A new study found a neurotoxin linked to diseases including ALS and Alzheimer's in blue-green algal blooms in Lake Winnipeg.

Researchers from the University of British Columbia tested samples of 30 different blue-green algae, or cyanobacteria, blooms in the Manitoba lake, gathered by Lake Winnipeg Research Consortium.

Susan Murch, a chemistry professor at the school, says the team found the toxin BMAA — beta-methylamino-L-alanine— present in "high concentrations" in a quarter of the samples they gathered.

"The idea that something that's natural may have a negative health outcome is new to a lot of people, so people tend to assume if it's natural, then it must be safe," Murch said. She's studied blue-green algae and BMAA around the world, including in Guam, China and Eastern Canada.

"What we know about blue-green algae is that they produce a range of toxins, and we need to be careful about how those cyanobacterial toxins enter the food chain."

​Murch and PhD candidate Stephanie Bishop started the project with the consortium in 2015, and analyzed samples collected between July and September of 2016.

They found the worst bloom had 22.5 micrograms of BMAA per gram, she said. A gram is equivalent to 1 million micrograms.

Blooms in the northeast part of the lake's north basin tended to have more of the toxin, she added.

Need to monitor lake conditions: researcher

The possible implications of BMAA in bodies of water is still under investigation, she said. But exposure to the toxin has been linked to neurodegenerative diseases such as ALS and Alzheimer's through studies on animals, cell cultures and epidemiological research on incidence of disease and proximity to the toxin, including her own.

"The idea that a cyanobacterial bloom, or a blue-green algae bloom, can produce toxins is not really new," she said.

"What we need to do is monitor the size of the bloom, and make sure that the conditions in the lake are maintained in a way that limits the growth of the bloom, the growth of the algae."

That includes looking at ways algae in the lake gets nitrogen and phosphorus — like agricultural runoff — and potentially monitoring algae growth in the lake going forward, she said.

Warmer waters caused by climate change have also contributed to larger, longer-lasting algal blooms around the world, she added.