Risk assessment of heavy metals bioaccumulation in Clarias gariepinus tissues from Jakara Reservoir, Kano, Nigeria

Abstract

The risk of heavy metals bioaccumulation in gills and liver of C. gariepinus of Jakara Reservoir, Kano was assessed for period of twelve months (March, 2020 to February, 2021). In situ and in vitro examinations were performed using standard procedures. Sites for sampling were categorized into three as offshore (A), midshore (B) and inshore (C) were chosen based on the impact of varying humans activities within the reservoir. The mean range of physicochemical parameters were water temperature (27.1 – 28.30 °C), Dissolved Oxygen (5.9 – 6.6mg/L), Biological Oxygen Demand (2.4 – 3.7mg/L), transparency (0.9 –1.2m), electrical conductivity (637.1– 1064μS/cm), pH (7.8 – 8.1), and Total Dissolved Solids (433.1–733.8mg/L).Gills had accumulation of Fe, Cr, Cu, Pb and Cd in a concentration graded fashion with Fe being the highest and Cd the lowest in terms of concentration. BAF in liver tissues recorded a decrease in the following sequence: Cu >Cr> Pb > Fe >Cd. Physicochemical parameters, heavy metals bioaccumulation differed significantly (P<0.05) between the sites and seasons with the exception of TDS, EC, turbidity and Cadmium. It can be deduced that fluctuation in water quality parameters and heavy metals concentrations in the reservoir could be attributed to high influx of nutrients due to farming activities among other anthropogenic input. It is hereby recommended that indiscriminate discharge of agro chemicals among other domestic inputs should be minimized in order to curtail degradation of the reservoir in the long run. Relevant authorities should develop strategies to control potential effect of the pollutants on the aquatic biota in the water body.