Sediment Emission and Water Column Oxidation of Methane in Alaskan Arctic Lakes

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McGowan, Gabriel E.
- Affiliation: Gillings School of Global Public Health, Department of Environmental Sciences and Engineering

Abstract

Methane (CH4) is a greenhouse gas and is important in lacustrine food webs. Cycling of CH4 in arctic lakes is poorly quantified, though arctic wetlands are key to the atmospheric CH4 budget. Sediment emission and water column oxidation of CH4 were studied in 3 shallow and 3 deep Alaskan arctic lakes during the 2010 and 2011 thaw seasons. Sediment CH4 emission was oxygen-regulated and significantly higher in shallow lakes, averaging 1.39 mmol m-2 d-1. Methane comprised a larger fraction of sediment catabolism in shallow lakes. Water column CH4 oxidation was significantly greater in shallow lakes, averaging 0.16 mmol m-2 d-1, with specific rates in bottom waters among the highest reported. Air-water CH4 exchange ranged up to 1.94 mmol m-2 d-1 in shallow lakes, similar to rates reported for tropical lakes. The data show that CH4 is important in C cycling in shallow Alaskan arctic lakes, which emit considerable CH4 despite extensive CH4 oxidation.

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