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  • 1
    Signatur: AWI Bio-21-94540
    Beschreibung / Inhaltsverzeichnis: This thesis investigates how the permafrost microbiota responds to global warming. In detail, the constraints behind methane production in thawing permafrost were linked to methanogenic activity, abundance and composition. Furthermore, this thesis offers new insights into microbial adaptions to the changing environmental conditions during global warming. This was assesed by investigating the potential ecological relevant functions encoded by plasmid DNA within the permafrost microbiota. Permafrost of both interglacial and glacial origin spanning the Holocene to the late Pleistocene, including Eemian, were studied during long-term thaw incubations. Furthermore, several permafrost cores of different stratigraphy, soil type and vegetation cover were used to target the main constraints behind methane production during short-term thaw simulations. Short- and long-term incubations simulating thaw with and without the addition of substrate were combined with activity measurements, amplicon and metagenomic sequencing of permanently frozen and seasonally thawed active layer. Combined, it allowed to address the following questions. i) What constraints methane production when permafrost thaws and how is this linked to methanogenic activity, abundance and composition? ii) How does the methanogenic community composition change during long-term thawing conditions? iii) Which potential ecological relevant functions are encoded by plasmid DNA in active layer soils? The major outcomes of this thesis are as follows. i) Methane production from permafrost after long-term thaw simulation was found to be constrained mainly by the abundance of methanogens and the archaeal community composition. Deposits formed during periods of warmer temperatures and increased precipitation, (here represented by deposits from the Late Pleistocene of both interstadial and interglacial periods) were found to respond strongest to thawing conditions and to contain an archaeal community dominated by methanogenic archaea (40% and 100% of all detected archaea). Methanogenic population size and carbon density were identified as main predictors for potential methane production in thawing permafrost in short-term incubations when substrate was sufficiently available. ii) Besides determining the methanogenic activity after long-term thaw, the paleoenvironmental conditions were also found to influence the response of the methanogenic community composition. Substantial shifts within methanogenic community structure and a drop in diversity were observed in deposits formed during warmer periods, but not in deposits from stadials, when colder and drier conditions occurred. Overall, a shift towards a dominance of hydrogenotrophic methanogens was observed in all samples, except for the oldest interglacial deposits from the Eemian, which displayed a potential dominance of acetoclastic methanogens. The Eemian, which is discussed to serve as an analogue to current climate conditions, contained highly active methanogenic communities. However, all potential limitation of methane production after permafrost thaw, it means methanogenic community structure, methanogenic population size, and substrate pool might be overcome after permafrost had thawed on the long-term. iii) Enrichments with soil from the seasonally thawed active layer revealed that its plasmid DNA (‘metaplasmidome’) carries stress-response genes. In particular it encoded antibiotic resistance genes, heavy metal resistance genes, cold shock proteins and genes encoding UV-protection. Those are functions that are directly involved in the adaptation of microbial communities to stresses in polar environments. It was further found that metaplasmidomes from the Siberian active layer originate mainly from Gammaproteobacteria. By applying enrichment cultures followed by plasmid DNA extraction it was possible to obtain a higher average contigs length and significantly higher recovery of plasmid sequences than from extracting plasmid sequences from metagenomes. The approach of analyzing ‘metaplasmidomes’ established in this thesis is therefore suitable for studying the ecological role of plasmids in polar environments in general. This thesis emphasizes that including microbial community dynamics have the potential to improve permafrost-carbon projections. Microbially mediated methane release from permafrost environments may significantly impact future climate change. This thesis identified drivers of methanogenic composition, abundance and activity in thawing permafrost landscapes. Finally, this thesis underlines the importance to study how the current warming Arctic affects microbial communities in order to gain more insight into microbial response and adaptation strategies.
    Materialart: Dissertationen
    Seiten: VI, 243 Seiten , Diagramme, Illustrationen
    Sprache: Englisch
    Anmerkung: Dissertation, Universität Potsdam, 2020 , Contents Preface Acknowledgements Contents Summary Zusammenfassung List of abbreviations Chapter 1. Introduction 1.1 Motivation 1.2 Carbon storage in Arctic permafrost environments and the permafrost carbon feedback (PCF) 1.3 Methane cycling microorganisms 1.4 The microbial ecology of permafrost 1.5 Plasmids and their potential role in stress tolerance 1.6 Objectives Chapter 2. Study sites 2.1 Regional settings 2.2 Kurungnakh and Samoylov Island 2.3 Bol'shoy Lyakhovsky Island 2.4 Herschel Island Chapter 3. Manuscripts 3.1 Overview of manuscripts, including contribution of co-authors. 3.2 Manuscript I Methanogenic response to long-term permafrost thaw is determined by paleoenvironment 3.3 Manuscript II Methane production in thawing permafrost is constrained by methanogenic population size and carbon density 3.4 Manuscript III Metaplasmidome-encoded functional potential of permafrost active layer soils Chapter 4. Synthesis 4.1 Introduction 4.2 Constraints behind methane production from thawing permafrost 4.3 The methanogenic community response to long-term permafrost thaw 4.4 The adaptive potential of the permafrost micro biota to cope with stress factors during global warming 4.5 Conclusion Chapter 5. Future research directions and perspectives Chapter 6. References Chapter 7. Appendix 7.1 Supporting information for manuscript I 7.2 Supporting information for manuscript II 7.3 Supporting information for manuscript III 7.4 ESR collaboration, manuscript IV
    Standort: AWI Lesesaal
    Zweigbibliothek: AWI Bibliothek
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2024-03-05
    Beschreibung: Arctic warming causes permafrost thaw and accelerates microbial decomposition of soil organic matter (SOM) to carbon dioxide (CO〈sub〉2〈/sub〉) and methane (CH〈sub〉4〈/sub〉). The determining factors for the ratio between CO〈sub〉2〈/sub〉 and CH〈sub〉4〈/sub〉 formation are still not well understood due to scarce in situ measurements, particularly in remote Arctic regions. We quantified the CO〈sub〉2〈/sub〉:CH〈sub〉4〈/sub〉 ratios of SOM decomposition in wet and dry tundra soils by using CO〈sub〉2〈/sub〉 fluxes from clipped plots and in situ CH〈sub〉4〈/sub〉 fluxes from vegetated plots. At the water‐saturated site, CO〈sub〉2〈/sub〉:CH〈sub〉4〈/sub〉 ratios decreased sharply from 95 at beginning of July to about 10 in August and September with a median of 12.2 (7.70–17.1; 25%–75% quartiles) over the whole vegetation period. When considering CH〈sub〉4〈/sub〉 oxidation, estimated to reduce in situ CH〈sub〉4〈/sub〉 fluxes by 10%–31%, even lower CO〈sub〉2〈/sub〉:CH〈sub〉4〈/sub〉 ratios were calculated (median 10.9–8.41). Active layer depth and soil temperature were the main factors controlling these ratios. Methane production was associated with subsoil (40 cm) temperature, while heterotrophic respiration was related to topsoil (5 cm) temperatures. As expected, CO〈sub〉2〈/sub〉:CH〈sub〉4〈/sub〉 ratios were substantially higher at the dry site (median 373, 292–500, 25%–75% quartiles). Both tundra types lost carbon preferentially in form of CO〈sub〉2〈/sub〉, and CH〈sub〉4〈/sub〉‐C represented only 0.27% of the dry tundra total carbon loss and 6.91% of the wet tundra total carbon loss. The current study demonstrates the dynamic of in situ CO〈sub〉2〈/sub〉:CH〈sub〉4〈/sub〉 ratios from SOM decomposition and will help improve simulations of future CO〈sub〉2〈/sub〉 and CH〈sub〉4〈/sub〉 fluxes from thawing tundra soils.
    Beschreibung: Plain Language Summary: Global warming causes the thaw of the permanently frozen soil in Arctic regions, exposing soil organic matter (SOM) previously frozen to decomposition, increasing the emission of carbon dioxide (CO〈sub〉2〈/sub〉) and methane (CH〈sub〉4〈/sub〉), which are greenhouse gases. It is crucial to quantify the ratio of CO〈sub〉2〈/sub〉 and CH〈sub〉4〈/sub〉 produced because CH〈sub〉4〈/sub〉 has a stronger global warming potential than CO〈sub〉2〈/sub〉. We partitioned SOM decomposition into CO〈sub〉2〈/sub〉 and CH〈sub〉4〈/sub〉 formation (CO〈sub〉2〈/sub〉:CH〈sub〉4〈/sub〉 ratios) in wet and dry tundra soils on Samoylov Island, Northeastern Siberia, and we related these ratios to environmental variables. Deeper active layer, which is the topsoil layer that freezes and thaws annually, and higher subsoil (40 cm) temperature at the interface between the active layer and the permafrost, foster CH4 production and decrease CO〈sub〉2〈/sub〉:CH〈sub〉4〈/sub〉 ratios. Carbon was preferentially lost in form of CO〈sub〉2〈/sub〉 by the soils, but CH〈sub〉4〈/sub〉 had a larger contribution to the carbon loss in the wet tundra. Our study indicates that warming and deepening of the active layer can result in rising CH〈sub〉4〈/sub〉 production. Further understanding of in situ CO〈sub〉2〈/sub〉:CH〈sub〉4〈/sub〉 ratios from SOM decomposition will help improve simulations on future CO〈sub〉2〈/sub〉 and CH〈sub〉4〈/sub〉 fluxes from thawing tundra soils.
    Beschreibung: Key Points: Topsoil (5 cm) warming increases the CO〈sub〉2〈/sub〉:CH〈sub〉4〈/sub〉 production ratio, while warming of subsoil (40 cm) leads to lower CO〈sub〉2〈/sub〉:CH〈sub〉4〈/sub〉 production ratios. The CO〈sub〉2〈/sub〉:CH〈sub〉4〈/sub〉 production ratio is associated with active‐layer depth (ALD) due to a direct effect of ALD on CH〈sub〉4〈/sub〉 production. Carbon was preferentially lost in form of CO〈sub〉2〈/sub〉 at wet and dry sites, but CH〈sub〉4〈/sub〉 had a higher contribution at the wet tundra site.
    Beschreibung: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Beschreibung: Clusters of Excellence CliSAP
    Beschreibung: https://doi.pangaea.de/10.1594/PANGAEA.944841
    Beschreibung: https://doi.pangaea.de/10.1594/PANGAEA.944844
    Schlagwort(e): ddc:631.4 ; thaw depth ; methanogenesis ; heterotrophic respiration ; chamber ; greenhouse gases ; active layer thickening
    Sprache: Englisch
    Materialart: doc-type:article
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Publikationsdatum: 2012-12-09
    Beschreibung: The currently observed Arctic warming will increase permafrost degradation followed by mineralization of formerly frozen organic matter to carbon dioxide (CO 2 ) and methane (CH 4 ). Despite increasing awareness of permafrost carbon vulnerability the potential long-term formation of trace gases from thawing permafrost remains unclear. The objective of the current study is to quantify the potential long-term release of trace gases from permafrost organic matter. Therefore, Holocene and Pleistocene permafrost deposits were sampled in the Lena River Delta, Northeast Siberia. The sampled permafrost contained between 0.6 and 12.4% organic carbon. CO 2 and CH 4 production was measured for 1200 days in aerobic and anaerobic incubations at 4°C. The derived fluxes were used to estimate parameters of a two pool carbon degradation model. Total CO 2 production was similar in Holocene permafrost (1.3 ± 0.8 mg CO 2 -C gdw −1 aerobically, 0.25 ± 0.13 mg CO 2 -C gdw −1 anaerobically) as in 34,000 to 42,000 year old Pleistocene permafrost (1.6 ± 1.2 mg CO 2 -C gdw −1 aerobically, 0.26 ± 0.10 mg CO 2 -C gdw −1 anaerobically). The main predictor for carbon mineralization was the content of organic matter. Anaerobic conditions strongly reduced carbon mineralization since only 25% of aerobically mineralized carbon was released as CO 2 and CH 4 in the absence of oxygen. CH 4 production was low or absent in most of the Pleistocene permafrost and always started after a significant delay. After 1200 days on average 3.1% of initial carbon was mineralized to CO 2 under aerobic conditions while without oxygen 0.55% were released as CO 2 and 0.28% as CH 4 . The calibrated carbon degradation model predicted cumulative CO 2 production over a period of 100 years accounting for 15.1% (aerobic) and 1.8% (anaerobic) of initial organic carbon, which is significantly less than recent estimates. The multi-year time series from the incubation experiments helps to more reliably constrain projections of future trace gas fluxes from thawing permafrost landscapes. © 2012 Blackwell Publishing Ltd
    Print ISSN: 1354-1013
    Digitale ISSN: 1365-2486
    Thema: Biologie , Energietechnik , Geographie
    Publiziert von Wiley
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
  • 5
    Publikationsdatum: 2011-09-01
    Print ISSN: 0038-0717
    Digitale ISSN: 1879-3428
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Publiziert von Elsevier
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Publikationsdatum: 2017-07-01
    Print ISSN: 0038-0717
    Digitale ISSN: 1879-3428
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Publiziert von Elsevier
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Publikationsdatum: 2018-03-20
    Beschreibung: Methane production as key to the greenhouse gas budget of thawing permafrost Methane production as key to the greenhouse gas budget of thawing permafrost, Published online: 19 March 2018; doi:10.1038/s41558-018-0095-z An organic carbon decomposition model, calibrated with laboratory incubations, indicates a greater production rate of CO2-C equivalents from waterlogged (compared to drained) permafrost soils, when the higher global warming potential of methane is factored in.
    Print ISSN: 1758-678X
    Digitale ISSN: 1758-6798
    Thema: Geologie und Paläontologie
    Publiziert von Springer Nature
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Publikationsdatum: 2020-02-07
    Beschreibung: Methane production in thawing permafrost can be substantial, yet often evolves after long lag phases or is even lacking. A central question is to which extent the production of methane after permafrost thaw is determined by the initial methanogenic community. We quantified the production of methane relative to carbon dioxide (CO2) and enumerated methanogenic (mcrA) gene copies in long-term (2–7 years) anoxic incubations at 4 °C using interglacial and glacial permafrost samples of Holocene and Pleistocene, including Eemian, origin. Changes in archaeal community composition were determined by sequencing of the archaeal 16S rRNA gene. Long-term thaw stimulated methanogenesis where methanogens initially dominated the archaeal community. Deposits of interstadial and interglacial (Eemian) origin, formed under higher temperatures and precipitation, displayed the greatest response to thaw. At the end of the incubations, a substantial shift in methanogenic community composition and a relative increase in hydrogenotrophic methanogens had occurred except for Eemian deposits in which a high abundance of potential acetoclastic methanogens were present. This study shows that only anaerobic CO2 production but not methane production correlates significantly with carbon and nitrogen content and that the methanogenic response to permafrost thaw is mainly constrained by the paleoenvironmental conditions during soil formation.
    Print ISSN: 0168-6496
    Digitale ISSN: 1574-6941
    Thema: Biologie
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Publikationsdatum: 2001-03-01
    Print ISSN: 0016-7037
    Digitale ISSN: 1872-9533
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Publiziert von Elsevier
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
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