|Title||Methane cycling. Nonequilibrium clumped isotope signals in microbial methane.|
|Publication Type||Journal Article|
|Year of Publication||2015|
|Authors||Wang DT, Gruen DS, Lollar BSherwood, Hinrichs K-U, Stewart LC, Holden JF, Hristov AN, Pohlman JW, Morrill PL, Könneke M, Delwiche KB, Reeves EP, Sutcliffe CN, Ritter DJ, Seewald JS, McIntosh JC, Hemond HF, Kubo MD, Cardace D, Hoehler TM, Ono S|
|Date Published||2015 Apr 24|
|Keywords||Animals, Carbon Cycle, Carbon Isotopes, Cattle, Groundwater, Hydrogen, Methane, Methanomicrobiales, Temperature|
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 (for example, (13)CH3D) has recently emerged as a proxy for determining methane-formation temperatures. However, the effect 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 (13)CH3D 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.