Irradicable zebra mussels. Microplastics from wastewater. Perennial E. coli concerns. Toxic algal blooms visible from space — all problems plaguing Lake Winnipeg that Manitobans have come to know and loathe.
But a lesser-known microscopic part of the story is now getting close attention that could shed light on the future health of one of the largest freshwater basins in our warming world.
“Viruses, in particular ones that are infecting microalgae, are overlooked,” said Prof. Emily Chase, an internationally trained microbiologist and virologist at the University of Winnipeg. “We’re kind of missing a key step in the process of understanding Lake Winnipeg.”
Last summer, Chase became the first researcher to begin analyzing how viruses infect Lake Winnipeg microalgae, the single-celled photosynthetic organisms that get a bad rap for clumping together in a scummy blue-green film that can contain neuro-toxins harmful to humans and animals.
In reality, microalgae in and of themselves play a critical role in the food web of Lake Winnipeg.
The algae harvest energy from the sun. Filter feeders and little spineless creatures eat the algae. They’re eaten by minnows, which are eaten by small fish, which are eaten by bigger fish like walleye that are caught by fishers.
And that’s how your beer-battered pickerel is made.
But there are long-running concerns climate change could throw an already imbalanced Lake Winnipeg ecosystem further out of whack, with longer summers and warmer waters conducive to toxic blue-green algal blooms, known as cyanobacteria, that can disrupt swimming and recreation or commercial fishing economies.
“We need to understand viruses to understand climate change,” said Chase.
“Using data on viruses and how other microbes are operating the lake, we can have a better idea to predict what could be happening in Lake Winnipeg in the future and how things might progress as our climate changes, as weather impacts become more intense.”
It’s been well-established that phosphorus, and to a degree nitrogen, from agricultural runoff and wastewater are among the main culprits contributing to toxic algal blooms on Lake Winnipeg. That’s one reason the lake earned the ominous distinction as the most threatened lake in the world in 2013.
What’s less well understood is how viruses may influence broader lake dynamics, but Chase and others in the nascent field have a hunch viruses play a role in algal bloom collapse.
“If we understand where the viruses are in the lake, how they’re interacting with the microalgal blooms, we can understand when these blooms might collapse and then make the water accessible again for people who want to swim, people who want to just enjoy looking at the lake, and also people who are fishing,” she said.
Warning signs in Lake Erie
Chase is drawing on algae-virus PhD work she did in the Mediterranean Sea at Aix Marseille Université in the south of France as a Marie Skłodowska-Curie fellow. She continued that work in recent years as a post-doc in Nashville.
The Nova Scotia-born scientist returned to Canada the same month last year that U.S. President Donald Trump was inaugurated, in part because “it wasn’t an ideal place to be working on climate change any longer,” she said.
One of the Great Lakes shared by Canada and the U.S. may hold warning signs for Lake Winnipeg, said Chase.
Lake Erie used to routinely freeze over, giving rise to a community of microbes and algae in and on the ice every winter that would seed the lake with nutrients critical to the food web each spring.
But Lake Erie’s ice has been disappearing for over two decades, and some researchers predict it could be ice-free year-round by the end of the century.
WATCH | Lake Erie is 96 per cent frozen. Here’s why that’s weird:
If Lake Winnipeg goes the way of Lake Erie, its prized walleye stocks could become even more threatened and with that, recreational fishing and tourism opportunities as a whole.
“If we understand what’s going on in the lake, we have lots of data that can help contribute to modelling climate change, we might know what could happen in Lake Winnipeg if we continue our current activities there,” said Chase.
“The hope is that we don’t have Lake Winnipeg transition to something like Lake Erie, but we would be able to look at kind of that timeline a bit more closely and also understand what happens in Lake Erie for it to get to this point.”
‘This is going to fill in some gaps’
If Lake Winnipeg does begin to see prolonged periods without ice due to global warming, that could ratchet up the bloom-bust toxic algae cycle, said Scott Higgins, a senior research scientist with the International Institute of Sustainable Development.
“Summers are getting longer … and so you get an initial bloom, and then it crashes potentially because of viruses or something else, and then this gives an opportunity for a second bloom to occur too, which can also contain toxins,” said Higgins, who works with the IISD’s Experimental Lakes Area in northwestern Ontario.
Higgins said another element of microalgae virus research he finds promising relates to what causes algal blooms to collapse once they get big — like the size of some that have been observable from space.
“There’s still a lot of misunderstandings or things that we’re trying to learn about what causes algal blooms to collapse once they get so large,” he said.
“If a large virus attack happens … and the algal bloom collapses quickly, all of these toxins can then be released into the water.”
He said Chase’s work will help Manitoba better prepare for the Lake Winnipeg of the future.
“This interaction between viruses and algae and climate change is all part of this process that we’re trying to understand,” he said.
“So I’m really excited to hear that Dr. Chase is doing this research, because this is going to fill in some gaps in knowledge that we’ve been wondering about for a long time.”
