在细胞水平上对高温珊瑚白化的初步研究

Preliminary study of coral bleaching at cellular level under thermal stress

全球变暖背景下的异常高温能够导致珊瑚及其虫黄藻组成的共生体系崩溃,虫黄藻大量损失,出现珊瑚白化,并可能进一步导致珊瑚礁生态系统退化。文章通过对6种造礁石珊瑚的急性高温胁迫实验,分析不同种属的石珊瑚虫黄藻共生体系对高温的耐受性差异,为全球变暖背景下珊瑚群落演替趋势提供理论依据。结果显示:1)在急性高温胁迫下,石珊瑚耐受的差异性与其形态有关,枝状珊瑚耐受性最低,在高温胁迫下最先白化、死亡,而叶片状和块状珊瑚对高温的耐受性较强,这与野外珊瑚礁白化的现场观测结果一致。2)在高温胁迫下,不同种属珊瑚共生虫黄藻损失的方式不同:珊瑚持续排出虫黄藻,如鹿角杯形珊瑚Pocillopora damicornis;珊瑚先排出一定的共生藻,之后珊瑚组织携带大量虫黄藻与珊瑚骨骼分离,如风信子鹿角珊瑚Acropora hyacinthus和松枝鹿角珊瑚Acropora brueggemanni;先排出部分虫黄藻后,虫黄藻以有丝分裂增殖的方式迅速补充其数量,如十字牡丹珊瑚Pavona decussata;虫黄藻细胞直接坏死而损失虫黄藻,如澄黄滨珊瑚Porites lutea。研究强调,预测珊瑚对全球变化的响应问题时,应当同时考虑珊瑚宿主和共生藻的作用。

Global warming and abnormal high temperature cause coral-zooxanthellae symbiosis collapse and significant loss of zooxanthellae（coral bleaching）,and further lead to degradation of coral reef ecosystems.In this study,the authors collected six species of corals from the Luhuitou fringing reef in Sanya,and designed a mesocosm experiment that those corals were cultured under a high temperature stress,for investigating the diversity of tolerance among different coral symbiosis at cellular level.The results are as follows.The diversity of tolerance among different coral species under acute thermal stresses was related to their morphologies： branching corals showed the lowest tolerance in thermal stress,while the foliose and massive corals showed stronger tolerance,which was similar to the result in the field monitoring.Different coral species showed different ways of zooxanthellae loss under thermal stresses： zooxanthellae discharging continuously,like Pocillopora damicornis;zooxanthellae discharging partly and followed by coral tissues containing zooxanthellae separating from skeletons,like Acropora hyacinthus and Acropora brueggemanni;the residual zooxanthellae in coral tissues using mitotic proliferation to replenish their numbers quickly,like Pavona decussate;cell necrosis of zooxanthellae in coral tissues,like Porites lutea.This study confirmed that the role of coral host and zooxanthellae should be considered simultaneously in further studies of coral responses to global warming.