What are blue-green algae (cyanobacteria)?
Blue-green algae, also known as cyanobacteria, are plant-like bacterial organisms naturally found in many types of water systems including ponds, lakes, rivers and wetlands. They are not normally visible, but under the right conditions (warm, slow moving, shallow water and enough sunlight and nutrients), blue-green algae are capable of forming blooms. Some types of blue-green algae produce toxins which can be poisonous to humans and animals.
What is a blue-green algal bloom?
Under the right conditions blue-green algae can increase in numbers quickly forming a bloom. A bloom can appear as surface scum, foam or a mat and/or discoloured water and can be blue, blue-green, green, red, brown or yellow in colour. Some look like paint streaks on the water, while others many not affect the look of the water. Blue-green algae toxins have the ability to reach high levels in blooms, which can be harmful to the health of humans and animals.
Fresh blooms smell like newly mown grass; older blooms smell like rotting garbage. Some conditions important for bloom growth include:
- Warmer water temperatures;
- Amount of light and length of daylight;
- Wind and water currents (blooms often occur in slow moving shallow water)
- Excess nutrients (nitrogen/phosphorous); and
- Correct pH.
Blooms usually occur in late summer and early fall.
What should I do if I see a blue-green algae bloom?
Do not swim or engage in any other recreational activity that may involve contact with water (e.g., water-skiing) in areas where a bloom is observed. Keep children, pets and livestock away. Do not drink the lake water. NOTE: Boiling water will not remove toxins.
What are possible health effects from blue-green algae toxin contaminated water?
If you swim in contaminated water, your eyes and skin may get itchy and irritated. You may also get other hay fever-like allergy symptoms. Skin contact with blue-green algae toxins may cause result in hives, rashes, blisters, etc. If contaminated water is swallowed (e.g., through drinking the water) or inhaled (e.g., inhaling water droplets from recreational activities such as water-skiing, boating, etc.) you may experience:
- sore throat;
- stomach cramps;
- diarrhea and
Symptoms from exposure to blue-green algae toxins can last for several days. Children and immuno-compromised individuals are at a higher risk for the more severe effects.
What should I do if I come into contact with water contaminated with blue-green algal toxins?
If you think you might have come into contact with blue-green algal toxins in the water, you should remove any affected clothing and shower with clean water as soon as possible. If you experience symptoms or health effects after recreational contact with affected water, please seek medical advice.
How harmful are blue-green algal toxins?
Very few incidents of human poisoning have been reported. People don't usually drink water contaminated with blue-green algae because of the scum and smell; however, contaminated water could accidentally be swallowed during recreational activities (e.g., swimming).
Extended exposure to low levels of toxins can potentially have long-term or chronic effects in humans. Children are at greater risk than adults of developing serious liver damage should they ingest high levels of toxins, mostly because of their comparatively lower body weight.
Can I still drink my tap water during a blue-green algae bloom?
Water should not be consumed from bodies of water that have blue-green algae blooms. It can’t be determined if a bloom is harmful or toxic simply by looking at it, so it should be assumed toxins are present. If you receive your drinking water directly from a source experiencing a blue-green algae bloom do not consume it, even if you have a water treatment system. Residential water treatment systems may not remove blue-green algae toxins from your drinking water.
If you are connected to a municipal water supply system, you can continue to use the water as normal unless notified otherwise by the system owner/ operator. If you have your own groundwater well supply, you can continue to drink the water as normal.
Can I cook using water with blue-green algae in it?
No. Boiling water does not remove toxins from the water.
Can I use water contaminated with blue-green algal toxins for washing?
If a safe source of water is available, don't use contaminated water for washing clothes or dishes. If an alternative safe source of water is not available, use rubber gloves to avoid direct contact with the water.
Bathing or showering in contaminated water should be avoided, as skin contact with the toxins can lead to skin irritation and rashes.
Can I eat fish from water contaminated with algal toxins?
Toxins can accumulate in the tissues of fish, particularly in the internal organs (liver, kidney, etc.). Levels in the tissues depend upon the severity of the bloom in the area where the fish are caught or collected. Caution should be taken when considering the consumption of fish caught in areas where blue-green algal blooms occur. The internal organs of fish should be removed and disposed of. Fish should be rinsed well with clean drinking water before being cooked and eaten.
Should pets or livestock drink water containing blue-green blooms?
If livestock or other domestic animals have no other source of drinking water, they may be poisoned by drinking water from open water bodies, such as lakes or ponds, contaminated with blue-green algae toxins. Animals are not more sensitive than people to the effects of the toxins; they are simply not as concerned with the way water looks or smells before they drink it.
Can water with blue-green algae blooms be used for recreational activities?
Swimming and any other recreational activities (e.g., waterskiing) that may involve contact with the water should be avoided in areas where a bloom is observed. Blue-green algae toxins, if present, could be accidentally swallowed or inhaled.
Why are public beach closures issued during blue-green algae blooms?
Since some blue-green algae species can produce toxins that are harmful to humans, blue-green algae blooms are considered a public health concern and beach closures are issued. Closures also serve to remind users to check the water for the formation of highly visible blooms and scum (which pose the most risk) before entering. Since conditions may change in a matter of hours, being aware is crucial to making good decisions and staying safe.
How long will an closure remain in effect?
Once a closure has been posted at a lake, it will remain in effect until the water has been deemed safe to use for recreational purposes. Regular sampling will take place to determine the status of municipal beaches. Our website will be updated when beaches when are reopened.
When is it safe to use the water?
If a closure is in effect, it is not safe to use the water. If there is no closure in place, the water has been deemed safe. It’s always a good idea to check the water before entering regardless of closure status as blooms can appear quickly and be suspended at different depths in the water where you can’t see them. So even if you can't see a bloom floating on the surface of the water, that doesn't mean one isn't present. After a closure, toxins can remain in the water for several weeks. The time for water to recover to its normal state varies by bloom based on local conditions.
How many lakes are monitored in the Halifax Regional Municipality?
Staff monitors 23 beaches across the municipality. A full list of beaches is located on our website. The municipality urges lake users to use caution when visiting other lakes in the region. Users should check the water for surface scum, foam or a mat and/or discoloured water and be aware that blooms can be blue, blue-green, green, red, brown or yellow in colour. Some look like paint streaks on the water, while others many not affect the look of the water. If the water appears to have this consistency, its best to avoid contact.
How does the Halifax Regional Municipality decide which beaches to monitor?
The Municipality only monitors beaches where lifeguard supervision is provided and at four locations where lifeguard supervision was historically provided but recently removed.
What can be done to avoid algae blooms?
There are many factors that contribute to the growth of algae blooms—excess nutrients are among the most important of these. Limiting the amount of phosphorus and nitrogen that enters the watercourse helps to protect against bloom formation. This can be done by limiting the use of fertilizers, performing regular maintenance on septic systems and cleaning up after pets.
Who do I call to report a suspected algae bloom?
If one of the 23 monitored municipal beaches appears to have an algae bloom, please call 311 to report.