Kenkel Carly D, Almanza Albert T, Matz Mikhail V
Ecology. 2015 Dec;96(12):3197-212. doi: 10.1890/14-2297.1.
Despite decades of monitoring global reef decline, we are still largely unable to explain patterns of reef deterioration at local scales, which precludes the development of effective management strategies. Offshore reefs of the Florida Keys, USA, experience milder temperatures and lower nutrient loads in comparison to inshore reefs yet remain considerably more degraded than nearshore patch reefs. A year-long reciprocal transplant experiment of the mustard hill coral (Porites astreoides) involving four source and eight transplant locations reveals that corals adapt and/or acclimatize to their local habitat on a < 10-km scale. Surprisingly, transplantation to putatively similar environmental types (e.g., offshore corals moved to a novel offshore site, or along-shore transplantation) resulted in greater reductions in fitness proxies, such as coral growth, than cross-channel transplantation between inshore and offshore reefs. The only abiotic factor showing significantly greater differences between along-shore sites was daily temperature range extremes (rather than the absolute high or low temperatures reached), providing a possible explanation for this pattern. Offshore-origin corals exhibited significant growth reductions at sites with greater daily temperature ranges, which explained up to 39% of the variation in their mass gain. In contrast, daily temperature range explained at most 9% of growth variation in inshore-origin corals, suggesting that inshore corals are more tolerant of high-frequency temperature fluctuations. Finally, corals incur trade-offs when specializing to their native reef. Across reef locations the coefficient of selection against coral transplants was 0.07 ± 0.02 (mean ± SE). This selection against immigrants could hinder the ability of corals to recolonize devastated reefs, whether through assisted migration efforts or natural recruitment events, providing a unifying explanation for observed patterns of coral decline in this reef system.
尽管数十年来一直在监测全球珊瑚礁的衰退情况，但我们在很大程度上仍无法解释局部尺度上珊瑚礁退化的模式，这使得有效的管理策略难以制定。与近岸珊瑚礁相比，美国佛罗里达群岛的离岸珊瑚礁温度较低，营养负荷也较低，但退化程度却比近岸斑块珊瑚礁严重得多。一项为期一年的关于芥菜山珊瑚（Porites astreoides）的相互移植实验，涉及四个来源地和八个移植地点，结果表明珊瑚在小于10公里的尺度上适应和/或驯化于其当地栖息地。令人惊讶的是，移植到假定相似的环境类型（例如，将离岸珊瑚移至新的离岸地点，或沿岸移植）导致的适应性指标下降，如珊瑚生长，比近岸和离岸珊瑚礁之间的跨海峡移植更大。沿岸地点之间唯一显示出显著更大差异的非生物因素是每日极端温度范围（而非达到的绝对高温或低温），这为这种模式提供了一种可能的解释。来自离岸的珊瑚在每日温度范围较大的地点生长显著减少，这解释了其质量增加变化的39%。相比之下，每日温度范围最多只能解释来自近岸的珊瑚生长变化的9%，这表明近岸珊瑚对高频温度波动更具耐受性。最后，珊瑚在适应其原生珊瑚礁时会面临权衡。在各个珊瑚礁地点，对珊瑚移植的选择系数为0.07±0.02（平均值±标准误差）。这种对外来者的选择可能会阻碍珊瑚通过辅助迁移或自然繁殖重新定殖到遭受破坏的珊瑚礁的能力，为该珊瑚礁系统中观察到的珊瑚衰退模式提供了一个统一的解释。
