Methane emissions from an alpine fen in central Switzerland

Methane emissions and below ground methane pore water concentrations were determined in an alpine fen at 1,915m a.s.l. in central Switzerland. The fen represented an acidic (pH 4.5-4.9), nutrient-poor to mesotrophic habitat dominated by Carex limosa, Carex rostrata, Trichophorum caespitosum and Sphagnum species. From late fall to late spring the fen was snow-covered. Throughout winter the temperatures never dropped below 0°C at 5cm below the vegetation surface. Methane emissions in June, July, August and September were in the range of 125 (±26)-313 (±71)mgCH4m−2day−1 with a tendency to decrease along the summer season. Mean methane pore water concentrations at a depth of 20-40cm below the vegetation surface were 526 (±32)μM in June and in the range of 144 (±10)-233 (±7)μM in July, August and September. At a depth of 0-20cm the mean methane pore water concentrations dropped back to <20μM with an almost linear decrease between 0 and 15cm. Oxygen pore water concentrations were close to air saturation in the first few centimeters and dropped back below detection limit at a depth of 20cm. In July and August the pore water concentrations of dissolved organic carbon (DOC) were in the range of 7.2-10.1mgCl−1 at all depths. The pore water concentrations of acetate, formate and oxalate were in the range of 2.0-8.2μM at all depths. Methanotrophic and methanogenic communities were quantified using pmoA and mcrA, respectively, as marker genes. The abundances of both communities showed a distinct peak at a depth of 10-15cm below the vegetation surfac

Adaptation, spatial variability, and phylogenetic characterization of methanotrophic communities in permafrost soils of the Lena Delta, Siberia

This work was integrated into the Russian-German joint venture project System Laptev Sea 2000. The focus of this project was to extent our knowledge about the Laptev Sea system in north-east Siberia obtained through previous Russian-German projects, such as the Laptev Sea System (1994-1997), and Taymyr (1994-1997). Studies on Quaternary environmental changes, Arctic coastal dynamics and recent periglacial processes including ecological studies on permafrost soils and ecosystems of the central Lena Delta were in the focus of the recent project (Schirrmeister et al., 2004). The present work contributes to the last aspect by investigating the field of methane fluxes in polygonal tundra environments of the Lena Delta. Field work and sampling of this study was conducted during the expeditions LENA 2002 and LENA 2005 (Samoylov Island, Lena Delta, Siberia) with a personal participation in the last expedition. The work was performed in the frame of the International Max Planck Research School for Marine Microbiology (MarMic) mainly at the Alfred Wegener Institute for Polar and Marine Research, Research Unit Potsdam. Some analyses were conducted at the Max Planck Institute for Marine Microbiology in Bremen. This study is presented in English as a cumulative Ph.D. thesis at the University of Bremen (Fachbereich 02). The thesis consists of a general introduction to the particular research field including the scientific background as well as aims and objectives of this study. The study area is described in an extra chapter. The main part of this thesis consists of three manuscripts with first authorship and a final synthesis representing the conclusions as well as critical remarks and future prospects of this work

Carbon Stocks and Potential Greenhouse Gas Production of Permafrost-Affected Active Floodplains in the Lena River Delta

Arctic warming increases the degradation of permafrost soils but little is known about floodplain soils in the permafrost region. This study quantifies soil organic carbon (SOC) and soil nitrogen stocks, and the potential CH4 and CO2 production from seven cores in the active floodplains in the Lena River Delta, Russia. The soils were sandy but highly heterogeneous, containing deep, organic rich deposits with >60% SOC stored below 30 cm. The mean SOC stocks in the top 1 m were 12.9 ± 6.0 kg C m−2. Grain size analysis and radiocarbon ages indicated highly dynamic environments with sediment re-working. Potential CH4 and CO2 production from active floodplains was assessed using a 1-year incubation at 20°C under aerobic and anaerobic conditions. Cumulative aerobic CO2 production mineralized a mean 4.6 ± 2.8% of initial SOC. The mean cumulative aerobic:anaerobic C production ratio was 2.3 ± 0.9. Anaerobic CH4 production comprised 50 ± 9% of anaerobic C mineralization; rates were comparable or exceeded those for permafrost region organic soils. Potential C production from the incubations was correlated with total organic carbon and varied strongly over space (among cores) and depth (active layer vs. permafrost). This study provides valuable information on the carbon cycle dynamics from active floodplains in the Lena River Delta and highlights the key spatial variability, both among sites and with depth, and the need to include these dynamic permafrost environments in future estimates of the permafrost carbon-climate feedback

Microbial nitrogen cycling in permafrost soils: implications for atmospheric chemistry

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Willingness of farmers to pay for reclaimed wastewater in Jordan and Tunisia.

Despite water scarcity and high agricultural water consumption in the Middle East and North Africa region, substantial amounts of treated wastewater are discharged into seas without proper utilization. This can be attributed to either farmers' unwillingness to use or to pay for reclaimed wastewater. Therefore, a field survey was conducted in Jordan and Tunisia, which are considered as representative to the MENA region, using a prepared and pilot tested questionnaire. This study applies the contingent valuation method to elicit the willingness of farmers to pay for reclaimed wastewater. Logistic regression analysis is applied in an attempt to build a model that correlates qualitative responses of farmers to monetary stimuli. The water price seriously affects farming profitability and farmers' willingness to pay for reclaimed wastewater. Farmers prove to be unwilling to pay more than 0.05 $/m3 of reclaimed wastewater primarily because of quality concerns, comparatively easy access to freshwater, and price

Carbon degradation and potential greenhouse gas production in a changing Arctic thermokarst landscape

Permafrost carbon pools are vulnerable to a warming climate and bear the potential to alter the terrestrial carbon cycle. In the extensive drained lake basins that span across Arctic lowlands, enhanced degradation of organic-rich deposits upon permafrost thaw could lead to greenhouse gas emissions to the atmosphere. Yet, little is known on the geochemical properties of the sediments in these basins and on the rate of release of greenhouse gases. This study investigates processes and intensity of organic matter decomposition and associated potential greenhouse gas production in thawed sediment from drained lake basins on the Yukon Coastal Plain in the western Canadian Arctic. We conducted a three-month low temperature (4 °C) incubation experiment, during which we measured carbon dioxide (CO2) and methane (CH4) production in thawed sediment from two permafrost cores from adjacent drained lake basins. To simulate current and near future greenhouse gas production potential we incubated material from the active layer as well as from the transition layer and permafrost to account for projected active layer deepening. Four replicates of each sample were incubated under aerobic and anaerobic conditions, respectively. CO2 and CH4 concentrations were measured by gas chromatography. The experiment was supplemented by a comprehensive lipid biomarker analysis of the same sample material before and after the incubation covering n-alkanes, n-fatty acids, triterpenoids and hopanes. Biomarker concentrations and indices (average chain length, carbon preference index, higher-plant fatty acid index) gave insights on the origin and degradation state of organic matter as well as changes to carbon accompanying the incubation experiment. In a multi-proxy approach, findings are further aligned with biogeochemical and sedimentological parameters. Results will reveal organic matter vulnerability to decomposition and potential greenhouse gas production in sediments after thawing, both of which are key elements in assessing future trajectories of carbon dynamics in drained lake basins

Unveiling Permafrost Transformations: Investigating Organic Carbon Characteristics and Dynamics in Alaskan Lowland Landscapes

Lowland permafrost landscapes are experiencing dramatic changes as the climate in the Arctic has been warming almost four times the rate of the global average in the past four decades. On the Alaskan North Slope, extensive thermokarst processes are steering the dynamics of lakes and drained lake basins (DLBs). With progressing climate change, re-aggradation of permafrost in DLBs becomes potentially impeded. Additionally, along the Beaufort Sea coast, thaw-induced destabilization is causing substantial erosion, exposing previously frozen terrestrial deposits to the marine environment. The consequences for the biogeochemical system, which holds significant amounts of organic carbon, remain understudied. Therefore, we aim to investigate the carbon pool characteristics in thermokarst terrain close to Utqiaġvik. Sediment cores were sampled in 2022 and include two thermokarst lakes, one DLB and one undisturbed upland core. While West Twin Lake has freshwater conditions, East Twin Lake exhibits brackish water. The up to 2 m long sediment cores are investigated with a multidisciplinary approach. Bio- and hydrochemical analyses offer a detailed understanding of the current carbon pool properties. Additionally, n-alkane biomarker analyses, accompanied by carbon isotopy and the C/N ratio, serve as proxies to characterize the degradation state of organic carbon and its changes post permafrost thaw. Initial findings on carbon quantity and quality are presented, along with preliminary results from a 12-month-long incubation experiment. In this experiment, carbon dioxide and methane production rates are measured at ten depths along the sediment cores. The outcomes of this study contribute to a more comprehensive understanding of organic carbon degradation and its implications for the future carbon pool at a landform-specific level

Relationships between greenhouse gas production and landscape position during short-term permafrost thaw under anaerobic conditions in the Lena Delta

Soils in the permafrost region have acted as car- bon sinks for thousands of years. As a result of global warming, permafrost soils are thawing and will potentially release greenhouse gases (GHGs) such as methane (CH4) and carbon dioxide (CO2). However, small-scale spatial heterogeneities of GHG production have been neglected in previous incubation studies. Here, we used an anaerobic incubation experiment to simulate permafrost thaw along a transect from upland Yedoma to the floodplain on Kurungnakh Island. Potential CO2 and CH4 production was measured during incubation of the active layer and permafrost soils at 4 and 20 ◦C, first for 60 d (approximate length of the growing season) and then continuing for 1 year. An assessment of methanogen abundance was performed in parallel for the first 60 d. Yedoma samples from upland and slope cores remained in a lag phase during the growing season simulation, while those located in the floodplain showed high production of CH4 (6.5 × 103 μg CH4-C g−1 C) and CO2 (6.9 × 103 μg CO2-C g−1 C) at 20 ◦C. The Yedoma samples from the permafrost layer started producing CH4 after 6 months of incubation. We conclude that landscape position is a key factor triggering CH4 production during the growing season time on Kurungnakh Island

Shifts in methanogenic community composition and methane fluxes along the degradation of discontinuous permafrost

Published version. Also available at http://dx.doi.org/10.3389/fmicb.2015.00356The response of methanogens to thawing permafrost is an important factor for the global greenhouse gas budget. We tracked methanogenic community structure, activity, and abundance along the degradation of sub-Arctic palsa peatland permafrost. We observed the development of pronounced methane production, release, and abundance of functional (mcrA) methanogenic gene numbers following the transitions from permafrost (palsa) to thaw pond structures. This was associated with the establishment of a methanogenic community consisting both of hydrogenotrophic (Methanobacterium, Methanocellales), and potential acetoclastic (Methanosarcina) members and their activity. While peat bog development was not reflected in significant changes of mcrA copy numbers, potential methane production, and rates of methane release decreased. This was primarily linked to a decline of potential acetoclastic in favor of hydrogenotrophic methanogens. Although palsa peatland succession offers similarities with typical transitions from fen to bog ecosystems, the observed dynamics in methane fluxes and methanogenic communities are primarily attributed to changes within the dominant Bryophyta and Cyperaceae taxa rather than to changes in peat moss and sedge coverage, pH and nutrient regime. Overall, the palsa peatland methanogenic community was characterized by a few dominant operational taxonomic units (OTUs). These OTUs seem to be indicative for methanogenic species that thrive in terrestrial organic rich environments. In summary, our study shows that after an initial stage of high methane emissions following permafrost thaw, methane fluxes, and methanogenic communities establish that are typical for northern peat bogs