Abstract

L. O. Odokuma and E. Akponah

The effect of nutrients supplements (NPK inorganic fertilizer and poultry litter) on the biodegradation of crude oil and metal uptake by three bacterial isolates (Bacillus sp, Pseudomonas sp and Aeromonas sp) in crude oil impacted fresh and brackish water aquatic systems of the Niger Delta were investigated. The abilities of these single cultures to reduce the contaminating oil levels as well as to bioconcentrate-associated heavy metals (Fe, Pb, Cd, Zn, Ni and Cu) were carried out for a period of 120 days. The effect of the nutrient supplements were monitored and enhanced by periodic re- addition to desired levels. Habitat water samples without nutrient supplements served as controls. Nutrient supplementation resulted in both increased pH as well as increase in biomass. In microcosms containing Bacillus sp and Pseudomonas sp, total viable cell counts increased while hydrocarbon, pH and the inorganic nutrients decreased. Significant reductions (64 and 82%) in oil and grease levels were obtained in fresh and brackish water respectively that received NPK. for Bacillus and Pseudomonas. Application of poultry litter resulted in 59.7 and 78.7% reductions in fresh and brackish water options respectively for both organisms. However, no significant changes occurred in microcosms containing Aeromonas sp except that counts declined considerably with time. Bacillus and Pseudomonas proved suitable for the uptake of the heavy metals present Aeromonas was unsuitable though it was resistant to the heavy metals. Bioconcentration of heavy metals followed the pattern: Pseudomonas > Bacillus. The pattern of heavy metal uptake by the three bacterial isolates was different in the various treatment options. The uptake of these metals was enhanced by increases in microbial biomass of the isolates. Peak uptake of metals occurred in the exponential phase for Bacillus while for Pseudomonas peak uptake of metals corresponded with the stationary phase. No significant difference in the amounts of heavy metals bioconcentrated when NPK fertilizer was used as supplement than when poultry litter was employed. The initial concentration of metals, pH of the medium as well as the cultural status of the isolates influenced metal uptake. Results indicated that addition of NPK inorganic fertilizer or poultry litter promoted both biodegradation of crude oil by Bacillus and Pseudomonas and heavy metal uptake by Bacillus and Pseudomonas in fresh and brackish water aquatic systems of the Niger Delta