Altered biotoxicity of cadmium to freshwater green algae by different concentrations of polystyrene

Microplastic pollution has become a global problem, threatening water bodies and aquatic organisms around the world. Heavy metal pollution in the aquatic environment is an environmental issue of long-term concern, and relatively few studies have been conducted on the compound toxic pollution of freshwater algae by microplastics and heavy metals. Therefore, in this study, Cd and polystyrene (PS) were selected as representative heavy metals and microplastics in the environment, and the toxic effects of the two pollutants on freshwater algae were investigated by determining the biomass of algal growth, chlorophyll a content, and the bioconcentration of heavy metals. It was found that the two pollutants alone could inhibit the growth and photosynthesis of the algae, and the toxicity increased with the increase of concentration. When the two pollutants were combined, the toxicity of Cd depended on the concentration of PS, and both low (1 mg/L) and high (100 mg/L) concentrations of PS increased the toxicity of Cd in a synergistic manner, whereas the medium concentration (10 mg/L) of PS showed an antagonistic effect, which was able to inhibit the toxicity of Cd.