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Carbon isotopes and lipid biomarker investigation of sources, transport and degradation of terrestrial organic matter in the Buor-Khaya Bay, SE Laptev Sea
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2011 (English)In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 8Article in journal (Refereed) Published
Abstract [en]

The world's largest continental shelf, the East Siberian Shelf Sea, receives substantial input of terrestrial organic carbon (terr-OC) from both large rivers and erosion of its coastline. Degradation of organic matter from thawing permafrost in the Arctic is likely to increase, potentially creating a positive feedback mechanism to climate warming. This study focuses on the Buor-Khaya Bay (SE Laptev Sea), an area with strong terr-OC input from both coastal erosion and the Lena river. To better understand the fate of this terr-OC, molecular (acyl lipid biomarkers) and isotopic tools (stable carbon and radiocarbon isotopes) have been applied to both particulate organic carbon (POC) in surface water and sedimentary organic carbon (SOC) collected from the underlying surface sediments. Clear gradients in both extent of degradation and differences in source contributions were observed both between surface water POC and surface sediment SOC as well as over the 100 s km investigation scale (about 20 stations). Depleted delta C-13-OC and high HMW/LMW n-alkane ratios signaled that terr-OC was dominating over marine/planktonic sources. Despite a shallow water column (10-40 m), the isotopic shift between SOC and POC varied systematically from +2 to +5 per mil for delta C-13 and from +300 to +450 for Delta C-14 from the Lena prodelta to the Buor-Khaya Cape. At the same time, the ratio of HMW n-alkanoic acids to HMW n-alkanes as well as HMW n-alkane CPI, both indicative of degradation, were 5-6 times greater in SOC than in POC. This suggests that terr-OC was substantially older yet less degraded in the surface sediment than in the surface waters. This unusual vertical degradation trend was only recently found also for the central East Siberian Sea. Numerical modeling (Monte Carlo simulations) with delta C-13 and Delta C-14 in both POC and SOC was applied to deduce the relative contribution of - plankton OC, surface soil layer OC and yedoma/mineral soil OC. This three end-member dual-carbon-isotopic mixing model suggests quite different scenarios for the POC vs SOC. Surface soil is dominating (63 +/- 10 %) the suspended organic matter in the surface water of SE Laptev Sea. In contrast, the yedoma/mineral soil OC is accounting for 60 +/- 9% of the SOC. We hypothesize that yedoma-OC, associated with mineral-rich matter from coastal erosion is ballasted and thus quickly settles to the bottom. The mineral association may also explain the greater resistance to degradation of this terr-OC component. In contrast, more amorphous humic-like and low-density terr-OC from surface soil and recent vegetation represents a younger but more bioavailable and thus degraded terr-OC component held buoyant in surface water. Hence, these two terr-OC components may represent different propensities to contribute to a positive feedback to climate warming by converting OC from coastal and inland permafrost into CO2.

Place, publisher, year, edition, pages
2011. Vol. 8
Keyword [en]
east siberian sea continental-shelf sediments arctic-ocean climate-change permafrost coastal cycle co2 preservation delta-c-13 Environmental Sciences & Ecology Geology
Research subject
SWEDARCTIC 2008, ISSS-08
Identifiers
URN: urn:nbn:se:polar:diva-1908DOI: 10.5194/bg-8-1865-2011OAI: oai:DiVA.org:polar-1908DiVA: diva2:810415
Note

ISI Document Delivery No.: 810UT Times Cited: 16 Cited Reference Count: 64 Karlsson, E. S. Charkin, A. Dudarev, O. Semiletov, I. Vonk, J. E. Sanchez-Garcia, L. Andersson, A. Gustafsson, O. Vonk, Jorien/H-5422-2011; Semiletov, Igor/B-3616-2013; Sanchez-Garcia, Laura/N-1172-2013 Sanchez-Garcia, Laura/0000-0002-7444-1242 Knut and Alice Wallenberg Foundation; Headquarters of the Far Eastern Branch of the Russian Academy of Sciences; Swedish Research Council (VR) [621-2004-4039, 621-2007-4631]; US National Oceanic and Atmospheric Administration; Russian Foundation of Basic Research [08-05-13572, 08-05-00191-a, 07-05-00050a]; Swedish Polar Research Secretariat; Nordic Council of Ministers [331080-70219]; US National Science Foundation [OPP ARC 0909546]; Swedish Royal Academy of Sciences through Knut and Alice Wallenberg Foundation; Marie Curie grant [PIEF-GA-2008-220424] We thank the crew and personnel around the International Siberian Shelf Study 2008 (ISSS-08), and particularly the crew of the sub expedition onboard TB0012. The ISSS-08 campaign was supported by the Knut and Alice Wallenberg Foundation, Headquarters of the Far Eastern Branch of the Russian Academy of Sciences, the Swedish Research Council (VR Contract No. 621-2004-4039 and 621-2007-4631), the US National Oceanic and Atmospheric Administration (Siberian Shelf Study), the Russian Foundation of Basic Research (08-05-13572, 08-05-00191-a, and 07-05-00050a), the Swedish Polar Research Secretariat, the Arctic Co-Op Program of the Nordic Council of Ministers (331080-70219) and the US National Science Foundation (OPP ARC 0909546). O. Gustafsson also acknowledges financial support as an Academy Research Fellow from the Swedish Royal Academy of Sciences through a grant from the Knut and Alice Wallenberg Foundation, L. Sanchez-Garcia acknowledges a Marie Curie grant (contract no. PIEF-GA-2008-220424), and A. Andersson his support from the Knut and Alice Wallenberg Foundation. Finally we thank H. Gustafsson and Y. Zebuhr at Stockholm University for instrumental and laboratory assistance. 16 Copernicus gesellschaft mbh Gottingen Ecology; Geosciences, Multidisciplinary

Available from: 2015-05-07 Created: 2015-05-06 Last updated: 2015-05-26

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