Why Do Some Lakes Turn Pink?

Pink lakes occur in hypersaline environments around the world, from Lake Hillier in Western Australia to Laguna Colorada in Bolivia and Retba (Lac Rose) near Dakar, Senegal. The vivid colour comes from extremophile organisms thriving in salt concentrations that would kill most life. Dunaliella salina, a single-celled green alga, produces massive quantities of beta-carotene (the same orange-red pigment in carrots) to protect itself from intense solar radiation and osmotic stress. Haloarchaea (salt-loving archaea) produce bacterioruberin, a red pigment that shields their cell membranes. In extremely salty conditions (often 10-35% salinity, vs 3.5% for seawater), these organisms dominate, turning the entire lake vivid pink or red. The colour intensity varies with season, sunlight, and salinity — stronger in warmer, sunnier, saltier conditions. Some pink lakes, like Lake Hillier, remain pink year-round, while others are seasonal.