Many crops rely on the addition of fertilizers to promote rapid growth. Fertilizers usually contain readily soluble nitrogen and phosphorus compounds. The problem is that some of these fertilizers are washed off the land or through the soil to surface water bodies where they can create too much algal growth. Livestock access to rivers and streams can also introduce nutrients as well as cause excessive bank erosion and increase the turbidity (i.e. cloudiness) of the water.
Eutrophicationmeans an increase in chemical nutrients - typically compounds containing nitrogen or phosphorus - in an ecosystem. It may occur on land or in water. The term is however often used to mean the resultant increase in the ecosystem's primary productivity - in other words excessive plant growth and decay - and even further impacts, including lack of oxygen and severe reductions in water quality and in fish and other animal populations.
Eutrophication is frequently a result of nutrient pollution such as the release of sewage effluent and run-off from lawn fertilizers into natural waters. Eutrophication is likely to cause severe reductions in water quality. In aquatic environments aquatic vegetation or phytoplankton causes a variety of problems such as a lack of oxygen in the water, needed for fish and shellfish to survive. The water then becomes cloudy, colored a shade of green, yellow, brown, or red. Human society is impacted as well: eutrophication decreases the resource value of rivers, lakes, and estuaries such that recreation, fishing, hunting, and aesthetic enjoyment are hindered. Health-related problems can occur where eutrophic conditions interfere with drinking water treatment.
An algal bloom or marine bloom or water bloom is a rapid increase in the population of algae in an aquatic system. Algal blooms may occur in freshwater as well as marine environments. Algal bloom concentrations may reach millions of cells per milliliter. Colors observed are green, yellowish-brown, or red. Bright green blooms may also occur. As more algae and plants grow, others die. This dead organic matter becomes food for bacteria that decompose it. With more food available, the bacteria increase in number and use up the dissolved oxygen in the water. When the dissolved oxygen content decreases, many fish and aquatic insects cannot survive. This results in a dead area.
4. Explain the following notions in writing:
fertilizer, eutrophication, runoff, algal bloom.
5. Answer the following comprehension questions in written form:
1. What problem arises from the application of fertilizers?
2. Can eutrophication be a natural process? Where? How does it work?