highsalinity

High salinity refers to water or mineral solutions with dissolved salt concentrations well above those of typical seawater. Salinity is commonly measured in practical salinity units (PSU) or parts per thousand (ppt). Seawater average salinity is about 35 PSU (35 g of dissolved salts per kilogram of seawater). Environments with salinity significantly above that level are often described as hypersaline, and may exceed 40 PSU or contain salt concentrations approaching several tens of percent by weight in extreme cases.

Causes of high salinity include evaporation in closed basins with limited freshwater inflow, which concentrates dissolved minerals over time. In coastal settings, evaporation in evaporitic basins can concentrate salts such as sodium chloride and calcium sulfate, forming evaporite deposits. In natural lakes, high salinity supports specialized ecosystems and unique geochemical conditions.

Biology in high-salinity environments is shaped by osmotic stress and high ionic strength. Most organisms are inhibited or excluded, while halophiles—certain archaea, bacteria, and algae—possess cellular adaptations that enable them to retain water and regulate ions.

Ecological and environmental effects include reduced biodiversity and altered chemical cycles. High salinity can degrade freshwater habitats when inland salinization occurs due to irrigation, drainage, or mining activities, and can influence nutrient availability and sediment chemistry.

Industrial relevance involves the production and handling of hypersaline brines. Such waters are used in salt production via solar evaporation ponds, but also pose corrosion, scaling, and material handling challenges. Desalination and salt/ mineral extraction are common processes in high-salinity contexts.

Examples of hypersaline systems include the Great Salt Lake, the Dead Sea, salt flats, and many solar-evaporite ponds found in arid regions worldwide. See also salinity, hypersaline lake, evaporite, halophile, and salt tolerance.