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Toxic Algae Can Spell Danger for Pets and Livestock:
When in Doubt, Best Keep Out!

Spending time in, on, or near one of Minnesota's thousands of lakes is a great way to beat the heat. And going to "the lake" for the weekend is a ritual for many Minnesotans. But lake lovers, especially those with pets or livestock, need to be aware of a potential hazard stemming from algae growth in lakes during summer. Under certain environmental conditions some algae species, called blue-green algae, can become toxic. Pets and livestock drinking lake water containing the toxic form of these algae may become sick and even die.

About Blue-green Algae

• What You Should Know About Blue-green Algae, fact sheet
• A Study of the Blue-green Algal Toxin Microcystin, Based on Select Lakes in McLeod and Blue Earth Counties
  • Presentation: A Study of Microcystin Levels in Eutrophic South Central Minnesota Lakes (as presented to the North American Lake Management Society, October 31, 2007)

How Can I Recognize It?

Algae occurs in virtually all lakes in Minnesota, but its concentration can vary considerably from lake to lake. It is most abundant during warm weather in water that is hard, alkaline, and rich in nutrients (primarily phosphorus and nitrogen, which fertilize aquatic plants as they do crops and lawns). Special characteristics of blue-green algae allow them to reach greater abundance than other types of algae. Some types of blue-green algae are able to use nitrogen from the air as well as other forms of nitrogen dissolved in the water, which gives them an advantage over other kinds of algae that depend only on nitrogen in the water.

Blue-green algae can use sunlight more efficiently than most algae. Some of them contain pockets of gas allowing them to float on upper layers of the water and out-compete other algae for sunlight. In nutrient-rich lakes, blue-green algae can become so abundant that they completely dominate other free-floating algae. The whole appearance of the lake water can be changed by these large concentrations of algae. This conditions is called an algae bloom.

The lake water will become cloudy, with a green or blue-green cast or hue. It often develops a strong musty or earthy odor as the algae accumulate in large floating mats and begin to decompose. In extreme cases, surface scums of dead and decomposing algae may occur. Fish in the lake may develop a temporary earthy flavor. The lake is best described as having a look of pea soup at this stage.

This poster was created by the Interagency Work Group on Blue-Green Algae.  Click on the image above to open a PDF version and print it, or copies may be ordered by contacting the MPCA Customer Assistance Center and requesting the toxic algae poster.

These are the blooms that can occasionally become toxic. Toxic blue-green algae blooms are strongly influenced by the wind. Sometimes, the wind can completely dissipate a toxic bloom in just a short time (hours) or longer (a day or so). At other times, the wind increases the danger of a toxic bloom by concentrating (windrowing) the floating algae mats toward the downwind shore of a lake.

Most problems occur when the algae are concentrated around a shoreline and livestock, pets, wild animals and birds drink the water or otherwise ingest the algae. Toxic effects in animals can occur only when they ingest the contaminated water or algae. Farmers can suffer severe livestock losses from blue-green algae poisoning of their cattle's watering source.

The degree to which an animal is affected depends on several factors: the amount of water or algal cells ingested, the animal's body size, amount of food in the animal's stomach, the sensitivity of the species and individual animal, and the type and amount of toxin present in the bloom.

An animal that has ingested toxins from an algae bloom can show a variety of symptoms, ranging from nausea and skin irritation to severe disorders involving the circulatory, nervous and digestive systems, and severe skin lesions. In the worst case, the animal may suffer convulsions and die.

Humans are seldom seriously affected by toxic algae because the unpleasant odor and taste of water associated with a blue-green algae blooms tends to make them avoid it. However, humans and animals may experience ilness or other health effects if there is skin contact with algal toxins or large amounts of algae are ingested while toxins are being produced.

The Minnesota Department of Health recommends that humans not ingest the water, nor let children or pets enter the water. Contact with these algal blooms should be avoided. If contact does occur the material should be washed off thoroughly, paying special attention to the swimsuit area. If your pet comes in contact with a bloom, wash off your pet's coat to prevent the pet from ingesting the algae while self-cleaning.

Swimming in water with an algal bloom may cause symptoms such as: skin rash, hives, runny nose, irritated eyes, and/or throat irritation. Swallowing or ingesting water with an algal bloom may cause symptoms such as: vomiting, diarrhea, or nausea; headache, throat irritation, or muscle pain; in severe cases paralysis, respiratory failure, or even death. It may also cause seizures or convulsions in your pets.

How Can I Tell if a Bloom is Toxic?

Not all blue-green algae blooms are toxic; in fact, the vast majority of them are not. But because they can occur so quickly and can vary so much in toxicity and frequency, all blue-green algae blooms are potentially dangerous. They cannot be accurately predicted and there are no easy laboratory tests for the toxins produced. A blue-green algae bloom can change from non-toxic to toxic or vice-versa without a significant change in appearance.

Since toxic blooms are unpredictable and laboratory analysis is expensive, it is best to approach the problem as one would changing weather conditions. If the water looks threatening, avoid it until a more "normal" appearance returns. A blue-green bloom should be avoided if it changes from just "greenish water" to a thick, blue-green or green, paint-like scum. Often the bloom can be avoided by simply moving livestock or recreational activities to the opposite side of the lake.

If you suspect that an animal has been affected by an algae bloom, you should contact your veterinarian as quickly as possible. Some of the toxins that can form in a bloom have the ability to kill in an hour or less, while some may take up to 24 hours to take effect. For more information on toxic algae or to report a possible toxic bloom, please contact: Matt Lindon, MPCA, at 651-757-2530, or toll-free from Greater Minnesota at 1-800-657-3864.

Photos of Toxic and Other Algae

Blue-green algae can be hard to distinguish from other types of algae. While it's often described as looking like pea soup or spilled green paint, it can take other forms as well. This photo gallery shows some of the diversity of blue-green's appearances and also provides some examples of other types of algae or plants that may be mistaken for blue-green algae.

Below are photos of plants and other forms of non-toxic algae or plants that are similar in appearance to blue-green algae.

Duckweed

Nuisance growth of a filamentous green algae

Chara, a form of filamentous algae; often found in lakes with good water clarity.

Links to Related Sites

Several states and other countries have programs or efforts in place to actively monitor waters for the presence of blue-green algae and their toxins and to keep the public informed about the possibility of toxic conditions. These efforts are often a collaboration among government agencies and universities. The following are offered as examples of these programs. This is not intended as an endorsement of these efforts, rather this is an attempt to provide additional information and a cross-section of responses to blue-green toxicity in other states and countries.

• Indiana Department of Natural Resources . This sight gives frequently asked questions on Cylindrospermopsis and other potential toxin-producing blue-green algae in Indiana waters.
• Nebraska Department of Environmental Quality. Lakes under watch are tested every Monday and the results are posted on the website by the following Friday for public viewing. Advisories are given for the particular lakes until they stay below 20 ppb for two consecutive weeks. This program was started in 2004 when they purchased the equipment to analyze the algae. This was because of a dog death resulting from blue-green algae in a Nebraska Lake .
• Nebraska Department of Environmental Quality Newsletter
• Wisconsin Department of Natural Resources General information given on what it is, and the health risk associated with blue-green algae. No information given on assessing/monitoring of blue-green.
• Vermont Blue Green Algae Information Lake Champlain is being monitored by the University of Vermont and the Vermont Department of Environmental Conservation for blue-green algae. Vermont Department of Health provides a map with "alerts" to lake users based on this bi-weekly sampling program.
• Health Canada shares their perspectives on blue-green algal toxicity with a focus on human health and drinking water.
• CYANONET, a network sponsored by researchers in South Africa reflect on the broad -- worldwide interest in blue-green algal toxicity.
• Australia, the Queensland Government has prepared a fact sheet on the topic that is intended to inform people recreating on the water as well as using water for livestock and irrigation.

Interagency Work Group on Blue-Green Algae

After several dog deaths due to contact with blue-green algae were reported in the summer of 2004, representatives from several environmental agencies began meeting to plan how to raise public awareness of the potential harmful effects of blue-green algae. Products of the work group include the following:

• news release,
• blue-green algae fact sheet, and
• poster.

The group includes the Minnesota Departments of Health and Natural Resources, Pollution Control Agency, and the Minnesota Veterinary Medicine Association. For further information on the work group, please contact Steven Heiskary at MPCA, at 651-757-2419 or toll free from Greater Minnesota at 1-800-657-3864.

More Information

As noted above, if you suspect that an animal has been affected by an algae bloom, you should contact your veterinarian as quickly as possible. Some of the toxins that can form in a bloom have the ability to kill in an hour or less, while some may take up to 24 hours to take effect.

For more information on toxic algae or to report a possible toxic bloom, please contact: Matt Lindon, MPCA, at 651-757-2530, or toll-free from Greater Minnesota at 1-800-657-3864.