Chiang Mai Journal of Science

 Concentration of trace metals (Cr, Mn, Cu, Fe, Ni, Zn, Pb and Cd) in soft tissue and shell of two marine bivalves Perna viridis and Crassostrea madtrasensis were analysed seasonally i.e. per-monsoon, monsoon and post-monsoon from the northeastern coast of the Bay of Bengal. The mean concentrations of Cr, Fe, Ni, Cu and Zn in mussel (P.virideis) were higher than these in oyster (C. madrasensis), however the latter contained more Mn, Pb and Cd than the former. Highest levels of most elements were found during monsoon period, this is probably due to freshwater discharges from the upstream regions with treated and untreated industrial effluents, agridultural run-off and domestic wastes. Metals like Cr, Fe, Zn, Cu and Cd were found to be more abundant in the soft tissue while Mn, Ni and Pb preferentially concentrated in the shells. The levels of various metals studied in these bivalves in these bivalves were high compared to other published result for unpolluted siteds and the levels of Pb and Cd in both species exceeded the WHO allowed limites for human consumption.