The Science of a Pink Lake
Tuz Gölü, which translates to "Salt Lake," is an immense, shallow body of water in Turkey. For much of the year, its vast, crystalline salt flats reflect the sky. But during the hot, dry summer months, the lake undergoes a dramatic transformation, blushing a bright pink or red. This spectacle is not geological but biological, driven by a bloom of microscopic life perfectly adapted to one of the planet's saltiest environments.
The lake's water reaches a salinity of up to 32.4%, a concentration that is lethal to most forms of life. In this extreme habitat, a specific type of unicellular green algae, Dunaliella salina, flourishes. To shield itself from the intense solar radiation amplified by the salt crystals, this micro-alga overproduces a protective red-orange pigment called beta-carotene. The bloom of trillions of these individual algae, along with certain species of halophilic archaea and bacteria like Salinibacter, collectively changes the entire lake's hue. As summer progresses, water evaporates, concentrating the salt and the microorganisms, which makes the color even more intense.
An Ecosystem on the Edge
Tuz Gölü is a terminal lake, meaning it has no outlet. It is fed by streams and groundwater but loses water only through evaporation. This process created its hypersaline conditions. The lake is extremely shallow, often less than half a meter deep, and in summer, large areas dry up completely, leaving a salt crust up to 30 centimeters thick. This ephemeral nature defines its entire ecosystem.
Despite the harsh conditions, a simple but important food web exists. The Dunaliella salina algae and other microbes are the primary producers. They are consumed by brine shrimp, which in turn become a critical food source for one of the largest breeding colonies of greater flamingos (Phoenicopterus roseus) in the Mediterranean. The flamingos' famous pink color is derived directly from the carotenoid pigments in the algae and shrimp they consume. The health and presence of the flamingos show the lake's condition. Scientists also study the extremophiles of Tuz Gölü for astrobiological purposes, as their survival strategies show how life might exist in salty environments on other planets.