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Salt lake

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Water salinity
Salinity levels
Fresh water (< 0.05%)
Brackish water (0.05–3%)
Saline water (3–5%)
Brine (> 5% up to 26%–28% max)
Bodies of water
One of two salt lakes in the northern end of the Danakil Depression known as Lake Karum

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).[1] 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.[2]

One saline lake classification differentiates between:

  • subsaline: 0.5–3‰ (0.05-0.3%)[2]
  • hyposaline: 3–20‰ (0.3-2%)[2]
  • mesosaline: 20–50‰ (2-5%)[2]
  • hypersaline: greater than 50‰ (5%)[2]
  • Large saline lakes make up 44% of the volume and 23% of the area of lakes worldwide[2]

Classification

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The classification of salt lakes involves various criteria, including salinity levels, hydrological features, and chemical compositions, all of which provide insights into their ecological and economic significance.[3]​ Salt lakes, also known as saline lakes, are bodies of water that have a higher concentration of salts and dissolved minerals than most other lakes, often significantly exceeding the salinity of seawater.[4] These lakes are commonly classified into categories such as subsaline, hyposaline, mesosaline, and hypersaline, depending on the concentration of salt, typically measured in parts per thousand or the percentage of total dissolved solids.[5] Sub Saline lakes contain 0.5 to 3‰ salinity; hyposaline lakes have salinity ranging from 3 to 20‰; meso saline lakes range from 20 to 50‰; and hypersaline lakes exceed 50‰ salinity.[6]

Many salt lakes are found in endorheic basins, which are hydrological systems where the inflow of water does not exit to the ocean or a sea but rather evaporates, leading to increased salinity.[7] These basins are often located in arid and semi-arid regions, where evaporation rates surpass precipitation, causing minerals to accumulate in the lakes and eventually become highly saline.[8] The geomorphology of these regions often includes features such as depressions formed by tectonic activity[9], glaciation[10], or volcanic processes[11], which further classifies them into tectonic, glacial, and volcanic lakes, depending on their origin.[12] The absence of outflow in these terminal basins makes salt lakes sensitive to changes in water balance and human activities, such as water diversion and dam construction, affecting their size and salinity over time.[13]

Lake Hillier shoreline with microorganisms including Dunaliella salina, red algae which cause the salt content in the lake to create a red dye

Salt lakes are also classified based on their chemical composition, which varies widely across different environments. Common types of salt lakes include chloride, sulfate, and carbonate lakes[14], each characterized by the dominant ion present in their waters.[14] This classification is crucial for understanding the potential for resource extraction, such as sodium chloride, potassium, and magnesium salts, which are economically valuable. High salinity levels in these lakes create unique ecological niches, allowing specialized organisms, such as halophiles, to thrive.[15] These microorganisms often give salt lakes a distinctive color due to their pigmentations, such as the reddish hues seen in some hypersaline environments.[16] These lakes support diverse ecosystems, including unique flora and fauna adapted to extreme conditions, and are important for studying ecological responses to high salinity.[16]

Salt lakes are critical to both local economies and biodiversity. Efforts to preserve their unique ecosystems are essential, considering their susceptibility to environmental changes and human-induced impacts.[17] Balancing ecological conservation with economic interests remains a significant challenge, highlighting the importance of ongoing research and sustainable management practices for these unique aquatic environments.[17]

Formation

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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.[18] Then, specific ions interact under controlled temperatures, which leads to solid-solution formation and salt crystal deposition within the lake bed.[18] This cycle of evaporation and deposition is the main process to the unique saline environment that characterizes a salt lake.[18]

Soltan lake in Iran with salt mounds

Environmental factors further shape the composition and formation of salt lakes. Seasonal variations in temperature and evaporation drive mineral saturation and promote salt crystallization.[19] In dry regions, water loss during warmer seasons concentrates the lake’s salts.[19] This creates a dynamic environment where seasonal shifts affect the salt lake’s mineral layers, contributing to its evolving structure and composition.[19] Furthermore, Geolimnology studies also highlight the role of groundwater in salt lake formation.[20] Groundwater rich in dissolved ions often serve as primary mineral sources that, combined with processes like evaporation and deposition, contribute to salt lake development.[20] The mineral diversity in salt lakes reflects both the geochemical input of regional groundwater and the unique climatic conditions of each lake basin, resulting in lakes with distinctive chemical compounds and salt formations.[20]

Biodiversity

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Salt Lake in Larnaca, Cyprus

Salt lakes host a diverse range of animals, yet high salinity is a significant environmental constraint.[21] Increased salinity worsens oxygen levels and thermal conditions, raising the water’s density and viscosity, which demands greater energy for animal movement.[21] Despite these challenges, salt lakes support biota adapted to such conditions with specialized physiological and biochemical mechanisms.[22] Common salt lake invertebrates include various parasites, with around 85 parasite species found in saline waters, including crustaceans and monogeneans.[21] Among them, the filter-feeding brine shrimp plays a crucial role as a keystone species by regulating phytoplankton and bacterioplankton levels.[23] The Artemia species also serves as an intermediate host for helminth parasites that affect migratory water birds like flamingos, grebes, gulls, shorebirds, and ducks.[23] Vertebrates in saline lakes include certain fish and bird species, though they are sensitive to fluctuations in salinity.[22] Many saline lakes are also alkaline, which imposes physiological challenges for fish, especially in managing nitrogenous waste excretion.[24] Fish species vary by lake; for instance, the Salton Sea is home to species such as carp, striped mullet, humpback sucker, and rainbow trout.[24]

Stratification

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Lake stratification in different seasons

Stratification in salt lakes occurs as a result of the unique chemical and environmental processes that cause water to separate into layers based on density.[25] In these lakes, high rates of evaporation often concentrate salts, leading to denser, saltier water sinking to the lake’s bottom, while fresher water remains nearer the surface.[25] These seasonal changes influence the lake’s structure, making stratification more pronounced during warmer months due to increasing evaporation, which drives separation between saline and fresher layers in the lake​, leading a phenomenon known as meromixis (meromictic state), primarily prevents oxygen from penetrating the deeper layers and create the hypoxic (low oxygen) or anoxic (no oxygen) zones.[26] This separation eventually influenced the lake’s chemistry, supporting only specialized microbial life adapted to extreme environments with high salinity and low oxygen levels.[27] The restricted vertical mixing limits nutrient cycling, creating a favorable ecosystem for halophiles (salt-loving organisms) that rely on these saline conditions for stability and balance​.[27]

The extreme conditions within stratified salt lakes have a profound effect on aquatic life, as oxygen levels are severely limited due to the lack of vertical mixing.[27] Extremophiles, including specific bacteria and archaea, inhabit the hypersaline and oxygen-deficient zones at lower depths.[28] Bacteria and archaea, for example, rely on alternative metabolic processes that do not depend on oxygen.[28] These microorganisms play a critical role in nutrient cycling within salt lakes, as they break down organic material and release by-products that support other microbial communities.[28] Due to limited biodiversity, the restrictive environment limits biodiversity, allowing only specially adapted life forms to survive, which creates unique, highly specialized ecosystems that are distinct from freshwater or less saline habitats.[28]

Conservation and Management

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Salt lakes declined worldwide in recent years. The Aral Sea, once of the largest saline lakes with a surface area of 67,499 km in 1960, diminished to approximately 6,990 km in 2016.[29] This trend is not limited to the Aral Sea; salt lakes around the world are shrinking due to excessive water diversion, dam construction, pollution, urbanization, and rising temperatures associated with climate change.[29] The resulting declines cause severe disruptions to local ecosystems and biodiversity, degrades the environment, threatens economic stability, and displaces communities dependent on these lakes for resources and livelihood.[29]

In Utah, if the Great Salt Lake is not conserved, the state could face potential economic and public health crises, with consequences for air quality, local agriculture, and wildlife.[30] According to “Utah’s Great Salt Lake Strike Team”, in order increase the lake's level within the next 30 years, see average inflows must increase by 472,00 acre-feet per year, which is about a 33% increase in the amount that has reached the lake in recent years.[31]

Water conservation is viewed as being the most cost-effective and practical strategy to save salt lakes like the Great Salt Lake.[31] Implementing strong water management policies, improving community awareness, and ensuring the return of water flow to these lakes are additional ways that may restore ecological balance.[31] Other proposed methods of maintaining lake levels include cloud seeding and the mitigation of dust transmission hotspots.[32]

List

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See also: List of saltwater lakes of China
See also: List of bodies of water by salinity

Note: Some of the following are also partly fresh and/or brackish water.

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See also

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References

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  1. ^ "Physical Characteristics of Great Salt Lake". learn.genetics.utah.edu. Retrieved 2024-11-16.
  2. ^ a b c d e f Hammer, U. T. (1986-04-30). Saline Lake Ecosystems of the World. Springer Science & Business Media. ISBN 978-90-6193-535-3.
  3. ^ "The chemical composition of saline lakes of the Northern Great Plains, Western Canada | Geochemical Society". www.geochemsoc.org. Retrieved 2024-11-16.
  4. ^ Florida, USF Water Institute, School of Geosciences, University of South. "Learn More: Salinity - Lake County Water Atlas - Lake.WaterAtlas.org". lake.wateratlas.usf.edu. Retrieved 2024-11-16.{{cite web}}: CS1 maint: multiple names: authors list (link)
  5. ^ Brock, M. A.; Hammer, U. T. (June 1987). "Saline Lake Ecosystems of the World". The Journal of Ecology. 75: 580. doi:10.2307/2260441. JSTOR 2260441. S2CID 129709761.
  6. ^ Saenger, C., Miller, M., Smittenberg, R. H., & Sachs, J. P. (2006). A physico-chemical survey of inland lakes and saline ponds: Christmas Island (Kiritimati) and Washington (Teraina) Islands, Republic of Kiribati. Saline systems, 2, 8. https://doi.org/10.1186/1746-1448-2-8
  7. ^ "Climate change, Land Surface, and Critical Zone Processes in Endorheic Basins | Frontiers Research Topic". www.frontiersin.org. Retrieved 2024-11-16.
  8. ^ "Chloride, Salinity, and Dissolved Solids | U.S. Geological Survey". www.usgs.gov. Retrieved 2024-11-16.
  9. ^ "Ocean Trenches - Woods Hole Oceanographic Institution". https://www.whoi.edu/. Retrieved 2024-11-16. {{cite web}}: External link in |website= (help)
  10. ^ "Glaciers and Glacial Landforms - Geology (U.S. National Park Service)". www.nps.gov. Retrieved 2024-11-16.
  11. ^ "Volcanic Processes - Volcanoes, Craters & Lava Flows (U.S. National Park Service)". www.nps.gov. Retrieved 2024-11-16.
  12. ^ Paguican, Engielle M. R.; Bursik, Marcus I. (2016-07-28). "Tectonic Geomorphology and Volcano-Tectonic Interaction in the Eastern Boundary of the Southern Cascades (Hat Creek Graben Region), California, USA". Frontiers in Earth Science. 4. doi:10.3389/feart.2016.00076. ISSN 2296-6463.
  13. ^ Seltenrich, Nate (June 2023). "A Terminal Case? Shrinking Inland Seas Expose Salty Particulates and More". Environmental Health Perspectives. 131 (6). doi:10.1289/EHP12835. ISSN 0091-6765. PMC 10286954. PMID 37347669.
  14. ^ a b "Water Chemistry". Mono Lake. Retrieved 2024-11-16.
  15. ^ Martínez, G. M., Pire, C., & Martínez-Espinosa, R. M. (2022). Hypersaline environments as natural sources of microbes with potential applications in biotechnology: The case of solar evaporation systems to produce salt in Alicante County (Spain). Current research in microbial sciences, 3, 100136. https://doi.org/10.1016/j.crmicr.2022.100136
  16. ^ a b "Extreme Microbes". American Scientist. 2017-02-06. Retrieved 2024-11-16.
  17. ^ a b US EPA, OA. "Climate Impacts on Ecosystems". 19january2017snapshot.epa.gov. Retrieved 2024-11-16.
  18. ^ a b c Yu, Zhangfa; Zeng, Ying; Li, Xuequn; Sun, Hongbo; Li, Longgang; He, Wanghai; Chen, Peijun; Yu, Xudong (Nov 2024). "Solid–Liquid Phase Equilibria of the Aqueous Quaternary System Rb+, Cs+, Mg2+//SO42− - H2O at T = 323.2 K". Separations. 11 (11): 309. doi:10.3390/separations11110309. ISSN 2297-8739.
  19. ^ a b c Huang, Shouyan; Ma, Yanfang; Liu, Xin; Ma, Xiuzhen; Fu, Zhenhai (2024-11-02). "Distribution and Evaporation Characteristics of Rb and Cs in Complex Salt Brine Systems". Applied Geochemistry: 106216. doi:10.1016/j.apgeochem.2024.106216. ISSN 0883-2927.
  20. ^ a b c Last, William M. (2002-12-01). "Geolimnology of salt lakes". Geosciences Journal. 6 (4): 347–369. doi:10.1007/BF03020619. ISSN 1598-7477.
  21. ^ a b c Kornyychuk, Yuliya; Anufriieva, Elena; Shadrin, Nickolai (Mar 2023). "Diversity of Parasitic Animals in Hypersaline Waters: A Review". Diversity. 15 (3): 409. doi:10.3390/d15030409. ISSN 1424-2818.
  22. ^ a b Finlayson, C. M. (2016), Finlayson, C. Max; Milton, G. Randy; Prentice, R. Crawford; Davidson, Nick C. (eds.), "Salt Lakes", The Wetland Book: II: Distribution, Description and Conservation, Dordrecht: Springer Netherlands, pp. 1–12, doi:10.1007/978-94-007-6173-5_255-1, ISBN 978-94-007-6173-5, retrieved 2024-11-16
  23. ^ a b Shadrin, Nickolai; Anufriieva, Elena; Gajardo, Gonzalo (Jan 2023). "Ecosystems of Inland Saline Waters in the World of Change". Water. 15 (1): 52. doi:10.3390/w15010052. ISSN 2073-4441.
  24. ^ a b Brauner, Colin J.; Gonzalez, Richard J.; Wilson, Jonathan M. (2012-01-01), McCormick, Stephen D.; Farrell, Anthony P.; Brauner, Colin J. (eds.), "9 - Extreme Environments: Hypersaline, Alkaline, and Ion-Poor Waters", Fish Physiology, Euryhaline Fishes, vol. 32, Academic Press, pp. 435–476, doi:10.1016/B978-0-12-396951-4.00009-8, ISBN 978-0-12-396951-4, retrieved 2024-11-16
  25. ^ a b Boehrer, Bertram; Schultze, Martin (Jun 2008). "Stratification of lakes". Reviews of Geophysics. 46 (2). doi:10.1029/2006RG000210. ISSN 8755-1209.
  26. ^ Radosavljevic, Jovana; Slowinski, Stephanie; Rezanezhad, Fereidoun; Shafii, Mahyar; Gharabaghi, Bahram; Van Cappellen, Philippe (2024-02-01). "Road salt-induced salinization impacts water geochemistry and mixing regime of a Canadian urban lake". Applied Geochemistry. 162: 105928. doi:10.1016/j.apgeochem.2024.105928. ISSN 0883-2927.
  27. ^ a b c Ladwig, Robert; Rock, Linnea A.; Dugan, Hilary A. (2023-02-01). "Impact of salinization on lake stratification and spring mixing". Limnology and Oceanography Letters. 8 (1): 93–102. Bibcode:2023LimOL...8...93L. doi:10.1002/lol2.10215.
  28. ^ a b c d Andrei, Adrian-Ştefan; Robeson, Michael S.; Baricz, Andreea; Coman, Cristian; Muntean, Vasile; Ionescu, Artur; Etiope, Giuseppe; Alexe, Mircea; Sicora, Cosmin Ionel; Podar, Mircea; Banciu, Horia Leonard (Dec 2015). "Contrasting taxonomic stratification of microbial communities in two hypersaline meromictic lakes". The ISME Journal. 9 (12): 2642–2656. doi:10.1038/ismej.2015.60. ISSN 1751-7370. PMC 4817630. PMID 25932617.
  29. ^ a b c Sultonov, Zafarjon; Pant, Hari K. (2024-01-30), Shared Environmental Challenges: A Comparative Analysis of Saline Lakes and Inland Seas' Decline., doi:10.21203/rs.3.rs-3900900/v1, retrieved 2024-11-16
  30. ^ "Emergency measures needed to rescue Great Salt Lake from ongoing collapse". Plant & Wildlife Sciences. Retrieved 2024-11-16.
  31. ^ a b c "A roadmap for rescuing the Great Salt Lake - @theU". attheu.utah.edu. Retrieved 2024-11-16.
  32. ^ "Research universities and state agencies team up to offer solutions for Great Salt Lake". Utah Department of Natural Resources.
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