Atlantic blue crab (Callinectes sapidus Rathbun, 1896): Microplastic pollution indicator in invaded Mediterranean coastal ecosystems

Plastic pollution has emerged as a pervasive global threat, impacting virtually all planetary ecosystems, from terrestrial to marine habitats. Plastic items smaller than 5 mm are known as microplastics (MPs). It is essential to assess the concentration of microplastics in marine organisms to understand their ecological impact and potential risks to food webs and human health. In this study, the Atlantic blue crab ( Callinectes sapidus Rathbun, 1896), an invasive species established in the Mediterranean Sea, was selected as the target organism for analysis. The combined protocol of digestion by KOH 10% and H2O2 30% at 40ºC was employed to eliminate organic matter and maintain the characteristics of the polymers. In blue crabs, the gills, hepatopancreas and muscle were dissected, and the microplastic content was studied using an Agilent Technologies 8700 LDIR instrument (Chemical Imaging System). The average number of MPs was 17.28 ± 2.90 items/individual. The hepatopancreas showed the highest concentration of microplastics, in contrast to the muscle and gills. Fragments were the predominant type found (87.7%) and were mainly composed of polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), and polymethylmethacrylate (PMMA), indicating a close relationship with pollution sources. White was the most frequently observed color and the predominant size range was 100–299 µm. Data from this pilot assessment provide encouraging evidence for the use of C. sapidus as a microplastics sentinel, though extensive multi-site monitoring remains required to substantiate its role throughout the Mediterranean region. • First microplastic analysis in C. sapidus from Mar Menor lagoon • Optimized digestion with 10% KOH and 30% H₂O₂ at 40ºC • Hepatopancreas showed highest microplastic concentration • Fragments (100–299 µm) were the dominant microplastic type • PP, PET, PMMA, and PE were the most frequent polymers