Effect of Chemical Corexit 9527 on 28 Day old TILAPIA GUINEENSIS FINGERLINGS

Abstract

The toxicity of the chemical Corexit 9527 to 28-day-old freshwater tilapia guineensis fingerlings was studied in the static renewal bioassay glass tank, using tap water. The 28-day-old tilapia guineensis fingerlings collected from Ikpoba Hill River, Edo State were used to access lethal concentrations of the dispersant Corexit 9527. Differential sensitivity of test organisms to Corexit 9527 was observed. This was achieved by predictive application. The LC50 is actually used as an estimate of the incipient lethal level which is also called the lethal threshold concentration, asymptotic LC50, or tolerant limit. The incipient lethal level is the concentration at which half the population will die in an indefinite period of time. It is estimated by the LC50 at that time for no further toxicity has been observed. This steady state LC50 is the incipient lethal level. In fish tests, this often occurs within 4 days, and this is one rationale behind the 96-hour length for a standard acute fish test.The median lethal concentration LC50 of the dispersant Corexit 9527 on tilapia guineensis was determined using a computerized probit analysis according to the methods of Finney. The median lethal concentration, LC50 for the 28-day-old tilapia guineensis was 409.71mg/l and 367.20mg/l for 3 and 4 days respectively. The 28-day-old tilapia guineensis showed a high-level tolerance to lower concentrations of Corexit 9527 and high-level toxicity at the highest concentration which recorded 100% mortality even at a 24-hour exposure period.