Since the late 1990s, Lake Erie has been plagued with blooms of toxic algae that turn its waters a bright blue-green. These harmful algae blooms are made up of Cyanobacteria that produce the liver toxin Microcystin. The blooms have led to public warnings to avoid water contact, and entire community water supplies can be shut down.

This year’s bloom is expected to measure 7.5 on the severity index, but could range between 6 and 9. An index above 5 indicates blooms having greater impact. The severity index is based on bloom's biomass – the amount of algae – over a sustained period.

"Algae blooms can be a mixture of toxic and non-toxic forms, and different species of Microcystin-producing Cyanobacteria can inhabit different parts of Lake Erie," says George Bullerjahn, director of the Great Lakes Center for Fresh Waters and Human Health.

In late summer, Cyanobacteria called Microcystis are found in Lake Erie's open waters. From spring through fall, another Cyanobacteria genus, Planktothrix, blooms closer to shore. Nutrients that fuel Cyanobacteria blooms usually come from the nitrogen in agricultural runoff; the runoff makes its way into streams and rivers, eventually flowing into large waterbodies such as lakes.

Areas near shore are prone to nitrogen loss as summer progresses and the amount of rainfall - and runoff - decreases. Nutrients from spring rains spark Planktothrix blooms, but their persistence through late fall is due to the ability of the Planktothrix Cyanobacteria to "scavenge" nitrogen from their environment better than Microcystis can.

Nitrogen seems to be the common driver for toxic blooms of Planktothrix not only in Lake Erie, but worldwide. The size of a bloom isn’t necessarily an indication of how toxic it is. For example, the toxins in a large bloom may not be as concentrated as in a smaller bloom. Each algal bloom is unique in terms of size, toxicity, and ultimately its impact to local communities.

Harmful algal blooms (HABs) of Cyanobacteria (blue-green algae) in Lake Erie can produce toxins that can pose a risk to drinking water, cause skin irritation, and negatively affect wildlife, companion animals and livestock.

Effects on Humans

  • Contact with skin can cause rash, hives, or skin blisters (especially on the lips and under swimsuits).
  • Inhalation of water droplets can cause runny eyes and nose, a sore throat, asthma-like symptoms, or allergic reactions.
  • Ingestion of the water can cause abdominal pain, headache, sore throat, nausea and vomiting, dry cough, diarrhea, blistering around the mouth, and pneumonia.

What you can do:

  • Contact your healthcare provider OR regional health department.

Effects on Animals

  • Ingestion of the water can cause lethargy, vomiting, diarrhea, weakness, pale mucous membranes, death.

What you can do:

  • Seek medical treatment immediately if you suspect your animals have been exposed.

How can you Avoid Exposure?

Drinking Water

Health officials conduct routine monitoring to ensure that public drinking water is safe.

What you can do:

  • Follow drinking water advisories and contact your regional health department with questions.

Recreational Water Safely

You can still boat and recreate in Lake Erie waters, but be aware that HABs may be present.

What you can do:

  • If you can, plan your trip by checking NOAA's HAB Bulletin before you go.
  • Respect any waterbody closures announced by local public health authorities.
  • Avoid activities in areas where the water is discolored by algae or scums are visible.
  • Thoroughly wash yourself and animals after suspected contact with a HAB.