TY - JOUR A1 - Serrano, Paloma A1 - Alawi, Mashal A1 - de Vera, Jean-Pierre Paul A1 - Wagner, Dirk T1 - Response of Methanogenic Archaea from Siberian Permafrost and Non-permafrost Environments to Simulated Mars-like Desiccation and the Presence of Perchlorate JF - Astrobiology N2 - Numerous preflight investigations were necessary prior to the exposure experiment BIOMEX on the International Space Station to test the basic potential of selected microorganisms to resist or even to be active under Mars-like conditions. In this study, methanogenic archaea, which are anaerobic chemolithotrophic microorganisms whose lifestyle would allow metabolism under the conditions on early and recent Mars, were analyzed. Some strains from Siberian permafrost environments have shown a particular resistance. In this investigation, we analyzed the response of three permafrost strains (Methanosarcina soligelidi SMA-21, Candidatus Methanosarcina SMA-17, Candidatus Methanobacterium SMA-27) and two related strains from non-permafrost environments (Methanosarcina mazei, Methanosarcina barkeri) to desiccation conditions (-80 degrees C for 315 days, martian regolith analog simulants S-MRS and P-MRS, a 128-day period of simulated Mars-like atmosphere). Exposure of the different methanogenic strains to increasing concentrations of magnesium perchlorate allowed for the study of their metabolic shutdown in a Mars-relevant perchlorate environment. Survival and metabolic recovery were analyzed by quantitative PCR, gas chromatography, and a new DNA-extraction method from viable cells embedded in S-MRS and P-MRS. All strains survived the two Mars-like desiccating scenarios and recovered to different extents. The permafrost strain SMA-27 showed an increased methanogenic activity by at least 10-fold after deep-freezing conditions. The methanogenic rates of all strains did not decrease significantly after 128 days S-MRS exposure, except for SMA-27, which decreased 10-fold. The activity of strains SMA-17 and SMA-27 decreased after 16 and 60 days P-MRS exposure. Non-permafrost strains showed constant survival and methane production when exposed to both desiccating scenarios. All strains showed unaltered methane production when exposed to the perchlorate concentration reported at the Phoenix landing site (2.4 mM) or even higher concentrations. We conclude that methanogens from (non-)permafrost environments are suitable candidates for potential life in the martian subsurface and therefore are worthy of study after space exposure experiments that approach Mars-like surface conditions. KW - Methanogenic archaea KW - Simulated Mars-like conditions KW - Subfreezing temperatures KW - Martian regolith analogs KW - Perchlorate KW - Permafrost Y1 - 2019 U6 - https://doi.org/10.1089/ast.2018.1877 SN - 1531-1074 SN - 1557-8070 VL - 19 IS - 2 SP - 197 EP - 208 PB - Liebert CY - New Rochelle ER - TY - JOUR A1 - Fritz, Michael A1 - Unkel, Ingmar A1 - Lenz, Josefine A1 - Gajewski, Konrad A1 - Frenzel, Peter A1 - Paquette, Nathalie A1 - Lantuit, Hugues A1 - Körte, Lisa A1 - Wetterich, Sebastian T1 - Regional environmental change versus local signal preservation in Holocene thermokarst lake sediments BT - a case study from Herschel Island, Yukon (Canada) JF - Journal of paleolimnolog N2 - Thermokarst lakes cover nearly one fourth of ice-rich permafrost lowlands in the Arctic. Sediments from an athalassic subsaline thermokarst lake on Herschel Island (69°36′N; 139°04′W, Canadian Arctic) were used to understand regional changes in climate and in sediment transport, hydrology, nutrient availability and permafrost disturbance. The sediment record spans the last ~ 11,700 years and the basal date is in good agreement with the Holocene onset of thermokarst initiation in the region. Electrical conductivity in pore water continuously decreases, thus indicating desalinization and continuous increase of lake size and water level. The inc/coh ratio of XRF scans provides a high-resolution organic-carbon proxy which correlates with TOC measurements. XRF-derived Mn/Fe ratios indicate aerobic versus anaerobic conditions which moderate the preservation potential of organic matter in lake sediments. The coexistence of marine, brackish and freshwater ostracods and foraminifera is explained by (1) oligohaline to mesohaline water chemistry of the past lake and (2) redeposition of Pleistocene specimens found within upthrusted marine sediments around the lake. Episodes of catchment disturbance are identified when calcareous fossils and allochthonous material were transported into the lake by thermokarst processes such as active-layer detachments, slumping and erosion of ice-rich shores. The pollen record does not show major variations and the pollen-based climate record does not match well with other summer air temperature reconstructions from this region. Local vegetation patterns in small catchments are strongly linked to morphology and sub-surface permafrost conditions rather than to climate. Multidisciplinary studies can identify the onset and life cycle of thermokarst lakes as they play a crucial role in Arctic freshwater ecosystems and in the global carbon cycle of the past, present and future. KW - Arctic KW - Permafrost KW - Athalassic subsaline lake KW - XRF scanning KW - Pore-water hydrochemistry KW - Ostracoda Y1 - 2018 U6 - https://doi.org/10.1007/s10933-018-0025-0 SN - 0921-2728 SN - 1573-0417 VL - 60 IS - 1 SP - 77 EP - 96 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Masyagina, Oxana. V. A1 - Evgrafova, S. Yu A1 - Bugaenko, T. N. A1 - Kholodilova, V. V. A1 - Krivobokov, L. A1 - Korets, M. A. A1 - Wagner, Dirk T1 - Permafrost landslides promote soil CO2 emission and hinder C accumulation JF - The science of the total environment : an international journal for scientific research into the environment and its relationship with man N2 - Landslides arc common in high-latitude forest ecosystems that have developed on permafrost. The most vulnerable areas in the permafrost territories of Siberia occur on the south-facing slopes of northern rivers, where they arc observed on about 20% of the total area of river slopes. Landslide disturbances will likely increase with climate change especially due to increasing summer-autumn precipitation. These processes are the most destructive natural disturbance agent and lead to the complete removal of pre-slide forest ecosystems (vegetation cover and soil). To evaluate postsliding ecosystem succession, we undertook integrated ecological research at landslides of different age classes along the Nizhnyaya Tunguska River and the Kochechum River (Tura, Krasnoyarsk region, Russia). Just after the event (at the one-year-old site), we registered a drop in soil respiration, a threefold lower microbial respiration rate, and a fourfold smaller mineral soil carbon and nitrogen stock at bare soil (melkozem) plots at the middle location of the site as compared with the non affected control site. The recovery of disturbed areas began with the re-establishment of plant cover and the following accumulation of an organic soil layer. During the 35-year succession (L1972), the accumulated layer (0 layer)at the oldest site contained similar C- and N stocks to those found at the control sites. However, the mineral soil C- and N stocks and the microbial biomass even of the oldest landslide area- did not reach the value of these parameters in control plots. Later, the soil respiration level and the eco-physiological status of soil microbiota also recovered due to these changes. This study demonstrates that the recovery after landslides in permafrost forests takes several decades. In addition, the degradation of permafrost due to landslides clearly hinders the accumulation of soil organic matter in the mineral soil. (C) 2018 Elsevier B.v. All rights reserved. KW - Landslides KW - Soil microorganisms KW - Permafrost KW - Soil C- and N stocks KW - Boreal ecosystems KW - Soil respiration Y1 - 2018 U6 - https://doi.org/10.1016/j.scitotenv.2018.11.468 SN - 0048-9697 SN - 1879-1026 VL - 657 SP - 351 EP - 364 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Schirrmeister, Lutz A1 - Meyer, Hanno A1 - Andreev, Andrei A1 - Wetterich, Sebastian A1 - Kienast, Frank A1 - Bobrov, Anatoly A1 - Fuchs, Margret A1 - Sierralta, Melanie A1 - Herzschuh, Ulrike T1 - Late Quaternary paleoenvironmental records from the Chatanika River valley near Fairbanks (Alaska) JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - Perennially-frozen deposits are considered as excellent paleoenvironmental archives similar to lacustrine, deep marine, and glacier records because of the long-term and good preservation of fossil records under stable permafrost conditions. A permafrost tunnel in the Vault Creek Valley (Chatanika River Valley, near Fairbanks) exposes a sequence of frozen deposits and ground ice that provides a comprehensive set of proxies to reconstruct the late Quaternary environmental history of Interior Alaska. The multi-proxy approach includes different dating techniques (radiocarbon-accelerator mass spectrometry [AMS C-14], optically stimulated luminescence [OSL], thorium/uranium radioisotope disequilibria [Th-230/U]), as well as methods of sedimentology, paleoecology, hydrochemistry, and stable isotope geochemistry of ground ice. The studied sequence consists of 36-m-thick late Quaternary deposits above schistose bedrock. Main portions of the sequence accumulated during the early and middle Wisconsin periods. The lowermost unit A consists of about 9-m-thick ice-bonded fluvial gravels with sand and peat lenses. A late Sangamon (MIS 5a) age of unit A is assumed. Spruce forest with birch, larch, and some shrubby alder dominated the vegetation. High presence of Sphagnum spores and Cyperaceae pollen points to mires in the Vault Creek Valley. The overlying unit B consists of 10-m-thick alternating fluvial gravels, loess-like silt, and sand layers, penetrated by small ice wedges. OSL dates support a stadial early Wisconsin (MIS 4) age of unit B. Pollen and plant macrofossil data point to spruce forests with some birch interspersed with wetlands around the site. The following unit C is composed of 15-m-thick ice-rich loess-like and organic-rich silt with fossil bones and large ice wedges. Unit C formed during the interstadial mid-Wisconsin (MIS 3) and stadial late Wisconsin (MIS 2) as indicated by radiocarbon ages. Post-depositional slope processes significantly deformed both, ground ice and sediments of unit C. Pollen data show that spruce forests and wetlands dominated the area. The macrofossil remains of Picea, Larix, and Alnus incana ssp. tenuifolia also prove the existence of boreal coniferous forests during the mid-Wisconsin interstadial, which were replaced by treeless tundra-steppe vegetation during the late Wisconsin stadial. Unit C is discordantly overlain by the 2-m-thick late Holocene deposits of unit D. The pollen record of unit D indicates boreal forest vegetation similar to the modern one. The permafrost record from the Vault Creek tunnel reflects more than 90 ka of periglacial landscape dynamics triggered by fluvial and eolian accumulation, and formation of ice-wedge polygons and post depositional deformation by slope processes. The record represents a typical Wisconsin valley-bottom facies in Central Alaska. (C) 2016 Elsevier Ltd. All rights reserved. KW - Permafrost KW - Interior Alaska KW - Loess KW - Cryolithology KW - Geochronology KW - Paleoecology KW - Landscape dynamics Y1 - 2016 U6 - https://doi.org/10.1016/j.quascirev.2016.02.009 SN - 0277-3791 VL - 147 SP - 259 EP - 278 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Schirrmeister, Lutz A1 - Bobrov, Anatoly A1 - Raschke, Elena A1 - Herzschuh, Ulrike A1 - Strauss, Jens A1 - Pestryakova, Luidmila Agafyevna A1 - Wetterich, Sebastian T1 - Late Holocene ice-wedge polygon dynamics in northeastern Siberian coastal lowlands JF - Arctic, antarctic, and alpine research : an interdisciplinary journal N2 - Ice-wedge polygons are common features of northeastern Siberian lowland periglacial tundra landscapes. To deduce the formation and alternation of ice-wedge polygons in the Kolyma Delta and in the Indigirka Lowland, we studied shallow cores, up to 1.3 m deep, from polygon center and rim locations. The formation of well-developed low-center polygons with elevated rims and wet centers is shown by the beginning of peat accumulation, increased organic matter contents, and changes in vegetation cover from Poaceae-, Alnus-, and Betula-dominated pollen spectra to dominating Cyperaceae and Botryoccocus presence, and Carex and Drepanocladus revolvens macro-fossils. Tecamoebae data support such a change from wetland to open-water conditions in polygon centers by changes from dominating eurybiontic and sphagnobiontic to hydrobiontic species assemblages. The peat accumulation indicates low-center polygon formation and started between 2380 +/- 30 and 1676 +/- 32 years before present (BP) in the Kolyma Delta. We recorded an opposite change from open-water to wetland conditions because of rim degradation and consecutive high-center polygon formation in the Indigirka Lowland between 2144 +/- 33 and 1632 +/- 32 years BP. The late Holocene records of polygon landscape development reveal changes in local hydrology and soil moisture. KW - Permafrost KW - cryolithology KW - radiocarbon dating KW - paleoecology KW - rhizopods KW - pollen KW - plant macro-fossils Y1 - 2018 U6 - https://doi.org/10.1080/15230430.2018.1462595 SN - 1523-0430 SN - 1938-4246 VL - 50 IS - 1 PB - Institute of Arctic and Alpine Research, University of Colorado CY - Boulder 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 - Heslop, J. K. A1 - Anthony, K. M. Walter A1 - Grosse, Guido A1 - Liebner, Susanne A1 - Winkel, Matthias T1 - Century-scale time since permafrost thaw affects temperature sensitivity of net methane production in thermokarst-lake and talik sediments JF - The science of the total environment : an international journal for scientific research into the environment and its relationship with man N2 - Permafrost thaw subjects previously frozen soil organic carbon (SOC) to microbial degradation to the greenhouse gases carbon dioxide (CO2) and methane (CH4). Emission of these gases constitutes a positive feedback to climate warming. Among numerous uncertainties in estimating the strength of this permafrost carbon feedback (PCF), two are: (i) how mineralization of permafrost SOC thawed in saturated anaerobic conditions responds to changes in temperature and (ii) how microbial communities and temperature sensitivities change over time since thaw. To address these uncertainties, we utilized a thermokarst-lake sediment core as a natural chronosequence where SOC thawed and incubated in situ under saturated anaerobic conditions for up to 400 years following permafrost thaw. Initial microbial communities were characterized, and sediments were anaerobically incubated in the lab at four temperatures (0 °C, 3 °C, 10 °C, and 25 °C) bracketing those observed in the lake's talik. Net CH4 production in freshly-thawed sediments near the downward-expanding thaw boundary at the base of the talik were most sensitive to warming at the lower incubation temperatures (0 °C to 3 °C), while the overlying sediments which had been thawed for centuries had initial low abundant methanogenic communities (< 0.02%) and did not experience statistically significant increases in net CH4 production potentials until higher incubation temperatures (10 °C to 25 °C). We propose these observed differences in temperature sensitivities are due to differences in SOM quality and functional microbial community composition that evolve over time; however further research is necessary to better constrain the roles of these factors in determining temperature controls on anaerobic C mineralization. KW - Carbon KW - Lake sediments KW - Methane KW - Permafrost KW - Talik KW - Temperature sensitivity Y1 - 2019 U6 - https://doi.org/10.1016/j.scitotenv.2019.06.402 SN - 0048-9697 SN - 1879-1026 VL - 691 SP - 124 EP - 134 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Tian, Fang A1 - Cao, Xianyong A1 - Dallmeyer, Anne A1 - Lohmann, Gerrit A1 - Zhang, Xu A1 - Ni, Jian A1 - Andreev, Andrei A1 - Anderson, Patricia M. A1 - Lozhkin, Anatoly V. A1 - Bezrukova, Elena A1 - Rudaya, Natalia A1 - Xu, Qinghai A1 - Herzschuh, Ulrike T1 - Biome changes and their inferred climatic drivers in northern and eastern continental Asia at selected times since 40 cal ka BP JF - Vegetation History and Archaeobotany N2 - Recent global warming is pronounced in high-latitude regions (e.g. northern Asia), and will cause the vegetation to change. Future vegetation trends (e.g. the "arctic greening") will feed back into atmospheric circulation and the global climate system. Understanding the nature and causes of past vegetation changes is important for predicting the composition and distribution of future vegetation communities. Fossil pollen records from 468 sites in northern and eastern Asia were biomised at selected times between 40 cal ka bp and today. Biomes were also simulated using a climate-driven biome model and results from the two approaches compared in order to help understand the mechanisms behind the observed vegetation changes. The consistent biome results inferred by both approaches reveal that long-term and broad-scale vegetation patterns reflect global- to hemispheric-scale climate changes. Forest biomes increase around the beginning of the late deglaciation, become more widespread during the early and middle Holocene, and decrease in the late Holocene in fringe areas of the Asian Summer Monsoon. At the southern and southwestern margins of the taiga, forest increases in the early Holocene and shows notable species succession, which may have been caused by winter warming at ca. 7 cal ka bp. At the northeastern taiga margin (central Yakutia and northeastern Siberia), shrub expansion during the last deglaciation appears to prevent the permafrost from thawing and hinders the northward expansion of evergreen needle-leaved species until ca. 7 cal ka bp. The vegetation-climate disequilibrium during the early Holocene in the taiga-tundra transition zone suggests that projected climate warming will not cause a northward expansion of evergreen needle-leaved species. KW - Siberia KW - China KW - Northern Asia KW - Model-data comparison KW - Pollen KW - Permafrost KW - Vegetation-climate disequilibrium Y1 - 2018 U6 - https://doi.org/10.1007/s00334-017-0653-8 SN - 0939-6314 SN - 1617-6278 VL - 27 IS - 2 SP - 365 EP - 379 PB - Springer CY - New York ER -