An intensive and seasonal coastal upwelling process, which attains maximal expression during late austral spring and summer, drives well-known changes in organic matter production and, therefore, in O
2 content in the water column. These variables have a concomitant effect on N sediment processes over the continental shelf off central Chile (36.5°S), which, in turn, can affect the , , and N
2O content in the bottom water. Hydrographic characteristics, benthic and fluxes, and denitrification rates were measured from 1998 to 2001 (with at least seasonal frequency). In order to elucidate how benthic N
2O recycling responds to different O
2 and nutrient levels and how it affects the bottom water N
2O content, net N
2O cycling was measured in December 2001 in sediment slurry incubations under different manipulated dissolved O
2 levels (anoxic: 0 μM; hypoxic: 22.3 μM; oxic: 44.6 μM) and without (natural) and with the addition of and (enriched experiments). Dissolved O
2 and contents (and also ) showed clear seasonal patterns according to the oceanographic regime,
i.e., from hypoxic waters rich in nutrients during the upwelling season to oxic waters with less nutrient contents during the non-upwelling season. The bottom water, on the other hand, was influenced by benthic organic mineralization, which consumes O
2 as well as other electron acceptor N-species such as . Benthic fluxes (2.62-5.08 mmol m
−2 d
−1) were always directed into the sediments, whereas denitrification rates varied from 0.6 to 2.9 mmol m
−2 d
−1. N
2O was also consumed at rates of 5.53 and 4.56 μmol m
−2 d
−1 under anoxia and hypoxia, but N
2O consumption rates were reduced to almost half under oxic conditions in both natural and a -enriched experiments. With the -enriched experiments, however, N
2O consumption was very high (up to 24.25 μmol m
−2 d
−1) under anoxic and hypoxic conditions, suggesting that high levels induce more N
2O reduction to N
2 by denitrification. N
2O production rates were only measured when oxic conditions were observed in the -enriched experiment, suggesting some role of nitrification. Thus, N cycling in the sediments seems to affect the observed , NO
2−, and N
2O content in the bottom water and, therefore, in the entire water column due to vertical advection associated with coastal upwelling.
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