Biomarker responses in mosquito fish (Gambusia affinis) to in vivo exposure to produced waters

The aim of this study was to assess the biochemical response of mosquito fish to the exposure to produced waters (PW) in short and long-term laboratory experiments. Produced water (PW) is a complex mixture containing residual hydrocarbons, trace elements, naturally occurring radioactive material and potentially toxic treatment chemicals such as biocides, dispersants, detergents and scale inhibitors used in hydrocarbon production. Male and females of mosquito fish (Gambusia affinis) were exposed for 8 and 30 days to PWs from an Italian on-shore oil plant and from an Italian off-shore gas platform. We measured a set of hepatic biomarkers: 7-ethoxyresorufin-O-deethylase (EROD) and benzopyrene-monooxygenase (BPMO), glutathione-S-transferase (GST), lipid peroxidation (LPO), enzymatic antioxidants (GPX, GR, CAT), a non-enzymatic antioxidant (glutathione-GSH); as well as biliary fluorescent aromatic compounds (FACs) metabolites. DNA damage was evaluated in erythrocytes by Comet and ENA assays. The experimental groups showed significantly higher EROD and BPMO activity compared with the control group during the exposure to PWs from gas and oil installations. The CYP1A responses were also compared with the other biomarkers, in particular positive Spearman correlations between EROD (or BPMO) activity and PAH metabolites in bile and Comet assay were observed. The results highlighted a clear indication of the degree of stress syndrome induced by PWs, showing an increasing pollution gradient of PWs (gas<oil). The test organism (Gambusia affinis) was revealed to be a good sentinel species for laboratory studies to investigate the PWs toxicity. The obtained results supported the usefulness of the combined use of biochemical markers to assess the impact of PWs, able to describe the evolution of the stress syndrome in Gambusia affinis.