Protecting and Preserving Black Lake and the Surrounding Watershed

Update on Algae Bloom in Black Lake

Public Health Awareness Bulletin Update on Algae Bloom in Black Lake

District Health Department No. 4, in consultation with the Michigan Department of Health and Human Services (MDHHS) and Michigan Department of Environment, Great Lakes and Energy (EGLE), is continuing to issue a public health awareness bulletin about an algal bloom in Black Lake near Onaway, Michigan. People and pets should avoid direct body contact with algae in the lake or with water that is blue-green or water that looks like it has a green sheen or spilled paint on its surface. The algae layers may contain flecks, foam, or clumps. People and pets should also avoid swallowing the lake water.

Cyanobacteria blooms have been observed again on the lake. Given the results received on 9/23/2020 from the latest testing, it should be assumed that the blooms that are present now are also toxin-producing.

Although most algal blooms are not harmful, there are some made of cyanobacteria that can produce toxins – and can result in a harmful algal bloom (HAB). Out of an abundance of caution, District Health Department No. 4 wants residents and visitors to be aware of the algal bloom on Black Lake. Advice may change based on additional testing or as more information becomes available. Also, the amount of algae in the lake can change quickly.

What should I do if I see a HAB?

  • Stay out of water that may have a HAB. Enter and swim in nonaffected areas of the lake.
  • Do not let your children or pets play in HAB debris on the shore.
  • Never swallow any lake or river water, whether you see HABs or not.
  • Do not let pets lick HAB material from their fur or eat HAB material.
  • Do not drink or cook with lake water.
  • See a doctor if you or your children might be ill from HAB toxins, or call Poison Control at 1-800-222-1222. If your pet appears ill, contact your veterinarian.
  • HABs should be reported to EGLE by calling the Environmental Assistance Center at 1-800-662-9278 or emailing

For more information about HABS

The Michigan Department of Health and Human Services’ website ( offers information about algal blooms along with The Center for Disease Control and Prevention’s Harmful Algal Bloom (HAB) – Associated Illness site (