Effects of Zn and Ti Nanoparticles on the Survival and Growth of Sclerophrys arabica Tadpoles in a Two Level Trophic System

Under natural conditions pollutants rarely affect only a single trophic level. This study investigated the effects of titanium dioxide (Ti-NPs) and zinc oxide (Zn-NPs) nanoparticles on survival and growth of Sclerophrys arabica tadpoles exposed directly in water, indirectly through their food source (decomposing leaves), or a combination of both. Zn-NPs did not cause significant mortality. The LC50 for tadpoles exposed to Ti-NPs directly was 74.9 mu g/L (95% CI 16.6-338.7 mu g/L) and 18.3 mu g/L (95% CI 6.5-51.9 mu g/L) for tadpoles exposed directly and with pre-treated leaves. Tadpoles fed only pre-exposed food did not show significant mortality. Exposure route also affected growth. On average the tadpoles with the lowest body mass were found in the water-only exposures, followed by the water and leaf treatments. However, the tadpoles with the greatest body mass were in the treatments fed with leaves pretreated with Ti-NPs. This suggests that the NPs made their contents more available to the tadpoles.