Previous work indicates that the particulate organic matter (POM) in sea ice of the Weddell Sea is strongly enriched in 13C and 15N relative to seawater POM. This project will test the hypothesis that stable isotopic values in Southern Ocean sediments are significantly affected by ice-algal input, which may have been misinterpreted as variations in nutrient utilization and productivity. The project will examine transects of surface sediments to determine if a north-south gradient exists consistent with the hypothesis, and will also determine stable isotope variations in several cores spanning the last glacial to track possible changes in ice-algal input.