Summary
During the mid April phytoplankton sampling the species diversity was very low at the Skagerrak stations. Whereas the total cell counts were the highest one month earlier at Å17, the situation was the opposite now with no diatoms. A few ciliates, small flagellates and dinoflagellates were present. The species numbers were high in the Kattegat compared to Skagerrak, only small flagellates were numerous. The integrated (0-20 meters) chlorophyll a concentrations were low but within average for this month at all of the Skagerrak sampling sites except at Å17. Spring bloom was ongoing at the Baltic phytoplankton stations. The dominating species were the diatoms Skeletonema costatum and Chaetoceros wighamii. The dinoflagellate Peridiniella danica was common at most of the stations. According to the integrated chlorophyll a 10 years average, spring bloom happened at the "right time".