Scripps Institution of Oceanography, Center for Marine Biodiversity and Conservation, University of California San Diego, La Jolla, California, United States of America.
School of Geographical Sciences and Urban Planning, Arizona State University, Tempe, Arizona, United States of America.
PLoS One. 2024 Jul 31;19(7):e0303779. doi: 10.1371/journal.pone.0303779. eCollection 2024.
Climate change is transforming coral reefs by increasing the frequency and intensity of marine heatwaves, often leading to coral bleaching and mortality. Coral communities have demonstrated modest increases in thermal tolerance following repeated exposure to moderate heat stress, but it is unclear whether these shifts represent acclimatization of individual colonies or mortality of thermally susceptible individuals. For corals that survive repeated bleaching events, it is important to understand how past bleaching responses impact future growth potential. Here, we track the bleaching responses of 1,832 corals in leeward Maui through multiple marine heatwaves and document patterns of coral growth and survivorship over a seven-year period. While we find limited evidence of acclimatization at population scales, we document reduced bleaching over time in specific individuals that is indicative of acclimatization, primarily in the stress-tolerant taxa Porites lobata. For corals that survived both bleaching events, we find no relationship between bleaching response and coral growth in three of four taxa studied. This decoupling suggests that coral survivorship is a better indicator of future growth than is a coral's bleaching history. Based on these results, we recommend restoration practitioners in Hawai'i focus on colonies of Porites and Montipora with a proven track-record of growth and survivorship, rather than devote resources toward identifying and cultivating bleaching-resistant phenotypes in the lab. Survivorship followed a latitudinal thermal stress gradient, but because this gradient was small, it is likely that local environmental factors also drove differences in coral performance between sites. Efforts to reduce human impacts at low performing sites would likely improve coral survivorship in the future.
气候变化通过增加海洋热浪的频率和强度来改变珊瑚礁，这通常会导致珊瑚白化和死亡。珊瑚群落已经表现出在反复暴露于中度热应激下适度增加耐热性，但尚不清楚这些变化是否代表单个群体的适应或对热敏感个体的死亡。对于能够多次经受白化事件的珊瑚，了解过去的白化反应如何影响未来的生长潜力非常重要。在这里，我们通过多次海洋热浪跟踪了毛伊岛背风面的 1832 株珊瑚的白化反应，并记录了七年期间珊瑚生长和存活率的模式。虽然我们在种群规模上发现了适应的有限证据，但我们记录到特定个体的白化反应随时间减少，这表明存在适应，主要是在耐受压力的石珊瑚 Porites lobata 中。对于能够两次白化事件都存活下来的珊瑚，我们发现，在所研究的四个珊瑚物种中的三个中，珊瑚的白化反应与生长之间没有关系。这种解耦表明，珊瑚的存活率是未来生长的更好指标，而不是珊瑚的白化历史。基于这些结果，我们建议夏威夷的修复实践人员关注 Porites 和 Montipora 等具有生长和存活率良好记录的群体，而不是将资源投入到实验室中识别和培育抗白化表型。存活率遵循纬度热应激梯度，但由于该梯度较小，因此当地环境因素也可能导致不同地点的珊瑚表现存在差异。减少低表现地点的人为影响的努力可能会提高珊瑚的未来存活率。
