EFFECTS OF MACROALGAL HOSTS ON THE GROWTH AND EPIPHYTIC BEHAVIOR OF FIVE GAMBIERDISCUS SPECIES FROM THE GREATER CARIBBEAN REGION 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 Lacey Kay Rains 2015 APPROVAL SHEET This thesis is submitted in partial fulfillment of the requirements for the degree of Master of Science ________________________________ Lacey Kay Rains Approved: ________________________________ Michael Parsons, Ph.D. Committee Chair / Advisor ________________________________ Ai Ning Loh, Ph.D. ________________________________ Mindy Richlen, Ph.D. 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. i ACKNOWLEDGMENTS I would like to thank my major advisor Dr. Michael Parsons for his continuous support and inspiration throughout my entire time as a graduate student at FGCU. His guidance, expertise, and continued confidence in my abilities throughout my research and writing process were invaluable. Thanks to his support and friendship, along with the various travel and field opportunities he provided, I could not imagine a better experience as a graduate student than mine was. I would also like to thank my committee members, Dr. Ai Ning Loh and Dr. Mindy Richlen, for their insight and support during my writing process, as well as the commitment to be a part of my work, even from long distances. Both Alex Leynse and Ashley Brandt played a large role in my research experiences, as we all began on this ciguatera journey, alongside Mike, together (as team Firecrest). Both above and below the water, they both were a tremendous help with every aspect of my lab work and field collections, and they always made the trips to the Florida Keys enjoyable, even under some of the coldest and windiest conditions. The support, encouragement, and friendship of so many other graduate students have gotten me to this point. Rheannon Ketover was helpful in too many ways to mention, and Laura Markley was invaluable for her help with culturing over the years. The friendship and guidance from both Lesli Haynes and Erin Rasnake over the past 15 years has played a large role in where I am today. I would like to recognize the ECOHAB funding grant for making my research possible, as it funded the field work that allowed for field collections that were vital for my research. ii Finally, I owe my largest thanks to my Mom and Dad, who have always supported me enormously in my educational journey. My Dad provided with a great sense of adventure and love for the outdoors and the water that has led me to where I am today, and I could not be more thankful for that. Thank you to my entire family and my husband for their continued support and encouragement in everything that I do. iii ABSTRACT Ciguatera fish poisoning is caused by toxins produced by dinoflagellates of the genus Gambierdiscus. This genus has recently been revised and new research on the physiology and ecology of the revised species is needed. While it has been demonstrated that Gambierdiscus spp. are predominately epiphytic, there is also evidence that they are conditional, not obligate, epiphytes and that not all algae hosts are preferred equally by Gambierdiscus populations. This experiment exposed five Caribbean species of Gambierdiscus to living conditions among 8 different species of macroalgal hosts, and their epiphytic behavior (attachment vs. non-attachment) and growth were monitored over 29 days. Additionally, the experiment was carried out under two separate nutrient conditions, ambient versus enriched Florida Keys seawater. Results demonstrate variable responses in epiphytic behavior within the Gambierdiscus genus to different macroalgal hosts, and stimulation and/or inhibition of Gambierdiscus growth by different macroalgal hosts. Attachment data indicate that Gambierdiscus populations prefer attachment to hosts that have a filamentous structure, but those species did not always support high cell abundances. Certain algal host species appear to stimulate growth of some Gambierdiscus species while others seem to inhibit the growth of other species. Control treatments (no host) reveal that some Gambierdiscus reached higher cell abundances without the presence of any host algae, suggesting inhibition by the hosts. No overall attachment preference was observed among Rhodophytes, Chlorophytes, and Phaeophytes, and no phyla stimulated growth or cell abundance more than the others. There was also no difference in attachment to hosts that were nutrient- enriched versus those that were not. The variability of growth responses and attachment iv behavior to different hosts by the various Gambierdiscus species in this experiment add complexity to our understanding of the epiphytic nature of Gambierdiscus and the dynamics of blooms. v TABLE OF CONTENTS Acknowledgments ............................................................................................................... i Abstract ............................................................................................................................. iii Table of Contents ...............................................................................................................v List of Tables ................................................................................................................... vi List of Figures .................................................................................................................. vii Chapter 1: General Introduction .................................................................................1 Chapter 2: Macroalgal host effects on the growth and epiphytic behavior of Gambierdiscus ..........................................................................................17 Introduction ...................................................................................18 Research Purpose ..........................................................................22 Methods .........................................................................................23 Results ...........................................................................................27 Discussion .....................................................................................42 Chapter 3: Ambient vs. enriched host nutrient condition effects on the growth and epiphytic behavior of Gambierdiscus ..............................................57 Introduction ...................................................................................58 Research Purpose ..........................................................................62 Methods .........................................................................................63 Results ...........................................................................................67 Discussion .....................................................................................86 Chapter 4: Overall discussion ....................................................................................90 References .......................................................................................................................105 Appendices ......................................................................................................................119 vi LIST OF TABLES Chapter 2 Table 2-1 Description of host algae used in experiments ..........................................24 Table 2-2 Growth rates of the various Gambierdiscus species for each of the host treatments. .................................................................................................30 Table 2-3 Abundance (# of cells at end of experiment, averaged across triplicates) of the various Gambierdiscus species for each of the host treatments ...........34 Table 2-4 Average attachment, growth, and abundance data for each Gambierdiscus, with the host that supported the highest attachment .................................34 Table 2-5 Average attachment (% of total cells that were attached to host, averaged across triplicates and throughout entirety of experiment) of the various Gambierdiscus species for each of the host treatments .............................37 Table 2-6 Averaged (by triplicate) attachment, cell abundance, and growth rate data is categorized for each of the host treatments ..................................................39 Table 2-7 Percent biomass changes for each host algae, averaged across all treatments ...................................................................................................41 Chapter 3 Table 3-1 Average growth rate values for all ambient and enriched treatments .......74 Table 3-2 Average percent attached cells for all ambient and enriched treatments ...80 Table 3-3 Average growth rate and cell attachment data for cluster groups ........ 81-81 Table 3-4 Cluster groupings ranked from highest values to lowest values, for both growth rate and average attachment percentages .......................................83 vii LIST OF FIGURES Chapter 2 Figure 2-1 Well plates used for experiments ...............................................................26 Figure 2-2 Gambierdiscus cells attached to host .........................................................27 Figure 2-3 Abundance (# of cells, averaged across triplicates) of the