Temporal and salinity impacts on the microbial diversity at the Eilat, Israel Solar Salt Plant

A major solar salt works in Israel is located just north of the town of Eilat and close to the
airport. This solar salt works has been in operation since 1977 and produces about 170,000
tons a year. A three-year study was initiated to examine the temporal and salinity impacts on
the microbial community throughout this saltern. At the time this study was begun in the late
1990's, there were several paradigms about the microbial community:
1. there is greatly reduced diversity as the water reaches saturation;
2. because of the relative stability of the salt concentrations in the various pans, there is little
change in the microbial community; and,
3. halophilic Archaea are not found in ponds with less than 15% salt and halophilic Bacteria
would not be found in pans at saturation.
The first paradigm was developed based on a few studies using one medium and single
observations of various salterns. The second paradigm was an assumption that had not been
systematically tested, and the third paradigm, at least for the Bacteria, was shown in 1980 not
to be true with the discovery of the genus Halomonas.
We examined these paradigms by systematically studying on a seasonal basis the saltern at
Eilat, Israel, as well as the Cargill Solar Salt Plant in Newark, California. Both traditional and
molecular techniques have been used throughout these studies.
Several different approaches were taken: plate counts were made on several different media,
whole community carbon requirements were determined, molecular fingerprinting of the whole
microbial community using the amplicon length heterogeneity approach was performed to
determine the changes in the community composition over time, and partial characterization
of the isolated pure cultures were all performed. Samples were taken at least twice a year
corresponding to the cooler and hotter times of the year.
Based on this extensive study there were significant differences in the plate counts and in the
ratios of the various peaks found during the fingerprinting. It is safe to say now that the
microbial community in the waters of a solar saltern is variable and both domains can be
found throughout the saltworks.