At Å17, the most westerly Skagerrak station and at Släggö near the coast, the phytoplankton diversity and chlorophyll concentrations were low, which is normal for this month. In the Kattegat however, the species diversity was high and some diatoms were found in very high cell numbers. The chlorophyll concentrations were high in the surface water, but the integrated (0-10 and 0-30 meters) numbers were normal for January. The phytoplankton community was in its winter rest in the Baltic Sea. Only small cells were present like cryptomonads, pico cyanobacteria colonies and ciliates. The chlorophyll concentrations were above normal for this month in the southwestern Baltic, and low at the rest of the Baltic stations.