Microplastic ingestion in demersal and benthic species from the Portuguese coast: S. canicula, T. luscus, P. henslowii

Microplastics (MPs) are increasingly prevalent pollutants in marine environments, impacting marine life and ecosystems worldwide. This study aimed to (i) characterise MPs in the gastrointestinal tracts (GITs) of three species commonly found on northeastern Atlantic waters: the small-spotted catshark (Scyliorhinus canicula), the pouting (Trisopterus luscus), and the Henslow's swimming crab (Polybius henslowii); and (ii) assess the potential for trophic transfer, as S. canicula is a known predator of the other two. Thirty individuals per species were collected by bottom-trawling off Figueira da Foz, Portugal. GITs were digested using 10% potassium hydroxide (KOH), filtered, and analysed by Fourier-transform infrared (FTIR) spectroscopy. 88 MPs were identified, primarily in S. canicula (0.89 ± 1.19 MP ind) and P. henslowii (0.54 ± 0.74 MP ind). No MPs were found in T. luscus, possibly due to its juvenile stage or short retention time. Frequencies of occurrence were 57% for S. canicula and 43% for P. henslowii, representing the first scientific record of MPs in the latter. The predominant MP types were fragments and fibres, mainly green, black, and transparent, with polyvinyl acetate and polyethylene terephthalate identified as the main polymers. Significant differences in MP colour and polymer composition between species suggest distinct exposure routes. Although the presence of MPs in a known prey species suggests potential trophic transfer, further research is needed to confirm bioaccumulation. These findings provide a valuable baseline for understanding plastic pollution in Portuguese coastal ecosystems and highlight the need for ongoing investigation into MP dynamics within marine food webs.