Most microalgal collection efforts carried out under the auspices of the ASP before 1987 focused on sites that were expected to naturally experience high temperatures; indeed, one subcontractor, Keith Cooksey (Montana State University) specifically searched for thermophilic strains isolated from hot springs. This was because the temperatures of production ponds in the southwestern United States during the prime growing season were expected to reach high levels; thus the production strains would have to thrive under such conditions. However, temperatures in this region are quite cool for several months of the year and can drop to below freezing at night. Consequently, an effort was initiated by SERI researchers to collect, screen, and characterize strains from cold-water habitats.

Four collecting trips were made between October 1986 and March 1987 to various inland saline water sites in Utah and eastern Washington, and to the coastal lagoon waters in southern California. Water samples were enriched with N, P, trace metals, and vitamins; artificial media were not used in the initial selection protocol for these experiments. The rotary screening apparatus was maintained at 15 °C for the duration of the screening process by including a copper cooling coil inside the screening chamber. The cultures were incubated for 5-10 days, which is longer than for warm-water strains because of the slower growth at the cooler temperature. This procedure created a problem, however, in that many more strains survived the selection process than when 30°C was used as the selection temperature. As a consequence, separating strains from each other and identifying which were the best for further characterization were more difficult.

An interesting finding from the cold water strain collection project was that many species that predominate after the enrichment procedure were the same as the warm water species selected in previous collection efforts. The genera and species that were commonly found in both the cold water and warm water screening projects were C. muelleri, Amphora coffeiformis, Cyclotella, Navicula, and Nitzschia. However, some ochromonids and green coccoid algae were also isolated from the cold water collection effort; these types of alga were less commonly isolated during the warm-water selection procedures. Additional work would be needed to characterize these strains with respect to lipid production potential. Future work should look at the fatty acid profiles of oil found in the cold-water strains. Such cold-water organisms often contain high levels of polyunsaturated fatty acids, which would perform poorly as a feedstock for biodiesel because of their low oxidative stability and tendency to polymerize during combustion (Harrington et al. 1986).

I Publications:

Johansen, J. R.; Doucette, G. J.; Barclay, W. R.; Bull, J. D. (1988) “The morphology and ecology of Pleurochrysis carterae var dentata nov. (Prymnesiophyceae), a new coccolithophorid from an inland saline pond in New Mexico, USA.” Phycologica 27:78-88.

Johansen, J.; Lemke, P.; Barclay, W.; Nagle, N. (1987) “Collection, screening, and characterization of lipid producing microalgae: Progress during Fiscal Year 1987.” FY 1987 Aquatic Species Program Annual Report, Solar Energy Research Institute, Golden, Colorado, SERI/SP-231 -3206, pp. 27-42.

Johansen, J. R.; Theriot, E. (1987) “The relationship between valve diameter and number of central fultoportulae in Thalassiosira weissflogii (Bacillariophyceae).” J. Phycol. 23:663-665.

Tadros, M. G.; Johansen, J. R. (1988) “Physiological characterization of six lipid-producing diatoms from the southeastern United States.” J. Phycol. 24:445-452.

I Additional References:

Harrington, K. J. (1986) Biomass 9:1-17.