Define Eutrophication, Types, Causes, problems, and solutions

Define Eutrophication

Define Eutrophication is the condition of a gradual increase in the concentration of phosphorus, nitrogen, and other plant nutrients in a body of water, which leads to the overgrowth of plants and algae.

Eutrophication is one of the most widespread challenges facing freshwater systems, and it also has a long history concerning water management.

It is a natural process that takes place in various water sources over centuries, but human activity has accelerated the process by increasing the rate of eutrophication and the extent of eutrophication.

The condition arises from the fact that the productivity or fertility of aquatic ecosystems increases due to the increase in organic matter that can be broken down into more easily usable nutrients.

The most prominent effect of the eutrophication of water resources is the formation of blooms of stinky phytoplankton. These microorganisms reduce the clarity of the water and can degrade the quality of the water.

The growth of such flowers interferes with the penetration of light and destroys plant growth in coastal areas.

Eutrophication threatens the ecological stability of the system as nutrient enrichment can interact with certain source conditions, such as the presence of other pollutants and infectious agents.

Eutrophic water resources generally host fewer larger animals such as fish and birds compared to non-eutrophic waters.

The destruction of water quality and the loss of ecological diversity is one of the most damaging consequences of eutrophication. These have realigned the focus of various studies on combating eutrophication.

The nutrient excess in water sources is generally due to runoff from land, which carries products from terrestrial ecosystems to the sources.

For decades, eutrophication was viewed as an irreversible process, but in recent years eutrophication has been reversed in several lakes by both controlling the release of human nutrients and cutting off the nutrient load on the springs.

Like other plants, the growth of algal blooms requires nutrients in certain proportions that differ from natural concentrations.

Eutrophication is an urgent threat as eutrophication affects more than 30% of the world’s lakes and reservoirs.

What are the Causes of Eutrophication?

Natural eutrophication is a natural process that has been part of the ecosystem cycle for centuries. However, the process has been enhanced by human activity which makes the process much faster and has immediate consequences. The main cause of eutrophication is the introduction of a large amount of readily available nutrients into water resources, which increases fertility and the overgrowth of various plants and algae. Some of the factors that improve the eutrophication process by increasing the nutrient content of water resources are:


The use of phosphate and nitrate fertilizers to increase plant productivity is one of the main causes of eutrophication in crops.

Fertilizers used on land near water resources are eventually deposited into water resources during rainfall and other natural processes.

The runoff from different areas eventually reaches lakes, rivers, and oceans and increases the availability of nutrients from water resources.

Because fertilizers contain readily available nutrients, they are absorbed by plankton, algae, and aquatic plants in the aquatic ecosystem.

The photosynthetic activity of the water resource increases, which further increases the concentration of organic matter in the ecosystem.

The increase in the nutrient content leads to the formation of dense growths of algal flowers and plants, which leads to eutrophication.

Concentrated animal feeding

  1. Concentrated animal feeding is an agricultural practice in which large numbers of animals are kept in a certain area for a period of time in order to increase the productivity and quality of the animals.
  2. Millions of tons of manure are produced each year on such farms, which eventually reach all water resources.
  3. Manure mainly contains nitrogen and phosphorus, which are essential components of the algal bloom.
  4. Nitrogen and phosphorus act as limiting factors in algae reproduction, as they occur in the smallest proportion in the sum formula of algae.
  5. The phytoplankton biomass in many ecosystems is limited by the low availability of phosphorus and nitrogen.
  6. However, the release of nitrogen- and phosphorus-rich animal manure into these ecosystems leads to increased production of phytoplankton, which induces eutrophication.

Sewage and Industrial waste Discharge

  1. In many developing countries, domestic sewage, as well as industrial sewage, are discharged into water resources such as lakes, ponds, and rivers.
  2. Wastewater entering from various sources usually contains high levels of chemical nutrients that stimulate the dense growth of algal blooms in these resources.
  3. Wastewater from households and communities has high levels of nitrogen and phosphorus, which have a direct impact on the health of the ecosystem.
  4. Industrial wastewater, even when treated, contains low concentrations of many chemicals. Over time, the continued deposition of such chemicals leads to increased availability of nutrients in the water resource, which eventually leads to eutrophication.

Environmental Factors

  1. Various environmental factors such as temperature, salinity and atmospheric conditions play an essential role in eutrophication, but the exact mechanism of their influence is not yet fully understood.
  2. Algal blooms generally occur between the temperature of 23 ° C and 28 ° C and the salinity of 23% and 28%. Changes in these factors affect the rate of algae growth, especially as temperature increases and salinity decreases.
  3. The concentration of carbon dioxide also affects the growth of cyanobacteria as these microbes can use small amounts of carbon dioxide and become buoyant to stay on the surface of the water and receive sunlight.
  4. The concentration of free carbon dioxide in the water also affects the pH of the water resource and further affects the growth of various microbes.
  5. Growth is also promoted by increasing the light intensity, with 4000 lux being the most favorable intensity.

What are the types of Eutrophication?

Eutrophication can be divided into two types depending on the root cause of the process;

Natural Eutrophication

  • Natural eutrophication is a process that occurs through the gradual accumulation of nutrients and organic matter in water resources over a very long period of time.
  • Natural eutrophication can take up to 100 years as natural and increased deposits of organic matter take a long time.
  • The natural eutrophication process is enhanced by natural conditions such as floods and landslides, which pull organic matter from the earth into water resources.
  • In addition, environmental factors such as temperature, carbon dioxide concentration, and light also play an essential role in natural eutrophication.
  • The natural eutrophication process begins in an oligotrophic water resource, where productivity increases as nutrients accumulate to achieve a stable state of eutrophy.
  • If the process of nutrient accumulation and utilization continues, the condition may shift towards eutrophication, but it will take hundreds of years. The time period depends on the type of water resource, the land area around the resource, and the climate.

Cultural (anthropogenic) Eutrophication

  • The cultural eutrophication of anthropogenic eutrophication is the process of accumulation of excess nutrients in aquatic ecosystems as a result of human activities.
  • Cultural eutrophication is the process that accelerates natural eutrophication, resulting in severe conditions in a short period of time.
  • The main cause of cultural eutrophication is the series of human activities that mainly increase the concentration of phosphorus and nitrogen in the ecosystem.
  • This type of eutrophication occurs in a shorter period of time and usually has significant consequences for the health of all living things.
  • Many human activities such as excessive fertilization, industrial and agricultural expansion, and the discharge of wastewater into water resources are among the main causes of the process.
  • Cultural eutrophication can occur in both fresh and saltwater bodies, among which shallow waters are the most susceptible.
  • Shallow lakes and ponds experience wind waves that cause the suspension of enormous nutrients in the overlying water.
  • Eutrophication restricts the use of such water resources for various purposes such as drinking, aquatic life, and industrial use as a result of the increased growth of undesirable algae.

What are the Process / Steps of Eutrophication?

The general process of eutrophication can be explained in the following steps;

Nutrient accumulation

  1. The first step in the eutrophication process is the enrichment of nutrients in different ecosystems.
  2. These nutrients are usually rich in nitrogen and phosphorus, the two limiting elements of algal bloom.
  3. Accumulation can be achieved through various natural and anthropogenic means. Natural processes such as soil erosion, landslides, rain, and storms shift the soil from adjacent areas into water resources, which significantly increases the nutrient content of the respective resources.
  4. Anthropogenic activities such as the discharge of domestic and industrial wastewater into water resources and the expansion of agricultural and settlement areas lead directly or indirectly to the enrichment of nutrients in the nearby water resource.
  5. At the beginning of the process, the aquatic ecosystem is oligotrophic with fewer nutrients available. As the concentration of nutrients increases, microbes and plant species use the nutrients to increase their productivity.

Increase in productivity

  • The increase in the concentration of nutrients in the aquatic system leads to the increased production of phytoplankton and plant species.
  • An aquatic ecosystem is made up of a diverse group of microorganisms that can use a wide variety of complex and simple nutrients.
  • The biomass of microorganisms and plant species increased significantly in the ecosystem. When organisms begin to die, more biomass accumulates in the ecosystem.
  • The process continues as long as the nutrient concentration in the ecosystem is sufficient.

Algal bloom formation

  • With the increased productivity of algae, algal blooms begin to form on the surface of water resources.
  • The formation of algal blooms also causes the vicious circle of algal blooms to release more nutrients into the water.
  • The algae in the water receive sufficient sunlight, which allows them to produce oxygen and nutrients through photosynthesis. This leads to an increase in the algae population, which leads to algal blooms on the water surface.
  • Eventually, these algae begin to cover most of the water’s surface, which prevents sunlight from penetrating the water. This affects the photosynthesis process, which leads to oxygen depletion.
  • This causes the algae to die, which are then broken down by various bacteria that use up the remaining oxygen for breathing.
  • All of this will eventually affect the health of the aquatic life in these water resources, as well as the quality of the water.

What are the Examples of Eutrophication?

Examples of Eutrophication

Eutrophication of Potomac river

  • The Potomac River in Washington County, Maryland is one of the classic examples of water resource eutrophication.
  • The river was initially identified as eutrophic based on the analysis of dissolved oxygen levels, biological oxygen demand, and the health of aquatic life.
  • Several studies found that the nutrient in the soil around the river led to the build-up of chemicals such as nitrogen and phosphorus.
  • The river is surrounded by land that is mainly used for forestry and agriculture and also supports livestock.
  • It is believed that manure and manure washed from the ground are the main cause of eutrophication.
  • The river is still home to some aquatic life such as fish and arthropods, but biodiversity has decreased every year.

What is eutrophication and why is it a problem?

Eutrophication is considered a water pollution problem that affects around 30-40% of all water bodies worldwide. In addition to water pollution, eutrophication has various other effects on the ecosystem as well as on the life of various living things. The following are some of the effects of eutrophication;

Increased biomass of Phytoplanktons

  • Increased phytoplankton biomass, particularly in the form of algal blooms, is one of the most prominent effects of eutrophication.
  • Algal blooms could even develop poisonous strains of cyanobacteria that harm both aquatic organisms and humans.
  • Flowers also lead to decreased water clarity and quality. Some of the phytoplankton can even form smelly algal blooms, which further damage the ecosystem.

Lack of oxygen

  • The formation of algal blooms on the surface of the water reduces the availability of sunlight to living things in the water source.
  • The lack of sunlight leads to a decrease in photosynthesis and ultimately the death of the plant species present in the water.
  • The dead plants are then broken down by various bacteria that use the remaining oxygen in the water.
  • All of this leads to a lack of oxygen in the water source, which brings with it other problems. The lack of oxygen leads to an anoxic process that produces various toxic and smelly gases.
  • Lack of oxygen leads to the death of various aquatic plants and animals.

Decrease in biodiversity

  • Eutrophication reduces the biodiversity of aquatic ecosystems. When the algae population increases due to increased nutrients, the population of other living things such as plants and animals decreases.
  • Algal blooms limit the availability of sunlight to soil-dwelling organisms and lead to a reduction in the variation in a population.


  • Various algal blooms are known as noxious algal blooms which produce a toxic compound that can move up the food chain to various trophic levels.
  • Freshwater blooms can be harmful to farm animals if they are consumed by multiple animals. The poisonous compounds then pass from animals to humans and pose a threat to human life.
  • One of the most common examples of algae toxins affecting the human body is shellfish poisoning, in which the toxins produced by the algae are ingested by shellfish and transmitted to the human who eats such shellfish.

Water pollution

  • The formation of algal blooms reduces the clarity of the water, which leads to extensive water pollution.
  • It makes the water unsafe for drinking or other recreational activities, which ultimately reduces the aesthetic value of the body of water.

What are the Solutions of Eutrophication?

With eutrophication affecting much of the world’s water bodies, it is important to control the process. Since anthropogenic activities are the main causes of nutrient enrichment and eutrophication, it is important to address these issues. Below are some of the solutions or control measures to minimize eutrophication;

Biological Control

  • Phosphorus is one of the important elements that induce the eutrophication process. Hence, it is important to eliminate phosphorus from various sources.
  • One of the tools for eliminating phosphorus is, of course, through periphytons. These microbes take part in phosphorus removal by absorbing and depositing phosphorus and filtering phosphorus from the water.
  • Various phytoremediation methods have also been proposed to effectively reduce aquatic toxicity.
  • Aquatic macrophytes such as Eichhornia crassipes and Salvinia auriculata reduce the concentration of nitrogen and phosphorus compounds in the water.
  • In addition, duckweed is also used in wastewater treatment as it removes the wastewater from the shrimp farm and large amounts of ammonia from the water.

Reduction of over-fertilization

  • Fertilizers are one of the major sources of nutrients that cause eutrophication, so reducing fertilizer use can be a good strategy to reduce nutrient input.
  • Optimized fertilizer use also requires regular soil tests to ensure that optimal fertilizers are used.
  • Similarly, users can also be made of an alternative source of fertilizer that can provide phosphorus in a slow-release form.
  • In soils that are high in phosphorus, other chemicals such as potassium and sulfur can be used to get the highest production.

Public Awareness and legislations

  • Public awareness determines the public’s ability to understand the surrounding world, sensitivity to the changing environment, and understanding of the cause-and-effect relationship between the environment and human behavior.
  • Public awareness can enable the use of organic fertilizers and the treatment of wastewater before discharge into water sources.
  • In addition, various organizations can propose important legislation to reduce the level of eutrophication.
  • Some of these legal regulations include those of the European Union, which aim to protect the water quality of ground and surface waters and to reduce the negative effects of urban wastewater discharge.
Define Eutrophication, Types, Causes, problems, and solutions

Define Eutrophication, Types, Causes, problems, and solutions

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