Department of Earth Sciences, University of St Andrews, Irvine Building, North Street, St Andrews, Fife KY16 9AL, UK.
The Interuniversity Institute of Eilat, PO Box 469, Eilat 88103, Israel.
Nat Commun. 2014 Dec 22;5:5741. doi: 10.1038/ncomms6741.
The sources of dissolved inorganic carbon (DIC) used to produce scleractinian coral skeletons are not understood. Yet this knowledge is essential for understanding coral biomineralization and assessing the potential impacts of ocean acidification on coral reefs. Here we use skeletal boron geochemistry to reconstruct the DIC chemistry of the fluid used for coral calcification. We show that corals concentrate DIC at the calcification site substantially above seawater values and that bicarbonate contributes a significant amount of the DIC pool used to build the skeleton. Corals actively increase the pH of the calcification fluid, decreasing the proportion of DIC present as CO2 and creating a diffusion gradient favouring the transport of molecular CO2 from the overlying coral tissue into the calcification site. Coupling the increases in calcification fluid pH and [DIC] yields high calcification fluid [CO3(2-)] and induces high aragonite saturation states, favourable to the precipitation of the skeleton.
用于产生珊瑚骨骼的溶解无机碳 (DIC) 的来源尚不清楚。然而，这一知识对于理解珊瑚生物矿化以及评估海洋酸化对珊瑚礁的潜在影响至关重要。在这里，我们使用骨骼硼地球化学来重建用于珊瑚钙化的流体中的 DIC 化学。我们表明，珊瑚在钙化部位将 DIC 浓缩到远高于海水值的水平，并且碳酸氢盐贡献了大量用于构建骨骼的 DIC 池。珊瑚主动增加钙化流体的 pH 值，降低了以 CO2 形式存在的 DIC 的比例，并创造了一个扩散梯度，有利于分子 CO2 从上方的珊瑚组织向钙化部位运输。钙化流体 pH 值和 [DIC] 的增加耦合产生了高的钙化流体 [CO3(2-)]，并诱导高的方解石饱和度状态，有利于骨骼的沉淀。
