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  • 1
    Monograph available for loan
    Monograph available for loan
    Potsdam : Alfred-Wegener-Inst. für Polar- und Meeresforschung
    Call number: AWI G3-08-0009
    Type of Medium: Monograph available for loan
    Pages: VIII, 108 S. : Ill., graph. Darst.
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    D.4.
    Language: English
    Note: Bremen, Univ., Diss., 2007
    Branch Library: AWI Library
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  • 2
    Call number: AWI Bio-21-94540
    Description / Table of Contents: 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.
    Type of Medium: Dissertations
    Pages: VI, 243 Seiten , Diagramme, Illustrationen
    Language: English
    Note: Dissertation, Universität Potsdam, 2020
    Location: AWI Reading room
    Branch Library: AWI Library
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  • 3
    Publication Date: 2015-06-26
    Description: Submarine permafrost degradation has been invoked as a cause for recent observations of methane emissions from the seabed to the water column and atmosphere of the East Siberian shelf. Sediment drilled 52 m down from the sea ice in Buor Khaya Bay, central Laptev Sea revealed unfrozen sediment overlying ice-bonded permafrost. Methane concentrations in the overlying unfrozen sediment were low (mean 20 µM) but higher in the underlying ice-bonded submarine permafrost (mean 380 µM). In contrast, sulfate concentrations were substantially higher in the unfrozen sediment (mean 2.5 mM) than in the underlying submarine permafrost (mean 0.1 mM). Using deduced permafrost degradation rates, we calculate potential mean methane efflux from degrading permafrost of 120 mg m−2 yr−1 at this site. However, a drop of methane concentrations from 190 µM to 19 µM and a concomitant increase of methane δ13C from −63‰ to −35‰ directly above the ice-bonded permafrost suggest that methane is effectively oxidized within the overlying unfrozen sediment before it reaches the water column. High rates of methane ebullition into the water column observed elsewhere are thus unlikely to have ice-bonded permafrost as their source.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 4
    Publication Date: 2018-05-27
    Description: Thawing submarine permafrost is a source of methane to the subsurface biosphere. Methane oxidation in submarine permafrost sediments has been proposed, but the responsible microorganisms remain uncharacterized. We analyzed archaeal communities and identified distinct anaerobic methanotrophic assemblages of marine and terrestrial origin (ANME-2a/b, ANME-2d) both in frozen and completely thawed submarine permafrost sediments. Besides archaea potentially involved in anaerobic oxidation of methane (AOM) we found a large diversity of archaea mainly belonging to Bathyarchaeota, Thaumarchaeota, and Euryarchaeota. Methane concentrations and δ13C-methane signatures distinguish horizons of potential AOM coupled either to sulfate reduction in a sulfate-methane transition zone (SMTZ) or to the reduction of other electron acceptors, such as iron, manganese or nitrate. Analysis of functional marker genes (mcrA) and fluorescence in situ hybridization (FISH) corroborate potential activity of AOM communities in submarine permafrost sediments at low temperatures. Modeled potential AOM consumes 72–100% of submarine permafrost methane and up to 1.2 Tg of carbon per year for the total expected area of submarine permafrost. This is comparable with AOM habitats such as cold seeps. We thus propose that AOM is active where submarine permafrost thaws, which should be included in global methane budgets.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 5
    Publication Date: 2018-07-05
    Description: Recent studies on permafrost organic matter (OM) suggest that a portion of previously frozen carbon will enter the active carbon cycle as high latitudes warm. Less is known about the fate of other OM components, including nutrients such as nitrogen (N). The abundance and availability of N following permafrost thaw will regulate the ability of plants to offset carbon losses. Additionally, lateral N losses could alter aquatic food webs. There is growing evidence that some N is lost vertically as N2O, a greenhouse gas 300 times stronger than CO2 over 100 years. Despite broad recognition of its role regulating both carbon and non-carbon aspects of the permafrost climate feedback, estimates of permafrost N remain uncertain. To address this knowledge gap, we quantified N content for different stratigraphic units, including yedoma, Holocene cover deposits, refrozen thermokarst deposits, taberal sediments, and active layer soils. The resulting N estimates from this one permafrost region were similar in magnitude to previous estimates for the entire permafrost zone. We conclude that the permafrost N pool is much larger than currently appreciated and a substantial pool of permafrost N could be mobilized after thaw, with continental-scale consequences for biogeochemical budgets and global-scale consequences.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 6
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    In:  (Diploma thesis), Universität Potsdam, Potsdam, 106 pp DOI hdl:10013/epic.25598.
    Publication Date: 2015-04-09
    Description: Die vorliegende Arbeit untersucht die Verbreitung und Aktivität der Methanoxidierenden (methanotrophen) Mikroflora in arktischen Böden des Lena-Deltas,Sibirien. Dazu wurden die Anpassungspotentiale der Methan oxidierenden Mikroflora anunterschiedliche Standortfaktoren ebenso untersucht, wie ihre Aktivitätspotentiale beiunterschiedlichen Temperaturen und Methankonzentrationen. Mit Hilfe einer Methode derGanzzellhybridisierung, der sogenannten Fluoreszenz-in-situ-Hybridisierung, konnten ausden gewonnenen Ergebnissen Unterschiede in der Populationszusammensetzung imTiefenprofil von Permafroststandorten aufgezeigt und erklärt werden.Die Anpassungspotentiale von Methan oxidierenden Bakterien wurden durch denVergleich eines Permafrost-Auengleys mit einem Tundra-Moorgley der Insel Samoylov imLena-Delta untersucht. Der Permafrost-Auengley stellte aufgrund seinerbodenphysikalischen und bodenchemischen Eigenschaften ein günstigeres Habitat für dieMethan oxidierenden Bakterien dar als der Tundra-Moorgley. Die maximalen Zellzahlenim Permafrost-Auengley waren mehr als dreimal so hoch wie die maximalen Zellzahlen imTundra-Moorgley. Die Methanoxidationsaktivität unter in-situ-Bedingungen betrug imPermafrsot-Auengley etwa das Zehnfache der Methanoxidationsaktivität des Tundra-Moorgleys. Ausschlaggebend für die Unterschiede in den Zellzahlen und den Aktivitätenwar das Bodensubstrat, die damit verbundene Porengrößenverteilung sowie die Qualitätdes DOC.· Der hohe Schluffanteil im Permafrost-Auengley und der damit verbundeneebenfalls hohe Anteil an Mittelporen korrelieren positiv mit den ZellzahlenMethan oxidierender Bakterien.· Das engere und damit günstigere C/N-Verhältnis des Permafrost-Auengleysscheint die Qualität des DOC und damit die Lebensbedingungen der Methanoxidierenden Bakterien positiv zu beeinflussen.· Die Zellzahlen Methan oxidierender Bakterien korrelieren in beiden Standortenpositiv mit dem Methangehalt und damit ebenso mit der Methanbildung imBoden. Die Sauerstoffkonzentration spielt in Bezug auf die Zellzahlen und dieAktivität Methan oxidierender Bakterien eine untergeordnete Rolle.ZUSAMMENFASSUNG IVAufgrund der Aktivitätspotentiale bei unterschiedlichen Temperaturen undMethangehalten konnte eine sehr gute Anpassung der Methan oxidierenden Mikroflora andie Temperatur- und Methankonzentrationsgradienten in arktischen Böden beobachtetwerden:· In den oberen Bodenhorizonten des Permafrost-Auengleys existieren Methanoxidierende Bakterien mit einer hohen Substrataffinität. Ihre maximale Aktivitäterreichen diese Organismen bei Temperaturen 〉 20 °C und einerMethankonzentration zwischen 5000 ppm und 10000 ppm. Bei 10 °C zeigen dieseOrganismen jedoch immerhin noch die Hälfte und bei 4 °C bzw. 0 °C noch einDrittel ihrer maximalen Aktivität.· In den tieferen Bodenhorizonten, dem Übergangsbereich zum Permafrost sowiedem Permafrostbereich selbst, die durch mehr als 10 °C niedrigere in-situTemperaturen und weitaus höhere Methankonzentrationen gekennzeichnet sindals die Oberbodenhorizonte, leben einerseits psychrophile Methan oxidierendeBakterien. Diese erreichen ihre maximale Aktivität bei 4 °C. Zum anderendominieren in diesen Horizonten Methan oxidierende Organismen mit einerniedrigen Substrataffinität. Ihre Km-Werte sind mehr als sechsmal so hoch wie imAi-Horizont (0- 5 cm Bodentiefe).Die Anpassungs- und Aktivitätspotentiale spiegeln sich in der Verbreitung von Typ I undTyp II Methan oxidierenden Bakterien wider und sind offensichtlich auf diephysiologischen Unterschiede beider Gruppen Methan oxidierender Bakterienzurückzuführen. Mit Hilfe der Fluoreszenz-in-situ-Hybridisierung wurde folgendeVerbreitung von Typ I und Typ II Methan oxidierenden Bakterien im Tiefenprofilbeobachtet:· In den oberen Bodenhorizonten existieren temperaturangepasste Typ I Methanoxidierende Bakterien, die entweder der Gruppe der psychrotoleranten Bakterienoder einer Mischflora aus psychrophilen und mesophilen Methan oxidierendenBakterien angehören und durch eine hohe Substrataffinität charakterisiert sind.· In den tieferen Horizonten leben zum einen psychrophile Typ I Methanoxidierende Bakterien, zum anderen Typ II Methan oxidierende Bakterien miteiner geringen Substrataffinität.
    Type: Thesis , NonPeerReviewed
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  • 7
    Publication Date: 2018-08-28
    Description: Thermokarst lakes are widespread features of changing periglacial environments. In this study, we analyze total organic carbon content (TOC), C/N, stable carbon isotopes and methane concentration in pore water from sediments of 18 tundra lakes in West Alaska and 11 boreal lakes in Central Alaska in order to discuss differences in carbon accumulation, sources of organic matter and their role in the carbon cycle. While a wide range of TOC content was measured in West Alaska with highest TOC in lakes that initiated in drained lake basins, some boreal lakes in Central Alaska, like Goldstream Lake show surprisingly low TOC. Similar finding in CH4 concentration suggest that state of permafrost, the age of the lakes and the catchment characteristics have an important influence on sources of organic carbon and, thus, different potential of thermokarst lakes to contribute to the global carbon cycle.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed , info:eu-repo/semantics/conferenceObject
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  • 8
    Publication Date: 2018-01-01
    Description: The methane oxidation potential of active layer profiles of permafrost soils from the Lena Delta, Siberia, was studied with regard to its respond to temperature, and abundance and distribution of type I and type II methanotrophs. Our results indicate vertical shifts within the optimal methane oxidation temperature and within the distribution of type I and type II methanotrophs. In the upper active layer, maximum methane oxidation potentials were detected at 21°C. Deep active layer zones that are constantly exposed to temperatures below 2°C showed a maximum potential to oxidize methane at 4°C. Our results indicate a dominance of psychrophilic methanotrophs close to the permafrost table. Type I methanotrophs dominated throughout the active layer profiles but their number strongly fluctuated with depth. In contrast, type II methanotrophs were constantly abundant through the whole active layer and displaced type I methanotrophs close to the permafrost table. No correlation between in situ temperatures and the distribution of type I and type II methanotrophs was found. However, the distribution of type I and type II methanotrophs correlated significantly with in situ methane concentrations. Beside vertical fluctuations, the abundance of methane oxidizers also fluctuated according to different geomorphic units. Similar methanotroph cell counts were detected in samples of a flood plain and a polygon rim, whereas cell counts in samples of a polygon centre were up to 100 times lower.
    Type: Article , PeerReviewed
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  • 9
    Publication Date: 2014-06-18
    Description: The transition from onshore to offshore permafrost during periods of low relative sea level rise is often the result of coastal retreat. Along the Laptev Sea coastline, ice-rich syngenetic permafrost is particularly susceptible to erosion due to changing climate, and coastal retreat floods about 10 km2 of permafrost each year. Changes to permafrost immediately after flooding provide an opportunity to study the mechanism of submarine permafrost degradation in general. Recent studies have drawn a link between observed methane release on the Laptev Sea shelf and surmised permafrost degradation. We combine direct observations of permafrost and methane to investigate the possibility of methane release from permafrost as a source. Our studies focus on a site in Buor Khaya Bay in the central Laptev Sea, for which coastal retreat rates have been studied. Following geophysical reconnaissance, we drilled a 52 m deep core in the near-shore zone of the eastern shore of Buor Khaya Bay and measured the permafrost temperature in the resulting borehole. Comparison of the submarine permafrost temperature to temperatures on land reveal warming of permafrost by 8 to 10 °C over a period of less than a millennium. During this time, the top of the ice-bearing permafrost (IBPF) degraded from 0 to 28.8 m b.s.l. at the borehole site, a mean degradation rate of almost 3 cm per year. Geoelectric resistivity measurements corroborate this observation and show a decline of the IBPF with increasing distance from shore. Similar to many other Siberian locations, the deeper permafrost at the study site contained less organic carbon by orders of magnitude when compared to the overlying syngenetic ice complex deposits. The same held true for methane concentrations in the frozen permafrost. Our data suggest that these comparatively low concentrations of methane are oxidized in the sediment column upon thawing. Analyses of the sediment and pore water chemistry demonstrate that sea water is probably advected to the IBPF, which contributes to permafrost degradation and provides sulfate for methane oxidation at the top of the thawing permafrost.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 10
    Publication Date: 2016-06-02
    Description: Large amounts of organic carbon are stored in Arctic permafrost environments, and microbial activity can potentially mineralize this carbon into methane, a potent greenhouse gas. In this study, we assessed the methane budget, the bacterial methane oxidation (MOX) and the underlying environmental controls of arctic lake systems, which represent substantial sources of methane. Five lake systems located on Samoylov Island (Lena Delta, Siberia) and the connected river sites were analyzed using radiotracers to estimate the MOX rates, and molecular biology methods to characterize the abundance and the community composition of methane-oxidizing bacteria (MOB). In contrast to the river, the lake systems had high variation in the methane concentrations, the abundance and composition of the MOB communities, and consequently, the MOX rates. The highest methane concentrations and the highest MOX rates were detected in the lake outlets and in a lake complex in a floodplain area. Though, in all aquatic systems we detected both, Type I and II MOB, in lake systems we observed a higher diversity including MOB, typical of the soil environments. The inoculation of soil MOB into the aquatic systems, resulting from permafrost thawing, might be an additional factor controlling the MOB community composition and potentially methanotrophic capacity.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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