Marina D Kravchishina

River flux of dissolved organic carbon (DOC) and particulate organic carbon (POC) to the Arctic Ocean: what are the consequences of the global changes?

An attempt was made to estimate an increase of particulate organic carbon (POC), dissolved organic carbon (DOC) and total organic carbon (TOC) delivery by the Russian Arctic rivers to the Arctic Ocean by 2100. The calculations are based on the previously published estimations of an increase of river water discharge (Peterson et al. 2002) and of suspended matter discharge (Gordeev 2006) to the end of 21st century. The Intergovernmental Panel on Climate Change (IPCC 2007) predicts the global surface air temperature increase in a range between 1.4° and 5.8°C by 2100. The climate warming will result in the thawing of the multiannual permafrost in Siberia. The enriched by organic carbon frozen peatlands will be the very effective source of organics to the rivers and streams. Frey and Smith (2005) predict an increase of DOC concentration in the rivers of West Siberia up to 400% due to this process.

Authigenic Mg-calcite at a cold methane seep site in the Laptev Sea

Authigenic minerals were studied in Holocene shelf sediments of the Laptev Sea (cold methane seep site, water depth 71 m). The study presents the first finds of large hard carbonate concretions with Mg-calcite cement in recent sediments of the Arctic shelf seas. These concretions differ from previously reported glendonites and concretions from bottom sediments of the White Sea, Kara Sea, Sea of Okhotsk, etc. A study of the morphology, microstructure, and composition of these newly reported concretions revealed the multistage formation of carbonates (structural varieties of Mg-calcite and aragonite). It was shown that organic matter played an important role in the formation of authigenic carbonates, i.e., in the formation of sedimentary–diagenetic Mg-calcite. The role of methane as a possible source for authigenic carbonate formation was estimated. It was found that methane-derived Mg-calcite accounts for 17–35% of concretion materials. Mg-calcite had δ13С-Сcarb values between–24 and–23‰ and δ13С-Сorg values between–44.5 and–88.5‰.

Early diagenesis in recent bottom sediments of the Dvina Bay (White Sea)

Investigations in the water column and bottom sediments including entrapped water were carried out on expeditions of the P.P. Shirshov Institute of Oceanology in the Dvina Bay, the White Sea. We studied the transformation of particulate organic matter at the biogeochemical barrier between the water and bottom and in the underlying Holocene sediments. Low rates of the early diagenesis of sediments caused by low values of primary production in the conditions of high fluxes of terrigenous organic matter were established. The low temperatures of microorganisms habitat play the secondary role.

Methane as an Organic Matter Source and the Trophic Basis of a Laptev Sea Cold Seep Microbial Community

ABSTRACT An area of cold methane seeps at the bottom of the Laptev Sea was investigated. High rates of methane oxidation were revealed in the sediments and in the water column. Anaerobic methane oxidation carried out by the ANME-2 a/b consortium was coupled to sulfate reduction. Bacteria of the genera Sulfurovum and Arcobacter were the agents of the sulfur cycle. Methane unconsumed in the sediments diffused into the near-bottom water, where it was oxidized by methanotrophic bacteria. Methanotrophic activity was essential for development of symbiotrophic tubeworms of the upper sediment layers, which were responsible for the process of bioturbation.

Spatial variability of concentrations of chlorophyll a , dissolved organic matter and suspended particles in the surface layer of the Kara Sea in September 2011 from lidar data

The article presents results of underway remote laser sensing of the surface water layer in continuous automatic mode using the UFL-9 fluorescent lidar onboard the R/V Akademik Mstislav Keldysh during cruise 59 in the Kara Sea in 2011. The description of the lidar, the approach to interpreting seawater fluorescence data, and certain methodical aspects of instrument calibration and measurement are presented. Calibration of the lidar is based on laboratory analysis of water samples taken from the sea surface during the cruise. Spatial distribution of chlorophyll a, total organic carbon and suspended matter concentrations in the upper quasi-homogeneous layer are mapped and the characteristic scales of the variability are estimated. Some dependencies between the patchiness of the upper water layer and the atmospheric forcing and freshwater runoff are shown.

Distribution and Feeding of Herbivorous Zooplankton in the Laptev Sea

Sampling was conducted along the quasi meridional transect at 130° E from the Lena River estuary to northern deep-sea regions of the Laptev Sea in September 2015. The latitudinal zonality and the impact of river runoff are manifested in the temperature and salinity distribution, concentration of particulate organic matter, and the structure of plankton communities. The differences in the chl a concentration and primary production along the transect are insignificant. The feeding rate of mesozooplankton herbivores was assessed by a fluorescence technique. The total consumption of phytoplankton biomass and primary production are estimated based on the feeding rate, abundance of zooplankton species, and their diel migrations. The daily grazing impact of zooplankton on phytoplankton biomass increases from 2% on the inner shelf to 3% on the mid-shelf, 5% on the outer shelf, and 10% in the deep-sea part of the basin. The consumption of primary production also increases: 1, 4.5, 5.7, and 13.9%, respectively. In the fall, the consumption of phytoplankton does not compensate the energy demands for respiration. The latitudinal zonality of the Laptev Sea appears not only in the hydrophysical water parameters and the structure of plankton communities, but also in their functional characteristics.

Suspended Particulate Matter as a Main Source and Proxy of the Sedimentation Processes

The material for our study was collected in the White Sea during 22 interdisciplinary expeditions organized by the Shirshov Institute of Oceanology, Russian Academy of Sciences (IO RAS), in 2000–2014. The researches were carried out mostly in June–August; however we have some samples for autumn–winter and early spring seasons. Here, we report the concentration of suspended particulate matter (SPM), its composition and properties, as well as their changes due to natural zoning and local conditions. This paper discusses the features in the distribution of SPM concentration, grain-size, mineral, and major phase composition. As far as possible, we involved our own and other published data on hydrology, bottom morphology, and particulate and dissolved river runoff from the catchment area, abundance and composition of marine phyto- and bacterioplankton. This new knowledge has been used to describe particles dispersion system of the White Sea, which forms a giant reservoir of micro- and nanoparticles, using terms adopted in sedimentology and oceanography.

Fluorescence quantum yield of CDOM in coastal zones of the Arctic seas

ABSTRACT Along with traditional optical indices, calculated from absorption and fluorescence spectra to describe chromophoric dissolved organic matter (CDOM) naturally occurring in water, the fluorescence quantum yield (FQY) becomes significant. Knowledge of CDOM optical properties is important for satellite remote sensing as well as for lidar ground-true measurements. The FQY as a function of excitation wavelength within 240–500 nm range for a variety of the Arctic shelf waters was determined for the first time in order to identify the characteristic chromophores peculiar to different regions of the Arctic basin affected by freshwater runoff. The surface water samples were collected during several cruises in 2015–2017 in the following sites: the mouth areas of the Khatanga and Lena Rivers (the Laptev Sea), the delta area of the Northern Dvina River (the White Sea), desalinated waters of the Kara Sea (influenced by freshwater of the Ob and Yenisei Rivers) and the East Siberian Sea (influenced by freshwaters of the Indigirka and Kolyma Rivers), as well the shelf areas of those seas not affected by terrigenous runoff. To characterize DOM, conventional optical indices SR, HIX, and BIX were calculated. In most cases, important humic character of DOM was established, while the contribution of autochthonous organic matter varied from low to intermediate level. For the samples with terrestrial impact, the FQY decreased from excitation at 240 nm to 270–280 nm and then increased, demonstrating two peaks at 340 and 380 nm, with constant decrease towards longer excitation wavelengths; at λex = 380 nm FQY varied from 1.4% to 3.1%. In some cases, additional maximum at 270 nm of FQY-excitation dependency was observed as an indicator of autochthonous nature of biological material. Minimal FQY was measured for the White Sea surface waters, the maximal for the Laptev and East Siberian seas.

Vertical Fluxes of Suspended Sedimentary Matter in Arctic Sedimentogenesis of Intracontinental Seas

Based on long-term studies of a small sea in the Arctic Ocean, new regularities in the sedimentary process under the conditions of Arctic sedimentogenesis were established. The quantitative transition of particulate sedimentary materials into the concentrated forms (bottom sediments) in the White Sea follows the linear dependence with a local maximum in the deep nepheloid layer. Marginal filters (Severnaya Dvina River, etc.), which are areas of ultrarapid sedimentation, were distinguished. The long-term data on the concentration of suspension and fluxes of particulate sedimentary material clearly indicate stable annual nepheloid layers, i.e., the distribution of particulate forms of sedimentary material (suspension) in the water column proceeds by new regularities, which may be distinguished ever more clearly.

Biooptical characteristics of the surface layer of the Baltic, Norwegian, and Barents seas in summer 2014–2016 from shipboard and satellite data

The article presents the results of shipboard and satellite measurements in the surface layer of the Baltic, Norwegian, and Barents seas during legs from the Baltic to the White Sea in June–August 2014–2016. Special attention is paid to marine phytoplankton blooms of cyanobacteria in the Baltic Sea and coccolithophores in the Barents Sea. No blooms were found in the Norwegian Sea. The efficiency of combined application of in situ and satellite optical methods for studying the parameters of phytoplankton blooms is shown.