Ongoing testing on Three Mile Lake shows the blue-green algae bloom that caused concern at the end of August is back to normal, according to the local health unit.
The Simcoe Muskoka District Health Unit lifted the warning this week after test results by the Ministry of the Environment showed the levels of microsystin, the toxin created by the algae, were below safe drinking levels.
“The only precaution to note is that the Ministry of Environment is still continuing to test, at least this week,” said Jerry Capko, manager of the safe water program for the health unit.
The warning was issued to lake residents on August 31, advising them not to drink the water and to avoid swimming and water activities because of blue-green algae blooms that were found on the west side of the lake.
On Sept. 5, the Ministry of the Environment (MOE) tested the lake again, confirming toxin levels were still above safe drinking levels.
On Sept. 12, tests showed the levels had fallen below safe drinking levels.
Capko said it was never a panic situation to begin with, only precautionary, and it continues to be that way.
“This is a normal environmental cycle,” Capko said. “Nothing horrible is happening here, this is the way blue-green algae works. It’s throughout Ontario.”
Throughout the warning period, the toxin levels remained well below the range where skin irritations usually occur, but at the time Capko said “it would be imprudent to say skin irritations won’t occur and it’s OK to go in the water.”
“They don’t sample every 15 feet. There may be areas of higher concentration, there may not,” he explained.
Water is considered unsafe for drinking once it reaches 1.5 micrograms/litre (ug/L) of microsystin. It is considered unsafe for swimming and bodily contact between 10-20 ug/L.
The health unit advises people to stay away from water that has algae blooms in it because of the unpredictability of the increase and decrease in blooms and the toxicity related to them.
Robert Fullerton, director of lake stewardship for the Three Mile Lake Association, said residents have been carrying on as usual this year.
“The very low levels in the majority of the lake indicate that the bloom in the west end is an anomaly. The summer, from a weather standpoint, has been amazing and the residents of Three Mile Lake have taken full advantage of the great boating, swimming and fishing the lake has to offer — with no ill effects.”
Capko said algae on the lake are going through their life cycle as usual.
“It tends to disappear towards the end of the year. It’s the difference of having prolonged, hot, dry weather with still air where algae bloom is very much encouraged, as opposed to rough weather and cold temperatures where it’s discouraged,” Capko said.
In 2005, the blue-green algae blooms appeared in alarming numbers on the lake, causing great concern for residents.
“The algae bloom of 2005 was significantly different,” said Rob Tanner, president of the Three Mile Lake Association. “Although it caused considerable concern at the time, the winter came, followed by a spring that saw a very clear and clean (algae-free) lake.”
Capko said he can’t compare this year’s blooms to 2005 because what they are looking for is different.
In 2005 the health unit was looking for blue-green algae blooms and they were very proactive, he said. Health unit staff analyzed the 2005 situation and now they test for the levels of microsystin in the water instead of looking only for the blooms.
They didn’t check the microsystin levels in 2005, so he doesn’t know how it compares, he said.
Tanner said the serious bloom in 2005 revived the Three Mile Lake Association, which encourages good lake stewardship by all lake residents.
Tanner said the 2005 incident also prompted the Township of Muskoka Lakes to inspect every septic system on the lake. Several didn’t work and a number were unacceptable, but he said a followup by the township showed the necessary work has been done.
“I believe it gave all of the residents a better understanding of what we need to do to keep our lake as healthy as possible,” continued Tanner.
The association, along with the Ministry of the Environment and Simcoe Muskoka District Health Unit, will continue to monitor the testing results. As they become available, they will be posted on the Three Mile Lake Association’s website at www.3milelake.ca.