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

摘要

Sphagnum peatlands are important ecosystemsin the methane cycle. Methanotrophs living inside thedead hyaline cells or on the Sphagnum mosses are ableto act as a methane filter and thereby reduce methaneemissions. We investigated in situ methane concentrationsand the corresponding activity and diversity of methanotrophsin different Sphagnum dominated bog microhabitats.In contrast to the Northern Hemisphere peat ecosystemsthe temperate South American peat bogs are dominatedby one moss species; Sphagnum magellanicum. Thispermitted a species-independent comparison of the differentbog microhabitats. Potential methane oxidizing activitywas found in all Sphagnum mosses sampled anda positive correlation was found between activity and insitu methane concentrations. Substantial methane oxidationactivity (23 μmolCH4 gDW~(-1) day~(-1)) was found inpool mosses and could be correlated with higher in situmethane concentrations (>35 μmolCH4 l~(-1) pore water). Littlemethanotrophic activity (<0.5 μmolCH4 gDW~(-1) day~(-1))was observed in living Sphagnum mosses from lawns andhummocks. Methane oxidation activity was relatively high(>4 μmolCH4 gDW~(-1) day~(-1)) in Sphagnum litter at depthsaround the water levels and rich in methane. The total bacterialcommunity was studied using 16S rRNA gene sequencingand the methanotrophic communities were studied usinga pmoA microarray and a complementary pmoA clonelibrary. The methanotrophic diversity was similar in the differenthabitats of this study and comparable to the methanotrophicdiversity found in peat mosses from the NorthernHemisphere. The pmoA microarray data indicated thatboth alpha- and gammaproteobacterial methanotrophs werepresent in all Sphagnum mosses, even in those mosses with alow initial methane oxidation activity. Prolonged incubationof Sphagnum mosses from lawn and hummock with methanerevealed that the methanotrophic community present was viableand showed an increased activity within 15 days. Thehigh abundance of methanotrophic Methylocystis species inthe most active mosses suggests that these might be responsiblefor the bulk of methane oxidation.