Lake Malawi: the flora and fauna.
SmalĺV (nyása) is a lake located in East Central Africa. The lake is elongated in a direction from North to South, and has a length of about 560 km. the Maximum depth of the lake is 706 m. the Height of the lake above sea level 472 meters, the water surface area of approximately 31 000 sq. km.
When David Livingstone (David Livingstone), during his next expedition to Africa, discovered Lake Malawi, he asked the local fishermen about the name of this impressive body of water. To which they replied – “Nyasa”. Livingstone called it the lake, unaware that the word “Nyasa” in the language of the local people and means “lake”. Nyanza – so still call Africans in Tanzania and Mozambique to this day.
The Northern and Eastern shores of lake Malawi with steep shelf poorly developed, but the southern and Western coasts have gently sloping shores. Shoreline of the lake in its landscape can be divided into three types. Approximately one third of the coast is rocky, the remaining part is represented by sandy beaches. The third type of marshy land, overgrown with reeds, located in the mouths of the rivers flowing into the lake rivers. From lake Malawito the South flows the river Shire, where it goes about 20% of the water volume of the lake, and the main loss of water – about 80 % fall on surface evaporation.
Water in Malawi has a lower concentration of ions up to 6 MeV/l, conductivity: 600 µS. This level of ionization is due to the confluence of lake of the rivers with low concentrations of soluble salts.
At the location of the lake are two climatic seasons: rainy, which falls on November — may and dry from may to November.
The temperature of the upper water of lake Malawi is higher than the bottom, and a natural mixing layer hardly occurs. As a result, the level of oxygen in the water at depths below 200 meters is very small, so in such conditions can only exist anaerobic microorganisms. The average temperature of the surface of the water in the lake ranges from 23 to 28 ºC. When a strong Southeast wind is increasing storm activity in waters of the southern coast that leads to more intensive mixing of warm upper water from cooler bottom. As a result, the temperature of the surface water in the southern part of the lake is lowered to 20 ºC.
Malawi is the richest in variety of species of fish lake in the world and home to several dozen species of aquarium fish. Currently there are more than 800 species, 600 of which inhabit the shallow water. Only a small number of species known today are deep. It is believed that at least 100-200 species can be found in the deeper waters of the lake.
Studies of sediments have shown that in prehistoric times the low water level established by a preponderance on the Earth hot and dry climate. Such global level fluctuations directly affected the process of speciation (extinction) of cichlids that inhabited ancient lake Malawi. About a thousand species living today in Malawi, are a small part of the diversity that was present in the lake for all its ancient history.