Factors Influencing the Clearance of Polystyrene Microplastics by Oysters: Roles of Environmental Conditions, Food Availability and Selection.

This study investigated the abiotic and biotic factors regulating the removal of polystyrene microplastics (PS-MPs) from the water column by the oyster Crassostrea hongkongensis. Our data revealed that MP sequestration is highly dependent on environmental conditions and food characteristics. Optimal clearance occurred at 25 °C and medium estuarine salinity (20 psu), while extreme thermal stress (30 °C) and hyposaline conditions (5 psu) significantly depressed filtration. Light condition had little effect on the removal of PS-MPs. Increased food density remarkably stimulated oyster's clearance of PS-MPs, though high concentrations shifted the removal mechanism toward pre-ingestive rejection via pseudofeces. Furthermore, selective feeding on preferred Isochrysis galbana, Chaetoceros gracilis and Phaeodactylum tricornutum yielded significantly higher removal efficiencies than Thalassiosira weissflogii, Dunaliella salina and Chlorella vulgaris. These findings improve our understanding of how abiotic and biotic factors regulate bivalve's removal and pelagic-benthic transport of microplastics in fluctuating coastal environments.