Vasylenko O. Peticularities of freshwater algae functioning under the influence of humic substances

The thesis is dealt with the study of the peculiarities of the influence of humic substances on the metabolism of freshwater algae and on the formation of their communities. It has been found that the influence of humic substances of natural waters results in functional transformations in the key chains of nitrogen, phosphorus, lipids, and energetic metabolism in algae cells, and also in changes in the content of carbohydrates and pigments. Physiological and biochemical analysis has shown that Chlorella vulgaris is most tolerant to the influence of humic substances, whereas Calothrix braunii - is most sensitive to their influence. The response of Еuglena gracilis is closely similar to that of Calothrix braunii. Mayamaea atomus occupies the intermediate place. It has been found that the peculiarities of the response of algae to the influence of humic substances depend on their concentration and composition, on the duration of exposure, and also on the taxonomic affiliation of algae. Short-term experiments with phytoplankton of various water bodies have shown that humic and fulvic acids are capable of inhibiting the development of Cyanophyta. In this case, the development of other groups of plankton algae was inhibited or stimulated depending on the concentration of humic substances. The revealed peculiarities of algae metabolism registered under the influence of humic substances are of considerable importance in studies of the mechanisms of the formation and functioning of freshwater algae communities.