Shellfish and elasmobranch as sentinel vector for microplastic contamination: Species and tissue-specific...

Microplastic (MP) pollution affects marine ecosystems and filter-feeding shellfish. This study assessed MP contamination in commercial shellfish and elasmobranchs from the Thoothukudi coast, South India, using hydrogen peroxide digestion and ATR-FTIR to identify MPs. MPs in shellfish (muscle) and organs ranged from 2.1 to 3.1 MPs/5 g of tissue, and 2.1 to 3.7 and 3.0 to 7.8 MPs/individual in the gills and gut, respectively. M. gladiator (3.19 MPs/5 g) and C. natator (2.9 MPs/5 g) exhibited the highest concentrations, whereas shrimps, P. indicus (2.9) and P. semisulcatus (2.1) showed elevated levels. MPs abundance in shellfish was: M. gladiator > C. natator > P. indicus > P. sanguinolentus > P. pelagicus > P. semisulcatus > P. merguiensis. The gut showed higher MP contamination than the gills and muscle. Minimum and maximum MP concentrations in gills were in P. pelagicus (2.1 MPs) and C. natator (3.7 MPs). In contrast, in the gut, P. merguiensis and C. natator had the highest concentrations (3.0 and 7.8 MPs). ATR-FTIR spectra showed polyethylene (37.3%), polypropylene (25.27%) and polyvinyl chloride (18.08%) as predominant polymers. The MPs' burden was highest in the gills and gut due to environmental interactions and diet. Daily intake through seafood consumption was 0.70-1.16 MP particles/kg/day, with M. gladiator and P. indicus showing the highest exposure. The hazard and pollution risk indices rated most species as low to medium risk, indicating that MP contamination does not pose immediate severe health risks. This study demonstrates the prevalence of MPs in shellfish/elasmobranchs and their safety implications, highlighting the need to reduce coastal pollution.