New Brunswick

2nd type of cyanobacteria in St. John River could be harmful to humans, researcher says

A New Brunswick researcher is warning people of a different type of cyanobacteria popping up along the St. John River this summer.

'We know that it’s toxic, we just don’t know quite how toxic,' says Janice Lawrence of UNB

Janice Lawrence, biology professor at UNB, says climate change could be causing the boom in cyanobacteria along the St. John River this summer. (Submitted)

A different type of cyanobacteria is popping up along the St. John River this summer that could be harmful to humans, a researcher warns.

Dr. Janice Lawrence, an associate professor of biology at the University of New Brunswick, has been studying cyanobacteria, also known as blue-green algae, along the river since the spring.

While most cyanobacteria found in ponds or lakes will cause skin irritation or gastrointestinal illness, the algae populations living at the bottom of the St. John River are producing potent neurotoxins that can cause immediate paralysis, suffocation and death in dogs and other vertebrates but also pose a risk to people. 

"We know that it's toxic," Lawrence said. "We just don't know quite how toxic."

Avoid ingesting algae

The Department of Health said the risk posed by neurotoxins is theoretically possible but "very unlikely" in a practical sense. A person would have to ingest a large amount.  

But health and veterinary officials are still urging people to take precautions to protect themselves and their pets along the river and other recreational waterways.

Dr. Cristin Muecke, New Brunswick's deputy chief medical officer of health, said there are subsets of the bacteria that emit different toxins, which can produce different health effects. 

"There are some that cause more skin effects, there are some that cause more gastrointestinal effects," Muecke said. "We've known for a while now that there exists cyanobacteria that can produce neurotoxins."

Muecke said it's important for people to supervise those who can't supervise themselves around the water.

The number one protective measure the public can take is to avoid ingestion, she said.

Two types of cyanobacteria

Lawrence emphasized there have been no recorded human deaths associated with the neurotoxins but said research done on lab animals indicates they do not recover from coming into contact with them. 

Symptoms of exposure to neurotoxins can include tremors, shaking, loss of cognitive function, and respiratory distress.

Lawrence said there is also no known treatment.   

Lawrence is warning the public to be cautious if they're going to swim in the St. John River. (Photo: CBC)

Blue-green algae are photosynthetic bacterial organisms naturally found in rivers, lakes and wetlands. In warm weather, they can form blooms that may look like scum, foam or discolorations of blue-green, green, red, brown or yellow that can appear fluorescent. 

This different form of cyanobacteria is being found in thick mats on the river bottom, cobbles and on top of other aquatic vegetation. It's also found in areas with fast-moving water, something Lawrence says isn't something typically associated with algae blooms.

"Along the river, it is not enough to see if there's a visible scum or an odour," Lawrence said. "These things are not immediately obvious."

Size of dinner plates 

Lawrence's cyanobacteria research has revealed clumps of the algae can get ripped up from the bottom and float downriver or onto the shoreline.

"We've seen them going by the size of dinner plates, these great big mats," she said. 

It can be brown, rust, burgundy, mossy or chalky.

"Typically, we think of cyanobacteria as being free-floating organisms that accumulate at surface and create very visible scum, very visible populations that people generally know to stay away from," Lawrence said.  

Muecke said the mats, which have been spotted "extensively" in the St. John River system, can wash up onshore and turn grey.

People can still be active and enjoy the outdoors, she said, but they should be aware that the algae can appear in different forms and in different locations in lakes and rivers.

Lawrence's research is funded by the Environmental Trust Fund, which is administered by the Department of Environment and Local Government. 

I would not want to come in contact with this material.- Janice Lawrence, associate professor at UNB

Over the past few months, she has been studying the river in the Woodstock area and from the Mactaquac Dam to Carleton Park in Fredericton, where two dogs died last year.  A third dog died after swimming in the river near Hartt Island RV Resort, 14 kilometres west of the city.

"It was fairly clear that what the dogs had ingested had washed up onshore, but had originated elsewhere at the bottom of the river," she said. 

This year, Lawrence said, cyanobacteria have been spotted everywhere in the Fredericton and Woodstock areas, Lawrence said. 

The volume of material we're seeing is very concerning," she said.

Blue-green algae grow in warm conditions, when water levels are low, and produce different toxins that can affect the brain. (Submitted by: University of Alberta)

Before 2018, the last case of blue-green algae toxicity was in 2010, when a Labrador puppy died after swimming in the St. John River below the Mactaquac Dam in the Island View area.

Government officials are now trying to determine whether blue-green algae caused the death of a dog that was swimming in the St. John River in Fredericton this past weekend. 

Climate change a culprit 

Lawrence expects to have more information about the cyanobacteria in the river by the end of the summer. 

She said climate change could be causing the boom in cyanobacteria, as the bacteria tend to dominate when temperatures are warm, giving them a leg up on organisms that keep them in check.

Cyanobacteria are also scavengers of nutrients, which are being added to the river from runoff, lawn applications, septic tanks that aren't adequately maintained and shorelines. This causes the blue-green algae population to proliferate. 

"I would not want to come in contact with this material," she said.


Elizabeth Fraser


Elizabeth Fraser is a reporter/editor with CBC New Brunswick based in Fredericton. She's originally from Manitoba. Story tip?

With files from Information Morning


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