Toxicity of nanoZnO in Daphnia magna fed with ZnO containing Chlorella vulgaris and Scenedesmus dimorphus algae

Nano ZnO is currently used in the rubber, electronics, electrical appliances, enamel, cosmetics and medical industry. Whereas most studies have used the ecological toxicity of nanoparticles, the toxic effects of nanoparticles in diet is not extensively explored. Because the algae are at the base of the food chain, any change in their density, biomass and population, would affect the food chain in aquatic ecosystems. Daphnia magna is widely used in environmental pollution control measures, especially in nanoparticle toxicity tests for its short reproduction time and high sensitivity. In this study, Chlorella vulgaris and Scenedesmus dimorphus algae were contaminated with nano ZnO. Five treatment concentrations and three replications at any concentration were compared between test and control groups and the results were analyzed by Probit method. LC50 of Chlorella vulgaris and Scenedesmus dimorphus algae fed by nano ZnO containing Daphnia magna was obtained at 1.78 and 2.59 mg/l levels after 96 hours respectively. Moreover the NOEC (No Observed Effect concentration) and LOEC (lowest observed effect concentration) were calculated as 0.17 and 0.25 mg/l for Scenedesmus dimorphus algae and Chlorella respectively. Our results showed that Daphnia magna is more sensitive to a diet comprising nano ZnO fed Scenedesmus dimorphus algae as compared to Scenedesmus dimorphus environmentally contaminated with nano ZnO.