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Harmful Algal Blooms
What You Need to Know
What are Harmful Algal Blooms (HABs)?
Many organisms live in the Great Lakes, including algae. When certain conditions are present, such as high
nutrient or light levels, these organisms can reproduce rapidly. Dense populations of algae are called a bloom.
Some blooms are harmless, but when the blooming organisms contain toxins, other harmful chemicals, or
pathogens, it is known as a harmful algal bloom (HAB). HABs can cause death of fish and fowl of nearby coastlines,
and produce harmful conditions to aquatic life, humans and pets.
What are toxic species of HABs?
There are many species of algae, and most do not produce toxins. Algae are a natural part of water ways. 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 area
are:
• Microcystis aeruginosa
• Anabaena circinalis
• Anabaena flos-aquae
• Aphanizomenon flos-aquae
• Cylindrospermopsis raciborskii
What types of health problems can people and pets experience from exposure to high numbers of Blue-Green
Algae and HABs?
• Skin contact may cause rashes, hives, or skin blisters (especially on the lips and under swimsuits).
• Breathing aerosolized (suspended water droplets) lake water mist from recreational activities and/or lawn
watering can cause runny eyes and noses, a sore throat, asthma-like symptoms, or allergic reactions.
• Swallowing HAB-contaminated water can cause:
o Severe diarrhea/vomiting and abdominal pain
o Abnormal liver function
o Kidney toxicity
o Weakness, salivation, tingly fingers, numbness, dizziness, difficulties breathing, death)
What is the treatment for people or animals that have been exposed to HAB toxins?
• Rinse off with clean, fresh water as soon as possible.
• Remove people from the exposure and seek medical treatment if symptoms occur.
• Thoroughly rinse off pets with clean, fresh water if they swam in an area with a HAB. If they lick their fur after
leaving the water they may ingest large amounts of the toxin.
• Seek medical treatment as soon as possible if you think you or your pet, might have been poisoned by toxic
HAB.
How can I protect myself, family and pets from exposure to HABs?
• Do not drink untreated surface water, whether or not blooms are present. Remember, boiling the water will
not remove the toxins.
• Obey posted signs for beach closings.
• Do not allow children or pets to play in or drink water where algae or scum is present.
• Do not swim, water-ski, or boat at high speeds in areas where algal blooms are occurring. Avoid direct
contact with the lake water, or aerosolizing the water.
• Do not water lawns, gardens, or golf courses with water from HAB-impacted lakes or ponds because it
aerosolizes the water.
• Report unpleasant tastes or smells in your drinking water to the local water utility.
• Do not use algaecides to kill cyanobacteria. When the cells die the toxins are released directly into the water.
What do HABs look like?
• Blue-green algae are the most common HABs. They are actually bacteria (cyanobacteria) which are able to
photosynthesize, hence the green color.
• Some blooms 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.
Blue-green algal bloom in Lake Erie on the shore of Catawaba Island, Ohio in summer 2009
Photo Courtesy of : http://www.miseagrant.umich.edu/downloads/hab/bluegreenalgae_2009factsheet.pdf
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