How Algal Blooms Affect The Environment

Algal blooms are thick layers of small green plants that appear on the surface of lakes and other water bodies due to excess nutrients, especially phosphorus and nitrogen. This covering on the surface of lakes and other water bodies is known as eutrophication. The excess level of nutrients that algae depend on results from human activities that cause pollution, such as fertilizer, wastewater, manure, and sewage runoff.

environmental impacts of algal blooms

Eutrophication can also be a natural occurrence from moderate accumulation of organic matter, silt, nutrients, and sediments gradually from the watershed. Algae come in different colors ranging from green, red, yellow, and brown. The most common algal blooms are blue-green cyanobacteria and microalgae, also known as red tides.

Algal blooms affect the environment in various ways, including causing harm to both humans and animals. Its presence contaminates water and makes it unfit for consumption. Algae multiplication depletes oxygen in the water leading to the death of aquatic life. There’s a need for awareness creation among communities on dealing with algal blooms to conserve the environment. Awareness can be created through informative forums where researchers and community leaders, among other vital people, discuss important topics like the Indian river lagoon algae bloom.

This article will discuss some causes of algal blooms and how they affect the environment. Read on to learn.

Causes Of Algal Blooms

Below are some causes of algal blooms:

1. Dead Organic Matter In Water

Dead organic matter and nutrients in water promote the growth of algae bacteria, leading to algal blooms.

2. Light Conditions

Cyanobacteria, also known as blue-green algae, grow faster and in fluctuating light conditions. They can thrive in intermittent high-light and low-light conditions.

3. Drainage Of Nutrients

The growth of algal blooms is increased by excess amounts of phosphatic and nitrogenous fertilizers drained by rain from farms into the water bodies like lakes, rivers, and streams. Untreated raw sewage rich in nitrates and ammonia also flows into water bodies through drainage systems, causing the growth of algal blooms.

4. Global Warming

As the ozone layer is gradually destroyed, temperatures rise. These high temperatures cause nutrients such as ammonia and nitrates to decompose speedily and are used up by algae bacteria and quickly form algal blooms.

5. Slow-Moving Water

Algal blooms thrive best in large and still water masses. Blue-green algae, for instance, grow well in slow-moving water, less turbulence, and light winds. This is why they may not grow in fast-moving streams and rivers.

How Algal Blooms Affect The Environment

The following are some of the effects of algal blooms on the environment.

1. Threaten Human Health

Algal blooms contaminate water, thus affecting aquatic life. Humans may fall sick from drinking water and eating infected seafood. The water also has toxins that irritate the skin when people come into contact with it when swimming.

2. Kill Aquatic Life

Animals that live in water depend on oxygen to survive, similar to algal blooms. Their fast and dense growth causes competition for oxygen, leading to the suffocation of sea animals.

why algal blooms are bad for the environment

3. Cause High Accumulation Of Biomass

Biomass is highly accumulated as algal blooms grow, destroying the environment by blocking light, clogging fish gills, and depleting oxygen after algal cells decompose.

4. Affect The Food Chain

As discussed earlier, algal blooms destroy aquatic life. This happens through the toxins that they produce. The food chain is affected when small fish and shellfish, which are food to other sea animals like turtles, dolphins, and sea lions, are harmed. These animals are physiologically stressed, and their feeding is threatened since they avoid toxic prey. As a result, the energy flow within the ecosystem is affected.

5. Pollution By Ozone

Ground-level ozone, formed by nitrogen oxides from nitrogen compounds in the air, causes visibility constraints. The ozone can be transferred by the wind far away from urban to rural areas causing damage to trees and vegetation.

6. Acid Rain

Acid rain results from nutrient pollution, where Sulphur Dioxide and Nitrogen Oxide are released into the atmosphere and react with water, oxygen, and other chemicals to form sulfuric and nitric acids. This combination damages water bodies, grasslands, and forests.


As discussed above, algal blooms produce toxins that affect the environment in various ways. It could threaten human health and aquatic life. Algal blooms also contribute to the high production of biomass.

Awareness of the dangers of algal blooms will help you be extra cautious. Therefore, be careful about discolored and smelly waters, as they could be home to algal blooms. The water is contaminated and therefore not fit for consumption and recreational activities like swimming because it irritates the skin.

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About Salman Zafar

Salman Zafar is the Founder of EcoMENA, and an international consultant, advisor, ecopreneur and journalist with expertise in waste management, waste-to-energy, renewable energy, environment protection and sustainable development. His geographical areas of focus include Middle East, Africa, Asia and Europe. Salman has successfully accomplished a wide range of projects in the areas of biomass energy, biogas, waste-to-energy, recycling and waste management. He has participated in numerous conferences and workshops as chairman, session chair, keynote speaker and panelist. Salman is the Editor-in-Chief of EcoMENA, and is a professional environmental writer with more than 300 popular articles to his credit. He is proactively engaged in creating mass awareness on renewable energy, waste management and environmental sustainability in different parts of the world. Salman Zafar can be reached at or

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