While blue-green algae blooms are 'pretty to look at,' here's why they could also be deadly

Freshwater blue-green algae blooms are "not all bad, and they're also pretty to look at," but a Waterloo region researcher is also reminding people that they could be "lethal to humans."

René Shahmohamadloo, a postdoctoral researcher working at the University of Guelph and Washington State University, says he's always been passionate about harmful algal blooms, which he describes as "a perfect example" of the relationship between humans and the environment.

"We can be intensively cultivating food to feed a growing population [while] not knowing that these nutrients of nitrogen and phosphorus that might run off into our waters could be impacting a whole range of aquatic life and could be causing cyanobacteria, which is commonly known as blue-green algae, to proliferate in our fresh waters," Shahmohamadloo told CBC K-W. 

Though blooms typically show up in shallow bodies of water with temperatures above 20 C in areas of higher agricultural activity, blooms in colder and more nutrient-poor lakes have been observed more frequently than previously expected.

On Sept. 13 the Grand River Conservation Authority (GRCA) issued an advisory about the presence of blue-green algae in three areas — Belwood Lake, Conestogo Lake and Guelph Lake reservoirs. 

Signage has been posted notifying the public of the conditions and the Ministry of the Environment, Conservation and Parks and the Wellington-Dufferin-Guelph Public Health Unit have been notified.

Cameron Irvine, supervisor of water quality at the GRCA, said the blooms typically occur in the late summer or early fall and have been known to occur on an annual basis at the three reservoirs.

Irvine said the blooms "tend to look like a kind of thick pea soup or spilled paint on the surface of the water … [and] the smell can vary. It can smell like fresh cut grass or rotting garbage."

The GRCA wants people to be aware that when blue-green algae are visible, the following precautions should be taken:

"The best advice is, if it's observed, just stay away," Irvine told CBC News.

Shahmohamadloo says there are multiple reasons why blue-green algae is showing up more frequently than in previous years. He listed some of the top reasons as follows:

Warming temperatures: He said scientists are pointing to a trend where the winter months seem to be shortening a bit more and summer months and spring are prolonging a bit more. This can spell for longer periods where harmful algal blooms or cyanobacterial blooms are residing in bodies of freshwater.

Agriculture and land management: With Ontario being an agricultural hub for Canada, Shahmohamadloo said there's high usage of nitrogen or phosphorus fertilizers. He said these can sometimes run off into nearby water bodies and blue-green algae thrive on these nutrients.

Shahmohamadloo said while there have been "unfortunate instances of dog deaths" linked to anatoxin produced by certain species of blue-green algae, there are other toxins produced by cyanobacteria which might take time to build up, and can be lethal in humans.