What you should know about toxic blue-green algae blooms

Ecologists are warning people in Fredericton that a blue-green algae bloom may be behind the sudden deaths of three dogs who died after swimming in the St. John River. Here's what you need to know about the pesky microbe and its troubling consequences.

The pesky microbe — actually bacteria — is lethal to animals and harmful to humans

A bloom of blue-green algae is shown by researchers near Edmonton. Toxins from the microbe — actually bacteria — are likely behind the deaths of three dogs in Fredericton last weekend. (University of Alberta)

Ecologists are warning people in Fredericton that a blue-green algae bloom may be behind the sudden deaths of three dogs who died after swimming in the St. John River.

New Brunswick's provincial veterinarian, Dr. Jim Goltz, said there's no definitive answer, but given the time of year, he suspects toxins from blue-green algae are the cause of death.

"We're pursuing that angle as our first investigation into the potential for toxins," he said.

Elsewhere in the province, Moncton is contending with a blue-green algae problem of its own.

Nicole Taylor, director of utilities, said the city is working with two consultants to address the algae, which has also been detected in the Turtle Creek watershed, the city's source of drinking water.

New Brunswick isn't the only province contending with the potentially deadly microbe. At least 246 Canadian bodies of water have been shown to have high concentrations of blue-green algae at various times in the last 15 years

Here's what you need to know about blue-green algae and its troubling consequences.

What is blue-green algae? 

Although it's commonly referred to as blue-green algae, it's actually bacteria (scientific name: Cyanobacteria) that can produce toxins harmful to people and animals.

A photosynthetic bacterium, it produces energy through photosynthesis, according to the British Columbia Ministry of Environment website. That's why it wreaks havoc mostly in the sunny summer months and early fall.

At one point, biologists grouped the bacteria with algae — possibly because they are similar in appearance. But blue-green algae is now recognized as its own phylum.

Two of the dogs died after visiting Carleton Park along the St. John River in Fredericton on Sunday. (Adam Travis/@adamtravis_)

Where do you find it?

The bacteria is present in almost all lakes in Canada, says David Schindler, a professor of ecology at the University of Alberta.

But blue-green algae is a bigger problem in the Prairies, where a lot of the soil has naturally high levels of phosphorous, which help the bacteria grow, Schindler said.

Still, blue-green algae has become a problem in waterways across Canada. "It's not that they've invaded, but that they've increased — from nearly undetectable levels to nuisance levels," said Schindler.

What causes the bacteria?

Blue-green algae typically grows rapidly in areas where there is an abundance of nutrients like phosphorus and nitrogen, according to the Ontario Ministry of the Environment, Conservation and Parks.

Blooms can also be created from polluted storm water run-off, run-off from agriculture, fertilizer, lawn waste or septic systems, or other materials that wash into lakes and decompose.

How do you recognize blue-green algae?

Blue-green algae is not normally visible in the water, but under the right conditions, the bacteria increase in number and form blooms — a soup-like layer on the water's surface that can actually be seen from space, said Diane Orihel, a freshwater ecologist who teaches at Queen's University.

The bacteria form in water that is shallow, warm and slow-moving or still. They are typically more common in the late summer and early fall, but may be present in deeper, cooler water.

A satellite image captures algal blooms on Lake of the Woods — which straddles the borders between Manitoba, Ontario and Minnesota — on Oct. 20, 2017. (Caren Binding, Environment and Climate Change Canada)

And although they are often blue-green, the bacteria can range in colour from olive green to red.

Fresh blooms often smell like newly mown grass, while older blooms may smell like rotting garbage.

What harm can it cause?

Harmful toxins are mainly released from the blue-green algae when the cells of the bacteria break open or die. This can happen because of cooler weather, rainfall and windy conditions.

Contact with blue-green algae blooms can be lethal to pets. Goltz, New Brunswick's head vet, said it "can kill animals within half an hour of exposure and after the toxin has been ingested."

Human reactions range in severity. While some toxins can attack the liver or the nervous system, others may just irritate the skin and eyes.

Health Canada said it is rare to be exposed to the toxins through ingestion because water sources are monitored for blue-green algae levels.

That's a good thing, because if water containing blue-green algae is consumed, it can cause headaches, fever, diarrhea, abdominal pain, nausea and vomiting.

Swimming in water containing the toxin can irritate the skin and eyes. Eating fish from water contaminated by the bacteria or using products with blue-green algae has similar effects, too.

A muscovy duck and its young swim through an algae-infested canal in North Fort Myers, Fla., on July 10. (Andrew West/Associated Press)

Not all kinds of blue-green algae are toxic. In fact, one variety is used as a food supplement, often in tablet or caplet form. Companies advertise spirulina as both a potential source of protein and a weight-loss agent.

Health Canada cautions that the safety of these products has not been firmly established, although supplements made with spirulina blue-green algae have been shown to be harmless.

What should I do to prevent algal blooms?

"Reduce external nutrients going into the lakes," said Paul Frost, a Trent University biologist and algae expert.

Ontario's Ministry of the Environment, Conservation and Parks recommends using phosphate-free products, avoiding fertilizers, maintaining a natural shoreline on lakes and riverfront properties, reducing run-off and checking septic systems.

Frost says people need to focus more on "diffused nutrient sources" — and not just in places next to lakes and streams.

"These are sources of nutrients coming from scattered places in the catchments, like storm water treatment ponds or from farm land," he said.

"Fertilize less. Keep a natural shoreline. Pick up your pet waste. It all has a positive value to reduce nutrient load into lakes"

What should I do if I find blue-green algae?

If you suspect you've come across blue-green algae, don't drink the water, or bathe or swim in it. Make sure to keep your pets out of it, too.


With files from Elizabeth Fraser, Tori Weldon and Kathryn Weatherley