Evaluation of heavy metal concentrations in water, sediment and fishes of New Calabar River in Southern Nigeria

Abstract

The aim of this study was to evaluate the levels of heavy metals in surface water, sediment and selected fish samples in New Calabar River. Samples for analyses were collected for six months across three stations between 08:00 and 12:00 hrs on each sampling day. Physicochemical parameters and metals in water, sediments and tissues of fishes were analyzed following standard procedure using a spectrophotometer. In surface waters, iron, nickel and zinc were above recommended limit while in sediments chromium, iron, nickel, lead and zinc were above the limit. No significant differences were observed in metal concentration in the tissues of the three species. The levels of heavy metals reported in Chrysichthys nigrodigitatus, Tilapia zilli and Papyrocranus afer were higher than that reported in surface waters and sediment, indicating bioaccumulation potentials of metals in fishes. Among the three species, the highest metal concentration was reported in the tissues of T. zilli followed by P. afer and C. nigrodigitatus. The presence of elevated non-essential metals like chromium and lead in fishery products of the New Calabar River requires regular assessment, regulatory and mitigative actions to reduce the burden of metal accumulation in human population through consumption of fishery products.