Chui Apple Pui Yi, Ang Put
Marine Science Laboratory, School of Life Sciences, Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, China.
PLoS One. 2017 Jun 16;12(6):e0179423. doi: 10.1371/journal.pone.0179423. eCollection 2017.
With projected changes in the marine environment under global climate change, the effects of single stressors on corals have been relatively well studied. However, more focus should be placed on the interactive effects of multiple stressors if their impacts upon corals are to be assessed more realistically. Elevation of sea surface temperature is projected under global climate change, and future increases in precipitation extremes related to the monsoon are also expected. Thus, the lowering of salinity could become a more common phenomenon and its impact on corals could be significant as extreme precipitation usually occurs during the coral spawning season. Here, we investigated the interactive effects of temperature [24, 27 (ambient), 30, 32°C] and salinity [33 psu (ambient), 30, 26, 22, 18, 14 psu] on larval settlement, post-settlement survival and early growth of the dominant coral Platygyra acuta from Hong Kong, a marginal environment for coral growth. The results indicate that elevated temperatures (+3°C and +5°C above ambient) did not have any significant effects on larval settlement success and post-settlement survival for up to 56 days of prolonged exposure. Such thermal tolerance was markedly higher than that reported in the literature for other coral species. Moreover, there was a positive effect of these elevated temperatures in reducing the negative effects of lowered salinity (26 psu) on settlement success. The enhanced settlement success brought about by elevated temperatures, together with the high post-settlement survival recorded up to 44 and 8 days of exposure under +3°C and +5°C ambient respectively, resulted in the overall positive effects of elevated temperatures on recruitment success. These results suggest that projected elevation in temperature over the next century should not pose any major problem for the recruitment success of P. acuta. The combined effects of higher temperatures and lowered salinity (26 psu) could even be beneficial. Therefore, corals that are currently present in marginal environments like Hong Kong, as exemplified by the dominant P. acuta, are likely to persist in a warmer and intermittently less saline, future ocean.
随着全球气候变化导致海洋环境的预计变化，单一应激源对珊瑚的影响已得到较为充分的研究。然而，如果要更现实地评估多重应激源对珊瑚的影响，就应更多地关注它们的交互作用。预计全球气候变化会使海面温度升高，同时预计未来与季风相关的极端降水也会增加。因此，盐度降低可能会成为一种更常见的现象，而且由于极端降水通常发生在珊瑚产卵季节，其对珊瑚的影响可能很大。在此，我们研究了温度[24、27（环境温度）、30、32°C]和盐度[33 psu（环境盐度）、30、26、22、18、14 psu]对来自香港的优势珊瑚尖锐扁脑珊瑚幼虫附着、附着后存活及早期生长的交互作用，香港是珊瑚生长的边缘环境。结果表明，温度升高（比环境温度高3°C和5°C）在长达56天的长时间暴露下，对幼虫附着成功率和附着后存活均无显著影响。这种热耐受性明显高于文献中报道的其他珊瑚物种。此外，这些升高的温度对降低盐度降低（26 psu）对附着成功率的负面影响有积极作用。温度升高带来的附着成功率提高，以及在分别比环境温度高3°C和5°C的条件下暴露44天和8天时记录到的高附着后存活率，导致温度升高对补充成功率产生总体积极影响。这些结果表明，预计下个世纪温度升高对尖锐扁脑珊瑚的补充成功率不应构成任何重大问题。较高温度和降低盐度（26 psu）的综合作用甚至可能是有益的。因此，目前存在于像香港这样边缘环境中的珊瑚，如优势种尖锐扁脑珊瑚，很可能在未来更温暖且盐度间歇性降低的海洋中持续存在。
