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Eutrophication

Eutrophication

Eutrophication (pronounced you-tro-fi-KAY-shun) is a natural process that occurs in an aging lake or pond as that body of water gradually builds up its concentration of plant nutrients. Cultural or artificial eutrophication occurs when human activity introduces increased amounts of these nutrients, which speed up plant growth and eventually choke the lake of all of its animal life.

In nature, eutrophication is a common phenomenon in freshwater ecosystems and is really a part of the normal aging process of many lakes and ponds. Some never experience it because of a lack of warmth and light, but many do. Over time, these bodies of freshwater change in terms of how productive or fertile they are. While this is different for each lake or pond, those that are naturally fed rich nutrients from a stream or river or some other natural source are described as "eutrophic," meaning they are nutrient-rich and therefore abundant in plant and animal life. Eutrophication is not necessarily harmful or bad, and the word itself is often translated from the Greek as meaning "well nourished" or "good food." However, eutrophication can be speeded up artificially, and then the lake and its inhabitants eventually suffer as the input of nutrients increases far beyond what the natural capacity of the lake should be.

Words to Know

Algae: Single-celled or multicellular plants or plantlike organisms that contain chlorophyll, thus making their own food by photosynthesis. Algae grow mainly in water.

Nitrate: A salt or ester of nitric acid, which is a transparent corrosive liquid composed of nitrogen, hydrogen, and oxygen.

Phosphate: A salt or ester of a phosphoric acid, which is any of three acids that are formed when the oxide of phosphorus reacts with water.

Too much of a good thing

Natural eutrophication is usually a fairly slow and gradual process, occurring over a period of many centuries. It occurs naturally when for some reason, production and consumption within the lake do not cancel each other out and the lake slowly becomes overfertilized. While not rare in nature, it does not happen frequently or quickly. However, artificial or human-caused eutrophication has become so common that the word eutrophication by itself has come to mean a very harmful increase and acceleration of nutrients. It is as if something receives too much fertilizer or has too much of what is a good thing.

Humans increase the rate of eutrophication

Human activities almost always result in the creation of waste, and many of these waste products often contain nitrates and phosphates. Nitrates are a compound of nitrogen, and most are produced by bacteria. Phosphates are phosphorous compounds. Both nitrates and phosphates are absorbed by plants and are needed for growth. However, the human use of detergents and chemical fertilizers has greatly increased the amount of nitrates and phosphates that are washed into our lakes and ponds. When this occurs in a sufficient quantity, they act like fertilizer for plants and algae and speed up their rate of growth.

Algae are a group of plantlike organisms that live in water and can make their own food through photosynthesis (using sunlight to make food from simple chemicals). When additional phosphates are added to a body of water, the plants begin to grow explosively and algae takes off or "blooms." In the process, the plants and algae consume greater amounts of oxygen in the water, robbing fish and other species of necessary oxygen.

All algae eventually die, and when they do, oxygen is required by bacteria in order for them to decompose or break down the dead algae. A cycle then begins in which more bacteria decompose more dead algae,

consuming even more oxygen in the process. The bacteria then release more phosphates back into the water, which feed more algae. As levels of oxygen in the body of water become lower, species such as fish and mollusks literally suffocate to death.

Eventually, the lake or pond begins to fill in and starts to be choked with plant growth. As the plants die and turn to sediment that sinks, the lake bottom starts to rise. The waters grow shallower and finally the body of water is filled completely and disappears. This also can happen to wetlands, which are already shallow. Eventually, there are shrubs growing where a body of water used to be.

In the 1960s and 1970s, Lake Erie was the most publicized example of eutrophication. Called a "dead lake," the smallest and shallowest of the five Great Lakes was swamped for decades with nutrients from heavily developed agricultural and urban lands. As a result, plant and algae growth choked out most other species living in the lake, and left the beaches unusable due to the smell of decaying algae that washed up on the shores. New pollution controls for sewage treatment plants and agricultural methods by the United States and Canada led to drastic reductions in the amount of nutrients entering the lake. Forty years later, while still not totally free of pollutants and nutrients, Lake Erie is again a biologically thriving lake.

[See also Lake ]

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eutrophication

eutrophication (yōōtrō´fĬkā´shən), aging of a lake by biological enrichment of its water. In a young lake the water is cold and clear, supporting little life. With time, streams draining into the lake introduce nutrients such as nitrogen and phosphorus, which encourage the growth of aquatic organisms. As the lake's fertility increases, plant and animal life burgeons, and organic remains begin to be deposited on the lake bottom. Over the centuries, as silt and organic debris pile up, the lake grows shallower and warmer, with warm-water organisms supplanting those that thrive in a cold environment. Marsh plants take root in the shallows and begin to fill in the original lake basin. Eventually the lake gives way to bog, finally disappearing into land. Depending on climate, size of the lake, and other factors, the natural aging of a lake may span thousands of years. However, pollutants from man's activities can radically accelerate the aging process. During the past century, lakes in many parts of the earth have been severely eutrophied by sewage and agricultural and industrial wastes (see water pollution). The prime contaminants are nitrates and phosphates, which act as plant nutrients. They overstimulate the growth of algae, causing unsightly scum and unpleasant odors, and robbing the water of dissolved oxygen vital to other aquatic life. At the same time, other pollutants flowing into a lake may poison whole populations of fish, whose decomposing remains further deplete the water's dissolved oxygen content. In such fashion, a lake can literally choke to death.

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eutrophication

eutrophication The process of nutrient enrichment (usually by nitrates and phosphates) in aquatic ecosystems, such that the productivity of the system ceases to be limited by the availability of nutrients. It occurs naturally over geological time, but may be accelerated by human activities (e.g. sewage disposal or land drainage): such activities are sometimes termed ‘cultural eutrophication’. The rapid increase in nutrient levels stimulates algal blooms. On death, bacterial decomposition of the excess algae may deplete oxygen levels seriously. This is especially critical in thermally stratified lakes, since the decaying algal material typically sinks to the hypolimnion where, in the short term, oxygen replenishment is impossible. The extremely low oxygen concentrations that result may lead to the death of fish, creating a further oxygen demand, and so leading to further deaths.

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"eutrophication." A Dictionary of Ecology. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

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"eutrophication." A Dictionary of Ecology. . Retrieved August 19, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/eutrophication

eutrophication

eutrophication The process of nutrient enrichment in aquatic ecosystems. It occurs naturally over geological time, but may be accelerated by human activities, e.g. sewage disposal, or land drainage: such activities are sometimes termed ‘cultural eutrophication’. The rapid increase in nutrient levels stimulates algal blooms. On death, bacterial decomposition of the excess algae may deplete oxygen levels seriously. This is especially critical in thermally stratified lakes, since the decaying algal material typically sinks to the hypolimnion where, in the short term, oxygen replenishment is impossible. The extremely low oxygen concentrations that result may lead to the death of fish, creating a further oxygen demand, and so leading to further deaths.

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"eutrophication." A Dictionary of Plant Sciences. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

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"eutrophication." A Dictionary of Plant Sciences. . Retrieved August 19, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/eutrophication-0

eutrophication

eutrophication Process by which a stream or lake becomes rich in inorganic nutrients by agricultural run-off or other artificial means. Compounds of nitrogen, phosphorus, iron, sulphur and potassium are vital for plant growth in water; in excess they overstimulate the growth of surface algae or cyanobacteria producing bloom that can consume all available dissolved oxygen with devastating effects on marine life.

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"eutrophication." World Encyclopedia. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

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"eutrophication." World Encyclopedia. . Retrieved August 19, 2017 from Encyclopedia.com: http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/eutrophication

eutrophication

eutrophication The nutrient enrichment (usually by nitrates and phosphates) of an aquatic ecosystem, such that the productivity of the system ceases to be limited by the availability of nutrients. An increase in photosynthetic activity is often followed by a depletion of dissolved oxygen as plants die and are decomposed by aerobic organisms. Deoxygenation has an adverse effect on the aquatic animal life.

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"eutrophication." A Dictionary of Zoology. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

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"eutrophication." A Dictionary of Zoology. . Retrieved August 19, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/eutrophication-1