EGU22-9032, updated on 28 Mar 2022
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Methane clumped isotope signature of anaerobic oxidation of methane

Jiarui Liu1, Rachel L. Harris2, Jeanine L. Ash3, James G. Ferry4, Jabrane Labidi5, Sebastian J.E. Krause1, Divya Prakash4, Barbara Sherwood Lollar6, Tina Treude1,7, Oliver Warr6, and Edward D. Young1
Jiarui Liu et al.
  • 1Department of Earth, Planetary and Space Sciences, University of California, Los Angeles, CA, USA (,
  • 2Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
  • 3Department of Earth, Environmental and Planetary Sciences, Rice University, Houston, TX, USA
  • 4Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA, USA
  • 5Université de Paris, Institut de Physique du Globe de Paris, CNRS, Paris, France
  • 6Department of Earth Sciences, University of Toronto, Toronto, Ontario, Canada
  • 7Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA, USA

Microbial anaerobic oxidation of methane (AOM) significantly mitigates atmospheric methane emissions on Earth and represents a thermodynamically favorable metabolic strategy for astrobiological targets where methane has been detected. The bulk carbon and hydrogen isotope ratios produced by AOM have been used to probe the thermodynamic drive for intracellular reactions that involve the bi-directional enzymes of the methanogenesis pathway. Recently, measurements of the abundance of doubly-substituted methane isotopologues provide another dimension for assessing kinetic and equilibrium isotope effects and thus the AOM process itself. Towards this end, we measured methane clumped isotope ratios of residual methane in AOM-active microbial incubations using sediment slurry and/or fracture fluid from Svalbard methane seeps, Santa Barbara Channel methane seeps, Nankai Trough, and Beatrix Gold Mine. We also analyzed methane isotopologue abundances in sub-seafloor fluids from a Mariana mud volcano where AOM occurs. Extremely high Δ13CH3D and Δ12CH2D2 values were found in the Svalbard sediment slurry and the Mariana fluids where minimal reversibility of AOM intracellular reactions preserved signatures of kinetic fractionation of clumped isotopologues. When conditions were consistent with a low thermodynamic drive for AOM, however, methane isotopologues approached intramolecular quasi-equilibrium. This was notably observed in the microbial incubations of the deep biosphere samples from Nankai Trough and Beatrix Mine. This presentation will highlight the environmental controls on the enzymatic activity of intracellular pathways and the reversibility of AOM, and their intrinsic link to methane isotopologue ratios.

How to cite: Liu, J., Harris, R. L., Ash, J. L., Ferry, J. G., Labidi, J., Krause, S. J. E., Prakash, D., Sherwood Lollar, B., Treude, T., Warr, O., and Young, E. D.: Methane clumped isotope signature of anaerobic oxidation of methane, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9032,, 2022.