Isotopic Evidence for an Aerobic Nitrogen Cycle in the Latest Archean

The nitrogen cycle provides essential nutrients to the biosphere, but its antiquity in modern form is unclear. In a drill core though homogeneous organic-rich shale in the 2.5-billion-year-old Mount McRae Shale, Australia, nitrogen isotope values vary from +1.0 to +7.5 per mil (‰) and back to +2.5‰...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 2009-02, Vol.323 (5917), p.1045-1048
Main Authors: Garvin, Jessica, Buick, Roger, Anbar, Ariel D., Arnold, Gail L., Kaufman, Alan J.
Format: Article
Language:English
Subjects:
Aerobiosis
Anaerobiosis
Archaea - metabolism
Australia
Bacteria - metabolism
Biological Evolution
Earth sciences
Earth, ocean, space
Exact sciences and technology
Fractionation
Geochemistry
Geologic Sediments - chemistry
Isotope geochemistry
Isotope geochemistry. Geochronology
Microorganisms
Nitrates - chemistry
Nitrates - metabolism
Nitrification
Nitrites - chemistry
Nitrites - metabolism
Nitrogen
Nitrogen - chemistry
Nitrogen - metabolism
Nitrogen cycle
Nitrogen Fixation
Nitrogen Isotopes - analysis
Oceans
Oceans and Seas
Oxidation
Oxidation-Reduction
Oxygen
Oxygen - chemistry
Oxygen - metabolism
Paleoecology
Quaternary Ammonium Compounds - chemistry
Quaternary Ammonium Compounds - metabolism
Radioisotopes
Shales
Stratigraphy
Time
Tissue oxygenation
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Summary:The nitrogen cycle provides essential nutrients to the biosphere, but its antiquity in modern form is unclear. In a drill core though homogeneous organic-rich shale in the 2.5-billion-year-old Mount McRae Shale, Australia, nitrogen isotope values vary from +1.0 to +7.5 per mil (‰) and back to +2.5‰ over ∼30 meters. These changes evidently record a transient departure from a largely anaerobic to an aerobic nitrogen cycle complete with nitrification and denitrification. Complementary molybdenum abundance and sulfur isotopic values suggest that nitrification occurred in response to a small increase in surface-ocean oxygenation. These data imply that nitrifying and denitrifying microbes had already evolved by the late Archean and were present before oxygen first began to accumulate in the atmosphere.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.1165675