In the Skagerrak and the Kattegat the biodiversity in the phytoplankton community was low and the chlorophyll concentrations were normal. The spring bloom was in its final days with quite high amounts of Guinardia delicatula and a few chains of Skeletonema marinoi. Furthermore, flagellates, such as several species of Pyramimonas spp. were found in high cell numbers. In the northern Skagerrak, Å17 displayed the highest cell number of Emiliania huxleyi. In the Kattegat Guinardia delicatula dominated, but there were also dinoflagellates such as Dinophysis acuminata* and ciliates. The flagellate community showed quite high diversity. The chlorophyll concentrations were normal for March at all stations, except at Fladen 0-20 m where it was slightly higher than normal. Signs of spring bloom were found at all phytoplankton stations in the Baltic, considering the observed species of diatoms, the ciliate Mesodinium rubrum and the dinoflagellate Peridiniella catenata. The bloom was the most intense at BY5 and Ref M1V1 in the southern Baltic Proper where both chlorophyll concentrations and cell numbers were high. At BY5, Ref M1V1, BY32 and BY38, the integrated chlorophyll concentrations (0-20 m) were above normal for this month.