Journal of Applied Ecology 2016, 53, 398–407

doi: 10.1111/1365-2664.12534

Coho salmon spawner mortality in western US urban
watersheds: bioinfiltration prevents lethal storm water
impacts
Julann A. Spromberg1, David H. Baldwin2, Steven E. Damm3, Jenifer K. McIntyre4,
Michael Huff5, Catherine A. Sloan2, Bernadita F. Anulacion2, Jay W. Davis3 and
Nathaniel L. Scholz2*
1

Ocean Associates, Under Contract to Northwest Fisheries Science Center, National Marine Fisheries Service,
NOAA, 2725 Montlake Blvd. E., Seattle, WA 98112, USA; 2Environmental and Fisheries Science Division, Northwest
Fisheries Science Center, National Marine Fisheries Service, NOAA, 2725 Montlake Blvd. E., Seattle, WA 98112,
USA; 3U.S. Fish and Wildlife Service, Washington Fish and Wildlife Office, 510 Desmond Dr. S.E., Lacey, WA 98503,
USA; 4Puyallup Research and Extension Center, Washington State University, 2606 W. Pioneer Ave., Puyallup, WA
98371, USA; and 5Suquamish Tribe, PO Box 498, 18490, Suquamish Way, Suquamish, WA 98392, USA

Summary
1. Adult coho salmon Oncorhynchus kisutch return each autumn to freshwater spawning
habitats throughout western North America. The migration coincides with increasing seasonal
rainfall, which in turn increases storm water run-off, particularly in urban watersheds with
extensive impervious land cover. Previous field assessments in urban stream networks have
shown that adult coho are dying prematurely at high rates (>50%). Despite significant management concerns for the long-term conservation of threatened wild coho populations, a causal role for toxic run-off in the mortality syndrome has not been demonstrated.
2. We exposed otherwise healthy coho spawners to: (i) artificial storm water containing mixtures of metals and petroleum hydrocarbons, at or above concentrations previously measured
in urban run-off; (ii) undiluted storm water collected from a high traffic volume urban arterial
road (i.e. highway run-off); and (iii) highway run-off that was first pre-treated via bioinfiltration through experimental soil columns to remove pollutants.
3. We find that mixtures of metals and petroleum hydrocarbons – conventional toxic constituents in urban storm water – are not sufficient to cause the spawner mortality syndrome.
By contrast, untreated highway run-off collected during nine distinct storm events was universally lethal to adult coho relative to unexposed controls. Lastly, the mortality syndrome was
prevented when highway run-off was pretreated by soil infiltration, a conventional green
storm water infrastructure technology.
4. Our results are the first direct evidence that: (i) toxic run-off is killing adult coho in urban
watersheds, and (ii) inexpensive mitigation measures can improve water quality and promote
salmon survival.
5. Synthesis and applications. Coho salmon, an iconic species with exceptional economic and
cultural significance, are an ecological sentinel for the harmful effects of untreated urban runoff. Wild coho populations cannot withstand the high rates of mortality that are now
regularly occurring in urban spawning habitats. Green storm water infrastructure or similar
pollution prevention methods should be incorporated to the maximal extent practicable, at
the watershed scale, for all future development and redevelopment projects, particularly those
involving transportation infrastructure.

Key-words: habitat restoration, non-point source pollution, Pacific salmon, run-off, storm
water, urban ecology, urban streams

*Correspondence author. E-mail: nathaniel.scholz@noaa.gov
© 2015 The Authors. Journal of Applied Ecology © 2015 British Ecological Society.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and
reproduction in any medium, provided the original work is properly cited.

 Toxic urban run-off and salmon survival

Introduction
In recent decades, non-point source run-off has become
the leading pollution threat to aquatic habitats in the
USA and similarly developed countries. In highly built
watersheds, the transport of toxic chemical contaminants
via storm water contributes to the well documented
‘urban stream syndrome’, as evidenced by various indicators of biological and ecological degradation (Walsh et al.
2005). These include declines in species abundance, species
diversity and the proliferation of non-native, pollutiontolerant taxa.
Nevertheless, field assessments in urban watersheds
rarely report fish kills or similar acute mortality events for
aquatic life. A notable exception is the recurring die-off of
adult coho salmon that return from the ocean to spawn
each year in large metropolitan areas of northern California, western Oregon and Washington in the USA, and
southern British Columbia in Canada. The coho mortality
phenomenon has been studied most extensively in lowland
streams of the greater Seattle area of Puget Sound. Coho
begin the freshwater phase of their spawning migration
with the onset of autumn rainfall. Typically within days
of arriving at stream reaches suitable for spawning,
affected fish become stricken with symptoms that progress
from a loss of orientation (surface swimming) to a loss of
equilibrium and death on a time-scale of a few hours
(Videos S1 and S2, Supporting information; Scholz et al.
2011). Year-to-year mortality rates within and across
urban watersheds are typically high (~50–90%), as measured by the proportion of unspawned females for an
entire annual run (Scholz et al. 2011).
As might be expected, initial modelling indicates that
such high mortality rates at the critical spawner life stages
pose a significant extinction risk for wild coho populations
(Spromberg & Scholz 2011). Coho distinct population segments, or evolutionarily significant units (ESUs; Waples
1991), are comprised of metapopulations that span large
river basins with varying degrees of urban and suburban
land use (e.g. Pess et al. 2002; Bilby & Mollot 2008). This
population structure and the highly migratory life histories
of salmonids have generally constrained ecotoxicological
studies (Ross et al. 2013). Nevertheless, if urban run-off is
killing adult coho, ongoing regional development pressures
may present an important obstacle to the recovery of coho
ESUs, including those designated as threated (Lower
Columbia River) or a species of concern (Puget Sound)
under the US Endangered Species Act.
To date, the evidence linking urban storm water run-off
and coho spawner mortality has been indirect. The uniform nature of the symptoms, over many years and across
many streams, is consistent with a common and prevalent
form of toxicity. A forensic investigation spanning nearly
a decade ruled out several other potential causes, including conventional water quality parameters (e.g. dissolved
oxygen, temperature), habitat availability, poor spawner
condition and disease (Scholz et al. 2011). Moreover, an

399

initial geospatial land cover analysis found a significant
positive association between the severity of the coho dieoff phenomenon and the extent of impervious surface
within a watershed (Feist et al. 2011).
The aim of the present study was to explore the connection between water quality and coho mortality more
directly by experimentally exposing freshwater-phase
spawners to both artificial and actual highway run-off.
Although urban storm water is chemically complex, field
collected samples consistently contain motor vehiclederived mixtures of metals and polycyclic aromatic hydrocarbons (PAHs), many of which are toxic to salmon at
other life stages (e.g. copper, McIntyre et al. 2012;
Sandahl et al. 2007; PAHs, Meador et al. 2006; Heintz
et al. 2000). If the mortality syndrome could be reproduced with an environmentally realistic mixture of metals
and PAHs, it would then be possible to identify the causal
agents by removing different components of the mixture.
To account for the possibility that some other contaminant(s) may be causal, we also exposed adult coho to
storm water collected from a dense urban arterial road
(i.e. highway run-off). Lastly, we exposed adult coho to
highway run-off which was pre-treated with a conventional green storm water infrastructure (GSI) technology
(bioinfiltration through soil columns) to remove pollutants, with the aim of lessening or eliminating any overtly
harmful impacts of unmitigated storm water.

Materials and methods
ANIMALS

Adult coho salmon were collected at the Suquamish Tribe’s Grovers Creek Hatchery near Poulsbo, Washington. Hatchery coho
are an appropriate surrogate for wild coho given that field observations have documented the mortality syndrome in spawners of
both wild and hatchery origins (Scholz et al. 2011). At Grovers
Creek, returning coho migrate <4 km in freshwater from Miller
Bay in Puget Sound to a hatchery pond via a fish ladder. The
pond was seined on Monday, Wednesday and Friday of each
week, and thus the fish were in the pond for a maximum of 72 h
prior to capture. The coho were strays from a net-pen operation
designed to provide a terminal fishery to the south of Miller Bay.
When available, females were used for the controlled storm water
exposures. For trials with an insufficient number of females,
males were also included, as the urban mortality syndrome affects
males and females alike (Scholz et al. 2011). Only fish exhibiting
normal behaviour and with no obvious signs of trauma, disease
or poor condition were included. One set of exposures was conducted on a given day.
Each individual coho spawner was placed in a holding tube constructed of PVC, of either 15 2 9 76 2 cm (diameter 9 length) or
20 3 9 106 7 cm with 1 1-cm-thick polyethylene gates fitted into
slots at either end. Ventilation was provided by six 2 5-cm-diameter
holes on either side of the anterior (head) end of each tube and five
1 75-cm-diameter holes in each gate. A ventilation hose attached to
a pump (for 2011–12, a Flotec Tempest 1/6 HP, 4 5 m3 h 1 (Flotec
Water, Delavan, WI, USA); for 2013–14, a Lifegard Aquatics
Quiet One 3000, 3 1 m3 h 1 (Lifegard Aquatics, Cerritos, CA,

© 2015 The Authors. Journal of Applied Ecology © 2015 British Ecological Society, Journal of Applied Ecology, 53, 398–407

 400 J. A. Spromberg et al.
USA)) submerged in the polyethylene tank supplied a minimum of
4 L min 1 flow through the forward gate and over each fish in an
anterior–posterior direction.
For each trial, four separate coho holding tubes were placed in
a large polyethylene tank containing 440 L of clean well water,
artificial storm water, highway run-off, or run-off pretreated with
soil infiltration. Adult coho were exposed for 4–48 h depending
on the treatment (see below). Aeration was provided with air
stones attached to an air pump (Coralife 05146 Model SL-38
Super Luft Air Pump, Central Aquatics-Coralife, Franklin, WI,
USA). Exposure waters were maintained at temperatures below
14 °C by flow-through (2011) and Aqua LogicÒ CycloneÒ DropIn Titanium Chillers (2012). Smaller ventilation pumps that produced less heat were used in 2013–14, and thus, chillers were not
needed.

EXPOSURES TO ARTIFICIAL STORM WATER

In the autumn of 2011, returning adult coho were exposed to
artificial storm water containing mixtures of PAHs and metals.
The mixtures were comprised of individual compounds at concentrations at or above those measured during autumn storm events
in Seattle-area urban streams (Seattle Public Utilities 2007), or at
levels representative of urban storm water run-off more generally
(Stein, Tiefenthaler & Schiff 2006; Gobel, Dierkes & Coldewey
2007; Tiefenthaler, Stein & Schiff 2008). The PAH profile of
urban run-off is compositionally similar to that of crude oil, particularly for toxic three- and four-ring compounds (McIntyre
et al. 2014). The exception is a lack of dissolved pyrene and fluoranthene in crude oil (Incardona et al. 2009). Thus, the PAH portion of the mixture was generated from a water-accommodated
fraction (WAF) of Alaska North Slope crude oil, to which pyrogenic pyrene and fluoranthene were added (Table S1). The WAFs
were prepared in a 3-speed commercial blender with a 3 8-L
stainless steel container (Waring CB15; Waring Commercial, Torrington, CT, USA), following a protocol developed to yield fine
oil droplets and bioavailable PAHs in the dissolved phase
(Incardona et al. 2013). In brief, the stainless steel container was
cleaned with acetone and dichloromethane, the rubber lid was
lined with dichloromethane-rinsed heavy-duty aluminium foil,
and the container was filled with 1 L of deionized water. The volume of crude oil added to the WAF (1 mL) was intended to produce a final maximum phenanthrene exposure concentration of
0 384 lg L 1 (Stein, Tiefenthaler & Schiff 2006). Pyrene and fluoranthene were then added to coequal final target exposure concentrations of 0 584 lg L 1. Water and oil were blended for 30 s
on the lowest speed four times. The oil–water mixture was then
poured into a 1-L separatory funnel and allowed to sit for 1 h.
With care to leave the surface slick undisturbed, 789 3 mL at the
bottom were then drawn off and added to the exposure chamber.
The metals fraction of the PAHs/metals mixture consisted of
cadmium, nickel, lead, copper and zinc (anhydrous CdCl2, NiCl2,
PbCl2, CuCl2 and ZnCl2; Sigma-Aldrich, St. Louis, MO, USA,
> 98% purity) added to clean well water at nominal concentrations (Table S1) that were in the upper range of metal detections
in urban streams (Stein, Tiefenthaler & Schiff 2006; Gobel,
Dierkes & Coldewey 2007; Seattle Public Utilities 2007; Tiefenthaler, Stein & Schiff 2008). Moreover, the concentrations of metals in urban run-off are transiently elevated during the first flush
interval (Kayhanian et al. 2012). To capture this exposure scenario, experiments in the autumn of 2012 used relatively higher

nominal concentrations of metals only (Table S1). Temperature
and dissolved oxygen were monitored and maintained at physiological ranges for adult salmon, and water samples were collected
for analytical verification of exposure concentrations.

EXPOSURES TO HIGHWAY RUN-OFF

Storm water was collected from the downspouts of an elevated
urban principal arterial road in Seattle, WA. The downspouts
receive run-off from the on-ramp to a four-lane (70 m wide)
highway over which approximately 60 000 motor vehicles travel
each day (WA DOT 2013a). The highway, paved with Portland
cement concrete (WA DOT 2013b), is a conventional urban
impervious surface. All of the flow to the downspouts originated
from precipitation falling on the active arterial road.
The captured run-off was transported to the hatchery facility in
either covered glass carboys or in a stainless steel tank. The holding
interval prior to exposures varied with the timing and intensity of
autumn storm events, but did not exceed 72 h. While some collections took place after an extended antecedent dry interval and
therefore included the first flush for a given storm, others spanned
periods of intermittent rainfall. Daily and cumulative rainfall for
each autumn season is shown in Fig. 1, with each storm water collection interval superimposed (solid rectangular boxes). Collected
run-off was used for one exposure only. Temperature, pH and dissolved oxygen were measured at the outset of each exposure, and
water samples were collected for chemical analyses to quantify concentrations of metals and PAHs (2012–13 but not 2014 storms).
After exposures, the run-off was transported to a Kitsap County
Wastewater Pump Station for disposal.
EXPOSURES TO FILTERED RUN-OFF

In the autumn of 2013, four 200-L bioretention columns were constructed and plumbed with outflow drains following conventional
guidelines for green storm water infrastructure (WA DOE 2012).
The filtration columns were composed of a 30 5-cm drainage layer
of gravel aggregate overlain by 61 cm of bioretention soil media
(60% sand: 40% compost) and topped with 5 cm of mulched bark.
In the autumn of 2014, the bioretention columns were emptied and
fresh media installed. In each year, the bioretention media were
conditioned by passing seven pore volumes (660 L) of clean well
water from the hatchery facility through each column at a rate of
2 L min 1: equivalent to 2 months of summer rainfall on a contributing area 20 times the size of the treatment area. Urban highway run-off was collected as described above, and the
homogenized volume was evenly divided to flow through one of
the four bioretention columns at a rate of 2 L min 1, with the outflows from the four columns recombined into a single post-treatment exposure volume. Adult coho spawners were exposed to
either untreated urban storm water or the same run-off postfiltration for 4–24 h. Water quality was measured, and samples
were collected for chemical analyses as described above.
OBSERVATIONS OF SYMPTOMATIC FISH

Hallmark characteristics of the adult coho spawner mortality syndrome include a progression from lethargy to a loss of orientation, a loss of equilibrium, followed by death (Scholz et al. 2011).
Individual fish were examined for these symptoms during and
after each exposure. Fish were moved from the large exposure

© 2015 The Authors. Journal of Applied Ecology © 2015 British Ecological Society, Journal of Applied Ecology, 53, 398–407

 Toxic urban run-off and salmon survival

401

Fig. 1. The presence or absence of the prespawn mortality syndrome in adult coho
salmon exposed to unfiltered highway runoff (E) or clean well water (C). Paired
exposures spanned three consecutive
autumn spawning seasons, 2012–14.
Shown in each panel are daily rainfall
(shaded bars), cumulative rainfall (dotted
lines), highway run-off collection intervals
for each separate exposure event (black
rectangles) and the presence or absence of
symptomatic (or dead) fish in each individual treatment (4–24 h duration; see Materials and methods). Symptoms included
lethargy, loss of orientation or loss of
equilibrium.
tank and released from their holding tubes into an observation
tank containing clean well water at a minimum depth of 50 cm.
Swimming ability and evasiveness (responses to light and gentle
prodding) were recorded over a 1- to 3-min observation interval.
For the trials using artificial storm water, symptomology was
assessed at 24 h and then again at the end of the exposure. Coho
exposed to highway run-off were visually examined at 2, 4 and
24 h. Live fish at 2 and 4 h were returned to their holding tubes
and exposure chambers for the remainder of the trial.

WATER QUALITY ANALYSES

Conventional water quality parameters, including pH, dissolved
oxygen, alkalinity, total suspended solids, N-ammonia, nutrients
and organic carbon, were measured for selected trails using standard instrumentation or by outside laboratories using US EPAapproved methods (Analytical Resources Inc., Tukwila, WA,
USA or Am Test Inc., Kirkland, WA, USA). Total and dissolved
concentrations of cadmium, copper, nickel, lead and zinc were
determined by inductively coupled plasma mass spectrometry
(ICP-MS) by Frontier Global Sciences (Bothell, WA, USA; EPA
method 1638) or Am Test Inc. (EPA method 200.8). Briefly, samples were preserved in 1% (v/v) nitric acid (total metals) or
passed through a 0 45-lm filter (dissolved metals) and then ovendigested prior to analysis by ICP-MS. Duplicate samples and laboratory blanks were included to ensure quality control. Selected
water samples for PAH determinations were preserved with 10%
dichloromethane and stored at 4 °C in amber glass bottles until
analysis at the NOAA Northwest Fisheries Science Center by gas
chromatography/mass spectrometry (GC-MS) with additional
selected ion monitoring for alkyl-PAHs (Sloan et al. 2014).

assessed. To confirm the bioavailability of PAHs in exposure
waters, bile was screened for PAH metabolites in a subset of
2011 and 2012 trials with both artificial storm water and highway
run-off. Fish were killed, and bile was collected from the gall
bladder and stored in amber glass vials at 20 °C until analysis
for PAH metabolites using high-performance liquid chromatography with fluorescence detection (Krahn et al. 1986; da Silva et al.
2006). The concentrations of fluorescent PAH metabolites in bile
are determined using naphthalene (NPH), phenanthrene (PHN)
and benzo[a]pyrene (BaP) as external standards and converting
the relative fluorescence response of bile to NPH, PHN and BaP
equivalents, and reported as ng g 1 bile or ng mg 1 biliary protein.
Coho gills were sampled to confirm uptake of metals in selected
2011 and 2012 artificial and collected storm water exposures. Tissues were excised with Teflon or titanium scissors and plastic forceps, placed in plastic Whirl-paks, and stored at 80 °C. Metals
analyses were determined by inductively coupled mass spectroscopy (ICP-MS) at the Trace Elements Research Laboratory
(TERL; College Station, TX, USA) using standard methods
(TERL Method Codes 001, 006). Briefly, gill tissues were wet
digested with nitric acid, freeze-dried, and homogenized by ballmilling in plastic containers. Samples were ionized in hightemperature argon plasma, and positively charged ions were separated on the basis of their mass : charge ratios by a quadrupole
mass spectrometer. Student’s t-tests assessed differences in the tissue concentrations between exposures and their respective paired
control.

Results
ADULT COHO RESPONSES ACROSS TREATMENTS

TISSUE SAMPLING AND ANALYSES

At the conclusion of each exposure, fish length, weight, reproductive status and origin (i.e. hatchery or wild spawned) were

Coho spawners exposed for 24 h to mixtures of PAHs
and metals at concentrations slightly higher than those
previously measured in urban run-off were asymptomatic

© 2015 The Authors. Journal of Applied Ecology © 2015 British Ecological Society, Journal of Applied Ecology, 53, 398–407

 402 J. A. Spromberg et al.
– that is behaviourally indistinguishable from controls
exposed to clean well water (Table 1). Although there was
some mortality across the four independent trials (n = 4
of 30 fish total), this was not significantly different by
treatment (Fisher exact tests, two-tailed, P ≥ 0 21) and
was therefore apparently attributable to handling stress.
Extending the exposures to 48 h did not increase the incidence of mortality or symptomology (n = 4 of 22 fish
total, two control and two exposed). Increasing the concentrations of metals fivefold or 10-fold in metal-only
mixtures was also insufficient to elicit the symptoms of
the pre-spawn mortality syndrome (Table 2). As with the
PAHs/metals mixture, there was a small but insignificant
amount of mortality across treatments (n = 2 of 38 fish;
Fisher exact tests, two-tailed, P = 1).
Although the artificial storm water preparations were
designed to have a similar composition to highway runoff for many PAHs and metals, the effects on coho
spawners were very different. Whereas the artificial mixtures did not elicit the distress characteristic of the mortalTable 1. Adult coho salmon spawner mortality following a 24-h
exposure to either clean well water (unexposed) or a mixture of
polycyclic aromatic hydrocarbons (PAHs) and metals. Shown in
parentheses are the numbers of symptomatic or dead fish as a
proportion of the total numbers of spawners in each exposure.
The PAH/metal exposures were based on measured levels in
urban creeks during storm events (see Materials and methods).
Relative to environmental samples, the artificial mixture contained higher concentrations of both total PAHs and metals.
Each exposure was conducted on a separate day
Mortality
Exposure (h)

Unexposed

PAHs/Metals mixture

24
24
24
24

25%
33%
0%
0%

0%
0%
50%
0%

(1/4)
(1/3)
(0/4)
(0/4)

(0/4)
(0/3)
(2/4)
(0/4)

Table 2. Exposures to relatively high levels of metals in artificial
mixtures are not sufficient to elicit the coho spawner mortality
syndrome. Similar to unexposed controls, nearly all of the adults
survived exposures to mixtures of metals (Cd, Cu, Pb, Ni, Zn)
that were fivefold (Low) or 10-fold (High) higher than measured
concentrations in urban creeks where coho mortality syndrome
was observed. Shown in parentheses are the numbers of symptomatic or dead fish as a proportion of the total numbers of
spawners in each exposure. Each exposure was conducted on a
separate day
Mortality
Exposure (h)

Unexposed

Low metals

24
24
24
24
24

0%
0%
0%
25%
0%

0% (0/4)
0% (0/3)

(0/4)
(0/4)
(0/4)
(1/4)
(0/3)

Table 3. Proportion of adult coho displaying the spawner mortality syndrome after placement in clean well water (unexposed) or
highway run-off that was either unfiltered or filtered through an
experimental soil bioretention system (during 2013 and 2014).
Shown in parentheses are the numbers of symptomatic or dead
fish as a fraction of the total number of coho in each treatment.
Each exposure was conducted on a separate day
Mortality
Exposure (h)

Unexposed

Unfiltered

Filtered

4
24
24
24
24

0%
0%
0%
0%
0%

100%
100%
100%
100%
100%

0%
0%
0%
0%
0%

(0/4)
(0/4)
(0/4)
(0/4)
(0/4)

(4/4)
(4/4)
(4/4)
(4/4)
(4/4)

(0/4)
(0/4)
(0/4)
(0/4)
(0/4)

ity syndrome, coho exposed to the unfiltered highway
run-off rapidly became symptomatic. For every discrete
rainfall collection interval (n = 9; 2012–2014), all of the
exposed fish were either symptomatic or dead within 4 h
(Fig. 1, Table 3). Those that survived the initial 4-h exposure were dead by 24 h. All of the paired control coho in
clean well water survived, showing no behavioural symptoms at 4 or 24 h (Fig. 1, Table 3). Each exposure
showed a statistically significant difference in mortality
(Fisher exact tests, two-tailed, P = 0 006). Examples of
asymptomatic control fish and symptomatic, run-offexposed spawners are shown in Video S3. For the purpose
of comparing symptoms, digital movies of affected coho
in Seattle-area urban watersheds are shown in Videos S1
and S2. Thus, despite the event-to-event variation in rainfall duration and intensity, and a corresponding variation
in water chemistry (conventionals, metals and PAHs,
Tables S2, S3 and S5), urban run-off was 100% lethal to
otherwise healthy adult coho salmon. The contribution of
handling stress was evidently minimal, as the survival rate
for controls across treatments in 2012–2014 was 100%.
The constructed bioretention columns effectively treated
the highway run-off in terms of both toxic chemical exposure and salmon spawner survival. Although the focal
(measured) contaminants were not completely removed by
infiltration, the overall improvement in water quality was
sufficient to completely prevent the lethal effects and sublethal symptomology caused by untreated storm water.
All of the adult coho exposed to filtered run-off survived
and showed no behavioural symptoms at either 4 or 24 h
(100% survival, n = 20; Table 3; Video S3). Thus, urban
storm water contains an as-yet unidentified chemical component(s) that, while lethal to salmon spawners, can be
removed using inexpensive bioinfiltration.

High metals
MEASURED LEVELS OF METALS, PAHS AND
CONVENTIONAL WATER QUALITY PARAMETERS

0% (0/4)
25% (1/4)
0% (0/4)

ACROSS TREATMENTS

The chemical properties of highway run-off were evaluated
for the six distinct collection events in the autumn of 2012

© 2015 The Authors. Journal of Applied Ecology © 2015 British Ecological Society, Journal of Applied Ecology, 53, 398–407

 Toxic urban run-off and salmon survival
and 2013. As expected, conventional water quality
parameters varied across storm water collections, as did
concentrations of PAHs and metals. The analytical results
are shown in Tables S2, S3 and S5. As expected, suspended
solids (TSS: 23–220 mg L 1) and organic matter (DOC:
8–92 mg L 1) were elevated in urban run-off relative to
control water (TSS < 1 1 mg L 1, DOC < 1 8 mg L 1). In
contrast, run-off had lower Mg (t(8) = 6 072, P < 0 001),
alkalinity (t(8) = 6 201, P < 0 001) and phosphate
(t(8) = 3 547, P = 0 008). The pH values for run-off were
circumneutral (6 12–7 47) and consistently lower than those
for control water (t(8) = 2 691, P = 0 027). Other conventional chemistry parameters were not significantly different
among
treatments,
including
Ca
(t(8) = 0 121, P = 0 907) and hardness (t(8) = 1 159,
P = 0 280). At the outset of exposures, dissolved oxygen
levels ranged from 8 1 to 10 7 mg O2 L 1 and were maintained above 6 5 mg L 1 with additional aeration as
needed.
Collected highway run-off had a more pyrogenic (or
combustion-driven) PAH profile relative to the artificial
storm water mixtures, as evidenced by a relative enrichment of higher molecular weight (5- and 6-ring) compounds and fewer low molecular weight (2- and 3-ring)
compounds (Fig. 2). Bile PAH metabolites were not significantly different between fish exposed to control well

403

water or storm water run-off after a 4-h exposure (Fig. 3).
Although the measured concentrations of PAH metabolites in the bile of fish exposed for 24 h to the PAHs/metals mixture were elevated relative to paired controls, the
difference was not significant (Student’s t-test; P = 0 1,
0 14, 0 11 for phenanthrene, benzo-a-pyrene and naphthalene metabolites, respectively). This indicates that
low-level PAH exposures typical of urban run-off do not
produce large increases in measurable bile metabolites,
consistent with bile PAH metabolite measurements from
symptomatic coho previously collected during field surveys of urban spawning habitats (Scholz et al. 2011).
Notably, in 2012, the levels of 2- and 3-ring PAHs in
the control exposure water were unexpectedly elevated relative to all other control treatments (Fig. 2, arrow). This
was attributed to the recent drilling of a new well at the
Suquamish hatchery facility. Measured PAH levels in the
well water declined sharply over a time span of 2 weeks
(Fig. 2), and adult coho controls that were exposed during the interval did not exhibit behavioural symptoms
(Fig. 1).
Whereas the levels of dissolved-phase Cd and Pb were
generally lower in collected run-off relative to all of the
artificial storm water mixtures (Fig. 2), Cu and Ni in runoff spanned the range of these two metals in the environmentally relevant mixture. Zinc levels in run-off were

Fig. 2. Dissolved metal (left column) and
dissolved polycyclic aromatic hydrocarbon
(right column) concentrations summarized
by ring number for adult exposures to well
water controls, polycyclic aromatic hydrocarbons (PAHs)/metal mixtures, highway
run-off and filtered run-off. Closed symbols indicate dead or symptomatic individuals were observed in the exposure. Lines
connect paired highway run-off and filtered run-off from the same collection.
Control points are the mean of samples
collected each year. The number of mean
values below the reporting limits (i.e. nondetects) is indicated by # ND.
© 2015 The Authors. Journal of Applied Ecology © 2015 British Ecological Society, Journal of Applied Ecology, 53, 398–407

 404 J. A. Spromberg et al.

Fig. 3. Left column shows the relative
measured concentrations of metals in adult
coho salmon gill tissue for Cd, Cu, Pb, Ni
and Zn (lg g 1). Control values are means
of control tests run in 2011 and 2012.
Closed symbols indicate dead or symptomatic individuals observed in the exposure. The right column shows bile
fluorescent aromatic compounds (FACs)
detected at naphthalene (NPH), phenanthrene (PHN), benzo-a-pyrene (BAP)
wavelengths shown as protein corrected
polycyclic aromatic hydrocarbons (PAH)
equivalents (ng mg 1).

higher, and within the range of corresponding Zn levels in
the high-metal mixture. The concentrations of metals in
the gills of storm water-exposed and unexposed coho
(4 h) were not significantly different (Student’s t-tests,
P > 0 05; Fig. 3) and, in both cases, were lower than gill
metal levels measured from symptomatic spawners collected from the field (Scholz et al. 2011). Similarly, exposures to the environmentally relevant artificial storm
water mixture of PAHs/metals did not produce a significant accumulation of metals in the gills, with the exception of Ni (Student’s t-test, P = 0 017). For the high
metals mixture, only gill Cd, Cu and Pb levels were significantly elevated relative to controls (Student’s t-test;
P = 0 002, 0 018, 0 003 for Cd, Cu and Pb, respectively).
Filtering collected highway run-off through the bioretention columns reduced total PAHs by 94% and total
metals by 58%. As expected, removal efficiency varied for
different contaminants. For example, the soil columns
removed lower molecular weight PAHs less efficiently
than higher molecular weight PAHs (e.g. 81–89% for 2–3
ring PAHs vs. 93% removal of 4- to 5-ring PAHs;
Table S5). Notably, the medium in the bioretention columns was a source (i.e. an exporter) of total Ni to the
treated run-off, resulting in a 57% increase over the prefiltration input (Table S3). All other total metals
decreased by an average of 48–88% across the two events

in the order of Cd < Pb < Cu < Zn. For each of the metals, concentrations in the dissolved phase also declined
after soil column infiltration (Table S3). In addition to
exporting Ni, the bioretention columns were also a source
of DOC (post-/pre-filtration increase of 164%), alkalinity
(+29%), Ca (+60%), Mg (+372%), ortho-P (+4000%) and
increasing hardness (+107%). By contrast, column infiltration reduced the ammonia content of storm water by
92% (Table S2).

Discussion
We have confirmed that controlled exposures to untreated
urban run-off are sufficient to reproduce the coho spawner mortality syndrome. Adult coho became symptomatic
and died within a few hours of immersion in collected
storm water. Mortality rates were 100% for exposed fish
vs. 0% in control fish held in clean well water, and these
results were consistent across nine distinct rainfall intervals that spanned three consecutive autumn spawning
runs. As evidence that one or more toxic chemical contaminants are causal, pre-treating the highway run-off
with soil bioinfiltration completely prevented the acutely
lethal impacts on coho spawners. Surprisingly, coho did
not develop symptoms in response to artificial mixtures of
PAHs and metals, even at concentrations that were higher

© 2015 The Authors. Journal of Applied Ecology © 2015 British Ecological Society, Journal of Applied Ecology, 53, 398–407

 Toxic urban run-off and salmon survival
than those typically measured in storm water, including
the first flush. Urban run-off is chemically complex, with
many chemical constituents that are very poorly characterized in terms of toxicity to fish. While it may take years
of additional assessment to identify precisely which of
these agents is killing coho, our initial results suggest that
simple GSI technologies hold promise as a means to
improve water quality and effectively prevent coho mortality in urban spawning habitats.
Our finding that road run-off alone is sufficient to
induce the spawner mortality syndrome aligns with previous evidence for a positive association between the
amount of impervious surface within an urban watershed
and the year-to-year severity of coho die-offs (Feist et al.
2011). It appears that other forms of water quality degradation are not necessary to produce the phenomenon.
Consistent with this, symptomatic spawners do not show
evidence of neurotoxic pesticide exposure (Scholz et al.
2011), and adult coho are not unusually vulnerable to
low-level mixtures of currently used pesticides (King et al.
2013). The link to impervious run-off also discounts a role
for personal care products, pharmaceuticals, and other
classes of compounds that are transported to some urban
streams via combined sewer overflows in heavy rains.
As noted above, urban road run-off contains a complex
mixture of chemicals, many of which originate from
motor vehicles in the form of exhaust, leaking crankcase
oil and the wearing of friction materials (i.e. brake pads)
and tyres. We assessed the toxicity of PAH and metal
mixtures because these compounds are ubiquitous in
storm water and are known to be disruptive to the fish
cardiovascular system (PAHs: Brette et al. 2014), as well
as the respiratory and osmoregulatory functions of the gill
(metals: Niyogi & Wood 2004). Although bile and gill tissue results suggest that PAHs and some metals are
bioavailable to the coho spawners (this study; Scholz
et al. 2011), artificial mixtures of PAHs and metals did
not produce the symptoms of the mortality syndrome.
Our results appear to rule out many of the PAHs that are
common to urban run-off and crude oil spills (e.g.
phenanthrenes). However, there may be a role for the
higher molecular weight pyrogenic PAHs found in particulate vehicle exhaust (i.e. soot), other than pyrene or fluoranthene. The remaining list of potential causal chemicals
is long and includes other organic hydrocarbons such as
methylphenols, quinones, thiazoles, thiophenes, furans
and quinolines. Given the logistical challenges associated
with adult coho exposures – seasonal availability of animals, large volume assays, limited number of fish, etc. – it
may be years before the causal agent(s) is identified.
Notably from a water resource management perspective,
this will likely be a chemical or chemicals for which there
are no existing water quality criteria.
Biological indicators play an important role in field
assessments to document the urban stream syndrome in
affected watersheds world-wide. Common examples are
benthic indices of biological integrity (B-IBIs), which are

405

used to characterize the health of streams based on the
diversity and abundance of macroinvertebrates (Karr
1999). Although poor B-IBI scores are diagnostic of aquatic habitat degradation, they do not necessarily differentiate between drivers that may be chemical (i.e. pollution)
vs. physical or biological. Conversely, biological indicators that are specific to toxic run-off may not have
directly meaningful implications for individual survival, as
a basis for guiding species conservation at the population
and community scales. This includes, for example, the
upregulation of sensitive and responsive cytochrome p450
enzymes in the livers of fish exposed in situ to certain
PAHs and other contaminants that act via the aryl hydrocarbon receptor (van der Oost, Beyer & Vermeulen 2003).
Coho spawners, by contrast, appear to be very sensitive
ecological indicators, with a response metric that is
directly attributable to toxic storm water. Moreover, the
implications of widespread and recurring mortality are
relatively clear at higher scales (e.g. Spromberg & Scholz
2011). Although the highway run-off used in this study
(at the point of discharge) presumably contained higher
concentrations of chemical contaminants than surface
water conditions in urban spawning habitats, it is evident
that run-off in urban waterways is not sufficiently diluted
to protect many or most coho from premature death
(Scholz et al. 2011). By establishing a direct link between
non-point source pollution and the mortality syndrome,
our findings set the stage for future indicator studies in
western North America. This includes, for example, more
refined predictive mapping of vulnerable habitats as a
function of impervious land cover, at present and with
future urban growth scenarios (Feist et al. 2011). Coho
survival in urban streams can also indicate the success of
pollution control programmes, via GSI or other strategies.
Intensive control measures will almost certainly be necessary, across large spatial scales, to: (i) recover viable coho
populations in the built environment, and (ii) prevent the
rapid future loss of coho as a consequence of expanding
impervious cover in watersheds that are currently productive but primarily non-urban.
In the future, it may be possible to narrow the focal list
of chemicals by determining more precisely why storm
water-exposed coho are dying. The gaping, surface swimming and disequilibrium of affected spawners suggest
adverse physiological impacts on the gill, the heart, the
nervous system or some combination of these. An earlier
forensic study found no evidence of physical injury to the
gills or other tissues (Scholz et al. 2011). An alternative
approach would be to screen the target organs of symptomatic fish for changes in gene expression, and specifically gene sets that are diagnostic for specific categories of
physiological stress (e.g. respiratory uncoupling). If the
cause of death is ultimately found to be heart failure, for
example, the candidate chemicals could be screened for
cardiotoxic potential. It may also be possible to develop
alternative exposure methods that reflect different sources
of contaminants on roadways. This includes, for example,

© 2015 The Authors. Journal of Applied Ecology © 2015 British Ecological Society, Journal of Applied Ecology, 53, 398–407

 406 J. A. Spromberg et al.
large-volume suspensions of particulate soot from motor
vehicle exhaust, dust from brake pad wear or fine particles from tyre wear.
Lastly, toxic run-off is likely to represent an increasingly important conservation challenge for west coast
coho populations in the coming years. Extant population
segments are generally at historically low abundances, as
evidenced by current US Endangered Species Act threatened designations in central and northern California, as
well as north-western Oregon and south-western Washington. Land cover change has been extensive in some lowland watersheds where coho spawn, as a consequence of
sprawl in recent decades (e.g. Robinson, Newell & Marzluff 2005). Over a similar period of time, coho habitat
use in areas affected by urbanization has declined sharply
(Bilby & Mollot 2008). Resource managers have been
aware of the urban pre-spawn mortality syndrome among
adult coho since at least the 1980s (Kendra & Willms
1990). However, the extent to which recurring adult dieoffs have driven down wild coho numbers in urbanizing
watersheds is not presently known. Initial modelling has
shown that local populations in urbanizing watersheds
cannot withstand the rates of mortality observed in Puget
Sound urban stream surveys since 2000 (Spromberg &
Scholz 2011). However, in terms of recovery planning,
this storm water-related threat has yet to be mapped out
for actual coho conservation units at the sub-basin scale.
In conclusion, a core objective of GSI is to slow, spread
and infiltrate storm water. As anticipated from recent
studies (e.g. McIntyre et al. 2015), the experimental soil
columns used here effectively prevented the acutely lethal
toxicity of run-off from a dense urban arterial road. This
extends the range of aquatic species and life stages that
demonstrably benefit from storm water bioinfiltration.
These include the early life stages of zebrafish (McIntyre
et al. 2014), juvenile coho salmon and their macroinvertebrate prey (McIntyre et al. 2015), and adult coho spawners (this study). Bioretention is therefore a promising
clean water technology from the standpoint of installation
cost, reliability, reproducibility and scalability. However,
the science of GSI effectiveness is still relatively young
(Ahiablame, Engel & Chaubey 2012), and fundamental
questions remain as-yet unanswered, for example how
much treatment will be needed, over what spatial scales,
to ensure coho salmon survival? Whereas bioretention
may work well for small-footprint sites that receive modest inputs of storm water, they are but one of many evolving non-point source pollution control and prevention
methods that are currently under development (Hughes
et al. 2014). For the urban watersheds of the future, the
coexistence of humans and wild coho will likely hinge on
the success of these innovations.

Acknowledgements
We appreciate the technical assistance of Allisan Beck, Richard Edmunds,
Tony Gill, Emma Mudrock, Tiffany Linbo, Kate Macneale, Jana Labenia,

Mark Tagal, Frank Sommers, Gina Ylitalo, Daryle Boyd, Barb French,
Ann England, Karen Peck, MaryJean Willis, Cathy Laetz, Sylvia Charles,
William Alexander, Ben Purser, Corey Oster, Luke Williams and the Kitsap Poggie Club. This study received agency funding from the NOAA
Coastal Storms Program (National Ocean Service, Coastal Services Center), the U.S. Fish & Wildlife Service, the Puget Sound’s Regional
Stormwater Monitoring Programme (RSMP as administered by the WA
State Dept. of Ecology), and the U.S. Environmental Protection Agency,
Region 10. Lastly, we appreciate the helpful suggestions of two anonymous reviewers. Findings and conclusions herein are those of the authors
and do not necessarily represent the views of the sponsoring organizations.

Data accessibility
Data generated from this study are included in the text, tables, figures and
uploaded online supporting information.

References
Ahiablame, L.M., Engel, B.A. & Chaubey, I. (2012) Effectiveness of low
impact development practices: literature review and suggestions for
future research. Water Air and Soil Pollution, 223, 4253–4273.
Bilby, R.E. & Mollot, L.A. (2008) Effect of changing land use patterns on
the distribution of coho salmon (Oncorhynchus kisutch) in the Puget
Sound region. Canadian Journal of Fisheries and Aquatic Sciences, 65,
2138–2148.
Brette, F., Machado, B., Cros, C., Incardona, J.P., Scholz, N.L. & Block,
B.A. (2014) Crude oil impairs excitation-contraction coupling in fish.
Science, 343, 772–776.
Feist, B.E., Buhle, E.R., Arnold, P., Davis, J.W. & Scholz, N.L. (2011)
Landscape ecotoxicology of coho salmon spawner mortality in urban
streams. PLoS One, 6, e23424.
Gobel, P., Dierkes, C. & Coldewey, W.C. (2007) Storm water runoff concentration matrix for urban areas. Journal of Contaminant Hydrology,
91, 26–42.
Heintz, R.A., Rice, S.D., Wertheimer, A.C., Bradshaw, R.F., Thrower,
F.P., Joyce, J.E. & Short, J.W. (2000) Delayed effects on growth and
marine survival of pink salmon Oncorhynchus gorbuscha after exposure
to crude oil during embryonic development. Marine Ecology Progress
Series, 208, 205–216.
Hughes, R.M., Dunham, S., Maas-Hebner, K.G., Yeakley, J.A., Harte,
M., Molina, N., Shock, C.C. & Kaczynski, V.W. (2014) A review of
urban water body challenges and approaches: (2) mitigating effects of
future urbanization. Fisheries, 39, 30–40.
Incardona, J.P., Carls, M.G., Day, H.L., Sloan, C.A., Bolton, J.L., Collier, T.K. & Scholz, N.L. (2009) Cardiac arrhythmia is the primary
response of embryonic Pacific herring (Clupea pallasi) exposed to crude
oil during weathering. Environmental Science & Technology, 43,
201–207.
Incardona, J.P., Swarts, T.L., Edmunds, R.C., Linbo, T.L., Aquilina-Beck,
A., Sloan, C.A., Gardner, L.D., Block, B.A. & Scholz, N.L. (2013)
Exxon Valdez to Deepwater Horizon: comparable toxicity of both crude
oils to fish early life stages. Aquatic Toxicology, 142–143, 303–316.
Karr, J.R. (1999) Defining and measuring river health. Freshwater Biology,
41, 221–234.
Kayhanian, M., Fruchtman, B.D., Gulliver, J.S., Montanaro, C., Ranieri,
E. & Wuertz, S. (2012) Review of highway runoff characteristics: comparative analysis and universal implications. Water Research, 46, 6609–
6624.
Kendra, W. & Willms, R. (1990) Recurrent coho salmon mortality at
Maritime Heritage Fish Hatchery, Bellingham: a synthesis of data collected from 1987–1989, 28 pp. Washington State Department of Ecology Report 90-e54, Olympia, Washington, USA.
King, K.A., Grue, C.E., Grassley, J.M. & Fisk, R.J. (2013) Pesticides in
urban streams and early life stages of Pacific coho salmon. Environmental Toxicology and Chemistry, 32, 920–931.
Krahn, M.M., Rhodes, L.D., Myers, M.S., Moore, L.K., MacLeod, W.D.
Jr & Malins, D.C. (1986) Associations between metabolites of aromatic
compounds in bile and the occurrence of hepatic lesions in English sole
(Parophrys vetulus) from Puget Sound, Washington. Archives of Environmental Contamination and Toxicology, 15, 61–67.
McIntyre, J.K., Baldwin, D.H., Beauchamp, D.A. & Scholz, N.L. (2012)
Low-level copper exposures increase visibility and vulnerability of juve-

© 2015 The Authors. Journal of Applied Ecology © 2015 British Ecological Society, Journal of Applied Ecology, 53, 398–407

 Toxic urban run-off and salmon survival
nile coho salmon to cutthroat trout predators. Ecological Applications,
22, 1460–1471.
McIntyre, J.K., Davis, J.W., Incardona, J.P., Anulacion, B.F., Stark, J.D.
& Scholz, N.L. (2014) Zebrafish and clean water technology: assessing
soil bioretention as a protective treatment for toxic urban runoff.
Science of the Total Environment, 500–501, 173–180.
McIntyre, J.K., Davis, J.W., Hinman, C., Macneale, K.H., Anulacion,
B.F., Scholz, N.L. & Stark, J.D. (2015) Soil bioretention protects juvenile salmon and their prey from the toxic impacts of urban stormwater
runoff. Chemosphere, 132, 213–219.
Meador, J.P., Sommers, F.C., Ylitalo, G.M. & Sloan, C.A. (2006) Altered
growth and related physiological responses in juvenile Chinook salmon
(Oncorhynchus tshawytscha) from dietary exposure to polycyclic aromatic hydrocarbons (PAHs). Canadian Journal of Fisheries and Aquatic
Sciences, 63, 2364–2376.
Niyogi, S. & Wood, C.M. (2004) Biotic ligand model, a flexible tool for
developing site-specific water quality guidelines for metals. Environmental Science and Technology, 38, 6177–6192.
van der Oost, R., Beyer, J. & Vermeulen, N.P.E. (2003) Fish bioaccumulation and biomarkers in environmental risk assessment: a review. Environmental Toxicology and Pharmacology, 13, 57–149.
Pess, G.R., Montgomery, D.R., Bilby, R.E., Steel, E.A., Feist, B.E. & Greenberg, H.M. (2002) Landscape characteristics, land use, and coho salmon
(Oncorhynchus kisutch) abundance, Snohomish River, Washington, USA.
Canadian Journal of Fisheries and Aquatic Sciences, 59, 613–623.
Robinson, L., Newell, J.P. & Marzluff, J.M. (2005) Twenty-five years of
sprawl in the Seattle region: growth management responses and implications for conservation. Landscape and Urban Planning, 71, 51–72.
Ross, P.S., Kennedy, C.J., Shelley, L.K., Patterson, D.A., Fairchild, W.L.
& Macdonald, R.W. (2013) The trouble with salmon: relating pollutant
exposure to toxic effect in species with transformational life histories
and lengthy migrations. Canadian Journal of Fisheries and Aquatic
Sciences, 70, 1252–1264.
Sandahl, J.F., Baldwin, D.H., Jenkins, J.J. & Scholz, N.L. (2007) A sensory system at the interface between urban stormwater runoff and salmon survival. Environmental Science and Technology, 41, 2998–3004.
Scholz, N.L., Myers, M.S., McCarthy, S.G., Labenia, J.S., McIntyre, J.K., Ylitalo, G.M. et al. (2011) Recurrent die-offs of adult coho salmon returning to
spawn in Puget Sound lowland urban streams. PLoS One, 6, e28013.
Seattle Public Utilities. (2007) City of Seattle State of the Waters 2007:
Volume I Seattle Watercourses, 240 pp. Seattle Public Utilities, Seattle,
WA.
da Silva, D.A., Buzitis, J., Krahn, M.M., Bicego, M.C. & Pires-Vanin,
A.S. (2006) Metabolites in bile of fish from Sao Sebastiao Channel, Sao
Paulo, Brazil as biomarkers of exposure to petrogenic polycyclic aromatic compounds. Marine Pollution Bulletin, 52, 175–183.
Sloan, C.A., Anulacion, B.F., Baugh, K.A., Bolton, J.L., Boyd, D., Boyer,
R.H. et al. (2014) Northwest Fisheries Science Center’s Analyses of Tissue,
Sediment, and Water Samples for Organic Contaminants by Gas Chromatography/Mass Spectrometry and Analyses of Tissue for Lipid Classes
by Thin Layer Chromatography/Flame Ionization Detection, 61 pp. U.S.
Dept. Commerce, NOAA Tech. Memo. NMFS-NWFSC-125, Seattle,
Washington, USA.
Spromberg, J.A. & Scholz, N.L. (2011) Estimating the future decline of
wild coho salmon populations due to early spawner die-offs in urbanizing watersheds of the Pacific Northwest. Integrated Environmental
Assessment and Management, 7, 648–656.
Stein, E.D., Tiefenthaler, L.L. & Schiff, K. (2006) Watershed-based
sources of polycyclic aromatic hydrocarbons in urban storm water. Environmental Toxicology and Chemistry, 25, 373–385.
Tiefenthaler, L.L., Stein, E.D. & Schiff, K.C. (2008) Watershed and land
use-based sources of trace metals in urban storm water. Environmental
Toxicology and Chemistry, 27, 277–287.

407

Walsh, C.J., Roy, A.H., Feminella, J.W., Cottingham, P.D., Groffman,
P.M. & Morgan, R.P. II (2005) The urban stream syndrome: current
knowledge and the search for a cure. Journal of the North American
Benthological Society, 24, 706–723.
Waples, R.S. (1991) Pacific salmon, Oncorhynchus spp., and the definition
of “species” under the Endangered Species Act. Marine Fisheries
Review, 53, 11–22.
Washington Department of Ecology (2012) Stormwater Management
Manual for Western Washington Volume V: Runoff Treatment BMPs.
Publication No. 12-10-030, 301 pp. Washington Department of Ecology, Olympia, Washington, USA.
Washington State Department of Transportation (WA DOT) (2013a) 2012
Annual Traffic Report, 231 pp. WA DOT, Olympia, Washington, USA.
Washington State Department of Transportation (WA DOT) (2013b)
State Highway Log Planning Report 2012: SR2 to SR 971, 1781 pp.
WA DOT, Olympia, Washington, USA.
Received 2 April 2015; accepted 2 September 2015
Handling Editor: Julia Blanchard

Supporting Information
Additional Supporting Information may be found in the online version
of this article.
Table S1. Nominal concentrations (lg L 1) for metals and
selected polycyclic aromatic hydrocarbons (PAHs) in the PAHs/
metals mixture and the metals-only mixture exposures.
Table S2. Measured conventional water chemistry parameters in
treatments used in adult coho experiments during 2012–2013.
Table S3. Measured metal concentrations in treatments used in
adult coho experiments during 2012–2013.
Table S4. Abbreviations and polycyclic aromatic hydrocarbon
(PAH) analytes, including sums of alkyl PAH isomers measured
in water samples.
Table S5. Measured parent and alkylated homologue polycyclic
aromatic hydrocarbons (PAHs) (lg L 1) in treatments used in
adult coho experiments during 2012–2013.
Video S1. Video 1 of a symptomatic adult coho spawner in a
Seattle-area urban stream.
Video S2. Video 2 of a field observation of a symptomatic adult
coho in a Seattle-area urban stream.
Video S3. Adult coho spawners exposed under controlled experimental conditions to either clean well water, unfiltered urban runoff, or run-off treated using bioinfiltration.

© 2015 The Authors. Journal of Applied Ecology © 2015 British Ecological Society, Journal of Applied Ecology, 53, 398–407