Mechanisms for the Persistence of the Coral Holobiont in the Warming Oceans of the Anthropocene
Doctor of Philosophy (PhD)
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Jose M Eirin-Lopez
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Integrative biology, terrestrial and aquatic ecology
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Coral Reefs are rapidly deteriorating in response to an onslaught of human-mediated stressors. Just one stressor alone, climate change, may extirpate coral reef ecosystems within a human lifetime, threatening societal and ecological catastrophe. Reef-derived ecosystem services are crucial for sustenance, coastal protection, and economic prosperity in over 100 countries. Near-term human decisions will determine whether reef-corals, the ecosystems they engineer, the 25% of marine biodiversity they support, and the human communities that depend upon them can be protected. My dissertation aims to characterize the potential for corals' adaptive mechanisms to facilitate their continued survival- information which will only represent hope if society takes decisive action on numerous environmental concerns. Even with swift action to curb carbon emissions, most of the world's reefs will come to experience annual hyperthermal stress beyond their current tolerances. Rapid warming necessitates improvement of physiological limits to prevent mass coral bleaching and disease. Bleaching metabolically deprives corals by terminating their ix obligate nutritional mutualism with symbiodiniacid dinoflagellates, while outbreaks of coral disease result in direct mortality. Using common garden experiments and coral species with disparate adaptive strategies, my dissertation appraises the feasibility of corals' adaptive mechanisms to facilitate survival under hyperthermal stress and environmental variability along a depth-cline. I characterized and monitored Symbiodiniaceae to detect adaptive changes in community identity, appraised the intrinsic capacity for corals to acclimatize, and estimated the potential for adaptation through coral evolution by comparing genotypes within the same species. Monitoring the dynamics of mass bleaching and disease outbreaks further enabled me to disentangle the frequently confounded effects of bleaching and thermal stress on an individual colony's risk of disease. Surprising results suggest that some bleaching may represent a mechanism of immune-activation by corals preparing to fight disease. I detected limited responsiveness of Symbiodiniaceae community rearrangement and no effect of innate acclimatization under the thermal stress, depth environments, and coral species investigated here. By contrast, variation between coral genotypes was a strong and highly significant predictor of all measurements made throughout this project. My dissertation provides recommendations for leveraging variability in host genotype performance and facilitating enormous evolutionary potential within a restoration framework.
Merselis, Daniel G., "Mechanisms for the Persistence of the Coral Holobiont in the Warming Oceans of the Anthropocene" (2019). FIU Electronic Theses and Dissertations. 4287.
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