Greater flamingoes also breed on the mud flats. Lake Natron is a safe breeding location because its caustic environment is a barrier against predators trying to reach their nests on seasonally forming evaporite islands. These flamingoes, the single large flock in East Africa, gather along nearby saline lakes to feed on Spirulina (a blue-green algae with red pigments). When salinity increases, so do cyanobacteria, and the lake can also support more nests. The lake is the only regular breeding area in East Africa for the 2.5 million lesser flamingoes, whose status of "near threatened" results from their dependence on this one location. In the slightly less salty water around its margins, some fish can also survive. Nonetheless, Lake Natron is home to some endemic algae, invertebrates, and birds. Most animals find the lake's high temperature (up to 60 ☌ ) and its high and variable salt content inhospitable. Salt marshes and freshwater wetlands around the edges of the lake do support a variety of plants. The alkali salt crust on the surface of the lake is also often coloured red or pink by the salt-loving microorganisms that live there. The red accessory photosynthesizing pigment in the cyanobacteria produces the deep reds of the open water of the lake and the orange colours of the shallow parts of the lake.
Such halophile organisms include some cyanobacteria that make their own food with photosynthesis as plants do.
As water evaporates during the dry season, salinity levels increase to the point that salt-loving microorganisms begin to thrive. The colour of the lake is characteristic of those where very high evaporation rates occur. The chemical properties of the water are known to calcify the bodies of birds and animals that die in the lake, turning them to stone before they decompose. This has allowed the lake to concentrate into a caustic alkaline brine. The lavas have significant amounts of carbonate but very low calcium and magnesium levels. The surrounding bedrock is composed of alkaline, sodium-dominated trachyte lavas that were laid down during the Pleistocene period. The alkalinity of the lake can reach a pH of greater than 12. High levels of evaporation have left behind natron ( sodium carbonate decahydrate) and trona (sodium sesquicarbonate dihydrate). Temperatures at the lake are frequently above 40 ☌ (104 ☏). The surrounding area receives irregular seasonal rainfall, mainly between December and May totalling 800 millimetres (31 in) per year.
The lake is a maximum of 57 kilometres (35 mi) long and 22 kilometres (14 mi) wide. It is quite shallow, less than three metres (9.8 ft) deep, and varies in width depending on its water level. The lake is fed principally by the Southern Ewaso Ng'iro River, which rises in central Kenya, and by mineral-rich hot springs. It is the only regular breeding area for Africa's lesser flamingoes, although this habitat is not protected and is under threat from planned development projects. The lake is within the Lake Natron Basin, a Ramsar Site wetland of international significance. It is in the Gregory Rift, which is the eastern branch of the East African Rift. Lake Natron is a salt or alkaline lake located in north Ngorongoro District of Arusha Region in Tanzania. Numerous near-white salt-crust "rafts" pepper the shallowest parts of the lake (inset). Fault scarps and the Gelai Volcano can also be seen.
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