Toxicity of Oil Spill Dispersant on freshwater fish Poeciliopsis occidentalis and microorganism Nitrobacter sp 1Renner Renner Nrior* and 2Lucky Odokuma 1Department of Microbiology, Faculty of Science, Rivers State University, Port Harcourt, Nigeria 2Department of Microbiology, Faculty of Science, University of Port Harcourt, Port Harcourt, Nigeria Logo Logo Introduction Methods Results Conclusions Dispersants are chemical agents that reduce interfacial tension between oil and water in order to enhance the natural process of dispersion by generating larger numbers of small droplets of oil that are entrained into the water column (Fingas et al., 1995). They are a class of chemical compounds employed in the control of oil spilled in aquatic environment (NRC, 2005). AIM: The aim of the study was to evaluate and compare the toxic levels of Oil Spill Dispersant used in the upstream sector of the Nigeria Petroleum Industry and the possible discharge dilution in freshwater environment.   The sensitivity of the bacterium Nitrobacter and freshwater fish Poeciliopsis occidentalis to the toxicity of the different concentrations of Oil Spill Dispersants in freshwater showed OSD/Seacre to be more toxic than OSD/LT Based on these findings; the use of Oil spill Dispersant OSD/Seacare should be with high caution or discontinued in the upstream sector of the Nigeria Petroleum Industry. The 96hour Median Lethal Dose (LD50 ppm) of the Oil Spill Dispersants at concentrations0, 10, 100, 1000, 10000, 100000ppm to higher organism; fresh water fish Poeciliopsis occidentalis OSD/LT (55999ppm) OSD/Seacare (1774ppm) The 24h median lethal concentration (LC50 ppm) of Oil Spill Dispersants to microorganism Nitrobacter sp. in freshwater were; OSD/LT (47185.7ppm), OSD/Seacare (29251.7ppm).   Materials and organisms used ASSAY USING HIGHER ORGANISM Freshwater Fish : Topminnow Poeciliopsis occidentalis Source/Collection of Test organism ↓ Acclimatization Selection of active organism for Test Choice of Bioassay Tank Bioassay tanks were made of glass of 30 x 21 x 25cm SET UP Test Medium prepared with habitat water (10, 100, 1000, 10000, 100000ppm) Range Finding Test Semi-static Acute Toxicity Test For 0h, 4h, 8h, 12h, 24h, 48h, 72h, 96h Mortality Count Percentage Mortality of Poeciliopsis occidentalis % Mortality = Number of Organism dead x 100 Total number of organisms Median Lethal Dose (LD50) Evaluation METHODS ASSAY USING MICROORGANISM Microorganism: Nitrobacter sp. Isolation of Test organism using ↓ Winogradsky Agar Preparation of Standard Inoculum Preparation of Test Medium SET UP Test Medium prepared with habitat water (10, 100, 1000, 10000, 100000ppm) Toxicity Test for 0h, 4h, 8h, 12h, 24h ↓, Survival Count Percentage Log Survival of Nitrobacter sp. % Log Survival = Log of Count in test tox. Conc. x 100 Log of count in zero tox. Conc. Median Lethal Concentration (LC50) Evaluation REFERENCES EGASPIN Environmental guidelines and standards for the petroleum industry in Nigeria, Revised Edition. (2002) Department of Petroleum Resources (DPR) pp. 277-288. NRC (National Research Council) (2005). Oil spill dispersants. The National Academic Press, Washington, DC, USA Correspondence: Nrior, R. R. E-mail: renner4nrior@gmail.com TEL: +2348065885566 Poster No.: pp04