Sediment Denitrification in Two Contrasting Tropical Shallow Lagoons

• Sediment denitrification was monthly evaluated in two tropical coastal lagoons with different trophic states using the N-15 isotope pairing technique. Denitrification rates were very low in both environments, always < 5.0 mu mol N-2 m(-2) h(-1) and were not significantly different between them. Oxygen consumption varied from 426 to 4248 mu mol O-2 m(-2) h(-1) 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 mu M) 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-denitrification rates. Sediment oxygen consumption was a good predictor of sediment denitrification in both studied lagoons.

Ämnesord

Natural Sciences  (hsv)

Earth and Related Environmental Sciences  (hsv)

Naturvetenskap  (hsv)

Geovetenskap och miljövetenskap  (hsv)

Nyckelord

Nitrogen; Denitrification; Oxygen consumption; Sediment; Tropical; Coastal lagoons