Comparative Analysis of Heavy Metal Accumulation in Prawn Species from Benin River, Nigeria

The concentration of heavy metals (Fe, Zn, Cu, Pb, Cd, and Cr) were determined in the water, bottom sediments, and prawn species of the Benin River using an Atomic Absorption Spectrophotoneter (AAS). The prawns identified included Macrobrachium macrobrachion, Macrobrachium vollenhovenii, and Macrobrachium felicinum. Results revealed significant seasonal variations (P<0.05), with higher metal concentrations during the dry season. Iron (Fe) had the highest concentration in all the prawns, and M. vollenhovenii showed the greatest overall accumulation. The metals followed the order Fe > Zn > Cu >Pb > Cd >Cr. Iron (Fe), Zinc (Zn) and Copper (Cu) were the dominant elements, while Cadmium (Cd) and Chromium (Cr) occurred in lower concentrations. Meanwhile, the heavy metals accumulated predominantly in the prawn heads, with lower levels in the shells, and the least in the flesh. Significant Bioaccumulation Factor (BAF > 1) was observed only for Fe, Zn, and Cu, whereas Pb, Cd, and Cr did not demonstrate notable BAF values. Furthermore, Biota-Sediment Accumulation Factor (BSAF > 1) was not significant for any of the metals examined across the prawn species. Overall, the study provides insight into heavy metal bioaccumulation patterns in prawns from the Benin River and identifies the prawn parts most affected.