Synergistic effect of microplastic fragments and benzophenone-3 additives on lethal and sublethal Daphnia magna toxicity

The interactive effect of polyethylene microplastic (MP) fragments and benzophenone-3 (BP-3) additives on Daphnia magna was assessed in the present study. The 48 h median effective concentration (EC₅₀) revealed that MP fragments (37.24 ± 11.76 μm; 3.90 mg L⁻¹) were over 80 times more acutely toxic than polyethylene microbeads (37.05 ± 3.96 μm; 323 mg L⁻¹), possibly because of their irregular shape and high specific surface area. Moreover, the addition of BP-3 (10.27 ± 0.40 % w/w) to MP fragments (MP + BP-3) resulted in greater acute toxicity to D. magna (EC₅₀ = 0.99 mg L⁻¹) compared to MP fragments (EC₅₀ = 3.90 mg L⁻¹) or BP-3 (EC₅₀ = 2.29 mg L⁻¹) alone. Additionally, MP + BP-3 exposure induced a synergistic increase in reactive oxygen species, total antioxidant capacity, and lipid peroxidation in D. magna. These synergistic effects can be attributed to enhanced bioconcentrations of BP-3 in D. magna caused by MP fragments. These findings suggest that MP fragments containing chemical additives represent a synergistic ecological risk and have the potential to harm aquatic organisms.