Print PageCoral reefs have declined significantly over the past decade, particularly in the Caribbean. Predictions of reef persistence in the face of progressing climate change range from minimal loss to complete devastation. Coral reef resilience depends largely on the ability of corals to track increasing temperatures with evolutionary adaptation. However, the patterns and mechanisms of coral adaptation to varying thermal environments remain poorly understood. In the southern Florida Keys, inshore corals are exposed to temperature extremes in both the summer and winter, while offshore corals are buffered by the Gulf Stream. We hypothesized that inshore corals would be more resilient to thermal stress since they annually experience a broad range of temperature conditions, while offshore corals would be more susceptible. To test this prediction, we conducted a six-week common garden thermal stress experiment using fifteen colonies of the mustard hill coral, Porites astreoides, from each of the inshore and offshore reefs. Growth was quantified as a proxy of fitness using a buoyant weighting method. To elucidate the observed differences in terms of underlying molecular mechanisms, we also measured expression of genes implicated in stress response, metabolism, and immunity at the completion of the experiment.
Results/Conclusions
We find significant reductions in growth under thermal stress for both inshore and offshore origin corals. Importantly, offshore corals also exhibited significantly reduced growth in comparisson to inshore corals under thermal stress, supporting our hypothesis of local thermal adaptation. Offshore corals show reduced expression of adenosine kinase, spondin 2 and complement component C3 under thermal stress in comparison to inshore corals, suggesting that metabolic and immunity deficiencies may be contributing to the observed differences in stress susceptibility between the two populations.
