The phytoplankton diversity and cell concentrations were low in the open Skagerrak area while the beginning of a spring bloom was recorded at the inner station Släggö. The diatom Skeletonema marinoi was found in relatively high concentrations at all stations and this species is often dominating the spring bloom. The diversity and cell concentrations in the Baltic Sea were low at all stations. The diatom Skeletonema marinoi was found in high numbers at the eastern stations whereas small flagellates dominated at the other stations. The integrated (0-10 m) chlorophyll a concentrations were low which is normal for the season at all stations visited.