An active atmospheric methane sink in high Arctic mineral cryosols

Abstract

Methane (CH 4 ) emission by carbon-rich cryosols at the high latitudes in Northern Hemisphere has been studied extensively. In contrast, data on the CH 4 emission potential of carbon-poor cryosols is limited, despite their spatial predominance. This work employs CH 4 flux measurements in the field and under laboratory conditions to show that the mineral cryosols at Axel Heiberg Island in the Canadian high Arctic consistently consume atmospheric CH 4 . Omics analyses present the first molecular evidence of active atmospheric CH 4 -oxidizing bacteria (atmMOB) in permafrost-affected cryosols, with the prevalent atmMOB genotype in our acidic mineral cryosols being closely related to Upland Soil Cluster α. The atmospheric (atm) CH 4 uptake at the study site increases with ground temperature between 0°C and 18°C. Consequently, the atm CH 4 sink strength is predicted to increase by a factor of 5-30 as the Arctic warms by 5-15°C over a century. We demonstrate that acidic mineral cryosols are a previously unrecognized potential of CH 4 sink that requires further investigation to determine its potential impact on larger scales. This study also calls attention to the poleward distribution of atmMOB, as well as to the potential influence of microbial atm CH 4 oxidation, in the context of regional CH 4 flux models and global warming.

Microbial diversity and functional capacity in polar soils

“…In contrast to many other extremophilic biomes, cold environments appear to have a higher level of spatial heterogeneity [20][21][22]. Within cold regions, both soils and permafrost niches appear to be dominated by bacterial (mainly Proteobacterial, Actinobacterial and Acidobacterial), archaeal (mostly Euryarchaeota) and fungal (dominated by Ascomycota) lineages [7,23,24,25 ] (Table 1).…”

“…Recent metagenomic studies have significantly contributed to our understanding of the functional capacity of microorganisms in cold soil environments [22,30 ], through the identification of genes and pathways implicated in key biogeochemical cycles. The genes of nitrogen cycling have been extensively studied in both Arctic and Antarctic soils [57,58], primary by targeting the nitrogenase (nifH) gene (Figure 2).…”

“…Changes in methane productivity were linked to a shift from formate-and H 2 -using Methanobacteriales to Methanomicrobiales and from the acetotrophic Methanosarcinaceae to Methanosaetaceae [63]. In Arctic soils, methanogenesis is driven principally by Euryarchaeota, based on detection of mcrABG genes, although homologous genes assigned to a-and g-proteobacterial taxa also appear to be ubiquitous [22,65]. Methanogenic processes appear to be dominant in peat soils in the Arctic while methanogens are less abundant in permafrost soils [66].…”

“…Through application of metagenomic approaches (Figure 1), it is now known that most extreme environments harbour lower levels of microbial diversity (species richness and relative 1 abundance), than more 'benign' ecosystems [16,17]. This is thought to be due to the requirement for specific physiological adaptations, which allow organisms to exploit the combination of physical and biochemical stressors, but result in simplified ecosystems dominated by a relatively few taxa [18,19].In contrast to many other extremophilic biomes, cold environments appear to have a higher level of spatial heterogeneity [20][21][22]. Within cold regions, both soils and permafrost niches appear to be dominated by bacterial (mainly Proteobacterial, Actinobacterial and Acidobacterial), archaeal (mostly Euryarchaeota) and fungal (dominated by Ascomycota) lineages [7,23,24,25 ] (Table 1).…”

Impacts of temperature and soil characteristics on methane production and oxidation in Arctic polygonal tundra

“…High-affinity methanotrophs oxidize substantial amounts of atmospheric methane in high Arctic mineral soils (Lau et al, 2015). Methane oxidation rates are usually greatest in oxic, surficial soils, and methane oxidation is known to occur under oxygen-limiting conditions as well (Roslev and King, 1996).…”