DETERMINATION OF LETHAL CONCENTRATION OF CADMIUM BY CARRYING OUT BIOASSAY ON APLOCHEILUS PANCHAX, A FRESHWATER SPECIES

Heavy metal pollutants have hazardous impact on living organisms, of which Cadmium (Cd) and Lead (Pb) are most common. Cd is a toxicant with potential for persistence and bioaccumulation in the body and produce versatile biotic changes in the aquatic ecosystem. The main objective of this study is to evaluate the acute toxicity of heavy metal Cd, which is a potential toxic metal present in Sasthamkotta freshwater lake, a Ramsar site in South India. Freshwater fish species namely, Aplocheilus panchax was subjected to bioassay in the laboratory conditions using Cd and the mortality was assessed in terms of Median Lethal Concentration (LC50) by plotting the Dose-Response assessment curve. The LC50 values corresponding to the 1st, 2nd,3rd,4th,5th,6th and 7th day was found to be 10 ppm, 7.5 ppm, 1.7 ppm, 1 ppm, 0.48 ppm, 0.28 ppm and 0.2 ppm respectively. The mortality of fish increased with the increase in the concentration of Cd, depicting a positive correlation between the mortality and the concentration of the test chemical. The 6th day LC50 value obtained were quite close to the highest concentration of Cd observed in the lake water sample indicating that if the heavy metal contamination goes on increasing, the fish resource of the lake may get considerably affected.