Possible blue-green algae bloom triggers risk advisory for Penhorn Beach

Haligonians are being asked to avoid swimming in Penhorn Lake until further notice due to a possible blue-green algae bloom.

A risk advisory has been issued for Penhorn Beach at the Dartmouth lake.

The Halifax Reginal Municipality is encouraging lake users to take the following precautions:

• Avoid water contact. If contact occurs, wash with tap water as soon as possible.
• Do not swim or wade (or allow your pets to swim or wade) in any areas where blue-green algae is visible or in areas where a risk advisory has been issued.
• Avoid consuming water from this lake.
• Avoid consuming fish that has come from this lake.

“Blue-green algae (cyanobacteria) is naturally occurring in freshwater environments and may become visible when weather conditions are calm,” said HRM in a news release. “These organisms can multiply rapidly during the summer, leading to extensive growth called a bloom.”

“Some types of blue-green algae produce toxins during blooms and when these blooms decay, the toxins may be released into the water, posing a risk to people and pets.”

For humans, the algae can cause skin irritation, rashes, sore throat, sore red eyes, swollen lips, fever, nausea and vomiting and/or diarrhea. The risk is higher for children and those who are immune-compromised.

And blue-green algae can be deadly for pets.

“It's highly toxic,” Bedford veterinarian Dr. Jeff Goodall told CityNews Halifax earlier this summer. “By the time your dog has contacted it, it's probably going to be pretty bad. You need to seek immediate care.”

“Simply licking the scum coat could be fatal.”

Staff at HRM's 18 supervised beaches are constantly on the lookout for blue-green algae.

Last month, Elizabeth Montgomery, a water resources specialist on HRM's environment and climate change team, told CityNews Halifax if something looks suspicious, lifeguards will snap a photo and send it to her team. 

If they can't determine it's something else like, like pollen, they will immediately close the beach and send a sample into a lab for analysis.

If the algae bloom is not toxin producing, the risk advisory will be lifted and no further testing is required, but if the bloom is toxin producing, the risk advisory will stay in place until results indicate the water is once again safe.

Nova Scotians are being encouraged to learn how to identify blue green algae themselves and be on the lookout for them as they explore the province this summer.

Potential blooms — which form on and below the water's surface — and mats — which grow on the bottom of rivers and lakes or attached to structures and plants in the water — can be reported by calling 1-877-936-8476.

The province maintains a list of potential blue-green algae blooms online.

Despite the name, according to Nova Scotia's Department of Environment and Climate Change, the algae can be a variety of colours, including turquoise, green, brown, red, white or mixes of those colours. 

“Blue-green algae blooms can look like fine grass clippings in the water, spilled paint or pea soup,” the department said on its website. “Sometimes they look like a thick scum on the surface.”

Along the shore, they can dry up and appear brown or grey. 

Algae mats at the bottom of clear shallow areas look like clumps of vegetation and can appear black, brown or dark green in the water.

“They often smell musty or grassy when healthy and like ammonia when decomposing,” the department stated, adding animals can be attracted to that odour.

More information on blue green algae can be found on both the province's website and HRM's website.

Haligonians can find the status of their favourite municipal beach by clicking here.