Occurrence of microplastics in some commercially important seafood varieties from Negombo, Sri Lanka

Microplastics have become one of the most pervasive pollutants found worldwide. The impacts of microplastics on biota as well as threats posed to humans are highly problematic, yet obscure. The present study evaluates the potential microplastic contamination in common wild-caught seafood varieties, namely, Sardinella gibbosa, Stolephorus commersonnii, Hemiramphus archipelagicus, Katsuwonus pelamis, Penaeus monodon, Scylla serrata, Sepia sp., and Perna perna representing different trophic levels and feeding habits including zooplanktivores, omnivores, carnivores, detritivores, and filter feeders. Samples were obtained from the Negombo fish market. Zooplankton samples were collected as planktivory from Negombo coastal waters. Microplastics were visually observed for type, length, and colour via a stereomicroscope. Characterization of polymers was done using Fourier-Transform Infrared (FTIR) spectroscopy. Among all the samples, 92% of finfish samples and 88% of shellfish samples exhibited microplastic contamination. The zooplankton samples were also contaminated with 0.06 mm–0.11 mm size microplastics. Fibrous microplastics were the prominent type followed by fragments, spheres, films, pellets, and foams. Polyethylene, Propylene, Polystyrene, and Nylon-6,6 were the major polymer types observed. According to the One-way ANOVA test, trophic transfer interactions of studied food chains were significant (p < 0.05) at a 95% level of confidence. The microplastic contamination in edible tissues (flesh) was significantly lower (p < 0.05) in the majority of studied organisms. Thus, the findings suggest that trophic transfer represents an indirect, yet potential prime pathway of microplastic ingestion for any individual that consumes seafood habitually. Besides, the gutting and processing of seafood may reduce the amount of MPs, that would not typically be ingested by humans.