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What are Algal Blooms?

There are many species of single-celled organisms living in the Great Lakes, including algae. When certain conditions are present, such as high nutrient or light levels, these organisms can reproduce rapidly.  This dense population of algae is called a bloom.

Blue-green algae are the most common, but not the only group of algae to form HABs. Blue-green algae are actually bacteria (cyanobacteria) which are able to photosynthesize, hence the green color. Cyanobacteria live in terrestrial, fresh, brackish, or marine water. They usually are too small to be seen individually, but  sometimes can form visible colonies. Some cyanobacterial blooms can look like foam, scum, or mats on the surface of fresh water lakes and ponds. The blooms can be blue, bright green, brown, or red and may look like paint floating on the water. Some blooms may not affect the appearance of the water. As algae in a cyanobacterial bloom die, the water may smell bad. If you detect an earthy or musty smell, taste or see surface scum's of green, yellow, or blue-green, the water may contain blue-green algae. Only examination of a water sample under the microscope will confirm the presence of blue-green algae.

What makes an Algal Bloom harmful?

Some of these blooms are harmless, but when the blooming organisms contain toxins, other noxious chemicals, or pathogens, it is known as a harmful algal bloom, or HAB. HABs can cause the death of nearby fish and foul up nearby coastlines, and produce harmful conditions to marine life as well as humans.  Algae are a natural part of our waterways. There are many species of algae, and most do not produce toxins.  However, all blue-green algae, or cyanobacteria, can produce skin irritants under  certain conditions, and some can produce multiple types of the more harmful toxins. The most common species of toxic cyanobacteria in the Great Lakes are: Microcystis aeruginosa, Anabaena circinalis, Anabaena flos-aquae, Aphanizomenon flos-aquae, and Cylindrospermopsis raciborskii.

How do Algal Blooms impact people, marine life, and ecosystems?

HAB toxins may kill fish or shellfish directly, and people who eat contaminated seafood may also become sick or suffer fatalities if they ingest sufficient toxins. Even blooms that are not toxic can cause damage by suffocating fish, blocking light from bottom-dwelling plants, or depleting the oxygen in the water.

Above explanations are excerpts from:

GLERL: Harmful Algal Blooms in the Great Lakes Fact Sheet:  What they are and how they can affect your health

NCCOS: Harmful Algal Blooms

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Click for health and safety information on  HABs from the Ohio EPA
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National Centers for Coastal Ocean Science News - Lake Erie


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