Stormwater runoff disrupts urban stream life

Noreen Parks in Chemical & Engineering News: Urban streams commonly have low abundances and poor diversity of many freshwater insects that fish and other aquatic animals eat. Even after people have restored these stream habitats, the waterways often remain biologically impoverished, with diminished numbers of fish. New research reported Nov. 8 at the annual meeting of the Society of Environmental Toxicology and Chemistry (SETAC) in Portland, Oregon, has identified a probable culprit: pollutants in stormwater runoff that flushes through the streams.

Scientists have demonstrated that increasing urbanization leads to declining stream health, but they have struggled to pin down the causes. Urban stormwater runoff is a leading suspect. The force of runoff water rushing into these streams can cause physical damage to the streams' habitats. In addition, stormwater carries pollutants from numerous sources including vehicle exhaust, industrial plants, homes, and construction sites.

Kate Macneale and her colleagues at the National Oceanic & Atmospheric Administration's Northwest Fisheries Science Center decided to focus on water quality's effects on the biological habitat of urban streams. They ran experiments to observe how runoff affected 35 types of insects that generally indicate good stream health and serve as valuable prey for juvenile salmon.

… Even relatively brief exposures to urban runoff can alter the diversity and abundance of stream communities," Macneale says. "We need to consider water quality in restoring fish habitat."

Springtime overnight rains runoff into La Ballona Creek in Los Angeles in this picture taken from a kite. Mar Vista Gardens can be seen on the right as a cleanup crew works under the Inglewood Blvd. overpass. Photo by Joelorama, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license