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 abundance and distribution of predatory cladoceran Leptodora kindtii was investigated in the estuarine lagoon (Curonian Lagoon, SE Baltic Sea). Three hydrodynamically different parts of the lagoon were selected, representing transitory oligohaline, intermediate freshwater and stagnant freshwater sites. L. kindtii was least abundant at the oligohaline site, never occurring at salinities greater than 4 psu. At the two freshwater sites, the abundance of L. kindtii varied from a low of <0.1 up to 2.2 indv. L−1 during peak abundance. Two peaks of L. kindtii abundance were observed with timing differences between stations: at the stagnant site the population of L. kindtii peaked two weeks earlier relative to the more hydrodynamically active sites, likely due to a 2°C higher May temperature. The small body size of L. kindtii in the lagoon (seasonal mean 2.68±0.6 mm) shows high fish predation pressure and predicts small cladocerans, juvenile copepods and rotifers being in the preferred prey size range. The calculated L. kindtii daily consumption during the population peak was as high as 100% of the daily zooplankton production, which implies high potential of this predator to shape the grazing zooplankton community in the lagoon.

The round goby (Neogobius melanostomus) is a very successful invasive fish species, which was unintentionally introduced to the central Baltic Sea (Gulf of Gdansk) in 1990. Several years later after initial introduction round goby established a viable population, highly increased in abundance and expanded to the south-eastern and northern Baltic Sea coastal waters, becoming a key component of benthic ichthyofauna in invaded areas. To evaluate a potential threat of round goby to the coastal zoobenthic communities, feeding patterns, including feeding activity and diet composition of this invasive fish was examined using gut content analysis. Sampling was performed in the SE Baltic Sea, Lithuanian coastal waters during May-October 2012. Round gobies >100 mm were caught with multimesh gill nets, while <100 mm individuals were collected using baited minnow trap. Dietary analysis was performed in 318 differently sized round gobies. Feeding activity of round goby varied depending on body size, sex and stage of the reproduction period. Diet composition of individuals with the body length <100 mm and ≥200 mm was relatively constant in the course of the study, while individuals of the intermediate 100-200 mm length had more variable diet, which used to change depending on season. The gut contents of <50 mm gobies were dominated by small zooplanktonic and meiobenthic organisms, shifting to amphipods and mollusks in larger individuals (50-99 mm). In spring 100-200 mm round gobies mainly consumed infaunal bivalves Macoma balthica, in summer - polychaetes Hediste diversicilor, while in autumn the share of epibenthic bivalves Mytilus trossulus and fish prey increased considerably in their diet. Diet of ≥200 mm individuals was predominated by mollusks during whole study period.