ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 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.
    Classification:
    Meteorology and Climatology
    Language: English
    Note: Bremen, Univ., Diss., 2007
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Call number: AWI Bio-23-95302
    Description / Table of Contents: Climate change of anthropogenic origin is affecting Earth’s biodiversity and therefore ecosystems and their services. High latitude ecosystems are even more impacted than the rest of Northern Hemisphere because of the amplified polar warming. Still, it is challenging to predict the dynamics of high latitude ecosystems because of complex interaction between abiotic and biotic components. As the past is the key to the future, the interpretation of past ecological changes to better understand ongoing processes is possible. In the Quaternary, the Pleistocene experienced several glacial and interglacial stages that affected past ecosystems. During the last Glacial, the Pleistocene steppe-tundra was covering most of unglaciated northern hemisphere and disappeared in parallel to the megafauna’s extinction at the transition to the Holocene (~11,700 years ago). The origin of the steppe-tundra decline is not well understood and knowledge on the mechanisms, which caused shifts in past communities and ecosystems, is of high priority as they are likely comparable to those affecting modern ecosystems. Lake or permafrost core sediments can be retrieved to investigate past biodiversity at transitions between glacial and interglacial stages. Siberia and Beringia were the origin of dispersal of the steppe-tundra, which make investigation this area of high priority. Until recently, macrofossils and pollen were the most common approaches. They are designed to reconstruct past composition changes but have limit and biases. Since the end of the 20th century, sedimentary ancient DNA (sedaDNA) can also be investigated. My main objectives were, by using sedaDNA approaches to provide scientific evidence of compositional and diversity changes in the Northern Hemisphere ecosystems at the transition between Quaternary glacial and interglacial stages. In this thesis, I provide snapshots of entire ancient ecosystems and describe compositional changes between Quaternary glacial and interglacial stages, and confirm the vegetation composition and the spatial and temporal boundaries of the Pleistocene steppe-tundra. I identify a general loss of plant diversity with extinction events happening in parallel of megafauna’ extinction. I demonstrate how loss of biotic resilience led to the collapse of a previously well-established system and discuss my results in regards to the ongoing climate change. With further work to constrain biases and limits, sedaDNA can be used in parallel or even replace the more established macrofossils and pollen approaches as my results support the robustness and potential of sedaDNA to answer new palaeoecological questions such as plant diversity changes, loss and provide snapshots of entire ancient biota.
    Description / Table of Contents: Der vom Menschen verursachte Klimawandel wirkt sich auf die biologische Vielfalt der Erde und damit auf die Ökosysteme und ihre Leistungen aus. Die Ökosysteme in den hohen Breitengraden sind aufgrund der verstärkten Erwärmung an den Polen noch stärker betroffen als der Rest der nördlichen Hemisphäre. Dennoch ist es schwierig, die Dynamik von Ökosystemen in den hohen Breitengraden vorherzusagen, da die Wechselwirkungen zwischen abiotischen und biotischen Komponenten sehr komplex sind. Da die Vergangenheit der Schlüssel zur Zukunft ist, ist die Interpretation vergangener ökologischer Veränderungen möglich, um laufende Prozesse besser zu verstehen. Im Quartär durchlief das Pleistozän mehrere glaziale und interglaziale Phasen, welche die Ökosysteme der Vergangenheit beeinflussten. Während des letzten Glazials bedeckte die pleistozäne Steppentundra den größten Teil der unvergletscherten nördlichen Hemisphäre und verschwand parallel zum Aussterben der Megafauna am Übergang zum Holozän (vor etwa 11 700 Jahren). Der Ursprung des Rückgangs der Steppentundra ist nicht gut erforscht, und die Kenntnis über die Mechanismen, die zu den Veränderungen in den vergangenen Lebensgemeinschaften und Ökosystemen geführt haben, ist von hoher Priorität, da sie wahrscheinlich mit denen vergleichbar sind, die sich auf moderne Ökosysteme auswirken. Durch die Entnahme von See- oder Permafrostkernsedimenten kann die vergangene Artenvielfalt an den Übergängen zwischen Eis- und Zwischeneiszeiten untersucht werden. Sibirien und Beringia waren der Ursprung der Ausbreitung der Steppentundra, weshalb die Untersuchung dieses Gebiets hohe Priorität hat. Bis vor kurzem waren Makrofossilien und Pollen die gängigsten Methoden. Sie dienen der Rekonstruktion vergangener Veränderungen in der Zusammensetzung der Bevölkerung, haben aber ihre Grenzen und Schwächen. Seit Ende des 20. Jahrhunderts kann auch sedimentäre alte DNA (sedaDNA) untersucht werden. Mein Hauptziel war es, durch den Einsatz von sedaDNA-Ansätzen wissenschaftliche Beweise für Veränderungen in der Zusammensetzung und Vielfalt der Ökosysteme der nördlichen Hemisphäre am Übergang zwischen den quartären Eiszeiten und Zwischeneiszeiten zu liefern. In dieser Arbeit liefere ich Momentaufnahmen ganzer alter Ökosysteme und beschreibe die Veränderungen in der Zusammensetzung zwischen Quartärglazialen und Interglazialen und bestätige die Vegetationszusammensetzung sowie die räumlichen und zeitlichen Grenzen der pleistozänen Steppentundra. Ich stelle einen allgemeinen Verlust der Pflanzenvielfalt fest, wobei das Aussterben der Pflanzen parallel zum Aussterben der Megafauna verlief. Ich zeige auf, wie der Verlust der biotischen Widerstandsfähigkeit zum Zusammenbruch eines zuvor gut etablierten Systems führte, und diskutiere meine Ergebnisse im Hinblick auf den laufenden Klimawandel. Mit weiteren Arbeiten zur Eingrenzung von Verzerrungen und Grenzen kann sedaDNA parallel zu den etablierteren Makrofossilien- und Pollenansätzen verwendet werden oder diese sogar ersetzen, da meine Ergebnisse die Robustheit und das Potenzial von sedaDNA zur Beantwortung neuer paläoökologischer Fragen wie Veränderungen der Pflanzenvielfalt und -verluste belegen und Momentaufnahmen ganzer alter Biota liefern.
    Type of Medium: Dissertations
    Pages: vi, 217 Seiten , Illustrationen, Diagramme, Karten
    Language: English
    Note: Dissertation, Universität Potsdam, 2023 , TABLE OF CONTENTS Acknowledgements Summary Zusammenfassung 1 General introduction 1.1 A changing world 1.1.1 Global changes of anthropogenic origin 1.1.2 Amplified crisis in the high latitudes 1.2 The past is the key to the future 1.2.1 The Quaternary glacial and interglacial stages 1.2.2 The Beringia study case 1.3 Investigating past biodiversity 1.3.1 Traditional tools 1.3.2 Newest sedaDNA proxies 1.4 Motivation and aims of the thesis 1.5 Structure of the thesis 1.6 Author’s contributions 2 Manuscript I 2.1 Abstract 2.2 Introduction 2.3 Materials and Methods 2.3.1 Geographical settings 2.3.2 Fieldwork and subsampling 2.3.3 Core splicing and dating 2.3.4 Sediment-geochemical analyses 2.3.5 Pollen analysis 2.3.6 Molecular genetic preparation 2.3.7 Processing of sedaDNA data 2.3.8 Statistical analysis and visualization 2.4 Results 2.4.1 Age model 2.4.2 Sediment-geochemical core composition 2.4.3 Pollen stratigraphy 2.4.4 sedaDNA composition 2.4.5 Comparison between pollen and sedaDNA 2.4.6 Taxa richness investigation 2.5 Discussion 2.5.1 Proxy validation 2.5.2 Vegetation compositional changes in response to climate inferred from pollen and sedaDNA records 2.5.3 The steppe-tundra of the Late Pleistocene 2.5.4 The disrupted Pleistocene-Holocene transition 2.5.5 The boreal forest of the Holocene 2.5.6 Changes in vegetation richness through the Pleistocene/Holocene transition inferred from the sedaDNA record 2.6 Conclusion Data availability statement Funding References 3 Manuscript II 3.1 Abstract 3.2 Introduction 3.3 Material and Method 3.3.1 Site description and timeframe 3.3.2 Sampling, DNA extraction and PCR 3.3.3 Filtering and cleaning dataset 3.3.4 Identification of taxa – species signal 3.3.5 Resampling 3.3.6 Assessment of the species pool stability 3.3.7 Quantification of extinct and extirpated taxa 3.3.8 Characterisation of species and candidate species 3.4 Results 3.4.1 Changes in the composition and species pool at the Pleistocene - Holocene transition 3.4.2 Decrease in the regional plant species richness between the Pleistocene and the Holocene 3.4.3 Identification of loss taxa events 3.4.4 Characterisation of lost taxa 3.5 Discussion 3.5.1 Biotic and abiotic changes in the ecosystem - a cocktail for extinction 3.5.2 Identification and quantification of potential plant taxa loss 3.5.3 Characterisation of potential taxa loss 3.5.4 Limits of the method 3.5.5 Conclusions and perspectives Funding References 4 Manuscript III 4.1 Abstract 4.2 Introduction 4.3 Material & Methods 4.3.1 Fieldwork and subsampling 4.3.2 Chronology 4.3.3 Pollen analysis 4.3.4 Isolation of sedimentary ancient DNA 4.3.5 Metabarcoding approach 4.3.6 Shotgun approach 4.3.7 Bioinformatic processing 4.4 Results 4.4.1 General results of the three approaches: pollen, metabarcoding and shotgun sequencing 4.4.2 Plants (Viridiplantae) 4.4.3 Fungi 4.4.4 Mammals (Mammalia) 4.4.5 Birds (Aves) 4.4.6 Insects (Insecta) 4.4.7 Prokaryotes (Bacteria, Archaea) and Viruses 4.5 Discussion 4.5.1 Interglacial communities 4.5.2 Glacial communities 4.5.3 Potential and limitations of the sedaDNA shotgun approach applied to ancient permafrost sediments 4.6 Conclusions Data availability statement Funding References 5 Synthesis 5.1 Ecological changes between glacial and interglacial stages 5.1.1 Changes in the compositional structure 5.1.2 Loss of plant diversity 5.1.3 Potential drivers of change 5.2 High potential of sedaDNA for past biodiversity reconstruction 5.3 Conclusions and future perspectives Bibliography Appendices Appendix 1: Supplementary material for Manuscript I Appendix 2: Supplementary material for Manuscript II Appendix 3: Supplementary material for Manuscript III Appendix 4: Manuscript IV Eidesstattliche Erklärung
    Location: AWI Reading room
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Call number: AWI G3-23-95073
    Description / Table of Contents: The Arctic is changing rapidly and permafrost is thawing. Especially ice-rich permafrost, such as the late Pleistocene Yedoma, is vulnerable to rapid and deep thaw processes such as surface subsidence after the melting of ground ice. Due to permafrost thaw, the permafrost carbon pool is becoming increasingly accessible to microbes, leading to increased greenhouse gas emissions, which enhances the climate warming. The assessment of the molecular structure and biodegradability of permafrost organic matter (OM) is highly needed. My research revolves around the question “how does permafrost thaw affect its OM storage?” More specifically, I assessed (1) how molecular biomarkers can be applied to characterize permafrost OM, (2) greenhouse gas production rates from thawing permafrost, and (3) the quality of OM of frozen and (previously) thawed sediments. I studied deep (max. 55 m) Yedoma and thawed Yedoma permafrost sediments from Yakutia (Sakha Republic). I analyzed sediment cores taken below thermokarst lakes on the Bykovsky Peninsula (southeast of the Lena Delta) and in the Yukechi Alas (Central Yakutia), and headwall samples from the permafrost cliff Sobo-Sise (Lena Delta) and the retrogressive thaw slump Batagay (Yana Uplands). I measured biomarker concentrations of all sediment samples. Furthermore, I carried out incubation experiments to quantify greenhouse gas production in thawing permafrost. I showed that the biomarker proxies are useful to assess the source of the OM and to distinguish between OM derived from terrestrial higher plants, aquatic plants and microbial activity. In addition, I showed that some proxies help to assess the degree of degradation of permafrost OM, especially when combined with sedimentological data in a multi-proxy approach. The OM of Yedoma is generally better preserved than that of thawed Yedoma sediments. The greenhouse gas production was highest in the permafrost sediments that thawed for the first time, meaning that the frozen Yedoma sediments contained most labile OM. Furthermore, I showed that the methanogenic communities had established in the recently thawed sediments, but not yet in the still-frozen sediments. My research provided the first molecular biomarker distributions and organic carbon turnover data as well as insights in the state and processes in deep frozen and thawed Yedoma sediments. These findings show the relevance of studying OM in deep permafrost sediments.
    Type of Medium: Dissertations
    Pages: xxiii, 178 Seiten , Illustrationen, Diagramme, Karten
    Language: English
    Note: Table of Contents Abstract Zusammenfassung Samenvatting Acknowledgements List of Figures List of Tables List of Abbreviations 1 Introduction 1.1 Motivation 1.2 Aims and research questions 1.3 Scientific background 1.3.1 The Arctic in a changing climate 1.3.2 Northern Hemisphere permafrost region 1.3.3 Permafrost degradation 1.3.3.1 Thermokarst development 1.3.3.2 Retrogressive thaw slumps 1.3.4 Organic matter in permafrost deposits 1.4 Material and methods 1.4.1 Study sites 1.4.2 Main laboratory methods 1.5 Thesis structure 1.6 Overview of publications 1.6.1 Publication “n-Alkane Characteristics of Thawed Permafrost Deposits Below a Thermokarst Lake on Bykovsky Peninsula, Northeastern Siberia” 1.6.2 Publication “Greenhouse gas production and lipid biomarker distribution in Yedoma and Alas thermokarst lake sediments in Eastern Siberia” 1.6.3 Publication “Organic matter characteristics of a rapidly eroding permafrost cliff in NE Siberia (Lena Delta, Laptev Sea region)” 1.6.4 Publication “Molecular biomarkers in Batagay megaslump permafrost deposits reveal clear differences in organic matter preservation between glacial and interglacial periods” 1.6.5 Contributions to complementary research 2 Bykovsky Peninsula 2.1 Abstract 2.2 Introduction 2.3 Study area 2.4 Material and methods 2.4.1 Field work 2.4.2 Laboratory analyses 2.4.2.1 Biomarker analysis 2.4.2.2 Biomarker indices 2.5 Results 2.5.1 Bulk sediment 2.5.1.1 Long core PG2412 2.5.1.2 Short core PG2420 2.5.2 Hydrochemistry 2.5.3 n-Alkane distributions 2.6 Discussion 2.6.1 Depositional history at the study site 2.6.1.1 Unit I - Early Weichselian fluvial sedimentation 2.6.1.2 Unit II – Yedoma deposition in wetland landscapes dominated by low-centered polygons 2.6.1.3 Unit III/Unit A – Yedoma deposition under cold-dry conditions during the Late Weichselian 2.6.1.4 Unit IV/Unit B – Holocene thermokarst lake formation and lacustrine sedimentation 2.6.2 Organic matter degradation 2.7 Conclusion 2.8 Acknowledgements 3 Yukechi Alas 3.1 Abstract 3.2 Introduction 3.3 Methods and materials 3.3.1 Study area 3.3.2 Field work 3.3.3 Laboratory analyses 3.3.3.1 Organic carbon content 3.3.3.2 Lipid biomarkers 3.3.4 Incubations 3.3.5 Statistical analysis 3.4 Results 3.4.1 Organic matter characteristics 3.4.1.1 Alas lake sediment core YU-L7 3.4.1.2 Yedoma lake sediment core YU-L15 3.4.2 Greenhouse gas production 3.4.2.1 Alas lake sediment core YU-L7 3.4.2.2 Yedoma lake sediment core YU-L15 3.4.2.3 Carbon mineralization 3.4.3 Statistical correlation and regression 3.5 Discussion 3.5.1 Organic matter degradation potential 3.5.1.1 Organic carbon quantity 3.5.1.2 Organic matter preservation and talik formation 3.5.1.3 Presence of methanogenic communities 3.5.2 Greenhouse gas production 3.5.2.1 Carbon dioxide production 3.5.2.2 Methane production 3.5.3 GHG links with other parameters and outlook 3.6 Conclusion 3.7 Acknowledgements 4 Sobo-Sise cliff 4.1 Abstract 4.2 Introduction 4.3 Study area 4.4 Methods 4.4.1 Fieldwork 4.4.2 Sedimentological organic matter parameters 4.4.3 Lipid biomarkers 4.4.3.1 Extraction and fraction separation 4.4.3.2 GC-MS measurements and compound quantification 4.4.4 Biomarker indices 4.4.4.1 Average Chain Length 4.4.4.2 Carbon Preference Index 4.4.4.3 Higher Plant Fatty Acids 4.4.5 Data analysis 4.5 Results 4.5.1 Sedimentological organic matter parameters 4.5.2 Biomarkers 4.5.2.1 n-Alkanes 4.5.2.2 Fatty acids 4.5.3 Clustering 4.6 Discussion 4.6.1 Terrestrial depositional environment 4.6.1.1 Organic matter source 4.6.1.2 Organic matter quality 4.6.2 Implications and outlook 4.7 Conclusion 4.8 Acknowledgements 5 Batagay thaw slump 5.1 Abstract 5.2 Introduction 5.3 Study site 5.4 Methods 5.4.1 Sample collection 5.4.2 Laboratory analyses 5.5 Results 5.5.1 Detected biomolecules 5.5.2 Lower Ice Complex 5.5.3 Lower Sand Unit 5.5.4 Woody Layer 5.5.5 Upper Ice Complex - Yedoma 5.5.6 Holocene Cover 5.6 Discussion 5.6.1 Biogeochemical legacy of glacial periods 5.6.2 Biogeochemical legacy of interglacial periods 5.6.3 Modern organic matter mobilization in the Batagay megaslump 5.7 Conclusion 5.8 Acknowledgements 6 Synthesis 6.1 Lipid biomarkers to characterize permafrost organic matter 6.1.1 Organic matter source 6.1.2 Organic matter quality 6.2 Mobilization of organic matter in thawing permafrost 6.2.1 Methane production vs. emission 6.2.2 Using the data in models 6.2.3 Transport of OM into aquatic systems 6.3 Recommendations for future research References Appendix A Supporting information for Chapter 2 Appendix B Supporting information for Chapter 3 Appendix C Supporting information for Chapter 4 Appendix D Supporting information for Chapter 5
    Location: AWI Reading room
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    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 , 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
    Location: AWI Reading room
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Publication Date: 2023-08-25
    Description: Since the beginning of the Anthropocene, lacustrine biodiversity has been influenced by climate change and human activities. These factors advance the spread of harmful cyanobacteria in lakes around the world, which affects water quality and impairs the aquatic food chain. In this study, we assessed changes in cyanobacterial community dynamics via sedimentary DNA (sedaDNA) from well-dated lake sediments of Lake Tiefer See, which is part of the Klocksin Lake Chain spanning the last 350 years. Our diversity and community analysis revealed that cyanobacterial communities form clusters according to the presence or absence of varves. Based on distance-based redundancy and variation partitioning analyses (dbRDA and VPA) we identified that intensified lake circulation inferred from vegetation openness reconstructions, δ13C data (a proxy for varve preservation) and total nitrogen content were abiotic factors that significantly explained the variation in the reconstructed cyanobacterial community from Lake Tiefer See sediments. Operational taxonomic units (OTUs) assigned to Microcystis sp. and Aphanizomenon sp. were identified as potential eutrophication-driven taxa of growing importance since circa common era (ca. CE) 1920 till present. This result is corroborated by a cyanobacteria lipid biomarker analysis. Furthermore, we suggest that stronger lake circulation as indicated by non-varved sediments favoured the deposition of the non-photosynthetic cyanobacteria sister clade Sericytochromatia, whereas lake bottom anoxia as indicated by subrecent- and recent varves favoured the Melainabacteria in sediments. Our findings highlight the potential of high-resolution amplicon sequencing in investigating the dynamics of past cyanobacterial communities in lake sediments and show that lake circulation, anoxic conditions, and human-induced eutrophication are main factors explaining variations in the cyanobacteria community in Lake Tiefer See during the last 350 years.
    Description: Virtual Institute of Integrated Climate and Landscape Evolution Analyses -ICLEA-
    Description: Leibniz-Gemeinschaft http://dx.doi.org/10.13039/501100001664
    Description: Helmholtz-Gemeinschaft (DE)
    Description: Deutsche Bundesstiftung Umwelt http://dx.doi.org/10.13039/100007636
    Description: Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum - GFZ (4217)
    Keywords: ddc:577.6 ; Late Holocene ; Methylheptadecanes ; Varves ; Anthropocene ; Sericytochromatia ; Melainabacteria
    Language: English
    Type: doc-type:article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Publication Date: 2022-04-07
    Description: The decomposition of thawing permafrost organic matter (OM) to the greenhouse gases (GHG) carbon dioxide (CO2) and methane forms a positive feedback to global climate change. Data on in situ GHG fluxes from thawing permafrost OM are scarce and OM degradability is largely unknown, causing high uncertainties in the permafrost‐carbon climate feedback. We combined in situ CO2 and methane flux measurements at an abrupt permafrost thaw feature with laboratory incubations and dynamic modeling to quantify annual CO2 release from thawing permafrost OM, estimate its in situ degradability and evaluate the explanatory power of incubation experiments. In July 2016 and 2019, CO2 fluxes ranged between 0.24 and 2.6 g CO2‐C m−2 d−1. Methane fluxes were low, which coincided with the absence of active methanogens in the Pleistocene permafrost. CO2 fluxes were lower three years after initial thaw after normalizing these fluxes to thawed carbon, indicating the depletion of labile carbon. Higher CO2 fluxes from thawing Pleistocene permafrost than from Holocene permafrost indicate OM preservation for millennia and give evidence that microbial activity in the permafrost was not substantial. Short‐term incubations overestimated in situ CO2 fluxes but underestimated methane fluxes. Two independent models simulated median annual CO2 fluxes of 160 and 184 g CO2‐C m−2 from the thaw slump, which include 25%–31% CO2 emissions during winter. Annual CO2 fluxes represent 0.8% of the carbon pool thawed in the surface soil. Our results demonstrate the potential of abrupt thaw processes to transform the tundra from carbon neutral into a substantial GHG source.
    Description: Plain Language Summary: Thawing of permanently frozen soils (permafrost) in the northern hemisphere forms a threat to global climate since these soils contain large amounts of frozen organic carbon, which might be decomposed to the greenhouse gases (GHGs) carbon dioxide (CO2) and methane upon thaw. How fast these GHGs are produced is largely unknown, since field observations of greenhouse gas fluxes from thawing permafrost are too sparse. Consequently, simulations on the effect of thawing permafrost soils on future climate are highly uncertain. We measured CO2 and methane fluxes from soils affected by abrupt permafrost thaw in Siberia during two summer seasons. We used these field observations and long‐term incubation data to calibrate two models that simulate the CO2 release over a whole year. We found that greenhouse gas fluxes were dominated by CO2 and that the minor importance of methane was due to the absence of methane producing microorganisms in the Pleistocene permafrost. The CO2 release in the first year accounted for 0.8% of thawed permafrost carbon but decomposition rates decreased after the depletion of the rapidly decomposable organic matter. Abrupt permafrost thaw turned the tundra into a substantial source of CO2, of which 25%–31% was released in the non‐growing season.
    Description: Key Points: Abrupt permafrost thaw turned the tundra into a substantial annual source of CO2 of which 25%–31% were released in the non‐growing season. About 0.8% of thawed permafrost carbon was decomposed to CO2 in one year but decomposition rates declined after the loss of labile carbon. Methane contributed a minor fraction to total greenhouse gas fluxes also because of a low methanogen abundance in Pleistocene permafrost.
    Description: German Ministry for Education and Research
    Description: German Research Foundation
    Description: https://doi.org/10.5281/zenodo.5584710
    Keywords: ddc:551
    Language: English
    Type: doc-type:article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Publication Date: 2021-10-15
    Description: As the Arctic coast erodes, it drains thermokarst lakes, transforming them into lagoons, and, eventually, integrates them into subsea permafrost. Lagoons represent the first stage of a thermokarst lake transition to a marine setting and possibly more saline and colder upper boundary conditions. In this research, borehole data, electrical resistivity surveying, and modeling of heat and salt diffusion were carried out at Polar Fox Lagoon on the Bykovsky Peninsula, Siberia. Polar Fox Lagoon is a seasonally isolated water body connected to Tiksi Bay through a channel, leading to hypersaline waters under the ice cover. The boreholes in the center of the lagoon revealed floating ice and a saline cryotic bed underlain by a saline cryotic talik, a thin ice-bearing permafrost layer, and unfrozen ground. The bathymetry showed that most of the lagoon had bedfast ice in spring. In bedfast ice areas, the electrical resistivity profiles suggested that an unfrozen saline layer was underlain by a thick layer of refrozen talik. The modeling showed that thermokarst lake taliks can refreeze when submerged in saltwater with mean annual bottom water temperatures below or slightly above 0°C. This occurs, because the top-down chemical degradation of newly formed ice-bearing permafrost is slower than the refreezing of the talik. Hence, lagoons may precondition taliks with a layer of ice-bearing permafrost before encroachment by the sea, and this frozen layer may act as a cap on gas migration out of the underlying talik.
    Keywords: 551.48 ; thermokarst lake ; talik ; lagoon ; subsea permafrost ; salt diffusion ; Siberia
    Language: English
    Type: map
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Publication Date: 2021-12-06
    Description: Abstract Although the majority of coastal sediments consist of sandy material, in some areas marine ingression caused the submergence of terrestrial carbon-rich peat soils. This affects the coastal carbon balance, as peat represents a potential carbon source. We performed a column experiment to better understand the coupled flow and biogeochemical processes governing carbon transformations in submerged peat under coastal fresh groundwater (GW) discharge and brackish water intrusion. The columns contained naturally layered sediments with and without peat (organic carbon content in peat 39 ± 14 wt%), alternately supplied with oxygen-rich brackish water from above and oxygen-poor, low-saline GW from below. The low-saline GW discharge through the peat significantly increased the release and ascent of dissolved organic carbon (DOC) from the peat (δ13CDOC − 26.9‰ to − 27.7‰), which was accompanied by the production of dissolved inorganic carbon (DIC) and emission of carbon dioxide (CO2), implying DOC mineralization. Oxygen respiration, sulfate (SO42−) reduction, and methane (CH4) formation were differently pronounced in the sediments and were accompanied with higher microbial abundances in peat compared to sand with SO42−-reducing bacteria clearly dominating methanogens. With decreasing salinity and SO42− concentrations, CH4 emission rates increased from 16.5 to 77.3 μmol m−2 d−1 during a 14-day, low-saline GW discharge phase. In contrast, oxygenated brackish water intrusion resulted in lower DOC and DIC pore water concentrations and significantly lower CH4 and CO2 emissions. Our study illustrates the strong dependence of carbon cycling in shallow coastal areas with submerged peat deposits on the flow and mixing dynamics within the subterranean estuary.
    Keywords: 550.724 ; coastal peatlands ; coastal peatlands ; biogeochemical processes ; carbon release ; column experiments
    Language: English
    Type: map
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...