What Is a Hypersaline Lake and What Lives There?

A hypersaline lake is a landlocked body of water with a salt concentration that surpasses ocean water. These environments are defined by salinity levels above the 3.5% found in the sea, creating unique and often extreme conditions. While seemingly inhospitable, these lakes are found across the globe and host specialized ecosystems.

Formation of Hypersaline Environments

Hypersaline lakes form in arid or semi-arid regions where the rate of water evaporation is greater than the rate of water inflow. Many are located in endorheic basins, which are closed depressions that trap water and prevent it from flowing to an ocean. As water evaporates over long periods, dissolved salts and minerals are left behind, gradually increasing the lake’s overall salinity.

The salts themselves originate from the weathering of rocks in the surrounding landscape, carried into the basin by rivers and streams. Some hypersaline lakes are remnants of ancient, much larger bodies of water from past geological eras. In these cases, the lakebed is an already concentrated flat of salts and minerals that dissolves into any water that collects there.

Unique Characteristics of Hypersaline Waters

The most immediate characteristic of hypersaline water is its high density, which creates significant buoyancy. This is why objects, and people, can float with ease in well-known locations like the Dead Sea. The chemical makeup of these lakes is not uniform; while sodium chloride is often a primary component, the specific ionic composition can vary greatly depending on local geology.

Some lakes may have high concentrations of magnesium, calcium, or sulfate ions, which can influence the water’s properties and the types of microbial life present. This dense, salty water does not mix easily with less saline layers, often leading to stratification known as a halocline. This layering can prevent oxygen from the atmosphere from reaching the deeper parts of the lake, resulting in anoxic, or oxygen-free, conditions at the bottom.

Notable Hypersaline Lakes Worldwide

The most famous example is the Dead Sea, which borders Jordan and Israel and is recognized as the world’s deepest hypersaline lake. In North America, the Great Salt Lake in Utah is a vast, shallow hypersaline body whose salinity fluctuates significantly with changing water levels, ranging from slightly saltier than the ocean to 7.7 times as saline. Other significant examples include Lake Assal in Djibouti and Gaet’ale Pond in Ethiopia, which is considered the saltiest water body on Earth with a salinity of 43%. Even cold regions host these environments; subglacial lakes have been discovered under the Devon Ice Cap in Canada, and Antarctica’s McMurdo Dry Valleys contain extremely saline lakes like Lake Vanda.

Extremophile Life in Saline Conditions

The extreme salinity of these lakes makes them inhospitable to most organisms, but they are home to specialized life forms called extremophiles, specifically halophiles, which are adapted to thrive in high-salt environments. These are primarily microbes, including bacteria, archaea, and algae. To survive, they must counteract the osmotic pressure that would otherwise draw water out of their cells and cause dehydration; many do this by accumulating solutes inside their cells to balance the external salinity.

These microbial communities form the foundation of the lake’s ecosystem. Photosynthetic microalgae and cyanobacteria convert sunlight into energy, creating a food source for the next level of organisms. This includes resilient invertebrates like brine shrimp and brine flies. The abundance of certain halophiles, such as archaea with reddish pigments, can give the water a distinct pink or red color, a phenomenon seen in lakes from Iran’s Lake Urmia to Laguna Colorada in Bolivia.

Ecological Roles and Vulnerabilities

The brine shrimp and flies that flourish in these waters become a concentrated, high-energy food source for vast populations of migratory birds. Millions of birds depend on lakes like the Great Salt Lake as stopover points during their long journeys to rest and feed.

These habitats are under increasing threat from human activities and climate change. The diversion of rivers and streams for agriculture and urban development starves the lakes of their water sources, causing them to shrink and become even saltier. The story of Owens Lake in California, which ran dry just 13 years after its water was diverted to Los Angeles, serves as a stark example of this vulnerability. Changes in precipitation and rising temperatures further disrupt the delicate balance of evaporation and inflow that sustains these ecosystems.