Enhancing Growth and Lipid Productivity of the Marine Diatom Chaetoceros sp

This research was conducted to study the effect of cultivating the diatom Chaetoceros sp under different nitrogen concentrations and varying light and dark periods on growth and lipid productivity. The diatom Chaetoceros sp was cultivated using the F2 nutrient medium, prepared with three different nitrogen concentrations (10%, 50%, and 100%) as a percentage of the recommended concentration for preparing the F2 medium, and under different light and dark cycles (18:6 and 12:12 hours of light: dark). Growth rate, chlorophyll a content, dry weight, and total lipid content were measured and evaluated as response factors to the interaction of the studied growth conditions. The results showed that cultivating Chaetoceros sp in the nutrient medium with 10% nitrogen inhibited growth rate and significantly reduced chlorophyll a content and dry weight. Although there was a noticeable decrease in total lipid content under the same conditions, the effect was less pronounced. The results also indicated a significant decrease in growth rate and dry weight of cultures grown in the nutrient medium with 50% reduced nitrogen concentration. However, the total lipid content recorded a significant increase (21.12%), particularly under the 12:12 (light: dark) regime, while chlorophyll a content did not show significant variation compared to the medium supplemented with a higher nitrogen concentration (100%).