Concentrations of some heavy metals in tilapia (sarotherodon melanotheron) from Ekerekana creek in the Upper Bonny estuary

Abstract

Heavy metals are naturally occurring elements but are also released into the environment from industrial processes, mining and other anthropogenic activities to levels that constitute pollution. High levels of heavy metals in aquatic organisms may pose a health risk to those consuming those organisms. The aim of this study was to evaluate the status of contamination of the Ekerekana creek in the Upper Bonny Estuary. Tilapia (Sarotherodon melanotheron)were collected from four different stations; the Point of discharge of refinery effluents into the Ekerekana creek (S1), the Boundary between Ekerekana and Okari creek (S2), refinery jetty (S3) and Ogoloma creek (presumed Control) (S4). The levels of Mn, Ni, Co, and Cr were determined using an Atomic Absorption Spectrophotometer (AAS). The mean concentrations of Mn, Ni and Co in the fish muscles ranged from 1.18 to 5.06mg/kg, 2.43 to 15.15mg/kg and 2.00 to 9.03mg/kg, respectively. The burdens of nickel and chromium were below the DPR target values. The concentrations of nickel in the fish muscles were found to be within the permissible limits of the United States Food and Drugs Administration; Cr was below detectable limits (<0.05 mg/kg) in the fish muscles. The metals studied were not found to be at levels above regulatory limits, but caution should be taken in consuming fish because of the possibility of an increase over time, especially when the refinery comes back into operation. It is recommended that further studies/continuous monitoring of heavy metals should be carried out especially when the operations of the refinery come back on steam.