Rift Valley Lakes - A Global Ecoregion
Hosts one of only two known flocks of cyprinid fish species
Snapshot: Ecoregion 182
Size:
780,000 sq. km (300,000 sq. miles)
Habitat type:
Large Lakes
Geographic Location:
East-central Africa: Burundi, Democratic Republic of Congo, Ethiopia, Kenya, Malawi, Mozambique, Rwanda, Tanzania, Uganda, and Zambia
Conservation Status:
Critical/Endangered
Quiz Time!
Lakes influencing weather?
Answer:
Lakes may be relatively quiet and still, but some are powerful enough to change the weather. Within a 31-49 mile (50-80 km) zone around Lake Victoria, the climate is different from that in places farther away.
Rainfall is heavier and droughts don't affect the water level as much. And even though this part of Africa can get very hot, the temperature around Lake Victoria is rarely higher than 27° C.
Answer:
Lakes may be relatively quiet and still, but some are powerful enough to change the weather. Within a 31-49 mile (50-80 km) zone around Lake Victoria, the climate is different from that in places farther away.
Rainfall is heavier and droughts don't affect the water level as much. And even though this part of Africa can get very hot, the temperature around Lake Victoria is rarely higher than 27° C.
About the Area
The Great Rift Valley, created by the moving of tectonic plates beneath the crust of Africa, is home to many lakes that harbour extraordinary endemic species.
Some such as Lakes Malawi (>800 meters deep) and Tanganyika (>1400 meters deep) have formed in the rifts, but the vast Lake Victoria is actually located in a shallow depression between the two rifts.Several small soda lakes in the eastern rift represent a globally rare habitat type with upwards of 800 cichlids living in them and many more species yet to be discovered. The species radiations of cichlids in the Rift Valley lakes rival radiations of terrestrial fauna in the Galápagos and serve as a classic example of evolutionary adaptation.
Local Species
The Rift Valley lakes are primarily known for the extensive radiations of fish species in the family Cichlidae . Endemic species of the Clariidae, Claroteidae, Mochokidae, Poecilidae, Mastacembelidae, Centropomidae, Cyprinidae, Clupeidae and other families are also found in these lakes.
A unique pelagic fish community has evolved in Lake Tanganyika including two endemic clupeids, Limnothrissa miodon and Stolothrissa tanganicae, that feed on zooplankton in the pelagic zone and, in turn, provide food for the four predatory centropomids, Lates angustifrons, L. mariae, L. microlepis, and L. stappersii.
Large numbers of cichlid species live adjacent to one another along the edges of the lakes. For example, one researcher caught 7,000 fish representing 38 families in one 4,300 square foot (400 sq. m) sampling area in Lake Tanganyika.
The cichlids have evolved specialisations to take advantage of their environment and to limit competition for resources. For example, one unusual group of fish, the scale-eaters, feed exclusively on the scales of other fish.
Most cichlids spend a lot of time caring for their young, but the young of mouth-brooders swim into their parent's mouth for protection in the face of imminent danger. It is not only the fish that are unique to these lakes.
Copepods, ostracods, shrimps, crabs, and mollusks are also represented by high numbers of endemic species. Lake Tana supports a group of cyprinid fish that are all descended from a common ancestor (called a "species flock"). This cyprinid species flock is one of only two known in the world, and the only one that is still intact.
Resources
• NationalGeographic.com
