Titanium dioxide nanoparticles (nTiO2) are the world's second most widely consumed nanomaterial and large quantities of this material enters the aquatic ecosystem annually. Therefore, understanding the effects of nTiO2 on aquatic organisms is very important. The present study used Daphnia magna as a model freshwater organism and Pontogammarus maeoticus as a brackish water organism to evaluate short term toxicity of a well characterized nTiO2 suspension. According to the results, acute exposure of D. magna and P. maeoticus to nTiO2 concentrations ranging from 0.1 to 200 mg/l did not cause any mortality; therefore, lethal concentrations could not be calculated (LC > 200 mg/l). Observations showed that the TiO2 nanoparticles were trapped on the surface of the body, under the carapace, and in the gut of the D. magna. Although the results of the present acute toxicity experiment did not show nTiO2 to be toxic to the tested aquatic organisms in an environmentally relevant concentration, further studies are needed on the chronic effects of lower concentrations of this nanomaterial in simulated natural ecosystems.
