skip to main content


Title: Microbial Greenhouse Gas Dynamics Associated With Warming Coastal Permafrost, Western Canadian Arctic
Permafrost sediments contain one of the largest reservoirs of organic carbon on Earth that is relatively stable when it remains frozen. As air temperatures increase, the shallow permafrost thaws which allows this organic matter to be converted into potent greenhouse gases such as methane (CH4) and carbon dioxide (CO2) through microbial processes. Along the Beaufort Sea coast in the vicinity of the Tuktoyaktuk Peninsula, Northwest Territories, Canada, warming air temperatures are causing the active layer above permafrost to deepen, and a number of active periglacial processes are causing rapid erosion of previously frozen permafrost. In this paper, we consider the biogeochemical consequences of these processes on the permafrost sediments found at Tuktoyaktuk Island. Our goals were to document the in situ carbon characteristics which can support microbial activity, and then consider rates of such activity if the permafrost material were to warm even further. Samples were collected from a 12mpermafrost core positioned on the top of the island adjacent to an eroding coastal bluff. Downcore CH4, total organic carbon and dissolved organic carbon (DOC) concentrations and stable carbon isotopes revealed variable in situ CH4 concentrations down core with a sub-surface peak just below the current active layer. The highest DOC concentrations were observed in the active layer. Controlled incubations of sediment from various depths were carried out from several depths anaerobically under thawed (5°C and 15°C) and under frozen (−20°C and −5°C) conditions. These incubations resulted in gross production rates of CH4 and CO2 that increased upon thawing, as expected, but also showed appreciable production rates under frozen conditions. This dataset presents the potential for sediments below the active layer to produce potent greenhouse gases, even under frozen conditions, which could be an important atmospheric source in the actively eroding coastal zone even prior to thawing.  more » « less
Award ID(s):
1756244
NSF-PAR ID:
10310443
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ;
Editor(s):
Jones, Benjamin
Date Published:
Journal Name:
Frontiers in earth science
Volume:
8
ISSN:
2296-6463
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Methane (CH4) concentrations were measured in dissolved organic carbon (DOC) leachates of permafrost soils collected from the frozen permafrost layer at five sites underlying tussock tundra or wet sedge vegetation on the North Slope of Alaska during the summers of 2018 and 2019. 
    more » « less
  2. Abstract

    The magnitude of future emissions of greenhouse gases from the northern permafrost region depends crucially on the mineralization of soil organic carbon (SOC) that has accumulated over millennia in these perennially frozen soils. Many recent studies have used radiocarbon (14C) to quantify the release of this “old” SOC as CO2or CH4to the atmosphere or as dissolved and particulate organic carbon (DOC and POC) to surface waters. We compiled ~1,90014C measurements from 51 sites in the northern permafrost region to assess the vulnerability of thawing SOC in tundra, forest, peatland, lake, and river ecosystems. We found that growing season soil14C‐CO2emissions generally had a modern (post‐1950s) signature, but that well‐drained, oxic soils had increased CO2emissions derived from older sources following recent thaw. The age of CO2and CH4emitted from lakes depended primarily on the age and quantity of SOC in sediments and on the mode of emission, and indicated substantial losses of previously frozen SOC from actively expanding thermokarst lakes. Increased fluvial export of aged DOC and POC occurred from sites where permafrost thaw caused soil thermal erosion. There was limited evidence supporting release of previously frozen SOC as CO2, CH4, and DOC from thawing peatlands with anoxic soils. This synthesis thus suggests widespread but not universal release of permafrost SOC following thaw. We show that different definitions of “old” sources among studies hamper the comparison of vulnerability of permafrost SOC across ecosystems and disturbances. We also highlight opportunities for future14C studies in the permafrost region.

     
    more » « less
  3. Non-thermal plasma Methane capture Carbon dioxide capture Metal organic framework Methanol synthesis Atmospheric remediation 1. Introduction The stabilization of CO2 and CH4 concentrations in the air to control global warming is accelerating. There are continued efforts to develop and optimize different technologies for capture and sequestration of these greenhouse gases from industrial emission sites. From these gases, CH4 is the most dominant anthropogenic greenhouse gas (after CO2). Methane can react with nitrogen oxides leading to tropospheric ozone pollution and posses a higher global warming potential (GWP) than CO2. It is 84 times more potent than CO2 over the first 20 years after release and ~28 times more potent after a century. Methane concentrations could be restored to preindustrial levels by removing ~3.2 of the 5.3 Gt of CH4 currently in the atmosphere [1]. Rather than capturing and storing the methane, CH4 could be oxidized to CO2, through the ther- modynamically favorable reaction: CH4 + 2O2 → CO2 + 2H2O; ΔHrx = –803 kJ mol–1. With the possible production of valuable condensates such as form- aldehyde and methanol when employing different reaction conditions (i. e., gas ratio, oxidant type, temperature) and rational selected catalysts. The large activation barrier associated with splitting methane’s C– H * Corresponding author. E-mail address: Maria.CarreonGarciduenas@sdsmt.edu (M.L. Carreon). https://doi.org/10.1016/j.jcou.2021.101642 The direct capture of CO2 and CH4 from the atmosphere to stabilize the concentrations in the air to control global warming is accelerating. There are continued efforts to develop and optimize different technologies for capture and sequestration of these greenhouse gases from industrial emission sites. In this work we employed MOF-177 as an efficient CO2 and CH4 adsorbent at standard temperature and pressure conditions. We demonstrated the possibility of desorbing the gases under study when employing gentle plasma pulses of He. Moreover, we per- formed the synthesis of methanol from CH4 using O2 and CO2 as oxidants respectively in the presence of MOF- 177. We observed the highest conversion for the CH4 + O2 system when employing the MOF-177 at (5:1) (CH4: O2) flow ratio of 23.5 % and methanol selectivity of 17.65 %. While the best performance for the CH4 + CO2 system at the same conditions i.e., (5:1) (CH4: O2) flow ratio was 18.4 % for the methane conversion and 11.68 % for the selectivity towards methanol. We expect this preliminary understanding of the adsorption-reaction system under non-thermal plasma environment can lead to future atmospheric remediation technologies. 
    more » « less
  4. Abstract

    Microorganisms drive many aspects of organic carbon cycling in thawing permafrost soils, but the compositional trajectory of the post-thaw microbiome and its metabolic activity remain uncertain, which limits our ability to predict permafrost–climate feedbacks in a warming world. Using quantitative metabarcoding and metagenomic sequencing, we determined relative and absolute changes in microbiome composition and functional gene abundance during thaw incubations of wet sedge tundra collected from northern Alaska, USA. Organic soils from the tundra active-layer (0–50 cm), transition-zone (50–70 cm), and permafrost (70+ cm) depths were incubated under reducing conditions at 4 °C for 30 days to mimic an extended thaw duration. Following extended thaw, we found that iron (Fe)-cycling Gammaproteobacteria, specifically the heterotrophic Fe(III)-reducing Rhodoferax sp. and chemoautotrophic Fe(II)-oxidizing Gallionella sp., increased by 3–5 orders of magnitude in absolute abundance within the transition-zone and permafrost microbiomes, accounting for 65% of community abundance. We also found that the abundance of genes for Fe(III) reduction (e.g., MtrE) and Fe(II) oxidation (e.g., Cyc1) increased concurrently with genes for benzoate degradation and pyruvate metabolism, in which pyruvate is used to generate acetate that can be oxidized, along with benzoate, to CO2 when coupled with Fe(III) reduction. Gene abundance for CH4 metabolism decreased following extended thaw, suggesting dissimilatory Fe(III) reduction suppresses acetoclastic methanogenesis under reducing conditions. Our genomic evidence indicates that microbial carbon degradation is dominated by iron redox metabolism via an increase in gene abundance associated with Fe(III) reduction and Fe(II) oxidation during initial permafrost thaw, likely increasing microbial respiration while suppressing methanogenesis in wet sedge tundra.

     
    more » « less
  5. Abstract

    The thawing of ancient organic carbon stored in arctic permafrost soils, and its oxidation to carbon dioxide (CO2, a greenhouse gas), is predicted to amplify global warming. However, the extent to which organic carbon in thawing permafrost soils will be released as CO2is uncertain. A critical unknown is the extent to which dissolved organic carbon (DOC) from thawing permafrost soils is respired to CO2by microbes upon export of freshly thawed DOC to both dark bottom waters and sunlit surface waters. In this study, we quantified the radiocarbon age and13C composition of CO2produced by microbial respiration of DOC that was leached from permafrost soils and either kept in the dark or exposed to ultraviolet and visible wavelengths of light. We show that permafrost DOC most labile to microbial respiration was as old or older (ages 4,000–11,000 a BP) and more13C‐depleted than the bulk DOC in both dark and light‐exposed treatments, likely indicating respiration of old,13C‐depleted lignin and lipid fractions of the permafrost DOC pool. Light exposure either increased, decreased, or had no effect on the magnitude of microbial respiration of old permafrost DOC relative to respiration in the dark, depending on both the extent of DOC oxidation during exposure to light and the wavelength of light. Together, these findings suggest that photochemical changes affecting the lability of permafrost DOC during sunlight exposure are an important control on the magnitude of microbial respiration of permafrost DOC in arctic surface waters.

     
    more » « less