N. oleoabundans (UTEX # 1185) was obtained from the Culture Collec­tion of Algae at the University of Texas (UTEX, Austin, TX, USA). Batch cultures were started by inoculation with 106 log growth phase cells into 1 liter glass flasks filled with 750 ml of Modified Bold-3 N medium [49] without soil extract. The concentration of nitrogen in the medium was ad­justed to 50 mg as N l-1 (nitrogen replete; denoted as + N) and 10 mg as N l-1 (nitrogen limited; denoted as — N) using potassium nitrate (KNO3) as the sole source of nitrogen. These concentrations were chosen based on preliminary experiments that identified incubation times and nitrogen con­centrations necessary to induce nitrogen depletion in the mid log-phase of the — N cultures and to ensure that the nitrogen-replete cultures never encountered nitrogen-limitation during the course of the experiment. For each nitrogen condition, cells were cultured in duplicate reactors. Reac­tors were operated at room temperature (25°C ± 2°C), and with a 14:10 h light:dark cycle of exposure to fluorescent light (32 Watt Ecolux, Gen­eral Electric, Fairfield, CT, USA) at a photosynthetic photon flux density of 110 pmol-photon m-2 s-1. Cultures were mixed by an orbital shaker at 200 rpm and continuously aerated with sterile, activated carbon filtered air at a flow rate of 200 ml min-1 using a mass flow controller (Cole-Parmer Instrument Company, IL, USA).