Anthropogenic nutrient loads and season variability drive high atmospheric N2O fluxes in a fragmented mangrove system
N. Regina Hershey, S. Bijoy Nandan, Neelima Vasu K., Douglas R. Tait
Abstract
Abstract Fragmented mangroves are generally ignored in N 2 O flux studies. Here we report observations over the course of a year from the Mangalavanam coastal wetland in Southern India. The wetland is a fragmented mangrove stand close to a large urban centre with high anthropogenic nitrogen inputs. The study found the wetland was a net source of N 2 O to the atmosphere with fluxes ranging between 17.5 to 117.9 µmol m −2 day −1 which equated to high N 2 O saturations of between 697 and 1794%. The average dissolved inorganic nitrogen inputs (80.1 ± 18.1 µmol L −1 ) and N 2 O emissions (59.2 ± 30.0 µmol m −2 day −1 ) were highest during the monsoon season when the rainfall and associated river water inputs and terrestrial runoff were highest. The variation in N 2 O dynamics was shown to be driven by the changes in rainfall, water column depth, salinity, dissolved oxygen, carbon, and substrate nitrogen. The study suggests that fragmented/minor mangrove ecosystems subject to high human nutrient inputs may be a significant component of the global N 2 O budget.