Article Title: Acute Toxic Effects of Petroleum Refinery Effluents on Fingerlings of Tilapia Oreochromis niloticus and Clarias gariepinus Catfish
The Ekerekana creek in Okrika Local Government Area of Nigeria has served as the recipient water body for the discharge of refinery effluents over the years, the extent of chemical contaminant in the effluents has always been a cause of worry to the community. The study was conducted to determine the toxic effects of the refinery effluents on fingerlings of Oreochromis niloticus and Clarias gariepinus. Standard methods where used to determine the physicochemical parameters of the refinery effluents with its turbidity being 3.56 NTU, nitrate 4.01 mg/l, chemical oxygen demand 1.566 mg/l, phosphate 1.01 mg/l, ammonium 0.66 mg/l, pH 6.90, sulphates, 1.01 mg/l, nickel <0.001 mg/l, chromium <0.001 and lead 0.031 mg/l. The results obtained indicated that the refinery effluents caused 100% mortality on Oreochromis niloticus and none on Clarias gariepinus at the 96hr static bioassay test. mortality was concentration dependent. The behavioural responses observed are erratic swimming, inconsistency in jumping, continuous gulping of air, loss of balance and eventual death. The results of this study showed that time of survival for O. niloticus increased at lower concentrations of 20- 40% and decreased at higher concentrations of 80- 100%. The Lc50 values for O.niloticus were 84% at 96 hrs, 89% at 72 hrs and 95% at 48 hrs. Results showed that the release of these effluents into water bodies is able to cause mortality in these species of catfish at increased concentration and as such the effluents should be properly treated before disposal.