Bioaccumulation of Toxic Metals by Fish in a Semi-Enclosed Tropical Ecosystem

Abstract

Concentrations of Zn, Cd, Pb, and Mn in different tissues of 17 species of fish from a tropical estuary (Cochin backwaters) are presented. The metal selectivity index (MSI) was found to be a better tool compared with the tissue selectivity index (TSI) for explaining bioaccumulation. Regardless of the tissue type, accumulation was maximum for Zn and minimum for Cd. A distinct metal accumulation capacity for each species was noteworthy. The low variability in metal content in the gills indicated its inertness towards bioaccumulation compared with muscle or liver. The high positive correlation between Zn and Pb in tissues is indicative of the anthropogenic impact in the estuary. Conclusions are that, in a weakly polluted area, the organ of choice for estimating bioaccumulation potential is the liver, whereas in a heavily polluted area, the tissue of choice is the gill. The data presented here may be of help for forensic investigations in tropical ecosystems, for evaluation of contaminant impact, and for assessing past contamination events. Fish are good indicators of contamination, and the composition of bioaccumulative data for different species can serve in establishing a bioaccumulation database for that area, useful as a starting point (background) in forensic investigations.