Experimental study results concerning the effect of different concentrations of superparamagnetic nanoparticles (MNP) of maghemite (iron oxide γ-Fe2O3) on growth features and morphology of the algal and yeast cultures are presented. MNP were obtained under laboratory conditions by the electric-physical method of target laser evaporation. A number of experiments with chlorella and yeast has demonstrated the stimulating and toxic effects of different concentrations of MNP relative to the MPD of free iron.