Contacts: Patricia McCann (MDH), 651-215-0923
Steve Heiskary (MPCA), 651-296-7217 or Ralph Pribble, 651-296-7792
St. Paul, Minn. - The stretch of hot, sultry weather from mid-summer into September, often called the "dog days," takes its name from ancient Roman mythology. But lately it's been getting a new meaning in Minnesota. The dog days are also when some lakes and rivers turn green and soupy with algae, and some of those algae can be harmful to animals and humans. In fact, several dogs died last summer from contact with toxic algae blooms.
The algae that can cause problems is a group of species called "blue-green" algae. A group of state agencies and veterinarians has launched an effort to prevent illness or death from blue-green algae this summer. The group is placing posters warning of the effects of blue-green algae around the state in vets' offices and other places where water enthusiasts and pet owners will see them. The group also has plans for responding to public concerns about blue-green algae.
"We want people to become better informed about the potential effects of blue-green algae," said Patricia McCann of the Minnesota Department of Health. "Many of us probably have swum in water with blue-green algae in it, and usually were none the worse for it. But we want people to know that when the water looks bad and smells bad, it may be from toxic algae, and contact should be avoided."
Algae are microscopic aquatic plants, and are a natural part of any aquatic ecosystem. There are hundreds of species. With lots of sunlight and nutrients, algae populations can "bloom" with dramatic growth, turning the water cloudy and green, a sight familiar to most late-summer lake-goers.
Most algae blooms are harmless. But blue-green algae, when present in high concentrations, can produce potent toxins that can affect humans or animals. Blue-green algae are found throughout Minnesota, but thrive particularly in warm, shallow, nutrient-rich lakes such as those in central and southern Minnesota.
Not every blue-green bloom is toxic. But it can be difficult to predict which ones will cause problems. High concentrations of algae seem to be needed to produce harmful conditions. Often the algae are on a windward shore. Most problems occur when the algae concentrate around a shoreline and animals drink the water or otherwise ingest the algae.
"Toxic blue-green blooms are not a new problem," said Steve Heiskary, a lake scientist with the Minnesota Pollution Control Agency (MPCA) and a member of the interagency group. "We periodically hear of dog or other animal deaths that are most likely caused by toxins produced by blue-green algae. In fact there are reports in Minnesota going back to the 1800s."
"However, if a dog dies or a swimmer gets sick, people don't always make the connection with the state of the water they may have been swimming in," he added. "Probably because we're so used to seeing nuisance algae blooms in late summer."
Harmful effects on people are not often reported, probably because the unpleasant appearance and odors of a blue-green bloom tend to keep people out of the water. But human health effects can include irritation of skin, eyes and nasal passages, and nausea and vomiting. Extreme cases can produce paralysis and respiratory failure.
Distinguishing blue-green algae from other types may be difficult for non-experts. But toxic blooms generally look pretty nasty, sometimes said to look like pea soup, spilled green paint, or floating mats of scum. They often smell bad as well. While such conditions would seem to keep most people away, it's surprising how many still will swim or wade in such waters or let their animals enter it.
Therefore the interagency group offers an easily remembered message about blue-green algae: "When in doubt, best keep out."
"You don't have to be an expert to recognize water that might have a toxic algae bloom," McCann said. "If it looks bad and smells bad, it's probably best not to take chances with it."
For more information about toxic algae blooms, check the group's Web page at/water/clmp-toxicalgae.html or call 651-296-6300 or 800-657-3864. The interagency work group on blue-green algae includes the Minnesota Departments of Health and Natural Resources, the MPCA, and the Minnesota Veterinary Medicine Association.