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A sluggish mid-Proterozoic biosphere and its effect on Earth's redox balance.
Geobiology. 2019 01; 17(1):3-11.G

Abstract

The possibility of low but nontrivial atmospheric oxygen (O2) levels during the mid-Proterozoic (between 1.8 and 0.8 billion years ago, Ga) has important ramifications for understanding Earth's O2 cycle, the evolution of complex life and evolving climate stability. However, the regulatory mechanisms and redox fluxes required to stabilize these O2 levels in the face of continued biological oxygen production remain uncertain. Here, we develop a biogeochemical model of the C-N-P-O2 -S cycles and use it to constrain global redox balance in the mid-Proterozoic ocean-atmosphere system. By employing a Monte Carlo approach bounded by observations from the geologic record, we infer that the rate of net biospheric O2 production was <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>3</mml:mn> <mml:mo>.</mml:mo> <mml:msubsup><mml:mn>5</mml:mn> <mml:mrow><mml:mo>-</mml:mo> <mml:mn>1.1</mml:mn></mml:mrow> <mml:mrow><mml:mo>+</mml:mo> <mml:mn>1.4</mml:mn></mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> Tmol year[-1] (1σ), or ~25% of today's value, owing largely to phosphorus scarcity in the ocean interior. Pyrite burial in marine sediments would have represented a comparable or more significant O2 source than organic carbon burial, implying a potentially important role for Earth's sulphur cycle in balancing the oxygen cycle and regulating atmospheric O2 levels. Our statistical approach provides a uniquely comprehensive view of Earth system biogeochemistry and global O2 cycling during mid-Proterozoic time and implicates severe P biolimitation as the backdrop for Precambrian geochemical and biological evolution.

Authors+Show Affiliations

School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia. NASA Astrobiology Institute, Alternative Earths Team, Mountain View, California. NASA Postdoctoral Program, Universities Space Research Association, Columbia, Maryland.School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia. NASA Astrobiology Institute, Alternative Earths Team, Mountain View, California.Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Japan.

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

30281196

Citation

Ozaki, Kazumi, et al. "A Sluggish mid-Proterozoic Biosphere and Its Effect On Earth's Redox Balance." Geobiology, vol. 17, no. 1, 2019, pp. 3-11.
Ozaki K, Reinhard CT, Tajika E. A sluggish mid-Proterozoic biosphere and its effect on Earth's redox balance. Geobiology. 2019;17(1):3-11.
Ozaki, K., Reinhard, C. T., & Tajika, E. (2019). A sluggish mid-Proterozoic biosphere and its effect on Earth's redox balance. Geobiology, 17(1), 3-11. https://doi.org/10.1111/gbi.12317
Ozaki K, Reinhard CT, Tajika E. A Sluggish mid-Proterozoic Biosphere and Its Effect On Earth's Redox Balance. Geobiology. 2019;17(1):3-11. PubMed PMID: 30281196.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - A sluggish mid-Proterozoic biosphere and its effect on Earth's redox balance. AU - Ozaki,Kazumi, AU - Reinhard,Christopher T, AU - Tajika,Eiichi, Y1 - 2018/10/03/ PY - 2018/07/06/received PY - 2018/08/27/accepted PY - 2018/10/4/pubmed PY - 2019/3/30/medline PY - 2018/10/4/entrez KW - biogeochemical cycles KW - oxygen cycle KW - proterozoic SP - 3 EP - 11 JF - Geobiology JO - Geobiology VL - 17 IS - 1 N2 - The possibility of low but nontrivial atmospheric oxygen (O2) levels during the mid-Proterozoic (between 1.8 and 0.8 billion years ago, Ga) has important ramifications for understanding Earth's O2 cycle, the evolution of complex life and evolving climate stability. However, the regulatory mechanisms and redox fluxes required to stabilize these O2 levels in the face of continued biological oxygen production remain uncertain. Here, we develop a biogeochemical model of the C-N-P-O2 -S cycles and use it to constrain global redox balance in the mid-Proterozoic ocean-atmosphere system. By employing a Monte Carlo approach bounded by observations from the geologic record, we infer that the rate of net biospheric O2 production was <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>3</mml:mn> <mml:mo>.</mml:mo> <mml:msubsup><mml:mn>5</mml:mn> <mml:mrow><mml:mo>-</mml:mo> <mml:mn>1.1</mml:mn></mml:mrow> <mml:mrow><mml:mo>+</mml:mo> <mml:mn>1.4</mml:mn></mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> Tmol year[-1] (1σ), or ~25% of today's value, owing largely to phosphorus scarcity in the ocean interior. Pyrite burial in marine sediments would have represented a comparable or more significant O2 source than organic carbon burial, implying a potentially important role for Earth's sulphur cycle in balancing the oxygen cycle and regulating atmospheric O2 levels. Our statistical approach provides a uniquely comprehensive view of Earth system biogeochemistry and global O2 cycling during mid-Proterozoic time and implicates severe P biolimitation as the backdrop for Precambrian geochemical and biological evolution. SN - 1472-4669 UR - https://www.unboundmedicine.com/medline/citation/30281196/A_sluggish_mid_Proterozoic_biosphere_and_its_effect_on_Earth's_redox_balance_ DB - PRIME DP - Unbound Medicine ER -