Lake Tanganyika is an African Great Lake. It is estimated to be the second largest freshwater lake in the world by volume, and the second deepest, after Lake Baikal in Siberia; it is also the world's longest lake. The lake is divided between four countries – Burundi, Democratic Republic of the Congo (DRC), Tanzania and Zambia, with the DRC (45%) and Tanzania (41%) possessing the majority of the lake. The water flows into the Congo River system and ultimately into the Atlantic Ocean.

Geography

The lake is situated within the Western Rift of the geographic feature known as the Great Rift Valley formed by the tectonic East African Rift, and is confined by the mountainous walls of the valley. It is the largest rift lake in Africa and the second largest lake by surface area on the continent. It is the deepest lake in Africa and holds the greatest volume of fresh water. It extends for 673 km in a general north-south direction and averages 50 km in width. The lake covers 32,900 km², with a shoreline of 1,828 km and a mean depth of 570 metres (1,870 ft) and a maximum depth of 1,470 metres (4,820 ft) (in the northern basin) it holds an estimated 18,900 km³ (4500 cubic miles). It has an average surface temperature of 25 °C and a pH averaging 8.4. Additionally, beneath the 500 m of water there are about 4,500 metres of sediment lying over the rock floor.

The enormous depth and tropical location of the lake prevent 'turnover' of water masses, which means that much of the lower depths of the lake is so-called 'fossil water' and is anoxic (lacking oxygen). The catchment area of the lake covers 231,000 km², with two main rivers flowing into the lake, numerous smaller rivers and streams (due to the steep mountains that keep drainage areas small), and one major outflow, the Lukuga River, which empties into the Congo River drainage.

The major inflow beginning 10.6 ka is the Ruzizi River, entering the north of the lake from Lake Kivu. The Malagarasi River, which is Tanzania's second largest river, enters the east side of Lake Tanganyika. The Malagarasi predates Lake Tanganyika and was formerly continuous with the Congo river. Lake Tanganyika is presently the second largest freshwater lake in the world by volume. Around 106 ka the lake level was reduced by 435 m. During LGM (34-14) ka dropped 261 m below present lake level. The lake is 9-12 Ma old.

Biology

The lake holds at least 250 species of cichlid fish and 150 non-cichlid species, most of which live along the shoreline down to a depth of approximately 180 metres (590 ft). Many species of cichlids from Lake Tanganyika are popular fish among aquarium owners due to their bright colors. Recreating a Lake Tanganyika biotope to host those cichlids in an habitat similar to their natural environment is also popular in the aquarium hobby.

Lake Tanganyika is thus an important biological resource for the study of speciation in evolution. The largest biomass of fish, however, is in the pelagic zone (open waters) and is dominated by six species: two species of "Tanganyika sardine" and four species of predatory lates (related to, but not the same as, the Nile perch that has devastated Lake Victoria cichlids). Almost all (98%) of the Tanganyikan cichlid species are endemic to the lake and many, such as fish from the brightly coloured Tropheus genus, are prized within the aquarium trade. This kind of elevated endemism also occurs among the numerous invertebrates in the lake, most especially the molluscs (which possess forms similar to those of many marine molluscs), crabs, shrimps, copepods, jellyfishes, leeches, etc.

credited to wikipedia and fickr: Fishwhisperer