BENTHIC INVERTEBRATE MACROFAUNA OF THE EASTERN CONTINENTAL SHELF OF THE BERING AND CHUKCHI SEAS A THESIS Presented to the Faculty of the University of Alaska in partial fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY By Samuel Whiteford Stoker, B.A., M.S. Fairbanks, Alaska December 1978 BENTHIC INVERTEBRATE MACROFAUNA OF THE EASTERN CONTINENTAL SHELF OF THE BERING AND CHUKCHI SEAS APPROVED: n L k gy\ II — Dean of the College of Environmental Sciences ______ P <?t• __!S~j 1 5 ----------------- Date Vice Chancellor for Research and Advanced Study BENTHIC INVERTEBRATE MACROFAUNA OF THE EASTERN CONTINENTAL SHELF OF THE BERING AND CHUKCHI SEAS A THESIS Presented to the Faculty of the University of Alaska in partial fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY By Samuel Whiteford Stoker, B.A., M.S. Fairbanks, Alaska December 1978 ABSTRACT The overall view presented by this study is of closely interrelated Bering/Chukchi benthic community system that extends unbroken over the entire continental shelf, with the Chukchi Sea benthos probably relying heavily on the Bering Sea for both food supply and possibly recruitment. Indications are that this is a highly productive and relatively stable benthic system comprised of at least eight major faunal zones of considerable complexity. The environmental factor correlating most strongly with the distribution of these faunal zones and with distribution of individual major species appears to be sediment type, though summer bottom temperature may also be critical. The distribution of standing stock biomass in relation to diversity suggests predation pressure on the southern and northern extremes of the study area, presumably the result of benthic- feeding marine mammal populations and possibly, in the case of the southern region, demersal fish. In general terms it appears to be a strongly detrital-based trophic system, with an elevated standing stock biomass observed in the Bering Strait and southern Chukchi Sea region, probably the combined result of high near-surface primary productivity distributions and current structure. The benthic fauna over this region appears to be dominated by boreal Pacific forms, probably also a result of the current structure, with high Arctic forms frequent only in the northern waters. iii ACKNOWLEDGEMENTS First, I would like to express special gratitude to Dr. C. Peter McRoy, who initiated this whole course of events, who kept the faith in times of doubt, and who offered help and advice when it was needed and refrained from doing so when it was not, and to the other members of my committee: Dr. Frances Fay, Dr. John Goering, Dr. Howard Feder, Dr. Ted Cooney, and Dr. Richard Neve. I would also like to express my appreciation and gratitude to the captain, officers, and crews of the various ships which were employed in the acquisition of the sample data: the U.S. Coast Guard Icebreakers CGC Northtiind, CGC Glacier, and CGC Burton Island, and the research vessels R/V Alpha Eel-ix and, especially, R/V Acona. In addition there is George Mueller of the Marine Sorting Center, University of Alaska, whose infinite patience, fortitude, and generosity of time and wisdom made possible the identifications related to this project. As regards taxonomy and identification, I would likewise like to express my thanks to Ken Coyle, also of the Marine Sorting Center, University of Alaska, for his invaluable assistance with the amphipods of this collection, to Ray Baxter of the Alaska State Department of Fish and Game, Bethel, for his expert advice on the mollusks collected during this study, and to numerous other personnel of the Marine Sorting Center for their advice and assistance. Especially, I would like to express my appreciation to Carol Robinson, formerly of the V Marine Sorting Center, who completed much of the initial sorting and identification of these samples. Thanks also to Dr. G. D. Sharma and Dr. S. Naidu, University of Alaska, and Joe Dygas, formerly of the University of Alaska, for advice and assistance with the geological samples and data. I would like to express gratitude also to those whose aid in the area of statistical application and computer programming was invaluable, particularly to Ivan Frome, James Dryden, Dr. Charles Geist, Sydnie Hanson, Grant Metheke, and Rosmarie Hobson, all of or formerly of the University of Alaska. Thanks also to personnel of the Alaska Department of Fish and Game, particularly John Burns and Carl Gravogle, whose coopera­ tion and assistance was crucial. To. A. J. Paul and Judy MacDonald I would like to extend very special gratitude, appreciation, and admiration for the very considerable expertise they provided and time that they expended in the analysis of molluscan age and growth patterns. There are numerous others whose aid was enlisted, in one form or another, in the completion of this study. Space does not permit the naming of all of them, but to all of them I would extend my great appreciation and the hope that I may someday be able to reciprocate. TABLE OF CONTENTS ABSTRACT............................................................iii ACKNOWLEDGEMENTS .................................................. iv TABLE OF CONTENTS.................................................... vi LIST OF FIGURES.................................................... viii LIST OF TABLES...................................................... ix LIST OF APPENDICES.................................................. xi INTRODUCTION ...................................................... 1 OBJECTIVES ........................................................ 1 DESCRIPTION OF STUDY AREA.......................................... 2 Bering Sea.................................................... 4 Chukchi S e a .................................................. 8 PREVIOUS INVESTIGATIONS OF THE BENTHOS ON THE BERING/CHUKCHI SHELF ............................................ 10 METHODS.............................................................. 15 Field Collection................................................ 15 Laboratory Analysis .......................................... 16 Data Processing................................................ 19 RESULTS.............................................................. 23 Physical Description of Stations................................ 23 Quantitative Biological Results .............................. 25 Comparison of Sieve Fraction Results............................ 29 Dominant Species................................................ 32 Station Cluster Analysis........................................ 37 Species Cluster Analysis........................................ 65 Environmental Correlations...................................... 67 Seasonal and Annual Fluctuations................................ 70 Nutrient Analysis ............................................ 78 Growth, Mortality, and Recruitment: Macoma oaloarea........... 100 Distribution, Standing Stock, and Productivity: M. catcavea ................................................. 102 Growth Rates: Clinocardiwn oiliatwn........................... 105 Growth Rates: Serripes gvoenlandiaus ........................ 107 f vi vii TABLE OF CONTENTS (Cont'd) DISCUSSION......................................................... 110 Standing Stock................................................. 110 Taxonomy........... 123 Feeding Type................................................... 129 Dominant Species............................................... 130 Cluster Groups................................................. 131 Environmental Correlations..................................... 144 Growth and Productivity ...................................... 148 Seasonal and Annual Stability ................................ 151 CONCLUSIONS......................................................... 152 APPENDICES............................. 156 LITERATURE CITED .................................................. 256 viii LIST OF FIGURES Figure 1. Benthic stations occjpied on the Bering/ Chukchi continental shelf .............................. 3 Figure 2. General patterns of surface circulation and extent of water masses over the Bering Sea continental shelf . 5 Figure 3. Dendogram generated by cluster analysis, based on faunal similarities, of benthic stations on the Bering/Chukchi Shelf................................ 39 Figure 4. Station cluster groups as determined by benthic faunal similarities on the Bering/Chukchi Shelf ........ 41 Figure 5. Major subgroups comprising station cluster group VIII, the Central Bering Supergroup, on the Bering/Chukchi Shelf.................................. 60 Figure 6. Relationship of shell length to age class for Cl-inoeavd-Lum ci-l-iatim on the Bering/Chukchi Shelf .... 106 Figure 7. Relationship of standing stock biomass (g/m2) to latitude (°N) at benthic stations on the Bering/Chukchi Shelf..................................... 112 Figure 8. Relationship of diversity (Brillouin) vs. latitude of benthic stations on the Bering/Chukchi Shelf ........ 117 Figure 9. Relationship of standing stock biomass (g/m2) to depth (m) at benthic stations on the Bering/Chukchi Sh e l f ................................................... 119 Figure 10. Relationship of diversity (Brillouin) to depth (m) at benthic stations on the Bering/Chukchi Shelf ........ 120 ix LIST OF TABLES Table 1. Means and percentages of total means for major taxonomic groups encountered on the Bering/Chukchi Shelf.....................................