Distribution and characterization of microplastics in the coastal areas of the Mediterranean Sea

The production and consumption of plastic have drastically increased over the years, due to its cost-effective, durable, lightweight, and resistant characteristics. The same characteristics determine its high dispersion in marine waters and, consequently, within marine organisms, affecting the abundance and diversity of their microbiota. The Mediterranean Sea, as is now well known, is one of the environments most affected by Microplastic pollution, and for this reason, it is becoming increasingly necessary to implement capillary and constant control and mitigation strategies. This is the context for the MICROPLASMED project, which studied the relationship between the role of the marine microbiome as an indicator of different levels of microplastic pollution. To this end, surface water samples were collected between April and August 2022 in different coastal areas of the Mediterranean Sea from five different FAO divisions, aiming to map the distribution, concentration, and composition of the microplastics present. At the same time, samples of Mullus Barbatus (red mullet) were collected and their guts were analyzed for comparison with the results obtained from the water samples analysis. The results showed the presence of microplastics in 95 percent of the water samples, where the highest concentrations were found in Ventotene (Italy) and Istanbul (Turkey), confirming a close correlation between the amounts of microplastics and highly populated areas with high rates of tourism, intense ship movement, and industrial, urban and agricultural discharges. Plastic polymers were characterized by micro-FTIR together with a high percentage of cellulose fibers and fragments of polysaccharide origin. The samples' analysis not only allowed us to obtain essential information on the concentration of microplastics along the Mediterranean coasts but also on the importance of a complete characterization through the speciation of the polymers. This aspect is fundamental to understanding their source, estimating the possible impacts on the marine and coastal ecosystem, and assessing their distribution, but above all to distinguishing synthetic from natural and not lead to an overestimation of the final data. The data obtained represent an important contribution not only to the study of the distribution of microplastics but also to the development of common analytical protocols that allow unambiguous methods of analysis and representation of the results obtained.