Induction of pollutant responsive biomarkers, ethoxyresorufin–Odeethylase, glutathione S-transferase and biliary fluorescent aromatic compounds in tilapia inhabiting Bolgoda North Lake, Sri Lanka.

Abstract

The presence of organic contaminants in aquatic systems poses a serious threat to environmental health. Biomarkers are sub-lethal biological measures of the response to and effect of pollutants in living organisms. Use of biomarkers has been identified as a powerful and cost-effective approach to obtain information on the state of the environment and the effect of pollutants on living biological resources. This study presents results of a part of the research project which focuses on evaluation of the use of biomarkers in food fish tilapia as tools in monitoring pollution in inland waterbodies in Sri Lanka. In the present study, activities of two enzyme biomarkers, ethoxyresorufin-O-deethylase (EROD) & glutathione S-transferase (GST) and biliary fluorescent aromatic compounds (FACs) in Nile tilapia (Oreochromis niloticus) collected from Bolgoda North Lake were evaluated in comparison to the baseline levels of the control fish in order to assess the biomarker responses in this fish. The results revealed that EROD and GST activities of tilapia inhabiting Bolgoda North Lake were significantly elevated several folds in comparison to the baseline levels. Liver somatic index and microsomal and cytosolic protein levels in the gill and liver tissues of fish collected from the lake were also elevated significantly compared to the controls. Induction of EROD and GST enzymes indicate the exposure of fish residing in the lake to organic contaminants such as polycyclic aromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCB). Analysis of biliary FACs in the fish showed recent uptake of naphthalene, pyrene and benzo(a)pyrene type PAHs. Occurrence of PAHs in the colloids and sediments of Bolgoda North Lake has been confirmed by chemical analysis. Results suggest that EROD and GST in liver and gill tissues and FACs in bile in this fish are promising biomarkers of organic contaminations especially PAHs in the aquatic environments.