From Pleistocene Permafrost to Lena River Water – Organic Matter Characteristics using Biomarker Analysis and Isotope Hydrochemistry

Organic matter stored in permafrost represents one of the largest global carbon pools that are especially vulnerable due to its susceptibility to thaw and mobilisation caused by climate warming across the Arctic. However, the amount and quality of the stored carbon (C) and nitrogen (N) as well as its composition during river transit is largely unknown. The purpose of this master’s thesis is to characterize and define the source and fate of riverine C and N from the delta interior to the nearshore zone and its possible effect on primary productivity in Arctic coastal waters using a multi-proxy approach. Organic matter quality and degradation state of a rapidly degrading yedoma cliff in the central Lena Delta (Sobo Sise Island) was analyzed using lipid biomarker analysis. To grasp the winter thaw impact, a transect of water samples from the cliff going seawards were primarily investigated for N species and stable isotope composition using a hydrochemical approach. Laboratory analyses showed an overall high organic matter quality and a low degradation state in yedoma deposits which suggests freeze-locking immediately after deposition. While the dominant winter water source was attributed mainly to subsurface permafrost flow, it was found that dissolved organic nitrogen (DON) rather than nitrate is the main N species to be released into the riverine environment and was susceptible to alteration by remineralization and denitrification. Describing organic matter associated with thawing permafrost at the terrestrial-marine interface in a season-explicit study leads to a better understanding of C and N dynamics and thus the effects of a warming climate in Arctic environments

Organic matter characteristics of a rapidly eroding permafrost cliff in NE Siberia (Lena Delta, Laptev Sea region)

Organic carbon (OC) stored in Arctic permafrost represents one of Earth’s largest and most vulnerable terrestrial carbon pools. Amplified climate warming across the Arctic results in widespread permafrost thaw. Permafrost deposits exposed at river cliffs and coasts are particularly susceptible to thawing processes. Accelerating erosion of terrestrial permafrost along shorelines leads to increased transfer of organic matter (OM) to nearshore waters. However, the amount of terrestrial permafrost carbon and nitrogen as well as the OM quality in these deposits is still poorly quantified. We define the OM quality as the intrinsic potential for further transformation, decomposition and mineralisation. Here, we characterise the sources and the quality of OM supplied to the Lena River at a rapidly eroding permafrost river shoreline cliff in the eastern part of the delta (Sobo-Sise Island). Our multi-proxy approach captures bulk elemental, molecular geochemical and carbon isotopic analyses of Late Pleistocene Yedoma permafrost and Holocene cover deposits, discontinuously spanning the last ~52 kyr. We showed that the ancient permafrost exposed in the Sobo-Sise cliff has a high organic carbon content (mean of about 5 wt %). The oldest sediments stem from Marine Isotope Stage (MIS) 3 interstadial deposits (dated to 52 to 28 cal ka BP) and are overlaid by last glacial MIS 2 (dated to 28 to 15 cal ka BP) and Holocene MIS 1 (dated to 7–0 cal ka BP) deposits. The relatively high average chain length (ACL) index of n-alkanes along the cliff profile indicates a predominant contribution of vascular plants to the OM composition. The elevated ratio of iso and anteiso-branched fatty acids (FAs) relative to mid- and long-chain (C�20) n-FAs in the interstadial MIS 3 and the interglacial MIS 1 deposits suggests stronger microbial activity and consequently higher input of bacterial biomass during these climatically warmer periods. The overall high carbon preference index (CPI) and higher plant fatty acid (HPFA) values as well as high C=N ratios point to a good quality of the preserved OM and thus to a high potential of the OM for decomposition upon thaw. A decrease in HPFA values downwards along the profile probably indicates stronger OM decomposition in the oldest (MIS 3) deposits of the cliff. The characterisation of OM from eroding permafrost leads to a better assessment of the greenhouse gas potential of the OC released into river and nearshore waters in the future

Seasonal nitrogen fluxes of the Lena River Delta

The Arctic is nutrient limited, particularly by nitrogen, and is impacted by anthropogenic global warming which occurs approximately twice as fast compared to the global average. Arctic warming intensifies thawing of permafrost-affected soils releasing their large organic nitrogen reservoir. This organic nitrogen reaches hydrological systems, is remineralized to reactive inorganic nitrogen, and is transported to the Arctic Ocean via large rivers. We estimate the load of nitrogen supplied from terrestrial sources into the Arctic Ocean by sampling in the Lena River and its Delta. We took water samples along one of the major deltaic channels in winter and summer in 2019 and sampling station in the central delta over a one-year cycle. Additionally, we investigate the potential release of reactive nitrogen, including nitrous oxide from soils in the Delta. We found that the Lena transported nitrogen as dissolved organic nitrogen to the coastal Arctic Ocean and that eroded soils are sources of reactive inorganic nitrogen such as ammonium and nitrate. The Lena and the Deltaic region apparently are considerable sources of nitrogen to nearshore coastal zone. The potential higher availability of inorganic nitrogen might be a source to enhance nitrous oxide emissions from terrestrial and aquatic sources to the atmosphere

Drug-induced mild therapeutic hypothermia obtained by administration of a transient receptor potential vanilloid type 1 agonist

<p>Abstract</p> <p>Background</p> <p>The use of mechanical/physical devices for applying mild therapeutic hypothermia is the only proven neuroprotective treatment for survivors of out of hospital cardiac arrest. However, this type of therapy is cumbersome and associated with several side-effects. We investigated the feasibility of using a transient receptor potential vanilloid type 1 (TRPV1) agonist for obtaining drug-induced sustainable mild hypothermia.</p> <p>Methods</p> <p>First, we screened a heterogeneous group of TRPV1 agonists and secondly we tested the hypothermic properties of a selected candidate by dose-response studies. Finally we tested the hypothermic properties in a large animal. The screening was in conscious rats, the dose-response experiments in conscious rats and in cynomologus monkeys, and the finally we tested the hypothermic properties in conscious young cattle (calves with a body weight as an adult human). The investigated TRPV1 agonists were administered by continuous intravenous infusion.</p> <p>Results</p> <p>Screening: Dihydrocapsaicin (DHC), a component of chili pepper, displayed a desirable hypothermic profile with regards to the duration, depth and control in conscious rats. Dose-response experiments: In both rats and cynomologus monkeys DHC caused a dose-dependent and immediate decrease in body temperature. Thus in rats, infusion of DHC at doses of 0.125, 0.25, 0.50, and 0.75 mg/kg/h caused a maximal ΔT (°C) as compared to vehicle control of -0.9, -1.5, -2.0, and -4.2 within approximately 1 hour until the 6 hour infusion was stopped. Finally, in calves the intravenous infusion of DHC was able to maintain mild hypothermia with ΔT > -3°C for more than 12 hours.</p> <p>Conclusions</p> <p>Our data support the hypothesis that infusion of dihydrocapsaicin is a candidate for testing as a primary or adjunct method of inducing and maintaining therapeutic hypothermia.</p

Organic matter characteristics: From Pleistocene permafrost to Lena river water

Climate change will enhance the release of organic and inorganic compounds such as carbon (C) and nitrogen (N) via increased permafrost thawing and river runoff in the Arctic. However, the amount of C and N as well as its composition during runoff is largely unknown. Our study aims to characterize and define the source and fate of riverine C and N and its effect on primary productivity in Arctic coastal waters. In order to assess the alteration of the erosion signal from land to sea, we analyzed a fastly degrading permafrost cliff in the Lena River delta (Sobo Sise Island). Furthermore, we collected Lena river water samples from 13 locations (CACOON on Ice Expedition, spring 2019) between the Sobo Sise Cliff and the coast. 28 permafrost samples were analyzed for terrestrial parameters (grain size, total organic carbon, stable isotopes and lipid biomarkers. In order to analyze the thaw impact on Lena river water, we used a hydrochemical approach to determine DON, TDN and respective isotope analysis of the water samples. Describing organic matter fluxes and characteristics will lead to a better understanding of the nutrient load associated with permafrost thaw, and thus warming climate in Arctic environments

Assessing the dynamic interface between land and ocean in the Arctic: results from the joint BMBF-NERC project Changing Arctic organic Carbon cycle in the cOastal Ocean Near-shore (CACOON)

No other region has warmed as rapidly in the past decades as the Arctic. Funded by the British Natural Environment Research Council (NERC) and the German Federal Ministry of Education and Research (BMBF), the Changing Arctic Carbon cycle in the Coastal Ocean Near-shore (CACOON) project investigates how this warming influences Arctic coastal-marine ecosystems. Arctic rivers annually carry around 13% of the globally transported dissolved organic carbon (despite the Arctic Ocean making up only approx. 1% of the Earth's ocean volume). Arctic shelf waters are therefore dominated by terrestrial organic carbon pools, so that shelf ecosystems are intimately linked to freshwater supplies. Arctic ecosystems also contain permafrost organic carbon that may be released with warming. Climate change already thaws permafrost, reduces sea ice and increases riverine discharge, triggering important feedbacks. The importance of the near-shore region, consisting of several tightly connected ecosystems that include rivers, deltas, and the shelf, is however often overlooked. Year-round studies are scarce but needed to predict the impact of shifting seasonality, fresher water, changing nutrient supply and greater proportions of permafrost-derived organic carbon on coastal waters. The aims of the CACOON project are to quantify the effect of changing freshwater export and permafrost thaw on the type and fate of river-borne organic matter (OM) delivered to the Arctic shore and resulting changes on ecosystem functioning in the coastal Arctic Ocean. We are achieving this through a combined observational, experimental, and modelling approach. We conduct laboratory experiments to parameterise the susceptibility of terrigenous organic carbon to abiotic and biotic transformation and losses, then use the results from these to deliver a marine ecosystem model capable of representing major biogeochemical cycles. We apply this model to assess how future changes to freshwater runoff and carbon fluxes alter the ecosystems. To reach these aims, we conducted 4 field campaigns in 2019 in the Lena (see https://epic.awi.de/id/eprint/53575/) and Kolyma Delta region. In the Lena Delta, during spring we were using a mobile camp on sledges to collect water samples, ice cores, surface sediments, gas samples as well as CTD profiles. A permafrost cliff (Sobo-Sise) was sampled to analyse terrestrial endmembers of organic matter entering the deltaic and eventually marine system following erosion and transport. During the summer campaign we retrieved samples along a 200 km transect from the centre of the Delta to the Laptev Sea covering the fresh-salt water transition. The aim of Kolyma field sampling was to capture the open water season from the ice breakup to re-freezing and sample the Kolyma River and the near shore area. The lab work on these samples is currently ongoing with first papers lead by CACOON or with project contributions being published already (available here: https://www.researchgate.net/project/CACOON-Changing-Arctic-Carbon-cycle-in-the-coastal-ocean-near-shore)

Changing Arctic Carbon cycle in the Coastal Ocean Near-shore (CACOON): a project focussing on the dynamic interface between land and ocean in the Arctic

No other region has warmed as rapidly in the past decades as the Arctic. Funded by the British Natural Environment Research Council and the German Federal Ministry of Education and Research, the CACOON project investigates how this warming influences Arctic coastal-marine ecosystems. Arctic rivers annually carry around 13% of the globally transported dissolved organic carbon (despite the Arctic Ocean making up only approx. 1% of the Earth's ocean volume). Arctic shelf waters are therefore dominated by terrestrial carbon pools, so that shelf ecosystems are intimately linked to freshwater supplies. Arctic ecosystems also contain permafrost carbon that may be released with warming. Climate change already thaws permafrost, reduces sea-ice and increases riverine discharge, triggering important feedbacks. The importance of the near-shore region, consisting of several tightly connected ecosystems that include rivers, deltas and the shelf, is however often overlooked. Year-round studies are scarce but needed to predict the impact of shifting seasonality, fresher water, changing nutrient supply and greater proportions of permafrost-derived carbon on coastal waters. The aims of the CACOON project are to quantify the effect of changing freshwater export and permafrost thaw on the type and fate of river-borne organic matter (OM) delivered to Arctic shore, and resulting changes on ecosystem functioning in the coastal Arctic Ocean. We are achieving this through a combined observational, experimental and modelling approach. We conduct laboratory experiments to parameterise the susceptibility of terrigenous carbon to abiotic and biotic transformation and losses, then use the results from these to deliver a marine ecosystem model capable of representing major biogeochemical cycles. We apply this model to assess how future changes to freshwater runoff and carbon fluxes alter the ecosystems. To reach these aims we conducted 4 field campaigns in 2019 in the Lena and Kolyma delta region. In the Lena Delta we were using a mobile camp on sledges to collect water samples, ice cores, surface sediments, gas samples as well as CTD profiles. A permafrost cliff (Sobo-Sise) was sampled to analyse terrestrial endmembers of organic matter entering the deltaic and eventually marine system following erosion and transport. During the summer campaign we retrieved samples along a 200 km transect from the centre of the delta to the Laptev Sea covering the fresh-salt water transition. The aim of Kolyma field sampling was to capture the open water season from the ice breakup to re-freezing and sample the Kolyma River and the near shore area. The lab work on these samples is currently ongoing

n-Alkane composition of organic matter in a rapidly eroding permafrost cliff

Organic matter stored in Arctic permafrost represents one of Earth's largest and most vulnerable terrestrial carbon pools. Amplified climate warming across the Arctic results in widespread permafrost thaw. Permafrost deposits exposed at river cliffs and coastlines are particularly susceptible to degradation. Accelerating erosion of terrestrial permafrost along shorelines leads to increased mobilization of organic matter to nearshore waters. However, the amount and quality of terrestrial permafrost carbon (C) (as well as nitrogen, N) in these deposits are poorly known. Here, we characterize the organic matter sources of C and N supplied to the Lena River at a rapidly eroded permafrost river cliff (Sobo-Sise Island) by a multi-proxy approach (sedimentological and lipid biomarker characteristics). We showed that Yedoma permafrost on Sobo-Sise Island has a high organic C content (5.13 wt%) as well as high organic matter quality with a relatively low degradation state (mean carbon preference index: 9.89). The lower part (0-16 m) of the cliff shows a slightly more decomposed signature, but overall, the analyses suggest that organic matter did not decompose considerably before being frozen into permafrost. Characterising organic matter associated with thawing permafrost leads to a better understanding of the C and N input into river and nearshore waters, which is important to assess the consequences of a warming climate in Arctic environments

Organic matter characteristics using lipid biomarker analysis of a rapidly eroding permafrost cliff

Organic matter stored in Arctic permafrost represents one of Earth's largest and most vulnerable terrestrial carbon pools. Amplified climate warming across the Arctic results in widespread permafrost thaw. Permafrost deposits exposed at river cliffs and coastlines are particularly susceptible to degradation. Accelerating erosion of terrestrial permafrost along shorelines leads to increased mobilization of organic matter to nearshore waters. However, the amount and quality of terrestrial permafrost carbon (C) (as well as nitrogen, N) in these deposits are poorly known. Here, we characterize the organic matter sources of C and N supplied to the Lena River at a rapidly eroded permafrost river cliff (Sobo-Sise Island) by a multi-proxy approach (sedimentological and lipid biomarker characteristics). We showed that Yedoma permafrost on Sobo-Sise Island has a high organic C content (5.13 wt%) as well as high organic matter quality with a relatively low degradation state (mean carbon preference index: 9.89). The lower part (0-16 m) of the cliff shows a slightly more decomposed signature, but overall, the analyses suggest that organic matter did not decompose considerably before being frozen into permafrost. Characterising organic matter associated with thawing permafrost leads to a better understanding of the C and N input into river and nearshore waters, which is important to assess the consequences of a warming climate in Arctic environments