Courses for Kids
Free study material
Offline Centres
Store Icon

Algal Bloom

Last updated date: 22nd Jul 2024
Total views: 370.8k
Views today: 5.70k
hightlight icon
highlight icon
highlight icon
share icon
copy icon


Algae are living organisms that can produce their own food by photosynthesis. They are present all over the world and present in distinct sizes, shapes and colours depending upon the ecosystem they survive. They have the ability to grow alone or grow upon various surfaces of rocks, the soil or the surface of other living organisms. Along with the plants, they are one of the most critical species as they are the source of a lot of oxygen produced as a result of their photosynthesis. They are classified as protists in the classification of living things. 

Characteristics of an Algae

As mentioned above, Algae are protists that are capable of making their own food. They are found widespread on the Earth and are present in differing sizes in various ecosystems. Microscopic algae are found in the oceans, lakes, phytoplankton, etc. The smallest species of algae are the phytoplanktons being small enough to be accommodated on a pin’s head in thousands. On the other hand, the largest species of algae are the corals and range in size from the bottom of the ocean to the water surface covering a height of 100m. 

Although most of the algae species live in seawater or freshwater, they can grow in soil, plants and animals like tortoises and polar bears, and below or above the porous rocks of sandstone and calcium carbonate rocks. Some of their species can survive extreme temperatures and pressure conditions as well. Algae are also found in the depths of polar ice in hot springs and on snowbanks. 

The algae absorb solar energy and turn inorganic substances into simple sugars via photosynthesis. Almost all the species of algae contain the pigments necessary for carrying out photosynthesis. They produce oxygen as the byproduct of photosynthesis unlike the photosynthetic bacteria such as the green and purple bacteria. Some of the unicellular algae are dependent on external sources of energy as their own photosynthetic capability has been reduced. 

What is Algal Bloom?

Whenever there is an increase in the population of algae in a given environment, it is referred to as algal bloom. Thus, the algal bloom definition is said to be an increase in the population of algae in a particular area owing to a variety of factors. The bloom definition holds true especially in freshwater or marine environments. The algal bloom meaning involves the rapid increase in the population of the aquatic photosynthetic organisms, microorganisms such as seaweeds and small unicellular organisms such as cyanobacteria. An example of the algal bloom definition is provided by the kelp forests which is a microscopic algal bloom.

Algal bloom can be caused by the release of nutrient-rich fertilizers such as nitrogen or phosphorus-containing fertilisers or any nutrition source into the freshwater or marine ecosystem. This causes a rapid increase in the population of the algae. The algal bloom effects can range from beneficial to the increasingly harmful effects of algae population. One of the beneficial outcomes is the increase of food for organisms coming in the higher trophic levels. On the other hand, the harmful effects of algal bloom can be dangerous with the prevention of sunlight being available to other organisms, oxygen loss in the environment i.e. increase in biological oxygen demand, and sometimes secretion of toxins into the ecosystem. This entire process of increase in the supply of nutrients leading to the algal bloom as per the algal bloom definition biology is known as eutrophication.

Upon discussing what is algal bloom, the causes for algal bloom are briefly described below.

Causes for Algal Bloom

The following are the causes of bloom that provide a basis to the algal bloom meaning. 

1. Nutrient Oversupply

According to the bloom definition, an increase in the population of the protists algae leads to an algal bloom. Most of the nutrient supply comes from the fertilizers that are leaked away into the water bodies by the rains from the fields to streams to rivers and following up to the oceans. They are majorly nitrogen-containing and phosphorus-containing fertilizers. Another source is the untreated or partially treated sewage water which is a source of nitrogen-containing compounds like nitrate, ammonia, etc. leaked or allowed to flow through the sewage treatment plants. One of the most rapid contributions to algal bloom is provided by the industrial wastes that are also a major cause of water pollution. Overall, most of the nutrient supply that gives algal bloom meaning a reality comes from the various sources of water pollution which often is contaminated with minerals and nitrogen and phosphorous compounds. 

2. Dead organisms

Diverse kinds of bacteria are present in the water bodies and the atmosphere. Many of them feed and survive on dead organic matter. The algae bacteria obtain significant nutrition from the dead living organisms in the water bodies as well. This in combination with the nutrient supply due to water pollution leads to the propagation of algal bloom. Thus, algal bloom meaning obtains a significant rise owing primarily to these two factors for nutrient supply. 

3. Global Warming

Although seemingly unrelated, global warming has a significant effect on the growth rate of algal bloom. When asked to define algal bloom, one can state it as a rise in the algal population especially in a water body because of the increase in the nutrient content of nitrogen and phosphorus from water pollution and dead organic matter. But these nutrients are present in compounds and cannot be utilised directly by the algae. It requires an increase in temperature for the decomposition of the compounds. Global warming provides the sufficiently needed temperatures not only for increasing the decomposition but also the rate of decomposition. 

4. Stagnancy of Water in Water Bodies

Many water bodies such as lakes and ponds are stagnant. This means that the concentration of the chemical compounds is not diluted or refreshed with time. Whenever there is any leak of chemicals into the water bodies, the concentration only keeps on increasing, providing an abundance of nutrition to the algae and thus giving rise to an algal bloom.

Effects of Algae

The following are the benefits of algae and the potential advantages of algal bloom within the critical limits. The algal bloom facts that are advantageous are:

1. Source of Oxygen

The byproduct of the photosynthesis of algae is oxygen. Thus it serves as an oxygen supply source for more than 40% of the oxygen requirement for all living animals.

2. Food source

Since they are capable of photosynthesis, algae are the primary producers. Hence, they are extremely important as food sources for aquatic organisms. As it serves as the base of the food chain it is quite essential for the food requirements of many aquatic living organisms. Examples include phytoplanktons.

3. Pollution Indicator

Because of the increase in the population of algae, it covers the surface of the water body or most of the aquatic body. This creates an increase in the biological oxygen demand of the water bodies and causes the death of many aquatic living organisms. Also, the sunlight is not able to penetrate the water surface preventing the growth and sustenance of many water plants and aquatic organisms.

FAQs on Algal Bloom

1. What is Algal Bloom and What Causes it?

Ans: The multiplication of the population of the algae in a water body is known as the algal bloom. This is caused by the increase of nutrients such as nitrogen and phosphorus in the water body owing to water pollution and dead organic matter present in the water body.

2. Why is an Algal Bloom Harmful?

Ans: With the increase in the algal bloom the oxygen content in a water body is reduced gravely. Also, due to an increase in the algae population, the sunlight is blocked and cannot reach the depths of the water body thus preventing the growth of organisms dependent upon the sunlight.