Baltic Coastal Ecosystems

Abstract

A total of 100 nonindigenous species (NIS) have been recorded in the Baltic Sea (including the Kattegat). Some 70 of these species have been able to establish reproducing populations. The Atlantic coast of North America and the Ponto-Caspian realm have been the most important source areas. Among the most successful and invasive species are the barnacle Balanus improvisus (1840s-), the bristle worm Marenzelleria viridis (1985-) and the cladoceran Cercopagis pengoi (1992-). Seven species of the NIS commonly occurring in the Baltic, inside the Danish Straits, have caused significant damage, namely three Ponto-Caspian species (the hydrozoan Cordylophora caspia, the predacious water flea C. pengoi and the zebra mussel Dreissena polymorpha), two North American species (B. improvisus and the American mink Mustela vison), the Japanese swim-bladder nematode Anquillicola crassus and the “ship worm” mollusc Teredo navalis. The invasive status of the Baltic is briefly described with regard to harmful NIS. Altogether, 20 species are classified according to the type of harmful impacts they are known to cause in this area.