Doctor of Philosophy (PhD)
First Advisor's Name
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Third Advisor's Name
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Fourth Advisor's Name
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Fifth Advisor's Name
Iliana B. Baums
Fifth Advisor's Committee Title
Dendrogyra cylindrus, holobiont, coral bleaching, symbiosis, coral genotype, hyperthermal stress, coral disease
Date of Defense
The iconic pillar coral, Dendrogyra cylindrus, is one of five Caribbean species listed in 2014 under the US Federal Endangered Species Act because of its extreme low abundance and continued decline in US waters. Until recently, little was known about the demographics or genetic diversity of Florida’s D. cylindrus population. This study represents the first time two holobiont partners (coral animal and associated photosynthetic algal endosymbionts) have been closely examined, spatially and temporally, in this little-studied species. The aim was to explore the influences of coral animal genotypes, mutualistic photosynthetic algal strains, and hyperthermal stress on bleaching and disease processes, resistance, and recovery through two consecutive hyperthermal events on the Florida Reef Tract (FRT) in 2014 and 2015.
Through geographically stratified, triannual assessments and tissue sampling of D. cylindrus colonies across three regions of the FRT from April 2014 to April 2016, I compared genotypic identities of the coral animal to bleaching and disease status and recovery. Additionally, I characterized the algal endosymbionts (Symbiodiniaceae family) in D. cylindrus between regions of the FRT using Illumina amplicon sequencing of the partial chloroplast 23S rDNA Domain V gene and correlated them to differential responses during bleaching and recovery. Finally, I examined the effects of hyperthermal stress on disease prevalence and changes in disease susceptibility in D. cylindrus throughout two consecutive hyperthermal events in 2014 and 2015.
Genotypic differences in D. cylindrus were associated with full or partial bleaching and/or disease resistance associated with some genets. Additionally, this study characterized unexpected diversity in the Symbiodiniaceae community within D. cylindrus and a site-specific, species-level switch in endosymbionts associated with acquired bleaching resistance during the 2015 hyperthermal event. Finally, this study demonstrated that two consecutive hyperthermal events were associated with an increase in prevalence of white plague in D. cylindrus and contributed to its susceptibility to black band disease, documented for the first time on the FRT.
Through understanding the response of the D. cylindrus holobiont partners to biotic and abiotic stressors, such as hyperthermal bleaching and associated diseases, we gained valuable insights into how this threatened species may respond to a changing climate.
Lewis, Cynthia Fairbank, "Florida's Pillar Coral (Dendrogyra cylindrus): The Roles of the Holobiont Partners in Bleaching, Recovery, and Disease Processes" (2018). FIU Electronic Theses and Dissertations. 3952.
Coral Reefs: Black Band Disease in Dendrogyra cylindrus
Lewis et al 2019_fmars-recurring episodes of thermal stress_DCYL-symbiont shift.pdf (2603 kB)
Frontiers in Marine Biology: Symbiont species shift in Dendrogyra cylindrus
Lewis et al 2019_fmars-supplemental_2_ETD.pdf (111 kB)
Frontiers in Marine Biology: supplemental material
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