n-Fatty acid composition per sediment mass in 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 2022
• Subjects: Biomarker; Carbon; erosion; n-alkane; n-fatty acids; Siberia; Yedoma; Event label; Sample ID; Height; 3-hydroxyl-fatty acid C60; n-fatty acid C80; 3-hydroxyl-fatty acid C70; n-fatty acid C90; 3-hydroxyl-fatty acid C80; iso-fatty acid C100; n-fatty acid C100; iso-fatty acid C110; anteiso-fatty acid C110; n-fatty acid C110; anteiso-fatty acid C120; n-fatty acid C120; iso-fatty acid C130; anteiso-fatty acid C130; n-fatty acid C130; iso-fatty acid C140; n-fatty acid C140; 10-methyl-fatty acid C140; iso-fatty acid C150; anteiso-fatty acid C150; n-fatty acid C150; iso-fatty acid C160; fatty acid C161w7cis; fatty acid C161w7trans; fatty acid C161w5; n-fatty acid C160; iso-fatty acid C171; 10-methyl-fatty acid C160; 12-methyl-fatty acid C160; anteiso-fatty acid C171; methyl-fatty acid C160; iso-fatty acid C170; anteiso-fatty acid C170; n-fatty acid C171; cyclo-fatty acid C17; n-fatty acid C170; 10-methyl-fatty acid C170; methyl-fatty acid C170; Phytanoic acid; iso-fatty acid C180; fatty acid C182w6,9; fatty acid C181w9; n-fatty acid C183; fatty acid C181w7cis; fatty acid C181w7trans; n-fatty acid C180; 10-methyl-fatty acid C180; 12-methyl-fatty acid C180; iso-fatty acid C190; cyclo-fatty acid C19; n-fatty acid C191; n-fatty acid C190; n-fatty acid C201; n-fatty acid C200; n-fatty acid C210; Standard deviation; n-fatty acid C220; n-fatty acid C230; n-fatty acid C241; n-fatty acid C240; n-fatty acid C250; n-fatty acid C260; n-fatty acid C270; n-fatty acid C280; n-fatty acid C290; n-fatty acid C300; Stigmastenone; n-fatty acid C320; 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.940135; https://doi.pangaea.de/10.1594/PANGAEA.940135

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.