Polystyrene microplastic absorption and egestion in Bivalve, Crassostrea gigas

Abstract

Traditionally, the variation of microplastic accumulation in marine organisms was seemed to be related to differences in regional microplastic contamination status. This study aimed to confirm the effect of microplastic absorption and discharge patterns of pacific oyster, Crassostrea gigas to understand microplastic accumulation. Based on the preliminary survey, this study uses polystyrene microplastic fragments of various sizes at a concentration of 300/L. The microplastics in the cultured C. gigas under absorption conditions were accumulated up to 1077.86 n/individual (ind.) and 73.20 n/g wet weight(wt.). Moreover, the absorption max values (Abmax), which represent the maximum polystyrene fragment absorption amount of single C. gigas was 994.33 n/ind. and 70.85 n/g wwt.. And also, by each polystyrene fragment size, were 461.51 n/ind., 200.25 n/ind., 150.39 n/ind., 108.82 n/ind., 55.19 n/ind., 14.34 n/ind., and 3.82 n/ind., respectively. In the egestion study, 62.89？65.64% of microplastics were released from the C. gigas for 7 days (1818.92 n/ind. to 624.97 n/ind. and 119.96 n/g wwt. to 44.52 n/g wwt.), implying that around 35% of microplastics remained. Interestingly, < 50 ？m microplastic showed exceptionally high emissions per hour compared with absorption amounts. As a result, it is thought that the size efficient for accumulation is between 50-300 ？m. In fact, microplastics of 300 ？m or less are the size that leads to the absorption of all the microplastics, while 100 ？m or less is the size that leads to the emission of all the microplastics.