Eight additional strains collected previously from warm-water sites that grew well during the initial screening procedures were characterized with respect to temperature and salinity tolerances, growth rates, and lipid content under various conditions. These strains were Chaetoceros muelleri (strains CHAET6, CHAET9, CHAET10, CHAET15, and CHAET39), Cyclotella cryptica (CYCLO4), Pleurochrysis carterae (PLEUR1), and Thalassiosira weissflogii (THALA2). Each strain was grown in a variety of temperature-salinity combinations by the use of a temperature-salinity gradient table. The maximal growth rate achieved under these conditions occurred with CHAET9, which exhibited a growth rate of 4.0 doublings^day-1. The remaining strains all had maximum growth rates that exceeded 1.4 doublings^day-1, and several grew at rates exceeding 2.5 doublings^day-1 (i. e., CHAET6, CHAET10, and CHAET39). All had an optimal temperature of 30°C or higher, except for PLEUR1 and THALA2, which had optimal temperatures of 25°C and 28°C, respectively. Most of the strains grew well in a wide range of salinities (e. g., five of the eight strains exhibited a growth rate greater than one doubling^day-1 at

conductivities between 10 and 70 mmho^cm’1). With respect to the effect of water type on growth, CHAET39, CYCLO4, and PLEUR1 grew best on SERI Type I medium. On the other hand, CHAET6, CHAET9, and CHAET10 grew best in SERI Type II medium, but also exhibited good growth on Type I medium and artificial seawater. CHAET15 and THALA2 achieved maximal growth rates on artificial seawater, and, along with PLEUR1, grew very poorly on Type II medium. These results again highlight the need to have a variety of algal strains available for the specific water resources that would be available for mass culture in various locations.

The lipid contents of these 10 strains were also determined for exponentially growing cells, as well as for cells that were grown under nutrient-limited conditions. Nitrogen deficiency led to an increase in the lipid contents of CHAET6, CHAET9, CHAET10, CHAET15, CHAET39, and PLEUR1. The mean lipid content of these strains increased from 11.2% (of the total organic mass) in nutrient-sufficient cells to 22.7% after 4 days of N deficiency. Silicon deficiency led to an increase in the lipid content of all strains (although in some cases the increase was small and probably not statistically significant). The mean lipid content of the eight strains increased from 12.2% in nutrient-sufficient cells to 23.4% in Si-deficient cells. A few strains were poor lipid producers, such as CHAET6, CYCLO4, and PLEUR1, which did not produce more than 20% lipid under any growth conditions.