Eutrophication

Eutrophication is the process where nutrients like phosphorus and nitrogen pile up in a water body, leading to increased growth of plants and algae. This is often due to human activities like farming and industry, which introduce these nutrients into the water. When these plants die, they consume oxygen, leading to a decrease in oxygen available for other aquatic life, resulting in a state called hypoxia. In this article, you will know about meaning and definition of Eutrophication, its types, causes and its effects. To explore more interesting UPSC Environment & Ecology topics of Class 12 and Class 8 like Eutrophication, check out other articles and IAS Notes of IASToppers.   

Table of Content

• What is Eutrophication?
• How does Eutrophication occur?
• Causes of Eutrophication
• Types of Eutrophication
• Effects of Eutrophication
• Existing Mitigation Strategies for Eutrophication
• Suggestions for prevention of Eutrophication
• Conclusion
• FAQs on Eutrophication

What is Eutrophication?

• Eutrophication is the slow, steady build-up of phosphorus, nitrogen, and other plant nutrients essential for plant growth in an aquatic ecosystem such as a lake.
• The term ‘eutrophication’ originates from a Greek word that implies ‘well-fed’ or ‘well-nourished’ (eu: true, trophos: feeding).
• It has also been defined as “nutrient-induced increase in phytoplankton productivity”.

How does Eutrophication occur?

• Eutrophication takes place when there’s a large inflow of organic materials into a water body, such as a lake from domestic waste or runoff from nearby land.
• The increasing human population, rigorous farming practices, and speedy industrial development results in the disposal of household garbage, farming byproducts, industrial wastes, and land runoff into various water bodies.
• This nutrient surge enhances the development of water plants and boosts the population of invertebrates and fish, given the increased availability of food.
• Aerobic bacteria, which require oxygen, break down the organic waste, releasing nutrients and using up the dissolved oxygen in the water. Thus, Eutrophication results in the reduction of dissolved oxygen.
• When more organic matter is introduced into a water body, it leads to a higher level of oxygen consumption and increases nutrient production.
• These nutrients promote an excessive growth of algae and other large water plants like duckweed.
• As plant growth accelerates, some plants die due to the increasing demand for oxygen, leading to oxygen scarcity, or deoxygenation (hypoxia), in the water body.
• This state of the water body is referred to as being eutrophic, and the process is known as eutrophication.

Causes of Eutrophication

Phosphorus and Nitrogen

• Phosphates in detergent, run-offs from industrial/domestic activities, and fertilizers are the primary sources of excess phosphate.
  • With the reduction of phosphate-based detergents in the 1970s, industrial/domestic run-off, sewage, and agriculture have become the main contributors to eutrophication.
• Natural nitrogen fixation, agricultural run-off (from fertilizers and animal wastes), sewage, and atmospheric nitrogen deposition from combustion or animal waste are the main sources of nitrogen.

Man-made Nutrient Pollution Sources

• Agriculture: Animal production or crops
• Urban/suburban: Stormwater run-off from roads and parking lots, excessive fertilizer uses on lawns, municipal sewage treatment plants, and emissions from motor vehicles.
• Industrial: Emissions from air pollution (for instance, electric power plants), wastewater discharges from different industries.
• Nutrient pollution from some air pollution sources may occur independently of the local land uses, due to long-range transport of air pollutants from distant sources.

Types of Eutrophication

Cultural Eutrophication

• Cultural eutrophication is triggered by human activities that introduce excess nutrients into water bodies, causing algal overgrowth.
• Urban development and agricultural practices like use of chemical fertilizers lead to a surge in water-enriching nutrients like phosphates and nitrates.
• The decomposition of these algal blooms depletes oxygen, creating anoxic conditions harmful to marine aerobic organisms.

Natural Eutrophication

• Eutrophication can also occur naturally in lakes due to climate change and geological factors.
• Some water bodies, especially artificial ones, can become less nutrient-rich over time, a process known as meiotrophication.
• The primary difference between cultural and natural eutrophication is their pace, with the natural process occurring on geological timescales.

Effects of Eutrophication

• Boost in Phytoplankton and Change in Aquatic Plants: Eutrophication can lead to a surge in phytoplankton, changing the types and amount of water plants. It can also deplete dissolved oxygen, causing an increase in fish deaths and loss of desirable fish types.
• Loss in Biodiversity: Nutrient overload benefits primary producers like algae, causing their numbers to explode. This is known as an algal bloom. This phenomenon blocks sunlight for bottom marine organisms and causes decrease in oxygen levels in the water, leading to fish and other marine life’s suffocation in severe cases. In extreme anaerobic conditions, growth of bacteria can be too much. Zones where this occurs are known as dead zones.
• Altering pH Levels: High rates of photosynthesis can deplete dissolved inorganic carbon and raise pH levels during the day due to eutrophication. This can impact the survival of aquatic species by interfering with their chemosensory abilities.
• Invasive Species: A sudden abundance of nutrients can give birth to new, competitive species to overrun native species. This was observed in New England salt marshes and common carp in eutrophic areas in Europe and Asia.
• Harmful Algal Blooms (HABs): Some eutrophication-induced algal blooms produce toxins harmful to flora and fauna. These toxins can come into the food chain, causing death in animals and potentially threatening human health. For example, shellfish contaminated with biotoxins during algal blooms can cause food poisoning in humans.
• Dominance of Toxigenic Cyanobacteria: Toxigenic cyanobacteria, which thrive in nutrient-rich, low-light, and high-temperature environments, are the primary phytoplankton associated with HABs. These cyanobacteria can lead to animal and human poisonings and are responsible for unpleasant taste and smell in drinking water.
• Impacts on Aquatic Food Chains: Cyanobacteria are poor quality food for most zooplankton grazers. This impacts the energy transfer efficiency in aquatic food webs.
• Changes in Fish Populations: Eutrophication can also influence fish community structures. Predatory fishes are prevalent in nutrient-poor lakes, whereas nutrient enrichment leads to the dominance of plankton-feeding fish.
• Increased Expenditure and Loss of Income: Eutrophication can increase water treatment costs, can cause losses on commercial and recreational fishing, and decrease tourism due to the deterioration of a water body’s aesthetic appeal. The need to treat turbid water can further increase costs.
• Potential Health Hazards: Eutrophication can lead to an excess of nitrate in drinking water, causing health problems like blue baby syndrome. Moreover, swimming in water contaminated by a harmful algal bloom can lead to skin rashes and respiratory issues.

Existing Mitigation Strategies for Eutrophication

• Diversion of excessive nutrients, modification of nutrient ratios, physical water mixing, shading water bodies, and the use of algaecides and herbicides are some of the Existing Mitigation Strategies.
• While algaecides like copper sulfate can temporarily reduce harmful algal blooms (HABs), they are expensive, do not address the root of the problem, and can pose risks to humans,

Suggestions for prevention of Eutrophication

Below are the Prevention Strategies for Addressing Eutrophication

Tackling Pollution from Sewage

• Since the 1970s, Finland has been implementing phosphorus removal measures to reduce the pollution of rivers and lakes.
• Upgrading sewage treatment plants to perform biological nutrient removal can significantly decrease the release of nitrogen and phosphorus.
• Enforcing regulations on sewage discharge and treatment can led to substantial nutrient reductions in nearby ecosystems.

Reducing Agricultural Nutrient Pollution

To combat eutrophication from agriculture, safe farming practices should be prioritized. These include:

• Efficient Nutrient Management: Fertilizers should be applied in appropriate amounts, at the right time, and through proper methods. Agricultural policy also needs to regulate the use of fertilizers and animal waste, while promoting the collection and recycling of animal waste, which could otherwise leach into groundwater.
• Maintaining Year-Round Ground Cover: Cover crops can prevent erosion and runoff of nutrients even after the growing season.
• Planting Field Buffers: Establishing trees, shrubs, and grasses along field edges can absorb some nutrients before they reach water bodies.
• Practicing Conservation Tillage: Less intensive and less frequent tilling can improve nutrient absorption into the ground.

Riparian buffer zones

• Riparian buffer zones, interfaces between water and land, can filter pollutants and nutrients Creating buffer zones near farms and roads is another possible way to prevent nutrients from traveling too far.

Public Participation

• Public participation is crucial for eutrophication prevention, which requires widespread awareness of the problem and its solutions, including recycling and rational water use.
• Economic incentives for clean water management technologies can encourage pollution prevention.

Cross-agency Cooperation

• Given that water bodies can impact a wide range of people beyond the watershed, cooperation among various organizations is critical to prevent eutrophication.
• In the US, the Chesapeake Bay initiative is a prominent example of inter-state cooperation to prevent eutrophication.

Nitrogen Testing and Modelling

• Nitrogen testing helps farmers optimize fertilizer use, leading to cost savings and pollution reduction.

Promotion of Organic Farming

• Organic farming can significantly reduce harmful nitrate leaching compared to conventional farming, although eutrophication impacts may sometimes be higher from organic production.

Revitalizing Estuarine Shellfish

• To combat estuarine eutrophication, shellfish populations like oysters and mussels need to be restored. Their filter-feeding habits improve water quality by controlling nutrient levels.
• Shellfish restoration projects have been successfully implemented in the US and Sweden.

Seaweed Aquaculture

• Seaweed farming, especially of nutrient-absorbing types like kelp, offers a way to counteract climate change and eutrophication.
• Cultivated seaweeds can absorb harmful elements and improves water quality.

Geo-engineering for Lakes:

• Geo-engineering methods changes phosphorus cycles to achieve desirable ecological outcomes in lakes. This technique uses phosphorus-inactivating substances to prevent algal overgrowth.
• Another method, using alum for chemical phosphorus removal, has proven effective in controlling phosphorus in lakes for several years.

Conclusion

Eutrophication is a critical environmental issue that needs urgent attention. Its impacts not only harm aquatic ecosystems but also human health and economies. Mitigation strategies like efficient nutrient management, sewage treatment upgrades, public participation, and cross-agency cooperation can significantly reduce the problem. However, the collective effort of individuals, industries, and governments is required for effective prevention and control.

Ref: Source-1

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