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Ciguatera in Florida Keys Patch Reefs: Biogeographic

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Ciguatera in Florida Keys Patch Reefs: Biogeographic CIGUATERA IN FLORIDA KEYS PATCH REEFS: BIOGEOGRAPHIC INDICATORS OF GAMBIERDISCUS DENSITY AND TEMPORAL ABUNDANCE (CFP:BIG DATA) A Thesis Presented to The Faculty of the College of Arts and Sciences Florida Gulf Coast University In Partial Fulfillment of the Requirement for the Degree of Master of Science By Meghan Elizabeth Hian 2018 APPROVAL SHEET This thesis is submitted in partial fulfillment of the requirements for the degree of Master of Science Meghan Elizabeth Hian Approved: Dr. Michael Parsons Committee Chair / Advisor Dr. Michael Savarese Dr. S. Gregory Tolley The final copy of this thesis has been examined by the signatories, and we find that both the content and the form meet acceptable presentation standards of scholarly work in the above mentioned discipline. ABSTRACT Ciguatera fish poisoning (CFP) is a global public health concern that is associated with Gambierdiscus, a genus of harmful algae found in coral reef environments that includes species known to produce toxins (ciguatoxins). Outbreaks of CFP have often been linked to elevated abundance of Gambierdiscus cells and disturbance-related degradation of coral reefs. However, the influence of human activities on CFP risk, both directly and indirectly within the broader context of reef health, has yet to be defined for highly exploited patch reefs in the Florida Keys. The objectives of this study were to define spatial and temporal patterns in reef health and Gambierdiscus abundance across the three regions (Upper, Middle, Lower), to determine whether the drivers of those patterns were natural or anthropogenic, and to identify biogeographic indicators of risk. To address these objectives, this study combined field sampling with a “big data” approach to spatial analysis. Six patch reefs (two per each of three regions) were selected as study sites from existing research stations. Datasets from long-term monitoring of benthic cover, fish species abundance, land use, and water quality were compiled and analyzed in ArcGIS to characterize the ecological context of each site. Analysis of samples of host macroalgae collected from all study sites biannually revealed that Gambierdiscus cell densities were consistently highest in the Upper Keys and lowest in the Middle Keys, regardless of season. Conversely, reef health was lowest in the Upper Keys and improved along a gradient to the Lower Keys. Multivariate analysis of site similarity indicated that this regional pattern was driven more strongly by grazing than substrate availability. Additionally, there is evidence that human activities have an indirect influence on CFP risk through reef health, as well as through overfishing, and the destruction of inshore habitats like seagrass and mangroves. Due to a strong positive correlation with cell densities, this study suggests that mangrove cover could be useful as a biogeographic indicator of potential CFP risk. Whereas surgeonfish, with a strong negative correlation with cell densities, could indicate the actual flow of toxins into higher trophic levels. The concordance of high regional risk and high population density necessitates continued monitoring of fish in those areas and the development of more comprehensive predictor of potential CFP outbreaks. Acknowledgements This study was funded in part by NOAA CiguaHAB Award # NA11NOS4780028. I would like to express my sincere gratitude to my advisor Dr. Parsons for his continuous support of my work and research. It was always a dream of mine to study dinos, and that dream came true when I joined the Parsons benthic dinoflagellate research lab. The dinos that I got to study were just a bit smaller by an order of magnitude or so. Regardless, I was extremely fortunate to work with such a respected researcher who also turned out to be a cool boss, to sample down in the keys and, even when faced with immediate tire blow-outs, extreme sun, equipment loss, and one small fire, to still do science! I would like to thank my committee members Dr. Tolley and Dr. Savarese for their time and support, both academically and professionally. I feel incredibly lucky to be part of CWI and have thoroughly enjoyed working with the faculty, staff and students as both a student and a colleague. Thanks to the lab, especially Adam Catasus, Jeff Zingre, Nick Culligan, Jesse Elmore, Alex Leynse, Anne Smiley, Andrea James, and Katie Ribble for making our eventful trips so enjoyable, and for all of their help with collecting data, processing samples, and creative repairs. Thanks to my fellow counters, Sammi Blonder and Jessica Schroeder, for making good musical choices in the microscope room. And thanks to Dr. Venture for betting on me. I cannot thank my husband Ryan enough for the endless encouragement, patience, and support through the entire endeavor. Thanks to Sherman, Stanley, and Schnitzel for all of their “help” with studying and writing, to my nephews Elijah and Elliot for adding the Moana soundtrack, to my sisters Jenn and Allie for believing in me (and putting up with my weirdness), and to my father for inspiring me to never give up. Table of Contents 1 INTRODUCTION ................................................................................................................................................ 3 1.1 History of CFP ........................................................................................................................................................... 4 1.2 Biogeography of Gambierdiscus ............................................................................................................................... 5 1.3 Dynamics of a Harmful Algal Bloom ......................................................................................................................... 7 1.4 Dynamics of the Reef Environment ........................................................................................................................ 11 1.5 Anthropogenic Factors in the Florida Keys ............................................................................................................. 13 1.6 Link to CFP risk—Trophic Transfer .......................................................................................................................... 15 1.7 Research Objectives................................................................................................................................................ 16 2 METHODS ....................................................................................................................................................... 19 2.1 Description of Study Sites ....................................................................................................................................... 19 2.2 Sampling ................................................................................................................................................................. 20 2.3 Sample Processing .................................................................................................................................................. 22 2.4 Measures of Reef Health ........................................................................................................................................ 23 2.5 Anthropogenic Factors ........................................................................................................................................... 24 2.6 Geodatabase and GIS Synthesis .............................................................................................................................. 25 2.7 Data Analysis .......................................................................................................................................................... 26 2.8 Relation to Gambierdiscus Density & Temporal Abundance .................................................................................. 29 2.9 CFP Risk Calculation ................................................................................................................................................ 30 3 RESULTS .......................................................................................................................................................... 32 3.1 Patterns in Land Use ............................................................................................................................................... 32 3.2 Patterns in Water Quality ....................................................................................................................................... 35 3.3 Patterns in Key Fish Species Assemblages .............................................................................................................. 37 3.4 Patterns in Benthic Cover ....................................................................................................................................... 39 3.5 Patterns in Reef Health ........................................................................................................................................... 42 3.6 Patterns in Gambierdiscus Cell Densities ................................................................................................................ 44 3.7 Biotic and Environmental Correlations ................................................................................................................... 46 3.8 Regional Risk Assessment ......................................................................................................................................
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