HETEROTROPHIC DINOFLAGELLATES IN THE ECOSYSTEM OF THE GULF OF GDANSK

Quantitative studies on heterotrophic dinoflagellates were carried out in 1987 at 3 stations located in the Gulf of Gdansk (southern Baltic) and differing in environmental conditions. Heterotrophic dinoflagellates were identified under an epifluorescence microscope and counted, using Uter-mohl's technique, in Lugol-solution-treated samples. Two biomass peaks were recorded over the year: one in the spring, co-occurring with the spring phytoplankton bloom, and the other in autumn. Heterotrophic dinoflagellates were the dominant component of the protozooplankton, particularly in the eutrophic, highly productive Gulf waters where they made up almost half of the total zooplankton and dominated over the metazooplankton.