Blue-green algae is back. Here are some tips to protect you and your pet

Although it isn’t quite summer yet, blue-green algae, also known as cyanobacteria, is already showing up in New Brunswick waterways.

Meghann Bruce, a researcher and instructor with the University of New Brunswick Canadian Rivers Institute, said as soon as the ice went out in early May, there was a “bloom” in Blue Bell Lake near Grand Falls.

“Blooms could be happening right now, so people should be watching for them anytime they’re around the water,” she said.

Bruce said there are two types of blue-green algae blooms.

A woman with brown curly hair stood against a white wall with her arms crossed.
Meghann Bruce is a researcher and instructor with the University of New Brunswick Canadian Rivers Institute. She’s studying cyanobacteria in the Fredericton area. (Submitted by Meghann Bruce)

A surface bloom is when there are thousands or millions of cells occurring throughout the water, which often results in a green color. Up until a few years ago, this type of bloom was more common in the province, she said.

But the other type, a benthic mat, grows at the bottom of rivers and lakes and can sometimes float up to the surface. Bruce said this type of bloom is more like a dense, slim carpet.

“They’re actually really important organisms. Like plants, they release oxygen. They were the organisms that gave Earth its first oxygen, so they changed the atmospheric composition of Earth, ultimately paving the way for humans to exist,” she said.

“But unfortunately, they can also be problematic for people and their pets, because sometimes in aquatic environments, they grow to very high densities, which is when we see a bloom appear.”

Both types can be toxic. Some can cause skin irritation, said Bruce, but the main danger comes if they are ingested.

Cyanobacteria and dogs

“I think it’s natural human behavior to want to avoid these types of areas when a bloom is occurring,” she said.

“Dogs on the other hand, the risk is a bit different because dogs will seek them out. Dogs are very attracted to some of these blooms.”

In 2018 and 2019, the CBC reported on four dogs that died from cyanobacteria, after swimming in, or playing near the St. John River, also known as the Wolastoq.

A green body of water
Blue-green surface algae blooms often cause green water. This photo was taken at Lac Unique near the Quebec border. (Meghann Bruce/Canadian Rivers Institute, UNB)

Bruce said to not let your dogs drink the water, and stop small children from playing in gooey things on the water’s edge. She also said if you have a boat, check to make sure there are no mats stuck to the side of the craft when taking it out of the water.

“Maybe you’ve even left your dog at home, but you wouldn’t want to bring a piece of mat home and have it fall off in your driveway and your dog to go after it.”

Water with a brown, slimy piece of blue-green algae floating on it.
Benthic cyanobacteria mats can sometimes lift off the bottom of the river or lake and float to the top. Bruce said blue-green algae can sometimes appear brown or gray in color from sun bleaching. (Meghann Bruce/Canadian Rivers Institute)

Bruce said it is good that the province put signs up around rivers and lakes reminding people about blue-green algae. She said people tend to forget about it until something serious happens, such as the death of a pet.

But she said the warning signage doesn’t necessarily mean the water is toxic or that the risk is there all the time, it just means the water body can produce it and people should be aware.

Bruce said people should watch for green water or green mats, but also golden brown or gray mats that had changed that color from sun bleaching.

She said people also tend to think that blooms can only occur in stagnant or slow moving water, but the toxic blooms she’s currently studying in Fredericton are in clear, fast-flowing waters.

An overhead view of a green lake with a dock and a speed boat parked next to it.
A surface bloom is when there are thousands or millions of cyanobacteria cells occurring throughout the water. This drone footage from 2021 shows the scope of blue-green algae blooms in Darlings Lake, near Hampton. (Mike Adams for Hammond River Angling Association)

But she said there’s no amount of sampling that can guarantee safety. She said even if it were possible to monitor every lake in New Brunswick, samples could be collected in the morning, and the status of the water could change by afternoon.

“Blooms can change that fast. It can be as simple as, you know, things move with changes in wind direction,” said Bruce.

“The best guarantee is to be on the lookout for the conditions around you.”

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