High sulfate concentration disturbs the sperm motility and fertilization of salmonids

Elevated sulfate ( SO 4 2 − ) effluents contribute to freshwater salinization, posing potential risks to aquatic organisms. This study aimed to evaluate the effects of increased sulfate concentrations on sperm motility and fertilization success in salmonids. The species examined included European whitefish ( Coregonus lavaretus ) and vendace ( Coregonus albula ) from freshwater and brackish environments, as well as freshwater brown trout ( Salmo trutta ). Experiments were conducted using natural water from each species' native habitat as a control and as a base for sulfate treatments, with concentrations ranging from 5–2400 mg/L in freshwater and 240–4400 mg/L in brackish water. Sperm motility was assessed at 10-, 20-, and 40-seconds post-activation using a CASA system. Increasing sulfate concentrations resulted in changes in sperm motility parameters and fertilization rate. In freshwater fish, significant difference in whitefish sperm motility compared to control treatment was observed at 450 mg/L, while in vendace, the significant differences in sperm motility and fertilization rate were observed at 1200 mg/L and 450 mg/L, respectively. For comparison, the lowest exposure concentrations where the sperm motility and fertilization rate of brackish water vendace differed from the control treatment were 1800 mg/L and 2000 mg/L, respectively. In anadromous whitefish, the significant difference in sperm motility was observed in 1200 mg/L. These findings suggest that increased sulfate levels may impair reproductive success of salmonids, underscoring the ecological risks of sulfate pollution in aquatic environments. • Sulfate exposure caused changes in sperm motility. • Fertilization rates decreased with increased sulfate levels. • Freshwater species were more sensitive to high sulfate than brackish water species. • The study highlights potential ecological risks of sulfate pollution.