A pink lake is a lake that has a red or pink colour. This is often caused by the presence of salt-tolerant algae that produces carotenoids, such as Dunaliella salina, usually in conjunction with specific bacteria and archaea, which may vary from lake to lake. The most common archaeon is Halobacterium salinarum.

Dunaliella salina is a type of halophile unicellular green algae especially found in hypersaline environments, such as salt lakes and salt evaporation ponds. Known for its antioxidant activity because of its ability to create a large amount of carotenoids, it is responsible for most of the primary production in hypersaline environments worldwide, and is also used in cosmetics and dietary supplements.