Natural Eutrophication

Introduction

Eutrophication refers to the process of mixing excess nutrients with a water body resulting in the overgrowth of plant life. The plants that are considered here are algae and plankton. In the process of natural eutrophication, soil rich in nutrients gets mixed with water bodies via sewers or due to flooding and this presents the plants that depend on the available nutrients an opportunity to grow heavily. This is a problematic situation because the growth of algae and plankton occurs so heavily that sunlight cannot reach the bed of the water bodies and as oxygen is absorbed by dead algae biomass extensively, the fish and other aquatic organisms die due to suffocation.

What is Eutrophication?

Image 1: Eutrophication

When inorganic nutrients get mixed with water and enrich the water bodies, the process is known as eutrophication. This results in an increase in the production of plankton and algae. In other words, eutrophication is the reaction of nutrients with aquatic ecosystems. The inorganic nutrients may include phosphates and nitrogen which get mixed with water, say in ponds, and make the pond more liveable for plant life like algae and plankton. Gradually, the density of algae and plankton becomes so heavy that no other plant or animal can live in the water body.

Eutrophic Lake

Lakes that are eutrophic by nature have great biological production. The amount of biological variability in such lakes is great in number in the early stages of vegetation. Moreover, the naturally eutrophic lakes stimulate the fauna varieties in the lake to a great extent. These lakes have a variety of plant life due to their nutrient-rich nature, especially due to the presence of nitrogen and phosphorous. However, at a later stage, when the lake becomes overcrowded by plants and algae blooms, the flora and fauna species suffer a big blow due to the high respiration of the vegetative matter in the lakes.

What is Natural Eutrophication?

Although natural eutrophication is a slow process, there is a theory that most water bodies go through a gradual process of enrichment of nutrients. This leads to the growth of simple plants in the water bodies. When the nutrient level is high, it is highly favorable for algae and plankton to thrive there. So, they reproduce and grow quickly in the water bodies, leaving hardly any opportunity for other aquatic organisms to live there.

The natural eutrophication process refers to the overabundance of nutrients in water bodies. These nutrients are often found in soil. Therefore, the mix-up of soil nutrients due to floods, landslides, or other reasons may lead to natural eutrophication.

Compared with anthropogenic eutrophication, natural eutrophication is a much slower process. Anthropogenic eutrophication is man-made and very fast in nature.

In the situation of a flood, for example, the nutrients of soil may be washed away to a nearby water body and the nutrients may get deposited there, making the water body ideal for the growth of simple plant life forms, such as algae and plankton.

Natural eutrophication also depends on the temperature of the surrounding environment. The process may also be made faster by global warming. This means that most of the water bodies get eutrophicated by anthropogenic eutrophication nowadays.

Natural Eutrophication Vs Man-made Eutrophication

Natural Eutrophication	Man−made Eutrophication
Natural eutrophication is the process of water bodies getting a state of overabundance with inorganic nutrients due to natural processes.	The water bodies get a state of an overabundance of nutrients due to man-made activities.
A slow process.	It’s a fast process.
Examples of nutrients: are from floods, runoff, and landslides.	Nutrients from: Fertilizers, untreated sewage, phosphorus-containing detergents, industrial waste

Table 1: Difference between Natural Eutrophication and Man-made Eutrophication

Biological Oxygen Demand (BOD) and Dissolved Oxygen (DO)

• The level of organic waste contamination is measured by Biological oxygen demand (BOD). The amount of oxygen needed to decompose organic waste by bacteria is known as BOD.

• The BOD of a water body is measured as milligrams of oxygen dissolved per liter of the water from the water body. This is known as Dissolved Oxygen (DO).

• The more the amount of BOD, the less the amount of DO.

• There must be an amount of DO present in water bodies for the aquatic organisms to survive.

• If the trash amount in water bodies is higher it consumes more BOD leaving less for the aquatic organisms.

• So, in the case of natural eutrophication, the level of BOD goes up increasingly, leaving no DO for other animals or plants.

Mechanism of Natural Eutrophication

Image 2: Chart Summarizing the process of Eutrophication

• Natural Eutrophication occurs due to natural factors, such as floods, excess rainfall, and landslides.

• These natural factors wash the organic materials such as slits, and decay of animals, plants, and other organic bodies to the nearby water body.

• The water bodies, therefore, get nutrient-rich which is favorable for simple plant life forms like algae and plankton.

• The algae, duckweed, and other plants grow heavily in the water body.

• As the thick cover of algae stops sunlight from penetrating into the water bed, other life forms die out.

• The dead algae biomass accumulates in the bed of the water body and absorbs oxygen while decomposing. As large amounts of algae biomass decompose, all oxygen from the water bed is absorbed, leaving no oxygen for other life forms like fish.

Effects of Natural Eutrophication

Image 3: Consequences of eutrophication on coral reef, seagrass and mangrove ecosystems.Eutrophication degrades the water quality and increases the BOD.

• Water bodies are transformed into terrestrial ecosystems from aquatic ecosystems due to natural eutrophication.

• Eutrophication leads to excess growth of algae in the water bodies.

• Eutrophication results in the death of aquatic plants as sunlight cannot penetrate through the algae bloom. It also affects oxygen replenishment.

• It may lead to attacks by invasive species. For example, the water bodies affected by eutrophication are affected by Silver Carp that can adapt to the conditions of eutrophic lakes readily.

• Coral reefs disappear as no sunlight reaches the water beds.

• Biomass of epiphytic and benthic algae increases due to eutrophication.

• The composition of species of macrophytes and their biomass undergoes notable variations. They grow large in numbers.

• The water gets an unpleasant odor and color; it becomes hard to treat the water.

• DO in the water body gets depleted very fast.

• The aesthetic value of the water body gets reduced to a large extent.

Conclusion

Natural eutrophication can turn costly if not treated at the right time. As it stops the life forms from existing in a water body, there can be palpable harm in the process of natural eutrophication. Therefore, everyone should know how to treat water bodies in order to save them from eutrophication.

FAQs

Qns 1. What is meant by Biological Oxygen Demand?

Ans. The level of organic waste contamination is measured by Biological oxygen demand (BOD). The amount of oxygen needed to decompose organic waste by bacteria is known as BOD.

Qns 2. What is meant by Dissolved Oxygen?

Ans. The BOD of a water body is measured as milligrams of oxygen dissolved per liter of the water from the water body. This is known as Dissolved Oxygen (DO).

Qns 3. How do ecosystems change due to Eutrophication?

Ans. Water bodies are transformed into terrestrial ecosystems from aquatic ecosystems due to natural eutrophication.