Eutrophication – Eutrophication of Lakes, Causes, Impact, Practice Problems and FAQ

Eutrophication, a serious issue, is affecting aquatic habitats all around the nation. Fish mortality, dead zones, and toxic algal blooms are all results of eutrophication.

But have you ever pondered the causes or effects of eutrophication?

Like people, plants need nutrients, but too much of a good thing can be dangerous. The majority of the nutrients in our waterways are a result of human activity, however, some nutrients, including nitrogen and phosphorus, are naturally occurring. By eating nutrients, algae grow, turning the water green. The oxygen that is dissolved in water and necessary for aquatic life to breathe is devoured by bacteria as they decompose dead algae.

A "dead zone" is generated when there is insufficient oxygen to sustain aquatic life. This happens when enough oxygen is removed.

Let’s get to know more about eutrophication on this concept page.

TABLE OF CONTENTS

• Eutrophication
• Eutrophication – Causes
• Eutrophication – Impacts
• Practice Problems
• Frequently Asked Questions – FAQ

Eutrophication

Eutrophication is the term used to describe the increase in nitrogen, phosphorus, and other plant nutrients inside an aquatic habitat.

The productivity or fertility of the ecosystem increases in direct proportion to the amount of organic matter that can be converted into nutrients. This substance mostly enters the ecosystem from discharges from the land, which also contains waste and byproducts of the reproduction and death of terrestrial animals.

Large concentrations of algae and other small organisms known as water blooms frequently accumulate on the surface, preventing light from penetrating and oxygen from being absorbed, both of which are necessary for underwater life. The majority of the time, eutrophic wate rs are muddy, and large animals like fish and birds may be less common than in non-eutrophic waters.

By introducing detergents, fertilisers, sewage, and other sources of nutrients into the ecosystem, human water pollution quickens the ageing process and leads to cultural eutrophication. Cultural eutrophication is a significant contributor to the decline of aquatic ecosystems and has had devastating effects on freshwater resources, fisheries, and recreational waterbodies.

Eutrophication – Causes

1. Phosphate and Nitrate Fertilisers

Humans are the main cause of eutrophication because they depend on phosphate and nitrate fertilisers. Agricultural practices and the application of fertiliser to lawns, golf courses, and other locations facilitate the building of nitrate and phosphate nutrients.

When surface runoff from rain storms carries these nutrients into lakes, oceans, rivers, and other surface waters, hungry plankton, algae, and other aquatic plant life are well fed, and their photosynthetic activity rises. As a result, there are extensive algae blooms and aquatic plant life, including water hyacinths.

2. Discharge of sewage and industrial waste into oceans, lakes, and other bodies of water

In many countries around the world, particularly in third world countries, sewage water is let directly into bodies of water like lakes, rivers, and seas. As a result, it introduces a lot of chemical fertilisers, which makes other aquatic plants and algal blooms develop rapidly and puts aquatic life in danger in several ways.

Even after being cleaned, sewage water is still dumped into bodies of water in several countries. Irrespective of how effectively the water is treated, it can still result in the accumulation of extra nutrients and eutrophication. Similar effects result from the direct discharge of industrial wastes into aquatic bodies.

3. Aquaculture

Aquaculture is the practice of growing fish, shellfish, and even aquatic plants without the use of soil in water that has dissolved nutrients. It counts as a significant cause of eutrophication because it has recently gained widespread acceptance as a technique.

If aquaculture is not kept under control, leftover food particles and fish waste can significantly increase the phosphate and nitrogen levels in the water, which will cause the dense growth of small floating plants.

4. Natural occurrences

Floods and the movement of rivers and streams can also carry extra nutrients from the land into the water systems, generating excessive algal blooms. Additionally, as lakes age, sediments and fertilisers like phosphorus and nitrogen build up naturally, accelerating the formation of phytoplankton and cyanobacteria blooms.

Eutrophication – Impacts

1. The excess of zooplankton, phytoplankton, detritus, fungi, bacteria, and other particulate matter that arises from eutrophication affects the water's turbidity and colour. In drinking water treatment facilities, it increases inorganic substances like nitrites, hydrogen sulphide, ammonia, and others, leading to the production of hazardous chemicals such nitrosamines, which are thought to be carcinogenic.

2. Algal blooms are exceedingly toxic, and when the water becomes anaerobic, more dangerous bacteria grow. When used as drinking water, high quantities of organic compounds in the water produce unpleasant odours or tastes that chlorination can only partly disguise.

3. In addition to obstructing standard purification procedures, these pollutants combine to create complex chemical compounds that deposit on the inside walls of water purifier intake tubes, accelerating corrosion and reducing flow rate. As a result, both the quantity and quality of safe drinking water have dramatically declined.

4. Cyanobacteria and dinoflagellates release extremely harmful poisons into the water in very small amounts. The dangerous compounds additionally quadruple due to the anaerobic circumstances brought on by the water's rapid plant growth.

5. Algal blooms and other aquatic plants that float on a sizable portion of the water's surface are indicators of eutrophication. It lessens water transparency and navigation, which reduces the lakes' recreational value and potential, particularly for boating and swimming.

6. Algal blooms, nile cabbage, and water hyacinth can all spread out across a wide area along the beaches and even drift onto land.

7. The faster the oxygen is depleted in the stream, the higher is the Biochemical Oxygen Demand (BOD). This means that less oxygen is available for aquatic life. Aquatic organisms start suffocating and dying. The release of nitrates and phosphorus from decomposition can cause eutrophication, resulting in increased fish mortality.

Practice Problems

Q1. Eutrophication is also referred as
A) Dystrophication
B) Hypertrophication
C) Both (A) and (B)
D) None of the above
Answer: C

Solution: Eutrophication is also referred as dystrophication and hypertrophication when the scale of eutrophication is large. Hence, options A and B are correct.

So, option C is the correct answer.

Q2. What happens when algae growth occurs?
A) An increase in the number of aquatic creatures
B) Animal deaths
C) Biomagnification
D) An extension of aquatic plants
Answer: B

Solution: The addition of phosphates to water promotes the growth of algae. The water's oxygen content is decreased by the thick layer of algae growth that covers the water's surface. As a consequence, anaerobic conditions develop, which frequently result in the accumulation of toxic deterioration and animal demise. This explains how algae growth leads to aquatic animal’s death.

So, option B is the correct answer.

Q3. Lower BOD is an indication of
A) More oxygen is taken out of the ocean
B) Less oxygen is taken out of water.
C) Both A and B
D) None of the above
Answer: B

Solution: The amount of oxygen needed by bacteria that break down organic materials in water is known as the biological oxygen demand, or BOD. The level of organic materials in the water suggests how contaminated that water is. BOD thus serves as a warning indication for contaminated water.

Lower water quality results from less oxygen being available for oxygen-hungry organisms to consume as a result of higher BOD. On the other side, a low BOD shows that less oxygen is removed from water, which makes it purer.

So, option B is the correct answer.

Q4. Does eutrophication occur naturally?
Solution: The term "eutrophication" refers to a natural process. Many lakes slowly fill up as they age and gather nutrients, sediment, and plant matter over many generations. The process finally comes to an end, and terrestrial plants begin to colonise the basin. Depending on the basin, watershed, and climate conditions, distinct periods of natural eutrophication take place.

Frequently Asked Questions – FAQ

Ques1. What elements are primarily responsible for eutrophication?
Ans. The accumulation of nitrogen and phosphorous is primarily responsible for eutrophication. Algae and aquatic plants feed on these nutrients, grow, spread and turn the water body green causing eutrophication.

Ques2. What is ocean acidification?
Ans. Due to eutrophication, the amount of algae and aquatic plants increases. These algae and aquatic plants eventually die and decompose, producing carbon dioxide in large quantities. This process decreases the pH of the ocean, turning it acidic. This is called ocean acidification.

Ques3. What is an algal bloom?
Ans. When the population of algae in freshwater or marine water systems increases or accumulates quickly, it is referred to as an algal bloom, or algae bloom. A common sign is the hue the algae's colours provide the water. This sort of biological waste exists.

Ques4. Is eutrophication impacted by sunlight?
Ans. A sufficient amount of sunshine raises the water's temperature, and the availability of nutrients creating the ideal environment for the development of algae and phytoplankton. This ultimately leads to eutrophication of the water.

Ques5. How can eutrophication be stopped?
Ans. There are two methods that could be used to reduce eutrophication:

1. Limit down the source of the nutrients (e.g. by phosphate stripping at sewage treatment works, reducing fertiliser inputs).
2. Reduce the amount of nutrients that are now available in the system.

Ques6. What makes eutrophication and red tide relate to each other?
Ans. The term "red tide" refers to the phenomenon of eutrophication in the ocean, which causes the population of some types of microscopic green algae to burst. Eutrophication has occasionally happened spontaneously, despite the fact that human activity is to blame for the majority of the worst occurrences.

Ques7. What is eutrophication caused by humans?
Ans. It is a form of eutrophication brought on by human activity and is typically brought on by the influx of fertilisers rich in potassium into the aqueous body. Deforestation, which leads to soil erosion and the movement of nutrient-rich soil into the water body, is another underlying factor in this problem.