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Recognizing the pathways of microbial methanogenesis through methane isotopologues in the subsurface biosphere

Shuai, Yanhua and Xie, Hao and Zhang, Shuichang and Zhang, Yongshu and Eiler, John M. (2021) Recognizing the pathways of microbial methanogenesis through methane isotopologues in the subsurface biosphere. Earth and Planetary Science Letters, 566 . Art. No. 116960. ISSN 0012-821X. https://resolver.caltech.edu/CaltechAUTHORS:20210626-183440633

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Abstract

Microbial methanogenesis is a significant component in the global carbon cycle, a driver of greenhouse warming from atmospheric methane, and contributes to natural gas resources. There are several metabolic pathways of methanogenesis, and it is challenging to discriminate between them and quantify their relative contributions in natural settings. Here we measure and compile four rare isotopologues of methane (¹³CH₄, ¹²CH₃D, ¹³CH₃D and ¹²CH₂D₂) from the Qaidam Basin (China) and a large set of previous data across the world to identify distinctive fingerprints of two principal sources of subsurface microbial methane — hydrogenotrophic and methylotrophic methanogenesis — and use those fingerprints to deconvolve the budgets of microbial methane in the Qaidam Basin. Our data show that biogenic methanes in the Qaidam Basin have equilibrium Δ₁₈/Δ¹³CH₃D values respect to reservoir temperature without anaerobic methane oxidation. Our results suggest that methylotrophic methanogenesis produces methane with large deficits in ¹³CH₃D and ¹²CH₂D₂ relative to that controlled by homogeneous equilibrium among methane isotopologues at ambient environmental temperatures, whereas hydrogenotrophic methanogenesis produces methane with ¹³CH₃D abundance near equilibrium and relatively subtle ¹²CH₂D₂ deficits. We find a good linear correlation between the Δ¹³CH₃D value of natural biogenic methane and independent estimates of the fraction of hydrogenotrophic (methylotrophic) methanogenesis, based on established interpretations of hydrogen isotope data. These findings are consistent with studies of laboratory cultures, which also show methylotrophic methane is more depleted in clumped isotopologues (¹³CH₃D and ¹²CH₂D₂) than hydrogenotrophic methane, though both forms of cultured (hydrogenotrophic vs. methylotrophic) methane exhibit strong deficits in both isotopic species. The sensitivity of clumped isotopologues to methanogenesis pathways in natural settings provides a powerful tool for monitoring the activity of methanogenic microbial communities in the subsurface. Anomalies of both studied clumped isotopologues (Δ¹³CH₃D and Δ¹²CH₂D₂) decrease over time in wells that have been re-sampled repeatedly, suggesting that such measurements are capable of detecting and quantifying shifts in proportions of these two metabolic pathways over the timescales of gas production history.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.epsl.2021.116960DOIArticle
ORCID:
AuthorORCID
Xie, Hao0000-0001-5656-2035
Eiler, John M.0000-0001-5768-7593
Additional Information:© 2021 Elsevier. Received 15 July 2020, Revised 4 March 2021, Accepted 15 April 2021, Available online 27 April 2021. We thank Prof. Louis Derry, Prof. Anna Martini and one anonymous reviewer for their valuable comments and suggestions to improve the manuscript. This work was cosponsored by the NSFC (41772135) and PetroChina Foundation (2017ycp014, YGJ2019-04-02). CRediT authorship contribution statement. Y.S. designed the research. Y.S. and H.X. analyzed the experiments. All authors contributed to the interpretation of the results. Y.S. and J.E. wrote the manuscript with contributions and input from H.X., S.Z. and Y.Z. The authors declare that they have no competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Funders:
Funding AgencyGrant Number
National Natural Science Foundation of China41772135
PetroChina Foundation2017ycp014
PetroChina FoundationYGJ2019-04-02
Subject Keywords:clumped isotopologue; biogenic methane; hydrogenotrophic methanogenesis; metabolism pathway; Δ13CH3D proxy
Record Number:CaltechAUTHORS:20210626-183440633
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20210626-183440633
Official Citation:Yanhua Shuai, Hao Xie, Shuichang Zhang, Yongshu Zhang, John M. Eiler, Recognizing the pathways of microbial methanogenesis through methane isotopologues in the subsurface biosphere, Earth and Planetary Science Letters, Volume 566, 2021, 116960, ISSN 0012-821X, https://doi.org/10.1016/j.epsl.2021.116960.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109606
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:28 Jun 2021 23:05
Last Modified:28 Jun 2021 23:05

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