Nitrous Oxide Consumption in Oxygenated and Anoxic Estuarine Waters
Weiyi Tang, Amal Jayakumar, Xin Sun, John C. Tracey, Julia Carroll, Elizabeth Wallace, Jenna A. Lee, Levy Nathan, Bess B. Ward
Abstract
Abstract Estuaries emit a large but highly uncertain amount of Nitrous oxide (N 2 O) into the atmosphere. To better understand N 2 O cycling processes in estuaries, we provide the first direct observations of N 2 O consumption in the seasonally anoxic Chesapeake Bay, the largest estuary in the United States. N 2 O consumption rates in anoxic waters reached up to 3.3 nmol L −1 d −1 but were generally undetectable in oxygenated waters. However, N 2 O consumption rates were substantially enhanced when the oxygen concentration was experimentally decreased in initially oxygenated samples, indicating the potential of N 2 O consumption in oxygenated environments, for example, surface waters. These potential N 2 O consumption rates followed Michaelis‐Menten kinetics as a function of increasing N 2 O substrate concentration. N 2 O‐consuming microbes that predominantly contained the clade II nitrous oxide reductase gene were detected throughout the water column. These new observations of environmental controls on N 2 O consumption will benefit the modeling of N 2 O cycling and help to constrain the estuarine N 2 O flux.