Macroplastic colonization by macroinvertebrates in a Mediterranean wetland: A biodiversity enrichment opportunity

Coastal wetlands are sensitive ecological systems that provide crucial ecosystem services, but often affected by anthropogenic pollutants. Plastics, in particular, represent a threat to the survival and fitness of many aquatic species. In fact, once plastics are released into freshwater environments, they can result in critical threats for fitness and survival of many aquatic organisms. Among these, macroinvertebrates represent a sensitive bioindicator for evaluating the environmental impacts of plastics. In this context, we investigated the colonization of virgin macroplastic substrates composed of two different polymers and located at two different depths in a protected wetland in Central Italy over a period of 10 months. The results show the tendency of macroinvertebrates to colonize plastic substrates artificially placed in water. Our findings highlight that macroinvertebrates mainly colonize polystyrene substrates over than polyethylene terephthalate ones. Moreover, floating substrates show a greater number of taxa found than dipped ones, highlighting that depth is also an important factor to discriminate the colonization of macroinvertebrates on plastic substrates. Furthermore, an ecologically diversified community emerged, in which there are mostly univoltine organisms, with dimensions between 5 and 20 mm, predators, choppers and scrapers that feed on plant organisms and animals. Consequently, plastic substrates might increase biodiversity in polluted waters by offering new surfaces for colonization. Overall, further studies are needed to determine whether the presence of plastic litter could also support the establishment of a macroinvertebrate community comprising taxa that exploit different ecological niches.