State officials are warning of the potential dangers of harmful algal blooms, or HABs, in Michigan waters during the summer or fall months.

HABs form due to a rapid overgrowth or bloom of cyanobacteria, also known as blue-green algae. Cyanobacteria are naturally present in lakes, rivers and ponds. Unfortunately, some cyanobacteria produce toxins, called cyanotoxins, that can be present in cyanobacterial blooms and at higher levels can be harmful to people and animals.

HABs usually occur in Michigan May through October, most commonly in August and September. The occurrence of cyanobacteria and their toxins has been confirmed in lakes across Michigan in previous years, and elevated toxin levels have been documented in a small percentage of Michigan lakes. During 2020, 61 HABs in 35 Michigan counties were reported to the Michigan Department of Environment, Great Lakes, and Energy.

Last summer, the Western Upper Peninsula Health Department, working with the Michigan Department of Health and Human Services and EGLE, issued a cyanobacteria HAB recreational public health advisory in late June 2020 for Portage Lake, Portage Canal and Torch Lake in Houghton County, although subsequent testing turned up no toxins.

HABs can look like algal scums or mats, spilled paint or pea soup, or colored streaks on the water’s surface. Blooms can last for days or sometimes weeks, and can change in size, toxicity and location within the same day.

Those who think they have found a HAB can consult the HAB Picture Guide at https://www.michigan.gov/documents/egle/egle-wrd-swas-habs-picguide_694983_7.pdf to compare a HAB to other algae and plants found in lakes.

If a suspected HAB is found —

— Do not let people, pets or livestock in the water or near the shore in affected areas;

— Unless the bloom covers a large part of the lake, any part of the lake that is not affected can be used;

— Always rinse off people and pets after contact with any lake water;

— If an HAB advisory or closing has been posted, follow its instructions.

Report suspected HABs to EGLE by e-mailing AlgaeBloom@Michigan.gov or calling 800-662-9278. If possible, include photos.

Symptoms of HAB exposure — by breathing or swallowing water that has the toxins — include runny eyes or nose, asthma-like symptoms, stomach pain, vomiting, diarrhea, weakness, numbness, headaches, dizziness or difficulty breathing. Skin contact can cause rashes, blisters and hives.

“If you may have had contact with or swallowed water with a HAB and feel sick, call your doctor or Poison Control at 800-222-1222. If symptoms are severe, seek emergency medical attention as soon as possible,” said Dr. Joneigh Khaldun, MDHHS chief medical executive and chief deputy for health.

Animals, especially dogs, also can become ill or die after contact with HABs. Signs of illness can include vomiting, diarrhea, staggered walking and convulsions. Preventative measures include keeping them out of the water wherever surface scums or discolored water are visible, bringing along clean, fresh water for them to drink and rinsing them off after contact with any lake water. If a pet or livestock animal becomes sick after contact with water that may have a HAB, contact a veterinarian right away.

Illness in an animal due to exposure to a HAB is reportable to the Michigan Department of Agriculture and Rural Development. Cases can be reported by submitting a Reportable Disease Form at Michigan.gov/dvmresources under “Reportable Diseases,” or by calling 800-292-3939 8 a.m. to 5 p.m. Monday through Friday.

How can HABs be prevented? Michigan residents should learn about nutrient pollution, such as excess nitrogen and phosphorus. Excess nutrients may come from detergents, sewers, fertilizers and malfunctioned septic systems.

For more information on health effects, causes, and reports on the occurrence of HABs in Michigan lakes, go to Michigan.gov/habs.