N. A. Belyaev

Transformation of suspended particulate matter into sediment in the Kara Sea in September of 2011

The biogeochemical processes participating in the transformation of the particulate matter into sediment along the Yenisei River-St. Anna Trough (Kara Sea) meridional profile were studied using hydrochemical, geochemical, microbiological, radioisotope, and isotope methods. The water-sediment contact zone consists of three subzones: the suprabottom water, the fluffy layer, and the surface sediment. The total number, biomass, 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 Corg 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 Corg in the fluffy layer and surface sediment as compared to the Corg 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.

Isotopic Markers of Organic Matter Transformation at the Water-Sediment Geochemical Boundary

83 The main transformations of energy and matter occur at the boundary zones of the ocean. The “water column–bottom sediment” boundary is related to those areas studied insignificantly because of the diffi� culty of its direct investigation. Suspension and com� ponents dissolved in seawater come onto this bound� ary from the top fixing the end of the sedimentation stage, and dissolved and gaseous compounds formed in the upper sedimentary horizons on the stage of early diagenesis are removed from the bottom. Organic matter (OM) from suspension and reduced compounds coming from sediments play the role of an energy source for biogeochemical processes at the water–sediment boundary.

Chlorophyll, primary production, fluxes, and balance of organic carbon in the Laptev Sea

Materials on the cycle of organic carbon in Russian Arctic seas (including the Laptev Sea) were summarized in the monograph [1]. One of the most important characteristics of organic matter (OM) fluxes is primary production, which was assayed for the Laptev Sea based on relatively scarce field observations [2–4] and the data of satellite-borne CZCS color-scanner measurements containing, despite eight years of observations (from 1978 to 1986), information on chlorophyll only in the coastal zone and only in September (because of permanent cloudiness).

Determination of the concentration of mineral particles and suspended organic substance based on their spectral absorption

A method to determine the concentrations of the particulate mineral matter (CPMM) and the particulate organic matter (CPOM) is suggested. The values of CPMM and CPOM are calculated from the measurements of the spectral coefficients of the light absorption aPOM(440) and aPMM(750) using empirical equations. The latter have been obtained by comparing the concentrations of the suspended solids measured by means of the gravimetric method with the spectral values of the optical density of the suspended matter settled on membrane filters. The data used are typical of the coastal waters of inland and marginal seas and the open ocean and cover the range of three and two orders of magnitude for the concentrations of CPMM and CPOM, respectively.

Lignin as an indicator of the sedimentation conditions on the Arctic shelf

It is shown for the first time that the proportion of lignin in shelf deposits may range from 1/3 to the total concentration of organic carbon. The distribution of wood residues and lignin in the studied sedimentary formation is very uneven, which reflects the dynamic flux environment of sedimentation and OM supply. The calculated molecular indexes showed that most of the OM in deposits underwent insignificant diagenetic alterations.

Alkanes in Quaternary deposits of the Laptev Sea

The distribution and genesis of n-alkanes in sediments from the 38-m sequence obtained during core boring in the Ivashkina lagoon were studied. Sediments were formed in the Holocene as a result of thermokarst and penetration of seawater. The sequence mostly includes permafrost rocks partially molten in the upper horizons and covered by Quaternary deposits, which are mostly the products of thermoabrasion.

Particulate organic matter along the Northern Sea Route

The comparative evaluation of the content of particulate organic carbon (POC) in surface seawater along the Northern Sea Route from Norway to the East Siberian Sea (the southern track) during the summer seasons of 2004–2011 was carried out based on the authors’ data. The content and distribution of organic component in particulate matter were estimated, as were the proportion of phytoplankton, detritus, and the mineral component in the composition of particulate matter.

The distribution of heavy metals in the near-bottom particulate matter, fluffy layer, and bottom sediments over the Yenisei profile in the Kara Sea

The chemical composition and concentrations of metals (Fe, Mn, Cu, Zn, and Cr) were determined for the first time in the marine basin at the water-bottom geochemical interface, including the particulate matter, fluffy layer (0.0–0.2 cm), and the surface layer of the sediments (0–2 cm). It was found that the content of metals in the aquatic particulate matter depended on the concentration of organic matter. The fluffy layer was enriched, compared to the underlying layers, by 5–10% in organic matter including the biomass of microorganisms, and by up to 50% in metals (to the maximum of doubled values for Zn). It is supposed that this low enrichment of the fluffy layer in metals was caused by the active near-bottom currents of marine basins.