Heavy Metal Pollution in the Surface Sediments from Cage Aquaculture Farms in the Volta Basin of Ghana: Source Identification and Ecological Risk Assessment

While aquaculture is quickly expanding throughout the Volta Basin and creating several economic benefits, environmental reservations about the cage fish farming industry’s externalities have risen. The pollution, potential sources, ecological risk, and concentrations of heavy metals (Cd, Pb, Ni, Cr, Mn, Fe, Zn, Cr, and As) in sediments were investigated in four cage aquaculture farms (fish farms A, B, C, and D) and control using an atomic absorption spectrometer. The metal concentrations of Zn (0.01 ± 0.001 mg/kg (dw)) and Mn (25.22 ± 1.509 mg/kg (dw)) were the lowest and highest in control and fish farm A, respectively. Heavy metal loads in the farms were in the order: fish farm C (50.14 mg/kg dw) > fish farm D (47.20 mg/kg dw) > fish farm A (40.98 mg/kg dw) > fish farm B (38.61 mg/kg dw) > control (8.44 mg/kg dw). Except for Pb in fish farms C and D, all other heavy metals found in the sediment were below the US EPA and WHO maximum residue levels. Pollution assessment using various indices suggested negligible anthropogenic disturbances except for Mn (moderate enrichment in farms A, B and the control) and Pb (severe enrichment in farms C and D). Ecological risk analysis suggested no potential risk to the benthos in the sediment. PCA revealed that metals were primarily from lithogenic and anthropogenic sources. Other physical, biological, and chemical aspects will need to be investigated in the future to obtain a greater understanding of the environmental impact of cage fish farming in the Basin.