08/28/2025
EDIT: The photo that originally accompanied this post was pollen and was posted in error. The photo now accompanying this post is of the current algal bloom at Chickenbone Lake.
Harmful Algal Bloom (HAB) Update
Algal blooms have been identified in Chickenbone Lake, Lake Richie, Lake Desor, and Todd Harbor. It is not recommended to filter water from any impacted areas of these water sources.
Suspected blooms are tested for toxin levels and monitored when possible. Given the consistently low toxin levels of blooms on Isle Royale, water quality safety guidance has been updated:
❌ It is not recommended to filter water in any areas where there is surface scum, strong odors, or other evidence of a significant bloom.
✅ Blooms move around depending on wind and rain – filter water from places where blooms are not present or a different water source.
✅ It is low risk to filter water from relatively clear areas of an impacted water source.
For more information on HABs, visit: https://www.nps.gov/isro/planyourvisit/hab.htm
📷 Example of surface scum from an algal bloom / NPS