School of Biological Sciences, Victoria University of Wellington, Kelburn 6140, Wellington, New Zealand;
Oceans Graduate School and Oceans Institute, The University of Western Australia, Crawley 6009, WA, Australia.
Proc Natl Acad Sci U S A. 2021 May 25;118(21). doi: 10.1073/pnas.2015265118.
Ocean warming and acidification threaten the future growth of coral reefs. This is because the calcifying coral reef taxa that construct the calcium carbonate frameworks and cement the reef together are highly sensitive to ocean warming and acidification. However, the global-scale effects of ocean warming and acidification on rates of coral reef net carbonate production remain poorly constrained despite a wealth of studies assessing their effects on the calcification of individual organisms. Here, we present global estimates of projected future changes in coral reef net carbonate production under ocean warming and acidification. We apply a meta-analysis of responses of coral reef taxa calcification and bioerosion rates to predicted changes in coral cover driven by climate change to estimate the net carbonate production rates of 183 reefs worldwide by 2050 and 2100. We forecast mean global reef net carbonate production under representative concentration pathways (RCP) 2.6, 4.5, and 8.5 will decline by 76, 149, and 156%, respectively, by 2100. While 63% of reefs are projected to continue to accrete by 2100 under RCP2.6, 94% will be eroding by 2050 under RCP8.5, and no reefs will continue to accrete at rates matching projected sea level rise under RCP4.5 or 8.5 by 2100. Projected reduced coral cover due to bleaching events predominately drives these declines rather than the direct physiological impacts of ocean warming and acidification on calcification or bioerosion. Presently degraded reefs were also more sensitive in our analysis. These findings highlight the low likelihood that the world's coral reefs will maintain their functional roles without near-term stabilization of atmospheric CO emissions.
海洋变暖与酸化威胁着珊瑚礁的未来生长。这是因为构建碳酸钙骨架并将珊瑚礁凝结在一起的钙化珊瑚礁生物对海洋变暖与酸化高度敏感。然而，尽管有大量研究评估了海洋变暖与酸化对个别生物钙化作用的影响，但仍缺乏对其对珊瑚礁净碳酸盐产量的全球影响的制约。在这里，我们提出了在海洋变暖与酸化条件下，对珊瑚礁净碳酸盐产量未来变化的全球预估。我们应用气候变化驱动的珊瑚覆盖率预测变化下的珊瑚礁生物钙化和生物侵蚀速率的元分析，来估计全球 183 个珊瑚礁的净碳酸盐产量在 2050 年和 2100 年的变化。我们预测，在代表性浓度路径（RCP）2.6、4.5 和 8.5 下，全球珊瑚礁的平均净碳酸盐产量将分别下降 76%、149%和 156%，到 2100 年。尽管在 RCP2.6 下，到 2100 年仍有 63%的珊瑚礁预计会继续积累，但在 RCP8.5 下，到 2050 年将有 94%的珊瑚礁开始侵蚀，到 2100 年，没有任何珊瑚礁的净碳酸盐产量会与预计的海平面上升率相匹配。这些下降主要是由珊瑚白化事件导致的珊瑚覆盖率降低所致，而非海洋变暖与酸化对钙化或生物侵蚀的直接生理影响所致。在我们的分析中，目前退化的珊瑚礁也更为敏感。这些发现强调了，如果大气 CO 排放不能得到近期稳定，世界珊瑚礁很可能无法维持其功能作用。
