A lake is an accumulation of water that forms on land in a natural depression. Moreover, it is a closed body of water. This natural formation consists of a bed, which is filled to the very edges with water. There are various types of lakes. There are tectonic and river water bodies, ice and coastal, artificial and crater, mountain and failure. Such a classification indicates their origin.
Lakes features
Unlike rivers, natural water accumulations have no currents. However, they do not belong to the oceans. Another distinguishing feature is the different salinity of the water. So, the deepest lake is Baikal. Moreover, it is absolutely bland. An amazing natural formation is the Caspian (see photo) lake. In terms of salt composition, its water is similar to oceanic. It used to be the Caspian Sea. Now it is a lake. Changes occurred after losing contact with the ocean.
Lakes are grouped by water balance and position, by the nutritional value of the substances contained in its water, and also by their composition.
There are many features. There are lakes of various bottom topography, as well as of various sizes and shapes. They get not only rainwater. They are also fed by underground rivers.
On the map of Russia there are more than two hundred thousand lakes. Among them, the largest in the world stands out - the Caspian. There is the deepest lake in Russia - Baikal, as well as the largest in Europe - Onega and Ladoga.
Habitat areas
The flora and fauna of the lakes has its own special character. Basically, natural water bodies are the habitat of a large number of representatives of freshwater species, as well as a few salt-water ones.
The organic population of the lake consists of the following components:
1. Plankton. It is a collection of small organisms that are passively carried by water.
2. Bentos. This group includes organisms whose habitat is the soil or bottom of the lake.
3. Necton. Organisms included in this group are actively moving aquatic animals.
Inhabitants of the lake, as a rule, are located in three main zones. The first is littoral. This is an area that completely covers the coastal zone. The second is profundal. This is a deep-water area of the lake, which includes the bottom and the adjacent water layer. The third zone is the pelagic. It covers the remaining water mass.
Flora
Lakes differ in the zonal location of thickets of aquatic and coastal plants. The nature of the flora changes with increasing depth. Thus, sedge thickets prevail in the shallow water zone. They are located no deeper than one meter, at the very edge of the water. Here grows arrowhead leaves and chythorn, buckwheat, as well as other species of wetland plants.
With an increase in depth to two to three meters, a zone of reeds begins. Water horsetail, reed, and some other plant species grow in this area.
The flora zone with floating leaves is even deeper. Here you can find water lilies (water lilies), floating rdest, as well as egg capsules. At a depth of four to five meters is an area of submerged plants. These include the head and urut, as well as broadleaf vines.
What fish live in the lake?
The fauna of water bodies is very diverse. In the lake you can find almost all types of freshwater fish. However, most live there permanently.
What fish live in the lake? In the littoral zone, bleak and pike, perch and goby are found. There are fish that prefer to stay deep. These include burbot and whitefish. These are the inhabitants of Russian lakes living in the pelagic region. Some species of fish migrate periodically. For example, in the summer, cyprinids find food and shelter in the waters of the littoral zone. In winter, they descend into the middle layers of the lake. They are followed by predators.
Division of lake fish into groups
Differentiate the fauna of water bodies according to the method of nutrition. The inhabitants of the lake, preferring plankton for food, are vendace and smelt, smelt and whitefish. Part of such fish include roach and ide, as well as bream, pikeperch and perch (some of them turn into predators over time). The inhabitants of the lake with bottom nutrition are chub and carp, crucian carp, bream and others. Airy and coastal foods are preferred by biting and trout, roach and ide. These fish catch insects flying near the water surface or crawling at the very edge of the water.
Fauna and flora of Ladoga and Onega lakes
The natural world of the largest European reservoirs is rich and diverse. They are home to about one hundred and twenty species of aquatic plants. Thickets of reeds stretch along the coast. In the waters of the lakes are blue-green algae. Moreover, there are seventy-six species. The abundance of microorganisms (up to three hundred thousand in a cubic centimeter) in the lakes allows for self-purification of waters.
The world of freshwater fish is also rich in these reservoirs. Here you can meet salmon and Ladoga slingshot, roach and trout, catfish and smelt, rudd and roach, burbot and pike, as well as many others.
Baikal
In large lakes and in small bays, the flora and fauna is practically no different from that of small fresh water bodies. In the silt, mollusks and snails take shelter. Pikes hunt and carps frolic in water layers. However, in those areas where the depth is significant, the conditions change dramatically. So, in some places, the bottom of Lake Baikal lies at a distance of one and a half kilometers from the surface of its water surface. Such a deep body of water has its own biological organisms. Communities of living beings that in the distant past formed in this isolated water kingdom do not receive replenishment from outside. A wandering animal can get into the lake only against the course of the river flowing into it. And this is not enough for anyone.
Inhabitants of Baikal
The deepest lake in the world is the habitat of five hundred species of plants and one thousand two hundred - animals. Moreover, almost eighty percent of them can be found only in the waters of Lake Baikal. Among them are large-sized flatworms with red and orange colors, painted in specks and stripes. The fish that can live at a kilometer depth, as well as mollusks with very thin shells due to a lack of calcium salts in the water, are also found in the lake.
A freshwater seal lives in Baikal. This is a unique mammal that resembles the Arctic ringed seal.
On Baikal, the population of this freshwater totals several tens of thousands of individuals. In the second half of winter, the animal whelps. Moreover, it brings one or two cubs. The Baikal seal is a wonderful diver, able to dive to a depth of two hundred meters and stay there for up to twenty minutes.
Small animals
Baikal is the habitat of the simplest unicellular organisms. Their food is bacteria, microalgae. Multicellular invertebrate animals on Lake Baikal are divided into many species. The most famous of them is the Baikal episode. These small crustaceans are inhabitants of the water column of the lake. At the same time, the epishura effectively cleans Baikal waters with its filtering device, consisting of hairs and bristles located on the oral apparatus.
The rocky soil of the lake is a habitat for sponges. These are the most exotic animals that inhabit zeros. Fixed colonies of small invertebrates are stained with microalgae in a variety of shades of green. Sometimes the shape of these colos resembles marine corals.
Larvae of fifty different species of caddis flies are found at the bottom of the Baikal bays and in coastal shallow waters. Growing, individuals leave the aquatic environment.
