EN
The diatom Dactyliosolen fragilissimus (Bergon) Hasle 1996 (syn. Rhizosolenia fragilissima Bergon 1903) occurs in the western Baltic Sea predominantly in summer, sometimes forming blooms. In autumn 2005, numerous D. fragilissimus cells were observed for the first time in the coastal waters of the Gulf of Gdańsk. In November 2005a bloom was formed: at its peak, the diatom count was 1.1×106 cells dm−3 and its biomass was 8.9 mg dm−3.