Methanotrophic activity and diversity in different Sphagnum magellanicum dominated habitats in the southernmost peat bogs of Patagonia

[摘要] Sphagnum peatlands are important ecosystems in the methane cycle. Methanotrophsliving inside the dead hyaline cells or on the Sphagnum mosses are able to act as amethane filter and thereby reduce methane emissions. We investigated in situ methaneconcentrations and the corresponding activity and diversity of methanotrophsin different Sphagnum dominated bog microhabitats. In contrast to the NorthernHemisphere peat ecosystems the temperate South American peat bogs aredominated by one moss species; Sphagnum magellanicum. This permitted a species-independentcomparison of the different bog microhabitats. Potential methane oxidizingactivity was found in all Sphagnum mosses sampled and a positive correlation wasfound between activity and in situ methane concentrations. Substantial methaneoxidation activity (23 μmol CH₄ gDW⁻¹ day⁻¹) was found inpool 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 livingSphagnum mosses from lawns and hummocks. Methane oxidation activity was relativelyhigh (>4 μmol CH₄ gDW⁻¹ day⁻¹) in Sphagnum litter at depthsaround the water levels and rich in methane. The total bacterial communitywas studied using 16S rRNA gene sequencing and the methanotrophiccommunities were studied using a pmoA microarray and a complementary pmoA clonelibrary. The methanotrophic diversity was similar in the different habitatsof this study and comparable to the methanotrophic diversity found in peatmosses from the Northern Hemisphere. The pmoA microarray data indicated thatboth alpha- and gammaproteobacterial methanotrophs were present in allSphagnum mosses, even in those mosses with a low initial methane oxidation activity.Prolonged incubation of Sphagnum mosses from lawn and hummock with methane revealedthat the methanotrophic community present was viable and showed an increasedactivity within 15 days. The high abundance of methanotrophic Methylocystis species in themost active mosses suggests that these might be responsible for the bulk ofmethane oxidation.

[学科分类] 地球化学与岩石