Glob Chang Biol. 2014 Jan;20(1):125-39. doi: 10.1111/gcb.12390.
Climate warming threatens to increase mass coral bleaching events, and several studies have projected the demise of tropical coral reefs this century. However, recent evidence indicates corals may be able to respond to thermal stress though adaptive processes (e.g., genetic adaptation, acclimatization, and symbiont shuffling). How these mechanisms might influence warming-induced bleaching remains largely unknown. This study compared how different adaptive processes could affect coral bleaching projections. We used the latest bias-corrected global sea surface temperature (SST) output from the NOAA/GFDL Earth System Model 2 (ESM2M) for the preindustrial period through 2100 to project coral bleaching trajectories. Initial results showed that, in the absence of adaptive processes, application of a preindustrial climatology to the NOAA Coral Reef Watch bleaching prediction method overpredicts the present-day bleaching frequency. This suggests that corals may have already responded adaptively to some warming over the industrial period. We then modified the prediction method so that the bleaching threshold either permanently increased in response to thermal history (e.g., simulating directional genetic selection) or temporarily increased for 2-10 years in response to a bleaching event (e.g., simulating symbiont shuffling). A bleaching threshold that changes relative to the preceding 60 years of thermal history reduced the frequency of mass bleaching events by 20-80% compared with the 'no adaptive response' prediction model by 2100, depending on the emissions scenario. When both types of adaptive responses were applied, up to 14% more reef cells avoided high-frequency bleaching by 2100. However, temporary increases in bleaching thresholds alone only delayed the occurrence of high-frequency bleaching by ca. 10 years in all but the lowest emissions scenario. Future research should test the rate and limit of different adaptive responses for coral species across latitudes and ocean basins to determine if and how much corals can respond to increasing thermal stress.
气候变暖威胁到大规模珊瑚白化事件的增加，有几项研究预计本世纪热带珊瑚礁将会灭绝。然而，最近的证据表明，珊瑚可能能够通过适应过程（例如遗传适应、驯化和共生体 shuffling）来应对热应激。这些机制如何影响因变暖引起的白化仍然知之甚少。本研究比较了不同适应过程如何影响珊瑚白化预测。我们使用了来自 NOAA/GFDL 地球系统模型 2（ESM2M）的最新偏置校正的全球海面温度（SST）输出，从工业化前到 2100 年预测珊瑚白化轨迹。初步结果表明，在没有适应过程的情况下，将工业化前气候应用于 NOAA 珊瑚礁观察白化预测方法会过高预测当前白化频率。这表明，在工业化时期，珊瑚可能已经对某些变暖做出了适应性反应。然后，我们修改了预测方法，使得白化阈值要么根据热历史永久增加（例如，模拟定向遗传选择），要么在白化事件后暂时增加 2-10 年（例如，模拟共生体 shuffling）。与“无适应响应”预测模型相比，白化阈值相对于前 60 年热历史的变化减少了 20-80%的大规模白化事件频率，这取决于排放情景。当应用这两种适应反应类型时，到 2100 年，多达 14%的珊瑚礁细胞可以避免高频白化。然而，单独增加白化阈值仅在除最低排放情景外的所有情景中延迟高频白化的发生约 10 年。未来的研究应该测试不同纬度和海洋盆地的珊瑚物种的适应反应的速度和限制，以确定珊瑚是否以及能在多大程度上应对不断增加的热应激。
