Discolored water is an aesthetic issue, but when blue-green algae reach bloom densities, they can actually reduce light penetration, which can adversely affect other aquatic organisms both directly (e.g., other phytoplankton and aquatic plants) and indirectly (e.g., zooplankton and fish that depend on phytoplankton and plants). What are the concerns associated with blue-green algae?Д¬oncerns associated with blue-green algae include discolored water, reduced light penetration, taste and odor problems, dissolved oxygen depletions during die-off and toxin production. Green algae can also bloom at nuisance levels and may be mistaken for blue-green algae. Small fish are then eaten by larger fish, and both small and large fish are eaten by mammals, raptors and people. Most algae are microscopic and serve as the main supply of 'high energy' food for larger organisms like zooplankton, which in turn are eaten by small fish. They are known as 'primary producers', a name given to living organisms that can convert sunlight and inorganic chemicals into usable energy for other living organisms. True algae (e.g., green algae) are very important to the food chain. However, blue-green algae are generally not eaten by other aquatic organisms, and thus are not an important part of the food chain. How do blue-green algae differ from true algae?Д«lue-green algae, like true algae, make up a portion of the phytoplankton in many water bodies. It is not always the same species that blooms in a given waterbody, and the dominant species present can change over the course of the season.

Many different species of blue-green algae occur in Wisconsin waters, but the most commonly detected include Anabaena sp., Aphanizomenon sp., Microcystis sp. When this happens, we call this a 'blue-green algae bloom.' In Wisconsin, blue-green algae blooms generally occur between mid-June and late September, although in rare instances, blooms have been observed in winter, even under the ice. Most species are buoyant and will float to the surface, where they form scum layers or floating mats. When environmental conditions are just right, blue-green algae can grow very quickly in number. Blue-green algae generally grow in lakes, ponds and slow-moving streams when the water is warm and enriched with nutrients like phosphorus or nitrogen. General Questions About Blue-Green Algae What are blue-green algae?Д«lue-green algae, also known as Cyanobacteria, are a group of photosynthetic bacteria that many people refer to as 'pond scum.' Blue-green algae are most often blue-green in color, but can also be blue, green, reddish-purple, or brown. The Wisconsin State Laboratory of Hygiene is unable to provide interpretation or guidance for testing results. You can submit samples for testing at your own cost to the Wisconsin State Laboratory of Hygiene.

The DNR is not currently conducting routine statewide monitoring for blue-green algae or blue-green algal toxins. Some local health agencies have the capacity to test for blue-green algae at their public beaches. To report a case with potential health effects caused by blue-green algae, visit the Department of Health Services or contact the Bureau of Environmental and Occupational Health at 60.ДЇor information on current public beach advisories, check out the DNR Beach Closings and Advisories Map.

If your pet displays symptoms such as seizures, vomitingВ or diarrhea after contact with surface water, contact your veterinarian right away. If you think you are experiencing symptoms related to exposure to blue-green algae (e.g., stomach cramps, diarrhea, vomiting, headache, fever, muscle weakness, difficulty breathing), contact your doctor or the Wisconsin Poison Center (1-80)В right away.

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