August algal bloom confirmed


Toxin levels not considered dangerous for drinking water


On September 8th, the lake association received the laboratory results regarding a possible blue green algal bloom on our lake. Based on the water sample they collected on the west side of the Upper Rideau on August 23rd, the Ontario Ministry of the Environment Conservation and Parks reported the "presence of an algae bloom which contained cyanobacteria (algal bloom), with potential for toxin production."

Fortunately, the levels of toxin were below those considered dangerous for drinking water. The results indicated that concentrations of toxins were low, ie., this particular algal bloom was unlikely to be harmful to humans. And, hopefully, the cooler weather in September will have changed the lake conditions that allowed the blue green algal bloom to occur in the first place.

Here is the summary of the Ministry report: "As a follow up to the samples collected on Aug 23, 2021, the results confirmed the presence of an algae bloom which contained cyanobacteria (blue-green algae), with potential for toxin production. In summary, the samples collected contained a total microcystin concentration of 0.44 ug/L and levels of anatoxin-A was measured at 0.39 ug/L.

To note: The Ontario Drinking Water Standard for microcystin-LR is 1.5 ug/L and Health Canada recreational limit for total microcystin is 20 ug/L.”

Here is a link to the technical report:

This August blue green algal bloom is a reminder that our lake water quality is officially "poor" and remains fragile. All of us – municipal governments, property owners and others alike – need to continue to take measures to support the health of the Upper Rideau Lake, particularly as we experience longer hotter summers.

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