Triple stable isotope analysis to estimate the diet of the Velvet Scoter (Melanitta fusca) in the Baltic Sea

This study quantifies contributions of different food sources in the winter diet of the Velvet Scoter (Melanitta fusca) in coastal waters of the Lithuanian Baltic Sea using non-lethal avian sampling. We highlight the application of stable sulphur isotope ratios as complementary to stable carbon and nitrogen isotope analysis in order to discriminate sandy bottom macrozoobenthos organisms as potential food sources for the Velvet Scoter. Selection of the most relevant trophic enrichment factors and Monte Carlo simulations in order to choose the best fitted model were undertaken. The stable isotope mixing model revealed the main contributions of a group of bivalves, Mya arenaria and Cerastoderma glaucum, to be 46–54%, and while the crustacean, Saduria entomon, comprised 26–35% of the diet

Algal toxins in the food chain – a comparative study of Chesapeake Bay and Baltic coastal food webs

Microcystin (MC) is a hepatotoxin produced by cyanobacteria (blue-green algae) which is found globally in eutrophic waters including lakes, lagoons and estuaries (Paerl and Paul 2012). The presence of MC in food webs is of concern due to adverse effects on biota and exposure to humans via commercial and recreational fisheries (Paerl and Otten 2013). Little is known regarding the factors which determine MC accumulation in food webs. We hypothesized that dietary exposure would be determined in part by sources of organic matter supporting the food web. We undertook a comparative study of the James River Estuary, a sub-estuary of Chesapeake Bay, and the Curonian Lagoon, a sub-estuary of the Baltic Sea and largest coastal lagoon in Europe. Both sites experience cyanobacteria blooms known to produce MC (Wood et al. 2014; Lesutienė et al. 2014), but differ in their sources of organic matter. The James receives large inputs of terrestrial organic matter due to the draining of a mountainous catchment. The Curonian Lagoon is fed by a lowland river which delivers low concentrations of terrestrial organic matter. We hypothesized that high internal production in the lagoon, coupled with lower dilution by terrestrial organic matter inputs, would results in greater exposure to MC among biota of the Curonian Lagoon

Trophic position and basal energy sources of the invasive prawn Palaemon elegans in the exposed littoral of the SE Baltic Sea

We investigated the abundance, trophic position, and linkages to basal energy sources of the non-indigenous prawn Palaemon elegans in shallow (0.5-1.6 m) stony habitats of the exposed coast of the SE Baltic Sea. Prawn abundance at the site with artificial stone was higher than that in the natural stony habitats. Stable isotope analysis (SIA) suggested similarity in feeding between different size classes of P. elegans. However, SIA of stomach contents showed greater variability of ingested food among large individuals (body length > 25 mm). Trophic position was estimated at 3.0 +/- 0.8 suggesting the prevalence of animal prey in the assimilated diet of P. elegans. However, filamentous green algae was also consumed by large-sized individuals, as indicated by their isotopic signature and the elemental (C:N) ratio of their stomach contents. Modeling of the contribution of Cladophora and particulate organic matter, as basal food sources, to the diet of P. elegans (two end-member mixing model) revealed that only 40% of the assimilated biomass was derived from macroalgae, either directly or through intermediate consumers. This finding suggests that pelagic production was the main carbon source supporting prawn's nutrition. In an experimental study, P. elegans readily consumed mysids, suggesting that this prey may be the prawn's link to the pelagic food chain

Migratory patterns and cyanotoxin concentrations of pikeperch (Sander lucioperca) in the coastal waters of the Baltic Sea

We used stable isotopes of sulfur (δ34S) and carbon (δ13C) to distinguish resident and migratory pikeperch (Sander lucioperca) among individuals captured from a coastal freshwater lagoon (Curonian Lagoon) and adjacent Baltic Sea waters. We found that non-migratory pikeperch collected from the lagoon had negative δ34S ratios (–1.84‰ to –0.17‰), whereas migrating individuals exhibited higher and more variable δ34S values (4.4‰ to 18.5‰). Our findings suggest that S isotopes may be a valuable tool for assessing migratory habits in the brackish waters. We also compared cyanotoxin concentrations among the resident individuals of Curonian Lagoon and the migratory individuals in or returning from the Baltic Sea. No difference in toxin levels was observed among the resident and migratory pikeperch, although toxin concentrations were frequently close to or exceeded the recommended concentrations for safe long-term human consumption

Increasing Population of the Invader Round Goby, <I>Neogobius Melanostomus</I> (Actinopterygii: Perciformes: Gobiidae), and its Trophic Role in the Curonian Lagoon, Se Baltic Sea

Conclusion. The further expansion of round goby inside the Curonian Lagoon is ongoing. However, there is evidence on population density stabilisation in the northern part of the lagoon. Native benthivorous fish, especially ruffe, may be affected through competition for food resources in habitats where the newcomer is numerous. Round goby significantly contributes to the diet of piscivorous fish and birds. That may promote the regulation of invader population abundance in the lagoon

Increasing population of the invader round goby, Neogobius melanostomus (Actinopterygii: Perciformes: Gobiidae), and its trophic role in the Curonian Lagoon, SE Baltic Sea

Conclusion. The further expansion of round goby inside the Curonian Lagoon is ongoing. However, there is evidence on population density stabilisation in the northern part of the lagoon. Native benthivorous fish, especially ruffe, may be affected through competition for food resources in habitats where the newcomer is numerous. Round goby significantly contributes to the diet of piscivorous fish and birds. That may promote the regulation of invader population abundance in the lagoon

Migratory patterns and cyanotoxin concentrations of pikeperch (Sander lucioperca) in the coastal waters of the Baltic Sea

We used stable isotopes of sulfur (δ34S) and carbon (δ13C) to distinguish resident and migratory pikeperch (Sander lucioperca) among individuals captured from a coastal freshwater lagoon (Curonian Lagoon) and adjacent Baltic Sea waters. We found that non-migratory pikeperch collected from the lagoon had negative δ34S ratios (–1.84‰ to –0.17‰), whereas migrating individuals exhibited higher and more variable δ34S values (4.4‰ to 18.5‰). Our findings suggest that S isotopes may be a valuable tool for assessing migratory habits in the brackish waters. We also compared cyanotoxin concentrations among the resident individuals of Curonian Lagoon and the migratory individuals in or returning from the Baltic Sea. No difference in toxin levels was observed among the resident and migratory pikeperch, although toxin concentrations were frequently close to or exceeded the recommended concentrations for safe long-term human consumption

Expert-based assessment and mapping of ecosystem services potential in the Nemunas Delta and Curonian Lagoon Region, Lithuania

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