Atmospheric CH sub(4) oxidation by Arctic permafrost and mineral cryosols as a function of water saturation and temperature

• Published in: Geobiology 2017-01, Vol.15 (1), p.94-111
• Main Authors: Stackhouse, B, Lau, MCY, Vishnivetskaya, T, Burton, N, Wang, R, Southworth, A, Whyte, L, Onstott, T C
• Format: Article
• Language: English
• ISSN: 1472-4677; 1472-4669
• DOI: 10.1111/gbi.12193

The response of methanotrophic bacteria capable of oxidizing atmospheric CH sub(4) to climate warming is poorly understood, especially for those present in Arctic mineral cryosols. The atmospheric CH sub(4) oxidation rates were measured in microcosms incubated at 4 degree C and 10 degree C along a 1-m depth profile and over a range of water saturation conditions for mineral cryosols containing type I and type II methanotrophs from Axel Heiberg Island (AHI), Nunavut, Canada. The cryosols exhibited net consumption of ~2 ppmv CH sub(4) under all conditions, including during anaerobic incubations. Methane oxidation rates increased with temperature and decreased with increasing water saturation and depth, exhibiting the highest rates at 10 degree C and 33% saturation at 5 cm depth (260 plus or minus 60 pmol CH sub(4) gdw super(-1) d super(-1)). Extrapolation of the CH sub(4) oxidation rates to the field yields net CH sub(4) uptake fluxes ranging from 11 to 73 mu mol CH sub(4) m super(-2) d super(-1), which are comparable to field measurements. Stable isotope mass balance indicates ~50% of the oxidized CH sub(4) is incorporated into the biomass regardless of temperature or saturation. Future atmospheric CH sub(4) uptake rates at AHI with increasing temperatures will be determined by the interplay of increasing CH sub(4) oxidation rates vs. water saturation and the depth to the water table during summer thaw.