Acute toxicity effect of copper and cadmium in single and binary exposure on mortality rate and behavioural responses of freshwater fish, cyprinus carpio

Most of the studies reported the effects of metals on fish under the exposure to a single metal, whereas the fishes in the polluted water bodies are typically exposed to mixtures of metals. Hence, the aim of the present study was to investigate the acute toxicity of copper (Cu) and cadmium (Cd) in single and co-exposure on mortality rate and behavioural changes in freshwater fish Cyprinus carpio. The static and renewable bioassay method was adopted to determine the lethal concentration (LC50) of tested metals through probit analysis. The 96 hr LC50 values were 38.36 mg/L for Cu, 92.23 mg/L for Cd and 23.90 mg/L for Cu plus Cd, respectively. The dose and time dependent increase in mortality rate was observed in C. carpio in response to individual and combined exposure of Cu and Cd. Behavioural response under this investigation showed prominent changes of erratic swimming activity, increase in opercular movement, exudation of mucous over the bodies, loss of equilibrium and body dispigmentation in C. carpio exposed to Cu, Cd and Cu plus Cd mixture at their various lethal concentrations. Comparing the 96 hr LC50 and behavioural changes, that Cu plus Cd was the most toxic, followed by Cu and Cd. The results further show that the single exposure of Cu was more toxic than the Cd, but in the binary exposure of Cu and Cd, both are interact with each other and enhance the toxic effect which indicates synergism. The observed data suggest that C. carpio considered as a good biomarker to access the metallic contaminants of freshwater aquatic bodies.