海洋酸化没有显著影响成体鹿角杯形珊瑚的钙化作用和光合能力

Ocean acidification does not significantly affect the calcification and photosynthesis capacity of hermatypic coral Pocillopora damicornis

工业革命以来,人类活动释放的大量CO2进入大气层,不仅产生严重的温室效应,也使得全球海洋出现酸化的现象。造礁珊瑚被认为是受海水酸化影响最大的类群。本研究以鹿角杯形珊瑚（Pocillopora damicornis）为研究对象,通过气体交换法模拟未来的酸化环境（2100年）研究鹿角杯形珊瑚的钙化率和光合能力（Fv/Fm）对酸化的响应。实验设置两个pH组（分别为7.8和8.1）,自然光下进行4周的实验,水温控制在（27.5±1）℃。由于珊瑚等生物的代谢过程（主要是呼吸作用）,实验系统的pH昼夜变化显著,酸化处理组和对照组的pH分别介于7.69~7.91和7.99~8.29。鹿角杯形珊瑚的生长率介于1.15%~2.09%/周,酸化对鹿角杯形珊瑚的钙化率和光合效率没有显著的影响,鹿角杯形珊瑚对酸化的敏感度低。对比历史研究数据,本研究的结果进一步表明酸化对造礁珊瑚的影响存在种的特异性。推测鹿角杯形珊瑚对酸化的抗性可能与该珊瑚在有光的条件下能够利用HCO-3以及能够上调钙化位点的pH有关。这种特异性的pH缓冲能力使得珊瑚能维持钙化位点钙质基质高的文石饱和度（Ωarag）,因此能以小的额外能耗提高造礁珊瑚的钙化率。

Since the industrial revolution,large amounts of CO2 released by human activities into the atmosphere not only produce serious greenhouse effect,but also cause ocean acidification （OA）.Reef-building corals are thought to the most sensitive to ocean acidification.Ocean acidification is predicted to impact the physiology of corals and re-duce the calcification rates.In the present study,the calcification and photosynthesis capacity （Fv/Fm ）of herma-typic coral Pocillopora damicornis was measured to study the physiological effect of OA by the simulation of fur-ther scenario of ocean acidification based on the gas exchange method.The experiment was conducted for 5 weeks in natural light with the seawater temperature controlled at 27.5℃ （±1℃）by the chiller.Two pH values （7.8 and 8.1,respectively）were set by pH regulation,which mediate the CO2 gas into experimental seawater.The diur-nal variation of pH during the experiment was observed,with the pH values varied from 7.69 to 7.91 for the OA treatment and from 7.99 to 8.29 for the control due to the metabolic process （mainly respiration from the organ-isms）.The results showed that the calcification rate of P .damicornis ranged from 1.15%~2.09%＆#183;week-1 ,and no significant difference was found in calcification and Fv/Fm between OA treatment and the control,indicating the low sensitivity of P .damicornis to OA.Compared to those previous publications,species-specific responses were further confirmed facing to OA.It is speculated that the tolerance of P .damicornis to OA may be due to the use of HCO-3 in the light and up-regulation of pH in at their site of calcification.The capacity to up-regulate pH may be central to the resilience of P .damicornis to OA because the buffer capacity of pH can maintain relatively high the saturation of aragonite at their site of calcification and thus the calcification of corals at relatively low cost.