The relationship of B group vitamins and phytoplankton under differen trophic conditions were investigated by bioassay experments. The scope of investigations was the seasonal – late spring (May) – succession of phytoplankton. The tests, carried out every two days indicated that clearly defined changes occurred in the composition and abudance of algae, the photosynthesis and respiration, the biomass of phytoplankton, the number of saprobic bacteria – when the level of vitamins in water fluctuated. The peaks in the development of cyanophytes coincited with clear and strong decreases in the concentrations of thiamine, pyridoxine and meso inositol in water; the peaks in green algae – with decreases in vitamin B12, para-aminobenzoic acid and biotin levels; the peaks in diatoms – decreases in para-aminobenzoic and pantothenic acids and, partially, in nicotinic acid. All the results of tests indicated that these vitamins play an important role in regulating phytoplankton succession.
Keywords: phytoplankton, succession, vitamin, meso inositol, biotin, pantothenic acid, thiamine, nicotinc acid, para-aminobenzoic acid, vitamin B12.