Denitrification: An Important Pathway for Nitrous Oxide Production in Tropical Mangrove Sediments (Goa, India)

Abstract

Net nitrous oxide production and denitrification activity were measured in two mangrove ecosystems of Goa, India. The relatively pristine site Tuvem was compared to Divar which is prone to high nutrient input. Stratified sampling at 2 cm intervals within the 0-10 cm depth range showed that N 2 O production at both the locations decreased with depth. Elevated denitrification activity at Divar resulted in maximum production of up to 1.95 nmol N 2 O-N g -1 h -1 at 2-4 cm which was 3 times higher than at Tuvem. Detailed investigations to understand the major pathway contributing to nitrous oxide production carried out at Tuvem showed that incomplete denitrification was responsible for up to 43-93% of N 2 O production. N 2 O production rates closely correlated to nitrite concentration (n=15; r=-0.47; p<0.05) and denitrifier abundance (r=0.55; p<0.05) suggesting that nitrite utilisation by microbial activity leads to N 2 O production. Nitrous oxide production through nitrification was below detection affirming that denitrification is the major pathway responsible for production of the greenhouse gas. Net N 2 O production in these mangrove systems are comparatively higher than those reported from other natural estuarine sediments and therefore warrant mitigation measures.

A poly-ε-caprolactone based biofilm carrier for nitrate removal from water

“…The gas composition analyses showed that the values of N 2 O were below 1.9 % for inlet nitrate concentrations between 10 and 40 mg N-NO 3 -/L, and slightly higher 5.8 % for 50 mg N-NO 3 -/L. According to Fernandes et al (2010), physical, chemical, biological and environmental factors like temperature, pH, organic carbon availability, and composition of the denitrifying community play an important role in N 2 O production. Rassamee et al (2011) reported that the presence of nitrite, resulting from process disturbance and abrupt changes in a lab-scale sequencing batch reactor fed with real municipal wastewater, is required for N 2 O production by heterotrophic denitrifying bacteria.…”

Nutrient gradients in Panamanian estuaries: effects of watershed deforestation, rainfall, upwelling, and within-estuary transformations

“…5, Table 4). The mid-estuary high suggested considerable release of ammonium into the water column, probably by action of ammonium regeneration from mangrove sediments (Mwa shote & Jumba 2002, Ferguson et al 2004, Alongi et al 2005, Fernandes et al 2010, Smith et al 2011, and perhaps some influence of dissimilatory nitrate reduction to ammonium (Fernandes et al 2012).…”

Nitrous Oxide Emission From Sediment of a Tropical Mangrove Forest in Central Vietnam-Implications of Short-Term Laboratory Experiments

“…Chen et al (2010) 12) found that N2O fluxes increased with soil organic carbon, nitrogen, iron concentrations and soil porosity while they were negatively correlated with salinity in mangrove swamps of South China. Pore-water nutrient concentrations, organic carbon availability, and denitrifiers were important sediment properties affecting the production of N2O in a mangrove in Goa, India 3) . Corredor and Morell (1994) 2)…”

“…They function as efficient buffer zones by reducing excess nutrients in estuarine systems 2) . Mangrove sediments are rich in organic matter under anaerobic conditions, which is favorable for denitrification 3) . Chiu et al (2004) 4) reported that as much as 55% of the nitrogen (N) input in mangrove sediment is lost through denitrification.…”