A recent study has uncovered alarming evidence of cross-regional marine plastic pollution affecting green sea turtles in the waters around the Ogasawara Islands, Japan. Researchers from Rissho University analyzed the diets of ten green turtles, discovering that seven of them had ingested various plastic materials. This finding highlights the substantial impact of transboundary marine pollution on wildlife.
Through an innovative combination of genetic, isotopic, and plastic analyses, the research team determined that the plastics consumed by these turtles originated from areas beyond their migratory range. The findings are detailed in a paper published in the journal PeerJ.
Understanding Plastic Ingestion in Sea Turtles
Plastic pollution poses a significant threat to marine life, with sea turtles being particularly vulnerable. These creatures often ingest plastics through two main pathways: by consuming natural food items mixed with plastic debris, or by mistaking plastics for their typical prey, such as jellyfish. Despite the growing body of research on marine plastic pollution, detailed data on the diet of green turtles remains scarce.
The green turtle, scientifically known as Chelonia mydas, is found in tropical and subtropical waters worldwide. In Japan, these turtles migrate to the Ogasawara Islands, located approximately 1,000 km south of the main island, for mating and nesting. During their long journey, they are likely to encounter and ingest plastic materials that are distributed across various marine environments.
Prof. Lee, one of the leading researchers in this study, explained, “During their long journey to the Ogasawara Islands, the green turtles are likely to ingest and accumulate plastic distributed across a wide range of marine areas in various forms, including floating debris, sedimentary particles, and items mixed with seaweed.”
Key Findings on Plastic Sources and Impacts
At the time of capture, the turtles were primarily feeding on macroalgae. The DNA analysis revealed that their feeding grounds included three locations known for specific seaweed species: Ectocarpus crouaniorum, Sargassum muticum, and Lobophora sp.. Additionally, stable isotope ratios of carbon and nitrogen in the turtles’ muscle tissue suggested a diet that included drifting seaweed and gelatinous plankton during their migration.
In total, plastics were found in the digestive tracts of seven out of the ten turtles examined, with an average of 9.2 plastic items per turtle (ranging from 0 to 31). Notably, macroplastics measuring between 10 cm² and 1 m² accounted for 56.5% of the total plastic items discovered. While the majority of marine plastics reported in other organisms are microplastics, this study indicates that green turtles also consume larger mesoplastics (5 mm to less than 2.5 cm) and macroplastics (2.5 cm to less than 1 m). Such ingestion is believed to have severe repercussions for both individual turtles and marine ecosystems.
The analysis of printed characters on the ingested plastics indicates that they originated from regions outside the turtles’ migratory routes. This finding underscores the reality of cross-border pollution and its impact on marine life. Prof. Lee emphasized the need for international cooperation to tackle this pressing issue, stating, “This study demonstrates that plastic pollution is a transboundary issue. Efforts to reduce plastic pollution—including reduction in the production, use, and disposal of plastic products—must be pursued through international cooperation, alongside continued research.”
The implications of this research extend beyond the immediate findings, calling attention to the broader environmental impacts of plastic pollution in our oceans. As the study suggests, the health of marine ecosystems is intricately linked to human activity, making it imperative for nations to work together to combat this global challenge.
For further details, the full study is available in the journal PeerJ, providing valuable insights into the dietary habits of green turtles and the sources of marine plastics affecting their health.
