LENTIC ECOSYSTEM: CHARACTERISTICS, BIODIVERSITY AND THREATS - BIOLOGY - 2025

The lentic ecosystems are aquatic environments where water bodies do not present a continuous stream. The waters are retained in a certain space and depending on their size, waves and tides can occur.

Lakes, ponds, reservoirs and wetlands are different types of lentic ecosystems. They have originated in different ways. Some due to meteorite impacts, others due to erosion or sedimentation.

Chaxas Lagoon, San Pedro de Atacama, Chile. Author: Negrorodrigo, from Wikimedia Commons

The biodiversity present in lentic ecosystems is determined by different abiotic factors. Temperature, luminosity, gas concentration and organic matter content are of great importance.

Within the fauna present, the zooplankton made up mainly of rotifers and crustaceans stands out. Also, there are various amphibian invertebrates and fish. The flora is made up of phytoplankton (microscopic algae) and various floating or rooted angiosperms.

Lentic ecosystems are distributed throughout the planet. They occur in both temperate and tropical zones. In the Arctic and Antarctica we can also find some lentic areas.

characteristics

Origin

Lentic ecosystems have very diverse origins. In some cases it is from the melting of mountain glaciers (glacial lakes).

They can also be caused by tectonic movements that produce fractures and generate depressions where river water can reach and form lagoons or lakes. Likewise, the impact of meteorites can form craters.

In other cases they can be caused by erosive processes. Also, some dormant volcanoes form depressions where accumulation of water can occur.

The mouths of large rivers produce wide deltas where various lentic ecosystems occur. On the other hand, in deserts oases are formed from underground water sources.

Finally, human beings have built artificial lakes, ponds and ponds where biotic communities have been established and a dynamic similar to natural ecosystems is generated.

Abiotic factors

The dynamics of lentic ecosystems is determined by various environmental factors. Among them, the most important are the availability of light, temperature, presence of oxygen and content of organic matter.

The amount of light that penetrates the body of water will depend on its depth, as well as on the turbidity produced by the accumulation of sediment.

Temperature is of great importance, particularly in temperate zones where seasonal cycles occur. In these areas, thermal stratifications are created in the body of water. This occurs mainly in the summer, when the surface layer is warmer and defines different thermal zones.

Among the most important gases in the dynamics of lentic ecosystems are CO ₂ and O ₂. The concentration of these gases is regulated by their atmospheric pressure.

The content of organic matter in these bodies of water is determined by the photosynthetic activity mainly of phytoplankton. On the other hand, bacteria determine the rate of degradation of the same

Structure

There is a vertical and a horizontal structure. In the case of the horizontal structure, the littoral, sub-littoral and limnetic (open water) zones are defined.

In the coastal zone the depth is less and there is a greater luminosity. It is subject to wave action and greater temperature fluctuations. In it there are deep-rooted aquatic plants.

The intermediate zone is called subcoastal. It is generally well oxygenated and the sediment is made up of fine grains. Here the calcareous remains of the mollusks that grow on the coast tend to be located.

Later the open water area is located. Here is the greatest depth of the body of water. The temperature tends to be more stable. There is little O ₂ content and CO ₂ and methane can be abundant.

In the horizontal structure, a well-lit surface layer (photic layer) is differentiated. Then the light gradually decreases until it reaches the aphotic layer (almost without the presence of light). This constitutes the benthic zone (bottom of the body of water). This is where most of the decomposition processes occur

Biodiversity

The flora and fauna present in the lentic ecosystems, is distributed in a stratified way. Based on this, the following classification has been given mainly associated with fauna:

Plankton

They are the organisms that live suspended. They have no means of locomotion or are poorly developed. They move associated with the movements of the currents. They are generally microscopic.

Phytoplankton is made up of photosynthetic organisms, mainly algae. Cyanobacteria, diatoms, Euglena and various species of the Chlorophyaceae stand out.

Within zooplankton, various protozoa, coelenterates, rotifers, and numerous crustaceans (cladocerans, copepods, and ostracods) are common.

Necton

Refers to free-swimming organisms. They can travel long distances, even against the current. They present efficient locomotion structures.

There is a diversity of species of amphibians, turtles and fish. In addition, insects are common in both larval and adult forms. Similarly, there are abundant crustaceans.

Benthos

They are located embedded or perched at the bottom of bodies of water. They make up a varied fauna. Among these we have ciliates, rotifers, ostracods and amphipods.

Insect larvae from groups such as Lepidoptera, Coleoptera, Diptera and Odonata are also frequent. Other groups are mites and mollusk species.

Neuston

This group of organisms is located at the water-atmosphere interface. There are large numbers of arachnids, protozoa, and bacteria. Insects spend at least one phase of their life in this area.

Angiosperms

The plants are located in the littoral and sub-littoral zone. They form a continuum from emerging, floating, to submerged. Emerging plants include Typha, Limnocharis and Sparganium species.

Floating plant groups are abundant. Among the most common genera we find Nuphar and Nymphaea (water lilies). Eichhornia and Ludwigia species are also present.

Subsequently, the fully submerged plants are located. We can highlight species of Cabomba, Ceratophyllum, Najas and Potamogeton, among others.

Geographic location

The diversity of geophysical phenomena that give rise to lakes, ponds and ponds, determines that these ecosystems are widely distributed on the planet.

Lentic ecosystems are located from sea level to altitudes above 4000 meters above sea level. We find them at various latitudes and longitudes on the earth's surface. The highest navigable lake is Titicaca at 3,812 meters above sea level.

From Lake Vostok in Antarctica, with its diversity of life under a layer of 4 km of ice, passing through the area of ​​the Great Lakes in North America with Lake Superior at the head, Lake Maracaibo and Titicaca in South America, Lake Victoria, Tanganyika and Chad in Africa, Alpine lakes in Europe, the Caspian Sea between Europe and Asia, to the Aral Sea and Lake Baikal in Asia.

On the other hand, human beings also create huge artificial lakes, by creating dams for the purpose of generating electricity and providing water for consumption.

For example, we have the gigantic Three Gorges dam of the Yangtze River in China, the Itaipu dam between Brazil and Paraguay or the Gurí dam in Venezuela.

Threats

Lentic ecosystems are part of the Earth's wetland system. Wetlands are protected by international conventions such as the Ramsar Convention (1971).

The various lentic ecosystems are an important source of fresh water and food. On the other hand, they play a relevant role in biogeochemical cycles and in the planetary climate.

However, these ecosystems are under serious threats, mainly due to anthropic activities. Global warming and deforestation of large basins is leading to the drying out and sedimentation of many lakes.

According to the World Water Council, more than half of the world's lakes and freshwater reserves are threatened. The most threatened are the shallower lakes located near regions of intensive agriculture and industrial development.

The Aral Sea and Lake Chad have been reduced to 10% of their original length. Lake Baikal is seriously affected by industrial activity on its shores.

More than 200 species of fish from Lake Victoria have disappeared due to the introduction of the 'Nile perch' for fisheries. Lake Superior, in the Great Lakes area between the US and Canada, is also affected by its native fauna due to the introduction of exotic species.

The contamination of Titicaca has made 80% of the population of the endemic giant frog disappear from this lake.

References

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