Eutrophication

What is Eutrophication?

Eutrophication refers to the process in which a water body gets overtly rich in nutrients. As a result, too many algae and plankton grow in such water bodies. They consume almost all the organic oxygen available in the water bodies leaving no oxygen left for the animals that use to exist in them, such as fish. Ultimately due to the growth of too many algae and plankton, the water bodies turn into dead zones. Moreover, eutrophication is also a major environmental concern because it deteriorates the quality of a water body.

Eutrophication is inorganic nutrient enrichment in large scales in water bodies which results in the overt growth of algae and plankton in them. There are many lakes and water bodies that are naturally eutrophic in nature. However, the concern is more for man-made eutrophication that makes water bodies ultra-rich in inorganic nutrients thus infiltrating the freshwater systems and turning them incapable of supporting life in the long term.

Eutrophication has grown with the increasing human population and its effects on agriculture and farming are now widely considered a major concern. The process is also now considered at the same level as global warming, and ozone layer depletion as the process is capable of polluting large water bodies and making them unable to sustain life forms in large areas of freshwater systems.

The major reason for concern with eutrophication is that it destroys the balance of aquatic ecosystems which can hold both simple and complex forms of life. In eutrophic systems, only algae and plankton are found while other life forms remain absent in the ecosystem in which these plants are found.

Lake with green algae and duckweed on water surface

Causes of Eutrophication

When large amounts of inorganic substances containing nitrogen and phosphorous mix with water bodies, the growth of small plants like algae and plankton gains more momentum than the growth of larger and more complex aquatic plants. This process gives rise to the growth of only algae and plankton in a water body. Gradually, algae and planktons cover up all the water bodies leaving no opportunity for other complex forms of life because the system is left with no oxygen.

In fact, the accumulation of algae creates a large biomass of dead algae in due course of time which settles at the bottom of the aquatic ecosystem. These dead algae are broken down by bacteria which absorb Oxygen in the process. As more biomass of algae is broken down all Oxygen dissolved in the water is absorbed by the large biomass of algae leaving no oxygen for complex forms of life, such as fish. Therefore, the complex life forms usually die leaving only algae and plankton in the ecosystem where there is a marked imbalance.

The main source of phosphorous is soil. As soil erosion takes place and it mixes with water bodies, the amount of phosphorus grows in the water body. This leads to the growth of plankton in the water ecosystem. Some other phosphorous sources that mix with water bodies include fertilizers, detergents containing phosphorus, untreated sewage, and industrial waste.

Classification of Eutrophication

Eutrophication can be divided into two types depending on the cause of the process. These are the following.

Natural Eutrophication

This process is natural in manner. For example, when a flood occurs, it may wash away nutrients from land and accumulate them in rivers or lakes. This results in the excessive deposit of nutrients in the water body leading to the growth of algae and plankton in huge numbers.

Natural eutrophication is slower than the other type of eutrophication, namely anthropogenic eutrophication. Moreover, natural eutrophication may depend on environmental conditions, such as temperature. It may also be affected by global warming.

Anthropogenic Eutrophication

Anthropogenic Eutrophication is man-made. For example, when detergents or fertilizers are allowed to mix with water in lakes, the phosphorous content in them may favor the growth of algae and plankton in the lake. With a gradual increase of exposure, the lakes may completely turn eutrophic in nature

Overpopulation of humans

Overpopulation of humans also leads to deforestation and this is the main reason for soil erosion. When soil erosion occurs, it may lead to a mix-up of phosphorous-rich soil with water bodies which may eventually lead to an increase of inorganic nutrients in the water ecosystem. This, in turn, may lead to eutrophication.

Sewage and industrial waste

Sewage and industrial waste containing nutrients may also get mixed with water, leading to anthropogenic eutrophication.

Effects of Eutrophication

Ecological Effects

Natural water changes from ultraoligotrophic to eutrophic due to eutrophication. This change may progress to newer levels that have higher productivity parameters. Eutrophication also affects the vertical structure of lakes, impacting the biological properties of freshwater systems. The transition from eutrophic to hypertrophic occurs due to man-made changes which may imbalance the whole water ecosystem.

Diminishing Biodiversity

Eutrophication affects the biodiversity of water ecosystems. When eutrophication occurs, the algae and plankton bloom in great quantity. These algae and plankton stop light from reaching the bottom of the water body. Moreover, as all dissolved oxygen is used by the dead-algae biomass, other organisms die due to suffocation.

Increase in water toxicity

Some toxic algae release neuro and hepatotoxins into the water they bloom in. These may get into the food chain and be toxic to animals and humans. The insertion into the food chain may usually occur via shellfish. When consumed, these toxins may cause neurotoxic, paralytic, and Diarrhetic poisoning

Invasion of new species

Eutrophic conditions usually invite new species that are experts in sustaining in new conditions. These new species may come into the eutrophic environments and outcompete the original inhabitants. For example, when water bodies are enriched with nitrogen, they may be occupied by common carp while other fish species may go away from them.

Conclusion

Eutrophication is a grave concern because it destroys water ecosystems. Learning about eutrophication is important because we must know how eutrophication should be controlled and stop water bodies from turning eutrophic. Eutrophication is a matter of scientific understanding related to water pollution and we must know how it can be minimized. We must take all steps to stop water bodies from turning eutrophic. This must be done to stop man-made eutrophication spread to many lakes and freshwater systems.

FAQs

Qns 1. How does eutrophication create dead zones? Discuss briefly

Ans. Eutrophication refers to the process in which a water body gets overtly rich in nutrients. As a result, too many algae and plankton grow in such water bodies. They consume almost all the organic oxygen available in the water bodies leaving no oxygen left for the animals that use to exist in them, such as fish. Ultimately due to the growth of too many algae and plankton, the water bodies turn into dead zones.

Qns 2. Discuss how eutrophication reduces biodiversity.

Ans. Eutrophication affects the biodiversity of water ecosystems. When eutrophication occurs, the algae and plankton bloom in great quantity. These algae and plankton stop light from reaching the bottom of the water body. Moreover, as all dissolved oxygen is used by the dead-algae biomass, other organisms die due to suffocation.

Qns 3. Which toxins are released by algae?

Ans. Some algae release neurotoxins and hepatotoxins.