Friday, May 14, 2010

African Rift Lakes

The African Rift Lakes refer to three major lakes in eastern Africa, specifically Lake Malawi, Lake Tanganyika, and Lake Victoria. Each lake has developed it's own unique habitat and inhabitants.

Along the rift, the northern most lake is Lake Victoria, and Lake Malawi is the southern most lake, with Lake Tanganyika situated between them.

Lake Malawi is the ninth largest lake in the world.with an overall area of about 12,000 square miles. It is the southern most lake of the rift lakes. This lake is bordered by Tanzania, Mozambique, and Malawi. The lake is long, narrow and quite deep, reaching depths of 2,300 feet at its deepest point. Only the upper 300 feet or so contains enough oxygen to sustain life of cichlids. Due to the geography of rapids to the north and south of the lake, this lake is effectively cut off. As a result, the dominant fish family, Cichlidae, have evolved from the riverine forms of Tilapia and Haplochromis have been totally isolated within the lake and have evolved to a point where the lake contains more known cichlid species  than in any other lake in the world. More of the popular species of cichlids among aquarium hobbyists come from Lake Malawi.

Lake Tanganyika contains by far the most unique and diverse array of freshwater fishes of any other lake on earth. NOtably, the cichlids of Lake Tanganyika show the greatest adaptation and uniqueness of shape and habitat preferences than elsewhere in Africa. In a 1986 review, Professor Max Poll defined 12 distinct  lineages among the lake Tanganyika cichlids, as compared to the three groups of Lake Malawi cichlids. Lake Tanganyika is 420 miles long and about 40 miles at its widest point. It's shores are bordered by four countries - Zambia (on the south), Congo (to the west), Tanzania (to the east), and Burundi (on the northeast end). The lake is nearly 4800 feet at its deepest. The pH ranges from 8.7 to 9.4, and the water is quite hard.

Lake Victoria, with its adjoining sister Lake Kyoga, are the northern most of the major African Rift Lakes, and is bordered by three countries - Tanzania to the south, Uganda to the north, and Kenya on the northeastern edge. Lake Victoria is around 240 moles long and about 190 miles wide, with a maximum depth of 300 feet, making it a shallow saucer-shaped lake with a large surface area. This makes it a well oxygenated body of water. The pH ranges from 7.0 to 9.0, and the temperature runs between 70 and 81 degrees F.

The chemical composition of the African Rift Lakes is hard and alkaline.The pH of the water varies from 7.7 to 8.7, and is quite alkaline, and also very hard. In general the water temperature at the shorelines where the cichlids are found averages about 78 degress F.

There is alot of interesting information about why these lakes are so unique. For more detailed about the geography and history of these unique lakes, check out: THE GREAT LAKES OF EAST AFRICA

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