Contaminant accumulation and biomarker responses in caged fish exposed to effluents from anthropogenic sources in the Karnaphuly River, Bangladesh

The possible ecotoxicological effects of a paper and pulp mill effluent were investigated by measuring selected contaminants and biomarkers in caged Nile tilapia (Oreochromis niloticus) and sharptooth catfish (Clarias gariepinus) from the Karnaphuly River, Bangladesh. Fish were caged for 28 d at two upstream reference sites (2 and 4 km) and four downstream sites (3, 5, 8, and 12 km) from the effluent outlets. Organochlorine contaminants and bile biomarkers were bioaccumulated to higher levels at downstream polluted sites than at the reference sites, including hexachlorobenzene (HCB), hexachlorocyclohexane (HCH), polychlorinated biphenyls (PCBs) in liver, and chlorophenolic compounds like 2,4-dichlorophenol and 2,4,6-trichlorophenol in bile. Levels of glucose, protein, and aspartate aminotransferase were analyzed in plasma, whereas cytochrome P4501A (CYP1A) levels were determined in S-12 supernatants of liver. The results, including CYP1A induction and bile biomarkers, clearly indicated that, in addition to the paper and pulp mill effluents, the downstream sites appear to receive other inputs of contaminants. This field assessment in a Bangladeshi river demonstrates biomarker measurements in caged fish as a promising approach for evaluating accumulation and effects of industrial effluents in fish of developing countries.