The highest number of species during the September cruise was found at Släggö and the dinoflagellates Scrippsiella-group and Ensiculifera carinata were numerous. The total cell numbers were however low at all of the west coast stations. There were more dinoflagellate species than diatoms in the samples and a few species that are potentially toxic were found in low cell numbers. Relatively high cell numbers of the diatom Pseudosolenia calcar-avis were found at all stations except at Å17. Chlorophyll measured at distinct depths was rather high from zero to ten meters at Släggö, but all integrated concentrations were within normal for this month at all of the west coast stations. The diversity and cell numbers of phytoplankton were normal at all stations in the Baltic Proper. The amount of the three bloom forming filamentous cyanobacteria were still quite high in the southern parts, while Aphanizomenon flosaquae was found at all stations. Diversity and abundance of diatoms were generally low at all stations and of dinoflagellates there were mostly gymnodiniales and Heterocapsa rotundata, even if some toxin producing species were found in low cell numbers. Among other plankton groups, cryptomonadales, Pyramimonas spp. and ciliates were very common. The integrated chlorophyll concentrations (0-10 and 0-20 m) were generally within the normal range for this month at most stations in the Baltic Proper.