Concentrations of some metals in sediment, Macrobrachium macrobrachion, and Tympanotonus fuscatus obtained from the Great Kwa River, Calabar, Nigeria

This study was carried out to determine the concentrations of some metals in sediment and flesh of Macrobrachium macrobrachion and Tympanotonus fuscatus obtained from the Great Kwa River, Calabar, Nigeria. Sampling and analyses were done between June and September, 2014 and the samples were collected from three sampling locations (location 1: Esuk Ekpoeyo; location 2: Esuk Atu; location 3: Obufa Esuk). The analysis was done through the buck scientific atomic absorption spectrophotometer model VGP210 after digestion of the samples. The concentration values obtained across the different sampling locations and between specimens were recorded. Mean concentration values of metals in sediment were: cadmium (Cd), 0.129±0.045 mg/kg; chromium (Cr), 0.112±0.020 mg/kg; copper (Cu), 0.061±0.012 mg/kg; manganese (Mn), 0.038±0.004 mg/kg; nickel (Ni), 0.062±0.006 mg/kg; lead (Pb), 0.143±0.047 mg/kg and zinc (Zn), 0.088±0.014 mg/kg. The concentration values of metals recorded in M. macrobrachion were: Cd, 0.0076±0.001 mg/kg; Cr, 0.016±0.005 mg/kg; Cu, 0.033±0.002 mg/kg; Mn, 0.02±0.001 mg/kg; Ni, 0.005±0.005 mg/kg; Pb, 0.032±0.002 mg/kg and Zn, 0.037±0.02 mg/kg while the values in T. fuscatus, were: Cd, 0.008±0.006 mg/kg; Cr, 0.017±0.004 mg/kg; Cu, 0.024±0.004 mg/kg; Mn, 0.023±0.0015 mg/kg; Ni, 0.008±0.006 mg/kg; Pb, 0.119±0.176 mg/kg and Zn, 0.035±0.017 mg/kg. There was no significant difference (P ˃ 0.05) in the concentrations of metals across stations (1-3) and amongst samples (sediment, M. macrobrachion and T. fuscatus). The concentrations of some metals in the samples were below acceptable limits except Cr which was slightly higher in all the samples, Cd and Ni in sediment, Cu in M. macrobrachion and Pb in T. fuscatus. This suggests that there is a slight deviation from the acceptable limit of metals in benthos from the Great Kwa River and the sediment is moderately unhealthy to support aquatic biota. However, activities resulting to anthropogenic input of metals in the Great Kwa River should be prohibited in other to avoid possible deleterious effects of these metals after a long period of accumulation.