Biodegradation of petroleum hydrocarbons under tropical estuarine conditions.

The physico-chemical parameters of water samples collected from three points in the Lagos lagoon were studied for 12 months. Safinity varied seasonally but the temperature pH, dissolved O2, conductivity, NO3 (-) and HPO4 (2-) concentrations were relatively constant. There was a direct proportionality between the population density of hydro-carbon-utilizing bacteria and the oil content of water samples. Twelve hydrocarbon-utilizing bacteria were isolated by selective enrichment and characterized as species ofPseudomonas, Alcaligenes, Acinetobacter andBacilius. The organisms grew mainly on long-chain aliphatic hydrocarbons. Laboratory and field biodegradation studies showed both quantitative and qualitative changes in the hydrocarbon content of crude oil due to microbial degradative activities and a faster rate of oil depletion from the Lagos lagoon during the rainy season. The results obtained could offer a predictive model for estimating the rate of disappearance of petroleum hydrocarbons from the tropical estuarine environment.