Benthic oxygen fluxes and denitrification rates from high-resolution porewater profiles from the Western Antarctic Peninsula continental shelf

Benthic fluxes of dissolved oxygen and nitrate were calculated from high-resolution porewater profiles collected on the continental margin of the Western Antarctic Peninsula. Profiles were collected in four seasons between March 2000 and February 2001 as part of the FOODBANCS program. Oxygen consumption rates ranged from 0.92 to 3.11 mmol O2 m−2 d−1 over the course of the year with an average annual oxygen consumption rate of 1.74 mmol O2 m−2 d−1. The oxygen fluxes follow a trend similar to the particulate carbon export flux with smaller fluxes during the winter and larger fluxes during the spring bloom period. However, the range in oxygen fluxes is substantially smaller than the range in the particulate carbon export. Denitrification rates ranged from 0.66 to 1.46 mmol N m−2 d−1, and the average annual denitrification rate was 1.29 mmol N m−2 d−1. The O2 consumption and denitrification rates are of similar magnitude to rates measured on other deep (∼500 m) continental margins. Denitrification rates are strongly coupled to nitrification rates, with coupled nitrification–denitrification accounting for more than 80% of the total denitrification rate in these sediments. The Antarctic continental-margin sediment denitrification rates correspond to ∼3–5 Tg N yr−1, and thus these continental-margin sediments account for roughly 1–2% of the global sediment denitrification signal.