Ottawa Riverkeeper finds `alarming' mercury levels
Toxin has bioaccumulated in fish like walleye and northern pike
Earlier spring floods, lower water levels in summer, and contaminants such as microplastics, road salt and toxic “forever chemicals” are just some of the concerns listed in a report on the health of the Ottawa River watershed.
But a surprising — and disturbing — finding was higher than expected levels of mercury in the water.
“The mercury levels in some fish species are alarming,” said Laura Reinsborough, CEO of Ottawa Riverkeeper.
The levels are akin to those found in rivers with a lot of heavy industry along them, something not present in the Ottawa River watershed. The source of the mercury is unknown, but the hypothesis is that it's airborne and blowing in from other regions, she said.
The mercury bioaccumulates in high-level predatory fish like walleye and northern pike, and it might mean that safe consumption guidelines for the Ottawa River will need to be adjusted, she said.
The mercury measurements aren't new, but the information was spread among various federal and provincial agencies, she said. This is the first time it's been collected together.
“It shows the value of looking at things across the whole watershed.”
The report, released Wednesday by the Ottawa Riverkeeper, gives an overall C grade to the watershed, which encompasses 300 municipalities and covers 146,300 square kilometres, an area roughly twice the size of New Brunswick. It's the source of drinking water for more than two million people.
“It's time to take action,” Reinsborough said. “We cannot afford to ignore the concerning trends highlighted in this report card. The leading causes that are degrading the river are all human-driven. This means we, as humans, can turn those trends around.”
On the “Good” side of the report card are decreases in the amount of sewage entering the river, and the report gives kudos to the City of Ottawa's $232-million Combined Sewage Storage Tunnel. It credits the project with greatly reducing the once-regular raw sewage discharge that occurred with every big rainstorm.
The report card also notes that most of the watershed remains forested, “excellent news” that helps insulate the river from ecological threats.
Top of the “Bad” side, however, is the change in flow patterns, which the report says is likely the result of human-driven climate change. The early spring freshet had led to record floods and disrupted natural ecosystems, while the low flow in summer raised water temperatures and reduced habitats for many aquatic species.
In the South Nation River, a tributary of the Ottawa River, testing by the province has shown “dangerously low” oxygen levels, likely the result of agricultural run-off and plant and algal growth that consume oxygen. “This will have profound implications for species that have adapted to the historical conditions of the Ottawa River watershed,” the report says.
Road salts and microplastics are also identified as a cause of concern. While the river flow washes most microplastics away, they remain in the environment downstream. Road salt, however, has been found in high concentrations even in summer, long after winter salting operations are done.
Per- and poly-fluoroalkyl substances (PFAS), also known as “forever chemicals” because they do not break down, are used in fire retardants, non-stick cookware and food packaging. PFAS are known to be harmful to humans and have been widely detected in fresh water in North America, says the report, which calls for the federal government to step up its testing and monitoring of PFAS so that steps can be taken to limit their spread.
The report also raises the alarm about invasive species, such as the spiny water flea and phragmites such as the European Common
Reed, and the loss of native species, such as the American Eel, cut off from its spawning areas by impassable hydroelectric dams.
The Riverkeeper is also closely watching developments at Chalk River Laboratories. Riverkeeper made submissions on the proposed near-surface disposal facility at Chalk River but doesn't have the capacity to monitor for radioactive contaminants, Reinsborough said.
The report card is the Riverkeeper's first full report on the river's health since 2006 and is the first based on reams of data it has amassed on 14 “key indicators” it began tracking in 2018.
“That first river report was trying to identify a number of issues,” Reinsborough said. “This is the first time we have the numbers to back it up.
“We can't shy away with `oh well we just don't know' anymore. Now we know. We can point to the evidence and we know what needs to be done.”
That first river report was trying to identify a number of issues. This is the first time we have the numbers to back it up.