Effects of diesel oil and environmental quality on the enzymatic activities of a tropical estuarine catfish and implications for contamination assessment

The contamination of coastal areas by petroleum and its derivatives is a relevant issue based on large-scale production and consumption. This study presents field and laboratory surveys on the detoxification enzymes on the estuarine/coastal catfish Genidens genidens to understand the enzymatic responses to oil derivatives and environmental conditions. Field catalase (CAT) and glutathione S-tranferase (GST) measurements suggest oxidative stress and acting repair mechanisms in fishes, but were not induced by diesel oil as indicated by laboratory studies. On the other hand, higher ethoxyresorufin-O-deethylase (EROD) activities following higher polycyclic aromatic hydrocarbon (PAH) concentrations in the estuarine waters suggested fish responsiveness to oil contamination, mainly due to the fact that such EROD values were similar to the magnitude measured in fish during a 24-h exposure to diesel oil in the laboratory. However, other environmental estuarine conditions may also act on field EROD activities since PAHs concentrations in the water-soluble fraction of diesel oil (WSFDO) were higher than those measured in estuarine waters.