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A flux-based threshold for anaerobic activity in the ocean
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  • Emily Zakem,
  • Jonathan Maitland Lauderdale,
  • Reiner Schlitzer,
  • Michael J. Follows
Emily Zakem
University of Southern California

Corresponding Author:zakem@usc.edu

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Jonathan Maitland Lauderdale
Massachusetts Institute of Technology
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Reiner Schlitzer
Alfred Wegener Institute for Polar Resea
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Michael J. Follows
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Anaerobic microbial activity in the ocean causes losses of bioavailable nitrogen and emission of nitrous oxide to the atmosphere, but its predictability at global scales remains limited. Resource ratio theory suggests that anaerobic activity becomes sustainable when the ratio of oxygen to organic matter supply is below the ratio required by aerobic metabolisms. Here, we demonstrate the relevance of this framework at the global scale using three-dimensional ocean datasets, providing a new interpretation of existing observations. Evaluations of the location and extent of anoxic zones and a diagnostic rate of pelagic nitrogen loss are consistent with previous estimates. However, we demonstrate that the flux-based threshold is qualitatively different from a threshold based solely on the ambient oxygen concentration. Since the framework is feasible for application in global biogeochemical models, it represents a way forward for more dynamic, mechanistic predictions of anaerobic activity and nitrogen loss.
16 Mar 2021Published in Geophysical Research Letters volume 48 issue 5. 10.1029/2020GL090423