Preconditioning in the reef-building coral Pocillopora damicornis and the potential for trans-generational acclimatization in coral larvae under future climate change conditions

Coral reefs are globally threatened by climate change-related ocean warming and ocean acidification (OA). To date, slow-response mechanisms such as genetic adaptation have been considered the major determinant of coral reef persistence, with little consideration of rapid-response acclimatization mechanisms. These rapid mechanisms such as parental effects that can contribute to trans-generational acclimatization (e.g. epigenetics) have, however, been identified as important contributors to offspring response in other systems. We present the first evidence of parental effects in a cross-generational exposure to temperature and OA in reef-building corals. Here, we exposed adults to high (28.9°C, 805 µatm PCO2) or ambient (26.5°C, 417 µatm PCO2) temperature and OA treatments during the larval brooding period. Exposure to high treatment negatively affected adult performance, but their larvae exhibited size differences and metabolic acclimation when subsequently re-exposed, unlike larvae from parents exposed to ambient conditions. Understanding the innate capacity corals possess to respond to current and future climatic conditions is essential to reef protection and maintenance. Our results identify that parental effects may have an important role through (1) ameliorating the effects of stress through preconditioning and adaptive plasticity, and/or (2) amplifying the negative parental response through latent effects on future life stages. Whether the consequences of parental effects and the potential for trans-generational acclimatization are beneficial or maladaptive, our work identifies a critical need to expand currently proposed climate change outcomes for corals to further assess rapid response mechanisms that include non-genetic inheritance through parental contributions and classical epigenetic mechanisms.

全球范围内的珊瑚礁正受到气候变化相关海洋升温和海洋酸化（OA）的严重威胁。迄今为止，遗传适应等慢响应机制被认为是珊瑚礁存续的核心决定因素，而快速响应驯化机制却鲜有被纳入考量范畴。不过，诸如可介导跨代驯化的亲本效应（例如表观遗传学（epigenetics））这类快速响应机制，在其他生物系统中已被证实是子代响应的关键影响因子。本研究首次报道了造礁珊瑚（reef-building corals）在跨代暴露于温度与OA胁迫下的亲本效应相关实验证据。本实验中，研究人员在幼体抚育期将成体珊瑚分别暴露于高胁迫处理组（28.9°C，805 µatm PCO₂）与对照处理组（26.5°C，417 µatm PCO₂）的温度与OA复合胁迫环境中。高胁迫处理对成体的生理表现产生了显著负面影响，但相较于亲代暴露于对照环境的幼体，经高胁迫处理的成体所产幼体在后续再次暴露于胁迫环境时，表现出明显的体型差异与代谢驯化现象。明确珊瑚应对当前及未来气候条件的内在潜能，对于珊瑚礁的保护与维持工作至关重要。本研究结果表明，亲本效应或可通过两种关键途径发挥重要作用：(1) 通过预适应与适应性可塑性缓解胁迫带来的负面影响；(2) 通过对后续生活史阶段的潜在效应放大亲代所受胁迫的负面后果。无论亲本效应的最终影响以及跨代驯化的潜力是有益还是适应不良，本研究均明确指出，当前针对珊瑚的气候变化影响预测框架亟需拓展，以进一步评估包含亲本介导的非遗传遗传以及经典表观遗传机制在内的快速响应机制。