TY - JOUR A1 - Berben, Tom A1 - Bo, Franco Forlano A1 - in 't Zandt, Michiel H. A1 - Yang, Sizhong A1 - Liebner, Susanne A1 - Welte, Cornelia U. T1 - The Polar Fox Lagoon in Siberia harbours a community of Bathyarchaeota possessing the potential for peptide fermentation and acetogenesis JF - Antonie van Leeuwenhoek : international journal of general and molecular microbiology N2 - Archaea belonging to the phylum Bathyarchaeota are the predominant archaeal species in cold, anoxic marine sediments and additionally occur in a variety of habitats, both natural and man-made. Metagenomic and single-cell sequencing studies suggest that Bathyarchaeota may have a significant impact on the emissions of greenhouse gases into the atmosphere, either through direct production of methane or through the degradation of complex organic matter that can subsequently be converted into methane. This is especially relevant in permafrost regions where climate change leads to thawing of permafrost, making high amounts of stored carbon bioavailable. Here we present the analysis of nineteen draft genomes recovered from a sediment core metagenome of the Polar Fox Lagoon, a thermokarst lake located on the Bykovsky Peninsula in Siberia, Russia, which is connected to the brackish Tiksi Bay. We show that the Bathyarchaeota in this lake are predominantly peptide degraders, producing reduced ferredoxin from the fermentation of peptides, while degradation pathways for plant-derived polymers were found to be incomplete. Several genomes encoded the potential for acetogenesis through the Wood-Ljungdahl pathway, but methanogenesis was determined to be unlikely due to the lack of genes encoding the key enzyme in methanogenesis, methyl-CoM reductase. Many genomes lacked a clear pathway for recycling reduced ferredoxin. Hydrogen metabolism was also hardly found: one type 4e [NiFe] hydrogenase was annotated in a single MAG and no [FeFe] hydrogenases were detected. Little evidence was found for syntrophy through formate or direct interspecies electron transfer, leaving a significant gap in our understanding of the metabolism of these organisms. KW - Bathyarchaea KW - Siberia KW - Thermokarst KW - Peptide fermentation Y1 - 2022 U6 - https://doi.org/10.1007/s10482-022-01767-z SN - 0003-6072 SN - 1572-9699 VL - 115 SP - 1229 EP - 1244 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Pestryakova, Luidmila Agafyevna A1 - Herzschuh, Ulrike A1 - Wetterich, Sebastian A1 - Ulrich, Mathias T1 - Present-day variability and Holocene dynamics of permafrost-affected lakes in central Yakutia (Eastern Siberia) inferred from diatom records JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - Thermokarst lakes are assumed to develop cyclically, driven by processes that are triggered by climate and maintained by internal feedbacks that may trigger lake drainage. However, the duration of these cycles remains uncertain, as well as whether or not they affect the stabilization of lake ecosystems in permafrost regions over millennial time scales. Our research has combined investigations into modern lake-to-lake variability with a study of the long-term development of individual lakes. We have investigated the physico-chemical and diatom compositions of a set of 101 lakes with a variety of different origins in central Yakutia (Eastern Siberia), including thermokarst lakes, fluvial-erosion thermokarst lakes, fluvial-erosion lakes, and dune lakes. We found a significant relationship between lake genesis and the present-day variability in environmental and diatom characteristics, as revealed by multi-response permutation procedures, indicator species analyses, and redundancy analyses. Environmental parameters also exhibit a significant correlation with variations in the diatom data, for which they may have been to a substantial extent responsible. Mg and SO4 concentrations, together with pH and water depth, were identified as the most important parameters, influencing the variations in the diatom data almost as much as the entire environmental parameter set. We were therefore able to establish a robust Mg-diatom transfer function, which was then applied to three Holocene lake records. From these reconstructions, together with a general interpretation of the diatom record (including, e.g., the ratio between benthic/epiphytic and planktonic taxa), we have been able to infer that all three of these lakes show (1) a continuous record with no desiccation events, (2) high lake water-levels during the early Holocene, (3) centennial to millennial scale variability, and (4) high levels of variability during the early Holocene but rather stable conditions during the late Holocene (a feature that is also known from other sites around the world). We therefore concluded that the development of these three lakes was mainly driven directly by the climate, rather than by thaw lake cycling. KW - Diatoms KW - Holocene KW - Thaw lakes KW - Thermokarst KW - Alas KW - Central Yakutia KW - Alkalinity Y1 - 2012 U6 - https://doi.org/10.1016/j.quascirev.2012.06.020 SN - 0277-3791 VL - 51 SP - 56 EP - 70 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Fritz, Michael A1 - Wolter, Juliane A1 - Rudaya, Natalia A1 - Palagushkina, Olga A1 - Nazarova, Larisa B. A1 - Obu, Jaroslav A1 - Rethemeyer, Janet A1 - Lantuit, Hugues A1 - Wetterich, Sebastian T1 - Holocene ice-wedge polygon development in northern Yukon permafrost peatlands (Canada) JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - Ice-wedge polygon (IWP) peatlands in the Arctic and Subarctic are extremely vulnerable to climatic and environmental change. We present the results of a multidisciplinary paleoenvironmental study on IWPs in the northern Yukon, Canada. High-resolution laboratory analyses were carried out on a permafrost core and the overlying seasonally thawed (active) layer, from an IWP located in a drained lake basin on Herschel Island. In relation to 14 Accelerator Mass Spectrometry (AMS) radiocarbon dates spanning the last 5000 years, we report sedimentary data including grain size distribution and biogeochemical parameters (organic carbon, nitrogen, C/N ratio, delta C-13), stable water isotopes (delta O-18, delta D), as well as fossil pollen, plant macrofossil and diatom assemblages. Three sediment units (SUS) correspond to the main stages of deposition (1) in a thermokarst lake (SW : 4950 to 3950 cal yrs BP), (2) during transition from lacustrine to palustrine conditions after lake drainage (SU2: 3950 to 3120 cal yrs BP), and (3) in palustrine conditions of the IWP field that developed after drainage (SU3: 3120 cal yrs BP to 2012 CE). The lacustrine phase (pre 3950 cal yrs BP) is characterized by planktonic-benthic and pioneer diatom species indicating circumneutral waters, and very few plant macrofossils. The pollen record has captured a regional signal of relatively stable vegetation composition and climate for the lacustrine stage of the record until 3950 cal yrs BP. Palustrine conditions with benthic and acidophilic diatom species characterize the peaty shallow-water environments of the low-centered IWP. The transition from lacustrine to palustrine conditions was accompanied by acidification and rapid revegetation of the lake bottom within about 100 years. Since the palustrine phase we consider the pollen record as a local vegetation proxy dominated by the plant communities growing in the IWP. Ice-wedge cracking in water-saturated sediments started immediately after lake drainage at about 3950 cal yrs BP and led to the formation of an IWP mire. Permafrost aggradation through downward closed-system freezing of the lake talik is indicated by the stable water isotope record. The originally submerged IWP center underwent gradual drying during the past 2000 years. This study highlights the sensitivity of permafrost landscapes to climate and environmental change throughout the Holocene. (C) 2016 Elsevier Ltd. All rights reserved. KW - Permafrost peatlands KW - Arctic KW - Thermokarst KW - Talik KW - Ice-wedge polygon KW - Pollen KW - Diatoms KW - Plant macrofossils KW - Stable water isotopes KW - Deuterium excess Y1 - 2016 U6 - https://doi.org/10.1016/j.quascirev.2016.02.008 SN - 0277-3791 VL - 147 SP - 279 EP - 297 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Palagushkina, Olga A1 - Wetterich, Sebastian A1 - Biskaborn, Boris A1 - Nazarova, Larisa B. A1 - Schirrmeister, Lutz A1 - Lenz, Josefine A1 - Schwamborn, Georg A1 - Grosse, Guido T1 - Diatom records and tephra mineralogy in pingo deposits of Seward Peninsula, Alaska JF - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences N2 - Vast areas of the terrestrial Subarctic and Arctic are underlain by permafrost. Landscape evolution is therefore largely controlled by climate-driven periglacial processes. The response of the frozen ground to late Quaternary warm and cold stages is preserved in permafrost sequences, and deducible by multi-proxy palaeoenvironmental approaches. Here, we analyse radiocarbon-dated mid-Wisconsin Interstadial and Holocene lacustrine deposits preserved in the Kit-1 pingo permafrost sequence combined with water and surface sediment samples from nine modern water bodies on Seward Peninsula (NW Alaska) to reconstruct thermokarst dynamics and determine major abiotic factors that controlled the aquatic ecosystem variability. Our methods comprise taxonomical diatom analyses as well as Detrended Correspondence Analysis (DCA) and Redundancy Analysis (RDA). Our results show, that the fossil diatom record reflects thermokarst lake succession since about 42 C-14 kyr BP. Different thermolcarst lake stages during the mid-Wisconsin Interstadial, the late Wisconsin and the early Holocene are mirrored by changes in diatom abundance, diversity, and ecology. We interpret the taxonomical changes in the fossil diatom assemblages in combination with both modern diatom data from surrounding ponds and existing micropalaeontological, sedimentological and mineralogical data from the pingo sequence. A diatom based quantitative reconstruction of lake water pH indicates changing lake environments during mid-Wisconsin to early Holocene stages. Mineralogical analyses indicate presence of tephra fallout and its impact on fossil diatom communities. Our comparison of modern and fossil diatom communities shows the highest floristic similarity of modern polygon ponds to the corresponding initial (shallow water) development stages of thermolcarst lakes. We conclude, that mid-Wisconsin thermokarst processes in the study area could establish during relatively warm interstadial climate conditions accompanied by increased precipitation due to approaching coasts, while still high continentality and hence high seasonal temperature gradients led to warm summers in the central part of Beringia. (C) 2017 Elsevier B.V. All rights reserved. KW - Microalgae assemblages KW - Palaeoenvironments KW - Thermokarst KW - Late Quaternary KW - Permafrost Y1 - 2017 U6 - https://doi.org/10.1016/j.palaeo.2017.04.006 SN - 0031-0182 SN - 1872-616X VL - 479 SP - 1 EP - 15 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Nitze, Ingmar A1 - Grosse, Guido T1 - Detection of landscape dynamics in the Arctic Lena Delta with temporally dense Landsat time-series stacks JF - Remote sensing of environment : an interdisciplinary journal N2 - Arctic permafrost landscapes are among the most vulnerable and dynamic landscapes globally, but due to their extent and remoteness most of the landscape changes remain unnoticed. In order to detect disturbances in these areas we developed an automated processing chain for the calculation and analysis of robust trends of key land surface indicators based on the full record of available Landsat TM, ETM +, and OLI data. The methodology was applied to the similar to 29,000 km(2) Lena Delta in Northeast Siberia, where robust trend parameters (slope, confidence intervals of the slope, and intercept) were calculated for Tasseled Cap Greenness, Wetness and Brightness, NDVI, and NDWI, and NDMI based on 204 Landsat scenes for the observation period between 1999 and 2014. The resulting datasets revealed regional greening trends within the Lena Delta with several localized hot-spots of change, particularly in the vicinity of the main river channels. With a 30-m spatial resolution various permafrost-thaw related processes and disturbances, such as thermokarst lake expansion and drainage, fluvial erosion, and coastal changes were detected within the Lena Delta region, many of which have not been noticed or described before. Such hotspots of permafrost change exhibit significantly different trend parameters compared to non-disturbed areas. The processed dataset, which is made freely available through the data archive PANGAEA, will be a useful resource for further process specific analysis by researchers and land managers. With the high level of automation and the use of the freely available Landsat archive data, the workflow is scalable and transferrable to other regions, which should enable the comparison of land surface changes in different permafrost affected regions and help to understand and quantify permafrost landscape dynamics. (C) 2016 Elsevier Inc. All rights reserved. KW - Trend analysis KW - Permafrost thaw KW - Thermokarst KW - Thermoerosion KW - Land cover disturbances KW - River delta KW - Arctic tundra KW - Vegetation greening KW - Vegetation change KW - Coastal dynamics KW - Siberia Y1 - 2016 U6 - https://doi.org/10.1016/j.rse.2016.03.038 SN - 0034-4257 SN - 1879-0704 VL - 181 SP - 27 EP - 41 PB - Elsevier CY - New York ER - TY - JOUR A1 - Strauss, Jens A1 - Schirrmeister, Lutz A1 - Grosse, Guido A1 - Fortier, Daniel A1 - Hugelius, Gustaf A1 - Knoblauch, Christian A1 - Romanovsky, Vladimir E. A1 - Schadel, Christina A1 - von Deimling, Thomas Schneider A1 - Schuur, Edward A. G. A1 - Shmelev, Denis A1 - Ulrich, Mathias A1 - Veremeeva, Alexandra T1 - Deep Yedoma permafrost: A synthesis of depositional characteristics and carbon vulnerability JF - Earth science reviews : the international geological journal bridging the gap between research articles and textbooks N2 - Permafrost is a distinct feature of the terrestrial Arctic and is vulnerable to climate warming. Permafrost degrades in different ways, including deepening of a seasonally unfrozen surface and localized but rapid development of deep thaw features. Pleistocene ice-rich permafrost with syngenetic ice-wedges, termed Yedoma deposits, are widespread in Siberia, Alaska, and Yukon, Canada and may be especially prone to rapid-thaw processes. Freeze-locked organic matter in such deposits can be re-mobilized on short time-scales and contribute to a carbon-cycle climate feedback. Here we synthesize the characteristics and vulnerability of Yedoma deposits by synthesizing studies on the Yedoma origin and the associated organic carbon pool. We suggest that Yedoma deposits accumulated under periglacial weathering, transport, and deposition dynamics in non-glaciated regions during the late Pleistocene until the beginning of late glacial warming. The deposits formed due to a combination of aeolian, colluvial, nival, and alluvial deposition and simultaneous ground ice accumulation. We found up to 130 gigatons organic carbon in Yedoma, parts of which are well-preserved and available for fast decomposition after thaw. Based on incubation experiments, up to 10% of the Yedoma carbon is considered especially decomposable and may be released upon thaw. The substantial amount of ground ice in Yedoma makes it highly vulnerable to disturbances such as thermokarst and thermo-erosion processes. Mobilization of permafrost carbon is expected to increase under future climate warming. Our synthesis results underline the need of accounting for Yedoma carbon stocks in next generation Earth-System-Models for a more complete representation of the permafrost-carbon feedback. KW - Perennial frozen ground KW - Thermokarst KW - Arctic KW - Late Pleistocene KW - Greenhouse gas source KW - Climate feedback Y1 - 2017 U6 - https://doi.org/10.1016/j.earscirev.2017.07.007 SN - 0012-8252 SN - 1872-6828 VL - 172 SP - 75 EP - 86 PB - Elsevier CY - Amsterdam ER -