Substantial high-affinity methanotroph populations in Andisols effect high rates of atmospheric methane oxidation

Authors

  • Pete J. Maxfield,

    1. Organic Geochemistry Unit, Bristol Biogeochemistry Research Centre, School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
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  • Ed R.C. Hornibrook,

    1. Bristol Biogeochemistry Research Centre, Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol, BS8 1RJ, UK.
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  • Richard P. Evershed

    Corresponding author
    1. Organic Geochemistry Unit, Bristol Biogeochemistry Research Centre, School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
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E-mail: r.p.evershed@bristol.ac.uk; Tel. (+44) 117 928 7671; Fax (+44) 117 925 1295.

Summary

Methanotrophic bacteria in soils derived from volcanic ash (Andisols) were characterized via time series 13C-phospholipid fatty acid (PLFA) labelling. Three Andisols were incubated under 2 ppmv 13CH4 for up to 18 weeks, thus enabling high-affinity methanotrophs to be selectively characterized and quantified. PLFA profiles from all soils were broadly similar, but the magnitude of the high-affinity methanotrophic populations determined through 13C-PLFA-stable isotope probing displayed sizeable differences. Substantial incorporation of 13C indicated very large high-affinity methanotrophic populations in two of the soils. Such high values are far in excess (10×) of those observed for a range of mineral soils incubated under similar conditions (Bull et al., 2000; Maxfield et al., 2006; 2008a, b). Two of the three Andisols studied also displayed high but variable CH4 oxidation rates ranging from 0.03 to 1.58 nmol CH4 g−1 d.wt. h−1. These findings suggest that Andisols, a previously unstudied soil class with respect to high-affinity methanotrophic bacteria, may oxidize significant amounts of atmospheric methane despite their low areal coverage globally.

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