Investigating the interactions between microplastics and freshwater bivalves.
Supervisor: J. Evan Ward (Univ. Connecticut)
Suspension-feeding bivalves interact with microplastics (MP) (< 5mm) as they are of the same size range as the planktonic organisms they typically feed on. Although extensive research has explored the interaction of marine bivalves with MP, there remains a dearth of knowledge regarding freshwater bivalves. The current study investigates the interaction between freshwater bivalves and MP to address this research gap. Elliptio complanata, a native North American freshwater bivalve, was exposed to polyester (PET) microfibers sized at 75 μm, 500 μm, and 1 mm (with a width of 15 μm), as well as polystyrene (PS) microspheres of 20 μm, 500 μm, and 1 mm, within a 2-hour exposure experiment. Biodeposits, pseudofeces (indicative of rejection), and feces (reflecting ingestion) at intervals of 3 hours, 24 hours, and 48 hours were collected. The proportion of rejection and egestion within the initial 3 hours was determined. Regardless of the polymer types, a notable trend emerged where larger MP were more frequently rejected than smaller MP, indicating a size-based rejection pattern. Moreover, postingestive selection was observed within the gut of bivalves, as smaller MP of distinct polymer types exhibited an extended retention period in the bivalves’ digestive system in contrast to larger MP. Consequently, the size of the microplastics is the primary factor influencing the ingestion and rejection of MP by E. complanata.