Abstract Summary
Rising seawater temperatures are a major threat to coral reefs worldwide, causing coral bleaching events that are occurring annually in some locations and are expected to be annual events globally this century. Corals with high levels of stored energy reserves are known to have increased survival and resilience potential to annual bleaching stress. In this study, we hypothesize that corals that catabolize storage lipids (i.e., triacyglycerols and wax esters) in response to thermal bleaching, but then quickly reassimilate them during recovery will be more resilent to annual bleaching events compared to those that do not. We experimentally bleached three species of Caribbean corals (Porites astreoides, Porites divaricata, and Orbicella faveolata) two years in a row (summer 2009 and 2010) by gradually elevating seawater temperature to 31.5C. We measured concentrations of the following lipid classes using thin layer chromatography: wax esters, triacylglycerols, free fatty acids, cholesterol, and phospholipids. Preliminary results suggest that species had different strategies to respond to environmental change. Overall, O. faveolata and P. divaricata had higher concentrations of storage lipids such as wax esters and triacylglycerols than P. astreoides, in agreement with other studies which show that P. astreoides is the least resilient to repeat bleaching stress of the three species examined. We support prioritization of conservation efforts for O. faveolata and P. divaricata for stock colonies and restoration projects as they are the most likely to survive annual bleaching events of the future. We also found that 1) lipid class composition of O. faveolata was affected by single bleaching, but not repeat bleaching, and those differences were determined by storage lipids; 2) lipid class composition in P. astreoides only changed with repeat bleaching, but not single bleaching with differences also driven by storage lipids; and 3) lipid class composition in P. divaricata was unaffected by single or repeat bleaching. These findings show a complex pattern of acclimation of different species of coral to climate change, which might have important implications for colony assessment and adoption of restoration policies .
