Aim Invasive species are of increasing global concern. Nevertheless, the mechanisms driving further distribution after the initial establishment of non‐native species remain largely unresolved, especially in marine systems. Ocean currents can be a major driver governing range occupancy, but this has not been accounted for in most invasion ecology studies so far. We investigate how well initial establishment areas are interconnected to later occupancy regions to test for the potential role of ocean currents driving secondary spread dynamics in order to infer invasion corridors and the source–sink dynamics of a non‐native holoplanktonic biological probe species on a continental scale. Location Western Eurasia. Time period 1980s–2016. Major taxa studied ‘Comb jelly’ Mnemiopsis leidyi. Methods Based on 12,400 geo‐referenced occurrence data, we reconstruct the invasion history of M. leidyi in western Eurasia. We model ocean currents and calculate their stability to match the temporal and spatial spread dynamics with large‐scale connectivity patterns via ocean currents. Additionally, genetic markers are used to test the predicted connectivity between subpopulations. Results Ocean currents can explain secondary spread dynamics, matching observed range expansions and the timing of first occurrence of our holoplanktonic non‐native biological probe species, leading to invasion corridors in western Eurasia. In northern Europe, regional extinctions after cold winters were followed by rapid recolonizations at a speed of up to 2,000 km per season. Source areas hosting year‐round populations in highly interconnected regions can re‐seed genotypes over large distances after local extinctions. Main conclusions Although the release of ballast water from container ships may contribute to the dispersal of non‐native species, our results highlight the importance of ocean currents driving secondary spread dynamics. Highly interconnected areas hosting invasive species are crucial for secondary spread dynamics on a continental scale. Invasion risk assessments should consider large‐scale connectivity patterns and the potential source regions of non‐native marine species.

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This research evaluated the growth, survival, proximate and fatty acid composition of water flea (Daphnia magna) fed baker's yeast (BY) and three types of microalgae diets. In this study, two freshwater microalgae; Botrycoccus braunii (BB) and Chlorella vulgaris (CV), one marine spray‐dried microalgae, Nannochloropsis oculata (SDN), and baker's yeast were evaluated for herbivorous zooplankton Daphnia magna. Survival, reproduction and population density of Daphnia magna have been studied. Daphnia reproduction was enhanced by utilization of baker's yeast diet with increasing egg number, juvenile and adult female numbers among treatments during the experimental period. Daphnia fed SDN diet increased egg number only 7th day of experiment. Population density and survival was positively affected by utilization of baker's yeast at the end of the experiment. Protein levels enhanced by SDN diets while Daphnia fed Botrycoccus braunii diet showed the highest lipid and EPA content in Daphnia. Overall, each diet improved different part of nutrients in Daphnia biomass.

IntroductionMucilage events are characterized by the appearance of gelatinous aggregates suspended in the water column. Massive aggregation is produced by various marine organisms under special seasonal and trophic conditions and meteorological conditions (Innamorati et al., 2001;Mecozzi et al., 2001). Mucilage can heavily affect marine ecosystems by covering large areas; in addition, fisheries and tourism industries can be seriously damaged (Innamorati et al., 2001). The appearance of mucilage formation in the Adriatic Sea has been reported since the 1800s, with major mucus aggregates forming during the 1990s (Totti et al., 2005). Mucilage events have been reported over a wide geographic range, including New Zealand, the Aegean Sea, and the East China Sea (

The comparative study of marine benthic hydrozoan assemblages can improve our understanding of environmental and ecological conditions in marine protected areas (MPAs) such as the large Mediterranean MPA of Datça-Bozburun, where important prospects for future intensive tourism development exist. The analysis of such assemblages may help managers detect changes in important parameters of ecosystem health within this MPA. In this study we compared the hydrozoan assemblages occurring on hard (rocky) and soft (Posidonia meadows) bottoms from stations belonging to three different conditions: i) small marinas (medium anthropogenic impact), ii) yacht stopovers (low impact), and iii) unspoiled sites (no impact) in the southern part of the Datça Peninsula during summer and winter 2015 and 2016. Significant differences in the structure, species composition and richness of benthic hydrozoans among the sampling sites were detected. In both seasons, hydroid assemblages in medium-impact sites significantly differed from little-impact and no-impact sites in terms of qualitative composition. Large structural species were widely represented in all hard-bottomed sampling sites, but small inconspicuous taxa with diverse life histories were much less abundant at the medium impacted sites. Species richness and diversity in Posidonia meadows was much higher in little- and no-impact sites, where highly specific hydroid epibionts were abundant.