Continental margin sediments underlying the NE Pacific oxygen minimum zone are a source of nitrous oxide to the water column

Abstract

Abstract Continental margin sediments are important sites of marine nitrogen cycling and potential contributors to atmospheric N2O emissions. We employed trace‐level N2O microsensors to measure vertical N2O profiles at submillimeter resolutions in intact cores from outer continental margin sediments underlying the NE Pacific oxygen minimum zone. We used mathematical modeling to estimate depth‐dependent rates of N2O production and fluxes to the overlying water along a transect of diminishing bottom water oxygen concentrations. Net sediment efflux was observed at all sites on the outer continental margin, with a mean value of 524 nmol m−2 d−1. N2O efflux increased with decreased oxygen penetration depth in sediments. Enhanced N2O production and efflux were obtained when outer continental shelf sediments were experimentally exposed to lower bottom‐water O2 concentrations, to simulate upwelling conditions. Our results underline the need for further investigation of the drivers of N2O production in continental margin sediments, and the relative importance of these environments to the global N2O budget.