 specimens, labelled
Laodice cruciata. (140) 59° N. 18' W., between Iceland and Rockall; Olrik. 3 specimens, labelled Laodice cruciata.
(165) 58-59° N. 13-15° W., north of Rockall; Rink, 1852. 5 specimens,
labelled Thaumantias (pilosellal). As demonstrated by Browne (1896, p. 482) there is only one single name among Haeckel's 25 synonyms of " Laodice cruciata ", which really refers to a Laodicea, viz. " Thaumantias mediterranea " Gegenbaur (one of Haeckel's synonyms was
A revision of Ernst HaeckeFs determinations of a collection of Medusae | 57
Thaumantias (Cosmetira) pilose/la Forbes, which is a Mitrocomid). I have previously discussed the specific name (Kramp, 1919, p. 21) and adopted the name umlulata Forbes & Goodsir, which was proposed by Browne (1907).
Orchistoma steenstrupii Haeckel. 1879, p. 139, PI. XV, figs. 3-5. [Orchistoma pileus (Lesson).] (154) 20°N. 81° W., south of Cuba; Hygom. 3 specimens. Two of the specimens are in good condition, and they agree quite well with the new description and figures by Mayer (1910, p. 211, PI. 25, figs. 1-4), which were based on specimens from near the Bahamas and Tortugas. I agree with Mayer that O. steenstrupii is identical with Mesonema pileus Lesson (1843) and should be called Orchistoma pileus.
Ptychogena pinuulata Haeckel. 1879, p. 148; 1881, p. 7, PI. II, figs. 1-8. [Ptychogena lactea A. Agassiz.] (139 and 141) 59° 07' N. 13° 32' W., between Ireland and Iceland; Moberg, 1857. 3 specimens, one of which is designated as the type. As previously mentioned by me (Kramp, 1942, p. 55) this locality is most probably due to a mistake. This species is arctic, circum-polar, and it is hardly possible that it should occur so far to the south in the Atlantic. Haeckel's figures (1881) are remarkably beautiful and entirely correct.
Irene viridula. 1879, p. 202. (60) Isafjord, north-western Iceland; Mariboe, 1865. 1 specimen. In the list this specimen is identified as Eirene {viridula']). It really belongs to Eutonina indicans (Romanes), (see Kramp, 1919, p. 99).
Mesonema pensile. 1879, p. 226. (156) Karimata Strait, west of Borneo; Caspersen, 1869. 1 specimen, diameter ca. 50 mm, about 125 radial canals and about 21 tentacles. Labelled
Mesonema sp. (152) 14° S. 34° W.,off San Salvador, east coast of Brazil; Hygom. 3 specimens,
with the following dimensions :
diam. ca. 65 mm, ca. 120 radial canals, ca. 20 tentacles. „ ca. 60 mm, ca. 80 „ „ ca. 16 „ ,, ca. 55 mm, ca. 90 ,, ,, '?
The specimens No. 152 are determined in the list as Mesonema pensilel None of the localities are mentioned in the monograph.
In all the specimens the tentacle bulbs are provided with a distinct apical keel and spur; they undoubtedly belong to Aequorea macrodactyla (Brandt).
158 P- L. Kramp
Mesonema macrodactylum Brandt.
1879, p. 226. [Aequorea macrodactyla (Brandt)] Besides the specimens mentioned above the collection contains one specimen of Aequorea macrodactyla, of which the label has been lost. It must have been derived from one of the following two localities, to which Haeckel has added the determina- tion Mesonema macrodactylum:
(155) 2° 04' N. 106° 50' E., near Singapore; Andrea, 1869. (157) 10 miles south of Sunda Strait; Bardenfleth, 1875. The specimen is about 50 mm in diameter, with about 125 radial canals and about 19 tentacles. None of these localities are mentioned in the monograph.
TRACHYMEDUSAE
Pectyllis arctica Haekel. 1879, p. 266. [Ptychogastria polaris Allman.] (148, 149) Proven, about 72° 20' N. on the west coast of Greenland; Olrik, 1860. 5 specimens. Besides these specimens Haeckel examined a specimen taken near Halifax by the Challenger expedition in 1873. When he described the species, in 1879, he was not aware that in the previous year it had been described by Allman as Ptychogastria polaris.
Aglantha digitalis. 1879, p. 272. [Aglantha digitale (O. F. Muller).] In the list this species is recorded from numerous localities; specimens are still retained from the following:
(24) 58° 17' N. 30° 59' W. Olrik, 1859. 6 specimens.
(30) 59° 07' N. 13° 32' W. Moberg. 10 specimens.
(31) 57° 32' N. 33° 31' W. Olrik, 1859. 5 specimens.
(32) Northern Atlantic Ocean; Olrik, 1860. 6 specimens.
(35) 58-59° N., between Iceland and Greenland; Rink. 2 specimens. (37) Ritenbenk, about 69° 40' N. on the west coast of Greenland; Andersen, 1862. 3 specimens.
(40) 58° 27' N. 26° 43' W. Moberg, 1857. 4 specimens.
(41) 57° 48' N. 43° 45' W. Olrik, 1861. 1 specimen. (128) 57° 43' N. 27° 03' W. Bang, 1868. 8 specimens.
(130) Davis Strait, off Disco, about 69° N. Olrik, 1862. 10 specimens. (132) Godhavn, Disco, about 69° 12' N. Moberg, 1857. 1 specimen. (134) Umanak, about 72° 40' N,, West Greenland; Brockdorff. 1 specimen. Haeckel altered O. F. Muller's original spelling of the specific name digitale to digitalis.
Haeckel has also added the name to two coloured sketches by H. P. C. Moller, made at Fiskenasset and Godthaab in Greenland,
A revision of Ernst Haeckei's determinations of a collection of Medusae 1 59
Liriope rosacea.
1879, p. 290.
[Liriope tetraphylla (Chamisso & Eysenhardt).]
The record of L. rosacea in the monograph is only a quotation from Eschscholtz
( 1 829), who described it from near the equator in the Pacific Ocean as Geryonia rosacea ;
but in our collection are several specimens identified by Haeckel as L. rosacea from
the following two localities:
(62, 63) 10= N. 105' E., in the Gulf of Siam; Strandgaard, 1860. 2 specimens.
(67) Red Sea; H. Koch, 1872. 6 specimens.
I agree with the authors who unite all the numerous " species " o^ Liriope into one: L. tetraphylla Chamisso & Eysenhardt.
Liriope crucifera Haeckel. 1879, p. 290. [Liriope tetraphylla Chamisso & Eysenhardt.] The description of this new species was based on the following specimen:
(150) 35° S. 24° 30' E., near Algoa Bay on the south coast of Africa; Andrea, 1870. 1 specimen. The description is in good accordance with the appearance of the specimen, but I see no reason for keeping the species distinct from L. tetraphylla.
Glossocodon lUtkenii Haeckel.
1879, p. 293, PI. XVIII, fig. 5.
[Liriope tetraphylla Chamisso & Eysenhardt.]
(65) 30° N. 17° W., north of the Canary Islands; Hygom, 1857. 1 specimen.
(66) 36-40° N. 26-45° W., west of the Azores; Andrea, 1861. 1 specimen.
(68) 35° N. 27° W., south of the Azores; Hygom, I860. 1 specimen.
The new genus Glossocodon, of which this is the type-species, was said to differ from Liriope by the absence of interradial tentacles in the adult stage, whereas they are present in young specimens (like that from No. 68); evidently these tentacles were lost by preservation in the other specimens. The species lUtkeni is further characterized by its very broad gonads, which have a peculiar distal incurvation, forming two lateral angular dilatations. There is no trace of this conformation of the gonads in the specimens Nos. 65 and 68, and in the specimen No. 66 it is distinct in only one of the four gonads. Accordingly there is no reason to retain L. liitkeni as a separate species.
NARCOMEDUSAE
Pegasia sieboldii Haeckel. 1879, p. 331. This new species was described from a single specimen collected by Hygom in the tropical Atlantic. The specimen is not in our collection, and no " Pegasia " is mentioned in the list. According to Mayer (1910, p. 444) the species is probably identical with Pegasia dodecagona Peron &. Lesueur; this is, however, a doubtful species. Haeckel's description seems to me to indicate that Pegasia sieboldii should be referred to Peg- antha triloba Haeckel.
160 P- L. Kramp
Genus Pegantha Haeckel.
In its modern sense the genus Pegantha comprises all the four genera, Polycolpa, Polyxenia, Pegasia and Pegantha, which in Haeckel's monograph constitute the family Peganthidae. A considerable advance towards a revision of the numerous species of this group was made by H. B. Bigelow in several papers, first and foremost in his beautiful work on the medusae collected in the eastern tropical Pacific by the S.S. Albatross in 1904 and 1905 (Bigelow^, 1909), in which adequate descriptions with pretty and elucidating figures are given of several species, in most cases based on his own examination of the specimens in life, or at least in the fresh condition. Valuable additions to our knowledge of these medusae are given in Bigelow^'s subsequent papers, and by means of the extensive material collected by the Discovery expeditions I have recently been able to carry through an almost complete revision of the species belonging to Pegantha (to be published in the near future in the " Discovery Reports "). This has enabled me to identify the specimens previously examined by Haeckel. None of these specimens were, however, provided with definite specific, or even generic, names, as will be seen from the following notes, and none of the localities are recorded in Haeckel's monograph.
There are four species o{ Pegantha in the collection; they are mentioned here under their proper names, as I have identified them, not according to the denominations given by Haeckel in the list.
Pegantha martagon Haeckel. Pegantha martagon Haeckel, 1879, p. 332. (92) 29-31° N. 33-34° W. Hygom. 3 specimens, determ. Polyxenia'^. sp. (99) Atlantic Ocean north of the equator; Warming, 1866. 1 specimen, determ. Cunina sp.
Pegantha triloba Haeckel. Pegantha triloba Haeckel, 1879, p. 333. (95) Atlantic Ocean south of the equator; Friis, 1861. 2 specimens, determ. Aegineta']
Pegantha laevis H. B. Bigelow. Pegantha laevis H. B. Bigelow, 1909, p. 97, PI. 16, fig. 1, PI. 20, figs. 4-6,
PI. 27, figs. 1-7. (90) 20° N. 40° W., between Africa and the West-Indies; Hygom, 1860. 2
specimens, determ. Cuninal sp. (94) 22° N. 22° W., between the Canary Islands and the Cape Verde Islands; Hygom. 1 specimen, determ. Aegineta sp.
(97) 25° 05' N. 30° W., N.W. of the Cape Verde Islands; R. Nielsen, 1868/69.
2 specimens, determ. Polyxenial sp.
(98) No locality given; Mathiasen. 1 specimen, determ. Polyxenia sp. (115) West-Indies; Suensson. 1 specimen, determ. Cuninal sp.
(160) 8° 38' N. 24° 58' W., S.W. of the Cape Verde Islands; Mathiasen, 1848. 4 specimens, determ. Cunina sp.
A revision of Ernst Haeckei's determinations of a collection of Medusae 161
Fegantha clara R. P. Bigelow. Pegantha clara R. P. Bigelow, 1909, p. 80, 2 figs. Fegantha smaragdina H. B. Bigelow, 1909, p. 90, PI. 14, f^gs. 1-2, PI. 19,
figs. 1-9, PI. 22-26. (93) 3^ S. 27° W., N.E. of Cape San Roque, Brazil; Hygom. 1 young specimen, determ. Polyxenia'? sp.
Aeginopsis lawentii Brandt. 1879, p. 342. (145) Greenland; Holboll, 1841. 3 specimens. Haeckel has only determined these specimens as Aegina sp. ?, and they are not mentioned in the monograph. They belong to the high-arctic species Aeginopsis lawentii Brandt, 1838.
SCYPHOMEDUSAE
In the collection of the Zoological Museum of Copenhagen are several ancient specimens of Stauromedusae, mainly identified by J. Steenstrup. They were not sent to Haeckel, and the localities where they had been taken are not mentioned in his monograph. They will therefore not be mentioned here.
Some of the specimens belonging to other groups of Scyphomedusae and examined by Haeckel have been re-examined and correctly identified by G. Stiasny, Leiden, whereas I am responsible for the revision of the others.
Periphylla hyacinthina.
1880, p. 419, PI. XXIV.
[Periphylla periphylla (Peron & Lesueur).
The collection contains several specimens of this species; all of them had previously been labelled as Charybdea hyacinthina by Steenstrup who had, however, never published any account of them. In the list as well as in his monograph Haeckel has altered the name to Periphylla hyacinthina Steenstrup, and since the time of Haeckel this name has usually been accepted. On a previous occasion (Kramp, 1947, pp. 40 IT) I have discussed the generic as well as the specific name of this medusa. I retained the generic name Periphylla, but I came to the conclusion that the specific name hyacin- thina had to be altered, because Steenstrup, who applied it to his specimens, never published it but merely wrote it on the labels of the specimens and in the hand-written journals of the museum, the "Acta Mus. Hafniensis " 1837 and 1842. which are quoted by Haeckel. As a specific name hyacinthina was first used for this species by LtJTKEN (1875) and then by Haeckel (1879), but the species had been described several times before under different names (for details, see Kramp, 1947), and to avoid further confusion I stuck to the first indubitable name, periphylla Peron & Lesueur, 1809. In my opinion the correct name of this medusa must be Periphylla periphylla (Peron & Lesueur).
With one insignificant exception (Greenland, without further particulars, 1842) the specimens determined by Haeckel are all in our collection, and since the localities have not previously been published in details, it may be desirable to give them here.
G
162 P- L- Kramp
(202, 203, 205, 210, 213) Greenland; Moller, Jorgensen a.o. 8 specimens.
(206) Godthaab, Greenland; Bloch, 1845. 1 specimen.
(207) 57' 28' N. 41° W. Olrik, 1864. 1 specimen.
(208) 43" N. 23" W., north of the Azores; Hygom, 1857. 1 specimen.
(209) 57° 27' N. 35° W. Olrik, 1864. 1 specimen.
(211) 57° 40'-57° 27' N. 35-39° W. Olrik, 1862 and 1864. 2 specimens.
(212) Davis Strait; Borch, 1859. 2 specimens.
(214) 48° N. 8° W., Bay of Biscay; Hygom, 1851. 1 specimen.
(215) 39° N. 13° W., off Lisboa, Portugal; Hygom, 1863; 1 specimen. (217) 46° N. 18° W., off the Bay of Biscay; Hygom, 1856. 1 specimen.
(227) 57° 49' N. 35° 24' W. Bang, 1868. 1 specimen.
(228) S.E. of Cape Farewell; Borch, 1859. 3 specimens.
(229) 60° 12' N. 52° 15' W. Olrik, 1864. 1 specimen.
(230) 66° 13' N. 55° 05' W. Moberg. 1 specimen.
With the exception of Nos. 208,214, 215 and 217 these localities are in the surround- ings of the southern parts of Greenland.
Moreover, Haeckel has applied the name Periphylla hyacinthina to coloured sketches by H. P. C. Moller from the following locahties: 60° 19' N. 17° W., 58° N. 28° W., 57° 12' N. 53° 58' W., and Julianehaab in Greenland, 1838-1840.
Charybdea marsupialis. 1880, p. 442. [Carybdea marsupialis (Linne).] (201) Harbour of Malaga, Mediterranean coast of Spain; Hygom, 1853. 3 specimens.
(216) During a journey to the West-Indies; Suensson. 1 specimen.
Chiropsalmus quadrigatus Haeckel. 1880, p. 447. (166) Indian Ocean off Rangoon; Thalbitzer, 1863. 1 specimen. This is the type specimen; it was re-examined by Stiasny (1922 a, p. 517), who retains the species in spite of its bad condition and refers a second specimen, collected in Johore Strait, 1901-02, to the same species.
Liner ges pegasus Haeckel. 1880, p. 495. [Linuche unguiculata (Schwartz, 1788) Eschscholtz, 1829.] (105) West-Indies, or on journey to the West-Indies; Suensson. 5 specimens. The description of this species was based partly on specimens from Campeche Bay in the Gulf of Mexico, partly on the present specimens. These latter evidently belong to the widely distributed species Linuche unguiculata (Schwartz).
Liner ges mercurius Haeckel. 1880, p. 495, PI. XXIX, figs. 4-6. [Linuche unguiculata (Schwartz).]
(101) 19° 54' N. 81° 45' W., south of Cuba; Caspersen, 1870. 1 specimen.
(102) 20° 20' N. 73° W., between Cuba and Haiti; Andrea, 1861. 1 specimen. This species is undoubtedly identical with Linuche unguiculata ; at least the present
specimens certainly belong to that species.
A levision of Ernst Haeckel's determinations of a collection of Medusae 163
Linerges draco Haeckel. 1880, p. 496. (100) 5°N. 107° E., China Sea; Caspersen, 1869. 1 specimen. Haeckel by a misprint gives the longitude as 107" W. in the China Sea. This is the type specimen. Later on the species has been recorded from the Malayan Archi- pelago (Maas, 1903, p. 24) and New Britain (Neu Pommern) N.E. of New Guinea (Thiel, 1927, p. 27). I think we should follow Thiel in regarding it as a valid species.
Liniscus sandalopterus Haeckel.
1880, p. 497. [Linuche unguiculata (Schwartz).] (167) 2° N. 21° W., off Sierra Leone, West Africa; Strandgaard, 1857. 4 specimens. In his monograph Haeckel also records this species from the tropical part of the Atlantic collected by Koch and Hedemann, but in the list these specimens are deter- mined as Liniscus cyamopterus (see below). Liniscus sandalopterus has not been observed, since it was described by Haeckel, and the specimens evidently belong to Linuche unguiculata. L. sandalopterus accordingly is ah obsolete name.
Liniscus cyamopterus Haeckel.
1880, p. 497. [Nausithoe punctata Kolliker.] (103) Atlantic Ocean, without particulars; Koch, 1860. 1 specimen. (106) Atlantic Ocean ; Hedemann. 3 specimens. The specimens are labelled L. cyamopterus, and they are provided with the same name in the list; they are, however, large specimens of Nausithoe punctata Kolliker.
Pelagia per la.
1880, p. 506.
[Pelagia noctiluca ( Forskal).]
(177) Northern Atlantic; Olrik, 1860. 3 specimens. Pelagia perla is identical with P. noctiluca.
Pelagia phosphora Haeckel.
1880, p. 506. [Pelagia noctiluca (Forskal).] (170 and 231) 7" N. 22° W. Hygom, 1850. 3 specimens.
(171) 8° 38' N. 24° 58' W. Mathiasen. 1 specimen.
(172) 36°N. 41"W. Galathea, 1842. 3 specimens. (175) 7-13° N. 57° W. Hygom. 6 specimens. (174) Atlantic Ocean ; Hygom. 2 specimens.
(178) 11°N. 22°W. Hygom, 1853. 1 specimen. (180) Cape Verde Current; Prosch. 4 specimens. (225) 14° N. 20° W. Prosch.
Haeckel has referred all these specimens to his new species Pelagia phosphora, which, however, cannot be kept apart from P. noctiluca (Forskal).
A young specimen, labelled Pelagia ju\.. No. 116 in the list, taken in the Bay of Biscay, 47° N. 7° 30' W., likewise belongs to P. noctiluca.
164 P- L. Kramp
Pelagia cyanella Peron & Lesueur. 1880, p. 507. [Pelagia noctiluca (Forskal).] (176) No locality stated. Galathea exped. 1 specimen, determined P. cyane/lal
Stenoptycha dactylometra Haeckel.
1880, p. 526.
Cyanea capiUata (L.).
This species is not in the list, and no specimen is preserved, but the coloured
drawing by H. P. C. Moller, mentioned by Haeckel in his monograph, is in our
possession. It evidently represents a young Cyanea capil/ata with only 5 tentacles
in each of the eight groups.
Cyanea arctica Peron & Lesueur. 1880, p. 530. [Cyanea capillata (L.).] (183) Davis Strait; Olrik, 1866. 2 specimens. (220) Greenland; Holboll, 1841. 1 specimen. Haeckel determined these specimens as Cyanea arctica. As previously demonstrated by me (Kramp, 1942, pp. 128 If) the common Cyanea occurring in the Greenland waters and along the east coast of North America differs in no way from the European C. capillata.
Aurelia flavidula Peron & Lesueur.
1880, p. 555.
[Aurelia limhata Brandt.]
(181) Davis Strait; Olrik, 1866. 5 specimens.
The complicated history of the Greenland and East- American forms of Aurelia
was thoroughly dealt with by me in a previous paper (Kramp, 1942, pp. 109 ff), to
which I refer, especially concerning the discussion (p. 122) of the specific names of
the two species. The present specimens belong to the yellow form with complexly
branching and anastomosing canals described from the northern Pacific by Brandt
(1838) as Aurelia limbata. It was probably the same species, which was observed at
Greenland by O. Fabricius (1780), and it was to this that Peron and Lesueur applied
the name A. flavidula. Unfortunately, L. Agassiz accepted this name for the common
American Aurelia which, however, belongs to the same species as the European
A. aurita (L.), though the American form differs somewhat from the European and
should be designated as a distinct variety, A. aurita var. occidentalis (Kramp, 1942,
p. 125).
This variety of A. aurita also occurs along the southern part of the west coast of Greenland ; it is not mentioned in Haeckel's list, but to a drawing by H. P. C. Moller of a six-rayed specimen (locality not stated) Haeckel has added the name Aurelia flavidula var. sex radiis. Another drawing by Moller ( Frederikshaab, 1 839) apparently represents A. limbata.
A revision of Ernst Haeckel's determinations of a collection of Medusae 1 65
Polyclonia frondosa. 1880, p. 568. [Cassiopea frondosa (Pallas).] (187 and 188) West-Indies; Nat. Hist. Mus. Copenhagen. 2 specimens.
(189) St. Croix, West-Indies; Orsted and Ravn, 1836. 3 specimens.
(190) West-Indies; Suensson. 1 specimen.
Polyrhiza vesiculosa. 1880, p. 577. [Netrostoma coerulescens Maas.] (185) Gulf of Suez, Red Sea; Koch, 1872. 1 specimen. The specimen is mentioned by Haeckel in his monograph. It was re-examined by Stiasny (1922 A, p. 527), who found that this specimen most probably belongs to Netrostoma coerulescens Maas, and I think he was right in this respect.
Stomolophus fritillaria Haeckel . 1880, p. 598, PI. XXXV. {Stomolophus meleagris L. Agassiz, \ar. fritillaria.] (195, 196, 197) Surinam, on the northern Atlantic coast of South America; Mus. zootom. Hafn. 3 specimens.
Haeckel's description and beautiful figures of this species were based on these specimens.
In our collection is a fourth specimen (No. 198 in the list) of unknown origin, likewise identified by Haeckel as S. fritillaria. The locality where it was taken is given as 43° N. 61° 30' W., i.e. near Nova Scotia! The specimen is in an excellent condition, and there is no doubt of the correctness of the identification, but it seems impossible that any of the two species of Stomolophus might occur so far to the north; the distribution of both species is decidedly tropical. Evidently the note of the locality, in the label as well as in the list, must be due to some error.
There is no doubt that Stomolophus agaricus Haeckel (see below) is identical with 5". meleagris Agassiz, and S. chunii Vanhoffen belongs either to meleagris or to fritillaria, but the relation between these two latter species has been much discussed.
Mayer (1910, p. 711) regards S. fritillaria as a southern variety of S. meleagris. " The only valid distinction between this medusa and S. meleagris are in its large number of marginal lappets, and in the cleft in the middle of each octant of velar lappets. Also the 16 scapulets are hidden well up under the bell instead of extending down to about the level of the bell margin." Moreover, S. fritillaria does not seem to grow to a larger size than 80 mm in diameter, whereas meleagris may attain a diameter of 120 mm. Bigelow (1914, pp. 239-241) likewise unites the two species. Stiasny, however, who examined several specimens from Dutch and British Guiana and Trinidad (Stiasny, 1922 b, pp. 55-59; 1931, pp. 169-175) recognizes S. Jritillaria as a valid species, though in the latter of these papers he points out so much variability in both forms that he admits that Bigelow may be right. Unfortunately, Stiasny had not seen the original specimens in Copenhagen; he even states in a footnote (1922, p. 55) that they had disappeared; fortunately, they have been rediscovered in our collection, so I have been able to examine them. Bigelow (1940, p. 316) once more discussed the question of the two species and concluded that *' the union of
166 P L. Kramp
meleagris and fritillaria may ... be allowed to stand, at least provisionally ". On the other hand, Ranson (1949, pp. 150-154) through a careful examination of speci- mens from French Guiana and others from the Gulf of California and Ecuador, once more separated the two forms, pointing out several distinguishing features, especially that in Jritillaria the scapulets are " plus profondement situees dans la sous-ombrelle ".
This latter feature, which was emphasized by Mayer as well as by Haeckel himself, is very distinct in all the original specimens and really seems to be characteristic of fritillaria. On the other hand, I can see no indication of the median incurvations of the umbrella margin between the rhopalia, described and figured by Haeckel. It is difficult to state the exact number of marginal lappets in the original specimens, but as far as I can see, the number of velar lappets does not exceed 12 or 16 in each octant; each lappet is, however, divided into two by a short median line; this was also observed by Ranson in the specimens from Trinidad examined by him
The specimen labelled 43° N. 61° 30' W. is particularly well preserved and about 60 mm in diameter. One of the three specimens from Surinam is about 50 mm wide and rather badly preserved; another of these specimens is about 80 mm wide and somewhat torn. The largest specimen, from which presumably Haeckel's figure of the entire medusa was drawn, and which may be designated as the type, has been cut into several pieces.
It seems to me that the differences between S. fritillaria and meleagris are so slight that they do not justify a distinction of two separate species, but sufficient to regard fritillaria as a distinct variety of meleagris ; so I am inclined to adhere to the views of Mayer and Bigelow.
Stomolophus agaricus Haeckel.
1880, p. 597.
[Stomolophus meleagris L. Agassiz.]
(199) Punta Arenas, Pacific coast of Costa Rica, Central America; ORSTed,
1843. 1 specimen. According to Stiasny (1922 a, p. 553), who has examined the specimen, it may be regarded as belonging to S. meleagris L. Agassiz, as already presumed by Mayer (1910, p. 710).
Versura palmata Haeckel. 1880, p. 606, PI. XL, figs. 9-12. [Mastigias ocellata (Modeer).] (186) Cheribon, north coast of Java; Andrea, 1870. 1 specimen. By a careful examination of the present type-specimen Stiasny (1922 a, p. 538) referred it to Mastigias ocellata (Modeer).
Cotylorhiza tuberculata (Macri). 1880, p. 610.
(200) Trieste, Adriatic Sea; Steenstrup. 1 specimen. Correctly identified.
Cotylorhizal {Stylorhizal). [Mastigias ocellata (Modeer).] (194) 1° N. 104° E., near Singapore; Strandgaard. 1 specimen. Stiasny (1922 a, p. 530) has identified this specimen as Mastigias ocellata (Modeer).
A revision of Ernst Haeckel's determinations of a collection of Medusae 1 67
Mastigias papua { Lesson ). 1880, p. 623. (191) China Sea, East Asia; Koch, 1872. 1 specimen. This locality is mentioned in Haeckel's monograph, and the identification is undoubtedly correct.
No. 192 in the list is a fragment collected by Strandgaard, 4° S. 106^ E. Haeckel denominated it " Rhizostomae fragmentum "". Stiasny (1922 a, p. 529) refers it to Mastigias papua (Lesson).
Cramborhiza flagellata Haeckel.
1880, p. 646. [Lychnorhiza luce ma Haeckel.] (193) Cotinguiba, Brazil; Hygom. 1 specimen. Haeckel mentions this specimen in his monograph as well as in the list as Cram- borhiza flagellata, together with a specimen from Pernambuco. Mayer (1910, p. 673) regards it as a young stage oi Lychnorhiza lucerna Haeckel, and Stiasny (1922 c, p. 235) agrees with Mayer in this respect. An examination of the present specimen does not contradict this view. It is in a fairly good condition, about 55 mm wide, and immature. The oral arms are slightly longer than the radius of the umbrella; some few filaments are present, and they are very short. Between two successive radial canals there is usually only one centripetal canal issuing from the ring-canal, but sometimes two, one of which is small.
REFERENCES
Agassiz, a. (1865), North American Acalephae. 234 pp.
BiGELOW, H. B. (1909), Reports of the scientific results of the Expedition to the Eastern Tropical
Pacific, 1904-1905. XVI. The Medusae. Mem. Miis. Comp. Zool., Harvard Coll., 37, 243 pp. BiGELOw, H. B. (1914), Note on the medusan Genus Stomotophus, from San Diego. Utuv. California
Publ., Zool., 13 (10), 239-241. BiGELOW, H. B. (1940), Medusae of the Templeton Crocker and Eastern Pacific Zaca Expeditions,
1936-1938. Zoologica, N.Y. Zool. Soc, 25 (3). 281-321. BiGELOW, R. P. (1909), A new Narcomedusa from the North Atlantic. Biol. Bull., 16, 80-82. Brandt, J. F. (1838), Ausfiihrliche Beschreibung der von C. H. Mertens auf seiner Weitumsegelung
beobachteten Schirmquallen. Mem. Acad. Imp. Sci., St. Petershourg, (6), 4 (2), 237-41 1. Browne, E. T. (1896), On British Hydroids and Medusae. Proc. Zool. Soc, London. 459-500. Browne, E. T. (1907), A revision of the Medusae belonging to the Family Laodiceidae. .Ann. Mag.
Nat. Hist. (7), 20, 457-480.
EscHSCHOLTZ, Fr. (1829). System der Acalephen . Ferdinand Diimmler, Berlin, 188 pp.
Fabricius, O. (1780), Fauna Groenlandica. Hauniae et Lipsiae, 452 pp.
Haeckel, E. (1879-80), Das Svstem der Medusen. Jena Denkschr. Med.-Natiir.-wiss. Gesell.. I (1,2).
1-672. Haeckel, E. (1881), Report on the deep sea Medusae. Rept. Sci. Res.. H.M.S. Challenger, Zool.,
4, 154 pp. Hartlaub, Cl. (1913-17), Craspedote Medusen. Nordisches Plankton. 12 (1). 237-379. Kramp, p. L. (1919), Medusae I. Leptomedusae. Danish Ingolf Exped.. 5 (8), 111 pp. Kramp, p. L. (1926), Medusae II. Anthomedusae. Danish Ingolf Exped., 5 (10), 102 pp. Kramp, P. L. (1932), A revision of the Medusae belonging to the Family Mitrocomidae. Vidensk.
Meddel. Dansk Naturhist. Foren.. 92, 305-383. Kramp, P. L. (1939), Medusae, Siphonophora, and Ctenophora. Zool. oj Iceland. 1 (5b), 1-37. Kramp, P. L. (1942), Medusae. " Godthaab " Expedition, 1928. Meddel. om Grdnland, 81 (1), I-I68. Kramp, P. L. (1947), Medusae 111. Trachylina and Scyphozoa, with zoogeographical remarks on all
the Medusae of the Northern Atlantic. Danish Ingolf E.xped., 5(14), 66 pp. Kramp, P. L. (1953), Hydromedusae. Great Barrier Reef Exped., 1928-29, 5(7. Repts., 6 (4), 259-322. LOtken, Chr. (1875), A revised list of the Acalephae and Hydrozoa of Greenland. Arctic Manual
and Instructions. Copenhagen. 187-190 Maas, O. (1903), Die Scyphomedusen der Siboga-Expedition. Sihoga-Exped., Monogr.. 11. 91 pp. Mayer, A. G. (1910), Medusae of the world. (3 vols.) Carnegie Inst.. Washington. Publ.. No. 109
735 pp.
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Ranson, G. (1949), Meduses. Resultats scientifiques des croisieres Navire-Ecole Beige " Mercator"
4 (2). Mem. Inst. Roy. Sci. Nat. de Belgique, (2), 33, 121-158. Stiasny. G. (1922 a). Die Scyphomedusen-Sammlung von Dr. Th. Mortensen nebst anderen Medusen
aus dem zoologischen Museum der Universitat in Kopenhagen. Vidensk. Meddel. Dansk Naturhist.
/b;r/7., 73, 513-558. Stiasny, G. (1922 b), Ergebnisse der Nachuntersuchung einiger Rhizostomeen-Typen Haeckel's und
Schultze's aus der Sammlung des Zoologischen Institutes der Universitat in Jena. Zool. Mededeel.,
Leiden, 7 (1-2), 61-79. Stiasny, G. (1922 c), Ergebnisse der Nachuntersuchung einiger Rhizostomeen-Typen Ehrenberg's,
Haeckel's und Vanhoffen's aus den Zoologischen Museen in Berlin und Konigsberg. Zool.
Mededeel., Leiden, 7 (3-4), 225-241. Stiasny, G. (1931), Die Rhizostomeen-Sammlung des British Museum (Natural History) in London.
Zool. Mededeel., Leiden., 14 (3), 137-178. Thiel, M. E. (1927), Die Scyphomedusen des Zoologischen Staatsinstituts und Zoologischen Museums
in Hamburg. I. Cubomedusae, Stauromedusae und Coronatae. Mitt. Zool. Staatsinst. u. Zool.
Mas., Hamburg, 43, 1-34.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 169-177.
Some very simple devices for various oceanographical uses
By J. N. Carruthers British National Institute of Oceanography
Summary — An account is given of some very simple ways of determining the underwater courses of suspension and towing lines in respect both of slope and direction. The means employed is to enclose pendulums and compasses within suitable vessels containing hot gelatine solution. These are affixed to the lines whilst the gelatine solution is hot. so that after the cooling which comes from immersion in the sea, the pendulums and compasses become immovably fixed to give the necessary records. It is shown that the devices could serve very usefully in studies of the pelagic trawl, and could be adapted to determine the shape of trawling cables leading all the way down into the greatest ocean depths.
It will be of assistance if brief reference is made at the outset to two recently published papers. In one of them (Carruthers, 195 4a, 181 et seq.) a preliminary account was given of a simple current-measuring instrument designed for use by commerical fishermen at echo-dictated depths. With that instrument, the speed and heading of the water movement are given by the amount and direction of tilt imposed by the current upon a cone made of non-magnetic mesh metal which is hung near its apex in a smooth roller bearing carried in a sort of tuning-fork bracket. The latter is borne on and can swing freely all round a rope strained between an anchor and a buoy well below surface. To the latter is attached (for recovery) a long length of strong thin line bent to a little marker buoy which serves as a finder — the whole system being cast freely into the sea without any need for the investigating ship to anchor. The bracket holds the cone well away from the line on which it is worked.
Though, in the definitive model, the record for slope and direction is given by the operation of a simple mechanism which locks a pendulum containing a compass within itself, in an earlier model the record was got as follows:
Rigidly fastened within the cone was a wide-necked bottle made of heat-resisting glass filled half with gelatine solution and half with common kerosene. After a brief sojourn of the bottle in the sea subsequent to its having first been stood in a bucket of hot water, the gelatine solution solidifies beneath the kerosene — the slant of the firm interface then formed being that imposed on the cone by the current. The slope is easily measurable after recovery, and is of course convertible into a speed value on reference to a calibration table.
It was additionally useful to arrange for a small ring compass of aircraft type to " float " at the interface of the two hot liquids. This was easily done by affixing a diminutive buoy above the compass to the end that, when congelation took place, the direction of the tilt was preserved. The arrangement can be appreciated from the appropriate illustration which shows such a compass floating unrestrained between the two hot liquids in a glass jug (Fig. 1). In use, the bottle is of course closed by means of a cork or a screw-on metal cap made of aluminium or copper.
In what follows attention will be paid to other uses of the simple device just described which will be referred to for brevity and convenience as a "jelly bottle ".
In the other paper (Carruthers, 1954 b) an account was given of a directional
169
1 70 J- N. Carruthers
wire-angle gauge designed for use on the hydrographical wire which carries the water bottles used for the routine collection of water samples and temperature data. The gauge is messenger-operated and is usable intermediately with the bottles. From it one learns the actual slope of the wire both in magnitude and direction so long as the wire is sufficiently weighted (<200 lbs) to preclude the heavy pendulous gauges from introducing local deformations into the wire because of their own weight.
We shall describe a simple method of checking the showings of such gauges— a method which could be extended to determine the underwater course of a deep-sea trawling cable leading all the way down into the greatest ocean depths. Then, it would be possible to learn the amount and direction of slope at discrete intervals all the way down such a cable as was used by Bruun from the Galathea when bottom- dredging in the Philippines Trench, in keeping with Kullenberg's calculations.
It should be remarked that when describing the earliest versions of the current- measuring cone above referred to, a description was added of how both direction and slope could be determined from a compass poised in hot gelatine only — without need to use the kerosene as well (Carruthers, 1954 a, p. 185).
We are particularly interested to detail simple ways of determining the underwater course of lines, wires, ropes or warps let down from stopped vessels occupied with the activities of routine oceanographical stations, or towed behind ships engaged in trawl- ing or analogous operations. Clearly, if jelly bottles of the kind described were suitably affixed to such lines, their simple round shape would be a great boon because it would not matter how they were disposed on the wire (above, below, or laterally) so long as parallelism were maintained.
It is not overlooked that a jelly bottle whose gelatine will remain uncongealed long enough to permit slope determinations to be made of hydro wires, may have too short a liquid life to be usable for investigating the underwater course (slope and direction) of the warps on which a pelagic trawl is towed, but it will be an easy-enough matter to achieve longer timings by using greater bulks of hot jelly in bigger bottles, or by encasing the jelly bottles in suitable covers to be filled with hot water before immersion in the sea. Whatever be the form of slope indicator decided upon, neutral buoyancy will be approximated to guard against the production of local deformations in the line.
This is a matter of importance because of the great interest which attaches to deciding the fishing depth of an off-bottom trawl.
It is believed that the simple devices here being considered could be profitably used to find at what depth a pelagic trawl had fished, at what height above bottom its foot-rope had ridden, what had been the distribution of its vertical gape and of its horizontal gape.
We have here no concern at all with the very ingenious instruments which use electronics and acoustics to telemeter net depth back to the towing ship whilst the tow is in progress, but fully appreciate the value to a fishing skipper of always knowing at what depth his pelagic net is fishing, so that he can alter his speed or warp length to keep it at the depth where his echo sounder tells him the fish are.
Because it seems quite unlikely that ordinary fishing craft will ever carry the tele- metering net-depth indicators now being tested, it has seemed well worth while to line up with opinion that a necessary pre-requisite to achieving anything simpler which can be relied upon, is to determine the exact underwater course of the towing warps all the way from ship to net.
Some very simple devices for various oceanographical uses 1 7 1
Though insufficiently acquainted with the latest achievements of Dr. J. Scharfe of the Net Research Institute at Hamburg, who has carried out some very interesting investigations of the pelagic trawl with the aid of instruments specially developed for the purpose (Scharfe, 1953), the writer knows of no such determination ever having been made as yet, but there seems no real need for the complexities of a recording instrument which would travel all the way along the warps to effect it. It seems amply good enough to measure the slope of a warp at a lot of discrete points where slope alone is the matter of interest, and to measure slope and direction at many points along the two warps where both slope and separation (roughly telling net gape) are wanted.
It could well be that, after learning the average slope of the whole warp lengths for different speeds of tow and various lengths of warp veered (which average slope would reveal fishing depth), it might be found possible to apply " corrections " to the readings of the deck inclinometer used to measure the entry angle of the warps. It is worth hoping that such " corrections " could become known for all lengths of warp out and all towing speeds so that the easily observed entry angles could be converted into approximate mean slope values and a table of implied net depths consulted with confidence.
WARP SLOPE
Where only one cable towed astern is being investigated, the rectangular instrument pictured (Fig. 2a and 2b) is a suitable and convenient one to use. It is a slender box of about cigar-box size and shape with front and back of clear perspex and is filled with gelatine solution only. Inside is a pendulum which can move freely so long as the gelatine solution remains liquid after prior immersion of the instrument in a bath of hot water. It is intentionally not fitted to the warp or towing rope by clamps, but through the medium of the bracket shown, which is secured on the warp, thin wire, or rope, by winding round it and the warp a strong stretched rubber thong, just as a runner bean in the garden winds itself on to and up its supporting stick.
Using such a cheap and easy method of attachment, one can affix all manner of instruments to all sizes of wire, cable, or rope and secure a firm non-slip grip without
trouble.
The rather heavy inclinometer is pictured fastened securely on to a very smooth brass wire no thicker than ordinary water-bottle wire. To facilitate attachment by one person working alone, the side of the bracket which is bound on to the warp has since been fitted with prongs after the manner of the wooden rods fixed across the tops of some of the bottles pictured. This makes it very easy to effect attachment by winding a lot of stretched office rubber bands round and round bracket-rod and warp in an obvious manner.
It does not matter if the warp twists at all because the rectangular inclinometer as pictured can swing all round it and still maintain parallelism— just as the passenger cages of the " Big Wheel " at a fair move round its axle.
There is a fiUing point (unscrew the domed knob) and also an air vent controlled by a removable grub screw. Inwards thumb and finger pressure exerted on the two small spring-loaded levers either side of the filler knob releases the rectangular box from its bracket.
172 J- N. Carruthers
The idea is to have a battery of such indinometers standing in a bath of hot water on deck with their brackets alongside as the cable is veered. With such a situation the brackets are simply affixed and the boxes no less easily clipped in. This inclino- meter has worked well in tests and has congealed conveniently in about 20 minutes, but it would be improved by being made semi-circular to avoid preferential congelation in the corners, and should be lighter.
If used on the warps of a trawl being towed, there will be some lateral pressure on the box on account of the warps not leading dead astern. The rectangular inclino- meter might not remain completely pendulous under such circumstances unless unduly weighted along its bottom edge. The result might be that the pendulum would not then give the true reading for slope which it provides when towed dead astern. If round jelly bottles be used as slope indicators however, there can be no difficulties due to any rolling out of a pendulous position. If the need be to use them on a thin stranded wire of water-bottle type, they can be used in clamp-fitted holders, as was kindly done for the writer aboard the German research vessel Gauss by Dr. Joseph in March 1955, during a cruise in the North Sea. Two results obtained by Dr. Joseph are pictured (Fig. 3). The slope of the firm slant interfaces which can be very clearly seen was measured with ease by means of a simple goniometer made specially for the purpose.
Dr. Joseph towed a terminally-weighted wire astern with six of the clamp-fitted jelly bottles affixed at equal intervals along its underwater part. The clear results he got revealed overall downwards concavity of the curved wire with increase of slope towards the weight.
On another occasion he streamed a buoy astern on a considerable length of wire with a weight hung on about half way along it. Jelly bottles spaced equally, four on each side of the weight, revealed very clearly the opposite slopes of the two halves of the wire. Between the ship and the weight the wire took on a downslope very little removed from straight, though with a very slight downwards concavity. From the weight to the buoy the wire sloped fairly steeply upwards with a very pronounced upward concavity.
The results will be reported upon in detail on some later occasion when more have been added.
The two bottles pictured (Fig. 3) had been used on opposite sides of the weight, which was hung midway along Dr. Joseph's towed buoy-line. With his jelly bottles the writer has preferred not to use clamps for attachment purposes, but to employ the same sort of method as was described above in connection with the rectangular inclinometer. To do so avoids limitation of use to one sort and size of line.
An accompanying picture (Fig. 4) shows two jelly bottles after use in experiments recently conducted in the Crouch estuary from a research vessel belonging to the Ministry of Agriculture and Fisheries. Mr. D. Waugh of the Burnham Fisheries Laboratory very kindly afforded the facilities and gave yeoman assistance. In this picture the convenient goniometer made by Dr. Joseph for measuring the jelly slopes is also to be seen.
The jelly bottles illustrated are of the usual heat-resistant glass and are of the compass-containing type. To affix them easily to lines of any size or nature the follow- ing was done:
A convenient length of clean, strong and heavily-lacquered wooden dowel rod was
Fie I. For explanation sec text.
r
Fig. 2a. For explanation see text.
Fig. 2b. For explanation see text.
Fig. 3. For explanation see text.
Fig. 4. For explanation see text.
Fit;. 5. For explanation see text.
Fig. 6a and b. For explanation see text.
Some very simple devices for various oceanographical uses 173
fastened immovably and diametrically across the top of the aluminium screw-on closure cap. This was effected by riveting on from the underside. In the cap is a disc of kerosene-resistant artificial rubber. On both sides of the disc the round wooden rod has had thin but stiff metal bars driven through it to present prongs projecting equally either side. Such a rod can be seen illustrated in another of the pictures (Fig. 5).
With this convenient arrangement all that is necessary to effect secure attachment is to hold the bottle-carrying rod against the rope^ wire or cable with one hand, and to hook good quality office rubber bands on to the individual prongs in succession — stretching them, winding them whilst in tension round rod and cable, and hooking their other ends on to whatever prong offers to hold them tight.
The last-mentioned picture (Fig. 5) shows a pair of compass-containing jelly bottles which had also been used in the Burnham experiments. In this case the bottles are wide-necked pyrex bottles which are a standard list item of laboratory furnishers. With them, the attachment rods were secured on to the cork closure bungs by means of slender washer-loaded bolts and small nuts.
Various additional (and much more elegant) mountings for the compass-containing jelly bottles were made by Mr. A. J. Woods of Messrs Kelvin & Hughes. He has been associated with the writer throughout the experiments, and is making improved devices (to be spoken of below) in the course of continuing collaboration.
The excellent little aircraft ring compasses used in the experiments were made and kindly loaned by Messrs. Kelvin & Hughes. For reasons of cost and space Mr. Wood's additional mountings are not illustrated in this article, but it should be mentioned that the two extra kinds which he constructed both made use of a pronged attachment bar and rubber bind-on bands. One of them simulated the " Fair Wheel " characteristics of the bracket-mounted rectangular inclinometer earlier described (Fig. 2a and 2b).
APPLICATION TO PELAGIC TRAWL INVESTIGATIONS
Because there is a likelihood that commercial fishermen of future years will find an ever-increasing need to operate on the stocks of non-bottom fish living in deep-water oceanic areas, it is probable that the passage of time will invest pelagic trawling with more and more importance.
From inquiries made of fisheries research experts who concern themselves with the modern one-ship pelagic trawl, need exists to know much more than is known at
present about it.
In the course of the experiments carried out in the Crouch estuary with jelly bottles, a situation resembling " fishing in reverse " with such a net was staged. Under Mr. Waugh's direction two boats were anchored a measured distance " X " apart across the stream, and a line some " 2X " (and other multiples of " X ") long was streamed from them— with one end secured at each boat and a large plankton net plus other drogue objects attached to the mid-point of the line.
In such circumstances, with a series of compass-containing jelly bottles secured on to each half of the streamed line, it should be easily possible to determine the mean angular divergence. By multiplying the total length of the line into the sine of half that angle, one should get a value equ^al to the distance of separation of the two anchored boats.
There were a few difficulties during the tests as can readily be imagined. For instance,
174 J- N. Carruthers
a strong pull by the drogues must urge the boats to close somewhat on each other, whilst less than a really strong pull must leave the lines bowed to some extent. Never- theless, the results were amply good enough to invest the application of the idea to studies of the pelagic trawl with real promise.
Certain full-scale experiments are envisaged thanks to expressions of interest and the promise of facilities from the two British fisheries laboratories. Of an ample assemblage of the compass-containing jelly bottles, half would have their " upper- works " enamelled red for attachment on the port warp, whilst the other half would have green floats and would go on the starboard warp.
In a first investigation the average overall downslope of both warps will be worked out from the mean of the jelly slopes, and the fishing depth of the net estimated accordingly. From the compass readings of the bottles the course of the warps as projected on the sea-floor will be derived and an estimate of the horizontal gape of the net made.
Apparently Dr. Scharfe holds the view that useful conclusions as to horizontal net gape can even be made from noting only the separation angle of the warps behind the slip hook. This he does by means of his special device the " Spreizmesser ".
Since the investigating ship will have an echo-sounder the net tests could be done in a chosen area with a flat bottom so that it could always be known that the foot-rope would never be higher off" bottom than a distance " H ". If, when the net was shot, a length of thin Kelvin wire of length about 1|H or 2H carrying an object like a smooth cannon-ball at its free end were hung from the bottom of the net, then, if several jelly bottles went down on this wire, one would learn on hauling what its slope had been and so would know how high above bottom the foot-rope had ridden during the tow. One would then have data enough to make an estimate of the vertical gape of the net. In a subsequent investigation much better things will be attempted :
A drogue of nearly neutral buoyancy will be towed inside the net from the midpoint of a light line of not much greater length than the distance the net doors would be apart if the net were stretched out tight on the quayside. An array of compass- containing jelly bottles on each half of such a line will give a much better triangulating situation with sound promise of an acceptable determination of horizontal gape.
How the same sort of thing could be done to investigate vertical gape at different points will readily suggest itself.
For some of the determinations the jelly bottles would not need to contain compasses.
The need to weigh a few considerations has led to postponement for the time being of the full scale net tests from a fisheries research vessel. For one thing there is the need to hit upon a long-enough timing (congelation period) as already stated. Then, although one could not possibly devise any other slope and direction indicators as simple as the jelly bottles, it is a fact that difficulty attaches to reading the compass directions precisely enough when (as so often must happen) the compasses are not on an even keel but are awkwardly canted.
Where slope only is needed, recourse will be had to a gelatine-filled perspex cylinder containing a rolling clinometer furnished with a finger which travels over a protractor. With this device (now being made), there will be no need for two liquids and no need to measure jelly slopes with an external goniometer.
At the time of writing this there is also being made (by my collaborator, Mr. A. J.
Some very simple devices for various oceanographical uses 1 75
Woods of Messrs Kelvin & Hughes) an instrument which is in effect a rolling clino- meter containing a compass which will always remain on an even keel. This also will be contained in a perspex cylinder filled with gelatine only, and it too will have a contained protractor permitting slopes to be read to one degree or so. Its compass will be pivoted and not dependent upon buoyancy of a small float. This is an advant- age because no depth limit will apply as it might if risk existed of a float being compressed by water pressure to a state of nil buoyancy. When these devices have been fully tested and made in sufficient number, the full scale net tests will be embarked upon without delay and with confidence. Sight will not be lost of the need to ensure that the compasses are held a sufficient distance from the warps to escape any dis- turbing influence of the latter.
So far we have discussed mainly the measurement of slopes of modest magnitudes below the horizontal. We turn now to slopes measured as departures from the vertical.
OFF-VERTICAL SLOPES: THE UNDERWATER COURSE OF DEEP-SEA WIRES
AND CABLES
Our first concern was to establish a means of checking the showings of the wire- angle gauge to which earlier reference has been made above (Carruthers, 1954 b). The need is to discover whether the pendulum gives a true value for the slope of a hydro graphical wire (with its load of water bottles) when the observing ship is some- what lively. It was decided to use jelly bottles to make an adequate series of tests.
The first requisite was to devise a way of using them on the hydrowire without interfering with the operation of water bottles and the wire-angle gauges at the same time. The way chosen was to construct a simple " messenger-passer " easily attach- able to the wire and able to carry a compass-containing jelly bottle held firmly parallel to the latter. It would then only be necessary to fit the fall-away messenger hung beneath such a device with an extra-long lanyard, to enable the two German clamp-on jelly bottles (Fig. 3) to be used as well as the compass-containing jelly bottle. This latter would be housed in a sort of little sentry box attached to the " messenger- passer ". Such an arrangement would furnish three jelly slope values and one direction reading for comparison with the readings of the wire-angle gauges under test.
Illustrations of the simple instrument made by Mr. Woods to the writer's design are presented (Fig. 6a and 6b). The first (6a) shows the situation before the arrival of a messenger from above, i.e. with the fall-away messenger still hanging beneath. The second (6b) shows the situation after the strike of the messenger from above, i.e. with the fall-away messenger gone down to trip other instruments below.
The device consists of a brass tube attachable by stretched rubber thongs to the hydrowire. Running down its interior is a flat bar of brass with a small hinged piece at its lower end. So long as this is bent upwards and contained in the tube, a messenger can be hung from it, but as soon as the central bar is pushed down to full extent the messenger must fall away. The central bar is bent over at the top as shown, and is forked to receive the wire. A length of it near the top of the tube is slotted, and through this slot a short length of thin glass rod can be passed and seated in a cupped collar at the top of the tube. The glass rod takes the weight of the internal bar and the hanging messenger when the device is cocked. The impact of a messenger from above infallibly breaks^the glass rod and lets the pendant messenger fall away.
The compass-containing jelly bottle is housed in the little fastened-on brass box
176 J- N. Carruthers
discernible on the face of the tube. A fin fused on one side of the bottle seats in a slot cut into the tube to provide direction fixation, and the bottle is held firmly in place by means of rubber bands as illustrated.
Six fathoms of water in the River Crouch afforded enough messenger travel for two wire gauges to operate with the " messenger-passer " in between them. The latter always functioned without fail. At the time of writing this the deep-sea tests to check the showings (pendulum behaviour) of the wire-angle gauges in the manner described, are in progress aboard the Royal Research Ship Discovery II.
If it were desired to observe the slope magnitudes and directions of a thick trawling cable leading all the way down to a trawl or dredge being dragged over the deep ocean floor, it would not be possible to use jelly bottles for time reasons. Also, any messengers for the use of which a devised method might call would necessarily have to be of rather mammoth size^ — each one something like a yard of heavy iron tube split and hinged to go on the cable. It is suggested that a simple " messenger-passer " after the style of that described could be made " rough, long, and strong " with a thin tight metal rod of water bottle wire diameter held a small distance off from it (but parallel to it), strained between two short spurs projecting out at right angles respectively at top and bottom. If such crude devices were fastened on to the cable at desired intervals in the manner already described, a wire-angle gauge could be operated at the bottom of the thin offset rod in each case. This could be done quite simply if, when a giant messenger struck to break the short length of thick glass rod or small phial which would be necessary in such case, a daughter messenger of ordinary weight and size were released to run down the offset rod to trip the gauge quite harmlessly.
OTHER POSSIBILITIES
In spite of the wide variety of current-meters already in existence, there remains a real need for one which could be used to make all-weather absolute observations of near-bottom currents from anchored vessels. The numerous and very convenient lightships are in mind. The problem has always been how to get acceptable records from a lively ship, and the suitable use of jelly bottles suggests itself as offering escape from the difficulties imposed by ship movement, because they would be self-damping systems.
If a length of Kelvin wire carrying a heavy terminal plummet were let down from a lightship, it would be easy to stream tow-nets from it at any desired depths. The nets could be made of very wide mesh fishing net near their mouths, and the rest of stramin. If streamed on up-and-down bridles the rings would not rotate. In such case there could be a horizontal diametric brass rod across each net mouth, and on it could be hung a semi-circular swinging plate carrying a compass-containing jelly bottle suitably mounted on its reverse.
Using some such simple arrangement with limp connection to the suspension line, absolute measurements of currents could, it is held, be acceptably made during quite bad weather. Such a method is well worth trying because of the great opportunities which exist for working from anchored vessels. The necessary calibrations would, of course, have to be made against logship runs. When the compass-containing and depth-ignoring rolling clinometer spoken of above becomes available with slope- reading possible to one degree and compass always on an even keel, the possibilities will be greatly enhanced. Then, the simple current-measuring instrument envisaged
Some very simple devices for various oceanographical uses 1 77
should be able to give good service used from a moving ship, to reveal currents differences between small and great depths.
It remains only to remark that such simple congealing inclinometers with direction- indicating powers as are being made, could be very usefully employed in non-captive instruments sent down to the ocean depths to record the bottom water movements there. The working principle would be that of the bathygraph of Ewing and Vine, which achieves self-ascent under the lift of an oil-filled balloon after the detachment of ballast left on the ocean floor. This is of course the principle of Professor Picard's bathyscaphe but, as Ewing and Vine remark, " the problem of locating the apparatus after it has reached the surface is a serious one ".
ACKNOWLEDGEMENTS AND NOTE
Thanks are expressed to Mr. A. J. Woods for his very valuable collaboration and instrumental ingenuity; to Mr. D. Waugh for generous help when carrying out tests; and to Doctors Bohnecke and Joseph for trials made aboard the German research vessel Gauss.
Though this is perhaps a strange finish to a paper such as the foregoing, the writer is obliged to remark that the jelly bottles come specifically under the coverage of a patent which runs in most countries having important fisheries. The patent in question relates to the Current Cone for which the licence holders are Messrs Kelvin & Hughes. From them the final models of the slope-and- direction indicators will presumably be procurable in due course.
REFERENCES
Carruthers, J. N. (1954 a). Some inter-relationships of oceanography and fisheries. Arch. f. Met.,
Geophvs. u. Bioklim.. B, 6 (12), 167-189. Carruthers, J. N. (1954 b). On the instrumental measurement of line-shape under water. Deutsche
Hvdrogr. Zeits., 7 (1/2), 1-14. Scharfe, J. (1953), Gerate zur Messung an Schleppnetzen. Die Fischwirtschaft, Bremerhavn, (12).
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 178-203.
The fauna of an inter-tidal mud flat
By J. E. G. Raymont
Zoology Department, University of Southampton, England
Summary — 1 . An account is given of the fauna of an inter-tidal mud flat (North Bay) in Kyle Scotnish, Loch Sween, Argyllshire.
2. The distribution of the more important species of the fauna over the shore is discussed.
3. Some indications are given of the growth rates of four lamellibranchs, Macoma, Scrobicularia, Cardium and Mytilus.
4. The changes in the density of the fauna are followed from 1943 to 1946, and the possible beneficial effects of the fertilization of Kyle Scotnish on the bottom fauna of the inter-tidal zone are reviewed.
INTRODUCTION
Some account has already been given of the bottom fauna of Kyle Scotnish — a northern arm of Loch Sween, Argyllshire (Raymont, 1950), but that investigation was confined to the fauna below low water mark. Very little inter-tidal shore exists in Kyle Scotnish, but near the head of the loch there is a fairly extensive mud flat which is designated in the text North Bay (Fig. 1). Although a small stream enters the area, most of the flat is not estuarine. It was thought desirable to investigate the fauna of the mud flat, since most of the work done on muds in Great Britain concerns estuaries (e.g. Eraser, 1932; Rees, 1940; Beanland, 1940; Spooner and Moore, 1940). Since also the main work in Kyle Scotnish has been concerned with the effect on general productivity of the addition of nitrate and phosphate fertilizers, it was decided to attempt to correlate population changes in the mud flat with the effects of fertilization.
The investigation extended over three years commencing in November 1943. Sampling over such a short period cannot give results on which very definite con- clusions may be based. Nevertheless, as the work at Loch Sween had to be ended in 1946, the samples have been worked through and some account of the work is presented.
METHODS
Sampling was confined to an autumn (November) and summer (July) period each year. Four transects were planned across North Bay, sited on permanent marks on shore, and three or four stations were selected at approximately equal distances along each of the four lines, beginning near High Water and extending to Low Water (Fig. 1). Altogether fourteen stations were regularly sampled. No exact tidal levels were taken, as the tidal range right at the head of Loch Sween is small, and moreover the tides are irregular, the periods of exposure of the flat being very largely dependent on the prevailing wind.
Various sampling techniques were tried during November 1943 involving the digging of a square (side 0-5 metres) and sieving the material, but such a procedure proved too laborious. In the method finally adopted a quadrat (side 0-5 metres) was dug to a depth of 10-12 cm, the material passed through a coarse (9-5 mm) sieve, and only the larger bivalves exceeding 10 mm length retained in the sieve were counted. At the same station three small " auger " samples were also taken. The auger consisted of a metal cylinder 10 cm diameter, 23 cm height, with a handle at the top. The auger was pushed into the
178
The fauna of an inter-tidal mud flat
179
substratum to a depth of 10 cm and then pulled out again with its mud core. Usually the consistency of the mud was such that very little of the core was lost. Each of the auger samples was passed separ- ately through a 1 mm sieve and all the organisms retained were preserved in alcohol and sorted later.
In estimating the total population at any station, the three auger samples were analysed first. Any bivalves exceeding 10 mm length in these samples were discounted, and the numbers of all other organisms then averaged. To this population was added the number of large bivalves only ( > 10 mm) obtained from the im^ quadrat sample at the same station. The whole population was expressed in numbers per m-.
The shore of North Bay is covered by a soft mud with a little sand, and with shell and gravel some few inches below the surface. There are a few isolated boulders and some patches of weed (mostly Fucus vesiculosus). None of the fourteen sampling stations was sited in weed or near boulders. Even so, the three auger samples at any one station could show considerable differences. Some idea of the great variation which could occur is given for two stations in July 1946, when six auger samples
Table I Variation in auger samples at two stations: Tr. 4, St. 2 and Tr. 3, St. 4, July 1946. A-F represent actual numbers in 6 samples taken a few feet from each sampling point. The average of 3 samples (A, B and C) has been used for calculating the population
per m^
|
Transect 4 |
Station 2 |
• |
Transect 3 |
Station 4 |
||||||||||
|
Aver- |
Aver- |
Aver- |
A ver- |
|||||||||||
|
Samples |
age A,B, |
age |
Samples |
age A,B, |
age |
|||||||||
|
A |
B |
C D |
E |
F |
C |
A-F |
A |
B |
C D |
E |
F |
C |
A-F |
|
|
Cardium |
|
2 — |
2 |
|
1 |
1 |
5 |
3 |
— — |
— |
4 |
3 |
2 |
|
|
Macoma |
. — |
|
1 — |
1 |
2 |
+ |
1 |
— |
2 |
1 2 |
— |
2 |
1 |
1 |
|
Hydrobia |
35 |
54 |
46 26 |
39 |
56 |
45 |
42 |
53 |
20 |
17 53 |
W |
86 |
30 |
41 |
|
Littorina |
— |
— |
— — |
1 |
— |
— |
+ |
— |
— |
— — |
— |
— |
— |
|
|
Oligochaetes |
— |
— |
— — |
— |
— |
— |
— |
— |
— |
— 4 |
— |
— |
— |
1 |
|
Crustacea |
2 |
1 |
6 2 |
1 |
10 |
3 |
4 |
5 |
1 |
— — |
— |
2 |
1 |
|
|
Chironomids |
— |
1 |
— — |
1 |
— |
+ |
+ |
1 |
— |
— — |
— |
3 |
+ |
i |
|
Nephthys |
1 |
— |
— 1 |
— |
2 |
+ |
1 |
1 |
— |
1 1 |
1 |
— |
1 |
|
|
Pygospio |
2 |
5 |
1 2 |
1 |
5 |
3 |
3 |
1 |
— |
— 1 |
— |
— |
+ |
+ |
|
Phyllodocids |
1 |
— |
— — |
— |
— |
+ |
+ |
|
1 |
~ " |
~ |
~ |
+ |
+ |
|
Total |
41 |
61 |
56 31 |
46 |
75 |
53 |
52 |
66 |
27 |
19 61 |
18 |
95 |
37 |
48 |
(A-F) were taken at a few feet distance radiating from the sampling point, instead of the normal three samples taken close together (Table I). The last columns in Table I, showing the average population based on the usual three augers and also an average based on six samples, indicate that the normal three samples probably give a reasonable picture of the average density of a sampling station. In many of the regular series of samples the agreement between the three auger samples was
remarkably good.
The efficiency of the sampling by means of a single im" quadrat for the larger bivalves was tested by taking two quadrats at each station instead of the usual one. There was normally reasonable agreement between the pairs of samples (Table II). Occasionally there were large discrepancies (e.g. Tr 1 St 3 and Tr. 3, St. 3), which appear to have been due mainly to a dense but patchy settlement ofMytilus. The bivalve population for July 1946 has been calculated by averaging the two quadrats
The loss during transport of an auger sample has occasionally made it necessary to calculate the average population at a station on the remaining auger samples. On certain occasions also, at the lowest station of a transect, it was necessary to sample the mud fauna with a small grab, as the area remained covered with water for several days owing to the irregular tides. Generally the whole sampl- ing for the fourteen stations took some three to four weeks.
180
J. E. G. Raymont
Table II Variation in quadrat samples. Two Im^ quadrats, A and B, were taken at each sampling station. Numbers indicate the counts of large bivalves (>10 mm) taken in each ^m-
sample.
|
Macoma |
Scrobicularia |
Cardiiim |
Mvtilus |
Total |
Total |
||||||
|
Station |
A verage |
||||||||||
|
1 |
|||||||||||
|
A |
B |
A |
B |
A |
B |
A |
B |
A |
B |
||
|
Transect 1 : |
|||||||||||
|
1 |
0 |
0 |
36 |
30 |
0 |
0 |
1 |
1 |
37 |
31 |
34 |
|
2 |
0 |
1 |
3 |
0 |
24 |
3 |
7 |
7 |
34 |
11 |
22-5 |
|
3 |
0 |
0 |
0 |
0 |
10 |
23 |
138 56 |
148 |
79 |
113-5 |
|
|
Transect 2 : |
|||||||||||
|
1 |
2 |
0 |
4 2 |
0 |
0 |
0 0 |
6 1 2 |
4 |
|||
|
2 |
0 |
2 |
35 1 26 |
0 |
0 |
5 1 |
40 29 |
34-5 |
|||
|
3 |
4 |
0 |
0 |
2 |
0 |
1 |
55 55 |
59 58 |
58-5 |
||
|
4 |
0 |
0 |
0 |
0 |
1 |
0 |
3 10 |
4 10 |
7 |
||
|
Transect 3 : |
|||||||||||
|
1 |
0 |
1 |
5 |
5 |
0 |
1 |
0 |
1 |
5 |
8 |
6-5 |
|
2 |
0 |
0 |
12 , 17 |
1 |
1 |
0 |
0 |
13 |
18 |
15-5 |
|
|
3 |
0 |
0 |
10 1 11 |
5 |
3 |
16 |
4 |
31 |
18 |
24-5 |
|
|
4 |
0 |
1 |
1 |
1 |
28 |
12 |
69 57 |
98 |
71 |
84-5 |
|
|
Transect 4 : |
|||||||||||
|
1 |
0 |
0 |
2 |
12 |
14 |
0 |
0 |
3* |
16 15 |
15-5 |
|
|
2 |
0 |
0 |
0 |
0 |
1 |
1 |
0 |
0 |
1 1 |
1 |
|
|
3 |
0 |
0 |
0 |
0 |
4 |
4 |
0 |
40 |
4 44 |
24 |
* _
1 Mya included
Table III List of fauna taken in regular samplings in North Bay
Polycladida
Nemertini
Peloscolex benedeni Udekem
Platynereis dumerilii (Audouin & Edwards)
Nereis diversicolor O. F. Miiller
Kefersteinia cirrata (Keferstein)
Phyllodoce maculata (L.)
Eteone longa (Fabricius)
Notophyllum sp.
Give era sp.
Nephthys hombergi Lamarck
Nephthys sp.
Scoloplos armiger (O. F. Miiller)
Pygospio elegans Claparede
Pectinaria koreni Malmgren
Arenicola marina L.
Capitelia capitata (Fabricius)
H e teromastus filiformis { Claparede)
Fabricia sabella Ehrenberg
Maldanidae
Syllidae
Macoma balthica (L.)
Scrobicularia plana (da Costa)
Cardium edule L.
Mytilus edulis L.
Mya arenaria L.
Modiolus sp.
Kellia suborbicularis (Montagu)
Abra prismatica (Montagu)
Paphia decussata (L.)
Paphia pullastra (Montagu)
Hydrobia ulvae (Pennant)
Littorina littorea (L.)
Littorina littoralis (L.)
Cylichna cylindracea (Pennant)
Philine aperta (L.)
Accra bullata O. F. Miiller
Amphipoda
Gammarus sp.
Corophium volutator (Pallas)
Isopoda
Jaera sp.
Idothea granulosa Sars
Sphaeroma rugicauda Leach
Crangon vulgaris L.
Praunus neglecta G. O. Sars
Chironomus salinarius Kieff.
Chironomid larvae
Chironomid pupae
Other larval Diptera
Ophiura texturata Lamarck
The fauna of an inter-tidal mud flat 181
In many cases, particularly among soft-bodied animals, the methods of sampling and sieving broke up the material so that identification has not been taken further than the genus. Some animals (chironomid larvae) have not been identified further than family, although the dominant species has been noted. The list of fauna has been constructed mainly from the identification of favourable specimens preserved in good condition.
GENERAL COMPOSITION OF THE FAUNA
Although no account was taken of the small bottom animals (protozoans, nema- todes, very small crustaceans, etc.) which were not usually retained by the sieve, more than 40 species were recorded from the area. Of these (Table III) comparatively
Table IV Average population for whole North Bay area based on 14 regular stations.
{All numbers per m'-)
|
A^ov. "43 |
July '44 |
Nov. '44 |
July '45 |
Nov. '45 |
July "46 |
|
|
Bivalves (large) |
110 |
66 |
44 |
44 |
130 |
125 |
|
Bivalves (small) |
149 |
418 |
233 |
206 |
1,064 |
129 |
|
Hydrobia |
10,077 |
7,640 |
10,143 |
6,977 |
13,759 |
6,961 |
|
Chironomids |
686 |
318 |
454 |
548 |
1,526 |
365 |
|
Oligochaetes |
2,394 |
984 |
948 |
712 |
1,288 |
415 |
|
Crustacea |
121 |
29 |
60 |
66 |
56 |
101 |
|
Polychaetes |
594 |
778 |
936 |
1,199 |
470 |
285 |
|
Other organisms |
91 |
91 |
249 |
157 |
415 |
313 |
|
Totals |
14,222 |
10,324 |
13.067 |
9,910 |
18,708 |
8.694 |
few appeared to be regular members of the fauna. Four bivalves {Scrobicularia, Macoma, Cardium, Mytilus), two gastropods (Littorina and Hydrobia) and several polychaetes (Arenicola, Nereis, Nephthys, Heteromastus, Pygospio, Phyllodoce and Eteone), with two other groups of animals (oligochaetes and chironomid larvae) were the most important numerically. Crustacea were very poorly represented throughout: the average population rarely reached even 1 % (Table IV). Echinoderms were practically absent altogether; only an occasional small Ophiura texturata was
taken.
The gastropod Hydrobia ulvae was overwhelmingly dominant in number. The average population calculated for the fourteen stations in North Bay showed that at times^Hydrobia formed 80% of the total population, and that it never fell below 70% during the whole period of the investigation. Hydrobia, with oligochaetes (chiefly Pehscolex benedeni), and chironomid larvae (mostly Chironomus salinarius)* together dominated the fauna over the whole area, comprising approximately 90% of the whole
population (Table V). . • t i lo^c
There was a slightly lowered percentage for these three organisms in July 1945, which was due to an increase in one species on\y-Pygospio. This polychaete formed 48% of the polychaete population in July 1945 (Fig. 4) and it occurred in 13 ol the
sampling stations. .
In November 1945 young bivalves made an appreciable contribution to the total fauna (Table IV), but only two species were abundant— Cfl/c/////» and to a lesser extent
* I am indebted to Professor A. Thienemann for this identification.
182
J. E. G. Raymont
Mytilus. In the summers of 1945 and 1946 young mussels settled in enormous numbers over North Bay, but they usually did not survive for very long probably because of the soft substratum. The ordinary samplings did not reflect the full extent of these temporary settlements, but special collections made in the summer of 1945 after the spatfall in Kyle Scotnish and in two nearby other unfertilized arms of Loch Sween (Linne Mhurich and Sailean More) demonstrated the richness of the settlement in parts of North Bay (Table VI). Larger Mytilus were not abundant in North Bay; in fact more were present in Sailean More (Table VI).
Table V
The percentage of Hydrobia, oligochaetes and chironomid larvae based on the average
populations for North Bay
|
A^ov. '43 |
July '44 |
Nov. "44 |
July '45 |
Nov. '45 |
July *46 |
|
|
„/ Hydrobia '^ Total fauna „ /Hydrobia + oligochaetes + chironomids |
71 93 |
74 87 |
78 88 |
70 83 |
74 89 |
80 89 |
|
''" Total fauna |
Table VI Abundance of large and small mussels in three arms of Loch Sween, Summer, 1945. Kyle Scotnish is the only fertilized water. (All figures are numbers per m^)
|
< 10 mm |
10-40 mm |
>40 mm |
||
|
KYLE SCOTNISH — North Bay (Fertilized) |
Area 1 Area 2 |
9,300 396,000 |
4.300 556 |
ca. 10 136 |
|
LINNE MHURICH (Unfertilized) |
Area 1 Area 2 |
0 32 |
160 8 |
184 72 |
|
SAILEAN MORE (Unfertilized) |
9,712 |
2,088 |
1,068 |
Of the " other organisms " in North Bay (Table IV), the commonest were Littorina littorea (almost all juvenile), Cylichna, nemertines and occasionally Philine. The slight rise in " other organisms " late in 1945 and 1946 was accounted for almost entirely by young Littorina. Accra bullata occurred in fair numbers in the deeper waters of Kyle Scotnish during 1946, and it appeared in the shore sampUngs during July of that year.
ZO NATION
Although the stations were not definitely related to exact tide level, for each transect Station 1 was sited high up on the flat, and the last station (Station 3 or 4) close to low water. Some attempt has therefore been made to relate very broadly the distribu- tion of the more important members of the fauna to level on the shore.
The fauna of an inter-tidal mud flat
183
Of the bivalves, Macoma was fairly evenly distributed across the shore, while Scrobicularia was somewhat more abundant at upper and middle levels (Fig. 2). Mytilus was absent near high- and mid-tide levels, and increased towards low water. In Transect 4, however, it was abundant in the middle region as well as towards low water, but still avoided the upper levels (Fig, 2). This difference may possibly be explained by the fact that Transect 4 was taken on a difierent portion of the shore close to a small permanent stream which ran across the mud (Fig. 1). This difference in distribution was also seen for Cardium: while in Transects 1-3 this bivalve was practically absent near high water mark and was common from mid-tide levels and towards low water, in Transect 4 Cardium was commonest at the uppermost levels and decreased in abundance down the shore (Fig. 2),
Fig 1 Sketch map of North Bay mud flat at head of Kyle Scotnish, showing positions of the four TmnsecrsNuSs along Transects indicate Stations. Flagged dots = permanent poles on road-
side used for bearings
Some of the polychaetes also showed fairly obvious distributions. Nereis diversi- color was hardly represented below mid-levels on the shore and was at its maximum at the uppermost stations (Fig. 2). This distribution applied to Transects 2 and 3; along the other Transects Nereis occurred hardly anywhere throughout the sampling period. Nephthys contrasted sharply with Nereis in that it was practically absent from the upper levels and increased sharply towards low water (Fig. 2). Nephthys also occurred quite commonly below low water mark. There is again the suggestion
184
J. E. G. Raymont
MACOMA
SCTOBICULARIi
CAR0IUI4 MYTIUS NEPMTHYS_ JCREIS _ ARENICOLA _ HE.TIROMASTyS^ _ f YGOSPIO
, CHIRONOMIDS OLIGOCHAETES
Fig. 2. The distribution of the more important lamellibranchs and polychaetes; also of chironomid larvae and oligochaetes. Along each transect, the stations are taken as equidistant down the shore, St. 1 being near high water mark. The numbers are densities per m^ calculated as averages of the populations of 6 sampling dates. Note : A different scale has been used for Pygospio in Transect 4
that Transect 4 was generally on a somewhat lower level of the shore. Nephthys, for example, was commonest at the mid-station of this Transect instead of at the lower station. Heteromastus also appeared to be reaching its maximum density at the high level of the shore in Transect 4, whereas in Transects 1-3 Heteromastus was absent
Table VII The distribution of Hydrobia ulvae over North Bay. The population of each station is expressed per m^ and represents the average of the 6 sampling dates. Numbers in brackets are rounded figures based on averaging 3 July samples
|
Transect 1 |
Transect 2 |
Transect 3 |
Transect 4 |
|
|
Station 1 |
8,529 (8,300) |
6,021 (6,700) |
10,593 (9,200) |
16,246 (15,300) |
|
Station 2 |
7,974 (6,700) |
9,809 (10,600) |
14,366 (10,500) |
9,264 (4,600) |
|
Station 3 |
5,944 (3,100) |
9,759 (5,600) |
16,149 (12,600) |
1,903 (300) |
|
Station 4 |
283 (300) |
12,793 (6,900) |
The fauna of an inter-tidal mud flat
185
from the uppermost station, was sparsely distributed towards low tide, and was quite sharply limited to the middle regions of the mud flat (Fig. 2). Arenicola appeared to decrease towards low tide levels, especially in Transect 4, while the very abundant Pygospio, while occurring across the whole shore, was more abundant at mid- and low-tide levels (Fig. 2).
Both chironomid larvae and oligochaetes (Pe/osco/ex) were commonest over the mid- and upper parts of the shore, and decreased sharply towards low-tide mark (Fig. 2). Perhaps they avoided the higher salinities towards low water, although in Loch Craiglin chironomids occurred over the bottom where the salinity was about 30^/^^ over most of the year (Raymont, 1947). The distribution of juvenile Littorina was rather irregular, although on the whole they were less abundant towards low water.
The commonest gastropod {Hydrobia ulvae) showed no very clear zonation, being widely distributed with populations of several thousand individuals per square metre over most of the shore (Table VII). It was clear from the analysis of individual samples that Hydrobia was extremely patchy, and the averaging of samples probably gave a misleading impression of its real distribution. It seems, however, that Hydrobia occurred in only relatively small numbers (below 1,000 per m-) at the lowest level along Transect 2, and also at the lowest station in Transect 4, where the density did not exceed 450 per m^ except for one dense patch of some 10,000 individuals recorded in November 1943. Similarly, the lowest level along Transect 1 showed a lower
Table VHI The changes in total population at the 14 stations. Two stations {Tr. 2, St. 4 and Tr. 4, St. 3) were not properly sampled in Nov. 1945. The autumn totals show these stations included (figures in brackets), and also excluded (figures unbracketed). (Populations to
nearest hundred per m^)
|
Station |
Autumn Populations Nov. '43 Nov. "44 Nov. "45 |
Nov. '43- Nov. '45 % Change |
Summer Populations July '44 July '45 July "46 |
Julv '44- July '46 °o Change |
||||
|
Transect 1 : 1 2 3 |
8,500 11,800 3,000 |
8,200 11,400 6,000 |
26,400 13,600 27,500 |
+ 211 + 15 + 817 |
7,500 4,200 5,000 |
15,000 12,300 1.900 |
12,800 12,500 4,500 |
, +71 + 200 -10 |
|
Transect 2 : 1 2 3 4 |
14,700 21,600 30,400 1,700 |
11,000 23,300 9,500 300 |
10,300 27,800 13,400 (?)300 |
-30 +29 -56 -82(?) |
21,900 15.200 11,600 1,400 |
5,200 17,900 7,200 3,100 |
7,800 15.800 3.800 3,300 |
-64 +4 ! -67 ^136 |
|
Transect 3 : 1 2 3 4 |
11,100 14,900 23,000 13,800 |
20,800 28,000 18,000 12,400 |
13,200 22,500 22,100 39,400 |
+ 19 + 51 -4 + 186 |
13,700 13,400 16,800 12,700 |
14,000 14.600 12.900 5,700 |
5,900 7.100 11.200 4,900 |
-57 -47 -33 -6! |
|
Transect 4 : 1 2 3 |
16,700 17,000 11,000 |
20,900 10,600 2,800 |
21,900 22,400 (7)1,100 |
+ 31 + 32 -90(?) |
10,100 7,400 3,800 |
18,600 8,200 2,000 |
23,200 6.700 2,200 |
i +130 -9 42 |
|
Total |
(199,200) 186.500 |
(183,200) (261.900) 180,100 260.500 |
( + 31) +40 |
144,700 |
138.600 |
121.700 |
-16 |
186
J. E. G. Raymont
Table IX
Changes in density of the main constituents of the fauna at the \A regular stations. (All numbers per m^)
Transect 1 Station 1
|
Nov. '43 |
July '44 |
Nov. '44 |
July '45 |
Nov. '45 |
July '46 |
|
|
Large Bivalves |
80 |
128 |
52 |
72 |
28 |
136 |
|
Small Bivalves |
88 |
127 |
127 |
212 |
127 |
84 |
|
Hydrobia |
6,256 |
4,961 |
5,809 |
9,921 |
14,289 |
9,921 |
|
Chironomids |
788 |
890 |
339 |
1,950 |
9,286 |
2,078 |
|
Oligochaetes |
960 |
890 |
1,272 |
2,502 |
1,993 |
382 |
|
Crustacea |
44 |
127 |
— |
— |
42 |
85 |
|
Polychaetes |
212 |
340 |
297 |
42 |
126 |
— |
|
Other Organisms |
52 |
— |
254 |
297 |
509 |
84 |
|
Totals |
8,480 |
7,463 |
8,150 |
14,996 |
26,400 |
12,770 |
Transect 1 Station 2
|
Large Bivalves |
108 |
48 |
36 |
80 |
152 |
88 |
|
Small Bivalves |
24 |
254 |
42 |
84 |
85 |
466 |
|
Hydrobia |
9,472 |
2,120 |
7,208 |
6,233 |
10,939 |
11,872 |
|
Chironomids |
792 |
— |
1.696 |
3,434 |
1,060 |
— |
|
Oligochaetes |
220 |
339 |
254 |
636 |
382 |
— |
|
Crustacea |
20 |
— |
— |
— |
85 |
— |
|
Polychaetes |
804 |
1,356 |
1,865 |
1,398 |
467 |
42 |
|
Other Organisms |
372 |
42 |
296 |
466 |
381 |
— |
|
Totals |
11,812 |
4,159 Transect 1 |
11,397 Station 3 |
12,331 |
13,551 |
12,468 |
|
Large Bivalves |
240 |
36 |
28 |
12 |
56 |
454 |
|
Small Bivalves |
176 |
255 |
127 |
127 |
6,275 |
85 |
|
Hydrobia |
596 |
4,586 |
5,427 |
1,102 |
20,267 |
3,689 |
|
Chironomids |
1,076 |
— |
— |
127 |
42 |
— |
|
Oligochaetes |
492 |
— |
— |
— |
— ■ |
— |
|
Crustacea |
48 |
— |
— |
42 |
— |
— |
|
Polychaetes |
260 |
128 |
382 |
508 |
679 |
212 |
|
Other Organisms |
108 |
— |
4 |
— |
169 |
42 |
|
Totals |
2,996 |
5,005 |
5.968 |
1,918 |
27,488 |
4,482 |
Transect 2 Station 1
|
Large Bivalves |
— |
48 |
— |
— |
— |
16 |
|
Small Bivalves |
— |
42 |
— |
— |
42 |
— |
|
Hydrobia |
3,567 |
10,685 |
6,190 |
4,282 |
6,402 |
5,003 |
|
Chironomids |
127 |
42 |
— |
— |
— |
— |
|
Oligochaetes |
10,192 |
9,286 |
3,010 |
127 |
42 |
297 |
|
Crustacea |
|
— |
42 |
— |
— |
42 |
|
Polychaetes |
764 |
1,102 |
764 |
806 |
509 |
340 |
|
Other Organisms |
— |
678 |
1,017 |
— |
3,265 |
2,247 |
|
Totals |
14,650 |
21,883 |
11,023 |
5,215 |
10,260 |
7,945 |
Transect 2 Station 2
|
Large Bivalves |
56 |
152 |
140 |
140 |
196 |
138 |
|
Small Bivalves |
84 |
339 |
212 |
170 |
212 |
212 |
|
Hydrobia |
3,689 |
11,194 |
13,653 |
11,406 |
9,625 |
9,286 |
|
Chironomids |
1,866 |
1,653 |
1,145 |
85 |
2,968 |
1,102 |
|
Oligochaetes |
15,264 |
1,569 |
7.378 |
4,706 |
13,907 |
4,155 |
|
Crustacea |
169 |
42 |
84 |
126 |
— |
127 |
|
Polychaetes |
466 |
255 |
339 |
1,059 |
678 |
84 |
|
Other Organisms |
— |
— |
338 |
254 |
254 |
636 |
|
Totals |
21,594 |
15,204 |
23,289 |
17,946 |
27,840 |
15,740 |
The fauna of an inter-tidal mud flat
187
Large Bivalves Small Bivalves Hydrobia Chironomids Oligochaetes Crustacea Polychaetes Other Organisms
Totals
Table IX (cont.) Transect 2 Station 3 A^ov. '43 July '44 Nov. '44 July '45 Nov. '45 July '46
|
32 |
64 |
16 |
40 |
80 |
210 |
|
212? |
127 |
296 |
85 |
1,865 |
42 |
|
26,966 |
10,770 |
4,918 |
3,307 |
9,922 |
2,671 |
|
1,484 |
85 |
1,654 |
1,272 |
636 |
339 |
|
1,145 |
— |
339 |
297 |
424 |
42 |
|
— |
— |
42 |
42 |
85 |
212 |
|
169 |
423 |
1,822 |
1,484 |
253 |
169 |
|
423 |
84 |
382 |
721 |
169 |
85 |
|
30,431 |
11,553 |
9,469 |
7,248 |
13,434 |
3,770 |
Transect 2 Station 4
|
Large Bivalves |
— |
— |
4 |
|
|
28 |
|
Small Bivalves |
127 |
84 |
42 |
85 |
16 |
170 |
|
Hydrobia |
678 |
382 |
85 |
42 |
48 |
466 |
|
Chironomids |
— |
— |
|
|
|
1,060 |
|
Oligochaetes |
— |
85 |
|
— |
— |
127 |
|
Crustacea |
42 |
|
|
170 |
16 |
127 |
|
Polychaetes |
763 |
805 |
127 |
2,801 |
208 |
297 |
|
Other Organisms |
42 |
— |
52 ' |
— |
— |
1,059 |
|
Totals |
1,652 |
1,356 |
310 |
3,098 |
288 |
3,334 |
Transect 3 Station 1
|
Large Bivalves |
211? |
100 |
164 |
76 |
52 |
26 |
|
Small Bivalves |
170 |
127 |
169 |
42 |
127 |
42 |
|
Hydrobia |
7,036 |
11,321 |
18,276 |
11,787 |
10,515 |
4,622 |
|
Chironomids |
678 |
1,103 |
636 |
254 |
1,738 |
85 |
|
Oligochaetes |
2,078 |
806 |
297 |
1,230 |
382 |
763 |
|
Crustacea |
297 |
— |
296 |
42 |
— |
42 |
|
Polychaetes |
635 |
253 |
296 |
594 |
296 |
296 |
|
Other Organisms |
— |
— |
636 |
— |
127 |
— |
|
Totals |
11,105 |
13,710 |
20,770 |
14,025 |
13,237 |
5,876 |
Transect 3 Station 2
Large Bivalves Small Bivalves Hydrobia Chironomids Oligochaetes Crustacea Polychaetes Other Organisms
Totals
|
140 |
136 |
64 |
24 |
84 |
58 |
|
42 |
42 |
212 |
211 |
423 |
212 |
|
12,126 |
11,999 |
26,627 |
12,762 |
16,070 |
6,614 |
|
1,357 |
297 |
— |
170 |
5,173 |
— |
|
636 |
339 |
127 |
170 |
678 |
— |
|
127 |
84 |
— |
42 |
— |
— |
|
423 |
424 |
933 |
1,100 |
— |
42 |
|
42 |
42 |
— |
84 |
42 |
169 |
|
14,893 |
13,363 |
27,963 |
14,563 |
22,470 |
7,095 |
Transect 3 Station 3
Large Bivalves Small Bivalves Hydrobia Chironomids Oligochaetes Crustacea Polychaetes Other Organisms
Totals
|
84 |
80 |
32 |
76 |
132 |
98 |
|
64 |
339 |
338 |
296 |
552 |
42 |
|
21,212 191 |
15,264 |
17,087 |
11,575 254 |
20,818 |
10.939 42 |
|
701 |
212 |
42 |
— |
42 |
— |
|
42 |
85 |
— |
42 |
||
|
573 |
762 |
211 |
381 |
212 |
85 |
|
191 |
169 |
212 |
212 |
339 |
|
|
23,016 |
16,826 |
17,964 |
12,879 |
22,095 |
11.248 |
188
J. E. G. Raymont
|
Table IX {cont.) |
||||||
|
Transect 3 |
Station 4 |
|||||
|
Nov. '43 |
July '44 |
Nov. '44 |
July '45 |
Nov. '45 |
July '46 |
|
|
Large Bivalves |
128? |
44 |
56 |
40 |
792 |
338 |
|
Small Bivalves |
509 |
128? |
255 |
169 |
2,586 |
296 |
|
Hydrobia |
11,530 |
12,358 |
10,049 |
4,664 |
34,344 |
3,816 |
|
Chironomids |
64 |
— |
890 |
— |
212 |
42 |
|
Oligochaetes |
382 |
— |
212 |
85 |
127 |
— |
|
Crustacea |
192 |
64 |
255 |
127 |
381 |
254 |
|
Polychaetes |
955 |
128 |
551 |
593 |
636 |
169 |
|
Other Organisms |
— |
— |
84 |
42 |
339 |
— |
|
Totals |
13,760 |
12,722 Transect 4 |
12,352 Station 1 |
5,720 |
39,417 |
4,915 |
|
Large Bivalves |
127? |
48 |
12 |
40 |
108 |
62 |
|
Small Bivalves |
84 |
212 |
933 |
1,187 |
1,018 |
— |
|
Hydrobia |
12,762 |
7,632 |
18,656 |
15,688 |
20,098 |
22,642 |
|
Chironomids |
1,187 |
382 |
— |
42 |
— |
127 |
|
Oligochaetes |
933 |
212 |
127 |
127 |
— |
42 |
|
Crustacea |
678 |
— |
— |
42 |
— |
42 |
|
Polychaetes |
889 |
1,611 |
1,145 |
1,357 |
424 |
296 |
|
Other Organisms |
42 |
— |
42 |
84 |
212 |
— |
|
Totals |
16,702 |
10,097 Transect 4 |
20,915 Station 2 |
18,567 |
21,860 |
23,211 |
|
Large Bivalves |
212? |
20 |
8 |
12 |
128 |
4 |
|
Small Bivalves |
339 |
2,459 |
297 |
85 |
1,483 |
85 |
|
Hydrobia |
15,137 |
3,265 |
7,674 |
4,664 |
19,122 |
5,724 |
|
Chironomids |
— |
— |
— |
85 |
254 |
42 |
|
Oligochaetes |
297 |
42 |
127 |
42 |
42 |
. — |
|
Crustacea |
42 |
42 |
— |
212 |
— |
381 |
|
Polychaetes |
1,018 |
1,315 |
2,336 |
3,053 |
1,399 |
423 |
|
Other Organisms |
— |
212 |
127 |
42 |
— |
— |
|
Totals |
17,045 |
7,355 Transect 4 |
10,569 Station 3 |
8,195 |
22,428 |
6,659 |
|
Large Bivalves |
126? |
16 |
8 |
— |
16 |
96 |
|
Small Bivalves |
170 |
1,314 |
212 |
127 |
80 |
64 |
|
Hydrobia |
10,049 |
424 |
339 |
254 |
160 |
191 |
|
Chironomids |
|
|
|
— |
— |
191 |
|
Oligochaetes |
212 |
|
85 |
42 |
16 |
— |
|
Crustacea |
42 |
42 |
84 |
— |
176 |
64 |
|
Polychaetes |
382 |
1,994 |
2,035 |
1,611 |
688 |
1,529 |
|
Other Organisms |
— |
42 |
42 |
— |
— |
64 |
|
Totals |
10,981 |
3,832 |
2,805 |
2,034 |
1,136 |
2,199 |
population than along the rest of the transect, except for one particularly dense patch of 20,000 individuals per m^ in November 1945. On the other hand, the lowest station along Transect 3 had a population almost as great as at higher levels, and the population was maintained over the period investigated. There is an indication that Transect 4 exhibited a slightly different distribution from the other transects in that the highest density of Hydrobia occurred at the uppermost level, and the population fell off sharply on passing down the shore (Table VII).
CHANGES IN THE POPULATION
The great majority of the stations showed a decline in total population from Novem- ber 1943 to the following July (Table VIII). This decrease affected most of the members of the fauna (Table IX). The total average population in November 1944 was almost identical with that of the previous autumn, but July 1945 showed a decline again.
The fauna of an inter-tidal mud flat
189
The counts for November 1943 are not entirely reliable, as the sampling method was still being worked out then. Nevertheless, the order of magnitude of the population is probably correct, and it is important, since that population represents a pre-fertiliza- tion autumn density for the North Bay area. Probably the data for July 1944 can also be taken as approximating to a mmmer pre-ferti/ization density, since, although fertili- zation began over Kyle Scotnish early in 1944, little effect may be expected for some months (cf. Raymont, 1947). In November 1945 the density increased to a relatively high level, but once more declined in the following summer, when there was a particularly marked drop (Tables IV, VIII and IX). In all three years therefore the July population was smaller than in the previous autumn.
40
cc u a
o
30
<
O 20
X
I- I
I- 10 —
3 a. o
] I
1943 1944 1945
m
/
/ / /
STA I 2 3
TRANSECT I
/
?
v\
/ /
/ / / / / / / / / /
tdJ
.m
12 3 4
TRANSECT 2
2 3 4
TRANSECT 3
1 2 3
TRANSECT 4
Fig. 3. A comparison of the total populations in November 1943, 1944 and 1945 at each of the 14 regular sampling stations. (Numbers per m'^.) (The figures at Tr. 2, St. 4 and Tr. 4, St. 3 are doubtful
owing to imperfect sampling)
In considering the changes at individual stations it is probably necessary to omit Transect 2, St. 4, and Transect 4, St. 3, since on some occasions the samples could be obtained only by a grab. Of the remaining twelve stations, nine show an increase in population in November 1945 as compared with November 1943 (pre-fertilization), and two stations a decrease (Table VIII; Fig. 3). Owing to the patchiness of the fauna and to sampling errors, small differences (e.g. Transect 1, St. 2; Transect 3, St. 3) should probably be disregarded. If changes exceeding — 30°„ be regarded as significant, six stations showed a real increase in population — three being really large, while only one station showed a significant decline.
If the July populations are now considered, from Summer 1944 to Summer 1945 there is no obvious change. The total populations when averaged differ by only 4%, and of the individual 14 stations four only show a real increase and five a decrease.
The decline in bottom fauna densities which appeared in every July sampling seems to be more obvious in the summer of 1946. If the population then is compared with
190
J. E. G. Raymont
that of July 1944, the average population shows a decline, and seven stations show significant decreases as against four showing increases (Tables IV and VIII). Although it is questionable whether a decline of some 16% in the average population from July 1944 to July 1946 is significant, it is at least obvious that the changes in summer population do not parallel those of the autumn,
SIZE DISTRIBUTION OF SOME BIVALVES An approximate picture of the size distribution of the four common bivalves in North Bay has been obtained. It is likely that, especially where very few small bivalves were taken, the combining of data obtained by the two sampling methods increases
Table X The size-frequencies of Macoma balthica in North Bay. The figures are averages per m^ based on 10 sampling stations. {Tr. 1, Sts. 1, 2 and 3; Tr. 2, Sts. 2 and 3; Tr. 3,
Sts. I, 2 and 3; Tr. 4, Sts. 1 and 2)*
|
Size |
|||||||||||||||
|
Groups |
1 |
2 3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
|
(mm) |
|||||||||||||||
|
July |
|||||||||||||||
|
1944 |
— |
6-5 8 |
13 |
4 |
17 |
13 |
19 |
30 |
5 |
5 |
6 |
3 |
2 |
0-5 |
0-5 |
|
Nov. |
|||||||||||||||
|
1944 |
4 |
8-5 8 |
13 |
34 |
13 |
8 |
25 |
30 |
1 |
— |
3 |
1 |
2 |
0-5 |
— |
|
July |
|||||||||||||||
|
1945 |
13 |
25 13 |
8 |
8 |
0-5 |
— |
13 |
8 |
2 |
2 |
5 |
3 |
2 |
2 |
— |
|
Nov. |
|||||||||||||||
|
1945 |
— |
— 8-5 |
4 |
8 |
13 |
8 |
8 |
21 |
2 |
5 |
8 |
8 |
3 |
2 |
0-5 |
|
July |
|||||||||||||||
|
1946 |
■ |
|
|
4 |
4 |
21 |
|
|
|
|
|
1 |
Table XI The size-frequencies of Scrobicularia plana in North Bay. The figures are averages per m- based on 6 stations. (Tr. 1, Sts. 1 and 2; Tr. 2, St. 2; Tr. 3, Sts. I, 2 and 3). The columns on the right of the table show the size-frequencies of small Scrobicularia
(<10 mm) *
|
Size |
|||||||||||||
|
Groups |
1-3 |
4-6 |
7-9 |
10-12 |
13-15 |
16-18 |
19-21 |
22-24 |
25-27 |
28-3C |
31-33 |
34-36 |
|
|
(mm) |
|||||||||||||
|
Julv '44 |
28 |
14 |
|
1 |
3 |
2 |
1 |
5 |
3 |
14 |
15 |
18 |
|
|
Nov. '44 |
7 |
28 |
— |
1 |
1 |
1 |
4 |
5 |
11 |
13 |
15 |
9 |
|
|
July '45 |
28 |
14 |
49 |
8 |
5 |
6 |
2 |
|
7 |
7 |
7 |
7 |
|
|
Nov. '45 |
— |
14 |
35 |
1 |
8 |
10 |
6 |
4 |
5 |
9 |
7 |
11 |
|
|
July '46 |
~ — ■ |
|
42 |
— |
4 |
9 |
13 |
10 |
3 |
4 |
5 |
7 |
|
|
Size |
|||||||||||||
|
Groups |
37 39 40-42 |
43^5 |
46^8 |
49-51 |
(mm) 1 |
2 3 |
4 5 |
6 |
7 |
8 |
9 10 |
||
|
(mm) |
|||||||||||||
|
July '44 |
5 |
1 |
|
|
_ |
7 21 |
7 7 |
_ |
_ |
_ |
_ _ |
||
|
Nov. '44 |
1 |
1 |
1 |
1 |
|
— 7 |
— 14 |
14 |
|
|
. |
||
|
July '45 |
3 |
1 |
1 |
— |
|
|
21 7 |
— 7 |
7 |
21 |
21 |
7 — |
|
|
Nov. '45 |
1 |
1 |
5 |
2 |
|
|
|
. |
14 |
21 |
7 |
7 — |
|
|
July '46 |
7 |
2 |
|
|
|
— |
|
— — |
14 |
28 — |
* Data for November 1943 omitted as sampling methods then not strictly comparable with later samples.
The fauna of an inter-tidal mud fiat
191
unduly the proportion of the smaller ones, and thus at 10 mm there may tend to be an artificially sharp break in the distribution pattern. Some confirmation of this, for example, was obtained for the distribution of Mytilus in November 1945 (Table XII) when some quadrat counts were also made of small bivalves. Nevertheless a fair indication of the general pattern of the size distribution has been obtained (Tables X, XI, XII, XIII). The growth rates have been based on an examination of modal lengths; the use of growth rings was attempted, but numerous " false rings " inter- fered with the analysis.
Table XII The size-frequencies o/ Mytilus edulis in North Bay. The figures are averages per m'- based on 6 stations. (Tr. 1 , St. 3; Tr. 2, St. 3; Tr. 3, Sts. 3 and 4; Tr. 4. Sts. 2 and 3) *
Size
Groups
(mm)
1-3 4-6 7-9 10-12 13-15 16-18 19-2! 22-24 25-27 28-30 31-33 34-36
July "44 Nov. '44 July "45 : Nov. '45 I July '46 I
75
35 21
11 7
7 21
21 —
168 294
7 7
87 15
36 14
0-5
0-5
0-5 —
13
15
0-5 20
20
20
1 16
1 15
0-5
0-5 11
Size
Groups
{mm)
37-39 40-42 43-45 46-48 49-51 52-54 55-57 58-60 61-63 64-66 67-69
July '44 Nov. '44 July '45 Nov. '45 Julv '46
0-5 0-5 — — — — 1 0-5 — — —
05 _____ — — — — —
4 4 2 10-5 0-5 0-5 1 0-5 0-5 0-5
Table XIII The size-frequencies o/Cardium edule in North Bar. The figures are averages per m- based on 6 stations. {Tr. 1, St. 3; Tr. 2, St. 3; Tr. 3, Sts. 3 and A: Tr. 4. Sts. 1 and 2). Note: Up to\0 mm length the groups are 3-5 tnm; thereafter 4 mm groupings are used*
|
Size |
||||||||||||||
|
Groups |
I- |
4- |
7- |
10- |
14- |
18- |
22- |
26- |
30- |
34- |
38- |
42- |
46- |
50- |
|
{mm) |
3-5 |
6-5 |
9-5 |
13 |
17 |
21 |
25 |
29 |
33 |
37 |
41 |
45 |
49 |
53 |
|
July '44 |
441 |
42 |
_ |
4 |
1 |
4 |
2 |
2 |
3 |
3 |
3 |
— |
— |
3 |
|
Nov. '44 |
98 |
63 |
14 |
1-5 |
4 |
2 |
5-5 |
2 |
1-5 |
2 |
0-5 |
U-5 |
— |
|
|
July '45 |
52 |
52 |
— |
1-5 |
— |
T |
0-5 |
0-5 |
1 |
T-5 |
1 |
— |
— |
|
|
Nov. '45 |
996 |
396 |
36 |
11-5 |
1 |
2-'^ |
1-5 |
5 |
3-5 |
— |
— |
— |
|
|
|
July '46 |
14 |
28 |
35 |
1 |
11-5 |
4-5 |
7 |
3 |
i |
1 |
1 |
0-5 |
* Data for November 1943 omitted as sampling methods then not strictly comparable uiih later samples.
As regards Macoma, almost all individuals were less than 15 mm. The July 1944 and July 1945 collections suggest that young bivalves, less than one year old (O-Group), were about 2-4 mm long (Table X). The November figures indicate a growth to about 5-6 mm, but the distributions for July in each year also suggest another peak at about 8-9 mm. It is suggested therefore that this would represent approximately one year of growth. On this hypothesis there would appear to be little growth from July to the
]92 J. E. G. Raymont
following November, since each autumn has a fairly clear peak at 9 mm. The numbers of Macoma larger than 10 mm is very small indeed, but those between 1 1 and 15 mm may be regarded as in their second year of growth. In summer 1946 there was no successful spatfall. A very few Macoma of about 9 mm length (presumably 1 year old) persisted, but all other age groups had disappeared (Table X).
Scrobiculaha, though never very numerous, grew to a considerable size in North Bay, a proportion reaching 40 mm (Table XI). In July 1944 and 1945 a new brood of Scrobicularia appeared only a few mm long but (as for Macoma) no successful spatfall occurred in summer 1946. A difficulty is that in July 1945 the smallest Scrobicularia included many of 2-3 mm, but also a large number about 8 mm. When the smallest bivalves (less than 10 mm) are separated into 1 mm groups, it appears that the 2-3 mm individuals were O-Group Scrobicularia, and that the 8 mm individuals were probably an older group (Table XI). By November 1944 O-Group Scrobicularia reached a length of some 5-7 mm, and the group of 7-9 mm in the following July would pre- sumably be one-year-old bivalves (Table XI). Thus the spat of 1944 reached about 7-9 mm by July 1945, and possibly this was the same year group which attained some 16 mm length by the following November, and about 20 mm by the next July (1946), when they would have been two years old (Table XI). If this is a true interpretation, there was some acceleration in growth rate late in 1945 and during 1946. This could well be a result of fertilization of Kyle Scotnish; the general bottom fauna in the loch did not begin to increase clearly until late 1945 (cf. Raymont, 1950).
As regards Mytilus, only the lower stations showed an appreciable population and even there mussels, especially large individuals, were extremely sparse until November 1945, when a marked increase appeared. The population then consisted mainly of small individuals, the spat of the previous summer. July 1945 figures, however, showed that very little spat had settled by that time. Gauld (private communication) observed very heavy spatfalls of Mytilus over the North Bay area somewhat later in that summer. Some random samplings made in collaboration with Dr. Gauld showed parts of North Bay where tremendously dense patches (even > 100,000 per m^) of very small mussels were present. Measurements on some of these collections in August and September showed the great majority of these mussels were below 5 mm— clearly the summer's spat (cf. also Table VI). Although a very large percentage of this spatfall died off very rapidly, by November 1945 a considerable population of young mussels was still present. By the following July the population had declined markedly (Table XII).
Comparison of the three July samplings shows that little spat had settled by that time each summer (Table XII). The somewhat higher figure for July 1944 may indicate a slightly earlier spatfall in that year. The 1944 brood grew to about 8 mm by Novem- ber, but thereafter they disappeared (Table XII). It is possible that as they grew larger they became smothered in the soft mud substratum. Frost may also have killed them off during the winter.
The abundant 1945 spat which appeared in August and September, mostly <5 mm length, attained a length by November 1945 of approximately 9 mm (Table XII). By July 1946, although no new spat had settled, the mussels had definitely established themselves over a considerable part of the shore. Their densities had declined with winter mortality, but there was a fairly rich group ranging from 10 to 35 mm (Table XII). The mode of this group appears to be about 23 mm, and this suggests that the
The fauna of an inter-tidal mud flat |93
9 mm peak of November 1945 has now shifted to the 23 mm peak of July 1946. This successful 1945 brood would therefore appear to have grown more than 20 mm in approximately one year. The growth rate is higher than that suggested for Macoma and for Scrobicularia, but an acceleration was suggested in the growth of Scrohicu/aria over the same period. The success of the 1945 brood of Mytilus and the considerable degree of colonization of the North Bay may be due in part to the general rise in productivity with fertilization noted at that time (Raymont, 1950).
For Cardium, an early spatfall occurred in summer 1944, the majority of cockles in July being about 2 mm. As for Mytilus, the population of Cardium of more than
10 mm length was generally extremely sparse over North Bay in 1944-45 (Table XIII). It would appear therefore that 1944 was an early spat year but that the brood was unsuccessful.
In 1945, spat was more abundant in the November samples than in July, indicating that the majority of the summer brood had not settled by mid-summer. Cardium also followed Mytilus in that 1945 appeared to be a much more successful year; over 1,000 small cockles per m- had settled by November 1945. All these were less than 10 mm length, and the great majority were in the smallest length class (1-3 -5 mm) (Table XIII). A few cockles occurred at this time in the 10-13 mm group, and these may represent a few individuals of the I-Group, i.e. those which had settled in the previous July. By July 1946 a very heavy mortality had occurred, and there was no real spatfall. There was, however, for the first time, some indication of a spread of the somewhat larger cockles (14-25 mm) which probably represented the spat of the previous summer. The numbers, although small, suggest a fairly sharp break in the size distribution between 10 and 13 mm (Table XIII). The numbers of cockles between 10 and 28 mm taken from all six stations added together were:
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 (Length (mm)) 0024 20 16 24 886822865233 (No. per m^)
This suggests a modal length of about 14-16 mm, indicating a fairly successful brood from the previous summer (1945) which has averaged 15 mm growth in a year. This growth would be an improvement on that for Macoma and Scrobicularia. but it was not as rapid as that of Mytilus.
There is undoubtedly a considerable degree of overlap between this brood and an older age group (20-28 mm). A second peak possibly occurs about 23-24 mm, and this would therefore represent a two year old group of Cardium. The very low figures for July 1944 might also indicate one group of cockles varying in size from 18-21 mm (II-Group) and another group of 10-13 mm (I-Group). An enhanced growth rate in 1945 would agree with the results on other lamellibranchs.
It seems clear that 1945 was a fairly successful year for both Cardium and Mytilus, and that some spread of these bivalves occurred over the North Bay. Although part of the success of the 1945 brood may be correlated with better feeding conditions due to fertilization, the bivalves still experienced the difficulty of establishing themselves for any length of time on a muddy shore, subject to prolonged exposure.
DISCUSSION The fauna of North Bay is a Macoma halthica community, and corresponds well to that studied by Smidt (1951) in the Danish waddens. The polychaele and lamelli- branch species of the infauna are very similar, with Hydrobia ulvae as the dominant
H
194 J- E- G. Raymont
gastropod. Smidt quotes Mytilus edulis and Littorina littorea as the two most import- ant members of the epifauna — a composition that accords well with the North Bay mud flat. One marked difference was the very low numbers of Corophium found in North Bay. Thamdrup (1935), Smidt (1951), Beanland (1940), Spooner and Moore (1940) all quote this species as an important member of the Macoma community. Beanland, and Spooner and Moore, suggest that one factor which limits its occurrence is lack of shelter, so that its maximum density is usually near high-water mark. Nevertheless Corophium might have been expected to occur abundantly at least at the higher levels of North Bay, which is at the end of a long, sheltered sea-loch. Moreover, Hydrobia, which is also said to be sensitive to water movement, was very abundant— in fact dominant numerically — in North Bay. There have been some suggestions that Corophium may occur only as a temporary visitor on shore; perhaps sampling only in July and November missed its abundant season. Possibly also Corophium competes with other members of the fauna that were plentiful in North Bay (cf. Thamdrup, 1935).
Another difference between other described Macoma communities and North Bay was the importance of chironomid larvae in the latter area. These larvae are not mentioned by Thamdrup (1935), Smidt (1951), Fraser (1932), Brady (1943) or Rees (1940). Spooner and Moore (1940) do list " dipterous larvae " on a few occasions in their tables, but the numbers are very low, and clearly if there were Chironomidae, they were never of importance. Wohlenberg (1937) also mentions chironomid larvae in a small area near a fresh water stream, but they did not apparently occur generally over the mud flat. Nicol (1935) found high densities (maximum 39,000 per m^) in muddy salt pools. Over the North Bay the average population varied between 300 and 1,500 per m^ from 1943 to 1946, but individual samples gave densities of 2,000-3,000 per m^ (maximum >9,000 per m^).
Oligochaetes (chiefly Peloscolex) were also very abundant in North Bay ; the average population for the shore ranged near 1,000 per m^ for a considerable period, and individual samples amounted sometimes to several thousands (maximum 13,900 per m^). Smidt (1951) comments on Ohgochaeta (including Peloscolex benedeni) as being exceedingly numerous on the higher parts of the waddens, and Brady (1943) found they occurred in muds off the Northumberland coast, though the densities in North Bay were very much higher. Peloscolex was also found by Wohlenberg (1937).
Most authors state that Hydrobia is concentrated in the upper tidal areas (cf. Spooner and Moore); in North Bay the lowest stations usually had few. However Rees (1940) found it in greater density towards low water, and Smidt states that the young Hydrobia occurred in great numbers in summer and autumn anywhere over the mud flats. This could account for the very dense patches occasionally encountered in North Bay, even at the lowest tidal levels (cf. p. 1 85). The maximum densities recorded by most workers in Great Britain do not usually exceed 20,000 per m- (Table XIV); though Nicol (1935) found up to 32,000 per m^ at Aberlady, Scotland. The richness of North Bay is therefore apparent. However, the densities there were not as high as those at Skalling (Table XIV). Smidt (1951) recorded even higher densities for the Danish waddens when O-Group Hydrobia were also counted (Maximum 600,000 per m^).
Of the bivalves typical of the Macoma community, Mya was taken only rarely in North Bay. Macoma seemed able to live over a very broad zone of the shore, though
The fauna of an inter-tidal mud flat | 95
the lowest station of Transects 2 and 4 was quite ddinitcly avoided— A/acowa occurred only once there during the whole period of sampling. The density of Macoma, even in comparatively rich zones, appears rarely to exceed 200-300 per m^ and North Bay would therefore be quite a dense area. However, Thamdrup recorded up to 1,000 per m- at Skalling, and Fraser far higher densities in the Mersey Estuary (Table XIV).
In general the great majority of individuals in the higher counts in North Bay were young (< 10 mm) ; a particularly striking example was the maximum count of 428 per m^ of which only four exceeded 10 mm. Densities of individuals ,10 mm rarely rose to 60 per m^ Wohlenberg (1937) found >6,000 0-Group Macoma at Sylt. Similarly the 6,300 individuals per m- recorded at Skalling (Table XIV) were all young. Smidt found even 16,000 0-Group Macoma per m- in the same area, though he also showed that the stock was reduced to some hundreds per m- in a few months.
Stephen (1931) believes that Macoma breeds about April-May, young individuals appearing by June and reaching a length of some 5 mm by the end of their first autumn. By the end of their second autumn, Stephen found an average length of 8-9 mm, and he believes that a heavy mortality occurs after the third summer. The growth rate of Macoma in North Bay would seem to parallel closely Stephen's results. Young spat, 2-4 mm, appeared in the July samplings and reached about 5-6 mm by the first autumn (November) and some 9 mm by the following autumn. The conditions for growth in North Bay would appear to be favourable. Brady (1943), for collections in June, gives an average length of 6 mm for I-Group and 12 mm for II-Group Macoma.
Thamdrup (1935) records Scrobiculaha at the lower levels at Skalling. Smidt and Wohlenberg found it occasionally in soft deposits, and Stephen (1930) records it in soft sticky mud in the Firth of Forth. In North Bay this bivalve was widespread in the soft substratum, though it definitely avoided the lowest tidal levels. Thus it was never taken at the lowest station in Transect 2, only once at the lowest station of Transects 1 and 4, and only twice at the lowest station in Transect 3. Spooner and Moore (1940) also indicate that Scrobicularia is commoner in the upper half of the inter-tidal zone. Except for one extraordinarily dense patch of 1,000 per m- recorded by Spooner and Moore (1940), the densities of Scrobicularia would not appear to exceed 300 per m- (Table XIV). Spooner and Moore describe the Tamar as a rich Scrobicularia area, and they regard this species as generally abundant in sheltered inter-tidal areas in the South of England (cf. also Holme, 1949). It would appear that North Bay was at least equally rich (Table XIV). The higher densities recorded by Spooner and Moore showed a high proportion of young spat. This was also true of the North Bay samples, but counts of 100-150 larger individuals per m- were quite common. Spooner and Moore do not give details of growth rates, but they remark that specimens <12 mm in length include both O-Group and I-Group. This would agree reasonably with the suggestion (p. 192) that in North Bay Scrobicularia grew to about 6 mm by the end of their first autumn, to about 8 mm by the following July, and to some 16 mm by the end of the second autumn when some acceleration is
postulated.
Spooner and Moore have suggested that Macoma and Scrobicularia may compete, since they seem to have similar feeding habits. The population of Scrobicularia in North Bay, while not very large, was about as rich as that of the Tamar Estuary, and possibly therefore Macoma was to some extent excluded from North Bay.
196
J. E. G. Raymont
Cockles were not very common in North Bay; the density of oWer individuals never exceeded 80 per m-. The much higher figures occasionally recorded showed without exception an overwhelming dominance of young cockles (<10 mm). The densities do not, however, compare unfavourably with those for other areas in Britain, especially as the high populations recorded by Stephen and by Spooner and Moore were composed mainly of O-Group cockles. By contrast, Thamdrup found very much higher densities at Skalling (Table XIV) ; indeed Cardium was the most abundant bivalve on the waddens. The maximum quoted even then (4,675) did not take account of O-Group individuals. Thamdrup showed that several thousand O-Group per m^
Table XIV
Comparison of the densities of some of the members of the fauna in North Bay and in
other areas. Numbers are maximal densities per m^. Figures in brackets indicate
extraordinarily high densities recorded only once
|
Locality |
Tamar |
Exe |
Bristol Channel |
Forth and Clyde |
Northum- berland |
Skalling |
Mersey |
North Bay |
|
Authority |
Spooner and Moore (1940) |
HOLMl (1949) |
Rees (1940) |
Stephen (1929,1930, 1931, 1932) |
Brady (1943) |
Thamdrup (1935) |
Fraser (1932) |
Raymont (this paper) |
|
Hydrobia |
10,000-14,000 (28,000) |
16,000 |
18,000 |
1,400 (3,000)* |
— |
1 5,000^6,000 (60,000) |
— |
10,000-26,000 (34,000) |
|
Macoma |
36 (76) |
20-30 |
800 |
1 50-200 |
150-220 (554) |
300-1,000 (6,300) |
2,000-5,000 (5,900) |
250 (428) |
|
Scrobicularia |
100-280 (1,000) |
230 |
— |
136 |
— |
20-60 |
— |
150-330 |
|
Cardium |
100-200 (383) |
200 |
— |
100-150 (300) |
50-160 (192) |
2,000-3,000 (4,675) |
64 |
1,000 (6.000) |
|
Pygospio |
— |
2,540 |
— |
— |
— |
14,000-20,000 |
— |
2,840 |
|
Heteromastus |
60-90 |
— |
— |
— |
— |
10-40 |
— |
1,400 (1,740) |
|
Arenicola |
3 |
50-60 |
— |
16 (76)* |
40-60 |
100 |
— |
200-380 (470) |
|
Nereis |
1,000 (> 3,000) |
20 (130) |
2,000 |
110 (396)t |
25 |
100-320 |
t |
600-700 (890) |
|
Nephthys |
100-300 (500) |
100 |
— |
36 |
50-60 |
90 |
— |
100-210 |
* = Loch Gilp, Scotland. j = Isle of Barra, Scotland. 1: = " abundant "\ no density quoted.
also occurred, but that the densities declined rapidly during autumn and winter. Smidt and also Wohlenberg found even larger settlements of O-Group cockles: Smidt found 20,000 to 30,000 per m^ quite frequently, and Wohlenberg recorded some 40,000 per m^ but he also showed how rapidly those numbers were reduced.
Stephen (1931) concluded that Cardium bred in summer at Millport, the smallest cockles appearing about August and reaching a length of <6 mm by the end of their first autumn. By the following July these cockles reached 12-13 mm. Brady (1943) states that in June one-year-old cockles had an average length of 11 mm, and Smidt (1951) shows in July one-year-old cockles reaching a length of 12 mm, or about 16 mm in a favourable year.
The results of the North Bay collections, and also the results from Loch Craiglin (Raymont, 1947) strongly support Stephen's view that Cardium spawns in summer, but the growth of the cockles up to November in North Bay was somewhat less than Stephen found. However, the 1945 spat attained a length of about 15 mm in North
The fauna of an inier-tidal mud flat |97
Bay by July 1946, i.e. their growth was of the same order as that given by Stephen and Brady, and (in a favourable year) by Smidt. This improvement may reflect the better feeding conditions in North Bay in 1945/46.
The density of Myti/us was usually very low over the whole of North Bay, the only heavy settlements being at spatfall (August), after which the animals did not come into the regular samplings. Chipperfield (1953) shows that April May is the most likely breeding time for Myti/us on British coasts; the period of settlement seems to be May to early July. Some authors, however, have recorded settlements in August, and this clearly was the main period for North Bay (p. 192).
Following a heavy spatfall the numbers of Myti/us declined very rapidly (cf. other bivalves), so that only once (July 1946) was an appreciable number of the larger mussels found. (200-400 per m-). Smidt found that the Danish waddens were unsuit- able for Myti/us; the numbers found were negligible, although on the banks very high denshies of mussels occurred. Similarly Thamdrup recorded densities of 2,000-1 2,000 mussels per m" on the banks, while over the mud flats only an occasional mussel was taken.
The growth rate of young Myti/us seems to vary greatly according to conditions (cf. White, 1937; Smidt, 1951). For example, Smidt quotes other workers as stating that young spat may grow to 8 mm in less than two months if permanently covered with water, whereas similar spat, left uncovered for a few hours daily, hardly attained 4 mm in three months. White (1937) states that under unfavourable conditions a mussel may add only a few mm in a year, but under good conditions, at St. Andrews, two-year-old mussels ranged from about 30-50 mm. This would indicate a growth at least of some 15-25 mm in a year. The long exposure periods over North Bay would suggest a rather unfavourable environment; nevertheless the 1945 spat grew to 9 mm by November and to about 20 mm in the following July, when these mussels would be one year old. This approximates to the figure mentioned by White, and emphasizes that feeding conditions in 1945/46 over North Bay must have been very good.
Of the polychaetes, Pygospio was obviously dominant in North Bay. Wohlenberg found Pygospio at upper tidal levels, though in relatively low densities, but Thamdrup recorded very high densities, mainly near high water (Table XIV). Smidt, however, found that very large concentrations of newly sQiW^d Pygospio (> 3 1,000 per m-) might occur right across the shore. In North Bay Pygospio was definitely more abundant at lower tidal levels, but it was so common that there was an average population for the whole mud flat of 160-J80 per m^ (Fig. 4). There are few records of large popula- tions of this polychaete in Britain. However, Holme (1949) found a density for the Exe Estuary similar to that of North Bay, though the populations are far below those of Thamdrup for Skalling (Table XIV). Brady (1943) records up to 600 Sco/op/os per m- and fairly high numbers of Spio and Sco/eco/epis in Northumberland muds: perhaps these polychaetes replace Pygospio.
Heteromastus fi/iformis was the next commonest polychaete in North Bay; apart from the sharp decline in July 1946, the average population was 30-290 per m- (Fig. 4). Heteromastus was quite sharply restricted to mid-tide levels (higher in Transect 4), and the maximal densities were considerably greater than either those recorded by Spooner and Moore for the Tamar, or by Thamdrup for Skalling, Denmark (Table XIV). However, Smidt (1951) found that in 1947 Heteromastus became abundant
198
J. E. G. Raymont
on the Danish waddens, with some dense patches of mostly young worms exceeding 2,000 per m-.
The average population of Arenicola over North Bay varied between 30 and 70 per m^ apart from the marked decline in July 1946 (Fig. 4). Densities up to 400 per m- occurred over part of the shore (Table XIV). However, Arenicola was absent from
1200 —
1000 —
800 —
K u a. —
tc ui m S 600—
3
O —
<
>
< 4 00 —
'OTHERS NEPHTHYS
ARENICOLA PHYLLODOCIDS
NEREIS
HETEROMASTUS
•^oo—
PYGOSPIO
t I t t 1 I
NOV 43
JULY 44
NOV 44
JULY 45
NOV 45
JULY 46
Fig. 4. Fluctuations in the density of polychaetes over North Bay. The changes in the total popula- tion and in the main species are shown. AH numbers represent densities per m^ calculated as averages
of the populations at 14 sampling stations
a considerable number of stations; possibly it was commoner above mid-tide level, but there was no clear distribution pattern. Many authors have shown that lugworms generally avoid soft substrata and live in essentially sandy bottoms. Thus in Spooner and Moore's work, Arenicola hardly ever appeared in the samples. However, in the Exe and off the Northumberland coast small populations of Arenicola occurred (Table XIV), and Stephen (1930) found a rich ground in Loch Gilp. Thamdrup
The fauna of an inter-tidal mud flat 1 99
found Arenicola fairly widely distributed at Skalling, but the densities were <35 per m-, except for occasional heavier populations of young worms.
Nereis diversicolor appears to be very restricted in North Bay. Most investigators (Stephen, Spooner and Moore, Brady, Wohlenberg, Smidt) have found that this species occurs abundantly oniy at upper tidal levels. This was true also in North Bay, but the only station where the polychaete was really abundant was Transect 2, Station 1, where densities of >800 per m- were recorded (Table XIV). At most stations in North Bay Nereis never appeared at any time. Holme (1949) also found it occurred infrequently in the Exe Estuary, and Brady's densities for Northumberland are low. Stephen recorded fairly small populations for the Forth and Clyde, though he did find a high density on the Isle of Barra (Table XIV). On the other hand, Wohlenberg (1937) found Nereis to be abundant at Sylt, and Spooner and Moore (1940) found it was a very common polychaete in the Tamar muds. Rees (1940) also recorded high densities for the Bristol Channel (Table XIV). Thamdrup (1935), in contrast to most workers, did not find Nereis diversicolor restricted to the upper tidal zones. His maximal densities were not very large, and varied from year to year (Table XIV). However, Smidt (1951) has recorded many thousands of young O-Group Nereis from the same area, though adults were few. Nicol (1935) also once recorded the extraordinary density of 95,700 Nereis per m^ (all young) from a salt mud pool at Aberlady.
Nephthys contrasted with Nereis over North Bay in being fairly restricted to low tidal levels. There appears to be general agreement that Nephthys occurs more fre- quently towards low tide mark. Although Nephthys occurred regularly in North Bay, the numbers were never high (Fig. 4). Indeed, the densities recorded for other areas are mostly rather low. Spooner and Moore, however, found somewhat higher populations in the Tamar (Table XIV).
It is clear that, while the fauna of North Bay is rich, comparatively few species reach really high densities (Hydrobia, chironomids, Peloscolex). These animals, though widespread, appear to be more typical of the upper tidal zones, and were probably favoured by the long and rather irregular periods of exposure over North Bay. The total average fauna varies between 8,700 and 18,700 animals per m- (Table IV), although individual stations showed populations exceeding 25,000 per m- (maximum 39,000). By contrast, Brady (1943) gives an average density for a North- umberland mud flat of <400 animals per m^
Smidt (1951) gives figures (Table 21, p. 138 of his paper) for the total numbers of animals per m^ for Danish shallow water areas. The extraordinary richness of the Danish waddens (30,000-60,000 per m-) is outstanding, and Smidt attributes this mainly to the predominance of small species (Hydrobia, Pygospio, etc.), and to the young of many species. Though the average density in North Bay was not nearly so high, the fauna was rich and, like the waddens, was characterized by the abundance of small animals (Hydrobia, Peloscolex, chironomids, Pygospio), and by young indivi- duals especially of molluscs. The fauna was also similar to that already described by Raymont (1947, 1949) for Loch Craiglin, where the total average density rose with fertilization to 16,000 and even 23,000 animals per m-, and where the same species (Hydrobia, chironomids, young Cardium) were dominant.
The results of the population changes over North Bay show a pronounced seasonal fluctuation which is not unexpected in an inter-tidal area. Previous studies in Loch
200 •'• ^- G- Raymont
Sween showed fairly clear seasonal effects, even in the bottom fauna below low-tide mark (Raymont, 1947, 1950). But in Loch Craiglin, and in the areas of Kyle Scotnish below low-water mark, the maximum population occurred during the summer, whereas in North Bay the populations in November were consistently larger than in July. In Loch Craiglin, however, the actual months in which the highest densities were experienced were August and September, and a few stations in the loch did show higher densities even in November. In Kyle Scotnish, too, the high " summer " peaks of the bottom fauna represented an average of the three months, July, August and September. It seems clear, as indeed might be expected in a marine area, that the high densities occurred in late summer or even afterwards.
It is not surprising that the July samplings should give a lower population than the November samples. Most of the young larvae produced during spring and summer will not have settled and grown to a sufficient size to appear in July samplings. For example, Smidt (1951) found that the vast majority of Hydrobia in June belonged to O-Group, and measured only 0-5 mm. Since they grow only some 2 mm by the winter, it is likely that sampling with a 1 mm sieve in July would miss the majority of the brood. The strong seasonal fluctuation is in fact dominated by Hydrobia (Tables IV and V), but the seasonal changes hold also for chironomids, bivalves, oligochaetes and " other organisms ". Chironomids may be expected to oviposit mainly during the summer, and therefore the new larvae will hardly appear in sievings before early autumn. It has also been shown that the main spatfalls of Cardium and Mytilus occur after July. During the ensuing winter and spring there will be heavy depredations on the bottom fauna, and also the physical conditions (especially frost) over winter will cause the fauna to decline. Little recruitment may be expected before July in the following year.
The results from November 1943 to July 1945 indicated then no real change in the overall population, apart from these seasonal fluctuations. This is borne out by both the average populations (Table IV) and by the results from individual stations (Table VIII, Fig. 3). The rise in November 1945, however, was definite and widespread. The average increase was 40%, and a large number of individual stations showed a rise (Fig. 3, Table VIII).
A rise of only 40% could easily result from a " natural " fluctuation, i.e. it might be attributed to some favourable condition other than increased food supply. Wide variation in the success of year-groups of bottom animals are well known (Boysen- Jensen, 1919; Thamdrup, 1935; Wohlenberg, 1937; Stephen, 1931, 1932, 1938). Nevertheless it is usual then for some species to show one particular year as a good brood year, while for other species that same year may be very poor (cf. Boysen- Jensen, 1919, for species of bivalves). The fact that so many of the main constituents of the fauna over North Bay showed an increase at the same time (Table IV), lends considerable support to the view that the rise in November 1945 was due to the improved conditions resulting from fertilization. The accelerated growth rate seen in some lamellibranchs (p. 192-193) would also agree with this conclusion.
By July 1946 the average population over the North Bay had declined sharply from the previous high autumn density to reach the lowest value for the period of sampling. This marked fall may be largely explained as a seasonal change as in previous years. It is not easy, however, to account for the especially severe drop in the density of the fauna in 1946. Kyle Scotnish had been stocked with plaice fry in 1945, and a more
The fauna of an inter-tidal mud flat 201
successful stocking involving ca. 1,500,000 fry was made in the spring of 1946 (Gross, 1950). To what extent the young flatfish fed over the mud Hat at high tide it is impos- sible to say; nevertheless a considerable increase in the amount of food taken by the fish was inevitable, especially in view of the very high growth rate (cf. Gross, 1950).
Possibly the drop in the fauna was also partly related to the severe frost in February and March of that year. Thus an extract from the log book states that work was impossible at the head of the loch (i.e. just off North Bay) on 28th February 1946, because of ice. The following day the whole of Kyle Scotnish was covered with ice, and this cleared from the northern parts of the loch only on 5th March. The general bottom fauna of Kyle Scotnish below low-tide mark was not severely checked by these frosts (cf. Raymont, 1950) but over an inter-tidal mud flat the bottom animals, except for those burrowing really deeply, would be exposed fully to the severe effects of freezing.
It is significant that almost all the fauna {Hydrobia, polychaetes, chironomids, oligochaetes, etc.) showed the great reduction in numbers by July 1946, i.e. it was not an unsuccessful spawning or a poor settlement by merely one important species of the community. On the other hand, the population of large bivalves remained almost stationary from November to July, and indeed the final population (125 large bivalves per m^) was higher, except for November 1945, than at any other time (Tables IV, XII, XIII). It is these larger bivalves which can burrow away from the surface, some like Scrobicularia to a considerable depth, and thus escape, to some degree, adverse conditions. By contrast, the youngest bivalves were decimated over the same period, falling from more than 1,000 to 129 per m^ (Table IV).
In the earher years few large bivalves occurred over North Bay (Tables XII and XIII). Probably these molluscs are periodically greatly reduced in numbers by adverse conditions in the area. The lack of the older bivalves is especially true of Mytilus which is of course a surface dweller. By contrast, Scrobicularia, which burrows deeply, and as older individuals may therefore escape the worst conditions, is not so poorly represented by the older age groups (Table XI).
The only marked exception to the general seasonal fluctuations, and to the large increase in November 1945, was in the polychaete group (Fig. 4). These animals exhibited a fairly steady increase in population from November 1943 onwards, and they reached an average of 1,200 animals per m- in the summer of 1945, after which there was a very sharp decline to the summer of 1946 (Table IV). These changes were mainly due to Pygospio (Fig. 4). This polychaete was numerically dominant over the whole period November 1943 to July 1946. It also appears to have reproduced in the years 1944 and 1945 sufficiently early for there to be a sharp increase in the polychaete populations in each summer. From November 1943 to July 1944, for example, the population o^ Pygospio more than doubled, and from November 1944 to July 1945 there was an increase of 50%.
Phyllodocidae also contributed to the sharp peak in the summer of 1945 (Fig. 4). The only other polychaete that played a significant part in the overall population changes was Heteromastus filiformis— the second most important polychaete. During 1944 there appears to have been a successful brood of Heteromasius, so that between July and November of that year the population more than doubled, but the most surprising change was the very sharp decline in Heteromastus from July 1945, so that the population was virtually wiped out by the summer of 1946. This was also true of
202 J- E. G. Raymont
Nereis diversicolor and Arenicola marina (Fig. 4). Not a single Arenicola was taken in July 1946, and Nereis and Heteromastus occurred only in one auger sample (Tran- sect 4, St. 1), at that time. The decline in the polychaete population affected the other species also, though not quite so obviously (Fig. 4) ; the only exception was Nephthys.
The increase in Heteromastus and Pygospio in 1944, and in Pygospio and Phyllo- docidae in the following year, may be " natural " fluctuations, though probably the increased food supply in Kyle Scotnish due to fertilization in the early years may have helped in their success. The decline in 1946, in contrast to the rise in the polychaete population below low-water mark, (Raymont, 1950) may be attributed to the adverse conditions over the exposed inter-tidal mud flats in the winter. It may not be without significance that Nephthys was the only polychaete which did not suffer the decline. This species was sharply limited to the lowest tidal limits on the shore, and it therefore would not be long exposed to freezing. Over the same period Nephthys was increasing, together with other polychaetes, in the areas below low water in Kyle Scotnish.
It would appear that fertilization, with the resulting increase in food over the North Bay area, had little lasting effect on the density of the bottom fauna. While some increase did occur when other environmental conditions were also favourable, the beneficial effect was more than wiped out by other adverse conditions, and the increase in density was at the most temporary. It is clear, therefore, that increase in food supply alone cannot compensate for other adverse features in the environment. Any attempt at fertilization in inter-tidal areas should therefore be made only in those areas where the species of animals whose increase is desired are either naturally " hardy ", or where the environmental conditions such as temperature, salinity, and so on are constantly favourable.
ACKNOWLEDGEMENTS
I wish to thank Imperial Chemical Industries Ltd., Billingham, for their generous financial assistance during the work at Loch Sween, and D.S.I. R. for a grant for an assistant for one year.
I am indebted to Dr. Gauld and Mr. Nutman for assistance in the taking of samples, and to Dr. A. C. Stephen of the Royal Scottish Museum for the identification of some specimens.
REFERENCES
Beanland, F. L. (1940), Sand and mud communities in the Dovey Estuary. J. Mar. Biol. Assoc, U.K., 24, 589-611.
Boysen-Jensen, p. (1919), Valuation of the Limfjord. I. Studies on the fish-food in the Limfjord 1909-1917. Kept. Danish Biol. Sta., 26, 1^5.
Brady, F. (1943), The distribution of the fauna of some inter-tidal sands and muds on the Northum- berland coast. J. Anim. Ecol., 12, 27^1.
Chipperfield, p. N. J. (1953), Observations on the breeding and settlement of Mytilus edulis (L.) in British waters. J. Mar. Biol. Assoc, U.K., 32, 449^76.
Fraser, J. A. (1932), Observations on the fauna and constituents of an estuarine mud in a polluted area. J. Mar. Biol. Assoc, U.K., 18, 69-85.
Gross, F. (1950), A fish cultivation experiment in an arm of a sea-loch. V. Fish growth in Kyle Scotnish. Proc Roy. Soc, Edinburgh, B, 64, 109-135.
Holme, N. A. (1949), The fauna of sand and mud banks near the mouth of the Exe Estuary. J. Mar. Biol. Assoc, U.K., 28, 189-237.
NicoL, E. A. T. (1935), The ecology of a salt-marsh. J. Mar. Biol. Assoc, U.K., 20, 203-261 .
Raymont, J. E. G. (1947), An experiment in marine fish cultivation: IV. The bottom fauna and the food of flatfishes in a fertilized sea-loch (Loch Craiglin). Proc Roy. Soc, Edinburgh, B, 63, 34-55.
Raymont, J. E. G. (1949), Further observations on changes in the bottom fauna of a fertilized sea- loch. J. Mar. Biol. Assoc, U.K., 28, 9-19.
The fauna of an inter-tidal mud flat 203
Raymont, J. E. G. (1950), A fish cultivation experiment in an arm of a sea-loch. IV. The bottom
fauna of Kyle Scotnish. Proc. Roy. Soc, Edinburgh, B, 64, 65-108. Rees, C. B. (1940), A preliminary study of the ecofogy of a mud-flat. J. Mar. Biol. Assoc, U.K 24,
185-199. Smidt, E. L. B. (1951), Animal production in the Danish Waddensea. Medd. Komm. Danmarks
Fisk. Havundersogelser, Ser. Fisk., 11 (6), 1-151. Spooner, G. M. and Moore, H. B. (1940), The ecology of the Tamar Estuary. VI. An account of
the macrofauna of the inter-tidal muds. /. Mar. Biol. Assoc, U.K., 24, 283-330. Stephen, A. C. (1929), Studies on the Scottish marine fauna: The fauna of the sandy and muddy
areas of the tidal zone. Trans. Roy. Soc, Edinburgh, 56, 291-306. Stephen, A. C. (1930), Studies on the Scottish marine fauna: Additional observations on the fauna
of the sandy and muddy areas of the tidal zone. Trans. Roy. Soc, Edinburgh, 56, 521-535. Stephen. A. C. (1931), Notes on the biology of certain lamellibranchs on the Scottish coast. J. Mar.
Biol. Assoc, U.K., 17, 277-300. Stephen, A. C. (1932), Notes on the biology of some lamellibranchs in the Clyde area. J. Mar. Biol.
Assoc, U.K., 18, 51-68. Stephen, A. C. (1938), Production of large broods in certain marine lamellibranchs with a possible
relation to weather conditions. J. Anim. EcoL, 7, 130-143. Thamdrup, H. M. (1935), Beitrage zur Okologie der Wattenfauna. Medd. Komm. Danmarks Fisk.
Havundersegelser, Ser. Fisk., 10 (2), 1-122. White, K. M. (1937), Mytilus. Liverpool Mar. Biol. Comm., Mem., No. 31, 1-177. Wohlenberg, E. (1937), Die Wattenmeer-Lebensgemeinschaften im Konigshafen von Syit. Helgo-
Idnder Wissensch. Meeresunters., 1 (1), 1-92.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of DeefvSea Research, pp. 204-211.
Distribution of planktonic Foraminifera in some Mediterranean
sediments*
By Frances L. Parker Scripps Institution of Oceanography, La Jolla
Summary — The planktonic foraminiferal populations of the Mediterranean Sea may be differentiated from those of the adjacent Atlantic Ocean.
Three distinct populations are found located in the western and eastern Mediterranean and the Aegean Sea, and additional discrete populations may occur in the unsampled areas.
Populations probably are derived from the Atlantic and from indigenous ancestral stock.
The direction of coiling of Globorotalia truncatulinoides shows a shift to left coiling dominance within the Mediterranean. Additional statistical analysis may give further evidence concerning derivation of species in the area.
INTRODUCTION The planktonic Foraminifera in sediment-surface samples from forty-six stations throughout the Mediterranean Sea have been studied and compared with planktonic assemblages in the adjacent Atlantic. These populations show some regional variation and the Mediterranean faunas as a whole differ from those of the Atlantic. The samples were collected, in 1947-48, by members of the Woods Hole Oceanographic Institution on KlV Atlantis Cruise 151. This study was supported by the Office of Naval Research (Project NR 081-050, Contract Nonr— 233 Task 1). The drafting was done by Miss J. F. Peirson and R. R. Lankford.
Much has been published on the description and taxonomy of Mediterranean faunas but few quantitative studies have been made. Phleger (1947) gives quantitative lists of planktonic species in top samples of three long cores from the Tyrrhenian Sea, but suggests that at least one of these does not represent the modern fauna. Muraour (1954 A, b) gives quantitative data for two stations near Algiers. Di Napoli-Alliata (1952) gives a very useful resume of the literature on Mediterranean planktonic faunas.
The stations (Fig. 1, Table I) are scattered throughout most of the area south of North Latitude 38° 51' with the exception of four in the northern part of the Aegean Sea. No samples were obtained from the Adriatic Sea, where many of the previous studies have been made, nor from the northern part of the western Mediterranean, The samples were collected with a gravity corer or with a coring tube attached to a camera and are believed to contain material from the surface of the sediment. Three hundred to five hundred planktonic specimens larger than 0-149 mm were counted from each and the relative abundances of the species calculated. Samples having fewer specimens are omitted ; the majority contain many more.
SURFACE TEMPERATURE AND SALINITY DISTRIBUTION
For convenience in the later discussion of the planktonic populations, the area may be divided into three parts: western Mediterranean, eastern Mediterranean, and the
* Contribution No. 20, Marine Foraminifera Laboratory; Contribution No. 803, Scripps Institu- tion of Oceanography.
204
Distribution of planktonic Foraminifera in some Mediterranean sediments 205
Aegean Sea. The depth of the surface-water layer in the Mediterranean is approxi- mately 200 m or less. Although planktonic Foraminifera have been found living at greater depths it is probable that they are most abundant in the upper layers (Phleger, 1954) and it is assumed here that the characteristics of the surface layer are those to which they are adapted.
The eastern and western basins of the Mediterranean are separated by a sill, between Sicily and Tunis, having a maximum depth of about 400 m. The western basin (Tyrrhenian Sea and Algiers-Provengal Basin) is separated from the Atlantic by a sill depth of 320 m. Water enters the Mediterranean from the Atlantic and passes from the western basin to the eastern basin by surface currents. In both cases water flows westward at intermediate depths. A study of numerous sources of information shows that the surface temperature variation in the western area is approximately 13" C to 24^ C, the warmest season being in July-August and the coldest in February- March. Greater extremes are found at various near-shore areas, especially along the coast of France. The temperature of the surface water just east of Gibraltar in August, 1938, was 19-5° C rising to 24° C farther east (Rough, 1940). Surface salinities vary from 36°j^^ at Gibraltar to 3^°Uo "^^r Sicily. Variable salinities are often found at near-shore localities. In 1949-50 at Monaco there was a winter variation from 36-8° ;, to 38-5°/„, and at Algiers 34-57,,. to 37-67'oo (Kruger, 1950). The eastern basin (Ionian Sea and Levantine Basin) apparently contains surface water derived chiefly from the west via the surface current through the Sicily-Tunis gap. The deep water, according to Pollak (1951), is all derived from the Adriatic Sea. Little is known at present about the influence of the Suez Canal, but it is probable that any water derived from this source would quickly lose its identity. Surface tempera- tures in this area vary from 16° C to 24° C in the western part and 16° C to 28' C in the extreme east. Surface salinities vary from 38°/,, in the west to appro.ximately 39-5°/,, in the east but here again local variations may occur near shore. An example of this is the comparatively low salinity of 30° ,, found ofi"Gaza, Israel, in September, 1947, due probably to the Nile flood (Oren, 1952). Surface currents enter the Aegean Sea from the southeast and from the Black Sea. Surface temperatures vary from 13° C to 25° C and surface salinities from approximately 30° ,, near the Dardanelles to 39°/,, just north of Crete. Due to the counter-clockwise surface circulation, salinities on the eatern side are higher than those on the western.
These data show that there are lower winter temperatures and somewhat lower salinities in the western than in the eastern Mediterranean. In the Aegean there are lower winter temperatures than in the eastern area and a complex salinity pattern with comparatively low salinities in the northern part.
Conditions in the Atlantic immediately west of Gibraltar are also of interest. Here the surface temperature variation is somewhat less than in the Mediterranean, 16° C to 22' C. The surface salinity is somewhat less than that obtaining at Gibraltar.
DISCUSSION OF PLANKTONIC POPULATIONS The identifications of the planktonic species are in most cases the same as those given by Phleger, Parker and Peirson (1954) in their study of Atlantic deep-sea cores Some species groups, as defined here, contain forms recognized as species or varieties by some authors. Their omission does not necessarily indicate that they are believed to be invalid. Glohigerinoides rubra probably includes, or in some cases is
206
Frances L. Parker
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"5 a> n c (U w. x: UJ 0 E 0) 13 >> JO 0 0 a. |
T3 C •♦- 0 Z 0 JH 0 Oi 3 cr c 3 CJ (3 |
■0 0 i- CO CD I "o w 01 0 D cr 01 0 0 0) c 01 C3> \a 0 c5 |
a> C7> o> UJ 0 ♦- 0 c '^ ■D 01 4- C k- a> 0 C3 |
□ m CD X 0 0 J3 0 CJ> c 0 0 c/> V ■0 0 c a> 01 ■a 0 cs |
c k. '•a 0 3 ca |
-0 0 w m OD X 0 01 «*- "5 <J 0 0 </) cri |
0 > OD c CJ> 0 3 0 3 in k. .c. a 0 0 k. 0 0 CD |
c o> X) 0 0 0 3 0 c 3 Q. C3 |
k. CD CD X 0 3 0 CD |
c c»> X) 0 •0 (A a> T3 0 C 0 u c 3 ■4- 13 |
C ? 0 C3> 0 01 0. 0 C k- a> o> *- in 0 X |
>■ P T3 0 •n w 01 > c 3 0 c 3 X3 k- 0 |
o> c 0 06 k. k- 0 Q. 0 0 3 0 0 "5 3 0 0 c 0 c HI I |
Distribution of planktonic Foraminifera in some Mediterranean sediments
207
c o
c o
so
c
o
so
208
Frances L. Parker
synonymous with, G. elongata (d'Orbigny) and G. helicina (d'Orbigny), reported by d'Orbigny from Rimini, Italy, G. adriatica (Fornasini), and G. rubra vslt. pyramidalis (vanden Broeck). G. sacculifera includes a form listed by various authors as G. triloba (Reuss) and described by Reuss from the Miocene of the Vienna Basin. Specimens of Globigerina eggeri are small but otherwise typical except for Aegean specimens which frequently have a final whorl consisting of 3i chambers. The latter are similar to G. bulloides and further study may modify the ratios of the two species in Aegean Sea samples. Hastigerina pe/agica, not reported from the Atlantic in significant numbers, is found in low frequencies chiefly in the eastern Mediterranean.
The relative percentages of the planktonic species are listed in Table I. Included in this table, for comparative purposes, are data for three stations from the Atlantic in the general vicinity of Gibraltar. The data for stations 4637 and 4736 are taken from Phleger, Parker and Peirson (1954). The following discussion deals only with occurrences as they appear in this table. Species with frequencies of less than 0-2%, therefore, are not included although they may occur. The sampling is sparse for such a large area but the percentage data show clearly that there are three distinctive populations. The first of these is that of the western Mediterranean which extends east to include station 4721 A. This assemblage differs from that of the adjacent mid- latitude Atlantic in the following ways:
Atlantic (mid-latitude)
Western Mediterranean
|
Globigerina digitata |
absent |
present |
|
G. inflata |
8-13% |
14-30% (usually more than 20%) |
|
G. quinqueloba |
absent |
present |
|
Globigerinoides conglobata |
present |
absent |
|
G. sacculifera |
9-10% |
less than 1-5% |
|
Globorotalia hirsuta |
present |
first 2 stas. east of Gibraltar only |
|
G. punctulata |
present |
absent |
|
G. scitula |
2% |
less than 1 % (scattered) |
|
Hastigerina pelagica |
absent |
present (1 sta.) |
|
Pulleniatina obliquiloculata |
present |
absent |
The second assemblage is found in the eastern Mediterranean. It differs from that of the western area in the following ways :
Western Mediterranean Eastern Mediterranean
Globigerina bulloides
G. inflata
Globigerinoides rubra
G. sacculifera
Globorotalia truncatulinoides
Hastigerina pelagica
20-56%
14-38%
1-25%
1-5%
less than 1-14 >;
at 1 sta.
8-18%
0-6%
41-77%
3-14% (except 4 stas.)
0-2 % (scattered)
consistent occurrence
Distribution of planktonic Foraminifera in some Mediterranean sediments 209
The third assemblage is found in the Aegean Sea. It differs from that of the eastern Mediterranean in the following ways :
Eastern Mediterranean Aegean Sea
Globigerina eggeri 2-13% (except 2 3-28% (mostly more than
stas. off Israel) 20%)
G. pachyderma slight consistent increase
Globigerinoides saccuUfera 3-14% 0-3%
In the western Med'terranean the population must be adapted to a wider tempera- ture range than that found in the adjacent Atlantic. The winter temperatures are more nearly analogous to those found on the western Atlantic continental slope in mid- latitudes. In some respects the western Mediterranean population reflects this and shows a resemblance to the populations in that area (Parker, 1948; Phleger, 1939, 1942) as shown by the high frequencies of Globigerina bulloides and G. inflata and the low frequency of Globigerinoides saccuUfera as well as in lesser respects. The fauna occurring at the three stations (4732-4734) just east of Gibraltar is of interest. Two of these stations lie within the low temperature area reported by Rough (1940). Here exceptionally high frequencies of Globigerina bulloides and low frequencies of Globigerinoides rubra and Globorotalia truncatulinoides are found. Whether or not these changes are due to a lowered mean temperature maximum is a matter of specula- tion. The presence of G. hirsuta in significant frequencies in this area may be due to transport by the entering Atlantic current. The faunas reported by Muraour ( 1954 A, b) from the vicinity of Algiers show a much lower percentage of Globigerinoides rubra. The populations reported by Phleger (1947) from the Tyrrhenian Sea are analogous to those found in the present study.
The increase in the mean minimum temperature in the eastern area from 13^ C to 16° C may account for some or all of the shifts in population found there, as similar trends occur when passing from mid to low latitudes in the Atlantic. In general there is a decrease in such species as Globigerina bulloides and G. inflata, which occur in high frequencies in mid-latitudes, and an increase in Globigerinoides saccuUfera which is found in increasingly high frequencies in low latitudes.
In the Aegean Sea the mean minimum temperature is 13° C, as it is in the western Mediterranean, which may account for the more consistent occurrence of Globigerina pachyderma and the decrease in Globigerinoides saccuUfera as compared to eastern area occurrences. Lower salinities in the northern part and/or changes in the chemistry of the surface water resulting from the inflow of water from the Black Sea may also account for these changes. This may be especially true in the case of the high fre- quencies of Globigerina eggeri and the fact that many of the specimens are atypical.
The populations at several stations, besides those noted previously, show unusual features but two are especially noteworthy. Station 4724A contains what appears to be a " colder water " fauna. There are higher frequencies of Globigerina eggeri, G. pachyderma, and G. quinqueloba and lower frequencies ofGlobigerinella aequilatcralis and Globigerinoides rubra. Globigerina eggeri is the only species of the group which does not fit this pattern, since that species is found in higher frequencies m low latitudes Further study may reveal whether or not this fauna is pre-modern. The sample from station 4718 contains a large percentage of weathered, discoloured
210 Frances L. Parker
Specimens, some of which are filled with glauconite. This suggests that little deposition has taken place in this area for a long time, since at most stations the planktonic specimens appear to be fresh and well-preserved, showing recent deposition. It is possible that there is a strong current in this area which removes the specimens as they are deposited, leaving the older, filled tests.
The planktonic populations in the Mediterranean probably are derived in two ways : from material brought in by the Atlantic current and from ancestral stock indigenous to the area, a so-called " relict " fauna. A third possible source may be transport through the Suez Canal, but too little is known about this at the present time to evaluate its importance. A study of Table I and of the specimens themselves leads to some interesting speculations on this point. Phleger (1947) believes that occasional specimens of GloborotaJia scitula are introduced from the Atlantic, but that the species is not found living here. The present findings point to the same source, but it is probable that there is some survival as there is a scattered occurrence of the species throughout the area. Globigerinoides conglobata and Globorotalia hirsuta, which occur rarely at many stations, may have a similar origin. On the other hand Globigerina digitata and Hastigerina pelagica, which are rare in modern Atlantic sediments, may be species indigenous to the Mediterranean. The atypical form of Globigerina eggeri found in the Aegean Sea is probably an indigenous form.
A recent study of the coiling direction of Globorotalia truncatulinoides by Ericson, WoLLiN and Wollin (1954), shows that the North Atlantic may be divided into provinces in which there occur " races " showing a dominance of left or right coiling. According to their interpretation the area immediately west of Gibraltar should contain a population showing equi-directional coiling. Samples from Atlantis stations 4637, 4735 and 4736 were examined and this was found to be the case. East of Gibraltar at station 4734 the ratio shifts to 79 % left coiling (based on 62 specimens) and increases rapidly to the east until at station 4730, just east of 0° Long., a domin- ance of 99 % left coiling is found. High ratios of 88 % or more are maintained eastward to station 4711, just west of 20° E. Long., which shows 62% left coiling. Farther east there are too few individuals to give significant results. Where possible, 400 specimens were counted and such samples served to check neighbouring stations containing fewer specimens. These results also suggest that at least part of the Mediterranean populations are indigenous and not directly derived from the Atlantic. A study of other species by statistical analysis of measurements or other characteristics and a comparison with Atlantic specimens would give additional data on this point,
REFERENCES
Di Napoli-Alliata, E. (1952), Foraminiferi pelagici e facies in Italia. Atti VII Com. Naz. Met. e
Petr., Taormina, 1952, 1-34. Ericson, D. B., Wollin, G. and Wollin, J. (1954), Coiling direction oi Globorotalia truncatulinoides
in deep-sea cores. Deep-sea Res., 2, 152-158. Kruger, D. (1950), Variations quantitatives des protistes marins au voisinage du Port d'Alger
durant hiver 1949-1950. Bull. Inst. Ocean., Monaco, 978, 1-20. Muraour, p. (1954 a), Sur quelques sediments dragues au large du littoral compris entre ie Cap
Djinet et rembouchure de j'Oued Sebaou. Recherches sur les Fonds Chalutables de la Region
d'Alger. Com. Loc. Ocean. Etudes Cotes Algerie, 91-107. Muraour, P. (1954 b), Etude d'une vase prelevee a 700 metres de profondeur, au large de la Baie
de Castiglione. Recherches sur les Fonds Chalutables de la Region d'Alger. Com. Loc. Ocean.
Etudes Cotes Algerie, 123-132. Oren, O. H. (1952), Some hydrographic features observed off the coast of Israel. Bull. Inst. Ocean.,
Monaco, 1017, 1-9.
Distribution of planktonic Foraminifera in some Mediterranean sediments 2 1 I
Parker, F. L. (1948), Foraminifera of the continental shelf from the Gulf of Maine to Maryland.
Bull. Mus. Camp. Zool.. 100 (2), 213-241 . Phleger, F. B (1939), Foraminifera of submarine cores from the coniincntal slope. Bull. (jeul. .Soc.
America, 50, 1395-1422. Phleger, F. B (1942), Foraminifera of submarine cores from the continental slope. Pt. 2, Bull. Geol.
Soc. America, 53, 1073-1098. Phleger, F. B (1947), Foraminifera of three submarine cores from the Tyrrhenian Sea. Guteburgs
Kungl. Vetensk. och. Vitferhets-Samluilles, Handl., Sjiitte Foljden, Ser. B, No. 5, 1-19. Phleger, F. B, Parker, F. L. and Peirson, J. F. (1953). North Atlantic core Foraminifera. Repts.
Swedish Deep-Sea E.xped., 7, 1-122. PoLLAK, M. (1951), The sources of the deep water of the eastern Mediterranean Sea. Jour. Mar. Res.,
10 (1), 128-152.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 212-223.
Hypotheses connecting fluctuations in Arctic climate with biological
productivity of the English Channel
By L. H. N. Cooper Marine Biological Laboratory, Plymouth, England
Summary — An explanation of variations in nutrient content and biological productivity in the English Channel in the last thirty-five years has been sought in terms of variations in Arctic climate. To provide the connecting links a series of interlocking hypotheses has been erected. These are summarized in the discussion.
For many years at Plymouth we have been concerned with the large variations in the phosphorus available for growth of plants and animals as represented by the amount of phosphate present at the midwinter maximum (Fig. 1). This was high during the nineteen-twenties, fell to a little more than half during the nineteen-thirties and forties, and is now tending to increase again. There have been large associated changes in the abundance and nature of the zooplankton in the English Channel.
Fig. 1. Annual variations in inorganic phosphate available for plant growth at a position in the English Channel, 22 miles south-west of Plymouth, as measured at the winter maxima. In 1922 and 1923 the maxima were probably missed; they were probably greater than shown.
For some years we sought an understanding from studies on the continental shelf within 200 miles of Plymouth (the Celtic Sea) and found none. The next step was to examine the conditions over the continental slope of the Celtic Sea (Cooper, 1952 b). Upwelling on the scale which occurs along the coasts of California, Peru and South- west Africa has never been recognized, since the prevaiUng winds are unfavourable
212
Fluctuations in Arctic climate with biological productivity of the tngiish Channel 2 1 3
for this. Even when winds have been favourable for upwclling of nutrients by the classical process, as in February, 1947, this has not occurred.
The phenomenon of cascading was first examined (Cooper and Vaux, 1949) and is now well authenticated (Lee, 1952; Boden and Kampa, 1953). It is primarily a process of impoverishment, stripping from the shelf whatever nutrients happen to be there. Work now in progress (1955) shows that this concept is too simple, and that there may be an associated mechanism which leads to enrichment of water overlying a cascade, though not of the area from which the cascade has come.
Other hypothetical processes of enrichment, such as capsizing and submarine eagres (Cooper, 1952 a, d) have also been proposed, but still lack observational basis.
At this point in the investigation, a satisfactory explanation of the fluctuations in phosphate and biological productivity was still not in sight. There was no escaping the conclusion that an answer would never be found whilst study was confined to the shallow shelf.
Then an investigation was undertaken which seemed at the time to be a false scent, viz. the search for an explanation of the sudden appearance off Plymouth in the autumn of 1950 of large numbers of boar fish, Capros aper. The hypothesis was erected that these had been ejected about six weeks earlier from their normal habitat in a coral-encrusted submarine canyon by a submarine eagre. A rider necessarily followed, that the conditions in the Atlantic abreast of the slope between depths of 200 and 500 m must have been very different in the nineteen-thirties and forties from what it had been in the nineteen-twenties. The Capros argument (Cooper, 1952 c) was a logical one, but the threads were as thin as gossamer. It may well prove utterly wrong. None the less it was this study which led to the decision that it was useless further to pursue studies in shallow water, but that the deeper Atlantic ocean must hold the key.
There is no need to invoke hypothesis to establish that — whatever the mechanisms may be — vertical mixing down to about 400 m occurs in winter south-west and west of the English Channel. The conclusion is evident from every station that has ever been worked there. There seems no good reason for believing that there has been any major change in the nature of the physical processes occurring in the upper 400 m during the last 40 years. However, the chemistry of these waters has changed, and we are forced to seek an explanation in terms of physical processes occurring at a greater depth. The enrichment with nutrients of the upper 400 metres can have come about only by some form of overall upward displacement of the deeper water. The idea is that, first, during the rich period, the layer of water containing, say, 0-8 to 0-9 ug- atom/1 phosphate-P had been displaced upwards by some hundreds of metres, so that the processes of vertical mixing always operative in the upper 400 metres can bring them right to the surface, and that, secondly, during the poor years from 1931 to about 1950, this layer had subsided so that the mixing processes could no longer bite into it. Nutrient evidence to establish this argument beyond doubt does not exist. Due to internal waves, the observed depth of a nutrient sample obtained by snap sampling may diff"er by scores of metres from the mean depth. Consequently the sparse data available from earlier years are hard to interpret. Argument can proceed
only ex hypothesi.
To achieve such a large-scale upward displacement of water, an equivalent volume
2]4 L. H. N. Cooper
at a greater depth, perhaps at the very bottom of the Atlantic, had to arrive from somewhere else. Such deep water is always cold and has sunk from the surface in polar regions.
Two events are necessary for the production of deep, bottom water in polar regions: one is that there must be present water of sufficiently high salinity, the other is that air temperatures must be low enough to cool this saline water sufficiently for it to become very heavy and so able to sink deep in the ocean.
Deacon (1937) has shown that this happens in the Weddell Sea and around the South Orkney Islands. Taking the world as a whole, this part of the Antarctic is by far the most important centre for creation of oceanic bottom water. As this water moves away from the Antarctic it may become much modified by mixing processes, particularly over the deep submarine ridges which separate the deep oceanic basins.
In the North Atlantic there are two areas of sinking of cold saline water. One is over the ridge which joins Faeroe to Iceland (Cooper, 1955) and the other is in the Denmark Strait and around East Greenland. In neither case can it be said with strict truth that the cold, heavy water which sinks deep in the Atlantic is formed in a localized area. Rather are we concerned with a continuous process which takes place all the way from Jan Mayen to the Southern tip of Greenland, It so happens, however, that events which happen between 300 metres depth and the sill of the two ridges connecting Iceland with Faeroe and Greenland stand out in high relief,
in the development for the Faeroe-Iceland area (Cooper, 1955) it was suggested that the density distribution associated with the Iceland-Faeroe current acts as a dynamic dam, parting the waters of the Atlantic from those of the Norwegian Sea. Whilst it runs steadily, little water need flow over the ridge. Our increasing knowledge of such currents (cf, Fuglister and Worthington, 1951) suggests that they rarely run steadily for very long and tend to meander all over the place. A meander to the south will carry cold Norwegian Sea water to the Atlantic, where it will lie above much lighter water through which it must sink. Again, if the current weakens, the isopycnals will flatten out. Saline surface Atlantic water will flow into the Norwegian Sea, and in compensation Norwegian Sea water below about 250 m will spill over into the Atlantic. In the neighbourhood of 62' N, 13° W, this cascading water sometimes has a salinity exceeding 35-07oo '^^^ ^ temperature of less than 2° C. It is responsible for the salinity maximum which can be followed south-west for many hundreds of miles along the Reykjanes Ridge (Cooper, 1955) and round into the Western Basin.
A similar process in the Denmark Strait may differ in detail. The cold but brackish East Greenland current flows south along the coast, whereas the warm saline Trminger current flows from the south of Iceland round by the west to the north coast of Iceland. These two currents throw off" spurs which coalesce with their opposite numbers, but in the centre there is a region where the two main currents must be moving more or less side by side and in opposite directions. This is an unstable situation, and must lead to a lot of eddying, swinging about of the main water masses, and mixing. The sill depth of the Denmark Strait is rather more than 500 m. At depths shallower than this north of the Strait there is much water heavier than 27-9 or 28-0 sigma-/ and able, if it can escape, to sink into the Atlantic. It comes through the strait banked against the west side. South of the sill it does not fall straight into the trough, but is held against the terrace at depths less than 600 m. It travels south banked against the continental slope of Greenland, and does not reach the bottom
Fluctuations in Arctic climate with biological productivity of the English Channel 2 1 5
until 60 N Lat. The evidence for these statements is being marshalled and will shortly be published. A great debt is due to the workers on the research ships, Meteor, General Greene, Dana and Heimland. Full acknowledgements will be made later.
On all sections this piling up of heavy water to the right against the slope is to be seen, but there is much variation in temperature; in some sections there is an abund- ance of water having potential temperature less than T and salinity near to 34-91 "Z,,^ In others there is no water colder than 2-5°, or, in one " Meteor " section, colder than 3°. There is always a deep current towards the south-west, but the presence of very cold Denmark Strait water is intermittent.
Such intermittent bursting of the dynamic dam, due to either process, would result not in a continuous stream of water flowing oil the ridge, but in a series of self- contained, cold, heavy balls or boluses of water. The calving of a large bolus of water from the ridge is likely to be completed in a matter of days or weeks at most, and is likely to occur most often in late winter or early spring. The descent of a bolus from 400-500 to 1,500-2,000 metres through much lighter water is likely to need a very short time. It is not surprising, therefore, that no research ship has ever recognized the birth process for what it may be.
This water does not sink by the shortest route to the bottom of the Atlantic, but is held to the right by the force of the earth's rotation, and so traverses the side of the continental slope for 300 miles to Cape Farewell, and continues in this way around the bottom of the Labrador Sea at least as far as Newfoundland.
The evidence I have presented gives no idea of the frequency with which these cold water masses or boluses are born or calved in the Denmark Strait. It could be a seasonal event, once a year. It seems more likely that the complex water movements there are constantly meandering, and that the thrust of a cold bolus to the south over the sill may be a rather irregular afl'air. If so, the sinking of boluses along the Greenland coast may also be an irregular affair.
It is helpful to think of one of these boluses as behaving like a solid but elastic object. As it thrusts forward and downward, it must displace the water already there.
Moreover, when passing over an irregular slope and bottom, the under surface of such a bolus of water must be expected constantly to adjust and re-adjust itself to the solid topography. Its free surface against the enveloping water must needs also constantly re-adjust itself. The picture one has is of a vigorously writhing interface which should initiate internal waves in the adjacent ocean, even if this is only weakly stratified.
Shortly after calving, whilst it is sinking rapidly from sill level at about 500 m to 1,500 m, the internal wave pattern should be intense but short lived. After a depth of 2,500 m has been reached, a number of such boluses are likely to be present and in some degree to have coalesced. The writhing will be gentler but unceasing. This writhing of boluses in the North Atlantic provides an origin for internal waves down to at least 4,000 m. In the North Pacific no such possible origin for internal waves has been recognized deeper than the bottom of the sub-Arctic water around L5(X) m. Deeper waves might however arrive in the North Pacific from the Antarctic.
It is commonly believed that the attenuation of such waves in the open ocean is not severe. They may travel great distances. If there is no friclional loss on passage, for a few hundred miles, the energy in a wave propagated in an equipotenlial surface from a point source will be inversely proportional to the distance run. For greater distances such waves, not accompanied by transport of water, should follow great
216 L. H. N. Cooper
circles, so that the law of attenuation would need to be worked out not from plane but from spherical trigonometry. However, in the Eastern North Atlantic the source of internal waves is postulated not as a point but as ridges or lines more than 600 miles long. Consequently the energy in waves from these lengthy sources arriving at the European continental slope may be considerable.
Let us now consider what may happen when such a wave system meets a continental slope. If it approaches head on at a smooth gentle slope, it is likely to run straight up it and to be reflected back. A standing wave might well develop off slope, but the conditions are unlikely to lead to a lot of mixing. From the usual snap oceanographical observations such a standing wave might be interpreted as evidence for a strong along- slope current. If the wave system approaches a smooth slope at a wide angle, the waves may swirl along it, and somewhat more mixing would result.
The really interesting case is when an internal wave system approaches a highly dissected continental slope or borderland at a glancing angle. The slope abreast of the English Channel is likely to provide an excellent site for this process, while the Southern Californian continental borderland may provide an even better one. Then, as I see it, there should be a very great deal of sloshing about indeed, much vertical mixing and a tendency for homogenization of all properties as far down as the internal waves occur. This means that nutrients will be brought up to such depths that the classical methods of wind-driven upwelling can bite into the enriched water and bring it right up to the surface. If, and when, cold Arctic winters produce large boluses and consequent internal waves of large amplitude, then upper-water enrichment with nutrients over continental slopes would be favoured.
Furthermore, we may be concerned not only with the conventional nutrients, but with associated organic growth accessory factors which we only dimly understand. Much dead plankton, faeces and organic detritus sink in the sea and decompose. This should happen to the greatest extent in the oxygen poor layer. Oxygen defect (saturation value less content of oxygen observed) provides a very rough but ready measure of the extent of decomposition products. During periods of minimum internal wave activity the maximum oxygen defect may well be more than in periods of great activity. But paradoxically, the depth range of the oxygen poor layer should be less. The inflexion should be more pointed. This is because the homogenizing action of internal waves beating against a dissected slope should spread the oxygen defect both above and below the point of inflexion. The upward spread would bring not only the oxygen defect but also the accompanying organic substances nearer the surface.
In this group of interlocking hypotheses, some may be rejected without gravely imperilling the rest. The concept of homogenization is not one of these for, if it falls, the others become useless. To illustrate the argument, let us assume that some property such as phosphate content is linearly proportional to depth, and is subject to a uniform process of homogenization from surface to an inert bottom. In mid water, exchanges of phosphate will occur, but the later state will remain analytically indistinguishable from the earlier. If a layer was labelled with radiophosphorus, homogenization would spread this up and down so that the result might be seen as a form of eddy diffusion. At the surface, exchange with the air being impossible, a homogeneous layer enriched from below would begin to build up. As the process proceeds, both depth and phosphate content of the homogeneous layer would increase. Similarly at the bottom, homogenization will increase the thickness of a uniform
Fluctuations in Arctic climate with biological productivity of the English Channel 2 I 7
bottom layer containing phosphate equal to that at the point of inflexion. The defect in phosphate content which would seem to have appeared near the bottom has actually been moved upwards, and equivalent enrichment has appeared near the sur- face. It should be clear that the molecules of phosphate which appear in the surface waters are not those which have left the bottom. The process is akin to water moving up a pipe. If the process went on long enough and unhindered, the whole ocean would become homogenized from top to bottom. At an intermediate stage, it might seem that phosphate was being transported from the bottom to the surface waters, without the middle layers being affected in any way that could be recognized by chemical analysis.
Homogenization is a two-way process. In an ocean in which a nutrient salt increases downwards, the shallower and poorer waters are enriched at the expense of the deeper. Temperature or heat content, on the contrary, decreases downwards so that the same process causes the deeper layers to warm up at the expense of the shallower. Now let us consider an area of the sea near a continental slope: (a) where the broad pattern of currents and winds as well as the amount of radiant energy received from the sun remain unchanged but (b) where the intensity of deeper internal waves derived from distant sources increases. Homogenization should increase so that the surface layers would become colder but richer in nutrients. If then for some years the process is reversed, internal waves from a distance would become weaker so that homogeniza- tion against slopes would decrease. Loss of nutrients and accessory growth factors from surface waters by sinking of faeces and detritus would not be fully made good. In consequence the surface waters become poorer. At the same time, radiation received from the sun would be retained in the upper waters, instead of being homogenized by mixing with deeper colder water. The sea surface would warm up. Something very like this seems to have happened in Western European waters in the last thirty years. The changes in heat balance would be expected to produce some local changes in winds, weather and currents, so that in places this generalization may not apply. Averaged over a large ocean, however, and granted the premises, it seems inevitable. Again, when very cold winters prevail in the Arctic, more cold heavy water will be produced, and will spill over the ridges between Greenland and the Faeroes into the Atlantic. The scale of everything will be increased, so that the amplitude of the system of deep internal waves in the ocean should also increase.
Let us now consider two oceans. In one, writhing boluses of newly arrived water may initiate internal waves and subsequent homogenization right to the bottom in 4,000-5,000 m. In such an ocean, combination of the two separate processes of upward displacement and homogenization will cause deep capital reserves of nutrients to be made relatively quickly available for biological production in illuminated waters. In the second ocean, sinking of cold water does not go deeper than, say, 1 ,500 m depth. Below this depth there can be no writhing surfaces, no appreciable internal waves and no homogenization against continental slopes. There is then no way by means ot which nutrients below this depth can be got into circulation. Vast resources of nutrient capital remain unused for long periods. In such an ocean only the resources above, say, 1,500 m would be in effective circulation.
In this parable the oceans in mind are the North Atlantic and the North Pacific. The North Pacific is much the larger, so that for it the ratio of length of slope to volume of water is much less than for the North Atlantic. This also militates against the
218 L. H. N. Cooper
efficient use of the capital resources of the North Pacific by a process of homogeniza- tion.
The North Atlantic seems on the whole to be subject to impoverishment by exchange across the equator. Loss of relatively rich deep water, tends to be compensated by inflow from the south of relatively poor surface water. This is a process similar in nature to the impoverishment of the Mediterranean by exchange of waters in the Straits of Gibraltar. Consequently the deep phosphate resources of the North Atlantic are only about one-third of those of the North Pacific. In spite of this, the North Atlantic contains many of the world's richest fisheries. It is true that the North Atlantic contains an undue proportion of the shallow shelves well suited to the growth of fish, and that it is bordered by enterprising communities who make the most of what nature offers. But when all allowance is made for these important considera- tions, it still seems that the biological productivity of North Atlantic waters is greater than it ought to be. The nutrient capital of the North Atlantic seems to be more efficiently used than that of the North Pacific, except around Japan. The interlocking hypotheses offered here provide a possible explanation of this.
Again, judged by its phosphate resources the Mediterranean should be a near- desert sea. Though not rich, it is certainly not a biological desert. Here again one is forced to the conclusion that the slender phosphate capital of the Mediterranean is put to maximum use. It might be worth enquiring whether the present hypotheses could be usefully applied there.
Attention has been focussed on the events possibly initiated by calving of boluses of heavy cold water over ridges in high latitudes. There is another and different mechanism which may produce similar results on a smaller and shallower but not negligible scale. It may be illustrated from the Straits of Gibraltar. Here, light Atlantic surface water flows into the Mediterranean, and heavy, relatively cold and very saline deeper Mediterranean water flows out. In nature it is becoming ever more evident that fluid motions such as this tend to be irregular or gusty. It is reason- able to suppose that the outflow of Mediterranean water may not be as a steady stream, but as a series of boluses separately calved. This would initiate a chain of events similar to those already described for Faeroe-Iceland water, and augment the efficient use of the nutrient capital of the Atlantic. It is less easy to see how this calving process into the Atlantic might influence the Mediterranean regime, but some effect there is possible.
Two distinct speculative mechanisms have been described to transfer energy through deep water from one part of an ocean to another and, by so doing, to facilitate enrich- ment of surface waters with nutrients. These are (1) the hypothesis of upward dis- placement due to the intrusion of colder and heavier waters at a greater depth, and (2) the hypothesis of transfer of energy by internal waves, initiated by the sinking of boluses of cold, heavy water calved from ridges in high latitudes. These two hypotheses need not be mutually exclusive, but may merely express facets of a complex system of energy transfer at depth. This, in the words of Otto Pettersson, might be described as the systole and diastole of the ocean. Only many observations well placed in space and time may show what weight should be given to each or any of the component hypotheses.
Finally, the whole argument suffers from a grave thermodynamic weakness. Ther- modynamically, energy can be obtained only from a source and never from a sink.
Fluctuations in Arctic climate with biological productivity of the English Channel 219
The areas around the Faeroe-Iceland Ridge and the Denmark Strait are sinks in every sense of the word. Consequently, not until the argument is geared to a thermodynamic source can it be fully satisfactory.
A chain of hypotheses has been constructed to link fluctuations in Arctic climate with fluctuation in the biological productivity of the English Channel. The author is under no illusions as to their vulnerability to attack from many directions. He can hope only that, by offering a target, something more substantial may emerge.
There is climatic evidence in support of the hypotheses.
Smed(1947, e^j'e^.) has collected and summarized all the records of surface tempera- ture which have been collected in the North Atlantic. Fig. 2 shows the areas into which he has divided the North Atlantic. His areas B, C, D are those in which we are most interested. A series of cold winters was experienced in the 'teens of this century, and
58*
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shown in brackets (alter Smed).
particularly in 1918, 1920 and 1921. In the same Figure the departures Irom ihc long term average of the sea temperatures in April, 1920, and April, 1921, are presemed^ These were the culmination of a series of cold winters when a great amount ot North Atlantic bottom water must have been formed. . ^ . „
Air temperatures between 60^ and 70° N have been recently summarized by Brown (1953) Fig 3 shows the area studied divided in Marsden squares. Unfortunately, for squares 220 and 221 (in which we are most interested) there are msuflicenl data for evaluating means. His decadal means for areas 217A and B and 218A and B are shown in Fig. 4. It will be seen that the decade 1910-1919 in December-March was
220
L. H. N. Cooper
40* 20* 0*
Fig. 3. Chart showing position of Marsden squares 217 and 218.
7f—
4 -
3^,
218 A.
.. 217 B
Fig. 4. Decadal mean air temperatures for Marsden square areas 217A and B and 218A and B for the season December to March (after P. R. Brown).
1|° colder than the three decades 1920-49. That is on a decadal basis the years 1910- 19 were more suitable for the formation of oceanic bottom water than the thirty years since. It is probable that in these decadal means the coldness of the years 1920 and 1921 was swamped by the eight following warm years. Nothing comparable was experienced for the next thirty years. In these years we had precisely the conditions which we need to explain the fluctuations in the English Channel. In each winter an amount greater than average sank in the Greenland area. In the first winter the excess sinking would have displaced the strata of water upwards by, perhaps, a few tens of metres. This would not have brought much nutrient rich water within reach of the processes of vertical mixing of surface waters which are always operative. The next winter would have been more effective and the third winter most effective of all. By this time the nutrient table would have been lifted by perhaps 100 metres or more, to a level at which processes of vertical mixing would readily and continually draw upon the upwardly displaced water to enrich the surface waters. The deep waters of the ocean move slowly, so that there may be a considerable time lag before events in polar regions come to influence upward displacement in temperate and tropic latitudes.
Fluctuations in Arctic climate with biological productivity of the English Channel
")-)i
On this line of argument, the maximum enrichment of ihc surface waters of the temperate Eastern North Atlantic with nutrients occurred in or shortly after the year 1921.
If unusually large amounts of water sank in the North in these winters, they had to be compensated by an equivalent amount of surface water, which could have been supplied only by increased intensity of the North Atlantic Drift system. One event associated with this increase in the North Atlantic Drift may be the incursion into the English Channel of much unseasonably warm water in the autumn of 1921 (Harvhy, 1925).
We have long had the suspicion that this incursion of warm water was in some way associated with the rich phosphate observed by Atkins in his first analyses in the Eng- lish Channel on 7 March, 1923. I, for one, have always had great difficulty in accepting this explanation, since warm surface water is nearly always poor in nutrients. Today there is no such warm water anywhere in the Bay of Biscay or Eastern North Atlantic carrying an equivalent supply of nutrients. This objection now vanishes.
This water in some area well to the south of the British Isles had been enriched with nutrients by upward displacement following a period of cold Arctic winters and the three winters of excessive polar sinking. During the warm summer of 1921 there was time for the water to warm up by solar heating, but no considerable redistribution of nutrients with the deeper water had taken place. The nutrient properties of this particular warm water may well have been very far from the equilibrium state that we commonly observe.
DISCUSSION
During the last thirty-five years there have been large changes in the distribution of phosphate in the Western English Channel whilst the zooplankton has changed in species and abundance. No explanation has been found locally, so that attention has been extended to events in the Atlantic Ocean.
A number of associated hypotheses have been erected to explain these changes in the English Channel:
(1) That in cold Arctic winters saline surface water is cooled further and made heavier than in relatively mild ones.
(2) That this leads to a greater recruitment of fresh deep water in the North Atlantic after cold Arctic winters.
(3) That to make room for this fresh deep water, an equal volume of water has to be displaced upwards, i.e. a supply of nutrient-rich deep water is displaced towards the illuminated surface layers. This process may be a diffuse one over the whole ocean basin.
(4) That the origin of the North Atlantic deep water should be considered not in terms of a localized area, but in terms of physical processes which are occurring all the way from Jan Mayen (72° N) to the southern tip of Greenland (58^^ N), and even further south.
(5) That in so far as special areas stand out, these lie over the ridges between Iceland and Greenland on the west, and the Faeroe Islands on the East. Over the two ridges the physical processes which yield heavy water seem to differ in detail, but m both are
222 L. H. N. Cooper
confined to depths between about 300 m and the sill depth of about 550 m. Local surface waters seem not to be overmuch concerned.
(6) That the cold heavy water flows away from the sills of the two ridges not as a smooth continuous current, but intermittently as discrete large boluses.
(7) That due to the effect of the earth's rotation these boluses are held strongly to the right against the eastern slope of the Reykjanes Ridge, and against the eastern con- tinental (or insular) slope of Greenland.
(8) That where the boluses are constrained by restricted topography, they move fast horizontally and sink slowly.
(9) That where narrow straits open out to oceanic dimensions and constraints are removed, then horizontal velocity decreases and the boluses sink rapidly.
(10) That where boluses of heavy water pass over a dissected bottom or slope, they mould themselves to the rock configuration, and that in consequence the free interface against the enveloping water writhes vigorously.
(11) That such a writhing interface, at what is effectively a strongly developed dis- continuity layer, initiates strongly developed internal waves which may travel great distances through the open ocean with little attenuation.
(12) That when such waves meet a continental slope vertical mixing should result, and that when they meet a highly dissected continental slope at a glancing angle, the mixing should be very vigorous indeed. Homogenization of all properties would be much favoured, i.e. shallower layers would be enriched with nutrients at the expense of the deeper and, conversely, deeper layers would, in most places, be warmed at the expense of the shallower.
(13) That the nutrients are finally brought to the surface by thermal and wind-driven mixing processes, and by upwelling processes which may be always operative. It is suggested that these processes are much more effective in producing surface enrich- ment when a series of cold Arctic winters has produced a situation in the deep Atlantic which favours upward displacement and homogenization of nutrients, especially against continental slopes.
(14) That in the North Pacific there is no exact parallel to events in the North Atlantic. The only comparable process would seem to be unable to affect the North Pacific waters deeper than about 2,000 m at most. Consequently the nutrient resources of the deep North Pacific seem to be much less effectively used than are those of the deep North Atlantic.
Some evidence for hypotheses 1-9 has been presented elsewhere (Cooper, 1955). Further evidence for hypotheses 1-9, applying to the Denmark Strait and East Green- land, is being marshalled for publication.
Hypotheses 10 and 11 are intuitive and no supporting evidence is known to the writer.
Direct observations in support of hypotheses 12 and 13 are now being sought in the Atlantic near Plymouth. Further evidence in support of hypothesis 14 is still being sought.
Fluctuations in Arctic climate with biological productivity of the English Channel 223
REFERENCES
BoDEN, B. P. and Kampa, E. M. (1953), Winter cascading from an oceanic island and its biological
implications. Nature, 171, 426-427. Brown, P. R. (1953), Climatic fluctuation in the Greenland and Norwegian Seas. Ouaii. J. Roy.
Met. Soc, 79, 272-281. Cooper, L. H. N. (1952 a). Processes of enrichment of surface water with nutrients due to strong
winds blowing on to a continental slope. J. Mar. Biol. Assoc, U.K., 30, 453^64. Cooper, L. H. N. (1952 b). The physical and chemical oceanography of the waters bathing the
continental slope of the Celtic Sea. J. Mar. Biol. As.soc., U.K., 30, 465-526. Cooper, L. H. N. (1952 c). The boar fish Capros aper (L.), as a possible biological indicator of water
movement. J. Mar. Biol. Assoc., U.K., 31, 351-362. Cooper, L. H. N. (1952 d). Water movements over the continental slope in relation to fisheries
hydrography. Rapp. Proc. Verb., Cons. Perm. Int. E.xpl. Mer. 131, 44 50. Cooper, L. H. N. (1955), Deep water movements in the North Atlantic as a link between climatic
changes around Iceland and the biological productivity of the English Channel and Celtic Sea.
J. Mar. Res. (in press). Cooper, L. H. N. and Vaux, D. (1949), Cascading over the continental slope of water from the Celtic
Sea. /. Mar. Biol. Assoc., U.K., 28, 719-750. Deacon, G. E. R. (1937), The hydrography of the Southern Ocean. Discovery Repis., 15, I -1 24. Fuglister, F. C. and Worthington, L. V. (1951). Some results of a multiple ship survey of the Gulf
Stream. Tellus, 3, 1-14. Harvey, H. W. (1925), Hydrography of the English Channel. Rapp. Proc. Verb., Cons. Perm. Int.
Expl. Mer, 2,1, 59-89. Lee, a. J. (1952), The influence of hydrography on the Bear Island cod fishery. Rapp. Proc. Verb.,
Cons. Perm. Int. Expl. Mer, 131, 74-102. Smed, J. (1947 etseq.). Monthly anomalies of the surface temperature in the sea round South Greenland
during the years 1876-1939. Ann. Biol., Cons. Perm. Int. Expl. Mer. 2, 16-22. (See also, 3, 12-24;
4,11-26,57-60; 5,11-15; 6,18-27; 7,9-13,85-88; 8,20-22; 9,16-21,95.)
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 224-238.
Review of the oceanography of Long Island Sound
By Gordon A. Riley
Bingham Oceanographic Laboratory
and
Woods Hole Oceanographic Institution*
Summary — Long Island Sound is a shallow, semi-enclosed body of slightly brackish (23-31 /^o) water with an area of about 900 nautical square miles. Moderate tidal currents permit a small seasonal thermocline and slight vertical gradients in salinity, oxygen and nutrient salts. The major feature of non-tidal circulation is a two-layered transport system in which a freshened surface layer moves east- ward out of the Sound and is replaced by a more saline inflow along the bottom. The latter contains more nutrients than the outflowing surface water, so that the transport system tends to accumulate and conserve nutrients. Freshwater drainage also makes a significant contribution of nitrate.
Phytoplankton concentrations are large, but the species composition is relatively limited. A large diatom flowering occurs in late winter, following an early winter minimum, with only minor fluctua- tions the rest of the year. There is sufficient mixing to prevent a large accumulation of nutrients in the bottom water, so that there is neither pronounced poverty in summer nor a big autumn flowering following destruction of the thermocline. Major limiting factors are the amount of efl'ective light in autumn and winter and the nitrogen supply in spring and summer. Variations in light and temperature from one year to the next aff"ect the winter species composition and the time of the flowering. Diatoms are largely replaced in summer by naked flagellates and other nannoplankton. During one summer when nitrate concentrations were higher than usual, diatoms were abundant and there was also an unusually large zooplankton crop. A causal connection is indicated but not well established.
The zooplankton consists of large numbers of small animals. Relatively few species are present. The dominants are two species of the copepod Acartia which alternate seasonally. Descriptive and experimental studies suggest that seasonal replacement is primarily a temperature-controlled competition rather than a direct, lethal temperature effect. Experiments show that the Acartias have high respiratory rates and low grazing rates compared with most other copepods that have been examined and possibly are able to achieve dominance only in waters sufficiently brackish to exclude more efficient oceanic species.
Preliminary studies of bottom fauna indicate a relatively large biomass, again consisting of large numbers of small animals. Fish eggs and larvae are abundant, and the Sound may be an important spawning and nursery ground. However, commercial fishery statistics show no indications of a large population of mature fish.
Total phytoplankton production is about the same as in the open coastal and bank waters off" New England. Most of this production is utilized in the support of small animals which do not provide an adequate food supply for the efficient production of large carnivores.
INTRODUCTION Long Island Sound, like other New England waters, has been a source of interest and livelihood since colonial times, and its general features are well described in early expedition narratives. Scientific studies of its waters began a little more than a hundred years ago with a survey of the morphometry, character of the bottom, tides, and currents, jointly sponsored by the Navy and the predecessor of the present Coast and Geodetic Survey. The pertinent information was printed on a series of three excellent hydrographic charts in 1855. More thorough surveys of tides and currents were made
* Contribution No. 762 from the Woods Hole Oceanographic Institution. Studies described herein have been aided by the Office of Naval Research, Department of the Navy, through contracts with Yale University (NR 163-118) and the Woods Hole Oceanographic Institution (N6onr— 277).
224
Review of the oceanography of Long Island Sound 225
during the late nineteenth and early twentieth centuries, and all available observations have been summarized by Le Lacheur and Sammons (1932).
The first oceanographic studies that may be regarded as modern in their general scope and outlook were begun in the 1870's under the able direction of Spenc er F. Baird, U.S. Commissioner of Fish and Fisheries. For the waters from Cape Cod to New Jersey, and including Long Island Sound, we find in his reports during the ensuing years not only accounts of the fishes and their physical environment, but also mono- graphs on the invertebrates (Verrill, 1873) and algae (Farlow, 1879), as well as other major works that are still in common use.
In 1935 the U.S. Fish and Wildlife Service established a laboratory at Milford, Connecticut, under the directorship of Victor L. Loosanoff. One of the most important contributions of this laboratory has been a thorough study of lamellibranch physiology and ecology by combined field and laboratory techniques. In addition, records have been maintained for fifteen to twenty years of temperature and salinity in the north-central part of the Sound, oyster spawning and setting, and other oceano- graphic matters of both practical and scientific interest.
In 1938 the Bingham Oceanographic Laboratory began a year's survey of plankton and associated environmental factors in the same area (Riley, 1941), and similar work was carried on during the summers of 1940, 1941, and 1950. A program of broader scope was instituted in 1952, consisting of weekly coverage of a grid of stations in the central part of the Sound for a two-year period, followed by a further expansion to coverage of the Sound as a whole at approximately monthly intervals. The latter work is still in progress.
The present paper reviews some of the work that has been done and attempts to extract some ecological generalizations that will be applicable to Long Island Sound in particular and perhaps in some cases to temperate littoral waters in general. For purposes of comparison it is pertinent to mention other work in nearby waters: a survey of temperature and salinity distribution by the Woods Hole Oceanographic Institution in the area from Woods Hole to the central part of Long Island Sound in 1946, a study of Block Island Sound from 1943 to 1946 and in 1949 by the Bingham Oceanographic Laboratory, and the work of Ryther (1954) and other Woods Hole staff members in the bays on the south shore of Long Island.
PHYSIOGRAPHY AND PHYSICAL OCEANOGRAPHY
Long Island Sound (Fig. 1) is a semi-enclosed body of water some 90 nautical miles long, with a maximum width of about 15 mi. and an area of 928 sq. mi. The maximum depth in the eastern end is about 100 m. There is little water of more than 35 m in the central and western basins, and the mean depth of the Sound as a whole is only 20 m. Free interchange with the waters of Block Island Sound occurs through a series of passes at the eastern end. In the west there is more limited interchange with the New York harbour and river waters.
The drainage basin is roughly eleven times the area of the Sound, and the annual volume of freshwater drainage averages 35 % of the volume of the Sound. However, three-quarters of the river water enters the relatively open eastern end, where it is flushed out rapidly and has a minimal effect on the Sound as a whole.
Tidal interchange totals 8-6% of the volume of the Sound below mean low water, leading to currents of three knots or more in the eastern passes and a maximum speed I
226
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Review of the oceanography of Long Island Sound 227
of about one knot in the central and western basins. Many current stations, particu- larly in the eastern part of the Sound, show that the ebb is stronger than the flood in the surface layer, while the reverse is true at the bottom. Thus there is a tendency here, as in many other sounds and estuaries, for the surface layer to move seaward and to be replaced by sahne water flowing in along the bottom. An analysis of the available current stations during the summer season (Riley, 1955 a) indicates that this inflow through the eastern passes is of the order of 15-20 thousand m ' per second. The bottom transport decreases rapidly as it moves west, approaching zero near the western end of the Sound. Clearly the slowing down is due to upwelling of bottom water and admixture with the surface layer, and current measurements demonstrate a corresponding augmentation of the eastward surface transport. The calculated mean rate of upwelling required to satisfy the principle of mass continuity is small, ranging from about 5 cm per month in the central and western part of the Sound to a maximum of 45 cm in the vicinity of the passes.
It would appear from current stations that about 1,100 m* sec enter the western end of the Sound from New York harbour and flow eastward as part of the surface layer. The latter is further augmented by freshwater drainage, amounting to about 300 m^/sec in summer. Thus the surface outflow at the eastern end should exceed the inflow by about 1,400 m^sec, although the statistically derived transport estimates are not accurate enough to demonstrate this.
Complete current surveys are available only for the summer period. Analyses of salt balance (Riley, 1952 a) indicated a seasonal variation correlated with freshwater drainage. Surface current measurements at Bartlett Reef Lightship in the eastern end of the Sound (Le Lacheur and Sammons, 1932) showed a similar relationship, but farther west, at Cornfield Lightship, the seasonal variation was slight and was not clearly correlated with river outflow.
The distribution of temperature and salinity has been described by Galtsoff and LoosANOFF (1939) and Riley (1952 a). Surface water temperatures have a seasonal range of roughly 3^ to 19° in the eastern end of the Sound and 0° to 23° in the western portion. The total salinity range is about 23 to 31%„, excluding occasional eddies of fresher water in the immediate vicinity of the rivers. The east-west salinity gradient is ordinarily about 57oo» and there is a seasonal variation of 2 to 4°/„„.
A two-year series of observations in the central part of the Sound (Riley, 1955 a) at station positions shown in Fig. 1 serves to illustrate general features of the tempera- ture and salinity cycles. There was a small thermocline in spring and summer, and the maximum difference between surface and bottom temperature was about 5 (Fig. 2). A slight salinity gradient was maintained throughout most of the year by the combined eff'ects of freshwater dilution of the surface layer and inflow of saline water along the bottom. Differences in the seasonal cycles from one year to the next show obvious correlations with the meteorological variables included in Fig. 2.
SEASONAL CYCLES OF PLANKTON AND CHEMICAL FACTORS
The upper part of Fig. 3 shows the seasonal cycles of surface and bottom phosphate and nitrate as averages of analyses at inshore stations 1, 6, 7, and 8 (Riley and CONOVER, 1955). Chlorophyll analyses included in the figure provide an estimate of the total phytoplankton population, and zooplankton catches obtained by oblique tows with a Clarke-Bumpus sampler are plotted as total displacement volumes.
228
Gordon A. Riley
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SALINITY
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of oceanographic observation.
The gross features of nutrient cycles are characteristic of temperate waters, but the proportions of nitrate-nitrogen and phosphorus are anomalous. During the winter maxima, the ratio of N :P by atoms has been of the order of 8 : 1 , about half the value that might be expected in oceanic waters. The late winter flowerings of 1953 and 1954 almost completely exhausted the supply of nitrate in about three weeks but left a residuum of about 0-5 (i.g-at of phosphate-P in the water.
Most of the spring and summer analyses have shown little or no nitrate in any part of the water column. Harris (unpublished) has found small but significant quantities of ammonia, and this, together with organic nitrogen compounds, constitutes the main source of supply. Phosphate values during the same period generally have been within the range of 0-2 to 1 lag-at P per litre. Phosphate tended to increase gradually during the summer and more rapidly in autumn. Nitrate remained low
Review of the oceanography of Long Island Sound
229
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ZOOPLANKTON VOLUMES ^ 10 NET
1952
1953
1954
Fig. 3. Average phosphate, nitrate, and chlorophyll at the surface (solid lines) and bottom (dotted lines) at inshore stations 1, 6, 7 and 8. Zooplankton displacement volumes, also at inshore stations. are averages for the water column obtained by oblique tows with a No. 10 net.
until September. The autumn increase in nutrients was interrupted in October, 1953, presumably because of plant growth. While there was not a pronounced autumn flowering in the ordinary sense of the term, both phytoplankton and zooplankton crops were larger than in the autumn of 1952.
Phosphate and nitrate increased slightly from surface to bottom during most of the spring and summer. Stability was loo slight to permit the accumukilion of a large store of regenerated nutrients in the bottom water. It was reasonable, then, lo tind neither a pronounced summer period of phytoplankton impoverishment nor a marked flowering following destruction of the summer thermocline. It was common in autumn and early winter to find a significant reduction in phosphate and nitrate in the bottom water. The reason for this peculiar phenomenon will be discussed later.
230 Gordon A. Riley
The major diatom flowering occurred in late winter, as previously reported in Long Island Sound (Riley, 1941) and some other littoral waters off the New England coast (BiGELOW, 1926; Fish, 1925). An early flowering in these latitudes requires that the phytoplankton be confined to a shallow stratum, since it is only in such an environ- ment that the effective light intensity in winter exceeds the threshold necessary for active growth. Hence the flowering is likely to be early in shallow water and to begin later in the deeper water, frequently only after the establishment of vernal stability (BiGELOW, LiLLiCK, and Sears, 1940; Riley, 1942). In a particular location the time of the flowering may vary from year to year in accordance with variations in the amount of light available (Atkins, 1928). However, in comparing the winters of 1953 and 1954 in Long Island Sound, there were no marked differences in incident radiation, and another explanation must be sought for the fact that the 1954 flowering was about three weeks earlier.
S. Conover (1955) found that the midwinter diatom population was dominated by two species, Skeletonema costatum and Thalassiosira nordenskioldii, in about equal proportions. In 1953 Skeletonema dominated the flowering, achieving an average concentration of 36 million cells per litre at the stations sampled on March 9, as compared with one million cells per litre of Thalassiosira. In 1954 Thalassiosira nordenskioldii rose to six million cells per litre on February 17, while Skeletonema achieved a peak concentration of nine million cells the following week. Considering the diff'erence in size of the two species, Thalassiosira clearly dominated the early flowering period in 1954.
Conover conducted a series of experiments in 1954 in wnich natural populations were bottled and treated to a variety of conditions of light, temperature and nii.rient enrichment. Table I shows a part of the data from the experiment of February 10 that is pertinent to the present discussion. It is apparent that Thalassiosira has an
Table I
Growth coefficients {fractional increase in cell number per day) o/Skeletonema costatum
and Thalassiosira nordenskioldii in two-day experimental exposures of natural surface
water phytoplankton populations to normal seasonal temperature and surface light
intensity, to reduced light, and to increased temperature
Temperature Growth coefficients
" C Skeletonema Thalassiosira
|
1-7 |
-0 021 |
0058 |
|
1-7* |
-0 025 |
0-015 |
|
5 0 |
0-144 |
-0133 |
|
8 0 |
0-258 |
-0163 |
* Average of four experiments at light intensities ranging from 1 to 24% of the surface value.
optimum growth rate at low temperatures and can tolerate low light intensities, while Skeletonema requires higher temperature and probably better illumination. Later experiments suggested that the critical temperature determining which species will dominate is between 2-4 and 3-7°C. The mean temperature in the Sound was 3-2° in February 1953, and 3-7'' in March, and the corresponding means for 1954 were respectively 1-7 and 3-5°. Conover concluded that the lower temperature in 1954
Review of the oceanography of Long Island Sound
231
favoured the dominance of Thalassiosira and that its tolerance to low light intensity permitted a relatively early flowering. Contrariwise, physical conditions promoted dominance by Skeletonema throughout February and March, 1953, and toward the end of the 1954 flowering.
In 1955 the flowering was even earlier. The major growth took place during the last ten days of January, and the peak was attained early in February. The New Haven Weather Bureau reported that the percentage of sunshine in January, 1955, was the highest that has been recorded in 55 years of observation, so that an early flowering was not unreasonable. The temperature in the Sound was 3-1 to 3-3' at the beginning of the flowering, and Skeletonema was the dominant species. As the flowering pro- gressed the temperature dropped to about 1 '. At this writing, counts of the phyto- plankton for this period have not been completed. Preliminary indications are that Thalassiosira gained in relative importance but was unable to achieve complete dominance.
Experiments by S. Conover (1955) showed that the 1954 flowering was terminated largely because of nitrogen deficiency. At this time and again in June, 1954, natural phytoplankton populations were enriched with phosphate, nitrate, iron, and man- ganese, singly and in combination. In all cases nitrogen was the one element that had a significant effect on the population as a whole, although individual species occasion- ally responded to other types of enrichment. Nevertheless, the percentage of nitrogen in the phytoplankton remained nearly constant through the year (Harris and Riley,
50
40
— MILLIONS OF CELLS PER LITER
pG. CHLOROPHYLL PER LITER
30
20
10
1952
Vj
M 'j 'j 'r's 'O In"VT) 'f 'm 'a 'mTT'j 'a 'S '0 'N 'D -J 'F 'M
1953
1954
Fig 4 Phytoplankton cell numbers and chlorophyll concentrations in the surface waters, plotted as
the average of all values obtained at inshore stations.
232 Gordon A. Riley
1955), so that the deficiency obviously does not approach the extremity of laboratory cultures, in which the nitrogen content may be reduced to one-third normal (Ketchum and Redfield, 1949).
It is beyond the scope of this paper to discuss seasonal succession in detail, but one other major feature is apparent in Fig. 4, which compares chlorophyll analyses with Conover's cell counts. The latter comprised mainly diatoms and armoured flagellates. In addition, occasional examinations of fresh material in summer have revealed two to five miUion naked flagellates per litre and many millions of small, unidentified Chlorella-Wkc cells. These small species are believed to be largely responsible for the disparity between chlorophyll and routine cell counts in summer. Long Island Sound seems to resemble, to a much less extreme degree, the situation described by Ryther
( 1954) in Great South Bay and Moriches Bay, Long Island, where there was an exces- sive summer dominance by " small forms ". These were shown by Ryther's experi- ments to be favoured in their competition with diatoms by reduced salinity, high temperature, a low N:P ratio, and the presence of nitrogen primarily in forms other than nitrate. Similar environmental tendencies have been noted in Long Island Sound. It is perhaps significant in this connection that the slightly higher nitrate values during the summer of 1952 were accompanied by much larger quantities of diatoms.
In the locality described by Ryther, the nannoplankton appeared to have a distinctly toxic effect on shellfish. There is no evidence of a similar situation in the Sound. LoosANOFF et al. (1947; 1953) have studied feeding rates and toxicity reactions of lamellibranchs, using a variety of nannoplankton species as food organisms. Their work indicates that the concentration of organisms required for toxic effects is well above the level of the population found in the Sound. On the other hand, R. Conover
(1955) found that Acartia, the dominant genus of copepods in these waters, feeds much more effectively on diatoms than on nannoplankton. Hence the value of the latter as zooplankton food is somewhat questionable.
Quantitative aspects of the total zooplankton population, as depicted in Fig. 3, provide little material for generalization except that there is a minimal population in autumn and early winter, a larger but rapidly fluctuating crop in spring and summer, and a vast diflference from one year to the next. Similar variability in the level of the summer population has been noted in previous studies during the summers of 1938 to 1941. There is no satisfactory explanation, although it may be argued on rather tenuous grounds that a causal relation exists between the relative abundance of nitrate, diatoms and zooplankton in 1952 as compared with their scarcity the following year.
According to Deevey (1955), copepods are the dominant zooplankton organisms in the Sound, the most important species being Acartia clausi and A. tonsa, with smaller but significant quantities of Temora longicornis, Pseudocalanus minutus, Paracalanus crassirosths, and Oithona spp. Several other copepods and three species of Cladocera occasionally constituted as much as 5 % of the population, as did the larvae of various bottom invertebrates. In general, the species composition was quite limited, and several species that are common in the outer coastal waters and are known to have a wide salinity tolerance were unable to maintain significant numbers in the Sound.
R. Conover (1955) has made a descriptive and experimental study of the two species of Acartia with particular reference to problems of seasonal succession. A. clausi appeared in November or December and increased to a maximum in May of
Review of the oceanography of Long Island Sound 233
102,000 per m^ in 1952 and 62,000 in 1953. A rapid decline followed, and the species disappeared from the water in early August. A. tonsa appeared in June and increased to 82,000 per m^ in August, 1952 and 46,000 in 1953. There was a more or less steady decrease during the autumn and early winter, a slight rise in early spring, and then virtual disappearance from the water. Thus A. clausi was dominant in winter and spring and was replaced by A. tonsa in summer and autumn, but both species persisted through almost the entire seasonal temperature range.
The data did not completely rule out the possibility that seasonal succession is controlled by direct, lethal temperature effects, but the form of the seasonal cycle suggested the more likely possibility of a temperature controlled inter-species com- petition. During the winter, when A. clausi was replacing A. tonsa. the latter was found mainly in the bottom waters. In laboratory experiments at low temperature, it was sluggish, but mortality was not excessive. The possibility of temperature- controlled competition was explored through the medium of grazing and respiratory experiments. The grazing experiments determined the quantity of water that each species could filter in a given length of time, and this, combined with the observed quantity of phytoplankton in the Sound, provided an estimate of total food intake. Respiratory experiments in turn determined how much of the food intake was required to satisfy immediate metabolic needs. In A. tonsa these two quantities were about equal during most of the winter. Only at the time of the flowering did the intake appear to be substantially larger than the requirement. A. clausi, on the other hand, was able to feed at a materially higher level than its rate of metabolic loss throughout the winter and hence was a favoured competitor for food at this season.
In summer A. tonsa was found in greatest abundance near the surface and A. clausi in the slightly cooler bottom layer, so that there was no close and immediate compe- tition for food. Despite the preference for low temperature, A. clausi also remained a more effective feeder in summer than A. tonsa. Thus the summer succession involved a different mechanism, and one which has not been worked out in detail. But since adult A. clausi remained in the Sound for some time after immature stages disappeared, Conover concluded that the replacement was due either to failure of the animals to reproduce at high temperatures or to competition among the juveniles.
HORIZONTAL DISTRIBUTION OF PLANKTON AND NUTRIENTS
Maximum concentrations of both phytoplankton and zooplankton are ordinarily found in the western end of the Sound and in the shallow waters along the north shore. Here the average concentration of phytoplankton is about three times as large as in the eastern end of the Sound or in Block Island Sound and ten times the con- centration in the outer coastal waters. Horizontal gradients in zooplankton and nutrients are similar but not so extreme.
Maximum concentrations are found in very shallow water, and the differences in the total population underlying a unit area of surface are not so marked. Ratios of the total populations in the Long Island and Block Island Sounds average about 1-5:1 for phytoplankton and 1:1 for zooplankton.
It has often been stated that inshore waters are very fertile and that this is primarily due to enrichment by freshwater drainage. However, it is apparent that there are no large regional differences in the total plankton population in southern New England waters, nor is there evidence of much difference in rates of production. Methods of
234 Gordon A. Rilev
measuring the latter are not accurate enough for precise estimates, but such informa- tion as is available (Riley, 1952 b and 1955 c) indicates little difference between the Long Island and Block Island Sounds as far as phytoplankton productivity is concerned.
To be sure, Long Island Sound maintains a slightly higher concentration of nutrients, although again not necessarily a larger total stock per unit area. Two factors tend to maintain this higher concentration. First, freshwater drainage contains a highly variable but generally higher concentration of nitrate (but not phosphate) than Sound waters. Secondly, two-layered transport exchange creates a mechanism whereby the biological system automatically regulates the nutrient supply at a slightly higher level than in the outside waters. During most of the spring and summer, plant growth is sufficiently active to impoverish the nutrient supply in the surface layer. Part of the phytoplankton produced at the surface is utilized elsewhere in the water column, as is sufficiently evident from the existence of a bottom fauna. Thus the surface layer that is transported out of the Sound is relatively poor in total nutrient content, and the latter tends to be conserved and concentrated within the Sound as long as plant growth is sufficiently active to maintain a vertical gradient in nutrients.
During the autumn, when regeneration of nutrients exceeds utilization, very large concentrations have been found toward the western end of the Sound. These tend to be reduced as the season progresses by the combined effects of lateral diffusion and transport exchange. It has been common in autumn and early winter to find positive vertical gradients in nutrients, where rich western water overrides the inflowing bottom water. It was the frequency of this rather unusual type of vertical distribution that first focussed attention on the subject.
Preliminary calculations of enrichment by transport exchange have been made, using transport data mentioned earlier and the observed distribution of phosphate and nitrate. The amount of enrichment in the western half of the Sound during the spring-summer season was estimated to equal one-third of the amount of phosphate present at the time of the midwinter maximum and one-tenth of the nitrate stock. More accurate evaluation of this problem, and of the relative importance of river drainage, awaits the completion of work in progress on seasonal variations in the exchange rate and the distribution of total as well as inorganic nutrient stocks.
ORGANIC PRODUCTION Two one-year series of measurements have been made of the photosynthetic rate of the surface phytoplankton in Long Island Sound (Riley, 1941 ; S. Conover, 1955) using the light and dark bottle technique. The later work also included a few measure- ments at a series of depths from surface to near bottom. Another type of analysis has also been used to estimate the biological rate of change of oxygen and phosphate at various levels in the water column and on the bottom (Riley, 1955 c). Having determined coefficients of vertical eddy conductivity from the vertical distribution and seasonal change in temperature, the coefficients were then appHed to the observed distribution of oxygen and phosphate. This provided information on the rate of accumulation or depletion of the element at a given depth by vertical mixing. Any difference between the calculated rate and the observed change was then ascribed to biological processes. The oxygen and phosphate analyses agreed within narrow limits. The calculated net rate of change of oxygen in the surface layer was about 50% larger
Review of the oceanography of Long Island Sound 235
than the increase in experimental light bottles. The discrepancy may have been due to experimental error, since it is well known that bacterial growth is abnormally large in bottled sea water. However, there are also several possible sources of error in the physical oceanographic calculations, so that there is an uncertainty factor of at least 50% in the results of the productivity compilation.
The consumption of organic matter by the benthic community was estimated by physical oceanographic computation of the rate of transfer of oxygen downwards through the lower few metres of water and by the rate of upward transfer of phosphate from the bottom. An estimate of the rate of consumption by the plankton community could be obtained from the net rate of utilization of oxygen in the lower part of the water column, since the vertical distribution of plankton was relatively uniform. However, it was a minimal estimate because experiments showed a slight but significant amount of photosynthesis at depths of 15 to 20 m in summer. Dark bottle respiration averaged approximately twice the net rate of change in the lower water column. Experimental values were presumably too high, and therefore an intermediate value was chosen to represent the total oxygen consumption of the plankton community. Results are shown in Table II, together with somewhat similar estimates by Harvey (1950) for the EngHsh Channel.
Table II Comparison of mean annual standing crops and organic production (grams organic matter per m^) in the English Channel (EC) and central Long Island Sound (LIS)
|
Daily |
loss bv |
||||||
|
Standing |
crop |
Daily production |
respiration |
||||
|
EC |
LIS |
EC |
LIS |
EC |
LIS |
||
|
Phytoplankton |
4 |
16 |
0-4-0-5t |
3-2* 107t |
— |
1-8* |
|
|
Zooplankton |
1-5 |
2 |
015 |
— |
0 06 |
0-28 |
|
|
Pelagic fish |
1-8 |
— |
00016 |
— |
0025 |
— |
|
|
Bacteria |
0 04 |
— |
— |
— |
0013 |
0-46t |
|
|
Demersal fish |
1-1-25 |
— |
0 001 |
— |
0015 |
1 |
|
|
Epi- and in-fauna |
17 |
19-38 |
0 03 |
— |
0-2-0-3 |
-0-33 |
|
|
Bacteria |
01 |
— |
— |
— |
0 03 |
||
|
Total consumption. |
exclusive |
of phytoplankton respirati |
on 0-34-O-44 1 |
•07 |
* Photosynthetic glucose production and loss of glucose by respiration.
t Production of phytoplankton of normal organic content in excess of respiratory requirement.
t Includes bacteria and microzooplankton. For further explanation of this item see text.
Data for the English Channel were obtained at a station in 70 m of water ofT Plymouth, as compared with a mean depth of 20 m in Long Island Sound. Nutrient concentrations were relatively low in the English Channel, although the total stock in the water column at the time of the winter maximum was about the same in both
areas.
The Sound has a larger standing crop of phytoplankton and greater basic pro- ductivity. The zooplankton crop is only slightly greater, in this connection, R. CoNOVER (1955) has pointed out that the dominant copepod Acartia is a relatively inefficient feeder, has a remarkably high respiratory requirement, and probably
236 Gordon A. Riley
achieves great dominance only in waters that are sufficiently brackish to exclude the more efficient oceanic forms.
The estimate of zooplankion respiration is based on Conover's work, and the phytoplankton respiratory rate is a compilation of field and laboratory data by Riley, Stommel, and Bumpus (1949). When these items are subtracted from the total estimated respiration in the water column, the remainder, representing 0-46 g of organic matter consumed per day, is ascribed in Table II to bacteria and the fraction of small zooplankton that is not captured by the Number 10 net. While both of these elements of the population appear to be important, it is apparent that the method of calculation allows a wide margin of possible error in the estimate.
Consumption on the bottom in Long Island Sound appears to be about the same as Harvey's total, although collections of benthic invertebrates in the Sound (Sanders, in preparation) are larger. Later work in the English Channel by Holme (1953) tends to reduce Harvey's estimate, so there is little doubt that the Sound has a larger total biomass. The number of animals is enormous, and the mean size of the individual is small compared with the English Channel.
Wheatland (1955) has demonstrated that the Sound is an important spawning and nursery ground for several species of fish. Little work has been done on adult fishes, but the commercial catch is small, and Wheatland's examination of catch statistics indicated that the catch per unit effort is smaller than in the adjacent Block Island Sound.
In short, the high basic production in Long Island Sound is utilized by great numbers of small animals. Conversion to high-level food chain carnivores appears to be relatively inefficient.
GENERAL DISCUSSION OF FOOD CHAIN EFFICIENCY Block Island Sound has a net production (excess of photosynthesis over respiration of the phytoplankton) estimated by Riley (1952 b) at 285 grams of carbon per square metre of sea surface in a year, as compared with 205 grams in Long Island Sound. However, a considerable fraction of phytoplankton appeared to be lost by horizontal dispersal into the outer coastal region and the amount utilized in situ by the biological association was estimated to be only 150 grams. The annual fish production in Block Island Sound is about 50 to 100 lb. per acre wet weight (estimated from data in Merriman and Warfel, 1947). In terms of carbon content, this amounts to between 0-4 and 0-8% of the net phytoplankton production. From Table II it may be seen that Harvey's estimate of the combined pelagic and demersal fish production in the English Channel is 0-52 to 0-65 % of the phytoplankton production. Hence both areas have about the same level of efficiency in food chain conversion, although Block Island Sound is more productive in the absolute sense.
Phytoplankton production on Georges Bank also nets about 150 grams of carbon per year (Riley, 1944). Commercial fish catches have ranged from 7 to 33 lb. per acre, according to Clarke (1946). Total production is probably more than twice the landings of table fish, so that the efficiency level is not very different from the figures listed for Block Island Sound and the English Channel.
A very different situation is found in such areas as the Sargasso Sea. Here the level of net production is uncertain, recent estimates var>ing from 30 g carbon per m^ per year (Steemann Nielsen, 1952) to 1 10 g (Riley, 1953). According to Riley, Stommel
Review of the oceanography of Long Island Sound 237
and BuMPUS (1949), the total displacement volume of zooplankton underlying a square metre of sea surface is equal to the amount found on Georges Bank or in the Gulf of Maine and double the crop in southern New England coastal waters. However, its organic content is very low, and it was suggested that the zooplankton is a starved population, possibly with a low rate of production. The extended disposition of the plankton through a long vertical column in such waters requires the expenditure of a relatively large amount of energy in food capture and theoretically should lead to inefficiency in food conversion, with progressive attenuation of the higher members of the food chain. Quantitative information on the total fish population is lacking, but there is no evidence to indicate that it is a large one. Thus the basic production is roughly of the order of magnitude of that found in the English Channel, but it is largely dissipated at the plankton level.
It would appear that a high level of plant production is necessary but not sufficient for a thriving fishery. Block Island Sound and Georges Bank are probably superior to the English Channel at all levels of the food chain, but the English Channel appears to produce more marketable fish than Long Island Sound despite the high basic production of the latter.
Optimum efficiency of conversion seems to be characteristic of coastal and bank waters of moderate depth and salinity of 30"".^ or more. A lesser degree of efficiency is probably to be expected in most deep oceanic waters. Two examples of brackish waters that have been examined, namely Long Island Sound and the Moriches-Great South Bay area, although productive in the basic sense also seem to be relatively inefficient in food chain conversions. The underlying reasons for this are not clearly understood, although some of the symptoms are obvious. There is a large proportion of nannoplankton existing in an environment which, according to Ryther's (1954) experimental studies, favours the dominance of such forms. They are not particularly good food for the large zooplankton which in turn would be the major source of food for larger animals. The brackish environment also apparently favours the dominance of zooplankton species that are inefficient feeders. Thus there exists in the water a relatively large quantity of unutilized phytoplankton and organic detritus. This in itself is a clear symptom of a low rate of turnover, and it probably promotes the dissipation of a rnajor fraction of the energy of the system at low levels by bacteria and microzooplankton. It also tends to produce a bottom sediment of high organic content. The latter generally supports a smaller biomass than a mixed sand and mud bottom and one tha^t is qualitatively less desirable for benthic carnivores. The mud bottoms in Long Island Sound have enomious numbers of nematodes and other microfauna which presumably have a high food requirement and rate of production but are of very limited value as food for groundfish.
REFERENCES
Atkins W R G (1928), Seasonal variation in the phosphate and silicate content of sea water d^ng 1926 and 1927 in relation to the phytoplankton crop. J. Mar. B.ol. Assoc. U.K.. n.s.. 15,
BiiEmw," H. B. (1926), Plankton of the offshore waters of the Gulf of Maine. Bull. U.S. Bur. Fish.,
BTr?,nw H^ B^' LiLLiCK L C. and Sears, M.ary (1940). Phytoplankton and planktonic protozoa of ?he offshore wat^^^^^^^^ the Gulf of Mame. I. Numerical d.stnbut.on. Trans. Anwr. Phd. Soc,
ClakkI: C^Ame), Dynamics of production in a marine area. Ecol. Monogr., 16 (4). 321-335.
238 Gordon A. Riley
CoNOVER, R. J. (1955), Oceanography of Long Island Sound, 1952-54. VI. Biology of the copepod
genus Acartia. Bull. Bingham Oceanogr. Coll., 15 (1). In press. CoNOVER, S. M. (1955), Oceanography of Long Island Sound, 1952-1954. IV. Phytoplankton. Bull.
Bingham Oceanogr. Coll., 15 (1). In press. Deevey, G. B. (1955), Oceanography of Long Island Sound, 1952-1954. V. Zooplankton. Bull.
Bingham Oceanogr. Coll., 15 (1). In press. Farlow, W. G. (1879), The marine algae of New England. U.S. Comm. Fish and Fish. VII. Rept.
for 1879, 1-120. Fish, C. J. (1925), Seasonal distribution of the plankton of the Woods Hole region. Bull. U.S. Bur.
Fish., 41, 91-179. Galtsoff, p. S. and Loosanoff, V. L. (1939), Natural history and method of controlling the starfish
{Asteriasforbesi, Desor). Bull. U.S. Bur. Fish., 49, 75-132. Harris, Eugene and Riley, G. A. (1955), Oceanography of Long Island Sound, 1952-54. VIII.
Chemical composition of the plankton. Bull. Bingham Oceanogr. Coll., 15 (1). In press. Harvey, H. W. (1950), On the production of living matter in the sea off Plymouth. J. Mar. Biol.
Assoc, U.K., n.s., 29, 97-137. Ketchum, B. H. and Redfield, A. C. (1949), Some physical and chemical characteristics of algae
growth in mass culture. J. Cell. Comp. Physiol., 33, 281-299. Lelacheur, E. a. and Sammons, J. C. (1932), Tides and currents in Long Island and Block Island
Sounds. U.S. Coast Geod. Surv., Spec. Publ., 174, 1-184. Loosanoff, V. L. and Engle, J. B. (1947), Effect of different concentrations of micro-organisms on
the feeding of oysters {O. virginica). Fish. Bull., U.S. Fish Wildlife Serw, 51, 29-57. Loosanoff, V. L., Davis, H. C. and Chanley, P. E. (1953), Behavior of clam larvae in different
concentrations of food organisms. Anat. Rec, 117, 586-587. Merriman, Daniel and Warfel, H. E. (1947), Studies on the marine resources of southern New
England. VII. Analysis of a fish population. Bull. Bingham Oceanogr. Coll., 11 (4), 131-163. Riley, G. A. (1941), Plankton studies. III. Long Island Sound. Bull. Bingham Oceanogr. Coll.,
7 (3), 1-93. Riley, G. A. (1942), The relationship of vertical turbulence and spring diatom flowerings. J. Mar.
Res., 5, 67-87. Riley, G. A. (1944), The carbon metabolism and photosynthetic efficiency of the earth as a whole.
Amer. Scient., 32, 129-134. Riley, G. A. (1952 a), Hydrography of the Long Island and Block Island Sounds. Bull. Bingham
Oceanogr. Coll., 13 (3), 5-39. Riley, G. A. (1952 b), Phytoplankton of Block Island Sound, 1949. Bull. Bingham Oceanogr. Coll.,
13 (3), 40-64. Riley, G. A. (1953), Letter to the Editor. /. du Cons., 19, 85-89. Riley, G. A. (1955 a). Oceanography of Long Island Sound, 1952-54. II. Physical oceanography.
Bull. Bingham Oceanogr. Coll., 15 (1). In press. Riley, G. A. (1955 b). Oceanography of Long Island Sound, 1952-54. IX. Production and utilization
of organic matter. Bull. Bingham Oceanogr. Coll., 15 (1). In press. Riley, G. A. and Conover, S. M. (1955), Oceanography of Long Island Sound, 1952-54. III.
Chemical oceanography. Bull. Bingham Oceanogr. Coll., 15 (1). In press. Riley, G. A., Stommel, Henry and Bumpus, D. F. (1949), Quantitative ecology of the plankton of
the western North Atlantic. Bull. Bingham Oceanogr. Coll., 12 (3), 1-169. Ryther, J. H. (1954), The ecology of phytoplankton blooms in Moriches Bay and Great South Bay,
Long Island, New York. Biol. Bull., 106, 198-209. Sanders, H. L. The Bottom Fauna of Long Island Sound. In preparation. Steemann Nielsen, E. (1952), The use of radio-active carbon (C^*) for measuring organic production
in the sea. J. du Cons., 18, 1 17-140. Verrill, a. E. (1873), Report upon the invertebrate animals of Vineyard Sound and the adjacent
waters, with an account of the physical characters of the region. U.S. Comm. Fish and Fish. I. Rept, for 1871-1872, 295-778. Wheatland, S. B. (1955), Oceanography of Long Island Sound, 1952-54. VII. Pelagic fish eggs and
larvae. Bull. Bingham Oceanogr. Coll., 15 ( 1 ). In press.
Papers in Marine Biology and Oceanography. Suppl. to vol. } of Deep-Sea Researcn. pp. 239-241.
Development and metamorphosis of the larva of Agalma elegans (Sars) (Siphonophora Physonectae)
By A. K. ToTTON British Museum (Natural History)
Although Fewkes (1885) published a detailed and illustrated account of the holo- blastic segmentation of the eggs of Agalma elegans, and of the subsequent develop- ment of the larva till it surfaces at the age of about seven days, he did not follow its metamorphosis into the adult. He had previously, however, given (1881, pi. IX, Figs. 1, 2) rather inadequate figures of a post-larval Athorybia stage, and a later one that he called the Physophora stage. The last is perhaps better called the '* Necialia " stage, as I have suggested (1954, p. 62).
Metchnikoff (1874) had, before Fewkes, watched segmenting eggs of this species without figuring them. He also gave an account, though not so good a one as Fewkes, of the development of the larva and the initial stage of its metamorphosis. But it is difficult to interpret Metchnikoff's later figures and to discriminate between the categories of buds that he figured.
Haeckel (1869) had been the first to describe the development of an Agalmid, after he had artificially raised about 60 larvae (one of them to the 27th day) of Agalma okenii {Crystallodes rigidum) at Lanzarote. He did not recognize the first gastrozooid or protozooid as such. It is labelled " d " (Dotter) and " dc " (Dolterhole) in all his figures, whilst his Magen-polyp (" p ") is really the second gastrozooid. He did not figure a larval tentacle for the protozooid, and I have never seen one either in Agalma okenii. In my Discovery report (1954, p. 66) I noted that the terminal gastrozooid— the primary zooid or protozooid — was smaller in Agalma okenii than its successors, and had a reduced basigaster. On page 69, however, 1 made the erroneous statement that such a protozooid was not formed. The sentence (lines 1 1-14) " The explanation . . . okenii " should be deleted.
Reduction of the protozooid in Agalma okenii has gone further than in Agalma elegans, whilst evolution of the bracts has progressed, giving the whole bud-colony
a character of its own.
Adult specimens of Agalma elegans were not available except on one day during three visits that I have paid to Villefranche, and I was not able to secure any of the very youngest larvae, either by attempts at breeding or in the tow-net; but I did colloci large numbers of post-larvae in various stages of development, and can now complete the account of growth and metamorphosis.
The fate of the larval bracts of the Athorybia-V±Q stage has been unknown. Gar- STANG (1946) several times suggested that they are dropped at metamorphosis. As a fact they, or at any rate the last-developed ones, are retained through life in their original very restricted position surrounding the proximal sides of the first and second gastrozooids to appear, where they can be seen figured by Fewkes (1881, pi. IX. Fig. 1) and by Totton (1954, frontispiece. Figs. A, D). But because of the secondary elonga- tion of the area between the budding zone (blastocrene) of the siphosome and the
239
240 A. K. TOTTON
bases of the first two gastrozooids, the area which bears these bracts takes up a subterminal position at the end of a long stem. These larval bracts, so often figured, and their successors of similar though slightly modified shape, are quite distinctive; and differ from the definitive bracts, which arise in hundreds proximally to them in several ventro-lateral meridians of the stem. The contrast in bracteal types is best seen in early stages of metamorphosis, when the definitive bracts first make their appearance.
Information has been wanting in published reports on the position and time of first appearance of the nectophores. Garstang suggested that, as the nectophores appeared, so the bracts, which hitherto had served for locomotion, dropped off, but as we have seen this is not so. The oldest of Metchnikoff's figured specimens, in what might be called the Me/ophysa stage of development, shows two functional nectophores, but unless the reader is familiar with the animals it is not easy to orientate and interpret the figure. The little group of four rounded buds, seen through the uppermost bract, probably represent buds of gastrozooids and palpons. Close by, though not figured, is the nectostyle to which the larval bracts are attached by their muscular lamellae. The nectostyle can be seen in sagittal section (Fig. 1a) to be an elongated, hollow, cone-shaped diverticulum of the general cavity. The larval bracts are attached by muscular lamellae at diflFerent levels on many meridians on either side of the ventral line from which the cormidia are budded. From the opposite side of the pneumatophore spring the nectophores. As pointed out by Garstang (1946), delamination of tissues starts on one side (called ventral, on which the nectostyle is found), and proceeds gradually towards the opposite, dorsal side. This explains why the nectophores are late in appearing where they do on the dorsal side. Metchnikoff says that the pneumatophore has become free, in his figure 1, through the loss of one of the larval bracts. He draws attention to the beginnings of a stem; to the one-sided position of the nectophores; to the first definitive bract below them; to four palpons; and to the two (larval and first definitive) tentacles and a single gastrozooid. Evidently he was unaware of the smaller protozooid or confused it with a palpon. This is the only published account known to me of the beginnings of metamorphosis in a physonect siphonophore.
But curiously enough metamorphosing Physonects, probably of more than one ■species, have been figured unwittingly as adult representatives of a distinct genus " Nectalia ". Garstang (1946, pp. 172-5) spent much time discussing " Nectalia " He quite correctly perceived that its long bracts were precormidial, or coronal as I prefer to call them, and homologous with the bracts of Athorybia rosacea and of Melophysa melo. But the reasons for his conclusion appear to be wrong in that he implied that these bracts would not be carried downwards with increase in number of the cormidia. The coronal (larval) bracts of Agalmids are in fact carried downwards with the first and second gastrozooids. They are " precormidial " in the earliest stages only. New bracts of this coronal type are formed for a long time after meta- morphosis, but only in this restricted area, which comes to be terminal, and on the distal (oral) side of their predecessors. The later-formed bracts of this type are much longer than the first-formed ones, and gradually diverge from them somewhat in shape. But from the start they have a distal pocket of nematocysts at the end of the bracteal canal (misinterpreted by Haeckel as a medusoid subumbrella), whereas the cormidial (definitive stem) bracts in Agalma elegans do not.
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Development and metamorphosis of the larva of .inalma vIcKons 241
Metamorphosis may be said to begin at the lime when, the second gastro/ooid being still smaller than the protozooid, and further cormidial buds having already made their appearance on the ventral side of the nectostyle (Figs. 3. 4), the stem of the future nectosome appears (Figs. 6, 7) as an elongation of that part of the oozooid that lies dorsal to the nectostyle. The nectostyle carries the larval bracts, rather like the tip of a man's umbrella with its bare ribs spread open, and also the cormidial buds. It remains at what may be called the nodal point of minimum growth, uhcrc it can be recognized at the side of the stem for some time, whilst the elongating stem of the nectosome carries the budding zone of the nectophores upwards and away from it in an aboral direction.
The second gastrozooid by now has overtaken the protozooid in size, and the adult type of tentilla on its tentacle can be seen (Fig. 8).
The upper end of the pneumatophore may have grown upwards as much as 4 mm above the nectostyle before there is a noticeable elongation of that part of the stem (siphosome) lying between the second and third gastrozooids. By the time that the nectosome, measured from tip of pneumatophore to nectostyle, is 5-5 mm in length, the siphosome, measurea from nectostyle to base of first and second gastrozooids, may be 2 mm in length (Fig. 9).
An interesting point about the post-larva during this stage of metamorphosis is that the second gastrozooid comes to exceed the protozooid in size, and to assume a terminal position, leaving the smaller protozooid on the dorsal side. The protozooid too has a much smaller basigaster, which is partially divided on the outer, dorsal side. Its relatively small size can be seen in my frontispiece (1954, Fig. D. Gz. (rd)). At that time I had not studied the earlier developmental stages, which I have since collected in abundance, and confused the protozooid with the first definitive gastro- zooid.
This side tracking of the protozooid is still more pronounced in Nanomia hijuga, where it becomes vestigial. The significance of this seems to be that it marks a new line of evolutionary experiment, an escape from the old line of specialization. This is all the more probable since the primitive type of tentacle found on the protozooid is replaced by a much more highly evolved type in the new series of gastrozooids. This " adult " trifid type of cnidosac demands more and bigger nemaiocysts. The basigasters of the secondary series of gastrozooids which supply the nematocysts are correspondingly better developed.
REFERENCES
Fewkes, J. W. (1881), Studies of the jelly-fishes of Narragansett Bay. Bull., Mus, Comp. Zooi, Harvard Coll., 8 (8), \4l-\S2. , ^., ^ ^. ^ ,
Fewkes, J. W. (1885), Studies from the Newport Zoological Laboratory. XV. On the development ol Agalma. Bull., Mus. Comp. ZooL, Harvard Coll., 11 (11), 239-275. , w c- •
Garstang, W. (1946), The morphology and relations ot the Siphonophora. Quart. J. SUcr. Set.,
87 (2) 103—193 Haeckel, E. (1869), ZurEntwickelungsgeschichtederSiphonophoren. Natuurk. Wrh.Prov. Utrecht sch.
Genoots, (I), 6, 1-120. . , .... j c u u -^
Metschnikoff, E. (1874), Studien uber die Entwickelung der Medusen und Siphonophorcn. Z
ToTTON, a!k. (1954), Siphonophora of the Indian Ocean together with systematic and biological notes from other oceans. Discovery Repts., 11, 1-162.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 242-249.
Observations on the biology of Microsetella norvegica *
By Charles J. Fish Narragansett Marine Laboratory, University of Rhode Island
Summary — Microsetella norvegica is one of two microcopepod species which appear significant in the natural economy of certain western Atlantic boreal waters. During the winter months it extends its range southward at least as far as the latitude of Chesapeake Bay. North of Cape Cod in the Gulf of Maine region it is widespread with a tendency to form concentrations of limited area.
Propagation in 1932 began in March in the outer area between Georges Bank and Cape Cod and gradually expanded as the season progressed until it reached a peak in the Gulf along a band seaward of the 100 metre curve from Casco Bay to the Bay of Fundy.
There is evidence of three and possibly four generations between March and September. As in other endemic pelagic species there was a progressive delay to the eastward in the time of spawning, but unlike most of these Microsetella was found propagating successfully at low summer temperatures, averaging 1 1 °-13-5° C, in the turbulent eastern (Frenchman's Bay) area.
INTRODUCTION
There has been increasing recognition of the importance of adult and larval micro- copepods in the natural economy of both coastal and open ocean waters. Because of their small size and frequent preference for subsurface levels they cannot be repre- sentatively sampled with nets of the mesh most frequently used for zooplankton, and, consequently, are commonly much more important members of the pelagic population than published records indicate.
One member of this group, 0///io/jfl5/m///5Claus,whichWiLSON( 1941) has concluded to be the most widely distributed and numerous of all copepods, is also one of the most prolific in western Atlantic boreal coastal waters where its young provide an abundant source of food for larval plankton feeders in midsummer (Fish, 1936 c).
Relatively little attention has so far been accorded Microsetella norvegica Boeck, a second and even smaller (0-3-0 -5 mm) microcopepod species, also endemic in boreal coastal waters. Although widespread, it has not been reported to be particularly abundant in north European coastal areas (Ruud, 1929; Stormer, 1929; Wiborg, 1954) or south of Cape Cod in the western Atlantic (Fish, 1925; Deevey, 1952).
Table I Mean numbers o/ Microsetella norvegica in Frenchman'' s Bay. Number per cubic metre.
Upper 50 metres
1930
July 10 July 18 August 1 August 7 August 14
Adults-Copepodites
Nauplii
208,360 293,467 248,850 152,820 295,460
404,720
195,567
169,523
92,850
93,600
* Narragansett Marine Laboratory Contribution No. 1 1 .
242
Observations on the biology of Microsetcllu norvcKicu
243
However in certain localities north of Cape Cod it is at times very numerous. For example, in Frenchman's Bay it was found by the author to be the dominant species during two months of weekly observations in July and August 1930, when adults and young often comprised over 90% by number of the total zooplankton population. Again in 1931 in the same region 17,907 adults per cubic metre were taken in the upper 50 metres near Monhegan Island on August 21.
To determine its importance elsewhere in the Gulf of Maine and Bay of Fundy, an analysis has been made of collections obtained between July 28, 193 1 , and September 29, 1932. The area covered, location of stations and methods have been described in a previous report (Fish, 1936 a).
Fig. 1. Distribution of adult Microsetella nonegica in April 1932. Number per minute of towing
REGIONAL DISTRIBUTION OF THE ADULT STOCK* In the western Atlantic M. norvegica ranges from Arctic waters (76° 02' N, Jesper- SEN, 1923) at least as far south as Chesapeake Bay where it was found by Wilson (1932) in December 1920 and January 1921. At Woods Hole it appeared m late March and early April 1923 (Fish, 1925), in Narragansett Bay in March 1906 (Sharpf. 1910) and in Block Island Sound in October and December 1949 (Dlevev. 1952). These records indicate that, like most boreo-arctic plankton anmials, M. norvegica extends its range southward along the coast during the winter months.
North of Cape Cod it is widespread in the Gulf of Maine and Bay ot Fundy, xs.ih a tendency to form local concentrations of limited area (Fig. 1). When hrst observed * Mature individuals and late copepodite stages have been combined in the counts.
244 Charles J. Fish
in April 1932, the numbers were everywhere relatively sparse except in three widely separated localities where more than 1,000 per minute were taken in oblique hauls with half metre nets of number 10 mesh. Two of these were near the Nova Scotian coast, one approximately 25 miles east of Briar Island (3,999 per minute) and the other off Halifax (3,744 per minute). A third (2,470 per minute) was located off the inner margin of Georges Bank between the middle and western channels.
Varying numbers, usually small, were taken at all stations east of Mt. Desert in the Gulf, the Bay of Fundy, and along the west and south coasts of Nova Scotia. West of Mt. Desert, Microsetella appeared at but five of ten stations in the inner Gulf, and in the outer Gulf at but four of nine stations. The two eastern centres of abund- ance coincided with similar local concentrations of O. similis (Fish, 1936 c), the numbers of the two species off Halifax being approximately the same. The richest hauls of both species in the inner Gulf, at this time, were also obtained at the same location, St. 24a, seaward of the 100 metre contour off Casco Bay.
With observations restricted to the inner Gulf and Bay during the balance of the season, it was not possible to determine the duration of the three Microsetella con- centrations observed in April. The distribution in succeeding months reveals a pro- gressive shoreward movement of the eastern and western adult-copepodite stocks and gradual expansion to a seasonal peak everywhere in the inner Gulf seaward of the 100 metre contour (Fig. 2). Here the members ranged from 1,360 to 5,662 per cubic metre in August.
Contrasted with 1932, records for August 1931 show much smaller numbers at all comparable stations, although the local swarm near Monhegan Island (p. 243) yielded the highest counts of the two seasons. By September the numbers in the Bay of Fundy had declined greatly both in 1931 (188 per cubic metre) and in 1932 (179 per cubic metre).
PRODUCTION AND DISPERSAL
There are few available data on the biology of Microsetella norvegica, in fact the developmental stages, some of which are shown in Fig. 3, have not yet been described to the author's knowledge. The seasonal occurrence of adults south of Cape Cod would suggest that, like Pseudocalanus, spawning may begin at the southern portion of its range as early as November or December. It is not known, however, whether propagation continues offshore in deeper water after the species disappears from neritic areas south of the Cape with rising spring temperatures.
Distribution of eggs and larvae in 1932
By mid-April propagation in the Gulf was most advanced in the outer part of the western basin between Georges Bank and Cape Cod. Here late nauplius stages up to 1 ,544 per minute were found at two stations. Farther east in the outer Gulf spawning was still taking place and egg sacs up to 926 per minute were found coinciding with the local concentration of adults. Smaller numbers of early nauplii (309 per minute) appeared at one station in this region. Still farther east along the outer Nova Scotian coast neither eggs nor larvae were found. In the inner Gulf spawning had just begun in the eastern basin (up to 1,666 egg sacs per minute) and small numbers of eggs were found extending into the Bay of Fundy. Only one station (St. 29) west of Petit Manan yielded eggs at this time, and no larvae appeared anywhere in the inner Gulf or Bay,
Observations on the biology of Microsi'tclla norve^ica
245
•u ■ f oHnlt Microsetella norvegica in 1932. May-June: number per minute of
Fig. 2. Distribution of aduU^M/rr^^^J^jto «^ number per cubic metre
246
Charles J. Fish
In late May propagation extended to the western part of the inner Gulf where local patches were found off Casco Bay and Mt. Desert. East of Mt. Desert, egg sacs were taken only along the Nova Scotian side of the Bay of Fundy.
The June distribution would suggest offshore production in the eastern and western basins of the Gulf. Eggs were restricted largely to the two outer stations of the most western section and along the course of the drift into the Bay.
Propagation in the inner Gulf reached its peak in July and early August. By mid- August the greater part of the stock was in late nauplius (Fig. 4) and copepodite
Fig. 4. Late nauplii of Microsetella norvegica, presumably the western stock, and early nauplii of the eastern stock in August 1932. Number per cubic metre
stages, the largest hauls (plus 2,0(X) per cubic metre) occurring along a band seaward of the 100 metre curve and extending from Casco Bay to the Bay of Fundy. Early nauplii, presumably the product of the eastern area, appeared in small numbers, restricted almost entirely to the eastern part of the Gulf (Fig. 4). Eggs were widely scattered in small numbers in the Bay of Fundy, particularly in the entering drift and at a few stations farther west in the Gulf.
Fig ^ Developmental stages of Microsetcllanoncgica taken in ^' ■ ■ Frenchman's Bay on August 1 , 19^0
Observations on the biology ol" Micro.\eicllu nurvcwicu
247
By September few eggs and young remained in the Bay, the largest number of nauplii, 374 per cubic metre, being taken in New Brunswick waters off Point Lipreau.
Table II Mean numbers of adults and egg sacs of Microsetella norvegica in successive months. April-June: number per minute. August-September: number per cubic metre.
.■ no observations
|
Gulf of Maine |
Bar oj Fundv |
||||
|
Year |
Mouth |
||||
|
Adult |
Egg sac |
Adult |
Egg sac |
||
|
1932 |
April |
150 |
9 |
104 |
38 |
|
May |
45 |
243 |
328 |
177 |
|
|
June |
425 |
109 |
103 |
321 |
|
|
August |
1264 |
170 |
776 |
250 |
|
|
September |
— |
— |
179 |
3'' |
|
|
1931 |
August |
423 |
189 |
|
_ |
|
September |
— |
18 |
188 |
T |
DISCUSSION AND CONCLUSIONS Annual cycle
Possibly because of its very unequal distribution during the early season, develop- mental stages of Microsetella were not taken in sufficient numbers to permit tracing with certainty successive generations in different areas until August.
Considering the region as a whole, it appears probable that, like Oifhona, there are at least three and possibly four generations of the stock spawning in late March and reaching late nauplius stages in mid-April. A second breeding period is indicated by an increase in egg sacs in the Gulf in late May (Table 11) followed by an increase of copepodite-adults in June. The abundance of late nauplius-copepodite stages com- bined with relatively few egg sacs in August (Table III) suggests a maturing of the second generation and the appearance of a third crop of eggs in July. Egg sacs in the Bay of Fundy on September 15-16 may represent a fourth relatively unimportant generation. There would thus appear to be propagation periods in March, May, July and possibly September, with a cycle of approximately two months.
Table III Mean numbers (per cubic metre) o/' Microsetella norvegica /// different areas in
and 1932
193
Total Gulf
1931
1932
Aug. 21-26
Aug. 8-15
Egg sac 376
Early nauplius 162
Late nauplius 698
Copepodite-Adult 2922
|
Western Area |
Central Area |
Bay |
oJ tunUy |
|
|
1931 1932 |
1931 |
1932 |
1931 |
1932 |
|
Aug. Aug. 21-25 11-14 |
Aug. 26 |
Aug. 8-15 |
Sept. 4 5 |
Sept. 15 16 |
Regarding regional production, Microsetella norvegica appears tirsi as an otlshorc species which later penetrates and propagates in the inner Gulf some lime after augmentation has taken place in the region of the outer banks. The brood in the
248
Charles J. Fish
vicinity of the south channel had attained late nauplius stages by mid- April in 1932, when eggs but no larvae were found in the eastern basin. No evidence of propagation was found farther east off Halifax at this time, or in the inner Gulf west of Mt. Desert where the first evidence of local production was found in late May and June. As in the outer region, and corresponding to Calanus finmarchicus (Fish, 1936 a), Pseudo- calanus minutus (Fish, 1936 b) and Oithona similis (Fish, 1936 c), a progressive delay to the eastward in the time of spawning was evident in the inner coastal area after the species had become established there in 1932. This is indicated in Fig. 4 showing early nauplii limited to the eastern Gulf at a time when late nauplii, presumably the western crop, dominated everywhere. By September, propagation had largely ceased in the Gulf, both in 1931 and 1932 (Table II).
Although the progressive delay to the eastward in the time of spawning, and the relatively small numbers of adults and larvae in the New Brunswick region of the Bay of Fundy (Figs. 2 and 4) indicate that Microsetella responds in a general way to the limiting factor of low temperature, in a manner characteristic of the boreal zooplankton population, there is evidence that it can reproduce at somewhat lower temperatures than Calanus and Pseudocalanus. In Frenchman's Bay in 1930 (Table I) M. norvegica propagated successfully in large numbers during July and August at surface tempera- tures averaging from 11 °-l 3 -5 ° C. and was the only pelagic copepod (with the exception of Temora longicornis) found developing in those waters. An abundant population of offshore species dominated by Calanus and Pseudocalanus (adults and late cope- podite stages) was present in the lower levels of Frenchman's Bay throughout the summer of 1930, but their eggs and larvae rarely appeared in the collections.
Table IV
Relative abundance of adults of Oithona similis and Microsetella norvegica in the
Gulf of Maine and Bay of Fundy in 1931 and 1932. April-June: mean numbers per
minute. August-September : mean numbers per cubic metre. .• no observations
|
1932 |
Gulf of Maine |
Bay |
of Fundy |
|||
|
O. similis |
M. |
norvegica |
O. similis |
M. |
norvegica |
|
|
April May June August September |
1380 3672 4534 3735 |
150 45 425 1635 |
in 983 1858 3120 332 |
78 246 11 110 179 |
||
|
1931 August September |
3550 |
423 |
94 |
188 |
It would appear, therefore, that although Microsetella and its nauplii ordinarily provide a less abundant supply of food for summer larval plankton feeders in the Gulf of Maine and Bay of Fundy than Oithona they do appreciably supplement the latter stock in those waters and seem to be of particular significance in areas like Frenchman's Bay and the adjacent turbulent coastal region eastward from Mt. Desert where low surface temperatures prevent successful summer propagation of the more dominant Gulf zooplankton species.
Observations on the biology of Microsetella norvenica 249
REFERENCES
Deevey, G. B. (1952), Quantity and composition of the zooplanklon ol Block Island Sound. 1949.
Bull. Bing. Oceanugr. Coll., 13, Art. 3, 120-164. Fish, C. J. (1925), Seasonal distribution of the plankton of the Woods Hole RcKion. Hull. U.S.
Bur. Fish., 41, 91-179. Fish, C. J. ( 1936 a). The biology of Calanu.s finmarchicus in the Gulf of Maine and Bay of Fundy.
Biol. Bull., Woods Hole, 70, 1 18-141. Fish, C. J. (1936 b), The biology of Pseudocalanus minutus in the Gulf of Maine and Bay of Fundy.
Ibid., 70, 193-216. Fish, C. J. (1936 c). The biology of Oithona similis in the Gulf of Maine and Bay of Fundy. Ihid.,
71, 168-187. Jespersen, p. (1923), Dr. Thorild Wulflf's plankton collections in the waters west of Greenland.
Den II. Thule ekspedition til Gronlands nord Kyst., 1916-18, No. 4. RuuD, J. T. (1929), On the biology of copepods off More, 1925-1927. Rapp. el Pioces.-Verb., Cons.
Perm. Int. Explor. Mer, 56, 1-84. Sharpe, R. W. (1910), Notes on the marine Copepoda and Cladocera of Woods Hole and adjacent
regions, including a synopsis of the genera of the Harpacticoida. Proc. U.S. Nat. Mus.. 38, 405-436. Stormer, L. (1929), Copepods from the Michael Sars Expedition, 1924. Rapp. et Proces-Verh., Cons.
Perm. Int. E.xplor. Mer, 56, 1-57. WiBORG, K. F. (1954), Investigations on zooplankton in coastal and offshore waters of western and
northwestern Norway. Fiskeridirektoratets Skr., 11, Art. 1, 5-246. Wilson. C. B. (1932), The copepod crustaceans of Chesapeake Bay. Proc. U.S. Nat. Mus., 80, An. 1 5.
1-54. Wilson, C. B. (1942), The copepods of the plankton gathered during the last cruise of the Carnegie.
Carnegie Inst. Wash., Pub. 536, 1-237.
Pajjers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 250-256.
The production of Liza ramada (Risso) in Lake Mariut, Egypt
By R. S. WiMPENNY
Fisheries Laboratory, Lowestoft, England
Summary — The production of the grey mullet Liza ramada in Lake Mariut, Egypt, is followed from its introduction in 1920 until 1935, special attention being paid to the years 1928-31 and 1933, when age censuses were available.
After an initial build-up to a steady state between 1923 and 1926, it is thought that a decline set in about 1927-8 due to a lowering of the lake-level, and that this ended in lower levels of the popula- tion from 1930 to 1933 and a further fall in 1934 and 1935. The decline in numbers estimated in the O group catch represented a heavy mortality in the first year, and it is thought that this occurred very soon after the fry were introduced into the lake, as the rate of growth of fish caught in their first year in the lake showed no fall, but a slight increase between 1928 and 1933.
On the delta coast of Egypt there are several large and extremely shallow lakes usually connected with the sea during the whole or a part of the year by shallow channels. They are of great fertility, 60-270 kgm per hectare compared with 100 to 400 kgm per hectare for cultivated carp ponds in Germany, and 5 to 250 kgm per hectare for cattle on grassland (Mortimer, 1954). Among the species that go to make up the yield are those of the genus Tilapia which can give over 9,000 kgm per hectare in the fertilized ponds of the Belgian Congo (Mortimer, 1954) and the grey mullets, a species of which constitutes 50-60% of a yield of 1,500-4,000 kgm per hectare for the brackish ponds in the New Territory of Hong Kong (Bromhall, 1954). It is one of the most important species of this latter group, Liza ramada (Risso) formerly called Mugil capita Cuv. and known locally as the " Tobar " which is the subject of this contribution.
The habit of the Tobar is to enter the lakes from the sea in great numbers between January and April. During this time it will be found to increase in modal size from 16 to 20 cm during the course of the run. The fry which enter the lakes already possess scales, the gut is short and simple and both animal and vegetable plankton is eaten. Subsequent growth is rapid and the intestine becomes lengthened and con- voluted as the fish changes its feeding habits to that of a mainly vegetarian browser.
The length range of the commercially caught population is from 14-30 cm long and the average size, which also happens to be near that at which both sexes may first be commonly found mature, can be taken as 20 cm. Growth to the end of the first year (" O group ") appears to vary a good deal and fish may be from 14-20 cm, indeed in exceptional circumstances in fresh water ponds 28 cm has been reached in this time. In the second year (" I group ") length can increase by from 1 to 6 cm, and in the third (" II group ") 1 or 2 cm. Generally, however, there appears to be little growth after maturity has been reached.
When in October and November sexually mature fish leave for the sea in large shoals, most of these are at the end of their second year. Spawning must take place in the immediate coastal belt, as no record is known of any individual of this species being caught in the trawl, or by any other method of fishing employed outside the littoral zone. Although I was fortunate enough to find and describe the planktonic
250
The production of Liza ramada (Risso) in Lake Mariul. Egypt 251
egg from a population introduced into Lake Quarun (Wivipfsw. 1936), none has been found in the water of the coastal belt either near Lake Mariut or anywhere else in the world, and the location of the actual spawning grounds, bearing the number of eggs that must necessarily be present to account for the origin of the huge runs of young fish into fresh water, remains a mystery.
There is, therefore, a gap in our knowledge of the life cycle of this species between the departure of the spawning shoals and the arrival of swarms of small scaled individuals in the out-flowing fresh water at the beginning of January.
Lake Mariut during the period to which this account refers was an area of approxi- mately 59,000 acres of water rarely more than 50 cm deep and situated behind the town of Alexandria. The Department of Irrigation maintained it around a level of 3 metres below sea-level (rather above this in the early part of the period, rather below- later), and it acted as a drainage reservoir for the farm lands of the north-west part of the Nile delta. The drain water reaches the lake chiefly through a large channel called the Omoom drain. A channel at sea-level runs from the sea to the lake-side at a place called Mex. Here powerful pumps force the water from a canal on the lake- side up into the sea canal. It was usual for these pumps to work from August to April, as during the rest of the year the evaporative power of the sun, estimated to have been 750,000 to 1,000,000 tons per day, was considered sufficient to keep the lake at the required level.
The eff'ect of these arrangements was that there was no contact between sea and lake when the pumps were not working, but for the rest of the time the water flowed with considerable velocity from the lake to the sea. The sea water never flowed into, nor was it on a level with the lake; thus the penetration of marine animals was obstructed. In these circumstances spawning shoals of Tobar found it easy to leave the lake in the spawning season, but the fry, attracted to the outflow of fresh water in the Mex channel, were prevented from passing in through the pumps, and gathered against the walls of the channel with their heads facing upstream as near the pumps as possible. There they collected in great numbers, and until 1920 this obstacle to their progress stopped other than stray individual Tobar, that had wandered into the lake by the inland drains, from populating the lake.
In 1920 the Director of Fisheries Research of that day, Mr. Paget, organized a service of transplantation which consisted in sweeping up the fry from alongside the walls of the marine canal by long-handled nets having a mosquito netting bag and a rectangular head. The fry thus caught were carried to the lake-side of the pumps in buckets, and poured into boats with perforated zinc removable sides. When the boats were sufficiently charged with fry, they were towed some distance out into the lake and the fry released. The bags of the nets were marked so that a record of the number of fry could be kept. This introduction, made at a cost of a few hundreds of pounds annually, resulted in a fishery for two species of grey mullet running into tens o\'
thousands each year.
For the fifteen years 1920-35 there are available (Egypt, Government Press, 1922-26)
(a) statistics concerning the weights and values of the different species of hsh collected at the landing places on Lake Mariut; (b) the record of numbers ot try introduced; (c) information on the number of fishing boats at work (from the licensing system) and (d) particulars relating to the water level and supply (from the Department of Irrigation). In addition to this, for the years 1928-31 and 1933, there
252 ^- S- WiMPENNY
are some observations on the age, length and weight composition from samples of the commercial catch. The age, length and weight data for 1930, 1931 and 1933 are published here for the first time. On this basis therefore and, as far as the data permits, it is proposed to follow the annual production of Tobar in Lake Mariut for the first fifteen years after its introduction, and to examine the changes revealed, paying special attention to the years 1928-31 and 1933.
\)— ^--o^ • ^^^*^
O CATCH PER BOAT
N? Of BOATS
(IOC*) -
- kg 200H
to-
I50H ICO 5- 50^
O LAHE LEVEL
• CATCH ^
200- 2-80
tons ~
- 2 90 I50-
^Ci - 300
\
\ lOO-
\
- 3IO
\
J L
FRY IN MILLIONS 5-
2-
I-
3 4
Fig. 1
Relation of fry to catch
The relation of fry introduced each year to the corresponding catch is shown in Fig. 1. In a general way the fry introductions built up parallel to the catch until 1927, and thereafter fell away to lower levels in the thirties. There are, however, two years, 1921 and 1930 in which the unusually high values of 28-6 and 51-1 millions are
The production of Liza ramada (Risso) in Lake Mariut. Egypt 253
associated with unexpectedly low catches. Inspection of the graph gives the impression that catch rises roughly in proportion to fry introduced up to about 25 million, but that two higher values than this correspond to lower catches, perhaps due to high mortality from more acute competition among the more numerous fry.
A correspondence between the catch and the number of fry introduced is not difficult to imagine, and it seems reasonable to suppose that it could happen in two ways. First of all it is to be noted that a substantial yield of catchable fish, 47 tons per 4-7 million fry, occurred in the year of first introduction, and it is reported that a number of these left the lake to spawn in the first year. The introduction of fry in any one year may therefore be expected to have a substantial effect on the yield. Secondly, as a fair proportion of the fish spawn in their first year, a successful year- group may be indicated by a good catch and the origin of a successful spawning. This would mean there might be a correspondence between the catch in one year and the number of fry that appeared in the succeeding year.
In fact when the catch and contemporary fry were correlated, a low but positive correlation of little significance was obtained. It is not without interest, in view of the preceding remarks, to report that for the relation between the catch and the fry introduced a year later the correlation was somewhat higher.
From age, length, and weight samples given in Table II, and in the Egyptian Fisheries Reports for 1920, 1928-31, and 1933, estimates of the numbers of O group fish caught in 1920, 1928-31 and 1933 have been devised and shown in Table I. The numbers have been obtained by dividing the estimated mean individual weight into the weight of the Tobar landings for the periods August-December of the appropriate years. These estimates may be compared with the corresponding fry introductions.
It will be seen that in 1920 nearly a million fish of commercial size were taken out of the lake within nine months of introducing about 4-7 millions. This is to say that it needed rather less than five fry to produce a marketable O group fish. By 1928 it took 50 fry to do this, and the O group caught had fallen to about 400,000— a fall which continued steadily until 1933. The number of fry necessary to produce one commercial O group fish increased until in 1930 it was nearly 800, but thereafter it went back to 269 in 1931 and 132 in 1933. These observations suggest that the conditions for survival must have deteriorated throughout the period. Against this it must be remarked that the estimated proportions of O group fish in the August- December catch, where they may form part of the spawning shoals, fell from 42% to 17% between 1928 and 1935, and it may be that more O group stayed on in the lake to become 1 group in this period. Nevertheless, from 1929 to 1931, when the percentage of O group was steady, it appears that the O group numbers continued to fall, and survival conditions were still getting worse.
Catch, Effort and Lake-level
The catch (Fig. 1) may be broken up into five periods, three of adjustment and change and two in which some stability is indicated. These are. first a period o( increase from 1920 to 1923, during which the fry introductions built up the popula- tion followed from 1923 to 1926 by a period of stability during which the catch fluctuated around a level of rather under a 100 tons. Then in 1927 there was a rise immediately succeeded by a sharp fall through 1928 and 1929 to 1930. From 1930 to
254 f^- S. WiMPENNY
1933 the catch stabiUzed again at around 30 tons a year, and finally in 1934 and 1935 there were indications that a decline had set in once more.
The catch per boat also shown in Fig. 1 corresponds to the catch, and indicates that the latter is also a reasonable measure of the stock density in the lake. Consider- ing the catch as a measure of the stock, we may therefore try to account for the catch changes just mentioned as stock changes, finding it profitable to examine these in relation to the annual mean water levels shown in Fig. 1 . The water levels of such a shallow lake as Mariut must be considered as of very great importance in deciding the actual size of the habitat. The period of increase to 1923, due to fry introduction, followed by the stability or slight increase to 1926, were years in which the lake level oscillated between —2-75 and —2-90 m. In 1927, however, there was a sudden descent of 12 cm in this level, and in 1928 and 1929 of another 5, bringing the lake to —2-99 m. It is thought that this lowering of the lake made the fish more vulnerable to capture in 1927, and so explained the great increase in availability of the fishable stock. By 1928 the effect had begun to wear off, and the Annual Fishery Report for that year recording a failure of the whole fishery of the lake says, " This failure has not been confined to one or two particular species but has been one of the organic production of the lake itself. The usual rich growth of Ruppia maritima and floating algae was very much diminished and in some parts and at some times absent." The lake level returned to —2-94 again in 1930, but thereafter fell sharply away again to a new low record of — 3-21m in 1933 and remained at — 3-18m for the last two years.
The evidence on lake level, therefore, looks as if the fish stock had to make some new adjustments to its environment — a critical lowering of the lake level which appears to have begun around —2-94 or —2-95.
Age, growth and maturity
Samples taken from the lake at or around the spawning season in 1928-1931 and in 1933 are given in Table II. Length measurements were made to the centimetre below, and 0-5 cm added to allow for the distribution of length within the centimetre. Age was determined by scale readings, it having been proved by direct observations in ponds that a ring is laid down in the first scaled winter. The weights, direct in the case of the 1933 sample, were derived from the lengths in the remaining samples, using an age-length relation taken from samples of this species collected from Lake Mariut and near the entrance to Lake Menzala in November 1931.
The numbers at the different ages show that there are few that have been in the lake three winters or more (III+ group), and that the majority of the fish that are leaving or preparing to leave the lake to spawn have been therein for one winter after their introduction, and are on the eve of their second. This group has increased its pro- portion by weight during the period from 45 to nearly 60%, whilst that of the fish of the O group that are not quite one year old has declined from 42 to 17%. This relative decline of the O group in the spawning and pre-spawning shoals, seems most likely to be due to successively smaller O group recruitment enhancing the importance of the I group, which each represent an O group of superior strength in the previous year. The estimates of the numerical strength of the O group given in Table I support this suggestion; but it would be unwise to take these estimates too exactly, in view of the many errors involved when using such small samples as are available to me.
The production of Liza ramada (Risso) in Lake Mariul, Egypt 255
Another possible alternative or supplementary cause of this change might be a defer- ment of maturity of O group fish resulting from the increasingly adverse conditions in the lake.
With regard to growth there is also the appearance of a change in my samples between 1928 and 1933. For all ages the trend is upwards (Table II).
The continued diminution in the numbers of O group coming into the catch between 1928 and 1933 is difficult to reconcile with the apparent stability of the stock from 1930 to 1935, and it may be that this has been achieved by a deferment of maturity causing more of the O group to stay in the lake and away from the spawning shoals until they become I group, and by an increase in the growth rate. The observations however are quite insufficient to make this any more than a reasonable conjecture.
The Incidence of Mortality
The decline in the landings and almost certainly of the whole stock of L. ramada in Lake Mariut does not appear to have been directly attributable to changes in the supply of fry, for, as we have seen, four million fry at the commencement of the period is estimated to have produced about a million O group fish and in 1933 only a little over thirty thousand. Indeed we have seen that there is some indication that the strength of the stock in the lake may have influenced the supply of fry.
Undoubtedly the shrinking habitat of the lake caused by successive reductions in its level has been the cause of the big and successive reductions of numbers indicated by the estimates of O group fish shown in Table 1. We then come to the question at what period in the life of the O group fishes is this reduction in numbers brought about.
On the observations here available I am inclined to think that the mortality takes place very early in the period. If there were a mortality acting slowly over the whole first year's life, such, for instance, as overcrowding on a ground where the food supply was not adequate for the whole population, there would be a corresponding effect on the growth-rate which has not been observed. In these circumstances I believe that an early mortality, perhaps of a catastrophic kind, occurs very soon after or possibly during the actual introduction. It must be remembered that the little mullet on first introduction has a short gut and is able to eat plankton animals, but that later it develops a long and much convoluted intestine and becomes a vegetable and detritus browser. This change-over takes place at a very early age, and would produce a condition when a food shortage caused by a shrinkage of the available shallow water habitats due to a reduction of the lake-level might be critical, and cause an immediate thinning out of stock sufficient to explain the successive reduction in O group strength.
If this is so, it would mean that each year the lake accepted a certain number o\' recruits corresponding to the lake level. After this acceptance was over, there appears to have been enough food for the survivors to make normal growth. Indeed, as we see in Table II, there are indications that growth has been rather better as the lake
level has fallen.
The mechanism of this sort of mortality is of the greatest interest in the study ol the populations of our food fishes. The parts played by the nature of the organic and inorganic environment, and in particular the role of competition, presents problems for solution by careful observation and experiment.
256
R. S. WiMPENNY
Table I. Analysis of conditions for L. ramada fishery in Lake Mariut.
|
1920 |
1928 |
1929 |
1930 |
1931 |
1933 |
|
|
Fry introduced (millions) |
4-698 |
20-884 |
17-734 |
51-100 |
10-225 |
4-101 |
|
Total Catch (metric tons) |
47-604 |
133 006 |
64-751 |
26-666 |
33-700 |
36-934 |
|
Aug.-Dec. catch (metric |
||||||
|
tons) |
47-604 |
31-355 |
31-587 |
17-580 |
11-110 |
13-525 |
|
O group % by weight in ■ |
||||||
|
Aug.-Dec. catch j |
100 0 |
42 0 |
23-4 |
23-4 |
23-8 |
17-2 |
|
Estimated numbers of O |
||||||
|
group caught (millions) |
0-952 |
0-411 |
0-147 |
0-065 |
0-038 |
0-031 |
|
Fry for each O group fish |
||||||
|
caught |
4-73 |
50-8 |
120-6 |
786 0 |
269-0 |
132-1 |
|
Mean length of O group fish i |
18-0* |
16-3 |
18-8 |
21-2 |
20-9 |
21-3 |
* Mid-point of size range mentioned by Paget in the text of the Egyptian Fisheries Report for 1921.
Table II. Age, length and weight distribution of L. ramada samples from Lake Mariut.
|
Age groups |
O |
/ |
II |
111+ |
Total |
|
|
1928 Aug.-Dec. |
Numbers Mean length (cm) Mean weight (g) % weight of sample |
184 16-3 32 42-0 |
85 20-9 75 45-5 |
15 21-5 11 8-2 |
9 20-3 67 4-3 |
293 |
|
1929 November |
Numbers Mean length (cm) Mean weight (g) % weight of sample |
162 18-8 50 23-4 |
200 21-7 80 46-2 |
98 22-5 90 25-5 |
20 22 84 4-9 |
480 |
|
1930 November |
Numbers Mean length (cm) Mean weight (g) % weight of sample |
41 21-2 63 23-4 |
53 22-0 84 40-3 - |
36 22-9 96 31-3 |
6 22-7 94 5 0 |
136 |
|
1931 November |
Numbers Mean length (cm) Mean weight (g) % weight of sample |
44 20-9 70 23-8 |
62 23-4 101 48-2 |
24 251 123 22-0 |
5 25-7 132 5-0 |
135 |
|
1933 November |
Numbers Mean length (cm) Mean weight (g) % weight of sample |
21 21-3 76 17-2 |
63 22-3 88 59-8 |
18 24 0 110 21-4 |
1 26-5 146 1-6 |
103 |
REFERENCES
Bromhall, J. D. (1954), A note on the reproduction of the Grey Mullet, Mugil cephalus Linneus.
Hong Kong Univ. Fish. J., I, 19-34. Mortimer, C. H. (1954). Fertilizer in fishponds. Colonial Off., Fish. Publ., 5, 1-155. Various Authors. (1922-1926), Reports on the Fisheries of Egypt, 1920-1935. Government Press,
Cairo, Egypt, Page references not given here because 16 volumes are involved. WiMPENNY, R. S. (1936), The ova and larvae of Mugil capito Cuv. from Lake Qarun, Egypt. Ann.
Mag. Nat. Hist., (10), 17, 405^12.
Papers in Marine Biology and Oceanography. Suppl. to vol. 3 of Deep-Sea Research, pp. 257-2W).
The mortality rates of Antarctic fin whale stocks
By JoHAN T. RuuD Universitetets Biologiske Laboratorium and Statens Institult for Hvalforskning, Oslo
In 1820, William Scoresby, Jr., advanced the theory that the transverse striations occurring at regular intervals on the surface of the baleen plates of a whalebone whale afford an intimation of the age of the whale. Eschricht and Reinhardt (1866) did not agree with this proposal, although they did agree that the striations were due to a periodicity in the growth of the plate.
Stimulated by the need for a method of making individual and direct age deter- minations of whales, we have studied the surface structure of the baleen plates and their possible application to age analyses since 1939. At the same time and quite independently, A. G. Tomilin (1945) examined baleen plates in the collections of Russian museums.
In a series of papers (Ruud, 1940, 1945; Ruud and Jonsgard, 1950). we have shown that the transverse striations of the baleen plates are due to variations in the thickness of the cortical layer or enamel. We have also described how records made of these variations reveal growth periods which we have assumed to be annual. On this assumption we have developed a method for age analyses. The method has limited apphcabiUty because the baleen plates are subject to wear at their distal ends and therefore growth periods are gradually worn away.
We believe, however, that the age of fin whales in their first, second, third and fourth years (age groups O, I, II and III) can be determined with great exactitude, because of the presence of structures on the distal portion of their baleen plates, which indicate that this part was formed during the suckling period or during the first krill-feeding season. We assume further that our analyses of records from baleen plates of whales in age groups IV and V give fairly accurate results. Admittedly we can give only minimum estimates of the ages of older animals, because at some undetermined age the annual growth increment of the baleen plates is balanced by the annual wear at the tip; from then on we find a maximum number of 4 to 7 growth periods in the plates. Hence, our age groups above V should more correctly be VI + , VII + , and VIII + , meaning that older animals are telescoped into our three highest baleen-record groups.
For some years we have engaged in age studies of Antarctic fin whales. The material consists of baleen samples from catches of Norwegian pelagic expeditions in post-war seasons. Details concerning the material, analyses and results will be published shortly in Hvalradets Skrifter by Hylen, Pike, Jonsgard and Ruud. The histogram (Fig. 1) shows the percentage age distribution of the Antarctic fin whales taken during this period. In 1945/46 and 1946/47 our samples were small. It is therefore questionable whether they were representative of the catches, but since 1947/48 we have determined the ages of 850 to 1250 fin whales each season. Chi-square tests on length distributions show that our samples from the last six seasons are fairly representative of the catches from which they are drawn.
K 257
258
JOHAN T. RUUD
In the history of whaling there is ample evidence that whale stocks are easily over- fished and depleted, if not to extinction, at least to such a degree that whaling is rendered unprofitable. It is only natural, therefore, that we, who have witnessed the gigantic expansion of modern pelagic whaling operations in the Antarctic, are on the alert for signs of over-fishing of the stocks of blue and fin whales. Such signs are now evident: (1) increasing numbers of small and sexually immature whales in the catches which result in a decrease in the mean length, indicate a corresponding decrease in the average age and (2) decreasing catches per unit of effort threaten the
30
20 -
10 -
1945-46
30
20 -
10 -
0 - 30
20
10 -
a
1946-47
iIl:
R
_D
1947-48
o u 30 r
II
20 -
10 -
1948-49
'op 1949-50
20 -
10 - r
oL ,-. n
30 201-
10 -
30
20 -
10-
_n_
illl
nilil.
XI
Jiiii£
JJlL
niJL
30
20 -
10 -
1952-53
Jilal-
0 1 n HI Ez V 3ZI+ ■2n+'2in+ o i n m c? v "n+yn+'cni+
Fig. 1
economy of the industry. This trend is influenced to some extent by the changes in the varying regulations imposed on the industry. Hence, although the trend seems to be unmistakable, the extent of the depletion may well be disputed.
It is agreed that carefully planned and extensive marking experiments may produce conclusive evidence of over-fishing, because the rates of fishing can be estimated from the rates of recovered marks. However, extensive whale marking is costly and there are great losses in the recoveries. Many marks are probably shed before recapture, and marks are easily overlooked when the whales are worked up. It would be better therefore, if the age composition of the catches were known, because, as
The mortality rate of Antarctic tin whale stocks 259
shown by Baranov (1918) and others, the right limb of the curves representing the age frequencies of the catches enables us to calculate the total mortality rates, pro- vided that the following conditions are satisfied :
1. For the age groups in question, the mortality rate, or its complement, the survival rate, is uniform.
2. In these age groups, the samples used for age analyses are representative of the stocks.
3. The recruitment is uniform over a period of years; that is, each age group in question was initially of the same numerical strength as each of the others under study.
The first condition is satisfied as a rule in all stocks subject to high rates of fish- ing. As mentioned above, the second condition is satisfied fairly well for the last six seasons in our series. For the third condition, we can safely rule out the possibility that the recruitment to the stocks is increasing from year to year. The best we can hope for is a constant recruitment, or a recruitment fluctuating from year to year around a constant average sufficiently high to balance the losses from natural causes and from whaling operations. On the other hand, if the recruitment is decreasing, as it well may be, then the mortality rates calculated from the age distributions will be too low.
From the age distributions in Fig. 1, it can be seen that only groups TV and V of males and possibly groups III, IV and V of the females can be used in a direct calcula- tion of survival or mortality rates. Thus, the ratios of Vs to IVs calculated for the period 1947/48 through 1952/53 give annual mortality rates which vary considerably from season to season, from a minimum of 0T7 (females. 1951/52) to a maximum of 0-65 (males, 1948/49). The means for the period are 0-42 and 0-40 for males and females respectively. Great seasonal variations might be expected if there were great fluctuations in the numerical strength of the year classes. This seems unlikely in a mammal such as a whale.
Systematic errors in our interpretation of the baleen records may, however, result in over-emphasis of age group V, because some older animals may be placed in that group. Such mistakes might vary in number from season to season. If this is the case, the calculated mortality rates will be lower than the actual ones.
Consequently, it is desirable to develop a formula which enables us to consider the total material contained in the right limb of the age-distribution curve. This is possible if we assume that the older animals telescoped into our age groups VI -f, VII+, and VIII- should in reality be spread in a regular way over a number of older
age groups.
/A-\- B . . Thus such a formula for the annual mortality rate is: a = 1 —^ - — . where A
is the sum of two age groups supposed to be fully represented in the catches, and B the sum of all higher age groups: hence, A ^ B \s the sum of all age groups
considered.
We have formed the sum A from age groups III and IV of the females, and IV and V of the males, and used it in calculating the mortality rate for the individual seasons. These results show much less seasonal variation; namely a minimum of 019 and a maximum of 0-34 for females, and a minimum of 0-29 and a maximum of 0-49 for
260 JOHAN T. RUUD
males. The mean mortality rate for the period 1947/48 through 1952/53 is 0-22 for females and 0-34 for males, with 0-28 as an average for both sexes. It should be borne in mind that this is either the true mortality rate, or, what is more likely, it is too low.
It is assumed that the female fin whale has her first pregnancy at an age of 3 or 4 years, and that she gives birth to one calf every second year. The maximum rate of increase for the stocks of fin whales should thus be 0-25 per adult per year. We know nothing about the annual mortahty rates of immature age groups, but most hkely they are considerable, because some will be taken in whaUng operations (compare the left limb of the age distribution curves). It must be assumed, therefore, that the real rate of increase for the whole stock of fin whales must be significantly lower than 0-25 per year.
Since the annual mortality rate calculated above was 0-28 or more, the inevitable conclusion is that the Antarctic stocks of fin whales were overfished in the period 1946/47 through 1952/53. In that period the annual catches were about 21 thousand fin whales. In subsequent seasons they have increased to more than 27 thousand fin whales per year. Unless the stocks have increased, this means increased mortahty rates also, and the stocks are being heavily overfished.
REFERENCES
Baranov, F. I. (1918), On the question of the biological foundation of fisheries. Bull. Bur. Fish.,
Petrograd, 1 (1), 81-128. EscHRiCHT, D. P., and Reinhardt, J. (1866), On the Greenland right whale. In: Recent memoirs
of the Cetacea, London, 1-143. Ruud, Johan T. (1940), The surface structure of the baleen plates as a possible clue to age in whales.
Hvalradets Skrift. 23, 1-24. RinjD, Johan T. i[1945). Further studies on the structure of the baleen plates and their application
to age determination. Hvalradets Skrift. 29, 1-69. Ruud, Johan T., and Jonsgard, Age (1950), Age studies on blue whales taken in Antarctic seasons
1945-46, 1946-47 and 1947^8. Hvalradets Skrift. 33, 1-66. ScoRESBY, W., Jr. (1820), An account of the Arctic regions. Edinburgh, 1. ToMiLiN, A. G. (1945), The age of whales as determined from their baleen apparatus. C.R. Acad.
Sci., U.S.S.R., 49 (6), 460-463.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 261-280.
Fish origins fresh or salt water?
By Alfred Sherwood Romer Museum of Comparative Zoology, Harvard University
Summary — There are discussed various general considerations entering into palacontological study of the problem as to whether the early evolution of fishes took place in fresh or salt water. Opposite conclusions as to the typical habitat of Silurian fishes have been reached by the author and Grovl on American evidence, on the one hand, and Gross, mainly concerned with European material, on the other. An attempt is made to reconcile this difference. Part may be due to the very different histories of the two continents in Silurian times. Close examination of the stratigraphy of European fossil fish localities suggests that many deposits which are often regarded as marine are of continental or near-continental nature. It is concluded that the evidence, taken as a whole, points strongly towards fresh waters as the common Silurian fish habitat.
INTRODUCTION
It is generally agreed that the early chordates originated, as in the case of all major animal groups, in the sea. But many of the more ancient geological records of fishes are from sediments of continental type, and the possibility that fish evolved in inland waters was long ago seen as a distinct possibility. T. C. Chamberlin in 1900 noted theoretical considerations favouring a fresh water origin, but failed to give any detailed consideration of the actual fossil evidence. In 1923 MacFarlane (a botanist!) wrote an entire volume attempting to prove the fresh water origin of fishes; but this cannot be taken too seriously as proof of the case, for the argument is a forced one in many regards, and MacFarlane's general attitude is that of the King of Hearts in A/Ice In Wonderland — " Verdict first, evidence afterwards "'.
Two decades ago I determined to make a study of at least a considerable body of the available fossil evidence. In this I associated myself with Dr. Brandon H. Grove. My own inclinations at the time were mildly in favour of the hypothesis of a fresh water origin; Dr. Grove (a student of invertebrate palaeontology) favoured, on the contrary, an early marine habitat. Under the circumstances any conclusion, one way or the other, which we could jointly reach, might be reasonably considered as attained in objective fashion. We decided to restrict our study to an attempt to determine the environmental conditions surrounding all fish finds recorded from North American pre-Carboniferous rocks. Our upper time boundary was set for the reason that by the end of the Devonian there definitely existed both fresh and salt water fish faunas and there was no need to go further. We limited ourselves to North .America in a belief that the American record would give us a representative sample of the total world assemblage without our being forced to a consideration of European localities- localities with which we were personally unfamiliar and concerning many of which we would have had difficulty in obtaining exact data.
The results of our study (Romer and Grove, 1935) led both of us strongly to the belief that the early vertebrates were continental forms and that Devonian and later marine types had invaded the seas from fresh waters. As summarized in the left-hand column of Table I, all American Silurian finds were indicative of a fresh water environ- ment; during the Devonian, however, there was an increasing trend toward the sea,
261
262 Alfred Sherwood Romer
SO that by the end of that period a truly marine as well as a continental fish fauna had been established.
At the time that we were considering the fossil evidence, the same general question was approached from an entirely different direction through the kidney studies of Homer Smith ; these are to be found summarized in various papers and books by that author (1932, 1936, 1953, etc.); his conclusions are briefly discussed in my text, "The Vertebrate Body" (1955). His studies furnish extremely strong proof that the early history of vertebrates was passed in fresh waters. It is well known that typical vertebrates cannot exist unless their blood and body fluids contain a specific series of salts in a given concentration which is considerably lower than that of sea water. The most generalized type of vertebrate kidney is a structure that functions most especially as a " pump " to rid the body of excess water rather than merely furnishing (as in the case of many invertebrate nephridia) a means for disposal of metabolic wastes.* Such kidneys are found in all fresh water fishes and amphibians. These animals live in an environment where death would ensue, owing to osmotic dilution of the salt content of their blood and body fluids, were not such a " pump " present to rid the body of excess water, thus keeping up a proper salt concentration. Salt water fishes live, on the other hand, in a water medium containing a higher concentration of salt than their body fluids and hence equally dangerous to existence. A marine fish must avoid the danger of becoming too salty in its body fluid content; it may do this either by conserving water or by excreting excess salt, or both. Actually two very different methods are found in the two major groups of marine fishes. Salt water bony fish have solved the problem by (1) the development of salt excretion in the gills, and (2) in many instances by kidney modification which reduces the water outflow. Sharks, in contrast, have retained the " pump " type of kidney present in fresh water forms, but nevertheless prevent excess salinity of the blood by a most unusual specialization — the retention of considerable amounts of urea in the blood, so that blood and sea water are in osmotic balance and hence loss of water through surface membranes (and consequent dehydration) does not occur.
These two contrasting types of marine adaptations are not derivable one from the other; the two can have as a common origin only the kidney type found in fresh water forms. This is, therefore, the ancestral type. Hence the ancestral fishes must have lived in inland waters, and sharks and bony fishes must have independently invaded the sea.
1 had hoped, since the time of our earlier publication, to be able on some occasion
* Amphioxus is remarkably similar to the vertebrates in almost every basic feature, and practically every student of vertebrate history agrees that this little marine chordate is closely related, in some fashion or other, to the primitive vertebrates. Amphioxus, however, does not have a kidney of vertebrate type, but in contrast has nephridia comparable to those of certain marine organisms quite unrelated to the vertebrates. For this reason Smith (1953) has felt forced to deny the relationship of Amphioxus to the vertebrates — this despite the strong evidence to the contrary seen in almost every other structural regard. This attitude seems to me quite unnecessary; in fact this contrast in kidney structure can be fitted satisfactorily into the assumed history. Although I am not aware of any precise functional study of the Amphioxus nephridia, these little organs appear to be (like comparable structures in many other invertebrates) primarily for the elimination of nitrogenous wastes, and not too efficient as eliminators of water. With the invasion of fresh water by the ancestral vertebrates, water elimination in quantity was a basic necessity, and the vertebrate kidney was evolved de novo as a water pump. But the kidney can also act as an eliminator of waste, and if nephridia were present in the fish ancestors, they could be done away with in safety once the new kidney mechanism was established. Thus the presence of nephridia in Amphioxus need not debar this animal from the vertebrate " family circle ".
Fish origins— fresh or salt water? 263
to extend our palaeontological study to the European deposits, much richer in Silurian and Devonian fish locaHties than North America, but had hesitated to do so because of the amount of time it would have taken to familiari/e myself with the complex stratigraphic situation involved. To my delight, this topic is now covered in an excellent comprehensive work by Gross (1950). In this he summarizes the pre- Carboniferous fish faunas of the entire world; since but few finds have been made in continents other than Europe and North America, the major new contribution is his careful review of the numerous and varied European assemblages. As one topic. Gross considers the fresh vs. the salt problem. Although he had previously voiced his belief in a marine origin for fishes (Gross, 1933, 134, etc.), he nevertheless treats the matter in a properly objective fashion. All finds from each locality are listed by genus or species, his conclusion as to the marine or continental nature of the desposit is stated, and totals for the two environments are computed.
For comparison, I have listed his summarized figures for the Silurian and the three subdivisions of the Devonian parallel to my own in Table I. For the Devonian stages we are in complete agreement. We both find that in the early Devonian, fishes were dominantly continental in habitat, but that there was a strong trend toward establish- ment of an important marine fauna before the end of the period.
As regards the Silurian, however, there is radical disagreement between our two studies. The American " sample " suggested that Silurian fishes were nearly or completely fresh water in habit, with the first marine invasion taking place only about the beginning of the Devonian. Gross, on the other hand, believes Silurian fishes to have been predominantly marine; following this, his figures indicate that there was a sharp shift to a fresh water life in the early Devonian and then a strong reverse trend toward the sea.*
It is to a more detailed consideration of the European Silurian record that (following consideration of some general questions) the present paper is devoted. Not so much
Table I Percentage of forms in seemingly fresh water deposits at successive horizons. Left, Romer and Grove i\935) for finds from all North American localities, right, for world totals by species as given by
Gross (1950, table IV)
|
Romer and Grove |
Gross |
|
|
U. Devonian |
29 |
50 |
|
M. Devonian |
13 |
64 |
|
L. Devonian |
77 |
81 |
|
U. Silurian |
100 |
36 |
* The sharp marine-continental shift indicated by Gross's figures would be turthcr accentuated if the American finds were excluded and if, as is done by many workers today, the Dountonuin and its equivalents were included in the Devonian. In this case, the apparent mcrcasc in Ircsh Nvaicr fishes from Upper Silurian to Lower Devonian instead of bemg from 36 per cent to M per cent would have been from close to 0 per cent to about 90 per cent !
264 Alfred Sherwood Romer
because of my own limited work on the fossil evidence as because of the seemingly conclusive nature of the evidence from kidney studies, I find it difficult to accept the conclusion to be drawn from Gross's figures that fishes were entering fresh waters in major numbers for the first time at such a late period in the evolution as the end of the Silurian. Further, I find it difficult on ecological grounds to conceive of circumstances under which a sudden and almost unanimous surge of fishes from the ocean into the streams at the end of the Silurian would be immediately followed by a Devonian reverse migration of nearly as strong an intensity. An inquiry into the nature of the supporting evidence seems warranted. The reader, however, must be warned that this present inquiry lays no claim to the objectivity in treatment which I believe was true of the work in the Romer-Grove paper. Our conclusions there favoured a fresh water origin, but were, of course, far from definitive ; the evidence for this same conclusion based on kidney structure is, however, of so substantial a nature that I am firmly convinced of its validity and hence find it difficult to believe that the palaeontological evidence truly indicates the opposite conclusion. The present discussion is thus, frankly, an attempt to reconcile Gross's presentation of the Silurian fauna with the — to me — more probable thesis that the ancestral vertebrates (and hence presumably those of this period) were in the main fresh water forms.*
GENERAL CONSIDERATIONS There may be noted here certain of the problems and difficulties encountered in attempting to evaluate the environment of early fishes. Most of the factors concerned (to my anguished regret) increase the difficulty of gathering evidence in favour of a fresh water origin .
Paucity of early continental sediments
If we were concerned with Tertiary deposits, a solution might be much more readily attained. From the late Cretaceous onward the fossil record includes not only abundant marine beds but also numerous formations of a definitely continental nature. But, as even an elementary consideration of geologic history would suggest, the continental record becomes increasingly scanty as we travel backwards in time. Period by period, successive cycles of erosion have tended to do away with inland and upland deposits, so that for the older epochs the sediments preserved include very few truly continental beds. The Mesozoic record of fresh water and terrestrial life is a fragmentary one. In the Upper Palaeozoic, extensive continental beds are rare, although they may be preserved in a few relatively stable areas, such as the South African Karroo. Going back to the Lower Palaeozoic, the elapsed time for the operation of diastrophic and erosional forces has been so great that practically no truly continental beds of that age survive today; the record is almost entirely marine- Our knowledge of the possible continental life of the Silurian and older periods is thus
* It would be unfair to be unduly sceptical of the reality of the " double shift ", salt-to-fresh-to-salt, which Gross's statistics would indicate, unless the data be broken down into its components. Might it be that this seeming anomaly has no real existence, and that the shift in the statistical totals is caused by changes in abundance of various groups and by the appearance of new groups which alter the total complex of the fauna without themselves changing notably in their environment? If the faunal components in Gross's Table IV be considered separately, it will be seen that of the major groups present in the Silurian, the ostracoderms (Agnatha), show no reversal of trend. However, the two remaining Silurian groups, the acanthodians and arthrodires which together form a large percentage of the statistical material, show, in Gross's table, a very sharp reversal.
Fish origins— fresh or salt water? 265
essentially confined to the inferences which may be drawn IVoni such lew marginal deposits, of dehaic and other coastal regions, which have alone survived.
But while the rarity of ancient deposits of typically continental type makes it difficult to estabUsh the presence of fishes in early fresh water, this very condition in itself affords strong support to the fresh water hypothesis. A startling feature of early fish history is the way in which, in late Silurian and Devonian times, one major group after another appears on the scene quite suddenly and yet fully difTerentiated, with little or no trace of ancestors in earlier deposits. The most reasonable explanation of this remarkable situation is that the early evolution took place in inland waters, and that our dearth of knowledge is due to the dearth of ancient continental sediments.
Importance of negative evidence
Seeing our newspapers filled with reports of murders, robberies, suicides and the like, we sometimes lament the fact that the reader of such journals tends to gain the impression that all men lead lives of violence, whereas in reality nearly all are peaceable citizens leading humdrum lives that are not at all newsworthy. The case of the pre- Devonian vertebrates is quite comparable. Proponents of a marine origin point with pride to the occurrences of vertebrates in relatively small numbers in a limited series of Silurian marine — or supposedly marine — deposits. What is not remarked is the much more important fact that in the vast majority of Lower Palaeozoic marine formations there is not the slightest trace of any vertebrate. Such marine deposits are widespread and highly developed, and frequently carry abundant invertebrate faunas — but no vertebrates.
If the early vertebrates were marine, why are they not commonly found in such beds? A variety of possible explanations has been advanced by proponents of marine origins and may be briefly discussed, seriatim. (1) Since vertebrates are relatively rare in marine beds, lack of specimens is due to the chances of random collecting. But this is unsatisfactory; in all post-Silurian periods, vertebrates, although seldom common, are nevertheless found in a great variety of marine beds. (2) Vertebrates did not evolve until the time when we begin to find them in marine beds. But vertebrates are known well down in the Ordovician. (3) Vertebrates were present earlier, but did not develop a hard skeleton until late Silurian times. But the few known Ordovician vertebrates were already well ossified. (4) Vertebrates were present in the ancient oceans, but acquired a bony skeleton capable of preservation only when they invaded fresh waters. This is a rather better argument. One thesis is that there might have arisen on entrance to fresh waters some physiologic condition causing deposition of calcium salts in the dermis. But the armour of ancient ostracoderms and placoderms is of varied and complex patterns, not a mere random deposition of calcium, and later fishes show no sign of physiologic discrimination between fresh and salt water as regards degree of ossification. I have myself aided the argument somewhat by the suggestion (Rosier, 1933) that vertebrate armour was important in defence against eurypterid enemies. Perhaps armour did arise on entrance into fresh water in connection with defence. But unless we believe that bone arose independently a very considerable number of times in the vertebrates, this does not aid the marine argument. And finally, under this sub-topic : if it be argued that presence of bone and fresh water life are correlated in early vertebrate history, claims that most Silurian vertebrates with armour were marine must be abandoned—" one cannot eat one's cake and have it too '*.
266 Alfred Sherwood Romer
Although believing strongly in a fresh water origin for vertebrates, I must confess I am surprised, not at the fact that there are a certain number of reports of reputed marine vertebrates from the Silurian, but rather at the fact that, when such reports are carefully scrutinized, there are so few instances of unquestionable marine occur- rences. During the Devonian and later periods there were various incursions from fresh water into the sea ; similar incursions of ostracoderms may well have occurred earlier. The record suggests that, on the whole, the Heterostraci were a relatively euryhaline group and may have had marine representatives in the Silurian, as appears rather definitely to be true in the Devonian.
Biocenosis vs. necrocenosis
Our object is to determine the conditions under which the early fishes lived. Study of the beds in which fossil remains are found does not necessarily tell us this. Habitat in life and place of burial may be far removed from one another. If a cadaver is destroyed by predators, its remains may be buried on the spot. But if the trunk of a dead fish remains intact, gradual decomposition results in buoyancy, and the cadaver may be transported by currents far from its proper habitat before settling to the bottom. The fact that water runs down hill works strongly to the detriment of one advocating a fresh water origin. An inland stream-dweller will tend to be carried down to lower reaches of a river system ; forms living in a coastal region may be carried out to sea, with resulting ecological confusion. If fish specimens in a given formation are abundant and well-preserved, a life habitat in or close to the spot where they are found is strongly indicated. If rare and fragmentary, remains in a marine deposit strongly suggest transportation by currents; but whether transportation from another marine locality or from fresh water cannot, of course, be proven.
Identification of fresh water deposits
Marine sediments are frequently identifiable in ready and positive fashion; there is generally an abundance of invertebrates of dominantly marine groups. Identifica- tion of Palaeozoic fish-bearing beds as continental in nature is a much more difficult task, for the evidence is essentially negative in nature. Sediments are no sure guide. While limestones are highly suggestive of marine conditions, calcareous deposition may take place in inland waters, but on the other hand shales and sandstones, although presumably derived ultimately from continental areas, have been in large measure deposited under marine conditions. It is only in the case of coarse elastics and conglomerates that continental conditions, or an approach to them, are strongly suggested by sediments. As to the associated fauna, the absence of typical marine invertebrates suggests continental conditions. This does not, however, prove the case, for there are numerous marine areas today in which invertebrates capable of fossil preservation are absent, and there are numerous geologic formations which were obviously laid down in a marine situation and yet contain few or no invertebrate remains. Further, absence of marine fossils in fish beds may be attributed by those advocating salt water environment to diagenetic removal, by solution, of carbonate shells once present. But this argument is one of which one may be reasonably sceptical if used too frequently.
In many Devonian beds which are generally agreed to be of a continental nature we find fishes associated with a sparse fauna including eurypterids, ceratiocarid
Fish origins — fresh or salt water? 267
crustaceans and very little, if anything, else (plant remains of probable Huvialile or terrestrial nature may be present as well). There are various Silurian deposits with a similar assemblage, and in default of evidence to the contrary, it is reasonable to consider them likewise continental in nature.
Need for detailed stratigraphic study
If a geologic formation or group is dominantly marine (or continental) in nature, it is frequently claimed that the fossil forms contained in it at every horizon must be entirely marine (or continental) in origin. Such statements should not be made or accepted without careful consideration of stratigraphic detail and possible facies differences. For example, the early Permian Redbeds of north central Texas in which I have worked extensively, are predominantly continental, with a wealth of terrestrial reptiles and fresh water amphibians and fishes. But it would be absurd for me to make a sweeping claim that all the fossil content of these beds (which includes, for example, a number of cephalopods) is of a continental nature. The deposit is a deltaic one, and from time to time the delta was invaded for a brief period by waters from a sea which lay not far away. When in doubt, it is thus important to know, in the case of such a continental formation, the exact horizon and locality from which a fossil has come before attempting to reach conclusions as to its ecologic position.
The same caution should be observed in the case of fossils contained in a dominantly marine formation or zone- — particularly so for fossils of the time under special consideration, the late Silurian, when over much of Europe there was occurring a transition from marine conditions to the continental " Old Red " of Devonian times. We are deahng with " Passage Beds ", tending toward and reaching deltaic conditions, where fluctuations of a very minor nature could readily cause alternations of salt and fresh water environments. Close examination of stratigraphic detail is requisite if the truth is to be sought for.
Fresh and brackish water invertebrates
Most invertebrate palaeontologists working in the Palaeozoic are dealing with marine faunas, and hence generally tend to assume, unthinkingly, that all Palaeozoic invertebrates are unquestionably marine. This was obviously not the case; there is an acknowledged, if small, fresh water fauna of invertebrates in the Carboniferous, and there is every reason to believe, on theoretical grounds, that at whatever earlier date a basal plant food supply had been established, an invertebrate fauna would have soon evolved to occupy this ecological niche. Before the close of the Devonian a continental flora of rather advanced and diversified nature was present. This must have had an antecedent history of some length. It is not necessary, however, to wait for the development of land floras to establish a fresh water biocenosis, and it may well be that fresh waters may have contained, as far back as the Cambrian, at least, a basal element in a potential food chain in the form of simple algae.
Two problems, among many, which must be *' solved " by any type of animal which attempts to leave the ocean and avail itself of the opportunities ofl'ered by a life in fresh waters, are: (1) physiological adaptations to counteract dilution o\' body liquids (with resulting death) in non-saline waters, and (2) some method — preferably active locomotion — for maintaining the population in an inland environment and preventing adults or young from being carried downstream, back the ocean.
268 Alfred Sherwood Romer
The modern fresh water invertebrate fauna is relatively sparse as compared with that of the ocean, but contains a considerable variety of types. As would be expected, sessile forms, and those with relatively poor locomotor ability, such as sponges, coelenterates, bryozoans and brachiopods are rare or absent; the molluscs, however, have achieved success by means of highly specialized modifications of developmental processes. More common are active-swimming bilaterally symmetrical forms including (in addition to fishes) a variety of members of the worm phyla and, most especially, diversified crustaceans, mainly phyllopods, cladocerans, copepods and ostracods. In addition to truly fresh-water assemblages, there are, of course, a variety of other invertebrates derived from both marine and inland faunas which are eury- haline, able to live in brackish water deposits of the sort which may be encountered in estuarine and deltaic regions (cf. O'Connell, 1916, 70-76).
Although it seems certain that a fresh-water invertebrate fauna containing elements analogous to those present today was developed at an early stage, little attention has been paid to this subject by invertebrate palaeontologists. As in recent times, however, most of the forms present would probably have been soft-bodied, and hence not likely to be fossilized, or of small size and hence liable to escape observation. In the Devonian and Silurian fish-bearing beds which are reasonably suspected of being of fresh-water origin recorded invertebrates are few in number. There are occasional reports of lingulids, Leperditia and a few other forms which may indicate a brackish layer or a brief incursion of salt waters. Two invertebrate types, however, occur time after time with fishes — ceratiocarids and eurypterids. It may be reasonably claimed that they are fresh water in habitat or are euryhaline forms which were able to inhabit, with fishes, fresh water streams into which typical marine life could not extend.
The ceratiocarids are small crustaceans, apparently of phyllopod affinities, which have attracted little scientific attention. Study of them from an ecological point of view should prove interesting. Dictyocaris is another phyllopod which has a distribu- tion likewise suggestive of fresh waters (Stormer, 1934).
The eurypterids are the one group of Palaeozoic invertebrates which exhibit such distinctive features in their apparent ecological surroundings that students of inverte- brate palaeontology have had to hesitate, at least, in their habitual tendency to claim a marine environment for all fossils. The eurypterid environmental picture is compar- able in many ways to that for the older fishes, but with somewhat less evidence for fresh water habitats. We can here but briefly note the main points in the discussion; among the major papers concerned are those of O'Connell (1916), Pompeckj, Versluys and other discussants in a 1923 symposium, and Ruedemann (1934, etc.); a recent resume is that of Prantl and Pribyl (1948, 108-111). Eurypterids are most abundant in the Silurian; they are rare earlier, and although surviving until the Permian become increasingly uncommon from the Middle Devonian onward. The post-Silurian forms are definitely fresh water, and these, together with certain of the Silurian finds, are often associated with fish faunas which likewise appear to be fresh water in nature. In the Silurian, however, the eurypterids occur in a number of situations in which the evidence for a fresh-water habitat is far from certain (as the " water limes ") and, further, are present to some degree in beds of definitely marine nature. As Prantl and Pribyl note, the " almost universally accepted opinion " today is that the eurypterids were fresh water organisms throughout their history. It appears to be rather generally accepted that occurrences of eurypterid remains in
Fish origins— fresh or salt water? 2 69
deep water deposits, such as graptolitic shales, are due to necrocenosis, the floating outward of cadavers or shed armour. But to Rueoemann and a minority of other workers, the number of occurrences of eurypterids in lagoonai and near-shore deposits suggests that the older Palaeozoic eurypterids were euryhaline, capable of living in sublittoral and neritic marine environments.
" No decision ? "
The work on kidney structure and function makes it reasonably certain that fresh waters were the original fish environment. However, it is obvious from the discussion above, that it is difficult to reach a positive confirmation of this conclusion from palaeontological studies, no matter how carefully conducted. Additional points are sometimes advanced which tend towards the discouraging conclusion that attainment of palaeontological proof is not only difficult but perhaps impossible.
WEST
DEVONIAN
EAST
Fig. 1. Diagrammatic east-west section through the Silurian of Pennsylvania, showing the transition from sediments of continental type at the east to an essentially marine section at the west. Known Silurian vertebrate occurrences are all in the eastern continental region, and although not confined to a single area, are here shown in approximately their vertical and horizontal position. Conglomerates and sandstones stippled; redbeds (essentially continental) hatched: limestone and other typical marine beds unshaded. (Modified from Moore; data from C. K. and F. M. Swartz.)
It may well be, for example, that the available material of early fishes is too late in date to be of great value. We have little evidence to go on before very late Silurian days, while the Ordovician scrap material shows that ostracoderms were well developed by the middle of that period and probably originated at a much earlier time. There may, therefore, have been considerable ecological shifting between streams and sea by Silurian times, so that evidence from that period may have little meaning in terms of truly primitive vertebrate environments. Again, it is possible that Silurian fishes may have been to a considerable degree euryhaline in nature, with an ecologically cosmopolitan range ; if such were the case, a distributional study would be meaningless. Still further, ontogenetic development must be considered. As Westoll (1945) has pointed out, it is probable that young ostracoderms had little or no armour, and hence cannot be found under normal conditions as fossils. In consequence we cannot
270
Alfred Sherwood Romer
tell where these " fry " lived; they may have stayed in the same environment through- out their lives, or may have migrated from salt to fresh waters or vice versa at the end of the larval period.
These are discouraging thoughts. But despite them, I feel it is nevertheless profitable to follow the known evidence as far as it can lead us.
THE EUROPEAN SILURIAN RECORD We now come to the specific problem under discussion — the fact that, while the North American Silurian fish fauna, although limited in extent, includes a series of finds extending over the greater part of the duration of the Silurian which is almost purely fresh water in apparent origin, the European record of fishes is confined almost entirely to the closing phases of the period and, according to Gross's interpretation, is dominantly marine in origin. How can these contrasts be reconciled?
Fig. 2. A map of the north-eastern United States area in Lower Silurian times to show the distribution of some major faunal elements. The midwestern region was one of typical marine conditions, with limestone deposition dominant. Farther east, toward the presumed land area, is a transitional zone with few fossils except the problematical Arthrophycus. The most easterly zone in which Silurian sediments are preserved is a seemingly continental deposit of conglomerates and sandstones with a
eurypterid-fis i fauna. (From Amsden.)
Part of the differences may be readily accounted for if we review the differences in the Silurian history of the two areas. In North America, as may be seen from the summaries in any standard text (as, for example, Moore, 1933, 159-177) the Mississippi Basin region was occupied throughout the Silurian by a sea. Along the eastern border of the present continent, however, there is believed to have been an area or areas of high land — the land mass of " Appalachia ", or an island chain. Throughout nearly the length of the Silurian period materials from this region were carried westward, to be deposited along the sea margins as conglomerates, sandstones and — particularly in late Silurian times — red shales. The gradual lateral change in sediments from eastern
Fish origins — fresh or salt water?
271
deposits dominantly continental in nature to western marine shales and limestones is well illustrated in the east-to-west section of deposits in Pennsylvania shown in Fig. 1, and the palaeogeography of the Silurian as a whole is well exemplified by the map for the early part of the period given by Amsden (1955) and reproduced in Fig. 2. The known vertebrates are present only in the most eastern and more dcfmiicly continental formations; there is no trace of any vertebrate in the marine beds to the west. This situation is in perfect agreement with the theory that the centre of distribu- tion of the vertebrates of that day lay in fresh waters.
In Europe, the Silurian geologic story is in strong contrast with that of North America. For most of the period much of Europe was occupied by a widespread ocean, in which were perhaps a few small islands; the shores of this ocean lay far to the north and east (Fig. 3). Toward the end of the Silurian, however, the oncoming of the Caledonian Revolution brought about an advance of the shore-line to the south,
Fig 3 Map of Europe to show changes in land-sea relations in late Silurian times At the end ol the Middle Silurian much of Europe was covered by a sea. Its northern shoreline (fulllme) is believed to have run Xng the northern part of the British Isles to central Scandinavia and then south-eastward through Finland and central Russia: islands are believed to have existed in Engand, in the rey.on of the oresent Belgian coast, and in Saxony and Bohemia. By the end of the Dou^tonian. continental ?oiSS had eSed southward over much of northern Europe (cross-hatched area). The Silurian verteb a"e loclS^^^^^^^^^ all lie within the area of advance of continental sediments or close
to the island areas. (Modihed from Born.)
over the areas indicated by cross-hatching on the map. This brought about the development in Downtonian times of beds of nearshore, estuarme and deltaic nature, leading to the characteristic Devonian continental deposits ot " Old Red Sandstone type It is in this area of advance of the shore-lines and oncoming ot continental conditions that nearly all of the European Silurian tish-bearing deposits, indicated by figures on the map, are to be found. The late appearance of fishes in the European sflurian is thus closely correlated with the late appearance of " transitional or truly continental beds in which remains of fresh-water dwellers would be expected.
Of the deposits numbered on the map, numbers 1 and 2 are recogni/ed by Gross as continental. The remainder are considered by him as dehmtely marine. Let us bnefly review the stratigraphic evidence concerning these depc.its to test the validity of such a conclusion. In doing so, 1 will restrict discussion to the materials considered
272 Alfred Sherwood Romer
in Gross's paper. As he has done, we will here include the Downtonian as part of the Silurian, although recognizing the growing tendency on the part of many strati- graphers to include it in the Devonian.
1 . Great Britain
In Great Britain (Jones, 1929; King, 1934, etc.) the Silurian was for most of its duration a time of marine deposition (Valentian, Wenlockian), and in correlation with this there are no vertebrates recorded until fairly late in the period. The upper Silurian Ludlow beds are likewise marine, but there are a few records of fragmentary vertebrate remains; Enghsh stratigraphers generally agree, however, that these are " strays " floated out from the shore-line of the advancing land areas at the summit of the Ludlow.
Vertebrates first appear in numbers in the famous Ludlow Bonebed, marking the arrival of continental conditions and the transition to the Downtonian. This last is obviously a deltaic formation. There are occasional eruptions of brackish to salt waters (as indicated by the presence of Lingula, etc.), but essentially it is a fresh- water deposit, with a paucity of invertebrates and a diversified fish fauna. As in many other Silurian and early Devonian continental deposits, the fishes are accompanied by eurypterids and ceratiocarids. The British record is thus consistent with beliefs as to the general fresh water nature of early fish faunas: fishes appear only as continental conditions are approached or reached.
2. Norway
Here again the fish record is clearly one indicating a fresh-water habitus. The Norwegian Silurian is restricted in area, and found mainly in the Oslo fiord region, as at Ringerike (Kiaer, 1908, 1924; Heintz, 1939). In Norway, marine Silurian beds are, as in England, succeeded by continental " redbeds " comparable to the English Downtonian but possibly somewhat earlier in age. In these beds typical marine fossils are absent; as usual, the vertebrates are accompanied by eurypterids and ceratiocarids. There are no vertebrates in the marine part of the section; fishes appear when continental deposits appear.
3. Podolia
The late Gotlandian and " Passage Beds " of Podolia contain a considerable fauna of vertebrates — about 24 types, described by Zych (1927), Brotzen (1933 a, 1936), and Stensio (1944) — which are similar to those of the continental Downtonian. However, there is a considerable marine fauna in the Podolian beds as a whole, and hence these forms are classed by Gross (46-49) as marine.
Let us, however, examine more closely the stratigraphic situation as described by KozLOWSKi (1929, 1-23; more recently summarized by Samsonowicz, 1950, 499- 503). KozLOWSKi distinguishes three successive Silurian stages. The lowest, the Skala stage, has a good marine invertebrate fauna; no vertebrates are present. In the second, Borszczow, stage there is likewise a good marine fauna. There are no reports of verte- brates except that Brotzen (1936) mentions that indeterminate acanthodian scales have been found. The fish remains are thus almost entirely confined to a final stage, the Czortkow, which is many ways comparable to the Downtonian, and is succeeded by typical continental Old Red deposits. Kozlowski cites a considerable marine
Fish origins— fresh or salt water "^ 273
invertebrate fauna from the Czortkow as a whole, but we should not jump to ihc conclusion that the fishes are intimately associated with this fauna. To cite (in trans- lation) KozLOwsKi's description (1929, 14) of the Czortkow, in part: " In the lower beds . . . the fauna is composed mainly of brachiopods, teniaculitcs, little ostracods and pelecypods. In the upper beds . . . the lentaculites and the brachiopods diminish progressively in number, while the leperditiids and the tishcs become more and more numerous. Finally, in the terminal beds ... the brachiopods are very rare (with the exception of lingulas), the fauna being principally made up of ostracods, among which the leperditiids dominate, filling entire beds, and of fishes; here one also finds frag- ments of Pterygotus. This difference between the fauna of the lower part of the stage and that of its upper part has been remarked on by most of the authors occupying themselves with the Silurian of Podolia. . . . However, the passage from one fauna to the other occurs in a gradual manner, and certain species characteristic of the first continue in the second until its disappearance. . . . This underlines the unity of the Czortkow fauna from its commencement until the moment when continental con- ditions have invaded the marine basin and put an end to its existence.""
KozLOWSKi further states, in litteris:
" Dans I'etage de Czortkow, en allant de sa base vers le sommet, on constate un developpement de plus en plus accentue du facies schisto-greseux. Ce que Brotzen appelle ' Uebergangsschichten " et ' Schichten mit griinen Sandsteinen " correspond a la partie superieure de la serie de Czortkow qui est separee de sa partie moyenne par un epais banc de gres micace. A partir de ce banc les gres et schistes dominent de plus en plus sur les calcaires a faune marine, ces derniers ne formant que de minces intercalations dans la serie schisto-greseuse. II me semble qu"on y a a faire a un empietement de plus en plus accentue du milieu continental sur le milieu marin. Et il est significatif qu' a ceci correspond un enrichissement progressif des sediments en restes de Vertebres, surtout de Pteraspides. Aujourd'hui— toutes mes notes ayant disparu pendant le guerre— je ne saurais dire si ces Vertebres se rencontrent seulement dans les couches de schistes et de gres ou s'ils se presentent egalement dans les intercalations calcaires a faune marine. Quoiqu'il en soit on a Timpression que leur presence dans le serie de Czortkow est essentiellement liee aux avancements periodiques des depots deltaiques dans le domaine marin. On y observe aussi que dans les inter- calations marines, en allant du bas vers le haut de la serie, les Brachiopodes sont progressivement remplaces par les Lamellibranches et surtout par les Ostracodes."
No extensive comment is, I think, needed. We have here an excellent example, in an area towards and over which continental Old Red deposition was advancing, of a transition from typical marine beds to brackish, presumably estuarine deposits, and to continental redbeds, much as in England or Norway. As in those countries, fishes appear in numbers only as continental conditions are approached. Far from indicating a marine fish habitat, the Podolian situation strongly supports the thesis that Iresh waters were the centre of Silurian vertebrate life.
4. Bohemia . , . •
We are here beyond the limits of the Downtonian advance of continental deposits from the north, but it appears that although much of Bohemia was covered by seas during the Silurian, there was present here an island area (ct. Fig. 3) which was the nucleus from which a larger land mass emerged in Devonian times. The Bohemian
274 Alfred Sherwood Romer
Silurian includes " Bandes " Ecj, Ee^, and Ffi of Barrande, termed ea, efi and ey by Kettner and Kodym (1919) and Boucek (1934). A certain amount of fish material is present which, as Gross notes (1950, 64-65), is as yet insufficiently described. Gross states that the beds containing fishes are " all of purely marine origin " and hence counts all the Bohemian fish as part of his Silurian marine assemblage. A closer examination of the actual sequence, however, suggests a somewhat different interpretation. The stratigraphy has been most recently reviewed by Prantl and Pribyl (1948, 67-73). Zones ea and e[3, which cover most of the extent of the Silurian^ appear to be typically marine. There are no described fish except for one and possibly tv^o spines of Onchus, with one of which some scales are associated; these are most reasonably regarded, like the equally rare fragments in the English Ludlow and in the Borszczow of Podolia, as strays from the adjacent land area.
In ey, the " Lochkov Limestones " there is a diversified fish fauna, although speci- mens are not abundant. Much of the Lochkov exposures show a typically marine reef facies; the fish, however, occur instead in a shaly facies in which a series of successive zones are present (Perner, 1918 a, 1918 b; Perner and Kodym, 1919, 1922; Prantl and Pribyl, 1948, 73). This facies is stated to be limited chiefly to a seam in the Radotin Valley between Prague and Kosor. The fish described by Perner occur in the lowest zone. Perner and Kodym (1922, 67) state that in this zone " other fossils are also rare "; since they give detailed faunal lists of invertebrates from all other Silurian horizons but name no invertebrates from this zone, it would seem that any non-vertebrate material present is inadequate to give evidence regarding ecological conditions. Following the fish zone is a layer of black bituminous limestones with thin intercalated shales, the lower part of which contains eurypterids and ceratiocarids but no other fossils. Above this, the remainder — and greater part — of the shaly facies contains typical marine invertebrate assemblages.
We have, thus, in the lower zones of the shaly facies of the Lochkov the familiar story of fishes, eurypterids and ceratiocarids with little or no indication of a marine invertebrate fauna. Far from indicating a typical marine environment for the Lochkov fishes, the evidence strongly suggests that their place of entombment was a near-shore and possibly deltaic deposit.*
5. Pas-de-Calais
A second " island " region, independent of the advance of the main Downtonian continental shore-line, is that of the Pas-de-Calais region of northern France. Here, Leriche (1906) has described from the late Silurian or Downtonian of pit number 6 of the Lievin mining company of Pas-de-Calais two species of Heterostraci which Gross appears to include in his marine list. The beds as a whole do contain good marine fossils; but Leriche (18-21) gives the section in detail, as shown below. This definitely
* Mr. Radvan Horny, of the Geological-Palaeontological Institute of the Charles University and Dr. Ferdinand Prantl, Vice-Director of the Narodni Museum (Prague), in letters received after completion of this paper, have furnished further information with regard to this situation. They feel certain that these beds are all marine in nature, but that, on the other hand, the fragment- ary and isolated condition of the fish remains indicates a necrocenosis, with post-mortem trans- portation from another habitat — quite possibly, of course, fresh water. It is obvious that the Bohemian fish faunas are of great interest, and it is to be hoped that our Czech colleagues will make a thorough study of them
Fish origins— fresh or salt water? 275
indicates that the fishes are not associated with the marine invcrtcbraics. The tigiires given are depths from the surface, in metres:
to 270-70 Typical Old Red sandstone (Gedinnian) with osiracoderms
270-70 to 295-80 Sandstones more drab than those above, micaceous,
somewhat calcareous; Cyathaspis harroisi at 278-281; no other
fossils reported 295-80 to 296-30 Dark blue schistoid sandstone with marine shells 296-30 to 298 Pale grey sandstone with Pteraspis i^osseleii 298 to 318-20 Dark blue schistoid sandstone with marine shells 318-20 to 331-70 Pale grey sandstone with Pteraspis gosseleti; a bonebcd
at base 331-70 to 350 Dark blue schistoid sandstone with marine shells 350 to 473 Marine beds of Ludlow age, with Dayia navicula, etc.
The section here is clearly comparable in its general nature to a typical English section — first marine Ludlow beds; then " Passage beds " in which final marine phases alternate with non-marine ostracoderm layers, including an initial bonebed; these are followed in turn by a typical Old Red sandstone of continental type.
6. Scania
The remaining European vertebrate localities are from the Baltic region. There are here excellent Silurian sections in the main typically marine in nature. As was true both to the north and west in Great Britain and Norway, and to the south in Podolia, we are in a region in which there was a change from marine to continental deposits at about the end of Silurian times. But although it is probable that typical " Old Red " deposits were formed in this area, none is preserved, and in consequence we are left to interpret the story from decapitated Silurian stratigraphic columns from which the terminal Old Red has been secondarily removed. Although the island of Gotland is the classic locality for study of the Baltic Silurian we shall use that of adjacent Scania instead, since but a single vertebrate specimen (not mentioned by Gross) has been found in Gotland, whereas Lehman (1937) has described numerous scales, spines and other fragments from Scania.
In Scania we find a Silurian sequence comparable in nature to those we have described in other regions. For most of its vertical extent the Silurian is purely marine in nature, including Rastrites, Cyrtograptus and colonus stages covering the Valentian and Salopian. The last is succeeded by the Oved-Rams^sa stage, generally equated with the Downtonian. As Born notes (1926, 160), this stage contains few invertebrates. " Es handelt sich hier um eine typische verarmte Fauna der Ober- gangsschichten, die zum kontinentaler Old Red uberleitet." The Oved-Ramsasa is composed mainly of coarse elastics. Limestone is found only in the lowest of four zones; it is followed by barren white and yellow sandstones; then by grey-blue clays containing fishes and eurypterids and also a variety of invertebrates; fuially by red sandstones containing nothing but Lingula and ostracods. The Oved-Ramsdsa is. thus, ecologically a Downtonian type of deposit. It is certainly no more marine in nature than an estuarine-deltaic situation, and even so. the fragmentary nature o\' the fish remains strongly indicates an upstream origin, with the remains, as Liuman
276 Alfred Sherwood Romer
suggests, brought to the area of deposition by currents. As far as I am aware, there are no published data showing the exact stratigraphic relation of the fish scales to the marine fossils contained in the same zone.
7. The Beyrichienkalk erratics
Among the numerous glacial erratics of the north German plain, a large percentage are derived from an upper Silurian formation termed the Beyrichienkalk which presumably was once widely developed in the west Baltic region but is now known only from erratics and deep borings (Krause, 1877; Roemer, 1885, etc.). A per- centage of the erratics have yielded scales and other fragmentary fish remains, best described by Gross (1947). From the nature of the case, the general stratigraphic situation cannot be determined, but the age is certainly quite late Silurian, and a general equivalence to the transitional Oved-Rarasasa beds is indicated. This is further suggested by such ecological data as can be derived from the erratics them- selves. In some cases, as the conglomeratic boulder described by Brotzen (1933 b), there may be no fossils other than the scales themselves; in other instances the scales are interbedded with invertebrate fossils. The remains are always fragmentary and the situation suggests, as in Scania, transport from a more continental type of habitat into an estuarine or near-shore deposit.
8. Oesel
Most famous, most interesting, and most controversial of all Silurian vertebrate deposits are those of the Baltic island of Oesel, Esthonia, famous since the days of EiCHWALD, Pander, Schrenk and Fr. Schmidt. The stratigraphy has been reviewed by HOPPE (1931). The lower to middle Silurian beds of Esthonia — the G, H and I stages — are purely marine in nature and, as would be expected, have yielded not the slightest trace of a vertebrate. The uppermost beds are those of the K stage of Oesel. The fauna is particularly interesting from an evolutionary point of view as the only notable vertebrate assemblage in the world which is clearly pre-Downtonian in age. Considered as a whole, K has an abundant invertebrate fauna, and hence Gross classes the numerous Oesel vertebrates as marine. As is generally the case, however, closer examination casts strong doubt on the truly marine nature of the vertebrate occurrences.
K is divided into four zones. Ki, the Rootzikiill-Karmel Zone, is a dolomitic formation which varies considerably in facies both vertically and horizontally. At several horizons in the western end of the island, notably at Rootzikiill and Wita, there are layers which carry an abundance of the familiar assemblage of eurypterids, Ceratiocaris, and a variety of ostracoderms — mainly cephalaspids with Tremataspis as the most common form. In the Kj zone as a whole only nine species of presumably marine invertebrates are recorded. Hoppe (43) notes that in the Eurypterus deposits proper the only definitely marine forms recorded are an Orthoceras and very rare specimens of Favosites and Conchidium; whether these are exactly in the fish- eurypterid layers or merely stratigraphically close to them is not stated by him. O'CoNNELL (1916, 143-147), after reviewing the earlier literature on this point says: " In summary, it may be said that the detailed sections bring out the sporadic occur- rence of the eurypterids in very thin beds, rarely intimately associated with the typical marine forms which occur in beds above and below the eurypterid marls."
Fish origins — fresh or salt water? 277
Quite in contrast is Ko, the Padel Zone. Here there is an abundant marine inverte- brate fauna, mainly of brachiopods and stromatoporites; forty-five species are listed. It is not surprising to find that eurypterids are unknown and that of fishes there are only isolated and apparently very rare scales of one species of Coe/o/cpis.
K3, the Kaugatoma Zone, is, again, typically marine, with a fauna of forty-one invertebrate species. Eurypterids are absent; fishes are found somewhat more commonly than in K2, but only in the form of isolated scales of Gomphoclus and a few spines of the Onchus type.
In the K4 or Ohesaare Zone, exposed only in a very restricted area of the island, we leave the limestone-dolomite formations typical of the lower zones, and find ourselves in a deposit characterized for most of its extent by a rapid alternation between thin limestones, typically crystalline and red in colour, and equally thin clay conglomerates; in a profile little more than 3 metres in thickness Hoppe distinguishes no less than 70 such alternating layers. The situation, as Hoppe notes, indicates that we are very close to the shore-line. There is a fairly good marine fauna in K4 as a whole, including 34 species of invertebrates. There are no eurypterids. There are, on the other hand, numerous remains of fishes. But nowhere are there articulated specimens, the whole material consisting of isolated scales, spines and fragments of various types, and Hoppe notes that the fish remains are not normally associated with the marine invertebrates, but occur only in bonebeds at three specific horizons.
In attempting to review this interesting Oesel series, the most striking general feature of the story is the fact that the fishes and marine invertebrates are (so to speak) " allergic " to one another. The beds here follow the " rule of thumb " which we have seen to apply in the Silurian in general : the more abundant the fishes, the fewer the marine invertebrates, and vice versa. Zones K, and K3 are typically marine, and fish are found rarely and only in fragmentary form; in K4 invertebrates and fish are both abundant but are not found in the same layers; in Ki fish (and eurypterids) are abund- ant and well preserved, while marine invertebrates are rare.
With regard to the scale and spine findings of Zones K2-K4, we have a situation comparable to that of the roughly contemporaneous Beyrichienkalk and the Scanian scale-bearing beds farther west in the Baltic. The fragmentary nature of the remains might be attributed to the work of scavengers if these fishes are considered marine or to disintegration during transportation from stream mouths if they are believed to be of fresh water origin. On the whole, however, consideration of the Oesel situation in its entirety seems to me to throw the balance rather strongly towards fresh water origin for these scales and spines.
The critical problem is that of Zone K,, with its abundant and well-preserved fauna. The assemblage here of fishes, eurypterids and ceratiocarids is one which we have seen repeatedly in Silurian and early Devonian localities which are clearly of fresh water nature, and O'Connell would have it that we are dealing here with a fluviatile deposit. I fail to be convinced that this is the case. The conditions of deposition suggest quiet waters, and the presence of at least a few definitely marine invertebrates strongly indicates that, for the beds as a whole, the region certainly lay no farther inland than could be reached by salt tidal waters.
On the other hand, claims that the eurypterid-fish beds are typically marine seem no better founded. The marine invertebrates reported are limited in variety and \cr\ limited in numbers and there is no published evidence, as far as I am aware, that they
278 Alfred Sherwood Romer
are closely associated with the eurypterids and fishes. Resort may be had to the supposition that the fauna was originally a typically marine one, and that diagenetic processes have removed most of the invertebrates. There has been a process of solution of carbonate shells in at least certain instances in the Ki Zone, but the known inverte- brate forms are adequately identifiable from the moulds remaining; considering the long series of students of these beds, had a richer marine fauna been present, indica- tions of it would surely have been discovered and described. Here, as in other instances, I find myself sceptical — reasonably, I think — of hypotheses which propose diagenetic disappearance of marine invertebrates exclusively in those beds of a series which carry fish.
On the whole, the evidence suggests that the eurypterid-fish beds of Ki are deposits laid down in lagoons in which on the average the water was of low salinity. With this much, I think most students of the subject would agree. From this point onwards advocates of fresh- or salt-water fish origins may reasonably disagree. (1) It may be assumed by those who favour marine origins that the lagoonal conditions were uniformily brackish during the time of deposition of the Ki beds and that the fishes were marine forms but euryhaline, tolerant enough of brackish conditions to exist here as well as in a normal marine environment. (2) Again assuming uniformity of brackish conditions, fresh water advocates may argue that the fishes of the time were normally inland dwellers but sufficiently euryhaline to descend to brackish waters. (3) A third possibility is that the lagoons were deltaic and fluctuated from time to time in salinity, with the fauna shifting from time to time between one of fish and euryp- terids when the waters were relatively fresh, and one with sparse invertebrates replacing them when the salt content increased.
All three assumptions are equally reasonable as far as the evidence from Oesel alone is concerned. I am strongly disinclined to accept the first hypothesis and tend to favour the second, and more especially the third; this not alone because of my admitted prejudice, but particularly because the complete lack, as we have seen, of any comparable fauna of fish of this age in any typical marine bed.
CONCLUSIONS
I have above reviewed all fish occurrences from the European Silurian (and Down- tonian) cited by Gross; these include all described pre-Devonian vertebrate finds except for those from the relatively few American continental localities previously studied and a few scattered European finds omitted by Gross or described too late to be included in his review. They may be grouped under the following headings :
(1) From typical marine deposits (as in England, Podolia, Bohemia) a very few rare and generally fragmentary remains, mainly scales or spines, which may most reasonably be regarded as strays.
(2) Finds in beds of Downtonian or " Old Red " facies of transitional or continental type, as in Great Britain, Norway, Podolia, Bohemia and Pas-de-Calais.
(3) Isolated scales and spines from late Silurian Baltic deposits (as the Beyrichien- kalk, Scania, Zones K2-K4 of Oesel) which are of somewhat questionable nature but on the whole reasonably interpreted as materials drifted out from the advancing shore-line.
Fish origins — fresh or salt water .' 279
(4) The Oesel Ki fauna of eurypterids and fish, which in iisclfcan be used as an argument for either fresh- or salt-water origins, but when viewed in the light of the whole picture is most reasonably interpreted on the hypothesis of continental origins.
In sum, the European record is in entire agreement with the thesis that the primary home of the vertebrates in Silurian times lay in fresh waters, and adds confirmatory evidence to the proof of fresh water vertebrate origins given by study of kidney structure and function. It is not at all improbable that evidence may be forthcoming that some vertebrates at least were euryhaline or even definitely marine in habitus as early as the Silurian. But unless or until a very considerable body of data of this sort — now lacking — be accumulated, I see no reason for serious consideration of a marine history for the early vertebrates. As I have said on an earlier occasion, " A consideration of selected portions of the evidence might permit of such an inter- pretation; but examination of the entire body of facts . . . leads unmistakably to the conclusion that the early vertebrates were dwellers in fresh water."
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?ERNER J -(^91 A vlriLflger Bench, (iber ^'^ ^f^r^'"-' /- f^'''""- -" "I--"" "'"' ■'" Fossiien verleilung in den F,-Schichten. Cnmclkl. J. Mm<n,l.. I9lh. Jlb-3-.
280 Alfred Sherwood Romer
Perner, J. (1918 b), O rybach z pasma Ffj (Lochkovske vapence) a vertikalnim rozslfeni zkamenelin
V techto vrstvach. Cas. Ndr. Musea Cesk., 92, 72-76. Perner, J. and Kodym, O. (1919), O rozcleneni svrchniho siluru v Cechach. Cas. Ndr. Musea Cesk.,
93, 3-19. Perner, J. and Kodym, O. (1922), On the zonal division and correlation of the Silurian of Bohemia.
Amer. Jour. Sci., (5) 4, 53-72. PoMPECKj, J. F. (1923), Gigantostraca und Scorpionida. Palaeont. Zeitschr., 5, 319-338. Prantl, F. and Pribyl, A. (1948), Revision of the Bohemian Silurian Eurypterida. Rozpravv Stat.
Geol. Cstavu Ceskoslov. Rep., 10, 60-1 16. Roemer, F. (1885), Lethae erratica. Palaeont. Abh., 2 (5), 1-173.
RoMER, A. S. (1933), Eurypterid influence on vertebrate history. Science, (n.s.) 78, 114-117. Romer, A. S. (1955), The Vertebrate Body. 2nd ed., Philadelphia. 644 pp. RoMER, A. S. and Grove, B. H. (1935), Environment of the early vertebrates. Amer. Midi. Natur.,
16 (6), 805-862. Ruedemann, R. (1934), Eurypterids in graptolite shales. Bull. New York State Mus., 27, 374-385. Samsonowicz, J. (1950), The Devonian in Volhynia. Acta Geol. Polonica, 1, 401-518. Smith, H. W. (1932), Water regulation and its evolution in the fishes. Quart. Rev. Biol., 7, 1-26. Smith, H. W. (1936), The retention and physiological role of urea in the Elasmobranchii. Biol. Rev.,
11, 49-82. Smith, H. W. (1953), From Fish to Philosopher. Boston. 264 pp. Stensio, E. a. (1944), Contributions to the knowledge of the vertebrate fauna of the Silurian and
Devonian of western Podolia. II. Notes on two arthrodires from the Downtonian of Podolia.
Arkivf. Zool, 35A (9), 1-83. Stormer, L. (1934), Merostomata from the Downtonian sandstone of Ringerike. Norsk Vid.-Akad.
Skr. I, Mat.-Naturv. KL, 1933 (10), 1-125. Stormer, L. (1935), Dictyocaris, Salter, a large crustacean from the Upper Silurian and Downtonian.
Norsk Geol. Tidsskr., 14, 267-298. Versluys, J. (1923), Die Abstammung und Differenzierung der Gigantostraken. Palaeont. Zeits.,
5, 292-319. Westoll, S. J. (1945), A new cephalaspid fish from the Downtonian of Scotland, with notes on the
structure and classification of ostracoderms. Trans. Roy. Soc. Edinburgh, 61, 341-357. Zych, W. (1927), Old-red de la Podolie. Trav. Serv. Geol. Pologne, 2, 1-65.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 281-286.
The production of antibiotics by plankton algae and its effect upon bacterial activities in the sea *
By E. Steemann Nielsen Department of Botany, Royal Danish School of Pharmacy, Copenhagen
Summary — Laboratory experiments with Chlorella and plankton diatoms show that small concen- trations of the algae produce antibiotics which highly decrease the bacterial activities, including respiration. If the concentration of organic matter is about the same as in natural sea water, the decrease in bacterial respiration is of a much higher order of magnitude than the rate of photo- synthesis of the algae.
The normal light and dark bottle oxygen experiments cannot be used for measuring organic productivity in oligotrophic water. Intense bacterial activities, which occur in the dark bottles as soon as natural sea water is enclosed in the bottles, are much reduced in the light bottles; thus there is an important difference in oxygen consumption between the two kinds of bottles, a difference which has nothing to do with photosynthesis. The disagreement for tropical oceanic water between the oxygen technique and the C-14 technique is thus easy to explain.
It is suggested that the average age of the dissolved organic matter found in sea water is some thousand years. This organic matter is most likely the most important food source— although indirectly — for the bottom animals living at very great depths.
INTRODUCTION
In PRODUCTIVE coastal areas the so called " light and dark bottle " o.xygen experi- ments originally introduced by Gaarder and Gran (1927) have been of great value for estimating organic productivity by the phytoplankton. Riley (1939), however, published results of such experiments lasting 3 days from the Sargasso Sea. which according to ail evidence is one of the regions in the oceans most scarce in organic life. According to Riley's measurements, this sea would be one of the most pro- ductive sea areas of the world— if not the most productive.
Steemann Nielsen (1954), by using the carbon-14 method, could not verify the high rate of organic production in the Sargasso Sea. On the contrary, this sea was found to be about the poorest area in all oceans regarding organic productions by the plankton algae. This result, on the other hand, is in absolute agreement with the general hydrographic conditions (minimum supply of nutrient salts), the low standing crop of phyto- and zooplankton found, and the scarcity of fish. It could further be shown that, theoretically, an organic production of the size claimed by Riley must be considered impossible in the clear water of the Sargasso Sea, where most light by far is absorbed by the water itself. The energy absorbed by the plankton algae is only sufficient for a small photosynthetic rate.
It could, however, be verified that the light and dark bottle oxygen cxpcnmcnis give results comparable with those obtained by Riley.
It is a well-known fact (cf. the next section) that the bacterial activities in sea water are highly intensified if the water is enclosed in glass bottles. The respiration rates
* Contribution No. 780 from the Woods Hole Oceanographic Institution.
281
282 E- Steemann Nielsen
found by using light and dark bottle experiments of long duration in tropical oceanic water must be considered almost entirely due to the increased bacterial activities. They do not tell anything about the rate of respiration under natural conditions in the sea. The smaller oxygen consumption in the light bottles as compared with the dark bottles (no oxygen production is ever observed) might of course be due to photosynthesis. A reduction of the bacterial respiration directly or indirectly due to light can, however, as well explain the fact. Originally (Steemann Nielsen, 1952) the idea of a direct bactericidal effect of sunlight was suggested. In the 1954 article it was, however, suggested instead that antibiotics produced by the plankton algae in light reduce the bacterial activity. It was shown first by Pratt et al. (1944) that antibiotics are produced by plankton algae.
Ryther (1954) suggests that the disagreement between the light and dark bottle technique and the 14C technique in tropical oceanic water is possibly due to (1) the supposition that plankton algae nearly exclusively respire the newly formed products of their photosynthesis and (2) the supposition that the rate of algae respiration is about equal to the photosynthetic rate in these waters.
Experiments presented by Ryther in order to give his suggestions an experimental background have now been repeated in this laboratory (Steemann Nielsen and Al Kholy, in press). No corro- boration of his results could, however, be obtained. These seem obviously to be the result of an un- satisfactory experimental technique. It is further shown that his suggestions would lead to some fantastic and quite unrealistic assumptions of what is going on in the oceans.
Ryther's suggestion that the algae nearly exclusively respire the newly formed products of their photosynthesis seems to be contradicted by the work of the Berkeley Group. According to Calvin and Massini (1952), algae in light respire, to a slight degree only, newly formed products. There is, however, as will be shown in a subsequent paper, really a connection between photosynthesis and respiration, although not of the extent supposed by Ryther. It has some influence on the measure- ment of the organic production by the 14C technique. Under very unfortunate conditions in nature the results from using this technique may possibly be up to about 15 % too low. Normally, however, the influence is negligible.
DISSOLVED ORGANIC MATTER IN SEA WATER AND ITS DECOMPOSITION
One of the most amazing statements about the sea is that by far the largest amount of the organic matter existing anywhere on this globe is found dissolved in the oceans. According to Keys, Christensen and Krogh (1935) the dissolved organic matter in water from all depths of the oceans corresponds to about 1 •2-2-0 mg C and 0-2 mg N per Utre. About 15 kg organic matter is thus found below every m- ocean surface. In comparison, the average annual net production per m^ by the phytoplankton is only about 1% of this (Steemann Nielsen, 1952).
Most of the organic matter produced by the plankton algae is presumably used rather soon for respiration in some organism or other. The magnitude of animal life in the sea could otherwise scarcely be explained. The organic matter dissolved in ocean water must therefore on an average be rather old, presumably several thousand years.
The nature of the organic matter in question has not yet been investigated. If the water is in situ, an extremely slow decomposition of the organic matter takes place. About 25-50 % is, however, readily decomposed by bacteria, if the water is stored in glass bottles (Keys, Christensen and Krogh, 1935; Waksman and Carey, 1935).
It has been shown by ZoBell and Anderson (1936) that the presence of solid surfaces is the factor which makes the bacterial decomposition of dissolved organic matter in ocean water possible. Small bottles in which the ratio — inner surface of
The production of antibiotics by plankton algae and its effect upon bacterial activities 2X3
the bottle : volume of the water — is high, give rise to a faster bacterial decomposiiion than bigger bottles, in which the ratio is lower. The addition of glass beads in the same way increases the bacterial activity. According to ZoBii.i. ( 1946) the influence of the surfaces may be explained (I) through accumulation of the organic matter due to surface activities, (2) by assuming that exoenzymes necessary for attacking the organic matter can only be maintained in sufficient concentration if solid surfaces are present.
In natural sea water, solid surfaces are of course found. The phytoplankton. zooplankton, and particulate dead material all have solid surfaces. In oceanic sur- face water these surfaces are, however, scarcely more than about 10 mm- per litre. In water from deeper layers they are much smaller. The inner surface of a one-litre bottle is about 10* as large.
The surfaces of plankton algae seem normally to be rather unsuitable for bacterial growth. If plankton algae are growing well, very few bacteria — if any— can be observed to be attached to their surfaces. If the surfaces of the algae are densely covered with bacteria, this indicates that they are not in a healthy state. The whole procedure of growing algae in a pilot plant, where it is impossible to keep the culture sterile, is based upon the fact that the culture itself is able to keep the bacterial activities at a minimum. This has been known for a long time. Thus Waksman et al. (1937) state that " The result . . . confirmed the previous observation that, in the presence of a living culture of Nitzschia (a plankton algae), the bacterial activities were very limited."
The statement above does not contradict the fact, often observed, that bacteria mostly are more abundant where a high phytoplankton population is found (e.g. Gran, 1933). The heterotrophic micro-organisms are first of all numerous at the end of a phytoplankton bloom. Beside bacteria, heterotrophic flagellates are also found. Due to the bloom of autotrophic organisms, relatively large quantities of easily accessible organic matter first of all originating from dying and half-digested cells, are contributed to the water. Solid surfaces apparently are not necessary for the bacteria attacking this easily accessible organic matter (no exoenzymes necessary?). They can thus also be in a real planktonic state.
It can be stated that the dissolved organic matter in sea water consists o\' the following components:
(1) matter very easily accessible for bacteria, (2) matter only accessible for bacteria if soHd surfaces are present, (3) matter which apparently cannot be de- composed by bacteria at all. In oligotrophic oceanic water, practically onl> the two last-mentioned components are found. If the hypothesis about the importance of solid surfaces for the bacteria to attack the normal stock of " old " organic matter is correct, a dense bacterial flora should always be found on the surface of plankton algae. As such a flora normally is not found, the algae must be able to prevent the development.
Pratt et al (1944) showed that the plankton alga Chlorclla produces antibiotics with a high effect on bacterial growth. The normal absence of bacteria in any amount from the surfaces of healthy plankton algae of all kinds indicates that all these spec.es produce antibiotics. The ability to avoid bacterial settlement to any higher degree by producing antibiotics may be considered to be a rather important condition, the lack of which would make these species fairly unsuitable lor aquatic lite.
284 E- Steemann Nielsen
As mentioned above, Pratt et al. (1944) showed that the antibiotics are given off by the alga to the water. In a sample of natural sea water containing phytoplankton, it must therefore be expected that the antibiotics produced are not only effective for the prevention of bacterial growth on the surface of the algae themselves, but also on other surfaces, thus on the inner walls of the experimental bottles.
EXPERIMENTS
Photosynthesis may be written CO2 + HgO^ (H2CO) + O2; respiration may be written (H2CO) + 02^ CO2 + H2O. Respiration by the plankton algae, and by all other organisms present, is going on both in the Hght and the dark, photo- synthesis by the plankton algae is going on only in the light.
When making experiments in which the amount of dissolved oxygen in the water is measured before the experiment, and in light and dark bottles at the end of the experiment, the difference in the O2 content between the initial bottles and the dark bottles represents the rate of respiration by all organisms. The rate of photosyn- thesis should be measured by the Og-difference in the light and in the dark bottles. A necessary condition is, however, that light neither directly nor indirectly decreases the rate of respiration, a condition which is not fulfilled.
Experiments were made in which bacteria were growing together with very few algae (the freshwater green alga, Chlorella pyrenoidosa or the marine diatom, Thalas- siosira nana). The rate of photosynthesis per number of cells was first measured in a special experiment using a sufficient concentration of the algae. The method was the same as used in the main experiment. There the concentration of the algae was made so low that it would have been impossible to measure the rate of photosyn- thesis by the Oz-production according to the normal Winkler technique. By counting the number of algae cells at the start and at the end it was possible to determine growth during the experiments, and thus the total rate of photosynthesis.
In the experiments with the marine diatom, sea water from the Sound enriched with some nutrient salts was employed. In the Chlorella experiments the culture solution D (OsTERLiND, 1949) was used in a slightly modified form. In both cases 7-8 mg glucose and 2-4 mg peptone was added per 1. The light intensity was 8,000 lux, the temperature 22° C. In every experiment 3 bottles of each kind was em- ployed. Two Winkler titrations were made with water from each bottle.
In order to get an incubation by bacteria, the culture solution used for the main experiments was incubated with 0-5 ml/htre of freshly collected surface water either from a lake near Woods Hole {Chlorella experiments) or from the Sound (the marine diatom). The water was filtered through a coarse paper filter before use.
In Table 1 is given a typical experiment.
Table I. Chlorella pyrenoidosa
Rate of photosynthesis (real assimilation) in preliminary experiment 1-46 ± 001 ml Oj/l per hour.
Dilution of the algae used in the main experiment 1 : 10000.
Duration of main experiment 72 hours — 3 light periods (44 hours together) alternating with 3 dark periods.
Rate of photosynthesis (real assimilation) by Chlorella in light bottles (corrected for growth) per 72 hours 004 ml02/l.
02-consumption in dark bottles per 72 hours 3-59 ::r 0-02 ml. Oj/l. Oj-consumption in light bottles per 72 hours 2-92 :r 003 ml O2/I. Reduction in Oz-consumption in light bottles as compared with dark bottles 0-67 ± 0-04 ml Oj/l.
The production of antibiotics by plankton algae and its cflcct upon bacterial activities 285
It is thus evident that the difference between the light and ilic dark bottles is not due to Chlorella photosynthesis. In a corresponding series made simultaneously but without Chlorella added the O2- consumption was the same in the light and in the dark bottles. The difference was 0-03 - 0-08. This indicates that no photosynthesiz- ing cells in any important number were introduced together with the bacteria, it further shows that light has no direct effect on the activity of the bacteria developing in the bottles. This is in accordance with the results published b\ Vaccaro and Ryther (1954).
There is no reason to give any details about the other similar experiments made, using either Chlorella or the marine diatom. The results are similar. The difference in oxygen consumption between light and dark bottles was between 12 and 30 times higher than the oxygen production due to the photosynthesis of the algae.
It turned out to be impossible in these experiments to use unsterilized, stored sea water. Products produced by the special bacterial flora developing made the use of Winkler titrations rather impossible. The water was therefore collected immediately before an experiment.
Experiments were made to investigate the influence of an addition of a substratum from which a rather dense, vigorously growing Chlorella population had been filtered off. Although a pronounced influence was found, the direct influence of a dilute Chlorella population was pronouncedly higher. By adding 4% of such a substratum at the start of an experiment lasting 2 days, only a decrease in Oz-consumption of 0-09 ml/1 was found. In the corresponding experiment the influence of a very dilute Chlorella population in the light bottles was 5 times as high. This is. however, in perfect agreement with the statements by Pratt (1948) according to which the concentration of the antobiotics produced by algae seems to be higher at a low con- centration of growing Chlorella than at a higher concentration.
The experiments presented in this article show that the presence of algae, presum- ably due to the production of antibiotics, effects a reduction in the Orconsumption of the bacteria in the light bottles. This reduction was of a higher order of magnitude than the Oo-production due to the photosynthesis of the algae. There is no reason to beUeve that the plankton algae living in oligotrophic oceanic water should not behave in just the same way. Thus it is not possible to use the light and dark bottle oxygen technique here. In eutrophic areas the technique is fully applicable.
In the culture medium used in the present experiments the organic matter present was easily accessible for the decomposing bacteria. It must be assumed that a number of different species took part in this decomposition. In oceanic water the dissolved organic matter presumably is only accessible for some few bacterium species able to excrete the necessary exoenzymes. It is therefore rather probable that the effect of the antibiotics produced can be still higher here. In the experiment shown in Table 1, oxygen consumption was reduced by 19",. in the light bottles. In light and dark bottle experiments in oligotrophic oceanic water the reduction is mostly more than 50%.
DISCUSSION
By looking at a series of light and dark bottle experiments made in the open ocean, it is evident that the rate of respiration in the dark bottles varies from one station to another. Thus the values published by Riley (1939) for 3 days" expermicnts u.th
286 E. Steemann Nielsen
surface water from the Sargasso Sea varies from 0-12 to 0-51 ml O2 consumed per 1. There is no reason to beUeve that the content of organic matter in the surface water of this rather uniform sea should vary much from place to place. It is more Hkely that the amount of antibiotics present in the water at the time it is collected varies somewhat from place to place. The time of the day for the collection may be rather important, too. Near sunset the concentration of antibiotics is possibly higher than near sunrise.
It is at present impossible to state if non-autotrophic organisms independent of light secrete antibiotics. This is by no means unbeUevable. Some observations on the Galathea expedition support this possibility. A verification is, however, needed.
Krogh (1934) — as he explained it himself — offered a vague suggestion that the animal hfe at great depths in the oceans depends on bacteria. At that time he knew the concentration of soluble organic matter in ocean water. He knew, too, that this organic matter normally was not decomposed by bacteria. He did not, however, know that a material part of this organic matter is easily decomposed if solid surfaces are present. At the sea bottom such soHd surfaces are present. A rather considerable decomposition of this organic matter is apparently going on here constantly. Most of the " old " organic matter diluted in sea water is most likely ultimately decomposed at the sea bottom. The bacteria living on this matter present most Hkely a very important, although not the only food source for the bottom animals at very great depths.
REFERENCES
Calvin, M., and Massini, P. (1952), The path of carbon in photosynthesis. (XX. The steady state.)
Experientia 8, 445-457. Gaarder, T., and Gran, H. H. (1927), Investigation of the production of plankton in the Oslo
Fjord. Rapp. Proc. Verb. Com. Perm. Int. Expl. Mer, 42, 3-48. Gran, H. H. (1933), Studies on the biology and chemistry of the Gulf of Maine. II. Distribution of
phytoplankton in August, 1932. Biol. Bull., 64, 159-182. Keys, A., Christensen, E. H., and Krogh, A. (1935), The organic metabolism of sea water with
special reference to the ultimate food cycle in the sea. J. Mar. Biol. Assoc, U.K., 29, 181-196. Krogh, A. (1934), Conditions of life at great depths in the ocean. Ecol. Monogr., 4, 430-439. Osterlind, S. (1949), Growth condition of the alga Scenedesmus quadricauda, with special reference
to the inorganic carbon sources. Symbolae Botanicae Upsaliensis, 10 (3), 1-141. Pratt, R., Daniels, T. C, Eiler, J. J., Gunnison, J. B., Kumler, W. D., Oneto, J. F., and Strait,
L. A. (1944), Chlorellin, an antibacterial substance from Chlorella. Science, 99, 351-352. Pratt, Robertson (1948), Studies on Chlorella vulgaris. XI. Relation between surface tension and
accumulation of chlorellin. Amer. J. Bot., 35, 634-637. Riley, G. A. (1939), Plankton studies. II. The western North Atlantic, May-June, 1939. /. Mar.
Res., 2, 145-162. Ryther, J. H. (1954), The ratio of photosynthesis to respiration in marine plankton algae and its
effect upon the measurement of productivity. Deep-Sea Res., 2, 134-139. Ryther, J. H., and Vaccaro, R. F. (1954), A comparison of the oxygen and "C methods of measur- ing marine photosynthesis. /. du Cons., 20, 25-34. Steemann Nielsen, E. (1952), The use of radio-active carbon (^^C) for measuring organic production
in the sea. /. du Cons., 18, 117-140. Vaccaro, R. F., and Ryther, J. H. (1954), The bactericidal effects of sunlight in relation to " light "
and " dark " bottle photosynthesis experiments. J. du Cons., 20, 18-24. Waksman, S. a., and Carey, C. L. (1935), Decomposition of organic matter in sea water by bacteria.
J. Bacteriol., 29, 531-543. Waksman, S. A., Stokes, J., and Butler, M. R. (1937), Relation of bacteria to diatoms in sea water.
/. Mar. Biol. Assoc, U.K., 22, 359-373. Zobell, C. E. (1946), Marine microbiology. Waltham, Mass., Chronica Botanica Co., 240 pp. ZoBELL, C. E., and Anderson, D. Q. (1936), Observations on the multiplication of bacteria in
different volumes of stored sea water and the influence of oxygen tension and solid surfaces. Biol.
Bull. 71, 324-342.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 287-297.
On the nature and action of coelenterate toxins*
By John H. Welsh The Biological Laboratories, Harvard University
Summary — Tetramethylammonium, known to occur in sea anemones, has been thought to be one or constituents of coelenterate nematocyst toxins. To test this suggestion it was first shown that the tendency to drop legs, or autotomize, in the fiddler crab Uca numlax, was reduced by previous injection of extracts of tentacles of two species of anemones and of Phy.sa/ia, the Portugucsc-man-of- war. It was then found that injected tetramethylammonium chloride or acetylcholine had similar actions to those of the extracts.
Further experiments of a comparable nature were done at another location, using as a test animal the shore crab, Hemigrapsus niidus. Extracts of tentacles of Metridiiiiih when injected into H. niulus, produced spontaneous autotomy of walking legs and chelae, followed by a degree of paralysis dependent upon the dose.
After the injection of tetramethylammonium chloride into H. niulus there were no spontaneous autotomies, but there was a type of paralysis similar to that produced by tentacle extracts.
Tetraethylammonium chloride, and a related compound called Banthine, were highly effective in blocking the autotomy-inducing and paralyzing actions of Metridiitm tentacle extracts. This is added evidence that a quaternary ammonium base similar to tetramethylammonium occurs in coelenterate tentacle extracts.
When Metridium and Cyanea tentacle extracts were tested on an isolated mollusc heart, evidence for the presence of an excitor amine was obtained. It appeared not to be histamine. Later experiments strongly suggested that the material with the marked action on the molluscan heart was 5-hydroxy- tryptamine, a known histamine-releaser and potent pain producer.
Through the use of paper chromatography further evidence has been obtained for the presence of 5-hydroxytryptamine in extracts of tentacles of Metridium and Physolia. This approach has also shown the presence of two or more quaternary ammonium bases, one of which has been tentatively identified as urocanylcholine, also known as murexine.
The pain producing factor in coelenterate tentacle extracts is probably 5-hydroxytryptaminc: while paralysis could be due to two or more related quaternary ammonium bases such as tetramethyl- ammonium and urocanylcholine.
The painful and paralyzing nature of the " sting '" of certain jellyfishes and the siphonophore, Physalia, is well known. Less well known is the fact that all coelenter- ates possess stinging organelles, called nematocysts, which serve two main functions; one, defence, and two, immobilization of prey for ease in feeding. The latter is well illustrated by a hydra subduing and engulfing a large and active Daphnia. The ability to produce a painful sting is not an indication of the amount of toxic substance prcseni in the tentacles of a given species; rather, it is the ability of the nematocysts to penetrate the skin. This ability varies greatly with species, and effective penetration of human skin is restricted to the nematocysts of relatively few species of coelenterales. For example, the sea anemone, Anemonia sulcata, has penetrants that enter the skin of the finger sufficiently to cause a stickiness between the tentacles and the skin, but seldom is there subsequent pain. However, when a tentacle of this species is placed on the tongue, a painful and long-lasting burning sensation results, indicating that
* This investigation was supported in part by a research grant (B-623) from the National Institutes of Health, Public Health Service.
287
288 John H. Welsh
the nematocysts have been able to penetrate the more delicate epithelium of the tongue.
Numerous attempts have been made to determine the nature of nematocyst toxins. Among the earlier studies were those of Richet, which began in 1902 (for complete report see Richet and Portier (1936)). He isolated two chemically unidentified substances which were named " thalassin " and " congestin ". Two papers summariz- ing much of the earlier work on nematocyst toxins are those of Thiel (1935) and SoNDERHOFF (1936). Recently, Boisseau (1952) has used histochemical procedures in an attempt to identify the capsular contents of nematocysts.
Coelenterates feed to a considerable extent on crustaceans, and there are close commensal associations between coelenterates and crustaceans (e.g. the several hermit crab-sea anemone pairs). It is natural, therefore, that attention should have been paid to the physiological action of coelenterate extracts when injected into crustaceans. Many interesting observations of this sort have been made by Cantacuzene (1925 a, B, 1926), Cantacuzene and Cosmovici (1925), Cantacuzene and Damboviceanu {1934 A, B, c), Cosmovici (1925 a, b, c, d, e), Rey (1940), Manuta (1943) and others. It is clear that extracts of coelenterate tentacles (the chief nematocyst-bearing struc- tures) have a powerful paralyzing action on crustaceans; also, that a crustacean which lives in close association with a coelenterate develops a resistance to the paralyzing factor(s).
This paper will summarize a series of observations on the chemical nature and physiological actions of nematocyst toxins. The studies were begun in 1950 and were subsequently carried on as part of a larger study on invertebrate pharmacology. Various localities have provided abundant experimental material, and different portions of the work have been carried out at the Lerner Marine Laboratory, Bimini, British West Indies; the Marine Field Laboratories of the University of Washing- ton, Friday Harbor, Washington; the Plymouth Laboratory, Plymouth, England; and the Bermuda Biological Station. I am indebted to the Directors and Staffs of these Marine Stations for the excellent facilities that have been provided. Work toward the identification of the active materials, mainly by use of paper chromato- graphy, has been done at Harvard University. Because the work at each laboratory was carried out on local representatives, it cannot readily be integrated. It seems best therefore, to give a brief account of the findings made at each location.
In view of Professor Bigelow's interest in the coelenterates, and especially the scyphomedusae, it is not unfitting that a discussion of nematocyst toxins be included in this volume. It is a privilege to dedicate this paper to one from whom I have learned so much.
I. OBSERVATIONS MADE AT BIMIN[ (MARCH 27-APRIL 7, 1950)
The earliest observations in this series were made at Bimini, and concerned mainly the effect of tentacle extracts and certain selected chemicals on the autotomy reflex of a species of fiddler crab. Welsh and Haskin (1939) had found the frequency of dropping of legs in certain crustaceans to be a sensitive indicator of the activity of injected substances, such as acetylcholine and adrenaline. On the assumption that nematocyst substance might act on some step in conduction or transmission of nerve impulses, the autotomy reflex was chosen as an indicator of such action.
Preliminary tests of three species of fiddler crabs found on North Bimini {Uca
On the nature and action of coelcnterate toxins 289
heterochelos (Lamarck), U. leptodactyla Ralhbun and U. mordax (Smith))* showed v. mordax to be most suitable. In all experiments to be reported here, this species was used.
Tentacle extracts were prepared from Physa/ia, the Portuguese-man-of-war, and from two common sea anemones, Condylactis gigantea and Aipiasia sp. The extracts were prepared by grinding a known volume of tentacles with an equivalent volume of sea water, either with or without the addition of enough hydrochloric acid to make the suspension weakly acid to litmus paper. If necessary, after filtration the pH was adjusted with NaHCOj until the solution was neutral. Extracts were diluted as indicated, and injected at the base of one of the last pair of walking legs in amounts varying from 002 ml to 0-05 ml depending on the size of the crab. Crabs were injected in lots of five, and after 5-10 minutes the walking legs were grasped firmly with forceps for one or two seconds while the crab was held in a fixed position. This was usually a sufficient stimulus to produce autotomy in an untreated crab. Legs were grasped in a random order (cf. Welsh and Haskin, 1939) and a record made of the number of autotomies in each crab. For each test the number of legs autotomized appears as the numerator of a fraction with a constant denominator of 40, this being the total number of walking legs possessed by 5 crabs.
Uninjected U. mordax, stimulated in the manner indicated, autotomized nearly all of their walking legs. Two lots of 5 males each dropped 36 of 40 legs. One lot of females dropped 37 of 40 legs. Two lots of males injected with 0-05 ml of sea water dropped 37 of 40 and 39 of 40 legs.
Table I shows the effects of extracts of three different species on the tendency to autotomize. It will be seen that the higher concentrations reduced the tendency to autotomize and even prevented any significant number of autotomies at the highest concentration used. The presence of a paralyzing agent in the extracts would account for such results.
Table 1 Effects of several dilutions of tentacle extracts on the autotomy reflex in Uca
mordax
Species
Physalia Aiptasia Condvlactis
No dilution 1:10 1:100 1:1000 1:10,000
0 40 5 40 23/40 40 40
0 40 7/40 40/40
0 40 9/40 14 40 36 40
The reason for the great effectiveness of the extract of tentacles of the sea anemone. Condylactis, is not entirely clear. This anemone may actually carry a larger amount of paralyzing substance than Physalia, in a given weight of tentacle, but the ground tentacles used in making this extract stood for a longer period before filtering than in other extractions. This may have released more active material into
solution.
Since U. mordax had responded to the extracts by showing clear signs ol paralysis and by a reduced tendency to autotomize their appendages, they were obviously
* Kindly identified by Dr. Fenner A. Chace of the National Museum. Washington. D.C. L
290 John H. Welsh
suitable for further study of possible paralyzing agents. The first to be tried was tetramethylammonium chloride (MeiN) for the following reasons: (1) it is a normal constituent of coelenterates (Ackerman, Holtz and Reinwein, 1923, and the hydroxide was named tetramine by these workers); (2) it has long been known to have curare-like properties in the vertebrates ; and (3) there were earlier indications that it caused paralysis in insects and crustaceans (Welsh, unpublished).
Tetramethylammonium chloride was dissolved in sea water and appropriate dilutions were made such that various amounts could be introduced by injection of a constant volume of fluid. After injection, legs were tested in the manner described for extracts. The results of two series of tests are given in Table II. It is clear that MciN is a moderately effective inhibitor of autotomy in U. mordax.
Since a tetraethylammonium salt (EtiN) often has an action opposing that of Me4N (e.g. Welsh and Taub, 1950), this was injected in amounts of 0-5 mg and 0-05 mg. At the lower concentration the frequency of autotomy was 36/40, 39/40 and 40/40 in three experiments. After Et4N, legs autotomized with remarkable ease.
Table II Effect of several concentrations of tetramethylammonium chloride {MciN) on the
autotomy reflex of Uca mordax
Me^N
Series 1 Series 2
5 mg 0-5 mg 0 05 mg 0 005 mg
0/40 11/40 30/40 38/40
0/40 22/40 30/40 40/40
If acetylcholine is involved in the normal autotomy reflex in U. mordax, as it appears to be in Petrolisthes (Welsh and Haskin, 1939), injected acetylcholine might facilitate autotomy or it might reduce it by raising the level to the inhibitory or paralytic range. With U. mordax, injected acetylcholine (0-5 mg/crab) reduced the frequency of auto- tomy. The triethyl analogue of acetylcholine (EtgAch) may antagonize acetylcholine (Welsh and Taub, 1950). When 0-5 mg. of EtsAch was injected into U. mordax, legs autotomized with remarkable ease when grasped, and in each series there was 100 per cent autotomy. When Mt^H and EtiN, or Ach and EtgAch, were injected simultaneously in 0-5 mg amounts, there was a significant antagonistic action between the pairs of compounds, and the tendency to drop legs was greater than with Me4N or Ach injected alone.
Atropine, which blocks Ach at certain neuro-eff'ector junctions, facilitated autotomy in U. mordax, when injected in a dose of 0-005 mg. Eserine, which prevents Ach from destruction by cholinesterase and therefore permits its accumulation, reduced auto- tomies to 31 of 40 at 0-001 mg and to 0 of 40 at 0-005 mg.
These results suggest that acetylcholine is involved in the autotomy reflex in U. mordax, and that any increase over normal body concentration results in some degree of paralysis. Me4N, frequently shown to act like Ach in small amounts and to be paralytic in larger amounts, produces paralysis resembling that produced by the coelenterate extracts. Agents which may antagonize Ach and MciN, such as EtgAch and EtiN, have actions on U. mordax which support the view that a methylated quaternary ammonium base might be a constituent of nematocyst toxins. There is yet
On the nature and action of coclcnterate toxins 291
no proof, however, that Me^N (" tetramine "), although found in large amounts in coelenterates, is the paralyzing agent in ncmatocysls.
A further observation made in Bimini deserves to be reported. The sea anemone, Aiptasia, was often found in the Bimini lagoon, occupying an empty conch shell. Such shells frequently contained a single specimen of the red snapping shrimp, Crangon armatus (Rathbun).* Hermit crabs living in close association with sea anemones (especially Eupagurus prideauxi, which is nearly enclosed by the cloak anemone, Adamsia palliata) are known to be highly resistant to nematocyst toxins (Cantacuzene, 1925 b; Cantacuzene and Damboviceanu, 1934 ( ; Rj;v. 1940; Manuta, 1943). To test for a possible acquired resistance of C. armatus to nemato- cyst toxins, appropriate doses of anemone tentacle extract were injected into several specimens. Three types of crustaceans were used as controls (U. mordax, Callianassa sp. and an unidentified shore crab). Crangon armatus survived for about 12 hours after injection with an amount of extract which, in less than one hour, killed the other crustaceans not found in association with sea anemones. This provides another example of the acquisition of a resistance to nematocyst toxins by a crustacean living in association with a sea anemone.
II. OBSERVATIONS MADE AT FRIDAY HARBOR (JULY 23, 1951, TO
AUGUST 19, 1951) (a) Autotomy experiments
At Friday Harbor, experiments similar to those done at Bimini were performed. As sources of toxins, the tentacles of the sea anemone, Metridium dianthus, and the large brown jellyfish, Cyanea capillata, were used. Tentacles were cut off and their volume determined. Hydrochloric acid was then added to pH 3-4. The tentacles were homogenized in a Waring blender and the homogenate strained through fine bolting silk. The pH of the liquid obtained was about pH 6. This extract was diluted with various proportions of sea water before use.
As a test animal the common shore crab of that region, Hemigrapsus nudus, was used. To compensate in part for a considerable size range, the crabs were sorted into two groups, those weighing about 2 to 4 gm and those weighing about 5 to 8 gm. Extracts and drugs were injected into the smaller crabs in a volume of 005 ml, while the volume used for the larger size was double this. Thus the amount of active material administered was, on the average, adjusted to body weight, since each test was done on a group of ten crabs.
Table III Effect of extract of tentacles q/' Metridium dianthus on autotomy in Hemigrapsus
nudus
Dilution
Total of walking legs autotomized
Spontaneous autotomies
1:10 1:20 1:50
80/80 78/80 72,80
42t 28 6
|
1:100 |
1 : 1 .(XX) |
|
74 80 |
78 80 |
|
0 |
0 |
t A second extract at this dilution when tested on two lots of 10 crabs each gave .^S and 40 spontaneous autotomies.
* Kindly identified by Mr. John C. Armstrong.
292 John H. Welsh
Preliminary autotomy experiments soon showed that H. nudus differed significantly from U. mordax. The legs of Hemigrapsus usually had to be crushed with heavy forceps to induce autotomy and, after the injection of extracts or drugs, there was no graded response to be seen in the per cent of legs autotomized. However, it was noted that Metridium tentacle extract induced spontaneous autotomy of both chelae and walking legs, and the frequency of autotomy was related to dose. The results of a typical experiment are given in Table III. Such a table does not reveal the true nature of the response. In order to do this, the protocol of a typical experiment follows:
July 30, Metridium tentacle extract number 3 (=M-3)
4.25 p.m. Injected 10 H. nudus with 005 ml M-3, 1 :1 with sea water.
4.30 p.m. 17 walking legs and 6 chelae had been spontaneously autotomized. Crabs are
paralyzed and fail to right themselves when turned on their backs. 8.00 p.m. All crabs dead.
4.55 p.m. Injected 10 H. nudus with 005 ml of M-3, diluted 1 :10 with sea water. 5.00 p.m. 18 walking legs and 10 chelae autotomized; crabs paralyzed. 8.00 p.m. All dead.
5.08 p.m. Injected 10 H. nudus with 005 ml of M-3, diluted 1 :20 with sea water. 5.15 p.m. 30 walking legs and 11 chelae autotomized; crabs slightly paralyzed. 8.00 p.m. All apparently dead.
5.23 p.m. Injected 10 H. nudus with 005 ml of M-3, diluted 1 :40 with sea water. 5.28 p.m. 21 walking legs and 8 chelae autotomized; crabs appear normal. 8.00 p.m. 3 crabs living but paralyzed.
5.35 p.m. Injected 10 H. nudus with 0 05 ml M-3 diluted 1 :80 with sea water. 5.40 p.m. 6 walking legs and 2 chelae autotomized ; crabs appear normal. 8.00 p.m. 3 crabs living but paralyzed.
5.45 p.m. Injected 10 H. nudus with 005 ml M-3 diluted 1 :150.
5.50 p.m. 3 walking legs and 1 chela autotomized.
8.00 p.m. 9 crabs living but partly paralyzed; few can turn over when placed on backs.
When extracts of Cyanea tentacles were injected into H. nudus, spontaneous auto- tomies rarely occurred at any of the dilutions. With dilutions up to 1 :50, paralysis occurred, but it was, if anything, less severe than with equivalent amounts oi Metridium extract.
It will be recalled that tetramethylammonium chloride (Me4N), like tentacle extracts, facilitated autotomy in U. mordax. When Me4N was injected into H. nudus, even in high concentration, it seldom produced spontaneous autotomy, and reduced somewhat the tendency of stimulated legs to autotomize. While its paralyzing action resembled that of extracts of Cyanea tentacles, it appeared that Metridium extracts contained an active material other than an Me^N-like component.
At Bimini it had been found that tetraethylammonium chloride (EtiN) had an action opposite that of Me4N and, likewise, that the actions of acetylcholine and its triethyl analogue (EtjAch) differed one from the other. Large doses of Et4N could be injected into H. nudus with little effect. For example, 5 crabs were injected with 0-05 ml of 10% EtiN. There were no spontaneous autotomies. In five minutes there were some twitching movements of the legs and the crabs were hyperexcitable, but twenty minutes after the injection they were normal in appearance and action.
On the nature and action of coclcntcratc toxins 293
If the spontaneous autotomies produced by extracts of Mcirii/ium tentacles were, in part, due to the presence of an MciN-likc substance, it might be possible to prevent these autotomies by previous or simultaneous injections of Et4N. Both procedures were followed. A given extract of Metridium tentacles (M-2), when diluted I :l() with sea water, produced 38 spontaneous autotomies of chelae and walking legs, and produced a moderately severe paralysis. When this extract was diluted 1 :10 with I % Et4N, rather than sea water, and 0-05 ml injected, there were no spontaneous autotomies and no signs of paralysis. In another experiment a given dilution of extract induced 40 spontaneous autotomies in ten crabs. In a second lot of crabs, 15 minutes after the injection of 0-05 ml of 1 % Et^N, the same dilution of extract produced no auto- tomies. Banthine, a drug used clinically to block acetylcholine action in vertebrate autonomic ganglia (as is Et4N), is a derivative of EtiN. In one experiment 005 ml of 10"^ Banthine completely blocked the autotomy-inducing and paralyzing action of a Metridium extract (M-3, 1 :20) that had produced 50 spontaneous autotomies in a control group of 10 crabs.
These experiments done at Friday Harbor provided further evidence for the occur- rence of a quaternary ammonium base (MciN derivative) in extracts of coelenterate tentacles. But Me4N alone could not account for all of the observed actions of the extracts on the autotomy reflex of ilea mordax and Hemigrapsus nudus.
(b) Evidence for an amine in tentacle extracts
It is a common observation that the sting of Physalia and certain jellyfishes is followed by a painful burning sensation, localized swelling or wheals, redness and urticarial eruptions. Among the more recent descriptions of these and other symptoms, the following may be referred to for further details: Allnutt, 1926; Wade, 1928; Frachtman and McCollum, 1945; McNeill, 1945; Bernstein, 1947. These symptoms are among those that might be expected if histamine were a constituent of nematocyst toxins or if a histamine releaser were present. Accordingly, crabs were injected with histamine. A dose of 0-05 ml of 1 % histamine caused marked paralysis but no spontaneous autotomies. One-tenth this dose caused a mild spastic stiffening of the legs. Pyribenzamine, an antihistamine, was tested. A dose of 0-05 ml o\' I % pyribenzamine caused rapid autotomy of 70% of the chelae but no walking legs were dropped, nor could they be made to autotomize by crushing. One-tenth this dose of pyribenzamine clearly inhibited autotomy of legs and antagonized the autotomizing effect of Metridium tentacle extract. These results further suggest that a histamine-like substance or a histamine releaser may be a constituent of nematocyst toxins.
(c) Action of extracts on the mollusc heart
The isolated ventricle of the heart of the quahog, Venus mercenaria, is a sensitive test object for the bioassay of a variety of quaternary ammonium compounds (Welsh and Taub, 1948; 1950; 1951). Me4N and many of its derivatives were known to decrease the amplitude and frequency of heart beat. Some amines, such as adrenaline and tyramine, were known to be excitatory when applied to the isolated I'enus heart. It was decided to test the action of coelenterate tentacle extracts on an isolated mollusc
heart.
Exploratory tests of hearts of several molluscs of the Friday Harbor region indicated
294 John H. Welsh
that the heart of the horse clam, Schizothaerus nuttaUii, was highly suitable for deter- mining the action of crude extracts of Metridium and Cyanea tentacle extracts. Using the isolated ventricle of Schizothaerus, as we had previously used the Venus ventricle, it was apparent that whole sea-water extracts of tentacles of both Metridium and Cyanea contained a mixture of heart excitor and inhibitor substances. However, a powerful excitor material usually was dominant and tended to obscure the action of the inhibitor material. The results will not be reported in detail, since later experi- ments done elsewhere are more readily interpreted. However, a sample set of records, comparing the action of extracts with histamine, deserve to be shown. Fig. 1 shows the marked excitor actions of Metridium and Cyanea extracts on the Schizothaerus heart. The former extract caused an increase in amplitude and frequency and a tonic shorten- ing of the heart (= rise in base line), while the Cyanea extract caused an increase in frequency and more marked tonic shortening of the heart. Such differences could be due to relatively greater amounts of the excitor substance in Cyanea tentacles.
When histamine was tested on the same heart, it was found to have a weak excitor action when added in an amount to give 0-5 mg histamine dihydrochloride per milhlitre of fluid bathing the heart. It is most unlikely that histamine could be the constituent of tentacle extract producing the marked excitation, and we shall see from later experiments that, in fact, it is not. These experiments done at Friday Harbor did, however, prompt further pursuit of the identity of the material with the marked excitor action, and this work will now be reported.
III. OBSERVATIONS MADE AT THE BIOLOGICAL LABORATORIES, HARVARD UNIVERSITY AND THE LABORATORY, PLYMOUTH, ENGLAND
(a) Evidence for the presence of 5-hydroxytryptamine in tentacle extracts
In the course of a study of cardio-excitor substances acting on the Venus heart, a recently-available indole amine, 5-hydroxytryptamine (5-HT), was tested. It was found to be far more active than other common biological amines such as adrenaline, nor-adrenaline, histamine and tyramine (Welsh, 1953 a). By means of paper chroma- tography and bioassay, 5-HT was found to occur in the nervous systems of several molluscs, including Venus mercenaria (Welsh, 1953 b; 1954). The excitor action of extracts of tentacles of Metridium dianthus tested on the Venus heart, and of the sea anemone, Calliactis parasitica, when tested on the Buccinum heart (Fig. 2), so closely paralleled that of 5-HT that an attempt to identify the unknown substance by chroma- tography was suggested. This was done for extracts of Metridium and Physalia tentacles, and clear evidence for the occurrence of 5-HT in these extracts was obtained. This study will be reported in some detail elsewhere. When equal weights of body wall and tentacles o{ Metridium were extracted, much more 5-HT was found in tentacles than in body wall. This suggests, but does not prove, that the 5-HT is contained in nematocysts, which are far more numerous on the tentacles than they are in the body wall tissues, even though pieces of acontia were doubtless included with the latter.
5-HT produces pain at a low concentration (10"* g/ml) when applied to a blister area on the forearm (Armstrong, Dry, Keele and Markham, 1953). 5-HT is also a very effective releaser of histamine (Feldberg and Smith, 1953). Thus, through direct action or through the release of histamine, 5-HT in nematocyst toxin could be respon- sible for the itching and burning, as well as the weals and haemorrhagic condition, that may follow contact with certain coelenterates. Recently, Jaques and Schachter
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On the nature and action of coelenterate toxins 295
(1954 a) have reported the presence of a histamine releaser in alcohol extracts of sea anemone tentacles. These same authors (1954 b) find that histamine and 5-HT are components of the venom of the common European wasp, Vcspa Yu/i^aris.
At the Plymouth Laboratory in the summer of 1953, 5-HT (in the form of the double sulphate with creatinine)* was injected into a series of Portunus depurator. The amounts varied by a factor of ten from 0 0001 mg to 01 mg 5-HT per crab. All concentrations produced excitation, as seen in constant movements of walking legs and chelae, with twitching of legs and rapid movements of the pincers. The larger the dose, the more severe were the symptoms. However, this was not followed by paralysis, and within one to two hours the crabs appeared normal. While 5-HT may be respon- sible for some of the activity of coelenterate toxin, it is clearly not the crustacean- paralyzing factor. When coelenterates are feeding on animals other than crustaceans, it is conceivable that 5-HT could act as a relaxing agent, since it has been found to relax certain molluscan muscle (Twarog, 1954).
Some of our chromatograms have given a spot which reacts as an indole amine but which has an Rf value differing from that of 5-HT. It is possible that more than one indole amine exists in coelenterates, as is the case in the skin of certain amphibians (Erspamer, 1954).
(b) Chromatographic evidence for the presence of quaternary ammonium bases in tentacle extracts
Methods outlined by Whittaker and Wijesundera (1952) and Bregoff, Roberts and Delw^iche (1953) for the chromatography of quaternary ammonium bases were used in an attempt to determine whether or not tetramethylammonium (Me4N) (or a derivative) was present in extracts of Metridium and Physalia tentacles. This led to a more extended study than was originally contemplated. The results to date will be briefly summarized.
Various methods were used to separate quaternary ammonium bases from other materials in acetone extracts of Metridium and Physalia tentacles. These partially purified bases were placed on paper and chromatographed with a variety of solvents. Ultraviolet absorption and chemical reagents were used to locate the spots. All procedures gave evidence of two or more quaternary ammonium bases present in the extracts in relatively very large amounts. Often only one large spot would be obtained, and added substances, such as Ach or MciN, would run with the unknowns rather than separately, thus suggesting a complex of related materials with a carrier substance. When certain areas were eluted and assayed on the Venus heart, the eluates inhibited the beat as does Me4N, Ach or other quaternary ammonium base with two or more methyl groups on the quaternary nitrogen. The action of these eluates was antagonized by EtiN and Mytolon (cf. Welsh and Taub, 1953).
We have tentatively identified one of the bases in the extracts as murexine or uro- canylcholine. This quaternary ammonium base was found in large amounts in the hypobranchial glands of the Mediterranean snail, Murc.x, by Erspamer (1948). It was chemically identified by Erspamer and Benati (1953) after synthesis by Pasini, Vercellone and Erspamer (1952). A generous sample of synthetic urocanylcholine has recently been received from Dr. Pasini. It should make possible certain identifica- tion of the material in the extract, which is clearly a quaternary ammonium base with
* Kindly supplied by Dr. R. K. Richards, Abbott Laboratories.
296 John H. Welsh
an ultraviolet absorption spectrum very similar to, if not identical with, that of urocanylcholine.
Erspamer and Benati (1953) report that urocanylcholine (murexine) has intense curariform action. A more detailed account of this phase of their work has not yet been seen. However, it appears that a substance such as murexine might account, at least in part, for the paralyzing action of nematocyst poison. Since the hypobran- chial glands of Murex also contain large amounts of 5-HT (see Erspamer (1954) for references), it could be that a combination of this with urocanylcholine yields a mixture with useful properties in defence and for securing food. It would be strange indeed, should this combination of newly discovered compounds be found in such unrelated structures as the nematocysts of coelenterates and the hypobranchial glands of certain moUusca.
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Soc. Biol., Paris, 54, 1438. RiCHET, C. (1903), Des poisons contenus dans les tentaculcs des Actinies, congestine et thalassinc.
C.R. Soc. Biol., Paris, 55, 246. RiCHET, C. and Portier, D. (1936), Recherches sur la toxine des coelentercs et les phcnomcncs
d'anaphylaxie. Res. Camp. Sci., Monaco, 95, 3-24. SoNDERHOFF. R. (1936), Uber das Gift der Seeanemonen. I. Ein Beitrag zur Kenntnis dcr Ncsscl-
gifte. Liebig's Ann., 525, 138-150. Thiel, M. E. (1935), Cber die Wirkung des Nesselgiftes der Quallen auf den Menschen. Ergeh. u.
Fortschr. Zool., 8, 1-35. TwAROG, Betty M. (1954), Responses of a molluscan smooth muscle to acetylcholine and 5-hydroxy-
tryptamine. /. Cell. Comp. Physiol., 44, 141-164. Wade, H. W. (1928), Post-mortem findings in acute jelly-fish p>oisoning with sudden death in status.
lymphaticus. Amer. J. Trop. Med., 8, 233-241. Welsh, J. H. (1953 a). Excitation of the heart of Venus mercenaria. Arch. Exp. Path. u. Pharniakol.,
219, 23-29. Welsh, J. H. (1953 b). The occurrence of an excitor amine in the nervous system of Buccinum and its
action on the heart. Anat. Rec, 117, 637. Welsh, J. H. (1954), Hydroxytryptamine : A neurohormone Jn the invertebrates. Federation Proc,
13, 162-163. Welsh, J. H. and Haskin, H. H. (1939), Chemical mediation in crustaceans. III. Acetylcholine and
autotomy in Petrolisthes armatus (Gibbes). Biol. Bull., 76, 405-415. Welsh, J. H. and Taub, R. (1948), The action of choline and related compounds on the heart of
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chromatography. Biochem. J., 51, 348-351.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 298-. 308
Patterns of deposition at the continental margin*
By Henry C. Stetson
Museum of Comparative Zoology, Harvard University
and Woods Hole Oceanographic Institution.
GENERAL STATEMENT
The term " continental shelf and slope ", " continental terrace ", or " continental platform ", as it has been used for decades in the geological hterature, connotes to most geologists the submerged margin of the land masses. But with our rapidly increasing knowledge of submarine geology the fact is becoming apparent that being under water is about the only attribute that many of these areas have in common. It is high time for a reappraisal of what these features really are, and to examine their origin, and to consider critically whether the term should be applied indis- criminately to the submerged margin of any large land mass, no matter how dis- similar the topography and the structure may appear to be.
A continental terrace, as the term will be used here, is a three-dimensional sedi- mentary structure. The shelf is the shallow, gently sloping upper surface, and the slope is the steep seaward face. It is our purpose here to trace the development of such a sedimentary structure from its earliest beginnings, and to try to show that, where continental margins do not exhibit this simple structure, the answer probably lies in unravelling the varied events of their geologic history rather than in trying to find an oceanographic interpretation. For it is on this point that much of the con- fusion in the present day literature has arisen as modern marine surveying reveals a bewildering variety of forms. We are fortunate in having preserved two large terraces which have remained basically unaltered ever since their earhest beginnings. For these two terraces, although ancient, are primitive in their structure; they are arche- types, to borrow a term from biology, of many other more complex forms that have evolved in other parts of the globe, whose origin has now been obscured by subse- quent events. I refer, of course, to the platforms bordering the eastern and Gulf coasts of the United States. And we are doubly fortunate in that these submerged margins together with their emerged coastal plains have been the sites of intensive geological investigation.
Around the world today the submerged continental margins are of varying widths. The extreme cases are the shelf off Siberia facing the Arctic Basin, three to four hundred miles in width, in contrast to the west coast of South America where the shelf is practically non-existent. At the present time all the continents are largely emergent and the shallow, interior seas which have repeatedly flooded them in the past have largely drained away. Consequently, the continental terraces are now the chief sites where marine sediments are accumulating. There is one major exception to this:
* Contribution No. 782 from the Woods Hole Oceanographic Institution.
298
Patterns of deposition at the continental margin 299
namely the deep basins and shallow inter-island platforms of the East Indies. This, however, is a completely different structural picture, and we will return to this case later.
The investigation of these submerged borderlands, their sediments, topography and structure, is one of the main fields of endeavour in submarine geology today. It should be clearly borne in mind that the present continental slope, however formed, is only a topographic feature and does not represent any sort of boundary between hypothetical continental and oceanic blocks of the crust. In fact, recent seismic work off Nova Scotia and Georges Bank (Officer and Ev/ing, 1954) would seem to suggest that there is no difference in the density of the basement complex which underlies this continental terrace, at least to the limits of this particular survey (Fig. 1). The terrace itself is made up of three major divisions of rocks with three distinct velocities. The aprons of detritus which have been deposited on and around con- tinental margins and in marginal geosynclines result in a very complex depositional picture. Progressive orogenies have in many cases further complicated an already intricate stratigraphy. Luckily modern advances in marine geophysics offer some hope that the tangle can some day be unravelled.
THE ATLANTIC AND GULF TERRACES
The Atlantic and Gulf terraces have had a parallel evolution, and, when considering their development, the coastal plain and continental platform should be taken as a unit. In the case of the Atlantic the oldest beds are Lower Cretaceous, and in the Gulf, Jurassic. In simplest terms both are comprised of wedges of inter-fingering continental and marine sediments which thicken in a seaward direction, and in both instances deposition is still going on in the same fashion (Fig. 2). In the Gulf Coastal Plain the formations may be considered a series of truncated wedges lying one on the other, and normal faulting that is contemporaneous with deposition is common (Storm, 1945). This fact should be remembered when the peculiar topography of the Gulf slope is discussed, because the major faults have been traced to the limit of drilhng, and furthermore the displacement increases downwards, amounting to hundreds of feet in the older beds, in contrast to but a few near the surface. No such extensive faulting occurs in the Atlantic Plain, although gentle archings and down- warps occur due to basement topography, as is also the case with the Gulf. Both of these terraces have been built unconformably on old erosion surfaces. Updip. where the basement is known, in the western section, the sediments of the Gulf Plain rest on the deformed Palaeozoic rocks of the Ouachita system, and in its eastern portions the Cretaceous laps over the southwestward plunging Appalachians (King. 1951); downdip the formations have thickened so much that the drill has not reached those rocks or any others which may form the basement in a seaward direction. The surface on which the Atlantic Plain rests is well known throughout due to lesser accumulation. The formations feather out updip against the crystallines of the Fall Line, and a crys- talHne igneous basement has been reached many times in drilling for oil or water over its whole extent (Spangler and Peterson. 1950; Spangler, 1950). It has every appearance of being a peneplaned surface which at present has a gentle seaward dip increasing towards the coastline.
The stratigraphic column at the present shoreline in the Gulf is many times thicker than it is on the Atlantic side; the seas advanced much farther inland and the plains
300
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are, therefore, considerably broader. But the same depositional pattern of over- lapping lenses is common to each. As Stephenson (1926) observed many years ago in commenting on the stratigraphy of both areas, " The different kinds of materials do not form separate, uniform sheets extending throughout the entire length of the Atlantic and Gulf Plain, for the sediments laid down at any given time differed from place to place and the conditions of sedimentation constantly shifted from time to time. Briefly stated, this means that no two columnar sections, unless closely adjacent to each other, are identical in lithologic succession ". In other words, major and minor transgressions and regressions followed each other with startHng rapidity. Deposition has been punctuated by many hiatuses, but the net result has been a growth in thick- ness and in width, until at present these terraces, coastal plain and continental plat- forms have attained tremendous proportions, particularly in the Gulf. Since Lower Cretaceous time, then, when both terraces began to assume their present shape, conditions governing transportation and deposition have remained virtually un- changed. The parallel development of these sedimentary wedges affords an excellent illustration of what will happen when a major sea is forced to deal for long periods of time with large supplies of sediment of varying texture over a fluctuating strand- line. The same structure will be built along any continental margin; the details will, of course, be modified, depending on the proportions of the variables, but the overall pattern should be recognized. It is not often that the oceanographic and geologic environment has remained so constant for such a long period to permit such a full development.
By way of illustration let us glance briefly at the contemporary oceanographic and sedimentary picture. The Atlantic shelf is, at present, an area of non-deposition, and in places is even undergoing erosion. From New Jersey southwards reworked material from outcropping Coastal Plain formations furnished much of the bottom material, as is evident from the fossils and from the lithology (Stetson, 1936). Con- sequently, the shelf is predominantly sandy. True, the northern rivers carry little sedi- ment, but although those of the middle and south Atlantic states which do have a large suspended load debouch into bays and sounds, all of the sediment is not trapped in them. What fine material is being delivered to the sea is by-passed to the slope. Cores taken in the silts and clays of varying textures on the slope from Cape Hatteras to New England and in the nearby Atlantic basin show that deposition has been of the order of 50-70 cm since the last cold period, which presumably can be correlated with the last advance of the Wisconsin ice (Stetson, 1949). South of Hatteras the slope and Blake Plateau have generally hard bottoms {Ibid, 1949). Temperature and salinity data indicate that the Gulf Stream impinges strongly against this portion of the slope (Iselin, 1936) and sweeps over the surface of the Blake Plateau, preventing any deposition in these two areas.
Turning now to the Gulf shelf, we find what is evidently an area of deposition. Silts of varying textures predominate except for a narrow, sandy strip close to the beach. This is the more usual condition around the world today; it is the large, sandy expanses that are unusual, and the only shelf that is in any way comparable to the one off the eastern United States is found off Argentina. In the case of the Gulf it is probable that more material is being supplied to the sea than it can transport, and the result is that the continental terrace is at present growing at the expense of the Gulf, a process that has been predominant since the beginning of the Tertiary.
Patterns of deposition at the continental margin 303
The slope is covered with a fine, uniform clay which has a median diameter of about 1 micron, and this texture continues across the bottom of the Sigsbcc I3ccp (Sti.ison, 1953). This has not always been the case, and, in fact, in the very recent past such uniformity was not present as the cores indicate. For instance, a brown clay now covers the central part of the eastern Gulf, while unconformably below it, at a depth of only a few inches, hes Globigerina ooze.
Our ignorance of bottom currents is profound, and any estimate of bottom veloci- ties must in most cases be based on the grain size of the sediment. It can be taken for granted, for instance, that clean, well sorted sands indicate bottom currents of half a knot or better, conversely, silts and clays can only be deposited under lesser veloci- ties. Waves and tides are the most obvious producers of bottom currents although the competence of the former with increasing depth has recently been questioned (DiETZ and Menard, 1951). But there can be no question as to the competence of both over the shallower bottoms, and bottom currents from these two sources cer- tainly have higher velocities in the Atlantic than in the Gulf. The winds of Atlantic storms, except for hurricanes, have, by and large, higher velocities and a longer fetch, and are therefore capable of building waves with longer periods. These in turn are capable of moving sedimentary particles at greater depths, and in far greater quantities along the strand, by beach drifting and strong longshore currents. The tidal range on the open Gulf coast is small compared with the Atlantic (roughly 1-5 feet at Galveston, as with 4-5 feet at Delaware Breakwater), and there must be a consequent reduction in the velocities of the tidal currents. I am well aware that this is tantamount to saying that we really don't know how sedimentary particles move over the deeper bottoms; but move they do, as their texture shows. For all intents and purposes, once they are out of sight their transport can only be inferred. There are few quanti- tative data, and in this direction the oceanographer has so far largely drawn a blank.
PRIMARY TERRACE CONSTRUCTION
Every advance and retreat of the sea leaves its impression on the stratigraphic record, and the numerous unconformities and facies changes exhibited by the over- lapping lenses of the Coastal Plain formations are concrete evidence of the numerous oscillations of the strandUne. A change of existing sea level, would, in fact, alter the sedimentary distribution which has been described above. For instance, a deepen- ing of the Atlantic shelf would once more make this platform an area of deposition, as it has been many times before.
Under the simplest conditions, during rising sea level, onlap means that the younger deposits overlap the older in a shoreward direction. The nearshore sediments are sandy or gravelly, while the offshore deposits resulting from the same sea-level, and therefore of the same age, will be muddy. In vertical cross-section this eventually results in an overlapping of shales on sandstones. It is a time of continuous accumu- lation of sediment in a deepening sea, and the continental shelf grows in thickness as well as in width, as successive layers are added to its surface as well as to its for- ward slope. Conversely, during falling sea-level, offlap means that the younger deposits overlap the older in a seaward direction. As the sea retreats, some of the coarser deposits of the shoal water zone are transported seaward and overlap the older and finer muds which had previously been laid down in deeper water. The surface of the shelf is undergoing erosion, with a reduction in thickness, or perhaps
304 Henry C. Stetson
the entire removal of strata deposited near shore during the previous onlap, but it con- tinues to grow in width because deposition is uninterrupted in the deeper water over the seaward slope. Equilibrium, or still stand, will hkewise produce a forward growth of the slope; httle or nothing is added to the thickness, although there is no loss.
Through all the oscillations of the strand, as well as during periods when sea-level remained constant, the face of the slope always progresses steadily seaward into deeper water. Since Cretaceous time the basement has been sinking with occasional reversals, and the sum total of these oscillatory movements has been downwards. The result has been a terrace constructed of a huge series of overlapping lenses of sediments of diverse Uthology. Consequently, although both terraces have grown intermittently in thickness with many depositional breaks, they have grown con- tinuously in width. For example, total thickness of the sedimentary formations along the axis of the geosynchne at the coast near the Texas-Louisiana line has been esti- mated at more than 40,000 feet (Lowman, 1949), but the maximum width of the whole terrace is measured by the 700 odd miles lying between Cairo, lUinois (the high water mark of the Upper Cretaceous seas) and the present continental slope. On the Atlantic side the sedimentary wedge at the shoreline is sUghtly less than 10,000 feet thick, as logged in an oil well drilled at Cape Hatteras. Offshore, seismic profiles run by the Lament Geological Observatory indicate a maximum thickness of the order of 16,000 feet in a basin southeast of Delaware Bay, with a rise in the basement seaward near the present continental slope (Ewing et ai, 1950). Its greatest width is about 175 miles lying on a traverse through Cape May from the Fall Line to the break-in slope. The thickness of the sedimentary prism offshore in the Gulf is, at present, unknown.
TURBIDITY CURRENTS AND SLOPE TOPOGRAPHY
The underwater topography of the Atlantic slope shows a dendritic drainage pattern (Veatch and Smith, 1939), characteristic of many land surfaces, of main stream valleys with tributaries, although the streams may have been submarine flows of muddy water known as turbidity currents, and not rivers flowing under the air. Numerous canyons gash the continental slope from Georges Bank to the Chesapeake, and some of them, such as the Hudson, are of considerable size. Perhaps a brief explanation of these submarine streams of muddy water is in order, as they are thought by many geologists to be the erosive agents responsible for the spectacular and enig- matic submarine canyons, which we are now discovering to be world wide. The density of any water mass is increased by a suspended load of sediment. Consequently muddy water will flow under clear water of the same temperature and salinity. Many of the silts and clays of the continental slope have a very high water content, fre- quently running over 150% of dry weight, and are consequently very unstable and will liquify easily by jarring such as could be produced by a submarine earthquake. Theoretically, the resultant flow may start out as a hquid slump and quickly change into a dense flow of turbid water, thought by some to attain considerable velocity, and hence great erosive power, as it slides down the steep continental slope. Flows of this type have never been observed in the ocean, but gentle turbidity currents are known to flow along the bottom of the whole length of man-made Lake Mead, where the muddy Colorado River plunges beneath the clear waters of that Lake. They have also been observed in some glacial lakes such as Geneva.
Patterns of deposition at the continental margin 305
What factual data exist at present are all on the dcpositional side. In areas of low gradients we have the deep sea plains, crossed by the mid-ocean channels with their leveed banks (Menard, 1955; Dietz, 1955; Heezen et ai, 1955), and the same t\pc of channels are found in various Swiss lakes (Daly, 1936). Graded bedding. long a somewhat obscure dcpositional process, can be best explained by turbidity flows.
So much attention has been focused on the supposed potential energy of the turbidity current by their proponents that the factors that will dissipate this energy such as friction of turbulent flow along boundaries, entraining of clear water, and settling of particles have all but been lost sight of. One source of confusion is the difference between a true turbidity current and a submarine slump or slide. Doubtless a slide starting on a steep slope would eventually grade into a turbidity current, but there must be a great diff'erence in energy at the start as well as in the mechanics of their motion and their erosive power. Witness the conflict of opinion over the veloci- ties and even the type of the Grand Banks " flow " which parted the Western Union cables following the earthquake of 1928 (Kullenberg, 1954). Possibly this may seem academic, but when the term " turbidity current " is mentioned many people visualize a suspension current such as flows along the bottom of Lake Mead or in the Swiss lakes. These patently have no erosive power; and it is not a question of having a super Colorado River and producing a turbid suspension of greater volume. Possibly a mud or sediment slide or flow would be a better term to apply to the initial slump of unstable sediment failing under gravitational stress, restricting turbidity current to the transporting and depositing agent. When looked at objectively, the dynamic role assigned to density currents by their advocates may be seen to have more than a tinge of wishful thinking induced by an attempt to escape from the horns of a dilemma. Obviously an enormous amount of vigorous erosion must have taken place to cut the submarine canyons and to make matters worse, during the late glacial period, which is only yesterday. Conventional rivers would require more relative displacement of land and sea than most geologists will admit is probable or possible. To circumvent this, the turbidity current has been hailed almost over- night as the answer to all vexing problems of submarine erosion.
The topography of the continental slope in the northwestern Gulf of Mexico is very complicated as Gealy (1955) has pointed out, and, according to her analysis, has probably been produced by a variety of causes. Sub-aerial erosion, the failure of unstable sediments which are under shearing stress, salt domes and crustal faulting have all played a part. An extensive scarp bounds the Sigsee Deep and continues around the continental slope off" the west Florida platform, where it is found to be over 7000 feet high (Jordan, 1951 and Fig. 3). Pronounced normal faulting could be the only cause for cuff's such as these. Higher up on the slope the troughs and ridges and hummocky topography is thought to be the surface expression of lesser shearing ai depth plus erosion by sediment flows and slumps. The material is largely furnished by the thick Pleistocene deposits lying on the upper parts of the slope.
MOBILE CONTINENTAL MARGINS
As an historical background to the existing terraces, consider the - long succession
of geosynclines of diff-ering kinds and trends ^ with their attendant island arcs, such
as has been postulated by many authors (Kay, 1951) lying along the Atlantic and
Gulf margins during Palaeozoic time. In a situation such as this the supply of detritus
306 Henry C. Stetson
comes from within the orthogeosynchnes themselves, from fluctuating upwarps of their floors, from volcanoes and igneous intrusions, and from the islands themselves. The volcanic rocks within the sedimentary series seem to be restricted to what are termed the eugeosynclines, while the miogeosynchnes contain only sediments. This is in direct contrast to the views of those who consider the hypothetical continent of Appalachia lying somewhere near the present 100 fathom Une the sole source. The Dutch East Indies have been cited as a modern large-scale parallel to the paleo- geography along the eastern seaboard and along the Gulf during the Palaeozoic.
Temporarily at least, orogenic activity and vulcanism has ceased along the eastern and Gulf coasts of the United States ; and the parallel geosynclinal belts, the Appala- chian, the Ouachita and the Witchita systems, have long been quiescent. The net result since Cretaceous time has been the construction of two " paraliageosynchnes " according to Kay's terminology. These are hnear troughs of undeformed sediments lying along the outer margins of the geosynchnal belts, and their seaward hmits form the present continental slope. Obviously their strata, which in the case of the Atlantic and Gulf are thickening seaward at the present shorehne, must thin as the outer margins are reached, but there are few data on this point.
Continental terraces like these obviously need an extensive hinterland to supply the sediments if they are to reach any sizable proportions, and furthermore the drainage must be into the ocean. These conditions are not always met, which may be the expla- nation for our inability to find comparable structures built during the Palaeozoic. KuENEN (1950) has speculated on what could have happened to them, reasoning that, because of the much greater interval of time that was available for their building, such structures would not be easy to hide. It well may be, however, that under mobile geosynclinal conditions they never existed.
Specifically, in the case which we are considering here, the two terraces are now building on what are probably the bevelled surfaces of the rocks forming the outer parts of the Palaeozoic eugeosyncHnes peneplaned after orogenic and plutonic activity had ceased. They serve as models of the simple forms which will be constructed by the processes of marine transportation and deposition when these operations are not interfered with by activity in the mobile belts.
The sediments, topography and structure of but very few submerged continental areas are well enough known to warrant critical comment. Aside from the two under discussion, we have only the areas off" Cahfornia, Norway, the West Indies, and Indonesia, for which adequate bathymetric charts exist. Some oceanic areas have been charted in considerable detail, but they have no bearing on this problem. The East Indies have already been mentioned as a modern illustration of deposition in eugeosynclines and miogeosynchnes. The West Indies present a somewhat analo- gous case, but very little is known about the sediments.
Off" California the sedimentary platforms have been extensively faulted and tecto- nically broken up into numerous basins and ridges. Occasional granitic outcrops have been found in the wafls of a few of the minor, nearshore submarine canyons, but extensive rock dredging shows that they are only small intrusions and that the continental terrace, hke that in the Atlantic, is composed of Cretaceous and Tertiary sediments. Nothing is known about the basement. The continental slope along the entire margin is in many cases controlled by long fault scarps of considerable dis- placement (Shepard and Emery, 1941). The same is true of the walls of the deep
Patterns of deposition at the continental margin 307
basins which are so characteristic of the southern section. The continental slope ofT the west Florida platform (Fig. 3) represents the most striking submarine fault scarp known at present, in places attaining a height of over 7000 feet. This can be traced around the Keys into Florida Strait, but its height has diminished to about 600 feet (Jordan, 1954).
HoLTEDAHL (1950) Concluded that the Norwegian shelf consists of consolidated rock which probably belongs to the same complex which makes up the hinterland, that is, granites and metamorphics, and that the whole is partially covered with a veneer of glacial debris of all types. The slope is controlled by what are apparently a series of step faults. Obviously, any comparisons as regards a depositional origin of the slope can no longer be made in this case, and there is nothing now to suggest a sedimentary origin for this entire borderland. Possibly it represents the eroded roots of a former eugeosyncline upon which no " paraliageosynclinc " has been built, for lack of an adequate area from which the sediments might have been supplied.
A case that appears to be somewhat analogous is found off the end of the Breton Peninsula. Extensive areas of rocky bottom extending out towards the continental slope are shown on the chart of bottom lithology appearing in the Atlas de France for 1935, with Dangeard as the authority. It would be reasonable to suppose that the igneous complex making up this peninsula plunges beneath the sea, although there is no notation of rock types, and there are no charts which give any clear picture of bottom topography.
There is enough diversity in the examples cited above to make the geologist pause before assigning any blanket mode of formation to the continental shelf and slope. It is not our purpose here to review the older mechanical theories such as the abrasion platform and the marine delta. Today they have few adherents (Dietz, 1952). It is becoming apparent that each continental margin must be studied on its own merits; its history, structure and hthology must be known, and we must also know something about the oceanographic conditions which control sedimentation beyond the coast- line. Without adequate marine topographic surveys we are still only guessing, and these must be supplemented by bottom coring and dredging. The case presented here for offlap and onlap is an attempt to reduce the sedimentary picture to its simplest, most primitive terms, in situations where oceanographic conditions have remamed constant for long periods of time. From this point on it will be obvious to anyone that an endless succession of variables can be introduced to alter the pattern of the prototype.
REFERENCES
Daly R A (1936), Origin of submarine " canyons ". Amer. J. Sci., 31 (186), '*0'-420 DiTTZ R. S. (1952), olomorphic evolution of continental terrace (contmental shelf and slope). Bull. Amer. Assoc. Petrol. GeoL, 36(9), \m2-\Sl9 .u. n^v «f H,.n>, ,1 Curn-nt Sci 23
Dietz, R. S. (1954), Possible deep sea turbidity current channels m the Bay of Bengal. Curnnt be. Z^
DiExtT's and Menard, H. W. (1951), Origin of abrupt change in slope at continental shelf
GBA.\^;l'r(r95ffTo1fogra1rhy-o1rion\S Nonhwes. Gulf of Mexico. B.,„ ..-oi
H^N.-'ra:, EwSo? M:'and ERicsoN, D. B. (1955) Reconnaissance survey of .he aby»al plain
south of Newfoundland. Deep-Sea Res., 2 (2), 122-133.
308 Henry C. Stetson
HoLTEDAHL, H. (1951), A Study of the topography and sediments of the continental slope west of
More, W. Norway. Univ. i Bergen. Arbok 1950, Naturvidensk. rekke, (5), 1-58. ISELIN, C. O'D. (1936), A study of the circulation of the Western North Atlantic. Pap. Phys. Oceanogr.
Meteorol., 4 (4), 1-101. Jordan, G. F. (1951), Continental slope off Apalachicola River, Florida. Bull. Amer. Assoc. Petrol.
Geol, 35 (9), 1978-1993. Jordan, G. F. (1954), Large sink holes in the Straits of Florida. Bull. Amer. Assoc. Petrol. Geol.,
38(8), 1810-1817. Kay, M. (1951), North American geosynclines. Geol. Soc. Amer. Mem., 48 1-143. King, P. B. (1951), The tectonics of Middle North America. Princeton Univ. Press, Princeton, N.J.,
224 pp. KuENEN, PH. H. (1950), The formation of the continental terrace. Adv. ScL, 7 (5), 76-80. KuLLENBERG, B. (1954), Remarks on the Grand Banks turbidity current. Deep-Sea Res. 1 (4),
203-210. LowMAN, S. W. (1949), Sedimentary facies in Gulf Coast. Bull. Amer. Assoc. Petrol. Geol., 33 (12),
1939-1997. Menard, H. W. (1955), Deep-sea channels, topography and sedimentation. Bull. Amer. Assoc.
Petrol Geol, 39 (2), 236-255. Officer, C. B. and Ewing, M. (1954), Geophysical investigations in the emerged and submerged
Atlantic Coastal Plain. Part VII: Continental shelf, continental slope, and continental rise
south of Nova Scotia. Bull. Geol. Soc, Amer., 65 653-670. Shepard, F. p. and Emery, K. O. (1941), Submarine topography off the California coast: Canyons
and tectonic interpretation. Geol. Soc, Amer., Spec. Pap. No. 31, 1-171. Spangler, W. B. (1950), Subsurface geology of Atlantic Coastal Plain of North Carolina. Bull.
Amer. Assoc. Petrol. Geol., 34 (1), 100-132. Spangler, W. B. and Peterson, J. J. (1950), Geology of the Atlantic Coastal Plain in New Jersey,
Delaware, Maryland, and Virginia. Bull. Amer. Assoc. Petrol Geol., 34 (1), 1-99. Stephenson, L. W. (1926), Major features in the geology of the Atlantic and Gulf Coastal Plain.
J. Washington Acad. Sci., 16 (17), 460-480. Stetson, H. C. (1936), Geology and paleontology of the Georges Bank canyons. Part 1, Geology.
Bull. Geol. Soc. Amer., 47 (3), 339-366. Stetson, H. C. (1949), The sediments and stratigraphy of the east coast continental margin, Georges
Bank to Norfolk Canyon. Pap. Phys. Oceanogr. Meteorol., 11 (2), 1-60. Stetson, H. C. (1953), The sediments of the Western Gulf of Mexico. Part 1. The continental
terrace of the Western Gulf of Mexico: its surface sediments, origin and development. Pap.
Phys. Oceanogr. Meteorol., 12 (4), 1-45. Storm, L. W. (1945), Resume of facts and opinions on sedimentation in Gulf coast region of Texas
and Louisiana. Bull. Amer. Assoc. Petrol Geol., 29 (9), 1304-1335. Veatch, a. C. and Smith, P. A. (1939), Atlantic submarine valleys of the United States and the
Congo submarine valley. Geol. Soc, Amer., Spec. Pap. No. 7, 1-101.
Papers in Marine Biology and Oceanography. Suppl. to vol. i of Deep- Sea Research, pp. 3l»..l20.
Scaphopods of the Atlantis dredgings in the Western Atlantic
with a catalogue of the scaphopod types in
the Museum of Comparative Zoology *
By Ruth D. Turner Museum of Comparative Zoology, Harvard University.
The following report is based mainly on the collection of scaphopods made by the Atlantis in 1938 and 1939 during two trips to Cuba. A small amount of hitherto unworked material in the collection of the Museum of Comparative Zoology is also recorded where it is of significance in the distribution of the species concerned. This material includes a number of lots collected by the late Dr. Leo A. Burry of Pompano Beach, Florida, who did a great deal of dredging off the Florida Keys and in the region off Fort Walton, Florida. In addition there are several lots of Blake and Hassler material that had not been previously worked, as well as miscellaneous lots that have come in from various sources. Localities given by Henderson (1920) have not been duplicated in this report; all records are of new locahties or new depth records.
Though there are no new species in this material, it is of great value in extending the ranges of many species, and in several cases these constitute the second known record for the species. Except for a few intertidal species which may be common, records of scaphopods are always rare, consequently it seems advisable to put these new data on record. This is especially important since Henderson's report is relat- ively recent and quite complete, so that a new monograph probably will not be attempted for some time.
It is interesting to compare the results of the Atlantis trips with those o*" the Johnson-Smithsonian Expedition to the Puerto Rican Deep as reported by W. K. Emerson (1952). Both collected fifteen species which could be positively identified, and of these only eight were taken by both, which would indicate a purely chance factor in collecting. Undoubtedly many species are far more widely and evenly distributed than would appear from the published record. Only after continued dredging over a long period of tme will it be possible to derive accurate distribution patterns of these deep-sea groups. When sufficient material is collected, most of the subspecies and even some of the species now recognized will probably be shown to be mere populations of widespread, polymorphic species. This was certainly evident from the study of the material covered in this present report. In most cases classifica- tion has been to species only, as it would appear that many of Henderson's sub- species are of doubtful value; in many cases the ranges of two subspecies overlap
almost completely.
According to his introduction, Henderson, at the time he wrote his monograph, had the entire collection of the Museum of Comparative Zoology for study; however,
* Contribution No. 779 of the Woods Hole Oceanographic Institution.
309
310 Ruth D. Turner
except in rare cases and in the case of a few types, he made no mention of this material. Much of the Blake material is in the Museum of Comparative Zoology and in most cases the specimens figured and so labelled by Dall, are contained in this collection. A catalogue of all of the types of Western Atlantic scaphopods in the Museum collection is appended to this report for the convenience of interested workers.
Henderson gave an excellent historical account of the work done in this group up to 1920, consequently only a brief bibhography is given here. No attempt has been made to describe the various species, for descriptions and figures may be found in the works of Watson (1895); Dall (1889); Pilsbry and Sharp (1898) and Henderson (1920). The classification to genera and subgenera follows that of Henderson.
Maps indicating the course of the Atlantis during the two circumnavigations of Cuba in 1938 and 1939, together with a complete hst of the stations, are given by Chace (1940). Unfortunately, several locahties where the Blake and the Atlantis did a small amount of dredging were not given station numbers. Consequently in this report where reference is made to the ship without station number it is because none was allotted.
NEW SCAPHOPOD RECORDS FOR THE WESTERN ATLANTIC
Dentalium (Dentalium) laqueatum Verrill Dentalium laqueatum Verrill 1885, Trans. Connecticut Acad. Arts and Sci. 6, pt. 2, p. 431, pL 44, fig. 18; Henderson 1920, Bull. U.S. Nat. Mus. No. Ill, p. 23, pi. 1, figs. 6-7.
Notes. Though Henderson fists a large number of lots for this species, they are largely restricted to the region of Cape Hatteras, North CaroUna and to the Lower Florida Keys. The following Atlantis records extend our knowledge of its distribu- tion to Cuba. One exceedingly large specimen from off Punta Alegre, Cuba, measured 85 mm in length, or 23 mm longer than any previously recorded. Henderson's sub- species regulare appears to be of doubtful value. Its range overlaps that of the typical form and, in addition, in the typical form there appears to be a wide range of variation in the strength of the secondary costae.
Records. CUBA: Atlantis, station 2963, off Bahia de Cochinos, Las Villas (N. Lat. 22° 07'. W. Long. 81° 08') in 180-190 fathoms; Atlantis, station 2982E, off Punta Alegre, Camaguey (N; Lat. 22° 45'; W. Long. 78° 45') in 150-180 fathoms; Atlantis, station 2999, off Bahia de Matanzas, Matanzas (N. Lat. 23° 10'; W. Long. 81° 29') in 145-230 fathoms.
FLORIDA: off Carysfort Light, Key Largo in 66-1 17 fathoms (L. A. Burry — 5 lots); off Beacon D, Key Largo in 65-108 fathoms (L. A. Burry — 2 lots); 3j miles N.E. of Pacific Reef, Key Largo in 66 fathoms (L. A. Burry).
Dentalium (Dentalium) obscurum Dall Dentalium gouldii obscurum Dall 1889, Bull. Mus. Comp. Zool. 18, p. 425, pi. 27, fig. 4. Dentalium obscurum Dall, Henderson 1920, Bull. U.S. Nat. Mus. No. Ill, p. 32, pi. 3, figs. 1, 3.
Notes. This is an exceedingly rare though probably widely distributed species. Dall thought it was only a variety of gouldii but I agree with Henderson that it is quite a different species. It has previously been known only from the Barbados, where it has been collected several times.
Records. CUBA : Blake, station 62, off Habana in 80 fathoms.
Scaphopods of the Atlantis drcdgings in ihc Western Atlantic 31 |
Dentalium (Dentalium) carduum Dull Dentalium cardims Dall 1889, Bull. Mus. Comp. Zool. 18, p. 423, pi. 27. fig. 3; HFNUtRsoN 1920. Bull. U.S. Nat. Mus. No. 1 1 1, p. 33, pi. 3, figs. 4, 5, 7.
Notes. Five lots of this rare species were taken by the Atlantis, and these are the first recorded for Cuba and Florida. The species is probably widespread throughout the West Indies for, though only eleven lots are known, they arc distributed from the Little Bahama Bank, south to Cuba, St. Thomas, Grenada and Barbados. One large specimen taken by the Atlantis measured 10 mm in greatest diameter, and if complete would probably have measured some 95 mm in length, or some 8 mm greater than the largest recorded specimen.
Records. FLORIDA: Atlantis, station 2951, about 55 miles off Fort Lauderdale (N. Lat. 26 08'; W. Long. 79° 02') in 155 fathoms. CUBA: Atlantis, station 2982A (N. Lat. 22 48'; W. Long. 78° 50') in 210 fathoms; Atlantis, station 2981D (N. Lat. 22° 48'; W. Long. 78" 51) in 190-230 fathoms; Atlantis, station 2982E (N. Lat. 22° 45'; W. Long. 78 45) in 150-180 fathoms; Atlantis, station 2980A (N. Lat. 22° 48'; W. Long. 78° 41') in 220-260 fathoms. All the above are from off Punta Alegre, Camagiiey, Cuba.
Dentalium (Antalis) entaie stimpsoni Henderson
Dentalium striolatum Stimpson 1851, Proc. Boston Soc. Nat. Hist. 4, p. 114 (non D. striolatum Risso 1826).
Dentalium entaie stimpsoni Henderson 1920, Bull. U.S. Nat. Mus. No. Ill, p. 35 (new name for striolatum Stimpson, non Risso 1826).
Notes. Only one lot of this rather common northern species was obtained by the Atlantis. Though there are many lots in the collection of the Museum of Compara- tive Zoology they do not extend the range beyond that given by Henderson.
Records. Atlantis, station 2661, off Nova Scotia (N. Lat. 43° 40'; W. Long. 67' 49') in 126 fathoms.
Dentalium (Antalis) antillarum d'Orbigny
Dentalium antillarum d'Orbigny (in) Sagra, Histoire Tile de Cuba, Mollusques, Atlas pi. 25, figs. 10-13; ibid. 1847, text 2, p. 202; Henderson 1920, Bull. U.S. Nat. Mus. No. 1 1 1, p. 44. pi. 5. figs. 1-4, 6-8
Notes. Though this more shallow water species was not collected by the Atlantis. several lots in the Museum collection are from localities not previously reported and so seem worthy of note here. These were collected largely by William J. Clench.
Records. BAHAMA ISLANDS: Simms, Long Island; Arthurs Town, Cat Island; Little San Salvadore, 18 miles W. of Cat Island. HISPANIOLA: Cape Haitien, Haiti; Monte Cristi. Santo Domingo. PUERTO RICO: Loiza Vieja. LESSER ANTILLES: Guadeloupe.
Dentalium (.\ntalis) disparile d'Orbigny
Dentalium disparile d'Orbigny 1842, (in) Sagra, Histoire I'lle de Cuba, Mollusques, Atlas pi. 25. figs. 14-17; ibid. 1847, text 2, p. 202; Henderson 1920, Bull. U.S.Nat. Mus. No. 1 1 1. p. 47. pi. 6. figs. 4-8.
Notes. Henderson records only eleven lots for this species and, though it was not taken by the Atlantis, two new records are noted.
Records. TRINIDAD: Gaspari. BRASIL: Maranhao.
Dentalium (Antalis) ceratuni Dall Dentalium ceratttm Dall 1881, Bull. Mus. Comp. Zool. 9 p^38. Dall 1889. Bull. Mus^Comp. Zool. 18, p. 424, pi. 26, fig. 5, pi. 27, fig. 2; Henderson 1920, Bull. U.S. Nat. Mus. No. III. p. 49, pi. 7, figs. 2-7.
312 Ruth D. Turner
Notes. The lot collected by the Atlantis at station 2996 greatly extends the depth at which this species is known to Uve. Henderson's subspecies flavum and tenax appear to be the only variants with no geographic significance, for it has been possible to find gradients between these and the typical form.
Records. FLORIDA: 3^ miles N.E. of Pacific Reef, Key Largo in 66 fathoms (L. A. Burry). CUBA: Atlantis, station 2996, off Bahia de Cardenas, Matanzas (N. Lat. 23" 22'; W. Long. 81° 050 in 470-665 fathoms; Atlantis, station 2963, off Bahia de Cochinos, Las Villas (N. Lat. 22° 07'; W. Long. 81° 08') in 180-190 fathoms.
Dentalium (Antalis) taphrium Dall Dentalium taphrium Dall 1889, Bull. Mus. Comp. Zool. 18, p. 422; Henderson 1920, Bull. U.S. Nat. Mus. No. Ill, p. 53, pi. 7, fig. 8.
Notes. This is a very characteristic species. It generally lives in depths from about 20 to 120 fathoms. The specimen from Yucatan Straits in 640 fathoms was dead at the time it was collected, and it does not necessarily follow that the species hves at such depths.
Records. MEXICO: Blake station, Yucatan Straits in 640 fathoms. FLORIDA: off Beacon D, Key Largo in 38-100 fathoms (6 lots); off Carysfort Light, Key Largo in 100-117 fathoms (2 lots); off Molasses Reef, Ley Largo in 66-75 fathoms (2 lots) ; 3 miles S.E. of Sombrero Light, Marathon in 58 fathoms (all L. A. Burry).
Dentalium (Antalis) bartletti Henderson Dentalium {Antalis) bartletti Henderson 1920, Bull. U.S. Nat. Mus. No. 1 1 1, p. 55, pi. 8, figs. 2, 7.
Notes. Specimens taken by the Atlantis off Puerto Sagua la Grande and Puerto de Tanamo were 66 mm and 74-5 mm long respectively, the latter being 19-5 mm longer than Henderson's largest specimen.
Records. CUBA: Atlantis, station 2991, (N. Lat. 23° 21'; W. Long. 80° 23') in 475 fathoms; Atlantis, station 2988, (N. Lat. 23° 15'; W. Long. 79° 57') in 380 fathoms; Atlantis, station 2989 (N. Lat. 23° 10'; W. Long. 80° 04') in 360 fathoms,— All off Puerto Sagua la Grande, Las Villas; Atlantis, station 3370, off Puerto de Tanamo, Oriente, (N. Lat. 20° 47'; W. Long. 75° 11') in 450 fathoms; Blake, station, off Bahia Honda, Pinar del Rio in 418 fathoms. BRITISH HONDURAS: Blake, station 18, off Belize (N. Lat. 18° 08'; W. Long. 87° 16') in 600 fathoms. LESSER AN- TILLES: Blake, station 265, off Grenada (N. Lat. 12° 03'; W. Long. 61° 49') in 576 fathoms.
Dentalium (Fissidentalium) meridionale verrilli Henderson Dentalium solidum Verrill 1884, Trans. Connecticut Acad. Arts and Sci. 6, p. 215, pi. 44, fig. 16
(non D. solidum Hutton 1873).
Dentalium {Fissidentalium) meridionale verrilli Henderson 1920, Bull. U.S. Nat. Mus. No. Ill,
p. 62, pl. 9, fig. 3,
Notes. A number of lots of this rather common northern species were collected by the Atlantis while working along the continental slope from New Jersey to Virginia. This is a large, strong species and one of the few that are readily obtained in large numbers by a dredge, and, at the same time, are not broken in the process. This fact probably accounts for its greater abundance in collections, and therefore the belief that it is common, though perhaps it is no more so than many other species.
Records. NEW JERSEY: Atlantis, 4 stations, off Cape May in 935-1050 fathoms; Atlantis, 2 stations, olT Little Egg Harbor in 820 and 935 fathoms; Atlantis, 2 stations, off Point Pleasant in 1105 and 1230 fathoms; Atlantis, off Long Branch in 520 fathoms. DELAWARE: Atlantis, station (N. Lat. 38° 31'; W. Long. 73° 03') in 915-975 fathoms. MARYLAND: Atlantis station, off AssateagueBay(N. Lat. 39°05'; W. Long. 73° 30') in 970 fathoms. VIRGINIA: Atlantis station, off Accoma (N. Lat. 37° 43'; W. Long. 73° 40') in 1105 fathoms.
Scaphopods of the Atlantis dredgings in the Western Atlantic 313
Dentalium (Graptacme) cborcum Conrad Dentalium eboreum Conrad 1846, Proc. Acad. Nat. Sci. Philadelphia 3, p M : HhNr>tRS<jN 1920. Bull. U.S. Nat. Mus. No. Ill, p. 66, pi. 10, figs. 3-5, 8-9; pi. II. fig. 6.
Notes. This may be a very common species in some localities. It lives apparently in fairly shallow water and down to depths of 80 to 100 fathoms. The shells being solid and strong are often washed up on the beaches in considerable numbers. The following data add to the distribution records of this species on the west coast of Florida and extend the range to Mustang Island, Texas.
Records. FLORIDA: Clearwater; Gulfport; Bradenton Beach. TEXAS: Mustang Island.
Dentalium (Graptacme) semistriolatum Guilding Dentalium semistriolatum Guilding 1834, Trans. Linn. Soc. London 17, pt. I . p. 34. pi. 3, figs. I -6; Henderson 1920, Bull. U.S. Nat. Mus. No. Ill, p. 69, pi. 11, figs. 1-3, 8-9.
Notes. Several additional records of this rather common West Indian species are added. The one from off Fort Walton, Florida, adds one more species to the list of West Indian forms that are found in deeper water in the northern Gulf. The record for Swan Island carries the distribution of the species well into the western Caribbean.
Records. FLORIDA: 15-35 miles off Fort Walton in 13-19 fathoms (L. A. Blrrv). CUBA: Pueblo Nuevo and Cardenas, Matanzas Bay, Matanzas. VIRGIN ISLANDS: Virgin Gorda. HISPANIOLA: Monte Cristi, Santo Domingo; LESSER ANTILLES: Guadeloupe. [CARIBBEAN ISLANDS: Swan Island in 60 fathoms.
Dentalium (Graptacme) calamus Dall Dentalium calamus Dall 1889, Bull. Mus. Comp. Zool. 18, p. 421 ; Henderson 1920, Bull. U.S. Nat. Mus. No. Ill, p. 72, pi. 12, figs. 7-8.
Notes. This is a rare but very characteristic species which is found in rather shallow water. The two records from the Bahamas were collected by Owen Bryant.
Records. BAHAMA ISLANDS: Whale Cay Channel, Great Abaco Island in 3 fathoms; Dick's Point, Nassau, New Providence.
Dentalium (Laevidentalium) callipeplum Dall Dentalium callipeplum Dall 1889, Bull. Mus. Comp. Zool. 18, p. 419, pi. 27, fig. 12b; Henderson 1920, Bull U.S. Nat. Mus. No. Ill, p. 74, pi. 12, fig. 5.
Notes. A very large, fine specimen of this rare species was collected by the Atlantis in 2075 fathoms, which greatly extends the known depth for this species.
Records. FLORIDA: 2h miles E.S.E. of Beacon D, Key Largo in 58 fathoms (L. A. Bi rrv). CUBA: Atlantis, station 2964, Banco Paz, Las Villas (N. Lat. 20 56'; W. Long. 80^ 1 1 ) in 2075 fathoms. VIRGIN ISLANDS: St. Thomas (T. Bland).
Dentalium (Laevidentalium) perlongum Dall Dentalium perlongum Dall 1881, Bull. Mus. Comp. Zool. 9, p. 36; Dall 1889, Bull. Mus. Comp Zool. 18, p. 419, pi. 27. fig. 6; Henderson, 1920, Bull. U.S. Nat. Mus. No. Ill, p. 75. pi. 9. fig. 1.
Notes. Four fine lots, one of them with 8 specimens, were collected by the Atlantis. The following are apparently the first Cuban records for this species.
Records. Atlantis, station 2992B, off Bahia de Santa Clara, Matanzas (N. Lat. 23" 26 ; \N I ong 80° 28') in 535 fathoms; Atlantis, station 2993, off Bahia de Santa Clara (N. Lat. 23° 24 ; W. Long. 80° 44') in 580 fathoms; Atlantis, station 3345, off Banco Paz, Las Villas (N. Lat. 21 08'; W. Long. 79° 56' 30') in 700 fathoms; Atlantis, station 3370, off Puerto de Tanamo, Oricnte (N. Lat. 20 47'; W. Long. 57° 1 1') in 450 fathoms.
314 Ruth D. Turner
Dentalium (Episiphon) sowerbyi Guilding Dentalium sowerbyi Guilding 1834, Trans. Linn. Soc. London 17, p. 35, pi. 3, fig. 7; Henderson 1920, Bull. U.S. Nat. Mus. No. Ill, p. 77, pi. 13, figs. 2-3, 10.
Notes. L. A. BuRRY obtained this species at seven stations during his dredging off Key Largo. It is a very small but characteristic and easily recognized species.
Records. FLORIDA : off Beacon D, Key Largo in 66-90 fathoms (4 lots) ; off Carysfort Light, Key Largo in 92 and 100 fathoms (2 lots); 3^ miles N.E. off Pacific Reef, Key Largo in 66 fathoms.
Dentalium (Bathoxiphus) dldymum Watson Dentalium didymum Watson 1879, J. Linn. Soc. London 14, p. 517; Watson 1885, Challenger Rept. Zool. 15, p. 10. pi. 1, fig. 11; Henderson 1920, Bull. U.S. Nat. Mus. No. Ill, p. 83, pi. 14, fig. 10.
Notes. Dr. William J. Clench obtained a large series of Dentalium from the
channel dredgings at Puerto Plata Harbor, Santo Domingo. Among them were a
number of fragments and a few nearly complete specimens of this very rare species.
They were taken from a fine grey mud brought up from a depth of 20 to 30 feet. A
single specimen was found in a lot of Blake material from off Tortugas.
Records. FLORIDA: Blake, station 43, from south of Dry Tortugas (N. Lat. 24° 08'; W. Long. 82° 15') in 33 fathoms. HISPANIOLA: Puerto Plata Harbor, Santo Domingo in 20 to 30 feet.
Entalina platamodes Watson
Siphodentalium platamodes Watson 1879, J. Linn. Soc. London 14, p. 519; Watson 1885, Challen- ger Rept., Zool. 15, p. 13, pi. 2, fig. 4.
Entalina platamodes Pilsbry and Sharp 1897, Manual of Conchology (1) 17, p. 133, pi. 23, fig. 3-5; Henderson 1920, Bull. U.S. Nat. Mus. No. ill, p. 87, pi. 15, figs. 1, 4, 5, 7.
Entalina quadrata Henderson 1920, Bull. U.S. Nat. Mus. No. Ill, p. 88, pi. 15, figs. 2, 3, 6, 10.
Notes. A lot of four specimens of this apparently rare species was taken by the
Atlantis. Henderson records three specimens from two locaUties off the coast of
Florida and his quadrata was repesented by a single specimen from off Grenada,
Lesser Antilles. Emerson reported five lots from off Puerto Rico totaling some 200
specimens which would indicate that in some localities at least they may be quite
common. This is the first record for Cuba.
Records. Atlantis, station 2989, off Puerto Sagua la Grande, Oriente (N. Lat. 23° 10'; W. Long. 80° 04) in 360 fathoms.
Cadulus (Polyschides) tetraschistus Watson
Siphodentalium letraschistum Watson 1879, J. Linn. Soc. London 14, p. 521; Watson 1885, Challenger Rept. Zool. 15, p. 15, pi. 2, fig. 8.
Cadulus {Polyschides) tetrachistus [sic] Watson, Henderson 1920, Bull. U. S. Nat. Mus. No. Ill, p. 97, pi. 17, fig. 1.
Notes. Two lots of this species are in the collection of the Museum of Comparative
Zoology. I agree with Henderson that this South American species appears to be
distinct from quadridentatus Dall. It is a sHghtly shorter, stouter species with a more
soUd shell. The apical lobes are shorter with broader clefts between them. The shell
surface has a slight chalky texture and is marked by distinct opaque white rings. In
quadridentatus the shell is very shiny, a clear translucent blue-white, and in perfect
specimens the apical lobes are long, straight sided and with very narrow clefts between
them. The only other known record is from Fernando Noronha in 25 fathoms,
collected by the Challenger.
Records. URUGUAY: off Montevideo (S. Lat. 35° 12', 15"; W. Long. 55" 30') in 7 fathoms {Hassler Exped.) ARGENTINA: Puerto Quequen, Buenos Aires.
Scaphopods of the Atlantis dredgings in the Western Atlantic 3 | S
Cadulus (Polyschides) quadridcnfatus Da 1 1 Siphonodentaliumqiiadndentatum Dall 1881, Bull. Mus. Comp. Zool. 9, p. 36. Cadulus qiiadridentatus Dall 1889, Bull. Mus. Comp. Zool. 18, p. 428, pi 27 fig 5- Hknoerson 1920, Bull. U.S. Nat. Mus. No. 1 1 1, p. 97, pi. 17, fig. 2-3.
Notes. Three new records for this rather common and characteristic species arc added.
Records. FLORIDA: 18 miles S by W of Destin in 18-20 fathoms (T. McGisiv). CLBA: La Chorrera, Habana. BERMUDA (O. Bryant).
Cadulus (Polyschides) tetrodon Pilsbry and Sharp Cadulus (Polyschides) tetrodon Pilsbry and Sharp 1897, Manual of Conchology (1) 17, p. 151, pi. 29, figs. 14-18; Henderson 1920, Bull. U.S. Nat. Mus. No. 1 1 1, p. iOI, pi. 17, fig. 5.
Notes. The lot from off Carysfort Light in 100 fathoms makes a new depth record for this species.
Records. FLORIDA: Boynton Beach in 40 feet (T. McGinty); 4 mi. N.E. of Beacon D, Key Largo in 66 fathoms; 5 mi. N.E. of Carysfort Light, Key Largo in 100 fathoms (both L. A. Burry).
Cadulus (Polyschides) carolinensis Bush Cadulus carolinensis Bush 1885, Trans. Connecticut Acad. Arts and Sci. 6, p. 471, pi. 45, fig. 19; Henderson 1920, Bull. U.S. Nat. Mus. No. Ill, p. 102, pi. 17, figs. 6-7.
Notes. This is a very common species in the region of Cape Hatteras, North CaroHna, but records from Florida, particularly the west coast, are rare.
Records. FLORIDA: 15-35 miles off Fort Walton in 13-20 fathoms (L. A. Burrv, 2 lots).
Cadulus (Platyschides) grandis Verrill Cadulus grandis Verrill 1884, Trans. Connecticut Acad. Arts and Sci. 6, pt. 1, p. 219: pt. 2, pi. 44, fig 20; Henderson 1920, Bull. U.S. Nat. Mus. No. Ill, p. 105, pi. 17, fig. 12.
Notes. Three lots of this large and common Cadulus were taken by the Atlantis.
Records. NEW JERSEY: Atlantis station (N. Lat. 39' 40'; W. Long. 71 43) in 820 fathoms; Atlantis station (N. Lat. 39° 34'; W. Long. 71° 44') in 935 fathoms, both about 120 miles E. of Great Bay. VIRGINIA: Atlantis station about 80 miles N.E. of Cape Charles (N. Lat. 37' 21'; W. Long. 74° 12') in 860 fathoms.
Cadulus (Platyschides) agassizii Dall Cadulus agassizii Dall 1881, Bull. Mus. Comp. Zool. 9, p. 35; Dall 1889, Bull. Mus. Comp. Zool. 18, p. 430; Henderson 1920, Bull. U.S.Nat. Mus. No. Ill, p. 110, pi. 18, figs. 1, 3.
Notes. Only a single new record for this rather common species is added. The species ranges from off Chesapeake Bay south to Key West, Florida, and HtNDtRSON records large series from off Fowey Light and Sand Key Florida.
Records. FLORIDA: Bibb station 179, ofi" Tennessee Reef (N. Lat. 24^ 35' 00'; W. Long. 80 39' 00") in 115 fathoms.
Cadulus (Platyschides) watsoni Dall Cadulus watsoni Dall 1881, Bull. Mus. Comp. Zool. 9, p. 34; Dall 1889, Bull. Mus. Comp. Zool. 18, p. 429, pi. 27, fig. 12a; Henderson 1920, Bull. U.S. Nat. Mus. No. 1 1 1. p. 120, pi. 18. fig. 12.
Notes. A large fine specimen of this very rare species was taken by the Atlantis; this is the third known record. The original lot was taken off Cape San Antonio, Cuba, and a second lot of five specimens in the United States National Museum is from off Old Providence Island, Caribbean Islands.
Records. CUBA: Atlantis, station 2989, off Sagua la Grande. Las Villas (N. Lat. 23 10'; W. Long. 80 04') in 360 fathoms.
316 Ruth D. Turner
Cadulus (Platyschides) elongatus Henderson Cadiilus {Platyschides']) elongatus Henderson 1920, Bull. U.S. Nat. Mus. No. Ill, p. 122, pi. 19, fig. 15.
Notes. This species was described by Henderson from a unique specimen dredged off the mouth of the Mississippi River in 68 fathoms. A series of five specimens and a number of fragments was obtained by Mrs. L. A. Weisenhaus by washing the mud from a shrimp boat net and anchor. The specimens agree well with Henderson's description.
Records. TEXAS: off Port Isabel in 50 fathoms.
Cadulus (Platyschides) braziliensis Henderson Cadulus {Platyschides) braziliensis Henderson 1920, Bull. U.S. Nat. Mus. No. Ill, p. 124, pi. 19, fig. 16.
Notes. The single specimen dredged by the Hassler makes the second known record for this species. Henderson described the species from a lot of two specimens dredged by the Albatross off Rio de Janeiro, Brazil. This coast is so poorly known that the few records available are no indication of the abundance or distribution of the species.
Records. URUGUAY: off Montevideo (S. Lat. 35° 12'; W. Long. 55° 30') in 7 fathoms {Hassler Exped.).
Cadulus (Platyschides) simpsoni Henderson Cadulus {Platyschides) simpsoni Henderson 1920, Bull. U.S. Nat. Mus. No. Ill, p. 127, pi. 19, fig. 17.
Notes. The Atlantis obtained two lots of this species, bringing the known records up to five. It is probably not a rare species, however, to judge by the size of some of the lots.
Records. CUBA: Atlantis station 2987E, off Sagua la Grande, Las Villas (N. Lat. 23° 19'; W. Long. 79° 59') in 315 fathoms; Atlantis, station 2963, off Bahia Cochinos, Las Villas (N. Lat. 22° 07'; W. Long. 81° 08') in 180-190 fathoms.
Cadulus (Gadlla) mayori Henderson Cadulus {Gadila) mayori Henderson 1920, Bull. U.S. Nat. Mus. No. Ill, p. 133, pi. 19, fig. 3.
Notes. Like Cadulus elongatus this species was obtained by Mrs. Weisenhaus from the mud on the net and anchor of a shrimp boat. The records from Cuba are the first for that island.
Records. FLORIDA: 2i miles S.S.E. of Looe Key, Marathon in 50 fathoms; 5 miles E. of Carysfort Light in 96-107 fathoms (both L. A. Burry). TEXAS: off Port Isabel in 50 fathoms. CUBA: Blake, station 20, off Bahia Honda (N. Lat. 23° 02'; W. Long. 83° 11') in 220 fathoms; Atlantis, station 2981C, off Punta Alegre, Camaguey (N. Lat. 22° 47'; W. Long. 78° 49') in 195 fathoms; Atlantis, station 2963, off Bahia Cochinos, Las Villas (N. Lat. 22° 07'; W. Long. 81° 08') in 180-190 fathoms.
Cadulus (Gadila) acus Dall Cadulus acus Dall 1889, Bull. Mus. Comp. Zool. 18, p. 432, pi. 27, fig. 11. Cadulus {Gadila) acus Dall, Henderson 1920, Bull. U.S. Nat. Mus. No. 1 1 1, p. 140, pi. 20, figs. 11,13. Cadulus {Gadilopsis) acus Dall, Emerson 1952, Smithsonian Misc. Coll. 117, No. 6, p. 10.
Notes. A very large lot of 250 or more specimens was collected by Dr. Clench from a fine grey mud brought up during the channel dredging operations in Puerto Plata Harbor, Santo Domingo.
Scaphopods of the Atlantis drcdgings in the Western Atlantic 3 1 7
Records. CUBA: La Chorrera, Habana. HISPANIOLA: Puerto Plata Harbor, Santo Domingo. VIRGIN ISLANDS: St. Thomas.
Cadulus (Gadila) verrilli Henderson Cadulus {Gadila) verrilli Henderson 1920, Bull. U.S. Nat. Mus. No. Ill, p. 1.^6. pi. 19. fig. LI.
Notes. Henderson records only four lots of this species, all from off Martha's Vineyard, Mass.
Records. RHODE ISLAND: 76 miles south of Block Island in 180-190 fathoms (J. Miujr).
Cadulus (Cadulus) ampullaceus Watson Cadidus ampullaceus Watson 1879, J. Linn. Soc. London 14, p. 529; Waison 1885. Challenger Rept., Zool. 15, p. 23, pi. 3, fig. 11; Henderson 1920, Bull. U.S. Nat. Mus. No. 1 1 1, p 144, pi 19. fig. 7.
Notes. Two lots that are referable to this minute but characteristic species were collected by the Atlantis. The only other known lot is that taken by the Challenger off Culebra Island.
Records. CUBA: /l//aA/m, station 2961C, off Bahia Cochinos (N. Lat. 22 07 ; W. Long. 81' 08') in 190-370 fathoms; Atlantis, station 2967B, off Guantanamo Bay, Oriente (N. Lat. 19' 43 ; W. Long. 74" 57' 30") in 1330-1650 fathoms.
Cadulus (Cadulus) exiguus Watson Cadulus exiguus Watson 1879, J. Linn. Soc. London 14, p. 528; Watson 1885, Challenger Rept., Zool. 15, p. 23, pi. 3, fig. 10; Henderson 1920, Bull. U.S. Nat. Mus. No. 111. p. 145, pi. 20, fig.9.
Notes. This is the seventh known record for this species. It has been recorded from Culebra Island, Barbados; from three stations off Puerto Rico, and one from the " Bahamas ". This is the first record for Cuba, and the specimens were dredged from a much greater depth than any previous lots.
Records. CUBA: Atlantis, station 2959, off the Isle of Pines (N. Lat. 21 17': W. Long. 83" 06') in 2050 fathoms.
CATALOGUE OF THE SCAPHOPOD TYPES IN THE MUSEUM OF COMPARATIN E
ZOOLOGY
In the following catalogue of the types it will be noted that the holotypes of many of the species that Dall described in the " Blake Report " are in the Museum of Com- parative Zoology. It is difficult to know just what Henderson (1920) meant by his use of the word " Type ". If he was referring to the holotype, he made some rather curious errors. He was probably using it to refer to any of the primary types, for indeed all his references are to either holotypes or paratypes. It is curious that he says, under Cadulus aequalis Dall "The type Cat. No. 95373, U.S.N. M. is from a lot of two specimens taken by the Blake . . ." and later " This is the unique museum record ", when, in the original description, Dall stated that he had three specimens. This third specimen was the one selected by Dall as the holotype and returned to the Museum of Comparative Zoology. Though Henderson says in the introduction to his paper that he had the entire collection from the Museum ol Comparative Zoology for study, one wonders if he actually did. In any event, he put very little of this material on record. acus Dall Caduh^s 1889, Bull. Mus. Comp. Zool. 18, p. 432. pi. 27. fig. 1 1. Holotype, MCZ 7751
Samana Bay, Santo Domingo in 16 fathoms. This is the specimen l.gured by Dall and was so
labelled by him.
318 Ruth D. Turner
aequalis Dall, Cadulus 1881, Bull. Mus. Comp. Zool. 9, p. 34; Dall 1889, Bull. Mus. Comp. Zool. 18, p. 429, pi. 27, fig. 9. Holotype, MCZ 7740, Blake, station 43, from off Tortugas, Florida (N. Lat. 24° 08'; W. Long. 82° 51') in 339 fathoms. This is the specimen figured by Dall.
agassizii iya\\, Cadulus 1881, Bull. Mus. Comp. Zool. 9, p. 35; Dall 1889, Bull. Mus. Comp. Zool. 18, p. 430, pi. 27, fig. 12c. Holotype, MCZ 7746, Blake, station 5, from south of Marquesas Keys, Florida (N. Lat. 24° 05'; W. Long. 82° 13') in 229 fathoms. This is the specimen figured by Dall.
amiantus Dall, Cadulus 1889, Bull. Mus. Comp. Zool. 18, p. 431, pi. 27, fig. 7. Holotype, MCZ 7749, Blake, station 19, from off Bahia Honda, Pinar del Rio, Cuba (N. Lat. 23° 03' 00"; W. Long. 83° 10' 30") in 310 fathoms.
atlanticus Henderson Cadulus (Gadila) 1920, Bull. U.S. Nat. Mus. No. Ill, p. 137, pi. 20, fig. 2. Paratype, MCZ 186815, from U.S.B.F. Albatross station 2862, from off Nantucket Island, Mass. (N. Lat. 39° 38' 00"; W. Long. 70° 22' 00") in 1004 fathoms.
barbadensis Henderson Cadulus {Cadulus) transitorius 1920, Bull. U.S. Nat. Mus. No. Ill, p. 144, pi. 19, fig. 7. Paratype MCZ 7744, Blake, station without number, from off the Barbados in 100 fathoms. This specimen was labelled as type by Henderson though curiously he does not mention the specimen in his paper.
bushii Dall Cadulus {carolinensis var. ?) 1889, Bull. Mus. Comp. Zool. 18, p. 430, not figured. Holo- type MCZ 7745, Blake, station from off Barbados in 100 fathoms. This is the specimen measured by Dall and returned to the Museum of Comparative Zoology.
bushi Henderson Siphonodentalium (Pulsellum) 1920, Bull. U.S. Nat. Mus. No. Ill, p. 94, pi. 16, fig. 6. Paratype MCZ 186822, Albatross station 2710, off [Bamegat Bay], New Jersey (N. Lat. 40° 06' 00"; W. Long. 68° 01' 30") in 984 fathoms.
callipeplum Dall, Dentalium 1889, Bull. Mus. Comp. Zool. 18, p. 419, pi. 27, fig. 12b. Holotype MCZ 7672, Blake, station 167, from off Guadeloupe, Lesser Antilles (N. Lat. 16° 09'; W. Long. 61° 29') in 175 fathoms. This is the specimen figured by Dall and so labelled by him. It even shows the hole in the side which is indicated in the figure. The type locality is that given above rather than U.S.B.F. station 2400, between the Mississippi River delta and Cedar Keys in 169 fathoms as given by Henderson.
callithrix Dall Dentalium 1889, Bull. Mus. Comp. Zool. 18, p. 427, pi. 27, fig. 10. Holotype MCZ 7734, Blake, station 236, off Bequia, Grenadines (N. Lat. 12° 52'; W. Long. 61° 96') in 1591 fathoms. This is the specimen labelled by Dall as ' Figured type ' and is the one figured in the Blake Report. Henderson reports the type as from a Blake station, in Yucatan Straits in 640 fathoms.
carduus Dall, Dentalium 1889, Bull. Mus. Comp. Zool. 18, p. 423, pi. 27, fig. 3. Holotype MCZ 7692, Blake, station 220, off St. Lucia, Lesser Antilles (N. Lat. 13° 50'; W. Long. 61° 03') in 116 fathoms. This is the figured specimen.
carolinensis Bush, Cadulus 1885, Ann. Report of the Commissioner of Fish and Fisheries for 1883, p. 587; Bush 1885, Trans. Connecticut Acad. Arts and Sci. 6, pt. 2, p. 471, pi. 45, fig. 19. Para- types MCZ 186818, Albatross, station 2114, off Cape Hatteras, North Carolina (N. Lat. 35° 20' 00"; W. Long. 75° 20' 00") in 14 fathoms.
ceratum Dall Dentalium 1881, Bull. Mus. Comp. Zool. 9, p. 38; Dall 1889, Bull. Mus. Comp. Zool. 18, p. 424, pi. 26, fig. 5, pi. 27, fig. 2. Paratype MCZ 7697, Blake, station 2, off Habana, Cuba (N. Lat. 23° 14'; W. Long. 82° 25') in 805 fathoms.
curcubita Dall Cadulus 1881, Bull. Mus. Comp. Zool. 9, p. 35; Dall 1889, Bull. Mus. Comp. Zool. 18, p. 431, pi. 27, fig. 12d. Holotype MCZ 7750, Blake, station 19, off Bahia Honda, (Pinar del Rio) Cuba in 310 fathoms.
elephas Henderson Cadulus (Platyschides) 1920, Bull. U.S. Nat. Mus. No. Ill, p. 107, pi. 17, fig. 10. Holotype MCZ 7741, Blake, station 230, off St. Vincent, Lesser Antilles (N. Lat. 13° 13' 20"; W. Long. 61° 18' 45") in 464 fathoms.
Scaphopods of the Atlantis drcdgings in the Western Atlantic 319
gouldii Dall Dentaliiim 1889, Bull. Mus. Comp. Zool. 18, p. 424 (not figured). I'aratype MCZ 7707. Blake, station 65, off Habana, Cuba in 127 fathoms. This was a poor and badly worn specimen. Better specimens were obtained off the Barbados at Blake station 299 in 140 fathoms along with obsciirum Dall.
grandis Verrill Cadiihis 1884, Trans. Connecticut Acad. Arts and Sci. 6, pt. 1, p. 219; 6. pt. 2, pi. 44, fig. 20. Paratype MCZ 186804, Albatross, station 2076. about 230 miles F-. of Marthas Vineyard, Massachusetts (N. Lat. 41 13' 00"; W. Long. 66 00' 50") in 906 fathoms.
lunula Dall Cadulus 1881, Bull. Mus. Comp. Zool. 9, p. 35; Dall 1889, Bull. Mus. Comp. Zool. 18, p. 431, pi. 27, fig. 8. Holotype MCZ 7747, Blake, station 2, off Morro Light, Habana, Cuba in 805 fathoms.
mayori Henderson Cadulus (Gadila) 1920, Bull. U.S. Nat. Mus. No. ill, p. 133, pi. 19, fig. 3. Para- type MCZ 48411, Eolis, station 43, off Key West, Florida in 63 fathoms.
miamiensis Henderson Cadulus (Platyschides) 1920, Bull. U.S. Nat. Mus. No. Ill, p. 129, pi. 19. fig. 18. Paratype MCZ 48413, Eolis, station 348, off Fowey Light, Florida in 1 10 fathoms.
nanus Clench and Aguayo Cadulus iota 1939, Mem. de la Soc. Cubana de Hist. Nat. 13, No. 3, p. 197. Holotype MCZ 89222, Gibara, Oriente Province, Cuba in 40 fathoms.
obscurum Dall Dentalium gouldii var. 1889, Bull. Mus. Comp. Zool. 18, p. 424, pi. 27, fig. 4 (not pi. 26 as given in the text). Holotype MCZ 7708, Blake, station 299, off Barbados, Lesser Antilles (N. Lat. 13° 05' 00", W. Long. 59" 39' 40") in 140 fathoms. This is the specimen figured by Dall and so labelled by him, [not station 229 as given by Henderson.]
occidentale Henderson, Siphonodentalium (Pulsellum) 1920, Bull. U.S. Nat. Mus. No. Ill, p. 93. pi. 16, fig. 4. Paratype MCZ 186823, from U.S.B.F. Fish Hawk, station 871, off Martha's Vineyard. Massachusetts (N. Lat. 40° 02' 54"; W. Long. 70° 23' 40") in 115 fathoms. Henderson records 86 fathoms for this station in his original description, but the station lists give 115.
ophiodon Dall Dentalium 1881, Bull. Mus. Comp. Zool. 9, p. 38; Dall 1889, Bull. Mus. Comp. Zool. 18, p. 427, pi. 26, fig. 9. Paratype MCZ 7729, Blake, station 21, off Bahia Honda (Pinar dd Rio) Cuba in 827 fathoms.
pandionis Verrill and Smith Cadulus 1880, Amer. J. Sci. 20, p. 399. Paratypes MCZ 186811, Fish Hawk, station 877, south of Marthas Vineyard, Massachusetts (N. Lat. 39^ 56'; W. Long. 70 54' 18") in 126 fathoms.
/jomw Henderson Cadulus {Platyschides) 1920, Bull. U.S. Nat. Mus. No. Ill, p. 113, pi. 18. figs. 2, 4. Paratypes MCZ 48414, State Univ. of Iowa, station 44 off the Barbados, Lesser Antilles in 90 fathoms.
perlongum Dall Dentalium 1881, Bull. Mus. Comp. Zool. 9, p. 36; Dall 1889. Bull. Mus. Comp. Zool. 18, p. 419, pi. 27, fig. 6. Holotype MCZ 7752, Blake, station 33 from north of the Yucatan Bank (N. Lat. 24° 01'; W. Long. 88° 58') in 1568 fathoms. This specimen is the only one in the four lots mentioned by Dall in his original description that measures 80 mm and agrees with his figure Consequently, though Dall did not label it as the figured specimen, there seems no question but that it is the holotype. Henderson states that •' the type is not m the L nited States National Museum ".
poculum Dall Cadulus 1889, Bull. Mus. Comp. Zool. 18, p. 429 (not figured). Holotype MCZ 7743. Blake station, off Cape San Antonio, Cuba [Yucatan Strait] in 640 fathoms. Dall did not hgure this species but the specimen which he measured, the largest of those obtained, is in the MCZ collection.
qt^adridentatus Dall Siphonodentalitm 1881, Bull. Mus. Comp. Zool 9 p. ^^- ;?;'! l^^^^'';;';;':^^ qt^adridentatus. Bull. Mus. Comp. Zool. 18, p. 428, pi. 27. hg. 5. Holotype MCZ 7739. Pourtales dredgings on the west coast of Florida in 30 fathoms.
sigsbeanum Dall Dentalium 1881, Bull. Mus. Comp. Zool. 9. p. 38. Holotype MCZ 7737. Blake, station from Yucatan Strait in 640 fathoms.
320 Ruth D. Turner
spectabilis Verrill Cadulus 1885, Trans. Connecticut Acad. Arts and Sci. 6, pt. 2, p. 432, pi. 44, fig. 19. Paratype MCZ 186801, Albatross, station 2221, about 180 miles off Ocean City, New Jersey (N. Lat. 39° 05' 30"; W. Long. 70° 44' 30") in 1525 fathoms. Henderson was in error when he stated that the type of this species was from U.S.B.F. station 271 1. This station was not included in Verrill's original description, and in fact station 2711 was made on September 16, 1886, and Verrill's description was published in June 1885. The holotype is in the U.S. Nat. Mus. No. 40,498 from station 2221.
taphrium Dall Dentalium 1889, Bull. Mus. Comp. Zool. 18, p. 422, (not figured). Paratype MCZ 7690 from off the Carolina Coast in 52 fathoms.
Ha/.so«/ Dall Cadulus 1881, Bull. Mus. Comp. Zool. 9, p. 34; Dall 1889, Bull. Mus. Comp. Zool. 18, p. 429, pi. 27, fig. 12a. Holotype MCZ 7742 from Blake, station off Cape San Antonio, Cuba in 413 fathoms.
verrilli Henderson Cadulus (Gadila) 1920, Bull. U.S. Nat. Mus. No. Ill, p. 136, pi. 19, fig. 13. Para- type MCZ 186819 U.S.B.F. Fish Hawk, station 871, off Martha's Vineyard, Massachusetts (N. Lat. 40° 02' 54"; W. Long. 70° 23' 40") in 115 fathoms.
verrilli Henderson Siphonodentalium (Siphonodentalium) 1920, Bull. U.S. Nat. Mus. No. Ill, p. 91, pi. 16, figs. 2 and 7. Paratype MCZ 186821 from Albatross, station 2710, off Nantucket (N. Lat. 40° 06' 00"; W. Long. 68° 01 ' 30") in 984 fathoms.
REFERENCES
Chace, F. a. (1940), The Atlantis Expedition to the West Indies in 1938 and 1939, under the joint
auspices of the University of Havana and Harvard University. List of Stations. Woods Hole
Oceanogr. Inst. Contrib. No. 274, 1-8. Dall, W. H. (1881), Reports on the Results of Dredging under the supervision of Alexander Agassiz
— by the coast survey Steamer Blake. Preliminary Report on the Mollusca. Bull. Mus. Comp.
Zool. 9, (2), 33-39. Dall, W. H. (1895), Reports on the Results of Dredging, etc. by the Blake. Report on the Mollusca
Part 2, Gastropoda and Scaphopoda. Bull. Mus. Comp. Zool. 18, 418-432, pis. 26-27. Emerson, W. K. (1952), The Scaphopod Mollusks collected by the First Johnson-Smithsonian
Deep-Sea Expedition. Smithsonian Misc. Coll. 117 (6), 1-14. Henderson, J. B. (1920), A Monograph of the East American Scaphopod Mollusks. Bull. U.S.
Nat. Mus. No. Ill, 1-177, pis. 1-20. PiLSBRY, H. a. and Sharp, B. (1897), Scaphopoda. Manual of Conchology (1) 17, 1-280, pis. 1-37. Watson, R. B. (1885), Scaphoda, Repts. Sci. Res., H.M.S. Challenger, Zool. 15, 1-24, pis. 1-3.
Papers in Marine Biology and Oceanography, Suppl. lo vol. .1 of Dccp-Sea Research, pp. 321-330,
Effect of freshets on Passamaquoddy plankton
By A. G. Huntsman Department of Zoology, University of Toronto
Summary— Sudden or heavy discharge into Passamaquoddy Bay, from streams at its head, works out through the 10-mile long Bay and through the S-mile long Head Harbour Passage, its main con- nection with the Bay of Fundy, in less than 10 days, as shown by the salinity of the water. Through the Bay, the outflow is more or less superficial and carries certain elements of the plankton out into the Passage. But, in the latter, strong tidal mixing prevents stratification, although the water is deeper. Under these circumstances, working of the freshet outward has a double effect, first a carrying out of the well-mixed plankton, and then an indraft of deep plankton from without. The latter provides an abundance of planktonic animals in the Passage at all depths.
Forty years ago, Dr. Johan Hjort, of Norway, brought Henry B. Bigelow and me together in the expedition (Hjort, 1919), which he was organizing for the Biological Board of Canada. It was for me a marvellous introduction to the oceanographic problem in our waters. The methods used were those with which Hjort had been concerned in north European waters and Bigelov/ in waters off the New England and Nova Scotian coasts. In the picture that was developed, the Bay of Fundy, which I was investigating for quite a few years from the Atlantic Biological Station at St. Andrews, New Brunswick, stands out like a sore thumb, in the peculiarity of both its plankton and its hydrography. This is in association with very heavy tidal action. There is also a striking peculiarity in the wealth offish as well as of zooplankton near the surface in the Passamaquoddy region near the mouth of the Bay (Huntsman, 1927). When the Passamaquoddy Power Project made the explanation of this condition desirable, Bigelow asked me whether temperature explained this. and. if not, what could the explanation be. This paper gives part of the answer to his question and is offered as a tribute to the stimulating effects of long and most enjoyable associa- tion with him in oceanographic investigations.
The herring is by far the most abundant fish in the Passamaquoddy region (Fig. 1). Its food consists mainly of Crustacean zooplanktons of the orders Copepoda and Euphausiacea, which are known to the local fishermen as " red feed " and " shrimp " respectively, as seen in herring stomachs. The distribution of such zooplankton both vertically and horizontally determines its availability to the herring, which take these forms individually as silhouetted against the sky when a matter of inches above them. The herring have their own peculiar vertical and horizontal distribution, and vary in condition in accordance with the food available at the place and the time (Battle, et al., 1936). Freshets in the rivers that discharge into Passamaquoddy Bay shift the herring about from one place to another (Huntsman. 1934). as do other factors that bring about movements of the water. Also, mixture over shoals under tidal action of the water of this Bay, which is stratified from river discharge, concentrates the herring and their planktonic food together for effective feeding (Battle, et al.. 1936). There has been need for elucidation of any effects of freshets in shifting the zooplankton from place to place.
M 321
322
A. G. Huntsman
ESTUARIAL CIRCULATION OF ZOOPLANKTON
The typical circulation of water in a river estuary is movement oceanward of the fresher and lighter surface water, and movement riverward of the Salter and heavier deeper water. This is dependent upon tidal mixing of the fresh river water with the salt sea water. It will depend upon the depth from the surface to which particular
\Ot60ECVASH Bt^fi
UR DE UWTRE
i ZL
Fig. 1. Passamaquoddy Bay, New Brunswick, showing principal rivers, passages to Bay of Fundy
and positions of the stations mentioned.
Effect of freshets on Passamaquoddy planklon 323
zooplanktonts keep, and upon the depths of the two movements, as to whether these will be carried oceanward out of the estuary or riverward to be concentrated at the head of the estuary. The strengths and depths of the movements will depend, not only upon the degree of tidal mixing, but also upon the amount of river water. Any estuarial concentration of zooplankton there may be, will be increased by freshets in the river.
HOURS OF DAY
Fig. 2. Vertical distribution of Calanus throughout the 24-hr. day at Prince station No. .'> in the Bay of Fundy, as inferred from vertical tows made on September 20, 1926, through ten metres of water at different depths on three occasions: (1) between 2.50 and 3.55 hr., (2) between 4.35 and 5.25 hr. and (3) between 7.15 and 7.55 hr., as shown by vertical lines. Periods of sunlight and moonlight arc
shown at the top, and numbers of Calanus arc per tow.
While the zooplanktonts may be at the proper depth during the day for transport riverward, their migration towards the surface at night may well result in their being carried oceanward. So complex is the situation that, as yet, only their actual distribu- tion can be depended upon to show in which direction particular zooplanktonts have moved.
324 A. G. Huntsman
DIURNAL MIGRATION OF CALAMUS The principal zooplanktont for food of Passamaquoddy herring is the copepod, Calanusfinmarchicus. Its vertical migrations are so complex (Esterly, 1919; Russell, 1926; Clarke, 1933; and Gushing, 1951) that local and temporal data seem necessary to show its vertical distribution that may determine how it will be shifted in the Passamaquoddy circulation. Fig. 2 gives an interpretation of the vertical distribution of this species throughout an entire day at Prince Station No. 5, in water about 90 metres deep in the Bay of Fundy just outside the main passage leading to Passama- quoddy Bay. It is believed that this is sufficiently representative of the times and places dealt with, except as altered by vertical movements of the water. The interpretation is based, as shown, mainly upon data obtained on September 20, 1926, in closing vertical tows through six different strata at three different times with rapidly increasing light intensity in the morning. It will be evident that these copepods were on the whole more heavily concentrated near the bottom, and least heavily near the surface.
CHARACTERISTICS OF THE REGION
Passamaquoddy Bay (Fig. 1) is about five miles wide and ten miles long. On its east side, it is connected with the Bay of Fundy through the relatively short and shallow Letite Passage, and also through the still shallower Little Letite Passage. The main connection, however, is at the south end through the long and tortuous, as well as deep, Western or Head Harbour Passage (also called " Quoddy River "), which virtually forms its mouth. The Passages have very rough, irregular and rocky bottom. The Bay inside is of rather uniform depth, from 20 to 35 metres, but it is still deeper near the Passages.
Fresh water is discharged into the Bay mainly from the St. Croix, Magaguadavic and Digdeguash Rivers. The St. Croix River discharges into the west side of the Bay near its mouth somewhat more than 2,000 sec/ft from a drainage basin of over 1,300 square miles. It is controlled for power purposes, so that in summer the discharge is comparatively steady, ranging for the most part from 500 to 2,000 sec/ft. The Magaguadavic River discharges on the average around 1,000 sec/ft from more than 600 square miles into the Bay on its east side near its head, and it is similarly controlled for power purposes. The Digdeguash River, together with other uncontrolled streams, discharges into the head of the Bay the drainage from about 300 square miles. The volume and availability of this discharge may be judged from records made on the Magaguadavic River at Elmcroft (above the level of storage) with a drainage area of about 350 square miles. From 2 to 6 inches of rain fell over the drainage basin on August 26 and 27, 1924, and the rates of discharge on successive days, beginning on August 25, were: 85; 246; 2,890; 2,520; 2,030; 518; 339; 276 sec/ft. Therefore, with heavy rains, the principal increase in river discharge is a day or so after the rain. With other rivers controlled, this is into the head of the Bay. It is to be noted that the discharges of the St. Croix and Magaguadavic Rivers reach the Bay only after having been mixed with sea water in estuaries, which are fifteen and four miles long respec- tively. The estuary of the Digdeguash River is about two miles long.
The tides of the region are very heavy, the amplitude ranging from 20 to 25 feet. The rough character of the bottom near shore and in the Passages makes the strong tidal currents very effective in mixing the light river water with the heavy sea water. This is evident for the Bay itself in that near the mouth the salinities at the surface and
Effect of freshets on Passamaqiioddy plankton 325
at 50 metres depth, which is deeper than the Bay in general, were for example on October 12, 1933: 30-99 and 31-73 respectively. Also, the salinities at the same depths on the same day at Station No. 5 outside Head Harbour Passage were: 31 ^X and 32-32° , respectively. Ket( hum and Kkhn (1953) have calculated that in August of 1951 the mixed water moving out of the Bay near its mouth was over 100 times as great as that of the discharge from rivers, and that outside the Passages it had increased to nearly 600 times.
Owing to their shallowness, the Letite Passages do not permit much movement of water through, so that the principal outlet for mixed water and the principal inlet for salt water is Head Harbour Passage. Also, movement through the Letite Passages is more inward than outward, as determined through a complete tidal cycle in 1951, But, there is very definite passage out of mixed water through Letite and passage in of salt water, as well as very heavy mixing of the two.
RAINFALL AND PLANKTON INDRAFT
Calanus is not produced to any particular extent in the Passamaquoddy region, but is there as an immigrant from the Gulf of Maine (Wright, 1929; Fish, 1936). It was very abundant at Prince Station No. 5 just outside Passamaquoddy Bay in the late summer of 1933. Vertical hauls with the No. 0 (bolting cloth measure) net from 90 to 0 metres gave the following quantities in cubic centimetres of settled plankton (chiefly Calanus) on the dates indicated: 13 on July 10; 9 on August II; 22 on September 15.
The quantity of Calanus at Station No. 5 varied greatly from September 23 to October 3. Deep tows were made on the former date, giving large quantities at from 100 to 50 metres and at about 90 metres. On October 2, a vertical haul gave only 2 cu.cm. Yet, deep tows made the next day revealed even greater abundance than on September 23.
During the night of September 17-18 there was a very heavy rainfall o\er the basin that drains into the head of Passamaquoddy Bay, over 5 in. falling at St. Andrews and 4-81 in. at St. George on west and east sides of the Bay, and 3-25 in. at Mc.Adam at the head of the drainage into the Digdeguash River. Three days later, another inch of rain fell over the area. It is estimated that these rainfalls more than doubled the amount of fresh water being discharged into the Bay.
Ketchum and Keen (1953) have calculated that the mean flushing time for the removal from Passamaquoddy Bay of freshwater discharged into it is I5-S days, and they conclude that "it seems probable that a flushing time of about 15 days should be approximately correct ". In late summer of 1933, there were three heavy rainfalls recorded, on August 25, September 18 and October 7. Weekly determina- tions of bottom salinity in the middle of Passamaquoddy Bay showed that higher salinity returned between 5 and 13, 9 and 16, and II and IS days respectively, if such return has a constant period, it will, therefore, lie between 1 1 and 13 days after the rainfall. After the freshet of September 18, salinities were measured for Prince Station No. 9, which is ofT Clam Cove Head at the mouth oi Passamaquoddy Bay where it joins Head Harbour Passage, on September 23, 26 and 29, and on October 3. The values at 50 metres depth were 31-78 , 31-67 , , 31-85 and 31-89 ;., respectively. This shows that Salter water was entering the mouth of the Bay 1 1 days after the rainfall. What relation this has to the flushing lime is not clear. It may
326
A. G. Huntsman
represent merely the beginning of heavy interchange at the mouth of the large mass of fresh water.
In Head Harbour Passage, particularly the outer part, heavy tidal action and irregular bottom keep the water quite thoroughly stirred, so that the plankton present can easily be obtained in tows at any depth. Tows were made at two Stations (H.F. 50 and 35) in the outer part of the Passage on September 18 (at 50 only), 23, 26, 29 and October 3. The quantities (cu.cm. after settling) of plankton (chiefly Calanus) were : 12; 8 and 16; 18 and 12; 180 and 95; and 80 and 27 respectively. There was thus a very marked increase in quantity between 8 and 1 1 days after the rainfall. It would seem to be possibly significant that, following the heavy indraft of Calanus into the Passage, as found on September 29, there was a low amount outside on October 2, but not on October 3. The movement outward of the mixed water from the freshet might be expected to have such temporary effect in carrying outward much of the plankton.
|
3 |
/ / / / |
y^ ^v |
|
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2 |
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\^ |
|
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1- |
/ |
^k |
|
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lU |
^^ |
||
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kJ |
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10
15
DAYS
20
Fig. 3. Height above low water of surface of Digdeguash River at the Stillwater bridge in August,
1951.
The very definite result was that a dearth of Calanus in Head Harbour Passage was changed to abundance when the water from the freshet worked its way out. Calanus had been abundant in deep water outside, but the freshet made it abundantly available to birds and to herring and other near-surface fishes by bringing it into the Passage, where vertical currents lift it rather steadily toward the surface, overcoming its tendency to descend from daylight. As far as the facts went, this was coincident with entrance of quite salt water into the Passage, presumably from the depths outside where Calanus was known to be abundant.
RAINFALL AND SHIFTING OF PLANKTON
On August 8 and 9, 1951, heavy rain (4-66 to 1-39 in.) fell over the drainage basin of the Digdeguash River. The course of the discharge from the River into the head of Passamaquoddy Bay was measured with a gauge at the first bridge above the point where the River falls into the tidal Digdeguash Basin (Fig. 3). The heaviest discharge was on August 10.
The progress of the outflow of fresher water was determined, beginning at different points on August 12, 13 and 14, by getting the salinities of surface samples taken
Effect of freshets on Passamaquoddy plankton
327
daily at high water at four difTerent points: (I) near the mouth of the Digdcguash estuary (James Carson's shore); (2) Indian Point at St. Andrews; (3) Mascabin Point in the outer part of Letite Passage; and (4) Wilson's Beach in the outer part of Head Harbour Passage. The results (Fig. 4) showed that the greatest effect at St. Andrews was on August 14, and that there was a clear effect at Wilson's Beach only on August 18. On that same day, the most marked efTect appeared at Mascabm Point. But there was a complexity, which seems to have been owing to the facts that there is on the whole more inward than outward movement through Letite Passage, and that the outflow is largely through the main Head Harbour Passage. Along such
25
JAMES CARSON S
_L
_L
_L
15
DAYS
20
A
/
25
Fig. 4. Shore salinity at high water at four different points in Passamaquoddy Bay and in the related Passages on successive days in August, 1951, following freshets on August 10 and 19.
course, Letite Passage and St. Andrews are on opposite shores of the half-way point. When the fresher water was most noticeable at St. Andrews four days after the hea\ icst discharge, there was very slight freshening at Mascabin Point in Letite Passage. But. another four days later, when the freshening was definite at Wilson's Beach, there was a more marked freshening at Mascabin Point. This is evidence that the outflow through Head Harbour Passage, which would be with the ebbing tide, was being carried with flooding tide north to the entrance into Letite Passage. At high tide, therefore, the latter showed a greater efTect from this than did Head Harbour Passage itself. The slighter drop at Mascabin Point on August 17 indicates that the fresher water was issuing from Head Harbour Passage on that day. Entrance of fresher water into the Bay through Letite Passage on August 17 and 18 serves to explain the
328 ^- G. Huntsman
otherwise anomalous slight drop in salinity at St. Andrews on those days. This would mean that the fresher water was in part making a circuit around Deer Island in its position between the two Passages.
It will be noted in Fig. 4 that the crest of the fresh water flood was sharp and lasted about a day only, at St. Andrews, while at Wilson's Beach it lasted for two days and was little pronounced. The definite return of Salter water to Head Harbour Passage was on August 20, that is, 1 1 days after the rainfall of August 9. This is in agreement with the data for the rainfall of September 17-18, 1933, which gave no increase in deep salinity at the inner end of Head Harbour Passage until 1 1 days or more later.
At the time of the freshet in 1951, August 9-10, Calanus finmarchicus was abundant in the passages leading out of Passamaquoddy Bay. There was also a most unusual plankton in the Bay, namely large numbers of Salps, mainly Salpa fusiformis and a few S. zonaria. Salpa seemed to be largely concentrated in the Bay, as Calanus certainly was in Head Harbour Passage. Such differential distribution was shown in tows made at 15 metres depth with a net of No. 5 mesh on August 8 at four stations, which were in the centre of the Bay (CJ, in the middle of Letite Passage (C g), at the inner end (C24) and at the outer end (Qs) of Head Harbour Passage. At these stations in the order given, the numbers of large Calanus and of Salpa respectively were as follows : C4, 0 and 5; Cg, 28 and 0; C24, 0 and 1 ; Qg, 347 and 1. The Salps must have come from the " Gulf Stream " water of the open Atlantic outside the continental slope, but they were, as near-surface forms, concentrated in the Bay, as was the locally produced Aurelia, which is quite in evidence in calm, clear weather. In contrast, Calanus was, as a deep-living form, concentrated in the Passages, as was also Sagitta elegans, another immigrant from the depths of the Gulf of Maine.
Surface tows were taken daily at Wilson's Beach in the outer part of Head Harbour Passage with net of No. 0 mesh from August 1 1 to 23. The numbers of Calanus in hundreds on successive days were: 347; 312; 712; 125; 372; 108; 34; 23; 6; 21; 104; 78; and 525. It will be noted that the number was definitely down by August 17 and lowest on August 19, with marked recovery by August 21. The numbers of 5'flg^///a, although small, show a similar course : 9; 3; 18; 10; 14; 1; 2; 1; 0; 2; 2; 5; 17. The freshet seemed to exert an effect in removing Cfl/a«w5 and Sa^/rra from the Passage, beginning perhaps on August 16, reaching a peak on August 19, and passing away by August 23 with full return of these planktonts. The freshet would thus have worked out of the Bay through Head Harbour Passage during a period of six days, centred on the 10th day after the rainfall, or the 9th day after the peak of the discharge into the head of the Bay.
Euphausiid Crustaceans, of the genera Meganyctiphanes and Thysanoessa, are also indicative of deep indraught from the Gulf of Maine. Like Calanus and Sagitta, they were to be found in Head Harbour Passage at the time of the freshet. They occur in schools and more or less avoid the net, which made their numbers in the plankton hauls less representative of their distribution. The numbers of individuals of those two genera respectively in the hauls of successive days from August 11 to 23 were : 1 and 0; 0 and 0; 10 and 4; 1 and 1 ; 14 and 0; 4 and 0; 5 and 1 ; 0 and 0; 451 and 3; 29 and 110; 85 and 22; 15 and 4; and 24 and 0. There was thus a marked increase in their numbers on August 19, at the very beginning of the strong resurgence of Salter water as shown at St. Andrews and at Mascabin Point, rather than at Wilson's Beach. It may be inferred that they had been in much greater abundance in deep
Effect of freshets on Passamaquoddy plankton 329
water outside the Passage than in the Passage. The Amphipod Crustacean, Euthemisto compressa, another immigrant from the Gulf of Maine, was present in quite small numbers which for the successive days were: 0; 0; 3; 6; 2; 8; I; 2; 7; 7; 22; 26; 17. Its numbers definitely increased on August 21.
Salpa fusiformis and S. zonaria were taken in the hauls on successive days in the following numbers respectively: 44 and 18; 28 and 0; 34 and 0; 71 and I; 54 and 0; 27^ and 0; 75 and 0; 22 and 0; 45 and 2; 23 and 1 ; 181 and); 25 and 2; 44 and 0. Since the more abundant species was in the aggregated stage, in which the individuals are attached together in rather long strings of as many as 18 individuals, there is considerable variation in its numbers, which will, therefore, not reflect very well its general abundance at the time and place. However, the numbers in italic mean that on August 16, 17 and 18 the individuals were in poor condition. It is to be expected that such open ocean forms as these would be injured by exposure to low salinity, and indeed those concentrated in the Bay were to be found in considerable numbers dead on the beaches as left by ebbing tide. It may be inferred that individuals that had been damaged by low salinity in the Bay were being carried out as the freshet worked out through the Passage. On this basis, the outflow occurred on August 16, 17 and 18, and the resurgence of Salter water began on August 19. This agrees with the behaviour of the Euphausiids.
DISCUSSION
The passage of fresh water through Passamaquoddy Bay and Head Harbour Passage from the Digdeguash River to the Bay of Fundy may be expected to vary in time with the forces that effect it. One of these variable forces is the hydrodynamic effect of lighter water at the head of Passamaquoddy Bay than in the Bay of Fundy outside. This will vary with the amount of warm and fresh, and thus relatively light, water discharged by the Digdeguash River. The freshets of September 18, 1933, and of August 9, 1951, would provide a strong force to drive the water through the Bay and the Passage. Correlatively, the heavy outside water would be driven inwards. This force would operate at the outer end of the Passage only when the fresher water reached that far.
Following the 1933 freshet, the greater force set in motion was clearly acting in the Passage between 8 and 1 1 days after the rainfall, as shown after 1 1 days by high salinity at the inner end and a great abundance of Calanus in the outer part. Following the 1951 freshet, the fresher water was in the Passage 7 days after the rainfall, as shown by drop in abundance of Calanus and Sagitta and by appearance of many Sa/pa in poor condition. The greater force had clearly acted through the Passage by 10 days after the rainfall, as shown by Salpa in good condition, as well as by increased numbers of Euphausiids and Euthemisto. By that same time, there were sharp rises in surface salinity at Mascabin Point and at St. Andrews.
It would seem to have taken in 1951 9 days, with the main discharge one day after the main rainfall, for the peak of the freshet to pass from Digdeguash Basin to the outer part of Head Harbour Passage. What relation this has to the calculated average flushing time of about 15 days for the Bay alone is uncertain. The latter is based upon average conditions, and certainly not upon the conditions following a freshet, as the authors clearly state (Ketchum and Keen, 1953).
Whatever may be the complex conditions in Passamaquoddy Bay, it seems clear that
330 ^- G. Huntsman
a freshet, in working out through the heavily stirred Head Harbour Passage to the Bay of Fundy, at first carries plankton into the Passage from within and also out from the Passage. Then, with a reflux of outer water, it brings deep-water forms into the Passage from without. The latter is of particular importance for providing food for herring. The fattest herring of the whole region are those in this Passage and its associated waters, namely Harbour de Loutre and Cobscook Bay (Battle, et al., 1936).
ACKNOWLEDGEMENTS The Atlantic Biological Station provided facilities for this work both in 1933 and in 1951. In the latter year, Messrs. Raymond Doucette and James Carson, weir operators at the Digdeguash, Mr. Prescott Dines, lighthouse keeper at Letite, and Mr. E. M. Steeves, Fishery Officer at Wilson's Beach, gave assistance. Also, Mrs. E. Jermolajew counted the planktonts.
REFERENCES
Battle, H. I., Huntsman, A. G., Jeffers, A. M., Jeffers, G. W., Johnson, W. H. and McNairn,
N. A. (1936), Fatness, digestion and food of Passamaquoddy young herring. /. Biol. Bd., Canada,
2 (4), 401^29. Clarke, G. L. (1933), Diurnal migration of plankton in the Gulf of Maine and its correlation with
changes in submarine irradiation. Biol. Bull., 65 (3), 402-436. CusHiNG, D. H. (1951), The vertical migration of planktonic Crustacea. Biol. Rev., 26, 158-192. Esterly, C. O. (1919), Reactions of various planktonic animals with reference to their diurnal
migrations. Univ. Calif. Publ., Zool., 19 (1), 1-83. Fish, C. J. (1936), The biology of Calanus finmarchicus in the Gulf of Maine and Bay of Fundy.
Biol. Bull., 70 (\), 118-141. Hjort, Johan (1919), Report of the Canadian Fisheries Expedition, 1914-1915. Dept. Naval Service,
Canada, Sess. Pap. 38^. Huntsman, A. G. (1927), The Passamaquoddy Bay power project and its effect on the fisheries.
Telegraph-Journal, Saint John., N.B. (also privately printed). Huntsman, A. G. (1934), Herring and water movements. In: James Johnstone Memorial Volume,
Univ. Liverpool Press, 81-96. Ketchum, B. H. and Keen, D. J. (1953), The exchange of fresh and salt waters in the Bay of Fundy
and Passamaquoddy Bay. J. Fish. Res. Bd., Canada, 10 (3), 97-124. Russell, F. S. (1926), The vertical distribution of marine macroplankton. IV. The apparent import- ance of light intensity as a controlling factor in the behaviour of certain species in the Plymouth
area. /. Mar. Biol. Assoc, U.K., 14 (2), 415^M0. "Wright, N.E. (1929), In: Report on the work of the Biological Board for 1928-29 (Cowie, J. J.).
Ann. Rept., Fish. Br., Dept. Mar. Fish., Canada, 62, 121-139.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 331-334.
Characteristics of surface water at Weather Ship J *
By R. B. Montgomery Chesapeake Bay Institute, The Johns Hopkins University, BaUimore, Maryland
Summary— Surface temperature and salinity observed 15 times a month for 3 years at Weather Ship J, west of Ireland, are presented in two-dimensional frequency distribution on a temperature- salinity diagram.
The temperature-salinity diagram was introduced by Helland-Hansen (1916). Helland-Hansen and Nansen (1926) and others have used it as a scatter diagram for representing a large number of discrete, non-uniformly spaced observations. The purpose of the present paper is to demonstrate the suitability of the tempcrature- saUnity diagram for quantitative representation of frequency distribution of water characteristics. A uniform series of data is used to prepare a diagram for a fixed point in the ocean.
o|o o|o 0|o ^,0 ^O ^0 ^O ^qI
Fig 1 Annualtemperature-salinity diagram for surface water at Weather Ship J. 1948-1950. Num- ber of occurrences per thousand is entered in each square (blank squares ha\e no occurrence). Heavy frequency isopleth (2U per miile) surrounds 51 percent of occurrences, hnc frequency isoplcth (54 per mille) surrounds 89 per cent. Monthly means are plotted as dots, each month idcntiticd by a Roman numeral. Anomaly of specific volume is shown by the family of cur\es.
* Contribution No 25 from the Chesapeake Bay Institute. This study was supported in part by the Office of Naval Research and by a research grant from the National Science Foundation.
331
332 R- B- Montgomery
The weather ships, occupying nearly fixed positions, are potential sources of data of great climatological and oceanographic interest. Surface water at Weather Ship J in the North Atlantic Ocean is chosen for the present example, because published observations are available for three years in Bulletin Hydrographique pour Vannee 1948, 1949, 1950. The data are credited to the Fisheries Laboratory, Lowestoft, Great Britain. Station J lies west of Ireland and south of Iceland. The usual position up to March 1950 was in the 1 -degree quadrangle with southeast corner at 53° N 18° W and from April 1950 was in the quadrangle with southeast corner at 52° N 20° W.
For most days there is one observation of temperature and sahnity, but for some days there is none. In order to obtain a homogeneous series from the somewhat irregular original series, 15 observations have been chosen for each of the 36 months. If available, the odd days 1, 3, ... 29 have been used. Missing odd days have been replaced with other days or with observations from nearby positions. January 1948 has the fewest observations, only 10, and has been completed by including 4 from late December 1947 {Bulletin Hydrographique pour Vannee 1947) and 1 from early February 1948.
The homogeneous series of 540 observations serves as the basis for the statistics presented on the temperature-salinity diagram in Fig. 1 . The frequency for each two- dimensional class with temperature interval 0-5 C and salinity interval 0-1 per mille is tabulated in per mille.
By arranging the frequencies in order of decreasing magnitude and summing cumu- latively, the result is found that about half (5 1 per cent) of the observations fall in classes with frequency 22 per mille and greater; these classes are enclosed by a heavy hne. About nine tenths (89 per cent) fall in classes with frequency 6 per mille and greater; these are enclosed by a fine Une.*
Summing the two-dimensional distribution horizontally and vertically respectively gives the one-dimensional frequency distributions of sahnity and temperature, shown by the histograms at the left and top of Fig. 1 .
Three-year monthly means for Weather Ship J are shown as points in Fig. 1 . This method of showing monthly means was used by Neumann (1940, Abb. 25). His Feld 1 (Abb. 25, Nr. 6), the 5-degree quadrangle with northeast corner at 50° N 20° W, is represented by a circuit of similar shape (nearly isohaline), but with tem- perature range 1-5 C greater, mean temperature 2C higher, and mean sahnity 0-4 per mille higher.
Specific volume of surface water at Weather Ship J is shown by including isopleths of specific-volume anomaly. This quantity (which for surface water equals ther- mosteric anomaly) is chosen in preference to density or sigma-/ for the reasons presented by Montgomery and Wooster (1954). Any other temperature-salinity
* Two items of terminology are needed for two-dimensional frequency distributions. First, for a frequency isopleth of stated frequency a handier term than Bilham's " constant-frequency graph " (Brooks and Carruthers, 1953) is desirable. Secondly, an even more useful term would represent a frequency isopleth that encloses a stated proportion of the occurrences. If the first isopleth were called alpha and the second beta, the 00055-alpha would separate 5-per-mille classes from 6-per-mille classes, while the 0-9-beta would enclose nine-tenths of the occurrences; in Fig. 1, these two isopleths coincide. The betas have the advantage of being approximately independent of class intervals, for the alphas expand as the class intervals increase. It may be noted that beta is not similar to the term quantile (Brooks and Carruthers, 1953) used with regard to one-dimensional frequency distribu- tions, because the maximum frequency coincides with 0-beta but with an intermediate quantile.
Characteristics of surface water at Weather Ship J 333
function, such as sound speed or surface conccntraiion of dissolved oxyyen. CDuld be shown in the same manner by including the appropriate family of isopleihs.
For lack of information, the accuracy of the observations is not discussed here.
The frequency distribution in Fig. 1 is self-evident, but some aspects are note- worthy. There is no apparent correlation between temperature and salinity at Weather Ship J. The frequency distribution of salinity is symmetric, but those of temperature and specific-volume anomaly are very asymmetric.
The peak frequency of temperature occurs near the minimum temperature. This pattern reflects the annual variation, which has a blunt minimum and a sharp maxi- mum. Presumably the explanation is to be found, at least in part, in the deep, per- sistent winter mixed layer of large heat capacity in contrast with the shallow, change- able summer mixed layer.
The two-dimensional frequency distribution contains a suggestion of a waist at middle temperatures and of a secondary peak at higher temperatures. Whether these features will remain if the series is extended over more years is uncertain.
It seems likely that the pattern of annual frequency distribution of water tempera- ture at Weather Ship J is characteristic of a large region in middle latitudes, but some very different patterns can be expected for other regions. As found by HhssfcLBhRG (1943, p. 14), SiPLE (1949-1952), and Feussner (1952, Abb. 4), the annual frequency distributions of air temperature at some land stations in middle latitudes show a rather symmetric bimodal pattern.
The annual frequency distribution of temperature is an economical expression of the temperature climate and might well be used more widely. The three references above are the only ones the author has found that employ this method.
The extreme range of temperature in the present series is 7-9 C,* while thediff'erence in mean temperature between the warmest and coldest month is only 4-5 C. The frequency of temperatures below IOC and above 15 C, hence outside the range of 0-5-C classes containing monthly means, is 17 per cent. It is clear that monthly mean temperatures, which are often the only statistics presented in climatological summaries, give but a faint picture of temperature conditions.
A welcome departure from the usual adherence to monthly means is off"ered by several series of oceanic Monthly Meteorological Charts published by the Meteoro- logical Office, London. These charts include upper and lower 5-percentiIe isotherms of both air and water temperature, based on 2-degree quadrangles. The preparation of these charts must have entailed compiling further statistics that would be of
interest if published.
The temperature-salinity diagram is but one of the oceanographic and meteoro- logical class that has been called characteristic diagrams (Montgomery, 1950). all of which would be suitable for the representation of frequency distributions.
Acknowledgements— The author wishes to lecord his benefit and pleasure from discussing this subject with Mr. John D. Cochrane, Mr. Arnold Court, and Dr. John B. Leighly.
* With access to all data, Frankcom (1954) reports the extremes at Station J as maximum 17-8 C and minimum 7-8 C.
REFERENCES
Brooks C E P and Carrutmrs, N. (1953), Handbook of statistical methods in meteorology. London, Her Majesty's Stationery Office, M.O. 538, 412 pp.
334 ^- J8- Montgomery
Feussner, K. (1952), Uber Wert und Verwendbarkeit von Temperatur-Haufigkeitsverteilungen fur die Urteilsbildung. Ber. Deutsch. Wetterdienstes, U.S. Zone, 7, (42), 440-446.
Frankcom, C. E. N. (1954), " Half-century " of voyages by each of the British ocean weather ships. Meteor. Mag., London, 83, 282-283.
Helland-Hansen, Bj0RN (1916), Nogen hydrografiske metoder. Fork. Skand. Naturf. Mote, 357-359.
Helland-Hansen, Bj0rn, and Nansen, Fridtjof (1926), The eastern North Atlantic. Geofys. Piibl., 4, (2), 76 pp., 71 pis.
Hesselberg, Theodor (1943), Die Verwendung des Maxwellschen Verteilungsgesetzes auf meteoro- logische Haufigkeitskurven. Geofys. Publ., 13, (9), 19 pp.
Montgomery, R. B. (1950), The Taylor diagram (temperature against vapor pressure) for air mix- tures. Arch. MeteoroL, Geophys., u. Bioklim., (A), 2, 163-183.
Montgomery, R. B. and Wooster, W. S. (1954), Thermosteric anomaly and the analysis of serial oceanographic data. Deep-Sea Res., 2, 63-70.
Neumann, Gerhard (1940), Die ozeanographischen Verhaltnisse an der Meeresoberflache im Golfstromsektor nordlich und nordwestlich der Azoren (Aus den wissenschaftlichen Ergebnissen der intemationalen Golfstrom-Untemehmung 1938, 1. Lief.). Ann. Hydrogr. Mar. MeteoroL, 68, (Beiheft zum Juniheft), 87 pp.
SiPLE, P. A. (1949), American cUmates. Bull. Amer. Inst. Archit., Sept., 16-36. (Also subsequent numbers.)
Papers in Marine Biology and Oceanography. Suppl. to vol. 3 of Deep-Sca Rcscarcn. pp. 335-345.
Manganese nodules and oceanic radium
By Hans Pettersson Goteborg
The manganese nodules found by the Challenger Expedition in great depths have been studied by Sir John Murray and A. F. Renard (1891). They were recognized a.s products of a very slow growth, from manganese dioxide and ferric hydroxide, accumulated round a nucleus, a fragment of waterlogged pumice, or a shark's tooth or some other object lying on the surface of the deposit. Chemical analyses carried out by Brazier et al. proved a considerable number of trace elements like copper, cobalt, nickel, barium and lead to be present in the nodules. Of special interest was their relatively high content of radium first proved through measurements made by J. JOLY (1908).
As I have been engaged on determinations of the radium present in deep-sea deposits since 1921 (1930; 1939; 1953), and later also of the radioactivity of sea-water, my interest was attracted by the radium contained in the nodules. The close affinity between radium and manganese,* well known from deposits at thermal sources on the continents, is no doubt responsible for the entry of radium into the manganese nodules. Granting this to be the case, I assumed that this radium is " unsupported " by its parent element ionium, in which case it should decay with age and consequently also with the depth below the surface of the nodule, according to the half-value period of radium, about 1,600 years.
Thanks to the courtesy of the British Museum of Natural History I obtained from their Challenger collections two small nodules, and through a similar courtesy of the Mineralogical Department of the Riksmuseum in Stockholm one half of a much larger nodule, also from the Challenger Expedition.
The results of my measurements on samples from these nodules, taken from thin layers in the surface and further inwards, confirmed my assumption. The radium content per gram of the samples fell off from a very high value in the uppermost surface, sometimes exceeding 100 units of the 12th decimal place, to a few units 7 to 10 mm deeper down. The rate of decline proved to be more rapid on the lower, flattened, side of the nodule, on which it had presumably been lying on the bottom, than on the upper, convex, side which must have been exposed to the settling o\' sediment from above, increasing the rate of growth over the value due only to aggrega- tion into the nodule. The rate of radial growth, calculated from the decrease in radium, proved to be rather less than 1 mm in 1,000 years on the lower side and about 50% more on the upper, convex, side (1943).
The conclusion drawn from these measurements was, thai the radium in ihc nodules is accumulated from the surrounding sediment. These results made it most desirable for me to obtain also other nodules from other parts of the ocean. Through the kind
* An addition of small quantities of powdered " braunstcin " and a thorough shaking of ihc mixture has been proved through experiments in Goteborg. to be a most elhcient method for extract- ing radium and its isotope ThX from extremely dilute solutions.
335
336
Hans Pettersson
intervention of Dr. Bigelow I obtained from the Harvard Museum of Comparative Zoology three manganese nodules, raised out of great depths in the SE Pacific Ocean, from Dr. Agassiz's expeditions with the Albatross.
Measurements of the radium content of these nodules were started in 1944, soon after they had arrived in Goteborg. However, due to pressure of other work in connection with preparations for a Deep-Sea Expedition with the Swedish Albatross, the values I found have not previously been published. As the results in some respects extend those of my earlier publication I have found the occasion propitious for publishing them here, expressing at the same time my sincere gratitude to Dr. Bigelow for his generous help, not only in this connection but also in other matters, and for the most valuable discussions it has been my privilege to have with him.
NODULES FROM THE "ALBATROSS" PACIFIC CRUISES UNDER DR. AGASSIZ
The nodules obtained were from three stations visited during the Third Expedition. The following descriptions are quoted from J. Murray and G. V. Lee (1909, p. 144):
Station 13. Lat. 09° 57' N, long. 137° 47' W, depth 2,690 fathoms. " At this station a large quantity of nodules was dredged, one of which is figured in Dr. Alexander Agassiz's preliminary report. . . . They average 4 to 6 inches in diameter, and are all irregularly spherical or irregularly cubical, and never tend to form slabs. Their most conspicuous feature is the high degree of mam- millated structure: the whole surface is covered with large protuberances, which may be as much as one inch in diameter. Sometimes these protuberances may be compounds, that is, formed of smaller ones, grafted the one on the other. On the one side of the nodule the mammillae have a relatively smooth surface, on which rubbing will develop a shining lustre; on the other side the mammillae are more dull, with a shagreen-like appearance."
Station Albatross 13. Lat. N 9'
Table I 57'. Long. W 137° 47'. Depth 4923 m
|
Radium in |
|||||
|
A |
verage |
" depth " |
10-12 g/g |
M/7O2 |
Fe |
|
0-2 |
mm |
upper side |
38 |
18-2% |
13-3% |
|
3-3 |
mm |
5-4 |
29-3 |
13-2 |
|
|
11 |
mm |
3-6 |
20-9 |
18-2 |
|
|
10 |
mm |
lower side |
102 |
||
|
3-5 |
mm |
19-5 |
|||
|
5-8 |
mm |
9 |
|||
|
13 |
mm |
3-5 |
|||
|
015 |
mm |
upper side |
61 |
||
|
0-45 |
mm |
33 |
|||
|
0-75 |
mm |
26 |
|||
|
11 |
mm |
34 |
|||
|
1-6 |
mm |
16-7 |
|||
|
2-1 |
mm |
7-2 |
|||
|
4 0 |
mm |
8-2 |
|||
|
4-6 |
mm |
10 |
|||
|
015 |
mm |
lower side |
189 |
||
|
0-2 |
mm |
180 |
|||
|
0-6 |
mm |
103 |
|||
|
10 |
mm |
85 |
|||
|
1-5 |
mm |
67 , ■ |
Manganese nodules and oceanic radium
337
As in earlier experiments, thin layers were removed from the surface and from layers immediately below it. Weighed quantities from these samples were dissolved in hot hydrochloric acid, leaving a small undissolved residue, which was practically free from radium. In some of the samples the content of manganese and of iron were measured by colorimetric methods. The first column in Table 1 gives the average " depth " of the sample below the surface of the nodule, the second column gives the content of radium in the usual units of the 12th decimal place in gram per gram of the sample. The maximum values obtained from the lower surface of the nodule are seen to be 102 and 189 units of Ra, respectively, whereas from the upper surface the values come out much lower, i.e. 38 and 61 units respectively. The fall-olf in radium inwards is quite steep, to one half of the surface value or less for an increase in depth
Table II Station Albatross 173. Lat. S 8= 55'. Long. W 146 32'. Depth 4462 m
|
Radium in |
||||
|
A verage |
" depth " |
\0''gg |
MnOi |
Fe |
|
0-2 mm |
upper side |
64 |
23-2% |
14-9% |
|
0-2 mm |
lower side |
114 |
191% |
15-8% |
|
01 mm |
upper side |
51 |
191% |
15-8% |
|
0-35 mm |
31 |
20-8% |
15-65% |
|
|
1 -35 mm |
15 |
20-6% |
50-8% |
|
|
005 mm |
35 |
|||
|
014 mm |
28 |
|||
|
0-28 mm |
25 |
|||
|
0-7 mm |
15 |
|||
|
0-2 mm |
lower side |
81 |
||
|
0-5 mm |
65 |
of 1 mm. Attempts to calculate the rate of radial growth from the rate of this fall-off gave values ranging from 0-6 mm to 1-4 mm in 1,000 years. The percentage of iron is fairly high, between 13% and 18%, whereas the content of manganese is of the same order varying between 18% and 29% of MnOj.
Station 173. Lat. 18 55' S, long. 146 32' W, depth 2,440 fathoms. The description of the nodules from this station given by Murray and Lf.f (1909, p. 146) runs as follows:
" These nodules . . . constitute one of the most remarkable hauls of the cruise, .^t this station, where the deposit is Red Clay, immense numbers were dredged, varying in size from that of a small hazel-nut to potato-shaped nodules, three or four inches in diameter, and slabs over si.x inches in length. . . . Although the shape varies, the surface characters are absolutely constant, and belong to a type which was met with only at this particular spot. The surface of all the nodules, large and small, is even, that is to say, not covered with protuberances, but it is not smooth, being covered with numberless, closely set mammillae, giving it the appearance of shaga-en or coarse leather. On account of the presence of these mammillae— I mm in diameter, as a rule— the surface is dull, not shining. The colour is brown, never black. The external layer, from 1 to 2 mm in thickness, peels off easily. In some cases the layer coming next to it shows shagreen structure; in other cases it docs not, being smooth. This external layer is generally the only one that can be removed ; the rest of the nodule is very compact, and so hard as to be scratched with a knife only with dilliculty. W hen whole and with no fracture previously existing, the nodules cannot be broken in the hand, even when great strength is exerted; the specific gravity is very high.
338 Hans Pettersson
This nodule arrived in Goteborg broken into fragments. However, by piecing the fragments together it was easy to reconstruct the nodule and decide which had been its surface. The results from the measurements are set out in Table II, showing maximum values (presumably on the lower side)* of 1 14 and 81 units of Ra, whereas samples from the upper side contained much less radium, 64, 51 and 35 units respec- tively. The content of manganese was somewhat lower than in the nodule from Station 13, the content of iron being much the same except for one sample taken at a depth of 1 -35 mm where an unusually high value of over 50% Fe was found. Two attempts to calculate the rate of radial growth from the fall-off in radium content gave a value of 0-4 mm in 1,000 years in each case.
The third nodule, taken from Station 4658, was the largest and, according to my view, the most remarkable of the three, both with regard to its shape and its colour. It is described by Murray and Lee (1909, p. 29):
" The nodules from this station are as remarkable for their large size as for their constant shape, which is on a definite pattern. These nodules have each two surfaces, which are, roughly speaking, respectively dome-shaped and cone-shaped. Looking normally at one of the surfaces, the wider portion is circular, so that there is practically an axis of symmetry passing through the apex of both surfaces. The dome-shaped one is due to the aggregation of a few smoothly undulating bosses or protuberances of large radius. It is very smooth and black, with a metallic lustre, and has a distinctly scaly structure. The other surface is mammillated, has a dull colour and is incoherent, breaking up with little exertion of the fingers. A certain amount of clay is, moreover, mixed with the oxides, filling the cavities between the mammillae."
" A section across a nodule shows it to be formed of successive concentric layers following exactly in their distribution the contours of the smooth surface. The innermost layer has abso- lutely the same shape as the outer one. The difference between the alternate layers is mainly one of hardness. In the samples cut, it has not been possible to find what was originally the centre of accretion; it probably consisted of some material which has since been transformed, or rather, replaced by the oxides.
" This particular kind of nodule does not appear to have been described before; the nearest approach to it, as regards shape, is one represented in Fig. 4, Plate 3, of the ' Challenger Report on Deep-Sea Deposits ' " (Murray and Lee, 1909, p. 30).
A greater number of samples from this nodule than from the two others were sub- mitted to analyses. Before sampling, the nodule was cut in two practically identical parts. The appearance of the section is shown in natural size by the drawing reproduced in Fig. 1, which reveals the concentric arrangement of the different layers in this cauliflower-shaped nodule. Its domed surface, presumably the upper one when lying on the sediment,! was smooth, whereas the lower, conical surface was scoriaceous, which made the sampling of this part rather difficult. Adopting Murray's views on the position of the nodule on the sediment surface, viz. that the scoriaceous, conical surface was the lower one, the higher radium values are ascribed to the lower surface
* According to a footnote given in the paper by Murray and Lee their views on the original position of this nodule differed (see above).
t Dr. Lee holds that the logical conclusion is that the cone-shaped mammillated surface is the upper surface, the smooth shining one being embedded in the clay, whereas Sir John Murray takes the view, from liis Challenger experience, that the smooth surface was the upper one, and points to Fig. 1, Plate IX, of the " Challenger report on deep-sea deposits " as confirmation of this, the smooth surface in his opinion being formed above the level of the deposit.
Manganese nodules and oceanic radium
339
with maxima varying between 85 and 330 units of Ra. The upper surface had much lower values, ranging from 25 to 61 units. The fall-olT in the radium content with depth is more difficult to estimate, owing to the uneven, mamillated lower surface. With due reserve for this uncertainty we find the rate of radial growth in the downward direction comes out at only 0-15 mm in 1,000 years, which is only a fraction of the rate of growth in the upward direction, 0-4 mm in 1,000 years. The content of man- ganese in this nodule is seen to be very high, ranging from 30% to 75% of .MnO,.* On the other hand the content of iron is very low, averaging 1-3% of Fc, with an absolute minimum of only 0-03 %.
Low values of radium content were found in the nucleus and its vicinity, viz. 5 to 6 units of Ra. Still lower values were found in depths of trom 4-5 to 15 mm in a series of samples taken from the back of the nodule, near the lower limit of the domed
73 mm
85 mm Fig. 1
surface, where radium values as low as 2-2 to 2-4 units were measured. The results found with this extraordinary nodule, when summarized, seem to tell of an intense transfer of both manganese and radium from the sediment to the nodule, especially
to the scoriaceous parts.
It would have been most interesting to measure the radium, manganese and iron contained in the sediment surrounding this nodule, but unfortunately no sediment from the station was available. I collected instead a sample of the sediment entrapped within the nodule and measured it (last entry in Table HI). The radium content was moderate (24 units), whereas the manganese dioxide was relatively low (9-1 ".,), and the content of iron quite high for this nodule, viz. 41 %. However, too much impori- ance should not be attached to these figures, since an exchange between this entrapped
* Only in one nodule, taken by the Challenger Expedition in the Pad (ic Ocean lat. 3.V 31' S i^no- 7i^4V W deoth 3 950 was a content of manganese dioxide as high as in this nodule reported ITmu^rIv a^d RenVr'd viz. 77% MnO, in a nodule from blue mud. The .ron content of that nodule was low, 4-5 %.
340
Hans Pettersson
sediment and the surrounding layers of the nodule may have occurred. With due reserve for the limited number of samples investigated, one may say that there is strong evidence for a transfer of radium from the sediment via the bottom v^ater to the nodule, whereas the accretion of radium from the water column above is not likely to have occurred to a notable extent.
By what kind of chemical action the solution of radium and other elements has taken place is unknown, owing to our ignorance regarding the chemical reactions, proceeding with immense slowness, in the contact region between sediment and bottom water.
Table III Station Albatross A65%. Lat. 14° 29'. Long. f^81°24'. Depth 4960 m
|
Radium in |
|||||
|
Series |
Average " depth " |
10-12 g/^ |
MnOz |
Fe |
|
|
a |
0-3 |
mm lower surf. |
186 |
49-8% |
3-2% |
|
b |
0-2 |
mm upper surf. |
58 |
43-4 |
6 0 |
|
b |
3-2 |
mm upper surf. |
3 0 |
64-9 |
0-4 |
|
d |
0-2 |
mm Scoriacae |
85 |
53-6 |
115 |
|
d |
12 |
mm |
29 |
58-3 |
1-3 |
|
e |
0-2 |
mm edge |
46 |
68-2 |
0-95 |
|
f |
0-2 |
mm shell |
31 |
71-2 |
10 |
|
c |
0-5 |
mm summit |
25 |
66-7 |
1-7 |
|
c |
0-5 |
mm summit |
9-5 |
68 |
11 |
|
c |
2-5 |
mm |
3 0 |
74-5 |
0-55 |
|
0-5 |
mm back of nodule |
25 |
74-8 |
0-67 |
|
|
1-5 |
mm |
9-6 |
70-4 |
0-47 |
|
|
2-5 |
mm |
3-3 |
62-2 |
0-44 |
|
|
3-5 |
mm |
3 0 |
70 0 |
0-55 |
|
|
10 |
mm |
2-4 |
69-8 |
— |
|
|
15 |
mm |
2-2 |
69-8 |
— |
|
|
m |
0-2 |
mm |
61 |
— |
— |
|
m |
0-5 |
mm |
170 |
61-6 |
— |
|
m |
0-85 |
mm |
100 |
61-4 |
— |
|
k |
14 |
mm nucleus |
5-5 |
64-9 |
— |
|
k |
14 |
mm cavity |
9 0 |
30-8 |
|
|
g |
015 |
mm Scoriacae |
160 |
44-7 |
.10 |
|
g |
0-7 |
mm Scoriacae |
13-7 |
64-4 |
0 03 |
|
g |
1-3 |
mm Scoriacae |
3 0 |
621 |
0-14 |
|
h |
0-2 |
mm Scoriacae |
330 |
44-5 |
0-35 |
|
sediment |
24 |
9-14 |
4-1 |
||
|
k |
12 |
mm nucleus |
61 |
64-9 |
It does not seem unlikely that submarine volcanic activity, which has undoubtedly played a dominant part in the building up of the islands and the "guyots" in the Pacific Ocean, may have given rise to magmatic acids, converting calcareous sediments into Red Clay and, at the same time, dissolved also other sediment components, thus facilitating their transfer into manganese nodules, manganese crusts and other concretions. It seems reasonable to assume that this acidulation has been con- centrated to a relatively thin bottom layer over low-lying parts of the ocean floor.
Manganese nodules and oceanic radium 34 1
OCEANIC RADIUM The early hypotheses, put forward by Joly and other early workers m the licld. for the origin of deep-sea radium, have not withstood later criticism. This applies also to other explanations for the surprisingly high radium content in the deepest deposits.
(A) A precipitation of radium as insoluble sulphate from the water (Joly).
(B) A production in situ from the uranium present in the sediment (Joly).
(C) A cosmic origin of the radium, like that of the cosmic spherules (Murray).
(D) A magmatic origin from submarine volcanoes (Murray).
(E) A biological extraction from sea water by plankton organisms (Evans, et a/., 1938).
Only the two last alternatives need to be considered seriously. The possibility that some of the deep sea radium is actually derived from volcanoes on the ocean floor cannot be denied. In several instances abnormally high radium values have been found both in the Tyrrhenian Sea and in the equatorial Atlantic, for which a magmatic origin seems probable. That radium to a certain extent becomes adsorbed by marine plankton has been supported by measurements in Goteborg and elsewhere. However, this biological extraction and subsequent transfer to the bottom deposits with siliceous or calcareous tests cannot be a major cause of the high radium content in deep-sea deposit. Such " unsupported " radium must have a highly transient existence in the very uppermost surface layer of the deposit.
In order to find a better explanation for the high radium content in the Red Clay and in the Radiolarian Ooze, found by Joly and confirmed through my own measure- ments, teamwork on the radioactive elements present in ocean water was started by me over 20 years ago in Goteborg in collaboration with specialists from Vienna and Oslo (1939). By a special technique, extraction of radium from large-volume samples of sea water (20-40 litres), through co-precipitation with radium-free sulphate of barium, dependable values for the radium content were obtained. They turned out to be surprisingly low, in general less than one unit of the 13th decimal place. At the same time, accurate measurements of the content of uranium in sea water were, for the first time, carried out by means of a fluorescence method, developed by Hfrnegger and Karlik (1935) of the Institut fiir Radiumforschung in Vienna. Their results indicated a fairly constant uranium content averaging 1 -3 ■. 10" gr uranium per Hire sea water of normal salinity (357„ J. In a state of radioactive equilibrium this uranium content would correspond to over 0-4 X lO-^^ g Ra per litre of sea water, or to 6 times more than the radium actually found.
In order to explain this partial disappearance of radium from the sea water, I suggested in 1937 (1938), that its parent element, ionium, is being constantly removed from the water through a co-precipitation with ferric hydroxide, which is known to go on in the sea. This transfer of the ionium produced from dissolved uranium to the ocean bottom would explain the high radium content in deep-sea deposits as due to ionium-supported radium. From this ionium-precipitation hypothesis it would necessarily follow that the radium content in the deposit should increase to a near- surface maximum, attained about 9,000 years after precipitation, characterized by a radioactive equilibrium between ionium and radium. From there downwards in the sediment the content of the two elements should decrease together, according to the half-value period of ionium, about 82,000 years.
342 Hans Pettersson
The first attempt to utilize the ionium-precipitation hypothesis for a submarine geochronology, based on radium measurements, was made in the early 70's by C. S. PiGGOT and W. D. Urry (1941) and by Urry (1949). Their first results, obtained from fairly long sediment cores from the Caribbean and the N, Atlantic Ocean (published as curves only), gave hopes of realizing a dependable method of dating different layers of a sediment core and of obtaining values for the rate of sedimentation from radium measurements. More extensive measurements on cores from the Swedish Deep-Sea Expedition, started after the return of the Expedition, are now being published by V. Kroll, who has for some years been working in Goteborg (1955). The results prove that the vertical distribution of radium in the cores is much more complicated than the ionium-precipitation hypothesis alone would imply. Often two, three, or even more maxima, beside that to be expected from radioactive equilibrium, Ra/Io, are actually found.
The opportunities offered by the Swedish Deep-Sea Expedition for studying the radioactivity of the ocean were used for an extensive sampling for radium analyses of large-volume water samples. After the return of the Expedition, the barium- sulphate precipitates were analyzed for radium, partly by the present author in Gote- borg and partly in Vienna by Dr. Traude Bernert. The results, which have not been published before, are here set out in Table IV. They are seen to confirm our earlier results, viz. that the radium present in the ocean waters is only a small fraction of the quantity in equilibrium with dissolved uranium. In addition, uranium measurements on most of the water samples were carried out in Vienna by G. Koczy (1950), with results agreeing with those found earlier by Hernegger and Karlik. There cannot then be any doubt about the partial disappearance from the ocean waters of the radium produced from dissolved uranium.
However, a missing link in the chain of evidence concerns the presence of ionium. in the deposits and in the water. Thanks to an ingenious method for photographic (nuclear-plate) determinations of ionium. Dr. E. Picciotto and his co-workers in the Institut des Recherches Nucleaires of the Universite Libre in Brussels, have been able to measure the ionium contained in sediments from the Swedish Deep-Sea Expedition (1954). It was found that, within the limits of experimental accuracy, the ionium present is in radioactive equilibrium with the radium in the same sample, except in the very uppermost surface layer, where there is an excess of ionium. On the other hand, more recent measurements of the ionium present in sea water, carried out by Picciotto and F. Koczy, have proved the ionium content to be extremely low, lower even than what could correspond to the radium content, which in itself, as we have seen, is only a fraction of the equilibrium value with dissolved uranium.
This result raises a problem of considerable interest. Since the scarcity of ionium in ocean water negatives the assumption that the radium in the water is produced in situ from its parent element ionium, the question arises, from what source is the radium contained in the ocean water derived ?
Dr. F. Koczy has proposed an explanation, put forward in a paper read before the meeting of the I.U.G.G. in Rome in Sept. 1954, that oceanic radium is dissolved through a chemical interaction between the bottom water and the uppermost 3-5 cm sediment layer. From the bottom water the radium is spread upwards through the water masses by diff'usion, aided by turbulence. This view Koczy finds supported by the curves in Fig. 3, giving the vertical distribution of the radium in the water
Manganese nodules and oceanic radium
343
column found from the measurements already quoted and set out in Tabic IV. The curves are seen to have maxima in the uppermost water layers, then to fall to inter- mediary minima at a depth of about 1,500 metres (possibly due to biologic extraction) and, after rising again to a maximum in a depth of 2,000 to 4,000 metres, attaining even higher values in still greater depths.
As has already been pointed out here on pp. 335 and 339, the passing over of radium from the sediment surface-layer to the manganese nodules resting on it speaks in favour of a solution of radium near or in the sediment surface actually taking place.
Accepting Dr. Koczy's explanation as plausible, we arrive at a rather unexpected picture of the origin of the radium in ocean water.
The ancestral element uranium is being carried into the ocean by rivers from denuded rocks on the continents. The ionium produced from the dissolved uranium
|
c 0 |
) |
5 |
|
^ |
< |
|
|
m |
^ |
|
|
2000 |
\ |
|
|
4000 |
- |
w
6000
SOOO V
/S ■ /0~^yPa//n/
Fig. 3
is very efficiently removed from solution through precipitation, and settles over the ocean bottom, there giving rise to its descendant radium. The radium in the upper- most few centimetres of the sediment passes readily over into solution, some oi it becoming reprecipitated or adsorbed together with manganese in the nodules. Another part which has become dissolved from the sediment is distributed through the super- natant water masses, giving them a radium content inlermcd.atc between that in equilibrium with the dissolved uranium and the much lower quantity in equilibrium with dissolved ionium.
344
Hans Pettersson
Table IV
|
Lai. |
Long. |
Depth |
Rag /Lit. ■10^'' |
UglLit. 10« |
|
NOO^ 13' |
W 18° 26' |
25 m |
007 |
11 |
|
500 m |
008 |
1-2 |
||
|
2500 m |
0 07 |
1-2 |
||
|
5000 m |
010 |
1-3 |
||
|
7500 m |
0115 |
1-4 |
||
|
N \A° 15' |
W71°02' |
0 m |
006 |
|
|
N 14^ 27' |
W66° 13' |
1000 m |
0 07 |
1-3 |
|
3000 m |
0075 |
1-2 |
||
|
5000 m |
0075 |
1-2 |
||
|
N 28" 05' |
W 60° 49' |
25 m |
0045 |
115 |
|
500 m |
007 |
1-2 |
||
|
1000 m |
0 08 |
1-4 |
||
|
2000 m |
0 07 |
1-3 |
||
|
4000 m |
008 |
1-3 |
||
|
6000 m |
008 |
1-1 |
||
|
N 43° 04' |
W 19° 40' |
25 m 500 m 1000 m 2000 m 4000 m 6000 m |
005 0 06 0065 0065 008 Oil |
|
|
N 21° 24' |
W 46° 24' |
Om 100 m 400 m |
0035 0035 0035 |
|
|
W 89° 56' |
20 m |
0 09 |
11 |
|
|
S 02^ 52' |
500 m |
009 |
11 |
|
|
1000 m |
015 |
1-3 |
||
|
S 13° 24' |
W 149° 30' |
0 m |
010 |
M |
|
1000 m |
012 |
1-4 |
||
|
2000 m |
013 |
1-3 |
||
|
3000 m |
017 |
11 |
||
|
4000 m |
017 |
11 |
||
|
N05" 10' |
E 127° 53' |
Om 500 m 2000 m 4000 m 5700 m 8200 m |
0035 0 050 010 013 Oil 012 |
|
|
soro9' |
E 126° 22' |
3000 m |
007 |
|
|
S00°00' |
E88° 18' |
10 m 500 m 2000 m |
0055 0 05 0 07 |
|
|
4000 m |
0 09 |
1-3 |
||
|
N 10° 06' |
E52° 15' |
20 m 500 m 2000 m 3750 m |
005 004 008 Oil |
|
|
N 21° 09' |
E38°07' |
20 m |
0 05 |
11 |
|
500 m |
0 06 |
1-3 |
||
|
2000 m |
0 06 |
11 |
||
|
N35°4r |
E21° 50' |
50 m 1000 m 2000 m 4000 m |
0 065 Oil 0 07 0 09 |
Average: 0-078
Manganese nodules and oceanic radium 345
REFERENCES
EvAND, R. D., Kip, A. F. and Moberg, E. G. (1938), The radium and radon contcni of Pacific Ocean
water, life and sediments. Amer. J. Sci., (5), 36, 241-259. FOYN, Ernst, Karlik, Berta, Pfttersson, Hans and Rona. Elisabeth (1939). Radioactivity of sea
water. Goteborgs Kiingl. Vetenskaps- och Vitlerhcis-Samhiillcs HanilL. Femtc Foljdcn, (B). 6 (12).
1^14. {Medd. Ocean. Inst., Gotehorg, No. 2.) Hernegger, F. and Karlik, Berta (1935), Uranium in sea water. Goteborg.<! Kungl. Vetenskaps- och
Vitterhets-Samhalles Hand!., Femte Foljden, (B), 4 (!2), 1-15. {Medd. Goteborgs Hogskolas Ocean
Inst., No. 12.) Isaac, N. and Picciotto, E. (1953), Ionium determination in deep-sea sediments, .\aiure, 171 (435h).
742-743. JOLY, J. (1908), On the radium content of deep-sea sediments. Phil. Mag. (6). 16, 190-197. KoczY, Gerda (1950), Weitere Uranbestimmungcn an Mcerwasscrprobcn. Osterreichische .Akad.
Wissenschaften, Sitzungsber. Mathem.-Natuiw. kl., Abt. 11a, 158 (1-5), 113 121. Kroll, V. S. (1955), The distribution of radium in deep sea cores. Repts. Swedish Deep-Sea Exped.,
1947^8, 10, (1), (in press). Murray, John and Lee, G. V. (1909), The depth and marine deposits of the Pacific. Mem. Mii\
Comp. ZooL, Harvard Coll., 38, 1-169. Murray, John and Renard, A. F. (1891), Report on deep-sea deposits. Chemical products formed
in situ on the floor of the ocean. Challenger Repts., 335^12. Pettersson, Hans (1930), Teneur en radium des depots de mer profonde. Res. Camp. Sci., Monaco,
80, 1-50. Pettersson, Hans (1938), Das Verhaltniss Thorium zu Uran in den Gesteincn und im Meer. Mitf.
Inst. Radiumforschimg, 400a, 1. Picciotto, E. and Wilgain, E. (1954), Thorium determination in deep-sea sediments. Mature, 173
(4405), 632-633. PiGGOT, C. S. and Urry, W. D. (1941), Radioactivity of ocean sediments. III. Radioactive relations
in ocean water and bottom sediment. Amer. J. Sci., 239, 81-91. Urry, W. D. (1949), Radioactivity of ocean sediments. VI. Concentrations of the radioelements
in marine sediments of the southern hemisphere. Amer. J. Sci., 241, 257-275.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 346-357.
The accumulation of river water over the continental shelf between Cape Cod and Chesapeake Bay *
By BosTwiCK H. Ketchum and D. Jean Keen-]- Woods Hole Oceanographic Institution
Summary — The depth mean salinities for the waters of the continental shelf between Cape Cod and Chesapeake Bay show a seasonal variation in the concentration of river water. The spring and the winter accumulations are about the same, but about 25% more river water is present in the summer. The total volume of fresh water in spring and winter is equivalent to that produced by the rivers in about one and a half years. The extra accumulation in summer is equal to half a year's flow, and reflects, in part, the fact that the high spring flows of two successive years are present on the shelf at this time.
There is a decrease in the average content of river water in the direction of the flow of the coastal current, in spite of the addition of river water along its course. It is concluded that considerable transport of river water and of salt normal to the coast is necessary. The horizontal mixing coeffi- cients normal to the coast are computed from the seasonal changes in salinity. They range from 0-58 to 4-96 X 10* cm^/sec, with the values for the decrease in salinity from spring to summer being smaller than those for the increase from summer to winter conditions. At both times, the values decrease with increasing depth and distance from shore.
Professor H. B. Bigelow initiated extensive studies of the distribution of tempera- ture and salinity over the continental shelf between Cape Cod and Chesapeake Bay in 1913. In a series of papers, he and his associates have described the seasonal variations and correlated these with vernal warming, river runoff and the water circulation of the area.
The sea water of this section of the continental shelf is greatly diluted by the fresh water continuously supphed by several major rivers. Both regional and seasonal variations in salinity are great, and the area is one of comphcated dynamic structure and circulation. The accumulation of river water affords a direct means of evaluating the rate of the circulation and mixing when compared to the rate of discharge of the rivers. This approach has been used extensively in estuaries in recent years. While it may be unorthodox to treat this open coastal area as an estuary, it was felt that some of the methods of study should be informative, and provide a time scale for the circulation in various parts of the region.
The area included in this study (Fig. 1) extends across the continental shelf and slope from the coastUne to the 1000 fathom depth contour. It is bounded to the north-east by a section extending SSE from the western tip of Martha's Vineyard, and to the south by a section extending ESE from the mouth of Chesapeake Bay. This region has a surface area of 104 x 10'" ft^ or 29,000 square nautical miles, and contains a volume of water equal to 732 x 10'^ ft' or 3400 cubic nautical miles (Table I).
* Contribution No. 775 from the Woods Hole Oceanographic Institution. t Present address: U.S. Navy Hydrographic Office, Washington, D.C.
346
The accumulation of river water between Cape Cod and Chcvipcakc Bay
347
The major rivers discharging into this region, their gaged dramagc basin and the average rates of flow, are Hsted in Table II. The total drainage area is estimated to be 1 16,000 square statute miles, nearly 62% of which is gaged in those rivers. Assuming
76°
Fig. 1 . The continental shelf from Cape Cod to Chesapeake Bay, showing the areas used m 1 able I and Fig. 2. The dashed line in Area E indicates the southern limit of Area D' and the northern
hmit of Area E' used for the summer observations.
the ungaged area to have similar drainage characteristics, the total river flow into this region is 167,764 cubic feet per second. The volume of water contributed by the rivers annuaUy is thus 5-29 x 10^- cubic feet, less than one per cent of the total
348
BosTwicK H. Ketchum and D. Jean Keen
volume of water within the region considered. The discharge of all of these rivers is already mixed with large volumes of sea water in the sounds and estuaries before reaching the continental shelf.
Table I The total volume of water contained between depth contours for various areas of the
continental shelf Cape Cod to Chesapeake Bay
|
Depth |
|||||||
|
range |
Total volume (10^^ |
'/r*) within |
region |
Total |
|||
|
fathoms |
A |
B |
C |
D |
E |
F |
|
|
0- 20 |
114 |
376 |
513 |
403 |
All |
498 |
2316 |
|
20- 30 |
363 |
981 |
509 |
613 |
360 |
220 |
3046 |
|
30- 40 |
869 |
964 |
715 |
407 |
378 |
98 |
3431 |
|
40- 50 |
643 |
740 |
292 |
248 |
103 |
157 |
2183 |
|
50- 100 |
1170 |
954 |
648 |
423 |
621 |
205 |
4021 |
|
lOO-lOOO |
8244 |
10386 |
8000 |
7151 |
17433 |
7038 |
58252 |
|
Total |
11403 |
14401 |
10677 |
9245 |
19307 |
8216 |
73249 |
Table II
The major gaged rivers discharging between Cape Cod and Chesapeake Bay
Data from U.S. Geological Survey Water-Supply Paper 1051
|
Group |
River |
Years of record |
Drainage area sq. miles |
River flow ft^Jsec. |
ft^jsecjsq. mi. |
|
A |
Thames Connecticut Housatonic others* |
29 19 19 |
711 9661 1545 1171 |
1210 16260 2494 1702 |
1-70 1-68 1-61 1-45 |
|
C |
Hudson Passaic Raritan |
49 |
8090 785 779 |
16510 1442 643 |
2-04 1-83 1-31 |
|
D |
Delaware Schuylkill |
34 24 |
6780 1893 |
11770 2715 |
1-74 1-43 |
|
F |
Susquehanna Potomac Rappahannock York |
16 17 40 |
25990 11560 1599 1072 |
35650 10830 1648 729 |
1-37 0-94 103 0-68 |
|
Total gaged: |
71636 |
103603 |
1-45 |
* The Taunton, Providence, Pawtuxet and Pawcetuck Rivers gaged flow for 1946-1947.
Direct precipitation on the area would add 2-38 x 10^^ ft'' per year, but the loss from evaporation would be 3-42 x 10^^ ft^ per year. Wust's data for 35° and 40° North Latitude of the Atlantic Ocean (Sverdrup et al., 1942, Table 30) give a mean precipitation of 2-29 feet and a mean evaporation of 3-29 feet per year. The excess of evaporation over precipitation of one foot per year gives a net loss for the exchanges across the sea surface of 1-04 x 10^^ cubic feet per year. This is equivalent to 20% of
The accumulation of river water b;twc;n Cape Cod and Chesapeake Bay 349
the water supplied by river drainage. The remaining 80% must be transported through the region by advection and eddy diffusion, and mixed away in ihe more sahne water offshore.
The Gulf Stream flows offshore, separated from the waters of the continental shelf by the slope water of intermediate characteristics (Lsixin, 1936, 1940). The upper 200 metres or so of the slope water is generally less saline than corresponding waters of the Gulf Stream, reflecting the effects of varying amounts of coastal water at different times of the year. Ultimately the river water which is not evaporated locally must be entrained, via the slope water, in the Gulf Stream system. The volume transport of the Gulf Stream varies between 76 and 93 milhon cubic metres per second (ISELIN, 1940). This flow is twenty thousand times greater than the rate of addition of river water to this part of the continental shelf, so that direct assimilation of all of this river water in the Gulf Stream would not make a measurable change in its salinity.
The general westerly and southerly drift of the inshore water is well known, and is indicated by the temperature and salinity sections given by Bighlow (1933) and BiGELOW and Sears (1935). Extensive current measurements from lightships through- out the area south of New York show non-tidal drifts largely paralleling the coast of from 1-8 to 2-8 nautical miles per day (Zeskind and LeLacheur, 1926; Hak.ht. 1938; Marmer, 1935). The non-tidal current observed at Ambrose Lightship flows nearly east, and Uttle or no residual drift was observed at Nantucket Shoals Lightship except for transitory effects of the winds. The Current Atlas of the North Atlantic Ocean (Hydrographic Office, 1946) gives consistent westerly and southerly drifts, paralleling the coast for the inshore areas south of New York, with frequent easterly components over the mid shelf area south of Martha's Vineyard and east of both the Delaware and Chesapeake Bays.
The general character of these coastal drifts has been recently confirmed by drift bottle studies (Redfield and Walford, 1951; Miller, 1952). Practically all of the bottles released close to shore south of New York drifted southward. Only two bottles, of several thousand released north of Cape Hatteras, were recovered south o{ that point, indicating an abrupt reversal of the current. Many of the bottles released to the east of New York were recovered north of the point of release, along the Long Island shore. The percentage returns of bottles released close to the coast was high, but decreased rapidly with increasing distance from the coast. Few bottles released more than 20 miles offshore were recovered on the beach, though several of these have crossed the Atlantic and have been recovered on European shores.
The question arises whether these drifts can be expected to add substantial amounts of fresh water to this area of the continental shelf. To the south, the Gulf Stream is very close inshore and the shelf is only 30 miles wide at Cape Hatteras. Bigelc.w and Sears (1935 p 87) state: "Just south of Cape Hatteras a wedge of pure oceanic water presses in across the shelf entirely separating the shelf and slope water bands to the north from the low coastal salinities farther south ". All of the ev.dencc thus indicates that no significant increment of fresh water may be expected to enter the
area from the south. ,
The possibility that freshened Gulf of Maine water may enter the area through the Martha's Vineyard section cannot be categorically excluded. B.gelow (1915) concluded that northern water in this area was hardly appreciable, except perhaps m
350 BosTwicK H. Ketchum and D. Jean Keen
unusual years. The Current Atlas of the North Atlantic Ocean shows southerly or easterly drifts most of the year south of Martha's Vineyard, and, when westerly components are present, adjacent currents suggest an eddy which does not penetrate beyond the tip of Long Island. Some of the drift bottles released by Bigelow (1927) in the Gulf of Maine were recovered on Nantucket and Martha's Vineyard, but rarely entered the area under consideration. Several bottles, however, which were released in July 1922 outside the 50 fathom contour southeast of Cape Cod, were recovered along the coast to the west. A series of drift bottles were released in October 1951 from the Caryn between Cape Cod and Nantucket Lightship, but none of these were returned from within the area considered here. It is concluded that, although there may be some influx of fresh water from the northeast into the area, it cannot be evaluated, and is probably small relative to the volumes supplied directly by the rivers.
The details of the salinity distribution are given by Bigelow^ and Sears (1935). The following brief review of their conclusions will be helpful in understanding the general patterns. " The basic feature in the pattern of salinity of the region, the year around, is that isohaUnes tend to parallel the coastal trend with values increasing continuously from the shore, seaward, along any given profile normal to the coast" (p. 6). The salinity is at a maximum during the winter months when water of salinity lower than 32° /oo is found only in the mouths of Delaware and Chesapeake Bays. About 50% of the total annual discharge of river water is concentrated in March, April and May. This produces local and irregular freshening off" the mouths of the rivers. The salinity off" the Husdon River and Chesapeake Bay falls to 21° I ^o 8-10 miles from land, and all of the inshore water is freshened to 32°/oo or less at this time. This vernal freshening may not culminate before late summer in exceptional years, though in all years of record the extent of water freshened to less than 32°/oo was greatest during the summer. The vertical stratification was also a maximum at this time, being most pronounced off" Chesapeake Bay, and least over Nantucket Shoals to the northeast, where turbulence keeps the waters nearly homogeneous throughout the suimner. During the autumn the vertical gradients of saUnity decrease and the surface salinities increase, so that by January the distribution has returned to the winter maximum condition.
THE ACCUMULATION OF RIVER WATER
The total volume of river water accumulated in the area has been computed from the distribution of salinity. When this is compared to the rate of river flow, the average flushing time can be determined. The calculations have been made for three periods of the year, namely (1) April, May and June; (2) July, August and Septem- ber; (3) October through March inclusive.
o — s
The fraction of fresh water (/) in any sample is given by : / =
a
in which s is the saUnity of the sample considered and o- is the saUnity of the undiluted sea water. For this value we have taken 35°/oo, since water of this salinity is found at the bottom along the continental slope, usually in a continuous band throughout this region. Data from 856 hydrographic stations were utihzed. These included stations reported by Bigelow and his associates, stations along the continental slope (IsELiN, 1936), and in the New York Bight (Ketchum, Redfield and Ayers, 1951),
The accumulation of river water between Cape Cod and Chesapeake Bay
351
as well as several stations occupied by the Atlantis and by other vessels of the Wdod-; Hole Oceanographic Institution during recent years.
The volume of water between depth contour lines for the various areas shown in Fig. 1 are listed in Table I. These were computed from the planimetercd surface area and the average depth which was obtained from the U.S. Coast and Geodetic Survey Navigation Chart #1000. All volumes, and the average fraction and accumulation of fresh water, are computed for the entire depth of the water column, the contour lines being the inshore and offshore limits of the area considered.
The average fraction of fresh water was computed from the graded depth mean of the salinity values for each station. The bottom bottle of each cast was used to characterize the water from that depth to the recorded or chart depth of the station. This results in an underestimate of the deep salinities, but the volume of river water calculated for the depths below the bottom bottle rarely exceeded 10 "„ of the total river water, even for the summer observations when stratification was greatest and the error would be most pronounced.
(n4
SPRING
1000-
SUMMER
-100-
-1000—
WINTER
-1000-
33
D'
Fip 7 The deoth mean salinity and proportion of fresh water for various areas indicated in Fig. 1. The numl^rsoTeaSrtrne indicate the depth, in fathoms, of the outer boundary of the subd.v.s.on
considered.
Soring- 328 stations occupied during April, May and June;
Summer- 203 stations occupied during July, August and September;
Winter: 325 stations occupied dunng October-March inc.
The average fraction of fresh water and the corresponding salinity for each sub- area of Fig 1 are given in Fig. 2 for the three periods of year. The nver water found in the spnng period decreases from a mean value of 7-02 ».. for the i""-"^^-; P^;';;" (shore-20 fathoms) to a mean value of 0-33% over the continental slope (100 1000 fathoms). The values also decrease from north to south. Th.s would ,iot appear obviously from the salinity charts of B.CHt.ow and Shaks (1935) wh.ch s ow lower surface salinities to the south. However, they also show max.mum vert.cal grad.ents of salinity m this area, and the average salinity over the enttre w.ter co umn ,s gru tcr^ The decreasing fresh water fraction to the south is observed tor all ol the depth Ganges to the 100 fathom contour. Between the 100 and 1000 fathom contours the fresh water fraction decreases somewhat toward the north.
352 BosTwiCK H. Ketchum and D. Jean Keen
In the summer period the fresh water content is at a maximum for all fo the depth ranges, decreasing from 7-86% for the innermost band to 0-41 % for the waters over the continental slope. Within the 30 fathom contour, there is an increase of fresh water content from the Martha's Vineyard section to the offing of the Hudson River, but to the southward there is a gradual decrease. Beyond the 40 fathom contour the fraction of fresh water shows little variation from north to south for the various areas.
The conditions observed in the October-March period have marked similarities to the spring distribution. The inshore band is least fresh (6-75 %) at this time of year. There is, however, a considerable accumulation of fresh water from the middle of the shelf to the 100 fathom contour over the southern part of the area. All of the areas south of New York between the 30 and the 100 fathom contour contain greater proportions of fresh water than are found in these areas in the spring, though they are consistently less than the concentration found in these areas in the summer.
The decrease in the concentration of fresh water over the inner part of the shelf to the south is remarkable. As mentioned above, there is a consistent southward drift of the inshore waters, at least below New York, and there are substantial increments of fresh water from the Hudson, Delaware and Chesapeake Bay systems. Thus in each succeeding area some of the river water entering from the adjacent area, and the water locally added, must be dispersed across the shelf, and mixed locally with higher salinity water to give the observed decreases in average concentration. Although the 20 and 30 fathom contours are further off shore in the south, the volume available for dilution (Table I) is not enough greater to give the observed decrease in the con- centration of fresh water. Qualitatively, such a distribution can be maintained only when the transport of fresh water normal to the coastUne exceeds the transport parallel to the coast. This will be discussed further in the section on diffusion co- efficients.
THE FLUSHING TIME
The ratio between the volume of river water accumulated and the rate of river flow gives the flushing time for the region. This has been calculated for the various depth ranges at three times of year with the result shown in Table III. The accumu- lation of river water during the spring (April-June) agrees closely with the accumula- tion found in the winter period (Oct.-March) and corresponds to the contribution from the rivers during a period of about one and a half years (1-61-1'65). The accumu- lation during the summer period (July-September) is about 25 % greater than at the other times. Using the annual average river flow, this corresponds to nearly half a year of excess. This excess does not necessarily indicate a slower circulation at this time, but may reflect the excess river flow during the period of maximum discharge. The lag of 3-4 months before this excess discharge is recognizable over the shelf is not unreasonable for the time required for the exchanges through the estuaries and sounds. With a three-month lag period, this 25% excess accumulation during the summer corresponds to expectation since " fifty per cent of the total annual discharge of river water is concentrated in March, April and May " (Bigelow and Sears, 1935, p. 88) and since the excess spring flows of two successive years are represented by the accumulation during the summer. The surface inshore waters reflect this increased flow within a month after maximum river discharge, but on the average the maximum
The accumulation of river water between Cape Cod and C hesapeake Bay 353
effect over the entire shelf is delayed, as would be expected considering the length of time required for transport of river water through the area.
Table III
Flushing times of the continental shelf between Cape Cod and Chesapeake Bay for an
average river flow of 14-5 x 10» ff'lday (167,764 ft^jsec.)
Depth Range Fathoms
FLUSHING TIME, DA YS April-June July-Sept. Oct.-March
|
0- 20 |
112 |
125 |
108 |
|
20- 30 |
127 |
156 |
130 |
|
30- 40 |
119 |
157 |
123 |
|
40- 50 |
62 |
83 |
62 |
|
50- 100 |
52 |
91 |
56 |
|
100-1000 |
131 |
140 |
110 |
|
Total, days: |
603 |
752 |
589 |
THE FLUX OF FRESH AND SALT WATER
The total transport through any complete cross-section must result in the move- ment seaward of a quantity of river water equivalent to the quantity contributed by the rivers in unit time if the distribution is to remain in steady-state. The cross- sections must completely surround the source of fresh water. Those we have used extend from shore at the eastern boundary of area A, to a depth contour, along the contour line to the southern boundary of area F, and back to the shore.
For any given part of the cross-section this transport is a complicated sum of the effects of horizontal and vertical advection and eddy diffusion. However, our method of averaging gives the depth mean salinity and obscures the vertical effects. Thus, it seems possible to treat the system as Stommel (1953) has treated estuarine circulation, as a two dimensional one in which the advection produced by river water entering the system is balanced by horizontal eddy diflusion normal to the coast.
The flux of material in the direction normal to the coast (Fx) is given by Stommel (1953):
F^= Qc- SA f- dx
in which c is the fraction of fresh (or salt) water, Q is the rate of river flow. 5 the cross-sectional area, A the horizontal mixing coefficient, and v is the distance normal to the coast. Under steady-state conditions the flux of river water through any cross-section equals the rate of river flow (F = 0, and the flux of salt through any cross-section is zero.
The eddy diff"usion parallel to the coast has been neglected in the above equation. If the coefficient of horizontal diff"usion is the same in the two directions, the transport by diffusion parallel to the coast must be proportionately very small. The gradients in this direction range from one tenth to one thirtieth the value o\' the gradients normal to the coast; and the cross-sectional areas at the ends are also small com- pared to the area along the contour line. For example, the product 5,J^//. >.vis
N
354
BosTWiCK H. Ketchum and D. Jean Keen
400 times as great as the product SyAf/i\y for the winter distribution and the 30 fathom contour. This product for the direction parallel to the coast never exceeds one per cent of the value normal to the coast.
As has been shown above, there is a decrease of salinity for this area between the spring and summer conditions, and a corresponding increase between the summer and winter conditions, with httle or no change between the winter and spring condi- tions. Since the flushing time of the area is a year and a half, and these changes occur in shorter periods, the distribution cannot be treated as a steady-state. How- ever, it is possible to evaluate the flux of salt from the seasonal changes, and to compute average mixing coefficients from these data. The necessary data are pre- sented in Table IV, and the coefficients are given in Table V,
Table IV The mean salinities at three seasons of year, and the flux of salt across different depth boundaries on the continental shelf between Cape Cod and Chesapeake Bay. The
contours selected average 28 kilometers apart
|
Depth |
Flux |
of Salt |
|||||
|
Contour |
Mean Salinities |
V |
Wglsec. |
||||
|
Fathoms |
Spring |
Summer |
Winter |
Sp.-Su. |
Su.-Wint. |
||
|
20 |
32-54 |
32-24 |
32-64 |
2-53 |
— 2-24 |
||
|
30 |
32-88 |
32-40 |
32-84 |
7-86 |
— 5-48 |
||
|
40 |
33-24 |
32-69 |
33-18 |
14-68 |
— 9-52 |
||
|
100 |
3406 |
33-57 |
34-04 |
25-78 |
—16-58 |
||
|
1000 |
34-88 |
34-86 |
34-91 |
3003 |
—23-63 |
Table V The coefficients of horizontal diffusion computed from the changes in salinity at different
seasons of the year
Depth Contour Fathoms
30
40
100
Horizontal Diffusion Coefficients
IQ^cm^ I sec. Sp.-Su. Su.-Wint.
2-52 1-72 0-58
4-96 3-41 1-48
The net flux of salt is positive for the change from spring to summer, since salt is being transported oflFshore in the plus x direction, and negative for the change from summer to winter when the salinity increases again. The net flux of salt resulting from changes from season to season range from about 15 to 50% of the offshore advection of salt with the river water escaping from the area. The coefficients of eddy diffusion (Table V) obtained for the spring-summer change range from 0-58 to 2*52 X lO^cmVsec, and the values obtained for the summer-winter change vary from 1-48 to 4-96 X 10® cmVsec. At both times the value decreases with increasing depth and distance from shore. Although the vertical component of turbulence has been
The accumulation of river water between Cape Cod and C hesapeake Ba> 355
averaged out of the data, it is worth noting that the smaller cocllicicnis are found at the time of year when vertical stability is developing to maximum values.
The value of horizontal mixing coefficients obtained for this area are in substantial
agreement with previous determinations for coastal areas. SvbRDRUF' and Fli;ming
(1941) obtained a coefficient for the California coastal region of 2 IO*cm' sec;
and BowDEN (1950) computed coefiicicnts for the Irish Sea ranging from 0-36 to 9-0
X lO'cm^sec.
It has been mentioned above that inclusion of the excess spring river flow of two successive years could account for the excess accumulation of river water during the summer. Such an increase in river flow would increase the spring-summer coeflkients of eddy diff'usion by only about 25%, and would not make them as great as those observed for the summer-winter change. It must be concluded, therefore, that the excess accumulation of river water in the summer is a joint efi'cct of the increased river flow and the decreased turbulence.
DISCUSSION
The flushing times estimated from the accumulation of fresh water, and some general aspects of the circulation, are approximately confirmed by the drift bottle studies described by Miller (1952). Practically all of the bottles were recovered south of the point of release, confirming the net drift southward parallel to the coast. The proportion of returns decreased greatly with distance from shore, however, and very few bottles released more than 15-20 miles from shore were returned. This confirms, for the surface waters at least, the active offshore transport as well as the narrow band of current parallel to the coast.
The rate of drift of the bottles released near shore varied over wide limits. Several gave velocities greater than 10 miles per day, but all of these were released either just south of Delaware Bay or off Chesapeake Bay, where the net drifts appear to occupy a very narrow coastal strip. Most of the bottles drifted at rates of 3-5 miles per day. A bottle travelling at this rate, which did not beach en route, could traverse the 350 mile stretch of coast in 70-117 days. This corresponds approximately to our flushing time within the 20 fathom contour of 108-125 days. Since very few bottles were recovered from greater distances offshore, it is impossible to check our flushing times for the deeper areas in this way.
The flushing times are based upon the assumption that no substantial volume of fresh water is added to the area except as river flow. Miller (1952) obtained eighteen returns of bottles released on or near the 20 fathom contour in our area A. Their average drift was about 3-5 miles per day. The drift bottles, of course, do not give an evaluation of the movement of the deeper waters, but it seems probable that the surface drifts are greater than the average. Thus a maximum estimate of the advection of fresh water into the area can be made assuming that the water at all depths within the twenty fathom contour is passing from area A to area B at this velocity. The appropriate cross-section area is 3-52 X 10" ft^ so that the total volume transport would be 7-5 x 10'° ft^day. Since the fresh water content ranges from 7-98-S-40°<„ the corresponding transport of fresh water would be 5-6-6-3 x 10» ft'/day. This includes the river water discharged directly into area A from the rivers emptying into Long Island Sound (Table II, Group A) which accounts for about one-fifth of the total gaged drainage, or about 2-9 :■: 10« ft« per day. Including the remainder.
356 BosTwicK H. Ketchum and D. Jean Keen
3-4 X 10* ftVday, in the total river flow used in calculating the flushing times, would decrease them from about 1-6 years to 1-3 years — a change which is not significant considering the other approximations which have been made.
One tacit assumption has been made in the calculation of the horizontal mixing coefficients which has not been discussed. It is assumed that the current produced by the escaping river water is the only advective process of importance. Other currents, such as density and wind-induced currents, are also present. From the continuity of volume, the net transport of these currents must be zero, but it does not follow that the net transport of salt and fresh water must be zero. If, as seems likely, there are one or more large scale, counter clockwise eddies over the shelf, with an onshore current in the northern, low salinity, part of the region, and an offshore current in the southern higher sahnity area, there will be a net offshore transport of salt. This would result in an underestimate of the coefficients of horizontal eddy diff"usion. Unfortunately, our knowledge of the currents dver the continental shelf, except for the narrow coastal strip, is inadequate to evaluate this effect.
A brief discussion of some of the forces which could produce the turbulence over the shelf may be of some interest. The tidal transport, the winds, the currents due to river flow and density structure, and the upwelling along the coast as a result of off'shore winds, are the most obvious turbulent forces. In estuaries the mixing process has been related to the tidal volumes moving over a mixing length determined by the excursion of the tidal currents (Arons and Stommel, 1951; Ketchum, 1951). The approximate contribution of tidal flow over the continental shelf to the overall mixing process can be evaluated. For turbulent flow, the mixing effect would be proportional to the product of the velocity and the transport distance (vj^). The coefficient of proportionahty will vary, depending upon the actual degree of turbu- lence resulting from the ffow, but the potential eff'ect will always be less than this product. Both velocity and transport distance depend on the shape of the bottom contour and distance from shore, and the product will be greatest where the ratio of distance from shore to depth is a maximum (Fleming, 1938). This product has been calculated for various depth contours for a semidiurnal tide with a mean amplitude of 50 cm, and has the following values, which may be compared with the coefficients of eddy diffusion hsted in Table V.
30 fathoms 0-65 x 10« cmVsec.
40 fathoms 1-08 x 10« cmVsec.
100 fathoms 0-32 x 10« cmVsec.
This product increases to a maximum value at the 40 fathom contour and decreases beyond this depth, whereas the mixing coefficients decreased with increasing depth throughout this range. The tidal mixing product is always less than the coefficients of horizontal diffusion and the coefficient of proportionality is probably much less than unity. It may be concluded that the tides alone can contribute only a small fraction of the total turbulence, and that the other forces must contribute substantially at all times of year.
REFERENCES
Arons, A. and Stommel, H. (1951), A mixing-length theory of tidal flushing. Trans. Amer. Geophys.
f/wo«, 32(3), 419-421. Bigelow, H. B. (1913), Oceanographic cruises of the U.S. Fisheries Schooner Grampus 1912-1913.
Sci. N.S. 38(982), 599-601.
The accumulation of river water between Cape Coil ami Chesapeake Hay 357
BiGELOw, H. B. (1915), Exploration of the coast water between Nova Scotia and Chesapeake Bay.
July and August 1913 by the U.S. Fisheries Schooner Cramptis. Oceanography and plankton
Bull. Mus. Comp. Zool. 59 (4). 151-359. BiGELOw, H. B. (1927), Physical oceanography of the Gulf of Maine. Hull. L S Hur /ish. 40 (2).
BiGELOW, H. B. (1933), Studies of the continental shelf. Cape Cod to Chesapeake Bay. I. The cycl«
of temperature. Pap. Phy.s. Oceanoar. Mcicorol. 2 (4), I 135. BiGELOW, H. B. and Sears, M. (1935), Studies of the waters of the continental shelf. Cape Cod jo
Chesapeake Bay. II. Salinity. Pap. Phys. Occanonr. Mcicorol. 4(1). I 94. BowDEN, K. F. (1950), Processes alVectmg the salinity of the Irish Sea. Roy. .AMton. Soc . deophvi
Stipp. 6 (2), 63-90. Fleming, R. H. (1938), Tides and tidal currents in the Gulf of Panama. J. Mar. Res I, 192 206. Haight, F. J. (1938), Currents in Narragansell Bay, Buz/ards Bay and Nantucket and Vineyard
Sounds. U.S. Dept. of Commerce, Coast and Geodetic Survey, Spec. Publ. No. 20K. lOK pp. IsELiN, C. O'D. (1936), Study of the circulation of the north Atlantic Ocean. Pap. Phw Occanofir.
and MeteoroL, 4 (4), 1-101. IsELiN, C. O'D. (1940), Preliminary report on long-period variations in the transport of the Ciulf
Stream system. Pap. Phys. Oceanogr. MeteoroL, 8(1), 1-40. Ketchum, B. H. (1951), the exchanges of fresh and salt waters in tidal estuaries. J. Mar Res.,
10(1), 18-38. Ketchum, B. H., Redfield, A. C. and Avers, J. C. (1951), The oceanography of New York Bight.
Pap. Phys. Oceanogr. MeteoroL, 10 (1), i-46. Marmer, H. a. (1935), Tides and currents in New York Harbor. U.S. Dept. of Commerce, Coast
and Geodetic Survey, Spec. Pubi. No. 1 1 1, VII : 198 pp. Miller, A. R. (1952), A pattern of surface coastal circulation inferred from surface salinity-tempera- ture data and drift bottle recoveries, W.H.O.I.. Ref. No. 52-28 (unpublished manuscript). Redfield, A. C. and Walford, L. A. (1951). A study of the disposal of chemical waste at sea. Sat.
Res. Coitnc. Nat. Acad. ScL, Puhl. 201. 49 pp. Stommel, H. (1953), Computation of pollution in a vertically mixed estuary. Sewage Indust. M'a.sies,
25(9), 1065-1071. Sverdrup, H. U. and Fleming, R. H. (1941), The waters off the coast of southern California. March
to July, 1937, Scripps Inst. Oceanogr. Bull. 4, 261-378. Sverdrup, H. U., Johnson, M. and Fleming, R. H. (1942), The Oceans. Prentice Hall, Inc., New
York, pp. 1-1087. U.S. Geological Survey (1946), Surface water supply of the United States. Part I, North Atlantic
Slope Basins. U.S. Dept. of Int. Geol. Surv. Water-Supply Paper 1051, XIII 676 pp. U.S. Navy Hydrographic Office (1946), Current atlas of the north Atlantic Ocean. (First ed.).
H.O. Misc. No. 10688. Zeskind, L. M. and Lelacheur, E. A. (1926), Tides and currents in Delaware River and Bay, U.S.
Dept. of Commerce, Coast and Geodetic Survey, Spec. Puhl. No. 123, 122 pp.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 358-372.
Report on the results of exploratory otter-trawling along the continental shelf and slope between Nova Scotia and Virginia during the summers
of 1952 and 1953*
By William C. Schroeder
Summary — No large fish populations were found comparable to those present on our known fishing banks.
The area designated as A, from Long. 63° 17' to Long. 65° 59' W, yielded considerably more fish both in number and pounds than did any of the areas from Long. 66° to Long. 74° 15' W. The 200- 400 fathom depth zone, on the overall average, produced the best catches throughout all these areas.
A total of 75 species of bottom dwelling fishes were caught, most of them in numbers so small as to suggest that they are of little economic importance within this region.
Among the dominant species were (a) the redfish, Sebastes marinus, which was taken in promising numbers, and large in size, in depths of 220-370 fathoms between Long. 63° 50' and Long. 65° 27' W; (b) the long-finned hake, Urophycis chesteri, found chiefly between 200-450 fathoms throughout all the areas fished ; (c) the oifshore hake, Merluccius albidus, taken west of Long. 66° and chiefly in 100-350 fathoms and {d) the grenadier, Coryphaenoides riipestris, present in greatest abundance east of Long. 66° and in depths of 300-500 fathoms.
Lobsters were caught in relatively large numbers off" southern New England between 70-150 fathoms and as deep as 260 fathoms. A deep water lobster fishery in this region has ensued as a result of the discovery of these grounds.
The red crab, Geryon quinquidens, was found to be distributed throughout the range of our explora- tory trawling in depths beyond 150-200 fathoms and in quantities that might prove sufficient to support a new fishery for this species which up to the present has been unexploited.
Bottom temperatures in 200-730 fathoms, throughout the region explored, varied but little either up and down the slope or from east to west, indicating a stability in this respect so far as concerns the bottom- and near bottom-dwelling marine life.
INTRODUCTION t
In the early 1880's the U.S. Fish Commission Str. Fish Hawk made a number of cruises to explore the bottom fauna along the southern New England coast, particu- larly in depths beyond 50 fathoms. Up until that time very little was known of the bottom dwellers of the outer shelf and the middle and upper slope of this region. However, the Fish Hawk, using a beam trawl, made about 100 successful hauls in depths ranging down to about 600 fathoms along a belt some 5 to 15 miles wide and extending about 150 miles from east of Nantucket to the offing of eastern Long Island. Here a rich fish and invertebrate fauna was found including many rare and previously
* Contribution No. 790 of the Woods Hole Oceanographic Institution.
t This Introduction is somewhat repetitious to that given in "Deep water elasmobranchs and chimaeroids from the northwestern Atlantic Slope" (Bigelow and Schroeder, 1954, pp. 38-39.
358
Reports of exploratory ottcr-trawling between Nova Scotia and Virginia 359
unknown species. In this same period a number of bottom hauls were made stilJ deeper along the slope, beyond 800 fathoms, by the Blake and the Albatross. It was just before these cruises, in 1879, that the tilefish had been discovered within this region. But, although various published reports appeared subsequently dealing with these catches, no organized deep water exploratory hshing was done along our northeastern Atlantic coast during the following seventy years, except a few stations made by the Albatross at widely separated times up until 1920.
The Woods Hole Oceanographic Institution vessel Caryn, in 194S and 1949, made a few short cruises along the slope off southern Nova Scotia and New England and. for the first time, an otter trawl was used here in depths as great as 460 fathoms, all the earlier fishing having been done with relatively small Blake trawls and beam trawls, both of which were attached to rigid frames. The Caryn, although not well adapted to this type of fishing, made a total of 20 successful otter trawl hauls between 100 and 460 fathoms, the deepest haul being limited by the capacity of the winch. Many interesting specimens of fish and invertebrates were taken.
It now seemed timely to explore more fully the outer part of the shelf and upper slope, not only to seek rare or little known species and to learn something about them ecologically, but to determine whether or not any fish or invertebrates were to be found there in quantities and of a sort that might be of interest to the commercial fishery; in other words, to locate new fishing grounds. Accordingly, Cap^n Bill II. an 83 ft. dragger built in 1952 in Thomaston, Maine, owned and captained by Henry W. Klimm, Jr., was chartered by the Woods Hole Oceanographic Institution for three cruises in June-July 1952 and three cruises in June-July 1953.
Up to the present time most of the bottom trawling done by the commercial fishing fleet along the Atlantic coast has been in less than 125 fathoms, although the redfish vessels have recently been operating near the southern part of the Grand Bank in depths approaching 200 fathoms. Beyond this extreme, most of the boats are not equipped to fish much deeper with otter trawls, being limited by the amount of wire that can be wound on the winches which they now carry. In the commercial fishery two wires, or v/arps, usually f or ^ inches in diameter, are used in fishing the traw Is which are upwards of 100 feet wide at the mouth with otter boards each weighing from 700 to 2000 pounds or more. In our experimental fishing we used a single wire of I inches with a 20-fathom bridle of -^ inches reaching to the otter boards. In making our earlier hauls various types of boards were used, but during most of 1952 and all of 1953 a standardized type was employed, each board having a weigh! of 160 pounds. The trawls measured, respectively, 35, 50, and 60 feet at the foot rope, and about 18 per cent less at the head rope, with body and wings of 3 inch, 15 thread stretched mesh, and the cod end of II inch, 24 thread. Double j^ inch galvani/cd chain was attached to the foot rope, and floats in varying number, to the head rope. Glass floats proved the most satisfactory for withstanding the great pressures beyond 300 fathoms, although some of them became partially filled with water and had to be replaced. Aluminium floats of the sort we used, were the least effective as most of them imploded beyond 200 fathoms.
The duration of the tows varied from one-half to one hour depending on depth, roughness of the bottom, and weather conditions. Fishing was done chiefly during daylight hours, but in some instances extended into late evening. In cases where long runs from one area to another were necessary, these were made at night without
360
William C. Schroeder
loss of fishing time. The towing speed averaged about 2^ knots. Bottom temperatures, recorded by a maximum-minimum thermometer, were obtained in 1953.
Six cruises were made, as follows: .Cruise No. 1: June 20 to June 27, 1952, from Hudson Canyon to the offing of Nantucket (Long. 72° 05' to Long. 69° 37' W); 50 hauls in depths ranging from 105 to 500 fathoms. Mr. James Barker accompanied me.
Cruise No. 2: July 10 to July 17, 1952, from the offing of Nantucket to the offing of Georges Bank (Long. 69° 37' to Long. 67° 45' W); 35 hauls in depths ranging from 75 to 530 fathoms. Dr. Benjamin Leavitt accompanied me, as well as Dr. P. ScHOLANDER and Dr. L. van Dam who took gas and blood samples of various .species of fish to supplement their data for shoaler water.
. Cruise No. 3: July 23 to July 30, 1952, from the offing of Georges Bank to the .offing of southeastern Nova Scotia (Long. 66° 55' to Long. 63° 17' W); 32 hauls in depths ranging from 67 to 540 fathoms. Dr. Richard H. Backus assisted me, and Drs. ScHOLANDER and van Dam continued their work on gas and blood samples. . Cruise No. 4: June 25 to July 1, 1953, from the offing of Cape Charles, Virginia .to Hudson Canyon (Long. 74° 15' to Long. 72° 04' W); 45 hauls in depths ranging from 63 to 720 fathoms. Dr. Benjamin Leavitt participated in this cruise, and Drs. ScHOLANDER and VAN Dam continued their gas and blood studies. V Cruise No. 5: July 10 to July 17, 1953, from the offings of Georges Bank to south- eastern Nova Scotia (Long. 65° 27' to Long. 63° 47' W); 31 hauls in depths ranging from 68 to 705 fathoms. Mr. Robert Wolf of U.S. Fish and Wildlife Service assisted me, while Drs. Scholander and van Dam continued their observations. ! Cruise No. 6: July 23 to July 30, 1953, from the offings of Nantucket to Georges Bank (Long. 70° 43' to Long. 66° 39' W); 34 hauls in depths ranging from 70 to .730 fathoms. Mr. Jan Hahn accompanied me and made a photographic record of the trip.
Table I A list of the total hauls, 32 of them by the Caryn and 227 by the Cap'n Bill U,
arranged by depths
Fathoms
Number of Hauls: Successful
Number of Hauls: Not Successful
|
0-50 |
0 |
1 |
|
51-100 |
20 |
2 |
|
101-150 |
18 |
2 |
|
151-200 |
16 |
10 |
|
201-250 |
22 |
5 |
|
251-300 |
18 |
8 |
|
301-350 |
22 |
4 |
|
351-400 |
15 |
8 |
|
401-450 |
21 |
11 |
|
451-500 |
21 |
5 |
|
501-550 |
8 |
2 |
|
551-600 |
4 |
2 |
|
601-650 |
4 |
4 |
|
651-700 |
2 |
0 |
|
701-730 |
2 |
1 |
|
830-890 |
0 |
1 |
Total
193
66
Reports of exploratory ottci -trawling between Nova Scotia and Virginia 361
In most cases the trawl fished bottom without apparent mishap, but there were occasions when a haul obviously was not successful lor one reason or another, as is to be expected when fishing an unexplored area and in depths where technical dilli- culties are multipHed. Catch statistics of unsuccessful boUom hauls were segregated from those hauls considered representative.
The causes for the 66 unsuccessful or otherwise unrepresentative hauls were: trawl did not fish bottom at all or for only a small part of the haul (22); net tore so that all or part of the catch was lost (13); drawstring opened before catch was landed (1); net lost (9); gear twisted (13); aluminium floats alMmploded ( 1 ); fathometer not operating (2); trawling wire snapped (2); cause unknown (3). Catch record^ of these hauls are not included in this report.
RESULTS
A total of 75 species of fishes that might be classed as dwelling part or all of the time on bottom, or close to it, were caught in the two years combined, of which 7 species were taken in 1952 only and 13 in 1953 only. These figures are subject to slight revision after a number of final indentifications have been established. In addition, some 30-40 species of bathypelagic fishes were captiired while the trawl was being payed out and/or hauled in and when an off-bottom haul was made. These species have not yet been critically studied. Accounts of the sharks, skates and chimaeras taken deeper than 200 fathoms have already been published (Bigelow, Schrof.dkr and Springer, 1953; Bigelow and Schroeder, 1954) as well as a paper dealing with two fishes of especial interest, the offshore hake Merluccius alhidus and the blue whilirig Gadus {Micromesistius) poutassou (Bigelow and Schroeder, 1955). Also, certain data concerning various fishes taken on these Atlantic slope cruises are included in recently published Fishes of the Gulf of Maine (Bigelow and Schroeder, 1953).
Much the greater number of the bottom-dwelling species that were taken deeper than 200 fathoms are at present of little commercial importance, either because of their relative scarcity in deep water or because they have not yet been accepted as food fishes. In fact, only the redfish {Sebastes marinus) was found in numbers suffi- cient to give some promise of supporting a profitable fishery. Others taken that might prove of some value to the fisheries include the gray sole (Glyptocephalis cyno^ilossus), the long-finned hake {Urophycis chesteri) and the whitings {Merhtccius hilincaris and M. albidus).
New and proHfic lobster grounds were discovered and considerable information was obtained on the distribution and abundance of the deep water red crab {Gcryon quinquidens), a species that may prove to form the basis of a new crab fishery.
As the area fished, although only about 5 to 20 miles wide, extended some 6(X1 nnles from the offing of Nova Scotia to that of Cape Charles. Virginia, it is expedient that it be divided into sectors, as follows: area A— Long. 63 17' to 65 59 \N , from the offing of southeastern Nova Scotia to the eastern slope of Georges Bank; area B— Long. 66 00' to 69 59' W, from the eastern slope of Georges Bank to the oiling of Nantucket; area C— Long. 70" 00' to 71" 59' W, from the offing of Nantucket to Hudson Canyon; and area D— Long. 72' 00' to 74 15' from Hudson Canyon to the offing of Cape Charles, Virginia. The most northerly latitude fished was 42 4S;, and the most southerly, 37° 38' (see Fig. 1).
362
William C. Schroeder
Table II
A list of the fish species taken by the Caryn and the Cap'n Bill II arranged by areas, depths, hauls, and aggregate catches, in which 50 hauls were made in area A, 56 hauls in area B, 49 hauls in area C, and 38 hauls in area D
|
Fathoms |
Caught in |
Number offish: |
|||||
|
Species |
Aggregate catch |
||||||
|
; |
|||||||
|
— 200 |
+ 200 |
I-IO Hauls U + Hauls |
1-10 |
11-100 |
101 + |
||
|
Myxine glutinosa |
D |
X |
X |
||||
|
Petromyzon marinus |
A |
X |
X |
||||
|
Scyliorhinus retifer |
B-C-D |
X |
X |
||||
|
Apristurus profundorum |
A-B-C-D |
X |
X |
||||
|
Mustelus canis |
D |
X |
X |
||||
|
Centroscymnus coelolepis |
B-C-D |
X |
X |
||||
|
Centroscyllium fabricii |
A-B-C-D |
X |
X |
||||
|
Etmopterus princeps |
A-B-C |
X |
X |
||||
|
Raja bathyphila |
B |
X |
X |
||||
|
erinacea |
B |
X |
X |
||||
|
fyllae |
A-B |
X |
X |
||||
|
garmani |
B-C-D |
X |
X |
||||
|
jenseni |
A D |
X |
X |
||||
|
laevis |
C |
A-B-C |
X |
X |
|||
|
mollis |
A |
X |
X |
||||
|
ocellata |
B |
X |
X |
||||
|
radiata |
B-C |
A-B-C-D |
X |
X |
|||
|
senta |
B-C-D |
A-B-C-D |
X |
X |
|||
|
spinicauda |
A-B |
X |
X |
||||
|
Harriotta raleighana |
A-B-C-D |
X |
X |
||||
|
Rhinochimaera atlantica |
A-B D |
X |
X |
||||
|
Argentina silus |
A |
X |
X |
||||
|
striata |
A-B-C-D |
X |
X |
||||
|
Notacanthus phasganorus |
A C |
X |
X |
||||
|
Polyacant/ionotus rostratus |
A |
X |
X |
||||
|
Simenchelys parasiticus |
A-B-C-D |
X |
X |
||||
|
Conger oceanica |
D |
X |
X |
||||
|
Synaphobranchus pinnatus |
A-B-C-D |
X |
X |
||||
|
Chlorophthalmus |
|||||||
|
chalybeius |
B-C-D |
B-C-D |
X |
X |
|||
|
truculentus |
B-C |
X |
X |
||||
|
Merluccius bilinearis |
A-B-C-D |
A-B-C |
X |
X |
|||
|
albidus |
BCD |
B-C-D |
X |
X |
|||
|
Gaidropsarus ensis |
A |
X |
X |
||||
|
Enchelyopus cimbrius |
C |
X |
X |
||||
|
Pollachius virens |
A |
X |
X |
||||
|
Melanogrammus |
|||||||
|
aeglefinis |
A-B D |
X |
X |
||||
|
Antimora rostrata |
A-B-C-D |
X |
X |
||||
|
Urophycis regius |
B-C-D |
X |
X |
||||
|
tenuis |
B-C-D |
A-B-C-D |
X |
X |
|||
|
chuss |
A-B-C-D |
X - |
X |
||||
|
chesteri |
B-C-D |
A-B-C-D |
X |
X |
|||
|
Laemonema barbatulum |
D |
X |
X |
||||
|
Brosme brosme |
A |
X |
X |
||||
|
Gadus (Micromesistius) |
|||||||
|
poutassou |
A-B |
X |
X |
||||
|
Macrourus bairdii |
B-C-D |
A-B-C-D |
X |
X |
|||
|
berglax |
^-^^ |
X |
X |
||||
|
Coelorhyncfius carminatus |
B-C-D |
B-C-D |
X |
X |
|||
|
Coryphaenoides rupestris |
A-B-C-D |
X |
X |
||||
|
Citharichtiiys arctifrons |
B-C-D |
X |
X |
||||
|
Monolene sessilcaudata |
C-D |
X |
X |
||||
|
Reinhardtius iiippoglos- |
|||||||
|
soides |
A-B |
X |
X |
||||
|
Hippoglossus hippoglossus |
A |
X |
X |
Reports of exploratory otter-trawling between Nova Scotia and Virginia
363
Table II {continued)
|
iathoms \ |
Caughl in |
A |
<». of fish |
|||
|
Species |
__ 1 |
Aggregate catch |
||||
|
_ _ _ 1 |
1 |
~ |
||||
|
1 |
— 200 |
+ 200 |
\-\Q Hauls |
1 1 //,;.'//s |
l-IO |
11-100 101 t |
|
Hippoglossoides |
||||||
|
plalessoides |
A |
A |
X |
\ |
||
|
Paralichthys oblong us |
BCD |
B |
X |
X |
||
|
Glyptocephalus |
||||||
|
cynoglossus |
B-C-D |
A-B-C-D |
X |
X |
||
|
Zenopsis ocellatus |
D |
X |
\ |
|||
|
Polymyxia nohilis |
C-D |
X |
X |
|||
|
Poronotus triacantltus |
BCD |
X |
X |
|||
|
Lopholatilus |
||||||
|
cfiamaeleonticeps |
C |
X |
\ |
|||
|
Sebastes maiinus |
A |
A-B-C |
X |
X |
||
|
Helicolenus dactylopterus |
B-C-D |
B-C-D |
X |
X |
||
|
Myoxocepfialus |
||||||
|
octodecemspinosus |
A |
X |
X |
|||
|
Cottunculus microps |
A-B |
X |
X |
|||
|
thompsoiii |
A-B-C-D |
X |
X |
|||
|
Paraliparis copei |
A-B |
X |
X |
|||
|
Peristedion miniatum |
B-C-D |
X |
\ |
|||
|
Tautogolabrus adspersus |
B |
X |
\ |
|||
|
Macrozoarces americanus |
B |
X |
X |
|||
|
Ly codes esmarkii |
B |
X |
X |
|||
|
frigidus |
A-B-C |
X |
X |
|||
|
Lycenchelys paxillus |
A |
X |
X |
|||
|
Dicrolene intronigra |
B-C-D |
X |
X |
|||
|
Lepophidium cervinum |
C-D |
X |
X |
|||
|
Lophius americanus |
A-B-C-D |
A-B-C-D |
X |
X |
||
|
Dibranclius atlanticus |
B-C-D |
A-B-C-D |
X |
X |
Thus the 193 hauls yielded only 21 species of which the aggregate catch was greater than 100 individuals, 21 species which ranged from 11 to 100, and 33 species from 1 to 10.
It is not surprising that most of our commercial species, including haddock, pollock and various flounders, were not taken as deep as 200 fathoms, for their known depth range does not extend that far. On the other hand, the total absence of cod in our hauls, and the capture of only 1 cusk and of 1 halibut deeper than 200 fathoms, indicate that they are much too scarce along the northwestern Atlantic slope, within the scope of our exploratory trawling, ever to support or contribute materially to a fishery there. While cod are not taken in substantial numbers deeper than 200 fathoms, in fact about 125 fathoms marks the ordinary limit in our fishery, the cusk descends to 250-300 fathoms (though most plentiful considerably shoaler), and the halibut to 400-500. It is possible that a scarcity of preferential food and type of bottom may be chiefly responsible for this paucity of cusk and halibut along the slope. On the other hand, temperature, per se, does not seem to be a limiting factor; for the 3S 42" which exists throughout the year aU along the route of our exploratory fishing, in 200-500 fathoms, is a favourable range for both these species.
While the shoaler water fishes (those which we caught above 200 fathoms and no deeper) are included in the preceding table, species other than those listed arc known to be present in winter but not in summer within this depth range— notably the spiny dogfish {Squalus acanthias), the summer flounder (Paralichthys dcntaius), the scup
364
William C. Schroeder
{Stenotomus versicolor) and the sea robin {Prionotus caroUnus), all of which I have seen taken in large numbers by commercial fishermen in mid-winter off southern New England, within the 50-100 fathom zone. On the other hand it is difficult to explain our capture of only one tilefish (Lopholatilus) for, while the population appears to be more scattered during the summer, it is a year around resident in about 60-150 fathoms, most abundantly between the offings of Nantucket and Delaware Bay where draggers, from late fall to spring, often take 10-20,000 pounds per trip. Certainly there is evidence here that some species may easily evade the small trawls such as were used in our exploratory fishing.
SABLE
ISUAMD BANK
irt""
Fig. 1 . Distribution of bottom otter-trawling stations along the shelf and slope made during June- July 1952 and 1953 by Capn Bill II.
In this connection it is of interest to note the difference in yield between our 50 foot and the 60 foot trawls in such cases where they could be reasonably compared for the same depth zone and area. Thus in 53 hauls of the 50 foot trawl, 16,618 fish of all sorts estimated to weigh about 9,500 pounds were caught, or an average of •314 fish and about 180 pounds per haul, while the catch in 33 hauls of the 60 foot trawl was 12,316 fish estimated to weigh about 11,500 pounds, or an average of 373 fish and about 350 pounds per haul. The larger trawl not only caught more fish by •number (as might be expected) but also fish that averaged larger in size . Much the same result was obtained in the catch of crabs {Geryon), for in 31 hauls of the 50 foot trawl the average catch per haul was 32 crabs weighing about 40 pounds, while
Reports of exploratory otter-trawling between Nova Scotia and Virginia
365
in 21 hauls of the 60 foot trawl the average catch was 4! crabs weighing abdui (•>() pounds, in areas and depths where the catches could be reasonably compared. These data are presented to emphasize the importance of giving due consideration
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366
William C. Schroeder
to the type of gear used when interpreting results quantitatively and qualitatively. It is a matter for speculation as to what our catches would have been had larger trawls been employed.
In the preceding table the catches of all the fishes taken during 1952-1953, deeper than 100 fathoms (excluding bathy pelagic species), are segregated by depths and areas and converted to a standard based on the 60 foot trawl dragged on bottom for 1 hour.
According to this summary the greatest number and poundage of fish, taken to- gether, was found between 200 and 400 fathoms, and the species contributing most to this were the redfish (Sebastes) and a macrourid (Coryphaenoides) in area A, the offshore hake {Merluccius albidus) in areas B, C, D, and the long-finned hake {Uro- phycis chesteri) in areas A, B, C, D.
The upper hundred fathoms of the slope (100-200 fathoms) produced the smallest yield in pounds of fish per haul, while deeper than 400 fathoms the decline was apparent, and here a substantial part of the catch comprised the macrourids {Macrou- rus bairdii and Coryphaenoides rupestris), the long-finned hake, and the gray sole (Glyptocephalus). Along the outer part of the shelf, in 50-100 fathoms (not included in Table III) the 20 hauls made averaged only about 100 fish weighing 50 pounds.
A 60 foot trawl having a footrope about 50 ft. wide, fishing a swath estimated to be 30 ft. wide in a one-hour drag at 2^ knots, would traverse an area equal to about 10^ acres.
Table IV Calculated catch offish in pounds per acre
|
Fathoms |
Area A Pounds |
Area B Pounds |
Area C Pounds |
Area D Pounds |
Average Pounds |
|
101-200 |
(no hauls) |
10-2 |
19-7 |
17-6 |
16 |
|
201-300 |
96-5 |
18-3 |
171 |
24-6 |
43 |
|
301-400 |
67-6 |
17-1 |
19-4 |
8-6 |
45 |
|
401-500 |
45-7 |
10-8 |
(no hauls) |
14-3 |
33 |
|
501-730 |
46-5 |
100 |
15-7 |
90 |
22 |
|
Average* |
67 |
14 |
18 |
15 |
* Based on the total number of hauls as given in Table III.
Thus Table IV (which presents in another form part of the data in Table III) shows that area A, from Long. 63° 17' W to 65° 59' W, was considerably more productive in pounds offish per acre than areas B, C, or D, from Long. 66° W to 74° 15', which were rather uniform in yield as compared one with the other.
These figures of yield per acre would be increased considerably by the use of a commercial-size otter trawl. And the amounts would have been substantially greater (regardless of trawl size) if our efforts had been directed chiefly in exploiting the most productive grounds rather than in exploring poor areas as well. From the
Reports of exploratory otter-trawling between Nova Scotia and Virginia 367
Standpoint of the food-fish fishery the most promising region is in area A between 200 and 400 fathoms where Sebastes was dominant, and for the so called Irash-fish fishery areas A to D in this same depth zone, together with areas C-D in 100-200 fathoms and area A in 400-730 fathoms.
So few records are available pertaining to the yield of fish per acre on the ocean bottom that it is of interest to note here data obtained during 1936 for a small area in the Gulf of Maine to the westward of Jeff"rey's Ledge where, in 80-100 fathoms, using an 82 foot shrimp trawl calculated to fish a breadth of 52 ft., the catch of fish per acre worked out to about 47 pounds.*
There follows a further discussion of certain of the species listed in Table II (p. 362) arranged by groups.
ELASMOBRANCHS AND CHIMAEROIDS The species comprising this group, caught deeper than 200 fathoms, have been discussed by Bigelow and Schroeder (1954). Only the black dog-fish (Centro- scyllium fabricii) was taken in relatively large numbers, chiefly in 300-550 fathoms within area A.
EELS
Of the several species of Apodes caught, the long-nosed eel Synaphohranchus pinnatus was the most plentiful, chiefly in area A between 450 and 500 fathoms, where the best 4 hauls averaged about 150 of this species. In areas B, C, and D, where it was found to be much less plentiful, the best catches likewise were made in the 450-500 fathom zone. The shoalest capture was in 220 fathoms, beyond which it was taken at all depths down to our deepest haul at 730 fathoms.
CODS AND HAKES
Both in numbers and poundage this group proved dominant in depths beyond 200 fathoms. Most plentiful is the long-finned hake Urophycis chesteri, taken in small numbers as shoal as 125 fathoms and as deep as 730 fathoms, with the best catches between 200 and 450 fathoms. For example, in area A 2 hauls averaged 676 hake in 200-250 fathoms, and 8 hauls averaged 360 hake in 250-300 fathoms; in area B the average of 3 hauls was 267 in 250-300 fathoms, in area C 6 hauls averaged 125 in 200-250 fathoms, and the best hauls in area D were 2 averaging 254 hake in 250- 300 fathoms. The general run of fish ran \-\\ pounds.
Moderate numbers of blue hake, Antimora rostrata, were taken in area A between 300-700 fathoms, the average catch per haul ranging from 14 to 29 individuals, while in areas B, C and D a scattering few were caught between 400-730 fathoms. In size the general run ranged from 10 to 14 inches, the extremes from 6 to 2n inches.
The red hake, Urophycis chuss, important chiefly in the inshore trash-fish fishery, and the white hake, U. tenuis, considered of more value as a food fish, were taken in scattering numbers throughout areas A to D, the former down to 200 fathoms and
the latter to 550 fathoms.
An account of the first western Atlantic records of the blue whiting Gadus {Mwro- mesistius) poutassou is given by Bigelow and Schroeder (1955). One specimen was
* See BIGELOW and Schroeder (1939) p. 322 where the ff^f "//•^^^Tt^r'ac^ ''''" "" " pounds per acre, of which the fish comprised about 85 per cent, or 47 pounds per acre.
368 William C. Schroeder
trawled on the seaward slope of Georges Bank, Lat. 40° 18' N, Long. 68° 01' W at 230-250 fathoms, July 15, 1952 and three others at 240-280 fathoms on the slope of Browns Bank between Lat. 42° 09' N Long. 65° 21' W and Lat. 42° 08' N, Long. 65° 27' W, July 16 1953. They ranged in standard length from 349 to 416 mm.
The offshore hake, Merluccius albidus, was next in importance, but none at all was taken in area A. In the other areas a scattering few were caught as shoal as 55-100 fathoms and deeper than 400 fathoms, but the best yields were as follows: area B, an average of 80 to 108 per 5 hauls between 200-350 fathoms; area C, 126 to 400 per 3 hauls between 150-350 fathoms; area D, 140-164 hake per 14 hauls in 100-300 fathoms. The majority of these hake ranged from 1 to 3 pounds, some as large as 4-4| pounds.
The silver hake, M. bilinearis, an important shoal water commercial species, was not found to be an important factor off shore. The best catches were in area B, where in 100-300 fathoms an average of 70 to 125 fish was taken in 6 hauls.
GRENADIERS OR MACROURIDS
More pounds of Coryphaenoides rupestris were taken than of any other macrourid, chiefly because of its relatively large size (most of those taken ranged from 1 to 6 pounds) and its abundance within area A where, between 300-550 fathoms, the averages for 36 hauls ranged from 220 to 535 fish of this species. The shoalest capture was in the 200-250 fathom zone, and the deepest around 700 fathoms. To the west- ward, within areas B, C, and D, relatively few were taken, and these deeper than 350 fathoms, the best catch being an average of 70 fish in 2 hauls made in area D in 450- 500 fathoms.
The common grenadier or rat-tail, Macrourus bairdii, was found to be very wide- spread in all depths from 150 fathoms to 730 (our deepest haul) throughout areas A to D. The better catches (between 300-700 fathoms) ran from about 75 to 150 fish per haul. But as this species averages only ^—j pound in weight, the poundage taken per haul was insignificant.
THE FLOUNDER TRIBE
The gray sole (Glvptocephalus cynoglossus) is the only flounder that was found to be widespread deeper than 200 fathoms. In fact, it was caught in a greater number of hauls than any other species of fish listed in Table II. On the other hand, although it was widespread, no large concentrations were found, and the general range in size was relatively small, only about ^ to 1 pound, with but few reaching 2 pounds or more. This flounder was taken just about everywhere between 120 and 730 fathoms from areas A to D. Excluding the smallest catches, the results were: Area A, 200- 550 fathoms, 23 to 96 fish per haul; area B, 250-600 fathoms, 17 to 45 fish per haul; area C, 150-730 fathoms, 18 to 120 fish per haul; area D, 150-730 fathoms, 12 to 114 fish per haul. The greatest number taken in a single haul was 218, area A, 350- 400 fathoms.
It is of interest to note that the gray sole is one of the important food fishes in the northern Atlantic where, off our coast, the best catches are made between about 60 and 150 fathoms.
Only 1 haUbut was caught during our exploratory fishing, this a 75 lb. fish taken in 340-360 fathoms in Lat. 42° 41' N, Long. 63° 58' W. The paucity of halibut along the slope is referred to on p. 363.
Reports of exploratory otter-trawling between Nova Scotia and Virgini
369
A few Greenland halibut {Reinhardtius hippoghssoUies) were taken, 20 of them between Long. 63° 47' and 65° 10' (area A) and 1 at 67 59' (area B), this latter being the most westerly known record. The depth range was 305-530 fathoms, the size from 13 to 36 inches long.
REDFISH OR OCEAN PERCH
Although the redfish occurs in great abundance in the North Atlantic, especially off New England, Nova Scotia and the Grand Banks, virtually all of our catch was taken within area A. A list follows of those hauls in which more than 100 redfish were caught:
Table V Catches o/ Sebastes marinus taken between Long. 63° 17' and Long. 65 59' W, converted to a 1 hour haul with a 60 ft. otter trawl, arranged by longitude
|
Rcdjisli |
Bottom * |
||||||
|
Station |
Date |
Lat. |
Long. |
Fathoms |
Number |
Bushels |
Temp. F. |
|
164 |
July 12, 1953 |
42=43' |
63= 50' |
310-335 |
210 |
6i |
39-4 |
|
173 |
July 13, 1953 |
42= 40' |
64= 10' |
240-270 |
450 |
15 |
40-3 |
|
105 |
July 27, 1952 |
42=41' |
64 13' |
260-290 |
386 |
9J |
|
|
172 |
July 13, 1953 |
42= 36' |
64= 15' |
220-370 |
744 |
25 |
39-6 |
|
176 |
July 14, 1953 |
42= 33' |
64= 17' |
280-320 |
189 |
6i |
40 I |
|
184 |
July 15, 1953 |
42=23' |
64= 52' |
265-295 |
728 |
28 |
40 1 |
|
188 |
July 15, 1953 |
42= 17' |
65=01' |
270-340 |
720 |
24 |
39 |
|
109 |
July 28, 1952 |
42= 20' |
65=03' |
305-320 |
510 |
17 |
|
|
189 |
July 15, 1953 |
42= 18' |
65=05' |
220-240 |
338 |
\\\ |
40-5 |
|
191 |
July 16, 1953 |
42=09' |
65 21' |
240-280 |
1056 |
32 |
40 |
|
193 |
July 16, 1953 |
42=08' |
65° 27' |
250-300 |
298 |
9 |
39 |
* As a maximum-minimum thermometer was used the temperatures given are presumed lo be lor the deepest part of a haul.
All of these fish ranged in length from 12 to 19 inches with a mean of about 15 to 16 inches, with the exception of one of 81 inches. The count in most cases ran from 30 to 35 fish to the bushel. Thus the populations sampled proved to contain exclusively very large redfish and, according to present age studies, such fish were probably from
15 to 20 years old.
A ready explanation as to why virtually no small or medium redfish were taken in these hauls is not available at the present time. True, this area had never been tishcd before with otter trawls, so far as is known, and therefore being a virgin territory might be the answer, at least in part. And it is of interest to note that the Fisheries Research Board of Canada engaged in exploratory dragging for redfish in the Gull of St. Lawrence during 1953 and 1954, and found areas in 100-175 fathoms where the dominant sizes of the fish likewise were very large, ranging from 35 to 40 cm. (14 to 16 inches).t On the other hand, the newly exploited redfish grounds m the Grand Banks region where trawlers have been operating as deep as 175 laihoms. and perhaps a Httle more, have from the beginning produced a substantial percentage of small to medium fish.
t MARTIN in Fish. Res. Bd., Canada. ^^ ' ,^^'-"% ^f ''f ^ /ri9M'u9'^sTpp'6U6?"' Steele and Martin in Fish. Res. Bd., Canada, Rept. Atlatitic B.ol. Sta. for 1954 ( 1955). pp. t.^ M.
370
William C. Schroeder
No hauls were made in 100-200 fathoms in area A, but it appears certain that red- fish occur there along the upper slope, perhaps in somewhat the same abundance as they are at present found on the slope of the Grand Banks. But it is not likely that any large bodies of fish are to be found deeper than about 370 fathoms in area A (Long. 63° 17' to Long. 65° 59' W), for only 11 were caught in 27 hauls made there in 400-700 fathoms, the deepest catch being at about 425.
While our best catches of redfish were taken within the narrow temperature range of 39°_40-5° F, they are known to occur in more or less abundance between about 36° and 48°, with the 38°-42° temperature zone probably the most favourable for it.* But factors other than tem_perature influence the presence and abundance of redfish, of which type of bottom and an adequate supply of preferred food (chiefly euphausiids, shrimps, small mollusks and various other invertebrates) must play an important part, as only a scattering few were taken by us in the many hauls made along the slope to the westward of Long. 66° in temperatures of 38°-42°.t
The black-beUied rosefish (Helicolenus dactylopterus), a close relative of the red- fish, was taken in small numbers in areas B, C, D, between 70 and 300 fathoms, the best catches being in 150-200 fathoms with averages per haul as foUows: area B, 66 fish in 3 hauls; area C, 160 fish in 8 hauls, and area D, 87 fish in 2 hauls. The usual size was 6-8 inches in length, the extreme range 3-13 inches.
MISCELLANEOUS SPECIES Of the remaining species listed in Table II, and not otherwise mentioned, there follows the depth ranges of those which were captured beyond 200 fathoms in this survey, the deepest haul made being in 730 fathoms.
Table VI Depth range offish not otherwise mentioned
|
Species |
Range in Fathoms |
|
Petromyzon marinus |
220-470 |
|
Argentina situs |
200-380 |
|
Notacanthus phasganorus |
270-570 |
|
Polyacanthonotus rostratus |
220-370 |
|
Simenchelys parasiticus |
250-730 |
|
Chloropthalmus chalybeius |
50-250 |
|
Gairdropsarus ensis |
415-545 |
|
Antimora rostrata |
300-730 |
|
Laemonema barbatula |
275-650 |
|
Macrourus berglax |
250-530 |
|
Coelorhynchus carminatus |
100-460 |
|
Hippoglossoides platessoides |
265-295 |
|
Paralichthys oblong us |
50-235 |
|
Cottunculus microps |
200-500 |
|
Cottunculus thompsoni |
250-700 |
|
Lycodes esmarkii |
400-430 |
|
Ly codes frigidus |
350-520 |
|
Lycenchelys paxillus |
250-480 |
|
Dicrolene intronigra |
450-730 |
|
Lophius americanus |
50-450 |
|
Dibranchus atlanticus |
150-500 |
* For a more detailed account see Bigelow and Schroeder 1953, p. 432.
t See Steele and Martin (1955), who trawled large redfish in the Gaspe region in 39-4''-40-9°, and who point out that the presence and abundance of the euphausiid Meganyctiphanes norvegica appeared to be an important factor determining the distribution and movements of redfish.
Reports of exploratory otter-trawling between Nova Scotia and Virginia 37 [
It is probable that some of the Argentina and Chloropthalmus were taken well otT bottom. Most of the species listed above are known from depths beyond those given here. None were taken in large numbers.
LOBSTERS AND RED CRABS
It is planned to present in a separate paper, an account of the lobsters (Homarus americanus) and red crabs (Geryon quinquidens) taken during this exploratory lishing. It can be said here that lobsters were found in quantities sutficicnt to support at least a limited amount of commercial fishing in depths of from about 70 to 150 fathoms where we trawled up to 4 bushels or more in a 1 hour drag between Long. 69' 30' and Long. 71°. Catches also were made as deep as 260 fathoms and as far westward and southward as fishing was done (Lat. 37° 38' N, Long, 74^ 15' W.)
It has long been known that lobsters, especially very large ones, occur off shore between the offings of Nova Scotia and North Carolina, and in the last few years otter trawlers have been bringing in fair catches from off the coast of New Jersey. But since releasing information concerning their whereabouts and relative abundance ofT the New England coast, based on our recent investigations, a number of boats have been operating successfully with catches reported as high as 8,000 pounds landed from a 5- or 6-day trip. All sizes of lobsters are present in this offshore area from about 5 inches in total length to those weighing 20 pounds or more. While the average size has been considerably larger than that taken inshore by the trap fishery, in which the size of the trap opening excludes large lobsters, nevertheless a good proportion of very small ones is present also. There is an indication from this that the offshore population, rather than being composed chiefly of large and very old individuals that may have gradually worked into deeper water, is in fact made up substantially of all ages. It would seem therefore that the offshore stock is not too dependent on emigrants from inshore but rather that much of this population owes its existence to lobsters being carried there during their planktonic existence.
The red crabs were found throughout the areas fished, but while they were taken in the deepest hauls their shoalest range was quite sharply defined. Thus in area A they first appeared at about 250 fathoms, in areas B and C at about 200 fathoms, and in area D at about 150 fathoms. The best average catches per 1 hour drag were as follows: area A, 23 to 115 crabs in 300-550 fathoms; area B, 30 to 79 in 200-400 fathoms; area C, 29 to 80 in 200-550 fathoms, and area D, 65 to 203 crabs in 150- 450 fathoms. They were well distributed, for catches were made in almost every haul made within these depths.
In size the great majority of the red crabs ranged from 1 to 2 pounds and, as they have proven very good to eat, there is a possibility that a fishery for them may develop.
BOTTOM TEMPERATURES
On the three cruises made in 1953, from June 25 to July 30, temperatures were obtained for most of the hauls with a maximum-minimum thermometer which was attached to an otter board. It may be presumed that these minimum temperatures, in most cases at least, were those prevailing at or very close to the bottom.
It must be admitted that the instruments used were not of a quality or calibration comparable to the precision of the best deep-sea reversing thermometers. However, from time to time the latter were used as a check on the former, and d.flerences in
372
William C. Schroeder
Table VII The average temperatures in °F for various depths in the four sub-areas with the number of stations or hauls shown in parentheses
|
Area A |
Area B |
Area C |
Area D |
|
|
Fathoms |
63° 17-65° 59' |
66° 00-69° 59' |
70°00'-71°59' |
72° 00 '-74° 15' |
|
101-125 |
(1) 53 |
(2) 50-8 |
(2) 47-8 |
|
|
126-150 |
(1) 45 |
(4) 46-8 |
||
|
151-200 |
(3) 42-7 |
(1) 46 |
(2) 46 |
|
|
201-250 |
(1) 40-5 |
(3) 41-3 |
(1) 42 |
(1) 42-4 |
|
251-300 |
(7) 40 |
(1) 40-5 |
(3) 40-6 |
|
|
301-350 |
(5) 391 |
(1) 40 |
(2) 40- 1 |
|
|
351^00 |
(3) 39-6 |
(1) 40 |
(1) 39 |
(4) 39-7 |
|
401-450 |
(2) 39-6 |
(2) 38-5 |
(3) 39 |
|
|
451-500 |
(3) 39- 1 |
(3) 39 |
(2) 39-2 |
|
|
501-550 |
(2) 39-7 |
(3) 39 |
||
|
551-600 |
(1) 38 |
(1) 39-6 |
(2) 38-8 |
|
|
601-650 |
(2) 39-7 |
(2) 39-7 |
(3) 38-7 |
|
|
651-700 |
(2) 38-9 |
|||
|
701-730 |
(1) 38 |
(1) 39 |
(1) 38-5 |
(2) 38-8 |
temperature between the two were seldom greater than 0-5°. It is of interest to note, also, that the results listed above agree very closely with those obtained in the same region, in summer, by the Blake, Fish Hawk and Albatross in the 1880's.
As we are concerned here chiefly with conditions along the Atlantic slope, within the region explored, as it pertains to the bottom-dwelHng fishes and other marine hfe, it seems evident that the temperatures at or near bottom, between 200 and 730 fathoms at least, are very uniform. And while this applies to June-July, the few readings obtained by the Albatross in February-March 1920 between Long. 64° and 68° W in 200-700 fathoms are in close agreement.
So far as the role of temperature, per se, is concerned with the presence and abun- dance of these fishes living beyond 200 fathoms, conditions appear to be very stable, and it would not be surprising if the results thus far obtained, with due consideration to the type and efficiency of the gear employed, would be found to be approximately the same for any season or year. Only further exploratory work can reveal whether or not this is so.
REFERENCES
BiGELOw, Henry B. and Schroeder, William C. (1939), Notes on the fauna above mud bottoms
in deep water in the Gulf of Maine. Biol. Bull., 76 (3), 305-324. BiGELOw, Henry B. and Schroeder, William C. (1953), Fishes of the Gulf of Maine. Fish. Bull.
lA, Fish and Wildlife Serv., 53, 1-577. BiGELOw, Henry B. and Schroeder, William C. (1954), Deep water Elasmobranchs and Chimae-
roids from the northwestern Atlantic Slope. Bull. Mus. Camp. ZooL, Harvard Coll., 112 (2),
37-87. BiGELOW, Henry B. and Schroeder, William C. (1955), Occurrence off the middle and north
Atlantic United States of the offshore hake Merluccius albidus (Mitchill) 1818, and of the blue
whiting Gadus (Micromesistius) poutassou (Risso) 1826. Bull. Mus. Camp. ZooL, Harvard Coll.,
113 (2), 205-226. BiGELOw, Henry B., Schroeder, William C. and Springer, Stewart (1953), New and little known
sharks from the Atlantic and from the Gulf of Mexico. Bull. Mus. Camp. ZooL, Harvard Coll.,
109 (3), 213-276. Martin, W. R. (1954), Redfish ecology in the Gulf of St. Lawrence. In: Fish. Res. Bd., Canada,
Kept. Atlantic Biol. St a. for 1953, 61-64 (unpublished manuscript). Steele, D. H. and Martin, W. R. (1955), Redfish ecology in the Gaspe area. In: Fish .Res. Bd.,
Canada, Rept. Atlantic Biol. St a. for 1954, 63-65 (unpublished manuscript).
Papers in Marine Biology and Oceanography. Suppl. lo vol. 3 of Dccp-Sca Research, pp. 373- J97.
Stromgeschwindi«?keiten im Tiefen- und Bodenvvasser des Atlantisehcn
Ozeans auf Grund dynamischer Berechnung der Meteor— ProiiW dcr
Deutschen Atlantischen Expedition 1925 27
Von Georg Wust Institut fiir Meereskunde der Universitiit Kiel
Summary— This new dynamic study of the Meteor profiles (German Atlantic Expedition. 1925-27) is based on the " dynamic reference surface " of Defant (1941), which admittedly is only a first approximation. It is particularly concerned with the current velocities of the deep and bottom water of the Atlantic Ocean. Selected transverse profiles, longitudinal sections and charts indicate unex- pectedly large measurable current velocities in the axis of the North Atlantic Deep Current and of the Antarctic Bottom Current flowing along the foot of the continental slope ofT South America. On the average, these have a velocity of 9-2 and 7-2 cm/sec, and reach maximal velocities of 17 4 and 12'5 cm/sec. These calculated current velocities are probably not too high because of the great distances between stations along the profiles.
The sources of error of the dynamic method are discussed. It appears reasonable to believe that a useful approximation has actually been determined.
EINLEITUNG
NiCHTS KANN den unbefriedigenden Stand unserer Kenntnisse iiber die Strom- geschwindigkeiten in der Tiefsee besser beleuchten als das Urteil eines so erfahrenen Ozeanographen wie G. E. R. Deacon (1954), der folgendes schreibt: " We have known for 150 years that there is water, nearly ice-cold, at the bottom of the tropical Atlantic Ocean, and that it must flow there from the Antarctic, but we can still argue whether it took 18 years or 1800, and there is as much uncertainty about the forces which move it there." Diese Ungewissheit riihrt daher, dass es bisher weder durch direkte Strommessungen auf Ankerstationen noch durch indirekte Methoden der Berechnung oder Schatzung gelungen ist, die kontinuierlichen Wasserbewegungen in den Tiefen von mehr als 2500 m nach Richtung und Geschwindigkeit geniJgend genau zu erfassen und damit zu einer brauchbaren quantitativen Losung des Zirku- lationsproblems zu gelangen. Hinsichtlich der Strommessungen auf Ankerstationen hat kurzHch K. F. Bowden (1954) gezeigt, dass " direct measurements have provided a comparatively small portion of our knowledge of subsurface currents in the oceans " und betont, dass es eine vordringliche Aufgabe der ozeanographischen Forschung sci. mit verbesserten Methoden und Instrumentcn— wenn moglich vollig unabhiingig von jeder Eigenbewegung des Schiffes und liber jevveils etwa 1 Woche -die mittlercn Stromungen und ihre nicht-periodischcn Schwankungcn in der Tiefsee zu mcsscn. Denn nur auf diesem Wege vermoge man— so argumentiert Bowden weiter^, die mit anderen, indirekten Methoden " geschatzten " Werte dcr ozeanischcn Ticfcn- zirkulation zu verifizieren, nur so konne man zu zuverlassigcn Werten gelangen. die nicht nur fur die Ozeanographic, sondern auch fiir die Mecresgcologic und die marine Biologic der Tiefsee im Hinblick auf die Bearbeitung dcr Sedimentproblcmc und der Probleme der Verbreitung der Organismen so unentbehrlich sind.
373
374 Georg Wust
Bei dieser Sachlage erscheint eine erneute dynamische Bearbeitung der Meteor — Profile 1925/27, wie sie vom Verfasser im folgenden in Angriff genommen ist und welche die Berechnung der absoluten Stromkomponenten und der transportierten Wassermengen senkrecht zu den Profilen in den Tiefen zwischen der DEFANr'schen Bezugsflache (Nullflache) und dem Tiefseeboden zum Ziel hat, durchaus geboten. Denn nur auf diese Weise besteht Aussicht, die von A. Defant (1936 a) und G. WiJST (1936) gewonnenen Vorstellungen raumlich und in quantitativer Richtung zu erweitern und zu fundieren.* Bei der Berechnung der zahlreichen Tabellen und der Eintragung der Werte in mehr als 30 grosse dynamische Profile und Karten, die spater in extenso an anderer Stelle verofifentlicht werden soUen, habe ich mich der sorgfaltigen Hilfe durch Herrn cand. rer. nat. E. Noodt erfreut.
rOckblick auf die bisherigen indirekten schatzungen der
stromgeschwindigkeit
Die Bedeutung unserer neu berechneten Werte der Stromgeschwindigkeit wird erst ersichthch, wenn wir sie in Beziehung stellen zu den bisherigen Ergebnissen der nicht sehr zahlreichen Versuche, auf indirekte Weise zu Schatzungen bzw. Naherungs- werten dieses Faktors fiir die Tiefsee zu gelangen. Aus diesera Grunde sei ein kurzer RiickbUck vorausgeschickt, wobei hinsichtlich der Geschichte der allgemeinen, d.h. mehr qualitativen Erforschung der Ausbreitung des atlantischen Tiefen- und Bodenwassers auf die ausfiihrUchen Darstellungen des Verfassers im Meteor — Werk (1933 und 1936) verwiesen werden kann.
Die ersten Versuche von Porch (191 1), Thoulet (1921, 1925), Wattenberg (1927), Deacon (1931), Castens (1931, 1932) und Seiwell (1939) haben heute im wesent- lichen nur historische und rechnerische Bedeutung, da die ihnen zugrundeliegenden Annahmen bzw. Voraussetzungen, wie im Meteor- Werk dargelegt worden ist, in der Tiefsee nicht erfullt sind. So hat der Verfasser (1933, S.55) gezeigt, dass " es verfehlt ist, in der Temperaturzunahme des antarktischen Bodenstroms von Siiden nach Norden in der Westmulde und Ostmulde einen sichtbaren Effekt der Erdwarme zu erblicken und aus dieser Temperaturzunahme und dem annahernd bekannten vom Erdinnern ausgehenden Warmestrom etwa die Geschwindigkeit des Boden- stroms berechnen zu wollen ", wie es C. Forch (1911) versucht hat. Denn " diese Zunahme der Temperatur beruht,. wie die Kurven lehren, ganz iiberwiegend auf dem Vorgang der Vermischung " (Wust 1933, S.55). Auch Thoulets (1921; 1925) beharrUche Auffassung von der Bewegungslosigkeit der Wassermassen in den Tiefen von mehr als 2000 m ist heute iiberholt. Denn " gerade im untersten Stockwerk des Ozeans sind die Wassermassen in der Temperatur und im Salzgehalt wesentUch starker differenziert als in der dariiberUegenden Tiefenschicht, verharren keineswegs in Bewegungslosigkeit, sondern befinden sich offenbar in der Mehrzahl der Tiefsee- becken in merkhch stromender Bewegung, die wir unmittelbar aus dem Verlauf der Isothermen ablesen konnen " (Wust 1933, S.34). Andererseits hat der Verfasser (1936, S. 182-201) durch eine kritische Priifung hinsichthch der von Wattenberg (1927) vermuteten jahreszeithch bedingten Schwankungen von Salzgehalt, Sauerstoff
* Die Durchfiihrung dieser umfangreichen Untersuchung, von der mit Genehmigung des Her- ausgebers der Wissenschaftlichen Ergebnisse der Deutschen Atlantischen Expedition, Herrn Prof. Dr. A. Defant, hier eine erste Mitteilung vorgelegt wird, ist dem Verfasser durch die Bewilligung einer Sachbeihilfe seitens der Deutschen Forschungsgemeinschaft ermoglicht worden, wofiir auf- richtig gedankt sei.
Stromgeschwindigkeiten im Ticfcn- iind Bodcnwasscr 375
und Temperatur in den Kernschichten des subantarktischen Zwischcnwasscrs und des nordatlantischen Tiefenwassers klargcstellt, dass aus den Bcobachtungcn dcs Meteor keine klar definierten raumlichen Unterschiede dicser 3 Faktorcn im " Slrom- strich " der Kernschichten nachweisbar sind, die mit Sichcrhcit auf jahrcszcitlich bedingte, periodische Einflusse in den Absinkgebieten zuriickgcfuhrt werdcn und dazu dienen konnen, die Geschwindigkeiten der Ausbrcitung dicser Wasserartcn zu berechnen. So erweist sich leider auch dicser origincilc von WAirhNHiRc. (1927) geausserte Gedanke, der dann von Deacon (1931), Castens (1931, 1932) und Si.iwei.l
(1934) aufgegriffen worden ist, nicht als realisicrbar, zumal anzunehmcn ist, " dass unperiodische Schwankungen cine grossere Rolle spielen, als man bisher im allge- meinen annimmt " (WiJST 1936, S.193), cine Vermutung, die durch cine ncucrc Untersuchung von Worthington (1954) gestiitzt wird. Wattenberg (1935) hat noch einen anderen, ebenfalls recht interessanten Weg zur Bercchnung dcs Massen- austausches iiber dem Tiefseeboden und damit zur Berechnung der Gcschwindigkcit des antarktischen Bodenstroms beschritten. Aus der Zunahmc der spez. Alkalinitat langs seinem Vordringen im Brasilianischen Becken, d.h. aus der Abgabe des aus dem Sediment gelosten Kalziumkarbonats berechnet er zunachst den vertikalen Austauschkoeffizienten A zu 4 cm'i g sec'i. Unter Benutzung des von A. Defant
(1935) zu 4-9 abgeleiteten Verhaltnisses A : c kommt Wattenberg (1935) zu dem Ergebnis, " dass cine mittlere Gcschwindigkcit (c) von 0-5 bis 1 cm/sck im Antark- tischen Bodenstrom einen hohen Grad von Wahrscheinlichkeit besitzt", was in guter Obereinstimmung stehe mit dem von H. Mosby (1934) geschatzten Wert von 1 cm/sck. In der definitiven Bearbcitung der " Ausbreitungs- und Vcrmischungs- vorgange im antarktischen Bodenstrom und im subantarktischen Zwischenwasser " berechnet A. Defant (1936 b) erneut aus den vom Verfasser konstruierten Langs- schnitten der potentiellen Temperatur und des Salzgehalts in den Bodenschichten auf der Westseite des Atlantischen Ozeans die Grosse des Verhaltnisses A : c in den einzelnen Ticfcn und Zonen und gelangt unter Annahme des WATTENBERGschen Austauschwertes A = 4 zu folgenden Geschwindigkeitswerten* im Hauptstrom- strich des antarktischen Bodenstroms:
iiber den Schwellen zwischen 1-5 und 2 cm/sek iiber den Mulden zwischen 0-5 und 1 cm/sek. Fiir den Stromstrich des unteren nordatlantischen Tiefenstroms crliiilt cr auf dicse Weise Geschwindigkeitswerte zwischen 0-3 und 0-8 cm/sek. Die eingchcndc Analyse der Ausbrcitung und Vermischung der Wassermassen in der atlantischen Kalt- wassersphare mittels der Kernschichtmethode hat den Verfasser (WiJST 1936, S.243) zu der Erkenntnis gefuhrt, " dass bei alien 5 Wasserartcn von meridionalcn Kom- ponenten und einem stromartigen Charakter der Ausbrcitung nur ganz auf der Westseite des Ozeans gesprochen werdcn kann. In die ostlichcren Rcgionen werdcn die Wasserartcn durch zonale Ausbrcitung, ja stellenwcise cntgcgcngcsclzte Bcwc- gungen bzw. durch ganz allmahliche Einwirbelung verfrachtct ". Und an andcrcr Stellc- "Denn die Verbreitung der verschiedenen Wasserartcn xm Ozcanraum .st nicht identisch mit der wahren Bewegung im Raume. Nur in den Achscn der Kcrn- massen kann durch Pfeile die Richtung der Tiefwasscrbcwegungcn dargcstcllt
* H,en.. hat Dhpant (1936 ^ ^ZS.^^^ -wS ^^^f^^t^^
376 Georg Wust
werden ". In einer zusammenfassenden Darstellung seiner verschiedenen Unter- suchungen iiber " Bodentemperatur und Bodenstrom in der atlantischen, indischen und pazifischen Tiefsee " hat sich der Verfasser (WtJST 1938 b) schliesslich auch der Frage der absoluten Geschwindigkeiten im Stromstrich des antarktischen Boden- stroms zugewandt. Unter der unbewiesenen Annahme, dass in der oberen Halfte der Grenzschicht zwischen dem Tiefen- und dem Bodenwasser, bei der in der atlantischen Westmulde vielfach (besonders im Argentinischen und Brasilianischen Becken) " geradezu von einer Sprungschicht der Temperatur und des Salzgehalts zwischen 3500 und 4500 m Tiefe " (Wust 1933, S.70) gesprochen werden kann, die dynamische Bezugsflache zu suchen ist, hat diese damalige vorlaufige dynamische Bearbeitung von 9 Meteor- Querprofilen zwischen 55 ° S und 5° S fiir den Stromstrich zu Nord- komponenten im Betrage von 0-8 bis 4-0 cm/sek, im Durchschnitt 2-2 cm/sek gefiihrt. Defant (1941) hat es aber in seiner umfassenden Bearbeitung des atlantischen Mas- senfeldes auf Grund von 629 Stationen sehr wahrscheinlich gemacht, dass die dyna- mische Bezugs- Oder NuUflache nicht identisch ist mit solchen Grenz — bzw. Sprung- schichten, sondern dass sie nur aus dem Massenaufbau des Meeres ermittelt werden kann und zwar als die Schicht, in welcher die Differenzen der dynamischen Tiefen zwischen benachbarten Stationen praktisch konstant sind und daher die Wasser- versetzungen als sehr nahe Null angenommen werden diirfen. NatUrlich ist sich Defant (1941) dariiber im klaren, dass es zunachst nur " eine reine Annahme ist, wenn man nun innerhalb dieser Schicht die Bezugsflache zur Uberfiihrung der rela- tiven Topographien der Druckflachen in absolute legt ". Defant (1941, S.242) fahrt fort: " aber die Annahme gewinnt sofort an grosser Wahrscheinlichkeit und innerer Sicherheit, wenn man bemerkt, dass die fiir einzelne Stationspaare bestimm- ten Lagen der Bezugsflache sich in ein in sich geschlossenes System zusammenfiigen, wenn man den ganzen Ozean betrachtet." Eine wesentliche Stiitze sieht Defant ferner in der inneren tJbereinstimmung seiner Stromfelder der stationaren Kon- vektionsstrome mit den Ausbreitungskarten der verschiedenen Wasserarten, welche der Verfasser mittels der Kernschichtmethode unter Eintragung von Pfeilen der Hauptausbreitung 1936 abgeleitet hat. Aus einem Uberblick iiber die " Fernwir- kungen antarktischer und nordatlantischer Wassermassen in den Tiefen des Welt- meeres ", in welchem der Verfasser (1951) in vereinfachter Form die DEFANTSchen Stromkarten fiir 800 und 2000 m Tiefe und die diesen Niveaus am nachsten kom- menden Ausbreitungskarten der Kernmassen des subantarktischen Zwischenwassers und des mittleren nordatlantischen Tiefenwassers gegeniibergestellt hat, geht diese grosse innere tJbereinstimmung der beiden voneinander unabhangigen Methoden besonders klar hervor. In der 2000-decibar-Flache findet Defant in der ganzen Westhalfte des Ozeans — ganz in tJbereinstimmung mit den Ergebnissen der Kern- schichtmethode— vorwiegend meridionale Stromungen nach Siiden, welche das in den gronlandischen Gewassern abgesunkene sauerstoffreiche Tiefenwasser auf direktem Wege bis nach 30°-40° S verfrachten mit mittleren Geschwindigkeiten im Stromstrich ganz auf der Westseite von 2 cm/sek und maximalen von 7 cm/sek. Nur in der Querschnittsverengung am Aquator vor Kap San Roque werden nach Defant Stromstarken von 8 bis 14 cm/sek erreicht. Seit 1941 sind dem Verfasser keine weiteren Berechnungen von Stromgeschwindigkeiten in der Tiefsee bekannt geworden ausser einem kiihnen und summarischen Versuch von G. A. Riley (1951), die mittleren Geschwindigkeiten der Nord- und Siidkomponenten zwischen 0 und 4000
Stromgeschwindigkeiten im Ticfcn- iind Bodcnwasscr
377
m und in den verschiedenen geographischen Breiten, gemiltcll jcwcils iibcr die ganze Breite des Ozeans, zu berechnen. Fur 4000 m Ticfe gibl Rilky Miltclwcrle zwischcn 001 und 0-08 cm/sek an, Werte, die fur unsere Problcmslcllung, die auf die absolutcn Geschwindigkeiten im Stromstrich des nordatlantischcn Tiefenstroms und des antarktischen Bodenstroms abzielt, keine Bedeutung besitzen.
35'
&!„ ^'S^!^^;^1^7S^3^'^?;il^'=--^
5°w o°
GREENWICH
. 10^ (a - ot35. o. p.). hostvrcn- Bcckcn in
is^-is^s.
DIE DYNAMISCHE BEARBEITUNO DER METEOR- PRO! H-E Topographie der dynamischen Bezugsflachc-an d.. LntLrMioiu t
378 Georg WiJsT
iiber " die absolute Topographie des physikalischen Meeresniveaus und der Druck- flachen, sowie die Wasserbewegungen im Atlantischen Ozean " an und erweitert sie auf die Schichten zwischen 2500 m Tiefe und dem Tiefseeboden, jedoch mit dem durch die geringere Beobachtungsdichte gegebenen Unterschied, dass wir nicht eine Losung fiir den Gesamtraum, d.h. nicht die Konstruktion von geschlossenen Stromfeldern fiir die einzelnen Niveaus wie Defant anstreben. Wir beschranken uns vielmehr auf die Stromkomponenten senkrecht zu den Meteor- Profilen und ver- suchen lediglich, fiir den Hauptstromstrich des Tiefen- und Bodenstroms ganz auf der Westseite des Ozeans die berechneten Werte der Stromstarke auf die " wahre " Stromrichtung zu reduzieren. Die wesentlichen Grundlagen unserer Berechnungen sind durch die Werte der Anomalien des spezifischen Volumens S = 10^ (a — a35,o,/?) gegeben, wie sie in den "Listen der dynamischen Werte fiir die Standardhorizonte an den Beobachtungsstationen " des Forschungsschiffes Meteor vom Verfasser (1938 a) veroifentlicht sind. Jedoch erweist es sich fiir unsere Aufgabe als erforderlich, ab 2500 m Tiefe nach unten den Abstand der Standard- tiefen — durch vertikale und horizontale Interpolationen und KontroUen mittels der im Atlas zu Band VI enthaltenen Vertikalschnitte und Horizontalkarten von t°, S°/oo und cTj (WusT, 1936) — grundsatzlich auf 250 m zu verringern und moglichst bis zum Tiefseeboden zu erweitern, urn die wahrscheinlichen Werte der Anomalien des spezifischen Volumens fiir unsere dynamische Berechnung einsetzen zu konnen, besonders im Bereich der submarinen Steilabfalle des Meeresbodens. Denn nur auf diese Weise ist es mogUch, die von Helland-Hansen (1934) angegebene Methode der " Fortsetzung der Berechnung in Gebiete geringerer Tiefe " anzuwenden. Die nunmehr zwischen 0 und 1000 m Tiefe fur alle 100 m, zwischen 1000 und 2000 m Tiefe fiir alle 200 m und zwischen 2000 m Tiefe und dem Tiefseeboden fiir alle 250 m Tiefenabstand vorliegenden Werte S (der AnomaUen des spezifischen Volumens) haben wir fiir alle Meteor- Profile in Vertikalschnitte grossen Masstabs eingetragen und durch eine moglichst engabstandige Konstruktion der Isosteren (fiir alle 5 Einheiten unterhalb S = 50) noch einmal kontroUiert und in ihrer raumhchen Verteilung festgelegt. Hierdurch ist eine geniigend gesicherte Extrapo- lation zum Tiefseeboden und die Fortfiihrung der dynamischen Berechnung in Gebiete geringerer Tiefe nach der Methode Helland-Hansens gegeben. In Fig. 1 und 2 sind als Beispiele in starker Verkleinerung die zwei Isosteren — Vertikalschnitte fur die Meteor- Profile VI (15°-18°S) und I (40°-42° S) reproduziert. In beiden Schnitten erkennen wir zunachst die grosse Zahl von Fixpunkten, welche der Isosterenkonstruktion zugrundeUegen und dann die bemerkenswerte Drangung und Schragstellung der Isosteren zwischen 3000 m und 5000 bzw. 5500 m Tiefe in der Westmulde, was uns schon darauf hinweist, dass die Hochstzahl der Solenoide nicht in der Kaltezunge der Westmulde, sondern links von ihr ganz am Westrande des BrasiUanischen und des Argentinischen Beckens gelegen ist. Ganz anders Uegen die Verhaltnisse in den grossen Tiefen der ostatlantischen Mulde. Hier bestehen noch bemerkenswerte Unterschiede zwischen dem Angola-Becken (nordlich des WalfischrUckens) und dem Kap-Becken (siidlich davon). Wahrend ansonsten die Anomahen des spezifischen Volumens mit der Tiefe abnehmen, wachsen sie in dem (durch den Walfischriicken gegen den antarktischen Bodenstrom) abgeriegelten Angola-Becken ab ca. 3000 m mit der Tiefe, so dass hier am Boden S - Werte > 50 existieren, gegeniiber < 30 bzw. 25 im Westen, wo sich also am Fusse des
Stromgeschwindigkeitcn ini Tiefcn- und Bodcnwasscr
379
Kontinentalabfalls jeweils die absoluten Minima der Anomalien der spczifischcn Volumina innerhalb der Vertikalschnitte befinden.
Mittels des so verdichteten Netzes von Fixpunkten sind fiir allc Meteor- Profile zwischen den benachbarten Stationen zunachst die Werte von A [ vdp, d.h.
die Anzahl der Solenoide berechnet und aus diesen unter Bcriicksichticung dor
550- so° 45° 40° 35° 30° 25° 20° 15° IO° 5°W 0° 5°E lO'
GREENWICH
Fig 2 Vertikalschnitt der Anomalien des spezifischen Volumens 8 = lO^a - /as, o,^.)^ nSenTn sfhnitt -Meteor-- Profit I (Juni-Juli 1925) durch das Argent.n.sche und das Kap-Bckcn in
40-42' S.
geographischen Breite 9 und des Abstandes L zwischen den Stationen die Geschwin- digkeitsdifferenzen c.-c.- unter Weglassung der Stationspaare. djc zw.schen 4° N und 4° S gelegen sind-ermittelt, und zwar nach der bckanntcn Formcl son Helland-Hansen und Sandstrom, die auf der BjERKNESschen Zirkulat.onsthcor.o
beruht:
A
^» ' ^^'^Iw.L
sm ?
380
Georg Wust
Die fiir jedes Stationspaar gultige dynamische Bezugsflache Do ist sodann aus Defants Karte der " Tiefenlage der Bezugsflache zur Ermittlung der absoluten Topo- graphic der einzelnen Isobarenflachen " (1941, Beilage XIX), welche Isobasen fiir
<-9
5°W 0° 5°E
GREENWICH
IO°
Fig. 3. Vertikalschnitt der berechneten Geschwindigkeitskomponenten (cm/sek) senkrecht zum " Meteor " — Profil VI (Mai-Juni 1926) durch das Brasilianische Becken und das Angola-Becken in 15°-18°S.
nordliche Komponenten ausgezogene Isotacheen,
siidliche Komponenten gestrichelte Isotacheen,
-O-O-O-O- dynamische Bezugsflache n. Defant (1941).
alle 100 m enthalt, auf 1 Hektometer genau entnommen und der Berechnung der absoluten Stromgeschwindigkeiten Ci zugrundegelegt worden. Diese Werte Ci stellen die Geschwindigkeitskomponenten des stationaren Konvektionsstroms senkrecht
Stromgeschwindigkeiien im Tiefcn- und Bodcnwasscr
381
zu den Meteor- Profilen dar, bezogen auf die ganze Strecke zwischcn zwei Stations- vertikalen. Dadurch, dass nach den Planen von A. Merz (1925) die Querprofilc des Meteor iiber den Ozean senkrecht zu den wichtigsten ozeanischen Boschungen der Kontinentalabfalle und des Atlantischen Zentralriickcns angclcgt worden sind, bestehen von vornherein gUnstige Voraussetzungen fiir die Anwcndung des Bjcrknes- schen Verfahrens; denn sowohl Theorie als Beobachtung lehrcn, dass das Relief
50° 45° 40° 35° 30° 25° 20° 15° ICf
J 1 I 1 I I
5"VV GREENWICH
Fig. 4. Vertikalschnitt der berechncten Gcschvindigkeiiskomponenten ic^^^
-Meteor --Profit I (Juni-Juli 1925) durch das Argentinische und das Kap-Bcxkcn in 40 -4. i.
nordliche Komponenten ausgezogene Isotachcen,
siidliche Komponenten gestrichelte Isotacheen,
-O-O-O-O-dynamische Bezugsflache n. Defant (1941).
von wesentlichem Einfluss auf die Wasserbewegung ist und dass die Stromlinien in den tiefsten Wasserschichten sich weitgehend den Isobathen angleichen. D.e Sirom- komponenten (senkrecht zu den Meteor- Profilen) werden sich also zum.ndesl in der Nahe des Stromstrichs stark den Werten des wahren slat.onarcn Konvck- tionsstromes annahern, wobei zwar zu bedenken ist, dass sie n.cht Punktwcrte der
382
Georg Wust
Geschwindigkeit, sondern Durchschnittswerte fiir einzelne Tiefenniveaus zwischen zwei benachbarten Stationen darstellen. Je weiter der Stationsabstand, umsomehr werden diese Durchschnittswerte Minimalwerte im Vergleich zu den mogUchen
30°
60°
B 20 ^tm/»lr
^ sudl. Stromkomponenten ■A SrvrrBtncti AntorktBodenstran
I lugttictt La/>ffnx:^*iiH Abb 8 )
Hauptausbreiiung Anfaiid. doden- in wii«( S33I Mjsser
ISKm
4500 m \ rnf»nlinf
SSOO m i f„^ uj^^, ,555
Fig. 5. Regionale Verteilung der Geschwindigkeitskomponenten (cm/sek) senkrecht zu den Meteor- Profilen (unter Weglassung der Stationen zwischen 4" N und 4° S) in der bodennahen Schicht der atlantischen Tiefsee (> 3500 m).*
Berechnet aus der Massenverteilung unter Zugrundelegung der von A. Defant (1941) abgeleiteten " dynamischen Bezugsflache ".
Punktwerten der Geschwindigkeit sein, worauf wir noch zuriickkommen werden. Andererseits ist zu bedenken, dass die dynamische Berechnung den Einfluss der Reibung volUg vernachlassigt. Hier hat W. Hansen (1950) in seinen " Bemerkungen
Der Pfeil von 21 cm/sek vor Kap San Roque ist zweifelhaft und zutilgen (cf. Fussnote S.386).
Stromgeschwindigkeitcn im Tiefen- und Bodcnwasscr 3{j3
zu neuzeitlichen Problemen der Ozeanographie " darauf hingcwicscn, dass die Bcrc- chnung der Stromgeschwindigkeitcn aus dem Masscnaufbau trot/, dcr Vcrnach- lassigung der Reibung in all den Fallen zu brauchbaren Rcsultaten fuhrt. in dcncn die senkrecht zur Hauptstromrichtung existierende Druckvcrtcilung bekannt ist und von dieser ausgegangen wird. Dies erklart auch nach Hanse;n, " warum die von Wusi (1924) durchgefiihrte Untersuchung des Floridastromcs so gutc Obercinstimmung zwischen Beobachtung und Rechnung nach dem dynamischen Vcrfahrcn trot/ Vernachlassigung der Reibung lieferte." (Hansen, 1950, S.27).* Die Orienticrung der Meteor- Profile senkrecht zu den Isobathen der Kontincntaiablallc bictet auch aus diesem Grunde gUnstige Voraussetzungen fiir die Anwcndung des Bjirknes- schen Verfahrens, besonders bei der Berechnung der Stromgeschwindigkeitcn in den Stromstrichen des nordatlantischen Tiefenstroms und des antarktischen Bodenstroms, die — wie wir noch zeigen werden — sich ganz an den Sudamerikanischcn Kontinen- talabfall anlehnen.
DIE VERTIKALE VERTEILUNG DER GESCHWINDIGKEITSKOMPONENTEN
IN DEN QUERSCHNITTEN
Auf Grund dieser Ci- Werte haben wir Isotacheen-Schnitte konstruiert, lediglich zu einer groben Veranschaulichung der Verteilung der Geschwindigkeitskomponenten senkrecht zu den Profilen und nicht etwa zur spateren Berechnung der transportierten Wassermengen, da ja eigenthch nur Punktwerte der Geschwindigkeit und nicht unsere Durchschnittswerte, die fiir relativ grosse Stationsabstiinde von 100 bis 500 km giiltig sind, fiir eine solche Konstruktion verwendet werden diirfen. Als Beispiele reproduzieren wir hier in Fig. 3 u. 4 wieder die A/ereor— Profile VI und I in starker Verkleinerung mit den Isotacheen fiir 1, 3, 5, 7 und 9 cm/sek, die im Falle nordlicher Komponenten ausgezogen, im Falle siidlicher Kom- ponenten gestrichelt sind. Wir erkennen, dass unterhalb der DEFANTschen Bezugsflache, welche ebenfalls eingetragen ist, nur an den submarinen Steilab- fallen des siidamerikanischen Kontinentalblocks (und bei Profil VI auch des Atlan- tischen Zentralriickens) Stromgeschwindigkeitcn von mehr als 3 cm/sek auftreten. dass also in der Tat im wesentlichen nur ganz auf der Westseite der atlantischen Westmulde von messbaren Geschwindigkeiten im Tiefen- und Bodenwasser gespro- chen werden kann. Profil VI lehrt, dass die Strommaxima (von mehr als 9 cm.sck) im Nordatlantischen Tiefenstrom (mit sudlichcn Komponenten) in ca. 2250 m Tiefe etwas weiter westlich liegen als die Strommaxima (von mehr als 7 cmsek) im ant- arktischen Bodenstrom (mit nordhchen Komponenten) am Tiefseeboden. d.h. dcr Stromstrich liegt bei dicsen beiden Zirkulationsgliedcrn nicht in ein und derselben Vertikalflachc. Dies aber gerade ist bisher stillschvveigend bei alien Bearbeitungen von Langsschnitten der Tempcratur und des Salzgehalts aus der Tatsache der relativ scharfen Grenzschicht zwischen Tiefen- und Bodenwasser und dcr Uberlagerunp des Bodenwassers durch das Ticfenwasser in der ganzen Westmulde vorausgesct/i worden. Zwischen den Stationspaaren, bei denen der Stromstrich des Bodenstroms mit nordhchen Komponenten erfasst wird, existiert gar kcin mcssbarer T'ctenstrom nach S. Bemerkenswert ist ferner, dass sowohl in Profil VI als auch m Prohl I dcr
* Nur im aquatorialen Be,.ich kann, wie auchHANSHN (1950) ^^^^^ ^ ti^;^;^^;. gung der Reibung verzichtet werden, weshalb wir bei unscrer Btrctnuuns zwischen 4° N und 4° S haben wegfallen lassen.
384
Georg WiJST
Stromstrich des antarktischen Bodenstroms westlich der tiefsten Einsenkungen des Brasilianischen bzw. Argentinischen Beckens gelegen und um rund 1000 m auf den Kontinentalabfall heraufgeschoben ist. Bei Profil I in 41° S besitzt der nordatlantische
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Stromgeschwindigkeitcn im Ticfcn- und Bodcnwasscr 385
Tiefenstrom keine messbaren Sudkomponcntcn mchr; ollcnbar ist h.cr scnc Incriric bereits erlahrat. Die andcren, hier nicht wicdcrgcgcbcncn Isotachcc-n-Prdilc (11 V, VII-XIV) zeigen ahnliche Verhaltnisse, wcnnglcich manclinial das cine odcr das andere der beiden Zirkulationsgliedcr wcnigcr ausgcpriigt crschcint. Abcr immcr zeigt sich— mit Ausnahme der sudlichsten Profile V und III. wo ofTcnbar zonule Hewe- gungen dominieren— auf der Westseite der westatlantischcn Mulde die Inlensinka- tion der Stromgeschwindigkeiten mit den durch dicsc beiden entgegcngesetzten Tiefwasserbewegungen bedingten Stromkomponenten nach N bzw. S. abcr in benachbarten Vertikalebenen. Auffallend ist schliesslich, dass sich der subantark- tische Zwischenstrom in unseren Isotachccnprolilen nicht- auch nicht auf der Westseite— durch intermediare Strommaxima mit messbaren Geschwindigkeiten ( > 3 cm/sek) heraushebt. Offenbar werden die salzarmen subantarktischen Wasser- massen noch durch die tiefreichenderen vorwiegend windbedingten Meeresstro- mungen der Deckschicht erfasst und bis in die tropischen Gebiete verfrachtet. und nicht durch einen eigenthchen, subantarktischen Zwischenstronr , der in der vertikalen Verteilung der Geschwindigkeit durch ein intermediares Strommaximum gekcnn- zeichnet ware.
DIE REGIONALE VERTEILUNG DER GESCHWINDIGKEITSKOMPONENTEN IN DEN BODENNAHEN SCHICHTEN UND IM 3000-M-NIVEAU
Aus den Arbeitskarten unserer Isotacheenprofile entnehmen wir die Geschwindig- keitskomponenten Ci der untersten, den Tiefseeboden Uberlagerndcn 250m-Schicht bei all den iiber 3500 m tiefen Stationspaaren und tragen sie mit Pfeilen entsprechendcr Lange und Richtung (positive Werte senkrecht zum Profil nach nordlichen, negative nach siidhchen Richtungen) in eine Karte der Bodenstrome ein (Fig. 5). Nordliche Komponenten sind durch ausgefiillte dicke Pfeile, sudliche durch otTene dicke Pfeile gekennzeichnet. Wir erkennen nunmehr noch klarer, dass der antarktischc Boden- strom auf der Siidhalbkugel messbare Geschwindigkeiten ( : • 3 cm/sek) nur ganz auf der Westseite der Westmulde, d.h. am Fusse des Kontinentalabfallcs etwa 1000 m iiber dem eigentlichen Tiefseeboden besitzt. Weiter ostlich existieren— von einigen Ausnahmen besonders im Kap— und Agulhasbecken abgesehen— nur ganz schwachc Komponenten. Nordlich des Aquators verlagert sich der Stromstrich des antark- tischen Bodenstroms offenbar mehr nach der Ostseite der westatlantischen Niulde. Durch die punktierte Linie A — B haben wir die Strommaxima in der Westmulde (siidHch des Walfischriickens auch in der Ostmulde durch die punktierte Linie a - h) verbunden und damit die Lage und Generalrichtung des Hauptstromslrichs des antarktischen Bodenstroms festgelegt. Die feinen langen Pfeile der Hauptausbreitung der Wasserart sind so genau wie moghch aus der Karte der " Ausbreitung des ant- arktischen Bodenwassers (dargestellt durch den prozcntischen Anteil der antark- tischen Komponente A^)" ubertragen, welche der Verfasser (1936, Beilage Wll) mittels der Kernschichtmethode erhalten hat. Wir stcllen fcst. dass sich die beiden auf unabhangige Weise gewonnenen Lagen der Achsen (Strommaxima und Haupt- ausbreitung des Bodenwassers) weitgehend decken. Im nordlichen Argenlinischen und im Brasilianischen Becken liegt der dynamische Stromstrich urn ein Slationspaar. d.h. urn durchschnitthch 200 km, weiter westlich als die Achse der Ausbreitung des antarktischen Bodenwassers, was aus dynamischen Grunden zu erwartcn ist. Denn
o
386 Georg WiJsT
das Strommaximum muss mit den starkeren horizontalen Gradienten von t und S — links von der Kaltwasserzunge der Hauptausbreitung der Wasserart — zusammen- fallen. Aus dem Verlauf des Hauptstromstrichs vermogen wir nunmehr angenahert die " wahre " Richtung des Bodenstroms zwischen den betr. Stationspaaren zu erschliessen und die Geschwindigkeitskomponenten auf diese " wahren " Rich- tungen zu reduzieren. Dies ist in Tabelle 1 geschehen, welche in Spalte 6 und 7 die Stromkomponenten Ci des Stromstrichs senkrecht zu den Profilen und in Spalte 8 und 9 die auf die " wahre " Richtung des Stromstrichs reduzierten Werte c^ enthalt. Wegen der giinstigen Orientierung der Me/eor-Querprofile (senkrecht zu den Steilabfallen und den vermuteten Stromrichtungen) gibt diese Reduktion beim Bodenstrom in den Geschwindigkeitswerten nur eine Vergrosserung der Geschwin- digkeit um durchschnitthch 10% aus (beim Tiefenstrom von nur durchschnittUch 6%). Wir sehen aus der Tabelle, dass die einzelnen Geschwindigkeiten zwischen 2-6 cm/sek und 12-5 cm/sek variieren. Der Mittelwert aus alien Profilen zwischen 10° N und 50° S (unter Weglassung der aquatorialen Stationen zw. 4° N und 4° S) betragt 7-2 cm/sek, ist also 4 bis 15 mal so gross wie die letzten Schatzungen von Watten- BERG (1935) und Defant (1936 b). Wir haben es also im Stromstrich des antarktischen Bodenstroms in Tiefen zwischen 3500 und 5500 m mit unerwartet grossen Geschwindig- keiten zu tun, die maximal auf 12-5 cm/sek* ansteigen, und diese Werte stellen, wie wir noch zeigen werden, wahrscheinhch keine Hochstwerte dar. Bei einem Mittelwert von 7-2 cm/sek wiirden die Wassermassen im Stromstrich des antarktischen Bodenstroms 3*3 Jahre benotigen, um die etwa 7700 km lange Strecke vom SUdrand des Argent inischen Beckens (48° S) bis zum Nordrande des Brasilianischen Beckens (5° S) zuriickzulegen. Die Gesamtlange des gewundenen Stromstrichs in der West- mulde von dem Entstehungsgebiet des antarktischen Bodenwassers in der siidhchen Weddellsee (72° S) bis zum Aquator diirfte rund 12000 km betragen. Um diese Strecke von der Antarktis bis zum Aquator zuriickzulegen, wiirde der Bodenstrom rund 5 Jahre und 4 Monate benotigen, also nur etwa den 3*4 ten Teil der Zeit von 18 Jahren, welche Deacon (1954) fiir den Weg des eiskalten Bodenstroms von der Antarktis zum tropischen Atlantischen als moglichen Minimalwert genannt hat. Unsere neuen Geschwindigkeitswerte gestatten uns auch, unter Benutzung der von Defant (1936 b) ermittelten Werte von A : c die Betr age des vertikalen Austausch- koeffizienten A zu schatzen; dies ist in Spalte 10 und 11 geschehen. Es ergibt sich mit 29 cm"i g sec "^ ein bemerkenswert hoher Mittelwert dieses Austauschkoeffizienten, der in den einzelnen Profilen zwischen den Werten A = 1 und ^ = 50 schwankt. Unsere bisherigen Vorstellungen iiber die Grosse des Austauschkoeffizienten bediirfen also auch einer Korrektur. Der neue Mittelwert von A — 29 ist 7 mal so gross als der bisher geschdtzte Wert A = 4; er gilt naturhch nicht fiir die unterste 20 — 50 m dicke Bodenwasserschicht in den Tiefseebecken, fiir welche es F. F. Koczy (1950) auf Grund der Albatross-Messungcn wahrscheinhch gemacht hat, dass sich hier die Wassermassen " anscheinend turbulenzfrei " iiber den Boden be wegen und der Austausch stark herabgesetzt ist. Nur an Schwellen und Bodenerhebungen ist" nach Koczy — die Turbulenz erhoht, wodurch der Austauch beschleunigt wird.
* Zusatz bei der Korrektur: Der fur 5-3° S (Profil IX) errechnete Maximalwert von 21-3 cm/sek, der noch in Fig. 5, 8 u.9 eingetragen ist, ist nachtraglich als zu hoch erkannt, daher in Tab. I als zweifelhaft eingeklammert und auch im Text nicht mehr verwendet.
Stromgeschwindigkcitcn iiii Ticlcn- und HodcnvNusscr
3S7
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Fig. 6. Regionale Verteilung der G^c/^/^A^yfJ'--:;^-^-^^ der Massenverteilung unter Zugrundelegung ^g^^^^^^^^^^he ".
388
Georg WiJST
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Stromgeschwindigkeiten im Ticfen- unci Bodcnwasscr 391
im Stromstrich als Mittelwert der Komponenten (scnkrccht /.urn Schniii) cm Wert von 8-7 cm/sek, bei Reduktion auf die " wahrc " Richtung von 9-2 cm/sck; die f;in/cl- werte schwanken zwischen 1-8 (bzw. 2-1) und 17-4 cm/sek. Dicsc Wcrtc liegcn ctw;is hoher als die Werte, die Defant (1941) fur 2000 m Tiefc, d.h. etwa fiir die Schitlu des oberen nordatlantischen Tiefenwassers, erhalten hat. Die Schatzung des verli- kalen Austauschkoeffizienten, der sich im Mittel zu A 27 cm'' g sec"i ergibt, ist hier mit grosseren Unsicherheiten behaftet, da fur diese Schichten nur sparlichere Angaben des Wertes A : c seitens Defant vorliegen.
Da das Strommaximum des Tiefenstroms mit sudlichcn Komponentcn im Miticl etwa bei 3000 m Tiefe liegt, wahlen wir dieses Niveau von 3000 m, um die regionalc Verteilung der Geschwindigkeitskomponenten in der Niihe der Kernschicht des mittleren Nordatlantischen Tiefenwassers kartographisch darzustellcn (Fig. 6). Wir erkennen, dass sich zwischen 10° N und 30° S der Stromstrich des Tiefenstroms — ^in noch starkerem Masse als der Bodenstrom — ganz an den sijdamcrikanischen Kontinentalabfall anlehnt und dass weiter ostlich und siidlich kaum noch mcssbare Geschwindigkeiten auftreten. Nur dort, wo der antarktischc Bodenstrom cine grosse vertikale Machtigkeit besitzt, treten in unserer Karte von 3000 m mcssbare nordliche Geschwindigkeitskomponenten auf (offene Pfeile). Die punktierte Linie C — D stellt den Hauptstromstrich des Tiefenstroms dar und ist gegeben durch die Verbindungslinie der Strommaxima. Siidlich 30° S ist diese Linie hypothetisch. da hier die meridionalen Komponenten unter die Grenze der Messbarkeit (3 cm/sek) sinken. Dieser Hauptstromstrich C — D des nordatlantischen Tiefenstroms decki sich, wie unsere Karte lehrt, weitgehend mit der Achse der Hauptausbrcitung des mittleren nordatlantischen Tiefenwassers, die wir 1936 aus der Kernschicht des intermediaren SauerstoflFmaximums erschlossen haben (Wust, 1936. Beilagc XVIII) — wiederum ein Beleg fur die innere Ubereinstimmung der Ergebnisse der heiden Methoden, des dynamischen Verfahrens und der Kernschichtmethode.
DIE LANGSSCHNITTE DER GESCHWINDIGKEIT IN DEN STROMSTRICHEN Das neue Bild, das wir durch die dynamische Bearbeitung der Meteoi'?ro(\\c von den Stromvorgangen in der atlantischen Tiefsee zwischen 10° N und 55 S gewonnen haben, wollen wir abrunden durch die Konstruktion von Liingsschnitten der Ge- schwindigkeit langs den Stromstrichen des nordatlantischen Tiefenstroms und des antarktischen Bodenstroms am Westrande der Westmulde (Figs. 7 und S). Die I age der beiden Liingsschnitte C — Z) und 5 — /I ergibt sich aus den beiden Karten der Geschwindigkeitskomponenten (Figs. 5 und 6). Durch Vergleich dieser beiden gewun- denen Linien erkennen wir, dass die vertikale Schnittfliiche, d.h. der Stromstrich des nordatlantischen Tiefenstroms zwischen 10° N und 35° S um durchschnittlich 200 km westlicher hegt als Schnittflache und Stromstrich des antarktischen Bodenstroms. Im Argentinischen Becken zwischen 35° S und 50° S ist das Umgekehrte der Fall.
Der Geschwindigkeitsldngsschnitt des Nordatlantischen Tiefenstroms (Fic. 7) zeigt zwischen 10° N und 33° S ein in sich geschlossencs und durchaus plausibles Isotacheenbild. Das von N nach S kontinuieriich abnehmende Stromnuixmuim liegt allenthalben 300-700 m, im Durchschnitt 500 m uber dem zwischen :>00 4500 m Tiefe gelegenen Meeresboden. Der Tiefenstrom reicht in dicscn Bre.ten uberall bis zum Meeresboden; er wird nicht von nordlichen Komponenten eines Boden- stroms unterlagert. Nur siidlich 40° S tritt der Bodenstrom schwach m Erschemung.
392 Georg WiJsT
Der nordatlantische Tiefenstrom mit seinen meridionalen Komponenten endet praktisch bereits in 33° S. Die Maximalwerte der Stromgeschwindigkeit nehmen in gesetzmassiger Weise von 17-4 cm/sek in 6-2° N (iiber der Para-Schwelle) bis auf 1-8 cm/sek in 29-8° S (iiber der Rio-Grande-Schwelle) ab. Diese Abnahme der maximalen Stromgeschwindigkeit nach S scheint nicht streng proportional mit der zuriickgelegten Entfernung zu erfolgen, sondern im Bereich der Schwellen (Para- Schwelle, Trinidad-Schwelle) rascher vor sich zu gehen. Der Tiefenstrom reicht nach oben bis zur Bezugsflache, die nach Defant (1941) von 600 m in 10° N auf 1700 m in 33 ° S abfallt. In den Zonen zwischen 10° N und 33° S wird innerhalb unserer Schnittflache der ganze Raum zwischen Bezugsflache und Meeresboden vom Tiefen- strom mit siidhchen Komponenten eingenommen. Dieses Strombild steht in guter innerer Ubereinstimmung mit der Ausbreitung des sauerstoff"reichen Tiefenwassers ( > 5 ccm), wie wir sie in dem ganz auf der Westseite gelegenen Hauptschnitt darge- stellt haben (Wust, 1936, Beilage XXIII), Auch hier endet diese Ausbreitung in ca. 35° S.
Der Geschwindigkeits-Langsschnitt des antarktischen Bodenstroms (Fig. 8) zeigt nicht ein so geschlossenes Strombild. Das Strommaximum Hegt mit variierenden Werten zwischen 2 und 13 cm/sek allenthalben in Bodennahe. Nur zwischen 5° N und 10° N, d.h. im Guyana-Becken, befindet es sich, nachdem der Bodenstrom die Para-Schwelle iiberschritten hat, merklich iiber dem Tiefseeboden, Die bodennahen Geschwindigkeitsmaxima nehmen nicht in gesetzmassiger Weise von S nach N, d.h. in der Richtung des Bodenstroms ab. In dieser um 200 km gegeniiber dem Stromstrich des Tiefenstroms seitlich nach E verschobenen Schnittflache wird vielfach der ganze Raum zwischen Bezugsflache und Tiefseeboden von Nordstrom einge- nommen. Nur im Brasihanischen Becken zeigt er mehrfach eine geringere vertikale Machtigkeit und gibt dariiber schwachen siidhchen Komponenten Raum. Auff"allend sind die isoherten Strommaxima von mehr als 12 cm/sek in 37° S und von mehr als 13 cm/sek in ca.5° S, die mit der Morphologic in Zusammenhang zu stehen scheinen. Auf jeden Fall sind im Isotacheenbild des antarktischen Bodenstroms die grossen Gesetzmassigkeiten, wie wir sie 1933 aus den Langsschnitten der potentiellen Tem- peratur ablesen zu konnen meinten, durch eine Reihe von Zufalligkeiten, die sicher z.T. in den Fehlerquellen des dynamischen Verfahrens hegen, iiberdeckt. Boden- strom und Tiefenstrom sind offenbar nicht GUeder einer in sich geschlossenen meridionalen Zirkulation innerhalb ein und derselben vertikalen Schnittflache, sondern sind nebeneinander gelagert am schrag zur Tiefsee einfallenden Kontin- entalabfall, so dass der nordatlantische Tiefenstrom den antarktischen Bodenstrom verdrangt und selbst bis zum Boden mit siidhchen Komponenten reicht und umge- kehrt. So sind die schematischen Auffassungen, die wir 1936 aus den Lansgschnitten der ozeanographischen Faktoren und mittels der Kernschichtmethode gewonnen haben, in dieser Hinsicht zu modifizieren. Wasserartgrenzen konnen nicht — auch nicht, wenn sie so ausgepragt sind wie in der Westmulde zwischen dem Bodenwasser und dem Tiefenwasser — identisch sein mit Zirkulationsgrenzen. In unseren Langs- schnitten der Geschwindigkeiten haben wir durch Pfeile die Starke der meridionalen Komponenten des stationaren Gradientstroms auch in den oberhalb der Bezugsflache gelegenen Schichten dargestellt. Es ist ersichtlich, dass die Stromgeschwindigkeiten in den grossen Tiefen und in Bodennahe in den Stromstrichen grdssenordnungsmdssig gelegentlich den Geschwindigkeiten der Konvektionsstromungen in den oberfldchlichen
I sec
Stromgeschwindigkeiten im Ticfcn- und Bodcnwasscr 393
Schichten nahekommen-t\nQ Konsequenz, die auf den ersten HIick uberraschen muss da sie zu den im Grunde noch immer vorhcrrschcndcn Vorslellunyen kaum mess- barer Wasserbewegungen in der Tiefsec (siehe Deacon 1954) im Widerspruch steht
KRITIK DER ERGEBNISSE
Unsere Ergebnisse uber die absolutcn Stromgeschwindigkeiten in der I iet> . stehen und fallen mit den Annahmen uber die Tiefcnlage der " dynamischen Be/.ugs- flache", in denen wir uns ganz an Defants Auffassungcn {l'941) angeschlossen haben. So lange nicht die praktische Brauchbarkeit der Annahmen uber diese in sich geschlossene gekrummte " Nullschicht " auf andere Wcise— etwa durch sysiema- tische Strommessungen in den grossen Tiefen (was bisher nicht moglich gewescn isl) — erwiesen ist, kann unsere Untersuchung nur als ein neuer Versuch gewertet wcrden, in dieser wichtigen Frage der absoluten Tiefwasserbewegungen einen Schritt weiter- zukommen. Die innere Ubereinstimmung der abgeleiteten Stromfcider in sich und mit den durch die Kernschichtmethode gewonnenen Vorstellungcn scheini wie auch bei der Untersuchung von Defant (1941)— dafiir zu sprechen, dass mit unscren Versuchen zunachst eine geophysikalisch sinnvoUe, ersie Approximation an die Wirk- lichkeit gefunden ist. Jedoch miissen wir uns im klaren sein, dass selbst dann, wcnn die DEFANTSche Bezugsfliiche sich als richtig erweisen soUte, unsere Geschwindig- keitswerte auch nur grobe Anndherungen darstellen konnen wegen der verschiedenen, schwer abschatzbaren weiteren Fehlerquellen des dynamischen Verfahrens. die sich aus der Vernachlassigung der Reibung, der Annahme stationiirer Bedingungen und der Weitabstandigkeit der Stationen ergeben.
Dass die aus der Vernachlassigung der Reibung resultierende Fehlerquelle in all den Fallen bedeutungslos ist, wo die Stromungen praktisch senkrecht zu den Meteor- Profilen verlaufen, d.h. besonders in den Stromstrichen am siidamerikanischcn Steilabfall, haben wir schon oben betont. Aber zweifellos kann durch diese Fehler- quelle in den iibrigen Gebieten die Vergleichbarkeit der berechneten Stromkomponen- ten herabgesetzt sein. Auch die Annahme stationiirer Bedingungen kann vielfach nur in grober Annaherung erfiillt sein, wenn wir mit A. DiiFam ( 1950) an die \\ ir- kungen der internen Wellen (von Gezeitenperiode) auf den vertikalen Massenaufhau denken und an die Verfalschungen, die hierdurch bei den dynamischen Berechnungen auftreten konnen. Auf die Moglichkeit solcher Verfalschungen war der Verfasser schon wahrend der Me/eor-Expedition aufmerksam geworden, als " die systematischc Untersuchung der periodischcn Schwankungen von Temperatur und Salzgehalt auf den Ankerstationen ergeben hatte, dass die einmalige Durchfiihrung der oberslen 200 m tief reichenden Serie zur Erfassung des mittleren Zustandes nicht ausreicht ". "Aus diesem Grunde wurden auf den Profilen VIII, IX und X wahrend der Slations- aufenthalte regelmassige dreistundigc Wiederholungen der obersten Serie \or- genommen ", gelegentlich bis 1000 m Tiefc (Wusr, 1932, S.37/38). In diesen Profilen beruhen also unsere dynamischen Berechnungen in den oberen Serien auf mittleren Zustandskurven, wodurch der Einfluss interner Wellen weitgehend ausgeschaltet ist. In alien anderen Profilen miissen wir damit rechnen, dass die Anzahl der Solenoide zwischen den Stationspaaren durch die Wirkungen interner Wellen mehr oder minder verfalscht sein kann.
394
Georg WiJST
Schliesslich haben wir schon betont, dass bei dem relativ weiten Stationsabstand die von uns berechneten Schichtmittelwerte der Stromgeschwindigkeit nur Minimal- werte sein konnen im Vergleich zu den moglichen Punktwerten der Geschwindigkeit, wie sie etwa durch direkte Strommessungen erhalten werden. AUe feineren Ziige der Zirkulation miissen durch diese Art der Berechnung und Mittelbildung abgeschwacht bzw. ausgetilgt werden, worauf Stommel (1949, S.214) in seinen ausgezeichneten Betrachtungen iiber " The Necessity of a Spectrum of Eddies in the Ocean " hinge- wiesen hat. Die Existenz eines ganzen Spektrums von den grossen Wirbeln der grossen Meeresstromungen iiber die kleineren Wirbel bis zu den kleinsten moleku- laren Wirbeln herab, ist also nach ihm notwendig fiir den Verbrauch der kinetischen Energie, welche durch die Tangentialkraft des Windes auf die Meeresoberflache iibertragen wird. Alle Spitzenwerte der Geschwindigkeit werden auf diese Weise reduziert, alle Kompenenten der Wasserbewegung, die zu einer niedrigeren Ordnung der ganzen Skala gehoren, miissen in den Ergebnissen so " weitabstandiger " Berech- nungen fehlen. " Therefore, it is important to recognize that the term " velocity "
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150
200
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400 km
Fig. 9. Beziehung zwischen den berechneten Stromgeschwindigkeiten in cm/sek (im Stromstrich des Antarktischen Bodenstroms) und den zugehorigen Stationsabstanden in km.
iR meaningless unless accompanied by some indication of the mode of averaging employed in its determination." (Stommel 1949, S.215). Wesenthch ware nun, dass, um wenigstens die regionale Vergleichbarkeit der berechneten Geschwindigkeiten sicherzustellen, die Stationspaare jeweils ungefahr denselben Abstand besassen. Der mittlere Stationsabstand auf den Meteo r-ProfilQn diirfte bei 200-300 km liegen, im einzelnen aber variieren die Abstande zwischen rund 100 und rund 500 km mit einer Verdichtung iiber den Steilabfallen. Das muss zur Folge haben, dass unsere neuen Geschwindigkeitswerte in den Tabellen, Karten und Schnitten nicht streng vergleichbar sind und dass eine Reihe der regionalen Unterschiede, wie z.B. in dem Geschwindigkeitslangsschnitt fiir den Stromstrich des antarktischen Boden- stroms, auf "Zufalligkeiten" in den Stationsabstanden beruhen, Darauf deutet auch Fig. 9, in welche die fiir den Stromstrich des Bodenstroms berechneten Geschwindig- keiten in Beziehung gesetzt sind zu den korrespondierenden Stationsabstanden.
Stromgershwindigkeitcn im Ticfcn- iind Bodcnwasscr 195
Bei aller Streuung der Punkte ist einc Abhiingigkcit unvcrkcnnbar: bci Abstandcn von 100-160 km liegen die Geschwindigkcitswcrtc zwischcn 12 und (21 )* cm/sck, bci Abstanden von 200-360 km liegen die Werte zwischcn 2 und 10 cm/sck. Hicraus konnen wir folgern, dass wir allenthalben im Stromstrich dcs antarktischcn Hodcn- stroms Geschwindigkeiten von mehr als 10 cm/sek gefundcn habcn wurdcn, wcnn der Stationsabstand grundsatzlich iiberall 100 km bctragcn hiittc. Das grossc Pro- gramm der systematischen Aufnahme eines ganzen Ozeanraumcs inncrhalb 2 1/4 Jahre hat damals bei der Meteor Expedition eine solche Verdichtung dcs Stations- netzes nicht gestattet. Merz hat damals auf die Erfassung von kicincrcn Grcnz- wirbeln, solcher 2. Ordnung, verzichtet, " die spiiterhin Aufgabcn fur oft wicdcrholle Spezialuntersuchungen abgeben konnten " (1925, S.575) und sich fur grosscrc Stationsabstande von ca. 2i Langengraden entschicdcn, die cr fur die Erfassung der " grossen stationaren Wirbelbildungen, deren Kenntnis fur eine tiefere Erkcnntnis der Bewegungsvorgange unentbehrlich erscheint ", erforderlich gehaltcn hat. Bc- wusst ist also Merz hinter den Auffassungen (besonders norwegischcr Forschcr) zuriickgeblieben, die fiir die dynamische Berechnung der Meeresstromungcn cincn wesentlich kleineren Stationsabstand — damals 20 sm, heute 10 sm — gefordert habcn. Bei der Bearbeitung des Bimini-Schnittes, bei dem der Abstand der Stationsvcriikalcn mit 16 km immer unter 10 sm geblieben ist, hat der Verfasser (Wlst 1924, S.35^1) unter Benutzung der aus Strommessungen und dem vertikalen Aufbau erschlos- senen Nullflache zeigen konnen, dass hier im Floridastrom die aus dem Massenfcld berechneten Schichtmittelwerte der Geschwindigkeit ganz im Einklang stehcn mit den von Pillsbury (1891) direkt gemessenen Punktwerten der Geschwindigkeit. Aus all diesen Uberlegungen miissen wir folgern, dass im Stromstrich des Ticfciv stroms bzw. des Bodenstroms die Spitzenwerte der berechneten Geschwindigkeiten noch hohere Beitrage als 17 bzw. 13 cm/sek erreichen konnten, wenn die Stations- abstande nur 20-40 km gross gewesen waren. Damit gewinnt unsere fruhere Behaup- tung noch mehr an Wahrscheinlichkeit, dass die Stromgeschwindigkeiten in der Tiefsee in den Stromstrichen an den Kontinentalahfdllen grdssenordmmgsmdssig gelegentlich den Geschwindigkeiten der Konvektionsstrdnnmgen in den oberfldchlichen Schichten nahe- kommen—v^enn man dabei natUrlich von den extremen Geschwindigkeiten im Golfstromsystem oder in ahnlich starken Gefallsstromungen absieht. Aber diese Behauptung gilt nur in dem Masse, in dem sich die DEFANTschen Annahmen uber die Tiefenlage der dynamischen Bezugsflache als brauchbare Anniiherungcn erwciscii. was heute nur aus verschiedenen Indizien vermutet, aber nicht bewiescn werdcn kann. Die Bewegungsgrosse ist der nach Raum und Zeit variabelste ozeanographischc Faktor, und nichts kann die heutige Lage der dynamischen Ozeanographie-auch im Hinblick auf die Tiefenzirkulation— besser charakterisieren als die folgcnden Woru Stommels (1949, S.224): In fact, there seems to be no means of achieving a sharply focused picture in the study of ocean currents. What appeared yesterday as a smooth broad stream appears today as an amazingly corrugated irregular one. and tomorrow probably ever finer details of greater complexity will make an appearance. S(^ the oceanographer is assailed by growing doubts as to whether or not he can ever hop.- to describe the details with any meaning." Eine solche Skepsis darf uns aber nalurl.ch nicht hindern, zu versuchen, das Problem der Geschwindigkeit der T.elwasscrbcwe- gungen mit alien nur denkbaren quantitativen Methoden we.tcrhm .n AngnU /u * Dieser Wert ist zu hoch (cf. Fussnote S.386).
396 Georg WiJsT
nehmen und zu immer grosseren Annaherungen an die Wirklichkeit zu gelangen. Hier mochte ich auf das ideenreiche, vielfach fast philosophisch anmutende Buch von H. B. BiGELOW (1931) hinweisen, betitelt " Oceanography, its scope, problems and economic importance ", wo er in dem noch heute sehr lesenswerten Abschnitt iiber die Zirkulationsprobleme schreibt: " In this field, the task immediately urgent is to determine, for as many sectors of different currents as possible, and for as many different ocean areas, whether the internal hydrostatic forces at work are, or are not, quantitatively sufficient, and do, or do not, act in the direction proper to produce the general type and velocity of circulation that other fines of evidence have shown to prevail ". Die vorfiegende Untersuchung, die spater an anderer Stelle durch die Berechnung der durch die Meteor-Profile transportierten Wassermengen fortgefiihrt wird, versucht, hinsichtUch der Tiefen- und Bodenstromungen in der atlantischen Tiefsee einen Beitrag zur Beantwortung dieser Fragen Bigelows zu liefern.*
* Wir haben es bisher vermieden, von den Ursachen dieser Tiefenzirkulation zu sprechen, zumal es sich ja hierbei um Kreisprozesse handelt. Letzten Endes steht naturlich die Asymmetrie der atlantischen, iiber den Aquator nach beiden Seiten weit hinausgreifenden Tiefwasserbewegungen in Zusammenhang mit der zum Aquator asymmetrischen Verteilung von Wasser und Land auf Nord- und Siidhemisphare, den starkeren kontinentalen Einflussen im N, den seitlichen Begren- zungen des " atlantischen Tales " und der Existenz von Nebenmeeren in seiner Nordhalfte. In dieser Frage sei auf das Referat eines Vortrags von E. T. Eady iiber " Circulation of waters in the oceans " {Nature, April 1951, S.513-515) verwiesen, in welchem sich folgende interessanten Ausfiihrungen finden: " Regarding the causes of this circulation, Dr. Eady hazarded the guess that the difference in ocean geography between the hemispheres is responsible. The wind-stress in the Roaring Forties' ' must generate a vertical circulation which in the absence of land barriers would cause descent near 30° S. But the Atlantic, unlike the Antarctic, is bounded laterally, and it seems possible that the water follows the path of least resistance, flowing up to high latitudes where its high density enables it to be easily forced down. (The existence of a land boundary is necessary to enable the water to adjust its angular momentum, through external pressure, during its change of latitude)." Leider hat Eady, soweit dem Verfasser bekannt ist, diese Untersuchungen iiber die Tiefenzirkulation bisher nicht in extenso veroff"entlicht.
REFERENCES
BiGELOW, H. B. (1931), Oceanography, its Scope, Problems and Economic Importance. London,
Chapman and Hall, 263 pp. BowDEN, K. F. (1954), The direct measurement of subsurface currents in the ocean. Deep-Sea Res.,
2 (1), 33-47. Castens, G. (1931), Stromgeschwindigkeiten und Wasserumsatze in den Tiefen des Ozeans. Ann.
Hydrogr., usw., 59, 335-339. Castens, G. (1932), Tiefenstrom-Geschwindigkeiten im Nordatlantischen Ozean. Ann. Hydrogr.,
usw., 60, 39-41. Deacon, G. E. R. (1931), Velocity of deep currents in the South Atlantic. Nature, 128, 267. Deacon, G. E. R. (1954), Exploration of the deep sea. /. Inst. Navig., 7 (2), 165-174. Defant, a. (1935), Zur Dynamik des antarktischen Bodenstromes im Atlantischen Ozean. Z.
Geophys., 11, 50-55. Defant, A. (1936 a), Die Troposphare. Wiss. Ergeb. Deutsch. Atlant. Exped. — " Meteor ", 6 (1, 3),
289^11. Defant, A. (1936 b), Ausbreitungs- und Vermischungsvorgange im Antarktischen Bodenstrom und
im subantarktischen Zwischenwasser. Wiss. Ergeb. Deutsch. Atlant. Exped. — " Meteor ", 6
(2, 2), 55-96.
EFANT, A. (1941), Die absolute Topographic des physikalischen Meeresniveaus und die Druck-
flachen, sowie die Wasserbewegung im Atlantischen Ozean. Wiss. Ergeb. Deutsch. Atlant. Exped. —
" Meteor", 1925-1927, 6 (2, 5), 191-260. Defant, A. (1950), Reality and illusion in oceanographic surveys. J. Mar. Res. 9 (2), 120-138. FoRCH, C. (1911), Kaysers Physik des Meeres. Paderbom, 377 pp. Hansen, W. (1950), Bemerkungen zu neuzeitlichen Problemen der Ozeanographie. Dtsch. Hydrogr.
Z., 3 (1/2), 20-23. Helland-Hansen, B. (1934), The Sognefjord section. In: James Johnstone Memorial Volume,
Liverpool Univ. Press, 257-274.
Stromgeschwindigkeiten im Ticfcn- und Bodcnwasscr 397
Koczy, F. F. (1950), Die bodennahen Wasserschichten dcr Ticfscc. Naturwisscinchulicn, 37 (1 5 ), UjO. Merz, a. (1925), Die Deutsche Atlantische Expedition auf dcm V'crmcssungs- und Forschungcns-
schifi Meteor. Sitziingsber. Preuss. Akad. Wissensclmjt, Berlin, Phys.-Math. Kl,. 31. 562 5H6. MOSBY, H. (1934), The waters of the Atlantic Antarctic Ocean. .SW. Res. Norwegian Anlarclic
Exped., 1927-1928, 1 (11), 1-131. PiLLSBURY, J. E. (1891), The Gulf Stream. A description of the methods employed in the investiga- tions and the results of the research. Repl. Superintendent, U.S. Coast and Geodetic Survey,
Appendix 16, Riley, G. A. (1951), Oxygen, phosphate and nitrate in the Atlantic Ocean. Bull. Bingham Occanogr.
Coll., 13 (1), 1-126. Seiwell, H. R. (1934), The distribution of oxygen in the western basin of the North Atlantic. I'ap.
Phys. Oceanogr., MeteoroL, 3 (1), 1-86. Stommel, H. (1949), Horizontal diffusion due to oceanic turbulence. J. Mar. Res., 8 H). 199 225. Thoulet, J. (1921), Sur la circulation oceanique profonde. Bull. Inst. Ocean., Monaco, 404. 1 10. Thoulet, J. (1925), Contribution a I'etude de la circulation oceanique. Ann. Inst. Oceanogr., Monaco,
2, 409^23. Wattenberg, H. (1927), Dritter Bericht iiber die chemischen Arbeiten. Z. Geselhchaft Erdkunde,
Berlin, 3, 137-143. Wattenberg, H. (1935), Kalkauflosung und Wasserbewegung am Meeresboden. Ann. Hydrogr.,
usw., 63, 387-391. WoRTHiNGTON, L. V. (1954), A preliminary note on the time scale in the North Atlantic circulation.
Deep-Sea Res., 1, 244-251. WiJST, G. (1924), Florida- und Antillenstrom. Fine hydrodynamische Untersuchung. Veroff.
Inst. Meereskimde, Berlin, 12, 1-48. WiJST, G. u.a. (1932), Ozeanographische Instrumente und Methoden. Das ozeanographischc
Beobachtungsmaterial. Wiss. Ergeb. Deutscli. Atlant. Exped. — ""Meteor", 1925-1927. 4 (1.2),
1-298. WiJST, G. (1933), Das Bodenwasser und die Gliederung der Atlantischen Tiefsee. Wiss. Ergeb.
Deiitsch. Atlant. Exped.—'' Meteor", 1925-1927, 6 (1, 1), 1-107. WiJST, G. (1935), Die Stratosphare. Wiss. Ergeb. Deutsch. Atlant. Exped.—"' Meteor", 1925-1927,
6, (1, 2, Atlas), 109-288. WiJST G (1938 a), Die dynamischen Werte fiir die Standardhorizonte an den Beobachtungsstationen.
Wiss. Ergeb. Deutsch. Atlant. Exped.— ' Meteor", 1925-1927, 6 (2, 3), 99-181. WOsT, G. (1938 B), Bodentemperatur und Bodenstrom in der atlantischen, indischen und pazifischen
Tiefsee. Gerlands Beitrdge zur Geophysik, 54 (1), 1-8. WtJST, G. (1951), tJber die Femwirkungen antarktischer und nordatiantischer Wassermassen \n
denTiefen des'Weltmeeres. Natiirwiss. Rundschau, 3, 97-108.
Papers in Marine Biology and Oceanography, Suppl. lo vol. 3 of Deep- Sea Research, pp. 398-405.
U.S. participation in conservation of international fishery resources
By Wm. C. Herrington
In the Fourth International Fishery Congress held in Washington, D.C., in 1908, Mr. Charles E. Fryer, Superintending Inspector of the Board of Agriculture and Fisheries of the United Kingdom, made the following statement: "The further afield the fishermen of any state go, the more certainly will they be brought into closer relations with the fishermen of fresh nationalities, and the longer will be the list of states which find that they have interests in common — interests which will, sooner or later, call for combined action in the direction of international regulations of the fisheries on the high seas."
Time has proven Mr. Fryer a most competent prophet. With the passing years and development of more efficient and intensive fishing activities, the international problems and frictions arising from fishing activities have multiplied. Numerous attempts have been made to find solutions to these problems through international agreements. Many of the most extensive and successful of these attempts have been in the Western Hemisphere.
Here, beginning some forty years ago, the United States and Canada working together, and in more recent years with other countries, have embarked on a system of fishery conservation conventions which are proving successful in restoring and safeguarding the productivity of common high-seas fishery resources. Progress has been made through careful step-by-step exploration and development. This explora- tion has been directed first towards developing and co-ordinating research, and secondly, after research demonstrated the necessity, towards devising practical and effective conservation measures to ensure the maximum sustainable productivity of the particular fishery. As one step proved itself, and convinced an always sceptical fishing industry and public, which watched with a critical eye this increasing delega- tion of responsibiUty and authority to an international body, it was possible to move on to development and adoption of additional measures to handle more difficult, involved, or controversial problems. Thus by means of much study, discussion, and negotiation since the Fur Seal Convention of 1911, a considerable assortment of procedures for handling a variety of international fishery conservation problems have been developed, tested and applied. The United States now is party to eight agree- ments involving twenty-one nations. The Great Lakes Convention, covering the principal waters of our northern boundary, is the latest addition to this group.
These conventions range from bilateral agreements providing for research in and regulation of a single species, to flexible multilateral agreements covering many species in a given ocean area. Among the features included in one or another of these conventions are provisions for the handling of any joint conservation problem by the signatory nations concerned with that problem; for research and management with special treatment for stocks of fish under full utihzation; and for the solution of special problems in cases where the established international commission cannot reach agreement.
398
U.S. participation in conservation of international fisheo' resources 399
Following is a brief commentary concerning each of these agreements:
INTERNATIONAL FUR SEAL AGREEMENTS
The supply of fur seal furs for the world market now comes ahnost entirely from three small island groups of the north Pacific, where this resource has been main- tained as a result of effective international action. The International Fur Seal Con- vention negotiated in 1911 was the first successful international action to restore and maintain the productivity of a major high-seas aquatic resource. These island groups are the Pribilofs of the Bering Sea, which furnish the major portion of the current supply, the Commander Islands off Kamchatka, and Robben Island off the southern part of Sakhalin Island.
In the latter half of the 19th century, it became clear that extensive killing of seals at sea — pelagic seaUng — was depleting the north Pacific seal herds and threatening their survival. Numerous efforts were made to bring the nations bordering the north Pacific together in a joint effort to prevent the destruction of the herds and ensure the preservation of the valuable industry founded upon them. It was not until 1911, however, that the United States, Japan, Russia, and Great Britain (on behalf of Canada) entered into an agreement for the protection of the seals.
Outstanding features of this agreement were the prohibition of pelagic sealing, provision for regulated kiUing on the rookeries, and provision for the sharing of the proceeds from annual kiUings among the nations party to the agreement. The agree- ment did not provide for joint research. Within a relatively short time the beneficial effects of the limitation on killing began to manifest themselves. The downward trend in the seal population reversed itself and by 1916 the population had approxi- mately doubled. By the 1930's, the Pribilof herd had increased to approximately H million individuals.
This convention operated successfully until October 1940, when the Japanese Government notified the other signatories to the convention of its intention to terminate the convention one year thereafter. In its opinion the fur seals of the north Pacific had grown so numerous that the objective of the convention, the protection of fur seals, had been achieved and, on the other hand, the direct and indirect damage inflicted by the fur seals on the fishing industry of Japan was proving more and more serious. Since no new agreement was reached, the convention was terminated on the 23rd of October 1941.
Protection of fur seals was continued through an agreement between the United States and Canada (1942) and the unilateral action of the Government of the U.S.S.R., and later of the Government of Japan after the Japanese Treaty of Peace. The governments of Japan, the U.S.S.R., and Canada have very recently accepted the invitation of the U.S. Government to a conference in Washmgton. D.C.. late in November 1955, to negotiate a new fur seal convention.
PACIFIC HALIBUT CONVENTION
The Hahbut Convention between the United States and Canada, negotiated in 1923 to provide for the conservation of halibut of the northeastern Pacific Ocean. was the first successful attempt involving joint action in research, and mternat.onal
400 ^^- ^- Herrington
conservation management, of a high-seas fishery. Prior to negotiation of the conven- tion the haUbut fishery had expanded rapidly, and following that expansion the yields in individual areas had precipitously decHned.
Several characteristics of the fishery contributed to the success of the Hahbut Convention. The fishery concerned two countries only, and was confined to one species and largely to a single type of fishing operation. However, success was furthered most of all by a reahstic and eff'ective research program which determined, then concentrated upon, the lines of research which revealed the relation between the fishery and the stocks of fish, and indicated the management measures which would be most effective. As first negotiated, this convention provided for an international commission empowered to conduct research but not to regulate. The results of the research were so convincing that the convention was renegotiated in 1930 to include provisions which gave the commission the authority to regulate the fishery. This commission has its own research staff, and makes use of an advisory committee of representatives from the halibut industry. The convention provides for equal sharing of the expenses by the United States and Canada.
The Hahbut Convention has been further revised — in 1937 and 1953 — in order to keep it up to date and permit the most effective handling of its responsibiUties.
Following inauguration in 1931 of the management program, the decline in the haUbut stocks was halted, and a major increase in productivity has resulted since. From a poundage of 44 millions in 1931, the catch rose to more than 70 million pounds in 1954. This production exceeds that of the early years when the fishery was drawing heavily upon accumulated stocks. About 75 per cent of the world's present supply of halibut is produced from the stocks managed by the Halibut Commission.
PACIFIC SOCKEYE SALMON CONVENTION The United States and Canada ratified their third effective fishery convention in 1937 to cover the sockeye salmon of the Fraser River. These salmon had been practically wiped out as a result of landslides on the river, and overfishing. The convention provided for regulation after research covering two cycles of the salmon run, or eight years. The costs of the convention are divided equally between the two governments, and the commission is required to regulate the fishery in such a way that the catch is divided as nearly as possible in equal shares between the fishermen of the two countries. After several years of investigation the commission proceeded with the construction of fishways at Hell's Gate and elsewhere, which the com- mission's investigations had clearly demonstrated were critical to the rebuilding of the salmon runs and, after the lapse of the required eight years, undertook regulation of the fishery.
The commission's work is now showing practical results in the rapid increase in the runs of sockeye. Through the continued operations of this commission it is con- fidently expected that the runs, worth many millions of dollars annually, will be restored and maintained at maximum productivity. During the peak years of the fishery the production averaged about 20,000,000 fish annually. From this level it was reduced to less than two million. The work of the Commission restored the run in 1954 to about 10,000,000 fish, and it is expected that, under continued sound research and management, runs can be built up to their original level.
U.S. participation in conservation of international fishcrv rcsour.is 401
INTERNATIONAL WHALING CONVhN HON
It has been recognized for some years that unrestricted whaling would deplete or even destroy the world whale stocks, and seriously afTcct the economy of countries dependent upon this resource for fats and oils. Multilateral agreements for the regulation of whaling have been in effect for more than twenty years, the first having entered into force in 1934. Revised agreements were negotiated in 1937, 1938, 1944. and 1946. The 1946 convention is now in effect with seventeen nations as signatories, including all the major whaling countries.
To the 1946 Convention was annexed a schedule of whaling regulations which is amended from time to time as the whaling commission established by the convention finds necessary. This device, coupled with mandatory reporting of whales killed, and related data, provides the flexibility needed to meet changing conditions in the whale stocks through modification of the open season, closed areas, minimum lengths, and so forth.
The International Whaling Commission, on which all parties to the 1946 conven- tion are entitled to be represented, is the supervising authority under that convention, meeting annually. Its main responsibility relates to amendment of the schedule of whahng regulations. These include fixing of species and minimum lengths of whales which may be taken, open and closed seasons and w-aters, types of gear permitted, methods of measurement, catch returns, and other statistical and biological records and reports. Additionally, it conducts scientific research on whales and whaling, and reviews enforcement by the contracting parties, on their own nationals, of the obhgations deriving from the convention.
Under the provisions of the agreements in force during the period from 1944 to 1953, the annual catch of whales in the Antarctic was limited to 16,000 blue whale units, which represented a reduction by one-third of the catch during six pre-war years. (The blue whale unit is a measure to equivalate the varying sizes of different whale species, e.g. one blue whale unit equals one blue whale or six sei whales, etc.) This was further reduced to 15,000 blue whale units in 1954. During this period the open season for Antarctic whaling has been progressively shortened, and the opening date advanced. All this has been accomplished while the production of whale oil has remained about the same as in 1938-39. The number of whales taken has been re- duced to encourage recovery of the stocks from their dangerous low, while oil production has been maintained by increasingly concentrating the season in months when the whales are the fattest, that is, yield the greatest amount of oil per animal.
INTER-AMERICAN TROPICAL TUNA CONVENTION The results of the halibut and salmon conventions, have encouraged a similar approach to other international high-seas fishery problems. In 1949 the United States negotiated with Costa Rica the Inter-American Tropical Tuna Convention. This convention provides for research on the yellowfin tuna, skipjack, and bait lish tound in the waters off the Pacific Coast of the Americas, and for recommending to the contracting parties the conservation measures found necessary. It adds two new features to U.S. fishery treaty practice: (1) The convention is open-ended; that is. any of the nations concerned with these fisheries can adhere to the convention at a later date with the consent of the countries then party to the convention; (2) It provides that the costs of operation shall be divided among the contracting parties
402 ^^- C. Herrington
in relation to the catch from the fish stocks covered by the convention. It is hoped through this convention eventually to develop the co-operation of all of the eastern Pacific coastal states, off which tuna are found, in a programme of research and, if necessary, regulation. Recently, Panama has adhered to this convention, and is now an active member.
NORTHWEST ATLANTIC FISHERY CONVENTION
For the past two decades many people interested in New England's high-seas fisheries have strongly advocated a fisheries convention among the nations fishing the northwest Atlantic. This finally led to the negotiation in February 1949 of the Northwest Atlantic Fisheries Convention, which convention includes all ten countries from the two sides of the Atlantic whose vessels fish in the area.
Several new features were developed in this convention to handle the special problems arising from so many countries fishing to varying extents in the different parts of the northwest Atlantic area. The convention divides the northwest Atlantic into five sub-areas and provides a separate panel for each sub-area, each panel including representatives only from those nations fishing in the sub-area concerned. It is possible by this means to bring the many separate problems involving the dif- ferent groups of countries in each sub-area under one over-all convention. This avoids the necessity of a multiplicity of separate agreements. The convention also provides that, when conservation measures recommended by the commission are accepted by all the parties which are members of the panel for a given sub-area, the measures then apply to all parties to the convention. The operations of the com- mission are financed on the basis of $500 annually from each contracting party, with the remaining costs divided among the parties in proportion to the number of panels on which they are members. In the field of research, the convention provides that the commission, when feasible, shall arrange for the co-operative study of the fishery problems of the area by the countries party to the convention, through preparation and co-ordination of an over-all research program, rather than by operating its own research staff as do the halibut, salmon, and tuna commissions.
NORTH PACIFIC FISHERIES CONVENTION
The north Pacific area includes the three oldest examples of successful international co-operation in the maintenance of the productivity of major aquatic resources — fur seals, hahbut, and salmon. It is also an area which has witnessed some of the most severe conflicts and disagreements between the fishermen of different countries in connection with their fishing operations. The fisheries for halibut and salmon of the northeastern Pacific were developed at an early stage because of the strong market demand which resulted in a premium price. The Governments of the United States and Canada have participated in extensive unilateral and joint efforts to study and regulate these fisheries, and to restore and maintain their maximum productivity. It is generally recognized that the continued productivity of these resources is the result of the expenditure of research and funds by the managing governments and the restraints placed upon their own fishermen by an extensive regulatory system. It is generally felt that if these resources, which have been maintained by the con- tiguous states, could be drawn upon by the fishermen of other countries which had
U.S. participation in conservation of international fishery resources 403
not participated in the research and regulatory programmes, the returns to the regulating countries would be so reduced that they would not be justified in main- taining these expensive programs.
A solution for the problems of this area finally was developed in the North Pacific Fisheries Convention negotiated between Japan. Canada, and United States, and ratified in 1953. This convention was designed to cover all the joint fishery problems of the three contracting parties in the north Pacific area. It concerns all stocks of fish under substantial exploitation by two or more of the contracting parties, with the decisions and recommendations concerning regulation of such stocks being con- fined to the parties engaged in their substantial exploitation. It sets up a new prin- ciple, " abstention ", which provides that, where a stock offish is being fully utilized by one or more of the contracting parties, and where such parties have enacted and are enforcing fishery conservation regulations and limitations developed through extensive scientific research, other contracting parties not sharing in exploitation of that stock should continue to abstain from participation.
To facihtate the administration of this abstention principle a provisional line was drawn in the north Pacific Ocean to separate the stocks of salmon of American and Asian origin, and a mandate placed upon the commission to undertake immediate research to verify or improve this provisional line. It was further provided that, in the event of the commission failing within a reasonable period of time to reach unanimous agreement on such a line, the matter should be referred to a special com- mittee of scientists consisting of three competent and disinterested persons, no one of whom should be a national of a contracting party, selected by mutual agreement of all parties. Majority determination by such a committee would determine the recommendation to be made by the commission.
OBJECTIVES OF THE CONVENTIONS The primary objective of the various international fishery conventions, involving north American countries, has been consistently confined to conservation ; that is, to making possible the maximum sustainable productivity of the aquatic resources covered by the conventions. It is obvious that such conservation programmes have many economic implications and involve economic considerations. The results of any such program must be in products useful to man, and regulations must be adapted to the practical operations of the fishery. However, the economic considerations have been secondary. The conventions provide for conservation management, not economic management.
POLICIES
In the process of studying the various problems, developing practical solutions, and operating the commissions, certain policies have been evolved and have proved themselves. The principal such policies are the following:
1 Specific Conventions for Specific Problems
' The fishery conventions have been individually tailored for specific situations and problems. As has been pointed out above, the first conventions covered single species and areas. As the procedures developed for these conventions proved successful, it has been possible to negotiate conventions covering a
404 Wm. C. Herrington
greater complexity of species and problems and wider areas. The Northwest Atlantic Convention covering all joint fishery conservation problems of the ten countries fishing the northwest Atlantic area, and the North Pacific Con- vention covering joint problems of the United States, Canada, and Japan in the north Pacific area, are examples of these recent developments.
2. Selection of Commissioners
Members of the various commissions should be selected with respect to the specific commission to which they are appointed. The requirements may vary with the particular commission and stage of its development, so that emphasis is in some cases upon special knowledge of the particular problem, and in others upon general quahfications. It is extremely important that the commissioners have the confidence and support of the public in their respective areas, for such confidence and support is an essential requirement for the success of the commissions. For this reason, in the United States, for example, except for Government members, the Commissioners are appointed from the area affected by the convention.
3. Advisory Committees
Experience in the U.S. with the several commissions has demonstrated the desirability of providing for advisory committees from the public, and interested state governments. They serve a 2-way function. They provide detailed and practical advice to the commission, particularly with respect to the relation between the problems and proposals considered by the commission and the practical operations of the fishery and the state governments. They also serve an invaluable function in informing the various segments of the interested public of the work of the commission and the justification for the various acts which it may perform. In the present commissions they are proving extremely helpful in maintaining public support.
4. Periodic review of Commission Work
Experience has indicated the desirabihty of providing for a periodic review of the work of a commission by the member parties. This would include a study of progress made in achieving the objectives of the convention, whether the convention served its purpose and should be terminated, or should be con- tinued as before or with modifications which would enable it to more effectively pursue its objectives. A provision of this kind was included in the North Pacific Convention. It is included in a more developed form in the Great Lakes Fisheries Convention. It seems desirable that it should be included in future conventions.
5. Provision for research under the conventions
Two general arrangements for research work are provided under the several conventions. These are to provide: (1) that the commission shall co-ordinate the research work of the contracting parties ; or (2) that the commission shall set up its own independent research staff". Co-ordination of the research work of the contracting parties is favoured in situations where the contracting parties involved in the particular problems covered by the convention have established research staff's engaged on these or related problems in the convention area,
U.S. participation in conservation of international fishery resources 405
unless other considerations govern; for example, if the fishery is located m substantial part off the coasts or in the territorial waters of one party. In the latter case, and in cases where the parties do not have adequate scientific staffs, the use of an independent commission staff has been favoured.
CONCLUSION It is not possible at present to draft an acceptable over-all convention to cover all areas of the Atlantic and Pacific. It is quite possible that further experience will confirm present indications that such over-all conventions never will be the most effective procedures for handling such problems. Furthermore, it is not likely that the expense of operation of such an over-all convention would be less than the costs of specialized conventions such as exist at present. In fact it might be increased. The maintenance of separate commissions does not involve an increase in the expense of operation through additional travel and working time since, whether one or a group of commissions handled the various problems, the number of regional meetings and travel would not be substantially affected. With an over-all convention it would be much more difficult to focus proper attention on specific problems and to maintain necessary public interest and support.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 406-417.
Hearing and acoustic orientation in marine animals*
By Donald R. Griffin Biological Laboratories, Harvard University, Cambridge, Mass.
Summary — The evidence that underwater sound is important in the behaviour of fishes and cetaceans is reviewed, with emphasis on the possible occurrence of acoustic orientation. Both these groups of marine animals have now been shown to have excellent hearing. At least one fish has a minimum auditory threshold of the same order of magnitude as the typical human threshold at 2000-4000 c.p.s. (about 10"i® watt/cm^ energy flux). Porpoises can hear sounds of moderate intensity at fre- quencies well above 100 kc. A series of recordings which may have resulted from a deep sea fish engaged in echo-sounding are analyzed and discussed, and the possible role of echolocation in marine animals is compared with the available evidence of its nature and occurrence in bats and other animals relying on airbourne sound. In this connection the possible usefulness of continuous sounds and standing wave patterns is discussed with reference to the observed fact that a low frequency sound in a small tank undergoes marked fluctuations in intensity over distances that are a small fraction of its wave-length in water.
In recent years it has become widely recognized that a variety of sounds are pro- duced by animals living in the ocean. The chief cause of this increased awareness has been the use of improved devices for listening to sounds in water. It had been known since the time of Aristotle that some fish produce sounds (for recent pre-war studies see Tower, 1908; Burkenroad, 1931; Dijkgraaf, 1932; and Hardenberg, 1934). But the unaided human ear is at a great disadvantage in hstening to underwater sounds, and hence only those of considerable intensity can be heard without devices to provide us with a sensitivity to sound waves in water that approaches our sensi- tivity for sounds arriving through the air. Such devices have been developed primarily for miUtary purposes, and it was during the second World War that sounds of fish and other marine animals first aroused serious concern when they interfered with underwater hstening operations. Surveys were therefore undertaken to determine the sources and seasonal occurrence of the more intense of these biological noises (LoYE and Proudfoot, 1946; Dobrin, 1947; Knudsen, Alford, and Emling, 1948). Since the war such surveys have continued on a broader basis with greater attention to their biological significance (Johnson, Everest, and Young, 1947; Johnson, 1948; Fish, Kelsey, and Mobray, 1952).
As a result of these studies it is now clear that sounds of considerably greater inten- sity than the ambient background noise level of the ocean are commonly produced by three major groups of animals: (1) many species of fish, (2) several species of marine mammals — certainly some of the smaller whales and porpoises and perhaps some of the larger whales as well, and (3) the snapping shrimps of the genera Crangon and Synalpheus among the Crustacea. Too little is known about the significance of the " snap " of these shrimps to warrant any discussion of it, and indeed the one serious study to date has led to the conclusion that the noise may well be incidental to some other function of these animals' highly modified claws (Johnson, Everest,
* Contribution No. 789 from the Woods Hole Oceanographic Institution.
406
Hearing and acoustic orientation in marine animals 4()7
and Young, 1947). But the sounds of fish and marine mammals are so numerous, so intense, and so diversified, that a review of what is known concerning their bio- logical significance is timely. While only a small minority of the known species of fish emit sounds that are more than mere by-products of other activities (such as the grinding of teeth), many of those that are consistent noisemakers have specialized structures for the generation of sound, such as muscles located in the walls of the swim bladder. It therefore seems likely that these sounds serve some dcfmite purpose in the lives of the fish that make them. Cases are known in which fish are attracted by sound (Westenberg, 1953), but more often they are repelled by artificially generated sounds, while under many circumstances they show no discernible reactions at all. Some species apparently communicate with each other by means of sound, for exam- ple the toadfish Opsanus tau, in which the male calls principally during the breeding season. There is suggestive evidence to be discussed below that orientation may be maintained with respect to the bottom by a process akin to echo-sounding; and it is not beyond the bounds of possibility that fish or marine mammals may employ a sort of natural sonar — an underwater analog of the process of ccholocation so highly developed by bats for use in air. Questions of this type deserve more attention than they have yet received, and the chief purpose of this paper is to review the available evidence of acoustic orientation by marine animals and to suggest pro- mising lines of inquiry for the future. It is particularly appropriate that such a review- should be part of a volume dedicated to Professor Bigelow, for he contributed significantly, in 1904, to the basic biological knowledge that has formed an essential groundwork for these recent developments.
The sensitivity of hearing in fish
Fundamental to any consideration of the role of underwater sound in orientation, or in other types of behaviour, is the question of sensory capacities of the animals concerned. No animal can react to a sound it cannot hear, and even the author of an authoritative textbook recently wrote, in introducing the auditory system, " Through the long and complex evolution of the fishes no progress was made, since no auditory receptors exist. . . . Fish do not hear, and there would be little to hear under water . . . Hearing is developed on the assumption of terrestrial hie. hence, is first encountered in the amphibia" (Krieg, 1942). Even when a particu- lar species has been shown, quaUtatively, to be able to react to underwater sound, any careful analysis of its behaviour is Ukely to require quantitative measurement of the range of frequencies and intensities that it can hear. It was to this basic question that Bigelow addressed himself more than fifty years ago.
There was already observational and anecdotal evidence that certain hsh reacted to sound, usually to sounds generated in air. On the other hand several attempts to demonstrate hearing in fish under controlled conditions had produced negative results, or at best ambiguous evidence. Among the more recent ol these investiga- tions Lad been those of Kre.dl (1895, 1896), who had a few years previously carried out in Sigmund Exner's laboratory in Vienna one of the classic experi- ments o^ comparative physiology (the substitution of iron n ngs - sand gnj.ns in the equiUbrium organs of ceriam shrimps so that he action of tlK o ths could be demonstrated unequivocally by the use ol \;^^-^^^^Z.\^ observed the responses of goldfish (Carassius auntus) to sounds ol nuxkratcK low
408 Donald R. Griffin
frequency, but the fish responded just as well after the inner ear had been exposed and the semi-circular canals plucked out with forceps — a procedure which seemed likely to damage the organs of hearing. Hence Kreidl concluded that goldfish detect underwater sound not by means of the inner ear but through mechanical receptors of the lateral fine or skin.
BiGELOW repeated Kreidl's experiments, working under the guidance of the late G. H. Parker, who had just demonstrated the auditory sensitivity of Fundulus, and he extended them with a simple elegance of experimental design which merits the respectful consideration of current investigators. Having found that his goldfish responded more than 80% of the time when stimulated by a 100 c.p.s. tuning fork, he cut virtually the entire sensory nerve supply to the skin and lateral line, and still observed almost the same percentage of responses. Yet when both eighth cranial nerves were cut there were no responses in 73 trials with seven different goldfish. As a control against side effects of exposing and cutting the auditory nerve, both eighth nerves were exposed but only one was cut; this fish still responded to sound, but ceased to do so when the remaining auditory nerve was severed. In another control the spinal cord, lateral fine nerves, and the cutaneous branches of cranial nerves V and VII were cut without effect on the response to sound. Bigelow went on to repeat Kreidl's operation, and he obtained the same result. But he also found from histological sections that plucking out the semi-circular canals left much of the sacculus and lagena intact, these being the portions of the ear that would be expected to play the major role in responses to sound. Q.E.D.: goldfish could hear.
Like many biological problems the question of hearing in fish underwent a long subsequent history of complications and controversies, and a generation later an active debate still centred around the simple question, " can fish hear, and if so, what ? " (For complete reviews see von Frisch, 1936, and Kleerekoper and Chagnon, 1954). In many of the earlier experiments spontaneous responses were obtained from fish when vibrations of various frequencies and intensities were imparted to the water by a wide variety of methods. In other cases fish were con- ditioned or trained to give responses when the water around them was set into oscilla- tion, and considerable evidence pointed to the importance of the lateral line and the skin, especially for low frequencies (Parker and van Heusen, 1917). The methods used to generate underwater sound in these earUer experiments were (1) to generate the sound in air near the tank containing the fish, (2) to place a vibrating object such as a tuning fork in contact with the tank, or (3) to immerse a buzzer or telephone receiver in the water itself. In all cases the stimulus undoubtedly set the water into vibrations with a complex frequency spectrum, but the component most obvious to the experimenter may not have been the one which was most effective in stimulating the fish. This situation was greatly clarified by the careful work of von Frisch and his associates from 1929 to 1941; and although most of the experiments employed freshwater fish, important general conclusions were reached which can be applied directly to marine species, as has recently been demonstrated by Dijkgraaf (1952).
Stetter reported in 1929 that two common freshwater fish, (the European minnow, Phoxinus laevis, and the common catfish, Ameiurus nebulosus) could be trained to come for food to a particular part of the tank (or to give other characteristic feeding movements) when a sound was produced in the air at some distance from the aquar- ium. The fish were blinded to prevent them from responding to visual rather than
Hearing and acoustic orientation in marine animals 409
auditory stimuli associated with feeding. Clear responses were obtained from sounds generated by tuning forks, whistles, and pipes, even when the frequency was as high as 6,960 c.p.s. with the minnows, and 13,139 c.p.s. with the catfish.
Von Frisch and Stetter (1932) later experimented with the cITects of sensory impairments on the abihty of minnows to respond to various frequencies. Damage to the utriculus and semicircular canals caused little reduction in sensitivity to sounds, although equilibrium was severely impaired. But when the sacculus and lagena were put out of action the sensitivity to frequencies above 150 c.p.s. was almost totally destroyed. Even frequencies as low as 32 c.p.s. were less elTective in arousing res- ponses than when the sacculus and lagena were intact. Very low frequencies such as 16 c.p.s., however, were almost as easily perceived as they had been before the opera- tion. Nor did impairment of the lateral line receptors reduce the fishes" sensitivity to low frequencies. These investigators therefore concluded that low frequencies must be detected through very sensitive tactile receptors in the skin (see also Rein- HARDT, 1935).
Absolute thresholds could not be determined in these experiments, because no cahbrated underwater transducers were available for the purpose. In an attempt to obtain approximate thresholds, the source of the stimulating sound was moved to greater and greater distances from the aquarium, and the threshold of response of the fish was compared with the threshold of hearing of men standing beside the aquarium. The fish ceased to respond at levels somewhat above the human threshold; but when a man was held entirely underwater in a large aquarium, he was unable to hear the sound at intensities to which the minnows would still react.
In later experiments at the same laboratory by Boutteville (1935) and Diessel- HORST (1938) the sound was generated by a loudspeaker close to the aquarium, and its intensity in the air was measured by means of a calibrated microphone. The thres- hold of response of a fish could thus be expressed in terms of sound pressure in the air just outside of the glass-walled aquarium. The most sensitive of the minnows gave consistent responses to 652 c.p.s. when the sound level in the air was 20 decibels above the customary reference level of 0-0002 dynes/cm% or ten times the threshold sound pressure for a typical human Ustener. This is a remarkable sensitivity when one considers that the energy loss was unquestionably great as the sound waves passed from air to water. I once duplicated approximately the acoustic conditions of this type of experiment and measured sound pressures inside the aquarium with a cali- brated hydrophone while those in the air were measured with a calibrated condenser microphone. The sound pressures in air and water were roughly the same (within 5 to 10 decibels). But the greater acoustic impedance of water causes a given sound pressure to correspond in water to a 35 db lower energy flux (watts cm') than in air. This means that the minnows studied by von Frisch and his associates had auditory thresholds of the same order of magnitude, in terms of energy flux, as the human
auditory threshold in air.
When a number of species were compared with the minnow Phoxinus with respca to their sensitivity and frequency range of hearing, it became clear that lish can be divided into two distinct groups. The minnow Phoxinus. the catfish Ame.urus, and certain other fish, display low thresholds and a wide frequency ^'^^^'-^'^'^^^''^''^^ fishes studied were less sensitive and responded only to frequences below 1000 .000 c.p.s. This difference is correlated with the anatomy of the fish : for the more sensitive
410 Donald R. Griffin
species have an air-filled chamber directly coupled to the inner ear labyrinth. In the order Ostariophysi (families Cyprinidae, Characinidae, Siluridae and Gymnotidae) this involves the Weberian apparatus, an intricate structure consisting of bones, cartilages and air ducts which serve to effect a mechanical coupling between the swim bladder and the inner ear. Von Frisch and Stetter (1932) demonstrated experimentally that the minnow suffered a considerable hearing loss when this mec- hanism was damaged surgically. Air chambers can improve the sensitivity of fish's hearing because sound travels almost without disturbance from one aqueous medium to another, and the soft tissues of any animal are so much Hke water in their acoustical properties that a " pure " fish is relatively " transparent " to underwater sound. An air bubble or an air-filled chamber, on the other hand, represents a marked acoustical discontinuity much as does a sohd object in the air. For a detailed consideration of the acoustical properties of the catfish swim bladder see Poggendorf (1952). Other fishes with keen hearing also have some type of air chamber coupled to the inner ear. These structures have different morphological origins, but seem to serve the same auditory function as the swim-bladder and its ramifications in the Ostariophysi.
This anatomical correlation is an important one; for it permits one to predict with some confidence that fish possessing structures that connect some air-filled chamber with the inner ear labyrinth will have keen hearing. Among marine fish there are very few groups which have such accessory organs of hearing. The sea catfishes are anatomically similar to the freshwater catfish Ameiurus, and they might be expected to have keen hearing on that account. In this connection it is interesting to note that sea catfishes are listed among the species reported by Burkenroad (1931) and DoBRiN (1947) as significant producers of underwater noise. The herrings (family Clupeidae) are another group which one would expect to have keen hearing because of their auditory structures, which have been described by Ridgewood (1891), WoHLFAHRT (1936), and Evans (1940). There is an elaborate set of air passages extending from the air bladder into close apposition with the membraneous labyrinth of the inner ear. There are also reports that herrings are easily frightened by noises made in fishing boats. Since the herring family is an abundant marine group having great commercial importance, their ability to hear various frequencies of underwater sound merits quantitative investigation.
Two recent investigations have included quantitative measurements of auditory thresholds in fish, and the results have amply confirmed the earher conclusions of VON Frisch and others regarding the approximate equaUty of auditory thresholds in fish and men, when expressed in terms of energy flux (watts/cm^). Autrum and Poggendorf (1951) and Poggendorf (1952) used a caUbrated Rochelle salt crystal to measure the sound pressure in a small aquarium containing single catfish {Ameuirus nebulosus), and they determined auditory thresholds at frequencies from 60 to 10,000 c.p.s. The threshold values varied considerably, but the average of the measurements at a given frequency is probably vahd within ± 10 db. Kleerekoper and Chagnon (1954) have estimated auditory thresholds of a small cyprinid fish, the creek chub Semotilus atromaculatus, and they report a rather narrow range of maximum sen- sitivity, the thresholds being lowest at about 300 c.p.s. and rising by tenfold at 100 and at 2000 c.p.s. In view of the absolute, though approximate, calibration of the measur- ing instruments used by Autrum and Poggendorf, their data for the catfish provide the best available evidence concerning the sensitivity of hearing in fish to underwater
Hearing and acoustic orientation in marine animals 4 | |
sound. They found the auditory threshold to be approximately constant from W) to 1600 c.p.s. at slightly above 0-01 dyne/cm- or approximately H)-"^ watt cm-. This threshold energy flux corresponds closely to the minimum human threshold m air (between 2000 and 4000 c.p.s.), but the catfish is considerably more sensitive at lower frequencies. Above about 2000 c.p.s., on the other hand, this fish's threshold rises much more steeply than the human threshold.
AUTRUM and Poggendorf also demonstrated that the catfish's responses depended upon sound pressure rather than amplitude or particle velocity. They confirmed the earlier quaUtative findings of von Frisch et al. that fish without air bladders have thresholds roughly 30 db higher than the catfish. Other experimenters have reported that the Ostariophysii at least can discriminate between sounds dilTering in frequency by as little as 1/4 octave (Wohlfahrt, 1939; Dukgraat and Vereijeb, 1949; and Kleerekoper and Chagnon, 1954). Directional sensitivity, or the ability to localize the source of an underwater sound, has not yet been adequately demonstrated, and indeed both Reinhardt (1935) and von Frisch and Dijkgraaf (1935) obtained negative results in attempts to demonstrate locaUzation of sound sources by stationary fish. On the other hand, Kleerekoper and Chagnon concluded, on the basis of extensive observations and photography of the movements of Semotilus in a tank approximately one metre square, that these small members of the order Ostariophysii could immediately turn towards the louder of two equidistant sources of 50 c.p.s. sound.
A possible case of echo-sounding in fish
Having thus reviewed the overwhelming evidence for a high degree of auditory sensitivity in fish, it must be admitted that very little critical evidence is available to indicate what significance sound may have in fish behaviour. Rather than sum- marizing unsatisfactory anecdotal evidence I shall merely describe one observation that suggests the occurrence of echo-sounding by a deep sea fish, with the hope that the need for substantial and imaginative investigation of auditory behaviour in fish will thus be emphasized. I am indebted to Dr. J. B. Hersey of the Woods Hole Oceano- graphic Institution for permission to make a detailed study of a series of underwater sound recordings made north of Puerto Rico in water approxmiately 5100 metres deep. Among many hours of recordings made far from land, that include noises of biological origin, those made about 3 p.m. on March 7. 1949 contain several loud calls, each followed after a short interval by a fainter repetition of itselt. n listening to these sounds, it is difficult to avoid the impression that they are the calls of some marine animal followed by echoes of these calls. While no similar ca Is and apparent echoes have been noted subsequently, as far as 1 can ascertain, a briet analysis ot this
'''?:^^^^. were a crystal hydrophone, amplifiers, filters, and receding equipment sensitive to 5(^1200 c.p.s. The hydrophone was w.Uun ^^ -^ ;' ^^ surface, and the background noise level was 75-80 db above O'^XX) d n . 1 h
calls of what was dubbed the " echo fish " consisted of ^^-t notes lasn 1 3 o seconds, and having a rather constant frequency of about 5(^0 _p.s^ J^^^^^ was not precisely cahbrated, but the calls were typically two to thrc t.r^c the b ack
ground noise level, and occasionally the -^^-''-^''^y^'Z^'^'^J^^^^^^ TTie interval between the loud call and its faint repetition was quite constant, and
412 Donald R. Griffin
when the recording was played through a 500 c.p.s. tuned filter both the call and the apparent echo could be seen clearly in oscillographic records. When the intervals between peaks of original call and apparent echo were measured in 1 1 oscillographic records showing the highest signal-to-noise ratio, the average interval was 1-58 seconds, the extremes being 1-47 and 1-77 seconds (cr = 0-08 second). The ratio of amplitudes of the apparent echo and original call averaged 0-405, the extreme values of this ratio being 0-27 and 0-56.
If these recordings do indeed consist of calls and echoes, the time interval between them, together with the amplitude ratio and the known depth of 5100 metres, estab- lishes certain geometrical requirements for the location of the " echo fish ". The difference in length of the direct path from source to hydrophone and the path followed by sound waves reflected from the bottom was approximately 2400 metres (the distance travelled by underwater sound in 1-58 seconds). In the simplest case we might assume that the source was directly below the hydrophone, so that its distance above the bottom would be 1200 metres or 3900 metres below the surface. If we make the further assumption that in these cases, when the bottom reflection was maximal, the angles of incidence and reflection were equal, the possible locations of the source are limited to a locus having the form of a shallow dish-like surface with its deepest point 3900 metres below the hydrophone and gradually rising towards the surface as the source is assumed to be displaced laterally. Unless one assumes the source to have been some miles away it must have been at a considerable depth, probably well below the levels to which light can penetrate, and below the depths reached by whales or other marine mammals. These geometrical relationships are thus consistent with the hypothesis that this recording reveals a deep sea fish emitting calls loud enough for them and their echoes from the bottom to be audible at the surface three to four thousand metres away.
This explanation of the " echo fish " recordings can be considered only as a specu- lative possibility, however, until means are devised to explore the depths of the ocean in greater detail, both acoustically and biologically. Alternate explanations for the sounds recorded in this instance are: (1) that a single fish emitted a double call, (2) that the second call came from a different fish, or (3) that the sounds had a non- biological origin. The third alternative seems quite unlikely because this type of sound was heard on several occasions during the day the recording was made, because it became louder and fainter from minute to minute, and because it was recorded when the ship was many miles from land or other ships under conditions when all possible precautions had been taken to avoid sound production by the ship herself. Reflections from other surfaces than the bottom are rendered most unUkely by the relatively high amphtude ratio and the difference of 2400 metres in path length for the direct and reflected sound. Finally it must be pointed out that even though this recording does reveal a fish call plus its echo from the bottom, we have no direct evidence that the unknown fish could hear such an echo, and still less that it would pay any attention if it did. Yet the " echo fish " could easily have heard these bottom echoes if it had an auditory sensitivity equal to that of any fish adequately studied to date, and in the unhghted depths of the ocean echolocation could be as advantageous to a fish as it is to a bat flying in darkness through the air. We are deahng here with one of many phenomena pertaining to the deeper layers of the ocean concerning which we can only speculate, and dream of future investigations by methods yet to be devised.
Hearing and acoustic orientation in marine animals 4 1 3
Sounds and hearing of marine mammals
A variety of complex sounds are produced by several species of ihc smaller looihcd whales, porpoises, and dolphins. As in the case of fish, a few observations of noises from cetaceans had been reported many years ago, but only during and after the war was it reahsed how vociferous some of them actually were. The white whale or beluga Delphinapterus leucas had long been known to make noises, for these could be heard in the air or through the hull of a ship; and Schevill and Lawrlnci. (1949) have described and analyzed in some detail their large vocabulary that includes whistles, squeals, chirps, clicks, and rasping noises. Several other species of porpoises and dolphins have also been studied in captivity or under natural conditions, and all appear capable of producing sounds (Schevill and Lawrence, 1949; Kritzlkr. 1952). The baleen whales, on the other hand, have not yet been definitely shown to emit sound, although there have been reports from several observers of loud, low pitched notes heard when humpback whales (Megaptera nodosa) were in the vicinity.
Excellent hearing has been demonstrated in porpoises and other cetaceans ranging in size up to the pilot whale or " blackfish " Glohicephala macrorhyncha (Ki,i.i.(KiG and KoHLER, 1952; Schevill and Lawrence, 1953; Kritzler, 1954). While auditory thresholds have not yet been measured, the observational evidence is adequate at least for the bottlenosed porpoise Tursiops truncatus to demonstrate that sensitivity of hearing is high. In the most carefully controlled of these studies, Schevill and Lawrence trained a Tursiops to come for food when it heard pure tones of short duration generated without switching transients or clicks. The inten- sity level was of the order of 10"'- watt/cm- or 1 dyne/cm-, and this porpoise learned to respond almost every time the tone w?is sounded in the frequency range from 150 c.p.s. to 120 kc, i.e. the animal's auditory threshold was below this level over a very wide range of frequencies. Above 120 kc. the percentage of positive responses fell rather rapidly to less than 20% at 150 kc.
Since marine mammals are often active at night or in turbid waters, it is natural to suggest, as Kellogg, Kohler, and Morris (1953) have done, that some of their complex and impulsive sounds may be used for echolocation, either to maintain orientation with respect to the bottom, surface, or large obstacles, or possibly to locate fish or other prey in the water as bats appear to do in the air (Griffin. 1953 a). Kellogg et ah have shown that certain of the noises emitted by these porpoises have components of considerable amplitude as high in frequency as 120 kc. and some energy as high as 170 kc; and when intense sounds of short duration are generated in the water there will of course be echoes from any solid objects in the \icinity. Since porpoises have a high degree of adaptability and intelligence as well as keen hearing (McBride and Hebb, 1948; Wood. 1953; and Lawrence and Schevill, 1954) it is plausible to infer that they might take advantage of the possibilities of echo ranging. No direct evidence has yet been forthcoming, however, to support this inference; and indeed Schevill and Lawrence report that porpoises remained silent, as far as could be discerned, even during long periods of swimming about through turbid water where it would seem that echolocation would have been most helpful. It may well be that porpoise sounds are used solely or primarily lor com- munication, especially since solitary porpoises seem ordinarily to be s.IaU Yet the observation of McBride (in press) that porpoises can avoid small mesh but not large mesh nets in turbid waters points towards some type of acoustic orientation.
414 Donald R. Griffin
It is pertinent to recall in this connection that the critical evidence that bats (and at least one species of bird) employ echolocation is not alone their production of sound but, more important, their ability to fly without seeing and the disorientation caused by impairment of hearing or sound production (Griffin and Galambos, 1941 ; Griffin, 1953 b). Comparable experiments are obviously more difficult with cetaceans, but observations of Winded porpoises, or even the use of intense interfering noises, should permit a resolution of this question. It is even possible that porpoises use fainter sounds for echolocation than those studied to date, and that more sensitive apparatus, or improved signal-to-noise ratios, would disclose a more continuous emission under conditions where vision is restricted. The most intense high-frequency sounds of bats are not the pulses used for echolocation, but the noisy cries of much longer duration (which are audible owing to minor low frequency components even though most of their energy is at frequencies above 20 kc). Prolonged listening to bats with relatively insensitive equipment in the presence of moderately high noise levels at ultrasonic frequencies might well have led to a picture of their sounds not unlike our present information that porpoise sounds are numerous, loud, and varied, but often not detectible when needed for acoustic orientation. This comparison is especially relevant for those species of neotropical bats that feed on fruit and orient themselves adequately by means of faint pulses which can easily be overlooked even with reasonably adequate apparatus (Griffin and Novick, 1955). All of these considerations warrant an open mind regarding the role of acoustic orientation in marine mammals, and further careful investigation of the matter is clearly called for.
Discussion
In most considerations of the possibility that marine animals orient themselves by echolocation it has been assumed that they would use an analogue of pulse sonar, emitting sounds of very short duration and hearing echoes arriving in the silent intervals between the pulses. Pulsed sounds are employed in the echolocation of all the bats studied to date, although in bats of the family Rhinolophidae the pulses may last about 100 msec, so that there must be considerable overlap between out- going sound and returning echo (Mohres, 1953). While some of the sounds emitted by fish and cetaceans consist of rapidly repeated clicks, others are continuous tones or noises ; and since sound travels faster in water than in air most of the known fish and porpoise sounds seem poorly suited for echolocation owing to the inevitable mixing of echoes with the outgoing sound. In this regard " echo fish " discussed above, and certain ticking sounds of uncertain origin recorded during Woods Hole Oceanographic Institution cruises, seem to be exceptions to the general rule. It is quite possible, however, for echolocation to be based upon continuous sound, but since the echoes will almost always be fainter than the outgoing sound some special means must be employed to discriminate between the two — frequency as in the case of frequency modulated radar, or the high degree of isolation of the ear from the source of the emitted sound that Mohres postulates for the bats of the family Rhinolo- phidae, which use 100 msec pulses to detect objects at such close range that echoes begin to return in 5-10 msec.
There is another aspect of underwater sounds which might be related to echo- location, and which has not been thoroughly considered. The wave lengths of the sounds emitted by most fish, and those to which they are most sensitive, range from
Hearing and acoustic orientation in marine animals 4| 5
about one to ten metres. Most of these sounds last for at least one second, so that in the immediate vicinity of the fish there is ample time for interference and reinforce- ment between successive waves to be set up, especially if it is close to the bottom or to other solid objects, as is very often the case. At first thought one would expect the principal nodes of such standing waves to be separated by distances equal to the wavelength in water of the particular frequency involved; for 500 c.p.s. this would mean nodes roughly three metres apart. Yet when I have arranged apparatus to generate sounds of a few hundred c.p.s. in small tanks, and measured the resulting sound levels with a hydrophone, there have always been wide fluctuations in the sound pressure over distances that were only a very small fraction of the wave- length. (See also Poggendorf, 1952, and Kleerekoper and Cmagnon, 1954, for similar observations.) The physical basis for these variations in sound level is no doubt somewhat complex, perhaps involving interactions between sound waves in the water and in the materials of which the tank is constructed. Comparable con- ditions would not ordinarily prevail in the open ocean, but they must often occur near the bottom, rocks, or other hard objects.
Since fish have keen hearing, they must experience fluctuations in the loudness of whatever sounds are present as they swim about in the proximity of any major acoustic discontinuity, and indeed their own movements would alter the standing wave patterns. Since such changes in sound level bear some relation to the geometry of the fish's environment, it is possible that they could learn to use them for orienta- tion (for evidence that fish can easily learn to react to sounds see Bull, 1928, and Haralson and Bitterman, 1950). Presumably such standing wave patterns would be simpler, and hence more readily interpreted by fish, if they were caused by relat- ively pure tones. Dijkgraaf (1933, 1947) and Kramer (1933) have described in fish and amphibians respectively a type of orientation based on very low frequency sounds or vibrations (or even perhaps static pressure). The sense organs involved are those in the skin or lateral fine, rather than the ear. This type of orientation which Dijkgraaf calls " Ferntastsinn " seems limited to distances of much less than one metre. At higher frequencies the speciahzed inner ear and accessory struc- tures provide a much greater sensitivity, and hence a potentially greater range of acoustic orientation. It therefore seems desirable to devote some future research to testing the possibihty that fish or cetaceans orient themselves by reacting to the complex standing wave patterns set up in water near solid objects.
Whether such a type of acoustic orientation would be based on variations in sound fields generated by the fish itself or those from other sources, if it occurs at all, am only be learned by further investigation. As stimuli for such investigations the attention of interested readers is called to the papers of Supa, Cotzin, and Dallen- . BACH (1944), Cotzin and Dallenbach (1950), and Twerskv (1951) tor convincing evidence that blind men detect obstacles by acoustic orientation based on a variety of continuous sounds, including pure tones. Furthermore Lissmann has reported that certain fish orient themselves by means o{ electrical fields ol their own making apparently sensing in some manner yet to be explained the changes in electrical field due to the proximity of objects differing from water in dielectric properties. (See Lissmann, 1951, and Gray, 1953, for preliminary accounts of these remarkable findings concerning which no complete report has yet been published). In view of the e4tence of such modes of orientation we should be prepared to lind cases of
416 Donald R. Griffin
acoustic orientation in fish or marine mammals based either upon pulsed or con- tinuous sounds.
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nebulosus). Naturwissenschaften, 18, 434-435. BiGELOW, H. B. (1904), The sense of hearing in the goldfish, Carassius awatus. Amer. Natiir., 38,
275-284. BouTTEViLLE, K. VON (1935), Untcrsuchungen iiber den Gehorsinn bei Characiniden und Gymnotiden
und den Bau ihres Labyrinthes. Z. Vergl. Physiol., 22, 162-191. Bull, H. O. (1928), Studies on conditioned responses in fishes. /. Mar. Biol. Assoc, U.K., n.s., 15,
485-533. Bull, H. O. (1930), Studies on conditioned responses in fishes. II. J. Mar. Biol. Assoc, U.K., n.s.,
16, 615-637. Burkenroad, M. D. (1931), Notes on the sound-producing marine fishes of Louisiana. Copeia,
1931, 20-28. CoTziN, M. and Dallenbach, V. M. (1950), " Facial vision ": the role of pitch and loudness in the
perception of obstacles by the blind. /. Psychol., 63, 485-515. DiESSELHORST, G. (1938), Horversuche an Fischen ohne Weberschen Apparat. Z. Vergl. PhvsioL,
25, 748-783. DiJKGRAAF, S. (1932), tjber Lautausserungen der Elritze. Z. Vergl. Physiol., 17, 802-805. Dijkgraaf, S. (1933), Untcrsuchungen iiber die Funktion der Seitenorgane an Fischen. Z. Vergl.
Physiol., 20, 162-214. Dijkgraaf, S. (1947), tJber die Reizung des Femtastsinnes bei Fischen und Amphibien. Experientia
3, 206-208. Dijkgraaf, S. (1952), Ober die Schallwahmehmung bei Meeresfischen. Z. Vergl. Physiol., 34,
104-122. Dijkgraaf, S., and Verheijen, F. J. (1949), Neue Versuche iiber das Tonunterscheidungsvermogen
der Elritze. Z. Vergl. Physiol., 32, 248-256. Dobrin, M. B. (1947), Measurements of underwater noise produced by marine life. Science, 105,
19-23. Evans, H. M. (1940), Brain and body offish. Blakiston Co., Philadelphia, 164 pp. Fish, M. P., Kelsey, A. S., Jr., and Mowbray, W. H. (1952), Studies on the production of under- water sound by North Atlantic coastal fishes. /. Mar. Res., 11, 180-193. Frisch, K. von (1936), Ueber den Gehorsinn der Fische. Biol. Rev., 11, 210-246. Frisch, K. von and Dijkgraaf, S. (1935), Konnen Fische die Schallrichtung wahmehmen? Z.
Vergl. Physiol., 22, 641-655. Frisch, K. von, and Stetter, H. (1932), Untcrsuchungen iiber den Sitz des Gehorsinnes bei der
Elritze. Z. Vergl. Physiol., 17, 686-801. Gray, James (1953), How animals move. Cambridge Univ. Press, p. 37. Griffin, D. R. (1953 a). Bat sounds under natural conditions with evidence for echolocation of
insect prey. J. Exp. Zool., 123, 435-466. Griffin, D. R. (1953 b), Acoustic orientation in the oil bird, Steatornis. Proc Nat. Acad. Sci., 39,
884-893. Griffin, D. R. and Galambos, R. (1941), The sensory basis of obstacle avoidance by flying bats.
J. Exp. Zool., 86, 481-506. Griffin, D. R. and Novick, A. (1955), Acoustic orientation in neotropical bats. /. Exp. Zool. (in
press). Haralson, J. V. and Bitterman, M. E. (1950), A lever depression apparatus for the study of learning
in fish. Amer. J. Psychol., 63, 250-256. Hardenberg, J. D. F. (1934), Ein tone erzeugender Fisch. Zool. Anzeiger, 108, 224-227. Johnson, M. W. (1948), Sound as a tool in marine ecology, from data on biological noises and the
deep scattering layer. J. Mar. Res., 7, 443-458. Johnson, M. W., Everest, F. A. and Young, R. W. (1947), The role of snapping shrimp (Crangon
and Synalpheiis) in the production of underwater noise in the sea. Biol. Bull., 93, 122-138. Kellogg, W. N., Kohler, R. and Morris, H. N. (1953), Porpoise sounds as sonar signals. Science,
117, 239-243. Kellogg, W. N. and Kohler, R. (1952), Responses of the porpoise to ultrasonic frequencies.
Science, 116, 250-252. Kleerekoper, H. and Chagnon, E. C. (1954), Hearing in fish with special reference to Semotilus
atromaculatus atromaculatiis (Mitchell). J. Fish. Res. Bd., Canada, 11, 130-152. Knudsen, V. O., Alford, R. S. and Emling, J. W. (1948), Underwater ambient noise. /. Mar. Res.,
7, 410-429. Kramer, G. (1933), Untcrsuchungen iiber die Sinnesleistungen und das Orientierungsverhalten von
Xenopus laevis Daud. Zool. Jahrb., Abt. Allg. Zool. u. Physiol, d. Tiere, 52, 629-679. Kreidl, a. (1895), Ueber die Perception der Schallwelien bei den Fischen. PflUgers Arch. f. d. Ges.
Physiol., 61, 450-464.
Hearing and acoustic orientation in marine animals 4 [ 7
J^R,EiDL, A. (1896), Ein weiterer Versuch uber das angebliche Horen eines Glocken/cichcns durch
die Fische. Pflugers Arch. f. d. Ges. Physiol., 63, 581-586. Kreig, W. J. S. (1942), Functional neuroanatomy. Blakiston Co., PhilaUvlphhi, 551 pp Kritzler, H. (1952), Observations on the pilot whale in captivity. J Mammal 33 321-334 Lawrence, B. and Schevill, W. E. (1954), Tursiops as an experimental subject! J. Mammal 35.
225-232. '
LissMANN, H. W. (1951), Continuous electrical signals from the tail of a fish, Gvmnarchus niloiicus
Cuv. Nature, 167, 201-202. LOYE, D. P. and Proudfoot, D. A. (1946), Underwater noise due to marine life. J. Acousi Soc.
Amer., 18, AA6-AA9. McBride, a. F. (in press). Evidence for echolocation by cetaceans. Deep-Sea Res. 3 (2). McBride, a. F. and Hebb, D. O. (1948), Behaviour of the captive bottle-nose dolphin, Tursiopa
truncatus. J. Comp. Physiol. Psychol., 41, 111-123. Mohres, F. p. (1953), Ober die Ultraschallorientierung der Hufeisennasen (Chiroptcra Rhmolo-
phinae). Z. Vergl. Physiol., 34, 547-588. Parker, G. H. (1903), Hearing and allied senses in fishes. Bull. U.S. Bur. Fish. Comm., 22, 45-64. Parker, G. H. and van Heusen, A. P. (1917), The reception of mechanical stimuli by the skm.
lateral line organs and ears in fishes, especially Ameiurus. Amer. J. Physiol., 44, 463-489. PoGGENDORF, D. (1952), Die absoluten Horschwellen des Zwergwelses (Ameiurus nehulosus) und
Beitrage zur Physik des Weberschen Apparates der Ostariophysen. Z. Vergl. Physiol.. 34, 111-1^1. Reinhardt, F. (1935), Uber Richtungswahrnehmung bei Fischen, besonders bei der E\n\.7C i Phoxinus
laevis L.) und beim Zwergwels {Amiurus nebulosus Ruf.) Z. Vergl. Physiol., 22, 570-603. RiDGEWOOD, W. G. (1891), The air-bladder and ear of British clupeoid fishes. J. .4nai. ami Phvsiol.,
26, 26-42. Schevill, W. E. and Lawrence, B. (1949), Underwater listening to the white porpoise {Delphinap-
terus leucas). Science, 109, 143-144. Schevill, W. E. and Lawrence, B. (1953), Auditory response of a bottlenosed porpoise. Tursiops
truncatus to frequencies above 100 kc. /. Exp. Zool., 124, 147-166. Steffer, H. (1929), Untersuchungen iiber den Gehorsinn der Fische, besonders von Phoxinus leavis
L. and Amiurus nebulosus Raf. Z. Vergl. Physiol., 9, 339-477. SuPA, M., COTZIN, M. and Dallenbach, K. M. (1944), " Facial vision '": the perception of obstacles
by the blind. Amer. J. Psychol., 57, 133-183. Tower, R. W. (1908), The production of sound in the drumfishes, the sea robm and the toad-fish.
Ann. N.Y. Acad. Sci., 18, 149-180. Twersky, V. (1951), On the physical basis of the perception of obstacles by the blmd. Amer. J.
Psychol., 64, 409-416. .o -,.■ ,-.c
Westenberg, J. (1953), Acoustical aspects of some Indonesian fisheries. J. du Cons., 18, J' 1-ii.^-^. Wohlfahrt, T. a. (1936), Untersuchungen uber das Tonunterscheidungsvermogen der EIritze
(Phoxinus laevis Agass.). Z. Vergl. Physiol., 26, 570-604. ,. .. • r
Wood, F. G., Jr. (1954), Underwater sound production and concurrent behaviour of captive por- poises, Tursiops truncatus and Stenella plagiodon. Bull. Mar. Sci., GulJ and Caribbean 3, UO-133.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 418-425.
Characteristics of the water-masses of the Philippine, Kermadec
and Tonga Trenches
By Anton Fr. Bruun and A. Kiilerich The Galathea Expedition 1950-52, Copenhagen
The chief purpose of the Galathea Expedition 1 950-52, The Danish Deep Sea Expedi- tion around the World, was to study the organisms in the deepest parts of the oceans. A considerable number of hydrographic observations, however, were made to learn about the environmental conditions. At least one full series from the surface to the bottom was made in each of the regions where biological work was concentrated. The hydrographic instruments were standard types. During the expedition a total number of 16 reversing thermometers were lost, six of them being simply crushed by pressure at the greater depths in the Philippine Trench.
The greatest care was taken in making observations. Even when only one ther- mometer was available for each water-bottle, most doubtful temperature readings were repeated. We are therefore fairly confident that our observations, including those presented here, are as exact as any made by specially equipped hydrographic expeditions.
Many technical difficulties resulted from the extreme depth of the PhiHppine Trench. The effect of high pressure has been mentioned. It was furthermore very difficult to keep the ship exactly above the bottom of the narrow trench, often less than one kilometre wide. We are extremely indebted to Captain S. Greve, R.D.N. and his officers, for their untiring efforts in fulfilling our requirements. Because of these difficulties we had to repeat the deepest series in the Philippine Trench no less than 10 times, but the efforts were rewarded by 17 observations from depths exceeding 6000 m. The skill and patience of our two assistant hydrographers, Mr. Ingolf Crossland and Mr. Ulrik Klaning, is also gratefully acknowledged.
All the observations of the Galathea Expedition are to be pubhshed in the scientific report of the expedition, but we think it of interest to pubhsh our observations from the Philippine and the Tonga-Kermadec Trenches at once. The first section of the lists of observations (Table I) gives the values observed while the second section (Table II) contains average figures and graphically interpolated figures derived from the total number of reliable observations.
THE PHILIPPINE TRENCH
The temperature from the observations of the Snellius Expedition (van Riel, Hamaker and van Eyck, 1950) and the Swedish Deep-Sea Expedition (Bruneau, Jerlov and Koczy, 1953) in the deep water of the trench, are plotted in Fig. 1. The agreement between these and those of the Galathea is obvious. The characteristics of the deep water of the trench appears to be very uniform. A minimum of 1-59° C occurs between 3500 and 4000 m. Below this, the temperature increase is very close
418
Characteristics of the water-masses of the Philippine, Kcrmadcc and Tonga Trenches 4|V
to that to be expected from adiabatic heating alone. The salinity and amount ol oxy- gen on the other hand are nearly constant for this same interval (Tables I and II).
Thus, it appears that any renewal of the deep water masses of the trench must be derived from that of the West Pacific Basin at the sill depth of the trench (i.e. 3-5-4
0.5"
1.0"
20*
M
2000
T — r
1 — r
1 — r
2.5*C
3000
4000
5000
- /
6000
7000
8000
9000
10000
Fig. 1. Temperatures of the PhiHppine. Tonga and Kemu|dec ^^^^^^^^^ te^peratures^n situ, brokenjne^potent.a. t^^^^^^^^^^^
420
Anton Fr. Bruun and A. Kiilerich
km) (Fig. 4). This agrees well with the general concept that the Pacific Deep Water is derived from the region south of AustraUa with roots in the Indian Ocean, and furthermore that there is a slow movement from south to north in the West Pacific. The velocity of this current is probably so slow that a renewal of the bottom water in the PhiUppine Trench would require very many years. We know Httle about the abundance of the organisms in the trenches (Bruun 1951, 1953 a, b; ZoBell, 1952; Zenkevitch, Birschtein and Beuaev, 1954; Zenkevitch, 1955); but in any case they require a certain amount of oxygen. The content of oxygen is relatively high. Therefore, as an additional possibility, acting in the renewal of the trench
Fig. 2. Four sections of the Philippine Trench. Base Une of all sections at 10000 m; distance between any two sections is a little more than 100 km (From Kiilerich, 1953).
water, turbidity currents are suggested. The deepest part of the trench (ca. 10000 m) is nowhere more than 90 km distant from the narrow coastal shelf of the Phihppines (Fig. 2). Here turbidity currents can easily get started; typhoons will disturb the bottom of the shelf and add to the velocity of the strong tidal currents in the narrow straits of the islands. Eruptions of submarine volcanoes or the frequent earthquakes, which have their epicentres on the western slope (Repetti, 1931 ; 199) should also be considered as the cause of bottom sediment shdes. The many stones with rounded edges found by Galathea must have been carried down in some such way. (Fig, 3); this is also in agreement with Shepard (1951).
F,, 3. scenes and .rave, brou.h, up b, a sIed.e..a.yVo„y,;c .o,,o,., o,' ,„. P.« ,.c.„
0190 m (From Bruun, 1953 B).
Charac,eris.,cs of ,he wa.er-masses or ,hc PK,„ppi„... K.nnadcc and U,„^ , ,.,.„„ 4,,
thermal convection. 'settlement ol the particles, must give rise to
THE TONGA-KERMADEC TRENCHES
c 34.00 20
I5» —
I0«
O*
34.50
8500
35 50 X.
T 1 1 r
-I — I — I — r
200
"1 — I — I — I — [-
,•200
V6e45 3500' igooo
1
I
X
J_ J
Fig. 4. T-S diagram of the water masses of the Philippine and Kerniadcc Trenches. I xccpt foi the uppermost and lowermost observations the figures along the cur\es denote hundreds of m
position, which is much closer to the sources of the bottom water of the Pacitic This is shown by the minimum temperature, 1-07^ C, at about 5000 m (see Figs. 1 and 4). Here also the increase in temperature towards the bottom closely rollings what would be expected from adiabatic heating.
Galathea Station nr. 686 was taken in the Tonga Trench. 8 degrees of latitude north of the full series of observations of St. 677 in the Kermadcc Trench. Lack oi time prevented us from making more than three observations, but they arc sullicicnt to prove that the deep water is essentially the same. This corroborates \sell the results from the echo-soundings, that the connection between these trenches is below the
422 Anton Fr. Bruun and A. Kiilerich
ievel of the surrounding basin. Lengthwise of the connection we found no depth shallower than 6000 m. Therefore it might even be reasonable to speak of one trench only, the Tonga-Kermadec Trench. The potential temperatures calculated are as constant as could be expected from the quality of thermometers, just as in the Philip- pine Trench. We want, however, to draw attention to the slight increase close to the bottom. It is only 0-04° C, but it has been recorded on four occasions with two different thermometers. This is the opposite of what was found by the SneUius Expedition (van Riel, et al, 1950, 29-30); it will be most important to have this disagreement further studied. As it is, it does not justify further comment.
Table I Values of temperature, salinity, density and oxygen at various depths as actually
observed by the Galathea
St. 412. Philippine Trench. iri3'N. 126° 21' E. 12-13/7 1951
|
Depth 8981-8956 |
m |
||||
|
o. |
|||||
|
m |
a |
5°' '-' oo |
<Jt |
mllL |
|
|
0 |
29-60 |
34-20 |
21-46 |
|
|
|
24 |
•15 |
•15 |
•41 |
4^38 |
|
|
47 |
•00 |
•28 |
•54 |
•41 |
|
|
71 |
28-70 |
•43 |
•76 |
•36 |
|
|
94 |
-38 |
•58 |
-97 |
•50 |
|
|
142 |
23-42 |
35-00 |
23-83 |
394 |
|
|
189 |
18-78 |
34-83 |
24-98 |
•55 |
|
|
283 |
12-44 |
•49 |
26-13 |
2-71 |
|
|
378 |
8-94 |
•33 |
-65 |
•10 |
|
|
472 |
7-55 |
•39 |
•92 |
1-62 |
|
|
567 |
6-40 |
•39 |
27^07 |
•67 |
|
|
756 |
5-00 |
•51 |
-34 |
•80 |
|
|
945 |
4-45 |
•55 |
-43 |
2^17 |
|
|
1133 |
3-77 |
•56 |
•50 |
•06 |
|
|
1417 |
•26 |
•58 |
-57 |
•20 |
|
|
1890 |
2-33 |
•60 |
•67 |
•39 |
|
|
2362 |
1-93 |
•62 |
•71 |
•66 |
|
|
2835 |
•72 |
•64 |
-74 |
•96 |
|
|
3307 |
•59 |
•66 |
•76 |
3-38 |
|
|
3779 |
•59 |
— |
__ |
|
|
|
4252 |
•63 |
-67 |
•77 |
•08 |
|
|
4724 |
•71 |
•68 |
•77 |
•32 |
|
|
5669 |
•81 |
•68 |
•76 |
2^92 |
|
|
6755 |
•95 |
•66 |
•74 |
•26 |
|
|
7700 |
— |
•66 |
— |
313 |
|
|
8076 |
2^22 |
•68 |
•73 |
•22 |
|
|
8503 |
— |
-66 |
— |
•06 |
|
|
St. 430. |
Philippine Trench. |
10° 20' N. |
126° 37' E. |
3-4/8 1951 |
|
|
Depth |
10110 w |
O2 |
|||
|
m |
C° |
5°oo |
ot |
ml/L |
|
|
945 |
4-82 (a) |
34-51 |
27-36 |
1-16 |
|
|
1606 |
2-99 |
-58 |
•59 |
•62 |
|
|
2079 |
•16 |
•61 |
•69 |
•92 |
|
|
7640 |
•12 |
— |
|
— |
Characteristics of the water-masses of the Philippine, Kermadec and Tonga Trcnchc^ 42 ^ St. 431. Philippine Trench. 10^ 21' N. 126- 38' r. 4 5/« I4M
|
Depth 1011 0/« |
||||
|
Oj |
||||
|
ni |
C |
S , 3469 |
Tt |
ml/L |
|
7558 |
201 (a) |
27-75 |
304 |
|
|
8503 |
•27 |
69 |
■73 |
1 1 |
|
9165 |
•35 |
■67 |
■72 |
2«8 |
|
9636 |
•50 |
■67 |
■71 |
3-27 |
|
St. 433. |
Philippine Trench. |
9^ 51' N. |
126 51' F. |
5-6/8 1951 |
|
Depth 10003 m |
||||
|
o. |
||||
|
m |
C |
■^ OO |
<Jt |
mliL |
|
3779 |
157 |
34^67 |
21-11 |
3-27 |
|
4252 |
•57 («) |
•69 |
■78 |
15 |
|
4724 |
•70 |
■67 |
•77 |
11 |
|
5669 |
80 |
■69 |
•77 |
12 |
|
6614 |
■95 |
■69 |
•76 |
36 |
|
7511 |
•97 (a) |
■68 |
•75 |
20 |
|
8456 |
218 |
■66 |
•72 |
■16 |
|
9498 |
■28 (a) |
■66 |
- -71 |
293 |
|
9589 |
■47 |
■69 |
■72 |
V3I |
(fl) Thermometer not absolutely reliable. St. 440. Philippine Trench. 10°25'N. 126 40' F. 14/8 1951
|
Depth 10016 m |
o. |
|||
|
m |
C° |
■^ OO |
'^1 |
ml/L |
|
3068 |
1-61 |
34^65 |
21-15 |
292 |
|
5900 |
•83 |
•67 |
•75 |
3 01 |
|
7788 |
213 |
•68 |
•74 |
290 |
|
9770 |
•56 |
•67 |
•70 |
31 9 |
|
9864 |
•55 |
•67 |
•70 |
11 |
St. 677. Kermadec Trench. 28°38'S. 175° 53' W. 4-5/3 1952
|
Depth |
9127-9192 m |
O, |
||
|
m |
C° |
•^ OO |
Ot |
ml/L |
|
0 |
24-02 |
3564 |
24-14 |
— |
|
47 |
C22- |
•58 |
•68 |
515 |
|
94 |
1792 |
•55 |
25^74 |
■02 |
|
182 |
1608 |
•46 |
2610 |
455 |
|
376 |
11 -77 |
34^97 |
■63 |
■35 |
|
564 |
8^25 |
•58 |
■93 |
61 |
|
766 |
6^42 |
•39 |
2703 |
•97 |
|
956 |
5^13 |
•37 |
18 |
50 |
|
1145 |
407 |
•37 |
30 |
16 |
|
2822 |
189 |
•68 |
•74 |
337 |
|
3762 |
•34 |
•72 |
•83 |
444 |
|
4232 4723 5194 5665 6496 7905 8845 |
•19 09 •07 •16 •27 •46 •68 |
•72 •72 •72 •70 •72 •70 •72 |
•83 •84 •84 •83 ■82 ■81 ■81 |
•52 •58 48 56 62 60 56 |
. 424 Anton Fr. Bruun and A. Kiilerich
St. 686. Tonga Trench. 20° 53' S. 173° 51' W. 11/3 1952
|
Depth 9818 w |
Oa |
|||
|
m |
C° |
•^ 'oo |
at |
ml/L |
|
7428 |
1-40 |
34-71 |
21-81 |
4-52 |
|
8373 |
•60 |
•71 |
•80 |
•46 |
|
9318 |
•74 |
•71 |
•79 |
•48 |
Table If Average values of temperature, salinity, density and oxygen at standard depths as derived from interpolation on graphs and based on the total number
of reliable observations
Philippine Trench. Interpolation referred to standard depths; based on all Galathea observations
|
O2 |
potential |
||||
|
m |
C° |
5°/oo |
fft |
ml/L |
temp. |
|
0 |
2940 |
3420 |
21-46 |
|
|
|
25 |
•14 |
•15 |
•40 |
4.4 |
|
|
50 |
28-97 |
•30 |
•57 |
•4 |
|
|
75 |
•65 |
•46 |
•79 |
•4 |
|
|
100 |
10 |
•63 |
2211 |
•5 |
|
|
150 |
22^65 |
•99 |
24-04 |
39 |
|
|
200 |
18-15 |
•79 |
25-09 |
•5 |
|
|
300 |
11^75 |
•47 |
26-24 |
2-7 |
|
|
400 |
8-50 |
•34 |
•74 |
•0 |
|
|
500 |
7-12 |
•39 |
-98 |
1^6 |
|
|
600 |
605 |
•40 |
2712 |
•7 |
|
|
800 |
4-86 |
•52 |
•36 |
•9 |
|
|
1000 |
•22 |
•55 |
•46 |
21 |
|
|
1200 |
3-62 |
•57 |
•53 |
•1 |
|
|
1500 |
•05 |
•59 |
•59 |
•2 |
|
|
2000 |
2^22 |
•61 |
•68 |
•4 |
207 |
|
2500 |
\-U |
•63 |
•72 |
•6 |
1-66 |
|
3000 |
•64 |
•65 |
•75 |
•9 |
-41 |
|
3500 |
•57 |
•67 |
•77 |
3-3 |
-29 |
|
4000 |
•60 |
•67 |
•77 |
•2 |
•27 |
|
4500 |
•66 |
•68 |
•77 |
•1 |
•26 |
|
5000 |
•73 |
•68 |
•77 |
•1 |
•27 |
|
5500 |
•79 |
•69 |
•76 |
•0 |
•26 |
|
6000 |
•85 |
•69 |
•76 |
•0 |
•25 |
|
6500 |
•92 |
•68 |
•75 |
•0 |
-24 |
|
7000 |
200 |
•68 |
•75 |
2-3 |
•24 |
|
7500 |
■09 |
•67 |
•74 |
30 |
•25 |
|
8000 |
•18 |
•68 |
•73 |
•0 |
■24 |
|
8500 |
•26 |
•68 |
•73 |
11 |
•24 |
|
9000 |
•34 |
•67 |
•72 |
•0 |
•22 |
|
9500 |
•45 |
•67 |
•71 |
29 |
•23 |
|
9864 |
•56 |
•67 |
•70 |
31 |
•26 |
Characteristics of the water-masses of the Phihppmc. kcrmadcc and I onga Trenches 42^
St. 677. Kermadec Trench. Interpolation referred to standard depths. 28°38'S. 175" 53' W. 4 5/. 3 1952
|
o. |
potential |
||||
|
m |
C° |
^ /oo |
Tl |
mill |
temp. |
|
0 |
2402 |
35-64 |
2414 |
||
|
50 |
C22- |
•58 |
•68 |
5-2 |
|
|
100 |
17-80 |
-54 |
25-76 |
0 |
|
|
200 |
15-75 |
•44 |
26- 16 |
4-5 |
|
|
400 |
11-30 |
34^91 |
•68 |
•4 |
|
|
600 |
7-90 |
•53 |
■98 |
6 |
|
|
800 |
615 |
•38 |
2710 |
50 |
|
|
1000 |
4-65 |
-36 |
•25 |
44 |
|
|
1200 |
3-95 |
-38 |
-34 |
•1 |
|
|
3000 |
1-74 |
-69 |
-77 |
3^5 |
151 |
|
3500 |
•45 |
-72 |
-82 |
43 |
18 |
|
4000 |
•27 |
■11 |
-83 |
•5 |
095 |
|
4500 |
•13 |
•72 |
•84 |
•5 |
075 |
|
5000 |
07 |
-72 |
-84 |
•5 |
063 |
|
5500 |
•12 |
•72 |
-84 |
•5 |
062 |
|
6000 |
•22 |
-72 |
-83 |
•6 |
064 |
|
6500 |
•27 |
-72 |
-83 |
•6 |
062 |
|
7000 |
•33 |
-72 |
-83 |
•6 |
060 |
|
7500 |
•40 |
-72 |
-82 |
■6 |
059 |
|
8000 |
■48 |
-72 |
•82 |
■6 |
0-58 |
|
8500 |
•58 |
•72 |
-81 |
■6 |
0-59 |
|
8845 |
•68 |
•72 |
-81 |
■6 |
063 |
St. 686. Tonga Trench. Interpolation referred to standard depths. 20° 53' S. 173° 51' W. 11/3 1952
|
O2 |
|||||
|
m |
C° |
■^ OO |
ot |
ml/L |
potential temp. |
|
7500 |
1-41 |
34^71 |
27-81 |
4-5 |
060 |
|
8000 |
■51 |
■71 |
■80 |
■5 |
061 |
|
8500 |
■62 |
-71 |
■80 |
■5 |
063 |
|
9000 |
■70 |
-71 |
■79 |
■5 |
062 |
|
9318 |
■74 |
-71 |
•79 |
•5 |
0-61 |
REFERENCES
Bruneau, L., Jerlov, N. G. and Koczy, F. F. (1953), Physical and chemical methods. Repii
Swedish Deep-Sea Exped., 1947-1948, Phys. Chem., 3 (4), 101-1 12. Bruun, a. Fr. (1951), The Philippine Trench and its bottom fauna. Saiure, 168. b92. BRimN, A. Fr. (1953 a), Problems of life in the deepest deep sea. Geogr. Mag., 26. 247-262. Bruun, A. Fr. (1953 b), Dybhavets Dyreliv. In: A. F. Bruun, Sv. Greve, H. Mielchc and R. Sp^a-k.
Galatheas Jordomsejling, 1950-52, 153-192. KnLERiCH, A. (1953), Ekkolod og hydrografiske Undersogelser. In: A. F. Bruun. Sv. Grcvc. H.
Mielche, R. Sparck, Galatheas Jordomsejling, 1950-52, 43-54. Repetti, Wm. C. (1931), Philippine earthquakes. Marme epicenters. Publ. Manila Observ.. 3. (9).
199-2)3. Shepard, F. p. (1951), Transportation of sand into deep water. Soc. Economic Paleontol. Mineral ,
Spec. Publ., 7, 53-65. ^ ^ ^, , ,u
Van Riel P M Hamaker, H. C. and van Eyck, L. (1950), Tables, serial and bottom obscr>alions.
temperature, salinity and density. Snellius Exped., Oceanogr. /?.-.v 1929-1430. 2 (6) 44 pp Zenkevitch, L. a. (1955), Erforschungen der Tiefseefauna im Nordwcstlichcn Icil des .Stilicn
Ozeans. fnt. Union Biol.' Sci., {B), 16, 72-S4. . ,. ,.,^,, , u f w it- .
Zenkevitch, L. A., Birschtejn, J. A. and Bujaev, O. M. (1954), i/utchcnic fauni Kiinlo-kami,
chatskoj viadinui. (The exploration of the fauna in Kunlc-Kamtchacka Deep). Pnr,'ila, I^.M,
/:t_'7i
Zobell/c. E. (1952), Bacterial life at the bottom of the Philippine Trench. Science. 115. 507 508.
Papers ill Marine Biology and Oceanography, Suppl. to vol. } of DeepSea Research, pp. 426-434.
Polarization of scattered sunlight in deep water*
By Talbot H. Waterman
Osborn Zoological Laboratory, Yale University, New Haven, Conn.
Summary — 1. Photographic measurements of the polarization pattern of underwater illumination were made at depths of 30, 60, 100, 150, and 200 m in oceanic water with a vertical extinction coefficient corresponding to Secchi disc readings between 22-26 m. A special polarization analyzer, attached to the outside of a deep-sea camera case, provided in a single photograph direct evidence for: (a) presence or absence of polarization with a high degree of sensitivity; (b) type of polarization; (c) plane of polarization, if linear; (d) rough comparative indication of the degree of polarization. By photographing the interference pattern formed by this analyzer when traversed by polarized light, records of the polarization of horizontally scattered sunlight were obtained in four azimuths relative to the sun's bearing: 0°, 90°, 180\ 270°, at eleven different stations, including two at each depth except 200 m.
2. Horizontally scattered light was found to be polarized at all depths, 200 m included, and in all directions tested; the type of polarization was linear in every instance. In so far as could be judged from the photographs (Fig. 3), the percentage polarization at 200 m appeared to be at least as great as at lesser depths.
3. The plane of polarization was always horizontal in lines of sight toward and away from the sun's bearing but was tilted toward the sun in azimuth's normal to these; this effect of the sun's position was still considerable at 200 m. The amount of tilting occurring in lines of sight 90° from the sun's bearing was primarily related to the angle of refraction for sunlight at the air-water interface (Fig. 2), but a second effect, resulting from depth of light penetration, was shown by the decrease in the tilting of the polarization plane as depth was increased.
4. [t is concluded that: (a) scattered sunlight underwater is linearly polarized to considerable depths, probably throughout the photic zone; (b) the pattern of polarization is dependent on the sun's position at least to a depth of 200 m and (c) such optical phenomena therefore may be important in the behaviour of photic zone bathypelagic animals as well as epipelagic forms.
INTRODUCTION
Previous measurements (Waterman, 1954 a) have shown that natural underwater illumination is linearly polarized in patterns which seem basically similar to those of the blue sky.j This is true of the upper 15 m or so of water to which the earlier work was limited. Since the most probable origin for this polarization would appear to be the molecular or fine particle scattering of directional light rays penetrating the water, it was predicted that linear polarization of submarine illumination should occur as deep as significant amounts of directional light are transmitted. It was also indicated that, since certain terrestrial and shallow water animals are known to be capable of utilizing polarized light in the sky for their orientation and navigation, underwater polarization may prove to be a factor of considerable ecological importance
* Contribution No. 763, Woods Hole Oceanographic Institution.
t This introductory statement refers only to polarization arising within the water itself. It does not include the direct underwater observation or measurement of polarized sky light. The known relation between these two sources of polarization has previously been described for shallow water (Water- man, 1954 a). Further measurements will be required to establish in deeper water the effective penetration and influence of polarized sky light, as opposed to direct sunlight, which is unpolarized in the atmosphere.
426
Polarization of scattered sunlight in deep water 42/
in the location and migration of animals of the whole photic /one. For these reasons the extension of our knowledge of submarine polan/ccl light into deep water is a matter relevant to several points of interest.
The present report describes the results of photographic polarization measurements down to 200 m which extend our information to depths in excess of ten times those previously studied. It clearly proves that polarization of sunlight under water is nof merely a superficial phenomenon but one which also must be reckoned witfi n considerable depths.
ACKNOWLEDGEMENTS
The author is greatly indebted to a number of people who helped hnn in many ways while preparing for and executing these measurements. Particular mention should be made of various Staff members of the Woods Hole Oceanographic Institu- tion and the Officers and Crew of R.V. Atlantis: Dr. C. O'D. Isflin, Mr. David Owen, Mr. Richard Edwards, Mr. Lloyd Hoadley, Mr. Valentine Worthington and Captain Scott Bray. Hearty thanks are also due to Miss Virginia Witmington, Mr. Charles Robinson and Mr. Wallace Phelps of the Edwards Street Laboratory at Yale University.
EQUIPMENT AND PROCEDURE
The data reported here were obtained in the southwest North Atlantic just west and northwest of Bridgetown, Barbados, B.W.I. (13° N, 59° W) working from R.V. Atlantis. Polarization measurements were made at 30, 60, 100, 150 and 200 m. The average echo-sounding depth at the various stations was about 1,200 m so that no effect of reflection or light scattering by the bottom could reasonably have influenced the results,
Secchi disc readings ranged from 22-26 m, indicating moderately clear oceanic water in the upper layers. These depths correspond to vertical extinction coefhcients of about 0-055-0-065 (Clarke, \9A\), or to overall transparency between Jkrlov's (1951) types I and II oceanic water. The sea was moderate (Beaufort 2-3), confused and occasionally had a large swell during the work.
While the measurements were being made, the sun was shining on the sea surface in all cases, although as work progressed on the 200 m station (No. 1 1 ). a high thin overcast slowly cut down the direct sunlight from full to a point where shadows were just visible. In all other cases the sky was either mainly clear overhead or nearly completely clear. Stations were made at various sun's altitudes from 26-52'. 1 ho latter was close to the local noon maximum for the period around December I when
this work was done.
In order that the results obtained may be eff"ectively presented, the optical equip- ment used and the procedure for making the measurements will first be described.
The basic units of equipment employed were (I) a special polarization analy/cr and (2) a camera. The latter was arranged to record the interference figure produced by the analyzer when it was traversed by polarized light. This analyzer, which has been used before for visual observations (Waterman, 1954 a) is made up of two essential optic components. The first of these is a calcite crystal about 3 5 mm thick
428 Talbot H. Waterman
cut at right angles to its optic axis; the second is a circular polarization analyzer. This consists of a quarter wave plate and a linear polarizer in that order with the slow axis of the former oriented 45° clockwise from the transmitting axis of the latter.
When convergent polarized light passes through this optic system, an interference pattern is formed. Four parameters of the pattern are directly dependent on the properties of the light traversing the analyzer. The figure's contrast and extent depend roughly on the intensity and percent polarization of the incident light. Its colour is related to the wavelengths transmitted. Finally, the geometry of the inter- ference figure varies with different kinds of polarized light whether linear, elliptical or circular.
Such patterns arise because light rays in the convergent beam which pass through the crystal plate obliquely, i.e., not parallel to its optic axis, will be split up into two rays by the calcite's birefringence. These undergo different retardations in passing through the crystal. On emerging from it and traversing the circular analyzer, they form areas of cancellation and reinforcement in a radially symmetrical pattern whose relative size depends on the thickness and birefringence of the crystal.
With monochromatic polarized light the interference pattern consists of alternating dark and light concentric rings, successive light areas of the pattern corresponding to differences of one wave-length in the oblique ray paths through the calcite. With white light a series of brilliant interference colours in isochromatic rings will be added to this basic pattern.
If the light entering the analyzer is circularly polarized, the interference figure obtained under the conditions specified will be a series of complete circular isochro- matic curves, starting from a white centre spot and becoming closer and closer together in the higher order rings (Fig. 1a). With elliptically polarized light these rings are distorted into a series of ellipses.
The interference figure produced by linearly polarized light is broken up into four quadrants at the limits of which the isochromatic rings are interrupted and displaced radially. In two diametric quadrants the arcs are moved outward and two dark spots appear in their central sectors (Fig. 1b); in the other sectors the arcs are displaced inward and the centre remains white.
The breaks in the concentric rings are parallel to the e and h vectors of the linearly polarized incident light. With a negative analyzer crystal, like calcite, and the circular analyzer axes set as described, the e vector will be parallel to the breaks which delimit the clockwise edges of the two dark centre sectors.
It should be emphasized that this type of analyzer, although simple, has several important advantages in an application like the present one. Unlike any other polar- ization analyzer, the present device provides the maximum information of which it is capable without the need of rotating it or moving any of its parts. The plane of linearly polarized light can be observed directly by inspection regardless of the angular relation between the plane of the incident light and the axes of the conjoined quarter wave plate and the linear polarizer.
This is true only when the latter two units are oriented relative to each other as specified. If their axes are not aligned at 45°, or if only a linear analyzer is used with the calcite crystal, the interference figure will change with the rotation of the analyzer. ^s this happens, a dark cross-like isogyre will be superimposed on the isochromatic lines. Its position and intensity will depend on the relation of the analyzer axis to the
Polarization of scattered sunlight in deep water 429
plane of incident light polarization. Hence the e vector cannot be recognized directly by inspection without rotating the instrument.
Another important property of the analyzer described lies in its high scnsiiiviiy. Small percentages of polarization of the order of 5% may readily be delected. The instrument has, therefore, proved useful in addition to its present application in monitoring the illumination of experimental apparatus where polarization of the light source or stray polarized light in the system had to be avoided (Wahrman 1950; 1954 b).
It is of interest that, although interference patterns provide a standard means of structural analysis in crystallography, their application in the present instance reverses the known and unknown factors in the optical parameters. In the measurements here described it is not the crystal plate whose characteristics are to be determined but rather the polarization of the deep-sea illumination which traverses it.
A further convenient property of the polarization analyzer used is the fact that the interference figure is optically located at infinity. Consequently the instrument may be fastened directly over the lens of a camera focussed at its principle focus and a record obtained which indicates whether or not polarized light is present or not, even in small amounts. Its type and plane, if it is linearly polarized, will likewise be recorded with precision.
A complication is introduced for deep-sea work, however, by the need for enclosing the camera in a water-proof case whose window is almost certain to exhibit strain birefringence when subjected to pressure. Such an effect was actually observed in some preliminary photographs taken at about 30 m depth with a hand-held camera.*
In that instance the camera with the analyzer attached over the lens was protected in a transparent plastic box. This was apparently birefringent when the pictures were taken since the figure recorded showed elliptical polarization in the horizontal light pattern. Such has never been observed visually under water in level lines of sight (Waterman, 1954 a) nor was it ever found in deep water photographs where the possibility of strain birefringence had been eliminated.
To obviate this difficulty in the present instance the analyzer was mounted outside the pressure case enclosing the camera. Both front and back of the optical sandwich involved were thus exposed to equal pressures. No detectable effect of the hydrostatic pressure itself (about 20 atmospheres at the deepest station) was ever observed. Of course, any strain birefringence arising in the window through which the camera looked out of its case would have no effect in this situation since it occurred between
the analyzer and the lens.
The camera employed was a 35 mm Robot with an f/2-8 Zeiss tessar lens. It Ns-as arranged to be triggered by a solenoid controlled from the ship. After each exposure the film was automatically advanced by the camera mechanism so that 15-20 pictures could be taken on a single lowering of the apparatus. The Robot was mounted in a Ewing-type deep-sea camera case sealed with an 0-ring. The lens was aligned with a plane glass window outside of which the polarization analyzer was attached as already described. A two-conductor insulated cable ran from the solenoid operating the camera shutter to the deck laboratory o^ Atlantis where the exposures were controlled.
430 Talbot H. Waterman
The whole deep-sea camera and case were mounted on a weighted frame suspended from the end of the ship's hydrographic cable. When the equipment was lowered into the water, the camera lens and interference analyzer were quite accurately directed horizontally. This was so even while the ship was steaming ahead at slow speeds, a fact which was checked by diving with the ship under way. Consequently the frame of the photographic negatives has been taken as the vertical and horizontal reference for analysis of the data.
Previous work (Waterman, 1954 a) had shown that the intensity and plane of the polarization of underwater illumination were dependent on the relation between the line of sight and the bearing of the sun. Consequently, it was important for the present deep-water measurements to control the azimuth in which the pictures of the polariza- tion pattern were taken. To do so a large fin of sheet aluminum was attached to the frame holding the camera in such a way that the horizontal direction in which the camera would point coincided with the ship's heading.
The procedure used in obtaining the photographic data was as follows. The camera, loaded with Eastman Kodak Tri-X film, which has an American Standards Exposure Index of 200, was lowered to the depth desired. Then the ship steamed slowly ahead in the sun's azimuth, a manoeuvre which would shortly bring the camera's direction of view into alignment with the sun's bearing. After a period which experience with the resulting negatives showed was adequate for the slowly towed camera to settle into this orientation, a series of three exposures was made separated by 5 second intervals.
Exposure times and diaphragm stops were first set on the basis of the estimated extinction coefficients of the water mass concerned, then, if necessary, corrected from experience. No photometric transparency measurements were made, but an approxi- mate value was obtained for the surface layers by the use of the Secchi disc at each station (Clarke, 1941) and by comparison with pubhshed data from stations made in nearby areas (Jerlov, 1951). Actual exposures used varied with the sun's altitude as well as depth of the camera from 1/25 sec at f/4 for 30 m to 20 sec at f/2-8 for 200 m.
After pictures had been taken in one direction, the ship's course was altered 90° clockwise, and after a suitable wait of about 5-10 min for the camera and cable to swing around, another three photographs were made, this time looking 90° to the right of the sun's azimuth. Similarly two more sets of exposures were made in direc- tions 180° and 270° to the right of the sun's bearing.
It should be mentioned that because of the wind (force 3-4 Beaufort) and sea running at the various stations, it was not always possible to obtain records under ideal conditions for each of the four azimuths tested. In some cases the wire angle instead of being negligible was appreciable, particularly for downwind or crosswind legs of the station. Similarly the behvaiour of the cable after a turn sometimes showed that the apparatus was slow in aligning its heading with that of the ship. Reasonable compromises between ideal recording conditions and practical handling circumstances of the ship and gear had therefore to be made.
In the absence of a more elaborate apparatus where the camera's direction could be immediately and accurately controlled from the surface and monitored with repeating compass and precise vertical reference, the reliability of the present results could be insured only by the care and experience exercised in carrying out the manoeuvres described. It could be checked, however, by the consistency of the data obtained,
Polarization of scattered sunlight in deep water
431
both internally and with reference to relations indicated by previous shaliow-walcr observations.
A total of 1 1 stations were made. Of these the first 4 and No. 6 showed considerable internal inconsistencies for azimuth, apparently arising from mcxpcrience w.th difficuhies like those outlined. But on the basis of their coherence, the data for the remaining 6 stations indicate that such interference had been minimized. These include one set of records each at 30, 60, 100, 200 m and two at 150 m.
RESULTS
The data of these measurements provide information relevant to four or live ditfereni aspects of the general problem.
In the first place every photograph taken during the present deep-water series showed a well-developed interference figure (Figs. 2, 3). This proved that the scattered hori- zontal underwater illumination in the directions photographed was polarized at all depths tested including the deepest, 200 m. Furthermore, as the interference pattern clearly consisted of four quadrants of isochromatic curves made up of broken con- centric rings with two diametrically opposite dark central sectors, this light must have been linearly polarized.
Station No. 9
Sun's altitude: 34' 40'
Angle of sunlight incidence: 55
Depth of measurements : 60 m
13'
Table I 08' N, 59° 50-5' W.
Dec. 2, 1954
Sun's azimuth: 129°
Calculated angle of refraction: 38"'
Depth to bottom: 1150 m
|
Direction relative to sun's bearing |
0° |
90° |
180 |
270 |
|
Tilt of polarization plane Exposure # 1 #3 |
0° 1 ° right 0° |
17° left 19° left |
i 1-5' left ( 2 0° left i 2 0° left |
1 ! ' right 16 right 19 right |
|
Average |
0-3° right |
18° left |
i 1-8" left 1 |
15-3° right |
Although the method of polarized light analysis employed does not permit any close estimate of percentage polarization, there is some evidence pertinent to this matter in the photographs. In so far as it can be gauged by the intensity and extent of the interference pattern photographed, the degree of light polarization at 200 m seemed to be about as great as at any shallower depths. The number of concentric isochromatic rings recorded at this deepest station is fully as large as at any other in
the present series.
Also it is clear from the same kind of evidence that in deeper water there is no marked change in percent polarization with direction of view relative to the sun's a/imuih. In fact No. 8 at 30 m (Fig. 2) was the only station obviously providing evidence for this relation which was always found visually in shallow water (Watlrman. 1*^54 a).
On the other hand, the effect of the relative bearing of the sun on the plane of polar- ization was a prominent and highly significant feature of the records at all stations. This is exemplified by the data for stations 9 and 1 1 which are presented m Tables I and II and by Figs. 2 and 3 for stations 8 and 1 1 .
432
Talbot H. Waterman
In general the e vector of the polarization was horizontal in the sun's and the anti- sun's bearings but was tilted towards the sun at azimuths normal to these lines of sight. When the polarization plane appeared to be tilted in bearings towards or away from the sun, it has been assumed that this was the result of the camera not being precisely horizontal or pointing accurately along the ship's heading as discussed under procedure. The magnitude of these influences, obvious in the directions cited, should in addition give some information on the reliability of the measurements made normal to the sun's azimuth where the present data do not otherwise provide any estimate of variance.
The tables and photographs illustrate two important points inherent in the total data. First is that the sun's position influenced the pattern of submarine polarization at all depths so far studied, including 200 m, the deepest of the present stations, and the shallow water observations made previously. The optical effects involved here were (1) the angle of refraction of the incident rays of sunlight and (2) the apparent origin of underwater polarization from primary Rayleigh scattering of directional light beams, which causes the polarization plane to be normal to the angle of refraction.
Station No. 11
Sun's altitude: 51° 40'
Angle of sunlight incidence: 38°
Depth of measurements : 200 m
Table II 13°07'N, 59°53'W.
Dec. 2, 1954
Sun's azimuth: 201°
Calculated angle of refraction: 27^
Depth to bottom:
|
Direction relative to sun's bearing |
0° |
90= |
180° |
270° |
|
Tilt of polarization plane Exposure # 1 #2 #3 |
0° 0-5° left 1° left |
7-5' left 7-5= left 7 0' left |
0° 0° |
11° right 7-5° right 8-5° right |
|
Average |
0-5° left |
7-3' left |
0 |
9 0° right |
This effect was certainly predominant in shallow water. It was also at the 30 m station (No. 8) in the present series (Fig. 2). Here the tilt of the polarization plane averaged 43° for lines of sight normal to the sun's bearing. This angle was almost identical with the corresponding angle of refraction (42°) calculated from the observed solar altitude, assuming a refractive index for the water of 1 -34.
Such an effect of the sun's altitude, and hence the angle of refraction of sunlight entering the water, must also be involved in the plane of polarization at greater depths, too. Yet the present data do not afford much direct evidence for this since repeated measurements were not made systematically at the same depth with different solar altitudes. However, in the single satisfactory case where such a comparison can be made, strong support for this generalization is found. This comes from the data of stations 7 and 10, both at 150 m.
Here the angles of refraction of sunlight, computed from the sun's elevations, were not the same because of the different times of day when the two sets of photographs were made. It will be seen in Table III that the deviations of the polarization planes
Fig. 1. Interference patterns formed by the analyzer when traversed by polarized light. A. Kigua- produced by circularly polarized light having a counterclockwise rotation; if its rotation \scre ckvk- wise, the pattern would have a dark centre instead of a light one. B. Figure obserNed with imcariv polarized light produced by a type Fi Polaroid filter. The interruptions in the isochromatic rings are parallel to the electric and magnetic vectors of the incident light. The plane of the c vector is hori- zontal, as labelled, and coincides with the clockwise edge of the dark central sectors.
Fig. 2. Interference patterns formed by natural light underwater at 30 m depth (station 8). The analyzer and camera were directed horizontally in azimuths of (A) 0\ (B) 90 , (C) 180 , and (D) 270° relative to the sun's bearing. The scattered sunlight is seen to be linearly polarized in all cases, with the polarization apparently weakest at 0 (A) and stronger particularly at 90 (B) and 270 (D). The planes of polarization (angles between plane of light vibration relative to the horizontal) measured in uncropped prints where the film frames provide the vertical and horizontal references were: {A) 8-5" tilt toward the right, (B) 42-5' left, (C) 4 right and (D) 43' right. Exposures: ^> sec, f/4,
Tri-X film. Sun's altitude 26°.
Fis. 3.
,„,c,rercnce pa,.er„s formed by na.un,, IjS'i' rlrJ^Sc^'^.^^K^nS-Sf in'
co.P.e. .... . ^^!,;BfEBE^-^^t^^^^MB
; lor I he
j/inuiihs
stx'n
of(/l)0 ,(fi)90 ,(0 180 and(Z))
to be linearly polarized in all cases ■
directions. Implied by the extent a..^ ""- f \,,
considerable even at this depth. The P'-^"^^ °' P^'.j jms Nvhcrc me - . „^ .
vibration and the horizontal) "leasurcd in uncroppccij^^ ^ \,(uU)0 (no till) and
vertical and honzontal refe^^^^ ^ .-g. Tri-X film. Sun's altitude 52 .
Polarization of scaltered sunlight in deep water
4U
from horizontal were correspondingly diflercnt even though ihcy do not agree numerically with the angles of refraction. Note, however, that the ratios of the observed angles to the calculated ones were more nearly alike. In other words, the observed angles of polarization deviated significantly from those calculated simply on the basis of surface refraction. This introduces the second pomt illustrated by Tables I, II, and Figs. 2, 3.
The second point is the effect of depth per se on the tilt of the polarization plane independent of the solar altitude. This influence was obvious in the data of all the stations deeper than 30 m. At 200 m (Table II), for example, the average tilt of the polarization plane 90° from the sun's azimuth was 8", which was only 30% of the angle of refraction of the sunlight at the surface when the photographs were made. For the stations at intermediate depths, the tilt of the polarization plane was also intermediate, being significantly less than the angle of refraction yet considerably larger than the tilt found at 200 m.
|
Tahle III |
||||
|
Station |
Suns altitude |
Calculated angle oj refraction (r) |
Polarization tilt(p) |
pr\ |
|
1 10 |
51- |
40° 27= |
15-5 11^ |
39% 43°, |
DISCUSSION
The new facts which have been presented above are mainly of interest for two reasons. One is their possible usefulness in solving physical optic problems relating to underwater polarization in particular and to light penetration in general. The other is their potential helpfulness in evaluating the biological importance of submarine polarization patterns.
With relation to the first point, it is interesting that two of the main findings reported here were predicted on a theoretical basis before the present measurements were made (Waterman, 1954 a). These were (I) that polarized light would occur down to consider- able depths in the sea, probably as far as the lower limits of the photic zone, and (2) that with increasing depth the influence of the sun's position on the pattern of polariza- tion would gradually diminish in the upper few hundred metres after which it would be negligible. Both of these effects were clearly apparent in the present data ; although at the maximum depth tested, 200 m, the sun's position still had considerable effect, it was only about a third of what it would have been near the surface.
Note that these predictions were made on the assumption that Rayleigh scattenng of unpolarized directional light in the water was the basis of the primary underwater polarization pattern and on the currently accepted ideas about the directionality o\ deep-water illumination (Whitney, 1941; Poole, 1945; Jhrlov. 1951). The tact that the deep polarization as it was actually found matched the predictions m these respects is in turn putative evidence for the validity of these elements in the original
analysis.
One might go a step further here and point out that, when the submarine polariza- tion pattern itself is understood more thoroughly, instrumentation and methods like those used in this work might be a convenient way to study the general problems of
434 Talbot H. Waterman
directionality and scattering of light under water. For instance, one might study the refractive effect of abrupt density changes where these are inaccessible for direct observation (Limbaugh and Rechnitzer, 1955).
As to their biological interest, the present results would seem to be significant because they greatly extend the known regions in which those animals whose eyes are sensitive to them might detect natural patterns of underwater polarization. This would now seem to be indicated for a good part, if not all, of the photic zone. Similarly, the possibility of some sort of a polarized light sun compass, comparable to that used in the sky by bees, and other animals, has been extended under water at least to 200 m, since changes in the sun's position result in corresponding modifications of the polarization pattern that far down.
Of the several fields in which further research on the subject of underwater polariza- tion and its significance may be profitable, the most interesting one related to the present deep-sea work would be the possibility of making measurements at still greater depths. Since a 20 sec exposure at f/2-8 was required to photograph the interference pattern at 200 m, the present method was being pushed close to its reason- able limit. This is obvious from the fact that the light energy penetrating the water mass would probably be reduced to 0-1 its value at 200 m by an additional 40-50 m of water. Hence to go from 200 m to 300 m would require 100 x as much time for comparable negative densities!
On the other hand, since directionality of penetrating light is maintained to the lower limit of the photic zone, even though obliquity is decreased eventually to zero, somewhat deeper measurements should be possible if the polarization pattern were photographed in an upward direction. At least the light intensity would be greater to a degree dependent on the relation between scattering and absorption in the water mass concerned (Pettit, 1936; Atkins and Poole, 1952). However, the percent polarization due to Rayleigh scattering would approach zero along the axis of the directional light beam so that the interference figure would become weak or disappear.
In any case it would be desirable to attempt such measurements and discover which of the various factors are actually critical under these circumstances. The presence of upwardly directed " telescopic " eyes in some bathypelagic fishes like Opistho- proctus and Argyropelecus is suggestive of the biological importance of vertical illumin- ation in deep water.
REFERENCES
Atkins, W. R. G. and Poole, H. H. (1952), An experimental study of the scattering of light by natural
waters. Proc. Roy. Soc, London, B, 140, 321-338. Clarke, G. L. (1941), Observations on transparency in the southwestern section of the North Atlantic
Ocean. /. Mar. Res., 4, 221-230. Jerlov, N. G. (1951), Optical studies of ocean waters. Rept. Swedish Deep-Sea Exped., 1947-1948,
3 (1), 1-59. ....
Limbaugh, C. and Rechnitzer, A. B. (1955), Visual detection of temperature-density discontmuities
in water by diving. Science, 121, 395-396. PExnT, E. (1936), On the color of Crater Lake water. Proc. Nat. Acad. Sci., 22, 139-146. Poole, H. H. (1945), The angular distribution of submarine daylight in deep water. Sci. Proc, Roy.
Dublin Sac, 24, 29^2. Waterman, T. H. (1950), A light polarization analyzer in the compound eye of Limulus. Science,
111, 252-254. Waterman, T. H. (1954 a), Polarization patterns in submarine illumination. Science, 120, 927-932. Waterman, T. H. (1954 b). Polarized light and the angle of stimulus incidence in the compound eye
of Limulus. Proc. Nat. Acad. Sci., 40, 258-262. Whttney, L. V. (1941), The angular distribution of characteristic diffuse light in natural waters
J. Mar. Res., 4, 122-131.
Papers in Marine Biology and Oceanography, Suppl. lo vol, 3 of Decp-Sea Research, pp. 4.15-437
Elevation of sea level caused by wind in a rectangular channel
By Walter Hansen
Summary — Inquiries are made into the rise of water level due to wind in a rectangular basin, and comparisons of the results made with observations during the storm surge on the Dutch coast in 1953.
In addition to normal tides, storm surges occur occasionally on the coasts of the North Sea, causing severe damage. In 1953, a storm surge — called the Holhind Hurricane — caused especially serious devastation, not only in the Netherlands but also in Great Britain.
Both scientists and engineers are anxious to learn about the development of such storm surges as effected by the morphology of the sea bottom and the configuration of the coast bounding the respective sea area within the storm field.
Fig. 1. Maximal elevation of the storm
surge of 31 January in the North Sea.
(From RossiTER.)
The following account deals with an experiment to detect the changes of sea level for a given wind field. Only a large-scale survey can be described here; detailed investigations are planned and -thanks to the kindness of Professor Rossby-w.II be carried out on the Besk in Stockholm.
Details of the problem are as follows: . , .- , , u ui
The elevation of water-level produced in a local, constant wind hold, but Nanablc with time, can be numerically ascertained in a rectangular basin corresponding in its position and dimensions approximately to those of the North Sea
The quantitative relation between known and unknown magnitudes is given b> hydrodynamical differential equations. As the configuration ot he ^^ - ; . Coriolis force and friction will be considered, it is not possible to represent the
435
436
Walter Hansen
solution in final analytical form. This is true also if — as is assumed here — there is no mass transport perpendicular to the coast. Likewise the transport of water masses across the northern Umit of the basin has been assumed to be zero. The problem therefore has to be treated numerically. For this purpose a system of differences equations was derived from hydrodynamical differential equations. These make it possible to determine the elevation of sea level due to wind and the components of the transport of the water masses at the points of intersection of a grid spread over the North Sea. Details of this method are given elsewhere (Hansen, 1954).
The grid used has been inserted on Fig. 1 . The wind field, used as a basis, has the same wind direction throughout, parallel to the longer side of the basin. It is assumed that the velocity of the wind is described as a sine function of the time co-ordinate having for all points on the grid the same amplitude and phase. In the numerical calculation, carried out for the values of 0 to tt, related to a time interval of 12 hours, the amplitude of the wind velocity has been chosen as 20 m/sec.
WIND DIRECTION
Fig. 2. Maximal elevation of a storm surge in the North Sea based on theory for a rectangular basin of variable depth
For the tangential stress which the wind exerts on the surface of the sea, the value in SvERDRUP, Johnson and Fleming (1942) of 3-2 x 10"^ x W^ was used, where W(m/sec) stands for the velocity of the wind.
The friction in the water is directly proportional to the current velocity or to the gradient of the surface of the sea.
The accessory value of the friction depends not only on the depth of the water but also on the maximum velocity. For a water depth of 50 m and a velocity of 1 m/sec this has a value of 0-48 X 10"*.
The numerical solution is found by applying the method of differences which has been described in the paper mentioned above.
In Fig. 2, the calculated fines of equal maximum elevation has been inserted. While in the northern part of the basin a trifling fall of water level can be observed, the elevation increases generally towards the south. The higher values in the western parts of the basin are noteworthy, being apparently a result of the Coriofis force as
Elevation of sea level caused by wind in a rectangular channel 437
well as of the depth distribution. In the regions to the east the values are considerably smaller. As the calculation is only a rough one, details of the distribution of elevation are not considered.
Fig. 1 comprises the lines of equal maximum elevation values for the Holland Hurricane from a paper by Rossiter (1954). Groen (1953) in his investigations in general obtained similar results. Both papers are based essentially on the observed elevations of the sea level along the coasts.
The trend of the calculated curve in Fig. 2 coincides in its characteristic features with those given by Rossiter and Groen. The calculated maximum elevation is about 2-0 m, the observed values in this area during the Holland Hurricane being 2-4 m.
REFERENCES
Groen, P. (1953), Voorlopig onderzoek van de waterstanden opgetreden langs de kusten der Noordzce op 31 Jan. en 1 Feb. 1953. Kon. Nederl. Meteovolog. Inst., Afd. Oceanogr. en Marit. Meteoroi,
Hansen,' Walter (1954), tJber ein Verfahren zur Ermittlung der Gestalt der Meeresoberflachc bci
zeitveranderlichem Windfeld. Deutsche Hydrogr. Z., 7 (1/2), 15-22. Rossiter J. R. (1954), The North Sea storm surge of 31 January and 1 February 1953. Phd. Trans.
A, 246 (915), 371-400. , ,.,..,
Sverdrup, H. U., Johnson, M. W. and Fleming, R. H. (1942), The Oceans: their physics, chemistry
and general biology. Prentice-Hall, Inc., New York, 1087 pp.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep- Sea Research, pp. 438-450.
On the breeding areas of the Swordfish {Xiphias)*
By A. Vedel Taning Marine Biological Laboratory, Charlottenlund Slot, Denmark
Summary — The Danish oceanographic expeditions with the Research Steamer Dana and other ships have obtained about 60 postlarval stages of Xiphias (between 5 and 46 mm in length) from all oceans. Most of these, however, were taken in the western North Atlantic.
The distribution of the smallest stages (i.e. smaller than 20 mm in length) indicates that an impor- tant breeding area lies north and northeast of the Lesser Antilles in the southern part of the Sargasso Sea. Breeding areas are also indicated by records of small postlarvae west of Sumatra, in the South China Sea, in the Celebes and Banda Seas and off the Marquesas.
Some spawning occurs during all seasons, but maximal spawning seems to take place during February-April in the North Atlantic. Spawning probably takes place at the same season in the western Pacific, but it occurs later in the year in the Mediterranean owing to the special temperature conditions there. The fry are usually found in water of about 24° C. or higher. They are generally captured between the surface and a depth of about 30 metres. The material at hand seems to show a growth rate of about 8 cms during the first year, but sufficient material is not yet available for an accurate determination of the growth rate. The fry preferably feed on fish larvae up to nearly the same size as the small voracious Xiphias larva itself (Fig. 1). Figures are given of three develop- mental stages and outline charts show where fry have been taken. Fishing for swordfish may be possible (by floating lines) in the main spawning area in the western North Atlantic.
Recently the importance of large oceanic fish has increased commercially as well as in sports fishing. It has therefore become not only desirable, but also possible, to broaden our knowledge of the fish fauna on the high seas. Among these large fish, the swordfish (Xiphias) is the most appreciated by epicures and sportsmen alike. Although landings of this fish have increased greatly in the last generation, our knowledge of this species still leaves much to be desired. Recently, however, Arata (1954) has made a valuable contribution to its biology, including a description of its earliest development. Therefore, detailed description of the various developmental stages is omitted here, but we have included a few figures of them (Fig. 1).
While many pelagic fish are represented by enormous numbers of fry in the material collected by the Dana and other Danish vessels, this is not the case for several of the large species, e.g. the tunny and bill-fish. Thus far, only 500 specimens of the latter have been found in more than 3000 pelagic samples. Some 400 of these belong to the Istiophoridae, and only about 60 to the Xiphiidae.
The reasons that so few specimens are taken in the youngest stages (about 5-45 mm in length) is undoubtedly chiefly due to the fact that the fry of these large predators of the sea are relatively scarce in comparison with the abundance of the fry of smaller species, and to the fact that they very quickly attain a size which enables them to escape the gear (2 or 1^ metre ring net of stramin or coarse silk) generally used by the Dana in catching fish fry. By the time Xiphias fry reach a length of about 12-13 mm, they attain sufficient swimming speed to escape the nets (generally towed at a speed of about 1 metre per second). Thus, only about 20% of the fry caught are over
* Papers from the Dana Oceanographical Collections No. 45.
438
On the breeding areas of the Swordfish (Xiphias)
439
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13 mm in length, and none are over 46 mm. A further reason for the infrequent catches of the fry is that they Uve near the surface. On the Dana expeditions, a ^- metre ring net was usually used in the surface layers rather than a larger one. Even small fry can certainly avoid such a small net. That the fry do indeed frequent the surface layers is also indicated by the fact that the specimens discussed by Chr. LtJTKEN (1880) were collected from a sailing ship at the surface. In addition, most of the 34 Xiphias specimens described by Arata (1954) were small (chiefly 2-3 cm in length), and were taken at the surface in a dipnet during the day. Therefore, in the future some attention should certainly be given to using this or some similar sampUng method to dehmit the areas frequented by Xiphias fry.
As we shall see later, catches of the young stages of Xiphias in the Dana collection presumably were chiefly taken while the nets were being hauled in, especially when these nets, which had no closing device, were fishing the surface layers just before being hauled in over the ship's side. Furthermore the adult swordfish is a solitary creature and never moves in schools. The scattered catches of the young stages sug- gests that this habit may be established very early in development.
So few Xiphias fry have been reported that they provide only a very Umited amount of data for determining the more important spawning areas, the seasonal occurrence, and the vertical and horizontal distribution. Similarly, it is difficult to deduce the relationship between the distribution of the fry and environmental factors. Never- theless, the material at hand does yield more information than has previously been obtained from earUer, more scattered observations. Therefore, I shall outUne the chief points that appear to be indicated by the evidence at hand with the hope that eventually sufficient data will be accumulated to outUne the complete life history of this interesting fish.
The map (Fig. 2) with the locations from which Danish vessels have taken specimens of Xiphias fry shows that the material comes almost exclusively from the area around the West Indies and the southern part of the Sargasso Sea, and from Indo-Malaya. The former area has yielded by far the greater proportion of these since the Sargasso Sea area has been fished especially intensively and at various times of year. The present paper chiefly aims, therefore, to add to our knowledge of the breeding areas of Xiphias in the western part of the North Atlantic.
HORIZONTAL DISTRIBUTION OF FRY
Most of the Xiphias specimens from the western part of the North Atlantic were taken on the expeditions of the Motor Schooner Dana in April- July 1920, and in February-May 1921, furthermore, on the expeditions of the Research Steamer Dana in November-April 1921-1922, and in August 1928. These voyages were under- taken in connection with the investigations of Johs. Schmidt on the breeding areas of the fresh water eel and most of the stations were therefore taken in the Sargasso Sea and adjacent areas.*
We will first consider the distribution of catches of Xiphias fry from this area, and the temperature conditions at the locaUties where they occurred. The captures of
* See list of references for the reports of these expeditions. From these it can be seen how extensive is the network of Dana stations in the Atlantic.
On the breeding areas of the Swordfish {Xiphius)
441
442 A. Vedel Taming
Xiphias in the Sargasso Sea were not in general from the central part of this area where the most concentrated fishing has been carried out and where the young Anguilla larvae have mostly been taken. On the contrary, the specimens were chiefly taken in the southern part of the Sargasso Sea, down toward and among the West Indian islands and thence northeastward. This distribution is clearly illustrated along the track of the Motor Schooner Dana in 1921 (Fig. 3). The ship left St. Thomas late in February and surveyed the area between about 20° N and 30° N and 45° W to about 67° W until mid-May. No Xiphias fry were taken north of 23° 10' N, but catches were made at almost all of the southern stations. These extended over the entire section fished between about 45° W and 67° W. At those stations, where the majority of the catches were made, the surface temperatures were about 25° C or more. At two stations, it was 24° C and at only one was it as low as 23-5° C. This locaUty was not far from an area where the temperatures were 24° C. Fig. 3 shows the positions of the catches in relation to the surface isotherms for 24° C and 25° C. The preceding year (1920), when the Motor Schooner Dana left the Mediterranean for this area in late April, Xiphias fry were taken as soon as the ship entered water where the surface temperatures were more than 24° C. Then, due to a leak, the schooner was forced to go directly to St. Thomas without making further observa- tions, and could not return to the area before June. At that time, the surface tem- peratures were 25° C or higher over almost the entire area under consideration, north to about 35° N Lat. (Fig. 4). Despite numerous stations mainly north of 27° N Lat., only a very few Xiphias fry were taken in that area, the northernmost being at 26° 19' N Lat. Therefore, the swordfish's principal spawning season in this area seems to be over by early summer (June).
During the winter of 1921-1922, the Research Steamer Dana was in this part of the Atlantic with headquarters at St. Thomas and St. Croix. The ship left the Cape Verde Islands on 3 November heading for French Guiana. It arrived at Barbados on 22 November and proceeded among the Lesser Antilles to a locaUty east of Bar- buda before the first Xiphias fry were caught. Since the surface temperatures through- out the area across the Atlantic to Barbuda were between 25° C and 29° C, tem- perature is not the only factor which Umits the distribution of the fry. In December, the vessel worked in the vicinity of St. Croix and then in January on her return from the Pacific (through the Panama Canal), she continued around Cuba to Florida, Haiti and back to St. Croix for further work in that area during March and April. Fishing with pelagic nets was particularly carried out at a locaUty just west of St. Croix, and here 20 specimens of Xiphias fry, chiefly early stages of 5-10 mm, were caught. Some few specimens were caught in other parts of the West Indies area. It may be that the connection with the open Atlantic through the Anegada Passage has something to do with the frequent presence of fry in this particular area. Later in April, the vessel continued into the central portion of the Sargasso Sea, but no Xiphias fry were taken there.
In 1928, on the world cruise, the Dana went from the Mediterraenean across the Atlantic towards Panama. In the middle of August, the ship passed through the area where most of the Xiphias fry had previously been caught. There the Dana again caught Xiphias fry at every station. Of eight specimens captured, half were 17-46 mm in length and half 6-10 mm. The surface temperatures at this time ranged from 27°-28° C. No more specimens were taken, however, after entering the Caribbean.
On the breeding areas of the Swordtish (Xipliias)
443
In 1911, and for many years thereafter, Johs. Schmidt arranged with various Dan- ish merchant vessels as well as with the Schooner Mari^rethe to fish for ccl larvae with pelagic nets, especially in the surface layers of the Atlantic. Later, from 1929 to 1938, the collecting was extended to the Pacific. A few Xiphias fry were found in these samples. These individuals were all taken in the area outlined above, i.e. in the especially warm parts of the western Atlantic where there are high temperatures down to a depth of at least 100 metres. When all the Danish records together with the locahties for Xiphias fry given by Arata (1954) and by Lutken (1880) in the Atlantic Ocean are plotted (Fig. 2), it is obvious that the portion of the western Atlantic just described, and parts of the Caribbean, must be considered as the most important spawning area for this species in the North Atlantic. Thus, all of Arata's and some of LUtken's specimens came from the western Atlantic and Caribbean. Lutken's specimens in the Zoological Museum, Copenhagen, range from 10 to 51 mm in length, but only one is smaller than 20 mm in length.
Fig. 3. Records of Xiphias postlarvae obtained during the cruise, February-May 1921 • positive stations, • negative stations. Surface isotherms for 24° C and 25'' C indicated.
Despite the extensive collecting by the Dana in the Indo-Pacific, especially in the Marquesas-Fiji area, north of New Guinea, Malaya, west of Sumatra and in the Madagascar area, only very few specimens were found (a total of seven specimens. 4-9-17-1 mm in length). These were Hmited to the area west of Sumatra, the South China, Celebes and Banda Seas and off the Marquesas. Lutken (1880) also mentions a few catches from a merchant ship (commanded by Captain A. F. Andrea) trom the Reunion area (Fig. 2), the lengths of three of these specimens (preserved in the Zoological Museum, Copenhagen) are 29-0, 29-5 and 44-5 mm. In addition to these, fry are known in the Pacific, from the North Equatorial Current and trom the kuro- shio Current (Yabe, 1951; Nakamura, 1951). We know of no other records ot try from the Atlantic or Pacific Oceans. Therefore, the boundaries ot the breeding areas in these waters cannot be more sharply defined until more specimens are obtained.
444
A. Vedel Taming
SEASONAL DISTRIBUTION OF FRY
Southwestern North Atlantic. To find the breeding areas of a species, the smallest larval stages are the most important, because these are carried by currents alone for comparatively short distances from the spawning area itself. Therefore we will consider only those specimens in postlarval stages smaller than 20 mm in length, in examining the seasonal distribution. As shown below, it is unUkely that any of the postlarval stages were taken in depths greater than 200 metres. Certainly they belong to the warmest, upper water layers, so that we need only consider the nets which fished with 600 metres of wire out or less, because these nets undoubtedly fished only in the upper 200 metres of the sea.
Since various sizes of nets were used, the fishing time was calculated as the number of hours a stramin ring-net 2-metres in diameter was towed.* In the areas where all
Fig. 4. Records of Xiphias postlarvae obtained during the cruise, April-July 1920. • positive stations, • negative stations. Areas with surface temperatures below 24° C indicated.
the catches were made in the western North Atlantic Ocean, namely in the Carib- bean Sea and that part of the Sargasso Sea between 15° N and 30° N and west of 40° W, there have been about 1690 2-metre-stramin-net hours fishing in the upper 200 metres of the sea.
From Table I, it can be seen that the postlarval stages smaller than 20 mm in length, which are mostly less than a month old, occur practically throughout the year. Even the smallest postlarval stages of 5-8 mm in length are found in nearly every month of the year. With so httle material, no definite estimate of a peak season can be given. However, omitting the catches for July-September, when Httle fishing was under- taken in the area, and considering only those months when more than 100 hours or more of fishing actually took place, one notices that the biggest catches occurred in February-March- April. The preceding months show a consistent increase towards
*One hour's fishing with this gear (S200) is calculated as equal to 2 hours with a U m stramin net (S150) or silk net (P150), and to 4 hours with a 1 m stramin net (SlOO) or silk net (PlOO).
On the breeding areas of the Swordfish (Xiphiax) 445
this maximum, while there is a decline in May through June. Thus, even if Xiphias breeds throughout the year in this tropical area, analysis of the data in this way sug- gests that the maximum is from February to April. Arata (1954, pp. 234 239), on the other hand, from his own records and those of others which note the appearance of the fry or of mature specimens, concludes that the peak of the spawning season off Florida and Georgia is from April through September. In this connection, it should be noted that our data too indicate the presence of a large number in August (Table I). However, this figure is due to the fact that the Dana, on her passage through the southern part of the Sargasso Sea in 1928, chanced on six small specimens in postlarval stages and two a little larger (33-0 and 46-3 mm in length) at the three stations in that area. Consequently, it seems possible that this particular year was an unusually favourable one for the reproduction of this species.
It should be stressed here that the area where the fry discussed in this paper were found must be one of the species' chief spawning areas, because equally intensive fishing in adjacent areas to the north and east was carried out from Danish vessels
Table I The monthly distribution of catches and number of specimens in postlarval stages less than 20 mm in length per 100 hours of fishing
Month I II III IV V VI VII VIII IX X XI XII Total
No. hrs.
fishing 45 156 274 365 164 214 44 20 4 113 61 216 1690
No. post- larvae
<20mm 1 6 12 14 0 I 2 6 0 1 I 5 49
No. per 100 hrs. fishing 2-3 4-6 4-4 40 0 0-5 4-5 300 0 0-9 15 2? '0
using the same type of gear without taking a single postlarval specimen. Although the area southeast of the main area was fished less intensively, it was sampled rather adequately without finding a single specimen. LUtken (1880) mentions some catches (undated) of specimens in young stages, some as small as 2 cm in length, taken with drag nets at the surface from sailing ships in the centre of the tropical-subtropical Atlantic, Hence, we know that the species must also breed there as well. Undoubtedly, spawning is much more scattered there than in the area delimited by the Danish surveys. Thus, when the Dana crossed from Capetown to the Canary Islands via St. Helena-Freetown in February-March 1930, no Xiphias larvae were taken there despite intensive fishing. In any event, this does not seem to have been the n^^ht season to find them in this part of the eastern tropical-subtropical Atlantic.
Mediterranean. In the Mediterranean, where environmental conditions are suitable for the development of a rather sizeable stock of Xiphias. only a single \tphias larva has been found to date in the Danish collections. It was taken in the Balearic Sea off Algiers in late September. At Messina (Sella, 1911 ; Sanzo, 1922; 1930), this species breeds in the summer (June-August) at a time when the surface temperatures
446
A. Vedel Taning
become high enough ( > 23°-24° C). Consequently, it is most pecuUar that post- larval specimens were not taken during the Thor expedition in 1910, since consider- able fishing was carried out with pelagic gear in July-August and in early September.
Indo-Pacific. The Dana in 1928-29 carried out approximately 1650 hours of pelagic fishing in the surface layers down to roughly 200 metres over wide areas of the Indo- Pacific (Fig. 2). Almost all of the tows were made in areas where the water tempera- tures were within the limits usual during spawning of this species. Nevertheless, only a few young specimens were taken there. These provide a very incomplete picture of the breeding areas and seasonal distribution. Except for a single specimen near the Marquesas Islands in late September, all of the others are from the Indo-Malaya region during the months of March, April, June, September and November or practically throughout the year.
As mentioned earUer, Lutken's specimens are undated so that they do not help to clarify this point. However, the postlarval specimens of 11-27 mm in length from the western Pacific mentioned by Yabe and Nakamura were taken from March to May. Consequently, the season seems to correspond to that of the western Atlantic.
VERTICAL DISTRIBUTION OF FRY
It has already been noted that all the evidence points to the fact that the fry are generally found in the uppermost water layers over deep water. The distribution also suggests some connection with island areas (i.e. West Indies, Indo-Malaya, East China Sea, Mediterranean). The reason may be that there is more food in such areas than in the open ocean. Since we only have any significant number of Xiphias fry from the western part of the North Atlantic, as previously pointed out, we will delimit the water layers where the fry were taken in that area and consider the size differences at various depths. The material included only two specimens over 2 cm in length : one 33 mm in length, which was taken in a net which was fished at a depth of approximately 30 metres, and one 46-3 mm in length which was taken in a dipnet at night with a light. Therefore our discussion of vertical distribution will include only a consideration of specimens of less than 2 cm in length.
The 53 specimens ( < approximately 20 mm) caught in this area of the Atlantic were taken in 43 hauls of the pelagic net. The number per tow was 1 specimen in
Table II Distribution of Xiphias fry according to number and size of specimens and
the depth of towing
|
Metres of |
Approximate |
No. of |
No. of |
No. of |
Size |
Average |
|
wire out |
depth of |
specimens |
firs* |
specimens |
range |
size in |
|
capture |
< 20 mm |
fishing |
per 10 hrs |
in mm |
mm |
|
|
in metres |
fishing |
|||||
|
Surface-65 |
0-ca. 20 |
16 |
61 |
2-6 |
5-9-16-3 |
8-5 |
|
80-100 |
ca. 30 |
20 |
61 |
3-3 |
5-8-18-6 |
9-7 |
|
150-200 |
ca. 50-70 |
5 |
35 |
1-4 |
6-3-18-2 |
10-6 |
|
300-600 |
ca. 100-200 |
8 |
110 |
0-7 |
5-7-200 |
11-2 |
|
700-5000 |
>ca. 230 |
4 |
75 |
0-5 |
5-6-15-6 |
10-7 |
* See p. 444 and footnote on that page for method of calculating fishing hours. The number of fishing hours includes only those stations where specimens were taken.
On the breeding areas of the Swordfish {Xiphias) 447
35 hauls, 2 in 7 hauls,- and 5 in 1 haul, fished at approximately 30 metres. It was exceptional therefore for more than one specimen to be taken in a haul. This indicates that the fry are scattered, and that they often may be captured when the net is bcmg drawn in. From Table II, it appears that the postlarval stages are to be found chiefly in the upper 30 metres. Furthermore, the smallest specimens of 5-6 mm in length were taken in nets which fished for one or more hours at depths down to more than 230 metres. Hence, it is hkely that the great majority, perhaps all, of the smaller specimens taken in the nets which were towed rather deep below the surface were actually caught when the nets were being drawn in.
The specimens taken in nets towed in the upper 30 metres were on the average the smallest. This may mean, as it does for the postlarval stages of many other oceanic species, that larger specimens are found deeper than the smaller ones. The latter, we must assume, remain chiefly at the surface where the pelagic eggs presumably float. The small size of our nets and the fact that these were not closing nets makes it im- possible, however, to reach any final conclusion on this point. Lutken's and Arata's findings show, however, that the fry do not avoid strong sunlight in the uppermost layers of the sea. They found postlarval stages of 10 mm and up to 5-8 cm at the surface both during the day and at night. Thus, Lutken has. as already mentioned, records from the Atlantic and Indian Ocean (Fig. 2) taken with a drag-net at the sur- face. Arata's series of postlarval specimens and of the adolescent stages of 6-3-80-9 mm from the Gulf of Mexico and Straits of Florida were for the most part taken at the surface in dip-nets. For the time being, it is not possible to determine whether most of the postlarval stages live just below the surface or whether they live somewhat deeper, perhaps within the upper 30 metres.
The few Danish specimens of Xiphias from the Indo-Pacific show a vertical dis- tribution similar to that in the Atlantic. Two specimens were taken with 50 metres of wire out, one with 100 metres of wire out, three with 200 metres of wire out and one with 350 metres of wire out. This means that they were from depths of 15-100 metres, unless they were captured when the gear was being hauled in. The size of the specimens ranged from 4-9 to 17-1 mm in length.
ENVIRONMENTAL FACTORS AND THE DISTRIBUTION OF THE FRY Temperature. The influence of temperature on the distribution of the fry was des- cribed above. It is clear that, in the breeding season, Xiphias seeks tropical or sub- tropical areas with high surface temperatures. Although the species migrates far north or south in northern or southern summers respectively, to feed where the water masses have temperatures as low as 12°-13°C or a little lower," during the breeding season it must migrate to areas where the temperatures are not lower than 23-5° C, more especially in water with temperatures between 25' and about 29 C. as shown by the fact that most fry have been taken at localities where the tempera- tures were within these hmits. Presumably Xiphias remains close to the surface during spawning, but there is no definite information on this point. Since the tem- perature at depths of 75-125 m is less than 23^ C at all localities where small
=:< In one of these hauls from roughly 30 metres depth, one specimen was taken together with the 33 mm-specimen mentioned above. The latter is not included m the table.
t Since Xiphias remains in the Mediterranean throughout the year, it must be able to surMvc m water of 13° C, for the whole water mass falls as low as this m wmter.
448 ^- Vedel Taning
post-larval stages have been taken, we may assume that the spawning fish do not go any deeper.
In the southwestern North Atlantic Ocean surface temperatures between about 23-5° C and 28-1° C have been encountered at all localities where postlarval stages have been taken. Surface temperatures of 24-5°-25-5° C are found during the breed- ing season from February-April, and this temperature seems accordingly to be the actual lowest spawning temperature. With the approach of summer the temperature rises to 27° to 28° C or a httle higher, and then about October it begins to fall again to about 25° C.
In the Mediterranean Sea, the surface temperature where the one postlarva was taken was 23-8° C (late September). As already mentioned, spawning apparently takes place in the Mediterranean much later in the year than in the West Indies. The reason for this is apparently that the temperatures favourable for spawning are not high enough until somewhat later (in August it is about 23-3° C-26-5° C).
In Indo-Malaya, the surface temperature at the places where postlarval specimens were taken was generally higher than in the Atlantic (namely about 28°-29° C). In the Pacific at the Marquesas it was however only about 26° C.
Salinity. Young fry are known to exist at localities where the surface sahnities range between about 33'8°/oo and 37-4°/oo; but the adult fish is found at very different salinities, e.g. at 39°/oo in the Mediterranean and at 6°/oo in the Baltic. The species thus tolerates a wide range of salinities, but it is not possible with the material at hand to determine any correlation between salinity and the breeding habits of Xiphias, other than that the salinity must apparently be higher than 34-00°/oo- Thus, in the general area of the Caribbean, most of the fry have been taken in water with salinities of about 35-9°/oo-36'7°/oo and in Indo-Malaya of about 33-9°/oo-35-5°/oo.
Light. Since fry up to 4-5 cm in length have been taken at the surface of tropical seas on clear, sunht days, and have also been taken there at night with artificial light, this species lives close to the surface under varying light conditions in a manner contrary to many other oceanic species. It is not definitely known how deep they can live and thrive.
GROWTH AND FOOD
Very httle is known about the growth of the swordfish. So far as I am aware, no one has made age analyses from the bones or otohths even in areas such as the Mediterranean where small specimens are regularly caught. Sanzo (1922) has reported on the growth under laboratory conditions of newly hatched larvae for a period of ten days.
A review of the postlarval specimens from West Indian waters (Arata's and the Danish material combined), although based on fewer than 100 specimens, gives some indication of the growth rate (Table III). Although the method of collection was not the same and the intensity of fishing varied from month to month, it appears that spawning as already mentioned is particularly intense during the early spring. Table III seems to give a rather clear indication of the growth from the early stages (about 8 mm) in March-April to rather larger fry (approximately 23 mm) in July, and to fry of about 70 mm in length by the next spring. To what extent the latter represent the smallest of a larger and far more numerous 1-year group cannot be determined without more material. If specimens of 5-8 cm are representative of the 1-year olds,
On the breeding areas of the Swordfish (Xip/,ia.,) 44^
a specimen taken in May of 192 mm (Arata, 1954) should be about 2 years old Th,s appears however to be far too slow a growth rate for a voracious species such as the swordfish. Unfortunately, Nakamura (1951) did not record the nK-asuremcnts of a rather large number of individuals of roughly this size found in the stomach contents of spearfish, measurements which would have provided some useful supple- mentary data on the growth rate of Xiphias. No further information is available on the growth although it is probably very fast, for such a predator, which, in the Pacific may weigh up to 680 kgs.
The
Table HI size of swordfish fry in different months based on the data 0/ Arata (1954)
and the Danish material
Size mm
Month
I If III IV V VI VII VIII IX X XI XII I II III n y y,
80-84 75-79 70-74 65-69 60-64 55-59 50-54 45-49 40-44 35-39 30-34 25-29 20-24 15-19 10-14 5-9
I
2 1
2 2 3
2 9 13
I
3 3 9 1
2 2
1 1 2 1 2
I I
The stomach contents of young stages indicate that the fry in the postlarval stages very soon progress from a copepod to a pure fish diet. Indeed, they often prey on close relatives (Arata, 1954). To show how greedy this species is even in very early stages, we need only refer to Fig. I. It shows a postlarval specimen of about 8 mm which has swallowed another fish larva, almost as large, so that the specimen appears to have eyes at both ends. The prey was swallowed head first. This was also the case in three other Xiphias specimens from the same haul with the prey in various stages of digestion. This exceptional catch of 5 postlarval specimens of 7-9 mm in one net, four of which were stuffed with food, suggests that they had become sluggish as a consequence. Thus, this may explain why so many were taken at one time. Normally, the majority would have escaped the net. Thus, it appears that even such small individuals must be very swift swimmers.
From our study, it is apparent how little is known of the breeding places, although it is clear that spawning takes place over all oceans where the surface temperatures are more than 23^-24' C. Little is known of the fry's migration away from the principal breeding areas and of the mature fish's migrations except in certain coastal areas. For example, it is not known whence come the migrants to northwest Euro- pean waters during the summer and fall months, whether from the stock in the vicinity of the Iberian peninsula and the Mediterranean or from that of the western Atlantic.
450 ^- Vedel Taning
With the development of fisheries for large pelagic, predatory species out on the open ocean, it is conceivable that a fishery can be developed in the chief Atlantic spawning area (floating line fishery).
In this and other areas of the open ocean there are also spawning places of other large pelagic fish. The closely related family of the Istiophorids is found in rather large numbers — we have over 400 postlarval specimens from all seas — in the same areas as Xiphias as well as over a large part of the Sargasso Sea. In contrast to Xiphias, we have however found numerous Istiophorids in the Madagascar area and many west of Sumatra. Otherwise there were relatively few Istiophorids in Indo-Malaya. As for Xiphias, the Istiophorids fry were totally absent in an area just north of New Guinea which has been intensively surveyed. The hydrographic conditions there gives no clue as to the reason for this. In the Samoa-Fiji area, there were a number of Istiophorid fry, but none of Xiphias.
From the above it becomes clear that, despite the extensive surveys of the Danish Oceanographic Investigations, relatively Httle has been learned of the life history of these large oceanic fish. Real progress on these problems can only be made with greater co-operation among the research organizations of the world. Thus, much useful information might be obtained with only a few extra hours of work in areas from which we have no records. It should moreover be noted that other fast pre- datory fish {Coryphaena, Istiophorus, etc.) are better able to catch fry which swim as swiftly as the Xiphias fry than is man. Collection of stomach contents of large pre- datory fish should accordingly always be carried out when possible.
REFERENCES
Arata, G. F., Jr. (1954), A contribution to the life history of the swordfish, Xiphias gladius Linnaeus,
from the south coast of the United States and the Gulf of Mexico. Bull. Mar. Sci., Gulf and
Caribbean, 4 (3), 183-243. BiGELOW, H. B. and Schroeder, W. C. (1953), Fishes of the Gulf of Maine. Fish. Bull., U.S. Fish
and Wildlife Service, (Fish. Bull. 74), 53, 1-577. Carlsberg Foundation (1934), Introduction to the reports from the Carlsberg Foundation's
Oceanographical Expedition Round the World, 1928-30. Dana-Rept. 1, 1-78. GooDE, G. B. (1883), Materials for a history of the swordfish. Rept. U.S. Comm. Fish and Fish, for
1880, 289-394. La Monte, F. (1944), Note on breeding grounds of blue marlin and swordfish off Cuba. Copeia,
1944, (4), 258. LiJTKEN, Chr. (1880), Spolia Atlantica. Bidrag til Kundskab om Formforandringer hos Fiske under
deres Voext og Udvikling, soerligt hos nogle af Atlanterhavets H0js0fiske. Vidensk. Selsk. Skr.
(5), 12, 441-447. Nakamura, H. (1951), Notes on the life history of the swordfish, Xiphias gladius Linnaeus. Japanese
J.Ichthyol. 1 r4), 264-271. Sanzo, L. (1922), Uova e larve di Xiphias gladius L. Mem. R. Com. Talassograf. Ital., 79, 1-17. Sanzo, L. (1930), Giovanissimo stadio larvale di Xiphias gladius L. di mm. 6, 4. Mem. R. Com.
Talassograf Ital., 170, 1-8. Schmidt, Johs. (1912), Introduction. Rept. Danish Ocean. Exped., 1908-1910, to the Mediterranean
and adj. Seas, 1, 1-49. Schmidt, Johs. (1919), Stations in the Atlantic, etc., 1911-15, with two charts and introductory
remarks. Medd. Komm. Havundersegelser, (Fisk.), 5 (7), 1-27. Schmidt, Johs. (1929), Introduction to the oceanographical reports including list of the stations
and hydrographical observations. Danish " Dana '"-Exped., 1920-22, in the N. Atlantic and Gulf
of Panama, Ocean. Repts. No. 1, 1-87. Schott, G. (1912), Geographic des Atlantischen Ozeans. Hamburg, 330 pp. Sella, M. (1911), Contributo alia conoscenza della riproduzione e dello sviluppo del Pesca-Spada
{Xiphias gladius L.). Mem. R. Com. Talassograf. Ital., 2, 1-16. SvERDRUP, H. U., Johnson, M. W. and Fleming, R. H. (1942), The Oceans: their physics, chemistry
and general biology. Prentice-Hall, Inc., New York, 1087 pp. Taning, A. V. (1944), List of supplementary pelagic stations in the Pacific Ocean and the Atlantic,
with an introduction. Dana-Rept. 26, 1-15. Yabe, H. (1951), Larva of the swordfish, Xiphias gladius. Japanese J. Ichthyoi, 1 (4), 260-263.
Papers in Marine Biology and Oceanography, Suppl. lo vol. 3 of Dccp-Sea Research, pp. 451-464
Factors affecting productivity in fertilized salt water*
By W. T. Edmondson Department of Zoology, University of Washington. Seattle 5, Washington
Summary — The response of phytoplankton populations to added nutrients was studied by filling large out-of-door concrete tanks with sea water, and adding phosphate and nitrate. In general there was an immediate increase in photosynthesis and in growth of the population. In some cases. but not all, addition of phosphate alone was ineffective.
A large part of the variation in photosynthetic rate over a 40-day period is attributable to variation in the amount of light falUng on the tanks, in the chlorophyll content of the phytoplankton. and m the phosphate concentration in the water. Large variations in the qualitative composition of the population had no apparent effect on this relation. The efficiency of the population in using light varied directly with the amount of fertilizer added, but not in proportion to it. Addition of nutrients to the bottles in which measurements of photosynthesis were made permitted evaluation of limiting factors.
The rate of phosphorus absorption, measured either as decrease of phosphate in the water or increase of phosphorus in particulate form, was directly related to the rate of photosynthesis.
INTRODUCTION
The STUDY of phytoplankton production in fresh and salt waters has been hampered by a paucity of experimental techniques applicable to large bodies of water; it is difficult enough to make the necessary observations. The invention of the suspended bottle method of measuring population growth and photosynthesis (Whippll, 1896. Gaarder and Gran, 1927) was a long step forward, but it is desirable that techniques be invented and improved to the extent that various population functions can be effectively studied beyond the hmits set by observation alone. Knowledge of algal physiology is at present too limited to permit widespread ecological prediction of the detailed behaviour of populations. Enough is known of the complex relations existing in natural habitats to make it clear that there is a need for developing methods of assessment of the condition of natural populations as they occur, and of the opera- tion of environmental factors. Since large bodies of water are difficult to experiment with, save in the crudest way by mass fertilization, the most promising approach seems to involve manipulation of samples of natural populations. For example. Hutchinson (1941) was able to demonstrate that both nitrate and phospiiate were acting as limiting factors to photosynthesis in Linsley Pond on several occasions by enriching the bottles in which measurements of photosynthesis were bemg made. Nelson and Edmondson (in press) used similar methods with photosynthesis and population growth prdiminary to fertilizing a lake. Lund (1949; 1950) was able to evaluate hmiting and controlling conditions in lakes in detail by such man.pulat,o.i. Furthermore, while the physiological role of chlorophyll has bcc.i elaborately studied, more information is needed on the ecological role of chlorophyll. Various studies have shown that, in a variety of aquatic populations, the rale ot photosynthesis was closely related to the chlorophyll content of the plankton population. .1 proper
* Contribution No. 781 from the Woods Hole Oceanographic Institution.
451
452 W- T- Edmondson
allowance was made for light intensity (Manning and Juday, 1941; review by Ed- mondson, in press).
The present paper is a contribution to the study of these matters. It briefly reports some of the main results of an investigation of the effects of added nutrients upon marine phytoplankton populations growing in large, out-of-door concrete tanks. It is based on the results of three experiments, one in 1947, two in 1948, and reference will be made to them by chronological number. Although several aspects of popula- tion biology were studied, the present paper is limited to a discussion of the effects of added nutrients upon the rate of photosynthesis, and relations with certain factors known to affect this rate. Since the work was undertaken with particular reference to the effect of fertilization on productivity of small bodies of salt water, high con- centrations of nutrients were added. Nevertheless, the general approach is applicable to all aquatic communities including the ocean. The work followed the prehminary experiments by Edmondson and Edmondson (1947).
This is one of a series of investigations carried out at the Woods Hole Oceano- graphic Institution, Massachusetts, under the general supervision of Dr. George L. Clarke. The author expresses his indebtedness to Dr. Clarke and to Dr. C. O'D. ISELiN, then Director of the Institution, for making available an institutional fellow- ship and for support for the work. Thanks are due to Miss Rosemary Hewlett who made all the counts of phytoplankton. Help with the work was received from a number of other persons, particularly Miss Jean Keen, Dr. B. H. Ketchum, Dr. D. M. Pratt, Dr. W. S. von Arx, Mr. Alburt Rosenberg, and my wife, Yvette H. Edmondson. Financial assistance for some of the computation was received from the State of Washington Research Fund in Biology and Medicine (Initiative 171). A grant from the Agnes Anderson Fund of the University of Washington is grate- fully acknowledged.
It is a pleasure to dedicate this paper to Professor Henry B. Bigelow, founder and former director of the Woods Hole Oceanographic Institution.
PROCEDURE
The tanks and most of the procedure and methods have already been described (Edmondson and Edmondson, 1947; Pratt, 1950). In the present experiments, one large concrete tank was divided by wooden partitions into four sections, each containing five cubic metres of water. The tanks were shaded by a whitewashed glass roof in order to reduce the inhibitory effect of full sunlight.
The tanks were filled by pumping sea water through two layers of #10 bolting silk to strain out the larger animals. After varying periods, sodium nitrate or dibasic potassium phosphate or both were added as concentrated tap water solutions, while the tanks were vigorously stirred with an oar. Subsequently, almost daily determinations were made of phytoplankton population, phosphate, oxygen, chlorophyll, light income, rates of photosynthesis and phosphate assimilation. Before each sampling, usually made between 7 and 9 a.m., the tanks were stirred. The morning temperature of the tanks was found to vary little over the entire period of time, and most of the temperatures were between 20 and IT.
Usually there was no attempt to dislodge material from the sides. It was realized that periphyton would grow, but felt that, to achieve interpretable results, most of the work should be limited to the organisms which naturally would be found free in the water, rather than a heterogeneous mixture of plankton and dislodged periphytic organisms. In Experiment 3, the sides of one of the tanks were scraped down daily prior to sampling. This procedure dislodged sessile organisms, and had a profound effect on the phosphorus metabolism of the tank, as described by Pratt (1950).
Since the details of the fertilization are important, the schedule of additions of nutrients is shown (Table I). It will be noticed that in some cases phosphate was added before nitrate, and various time
Factors affecting productivity in fertilized salt water 453
intervals elapsed between additions. The only method uhcd not adequately described in cxisiing publications is that used for measuring light.
An integrating photometer was used. The instrument was designed by Dr. W. S. von Arx and built by Mr. Robert Walden. it consists essentially of a photo-tube mounted under a flat sheet of flashed opal glass and fed by a constant-voltage power supply. The output, which vanes linearly with the incident light, is fed into a condenser. The condenser, upon reaching a pre-detcrmmcd voltage, is discharged by a thyratron tube, actuating a relay which operates a counter. The photo- lube used is RCS #926, which has its maximum sensitivity at 425 ma and is relatively insensitive to red. The condenser was chosen to have a capacity such that the discharge interval is slightly less than one second in the brightest sunlight encountered in Woods Hole during the summer.
The instrument was calibrated in 1947 by comparison with an Fpplcy pyrhcliomctcr mounted on the roof of the Oceanographic Institution at Woods Hole, and early in the summer of 1948 by similar comparison at the Blue Hill Meteorological Observatory. I am indebted to Mr. I. F. Hand for making the latter comparison possible, and Messrs. von Arx, Andrew Bunker, and Kenneth McCasland for the former. Values are given as visible light on the basis that one half the value gi\en by the Eppley pyrheliometer is visible (see Edmondson, in press, for further discussion).
Reference will be made in this paper to the rate of photosynthesis; what was actually measured is the rates of oxygen change in illuminated and covered bottles suspended in the tanks for two-day periods.
Table I Schedule of fertilization in the three experiments. Quantities of nitrogen and phos- phorus are given as microgram atoms per litre
|
1947 |
Experiment 1 |
||||
|
Date |
Tank 1 |
Tank! |
Tank 3 |
Tank 4 |
|
|
July 1 July 2 July 3 August 11 August 18 August 25 |
Tanks filled 0 0 0 5P 0 |
5P 80N IP, I6N 0 0 |
lOP I60N 0 0 5P |
160N lOP IP, 16N 0 0 |
|
|
1948 Experiment 2 |
June 28 Tanks filled
July 2
July 6
5P 5P 5P 5P
80N 80N 80N 80N
1948 Experiment 3
Augus,6 5P 5P 5P.80N 5P. 80N-
August 23 SON 80N 0 0
* Walls of tank 4 were scraped daily.
EFFECT OF FERTILIZATION ON PHOTOSYNTHESIS Bottles were filled and set out for the measurement of photosynthests just before and just after addition of fertilizer. The two sets of bottles were 'h^-^f-; "P-"' ,0 almost identical conditions, the only difference be.ng ,n '^c amount o nut cm. .^s already reported (1947) the addition of such nutr.ents to "j"""' P^P"'' ""^ "^ creases the rate of photosynthesis greatly, as determtned tn '"'^'^^ ""^ ^Z present work, large increases in oxygen production were observed, up to an .n.r.nsc
454
W. T. Edmondson
by a factor of as much as 5 (Fig, 1). It is interesting that the difference in order of addition of nitrogen and phosphorus in Tanks 3 and 4 in Experiment 1 appears to have made a difference in the subsequent behaviour of the populations. Addition of the large amount of phosphate in Tank 3 was not followed by an increase, whereas in Tank 2, a smaller amount of phosphate had doubled the rate. In Tank 4, nitrogen was added first and the subsequent addition of phosphorus had a further effect. The refertihzation of Tank 3 on August 25 was followed by an increase in photosynthesis.
lO AUGUST
Fig. 1. Gross photosynthesis, incident light and chlorophyll in the four tanks. Photosynthesis as mg/l/day of oxygen produced, light as cal/cm^/day of visible light, and chlorophyll as (Jig/1. Note that chlorophyll is plotted on a logarithmic scale. The first two sets of points in the top panel are for bottles filled on July 2 before and after the first fertilization. The histogram at the right of the top panel gives the relative frequency of the rates in the ranges shown.
It was necessary to know whether removal of the population from the open water to the tanks would have an effect aside from the effects of added nutrients. For that reason, in Experiment 2, fertihzation with phosphorus was delayed for four days after filling, and addition of nitrogen delayed another four days. Population density and photosynthesis did not change significantly until after the second fertihzation.
Fertilization was usually followed by an increase in population, but at first the increase was not as great as that in rate of photosynthesis, suggesting that lack of nutrients had been inhibiting the photosynthesis of the individual organisms.
After the initial increase in the rate of photosynthesis following fertihzation, there were large changes in the rate in all four tanks. The changes will be discussed in
Factors affecting productivity in fertilized salt water
455
detail only in Experiment 1. During this experiment, the values varied greatly, from a low of 0-07 mg/l/day of oxygen to a high of 2-50, mean I 07. standard devia- tion 0*55 (Fig. 1). The mean values for the tanks separately for the period ending just before the fertiHzation of August 11 were 0-74, 0-90, 1-30 and 1-29 in order. The diflFerence between Tank 2 and Tank 3 is significant to the 5% level of probability, but that between Tank 1 and Tank 2 is not quite significant. Tank 1 had been intended as a control, but failure of the caulking between Tanks 1 and 2 permitted some ex- change of water. The increase of phosphorus in Tank 1 was 0-69 Mg at 1 .
CHLOROPHYLL /yqm/l
The maximum rate of photosynthesis was reached in hve to twelve days after ferti- lization, and the rate then fluctuated with a general tendency to decrease fhe two Zl h;avily.fertilized tanks remained at a much higher level after the ,n,tK,l max,- mum was achieved.
VARIATIONS IN PHOTOSYNTHESIS
The large variations in photosynthesis may be attributed to variations in both popuaion and environment. The relationship between rate of photosynthes. nd Zol factors known to affect it was analyzed; much °f '^e var,M,on ,n P^.^^ synthesis turned out to be attributable to variations ,n chlorophyll, hght. and ph. phate concentration in the w-r^m details now fo ow^^^ ^ ^ ^^^^^,_
relS :^:X^^^^^^^'- -= --' "^ -"•" -^ ""'"^'^
456
W. T. Edmondson
tended to coincide with periods of high illumination ; nevertheless, the coincidence is not perfect, and many variations in photosynthesis are not related to light (Fig. 1). Obviously, the size of the population must be taken into account, since it showed large variations. The rate of photosynthesis per unit volume of water is the product of the population and the rate per unit of population. Even more pertinent to an explanation of the changes in photosynthesis is the amount of chlorophyll in the population (Fig. 1). After fertilization the population of phytoplankton increased greatly, and with it, chlorophyll. It is seen that the large amount of chlorophyll present in Tanks 3 and 4 during the period of time centred around July 20 partly
CHLOROPHYLL //qm/l
Fig. 3. Photosynthesis per unit of light as a function of chlorophyll concentration. The rates of
photosynthesis shown in Fig. 2 have been divided by the mean light income (cal/cm^/day) during the
period of measurement, and the values multiplied by 1000.
compensated for the much lower light intensity relative to the period around July 13. The generally higher level of photosynthesis in Tanks 3 and 4 is matched by generally higher concentration of chlorophyll. The chlorophyll concentration in Tank 2 achieved a value only slightly more than that obtained in the 1946 experiment with the same amount of fertihzer in an unshaded tank, (erroneously recorded as mg/1 in the 1947 paper).
The relationships just discussed are more clearly visuaUzed if reference is made to correlation graphs (Figs. 2, 3, 4), in which consideration is Hmited to the 90 measure- ments made in the period before the re-fertiHzation on August 11. In the discussion which follows, the conventional correlation coefficient is designated as r^g.
Factors affecting productivity in fertilized
salt water
The following symbols will be used : P Gross rate of photosynthesis, as mg/l/day of oxygen Chlorophyll concentration, as i^gjl Light at surface of tanks, cal/cm2/min of visible light Light at mid-depth of tanks, same units Phosphate concentration, /ng at/1 PIL PIL'
Rate of respiration of the population, mgm/1/day of oxygen Net rate of photosynthesis, P-R
457
C
L
L'
F
P'
P"
R
N
lOO
2^
2 <
X
o o
X a.
CHLOROPHYLL //qm/
Fig. 4. As in Fig. 3, but the values of light used are those at a depth of 50 cm in the water. The
points marked by lines are for periods when diatoms made up less than half the photos>nthctii:
population by volume. The insert at the upper left is a copy of Fleischer's Fig. 7 (sec text).
The simple relationship between photosynthesis and chlorophyll (Fig. 2) is seen to be rather low with a wide range of rate existing at all levels of chlorophyll con- centration (rpc = 0-64). When each value of photosynthetic rate is divided by the corresponding light income, the degree of scatter is considerably reduced (Fig. 3) and the field of points is more nearly linear (r^.^^ ^^ 0-81).
These coefficients show that, under the existing circumstances, a largo part o^ the variation in photosynthesis is closely correlated with variations in but two factors known to have influence, chlorophyll and light, and suggest that chlorophyll was controlling more often than was light.
To give the results in a more complete numerically descriptive form, several hnear regression equations were calculated. Of particular use in these equations is
458 W- T. Edmondson
the standard error of estimate (S.E.E.) which, following Snedecor (1946, p. 117), can be used as a measure of dispersion of the points from the line of best fit, entirely analagous to the standard deviation in a frequency distribution.
It will be of interest to compare the standard errors of estimate of the regression equations with the standard deviation of the rate of photosynthesis, 0-545.
When photosynthesis is taken as a function of chlorophyll concentration alone (Fig. 2), the standard error of estimate is 0-420. When surface Hght intensity is added as a second independent variable, the standard error of estimate is reduced to 0-382 (Fig. 3). The equation relating these variables is P = 0-0172C — 0-0056L - 0-273. Taking further account of the volume of plankton does not decrease variability, but taking account of phosphate concentration reduces the standard error of estimate still further to 0-283. In this analysis, phosphate concentration gives better results than does the rate of phosphate assimilation.
Thus, a large fraction of the deviation from the regression line can be accounted for statistically by variations in chlorophyll, light, and phosphate concentration. (Compare with Riley, Stommel and Bumpus, 1949.) The regression equation which relates these four variables is :
P = 0-0304C + 0-0052L + 0-0275F - 0-239 (S.E.E. 0-28). This equation des- cribes the relationships which existed among the variables during the course of the experiment; but, on the basis of the known physical mechanisms involved, we can regard it additionally as a statement of relative effect of controlUng factors.
The massive doses of phosphate which were added to the tanks do not represent usual concentrations available in natural conditions. Examination of the data shows that a positive relation with phosphate concentration existed only when the entire range of concentration was considered. Within the small range of variation of phos- phate concentration usually met in natural waters, no correlation existed. Each tank behaved somewhat differently from the rest, and the relationships with phosphate concentration in the water are too complex for further discussion in this paper.
The hght intensity to which reference has been made above is that at the surface of the water. Since the transparency of the water changed with the size of the popula- tion, the intensity to which the bottles were exposed is different, and not by a constant ratio. The intensity at a depth of 50 cm was calculated from measurements of trans- parency made by Mr. C. M. Weiss, and used in computing the points shown in Fig. 4, derived from Fig. 3. It is seen that, by taking account of the transparency of the water, the field of points is made more nearly linear and the regression line comes closer to the origin than in Fig. 3. The correlation coefficient r^^c is 0-86. While the difference from rp-^ is not significant statistically, it is distinctly larger. The equation shown in the figure is:
P" = 0-735C + 3-057 (S.E.E. 10-72)
This treatment of the light data is something of an over-simplification, since it implies that there is a direct and hnear correlation between rate of photosynthesis and hght intensity. While the tanks were shaded to prevent inhibition by bright hght, the sun was able to shine in during a small part of the day, and a simple pro- portionahty is not to be expected. However, deviation is not serious, and a more detailed analysis of the available data is not justified. Nevertheless it should be reahzed that a more elaborate treatment of light might result in considerable reduction in
Factors affecting productivity in fertilized salt water 459
the standard error of estimate. The relation of photosynthesis to Hght in natural aquatic populations has been reviewed in some detail by Edmondson (in press).
Because of considerations just discussed, and because certain mflucniial factors were not measured, calculations were made to ascertain how much of the variation might have been ehminated by more rigorous control of conditions. Data published by Fleischer (1935) permit evaluation of variation when measurements of photo- synthesis of pure cultures of Chlorella sp. were taken as a function of chlorophyll concentration under uniform environmental conditions. The amount of chlorophyll in the population was varied by raising the cells in media deficient in one of the nutrients; thus, in the example selected, the past history of the various cultures differed only in the concentration of iron in the medium in which the colls had grown. Otherwise, conditions were uniform, the cells of fairly uniform age being suspended in a standard medium for the measurement of photosynthesis under constant illumina- tion and temperature. Despite the carefully controlled environment, and the presence of only one species, there was variation in the amount of photosynthesis accom- plished by a given amount of chlorophyll. Some of Fleischer's series were somewhat less variable. Measurements made from Fleischer's Fig. 7 shows that the cocflicient of correlation is 0-97. His data are plotted in the insert of Fig. 4, with which they may be directly compared. It has been shown that differences in the age of cultures of Chlorella make a difference in the effectiveness of chlorophyll, as do differences in the culture conditions. (Emerson, Green and Webb, 1940; Winoklr, 1949; Sar- gent, 1940). Thus, with material and conditions very much more uniform than in the tanks, there was a variabiUty which was a relatively large part of that found in the tanks.
EFFECT OF TAXONOMIC COMPOSITION OF POPULATION
The analysis made above takes no account of the qualitative changes in the taxono- mic composition of the populations. It might be expected that, as the specific composi- tion of the plankton changed, there would be consequent changes in the photo- synthetic rate for given amounts of chlorophyll and light. If so, there are two possi-
biUties to discuss.
If the appearance or disappearance of particular forms were to make a large difference in the relationships under discussion, it might be argued that the largest differences would be made by changes in the representation of major taxonomic groups on the basis that, for example, any dinoflagellate is likely to be more like another dinoflagellate in its ecological requirements than a diatom.
There is a second possibility; that is, within each major taxonomic group there may be a wide variation in photosynthetic efficiency or ecological requirements Irom one species to the next. Thus, particular species of diatoms may be ecologically almost equivalent to particular species of dinoflagellates and dilTercnt from other diatoms as far as photosynthetic effectiveness goes. Thus, replacement ol a particular diatom by a dinoflagellate might not result in a measurable change in the relationships discussed, but replacement of the same diatom by another might --' '" '-^^ change Such adaptive radiation within the major groups .s very probable, but data apparently do not exist to permit this question to be decided. There seem to fK no comparative studies of the genera which were prominent in the tank populations
460 ^- T. Edmondson
comparable to Winokur's (1948, 1949) work on eight species of Chlorella, and that stops short of a study of comparative nutrition.
Considerable effort was expended in trying to discern such qualitative sources of variation in the present data. As one approach, the fraction of the volume of phyto- plankton material made up by diatoms was computed. This fraction varied from less than 1 % to 97 % by volume, with the other organisms being a great variety of kinds including dinoflagellates and Chlorella, but there was no discernible tendency for periods of large diatom content to be low or high in the amount of photosynthesis per unit light and chlorophyll. The periods during which the population was com- posed of less than 50% diatoms are indicated by lines attached to the points of Fig. 3. Thus, large variations in the representation of diatoms did not alter the relationships discussed. Likewise there was no relation with the fraction of the population made up by non-photosynthetic protista. This is not to say that many aspects of popula- tion biology will not be altered by taxonomic changes of this kind, or that such pheno- mena did not exist during the tank experiments, but merely that the relation of photosynthesis to chlorophyll and light depended more on the sheer quantity of chlorophyll than on the way the chlorophyll was distributed among the major taxono- mic groups present.
PHOTOSYNTHETIC POPULATION EFFICIENCY
Having measurements of the rate of energy input into the tanks and the gross rate of photosynthesis, we can calculate the gross population efficiency, or fraction of energy used in photosynthesis. In Experiment 1, gross efficiency for the four tanks together was 0-34% when computed on the basis of surface intensity of visible Hght, and 0-95 % on the basis of the intensity of the depth of the bottle. The figures for each tank are in order, for surface intensity, 0-23, 0-31, 0-41. and 0-43%. For intensity at the depth of the bottles, the corresponding figures are 0-51, 0-67, 1-29, and 1-56%.
Since these figures are based on the intensity of visible light, they should be multi- plied by 2 before comparing them with figures in the literature which are based on total radiation. Efficiencies of natural, unfertihzed populations have been reported between 0-02 and 0-40 %. Nelson and Edmondson (in press) discuss a lake the effici- ency of which was greatly increased by fertihzation. That the heavily fertihzed tanks are not much more efficient relative to natural populations may be surprising, but is easily explained by the fact that the tanks were so shallow that much of the available fight must have been wasted by absorption into the sides and bottom and by reflection back out of the water. That fertihzation increased efficiency can best be seen by com- paring each tank with Tank 1, bearing in mind that Tank 1 was inadvertently fertilized lightly.
ASSESSMENT OF CONDITION BY ENRICHMENT
As shown in previous sections, the responsiveness of different populations to fer- tilization was different, and varied with the amount of fertiUzer. For full interpreta- tion of events in natural populations, it is necessary to obtain information on respon- siveness in order to identify limiting and controlling factors. The work of Lund on lakes is the most successful to date, basing interpretation of seasonal events on labora- tory analysis of the physiological condition of the population and its response to changed conditions (1949, 1950).
Factors affecting productivity in fertilized salt water
461
In the present work a number of enrichments were made with nutncnts added to the bottles, not the whole tanks, in order to determine the degree to wh.ch these sub- stances might be hmiting photosynthesis.
For example, on July 29 the population of Tank 2 was highly responsive to enrich- ment with phosphate and nitrate, while that of Tank 4 showed no response (Tabic II) The results are mterpretable on the basis that Tank 4 had previously been more heavily fertiUzed, relative to Tank 2, and the population of the former tank was not inhibited by lack of nutrients. The phosphate concentration in the two tanks before enrichment was 0-13 and 0-46 /xg at/1 of P, respectively.
Table II Results of enrichment with nutrients, July 29-31 1947. The rate of photosynthesis is tabulated for bottles enriched with phosphate, nitrate, both, and nothing
Photosynthesis hi Tank 2 Tank 4
Added :
O (control) 0-6 mg/l/day 0-9
P(0-5^g/l) 0-7 0-9
N(80ng/1) M . 0-9
PandN 1-3 0 9
PHOTOSYNTHESIS AND PHOSPHATE ASSIMILATION
Previously, it was demonstrated that there was a close correlation between amount of oxygen produced by a population and amount of phosphate removed from the water (Edmondson and Edmondson, 1947). This relation was investigated further in the present work. In Experiment 3, phosphate assimilation was measured in a manner analogous to that by which photosynthesis was measured, by measuring the phosphate concentration in suspended bottles. In most series, phosphate increased in the dark bottle and decreased in the light bottle. By subtracting the change in the dark bottle from that in the Hght bottle, one obtains a gross phosphate assimilation which, in most cases, is a negative number, indicating decrease of concentration in the water. Similarly, the changes in particulate phosphorus were measured. The data on phosphorus were taken by Dr. David M. Pratt, who made a detailed study of the phosphorus cycle in Experiment 3 (Pratt, 1950); his paper should be con- sulted in connection with this section. It is of interest to compare assimilation of phosphorus with the measurements of photosynthesis.
The phosphate which appears as net change in the dark bottle is most likely released by bacteria and animals, not by intact algae. It would seem, therefore, that in addition to comparing the gross changes in phosphorus with gross photosynthesis, it would be meaningful also to study the relation between gross phosphate assimilation and net photosynthesis, where the latter is the rate of change of oxygen in the light bottle, and is equivalent to the quantity (gross photosynthesis-respiration). That it is reasonable to study this relation is shown by considering the fact that carbon dioxide but not phosphate is freely released by algae in the dark bottle. Unfortunately, with present techniques, a true measurement of net photosynthesis is not obtained, since a large population of bacteria develops on the glass surface of the bottle. Thus, the rate of respiration and presumably phosphorus metabolism is higher in the bottle
462
W. T. Edmondson
than in the relatively unconfined population of the tank. Nevertheless, under the circumstances which existed, the bacterial population is probably similar in the two bottles. Plate counts differed httle. Thus, the difference between the bottle popula- tion and the tank population is that the former had a higher proportion of bacteria. Any relation which would depend upon the ratio of bacteria to other organisms would be modified. (See Ryther, 1954).
Both the rate of disappearance of phosphate from the water and the rate of increase of phosphorus in particulate form (organisms) showed a rather close relation with net photosynthesis and with gross photosynthesis. In the latter measurements, there were three pairs of points which diverged greatly from the general pattern, because of a high rate of photosynthesis not matched by the high rate of phosphorus
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CROSS PHOTOSYNTHESIS
1-5
- O + O 5
NET PHOTOSYNTHESIS
lO
Fig. 5. Rate of change of phosphorus as a function of gross photosynthesis (left) and net photo- synthesis (right) in Experiment 3. Particulate phosphorus is shown by filled circles and phosphate phosphorus by open circles. The rate of change of phosphorus is given as (xgrn at/l/day., photo- synthesis as before.
uptake (Fig. 5). The reason for the divergence of the aberrant points is not evident. The data are for determinations made toward the end of the period of investigation, and the rate of respiration was unusually high. It is possible that photosynthesis was able to proceed rapidly, without a corresponding uptake of phosphate, because of phosphorus stored in the cells (Ketchum, 1939).
In both cases, the rate of increase of particulate phosphorus very closely matches the rate of decrease of phosphate in the water. Individual pairs may not match well because phosphorus can be lost from the particulate fraction without immediately appearing as phosphate, but the fields of points do match.
DISCUSSION
The investigation partially summarized in this paper was intended primarily to explore certain problems of aquatic productivity. The ideas discussed concern fresh- water as well as marine populations. Extrapolation from pure culture work to natural
Factors affecting productivity in fertilized salt water 463
populations is complicated by the existence of many phenomena which do not operate in one-phase, single-species cultures, and which may be exceedingly dillicult to dupUcate in ordinary laboratory conditions. While the large outdoor tanks do not provide the elegance of complete environmental control available in the laboratory, they permit some control, as well as a degree of simplification not available in natural shallow habitats, in which the mud-water interface makes complications. They proved to be very useful in providing a large, manipulable environment, intermediate between laboratory cultures and natural bodies of water, from which large samples could be withdrawn without seriously depleting the population. They may profitably be used in the problem of interpreting natural situations, and in designing etlicient programs of experiments with controlled conditions.
One of the pressing problems is to establish relationships among the various popu- lation functions which are involved in biological production. Of these, the relation of photosynthetic rate to amount of chlorophyll present, and the degree to which this relation may be modified by various environmental conditions, has been dis- cussed at length. The ecological position of chlorophyll is obvious, but critical studies must be continued before much useful prediction from measurements of chlorophyll can be made. A second problem of interest is that of the interrelations Bmong photosynthesis, population growth, and nutrient uptake. It must be expected that in general these functions will be related, and measurements of one will give information about others which may in some situations not be measurable directly. Finally, further development of methods of evaluating the extent to which various factors are limiting production at any moment should lead to greater understanding of the general problem of productivity.
REFERENCES
Edmondson, W. T. and Edmondson, Y. H. (1947), Measurements of production in fertilized salt
water. /. Mar. Res., 6, 228-245. ... , , , i u. i i.„
Edmondson, W. T. (in press), The relation of photosynthesis by phytoplankion to light in lakes.
EmerIw,'r., Green, L. and Webb, J. L. (1940), Relation between quantity of chlorophyll and capac- ity for photosynthesis. P/ow? P/i>'.y/o/., 15, 311-317. f „l,„,„cv.r,th«.c Fleischer, W. E. (1935), The relation between chlorophyll content and rate of photosynthesis.
GAAS.?R,^Sd GiSn, hT H^(1927), Investigation of the production of plankton m the Oslo Fjord. RavD Proc Verb., Cons. Perm. Int. Expl. Mer, 42, 1-4S. -c j ■ i c i */.,-^»,
HUTCHINSON.G. E. (1941), Mechanism of intermediary metabolism in stratified lakes. Ecol. \fonogr.,
Je^^,'rV. (1937), Oxygen production by the diatom ^^f"'^^;^'^^^^^^^ '°
KSS^t ^^i? Tlie ^^cSff c^SpHai ^L^a^e tn^^eJ^ui^t;^......
KE?cS; B. H.'(1939),^t' dl'd'pme'in and restoration of deficienceis in phosphorus and nitrogen
Lr;^^^^^(y5S"s^c^s^n i;Sr^.^e'^i.!n'a:^ie of the cells producing
seasonal maxima. -^^ -^^<'^-'. ^'^' ^^^"f '^^ .. r„^„,„^„ Hass II Nutrient depletion and the spring
"rxiLl ''■i!^^?^^£^n:i::^^t/^:E:^^!^^^^^r and ei^lhan, Tarn J. W..
MA^^N^'w. M. and Jt;DAV, R. E. (1941), The chlorophyll content and productivity of sonK lakes
in Northern Wisconsin. Trans^ %iZrLi'umno\o^^^^^^ of fertilizing Bare Lake. Alaska.
Nelson, P. R. and Edmondson, W. 1. (in press;, Liiiiiiuiugiv-a
U.S. Fish and Wildlife Sery., Fish Bull. nho<;nhorus cycle in fertilized salt water. J. Mar.
Pratt, D. M. (1950), Experimental study of the phosphorus cycie
Res'., 9, 29-54. «„mptis D F (1949), Quantitative ecology of the plankton of the
Riley G A., Stommel, H. and Bumpus, l^. r. i,i7t?y, vf !•> n^ t-l69 wite^ North Atlantic. Bull. Bingham Oceanogr. Coll., 12 (3). I 169.
464 ^- T. Edmondson
Ryther, J. H. (1954), The ratio of photosynthesis to respiration in marine plankton algae and its effect upon the measurement of productivity. Deep-Sea Res., 2, 134-139.
Sargent, M. C. (1940), Effect of light intensity on the development of the photosynthetic mechanism. Plant Physiol., 15, 275-290.
Snedecor, G. W. (1946), Statistical methods. Ames, Iowa, 4th Ed., xvi 485 pp.
Whipple, G. C. (1896), Some experiments on the growth of diatoms. Technology Quarterly, 9, 145-168.
WiNOKUR, M. (1948), Growth relationships of Chlorella species. Amer. J. Bot., 35, 118-129.
WiNOKUR, M. (1948), Photosynthesis relationships of Chlorolla species. Amer. J. Bot., 35, 207-214.
WiNOKUR, M. (1949), Aging effects in Chlorella cultures. Amer. J. Bot., 36.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Dccp-Sca Research, pp. 46J.470.
Die Ausbreitung des Mittelmeerwassers im Nordatlantischtn O/tan
By A. Defant
Summary— The spreading of Mediterranean water flowing out through the Straits of Gibrali.ir into the open Atlantic is essentially a pure mixing process. This process is significant in the formation of oceanic water masses in the open ocean.
Der auf das thermo-haline Kraftesystem beruhende Wasscraustausch zwischcn den grossen Nebenmeeren und dem freien Ozean durch die sic vcrbindcndcn Mccrcs- strassen hat sich fur die Tiefenzirkulation der grossen Ozeane als hochst wirksam erwiesen. Die schweren Wassermassen aus den grossen subtropischen Nebenmeeren. wie es das Europaische Mittelmeer und das Rote Meer sind, ergiessen sich in den Ozean, wenn sic die Miindung der Meeressstrasse in den freien Ozean verlasscn haben. Infolge des hohen Salzgehaltes sind sic schwerer als jene Wassermassen, die im freien Ozean in der Miindungstiefe des Unterstromcs aus dem Mittelmeer lagern. Dadurch erhahen sic cine sinkende Tendenz und folgcn dem Prinzip der stratospharischen Zirkulation, namhch absinkend sich jene Tiefenschicht auszusu- chen, die ihrer Dichte entspricht. Hier breiten sie sich dann unter ausgedehntcn Vermischungsvorgangen auf isopyknischen (isentropen) Fliichen. im wesenthchcn also horizontal aus. Durch Verfolgung des Salzgehalts-maximums, das den eindrin- genden Wassermassen eigen ist, lasst sich der Weg angeben, den diese Wassermassen bei ihrer Ausbreitung und Vermischung nehmen. Klarer als durch die Linien gleichcn Salzgehaltes in dieser Kernschichte des Mittelmeerwassers vor der Strasse von Gibraltar lasst sich die Ausbreitung des Mittelmeerwassers im Atlantischen Ozean vor der Miindung der Gibraltarstrasse nicht zeigen (Abb. 1). G. Wlst hat im "Meteor "-Werk eine vollstiindige Bearbeitung der vorhandenen ozeanographischcn Reihenmessungen durchgefuhrt und in zwingender Weise den Nachweis erbrachi. dass fur das obere nordatlantische Tiefenwasser die durch die Strasse von Gibraltar im Unterstrom in den Atlantischen Ozean eindringenden salzreichen und warmcn Mittelmeerwassermassen weitaus die Hauptquelle bilden. In den spanischen Gewiis- sern vor der Meeresstrasse breitet sich das Mittelmeerwasser in ctwa 1000 bis 1 KX) m Tiefe radial nach alien Seiten aus, verliert hierbei seincn hohen Salzgehait und seine hohe Temperatur durch Vermischung mit den Wassermassen, zwischcn dencn cs sich ausbreitet. WiJST hat gezeigt, dass die Mittelmeerwasserart gegen den Sudat. lantischen Ozean allmahlich auf 2000 m absinkt, aber schon am Aequalor ist d.cse Wasserart nur noch mit 20 bis 10 Prozent im Aufbau der dort lagernden Wasser- massen vorhanden. Die Abb. 1 zeigt eindrucksvoll die Reichweite der unmittclbarcn mittelmeerischen Beeinflussung nordlich von 15° N und der mittelbarcn sudl.ch davon durch den nach Siiden gehenden nordatlantischen Tielenstrom.
Ganz ahnlich sind die Verhaltnisse im nordlichcn Indi.schen Ozean, wo der Ausfluss des sehr salzreichen Wassers aus dem Roten Meer durch die Strasse von Bab el Mandeb sich weit in den Arabischen Golf und noch weiter gegen Suden .m Ind.schen Ozean bemerkbar macht. Hier steht allerdings keine solche genaue Untersuchung
465
466
A. Defant
der Verhaltnisse im Raum, wie bei der Strasse von Gibraltar zur Verfugung, aber die Langsschnitte, die vom Golf von Aden ausgehend durch den Indischen Ozean gelegt sind, zeigen die Zunge hohen Salzgehaltes, die von der Strasse von Bab el Mandeb aus sich weit nach Osten und spater nach Siidosten ausbreitet.
Es mag erstaunUch erscheinen, dass die Wassermassen, die durch die relativ engen Strassen von Gibraltar und Bab el Mandeb hinausfliessen, einen so grossen Einfluss auf die Zusammensetzung und die ozeanische Zirkulation der Wassermassen der freien Ozeane unterhalb 1000 m Tiefe haben soUen. Aber schon eine kleine Ueber- schlagsrechnung zeigt, dass dies tatsachlich durchaus moglich ist, ja zu erwarten ist.
Abb. 1. Die Ausbreitung und Tiefenlage der Kemschicht des Mittelmeerwassers im Atlantischen
Ozean (intermediares Salzgehaltsmaximum).
Aus dem Mittelmeer fliessen durch die Strasse von Gibraltar pro Jahr rund 52,000 km^ Mittelmeerwasser in den Atlantischen Ozean. Nimmt man als ungefahre mittlere Ausbreitungsgeschwindigkeit im Ozean etwa 4 cm/sek, dann wiirde ein Wasserteilchen in sechs Jahren bis auf die Hohe von Buenos- Aires-Kapstadt (etwa 35° S Br.) gelangen. In diesen 6 Jahren Uefert die Strasse von Gibraltar 312,000 km' Mittelmeerwasser, das sich iiber die ganze Wassermasse bis in diese Breiten verteilt, Nimmt man an, dass die Verteilung gleichformig auf die Schicht von 500 m Machtigkeit von 45° N bis 35° S Br erfolgt, so ergibt sich immerhin eine mittlere Beimengung von rund 1-2 Prozent Mittelmeerwasser. Die Schichten der Spanischen Bucht werden natiirlich viel mehr Prozent aufweisen, jene weiter im Siiden viel weniger; aber man erkennt, welch bedeutenden Einfluss auf diese Weise die subtropischen Nebeimieere auf die
Die Ausbreitung des Mittelmeerwassers im Nordatlantischcn O/can
Mil
Abb. 2. S=f(.T) — Kurve der Beziehung zwischen Temperatur und Salzgehalt in dcr Kcrn- schicht des Mittelmeerwassers im Atiantischen Ozean (nach Wlst).
ozeanische Zirkulation in den Tiefen der Ozeane gewinnen. Wust hat mittels dcr S = (r)-Methode in eingehender Weise den prozentuellen Anteil des Mittelmeer- wassers am Aufbau der Wassermassen des Atiantischen Ozeans ermittelt und in Abb. 2 gezeigt, wie allmahlich dieser Anteil von 100 Prozent in der Strasse von Gibraltar auf 20 Prozent in 10° N bis 0° Br. herabgeht, indem durch die Vermischung mit anderen Wasserarten eine allmahliche Herabsetzung der Mittelmeeranteils statt- findet. Die Abb. 1 zeigt in zwingender Weise, dass dieser Vorgang der Vermischung
r + Ar
Abb. 3. Modell zur Erfassung der Ausbreitung eines F.inschubcs salzrcichcn Wasscrslbci C.
468 ^- Defant
vor der Strasse von Gibraltar ein Austauschproblem ist. Es kann in einfacher Weise in einem Modell etwa folgenderweise beschrieben werden.
Die MiJndung eines Nebenmeeres in den freien Ozean kann als eine Salzquelle angesehen werden, deren Ergiebigkeit vom Wasseraustausch zwischen den beiden Meeren abhangt. Die aus der Miindungsstrasse ausfliessenden Wassermassen breiten sich auf Isentropenflachen im freien Ozean aus, wobei eine standige Vermis- chung mit den Wassermassen der Umgebung stattfindet. Die Salzquelle befinde sich im Punkte C und die anschliessenden Kiisten bliden dort den Winkel 2^o (siehe Abb. 3). Die Entfernung eines Punktes auf einer Isentropenflache von C sei r; die ausschliesslich radiak Grundgeschwindigkeit ist dann v^dr/dt. Die Strombahnen der Wasserausbreitung divergieren also vom Punkte C aus. Betrachtet man ein Volumele- ment des ringformigen Sektors r und r + A r, dann miissen sich in ihm bei statiomren Verhaltnissen die Advektion der Salzmenge und die Ausbreitung durch turbulente Vermischung das Gleichgewicht halten. Dies fiihrt in bekannter Weise zur Beziehung
Ad^ _ d{vrS) _ Q
wenn nur die seitliche Vermischung mit dem Austauschkoeffizienten A Beriick- sichtigung findet. Die Kontinuitatsgleichung verlangt, dass
'/ = 0 (2)
ist, Oder v.r = const. = roVo, wenn vo und to sich auf einen beliebigen Anfangssektor in der Nahe von C beziehen. Setzt man r = a^ und ro = alo, so hat mit der Bezieh- ung (2) die Differentialgleichung (1) eine Losung in der Form
s=f{Oy F{i), (3)
wobei man auf die Grenzbedingung /(^) = 0 fUr ^ = ± ^o zu achten hat. Aussserdem soil 5 = 5o + Sq fiir I = ^o und ^ = 0 sein. Dann wird aud (3):
worm
ist.
^»+M5f-^2T.- (^>
i8 = — • -^ (5)
Die Losung lasst sich durch eine Fourier'sche Entwicklung des Anfangszustandes auf den Ausgangssektor ro beliebig verallgemeinern.
Die Anwendung dieser theoretischen Ableitungen auf den vorliegenden Fall vor der Strasse von Gilbraltar und der Ausbreitung des Mittelmeerwassers vor dieser im freien Ozean ergibt folgende Berechnungen. 5*0 ist gemass der Beziehung (4) der Salzgehalt in grosser Entfernung von C und man hat, wenn man der Einfachheit halber nur die Verhaltnisse bei ^ = 0 betrachtet :
io\^
Sro = 5o + So und Sr = So^ So (^\
(6)
Die Ausbreitung des Mittelmeerwasscrs im Nordatlantischcn O/can 46<^
Daraus folgt:
(7)
(.")'■
Sto — So
Die Grossen auf der linken Seite lassen sich aus den Beobachtungstatsachcn als Funktion von ^ ableiten, sodass die Moglichkeit bestcht, Bcobachtungcn und Theorie miteinander zu vergleichen. Den Anganfssektor wollcn wir in ro a^o 320 km vom Querschnitt Trafalgar— Tanger am Westrand der Gibraltarstrassc sclzcn. Aus einer grosseren Zahl von strahlenformig von der Mitte dieses Qucrschniiles ausgehenden Kurven wurde aus der Abb. 1 die Entfernungen der in ihr eingetragcncn Isohalinen vom Ausgangsquerschnitt bestimmt und aus alien diesen Wertcn auf graphischen Wege eine mittlere Verteilung von 5 in Abhiingigkeit von r abgclcilet. Die folgende Tabelle gibt diese Werte von 5" flir die einzelnen J r ^ r — ro. Die Crosse .So lasst sich zu 34-95''/o:^ ansetzen, sodass
Sro — S= 1-50
Tabe/le I
|
Ir |
S |
Sr — S^ |
k |
M" |
|
km |
/ oo |
Sro — -jq |
||
|
7o |
% |
|||
|
0 |
36-45 |
99 |
1 |
100 |
|
200 |
36-20 |
82 |
0-615 |
74 |
|
400 |
35-90 |
62 |
0-444 |
59 |
|
600 |
35-80 |
56 |
0-348 |
51 |
|
800 |
35-68 |
48 |
0-286 |
45 |
|
1000 |
35-58 |
41 |
0-242 |
40 |
|
1200 |
35-54 |
39 |
0-210 |
37 |
|
1400 |
35-48 |
35 |
0-186 |
34 |
|
1600 |
35-45 |
33 |
0-167 |
32 |
|
1800 |
35-43 |
32 |
0-151 |
30 |
|
2000 |
35-38 |
28 |
0-138 |
28 |
|
2200 |
35-30 |
23 |
0127 |
11 |
|
2400 |
35-29 |
22 |
0118 |
25 |
|
2600 |
35-29 |
22 |
0-1 10 |
24 |
|
2800 |
|
— |
0-102 |
23 |
|
3000 |
35-30 |
23 |
0096 |
22 |
|
3200 |
|
0-091 |
22 |
|
|
3400 |
|
— |
0086 |
21 |
|
3600 |
35-25 |
20 |
0-082 |
20 |
|
3800 |
|
— |
0078 |
20 |
|
4000 |
35-20 |
17 |
0076 |
19 |
wird. Damit konnen die in der Tabelle stehenden Werte von '' ° , ausgedruckl in Prozenten des Anfangswertes, ermittelt werden, Die Werte '^ ergeben sich aus
'' - ; auch sie stehen in obiger Tabelle. Bildet man ^J] mit ^ -0-65, so
findet man, wie die Tabelle zeigt, eine sehr befriedigende Uebereinstimmung m,t den aus den Beobachtungen abgeleiteten Werten. Abb. 4 gibt d.escn Vcrglc.ch zwischen Beobachtung und Theorie und zeigt, dass die theoretischen Grundlagon durch die Beobachtungen vollig bestatigt werden. Eine bessere Uebcremstmimung hatte sich bei anderer Wahl des Zahlenwertes von ^i nicht erzielen lassen.
470
A. Defant
S,-So_/^/3
Op Oq \ C;
S„ = 34.95
r(r)
20 Ar IN 100 KM
40
Abb. 4. Die Ausbreitung des Mittelmeerwassers im Atlantischen Ozean vor der Strasse von Gibral- tar. nach der Theorie, o o o nach den Beobachtungen.
Nun zeigt die geographische Karte des Gebietes vor der Strasse von Gibraltar* dass 2^0 zu ungefahr 130° anzusetzen ist; dies ergibt I -3-1 = 1-9 und mit
26.}
/•fl = a$o = 3-2 X 10' cm wird aus der Definitionsgleichung fiir ^
A pv
M X 10' cm.
Man erhalt also auch hier, wie es sonst bei ahnlichen Berechnungen der Fall ist, nur das Verhaltnis des Austauschgrosse zur Grundgeschwindigkeit. Nimmt man letztere zu etwa vo = 5 cm/sek an, so wird Ajp = 5-5 X 10' cmVsek. Dieser Wert fiir den seitlichen Austauschkoeffizienten fiigt sich in bester Weise in die Reihe der Bestim- mungen dieser Grosse aus ganz anderen Strombedingungen (siehe Sverdrup, John- son and Fleming, 1942, p. 485; oder Proudman, 1953, p. 120 u.f.).
Die Vorgange der Ausbreitung des aus der Strasse von Gilbralter ausfliessenden Mittelmeerwassers in den freien Atlantischen Ozean sind somit im wesentlichen ein reiner Vermischungsvorgang und man erkennt, welche Bedeutung diesen Prozessen fiir den Aufbau der ozeanischen Wassermassen im freien Ozean zukommt.
Innsbruck, April 1955.
LITERATUR
Proudman, J. (1953), Dynamical Oceanography. London, Methuen & Co., Ltd., 409 pp. Sverdrup, H. U., Johnson, M. W. and Fleming, R. H. (1942), The Oceans: their Physics, Chemistry, and general Biology. New York, Prentice-Hall, Inc., 1087 pp.
Papers in Marine Biology and Oceanography. Suppl. to vol. J of Dccp-Sca Research, pp 471-471
New directions in fishery research
By Lionel A. Walford
The Fishes of the Gulf of Maine, by Bigelow and Schroi.der, published two years ago, brings up to date a work that has been an American ichthyological classic for 30 years. It sums up our knowledge about every species of the northwest Atlantic that regularly occurs in the oceanic bight from Nantucket Shoals and Cape Cod eastward to about 65° W. longitude and including the Bay of Fundy. When read in comparison with the 1924 edition, it measures the progress which biologists have been making in their studies of fishes in this area. In bringing together the work of three generations, it marks where we are now, and serves as a basis on which to consider the question of where to go from here. In the following paragraphs, I propose to examine some facets of this question from the viewpoint of fishery research.
In general, the ichthyological fauna of the North Atlantic is now fairly well known; at least the species which are of actual or potential commercial interest are well known. This does not mean that taxonomy is finished in the Gulf of Maine (or any- where else for that matter) leaving only the routine job of keeping the bottles on the museum shelves properly labelled and filled with alcohol. What has been done so far is to lay the foundation on which the taxonomy of the future must be built; for there remains the enormously important and difficult work of clarifying conceptions of the sub-populational structure of the species. This is not of '" mere academic interest ", as people who are unsympathetic to this line of research sometimes scorn- fully assert. Fishery investigators have everywhere shown it to be a fundamental necessity; for sub-populations often differ enough from each other in many ways— in rates of growth and mortality, in fecundity, in migratory habits, and in various other biological characteristics, that these segments of species must be studied, fished and regulated as distinct entities.
No matter how distinct they may be genetically, however, they are exceedingly diflficult to define, for body proportions and meristic counts vary widely within sub- populations; they overlap broadly between populations; and they are affected by the continually varying conditions of the environment, particularly temperature. Because of the consequent hmitations in the usefulness of anatomical features, other means of identifying sub-populations are being sought in the fields of biochemistry, serology, parasitology, and experimental marking. Whatever methods be used for analysing sub-populations, it is necessary to systematically sample large quantities of fish throughout the range of each species under study. In the northwest Atlantic, this laborious and costly work has hardly begun. So far. it has necessarily been concentrated on only the species of greatest commercial importance, namely haddock, cod and red-fish; and even these few species have been studied intensely only over a part of their total distributions. Thus, the study of sub-populations oi these must continue, while that of all the other species still lies ahead.
The Fishes of the Gulf of Maine is full of information that is best classed as Natural History. There is much more of this than could be assembled for other parts of North
471
472 Lionel A. Walford
America, since history is longer and the facihties for keeping records go back further there; universities and museums are more ancient, great fisheries and fishery researches have been longer established, and there has been more opportunity to observe the habits of fishes and to record the vagaries of fisheries there than in other sections of the country. Thus over the course of over 300 years there has accumulated a great store of knowledge about western north Atlantic fishes — about the charac- teristics of their environment, their seasons and places of spawning, the structure of their eggs and larvae, their food habits, routes of migrations, anomaUes of occur- rences, and many other matters relating to normal patterns of life history and to the deviations therefrom.
Natural History has been unappreciated for a long time, and is now at last again coming into its own, though perhaps under a different label. During the 1920's and 1930's the extraordinary growth of new fisheries such as for haddock in New England, for sardines in California, and for shrimp in the Gulf of Mexico, aroused concern for the future productivity of those natural resources that were being subjected to unprecedented exploitation. It was logical that these fisheries should be regulated as promptly as possible in order to safeguard them from extermination, and that to be effective, the regulations must be based on scientific information. It transpired from preliminary inquiries that a special kind of information was required which in fact did not exist. Although there was a large store of facts, none of it was suitable for calculating estimates of the sizes and ages at most profitable capture. Under the impetus of the demands of the time, therefore, biologists whose interests might otherwise have been natural history took up the study of fishery biology. At first they were preoccupied with determining the effect of fishing on the abundance and pro- ductivity of populations of fish. For this they paid the bulk of their attention to founding useful systems of commercial statistics and to the analysis of the quantities, sizes and ages offish caught in relation to the amount of eff'ort required in the catching. They tended to limit biological studies to those features of life history required for scientific regulation, i.e. rates of growth, death and replacement.
• Fishery research might have remained so for a much longer time had it been proved unequivocally that fishing alone causes depletion, which can always be corrected simply by controlling the catch. However, one of the principal results of studies over the past 30 years has been to bring out that, although fishing certainly does affect the abundance of fishes, so also do events which happen in the ever changing environment. Long period trends in climate and hydrography, for example, affect distribution and abundance of all species, whether they are fished or not; and they affect different species in different ways. Thus there is continuous change in the numerical interrelations among the many species inhabiting an environment, perhaps with some kind of pattern of oscillations which has yet to be deciphered.
Fishery researchers had first thought to speed their progress towards practical results by limiting the scope of their studies to the species of greatest importance and to the problems of greatest urgency. Every study about those species, however, has made it more evident that they can not be understood out of context from the intricate system of their biological environment composed by their predators (includ- ing man), their competitors and their prey. So it is that fishery researchers have been finding it necessary to rediscover natural history (now called ecology), and to enlarge the scope of their programmes in order to establish a proper balance between studies
New directions in fishery research 473
of fisheries and of fishes. The average fishery programme of today is neither a one- man nor a one-agency enterprise. It generally involves the collaboration of several institutions, sometimes of several nations, and the participation o\' many scientists having among them a wide variety of disciplines and talents.
Most fishery investigations begin with the tacit hope that a solution to what had looked Hke a clear-cut problem will be reached, and the work concluded in live or six years. Of course this never happens. Research about the effect of varying ex- ploitation upon irregularly oscillating populations of fishery organisms can not be concluded for all time any more than can research about any other constantly changing natural phenomena. In this connection, it might be helpful in our thinking to alter our concept of the dimensions of time from years to generations. The time required for a brood of fishes to reproduce itself (i.e. a generation) varies from one species to another, but commonly runs about three to eight years. To formulate dependable principles about fishes, it is necessary to follow many generations. Most fishery problems also involve human affairs. Those that concern us now will probably be much more acute a generation hence (i.e. 30 years from now) when people will be more numerous and their food needs consequently greater.
Thus the new directions in fishery research are towards greater comprehensiveness — the whole of species with all their sub-populations; the whole of environments with all their component species. This takes up again the tradition established far back in the past, which is behind books like Fishes of the Gulf of Maine, and promises to carry it forward to further enrich human knowledge about the sea.
REFERENCES
BiGELOW, Henry B. and Schroeder, William C. (1953), Fishes of the Gulf of Maine. Fishery Bull.
74, Fish. Bull., Fish and Wildlife Sen:, 53, 1-560, 288 text figs. BiGELOW, Henry B. and Welsh, William W. (1924), Fishes of the Gulf of Maine. Bull. i.S. Bur.
Fish., 40, 1-550, 278 text figs.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 474-478.
Coastal currents and the fisheries *
By C. O'D. IsELiN Woods Hole Oceanographic Institution, Woods Hole, Mass.
The waters over the continental shelf from Labrador to Cape Hatteras have been examined and described many times over the last 40 years or so. Certain characteris- tic features of the distribution of temperature and sahnity are to be found along this whole stretch of coastUne. Here many clear-cut examples of the basic problems of the circulation of coastal waters are to be encountered, yet it cannot be claimed that much additional understanding has been gained since the pioneer studies of Bigelow (1927; 1933).
When the present writer was a graduate student at Harvard, Dr. Bigelow had reached the conclusion that significant advancements in marine biology would in all probabihty have to await a much better understanding of the circulation of the ocean. He planned his own work, and also the early programme of the Woods Hole Oceanographic Institution, accordingly. After 25 years, the best that can be said is that we have gained a clearer picture of the deep-water current systems, and that there is hope that a corresponding advance will soon take place in the more difficult problems of coastal currents. The purposes of this paper are to discuss briefly the present status of the shallow-water circulation problem, to point out the more pro- mising Unes of attack, and especially to give fisheries biologists some hope that physi- cal oceanographers will soon be able to answer some of their more pressing questions concerning fluctuations in the physical and chemical environment of coastal fisheries.
Certain general rules of coastal circulation have become well established. In the northern hemisphere the average flow is paraUel to the shore line with the land on the right hand side. It follows that the average motion of the surface water is anti- clockwise in a bay or gulf and clockwise around a bank. The reverse is of course true in the southern hemisphere. There is a tendency for the most pronounced surface current to be located near the 100 fathom curve, but it is also characteristic to find a second — somewhat shallower and fresher — band of current near the beach. Unfor- tunately, from the biological standpoint it is the rates of cross-current transport at different levels that are important, and these we know very httle about as yet.
It is typical of coastal waters that sahnity everywhere increases with depth. The only exceptions to this statement are to be found briefly in winter where convection has extended downward to the bottom, or where tidal stirring is especially vigorous. In any case, whether or not vertical stabihty is present, sahnity increases gradually across the continental shelf and then increases more suddenly near the 100 fathom curve, where the contact between the relatively fresh coastal water and the more saUne oceanic waters is usually located. It is also characteristic of coastal waters from the higher latitudes on the westward margin of an ocean that, throughout much of the year, there is a temperature minimum at mid-depths. The reason for this is that there is an inshore component to the flow of the bottom water, and an offshore
* Contribution No. 792 of the Woods Hole Oceanographic Institution.
474
Coastal currents and the fisheries 475
component to that of the surface water. Along the whole stretch of coastline under consideration here the bottom water near the 100 fathom curve has the charac- teristics of truly oceanic water. That is to say, salinity approaches 35 , and tem- perature is at least several degrees higher than is to be found over the continental shelf at mid-depths at the latitude in question.
The temperature-minimum layer normally extends offshore as a tongue a few miles beyond the 100 fathom curve. This cold tongue overlies a maximum-salinity layer that appears to have an inshore component, and an origin well offshore in the slope- water area. The mixing processes at the contact between the coastal water and the oceanic water are by no means clear. As normally drawn from serial observations of temperature and sahnity the isotherms and isohalines cross each other at a con- siderable angle near the extremity of the cold tongue, a pattern which is difficult to explain, if indeed it really exists. On none of the sections so far examined have suffi- ciently closely spaced sahnity observations been secured for one to be certain of the changes in the T-S correlation curve as one moves from typical coastal water to typical slope water. It is evident that vertical mixing plays an important role near the outer limit of the coastal water.
Not only are the small-scale mixing processes near the 100 fathom curve complex and poorly understood, but also large-scale mixing processes are present. Bubbles or tongues of nearly undiluted coastal water are often encountered just below the surface layer in the slope-water area, even as far offshore as the outermost filament of the Gulf Stream System. Much less frequently has oceanic water been observed invading the area inside the 100 fathom curve, except very near the surface and close to the bottom. While the coastal water near the 100 fathom curve is clearly on the average moving towards the south and west, just beyond it the apparently detached masses of coastal water often seem to have an easterly component. In short, it is as yet impossible to describe a sector near the edge of the continental shelf in three dimensions in a rehable manner. No network of observations has been sufficiently closely spaced to permit only one solution to the contouring of the physical properties. The situation, although on a much smaller scale, may be even more ambiguous than FuGLiSTER (1955) has recently shown to be the case further offshore in the Gulf Stream System.
The least complex stretch of coastal water in the area under consideration, and the one having the most sluggish circulation, is to be found between Nantucket Shoals and Cape Hatteras. Along this 500 mile stretch of coastline many rivers are con- tinually pouring in fresh water which reaches the sea with a salinity of about 30 after having undergone the mixing processes at work in the estuaries. In the further mixing which occurs over the continental shelf the salinity is gradually increased, both in the offshore direction and, as Ketchum has recently shown (1955), also in the downstream direction. Since the flow past Nantucket from the Gulf of Maine is weak and probably intermittent, and since little coastal water passes Cape Hatteras. it one assigns an average salinity to the water leaving the continental shelf ot 33 . and a value of 357oo to the slope water inflow along the bottom, then it is evident that the offshore component must approximate 16 times the volume ot all the land drainage. As previously stated, part of this exchange between coastal and offshore waters is accomplished by small-scale mixing processes, both vertical and horizontal, and part of it by much larger eddy-type movements. The first process probably proceeds at
476 C. O'D. IsELiN
a fairly constant rate, while the second is Hkely to be intermittent in character and to be triggered off by the offshore currents. It is the intermittent large-scale losses of coastal water that are probably the important events from the standpoint of a fisheries biologist. If physical processes are an important factor in the widely fluctuating annual recruitment of young fish, then it seems likely that major changes in the environment must be involved. Presumably the fish, even very young ones, are able to deal with the normal, small-scale mixing mechanisms. Thus we can ask the question: from the standpoint of a fish, what constitutes a physical catastrophy? The answer may be somewhat different for each species of fish.
The two primary variables in coastal circulation are undoubtedly the river inflow and the weather. The former supplies most of the energy, and the latter is important both in maintaining the small-scale mixing processes and also in causing the mass movements of considerable bodies of water, especially in winter. How great a varia- tion from the normal can be produced by either factor? The larger eddying motions of an intermittent character occurring near the edge of the continental shelf are a third factor capable of producing considerable variations in the coastal environment. South of New England the available evidence indicates that these are most likely to take place along the southern edge of Georges Banks and off Chesapeake Bay. In both cases the currents of the Gulf Stream System are relatively close to the 100 fathom curve. If it is true that the offshore currents can sometimes cause relatively large eddies to form, and thus remove considerable masses of coastal water, then these events are probably not unrelated to the variations in transport of the Gulf Stream System.
If the above summary of the problem is reasonably correct, a physical oceano- grapher, in order to be of help to his friends concerned with fluctuations in the fisheries, needs to find answers to the following questions. By how much does land drainage have to change before the normal environment of coastal water is seriously affected ? How abnormal does the weather have to become before the winds produce a corresponding change ? How important to the larger-scale exchange of coastal and oceanic waters are the variations of the deep, offshore currents ?
The available observations of temperature and salinity cannot be expected to yield clear-cut answers to these questions. The data consist of spot observations, separated widely in time and usually also in space. Observations from some of the extreme winters, for example 1918 and 1934, are entirely lacking. While the winds and the inflow of several of the rivers are known continuously for a good many years back, the only reasonably continuous oceanographic data are some temperature records close to the beach, and these of course mainly reflect the local weather. OflFshore on the bottom where the main commercial fisheries are located we have no continuous information, nor do we have records of the variations in the offshore component of the upper half of the water column.
Why have we at Woods Hole seemingly so long avoided problems in coastal cir- culation ? In the first place, of course, the more spectacular problems of the Gulf Stream System were close at hand. In 1933 and 1934 we did survey the Gulf of Maine on 17 occasions. Not a single paper dealing with the dynamics of the system appeared. None of us interested primarily in the causes of the circulation were able to use these extensive data to add anything of significance to Dr. Bigelow's classical studies. Tidal currents and internal waves so compHcated the picture that one could draw no
Coastal currents and the fisheries 477
important additional conclusions from the relatively complete grids of new stations
Much improved navigation is of course now available. Underway instruments such as the bathythermograph can now provide much more detailed profiles (about 75 such profiles across the continental shelf have been accumulated), but the fact remains that nobody has had the courage to make a sustained attack on the three- dimensional mixing mechanisms going on near the 100 fathom curve. Without the help of entirely new techniques it has seemed too difficult an observational problem, and it has been clear all along that the important clues were to be found in this /one!
It is a pleasure to be able to announce here that a new programme in coastal cir- culation is being planned at the Woods Hole Oceanographic Institution and has already been set in motion. It has been made possible by funds supplied by the U.S. Fish and WildHfe Service, and made available to the Service by the Saltonstall- Kennedy Act. The present writer is most hopeful that this three-year study will be of real assistance to fisheries biologists, because it is planned to obtain continuous data of various kinds at several key points in the system, as well as to secure some periodic ship surveys. As Ketchum, Redfield and A vers (1951) showed so clearly in their studies of inshore waters off New York, spot observations of tem.peraiurc and salinity can be illuminating if they must also satisfy some continuous require- ment such as the transfer of fresh water through the network of stations. Elsewhere in this volume Dr. Ketchum has attempted to treat the whole continental shelf area from Nantucket to Cape Hatteras as a very wide estuary. This is an important step forward in our thinking, and perhaps all that is needed to refine and to clarify the picture are some long series of current measurements at various depths.
The new programme will emphasize first of all the more systematic collection of continuous records of temperature and salinity at as many fixed points in the area as possible. The submerged recovery buoy developed by Mr. David H. Frantz at Woods Hole will also be used for temperature observations at some critical points where moored surface buoys cannot be easily maintained. Free floating buoys carry- ing radio transponders will be set out and then located frequently by a plane. Con- tinuous current measurements will be obtained at a number of points, both near the bottom and near the surface. In these ways it is hoped to gain reliable information on how strong and how persistent the winds have to be, to cause a significant dis- turbance in the normal exchange between coastal and ofi"shore waters.
A recent study by Chase (1955) has indicated that, at least in the case of young haddock, exceptionally prolonged offshore winds during the early spring can be an important factor on Georges Bank. Lacking any current measurements from the waters in which the young haddock float. Chase was forced to use the record of the relative success of the year classes as an indicator of wind-induced currents. His reasoning, while satisfactory to a physical oceanographer, leaves something to be desired from the biological standpoint. A physical oceanographer should be able to state with conviction, on the basis of physical measurements, what the large-scale water movements have been, and then leave it to the biologists to decide whether or not these have had any biological consequences.
Once the influence of the winds and of the variations in river inflow have been properly assessed, and once the cause and importance of the large-scale mixing processes at the edge of the continental shelf have been worked out, it should be possible to go back over the available data and indicate when and where the coastal
478 C. O'D. ISELIN
environment was seriously disturbed. The biologists are by no means satisfied that environmental changes of sufficient magnitude have occurred to account for the goings and comings of fish. It is the aim of the new programme to find means of setthng this matter one way or another. Even if it only serves to bring the circulation problem into closer contact with biological needs, an important step forward will have been taken.
To summarize the present situation in coastal oceanography, our basic problems can be set forth as follows:
(1) The available data are inadequate to establish how variable the coastal environ- ment may be because of fluctuations in its principal energy source, namely land drainage,
(2) So far as the oceanic currents are concerned, it is beheved that the winds, either directly or indirectly, supply most of the energy. Considerable variations in the offshore currents are known to exist, but to what degree these influence the inshore currents remains obscure,
(3) Coastal currents, on the other hand, for the most part operate without the direct help of the winds, yet strong and prolonged winds could be a cause of im- portant variations in the environment from the biological standpoint, especially for fishes which spawn near the edge of the continental shelf,
(4) Occasional surveys of the distribution of temperature and salinity are unlikely to provide more than limited understanding of the coastal currents, for the classical theories of physical oceanography assume steady-state conditions and, because of tidal currents, this simplification is far from being justified in coastal waters.
(5) Continuous observations, even of a rather simple sort at well-selected points over the continental shelf, should provide means of evaluating the influences of varia- tions in river inflow, of the local winds, and of the off'shore currents. Fortunately, new means of obtaining such observations have been developed in recent years.
(6) Once these factors have been evaluated, the major environmental fluctuations can probably be deduced as far back as the weather record extends.
(7) The general distribution of temperature and sahnity in coastal waters indicates that, except briefly in mid-winter, it operates as a three-layered system. The warm wind-stirred surface layer and the cold stable layer just below both have off'shore components, but probably quite different ones. Near the bottom, and especially where guUies and drowned river valleys exist, there is an inshore component. By moving up or down in the water column an organism can be carried either inshore or off'shore. By the large-scale interaction of coastal and oceanic water it can either be carried up-coast or down-coast. From the biological standpoint it is important to estabhsh how steady or how variable these current systems may be.
REFERENCES BiGELOw, H. B. (1927), Physical oceanography of the Gulf of Maine. Bull. U.S. Bur. Fish., 40 (2),
511-1027. BiGELOW, H. B. (1933), Studies of the waters on the continental shelf, Cape Cod to Chesapeake Bay.
1. The cycle of temperature. Pap. Phys. Oceanogr. Meteorol., 2 (4). Chase, Joseph (1955), Winds and temperatures in relation to the brood strength of Georges Bank
haddock. J. du Cons., (in press). FuGLiSTER, F. C. (1955), Alternative analyses of current systems. Deep-Sea Res., 2, 213-229. Ketchum, B. H. and Keen, D. J. (1955), The accumulation of river water over the continental shelf
between Cape Cod and Chesapeake Bay. Pap. Mar. Biol, and Oceanogr., Deep-Sea Res., SuppL, 3. Ketchum, B. K., Redfield, A. C. and Ayers, J. C. (1951), The oceanography of the New York
Bight. Pap. Phys. Oceanogr. Meteorol., 12 (1), 1-46.
Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Decp-Sea Rcwarch, pp. 47V.4H1.
Electron microscopy in oceanographic research
By Trygve Braarud Biological Laboratory B, University of Oslo
The phytoplankton of offshore waters is composed of unicellular species encom- passing a broad size range. The larger forms are caught by finc-mcshcd nets, while the smaller forms are obtained by sedimentation of water samples and examined by means of inverted microscopes. After subsequent transfer to regular microscopes, the minute specimens can be examined with the best optical equipment available. Even then it is obvious that in many oceanic phytoplankton species the morphological details are too fine to be adequately observed in the light microscope. The taxonomi- cal treatment of the nannoplankton component of oceanic populations, which includes representatives of several taxonomic groups, has, therefore, been inadequate. Recently the electron microscope has been introduced in this field and has shed light on many of the problems encountered.
As a rule diatoms are dealt with without difficulty in light microscopes, but in some cases they are so small that adequate descriptions cannot be produced. .\n example of this is Fragilaria nana Steemann Nielsen. This species forms an im- portant part of the summer vegetation in oceanic waters of the North Atlantic, including the Norwegian Sea,(STEEMANN Nielsen, 1935; Halldal. 1953). Indentifica- tion of this species and similar small diatoms is now possible by means of electron microscopy (Halldal and Markali, 1955 a).
In the case of the " guinea pig " Nitzschia closteriwn f. minutissima. which has been used extensively for experimental work, electron microscope observations by Hendey (1954) have revealed that it does not belong to the diatoms at all. Con- sequently the numerous physiological observations on this species, now referred to as Phaeodactylum tricomutum BohUn, can no longer be considered relevant for diatoms.
The extensive electron-microscopical studies of the thecal structure in diatoms (for Uterature see Helmcke and Krieger, 1953-54) will doubtless prove useful in future marine plankton research.
The systematic group which has represented the greatest obstacle in the study ol oceanic phytoplankton is the chrysophyceans and especially the coccoliihophorids.
Naked chrysophyceans have been cultured, and in the electron microscope interest- ing morphological details of importance for the systematics of the group, such as the. structure of their flagella, have been observed (Parke, 1954).
In the study of coccohthophorids, which form such an important part of the phytoplankton in warm seas, electron microscopy has proved especially usctul. 1 he calcified coccoliths of these forms represent the most characteristic morphological feature of their cell structure, and from the time of the lirst description ot species ot this group they have been used in identification and systematical grouping. 1 he tirst electron microscope pictures of coccoliths (Braarud and Nordli, 1952; Kamimner, 1952) made it evident at once that, for this group, electron microscopy would in.uatc a new era for the study of taxonomy, systematics and phylogeny.
479
480 Trygve Braarud
During the last few years observations have been made on approximately 50 species (for literature see Halldal and Markali, 1955 b). A new terminology for the descrip- tion of the coccolith morphology has been introduced, and the first outline has been drawn up for a coccolith typology based upon electron microscope observations (Braarud, Deflandre, Halldal and Kamptner, 1954; Halldal and Markali, 1955 b). To a large extent the old coccolith types have had to be discarded. It has also been revealed that some of the old species actually include more than one taxo- nomical unit. It seems obvious that, in future, electron microscopy will be indispens- able when describing new species of this group.
Electron microscope observations have disclosed an unforeseen variety in the microstructure of the coccoliths, and definite taxonomic groups based upon clear-cut differences in the microstructure of the coccoHths can already be distinguished. In PI. I and II are shown examples of some coccolith types which illustrate the striking diversity in their architecture. Species which, because of their coccolith micro- structure, must be assumed to be closely related, may exhibit increasing differentiation in the coarser features of their coccolith morphology. As an example PI. II, 1-6, shows coccoliths from four species, all of which have coccoliths of the holococcolith type, ranging from Crystallolithus hyalinus with its very simple coccoliths to Homo- zygosphaera tholifera with its elaborate " mitras ". In this case the microstructure of the coccoliths, which can be revealed only through electron microscopy, must form the basis for a revised systematical treatment of the group. The extremely different microstructure of such coccoliths as shown in PI. I and II may, in time, give proof of a more complex origin of the coccolithophorids than hitherto suspected.
The study of this group with the electron microscope is at its beginning. Much work is still ahead before full advantage can be taken of this new tool, but already one may point to useful applications of these results in other fields, as for instance the study of coccoliths in rocks and in oceanic sediments of different ages.
Coccoliths form a part of sediments in the oceans, and of calcareous rocks from various periods (Deflandre, 1952). In most cases the coccoliths are found detached, but since observations on the planktonic forms of today have established the specific nature of the coccolith structures, their identification is now possible through electron microscopy. Considerable work has already been done on fossil forms (for literature see Deflandre and Pert, 1954). In some cases their coccoliths have been found to be identical with those of species living in the oceans today, while in other cases they are different from any yet observed in living plankton.
In examining stratification in oceanic sediments the study of the small coccoliths, which hitherto have been unidentifiable, may become most useful.
The dinofiagellates, another important group of marine phytoplankton, for the most part are large enough to be studied adequately in the light microscope. How- ever, some oceanic species are so small that essential morphological features escape observation. Exuviaella baltica, a species which has a wide distribution in the North Atlantic and which forms an important component of the summer populations (Braarud, Gaarder and Grontved, 1953; Halldal, 1953), has been shown to have a spiny surface structure which was quite unexpected from observations in the fight microscope (see PI. II, 7). This morphological detail may be of considerable ecological importance in view of the fact that the spines increase the absorbing surface of the cell. In part, an explanation of the wide distribution of this species and its growth in
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graph of coccolilh. (From Brxxrui), Oaarim k. M vkkm ^'«:^;;;w;J'i:'/i.n <..... <.» modd and (M ciccuon.
graph of coccoli.h. ( From H a. . om _;^d NUhk a . 1 ^.^4^v . Hvmenomonas rosea a. U) ^"^f ''"\ * ";' y-;,. micrograph of cocco th . ^^^^^^:i^;^^^,Ms
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7. Exiniaella haliica. Detail of electron-micrograph of theca and NoRDi 1. 1955.)
Pi. 11 1. Ciystallolithiis hyalinus. Electron-micro- graph of coccolith. (From Gaarder and Markali, 1955.)
2. Spluieiocalyptia papiUifeiu. Electron- micrograph of coccolith. (From Hall- dal and Markali, 1954 a.)
3. Hoinozygospluiera wettsteini. Electron- micrograph of coccoliths. (By courtesy of J. Markali.)
4. Calyptiosphaeruohloni^'ii. Electron-micro- graph of coccoliths. (From Halldal and Markali, 1955 b.)
Electron-micrograph of coccolith. (From Halldal and
Electron-micrograph of coccolith. (From Halldal and
(From Braarud, Markali
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waters poor in nulrients mav be found in this feature (Bkavk,,, Mvkkmi and NoKDi.i, 1955).
Electron microscopy has opened neu vistas for the student of oceanic phyio- plankton populations. It will lead to a revision of the taxononi> of the manN mnnnc forms, and a sound basis for ecological surveys mav thus be established It is not difficult to foresee that in experimental studies on the phvsioloiiical and ecological characters of marine phytoplankton as well, the electron microscope vmII turn out lo be a valuable tool.
REFERENCES
Braarud, T. (1954). Coceolith morphology and taxonomic position of Hvim-nomonas nn,-ola Stem
and ^.vramv/j/?«f/a C«;7f/«e' Braariid and Eauerland. Nvti Muf; Boi 3 14 Braarud, T.. Deflandre. G., Hali ha. , P. and Kamptner. E. (1954), Tcrminologie. nomcndalurc
et systematique chez ies Coccolithophorid.s. Tiuv., VIII Con^ri", hit Boi Paris Braarud, T.. Gaarder, K. R. and Grontved, J. (1953), The phylopiankion'of ihe Norlh Sea and
adjacent waters in May 1948. Ranp. Proc. Verb., Cons. Perm. int. Expl Mer 133 1-87 Braarud, T., Gaarder, K. R., Markai i, J. and Nordli, E. (1952). Coccolithophorids studied in
the electron microscope. Observations on Coccolitluis Huxlevi and Svrucosninieru Curierac
.Wytr Mag. Bot., 1, 129-133. Braarud, T., Markali. J. and Nordi i. E. (1955). .A note on the thecal structure of /^.v/zwurZ/M
halrica Lohm. ^fytr Mag. Bot. 4. Deflandre, G. (1952), Classe des Coccolithophond.s. In: Trai'ie de Zoologie. ed. Picrre-P Grassc
Masson et Cie.. Paris, 439-470. Deflandre, G. and Pert, Ch. (1954), Observations sur Ies Coccolithophoridcs actueis ct fosMlcs
en microscopic ordinaire et electronique. Ann. Puleont.. 40. Gaarder. K. R. and Markali, ,1. (1955), On the coccolithophorids Crystallolithm hyaiinu^ n gen .
n.sp. and Braannlospluiera Bigclowi. (in preparation.) Halldal, p. ( 1953), Phytoplankton investigations From Weathership M in the Norwegian Sea, I94H
49, including observations during the '" Arniauer Hansen "" cruise. Julv 1949. HvalraJcis Skrifi
Norske Viren.sk. Akac/.. 3>S, 1-91. Halldal, P. and Markali. .1. (1954 a), Morpholog\ and micro-structure of coccoliths studied in
the electron microscope. Observations on .Anthosphacra lohnsta (l.ohm.) Kamptner and iaiyp-
trosphaera papillifera Halldal. Sytt Mag. Rot.. 2, 117 119. Halldal, P. and Markali, J. (1954 b). Observations on coccoliths of Syrucospliaera nwiliierraneu
Lohm.. S. piilchra Lohm. and 5. inolischi Schill.. in the electron microscope. J. tin Con.\ . 19 (2).
329-336. Halldal, P. and Markali, J. (1955 a). The thecal structure of Frugiiaria nana Steemann Nielsen
(In preparation.) Halldal, P. and Markali, .L (1955 b). Electron microscope studies on coccolithophorids from
the Norwegian Sea, the Gulf Stream, and the Mediterranean. A\h.. \orske \iiensk Akati . 0\li>.
Mat.-Naturv. Kl., (In press). Helmcke, J. -G. und Krieger, W. (1953 54), Atlas der Diatomeenschalcn im elektronmikros-
kopischen Bild, Berlin-Wilmersdorf, I 2. Hendev, N. I. (1954). Note on the PIvmouth ■" Nit/schia "" culture, J. \lcir. Biol A\uh . I K . 33
(2), 335-339. Kamptner. E. (1952). Das mikroskopische Studium des Skelettes der Coccoliihineen (Kaiktlageilateni
11. Der Feinbau der Coccolithen. Mikroskopie, 7, 375-386. Nielsen E. Steemann (1935), The production of phytoplankton at the haroc isles. Iceland, last
Greenland and in the waters around. MeM. Komni. Ihmniarks Fi.sk. og HaMimhruigfhn . .SVr
Plankton. 3(1). 1-93. . ,,, , • , »
Parke, M. (1954), New observations on marine C'hr>sophyceae. Proc. \ III C ongrro hit Hot.
Paris. Sect. 17.
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Papers in Marine Hiology aad Oceanography. Suppl. lo vol. 3 of Deep-Sea Research, pp. 482-498.
Long-term trends and changes in the hydrography of the Faroe-Shetland Channel region
By John B. Tatt
Summary Between the years 1927 and 1952 inclusive, more or less systematic temperature and salinity observations on two roughly parallel hydrographic cross-sections of the Faroe-Shetland Channel have revealed certain fluctuations, both dynamic and characteristic, which exemplify the phenomenon of marine climatic change.
Except perhaps in 1947, the Atlantic Current through the Channel evidently flowed more strongly in the autumn-winter than in the spring-summer seasons of the period from 1946 to 1952, and these autumnal-winter intensities themselves apparently increased in magnitude to a maximum in December
1 95 1 .
In the fourth decade, the oceanic water-mass in the Channel was infused with extra-Mediterranean water which has not appeared, save sporadically in isolated trace in the years before or since, and which from small beginnings in 1930-1931 showed maximum concentration in 1933 1934 and there- after waned to extinction in 1938-1939.
Similar circumstances marked the appearance of first one, and then two, types of Arctic water-mass in the bottom layers of the Channel in the latter years of the fifth and the first years of the sixth decades.
Probably most oceanographers at least entertain the idea, and indeed, from much practice in a given oceanic region, many may have formed some sort of empirical conception in regard to the circulation of the oceans, to the effect that this pheno- menon, besides varying seasonally and in greater or less degree annually, is subject also to longer-term fluctuation which may or may not be periodic in character. Such a conception, even discounting the probability of connection or connections between the respective phenomena, is similar to that of climatic change in regard to which much and various evidence has been adduced in recent years, e.g. glacier recession, timber line advance, seasonal mean atmospheric temperature changes, etc.
A major handicap to the adducement of oceanographic evidence of long-term fluctuation in hydrospheric conditions lies in the general inadequacy to date of the raw material of oceanographic observations. The collection and compilation of data of the necessary reliability is not yet of long duration — a prerequisite of effective research into the question of long-term fluctuation — and, moreover, has already been seriously interrupted by two world wars in those regions where it was being most intensively prosecuted. Nevertheless, it has been possible, for instance, to deduce from the trend of mean sea surface temperature in high northern latitudes that, during the past half-century or so, the Arctic region has on the whole been slowly warming up. A similar tendency to the extent of at least 0-5" C up to 1951 has recently been noted also in respect of the North Sea and English Channel regions.
Still another example of longer-term change in sea conditions than the familiar seasonal and annual variations is that instanced by Kemp (1938) in regard to the annual maximum phosphate content of English Channel waters between the third and fourth decades of the present century, with apparently correlated changes in the plankton, young fish, and, ultimately, adult fish populations of the region. These later mdications. from an economic standpoint alone, point a moral which is not to
482
Long-term trends and changes in the hydrography of the Faroe-Shetland Channel region 483
be ignored, especially as much other real and circumstantial evidence points more or less strongly in the same direction. In the aggregate, this evidence which, piece- meal, tends to present a somewhat irregular and confusing picture from one region to another, and between one organic species and another, appears to fall more rationally into focus when considered from the standpoint of the characteristically different water-masses in the ocean, their fluctuations in circulation and in quantity (Tait, 1952, p. 92).
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In the seas about west and north-west Europe, for example, there are permanently present at least six different and, for the most part, converging and, to some extent, intermingling water-masses. These are the oceanic, continental, Arctic, Norwegian Sea, North Sea and Mediterranean water-masses, each with its characteristic tem- perature, but more especially sahnity, and doubtless also other properties. A variety of biological and other evidence has given rise to the conception that the most signifi- cantly important of these, at least in many respects, is the oceanic water-mass. Special attention has accordingly been directed to the oceanic incursion into European seas in an endeavour quantitatively to assess its magnitude and variations. This has been done by the normal hydrodynamic method, stemming through Helland-Hansen
4S4
John B. Tait
(1905), Hessflberg and Sverdrup (1915), Sverdrup (1933), Jakelln (1936), Jacob- sen (1943), and others, from the Bjerknes' Circulation Theorem, of volume transport computation through two roughly parallel hydrographic sections laid approximately at right angles to the course of the Atlantic Current through the Faroe-Shetland Channel, scene of the pioneering oceanographical investigations of C. Wyville Thomson in 1868 and 1869, which led up to the classic Challenger Expedition.
There are special physical features of the Faroe-Shetland Channel region, as illustrated in Fig. 1, and of its waters, which make this a peculiarly appropriate site for an investigation of the kind indicated. As Mohn, the Norwegian meteorologist, first pointed out in 1887, by far the greater bulk, if not almost the entire mass of the oceanic water which pervades north-west European seas, flows within relatively restricted lateral limits through this Channel. It possesses, moreover, in the Wyville Thomson Ridge, a well-defined threshold from the North-Eastern Atlantic Ocean, thus defining, at its mean summit depth of about 550 metres beneath the sea surface, the thickness of the oceanic water-mass which, so far as is known, continuously passes in an east to north-easterly direction over it. Initially, then, as a first approxi- mation, the level of zero horizontal current — the basis of conversion of relative into
Fig. 2
absolute computational values— was assumed to lie at this depth of 550 metres over the major part of a hydrographic section between the Butt of Lewis, (the northmost point of the Outer Hebrides off" the west Scottish coast), and Faroe Bank, the section thus passing obliquely across the Wyville Thomson Ridge and, as nearly as may be judged, at right angles to the general course of the Atlantic Current over it. Between those stations of the section which lie over the continental shelf and slope, zero horizontal potential was assumed at the mean bottom depth between successive pairs of stations, and the modification of the computational method introduced by Helland-Hansen (1934) to suit such circumstances, applied.
As regards the assumption of zero horizontal current along the summit of the Wy- ville Thomson Ridge, this was experimentally confirmed in May 1953. In remarkably calm conditions, and after repeated testing in each instance at higher levels where considerable current of an order to be expected was in fact registered, an old-style but technically efficient Ekman current meter was, by means of the large, tubular.
Long-term trends and changes in the hydrography of the Faroe-Shetland Channel region 485
metal tripod illustrated in Fig. 2, deposited within one metre of the sea bottom, independently of the ship from which it was lowered, at no fewer than three well- spaced positions along the summit of the Ridge. The meter was activated and re- locked at precise instants by the operation of a moveable foot-plate, P, which, through its connecting rod, R, and an attached cord, released and withdrew the operative messenger M immediately on contact with, and on withdrawal from, the sea-bed. In all three instances zero current was registered during an interval of thirty minutes.
In view of the uncertainties of the normal dynamic computational method, however, the need was recognised from the outset of some form of corroboration of results obtained by its means. This was sought in similar dynamic computations of the volume transport of oceanic water through an approximately parallel and, within a matter of not more than two weeks, contemporary, hydrographic section across the debouchment of the Faroe-Shetland Channel proper into the Norwegian Sea, that is, between the Faroe and the Shetland Islands. As illustrated in Fig. 1, this section to begin with was situated in a more southerly position than that in which, from 1934 onwards, it became established.
For computation of the absolute oceanic volume transport through this more northerly section, in the absence of such a convenient feature as a submarine ridge as in the case of the southern section, the initial difficulty of determining the level of zero horizontal current was overcome in the Hght of the following reasoning.
Throughout the length of the Faroe-Shetland Channel to the Wyville Thomson Ridge, the situation has long been known, of an upper relatively warm and salt water-mass, the oceanic water-mass, over-riding a substantially colder and fresher water-mass which emanates from the deep waters of the Norwegian Sea ; and also the fact that these two different water-masses move in contrary directions along the Channel. The more so, therefore, as cross-sectional representations of temperature and sahnity distributions almost invariably reveal a well-marked boundary between these two water-masses, it is legitimate and reasonable to assume the existence of an interface of zero or neghgible horizontal motion between them. The same diagrams in considerable number, by the obvious and increasing concentration of both iso- therms and isohalines towards the isohahne of 35-00 °/oo, which of course was zero. Pettersson's definition of the lower limit of demarcation of oceanic water, indicate that this isohaline probably represents in cross-section also the said interface in the Faroe-Shetland Channel of neghgible or zero horizontal current. In point of fact, after trials with the isohalines of 35-05 °/oo and 34-95 °/oo as zero reference bases, and subject to one other consideration which is apphcable to both sections but not altogether relevant to the present issue, but which will be mentioned in another connection below, the closest agreements between the resultant oceanic volume trans- ports through the two sections above cited when traversed within short intervals of each other, were obtained on the basis of zero horizontal potential along the 35-00 "/oo isohaline on the northern section.
The fact of these agreements, most of which are very close as will be seen from Table I, in no fewer than twenty-one instances between the years 1927 and 1952, that is, in all cases save one in which during this period the two sections were accom- pUshed more or less together, reflects favourably on the accuracy of the above assump- tion. Its experimental verification by current meter with the means then at disposal- it may the more readily be accomplished now since the ingenious inventions of
486
John B. Tait
Carruthhrs (1954) for warp- or cable-angle measurement and current meter anchoring have become known -was of course less reliable on account of the necessity to suspend the current meter from a drifting ship. Nevertheless, m the
Table I Volume transport of oeeanic ^vater {salinity > 34-99 7oo) through the linear hydro- graphic sections, {a) Faroe Bank to Butt of Lewis, and (b) Faroe Islands to Shetland {in 1927 to Fair Isle), when the pair of sections was traversed within an interval of
14 days
|
Year |
Inclusive dates of Sections DaylMonth |
Volume transport km^jhr |
||
|
(a) (b) |
(«) (*) |
|||
|
1927 |
18/8-20/8 |
7/8-9/8 |
1-4 i 1-7 |
|
|
1929 |
28/5-29/5 |
17/5-18/5 |
140 |
13.2 |
|
1931 |
27/5-28/5 |
16/5-18/5 |
2-5 |
2.2 |
|
1933 |
20/6-22/6 |
9/6-11/6 |
3.6 |
2-9 |
|
1935 |
27/5, 5/6-6/6 |
15/6, 17/6-19/6 |
5-5 |
5-7 |
|
1936 |
28/5, 2/6-4/6 |
5/6, 13/6-15/6 |
3-9 |
3.9 |
|
1937 |
28/5-30/5, 3/6 |
21/5-23/5 |
8-8 |
8.8 |
|
1938 |
26/6-27/6, 2/7-3/7 |
5/7-6/7 |
12-8 |
9.6 |
|
1939 |
26/6-27/6 |
17/6-18/6 |
8-3 |
8-3 |
|
1947 |
18/6-19/6 |
10/6-12/6 |
19-9 |
19-3 |
|
1948 |
3/5-4/5 |
8/5-10/5 |
5.9 |
6.2 |
|
1949 |
3/9-4/9 |
12/9-13/9 |
124 |
100 |
|
n/li-12/11 |
22/11-24/11 |
139 |
143 |
|
|
1950 |
12/5-13/5 |
21/5-23/5 |
2-5 |
34 |
|
16/6-17/6 |
27/6-29 6 |
6.1 |
5.5 |
|
|
19/7-21/7 |
2/8^/8 |
4-9 |
3.8 |
|
|
1951 |
18/5-20/5 |
1/6-2/6 |
3.5 |
13.2 |
|
■ 16/6-17/6 ' 7/6-9/6, 16/6 |
14-7 |
135 |
||
|
1 13/7-15/7 ! 23/7-25/7 |
26 2-0 |
|||
|
1952 |
8/5-11/5 1 18/5-19/5 |
34 |
31 |
|
|
5/7-6/7 17/7-18/7 |
6-8 |
9.8 |
||
|
4/11,8/11-9/11 i 17/11-18/11 |
i 112 1 10-3 |
remarkably calm conditions prevailing, the endeavour was made with not unsatis- factory results within a few days of the corresponding experiments on top of the Wyville Thomson Ridge in the month of May 1953. The depth of the 35-007oo
Long-term trends and changes in the hydrography of the Faroe-Shetland Channel region 487
isohaline having been estimated as at 260 metres by rapid hydrometric measurements at a position over the lower continental slope north-west of Shetland, the result of repeated short-interval current meter suspensions to this depth yielded the incon- siderable vector of only 0-63 centimetres per second. When the more accurate salinity determinations were made it transpired that the above-estimated depth of the 35°/oo isohaline at the position concerned was less by some 12 or 13 metres than the probable true depth, so that sufficiently near confirmation of the basic assumption underlying the volume transport computations on this northern section may be said also to have been achieved. Unfortunately, the favourable conditions which had prevailed to this point broke down thereafter, thus precluding further similar experi- mentation at other positions on the section.
Table I gives the results of the volume transport computations on the foregoing Hnes through the above-mentioned two Faroe-Shetland Channel cross-sections in contemporary pairs. The unit of cubic kilometres per hour has been chosen in preference to the hitherto more usual unit of milhons of cubic metres per second, as affording to fishery research biologists, in whose interest these investigations were primarily carried out, a more readily grasped conception of the phenomenon of the intensity of the oceanic incursion into north-west European fishery regions.
As already indicated, the agreement between the pairs of values is remarkably close in all cases except one, namely, that for the latter half of May 1951. The im- mediately succeeding values, referring to the second and third weeks of June, being not only in close mutual agreement, but in agreement also with the higher of the two values for the preceding period, suggest that the disagreement in respect of this earlier period was in fact real, and significant of a radical change in the intensity of the Atlantic Current within the short interval of the two latter weeks of May 1951.
For present purposes, however, the interest of Table 1 is mainly in such evidence as it yields of longer than annual variations in the intensity of the Atlantic Current in the Faroe-Shetland Channel. Because of the highly disproportionate seasonal, and to a somewhat less extent annual distributions of the values, this evidence can only be regarded on the whole as of a very tentative nature.
The majority of the entries in Table I relate to the months of May, June and July, especially the two former months. Considering these values apart, their range is very considerable, namely, taking the means of paired values, from about 2-3 km^hr in July 1951, and 2-4 kmVhr in May 1931, to 19-6 km^hr in June 1947, which in fact all but embraces the entire range of the values of Table I. It may of course be entirely fortuitous, the frequency of the values being insufficient for anything approaching positive assertion, but it can at least be observed that the highest spring-summer oceanic transports, as chronologically entered in Table I, occur in the years 1929, 1938, 1947, and 1951, that is, apparently after intervals of nine, nine, and four years respectively.
On the other hand, the lowest spring-summer values do not admit any similar inference of long-term periodicity. Their main feature in Table 1 would seem to be an unbroken succession of them in the six years from 1931 to 1936.
More or less in parenthesis at this still early stage in scientific oceanographical investigation, but nevertheless perhaps associated in some at present indefinable way with the subsequent phenomenon, brief notice may be taken in passing of the lowest
Auu John B. Tait
transport value of all in Table I, namely that of 1-4 km^/hr for the third week of August 1927, and of the quite unique occurrence, so far as is known, of an iceberg within the limits of the North Sea, sighted on 23rd October 1927 about 30 miles ESE of the Outer Skerries of east Shetland (Marine Observer, 1928).
Oppositely, it may here also be pointed out that the highest transport value in Table I of almost 20 km^hr occurred during a summer which was outstanding meteorologically over the greater part of the continent of Europe.
Further as regards the higher transports, however, it is to be noted that not all of these are recorded against the spring-summer months of May, June, and July, as witness, for instance, the figures for September and November 1949, and also that for November 1952. This feature of the results is considerably enhanced and extended when further available material is added to that of Table I. Besides the paired hydrographic sections there represented, no fewer than twenty-four single sections, a number of them traversed by the Danish research vessel Dana, and one due to the Norwegian vessel Armauer Hansen, embracing the same period of years, are available for dynamic computation on the same lines as those adopted for the Scottish sections. Single section computational results must, of course, lacking similar corroboration to those of the paired sections, be regarded as probably somewhat less rehable on that account. None the less, they are of no small value in extension of Table I, and have accordingly been incorporated along with the means of the paired values, in Table II, single section values being distinguished by an asterisk.
In this table, the high figure of 13-3 km^hr for the month of June 1929 as derived by Helland-Hansen (1934) clearly supports the mean value of 13-6 km^hr in respect of the previous month; and the introduction of an additional year, namely 1934, on the basis of single sections only, but in no fewer than three separate assessments, in no way impairs the inference already tentatively made as regards the apparent suc- cession of low summer oceanic transports between 1931 and 1936 inclusive. Like- wise, the slightly high figure of 9-3 km^hr for May 1938 probably anticipates in truth the subsequent increase to 11-2 km^hr some six weeks later, and the assessments for June and July 1939 would appear to be very similarly related.
It is only from the year 1949 onwards that autumn- winter transports are available, and these, to 1952 inclusive, reveal conditions which, although hitherto perhaps occasionally suspected on empirical circumstantial evidence, are here for the first time given quantitative expression. In each of the four years concerned, the oceanic volume transports through the Faroe-Shetland Channel were evidently of greater intensity than the preceding spring-summer incursions. It is material also that the years are consecutive, for, from the standpoint of long-term variations, it would almost appear from the values given that the successive autumnal accessions to the intensity of the oceanic influence in the Channel themselves increased annually to a high maximum in December 1951. It can be taken as practically certain that the phenomenon of greater autumn-winter than spring-summer oceanic transports is not an annual occurrence, the combination of circumstantial with the factual evidence of Table II and such assessments as are available for earher years (Helland-Hansen, 1905, and Robertson, 1905, 1907, 1909a, 1909b, 1913), suggesting that this oceano- graphic feature, hke that of the succession of low summer transports between 1931 and 1936 inclusive, occurs in groups of years, and recurs only at more or less long- term intervals of the order each of at least several years. Qualitative evidence in
Long-term trends and changes in the hydrography of the Faroe-Shetland Channel region 489
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491)
John B. Tait
support of the suggestion is contained in another aspect of the results of this com- prehensive investigation of the hydrography of the Faroe-Shetland Channel which is about to appear elsewhere* in extenso.
II was mentioned earlier that the remarkably close agreements recorded between the contemporary paired sections across the Channel depended also in a number of cases and as it turned out depended very materially in some instances, on a certain condition which referred to both sections. This condition was the re-inclusion of apparently aberrant original observations of temperature or sahmty, principally
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f R.S "EXPLORER" 20-22 JUNE I9J3
Fig. 3
the latter, which by former standards were customarily excluded, or replaced by interpolation from smooth curves, if they implied more or less radical inversion of density in the vertical water column. In the present investigation, the years in which this condition of reinsertion of such observations had most frequently to be applied were those between 1931 and 1936 inclusive, when considerable numbers of high and even of extraordinarily high salinity values were registered, of maximum magnitude and frequency in the year 1933 in the Faroe-Shetland Channel, in 1934 in the northern North Sea, and almost without exception as subsurface values. It was in the latter region, in fact, that these recurring abnormally high saMnity records were first
* In the Scottish Home Department's series of " Marine Research " publications.
Long-term trends and changes in the hydrography of the Faroe-Shetland Channel region 49 1
noticed and recognised, after investigation (Tait 1935), to be true records, indicative, it was then empirically concluded, of abnormally powerful oceanic incursion into the region. As illustrated in Figure 1 of this reference, a not insignificant aspect of the geographical incidence of these abnormal northern North Sea salinity observations in adducement of evidence towards their reality, links that particular research with the results of an investigation into the current system of the region (Tait, 1937).
The dynamic results of Table II, however, in respect of the Faroe-Shetland Channel, belie the earlier conclusion reached in interpreting these abnormal North Sea observa- tions, clue to the origin and meaning of which was found on the Butt of Lewis to Faroe Bank hydrographic section of June 1933 (Fig. 3). Here, on and off the southern slope of the Wyville Thomson Ridge, there occurred in the depths of 840 metres and 700 metres at two adjacent stations the high salinities of 35-73° , and 35-61 1^^ respectively, with related high observations, although of lower order, both above and below the latter especially. The two outstanding values, in conjunction with the simultaneously recorded temperatures at the same depths, furnish densities (a,) of 27-74 and 27-63 respectively, that is, within the bracket which Sverdrup, Johnson, and Fleming (1942, p. 670) cite as characteristic and significant of the North Atlantic Ocean intermediate layer of so-called Mediterranean water effluent. It is clear from Fig. 3 that the above salinity records signify the core of such a body of Mediterranean water impinging upon the southern slope of the Wyville Thomson Ridge, and thereby, by the consequent turbulent motion which the trends of isotherms, and especially of isohalines, almost invariably indicate in this region, becoming disintegrated, to appear in the upper water levels northward of the Ridge. — but only extremely seldom at the surface — as isolated high salinity nuclei within the body of the oceanic water- mass, the maximum saUnity of which here normally lies between 35-35 °/o o and 35-45 % ^ • Such isolated nuclei did in fact occur on the Faroe-Shetland Channel sections of 1931 (as Table II indicates, there was no 1932 section), 1933, 1935, 1936, and 1938, being absent, however, from the 1934 and 1937 sections. Despite the increased frequency of traverse of these sections since 1946, high salinity values suggestive of Mediterranean water intrusion into the oceanic water-mass have occurred only spora- dically, as in May 1948, August 1951, and November 1952, and then only as singular records on the southern section over the threshold to the Channel. It may be that, by application of the principle of discarding apparently aberrant observations, previous indications of the presence of Mediterranean water in the Faroe-Shetland Channel, and even within the northern North Sea, have thus been lost. It is safe to say, however, that this is a phenomenon which, substantially, occurs only once in a while, and probably, as in the fourth decade, in groups of years, in other words it is a phenomenon of only long-term recurrence.
Yet another example, this time with reference to the deep waters of the Faroe- Shetland Channel, may be cited from this investigation as suggestive of probably similar long-term fluctuation. What have hitherto been accepted as the normal deep water temperature and salinity distributions in the Channel, i.e., below the oceanic water-mass, are almost uniform conditions in both characters, namely, thermal registrations at or near zero temperature Celsius, and salinity records of around 34-92° I ^^ to 34-94°/^ „. These properties define the origin of the deep Channel water as from deep levels of the Norwegian sea to the northward. Since the eff'ective commencement of observations in the Faroe-Shetland Channel at the beginning of
492
John B. Tait
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F. U.S. "EXPLORER" 10-12 JUNE, IS47
Fig. 4
HORIZONTAL SC4LE VERTICAL SCALE
NOLS0, FAROE -FLUCCA, SHETLAND
f R.S. "SCOTIA" «-IO MARCH, l<)'J9
Fig. 5
Long-term trends and changes in the hydrography of the Faroe-Shetland Channel region 493
the present century, little if any specific notice has been taken of the relatively infre- quent occurrence of salinity values below 34-90%o. There is, however, clear evidence in the tabulated observations of a frequency concentration of such low salinity records, from 34-82°/,,^ to 34-887oo with occasional instances of 34-76 ^/, to 34-79 /_, in the years between 1907 and 1910 inclusive, such as occurred again towards the end of the fifth and the beginning of the sixth decades.
TEMPERATURE AND SALINITY
HORIZONTAL SCALE = I 1,000,000 VERTICAL SCALE = I 5,000
NOLSO). FAROE -FLUCCA, SHETLAND.
F R S "SCOTIA" 12-13 SEPTEMBER, ("J^S
Fig. 6
Apart from a singular, isolated, 34-87 '/^o saUnity record in July 1934, no Faroe- Shetland deep water sahnity value below 34-90°/^^ was encountered in the years be- tween 1931 and 1939 inclusive. Similar isolated results were again evident in July and August 1946, but by the month of June 1947 (Fig. 4) almost one-half of the deep water mass underlying the oceanic water-mass was of the relatively low sahnity of 34-877oo to 34-897oo. and had a higher minimum temperature than the neighbouring deep Norwegian Sea water-mass. It seems clear from Helland-Hansen and Nansen (1909) that this low sahnity (34-867oo-34-89''/oo) intrusion into, and sometimes dis- placement of, the deep Norwegian Sea water-mass of the Faroe-Shetland Channel,
494
John B. Tait
is Arctic water emanating from the deeper layers of the East Icelandic Arctic Current and found in depths of about 300 to 400 metres " from the continental slope off the east coast of Iceland along the slope of the Faroe-Iceland Ridge and off the Faroes, past the Faroe-Shetland Channel." Evidently, however, this Arctic water layer does
E
Long-term trends and changes in the hydrography of the Faroe-Shetland Channel region 495
not in fact at all times bypass tiie Channel in its eastward trend across the southern reaches of the Norwegian Sea.
Except for a single 34-89" ,^ record in August 1948, this year appears to have been devoid of any Arctic water in the Channel, but in early March 1949 (Fig. 5), deep water conditions there were radically different from those normally anticipated. The expected Norwegian Sea water bottom layer was then entirely displaced below about 350 to 700 metres by the Arctic water-mass, being sandwiched in a narrow undulatory band in cross-section between it and the uppermost oceanic water-mass. Not only so, but apparently still another water-mass of still lower temperature and lower saUnity (34-79 °/o„ to 34-84°/3o) than the above-defined Arctic water-mass seems to have underlain to some extent the latter in the deepest part of the Channel against
1000
TEMPERATURE AND SALINITY
H0BI20NTAL SCAIE = I: 1,000,000 VERTICAL SCALE = I' 5,00O
NOLS0, FAROE -FLUCCA, SHETLAND
F. U.S. "SCOTIA" 22-24 NOVEMBEB, 1949
Fig. 8
the bottom of the continental slope. There is sufficient reason to designate this new water-mass surface Arctic water, thus distinguishing it from the intermediate Arctic water-mass immediately above it in the Channel region. At the end of April 1949 the intermediate Arctic water-mass was located at the southern extremity of the Channel, in its toe, so to speak, between the Wyville Thomson Ridge and the Faroe Bank. Five months later, in September 1949 (Fig. 6), not only did surface Arctic water occupy more than half of the deep-water cross-sectional area of the northern part of the Channel, the two Arctic water-masses together there again ' supporting ' only a narrow band of Norwegian Sea water beneath the oceanic mass — except against the continental slope where surface Arctic water appears to have been directly contiguous
496
John B. Tait
With the underside of the oceanic layer-but surface Arctic water also as distinct rron. intermediate Arctic water, was encountered in the deep toe of the Channel as well as in similar depths of the other, i.e. north-western, side of Faroe Bank, the Butt of Lewis to Faroe Bank section having on this occasion been extended considerably
northwestwards (Fig. 7). . . ;/ j
By November of the same year (Fig. 8), the surface Arctic water-mass totally under- liid intermediate Arctic, Norwegian Sea, and oceanic waters across the northern part of the Cha.mel, there being relatively very little apparently of either of the two sand- wiched water-masses present at all.
BOO 90O lOOO 1100 1200 l]00
TEMPERATURE AND SALINITY
HORIZONTAL SCALE = I M, 000,000 VIRTICAL SCALE = I SPOO
NOLS0, FAROE - FLUCCA, SHETLAND
f.R.S. "SCOTIA" 21-23 MAY, I950
Fig. 9
This was still relatively the position in the latter half of May 1950 (Fig. 9) with, however, a substantial cross-sectional area of still lower (34-79°/oo-34-77°/oo) salinity water within surface Arctic mass, probably indicating still more intensive influence from this source than in the previous year in the deeper Channel layers. By the begin- ning of the following August there were signs on the northern section of Norwegian Sea water beginning to displace both types of Arctic water along the continental slope to the considerable depth of nearly 1,100 metres, although the latter, i.e. the Arctic waters, still formed the main bulk of the bottom waters over the greater part of the section.
Long-term trends and changes in the hydrography of the Faroe-Shetland Channel region 497
Three months later, in November 1950, only the intermediate Arctic water-mass and no surface Arctic water, was found on the northern section, and even this was in process of cleavage in mid-section by Norwegian Sea water as illustrated in Fig. 10.
The intermediate Arctic water-mass was entirely absent from the toe of the Channel by May 1951, and almost totally excluded by Norwegian Sea water from the depths of the northern section in June. There was no evidence whatever of its presence on the same section by the month of October, and only an isolated trace appeared two months after.
500
TEMPERATURE AND SALINITY
HORIZONTAL SCALE = 11,000,000 VERTICAL SCALE =1 i.OOO
NOLSiZl, FAROE - FLUCGA, SHETLAND
(INCOMPLETE)
F.R.S. "SCOTIA"
6-7 NOVEMBER, 1950
Fig. 10
A return of both Arctic water types was recorded along the entire length of the Faroe-Shetland Channel in May and June 1952, but both were obviously receding from the region one month later, and towards the end of the year had left only isolated " nuclear " traces within the Norwegian Sea water-mass.
Once again, then, a phenomenon has been witnessed over a group of years which seems not to have been in evidence for at least a number of years previously: and at all events in respect of the Faroe-Shetland Channel region, the conception of long- term trends and changes in hydrographic, including dynamic, conditions seems amply to be in accordance with observational facts. Only systematic and sufficiently intensive and continuous observations on similar lines to those practised in the past few years particularly can serve further to elucidate these interesting and doubtless, in several respects, more or less highly important geophysical phenomena.
49S
John B. Tait
REFERENCES
Carruihers J. N. (1954), Some inter-relationships of oceanography and fisheries. Arch. MeteoroL,
Geophvs. li. Rioklim. (B). 6 (1/2), 167-189. Carrimhi Rs, J. N., Woods, A. J. and Lee, A. J. (1954), On the instrumental measurement of line
shape under water. Deutsche Hyclrogr. Zeits., 7 (1/2), 22-35. Helland-Hansln, B. (1905), Report on the hydrographical investigations in the Faroe-Shetland
Channel and the northern part of the North Sea in the year 1902. North Sea Fish. Invest. Comm.
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