The Toxicity of Poly(acrylonitrile-styrene–butadiene) Microplastics toward <i>Hyalella azteca</i> Is Associated with Biofragmentation and Oxidative Stress

Acrylonitrile-butadiene-styrene (ABS) is a thermoplastic copolymer commonly used in the electronics, automotive, and construction industries. In the aquatic environment, the formation of microplastics from larger-sized plastic waste occurs naturally, induced by physical, chemical, and biological processes that promote the aging of these particles. Here, we investigated the interactions between the freshwater amphipod <i>Hyalella azteca</i> and ABS microplastics (10-20 μm) (pristine and after accelerated aging) over 7 days of exposure. At the end of the exposure period, we evaluated the ability of <i>H. azteca</i> to fragment the ABS particles, as well as the changes in its oxidative stress biomarkers (SOD, CAT, MDA, and GST) as the result of ABS exposure. <i>H. azteca</i> promoted a significant fragmentation of ABS particles. The ratio of this biofragmentation was more pronounced in pristine particles. Despite the absence of significant changes in the mortality of exposed organisms, alterations in the oxidative stress biomarkers were observed. The results demonstrate the ability of <i>H. azteca</i> to fragment pristine and aged ABS microplastics and, the consequent susceptibility of these organisms to the effects of microplastic exposure.