Abstract The toxicological risk of such metal oxide nanoparticles in the environment is hard to evaluate due to a lack of knowledge on the mechanisms of these nanoparticles interaction with biological systems. In this study, we investigated the effect of nano-ZnO on three different freshwater blue green algae such as Microcystis sp., Anabaena sp. and Tribonema sp. Nano-ZnO had a negative effect on freshwater aquatic algae, as manifested by algal growth inhibition, inhibited photosynthetic efficiency, reduced chlorophyll content, induced lipid peroxidation, reduced soluble protein content and cell structure alternation, cell aggregations, leakage and degradation of organelles and plasmolysis occurred in all the species of algae within irrespective of dose of nano-ZnO. Nano-ZnO have a negative effect on freshwater algae and these alternations might have serious consequence and create a serious concern and steps to be made for protecting aquatic ecosystem from exposure to nanoparticles.

Keywords: algae; aquaculture;freshwater; toxicity; nanoparticles; zinc oxide