title: The active methanotrophic community in a wetland from the High Arctic.
abstract: The dominant terminal process of carbon mineralization in most freshwater wetlands is methanogenesis. With methane being an important greenhouse gas, the predicted warming of the Arctic may provide a positive feedback. However, the amount of methane released to the atmosphere may be controlled by the activity of methane-oxidizing bacteria (methanotrophs) living in the oxic surface layer of wetlands. Previously, methanotrophs have been isolated and identified by genetic profiling in High Arctic wetlands showing the presence of only a few genotypes. Two isolates from Solvatnet (Ny-Ålesund, Spitsbergen; 79°N) are available: Methylobacter tundripaludum (type I) and Methylocystis rosea (type II), raising the question whether the low diversity is a cultivation effect. We have revisited Solvatnet applying stable isotope probing (SIP) with (13) C-labelled methane. 16S rRNA profiling revealed active type I methanotrophs including M. tundripaludum, while no active type II methanotrophs were identified. These results indicate that the extant M. tundripaludum is an active methane oxidizer at its locus typicus; furthermore, Methylobacter seems to be the dominant active genus. Diversity of methanotrophs was low as compared, e.g. to wetland rice fields in the Mediterranean. This low diversity suggests a high vulnerability of Arctic methanotroph communities, which deserves more attention.
authors.affiliation: Department of Arctic and Marine Biology, Faculty of Biosciences, Fisheries and Economics, University of Tromsø, N-9037 Tromsø, Norway. Max-Planck-Institute for Terrestrial Microbiology, D-35043 Marburg, Germany.
authors.forename: Christiane
authors.initials: C
authors.lastname: Graef
authors.forename: Anne Grethe
authors.initials: AG
authors.lastname: Hestnes
authors.forename: Mette Marianne
authors.initials: MM
authors.lastname: Svenning
authors.forename: Peter
authors.initials: P
authors.lastname: Frenzel