|Published in||Estuaries and Coasts, v. 39(3):657-663|
Enrich-Prast, A., Santoro, A.L., Coutinho, R.S., Nielsen, L.P. and Esteves, F.A.
Sediment denitrification was monthly evaluated in two tropical coastal lagoons with different trophic states using the 15N isotope pairing technique. Denitrification rates were very low in both environments, always <5.0 &mumol N2 m&minus2 h&minus1 and were not significantly different between them. Oxygen consumption varied from 426 to 4248 &mumol O2 m&minus2 h&minus1 and was generally three times higher in the meso-eutrophic than the oligotrophic lagoon. The low denitrification activity was ascribed to both low water NO3- concentrations (<2.0 &muM) and little nitrate supply from nitrification. There was no correlation of denitrification with nitrate or ammonium fluxes. Sediments in temperate environments with similar oxygen consumption rates usually presented a higher proportion of nitrification&ndashdenitrification rates. Sediment oxygen consumption was a good predictor of sediment denitrification in both studied lagoons.