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Frequently Asked Questions
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Harmful Algae Bloom FAQs

Q: What is blue-green algae?

A: It's not algae at all but a primitive single celled bacteria found naturally in fresh and salt water. Scientists call them cyanobacteria.

Q: Why is it called blue-green algae?

A: Like algae, cyanobacteria use sunlight to photosynthesize and phosphorous and nitrogen for food. The word "cyan" means blue which is an appropriate name since most blooms are blue-green in color.

Q: What is a blue-green algae bloom?

A: When weather, sunlight and nutrients (food) are ideal, cyanobacteria can multiply into what we call a bloom. As long as these bacteria get what they need to survive they can continue to multiply.

Q: What do these blooms look like?

A: There are two major groups. One can look foamy, scummy or thick like paint and blue-green, brownish red, pea green or white in color. The other looks like a dark green or black slimy mat that can have a smelly, offensive odor. 

Q: Why do blooms sometimes appear overnight?   

A: Most cyanobacteria have evolved to be able to control their buoyancy. By being able to sink and rise at will, they are able to move to where nutrient and light levels are at their highest. At night, when there is no light, cells are able to adjust their buoyancy and often float to the surface forming a surface scum. This scum literally appears overnight and lingers until the wind and waves scatter the cells throughout the water.

Q: Why are these blooms a health concern?  

A: Not all blooms are harmful, but some species of cyanobacteria can produce toxins that can cause serious illness or death in pets, livestock and wildlife. These toxins can also make people sick and in sensitive individuals also cause a rash or irritation.

Q: How will I know if the bloom is toxic? 

A: Unfortunately, you can't tell if a bloom is toxic just by looking at it. Nor is the size of the bloom associated with the amount of toxins that can be produced. Because we don't know why or when cyanobacteria produce toxins it's impossible to predict when a bloom is toxic unless toxin testing is done. This type of testing is only performed on a few lakes.
Q: What are the health risks posed by exposure to these toxins? 

A: Although these toxins are not absorbed through the skin, a rash or irritation of the skin and eyes can develop after contact with toxins in the water. If affected water is swallowed, you may experience one or more of these symptoms; headaches, cramps, diarrhea, nausea and vomiting, numbness, dizziness, fever. Children and pets are at increased risk of exposure because of their size and level of activity. The most severe reactions occur when large amounts of water are swallowed. The chronic effects of long-term exposure to algae toxins are currently being studied. 

Q: How can I protect myself when I am camping or recreating at a lake with a bloom? 

A: Stay out of the affected water and keep children and pets away. Never drink or cook with affected water. If you come in contact with affected water, wash off thoroughly with another source of water and soap if available.
Q: Can I treat toxins in the water to make it safe to drink? 

A: No. Personal water filtration devices for camping or hiking have not been proven to be effective, and boiling water will not remove the toxins. Home filtration devices used to purify well water drawn from a lake affected by a bloom are also inefficient.
Q: Is it safe to eat fish? 

A: Fish caught in affected waters pose unknown health risks. If you choose to eat them, remove all fat, skin and organs before cooking because toxins are more likely to collect in these tissues. Crayfish (crawdad) muscle can be eaten but discard all organs and liquids before preparing. It is illegal to harvest clams or muscles from freshwater lakes.
Q: My drinking water comes from a water source that is affected by algae blooms. Am I at risk? 

A: People and water suppliers who draw water directly from an affected waterbody are advised that it may be dangerous to drink. Testing for toxins is the only way to know for sure. Call your supplier and ask if the water has been tested. If not tested, it is recommended that you use an alternative water source not affected by the bloom. To learn more about harmful algae blooms and your drinking water visit the Oregon Health Authority Algae Resources for Drinking Water webpage.
Q: What about other outdoor activities? 

A: Camping, picnicking, hiking, biking, bird watching and other activities that do not involve water contact are encouraged. Boating is safe as long as speeds don't whip up excessive water spray, which could create an inhalation risk.

Q: Are these blooms a new problem?

A: No. The earliest reliable account of a cyanobacterial bloom dates back to the 12th century; the toxic effects on livestock have been recognized for more than 100 years. Since bloom formation seems to be linked to nutrient-rich waterbodies (those influenced by animals and people where phosphorous and phosphate containing compounds such as fertilizers are used), the problem is not likely to go away in the near future.