Activity of antioxidant enzymes in Mytilus galloprovincialis exposed to tar: integrated response of different organs as pollution biomarker in aquaculture areas

Abstract

This paper analyses the antioxidant enzymes response of Mytilus galloprovincialis exposed to a tar mixture during a laboratory assay. These tar mixtures are generally used in the cleaning and waterproofing of the wooden rafts used in mussel culture, and are characterized by their high content in PAHs and transition metals. The punctual spillage of these mixtures around the rafts could cause mussel stress, affecting culture sustainability and product quality for human consumption. The analysis of kinetic parameters and specific activity of the enzymes analysed revealed important tissue differences, which can be summarized as high affinity for reactive species in gills, and high antioxidant efficiency in digestive gland and mantle tissue. Furthermore, the analysis of variance demonstrates dose- and time-dependent response of most enzymes to tar exposure, as well as influence of the dose-time interaction. Antioxidative metabolism of gills constitutes an early response against pollution-stimulated ROS production and is mainly mediated by SOD and CAT activities. While antioxidant defence of digestive gland and mantle is carried out mainly by peroxidases and glyoxalases. These results suggest the necessity of taking into account the integrated antioxidant response of different organs from bioindicator species in toxicological studies. Multivariate analysis of all data obtained corroborates the antioxidant tissular differences, and highlights the activities SOD of gills, GST of digestive gland and Se-GPX of mantle from mussels as suitable biomarkers of PAHs pollution. In the natural environment, the relationship of these enzyme activities, independently of their seasonal or physiologic variation, discriminates between different PAHs and Pb concentrations accumulated in mussels, validating their utility in the assessment of aquaculture areas quality.