PP53C-0654 Variations in the Carbon Isotopic Composition of Particulate Organic Material since the Last Glacial Maximum as inferred from Planktonic Foraminifera Test Bound δ13Corg

The study of Rau et al. (1991) hypothesized that lower atmospheric CO2 concentrations and sea surface temperatures during the Last Glacial Maximum (LGM) caused the enrichment of the carbon isotopic signal of particulate organic matter in the ocean (δ13Corg-POM), as evidenced by trends in sedimentary bulk δ13C (δ13Corg-BULK) from the tropical/subtropical Indian and Atlantic Oceans. δ13Corg-BULK records however are not always representative of δ13Corg-POM due to several issues relating to diagenesis and contamination. To avoid such issues, foraminifera bound organic matter δ13C (δ13Corg-pforam) has been proposed as a δ13Corg-POM proxy. This specific organic material is sheltered and protected inside the tests of foraminifera. Here, we present the first δ13Corg-pforam record from the South Atlantic covering the last 25,000 years (including the LGM) and we assess if the trends in δ13Corg-BULK found by Rau et al. (1991) are replicated in δ13Corg-pforam. Compared to Rau et al. (1991) our results from the Southern Ocean do show a δ13Corg-pforam enrichment during the LGM, but to a much lesser extent than observed in Rau’s δ13Corg-BULK records. Using a simple box model, we propose that this minor enrichment in δ13Corg-pforam is driven by differences in dissolved CO2, sea surface temperatures and biological effects.