Onset of the aerobic nitrogen cycle during the Great Oxidation Event.
The rise of oxygen on the early Earth (about 2.4 billion years ago) caused a reorganization of marine nutrient cycles, including that of nitrogen, which is important for controlling global primary productivity. However, current geochemical records lack the temporal resolution to address the nature and timing of the biogeochemical response to oxygenation directly. Here we couple records of ocean redox chemistry with nitrogen isotope (15N/14N) values from approximately 2.31-billion-year-old shales of the Rooihoogte and Timeball Hill formations in South Africa, deposited during the early stages of the first rise in atmospheric oxygen on the Earth (the Great Oxidation Event). Our data fill a gap of about 400 million years in the temporal15N/14N record and provide evidence for the emergence of a pervasive aerobic marine nitrogen cycle. The interpretation of our nitrogen isotope data in the context of iron speciation and carbon isotope data suggests biogeochemical cycling across a dynamic redox boundary, with primary productivity fuelled by chemoautotrophic production and a nitrogen cycle dominated by nitrogen loss processes using newly available marine oxidants. This chemostratigraphic trend constrains the onset of widespread nitrate availability associated with ocean oxygenation. The rise of marine nitrate could have allowed for the rapid diversification and proliferation of nitrate-using cyanobacteria and, potentially, eukaryotic phytoplankton.
School of Earth and Environmental Sciences and Centre for Exoplanet Science, University of St Andrews, St Andrews KY16 9AL, UK.
Aubrey L
AL
Zerkle
School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK.
Simon W
SW
Poulton
School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK.
Robert J
RJ
Newton
School of Earth and Environmental Sciences and Centre for Exoplanet Science, University of St Andrews, St Andrews KY16 9AL, UK.
Colin
C
Mettam
School of Earth and Environmental Sciences and Centre for Exoplanet Science, University of St Andrews, St Andrews KY16 9AL, UK.|Blue Marble Space Institute of Science, PO Box 88561, Seattle, Washington 98145, USA.
Mark W
MW
Claire
Department of Earth Sciences, University of California-Riverside, Riverside, California 92521, USA.
Andrey
A
Bekker
Department of Earth Sciences, Syracuse University, Syracuse, New York 13244, USA.
Christopher K
CK
Junium
D000332:Aerobiosis; D059001:Aquatic Organisms / Q000378:metabolism; D002247:Carbon Isotopes / Q000032:analysis; D000458:Cyanobacteria / Q000378:metabolism; D019015:Geologic Sediments / Q000737:chemistry; D049690:History, Ancient; D007501:Iron / Q000737:chemistry; D009566:Nitrates / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D058458:Nitrogen Cycle; D009587:Nitrogen Isotopes / Q000032:analysis; D009792:Oceans and Seas; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D010839:Phytoplankton / Q000378:metabolism; D012623:Seawater / Q000737:chemistry*; D013019:South Africa; D013997:Time Factors
D002247:Carbon Isotopes; D009566:Nitrates; D009587:Nitrogen Isotopes; D007501:Iron; D009584:Nitrogen; D010100:Oxygen