Research Article

Comparative Assessment of Heavy Metal Bioaccumulation in Crabs and Prawns from Selected Creeks in Trans-Amadi, Port Harcourt, Nigeria: Implications for Ecological Risk Assessment

Abstract

This study assessed comparative heavy-metal bioaccumulation in crabs and prawns collected from five creek systems within the Trans Amadi area of Port Harcourt, Rivers State, Nigeria, and evaluated the associated human-health and ecological risks. Ten metals comprising Pb, Cd, Cr, Ni, Cu, Zn, Fe, Mn, Co and Hg were determined in crab and prawn tissues. Mean concentrations in crabs ranged from 0.14–0.98 mg/kg for Cd, 0.36–0.53 mg/kg for Cr, 0.63–0.84 mg/kg for Ni, 3.84–5.03 mg/kg for Cu, 16.85–22.14 mg/kg for Zn, 28.74–39.17 mg/kg for Fe, 5.17–6.88 mg/kg for Mn, 0.26–0.39 mg/kg for Co and 0.016–0.031 mg/kg for Hg, while Pb ranged from 0.67–0.98 mg/kg. Prawn concentrations were comparatively lower across the investigated metals. All metals showed bioaccumulation factors greater than unity, with Zn recording the highest BAF in crabs (2.43) and prawns (1.82). The combined hazard index was 1.91 for adult crab consumers and 1.28 for adult prawn consumers, increasing to 5.69 and 3.84, respectively, among children. Total carcinogenic risks were 9.0 × 10−5 and 6.2 × 10−5 for adult crab and prawn consumers, respectively, and 2.70 × 10−4 and 1.86 × 10−4 for children. Potential ecological risk indices ranged from 96.9 at Ntawogba Creek to 146.3 at Okujagu/Okuruama. The findings indicate species- and location-dependent metal accumulation and highlight the need for continued monitoring of seafood safety and ecological quality within the creek system.