Distribution, characteristics, and health risk of microplastics in marine mussels and selected fish species from the south-eastern part of the Gulf of Trieste (Northern Adriatic Sea)

Plastic pollution across all oceanic environments and marine organisms has increasingly been recognized as a critical issue, particularly in semi-enclosed basins such as the Gulf of Trieste. The ubiquitous presence of microplastic pollution underscores its status as one of the most pressing global environmental concerns. In this study, microplastics were extracted from the gastrointestinal tracts of 90 specimens belonging to three different demersal fish species ( Sparus aurata , Chelon labrosus , and Merlangius merlangus ) and from 330 specimens of Mytilus galloprovincialis across 11 sampling sites in the south-eastern part of the Gulf of Trieste. Plastic particles were found in 43% of the mussels, 43% of the gilt-head seabreams, 37% of the thick-lipped mullets, and 13% of the whiting. Microplastics abundance ranged from 0 to 5 items per individual in mussels and 0 to 8 in fish. Microplastic particles measuring less than 0.1 mm were the most abundant in both fish and mussels. Most ingested microplastics were filaments of polypropylene and polyethylene terephthalate, and the most abundant colours were black and blue in both fish and mussels. Our findings demonstrate the accumulation of microplastics in the selected marine organisms, highlighting the pervasive presence of these pollutants in marine ecosystems and the potential risks they pose to marine life. The overall risk to human health associated with microplastic pollution in the south-eastern part of the Gulf of Trieste was categorised as medium. These findings provide a crucial baseline for marine governance and the development of regional coastal management strategies in the Northern Adriatic, supports the implementation of targeted mitigation measures and offers a framework for monitoring the effectiveness of EU plastic reduction policies in semi enclosed basins.