ALBERT

Beschreibung: A terrestrial permafrost core from Buor Khaya in northern Siberia comprising deposits of Late Pleistocene to Early Holocene age has been investigated to characterize living and past microbial communities with respect to modern and paleoclimate environmental conditions, and to evaluate the potential of the organic matter (OM) for greenhouse gas generation. Microbial life markers - intact phospholipids and phospholipid fatty acids - are found throughout the entire core and indicate the presence of living microorganisms also in older permafrost deposits. Biomarkers for past microbial communities (branched and isoprenoid GDGT as well as archaeol) reveal links between increased past microbial activity and intervals of high OM accumulation accompanied by increased OM quality presumably caused by local periods of moister and warmer environmental conditions. Concentrations of acetate as an excellent substrate for methanogenesis are used to assess the OM quality with respect to microbial degradability for greenhouse gas production. For this purpose two acetate pools are determined: the pore-water acetate and OM bound acetate. Both depth profiles reveal similarities to the OM content and quality indicating a link between the amount of the stored OM and the potential to provide substrates for microbial greenhouse gas production. The data suggest that OM stored in the permafrost deposits is not much different in terms of OM quality than the fresh surface organic material. Considering the expected increase of permafrost thaw due to climate warming, this implies a potentially strong impact on greenhouse gas generation from permafrost areas in future with positive feedback on climate variation.

Beschreibung: The investigation of microbial ecosystems in permafrost sediments is an important approach to understand the role of microbial organic matter transformation in permafrost sediments for past and future climate changes, and is of high relevance in today’s geoscience research (Wagner, 2008) due to the current debate on the temperature vulnerability of permafrost deposits. Especially, the interplay between the organic substrate and the distribution of the living and past microbial communities in Late Pleistocene (Yedoma) and Holocene permafrost deposits, as well as the substrate potential of the organic matter stored in potentially thawing permafrost deposits are in the focus of the current study. Our investigation is part of the BMBF CarboPerm project an interdisciplinary Russian-German cooperation on the formation, turnover and release of carbon from Siberian permafrost landscapes. Sample material derived from terrestrial permafrost cores drilled at the coast of Bour Khaya in the North-Eastern Siberian Arctic. The gathered core material comprises Late Pleistocene to early Holocene deposits separated by an ice wedge. The microbial life markers (intact phospholipids, PLs) prove the presence of currently living microorganisms in the entire permafrost sequence and show the highest concentration in the uppermost sample indicating an abundant microbial life in the active layer. In comparison, the PL profile is strongly decreased in the underlying permafrost deposits. Nevertheless, the inventory of the Phospholipid fatty acids (PLFAs) suggests that the cell membrane temperature adaptation to cold environmental conditions is mainly regulated via the ratio between iso- and anteiso-fatty acids (FAs) as well as the ratio between saturated and unsaturated FAs. The surface samples show higher proportions of anteiso and unsaturated FAs (adaptation to cooler conditions), which might derive from the fact that surface layers are more affected from the harsh Siberian winter conditions than the deeper constantly cold permafrost deposits, where the above-ground temperature extremes are buffered due to the overlying deposits. Indeed within the deeper permafrost sequence the variations of the ratios are rather small, indicating adaptation to similar constantly cold temperature conditions. Other microbial markers (GDGTs), already partly degraded and, therefore, not indicating microbial life, reveal similarities with the TOC content and an increase especially in Late Pleistocene deposits. This suggests increased microbial life during intervals in the Late Pleistocene presumably caused by periods of moisture and temperature increased environments. Pore water analysis reveals the presence of low molecular weight organic acids (LMWOA) such as acetate, being excellent substrates for microbial metabolism. In the Late Pleistocene deposits below the ice wedge the substrate depth profiles show significant similarities to the TOC content. These points to a link between the organic matter and the LMWOA concentrations solved in the pore water and to the potential of those permafrost layers to provide substrates for microbial greenhouse gas production. In contrast, in the active layer the LMWOA concentrations are low, reflecting an active microbial turnover in the surface layers. Ester cleavage experiments on the residual organic matter resulted in the release of ester linked LMWOAs forming a potential substrate pool when released in future. These bound LMWOA profiles are even better correlated to the TOC content suggesting that the deeper permafrost deposits (older organic material)are not significantly different from those in the surface sediment (fresh organic material). Overall this indicates that the organic matter stored in the permafrost deposits and, therefore, removed from the surface carbon cycle is not much different in terms of organic matter quality than the fresh surface organic material. Considering the discussed increase of permafrost thawing, this might imply a strong impact on the generation of greenhouse gases from permafrost areas in future with its feedback on climate evolution. In a second and ongoing study, four terrestrial permafrost cores spanning from the Eemian interglacial into the Holocene form Bol’shoy Lyakhovsky Island are investigated with the focus on the differences and potential of the organic matter by comparing Eemian, Late Pleistocene and Holocene deposits. First results already reveal similar relations between the living and dead microbial communities with respect to the availability of free substrates, and the quality and amount of the total organic carbon. The results on the future potential of these deposits will also be presented.

Beschreibung: . In this study the organic matter (OM) in several permafrost cores from Bol´shoy Lyakhovsky Island in NE Siberia was investigated. In context of the observed global warming the aim was to evaluate the potential of freeze-locked OM from different depositional ages to act as a substrate provider for microbial production of greenhouse gases from thawing permafrost. To assess this potential, exemplarily the concentrations of free and bound acetate, which form an appropriate substrate for methanogenesis, are determined. The largest free (in pore water) and bound (organic matrix linked) acetate substrate pools are present in layers that cover interstadial MIS 3 and stadial MIS 4 Yedoma permafrost deposits. In contrast, deposits from the last interglacial MIS 5e (Eemian) contain only a small pool of substrates. The Holocene (MIS 1) deposits reveal a significant bound acetate pool, representing a future substrate potential upon release during OM degradation. Additionally, pyrolysis experiments on the OM allocate an increased aliphatic character to the MIS 3 and 4 Late Pleistocene deposits, which might indicate less decomposed and presumably better degradable OM. Biomarkers for past microbial communities including those for methanogenic archaea show also highest abundance during MIS 3 and 4, which indicates that the OM stimulated microbial degradation and presumably greenhouse gas production during time of deposition. On a broader perspective, Arctic warming will increase and deepen permafrost thaw and favour substrate availability from freeze-locked older permafrost deposits. Therefore, especially the Yedoma deposits show a high potential for providing substrates relevant for microbial greenhouse gas production

Beschreibung: The deep subseafloor biosphere contains two-thirds of Earth's prokaryotic biomass, which may indicate the presence of novel mechanisms of energy generation as temperatures increase in the subsurface. In sediment slurry experiments (0-100 {degrees}C) with a range of common minerals and rocks (including basalt and quartz), there is significant H2 formation at elevated temperatures, but only in the presence of prokaryotes. This stimulates further prokaryotic activity, typical of deep sediments (sulfate reduction, acetogenesis, and CO2 production, plus continuing methanogenesis), and Bacteria and Archaea representative of many deep sediment types develop. H2 and acetate formation is particularly stimulated above 70 {degrees}C. This prokaryotic activity even enhances reactions when temperatures are raised to thermogenic levels ([~]125-155 {degrees}C), including hydrocarbon generation. Mechanochemistry may be important for mineral H2 formation; this is enhanced by prokaryotes (biomechanochemistry), and subsurface stress and fracturing, which is widespread on Earth.

Beschreibung: The origin of the immense oil sand deposits in Lower Cretaceous reservoirs of the Western Canada sedimentary basin is still a matter of debate, specifically with respect to the original in-place volumes and contributing source rocks. In this study, the contributions from the main source rocks were addressed using a three-dimensional petroleum system model calibrated to well data. A sensitivity analysis of source rock definition was performed in the case of the two main contributors, which are the Lower Jurassic Gordondale Member of the Fernie Group and the Upper Devonian–Lower Mississippian Exshaw Formation. This sensitivity analysis included variations of assigned total organic carbon and hydrogen index for both source intervals, and in the case of the Exshaw Formation, variations of thickness in areas beneath the Rocky Mountains were also considered. All of the modeled source rocks reached the early or main oil generation stages by 60 Ma, before the onset of the Laramide orogeny. Reconstructed oil accumulations were initially modest because of limited trapping efficiency. This was improved by defining lateral stratigraphic seals within the carrier system. An additional sealing effect by biodegraded oil may have hindered the migration of petroleum in the northern areas, but not to the east of Athabasca. In the latter case, the main trapping controls are dominantly stratigraphic and structural. Our model, based on available data, identifies the Gordondale source rock as the contributor of more than 54% of the oil in the Athabasca and Peace River accumulations, followed by minor amounts from Exshaw (15%) and other Devonian to Lower Jurassic source rocks. The proposed strong contribution of petroleum from the Exshaw Formation source rock to the Athabasca oil sands is only reproduced by assuming 25 m (82 ft) of mature Exshaw in the kitchen areas, with original total organic carbon of 9% or more.