Integrated response of the toxicity of environmentally relevant concentrations of copper in the backwater clam Meretrix casta

Abstract

Copper is released into the aquatic environment as a consequence of anthropogenic activities such as mining and runoffs of copper-containing pesticides and fertilisers. This may pose a threat to the health of the organisms inhabiting coastal water bodies or estuaries. The present study was therefore carried out to assess the toxicity of environmentally relevant concentrations of copper in the estuarine backwater clam Meretrix casta. In the experimental setup, clams were exposed to five concentrations of CuCl sub(2) (0.5, 1.0, 1.5, 2.0 and 2.5 Microgram/L) for 15 days in water. Biomarkers of genotoxicity (Micronucleus test and comet assay), oxidative stress (Catalase and malondialdehyde assays), acetylcholinesterase activity and condition index were employed to study the effects of copper on the clams. Genotoxicity, oxidative stress, acetylcholinesterase activity and condition index were found to be non-significant in all the concentration groups indicating that such low concentrations of copper were unable to induce any toxic response. However, using the Integrated Biomarker Response index, a concentration-dependent increase was observed indicating that the integration of these biomarker responses could give information on early signs of copper contamination in aquatic habitats. Meretrix casta could potentially be used as a sentinel species for monitoring copper contamination in the estuarine environment.