Skip to main content
Select Source:

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 ]

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Eutrophication." UXL Encyclopedia of Science. . Encyclopedia.com. 19 Oct. 2018 <http://www.encyclopedia.com>.

"Eutrophication." UXL Encyclopedia of Science. . Encyclopedia.com. (October 19, 2018). http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/eutrophication-1

"Eutrophication." UXL Encyclopedia of Science. . Retrieved October 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/eutrophication-1

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

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.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"eutrophication." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 19 Oct. 2018 <http://www.encyclopedia.com>.

"eutrophication." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (October 19, 2018). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/eutrophication

"eutrophication." The Columbia Encyclopedia, 6th ed.. . Retrieved October 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/eutrophication

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

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.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"eutrophication." A Dictionary of Ecology. . Encyclopedia.com. 19 Oct. 2018 <http://www.encyclopedia.com>.

"eutrophication." A Dictionary of Ecology. . Encyclopedia.com. (October 19, 2018). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/eutrophication

"eutrophication." A Dictionary of Ecology. . Retrieved October 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/eutrophication

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

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.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"eutrophication." A Dictionary of Plant Sciences. . Encyclopedia.com. 19 Oct. 2018 <http://www.encyclopedia.com>.

"eutrophication." A Dictionary of Plant Sciences. . Encyclopedia.com. (October 19, 2018). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/eutrophication-0

"eutrophication." A Dictionary of Plant Sciences. . Retrieved October 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/eutrophication-0

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

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.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"eutrophication." World Encyclopedia. . Encyclopedia.com. 19 Oct. 2018 <http://www.encyclopedia.com>.

"eutrophication." World Encyclopedia. . Encyclopedia.com. (October 19, 2018). http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/eutrophication

"eutrophication." World Encyclopedia. . Retrieved October 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/eutrophication

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

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.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"eutrophication." A Dictionary of Zoology. . Encyclopedia.com. 19 Oct. 2018 <http://www.encyclopedia.com>.

"eutrophication." A Dictionary of Zoology. . Encyclopedia.com. (October 19, 2018). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/eutrophication-1

"eutrophication." A Dictionary of Zoology. . Retrieved October 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/eutrophication-1

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

Eutrophication

Eutrophication

The process by which a body of water becomes overly productive is called eutrophication. The major factors controlling eutrophication, which in Greek means well nourished, are nutrient input, light and

temperature. All three of these factors are required for the increased growth rates of phytoplankton that lead to eutrophication. Bodies of water with factors that limit plant growth are called oligotrophic. Those with intermediate levels of biological productivity are called mesotrophic. Eutrophication may occur in freshwater or marine environments.

Water bodies around developed areas experience cultural eutrophication, or an accelerated rate of plant growth, because additional nitrates and phosphates that encourage plant growth flow into the water from human activities. Fertilizers, soil erosion, and animal wastes may run off from agricultural lands, while detergents, sewage wastes, fertilizers, and construction wastes are contributed from urban areas. These nutrients stimulate the excessive growth of planktonic algae. Eventually these plants die and fall to the bottom, where decomposers use the available oxygen in the process of breaking down the plant material. With accelerated plant growth and subsequent death, these decomposers consume greater amounts of available oxygen in the water. Animal species such as fish and mollusks are harmed by low concentrations of oxygen in the water. The water also becomes less clear as the concentration of algae and bacteria increases. Native species may eventually be replaced by those tolerant of pollution and lower oxygen levels, such as worms and carp.

While at least one-third of the mid-sized or larger lakes in the United States have suffered from cultural eutrophication at one time or another over the past 40 years, Lake Erie is the most publicized example of excessive eutrophication. Called a dead lake in the 1960s, the smallest and shallowest of the five Great Lakes was inundated with nutrients from heavily developed agricultural and urban lands surrounding it for most of the twentieth century. 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. Pollution controls for sewage treatment plants and improved agricultural restrictions by Canada and the United States led to drastic reductions in the amount of nutrients entering the lake. By the turn of the millennium, Lake Erie had again become a biologically thriving lake. Recreational swimming, fishing, and boating were again strong components of the regions economy and aesthetic benefits.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Eutrophication." The Gale Encyclopedia of Science. . Encyclopedia.com. 19 Oct. 2018 <http://www.encyclopedia.com>.

"Eutrophication." The Gale Encyclopedia of Science. . Encyclopedia.com. (October 19, 2018). http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/eutrophication

"Eutrophication." The Gale Encyclopedia of Science. . Retrieved October 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/eutrophication

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

Eutrophication

Eutrophication

The process of heightened biological productivity in a body of water is call eutrophication. The major factors controlling eutrophication in a body of water, whether large, small, warm, cold, fast-moving, or quiescent, are nutrient input and rates of primary production. Not all lakes experience eutrophication. Warmth and light increase eutrophication, (which in Greek means "well nourished") if nutrient input is high enough. Cold dark lakes may be high in nutrients , but if rates of primary production are low, eutrophication does not occur. Lakes with factors that limit plant growth are called oligotrophic. Lakes with intermediate levels of biological productivity are called mesotrophic.

Many lakes around developed areas experience cultural eutrophication, or an accelerated rate of plant growth, because additional nitrates and phosphates (which encourage plant growth) flow into the lakes from human activities. Fertilizers , soil erosion and animal wastes may run off from agricultural lands, while detergents, sewage wastes, fertilizers, and construction wastes are contributed from urban areas. These nutrients stimulate the excessive growth of green plants, including algae . Eventually these plants die and fall to the bottom of the lake , where decomposer organisms use the available oxygen to consume the decaying plants. With accelerated plant growth and subsequent death, these decomposers consume greater amounts of available oxygen in the water; other species such as fish and mollusks thus are affected. The water also becomes less clear as heightened levels of chlorophyll are released from the decaying plants. Native species may eventually be replaced by those tolerant of pollution and lower oxygen levels, such as worms and carp .

While at least one-third of the mid-sized or larger lakes in the United States have suffered from cultural eutrophication at one time or another over the past 40 years, Lake Erie is the most publicized example of excessive eutrophication. Called a "dead" lake in the 1960s, the smallest and shallowest of the five Great Lakes was inundated with nutrients from heavily developed agricultural and urban lands surrounding it for most of the twentieth century. 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 Canada and the United States led to drastic reductions in the amount of nutrients entering the lake. Almost forty years later, while still not totally free of pollutants and nutrients, Lake Erie is a biologically thriving lake, and recreational swimming, fishing, and boating are strong components of the region's economy and aesthetic benefits.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Eutrophication." The Gale Encyclopedia of Science. . Encyclopedia.com. 19 Oct. 2018 <http://www.encyclopedia.com>.

"Eutrophication." The Gale Encyclopedia of Science. . Encyclopedia.com. (October 19, 2018). http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/eutrophication-0

"Eutrophication." The Gale Encyclopedia of Science. . Retrieved October 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/eutrophication-0

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

Eutrophication

Eutrophication


Eutrophication is a natural process that occurs in an aging lake or pond as it gradually builds up its concentration of plant nutrients. Cultural or artificial eutrophication occurs when human activity introduces increased amounts of these nutrients. These speed up plant growth and eventually choke the lake of all of its animal life.

In nature, eutrophication is 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 fresh water change in terms of how productive or fertile they are. While this is different for each lake or pond, those that are 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 from too much of a good thing.

HUMANS INCREASE RATE OF EUTROPHICATION

Artificial or cultural eutrophication has become so common, that the word eutrophication by itself has come to mean this harmful acceleration of nutrients. 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 by photosynthesis (using sunlight to make food from simple chemicals). As plants begin to grow explosively and algae "blooms," two harmful things occur, both involving oxygen. First, the fast-growing plants and algae consume more oxygen than usual. Algae consume oxygen even at night. This in itself is not that harmful, but when combined with the second effect, it sometimes has a fatal result on the body of water. All algae eventually die, and when they do, oxygen is required by bacteria in order for them to decompose this dead material and break it down. A cycle then begins in which more bacteria decompose more dead algae (consuming more oxygen). The bacteria then release more phosphates back into the water. These phosphates feed more algae.

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 can also 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 alsoAlgae; Bacteria; Pollution ]

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Eutrophication." U*X*L Complete Life Science Resource. . Encyclopedia.com. 19 Oct. 2018 <http://www.encyclopedia.com>.

"Eutrophication." U*X*L Complete Life Science Resource. . Encyclopedia.com. (October 19, 2018). http://www.encyclopedia.com/social-sciences/applied-and-social-sciences-magazines/eutrophication

"Eutrophication." U*X*L Complete Life Science Resource. . Retrieved October 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/social-sciences/applied-and-social-sciences-magazines/eutrophication

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

Eutrophication

Eutrophication

Eutrophication is a process in which a body of water changes with time as deposits of nutrients and sediments (particles of sand, silt, and clay) from the surrounding area accumulate.

The process of eutrophication

In euthrophication, the chemical characteristics of the water changes. The biology of the water, in terms of the types of organisms that can live in that water body, also changes. Eutrophication involves an increase in the level of plants' food sources in the water. Younger water bodies that have lower levels of nutrients do not support much life. As the nutrients increase, more life can develop in the water. Indeed, the word eutrophic comes from the Greek word eu meaning "well" and trophic, meaning "feeding." The term eutrophic, therefore, literally means "well nourished." At the other end of the scale is an overgrowth of plants including the microscopic chlorophyll-containing algae, which will rob the lake of oxygen and cause the deaths of animals and other aquatic life.

Consequences of eutrophication

While eutrophication is a natural process that occurs over thousands of years, it has become associated with what can happen to water when human activities alter the water composition. This form of eutrophication has sometimes been called cultural eutrophication.

The human-made form of eutrophication occurs when food sources for plants and microorganisms find their way into the water. Fertilizer, cleaning detergents, and other human products contains compounds such as phosphorus, nitrogen, and carbon that cause the growth of plants and specifically of algae. Rain washes these compounds off of farm fields, lawns, golf courses, roads, and parks into stream, rivers, ponds, lakes, and ocean waters.

Eutrophication that is artificially accelerated, mainly because of the addition of fertilizer from agricultural run-off and home-owner's lawns and other chemicals from paved surfaces such as parking lots, can destroy the recreational quality of a lake for people. A formerly beautiful lake can become a smelly dead zone.

In the 1970s and 1980s in a benchmark series of studies that has set the standard for the discipline, Canadian scientists studied the effects on the controlled addition of various fertilizers to a series of small lakes. Because the lakes were isolated, the scientists were able to study what affect each fertilizer had on the health of the lake. These studies demonstrated that, among the various compounds that were added to test sections of lakes, phosphorus was the key chemical that drove the eutrophication process. One lake was split in half by a plastic divider. Carbon and nitrogen were added to one half of the lake and carbon, nitrogen, and phosphorus were added to the other half. The half that received phosphorus developed huge numbers of a type of microorganism called blue-green algae. This rapid and huge increase in numbers of algae is called an algal bloom. The resulting algal bloom used much of the available oxygen in the water, causing the death of fish and other creatures that depend on oxygen for survival. This experiment was key in convincing people around the world that the addition of phosphorus compounds to water was a problem. Later, laws were enacted in Canada that banned the use of most phosphorus compounds in laundry detergent (phosphorus was initially added to laundry detergent to add softness to clothes). As well, these studies have helped drive the creation of environmental regulations elsewhere.

Another source of nitrogen and phosphorus is sewage. In many large cities throughout the world, millions of gallons of raw sewage are still pumped into local waters every day. Whether rain-washed or flushed, nitrogen and phosphorus compounds entering a water body can be used as a source of food by microorganisms in the water, in particular algae.

Gulf of Mexico

In the Gulf of Mexico eutrophication has occurred on a vast scale. The eutrophic "dead zone," an area where the oxygen content in the water is too low to support many fish and plants that normally live in the Gulf, extends along the coasts of Louisiana and Texas for hundreds of miles (kilometers). The zone grows larger in the summer months as the tropical waters become warmer, and shrinks in the fall as the water temperature cools. The excess nutrients are deposited by the waters that flow into the Gulf of Mexico from the Mississippi River, and large oxygen-depleting algal blooms are the result.

Surveys have shown that the eutrophic area during summer months is about 6,950 square miles (18,000 square kilometers), or about the size of New Jersey. The fishing industry along the Gulf that normally brings in over $26 billion dollars worth of shrimp, crab, and fish each year has felt an impact of the dead zone. Fishing fleets are forced to travel farther out to sea for their catch, around or past the barren area.

A number of government organizations including the U.S. Environmental Protection Agency are working to understand the causes of the Gulf eutrophication and to lessen the damage. This task is challenging as the Mississippi River delivers water from a large portion of the central United States, and the Mississippi River basin contains over half of all U.S. farms. Controlling the nutrients entering the Mississippi will be a multi-state effort between federal, state, and local governments.

Effects of eutrophication

The human-made form of eutrophication occurs much faster than natural eutrophication. Instead of a water body changing over thousands of years, a lake undergoing eutrophication as a result of excess runoff (surface water that flows off land) of nitrogen-, phosphorus- and carbon-containing compounds can go from being clean, clear, and home to a variety of life, to a green algae-filled body in only a few years. Reversing the damage from human-made eutrophication in a body of water can be a difficult process. This is especially true in lakes where the replacement of water, as water flows into the lake at one end and flows out at the other, occurs slowly. During the 1960s Lake Erie underwent eutrophication. For over a decade, scientists assumed that the lake might never recover. Fortunately, environmental measures such as reducing the use of detergents that contain phosphorus and careful management of agriculture near the lake has helped restore Lake Erie to health.

Harmful effects of eutrophication are also found in the Chesapeake Bay. The bay, located in Maryland, is a large estuary (area where freshwater meets saltwater). In the 1970s the bay was healthy and home to a wide variety of underwater life. But as massive amounts of nutrients from agricultural and urban activities slowly washed into the bay, the blooms of algae cut off sunlight and reduced the oxygen in the water. As a result, animal life in the bay, such as the famous Maryland crabs, are reducing in numbers. Citizen groups and government agencies are joining forces to restore the water quality of the Chesapeake bay by reducing the amount of sediments and nutrients that are introduced into the bay, and by protecting the nearby forests and wetlands that serve as natural filters for contaminants. Their joint goal is to restore the Chesapeake water quality to a level that will sustain its natural plant and animal inhabitants by the year 2010.

Brian Hoyle, Ph.D.

For More Information

Books

Dennis, Jerry. The Living Great Lakes: Searching for the Heart of the Inland Seas. New York: Thomas Dunne Books, 2003.

National Research Council. Clean Coastal Waters: Understanding and Reducing the Effects of Nutrient Pollution. Washington: National Academy Press, 2000.

Websites

"Eutrophication (Nutrient Pollution)." University of Manitoba.http://www.umanitoba.ca/institutes/fisheries/eutro.html (accessed on September 1, 2004).

"Eutrophication." U.S. Environmental Protection Agency.http://www.epa.gov/maia/html/eutroph.html (accessed on September 1, 2004).

"Tributary Strategies: Charting the Path to a Healthy Bay." Chesapeake Bay Program.http://www.chesapeakebay.net/wqctributarytech.htm (accessed on September 1, 2004).

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Eutrophication." U*X*L Encyclopedia of Water Science. . Encyclopedia.com. 19 Oct. 2018 <http://www.encyclopedia.com>.

"Eutrophication." U*X*L Encyclopedia of Water Science. . Encyclopedia.com. (October 19, 2018). http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/eutrophication-0

"Eutrophication." U*X*L Encyclopedia of Water Science. . Retrieved October 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/eutrophication-0

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.