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Summary Recent studies point to the importance of oxygen (O 2 ) in controlling the distribution and activity of marine ammonia‐oxidizing archaea (AOA), one of the most abundant prokaryotes in the ocean. The AOA are associated with regions of low O 2 tension in oceanic oxygen minimum zones (OMZs), and O 2 availability is suggested to influence their production of the ozone‐depleting greenhouse gas nitrous oxide (N 2 O). We show that marine AOA available in pure culture sustain high ammonia oxidation activity at low μM O 2 concentrations, characteristic of suboxic regions of OMZs (<10 µM O 2 ), and that atmospheric concentrations of O 2 may inhibit the growth of some environmental populations. We quantify the increasing N 2 O production by marine AOA with decreasing O 2 tensions, consistent with the plausibility of an AOA contribution to the accumulation of N 2 O at the oxic‐anoxic redox boundaries of OMZs. Variable sensitivity to peroxide also suggests that endogenous or exogenous reactive oxygen species are of importance in determining the environmental distribution of some populations.
Qin et al. (Fri,) studied this question.