Seasonal variations in trace metal content in bivalve molluscs, <i>Villorita cyprinoides</i> var. <i>cochinensis</i> (Hanley), <i>Meretrix casta</i> (Chemnitz) and <i>Perna viridis</i> (Linnaeus)

Abstract

Concentrations of Fe, Cu, Zn and Pb in the molluscs studied were influenced by season. Highest concentrations of these metals were found during low salinity and low <i>p</i>H of the habitat water (monsoon periods). Metal concentrations decreased in these species in summer months-the period of high salinity and <i>p</i>H. Fe was the most abundant trace metal in all the 3 species. Significant negative correlations were observed between trace metal content in the tissues of the molluscs and habitat water salinity. Nearly all the 4 metals were positively correlated in the clams, <i>V. cyprinoides</i> and <i>M. casta</i>. In <i>P. viridis</i> only a few combinations (Cu/Zn, Cu/Pb and Zn/Pb) were significantly correlated. The levels of various metals studied, in these bivalves were well below the permitted limits recommended for these metals in marine products.