Eutrophication (Encyclopedia of Environmental Issues, Revised Edition)
From a geologic perspective, lakes are relatively temporary features of a landscape. For example, the Great Lakes were formed over the last two million years by four or more major advances of huge ice sheets. Only relatively recently (about twelve thousand years ago) did these lakes develop into their current shapes.
Most lakes go through a series of trophic (nutrition-related) states that can take thousands of years before the lake basins eventually fill in with sediment. Oligotrophy is the first trophic stage; it is characterized by clear water, low plant productivity because of limited nutrient inputs, and high levels of dissolved oxygen throughout the water column. Crater Lake in Oregon is a good example of an oligotrophic lake. The next stage is mesotrophy, which has moderately clear water and moderate plant productivity and lower levels of oxygen in the hypolimnion, which is the lowest level in a lake. In the third stage, eutrophy, excess nutrients are present, transparency is reduced, algal scums start to appear, and oxygen (which fish need) is not present in the summer in the hypolimnion. Hypereutrophy is the final stage; in this stage algal scums dominate in the summer, few macrophytes (plants that can be seen without magnification) exist, and the hypolimnion is devoid of oxygen.
Anthropogenic (human-caused) changes in lakes result from excessive inputs of sediment, fertilizers (such as nitrates and phosphates), pesticides...
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Further Reading (Encyclopedia of Environmental Issues, Revised Edition)
Cech, Thomas V. Principles of Water Resources: History, Development, Management, and Policy. 3d ed. New York: John Wiley & Sons, 2010.
Cunningham, William P., and Mary Ann Cunningham. Principles of Environmental Science: Inquiry and Applications. 4th ed. New York: McGraw-Hill, 2008.
Gray, N. F. Drinking Water Quality: Problems and Solutions. 2d ed. New York: Cambridge University Press, 2008.
Laws, Edward A. “Cultural Eutrophication: Case Studies.” In Aquatic Pollution: An Introductory Text. 3d ed. New York: John Wiley & Sons, 2000.
North American Lake Management Society and Terrene Institute. Managing Lakes and Reservoirs. Madison, Wisc.: Author, 2001.
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Definition (Encyclopedia of Global Resources)
The word “eutrophic” comes from the Greek eu, which means “good” or “well,” and trophikos, which means “food” or “nutrition.” Eutrophic waters are well nourished and rich in nutrients; they support abundant life. Eutrophication refers to a condition in aquatic systems (ponds, lakes, and streams) in which nutrients are so abundant that plants and algae grow uncontrollably and become a problem. The plants die and decompose, and the water becomes stagnant. This ultimately causes the death of other aquatic animals, particularly fish, that cannot tolerate such conditions. Eutrophication is a major problem in watersheds and waterways such as the Great Lakes and Chesapeake Bay that are surrounded by urban populations.
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Overview (Encyclopedia of Global Resources)
The stagnation that occurs during eutrophication is attributable to the activity of microorganisms growing on the dead and dying plant material in water. As they decompose the plant material, microbes consume oxygen faster than it can be resupplied by the atmosphere. Fish, which need oxygen in the water to breathe, become starved for oxygen and suffocate. In addition, noxious gases such as hydrogen sulfide (H2S) can be released during the decay of the plant material. The hallmark of a eutrophic environment is one that is plant-filled, littered with dead aquatic life, and smelly.
Eutrophication is actually a natural process that occurs as lakes age and fill with sediment, as deltas form, and as rivers seek new channels. The main concern with eutrophication in natural resource conservation is that human activity can accelerate the process and can cause it to occur in previously clean but nutrient-poor water. This is sometimes referred to as “cultural eutrophication.” For example, there is great concern with eutrophication in Lake Tahoe. Much of Lake Tahoe’s appeal is its crystal-clear water. However, development around Lake Tahoe is causing excess nutrients to flow into the lake and damaging the very thing that attracts people to the lake.
The nutrients that cause eutrophication usually come from surface runoff of soil and fertilizer associated with mismanaged agriculture or from domestic and industrial wastes discharged...
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Eutrophication (Encyclopedia of Science)
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.
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