The Great Salt Lake in Utah is known for sections of its water taking on a vivid, almost bubblegum pink color. This coloration is not a geological accident but a direct result of biological activity occurring in extremely salty conditions. The pink color is a visible manifestation of certain microorganisms that thrive in high-salinity environments, producing specialized pigments. This unique coloration primarily affects the northern portion of the lake, contrasting sharply with the typically blue-green southern waters.
The Role of Hypersalinity
The pink coloration is enabled by the extreme concentration of salt, or hypersalinity, largely confined to the lake’s North Arm. The lake was divided in the late 1950s by the construction of a railroad causeway that spans its width. This causeway severely restricts the flow of water between the northern and southern sections of the lake.
Most freshwater inflow enters the South Arm, creating a significant salinity difference between the two halves. The South Arm typically maintains a salinity between 7% and 15%. In contrast, the restricted North Arm often reaches saturation, climbing to 26% to 30% salt concentration. This hypersaline environment is roughly ten times saltier than the ocean and is far beyond the tolerance level of nearly all aquatic life. This chemical barrier creates the specialized habitat necessary for the organisms that produce the distinctive pink hue.
The Microorganisms That Produce the Color
The pink and red colors are produced by two primary groups of microorganisms uniquely adapted to this saline environment. One group is the halophilic archaea, such as Halobacterium, which are ancient, single-celled organisms that flourish in high salt. These archaea produce a reddish-pink protein called bacteriorhodopsin, which captures light energy.
The other major contributor is the single-celled algae, Dunaliella salina. This algae tolerates high salt levels by accumulating massive amounts of beta-carotene, the orange-red pigment also found in carrots. This pigment protects the algae’s photosynthetic machinery from intense sunlight and high salt concentration. As these archaea and algae reproduce, their collective pink and red pigments visibly transform the water’s color.
Life Adapted to Pink Water
The hypersaline North Arm supports a simplified food web centered on the salt-loving microorganisms. While the extreme conditions are too harsh for fish, a few specialized invertebrates thrive. The most prominent of these are the brine shrimp (Artemia franciscana), a tiny crustacean that feeds on the pigmented algae and bacteria.
Brine shrimp can tolerate a wide salinity range, up to near saturation, by using specialized gills to excrete excess salt. They are a primary consumer in the lake’s ecosystem and a foundational food source for the millions of migratory birds that visit the Great Salt Lake annually. The brine fly also thrives in the saline water. The abundant populations of these two invertebrates are directly supported by the microbial bloom that gives the lake its coloration.