Microplastic ingestion by sea turtles around Tokyo Bay: Level of water pollution influences ingestion amounts.

We investigated the contents inside the esophagus and stomach of turtles inside and outside of the Tokyo Bay area, which face high and low risks of microplastic (MP) exposure, respectively. 65 synthetic particles were recovered from 8 out of 22 turtles, using ATR-FTIR followed by density separation with calcium chloride solution. Statistical analysis indicated that turtles in high-risk areas ingested significantly more MPs than those in low-risk areas. As the inflow of MPs from major rivers influences pollution levels in the ocean, the results of this study highlight the importance of major rivers for MP ingestion by turtles. Additionally, we discussed the current methodology's shortcomings and addressed scope for subsequent research, along with suggestions on future conservation.