The effect of various concentrations (1 μM – 100 mM) of citrate-stabilized cerium dioxide nanoparticles or cerium ions (3+) on the biomass production of two species of unicellular green algae Desmodesmus armatus (Chod.) Hegew and Acutodesmus dimorphus (Turpin) Tsarenko was studied, the amount of chlorophyll, proteins and lipids in the algae biomass was determined. It was shown that at the concentrations of 0.01 M to 0.1 M nanoparticles and cerium salt have pronounced toxic effects on the algal cultures, manifested by a sharp increase in the level of lipids in the biomass combined with the decrease in chlorophyll and protein. At lower concentrations, cerium dioxide nanoparticles stimulate algae biomass accumulation, probably due to a change in key metabolic pathways, accompanied by an increase in the accumulation of carbohydrates in the biomass. For cerium salt, these effects are less pronounced. Thus, depending on the concentration of the objects used, it is possible to obtain an increase in the food biomass production enriched with lipids or carbohydrates as appropriate to the biotechnological objectives.