Seasonal Variation in Occurrence of Heavy Metals in<i> Perna Viridis</i> from Manora Channel of Karachi, Arabian Sea

Abstract

Seasonal sampling of the edible green mussel Perna viridis of two different sizes 6-8cm (n=100) and 4-6cm (n=100) from Manora channel of Karachi, were analyzed for their total Hg, Pb, Cu, Ni, Zn, Co, Fe, Cr, Cd and Mn concentration. There are large seasonal variations in the metal concentrations found in green mussel Perna viridis . The high accumulations of metals were found mostly in small size 4-6 cm mussels as compare to largeones. The present study has confirmed thatgreen mussels have greater capacity for accumulation ofmetals.All the studied metal levels found in green mussels collected in 2012 were higher than those detected in mussels collected in 1993, irrespective of mussel body size. The concentrations of Fe was highest compared to other heavy metals. The results of heavy metals are in the following descending order of concentration: Fe>Pb> Zn>Cu>Mn> Ni> Cr> Cd> Co> Hg. It is supposed that in Manora channel water, high input of metals and other inorganic and organic substances are coming in the form of industrial and domestic wastes and need to be monitored on a regular basis.