Impact of ocean warming on coral thermal tolerance (ANCHOR)

气候变化以前所未有的规模影响珊瑚礁生态系统，热应激事件的频率、强度和持续时间在全球范围内增加，导致珊瑚白化（即光合藻类内共生体的丧失）和死亡率上升。耐热珊瑚很可能是未来珊瑚礁的主要建造者和生态系统维护者，但我们不知道预计的海面温度上升将如何影响它们应对更热的夏季峰值的能力。在这里，我们建议确定假定的“应力弹性”珊瑚是否以及如何调整其热耐受阈值，或者如果这些阈值是遗传固定的。我们建议进行一项长期变暖实验（遵循IPCC RCP-2.6和4.5轨迹），并穿插模拟夏季峰值的短期热应激试验。新的标准化珊瑚白化自动压力系统（CBASS）将用于确定珊瑚的热阈值随时间的变化，并评估在返回基线条件后是否有任何可能的适应性丧失。在所研究的珊瑚群落中，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热耐受阈值的关键过程，以及生物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.