The activities of microorganisms in and around anoxic zones control the losses of bioavailable nitrogen and emissions of nitrous oxide. Accurate quantification of these activities is critical for understanding microbial feedbacks to current climate change. Theory and observations suggest that aerobic and anaerobic metabolisms can coexist in anoxic zones when some oxygen is supplied, even though oxygen concentrations may remain undetectable. This complicates traditional parameterizations in models where the presence or absence of a metabolism is dictated by oxygen concentration alone. I will use theory and modeling to show how obligately aerobic nitrite-oxidizing bacteria (NOB) can subsist alongside aerobic heterotrophy in anoxic zones when there is a variable supply of oxygen. Genome-based evidence supports the model implication that NOB can be considered as ``opportunists” that thrive in anoxic zones with infrequent oxygen intrusions. Results suggest that resolution of time-varying circulation is necessary for predicting nitrogen cycling in anoxic zones.

Tutorial/Invited: Invited

Primary Presenter: Emily Zakem, Carnegie Institution for Science (ezakem@carnegiescience.edu)

Authors:

Emily Zakem, Carnegie Institution for Science  (ezakem@carnegiescience.edu)

Pearse Buchanan, Carnegie Institution for Science  (pbuchanan@carnegiescience.edu)

Xin Sun, Carnegie Institution for Science  (xsun10@carnegiescience.edu)

JL Weissman, Chapman University  (jweissman@chapman.edu)