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.