Lake Natron, Tanzania

Lake Natron, in Africa Great Rift Valley, practically sends a warning
with its color. This bright red lake is the world's most caustic body
of water, but not to everything. An endemic species of fish, the alkaline
tilapia, lives along the edges of the hotspring inlets, and the lake actually
derives its color from salt-loving microorganisms that thrive in its alkaline
waters. Spirulina, a blue-green algae with red pigments, passes its pigments
along to the Lesser Flamingoes that feed on the algae and raise their young here.

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER)
flying on the Terra satellite captured this image on March 8, 2003. This image
simulates natural color, showing where the salt-loving microorganisms have colored
the lake's salt crust red or pink. The salt crust changes over time, giving the
lakea slightly different appearance each time it is photographed by astronauts or
imaged by satellites.

Volcanic ash from the Great Rift Valley has collected in local lake basins,
creating a network of soda lakes hostile to most organisms. This forbidding
environment enables Lake Natron to serve millions of flamingoes as the ideal
nursery; would-be predators avoid the saline lake and leave young birds in peace.
Flamingoes must exercise caution, however, because the lake can turn deadly
even to them. Depending on rainfall, its alkalinity can approach that of
straight ammonia, and when the lake is flooded with water that has heated
underground, its temperature can reach a scalding 60 degrees Celsius
(140 degrees Fahrenheit).

The uniqueness of Lake Natron prompted Tanzania to add the lake to the Ramsar
List of Wetlands of International Importance on July 4, 2001.