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

• Main Authors: Haugk, Charlotte, Jongejans, Loeka Laura, Mangelsdorf, Kai, Fuchs, Matthias, Ogneva, Olga, Palmtag, Juri, Mollenhauer, Gesine, Mann, Paul James, Overduin, Pier Paul, Grosse, Guido, Sanders, Tina, Tuerena, Robyn, Schirrmeister, Lutz, Wetterich, Sebastian, Kizyakov, Alexander, Strauss, Jens
• Format: Dataset
• Language: English
• Published: PANGAEA - Data Publisher for Earth & Environmental Science 2021
• Subjects: Biomarker; Carbon; erosion; n-alkane; n-fatty acids; Siberia; Yedoma; Event label; Sample ID; Height; Lithologic unit/sequence; AGE; Carbon, organic, total; Nitrogen, total; Carbon/Nitrogen ratio; δ13C, organic matter; Sum n-alkanes C14-C35, per unit sediment mass; Sum n-alkanes C14-C35, per unit mass total organic carbon; n-Alkanes, short-chain per unit sediment mass; n-Alkanes, short-chain per unit mass total organic carbon; n-Alkanes, long-chain per unit sediment mass; n-Alkanes, long-chain per unit mass total organic carbon; n-Alkane, average chain length; Carbon Preference Index, n-Alkanes; n-fatty acids, per unit sediment mass; n-fatty acids, per unit mass total organic carbon; n-fatty acids, short-chain per unit sediment mass; n-fatty acids, short-chain per unit mass total organic carbon; n-fatty acids, C21-C23, per unit sediment mass; n-fatty acids, C21-C23, per unit mass total organic carbon; n-fatty acids, long-chain per unit sediment mass; n-fatty acids, long-chain per unit mass total organic carbon; Higher plant n-fatty acids, per unit sediment mass; Ratio; Sampling permafrost; RU-Land_2018_Lena_Sobo-Sise; AWI Arctic Land Expedition; Changing Arctic Carbon cycle in the cOastal Ocean Near-shore CACOON; Arctic; lena river; permafrost
• Online Access: https://dx.doi.org/10.1594/pangaea.935671; https://doi.pangaea.de/10.1594/PANGAEA.935671

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 are still poorly quantified. 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 ka. We show that the ancient permafrost exposed in the Sobo-Sise cliff has a high organic carbon content (mean of about 5 wt%).We found that the OM quality, which we define as the intrinsic potential to further transformation, decomposition, and mineralization, is also high as inferred by the lipid biomarker inventory. The oldest sediments stem from Marine Isotope Stage (MIS) 3 interstadial deposits (dated to 52 to 28 cal kyr BP) and is 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 FAs relative to 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 of HPFA values downwards along the profile probably indicates a relatively stronger OM decomposition in the oldest (MIS 3) deposits of the cliff.