Effects of Nano-Titanium Dioxide on Freshwater Algal Population Dynamics

Konrad J. Kulacki, Bradley J. Cardinale

To make predictions about the possible effects of nanomaterials across environments and taxa, toxicity testing must incorporate not only a variety of organisms and endpoints, but also an understanding of the mechanisms that underlie nanoparticle toxicity. Here, we report the results of a laboratory experiment in which we examined how titanium dioxide nanoparticles impact the population dynamics and production of biomass across a range of freshwater algae. We exposed 10 of the most common species of North American freshwater pelagic algae (phytoplankton) to five increasing concentrations of n-TiO(2) (ranging from controls to 300 mg n-TiO(2) L(-1)). We then examined the effects of n-TiO(2) on the population growth rates and biomass production of each algal species over a period of 25 days. On average, increasing concentrations of n-TiO(2) had no significant effects on algal growth rates (p = 0.376), even though there was considerable species-specific variation in responses. In contrast, exposure to n-TiO(2) tended to increase maximum biomass achieved by species in culture (p = 0.06). Results suggest that titanium dioxide nanoparticles could influence certain aspects of population growth of freshwater phytoplankton, though effects are unlikely at environmentally relevant concentrations.