Over the past century, the potential for aquatic species to expand their ranges in Europe has been enhanced both as a result of the construction of new canals and because of increased international trade. A complex network of inland waterways now connects some previously isolated catchments in southern (Caspian, Azov, Black, Mediterranean seas) and northern (Baltic, North, Wadden, White seas) Europe, and these waterways act as corridors for nonnative species invasions. We have developed a conceptual risk assessment model for invasive alien species introductions via European inland waterways, with specific protocols that focus on the development of environmental indicators within the socioeconomic context of the driving forces-pressures-state-impact-response framework. The risk assessment protocols and water quality indicators on alien species were tested for selected ecosystems within 3 main European invasion corridors, and these can be recommended for application as part of the Common Implementation Strategy of the European Commission Water Framework Directive, which aims to provide a holistic risk-based management of European river basins. The conceptual structure of the online Risk Assessment Toolkit for aquatic invasive alien species is provided and includes 3 main interlinked components: online risk assessment protocols, an early warning system, and an information transmitter for risk communication to end users.

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Summary We studied the fatty acid (FA) composition of six species of Cladocera and six species of Copepoda from five cold‐water lakes, situated in the tundra and/or in the mountains, and eight species of Cladocera and four species of Copepoda from eight warm‐water lakes (including one reservoir) in temperate regions. We asked whether the contrasting temperature would result primarily simply in changes in the percentages (i.e. percentage of total FAs) and absolute contents (quantities) of the long‐chain polyunsaturated fatty acids (PUFAs), eicosapentaenoic acid (20:5n‐3, EPA) and docosahexaenoic acid (22:6n‐3, DHA), or whether there are other FAs with various number of double bonds and/or chain lengths which could be responsible for a putative homeoviscous adaptation. We also aimed to reveal any consistent phylogenetic differences in FA percentages and contents between Cladocera and Copepoda, separable from any temperature effects. Both taxa in warm waters had greater percentages of 18:0, and lower percentages of 14:0 and 18:4n‐3, than in cold waters, but there were no differences in percentages of DHA. In addition, Cladocera, besides the lower percentage of EPA, had higher percentages of 20:0 and 22:0 in warm waters. These patterns in the percentages of 14:0, 18:0, 18:4n‐3, 20:0 and 22:0 are in a good agreement with the hypothesis of homeoviscous adaptation. Thus, the role of EPA, and particularly DHA, as unique regulators of the homeoviscous adaptation of the zooplankton may have been overestimated. Overall, we confirmed the known differences between Cladocera and Copepoda, namely higher percentages of EPA in Cladocera and higher percentages of DHA in Copepoda. However, there was c. 50% overlap in the ranges of the percentage of EPA in Cladocera and Copepoda, while the ranges in the content of EPA per unit organic carbon in Cladocera and Copepoda overlapped completely. Differences in the percentages and content of DHA between Cladocera and Copepoda were statistically significant and invariant with temperature, and therefore are probably due to phylogenetic factors, rather than any temperature adaptation. Contrasting temperature was not associated with significant differences in the contents of EPA and DHA per unit of organic carbon within the taxa studied. If this remained the case in a warming climate, such warming would be unlikely to reduce the accumulation of these important PUFAs in the zooplankton, at least if species composition was unchanged. However, if there were shifts in the proportions of Cladocera and Copepoda in the zooplankton, for example fewer copepods as temperature rises, a decrease of the flux of PUFA in the ecosystem is plausible, taking into account the phylogenetic (and temperature invariant) differences in DHA between the two groups.

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a b s t r a c tIn 11 lakes from cold and warm regions we studied the content of highly unsaturated fatty acids (HUFA) in seston (<130 m) and crustacean zooplankton using gas chromatography-mass spectrometry. An increase of temperature correlated with a decrease of HUFA content in zooplankton. A multivariate canonical correlation analyses revealed, that the decrease of HUFA content was related with a decrease of per cent of copepods in zooplankton communities, which are known to have higher HUFA levels in their biomass, than cladocerans. This means that temperature primarily affected the HUFA levels indirectly, via changing of taxonomic structure of zooplankton community, while the homeoviscous adaptation of zooplankton individuals had comparatively lower importance. As found, water temperature was better predictor of HUFA contents of zooplankton, than the fatty acid composition of seston. Thus, it can be predicted, that a probable climate warming will decrease the content of the essential HUFA in freshwater zooplankton with possible negative consequences for animals of higher trophic levels.