**Preassessment Data Report #3**

***Selendang Ayu* oil risk to early life stage salmon**

Mark G. Carls, John Hudson and Stanley D. Rice

Auke Bay Laboratories, Alaska Fisheries Science Center,

NOAA Fisheries, 17109 Lena Loop Rd., Juneau, AK 99801

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**Abstract**

Polynuclear aromatic hydrocarbons (PAH) from the *Selendang Ayu* oil
spill were biologically available at detrimental concentrations in 1 of
14 streams examined, likely placing resident juvenile fish and possibly
embryos at risk. Assessment began several months after the spill;
aqueous total PAH (TPAH) concentrations were likely higher before
sampling commenced. Estimated aqueous TPAH concentrations in that stream
(SKN14) were high enough to have negative impacts on survival and growth
but pink salmon embryos were generally absent in the affected river area
and we conclude this was due to marginal habitat quality (too much sand
and mud) rather than oil related mortality. Species that reared in oiled
reaches of the main channel (Dolly Varden and coho) were also at risk;
analysis of tissues for hydrocarbon exposure can be conducted if
warranted. Although bioavailable PAH in bays was widely distributed,
only the water of Skan Bay posed a potential risk to emigrant juvenile
pink salmon during the sampling period. Although bioavailable TPAH
concentrations in Skan Bay were significant, several unknowns precluded
definitive assessment of risk in marine water, including the residence
time of juvenile pink salmon, their dependence on potentially oiled
prey, and true aqueous TPAH concentrations. Overall, we conclude that
the *Selendang Ayu* spill placed a relatively small number of pink
salmon embryos and fry at lethal and sublethal risk in stream habitat.

**Introduction**

Oil spilled by the freighter *Sendang Ayu* on December 8, 2004
(approximately 321,000 gallons of IFO 380 intermediate fuel oil and
15,000 gallons of Marine diesel fuel) spread into adjoining bays of
Unalaska Island, along an estimated 70 miles of shoreline (Fig. 1). The
impacted area contained 19 streams utilized by pink salmon
(*Oncorhynchus gorbuscha*) and other species as spawning and rearing
habitat (from Kashega Bay through Volcano Bay; ADF&G), raising concerns
that incubating eggs, alevins, and fry could be damaged by oil exposure.
These concerns were based on prior field experience, where toxic effects
of *Exxon Valdez* oil on pink salmon were observed for up to four years
after the spill (Bue et al. 1996,1998; Wertheimer et al.1996; Willete et
al. 1996). Long term follow-up studies demonstrated that low part per
billion level exposures \[1 to 18 μg/L total polynuclear aromatic
hydrocarbons (TPAHs)\] were effective in causing both short term (Marty
et al 1997, and long term effects, including reductions in adult returns
after embryonic exposures (Heintz et al. 1999, 2000; Carls et al. 2005).

*Selendang Ayu* oil was deposited primarily on gravel beaches, including
storm-created berms adjacent to the intertidal reaches of salmon
streams, but also inland on banks along two streams (SCAT data). Areas
surrounding low-gradient stream mouths were often oiled. This caused
considerable concern because the *Exxon Valdez* experience demonstrated
significant multi-year negative effects in pink salmon when banks of
streams were contaminated with oil. Dye studies in Prince William Sound
(PWS) after the *Exxon Valdez* oil spill demonstrated gravity-driven
groundwater flow from contaminated intertidal substrate into stream
channels, including the hyporheic zone utilized by developing pink
salmon embryos (Carls et al. 2003). Sensitive passive samplers
(low-density polyethylene membrane devices (PEMDs) detected a PAH
concentration gradient in at least one affected stream a decade after
the *Exxon Valdez* spill, demonstration of the long, slow release from
stranded intertidal crude oil (Carls et al. 2004a). Consistent with
drainage of PAH into stream systems, cytochrome P4501A (CYP1A) was
induced in pink salmon alevins (1989 to 1991; Wiedmer et al. 1996). All
of these observations in PWS explain the elevated pink salmon egg
mortality that persisted for 4 years in oiled PWS streams (Bue et al.
1998).

Experience and sampling strategy developed in the study of the *Exxon
Valdez* spill was applied to the *Selendang Ayu* spill, including
division of streams into zones with oil contamination plus upstream
zones above oil to act as stream-specific reference sites. Deployment of
passive samplers (PEMDs) to detect oil began 3 months after the
*Selendang Ayu* spill, a technology developed after the *Exxon Valdez*
oil spill (Huckins et al. 1990; Carls et al. 2004b). Advantages of PEMDs
are high sensitivity; hydrocarbons are concentrated by 10^4^ to 10^5^
times above those in surrounding water, hydrocarbon analysis requires
fewer cleanup steps than tissue, PAH are not metabolized by passive
samplers, samplers can be placed and retrieved at known times, and they
capture intermittent exposures such as those driven by tidal pumping and
surface runoff. Stream and bank sediment was also collected to quantify
oil concentrations within and around the streams and to confirm PAH
composition and source. Alevins (hatched embryos, but still with yolk
and resident within the spawning gravels) were hydraulically pumped from
stream sediment to examine the CYP1A biomarker and for direct analysis
of hydrocarbon burdens. This sampling would also confirm whether a
stream reach was a spawning habitat or not. CYP1A is induced by planar
hydrocarbons such as PAH; induction provides evidence of recent or
ongoing exposure.

Our specific objectives were to: 1) determine if oil was visible on
stream banks in pink salmon spawning habitat for streams designated as
priority by preliminary NOAA surveys (*n* = 15), 2) determine the
potential for early life stage salmon exposure in 3 oiled and 2
reference streams using PEMDs as surrogate accumulators of biologically
available oil, 3) determine PAH exposure in pink salmon alevins using
direct hydrocarbon analyses and cytochrome P4501A (CYP1A) induction
techniques, 4) determine bioavailability in marine waters near the
mouths of salmon streams where out-migrating fry might first feed and
reside using PEMDs, 5) determine concentration and PAH composition in
stream and bank sediment to augment PEMD measurements and aid in
interpretation, and finally, 6) evaluate the risk to salmonids in
oil-affected streams and marine water. To date, CYP1A analyses not been
completed; these samples may be analyzed, if warranted in the Assessment
Phase.

**Methods**

# **Stream sampling**

Preliminary identification of oiled salmon streams was based on
Shoreline Cleanup Assessment Team (SCAT) data collected after the
*Selendang* spill and on Alaska Department of Fish and Game (ADF&G)
salmon data. Oiling conditions were verified visually at each of 14
streams identified by NOS as important and classified as no oil, light,
moderate or heavy oil. The fifteenth priority stream (Spray Cape[^1])
could not be sampled due to weather. The suitability of habitat for
spawning in oiled areas was assessed visually (based on substrate type)
and confirmed by hydraulic pumping for alevins. Results of these
subjective measures were used to define a subset of streams for
objective, quantitative chemical and biological sampling including both
oiled and non-oiled streams. All data were collected in 2005, beginning
in March (approximately 4 months after the spill) and prior to alevin
swim up from the spawning gravels and emigration from the streams.

Streams were subdivided into two zones: oiled (downstream) and non-oiled
(upstream) sections based on visual observation oil. Three streams with
oil (SKN4, SKN14, and MKS5) and two non-oiled reference streams (PMS16
and PMN20) were sampled. A tributary in one of the oiled streams (SKN14)
was also examined. To estimate the potential bioavailability of
dissolved PAH, PEMDs were placed at 3 oiled sites and 1 non-oiled site
in each stream in March and collected about 1 month later (1 device per
site). Non-oiled sites were located above the oiled zones and served as
stream-specific references. Stream gradients varied considerably, thus
site elevations and spacing between sites varied from stream-to-stream.
Observation by PEMD of two oiled streams with overlap between spawning
habitat and oil (SKN14 and MKS5) and the tributary (of SKN14) continued
monthly through September, an extension of the original study design.

*Assessment of spawning habitat suitability.* Field determination of the
suitability of habitat for salmon spawning was based on observation of
stream sediment, water flow, and exploratory hydraulic pumping to
determine the presence or absence of eggs and alevins.

## *Alevin and fish sampling.* To confirm oil exposure, pre-emergent alevins collected by hydraulic pumping were either frozen in glass jars for hydrocarbon analysis or fixed in 10% phosphate-buffered formalin to estimate CYP1A induction . In August, additional resident Dolly Varden char (*Salvelinus malma*) and coho salmon (*O. kisutch*) smolts were collected for CYP1A induction and PAH analysis from two oiled streams (SKN14 and MKS5). Analysis of these samples could be conducted in the Assessment Phase, if warranted. 

*Sediment sampling*. Sediment samples were collected from stream
channels at each site and sediment from adjacent banks was collected and
frozen in certified hydrocarbon-free jars. These samples are pending
analysis. Blank jars were included in the collection for quality
control.

## Assessment of nearshore marine habitat

Additional PEMDs were deployed in the nearshore marine environment and
remained approximately 1 m below the surface on anchored buoys in bays
adjacent to stream mouths for 1 month intervals (Appendix 1). These
PEMDs were deployed in March, April, May, and August 2005; sampler loss
in this high energy environment was relatively frequent, resulting in
discontinuous sampling. Lack of vessel support precluded sampler
replacement in June. In total, 17 marine PEMDs were retrieved and
analyzed.

**PEMD preparation and quality assurance**

The PEMDs were prepared according to Carls et al. (2004b). In brief,
low-density polyethylene tubing (98 µm × 4.9 cm × 50 cm) was sonicated
twice in pentane to remove hydrocarbons, placed in aluminum samplers
(11.5 mm diameter × 6.6 cm with perforated endplates, 3 mm holes spaced
4.8 mm apart, precleaned in dichloromethane), wrapped with two layers of
aluminum foil, heat-sealed in two plastic bags, and frozen until
shipment to Dutch Harbor. Laboratory and field blanks were included in
each sampling event for quality control. The field blanks were used as
transportation and handling blanks; they were transported to the field
with all other PEMDs, opened briefly (1 per stream), then repackaged and
as handled as all other samples. Deployed PEMDs were tethered to
solvent-cleaned Duckbill^®^ anchors with solvent-cleaned steel cable and
zip ties or to nylon line fastened to rock-filled polypropylene mesh
bags. The PEMDs were buried about 3 to 6 cm below the stream bed during
the first installation. Because many were excavated by stream activity,
subsequent devices were not buried. Additional anchors were often placed
a meter or two downstream to secure small marker floats. Retrieved PEMDs
were rinsed in place as they were retrieved to remove accumulated
sediment, double-wrapped in aluminum foil, placed inside two Ziplock^®^
bags, and frozen as soon as possible.

**PAH Analyses**

All hydrocarbon samples were extracted with organic solvent. The PEMDs
were wiped to remove gross surface contamination, placed in centrifuge
tubes and spiked with 6 deuterated PAH standards (naphthalene-d~8~,
acenaphthene-d~10~, phenanthrene-d~10~, chrysene-d~12~, perylene-d~12~,
and benzo\[a\]pyrene-d~12~). Spike solvent (hexane) was allowed to
evaporate, then the tubes were placed in a sonic bath, and extracted in
80:20 ml pentane/dichloromethane for 130 min. The sonicator was on for
the first 20 min of each 50 min period. The PEMDs were rinsed without
delay with pentane as they were removed after the final sonication;
extracts were concentrated to 20 to 30 ml, dried with 2 to 4 g of sodium
sulfate, concentrated to 1 to 2 ml in hexane, and passed through 1.5 g
silica gel columns. All extracts were spiked with an internal standard
(hexamethyl benzene) and frozen pending analysis. Sediment and tissue
samples were analyzed using the methods of Short et al. (1996). Samples
were extracted twice with dichloromethane after addition of previously
identified 6 internal standards. Extracts were reduced in volume,
exchanged with hexane over a steam bath, and fractionated and purified
by alumina/silica gel chromatography.

Extracts were analyzed by gas chromatography equipped with a mass
selective detector and PAH concentrations were determined by the
internal standard method (Short et al. 1996). Experimentally determined
method detection limits (MDL) were generally 0.18 to 3.94 ng/g in PEMDs,
about 1 ng/g in tissue, and \<2 ng/g in sediment; concentrations below
MDL were considered equivalent to zero and are not reported. The
accuracy of the hydrocarbon analyses was within 15% (i.e., ± 15%) based
on comparison with National Institute of Standards and Technology
values, and precision expressed as coefficient of variation was usually
less than about 20%, depending on the PAH. All internal standard
recoveries were within acceptable limits (32 to 136%; mean 93%).
Internal standard recoveries in PEMDs increased from naphthalenes (87 
10%) to phenanthrenes (99.7  8%) and declined toward higher molecular
mass PAH (90  19% for peryelene).

Total PAH concentrations were calculated by summing concentrations of 44
individual PAH, ranging from 2 to 5 rings (naphthalenes (N0 to N4),
fluorenes (F0 to F4), dibenzothiophenes (D0 to D4), phenanthrenes (P0 to
P4), anthracene (AN), fluoranthene (FL), pyrene (PY), substituted
fluoranthenes/pyrenes (A1 to A4), chrysenes (C0 to C4),
benzo(b)fluoranthene (BB), benzo(k)fluoranthene (BK), benzo(e)pyrene
(BE), benzo(a)pyrene (BA), perylene (PE), indeno(1,2,3-cd)pyrene (IC),
benzo(a,h)anthracene (DB), and benzo(ghi)perylene (BZ).

*Interpreting PAH concentrations in PEMDs*. Passive samplers accumulate
PAH over time and higher concentrations indicate substantially greater
exposure during the period of deployment. The relationship between
deployment time and PAH concentration in PEMDs is inexact because PEMDs
might capture transient high concentrations or measure a more stable
concentration, different situations that cannot be distinguished with
multi-day deployments. In a laboratory study (Carls et al. 2004), TPAH
concentrations in PEMDs in contact for 52 d with exponentially declining
aqueous TPAH concentrations were 94% of those deployed for 26 d,
demonstrating good retention capacity. PEMDs are very sensitive to all
water or airborne organics, hence laboratory and field blanks are
required for interpretation. Laboratory and field blanks often have TPAH
concentrations between zero and 100 ng/g. Concentrations between 100 and
500 ng/g usually indicate low exposures.

A summary oil-identification model comprised of multiple
oil-identification models was used to determine if PAH composition in
PEMDs, sediment, and tissue was consistent with a petrogenic source,
presumptively *Selendang Ayu* oil, the only known and largest potential
source of oil (Carls 2006). Contributing models were authored by Short
and Heintz (1997), Bence and Burns (1995), and Carls (2006). Summary
scores range from 0 to 6; a score of 4 is considered probably
petrogenic, hence probably *Selendang Ayu* oil, and scores greater than
5 are considered definite evidence of oil. Oil was considered fresh when
PAH composition was dominated by naphthalenes and weathered when higher
molecular weight PAH were dominant.

**CYP1A analyses**. Samples were collected and will be analyzed if
warranted in the Assessment Phase.

**Study area**

The *Selendang Ayu* grounded on the western coast of Unalaska Island,
near Spray Cape (53.6297°N, 167.1392°W). The reference streams were
located south of the wreckage along the outer coastline (Outer
Pumicestone) or near the head of the long, narrow Pumicestone Bay (Fig.
1). Oiled streams were located to the north or northwest in Skan Bay
(two streams) and Makushin Bay (Fig. 1).

**Oiled area.**

Stream SKN4 in Skan Bay was lightly oiled; oil was observed only near
the mouth and in the intertidal berm, consistent with SCAT observations
(Fig. 1). The stream did not discharge directly into the bay, when the
PEMDs were placed (March 2005) and retrieved (April), rather it
percolated through the rocky beach berm. The stream broke through the
berm a few days after samplers were placed but the berm reformed before
the PEMDs were retrieved. The lowest sample elevation was 1.04 m above
mean lower low water (MLLW) and water was fresh (0 ppt) throughout. The
stream was deep, broad (23 m near site 2), and had a low gradient (0.1
cm/m). Sampling extended about 475 m upstream; this reach was almost
lake-like, with a slow flow rate (mean less than 0.1 m/s). The stream
substrate was gravel-cobble. Alevins were encountered above site 3
(greater than 380 m stream distance) and collected only from the
uppermost elevation (site 4; about 500 m stream distance). A few dead
eggs were discovered near site 3; no eggs or alevins were encountered in
lower zones. The mean pink salmon run in SKN4 is 6000 fish (Appendix 2).
Samplers, including two in the bay, were placed in March and retrieved
in April (26 d).

Stream SKN14 in northern Skan Bay was heavily oiled, consistent with
SCAT observations (Fig. 1). This was a wide, generally shallow,
low-gradient stream with generally low water velocities (mean 0.1 m/s,
excluding one apparent measurement error; *n* = 14). The first 300 m of
streambed consisted of 75% sand and 25% gravel/cobble substrate. Above
this point the stream widened (about 100 m) into a shallow lake
primarily consisting of sand and mudflats. In June 2005, numerous adult
salmon carcasses, apparently pink salmon, were observed partially buried
in fine bottom sediments in this area. The channel narrowed near site 3
but was similarly broad in places between sites 3 and 4. The river bank
and adjacent vegetation was oiled for about 1.7 km and a boom was
located 40 m upstream of this point. Surveying over these distances was
not feasible and gradient was not determined. Water was fresh throughout
(0.0 ppt); temperatures declined from 6.2 °C (site 1) to 2.9 °C (site 4)
in March. Habitat in vicinity of sites 1, 2, and 4 was apparently not
suitable for salmon spawning; dead eggs but no alevins were discovered
at site 3 (about 400 m stream distance and adjacent to the tributary).
However, pink salmon spawning between sites 3 and 4 was observed in
August. Site 4 was the above-oil reference in this stream. Stream
samplers were first placed in March 2005 then retrieved and replaced at
roughly 1 month intervals (24 to 41 d; Appendix 3). Two to three PEMDs
were placed in the bay in March, April, and August and retrieved 24 to
33 d later (Appendix 3). The lower portion of SKN14 had been cleaned in
the vicinity of site 1 before sampling began; the remainder was cleaned
during the April-May deployment. Stream SKN14 supports a pink salmon run
(mean 12,000 fish, *n* = 3; Appendix 2).

A partially oiled tributary that entered SKN14 near site 3 and rose to
the north was also sampled (Fig. 1). The tributary had several channels;
the main channel was always filled with water, side channels were
sometimes filled. The channel was relatively narrow (6.6 m at the delta
where it entered SKN14), rose quickly (3.5 cm/m), and extended above the
oiled zone within 36 m. Flow was rapid (mean 0.7 m/s) and the water was
fresh (0.0 ppt). The substrate was gravel-cobble. Alevins were collected
from the gravel at both below and above oil sites. Samplers were first
placed in March 2005, then retrieved and replaced at roughly 1 month
intervals (22 to 41 d; Appendix 3).

A braided, glacially turbid stream (MKS5) in Makushin Bay was lightly or
moderately oiled to about 350 m stream distance, consistent with SCAT
observations (Fig. 1). In June and August, high densities of juvenile
coho and Dolly Varden were observed in turbid main channels, clear
side-channels, and isolated pools. Water velocity was low in an eastern
channel and orange clay coated the rocky substrate, though in September
when flow rates increased, adult fish were observed in this channel.
Mean flow in the braided portions of the stream was 0.9 m/s and the mean
gradient was 1.0 cm/m. The first section of the river paralleled the bay
and was separated from it by a rocky berm in the spring. The stream
broke through the berm in the fall as apparent flow volumes increased.
Some oil was evident on the berm. A boom was located along this stretch,
about where the river turned uphill. Sediment and plants inland were
oiled up to an elevation of 2.8 m above MLLW. Salinity was consistently
0.1 ppt. Water temperature ranged from 7.2 to 7.6°C in March with no
obvious elevation-related pattern. The lowest site (1) was 1.25 m above
MLLW and the highest (4) was 3.71 m above MLLW. Site 4 was the above-oil
reference in this stream (430 m stream distance). The substrate was
gravel-cobble. Pink salmon alevins were collected near sites 2 (270 m
stream distance), 3, and 4. Samplers, including two in the bay, were
first placed in March 2005, then retrieved and replaced at roughly 1
month intervals (24 to 41 d; Appendix 3). Beginning in April, Makushin
Bay samplers were relocated to the ends of the straight beach section,
about 2 km apart. Stream MKS5 supports a salmon run (mean 22,000;
Appendix 2). Stream MKS5 was cleaned in July.

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**Reference area.**

The reference stream in Outer Pumicestone Bay (PMN20) was broad (nearly
60 m at the widest point near site 2) with a low gradient (about 0.6
cm/m; Fig. 1). No oil was observed, consistent with SCAT observations.
Salinity ranged from 0.9 ppt at site 1 (near mouth) to 0.1 ppt at site 4
(about 600 m upstream). The elevation at site 1 was less than 0.9 meters
above MLLW and the mean flow rate was 0.4 m/s. The stream channel
habitat, primarily sand and mud, was unsuitable as pink salmon spawning
habitat; no eggs or alevins were found during exploratory pumping.
Stream PMN20 supports a pink salmon run (mean 9,000, *n* = 19; Appendix
2); presumably the primary spawning habitat is upstream of the area
sampled. Samplers, including two in the bay, were placed in March 2005
and retrieved in April (25 d).

The mouth of stream PMS16 consisted of three channel braids flowing into
Pumicestone Bay over a broad alluvial fan. No oil was observed,
consistent with SCAT observations. Stream gradient (greater than 1.4
cm/m), water velocities were high (mean = 1.2 m/s), and the central
channel was often too deep to sample (Fig. 1). The streambed substrate
was dominated by cobbles and small boulders. Water was fresh (0.0 ppt)
and cold (2.9 °C) throughout. The alluvial fan and other areas around
this stream have been used as a cattle pasture; no cattle were observed
during sampling. Site 1 was 0.75 m above MLLW; the uppermost site (4)
was greater than 2.66 m above MLLW and was 166 m upstream. The sampled
habitat was suitable for spawning and alevins were present in stream
gravel. The stream supports a pink salmon run (mean 31,000; Appendix 2).
Samplers, including two in the bay were placed in March 2005 and
retrieved in April (24 d).

**Results**

All PEMD samples (105) have been analyzed. Hydrocarbons in sediment and
tissue and CYP1A induction will be analyzed if warranted in the
Assessment Phase.

**Oil and spawning habitat distributions**

There was little overlap between oiled habitat and pink salmon spawning
habitat in most streams. Of the 14 streams visually surveyed for pink
salmon alevins and the presence of oil, alevins were potentially exposed
to oil in 2 (SKN14 and MKS5) but not in the remaining 12 (Appendix 2).
\[This assessment was based on visual evidence of oil contamination on
the stream banks and surrounding vegetation and the presence of spawning
gravel (not mud or sand), plus confirmation of spawning habitat through
the hydraulic pumping for embryos and alevins\]. Chemical confirmation
of biological availability of oil in these streams is reported in the
next section. All visual assessments were consistent with SCAT data.
There was no evidence of intertidal spawning at any stream (examined
with hydraulic pumping); the habitat in the Aleutians was not similar to
the intertidal habitat in PWS. Tides are significantly smaller in the
Aleutians and beaches and stream mouths are typically subjected to
higher energy surf. In addition, stream gradients in the lower reaches
above the surf zone are often too low to provide spawning gravels.
Observed oiling was generally confined to beach areas and usually did
not extend upstream to spawning habitat.

*MKS5 stream*. Salmon habitat and oil overlapped in the lightly or
moderately oiled braided portion of the MKS5 stream. Bank sediment and
terrestrial plants were oiled inland up to 2.8 m above MLLW (about 350 m
stream distance). Pink salmon alevins were discovered by hydraulic
pumping within the oiled zone (270 and 315 m stream distance) and above
it (430 m). Juvenile coho and Dolly Varden also utilized this habitat
and were sampled in August for potential hydrocarbon and CYP1A analyses.

*SKN14 stream*. Salmon habitat and oil overlapped in the heavily oiled
SKN14 stream. The stream banks and surrounding vegetation were heavily
oiled for at least 900 m and oiling extended to about 1.7 km upstream.
Suitability of the main stream channel was questionable as pink salmon
spawning habitat; the only main channel location where evidence of
spawning was discovered in the spring was site 3, adjacent to a
tributary with suitable spawning habitat. Thus, oil and spawning habitat
overlapped in less than 1% of the study area. However, some spawning
activity was observed in the main channel in the fall. A tributary in
the vicinity of site 3 was prime spawning habitat; alevins were abundant
both above and below oiled area. The lower portion of this tributary was
oiled for about 35 m. Juvenile coho and Dolly Varden were abundant along
the margins of the main channel and were observed in areas covered with
oil sheen. Both species were sampled in August.

**Potential biological availability of PAH, measured in PEMD
surrogates.**

*Oiled streams.* **SKN14**. Total PAH concentrations were at least 1 to
2 orders of magnitude greater in stream SKN14 than in others; visibly,
this stream was the most extensively and heavily oiled of all streams
sampled (Fig. 2) and the passive samplers confirmed the visual
observations with chemical evidence of bioavailability. Total PAH
concentrations in the lower three elevations (within the oiled zone)
initially ranged from 42,044 to 463,080 ng/g with the highest
concentrations at the lowest elevation (Fig. 2). Oil was present in all
these PEMD samples (Table 1). Concentrations dropped exponentially in
the following months, except trends reversed in the last sample period
(August -- September 2005; Fig. 2). The decline in concentrations over
time suggests that even higher concentrations were possible in the
earlier months of the spill. Oil was not present in passive samplers
placed above the oiled zone (the stream-specific background), where the
TPAH concentration ranged from 23 to 93 ng/g, or in the site blanks
where the TPAH concentration ranged from 30 to 140 ng/g (Table 1). In
the contaminated tributary of SKN14, TPAH concentrations within the
oiled zone peaked at 426 ng/g, substantially less than in the main
stream. Total PAH concentrations above oil in the tributary ranged from
31 to 67 ng/g with no evidence of oil (Fig. 2). PAH composition in
SKN14, including the lower portion of the tributary, was consistent with
oil from the *Selendang Ayu* (Fig. 2, Table 1).

**SKN4**: oil was observed only near the mouth and in the intertidal
berm, consistent with SCAT observations (Fig. 1). Oil was probable in a
PEMD placed below an oil band on the bank near site 1 and the mouth
(4547 ng/g TPAH) but not in adjacent stream water (111 ng/g, retrieved
April 2005; Table 1). Total PAH concentration dropped from 111 to 25
ng/g in the upstream direction. The site blank was 56 ng/g.

**MKS5**. Oil was present in stream MKS5 (Glacier Valley Creek) in
Makushin Bay at concentrations about 1 to 2 orders of magnitude lower
than in SKN14 (Fig. 2). Visible oil extended well above tidal influence
but oiling levels were light compared to those at SKN14 and these
qualitative differences were consistent with the differences in TPAH
concentration between streams. Oil was detected in PEMDs at site 2 and
peaked at 976 ng/g (in June) before dropping to 98 ng/g (in August; Fig
2). Low concentrations of oil were also possible in water at site 1
(near the stream mouth). Oil was not detected at site 3. Total PAH at
the stream reference site ranged from 10 to 35 ng/g and was 23 to 178
ng/g in the site blanks; oil was not present in either (Table 1).

*Oiled bays.* Total PAH concentrations in marine water of Skan Bay near
SKN14 were greater than in other bay samples (4,150 to 18,278 ng/g) with
clear compositional evidence of oil in the PEMDs (Fig. 2, Table 1). Oil
was also present near SKN4; TPAH concentrations ranged from 4,844 to
6,295 ng/g (Table 1).

*Comparison of oiled bays and oiled streams.* The composition of PAH in
Skan Bay marine PEMD samples was more weathered than in adjacent
streams. This relationship is clear in SKN14 where initial and final
TPAH concentrations in stream water were high and the oil was fresh
(Fig. 3 and Appendix 4). Naphthalenes (which are dominant in unweathered
oil) accounted for 61 to 76% of the TPAH near the mouth of SKN14
(site 1) in March through May and August---September 2005. As
concentrations in the stream declined during the summer (and after oil
removal from banks in April and May), composition became more weathered;
percent naphthalenes dropped to 40 to 43%. Total PAH concentrations
increased in the final sample (August---September) and the oil was less
weathered. In contrast, PAH in the bay was consistently more weathered
than water near the stream mouth, ranging from 19 to 22% naphthalenes in
March---April to 15 to 18% naphthalenes in August---September. The same
contrast was evident between the single definitively oiled sample in
stream SKN4 (74% naphthalenes) and adjacent bay water (18 to 23%
naphthalenes; March---April).

*Reference streams and bays.* Except at the mouth of PMN20, no oil was
visible or detected in either reference stream, both sampled from March
to April 2005. Total PAH concentrations in PEMDs in PMS16 ranged from 14
to16 ng/g (*n* = 4); the site blank was 28 ng/g (Fig. 2; Table 1). There
was no evidence of oil in these samples (Table 1). Concentrations in
PMN20 were similar at most elevations (6 to 37 ng/g, *n* = 3) with no
evidence of oil; the site blank was 21 ng/g (Fig. 2; Table 1). Analyte
concentrations were below calibration standards or there was no signal
at these sites. However, the TPAH concentration at the lowest PMN20
elevation was 589 ng/g and the composition was consistent with
*Selendang Ayu* oil (Table 1). Some beaches along the coastline both
north and south of PMN20 were characterized as oiled by the SCAT team
(Fig. 1).

Total PAH was slightly elevated (115 to 135 ng/g, *n* = 3) in PEMDs in
adjacent reference bays (Fig. 4) compared to the reference streams and
composition was consistent with a petrogenic source (Table 1). These
concentrations were greater than in the site blanks (21 to 28 ng/g) but
1 to 2 orders of magnitude less than in bays with visibly oiled beaches
(Fig. 4).

*Quality assurance: PEMD blanks.* There was no evidence of oil in
laboratory blanks; mean TPAH concentrations were lowest in this group
and ranged from 0 to18 ng/g. Analyte concentrations in laboratory blanks
were below calibration standards or there was no signal (Table 1).

Total PAH concentrations in site blanks (exposed briefly to air) ranged
from 0 to 178 ng/g and there was no evidence of oil in them (Table 1).
Analyte concentrations generally were below calibration standards or
there was no signal.

**Oil in sediment.**

*Selendang Ayu* oil was detected in visibly oiled stream banks (Table
2). The TPAH concentration was 94000 ng/g in an oily band at the mouth
of SKN4 and composition was consistent with *Selendang Ayu* oil; oil was
not detectable in sediment slightly below this band where the TPAH
concentration was 13 ng/g. *Selendang Ayu* oil was detected in SKN14
stream banks at all sites including the oiled portion of the tributary
(1100-89700 ng/g) except the reference sites (3 to 19 ng/g). *Selendang
Ayu* oil was detected in stream banks at all MKS5 sites (≤727000 ng/g
TPAH) except the reference site (0 ng/g).

With one exception, *Selendang Ayu* oil was not detected in stream
channels (Table 3). Sediment from the mouth of SKN14 was exceptional
(2300 ng/g TPAH) with a composition consistent with *Selendang Ayu* oil.
Elsewhere the mean TPAH concentration in stream channels was 2.6 (95%
CI, -1.1 to 6.3). No detection of PAHs was typical.

**Oil in pink salmon alevins.**

There was little evidence of oil in pink salmon alevins (Table 4). Pink
salmon spawning habitat and oiled stream reaches rarely overlapped, thus
few alevins samples were collected. Of these, TPAH concentrations were
slightly elevated in two samples collected in the oiled portion of the
SKN14 tributary (54-81 ng/g). *Selendang Ayu* oil could not be verified
in either and naphthalenes were the only detectable PAH in one of them.
Elsewhere, TPAH concentrations in alevins ranged from 0 to 16 ng/g (mean
2.8 ng/g, *n* = 10), significantly lower than in the oiled portion of
the tributary (*P* = 0.017). The tissues of resident coho and Dolly
Varden juveniles have not been analyzed.

**Relationship between oil in PEMDs and oil in sediment.**

Dissolved *Selendang Ayu* oil constituents were consistently detected in
PEMDs in streams where banks were oiled despite the nearly ubiquitous
absence of *Selendang Ayu* oil in stream sediment. Consistent with a
dissolved source, the relative quantities of the smallest PAHs
(naphthalenes) were significantly enhanced in PEMDs \[*P* = 0.002, mean
48%, 95% confidence interval (CI) 33 to 63%, *n* = 6\] with respect to
those in oiled sediment (mean 21%, 95% CI 11 to 31%, *n* = 9). Also
consistent with a dissolved source, few high molecular weight PAHs were
observed in PEMDs (mean 0.1%, 95% CI -0.1 to 0.2%, n = 6). Significantly
more high molecular weight PAHs were observed in oiled sediment (*P* \<
0.001; mean 2.8%, 95% CI 1.4 to 3.4%).

**Discussion**

**Pink salmon embryo exposure and risk**

Polynuclear aromatic hydrocarbons (PAH) from the *Selendang Ayu* oil
spill were biologically available at detrimental concentrations in 1 of
14 streams examined (SKN14), likely placing resident juvenile fish and
possibly embryos at risk. (Assessment began several months after the
spill; aqueous TPAH concentrations were likely higher before sampling
commenced.) In most cases (12 of 14 streams examined), spawning and
rearing habitat did not intersect oiled habitat. Two of the 12 streams
may not host salmon runs (SKS14 and SKN8). The other 12 spawning streams
examined represent 63% of all known salmon streams in the spill area
(*n* = 19, from Kashega Bay to Volcano Bay; Appendix 5). No oil was
reported by SCAT surveys in any of the 7 spawning streams not examined
and oiling on adjacent beaches was light with no evidence of buried oil.
Oiling near salmon streams was generally confined to beach areas;
suitable spawning and rearing habitat was consistently located further
upstream. No intertidal spawning habitat was observed and gradients were
generally low in lower stream reaches thus usually not suitable for
spawning due to the lack of appropriate gravel substrate. The intertidal
and lower reaches of the streams in Unalaska were fundamentally
different than the short streams in PWS where oil and spawning habitat
intersected on all oiled stream mouths.

Pink salmon spawning habitat utilization in Unalaska differs sharply
with that in PWS, where oil from the *Exxon Valdez* had a significant
impact on pink salmon embryos in the intertidal portions of streams
(Rice et al. 2001). In Unalaska, pink salmon generally do not utilize
intertidal habitat for spawning (A. Shaul, ADF&G, personal
communication) and we found no evidence of intertidal spawning activity.
In contrast, up to 75% of spawned pink salmon eggs are deposited
intertidally in PWS (Helle et al. 1964; Heard 1991). At least three
prominent physical differences probably explain the differences: 1)
There is a much smaller tidal range in Unalaska (range -0.5 to 1.5 m
above MLLW) versus that in PWS (range -1.0 to 4.7 m above MLLW), thus
the potential size of suitable intertidal habitat in Unalaska is far
more limited. 2) The average wave energy in Unalaska is apparently
greater than in PWS, reducing the likelihood of embryo retention in
intertidal gravel and increasing substrate coarseness. Inland incursions
of oil along Unalaska streams but not along PWS streams is an indication
of the energy differences between these locations as is a dearth of
mussels on gravel beaches in Unalaska. 3) Many of the Unalaska streams
had low gradients near stream mouths, precluding the occurrence of
suitable gravels for spawning.

Salmonids were at risk in stream SKN14, where stream banks were heavily
oiled and dissolved oil was detected chemically about 400 m from the
mouth and above some of the spawning habitat. Oil was deposited along
the river banks and generally followed their course, suggesting
deposition by a storm surge flood event. River substrate was oil-free,
except for contamination in the high-energy environment at the mouth.
Observed bioavailability of PAH was greatest at the first sampling in
March, when alevins were still present. The decline in TPAH
concentrations measured from March to August indicates that exposure
concentrations were likely higher prior to sampling. Even though this
stream was heavily contaminated for at least 900 m, including some
spawning habitat, the risk to pink salmon in this stream was still not
great, as most of the spawning habitat was above the oiled zone (oil and
spawning habitat overlapped in less than 1% of the study area in SKN14
and the estimate for the entire stream system would be much smaller).
Thus, the principal risk in this stream system was to resident coho and
Dolly Varden juveniles.

Given the physical nature of the bunker oil spilled, persistence of the
oil is virtually guaranteed in the freshwater environment for several
months if not physically removed[^2]. Prior to the March sampling,
higher TPAH concentrations in earlier months (December 2004 -- February
2005) were likely in oiled streams (SKN14 and MKS5) and unlikely in
streams without visible oil. If the streams were oiled, the oil would
have persisted through the March sampling, and been both visible and
detected with the passive samplers.

The observed movement of dissolved PAHs from stream banks into stream
water is consistent with the mechanism previously observed in Prince
William Sound after the *Exxon Valdez* oil spill (Heintz et al. 1999;
Carls et al. 2003, 2004). Dissolved PAHs leached from *Selendang Ayu*
oil in stream banks into stream water; PAHs were absent in stream
channel sediment (with one exception) and composition in PEMDs was
consistent with accumulation from PAHs dissolved in water. Even where
stream sediment was oiled (at the high-energy mouth of SKN14),
accumulation in the PEMD was characteristic of a dissolved source.
Flowing stream water generally protected stream sediment from contact
with whole *Selendang Ayu* oil just as was observed in Prince William
Sound after the *Exxon Valdez* oil spill (Brannon et al. 1995). Thus,
although protected from direct oiling, biota that inhabit streams
surrounded by oil deposits are placed at risk by movement of
oil-contaminated water. The principal source of contaminated water in
Prince William Sound streams was groundwater driven by tidal exchange;
in Unalaska the principal source was groundwater movement driven by
precipitation.

Despite the obvious physical differences between bunker and crude oils,
the PAH toxins that leached into the water from *Selendang Ayu* oil are
the same as those leached from *Exxon Valdez* crude oil, thus previous
research focused on the effects of crude oil is applicable to the
Selendang spill. Composition of the biologically available PAH from
*Selendang Ayu* oil (IFO 380, a refinement residue plus diesel fuel) was
so similar to biologically available PAH from *Exxon Valdez* crude oil
that the highly discriminatory first-order loss-rate model of Short and
Heintz (1997) generally failed to distinguish the two[^3]. Not only was
PAH composition about the same, it also followed the weathering patterns
observed for crude oil (more rapid loss of smaller molecular weight
PAH). Similar effects in the Selendang spill could be expected if
exposure concentrations and conditions (similar exposure periods,
comparable life stages and species) were similar to the *Exxon Valdez*
crude oil spill.

Estimating aqueous exposure concentrations from the passive samplers is
challenging, and requires interpretation. It is not an exact science.
Relative exposure differences from the integrating passive samplers can
be compared from site to site, but the exact concentration history in
the water during sampling periods remains unknown. There is no way, for
example, to determine if accumulations represent a constant aqueous TPAH
concentration or transient higher concentration spikes (Carls et al.
2004). Direct aqueous observation was not attempted because it was not
feasible to conduct these measurements in the field and because such
samples only represent brief periods of time.

A rough, order-of-magnitude estimate of aqueous TPAH in Unalaska streams
is possible by comparison of PAH concentrations in PEMDs to data from a
controlled laboratory experiment. The consistent overall pattern was an
exponential TPAH decline in the heavily oiled SKN14 stream. A similar
decline was evident in PEMDs serially deployed in a laboratory
experiment where measured aqueous concentrations were falling
exponentially (Appendix 6; Carls et al. 2004b; 2005a). The PAH
composition, temperature, and deployment times were similar in both.
Naphthalene concentrations initially dominated in the laboratory (70%)
and ranged up to 76% in SKN14, attributes of fresh oil. Relative
phenanthrene concentrations increased with weathering, reaching 32% in
the laboratory and 41% in SKN14. Temperatures in the laboratory and
SKN14 ranged from 2 to 10° C and 3 to 13° C, respectively. Deployment
times in the laboratory[^4] were 26 and 52 d, those in SKN14 were 24 to
41 d. With this approach, we estimate that 1,000,000 ng/g TPAH in PEMDs
corresponds to roughly 20 μg/L in water and 100,000 ng/g corresponds to
roughly 2 μg/L.

Based on these approximations, fish in portions of stream SKN14 were at
risk for a portion of the sampling period; this risk probably extended
back to the oiling event and was probably even greater in the months
prior to sampling. PAH are highly toxic to fish embryos (0.4 to 23 μg/L
TPAH; Marty et al. 1997; Carls et al. 1999; Heintz et al. 1999, 2000;
Barron et al. 2003; Colvaecchia et al. 2004; Rhodes et al. 2005) and
concentrations in this range and above represent a risk. Aqueous
concentrations in SKN14 may have ranged up to about 10 µg/L at the
lowest sample elevation and up to 1 µg/L at other oiled sites
(March-April), placing developing embryos and other young salmon at
risk, particularly in the lowest reaches of the stream[^5]. Although
apparently very few pink salmon developed successfully in the main
channel of SKN14 between 2004 and 2005 due to lack of suitable habitat,
sculpin eggs and juvenile salmonids that utilized this habitat for
rearing were potentially at risk: a few pink salmon fry were also
observed in the main channel. However, TPAH concentrations fell
exponentially, progressively reducing the risk except for a reversal in
the fall[^6]. Estimated aqueous TPAH concentrations near the mouth of
SKN14 were greater than 2 µg/L in April, May, and June and 0.5 µg/L in
September, placing fish in this area at risk for most of the observation
period. After April, estimated aqueous concentrations upstream of the
mouth were less than 0.2 µg/L, suggesting the risk was low for the
majority of the stream for the majority of the study.

Risk in the lightly oiled stream MKS5 was negligible. Embryos and
alevins were probably exposed to less than 0.02 μg/L, well below
concentrations of concern.

**Risk to juvenile salmonids in freshwater and marine environments**

Oil was detected, visually on the beaches and chemically in the passive
samplers, in both the marine environment (5 bays) and the lower reaches
of 4 streams, particularly in the Skan Bay area (Table 1, Appendix 2).
Concentrations were likely highest in the first month of the spill and
greater than when first sampled in March. While oil exposure was evident
in these areas, risk assessment is difficult. In freshwater, overwinter
rearing habitat was contaminated for juvenile coho and Dolly Varden in
two streams and possibly HMP11. We do not know the length of exposure
nor the fidelity to the contaminated sites for these fish. Out migrating
pink salmon would have transited the area from spawning habitat
upstream, but again, the length of exposure would have been relatively
short. Likewise, in the marine environment, we do not know the length of
time outmigrating fry or smolts would have spent transiting and foraging
in the shallow nearshore environment. Exposure to elevated PAH
concentrations was likely in Skan Bay but these life stages are less
susceptible to transient sublethal concentrations than embryos.

Risk to species that utilized the oiled reach of SKN14 for rearing
before emigration (coho and Dolly Varden) was greater than for the
nearly absent pink salmon embryos. Juvenile salmonid growth can be
reduced by aqueous exposure to crude oil and by ingestion of oil
particles or oiled food and high concentrations are lethal (Carls et al.
1996a,b). After the 1989 *Exxon Valdez* oil spill, wild juvenile pink
salmon in PWS were exposed to roughly 1 to 3 μg/L TPAH in saltwater[^7]
and growth was reduced (Wertheimer et al. 1996; Willette et al. 1996;
Short & Harris 1996a,b; Carls et al. 2002). Reduced growth translates
into increased predation and reduced adult returns (Gieger et al. 1996;
Heintz et al. 2000). Comparing the previous rough estimates of aqueous
TPAH concentration in SKN14 to those in PWS suggests juvenile salmonids
in this stream were at risk. Analysis of hydrocarbon body burdens and
CYP1A induction would determine if the fish sampled had been exposed to
oil but cannot demonstrate population effects.

Juvenile salmon in bays affected by the *Selendang Ayu* were potentially
placed at risk. A large volume of water over a very wide area was
apparently affected by the spill, with evidence of oil in marine water
extending to the southern-most reference area (Pumicestone Bay) to
oil-contaminated Makushin Bay. The most affected bay by far was Skan
Bay; TPAH concentrations in Makushin Bay were roughly an order of
magnitude smaller and concentrations in the reference bays were yet
another order of magnitude smaller with little risk in the latter at the
time of sampling. However, concentrations between the time of the spill
and sampling were likely greater than those observed.

**Oil persistence.**

The oil in Skan Bay was persistent; the highest observed TPAH
concentration was in a cove south of SKN14 in September, perhaps a
result of disturbances caused by ongoing shoreline cleanup activities.
Evidence from other spills suggests that not all intertidal oil will be
removed by cleanup activity and that remaining oil will be a persistent
source of biologically available hydrocarbons for many years. Persistent
cryptic patches *Exxon Valdez* oil were present 12 years after the spill
in PWS beaches and remain today (Short et al. 2004). Oil retention in
sediment is consistent with data from other spills, e.g., the *Amoco
Cadiz*, the BIOS experiment, and the West Falmouth spill (Mille et al.
1998; Prince et al. 2002; Reddy et al. 2002; White et al. 2005). The
sticky nature of the bunker oil spilled by the *Selendang Ayu* may
increase persistence, now present more than a year in some beaches. Some
similarly viscous Monterey oil spilled in 1964 remains adherent to PWS
beaches (Kvenvolden et al. 1995; Short et al. 2004).

Not only does oil persist in the environment, but it often remains
biologically available and toxic for many years. Pink salmon embryos
bioaccumulated *Exxon Valdez* oil for at least 3 years in oiled streams
in PWS and mortality was elevated for 4 years (Wiedmer et al. 1996; Bue
et al. 1998). Contaminated prey and disturbance of oiled substrate
during feeding activities explains the failure of sea otter and
harlequin duck populations to recover in oiled areas of PWS for more
than a decade (Esler et al. 2000; Bodkin et al. 2002). For both species,
chronic exposure to oil (elevated cytochrome P4501A) and struggling
populations in the most heavily oiled areas of Prince William Sound were
observed in the decade after the spill (Esler et al. 2000; Bodkin et al.
2002). Salt marsh fiddler crabs (*Uca pugnax*) populations, feeding
rates, and burrowing have been affected by buried oil for greater than
30 years in a West Falmouth marsh (Culbertson et al. 2005). In a review
of seven well-studied oil spills, Teal and Howarth (1984) conclude that
oil effects can persist for at least 6 to 12 years in sediment.

Intuitively, removal of oil from surrounding banks during cleanup should
have reduced aqueous PAH concentrations in stream water, although
temporary increases in bioavailability were anticipated during removal.
However, exponential depletion of biologically available PAH was evident
before oil was removed in SKN14 and there was no abrupt concentration
drop after cleanup. Because PEMDs integrate concentration over time,
failure to observe an abrupt change may be due in part to concentration
averaging and cleanup activity. That may not be the entire story,
however. Some oil may have penetrated into the ground surrounding the
rivers and thus remained after cleanup. Limited visual observation of
slicks weeping from banks after cleanup supports this hypothesis.
Stronger support for the hypothesis and for aqueous transport comes from
an unexpected reversal in TPAH concentration and weathering in SKN14.
Oil in bay water was considerably more weathered than in stream water
between August and September, eliminating marine input as the source of
increased oil in the river. Stream bed disturbance by salmon digging
redds might explain the greater oil mobility and freshness, but only if
there were substantive quantities of oil on stream sediment that had
avoided weathering; this is unlikely. Measurement of PAH in stream
sediment will likely eliminate this possibility. That leaves oil in
surrounding banks as the most likely source of dissolved PAH and
increased fall precipitation as a possible reason for renewed
transportation of fresh oil into the stream: precipitation declined
during deployments in May through August and increased between August
and September (Appendix 3).

## Timing of sampling

With the first sampling in March, peak concentrations in the marine
environment and in oiled streams were missed because concentrations in
the first month of the spill were probably highest in both habitats.
Repeated sampling during the summer months provided a loss rate curve,
indicating stream recovery due to cleaning activity and natural
processes.

The March sampling preceded the emergence of pink salmon fry from the
spawning gravels. The alevins sampled were relatively immature and had
considerable yolk, indicating that peak emergence was probably in late
April at the earliest.

## Summary

In summary, PAH from the *Selendang Ayu* posed a risk to developing pink
salmon embryos and resident fish in 1 of 14 streams sampled and probably
1 of all 19 recognized salmon streams in the affected area. This
conclusion is predicated on correspondence between visual observation of
oil and measured TPAH concentrations, the minimal overlap of spawning
habitat based on observation of spawning habitat and hydraulically
sampled alevins, and limited evidence of oil exposure in these embryos.
Estimated aqueous TPAH concentrations in that stream (SKN14) were
theoretically high enough to have negative impacts on survival and
growth of pink salmon embryos in the oiled zone, although the majority
of the spawning habitat was above the oiled zone. The lower reaches of
stream were generally not suitable for spawning habitat, thus posing
little risk to pink salmon despite the oil contamination. However, this
habitat may have been overwintering habitat for juvenile coho and Dolly
Varden; juveniles were present but assessing risk is difficult without
knowing exposure levels and residence time. Direct analysis of
potentially affected fish tissues may allow confirmation of exposure but
will still not permit an estimate of risk for the population. Estimated
risk to resident fish and embryos in a second, lightly oiled stream was
negligible because estimated aqueous concentrations were below the level
of concern (less than 0.02 ug/L). Risk was very low in 13 other streams
because spawning and rearing habitat did not overlap with oiled areas
and oil was not detected in PEMDs placed where oil was not visible[^8].

Although bioavailable PAH in bays was widely distributed, only the water
of Skan Bay posed a potential risk to emigrant juvenile pink salmon.
Total PAH concentrations were significant in the passive samplers during
the observation period but concentrations were probably higher in the
first months of the spill. Risk to outmigrant smolts and pink salmon fry
from Skan Bay streams is difficult to assess: exposure was probable, but
residence time in the nearshore area is unknown. Contamination levels in
prey are unknown. Overall, we conclude that the *Selendang Ayu* oil
spill placed a relatively small number of salmon at risk. Because PAH
concentrations remained elevated in bays and the most heavily oiled
stream (SKN14) during the final sampling interval, some risk remained at
the end of sampling. However, trends in freshwater salmon habitat and
experience with other spills suggest that the oil concentrations will
decline to background levels; persistence will be dependent primarily on
how much oil is retained by surrounding sediment.

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**Table 1.** Summary TPAH concentrations and composition model scores.
Total PAH concentrations greater than the maximum observed in reference
samples (108 ng/g) are printed in bold type. Model scores and means
greater than 3 are printed in bold type to signify that the PAH source
is consistent with *Selendang Ayu* oil.

Number range CHAPTER

  ----------------- ------------ --------------- -------- --------- --------- ------------- --------- --------- -------
                                 **TPAH                                       **PAH                             
                                 concentration                                composition                       
                                 (ng/g)**                                     model                             
                                                                              results**                         

                                                                                                                

  **stream**        **zone**     **mean**        **se**   **min**   **max**   **mean**      **min**   **max**   **n**

  laboratory blanks blank        8               3        0         18        0.2           0         1         6

  site blanks (all) blank        71              14       21        178       0.9           0         2         14

  references (all)  reference    39              6        6         108       0.7           0         2         23

                                                                                                                

  PMS16             blank        28                                           0.0                               1

                    reference    15              0.5      14        16        0.3           0         1         4

                    intertidal   38                                           1.0                               1

                    bay          **134**         1        132       135       **4.0**       **4**     **4**     2

                                                                                                                

  PMN20             blank        21                                           1.0                               1

                    reference    21              9        6         37        0.3           0         1         3

                    oiled        **589**                                      **4.0**                           1

                    bay          **115**                                      **4.0**                           1

                                                                                                                

  SKN14             blank        78              24       28        140       0.8           0         2         5

                    reference    55              15       23        93        0.6           0         1         5

                    oiled        **58872**       31711    260       463080    **5.2**       **4**     **6**     15

                    bay          **8169**        2149     4150      18278     **6.0**       **6**     **6**     6

                                                                                                                

  SKN14-tributary   reference    55              6        31        67        1.0           1         1         5

                    oiled        **194**         67       42        426       2.8           1         **4**     5

                                                                                                                

  SKN4              blank        56                                           2.0                               1

                    reference    53              27       25        108       1.3           1         2         3

                    oiled        **111**                                      2.0                               1

                    intertidal   **4547**                                     **4.0**                           1

                    bay          **5569**        726      4844      6295      **6.0**       **6**     **6**     2

                                                                                                                

  MKS5              blank        84              24       23        178       0.8           0         2         6

                    reference    23              7        10        35        1.0           1         1         3

                    oiled        **218**         88       16        976       2.6           1         **4**     11

                    bay          **531**         44       382       695       **4.7**       **4**     **6**     6
  ----------------- ------------ --------------- -------- --------- --------- ------------- --------- --------- -------

Table 2. Oil in stream bank sediment. Units are ng/g for all
concentrations, including alkanes, the unresolved complex mixture (UCM),
total polynuclear aromatic hydrocarbons (TPAH), and sum napthalenes
(sNaph), sum fluorenes (sFluor), sum dibenzothiophenes (sDibenz), sum
phenanthrenes (sPhena), sum chrysenes (sChry), and sum higher molecular
weight PAH (sHMW). Site 1 is at the mouth of the stream; site 4 is the
stream reference site (highest elevation); the others are intermediate;
SKN14t is the tributary. Model scores greater than 3 are printed in bold
type to signify that the PAH source is consistent with *Selendang Ayu*
oil.

  ----------- ------------ ---------- ------------- ---------- ---------- ----------- ----------- ------------ ------------- ------------ ----------- ---------- --------------
  **Date**    **Stream**   **Site**   **Alkanes**   **UCM**    **TPAH**   **Model**   **sNaph**   **sFluor**   **sDibenz**   **sPhena**   **sChry**   **sHMW**   **comments**

  3/20/2005   PTN6         \-         27207389      71073584   12186865   **6**       5414293     780213       1475464       3559689      180150      8485       tar ball

  5/16/2005   SKN14        1          116788        2602462    1141       **6**       20.3        53.9         258.6         490.0        96.9        8.0        

  3/19/2005   SKN14        3          155864        560431     89672      **6**       27704.2     8977.6       16058.3       24099.9      3903.3      267.9      

  4/12/2005   SKN14        4          2328          4991       19         0           2.6         0.0          0.0           0.0          0.0         15.9       

  4/13/2005   SKN14t       4          1245          4381       3          0           3.4         0.0          0.0           0.0          0.0         0.0        

  4/14/2005   SKN14t       1          46775         329582     46516      **6**       5379.6      4027.7       9404.1        21642.4      1192.0      162.7      

  3/20/2005   MKS5         1          63            502        13         1           0.0         0.0          5.5           7.4          0.0         0.0        

  3/20/2005   MKS5         1          387032        1159965    132197     **6**       27809.4     14704.0      23742.8       51133.3      3717.9      177.7      tar balls

  4/15/2005   MKS5         2          496072        1516041    179769     **6**       37122.6     17027.6      33870.7       68963.5      5571.9      350.9      

  3/20/2005   MKS5         3          420           5181       126        2           11.0        7.2          31.4          62.6         0.0         0.0        no oil visible

  3/20/2005   MKS5         3          2352302       6831061    727293     **6**       162515.2    61818.5      145927.8      276336.9     22312.2     1240.2     visibly oiled

  3/20/2005   MKS5         4          0             1981       0          0           0.0         0.0          0.0           0.0          0.0         0.0        

  3/20/2005   MKS5         4          133           0          0          0           0.0         0.0          0.0           0.0          0.0         0.0        

  3/16/2005   SKN4         1          64            869        13         1           2.6         1.1          2.9           6.1          0.0         0.0        no oil visible

  3/16/2005   SKN4         1          346440        1127383    94253      **6**       25185.1     11645.0      17807.0       28845.2      3264.5      150.3      visibly oiled

  4/12/2005   SKN4         2          7907          3791       8          0           2.3         0.0          0.0           0.0          0.0         5.8        

  4/13/2005   SKN4         3          7504          4389       1          0           0.0         0.0          0.0           0.0          0.0         0.8        

  4/14/2005   SKN4         4          7354          4690       2          0           1.6         0.0          0.0           0.0          0.0         0.0        

  4/11/2005   PMN20        1          414           3762       7          0           7.1         0.0          0.0           0.0          0.0         0.0        

  4/11/2005   PMN20        2          403           3452       2          0           2.2         0.0          0.0           0.0          0.0         0.0        

  4/11/2005   PMN20        3          229           3287       3          0           3.2         0.0          0.0           0.0          0.0         0.0        

  4/11/2005   PMN20        4          458           3121       0          0           0.0         0.0          0.0           0.0          0.0         0.0        

  4/11/2005   PMS16        1          1373          0          2          0           1.5         0.0          0.0           0.0          0.0         0.0        

  4/11/2005   PMS16        2          380           3          0          0           0.0         0.0          0.0           0.0          0.0         0.0        

  4/11/2005   PMS16        3          500           0          2          0           1.9         0.0          0.0           0.0          0.0         0.0        

  4/11/2005   PMS16        4          2318          3431       7          0           3.9         0.0          0.0           0.0          0.0         2.8        
  ----------- ------------ ---------- ------------- ---------- ---------- ----------- ----------- ------------ ------------- ------------ ----------- ---------- --------------

Table 3. Oil in stream channel sediment. Units are ng/g for all
concentrations, including alkanes, the unresolved complex mixture (UCM),
total polynuclear aromatic hydrocarbons (TPAH), and sum napthalenes
(sNaph), sum fluorenes (sFluor), sum dibenzothiophenes (sDibenz), sum
phenanthrenes (sPhena), sum chrysenes (sChry), and sum higher molecular
weight PAH (sHMW). Site 1 is at the mouth of the stream; site 4 is the
stream reference site (highest elevation); the others are intermediate;
SKN14t is the tributary. Model scores greater than 3 are printed in bold
type to signify that the PAH source is consistent with *Selendang Ayu*
oil.

  ----------- ------------ ---------- ------------- --------- ---------- ----------- ----------- ------------ ------------- ------------ ----------- ----------
  **Date**    **Stream**   **Site**   **Alkanes**   **UCM**   **TPAH**   **Model**   **sNaph**   **sFluor**   **sDibenz**   **sPhena**   **sChry**   **sHMW**

  3/19/2005   SKN14        1          3187.4        31639.1   2328.567   **6**       186.249     249.892      466.906       1053.1       140.315     7.71469

  3/19/2005   SKN14        2          36.0          1034.9    0          0           0           0            0             0            0           0

  3/19/2005   SKN14        3          0.0           171.2     27.49341   1           2.86737     1.73165      5.83503       15.6522      0           0

  3/19/2005   SKN14        4          0.0           0.0       26.51628   0           0           0            0             0            0           26.5163

  3/21/2005   SKN14t       1          0.0           22.7      0          0           0           0            0             0            0           0

  3/19/2005   SKN14t       4          0.0           0.0       0          0           0           0            0             0            0           0

  3/20/2005   MKS5         1          0.0           0.0       0          0           0           0            0             0            0           0

  3/20/2005   MKS5         2          230.9         777.4     0.971498   0           0.9715      0            0             0            0           0

  3/20/2005   MKS5         3          0.0           519.4     0          0           0           0            0             0            0           0

  3/20/2005   MKS5         4          0.0           0.0       0          0           0           0            0             0            0           0

  3/16/2005   SKN4         1          0.0           0.0       0          0           0           0            0             0            0           0

  3/16/2005   SKN4         2          0.0           0.0       0          0           0           0            0             0            0           0

  3/16/2005   SKN4         3          836.9         0.0       0          0           0           0            0             0            0           0

  3/16/2005   SKN4         4          12.7          0.0       0          0           0           0            0             0            0           0

  3/17/2005   PMN20        1          0.0           1575.0    0          0           0           0            0             0            0           0

  3/17/2005   PMN20        2          0.0           103.8     0          0           0           0            0             0            0           0

  3/17/2005   PMN20        3          0.0           1328.0    0          0           0           0            0             0            0           0

  3/17/2005   PMN20        4          59.4          783.7     0          0           0           0            0             0            0           0

  3/18/2005   PMS16        1          0.2           281.0     0          0           0           0            0             0            0           0

  3/18/2005   PMS16        2          0.0           317.0     0          0           0           0            0             0            0           0

  3/18/2005   PMS16        3          0.0           0.0       0          0           0           0            0             0            0           0

  3/18/2005   PMS16        4          0.0           0.0       0          0           0           0            0             0            0           0
  ----------- ------------ ---------- ------------- --------- ---------- ----------- ----------- ------------ ------------- ------------ ----------- ----------

Table 4. Oil in pink salmon alevins. Units are ng/g for all
concentrations, including alkanes, the unresolved complex mixture (UCM),
total polynuclear aromatic hydrocarbons (TPAH), and sum napthalenes
(sNaph), sum fluorenes (sFluor), sum dibenzothiophenes (sDibenz), sum
phenanthrenes (sPhena), sum chrysenes (sChry), and sum higher molecular
weight PAH (sHMW). Site 1 is at the mouth of the stream; site 4 is the
stream reference site (highest elevation); the others are intermediate;
SKN14t is the tributary. Model scores greater than 3 are printed in bold
type to signify that the PAH source is consistent with *Selendang Ayu*
oil.

  ----------- ------------ ---------- ------------- --------- ---------- ----------- ----------- ------------ ------------- ------------ ----------- ----------
  **Date**    **Stream**   **Site**   **Alkanes**   **UCM**   **TPAH**   **Model**   **sNaph**   **sFluor**   **sDibenz**   **sPhena**   **sChry**   **sHMW**

  3/21/2005   SKN14t       1          16427.0       855.2     53.70504   0           53.705      0            0             0            0           0

  3/19/2005   SKN14t       1          14564.7       3584.8    81.33157   1           49.6754     0            7.76996       23.8862      0           0

  3/19/2005   SKN14t       4          10570.1       1521.8    0          0           0           0            0             0            0           0

  3/20/2005   MKS5         2          21704.9       3568.0    0          0           0           0            0             0            0           0

  3/20/2005   MKS5         3          11090.7       5805.2    0          0           0           0            0             0            0           0

  3/20/2005   MKS5         4          10555.4       19235.9   10.62139   0           10.6214     0            0             0            0           0

  3/20/2005   SKN4         4          12096.8       4921.9    2.069591   0           2.06959     0            0             0            0           0

  3/17/2005   PMS16        1          6262.3        13779.6   0          0           0           0            0             0            0           0

  3/18/2005   PMS16        1          11214.6       2651.2    0          0           0           0            0             0            0           0

  3/17/2005   PMS16        2          10006.4       0.0       0          0           0           0            0             0            0           0

  3/17/2005   PMS16        4          12845.6       2831.8    0          0           0           0            0             0            0           0
  ----------- ------------ ---------- ------------- --------- ---------- ----------- ----------- ------------ ------------- ------------ ----------- ----------

[^1]: No salmon escapement data are available for this stream.

[^2]: Similarly long exposure times damaged pink salmon embryos at
    part-per-billion levels (Marty et al. 1997; Heintz et al. 1999,
    2000; Carls et al. 2005). However, experimental exposures began
    shortly after fertilization, whereas any pink salmon embryo exposure
    to Selendang oil began about 3 to 4 months later. The toxicological
    implications of this offset are not known with certainty. Larval
    salmonids may be as sensitive to PAH as embryos if the relationship
    observed in short-term acute bioassays with monoaromatic
    hydrocarbons applies (Moles et al. 1979); more study is needed for
    definitive understanding.

[^3]: This model is included in the combined composition model used for
    source identification in this study.

[^4]: In the laboratory experiment, TPAH concentrations in PEMDs
    deployed 52 d were similar to those in PEMDs deployed 26 d (94%
    retention).

[^5]: At 10 μg/L, the risk of embryonic abnormalities caused by fresh
    oil (as was the case in initial SKN14 samples) is roughly 10% and
    roughly 10% of the embryos may die (Carls et al. 1999; Heintz et al.
    1999). However, growth of pink salmon, measured 6 months after
    exposure, was significantly reduced when exposed to 1 μg/L fresh
    Alaska North Slope crude oil (Carls et al. 2005). Because pink
    salmon rely on rapid growth to escape mortality from size-selective
    predation (Hargreaves and LeBrasseur 1985), such effects can lead to
    depressed marine survival (significant at 5 μg/L; Heintz et al.
    2000).

[^6]: The estimated aqueous TPAH concentration at site 1 in September
    was 0.5 μg/L, slightly above the lowest concentration (0.4 μg/L)
    known to adversely affect fish embryos (Carls et al. 1999); this
    toxicity estimate was based on moderately weathered oil (*w* \~
    3.3).

[^7]: Exact estimates are not available. Total PAHs in mussel tissue
    were analyzed as site-specific surrogates of exposure; mean
    concentrations at oiled sites ranged from 3772 to 8282 ng/g (Carls
    et al. 1996b). Assuming peak concentrations in water and peak
    concentrations in mussels observed in two specific areas where
    mussel and aqueous TPAH data were collected concurrently (Short &
    Harris 1996a,b; Carls et al. 2002) provide a reasonable measure of
    bioaccumulation by PWS mussels (mean 2652 times), then aqueous
    exposure concentrations ranged from about 1.4 to 3.1 µg/L. This
    estimate is within the directly observed range of aqueous TPAH
    concentrations (range of means 0.9 to 6.2 µg/L ) observed elsewhere
    in the slick area in 1989 (Short and Harris 1996a). The derived
    bioaccumulation factor is far lower than theoretically possible in
    mussels (2 × 10^5^; Livingstone 1991); bioaccumulations this high
    would imply aqueous TPAH concentrations less than 0.1 µg/L, i.e.,
    background concentration. This concentration is too low to explain
    the observed significant CYP1A induction in the juvenile pink salmon
    fry in PWS and too low to explain the significant TPAH differences
    in mussel tissue between reference and oiled areas of PWS (Carls et
    al. 1996b, Carls et al. 2005a).

[^8]: Except at the mouth of reference stream PMN20, apparently oiled by
    incursion of marine water.