Microplastics in spotted seal cubs (Phoca largha): Digestion after ingestion?

Microplastic pollution is a growing global concern. Early evidences have suggested that microplastics ingestion occurs in various marine organisms. However, there is very limited information regarding the fate of microplastics after ingestion by marine mammals. The present study investigated the characteristics of microplastics identified in spotted seal cubs, Phoca largha. Microplastics were identified in the stomach, small intestine and large intestine of the seal cubs. Poly(ethylene terephthalate), polypropylene and poly(acrylonitrile:acrylic acid) were the main components of the total microplastic contents isolated, with fibers being the main morphological categorization. Importantly, the average size of microplastics detected in the stomach were larger than those in the small intestine (p < 0.05) and large intestine (p > 0.05), while the average abundance in stomach was lower than in the small intestine and large intestine (p > 0.05); these findings imply that microplastics that are ingested might be fragmented into smaller particles in the stomach during digestion before reaching the intestine. These data provide a novel signal for further understanding the fate of microplastics in marine mammals.