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Underestimated microplastics in sea turtles: Implications of a 200 μm detection limit for ingestion monitoring

Original title: Underestimated microplastics in sea turtles: Implications of a 200 μm detection limit for ingestion monitoring

Environmental Pollution 2026
Aina Jaume-Comas, Miguel Jorge Sánchez-Guerrero-Hernández, Carolina Fernández, Sandra Manzano-Medina, A.L. Cerezo, Elisa Martí, Rocío Quintana, Andrés Cózar, Remedios Cabrera‐Castro, Gonzalo M. Arroyo, Carmen Morales‐Caselles

Summary

Scientists found plastic in 95% of the sea turtles they studied, and by using more sensitive detection methods, they discovered nearly a third of these plastic pieces were tiny microplastics that older studies would have completely missed. This matters because sea turtles are often used as an early warning sign for ocean pollution, and if we've been underestimating plastic contamination in them, we may also be underestimating how much of this plastic — including from materials marketed as "biodegradable" — is working its way through marine food chains and potentially onto our own plates.

Polymers
Body Systems

Marine litter, particularly plastic pollution, poses a significant threat to marine ecosystems. Sea turtles are especially vulnerable to plastic ingestion due to their feeding behaviour and migratory patterns, making them valuable bioindicators of marine plastic pollution. This study aimed to introduce a methodological improvement by reducing the minimum particle size analysed from 1 to 0.20 mm, and to quantify and characterize plastics found in the digestive tracts of sea turtles. We report a high incidence of plastic ingestion in nearly every turtle examined (n = 39; frequency of occurrence = 95%), including individuals from three distinct marine turtle species. The most frequently ingested plastics were films and fragments, primarily composed of polyethylene (PE) and polypropylene (PP), with a notable prevalence of light-coloured items. The number of plastic items was significantly higher in the intestine than in the stomach and oesophagus. Notably, 31.93% of the plastic identified were microplastics smaller than 1 mm. These results suggest that previous studies relying on the 1 mm threshold may have underestimated the occurrence of microplastics in sea turtles, including those originating from biodegradable plastic materials, underscoring the need to revise current monitoring protocols and assumptions regarding alternative plastics.

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