Eutrophication: Definition, Causes and Control

Eutrophication UPSC

What is eutrophication?

• Eutrophication meaning: Eutrophication is a process of pollution that occurs when a lake or stream becomes over-rich in plant nutrient, thus leading to overgrowth of algae and other aquatic plants.
• Eutrophication leads to results like harmful algal blooms, dead zones, and fish kills.
• It is more widely known in relation to anthropogenic activities where the artificial introduction of plant nutrients leads to community changes and a deterioration of water quality in many freshwater ecosystems.

यूट्रोफिकेशन: परिभाषा, कारण और नियंत्रण

Causes of eutrophication

• When water bodies are overly enriched with nutrients like nitrogen and phosphorus; algae, plankton, and other simple plant are over grown, thus affecting the life of other marine animals.
• How water become overly enriched with nutrients?
• In plant life, phosphorus is considered as one of the primary limiting factors. Some of the sources of phosphorus are:
  • Fertilizers
  • Untreated sewage
  • Detergents containing phosphorus
  • Industrial discharge of waste.

Eutrophication consequences

• The most visible effect of cultural eutrophication is the creation of dense blooms of foul-smelling phytoplankton that reduce water clarity and harm water quality.
• Algal blooms limit light penetration, reducing growth and causing die-offs of plants in littoral zones while also lowering the success of predators that need light to pursue and catch prey.
• Also, high rates of photosynthesis associated with eutrophication can deplete dissolved inorganic carbon and raise pH to extreme levels during the day.
• When the dense algal blooms eventually die, microbial decomposition severely depletes dissolved oxygen, creating a hypoxic or anoxic ‘dead zone’ lacking sufficient oxygen to support most organisms.
• Furthermore, such hypoxic events are particularly common in marine coastal environments surrounding large, nutrient-rich rivers.
• Hypoxia and anoxia as a result of eutrophication, continue to threaten lucrative commercial and recreational fisheries worldwide.
• If a nutrient deficient water body is suddenly enriched with it, many other competitive species might relocate to the water body and out-compete the original inhabitants of the ecosystem. Example: common carp.

Eutrophication control

• diversion of excess nutrients
• altering nutrient ratios
• physical mixing
• shading water bodies with opaque liners or water-based stains
• application of potent algaecides and herbicides
• biomanipulation: the alteration of a food web to restore ecosystem

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