Effects of TiO2 Nanoparticles on the Neotropical Cladoceran Ceriodaphnia silvestrii by Waterborne and Dietary Routes

The impact of nanoparticles (NPs) in zooplankton is poorly studied, particularly when organisms are exposed through diet. Food, constituted mainly by unicellular algae, can act as an important route of contamination for zooplankton. Since unicellular algae have a high surface area in relation to their volume, NPs can interact with their cell membranes and walls, as well as with exopolysaccharides secreted by them. In the present research, we investigated both the acute effects of waterborne titanium dioxide nanoparticles (TiO2 NPs), and its chronic effects via dietary exposure on the Neotropical freshwater zooplankton Ceriodaphnia silvestrii Daday, 1902 (Crustacea: Cladocera). The observed acute effects served as support for chronic tests, in which we investigated the effects of TiO2 NPs on survival and life history parameters (body length, numbers of eggs, and neonates produced) of cladoceran adult females, using the freshwater cosmopolitan chlorophycean Raphidocelis subcapitata as source of contamination of TiO2 NPs for zooplankton. R. subcapitata cells were exposed to concentrations of 0, 0.01, 1, and 10 mg L-1 of TiO2 NPs for 96 h, and then provided as food for females of C. silvestrii until the third brood was released. Significant toxic effects were observed in body length and total number of neonates and eggs produced by females of C. silvestrii at concentrations of 1 and 10 mg L-1 of TiO2 NPs. Survival was the most sensitive parameter when exposure was given via food. From the concentration of 0.01 mg L-1 of TiO2 NPs, there was a decrease in the survival of C. silvestrii females. The quantification of TiO2 NPs in algae evidenced that they have retained NPs in their cells, being, therefore, an important route of exposure and toxicity of TiO2 NPs to the studied microcrustacean. (AU)