Potential Contributions of Ammonia‐Oxidizing Microorganisms to the Distributions of Nitrous Oxide in the Northern Bering Sea

Abstract

AbstractOceanic N2O is a major source of atmospheric N2O gas and is involved in global warming and ozone depletion. It is thought to be mainly produced by nitrification, denitrification and nitrifier denitrification processes mediated by ammonia‐oxidizing bacteria, ammonia‐oxidizing archaea (AOA) and denitrifying bacteria. The Bering Sea, especially its continental shelf area, is considered a typical source of atmospheric N2O. During the 7th Chinese National Arctic Research Expedition (CHINARE2016), the distributions of N2O and ammonia‐oxidizing microorganisms (AOOs) in the Bering Sea continental shelf and abyssal basin water were investigated. At a depth of 50∼900 m within the abyssal basin, the in‐situ ammonia oxidation process, particularly performed by AOA, exhibits considerable potential for the formation of supersaturated N2O. Meanwhile, beneath the oxygen minimum zone (depth range is approximately 800∼1,000 m), supersaturated N2O is primarily driven by mixing processes, while the ammonia oxidation mediated by AOA also contributes to a certain extent. In addition, the N2O distribution characteristic exhibits a substantial disparity between the southern and northern Bering Sea shelves, with the former characterized as a mild sink and the latter as a weak source. The water column of the Bering Sea demonstrates a considerable potential for generating supersaturated N2O through ammonia oxidation, as corroborated by the current study.