1. University of Copenhagen, Dept of Mycology and Phycology, Øster Farimagsgade 2D, DK-1353 Copenhagen K, Denmark
2. Finnish Institute of Marine Research, PO Box 33, FIN-00931 Helsinki, Finland
3. Hydrobiology Laboratory, PO Box 4, FIN-00014 University of Helsinki, Helsinki, Finland
4. Tvärminne Zoological Station, FIN-10900 Hanko, Finland