Researchers investigated the diet and plastic consumption of green sea turtles living in the waters near the Ogasawara Islands, Japan, finding plastics in 7 out of 10 turtles studied. By combining genetic, isotopic, and plastic analyses, they inferred that the plastics had come from regions outside the turtles’ usual migratory routes, highlighting the impact of transboundary marine pollution. The study was published in the journal PeerJ.
Effects of Plastic Pollution on Sea Turtles
Researchers have detected plastics in a diverse array of marine life, ranging from open-ocean fish and whales to tiny zooplankton. Plastic pollution particularly impacts sea turtles, which scientists often identify as one of the most affected marine species.
Sea turtles ingest plastics through two main routes: unintentionally, when plastics mix with their regular food such as algae, and intentionally, when turtles mistake plastic items for prey like jellyfish. Despite this, researchers still lack comprehensive information on sea turtle diets.
Migration Patterns and Dietary Behavior of Green Turtles
Green turtles inhabit oceans worldwide, primarily in tropical and subtropical waters. In Japan, it breeds on the Ogasawara Islands, situated roughly 1,000 km south of the main islands. Green turtles migrate from the Pacific coasts of Japan to the Ogasawara Islands for mating and nesting.
“During their extensive journey to the Ogasawara Islands, green turtles are prone to ingesting plastics present throughout the ocean in various forms, such as floating debris, sediment particles, and materials entangled with seaweed,” explains Prof. Lee.
“To investigate the factors affecting plastic ingestion and determine the sources of the plastics consumed, we combined morphological and genetic analyses of gut contents with isotopic and plastic examinations of ten green turtles captured on the Ogasawara Islands.”
Insights into Plastic Intake and its Sources
When researchers captured them, the turtles primarily ate macroalgae. DNA analysis suggested that their feeding areas corresponded to three regions where their preferred seaweed species—Ectocarpus crouaniorum, Sargassum muticum, and Lobophora sp.—are abundant. Stable isotope and DNA analyses suggest that during their southward migration to the Ogasawara Islands, the turtles may have eaten drifting seaweed and gelatinous plankton.
Researchers found plastics in the digestive tracts of 7 out of 10 turtles examined. On average, each turtle contained 9.2 ± 8.5 plastic items, ranging from 0 to 31. Notably, larger macroplastics, ranging from 10 cm² to 1 m², made up 56.5% of all items.
Sea turtles ingest not only microplastics (<5 mm) but also larger mesoplastics (5 mm–<2.5 cm) and macroplastics (2.5 cm–<1 m), unlike most studies that focus only on microplastics in marine organisms. These larger items can have more severe impacts on individual turtles and marine ecosystems. The results of this study further support this observation.
The findings suggest the turtles likely ate meso- and macroplastics tangled in drifting seaweed, mistaking them for gelatinous plankton. Markings on the ingested plastics show they came from beyond the turtles’ migratory range, highlighting cross-border pollution.
Prof. Lee emphasized, “This study underscores that plastic pollution crosses borders.” “Reducing plastic pollution—through measures targeting the production, use, and disposal of plastics—requires international collaboration, alongside ongoing research.”
Read the original article on: Phys.Org
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