Assessment of Heavy Metal Concentration in Chrysichthys nigrodigitatus (Lacépède, 1803) and Eichhornia crassipes [Mart.] Solms from Ologe Lagoon and its Tributaries in Lagos, Nigeria

This study investigated the health status of Ologe Lagoon and its tributaries (Agbara, Era, Imude and Morogbo). Samples were collected between June, 2015 and November, 2015 from the stations on monthly basis. Some physic-chemical parameters (alkalinity, salinity, pH, turbidity and hardness) and the levels of five heavy metals (Zn, Fe, Cu, Cd and Pb) in water, sediment, Eichhornia crassipes and a commercially important fish, Chrysichthys nigrodigitatus (silver catfish) were studied using standard procedures. The results showed significant (p<0.05) seasonal variation in hardness and turbidity. Water samples from Agbara were more turbid than all other stations. The pH values (5.55 - 6.60) recorded in this study is ideal for fish growth and survival of freshwater species. Fe and Cu exhibited significant (p<0.05) spatio-temporal variation in the water column. The concentrations of heavy metals (except Cd and Cu) in Eichhornia crassipes have exceeded FEPA and WHO maximum permissible limits. The mean concentration of heavy metals (except Zn) in Chrysichthys nigrodigitatus was above the limit recommended by FEPA and WHO. The study showed that the water quality variables of Ologe Lagoon and its tributaries can still sustain fish but the metal load in their biota is increasing and this may be harmful to inhabitance of the community, who depend on the services provided by these aquatic ecosystems. Therefore, efforts should be made by all users of these water bodies especially the industries to treat their wastes before discharging them into these aquatic ecosystems.