First ecotoxicological characterization of paraffin microparticles: a biomarker approach in a marine suspension-feeder,Mytilussp

Abstract

Microplastics are one of the main environmental pollutants in marine ecosystems, and their presence in seawater is a consequence of the widespread use of plastic materials in modern commodities. This wide usage of plastics includes the employment of microspheres in common personal care products, which end up being ultimately released into the aquatic compartment. Known ecotoxicological effects of microplastics favoured the search for technologically viable and environmentally safer alternatives, such as paraffin wax microparticles, whose ecotoxicological risks have not been entirely characterized. To address this gap, the present study exposed mussels (Mytilussp.) for 96 h to three densities (5 mg/L, 20 mg/L and 80 mg/L) of four size ranges (100-300 mu m, 300-500 mu m, 400-850 mu m, and 800-1200 mu m) of paraffin wax particles. Toxicological endpoints were the activities of four enzymes involved in key cellular processes, including antioxidant defence (catalase (CAT), glutathione reductase (GRed) and glutathione peroxidase (GPx)) and phase II metabolism (glutathioneS-transferases (GSTs)), as well as lipid content and fatty acid profiles of the digestive gland. Significant interactions between the presence/absence of food and paraffin particle density were found, as food sometimes worked as a confounding factor in the analysed biomarkers. Despite this uncertainty, some overall patterns emerged. In general, smaller paraffin wax particles (100-300 mu m) caused little effects on the activity of the four enzymes tested, whereas larger particles (800-1200 mu m) caused significant effects on almost all biomarkers. CAT activity was enhanced in animals exposed to larger paraffin particles, whilst GPx activity was depressed; GRed activity was not affected by the exposure to paraffin particles. The activity of GSTs was enhanced, but only in one tested condition. No effects were observed in terms of the total lipid content and fatty acids of exposed animals. Overall, data obtained in this work suggest that, at densities of p