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Microbial and isotopic evidence for methane cycling in hydrocarbon-containing groundwater from the Pennsylvania region

Lookup NU author(s): Dr Adrien Vigneron, Professor Ian Head

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract

The Pennsylvania region hosts numerous oil and gas reservoirs and the presence of hydrocarbons in groundwater has been locally observed. However, these methane-containing freshwater ecosystems remain poorly explored despite their potential importance in the carbon cycle. Methane isotope analysis and analysis of low molecular weight hydrocarbon gases from 18 water wells indicated that active methane cycling may be occurring in methane-containing groundwater from the Pennsylvania region. Consistent with this observation, multigenic qPCR and gene sequencing (16S rRNA genes, mcrA, and pmoA genes) indicated abundant populations of methanogens, ANME-2d (average of 1.54 × 10⁴ mcrA gene per milliliter of water) and bacteria associated with methane oxidation (NC10, aerobic methanotrophs, methylotrophs; average of 2.52 × 10³ pmoA gene per milliliter of water). Methane cycling therefore likely represents an important process in these hydrocarbon-containing aquifers. The microbial taxa and functional genes identified and geochemical data suggested that (i) methane present is at least in part due to methanogens identified in situ; (ii) Potential for aerobic and anaerobic methane oxidation is important in groundwater with the presence of lineages associated with both anaerobic an aerobic methanotrophy; (iii) the dominant methane oxidation process (aerobic or anaerobic) can vary according to prevailing conditions (oxic or anoxic) in the aquifers; (iv) the methane cycle is closely associated with the nitrogen cycle in groundwater methane seeps with methane and/or methanol oxidation coupled to denitrification or nitrate and nitrite reduction.

Publication metadata

Author(s): Vigneron A, Bishop A, Alsop EB, Hull K, Rhodes I, Hendricks R, Head IM, Tsesmetzis N

Publication type: Article

Publication status: Published

Journal: Frontiers in Microbiology

Year: 2017

Volume: 8

Online publication date: 05/04/2017

Acceptance date: 22/03/2017

Date deposited: 25/04/2017

ISSN (electronic): 1664-302X

Publisher: Frontiers Research Foundation

URL: https://doi.org/10.3389/fmicb.2017.00593

DOI: 10.3389/fmicb.2017.00593

PubMed id: PMC5380731

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