Tanganyka Lake
“For me, one of the happiest moments in life is the beginning of a journey to unexplored lands. Only when the shackles of Habit, the burden of Routine, the mantle are freed free from the numerous cares and slavery of Civilization, man will know happiness again.”
The British traveler, linguist, writer, soldier, cartographer – wanderer wrote those words in his diary Richard Francis Burton, the first European who, in 1858. saw the great Lake Tanganyika.
Tanganyika (roughly translated – large water that spreads like a plain) is a large lake in central Africa. It is considered to be the second largest lake in the world by volume of water, right after Baikal in Siberia. It is also the longest freshwater lake in the world.
Geographical and Biological Significance of Lake Tanganyika
In the western part of the Great Rift Valley, limited by the mountainous sides of the same, it stretches for a length of 673 km in the north-south direction, with an average width of 50 km. The surface of the lake is slightly less than 33,000 km2, with a coastline 1,828 km long, an average depth of 570 m and a maximum depth of 1,470 m (in the northern part). Given that the greatest depth of the lake is below sea level, it represents cryptodepression. (kryptos – which means “hidden” and depressio – descent, or depression, which in geography is a term for an area lower than sea level). It is estimated that there are 18,900 cubic kilometers of water. The average water temperature on the surface is 25 degrees Celsius, and the average pH value is 8.4.
Lake Tanganyika
The great depth and tropical location of the lake prevent a large outflow of water, which means that the water in the depths is so-called. “fossil water” without oxygen. The lake is stratified – layered, which is again a direct consequence of seasonal mixing it generally does not reach depths below 150 m. Due to wind-induced mixing, it occurs in the south, as well as to a lesser extent in several other parts of the lake. Therefore, the water in the deeper parts is anoxic, which essentially limits fish and other aerobic organisms to the upper, shallower part. Variations of this limit exist, although it is typical at depths of about 100 m in the northern part of the lake, and 250 m, due to the aforementioned influence of the wind, in the south. The deepest oxygen-free sections have high levels of toxic hydrogen sulfide and, except for some types of bacteria, are completely lifeless.
The area of the lake covers 231,000 square km, with two large rivers flowing into the lake, many smaller rivers and streams, while the largest outflow, the river Lukuga, which later became the basin of the Congo River. Thanks to the very steep mountain coast, the drainage of the lake is very little. The biggest tributaries are therefore the river Ruzizi, which flows from Lake Kivu on the north side, while the Malagarasi River, the second largest river in Tanzania, pours its water into the lake from the east side. The lake is a natural border between four states. That ancient lake, about 12 million years old, floods the shores of Burundi, DR Congo, Zambia, and Tanzania, with Congo holding 40% and Tanzania 46% of the lake.
photo by Alvise Forcellini
Biodiversity and Ecology of Lake Tanganyika
Lake fish are the biggest source of protein for the local population. About 45,000 people, from almost 800 settlements, are directly engaged in fishing, and about a million inhabitants, mostly from the basin, are connected in one way or another with fishing. Fish from Tanganyika is exported throughout East Africa. Also, goods are transported between coastal countries via the lake, which is a very important waterway. The surroundings of the lake are rich in forest, which is cut down for timber, coal and other raw materials.
The flora and fauna of the lake are extremely rich. It is home to Nile crocodiles, Zambian articulated turtles, ring-necked turtles. At least 300 species of fish live in the lake – cichlids and 150 other species, most of which live at the bottom of the lake. The largest biomass of fish, however, is found in open waters dominated by six species – two species of sardines and four species of predatory fish.
Tanganyika cichlid species are (98% of them) endemic. There are many endemic species among invertebrates, especially molluscs (which are largely like marine morphology), crabs, copepods, leeches, etc.
The lake contains at least 250 species of cichlid fish. Cichlids of the great African lakes, including Tanganyika, represent the most diverse range of adaptive radiation in vertebrates. Cichlids (lat. Cichlidae) are a family of fish from the order Perciformes. Cichlids are the most extensive order of vertebrates, with over 7,000 species of modern fish. They can be found in almost all aquatic habitats. In addition to cichlids, well-known representatives are perch, barracuda, tuna, bass…
Cichlids are therefore traditionally classified as suborder Labroidei. This family has about 1,300 described species, and it is assumed that the total number of species is around 2,000. The size of fish from that family varies from 2.5 cm (female Neolamprologus multifasciatus) to 1 m (Boulengerochromis and Cichla). Despite being a large family, most species of cichlids have a similar body shape (perch-like) with rare exceptions (Altolamprologus, Pterophyllum).
Most Tanganyika cichlids live along the coasts, up to a depth of 100 m, although some deep-water species descend to a depth of 200 m. The Trematocara species was found at depths greater than 300 m, which is a kind of world record for that type of fish. An enigma for science is the fact that several representatives of the species were hanging around at those depths that are completely devoid of oxygen. The mechanism and way of working of the organism that keeps these animals alive in such extreme conditions is also a puzzle for world authorities.
Tanganyika cichlids are generally benthic (dwelling on or near the bottom) or littoral. None of the families are truly pelagic, nor does it live far from the coast, except for some deep-water ones (Bathybates). Great Lakes cichlids vary widely in ecology and include species that are herbivores, vultures, and carnivores. When it comes to mating, there are two main groups – species with susceptible spawning (caves, crevices in rocks) and those that incubate their eggs in their mouths.
Many Lake Tanganyika cichlids such as Altolamprologus, Cyprichromis, Eretmodus, Julidochromis, Neolamprologus, Lamprologus, Tropheus and Xenotilapia are popular aquarium fish due to their bright colors, patterns, and interesting behavior.
Unfortunately, this extraordinary natural, freshwater beauty, surrounded by mountains with their peaks immersed in low clouds, was not spared the war operations of a large, by no means endemic “sane” race. The whole world was not enough for these people, but they sought an armed confrontation and a fight – and that on two occasions, in a very short space of time – therefore, they sought in such an ancient and mystical place, towards which, according to all the rules, they would have to feel, if not love, but at least due respect. That it is at the moment, when it has already been mentioned Richard saw the lake, could see and understand what his compatriots, neighbors and countrymen, in a little less than 90 years later, would be working on the same, what kind of destruction they would be engaged in, would he joyfully exclaim, so that it echoes for a long time among the volcanic giants, soothed by the eternal caress of gentle waves, or else he would return to the camp, among his men, and there, encouraged by their questioning looks, he would briefly say:
-Let’s go back, friends. There is nothing here for us.
A coupling between two different but equally magical worlds – the untouched wilderness along the coast that is home chimpanzees, elephants, antelopes, big cats and an incredibly diverse and rich underwater world; the beating heart that, with its constant, sure, comfortingly eternal rhythm, selflessly feeds and supplies the entire surrounding living world with vital fluid, rightfully bears the name: The Blue Heart of Africa.
Richard Francis Burton
by Rischgitz, 1864
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