SEATTLE, Wash. – Salmon exposed to toxic stormwater can die in a matter of hours. But preliminary new findings by Washington State University researchers suggest that bioretention systems, such as rain gardens, that filter out contaminants from stormwater runoff are key for preventing lethal impacts on fish.
Effective bioretention systems include sand and organic matter like compost and bark.
Washington State University aquatic toxicologist Jenifer McIntyre described new findings about how coho salmon die when exposed to urban stormwater runoff at the WSU Innovators Lecture in Seattle today. Her presentation was titled, “Stormwater detox: How natural infrastructure can help save salmon.”
“Urban stormwater runoff carries a complex mixture of hydrocarbons, some of which are toxic to the cardiovascular system of animals, into fish habitats,” McIntyre said. “We have seen that stormwater runoff can kill adult coho salmon in urban creeks, and we know that it can cause defects in the heart of developing fish.”
She studies coho salmon in particular because they spend a significant amount of their lives in freshwater compared to other types of salmon.
She also presented initial results on the ability of bioretention to prevent toxicity in coho embryos that have had acute and intermittent exposure to runoff during development.
“Episodic exposure is what happens in the ‘real world’ – which is what we were trying to approximate over the course of the three-month-long embryonic development of coho embryos,” McIntyre said.
The bioretention filtration system used was able to remove contaminants that caused the worst effect: death.
“One of the new results I am most excited about is the cause-of-death research,” McIntyre said. “For more than a decade we have been studying pre-spawn mortality in coho returning to urban areas. For the first time, we have a real path forward for figuring out what about urban runoff is causing the problem.”
The cause-of-death research has shown that, based on blood gas and blood chemistry, coho exposed to urban runoff appear to suffer from a lack of oxygen at the tissue level.
“We know there is oxygen in the water, and oxygen is in the fish’s blood, but that oxygen either isn’t getting to their tissues or their tissues aren’t able to use it,” McIntyre said. “With this new information, we can start tracking down the precise mechanism causing the hypoxia, which we hope will help us identify the responsible contaminants.
Video of the presentation “Stormwater detox: How natural infrastructure can help save salmon,” will be available courtesy of TVW.
Jenifer McIntyre, Postdoctoral Research Associate, WSU Puyallup Research & Extension Center, LID Stormwater Program, 206-369-1832, firstname.lastname@example.org