Abstract

Abstract: Introduction: Heavy metals are useful for essential animal tissue metabolism; however, when these metals exist beyond the permissible limits, they cause ecological damage and constitute threat to human health. Freshwater prawns, including Macrobrachium vollenhovenii, are bio-indicators of metal pollution. M. vollenhovenii is an important source of protein and abundant in the Asejire Lake, which serves as a major source of drinking water to people living around the Lake. Aims: This study was therefore designed to examine the concentrations of some heavy metals (Mn, Pb, Cd, Cu and Zn) in water, sediment and different sizes of Macrobrachium vollenhovenii in Asejire Lake, southwest Nigeria. Materials and Methods: Quarterly sampling of M. vollenhovenii, water and sediment was conducted on Asejire Lake in the months of November, February and May. Analysis of the selected heavy metals in the various samples was done using Atomic Absorption Spectrophotometer. Bioaccumulation Factors (BAF) of the metals were also determined. Results: Heavy metals concentration in prawns was in this order: Zn > Cu > Mn > Pb > Cd. Ranked mean concentration of heavy metals in different prawn sizes was large > small > medium. There was no significant difference, at p > 0.05, among heavy metals concentrations in different prawn sizes, except in Cadmium. Pb, Cu and Zn were detected in water, while all the five metals were detected in sediment. Large prawns bioaccumulated the most heavy metals while medium prawns bioaccumulated the least. Cu was the most bioaccumulated heavy metal. Concentrations of Mn, Pb, Cu and Cd were above the FAO limit for prawn; concentrations of Cu and Zn in water were below the WHO limit, while Pb was above the limit. Concentrations of heavy metals in sediment were lower than the FAO limit. Conclusion: These results suggest that prawns and water from Asejire Lake are not safe for human consumption, and it is recommended that proper managerial policy be put in place to check the influx of these metals into the Lake. Keywords: Heavy Metals, Size, Macrobrachium vollenhovenii, Asejire Lake

Keywords: Heavy Metals, Size, Macrobrachium vollenhovenii, and Asejire Lake