First report on the presence of small microplastics (≤ 3 μm) in tissue of the commercial fish Serranus scriba (Linnaeus. 1758) from Tunisian coasts and associated cellular alterations

There is limited research on the ingestion of microplastic particles (MPs) by fish from the southern part of the Mediterranean Sea. This study provides the occurrence of small MPs (≤3 μm) in the gastrointestinal tract and muscle of adult benthopelagic fish Serranus scriba (L.1758), caught along Tunisian coasts. MPs were extracted from selected tissues using a potassium hydroxide digestion method (KOH 10%) and then quantified, and their chemical structure was characterized through Raman microspectroscopy. The results highlighted that MPs were present in all samples. The average abundance of MPs per gram of fish tissue identified through successive filters of 3 μm, 1.2 μm, and 0.45 μm differed significantly among the sites. The properties of the MPs extracted indicated that polyethylene-vinyl-acetate (PEVA: 33.45%), high density polyethylene (HD-PE: 17.33%), and fragments were the most abundant plastic types and shape found, respectively. Among those, most MPs were found at a size class of 3-1.2 μm (∼60%), especially in the muscle, suggesting a high transfer of MPs into the human diet. Our field work also aimed to explore the effects observed in the gastrointestinal tract with a battery of biomarkers assessing oxidative stress and neurotoxicity. The preliminary results of this study showed the existence of a link between small MPs, sites, and their associated urban activities and induced oxidative stress. However, more detailed studies are required to evaluate the transfer of MPs into tissues and the potential impacts of this transfer on human health.