Methane stimulates massive nitrogen loss from freshwater reservoirs in India.

The fate of the enormous amount of reactive nitrogen released to the environment by human activities in India is unknown. Here we show occurrence of seasonal stratification and generally low concentrations of dissolved inorganic combined nitrogen, and high molecular nitrogen (N) to argon ratio, thus suggesting seasonal loss to N in anoxic hypolimnia of several dam-reservoirs. However, N-experiments yielded low rates of denitrification, anaerobic ammonium oxidation and dissimilatory nitrate reduction to ammonium-except in the presence of methane (CH) that caused ~12-fold increase in denitrification.

Dissolved methane in Indian freshwater reservoirs.

Emission of methane (CH4), a potent greenhouse gas, from tropical reservoirs is of interest because such reservoirs experience conducive conditions for CH4 production through anaerobic microbial activities. It has been suggested that Indian reservoirs have the potential to emit as much as 33.5 MT of CH4 per annum to the atmosphere.