Expressive Biofragmentation of Polystyrene Microplastics by the Amphipod Hyalella Azteca

Microplastics are widespread pollutants in the environment and are considered a global pollution problem. Microplastics mostly originate from larger plastics and due to environmental conditions are undergoing constant fragmentation processes. It is important to understand the fragmentation pathways, since they play a key role in the fate of the particles, and also directly influence toxicity. Amphipods are potential inducers of plastic debris fragmentation. Here, Hyalella azteca was exposed to different concentrations (540, 2700, 5400 items/L) of 24.5 µm polystyrene microplastics (PS-MP) for 7 days. After exposure, particle size reduction, mortality and oxidative stress in the organisms were checked. It was observed that throughout the ingestion and egestion of PS-MP by H. azteca , particles suffered intense fragmentation, presenting a final size up to 25.3% smaller than the initial size. The fragmentation rate over time (24, 72, 120, 168h) was verified and the results showed a constant rate reduction in average particle size. No significant mortality was seen in any of the treatments, although changes were recorded in all enzymatic biomarkers analyzed. It was possible to assume that H. azteca are able to induce PS-MP fragmentation and this process may lead to nanoparticle formation, which may facilitate bioaccumulation and trophic particle transfer.