ISSN: 2577-4050
Authors: Ezeonyejiaku CD*, Okoye CO and Ezenwelu CO
Heavy metals are stable and persistent environmental contaminants of aquatic environments. Toxicological survey was done to investigate the toxicity of selected hazardous heavy metals and also to determine the rates and levels of bioaccumulation attainable in Clarias gariepinus when exposed to single, binary and multiple mixtures of heavy metals in laboratory bioassays. There were significant departures when the toxicity levels of mixtures (binary and multiple) were compared to the toxicity levels of the individual metals when acting alone against the same test animal. When most of the mixtures were tested against the test Clarias gariepinus, the interaction between the constituents was mainly in conformity with the model of synergism while only a few cases conformed to the model of antagonism. Exposure of the test animal Clarias gariepinus to sublethal concentration of the metal mixtures under the joint action studies resulted in a reduction in the concentration of Cd, Pb, and Cr accumulated by the test organism, when compared to the concentrations accumulated by the animal during the single action studies. Therefore, Clarias gariepinus was found to bioaccumulate heavy metals (Cd, Cr and Pb) to varying degrees, dependent on the type of metals, period of exposure, and concentration of metal compound in the test media and the joint action of the metals in the system.
Keywords: Heavy Metals; Toxicity, Clarias gariepinus; Bioaccumulation; Synergism; Antagonism
