Planktonic Foraminiferal Mg/Ca as Indicator of Seawater Carbonate-Ion Saturation

了解海水的碳酸盐饱和状态如何影响有孔虫测试的地球化学仍处于初级阶段。我们的主要目标是研究溶解作用对南中国海47个表层浮游有孔虫中8个浅层、温跃层和深部浮游有孔虫的初级稳定氧同位素和镁/钙信号的影响。使用综合方法(镁/钙比、δ18O值、试验重量、扫描电子显微镜)，我们将确定随深度的部分溶解开始，并量化与底层水碳酸盐离子浓度变化有关的镁/钙比的溶解偏差。我们的工作还将提供一个机会，以评估镁/钙比作为海水腐蚀性的替代指标的敏感性，并评估其对过去气候重建的适用性。

Understanding how the carbonate-saturation state of seawater affects the geochemistry of foraminiferal tests is still in an elementary phase. Our primary goals are to investigate how dissolution affects the primary stable oxygen isotope and Mg/Ca signals in eight shallow-, thermocline-, and deep-dwelling planktonic foraminifera from 47 sediment-surface samples of the South China Sea. Using an integrated approach (Mg/Ca ratios, δ18O values, test weights, scanning-electron micrographs), we will determine the onset of partial dissolution with depth and quantify the dissolution bias in Mg/Ca ratios in relation to changes in the carbonate-ion concentration of bottom waters. Our work will also provide an opportunity to evaluate the sensitivity of Mg/Ca ratios as a proxy for seawater corrosiveness and assess the applicability for past climate reconstructions.