The rapid growth of zinc oxide nanoparticles (ZnO NPs) production leads to their accumulation in the environment. However, the impact of ZnO NPs on aquatic ecosystems has not been fully studied. The question of assessing the impact of this pollutant on microalgae and cyanobacteria as the primary-productive link of aquatic biocenoses remains relevant. In the presented study, changes in morphology, structural-functional and fluorescent indices of cyanobacterium Synechococcus sp. were established for concentrations of zinc oxide nanoparticles (ZnO NPs) ranging from 0.3-14 mg L