Seasonal impacts of ocean acidification and warming on coral physiology from pre- and post-summer temperature and pCO2 conditions of Acropora digitifera and Montipora digitata

This study examines the impact of ocean acidification (OA), ocean warming (OW), and combination of OA + OW on the physiology of branching corals Acropora digitifera and Montipora digitata before and after a summer bleaching event. The experiments were conducted in pre- and post-summer of 2017 to evaluate changing coral calcification rates and the maximum quantum yield of PSII (Fv/Fm). Our finding showed that both species experience reduced calcification rates and Fv/Fm under these stress conditions. Notably, the most severe impacts were observed in the post-summer period, suggesting that the prior summer conditions, including bleaching stress, exacerbated the effects of additional stressors. The increased sensitivity observed post-summer highlights the potential for synergistic impacts of multiple stressors, with prior exposure to high temperatures and bleaching events contributing to diminished thermal tolerance. These findings underscore the importance of considering the timing and cumulative effects of climate stressors on coral physiology. Further research is needed to explore the physiological and ecological mechanisms driving these seasonal responses to better predict and mitigate the impacts of climate change on coral reef ecosystems.