title: Denitrification prevails over anammox in tropical mangrove sediments (Goa, India).
abstract: Denitrification, anammox (Anx) and di-nitrogen fixation were examined in two mangrove ecosystems- the anthropogenically influenced Divar and the relatively pristine Tuvem. Stratified sampling at 2 cm increments from 0 to 10 cm depth revealed denitrification as the main process of N₂ production in mangrove sediments. At Divar, denitrification was ∼3 times higher than at Tuvem with maximum activity of 224.51 ± 6.63 nmol N₂ g⁻¹ h⁻¹ at 0-2 cm. Denitrifying genes (nosZ) numbered up to 2 × 10⁷ copies g⁻¹ sediment and belonged to uncultured microorganisms clustering within Proteobacteria. Anammox was more prominent at deeper depths (8-10 cm) mainly in Divar with highest activity of 101.15 ± 87.73 nmol N₂ g⁻¹ h⁻¹ which was 5 times higher than at Tuvem. Di-nitrogen fixation was detected only at Tuvem with a maximum of 12.47 ± 8.36 nmol N₂ g⁻¹ h⁻¹. Thus, in these estuarine habitats prone to high nutrient input, N₂-fixation is minimal and denitrification rather than Anx serves as an important mechanism for counteracting N loading.
authors.affiliation: Marine Microbiology Laboratory, National Institute of Oceanography, CSIR, Dona Paula, Goa 403004, India.
authors.forename: Sheryl Oliveira
authors.initials: SO
authors.lastname: Fernandes
authors.forename: Valérie D
authors.initials: VD
authors.lastname: Michotey
authors.forename: Sophie
authors.initials: S
authors.lastname: Guasco
authors.forename: Patricia C
authors.initials: PC
authors.lastname: Bonin
authors.forename: P A Loka
authors.initials: PA
authors.lastname: Bharathi
mesh_terms: D058440:Denitrification; D017753:Ecosystem; D019015:Geologic Sediments / Q000737:chemistry* / Q000382:microbiology; D006801:Humans; D007194:India; D009584:Nitrogen / Q000378:metabolism; D009586:Nitrogen Fixation; D020560:Proteobacteria / Q000378:metabolism; D043982:Rhizophoraceae; D014329:Tropical Climate
chemical_list: D009584:Nitrogen