in Chatsworth, Grey Highlands, Southgate, West Grey
July 24, 2025
BY SOUTHGREY.CA STAFF — Blue-green algae, also known as cyanobacteria, are microscopic, plant-like organisms that occur naturally in lakes, ponds, rivers and streams. The aquatic menace thrives in areas where the water is shallow, slow-moving and warm, but may also be present in deeper, cooler water. Some varieties of blue-green algae can produce cyanotoxins, which are harmful to humans and animals.
Recently, a pea-soup-like scum has been witnessed at various locations on Eugenia Lake in the Municipality of Grey Highlands. White foam also seen on the lake or shoreline, may be another sign of the harmful algal bloom. While these sightings have not yet been confirmed as the toxic bacterial variety, cottagers and residents are not taking any chances. Over the past few years, blue-green algae has been a recurring and unwanted visitor to the lake. Many are desperate to find a solution.
On July 22, the Lake Eugenia Property Owners Association (LEPOA) took some baseline water samples in order to measure the fluctuation of phosphate levels. The group has also funded the use of biochar to bind and remove toxins in the water. Biochar is a charcoal-like material produced from biomass, and can be used to mitigate harmful algal blooms, including those caused by blue-green algae. It works by absorbing excess nutrients like phosphorus and nitrogen, which are the primary drivers of algal growth.
A total of 60 Biochar bags are being installed under docks around the lake, with more planned for the future of the man-made waterway.
A company from Cobourg has also set up a test pilot site for their WaterIQ Technologies algae-killing device that utilizes ultrasonic frequencies to target and eliminate algae and biofilm without the use of chemicals. According to Stewart Halliday, the cottage-owner whose location was chosen for the test, "The use of Ultrasonics is big in Europe and the US." Halliday added, "We will be testing throughout the season. It will take about 30 days before we will see any results."
According to Grey Highlands Councillor Nadia Dubyk, lake health is beginning to be addressed at the local government level too. "Council has already directed staff to bring back a report on a mandatory septic re-inspection program targeting properties around the lakes." Dubyk also noted, "The (Lake Management) Task Force is drafting a fertilizer by law that will be brought to Council in the coming months. The task force is also looking at education and communication campaigns, shoreline vegetation and buffer best practices, enhanced monitoring and more."
Blue-green algae blooms are most common in late summer or early fall but can also occur in other seasons. Bloom development can be promoted by calm water conditions, high temperatures and an increase in nutrients such as phosphorus.
If you think you see a blue-green algal bloom:
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