Biomarkers (glutathione S-transferase and catalase) and microorganisms in soft tissues of Crassostrea rhizophorae to assess contamination of seafood in Brazil

The goal of this study was to evaluate biomarkers (glutathione S-transferase and catalase) and microorganisms in soft tissues of Crassostrea rhizophorae to assess possible contamination of seafood in Brazil. The oysters were sampled from a reference area (Ports 1 and 2) and an impacted area (Ports 3 and 4) in Brazil (São Luís Island, Maranhão). Six attributes were examined in sampled oysters: glutathione S-transferase activity, catalase activity, concentrations of total coliforms and thermotolerant coliforms, and levels of Escherichia coli and Aeromonas hydrophila. Water samples were analysed for aluminium, cadmium, iron, manganese, lead, mercury, phenolics, and polychlorinated biphenyls. We found that Ports 3 and 4 are impacted by several contaminants (mercury, phenolics, and polychlorinated biphenyls), while Ports 1 and 2 are still relatively free of these contaminants. Changes in enzymes activity as well as the highest tissue bacterial concentrations were recorded in oysters from Ports 3 and 4 during the rainy season. •Oysters were reliable bioindicators of contamination in port areas.•E. coli was detected in oysters analysed in the dry period.•Oysters from these areas may be a significant vehicle for foodborne pathogens.•GST activity in the oysters increased in the rainy season.•Changes in enzymatic activity are sensitive indicator of environmental stress in oysters.