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A comparative study of cultural and biochemical parameters of two microalgal species, Tetraselmis sueciaca and Phaeodactylum tricornutum, was performed. Cell density in the storage culture was 2.88 million cells per one ml for T. sueciaca and 20.37 million cells per one ml for Ph. tricornutum. As shown, determination of op-tical density of the culture medium is a more objective characteristic of the cumulative culture growth. For T. sueciaca, cell growth rate during the course of experiment made 400% and for Ph. tricornutum – 700%. Dif-ference in the chemical composition of microalgal biomass was revealed. The microalgae did not differ in their energy value. The prospects of cumulative culture of microalgae in mariculture farms are discussed.

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The article considers the use of salicylic acid as a stimulator of microalgae growth. The influence of a wide range of salicylic acid concentrations on the growth dynamics of Tetra-selmis suecica in enrichment culture has been evaluated. Cultivation was carried out in monoculture. An increase in algal biomass was measured by the increasing number of cells counted in each experiment in three Goryaev chambers under a light microscope. The duration of the experiments was 14 days. It is shown that salicylic acid in concentrations of 0.4-1.9 • 10–5 M inhibits the growth of algae. The growth of the control culture has two pronounced peak numbers on 4th and 12th days of the experiment. The introduction of salicylic acid in concentrations of 0.44-1.9 • 10–5 M was accompanied by a change of the growth curves: the maximum number of cells was observed on 12th day of the experiment. A higher concentration of phytohormone (3.75.• 10–5 M) provided an increase in crop density by 414% over 14 days of the experiment. The growth of T. suecica culture in the control group was 332%. The values of the specific growth rate of T. suecica were calculated for different periods of cultivation. After 14 days of the experiment, the biochemical composition of the microalgae biomass was evaluated, which showed stimulation with salicylic acid at a con-centration of 3.75 • 10–5 M carbohydrate accumulation. The high concentration of phytohormone suppressed the accumulation of protein, lipids and chlorophyll in the culture and stimulated the accumulation of carbohydrates. It has been suggested that a possible mechanism for the multidirectional action of salicylic acid is its effect on synthesis and catabolism through inhibition of the synthesis and metabolism of endogenous plant hormones.