Ephemeral acid saline lake

An ephemeral acid saline lake is a lake that is relatively high in dissolved salts and has a low pH, usually within the range of <1 - 5 and does not have standing water year round. These types of lakes are identified by high concentrations of evaporite minerals, notably halite, gypsum, and various iron oxides allowing the lakes to become hypersaline. Low pH and evaporite minerals are positively correlated, allowing lakes with lower pH's to have visible evaporite mineral "crusts". Due to the highly unusual geochemistries present in these lake systems, they are considered extreme environments in nature.

Due to the low acidity and high salinity, as well as the periodic total evaporation of the lakes, the waters are generally uninhabitable to life larger than microbes. The microscopic organisms that do live there possess a startling array of biodiversity, spanning from halophilic bacteria and archaea to acidophilic fungi.^[1] Because of the unusual ability for life to survive in such a harsh environment, acid saline lakes have recently been studied for their relevance to the field of astrobiology.

Acid saline lake systems are considered a rarity within the natural world, and the highest concentration of acid saline lakes occur in Western Australia. They form most favorably under semi-arid to arid conditions and have been closely connected to stable interior cratons and closed paleodrainage basins, allowing groundwaters to evaporate to the extreme salinity and acidity values present today. Unlike most natural acid saline systems, these lakes are unusual in that they are neither volcanically or hydrothermally fed and are not in direct contact with large sulfide deposits yet have brines with pH that can reach <1.^[2]