Berkelmans Ray, van Oppen Madeleine J H
Australian Institute of Marine Science, PMB 3 MC, Townsville, Australia.
Proc Biol Sci. 2006 Sep 22;273(1599):2305-12. doi: 10.1098/rspb.2006.3567.
The ability of coral reefs to survive the projected increases in temperature due to global warming will depend largely on the ability of corals to adapt or acclimatize to increased temperature extremes over the next few decades. Many coral species are highly sensitive to temperature stress and the number of stress (bleaching) episodes has increased in recent decades. We investigated the acclimatization potential of Acropora millepora, a common and widespread Indo-Pacific hard coral species, through transplantation and experimental manipulation. We show that adult corals, at least in some circumstances, are capable of acquiring increased thermal tolerance and that the increased tolerance is a direct result of a change in the symbiont type dominating their tissues from Symbiodinium type C to D. Our data suggest that the change in symbiont type in our experiment was due to a shuffling of existing types already present in coral tissues, not through exogenous uptake from the environment. The level of increased tolerance gained by the corals changing their dominant symbiont type to D (the most thermally resistant type known) is around 1-1.5 degrees C. This is the first study to show that thermal acclimatization is causally related to symbiont type and provides new insight into the ecological advantage of corals harbouring mixed algal populations. While this increase is of huge ecological significance for many coral species, in the absence of other mechanisms of thermal acclimatization/adaptation, it may not be sufficient to survive climate change under predicted sea surface temperature scenarios over the next 100 years. However, it may be enough to 'buy time' while greenhouse reduction measures are put in place.
珊瑚礁在全球变暖导致的预计温度升高情况下生存的能力，将在很大程度上取决于珊瑚在未来几十年适应温度极端升高的能力。许多珊瑚物种对温度胁迫高度敏感，且近几十年来胁迫（白化）事件的数量有所增加。我们通过移植和实验操作，研究了一种常见且分布广泛的印度-太平洋硬珊瑚物种——多孔鹿角珊瑚的适应潜力。我们发现，成年珊瑚至少在某些情况下能够获得更高的耐热性，且这种耐受性的提高是其组织中占主导地位的共生体类型从C型虫黄藻转变为D型的直接结果。我们的数据表明，我们实验中共生体类型的变化是由于珊瑚组织中已存在的现有类型的重新排列，而非通过从环境中外源摄取。将其主导共生体类型转变为D型（已知耐热性最强的类型）的珊瑚所获得的耐受性提高水平约为1-1.5摄氏度。这是第一项表明热适应与共生体类型存在因果关系的研究，并为珊瑚拥有混合藻类群体的生态优势提供了新的见解。虽然这种耐受性的提高对许多珊瑚物种具有巨大的生态意义，但在缺乏其他热适应/适应机制的情况下，在未来100年预测的海表面温度情景下，这可能不足以使其在气候变化中生存。然而，在实施温室气体减排措施的同时，这可能足以“赢得时间”。
