A lake is an accumulation of water that forms on land in a natural depression. At the same time, it is a closed reservoir. This natural formation consists of a bed, which is filled to the very edges with water. There are different types of lakes. Allocate reservoirs tectonic and river, ice and seaside, artificial and crater, mountain and failure. This classification indicates their origin.
Features of lakes
Unlike rivers, natural pools of water do not have 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. It is, however, absolutely fresh. An amazing natural formation is the Caspian (see photo) lake. The composition of s alts of its water is similar to that of the ocean. It used to be the Caspian Sea. Now it is a lake. Changes occurred after the loss of communication with the ocean.
The 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 various sizes and shapes. They get more than just rainwater. They are also fed by underground rivers.
There are more than two hundred thousand lakes on the map of Russia. Among them stands out the largest in the world - the Caspian. There is the deepest lake in Russia - Baikal, as well as the largest in Europe - Onega and Ladoga.
Habitats
Flora and fauna of the lakes has its own special character. Mostly natural waters are home to a large number of freshwater species, as well as a few s altwater species.
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. Benthos. This group includes organisms whose habitat is the ground or the bottom of the lake.3. Nekton. Organisms included in this group are actively moving aquatic animals.
The inhabitants of the lake, as a rule, are located in three main zones. The first is the littoral. This is an area that completely covers the coastal zone. The second is profundal. This is the deep-water region of the lake, which includes the bottom and the adjacent water layer. The third zone is the pelagial. It covers the remaining water mass.
Flora
Lakes are distinguished by the zonal arrangement of thickets of aquatic and coastal plants. At the same time, the nature of the flora changes with increasing depth. Thus, sedge thickets predominate in the shallow water zone. They are located no deeper than one meter, at the very edge of the water. Arrowhead and rush, water buckwheat, as well as other types of wetland plants grow here.
With an increase in depth to two or three meters, the zone of reeds begins. This area is home to water horsetail, reeds, and some other plant species.
Even deeper is the flora zone with floating leaves. Here there are water lilies (water lilies), floating pondweed, as well as egg-pods. At a depth of four to five meters, there is an area of submerged plants. These include burrweed and urut, as well as broad-leaved pondweeds.
What fish live in the lake?
The fauna of water bodies is very diverse. Almost all types of freshwater fish can be found in the lake. However, most live there permanently.
What fish live in the lake? In the littoral zone there are bleak and pike, perch and goby. There are fish that prefer to stay at depth. These include burbots and whitefish. These are the inhabitants of the lakes of Russia, living in the pelagic region. Some fish species migrate periodically. For example, in summer, cyprinids find food and shelter in the waters of the littoral zone. In winter, they descend into the middle layers of the lake. Predators follow them.
Division of lake fish into groups
Delimit the fauna of reservoirs according to the way of feeding. The inhabitants of the lake, who prefer plankton as food, are vendace and smelt, smelt and whitefish. In part, such fish include roach and ide, as well as bream, pike perch and perch (some of them turn into predators over time). Inhabitants of the lake with bottom food are chub and carp, crucian carp, bream and others. Air and coastal food is preferred by bleak andtrout, roach and ide. These fish catch insects flying near the surface of the water 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. Reed thickets stretch along the banks. Blue-green algae are common in lake waters. At the same time, there are seventy-six types of them. The abundance of microorganisms (up to three hundred thousand per 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 find salmon and Ladoga slingshot, roach and trout, catfish and smelt, rudd and roach, burbot and pike, and many others.
Baikal
In large lakes and in small bays, flora and fauna are practically no different from those that characterize small fresh water bodies. Clams and snails hide in the mud. In the water layers pike hunt and carp frolic. However, in those zones where the depth is significant, the conditions change dramatically. So, in some places the bottom of Baikal lies at a distance of one and a half kilometers from the smooth surface of its water surface. In such a deep reservoir there are biological organisms. The communities of living beings that in the distant past developed in this isolated water kingdom do not receive replenishment from outside. A wandering animal can enter the lake only against the current of the river flowing into it. And few people can do it.
Inhabitants of Baikal
The deepest lake in the world is the placehabitats 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 flatworms, having red and orange color, painted in specks and stripes. There are also fish in the lake that can live at a kilometer depth, as well as mollusks that have very thin shells due to a lack of calcium s alts in the water. A freshwater seal lives in Baikal. This is a unique mammal that bears a resemblance to the Arctic ringed seal.
On Baikal, the population of this freshwater has several tens of thousands of individuals. In the second half of winter, the animal whelps. At the same time, it brings one or two cubs. The Baikal seal is an excellent 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 invertebrates in Baikal are divided into many species. The most famous of them is the Baikal epishura. These small crustaceans are inhabitants of the water column of the lake. At the same time, the epishura effectively cleans the 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 inhabiting zero. Non-motile colonies of small invertebratesare stained by microalgae in various shades of green. Sometimes the shape of these colonies resembles sea corals.
At the bottom of the Baikal bays and in coastal shallow waters there are larvae of fifty different species of caddisflies. Growing up, individuals leave the aquatic environment.
Fauna
What fish are found in Lake Baikal? In total, fifty-two species have been found in its waters. This number includes the Baikal omul. He is a member of the whitefish family. The Baikal omul belongs to commercial fish and is an object of sport fishing. It lives in areas of underwater slopes located at a depth of three hundred and fifty meters.
What other fish in Lake Baikal is typical only for this area? Among the unique inhabitants there are two species belonging to the endemic golomyanka family (small and large golomyankas). They are small fish (a little more than twenty centimeters long) that live at different depths of the lake and feed on epishura, as well as crustaceans. Golomyanki - food for seals and omul.
The largest Baikal fish is the sturgeon. Not inferior to him in size and taimen. The sturgeon living in the deepest lake is listed in the Red Book of Russia. His life expectancy is fifty years. At the same time, he is gaining weight up to one hundred and thirty kilograms. The inhabitants of Lake Baikal - small fish and bottom invertebrates - are the main food for sturgeon.
