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Frequently Asked Questions

Harmful Algae Bloom FAQs

Q: What is blue-green algae?

A: It's not algae at all but a primitive photosynthetic single celled bacteria found naturally in fresh and salt water all over the world. 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-green 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, water temperature and nutrients (food) are ideal, cyanobacteria can multiply very quickly 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. Sometimes cells can be suspended in the water making it look bright green, or they can be lower in the water column so that a layer of scum is not visible.

Q: Are all waterbodies in Oregon monitored?

A: No, only a small number of lakes in Oregon are monitored for cyanobacteria and any potential toxins produced. This is because many of the agencies responsible for our lakes do not have enough money or personal resources to monitor the overwhelming number of lakes Oregon has. Since cyanobacteria is naturally occurring in the water, blooms can develop on any waterbody if lake conditions and nutrient levels are ideal. People should learn to recognize blooms, and when in doubt stay out of the water.

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 they are able to move to where nutrient and light levels are at their highest. At night, when there is no sunlight, cells lose their buoyancy causing them to float to the surface forming a surface scum. Scum can seem to appear overnight for this reason and linger until the wind and waves scatter the cells throughout the water and to other parts of a waterbody.

Q: Why are these blooms a health concern?

A: Not all blooms are harmful, but some species of cyanobacteria such as Microcystis, Dolichospermum, Cylindrospermopsis and some other genera 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 red, raised 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: When are health advisories issued for harmful algae blooms?

A: A health advisory is issued when bloom sampling shows cell counts or toxins above our Oregon Health Authority guideline values (GVs). We have established recreational GVs for people and for dogs but advisories are only issued when levels are over the GVs for people. You should know that even if an advisory is not in place on a waterbody (cell counts or toxins are below GVs for people) that these levels can still be very high for dogs and could result in your pet getting extremely sick or in some cases casue death. If your pet exhibits any unusual symptoms you should seek advice from your veterinarian as soon as possible.

Q: What are the health risks posed by exposure to these toxins? 

A: Although these toxins are not absorbed through the skin, a red, raised 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. Symptoms of exposure can mimic food poisoning. Food poisoning symptoms usually go away fairly quickly once your body gets rid of the spoiled food. Symptoms of exposure to a HAB will go away, but not as fast. Again, if symptoms are severe or persist you should seek medical attention.

Q: Is there an antidote for these toxins?

A: No. If symptoms persist or are severe you should seek medical attention and let your doctor or veterinarian know that you, your family or your pet may have been exposed to a potential HAB. Your doctor or vet will treat you or your pet for the symptoms of exposure. Depending upon the potential toxin they may do tests to determine if any other internal damage has occurred. People begin to exhibit symptoms within the first 24 hr. period after an exposure. These symptoms usually go away within 48 to 72 hours. Dogs will exhibit symptoms after the first hour of exposure. Because dogs are susceptible to these toxins at extremely low levels it is very important to get your pet to the veterinarian as soon as possible if they show signs of diarrhea, vomiting, breathing problems, difficulty walking or standing or loss of appetite.

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.

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