Do different size classes influence the absorption of microplastics? Evaluation in Donax hanleyanus R. A. Philippi, 1847 (Bivalvia: Donacidae)

Microplastics (MPs) pollution has become a major problem in terrestrial, atmospheric, and aquatic environments, especially in the oceans. MPs have been reported in various marine species through direct or indirect ingestion, affecting the ecological dynamics of these ecosystems. In this study, 20 specimens of Donax hanleyanus were collected for each of four size classes (0.5–1.5 cm; 1.5–2.5 cm; 2.5–3.5 cm; > 3.5 cm), totaling 160 individuals, from two sampling points in Vitória Bay, Espírito Santo, Brazil. Additionally, mesolittoral sediment samples were collected in triplicate at each sampling point. Deionized water was added to the sediment and the mixture was stirred. The supernatant was then filtered through a geological sieve, and the retained material was subsequently analyzed. MPs were classified by size, color, and type under a stereomicroscope. A total of 844 MPs were found, with 361 in bivalve tissues and 483 in sediment samples. Among the observed colors, black was the most abundant (44.59 % in tissue and 38.74 % in sediment), followed by blue, transparent, red, yellow, green, and purple. Although no significant difference was found in the amount of MPs among size classes, a positive correlation was observed between the quantity of MPs and organism size. This study reports, for the first time, the presence of MPs in D. hanleyanus, assesses contamination levels across different size classes and in sediments where the species occurs, and adds another marine invertebrate species to the list of organisms affected by plastic contamination in the marine environments, reinforcing the issue of plastic waste and the urgent need for regulatory measures.