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Blue-green algae are a natural part of water-based ecosystems. They become a problem when nutrients (phosphorus and nitrogen) are present in concentrations above what would occur naturally. Under these conditions, algae can “bloom,” or grow very quickly to extreme numbers. Summer heat and calm water can increase the likelihood of bloom occurring because blue-green algae are specially adapted to take advantage of such conditions.
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There are many different aquatic organisms that have historically been called “algae.” Though there are some similarities in the different forms of “algae” (they are aquatic and can photosynthesize), these organisms have a wide range of physical attributes. Our scientific understanding of these organisms has increased through time, and we now recognize the term “algae” as a non-scientific description of organisms that are not necessarily related.
“Blue-green algae” are actually bacteria and are thus even more distinct from other types of algae. Blue-green algae are simple aquatic organisms that exist naturally in marine and freshwater waters, rivers, lakes, and ponds. When they are present in low numbers, they are a normal part of a healthy ecosystem.
The terminology for harmful algal blooms can be confusing, as many are used interchangeably.
Blue-green algae can also be known as cyanobacteria. Some researchers prefer the term “cyanobacteria” as blue-green algae is a type of bacteria.
An “algal bloom” refers to a dense growth of any type of algae. A “harmful algal bloom” refers to a dense growth of algae that has the potential for creating toxins or other nuisance compounds. “Harmful algal bloom” is often condensed into the acronym “HAB.” Some researchers have started using the phrase “CyanoHAB” to further define a harmful algal bloom that consists of blue-green algae.
At times, blue-green algae can reproduce very rapidly, creating a dense growth known as a bloom. Some species or strains of blue-green algae produce toxins, which can be released when they become stressed and/or die. It is still not fully understood why these compounds are produced - whether they are adaptations that benefit the organism, or whether they are merely by-products of some other important process. Some other types of algae can also produce harmful blooms; the famous marine “red tides,” produced by overgrowth of red algae, are an important example.
Blue-green algae are the culprits behind harmful algal blooms (HABs) in Kansas. They can have the ability to produce toxins, and even non-toxic blooms can cause skin irritation. Not all strains of a given species produce toxins, but most of the potentially harmful blue-green algae that have been seen in Kansas belong to one of three genus groups: Microcystis, Aphanizomenon, and Dolichospermum (formerly called Anabaena).
Due to the potential size of the blooms created by these groups and the possibility of the toxin production, a blue-green algae bloom is often known as a harmful algal bloom, or HAB. If the water is scummy, has a thick mat of growth, or is foamy, it can be an indication that there is a HAB present. Another indicator of a potential HAB is the color. The water could be colored pea-green, blue, or blue-green, and a cyanobacterial bloom can look like a vivid paint spill or floating grass clippings.
Because HABs are of national and international importance, many agencies and organizations post and publish relevant information. Please refer to the Links of Interest page on our site for a selection of these.
To view a presentation on general information about harmful algal blooms, refer to this video presentation by Ed Carney.