The Minnesota Pollution Control Agency (MPCA) has urged the public to stay clear of lakes filled with algae this holiday weekend after a child and two dogs were poisoned by the blue-green organisms in Alexandria last month.

According to experts, poisonous algae can easily be identified in the water by their pea soup or green paint-like appearance. These dangerous clusters often give off a strong stench similar to cow manure.

MPCA scientist Steve Heiskary said blooms of blue-green algae can often be seen in several lakes throughout the state during summer, especially after periods of rainfall followed by high temperatures.

Last month, a young boy was hospitalized after swimming in a lake filled with the highly toxic organism, according to Dan Olson, the MPCA's representative at Detroit Lakes. Scientists confirmed the contamination after analyzing water samples gathered from the lake.

The boy was able to make a full recovery after the incident.

Two dogs were also reported to have died because of exposure to algal blooms in Douglas County's Red Rock Lake.

Several water advisory signs were placed around Lake Henry before it was opened for the season to warn swimmers about the dangers of the blue-green algae in the water.

Olson pointed out that it is difficult to determine whether there are more algae outbreaks this season compared to previous summers as lakes in Minnesota are not tested regularly.

The formation of blue-green algae often occurs when extra nutrients such as phosphorus reach bodies of water, which is often the result of different agricultural practices.

Olson said most of time these algal blooms limit themselves because of weather conditions and they no longer persist. He added that the blue-green organisms eventually disperse in wind and low temperatures.

Officials, however, still urge vacationers to be careful as it is difficult to monitor an algal outbreak as environmental conditions can often change quickly.

Olson said the incident at Lake Henry is the first case of a human getting exposed to the organism that he has heard of.

In most cases, swimmers stay away from the stench and latex-like consistency of algal bloom, but those who still choose to boat, swim or bathe in contaminated lakes can become ill.

People who come into contact with toxins from blue-green algae either through having skin contact, swallowing, or inhaling airborne water droplets may experience symptoms such as eye irritation, rash, cough, diarrhea, vomiting, headache and sore throat.

Photo: Mark Sadowski | Flickr