Effects of Titanium Dioxide Nanoparticles on Photosynthetic and Antioxidative Processes of .

The effects of the photocatalytic toxicity of titanium dioxide nanoparticle (nano-TiO) on phytoplankton are well understood. However, as UV light intensity decreases sharply with the depth of the water column, the effects of nano-TiO itself on deeper water phytoplankton, such as green algae, need further research. In this research, we investigated the effects of three sizes of TiO (10, 50 and 200 nm) on the photosynthetic and antioxidative processes of in the absence of UV light. We found that 50 nm and 10 nm TiO (10 mg/L) inhibited growth rates and the maximal photosystem II quantum yield compared to the control in . The minimal and maximal fluorescence yields, and the contents of reactive oxygen species and lipid peroxidation, increased, indicating that photosynthetic energy/electrons transferred to oxygen and induced oxidative stress in nano-TiO-treated samples. In addition, we found that aggregations of algae and 10 nm TiO were present, which could induce cell membrane disruption, and vacuoles were induced to cope with nano-TiO stress in . These results enhance our understanding of the effects of nano-TiO on the photosynthetic and antioxidative processes of green algae, and provide basic information for evaluating the ecotoxicity of nano-TiO in freshwater ecosystems.