The Color-Changing Lake

Lake Urmia in Iran is suffering the fate of many lakes, and is shrinking. One factor is drought, and the other is all the water that is diverted for agriculture. As the lake shrinks, it becomes saltier, and that is causing it to actually change color during the year. NASA’s Aqua satellite captured the image on the left on April 23, and the image on the right on July 18. Rains and snowmelt bring fresh water to the lake in spring, but by July, that starts to change.

The fresh water in the spring drives salinity levels down, but the lake generally becomes saltier as summer heat and dryness take hold. That’s when the microorganisms show their colors, too. Careful sampling of the water would be required to determine which organisms transformed the lake in 2016, but scientists say there are likely two main groups of organisms involved: a family of algae called Dunaliella and an archaic family of bacteria known as Halobacteriaceae.
“Previous research suggests that Dunaliella salina is responsible for reddening of Lake Urmia,” explained Mohammad Tourian, a scientist at the University of Stuttgart. “In the marine environment, Dunaliella salina appears green; however, in conditions of high salinity and light intensity, the microalgae turns red due to the production of protective carotenoids in the cells.”

Read more about how Lake Uremia changes at NASA’s Earth Observatory.