Evaluation of Microplastics in Japanese Fish Using Visual and Chemical Dissections

Up to 12.7 million tonnes of plastic is estimated to be polluting oceans. Ranking as the fifth-highest plastic using country, Japan has an exceptionally high usage of single wrapped items. Additionally, as an island-nation, fish is vital to everyday life, making up approximately 40% of protein in Japanese diets. Based on these observations, I wondered how the overuse of plastic in Japan poses an ecological risk to marine species and their consumers local to Kanagawa Prefecture. To answer this question, I completed a plastic audit at a convenience store, took qualitative observations of plastic waste at three waterways, and dissected locally sourced fish to characterize ingested plastic. I found 83.4% of the convenience store’s items within the recorded sections had plastic wrapping or pieces. Additionally, each waterway observed had both plastic and marine species present. Using visual and chemical dissection, all fish had microplastics present in their gastrointestinal tract, including two species that are typically eaten whole in Japan. Out of the fourteen microplastics found through the chemical digestion method, six were classified as plastic microfibers, four were likely thread plastic, three were see-through pieces of plastic film, and one was a foam pellet. Overall, these results are concerning as previous studies have found that microplastics can carry persistent organic pollutants. Both bioaccumulation and biomagnification result in large levels of contaminants building up at the top of the food chain. It is presumed that the increasing consumption of microplastics will have negative implications on organ systems such as the liver, gut, and hormones.