The Marine Biomonitor Mytilus galloprovincialis: A Study on Microplastics as a Vector for Heavy Metals Pollution in Sardinia (Italy)

The main objective of the present study was to assess the contamination level and nature of microplastics and their role as vectors of trace elements in Mediterranean mussels (Mytilus galloprovincialis). A total of 39 samples were collected from four farming areas (1–4) located in Sardinia (Italy) and selected according to the principles of the risk assessment. The concentrations of 22 trace elements (Be, Tl, Sb, Ag, Hg, Th, U, Sn, Co, Cd, Li, Mo, Cr, Ba, V, Ni, Pb, Se, Mn, Cu, As, Zn) in mussels and plastic particles extracted from mussels was determined by inductively coupled plasma mass spectrometry (ICP-MS/MS). The isolated plastic particles were characterized by Fourier Transform Infrared Spectroscopy (µ-FTIR). All samples were compliant with the European Union official limits set for Hg, Cd and Pb (Reg. UE 915/2023). Plastic particles were identified in all the samples with a total of 1007 isolated microfibers. Qualitative characterization of microplastics showed that natural polymers predominated, accounting for over 85% of the isolated microfibers. Cellulose was the most abundant polymer (55.29%), followed by cotton (30.59%). Synthetic polymers were present only as a minor fraction (~15%). These results support the use of Mytilus galloprovincialis as a reliable bioindicator of microplastics pollution. Heavy metal concentrations associated with microplastics ingested by Mytilus galloprovincialis were markedly lower than those measured directly in the edible tissues of the mussels, highlighting that microplastics likely contribute minimally as vectors of metals to human consumers. The results of the present study allowed for a comprehensive evaluation of both microplastics contamination and the distribution of heavy metals in mussels reared in Sardinia, providing a robust framework for subsequent risk assessment studies.