TY  - JOUR
A1  - Melchert, Jan Olaf
A1  - Wischhöfer, Philipp
A1  - Knoblauch, Christian
A1  - Eckhardt, Tim
A1  - Liebner, Susanne
A1  - Rethemeyer, Janet
T1  - Sources of CO2 Produced in Freshly Thawed Pleistocene-Age Yedoma Permafrost
JF  - Frontiers in Earth Science
N2  - The release of greenhouse gases from the large organic carbon stock in permafrost deposits in the circumarctic regions may accelerate global warming upon thaw. The extent of this positive climate feedback is thought to be largely controlled by the microbial degradability of the organic matter preserved in these sediments. In addition, weathering and oxidation processes may release inorganic carbon preserved in permafrost sediments as CO2, which is generally not accounted for. We used C-13 and C-14 analysis and isotopic mass balances to differentiate and quantify organic and inorganic carbon released as CO2 in the field from an active retrogressive thaw slump of Pleistocene-age Yedoma and during a 1.5-years incubation experiment. The results reveal that the dominant source of the CO2 released from freshly thawed Yedoma exposed as thaw mound is Pleistocene-age organic matter (48-80%) and to a lesser extent modern organic substrate (3-34%). A significant portion of the CO2 originated from inorganic carbon in the Yedoma (17-26%). The mixing of young, active layer material with Yedoma at a site on the slump floor led to the preferential mineralization of this young organic carbon source. Admixtures of younger organic substrates in the Yedoma thaw mound were small and thus rapidly consumed as shown by lower contributions to the CO2 produced during few weeks of aerobic incubation at 4 degrees C corresponding to approximately one thaw season. Future CO2 fluxes from the freshly thawed Yedoma will contain higher proportions of ancient inorganic (22%) and organic carbon (61-78%) as suggested by the results at the end, after 1.5 years of incubation. The increasing contribution of inorganic carbon during the incubation is favored by the accumulation of organic acids from microbial organic matter degradation resulting in lower pH values and, in consequence, in inorganic carbon dissolution. Because part of the inorganic carbon pool is assumed to be of pedogenic origin, these emissions would ultimately not alter carbon budgets. The results of this study highlight the preferential degradation of younger organic substrates in freshly thawed Yedoma, if available, and a substantial release of CO2 from inorganic sources.
KW  - yedoma ice complex
KW  - permafost
KW  - carbon cycle
KW  - climat change
KW  - thermokarst
KW  - radiocarbon
KW  - greenhouse gas
Y1  - 2022
U6  - https://doi.org/10.3389/feart.2021.737237
SN  - 2296-6463
VL  - 9
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Nwosu, Ebuka Canisius
A1  - Roeser, Patricia Angelika
A1  - Yang, Sizhong
A1  - Pinkerneil, Sylvia
A1  - Ganzert, Lars
A1  - Dittmann, Elke
A1  - Brauer, Achim
A1  - Wagner, Dirk
A1  - Liebner, Susanne
T1  - Species-level spatio-temporal dynamics of cyanobacteria in a hard-water temperate lake in the Southern Baltics
JF  - Frontiers in microbiology
N2  - Cyanobacteria are important primary producers in temperate freshwater ecosystems. However, studies on the seasonal and spatial distribution of cyanobacteria in deep lakes based on high-throughput DNA sequencing are still rare. In this study, we combined monthly water sampling and monitoring in 2019, amplicon sequence variants analysis (ASVs; a proxy for different species) and quantitative PCR targeting overall cyanobacteria abundance to describe the seasonal and spatial dynamics of cyanobacteria in the deep hard-water oligo-mesotrophic Lake Tiefer See, NE Germany. We observed significant seasonal variation in the cyanobacterial community composition (p < 0.05) in the epi- and metalimnion layers, but not in the hypolimnion. In winter-when the water column is mixed-picocyanobacteria (Synechococcus and Cyanobium) were dominant. With the onset of stratification in late spring, we observed potential niche specialization and coexistence among the cyanobacteria taxa driven mainly by light and nutrient dynamics. Specifically, ASVs assigned to picocyanobacteria and the genus Planktothrix were the main contributors to the formation of deep chlorophyll maxima along a light gradient. While Synechococcus and different Cyanobium ASVs were abundant in the epilimnion up to the base of the euphotic zone from spring to fall, Planktothrix mainly occurred in the metalimnetic layer below the euphotic zone where also overall cyanobacteria abundance was highest in summer. Our data revealed two potentially psychrotolerant (cold-adapted) Cyanobium species that appear to cope well under conditions of lower hypolimnetic water temperature and light as well as increasing sediment-released phosphate in the deeper waters in summer. The potential cold-adapted Cyanobium species were also dominant throughout the water column in fall and winter. Furthermore, Snowella and Microcystis-related ASVs were abundant in the water column during the onset of fall turnover. Altogether, these findings suggest previously unascertained and considerable spatiotemporal changes in the community of cyanobacteria on the species level especially within the genus Cyanobium in deep hard-water temperate lakes.
KW  - Cyanobium
KW  - picocyanobacteria diversity
KW  - amplicon sequencing
KW  - lake monitoring
KW  - ecological succession
KW  - lake stratification
KW  - psychrotolerant
Y1  - 2021
U6  - https://doi.org/10.3389/fmicb.2021.761259
SN  - 1664-302X
VL  - 12
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Mitzscherling, Julia
A1  - MacLean, Joana
A1  - Lipus, Daniel
A1  - Bartholomäus, Alexander
A1  - Mangelsdorf, Kai
A1  - Lipski, André
A1  - Roddatis, Vladimir
A1  - Liebner, Susanne
A1  - Wagner, Dirk
T1  - Nocardioides alcanivorans sp. nov., a novel hexadecane-degrading species isolated from plastic waste
JF  - International journal of systematic and evolutionary microbiology
N2  - Strain NGK65(T), a novel hexadecane degrading, non-motile, Gram-positive, rod-to-coccus shaped, aerobic bacterium, was isolated from plastic polluted soil sampled at a landfill. 
Strain NGK65(T) hydrolysed casein, gelatin, urea and was catalase-positive. It optimally grew at 28 degrees C. in 0-1% NaCl and at pH 7.5-8.0. Glycerol, D-glucose, arbutin, aesculin, salicin, potassium 5-ketogluconate. sucrose, acetate, pyruvate and hexadecane were used as sole carbon sources. 
The predominant membrane fatty acids were iso-C-16:0 followed by iso-C(17:)0 and C-18:1 omega 9c. The major polar lipids were phosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and hydroxyphosphatidylinositol. 
The cell-wall peptidoglycan type was A3 gamma, with LL-diaminopimelic acid and glycine as the diagnostic amino acids. MK 8 (H-4) was the predominant menaquinone. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain NGK65(T) belongs to the genus Nocardioides (phylum Actinobacteria). appearing most closely related to Nocardioides daejeonensis MJ31(T) (98.6%) and Nocardioides dubius KSL-104(T) (98.3%). 
The genomic DNA G+C content of strain NGK65(T) was 68.2%. 
Strain NGK65(T) and the type strains of species involved in the analysis had average nucleotide identity values of 78.3-71.9% as well as digital DNA-DNA hybridization values between 22.5 and 19.7%, which clearly indicated that the isolate represents a novel species within the genus Nocardioides. 
Based on phenotypic and molecular characterization, strain NGK65(T) can clearly be differentiated from its phylogenetic neighbours to establish a novel species, for which the name Nocardioides alcanivorans sp. nov. is proposed. 
The type strain is NGK65(T) (=DSM 113112(T)=NCCB 100846(T)).
KW  - Nocardioides alcanivorans
KW  - hexadecane
KW  - plastic degradation
KW  - terrestrial
KW  - plastisphere
KW  - bacteria
Y1  - 2022
U6  - https://doi.org/10.1099/ijsem.0.005319
SN  - 1466-5026
SN  - 1466-5034
VL  - 72
IS  - 4
PB  - Microbiology Society
CY  - London
ER  - 
TY  - JOUR
A1  - Angelopoulos, Michael
A1  - Overduin, Pier Paul
A1  - Westermann, Sebastian
A1  - Tronicke, Jens
A1  - Strauss, Jens
A1  - Schirrmeister, Lutz
A1  - Biskaborn, Boris
A1  - Liebner, Susanne
A1  - Maksimov, Georgii
A1  - Grigoriev, Mikhail N.
A1  - Grosse, Guido
T1  - Thermokarst lake to lagoon transitions in Eastern Siberia
BT  - do submerged taliks refreeze?
JF  - Journal of geophysical research : Earth surface
N2  - 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 degrees 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.
KW  - thermokarst lake
KW  - talik
KW  - lagoon
KW  - subsea permafrost
KW  - salt diffusion
KW  - Siberia
Y1  - 2020
U6  - https://doi.org/10.1029/2019JF005424
SN  - 2169-9003
SN  - 2169-9011
VL  - 125
IS  - 10
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Knoblauch, Christian
A1  - Beer, Christian
A1  - Liebner, Susanne
A1  - Grigoriev, Mikhail N.
A1  - Pfeiffer, Eva-Maria
T1  - Methane production as key to the greenhouse gas budget of thawing permafrost
JF  - Nature climate change
N2  - Permafrost thaw liberates frozen organic carbon, which is decomposed into carbon dioxide (CO2) and methane (CH4). The release of these greenhouse gases (GHGs) forms a positive feedback to atmospheric CO2 and CH4 concentrations and accelerates climate change(1,2). Current studies report a minor importance of CH4 production in water-saturated (anoxic) permafrost soils(3-6) and a stronger permafrost carbon-climate feedback from drained (oxic) soils(1,7). Here we show through seven-year laboratory incubations that equal amounts of CO2 and CH4 are formed in thawing permafrost under anoxic conditions after stable CH4-producing microbial communities have established. Less permafrost carbon was mineralized under anoxic conditions but more CO2-carbon equivalents (CO2Ce) were formed than under oxic conditions when the higher global warming potential (GWP) of CH4 is taken into account(8). A model of organic carbon decomposition, calibrated with the observed decomposition data, predicts a higher loss of permafrost carbon under oxic conditions (113 +/- 58 g CO2-C kgC(-1) (kgC, kilograms of carbon)) by 2100, but a twice as high production of CO2-Ce (241 +/- 138 g CO2-Ce kgC(-1)) under anoxic conditions. These findings challenge the view of a stronger permafrost carbon-climate feedback from drained soils1,7 and emphasize the importance of CH4 production in thawing permafrost on climate-relevant timescales.
Y1  - 2018
U6  - https://doi.org/10.1038/s41558-018-0095-z
SN  - 1758-678X
SN  - 1758-6798
VL  - 8
IS  - 4
SP  - 309
EP  - 312
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Wen, Xi
A1  - Unger, Viktoria
A1  - Jurasinski, Gerald
A1  - Koebsch, Franziska
A1  - Horn, Fabian
A1  - Rehder, Gregor
A1  - Sachs, Torsten
A1  - Zak, Dominik
A1  - Lischeid, Gunnar
A1  - Knorr, Klaus-Holger
A1  - Boettcher, Michael E.
A1  - Winkel, Matthias
A1  - Bodelier, Paul L. E.
A1  - Liebner, Susanne
T1  - Predominance of methanogens over methanotrophs in rewetted fens characterized by high methane emissions
JF  - Biogeosciences
N2  - The rewetting of drained peatlands alters peat geochemistry and often leads to sustained elevated methane emission. Although this methane is produced entirely by microbial activity, the distribution and abundance of methane-cycling microbes in rewetted peatlands, especially in fens, is rarely described. In this study, we compare the community composition and abundance of methane-cycling microbes in relation to peat porewater geochemistry in two rewetted fens in northeastern Germany, a coastal brackish fen and a freshwater riparian fen, with known high methane fluxes. We utilized 16S rRNA high-throughput sequencing and quantitative polymerase chain reaction (qPCR) on 16S rRNA, mcrA, and pmoA genes to determine microbial community composition and the abundance of total bacteria, methanogens, and methanotrophs. Electrical conductivity (EC) was more than 3 times higher in the coastal fen than in the riparian fen, averaging 5.3 and 1.5 mS cm(-1), respectively. Porewater concentrations of terminal electron acceptors (TEAs) varied within and among the fens. This was also reflected in similarly high intra- and inter-site variations of microbial community composition. Despite these differences in environmental conditions and electron acceptor availability, we found a low abundance of methanotrophs and a high abundance of methanogens, represented in particular by Methanosaetaceae, in both fens. This suggests that rapid (re) establishment of methanogens and slow (re) establishment of methanotrophs contributes to prolonged increased methane emissions following rewetting.
Y1  - 2018
U6  - https://doi.org/10.5194/bg-15-6519-2018
SN  - 1726-4170
SN  - 1726-4189
VL  - 15
IS  - 21
SP  - 6519
EP  - 6536
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Koebsch, Franziska
A1  - Winkel, Matthias
A1  - Liebner, Susanne
A1  - Liu, Bo
A1  - Westphal, Julia
A1  - Schmiedinger, Iris
A1  - Spitzy, Alejandro
A1  - Gehre, Matthias
A1  - Jurasinski, Gerald
A1  - Köhler, Stefan
A1  - Unger, Viktoria
A1  - Koch, Marian
A1  - Sachs, Torsten
A1  - Böttcher, Michael E.
T1  - Sulfate deprivation triggers high methane production in a disturbed and rewetted coastal peatland
JF  - Biogeosciences
N2  - In natural coastal wetlands, high supplies of marine sulfate suppress methanogenesis. Coastal wetlands are, however, often subject to disturbance by diking and drainage for agricultural use and can turn to potent methane sources when rewetted for remediation. This suggests that preceding land use measures can suspend the sulfate-related methane suppressing mechanisms. Here, we unravel the hydrological relocation and biogeochemical S and C transformation processes that induced high methane emissions in a disturbed and rewetted peatland despite former brackish impact. The underlying processes were investigated along a transect of increasing distance to the coastline using a combination of concentration patterns, stable isotope partitioning, and analysis of the microbial community structure. We found that diking and freshwater rewetting caused a distinct freshening and an efficient depletion of the brackish sulfate reservoir by dissimilatory sulfate reduction (DSR). Despite some legacy effects of brackish impact expressed as high amounts of sedimentary S and elevated electrical conductivities, contemporary metabolic processes operated mainly under sulfate-limited conditions. This opened up favorable conditions for the establishment of a prospering methanogenic community in the top 30-40 cm of peat, the structure and physiology of which resemble those of terrestrial organic-rich environments. Locally, high amounts of sulfate persisted in deeper peat layers through the inhibition of DSR, probably by competitive electron acceptors of terrestrial origin, for example Fe(III). However, as sulfate occurred only in peat layers below 30-40 cm, it did not interfere with high methane emissions on an ecosystem scale. Our results indicate that the climate effect of disturbed and remediated coastal wetlands cannot simply be derived by analogy with their natural counterparts. From a greenhouse gas perspective, the re-exposure of diked wetlands to natural coastal dynamics would literally open up the floodgates for a replenishment of the marine sulfate pool and therefore constitute an efficient measure to reduce methane emissions.
Y1  - 2019
U6  - https://doi.org/10.5194/bg-16-1937-2019
SN  - 1726-4170
SN  - 1726-4189
VL  - 16
IS  - 9
SP  - 1937
EP  - 1953
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Heslop, J. K.
A1  - Winkel, Matthias
A1  - Anthony, K. M. Walter
A1  - Spencer, R. G. M.
A1  - Podgorski, D. C.
A1  - Zito, P.
A1  - Kholodov, A.
A1  - Zhang, M.
A1  - Liebner, Susanne
T1  - Increasing organic carbon biolability with depth in yedoma permafrost
BT  - ramifications for future climate change
JF  - Journal of geophysical research : Biogeosciences
N2  - Permafrost thaw subjects previously frozen organic carbon (OC) to microbial decomposition, generating the greenhouse gases (GHG) carbon dioxide (CO2) and methane (CH4) and fueling a positive climate feedback. Over one quarter of permafrost OC is stored in deep, ice-rich Pleistocene-aged yedoma permafrost deposits. We used a combination of anaerobic incubations, microbial sequencing, and ultrahigh-resolution mass spectrometry to show yedoma OC biolability increases with depth along a 12-m yedoma profile. In incubations at 3 degrees C and 13 degrees C, GHG production per unit OC at 12-versus 1.3-m depth was 4.6 and 20.5 times greater, respectively. Bacterial diversity decreased with depth and we detected methanogens at all our sampled depths, suggesting that in situ microbial communities are equipped to metabolize thawed OC into CH4. We concurrently observed an increase in the relative abundance of reduced, saturated OC compounds, which corresponded to high proportions of C mineralization and positively correlated with anaerobic GHG production potentials and higher proportions of OC being mineralized as CH4. Taking into account the higher global warming potential (GWP) of CH4 compared to CO2, thawed yedoma sediments in our study had 2 times higher GWP at 12-versus 9.0-m depth at 3 degrees C and 15 times higher GWP at 13 degrees C. Considering that yedoma is vulnerable to processes that thaw deep OC, our findings imply that it is important to account for this increasing GHG production and GWP with depth to better understand the disproportionate impact of yedoma on the magnitude of the permafrost carbon feedback.
KW  - permafrost
KW  - carbon
KW  - yedoma
KW  - Alaska
KW  - FT-ICR MS
KW  - microbes
Y1  - 2019
U6  - https://doi.org/10.1029/2018JG004712
SN  - 2169-8953
SN  - 2169-8961
VL  - 124
IS  - 7
SP  - 2021
EP  - 2038
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Heinrich, Ingo
A1  - Balanzategui, Daniel
A1  - Bens, Oliver
A1  - Blasch, Gerald
A1  - Blume, Theresa
A1  - Boettcher, Falk
A1  - Borg, Erik
A1  - Brademann, Brian
A1  - Brauer, Achim
A1  - Conrad, Christopher
A1  - Dietze, Elisabeth
A1  - Dräger, Nadine
A1  - Fiener, Peter
A1  - Gerke, Horst H.
A1  - Güntner, Andreas
A1  - Heine, Iris
A1  - Helle, Gerhard
A1  - Herbrich, Marcus
A1  - Harfenmeister, Katharina
A1  - Heussner, Karl-Uwe
A1  - Hohmann, Christian
A1  - Itzerott, Sibylle
A1  - Jurasinski, Gerald
A1  - Kaiser, Knut
A1  - Kappler, Christoph
A1  - Koebsch, Franziska
A1  - Liebner, Susanne
A1  - Lischeid, Gunnar
A1  - Merz, Bruno
A1  - Missling, Klaus Dieter
A1  - Morgner, Markus
A1  - Pinkerneil, Sylvia
A1  - Plessen, Birgit
A1  - Raab, Thomas
A1  - Ruhtz, Thomas
A1  - Sachs, Torsten
A1  - Sommer, Michael
A1  - Spengler, Daniel
A1  - Stender, Vivien
A1  - Stüve, Peter
A1  - Wilken, Florian
T1  - Interdisciplinary Geo-ecological Research across Time Scales in the Northeast German Lowland Observatory (TERENO-NE)
JF  - Vadose zone journal
N2  - The Northeast German Lowland Observatory (TERENO-NE) was established to investigate the regional impact of climate and land use change. TERENO-NE focuses on the Northeast German lowlands, for which a high vulnerability has been determined due to increasing temperatures and decreasing amounts of precipitation projected for the coming decades. To facilitate in-depth evaluations of the effects of climate and land use changes and to separate the effects of natural and anthropogenic drivers in the region, six sites were chosen for comprehensive monitoring. In addition, at selected sites, geoarchives were used to substantially extend the instrumental records back in time. It is this combination of diverse disciplines working across different time scales that makes the observatory TERENO-NE a unique observation platform. We provide information about the general characteristics of the observatory and its six monitoring sites and present examples of interdisciplinary research activities at some of these sites. We also illustrate how monitoring improves process understanding, how remote sensing techniques are fine-tuned by the most comprehensive ground-truthing site DEMMIN, how soil erosion dynamics have evolved, how greenhouse gas monitoring of rewetted peatlands can reveal unexpected mechanisms, and how proxy data provides a long-term perspective of current ongoing changes.
Y1  - 2018
U6  - https://doi.org/10.2136/vzj2018.06.0116
SN  - 1539-1663
VL  - 17
IS  - 1
PB  - Soil Science Society of America
CY  - Madison
ER  - 
TY  - JOUR
A1  - Mitzscherling, Julia
A1  - Horn, Fabian
A1  - Winterfeld, Maria
A1  - Mahler, Linda
A1  - Kallmeyer, Jens
A1  - Overduin, Pier Paul
A1  - Schirrmeister, Lutz
A1  - Winkel, Matthias
A1  - Grigoriev, Mikhail N.
A1  - Wagner, Dirk
A1  - Liebner, Susanne
T1  - Microbial community composition and abundance after millennia of submarine permafrost warming
JF  - Biogeosciences
N2  - Warming of the Arctic led to an increase in permafrost temperatures by about 0.3 degrees C during the last decade. Permafrost warming is associated with increasing sediment water content, permeability, and diffusivity and could in the long term alter microbial community composition and abundance even before permafrost thaws. We studied the long-term effect (up to 2500 years) of submarine permafrost warming on microbial communities along an onshore-offshore transect on the Siberian Arctic Shelf displaying a natural temperature gradient of more than 10 degrees C. We analysed the in situ development of bacterial abundance and community composition through total cell counts (TCCs), quantitative PCR of bacterial gene abundance, and amplicon sequencing and correlated the microbial community data with temperature, pore water chemistry, and sediment physicochemical parameters. On timescales of centuries, permafrost warming coincided with an overall decreasing microbial abundance, whereas millennia after warming microbial abundance was similar to cold onshore permafrost. In addition, the dissolved organic carbon content of all cores was lowest in submarine permafrost after millennial-scale warming. Based on correlation analysis, TCC, unlike bacterial gene abundance, showed a significant rank-based negative correlation with increasing temperature, while bacterial gene copy numbers showed a strong negative correlation with salinity. Bacterial community composition correlated only weakly with temperature but strongly with the pore water stable isotopes delta O-18 and delta D, as well as with depth. The bacterial community showed substantial spatial variation and an overall dominance of Actinobacteria, Chloroflexi, Firmicutes, Gemmatimonadetes, and Proteobacteria, which are amongst the microbial taxa that were also found to be active in other frozen permafrost environments. We suggest that, millennia after permafrost warming by over 10 degrees C, microbial community composition and abundance show some indications for proliferation but mainly reflect the sedimentation history and paleoenvironment and not a direct effect through warming.
Y1  - 2019
U6  - https://doi.org/10.5194/bg-16-3941-2019
SN  - 1726-4170
SN  - 1726-4189
VL  - 16
IS  - 19
SP  - 3941
EP  - 3958
PB  - Copernicus
CY  - Göttingen
ER  -