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Combined effects of polyethylene and organic contaminant on zebrafish (Danio rerio): Accumulation of 9-Nitroanthracene, biomarkers and intestinal microbiota
Summary
Researchers studied how polyethylene microplastics interact with the pollutant 9-Nitroanthracene in zebrafish, both individually and in combination. The study found that while microplastics can carry the pollutant into the fish, they actually reduced its accumulation by adsorbing it away from biological tissues. However, long-term combined exposure proved more toxic than either pollutant alone, suggesting delayed harmful effects when microplastics and chemical contaminants coexist in waterways.
Microplastics, as emerging pollutant, are predicted to act as carriers for organic pollutants, but the carrier role and bio-toxic effects with other pollutants in environments are poorly acknowledged. In this study, both the single and combined effects of polyethylene (PE, 10 and 40 mg/L) with the particle size of 100-150 μm and 9-Nitroanthracene (9-NAnt, 5 and 500 μg/L) on zebrafish (Danio rerio) had been investigated. The results illustrated that PE could be as 9-NAnt carrier to enter into zebrafish body, but significantly reduced the bioaccumulation of 9-NAnt, due to the occurrence of adsorption interactions between the simultaneous presence of both PE and 9-NAnt. After 4 days, the enzymes activity of cytochrome P4501A, acetylcholinesterase (AChE), superoxide dismutase (SOD), catalase (CAT), lactate dehydrogenase (LDH), and the abundance of malondialdehyde (MDA), lipid peroxide (LPO) responded strongly to low-dose PE exposure (10 mg/L). After 7 days exposure to PE-9-NAnt (40 mg/L), the P4501A activity increased significantly, but the activities of AChE and LDH were inhibited clearly, causing certain neurotoxicity and disorders of energy metabolism to zebrafish. The analysis of integrated biomarker response index (IBR) suggested that PE had greater bio-toxicity to zebrafish in all exposure groups after short-term exposure, but the PE-9-NAnt complex showed greater bio-toxicity after 7 days, which indicated that complex exposure of PE-9-NAnt had a delayed effect on the bio-toxicity of zebrafish. Furthermore, analysis of the intestinal microbiota exhibited that under the conditions of the exposure group with 9-NAnt, the relative abundance of the five dominant bacterial phyla (Proteobacteria, Firmicutes, Fusobacteriota, Bacteroidota and Verrucomicrobiota) changed greatly. Overall, this study confirmed that PE could carry 9-NAnt into fish causing bioaccumulation, but in the case of coexisting exposures, PE reduced 9-NAnt bioaccumulation, suggesting that microplastics with other emerging pollutants in chronic toxicity are probably next objects in future works.
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