The federal government is putting $1.8 million into a U小蓝视频 study that could one day help prevent mass fish kills like the one the North Shore saw in October.
Dozens of coho salmon were killed as they returned to spawn the Brothers Creek system. The most likely culprit was 6PPD-quinone – a chemical that’s sprayed on tires to extend their life, but among the most toxic in the world for salmon. It tends to accumulate on roadsides and then is washed into the creeks by stormwater. While some species aren’t so susceptible, coho will die within hours of exposure to as little as a millionth of a gram of 6PPD per litre of water.
The U小蓝视频 study led by researchers Rachel Scholes and Timothy Rodgers builds on a partnership with Fisheries and Oceans Canada researchers measuring the presence of 6PPD-quinone in more than 70 creeks on the South Coast, Vancouver Island and Fraser Valley.
Over the next three years, they’re hoping to zero in on where the hotspots are and start planning mitigation measures.
“We’re actually really interested in implementing our findings,” Scholes said. “Hopefully, it means healthier urban creeks and streams.”
The good news is that the first phase of their study found very promising results using rain gardens or other biofiltration systems that include rocks, soil and plants, as a means to keep contaminants out of the gills of fish.
“The big result was just that for all but the biggest storms, the 6PPD-quinone was really well-captured by these rain gardens,” Rodgers said. “More than 90-plus per cent.”
Although rain gardens have already shown promise, the second phase of the study will also look at how they could be made even more effective by adding different levels of biochar to the soil mix to see if it will capture even more of the chemical.
It’s highly possible that one of the reasons for a general absence of salmon in urban areas is the presence of 6PPD-quinone, Rodgers said.
“These levels have been high for a long time. This chemical has been on tires since the '60s,” he said.
And Scholes added there is growing research into the toxic runoff we funnel into the creeks doing harm to aquatic life more generally.
“The combined sub-lethal effects of many contaminants in that runoff are probably also adversely affecting aquatic ecosystems,” she said. “But it was not as obvious to us as when a group of coho dies all at once.”
The City of Vancouver has shown great interest in implementing any recommendations that come from the study, and Scholes and Rodgers plan to make their work available to any municipality that wants to help.
Rodgers said they are also now beginning to look at whether artificial turf sports fields might be a source of 6PPD-quinone in local creeks.
Streamkeepers groups on the North Shore are on the lookout for any other mass fish kills, so they can alert researchers to collect water samples for testing.
Weeks after the Brothers Creek fish kill, DFO researcher Tanya Brown said study results were “a bit inconclusive,” but samples had been collected downstream from where the dead fish were found. Since then, Brown has added a new location into the study.
6PPD is “for sure” still the prime suspect in the deaths of the coho, Brown said.
North Vancouver already a garden city
Residents walking some of the North Shore’s streets have been passing by rain gardens for years possibly not even knowing it.
Karyn Magnusson, direct of engineering for the City of North Vancouver, said the city built its first rain gardens more than 20 years ago, but in the last decade, they’ve added more than 100 to local streets.
Often, they may look like not much more than a patch of dirt next to the curb with some plants sticking out, but city staff have been monitoring what effect they have on benthic invertebrates – the tiniest aquatic life in the creeks and streams.
“We are seeing an improvement in the quantity of these invertebrates in our natural creek ecosystems, which is a really good signal,” she said. “They’re doing exactly what they were designed to do, even though they just look like they’re collecting mud.”
Apart from the filtration of toxins, rain gardens provide other benefits that fish would approve of – they cool the stormwater and allow it to flow into creeks at a more consistent and predictable rate rather than sudden flashes that follow storms.
Magnusson said the city treats pretty much any street project or redevelopment as an opportunity to add more.
“Definitely, we’re accelerating. They’re becoming more the norm. Anytime we’re adjusting curb locations in a place that is appropriate for introducing stormwater runoff into the earth, we’re looking to install them,” she said.
The city also adds oil grit separators – larger pieces of infrastructure that capture and treat rainwater at the point where storm sewers connect with creeks. And the city puts a big effort into street sweeping, not just to make things look nicer but because it removes tire debris and other pollutants before rainwater washes them into the natural environment.
“We’re doing whatever we can to really reverse some of the challenges of our early-year infrastructure,” Magnusson said.
