Methane oxidation associated with submerged brown mosses reduces methane emissions from Siberian polygonal tundra

Abstract

Summary1. Methane (CH 4 ) oxidation (methanotrophy) associated with submerged brown moss species occurs in polygonal tundra environments of the Siberian Arctic. Methanotrophic bacteria living in close association with mosses are thus not restricted to Sphagnum species and low-pH peatlands. 2. Moss-associated methane oxidation (MAMO) can be an effective buffer for CH 4 emissions from permafrost-affected tundra, a region that is of high importance for the global greenhouse gas budget. Combining biogeochemical and molecular approaches revealed that MAMO in polygonal ponds exceeds methanotrophic activity in terrestrial sites by up to two orders of magnitude. 3. Moss-associated methane oxidation is not only promoted by submerged conditions but also by light exposure. Polygonal ponds covered by the brown moss Scorpidium scorpioides became a net sink for atmospheric CH 4 ()1.7 mg CH 4 m )2 day )1 ) when exposed to sunlight but a CH 4 source (21.6 mg CH 4 m )2 day )1) in the absence of light. 4. Based on stable isotope probing with 13 CH 4 , carbon deriving from CH 4 was incorporated into the bacterial fatty acids 16:1x7 and 18:1x9 ⁄ x7 common in methanotrophs and into plant phytol, sitosterol and stigmastanol, all of which are highly abundant in moss biomass. 5. Synthesis. A mutualistic symbiosis between methanotrophic bacteria and brown mosses reduces CH 4 emissions from Arctic polygonal tundra by at least 5%. Both partners benefit from this association: the moss from the additional CO 2 supplied through methane oxidation and the methane-oxidizing bacteria from the oxygen produced through photosynthesis. Considering that submerged mosses are widely abundant in the polar region, MAMO may have a major impact on carbon turnover rates in Arctic freshwater environments.

An active atmospheric methane sink in high Arctic mineral cryosols

“…Surprisingly none of the transcript contigs from the polygon interior sample matched with our MMO-containing metagenome contigs. The higher pmo gene expression at the more vegetated, moist trough suggests that, like other MOB (Liebner et al, 2011), the USCα-like atmMOB has preference for vegetated micro-niches in polygonal terrains.…”

Bacterial genome replication at subzero temperatures in permafrost

“…Many recent studies on permafrost bacterial growth and metabolism have focused on temperatures at or above 0 1C, assuming that metabolic activity predominantly occurs when permafrost soils have thawed (Martineau et al, 2010;Liebner et al, 2011;Mackelprang et al, 2011;He et al, 2012;Nicholson et al, 2013). However, the concept that bacterial activity in frozen soils can also have a major role in biogeochemical cycles is changing (Bergholz et al, 2009;McMahon et al, 2009;Vishnivetskaya et al, 2009;Mykytczuk et al, 2012;Tveit et al, 2013).…”

“…Prior research in Arctic systems has used SIP to monitor active methanotrophs with 13 CH 4 , but the studies were performed at higher incubation temperatures ranging from 4 to 25 1C (Martineau et al, 2010;Liebner et al, 2011;He et al, 2012). Here, we used the SIP method to elucidate how specific members of the bacterial community responded to various subzero incubation temperatures ranging from 0 to À 20 1C.…”

Importance of vegetation classes in modeling CH4 emissions from boreal and subarctic wetlands in Finland

“…However, considerable differences were reported in CH 4 oxidation through the vascular transport between vegetation species (Popp et al, 2000;Ström et al, 2005). Recently, cooperation between methanotrophic bacteria and water-submerged Sphagnum was shown to reduce methane emissions (Bridgham et al, 2013;Kip et al, 2012;Larmola et al, 2010;Liebner et al, 2011;Parmentier et al, 2011). The rates of potential oxidation ranged from 0 to 80 μmol g dw −1 day − 1 (Kip et al, 2012;Larmola et al, 2010;Raghoebarsing et al, 2005).…”