Biological nitrous oxide consumption in oxygenated waters of the high latitude Atlantic Ocean

Nitrous oxide (N₂O) is important to the global radiative budget of the atmosphere and contributes to the depletion of stratospheric ozone. Globally the ocean represents a large net flux of N₂O to the atmosphere but the direction of this flux varies regionally. Our understanding of N₂O production and consumption processes in the ocean remains incomplete. Traditional understanding tells us that anaerobic denitrification, the reduction of NO₃⁻ to N₂ with N₂O as an intermediate step, is the sole biological means of reducing N₂O, a process known to occur in anoxic environments only. Here we present experimental evidence of N₂O removal under fully oxygenated conditions, coupled with observations of bacterial communities with novel, atypical gene sequences for N₂O reduction. The focus of this work was on the high latitude Atlantic Ocean where we show bacterial consumption sufficient to account for oceanic N₂O depletion and the occurrence of regional sinks for atmospheric N₂O.