Blue-Green Algae Toxic to Swimming Pets and Humans

OnFocus – It’s blue-green algae season again. Blue-green algae is very toxic to humans and dogs. The DNR reports blooms have been earlier and more widespread than usual.

According to the DNR, blue-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. 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.

When environmental conditions are just right, blue-green algae can grow very quickly in number. Most species are buoyant and will float to the surface, where they form scum layers or floating mats. 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.

Concerns associated with blue-green algae include discolored water, reduced light penetration, taste and odor problems, dissolved oxygen depletions during die-off, and toxin production.

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 (800-222-1222) right away.

If your pet displays symptoms such as seizures, vomiting, or diarrhea after contact with surface water, contact your veterinarian right away.

To report a case with potential health effects caused by blue-green algae, visit the Department of Health Services [exit DNR], or contact the Bureau of Environmental and Occupational Health at 608-266-1120.

To report an algae bloom email [email protected]. Include the bloom size, duration, and location with water body name, town name, and county name. Please submit photos for verification including close-ups and overall views. We are not able to test every bloom.

Swimming advisory levels have been developed by the United States Environmental Protection Agency [exit DNR] for the toxins microcystin (8 µg/L) and cylindrospermopsin (15 µg/L) and may be used by local health departments as the basis for issuing advisories or closing public beaches. Most local health departments in Wisconsin do not have the capacity to monitor blue-green algae toxins at public beaches, so treat any accumulation of blue-green algae with caution. When in doubt, stay out!

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