Blue-Green Algae in Lakes, Ponds; No High Levels of Toxins Found

For immediate release:
August 9, 2002

For More Information:
Patsy Tassler, Ph.D.
Health Department Epidemiologist
Mary Watzin, Ph.D.
UVM School of Natural Resources

BURLINGTON—The Vermont Department of Health has been notified by researchers at the University of Vermont that blue-green algae blooms have been detected at testing sites in Missisquoi Bay and St. Albans Bay.

Hot, dry, calm weather conditions promote the growth of blue-green algae, which are commonly seen in Lake Champlain and other lakes and ponds throughout the state. The blue-green algae appears as a heavy greenish-blue scum on the water or shoreline.

In some cases, these algae blooms can release toxins such as microcystin or anatoxin.

According to UVM researchers who have been sampling several sites in the Burlington Bay area of Lake Champlain for the past three years, only a very small amount of toxin has been detected at the St. Albans site.

Higher levels have been detected along the shore at Vermont 78 at Missisquoi Bay; those levels drop off rapidly away from the shoreline. The algae were probably washed to the shoreline by the persistent winds from the north this past week.

“We’re testing in areas most likely to have problems,” said Mary Watzin, principal investigator of the research team. “So far we are only seeing elevated numbers of algae and some toxin at these two test sites.”

People should avoid swimming in areas where there is visible green or blue-green scum collected on the surface of the water. Ingestion (drinking) of algae that are producing toxin can result in symptoms including nausea, vomiting, and diarrhea. Skin exposure can result in irritation or allergic reactions. Children should especially be kept from entering scummy water since they are more likely to ingest the water than adults.

In the hot summer of 1999, several dogs died after ingesting large quantities of blue-green algae in Lake Champlain.

Dogs are at risk if they eat the algae or drink the water in an area where a toxic algae bloom is taking place. They may also ingest the algae by licking their fur after they have been in water that is thick with algae.

“Our advice to pet owners is to keep your dogs away from the algae,” said Dr. Bob Johnson, state public health veterinarian. “And, if your dog does get into the water in an area where you see the algae, wash the dog off with clean water.”

Not all blue-green algae blooms produce toxin. However there is no way to tell just by looking at it. Most other algae lake plants do not produce any toxin.

“The best way to protect yourself is to stay out of any water that has a thick surface scum,” says Mary Watzin.

When blue-green algae bloom, they look thick like pea soup or blue or green paint on the water. They are mostly blue-green, although they can also be brown or purple. When blue-green algae washes up on shore, it can form a thick mat or foam on the beach.

Generally, lots of wind, cooler weather, rainfall, and cloudy days will lead to the collapse of an algae bloom. Some blooms die off after a few days or weeks, while others persist for a few months.