Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
doi:10.5194/bg-2017-119
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
13 Apr 2017
Review status
This discussion paper is under review for the journal Biogeosciences (BG).
Carbon mineralization in Laptev and East Siberian Sea shelf and slope sediment
Volker Brüchert1,3, Lisa Bröder2,3, Joanna E. Sawicka1,3, Tommaso Tesi2,3,5, Samantha P. Joye6, Xiaole Sun4,5, Igor P. Semiletov7,8,9, and Vladimir A. Samarkin6 1Department of Geological Sciences, Stockholm University, Stockholm, Sweden
2Department of Environmental Sciences and Analytical Chemistry, Stockholm University, Stockholm, Sweden
3Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
4Baltic Sea Research Center, Stockholm University, Stockholm, Sweden
5Institute of Marine Sciences – National Research Council, Bologna, Italy
6Department of Marine Sciences, University of Georgia, Athens, USA
7International Arctic Research Center, University Alaska Fairbanks, Fairbanks, USA
8Pacific Oceanological Institute, Russian Academy of Sciences, Vladivostok, Russia
9Tomsk National Research Politechnical University, Tomsk, Russia
Abstract. The Siberian Arctic Sea shelf and slope is a key region for the degradation of terrestrial organic material transported from the organic carbon-rich permafrost regions of Siberia. We report on sediment carbon mineralization rates based on O2 microelectrode profiling, intact sediment core incubations, 35S-sulfate tracer experiments, porewater dissolved inorganic carbon (DIC), δ13CDIC, and iron, manganese, and ammonium concentrations from 20 shelf and slope stations. This data set provides a spatial overview of sediment carbon mineralization rates and pathways over large parts of the outer Laptev and East Siberian Arctic shelf and slope, and allowed us to assess degradation rates and efficiency of carbon burial in these sediments. Rates of oxygen uptake and iron and manganese reduction were comparable to temperate shelf and slope environments, but bacterial sulfate reduction rates were comparatively low. In the topmost 20 to 50 cm of sediment, aerobic carbon mineralization dominated degradation and comprised on average 82 % of the depth-integrated carbon mineralization. Oxygen uptake rates and 35S-sulfate reduction rates were higher in the eastern East Siberian Sea shelf compared to the Laptev Sea shelf. DIC/NH4+ ratios in porewaters and the stable carbon isotope composition of remineralized DIC indicated that the degraded organic matter on the Siberian shelf and slope was a mixture of marine and terrestrial organic matter. Based on dual end member calculations, the terrestrial organic carbon contribution varied between 32 % and 36 %, with a higher contribution in the Laptev Sea than in the East Siberian Sea. Extrapolation of the measured degradation rates using isotope end member apportionment over the outer shelf of the Laptev and East Siberian Sea suggests that about 16 Tg C per year are respired in the outer shelf sea floor sediment. Of the organic matter buried below the oxygen penetration depth, between 0.6 and 1.3 Tg C per year are degraded by anaerobic processes, with a terrestrial organic carbon contribution ranging between 0.3 and 0.5 Tg per year.

Citation: Brüchert, V., Bröder, L., Sawicka, J. E., Tesi, T., Joye, S. P., Sun, X., Semiletov, I. P., and Samarkin, V. A.: Carbon mineralization in Laptev and East Siberian Sea shelf and slope sediment, Biogeosciences Discuss., doi:10.5194/bg-2017-119, in review, 2017.
Volker Brüchert et al.
Volker Brüchert et al.
Volker Brüchert et al.

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Short summary
The potential oxidation of land-derived organic material material in shelf sediments of the Arctic Ocean can have a large influence for the Arctic marine carbon budget. We studied the active degradation of land- and marine-derived organic material in East Siberian shelf sediment and found that the total amount of carbon dioxide produced was about 16 × 1012 g C/year. Terrestrial organic material contributed 0.3 to 0.5 × 1012 g C/year and plays a minor role in the outer Siberian shelf carbon budget.
The potential oxidation of land-derived organic material material in shelf sediments of the...
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