Hulver Ann Marie, Béraud Éric, Dixon Shannon, Moya Aurélie, Alderdice Rachel, Muñoz-Garcia Agustí, Voolstra Christian R, Ferrier-Pagès Christine, Grottoli Andréa G
School of Earth Sciences, The Ohio State University, 125 South Oval Mall, Columbus, OH 43210, USA.
Centre Scientifique de Monaco, Equipe Ecophysiologie Corallienne, Monaco, Monaco.
Sci Total Environ. 2025 Aug 28:180234. doi: 10.1016/j.scitotenv.2025.180234.
Coral reefs are threatened worldwide from unprecedented increases in ocean temperatures, resulting in corals gradually living closer to their maximum thermal threshold. With ocean temperatures expected to warm up to 3 °C by 2100, understanding the effects of chronic elevated baseline temperature is important in determining the thermal physiological limits of corals and developing realistic restoration strategies to ensure the future of coral reefs. Here, we tested the effects of 26 weeks (i.e., six months) of elevated temperatures of + 2.5 °C (27.5 °C) and + 5 °C (30 °C) above a baseline of 25 °C on surface area growth, metabolic rates, energy reserves, assimilation of heterotrophically acquired food, and Symbiodiniaceae species composition in the aquaria-reared thermally tolerant coral Stylophorapistillata sourced from the northern Red Sea. Corals initially catabolized lipids while maintaining growth after 4 weeks of elevated baseline temperatures but acclimated after only 11 weeks. However, there was evidence of a long-term cumulative impact of chronic elevated temperatures after 26 weeks at 30 °C with corals experiencing higher metabolic demand and lower growth while maintaining biomass and energy reserves. Therefore, maintenance of tissue biomass and energy reserves appears to come at the cost of skeletal accretion but allows these corals to survive changes in baseline temperatures up to 30 °C. These physiological changes were not associated with Symbiodiniaceae species composition, which remained constant throughout the experiment. We also discovered that a return to 25 °C for four weeks allowed for recovery of metabolic demand and growth. Our data suggests that chronic exposure to high, sub-bleaching temperatures, a plausible scenario in the near future, will have some negative effects on coral growth and metabolism, but not survival. Thus, while S. pistillata survives but does not thrive under projected shifts in baseline temperature, this study shows hope for acclimatization to temperature shifts expected in the next 50 years.
全球范围内，珊瑚礁正受到海洋温度前所未有的上升威胁，导致珊瑚逐渐接近其最高热阈值。预计到2100年海洋温度将上升3摄氏度，了解长期升高的基线温度的影响对于确定珊瑚的热生理极限以及制定切实可行的恢复策略以确保珊瑚礁的未来至关重要。在此，我们测试了在25摄氏度的基线温度之上，分别升高2.5摄氏度（27.5摄氏度）和5摄氏度（30摄氏度）并持续26周（即六个月），对来自红海北部、在水族箱中饲养的耐热珊瑚细指蔷薇珊瑚的表面积生长、代谢率、能量储备、异养获取食物的同化以及共生藻物种组成的影响。在基线温度升高4周后，珊瑚最初分解脂质以维持生长，但仅在11周后就适应了。然而，在30摄氏度下持续26周后，有证据表明长期升高的温度存在累积影响，此时珊瑚代谢需求更高，生长更低，但能维持生物量和能量储备。因此，维持组织生物量和能量储备似乎是以骨骼生长为代价的，但能使这些珊瑚在高达30摄氏度的基线温度变化中存活下来。这些生理变化与共生藻物种组成无关，共生藻物种组成在整个实验过程中保持不变。我们还发现，恢复到25摄氏度四周可使代谢需求和生长恢复。我们的数据表明，长期暴露于接近白化的高温下（这在不久的将来是一种可能的情况），将对珊瑚生长和代谢产生一些负面影响，但不会导致死亡。因此，虽然细指蔷薇珊瑚在预计的基线温度变化下能够存活但无法茁壮成长，但这项研究为适应未来50年预期的温度变化带来了希望。
