Ecological effect of nicotinic and para-aminobenzoic acids on the succession of phytoplankton. 1. Experimental bioassays of the late spring phytoplanktocenosis [Ekologinis nikotino rūgšties ir para-aminobenzenkarboksirūgšties poveikis fitoplanktono sukcesijai. 1. Vėlyvo pavasario fitoplanktocenozės ekspermentiniai tyrimai]. – Botanica Lithuanica, 7(1): 41–72

Attempting to explain ecological effects of nicotinic and para-aminobenzoic acids on the succession of phytoplankton, various experimental bioassays were carried out under different tropic condictions of water. After enriching the water with these vitamins, the following changes were evaluated: number of algae species, their diversity and abundance, biomass of phytoplankton, intensity of the photosynthesis of phytoplankton, also the changes in content of B group vitamins in water. After the enrichment of water with nicotinic acid, the intensity of phytoplankton photosynthesis, abundance of cyanophyces and green algae increased on the second day under mean and high eutrophic conditions and after four days the parameters were even higher. Under mean eutrophic conditions the enrichment of the water with para-aminobenzoic acids on days 2 and 4 resulted in more intensive photosynthesis of phytoplankton and clearly increased abundance of green algae. Under high eutrophic conditions both green algae and diatom abundance increased. The changes in phytoplankton coincided with obvious reduction of nicotinic and para-aminobenzoic acids, and vitamin B12 in water. The results of bioassays lead to the assumption, that nicotinic and para-aminobenzoic acids both together in a complex with vitamin B12 influence the succession of phytoplankton.

Keywords: phytoplankton, succession, vitamin, meso inosolin, biotin, pantothenic acids, thiamine, pyridoxine, nicotinic acid, para-aminobenzoic acids, vitamin B12.