Abstract Title

Session S-09B: Bioretention for Improving Water Quality

Keywords

Stormwater

Start Date

2-5-2014 10:30 AM

End Date

2-5-2014 12:00 PM

Description

Urban streams in the greater Seattle area have been the focus of habitat restoration projects since the 1990s. Post-project effectiveness monitoring surveys revealed anomalous behaviors among adult coho salmon returning to spawn in these restored streams. Behaviors included erratic surface swimming, gaping, fin splaying, and loss of orientation and equilibrium. Affected fish died within hours, and female carcasses showed high rates (> 90%) of egg retention. This phenomenon was termed coho pre-spawn mortality (PSM). From 2002-2012, rates of coho PSM ranged from ~30-90% in monitored urban streams. The severity of PSM was closely associated with both the timing and amount of fall rains. Affected coho exhibited evidence of exposure to metals and petroleum hydrocarbons, both of which commonly originate from motor vehicles. The weight of evidence suggests that an as-yet unidentified toxic contaminant or contaminant mixture in urban stormwater runoff is killing coho spawners. Geospatial analyses point to urban land uses, impervious surfaces and specifically road density as being directly related to the levels of PSM across watersheds. During the autumns of 2012 and 2013 we exposed adult coho recently returned to freshwater to collected urban road runoff. Across multiple rainfall events, untreated stormwater produced the familiar PSM symptomology in all fish within 4 hours. These behavioral effects were eliminated when the runoff was filtered through a mix of sand and compost (60:40). These protective effects of simple bioremediation were also evident in coho exposed to treated runoff for longer durations (24 h). Our findings show that exposure to urban stormwater is sufficient to cause coho PSM. Moreover, although the causal chemical agent(s) have not yet been identified, conventional green stormwater infrastructure can effectively protect adult spawners from the acutely toxic effects of runoff.

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May 2nd, 10:30 AM May 2nd, 12:00 PM

Adult coho salmon pre-spawn mortality is caused by urban runoff and prevented by bioremediation

Room 608-609

Urban streams in the greater Seattle area have been the focus of habitat restoration projects since the 1990s. Post-project effectiveness monitoring surveys revealed anomalous behaviors among adult coho salmon returning to spawn in these restored streams. Behaviors included erratic surface swimming, gaping, fin splaying, and loss of orientation and equilibrium. Affected fish died within hours, and female carcasses showed high rates (> 90%) of egg retention. This phenomenon was termed coho pre-spawn mortality (PSM). From 2002-2012, rates of coho PSM ranged from ~30-90% in monitored urban streams. The severity of PSM was closely associated with both the timing and amount of fall rains. Affected coho exhibited evidence of exposure to metals and petroleum hydrocarbons, both of which commonly originate from motor vehicles. The weight of evidence suggests that an as-yet unidentified toxic contaminant or contaminant mixture in urban stormwater runoff is killing coho spawners. Geospatial analyses point to urban land uses, impervious surfaces and specifically road density as being directly related to the levels of PSM across watersheds. During the autumns of 2012 and 2013 we exposed adult coho recently returned to freshwater to collected urban road runoff. Across multiple rainfall events, untreated stormwater produced the familiar PSM symptomology in all fish within 4 hours. These behavioral effects were eliminated when the runoff was filtered through a mix of sand and compost (60:40). These protective effects of simple bioremediation were also evident in coho exposed to treated runoff for longer durations (24 h). Our findings show that exposure to urban stormwater is sufficient to cause coho PSM. Moreover, although the causal chemical agent(s) have not yet been identified, conventional green stormwater infrastructure can effectively protect adult spawners from the acutely toxic effects of runoff.