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

Abstract

Methane uptake and diversity of methanotrophic bacteria was investigated across six hydrologically connectedwetlands in a mountainous forest landscape upstream of lake Langtjern, southern Norway. From floodplain through shrubs, forest and sedges to aSphagnum covered site, growing season CH4 production was insufficiently consumed to balance release into the atmosphere. Emission increased by soil moisture ranging 0.6-6.8mg CH4 m-2 h-1 . Top soils of all sites consumed CH4 including at the lowest 78 ppmv CH4 supplied, thus potentially oxidizing 17-51 nmol CH4 g-1 dw h-1 , with highest Vmax 440 nmol g-1 dw h-1 under Sphagnum and lowest Km 559 nM under hummocked Carex. Nine genera and several less understood type I and type II methanotrophs were detected bythe 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 CH4 cycle in elevated wetlands.