Heavy metals in shell fishes of Ojo River, Lagos State, Nigeria

R.Y Oladunjoye,A.H Adedeji,O.O Fafioye,A.S Edoh,S.T Bankole

doi:10.4314/as.v20i3.13

Abstract

   The research examined the accumulations of six heavy metals including chromium (Cr), lead (Pb), iron (Fe), zinc (Zn), cadmium (Cd), and copper (Cu) in water as well as in three male and female species of crab (Cardisoma armatum, Callinectes danae, Callinectes ornatus) sampled from Ojo River in Lagos State of Nigeria. Physico-chemical parameters of the water samples from the River and heavy metal concentrations in the crab species obtained also from the River were examined using standard methods. The results showed that total dissolved solute (TDS), electrical conductivity (EC), salinity, dissolved oxygen, biological oxygen demand and chemical oxygen demand varied significantly along the River course, with TDS and EC being relatively high. Heavy metals detected in the crabs were Fe, Cu and Zn, with Cu being the highest in the species examined. The species C. ornatus presented the highest content of Cu followed by C. armatum and C. danae. The content of heavy metals (mg kg–1) among the crab species showed that Cu (23.47±0.10) > Zn (19.06±0.01) > Fe (16.85±0.01) in all the species except in C. armatum where Fe (1.26±0.44) was > Zn (1.19±0.02). Furthermore, Pb, Cd and Cr were not found in the crabs and this could be associated with the fact that the area consists mainly of residential houses, farms and a few industries. Notably, the content of the heavy metals was larger in the female than the male crabs. This study reported different levels of heavy metal accumulation in male and female species of crabs. Also, the shell fishes from Ojo River might be considered safe for consumption, but the need for continuous monitoring to prevent bioaccumulation is recommended.  

Highlights

Investigation of heavy metals in the aquatic environments including aquatic organisms is not a new area of science; it exists around more than a century
The values of total dissolved solute (TDS) and electrical conductivity (EC) were relatively high in the water samples
Lead (Pb), cadmium (Cd) and chromium (Cr) were not detected, while the concentration of copper (Cu) was higher followed by zinc (Zn) and in C. ornatus

Summary

Introduction

Investigation of heavy metals in the aquatic environments including aquatic organisms is not a new area of science; it exists around more than a century. Heavy metals are natural constituents of the earth crust which unsystematic anthropogenical activities have significantly distorted their geochemical cycles and biochemical balance (Singh et al, 2011). They comprise elements that are necessary for living organisms including manganese, cobalt, zinc, copper, molybdenum and others (Duffus, 2002), but at high concentration, are harmful (Popek et al, 2008). Toxic metals naturally occur in aquatic environments in very low concentration, but their concentration level has increased due to persistent discharge of anthropogenic, agricultural and industrial pollutants over time (Anim et al, 2011). Industrial activities as well as agriculture and mining create a potential source of metals pollution in the aquatic environment (Hosseini et al, 2014)

Methods

Results

Conclusion