Gulf Of Finland Research Articles

Joint research in the Baltic Sea by the Atlantic Branch of the VNIRO and the Atlantic Branch of the Shirshov Institute of Oceanology of the RAS

The aim: complex study of the Baltic Sea ecosystem, including the habitat conditions of aquatic biological resources based on the results of joint research by AtlantNIRO and the P.P. Shirshov Institute of Oceanology RAS (Atlantic Branch). Methods used: analysis of long-term data of joint expeditionary research in the open part and coastal zone of the Baltic Sea.Results: owing to the interaction of AtlantNIRO with AB IO RAS in 2018–2022, the continuity of long-term observations has been preserved and the volume of scientific information necessary for assessing the state of the habitat of aquatic biological resources in the Russian sectors of the Baltic Sea has been increased. Modern data on eutrophication and pollution, on distribution of phytoplankton, zooplankton, benthos, as well as the early ontogenetic stages of the main commercial fish have been obtained. The spatial distribution of plankton and benthic communities, including areas favorable for spawning and feeding of fish, has been detailed. A rather high contamination of bottom sediments with radionuclides in certain areas of the Baltic Sea, primarily in the Gulf of Finland, has been found.Practical significance: the implementation of the areas provided by the Agreement between Rosrybolovstvo and RAS, and above all, the participation of AtlantNIRO scientific groups in expeditions in the Baltic Sea in 2018–2022, was a significant addition to the annual research and state monitoring of aquatic biological resources and their habitats conducted by VNIRO in the Baltic Sea.

Long-term changes in bloom dynamics of Southern and Central Baltic cold-water phytoplankton

In the Baltic Sea, cold-water adapted dinoflagellates and diatoms dominate the phytoplankton spring bloom of the Northern and Eastern Basins of the Baltic Sea. In the Central and Southern parts, where such species are less prominent, they cause occasional biomass peaks. We hypothesized that these dynamics correlate with ice cover, sea surface temperature (SST), and water transport processes, as the large Basins of the Central Baltic Sea are too deep to build-up blooms from their own seed banks. Long-term monitoring data from the past 40 and 20 years in the central and southern Baltic Sea, respectively, were analyzed here for biomass development of five cold-adapted taxa: the diatoms Pauliella taeniata, Thalassiosira baltica, Thalassiosira levanderi and Melosira spp. and the dinoflagellate Peridinella catenata. Results show that diatoms generally reached high biomass peaks in the 1980s and in shorter periods from 1995-1997, 2003- 2006, and 2010-2013 in all areas. We detected good correlations with the length of the ice cover period as well as low minimum and mean winter and spring SSTs. In contrast, biomass dynamics of the dinoflagellate P. catenata are more independent from these factors but have decreased strongly since the beginning of the 21st century. A numerical ocean model analysis confirmed the hypothesis that large blooms in the deep basins are seeded through water transport from adjacent shallow, ice-covered coastal areas such as the Gulf of Finland and the Gulf of Riga. Our results show that under ongoing climate warming, the common cold-water species may disappear from spring blooms in southern and central areas with unknown consequences for the ecosystem.

Expeditional Studies in the Baltic Sea in Cruise 54th of the R/V “<i>Akademik Sergei Vavilov</i>”

Brief results of oceanological studies of the southeastern part of the Baltic Sea and the Gulf of Finland during 54th cruise of the R/V Akademik Sergei Vavilov (2022) are presented. Hydrology, hydro- and geochemistry, hydrobiology, geoecology, geology and geophysics investigations were carried out. New data on the state and dynamics of the natural complexes of the Baltic Sea under the conditions of increasing anthropogenic pressure and climate change were obtained.

Upwelling characteristics in the Gulf of Riga (Baltic Sea): multiple data source approach

Upwellings are characteristic for the Baltic Sea region including the Gulf of Riga, although the current knowledge is rather limited with only few research conducted in the Gulf itself. Upwelling events in the Gulf of Riga in 2010–2022 were studied by analyzing sea surface temperature time series from coastal stations and SmartBuoy, together with satellite data, model data, and CTD (conductivity, temperature, and depth) surveys. The starting/end point, active, and relaxation phases were defined in each event to describe the characteristics and length of each phase. Upwellings were less frequent (41%) on the eastern coast but lasted longer and had higher temperature drops than on the western coast. On the western coast, a variety of upwelling characteristics between stations only 30 km apart were found with the likely reason being the different orientations of the coastline with respect to the wind direction. Satellite data revealed that on the western coast of the Gulf, rather small upwelling events form along specific sections of the coastline. Of all upwelling events, 30% were characterized by an immediate temperature increase after reaching the minimum temperature, and we suggest that this is related to a distinct change in wind direction. The results from the simulations indicated smaller lateral density and salinity gradients in the sea surface than in larger Baltic Sea gulfs. It signals that conditions for the occurrence of baroclinic instabilities are rather small; thus, we suggest that weaker gradients could explain quite fast upwelling relaxation in the basin if compared to, e.g., the Gulf of Finland.

Assessment of the Conservation Value of Abandoned Land on Gogland Island, Baltic Sea

Gogland Island, located in the Gulf of Finland in the Baltic Sea, was densely populated in the past but has been nearly abandoned since the Second World War. The self-restoration of wildlife takes place there. Recent research on the island aimed to evaluate the conservation value of this process. It was expected that the island would demonstrate a standard for the perfect state of protected areas of the boreal zone of Europe. The island has been overgrown with forests; open areas occupy insignificant parts and tend to shrink. Picturesque landscapes have been formed, but the conservation value of these areas are questionable as the biodiversity is rather low there. They contain “empty forest” that is partly impassable. The island demonstrates that to achieve the maximum effect for biodiversity conservation, the abandonment of land without any management would be insufficient. The fate of the island partly supports the concept of Pleistocene rewilding: a mosaic of forests and meadows, maintained by ungulates, should be considered a normal state of environments.

Algicidal Activity and Microcystin-LR Destruction by a Novel Strain Penicillium sp. GF3 Isolated from the Gulf of Finland (Baltic Sea).

The present article focuses on a strain of ascomycete GF3 isolated from a water sample taken in the Gulf of Finland. Based on phylogenetic analysis data, the isolate was identified as Penicillium sp. GF3. The fungus GF3 demonstrates algicidal activity towards cyanobacteria (98-100%). The algicidal effect on green algae did not exceed 50%. The isolate GF3 exhibits an indirect attack mode by releasing metabolites with algicidal and/or lytic activity into the environment. Moreover, the strain Penicillium sp. GF3 is able to degrade MC-LR. After 72 h of GF3 cultivation, the MC-LR content was reduced by 34.1% and 26.7% at initial 0.1 μg/mL and 0.45 μg/mL concentrations, respectively. The high stress resistance of the GF3 to toxic MC-LR is provided by a 1.5-fold activation of catalase activity and a change in the reduced glutathione content. Additionally, during the MC-LR biotransformation, a MC-LR-GSH conjugate and linearized MC-LR were identified. The linearized MC-LR in the presence of fungi capable of degrading MCs was revealed for the first time. Using Daphnia magna as a bioindicator, it was shown that the MC-LR biotransformation led to the formation of less toxic intermediates. The toxicity of the fungal filtrate is reduced by five times compared to the abiotic control. Our findings enhance the understanding of the role that ascomycete fungi have as potential bioagents for cyanoHABs to control and detoxify water bodies.

Wind-driven salinity tongue migration in the Gulf of Finland according to NEMO and ERA5 reanalyses

Two hypothesis that can be responsible for the wind-driven migration of the salinity tongue in the bottom layer of the Gulf of Finland (GoF) are tested based on the NEMO and ERA5 reanalyses. The first hypothesis authored by Krauss and Brügge (1991) implies along-channel wind developing upwelling and downwelling jet-like currents in the wind direction at opposite lateral boundaries of the channel, and a compensatory countercurrent in the deep layer (the so-called coastal jet hypothesis). The second hypothesis implies the cross-channel wind developing the along-channel Ekman transport in the upper layer, and a countercurrent in the deep layer (so-called Ekman transport hypothesis). The salinity tongue migration velocity along the GoF thalweg as estimated from the NEMO output is found to be extremely correlated with the along-thalweg projection of the wind stress calculated from the ERA5 output. This is a convincing evidence in favor of the coastal jet hypothesis as opposed to the Ekman transport hypothesis to correctly describe the mechanism of the wind-driven migration of salinity tongue in GoF. Based on a theory of coastal upwelling/downwelling in a two-layer fluid, some analytical considerations and related empirical estimates are presented to explain the prevailing coastal jet mechanism in GoF.

Environmental Assessment with Cage Exposure in the Neva Estuary, Baltic Sea: Metal Bioaccumulation and Physiologic Activity of Bivalve Molluscs

The rise in anthropogenic impacts on the marine environment requires new water management. The use of a triadic approach (bioaccumulation, bioassay, and physiological biomarkers) has been shown to have good applicability for the comparative assessment of the environmental state of the Neva Estuary (Gulf of Finland, Baltic Sea). The novelty of the methodological approach of the study was that it involved both active and passive bio-monitoring methods for assessing the quality of estuarine environment. The classical analyses of metal concentration in bottom sediments, in field biota (fish and molluscs), and in caged molluscs were accompanied by a bioassay of sediment toxicity using amphipods. The physiological state of molluscs kept in cages was assessed according to two functional characteristics, such as cardio-tolerance and metabolic activity (oxygen consumption rate), after exposition in cages. The method of active monitoring (caging exposure with molluscs) as a measurement of parameters in clean molluscs has proven itself well in controlling the accumulation of both metals and oil products. Macroalgae that are abundant in estuarine ecosystems are also good indicators of metals, at least showing the transition from bottom sediments to the next level of food webs. Unionid molluscs were found to be a more sensitive and effective indicator of contaminant accumulation than dreissenid molluscs, characterized by a low tolerance to changeable environmental conditions in the estuarine ecosystem and rather high mortality in cages. Our results have shown that caging exposure with unionids can be a widely used methodological approach for the assessment of estuarine environmental quality through the determination of metal concentrations in molluscs and their physiological state.

Multi-level assessment of the origin, feeding area and organohalogen contamination on salmon from the Baltic Sea

The Atlantic salmon (Salmo salar) population in the Baltic Sea consists of wild and hatchery-reared fish that have been released into the sea to support salmon stocks. During feeding migration, salmon migrate to different parts of the Baltic Sea and are exposed to various biotic and abiotic stressors, such as organohalogen compounds (OHCs). The effects of salmon origin (wild or hatchery-reared), feeding area (Baltic Main Basin, Bothnian Sea, and Gulf of Finland), and OHC concentration on the differences in hepatic proteome of salmon were investigated. Multi-level analysis of the OHC concentration, transcriptome, proteome, and oxidative stress biomarkers measured from the same salmon individuals were performed to find the key variables (origin, feeding area, OHC concentrations, and oxidative stress) that best account for the differences in the transcriptome and proteome between the salmon groups. When comparing wild and hatchery-reared salmon, differences were found in xenobiotic and amino acid metabolism-related pathways. When comparing salmon from different feeding areas, the amino acid and carbohydrate metabolic pathways were notably different. Several proteins found in these pathways are correlated with the concentrations of polychlorinated biphenyls (PCBs). The multi-level analysis also revealed amino acid metabolic pathways in connection with PCBs and oxidative stress variables related to glutathione metabolism. Other pathways found in the multi-level analysis included genetic information processes related to ribosomes, signaling and cellular processes related to the cytoskeleton, and the immune system, which were connected mainly to the concentrations of Polychlorinated biphenyls and Dichlorodiphenyltrichloroethane and their metabolites. These results suggest that the hepatic proteome of salmon in the Baltic Sea, together with the transcriptome, is more affected by the OHC concentrations and oxidative stress of the feeding area than the origin of the salmon.

Research of the Baltic Sea in the 61 Cruise of the R/V <i>Akademik Ioffe</i> (June–July 2022)

In the 61st cruise of the R/V Akademik Ioffe (June 28–July 12, 2022), complex oceanographic survey was carried out in the Russian sectors of the South-Eastern Baltic Sea and the Gulf of Finland. In the conditions of long-term absence of major inflows of North Sea waters, hypoxia and anoxia continue to develop in deep waters. In the eastern part of the Gdansk Deep, a contourite drift was identified for the first time, formed during the Littorina phase of the Baltic Sea. Together with the Kant Baltic Federal University, complex study was carried out on the offshore site of the Kaliningrad carbon polygon and the V International Summer School “Coastal zone of the sea: research, management and prospects” was held.

Heavy Metal Content in Macroalgae as a Tool for Environmental Quality Assessment: The Eastern Gulf of Finland Case Study

Macroalgae are widely used for bioindication and assessment; however, in the case of pollutants of different origin, it is still unclear which contaminants in thalli can be regarded as indicative because too many factors influence the ability of algae to uptake them. The present study is a part of an international HAZLESS project and was conducted in the eastern Gulf of Finland (GoF). The main goal of our study was the application of metal concentrations in macroalgae as a tool for environmental quality assessment. To achieve this goal, we calculated the threshold metal concentrations in macroalgae (Cladophora glomerata) and compared our obtained values with actual concentrations. We found significant Spearman correlations in May between metals in sediments and pore water (−0.73 for Zn, −0.62 for Cd, 0.85 for Pb) and also between metals in algae and metals in pore water (1 for Cu and Cd, 0.98 for Zn and Pb). In July, Pb in algae were significantly correlated with Pb in pore water (0.88). The application of the calculated environmental quality standard (EQSMPC) for macroalgae has shown moderate pollution by Cu and Pb in the coastal zone of the eastern GoF. This was confirmed by an assessment based on the comparisons of metal concentrations in water with Environmental Quality Standards for water (EQSw). However, differences in the bioaccumulation factor and EQSMPC between May and July have shown that it is necessary to compare samples taken during the same period every year for adequate results in long-term monitoring. Considering the sensitivity of accumulating processes to the surrounding environment, we believe that in the case of habitats with diverse conditions, even for the same species of algae, threshold values should be calculated and used individually for every habitat. Our results have shown that this approach can be widely used for an assessment of environmental quality via metal concentrations in opportunistic macroalgae and can be recommended for further use.

The Gulf of Finland as an Unknown Waterscape that Needs to Be Tamed Perceptions, Imaginaries and Knowledge in Imperial St. Petersburg

The paper summarizes the study of St. Petersburg as a center of multifaceted control and management of the adjacent lagoonscape through the perspective of knowledge as a social construct. We argue that the dwellers of the Russian capital knew their surrounding environment in a variety of ways. We can distinguish knowledge based on perception, imagination, and observation, and these three societal mechanisms of dealing with the nature of the Neva inlet, the most eastern part of the Gulf of Finland, shaped the ways of development of St. Petersburg as the center of complicated network interactions that eventually created the St. Petersburg maritime empire.

Forecasting of absolute dynamic topography using deep learning algorithm with application to the Baltic Sea

Accurate sea-level forecasting is crucial for navigation, engineering and coastal conservation. One of the major obstacles in obtaining accurate sea-level data, both at coastal and offshore areas, has been in defining a realistic vertical datum. The Baltic Sea countries, however, have collaborated in calculating a high-resolution regional geoid model (NKG2015). This now paves the way for determining accurate sea-levels over the entire sea. Accordingly, this study explores the application of a deep learning two-dimensional Convolutional Neural Network (Conv2D) technique along with using essential inputs (e.g. accurate dynamic topography (DT), wind speed and direction, surface pressure and temperature). The method was tested for a three-year 2017–2019 period in the Baltic Sea. The evaluation was based on two statistical criteria: spatial root mean squared error (RMSE) and R-squared (R2). Results revealed that the proposed Conv2D model allows predicting the DT of the Baltic Sea, with an R2 of 0.91. The spatial RMSE plot also confirms accurate DT predictions for most of the Baltic Sea points, with the discrepancies distributed within ±4 cm. Spatially, some larger RMSE values (∼10 cm) were obtained at particular locations in south-eastern Baltic Sea, which may be due to the input sources utilized. Examination of sea level maxima also showed that the Conv2D model reproduced the maxima events in most scenarios (9 of 10 and 8 of 11 in Gulf of Finland and Riga, respectively) with residuals that varied up to 7 cm–18 cm. For the higher residuals, the Conv2D tended to underestimate the sea level. This suggests the importance of considering the necessary inputs (e.g waves) for forecasting storm surges and that the Conv2D model can still be improved. External validation was also performed using along-track sea level satellite altimetry data, with differences between forecasted model and satellite being within 5 cm. This confirms the validity of the forecasted model and the occurrences of model biases to be minimum. The method utilized shows the potential to contribute toward operational sea level forecasting in the Baltic Sea.

A machine learning method for the prediction of ship motion trajectories in real operational conditions

This paper presents a big data analytics method for the proactive mitigation of grounding risk. The model encompasses the dynamics of ship motion trajectories while accounting for kinematic uncertainties in real operational conditions. The approach combines K-means and DB-SCAN (Density-Based Spatial Clustering of Applications with Noise) big data clustering methods with Principal Component Analysis (PCA) to group environmental factors. A Multiple-Output Gaussian Process Regression (MOGPR) method is consequently used to predict selected ship motion dynamics. Ship sway is defined as the deviation between a ship and her motion trajectory centreline. Surge accelerations are used to idealise the time-varying manoeuvring of ships in various routes. Operational conditions are simulated by Automatic Identification System (AIS), General Bathymetric Chart of the Oceans (GEBCO), and nowcast hydro-meteorological data records. A Dynamic Time Warping (DTW) method is adopted to identify ship centre-line trajectories along selected paths. The machine learning algorithm is applied for ship motion predictions of Ro-Pax ships operating between two ports in the Gulf of Finland. Ship motion dynamics are visualised along the ship's route using a Gaussian Progress Regression (GPR) flow method. Results indicate that the present methodology may assist with predicting the probabilistic distribution of ship dynamics (speed, sway distance, drift angle, and surge accelerations) and grounding risk along selected ship routes.

Решение задачи гашения свободных колебаний уровенной поверхности воды в Финском заливе

The proposed article is the third paper of the authors from Mozhaisky Military Space Academy published in Hydrometeorological Research and Forecasting journal (No. 1 (371) in 2019, No. 2 (380) in 2021), which show how optimization methods (from the classic calculus of variations to modern Pontryagin methods and the method of moments) can be applied for solving specific problems of managing natural processes. In the present paper, a system of equations was chosen for forecasting storm surges in the Gulf of Finland, which, as calculations based on observations showed, allows predicting the maximum level of water rise at the Neva River mouth with an error not exceeding 10%. An algorithm for solving the problem of damping free oscillations of the water level surface in the Gulf of Finland is proposed. The results of calculations of control actions, as well as the levels of water rise during the damping of a free gravity wave with unilateral and bilateral actions are presented. The results of the calculations on the example of the flood on September 28-29, 1975 showed that when damping the free gravity wave of the storm surge, the maximum level of water rise at the Neva River mouth could be reduced from 280 to 194-195 cm, that is, by 85-86 cm (30%). Keywords: storm surge, free oscillations of the water surface, control action

A comparison of Baltic Sea wave properties simulated using two modelled wind data sets

We calculated two sets of idealised ice-free wave hindcast data on a high-resolution, three-layer nested grid covering the Baltic Sea, using two different wind datasets (ERA5 and BaltAn65+), to evaluate the performance of the model in the open and sheltered parts of the sea. The highest resolution of the grids is 260 m. The outcome of simulations is compared against the available in-situ measurements. The main statistical properties of the Baltic Sea wave climate as well as the timing and maximum values of extreme significant wave heights are well replicated in the Baltic proper using the 3 nautical mile (nmi) grid. Simulations using BaltAn65+ have a better match with recorded average wave properties while the ERA5 forcing better replicates wave extremes. The largest differences between the two simulations occur in the Sea of Bothnia, Bay of Bothnia and to the east of large islands. Wave climate in the Gulf of Finland is replicated with a resolution of 1 nmi in the open part of the gulf a down to a resolution of 260 m in selected coastal areas. The wave intensity is the largest in the central part of the gulf and decreases towards the coast and from the West to the East. The use of ERA5 winds yields higher wave heights at the entrance of the gulf and in the central part of the gulf along its axis. Simulations using BaltAn65+ winds show higher waves in the nearshore regions.

Determining the distribution and accumulation patterns of floating litter in the Baltic Sea using modelling tools

Marine plastic floating on the sea surface is an extensive environmental problem. The present study investigated the transport patterns of marine litter and areas of its accumulation in the Baltic Sea by using a hydrodynamic model coupled with a particle-tracking model. We also studied the extent of marine litter from the main polluting rivers. Mapping of marine plastic debris distribution in 2017–2018 revealed that the largest plastic accumulation area is between latitude 59° N and 61° N, which includes the Northern Baltic Proper, Archipelago Sea, and the Gulf of Finland. The floating plastic spreads from the largest plastic pollution sites River Vistula, Oder and Neman to the waters of all the countries around the Baltic Sea.

A deep learning method for the prediction of 6-DoF ship motions in real conditions

This paper presents a deep learning method for the prediction of ship motions in 6 Degrees of Freedom (DoF). Big data streams of Automatic Identification System (AIS), now-cast, and bathymetry records are used to extract motion trajectories and idealise environmental conditions. A rapid Fluid-Structure Interaction (FSI) model is used to generate ship motions that account for the influence of surrounding water and ship-controlling devices. A transformer neural network that accounts for the influence of operational conditions on ship dynamics is validated by learning the data streams corresponding to ship voyages and hydro-meteorological conditions between two ports in the Gulf of Finland. Predictions for a ship turning circle and motion dynamics between these two ports show that the proposed method can capture the influence of operational conditions on seakeeping and manoeuvring.

Effects of Eulerian current, Stokes drift and wind while simulating surface drifter trajectories in the Baltic Sea

The simulation of Lagrangian drift is an important task in applications such as dispersion of pollutants, larvae and search and rescue activities. In this study, the Eulerian current, Stokes drift and wind effect on the simulation of observed drifters were analysed. The Lagrangian OceanParcels model was used, and the surface trajectories were assessed by comparison with 9 GPS drifter trajectories in the Gulf of Finland, Gulf of Riga and Lithuanian coast. The Normalised Cumulative Lagrangian Separation (NCLS) distance between the simulated and the satellite-tracked drifter trajectories, and the mean absolute error (MAE) were used as comparison metrics. The present study suggests the need to consider the Stokes drift and the wind factor in addition to the modelled Eulerian currents to obtain a better description of the trajectories of particles. By making these considerations, the OceanParcels model could adequately simulate particle trajectories in the sub-basins within the Baltic Sea. The realized model tests showed that motion of surface drifters are strongly controlled by the Stokes drift when the significant wave height is >1 m, whereas the wind component and the Eulerian currents are crucial when the significant wave height is <0.6 m or the wave (Stokes drift) directions do not match the wind direction.

Diffraction of the Field of a Grounded Cable on an Elongated Dielectric Spheroid in a Conducting Layer

Based on a rigorous solution to the problem, analytical expressions are obtained for calculating the diffraction of the electromagnetic field of a grounded cable on an elongated dielectric spheroid in a conductive layer. The field of a grounded AC cable in a conductive layer is determined by solving the Helmholtz equation for the vector potential by using the method of integral Fourier–Bessel transformations, taking into account the boundary conditions at the bottom and surface of the conductive layer. The process of finding the secondary field of an elongated dielectric spheroid on an alternating current in a conducting layer is divided into two stages. First, we find an exact solution to the problem of an elongated dielectric spheroid at a constant current in a homogeneous field, in free space, decomposing this solution into a Taylor series and retaining the first term, which is a dipole approximation. In the second stage, the resulting field as the sum of the fields of the horizontal and vertical dipoles is analytically continued into the frequency domain. The field of the horizontal and vertical dipoles in the conducting layer is obtained by using the method of integral Fourier–Bessel transformations, taking into account the boundary conditions at the bottom and surface of the conducting layer. The resulting solution is presented in a closed form in elementary functions and has an accuracy level acceptable for the practice. Graphs showing the flow characteristics of an elongated dielectric spheroid modeling a swimmer in a light diving suit are given. The influence of the water–air boundary on the increase in the secondary field of the dielectric spheroid, which leads to an increase in the reliability of object detection, is revealed. The practical implementation of the described device protected by a patent and the experimental data of testing the device layout on the Gulf of Finland are given. A good agreement between the theoretical and experimental flow characteristics of a dielectric object both in shape, amplitude, and phase, is revealed.