A brief review of recent studies of internal waves in the Baltic Sea is given. The data of various observations of internal waves in the Baltic region are discussed and a database for the background hydrological parameters that govern the basic appearance of the internal wave shape is introduced. These data sets are employed to select examples of pathways of wave propagation that contain critical points. Numerical modeling of propagation of internal solitary waves across the sea is carried out using the relatively simple model based on Gardner’s equation. This model was chosen due to its clear advantages. It is robust, allows high-resolution calculations with modest computer resources, and is able to reproduce the transformation of internal waves in horizontally inhomogeneous sea. The results of calculations of the transformation of internal solitons in the Baltic Sea along such pathways in a realistic (spatially variable) set of hydrological conditions are presented.

Velocity field simulated by a circulation model with extremely high horizontal resolution (the grid bin is 232×232 m) in the Gulf of Finland during a period of summer upwelling events is used to calculate advection of floating Lagrangian particles that are uniformly distributed on the sea surface initially. For a relatively short time of advection τ (of the order of one day), the particles are found to gather within narrow, elongated stripes characterized by extremely high, positive values of vorticity, Finite-Time Lyapunov Exponent, and lateral thermohaline gradients module (fronts). The clustering rate, defined as the time derivative of the standard deviation of normalized particle concentration, tends asymptotically at small τ to the standard deviation of flow divergence. The standard deviation of flow divergence, in its turn, displays a considerable growth with the refinement of the model grid, confirming the paramount role of submesoscale dynamics in clustering of floating stuff. At large τ, the probability density function of floating particle concentration is shown to tend to lognormality. Based on the backward-time integration of the Lagrangian velocity convergence, a criterion for finite-time clustering is introduced.

The intense erosion of shores of the Kotlin Island in the Gulf of Finland during the last 70 years can lead to the complete disappearance of sandy beaches of the western Kotlin Island in the near future. We assess the intensity of the coastal erosion of the western Kotlin Island and propose the method of artificial sand nourishment in order to maintain the sandy beaches. The geological near-shore and onshore surveys revealed the following features of the western Kotlin Island coastal zone: 1) significant sediment deficit; 2) small (about 30 cm) thickness of the active sand layer, 3) predominance of narrow (10—15 m) sand beaches and 4) low and smooth offshore and onshore topography. The parameters of artificial beaches are determined by coupling the models of water circulation, waves, and sediment dynamics. Calculations of currents and waves were performed using a three-dimensional hydrodynamic model of the eastern Gulf of Finland and the SWAN wave model, respectively. The coast deformation due to storms was calculated using the CROSS-P model. Initial data were the existing depth profile, sediment characteristics, wind properties, wave parameters, the height of storm surges, and the duration of a storm. The actual external forcing (atmospheric forcing from the HIRLAM model, open boundary conditions from the HIROMB model, and bathymetry and topography of the beach obtained from geological surveys) is given, the parameters of artificial beach profiles have been calculated to withstand the maximum storm surge, and the annual volume of sand necessary for the conservation of the artificial beaches has been estimated.

188 taxa of benthic animals were recorded in the Neva estuary in 1994—2015. At present, zoobenthic communities in the estuary are dominated by eurybiont indicator species inhabiting “polluted” and “dirty” waters. We used integrated index IP' specially devised for water-bodies and rivers of the north-western Russia to assess the water quality and a state of ecosystems of the Neva estuary. It bases on structural parameters of zoobenthic communities and makes it possible to take into consideration the pollution by toxic and organic substances. On average the water quality of the Neva Bay assessed from IP′ values was relatively stable during 1994—2015. It was assessed as «polluted» with exception for 2006 and 2015 caused by large-scale dredging works. The average number of zoobenthic species in the Neva Bay increased during the period of 1982—2015 almost 2 times from 11±1 in 1982 to 20±2 species on a single station in 2014. Average values of Shannon’s indexes of benthic animals in the Neva Bay increased by one and half from 2±0.1 in 1982 to 3.0±0.3 bit/ind. in 2014. In 1994—2015 values of species richness and Shannon’s index, average for the Resort zone of the eastern Gulf of Finland, varied from 5±0.6 to 11±2 species at single station, and from 1.1±0.2 to 2.1±0.3 bit/ind. that were much lower than in the Neva Bay. This is caused not only by the influence of salinity, but also by the more intensive pollution of this zone.

The Baltic Sea is a sea basin affected by human-induced eutrophication. As required by the Baltic Sea Action Plan and Marine Strategy Framework Directive, the status of the marine areas is assessed based on indicators showing whether the good environmental status (GES) is achieved or not. The main result of the present work is that based on the national monitoring data from 2011-2016 and used nutrients, direct effects and indirect effects indicators, the entire Estonian marine area is affected by eutrophication. The overall eutrophication status is mostly defined by nutrient concentrations in the water or direct effects of eutrophication (chlorophyll-a, phytoplankton biomass, and water transparency). The non-GES result in the shallow Moonsund area is mostly determined by total phosphorus (TP) suggesting that threshold values for TP should be studied in more detail. The assessment results derived based on the proposed dissolved inorganic nutrients thresholds for the Estonian coastal waters agree well with the adjacent offshore assessment results. According to the suggested confidence evaluation scheme, the overall assessment result has mostly intermediate confidence, but high confidence in the open Gulf of Finland and coastal water bodies covered with yearly monitoring. Intermediate confidence in status assessment and the noticed high variability in the assessment results in the basins with monitoring data from only one year, point to the need for an increase of monitoring frequency there.

The aim of the present paper was to review the results obtained in our previous field and laboratory studies using cardiac monitoring system worked out in SRCES RAS for assessing of environmental pollution in a few problem aquatoria of the Baltic Sea Region. Paper is concerned also to the experience of development and approbation of proposed approach to the assessment of biological effects of environmental chemical stress based on evaluation of adaptive potential of indigenous species of the invertebrates from different in anthropogenic pressure fresh water, brackish water or marine areas, with the emphasize on subregions of the Baltic Sea (including estuary of the Neva River). The assessment of adaptivity was performed using method of physiological loading on bivalve mollusks (Anodonta anatina, Mytilus edulis, Mytilus trossulus and Macoma (Limecola) balthica) and anti-orthostatic test in crustacean (Carcinus maenas and Astacus leptodactylus), based on measuring the heart rate recovery time after removal of stress load. Rapid recovery (less than 50-60 min) signifies a good adaptive potential in different species, indicating good ecological status of the study site they inhabit. The paper presents a number of examples demonstrating how methodology for the evaluation of invertebrate’s physiological state can be used in ecosystem health assessment in the Baltic Sea Region.

The results of the beam attenuation coefficient measurements in the shelf and depth areas of Black Sea obtained during two cruises of R/V “Professor Vodyanitsky” in July and October 2016 are discussed. The methods of determining the concentration and scattering of suspended matter and absorption of dissolved organic matter in seawater are presented. The methods include empirical and analytical calculations based on measurements of the beam attenuation coefficient in four spectral channels, calculations of suspended matter backscattering and dissolved organic matter absorption from satellite measurements in the visible spectral range. A method allowing to obtain estimates of dissolved organic and suspended matter content using beam attenuation coefficient measurements in two spectral channels is proposed. Retrieved spatial distributions of suspended matter backscattering and dissolved organic matter absorption from satellite data are in good agreement with in situ measurements. There is a high correlation between the values calculated by contact and satellite data. The basic characteristics of suspended matter and dissolved organic matter calculated for two research cruises are presented. Results of this work represent the spatial and temporal variability of the primary hydrooptical characteristics of the investigated area. Considered methods make possible to assess the composition, bio-productivity and ecological state of waters.

We present a review of our long-term research of the bottom water flow in the Vema Channel in the South Atlantic. The Vema Channel is the main conduit for Antarctic Bottom Water between the Argentine and Brazil basins and further to the north. This channel is characterized by strong bottom flow. The bottom velocities are usually in the range 25—40 cm/s. The maximum measured velocities were as high as 60 cm/s. The total transport of Antarctic Bottom Water through the channel ranges from 1.6 to 4.0 (±0.2) Sv. The core of the coldest (θ = −0.120°C) and low salinity (34.665 psu) water is usually displaced to the eastern wall due to the Ekman friction. We used the numerical model for ocean circulations developed at the Institute of Numerical Mathematics to simulate the bottom flow in the Vema Channel. This is a σ-model based on the full system of thermo-hydrodynamic equations with the hydrostatic and Boussinesq approximations, which describes bottom currents more adequately than the z-models. Numerical simulations confirm the field measurements and reveal significant variability in the intensity and spatial structure of the velocity field in the channel.

The present modeling results support a view that the surface resulting circulation of waters in the Kara Sea is cyclonic, including one large-scale gyre in the south-western part of the Sea, one mesoscale gyre in the eastern part of the Sea and differently directed currents in the southern, central and northern parts of the Sea. The use of a high-resolving grid allows to reveal two mesoscale gyres in the south-western part of the Sea and an additional six mesoscale gyres having a different direction of rotation in the remaining part of the Sea. A comparison of two solutions performed, obtained for the overall (tidal + wind+ thermohaline) and combined (wind + thermohaline) forcing allows to quantify a contribution of tides to the formation of surface resulting circulation of waters. It turns out that tides introduce detectable changes in this circulation which origin is assumed to owe to wind and thermohaline factors.

The work is focused on the further development of a regional coupled eco-thermohydrodynamic model of the Arctic seas with the aim of using it to better understand the interaction of dynamic and ecosystem processes in the ocean under a changing climate in the Arctic. We used the MITgcm as a thermohydrodynamic block and an original 7-component ecosystem model which includes the carbon cycle as an ocean biogeochemistry block. The results of a model climatic run for a 40-year modern period for the Arctic shelf region (Kara, Barents and White Seas) are presented. The estimates of the spatial distribution of the chlorophyll-a concentration in the surface layer have clarified the effect of sea ice on primary production in the Arctic seas, including under conditions of a changing climate that leads to a significant reduction of ice cover in the Arctic Ocean. The clear relationship between the area of the marginal ice zone and primary production has been obtained: the moments of their spring-summer peaks coincide completely and they are highly correlated (0.87), proving the importance of this zone in the functioning of the marine ecosystem. As expected, the interannual variability of the integrated primary production and the total sea ice area (both averaged over the hydrological year — from October to September) have demonstrated an antiphase oscillation which means that the reduced sea ice cover area in the previous winter is one of the main reasons for the increase in primary production in the current year.