Benthic Microalgae and Nutrient Flux in Florida Bay, USA by Merrie Beth Neely A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy College of Marine Science University of South Florida Co-Major Professor: Gabriel A. Vargo, Ph.D. Co-Major Professor: Kent A. Fanning, Ph.D. Paul R. Carlson, Ph.D. Peter Howd, Ph.D. Karen Steidinger, Ph.D. Laura Yarbro, Ph.D. Date of Approval: November 20, 2008 Keywords: phosphorus, nitrogen, chlorophyll, mesocosm, microphytobenthos © Copyright 2008, Merrie Beth Neely Acknowledgements Portions of this project were funded by: USDOC/NOAA Award # NA06OP0519 to Dr. Gabriel A. Vargo and Dr. Gary L. Hitchcock (PI‟s) and a Florida Institute of Oceanography Student Grant in Aid to Merrie Beth Neely and Jennifer Jurado. Special thanks go to the Keys Marine Laboratory Staff; Jennifer Jurado, Gary Hitchcock, and Chris Kelble from the University of Miami; Dr. Rob Masserini, USF College of Marine Science; and Bill Sargeant and Dr. Cynthia Heil, Florida Fish and Wildlife Conservation Commission-Fish and Wildlife Research Institute; the Florida Institute of Oceanography SEAKEYS buoy system; Dr. Carmelo Tomas and Dr. Larry Cahoon, University of North Carolina,Wilmington. i Table of Contents List of Tables .................................................................................................................... vi List of Figures ................................................................................................................. viii Chapter 1. Benthic microalgae and nutrient flux in Florida Bay, USA ...................... 1 Introduction ..................................................................................................................... 1 Florida Bay Ecosystem ............................................................................................... 2 Benthic Microalgae ..................................................................................................... 4 Benthic Microalgae and Sediment Resuspension ....................................................... 5 Dissertation Objectives ............................................................................................... 6 Chapter 2. Sediment phosphate flux in Florida Bay, USA. .......................................... 7 Introduction ..................................................................................................................... 7 Materials and Methods .................................................................................................... 8 Results and Discussion ................................................................................................. 12 Nitrogen .................................................................................................................... 44 Summary ....................................................................................................................... 45 Chapter 3. Benthic Microalgal Chlorophyll a Standing Stock in Florida Bay ......... 48 Introduction ................................................................................................................... 48 Benthic Microalgae and Sediment Resuspension ..................................................... 51 Benthic Microalgal primary productivity and models .............................................. 52 Benthic Microalgae in Florida Bay ........................................................................... 54 Goals and objectives ................................................................................................. 57 Materials and methods .................................................................................................. 57 ii Results ........................................................................................................................... 59 Statistical analysis ..................................................................................................... 63 Discussion ..................................................................................................................... 64 Summary ....................................................................................................................... 66 Chapter 4. Mesocosm bioassays as a tool to investigate microalgal benthic- pelagic coupling in Florida Bay ..................................................................................... 67 Introduction ................................................................................................................... 67 Florida Bay Nutrient Limitation ............................................................................... 67 Bioassays................................................................................................................... 70 Materials and methods .................................................................................................. 71 Results ........................................................................................................................... 75 Nutrients: Initial Field Conditions ............................................................................ 75 Mesocosm results ...................................................................................................... 76 Chlorophyll concentration ........................................................................................ 98 Discussion ................................................................................................................... 107 Nutrient concentrations ........................................................................................... 107 Chlorophyll concentration ...................................................................................... 108 Summary ..................................................................................................................... 112 Chapter 5. Short term response of benthic microalgae to 33P additions to the sediment. ........................................................................................................................ 114 Introduction ................................................................................................................. 114 Materials and Methods ................................................................................................ 116 Results ......................................................................................................................... 121 Preliminary experiments ......................................................................................... 121 Laboratory experiments .......................................................................................... 122 Sediment-water column P pools ............................................................................. 126 Discussion ................................................................................................................... 129 Summary ..................................................................................................................... 130 iii Chapter 6. The use of dissolved oxygen probes and Pulse Amplitude Modulated (PAM) fluorometry in the evaluation of benthic microalgal primary production in Florida Bay ............................................................................. 131 Introduction ................................................................................................................. 131 Oxygen probes ........................................................................................................ 132 PAM fluorometry .................................................................................................... 132 Materials and Methods ................................................................................................ 134 Dissolved Oxygen ................................................................................................... 134 PAM Fluorometry ................................................................................................... 136 Results ......................................................................................................................... 137 DO Electrodes ......................................................................................................... 137 PAM Fluorometry ................................................................................................... 149 Discussion ................................................................................................................... 158 Summary ..................................................................................................................... 161 Chapter 7. Conclusion .................................................................................................. 163 Sediment Phosphate Flux ............................................................................................ 163 Benthic microalgal chlorophyll a standing stock ........................................................ 164 Mesocosms as a tool to measure limiting nutrients in benthic microalgae ................ 165 Radiolabelled tracers of P flux through benthic microalgae ....................................... 166 Measuring primary production in benthic microalgae ................................................ 166 Everglades restoration efforts ..................................................................................... 167 Future