Blue-green algae or cyanobacteria, is a naturally occurring plant-like organisms and may be harmful if blooms are present. While the colour is typically blue-green, it can also be observed from olive-green to red. Blue-green algae is not visible in the water, but under favourable conditions it produces blooms. Blooms are visible in water and often described as scum on the surface of the water. Typically, the bloom is noted at the end of summer in locations exposed to a lot of sunlight and calm water conditions. Bodies of water high in phosphorous and nitrogen may see increased bloom activity as these are the nutrients the algae feed on.
Some species of blue-green algae are capable of producing cyanobacterial toxins or cyanotoxins. Cyanotoxins can make the water look cloudy or soupy. They may also have an affect on the health of humans and animals by causing itchy, irritated eyes and skin, flu-like symptoms, and in severe cases liver damage or other symptoms.
Public beaches are not tested by the Health Unit for cyanobacteria. However sites that have been reported by the Ministry may have a notice present that advises the public about the potential exposure.
If you see blue-green algae blooms in the water:
- Avoid any skin contact with the water.
- Do not ingest the water.
- Keep pets/livestock away.
- Do not eat internal organs of fish caught when blooms are visible or suspected.
- Do not drink, cook, or shower with water experiencing an active bloom. Toxins are not removed by boiling. Contact a qualified water treatment specialist.
If spotted, report blue-green algae to Spills Action Centre 1-866-MOETIPS (6638477)
TTY: 1-855-889-5775
Resource
- Blue-green Algae – Ministry of the Environment, Conservation and Parks
- Canadian Drinking Water Guidelines: Cyanobacterial toxins – Health Canada
- Blue-green algae factsheet – Ministry of the Environment, Conservation and Parks
