The calcification process of planktic foraminifers and its implication for the incorporation of paleo-oceanographic signals to their shells

在海洋沉积物中发现的浮游有孔虫的壳经常被用于古海洋重建。该项目主要研究浮游有孔虫的生态学和壳类地球化学。为了准确可靠地解释沉积记录中的有孔虫同位素特征，需要在代理应用之前详细了解生物物种的现代行为及其环境。我们的目标是通过使用最近开发的浮游有孔虫壳生长的氧同位素质量平衡模型来解开、理解和量化浮游有孔虫壳的深度依赖性钙化。该模型将通过浮游生物拖网和沉淀物捕集器在西北非洲海域收集有孔虫进行测试。稳定同位素测定将使用一种新技术（二次离子质谱法）进行，该技术允许对有孔虫方解石测试的连续室进行分析。对特定物种深度栖息地的详细量化，使我们能够进一步研究在西北非洲地区整个水柱垂直的深度整合壳生长过程中，海水碳酸盐化学（[co32 -]）如何控制碳和氧同位素进入有孔虫方解石。在校正了物种特有的δ13Cshell/[co32 -]关系后，古海洋学家将能够利用物种特有的校正因子从古记录中估计δ13CDIC。此外，水柱和岩心顶部沉积物的有孔虫δ13C数据的比较可能提供人为CO2入侵海洋表层水的信息。定量分析[co32 -]对氧同位素的影响可以改善对古温度的估计。

The shells of planktic foraminifers found in ocean-sediments are frequently used for paleooceanographic reconstruction. The proposed project focuses on the ecology and shell geochemistry of planktic foraminifers. An accurate and reliable interpretation of foraminiferal isotopic signature in the sedimentary record requires a detailed knowledge of the modern behavior of living species with regard to their environment prior to proxy application. We aim to unravel and understand and quantify the depth dependent calcification of planktic foraminiferal shells by using a recently developed oxygen isotope mass balance model for planktic foraminiferal shell growth. The model will be tested using plankton tow and sediment trap collected foraminifers in the region off NW Africa. Stable isotope determination will be carried out using a new technique (Secondary Ion Mass Spectrometry) which allows analyses of successive chambers of foraminiferal calcite tests. Detailed quantification of species-specific depth habitat allows us further to investigate how the seawater carbonate chemistry ([CO3 2-]) controls the incorporation of carbon and oxygen isotopes into foraminiferal calcite during the depth-integrated shell growth process vertically throughout the water column in the region of NW Africa. After the calibration of the species-specific δ13Cshell/[CO3 2-] relationship, paleo-oceanographers will be able to estimate the δ13CDIC from the paleo-record by applying a species-specific correction factor. Additionally, the comparison of foraminiferal δ13C data from the water column and from core top sediments gives potentially information about invasion of anthropogenic CO2 into the surface ocean water. Quantifying an effect of [CO3 2-] on oxygen isotopes may improve estimation of paleo-temperatures.