Ingestão de microplásticos por pequenos cetáceos na região do Banco dos Abrolhos, Brasil

Abstract

Plastic pollution is a global threat. Microplastics (< 5 mm) can be primary, manufactured as raw materials, or secondary, resulting from the degradation of larger plastics. Among various problems, microplastics easily enter the food chain of being incorporated by biota. Because they occupy the top of the food chain and are sensitive to environmental changes, cetaceans are considered sentinels. With the aim of evaluating microplastic ingestion in stranded odontocetes in the Southwest Atlantic Ocean, individuals were sampled from northern coast of Espírito Santo to the extreme south coast of Bahia, between 2023 and 2025. For this, stomach contents were collected from 50 individuals of the species Sotalia guianensis (N=36), Pontoporia blainvillei (N=11), Steno bredanensis (N=2), and Stenella clymene (N=1). Microplastics were extracted following an organic digestion protocol with KOH. The microplastics found were visualized under a stereomicroscope and classified according to shape, color and size. Procedural blanks were performed to control contamination. Of the individuals analyzed, 92% (n=46) ingested microplastics, totaling 483 particles. The most common shape was fiber, the most abundant color was blue, and most were smaller than 0.5 mm. The results show the consumption of microplastics by almost all specimens analyzed, including a calf of P. blainvillei. Therefore, this is the first study to report the presence of microplastics in S. bredanensis. The predominance of blue fibers suggests a strong influence from sources such as synthetic fabrics and fishing nets, and despite the existence of several protected areas and low population density in coastal cities, the region is exposed to microplastics. The results reinforce that the transfer of microplastics occurs through food, including through breastfeeding. In conclusion, microplastic ingestion was common among the studied odontocete cetaceans in the region, highlighting yet another threat to the species and the need for attention to the Abrolhos region, which is one of the areas with the greatest marine biodiversity in the South Atlantic Ocean.