Algoma Public Health
- Blue-green algae
What is blue-green algae?
What are blue-green algae blooms?
Are blue-green algae blooms harmful?
What are the health effects?
I get my drinking water from the lake and I have a water treatment device. Is the water safe to drink during a bloom?
Does boiling the water make it safe for drinking?
I no longer see the blue-green algae bloom in the water. Is the water safe?
Why does my lake have blue-green algae blooms?
How can I help prevent the growth of blue-green algae?
What do I do if I see a bloom?
Blue-green algae, also known as Cyanobacteria, are a type of bacteria that can be found in lakes, ponds, rivers and streams and have been around for thousands of years. Like algae, they are photosynthetic. That is, they convert sunlight into the energy required for growth and reproduction. Blue-green algae are often present in low numbers and are barely visible. When you can see them, they may range in colour from olive-green to red.
When conditions are right, blue-green algae may increase in numbers forming a visible scum called a bloom. Blooms are more common in late summer and early fall, and often occur in water that is shallow, slow moving and warm. Blooms can last for several weeks and can occur more than once per year. Affected water can look like pea soup or turquoise paint and some blooms form solid looking clumps. They may smell like freshly mowed grass or rotting garbage. One condition affecting the growth of blue-green algae is the amount of available nutrients particularly nitrogen and phosphorous.
Some types of blue-green algae produce toxins which are harmful to humans and pets when they are breathed in, swallowed or touched. During a bloom, you can be exposed to toxins through swimming, waterskiing or showering in affected water, and drinking or eating fish caught in affected water. Toxins are not produced by all blue-green algae and there is no way to tell if toxins are present by looking at a bloom. A bloom should be assumed toxic until proven otherwise by laboratory results.
Skin Contact: symptoms may include skin, eye, nose and throat irritation.
Swallowed: symptoms may include vomiting, fever, diarrhea, headaches, nausea and abdominal cramps. Drinking large quantities over a long period of time may lead to more serious health effects including damage to the liver or nervous system.
No. Small-scale, residential treatment devices are not capable of removing toxins from the water. The recommendation is to use an alternate source of water during a bloom. If you continue to draw water from a lake during a blue-green algae bloom, you do so at your own risk.
No. Boiling the water does not remove the toxins. In fact, boiling the water increases the amount of toxins making the situation even worse. The recommendation is to use an alternate source of water during a bloom.
We do not know. Blue-green algae blooms are unpredictable. Nutrient and sunlight availability, air and water temperatures, and the wind affect the timing, intensity and duration of a bloom. Blue-green algae can move up and down the water column in search of nutrients and sunlight which means you may not always be able to see them. Wind can blow the bloom to a different area of the water body. Even when a bloom disappears, toxins may last for a long time. This is why laboratory results of a water sample taken a specific time of day and in one area of a water body may not be an accurate representation of the whole water body.
Although blooms can occur naturally, human activities provide conditions favourable for the growth of blue-green algae. Storm water and agricultural runoff, use of fertilizers, industrial waste water, and waste from faulty septic systems can lead to the nutrient enrichment of water bodies and promote the occurrence of blooms.
- Use phosphate-free soaps, detergent and cleaning products
- Avoid using lawn fertilizers, especially those containing phosphorus
- Leave an area of natural vegetation extending back from the shoreline on waterfront properties
- Recreate a natural shoreline on waterfront properties if the shoreline has been altered through tree and vegetation removal. Allow it to return to its natural state or plant native species of flowers, grasses and shrubs.
- Maintain your septic system and ensure it is not leaking into the water
- Reduce agricultural runoff by planting or maintaining vegetation along waterways
- Do not use the water for recreational activities such as swimming or water skiing
- Do not drink the water
- Do not use the water for food preparation
- Do not bath or shower in the water
- Do not let pets or livestock use the water for drinking or wading
- Do not eat the liver, kidneys or other organs of fish caught in the water
- Use alternative safe water sources such as bottled or municipally treated water
- Report the bloom to the Ministry of the Environment or Climate Change at 1-800-268-6060