Methane transport mechanisms and isotopic fractionation in emergent macrophytes of an Alaskan tundra lake

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Chanton, J.P.
- Other Affiliation: Florida State University
Martens, C.S.
- Affiliation: College of Arts and Sciences, Department of Marine Sciences
Kelley, C.A.
- Affiliation: College of Arts and Sciences, Department of Marine Sciences
Crill, P.M.
- Other Affiliation: University of New Hampshire
Showers, W.J.
- Other Affiliation: North Carolina State University

Abstract

The carbon isotopic composition of methane emitted by the Alaskan emergent aquatic plants Arctophila fulva, a tundra mid-lake macrophyte, and Carex rostrata, a tundra lake margin macrophyte, was -58.6±0.5 (n=2) and -66.6±2.5 (n=6) ‰ respectively. The methane emitted by these species was found to be depleted in 13C by 12‰ and 18‰, relative to methane withdrawn from plant stems 1 to 2cm below the waterline. As the macrophyte-mediated methane flux represented approximately 97% of the flux from these sites, these results suggest the more rapid transport of 12CH4 relative to 13CH4 through plants to the atmosphere. Plant stem methane concentrations ranged from 0.2 to 4.0% (x̄, 1.4; standard deviation (sd), 0.9; n=28) in Arctophila, with an isotopic composition of -46.1±4.3‰) (n=8). Carex stem methane concentrations were lower, ranging from 150 to 1200 ppm (x̄, 500; standard deviation, 360; n=8), with an isotopic composition of -48.3±1.4‰ (n=3).

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