Despite the various marine contaminants that can be adsorbed on the surface of MPs, as previously mentioned, a multitude of chemical pollutants can also be incorporated into them during the production, recycling, and incineration of plastics [33]. Therefore, consumption of fish and shellfish is among the probable routes of human exposure to MPs and associated pollutants. According to the results of previous studies, micro-scale plastic fragments have been detected in the gut of mussels and fish, as well as in the liver, gills, and even in the edible tissue of some fish species, thus raising serious concerns about the risk of MP exposure through seafood [34; 35]. Several studies have reported that ingestion of MPs may be associated with some common toxic effects on marine organisms, such as changes in the immune response and reduced growth rate, as well as blockage and severe damage to the gastrointestinal tract, reduced stomach capacity, or even death [36]. In some works, the polymer risk index (H) was employed to evaluate the potential ecological risks of MPs to marine organisms. Specifically, [PERSON] et al. (2022) [37], based on the calculated H values, found that the risk of MPs in commercial fish species of Lake Chaohu was between risk levels I (<10) and II(10-100), while [PERSON] et al. (2019) [38] reported higher H values in the range of risk level IV (1000-10,000) for both bivalve and fish species of Fujian Province in China. Also, according to the results of studies that focused on the ecotoxicity risk assessment of MPs, no risk is expected to occur for risk characterization ratio (RCR) values lower than 1 (current global average RCR-4 \(\times\) 10\({}^{-4}\)) [39]. Today, the screening of MPs in marine organisms has primarily focused on mussel and fish species [40]. In particular, mussels tend to ingest MPs as they filter seawater by pumping it through their bodies to feed on small particles and organisms (filter feeders), while fish may either actively or mistakenly feed on MPs [41]. Many reports indicate that MPs are present in both fish species (e.g., _Xiphias gladius_, _Dicentrachus labrax_, _Diplodus vulgaris_, _Platchthys flesus_, _Alepes djedaba_, _Galeus melanstomus_) and mussel species (e.g., _Mytilus edulis_, _Mytilus galloprovincialis_) that are widely commercially available for human consumption [29; 42; 43]. A screening study for MPs in commercial fish from Malaysia identified many microparticles composed of common polymer types, including PE, PP, PS, and PET, while heavy metals (chromium and iron) were detected, adsorbed on the surface of some MPs [32]. [PERSON] et al. (2022) [44] reported that PE and PP were also the most prevalent polymers in both seawater and fish samples from the North Tyrrhenian Sea, with no particular differences observed between sampling sites during their two-year study. Despite the various reports on the presence of MPs in the Mediterranean, the data regarding the consumption of MPs by marine organisms in the Ionian Sea region are scarce. In particular, a previous study conducted in the North Ionian Sea found the frequency of MP ingestion to be 46.25% for mussels and 47.20% for _Sardina pilchardus_, with PE being the most abundant polymer type [15], while another work was carried out in the deep waters of the Eastern Ionian Sea and reported ingestion of meso-macro debris (5-60 mm) in deep-sea fish species [45]. Based on the above, the present study focuses on a first attempt to screen MPs in mussels (_Mytilus galloprovincialis_) and fish (_Dicentrachus labrax_, _Sparus aurata_) species of high commercial value from aquaculture systems in the Ionian Sea. Also, a screening study of MPs in seawater is conducted in order to record the types and weathering of MPs in the marine environment.