Eutrophication in Ecology Definition, Causes, and Examples

What Is Eutrophication?

Eutrophication is a process in ecology whereby there is a concentration increase of nutrients in an aquatic ecosystem leading to an explosive increase in the growth of algae (algal bloom) and other plant life. During eutrophication, there is an increase in sedimentary material and nutrients like phosphorous and nitrogen.

Eutrophication is one of the most severe environmental problems for rivers, lakes, coastal waters, and estuaries. A form of water pollution known as nutrient pollution is the primary cause of eutrophication in water bodies. As a result of nutrient pollution, excess nutrients stimulate aquatic plants, plankton, and algal growth.

This eutrophic process is characterized mainly by dense plant and algal growth due to the enrichment of the water by nitrogen and phosphorus nutrients. These nutrients are needed by plants and algae for photosynthesis. Hence, eutrophication is the reason for the formation of extensive mats of floating plants on water surfaces. Examples of such plants are Nile cabbage, algal bloom, and water hyacinths. Algae bloom and other microscopic organisms usually develop on the water surface. By doing so, they prevent the light penetration and oxygen absorption that is needed for the life underwater. This is why eutrophic waters are usually murky. Such waters may support fewer animals than non-eutrophic waters. Advanced eutrophication can also be called dystrophic and hypertrophic conditions.

How does eutrophication occur?

Before human interference, eutrophication was and is a very slow natural process. It’s a natural process whereby nutrients and organic matter accumulate in an aquatic ecosystem. These nutrients are derived from the degradation and solution of minerals in rocks. Also, they are derived too from the active activities of lichen, fungi, and mosses, scavenging nutrients from rocks.

Naturally, eutrophication takes place as the water body grows old over thousands of years and gets filled with sediments. Some organic matter enters the water body mainly by runoffs from land that contains debris and remains of reproduction or dead terrestrial organisms. The nutrient concentration and productivity of the water body definitely increase naturally as the amount of organic matter that is broken down into nutrients increases.

Nowadays, eutrophication doesn’t only happen naturally. Human activities have sped up the rate of eutrophication in the aquatic ecosystem. This is through pollution– a point source and non-point source discharges of chemical compounds into the water system. Human-influenced eutrophication is known as anthropogenic or cultural eutrophication.

In this type of eutrophication, nutrients are added to a water body from various polluting inputs. Such polluting inputs like untreated or partially treated sewage, fertilizer from farm operations, and industrial wastewater. Most times nutrients are washed by irrigation or rain through surface runoffs from animal wastes, sewage, and fertilizers into water bodies. Hence eutrophication is of two types: natural eutrophication and cultural eutrophication.

What causes eutrophication?

1. Use of fertilizers
2. Concentrated animal feeding operations
3. Direct discharge of sewage and industrial waste into water bodies
4. Agricultural activities
5. Natural occurrence

• Use of fertilizers

Eutrophication is predominantly caused by human dependence on using phosphate and nitrate fertilizers. The use of fertilizers on golf courses, lawns, and other fields contributes to the accumulation of nitrate and phosphate nutrient.

Eutrophication is caused by using fertilizers. When it rains, these nutrients from the fertilizers are washed by surface runoff into water bodies. Hence enriching the water and feeding the algae, plankton,  and other aquatic plant life well enough for their photosynthesis activity to increase. This results in a dense growth of plant life and algal blooms in the aquatic ecosystem.

• Concentrated animal feeding operations

The concentrated animal feeding operations (CAFOs) also are the most contributor of nitrogen and phosphorus nutrients liable for eutrophication in lakes, rivers, streams, and oceans.

Eutrophication is caused by concentrated animal feeding operations. These animal feeding operations usually discharge a high amount of the nutrients that find a way into water bodies. In the water body, the nutrients accumulate in high concentrations. Hence, plaguing the water body by recurring algal blooms and cyanobacteria.

• Direct discharge of sewage and industrial waste into water bodies

Eutrophication is caused by sewage water being discharged into water bodies. Sewage water is discharged directly into water bodies in some countries, most especially in developing countries. Due to this practice, high amounts of chemical nutrients are introduced into the water. Hence the dense growth of aquatic plants and algal blooms is stimulated. The growth of these organisms thereby threatens the survival of aquatic life in various ways.

Nevertheless, some countries may treat sewage water and still discharge it into water bodies. Unfortunately, the sewage water can still cause the accumulation of excess nutrients in as much as the sewage was treated. Hence bringing about eutrophication in the water body. Also, the discharge of industrial wastewater directly into water bodies brings about the same outcome.

• Agricultural practice

There is an aquicultural practice that involves growing fish, shellfish, and aquatic plants in water containing dissolved nutrients, without soil. As this agricultural practice is widely and highly embraced in recent times, it also qualifies as a great contributor to eutrophication.

Eutrophication can be caused by this aquacultural practice if not managed properly. The fish excretion, as well as the unconsumed food particles, can cause a significant increase in the nitrogen and phosphorous levels in the water. Thereby, leading to the dense growth of microscopic floating plants.

• Natural occurrence

Eutrophication can be caused by natural occurrences like the natural flow of streams, rivers, and floods. These natural occurrences can wash excess nutrients off the land into the water bodies. Hence resulting in the excessive growth of algal blooms. Moreso, as lakes grow old, they accumulate nutrients (nitrogen and phosphorous) and sediments naturally. This eventually contributes to the excessive growth of cyanobacterial blooms and phytoplankton.

Naturally, eutrophication takes place as the water body grows old over thousands of years and gets filled with sediments. Some organic matter enters the water body mainly by runoffs from land that contains debris and remains of reproduction or dead terrestrial organisms. The nutrient concentration and productivity of the water body definitely increase naturally as the amount of organic matter that is broken down into nutrients increases.

What is eutrophication in biology?

Eutrophication can be defined in biology as an enrichment of nutrient salts in water bodies that causes structural changes to the aquatic ecosystem. Such structural changes could include depletion of oxygen in the water body, increased growth of aquatic plants and algae, deterioration of water quality, depletion of fish species, and other effects that reduce and preclude use.

Eutrophication poses to be a serious environmental problem in the ecosystem because it results in the depletion of dissolved oxygen in water bodies and a deterioration of water quality. Also, aquatic ecosystems affected by eutrophication can eventually become dead zones that are no longer capable of supporting life. However, eutrophication affects 54% of Asian lakes, 41% of those in South America, 48% of those in North America, 53% of those in Europe, and 28% of those in Africa. The data stated are based on the Survey of the State of the World’s Lakes, a project promoted by the International Lake Environment Committee.

Eutrophication is more widely explained in relation to anthropogenic activities where the artificial introduction of plant nutrients has led to a deterioration of water quality in many freshwater systems and community changes. Eutrophication has become increasingly important with the more extensive development of agriculture and increases in the human population. Moreso, eutrophication now ranks with other major anthropogenic effects like global warming, deforestation, depletion of the ozone layer, and large-scale environmental disturbance in relation to its potentially adverse effect on natural ecosystems.

Eutrophication process

1. Excess nutrients
2. Algae bloom
3. Oxygen depletion
4. Dead zones

The eutrophication process occurs in 4  steps:

• Excess nutrients

Firstly, in the eutrophic process, there is the availability of excess nutrients in the water either naturally, from runoffs, or by the direct discharge of chemical compounds into the water. Eutrophic conditions are described by a significant increase of algae due to the great availability of sunlight, carbon dioxide, and nutrients (nitrogen and phosphorus) for photosynthesis.

Eventually, over-fertilization and nutrient concentration of the water causes algae to grow on the surface. This is because the nutrients that enter the water become food for algae. Eutrophication however stimulates the growth of algae. This is why it is common to see thick green blooms in the water.

• Algae bloom

The water body being rich in nitrate and phosphate stimulates the excessive growth of algae in the water. As more nutrients find their way into the water, eutrophication repeats in a severe algal bloom cycle and releases more nutrients. However, the problem with excessive algae growth is that it absorbs sunlight and prevents it from reaching the bottom of the water.

Also, in regard to water quality, blue-green algae (cyanobacteria) for instance if consumed can be toxic and harmful to plants and humans. This algae type is becoming a major ecological issue in most parts of the world. Furthermore, when algae grow to an extreme level, it stops light entirely from reaching plants in the water. As a result of this, plants that need sunlight cannot photosynthesize and eventually die. As algae begin to grow in an uncontrolled manner, large algal biomass is formed which is destined to degrade.

• Oxygen depletion

As algae blooms, it prevents sunlight from entering the water. Also as it uses up oxygen, the water becomes oxygen-depleted. Algae produce oxygen through photosynthesis when it receives enough sunlight. The algae release oxygen in the water. Then when there is no sunlight, algae stop producing oxygen and consumes it rather.

Eventually, when algae die, bacteria using up oxygen for respiration decomposes the algae remains. Excessive or total consumption of oxygen is required by microorganisms to decompose the dead algae. Thereby, on the bottom of the water body, an anoxic (oxygen-free) environment is created. Supporting the growth of organisms capable of living in an anaerobic (absence of oxygen) environment. These organisms are responsible for the degradation of the algae biomass. The microorganisms in the absence of oxygen decompose the organic matter and release compounds that are toxic. Toxic compounds like ammonia and hydrogen sulfide are released into the water.

Eventually, this decomposition process causes the water to become depleted of oxygen, and with time the water carries less oxygen than it before. This can get to a severe point when fishes cannot swim and suffocate to death in the water. Generally, a eutrophic water body can no longer support life because the absence of oxygen reduces biodiversity. Hence causing the death of plant and animal species in the water. Oxygen depletion happens when the rate of algae degradation by microorganisms is greater than the rate of oxygen regeneration in the water body.

• Dead zones

A water body without oxygen becomes anoxic and with time, a dead zone. Dead zones are the worst-case scenarios as they can no longer support fishes and other aquatic life. Dead zones are more common in industrialized nations. Especially places with industrial farming practices that involve phosphate and nitrogen or animal waste. A typical eutrophication example is the largest dead zone in the world that lies in the Arabian Sea and the second largest dead zone that sits in the Gulf of Mexico in the United States, adjacent to the Mississippi River.

Types of eutrophication

1. Natural eutrophication
2. Cultural or anthropogenic eutrophication

Natural eutrophication

A natural process whereby nutrients and organic matter accumulate in an aquatic ecosystem is called natural eutrophication. It involves the natural process of the flow, accumulation, and addition of nutrients to the aquatic ecosystem leading to changes in the species composition and primary production of the aquatic community. In natural eutrophication, these nutrients are derived from the degradation and solution of minerals in rocks. Also, they are derived too from the active activities of lichen, fungi, and mosses, scavenging nutrients from rocks.

Natural eutrophication has been occurring for millennia. The major difference between natural eutrophication from anthropogenic eutrophication is that the natural eutrophic process is very slow and occurs on geological time scales. Naturally, eutrophication takes place as the water body grows old over thousands of years and gets filled with sediments. Some organic matter enters the water body mainly by runoffs from land that contains debris and remains of reproduction or dead terrestrial organisms. The nutrient concentration and productivity of the water body definitely increase naturally as the amount of organic matter that is broken down into nutrients increases.

Over centuries, the gradual buildup of sediments, nutrients, and organic material begins to fill many lake basins. As the lake’s eutrophic levels grow, it begins to accommodate more damaging algae due to higher nutrient levels. Moreso, as a result of sedimentary buildup, their littoral area increases. This process eventually affects the water quality and allows terrestrial vegetation colonization in the expanding shallows. However, the duration of this process depends on the characteristics of the lake basin, climate, and watershed.

Paleolimnologists have recognized that geology, climate change, and other external factors are also crucial in regulating the natural productivity of lakes. However, a reverse process of eutrophication known as meiotrophication is demonstrated by few lakes. This process involves the lake becoming less nutrient-rich with time as nutrient-poor inputs slowly remove the nutrient richer water mass of the lake. Meiotrophication may be seen in artificial reservoirs and lakes. On first filling, the lake or reservoirs tend to be highly eutrophic but may become more oligotrophic with time.

Cultural eutrophication

Human-influenced alteration of nutrient input in water bodies is known as anthropogenic or cultural eutrophication. Nowadays, human activities have sped up the rate of eutrophication in the aquatic ecosystem. This is through a point source and non-point source discharges of chemical compounds into the water system. In this type of eutrophication, water pollution speeds up the aging process of the water. This by humans introducing detergents, sewage, fertilizers, and other nutrient sources into the water body. This whole process has led to aquatic ecosystem degradation and has also had severe consequences on fisheries, freshwater resources, and recreational water bodies.

Unlike natural eutrophication, in cultural eutrophication, nutrients are added to a water body from various polluting inputs. Such polluting inputs may include untreated or partially treated sewage, fertilizer from farm operations, and industrial wastewater. Most times nutrients are washed by irrigation or rain through surface runoffs from animal wastes, sewage, and fertilizers into water bodies. Triggered by human activities, eutrophication is sped up.

Anthropogenic eutrophication is mainly associated with phosphorus. Phosphorous is one of the strongest stimulants of algae growth and is found in partially treated sewage and fertilizers. Usually, eutrophication in freshwater bodies is caused by excess phosphorus. Humans have increased the rate of phosphorus cycling in the ecosystem by four times. This is primarily due to agricultural fertilizer application and production. About 600,000,000 tonnes of phosphorus was applied to the surface of the earth, mainly on croplands just between 1950 to 1995.

Human-influenced sedimentary eutrophication is a result of soil erosion which is caused by the removal of vegetation and trees. Land clearing by man accelerates land runoff. Hence more nutrients like nitrate and phosphates are added to rivers, lakes, and then bays and coastal estuaries. The use of fertilizers in farms also supplies extra nutrients to the water bodies. Some activities in fish farming, treatment plants, and untreated sewage contribute too.

Usually, cultural eutrophication may exhibit extremely low oxygen concentrations in bottom waters. This condition is known as hypoxia. Hypoxic condition is common in stratified systems like lakes during summer. Low oxygen concentration can further be intensified by water bloom that accompanies excessive nutrients in waters. Thus the water may end up poisoning wildlife. Hypoxic waters due to cultural eutrophication have led to massive fish kills and rippling effects throughout the food chain and local economies. However, the health of the aquatic ecosystem is directly linked to the human activity that takes place throughout the entirety of their watersheds. Hence environmental policy and effective land management are required.

Eutrophication Sources

1. Point source
2. Non-point source

• Point source

Eutrophication could come from point sources. Point sources could be stationary locations or fixed facilities. Hence point source pollution is from contaminants that enter a waterway from a single identifiable source. They are definitive and localized sources of nutrients and sedimentary pollution. Main point sources include runoff from industrial wastewater, municipal wastewater, and large construction sites. Typical examples are discharges from industrial plants, fish farms, or sewage treatment plants. Others include leaching and runoff from animal feedlots, waste disposal systems, industrial sites, and chicken or hog farming operations.

• Non-point source

Eutrophication could come from non-point sources. Non-point sources include human activities with no specific identifiable point of entry or discharge into the receiving waterway or watercourses. These sources are diffuse sources of sedimentary and nutrients pollution. A main non-point source of eutrophication is runoff from pastures and agriculture. Examples include runoff from urban areas without sewer systems, and runoff from abandoned mines, nitrogen compounds leaching from fertilized agricultural lands, leaching from septic tanks, and atmospheric deposition of nitrogen. However, the 3 main nonpoint sources of nutrient input are:

• Atmospheric deposition of nitrogen from combustion gases and animal breeding
• Sewage from industrial wastewater and cities
• Leaching and erosion from fertilized agricultural areas

Eutrophication effects

• The growth and survival of aquatic life is threatened
• Fishing is endangered
• An abundance of unwanted organisms and substances
• Limits access to safe drinking water and deteriorate water quality
• Adverse effect on terrestrial plants
• Recreational opportunities are degraded
• Decreases biodiversity
• Cause poisoning and adverse effects on human health
• Invasion of new species

• The growth and survival of aquatic life is threatened

Eutrophication has an adverse effect on the survival and growth of aquatic life because the increase in phytoplankton biomass and algal bloom threatens aquatic life forms. When there is a nutrient increase in an aquatic ecosystem, phytoplankton and other plants grow excessively. This growth is referred to as algal bloom. As a result of algal bloom, the amount of dissolved oxygen is limited in the water when the algae die and decomposes. Like humans, aquatic animals and plant species need this oxygen for respiration too.

Hence when there is depletion of oxygen, the growth and survival of fishes and other aquatic life forms are threatened. These organisms such as fish, shrimp, corals, oysters, immobile bottom dwellers, and other aquatic biotas may suffocate to death. A water body without oxygen becomes anoxic and with time, a dead zone. Dead zones are the worst-case scenarios because they can no longer support fishes and other aquatic life.

In severe cases, the hypoxic levels of the water encourage bacteria growth that produces toxins. These toxins are definitely deadly to marine organisms. Algal blooms are toxic to animals as well as humans. They can release hepatotoxins, neurotoxins, gastrointestinal toxins,  dermatotoxins, and cytotoxins. Eutrophication examples are brown tides, red tides, and Pfiesteria which are all a result of algal bloom.

• Fishing is endangered

One effect of eutrophication is that it endangers fishing. The increased growth of tiny floating plants (algae and bacteria) together with the development of extensive dense mats of floating plants (water hyacinths and Nile cabbage) are associated with eutrophication. Once this floating plant growth happens on the surface of the water body, fishing becomes difficult and endangered. Setting the fishing net in the water becomes outrightly difficult. Also, the sailing of boats and the mobility of other fishing vessels are limited as a result of the plants that are floating on the water.

• An abundance of unwanted organisms and substances

Eutrophication is bad because it results in the abundance of unwanted organisms and substances. It causes an abundance of organisms and substances like bacteria, phytoplankton, zooplankton, fungi, and debris. The coloration and turbidity of the water depend on these organisms.

It also increases inorganic chemicals in the water. There is an increase in hydrogen sulfide, ammonia, nitrites, etc. which induce the formation of harmful substances like nitrosamines. In drinking water treatment plants, nitrosamines are suspected of mutagenicity.

• Limits access to safe drinking water and deteriorate water quality

Eutrophication is associated with the deterioration of water quality, thereby limiting access to safe drinking water. Since algal blooms are toxic and encourage the anaerobic condition of the water, toxic bacteria growth is promoted as well. For instance, blue-green algae in water are harmful for water consumption and to humans and animals. These organisms and other organic substances at high concentrations give the water a distasteful odor and taste. The taste and odor of such water can be barely masked by chlorination to be used as drinking water.

These substances formed in the water as a result of eutrophication form complex chemical compounds. Such chemical compounds prevent normal purification processes. Also, they accelerate corrosion and limit the water flow rate during purification processes as they get deposited on the walls of the water purifier inlet tubes.  Hence there is a decline in the availability of safe clean drinking water.

The consequence of eutrophication results in an extensive deterioration of water quality. Clean and healthy water is a necessity as humans, aquatic life, and animals rely and count on it. Also, the dense growth of photosynthetic bacteria and algae in water surfaces can block water systems. Thus, the availability of piped water is limited. Across the globe, toxic algal bloom happens to have shut down several water supply systems. A eutrophication example happened during the last decade in China, where about 2 million and more residents of Wuxi could not access piped drinking water for more than a week. This was a result of a severe attack of algal blooms on Lake Taihu.

• Adverse effect on terrestrial plants

The aquatic ecosystem is not the only habitat that is affected by eutrophication. The terrestrial ecosystems are actually subject to similarly adverse effects from eutrophication. An increase of nitrates in soil is usually undesirable for plants. Hence, many terrestrial plant species are endangered due to soil eutrophication. A typical example is seen in the majority of orchid species in Europe.

Forests, meadows, and bogs are adapted by low nutrient content. Hence slow-growing species are adapted to those levels. However, with high nutrient content, they can be overgrown by faster-growing and more competitive species.  For instance, tall grasses in meadows that can take advantage of higher nitrogen levels may change the area. As a result, natural species may be lost. Also, species-rich fens can be overtaken by reedgrass species.

Furthermore, plants need nitrogen to stimulate plant growth. However, nitrogen is not usually available in soil because the gaseous form of nitrogen is very stable and directly unavailable to higher plants. As a result, the terrestrial ecosystems depend on microbial nitrogen fixation to convert the gaseous form of nitrogen (N2) into other forms such as nitrates. However, there is a limitation to the amount of nitrogen that can be utilized. Once the ecosystem is receiving more nitrogen than is required by plants, it is referred to as nitrogen-saturated. A saturated terrestrial ecosystem can then contribute both organic and inorganic nitrogen to the eutrophication of water bodies.

• Recreational opportunities are degraded

Degradation of recreational opportunities can occur due to eutrophication in lakes, oceans, streams, and other water bodies. Algal blooms, Nile cabbage, and water hyacinth for instance would spray over an extensive area along the shores. Also, they sometimes float over the entire water surface into the land areas. The algal bloom and other aquatic plants floating on the water surface as a result of eutrophication reduce the transparency and navigation in the water. This, however, reduces and degrades the recreational opportunities and value of the water especially for swimming, waterskiing, sailing, aquatic sports, surfing, canoeing, kayaking, and recreational fishing.

• Decreases biodiversity

Eutrophication effects can result in a decrease or loss of biodiversity. Algal blooms affect the amount of dissolved oxygen. Also in the water, they limit the sunlight available to bottom-dwelling organisms. Under eutrophic conditions, the dissolved oxygen increases in the daytime and reduces after dark. The algae use the dissolved oxygen in the dark and microorganisms make use of oxygen as they decompose the dead algae. As a result of algal bloom, the amount of dissolved oxygen is limited in the water.

A water body without oxygen becomes anoxic and with time, a dead zone. Organisms such as fish, shrimp, corals, oysters, immobile bottom dwellers, and other aquatic biotas may suffocate to death as a result of the anoxic condition of the water. As dead zones no longer support aquatic life, biodiversity is lost and reduced in the water. In severe cases, the hypoxic levels of the water encourage bacteria growth that produces toxins. These toxins are definitely deadly to aquatic organisms and affect the biodiversity of an aquatic ecosystem.

• Cause poisoning and adverse effects on human and animal health

Eutrophication can cause poisoning and adverse effects on human and animal health. Cyanobacteria, for example, generate red tide and release very powerful toxins with high poison levels in the water. These toxins are doubled due to explosive algae growth. This is because when the algae die and are decomposed by microorganisms, neurotoxins and hepatotoxins are released. These toxins can kill animals and are threats to humans as well.

Toxins even at minute concentrations can cause death in animals and humans when ingested in drinking water. The toxins can also find their way up the food chain and contribute to several health issues like cancers. Also, these toxins are linked to an increased incidence of paralytic, neurotoxic and diarrhoetic shellfish poisoning in humans. During the algal bloom, the biotoxins created are taken up by shellfish such as oysters, mussels. These shellfish as human foods acquire the toxin and poisons humans which can lead to death. Also, a high concentration of nitrogen in drinking water is associated with a condition known as blue baby syndrome. Additionally, other marine animals can be vectors, harboring the toxins. For example is the case of a predatory fish, ciguatera that accumulates the toxin and later poisons humans when eaten.

• Invasion of new species

The invasion of new species in an aquatic ecosystem can be associated with eutrophication. The eutrophic process causes shifts in the species composition of aquatic ecosystems and the surrounding ecosystems. An increase in nitrogen may allow new competitive species to invade an ecosystem. Hence out-competing the original inhabitant species. This has been seen to occur in New England salt marshes.

In Asia and Europe, the common carp or European carp (Cyprinus carpio), a freshwater fish frequently lives and is adapted in naturally eutrophic or hypereutrophic waters. If a water body deficient in nitrogen is suddenly enriched with nitrogen, many competitive species might navigate and relocate to the water body and out-compete the original native species of the waterbody. However, this partially explains the success of the common carp in colonizing eutrophication areas outside its natural range after being introduced.

How to prevent eutrophication

• Pollution reduction
• Practicing composting
• Nitrogen testing and modeling
• Technology, laws, and regulations against water pollution should be strengthened
• Creating riparian buffer zones
• Use of ultrasonic Irradiation
• Restoring shellfish population

• Pollution reduction

Reducing and limiting pollution will help prevent eutrophic conditions in water bodies. This poses to be an easy and effective method of cutting down on the number of phosphates and nitrogen that are discharged into water bodies. Municipalities, industries, and manufacturing companies have to reduce pollution by desisting from discharging waste into water systems. This will help to reduce the number of nutrients and toxins that end up in the water. Once they are reduced, there will be fewer nutrients to promote the growth of algae and other microscopic organisms that will result in eutrophication. The nutrient content is reduced in the water systems if municipalities, industries, and manufacturing companies can cap their waste discharge and pollution to a lower level. This can subsequently control eutrophication.

• Practicing composting

Since eutrophication primarily occurs due to the use of phosphate and nitrate and phosphate fertilizers. To prevent and control eutrophic conditions, composting can be used in place of fertilizers. Composting involves converting organic matter such as food wastes and decaying vegetation into compost manure. This practice should be adopted and used frequently, especially as organic wastes are readily generated around us every day.

The compost manure has nutrients that are deficient in the high concentration of nitrates and phosphates. Hence there is less or no nutrient from the use of compost enough to feed the algae and other microbes in water bodies. All the essential elements in compost fertilizers are broken down and synthesized by the plants. Hence it does not create the cycle of eutrophication. This method of controlling eutrophication is referred to nutrient limitation.

• Practicing nitrogen testing and modeling

Farmers should be enlightened and adopt nitrogen testing and modeling to their farming operations. Soil Nitrogen Testing (N-Testing) is a technique. This technique helps farmers optimize the amount of fertilizer applied to crops. The bare minimum amount of fertilizers are needed by testing the soil and modeling. By testing fields with this method, farmers see both or either a decrease in the fertilizer application costs or a decrease in nitrogen lost to surrounding sources. Hence farmers reap economic benefits as they help reduce pollution.

• Technology, laws, and regulations against water pollution should be strengthened

Non-point pollution happens to be the most difficult source of nutrients to curtail. Eutrophication will decrease once these sources are controlled. However, strengthening regulations and laws against non-point source pollution will help control and prevent eutrophication. Non-point pollution poses the most severe challenge in the management of nutrient entry into water systems according to EPA.

The laws that aim at enhancing high water quality standards should be made and enforced. Also, regulation to zero-tolerance of the non-point pollution source should be emphasized. It is easier that way to prevent and curtail eutrophic conditions with the support of citizens,  policymakers, government, and pollution regulatory authorities.

Furthermore policy concerning the control and prevention of eutrophication can be broken down into 4 sectors:

1. Technologies
2. Public participation
3. Economic instruments
4. Cooperation

• Technologies

Non-point sources of pollution are the main contributors to eutrophication. However, their effects can be reduced and minimized easily through simple agricultural practices. The number of pollutants that reach a watershed can be reduced by protecting its forest cover. This will help reduce the amount of erosion leeching into a watershed. Also by using sustainable agricultural practices, land use is controlled to minimize land degradation. This in turn reduces the amount of soil runoff and nitrogen-based fertilizers that reach the watershed.

Since a major non-point source is untreated domestic sewage, waste disposal technology is another factor in the prevention of eutrophication. Hence it is important to provide waste treatment facilities to urbanized areas. More attention should be given to those urbanized areas in underdeveloped countries where domestic wastewater treatment is scarce. Moreso, in regard to eutrophication, developing technologies to efficiently and safely reuse wastewater from domestic and industrial sources should be of primary concern.

• Public participation

The public role in the prevention of eutrophication cannot be ruled out. It is a major factor for effective eutrophication prevention and control. For any policy to have an effect, the public has to be aware of its contribution to a problem. The public should be enlightened on ways in which they can reduce their effects on the existing problems. Programs that will promote public participation in recycling and the elimination of wastes should be instituted. Also, education on the issue of rational water use is necessary to protect water quality within urbanized areas and adjacent water bodies.

• Economic instruments

Economic instruments include property rights, charge systems, liability systems, water markets, fiscal and financial instruments. These instruments are gradually becoming a substantive component of the management toolset used for water allocation decisions and pollution control. Giving incentives to encourage those that practice clean, renewable, water management technologies. This is an effective means of encouraging pollution prevention. The governments are able to encourage cleaner water management by internalizing the costs associated with the negative effects of pollution on the environment.

• Cooperation

Cooperation is necessary because a body of water can have an effect on people reaching far beyond that of the watershed.  Agencies such as water resource management, state governments, non-governmental organizations, and even the local population are responsible for preventing eutrophic water bodies. Cooperation between different organizations is needed to prevent the introduction of contaminants that lead to eutrophication. For example, the Chesapeake Bay is the most well-known inter-state effort to prevent eutrophication in the United States.

• Creating riparian buffer zones

Creating riparian buffer zones can be a way of preventing eutrophic levels in water bodies. Studies have shown that intercepting non-point pollution between the water and the source is a successful means of prevention. Riparian buffer zones serve as interfaces between a flowing water body and land. Its usually created near waterways in order to filter pollutants. Hence, nutrients and sediment are deposited in the riparian buffer zone rather than in the water, serving as a eutrophication solution.

Therefore, the creation of buffer zones near farms and roads is a possible way to prevent nutrients from going too far. Nevertheless, the most effective means of prevention is still from the primary source as studies have shown that the effects of atmospheric nitrogen pollution can reach far past the buffer zone.

• Use of Ultrasonic Irradiation

The use of ultrasonic irradiation can be an advanced method in controlling the eutrophic levels in the water. Globally, advanced methods are being sought for resolving some of the environmental problems. The use of ultrasonic irradiation is one such mechanism when it comes to eutrophication. It has been exploited as an alternative solution to manage and control algal blooming. Ultrasonic irradiation works by causing cavitations. These cavitations produce free radicals that destroy algae cells. However, research is still ongoing to determine the uniqueness of its use in controlling eutrophication.

• Restoring shellfish population

Restoring the shellfish (oyster and mussels) population is one proposed eutrophication solution to control and reverse eutrophication in water bodies. Oyster reefs reduce the extent of algal bloom or anoxic conditions in the water by removing nitrogen from the water column and filtering out suspended solids. Generally, filter-feeding activity is beneficial to water quality. This is done by controlling phytoplankton density and removing nutrients. Shellfish restoration projects have been conducted on the West, East, and Gulf coasts in the United States.

Eutrophication solutions

There are curative eutrophication solutions when the quality of the water is so compromised that preventive initiative has been proven abortive and ineffective.

Such curative procedures can be implemented:

• The hypolimnetic water can be removed and treated. This Involves treating and removing the deep water that is rich in nutrients and in contact with the sediments. Removing and treatment are done as it is in direct contact with the release source.
• About the first 10-20 cm of sediment should be drained. The sediment that is with high phosphorus concentrations and is subject to biological reactions.
• The water should be oxygenated to reduce the negative effects of the eutrophic process. This will restore the anoxic condition and formation of toxic compounds as a result of anaerobic metabolism.
• Chemical precipitation of phosphorous. This is achieved by adding aluminum or iron salts or calcium carbonate rather to the water. The increase in the precipitation of the aluminum,  iron, or calcium orthophosphates, reduces the negative effects that arise from the excessive concentration of phosphorus in the sediments.

Assessment of eutrophication

Usually, eutrophication is assessed and identified by smell and sight when already at extreme levels. Identifying the cause and scale of a problem when a water body changes its chemical and biological status is essential to propounding a remediation strategy.

However, nutrients are in constant flux within the eutrophic aquatic ecosystem. Thus, determining the concentrations of nitrogen and phosphorous may not give good evidence of the current eutrophic state of a water body. Citing the early studies on the Great Lakes for instance. The total amount of solids, sodium, calcium, potassium, chloride, and sulfate in the lake gave good supporting evidence of eutrophication. Even though the water itself was not compromised, these ion parameters were indications of general anthropogenic inputs. Hence, providing a good substitute for nutrient inputs.

However, qualitative water assessments based on obvious signs of eutrophication will be too late to prevent the damage the eutrophic levels may cause to biodiversity.  Such qualitative assessment like the changes to the species of algae present in the water or their relative abundance only spells out damage in progress.

Therefore, the quantitative assessments of bioindicators and key chemicals at regular intervals are safe and reliable. This assessment can propound statistically valid data in order to identify the earliest onset of eutrophic levels and monitor its progress. The common parameters used for monitoring and assessment are:

• Chlorophyll-a
• Total nitrogen
• Biological or chemical oxygen demand
• Total and dissolved phosphorus
• Secchi depth level