Comparative study on limnological parameters and bioconcentrations of heavy metals in an air-breathing carnivorous teleostean fish, Gaducia sp. of the upstream and downstream regions of Damsal Nala in Sukinda valley region, Odisha

Damsal nala in Sukinda valley region is incessantly receiving the discharge of mining effluents and runoff or leaching from chrome ore overburden. Different physicochemical parameters of Damsal nala are analysed seasonally (winter, summer and monsoon) during the year 2011 -’12 and compared between uncontaminated upstream and contaminated downstream regions. Analysis reveals that some parameters are within the safe limit (pH: 6.37 -7.46; TDS: 83.10 -127 mg l⁻¹; alkalinity: 66.0 -111.0 mg l⁻¹; hardness: 73.0 -106.0 mg l⁻¹; lead: 10.40 -109.30 μg l⁻¹ and cadmium: 0.00 -2.50 μg l⁻¹) but some of them are excessively high in comparing with standards (WHO, 1994) considering both the upstream and downstream regions. Concentration of heavy metals in the water viz., hexavalent chromium (0.03 -0.06 mg l⁻¹), total chromium (0.14 -0.724 mg l⁻¹), total iron (0.75 -3.42 mg l⁻¹) along with TSS (14.0 -25.0 mg l⁻¹) and COD (24.0 -36.0 mg l⁻¹) has crossed the specified limit (WHO, 1994) in contaminated areas (downstream) posing serious threat to the aquatic organisms of this nala. In contaminated region bioconcentrations of chromium in intestine (13.33 -16.36 g kg⁻¹), liver (5.00 -5.15 g kg⁻¹), gill (2.12 -2.21 g kg⁻¹), kidney (1.40 -1.57 g kg⁻¹) and muscle (0.005 -0.009 g kg⁻¹) are excessively high; and lead in intestine (39.93 -43.24 mg kg⁻¹), liver (49.93 -55.69 mg kg⁻¹), gill (30.06 -33.12 mg kg⁻¹), kidney (19.96 -23.45 mg kg⁻¹) and muscle (10.00 -11.15 mg kg⁻¹) are also higher than the standard safe limit. But the values obtained for cadmium even in the contaminated region in the intestine (1.02 -1.43 mg kg⁻¹), liver (0.61 -0.73 mg kg⁻¹), gill (0.39 -0.43 mg kg⁻¹), kidney (0.20 -0.24 mg kg⁻¹) and muscle (0.09 -0.14 mg kg⁻¹) are well below the standard safe limit by WHO (1994) in food fish.