Spatial Variations of N2O Fluxes Across the Water‐Air Interface of Mariculture Ponds in a Subtropical Estuary in Southeast China.

While aquaculture ponds are potentially important sources of atmospheric N2O, the magnitude and variability of N2O concentrations and fluxes both within and across the ponds remain poorly understood. In this study, we examined the small‐scale spatial variations of dissolved N2O concentrations in water and N2O fluxes across the water‐air interface from three mariculture ponds in a subtropical estuary in southeast China. Our results showed that the dissolved concentrations and diffusive fluxes of N2O in the shrimp ponds ranged between 2.3–19.2 nM and 16.4–589.7 nmol m−2 hr−1, respectively, over the culture period. Significant variations of N2O concentrations and fluxes were observed within the ponds, with higher values being observed in the aeration area that could be attributed to the high rates of nitrification in the water column, as well as sediment N2O production and diffusive flux into the overlying water. Also, N2O concentrations and fluxes varied significantly among the three ponds as a result of the difference in N‐NO3− and N‐NH4+ concentrations in the water column. The large fine‐scale spatial variations of N2O concentrations and fluxes observed in our aquaculture ponds suggested that management practices such as aeration and bait feeding could largely affect the extent that aquaculture activities have on N2O emissions and climate change through their influence on the physicochemical environment (e.g., oxygen and N‐NH4+ concentrations) of the ponds. Key Points: Marked spatial difference in N2O flux both between and within pondsNitrogen substrate availability and aeration affected the spatial variations of N2O fluxSubtropical estuarine aquaculture ponds were important sources of N2O [ABSTRACT FROM AUTHOR]