Microplastics in the Mediterranean marine environment: a combined bibliometric and systematic analysis to identify current trends and challenges

In recent decades, the potential toxicological and environmental effects of microplastics (MPs) in the Mediterranean Sea region have received growing attention. The number of studies in this area has increased; however, presently there is no scientometric perspective addressing this topic. The purpose of this study was to identify the intellectual base and research front using the visualization and analysis software, CiteSpace, in combination with a systematic review. We retrieved 150 articles, published in print or online as an early-access article between 1979 and 2020, from the Web of Science with a topic search related to MPs, environment, and uptake by biota. We then analysed synthesized networks of co-authorship (author, institution, country), co-citation (author document, journal) and co-occurring keywords. The annual publication output has trended upwards since 2011, with interest in MP abundance in the Mediterranean Sea particularly high in the past 5 years (2016–2020). Authors based in Italy accounted for 25% of the total publications, followed by Spain (16%); but overall publications from Belgium and the Netherlands were more influential. Major research themes identified include the abundance of MPs on beaches, in surface waters, sediments and biota. Secondary microplastics, such fibres and fragments, of a wide range of sizes and chemical composition were dominant in scientific reports, albeit citizen science collection of plastic resin pellets for International Pellet Watch suggests such primary MPs are also widespread, even if their numerical abundance from such collections is unclear. Few studies reported chemical contamination of MPs in the Mediterranean albeit a significant amount of information on the level of chemical contamination of plastic resin pellets is available on the International Pellet Watch website.