**** Via NS Government

As the weather gets warmer, it is important for people to know about and watch for blue-green algae while enjoying Nova Scotia’s freshwater shorelines

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.

Blue-green algae tends to develop when a period of hot, dry weather is followed by a heavy rainfall. It’s becoming more common because of warmer temperatures and more intense storms caused by climate change. Once blue-green algae appears, it’s more likely to reappear in the same body of 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: 11 July 2023 at 09:01 am

Lake	County	Month
Ainslie	Inverness	July
Morris Lake (Kiwanis Beach, 759 Caldwell Road, Dartmouth)	Halifax	July
Lochaber Lake, Lochaber	Antigonish	July
Scotts Lake (near Hassett)	Digby	July
Ameros Lake (near Danvers)	Digby	July
Mattatall Lake	Cumberland	July
Fox Point Lake	Lunenburg	July
Indian Harbor Lake	Guysborough	July
Long Lake, Hammonds Plains (between Lakefront Dr and Long Lake Dr, Kingswood subdivision)	Halifax	July
Loon Lake	Halifax	June
Lake Ogden	Yarmouth	June
Lake Fanning	Yarmouth	June
Lake Martha	Hants	June
Three Mile Lake	Halifax	June
Kinsac Lake	Halifax	June
Second Lake	Halifax	June
First Lake	Halifax	June
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)
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