Eutrophication damages biodiversity and human use of water


Process multiplies quantity of algae in lakes and dams, hindering the passage of light and the dissolution of oxygen


Do you know what eutrophication is? It is a process of algae multiplication , common in bodies of water without as much movement, as lakes and dams. Although it means a large amount of organic matter present in water, it can bring various harms to man and to nature itself. But why?

The great availability of nitrogen (N) and phosphorus (P ) in the water of lakes, dams or ponds provides an environment totally favorable to the large and fast multiplication of algae. When the level of water eutrophication increases from time to time (at large intervals of time), it is considered a natural process . But when it happens in a short period, scientists consider that it is an anthropic cause, that is, occurred by human influence.

Where does it come from?

The study describes that the supply of nitrogen and phosphorus occurs in several ways. It may originate from domestic sewage, where nutrients are found in feces, urine, food waste and detergents. Certain shampoos containing sodium lauryl ether sulfate or sodium lauryl sulfate may also contribute to eutrophication by the fact that they contain sulfate in their composition. It can also come from untreated industrial effluents. In plantations, the pesticides used are rich in nitrogen and phosphorus and provide more nutrients than the plants can absorb – the excess of them ends up being carried to the nearest body of water, through the flow of irrigation water or contamination of groundwater . Livestock also contributes to the dumping of water contaminated with feces and urine from animals and other wastes.


The huge population of algae creates a green curtain on the surface of the body of water, preventing the passage of light . Thus, the bottom plants are unable to photosynthesize and the dissolved oxygen level becomes smaller and smaller, causing the death of many organisms, such as fish, for example. The process of decomposition of organisms also uses oxygen. Then, when this amount of dissolved oxygen can no longer be measured, it is considered that the lake or pond has reached the state of anoxia .

In addition to decreasing numbers and biodiversity of organisms, excessive eutrophication is also responsible for reducing transparency, changing the color and odor of water, producing foul odors, toxic substances from some algae and inability to use water for consumption, recreation, tourism, landscaping, irrigation and hydropower.


Preventive or corrective techniques may be used to control eutrophication. Preventive measures are based on reducing the supply of nutrients to the lake by an external source, controlling urban sewage, treating industrial effluents and reducing the use of pesticides. On the other hand, the corrective ones act on the body of water already eutrofizado, like use of reagents to diminish the availability of phosphorus and harvest of the algae of the surface.

In order not to contribute to the eutrophication of lakes and ponds, feed yourself through organic food , which is not cultivated with fertilizers , and is also healthier. Pay attention to the types of cleaning materials you use in your home, avoiding detergents and giving preference to biodegradable products. Also be concerned with whether the sewage from your neighborhood or city is treated and claim this measure to the public power.

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