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The Effects of Single and Combined Exposure to Polystyrene Nanoplastics and Copper on the Behavior of Adult Zebrafish
Summary
Researchers studied how polystyrene nanoplastics and copper ions affected zebrafish behavior when the fish were exposed to both pollutants simultaneously. The combination was more toxic than either pollutant alone, reducing the concentration needed to kill fish by up to 32%. Since nanoplastics and heavy metals commonly occur together in polluted water, their combined effects on aquatic life could increase the risks associated with consuming contaminated fish.
Different pollutants often coexist in natural environments, making it crucial to monitor and study the ecotoxicological effects of composite pollutants in aquatic environments. Nanoplastics and heavy metals are emerging environmental pollutants that can affect the health of aquatic organisms and threaten human health via the food chain. In this study, zebrafish was employed as a model organism to explore the effects of short-term exposure to polystyrene nanoplastics (PS-NPs) and heavy metal copper ions (Cu2+) either individually or in combination on fish behavior. First, the single and combined toxicity of Cu2+ and PS-NPs to adult zebrafish was investigated to obtain the LC50 values of the two pollutants at 24, 48, 72, and 96 h. Then, the effects of sub-lethal concentrations of Cu2+ (0.06, 0.15, and 0.3 mg/L), PS-NPs (5, 10, and 15 mg/L) and binary mixtures containing Cu2+ and PS-NPs (0.06 mg/L + 10 mg/L, 0.15 mg/L + 10 mg/L, and 0.3 mg/L + 10 mg/L) on the swim speed and individual distance of zebrafish within 4 h were studied. The results show that the LC50 value for single exposure of zebrafish to Cu2+ decreased with the increase in the exposure time, while PS-NPs showed no significant acute toxicity to zebrafish when the concentration was less than 20 mg/L and the exposure time was less than 96 h. The combined exposure of zebrafish to Cu2+ and PS-NPs resulted in a 3.1–32.2% reduction in the LC50 value at different time points compared with Cu2+ alone. In the behavioral study, both single and combined exposure to Cu2+ and PS-NPs induced hyperactivity and aggregation phenomena in the zebrafish at different levels; the duration of these two phenomena was correlated with the concentration of the pollutants. The combined exposure to Cu2+ and PS-NPs exacerbated the behavioral changes in zebrafish compared with exposure to Cu2+ alone, reducing their hyperactivity time, average swim speed and aggregation time by 30.7–41.0%, 13.6–15.4%, and 28.3–28.8%, respectively. Therefore, this study indicates that the combined short-term exposure to PS-NPs and Cu2+ can exacerbate the toxicity of pollutants, and also proves the feasibility for early warning of combined NPs and heavy metals pollution based on adult zebrafish behavioral indicators.