Algae

Blue-green algae, also called cyanobacteria, are actually bacteria that have features in common with algae. Many of them are green or blue-green in colour and some species have the ability to produce toxins. These toxins can make humans or animals sick if they're exposed to high concentrations.

Blue-green algae are always present in lakes, reservoirs and rivers, but usually in very small numbers. Under the right conditions, they can reproduce rapidly to form large mats or scums referred to as blooms. These blooms typically form in late summer or early fall in areas where water is slow moving and warm. Wind and wave action can cause the bloom to move or break up, so a bloom may be visible in an area one day and gone the next. 

Blue-green algae blooms often look like thick pea soup or large areas of spilled paint on the surface of the water. Fresh blooms usually smell like fresh cut grass. As a bloom becomes established, it begins to smell like rotting garbage.

The above examples show strains of Microcystis, Anabaena, and Planktothrix blooms. (Photo Credit: Ohio Environmental Protection Agency)

No, most algae found in the Grand River watershed pose no risk to human or animal health. Aquatic weeds and algae grow excessively in the Grand River and its tributaries, because there are a lot of nutrients in the water to allow them to grow. Sources of nutrients that feed algae include fields, pastures and lawns where runoff carries phosphorus into local waterways. Faulty septic systems or discharges from wastewater treatment plants can be other sources of nutrients.

There are many different species of non-toxic algae. These species naturally occur in all water bodies and can become a nuisance, because they can impede water flow, reduce local biodiversity and create an unsightly and smelly mess.

The above examples show strains of non-toxic Cladophora and Spirogyra blooms as well as Duckweed. (Photo Credit: Ohio Environmental Protection Agency)

There is always a level of risk when participating in recreational activities like swimming in a natural water body, whether it's on the shores of Lake Erie, jumping off a dock at a cottage or going to a GRCA beach.

If the water colour appears to have a shade of green to it, or becomes cloudy, preventing you from seeing your feet while standing in knee-deep water, it is recommended that swimming be avoided. Pets should also avoid contact with water when it appears this way.

If there is a visible scum on the water surface, similar to spilled paint, all contact with the water should be avoided. This includes keeping pets away from the water. When these conditions are present, there is a higher risk of getting sick or experiencing skin or eye irritation as a result of water contact. 

If a blue-green algae bloom affects one of our reservoirs, we will issue an advisory to the media, on our website and through our social media channels. We will also include notification on our conservation area status page.

Please see the Wellington-Dufferin-Guelph Health Unit for more information on potential health concerns related to blue-green algae.

• Always assume that toxins are present in any algae bloom that forms a thick scum on the surface of the water
• Avoid contact with the blue-green algae, this means keeping children, pets and livestock away from the water
• Avoid drinking, bathing or swimming in the water when algal blooms are present
• Do not eat fish from water containing a blue-green algae bloom

If you think you see a bloom developing in a GRCA reservoir or other water body within GRCA lands, please contact us with pictures and/or a description of any suspected blooms. In your description, please provide as much information as possible about the location of the suspected bloom.

The Ministry of Environment, Conservation and Parks (MECP) records the occurrence of blue-green (cyanobacteria) blooms in Ontario. You can report the occurrence by calling the Spills Action Centre at 1-800-268-6060.

For more information on blue-green algae, please refer to the MECP blue-green algae webpage.