Biomonitoring of organic pollutants in local coastal waters using EROD activity in fish

Abstract

Mixed Function Oxidases are a group of detoxification enzymes which can be induced in fish livers by the presence of organic contaminants in the seawater or sediments. Quantification of these group of enzymes in fish livers is nowadays being used in conjunction with chemical monitoring to assess the extent of organic pollution present in a particular area. The main aim of this biomonitoring exercise was to determine the induced levels of EROD activity in the fish Serranus cabrilla collected from three sites along the Wied Ghammieq sewage pollution gradient, namely from Xghajra, Zonqor Point and Delimara areas and from Wied iz-Zurrieq area, a sewage-free reference site. Seasonal variation in hepatic EROD activity levels (both specific and total) were also investigated as well as any correlation with liver mass and condition factor. Mean specific hepatic EROD activity levels from Serranus cabrilla was found to be 2.06 + 0.13 picomoles per minute per mg protein, these being lower than values quoted for Serranus cabrilla by other scientists but comparable to values quoted for other Serranus species. The pollution gradient was reflected in specific hepatic EROD activity values in spring and in winter as well as in Liver Somatic Index values in summer and winter. Monoxygenase activity in Serranus cabrilla was found lowest during the reproductive season. In this study, the effects of bromoform exposure via an intraperitoneal injection, on hepatic EROD activity levels was also investigated in the seabream Sparus aurata to investigate further the effects of increasing bromoform concentrations in the marine environment on local fish populations as well as the effect of bromoform on biomonitoring in general. A dose of SOµg/kg was administered. A negative control group using ethanol and a positive control group using f3naphthoflavone were also used to determine any significant induction. Specific EROD activity levels in the bromoform-exposed group were found to be lower than those of the negative control group, possibly indicating that bromoform is an inhibitor of Mixed Function Oxidases. The condition factor values obtained for the bromoform-exposed group were lower than the values for the other groups, confirming that bromoform stresses fish. This project was part of an international research programme sponsored by the European Community within the framework of its Avicenne Initiative 1994 (Research Contract Number: JRP A Vl-CT94-0010).