Eutrophication

Eutrophication or nutrient input ( rare nutrient enrichment ) is a term used in ecology. It generally refers to the accumulation of nutrients in an ecosystem or ecosystem part, such as the Trophiesystem of waters.

In waters but is understood to eutrophication usually exceeding the cheapest food supply ( the eutrophication ), ie the undesired increase in nutrients in the water. Thus, a useless or harmful plant growth is connected, for example, the undesirable proliferation of certain plant species ( eg algae) and consequent disturbance of the ecological balance.

In this sense, Eutrophication means an over-fertilization and over-nutrition of plants and other photosynthetic organisms ( cyanobacteria, algae ), especially of aquatic plants. In the strict sense is understood to eutrophication caused by man increasing the nutrient supply, particularly of nitrate and phosphate in the aquatic environment. This is done by the influx of nutrients from waste water or by the entry from intensively fertilized agricultural land. Eutrophication in an increase in primary production result, this follows on strong eutrophication high oxygen depletion in the water.

Natural eutrophication

Eutrophication is a natural process in rather rare cases. Thus, increased access nutrients in the lake during the sedimentation of a lake. In the past, the nutrient input increased by climatic changes, such as in Scandinavian lakes after the retreat of the glaciers at the end of the last ice age.

Anthropogenic eutrophication

Today, under eutrophication is mainly understood by phosphate mostly caused by humans ( anthropogenic ) supply. The phosphates from waste waters and reach the bottom entry of agricultural fertilization by precipitation into water. The increased phosphate input leads primarily to increased crop production. The effect is in lakes than in rivers, as in the latter, the nutrients are washed out much faster. Following the plant biomass and the biomass of consumers and decomposers increases. This will also increase the amount of organic material that sinks to the bottom ( sedimentation ). In this area ( profundal ) rises through the microbial degradation of organic matter, oxygen consumption ( oxygen consumption ). Decreases the concentration of oxygen in the water below 1 mg / l, an additional phosphate release from the sediment occurs ( phosphate mobilization). This leads to self-reinforcement of the eutrophication. At the waters edge ( Litoral) eutrophication also causes a change in the growing plant communities here.

In flowing waters eutrophication also leads to an increase in production. Here proliferate in mountain streams especially the epilithischen algae, aquatic macrophytes in larger, leading to so-called weeds. Add pent-up rivers particularly phytoplankton, resulting in the " algae " growing. It also leads to a shift in species composition.