Blue-green algae

Rock County Public Health Department officials report that conditions are right for Cyanobacteria, also known as blue-green algae, to be showing up in local waters. They have recently observed blue-green algae in the Rock River and Lake Koshkonong. Because it is hard to determine exact levels of blue-green algae toxin concentrations, anyone considering recreation on or in the water should use caution and common sense.

The Public Health Department recommends taking the following precautions:

• Avoid swimming in areas of high algae concentration. Stay away from water with a floating scum layer that looks like green, blue, or white paint or pea-soup.

• Do not swallow pond, lake, or river water. This is especially important for small children and pets.

• Rinse off after coming in contact with pond, lake, or river water. If you think you have become ill from exposure to blue-green algae, contact your healthcare provider immediately.

Blue-green algae are naturally present in Wisconsin ponds, rivers, and lakes. When conditions are favorable, the algae can grow rapidly and form blooms of bright green, blue-green, or white. They can form thick scum layers on the surface of the water and may look bubbly or frothy. The blooms may have a foul odor, particularly in warm summer months. Some of the algae can produce a toxin that may lead to harmful health effects if ingested.

Some symptoms of exposure can be:

• skin or eye irritation,

• vomiting,

• diarrhea, or

• cold or flu-like symptoms.

Pets and children are particularly vulnerable to these conditions because of their size and because they don't have a natural tendency to avoid these water conditions. Dogs also have an increased risk of illness from the toxins as they are likely to ingest the water.

More information on blue-green algae can be found at or by calling the Rock County Public Health Department at 608-757-5440.

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