W&M ScholarWorks Dissertations, Theses, and Masters Projects Theses, Dissertations, & Master Projects 1971 Distribution and structure of benthic communities in a gradient estuary Donald F. Boesch 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 Recommended Citation Boesch, Donald F., "Distribution and structure of benthic communities in a gradient estuary" (1971). Dissertations, Theses, and Masters Projects. Paper 1539616575. https://dx.doi.org/doi:10.25773/v5-ag1e-8h38 This Dissertation 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]. 72-6515 BOESCH, Donald Friedrich, 1945- DISTRIBUTION AND STRUCTURE OF BENTHIC COMMUNITIES IN A GRADIENT ESTUARY. The College of William and Mary, Ph.D., 1971 Marine Sciences University Microfilms, A XEROX Company , Ann Arbor, Michigan DISTRIBUTION AND STRUCTURE OF BENTHIC COMMUNITIES IN A GRADIENT ESTUARY A Dissertation 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 Doctor of Philosophy By Donald F. Boesch 1971 APPROVAL SHEET This dissertation is submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Donald F. Boesch Approved, June 1971 Marvin L. Wass, Ph.D. * Q^-VVY l( - 771i/<Lyi<Jc _______ John A. Musick, Ph.D. Maynard M. Nichols, Ph.D. (-1 PldiCAjM^ Jdrvh J. Nohcross, M. S. Webster VanWinkle, Jr., Ph.D. ’’ Department of Biology PLEASE NOTE: Some Pages have indistinct print. Filmed as received. UNIVERSITY MICROFILMS TABLE OF CONTENTS Page ACKNOWLEDGMENTS ................................................ v LIST OF TABLES ................................................ vii LIST OF FIGURES ................................................... viii ABSTRACT ....................................................... X INTRODUCTION .................................................. 2 METHODS ......................................................... 5 Sampling .................................................. 5 Sediment Analyses ......................................... 7 Ordination Analyses ....................................... 8 Structural Analyses ....................................... 11 DESCRIPTION OF THE E S T U A R Y .................................. 16 Geomorphology .............................................. 16 Salinity Structure ....................................... 17 Temperature and Dissolved Oxygen ....................... 20 S e d i m e n t s .................................................. 24 E c o l o g y .................................................... 30 Alteration by M a n ......................................... 31 RESULTS .................................................... 32 Distribution of the Fauna ................................ 32 Q-matrix Analyses ......................................... 34 R-matrix Analyses ......................................... 37 Direct Gradient Analysis ................................ 45 Species Diversity ......................................... 48 Dominance and Dominants .................................. 52 Species-Importance Distributions ....................... 57 DISCUSSION .................................................... 6 5 Fauna1 Distribution ....................................... 65 The True Estuarine Component ........................... 70 Community Continuity .................................... 74 The Structure of Estuarine Benthic Communities .... 81 Relationships of Diversity Measures ..................... 89 The Estuarine Ecosystem .................................. 90 iii Page APPENDIX .......................................................... 9 5 LITERATURE CITED .............................................. 110 VITA .............................................................. 120 iv ACKNOWLEDGMENTS Invaluable field assistance was rendered by my colleagues Thomas D. Cain, Michael D. Richardson, and Robert J. Orth. To these individuals, and especially to Mr. Orth, go my appreciation and an apology for the inconveniences suffered. Dr. David G. Cook of the National Museum of Canada identified representatives of the oligochaete species collected. Mrs. Sarah Q. Eckhause wrote most of the computer pro­ grams and must be thanked for her uncomplaining efficiency. Richard Moncure and Robert J. Diaz readily supplied assistance with programming problems. Dr. Edward W. Fager of the Scripps Institution of Oceanography provided listings of his recurrent group programs. I am grateful to the members of my graduate committee, especially Drs. Marvin L. Wass and John A. Musick, for critically reviewing the manuscript. I am in appreciation of the skills of the illustrators, under the direction of Mrs. Jane Davis, and the typist, Mrs. Barbara Kerby. The extensive groundwork on the taxonomy and distribution of Chesapeake Bay benthos by Marvin L. Wass freed me of many taxo­ nomic problems and allowed more time to think about ecology. I am grateful for the support of the Federal Water Pollution Control Administration (now Office of Water Quality, Environmental Protection Agency) in the form of a predoctoral research fellowship. Finally, to my wife, Mike, go special thanks for her material assistance and her great understanding and support during the course of this study. vi LIST OF TABLES Table Page 1. Descriptions of variables and subscripts used' in formulas................................................... 10 2. Estimated bottom salinity range at each station and classification according to the Venice System . 21 3. Water depth, mean sediment size parameters, and percent organic carbon for the stations at each sampling period........................................... 2 5 4. Recurrent groups of species and species with affinities only with members of single groups............40 5. Diversity measures for each station at each sampling period.............................................. 50 6. Rank score dominants at each station ..................... 54 7. The TTestuarine endemic" macrobenthos of Chesapeake B a y ............................................................ 71 8. Taxonomic parallels of common estuarine endemic species of Chesapeake Bay ................................... 72 vii LIST OF FIGURES Page Lower Chesapeake Bay and the York River estuary. 6 Bottom salinity structure of the Chesapeake-York- Pamunkey estuary ....................................... 19 Bottom temperature at the mouth, head, and middle reaches of the estuary ................................ 23 Sand-silt-clay ratios.................................. 28 Relationship of organic carbon content and clay content of sediments .................................. 29 A) The number of species known from four segments of the estuary ..................................... 33 B) Representation of five distribution types in the estuary......................................... 33 Trellis diagrams of similarity values of T0 and R0 . 35 Overlap between stations 4 and 9 and all other stations ................................................ 38 Distribution of recurrent groups and intergroup affinities .............................................. 44 Direct gradient analysis of abundant taxa ........... 46 Distribution of informational diversity, species richness, and evenness in the estuary................ 49 Ranges and medians of the dominance index at each station ........................................... 53 Distribution of relative importance by octaves at station 4 ........................................... 59 Dominance diversity plots for four sampling periods at station 4 ........................................... 61 Dominance diversity plots for stations 1-5 ......... 62 viii Figure Page 16. Dominance diversity plots for stations 6-10......... 63 17. Hypothetical distribution of species abundance and faunal congruity .................................. 77 18. Faunal congruity curves for each station ........... 79 19. Rarefaction curves for polychaete and bivalve species.................................................. 83 20. Hypothetical dominance diversity curves............. 85 ix ABSTRACT The macrobenthos of soft-bottoms was sampled quarterly throughout the estuary formed by the lower Chesapeake Bay and the York and Pamunkey Rivers. This is a long and stable, gradient estuary in which salinity fluctuations are mild and seasonal. An investigation of the known distributions of 360 macro- benthic species showed that most species are distributed throughout the polyhaline portion of the estuary. There are few truly steno- haline species and the numbers of species diminish in the mesohaline and oligohaline zones. Grades of euryhalinity of species are dis­ tinguishable. There are only a few estuarine endemic species; however, these dominate in the upper and middle reaches of the estuary. Freshwater species are of very minor importance in the estuary. Analyses of station similarity and faunal affinity showed that communities are virtually continuous along the estuarine gradient and that species are generally distributed independently. The distribution of communities is predominantly in response to a continuous complex gradient,