Effects of microplastics and their adsorption of cadmium as vectors on the cladoceran Moina monogolica Daday: Implications for plastic-ingesting organisms

As pervasive and resilient contaminants, microplastics (MPs) have potential to interact with the toxicity of metals through adsorption on the surface. In this study, we focused on 7-day adsorption of cadmium (5, 10 μg/L) to aged polyethylene-MPs particles (300 μg/L), and further examined 21-day chronic effects of MPs and MPs-Cd on cladoceran Moina monogolica Daday. The effects criteria selected were physiological changes (e.g., parental survival time, somatic growth and reproductive parameters) and nutritional profiles in offspring. Exposure of M. monogolica to both MPs and MPs-Cd can impair the development, reproductive output and fecundity across treatment groups, ultimately leading to parental mortality and poor nutritional status in progeny. Importantly, MPs with adsorbed Cd showed greater adverse dose-dependent effects than bare MPs, likely due to the mechanisms of physico-chemical interactions related to the Cd release from MPs-Cd inside organisms. MPs can pose not only a direct harm to the organisms but also an indirect hazard via adsorption as "transport vector", having implications for the function and resilience of aquatic ecosystems. Our findings experimentally highlight the importance of characterizing chemical profiling of contaminants adsorbed to field plastics in order to better assess environmentally relevant risks associated with MPs and metals in coastal areas.