Dangerous blue-green algae found in Woolwich Reservoir, Belwood Lake, GRCA warns

Keep kids and pets away from blue-green algae growing at Belwood Lake and Woolwich reservoirs, the Grand River Conservation Area is warning.

People should avoid contact with the algae and not eat fish from the lakes, the GRCA said in a release Friday.

While boating is still allowed, boaters should avoid touching the algae.

Visitors to Belwood Lake also shouldn’t swim in areas where green or brown algae scum is visible.

Blue-green algae, also called cyanobacteria, are actually bacteria that have features in common with algae, GRCA said.

Some varieties have the ability to produce to toxins that can make people and animals sick in high concentrations.

“Blue-green algae thrive on nutrients from fields and lawns that find their way into local waterways and reservoirs during heavy rainfall and spring melts and cause their populations to grow rapidly, forming blooms or scum on the surface of the water,” GRCA said.

A sign warns of the presence of high concentrations of blue-green algae at Woolwich Reservoir and Dam on Sept. 5, 2023. (Hannah Schmidt/CTV Kitchener)

The blooms are most common in late summer or early fall in areas where water is slow moving and warm.

“When an algal bloom starts to grow, a noticeable green or brown scum will form on the surface of water bodies and the water looks like green or bluish-green pea soup,” GRCA said. “Once blue-green algae are in full bloom, it may look like spilled paint along the shoreline. A new blue-green algal bloom often smells like fresh cut grass, while an older bloom can smell like rotting garbage.”