Blue-green algae blooms are natural in our lakes, but harmful to people, pets

Photos of blue-green algae, known also as cyanobacteria. (Township of Severn)

Unfortunately for Lake Simcoe, August’s warm and calm water is the natural habitat for blue-green algae (cyanobacteria).

While not all blooms are harmful, sporadic toxins found in the algae can cause people, pets and wildlife to fall ill. Side-effects include everything from itchy eyes to vomiting, diarrhea, fever and dizziness, etc.

In severe cases, swallowing affected water can damage the liver or kidneys. Anyone who develops serious symptoms after exposure should seek medical advice, says the Simcoe Muskoka District Health Unit (SMDHU).

Additionally, pets can become seriously ill if they drink affected water or ingest blue-green algae while grooming after swimming. If your pet was exposed to a bloom and shows unusual behaviour or signs of illness, contact your veterinarian.

A blue-green algae bloom can cause water to:

• Appear blue-green, bright green or turquoise
• Look like pea soup or as though paint has been spilled on the surface
• Develop floating scum, streaks or thick mats.
• Produce a musty, garbage-like or rotten-egg odour.

People are reminded to never use untreated water from a lake or river for drinking, cooking or preparing infant formula. The health unit says boiling water does not destroy blue-green algae toxins and may increase their concentration when water evaporates.

Even residential water treatment systems may not effectively remove these toxins.

For safety’s sake:

• If water appears to contain a bloom, assume toxins are present and avoid contact.
• Do not swim, wade or participate in water sports where a bloom is visible.
• Do not allow pets or livestock to swim in or drink affected water.
• Be cautious about eating fish caught from water where a bloom is present, particularly the organs, where toxins may accumulate.
• Do not apply herbicides, copper sulphate or other algaecides, as these can cause algae cells to break open and release additional toxins into the water.

Areas of the same lake or river that are well away from a visible bloom are generally considered safe for recreational use. However, avoid water where a bloom is present or where algae accumulate along the shoreline.

If you suspect a blue-green algae bloom, avoid the area and report it to the Ontario Ministry of the Environment, Conservation and Parks through the Spills Action Centre. Public health, municipalities and environmental agencies work together to investigate confirmed blooms and inform the public.

When on the water, watch for signs of blue-green algae and avoid it where a bloom is visible. Sharing the information with family and friends can help protect people, pets and the community.