Fundamental Investigation of Glacial/interglacial Deep-sea pH and Carbonate Saturation Effects on Paired Benthic Foraminiferal Trace Element and Stable Isotope Signatures

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Trace elements and stable isotopes incorporated into the shells of deep-sea foraminifera record information on the ocean environment during their calcification. Paleoceanographers depend on these foraminiferal proxies to characterize past environmental conditions (i.e., temperature, salinity, glacial ice volumes). We hypothesize that pH excursions, manifested by changing CO2 concentrations in the deep sea, induce significant changes in the benthic foraminiferal biomineralization process, which in turn can lead to systematic offsets of trace element and isotope paleoproxy calibrations. We propose to measure the effect that pH has on metal incorporation into biogenic calcite grown under stringently-controlled environmental conditions in the laboratory. The University of South Carolina maintains the only long-term deep-sea benthic foraminiferal culturing system in the world specifically designed to experimentally-vary deep-sea trace element and pH conditions. The experimental pH range is chosen to represent chemistries in the deep-ocean without reproducing in situ pressures. This project will broaden our understanding of proxy response to varying environmental conditions relevant to past and present deep-ocean chemistries and improve our knowledge of the dynamic ocean-atmosphere system. It will directly support at least two graduate student theses and two undergraduate science majors and will involve traditionally under-represented groups in science at the undergraduate and graduate levels.