Oxygen depletion, or hypoxia, is a common effect of eutrophication in water. The direct effects of hypoxia include fish kills, especially the death of fish that need high levels of dissolved oxygen. Changes in fish communities may have an impact on the whole aquatic ecosystem and may deplete fish stocks.

Eutrophication sets off a chain reaction in the ecosystem, starting with an overabundance of algae and plants. The excess algae and plant matter eventually decompose, producing large amounts of carbon dioxide. This lowers the pH of seawater, a process known as ocean acidification.

We do know that eutrophication diminishes the ability of coastal ecosystems to provide valuable ecosystem services such as tourism, recreation, the provision of fish and shellfish for local communities, sportfishing, and commercial fisheries.

“Eutrophication is an enrichment of water by nutrient salts that causes structural changes to the ecosystem such as: increased production of algae and aquatic plants, depletion of fish species, general deterioration of water quality and other effects that reduce and preclude use”.

How does eutrophication cause fish kills? One of the negative impacts of eutrophication and increased algal growth is a loss of available oxygen, known as anoxia. As a result, eutrophication can quickly remove much of the oxygen from a lake, leading to an anoxic — and lethal — underwater environment.

If the soil is rich in phosphorus, it can lead to eutrophication and severely damage the ecosystem in and around the water body. When sewage pipes and industrial wastes are directed to water bodies, the nutrients present in the sewage and other wastes increase the rate at which eutrophication occurs.

It is the process in which excessive growth of algae (algal bloom) occurs as a result of extra loading of nutrients (nitrates ans phophates) in the water body. Eutrophication leads to depletion of dessolved oxygen in water resulting in killing of aquatic organisms.

Eutrophication, the gradual increase in the concentration of phosphorus, nitrogen, and other plant nutrients in an aging aquatic ecosystem such as a lake. The productivity or fertility of such an ecosystem naturally increases as the amount of organic material that can be broken down into nutrients increases.

There are two types of eutrophication: natural and cultural. Furthermore, there are two types of sources for the nutrients and sedimentary materials: point and nonpoint.

Nitrates and phosphates, especially from lawn fertilizers, run off the land into rivers and lakes, promoting the growth of algae and other plant life, which take oxygen from the water, causing the death of fish and mollusks. Cow manure, agricultural fertilizer, detergents, and human waste are often to blame as well.

In principle, eutrophication is reversible, but from the perspective of a human lifetime, lake eutrophication can appear to be permanent unless there are substantial changes in soil management.

With eutrophication, excessive nutrients encourage the rapid growth of algae and plants. The resulting increase in photosynthesis uses up dissolved inorganic carbon and increases pH to extreme alkaline levels. As more and more algae grown, the lack of oxygen reduces biodiversity, causing plants and animals to die.

Humans can speed up the process of eutrophication by adding excess nutrients and sediment quickly, where the lake will change trophic states in a matter of decades. The additional nutrients cause algal blooms, additional plant growth and overall poor water quality, making the lake less suitable for recreation.

A common method for measuring this parameter is a Secchi disk. The disc is being lowered into the water and the depth at which the disc is no longer visible, is a measure of the clarity of the water. The chlorophyll a (Chl a) concentration is a measure for the amount of algae in the water column.

The most common nutrients causing eutrophication are nitrogen N and phosphorus P. The main source of nitrogen pollutants is run-off from agricultural land, whereas most phosphorus pollution comes from households and industry, including phosphorus-based detergents.

Eutrophication was recognized as a water pollution problem in European and North American lakes and reservoirs in the mid-20th century. Since then, it has become more widespread.

WHAT IS EUTROPHICATION? Algae grow in the sea sustained by nutrients and light. But, when there are too much nutrients in the water (nitrates and phosphates), the algae overgrow and disturbs the marine environment. This enhanced growth of algae phenomenon is called eutrophication.

Fertilizer

Eutrophication is a natural process that results from accumulation of nutrients in lakes or other bodies of water.