Transformation of Suspended Particulate Matter into Sediment
in the Kara Sea in September of 2011

A. Yu. Lein^a, P. N. Makkaveev^a, A. S. Savvichev^b, M. D. Kravchishina^a, N. A. Belyaev^a, O. M.
Dara^a, M. S. Ponyaev^a, E. E. Zakharova^b, A. G. Rozanov^a, M. V. Ivanov^b, and M. V. Flint^a

^aShirshov Institute of Oceanology, Russian Academy of Sciences, Russia

e-mail: lein@ocean.ru

^bWinogradskii Institute of Microbiology, Russian Academy of Sciences, Russia

e-mail: savvichev@mail.ru

Received November 28, 2012; in final form, January 12, 2013

Abstract—The biogeochemical processes participating in the transformation of the particulate matter into sed-
iment along the Yenisei River–St. Anna Trough (Kara Sea) meridional profile were studied using hydrochemi-
cal, geochemical, microbiological, radioisotope, and isotope methods. The water–sediment contact zone con-
sists of three subzones: the suprabottom water, the fluffy layer, and the surface sediment. The total number, bio-
mass, and integral activity of the microorganisms (dark ¹⁴CO₂ assimilation) in the fluffy layer are usually higher
than in the suprabottom water and sediment. The fluffy layer shows a decrease in the oxygen content and the
growth of the dissolved biogenic elements. It was provided by the particulate organic matter supporting the vital
activity of the heterotrophs from the overlying water column and by the flux of reduced compounds (NH₄, H₂S,
CH₄, Fe²⁺, Mn²⁺, and others) from the underlying sediments. The C_org isotopic composition of the fluffy layer
and the sediments is 2–4 ‰ heavier than that of the particulate matter and sediment due to the presence of the
isotopically heavy biomass of microorganisms. A change in the isotopic composition of the C_org in the fluffy
layer and surface sediment as compared to the C_org of the particulate matter is a widespread phenomenon in the
Arctic shelf seas and proves the leading role of microorganisms in the transformation of the particulate matter
into sediment.

DOI: 10.1134/S0001437013050081

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