Eutrophication (Critical Analysis)

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Eutrophication is a process by which a water body gets enriched in dissolved nutrients (mainly Nitrates and Phosphates) that stimulate the growth of aquatic plant life (usually algal bloom) resulting in the depletion of oxygen (hypoxia). 

Factors lead to discharge of nutrients in the waterbody:  

• Fertiliser leaching and runoff: Surface run-off of nutrients from an agricultural field, lawns, golf courses etc. into a water body. 
• Direct Sewage Discharge and Industrial Waste into Water Bodies: Other than adding  nutrients to the water body, the thermal wastewater may also enhance the growth of plants. 
• Concentrated Animal Feeding Operations (CAFOs): they normally discharge high amounts of nutrients (animal feed, faeces and other wastes) that find a way into the water body. 
• Aquaculture: Growing shellfish, fish and plants (without soil) in water containing dissolved nutrients leads to increased fertility of the water body.

Effects of Eutrophication: 

• Degrades water quality: creation of dense blooms of noxious, foul-smelling phytoplankton reduces water clarity and degrades water quality, making it unsafe for consumption. 
• Decreases biodiversity: Algal blooms limit light penetration, reducing growth and causing  die-offs of plants in littoral zones. It increases the Biological Oxygen Demand (BOD) of water and results in suffocation and death of marine organisms leading to formation of ‘Dead Zones’.  
• Invasion of New Species: Eutrophication may cause competitive release by making abundant a normally limiting nutrient. This process causes shifts in the species composition of ecosystems.  Example: water hyacinth and common carp. 
• Loss of waterbody: The excess algae and plant matter eventually decompose. As silt and organic debris pile up, the lake grows shallower, eventually turning into a bog (large mass of floating plants) and finally into marshy land.  
• Ocean acidification: Decomposition of organic matter in the ocean produces large amounts of carbon dioxide. This lowers the pH of seawater and acidification slows the growth of fish and  shellfish and can prevent shell formation in bivalve mollusks.  

Measures to tackle Eutrophication: 

• The quality of water, especially the nutrient composition, should be assessed at regular intervals. 
• Regulations should be brought to mitigate nutrient losses, such as standards, technology requirements, or pollution caps for various sectors. 
• Nutrient reducing actions should be incentivised through exemption in taxes and fees, subsidies, or environmental markets.
• The natural ecosystems that capture and cycle nutrients should be preserved and restored.
• Educational outreach programs to raise awareness and promotion of Composting and Phosphorus free detergents should be undertaken.  

A large number of water bodies especially in urban areas are facing eutrophication. In cognizance to this, the National Green Tribunal has highlighted the need of mapping water bodies on GPS platforms and suggested unique ID for all water bodies existing in Delhi. It directed local bodies and concerned departments to ensure 100% treatment of sewage entering rivers across the country.