A salt lake or saline lake is a landlocked body of water that has a concentration of salts (typically sodium chloride) and other dissolved minerals significantly higher than most lakes (often defined as at least three grams of salt per liter). In some cases, salt lakes have a higher concentration of salt than sea water; such lakes can also be termed hypersaline lake, and may also be pink lakes on account of their color. An alkalic salt lake that has a high content of carbonate is sometimes termed a soda lake. Salt lakes are classified according to salinity levels. The formation of these lakes is influenced by processes such as evaporation and deposition. Salt lakes face serious conservation challenges due to climate change, pollution and water diversion.
Classification The primary method of classification for salt lakes involves assessing the chemical composition of the water within the lakes, specifically its salinity, pH, and the dominant ions present.
Subsaline Subsaline lakes have a salinity lower than that of seawater but higher than freshwater, typically ranging from 0.5 to 3 grams per liter (g/L).
Hyposaline Hyposaline lakes exhibit salinities from 3 to 20 g/L, which allows for the presence of freshwater species along with some salt-tolerant aquatic organisms. Lake Alchichica in Mexico is a hyposaline lake.
Mesosaline Mesosaline lakes have a salinity level ranging from 20 to 50 g/L. An example of a mesosaline lake is Redberry Lake in Saskatchewan, Canada.
Hypersaline Hypersaline lakes possess salinities greater than 35 g/L, or 50 g/L, often exceeding 200 g/L. The extreme salinity levels create harsh conditions that limit the diversity of life, primarily supporting specialized organisms such as halophilic bacteria and certain species of brine shrimp. These lakes can have high concentrations of sodium salts and minerals, such as lithium, making such lakes vulnerable to mining interests. Hypersaline lakes can be found in the McMurdo Dry Valleys in Antarctica, where salinity can reach ≈440‰.
Formation Salt lakes form through complex chemical, geological, and biological processes, influenced by environmental conditions like high evaporation rates and restricted water outflow. As water carrying dissolved minerals (sodium, potassium, and magnesium) enters these basins, it gradually evaporates, concentrating these minerals until they precipitate as salt deposits. Then, specific ions interact under controlled temperatures, which leads to solid-solution formation and salt crystal deposition within the lake bed. This cycle of evaporation and deposition is the main process to the unique saline environment that characterizes a salt lake.Environmental factors further shape the composition and formation of salt lakes. Seasonal variations in temperature and evaporation drive mineral saturation and promote salt crystallization. In dry regions, water loss during warmer seasons concentrates the lake's salts. This creates a dynamic environment where seasonal shifts affect the salt lake's mineral layers, contributing to its evolving structure and composition. Groundwater rich in dissolved ions often serve as primary mineral sources that, combined with processes like evaporation and deposition, contribute to salt lake development.
Biodiversity
Salt lakes host a diverse range of animals, despite high levels of salinity acting as significant environmental constraints. Increased salinity worsens oxygen levels and thermal conditions, raising the water's density and viscosity, which demands greater energy for animal movement. Despite these challenges, salt lakes support biota adapted to such conditions with specialized physiological and biochemical mechanisms. Common salt lake invertebrates include various parasites, with around 85 parasite species found in saline waters, including crustaceans and monogeneans. Among them, the filter-feeding brine shrimp plays a crucial role as a keystone species by regulating phytoplankton and bacterioplankton levels. The Artemia species also serves as an intermediate host for helminth parasites that affect migratory water birds such as flamingos, grebes, gulls, shorebirds, and ducks. Vertebrates in saline lakes include certain fish and bird species, though they are sensitive to fluctuations in salinity. Many saline lakes are also alkaline, which imposes physiological challenges for fish, especially in managing nitrogenous waste excretion. Fish species vary by lake; for instance, the Salton Sea is home to species such as carp, striped mullet, humpback sucker, and rainbow trout.
Stratification
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