Controlling factors of Ca isotope fractionation in scleractinian corals evaluated by temperature, pH and light controlled culture experiments
Controlling factors of Ca isotope fractionation in scleractinian corals evaluated by temperature, pH and light controlled culture experiments
复制标题
DOI：
10.1016/j.gca.2015.06.009
复制
发表时间：
2015-10
影响因子：
5
通讯作者：
M. Inoue;N. Gussone;Y. Koga;A. Iwase;A. Suzuki;K. Sakai;H. Kawahata
中科院分区：
文献类型：
--
作者：
M. Inoue;N. Gussone;Y. Koga;A. Iwase;A. Suzuki;K. Sakai;H. Kawahata
本研究通过温度、pH和光控培养三种不同的培养实验，测定了澳大利亚波特氏岩的44ca /40Ca比值。本研究推断的0.02‰/°C的温度依赖同位素分馏与无机文石相似，但在珊瑚中同位素分馏的程度约为+0.4‰偏移。这些观察结果与早期不同珊瑚物种的结果一致，表明钙在珊瑚中的跨膜运输过程中存在同位素分异。虽然在养殖珊瑚中观察到δ44Ca的显著温度依赖性，但钙同位素分异与pH和光强之间的关系可以忽略不计。因此，孔隙中δ44Ca的变化主要受温度控制。温度控制实验中珊瑚δ44Ca和Sr/Ca的组合不能用瑞利型分馏直接解释，因为流体在δ44Ca和Sr/Ca方面与海水相似。通过珊瑚特有的生物矿化过程，包括以往研究在内的核状珊瑚的总体平均δ44Ca与硬海绵动物和翼足类动物分泌的生物文石不同，但与双壳类、钙质粒石藻和有孔虫相当。这些发现对于更好地了解珊瑚的生物矿化作用，以及限制海洋钙汇中钙同位素组成对气候变化的响应以及与方解石和文石海洋移动相关的变化具有重要意义。
In this study, the44Ca/40Ca ratios ofPorites australiensisgrown under three different culture experiments composed of temperature, pH and light controlled culture experiments are measured. The temperature dependent isotope fractionation of 0.02‰/°C deduced from this study is similar to inorganic aragonite, but the degree of isotope fractionation is about +0.4‰ offset in corals. These observations agree with earlier results on different coral species, suggesting Ca isotope fractionation during Ca transmembrane transport in corals.While in cultured corals a significant temperature dependence of δ44Ca is observed, the relationships between calcium isotope fractionation and pH as well as light intensity are negligible. Therefore variation of δ44Ca inPoritescorals is mainly controlled by temperature. A combination of δ44Ca and Sr/Ca of corals in temperature controlled experiments cannot be explained by Rayleigh type fractionation directly from a fluid, which is seawater-like in terms of δ44Ca and Sr/Ca. Through coral-specific biomineralization processes, overall mean δ44Ca of scleractinian corals including previous studies are different from biogenic aragonites secreted by sclerosponges and pteropods, but are comparable with those of bivalves as well as calcitic coccolithophores and foraminifers. These findings are important for better understanding biomineralization in corals and in order to constrain the Ca isotopic composition of oceanic Ca sinks in response to climate changes and associated with shifts of calcite and aragonite seas.