Comparative assessment of heavy metal bioaccumulation in skeletal muscles of softshell and hard-shell freshwater turtles

Abstract

The heavy metal ions originating from the various point and nonpoint sources seriously threatening the lotic ecosystem by posing severe health crises to the aquatic organisms of higher trophic levels. The freshwater turtles with delicate body structure and devoid of any hardcovers are prone to higher heavy metal bioaccumulation risks. The present study was conducted to determine heavy metals bioaccumulation in three soft-shelled and hard-shelled freshwater turtle species in Pakistan. We collected the water samples and cadaver turtle bodies at both sites and transported them to the laboratory for heavy metal content evaluation. The skeletal muscles (1 g) and water samples (100 ml) were processed by acid digestion and prepared metals analyses by AAS. The results indicated that the mean concentrations of Copper (Cu), Zinc (Zn) and Cadmium (Cd) were significantly lower, while Nickel (Ni), Cobalt (Co), Lead (Pb) and Chromium (Cr) were significantly higher at both sites compared with world health organization (WHO, 2004) standards. Muscles of softshell turtle (Lissemys punctata) showed the maximum bioaccumulation of targeted metals than other two species of hard-shell turtles i.e. Cu (7.61 ± 1.88), Zn (49.17 ± 4.11), Ni (2.77 ± 0.41), Cd (0.21 ± 0.02), Co (3.31 ± 0.43), Pb (4.70 ± 0.62) and Cr (6.09 ± 0.39). The mean concentrations of Cu, Ni, Pb, and Cr were maximum in water and turtle species muscles collected from Trimmu Barrage. In conclusion, the heavy metal loads in water and bioaccumulation patterns in the skeletal muscles of freshwater turtle species illustrated species and location-based variations with overall similar pattern corroborations among the sequence of heavy presence levels.