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

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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.