Large contribution of non-aquaculture period fluxes to the annual N2O emissions from aquaculture ponds in Southeast China

Abstract

Nitrous oxide (N2O) is one of major potent long-lived atmospheric greenhouse gases (GHGs) with a global warming potential of approximately 300 times that of carbon dioxide (CO2) over a 100-year timespan. To date, only several studies have explored the contribution of N2O emission from aquaculture systems to global emission, but with large uncertainty. In this study, the spatiotemporal distribution of dissolved N2O concentrations along the water column within ponds, and the N2O fluxes over the whole annual cycle were determined in the shrimp ponds in the Min River Estuary, Southeast China. Our results showed that N2O concentrations did not differ among sampling depths, but varied significantly among sampling dates. The temporal variation of N2O concentration was significantly correlated with the concentrations of N-NH4+ and total dissolved nitrogen. The one year study found an annual mean N2O emission of 57.63 μg N2O m−2 h−1 that was equivalent to an annual emission of 504.9 mg N2O m−2 yr−1, demonstrating the aquaculture ponds as an important source of atmospheric N2O. The N2O fluxes during the non-aquaculture period were one to three orders larger than those in the aquaculture period, and accounted for approximately 97% of the annual total emissions from aquaculture ponds. Our results showed that the N2O emission during the non-aquaculture period should not be overlooked owing to its marked contribution to the annual N2O budget in mariculture ponds. Further studies on N2O production dynamics including the abundance and activity of nitrifying and denitrifying bacteria in coastal aquaculture ponds are needed to improve our understanding of N2O biogeochemical cycle and facilitate strategies to reduce N2O emission.