Impact of ocean warming on coral thermal tolerance (ANCHOR)

气候变化以前所未有的规模影响着珊瑚礁生态系统，全球热应力事件的频率、强度和持续时间都在增加，导致珊瑚漂白率不断上升（即，失去它们的光合藻类内共生体）和死亡率。耐热珊瑚很可能是未来珊瑚礁的主要造礁者和生态系统维持者，但我们不知道预测的海面温度上升将如何影响它们应对更热夏季最高温度的能力。在这里，我们建议确定是否以及如何假定的“压力弹性”珊瑚可以调整其耐热阈值，或者如果这些阈值是遗传固定的。我们建议进行长期变暖实验（遵循IPCC RCP-2.6和4.5轨迹），并穿插模拟夏季最大值的短期热应力试验。新的标准化珊瑚漂白自动压力系统（CBASS）将用于确定珊瑚热阈值随时间的进展，并评估在恢复到基线条件后是否失去任何可能的适应。在所调查的珊瑚群落中，耐热性的基因组和遗传基础将通过其基因表达和微生物群落组成来表征。我们的研究结果可以揭示珊瑚耐热阈值的关键过程，以及生物体如何在变暖的世界中应对急性热应激事件，最终更好地预测气候变化对未来珊瑚礁的影响。

Climate change affects coral reef ecosystems at an unprecedented scale, with a global increase of the frequency, intensity, and duration of heat stress events, resulting in escalating rates of coral bleaching (i.e., loss of their photosynthetic algal endosymbionts) and mortality. Thermally tolerant corals will most likely be the main reef builders and ecosystem sustainers of future reefs, but we do not know how the predicted increase in sea surface temperatures will affect their ability to respond to even hotter summer maxima. Here, we propose to determine if and how putative 'stress resilient' corals can adjust their thermal tolerance thresholds, or alternatively if those thresholds are genetically fixed. We propose to conduct a long-term warming experiment (following the IPCC RCP-2.6 and 4.5 trajectories) interspersed with short-term heat stress assays that mimic summer maxima. The new standardized Coral Bleaching Automated Stress System (CBASS) will be used to determine the progression of corals’ thermal thresholds over time and assess if any possible acclimation is lost upon return to baseline conditions. The genomic and genetic underpinnings of thermal tolerance in the investigated coral colonies will be characterized via their gene expression and microbial community composition. Our results could uncover critical processes underlying coral thermal tolerance thresholds and how organisms respond to acute heat stress events in a warming world, to ultimately better forecast the impact of climate change on coral reefs of the future.