GROWTH OF MICROALGAE

This study investigated the effect of water soluble fractions of crude oil on the growth of Monoraphidium contortum and Dimorphococcus lunatus over a 14 day period. The test algae were grown in concentrations of CHU 10 nutrient media mixed with varying concentrations of 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 intervals over a 14 day period. Physicochemical parameters (pH, EC, and TDS) were assessed on day 14 of the experiment and were compared to the stock concentration before exposure to the test microalgae. The results showed that there was growth stimulation for all concentrations of 0%, 5%,10%, 25%, 50%,75%, and 100% from day 0 to day 2, and a lag phase from day 2 to day 4 for 10% and 100%. The highest growth was recorded at 5% concentration on day 14
with 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 differ significantly (p > 0.005). Generally the percentage yield was higher in M.contortum compared to D.lunatus. The physicochemical properties of Dimorphococcus lunatus and onoraphidium contortum showed that when the quantity of WSF was reduced, both TDS and electrical conductivity rose. On the other hand, the pH revealed that it was somewhat more alkaline with a lower WSF concentration, suggesting acidity with a higher WSF. To summarize, Dimorphococcus lunatus exhibited a strong inhibitory reaction, and Monoraphidium contortum is better suited for bioremediation of crude oil in contaminated water.