Differential accumulation of microplastics in the gills and gastrointestinal tract of fish species of commercial and ecological importance in the Colombian Caribbean Sea

Microplastic (MP) pollution poses a critical threat to marine ecosystems, yet knowledge of organ-specific accumulation in fish from the Colombian Caribbean remains limited. This study presents the first assessment of MPs in the gastrointestinal tract (GIT) and gills of three fish species collected from the Caribbean Sea (Magdalena, Colombia) during rainy and dry seasons. MPs were detected in all GIT samples and in 96% of gill samples. Total MPs abundance followed the order Euthynnus alletteratus > Pterois volitans > Caranx crysos. Species-specific patterns emerged: E. alletteratus accumulated more MPs in larger individuals, C. crysos showed no size-related trend, and P. volitans exhibited higher loads in smaller individuals. The GIT retained more MPs, mainly fragments, whereas fibers dominated gills. MPs abundance was significantly higher during the rainy season, potentially indicating the influence of hydrological regimes and freshwater–marine connectivity on plastic transport. Polymer composition was diverse, dominated by synthetic–natural blends, polyamide (PA), and polyethylene terephthalate (PET), commonly associated with textiles, fishing gear, and packaging. Less frequent polymers, including polypropylene (PP), polyurethane (PU), and polyethylene (PE), indicated multiple sources. These findings demonstrate extensive MP exposure in Colombian Caribbean fish and provide essential baseline information for ecological risk assessment in tropical coastal ecosystems.