Τhis study aims to measure the abundance of microplastic (MP) particles in the soft tissue of mussel (Mytilus galloprovincialis) and pearl oyster (Pinctada imbricata radiata) specimens. Samples were collected at four sites in Greece (Sagiada, Malesina, Elounda, Rhodes) from wild and farmed populations. The identification of MPs was accomplished by Raman spectroscopy. Comparisons were made between the two different species where the two species co-existed (Malesina), between the four study sites (five sampling stations) in relation to P. imbricata radiata individuals, and also in every station for the different MP types found. For the specimens from Malesina, M. galloprovincialis had more MPs in their soft tissue compared to P. imbricata radiata. Microfibers were found in abundance in M. galloprovincialis, while microfragments were found in P. imbricata radiata specimens. The main MP type found in P. imbricata radiata specimens was microfragments in all five sampling stations, and ranged between 1.54 ± 0.63 (Rhodes-baskets) and 3.56 ± 0.35 (Sagiada) MP particles/g. While the samples of mussels and pearl oysters were similar in age, the differences found in the concentrations of MPs appears to be due to their different farming methods and location characteristics concerning the five sampling stations of pearl oysters. This study indicates that the culturing system does not affect MP concentration in bivalves, and further investigation is needed to find the most appropriate method to limit and reduce MPs that end up in the farmed organisms.

Nowadays, microplastic (MP) pollution has attracted increasing interest from the scientific community. This systematic review investigated the MP concentration in various tissues of five commercial fish species (Engraulis encrasicolus, Boops boops, Sardina pilchardus, Sardinella aurita, and Trachurus mediterraneus) in different Mediterranean water bodies in order to identify spatial trends and key analytes influencing their variation. The reported concentrations of MPs in all fish ranged from 4.2 particles/individual in the southeastern Mediterranean to 1.2 particles/individual in the western part, but these values are highly uncertain due to inconsistent methodologies, absence of recovery tests, and incomplete data reporting. No significant difference was found in the MP concentration of the different tissues of these species. The key factor affecting the MP concentration was the water body from which they were collected. This systematic review suggests that fewer than six samples may not provide statistically reliable results, and that a lack of detailed data reporting, despite the advances in chemical characterization techniques, continues to limit the robustness of MP studies. Additionally, this study evaluated how methodological differences could influence the reported MP concentrations. These findings offer a comprehensive overview of the MP expansion in the Mediterranean waterbodies and fish species, and provide recommendations for future research design improvement.