Nitrous oxide (N2O), a potent green house gas is produced due to the microbial transformation of nitrogen. Expansion of hypoxic zones in oceans leads to an increase in N2O emissions. Recent studies suggest that ammonia oxidizing archaea (AOA) significantly contribute to the N2O production through the nitrification process. However, the role of environmental conditions, in particular oxygen concentration and substrate availability on N2O emission by AOA is poorly understood.