The use of biomarkers to analyze the effects of exposure to chemical contaminants in the aquatic environment is more extended nowadays. Mussels are sedentary filter-feeding organisms which may be exposed to large amounts of chemical pollutants. Mussels are prone to bioaccumulation and magnification of contaminants. In the present work, biological effects of environmental pollution were evaluated, mainly related to presence of PAHs and heavy metals, through several antioxidants and detoxification biomarkers in mussels (Mytilus galloprovincialis) from three areas located in the Eastern coastline of Sicily (Italy), previously transplanted (active biomonitoring). One of these three areas corresponds to the industrial harbour area between Augusta and Priolo, considered one of the most extensive areas of petrochemical industrial activity in Europe, severely contaminated by PAHs and heavy metals; a second point is located in Brucoli, littoral zone where the presence of xenobiotics in the environment is considered negligible; and a third point (reference site) from which proceed the pristine population of M. galloprovincialis. Changes at molecular and biochemical level in the tissue of the digestive gland were quantified. The results showed a significant increase (p<0.05) in the activity of the antioxidant enzyme catalase, the activity and expression of the detoxifying enzyme glutathione-S-transferase, and malondialdehyde levels, as a marker of lipid peroxidation, in mussels from the area of Priolo. The metallothioneins (MTs) gene expression was significantly induced in mussels (p<0.05) from Priolo when compared to those from the reference site. AChE was negatively affected by pollutants evidencing a decreased activity in Priolo (p<0.05). No significant differences were observed between the three sampling sites in the expression of the CYP3A1. In conclusion, the observed results demonstrate that the pollution associated with petrochemical industrial area (mainly of PAHs and heavy metals) causes the activation of the detoxification and antioxidant defence systems in the digestive gland of the mussels M. galloprovincialis, indicative of oxidative stress. This study provides further evidence of the criticality representing harbour areas, due to the presence of xenobiotics in high concentrations, which can accumulate in sediments and in living organisms due to the limited hydrodynamic inside harbour
