EFFECTS OF HABITAT QUALITY ON SECONDARY PRODUCTION IN SHALLOW ESTUARINE WATERS AND THE CONSEQUENCES FOR THE BENTHIC-PELAGIC FOOD WEB 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 David James Gillett 2010 APPROVAL SHEET This dissertation is submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy David J. Gillett Approved, by the Committee, January, 2010 Linda C. Schaffner, Ph.D. Committee Chairperson / Advisor Iris C. Anderson, Ph.D. Elizabeth A. Canuel, Ph.D. Romuald N. Lipcius, Ph.D. Walter R. Boynton, Ph.D. Chesapeake Biological Laboratory University of Maryland Center for Environmental Science TABLE OF CONTENTS DEDICATION..................................................................................................................v ACKNOWLEDGEMENTS............................................................................................ vi LIST OF TABLES......................................................................................................... vii LIST OF FIGURES ...................................................................................................... viii ABSTRACT.................................................................................................................... ix CHAPTER I. ASSESSMENT OF HABITAT DEGRADATION IN THE COASTAL ZONE AND THE CONSEQUENCES FOR RESIDENT BIOTA...................................2 Introduction..............................................................................................................3 Motivations and Investigative Approach...............................................................12 Literature Cited......................................................................................................15 CHAPTER II. THE INFLUENCE OF HABITAT QUALITY ON SECONDARY PRODUCTION IN SHALLOW ESTUARINE WATERS ............................................28 Abstract..................................................................................................................29 Introduction............................................................................................................30 Materials and Methods...........................................................................................33 Site Selection...................................................................................................33 Data Collection................................................................................................34 Analysis............................................................................................................37 Results....................................................................................................................39 Discussion..............................................................................................................41 Interpreting the Saline Estuary.........................................................................42 Interpreting the Tidal Freshwater.....................................................................46 Some Comments on Biodiversity and Productivity.........................................47 Conclusions............................................................................................................49 Literature Cited......................................................................................................50 CHAPTER III. THE INFLUENCE OF HABITAT QUALITY AND MACROBENTHIC COMMUNITY COMPOSITION ON NEKTON UTILIZATION OF SECONDARY PRODUCTION AS A FOOD SOURCE ........................................................................68 Abstract..................................................................................................................69 Introduction............................................................................................................70 Materials and Methods...........................................................................................74 Site Selection...................................................................................................74 Data Collection................................................................................................74 Analysis............................................................................................................77 Results....................................................................................................................80 Site Characterization........................................................................................80 iii Caging Artifacts and Environmental Parameters.............................................80 Production........................................................................................................82 Discussion..............................................................................................................89 Predation Patterns Among Sites.......................................................................90 Predation Patterns Among Faunal Groups.......................................................95 Conclusions.....................................................................................................................97 Literature Cited......................................................................................................99 Appendices...........................................................................................................124 Appendix 1.....................................................................................................124 Appendix 2.....................................................................................................125 Appendix 3.....................................................................................................126 Appendix 4.....................................................................................................127 CHAPTER IV. NATURAL ABUNDANCE 13C AND 15N ISOTOPES OF SHALLOW, SUBTIDAL ESTUARINE MACROBENTHOS AND THEIR RELATION TO HABITAT QUALITY ..................................................................................................128 Abstract................................................................................................................129 Introduction..........................................................................................................130 Materials and Methods.........................................................................................134 Study Sites.....................................................................................................134 Sample Collection..........................................................................................134 Data Analysis.................................................................................................136 Results..................................................................................................................139 Spatial and Temporal Comparisons...............................................................139 Organic Matter-Consumer Relationships ......................................................140 Discussion............................................................................................................144 The Contribution of Salt Marsh Detritus .......................................................146 The Contribution of Phytoplankton ...............................................................147 The Influence of Habitat Quality ...................................................................147 Conclusions..........................................................................................................150 Literature Cited....................................................................................................152 Appendix..............................................................................................................168 CHAPTER V. OVERALL CONCLUSIONS AND IMPLICATIONS.......................169 VITA.............................................................................................................................175 iv DEDICATION This work is dedicated in part to my family, who have always trusted that I knew what I was doing (even if they did not) and in part to Dr. A. Fred Holland, who was the first real mentor I ever had and who taught me how to do ecology. v ACKNOWLEDGEMENTS Field-based, ecosystem-scale benthic ecology is a relatively difficult and time-consuming process that requires the work of many hands. This is further exacerbated when incorporating multiple trophic levels and biogeochemical processes into the structure and functioning of the macrobenthic community. As such, I must first and foremost acknowledge the hard work and support of all the members of the Benthic Processes and Anderson labs for their help with the collection and processing of samples this dissertation is based upon. Alice Brylawski, Leandra Lockwood, Jennifer Buehrle, Shanay Butler, Elizabeth Wells, Payal Dharia, Bill Metcalfe, and Treda Grayson all deserve special recognition for countless hours they spent in the field and the lab with me, putting up with my odd sense of humor and the physical/mental rigors of long days spent slogging through the shallow estuarine waters of Chesapeake Bay. Most of this work would not exist if not for the patience