Methanotrophic activity and diversity in different Sphagnum magellanicum dominated habitats in the southernmost peat bogs of Patagonia
1Radboud University Nijmegen, Institute for Water and Wetland Research (IWWR), Department of Microbiology, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
2Radboud University Nijmegen, Institute for Water and Wetland Research (IWWR), Department Aquatic Ecology Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
3University of Groningen, Centre for Energy and Environmental Studies, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
4Bioresources Unit, AIT, Austrian Institute of Technology GmbH, 2444 Seibersdorf, Austria
5CSIRO, Marine and Atmospheric Research and Wealth from Oceans, National Research Flagship, Hobart Tasmania 7000 Australia
6CADIC-CONICET, B. Houssay 200, 9410 Ushuaia, Tierra del Fuego, Argentina
Abstract. Sphagnum peatlands are important ecosystems in the methane cycle. Methanotrophs living in and on the Sphagnum mosses are able to act as a methane filter and thereby reduce methane emissions. We investigated in situ methane concentrations and the corresponding activity and diversity of methanotrophs in different Sphagnum dominated bog microhabitats. In contrast to the Northern Hemisphere peat ecosystems the temperate South American peat bogs are dominated by one moss species; Sphagnum magellanicum. This permitted a species-independent comparison of the different bog microhabitats. Potential methane oxidizing activity was found in all Sphagnum mosses sampled and a positive correlation was found between activity and in situ methane concentrations. Substantial methane oxidation activity (23 μmol CH4 gDW−1 day−1) was found in pool mosses and could be correlated with higher in situ methane concentrations (>35 μmol CH4 l−1 pore water). Little methanotrophic activity (<0.5 μmol CH4 gDW−1 day−1) was observed in living Sphagnum mosses from lawns and hummocks. Methane oxidation activity was relatively high (>4 μmol CH4 gDW−1 day−1) in Sphagnum litter situated at depths around the water levels and rich in methane. The total bacterial community was studied using 16S rRNA gene sequencing and the methanotrophic communities were studied using a pmoA microarray and a complementary pmoA clone library. The methanotrophic diversity was similar in the different habitats of this study and surprisingly comparable to the methanotrophic diversity found in peat mosses from the Northern Hemisphere. The pmoA microarray data indicated that both alpha- and gammaproteobacterial methanotrophs were present in all Sphagnum mosses, even in those mosses with a low initial methane oxidation activity. Prolonged incubation of Sphagnum mosses from lawn and hummock with methane revealed that the methanotrophic community present was viable and showed an increased activity within 15 days. The high abundance of methanotrophic Methylocystis species in the most active mosses suggests that these might be responsible for the bulk of methane oxidation.