Yellow perch (Perca flavescens) show subtle changes in the cellular stress response following exposure to...

Microplastics are found worldwide and are ingested by a wide range of organisms, yet the drivers of toxicity of these common environmental contaminants are still not fully understood. To better understand the contribution of plastic additives in the toxicity of microplastics to organisms, yellow perch (Perca flavescens) were exposed for 9 weeks to additive-free or additive-containing microplastics using in-lake pelagic mesocosms. Microplastics were fragments (37-1,408 µm) of polymers commonly used in consumer plastics (linear low-density polyethylene, polystyrene, and polyethylene terephthalate). One objective of this work was to understand the contribution of additives to the overall toxicity of microplastics on yellow perch using targeted gene expression analysis via real-time quantitative polymerase chain reaction. After 9 weeks of exposure, fish were sampled, and whole fish were assessed for selected metal additives (aluminum, titanium, and bismuth). Liver and gonads were also assessed for gene expression analysis. No significant differences of metal contamination in fish tissue exposed to microplastics with additives were detected in comparison with fish exposed to plastic without additives or the control. While only limited effects on gene expression were observed, our work revealed that the genes hsp90aa and mgst1 in livers and mhc-I in gonads were differentially expressed when fish were exposed to microplastics with or without additives in comparison with the control fish. This finding indicated cellular stress and detoxification responses to microplastic exposure. Overall, there was no clear pattern demonstrating that toxic effects on fish were driven by either the physical or chemical aspects of the microplastics. Future work should measure the accumulation of the organic additives and assess the health of organs using histopathology.