Transformation of particulate organic matter at the water-bottom boundary in the Russian Arctic seas: Evidence from isotope and radioisotope data |
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| Authors: | A Yu Lein M D Kravchishina N V Politova A S Savvichev E F Veslopolova I N Mitskevich N V Ul’yanova V P Shevchenko M V Ivanov |
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| Institution: | 1.Shirshov Institute of Oceanology,Russian Academy of Sciences,Moscow,Russia;2.Vinogradskii Institute of Microbiology,Russian Academy of Sciences,Moscow,Russia |
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| Abstract: | Complex biogeochemical studies including the determination of isotopic composition of Corg in both suspended particulate matter and surface horizon (0–1 cm) of sediments (more than 260 determinations of δ13C-Corg) were carried out for five Arctic shelf seas: White, Barents, Kara, East Siberian, and Chukchi. The aim of this study is
to elucidate causes that change the isotopic composition of particulate organic carbon at the water-sediment boundary. It
is shown that the isotopic composition of Corg in sediments from seas with a high river runoff (White, Kara, and East Siberian) does not inherit the isotopic composition
of Corg in particles precipitating from the water column, but is enriched in heavy 13C. Seas with a low river runoff (Barents and Chukchi) show insignificant difference between the value of δ13C-Corg in both suspended load and sediment because of a low content of the isotopically light allochthonous organic matter (OM)
in particulates. Complex biogeochemical studies with radioisotope tracers (14CO2, 35S, and 14CH4) revealed the existence of specific microbial filter formed from heterotrophic and autotrophic organisms at the water-sediment
boundary. This filter prevents the mass influx of products of OM decomposition into water column, as well as reduces the influx
of a part of OM contained in the suspended particulate matter from water into sediment. |
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