Effects of titanium dioxide nanoparticles on Microcystis aeruginosa and microcystins production and release

Abstract Due to growing production and use, release of nanoparticles (NPs) into the aquatic environment may pose a hazard to ecosystem. In this study, Microcystis aeruginosa was exposed to different concentrations (0.1, 1, 10, 50, 100 mg/L) of titanium dioxide (TiO 2 ) NPs to assess their impact on algae. Meanwhile, the production and release of microcystins (MCs) was determined. Results showed that TiO 2 NPs significantly decreased the maximal photochemical efficiency of photosystem II, and thus inhibited the photosynthetic activity of M. aeruginosa . They also increased the content of reactive oxygen species (ROS) and malondialdehyde (MDA), indicating their oxidative damage on algae. Besides, TiO 2 NPs at high concentrations (50 and 100 mg/L) aggregated on the algal surface and block the light, herein inhibited algae growth (16.03%±2.50% and 54.13%±0.93%) but induced the production (25.02%±1.23% and 114.43%±2.96%) and release (20.96%±13.30% and 12.10%±8.80%) of MCs. These results indicated that high concentrations of TiO2 NPs increased MCs concentration in water system, which may be harmful to aquatic ecosystem.