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Causes, effects and control measures of eutrophication


Date Posted: 2/2/2014 3:40:45 AM

Posted By: Karjosse  Membership Level: Silver  Total Points: 615

Eutrophication is the chemical enrichment of fresh water bodies or aquatic ecosystems with excess or additional nutrients especially inorganic plant nutrients such as nitrates and phosphates from agricultural runoff which finds its way to these water bodies. This enrichment usually causes hypertrophication which is the ecosystems’ response to this addition of nutrients and includes widespread growth of algae causing algal blooms.

Causes of eutrophication:
Eutrophication has several factors that lead to its occurrence in water bodies. These causes can be as a results of human activities (human-induced) as well as natural causes.
Human induced causes involve the occurrence of sewerage which is a collection of wastes. Poor sewerage management leads to untreated sewerage effluents been discharged off to fresh water bodies hence causing eutrophication. Discharge of detergents into water bodies may also cause eutrophication. Detergents are mainly composed of phosphorous hence its discharge in water bodies may be hazardous to life in water.
Secondly, human take part in agricultural activities. They use chemicals and fertilizers in farms which contain nitrogen and phosphorous components. Rainfall causes surface runoff fro these farms which makes these chemicals flashed into water bodies hence leading to algal bloom as the immediate response with adverse effects thereby.
Natural causes involve the accumulation of nutrients in water bodies as they age and also through flowing into the ecosystems on a continuous basis. The nutrients will accumulate until a certain level which is favourable for the eutrophication process and therefore fuel the entire process.
Another major cause of eutrophication could be the atmospheric deposition of nutrients. The atmosphere may contain many harmful nutrients which may be deposited in water bodies causing the widespread of algae hence causing the dramatic effects to the aquatic ecosystem.

Effects of eutrophication:

Eutrophication can be very disastrous but this depends on the magnitude of the deposition of chemicals

and the amount of chemicals that are discharge to the water bodies through runoff. The effects of eutrophication are felt mostly by the aquatic environment.
Eutrophication results in the widespread growth of algae and other simple plants over the complicated plants commonly referred to as algal blooms due to the increase in favourable nutrients. Algae blooms cause foul smelling phytoplankton reducing water clarity hence leading to diminished water quality. The subsequent effect is water pollution which adversely affects the health of living organisms. The reduced water clarity reduces light penetration causing death for the underwater plants that require sunlight for photosynthesis.
Eutrophication causes algae growth which causes assimilation of other nutrients available in water for plants and animals. Algae death cause decomposition which uses oxygen and nutrients contained in water as they are converted to inorganic form by bacteria. The use of oxygen in this process creates a death zone of hypoxic as it causes deficiency in oxygen to deep aquatic organisms which eventually lead to their death.
It also leads to changes in the aquatic community structure. During blooms, zooplanktons dominate plankton's’ communities. Algae produce toxins which are harmful to higher life organisms. This causes the domination of the algae in food chains hence changing the aquatic structure and disrupts normal functioning of the ecosystems.

Mitigation measures of eutrophication:

As well known, eutrophication cause algal blooms and foul smelling phytoplankton therefore, any control of eutrophication should target the reduce or elimination of these factors. Controls therefore include;
i) Restoring shellfish population into the freshwater bodies. The shellfish estuaries remove nitrogen from the water column and filter out suspended solids hence reducing the likelihood of harmful algal blooms or anoxic condition. They also improve water quality by controlling phytoplankton density and sequestering nutrients which can be removed by harvesting the shellfish buried in sediments.
ii) Minimizing and regulation of non-point pollution sources. Though it is hard to manage these sources, control is usually easy. This involves control of phosphorous and other chemicals which favour eutrophication before entering water bodies by intercepting non-point pollution sources before getting into contact with water bodies. This is usually done by creating riparian buffer zones near waterways. This ensures sediments and nutrients are deposited in this buffer instead of in water.
iii) Bio-manipulation which involves alteration of a food web. This involves the use of other form of simple lives other than algae, introducing them to the water bodies so as to feed on the algae and bacteria which cause decomposition of the algae bloom faster hence eliminating the occurrence of eutrophication.
iv) Providing of education about the causes of eutrophication, and the effects on life to the society. Also include raising the awareness about the best measures to put in place to control its effects.
v) Posing of laws that regulate the point sources of wastes. These laws ensure that the disposal of waste products is controlled and contain products that are not harmful. It also ensures that any sewerage systems has been treated to avoid disposal of nitrates and phosphates to water bodies.

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