Impacts and uptake of environmentally relevant microplastics by Daphnia pulex

As microplastic toxicology research becomes more common, a gap in knowledge has emerged in how microplastics in environmentally relevant shapes and concentrations affect freshwater indicator organisms such as the genus Daphnia. Most Daphnia microplastic research has been conducted using spherical microplastics that are not indicative of those found in natural environments. Therefore, the goal of this study was to address this gap by examining the biological impacts and uptake of polyvinyl chloride (PVC) microplastics that represented environmentally realistic shapes and concentrations on Daphnia pulex life history. Daphnia were exposed to three different treatments including environmentally relevant (5,000 particles/L), 10x environmentally relevant (50,000 particles/L), and control (0 particles/L) over a 7-day life table experiment. We also conducted a 48-hour exposure study to determine if Daphnia uptake microplastics under these treatments. We found that PVC microplastic exposure did not significantly affect total reproduction or clutch size, and that D. pulex survivorship curves were similar across all treatments. There was also no clear evidence to suggest that microplastic uptake occurred at environmentally relevant or elevated concentrations. Future studies should assess chronic exposure, the role of microplastics as vectors for chemical contaminants, and potential bioaccumulation to higher trophic levels such as fish.