W&M ScholarWorks Dissertations, Theses, and Masters Projects Theses, Dissertations, & Master Projects 1982 The distribution and ecology of gammaridean amphipods in the plankton of the middle Atlantic Bight Cathy J. Womack College of William and Mary - Virginia Institute of Marine Science Follow this and additional works at: https://scholarworks.wm.edu/etd Part of the Marine Biology Commons, and the Oceanography Commons Recommended Citation Womack, Cathy J., "The distribution and ecology of gammaridean amphipods in the plankton of the middle Atlantic Bight" (1982). Dissertations, Theses, and Masters Projects. Paper 1539617531. https://dx.doi.org/doi:10.25773/v5-3cwq-yk84 This Thesis is brought to you for free and open access by the Theses, Dissertations, & Master Projects at W&M ScholarWorks. It has been accepted for inclusion in Dissertations, Theses, and Masters Projects by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. THE DISTRIBUTION AND ECOLOGY OF GAMMARIDEAN AMPHIPODS IN THE PLANKTON OF THE MIDDLE ATLANTIC BIGHT A Thesis Presented to The Faculty of the School of Marine Science The College of William and Mary in Virginia In Partial Fulfillment of the Requirements for the Degree of Master of Arts by Cathy J. Womack 1982 APPROVAL SHEET This thesis is submitted in partial fulfillment of the requirement for the degree of Master of Arts LJ^qrYtouckj Author Approved, August 1982 George C. Robertr\ -v* +- JordanT /I rtr> V C^> , Christopher S. Welch Richard Wetzel Donald F. Boesch Louisiana Universities Marine Consortium This thesis is dedicated to my parents, Andrew and Norma Womack iii TABLE OF CONTENTS Page ACKNOWLEDGMENTS ......... v LIST OF TABLES.......... vii LIST OF FIGURES....... ix ABSTRACT.............. xi INTRODUCTION.................. 2 MATERIALS AND METHODS................. 9 RESULTS............................................................ 16 DISCUSSION....... 86 BIBLIOGRAPHY....................................................... 108 VITA.............. 115 iv ACKNOWLEDGMENTS I would like to express my deepest appreciation to Dr. George C. Grant for his patience and support as my major professor. I also thank Dr. Don Boesch, Dr. Bob Jordan, Dr. Chris Welch, and Dr. Dick Wetzel, for critically reading this manuscript and serving on my committee. A critical part of this thesis was data collected, analyzed, and reported by the VIMS Department of Invertebrate Zoology. I appreciate the work done by all members of that department and particularly thank Dr. Don Boesch for allowing me access to the benthic data, Ms. Marcia Bowen for her assistance in identification of amphipods, and Ms. Linda Schaffner for allowing me to examine specimens in her care. I cherish the memories of my stay at VIMS, not only because of all that I learned and did, but also because of the friends and acquaintances I made. I extend my warmest appreciation to all of those people. I especially thank Alyce Thomson for always being a cheerful and considerate housemate during my time at Gloucester Point. I feel that I was extremely fortunate to have been a member of the VIMS Department of Planktology. The following friends and co-workers each in his or her own way contributed to this thesis: Steve Berkowitz, Shelia Berry, Burt Bryan, Willy Burton, Mike Canino, Pat Crewe (our unofficial boss), Fred Jacobs, Cathy Meyer Lascara, John Olney, Jim Price, Jo Ellen Robins, Russ Short, Pete Smyth, Mike Vecchione, and Roberta Wallace. I miss all of them. In addition, I thank my present coworker, Ms. Anne Morrison, for her physical and moral support while I completed this thesis. Ms. Norma Womack and Ms. Beth Knight did excellent jobs inter­ preting my handwriting and various scribbled notes in typing this thesis. Finally, I most especially thank my husband David Ludwig. With­ out his support and encouragement this thesis most certainly would not have been completed. LIST OF TABLES Table Page 1. Time periods in which sampling occurred............... 10 2. Stations sampled for zooplankton........................... 13 3. Species list, frequency of occurrence and maximum abun­ dance in subsurface collections, arid occurrence in surface collections.......... 17 4. Occurrence of gammaridean amphipods in neuston collections....... 27 5. Occurrence of Ampelisca agassizi in the Middle Atlantic Bight in the water column (this study) and in the benthos at stations also sampled for zooplankton (from Boesch, 1979)...... 30 6. Occurrence of Ampelisca vadorum in the Middle Atlantic Bight in the water column (this study) and in the benthos at stations also sampled for zooplankton (from Boesch, 1979)................ 34 7. Occurrence of Byblis serrata in the Middle Atlantic Bight in the water column (this study) and in the benthos at stations also sampled for zooplankton (from Boesch, 1979)....,......................... 39 8. Occurrence of Argissa hamatipes in the water column in the Middle Atlantic Bight.................. 50 9. Occurrence of Erichthonius rubricornis in the Middle Atlantic Bight in the water column (this study) and in the benthos at stations also sampled for zooplankton (from Boesch, 1979).............. 52 10. Occurrence of Unciola irrorata in the Middle Atlantic Bight in the water column (this study) and in the benthos at stations also sampled for zooplankton (from Boesch, 1979) ......... 56 11. Occurrence of mature females of the species Unciola irrorata in the plankton at B5.................. 62 vii List of Tables (Continued) Table Page 12. Occurrence of Microprotopus raneyi in the plankton of the Middle Atlantic Bight. ...... 66 13. Occurrence of Liljeborgia fissicornis in the plankton of the Middle Atlantic Bight............ ... 71 14. Occurrence of Monoculodes edwardsi in the Middle Atlantic Bight in the water column (this study) and in the benthos (from Boesch, 1979)........ 74 15. Degree of maturity of Monoculodes edwardsi by station 78 16. Occurrence of Synchelidium americanum in the water column. 82 viii LIST OF FIGURES Figure Page 1. Location of stations sampled for zooplankton............ 12 2. Abundance and species composition of gammaridean amphipods across the shelf in subsurface collections during the fall.................. ... 19 3. Abundance and species composition of gammaridean amphipods across the shelf in subsurface collections during the winter. .................. 21 4. Abundance and species composition of gammaridean amphipods across the shelf in subsurface collections during the spring................... 23 5. Abundance and species composition of gammaridean amphipods across the shelf in subsurface collections during the summer................... 25 6. Size and sex frequencies of Ampelisca agassizi at selected water column and benthic stations..... 32 7. Size and sex frequencies of Ampelisca vadorum at selected water column and benthic stations..... 36 8. Size and sex frequencies of Byblis serrata at station B5 in the water column and benthos.............. 42 9. Diel cycle of Ampithoe longimana. in the neuston at station LI during the summer, 1977....... 45 10. Occurrence of Ampithoe longimana in the water column at station Ll and from the Chesapeake Bay.......... 47 11. Size and sex frequencies of Erichthonius rubricornis in the water column and the benthos at B5 during the fall, winter, and spring.................... 55 12. Size and sex frequencies of Unciola irrorata at B5 during the fall, winter, and spring............. 59 13. Size and sex frequencies of Unciola irrorata in the water column at L2 and N 3 ........................ 61 List of Figures (.Continued) Fi gure Page 14. Diel cycle of Microprotopus raneyi in the neuston at Cl during the summer. ..... ...... ...... 68 15. Size and sex frequencies of Monoculodes edwardsi in the water column at all stations during all four cruises ...... ............ ....... 77 16. Mean lengths and range of lengths of Monoculodes edwardsi by station for each cruise......... 80 17. a) Cumulative percent and percent of tows in which gammaridean amphipods were collected by distance-from-bottom intervals, b) Percent of tows which had no maximum depth within specified distance-from-bottom interval. 89 x ABSTRACT Gammaridean amphipods collected during a plankton survey of the outer continental shelf of the Middle Atlantic Bight were identified, measured, sexed, and compared with amphipods collected during a con­ current benthic survey of the same area. Twenty-nine species com­ prising 18 families were identified from plankton collections. The occurrence of seven species in surface samples was indicative of important hydrographic phenomena which influence the composition of Middle Atlantic Bight zooplankton. Microprotopus raneyi and Ampithoe longimana were by far the most abundant gammaridean amphipods in surface collections. These were the only species to occur in more than two of the 75 neuston samples taken during any single cruise and comprised 80% of all neuston specimens. Gammaridean amphipods were most consistently collected in subsurface tows at central and outer shelf stations and were absent from slope stations. Monoculodes edwardsi was the most frequently collected gammaridean amphipod. It is suggested that its superior dispersal capabilities facilitate exploitation of new habitats. The corophiids Erichthonius rubricornis and Unciola irrorata exhibited a constant flux of low numbers into the water column. Short-range dispersal via the water column by corophiids improved the ability of these species to recolonize small defaunated