Acute exposure to high concentrations of polystyrene nanoparticles induces genotoxicity in Daphnia pulex

Micro- and nanoplastics (MNPs) are known to detrimentally impact a wide range of aquatic species, inducing mortality, decreased growth, a reduction in offspring production and increase in reactive oxygen species in their tissues. However, the genotoxic impact of MNPs in freshwater organisms remains understudied. In the present study we investigate the genotoxic impact of acute exposure to polystyrene nanoparticles (PSNPs) in Daphnia pulex using the comet assay, alongside immobilisation rate and hopping frequency. Daphnids were exposed to 100 nm PSNPs for 24 and 48 h at concentrations between 10 and 200 mg/L. Immobilisation increased with PSNPs concentration and exposure time, while hopping frequency among surviving daphnids decreased at concentrations above 100 mg/L after 24 h, and above 50 mg/L after 48 h. Comet assay results showed increasing DNA damage with concentration and exposure time, with significant DNA damage after 24 h of exposure to 200 mg/L PSNPs, and after 48 h of exposure to 100 and 200 mg/L. These results suggest that exposure to MNPs increases daphnid mortality, impacts behaviour, and induces genotoxicity. The incorporation of the comet assay into freshwater monitoring methods alongside existing techniques could further understanding of the full impact of MNP pollution upon ecosystem health.