Realistic environmental exposure to secondary PET microplastics induces biochemical responses in freshwater amphipod Hyalella azteca

<title>Abstract</title> Aquatic environments are especially susceptible to microplastic contamination. This is mainly because these water bodies serve as a transport route for these particles from the terrestrial environment until they reach the oceans. Also, there is a lack of available data about the effects of this pollutant on freshwaters making difficult the conservation of these environments. Benthic species, such as the freshwater amphipod <italic>Hyalella azteca</italic>, have been superficially studied so far. Considering its essential role in the trophic chain as a primary consumer, it becomes a topic of great relevance to investigate the responses triggered by microplastics in these organisms. In this study, we analyzed whether polyethylene terephthalate microplastics could lead to reduced survival of <italic>H. azteca</italic> or changes in biochemical markers (SOD, CAT, MDA, and GST) at environmentally relevant concentrations (60 and 600 particles per treatment) after 7 days of exposure. The results showed that there was no significant mortality at any of the concentrations tested. The enzyme CAT showed no variation compared to the control group at any of the concentrations. SOD, MDA, and GST were statistically different (p &lt; 0.05). Our study demonstrates that although there was no significant mortality after exposure at an environmentally realistic concentration, the macrobenthic invertebrate community may be under threat in environments where there is microplastic pollution since biochemical changes may be detected at such concentrations as low as 60 particles.