| 1. |
- Benjamin, Bolduc, et al.
(författare)
-
The IsoGenie database : an interdisciplinary data management solution for ecosystems biology and environmental research
- 2020
-
Ingår i: PeerJ. - : PeerJ. - 2167-8359. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- Modern microbial and ecosystem sciences require diverse interdisciplinary teams that are often challenged in “speaking” to one another due to different languages and data product types. Here we introduce the IsoGenie Database (IsoGenieDB; https://isogenie-db.asc.ohio-state.edu/), a de novo developed data management and exploration platform, as a solution to this challenge of accurately representing and integrating heterogenous environmental and microbial data across ecosystem scales. The IsoGenieDB is a public and private data infrastructure designed to store and query data generated by the IsoGenie Project, a ~10 year DOE-funded project focused on discovering ecosystem climate feedbacks in a thawing permafrost landscape. The IsoGenieDB provides (i) a platform for IsoGenie Project members to explore the project’s interdisciplinary datasets across scales through the inherent relationships among data entities, (ii) a framework to consolidate and harmonize the datasets needed by the team’s modelers, and (iii) a public venue that leverages the same spatially explicit, disciplinarily integrated data structure to share published datasets. The IsoGenieDB is also being expanded to cover the NASA-funded Archaea to Atmosphere (A2A) project, which scales the findings of IsoGenie to a broader suite of Arctic peatlands, via the umbrella A2A Database (A2A-DB). The IsoGenieDB’s expandability and flexible architecture allow it to serve as an example ecosystems database.
|
|
| 2. |
- Ellenbogen, Jared B., et al.
(författare)
-
Methylotrophy in the Mire : direct and indirect routes for methane production in thawing permafrost
- 2024
-
Ingår i: mSystems. - 2379-5077. ; 9:1
-
Tidskriftsartikel (refereegranskat)abstract
- While wetlands are major sources of biogenic methane (CH4), our understanding of resident microbial metabolism is incomplete, which compromises the prediction of CH4 emissions under ongoing climate change. Here, we employed genome-resolved multi-omics to expand our understanding of methanogenesis in the thawing permafrost peatland of Stordalen Mire in Arctic Sweden. In quadrupling the genomic representation of the site’s methanogens and examining their encoded metabolism, we revealed that nearly 20% of the metagenome-assembled genomes (MAGs) encoded the potential for methylotrophic methanogenesis. Further, 27% of the transcriptionally active methanogens expressed methylotrophic genes; for Methanosarcinales and Methanobacteriales MAGs, these data indicated the use of methylated oxygen compounds (e.g., methanol), while for Methanomassiliicoccales, they primarily implicated methyl sulfides and methylamines. In addition to methanogenic methylotrophy, >1,700 bacterial MAGs across 19 phyla encoded anaerobic methylotrophic potential, with expression across 12 phyla. Metabolomic analyses revealed the presence of diverse methylated compounds in the Mire, including some known methylotrophic substrates. Active methylotrophy was observed across all stages of a permafrost thaw gradient in Stordalen, with the most frozen non-methanogenic palsa found to host bacterial methylotrophy and the partially thawed bog and fully thawed fen seen to house both methanogenic and bacterial methylotrophic activities. Methanogenesis across increasing permafrost thaw is thus revised from the sole dominance of hydrogenotrophic production and the appearance of acetoclastic at full thaw to consider the co-occurrence of methylotrophy throughout. Collectively, these findings indicate that methanogenic and bacterial methylotrophy may be an important and previously underappreciated component of carbon cycling and emissions in these rapidly changing wetland habitats.
|
|
| 3. |
- Fofana, Aminata, et al.
(författare)
-
Mapping substrate use across a permafrost thaw gradient
- 2022
-
Ingår i: Soil Biology and Biochemistry. - : Elsevier Ltd. - 0038-0717 .- 1879-3428. ; 175
-
Tidskriftsartikel (refereegranskat)abstract
- Permafrost thaw in northern peatlands is likely to create a positive feedback to climate change, as microbes transform soil carbon (C) into carbon dioxide (CO2) or methane (CH4). While the microbiome's encoded C-processing potential changes with thaw, the impact on substrate utilization and gas emissions is less well characterized. We therefore examined microbial C-cycling dynamics from a partially thawed Sphagnum-dominated bog to a fully thawed sedge-dominated fen in Stordalen Mire (68.35°N, 19.05°E), Sweden. We profiled C substrate utilization diversity and extent by Biolog Ecoplates™, then tested substrate-specific hypotheses by targeted additions (of glucose, the short chain fatty acids (SCFAs) acetate and butyrate, and the organic acids galacturonic acid and p-hydroxybenzoic acid, all at field-relevant concentrations) under anaerobic conditions at 15 °C. In parallel we characterized microbiomes (via 16S rRNA amplicon sequencing and quantitative polymerase chain reaction) and C gas emissions. The fen exhibited a higher substrate use diversity and faster rate of overall substrate utilization than in the bog, based on Biolog Ecoplate™ incubations. Simple glucose additions (akin to a positive control) to peat microcosms fueled fermentation as expected (reflected in enriched fermenter lineages, their inferred metabolisms, and CO2 production), but also showed potential priming of anaerobic phenol degradation in the bog. Addition of SCFAs to bog and fen produced the least change in lineages and in CO2, and modest suppression of CH4 primarily in the fen, attributed to inhibition. Addition of both organic acids greatly increased the CO2:CH4 ratio in the deep peats but had distinct individual gas dynamics and impacts on microbiota. Both organic acids appeared to act as both C source and as a microbial inhibitor, with galacturonic acid also likely playing a role in electron transfer or acceptance. Collectively, these results support the importance of aboveground-belowground linkages - and in particular the role of Sphagnum spp.- in supplying substrates and inhibitors that drive microbiome assembly and C processing in these dynamically changing systems. In addition, they highlight an important temporal dynamic: responses on the short time scale of incubations (which would reflect transition conditions in the field) differ from those evident at the longer scales of habitat transition, in ways consequential to C gas emissions. In the short term, substrate addition response reflected microbiome legacy (e.g., bog communities were slower to process C and better tolerated inhibitors than fen communities) but led to little overall increase in C gas production (and a high skew to CO2). At the longer time scale of bog and fen thaw stages (which are used to represent these systems in models) the concomitant shifts in plants, hydrology and microbiota attenuate microbiome legacy impacts on substrate processing and C gas emissions over time. As habitat transition areas expand under accelerating change, we hypothesize an increased role of microbiome legacy in the landscape overall, leading to a lag in the increase of CH4 emissions expected from fen expansion.
|
|
| 4. |
- Perryman, Clarice R., et al.
(författare)
-
Thaw Transitions and Redox Conditions Drive Methane Oxidation in a Permafrost Peatland
- 2020
-
Ingår i: Journal of Geophysical Research - Biogeosciences. - : American Geophysical Union (AGU). - 2169-8953 .- 2169-8961. ; 125:3
-
Tidskriftsartikel (refereegranskat)abstract
- Permafrost peatlands are a significant source of methane (CH4) emissions to the atmosphere and could emit more CH4 with continued permafrost thaw. Aerobic methane-oxidizing bacteria may attenuate a substantial fraction of CH4 emissions in thawing permafrost peatlands; however, the impact of permafrost thaw on CH4 oxidation is uncertain. We measured potential CH4 oxidation rates (hereafter, CH4 oxidation) and their predictors using laboratory incubations and in situ porewater redox chemistry across a permafrost thaw gradient of eight thaw stages at Stordalen Mire, a permafrost peatland complex in northernmost Sweden. Methane oxidation rates increased across a gradient of permafrost thaw and differed in transitional thaw stages relative to end-member stages. Oxidation was consistently higher in submerged fens than in bogs or palsas across a range of CH4 concentrations. We also observed that CH4 oxidation increased with decreasing in situ redox potential and was highest in sites with lower redox potential (Eh < 10 mV) and high water table. Our results suggest that redox potential can be used as an important predictor of CH4 oxidation, especially in thawed permafrost peatlands. Our results also highlight the importance of considering transitional thaw stages when characterizing landscape-scale CH4 dynamics, because these transitional areas have different rates and controls of CH4 oxidation relative to intact or completely thawed permafrost areas. As permafrost thaw increases the total area of semiwet and wet thaw stages in permafrost peatlands, CH4 oxidation represents an important control on CH4 emissions to the atmosphere.
|
|
| 5. |
- Varner, Ruth K., et al.
(författare)
-
Permafrost thaw driven changes in hydrology and vegetation cover increase trace gas emissions and climate forcing in Stordalen Mire from 1970 to 2014
- 2022
-
Ingår i: Philosophical Transactions. Series A. - : The Royal Society. - 1364-503X .- 1471-2962. ; 380:2215
-
Tidskriftsartikel (refereegranskat)abstract
- Permafrost thaw increases active layer thickness, changes landscape hydrology and influences vegetation species composition. These changes alter belowground microbial and geochemical processes, affecting production, consumption and net emission rates of climate forcing trace gases. Net carbon dioxide (CO2) and methane (CH4) fluxes determine the radiative forcing contribution from these climate-sensitive ecosystems. Permafrost peatlands may be a mosaic of dry frozen hummocks, semi-thawed or perched sphagnum dominated areas, wet permafrost-free sedge dominated sites and open water ponds. We revisited estimates of climate forcing made for 1970 and 2000 for Stordalen Mire in northern Sweden and found the trend of increasing forcing continued into 2014. The Mire continued to transition from dry permafrost to sedge and open water areas, increasing by 100% and 35%, respectively, over the 45-year period, causing the net radiative forcing of Stordalen Mire to shift from negative to positive. This trend is driven by transitioning vegetation community composition, improved estimates of annual CO2 and CH4 exchange and a 22% increase in the IPCC's 100-year global warming potential (GWP_100) value for CH4. These results indicate that discontinuous permafrost ecosystems, while still remaining a net overall sink of C, can become a positive feedback to climate change on decadal timescales.This article is part of a discussion meeting issue ‘Rising methane: is warming feeding warming? (part 2)’.
|
|
| 6. |
- Chang, Kuang-Yu, et al.
(författare)
-
Methane Production Pathway Regulated Proximally by Substrate Availability and Distally by Temperature in a High-Latitude Mire Complex
- 2019
-
Ingår i: Journal of Geophysical Research - Biogeosciences. - 2169-8953 .- 2169-8961. ; 124:10, s. 3057-3074
-
Tidskriftsartikel (refereegranskat)abstract
- Projected 21st century changes in high-latitude climate are expected to have significant impacts on permafrost thaw, which could cause substantial increases in emissions to the atmosphere of carbon dioxide (CO2) and methane (CH4, which has a global warming potential 28 times larger than CO2 over a 100-year horizon). However, predicted CH4 emission rates are very uncertain due to difficulties in modeling complex interactions among hydrological, thermal, biogeochemical, and plant processes. Methanogenic production pathways (i.e., acetoclastic [AM] and hydrogenotrophic [HM]) and the magnitude of CH4 emissions may both change as permafrost thaws, but a mechanistic analysis of controls on such shifts in CH4 dynamics is lacking. In this study, we reproduced observed shifts in CH4 emissions and production pathways with a comprehensive biogeochemical model (ecosys) at the Stordalen Mire in subarctic Sweden. Our results demonstrate that soil temperature changes differently affect AM and HM substrate availability, which regulates magnitudes of AM, HM, and thereby net CH4 emissions. We predict very large landscape-scale, vertical, and temporal variations in the modeled HM fraction, highlighting that measurement strategies for metrics that compare CH4 production pathways could benefit from model informed scale of temporal and spatial variance. Finally, our findings suggest that the warming and wetting trends projected in northern peatlands could enhance peatland AM fraction and CH4 emissions even without further permafrost degradation.
|
|
| 7. |
- Deng, Jia, et al.
(författare)
-
Adding stable carbon isotopes improves model representation of the role of microbial communities in peatland methane cycling
- 2017
-
Ingår i: Journal of Advances in Modeling Earth Systems. - 1942-2466. ; 9:2, s. 1412-1430
-
Tidskriftsartikel (refereegranskat)abstract
- Climate change is expected to have significant and uncertain impacts on methane (CH4) emissions from northern peatlands. Biogeochemical models can extrapolate site-specificCH(4) measurements to larger scales and predict responses of CH4 emissions to environmental changes. However, these models include considerable uncertainties and limitations in representing CH4 production, consumption, and transport processes. To improve predictions of CH4 transformations, we incorporated acetate and stable carbon (C) isotopic dynamics associated with CH4 cycling into a biogeochemistry model, DNDC. By including these new features, DNDC explicitly simulates acetate dynamics and the relative contribution of acetotrophic and hydro-genotrophic methanogenesis (AM and HM) to CH4 production, and predicts the C isotopic signature (delta C-13) in soil C pools and emitted gases. When tested against biogeochemical and microbial community observations at two sites in a zone of thawing permafrost in a subarctic peatland in Sweden, the new formulation substantially improved agreement with CH4 production pathways and delta C-13 in emitted CH4 (delta C-13-CH4), a measure of the integrated effects of microbial production and consumption, and of physical transport. We also investigated the sensitivity of simulated delta C-13-CH4 to C isotopic composition of substrates and, to fractionation factors for CH4 production (alpha(AM) and alpha(HM)), CH4 oxidation (alpha(MO)), and plant-mediated CH4 transport (alpha(TP)). The sensitivity analysis indicated that the delta C-13-CH4 is highly sensitive to the factors associated with microbial metabolism (alpha(AM), alpha(HM), and alpha(MO)). The model framework simulating stable C isotopic dynamics provides a robust basis for better constraining and testing microbial mechanisms in predicting CH4 cycling in peatlands.
|
|
| 8. |
- Fisher, Rebecca E., et al.
(författare)
-
Measurement of the C-13 isotopic signature of methane emissions from northern European wetlands
- 2017
-
Ingår i: Global Biogeochemical Cycles. - 0886-6236 .- 1944-9224. ; 31:3, s. 605-623
-
Tidskriftsartikel (refereegranskat)abstract
- Isotopic data provide powerful constraints on regional and global methane emissions and their source profiles. However, inverse modeling of spatially resolved methane flux is currently constrained by a lack of information on the variability of source isotopic signatures. In this study, isotopic signatures of emissions in the Fennoscandian Arctic have been determined in chambers over wetland, in the air 0.3 to 3m above the wetland surface and by aircraft sampling from 100m above wetlands up to the stratosphere. Overall, the methane flux to atmosphere has a coherent delta C-13 isotopic signature of -71 +/- 1%, measured in situ on the ground in wetlands. This is in close agreement with delta C-13 isotopic signatures of local and regional methane increments measured by aircraft campaigns flying through air masses containing elevated methane mole fractions. In contrast, results from wetlands in Canadian boreal forest farther south gave isotopic signatures of -67 +/- 1%. Wetland emissions dominate the local methane source measured over the European Arctic in summer. Chamber measurements demonstrate a highly variable methane flux and isotopic signature, but the results from air sampling within wetland areas show that emissions mix rapidly immediately above the wetland surface and methane emissions reaching the wider atmosphere do indeed have strongly coherent C isotope signatures. The study suggests that for boreal wetlands (>60 degrees N) global and regional modeling can use an isotopic signature of -71 parts per thousand to apportion sources more accurately, but there is much need for further measurements over other wetlands regions to verify this.
|
|
| 9. |
- Hodgkins, Suzanne B., et al.
(författare)
-
Changes in peat chemistry associated with permafrost thaw increase greenhouse gas production
- 2014
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 111:16, s. 5819-5824
-
Tidskriftsartikel (refereegranskat)abstract
- Carbon release due to permafrost thaw represents a potentially major positive climate change feedback. The magnitude of carbon loss and the proportion lost as methane (CH4) vs. carbon dioxide (CO2) depend on factors including temperature, mobilization of previously frozen carbon, hydrology, and changes in organic matter chemistry associated with environmental responses to thaw. While the first three of these effects are relatively well understood, the effect of organic matter chemistry remains largely un-studied. To address this gap, we examined the biogeochemistry of peat and dissolved organic matter (DOM) along a similar to 40-y permafrost thaw progression from recently- to fully thawed sites in Stordalen Mire (68.35 degrees N, 19.05 degrees E), a thawing peat plateau in northern Sweden. Thaw-induced subsidence and the resulting inundation along this progression led to succession in vegetation types accompanied by an evolution in organic matter chemistry. Peat C/N ratios decreased whereas humification rates increased, and DOM shifted toward lower molecular weight compounds with lower aromaticity, lower organic oxygen content, and more abundant microbially produced compounds. Corresponding changes in decomposition along this gradient included increasing CH4 and CO2 production potentials, higher relative CH4/CO2 ratios, and a shift in CH4 production pathway from CO2 reduction to acetate cleavage. These results imply that subsidence and thermokarst-associated increases in organic matter lability cause shifts in biogeochemical processes toward faster decomposition with an increasing proportion of carbon released as CH4. This impact of permafrost thaw on organic matter chemistry could intensify the predicted climate feedbacks of increasing temperatures, permafrost carbon mobilization, and hydrologic changes.
|
|
| 10. |
- Hodgkins, Suzanne B., et al.
(författare)
-
Elemental composition and optical properties reveal changes in dissolved organic matter along a permafrost thaw chronosequence in a subarctic peatland
- 2016
-
Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 187, s. 123-140
-
Tidskriftsartikel (refereegranskat)abstract
- The fate of carbon stored in permafrost-zone peatlands represents a significant uncertainty in global climate modeling. Given that the breakdown of dissolved organic matter (DOM) is often a major pathway for decomposition in peatlands, knowledge of DOM reactivity under different permafrost regimes is critical for determining future climate feedbacks. To explore the effects of permafrost thaw and resultant plant succession on DOM reactivity, we used a combination of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), UV/Vis absorbance, and excitation-emission matrix spectroscopy (EEMS) to examine the DOM elemental composition and optical properties of 27 pore water samples gathered from various sites along a permafrost thaw sequence in Stordalen Mire, a thawing subarctic peatland in northern Sweden. The presence of dense Sphagnum moss, a feature that is dominant in the intermediate thaw stages, appeared to be the main driver of variation in DOM elemental composition and optical properties at Stordalen. Specifically, DOM from sites with Sphagnum had greater aromaticity, higher average molecular weights, and greater O/C, consistent with a higher abundance of phenolic compounds that likely inhibit decomposition. These compounds are released by Sphagnum and may accumulate due to inhibition of phenol oxidase activity by the acidic pH at these sites. In contrast, sites without Sphagnum, specifically fully-thawed rich fens, had more saturated, more reduced compounds, which were high in N and S. Optical properties at rich fens indicated the presence of microbially-derived DOM, consistent with the higher decomposition rates previously measured at these sites. These results indicate that Sphagnum acts as an inhibitor of rapid decomposition and CH4 release in thawing subarctic peatlands, consistent with lower rates of CO2 and CH4 production previously observed at these sites. However, this inhibitory effect may disappear if Sphagnum-dominated bogs transition to more waterlogged rich fens that contain very little to no living Sphagnum. Release of this inhibition allows for higher levels of microbial activity and potentially greater CH4 release, as has been observed in these fen sites.
|
|
| 11. |
- Hodgkins, Suzanne B., et al.
(författare)
-
Soil incubations reproduce field methane dynamics in a subarctic wetland
- 2015
-
Ingår i: Biogeochemistry. - : Springer Science and Business Media LLC. - 0168-2563 .- 1573-515X. ; 126:1-2, s. 241-249
-
Tidskriftsartikel (refereegranskat)abstract
- A major challenge in peatland carbon cycle modeling is the estimation of subsurface methane (CH4) and carbon dioxide (CO2) production and consumption rates and pathways. The most common methods for modeling these processes are soil incubations and stable isotope modeling, both of which may involve departures from field conditions. To explore the impacts of these departures, we measured CH4/CO2 concentration ratios and C-13 fractionation factors (alpha(C), indicating CH4 production pathways) in field pore water from a thawing subarctic peatland, and compared these values to those observed in incubations of corresponding peat samples. Incubation CH4/CO2 production ratios were significantly and positively correlated with observed field CH4/CO2 concentration ratios, though observed field ratios were similar to 20 % of those in incubations due to CH4's lower solubility in pore water. After correcting the field ratios for CH4 loss with an isotope mass balance model, the incubation CH4/CO2 ratios and alpha(C) were both significantly positively correlated with field ratios and alpha(C) (respectively), both with slopes indistinguishable from 1. Although CH4/CO2 ratios and alpha(C) were slightly higher in the incubations, these shifts were consistent along the thaw progression, indicating that ex situ incubations can replicate trends in in situ CH4 production.
|
|
| 12. |
- Mondav, Rhiannon, 1972-, et al.
(författare)
-
Discovery of a novel methanogen prevalent in thawing permafrost
- 2014
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 5
-
Tidskriftsartikel (refereegranskat)abstract
- Thawing permafrost promotes microbial degradation of cryo-sequestered and new carbon leading to the biogenic production of methane, creating a positive feedback to climate change. Here we determine microbial community composition along a permafrost thaw gradient in northern Sweden. Partially thawed sites were frequently dominated by a single archaeal phylotype, Candidatus ‘Methanoflorens stordalenmirensis’ gen. nov. sp. nov., belonging to the uncultivated lineage ‘Rice Cluster II’ (Candidatus ‘Methanoflorentaceae’ fam. nov.). Metagenomic sequencing led to the recovery of its near-complete genome, revealing the genes necessary for hydrogenotrophic methanogenesis. These genes are highly expressed and methane carbon isotope data are consistent with hydrogenotrophic production of methane in the partially thawed site. In addition to permafrost wetlands, ‘Methanoflorentaceae’ are widespread in high methane-flux habitats suggesting that this lineage is both prevalent and a major contributor to global methane production. In thawing permafrost, Candidatus ‘M. stordalenmirensis’ appears to be a key mediator of methane-based positive feedback to climate warming.
|
|
| 13. |
- Mondav, Rhiannon, 1972-, et al.
(författare)
-
Microbial network, phylogenetic diversity and community membership in the active layer across a permafrost thaw gradient
- 2017
-
Ingår i: Environmental Microbiology. - : Wiley. - 1462-2912 .- 1462-2920. ; 19:8, s. 3201-3218
-
Tidskriftsartikel (refereegranskat)abstract
- Biogenic production and release of methane (CH4 ) from thawing permafrost has the potential to be a strong source of radiative forcing. We investigated changes in the active layer microbial community of three sites representative of distinct permafrost thaw stages at a palsa mire in northern Sweden. The palsa site (intact permafrost and low radiative forcing signature) had a phylogenetically clustered community dominated by Acidobacteria and Proteobacteria. The bog (thawing permafrost and low radiative forcing signature) had lower alpha diversity and midrange phylogenetic clustering, characteristic of ecosystem disturbance affecting habitat filtering. Hydrogenotrophic methanogens and Acidobacteria dominated the bog shifting from palsa-like to fen-like at the waterline. The fen (no underlying permafrost, high radiative forcing signature) had the highest alpha, beta and phylogenetic diversity, was dominated by Proteobacteria and Euryarchaeota and was significantly enriched in methanogens. The Mire microbial network was modular with module cores consisting of clusters of Acidobacteria, Euryarchaeota or Xanthomonodales. Loss of underlying permafrost with associated hydrological shifts correlated to changes in microbial composition, alpha, beta and phylogenetic diversity associated with a higher radiative forcing signature. These results support the complex role of microbial interactions in mediating carbon budget changes and climate feedback in response to climate forcing.
|
|
| 14. |
- Singleton, Caitlin M., et al.
(författare)
-
Methanotrophy across a natural permafrost thaw environment
- 2018
-
Ingår i: The ISME Journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370. ; 12:10, s. 2544-2558
-
Tidskriftsartikel (refereegranskat)abstract
- The fate of carbon sequestered in permafrost is a key concern for future global warming as this large carbon stock is rapidly becoming a net methane source due to widespread thaw. Methane release from permafrost is moderated by methanotrophs, which oxidise 20-60% of this methane before emission to the atmosphere. Despite the importance of methanotrophs to carbon cycling, these microorganisms are under-characterised and have not been studied across a natural permafrost thaw gradient. Here, we examine methanotroph communities from the active layer of a permafrost thaw gradient in Stordalen Mire (Abisko, Sweden) spanning three years, analysing 188 metagenomes and 24 metatranscriptomes paired with in situ biogeochemical data. Methanotroph community composition and activity varied significantly as thaw progressed from intact permafrost palsa, to partially thawed bog and fully thawed fen. Thirteen methanotroph population genomes were recovered, including two novel genomes belonging to the uncultivated upland soil cluster alpha (USCa) group and a novel potentially methanotrophic Hyphomicrobiaceae. Combined analysis of porewater delta C-13-CH 4 isotopes and methanotroph abundances showed methane oxidation was greatest below the oxic-anoxic interface in the bog. These results detail the direct effect of thaw on autochthonous methanotroph communities, and their consequent changes in population structure, activity and methane moderation potential.
|
|
| 15. |
- Wik, Martin, et al.
(författare)
-
Large isotopic variations and similarities in methane ebullition from northern lakes
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Lakes are abundant in northern, high latitude landscapes and considered a substantial source of atmospheric methane (CH4). In spite of this, little is known about how CH4 release mechanisms relate to underlying organic sources and biogenic production pathways in different types of water bodies. Here, we present a substantial, multiyear dataset of the stable isotopes of CH4 ebullition from three interconnected, subarctic post-glacial lakes. The δ13C-CH4 and δD-CH4 vary from -78.4 to -53.1‰ and from -369.8 to -218.8‰, respectively. Overall, these observations suggest predominantly acetoclastic methanogenesis in the shallow zones, possibly fueled by in-situ plant production, and a shift towards a mix with hydrogenotrophy at depth. The bubbles’ δ13C-CH4 are similar to most of those reported from other northern natural systems, but we found differences in δD-CH4, possibly due to evaporation-driven fractionation over summer. Stable isotopes provide valuable information about underlying organic sources and production pathways, however, due to large overlaps they may not be effective in reducing uncertainties in emissions potentials among different water body types, and in general between lakes and wetlands.
|
|
| 16. |
- Wik, Martin, et al.
(författare)
-
Stable Methane Isotopologues From Northern Lakes Suggest That Ebullition Is Dominated by Sub-Lake Scale Processes
- 2020
-
Ingår i: Journal of Geophysical Research - Biogeosciences. - 2169-8953 .- 2169-8961. ; 125:10
-
Tidskriftsartikel (refereegranskat)abstract
- Stable isotopes have emerged as popular study targets when investigating emission of methane (CH4) from lakes. Yet little is known on how isotopic patterns conform to variations in emission magnitudes—a highly relevant question. Here, we present a large multiyear data set on stable isotopes of CH4 ebullition (bubbling) from three small adjacent subarctic lakes. The δ13C‐CH4 and δD‐CH4 range from −78.4‰ to −53.1‰ and from −369.8‰ to −218.8‰, respectively, and vary greatly among the lakes. The signatures suggest dominant hydrogenotrophic methanogenesis, particularly in the deep zones, but there are also signals of seemingly acetoclastic production in some high fluxing shallow areas, possibly fueled by in situ vegetation, but in‐sediment anaerobic CH4 oxidation cannot be ruled out as an alternative cause. The observed patterns, however, are not consistent across the lakes. Neither do they correspond to the spatiotemporal variations in the measured bubble CH4 fluxes. Patterns of acetoclastic and hydrogenotrophic production plus oxidation demonstrate that gains and losses of sediment CH4 are dominated by sub‐lake scale processes. The δD‐CH4 in the bubbles was significantly different depending on measurement month, likely due to evaporation effects. On a larger scale, our isotopic data, combined with those from other lakes, show a significant difference in bubble δD‐CH4 between postglacial and thermokarst lakes, an important result for emission inventories. Although this characteristic theoretically assists in source partitioning studies, most hypothetical future shifts in δD‐CH4 due to high‐latitude lake area or production pathway are too small to lead to atmospheric changes detectable with current technology.
|
|
| 17. |
- Wilson, Rachel M., et al.
(författare)
-
Plant organic matter inputs exert a strong control on soil organic matter decomposition in a thawing permafrost peatland
- 2022
-
Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 820
-
Tidskriftsartikel (refereegranskat)abstract
- Peatlands are climate critical carbon (C) reservoirs that could become a C source under continued warming. A strong relationship between plant tissue chemistry and the soil organic matter (SOM) that fuels C gas emissions is inferred, but rarely examined at the molecular level. Here we compared Fourier transform infrared (FT-IR) spectroscopy measurements of solid phase functionalities in plants and SOM to ultra-high-resolution mass spectrometric analyses of plant and SOM water extracts across a palsa-bog-fen thaw and moisture gradient in an Arctic peatland. From these analyses we calculated the C oxidation state (NOSC), a measure which can be used to assess organic matter quality. Palsa plant extracts had the highest NOSC, indicating high quality, whereas extracts of Sphagnum, which dominated the bog, had the lowest NOSC. The percentage of plant compounds that are less bioavailable and accumulate in the peat, increases from palsa (25%) to fen (41%) to bog (47%), reflecting the pattern of percent Sphagnum cover. The pattern of NOSC in the plant extracts was consistent with the high number of consumed compounds in the palsa and low number of consumed compounds in the bog. However, in the FT-IR analysis of the solid phase bog peat, carbohydrate content was high implying high quality SOM. We explain this discrepancy as the result of low solubilization of bog SOM facilitated by the low pH in the bog which makes the solid phase carbohydrates less available to microbial decomposition. Plant-associated condensed aromatics, tannins, and lignin-like compounds declined in the unsaturated palsa peat indicating decomposition, but lignin-like compounds accumulated in the bog and fen peat where decomposition was presumably inhibited by the anaerobic conditions. A molecular-level comparison of the aboveground C sources and peat SOM demonstrates that climate-associated vegetation shifts in peatlands are important controls on the mechanisms underlying changing C gas emissions.
|
|
| 18. |
- Woodcroft, Ben J., et al.
(författare)
-
Genome-centric view of carbon processing in thawing permafrost
- 2018
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 560:7716, s. 49-
-
Tidskriftsartikel (refereegranskat)abstract
- As global temperatures rise, large amounts of carbon sequestered in permafrost are becoming available for microbial degradation. Accurate prediction of carbon gas emissions from thawing permafrost is limited by our understanding of these microbial communities. Here we use metagenomic sequencing of 214 samples from a permafrost thaw gradient to recover 1,529 metagenome-assembled genomes, including many from phyla with poor genomic representation. These genomes reflect the diversity of this complex ecosystem, with genus-level representatives for more than sixty per cent of the community. Meta-omic analysis revealed key populations involved in the degradation of organic matter, including bacteria whose genomes encode a previously undescribed fungal pathway for xylose degradation. Microbial and geochemical data highlight lineages that correlate with the production of greenhouse gases and indicate novel syntrophic relationships. Our findings link changing biogeochemistry to specific microbial lineages involved in carbon processing, and provide key information for predicting the effects of climate change on permafrost systems.
|
|
