Mussels send us a dire message about the health of our water, researcher says

Patricia Gillis researches mussel populations downstream from sewage treatment plants. She doesn't have good news.

'With 15 species at risk in Ontario alone, they're already telling us something's wrong'

Patricia Gillis, a freshwater toxicologist at the Canada Centre for Inland Waters, says mussels died en masse downstream from a Grand River sewage treatment plant, and their populations still haven't recovered. (Samantha Craggs/CBC)

Standing in a lab at the Canada Centre for Inland Waters, Patricia Gillis can't hide her enthusiasm for mussels.

Gillis is a freshwater toxicologist studying mussels in Ontario. There's the white heelsplitter, with its large, rough shell that could damage the foot of someone stepping on it. There's the rainbow mussel, threatened and dainty, and so tiny researchers can't find them in Ontario's muddy riverbeds.

"Mussels are awesome," said Gillis. They have rings on their shells that count their age like tree rings, she said, so researchers can tell how long they've been buried in that location. They also eat particles in the water, and are a valuable food source for larger species.

Lately, though, it's been a hard time to love mussels. Gillis researches their populations downstream from sewage treatment plants, and the news isn't good.

"They are that canary (in the coal mine)," Gillis said. "With 15 species at risk in Ontario alone, they're already telling us something's wrong."

Mussels are an indicator species, Gillis says, and their populations are declining. (Samantha Craggs/CBC)

Gillis is one of the many researchers talking to the public about her work at an open house at the Canada Centre for Inland Waters Wednesday. It runs from 9 a.m. to 4 p.m. Various school classes will attend, said Bob Rowsell, manager of the research support section. But the public can visit too.

It's the third annual open house for the centre at 867 Lakeshore Rd. in Burlington, which houses researchers from the Department of Fisheries and Oceans, the Canadian Coast Guard, and, like Gillis, Environment and Climate Change Canada.

Gillis's team is focused on a sewage treatment plant on the Grand River in Kitchener and Mississaugas of the Credit First Nation. In the latter case, mussel populations downstream were relatively unscathed. But in the case of the Kitchener plant, nearly all of them died in an eight-kilometre span.

Even after millions of dollars worth of upgrades to the plant, something in the treated effluent is killing mussels, Gillis said. Her team discovered this years ago, and she thought the populations would have rebounded by now, but they haven't.

Her team has tested the mussels downstream and found them loaded with antidepressants, hormones, blood pressure medication and various metals, Gillis said. Those toxins likely come from our bodies, what we flush down the toilet, and the plant itself. 

Mussel populations upstream from the plant are normal, she said. So the plant is definitely causing it.

Even more puzzling is why fish populations are rebounding, but mussel populations aren't. Mussels and fish have a codependent relationship, starting from mussel larvae hitching a ride on the gills of fish and burying themselves in the sediment where they fall.

"If the water is clean enough for fish to come back, they should be bringing mussels," Gillis said. "If the mussels are falling off fish and they're burrowing down, I'm looking forward to finding them."

About the Author

Samantha Craggs is a CBC News reporter based in Hamilton, Ont. She has a particular interest in politics and social justice stories, and tweets live from Hamilton city hall. Follow her on Twitter at @SamCraggsCBC, or email her at samantha.craggs@cbc.ca


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