An algal bloom or algae bloom refers to the rapid increase or accumulation in the population of algae in freshwater or marine water systems. It can be recognised by the discoloration in water from the algae’s pigments.
- The term “algae” involves many types of aquatic photosynthetic organisms including macroscopic multicellular and microscopic unicellular organisms.
- Overabundance of algae in waterbodies occurs due to availability of plenty of nutrition, generally, due to more photosynthesis rate.
- An algae film above the water sarface will cause the problem in ecosystem and disturb many fuctions of an aquatic ecosystem.
- It will consume all the sunlight and prevent the gaining of light and oxygen to other aquatic animals and plants
Read Also: Biomagnification
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Keywords: Algae, Photosynthesis, Ecosystem, Nutrition, Oxygen, Organism, Aquatic animals and plants, Water
Definition of Algal Bloom
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“An algal bloom is the rapid increase in the population of algae in an aquatic ecosystem”.
Algae bloom can either be found in freshwater environments or in marine environments. This condition is often recognised by the discoloration in the water.
- Blooms are usually of green, yellow or red in colour.
- The process of discoloration occurs due to the increase in concentration of pigmented cells in water.
- Moreover, algal bloom is formed because of various nutrients like nitrogen, phosphorus which enters into the aquatic system through various fertilizers.
- Algae are usually considered to be blooming if the number of algae cells per millilitre crosses 10,000.
- The number of algae per millilitre can even reach millions.
- In 1991 world’s largest algae boom was recorded in the darling river between the months of October and December.
- This bloom has taken place on a 1000 km long river system.
Representation of an algal bloom
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What Causes Algal Bloom?
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The algae are always present In water bodies but their amount remains in control. When these algae start to grow and concentrate themselves in water bodies it creates problems. There are various factors that causes algae bloom in the water bodies, which are as follows:
High Temperature
As increasing global warming causes depletion of the ozone layer and this forms a major factor behind the immense growth of algal bloom
- Appropriate temperature is required for the proper growth of algal bloom.
- High temperature leads to rapid decompositions of the nutrients like nitrogen, phosphorous which become easy for the bacteria to use up and grow rapidly.
Run of the Nutrients
The cause of excessive increase in the number of algae is nutrients, in particular phosphates. So, during runoff from land or agricultural fields many nutrients rich elements enter water, which mixes with water rapidly and provides nutrition to these algae. The increase in the amount of these algae is beneficial to the ecosystem if their it is not very rapid. These algae can become food of other organisms present in the water bodies.
Existence of Dead Organic Material
There are multitudes of bacteria which are present in the water bodies as well as in the atmosphere. And all these bacteria encourage the growth of algae bacteria like all other bacteria as nutrients in matter along with dead organic causes increase in the growth of algal bloom.
Large Mass of Water
For the rapid growth of the algae bloom, a large mass of water is required. As less disturbance in the propagation of water brings about tremendous growth of algae bloom.
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Harmful Effects of Algal Bloom on Ecosystem
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If the number of algae in a water body increases very rapidly it can create many problems to the water ecosystem. The algal bloom can lead to so many serious problems on aquatic ecosystem, some of these harmful effects are mentioned below:
Death of Aquatic Animals and Plants
With the increase in concentration of algae in the water body, algae completely cover the water body from the top. They form a thick layer of algae on the top and which stops the sunlight from reaching the bottom of the water body.
- Many plants and organisms are present at the lower levels of water will not get proper sunlight due to the layer of the thick formation of algae.
- This affects their life cycle adversely.
- Due to the shortage of sunlight at the bottom, many organisms can’t do photosynthesis properly and hence left with less food to survive upon.
Deterioration of Oxygen Level
As the average life of these unicellular microorganisms are very less, the decomposition process of the body of algae has a huge effect on the ecosystem.
- To decompose the body of an algae, oxygen is consumed.
- When a large number of algae come into life and a large number of bodies of algae decompose, the amount of oxygen used will increase exponentially.
- As during the process no new source of oxygen is created and all the demands have to be met with existing supplies.
- Due to shortage of oxygen under water, a large number of animals and plants die.
Risk on Human Health and Life
Algal bloom produces toxins in the water bodies which, if indirectly consumed by human beings, can cause fatal disorders or diseases like itching or several skin related diseases.
Read More: Effects of air pollution on environment
Types of Algal Bloom
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There are three different types of algal bloom, which are:
Fresh Water Algal Bloom
Due to the deposition of extra nutrients particularly phosphates which originate from the fertilizers used up in the agricultural land, these algae are formed. And higher concentration of nutrients lead to algal bloom formation in freshwater. These blooms may also be absorbed in freshwater aquariums.
Ocean bloom
These types of blooms are found in large water reservoirs like the ocean. This algal bloom harms the aquatic organisms in the ocean. These algal blooms mainly cause depletion of oxygen levels in the ocean which have harmful effects on the aquatic ecosystem.
Harmful Algal Bloom
These blooms have a negative impact on the aquatic system. This impact can be of various types such as depletion of oxygen level, death of aquatic animals and plants.
Also read: Air pollution control
Things to Remember
- Algae bloom is the condition of rapid increase in the population of algae in the water body.
- The algae forming part of the algae bloom are generally unicellular microorganisms.
- The algae bloom in water is generally spotted by decolourisation of water into red, green and yellow in colour.
- Algae bloom led to the increase in the amount of nutrients in water.
- Algae bloom reduces the amount of oxygen in water bodies. Due to which many organisms living under the water either left that water or just died.
- Due to extensive sunlight available to the algae, it grows faster.
- As algae is taking all the sunlight coming to water and stopping the sunlight from reaching the bottom, the organisms at the bottom of water are adversely affected.
Sample Questions
Ques: What are some catalysts for algae bloom? (3 marks)
Ans: Some Catalysts for algae bloom are:
- Stagnant water -Stagnation in the water bodies lead to the thermal stratification, which promotes the growth of algae in water.
- High intensity of sunlight
- If water has excess nutrients, especially phosphorus.
Ques: What type of organisms are usually part of algae? (1 mark)
Ans: Algae bloom usually occurs for unicellular microorganisms. Common example is cyanobacteria.
Ques: What can be the effect of an algae bloom outside the waterbody? (3 marks)
Ans: Effect of algae bloom on:
Economy - Due to the algae bloom, the complete ecosystem gets disturbed. This can lead to the destruction of endangered plants and other organisms. Which will skew the biological diversity. Due to the revenue and employment generating avenues shut down like tourism, fisheries and seafood avenues.
Employment – As fishes and many other organisms will be affected due to algae bloom, people depending upon them for their living will also face a setback. As employment has a multiplier effect, means that If one sort of employment gets affected then this will have a carry on effect on other sectors and on employment of those people who are not directly employment In fishing and seafood sector.
Ques: How can we reduce the cases of algae blooming? (2 marks)
Ans: We can reduce the cases of algae bloom by controlling the overuse of fertilizers in agriculture and reducing the runoff incidents into water bodies. With better surveillance of water bodies, the extreme cases of bloom can also be prevented.
Ques: How does algae bloom destroy the quality of fresh water? (2 marks)
Ans: Algae bloom has a very bad effect on the water. Algae bloom consumes all the oxygen from the water and makes it inhabitant for other organisms. Some algae are even toxic in nature and are harmful to the skin of humans.
Ques: What are the types of algal bloom? (3 marks)
Ans: There are three different types of algal bloom, which are:
Fresh Water Algal Bloom: Due to the deposition of extra nutrients particularly phosphates which originate from the fertilizers used up in the agricultural land, these algae are formed. And higher concentration of nutrients lead to algal bloom formation in freshwater.
Ocean bloom: These types of blooms are found in large water reservoirs like the ocean. This algal bloom harms the aquatic organisms in the ocean. These algal blooms mainly cause depletion of oxygen levels in the ocean which have harmful effects on the aquatic ecosystem.
Harmful Algal Bloom: These blooms have a negative impact on the aquatic system. This impact can be of various types such as depletion of oxygen level, death of aquatic animals and plants.
Ques: What are the negative impacts of harmful algal bloom? (3 marks)
Ans: The negative impacts of the harmful algal bloom are:
- As it produces various toxins thus it causes the death of aquatic organisms.
- It increases the risk of liver disease in affected individuals.
- Disruption of epithelial gill tissues in fish that results in asphyxiation.
Ques: How does the algal bloom affect the lives in water bodies? (All India 2013)
Ans: Algal bloom leads to the deterioration of the water quality. They reduce the dissolved oxygen content in water and cause the mortality of aquatic animals like fish. Moreover, they also secrete chemicals, toxic to humans and many other animals.
Ques: Explain the cause of algal bloom in the water body. How can it affect an ecosystem? (All India 2009)
Ans: Algal bloom is caused by excess presence of nutrients, mainly nitrogen, phosphorus in the water body. They cause:
- Fish mortality
- Deterioration of water quality
- Depletion in oxygen level
- Toxic effect on aquatic animals and human beings
Ques: How does an algal bloom cause eutrophication of a water body? Name the weed that can grow in such a eutrophic lake? (Delhi 2012)
Ans: Algae are considered as the major producers of any aquatic ecosystem. Run-off of nutrients like animal wastes, fertilisers (N and P) and sewage from land cause an increase in the fertility of the lake. It causes a tremendous increase in the primary productivity of the water body leading to increased growth of algae that result in algal bloom.
Eventually, the decomposition of these algae depletes the supply of oxygen, leading to the death of other aquatic animal life and this is called eutrophication.
Eichhornia crassipes (water hyacinth) which is also known as Terror of Bengal can grow in such eutrophic lakes.
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