Nonequilibrium clumped isotope signals in microbial methane

Science
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Abstract

Methane is a key component in the global carbon cycle with a wide range of anthropogenic and natural sources. Although isotopic compositions of methane have traditionally aided source identification, the abundance of its multiply-substituted “clumped” isotopologues, e.g., 13CH3D, has recently emerged as a proxy for determining methane-formation temperatures; however, the impact of biological processes on methane’s clumped isotopologue signature is poorly constrained. We show that methanogenesis proceeding at relatively high rates in cattle, surface environments, and laboratory cultures exerts kinetic control on 13CH3D abundances and results in anomalously elevated formation temperature estimates. We demonstrate quantitatively that H2 availability accounts for this effect. Clumped methane thermometry can therefore provide constraints on the generation of methane in diverse settings, including continental serpentinization sites and ancient, deep groundwaters.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Nonequilibrium clumped isotope signals in microbial methane
Series title Science
DOI 10.1126/science.aaa4326
Volume 348
Issue 6233
Year Published 2015
Language English
Publisher American Association for the Advancement of Science
Contributing office(s) Woods Hole Coastal and Marine Science Center
Description 4 p.
First page 428
Last page 431
Online Only (Y/N) N
Additional Online Files (Y/N) Y