The Great Salt Lake, a vast body of water in Utah, is the largest natural lake west of the Mississippi River. It is a terminal lake, meaning water flows into it but has no outlet to the ocean. This characteristic, combined with high evaporation, leads to exceptionally high salinity, creating a unique and challenging ecosystem.
The Lake’s Extreme Conditions
The main factor shaping life in the Great Salt Lake is its extreme salinity, which largely prevents the presence of typical fish species. The lake’s closed basin and high evaporation rates cause dissolved minerals, including salts, to accumulate. This makes the lake significantly saltier than the ocean, with salinity levels fluctuating between approximately 5% and 27%, two to nine times saltier than the average ocean salinity of 3.5%.
This concentrated salt environment creates physiological challenges for most aquatic organisms. The high salt content draws water out of living cells through osmosis, making it difficult for organisms to maintain internal water balance. For common freshwater or marine fish, this osmotic stress is lethal, as their bodies are not equipped to handle such intense external salinity. The lake’s northern arm, Gunnison Bay, often becomes significantly saltier, sometimes reaching saturation due to limited freshwater inflows and a dividing causeway, creating an even more extreme environment.
Organisms That Thrive in the Lake
Despite the lake’s harsh conditions, a few unique organisms have evolved adaptations to survive and thrive. The most prominent are brine shrimp (Artemia franciscana) and brine flies (Ephydra hians and Ephydra cinerea). These invertebrates form the foundation of the Great Salt Lake’s unique food web.
Brine shrimp are small crustaceans that tolerate salinities from 3% to 33%. They have specialized gills to excrete excess salt while feeding on algae and detritus. Their life cycle includes producing dormant cysts, or eggs, which are highly resilient and can remain viable for many years, hatching when conditions are favorable. Billions of brine shrimp populate the lake, serving as an important food source.
Brine flies, particularly their larval and pupal stages, also exhibit high salt tolerance. Female flies lay eggs in the lake, which hatch into larvae that feed on algae and other organic matter on the lake bottom. These larvae then metamorphose into pupae before emerging as adult flies. Adult brine flies do not bite and live only a few days, focused solely on reproduction, with populations reaching billions.
Fish in Tributaries and Nearby Waters
While the main body of the Great Salt Lake is largely devoid of fish due to its high salinity, the less saline waters feeding into it support various fish species. These include major tributaries like the Bear, Weber, and Jordan Rivers, along with numerous smaller streams, freshwater ponds, and marshes. These connected waterways provide vital habitat where fish can thrive away from the lake’s highly saline conditions.
Common fish in these peripheral and inflowing waters include cutthroat trout, such as the native Bonneville cutthroat trout, which historically inhabit the Great Salt Lake’s tributaries. Other species like common carp and rainbow trout are also present. The least chub, a rare species, can survive in areas close to the lake due to its broad tolerance. Occasionally, during significant freshwater runoff, some fish, like carp, might temporarily enter the less saline bays, such as Bear River Bay and Farmington Bay, but they cannot establish permanent populations in the main lake.
The Lake’s Broader Ecological Role
Beyond the specific organisms within its waters, the Great Salt Lake plays a significant ecological role, especially as a significant hub for migratory birds. It serves as an important stopover and nesting ground for millions of birds traveling along the Pacific Flyway, a major migratory route in North America. Approximately 10 to 12 million migratory birds, representing over 330 species, visit the lake annually to rest, refuel, and breed.
The abundant brine shrimp and brine flies are an important food source for these bird populations, providing the energy needed for their long migrations. Species such as Eared Grebes, Wilson’s Phalaropes, American Avocets, and Black-necked Stilts rely on these invertebrates. For instance, Eared Grebes can consume up to 30,000 brine shrimp daily, and Wilson’s Phalaropes can double their weight before continuing their journey. The lake’s extensive wetlands, covering about 360,000 acres, also provide important habitat, making it the largest wetland area in the American West and supporting 80% of Utah’s wetlands.