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  • Eutrophication is the process of enrichment of an aquatic system by addition of nutrients.
  • The addition of nutrients can be due to man-made as well as natural factors.
  • Natural factors include leaching of rock phosphates, increase in organic matter derived from plants and animals, etc.
  • Man-made activities include discharge of nutrient-rich water from agricultural lands to water bodies, discharge of untreated industrial wastewater into water bodies, etc.

Cultural Eutrophication

  • Eutrophication is a naturally occurring and slow process. However, when it is accelerated by human activities, it is called as, ‘Cultural Eutrophication’; it can lead to the premature ageing and death of a water body.                          EUTROPHICATION AND ITS CONSEQUENCES
  • In other words, it refers to an increase in the rate of eutrophication due to human activities.
  • Human activities such as addition of fertiliser-mixed water into water bodies, discharge of untreated industrial wastewater into water bodies, levelling of land which increases rate and direction of flow of water, etc., speed-up the natural eutrophication process.

Consequences of Eutrophication

Primary Consequences

Growth of algal blooms

  • Growth of algae on the surface of water body symbolises eutrophication.
  • Algal bloom results in the change of colour of a water body. Depending upon the colour of algae, algal blooms in the water body can be red, brown, green or reddish-orange.
  • Most algal blooms are not harmful in themselves but some produce toxins which enter the food web.
  • These toxins may be consumed by humans as well. Some of these toxins are neurotoxins which have an effect on the nervous system.
  • The algal blooms which produce harmful toxins are called Harmful Algal Blooms (HAB).
  • The HAB can have a significant detrimental effect on an aquatic ecosystem, because algae are primary producers, and many aquatic species are dependent on them for food.

Red tide

  • ‘Red tide’ is the common term for algal blooms. Algal blooms convert discoloured water body into red, brown, green, etc.
  • The word ‘red tide’ is a misnomer because algal blooms can be of some other colour as well.
  • Even the word ‘tide’ is misnomer because algal blooms are not tides.                    EUTROPHICATION AND ITS CONSEQUENCES

Secondary Consequences

  • Algal blooms restrict penetration of sunlight in a water body. As a result, many plant species are unable to carry out photosynthesis, thus leading to their death.
  • Lack of photosynthesis leads to reduction in oxygen levels in a water body and causes death of aquatic animals.
  • Bacteria grow on dead bodies of plants and animals to undertake decomposition of dead organic matter.
  • The remaining oxygen in the water body is consumed by bacteria leading to further death of aquatic animals.
  • Anaerobic conditions promote growth of certain bacteria such as Clostridium botulinum, etc., which produce deadly toxins.


Environment & Biodiversity

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