The phytoplankton diversity was low in the Skagerrak area and at the station Släggö, the chlorophyll a concentrations were below normal for this month. The number of species and the number of cells were higher in the Kattegat than in the Skagerrak, but chlorophyll a concentrations were low. In the Baltic Sea, filamentous cyanobacteria were abundant and surface accumulations were observed at REF M1V1, BY15 and at BY32. The dinoflagellate Prorocentrum minimum* was abundant at several stations, the highest cell number was found at BY15. The integrated chlorophyll a concentrations (0-10 meters) were above normal for this month in the southern Baltic and at the stations BY10 and BY15.