Microplastic composition in Pacific oyster (Crassostrea gigas) from different mariculture methods in coastal environments

The concentration and composition of microplastics was investigated in the cultivated oyster Crassostrea gigas at two different mariculture sites in Korea, the South Sea and West Sea. The number and mean values of microplastics observed were higher in the South Sea, but the difference was not significant. Overall, small microplastics were most abundant, with fragments < 300 µm accounting for 96.7% of the total observed microplastics, and the fragment shape dominated, with 95.8%. Microplastics in the South Sea were predominantly composed of polystyrene (68.5%), whereas those in the West Sea were predominantly composed of polyethylene (27.7%) and polyurethane (15.8%). The culture methods used for C. gigas in the two regions were found to ecologically differ, in which long-line hanging culture and intertidal long-line culture were the preferred methods in the South Sea and West Sea, respectively. This resulted in a significant difference in the microplastic composition in C. gigas between the two sites. These results suggest that the concentration and shape of microplastics in C. gigas can vary by mariculture method, environment, and habitat. This study highlights the need for further investigation into microplastic concentrations in mariculture organisms and emphasizes that the composition of microplastics can vary depending on the culture method used.