Abstract
Heavy metal discharge is the primary cause of freshwater pollution, harming fish health. This research was planned to calculate the seasonal variations in metal (Pb, Cu, and Ni) bioaccumulation in different tissues of Gills, Liver, Kidney, and Muscle from Cirrhinus mrigala sampled from River Chenab from an area of high-intensity pollution near Thatta Muhammad Shah. The results revealed significant (P ≤ 0.5) variations in metals bioaccumulation in different seasons. The lowest level of selected metals was observed in winter, whereas the maximum level was noted in the summer. The concentration of selected heavy metals differed seasonally. During winter Pb concentration distribution in descending order was observed in liver (0.823 ± 0.009 ppm) > kidney(0.817 ± 0.011 ppm) > muscle(0.758 ± 0.009 ppm) > gills(0.742 ± 0.011 ppm). Whereas, in summer it was noted as liver (1.726 ± 0.066 ppm) > gills (1.633 ± 0.060 ppm) > kidney (1.575 ± 0.051 ppm) > muscle (1.532 ± 0.050 ppm). While during winter, the bioaccumulation of Cu in organs was noted with descending order of kidney (1.88 ± 0.038) > liver(1.75 ± 0.037) > gills (1.67 ± 0.043) > muscle (1.45 ± 0.031)ppm, while in summer, it was gills (2.85 ± 0.071) > kidney (2.84 ± 0.082) > liver (2.83 ± 0.068) > muscle (2.72 ± 0.065) ppm. In winter, the Ni bioaccumulation with descending order was in the kidney (7.83 ± 0.139) > liver (7.68 ± 0.159) > muscle (7.63 ± 0.162) > gills (7.61 ± 0.129)ppm and in a season of summer, it was detected as in kidney (8.71 ± 0.129) > muscle (8.59 ± 0.131) > liver (8.56 ± 0.141) > gills (8.56 ± 0.131) ppm. All studied heavy metals were found to be above the WHO permissible limits. Histopathological evaluation of fish tissues has been considered an important indicator of environmental pollution monitoring. Histology of kidney and liver tissues showed congestion, necrosis, dilation in Bowman capsule space, while liver showed necrosis, cytoplasmic vacuolation, and sinusoid dilation. This study revealed that the Chenab River is being polluted due to the untreated discharge of industrial effluents and sewage runoff from the city, and these heavy metals from anthropogenic pollution load have adverse effects on the fish population in the river system.