Toxicity of Water-Soluble Fractions of Petrol on Some Freshwater Microalgae

This study assessed the toxicity of water-soluble fractions of petrol on Chlorella vulgaris and Scenedesmus obliquus. Water soluble fractions of petrol were prepared into various concentrations as follows: 0%, 5%, 10%, 25%, 50%, 75% and 100%. These treatments were inoculated with 5 mL of the test microalgae and read at 750 nm at two-day intervals for 14 days using a UV/VIS Spectrophotometer. Both Chlorella vulgaris and Scenedesmus obliquus exhibited stimulatory growth response at lower concentrations (5%, 10%, 25% and 50%) while higher WSF concentrations (75% and 100%) were inhibitory to their growth. Comparatively, Chlorella vulgaris showed better growth response than Scenedesmus obliquus. The concentration of TPH was 5831.25 µg/L in the 25% petrol WSF before inoculation and it reduced to 3849.99 µg/L and 3879.50 µg/L for C. vulgaris and S. obliquus, respectively at the end of the experiment. Based on the results of total petroleum hydrocarbon, the test microalgae were shown to have bioremediation potentials. The oxidative biomarker activity for C. vulgaris and S. obliquus was not dependent on the concentrations of petrol WSF. Therefore, these species can be exploited as potential candidates in bioremediation of hydrocarbon contaminated aquatic environments when the level of contamination is low