Sediment Denitrification in Two Contrasting Tropical Shallow Lagoons

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    Alex Enrich-Prast, Laboratory of Biogeochemistry, University Federal of Rio de Janeiro, BrazilAna Lucia Santoro, Federal University of Rio de Janeiro, BrazilRodrigo S. Countinho, Federal University of Rio de Janeiro, Brazil
  • Lars Peter Nielsen
  • Francisco A. Esteves, Federal University of Rio Grande, Brazil
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.
Original languageEnglish
JournalEstuaries and Coasts
Issue number3
Pages (from-to)657-663
Number of pages7
StatePublished - 2016

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