EFFECT OF CRUDE OIL ON THE GROWTH OF MICROALGAE

This study investigated the effect of water soluble fractions of crude oil on the growthofMonoraphidium contortum and Dimorphococcus lunatus over a 14 day period. The test algaewere grown in concentrations of CHU 10 nutrient media mixed with varying concentrationsof WSF of crude oil (5%,10%, 25%, 50%, 75% 100%) which were prepared in triplicates. The growth response was measured using a visible spectrophotometer at two day intervalsover a 14 day period. Physicochemical parameters (pH, EC, and TDS) were assessedonday14 of the experiment and were compared to the stock concentration before exposure tothetest microalgae. The results showed that there was growth stimulation for all concentrationsof 0%, 5%,10%, 25%, 50%,75%, and 100% from day 0 to day 2, and a lag phase fromday2to day 4 for 10% and 100%. The highest growth was recorded at 5% concentration onday14with an absorbance value of 0.035, followed closely by 100%, 50%, and 75%concentrations, while 10% WSF showed the least growth on day 14 with an absorbance value of 0.02. Statistically, the growth response of the microalgae to the WSF concentrations did not differsignificantly (p > 0.005). Generally the percentage yield was higher in M.contortumcompared to D.lunatus. The physicochemical properties of Dimorphococcus lunatus and Monoraphidiumcontortumshowed that when the quantity of WSF was reduced, both TDS and electrical conductivityrose. On the other hand, the pH revealed that it was somewhat more alkaline witha lowerWSF concentration, suggesting acidity with a higher WSF. To summarize, Dimorphococcuslunatus exhibited a strong inhibitory reaction, and Monoraphidium contortumis better suitedfor bioremediation of crude oil in contaminated water.