Toxicity of the veterinary sulfonamide antibiotic sulfamonomethoxine to five aquatic organisms

• The sulfonamide sulfamonomethoxine exhibited greater toxicity to the microalgae than to the Daphnia and fish.
• Sulfamonomethoxine had higher toxicity on microalgae than Daphnia.
• Sulfamonomethoxine had no significant toxicity to the medaka fish.
• Sulfamonomethoxine can risk the aquatic organisms in aquaculture waters.

The purpose of this study was to investigate the acute and chronic toxicity of sulfamonomethoxine (SMM) to aquatic organisms to evaluate its impact at different trophic levels in the ecosystem. Regarding the growth inhibition of microalgae, SMM exhibited 72-h median effective concentration (EC50) values of 5.9 mg L−1 for freshwater Chlorella vulgaris and 9.7 mg L−1 for marine Isochrysis galbana. In a study on the cladocerans, SMM exhibited acute toxicity and 48-h median lethal concentrations of 48 mg L−1 for Daphnia magna and 283 mg L−1 for D. similis. An examination of chronic toxicity revealed that SMM inhibited the brook production of the cladocerans and exhibited 21-day EC50 values of 14.9 mg L−1 for D. magna and 41.9 mg L−1 for D. similis. This study investigated the potentially adverse effects of SMM on aquatic organisms and revealed that microalgae exhibited higher sensitivity to SMM than cladocerans did. The residue of SMM in water is recommended to be carefully evaluated to reduce ecological impacts after applied to cultured animals.