Six promising strains were analyzed in SERI Type I, Type II, and ASW (Rila) using the temperature-salinity gradient described previously. These included the diatoms Chaetoceros muelleri (CHAET14), Navicula (NAVIC1), Cyclotella (CYCLO2), Amphora (AMPHO1 and AMPHO2), and the chlorophyte Monoraphidium minutum (MONOR2). (NAVIC1 and CYCLO2 were actually collected from the Florida keys; the remaining strains were collected in Colorado and Utah.) All strains exhibited rapid growth over a wide range of conductivities in at least two media types. Furthermore, all strains exhibited temperature optima of 30°C or higher. Maximal growth rates of these strains, along with the optimal temperature, conductivity, and media type determined in these experiments are shown in Table II. A.1. (Higher growth rates were determined for some of these strains in subsequent experiments; see results presented in Barclay et al. [1987]). Temperature-salinity growth contours are provided for these strains in the 1986 ASP Annual Report (Barclay et al. 1986).

Experiments were also conducted in an attempt to identify the chemical components of SERI Type I and Type II media most important for controlling the growth of the various algal strains. Bicarbonate and divalent cation concentrations were found to be important determinants in controlling the growth of Boekelovia sp. (BOEKE1) and Monoraphidium (MONOR2). The growth rate of MONOR2 increased by more than five-fold as the bicarbonate concentration of Type II/25 medium was increased from 2 to 30 mM, and the growth of BOEKE1 by approximately 60% over this range. These results make sense, since media enriched in bicarbonate would have more dissolved carbon available for photosynthesis. An unexpected finding was that there was a decrease of nearly 50% in the growth rate of BOEKE1 as the divalent cation concentration increased from 5 mM to 95 mM (in Type I/10 medium containing altered amounts of calcium and magnesium). The effects of magnesium and calcium concentration on the growth of MONOR2 were less pronounced. These results indicate that matching the chosen strain for a particular production site to the type of water available for mass cultivation will be important.