Ecosystem of the lake: general description

In its structure and principle of operation, natural ecosystems are open systems. An inalienable condition for their functioning lies in the ability to give and receive various types of energy and resources. Without this eternal cycle, the limited resources of the Earth would sooner or later have been exhausted. In addition, only the system that can exist without external intervention is considered an ecosystem. Everything that is necessary for the functioning it produces itself. To maintain a continuous flow of substances in any single ecosystem, there must be functionally different groups of living organisms.

In terms of the size of the occupied territory, as well as the number of elements of living and inanimate nature involved in the cycle, the systems of four types are distinguished. At the very bottom is a microecosystem, the simplest example of which is a drop of human blood or water from a river. Then mesoecosystems follow. This category includes the ecosystem of a lake, pond, prairie, steppe or, for example, forests. On the third place are macroecosystems, which are entire continents and oceans. And the largest ecosystem is the planet Earth itself, more precisely, the whole life on it. This system is called global.

Ecosystem structure

The main source of energy in the lake is sunlight. When the rays pass through the water column, most of the energy is absorbed by plankton, in order then to use it for photosynthetic processes. The remaining light is gradually absorbed by the water itself. Therefore, the illumination at the upper levels is always large, and closer to the bottom decreases. Any sufficiently large lake ecosystem has a so-called compensation level. This is the depth that reaches the minimum amount of light necessary for plants. Photosynthesis in these plants slows down to balance other indicators - breathing and food consumption.

The location of the compensation level directly depends on the properties of the water, its purity and transparency. It is a conditional dividing line. Above it, plants produce excess oxygen, which is then used by other living organisms. And below the oxygen separation line, on the contrary, too little. Its main part falls to the depth from other, upper layers of water. Thus, below the compensatory level, only living organisms that can live with a minimal amount of oxygen live.

General distribution of inhabitants

It is obvious that at the upper levels the ecosystem of the lake is inhabited much more in a variety of species than in the bottom zone. This fact is due to more favorable conditions for life, the amount of food, heat and oxygen in the shallow water areas. There, a multitude of planting light-loving plants inhabit : lilies, reeds, reeds, and arrowhead.

They, in turn, serve as a refuge for insects and arthropods, worms, mollusks, tadpoles. Many species of fish also find their food here. The smallest arthropods, whose existence requires a large amount of light, live near the surface. There also grows freely floating duckweed.

At its lower levels, the lake ecosystem becomes a habitat for various kinds of decomposers feeding on dead animal and plant remains. Also, many predatory fish species live here, such as pike and perch, and some invertebrate organisms. These species either feed on dead creatures descending from the upper layers of the water or hunt each other.

Impact of pollution on lake ecosystems

One of the most important natural elements for such systems is phosphorus. The total productivity of the ecosystem depends on its quantity . The natural content of this substance in the lake water is small, but human activity leads to a significant increase in concentration. For the main reasons, it is necessary to include waste of production falling into the lake , discharge of waste water, excessive use of fertilizers, which are then washed away by rain and underground streams. All this brings to the ecosystem an unusual excess of phosphorus.

As a result, the structure and productivity of the well-functioning system is disturbed: the amount of plankton begins to increase rapidly, from which the water acquires a hazy-greenish shade. The lake begins to "bloom", but this is only the first stage. Further, it becomes contaminated with nutrients, water becomes less saturated with oxygen and sunlight (plankton in huge quantities absorbs what other inhabitants should have received). The latter breaks down the activity of the decomposers, because of what the water is filled with slowly decaying remains. At the final stage, plants begin to produce toxins that cause massive loss of fish.

Another type of pollution, due to which the ecosystem of the lake is severely affected is the thermal one. At first glance, it does not seem serious: thermal pollution does not add any chemicals to the water. But the normal functioning of the system depends not only on the composition of the medium, but also on the temperature. Its increase is also capable of provoking plant growth, which triggers a slow but sure fatal reaction. In addition, certain species of fish and invertebrates are adapted to life in a narrow temperature range. Increasing or lowering the temperature in this case slows down the growth of organisms or kills them.

This type of pollution occurs as a result of human industrial activities. For example, one that uses lake water to cool turbines in factories and power plants.