An Assessment of the Bivalve Perna viridis, as an Indicator of Heavy Metal Contamination in Paradise Point of Karachi, Pakistan

Heavy Metals Concentration in Perna viridis

Abstract

The edible bivalves Perna viridis (green mussel), (n = 100) were analysed for their total Hg,
Pb, Cu, Ni, Zn, Co, Fe, Cr, Cd, and Mn concentrations to indicate heavy metal contamination in Paradise
Point of Karachi coast using atomic absorption spectrophotometer. There are large seasonal variations in
the metal concentrations of Mn (0.025-0.67 µg/g), Fe (0.055-7.740 µg/g), Ni (0.004-0.52 µg/g), Hg (0.0001-
0.004 µg/g), Zn (0.04-3.32 µg/g), Cu (0.008-1.66 µg/g), Pb (0.022-2.43 µg/g), Co (0.01-0.044 µg/g), Cd
(0.04-0.88 µg/g) and Cr (0.13-1.20 µg/g) recorded in bodies/soft tissues of P. viridis obtained in the samples
of the year 1993 and 2012 at the Paradise Point of Karachi coast. The results of heavy metals are in the
following descending order of concentration in the samples collected in the year 1993: Fe>Cr>Zn>Mn>
Pb>Cd>Cu>Ni>Co>Hg, while Fe>Zn>Pb>Cu>Cr>Cd>Mn>Ni>Co>Hg order was recorded in samples
collected in the year 2012. The high accumulation of metals was found mostly in the samples collected
in the year 2012 when compared with the samples of the year 1993. This is an indication that the area
under study showed signs of being exposed to significant levels of heavy metal pollution due to direct
discharge of industrial and domestic wastes along the coast. The concentrations of these heavy metals were
lower than the permissible limits for human consumption. However, if this pollution persists, it can prove
to be very detrimental in future.