Assessment of inorganic nitrogen fluxes across the sediment-water interface in a tropical lagoon

Abstract

Fluxes of ammonium and nitrate plus nitrite between the sediment and the water column in a shallow tropical lagoon were computed using experimental incubations and theoretical calculations based on observed gradients. Rates computed by the two methods compared favourably in the case of ammonium but differed significantly in the case of nitrate plus nitrite. Whereas calculations based on observed gradients predict a net flux of the latter species from the sediment to the water column, experimental incubations show active uptake of nitrate and nitrite by the sediment. We demonstrate that this uptake is biologically mediated.