Using modern low-oxygen marine ecosystems to understand the nitrogen cycle of the Paleo- and Mesoproterozoic oceans
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During the productive Paleoproterozoic (2.4–1.8 Ga) and less productive Mesoproterozoic (1.8–1.0 Ga), the ocean was suboxic to anoxic and multicellular organisms had not yet evolved. Here, we link geologic information about the Proterozoic ocean to microbial processes in modern low‐oxygen systems. High iron concentrations and rates of Fe cycling in the Proterozoic are the largest differences from modern oxygen‐deficient zones. In anoxic waters, which composed most of the Paleoproterozoic and ~40% of the Mesoproterozoic ocean, nitrogen cycling dominated. Rates of N2 production by denitrification and anammox were likely linked to sinking organic matter fluxes and in situ primary productivity under anoxic conditions. Additionally autotrophic denitrifiers could have used reduced iron or methane. 50% of the Mesoproterozoic ocean may have been suboxic, promoting nitrification and metal oxidation in the suboxic water and N2O and N2 production by partial and complete denitrification in anoxic zones in organic aggregates. Sulfidic conditions may have composed ~10% of the Mesoproterozoic ocean focused along continental margins. Due to low nitrate concentrations in offshore regions, anammox bacteria likely dominated N2 production immediately above sulfidic zones, but in coastal regions, higher nitrate concentrations probably promoted complete S‐oxidizing autotrophic denitrification at the sulfide interface.
Fuchsman , C & Stueeken , E E 2020 , ' Using modern low-oxygen marine ecosystems to understand the nitrogen cycle of the Paleo- and Mesoproterozoic oceans ' , Environmental Microbiology , vol. Early View . https://doi.org/10.1111/1462-2920.15220
Copyright © 2020 Society for Applied Microbiology and John Wiley & Sons Ltd. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the author created accepted manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1111/1462-2920.15220
DescriptionCAF was funded by University of Maryland Horn Point Laboratory start-up funds.
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