Summary
The species diversity was high in the Kattegat although the total cell numbers were low. In the Skagerrak the diversity was lower. Everything is well adjusted for spring bloom to occur which usually begins in the southern Kattegat moving northwards. It will probably be the same scenario this year considering the relatively higher species diversity in the Kattegat compared to the Skagerrak phytoplankton samples. The integrated chlorophyll concentrations (0-10m and 0-20 m) were within normal for this month at all stations. Diversity and cell abundance of phytoplankton were low in the Baltic Sea, with mostly smaller cells such as Cryptomonadales and smaller Gymnodiniales as well as various ciliates. Three stations: BY4, BY15 and BY29, had several filaments of the cyanobacterium Aphanizomenon sp. Station BY31 had the highest diversity with, among all, presence of the toxin-producing dinoflagellate Dinophysis acuminata*. The integrated chlorophyll concentrations (0-10m and 0-20 m) were within the normal range for this month at all stations.