Introduced Marine Algae and Vascular Plants in European Aquatic Environments

Abstract

Literature compilations for all Europe revealed totally 529 introduced vascular plants (established or occasional) in aquatic environments, 214 being true aquatic or semiaquatic species. Species are listed for all countries and around 75% came from other continents. Totally, 72% occurred in freshwater surroundings, but only 37% in marine-brackish environments, some in both habitats (thus the sum is > 100%). For the aquatic and semiaquatic vascular plants corresponding figures were 95% and 17%. Around 50% are weeds, slightly more among the aquatic and semiaquatic species, and totally 20% have a potential to cause serious problems, of which 65% are aquatic. Of the 113 likely introduced marine macroalgae 27 are invasive. Tentatively, 40 marine microalgae were introductions, nearly 50% bloom-forming and/or toxic. Half of the introduced vascular plants are ornamentals or cultivated, and 43 species used in aquaria, but also occur as rice-field weeds. Other vectors have also been important. Macroalgae have mainly been spread accidentally as epibionts in aquaculture, with ship-fouling also being significant. Ballast is most likely the main vector for microalgae, but also mollusc movements contribute. For some algae and vascular plants different vectors have been involved in different areas. Effects, survival and dispersal strategies, management and utilization are exemplified.