INVESTIGATING THE TOXICOLOGICAL EFFECTS OF MICROPLASTICS EXPOSURE TO WATER FLEAS

Abstract

The ubiquitous presence of microplastics across all aquatic ecosystems, stemming from plastic pollution, necessitates their classification as emerging contaminants. This widespread distribution is concerning due to the propensity of aquatic organisms to ingest microplastics, this behavior likely arises from the similarity between microplastics and natural organic matter suspended in the water column. The current study investigated the toxicological impacts of microplastics of three prevalent plastic polymers—high-density polyethylene (HDPE), lowdensity polyethylene (LDPE), and polypropylene (PP) on the freshwater crustacean Daphnia magna in mono exposure and co-exposure settings. The microplastics ranging size 0-32 μm were synthesized in the laboratory in concentrations ranging from 30 to 150 mg/l. The lethal concentration 50 (LC50) for combined exposure was determined to be 77 mg/L, contrasting with LC50 values of 120 mg/L, 123 mg/L, and 109 mg/L for exposures to PP, LDPE, and HDPE alone, respectively. This variability in toxicity levels is attributed to the differential densities of the polymers and the distinct preferences of Daphnia magna for specific polymers within the aquatic environment. Co-exposure also induced a 10% increase in microplastic ingestion due to compromised egestion mechanisms, alongside a 21% reduction in reproductive rates due to impaired reproductive functionality under stress-induced conditions. Furthermore, combined exposure resulted in reduced population densities, with LDPE exhibiting the highest absorption rates at lower concentrations, followed by HDPE and PP at higher concentrations. Moreover, Daphnia exhibited extreme erratic swimming patterns indicative of heightened behavioral stress under combined exposure conditions relative to singular exposures. These findings underscore the potential threat that synergistic interactions