Comparative Studies on the Green Algae Chlorella homosphaera and Chlorella vulgaris with Respect to Oil Pollution in the River Nile

The effect of oil pollution on growth and metabolic activitiesof the fresh water algae Chlorella homosphaera and C.vulgaris was studied. The study was conducted on two locationsin the river Nile, one is oil polluted and the other is notpolluted. The assemblage of the different algal groups wasmonitored in both locations. Chlorophyta was more dominant thanCyanophyta and Bacillariophyta in both locations during allseasons except in winter when Bacillariophyta is the mostdominant group. The presence of crude oil or its refineryproducts (solar and lubricating) in the culture media of algaemarkedly influenced their growth, proteins and nucleic acidcontents. The toxicity of oil was a concentration dependent. Thelow concentrations stimulated growth, protein content andnucleic acids, whereas high concentrations had an inhibitoryeffect. Although DNA and RNA responded similarly to crude oil inthe two tested organisms, DNA showed more sensitivity than RNAto solar oil. Lubricating oil had a little phytotoxic effect onnucleic acids. Different species of algae response differentiallyto oil pollution; Chlorella vulgaris can be referred to asoil-sensitive, while Chlorella homosphaera can toleraterelatively higher concentrations of oil.