Persistent organic pollutants, metals, and the bacterial community composition associated with microplastics in Muskegon Lake (MI)

Three different types of microplastics (MPs): low density polyethylene; polypropylene; and polyester, were incubated for one and three months at two sites (Channel and Lake) in Muskegon Lake (MI). After retrieval, MPs were analyzed for polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organochlorine pesticides (OCs), select metals, and genomic characterization of the attached microbial biofilm. Polyaromatic hydrocarbons accumulated at similar levels on all microplastic types, but were ~one order of magnitude lower than sediment concentrations and ~three orders of magnitude lower than the Probable Effect Concentration (PEC): the concentration in sediment above which adverse biological effects are likely to occur. In contrast, PCB levels were 4–6× greater on polyethylene than on polypropylene or polyester, although all plastic-associated PCB concentrations were at least one order of magnitude less than the PEC. Organochlorine pesticide concentrations were very low (<1 ppb) on all microplastics and at all sites. Metal concentrations also were well below their respective PEC levels. The most abundant bacterial groups as part of the plastisphere were Burkholderiales, Rhodocyclaceae, Comamonadaceae, and Pseudomonadaceae. Polyester microplastics contained a higher number of bacterial families and the relative abundance of those families were more evenly distributed compared to the other plastic types. Overall, our results indicate that persistent organic pollutants are capable of accumulating on MPs but the concentrations generally were low; feeding trials are needed to determine if these environmentally realistic concentrations of pollutants attached to microplastics result in impacts to aquatic biota.