Las Coloradas, on the northern coast of Mexico’s Yucatán Peninsula, is renowned for its intensely colored pink waters. This striking visual phenomenon transforms a series of shallow pools under the tropical sun. The vibrant hue is often mistaken for a chemical anomaly or industrial byproduct, but it is a natural process driven by biological and environmental factors. Microscopic organisms thrive in the extreme conditions of these pools, producing the characteristic rose shade.
The Unique Environment of Las Coloradas
Las Coloradas is situated on a semi-arid coastline, part of the Ría Lagartos Biosphere Reserve. The high rates of solar evaporation are key to the pools’ existence. The pools are not natural lakes but a vast network of shallow, man-made evaporation ponds, or salt flats, constructed for commercial salt harvesting.
These ponds are engineered to maximize the evaporation of seawater, which is continually funneled into the system. As the water volume decreases, the concentration of dissolved salts dramatically increases. This creates a hypersaline environment, where salt concentration far exceeds that of normal ocean water.
This extreme chemistry acts as a powerful ecological filter, eliminating nearly all aquatic life. Only specialized organisms, known as extremophiles, can survive this harsh, high-salt environment. Salinity levels can reach up to ten times that of the sea, setting the stage for the microbial life that produces the pink pigment.
The Biological Source of the Pink Pigment
The striking pink color is produced by microorganisms that flourish in the hypersaline waters. The primary source is the microalgae Dunaliella salina. While D. salina appears green in normal salinity due to chlorophyll, the high salt concentration triggers a protective response.
Under intense sunlight and extreme salt stress, D. salina overproduces beta-carotene. This reddish-orange carotenoid pigment acts as a shield, protecting the algae from intense light and chemical stress. The density of the algae, combined with the accumulated beta-carotene, turns the water a bright pink or reddish color.
A second significant contributor is halobacteria, a type of Archaea distinct from bacteria. These halophiles thrive in the high-salt brine and possess reddish-pink pigments in their cell membranes, such as bacteriorhodopsin. The combination of Dunaliella algae and halobacteria creates the cumulative effect of the intensely pink water.
Furthermore, tiny crustaceans called brine shrimp (Artemia salina) feed on the pigmented algae. The shrimp ingest and store the beta-carotene, and their resulting red-pink bodies further amplify the color of the water.
How Salt Production Maintains the Color
The industrial operation at Las Coloradas is directly responsible for maintaining the conditions necessary for the pink color to persist. The ponds are managed by a commercial salt harvesting company, which uses a multi-stage process to extract sea salt. This human-controlled process ensures the stable, hypersaline environment required by the extremophiles.
Seawater is systematically channeled through a sequence of evaporation ponds, each designed to hold water at a specific salinity level. The commercial goal is to gradually increase the salt concentration until crystals precipitate. This methodical water management creates consistently high salinity levels in the final ponds, which is the exact stress condition that forces the Dunaliella salina to produce its protective beta-carotene.
The controlled flow and evaporation rates ensure the environment remains stable enough for the pigmented organisms to thrive year after year. Without this continuous maintenance of the shallow, hypersaline conditions by the salt industry, the water would eventually dilute or dry out completely. The sustained pink color is a natural biological phenomenon preserved and amplified by this ongoing industrial process.