Acute Toxicity of Copper, Cadmium and Arsenic to Zebrafish, Danio rerio (Cyprinidae)

Pollution has focused the attention of both the scientific community and the public on environmental problems. Not only does water pollution affect the health and welfare of people and organisms, but it also damages vegetation and properties. Environmental pollutants are categorized as heavy metals, pesticides etc. Metals and metal compounds are constituents of our natural environment. Their distribution depends on the existence of natural sources (e.g. volcanoes or erosion) and their use in human's activity. They are transformed naturally (e.g. by bacterial activity) with formation of organic species that influence their mobility and accumulation in biotic as well as biotic systems. In the present study, Zebrafish, Danio rerio was exposed to different concentrations of copper (Cu), cadmium (Cd) and arsenic (As) up to 96 hours. The acute toxicity levels were derived from LC₅₀ concentrations of these heavy metals. The lethal concentrations were established by static bioassay for 24, 48, 72 and 96 hours with the 95% confidence limits through probit analysis. The 96 hour LC₅₀ values were calculated to be 5.22 mg/L for Cd, 0.03 mg/L for As and for Cu was 78.17 mg/L. The toxicity of these metals in zebrafish increases with the increasing concentrations and exposure periods. The toxicity ranking of the three heavy metals was As>Cu>Cd for experimental fish zebrafish. The fishes showed behavioral abnormalities like rapid opercular movement, erratic and fast swimming, abrupt change in position and direction; jumping and overall hyperactivity was observed during the initial stages of exposure.