FY 2019 Microbial ecosystem dynamics drive fluctuating nitrogen loss in marine anoxic zones Penn, J.L., T. Weber, B.X. Chang, and C. Deutsch Proc. Nat. Acad. Sci., 116(15), 7220–7225, doi: 10.1073/pnas.1818014116, View online (2019) The dynamics of nitrogen (N) loss in the ocean’s oxygen-deficient zones (ODZs) are thought to be driven by climate impacts on ocean circulation and biological productivity. Here we analyze a data-constrained model of the microbial ecosystem in an ODZ and find that species interactions drive fluctuations in local- and regional-scale rates of N loss, even in the absence of climate variability. By consuming O2 to nanomolar levels, aerobic nitrifying microbes cede their competitive advantage for scarce forms of N to anaerobic denitrifying bacteria. Because anaerobes cannot sustain their own low-O2 niche, the physical O2 supply restores competitive advantage to aerobic populations, resetting the cycle. The resulting ecosystem oscillations induce a unique geochemical signature within the ODZ—short-lived spikes of ammonium that are found in measured profiles. The microbial ecosystem dynamics also give rise to variable ratios of anammox to heterotrophic denitrification, providing a mechanism for the unexplained variability of these pathways observed in the ocean. Feature Publications | Outstanding Scientific Publications Contact Sandra Bigley | Help
