Hot weather triggers blue green algae in Oneida County
The record hot sunny weather the last couple weeks has triggered blue green algae blooms in waters across the state. Exposure to this algae poses a health risk to people and pets, with a report of a dog dying from exposure this week in Oneida County.
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.
Many different species of blue-green algae occur in Wisconsin waters, but the most commonly detected include Anabaena sp., Aphanizomenon sp., Microcystis sp., and Planktothrix sp. 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.
Animals are not necessarily more sensitive to blue-green algal toxins than humans. However, many animals, such as dogs and cattle, enjoy being in the water, even if there is an unsightly green scum layer floating on top. When such a bloom is present, animals may consume large quantities of blue-green algae if they drink the water, and if those blue-green algae happen to be producing toxin(s), the animals can become very ill, and even die. Symptoms of blue-green algal toxin poisoning may range from lethargy and loss of appetite to seizures, vomiting, and convulsions. Dogs are particularly susceptible to blue-green algal poisoning because scums can attach to their coats and be swallowed during self-cleaning.
People and pets should avoid contact with water that has a blue-green scum, and both people and pets should shower or rinse off after swimming in any Wisconsin water body.