Vol 59, No 5 (2019)

Based on the materials of several voyages of the Institute of Oceanology, Russian Academy of Sciences, and archival hydrological and hydrochemical data, the dynamics of dissolved inorganic carbon in the Yenisei Gulf was investigated. There are three main areas with extensive sedimentation of suspended material and oxidation of organic matter (OM) in the upper layer of sediments. The first region of OM oxidation was to the south from 72° N; its existence associated with extensive sedimentation of dissolved and suspended matter at the geochemical barrier. Two other areas of OM decomposition were located downstream (between 73° and 74° and to the north from 75° N) and most likely originated at the orographic barrier, where the change in the dynamic characteristics of the riverine flow and the topography of the bay bottom stimulated precipitation of suspension carried by water. Comparison of the difference in the observed C_tot with the AOU value showed that in 1993, oxidation of OM resulted in a change in C_tot. In 2011, carbon emission into water was most likely controlled by the transformation of mineral suspension and/or carbon exchange between bottom water and bottom sediments. In 2016, a decrease in the C_tot content was registered in deep water over the most part of the section. Despite many similar features in the distribution of hydrochemical characteristics in the bay, the change in the content of dissolved inorganic carbon over the section was significant in different years.

The studies were conducted along the transect (11 stations) from the inner part of Khatanga Bay in the south to the Laptev Sea continental slope in the north in September 17—20, 2017. Four biotopes with different parameters of the pelagic environment, composition, quantitative characteristics and vertical distribution of phytoplankton have been distinguished: the inner part of the Khatanga Bay, estuarine frontal zone, western shelf of the Laptev Sea and continental slope area. The inner part of Khatanga Bay and the continental slope are characterized by the highest values of phytoplankton abundance and biomass, which reach 1 × 10⁶ cell/L and 160 mg/m³, respectively. The formation of the maximum at a depth of 45 m is typical for the phytoplankton vertical distribution in the continental slope area. Algal biomass in the maximum reaches 400 mg/m³ which is the highest value for the transect. Well-pronounced latitudinal zoning in the structure of phytoplankton communities has been determined in the western part of the Laptev Sea similar to that in other regions of the Arctic seas under a strong impact of Siberian rivers discharge.

The role of plankton in the vertical flux in the East Siberian Sea was studied in the 69 cruise of the RV “Akademik Mstislav Keldysh” in September 2017. Vertical fluxes were measured in sediment traps on two buoy stations in the area of the Indigirka River plume and in the marine shelf area. Mass vertical flux and particulate organic carbon flux varied from 80 to 530 mg/m²/d and from 16 to 49 mgС/m²/d, accordingly. Phytoplankton in sediment traps was dominated by cysts and spores of diatoms and dinoflagellates. Phytoplankton flux increased with depths from 0.22–0.33 to 1.2–1.3 mgС/m²/d. Fecal pellet fluxes (7–12 mgС/m²/d) were similar at two studied stations and did not change with depth. Zooplankton in the traps was dominated by larvacean houses and carcasses of copepods Jashnovia tolli and Calanus glacialis. Flux of zooplankton varied from 3 to 17 mgС/m²/d. The influence of the continental runoff reflected in a decrease of the proportion of planktonogenic components in the vertical flux of organic carbon. In the river plume area, their total contribution to organic carbon flux did not exceed 30%; on the marine shelf it reached 80% of organic carbon flux.

The article presents the results of a study of black carbon concentrations in the atmospheric boundary layer over the Baltic and North seas, the North Atlantic, and Norwegian, Barents, Kara, and Laptev seas from June 30 to September 29, 2017, on cruises 68 and 69 of the R/V Akademik Mstislav Keldysh. Black carbon has a significant impact on climate change and pollution in the Arctic. It forms as a result of incomplete combustion of fossil fuels (primarily coal and oil) and biomass or biofuels. It consists of submicron particles and their aggregates and can be transported long distances from their source. Samples were taken by pumping air for 4–6 h through Hahnemule quartz filters at a height of 10 m above sea level in a headwind to prevent exhaust from the smokestack from entering the filters. The black carbon content was subsequently determined in a laboratory with an aethalometer. The backward trajectories of air mass transfer and the transported black carbon particles to the sampling points were calculated by the HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) model on the NOAA website at http://www.arl.noaa.gov/ready.html. Studies show low black carbon concentrations (<50 ng/m³) along the expedition’s route when the air masses came from background regions of the North Atlantic and Arctic. High black carbon concentrations (100–200 ng/m³ or more) are characteristic of active shipping areas (southwestern Baltic, North Sea) and near ports (e.g., Reykjavik), as well as the arrival of air masses from industrialized areas of Europe in the southeastern Baltic and from oil and gas field areas where gas flaring is carried out (North, Norwegian, and Kara seas).

Comparative studies of the geochemistry of bone detritus were performed for the bottom of the Melovoe deposit (south of the Mangyshlak Peninsula; Oligocene–Miocene) and for the recent uranium-bearing sediments at the shelf of Namibia in which the concentrations of trace elements were determined. The similarity of trace-elemental compositions of bones and enclosing sediments was revealed for both cases, as well as a partial similarity of ancient and recent sediments and bones. Moreover, the similarity of uranium mineralization in Maikop bones and in the bone matter of the recent shelf was found. Paleographic data on the Maikop basin showed that the ore bodies were formed in shoal productive shelf zone characterized by frequent mass die-offs of fauna similarly to occasional events at the recent oceanic shelves. Certain geochemical differences in mineral and chemical compositions of ancient and recent bones are related to the increased concentrations of uranium and other trace elements in the Tethys waters owing to the evaporation of seawaters and associated concentrating of dissolved metals under the ocean regression.

Spatial distribution of the liquid and solid phases in the pores of first-year sea ice in Amursky Bay was studied using the method of nuclear magnetic resonance and magnetic resonance imaging in the period from 2013 to 2016. We describe the influence of snow cover on the brine content in the pores of sea ice, on the bulk structure of crystalline formations, and on the formation of its individual layers. The difference in vertical profiles of temperature and salinity in the winter and spring periods is shown. The characteristic features of the bulk crystal structure and liquid phase in thin first-year ice are compared with the thick ice of the polar regions. A new empirical relationship is given for the calculation of the entire thickness and separate ice layers as applied to thin young ice.

A new technology for coring of weakly consolidated sediment is proposed. The technology includes the original coring system and the way it is operated. The technology is based on a number of original solutions: (1) unification of the elements of the drill string, where household pipes made of PVC are used as a sampler and rods; (2) the use of the valve mechanism of a simple conical construction; (3) the method of vertical freezing of the core in open air. The coring system makes it possible to obtain the cores of the soft bottom sediment in winter from ice at a water depth of up to 7–10 m. Field tests have shown that the proposed system is inexpensive, easy to assemble and operate, very effective, and reliable. The new system can be used as an alternative or complement to existing systems for coring of bottom sediments.

The information is presented on hydrochemical studies performed in August 2018 at the middle and lower reaches of the Lena River from Yakutsk to Kyusyur settlements. The studies resulted in generating the database containing 80 parameters of water chemical composition including the stable isotopes of water, particulate matter, and DOC. The results obtained made it possible for the quantitative evaluation of the fluxes of dissolved and particulate matter from the headwaters towards the mouth of the Lena River and to ascertain the regularities in the transformation of these fluxes.

The 44th cruise of R/V Akademik Boris Petrov was carried out from October 5 to 30, 2018 in the Baltic Sea and Skagerrak Strait. The studies included investigation of the water column structure, bottom currents, bottom sediments, and biological communities.