ARC Centre of Excellence for Coral Reefs Studies, Oceans Institute and School of Earth Sciences, The University of Western Australia, Crawley, 6009, Australia.
Sci Rep. 2017 May 19;7(1):2207. doi: 10.1038/s41598-017-02306-x.
Severe, global-scale thermal stress events like those of 1998 and 2016, are becoming more frequent and intense, potentially compromising the future of coral reefs. Here we report the effects of the 1998 bleaching event on coral calcification as well as the composition of the calcifying fluid (cf) from which corals precipitate their calcium carbonate skeletons. This was investigated by using the Sr/Ca, Li/Mg (temperature), and boron isotopes (δB) and B/Ca (carbonate chemistry) proxies in a Porites sp. coral. Following the summer of 1998 the coral exhibited a prolonged period (18 months) of reduced calcification (60%) and a breakdown in the seasonality of the geochemical proxies. However, the maintenance of elevated dissolved inorganic carbon (DIC; >×2 seawater) and pH (>8.3 compared to seawater 8.0) even during severe stress of 1998 indicate that a minimum threshold of high aragonite saturation state (Ω) of ~14 (×4 seawater), is an essential pre-requisite for coral calcification. However, despite maintaining elevated levels of Ω even under severe stress, coral growth is still impaired. We attribute this to reductions in either the effective active volume of calcification and/or DIC as bleaching compromises the photosynthetically fixed carbon pool available to the coral.
严重的、全球性的热应激事件，如 1998 年和 2016 年的事件，变得越来越频繁和强烈，这可能危及珊瑚礁的未来。在这里，我们报告了 1998 年白化事件对珊瑚钙化的影响，以及珊瑚沉淀碳酸钙骨骼的钙化液（cf）的组成。这是通过使用 Sr/Ca、Li/Mg（温度）和硼同位素（δB）以及 B/Ca（碳酸盐化学）示踪剂在一种 Porites sp.珊瑚中进行研究的。1998 年夏天过后，珊瑚表现出长时间（约 18 个月）的钙化减少（约 60%）和地球化学示踪剂季节性的破坏。然而，即使在 1998 年的严重压力下，仍维持着较高的溶解无机碳（DIC；>×2 海水）和 pH 值（>8.3，而海水约为 8.0），这表明高方解石饱和度状态（Ω）的最低阈值（14（×4 海水））是珊瑚钙化的必要前提。然而，尽管在严重压力下仍维持着较高的 Ω 值，珊瑚生长仍受到损害。我们将这归因于钙化的有效活性体积和/或 DIC 的减少，因为白化会损害珊瑚可用的光合作用固定碳库。
