Lake McDonnell, a rare natural site in South Australia, sits at the eastern edge of the Great Australian Bight on land that once served as a salt mine above the continent’s largest gypsum deposit. A narrow dirt road, Point Sinclair, cuts through the lake and divides its waters into two strikingly different colors, deep blue on one side and vivid pink on the other, creating an aerial view that resembles a colorful birthday cake slice.
The pink color comes from extremely high salinity combined with salt-loving microorganisms. Scientists once blamed Dunaliella algae, but more recent research says the main cause is the bacterium Salinibacter ruber. These organisms produce red carotenoid pigments that protect them and tint the water a strong magenta or lipstick pink.
Where the water is very salty, the lake turns pink, while nearby channels with lower salinity remain clear blue-turquoise. The effect is not fixed: the colors shift and intensify with the seasons, cloud cover, and time of day. The water appears brightest when levels are lower.
At those times, the shades can range from soft bubblegum pink to deep lilac, making each visit different. The article describes the lake as a unique sensory experience in the wild landscapes of South Australia.
