Stormwater biofiltration increases coho salmon hatchling survival

A new study finds that the green stormwater practice bioretention filtration can help protect coho salmon hatchlings from the lethal toxicity of runoff exposure.

A relatively simple, inexpensive method of filtering urban stormwater runoff dramatically boosted survival of newly hatched coho salmon in an experimental study, according to a press release from Washington State University (WSU).

The findings, published in the journal Science of the Total Environment, are consistent with previous research on adult and juvenile coho that found exposure to untreated roadway runoff that typically winds up in waterways during storms resulted in mortality of 60% or more. For the coho hatchlings in this study, mortality from runoff exposure was even higher at 87%.

When the stormwater was run through a biofiltration method — essentially layers of mulch, compost, sand and gravel — nearly all the coho hatchlings survived, though many of resulting fish had smaller eyes and body sizes than a control group.

“This study highlights how vulnerable the fish are as soon as they hatch to the toxic impacts of stormwater runoff,” said lead author Jen McIntyre, an associate professor in WSU’s School of the Environment. “Biofiltration appears to be very effective at preventing that acute lethal toxicity. We also found that it prevented some of the sub-lethal effects but not all of them.”

To understand runoff impacts and possible interventions, researchers set up […]

Full article: www.stormwater.com