A Flux?Based Threshold for Anaerobic Activity in the Ocean

Anaerobic microbial activity in the ocean causes losses of bioavailable nitrogen and emission nitrous oxide to atmosphere, but its predictability at global scales remains limited. Resource ratio theory suggests that anaerobic becomes sustainable when oxygen organic matter supply is below required by aerobic metabolisms. Here, we demonstrate relevance this framework scale using three-dimensional datasets, providing a new interpretation existing observations. Evaluations location extent anoxic zones diagnostic rate pelagic loss are consistent with previous estimates. However, threshold based on substrate-supply fluxes qualitatively different from solely ambient concentration. This implies use flux-based biogeochemical models can result predictions loss.