2016年和2017年的背靠背海洋热浪导致大堡礁(GBR)的珊瑚严重白化和死亡。令人鼓舞的是,在这些事件中幸存下来的一些珊瑚表现出增强的抗漂白性,并且可能代表能够更好地应对海洋变暖的耐热种群。使用GBR作为自然实验室,我们调查了2016年和2017年的最小(苍鹭岛)或严重(蜥蜴岛)珊瑚白化的历史是否等同于连续热浪(2020年)的压力耐受性。我们检查了遗传多样性,生理表现,和两个常见属(Pocillopora和Stylophora)的幼年(<10cm)和成年(>25cm)珊瑚的营养可塑性。尽管忍受了更大的累积热应激(6.3°C第1周与5.6°C周-1),5年内经历第三次海洋热浪的珊瑚(蜥蜴)的存活率和视觉漂白阈值是10年内未经历明显漂白的珊瑚(Heron)的两倍。令人惊讶的是,在位置之间仅发现了一个共享的寄主-共生科关联(Pistillata-Cladocopium\“C8组”),并且在Pocillopora-Cladocopium伙伴关系中没有遗传重叠,表明最近海洋热浪造成的物种组成周转。在蜥蜴岛的2016年和2017年海洋热浪中幸存下来的Pocillopora物种中的珊瑚最具弹性,在苍鹭岛表现出的钙化率是同种异体的三倍。Further,幸存的珊瑚(蜥蜴)具有明显的同位素生态位,较低的主体碳,和更大的宿主蛋白,虽然最近没有经历过漂白的物种(Heron)的共生体碳含量高了两倍,建议影响生存的不同营养策略(即,更多地依赖异型萎缩与共生体自养,分别)。最终,虽然珊瑚可能经历较少的漂白并在反复的热应激事件中幸存下来,确实会发生特定物种的权衡,面对日益加剧的海洋热浪,留下了许多与珊瑚礁生态系统长期健康和恢复有关的问题。
Back-to-back marine heatwaves in 2016 and 2017 resulted in severe coral bleaching and mortality across the Great Barrier Reef (GBR). Encouragingly, some corals that survived these events exhibit increased bleaching resistance and may represent thermally tolerant populations that can better cope with ocean warming. Using the GBR as a natural laboratory, we investigated whether a history of minimal (Heron Island) or severe (Lizard Island) coral bleaching in 2016 and 2017 equates to stress tolerance in a successive heatwave (2020). We examined the genetic diversity, physiological performance, and trophic plasticity of juvenile (<10 cm) and adult (>25 cm) corals of two common genera (Pocillopora and Stylophora). Despite enduring greater cumulative heat stress (6.3°C week-1 vs. 5.6°C week-1), corals that experienced the third marine heatwave in 5 years (Lizard) exhibited twice as high survival and visual bleaching thresholds compared to corals that had not experienced significant bleaching in >10 years (Heron). Surprisingly, only one shared host-Symbiodiniaceae association was uncovered between locations (Stylophora pistillata-Cladocopium \"C8 group\") and there was no genetic overlap in Pocillopora-Cladocopium partnerships, suggesting turnover in species composition from recent marine heatwaves. Corals within the species complex Pocillopora that survived the 2016 and 2017 marine heatwaves at Lizard Island were the most resilient, exhibiting three times greater calcification rates than conspecifics at Heron Island. Further, surviving corals (Lizard) had distinct isotopic niches, lower host carbon, and greater host protein, while conspecifics that had not experienced recent bleaching (Heron) had two times greater symbiont carbon content, suggesting divergent trophic strategies that influenced survival (i.e., greater reliance on heterotrophy vs. symbiont autotrophy, respectively). Ultimately, while corals may experience less bleaching and survive repeated thermal stress events, species-specific trade-offs do occur, leaving open many questions related to the long-term health and recovery of coral reef ecosystems in the face of intensifying marine heatwaves.