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If you have ever driven north on U.S. Highway 395 along the eastern side of the Sierra Nevada in late summer, you may have noticed the vast, pinkish-red, salt flats of Owens Lake gleaming in the desert sun. Near the abandoned Pittsburgh Plate Glass soda ash plant, along the northwestern end of the lake, solar evaporation ponds may be colored a brilliant red. Similar pinkish brine pools can be seen along Highway 50, east of Fallon, Nevada. Pink salt lakes and playas, and the bright red evaporation ponds of salt recovery plants along their shores, are among nature's most remarkable biological phenomena, and occur in arid regions throughout the world. The red coloration is caused by astronomical numbers of microscopic, unicellular organisms living in the water and salt crust. How they survive the blistering summer heat and concentrated brine is truly remarkable.

Before the end of the last great ice age of the Pleistocene Epoch (over 11,000 years ago), huge snow packs and glaciers covered the Sierra Nevada. Melting of this snow and ice sent enormous quantities of water down Owens River, filling the deep valleys and basins along its path to overflowing. Remnants of ancient beaches at the southern end of Owens Valley indicate that glacial Owens Lake was over 200 feet deep and covered nearly 200 square miles. Glacial Owens Lake ran south to China Lake, where it overflowed into vast Searles Basin and Panamint Valley, forming lakes estimated to be more than 600 feet deep. Some geologists believe that glacial Lake Panamint may have overflowed into Death Valley, where it joined forces with the Amargosa and Mojave Rivers to form ancient Lake Manly, over 600 feet deep. During thousands of years of evaporation the lakes gradually dried up, as enormous quantities of salts precipitated out in vast salt flats.

Because of the extensive salt accumulation over countless centuries of time, some of these dry lake basins have become veritable chemical reservoirs. For example, at Searles Lake (southeast of Owens Lake), mineral-rich brine is pumped to the large Kerr-McGee Chemical Plant in Trona, California where valuable minerals are recovered. In 1913 a tramway was completed across the rugged 9,000 foot crest of the Inyo Range, east of Owens Lake. During its peak operation, the tram bucket brigade carried 20 tons of salt per hour from isolated Saline Valley on the east side of the range. Remnants of the ingenious salt tram can still be seen along the Owens Lake Loop (Highway 190). The historical sites in this fascinating region of California are summarized by G.S. Smith (editor) in Deepest Valley: A Guide to Owens Valley--Its Roadsides and Mountain Trails, 1978.

Before the Owens River was diverted into the Los Angeles Aqueduct in 1913, Owens Lake was a large, blue salt lake covering 100 square miles. During the late 1800s, a steamship crossed Owens Lake to carry lumber, mine timbers, charcoal and other supplies to the east shore, where it was packed up to the Cerro Gordo Mine near the crest of the Inyo Range. On the return trip the steamer carried hundreds of bars of silver bullion to Cartago Landing at the south end of the lake, saving days of freight time by mule trains. Today as you gaze across the immense, rose-pink salt flat, it is hard to imagine that this was once a beautiful blue lake with a busy steamship and two bustling ports at distant shores.

Owens Lake is a playa or intermittent dry lake bed that may contain standing water during wet years. Even when the lake appears dry, a layer of brine occurs beneath the salt crust. It is fed (in part) by the Owens River and the tributaries that drain the snow-covered Sierra Nevada. Owens Lake had been gradually drying up for thousands of years, and was already saline when the Owens River was diverted to supply Los Angeles with water. Brine fly pupae (Ephydra), common insects of saline ponds and lakes, were an important food in the diet of local Paiute Indians. The pupae, which look like grains of rice, occur in enormous numbers and can still be found around the shoreline where there is standing water. They can also be found by the thousands, embedded in the salty crust.

The reddish coloration of Owens Lake is caused by astronomical numbers of microscopic, salt-loving bacteria, called halobacteria. A single drop of the brine contains millions of rod-shaped bacterial cells. The bacteria produce a red carotenoid pigment which is similar to that found in tomatoes, red peppers, pink flamingos, and in many colorful flowers and autumn leaves. [Flamingos actually get their carotenoid pigments from their diet of shrimp and other crustaceans.] Carotenoid pigments are also the source of Beta-carotene, an important antioxidant and the precursor of vitamin A. In fact, in some parts of the world, B-carotene is extracted from salt ponds containing red salt-living bacteria and algae. In the case of the halobacteria living in Owens Lake, the red pigment may protect their delicate cells from the intense desert sunlight.

To appreciate the tenacity of halophilic cells, I once sent some pieces of salt crust from Owens Lake to Dr. Richard Norris, an expert on flagellates at the University of Witwatersrand in Johannesburg, South Africa. Dr. Norris was able to dissolve the salt crystals and extract the algal cells which he identified as Dangeardinella saltitrix. This species has a slender, pear-shaped cell with two peculiar flagella, one extending forward and one trailing behind. Extreme halophilic algal cells such as Dangeardinella and pinkish-red halobacteria (Halobacterium) can survive completely encased in salt crust for extended periods of time. In fact, bacterial spores of the genus Bacillus were isolated from pockets (inclusions) in salt crystals harvested from an underground salt bed 2,000 feet below the surface. The salt deposits were formed from an ancient sea in a geologic formation that dates back about 250 million years.

The amount of salt in a lake or sea is often expressed as a percent, and refers to the total grams of dissolved salts in 100 milliliters of water. The total percent salinity includes all salts present, such as sulfates, chlorides, carbonates, magnesium, calcium and sodium; however, the most abundant salt in the brine where halophilic algae and bacteria thrive is ordinary table salt, or sodium chloride. The percent salinity may vary in a salt lake or playa, depending upon where the water is tested, such as close to freshwater springs or a river inlet. For example, in the northern arm of the Great Salt Lake, the total dissolved salt content is more than 30 percent, whereas in the southern arm (where the rivers enter) the salt concentration ranges from 12 to 20 percent. Unlike most living things, the halophilic bacteria thrive in saline lakes with salt concentrations of 15 to 30 percent. This is roughly four to nine times the salinity of sea water (3.5 percent). Their optimum growth condition is 20-30 percent salinity. They can even live in saturated salt and remain alive in salt crystals for years. In fact, they cannot survive if the salt concentration drops much below 12 percent. Very few life forms on earth are known to be adapted to this extreme salinity. The brine ponds of Owens Lake are so alkaline and hot in mid-August that they can actually burn and dehydrate your fingers. In many places, the brine is saturated with sodium chloride (over 30 percent salinity) and salt is precipitating out. So, when you consider the extreme environment of the brine, it is rather easy to narrow the field of possible organisms responsible for the startling coloration.

If samples of the red brine from Owens lake are spun in a high speed centrifuge at 5,000 rpm, the water becomes clear as the red bacterial cells are forced to the bottom under about 3,000 g's. The bacteria may then be grown in a special nutrient agar containing at least 25 percent sodium chloride and incubated in a warm oven. After several weeks, small reddish colonies of bacteria begin to appear in the culture dishes. There are two main kinds of extreme salt-loving bacteria, the rod-shaped halobacteria and the spherical halococci. They are extremely small unicellular organisms, visible only under high magnification. To get a rough idea of how small these bacterial cells really are, it would take more than half a million to cover the surface of an ordinary pinhead. A single drop of brine from Owens Lake may contain millions of the minute, rod-shaped Halobacterium, squirming about with seemingly perpetual motion. They are able to swim about by means of minute, hairlike flagella at their ends. They are found in salt lakes and brine ponds throughout the world, including the Great Salt Lake and the Dead Sea.

The exact chemical explanation for the extreme salt tolerance of these bacteria, and their need for salinity at least three to four times that of sea water, is very complicated. The cells themselves contain a very high internal salt concentration (primarily potassium and sodium), equal to or higher than their environment, otherwise, they would be rapidly dehydrated (plasmolyzed) in the brine. It has also been shown that the highly saline environment is essential for normal enzyme function within the cells, and to maintain the fragile protein coating or "wall" around the delicate cell membrane. In fact, if the salt concentration drops too low, the outer protein "wall" actually dissolves and the inner cell membrane disintegrates, thus destroying the cell (Larsen, 1967).

Halobacteria can thrive in concentrated brine nine times the salinity of sea water, and can even remain alive in dry salt crystals for years. In fact, their extreme tolerance for ordinary table salt (sodium chloride) makes them a nuisance to companies using solar evaporation ponds for the production of solar salt. Freshly produced solar salt is often contaminated with these organisms, and they occasionally cause spoilage of fish, meats, vegetables and hides when salt has been used in the preservation process. They may also cause an unsightly, pinkish discoloration of pickled foods known as "pinkeye" in salted fish and "red heat" in salted hides.

Halobacteria are placed in the "Archaebacteria," a group of unusual bacteria that survive under some of the most extreme conditions on earth. In fact, some biologists feel that these bacteria should be placed in their own Kingdom Archaebacteria, separate from the Kingdom Monera that contains most of the true bacteria. Heat-loving (thermophilic) Archaebacteria have been found thousands of feet deep at the bottom of the ocean, near steam vents where the water temperature is three times that of boiling water. They can live in this black world of boiling water without oxygen. It has been suggested that if any bacteria could survive on the surface of Mars, it might be a form similar to the Archaebacteria.

The salt crust and brine of Owens Lake is sometimes greenish, due to the abundance of another organism called Dunaliella. This is a unicellular green alga, much larger than the bacteria, though visible only under high magnification (see Figure 1). Each individual oval or pear shaped cell has two whip-like tails or flagella at its anterior (head) end. The moving flagella propel Dunaliella through the water in a spiral motion. Under high magnification, numerous Dunaliella can be seen swimming among the gleaming, geometrically shaped crystals of salts. Dunaliella is clearly a green alga because of a distinct, green, cup-shaped chloroplast that occupies most of the cell. In nearby Searles Dry Lake to the southeast, Dunaliella and a closely related species Stephanoptera may be so abundant that they color the salt crust a bright green. Here they thrive in water with 33 percent dissolved salts, and where the salt forms a solid surface crust strong enough to bear the weight of automobile. In solar evaporation ponds of the large Kerr-McGee Chemical Plant at Trona, Dunaliella sometimes forms a thick, green, "pea soup." A single drop of this thick water may contain several thousand individuals of Dunaliella. Unlike the halobacteria, a high osmotic concentration within the cells of Dunaliella is produced by a very high concentration of glycerol molecules instead of salt ions (Borowitzka and Brown, 1974). Under unfavorable conditions, Dunaliella produces a red carotenoid pigment similar to that found inside the halophilic bacteria. The red pigment may completely mask the green of its chloroplast, and salt lakes practically anywhere in the world may be colored reddish by dense populations of this organism.

For decades, scientists in Russia were puzzled by the pinkish coloration of salt lakes in the hot, lower Volga region, north of the Caspian Sea. The pinkish water was finally attributed to the presence of Dunaliella salina, either dying naturally or excreted in the fecal mass of brine shrimp (Artemia), which feed exclusively on it. Dunaliella in the very saline northern arm of the Great Salt Lake in Utah are brilliant red. There the water is colored red by both the Dunaliella and the red halophilic bacteria. Some authorities recognize a red and a green species of Dunaliella; however, all the Dunaliella I have observed in Searles Lake and Owens Lake were bright green. It appears that the brilliant red coloration of brine in these lakes is caused primarily by halobacteria.

Another smaller, unicellular green alga called Dangeardinella saltitrix also thrives in the brine of Owens Lake. Under high magnification (1000x) this species is rather distinctive with its elongate, pear-shaped cell and two long, whip-like flagella at its anterior end, one extended forward and the other trailing behind (see Figure 1). Like the halobacteria it can survive in solid salt crust. In fact, I once mailed a sample of the salt crust to Dr. Richard Norris, a world authority on flagellates at the University of Witwatersrand, Johannesburg, South Africa. Dr. Norris recognized this very unusual salt-loving alga in my salt sample from Owens Lake and was able to identify it from an earlier scientific reference. Apparently it had rarely been seen by biologists.

The distribution of halobacteria and halophilic algae, such as Dangeardinella and Dunaliella, in highly saline habitats throughout the world is convincing evidence that its dormant cells are dispersed by the wind in the form of dust clouds. Much to the chagrin of Owens Valley residents, alkali dust clouds are a common sight over Owens Lake. This has also occurred at Mono Lake to the north as its main supply streams have been diverted to provide Los Angeles with more water.

In addition to red saline lakes, microorganisms are responsible for the coloration of other bodies of water, tree trunks and even rocks. Enormous populations of algae are responsible for the coloration of the Red Sea and for a periodic condition of coastal waters known as the "red tide." Another alga, closely related to Dunaliella, thrives and multiplies by the millions in snow banks. It is called "snow algae" and it is known in technical circles as Chlamydomonas nivalis. The individual cells are bright red, and from a distance the snow actually appears pink. Compacting the snow increases the density of the red cells and heightens the color.

Algal cells also color the trunks of trees velvety green, and the trunks of Monterey cypress on the Monterey Peninsula in California a brilliant orange. In extreme arid deserts, the boulders are covered with colonies of bacteria that precipitate microscopic layers of red or black desert varnish. The colorful crusted growth on rocks and boulders throughout the tropical and temperate regions of the world is caused by an intimate association of algae and fungi known as lichen. Several different kinds of algae and fungi are responsible for the many colors of lichen, including black, red, orange, green, yellow and chartreuse. For years, people have wondered about the peculiar green coats of polar bears in zoos, particularly during the warmer months. It has been shown that green algal cells actually live and multiply inside the hollow core of each hair, thus producing the "green polar bear syndrome." There are numerous other examples of colorful algae and bacteria in our environment.

Except for coloring salt lakes red, the salt-loving bacteria probably seem insignificant to most people; however, they have been studied extensively in recent years by biologists and biochemists. A pigment has been discovered in the cell membrane of Halobacterium that is remarkably similar to the light sensitive pigment (rhodopsin) in the rod cells of human eyes which enables us to see in dim light. When we enter a dimly lighted room, it takes several minutes for our eyes to adjust as the pigment rhodopsin gradually increases in concentration. In fact, during World War II night-flying aviators sometimes wore special goggles just before the start of a mission. The goggles enabled the pilots to see and carry on normal activities while stimulating rhodopsin production in the eye for maximum night vision. The pigment in salt-loving bacteria (called bacteriorhodopsin) enables them to utilize sunlight for energy, just as green photosynthetic plants are able to capture the sun's energy (Stoeckenius, 1976). Future studies of these amazing solar-powered bacteria may lead to new and more efficient uses of the sun as a source of energy, and perhaps a better understanding of the remarkable mechanisms of vision.

The gleaming red salt flats of Owens Lake can be quite spectacular in the early morning or late afternoon of summer, but not nearly so beautiful as the enormous blue Owens Lake that once filled this deep, sunken valley between the massive Sierra Nevada and Inyo ranges thousands of years ago. Like Mono Lake today, Owens Lake was once a haven for many forms of life, from insects and brine shrimp to water fowl. As the water evaporated and the salinity increased, only the most salt tolerant micro-organisms could survive in the brine. How these minute cells survive and multiply through countless centuries in a world of gleaming salt crystals, and how they travel around the world in dust clouds to colonize desert salt lakes, is truly remarkable.

In recent years, the traditional 5-kingdom or 6-kingdom system of classification has been challenged by authorities. Data from DNA and RNA comparisons indicate that archaebacteria are so different that they should not even be called a type of bacteria. Systematists have devised a classification level higher than a kingdom, called a domain or "superkingdom," to accomodate the archaebacteria. These remarkable organisms are now placed in the domain Archaea. Other prokaryotes, including eubacteria and cyanobacteria, are placed in the domain Bacteria. All of the traditional eukaryotic kingdoms are placed in the domain Eukarya. The 3-domain system of classification is shown in the following table:

Armstrong, W.P. 1981. "The Pink Playas of Owens Valley." Fremontia 9: 3-10. Armstrong, W.P. 1982. "Dangeardinella: In Every Drop of Brine." Environment Southwest Number 499: 18-19. Borowitzka, L.J. and A.D. Brown. 1974. "The Salt Relationships of Marine and Halophilic Species of the Unicellular Green Alga, Dunaliella." Archives of Microbiology 96: 37-52. Larsen, H. 1967. "Biochemical Aspects of Extreme Halophilism." Advances in Microbal Physiology 1: 97-132. Smith, G.M. 1950. The Fresh-Water Algae of the United States. 2nd Edition. McGraw-Hill Book Co., Inc., New York. Smith, G.S. (Editor). 1978. Deepest Valley: A Guide to Owens Valley--Its Roadsides and Mountain Trails. William Kaufmann, Inc., Los Altos, California. Stoeckenius, W. 1976. "The Purple Membrane of Salt-Loving Bacteria." Scientific American 234: 38-46.

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