Potentially harmful algae blooms showing up in St. Croix River

Too much warm weather and nutrient run-off is causing algae blooms which pose potential health risks to humans and animals.




2 minute read

Conservation news on St. Croix 360 is supported by the St. Croix River Association, which works to protect, restore and celebrate the St. Croix River and its watershed.

Blue green algae bloom
Blue green algae bloom (MN Pollution Control Agency)

The National Park Service is reporting that blue-green algae blooms have been spotted in the lower St. Croix River:

Blue-green algae blooms have been seen on the lower St. Croix River. If the water has visible layers of algae or is green or discolored, it is best to avoid contact with the it. Some algae blooms have the potential to form toxins that pose health risks.

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The algae blooms are are caused by a combination of warm weather, excessive nutrients like phosphorus and nitrogen in the water, and lots of bright sunlight. Reducing phosphorus and other nutrients is a major challenge in Lake St. Croix, with several agencies working to protect the water.

Health Risks

People and pets should stay away from blue green algae blooms. Coming in contact with the algae can cause skin irritation and respiratory problems. Rinse off after swimming and make sure your pets don’t drink the water. More information about the risks is available here.

Help Prevent Algae Blooms

St. Croix River region citizens can do several things to help improve water quality in the river:

  • Don’t use fertilizers on your lawn and garden — or at least use low-phosphorus products
  • Make sure your septic system is working — and empty it every two to three years
  • Use rain barrels and rain gardens to filter water before it runs off your property
  • Support farming practices that help protect clean water
  • More…




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Potentially harmful algae blooms showing up in St. Croix River