Heavy metal content of water, sediment and fish (Oreochromis niloticus, Linnaeus, 1758) from industrial effluent-polluted aquatic ecosystem in Lagos, Nigeria

Some physico-chemical parameters and heavy metal content of water, sediment and fish (Oreochromis niloticus) from a section of the Lagos Lagoon complex were studied for ten months (July, 2012 – April, 2013). Three sampling stations were used; Ologe, which is the closest to the effluent discharge point from Agbara Industrial Estate, Ijon is located upstream before the point of discharge of industrial effluent and Etegbin is downstream and has a lot of human activities like selling, recreation, washing etc. The heavy metals investigated are Cu, Zn, Pb and Fe while the physico-chemical parameters are temperature, pH, conductivity, total dissolved solids, total suspended solids, salinity, dissolved oxygen, BOD, COD, and alkalinity. All the heavy metals studied showed significant (p<0.05) monthly and seasonal variation in sediment and tissue of Oreochromis niloticus. However, only Zn showed significant (p<0.05) monthly and seasonal variation in the water column of the sampling stations. The values of copper and iron obtained in this study are higher than the limits recommended by World Health Organisation, Nigeria’s Federal Environmental Protection Agency and United States Environmental Protection Agency. This study shows that copper and iron concentrations of Ologe Lagoon, Etegbin and Ijon are increasing. Therefore, there is need for regular monitoring of heavy metals in these water bodies to promptly detect sudden increases and take necessary steps to prevent its harmful effects on man.