A salt lake in Yuncheng, often called China’s “Dead Sea,” has tourists flocking to it for an unusual reason. Its waters are appearing in intense shades of magenta, green, and yellow due to algal blooms and rapidly breeding insects.
The rare phenomenon is caused by the algae species Dunaliella salina, which NASA has reported appears green in marine environments but can turn red if exposed to conditions of high salinity and light intensity due to “the production of protective carotenoids in the cells.” Carotenoids are the plant pigments responsible for the lake’s brightly colored hues.
A study done on the unique algae species by faculty at the University of Concepción, Chile says that D. salina is presently the most salt-tolerant eukaryote (any organism that possesses a clearly defined nucleus) known. It can be found in saline lakes around the world, in places such as Chile, Australia, Mexico, and Israel.
Some strains of the algae can accumulate more than 10 percent of their dry weight in β-carotene if triggered by environmental stresses like intense irradiance, high salinity, nutrient starvation, or extreme temperatures—which creates the “richest natural source of this pigment known so far.”
D. salina’s rich color makes it a popular food coloring agent and additive in cosmetics. It is also used in multivitamins.
Yuncheng’s Xiechi Lake was formed around 500 million years ago during the early Cenozoic Era, and it has been harvested for salt by the local community for 4,000 years. It is the world’s third largest sodium sulfate inland lake, covering an area of 120 square kilometers.
Similar to Israel’s famed Dead Sea, Yuncheng’s salt lake is rich in minerals that said to be beneficial for the skin. But while the black mud in the Dead Sea is chloride-based, Yuncheng’s is sulfate-based and can support a rich diversity of flora and fauna.
Unfortunately, algal blooms, which are sometimes caused by an excess of nutrients in the water, can result in what is known as a dead zone or hypoxic zone. (Read about a record-setting dead zone in the Gulf of Mexico.) As more algae continue to grow, sometimes reaching counts of millions of cells per milliliter, other forms of life are choked out. Those other life forms begin to die and are then decomposed by bacteria in the water.
All of that decay depletes the oxygen available in the water. Many fish and aquatic insects cannot survive in such conditions.