The integrated (0-20 m) chlorophyll concentrations were within normal for this month at most stations in the Kattegat and Skagerrak and chlorophyll fluorescence maxima in these areas were caused by diatoms. The diatoms Rhizosolenia spp., Chaetoceros decipiens and Thalassionema nitzschioides were most abundant in these peaks.
The integrated chlorophyll a concentrations in the Baltic Sea where within normal at most of the stations except for Hanö bight and BY32 where the concentrations were above normal. The dinoflagellate Peridiniella catenata was found in relatively high numbers at most stations. Several filaments of the cyanobakterium Aphanzomenon flos-aquae were also recorded at several stations. The beginning of the spring bloom at REF M1V1 recorded on the previous cruise was now at the end at this station.