Effects of Oil Spill Dispersants on the Growth of Brackish Water Heterotrophic Bacteria

Five heterotrophic bacteria isolated from brackish water collected from Nembe waterside, Port Harcourt, Rivers State were cultured aerobically in the presence of varying concentrations (0, 25, 50, 75 and 100mg/ml) of oil spill dispersants (Gold Crew and Camol) to determine the effects of the toxicants on their growth. The isolates were identified as Staphylococcus, Enterobacter, Bacillus, Pseudomonas and Citrobacter. The lag phases of growth of these isolates were affected differently with increasing concentrations of dispersants. Gold Crew increased the lag phases of the bacterial isolates with increasing concentrations while Camol depressed their lag phases at all concentrations. There was a depressive effect on the growth rates of isolates in the presence of Gold Crew but their growth rates at 25mg/ml was slightly depressed compared to higher concentrations of the dispersant. Camol elicited toxic effects on the isolates since their exponential phases of growth were inhibited at all concentrations of the dispersants. The results of this study indicated that the test dispersants have toxic effects on the brackish water heterotrophic organisms and hence support the view that ecotoxicological studies should be carried out on dispersants before field application.