Umpqua National Forest

Questions and Answers

(Espanol)

What are blue-green algae?

Blue-green algae are simple plants that occur naturally in water and wet areas.

What is a blue-green algae bloom?

A bloom is a rapid buildup of algae that creates a green, blue-green, white or brown color on the surface of the water. They are often found in standing water in lakes, reservoirs, ditches, ponds, streams, and rivers and the algae can be found near the shore due to wind or waves.

What causes blooms?

Warm, calm water and nutrients contribute to the rapid growth of algae. Blooms can occur anytime of the year, but are most common between June and September.

How do I know if a bloom is toxic?

Only a few types of blue-green algae are known to produce toxins. Many of the lakes and reservoirs in the state are monitored for toxic algae blooms and the public is notified when these blooms occur. However, it is important to always look for the signs of an algae bloom before you enter the water.

How dangerous is toxic algae?

If toxic algae is swallowed it can cause diarrhea, nausea, cramps, fainting, numbness, dizziness, tingling, and paralysis. Skin contact can cause rashes or irritation. Children and pets are at greatest risk.

What should I do if I see a bloom?

When a bloom is present it is best to stay out of the water and to keep pets away. If you do contact the water, wash thoroughly with a clean source of water. Do not use the affected water for drinking or cooking because toxins cannot be removed with filtration, boiling or chemical treatments. However, activities near the water such as camping, picnicking, biking, and hiking are safe.

What about fishing?

Eating fish caught during a bloom can pose a health risk. For additional information about fish consumption contact the Department of Human Services.