How temperature modulates the combined toxicity of aged polystyrene microplastics and copper in early zebrafish development.

Environmental factors, such as temperature, exert a critical influence on aquatic ecosystems. It is important to assess how climate change and pollutants affect contaminants released into water. In this study, the combined effects of environmentally relevant temperature variation, polystyrene microplastics (PSMPs), and copper were evaluated in zebrafish. Toxicity tests were conducted at 23, 26, and 29°C. The PSMPs were aged via the Fenton reaction, to simulate environmental oxidative conditions. Temperature influenced embryonic development, with hatching strongly delayed at 23 °C, while contaminant-related effects exhibited variability at 26 and 29 °C. The combination of aged PSMPs and Cu²⁺ produced pronounced effects on hatching and increased mortality under thermal conditions, particularly at 29 °C. Swimming activity showed significant temperature-dependent alterations, with interactions between developmental temperature and contaminant exposure for swimming distance and velocity. These findings highlight the importance of considering temperature when assessing the effects of microplastics and metals on fish development.