I.A.1.c. Collection and Screening Activities-1984

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National Renewable Energy Laboratory

II.A.1.c. Collection and Screening Activities-1984

The screening and characterization protocols used by SERI researchers were refined for the 1984-

collecting season. Included in these refinements was the development of a modified "rotary

screening apparatus," a standard type of motorized culture mixing wheel for 16x150-mm culture

tubes. The rotating wheel was constructed of Plexiglas to allow better light exposure (see Figure

II.A.1). The wheel was typically illuminated with a high-intensity tungsten stage lamp, and could

be placed inside a box behind a CuSO4-water heat filter for temperature control. The Plexiglas

wheel allowed all the cultures to receive equal illumination. Another technological advance used

a temperature-salinity gradient table to characterize the thermal and salinity preferences and

tolerances of the isolates.

Development of artificial saline media.

One of the most significant contributions made by SERI researchers during 1984 was the

development of media that mimicked the saline water in shallow aquifers in the southwestern

United States. This was an important undertaking because it allowed algal strains to be screened

for growth in the types of water that would likely be available in an outdoor mass culture facility.

To identify the major water types available in the southwestern United States, state and federal

reports that described the chemical characteristics of water from 85 saline wells in New Mexico

were studied. The data were statistically analyzed to identify the relationships between the various

ionic constituents. (Data from wells deeper than 83 m was not used in this analysis, because the

cost of pumping water from those depths was prohibitive.) R-mode factor analysis indicated that

two factors were largely responsible for the differences between the waters examined (Barclay et

al. 1988). The first factor, monovalent ion concentration, was responsible for 40% of the

variance; the second, divalent ion concentration, for 30%. A plot of these factors against each

other clearly delineated two primary water types, referred to as "Type I" and "Type II." Type I

waters were characterized by a low monovalent-to-divalent ion ratio (average value = 0.4),

whereas Type II waters had a higher level of monovalent ions (a monovalent-to-divalent ion ratio

of 9.4). The major ions present in Type I water were Na+, Cl-, Mg2+, and Ca2+. The major ions

of Type II water were Na+, Cl-, SO42-, and HCO3-. Type II water is consequently termed a

"sodium bicarbonate class" of water. Approximately three-fourths of the saline well waters were

of the Type II variety, and one-fourth could be characterized as Type I.

The survey indicated that both types of water exhibited a range of conductivities; the researchers

believed that the higher-conductivity waters resulted from evaporation of the lower conductivity

waters. In addition, they recognized that the conductivity of the water in an outdoor production

pond would increase with time because of the high rates of evaporation in the southwestern

United States (as high as 1 cm$d-1). Therefore, artificial media that covered a wide range of

conductivities had to be developed. To this end, an experiment was conducted in which media that

contained the salts typically present in low-conductivity Type I and Type II waters were allowed

to evaporate with stirring at 351C. Samples were removed at various times and filtered. The ions

still dissolved in the waters were quantified using an inductively coupled plasma spectrometer and

a high-performance liquid chromatograph. In this manner, media formulations were derived at

A Look Back at the Aquatic Species Program--Technical Review