Comparative toxicity of water soluble fractions of four oils on the growthof a microalga

Toxic effects of water soluble fractions (WSF) of four different fuel oils on a microalga, Tetraselmis gracilis, were examined and compared. On applyi ng different concentrations of WSF, a decrease in cell population was obser ved. Depending on different physico-chemical properties, the hydrocarbons s howed different inhibitory effects on the growth of Tetraselmis gracilis. P etrol was the most toxic and produced inhibitory effects even at low concen trations while HDD and crude oil inhibited growth at higher concentrations. Kerosene did not appreciably alter the growth either at lower or higher co ncentrations. The increase in toxicity was attributed to the presence of ar omatic hydrocarbons of medium to higher molecular weight and their chemical modifications. The experimental data has shown that different oils have di fferent potential for environmental damage, depending on the types and conc entration of soluble and dispersed hydrocarbon present in the WSF.