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Updated: May 26, 2026

Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O
Published on: October 7, 2020
Denitrification prevails over anammox in tropical mangrove sediments (Goa, India)
Sheryl Oliveira Fernandes1, Valérie D Michotey, Sophie Guasco
1Marine Microbiology Laboratory, National Institute of Oceanography, CSIR, Dona Paula, Goa 403004, 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.
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