NATIONAL PARK SERVICE · alerts
Harmful Algal Blooms Occurring in Lake Richie and Intermediate Lake
August 21, 2026 · Source: National Park Service
Blooms are tested for toxin levels and monitored. Toxin levels are consistently low on Isle Royale. 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.
Read the official NPS sourceWhat Travelers Need to Know
Use the official notice to confirm the affected destination, dates and visitor arrangements before finalizing your trip.
This is an archived notice. Confirm its current status on the official conditions page before traveling.
Traveler guidance by State & Nation Staff Writer.