Toxicokinetics and responses of multiple biomarkers of sediment-associated fluoroquinolones in the freshwater benthic gastropod Bellamya aeruginosa

Fluoroquinolones (FQs) have the propensity to accumulate in sediments once introduction into aquatic environments, thereby posing potential threats to benthic organisms, yet the ecotoxicity of sediment-associated FQs remains unclear. In this study, the toxicokinetics and responses of multiple biomarkers in Bellamya aeruginosa, exposed to the three commonly used FQs (norfloxacin, NOR; ciprofloxacin, CIP; levofloxacin, LEVO) at environmentally relevant concentrations were investigated under sediment exposure scenario. The results revealed that FQs were effectively ingested by B. aeruginosa from sediments, CIP showing the highest bioaccumulation (180.59 µg/kg), followed by NOR (74.49 µg/kg) and LEVO (36.02 µg/kg). CIP exhibiting a highest uptake rate constant (K_s) (4.64 g/(g·day)) and the lowest elimination rate constant (K_e) (0.05 g/(g·day)). The descending order of biological half-life is as follows: CIP (13.62 days), LEVO (8.14 days), and NOR (6.83 days). NOR induced the activity of superoxide dismutase, catalase, and glutathione-S-transferase while CIP and LEVO depressed their activities and increased malondialdehyde content, indicating a more pronounced oxidative damage to B. aeruginosa caused by CIP and LEVO than NOR. Furthermore, all three FQs were found to induce DNA damage and elevate acetylcholinesterase activity, suggesting distinct genotoxic and neurotoxic effects. Interestingly, despite its low bioaccumulation potential, LEVO exhibited high toxicity towards B. aeruginosa. These findings enhance our understanding of the ecotoxicity of FQs in sediments, providing further evidence of their potential ecological risks.