Baltic Sea Basin Research Articles

Seasonality and long-term trends of NDVI values in different land use types in the eastern part of the Baltic Sea basin

This study analyses changes in Normalized Difference Vegetation Index (NDVI) values in the eastern Baltic region. The main aim of the work is to evaluate changes in growing season indicators (onset, end time, time of maximum greenness and duration) and their relationship with meteorological conditions (air temperature and precipitation) in 1982–2015. NDVI seasonality and long-term trends were analysed for different types of land use: arable land, pastures, wetlands, mixed and coniferous forests. In the southwestern part of the study area, the growing season lasts longest, while in the northeast, the growing season is shorter on average by 10 weeks than in the other parts of the analysed territory. The air temperature in February and March is the most important factor determining the start of the growing season and the air temperature in September and October determines the end date of the growing season. Precipitation has a much smaller effect, especially at the beginning of the growing season. The effect of meteorological conditions on peak greenness is weak and, in most cases, statistically insignificant. At the end of the analysed period (1982–2015), the growing season started earlier and ended later (in both cases the changes were 3–4 weeks) than at the beginning of the study period. All these changes are statistically significant. The duration of the growing season increased by 6–7 weeks.

COVID-19 Anchor for Cruise Tourism. An analysis of Gdańsk’s and Gdynia's Cruise Tourism in the 2017-2020 Period

In many Member States, European regions and cities, tourism is a key factor in the economic and social structure. The COVID-19 pandemic that broke out in 2020 caused significant losses in the tourism sector area in all European Union (EU) countries. This applies in particular to one of the elements of the tourism sector of any economy with access to the sea - the possibility of accepting cruise ships. This cruise tourism sector has also been hit hard by the COVID-19 pandemic.
 The aim of this paper is to estimate the number of selected expenditures of passengers and cruise ship crews entering the ports of Gdańsk and Gdynia, which are a source of revenue for the region, as well as the impact of the COVID-19 pandemic on limiting the growth of this tourism segment. Our study takes a holistic approach by estimating the amount of revenue generated by tourists arriving in the two ports in the Gulf of Gdańsk capable of handling large cruise ships. Based on the number of arriving tourists in 2017-2020, the study estimates the income of tourism enterprises that receive a direct cash inflow from offering services to arriving tourists.
 The tourism sector that was particularly affected by the pandemic was cruise tourism. In 2020, this sector recorded an over 5-fold decrease in the number of cruise ship passengers. The conclusions of the study show that the number of cruise ships arriving in the analysed ports in 2020 decreased significantly compared to the previous year, similarly to other ports in the region. At the same time, the number of passengers visiting the analysed ports decreased substantially. Nevertheless, the dynamic growth of cruise tourism in the Baltic Sea basin, which began before the COVID-19 pandemic, allows for conclusions about further development of this tourism segment and its potential impact on the region’s economy after the crisis which occurred in 2020.

Re‐meander, rewet, rewild! Overwhelming public support for restoration of small rivers in the three Baltic Sea basin countries

Baltic Sea is one of the World's most oxygen‐depletes seas, so the region requires urgent mitigation measures to significantly reduce nitrogen and phosphorus inputs from land through rivers, which cannot be achieved without large‐scale restoration of wetland buffer zones. The manuscript summarizes the findings of the discrete choice experiment aimed at assessment of the preferences of Danish, German, and Polish citizens toward ecosystem services of lowland small rivers of the Baltic Sea basin. Our results suggest that respondents in all the studied countries are willing to pay substantial amounts to improve water quality in rivers and the Baltic Sea, as well as to restore naturally meandering rivers and natural riparian vegetation. Wild marshes and Wetland agriculture were equally valued as the most desirable options. Respondents systematically cared about the appearance of small rivers in their neighborhood. We conclude that re‐meandering, rewetting of floodplains, and restoration of wild marshes (i.e. natural wetland vegetation) or development of wetland agriculture could gain a lot of public support in Europe.

Co-evolution of the terrestrial and aquatic ecosystem in the Holocene Baltic Sea

Abstract. The Baltic Sea experienced changes in marine input throughout the Holocene as substantial regional ice retreat led to isostatic adjustment, eustatic sea level change, and periodic isolation from the North Sea. Here, we determine the distributions and isotopic signatures of organic compounds preserved in a sediment record spanning the last ∼11 kyr to reconstruct environmental change under these dynamic conditions. Carbon and hydrogen isotope ratios of short-, mid-, and long-chain n-alkanes, along with long-chain diol and glycerol dialkyl glycerol tetraether abundances, were analyzed in sediments sampled from the Arkona Basin in the southwestern Baltic Sea. In the earlier part of the record (specifically 10–8.2 ka), hydrogen isotope values of higher plant-derived n-alkanes revealed a change in dominant water source from an ice-melt-derived to a precipitation-dominated hydrological regime. Following this shift in water source, carbon isotope values of n-alkanes suggest diversification of vegetation. Shifts in hydrology and vegetation did not coincide with established phase boundaries but instead occurred mid-phase or spanned phase transitions. For this reason, we suggest describing the Ancylus Lake in two phases: a meltwater phase (10.6 to 9.2 ka) and a precipitation phase (9.2 to 7.7 ka). Our results highlight the utility of using C and H isotope ratios in conjunction with other compound abundance proxies to better understand the complex environmental change recorded in paleoarchives.

Acid sulfate soils and their impact on surface water quality on the Swedish west coast

Study regionHalland county, located on the Swedish west coast, with a special focus on the area around Ramsjö canal (Falkenberg municipality). Study focusThis study contributes to the understanding of the development of active acid sulfate soils and environmental consequences of leaching from these soils in an area without previous investigations. Samples taken from different soil profiles in an agricultural area and water samples from the agricultural drainage system were analysed in pH, electrical conductivity, and metal concentrations. To evaluate the on-site situation, the results of the soils sample analysis were compared to the national soil classification system and the water samples to areas in northern Europe affected by acid sulfate soils. New hydrological insights for the regionThe results prove the existence of active acid sulfate soils in a coastal area in Halland. In the study region, acid sulfate soils were discovered in an agricultural area of drained wetland and peatland. Water samples taken from the drainage system and a man-made canal flowing into Kattegat Sea have low pH combined with high electrical conductivity and increased metal concentrations. This is a direct consequence of intensive leaching from the discovered acid sulfate soils in that area. Therefore, this is the first case study proving the existence of acid sulfate soils and highlighting their environmental impact on surface water quality on the Swedish west coast (i.e. outside the Baltic Sea Basin).

Coastal regions in the geography of innovation activity: A comparative assessment of marine basins

Across the globe marine coasts are experiencing an outstripping growth of the population and economic activity, a phenomenon known as coastalization. Most global cities and industry clusters are located in coastal regions acting as economic growth nodes for their respective countries. This divergence is equally true for national innovation systems, gravitating towards highly urbanized coastal areas. The study is designed to evaluate the spatial stratification of the knowledge production between the coastal regions located in different marine basins - Azov-Black, Caspian, Baltic, Arctic, and Pacific. In order to level-out the national differences of the innovation policy and institutional architecture, the research is held in a single country - the Russian Federation. Our research hypothesis suggests that the knowledge production domain of the innovation activity is influenced by urbanization and coastalization, i.e. the proximity to the core city and the coast. We also expect that the coastalization factor would be reflected in intensified involvement of coastal municipalities in knowledge production networks. The study is based on processing the ROSRID database of 66,647 research projects implemented in 2017-2019 and geocoded using the Yandex.Maps API. The research has shown that the urbanization factor has the strongest influence in configuration of R&D networks - the core centers of knowledge production are the largest cities in marine basins that give further impetus to the involvement of neighboring municipalities. Nearly 70% of municipalities across marine basins have limited or no involvement in the knowledge production, except the Baltic and Azov-Black Sea basins that feature the strongest performance. Overall, the proximity to the coast of non-freezing seas has a positive correlation with the number of R&Ds executed and funded. Considering the research topics, the share of marine-related research is typically funded by coastal regions, whereas the executed R&Ds cover a broad variety of topics. Research results enrich the notion of geography of innovation and advance our understanding of the spatial factors in knowledge distribution within the national innovation system.

Interplay between eutrophication and climate warming on bacterial communities in coastal sediments differs depending on water depth and oxygen history

Coastal aquatic systems suffer from nutrient enrichment, which results in accelerated eutrophication effects due to increased microbial metabolic rates. Climate change related prolonged warming will likely accelerate existing eutrophication effects, including low oxygen concentrations. However, how the interplay between these environmental changes will alter coastal ecosystems is poorly understood. In this study, we compared 16S rRNA gene amplicon based bacterial communities in coastal sediments of a Baltic Sea basin in November 2013 and 2017 at three sites along a water depth gradient with varying bottom water oxygen histories. The shallow site showed changes of only 1.1% in relative abundance of bacterial populations in 2017 compared to 2013, while the deep oxygen-deficient site showed up to 11% changes in relative abundance including an increase of sulfate-reducing bacteria along with a 36% increase in organic matter content. The data suggested that bacterial communities in shallow sediments were more resilient to seasonal oxygen decline, while bacterial communities in sediments subjected to long-term hypoxia seemed to be sensitive to oxygen changes and were likely to be under hypoxic/anoxic conditions in the future. Our data demonstrate that future climate changes will likely fuel eutrophication related spread of low oxygen zones.

Spatio-temporal variation in stable isotope and elemental composition of key-species reflect environmental changes in the Baltic Sea

Carbon and nitrogen stable isotope ratios are increasingly used to study long-term change in food web structure and nutrient cycling. We retrospectively analyse elemental composition (C, N and P) and stable isotopes (δ13C, δ15N) in archived monitoring samples of two important taxa from the bottom of the food web; the filamentous ephemeral macroalgae Cladophora spp. and the blue mussel Mytilus edulis trossulus from three contrasting regions in the Baltic Sea (coastal Bothnian Sea and Baltic Proper, open sea central Baltic). The aim is to statistically link the observed spatial and interannual (8–24 years’ time-series) variability in elemental and isotope baselines with their biomass trends and to the oceanographic monitoring data reflecting the ongoing environmental changes (i.e., eutrophication and climate) in this system. We find clear differences in isotope baselines between the two major Baltic Sea basins. However, the temporal variation in Mytilus δ13C was similar among regions and, at the open sea station, mussels and algae δ13C also correlated over time, likely reflecting a global (Suess) effect, whereas δ15N of both taxa varied with local and regional dissolved nitrogen concentrations in water. δ15N in source amino acids allowed detection of diazotrophic N in Mytilus, which was masked in bulk δ15N. Finally, Cladophora N:P reflected regional nutrient levels in the water while P%, which differed for both taxa, was linked to food quality for Mytilus. This study highlights the potential of a multi-taxa and multi-stable isotope approach to understand nutrient dynamics and monitor long-term environmental changes.

Distribution of perfluoroalkyl acids in fish species from the Baltic Sea and freshwaters in Finland

Occurrence and distribution of perfluoroalkyl acids (PFAAs), a sub-category of per- and polyfluoroalkyl substances (PFASs), is widespread in the environment. Food, especially fish meat, is a major pathway via which humans are exposed to PFAAs. As fish is an integral part of Nordic diet, therefore, in this study, several fish species, caught in selected Baltic Sea basins and freshwater bodies of Finland, were analysed for PFAAs. Perfluorooctane sulfonate (PFOS) was detected in all Baltic Sea fish samples and in >80% fish samples from freshwaters. PFOS contributed between 46 and 100% to the total PFAA concentration in Baltic Sea fish samples and between 19 and 28% in fish samples from freshwaters. Geographically, concentration ratios of PFOS to other PFAAs differed between fish from the Baltic Sea and Finnish lakes suggesting that distribution of PFAAs differ in these environments. Results were compared with current safety thresholds – environmental quality standard for biota (EQSbiota) set by the European Commission and a group tolerable weekly intake (TWI) for the sum of four PFASs (∑PFAS-4) i.e. perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorohexane sulfonate (PFHxS) and PFOS, recommended by the European Food Authority (EFSA). EQSbiota compliance was observed for PFOS in all species except smelt caught in the Baltic Sea and also in the River Aurajoki, where smelt had migrated from the Baltic Sea for spawning. Moderate consumption of most Baltic fishes (200 g week−1) results in an exceedance of the new TWI (4.4 ng kg−1 body weight week−1) for ∑PFAS-4.

Low neutral and immunogenetic diversity in northern fringe populations of the green toad Bufotes viridis: implications for conservation

Genetic variation is often lower at high latitudes, which may compromise the adaptability and hence survival of organisms. Here we show that genetic variability is negatively correlated with northern latitude in European green toads (Bufotes viridis). The result holds true for both putatively neutral microsatellite variation and supposedly adaptive MHC Class IIB variation. In particular, our findings have bearing on the conservation status of this species in Sweden, on the northern limit of its distribution where local populations are small and fragmented. These genetically impoverished populations are closely related to other populations found around the Baltic Sea basin. The low neutral and adaptive variation in these fringe populations compared to population at central ranges confirms a pattern shared across all other amphibians so far studied. In Sweden, the situation of green toads is of concern as the remaining populations may not have the evolutionary potential to cope with present and future environmental challenges.

Potential Activities and Long Lifetimes of Organic Carbon-Degrading Extracellular Enzymes in Deep Subsurface Sediments of the Baltic Sea.

Heterotrophic microorganisms in marine sediments produce extracellular enzymes to hydrolyze organic macromolecules, so their products can be transported inside the cell and used for energy and growth. Therefore, extracellular enzymes may mediate the fate of organic carbon in sediments. The Baltic Sea Basin is a primarily depositional environment with high potential for organic matter preservation. The potential activities of multiple organic carbon-degrading enzymes were measured in samples obtained by the International Ocean Discovery Program Expedition 347 from the Little Belt Strait, Denmark, core M0059C. Potential maximum hydrolysis rates (Vmax) were measured at depths down to 77.9mbsf for the following enzymes: alkaline phosphatase, β-d-xylosidase, β-d-cellobiohydrolase, N-acetyl-β-d-glucosaminidase, β-glucosidase, α-glucosidase, leucyl aminopeptidase, arginyl aminopeptidase, prolyl aminopeptidase, gingipain, and clostripain. Extracellular peptidase activities were detectable at depths shallower than 54.95mbsf, and alkaline phosphatase activity was detectable throughout the core, albeit against a relatively high activity in autoclaved sediments. β-glucosidase activities were detected above 30mbsf; however, activities of other glycosyl hydrolases (β-xylosidase, β-cellobiohydrolase, N-acetyl-β-glucosaminidase, and α-glucosidase) were generally indistinguishable from zero at all depths. These extracellular enzymes appear to be extremely stable: Among all enzymes, a median of 51.3% of enzyme activity was retained after autoclaving for an hour. We show that enzyme turnover times scale with the inverse of community metabolic rates, such that enzyme lifetimes in subsurface sediments, in which metabolic rates are very slow, are likely to be extraordinarily long. A back-of-the-envelope calculation suggests enzyme lifetimes are, at minimum, on the order of 230days, and may be substantially longer. These results lend empirical support to the hypothesis that a population of subsurface microbes persist by using extracellular enzymes to slowly metabolize old, highly degraded organic carbon.

Geographical concerns regarding flood hydrology in the southeastern area of the Baltic Sea basin

ABSTRACT In the Baltic Sea region, the impact of physico-geographical factors is not very clear, although it is relevant in this basin. This study assessed the interaction of geographical factors (lakes, wetlands, forests, watercourse slope, and river network density) with selected flood characteristics (specific runoff of maximum discharge of spring flood (qmax ) and the date of maximum discharge of spring flood (Qmax_date )). In 1985, 2000, 2015, and 2019, the lakes, wetlands, and forests were investigated in 11 catchment areas using satellite images and semi-automatic classification. The highest correlation coefficients were for the average of qmax (0.97–0.98) during the calibration. The validation of Qmax_date revealed a weaker relationship (0.67 to 0.83) with the selected geographical factors. Based on regression models, forests and river network densities were the most influential geographical parameters. The findings of this study can be used to assess spring floods and geographical factors in ungauged catchments.

A Holocene relative sea-level database for the Baltic Sea

We present a compilation and analysis of 1099 Holocene relative shore-level (RSL) indicators located around the Baltic Sea including 867 relative sea-level data points and 232 data points from the Ancylus Lake and the following transitional phase. The spatial distribution covers the Baltic Sea and near-coastal areas fairly well, but some gaps remain mainly in Sweden. RSL data follow the standardized HOLSEA format and, thus, are ready for spatially comprehensive applications in, e.g., glacial isostatic adjustment (GIA) modelling. We apply a SQL database system to store the nationally provided data sets in their individual form and to map the different input into the HOLSEA format as the information content of the individual data sets from the Baltic Sea area differs. About 80% of the RSL data is related to the last marine stage in Baltic Sea history after 8.5 ka BP (thousand years before present). These samples are grouped according to their dominant RSL tendencies into three clusters: regions with negative, positive and complex (transitional) RSL tendencies. Overall, regions with isostatic uplift driven negative tendencies dominate and show regression in the Baltic Sea basin during the last marine stage. Shifts from positive to negative tendencies in RSL data from transitional regions show a mid-Holocene highstand around 7.5–6.5 ka BP which is consistent with the end of the final melting of the Laurentide Ice Sheet. Comparisons of RSL data with GIA predictions including global ICE-5G and ICE-6G_C ice histories show good fit with RSL data from the regions with negative tendencies, whereas in the transitional areas in the eastern Baltic, predictions for the mid-Holocene clearly overestimate the RSL and fail to recover the mid-Holocene RSL highstand derived from the proxy reconstructions. These results motivate improvements of ice-sheet and Earth-structure models and show the potential and benefits of the new compilation for future studies.

Colonization history and human translocations explain the population genetic structure of the noble crayfish (Astacus astacus) in Fennoscandia: Implications for the management of a critically endangered species

Abstract The noble crayfish (Astacus astacus) is an endangered freshwater species in Europe. The main threat is from lethal crayfish plague, caused by the oomycete Aphanomyces astaci that has been spread over Europe by introduced North American crayfish species, acting as chronic carriers of the disease. Most of the remaining noble crayfish populations are found in the Baltic Sea area, and there is an urgent need to implement conservation actions to slow down or halt the extinction rate in this region. However, limited knowledge about the genetic structure of populations in this area has so far precluded the development of conservation strategies that take genetic aspects into consideration. Key objectives of this large‐scale genetic study, covering 77 locations mainly from northern Europe, were to describe the contemporary population genetic structure of the noble crayfish in the Fennoscandian peninsula (Sweden, Norway, and Finland), taking postglacial colonization history into account, and to evaluate how human activities such as stocking have affected the genetic structure of the populations. Analyses of 15 microsatellite markers revealed three main genetic clusters corresponding to populations in northern, middle, and southern Fennoscandia, with measures of genetic diversity being markedly higher within populations in the southern cluster. The observed genetic structure probably mirrors two main colonizations of the Baltic Sea basin after the last glaciation period. At the same time, several deviations from this pattern were observed, reflecting past human translocations of noble crayfish. The results are discussed in relation to the conservation and management of this critically endangered species. In particular, we recommend increased efforts to protect the few remaining noble crayfish populations in southern Fennoscandia and the use of genetic information when planning stocking activities, such as reintroductions following local extinctions.

Characterization of sedimentary depositional environments for land use and urban planning in Espoo, Finland

The capital region of Finland is growing rapidly and into areas with challenging con­struction conditions such as deep fine-grained sediments. In the coastal city of Espoo, present land use is mainly focused in the southern and central parts, which were submerged by the Baltic Sea during the early and mid-Holocene. These areas have experienced saline and brackish water phases during the history of the Baltic Sea Basin. The deposition environments of the presently studied onshore areas are an analogue for the present day offshore Baltic Sea sedimentation settings for fine-grained material. The results from Baltic Sea studies have demonstrated that the seabed topography has a significant role in the deposition of sediments and their properties. In this study, paleotopographic models were created for the ancient Baltic Sea Basin in the Espoo area 1) after deglaciation and 2) during the Litorina transgression and classified into bathymetric (terrain) zones and structures. Topographic classification was combined with the water depth of the Litorina stage, the thickness of fine-grained deposits and wind fetch to establish the overall characteristics of sedimentary environments in the coastal area. Fine-grained sediments can be found mainly in depressions that are classified here as broad, narrow or local. The study found the most challenging environments for construction purposes in sheltered narrow depressions that contain thick layers of fine-grained sediments deposited during the Litorina transgression. These are mainly located in the southern and central parts of Espoo. Minor deep canyons were also found in the northern parts of Espoo. This study provides new prior knowledge for urban planning and construction design in Espoo. The methodology could be applied to other Baltic Sea coastal cities and areas with fine-grained sediments.

The second stage of development of artificial reproduction technology of northern pike in the Kaliningrad lagoon basin

The second stage of development of northern pike artificial reproduction technology for stocking with larvae and fry in the Kaliningrad lagoon basin is considered in this paper. Today northern pike natural stocks in the Kaliningrad lagoon basin are not numerous due to unregulated fishery and limited spawning habitat. Since the 1990s, in many countries of the world, the number of natural stocking northern pike has gradually decreased and at present does not exceed several thousand tons. This problem is also relevant for the Baltic Sea basin, where the modern catches of northern pike in the Curonian and Kaliningrad lagoons make 7,2 and 0,6 tons respectively. At the present time different scientific programs and actions are realized in many countries to restore natural stocks of northern pike. One of the most promising solutions of low northern pike numbers problem is organization of northern pike artificial reproduction in the territory of the Kaliningrad Region. Based on our earlier research in the Curonian lagoon basin, the second stage of development of the technology of northern pike artificial reproduction was carried out on the basis of the educational and experimental farm of KSTU in 2020. Prespawning maintenance of 25 northern pike producers with the use of cages from deli, ponds and reclamation canal was carried out, as well as egg incubation and holding of prelarvae in RAS. As a result of the conducted researches, it was established, that the reproductive products of northern pike producers have high quality and the prelarvae at the stage of incubation have high survival rate (82,2–91,7%). The calculated of biometric parameters of producers and their reproductive products, confirmed the correlation between the weight of females and their fecundity, which was 0,86 and 0,95. The scheme of keeping of producers and incubation of northern pike eggs tested at the second stage has shown the prospect of providing 50% of the need in stocking of young northern pike in the Kaliningrad lagoon with the use of 100% stock of producers.

Modelling framework for flow, sediments and nutrient loads in a large transboundary river watershed: A climate change impact assessment of the Nemunas River watershed

This study provides an in-depth analysis of the Nemunas River watershed, situated in the Baltic Sea basin, and possible future changes to the stream flow, hydrologic regime, sediment (SS), Total Nitrogen (TN) and Total Phosphorus (TP) load from the river to the Curonian Lagoon under different climate change scenarios using high-resolution modelling. The sub-regions of the watershed, represented by sub-basins of the Nemunas River tributaries and the main river branch, were modelled using the Soil and Water Assessment Tool (SWAT). The model setup was performed using the developed customizable MATLAB scripts for an advance Hydrologic Response Unit configuration and a hillslope delineation procedure. The modelling framework was used to assess the climate changes in the watershed under two future scenarios: RCP4.5 and RCP8.5, using the projected changes to precipitation, temperature, and carbon dioxide concentrations for the near-term (up to 2050) and long-term period (up to 2100) compared to the baseline period (1995–2010). The projections show that the annual long-term trends for flow, depending on the scenario, are small or not existing. Even if there is no visible change in trends over the years, inter-annual changes on flow, sediment and nutrient load will occur. The findings of the study suggest that the conditions of the RCP4.5 are likely to be more “wet”, whereas RCP8.5 will likely be “drier”. Most shifts will occur in the winter season, especially in January and February. A decrease in snow cover across the watershed, together with the greater frequency of soil freeze-thaw cycles can weaken the nutrient retention of soils and increase nitrogen and phosphorus losses. Coupled with the increased flows in winter, the projected nutrient load changes during winter season indicate a two-fold increase in sediment, up to 42% and 62% in TN and TP load to the Nemunas River and subsequently, to the Curonian lagoon.

Basin-Scale 3D Sedimentary Modelling: An Approach to Subdivide Baltic Sea Onshore Sediments for Land use and Construction

Understanding the local stratigraphy and geometry of sediment units is necessary for successful 3D modelling and the prediction of ground behaviour and engineering-geological properties for urban land use and construction. A detailed 3D model of the main sediment units for the Rastaala basin in southern coastal Finland was constructed, combining a conceptual geological model and information from local drill-hole logs and geotechnical drilling. The 3D modelling was based on a cross-section approach, where sediment units were defined on the basis of lithological boundaries that are of major geotechnical importance for land use and construction. The conceptual geological model was based on a sequence of events that characterize the late- and postglacial evolution of the Rastaala basin. The present study combines the allostratigraphy and lithostratigraphy of unconsolidated glacial, late-and postglacial sediment units in southern coastal Finland. It also investigates the appearance and distribution of sediment units in the Rastaala basin and compares modelling and visualization results for unit surfaces and solids using two independent modelling software packages. Finally, information on the geotechnical properties of different sediment units in the Rastaala basin is provided so that they can be applied to other onshore regions with similar geological settings in the coastal Baltic Sea Basin.

Airborne nitrogen deposition to the Baltic Sea: Past trends, source allocation and future projections

Despite significant reductions in nitrogen emissions achieved in Europe during the last three decades, eutrophication remains an environmental concern in the Baltic Sea basin. Recently, a number of comprehensive modelling studies have been conducted for the HELCOM Commission to inform the 2021 update of the Baltic Sea Action Plan. The calculations have focused on trends in airborne nitrogen deposition to the Baltic Sea and its nine sub-basins during the 2000–2017 period, the identification and ranking of the main contributors to deposition, as well as future projections for 2030, assuming compliance with the Gothenburg Protocol and the EU NEC Directive. This paper synthesizes the main results from these studies and puts them into the context of maximum allowable nutrient inputs to the Baltic Sea.According to our results, the airborne annual deposition to the Baltic Sea in 2017 amounted to 122.6 Gg(N) of oxidized nitrogen and 105.3 Gg(N) of reduced nitrogen, corresponding to a decrease since 2000 by, respectively, 39% and 11%. In order to filter out the large inter-annual variability due to meteorology and to better reflect trends in emissions, weather-normalized depositions of nitrogen have been calculated as well, according to which the decreases since 2000 amount to 35%, 7% and 25% for oxidized, reduced and total nitrogen, respectively.In 2017, Germany, Poland and Denmark were the most important contributors to airborne deposition of total (oxidized + reduced) nitrogen to the Baltic Sea. Agriculture contributed most to reduced nitrogen deposition, while the transport sector contributed most to oxidized nitrogen deposition. Agriculture in Germany was the single-most important contributor to nitrogen deposition to the Baltic Sea in 2017 (accounting for about 15% of the total), but there are numerous other important sectoral contributions. Emissions of nitrogen from the nine HELCOM Contracting Parties contributed 49%, 76% and 61% to oxidized, reduced and total nitrogen deposition, respectively.Assuming full compliance with the EU NEC Directive and the Gothenburg Protocol, significant further reductions in nitrogen deposition can be achieved by 2030, down to an annual deposition of 72.7 Gg(N) and 84.7 Gg(N) of oxidized and reduced nitrogen, respectively.

Features of the restoration of biological communities after the technogenic transformation of the estuary area of the Pregolya River (the Baltic Sea basin)

The structural parameters of plankton, benthos and macrophytes after large-scale technogenic transformation of the mouth area of the river were studied. Pregolya. A decrease in the species richness and area of growth of macrophytes, a simplification of the structure of communities was noted. The renewal of plant communities in the places of their origin was recorded, primarily due to the species resistant to biogenic pollution. A decrease in the abundance of submerged species with wide leaves was revealed, which is an indicator of an increase in water turbidity. The species were found in the phyto- and zooplankton community, living in conditions of an increased content of nutrients and suspended matter. There was no significant decrease in the species diversity of summer plankton and benthos, and the quantitative indicators are comparable with the data before the work. A feature of the restoration of the zooplankton and benthic community was the appearance of brackish-water species in the river branches, which were not previously recorded there, incl. alien species of mollusks and polychaetes.