Effects of combined exposures of fluoranthene and polyethylene or polyhydroxybutyrate microplastics on oxidative stress biomarkers in the blue mussel (<i>Mytilus edulis</i>)

A growing interest in developing and commercialization of new eco-friendly plastic polymers is occurring attributed to the impact of marine plastics debris and microplastics that result from the degradation of oil-based polymers as these substances adversely affect ecosystem health. Recently, polyhydroxybutyrate (PHB) has become of interest due to its biodegradability and physicochemical properties. However, biological consequences resulting from bioplastics exposure remain to be determined. Further, few data are apparently available regarding the potential for bioplastics to act as a vector for exogenous chemicals in the environment. The aim of the study was to compare the effects of polyethylene (PE MPs) and polyhydroxybutyrate (PHB MPs) microplastics administered alone or in combination with fluoranthene (Flu) on detoxifying enzymes in digestive glands and gills of <i>Mytilus edulis</i>. Blue mussels were exposed for 96h to eight experimental groups: control, Flu-only, PE MPs-only, PHB MPs-only, PE MPs-Flu co-exposure, PHB MPs-Flu co-exposure, Flu-incubated PE MPs, and Flu-incubated PHB MPs. Activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPx), glutathione S-transferase (GST), and glutathione reductase (GR) were found to be significantly susceptible to Flu and plastics in both tissues. Interestingly, a single exposure to PHB MPs led to decreased activity levels of CAT and GST in gills, SOD in digestive glands and SeGPx in both tissues. In co-exposure and incubation treatments, biochemical responses were generally comparable with those exerted by PE MPs or PHB MPs only, suggesting an apparent absence of combined effects of microplastics with the pollutant. Data demonstrated the ecotoxicological impact of bioplastics materials on digestive glands and gills of <i>Mytilus edulis</i>.