The synergistic effect of mono and co-exposure of microplastic suspensions on Daphnia magna’s survival, population density, reproduction rate & swimming behavior.

Abstract Microplastics represent a pervasive contaminant in aquatic ecosystems, posing substantial risks to aquatic biota. This study sought to elucidate the toxicological impacts of three prevalent plastic polymers high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polypropylene (PP) in both mono and co-exposure scenarios on Daphnia. Employing a range of toxicological endpoints, investigation assessed Daphnia magna's ingestion, bioaccumulation, population density, swimming behavior, and reproduction rate in response to microplastics measuring 0–32 µm, which were synthesized in laboratory using virgin polymer beads . The findings revealed that synergistic effects of microplastics in a co-exposure medium pose a greater hazard to the organism than mono-exposure to individual microplastics (PP, LDPE, and HDPE). In co-exposure scenerio, LC50 value decreased to 77 mg/L, compared to 120, 123, and 109 mg/L for PP, LDPE, and HDPE, respectively. Daphnia magna exhibited a more pronounced response to co-exposure, characterized by reduced survival rates, increased microplastic ingestion, reduced reproduction rates and population densities. Furthermore, co-exposure scenarios led to increased erratic swimming movements relative to mono-exposure, with immobility and energy deficiency observed across all exposure types, albeit with a greater magnitude in co-exposure settings.