This information is presented in response to questions often asked by people who have found an algae bloom in a lake or pond on their private property.
Algae are microscopic organisms that grow naturally in all waters. Under certain conditions, algae can grow into a large visible mass called a bloom. Cyanobacteria (also called blue-green algae) grow in fresh waters and can produce toxins that may cause harm to humans and animals.
How can I tell if this algae bloom is one that makes toxins?You cannot tell if a bloom contains a toxic algae species just by looking. Laboratory analysis of a water sample is the only way to determine what kind of algae is present. As a precaution, it is advisable to always avoid water that looks thick like pea-green soup or a bright green or blue-green paint scum or has white or brownish-red foam.
Should I take a water sample? If people or animals use the water as a drinking water source or if it is used for water recreation, such as swimming or wading, it is recommended that you have the water tested.
Who does the sampling and what is the process? You can hire a consultant or draw a water sample yourself. The Harmful Algae Bloom Surveillance (HABS) program has developed a sampling protocol. For more information, refer to the HABS Sampling Guidelines (pdf).
Who pays the sampling cost? As the property owner, you are responsible for paying expenses associated with water sampling. Costs may range from $45 to $250, depending on the type of test you request and the fee the laboratory charges.
How can I find a qualified laboratory? The HABS program has compiled a list of Recommended Laboratories for Cyanobacteria Testing. Please note that HABS does not endorse any specific laboratory. .
What should I ask the lab to test for? The most economical test is to identify the algae species that are present and at what levels (Identificaton and enumeration). HABS issues health advisories when a toxigenic species is found to be present at 100,000 cells per milliliter of water. (Detailed information can be found on Table 1, page 6 of the HABS Sampling Guidelines.) Another option, although more expensive, is toxin analysis, which will determine if specific toxins are present and at what levels. Contact the HABS program if you need assistance in understanding the results provided by the lab
How do I ship the water sample? The HABS Sampling Guidelines (pdf) explains shipping methods, which depends on the test you request. It is also advisable to ask the lab if they have a preference for how the sample should be packed.
What should I do while I’m waiting for laboratory results? Lab results can take from one to two weeks, and sometimes longer. Meanwhile, it is recommended that you post a warning sign to alert people that an algae bloom is present that may contain toxins. If livestock, small animals or pets are likely to get into the water, consider putting up a temporary fence.
What kinds of illness can cyanobacteria cause? Different cyanobacteria species produce different toxins: neurotoxins affect the nervous system, hepatotoxins affect the liver and lipopolysaccharides affect the skin. Detailed information can be found on Table 1, page 7 of the HABS Sampling Guidelines (pdf).
The most commonly reported health effect is skin irritation or rash, caused by skin contact with bloom-affected water. Inhaling water droplets can result in allergy-like symptoms such as eye, ear and throat irritation. Swallowing the water can cause flu-like illness, including diarrhea, cramps and vomiting. More severe symptoms are fainting, numbness and dizziness. The most severe reactions occur when large amounts of water are swallowed.
Children and pets are more susceptible to algae toxins.
Is it safe to eat fish caught from bloom-affected water? Eating fish from affected waters presents an unknown health risk. Toxin accumulation studies suggest that muscle tissue is less affected by algae toxins, but there has not been definitive research in this area. If you decide to eat the fish, remove the fat, skin and organs.