Life in the World’s Most Caustic Lake
Lake Natron, located in Tanzania, is said by NASA to be the world’s most caustic body of water. Fed by mineral rich hotsprings, constant evaporation concentrates salts, leaving water that has a pH of 9 - 10.5 (almost the pH of household ammonia!).
Despite the hostility of the habitat, the high salt levels and pH are ideal environments for halophiles, microscopic organisms that are adapted to salt. Cyanobacteria and spirulina, which are responsible for the red colour of the lake, photosynthesise and provide energy for more complex organisms to feed on.
The Lake is the only regular breeding place for 2.5 million Lesser Flamingos (Phoenicopterus minor) which feed on the spirulina in the lake. The birds take advantage of the deterrent waters and plentiful amounts of food provided in an otherwise harsh environment.
The Alkaline Tilapia fish (Alcolapia sp.) also live in the waters, inhabiting the niches at the edges of hot spring inlets. They are well adapted to the high temperatures (up to 110°F or 43°C) and pH of the lake. The fish excrete urea, as the usual ammonia is hard to diffuse in the environment. They can also gulp atmospheric air to compensate for the hypoxic waters.
Images: NASA, public domain; Robbie Veldwijk on Flickr; Michael K Oliver via Wikimedia Commons