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Eutrophication in a pond Source
1 Eutrophication is the addition of artificial or natural substances, such as nitrates and phosphates to an aquatic system. These excess minerals and nutrients have negative effects on water quality, and on plant and animal life. Eutrophication can be human-caused or natural. Untreated sewage effluent and agricultural run-off carrying fertilizers are examples of human-caused eutrophication. Eutrophication also occurs naturally in situations where nutrients accumulate, or where nutrients flow into systems temporarily.
Ecological effects
2 Many ecological effects can result from eutrophication, but there are three particularly worrisome ecological impacts: decreased biodiversity, changes in species composition and dominance, and toxicity effects.
Decreased biodiversity
3 When an ecosystem experiences an increase in nutrients, certain species of plants and organisms increase. In aquatic ecosystems, species such as algae experience a population increase (called an algal bloom). Algal blooms limit the sunlight available to bottom-dwelling organisms and cause changes in the amount of oxygen in the water. When oxygen levels are reduced to hypoxic (not enough oxygen in the water) levels, fish and other marine animals die.
New species invasion
4 Eutrophication may cause changes in the variety of species in an ecosystem. For instance, an increase in nitrogen might allow new species to invade and replace original inhabitant species. This has occurred in New England salt marshes.
Toxicity
5 Some algal blooms are toxic to plants and animals. They produce toxic compounds which can make their way up the food chain to other animals and even humans. An example of algal toxins reaching humans is the case of shellfish. Bio-toxins created during algal blooms are eaten by shellfish, which then makes the shellfish toxic. When humans eat these shellfish, they get poisoned.
Effects for Humans
6 In addition to negative environmental effects, eutrophication affects the use of water for recreation, fishing, hunting, and scenic enjoyment. Furthermore, health problems can occur where eutrophic conditions interfere with drinking water treatment. There are strict regulations that control how much nitrate can be in drinking water because nitrates can be converted to highly reactive nitrites by microorganisms in the gut (i.e. the long tube in the body through which food flows). Nitrites are absorbed from the gut and bind to hemoglobin (the pigment in blood that helps to transport oxygen around the body). This reduces the ability of the hemoglobin to carry oxygen. In young babies this can lead to breathing problems, a condition known as “blue baby syndrome”.
Prevention policy
7 Despite the impacts, there are a number of ways to prevent eutrophication from taking place. Cleanup measures can directly remove the excess nutrients such as nitrogen and phosphorus from the water. Creating buffer zones near farms, roads and rivers can also help. These act as filters and cause nutrients and sediments to be deposited there instead of in the aquatic system.
8 Regulating fertilizer use is another prevention measure. By assessing exactly how much fertilizer is needed by crops and other plants, farmers can make sure that they only apply just enough fertilizer. This means that there is no excess to run off into neighboring streams during rain.
9 Waste disposal technology is another factor in eutrophication prevention. Because a major contributor to excess nutrients in water is untreated sewage, it is necessary to provide treatment facilities in highly urbanized areas. The technology to safely and efficiently reuse waste water, should be a main concern for policies regarding eutrophication.
Cyanotic Newborn Source
10 The role of the public is a major factor for the effective prevention of eutrophication. In order for a policy to have any effect, the public must be aware of their contribution to the problem, and ways in which they can reduce their effects. Programs to promote participation in the recycling and elimination of wastes, as well as education on the issue of rational water use are necessary to protect water quality within urbanized areas.
Note:The words in bold are assessed.See Unit 5 Vocabulary The words in italics are in the glossary below.
Glossary
Glossary
Dominance (n) -The dominance of a particular person or thing is the fact that they are more powerful, successful, or important than other people or things.
Dwelling (n) - A dwelling is a place to live in; residence; house; abode.
Marsh (n) - A marsh is a type of wetland, an area of land where water covers ground for long periods of time.
Microorganism (n) - A micro-organism is a very small living thing which you can only see if you use a microscope .
Buffer zone (n) -A buffer zone is an area created to separate opposing forces or groups which belongs to neither of them.
Sediment (n) - A sediment is solid material that is moved and deposited in a new location. Sediment can consist of rocks and minerals, as well as the remains of plants and animals.
Elimination (n) - Elimination is the complete removal or destruction of something.
understanding the text: Skimming & Scanning
understanding the text: Skimming & Scanning
Answer the following questions from Text 2.
1. Run-off from farms which contains fertilizers is an example of eutrophication caused by nature.
True or False?
2. In paragraph 1, the word accumulate means
a. decrease b. build up c. leave d. happen
3. In eutrophication, biodiversity decreases because
a. some plants increase so much that they kill other plants and marine animals.
b. certain marine animals cause other fish and marine animals to increase.
c. bottom-dwelling organisms are depleted due to hypoxic levels.
d. too much sunlight kills off the bottom dwelling organisms
4. Which is not an effect of eutrophication?
a. new species invade an area, killing off original species
b. fish and shellfish can become toxic
c. algal blooms turn hypoxic lakes into salt marshes
d. plants and organisms that live under water die from lack of sunlight
5. Name TWO ways that humans are affected by eutrophication.
_____________
_____________
6. There are rules about nitrates in drinking water because...
a. they are converted to hemoglobin which carries oxygen in the blood
b. they are converted to nitrites which affect the transport of oxygen
c. the gut cannot absorb them resulting in lack of nutrients
d. they cause microorganisms in the gut to increase
7. To reduce agricultural run-off, farmers should be careful about the amount of __________________ they use on their _______________.
(ONE WORD in each gap)
8. Which is NOT a way the general public can prevent eutrophication?
a. recycle
b. use water carefully so there is less waste
c. become educated on the issue
d. move to an urbanized area
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