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Frequently Asked Questions

Cyanobacteria (Harmful Algae) Bloom FAQs

Q: What is cyanobacteria (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. Although blooms that produce cyanotoxins can be harmful, these bacteria are very beneficial and helped to create our oxygen atmosphere. 

Q: Why is it called cyanobacteria (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 cyanobacteria (blue-green algae) bloom?

A: When weather, sunlight, water temperature and nutrients (food) are ideal, cyanobacteria can multiply very quickly into a colony 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 water bodies in Oregon monitored or sampled?

A: No, only a small number of water bodies in Oregon are monitored for cyanobacteria and any potential toxins produced. This is because many of the agencies responsible for our water bodies do not have enough money or personal resources to monitor or sample the overwhelming number of water bodies Oregon has. Since cyanobacteria is naturally occurring in fresh and marine waters worldwide, blooms can develop on any water body if environmental 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 recreational use health advisories issued for cyanobacteria blooms?

A:  A health advisory is issued when bloom sampling data shows cell counts or cyanotoxin levels above our Oregon Health Authority recreational use values (RUVs). We have established RUVs for people and for dogs, but advisories are only issued when levels are over the RUVs for people. You should know that even if an advisory is not in place on a water body (cell counts or toxins are below RUVs for people, or sampling has not been performed) that these levels can still be very high for dogs and could result in your pet getting extremely sick, or in some cases cause death. If your pet exhibits any unusual symptoms after being in a water body, 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 cyanotoxin 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 potentially been exposed to a cyanotoxin from a cyanobacteria bloom. Your doctor or vet will treat you or your pet for the symptoms of exposure mentioned above. 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, and do not allow your pet to drink from the water body. 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. In fact, boiling can increase the toxins in the water. Home filtration devices used to purify water drawn from an intake in an affected water body affected by a bloom are also inefficient.
Q: Is it safe to eat fish? 

A: Fish caught in affected waters pose unknown health risks. Some studies have shown that certain cyanotoxins can accumulate in fish tissue. 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 a cyanobacteria bloom. Am I at risk? 

A: Most drinking water facilities supplying in-home water are equipped to test for and treat cyanotoxins that may be found in your drinking water. Testing for toxins is the only way to know for sure. If you are on a public water system and you are concerned, you should contact your provider. If you have a private intake in an affected water body and an in-home system, OHA recommends that you use an alternative water source not affected by the bloom. To learn more about cyanotoxins 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 recreational activities that do not involve the potential ingestion of affected water 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 cyanobacteria bloom dates back to the 12th century; the toxic effects on livestock have been recognized for more than 100 years. Because bloom formation is linked to environmental conditions and nutrients that provide the elements necessary for cyanobacteria to multiply into a bloom, and conditions that foster blooms are increasing - higher air temperatures, more sunlight, lower snowpack (creating warmer water temperatures), the problem with blooms is not likely to go away in the near future.

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