Microbial CH4 and N2O Consumption in Acidic Wetlands

Abstract

Acidic wetlands are global sources of the atmospheric greenhouse gases methane (CH4), and nitrous oxide (N2O). Consumption of both atmospheric gases has been observed in various acidic wetlands, but information on the microbial mechanisms underlying these phenomena is scarce. A substantial amount of CH4 is consumed in sub soil by aerobic methanotrophs at anoxic–oxic interfaces (e.g., tissues of Sphagnum mosses, rhizosphere of vascular plant roots). Methylocystis-related species are likely candidates that are involved in the consumption of atmospheric CH4 in acidic wetlands. Oxygen availability regulates the activity of methanotrophs of acidic wetlands. Other parameters impacting on the methanotroph-mediated CH4 consumption have not been systematically evaluated. N2O is produced and consumed by microbial denitrification, thus rendering acidic wetlands as temporary sources or sinks for N2O. Denitrifier communities in such ecosystems are diverse, and largely uncultured and/or new, and environmental factors that control their consumption activity are unresolved. Analyses of the composition of N2O reductase genes in acidic wetlands suggest that acid-tolerant Proteobacteria have the potential to mediate N2O consumption in such soils. Thus, the fragmented current state of knowledge raises open questions concerning methanotrophs and denitrifiers that consume atmospheric CH4 and N2O in acidic wetlands.

Actinobacterial Nitrate Reducers and Proteobacterial Denitrifiers Are Abundant in N 2 O-Metabolizing Palsa Peat

“…Acidic wetlands including vegetated palsa peats represent temporary sinks of atmospheric N 2 O, and N 2 O consumption of atmospheric levels was detected in situ at the Skalluvaara palsa peat site and in microcosms ( Fig. 1 and 2) (11,24,39,45,48). The acetylene inhibition technique indicated that N 2 was a denitrification end product in unsupplemented palsa peat soil microcosms (Fig.…”

Nitrous oxide emission potentials of Burkholderia species isolated from the leaves of a boreal peat moss Sphagnum fuscum*

“…14) Acidic Sphagnum peat-covered wetlands are a global carbon sink, while simultaneously a source of GHGs methane (CH 4 ) and N 2 O. 15) In fact, an anoxic environment can accelerate the process of denitrification, while low pH generally inhibits reduction of N 2 O to N 2 gas by interfering in the assembling of nitrous oxide reductase (N 2 OR), leading to the promotion of an N 2 O flux. 16) In addition, deposition of ammonia-form N by nitrogen-fixers results in the dominance of certain species of Sphagnum mosses, 17) even though uptake of excess NH þ 4 cannot be performed by Sphagnum mosses in the interstitial water.…”

Exchange of the Greenhouse Gases Methane and Nitrous Oxide Between the Atmosphere and a Temperate Peatland in Central Europe

“…The negative N 2 O fluxes observed at our site under relatively wet conditions (WTD did not drop below 15.6 cm from the surface) indicate that N 2 O can be taken up from the atmosphere, induced by the N-limited situation of our wetland. Other researchers have already indicated that under such conditions, denitrification may be responsible for N 2 O uptake from the atmosphere in peatlands (Chapuis-Lardy et al 2007;Lohila et al 2010;Kolb and Horn 2012). On the other hand, it is well known that rapid waterlogging of the peat due to a precipitation event, particularly after 2-3 weeks of dry conditions may promote subsurface N 2 O production and increase emissions of N 2 O within several hours of the event (Jǿrgensen and Elberling 2012).…”