Friday, 16 June 2017

TANZANIA: Lake Tanganyika Longest Freshwater Lake In The World

Lake Tanganyika, second largest of the lakes of eastern Africa. It is the longest freshwater lake in the world (410 miles [660 km]) and the second deepest (4,710 feet [1,436 metres]) after Lake Baikal in Russia. Comparatively narrow, varying in width from 10 to 45 miles (16 to 72 km), it covers about 12,700 square miles (32,900 square km) and forms the boundary between Tanzania and the Democratic Republic of the Congo (DRC) and part of the boundary between Burundi and the DRC as well as part of the boundary between Tanzania and Zambia.

It occupies the southern end of the Western Rift Valley, and for most of its length the land rises steeply from its shores. Its waters tend to be brackish. Though fed by a number of rivers, the lake is not the centre of an extensive drainage area. The largest rivers discharging into the lake are the Malagarasi, the Ruzizi, and the Kalambo, which has one of the highest waterfalls in the world (704 feet [215 metres]; see Kalambo Falls). Its outlet is the Lukuga River, which flows into the Lualaba River.

Lake Tanganyika is situated on the line dividing the floral regions of eastern and western Africa, and oil palms, which are characteristic of the flora of western Africa, grow along the lake’s shores. Rice and subsistence crops are grown along the shores, and fishing is of some significance. Hippopotamuses and crocodiles abound, and the bird life is varied.

Many of the numerous peoples (predominantly Bantu-speaking) living on the lake’s eastern shores trace their origins to areas in the Congo River basin. The lake was first visited by Europeans in 1858, when the British explorers Sir Richard Burton and John Hanning Speke reached Ujiji, on the lake’s eastern shore, in their quest for the source of the Nile River.

In 1871 Henry (later Sir Henry) Morton Stanley “found” David Livingstone at Ujiji. Important ports situated along Lake Tanganyika are Bujumbura, the capital of Burundi, Kalemi in the DRC, Mpulungu in Zambia, and Ujiji and Kigoma in Tanzania.

Lake Tanganyika is an African Great Lake. It is the second oldest freshwater lake in the world, second largest by volume, and the second deepest, in all cases after Lake Baikal in Siberia;it is also the world's longest freshwater lake.

The lake is divided among four countries – Tanzania, Democratic Republic of the Congo (DRC), Burundi, and Zambia, with Tanzania (46%) and DRC (40%) possessing the majority of the lake. The water flows into the Congo River system and ultimately into the Atlantic Ocean.

The name apparently refers to "Tanganika, 'the great lake spreading out like a plain', or 'plain-like lake'.

Lake Tanganyika is situated within the Albertine Rift, the western branch of the 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 volume in the world. It is the deepest lake in Africa and holds the greatest volume of fresh water, accounting for 16% of the world's available fresh water.

It extends for 676 km (420 mi) in a general north-south direction and averages 50 km (31 mi) in width. The lake covers 32,900 km2 (12,700 sq mi), with a shoreline of 1,828 km (1,136 mi), a mean depth of 570 m (1,870 ft) and a maximum depth of 1,470 m (4,820 ft) (in the northern basin). It holds an estimated 18,900 cubic kilometres (4,500 cu mi).

The catchment area of the lake is 231,000 km2 (89,000 sq mi). 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). There is one major outflow, the Lukuga River, which empties into the Congo River drainage.

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. The Malagarasi is older than Lake Tanganyika and, before the lake was formed, directly drained into the Congo River.

The lake has a complex history of changing flow patterns, due to its high altitude, great depth, slow rate of refill and mountainous location in a turbulently volcanic area that has undergone climate changes. Apparently it has rarely in the past had an outflow to the sea. It has been described as 'practically endorheic' for this reason.

The lake's connection to the sea is dependent on a high water level allowing water to overflow out of the lake through the Lukunga into the Congo.

Due to the lake's tropical location, it has a high rate of evaporation. Thus it depends on a high inflow through the Ruzizi out of Lake Kivu to keep the lake high enough to overflow. This outflow is apparently not more than 12,000 years old, and resulted from lava flows blocking and diverting the Kivu basin's previous outflow into Lake Edward and then the Nile system, and diverting it to Lake Tanganyika.

Signs of ancient shorelines indicate that at times Tanganyika may have been up to 300 m (980 ft) lower than its present surface level, with no outlet to the sea. Even its current outlet is intermittent and may not have been operating when first visited by Western explorers in 1858.

The lake may also have at times had different inflows and outflows: inward flows from a higher Lake Rukwa, access to Lake Malawi and an exit route to the Nile have all been proposed to have existed at some point in the lake's history.

Lake Tanganyika is an ancient lake. 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.

There are several islands in Lake Tanganyika. The most important of them are

- Kavala Island (The Democratic Republic of the Congo)

- Mamba-Kayenda Islands (The Democratic Republic of the Congo)

- Milima Island (The Democratic Republic of the Congo)

- Kibishie Island (The Democratic Republic of the Congo)

- Mutondwe Island ( Zambia)

- Kumbula Island ( Zambia)

The lake's water is alkaline with a pH of around 9 at depths of 0–100 m (0–330 ft).Below this it is around 8.7, gradually decreasing to 8.3—8.5 in the deepest parts of Tanganyika. A similar pattern can be seen in the electric conductivity, ranging from about 670 μS/cm in the upper part to 690 μS/cm in the deepest.

Surface temperatures generally range from about 24 °C (75 °F) in the southern part of the lake in early August to 28–29 °C (82–84 °F) in the late rainy season in March—April. At depths greater than 400 m (1,300 ft) the temperature is very stable at 23.1–23.4 °C (73.6–74.1 °F).

The lake is stratified and seasonal mixing generally does not extend beyond depths of 150 m (490 ft).The mixing mainly occurs as upwellings in the south and is wind-driven, but to a lesser extent there are also up- and downwellings elsewhere in the lake.As a consequence of the stratification, the deep sections contain "fossil water".

This also means that there is no oxygen (it is anoxic) in the deeper parts, essentially limiting fish and other aerobic organisms to the upper part. There are some geographical variations in this limit, but it is typically at depths of around 100 m (330 ft) in the northern part of the lake and 240–250 m (790–820 ft) in the south.

The oxygen-devoid deepest sections contain high levels of toxic hydrogen sulphide and are essentially lifeless,except for bacteria.

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). The 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.The cichlids of the African Great Lakes, including Tanganyika, represent the most diverse extent of adaptive radiation in vertebrates.

Although Tanganyika has far fewer cichlid species than Lake Malawi and Victoria which both have experienced relatively recent explosive species radiations (resulting in many closely related species),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. All Tanganyika cichlids are in the subfamily Pseudocrenilabrinae. Of the 10 tribes in this subfamily, half are largely or entirely restricted to the lake (Cyprichromini, Ectodini, Lamprologini, Limnochromini and Tropheini) and another three have species in the lake (Haplochromine, Tilapiini and Tylochromini).

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).

Most Tanganyika cichlids live along the shoreline down to a depth of 100 m (330 ft), but some deep-water species regularly descend to 200 m (660 ft).Trematocara species have exceptionally been found at more than 300 m (980 ft), 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.

Tanganyika cichlids are generally benthic (found at or near the bottom) and/or coastal.No Tanganyika cichlids are truly pelagic and offshore, except for some of the piscivorous Bathybates.Two of these, B. fasciatus and B. leo, mainly feed on Tanganyika sardines.

Tanganyika cichlids differ extensively in ecology and include species that are herbivores, detritivores, planktivores, insectivores, molluscivores, scavengers, scale-eaters and piscivores.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 4–5 cm (1.6–2.0 in),and one of the largest, the giant cichlid (Boulengerochromis microlepis) at up to 90 cm (3.0 ft).

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.Recreating a Lake Tanganyika biotope to host those cichlids in a habitat similar to their natural environment is also popular in the aquarium hobby.

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).

Two additional lates are found in the lake, the Tanganyika lates (L. angustifrons) and bigeye lates (L. mariae), but both these are primarily benthic hunters, although they also may move into open waters.The four lates, all endemic to Tanganyika, have been overfished and larger individuals are rare today.

There are 11 species of Synodontis catfish in the lake and 10 of these, including S. polli (pictured), are endemic

Among the more unusual fish in the lake are the endemic, facultatively brood parasitic "cuckoo catfish", including at least Synodontis grandiops and S. multipunctatus.A number of others are very similar (e.g., S. lucipinnis and S. petricola) and have often been confused; it is unclear if they have a similar behavior.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.Five catfish genera are entirely restricted to the lake basin: Bathybagrus, Dinotopterus, Lophiobagrus, Phyllonemus and Tanganikallabes.

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; in the latter habitat they are the primary predators and scavengers. A unique evolutionary radiation in the lake is the 15 species of Mastacembelus spiny eels, all but one endemic to its basin.

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 non-endemic fish, some are widespread African species but several are only shared with the Malagarasi and Congo River basins, such as the Congo bichir (Polypterus congicus), goliath tigerfish (Hydrocynus goliath), Citharinus citharus, six-banded distichodus (Distichodus sexfasciatus) and mbu puffer (Tetraodon mbu).

A total of 68 freshwater snail species (45 endemic) and 15 bivalve species (8 endemic) are known from the lake.Many of the snails are unusual for species living in freshwater in having noticeably thickened shells and/or distinct sculpture, features more commonly seen in marine snails. They are referred to as thallasoids, which can be translated to "marine-like".

All the Tanganyika thallasoids, which are part of Prosobranchia, are endemic to the lake.Initially they were believed to be related to similar marine snails, but they are now known to be unrelated. Their appearance is now believed to be the result of the highly diverse habitats in Lake Tanganyika and evolutionary pressure from snail-eating fish and, in particular, Platythelphusa crabs.

A total of 17 freshwater snail genera are endemic to the lake, such as Hirthia, Lavigeria, Paramelania, Reymondia, Spekia, Stanleya, Tanganyicia and Tiphobia.There are about 30 species of non-thallasoid snails in the lake, but only five of these are endemic, including Ferrissia tanganyicensis and Neothauma tanganyicense. The latter is the largest Tanganyika snail and its shell is often used by small shell-dwelling cichlids.

Crustaceans are also highly diverse in Tanganyika with more than 200 species, of which more than half are endemic.They include 10 species of freshwater crabs (9 Platythelphusa and Potamonautes platynotus; all endemic), at least 11 species of small atyid shrimp (Atyella, Caridella and Limnocaridina), an endemic palaemonid shrimp (Macrobrachium moorei), at least 23 endemic ostracods and several copepods.

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 is Lake Kivu with two species.

The diversity of other invertebrate groups in Lake Tanganyika is often not well-known, but there are at least 20 described species of leeches (12 endemics), 9 sponges

It is estimated that 25–40% of the protein in the diet of the approximately one million people living around the lake comes from lake fish. Currently, there are around 100,000 people directly involved in the fisheries operating from almost 800 sites. The lake is also vital to the estimated 10 million people living in the greater basin.

Lake Tanganyika fish can be found exported throughout East Africa. Commercial fishing began in the mid-1950s and has had an extremely heavy impact on the pelagic fish species; in 1995 the total catch was around 180,000 tonnes. Former industrial fisheries, which boomed in the 1980s, have subsequently collapsed.

Two ferries carry passengers and cargo along the eastern shore of the lake: MV Liemba between Kigoma and Mpulungu and MV Mwongozo between Kigoma and Bujumbura.

- The port town of Kigoma is the railhead for the railway from Dar es Salaam in Tanzania.

- The port town of Kalemie (previously named Albertville) is the railhead for the D.R. Congo rail network.

- The port town of Mpulungu is a proposed railhead for Zambia.

On Dec. 12, 2014, the ferry MV Mutambala capsized on Lake Tanganyika, and more than 120 lives were lost.

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, and in 1927 this was chosen as the new name for the conquered German First World War ship Graf von Götzen which is still serving the lake up to the present time.

In 1965 Argentinian revolutionary Che Guevara used the western shores of Lake Tanganyika as a training camp for guerrilla forces in the Congo. From his camp, Che and his forces attempted to overthrow the government, but ended up pulling out in less than a year since the National Security Agency (NSA) had been monitoring him the entire time and aided government forces in ambushing his guerrillas.

Because of increasing global temperature there is a direct correlation to lower productivity in Lake Tanganyika.Southern winds create upwells of deep nutrient-rich water on the southern end of the lake. This happens during the cooler months (May to September).

These nutrients that are in deep water are vital in maintaining the aquatic food web. The southernly winds are slowing down which limits the ability for the mixing of nutrients. This is correlating with less productivity in the lake.