Acute Toxicity of Tilapia guineensis Fingerlings Exposed to Treated Produced Water from the Niger Delta Region of Nigeria

Abstract

This study evaluated the acute toxicity of Tilapia guineensis fingerlings exposed to treated produced water from the Niger Delta region of Nigeria. The produced water was obtained from an Oil and Gas facility within Mbo LGA, Akwa Ibom State, along the Calabar estuary in the Niger Delta Region of Nigeria while the fishes were sourced from African Regional Aquaculture Centre (ARAC), Buguma, in Rivers State, Nigeria. The fishes were allowed to acclimatize in an aquarium for 10 days. Range finding tests of the produced water toxicity was conducted. Based on the preliminary results, main test was defined at 3.125, 6.25, 12.5, 25, 50 and 100%. Reference experimental group was also established using potassium chloride at concentrations of 0.016%, 0.031%, 0.063%, 0.125% and 0.250%. The LC 50 was calculated from the mortality value following standard procedure. Mortality rates increased significantly (p<0.05) as the concentration of the produced water and reference chemical (potassium chloride) increased. The LC 50 values at 24 hours, 48 hours, 72 hours and 96 hours obtained were 50.33%, 24.70%, 17.90% and 13.68% respectively for produced water, and 0.16%, 0.08%, 0.06% and 0.05% respectively for the reference chemical. The LC 50 values showed that the treated produced water is toxic to Tilapia guineensis fingerlings. Hence, there is need to properly treat produced water before it is discharged into surface water systems, in order to forestall potential toxicity associated with it.