Biochemical and physiological responses of the water flea Moina macrocopa to microplastics: a multigenerational study

Numerous studies have measured the harmful effects of microplastics (MPs) and nanoplastics (NPs) (e.g., ingestion, temporal bioconcentration, acute and chronic responses, and the trophic transfer from primary producers to consumers) on aquatic invertebrates due to their ubiquitous and persistent nature in waterbodies. An experimental water flea model, Moina macrocopa, was exposed to different concentrations (0.001, 0.01, 0.1, 1, 10, 50, 100, and 500 μg L−1) of polystyrene microbeads (1 μm). The effects of polystyrene microbeads were investigated by measurement of multigenerational survival rate, growth, and reproduction parameters with further analysis of biochemical responses across three generations. Exposure to polystyrene microbeads resulted in clear ingestion and egestion in feces. The survival rate was significantly decreased by relatively higher concentrations of polystyrene microbeads compared to control groups. Multigenerational experiments across three generations revealed that exposure to relatively higher concentrations of polystyrene microbeads reduced the growth rate with longer intermolt durations compared to that in the first generation of each group, but similar patterns were observed in reproduction parameters between generations. Initial exposure to polystyrene microbeads resulted in oxidative stress and the induction of antioxidant defense, while 14-day exposure significantly inhibited the antioxidant response. Our results suggest that the detrimental effects of prolonged exposure to polystyrene microbeads would be concentration dependent and harmful for the maintenance of water flea populations by induction of oxidative stress and failure in antioxidant defense.