As sea surface temperatures increase worldwide due to climate change, coral bleaching events are becoming more frequent and severe, resulting in reef degradation. Leveraging the inherent ability of reef-building corals to acclimatize to thermal stress via pre-exposure to protective temperature treatments may become an important tool in improving the resilience of coral reefs to rapid environmental change. We investigated whether historical bleaching phenotype, coral host genotype, and exposure to protective temperature treatments would affect the response of the Hawaiian coral Montipora capitata to natural thermal stress. Fragments were collected from colonies that demonstrated different bleaching responses during the 2014–2015 event in Kāne‘ohe Bay (O‘ahu, Hawai‘i) and exposed to four different artificial temperature pre-treatments (and a control at ambient temperature). After recovery, fragments experienced a natural thermal stress event either in laboratory conditions or their native reef environment. Response to thermal stress was quantified by measuring changes in the algal symbionts’ photochemical efficiency, community composition, and relative density. Historical bleaching phenotype was reflected in stable differences in symbiont community composition, with historically bleached corals containing only Cladocopium symbionts and historically non-bleached corals having mixed symbiont communities dominated by Durusdinium. Mixed-community corals lost more Cladocopium than Cladocopium -only corals during the natural thermal stress event and preferentially recovered with Durusdinium . Laboratory pre-treatments exposed corals to more thermal stress than anticipated, causing photochemical damage that varied significantly by genotype. While none of the treatments had a protective effect, temperature variation during treatments had a significant detrimental effect on photochemical efficiency during the thermal stress event. These results show that acclimatization potential is affected by fine-scale differences in temperature regime, host genotype, and relatively stable differences in symbiont community composition that underpin historical bleaching phenotypes in M. capitata.

中文翻译：

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藻类共生体群落的宿主基因型和稳定差异解释了在热暴露后和多次漂白事件后，头顶珊瑚的热应激反应模式

由于气候变化导致全球海面温度升高，珊瑚白化事件变得越来越频繁和严重，导致珊瑚礁退化。利用造礁珊瑚通过预先暴露于保护性温度处理来适应热应力的固有能力，可能成为提高珊瑚礁对快速环境变化的适应能力的重要工具。我们调查了历史漂白表型、珊瑚宿主基因型和暴露于保护性温度处理是否会影响夏威夷珊瑚蒙蒂波拉对自然热应激的反应。在 2014-2015 年卡内奥赫湾 (O'ahu, Hawai'i）并暴露于四种不同的人工温度预处理（以及环境温度下的对照）。回收后，碎片在实验室条件或其原生珊瑚礁环境中经历了自然热应力事件。通过测量藻类共生体的光化学效率、群落组成和相对密度的变化来量化对热应力的响应。历史漂白表型反映在共生体群落组成的稳定差异中，历史上漂白的珊瑚仅包含 Cladocopium 共生体，而历史上未漂白的珊瑚则具有以 Durusdinium 为主的混合共生体群落。在自然热应激事件期间，混合群落珊瑚失去的 Cladocopium 比仅 Cladocopium 珊瑚多，并且优先与 Durusdinium 一起恢复。实验室预处理使珊瑚暴露在比预期更多的热应力下，导致光化学损伤因基因型而异。虽然没有一种处理具有保护作用，但处理过程中的温度变化对热应力事件期间的光化学效率有显着的不利影响。这些结果表明，驯化潜力受温度状况、宿主基因型和共生群落组成的相对稳定差异的影响，这些差异支持 M.capitata 的历史漂白表型。处理过程中的温度变化对热应力事件期间的光化学效率有显着的不利影响。这些结果表明，驯化潜力受到温度状况、宿主基因型和共生群落组成的相对稳定差异的影响，这些差异支持 M.capitata 的历史漂白表型。处理过程中的温度变化对热应力事件期间的光化学效率有显着的不利影响。这些结果表明，驯化潜力受温度状况、宿主基因型和共生群落组成的相对稳定差异的影响，这些差异支持 M.capitata 的历史漂白表型。