As a potential biofuel feedstock, the marine microalga, Heterosigma akashiwo, accumulates significant lipids, is capable of long-term growth in outdoor photobioreactors, and is an excellent candidate for the bioremediation of industrial emissions. Here, we evaluated resource partitioning in H. akashiwo growing on a CO2 and NO gas mixture under three light intensities: 160, 560, or 1200 mu mol quanta m(-2) s(-1). Light levels had no effect on growth; however, cultures in high light accumulated 2.3-fold more carbohydrates and 17% fewer lipids. Light levels did not affect the percentage of saturated fatty acids, but mono-unsaturates increased by 6% and poly-unsaturates decreased by 12% in high light. The fatty acid profiles reported here suggest that H. akashiwo is a good candidate for the production of neutral lipids for biodiesel and also omega-3 fatty acids, and that the quality of biodiesel acquired from feedstocks grown under fluctuating light conditions would be relatively stable. (C) 2016 Elsevier Ltd. All rights reserved.