Ecological influences on {delta}¹³C of particulate matter in seasonally ice-covered Ryder Bay, Antarctica

Carbon isotopes may be a useful paleoceanographic tool for reconstructing past pCO2 of surface water, but isotopic composition of particulate organic carbon has been shown in both field and laboratory studies to be affected by pCO2, growth rate, cell size, cell geometry, light availability, carbon metabolism and species composition. To date, field studies have not constrained the dominant factors controlling surface water {delta}13CpOC. We present high-resolution time series data from a study in Ryder Bay, Antarctica, which compares seasonal fluctuations in mixed-layer {delta}13CpOC with detailed ecological and morphological analysis of phytoplankton communities, community productivity, {delta}13CDIC, nutrient dynamics, and hydrographic parameters. Preliminary results indicate that physical processes such as ocean-atmosphere gas exchange and upwelling do not significantly affect {delta}13CpOC signatures. In contrast, speciation shifts of diatom assemblages show strong correlation with changes in {delta} 13CpOC signals, supporting recent suggestions that taxonomic data are necessary for confident interpretation of sedimentary {delta}13C records