Biological signatures in clumped isotopes of O2

The abundances of molecules containing more than one rare isotope have been applied broadly to determine formation temperatures of natural materials. These applications of "clumped" isotopes rely on the assumption that isotope-exchange equilibrium is reached, or at least approached, during...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 2015-04, Vol.348 (6233), p.431-434
Main Authors: Yeung, Laurence Y., Ash, Jeanine L., Young, Edward D.
Format: Article
Language:English
Subjects:
Arrays
Cycles
Equilibrium
Formations
Isotopes
Methane
Molecules
Oxygen
Photosynthesis
Signatures
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Summary:The abundances of molecules containing more than one rare isotope have been applied broadly to determine formation temperatures of natural materials. These applications of "clumped" isotopes rely on the assumption that isotope-exchange equilibrium is reached, or at least approached, during the formation of those materials. In a closed-system terrarium experiment, we demonstrate that biological oxygen (O2) cycling drives the clumped-isotope composition of O2 away from isotopic equilibrium. Our model of the system suggests that unique biological signatures are present in clumped isotopes of O2—and not formation temperatures. Photosynthetic O2 is depleted in 18O18O and 17O18O relative to a stochastic distribution of isotopes, unlike at equilibrium, where heavy-isotope pairs are enriched. Similar signatures may be widespread in nature, offering new tracers of biological and geochemical cycling.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.aaa6284