[env-trinity] CBB: Urban Stormwater Runoff Killing Adult Coho Salmon In Streams Along West Coast

[Sari Sommarstrom]

THE COLUMBIA BASIN BULLETIN: Weekly Fish and Wildlife News

www.cbbulletin.com      October 16, 2015              Issue No. 767

 

* Study: Urban Stormwater Runoff Killing Adult Coho Salmon In Streams Along
West Coast

 

Toxic runoff from highways, parking lots and other developed surfaces is
killing many of the adult coho salmon in urban streams along the West Coast,
according to a new study that for the first time documents the fatal
connection between urban stormwater and salmon survival.

 

The good news is that the same study published this month in the Journal of
Applied Ecology
http://onlinelibrary.wiley.com/doi/10.1111/1365-2664.12534/abstract

also found that inexpensive filtration of urban runoff through simple
columns of sand and soil can completely prevent the toxic effects on fish.

 

"Untreated urban runoff is very bad for salmon health," said Julann
Spromberg, a research scientist at NOAA Fisheries' Northwest Fisheries
Science Center in Seattle. "Our goal with this research is to find practical
and inexpensive ways to improve water quality. The salmon are telling us if
they work."

 

Scientists have studied the impacts of urban stormwater on salmon most
extensively around Puget Sound in Washington, where more than half of the
coho returning to stormwater-dominated streams every year die before they
can spawn.

 

Coho salmon in California, Oregon and southwestern Washington are listed
under the Endangered Species Act, and the loss of so many wild coho to toxic
stormwater before they spawn could push them further toward extinction, the
study finds.

 

The filtration columns, similar to "rain gardens" gaining ground in the
Northwest, are an example of emerging green stormwater infrastructure that
should be integrated into future development and redevelopment to reverse
the trend and help coho recover, the authors conclude.

 

"If we can incorporate clean water design strategies into future growth, as
some transportation projects are already doing, wild salmon might have a
chance," said Nat Scholz, manager of the Ecotoxicology Program at the NWSFC
in Seattle and a coauthor of the study. "They can't take the kinds of losses
we've documented in urban streams."

 

The study demonstrated that coho salmon are an ecological sentinel for the
harmful effects of urban runoff. The study exposed adult coho from the
Suquamish tribal hatchery in Poulsbo, Washington, to different degrees of
polluted and clean water, including runoff from a busy urban highway in
Seattle. All fish exposed to the highway runoff died within 24 hours.

 

But after researchers filtered the water through a roughly three-foot-high
soil column containing layers of gravel, sand, compost and bark, all the
exposed coho survived as well as they did in clean water. Tests showed the
filtration columns reduced toxic heavy metals by 58 percent and polyaromatic
hydrocarbons, which are byproducts of gasoline combustion, by 94 percent.

 

"What impressed me most was the effectiveness of the treatment," said Jen
McIntyre, co-author and researcher at the stormwater program at WSU's
Puyallup Research and Extension Center. "It's remarkable that we could take
runoff that killed all of the adult coho in less than 24 hours - sometimes
less than four hours - and render it non-toxic, even after putting several
storms worth of water through the same soil mixture."

 

The study also includes coauthors from the U.S. Fish and Wildlife Service
and Suquamish Tribe. "Academic, governmental, and tribal scientists came
together on this project," Spromberg said. "The participation of the
Suquamish Tribe was particularly vital, as most hatcheries would be
understandably wary of a small army of storm chasers, trucking large volumes
of toxic runoff." 

 

In an unusual twist, scientists first tried unsuccessfully to create
artificial stormwater by mixing up a brew of metals and components of crude
oil known from urban runoff. However, the artificial stormwater did not have
the fatal effects of the actual highway runoff, with the fish exposed to it
surviving as well as they did in clean water.

 

This suggests that the contents of urban runoff may include as-yet unknown
toxins from exhaust, leaking oil and dust from brakes and tires as they
wear.

 

Researchers said it could take years of further testing and analysis to
determine precisely what in the runoff is killing the coho. Previous
research connected coho mortality rates to the amount of paved surface in a
watershed, so the fatal ingredients appear linked to urban runoff and not
household or agricultural pollutants such as pharmaceuticals or pesticides.

 

"The recurring coho spawner deaths have been a high-profile mystery for many
years, and we're now much closer to the cause," Scholz said. "Although we
haven't identified a smoking gun, our study shows that toxic stormwater is
killing coho, and that the problem can be addressed."

 

The research was funded by Region 10 of the U.S. Environmental Protection
Agency, Washington Sea Grant, NOAA Coastal Storms Program and Puget Sound
Regional Stormwater Monitoring Program. 

 

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