Diatoms dominated along the Swedish west coast. The total cell concentrations were overall quite low. Chlorophyll concentrations were within normal at most stations except in the northern stations Å15 and Å13 where they were above normal for the month. The flagellate Pseudochattonella spp.*, potentially toxic to fish, was found at a fluorescence maximum at W Landskrona. The flagellate has been observed during the three previous cruises as well. The cell concentrations were quite low at all stations in the Baltic Sea. The filamentous cyanobacterium Aphanizomenon flos-aquae was found in high cell numbers at all stations except in Kalmar Sound where it was only noted. The chlorophyll concentrations were within normal at all stations except the eastern part of the Baltic where they were above normal.