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 shorelines, 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:
What types of health problems can be caused by high numbers of Blue-Green Algae and HABs?
People and pets can experience the following:
- 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:
- Severe diarrhea/vomiting and abdominal pain
- Abnormal liver function
- Kidney toxicity
- Weakness, salivation, tingly fingers, numbness, dizziness, difficulties breathing, death
What is the treatment for people or animals that have been exposed to HAB toxins?
- 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 veterinary treatment as soon as possible if you think 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 public health advisories and/or 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 sprinklers.
- 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.
- Do not eat mussels or other bivalves collected from impacted areas.
- Limit or avoid eating fish from impacted areas. If fish are consumed, eat only the filets - remove guts and liver and rinse filets in clean drinking water. Always follow the Eat Safe Fish waterbody-specific guidelines or Statewide Safe Fish Guidelines, even if a waterbody does not look impacted. Read more about eating safe fish at
Report HABs by calling Environmental Assistance Center at 800-662-9278.
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.
HAB Photos Courtesy of Michigan Department of Environmental Quality