Algal growth requires optimal irradiance.  In photobioreactors, optimal light supply requirements change during the growth cycle because with the increase in culture density, the penetration of light through the algal suspension in the reactor is reduced. This creates zones of dissimilar photon flux density (PFD) inside the reactor, which can cause sub-optimal algal growth. However, it is possible to improve growth through design of mixing patterns that cycle cells between high- and low- PFD zones, and by changing light intensities as culture density increases. In this study a lipid producing algal strain, Neochloris oleoabundans, is being grown in bioreactors to test the effects of sequential increase in light intensities on growth rates and yields. Our experiments involve studies at three different light levels - 150, 250, 380 micromoles per square meter per second under fixed illumination as well as temporally changing intensities to ascertain optimum light requirements during batch growth. Preliminary results show that a sequential increase in irradiance levels yields up to a 2-fold increase in culture densities over those obtained with experiments performed with single light levels throughout the growth. We are also examining lipid production during our tests to correlate biofuel potential with irradiance and growth yields.