Coral and associated symbiont physiologies are resilient to changes in pCO2 but are negatively affected by temperature stress

Undergraduates: Jessica Boulton, Sarah Davies Colleeen Bove, Justin Ries Alyssa Knowlton

Faculty Advisor: Karl Castillo
Department: Biology

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Corals and the dinoflagellate algae Symbiodinium exist in an obligate symbiosis where photosynthetically derived nutrients translocated to the host from intracellular Symbiodinium can provide up to 100% of the coral¿¿¿s energy budget. Increases in sea surface temperature and decreases in oceanic pH reduce the competency of corals to maintain this symbiosis. As a result, increased coral bleaching events have been observed globally as climate change progresses. To quantify the immediate, transitional, and long-term physiological responses of coral hosts and algal symbionts to climate change stressors, we exposed the Caribbean corals Siderastrea siderea and Pseudodiploria strigosa to various temperature (28, 31 C) and pCO2 (280, 400, 700, and 2800 ppm) treatments for 90 days. Temperature and pCO2 were fully crossed and four fragments of each colony were maintained in each treatment. One colony fragment was removed at each time point (0, 30, 60, 90 days) and coral tissue protein and chlorophyll a concentrations were quantified as proxies for coral host and algal symbiont physiology. Preliminary results suggest that both host and symbiont physiology are negatively affected by temperature, however both partners appear resilient to changes in pCO2. The results from this study shed light on how pCO2 and temperature stress interact to affect the physiology of coral holobionts.