Evaluation of Microplastic Pollution in Gills of Freshwater Fish in a Neotropical Hydrographic Basin, Brazil

The disposal of plastic materials in recent years has increased exponentially due to human activity. Thus, the accumulation of these residues represents a major concern due to the impact that has been observed, mainly in freshwater aquatic environments and their biota. This study aimed to analyze the presence of microplastics in the gills of fish from the Sorocaba River basin, relating the natural history of the species and the rivers where they were collected. 98 gill samples from eight species sampled at 9 different points of the 4 main Rivers of the basin were analyzed. A total of 385 particles were found, the majority being fibers (74%), predominantly black (63%) and sizes ranging from 2 to 5 mm. The presence of microplastics was verified in all individuals studied, as they are highly susceptible to exposure and retention of plastic microparticles. The highest occurrence of microparticles in fish occurred in the Tatuí River, being verified in the Principal Component Analysis (PCA), considered one of the most disturbed Rivers in the evaluated basin. The particles were identified as polyethylene, polyester, polymethyl methacrylate and polyethylene terephthalate. The present study showed that the gills constitute an important microplastic transfer route for freshwater fish species, and the ecological traits of the species may explain differences in contamination. Considering space–time sampling and different species that make up the fish community is vitally important to understand the scale of microplastic contamination and, subsequently, take effective mitigation measures.