Collaborative Research: Acquisition, Allocation, and Utilization of Carbon in Bleached and Recovering Corals

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Drs. Grottoli and Pease will investigate the underlying mechanisms influencing coral recovery and mortality during bleaching by studying carbon acquisition, allocation and utilization of the coral host. During bleaching, when corals loose their symbiotic algae and their supply of photosynthetically fixed carbon is dramatically reduced or lost, they must rely on other sources of energy such as stored lipids and carbohydrates, or heterotrophically acquired carbon to sustain their energetic demands. If (1) corals are better able to acquire carbon by increasing heterotrophic feeding, they may be more likely to survive bleaching and fully recover. Alternatively, if (2) corals are able to store larger amounts of excess energy reserves during non-bleaching periods (e.g., as lipids), they may be able to sustain themselves by utilizing these reserves until fully recovered. If (3) corals are more efficient at utilizing these stored energy reserves, they may be more likely to recover from bleaching. All three of these strategies are hypothesized mechanisms used by corals to promote recovery following bleaching. In order to evaluate each mechanism, these investigators will perform a series of 13C-pulse labeling experiments designed to track the source of the fixed carbon, its allocation and storage within the host, and its utilization in bleached Montipora capitata and Porites compressa corals over the course of 14 months of recovery (relative to non-bleached controls). The experimental design allows for simultaneously measured variables to be comprehensively interpreted within the overall picture of the coral-algal symbiont-skeleton system relative to a control group. The results of this research will contribute to a better understanding in fundamental biology of coral bleaching by experimentally evaluating the physiological and biogeochemical responses of corals to temperature-induced bleaching stressors both during bleaching and recovery. This work will build the framework for understanding the causes and consequences of bleaching on corals. This project involves the training of two PhD students (one with each collaborating investigator), a Postdoc, and two undergraduate students. Both investigators will incorporate research results from this project in their teaching and present the research in public lectures and through established K-12 outreach and teacher in-service training workshops.