Contrasting regimes for organic matter degradation in the East Siberian Sea and the Laptev Sea assessed through microbial incubations and molecular markers

E. S. Karlsson, V. Brüchert, T. Tesi, A. Charkin, Oleg Victorovich Dudarev, Igor Petrovich Semiletov, O. Gustafsson

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16 Citations (Scopus)

Abstract

Compositional studies of organic matter on the East Siberian Arctic Shelf (ESAS) suggest that different terrestrial carbon pools have different propensities for transport and/or degradation. The current study combined laboratory-based microbial degradation experiments with earlier published degradation-diagnostic composition of several classes of terrestrial biomarkers on the same sediments to investigate differences and driving forces of terrestrial organic matter (TerrOM) degradation in two biogeochemically-contrasting regimes of the ESAS.The incubation-based anaerobic degradation rates were consistently higher (by average factor of 6) in the East Siberian Sea Kolyma Paleoriver Channel (ESS-KPC) (15μmolCO2gOC-1day-1) compared to the Laptev Sea Buor-Khaya Bay (LS-BKB) (2.4μmolCO2gOC-1day-1).The reported molecular markers show similarities between the terrestrial carbon pools in the two systems, but impose contrasting degradation regimes in combination with the incubation results. For the LS-BKB, there was a strong relationship between the degradation rates and the three lignin phenol-based degradation proxies (r2=0.93-0.96, p<0.01, linear regression) and two wax lipid-based degradation proxies (r2=0.71 and 0.66, p<0.05, linear regression). In contrast, for the ESS-KPC system, there was no relationship between incubation-based degradation rates and molecular marker-based degradation status of TerrOM. A principal component analysis indicated that short-chain fatty acids and dicarboxylic acids from CuO oxidation are mainly of terrestrial origin in the LS-BKB, but mainly of marine origin in the ESS-KPC. Hence, the microbial degradation in the western (LS-BKB) system appears to be fueled by TerrOM whereas the eastern (ESS-KPC) system degradation appears to be driven by MarOM. By combining molecular fingerprinting of TerrOM degradation state with laboratory-based degradation studies on the same ESAS sediments, a picture evolves of two distinctly different modes of TerrOM degradation in different parts of the ESAS system.

Original languageEnglish
Pages (from-to)11-22
Number of pages12
JournalMarine Chemistry
Volume170
DOIs
Publication statusPublished - 1 Mar 2015

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Keywords

  • Arctic Ocean
  • Coastal shelf
  • Continental margin
  • CuO oxidation
  • Decomposition
  • Incubations
  • Lignin
  • Organic geochemistry
  • Organic matter lability
  • Permafrost
  • Reactivity
  • Remineralization
  • Sediment
  • Terrestrial organic carbon
  • Wax lipids

ASJC Scopus subject areas

  • Oceanography
  • Chemistry(all)
  • Environmental Chemistry
  • Water Science and Technology

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