As climate change poses an ever increasing threat to coral reefs globally, understanding why particular corals are resistant to bleaching is paramount to their continued survival. The coral reefs of Ofu Island, American Samoa, provide a living laboratory to examine mechanisms of coral adaptation to extreme thermal conditions and serve as an analog for a future environment impacted by climate change. Three backreef pools exhibit remarkably different temperature regimes, which consequently results in varying levels of coral thermal tolerance. In pool 300, temperatures can reach 35 °C and fluctuate up to 6 °C throughout the day. Pools 400 and 500 are less variable, with temperatures rarely exceeding 32 °C. Yet, the pools contain a highly diverse community of corals, including an abundance of thermally sensitive species. This review summarizes the results of nearly two decades of research into the mechanisms contributing to differential bleaching resistance among pools. Factors examined include the effects of intermittent water flow, previous exposure to subbleaching temperatures, Symbiodinium genotype, modifications of genetic expression within the polyp, and the associated bacterial microbiome. Corals within the highly variable pool 300 appear to be more adequately adapted to thermal extremes by retaining chlorophyll concentrations during frequent heat pulses, associating with thermally tolerant endosymbionts, upregulating gene expression associated with heat acclimatization, and potentially possessing an advantageous microbiome composition. Though encompassing a small geographic area, the findings from Ofu’s reefs have widespread implications for coral conservation as they serve to elucidate the impacts of these many confounding factors and their contributions to bleaching resistance.

中文翻译：

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美属萨摩亚珊瑚礁的超高耐热性：综述

由于气候变化对全球珊瑚礁构成越来越大的威胁，因此了解为什么特定的珊瑚具有抗漂白性对它们的持续生存至关重要。美属萨摩亚Ofu岛的珊瑚礁提供了一个活着的实验室，用于研究珊瑚对极端温度条件的适应机制，并作为受气候变化影响的未来环境的类似物。三个后礁池显示出明显不同的温度状况，因此导致珊瑚的耐热性水平不同。在游泳池300中，温度可能会达到35°C，并且全天最多会波动6°C。池400和500的变化较小，温度很少超过32°C。但是，水池中包含高度多样的珊瑚群落，其中包括大量的热敏感物种。这篇综述总结了近二十年来对导致池中不同的耐漂白性的机理的研究结果。检查的因素包括间歇水流的影响，先前暴露于亚漂白温度，共生菌基因型，息肉内基因表达的修饰以及相关的细菌微生物组。通过在频繁的热脉冲期间保持叶绿素浓度，与耐热的内共生菌相关联，上调与热适应相关的基因表达，并且潜在地具有有利的微生物组组成，高可变库300内的珊瑚似乎更充分地适应了极端温度。尽管占地很小，但是Ofu珊瑚礁的发现对珊瑚保护具有广泛的意义，因为它们有助于阐明这些许多混杂因素的影响以及它们对耐漂白性的贡献。