Microbial ecosystem dynamics drive fluctuating nitrogen loss in marine anoxic zones
| Autor: | Curtis Deutsch, Bonnie X. Chang, Thomas C. Weber, Justin L. Penn |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Aquatic Organisms
Denitrification 010504 meteorology & atmospheric sciences Nitrogen Climate Microbial Consortia microbial ecology 01 natural sciences Bacteria Anaerobic 03 medical and health sciences Denitrifying bacteria Microbial ecology Ammonia nitrogen cycle Ecosystem oxygen minimum zones Nitrogen cycle 030304 developmental biology 0105 earth and related environmental sciences species oscillations 0303 health sciences Multidisciplinary Ecology Biological Sciences Anoxic waters Oxygen Productivity (ecology) Anammox Physical Sciences Environmental science Environmental Sciences |
| Zdroj: | Proceedings of the National Academy of Sciences of the United States of America |
| ISSN: | 1091-6490 0027-8424 |
| DOI: | 10.1073/pnas.1818014116 |
| Popis: | Significance The removal of bioavailable nitrogen (N), a critical nutrient that limits marine primary production, is thought to vary due to climate forcing of the ocean’s low oxygen zones. Here we demonstrate that competition between aerobic and anaerobic microbes for scarce resources drives fluctuations in the rate of marine N loss over time, even in a stable environment. Biological oscillations have been theorized for nearly a century in idealized models, but are shown here for the first time in a three-dimensional and data-constrained model of ocean circulation. A predicted geochemical signature of the oscillations is detected in environmental samples. This previously overlooked source of natural variability reconciles conflicting empirical evidence for the dominance of heterotrophic versus autotrophic pathways of N removal. 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. |
| Databáze: | OpenAIRE |
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