Bioaccumulation of heavy metals in marine blue crab (Callinectes amnicola) and freshwater crab (Sudanonautes aubryi)

Abstract

Crabs can be particularly sensitive to heavy metals because, typically, they inhabit benthic zones. In this study, selected heavy metals (Copper (Cu), Cadmium (Cd), Lead (Pb), Nickel (Ni), Arsenic (As), Zinc (Zn), Iron (Fe) and Chromium (Cr) were analysed in the organs/tissues (gills, hepatopancreas, gonads, stomach and muscle) of Callinectes amnicola and Sudanonautes aubryi samples collected from Akodo beach and Asejire reservoir respectively using Atomic Absorption Spectrophotometer. The results obtained showed that Cr had the highest concentration in the stomach of male S. aubryi (3.003 mg.kg-1) and Cu (3.016 mg.kg-1) in the gills of female C. amnicola. From the two study sites, it was observed that the concentration of As (0.064 mg.kg-1, 0.131 mg.kg-1), Cr (3.110 mg.kg-1, 1.110 mg.kg1), Cd (1.220 mg.kg-1, 1.110 mg.kg-1) and Pb (2.085 mg.kg-1, 1.003 mg.kg-1) in crabs (C. amnicola and S. aubryi) respectively were above the range of WHO acceptable limit for consumption (As 0.0001 mg.kg-1, Cr 0.050 mg.kg-1, Cd 0.003 mg.kg-1 and Pb 0.500 mg.kg-1). Input of heavy metals into the aquatic environment occurs probably through anthropogenic activities such as municipal wastewater, antifouling measures, indiscriminate use of manure and fertilizers, disposal of household and manufacturing industrial wastes. It is therefore recommended that there is a need for bio-monitoring and constant re-evaluation of heavy metals in fish and shellfish resources from the two study sites considering the status and importance of Akodo Beach and Asejire reservoir to the society.