Lake Urmia was once one of the biggest saltwater lakes in the world

The organisms that are thriving are the reason the water turns red. The algae that grows in the lake, Dunaliella salina, would normally appear green, but with less water in the lake and more exposure to sunlight, the algae produces carotenoids in its cells to absorb the excess light, which makes it appear red. It is also thought that a salt-loving bacteria called Halobacteriaceae, which has a red pigment to absorb sunlight for energy, is involved.