Recycling of organic matter in Antarctic sediments: A transect through the polar front in the Southern Ocean (Indian sector

Sediments from the Polar Front Zone were sampled in the Indian Sector of the Antarctic Ocean as part of the French JGOFS expedition Antares 1. The first porewater distributions of 0, and NO, and organic carbon data in the solid phase in this part of the ocean were used to model the recycling of organic matter in sediments. The data are described by a model containing two types of degradable organic matter with distinct reactivities. We estimate that the reactivity of the most labile organic carbon is very close to that of fresh organic matter with an average C: N ratio of 7. We estimate that particulate organic carbon fluxes deposited at the sediment-water interface range between 0.2 and 0.8 mol C m--l y-l, with two peaks near the Polar Front and the Subantarctic Front. The flux 01 organic carbon deposited at the sediment-water interface is unusually high and represents-lo-20 % of estimated primary production. From these findings, we conclude that production in the pelagic zone of this region is strongly linked to deposition and recycling in the sediment. The processes leading to recycling and burial of particu-late organic matter in marine sediments affect the global oceanic carbon cycle over geological timescales. The oxi-dation of organic matter is the driving reaction of early dia-genesis (Berner 1980). It is coupled directly to a suite of biogeochemical processes that influence atmospheric pC0, on climatic timescales, including denitrification (Christense