Harmful Algae Blooms
Algae are microscopic plants that naturally live in freshwater and saltwater environments. Algae can grow quickly during the summer and form a larger growth called a bloom. Some types of blue-green algae, also known as cyanobacteria, form toxin-producing blooms. When toxin-producing blooms die and decay, the toxins may be released into the water and could pose health concerns.
Risk Advisories
It is very difficult to predict if blooms will form. It is even more difficult to predict if blooms will release toxins. Blooms of algae and blue-green algae may vary considerably in colour, consistency and overall appearance. The presence of blooms triggers monitoring since toxins are only formed if there are blooms.
A risk advisory is issued when an algae bloom is observed. Initial testing is done to confirm if there are toxin-producing cyanobacteria present in the algae bloom. Certain cyanobacteria are toxin producing and others are not. Due to the difficulty of quickly identifying the presence of toxin-producing algae in a bloom, and the changing nature of water quality, risk advisories are issued using an abundance of caution for public health and safety.
- If there is no risk for toxin production, i.e., there are no toxin-producing algae present in the bloom, the risk advisory will be lifted, and no further testing is required.
- If there is a risk for toxin production, i.e. there are toxin-producing algae present in the bloom, the risk advisory remains in effect. At municipally supervised beaches, visual bloom monitoring will continue until blooms have disappeared and remain absent for seven consecutive days. At that time, water samples will be tested for toxins at a certified lab. The risk advisory will be lifted if toxins are within safe limits. If the toxin levels are above safe limits, the risk advisory will remain in effect until later test results reveal they are within safe limits (below current guideline values).
Reporting suspected contamination
A bloom can appear as surface scum, foam, a mat and/or discoloured water. A bloom can be blue, blue-green, green, red, brown or yellow in colour. Some look like paint streaks on the water, while many others do not affect the look of the water. The municipality asks anyone who observes water conditions with these characteristics to call the provincial Inspection Compliance and Enforcement office at 1-877-9ENVIRO (1-877-936-8476) and Halifax Regional Municipality at 311.
Alerts and closures
Municipal staff monitor and report on the status of 18 beaches across the municipality. Watch for advisories by visiting halifax.ca/beaches and following @hfxgov on Twitter. Updates can also be found at www.NovaScotia.ca/Blue-Green-Algae. The municipality monitors our supervised beaches for fecal bacteria, blue-green algae, and other waterborne contaminants between July 1 – August 31 annually. If a suspected blue-green bloom is observed at one of our supervised beaches, the beach is closed immediately and water samples are analyzed for toxins. The beach is not reopened until analysis confirms toxin levels are within safe limits for recreation. When a bloom is reported to the province in a lake where the municipality supervises a beach, municipal staff conduct follow-up monitoring to ensure water quality is safe for recreational use.
If a beach is closed, do not swim or engage in any other recreational activity that may involve contact with water (e.g., paddling). Keep children and pets away from the water. Do not drink the lake water and please note that boiling water will not remove toxins.
We encourage everyone to follow beach rules and restrictions to be safe when visiting the beaches.
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**** Via NS Government
Blue-green algae
Watch for blue-green algae from May to October. Blue-green algae (also called cyanobacteria) occur naturally in surface waters like lakes, ponds, rivers and streams. The toxins in the algae can make people sick and be fatal for pets if ingested.
If you think you see blue-green algae, don’t touch it, swim or play in it, or drink the water.
Reporting blue-green algae
If you think you see blue-green algae, you should treat it as potentially toxic. Report it to your local Department of Environment and Climate Change office or call 1-877-936-8476.Where to find blue-green algae reports
The Department of Environment and Climate Change publishes a list of potential blue-green algae blooms online and shares new reports on social media. In the case of public drinking water supplies, an inspector will visually confirm the presence of blue-green algae and work directly with the water supply owner. Supervised beaches in Halifax Regional Municipality monitor for blue-green algae and publish advisories online. The Nova Scotia Lifeguard Service shares notices about water quality and beach closures on social media. You can also look for signs posted near provincial beaches.Identifying blue-green algae
Despite the name, blue-green algae can be turquoise, green, brown, red, white or mixes of these colours. Blue-green algae blooms can look like fine grass clippings in the water, spilled paint or pea soup. Sometimes they look like a thick scum on the surface. They often smell musty or grassy when healthy and like ammonia when decomposing. There may also be algae mats at the bottom of clear shallow areas of lakes and rivers or on the shoreline. The algae mats look like clumps of vegetation and can appear black, brown or dark green in the water. On the shoreline, they may appear brown or grey once they have dried. Animals are attracted to their odour and may try to eat them. Keep children and pets away from algae mats.
A low-density bloom of blue-green algae species in Nova Scotia, near the shoreline of a lake. (Photo: Department of Environment and Climate Change)
A medium-density bloom of blue-green algae species in Nova Scotia, near the shoreline of a lake. (Photo: Department of Environment and Climate Change)
A blue-green algae bloom resembling spilled paint near the shoreline of a lake. (Photo: Jean Cleveland)
A decaying bloom with blue-green colour visible on the shoreline of a lake. (Photo: Jean Cleveland)
A blue-green algae mat attached to the bottom of a river. (Photo: Meghann Bruce)
A blue-green algae bloom resembling grass clippings. (Photo: Jacob Kann)
A blue-green algae mat in salt water. Blue-green algae is less common in marine environments. (Photo: Kelly Maher)
Blue-green algae reported in 2023
Last updated:
| Lake | County | Month |
|---|---|---|
| Molega Lake | Queens | June |
| Aylesford Lake | Kings | June |
| Shubenacadie Grand Lake | Halifax | June |
| Wrights Lake | Halifax | June |
| Covey Lake | Lunenburg | June |
| Lake Torment | Kings | June |
| Armstrong Lake | Kings | June |
| Oathill Lake | Halifax | June |
Health effects
In people, blue-green algae exposure when swimming can cause itchy, irritated eyes and skin. Swallowing or inhaling the water can cause headaches, fever, diarrhea, abdominal pain, nausea and vomiting. Prolonged exposure can damage the liver. Children are at greater risk because of their lower body weight. They also tend spend more time in water and are more likely to swallow it. In pets, exposure to blue-green algae can be fatal.Safety
If blue-green algae is present:- don’t drink, swim, bathe, shower or brush your teeth with the water
- don’t allow children, pets or livestock to drink or swim in the water
- if you come in contact with blue-green algae, wash yourself and any items that came in contact
- use alternative water sources for drinking, cooking, bathing, laundry and watering vegetables (contaminated water isn’t safe even if it’s boiled, filtered in a jug or pitcher or treated with bleach, herbicides, copper sulfate or other algicides)
- be careful with recreational water activities that generate spray (like boating) because the toxins can be inhaled
- be careful when eating fish caught in water where blue-green algae blooms occur (do not eat the liver, kidneys or other organs because the toxins can be stored there)
- if you get sick, seek medical attention
- if your pet ingests blue-green algae, contact a veterinarian immediately
