Microplastics in a pelagic dolphinfish (Coryphaena hippurus) from the Eastern Pacific Ocean and the implications for fish health

Microplastic pollution in fish is a growing concern worldwide due to its implication for human health. Microplastic contaminations and impacts were investigated in 15 wild-caught commercially important dolphinfish (Coryphaena hippurus L.) from the Eastern Pacific Ocean waters. 1741 suspected particles were extracted from gills, esophagus, stomachs, intestinal tracts, and muscle of C. hippurus. Only 139 of them were identified as microplastics by microscopic inspections and micro-Raman spectroscopic analysis. 10, 34, 51, 35, and 9 out of these 139 microplastic particles were extracted from the gill, esophagus, stomach, intestinal tract, and muscle respectively. Overall, microplastics were detected in 15 out of 15 fish (100%), with ~9.3 pieces per individual on average. The prevalence and high incidence of occurrence of microplastics in the C. hippurus suggest that this pelagic species are at high risk of exposure to microplastic pollutions. The chemical composition of microplastics was made of polyester (PES, 46.8%), polyethylene terephthalate (PET, 38.1%), polypropylene (PP, 7.9%), polystyrene (PS, 5.0%), polyethylene-polypropylene copolymer (PE-PP, 1.4%), and polyethylene (PE, 0.7%). 36.7% and 13.7% of microplastics in the fish were 1-2.5 mm and 2.5-5 mm, respectively. Microplastics of 0.1-0.5 mm and 0.5-1 mm roughly shared equally the remaining 50%. Molecular docking results implied that interaction of the four dominant microplastic polymers (PES, PET, PP, and PS) with cytochrome P450 17A1 would lead to impairment of the reproductive function of C. hippurus. The findings provide insights on the harms from microplastic exposure, along with quantitative information of occurrence, abundance, and distribution of microplastics in the fish tissues, which will ultimately improve understanding of bioavailability and hazards of microplastics to the organisms and beyond to human via food chain transfer.