Situated in Africa’s Great Rift Valley, Lake Natron’s bright pink waters stand out in more ways than one. In addition to its eye-catching colour, the lake is also hypersaline, meaning that it is supersaturated with salt.
Ash from the once volcanic mountains nearby has enriched the soil on the lake bed with natron, the chemical compound from which the lake gets its name. Natron consists mainly of sodium carbonate, a salt that dissolves in the water to make it strongly alkaline. This type of lake is known as a soda lake, as its water has an extremely alkaline pH of between 9 and 10.5. Acidic rain sometimes reduces this value, but wet weather is erratic in the region.
Additional salts are also fed into the lake from nearby hot springs, and because the lake has no outlet, it is all left behind as the water evaporates. In fact, Lake Natron was originally a much larger freshwater lake, but as the hot, dry climate evaporated much of the water, it shrank and became very salty. The water is also a very warm 40 degrees Celsius (104 degrees ahrenheit), but can sometimes reach a scolding 60 degrees Celsius (140 degrees Fahrenheit).
The lake’s distinctive colour comes from the microorganisms that thrive on the salt within, but there aren’t many other creatures that can survive these extreme conditions. Only one species of fish, the tilapia, is tough enough to live in the lake, but most other animals that venture into the water will die and become encrusted with salts when water levels drop. The natron, which was used in Egyptian mummifi cation, helps to preserve their bodies, causing eerie stone-like fi gures to occasionally wash up onto the shore.
The wonderful wildlife of Lake Natron
One of the very few creatures that can thrive at Tanzania’s hypersaline lake is the flamingo. The birds take advantage of the lake’s extreme conditions, which keep their predators at bay, and more than 2 million lesser flamingos flock there during breeding season.
When the water level is just right, salt islands are exposed in the centre of the lake, providing the perfect nesting site. If the lake is too dry, predators are able to reach the young birds, and if there is too much rain, the nests can be flooded, so the conditions must be perfect for a successful breeding season.
The lake also provides the flamingos with an abundant source of food, as they feed on the blue-green algae in the water, and pigments called carotenoids that are found in the algae give the birds their bright pink colour.
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