The biodiversity and total cell concentrations were both low in Skagerrak. The spring bloom forming species Skeletonema marinoi was found in highest cell numbers. In the Kattegat however, the species diversity and total cell numbers were high. Diatoms dominated and S. marinoi was found in highest cell numbers. The diatom Guinardia delicatula was also found in high cell numbers. The chlorophyll concentrations were high for this month and the integrated (0-20 meters) concentrations were above what is normal for the month. The phytoplankton community was in its winter rest at many stations in the Baltic Proper. The only exception was RefM1V1, in Kalmar sound and the northern stations BY29 and BY31. At Kalmar sound the diatom Skeletonema marinoi and Thalassiosira baltica were found in highest cell numbers. At the northern stations high cell numbers of S. marinoi together with the mixotrophic ciliate Mesodinium rubrum were found. The chlorophyll concentrations were low except for Kalmar sound where it was above what is normal for this month.