Great Salt Lake Ecology

Category: Inland Aquatic Biomes.

Geographic Location: North America.

Summary: This hypersaline lake in northwestern Utah is bordered by marshlands that provide habitat for shorebirds and a resting point for migratory birds.

The Great Salt Lake is a remnant of the vast, ancient Lake Bonneville, which, at the end of the Pleistocene, covered parts of Nevada and Idaho as well as most of northern Utah west of the Wasatch Range. Lake Bonneville stretched across more than 19,000 square miles (49,000 square kilometers) of surface area. Its dimensions are estimated to have been approximately 325 miles (523 kilometers) long by 135 miles (217 kilometers) wide and as much as 1,000 feet deep.

Comparatively, in its present state, the variable-sized Great Salt Lake covers between roughly 2,000 to 3,000 square miles (5,180 to 7,770 square kilometers); it averages about 70 miles (112 kilometers) in length and 30 miles (48 kilometers) in width. The lake is located on the eastern edge of the Great Basin, bordered by the Wasatch Mountains to the east and the Oquirrh and Stansbury ranges to the west and south. It is the largest saltwater lake in the Western Hemisphere; however, its size and salinity levels fluctuate considerably as they are dependent on yearly runoff, evaporation, and diversion of tributary waters for irrigation and other human uses.

Because the Great Salt Lake is located on a flat plain, its shape is that of a wide, flat basin, and even a slight rise in water level expands the surface area considerably. The first series of scientific measurements were taken in 1849, and since then the lake water level has varied by 20 feet (6 meters), shifting the shoreline in some places by as much as 15 miles (24 kilometers). Salinity levels vary greatly also, typically between three to five times greater than seawater, but can reach up to 28 percent, which is roughly eight times saltier than seawater. The lake is situated at approximately 4,000 feet (1,300 meters) above sea level; winters are cold. Because the Great Salt Lake is located in an arid region, precipitation is typically low. However, this area receives a boost from lake-effect rain and snow.

Three major river systems enter the lake: Bear River from the northeast; Weber River from near Ogden, Utah; and the Jordan River from the south. The Jordan drains Utah Lake, a freshwater lake fed by melted snow and rainwater from the Uintah and Wasatch ranges. There is no outlet for the Great Salt Lake other than evaporation.

Geological History

As a consequence of climatic cooling and warming cycles at the end of the last major glacial advance, water from melting ice and rain began accumulating in the east side of the Great Basin. Approximately 28,000 years ago, Lake Bonneville began to rise rapidly, reaching its maximum surface area and greatest depth—of more than 1,000 feet (300 meters)—about the current size of Lake Michigan, but much deeper. A body of water of that size greatly controlled the local climate and likely resulted in a highly biologically diverse community.

Lake Bonneville eventually shrank, mainly because of a warming, drying climate. However, there is geologic evidence of an enormous flood that took place about 15,000 years ago, as the lake's waters overspilled into what is now Red Rock Canyon, Idaho. This is known as the Bonneville Flood. As the climate continued warming, Bonneville Lake continued to evaporate. The Great Salt Lake and the Bonneville Salt Flats in the desert are relics of Lake Bonneville, their salts derived from millenniums of mineral accumulations and high evaporation rates in these closed basins.

Human Impact

As a result of thousands of years of evaporation, additional minerals being transported by its feeder rivers, and the fact that Great Salt Lake is a terminal lake (no outlets), the salinity and mineral content of the water have continued to rise. There are several major companies located in the region around the lake that own extraction industries for the minerals and salts found here. This activity extracts about 2.5 million tons (2.3 million metric tons) of salts and ores from the lake annually. These minerals include significant amounts of sodium chloride (used primarily as common table salt), potash of sodium (low-chlorine fertilizer), magnesium chloride (used in the production of magnesium metal, premium deicing products, and for dust and erosion control), and potassium chloride (used as an ingredient in deicing and water-conditioning products).

Production of another high-profit compound, lithium chloride, is currently underway. This compound is used in the production of lithium metal for use as the anode in lithium batteries, as a brazing flux for aluminum in automobile parts, and as a desiccant for drying air streams. These products are created by pumping water from the lake through a series of near-shore drying ponds; the salts precipitate as the water evaporates.

Humans have also had an impact on the Great Salt Lake in other ways. A section of the first transcontinental railroad was eventually redirected across the lake, and in 1959 the original wood trestle structure was replaced with a stone causeway. This acted as a barrier to water circulation, creating the sections of the lake known as the north and south arms. The smaller north arm is extremely salty, generally standing around 26–28 percent saline, while the south arm averages 13 percent but is highly variable based on floods or droughts. The lack of circulation is also responsible for the characteristic reddish color of the water in the north arm, which is caused by the halophile bacteria that thrive in the high saline water.

The Great Salt Lake is also a major tourist attraction for Utah, with most activity directed out of Salt Lake City and other nearby communities such as Ogden. Bathing in the mineral-rich waters, which provide greater buoyancy than regular seawater, has at times been considered to have curative properties, and resorts have been established along the shore. However, the variable water level and the common occurrence of foul smells due to natural hydrogen sulfide and bacteria (as well as sewage treatment facilities) have limited some forms of recreation on the lake. The lake's effect on local weather patterns also makes swimming and boating occasionally challenging. However, boating and swimming both remain popular, while hunting and birdwatching also draw many visitors.

Climate change is having a devastating effect on the Great Salt Lake. As of 2022, two-thirds of the lake has dried up because of increased temperatures and evaporation caused by global warming. Ecologists have said the reduced size of the lake is already affecting Utah's fauna and flora. Experts also fear that the lake will continue to shrink in the future, possibly until it no longer exists. If the lake should completely dry up, its flies and brine shrimp would die off, which would threaten the 10 million migratory birds that stop at the lake each year to eat the tiny creatures. Of even greater concern is the outlook for the surrounding area without the Great Salt Lake. The lake bed contains high levels of arsenic. If exposed, it could get into the air, poisoning Utah's residents.

Wildlife

The Great Salt Lake is biotically depleted because of its high salinity. The ecosystem of the lake is highly simplified, consisting of several species of salt-tolerant bacteria, protozoa, algae, brine flies, and brine shrimp. Yet another economic draw, the brine shrimp and their eggs are used as food for pet fish. While no vertebrates inhabit this lake per se, at three locations where freshwater enters the lake a series of dikes and borrow pits have been constructed to keep the two water types from mixing.

The Bear River Migratory Bird Refuge, part of the National Wildlife Refuge System, was created by capturing the water from the Bear River on the northeast edge of the lake. The Ogden Bay Waterfowl Management Area is another tract created by diverting freshwater from the Weber River. Additionally, the Farmington Bay Wildlife Management Area was created by diverting water from the Jordan River.

The latter two refuges are administered by the Utah Division of Wildlife Resources. These refuges support more than 200 species of birds and numerous other animal species.

There are between eight and 11 islands (depending on water levels) in the Great Salt Lake. Some of these provide habitat for various mammal species. Antelope Island is the largest; animals that can be found here include: bison, mule deer, pronghorn antelope, coyotes, bobcats, badgers, porcupines, jackrabbits, and several species of rodents. The refuges and marshes around the lake support between 2 and 5 million shorebirds, augmented by hundreds of thousands of waterfowl during spring and fall migration.

The Great Salt Lake region, which accounts for about 75 percent of Utah's wetlands, provides a resting and staging area for these birds, as well as an abundance of brine shrimp and brine flies that serve as their food. Some birds that may readily be found here include: Wilson's phalarope and red-necked phalarope, snowy plover and western sandpiper, American white pelican, white-faced ibis, and eared grebe. Raptors include the bald eagle and peregrine falcon. Large populations of ducks and geese also frequent the biome.

Because the lake's marshes provide a stopover point for millions of birds, there is increasing concern about how climate change in the region will affect these habitats. Winters have already been warmer. There is the possibility that an increase in precipitation would cause the salty lake water to flood into marshlands, killing off freshwater species and disrupting the entire ecosystem. An event of this type occurred in the 1980s. Drought, on the other hand, raises the threat of even higher salinity levels that would kill off even native brine shrimp and drastically alter the local food web. Other concerns include pollution, especially levels of mercury that are the highest in the United States. Research into these elevated mercury levels has led scientists to caution against the consumption of three species of duck in the Great Salt Lake ecosystem.

Bibliography

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