Eutrophication of Water Bodies

The eutrophication of a water body is a dynamic process in which various nutrients are introduced into the water. This can occur through direct input from the surrounding environment, the leaching of pollutants from the air, or the deposition of dust and biomass. Hydrobiological research has identified nitrogen and phosphorus as the two primary nutrients responsible for most eutrophication processes. In systems with high carbon dioxide content, phosphorus plays a dominant role, whereas nitrogen is particularly significant in coastal areas and estuaries.

These nutrients accumulate in the water body and are absorbed by aquatic organisms and sediments, leading to complex interactions. Two main groups of aquatic organisms are involved in eutrophication: rooted aquatic plants, such as reeds and yarrow, and floating single-celled algae, known as phytoplankton. Phytoplankton, in particular, has a significant impact on water quality, as it reduces water transparency and makes the water appear cloudy.

Some of the biomass produced by phytoplankton is not fully decomposed and sinks to the bottom of the water body, forming a layer of organic sediment. Over time, this leads to the silting of the water body. In addition to nutrient concentrations, other physical and chemical parameters also influence eutrophication. One critical factor is the fluctuation of dissolved oxygen levels in eutrophic waters, which can vary significantly between day and night, sometimes leading to anoxic conditions in deeper areas.

Eutrophication also alters the composition of species within the water body. Some species disappear, while others that are better adapted to the changed conditions proliferate. For example, chironomid midges (Chironomidae) often dominate in the sediments of eutrophic lakes, while a different chironomid subgenus (Tanytarsus) prevails in oligotrophic lakes.