Activity and abundance of methanotrophic bacteria in a northern mountainous gradient of wetlands.

Methane uptake and diversity of methanotrophic bacteria was investigated across six hydrologically connected wetlands in a mountainous forest landscape upstream of lake Langtjern, southern Norway. From floodplain through shrubs, forest and sedges to a Sphagnum covered site, growing season CH 4 production was insufficiently consumed to balance release into the atmosphere. Emission increased by soil moisture ranging 0.6-6.8 mg CH 4 m -2  h -1 . Top soils of all sites consumed CH 4 including at the lowest 78 ppmv CH 4 supplied, thus potentially oxidizing 17-51 nmol CH 4 g -1 dw h -1 , with highest V max 440 nmol g -1 dw h -1 under Sphagnum and lowest K m 559 nM under hummocked Carex. Nine genera and several less understood type I and type II methanotrophs were detected by the key functional gene pmoA involved in methane oxidation. Microarray signal intensities from all sites revealed Methylococcus, the affiliated Lake Washington cluster, Methylocaldum, a Japanese rice cluster, Methylosinus, Methylocystis and the affiliated Peat264 cluster. Notably enriched by site was a floodplain Methylomonas and a Methylocapsa-affiliated watershed cluster in the Sphagnum site. The climate sensitive water table was shown to be a strong controlling factor highlighting its link with the CH 4 cycle in elevated wetlands.