Eutrophication

Eutrophication (from greek. εύτροφος eútrophos, ‚well nourishing‘) is a term from the ecology. This generally leads to the enrichment of Nutrients in a ecosystem or a part thereof. In the narrower sense, the human-induced (anthropogenic) increase in the nutrient content of waters by dissolved nutrients, especially nitrogen and phosphorus^[1], which is usually associated with adverse consequences for the ecology of water bodies and their usability by humans. Eutrophication is therefore based on Nutrient input with Nutrient enrichment in the system. The Duden defines it „as an undesirable increase in nutrients in a body of water and associated useless and harmful plant growth“.

The increase is usually due to the inflow of nutrients from wastewater and through entry out of intensively fertilized agricultural land. Eutrophication of a body of water causes an increase in its Primary production, which increased a Oxygen depletion has the effect of.

Eutrophication of water bodies: definition

The eutrophication of a body of water is not a condition, but a process. Plant nutrients are derived from the catchment area into the body of water, which acts as a natural depression; today, in some cases, airborne input (leaching of air pollutants or dust by rain) is also significant. The input can be in inorganic form, as dissolved nutrient salts, or in the form of biomass. Hydrobiological research has identified two key nutrients that are responsible for almost all eutrophication processes, nitrogen and phosphorus. In lakes and other limnic Systems almost always phosphorus is crucial, while nitrogen is mainly found in marginal seas and estuaries (as well as in terrestrial systems) is significant. The nutrients accumulate in the system. The free water body forms the aquatic organisms and that sediment each consists of nutrient reservoirs between which there are intensive and diverse interrelationships. Among the organisms, the „higher“, usually rooting aquatic plants are, for example reed-Species, aquatic plants such as Waterweed and Water milfoil (the so-called Macrophytes), and the single-celled algae floating in the water, which phytoplankton, to distinguish. In eutrophication, apart from extremely shallow waters, phytoplankton is usually of greater importance for the water condition. The biomass formed by the organisms is usually not completely mineralized, some sinks to the ground and forms a gradually increasing organic sediment layer, which ultimately leads to silting up of a body of water.

The respective condition of the water body is determined by the so-called Trophy system classified. While limnologists distinguished only two classes until the 1950s, oligotroph (low in nutrients) and eutroph (rich in nutrients), further conditions were added later. In particular, beyond the eutrophic class polytrophic and hypertrophic A distinction was made between waters whose nutrient content is even higher than the eutrophic level. While a eutrophic body of water represents the natural final stage of a silting-up shallow body of water and is in principle a natural state, (with rare exceptions) the higher trophic levels no longer occur naturally. Eutrophication is the change in state along the so defined trophy-Axis towards the more nutrient-rich states. A body of water, both naturally and due to remediation measures, can move in the opposite direction along the axis, thus becoming nutrient-poor; this is then called oligotrophication. Only those nutrients that are dissolved or soluble and therefore available to plants are decisive for the condition of the water body. The establishment of phosphate in insoluble minerals or by precipitation of sea chalk in calcareous waters therefore counteracts eutrophication.

When defining eutrophication, many consider Hydrobiologists Not only nutrient levels alone, but also partially take into account their effects in the water body. This is because different water bodies can react very differently to eutrophication processes, despite the same absolute nutrient levels. Eutrophic waters are usually characterized by high phytoplankton stocks, which Algal blooms can train, are severely clouded and have a low Visibility depth. In addition to nutrient levels, other physical and chemical parameters are influenced by the effects of organisms, in particular the content of dissolved oxygen, which in eutrophic waters usually has a pronounced diurnal cycle between supersaturation during the day and oxygen consumption at night. In deep water, where algae growth is not possible due to a lack of light, grazing predominates, so that in deep water and sediment often anoxic Conditions occur. The species composition of living organisms is also shifting, as many species can no longer exist under these conditions, while a few favored species are now prone to mass reproduction. In the sediment of eutrophic lakes, the midges-Genus Chironomus, in oligotrophic the genus Tanytarsus. Many limnologists have included these effects in their respective definitions of eutrophication. In addition to nutrient levels, they depend on other factors such as temperature, light (and thus the depth of the water body), its base content and others.

Source: 

https://de.wikipedia.org/wiki/Eutrophierung
- Anne Jones-Lee & G. Fred Lee: Eutrophication (Excessive Fertilization). In: Jay H. Lehr, Jack Keeley (Editors): Water Encyclopedia: Volume 3, Surface and Agricultural Water. Wiley, Hoboken, NJ, 2005, ISBN 978-0-471-73685-1, pages 107–114.
- Walter Rast, Jeffrey A. Thornton: Trends in eutrophication research and control. Hydrological Processes 10:295–313. doi:10.1002/(SICI)1099-1085(199602)10:2<295::AID-HYP360>3.0.CO;2-F
- Sikko Parma (1980): The history of the eutrophication concept and the eutrophication in the Netherlands. Hydrobiological Bulletin 14: 5–11. PDF download