Fiber ingestion by the bivalve Perna perna(Linnaeus, 1758): the importance of using concentrations, sizes, and thicknesses similar to the environment

The ingestion of microplastics (particles smaller than 5 mm) by bivalves in the environment is already well established, but more laboratory studies are still needed to enable the assessment of the impacts of these particles in these organisms. In this sense, this study aimed to verify the ingestion of microplastics by bivalves in different experimental environments. For this, 60 specimens of the mussel Perna perna (Linnaeus, 1758) were exposed to different concentrations (25, 50, and 100 MPs.L-1), sizes (1 to 2; 2.5 to 3.5; and ≥ 5 mm), and thicknesses (thick: 0.2 mm, polyethylene; and thin: 0.03 mm, polyester) during 24 h. The results showed that organisms prefer thin particles, and it was found that only one thick fiber was retained, while 23 thin particles were ingested. On the other hand, no significant differences in the uptake of fibers at different concentrations and sizes were identified, showing low concentrations of particles regardless of the treatment. We concluded, via this study, that mussels can ingest fibers of different sizes, thicknesses, and concentrations in the experimental environment, even over a short period of time (24 h). Moreover, it was observed that thickness probably was the main factor for fiber ingestion by mussels, with the thinner particles being preferentially ingested. Therefore, we suggest that new physiological studies employ fiber thickness as a preponderant factor for the ingestion of microplastics in bivalves and also that they choose sizes and concentrations similar to those found in the environment, enabling more robust and accurate results.