THE INTRODUCTION OF MARENZELLERIA-VIRIDIS (POLYCHAETA, SPIONIDAE) INTO THE GULF-OF-FINLAND AND THE GULF-OF-BOTHNIA (NORTHERN BALTIC SEA)

The spionid polychaete Marenzelleria viridis (Verrill 1873) was for th e first time observed in the Finnish coastal waters at the entrance of the Gulf of Finland in 1990. During 1990-1993 M. viridis expanded its distribution into the eastern parts of the Gulf of Finland and into t he southern part of the Gulf of Bothnia. Its introduction into the Bal tic Sea has probably occurred through ship transport, as all the first findings are connected to harbour areas. Although the abundance and b iomass of M. viridis is comparatively low the species seems to have be come a permanent member of the macrozoobenthos in the northern Baltic.