Pink lake

Notable lakes with this coloration include:

• Masazirgol near Baku, Azerbaijan.
• Maharloo Lake near Shiraz, Iran.
• Dusty Rose Lake in British Columbia, Canada.
• Pink Lake (Western Australia) near Esperance, Western Australia
• Lake Retba or Lac Rose, in Senegal
• Pink Lake (Victoria) in western-Victoria, Australia
• Hutt Lagoon in midwest Western Australia
• Lake Hillier in the Recherche Archipelago, Western Australia
• Lonar Lake in Maharashtra, India
• Las salinas de Torrevieja in Alicante, Spain

The orange/pink colour of salt lakes across the world is caused by the green alga Dunaliella salina and the archaea Halobacterium cutirubrum.

Dunaliella salina is the most salt tolerant alga known and can grow in salinity as high as 35% NaCl (in comparison to seawater, which contains approximately 3% NaCl).

At high salinity, temperature and light, this alga accumulates the red carotenoid pigment, beta-carotene. This is the same pigment that gives carrots, which contain 0.3% of beta-carotene, their colour. Concentrations as high as 14% of the dry weight can occur in Dunaliella salina, which is the highest in any organism. The beta-carotene protects the alga against damage from high light, coating the green chlorophyll and giving the alga an orange/red colour.

Dunaliella salina is found in salt lakes around the world including Antarctica, Chile, US, China, Tibet, France, South Africa, and in Western Australia off the coast of Cape Arid, and Lake Hillier. The alga was named after Michel Félix Dunal who first recognised the red colour of certain salt lakes in France was due to an organism.

The archaea Halobacterium cutirubrum is pink in colour and generally grows within the salt crust on the bottom of the lake. The exact colour of the lake depends on the balance between Dunaliella salina and Halobacterium cutirubrum, with salt concentration having a direct impact.