I.A.1.c. Collection and Screening Activities-1984 (cont)

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National Renewable Energy Laboratory

SERI that covered a range of conductivities (from 10 to 70 mmho$cm-1) for both media types.

The media most commonly used were designated SERI Type I/10, Type I/25, Type I/55, Type

I/70, Type II/10, Type II/25, Type II/55, and Type II/70, in which the number following the slash

indicates the specific conductivity of the medium. The compositions of these media are given in

Figure II.A.2.

To assess whether these media formulations accurately reflected the types of water in desert region

surface waters, samples of the water at numerous algal collection sites in the southwestern United

States were chemically analyzed. The relative compositions of the anionic and cationic

constituents were then plotted on separate trilinear plots, which allowed a graphical representation

of the various water samples relative to SERI Type I and Type II media (Figure II.A.3). This

analysis indicated that Type I water has higher proportions of Mg2+ and Ca2+ than most surface

waters examined, whereas Type II water was fairly representative of the sampled waters with

respect to these cations. On the other hand, natural surface waters often had an anion composition

similar to both SERI Type I and Type II media. The researchers concluded that these artificial

media would serve well as standardized media for testing newly acquired strains, thereby allowing

all ASP researchers (both in-house personnel and subcontractors) to screen strains for growth

potential in waters similar to those that would be available for commercial production.

Collection activities.

Collecting trips made by SERI researchers in 1984 focused on shallow saline habitats, including

ephemeral ponds, playas, and springs in the arid regions of Colorado and Utah. After collection,

the water and sediment samples were kept under cool, dark conditions for 1 to 3 days until they

could be further treated in the laboratory. The pH, temperature, conductivity, redox potential, and

alkalinity of the collection site waters were determined, and water samples were taken for

subsequent ion analysis. In the laboratory, the samples were enriched with 300 µM urea, 30 µM

PO4, 36 µM Na2SiO3, 3 µM NaFeEDTA, trace metals (5 mL/L PII stock, see Figure II.A.2), and

vitamins. The enrichment tubes were then placed in the rotary screening apparatus (maintained

at 251C or 301C) and illuminated at ~400 µE$m-2$s-1. During a 5-day period, the illumination

provided by the stage lamp was gradually increased to 1,000 µE$m-2$s-1. The predominant

strains in the tubes were isolated as unialgal cultures by agar plating or by serial dilution in liquid

media.

The isolated strains were then tested for their ability to grow in incubators at 251C at 150-200

µE$m-2$s-1 in the standard media types described earlier and in artificial seawater (termed "Rila

Salts ASW," using Rila Marine Mix, an artificial sea salt mixture produced by Rila Products,

Teaneck, New Jersey. The strains that grew well in at least one of these media were further

characterized with respect to growth on a temperature-salinity gradient table at a light intensity

of 200 µE$m-2$s-1. Thirty combinations of temperature (101 to 351C) and salinity (10 to 70

mmho$cm-1) were included in this analysis, representing the ranges that might be expected in

actual outdoor production systems. Once again, the cultures were enriched with nutrients to

maximize growth rates. The cultures used to inoculate the test cultures were preconditioned by

growth in the media at 17° and 271C. The optical density at 750 nm (OD750) of the cultures was

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