Танганьика: Древнее озеро Восточной Африки

Rift lake in east central Africa

Lake Tanganyika (,/t//æ//ŋ//ɡ//ə//n/'/j//iː//k//ə//, // //ɡ//æ//n// /; Kirundi : Ikiyaga ca Tanganyika) is an African Great Lake. It is the second oldest freshwater lake in the world, the second largest by volume, and the second deepest, in all cases after Lake Baikal in Siberia. It is the world's longest freshwater lake. The catchment area of the lake is Two main rivers flow into the lake, as well as numerous smaller rivers and streams (whose lengths are limited by the steep mountains around the lake). The one major outflow is the Lukuga River, which empties into the Congo River drainage. Precipitation and evaporation play a greater role than the rivers. At least 90% of the water influx is from rain falling on the lake's surface and at least 90% of the water loss is from direct evaporation. The major river flowing into the lake is the Ruzizi River, formed about 10,000 years ago, which enters 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. Lake Tanganyika is an ancient lake, one of only twenty more than a million years old. Its three basins, which in periods with much lower water levels were separate lakes, are of different ages. The central began to form 9–12 million years ago (Mya), the northern 7–8 Mya and the southern 2–4 Mya.

The lake's water is alkaline with a pH around 9 at depths of Below this, it is around 8.7, gradually decreasing to 8.3–8.5 in the deepest parts of Tanganyika. At depths greater than , the temperature is very stable at The water has gradually warmed since the 19th century and this has accelerated with global warming since the 1950s. The lake is stratified and seasonal mixing generally does not extend beyond depths of As a consequence of the stratification, the deep sections contain "fossil water". This also means it has no oxygen (it is anoxic) in the deeper parts, essentially limiting fish and other aerobic organisms to the upper part. Some geographical variations are seen in this limit, but it is typically at depths around in the northern part of the lake and in the south. The oxygen devoid deepest sections contain high levels of toxic hydrogen sulphide and are essentially lifeless,

Lake Tanganyika and associated wetlands are home to Nile crocodiles (including famous giant Gustave), Zambian hinged terrapins, serrated hinged terrapins, and pan hinged terrapins (last species not in the lake itself, but in adjacent lagoons). Storm's water cobra, a threatened subspecies of banded water cobra that feeds mainly on fish, is only found in Lake Tanganyika, where it prefers rocky shores.

The lake holds at least 250 species of cichlid fish and undescribed species remain. Almost all (98%) of the Tanganyika cichlids are endemic to the lake and it is thus an important biological resource for the study of speciation in evolution. Some of the endemics do occur slightly into the upper Lukuga River, Lake Tanganyika's outflow, but further spread into the Congo River basin is prevented by physics (Lukuga has fast flowing sections with many rapids and waterfalls) and chemistry (Tanganyika's water is alkaline, while the Congo's generally is acidic). its cichlids are the most morphologically and genetically diverse. This is linked to the high age of Tanganyika, as it is far older than the other lakes. Tanganyika has the largest number of endemic cichlid genera of all African lakes. Others have proposed splitting the Tanganyika cichlids into as many as 12–16 tribes (in addition to previous mentioned, Bathybatini, Benthochromini, Boulengerochromini, Cyphotilapiini, Eretmodini, Greenwoodochromini, Perissodini and Trematocarini). Trematocara species have exceptionally been found at more than , which is deeper than any other cichlid in the world. Some of the deep water cichlids (e. g., Bathybates, Gnathochromis, Hemibates and Xenochromis) have been caught in places virtually devoid of oxygen, but how they are able to survive there is unclear. No Tanganyika cichlids are truly pelagic and offshore, except for some of the piscivorous Bathybates. Their breeding behavior fall into two main groups, the substrate spawners (often in caves or rock crevices) and the mouthbrooders. Among the endemic species are two of the world's smallest cichlids, Neolamprologus multifasciatus and N. similis (both shell dwellers) at up to , and one of the largest, the giant cichlid (Boulengerochromis microlepis) at up to
Many cichlids from Lake Tanganyika, such as species from the genera Altolamprologus, Cyprichromis, Eretmodus, Julidochromis, Lamprologus, Neolamprologus, Tropheus and Xenotilapia, are popular aquarium fish due to their bright colors and patterns, and interesting behaviors.

Lake Tanganyika is home to more than 80 species of non cichlid fish and about 60% of these are endemic. The open waters of the pelagic zone are dominated by four non cichlid species: Two species of "Tanganyika sardine" (Limnothrissa miodon and Stolothrissa tanganicae) form the largest biomass of fish in this zone, and they are important prey for the forktail lates (Lates microlepis) and sleek lates (L. stappersii). and S. multipunctatus. The facultative brood parasites often lay their eggs synchronously with mouthbroding cichlids. The cichlid pick up the eggs in their mouth as if they were their own. Once the catfish eggs hatch the young eat the cichlid eggs. Although not endemic on a genus level, six species of Chrysichthys catfish are only found in the Tanganyika basin where they live both in shallow and relatively deep waters; Although other African Great Lakes have Synodontis catfish, endemic catfish genera and Mastacembelus spiny eels, the relatively high diversity is unique to Tanganyika, which likely is related to its old age. Among the endemic bivalves are three monotypic genera: Grandidieria burtoni, Pseudospatha tanganyicensis and Brazzaea anceyi. All the Tanganyika thalassoids, which are part of Prosobranchia, are endemic to the lake. A total of 17 freshwater snail genera are endemic to the lake, such as Hirthia, Lavigeria, Paramelania, Reymondia, Spekia, Stanleya, Tanganyicia and Tiphobia. Crustaceans are also highly diverse in Tanganyika with more than 200 species, of which more than half are endemic. at least 11 species of small atyid shrimp (Atyella, Caridella and Limnocaridina), an endemic palaemonid shrimp (Macrobrachium moorei), about 100 ostracods, including many endemics, and several copepods. Among these, Limnocaridina iridinae lives inside the mantle cavity of the unionid mussel Pleiodon spekei, making it one of only two known commensal species of freshwater shrimp (the other is the sponge living Caridina spongicola from Lake Towuti, Indonesia). Among Rift Valley lakes, Lake Tanganyika far surpasses all others in terms of crustacean and freshwater snail richness (both in total number of species and number of endemics). For example, the only other Rift Valley lake with endemic freshwater crabs are Lake Kivu and Lake Victoria with two species each.

Lake Tanganyika supports a major fishery, which, depending on source, provides 25–40% or 60% of the animal protein in the diet of the people living in the region. Lake Tanganyika fish can be found exported throughout East Africa. Major commercial fishing began in the mid 1950s and has, together with global warming, had a heavy impact on the fish populations, causing significant declines. There are many methods in which the native people of the area were fishing. Most of them included using a lantern as a lure for fish that are attracted to light. There were three basic forms. One called Lusenga which is a wide net used by one person from a canoe. The second one is using a lift net. This was done by dropping a net deep below the boat using two parallel canoes and then simultaneously pulling it up. The third is called Chiromila which consisted of three canoes. One canoe was stationary with a lantern while another canoe holds one end of the net and the other circles the stationary one to meet up with the net. The first known Westerners to find the lake were the British explorers Richard Burton and John Speke, in 1858. They located it while searching for the source of the Nile River. Speke continued and found the actual source, Lake Victoria. Later David Livingstone passed by the lake. He noted the name "Liemba" for its southern part, a word probably from the Fipa language. Tanganyika means "stars" in the Luvale language. The lake was the scene of Battle for Lake Tanganyika during World War I. With the aid of the Graf Goetzen, the Germans had complete control of the lake in the early stages of the war. The ship was used both to ferry cargo and personnel across the lake, and as a base from which to launch surprise attacks on Allied troops. It therefore became essential for the Allied forces to gain control of the lake themselves. Under the command of Lieutenant Commander Geoffrey Spicer Simson the British Royal Navy achieved the monumental task of bringing two armed motor boats HMS Mimi and HMS Toutou from England to the lake by rail, road and river to Albertville (since renamed Kalemie in 1971) on the western shore of Lake Tanganyika. The two boats waited until December 1915, and mounted a surprise attack on the Germans, with the capture of the gunboat Kingani. Another German vessel, the Hedwig, was sunk in February 1916, leaving the Götzen as the only German vessel remaining to control the lake. In order to avoid his prize ship falling into Allied hands, Zimmer scuttled the vessel on July 26, 1916. The vessel was later raised in 1924 and renamed MV Liemba.