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We analyse the cumulative impacts of climate change in a complex basin-lagoon-sea system continuum, which covers the Nemunas River basin, Curonian Lagoon, and the south-eastern part of the Baltic Sea. A unique state-of-the-art coupled modelling system, consisting of hydrological and hydrodynamic models, has been developed and used for this purpose. Results of four regional downscaled models from the Rossby Centre high-resolution regional atmospheric climate model have been bias-corrected using in situ measurements, and were used as forcing to assess the changes that the continuum will undergo until the end of this century. Results show that the Curonian Lagoon will be subjected to higher river discharges that in turn increase the outgoing fluxes into the Baltic Sea. Through these higher fluxes, both the water residence time and saltwater intrusion event frequency will decrease. Most of these changes will be more pronounced in the northern part of the lagoon, which is more likely to be influenced by the variations in the Nemunas River discharge. The southern part of the lagoon will experience lesser changes. Water temperatures in the entire lagoon and the south-eastern Baltic Sea will steadily increase, and salinity values will decrease. However, the foreseen changes in physical characteristics are not of the scale suggesting significant shifts in the ecosystem functioning, but are expected to manifest in some quantitative alterations in the nutrient retention capacity. However, some ecosystem services such as ice fishing are expected to vanish completely due to the loss of ice cover.

The assessment of connectivity in marine ecosystems is a requirement to adequate fisheries management. In this study we have selected two commercially exploited migratory species, European perch (Perca fluviatilis) and European smelt (Osmerus eperlanus), to evaluate the connectivity between the Curonian Lagoon and the coastal Baltic Sea. Our results indicate that isolation between the coastal lagoon and the adjacent sea area does not lead to the formation of genetic structure in migratory fish species. However, both species do register subpopulations coexisting in the area without interbreeding. This indicates that the fisheries management for migratory fishes in coastal lagoons affects a wider area than just the coastal lagoon. European perch, being a postglacial recolonizer from various refugees, has four different subpopulations, while the mechanism that maintains this division remains unexplored. The feeding migrations of European perch to the coastal zone suggest that the reproduction might occur elsewhere and that the factors for genetic structure suggested at the Baltic Sea scale might operate during these migrations. For European smelt, we discuss the existence of two different ecotypes, one lagoonal and one diadromous, and the different registered spawning locations as explicative causes for the maintenance of two genetically divergent clusters. The lagoonal ecotype reproduces and spawns inside the Curonian Lagoon while the diadromous one lives in the open Baltic Sea, performing spawning migrations to the lagoon and the mouth of Nemunas river, thus, maintaining the genetic divergence among them. However, our results indicate that there are no differences in size between both clusters, while the lagoonal population is expected to be smaller, forbidding the determination of two genetically different ecotypes. We conclude that there are no geographically and genetically separated populations of these two species in the lagoon-sea- terrestrial inlets continuum, and unified stock management for the coastal Baltic Sea and the Curonian lagoon is required.

The aim of the study is the evaluation of land cover changes in selected areas next to three lagoons (the Curonian Lagoon, the Vistula Lagoon and the Szczecin Lagoon) located on the southern coast of the Baltic Sea (in Lithuania, Russia, Poland and Germany) from 1984 to 2021. The changes are evaluated using multispectral (visible light—RGB and near infrared—NIR) satellite images from the Landsat 5 and Sentinel-2 sensors. Due to their high importance for ecosystem services, two main land cover types are evaluated, i.e., forest area and inland water reservoirs. The classification of the images is performed using a random forest algorithm. Areas of water bodies and forests are evaluated for the years 1984 and 2021. During period 1984–2021, positive changes in land cover are observed in all three regions included in the study. In almost all parts, with the exception of the Polish part of the area located next to the Szczecin Lagoon, of these regions, an increase in forest area is observed. The increase ranges from 0.1% (Poland, area next to the Vistula Lagoon) to 1.2% (Germany, area next to the Szczecin Lagoon). The area of inland water reservoirs has not changed significantly in the long term. Despite the global warming, no reduction in the area of these water reservoirs is observed, even new seminatural reservoirs have been created in some parts of the study area.

Engaging relevant stakeholders to identify ecosystem services is an important step in ensuring better management actions and nature protection. In this study, we involved three stakeholder groups that gave their opinions on different aspects regarding the usage, threats and protection of ecosystem services in the Nemunas Delta region (south-eastern Baltic Sea). Opinions from 178 respondents, representing local farmers, birdwatchers and scientists were collected in order to evaluate the importance of ecosystem services and to distinguish the most effective actions to sustain them. Despite many differences, there was a clear consensus among all three respondent groups about the importance of some ecosystem services such as water quality, water cycle, habitats for migratory animals, existence value, nature watching, subject for education and research and recreation. Birdwatchers appeared to be helpful in ecosystem services evaluation for their experience-based knowledge in this study region, but the differing perceptions of different groups on the majority of ecosystem services showed how important it is to include more than one stakeholder group in the assessment. The respondents did not agree about the actions needed to sustain ecosystem services––this highlights a need for compromises between anthropogenic activities and environmental protection, while an agreement on the necessity (willingness) to preserve natural values points to future development directions for the Nemunas Delta Region.

The Curonian Lagoon (SE Baltic Sea) and the coastal wetland system play a vital role in maintaining the overall cultural, economic and ecological health of the region. However, its value is still largely underestimated and there is a lack of integrated ecosystem management based on multiple ecosystem services assessment. In this study, 34 ecosystem services (ES) were identified, assessed and mapped following the Common International Classification of Ecosystem Services (CICES). Using expert opinion, 35 land cover classes were scored for their ES potential, these being 15 CORINE land cover classes (CLC) and 20 Natura 2000 areas of conservation (habitat types, i.e., Sites of Community Importance). The total ES potential was calculated by averaging the opinions of experts, using self-confidence scoring as weights, and the ES relative importance index was derived from a questionnaire. As a result, three maps corresponding to each ES potential category (provisioning, regulation and maintenance and cultural) were calculated and further used for hot- and coldspot analyses. Regulation and maintenance and cultural ES were highly interrelated and had the highest potential in the studied area. Forested areas had the highest total ES potential and contributed significantly to the land cover of the ES hotspots.

The aim of the present paper is to propose and elaborate on the concept of Emerald Growth as a new framework concept for managing ecological quality and ecosystem services of transitional waters. The research approach combines the longstanding experience of the authors of this article in the investigation of transitional waters of Europe with an analysis of relevant European Union directives and a comparative case study of two European coastal lagoons. The concept includes and reassesses traditional knowledge of the environment of lagoons and estuaries as an engine for sustainable development, but also proposes locally tailored approaches for the renewal of these unique areas. The investigation results show that the Emerald Growth concept enables to extricate better specific management aspects of ecosystem services of transitional waters that fill-in the continuum between the terrestrial (Green Growth) and the maritime areas (Blue Growth). It results from adjusting of both Green Growth and Blue Growth concepts, drivers, indicators and planning approaches regarding durable ways of revitalising coastal communities and their prospects for sustainable development. We conclude that the Emerald Growth concept offers a suitable framework for better dealing with complex and complicated issues pertinent to the sustainable management of transitional waters.

A macroscopic food web network for the exposed sandy coastal zone of the south-eastern Baltic Sea was reconstructed using ECOPATH software to assess the matter and energy balance in the ecosystem. The model incorporated 40 living functional groups representing the Baltic Sea coastal system of Lithuania during the first decade of 21rst century. The overall pedigree index of our model was relatively high (0.66) as much of the input data originated from the study area. The results indicate net heterotrophy of the coastal zone due to strong influences from the nearby river – lagoon system (Curonian Lagoon). The majority of fish species and waterbirds were present in the coastal system on a seasonal basis and their migrations contributed to heterotrophic conditions. Among fish, the freshwater stragglers possibly contribute to the reversal of flow in biomass and energy from the coastal zone to the river-lagoon system. Top predators such as breeding and wintering piscivorous waterbirds and large pike-perch were identified as keystone species. There was a clear negative balance for the biomass of small marine pelagic fishes such as smelt, sprat and Baltic herring which represent the main prey items in this system.

Summary In the current study we present the first report on the bioaccumulation of microcystins (MC) in zebra mussel Dreissena polymorpha from the eutrophic brackish water Curonian Lagoon. The bioaccumulation capacity was related to age structure of mussels and ambient environmental conditions. We also discuss the relevant implications of these findings for biomonitoring of toxic cyanobacteria blooms in the Curonian Lagoon and potential consequences for D. polymorpha cultivation activities considered for the futures as remediation measure. Samples for the analysis were collected twice per year, in June and September, in 2006, 2007 and 2008, from two sites within the littoral zone of the lagoon. The highest microcystin concentrations were measured in mussels larger than 30 mm length and sampled in 2006 (when a severe toxic cyanobacteria bloom occurred). In the following years, a consistent reduction in bioaccumulated MC concentration was noticed. However, certain amount of microcystin was recorded in mussel tissues in 2007 and 2008, when no cyanotoxins were reported in the phytoplankton. Considering high depuration rates and presence of cyanotoxins in the bottom sediments well after the recorded toxic blooms, we assume mechanism of secondary contamination when microcystin residuals could be uptaken by mussels with resuspended sediment particles.

The term transitional waters embraces a wide array of ecosystems' types, including river mouth ecosystems, lagoons, coastal lakes, rias, fjords and fjards, brackish wetlands and hyper-saline ecosystems. The paper analyzes the challenges of integrated environmental planning of the transboundary transitional waters based on the case study of the Curonian Lagoon, which is the largest coastal lagoon in Europe shared by Lithuania and Russia. In terms of the water quality management framework on the basin level, the Russian Neman river water management district is by and large complementary to the Lithuanian Nemunas River Basin District. Yet, differently from the European Union, transitional or coastal waters are not integrated into the river basin management schemes or action programmes in Russia. Since there is no equivalent term for ‘transitional waters’ in the legislation of the Russian Federation, the Russian part of the Curonian Lagoon is classified as an ‘internal marine water body’ and, therefore, it is not subject to the river basin management regulations. There is significant transboundary coherence in the management of the terrestrial protected areas adjacent to the Curonian Lagoon. However, the aquatic protected areas, which cover the marine nearshore of the Baltic Sea and the entire lagoon area in the Lithuanian part of the region are not matched by reciprocal aquatic nature protection in the Russian part, except of the 1 km wide nearshore strip in front of the Nemunas Delta. Currently, there is no cross-border management plan for the entire Curonian Lagoon as a single transboundary transitional water body. Concise yet straightforward planning scope, high-ranking governmental support, proper financing, dedicated cooperation between local, regional, and national authorities, and the participatory approach are the essential principles for the successful cross-border integrated environmental planning and management of the transboundary transitional waters.

This study shows that cyanobacteria blooms support secondary production in a diverse group of benthic and pelagic consumers and illustrate the utility of stable isotopes for tracking the cyanobacteria signal in aquatic food webs. We characterized seasonal patterns in δ13C and δ15N signatures of particulate organic matter (POM) and consumers in a eutrophic coastal lagoon (Curonian Lagoon, SE Baltic Sea) before, during and after a cyanobacteria bloom. We found that during the pre- and post-bloom periods (spring and autumn), POM from the lagoon was isotopically indistinguishable from riverine POM. During the bloom, the increase in phytoplankton biomass and dominance by N2-fixing cyanobacteria resulted in higher δ13C and lower δ15N of POM. These changes in POM were reflected in isotopic signatures of primary consumers with greatest response among fast-growing planktonic and nectobenthic crustaceans and chironomids. Results from end-member mixing analyses suggest that cyanobacteria accounted for 50–80% of production by these consumers during the bloom period. Weaker responses were observed among slow-growing species, particularly long-lived bivalves such as Dreissena. Cyanobacteria-induced shifts in δ13C and δ15N could be tracked to secondary consumers, particularly fast-growing forms such as predatory zooplankton (Leptodora) and juvenile fishes (European perch). We suggest that reconstruction of the food web at the upper trophic levels should incorporate isotopic baselines of both fast- and slow-growing primary consumers to reflect the contribution of blooms events.

The aim of this study was to reveal the patterns of structural and quantitative alterations of the plankton communities along the Nemunas River–Curonian Lagoon transition of the south-eastern Baltic Sea. Authors hypothesised the influence of the different phases of the seasonal plankton development (Bacillariophyceae vs. Cyanobacteria dominance) on the response of plankton communities due to hydrodynamic forcing. In order to assess spatial patterns of physical forcing, we used sediment grain size distribution data as a proxy for hydrodynamic regime. Zooplankton and phytoplankton communities in the Nemunas River were sampled to obtain a point of reference for their structure and seasonal dynamics. The changes in sediment grain size distributions, quantitative and structural alterations in zooplankton communities, as well as structural trends in phytoplankton communities were detected in the Nemunas River–Curonian Lagoon transition area. However, the expected abundance trend was not observed in the phytoplankton community, even during the Cyanobacteria–dominated period. Despite the observed gradient of the sediment structure along the river–lagoon transition, the expected value of the sediment characteristics for the pelagic conditions was not statistically proved.

DAILIDIENĖ, I.; DAVULIENĖ, L.; KELPSAITEĖ, L., and RAZINKOVAS, A., 2012. Analysis of the climate change in Lithuanian coastal areas of the Baltic Sea. This paper investigates the changes in the long-term hydroclimatic conditions in the SE Baltic Sea, along the Lithuanian coast, on the basis of the monitoring data obtained within a 45-year period (1961–2005). Furthermore, the paper discusses the processes behind those changes. Time series of relevant data along the Lithuanian coast from previous centuries were used to investigate climatic variability and trends. The study finds an increased period of westerly winds during winter. During recent decades, the impact of global climate change on sea-level rise has drawn wide interest, since the coastline changes have ecological, economic, and social impacts on the coastal areas of the Baltic Sea. The analysis of the trends for the Lithuanian coastal zone found results similar to those obtained from global and regional analyses showing increasing sea le...

The Curonian Lagoon, the largest in Europe (total surface area 1584 km2), is located in the southern part of the Baltic Sea, from which it is separated by a narrow sand bar and to which it is connected by the Klaipeda Straits. It is characterised by shallow eutrophic waters (mean depth 3.8 m) with average low salinity (

Following the EU Water Framework Directive along with the earlier Nitrate and Wastewater treatment directives there was a national programme to reduce the nutrient and organic load into the Nemunas river and the Curonian lagoon that was adopted in 2006. However, the implementation of the programme could shift N:P ratio even more towards the nitrogen limitation, facilitating the development of the cyanobacteria blooms. The role of the foreseen climatic trends in the region discussed along with the possible ecological consequences.

A combination of enclosure nutrient enrichment experiments and historical data analysis was used to identify the factors controlling seasonal dynamics and competition of the phytoplankton community in the Curonian lagoon (Southeast Baltic Sea). Experiments using different nutrient (N, P and Si) manipulations were performed in 10-l enclosures for 48 h. Changes in chlorophyll a concentrations, inorganic nutrient concentrations, and plankton cell density were monitored. Results revealed that phytoplankton development in the lagoon is strongly affected by ambient physical factors (wind, temperature). Nutrient limitation, however, also plays an important role in seasonal succession mechanisms showing quite distinct seasonal development patterns. Based on the data, available phytoplankton seasonal succession in the Curonian lagoon could be described as composed by three phases corresponding to different domination and regulatory mechanisms.