By Channade Sampong
What is an algal bloom?
Harmful algal blooms, HABs for short, occur when there is an overgrowth of algae in the water, which could potentially contain toxins that have a detrimental impact on the health of people and animals, causing them to become very ill and possibly die. They can thrive in freshwaters, saltwaters, and brackish waters throughout the United States. HABs are harmful so when they become too dense, use up the oxygen in the water that is for the aquatic organisms, and produce toxic gases.
This is a bird’s eye view of what an algal bloom looks like. This is an algal bloom that is adjacent to a town.
What are the causes of an algal bloom?
HABs can be a result of human activities that produce and accelerate the growth of algae. Some of these human activities include runoff from agriculture and dissolved chemicals going into the water supply via rainfall or irrigation to create nutrients that the algae live off. Some more factors that may contribute to the appearance of HABs are high temperatures, a high light intensity, stable conditions with mild winds and minimal turbulence, and low turbidity.
The appearance of blooms
There are different colors of algae depending on the type of phytoplankton in these blooms.
Cyanobacteria (aka blue-green algae not really algae however):
Cyanobacteria is a type of phytoplankton found in water and soil.Despite it not being harmful to people or animals, toxins can still arise from the buildup of this bacteria. Cyanobacteria make the water blue, green, red, or brown with scum, mats or paint floating on the surface.
Dinoflagellates & Diatoms (aka microalgae or red tide):
Dinoflagellates and Diatoms are two different types of phytoplankton found in saltwater or brackish water, and they are often called red tides because they make water appear red. Besides the color red, these phytoplankton can make water appear brown and gold. These phytoplankton are also harmful to people and animals by making toxins or growing too dense.
An example of cyanobacteria floating on the top of a body of water
Red tide algae floating on the top of a body of water
How to protect yourself and others
To protect yourself, others, and your pets, you must do the following:
Check local and state swimming and fishing advisories before visiting lakes, rivers, and oceans.
Avoid water that smells bad, looks discolored, has dead fish or other animals washed up on the shore
Avoid water that has foam, scum, algal mats, or paint like streaks on the surface
Eschew pets or livestock from water that suspiciously bloomed
Some ways to prevent and treat HABs and Cyanobacteria
Pick up and dispose pet waste since it contains excess nutrients and bacteria
Use phosphorus-free fertilizers and detergents to limit nutrient-rich runoff
Consult a qualified water-management professional who can monitor the water quality regularly and advise appropriate treatments
Create an area where plants absorb the nutrients from runoff
Harmful Algal Blooms (HABs)-Associated Illness:Avoid Harmful Algal Blooms. 2021, June 28 CDC. September 20, 2021, from
Harmful Algal Blooms (HABs)-Associated Illness:Causes and Ecosystem Impacts. 2021, April 19. CDC. September 20, 2021, from
Harmful Algal Blooms. 2020, November 30. Environmental Protection Agency. September 20, 2021, from
Harmful Algal Blooms. n.d. Pollution Prevention Institute. September 20, 2021, from https://www.sbeap.org/water-quality/harmful-algal-blooms
Top 10 Ways: How to Prevent Harmful Algal Blooms and Cyanobacteria. n.d. Solitude Lake Management. September 20, 2021 from https://www.solitudelakemanagement.com/blog/10-ways-prevent-harmful-algal-blooms-cyanobacteria-toxic-blue-green-algae/
What causes algal blooms? n.d. Center for Earth and Environmental Science. September 20, 2021, from