ALBERT

Description: Macrobenthos biomass and bottom biocoenoses were studied in the sublittoral zone of the southern East Siberian Sea. The macrobenthos is characterized by relatively high abundance (from 30 to 2680 #/m**2), biomass (from 0.25 to 578.8 g/m**2), and diversity (83 species in total). Lateral distribution of macrobenthos biomass correlates with a substrate type and salinity and is substantially higher in areas washed by the Arctic water mass than in estuaries with mixed fresh and Arctic waters and shows a tendency to decreasing in the convergence zone of different water masses. The highest macrobenthos biomass is observed in cores of water masses in the Long Strait area and in the eastern part of the sea.

Description: Organic matter origins are inferred from carbon isotope ratios (delta13C) in recent continental shelf sediments and major rivers from 465 locations from the north Bering-Chukchi-East Siberian-Beaufort Sea, Arctic Amerasia. Generally, there is a cross-shelf increase in delta13C, which is due to progressive increased contribution seaward of marine-derived organic carbon to surface sediments. This conclusion is supported by the correlations between sediment delta13C, OC/N, and delta15N. The sources of total organic carbon (TOC) to the Amerasian margin sediments are primarily from marine water-column phytoplankton and terrigenous C3 plants constituted of tundra taiga and angiosperms. In contrast to more temperate regions, the source of TOC from terrigenous C4 and CAM plants to the study area is probably insignificant because these plants do not exist in the northern high latitudes. The input of carbon to the northern Alaskan shelf sediments from nearshore kelp community (Laminaria solidungula) is generally insignificant as indicated by the absence of high sediment delta13C values (-16.5 to -13.6 per mil) which are typical of the macrophytes. Our study suggests that the isotopic composition of sediment TOC has potential application in reconstructing temporal changes in delivery and accumulation of organic matter resulting from glacial-interglacial changes in sea level and environments. Furthermore, recycling and advection of the extensive deposits of terrestrially derived organic matter from land, or the wide Amerasian margin, could be a mechanism for elevating total CO2 and pCO2 in the Arctic Basin halocline.

Description: An analysis of earlier measurements and author's data serves as a basis for a discussion of origin of deep-sea hydrogen. High hydrogen concentrations (0.001 ml/l or higher) in geothermal brines of the Atlantis II Deep depression are of abiogenic origin.

Description: The chemical composition of organic matter (Corg, Norg, d13C, d1SN, and n-alkanes) was studied in the top layer of bottom sediments of the East Siberian Sea. Possible ways were proposed to estimate the amount of the terrigenous component in their organic matter (OM). The fraction of terrigenous OM estimated by the combined use of genetic indicators varied from 15% in the eastern part of the sea, near the Long Strait, to 95% in the estuaries of the Indigirka and Kolyma rivers, averaging 62% over the sea area.

Description: Dissolved stable silicon isotopes were determined in seawater samples collected during the 73rd expedition onboard RV Akademik Mstislav Keldysh (AMK73) in the Laptev Sea in October 2018 under ice free conditions. Seawater samples were filtered inline from Niskin bottles or the ship's underway system, acidified to 0.1% v/v with HCl and kept at 4°C until analysis on land. Samples were measured for δ29Si(OH)4 with reference to international reference material NBS28 on a Nu Plasma II MC-ICP-MS (The University of Edinburgh, School of Geosciences) using the MAGIC co-precipitation method and purified through column chemistry. International standards BigBatch, ALOHA300 and ALOHA1000 were run alongside seawater samples for inter-comparability. Final values were converted to δ30Si(OH)4 using the conversion factor of 1.96 for comparability. Reproducibility is 0.05 and 0.1‰ for δ29Si(OH)4 and δ30Si(OH)4 respectively. This dataset includes salinity, silicic acid concentrations and stable silicon isotope signatures of seawater, which provides useful information on the silicon biogeochemical cycle of the Laptev Sea, as influenced by the Lena river.