be careful where you swim or walk your dog: blue-green algae season arrives in nova scotia
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an example of blue-green algae near the shoreline of a lake in nova scotia. - supplied by the government of nova scotia
the incoming heat wave has nova scotia’s boaters and swimmers on top of the world, but it also brings the annual risk of blue-green algae in lakes, ponds, rivers and streams.
spikes in temperature, combined with low winds and stagnant water, create ideal conditions for blooms of the toxic scum, otherwise known as cyanobacteria. rapid growth also typically follows a spell of heavy rainfall, which some areas had a few days ago.
with short-term forecasts calling for consecutive days above 30 c, freshwater temperatures should quickly climb above 20, which is when the algae thrives.
here’s what the province could see in coming days and why it’s wise to be on the lookout.
algae bloom basics
“it’s becoming more common with warmer temperatures and more intense storms caused by climate change,” reads part of the nova scotia government’s information page.
“increased amounts of nutrients (like nutrients from fertilizers, septic systems and paved surfaces near the water) can also help blue-green algae grow.
“blue-green algae isn’t normally visible in the water, but it can quickly reproduce to form a large mass called a bloom or mat. once blue-green algae appears, it’s more likely to reappear in the same body of water.
“algae blooms come in many shapes and sizes, and harmful blooms can look very similar to harmless blooms. it can be blue-green, turquoise, green, brown, red, white or mixes of these colours.”
the most visible formations of the algae are on the surface in shallow areas, especially close to the shore. these are called planktonic algae blooms and the nova scotia government describes them as looking “like spilled paint or pea soup.”
a decaying version of this type of algae mat can resemble grass clippings and is usually found near the shoreline.
an example of a decaying planktonic algae bloom. – supplied by the nova scotia government
there are other blooms called benthic mats that form at the bottom of ponds, lakes and stagnant areas in rivers. the government said these “look like sheets of slimy green, brown or reddish growth, with visible bubbles or air pockets that can appear black, brown or dark green in the water.”
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“they can also look like web-like grey, brown or yellowish growth on rocks, shorelines, lakebeds or riverbeds. they may detach from the bottom, wash up on the shoreline, and appear brown or grey once they have dried.”
the effects of algae
the reason all this is important to know is because swimming in blue-green algae can be irritable to the skin and eyes, especially with kids. ingesting it is even worse because it can cause headaches, fever, diarrhea, abdominal pain, nausea and vomiting.
an example of a benthic algae bloom. – supplied by the nova scotia government
drinking water that contains blue-green algae is even more dangerous for pets and livestock because it can be fatal in extreme cases. the most high-profile local incidents were in 2021 at grand lake near enfield and in 2023 at long lake in hammonds plains after it was suspected dogs died in connection with exposures.
it’s worth noting animals are attracted to the smell of algae mats, so owners need to be vigilant when near contaminated sites. the best practice is to contact a veterinarian immediately if an owner suspects an animal drank from a toxic source.
new brunswick dog owner sandy kitchen-brewer holds a photo of her pet, flint, after samples of a neurotoxin produced by blue-green algae were found in its system after its 2019 death. – postmedia file
how to handle yourself around algae
for humans, the government’s advice is a combination of prevention and troubleshooting in the case of a possible exposure.
“don’t touch the algae or the water,” read the guidelines. “don’t drink the water. don’t swim, bathe, shower or play in the water. don’t brush your teeth with the water. wash yourself with clean water if you come into contact with the algae (and any items that come in contact with it).
“use alternative water sources for drinking, cooking, bathing, laundry and watering your vegetable garden (contaminated water isn’t safe even if it’s boiled, filtered or treated with bleach, herbicides, copper sulfate or other algicides). be careful with recreational water activities that generate spray (like boating) because you can inhale the toxins
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“be careful when eating fish caught in the water and don’t eat the liver, kidneys or other organs because toxins can be stored there. seek medical attention if you get sick.”
the provincial government also maintains a list of contaminated sites online and circulates frequent updates, especially now that public swimming sites are open for the season. it’s also common for warning signs to be posted at at-risk locations.
a dog pounces on a ball in a lake. – postmedia file
aylesford lake in the annapolis valley and minamkeak lake in lunenburg county are the only two reported exposures so far this summer.
the best resource to track updates is lifesavingns.ca. another helpful site for halifax regional municipality residents is halifax.ca/parks-recreation.
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