Biodiversity, Queensland Museum, Townsville, Queensland, 4811, Australia
Global Change Institute, ARC Centre of Excellence for Environmental Decisions, University of Queensland, Brisbane, Queensland, 4072, Australia.
Proc Biol Sci. 2017 Oct 11;284(1864). doi: 10.1098/rspb.2017.1551.
Mass bleaching associated with unusually high sea temperatures represents one of the greatest threats to corals and coral reef ecosystems. Deeper reef areas are hypothesized as potential refugia, but the susceptibility of Scleractinian species over depth has not been quantified. During the most severe bleaching event on record, we found up to 83% of coral cover severely affected on Maldivian reefs at a depth of 3-5 m, but significantly reduced effects at 24-30 m. Analysis of 153 species' responses showed depth, shading and species identity had strong, significant effects on susceptibility. Overall, 73.3% of the shallow-reef assemblage had individuals at a depth of 24-30 m with reduced effects, potentially mitigating local extinction and providing a source of recruits for population recovery. Although susceptibility was phylogenetically constrained, species-level effects caused most lineages to contain some partially resistant species. Many genera showed wide variation between species, including previously considered highly susceptible. Extinction risk estimates showed species and lineages of concern and those likely to dominate following repeated events. Our results show that deeper reef areas provide refuge for a large proportion of Scleractinian species during severe bleaching events and that the deepest occurring individuals of each population have the greatest potential to survive and drive reef recovery.
大规模白化现象与异常高的海水温度有关，是珊瑚和珊瑚礁生态系统面临的最大威胁之一。较深的珊瑚礁区域被假设为潜在的避难所，但在深度方面石珊瑚物种的易感性尚未量化。在有记录以来最严重的白化事件中，我们发现马尔代夫的珊瑚礁在 3-5 米的深度上，高达 83%的珊瑚覆盖率受到严重影响，但在 24-30 米的深度上影响显著降低。对 153 个物种响应的分析表明，深度、遮蔽和物种身份对易感性有强烈的、显著的影响。总体而言，浅海珊瑚礁组合中有 73.3%的个体在 24-30 米的深度上受到的影响较小，这可能减轻了局部灭绝的风险，并为种群恢复提供了新的补充来源。虽然易感性受到系统发育的限制，但物种水平的影响导致大多数谱系包含一些部分抗性物种。许多属种之间存在广泛的变异，包括以前被认为高度易感的属种。灭绝风险估计表明，存在受关注的物种和谱系，以及在反复发生事件后可能占主导地位的物种和谱系。我们的研究结果表明，在严重白化事件期间，较深的珊瑚礁区域为大量石珊瑚物种提供了避难所，而且每个种群中出现的最深个体最有可能存活下来并推动珊瑚礁恢复。
