Benthic fluxes of dissolved inorganic nitrogen in a coastal lagoon of the northern Adriatic Sea: an interpretation of spatial variability based on sediment features and in fauna activity

Dark respiration rates, dissolved inorganic nitrogen (DIN) fluxes and nitrification rates were measured at two sites in the microtidal Sacca di Goro lagoon in September 2000. DIN fluxes correlated with the biomass of the dominant macrofauna species (the amphipod Corophium spp. at station Giralda and the polychaete Neanthes spp. at station Faro). Respiration (> 6 mmol O 2 m -2h -1) and ammonium fluxes (> 80 μmol Nm -2h -1) were higher at station Giralda despite the lower organic matter content (4.5 %) and lower macrofauna biomass (4 gAFDW m -2). At both sites ammonium fluxes were significantly correlated with the biomass of the benthic infauna, but Corophium stimulated ammonium NH 4 + fluxes 3-fold compared to Neanthes. The amphipod also enhanced nitrification rates (> 300 μmol N m -2h -1) due to the high density of its burrows, the higher NH 4 + regeneration rates and the enhanced oxygen supply to the bacteria