The Kattegat and the southern part of the Skagerrak were dominated by an unidentified flagellate. It has also been recorded in the Danish monitoring programme. In the Skagerrak, the dinoflagellate Peridiniella danica and large cells from the diatom Cerataulina pelagica were common. The unidentified flagellate was present in the Arkona and the Bornholm basins. The Baltic Sea samples were in addition to the flagellate dominated by small coccoids, ciliates and dinoflagellates from the genera Scrippsiella/Biecheleria/ Gymnodinium. The chlorophyll a concentrations were normal in the Skagerrak but very high at N14 and Fladen in the Kattegat. In the Baltic, the chlorophyll a concentrations were very low, with the exception of BY5 with very high concentrations. Chlorophyll a samples from several stations have been discarded due to too long transport duration without the right temperature conditions.