Columbia Environmental Research Center

Selenium and other trace elements in water, sediment,

aquatic plants, aquatic invertebrates, and fish from streams
in southeastern Idaho near phosphate mining operations:
September 2000.

Final Report as part of the USGS Western U.S. Phosphate Project

May 15, 2003

Prepared by
S.J. Hamilton and K.J. Buhl

U.S. Department of the Interior

U.S. Geological Survey
____________________________________________________________________________________________

U.S. Geological Survey, Columbia Environmental Research Center, Field Research Station, 31247 436th Avenue,
Yankton, SD 57078-6364, steve_hamilton@usgs.gov
 TABLE OF CONTENTS
Page

LIST OF FIGURES ................................................................................................................... ii

LIST OF TABLES..................................................................................................................... ii

LIST OF APPENDICES............................................................................................................ iii

ABSTRACT............................................................................................................................... 2

INTRODUCTION ..................................................................................................................... 2

METHODS AND MATERIALS............................................................................................... 4

Site description............................................................................................................... 4
Sample collection........................................................................................................... 9
Water quality analyses and flow measurement.............................................................. 10
Inorganic element analysis............................................................................................. 10
Statistical analyses ......................................................................................................... 11

RESULTS .................................................................................................................................. 11
Water quality.................................................................................................................. 11
Inorganic element analyses ............................................................................................ 11
Water.............................................................................................................................. 15
Sediment ........................................................................................................................ 15
Aquatic plants ................................................................................................................ 21
Aquatic invertebrates ..................................................................................................... 21
Fish................................................................................................................................. 24
Streams........................................................................................................................... 32

DISCUSSION ............................................................................................................................ 32
Water.............................................................................................................................. 32
Comparison to other Idaho water data ............................................................... 33
Sediment ........................................................................................................................ 33
Comparison to other Idaho sediment data ......................................................... 35
Aquatic plants ................................................................................................................ 35
Comparison to other Idaho aquatic plant data ................................................... 36
Aquatic invertebrates ..................................................................................................... 37
Comparison to other Idaho aquatic invertebrate data ........................................ 39
Fish................................................................................................................................. 39
Comparison to other Idaho fish data.................................................................. 41
Other considerations .......................................................................................... 43
Hazard assessment ......................................................................................................... 44

REFERENCES .......................................................................................................................... 49

i
 LIST OF FIGURES
Page
Figure
1. Diagram of surface water flow from phosphate mine areas (generalized to
25% increments) to drains, creeks, and rivers in southeastern Idaho ............................ 3
2. Map of study area........................................................................................................... 5
3. Map of sample sites ....................................................................................................... 6

LIST OF TABLES
Table
1. Latitude and longitude of nine sites sampled in the Blackfoot River watershed........... 7
2. Water quality characteristics measured by BRD in water from nine sites in the
Blackfoot River watershed............................................................................................. 12
3. Water quality characteristics measured by WRD in water from nine sites in the
Blackfoot River watershed............................................................................................. 13
4. Quality assurance and quality control measures of selenium analysis of water,
sediment, aquatic plants, aquatic invertebrates, and fish from nine sites in the
Blackfoot River watershed............................................................................................. 14
5. Quality assurance and quality control measures of analyses of inorganic elements
in water (W), sediment (S), aquatic plants (P), aquatic invertebrates (I), and fish
(F) from nine sites in the Blackfoot River watershed .................................................... 16
6. Selenium concentrations (µg/L for water and µg/g dry weight for sediment,
aquatic plants, and aquatic invertebrates) in water, sediment, aquatic plants,
and aquatic invertebrates from nine sites in the Blackfoot River watershed................. 18
7. Inorganic element concentrations (µg/L) in water from nine sites in the
Blackfoot River watershed............................................................................................. 19
8. Inorganic element concentrations (µg/g dry weight) in sediment from nine
sites in the Blackfoot River watershed........................................................................... 20
9. Significant (P<0.05) Pearson correlation coefficients for various aquatic
ecosystem components and inorganic elements ............................................................ 22
10. Inorganic element concentrations (µg/g dry weight) in aquatic plants from
nine sites in the Blackfoot River watershed................................................................... 23
11. Inorganic element concentrations (µg/g dry weight) in aquatic invertebrates
from nine sites in the Blackfoot River watershed.......................................................... 25
12. Fish species collected during June (●) and September (○) 2000 from nine
sites in the Blackfoot River watershed........................................................................... 26
13. Selenium concentrations (µg/g dry weight) in whole-body fish from nine
sites in the Blackfoot River watershed........................................................................... 27
14. Inorganic element concentrations (µg/g dry weight) in whole-body fish
from nine sites in the Blackfoot River watershed.......................................................... 28
15. Geometric mean of inorganic element concentrations (µg/g dry weight) in
whole-body fish from nine sites in the Blackfoot River watershed............................... 31
16. Aquatic ecosystem components and selenium concentrations posing various
hazards based on Lemly (1996a) ................................................................................... 45
17. Hazard assessment of selenium at nine sites in the Blackfoot River watershed
using modified scores .................................................................................................... 47

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 LIST OF APPENDICES
Page
Appendix
1. Wet weight (g) of aquatic plant (white-water buttercup Ranunculus
longirostris) from nine sites in the Blackfoot River watershed submitted
for either selenium analysis (Se) or inorganic element analysis (ICP).......................... 58
2. Wet weight (g) of aquatic invertebrates from nine sites in the Blackfoot
River watershed submitted for either selenium analysis (Se) or inorganic
element analysis (ICP) ................................................................................................... 59
3. Total length (mm), weight (g), and use (selenium analysis [Se], inorganic
analysis [ICP], or archive [A]) of fish from nine sites in the Blackfoot
River watershed ............................................................................................................. 60

iii
Abstract
Nine stream sites in the Blackfoot River watershed in southeastern Idaho were sampled
in September 2000 for water, surficial sediment, aquatic plants, aquatic invertebrates, and fish.
Selenium and other inorganic elements were measured in these aquatic ecosystem components,
and a hazard assessment was performed on the data. Water quality characteristics such as pH,
hardness, and specific conductance were relatively uniform among the nine sites examined.
Selenium and several inorganic elements were elevated in water, sediment, aquatic plants,
aquatic invertebrates, and fish from several sites suggesting deposition in sediments and food
web cycling through plants and invertebrates. Selenium was elevated to concentrations of
concern in water at 8 sites (>5 microgram/liter, µg/L), sediment at 3 sites (>2 µg/g), aquatic
plants at four sites (>4 µg/g), aquatic invertebrates at 5 sites (>3 µg/g), and fish at 7 sites (> 4
µg/g in whole body). A hazard assessment of selenium in the aquatic environment suggested
low hazard at Sheep Creek, moderate hazard at Trail Creek, upper Slug Creek, lower Slug Creek,
and lower Blackfoot River, and high hazard at Angus Creek, upper East Mill Creek, lower East
Mill Creek, and Dry Valley Creek. The results of this study are consistent with results of a
previous investigation and indicate that selenium concentrations from the phosphate mining area
of southeastern Idaho were sufficiently elevated in several ecosystem components to cause
adverse effects to aquatic resources in the Blackfoot River watershed.

Introduction
Phosphorus is present in economically mineable quantities in organic-rich black shales of
the Permian Phosphoria Formation, which constitutes the Western Phosphate Field. There are
four active open pit mines (Dry Valley Mine, Smoky Canyon Mine, Enoch Valley Mine,
Rasmussen Ridge Mine) in southeastern Idaho Phosphate District that produce phosphate from
the Meade Peak Phosphatic Shale Member, and 11 inactive mines (Gay Mine, Lanes Creek
Mine, Conda Mine, Henry Mine, Ballard Mine, Mountain Fuel Mine, Champ Mine, North
Maybe Mine, South Maybe Mine, Georgetown Canyon Mine, Wooley Valley Mine) in the
Southeast Idaho Phosphate Resource Area (MW 1999). Most mining of these phosphatic shales
is by open-pit or contour strip surface mining, and waste materials are generally deposited on the
surface in tailings piles, ponds, landfills, and dumps. Many of the waste piles have drainage
systems to move surface water and groundwater away from waste-rock piles. These drainage
systems transfer leachates from mining areas to surface waters, eventually draining into
tributaries, and later, the Blackfoot River and Blackfoot Reservoir. Thus, water movement
releases toxic inorganic elements to aquatic and terrestrial ecosystems.
The Blackfoot River watershed has several active and inactive phosphate mines that
could adversely affect aquatic resources in several tributaries of the Blackfoot River (Figure 1).
As early as 1970-1976 concerns about contamination of the Blackfoot River and its tributaries by
inorganic elements released from phosphate mining were expressed (Platts and Martin 1978).
Recent concerns about the potential impact on aquatic and terrestrial ecosystems from phosphate
mining have been the subject of several reports (MW 1999, 2000, 2001a, 2001b). Several
investigations by the U.S. Geological Survey (USGS) have reported the chemical composition of
weathered and less-weathered strata of the Meade Peak Phosphoatic Shale (e.g., Desborough et
al. 1999, Herring et al. 2000a, 2000b). Other USGS investigations have reported inorganic
element concentrations in aquatic bryophytes and terrestrial plants that were influenced by

2
Figure 1. Diagram of surface water flow (generalized to 25% increments) from phosphate mines to drains, creeks, and rivers in southeastern Idaho. Numbers are
sample locations: 1 Angus Creek, 2 upper East Mill Creek, 3 lower East Mill Creek, 4 Trail Creek, 5 upper Slug Creek, 6 lower Slug Creek, 7 Sheep Creek, 8
Dry Valley Creek, 9 lower Blackfoot River.

Unknown mining activity Upper Slug Creek 5

Mountain Fuel Mine Lower Slug Creek 6
Champ Mine Goodheart Creek
North Maybe Mine East Mill Creek 2 3 Spring Creek
South Maybe Mine French Drain Maybe Creek
Dry Valley Mine Dry Valley Creek 8
25% Rasmussen Ridge Mine
>75% Wooley Valley Mine Angus Creek 1 Blackfoot River 9
75% Enoch Valley Mine (above reservoir)

50% Conda Mine French Drain State Land Creek

75% Rasmussen Ridge Mine Sheep Creek 7
Lanes Creek
Lanes Creek Mine
Unknown mining activity Trail Creek 4
Ballard Mine
Henry Mine Snake River
25% Enoch Valley Mine Little Blackfoot River Blackfoot River
<25% Wooley Valley Mine (mid reservoir)

25% Gay Mine Lincoln Creek Blackfoot River

(below reservoir)
75% Gay Mine Ross Fork Portneuf River
Smoky Canyon Mine Sage Creek
Smoky Canyon Mine Pole Creek Sage Creek Salt River
Georgetown Mine
Georgetown Creek
Montpelier Mine
Diamond Gulch Mine Dry Canyon Creek Bear River Great Salt Lake
50% Conda Mine Formation Creek

3
mining (Herring and Amacher 2001, Herring et al. 2001).
Release of toxic inorganic elements from phosphate mining in southeastern Idaho and
accumulation in the food chain has resulted in adverse biological effects. In recent years, seven
horses in the Dry Valley and Woddall areas were euthanized, and 60-80 sheep died in the
Caribou National Forest on the old Stauffer Mine site due to selenium poisoning according to
toxicologist and veterinarian reports (Caribou County Sun 1999). Twenty-six dead sheep were
found at the south end of Rasmussen Ridge Mine near a spring or seep at an overburden ore site.
Elevated concentrations of selenium and other inorganic elements have been reported in limited
samples of fish fillets and aquatic invertebrates (MW 1999). Recent USGS reports suggest that
selenium concentrations in fish and wildlife were sufficiently elevated to cause adverse effects in
sensitive fish species (Piper et al. 2000, Hamilton et al. 2002).
The purpose of this study was to determine the concentrations of selenium and other
inorganic elements in water, surficial sediment, aquatic plants, aquatic invertebrates, and fish
from streams in southeastern Idaho near phosphate mining operations during the fall, low flow
period. This information was used for comparison with samples from the spring, high flow
period (Hamilton et al. 2002), and in a hazard assessment of the potential effects of selenium and
other inorganic elements on aquatic resources in areas of the Blackfoot River watershed that are
potentially impacted by phosphate mining.

Methods and Materials

Samples of water, surficial sediment, aquatic plants, aquatic invertebrates, and fish were
collected from nine sites in the Blackfoot River watershed located in southeastern Idaho (Figures
2 and 3, Table 1). Sample collection occurred in September 2000 and was a joint effort of the
USGS Water Resources Discipline (WRD), USGS Biological Resources Discipline (BRD), and
the U.S. Forest Service (USFS).

Site description
The collection sites were as follows:
1. The Angus Creek near mouth (ACM) site was located at the crossing of the creek by
Forest Route 095 (USFS map, Caribou National Forest, Montpelier and Soda Springs Districts,
1988), and was approximately a half kilometer (km) above the confluence with the Blackfoot
River. The sampling site was below the active Rasmussen Ridge, inactive Wooley Valley, and
active Enoch Valley mines. The land on either side of the road was managed by the Idaho
Department of Fish and Game and was composed primarily of grassland habitat with sparse
forbs and very limited grazing (no grazing impacts noted). Sample collection was primarily on
the upstream side of the road crossing.
2. The upper East Mill Creek (UEMC) site was located near an unmaintained dirt road
(Forest Route 309) about 2 miles from the intersection of Forest Route 102 and Forest Route
309, and was approximately 8 km above the confluence with the Blackfoot River. The sampling
site was below the inactive North Maybe Mine. The land was owned by the USFS and was
composed of pine forest with some sagebrush in open areas. Sample collection was in a
generally open area of forbs, grass, and spare pine trees with very limited grazing (no grazing
impacts noted).
3. The lower East Mill Creek (LEMC) site was located at the crossing of the creek by

4
Figure 2. Map of study area. Dots are general locations of sample sites. (Map source: modified
from Herring et al. 2001).

5
Figure 3. Map of sample sites: 1 Angus Creek, 2 upper East Mill Creek, 3 lower East Mill Creek, 4
Trail Creek, 5 upper Slug Creek, 6 lower Slug Creek, 7 Sheep Creek, 8 Dry Valley Creek, 9 lower
Blackfoot River. (Map source: Bureau of Land Management, BLM/ID/GI-94/026+421A0 and
BLM/GI-94/026+421A).

6
Table 1. Latitude and longitude of nine sites sampled in the Blackfoot River watershed.

Site name & ID Site1

Angus Creek N42º49’42.24” ±11m

(ACM) W111º20’15.04”

Upper East Mill Creek N42º48’26.74” ±14m

(UEMC) W111º18’38.82”

Lower East Mill Creek N42º48’53.56” ±11m

(LEMC) W111º18’25.98”

Trail Creek N42º45’29.82” ±8m

(TC) W111º26’47.53”

Upper Slug Creek N42º37’50.85” ±14m

(USC) W111º18’20.51”

Lower Slug Creek N42º42’23.79” ±9m

(LSC) W111º22’03.89”

Sheep Creek N42º51’46.92” ±18m

(ShpC) W111º20’00.53”

Dry Valley Creek N42º46’58.71” ±14m

(DVC) W111º22’26.47”

Lower Blackfoot River N42º49’12.49” ±10m

(LBR) W111º33’09.33”
1
Global positioning system: Rockwell International, type HNV-560C, Cedar
Rapids, Iowa (courtesy of Phil Moyle, USGS).

7
Forest Route 102. The site was located approximately 4 km below the upper East Mill Creek
site and about 4 km above the confluence with the Blackfoot River. The sampling site was
below the inactive North Maybe Mine. The site was on private land (Bear Lake Grazing
Company) accessed by landowner permission (Ms. Joan Bunderson). The land on either side of
the road was composed of grass and sagebrush and had moderate grazing (some grazing impacts
noted). Sample collection was about equally distributed upstream and downstream of the road
crossing.
4. The Trail Creek (TC) site was located at the crossing of the creek by Trail Creek Road
(Forest Route 124), and was approximately 8 km above the confluence with the Blackfoot River.
The site was on private land accessed by landowner permission (Mr. Val Bloxham). The
sampling site was not below any mining activity. The land on either side of the road was grazed
grassland. Sample collection was primarily downstream of the crossing in an area with light
grazing, whereas the upstream side of the crossing had moderate to heavy grazing.
5. The upper Slug Creek (USC) site was located about 2 km inside the U.S. Forest
Service boundary on Slug Creek Road (Forest Route 095) and approximately a quarter mile off
the gravel road that paralleled the stream. The site was located above the influence of mining
and >20 km above the confluence with the Blackfoot River. The sampling site was not below
any mining activity. The land was owned by the USFS. The vegetation around the stream was
primarily willow-type shrubs with sparse grass, but there was a substantial amount of sagebrush
and quaking aspen trees nearby. The site had moderate grazing (some grazing impacts noted).
This site was considered the reference site.
6. The lower Slug Creek (LSC) site was located at the intersection of Slug Creek Road
(Forest Route 095) and Old Mill Road (Forest Route 124). The site was in the road right-of-
way, and about 10 km above the confluence with the Blackfoot River. The sampling site was
below the inactive Mountain Fuel Mine. The land around the stream was primarily grassland
and was heavily grazed in one area downstream and lightly grazed in two other areas upstream.
Sample collection was upstream of the heavily grazed area in a stream section with little grazing.

7. The Sheep Creek (ShpC) site was located on private land (Sheep Creek Guest Ranch)
about 3 km upstream of the crossing of the creek by Forest Route 095. The site was accessed
with landowner permission (Mr. Phil Baker). The sampling site was below the active
Rasmussen Ridge Mine. The land along the stream was primarily pine forest with some forbs,
shrubs, and grass. Sample collection for water, sediment, and fish was upstream of most animal
and human activity at the end of a private road and about 2 km above Lanes Creek, which flowed
into the Blackfoot River about 4 km downstream. Aquatic plants and one fish species were
collected about 1.5 km downstream of the primary sample collection site and near the stream
crossing with Forest Route 095 in an area of sagebrush and grass with moderate grazing.
8. The Dry Valley Creek (DVC) site was located on private land (Hunsacker Ranch)
about a half km from Forest Route 122 and accessed along a railroad track that paralleled the
creek. The site was about 0.75 km above the confluence with the Blackfoot River. The
sampling site was below the inactive South Maybe and active Dry Valley mines. The land was
accessed with landowner permission (Mr. and Mrs. Keith Hunsacker). The land along the
stream was primarily grassland with some shrubs nearby and moderate grazing.
9. The lower Blackfoot River (LBR) site was located on county parkland on the
upstream side of a large steel and concrete bridge located on Blackfoot River Road about 0.5 km
east of State Highway 34. The site was located approximately 1 km above the confluence with

8
Blackfoot Reservoir. The sampling site was below all the other sampling sites and several active
and inactive mines (Figure 1). The land was accessed by landowner permission (Caribou County
Commissioner Carol Davids-Moore). The land along the river was primarily riparian with some
grass and light camping.

Sample collection
Samples of water, surficial sediment, aquatic plants, aquatic invertebrates, and fish were
collected at each of nine stream sites. Water sample bottles were conditioned by immersion in
site water three times. Sample container conditioning and sample collection of water collected
by WRD technicians followed procedures of the WRD (USGS 1998). Water samples were
collected using width and depth-integrated sampling techniques. For each sample site, water
was filtered through a 0.45 micrometer (µm) polycarbonate filter using standard sampling
techniques of the WRD (USGS 1998). One water subsample was collected for measurement of
major cations and anions, a second subsample of 200 milliliter (ml) sample of water was
collected in an acid-cleaned polyethylene bottle for analysis of selenium concentrations, a third
subsample collected for analysis of inorganic element concentrations, a fourth subsample for
water quality measures by WRD, and a fifth subsample for water quality measurements by BRD.
Water samples for selenium analysis were acidified with ultrapure hydrochloric acid (HCl) and
those for inorganic elements were acidified with ultrapure nitric acid (HNO3). A reagent blank
was collected for analysis of selenium and inorganic element concentrations, and consisted of
deionized water from a mobile laboratory combined with the acid preservative. All samples for
selenium and other inorganic element analyses were stored frozen.
Two sediment samples were collected at each site using a plastic scoop to gently acquire
surficial sediments including detritus, but not pebbles or plant material. The scoop and acid-
cleaned sample container were rinsed in ambient water for sufficient time to condition the
equipment to ambient conditions prior to sample collection. After sediments settled, excess
water was discarded and the sample stored frozen. One sample was used for analysis of
selenium concentration, and a second sample used for analysis of inorganic element
concentrations.
Submerged aquatic plants (white-water buttercup, Ranunculus longirostris) were
collected from each site, except lower East Mill Creek, Trail Creek, and Dry Valley Creek. At
lower East Mill Creek over 30 meters of stream were searched, but no white-water buttercup was
found, so a filamentous green algae was collected. Similar search effort was accomplished at
Trail Creek and Dry Valley Creek, but no white-water buttercup was found, so watermilfoil
(Myriophyllum) was collected. Plants were collected by hand. The sample consisted of leaf
whorls removed from stems using plastic or stainless steel forceps. Two plant samples were
collected from each site, squeezed to remove excess water, weighed, bagged in Whirl-Pak bags,
labeled, and stored frozen. One composite sample was analyzed for selenium concentration and
the other sample analyzed for inorganic element concentrations.
Aquatic invertebrates were sieved from bed substrate materials collected either by D-
frame kick nets or by removing large stones with attached invertebrates. Substrate was placed in
large polypropylene trays and invertebrates separated from substrate using forceps or glass tubes
with suction bulbs. Invertebrate samples were separated by taxa group, and weighed by taxa
group. One half of the weight of each taxa group was combined as a composite invertebrate
sample. One composite sample was analyzed for selenium concentration and the other sample
analyzed for inorganic element concentrations.

9
 Fish were collected by electrofishing with a Coffelt Mark-10 electroshocker provided and
operated by the USFS, Caribou National Forest, Soda Springs, ID. The anode and cathode
wands were rinsed in ambient water for sufficient time to condition the equipment to ambient
conditions. Fish samples were collected from each site, euthanized with MS-222 (tricaine
methanesulfonate), identified to species, measured for total length and weight, bagged in Whirl-
Pak bags, labeled with identification information, and stored frozen. When possible, one or
more fish of each species from each site was analyzed for selenium concentrations in whole body
and other fish of the same species from the same site analyzed for inorganic element
concentrations in whole body. A specimen of some species was retained to confirm
identification. Year class information was not collected on fish.

Water quality analyses and flow measurement

Water samples (~1L) at each site were collected by WRD technicians and analyzed for
general water quality characteristics in a mobile laboratory according to standard methods
(APHA et al. 1995). Site water was analyzed in situ for the following general water quality
characteristics: conductivity, pH, temperature, dissolved oxygen, and percent saturation of
dissolved oxygen concentration. Flow measurements were taken following WRD techniques
(USGS 1998).
Immediately after arrival of the site water at the mobile laboratory, the following water
quality characteristics were measured: conductivity, pH, alkalinity, hardness, calcium,
magnesium, and temperature. A subsample of 200 ml water was collected and stored at 4ºC with
no preservative, and transported to the Columbia Environmental Research Center Field Research
Station (FRS), Yankton, SD, for analysis of sulfate and chloride. A second subsample of 125 ml
water was collected, acidified with 0.5 ml concentrated sulfuric acid (H2SO4), and transported to
Yankton for analysis of ammonia concentrations. All water quality characteristics were
measured according to standard methods (APHA et al. 1995), except ammonia and chloride.
Ammonia was measured using ion-selective electrodes and following the procedures for low
concentration measurements of the electrode manufacturer (Orion Research 1990, 1991, ATI
Orion 1994). Chloride was measured by the mercuric nitrate titration method (Hach Company
1997).
WRD technicians also collected and measured water quality characteristics as part of
WRD water sample collection efforts (pH, conductivity, alkalinity, bicarbonate, carbonate,
dissolved oxygen, percent oxygen saturation, and water temperature). This duplication of effort
allowed the Yankton FRS to cross check measurement analyses of water quality characteristics
collected in the field.

Inorganic element analysis

Water, surficial sediment, aquatic plants, aquatic invertebrates, and fish were analyzed
for selenium concentrations by atomic absorption spectroscopy graphite furnace (AA-GF) at the
Research Triangle Institute (RTI), Research Triangle Park, NC. Analyses incorporated
appropriate quality assurance/quality control (QA/QC) procedures such as standardizing
equipment with certified reference material, determination of limit of detection, analysis of
reagent blanks, duplicate samples, certified reference materials, and spiked samples. Analysis of
selenium concentrations was based on U.S. Environmental Protection Agency (USEPA) method
7740 (USEPA 1983). Results were reported on a dry weight basis for sediment, aquatic plants,
aquatic invertebrates, and fish.

10
 Water, surficial sediment, aquatic plant, aquatic invertebrate, and fish samples were
analyzed for inorganic element concentrations (aluminum, arsenic, barium, beryllium, boron,
cadmium, chromium, copper, iron, lead, magnesium, manganese, molybdenum, nickel,
strontium, vanadium, and zinc) by inductively-coupled plasma (ICP) spectrophotometry.
Analyses were conducted by the RTI and incorporated appropriate QA/QC described above.
Analysis of inorganic elements by ICP was based on USEPA method 6020 (USEPA 1983),
except arsenic analysis which was method 7060A (USEPA 1983). Results were reported on a
dry weight basis for sediment, aquatic plant, aquatic invertebrate, and fish samples.

Statistical analyses
Data were analyzed (SAS 2002) to determine the relation among various measures made
during the study. Pearson correlation analyses tested for relations among water quality
characteristics, and selenium concentrations in water, sediments, aquatic plants, aquatic
invertebrates, and fish. For fish residue data for each sample location, the geometric mean was
used in correlation analyses with other variables.
The nonparametric Freidman test (Conover 1980) ranked the streams from highest
inorganic concentrations to lowest for each ecosystem component (water, sediment, plant,
invertebrate, and fish). Significant differences (P=0.05) among streams were determined with
Freidman’s multiple comparison test.

Results
Water quality
Water quality characteristics measured by BRD are given in Table 2 and those measured
by WRD were given in Table 3. The measurements for pH, conductivity, and alkalinity were
similar between the two groups. Correlation coefficients for the two measures for pH were
r=0.98 (P<0.0001, n=9), conductivity r=0.99 (P<0.0001, n=9), and alkalinity r=0.96 (P<0.0001,
n=9).
In general, Dry Valley Creek had the highest conductivity, hardness, calcium, and sulfate
concentrations of the nine sites examined. The other stream sites had similar water quality
characteristics to each other, except that sulfate was greater at Angus Creek and lower at upper
Slug Creek than most other sites. The nine sites were well oxygenated at the time of sampling.

Inorganic element analyses

The results of QA/QC sample analysis by AA-GF for selenium concentrations are given
in Table 4. The QA/QC results were within acceptable ranges, except that the percent relative
standard for aquatic invertebrate samples was 17%, which was higher than normal, i.e., ~10%.
Analysis of the procedure blank indicated no contamination from reagents or sample handling;
duplicate sample preparation and analysis indicated consistent sample handling during
preparation, digestion, and analysis; recovery of certified material indicated the digestion and
analysis procedure accurately measured selenium concentrations; and recovery of samples
spiked before digestion indicated the digestion procedure did not alter the amount of spiked
selenium in the sample, i.e., suggested no loss of selenium during digestion.

11
Table 2. Water quality characteristics measured by BRD in water from nine sites in the Blackfoot River watershed. Number of samples [n] in brackets. If n>1,
water quality measure is the mean; <: indicates below limit of measurement.

1
Site
Measure ACM UEMC LEMC TC USC LSC ShpC DVC LBR

pH 8.6 8.3 8.4 8.7 8.3 8.1 8.3 8.1 8.0

[2] [1] [1] [1] [2] [1] [2] [1] [1]

Conductivity 404 352 349 359 421 369 371 511 443
(µmhos/cm) [1] [1] [1] [1] [1] [1] [1] [1] [1]

Hardness 205 178 178 180 212 177 192 262 231
(mg/L as CaCO3) [2] [1] [1] [1] [2] [1] [2] [1] [1]

Calcium 62 52 52 54 62 47 58 75 59
(mg/L) [2] [1] [1] [1] [2] [1] [2] [1] [1]

Magnesium 12 12 12 11 14 14 12 18 20
(mg/L) [2] [1] [1] [1] [2] [1] [2] [1] [1]

Alkalinity 178 177 176 176 217 168 192 212 222
(mg/L as CaCO3) [2] [1] [1] [1] [2] [1] [2] [1] [1]

Chloride 4.9 1.6 1.6 5.9 4.2 7.5 2.1 7.2 3.2
(mg/L) [1] [1] [1] [1] [2] [1] [2] [1] [1]

Sulfate 22.5 7.6 7.7 9.1 <6.0 12.6 7.1 52.5 12.6
(mg/L) [1] [1] [1] [1] [2] [1] [1] [1] [1]

Total ammonia <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01
(mg/L as N) [1] [1] [1] [1] [1] [1] [1] [1] [1]

1
ACM: Angus Creek, UEMC: upper East Mill Creek, LEMC: lower East Mill Creek, TC: Trail Creek, USC: upper Slug Creek, LSC: lower Slug Creek,
DVC: Dry Valley Creek, ShpC: Sheep Creek, LBR: lower Blackfoot River.

12
Table 3. Water quality characteristics measured by WRD in water from nine sites in the Blackfoot River watershed. n=1.

1
Site
Measure ACM UEMC LEMC TC USC LSC ShpC DVC LBR

pH 8.7 8.2 8.5 8.8 8.4 8.0 8.3 8.0 7.8

Conductivity 394 347 344 343 413 357 366 504 440
(µmhos/cm)

Alkalinity 182 176 182 160 211 156 194 196 219
(mg/L as CaCO3)

Bicarbonate 207 200 198 185 257 190 237 240 267
(mg/L)

Carbonate 7.3 7.3 12.2 4.9 - - - - -

(mg/L)

Dissolved oxygen 7.3 9.2 9.3 10.9 9.4 8.2 9.2 8.5 9.7
(mg/L)

% Saturation 146 98 103 149 96 108 96 106 123

dissolved oxygen

Water temperature 17.0 7.6 10.8 19.0 6.1 16.8 6.7 14.5 16.1
(°C)

Discharge (cfs) 0.36 1.36 0.56 1.96 0.56 1.02 2.67 0.41 50

1
ACM: Angus Creek, UEMC: upper East Mill Creek, LEMC: lower East Mill Creek, TC: Trail Creek, USC: upper Slug Creek, LSC: lower Slug Creek,
DVC: Dry Valley Creek, ShpC: Sheep Creek, LBR: lower Blackfoot River.

13
Table 4. Quality assurance and quality control measures of selenium analysis of water, sediment,
aquatic plants, aquatic invertebrates, and fish from nine sites in the Blackfoot River
watershed. n=1 for water, sediment, plant, invertebrate; n=2 for fish (mean and
standard error in parentheses).

Ecosystem component
Aquatic Aquatic
Measure Water Sediment Plant Invertebrate Fish

Limit of 5 0.5 0.5 0.5 0.5

detection
(LOD)
(µg/L or
µg/g)

Procedural <LOD <LOD <LOD <LOD <LOD

blank

% RSD1 0.4 2 1 17 4 (4)

% Recovery 1032 1013 NG4,5 1176 90 (4)6

of reference
material

% Recovery 105 100 93 96 118 (5)

of digested
spike
1
%RSD: percent relative standard deviation.
2
Leeman Labs commercial standard solution (lot number 387201).
3
National Institute of Standards and Technology (NIST) standard reference material 2709 (San
Joaquin soil; 1.57 µg/g).
4
NG: not given.
5
NIST standard reference material 1547 (peach leaves, 0.12 µg/g).
6
National Resource Council of Canada standard reference material TORT-2 (lobster
hepatopancreas; 5.63 µg/g).

14
 The results of QA/QC sample analyses by ICP for inorganic element concentrations are
given in Table 5. In general the LOD, procedural blanks, relative standard deviation of duplicate
preparation and analysis, and spike recoveries were comparable to those in the selenium
analyses. Percent relative standard deviations were elevated (i.e., >30%) in sediments for boron,
in invertebrates for arsenic and vanadium, and in fish for chromium, nickel and vanadium (Table
5). Measurement of inorganic elements in reference materials (% recovery of reference material)
was outside the normal range of recovery (i.e., ~80 to ~120%) in sediments for aluminum,
barium, cadmium, lead, strontium and vanadium, in invertebrates for chromium and lead, and in
fish for chromium (Table 5). Measurement of recovery of spiked elements in samples was
outside the normal range of recovery (i.e., ~80% to ~120%) in plants for arsenic and boron, in
invertebrates for copper, and in fish for lead and nickel (Table 5). There was no consistent
pattern for percent relative standard deviations, percent recovery of reference material, or percent
recovery of digested spikes. In general, concentrations of inorganic elements were relatively
low, which may have contributed to the variability in the analysis of duplicate samples.

Water
The selenium concentration in water from the lower Blackfoot River was less than the
LOD (<5 µg/L), relatively low (5-8 µg/L) at six other sites, but substantially elevated at upper
and lower East Mill Creek (Table 6). Concentrations of inorganic elements in water were
generally similar among the nine sites (Table 7). Although upper and lower East Mill Creek
water contained elevated selenium concentrations, they were not among the highest in other
inorganic element concentrations, except for strontium. Relative to the other sites, Dry Valley
Creek water contained elevated lead, manganese, and zinc, Sheep Creek water contained
elevated aluminum, iron, and zinc, Trail Creek water contained elevated vanadium, and Angus
Creek water contained elevated boron and copper. However, based on the Friedman test, there
was no significant difference among streams in the ranking of inorganic element concentrations
in water (with selenium in dataset). In contrast, there were clear differences among streams
based on selenium concentrations alone.

Sediment
Selenium concentrations in surficial sediment were relatively low at six sites (<2 µg/g),
moderately elevated at Dry Valley Creek (3.0 µg/g), and very elevated at upper and lower East
Mill Creek (32-39 µg/g) (Table 6). Angus Creek and Trail Creek sediment contained the lowest
selenium concentrations in surficial sediment.
Concentrations of inorganic elements in surficial sediments followed a similar pattern as
selenium in sediments (Table 8). Upper and lower East Mill Creek sediment contained the
highest concentrations of chromium, copper, molybdenum, and vanadium, and second highest
concentrations of cadmium, nickel, and zinc. Dry Valley Creek sediment contained the highest
concentrations of barium, cadmium, manganese, nickel, and zinc, and the second highest
concentrations of chromium, copper, iron, lead, and vanadium. Angus Creek sediment contained
the highest concentrations of aluminum and iron, second highest manganese, and the third
highest barium, lead, nickel, vanadium, and zinc, thus suggesting some contamination by
inorganic elements. The remaining five sites contained relatively similar concentrations of
inorganic elements.

15
Table 5. Quality assurance and quality control measures of analyses of inorganic elements in water (W), sediment (S),
aquatic plants (P), aquatic invertebrates (I), and fish (F) from nine sites in the Blackfoot River watershed. n=1
for water, sediment, aquatic plants, and aquatic invertebrates; n=2 for fish (mean and standard error in
parentheses); all procedural blanks less than limit of detection.

LOD1 % RSD2
W S P I&F
Element (µg/L) (µg/g) (µg/g) (µg/g) W S P I F

Aluminum 10 100 20 5 <LOD 12 20 23 15 (4)

Arsenic 5 1 0.5 1 0 10 5 57 8 (6)
Barium 1 1 0.2 0.5 0 2 4 28 6 (4)
Beryllium 1 0.2 0.2 0.1 <LOD 8 <LOD <LOD <LOD
Boron 10 1 1 2 <LOD 33 12 16 8 (-)
Cadmium 1 0.1 0.1 0.1 <LOD 1 3 25 6 (-)
Chromium 3 1 0.5 0.5 <LOD 13 0 21 39 (31)
Copper 6 1 0.5 0.5 <LOD 6 12 1 4 (1)
Iron 20 100 20 5 <LOD 5 14 22 14 (8)
Lead 7 1 0.5 0.5 0.4 8 17 <LOD <LOD
Magnesium 50 50 20 5 0 9 2 <1 4 (2)
Manganese 5 2 2 0.5 <LOD 2 2 8 8 (7)
Molybdenum 2 0.5 0.5 0.5 <LOD 6 5 <LOD <LOD
Nickel 6 0.5 0.5 0.5 <LOD 4 11 11 65 (44)
Strontium 5 0.5 0.5 0.5 0.4 4 1 11 7 (1)
Vanadium 5 0.5 0.3 0.5 0 9 6 34 36 (27)
Zinc 10 2 2 0.5 10 8 1 6 3 (0)

16
 Table 5. Continued.

% Recovery of reference material % Recovery of digested spike

3
Element W S4 P5 I6 F6 W S P I F

Aluminum 101 45 93 NG7 NG 91 NG NG 84 104 (6)

Arsenic 103 79 NG 108 109 (0) 97 96 149 108 112 (14)
Barium 102 40 85 NG NG 102 114 97 88 95 (6)
Beryllium 104 NG NG NG NG 104 108 121 90 91 (-)
Boron 96 NG 95 NG NG 94 82 160 95 100 (2)
Cadmium 98 242 NG 94 88 (8) 105 105 77 86 92 (6)
Chromium 91 89 NG 287 238 (-) 99 109 77 85 88 (8)
Copper 94 94 102 99 99 (13) 99 104 79 63 98 (6)
Iron 100 101 95 85 81 (5) 102 NG 96 80 96 (4)
Lead 106 68 100 163 NG 104 107 90 87 74 (22)
Magnesium 103 109 101 NG NG 102 NG NG 74 106 (8)
Manganese 96 103 85 82 83 (2) 98 NG NG NG 92 (1)
Molybdenum 92 NG NG 106 83 (6) 99 91 111 92 94 (2)
Nickel 101 94 123 107 92 (4) 98 110 90 91 75 (23)
Strontium 94 45 97 84 84 (2) 97 107 123 96 96 (2)
Vanadium 100 61 90 121 98 (8) 98 104 113 93 96 (3)
Zinc 97 90 108 96 90 (8) 96 115 95 82 94 (2)
1
LOD: Limit of detection.
2
%RSD: percent relative standard deviation.
3
Leeman Labs commercial standard solution (lot number 387201).
4
National Institute of Standards and Technology (NIST) standard reference material 2709 (San Joaquin soil).
5
NIST standard reference material 1547 (peach leaves).
6
National Resource Council of Canada standard reference material TORT-2 (lobster hepatopancreas).
7
NG: not given.

17
 Table 6. Selenium concentrations (µg/L for water and µg/g dry weight for sediment, aquatic plants, and aquatic invertebrates)
in water, sediment, aquatic plants, and aquatic invertebrates from nine sites in the Blackfoot River watershed. n=1;
<: less than limit of detection.

Ecosystem Site1
component ACM UEMC LEMC TC USC LSC ShpC DVC LBR

Water 6 24 24 5 7 6 8 8 <5

Sediment 1.0 32.2 38.9 1.2 1.8 1.7 1.5 3.0 1.8

Aquatic plant 2.0 30.3 25.72 1.73 1.6 1.7 1.2 4.43 5.8

Aquatic 6.7 26.9 75.2 <0.5 0.5 <0.5 1.9 12.8 7.7
invertebrate
1
ACM: Angus Creek; UEMC: upper East Mill Creek; LEMC: lower East Mill Creek; TC: Trail Creek; USC; upper Slug
Creek; LSC: lower Slug Creek; DVC: Dry Valley Creek: ShpC: Sheep Creek; LBR: lower Blackfoot River.
2
Filamentous green algae.
3
Watermilfoil (Myriophyllum).

18
Table 7. Inorganic element concentrations (µg/L) in water from nine sites in the Blackfoot River watershed. n=1; <: less than
limit of detection.

Site1
Element ACM UEMC LEMC TC USC LSC ShpC DVC LBR

Aluminum <10 <10 <10 <10 <10 <10 239 11 <10

Arsenic 15 12 11 <5 17 11 14 10 <5
Barium 28 20 21 51 78 38 67 42 50
Beryllium <1 <1 <1 <1 <1 <1 <1 <1 <1
Boron 39 26 <10 <10 30 <10 <10 <10 <10
Cadmium <1 <1 <1 <1 <1 <1 <1 <1 <1
Chromium <3 <3 <3 <3 <3 <3 <3 <3 <3
Copper 19 11 <6 <6 10 <6 <6 <6 <6
Iron <20 <20 <20 23 <20 <20 55 <20 <20
Lead 10 18 10 14 19 20 8 26 12
Magnesium 12,200 11,800 11,400 11,400 14,700 14,600 12,700 15,200 20,800
Manganese 48 <5 <5 35 17 85 13 200 12
Molybdenum <2 <2 <2 <2 <2 <2 <2 <2 <2
Nickel <6 <6 <6 <6 <6 <6 <6 <6 <6
Strontium 190 239 235 143 150 226 113 160 224
Vanadium 6 5 5 14 8 7 6 8 9
Zinc 11 10 10 12 11 10 30 17 10
1
ACM: Angus Creek; UEMC: upper East Mill Creek; LEMC: lower East Mill Creek; TC: Trail Creek; USC; upper Slug
Creek; LSC: lower Slug Creek; DVC: Dry Valley Creek: ShpC: Sheep Creek; LBR: lower Blackfoot River.

19
Table 8. Inorganic element concentrations (µg/g dry weight) in sediment from nine sites in the Blackfoot River watershed.
n=1; <: less than limit of detection.

Site1
Element ACM UEMC LEMC TC USC LSC ShpC DVC LBR

Aluminum 19,800 11,600 11,200 11,800 11,600 9,730 16,800 19,000 13,200
Arsenic 4.1 4.3 3.9 2.0 5.1 1.8 3.7 3.6 2.8
Barium 229 100 111 150 157 97 237 240 169
Beryllium 1.0 0.6 0.6 0.8 0.7 0.5 1.1 1.0 0.6
Boron 63 60 63 85 52 66 59 65 93
Cadmium 3.2 8.3 6.3 1.4 4.5 2.0 1.3 13.9 1.5
Chromium 30 67 61 19 28 21 23 41 20
Copper 16 25 22 11 14 8 16 18 11
Iron 25,400 15,800 15,700 15,400 14,400 10,890 20,600 25,100 17,800
Lead 16 10 9 11 12 10 18 17 13
Magnesium 6,150 4,900 4,630 4,160 3,480 3,250 6,000 5,330 6,010
Manganese 3,210 1,280 1,390 1,310 550 540 1,350 6,630 940
Molybdenum 0.6 3.0 2.3 0.9 0.5 <0.5 <0.5 0.7 0.6
Nickel 29 57 53 15 23 12 24 76 16
Strontium 51 99 80 53 44 133 42 44 115
Vanadium 34 68 58 18 21 17 26 41 20
Zinc 138 254 245 67 116 65 92 765 90
1
ACM: Angus Creek; UEMC: upper East Mill Creek; LEMC: lower East Mill Creek; TC: Trail Creek; USC; upper Slug
Creek; LSC: lower Slug Creek; DVC: Dry Valley Creek: ShpC: Sheep Creek; LBR: lower Blackfoot River.

20
 Based on the Freidman test, the streams were ranked from highest inorganic element
concentrations in sediment (with selenium in dataset) to lowest as follows (streams with lower
case letters in common are not significantly different at P=0.05): DVCa, ACMab, UEMCab,
LEMCab, ShpCbc, LBRbc, USCc, TCcd, LSCd. Based on selenium concentrations alone, the
streams from highest concentration to lowest were: LEMC, UEMC, DVC, LBR, USC, LSC,
ShpC, TC, ACM. Major disparities in order between the two approaches occurred for lower and
upper East Mill Creek and Angus Creek.
Significant correlation coefficients were found between concentrations of inorganic
elements in sediment and water for manganese, selenium, and strontium (Table 9).

Aquatic plants
Selenium concentrations in aquatic plants were low at Sheep Creek, upper and lower
Slug Creek, Trail Creek, and Angus Creek (1.2-2.0 µg/g); moderately elevated at the Dry Valley
Creek and lower Blackfoot River (4.4-5.8 µg/g); and very elevated at the upper and lower East
Mill Creek (26-30 µg/g) (Table 6). Filamentous green algae collected at lower East Mill
contained 25.7 µg/g selenium, which was similar to that in white-water buttercup collected at
upper East Mill Creek (30.3 µg/g). The pattern of selenium concentrations in aquatic plants was
consistent with selenium concentrations in surficial sediment and water, and resulted in
significant correlation coefficients (Table 9).
Concentrations of inorganic elements in aquatic plants followed a somewhat similar
pattern as selenium in surficial sediments (Table 10). East Mill Creek plants contained the
highest concentrations of arsenic, barium, cadmium, chromium, copper, nickel, vanadium, and
zinc, whereas Dry Valley Creek plants contained an intermediate amount of these elements
relative to East Mill Creek and the other seven sites. In general, aquatic plants from Sheep
Creek and Trail Creek contained low inorganic element concentrations compared to the other
sites. Upper Slug Creek, the reference site, contained higher concentrations of aluminum,
barium, cadmium, chromium, iron, lead, manganese, and zinc in aquatic plants than observed at
Sheep Creek.
Based on the Freidman test, the streams were ranked from highest inorganic element
concentrations in aquatic plants (with selenium in dataset) to lowest as follows (streams with
lower case letters in common are not significantly different): LSCa, DVCa, UEMCa, LEMCa,
LBRa, USCa, TCab, ACMab, ShpCb. Based on selenium concentrations alone, the streams from
highest concentration to lowest were: UEMC, LEMC, LBR, DVC, ACM, LSC, TC, USC, ShpC.
The only major disparity in order between the two approaches was for lower Slug Creek.
Significant correlations were observed for inorganic element concentrations in aquatic
plants and water for magnesium, and in aquatic plants and surficial sediments for chromium,
manganese, nickel, and zinc (Table 9).

Aquatic invertebrates
Selenium concentrations in aquatic invertebrates followed a similar pattern as those in
sediment: low at Trail Creek, upper and lower Slug Creek, and Sheep Creek (<0.5-1.9 µg/g),
moderately elevated at Angus Creek, lower Blackfoot River, and Dry Valley Creek (6.7-12.8
µg/g), and highly elevated at upper and lower East Mill Creek (27-75 µg/g) (Table 6).
The correlation coefficient between selenium concentrations in aquatic invertebrates was

21
Table 9. Significant (P<0.05) Pearson correlation coefficients for various aquatic ecosystem components and inorganic elements
(standard symbols in table).

Inorganic element
Ecosystem component As Cd Cr Cu Mg Mn Ni Se Sr V Zn
Water
Sediment 0.85 0.99 0.82
Aquatic plant 0.74 0.99
Aquatic invertebrate 0.83
Fish 0.91 -0.70

Sediment
Aquatic plant 0.71 0.87 0.74 0.97 0.74
Aquatic invertebrate 0.84 0.78 0.89 0.80
Fish 0.96

Aquatic plant
Aquatic invertebrate 0.97 0.80 0.87 0.78 0.76
Fish 0.88 0.87

Aquatic invertebrate
Fish -0.84 0.90 0.98

22
Table 10. Inorganic element concentrations (µg/g dry weight) in aquatic plants from nine sites in the Blackfoot River
watershed. n=1; <: less than limit of detection.

Site1
2 3
Element ACM UEMC LEMC TC USC LSC ShpC DVC3 LBR

Aluminum 1,290 1,040 3,490 4,140 14,300 5,380 1,560 3,120 5,790
Arsenic 1 1 2 1 1 1 1 1 1
Barium 239 23 3,120 274 174 192 105 571 133
Beryllium <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2
Boron 12 12 5 12 15 17 6 18 15
Cadmium 2 40 11 1 4 1 1 4 2
Chromium 1 8 8 2 4 5 1 1 2
Copper 1 4 2 1 1 2 2 1 1
Iron 870 810 2,580 2,840 8,650 3,264 1,010 2,800 4,210
Lead 1 1 1 2 6 2 1 1 3
Magnesium 4,360 3,270 2,830 2,840 4,160 3,980 2,390 5,050 5,050
Manganese 12,400 990 250 6,890 5,850 8,690 860 26,100 6,400
Molybdenum <0.5 1 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5
Nickel 3 8 5 2 2 4 3 5 2
Strontium 181 60 30 104 48 113 81 58 68
Vanadium 1 4 4 3 3 4 2 3 2
Zinc 25 330 150 25 97 38 18 301 142
1
ACM: Angus Creek; UEMC: upper East Mill Creek; LEMC: lower East Mill Creek; TC: Trail Creek; USC;
upper Slug Creek; LSC: lower Slug Creek; DVC: Dry Valley Creek: ShpC: Sheep Creek; LBR: lower Blackfoot River.
2
Filamentous green algae.
3
Watermilfoil (Myriophyllum).

23
significant with water, surficial sediment, and aquatic plants (Table 9). Selenium concentrations
in aquatic invertebrates were distributed somewhat evenly across sites, whereas selenium
concentrations in sediments and aquatic plants were not (5-6 low values and 2 high values), thus
the correlations were probably dominated by elevated selenium concentrations in sediment and
aquatic plants at the upper and lower East Mill Creek and Dry Valley Creek sites (Table 6).
Concentrations of inorganic elements in aquatic invertebrates from the nine sites
followed a similar pattern as found in surficial sediments and aquatic plants (Table 11). Low
concentrations of inorganic elements occurred in aquatic invertebrates from Sheep Creek and
Trail Creek, moderate concentrations in Angus Creek, upper and lower Slug Creek, and lower
Blackfoot River, and elevated concentrations in upper and lower East Mill Creek and Dry Valley
Creek. East Mill Creek invertebrates contained the highest concentrations of aluminum, boron,
cadmium, chromium, iron, vanadium, and zinc. Dry Valley Creek invertebrates contained the
highest concentrations of manganese, molybdenum, nickel, and zinc.
Based on the Freidman test, the streams were ranked from highest inorganic element
concentrations in aquatic invertebrates (with selenium in dataset) to lowest as follows (streams
with lower case letters in common are not significantly different): DVCa, ACMa, UEMCa, LBRa,
LEMCa, LSCa, USCa, TCbc, ShpCc. Based on selenium concentrations alone, the streams from
highest concentration to lowest were: LEMC, UEMC, DVC, LBR, ACM, ShpC, USC, TC, LSC.
The disparities in order between the two approaches occurred for Angus Creek, lower East Mill
Creek, and Sheep Creek.
Significant correlations were observed for inorganic element concentrations in aquatic
invertebrates and surficial sediments for chromium, manganese, and vanadium (Table 9). There
also were significant correlations for inorganic elements between aquatic invertebrates and
aquatic plants for cadmium, chromium, manganese, and zinc (Table 9).

Fish
Fish collected included cutthroat trout (Oncorhynchus clarki), brook trout (Salvelinus
fontinalis), mottled sculpin (Cottus bairdi), longnose dace (Rhinichthys cutaractae), speckled
dace (Rhinichthys osculus), and redside shiner (Richardsonius balteatus) (Table 12). No one
fish species was collected at all nine sites. Mottled sculpin were collected at seven sites,
speckled dace at six sites, and cutthroat trout at five sites (Table 12). Trout at upper East Mill
Creek contained the highest whole-body selenium concentrations, and speckled dace contained
the second highest whole-body selenium concentrations of the species collected (Table 13).
Redside shiner were collected from only four sites, and contained the lowest whole-body
selenium concentrations of the species collected, except at lower Slug Creek. Geometric mean
selenium concentrations in fish ranged from 2.7 µg/g at Sheep Creek to 52.3 µg/g at lower East
Mill Creek (Table 13).
Significant correlation coefficient were observed for selenium concentrations in the
combined fish data for six species with water, sediment, aquatic plants, and aquatic invertebrates
(Table 9).
Few inorganic elements other than selenium were elevated in whole-body fish from the
nine sites (Table 14). The few elements elevated in fish were primarily in speckled dace,
whereas the lowest inorganic element concentrations tended to occur in redside shiner. No site
seemed to have fish with consistently elevated inorganic elements based on geometric means
(Table 15).

24
Table 11. Inorganic element concentrations (µg/g dry weight) in aquatic invertebrates from nine sites in the Blackfoot
River watershed. n=1; <: less than limit of detection.

Site1
Element ACM UEMC LEMC TC USC LSC ShpC DVC LBR

Aluminum 975 1,460 710 400 590 320 380 750 840
Arsenic 1 1 1 1 2 5 0 1 1
Barium 56 14 17 32 196 112 14 60 25
Beryllium <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1
Boron 5 6 2 3 1 2 1 2 2
Cadmium 4 16 4 1 1 1 0 1 0
Chromium 3 6 10 1 2 2 2 2 2
Copper 47 16 31 39 92 176 52 32 50
Iron 802 1,220 581 308 377 251 320 670 750
Lead 1 1 <0.5 <0.5 <0.5 1 <0.5 <0.5 1
Magnesium 1,420 1,680 1,280 1,040 2,280 1,880 1,470 1,610 1,730
Manganese 1,190 125 188 543 195 392 180 1,530 1,030
Molybdenum <0.5 <0.5 1 <0.5 <0.5 <0.5 <0.5 2 1
Nickel 7 2 7 4 5 8 3 18 5
Strontium 8 15 6 9 147 260 3 50 9
Vanadium 3 3 4 1 1 2 2 3 2
Zinc 175 315 196 80 76 68 170 210 190
1
ACM: Angus Creek; UEMC: upper East Mill Creek; LEMC: lower East Mill Creek; TC: Trail Creek; USC; upper Slug
Creek; LSC: lower Slug Creek; DVC: Dry Valley Creek: ShpC: Sheep Creek; LBR: lower Blackfoot River.

25
Table 12. Fish species collected during June (●) and September (○) 2000 from nine sites in the
Blackfoot River watershed.

Fish species
Cutthroat Brook Mottled Longnose Speckled Redside
Site1 trout trout sculpin dace dace shiner
ACM ● ○ ● ○ ● ○ ● ○
UEMC ● ○ ●
LEMC ○
TC ● ○ ● ○ ● ○ ● ○
USC ● ○ ● ○ ● ○
LSC ○ ● ○ ● ○
ShpC ● ○ ● ○ ●
DVC ● ○ ○ ● ○ ● ○
LBR ● ○ ○ ● ○ ● ○
1
ACM: Angus Creek, UEMC: upper East Mill Creek, LEMC: lower East Mill Creek, TC:
Trail Creek, USC: upper Slug Creek, LSC: lower Slug Creek, DVC: Dry Valley Creek,
ShpC: Sheep Creek, LBR: lower Blackfoot River.

26
Table 13. Selenium concentrations (µg/g dry weight) in whole-body fish from nine sites in the Blackfoot River watershed. n=1.

Site1
Species ACM UEMC LEMC TC USC LSC ShpC DVC LBR

Brook trout -2 - - - 2.4 - - 8.0 -

Cutthroat trout 6.3 27.0 52.3 - - - 1.8 10.2 -

Mottled sculpin 8.3 - - 10.5 5.3 6.0 4.1 8.8 5.2

Longnose dace - - - 6.2 - - - - 6.2

Speckled dace 8.5 - - 6.1 6.9 2.6 - 7.5 5.6

Redside shiner 6.0 - - 2.2 - 3.8 - - 2.7

Geometric 7.2 27.0 52.3 5.5 4.5 3.9 2.7 8.6 4.7
mean
1
ACM: Angus Creek; UEMC: upper East Mill Creek; LEMC: lower East Mill Creek; TC: Trail Creek; USC; upper Slug
Creek; LSC: lower Slug Creek; DVC: Dry Valley Creek: ShpC: Sheep Creek; LBR: lower Blackfoot River.
2
-: not collected.

27
 Table 14. Inorganic element concentrations (µg/g dry weight) in whole-body fish from nine sites in the Blackfoot River watershed.
n=1; <: less than limit of detection.

Site1 and Species

ACM ACM ACM ACM UEMC LEMC TC TC TC TC
Cutthroat Mottled Speckled Redside Cutthroat Cutthroat Mottled Longnose Speckled Redside
Element trout sculpin dace shiner trout trout sculpin dace dace shiner

Aluminum 51 105 17 130 83 55 87 17 54 29

Arsenic 3 4 3 4 3 3 4 5 3 <1
Barium 5 10 6 6 1 3 6 19 15 7
Beryllium <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1
Boron <2 <2 <2 <2 <2 <2 <2 <2 <2 <2
Cadmium <0.1 0.2 <0.1 0.3 1.0 0.1 0.4 <0.1 0.1 0.5
Chromium 5 4 1 24 2 6 4 7 5 8
Copper 4 3 3 5 26 5 4 5 7 3
Iron 160 150 53 260 94 110 130 110 130 125
Lead <0.5 1 <0.5 1 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5
Magnesium 1,570 1,610 1,350 1,560 1,010 1,310 1,330 1,220 1,460 1,500
Manganese 24 130 17 63 6 13 31 21 30 26
Molybdenum <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5
Nickel 1 4 <0.5 3 2 1 1 2 1 1
Strontium 20 37 35 33 16 20 31 24 26 25
Vanadium 1 5 1 1 1 1 1 1 1 <0.5
Zinc 200 140 140 260 98 180 120 140 190 180

Table 14. Continued.

28
 Site1 and Species
USC USC USC LSC LSC LSC ShpC ShpC DVC DVC
Brook Mottled Speckled Mottled Speckled Redside Cutthroat Mottled Brook Cutthroat
Element trout sculpin dace sculpin dace shiner trout sculpin trout trout

Aluminum 104 340 28 130 33 119 26 67 37 38

Arsenic 3 5 4 5 <1 <1 <1 <1 <1 <1
Barium 3 14 15 13 4 11 2 7 3 2
Beryllium <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1
Boron <2 <2 <2 <2 <2 <2 <2 <2 <2 <2
Cadmium <0.1 <0.1 <0.1 0.2 0.7 0.8 0.5 0.5 0.5 0.5
Chromium 9 7 6 19 6 7 3 1 26 49
Copper 3 4 7 6 3 6 5 3 4 6
Iron 120 290 100 160 110 200 96 97 210 350
Lead <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5
Magnesium 890 1,500 1,540 1,380 1,330 1,690 1,220 1,440 1,360 1,500
Manganese 11 21 12 99 38 22 8 15 34 33
Molybdenum <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 0.8
Nickel 3 1 2 12 2 2 <0.5 <0.5 10 12
Strontium 8 24 <0.5 40 33 40 6 15 15 12
Vanadium 1 2 1 3 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5
Zinc 170 97 170 110 180 160 77 54 110 87

29
Table 14. Continued.

Site1 and Species

DVC DVC LBR LBR LBR LBR
Mottled Speckled Mottled Longnose Speckled Redside
Element sculpin dace sculpin dace dace shiner

Aluminum 43 3 14 8 41 16
Arsenic <1 <1 <1 <1 <1 <1
Barium 4 4 5 5 7 4
Beryllium <0.1 <0.1 <0.1 <0.1 <0.1 <0.1
Boron <2 <2 <2 <2 <2 <2
Cadmium 0.7 0.6 0.5 0.6 0.6 0.5
Chromium 8 <0.5 17 <0.5 7 <0.5
Copper 3 4 4 7 5 3
Iron 160 61 160 41 130 60
Lead <0.5 <0.5 <0.5 <0.5 <0.5 <0.5
Magnesium 1,520 1,410 1,540 1,360 1,320 1,520
Manganese 48 12 24 14 21 6
Molybdenum <0.5 <0.5 <0.5 <0.5 <0.5 <0.5
Nickel 2 <0.5 5 <0.5 2 <0.5
Strontium 31 22 35 33 29 41
Vanadium 1 <0.5 1 <0.5 <0.5 <0.5
Zinc 100 160 110 91 130 140
1
ACM: Angus Creek; UEMC: upper East Mill Creek; LEMC: lower East Mill Creek; TC: Trail
Creek; USC; upper Slug Creek; LSC: lower Slug Creek; DVC: Dry Valley Creek: ShpC: Sheep
Creek; LBR: lower Blackfoot River.

30
Table 15. Geometric mean of inorganic element concentrations (µg/g dry weight) in whole-body fish from nine sites in the Blackfoot
River watershed.

Site1
Element ACM UEMC LEMC TC USC LSC ShpC DVC LBR

Aluminum 59 83 55 39 99 80 42 21 17
Arsenic 4 3 3 4 4 1 <1 <1 <1
Barium 6 1 3 11 9 8 3 3 5
Beryllium <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1
Boron <2 <2 <2 <2 <2 <2 <2 <2 <2
Cadmium 0.2 1.0 0.1 0.3 <0.1 0.5 0.5 0.6 0.5
Chromium 5 2 6 6 7 9 1 22 11
Copper 3 26 5 5 4 5 4 4 5
Iron 130 94 110 120 150 150 97 160 83
Lead 1 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5
Magnesium 1,520 1,010 1,310 1,370 1,270 1,460 1,330 1,450 1,420
Manganese 44 6 13 27 14 44 11 29 14
Molybdenum <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 0.8 <0.5
Nickel 2 2 1 1 2 3 1 7 3
Strontium 31 16 20 26 14 38 9 19 34
Vanadium 1 1 1 1 1 3 <0.5 <0.5 1
Zinc 180 98 180 160 140 150 64 110 120
1
ACM: Angus Creek; UEMC: upper East Mill Creek; LEMC: lower East Mill Creek; TC: Trail Creek; USC; upper Slug Creek;
LSC: lower Slug Creek; DVC: Dry Valley Creek: ShpC: Sheep Creek; LBR: lower Blackfoot River.

31
Streams
Based on the Freidman test, the streams were ranked from highest geometric mean
inorganic element concentrations in fish (with selenium in dataset) to lowest as follows (streams
with lower case letters in common are not significantly different): LSCa, ACMab, DVCab, TCab,
USCab, LBRab, LEMCb, UEMCb, ShpCc. Based on selenium concentrations alone, the streams
from highest concentration to lowest were: LEMC, UEMC, DVC, ACM, TC, LBR, USC, LSC,
ShpC. There was a major disparity in order between the two approaches for lower and upper
East Mill Creek and lower Slug Creek.
There were few significant correlations observed for concentrations of inorganic
elements in fish (using the geometric mean for all fish at each site) and water (zinc), surficial
sediment (none), aquatic plant (copper), and aquatic invertebrates (arsenic and nickel) (Table 9).
There was no significant difference among streams based on inorganic element
concentrations including selenium in water, sediment, aquatic plant, aquatic invertebrate, and
fish using the individual Freidman test ranks. In contrast, there were significant differences
among streams based on selenium concentrations using the individual ranks for the five matrices.
Streams were ranked from highest selenium concentration to lowest as follows (streams with
lower case letters in common are not significantly different): LEMCa, UEMCa, DVCab, LBRbc,
ACMc, USCc, ShpCc, LSCc, TCc.

Discussion
Water
Upper and lower East Mill Creek water contained substantially elevated selenium
concentrations in water compared to the seven other sites. Selenium concentrations in water
from East Mill Creek collected in June 2000 (15-30 µg/L, Hamilton et al. 2002) were similar to
those in the present study. Selenium in East Mill Creek was substantially higher in both June
and September 2000 than the current national water quality criterion for the protection of aquatic
life of 5 µg/L (USEPA 1987).
The upper Slug Creek site was used as the reference site because it was not influenced by
mining (Figure 1). In general, most of the other eight stream sites contained similar inorganic
element concentrations in water to those in upper Slug Creek, except for selenium. Upper and
lower East Mill Creek, in addition to elevated selenium concentrations, also contained elevated
strontium concentrations compared to upper Slug Creek, which was similar to the June collection
(Hamilton et al. 2002).
A recent workshop on selenium aquatic toxicity and bioaccumulation was held to discuss
the technical issues underlying the federal freshwater aquatic life chronic criterion for selenium
(USEPA 1998a) and concluded that water was a poor choice for a criterion for selenium. Even
though there has been a substantial number of papers calling for a water criterion of 2 µg/L
(reviewed by Hamilton and Lemly, 1999), there was also a substantial number of examples of
aquatic situations where waterborne selenium concentrations of 2-4 µg/L have allowed selenium
accumulation in the food chain to approach concentrations near or above the proposed dietary
toxic threshold of 3 µg/g for fish (Lemly 1993, 1996b, Hamilton 2002). This latter scenario
seems to be occurring at several sites in the present study.
Water concentrations of inorganic elements are generally the basis of water quality
standards issued by the USEPA (USEPA 1998b, 1999). However, investigations have been
reported that indicate that dietary routes of exposures of inorganic elements were important in
discerning effects on biota (reviewed in Hamilton and Hoffman 2002). For example, Kiffney

32
and Clements (1993) reported that monitoring concentrations of cadmium, copper, and zinc in
aquatic invertebrates was a better indicator of element bioavailability in the Arkansas River of
Colorado, which was impacted by acid mine drainage, than element concentrations in water.

Comparison to other Idaho water data

The Idaho Mining Association Selenium Subcommittee (Selenium Subcommittee)
investigated concentrations of selenium, cadmium, manganese, nickel, vanadium, and zinc in
water from numerous sites in the Southeastern Idaho Phosphate Resource Area and concluded
that selenium was the major contaminant of potential concern (MW 1999). In May 1998,
selenium concentrations in water at 12 of 37 stream sites exceeded the USEPA criteria of 5 µg/L,
whereas in September 1998 only one stream, East Mill Creek (32 µg/L), exceeded the USEPA
criteria (MW 1999). In the May 1998 sampling, the stream sites exceeding the criterion included
five on the Blackfoot River (5-12 µg/L), Trail Creek (8.7 µg/L), Dry Valley Creek (5.6 µg/L),
and two on East Mill Creek (210 and 260 µg/L). The values reported by MW (1999) for East
Mill Creek were higher than those measured in the present study, but were similar for Trail
Creek and Dry Valley Creek.
MW (2000) continued measuring selenium concentrations in waters of the Blackfoot
River in 1999. Concentrations in the lower Blackfoot River near our sampling site were 6.7
µg/L in May, 2.1 µg/L in June, 2.4 µg/L in July, and 1.5 µg/L in August, which shows the
variability over time that can occur in the river. MW (2002) reported similar variability in Dry
Valley Creek: 49 µg/L in May, 6.8 µg/L in June, 2.7 µg/L in July, and 1 µg/L in August. In
May 1999 Dry Valley Creek (49 µg/L) and Spring Creek (46 µg/L) were major selenium
contributors to the Blackfoot River. Thus, substantial contamination of the Blackfoot River
occurred during 1999.
MW (2001a, 2001b) reported additional selenium concentrations in water sampled in
September 1999 and May 2000. Most water samples in September 1999 to April 2000 contained
<5 µg/L, except for Dry Valley Creek, which contained 12 µg/L above the Blackfoot River, and
East Mill Creek, which contained 19 µg/L (MW 2001a). In May 2000 selenium concentrations
>5 µg/L were reported in the Blackfoot River (5.5-7.1 µg/L) and several creeks including lower
Slug Creek (6.3 µg/L), Dry Valley Creek (8-87 µg/L), Angus Creek (6.5 µg/L), and East Mill
Creek (400 µg/L) (MW 2001b). These data and those from Hamilton et al. (2002) demonstrate
continued selenium contamination of the Blackfoot River watershed. The data also demonstrate
that selenium contamination occurs primarily during spring runoff. This contamination was
evidenced in selenium concentrations in sediment, aquatic plants, aquatic invertebrates, and fish
measured in the current study and as discussed below.

Sediment
Selenium concentrations in surficial sediment from upper and lower Slug Creek, Sheep
Creek, Trail Creek, Angus Creek, and the lower Blackfoot River were 1.0 to 1.8 µg/g, which was
above the value that Presser et al. (1994) and Moore et al. (1990) used (0.5 µg/g) as a reasonable
selenium concentration in sediment to represent the threshold between uncontaminated,
background conditions and environments with elevated selenium concentrations. Selenium in
surficial sediment from Dry Valley Creek and upper and lower East Mill Creek were elevated
and suggested a substantial contamination concern. Selenium concentrations in surficial
sediments in the present study were similar to those in the June 2000 collection from the same
nine sites (Hamilton et al. 2002).

33
 Selenium concentrations in surficial sediment from East Mill Creek were in the same
range as measured in North Pond at Walter Walker State Wildlife Area near Grand Junction, CO
(25.1 µg/g in 1996 and 38.9 µg/g in 1997) where elevated selenium in sediments were associated
with elevated selenium in the food chain, and mortality of endangered razorback sucker larvae
(Xyrauchen texanus) in two 30-day studies with water and dietary exposure (Hamilton et al.
2001a, 2001b).
Elevated selenium in sediments is an important consideration in assessing the health of
aquatic ecosystems and has been considered as a federal criterion for selenium in a workshop
(USEPA 1998a). However, the workshop participants concluded that the sediment compartment
was a poor choice (USEPA 1998a). Two papers have proposed the use of a sediment-based
criterion for selenium expressed on a particulate basis, such as sediment selenium concentration
or a measure of the organic content of sediment (Canton and Van Derveer 1997, Van Derveer
and Canton 1997). Hamilton and Lemly (1999) reviewed these two papers and pointed out how
they incorrectly interpreted contaminant survey reports as being exposure-response studies, did
not acknowledge the importance of the waterborne entry of selenium in aquatic food webs,
overlooked key studies from the extensive body of selenium literature, and failed to consider the
off-stream consequences of proposing high in-stream selenium standards.
In the present study, the significant correlation of selenium concentrations in surficial
sediment and water (r=0.99), sediments and aquatic plants (r=0.97), and sediment and aquatic
invertebrates (r=0.89) suggested that selenium moves easily among aquatic ecosystem
components and accumulates in the food web. Similar movements of selenium through the food
web were reported in two field studies conducted in seleniferous areas of the upper Colorado
River (Hamilton et al. 2001a, 2001b).
Surficial sediment concentrations of cadmium, chromium, copper, molybdenum, nickel,
vanadium, and zinc in upper and lower East Mill Creek were 1.4 to 6 times higher than
nonimpacted upper Slug Creek. In contrast, selenium concentrations were 18 to 22 times higher
in upper and lower East Mill Creek compared to upper Slug Creek, thus suggesting a major
disparity between selenium enrichment in the East Mill Creek compared to upper Slug Creek.
These findings were similar to those observed in the June 2000 sampling of sediment from the
same nine sites (Hamilton et al. 2002).
The sediment component of aquatic ecosystems is an important pathway of inorganic
element movement through the food web (Seelye et al. 1982). Sediments represent the most
concentrated pool of inorganic elements in aquatic environments, and many types of aquatic
organisms ingest sediment during the foraging process (Luoma 1983). Fish can ingest inorganic
elements from sediment and detritus (Kirby et al. 2001a, 2001b). For example, Campbell (1994)
reported that in lakes and ponds contaminated by inorganic elements, bottom feeding redear
sunfish (Lepomis microlophus) accumulated significant concentrations of cadmium, nickel,
copper, lead, and zinc, whereas predatory largemouth bass (Micropterus salmoides) significantly
accumulated cadmium and zinc, and omnivorous bluegill (Lepomis macrochirus) significantly
accumulated copper. Others have reported similar findings (Delisle et al. 1977, Van Hassel et al.
1980, Ney and Van Hassel 1983). Dallinger and Kautzky (1985) and Dallinger et al. (1987)
concluded that sediments were an important link in the contamination of food webs with
inorganic elements and in the resultant adverse effects in fish.
Specific to selenium, Woock (1984) demonstrated in a cage study with golden shiner
(Notemigonus crysoleucas) that fish in cages with access to bottom sediments accumulated more
selenium than fish held in cages suspended about 1.5 m above the sediments. That study

34
revealed that effects in fish were linked to selenium exposure via sediment, benthic
invertebrates, or detritus, or a combination of sediment components. A similar finding was
presented by Barnhart (1957) who reported that “numerous species of game fish” lived at least 4
months when held in a livebox, which limited access to food organisms and sediment, but fish
lived less than 2 months when released in selenium-contaminated Sweitzer Lake, CO. The
highly toxic nature of benthic invertebrates from selenium-contaminated Belews Lake, NC, was
reported by Finley (1985) in an experiment where bluegill died in 17 to 44 days after being fed
Hexagenia nymphs containing 13.6 µg/g wet weight selenium.

Comparison to other Idaho sediment data

The Selenium Subcommittee investigated concentrations of inorganic elements in
sediment from numerous sites in the Southeastern Idaho Phosphate Resource Area in September
1998 (MW 1999). Out of 54 sites investigated, 11 contained selenium concentrations of 2-4
µg/g in sediment including Slug Creek, Dry Valley Creek, Rasmussen Creek (tributary to Angus
Creek), and East Mill Creek. The selenium concentrations in sediment reported by MW (1999)
in East Mill Creek (2.9 µg/g) were substantially lower than those in the present investigation
(32-39 µg/g), whereas their value for Dry Valley Creek (3.3 µg/g) was similar to our value (3.0
µg/g). MW (2001a) reported elevated selenium concentrations in sediment collected in
September 1999 from Dry Valley Creek upstream of Maybe Creek (3.9 µg/g), Dry Valley Creek
downstream of Maybe Creek (6.2 µg/g), Angus Creek (5.1 µg/g), East Mill Creek (5.0 µg/g), and
Blackfoot River (2.1-3.0 µg/g).
Much of the selenium loading in Dry Valley Creek comes from Maybe Creek where
selenium concentrations were 261 µg/g in sediment from Maybe Creek near its mouth (TRC
Environmental 1999). Other portions of Maybe Creek contained 12-77 µg/g of selenium in
sediment (TRC Environmental 1999).
Overall, the elevated concentrations of selenium and other inorganic elements in
sediments from several streams in the Blackfoot River watershed that were reported by TRC
Environmental (1999), MW (1999, 2001a), Hamilton et al. (2002), and in the present study
suggest widespread selenium contamination of the aquatic environment by phosphate mining.

Aquatic plants
No guidelines were found that propose toxicity threshold concentrations for selenium in
aquatic plants that might be considered hazardous to aquatic organisms. However, most
domestic animals exhibit signs of selenium toxicity on terrestrial vegetative diets containing ≥3-
5 µg/g natural selenium (NRC 1980, Eisler 1985, Olson 1986). Selenium concentrations in
aquatic plants from upper and lower Slug Creek, Trail Creek, Sheep Creek, and Angus Creek
were 2.0 µg/g or less, and thus, this concentration might be considered near background for the
Blackfoot River watershed. By comparison, selenium concentrations in aquatic plants at Dry
Valley Creek (4.4 µg/g) and lower Blackfoot River (5.8 µg/g) were elevated, and those at upper
and lower East Mill Creek (26-30 µg/g) were substantially elevated. Selenium concentrations in
aquatic plants in the present study were similar to those in the previous study (Hamilton et al.
2002). Selenium concentrations in watermilfoil collected at Trail Creek (1.7 µg/g) and Dry
Valley Creek (4.4 µg/g) in the present study were similar to concentrations in white-water
buttercup collected at these two sites in June 2000 (0.8 and 3.8 µg/g, respectively; Hamilton et
al. 2002). Selenium concentrations in aquatic plants were significantly correlated with those in
water (r=0.99) and in surficial sediments (r=0.97), thus demonstrating that selenium was easily

35
transferred among these aquatic components.
Substantial accumulation of selenium has been reported in aquatic macrophytes by Saiki
(1986), Schuler et al. (1990), Gutenmann et al. (1976), and Barnum and Gilmer (1988) in
selenium-contaminated environments. Submerged macrophytes provide a substrate upon which
periphyton and some macroinvertebrates colonize, and which benthic invertebrates and some
aquatic and semi-aquatic birds and mammals feed.
When macrophytes die, they become an important contributor to the detrital food chain.
Detritus has been reported to contain highly elevated selenium concentrations in selenium-
contaminated environments (9.8-440 µg/g, Saiki 1986; 7-22 µg/g, Saiki et al. 1993; 36-307 µg/g,
Saiki and Lowe 1987), whereas reference areas contained 1 µg/g or less (Saiki and Lowe 1987).
Benthic invertebrates readily accumulate selenium from detritus (Alaimo et al. 1994), which in
turn is bioaccumulated by predators such as fish and waterbirds. Saiki et al. (1993) concluded
that high concentrations of selenium in aquatic invertebrates and fish in selenium-contaminated
areas of central California were the result of food-chain transfer from selenium-enriched, plant-
based detritus rather than other pathways. Thus, aquatic plants with elevated selenium
concentrations from four of the stream sites in the Blackfoot River watershed (upper and lower
East Mill Creek, Dry Valley Creek, lower Blackfoot River) were probably contributing to
selenium transfer in the aquatic food web.
Inorganic elements accumulate in aquatic plants both from water column uptake (Bryson
et al. 1984, Devi et al. 1996) and sediment uptake (Cherry and Guthrie 1977, Dallinger and
Kautzky 1985, Dallinger et al. 1987). The significant correlation coefficients between surficial
sediments and aquatic plants for several inorganic elements (chromium, manganese, nickel, zinc;
r=0.71-0.87) suggested a strong interconnectedness in some element cycles. In the June 2000
study, significant correlations between aquatic plants and sediments were reported for cadmium,
nickel, and zinc (r=0.71-0.91; Hamilton et al. 2002).
Uptake of inorganic elements by aquatic plants alone might seem unimportant; however,
inorganic elements in dead plant material can play an important role in the movement of
elements and energy through the detrital food web to aquatic invertebrates and fish in the
Blackfoot River watershed similar to selenium. When rooted aquatic plants die, their biomass
constitutes greater than 90% of the detrital food chain, whereas the remaining 10% is from algal
detritus and animal detritus (Teal 1962, Mann 1972). Much of the nutritional content in detritus
comes from microbe enrichment and metabolic products, which add proteins and amino acids to
detritus (Odum and de la Cruz 1967, Foda et al. 1983). Although not sampled in the present
study, periphyton (composed of diatoms, green algae, and cyanobacteria) are another source of
nutrients and inorganic elements for grazing aquatic invertebrates and contributes to the detrital
food web (Allan 1995). Uptake of inorganic elements by periphyton could have also contributed
to elevated elements in sediments and aquatic invertebrates, especially in western streams where
aquatic macrophytes might be limited. Plant litter and other coarse debris that enter a stream are
a major source of energy that fuels higher trophic levels (Allan 1995).

Comparison to other Idaho aquatic plant data

A native bryophyte that was collected in 2000 from a seep at the base of the Wooley
Valley Phosphate Mine Unit 4 waste-rock pile in the headwater area of Angus Creek contained
very elevated concentrations of several inorganic elements including cadmium (160 µg/g), cobalt
(180 µg/g), chromium (210 µg/g), manganese (33,000 µg/g), nickel (2,000 µg/g), vanadium
(1,000 µg/g), zinc (11,000 µg/g), and selenium (750 µg/g) (Herring et al. 2001). This site and

36
others on Angus Creek were previously monitored for inorganic element accumulation in late
spring and late summer 1999 using an introduced bryophyte, Hygrohypnum ochraceum (Herring
et al. 2001). The same elements that were present in the native bryophyte also accumulated in
the introduced bryophyte, but selenium was the most enriched of the elements measured.
Elevated mean selenium concentrations have been reported in grasses (64 µg/g), forbs
(78 µg/g), and shrubs (11 µg/g) in Maybe Creek (TRC Environmental 1999), a tributary of Dry
Valley Creek. These concentrations were higher than those in Dry Valley Creek in the present
study (4.4 µg/g) and the previous study (3.8 µg/g; Hamilton et al. 2002).
MW (2001a) reported selenium concentrations in periphyton collected from artificial
substrates placed in streams between September and October 1999. Elevated selenium
concentrations were found in the Blackfoot River (3.0 µg/g), Angus Creek (3.3-9.2 µg/g), and
very high values in East Mill Creek (12-25 µg/g). MW (2001b) reported elevated selenium
concentrations in periphyton collected from artificial substrates placed in the Blackfoot River
(4.3 µg/g) and Angus Creek (6.0 µg/g) between May and June 2000.
Plankton samples (combined phytoplankton and zooplankton) collected from various
sites in Blackfoot Reservoir contained selenium concentrations of ≤1.5 µg/g in September 1999
(MW 2001a). However, in the May 2000 sampling, 9 of 12 samples contained a geometric mean
selenium concentration of 3.3 µg/g (MW 2001b).
Submerged macrophytes were collected in September 1999 from numerous stream sites
in the Blackfoot River watershed and analyzed for selenium concentrations (MW 2001a). They
reported several samples with elevated concentrations ranging from 3.2 to 4.8 µg/g, 10 samples
with high concentrations ranging from 5.1 to 8.8 µg/g, and one site, East Mill Creek, with very
high concentrations ranging from 31 to 46 µg/g. These concentrations were similar to those in
the present study measured at East Mill Creek (26-30 µg/g) and the previous study (30-74 µg/g;
Hamilton et al. 2002). Submerged macrophytes collected by MW (2001b) in May 2000
contained similar selenium concentrations as in the September 1999 collection.
Taking the periphyton, plankton, and submerged macrophyte data together, the elevated
selenium concentrations demonstrated that aquatic plants were accumulating selenium from both
water and sedimentary sources. MW (2001a, 2001b) acknowledged that submerged aquatic
plants were efficient accumulators of selenium. Their values for several locations in the
Blackfoot River watershed were similar to data in the present study and the previous
investigation (Hamilton et al. 2002). Aquatic plants, i.e., periphyton, plankton, submerged
macrophytes, are the foundation of the food web including detritus. As such, they are the first
link in the bioaccumulation of selenium to higher trophic consumers such as aquatic
invertebrates and fish.

Aquatic invertebrates
Selenium concentrations in aquatic invertebrates from Sheep Creek, Trail Creek, and
upper and lower Slug Creek (<0.5-1.9 µg/g) were less than the proposed dietary selenium
threshold of 3 µg/g for fish (Lemly 1993, 1996b, Hamilton 2002). Selenium concentrations of
4.6 µg/g in zooplankton caused nearly complete mortality of razorback sucker larvae in about
10-13 days (Hamilton et al. 2001a, 2001b). Several other studies summarized in Hamilton
(2002) have reported that dietary selenium concentrations of 4 to 6 µg/g have caused adverse
effects in larval fish. Consequently, the moderate dietary selenium concentrations in lower
Blackfoot River and Angus Creek (6.7 to 7.7 µg/g), and the elevated concentrations in Dry
Valley Creek (12.8 µg/g) and upper and lower East Mill Creek (27 to 75 µg/g) were of concern

37
to the health of fishery resources and species that use these resources. A very similar pattern of
selenium concentrations in aquatic invertebrates was reported in the June 2000 study (Hamilton
et al. 2002).
Although selenium concentrations in invertebrates from upper Slug Creek were low in
the present study (0.5 µg/g), they were elevated in the previous study (4.9 µg/g) in spite of low
selenium concentrations in water, sediments, and aquatic plants (Hamilton et al. 2002). The
difference in selenium concentrations between these two studies may be due to a shift in the
composition of taxa in the composite samples. In the June study the composite sample contained
0.6 g Gammaridae, 1.9 g caddisfly larvae, and 0.5 g mayfly larvae (Hamilton et al. 2002),
whereas in the present study, the composite sample contained 4.0 g Gammaridae, 0.3 g caddisfly
larvae, and 0.2 g mayfly larvae (Appendix 2).
Benthic invertebrates can be efficient accumulators of selenium and can retain elevated
concentrations over long time periods. For example, Maier et al. (1998) reported that aquatic
invertebrates contained selenium concentrations of 1.7 µg/g at pretreatment of a watershed with
selenium fertilizer, and elevated concentrations during post-treatment monitoring: 4.7 µg/g at 11
days, 4.0 µg/g at 2 months, 5.0 µg/g at 4 months, 4.2 µg/g at 6 months, 4.3 µg/g at 8 months, and
4.5 µg/g at 11 months.
Much of the selenium in invertebrates likely came from the food web transfer from
detritus, which have been documented as the primary route of uptake by aquatic invertebrates
and fish (Maier and Knight 1994, Lemly 1993, 1996b). Three investigations have reported high
correlations between selenium concentrations in sediment and benthic invertebrates (r=0.94,
Zhang and Moore 1996; r=0.87, Malloy et al. 1999 and Hamilton et al. 2001b), which suggested
that selenium concentrations in invertebrates were linked with sedimentary selenium. Recently,
Peters et al. (1999) reported that two benthic organisms, a eunicid polychaete and a bivalve
mollusk, accumulated selenium directly from spiked sediments. In our study, the linkage
between selenium concentrations in invertebrates, sediment, and plants, was supported by the
significant correlation between aquatic invertebrates and surficial sediments (r=0.89) and
between aquatic invertebrates and aquatic plants (r=0.78). Similar significant correlations
between sediments and aquatic plants or aquatic invertebrates were reported in the previous
study of these nine sites (Hamilton et al. 2002). Several investigators have reported that
selenium concentrations in invertebrates bioaccumulate through the food web to higher trophic
organisms such as fish (Sandholm et al. 1973, Finley 1985, Bennett et al. 1986, Dobbs et al.
1996, Hamilton et al. 2001a, 2001b).
Several inorganic elements (aluminum, boron, cadmium, chromium, iron, manganese,
nickel, vanadium, and zinc) were elevated in aquatic invertebrates collected from East Mill
Creek and Dry Valley Creek. Several of these elements were also elevated in surficial sediments
and aquatic plants, and significantly correlated with concentrations in aquatic invertebrates.
Similar to the present study, investigators have reported enrichment of aquatic invertebrates with
inorganic elements in contaminated aquatic environments (Cherry and Guthrie 1977, Patrick and
Loutit 1978, Furr et al. 1979, Dallinger and Kautzky 1985, Dallinger et al. 1987), and adverse
effects on fish (Woodward et al. 1995, Farag et al. 1998, 1999). Kiffney and Clements (1993)
reported that benthic invertebrates readily accumulated cadmium, copper, and zinc in a stream
impacted by acid mine drainage, and the accumulation was strongly linked with element
concentrations in aufwuchs (defined as biotic and abiotic materials accumulating on submerged
surfaces).

38
Comparison to other Idaho aquatic invertebrate data
Elevated selenium concentrations have been reported in benthic invertebrates collected
from ponds (110-390 µg/g) and a lotic area (14 µg/g) of mining-impacted Maybe Creek, a
tributary of Dry Valley Creek (TRC Environmental 1999). These selenium concentrations in
invertebrates in ponds were substantially higher than those measured in benthic invertebrates
from Dry Valley Creek in the present study, but were similar to lotic areas in the present study.
Benthic invertebrate samples collected from various sites in Blackfoot Reservoir
contained ≤2 µg/g in September 1999, except for three samples, which contained selenium
concentrations of 3.8, 4.6, and 10 µg/g (MW 2001a). However, in the May 2000 sampling, 8 of
12 samples from Blackfoot Reservoir contained a geometric mean selenium concentration of 7.8
µg/g (range 5.3 to 12 µg/g; MW 2001b).
Benthic invertebrates collected in September 1999 from numerous stream sites in the
Blackfoot River watershed contained low selenium concentrations in 5 of 26 samples (3.0 to 4.6
µg/g), moderately elevated concentrations in 5 samples (5.0 to 15 µg/g), and highly elevated
concentrations at East Mill Creek (72 µg/g) (MW 2001a). In the May 2000 sampling, low
selenium concentrations occurred in 11 of 42 samples (3.0 to 4.9 µg/g), 17 samples contained
moderately elevated concentrations (5.0 to 37 µg/g), and East Mill Creek contained 100, 120 and
170 µg/g (MW 2001b).
Selenium concentrations in aquatic invertebrates reported by MW (2001a, 2001b) tended
to be higher than those in the present study and previous study (Hamilton et al. 2002) for similar
collection sites. The large number of samples with substantial selenium concentrations above
the proposed dietary toxic threshold of 3 µg/g for fish suggested that benthic invertebrate
populations were highly contaminated with selenium. Aquatic invertebrates are an important
link in the food web, and as such, they allow higher trophic consumers like predatory aquatic
invertebrates and fish to bioaccumulate selenium.

Fish
Selenium concentrations in fish from the nine sites, based on geometric mean values,
followed the same pattern of accumulation as in surficial sediments, aquatic plants, and aquatic
invertebrates. The similarity in selenium accumulation between aquatic ecosystem components
also paralleled the significant correlations between selenium concentrations in fish and water,
sediments, aquatic plants, and aquatic invertebrates, which demonstrated the interconnectedness
of the aquatic ecosystem components. This accumulation pattern was also observed in the
previous investigation in June 2000 at the same nine sites (Hamilton et al. 2002) and is supported
in reviews of the selenium literature (Maier and Knight 1994, Lemly 1993, 1996b).
There were consistent differences in whole-body selenium concentrations among fish
species within a site in the present study. For example, trout and speckled dace contained the
highest selenium concentrations, and redside shiner contained the lowest selenium
concentrations. This pattern was similar to the findings in the June 2000 investigation (Hamilton
et al. 2002). Brook trout and cutthroat trout are insectivores and accordingly seemed to
accumulate elevated concentrations of inorganic elements. Speckled dace are bottom browsers
that feed on invertebrates and plant material (Lee et al. 1980), possibly detritus, and thus seemed
to accumulate elevated inorganic elements similar to bottom-feeding redear sunfish reported by
Campbell (1994). Redside shiner are omnivores (Lee et al. 1980), and thus seemed to
accumulate low organic element concentrations similar to omnivorous bluegill reported by
Campbell (1994). We concluded that feeding niche differences (benthic versus water column

39
and plant versus animal diet) resulted in different dietary exposures, and more importantly,
different selenium bioaccumulation in fish collected in the present study.
The conclusion that a fish’s feeding niche can influence the residues accumulated seems
to be supported by studies of inorganic element accumulation. For example, Campbell (1994)
reported that bottom feeding redear sunfish accumulated the most inorganic elements (cadmium,
copper, lead, nickel, zinc), piscvorous largemouth bass contained the second most accumulation
of inorganic elements (cadmium, zinc), and omnivorous bluegill contained the least
accumulation of inorganic elements (copper). Ney and Van Hassel (1983) reported that the
benthic species fantail darter (Etheostoma flabellare) and blacknose dace (Rhinichthys atratulus)
contained the highest accumulation of cadmium, lead, nickel, and zinc, bottom-dwelling northern
hog sucker (Hypentelium nigricans) and white sucker (Catostomus commersoni) contained
intermediate accumulations, and water-column dwelling redbreast sunfish (Lepomis auritus) and
rock bass (Ambloplites rupestris) contained the least accumulations. Similar differences in
bioaccumulation of inorganic elements among fish species due to trophic niche has been reported
by Murphy et al. (1978). However, others have reported that inorganic element residues can
vary among fish species, but the variation was not conclusively related to food habits and trophic
status (summarized in Wiener and Giesy 1979). In contrast, Besser et al. (1996) studied
selenium concentrations in fish in waters with the fly ash disposal ponds and concluded that
differences in habitat preference was probably the dominant factor in accumulation because
limnetic species generally contained greater selenium concentrations than benthic species.
In contrast to selenium concentrations in fish, concentrations of inorganic elements in
fish were not consistently elevated in one stream, but rather the highest inorganic element
concentrations were distributed among streams: Angus Creek and Dry Valley Creek fish
contained the highest concentrations (or tied for highest concentrations) of four elements each,
and East Mill Creek, Trail Creek, and upper and lower Slug Creek fish contained the highest
concentrations of two elements each. Neither Sheep Creek nor lower Blackfoot River fish
contained a “highest” concentration of the elements measured. There seemed to be no parallel
bioaccumulation of inorganic elements in fish from the nine sites in the same pattern as
selenium. This lack of a dominant stream with numerous elevated inorganic elements was
similar to findings in the June 2000 study (Hamilton et al. 2002).
This scenario of selenium being a more important contaminant than other inorganic
elements in the Blackfoot River watershed has occurred in other contaminant investigations. For
example, Furr et al. (1979) examined contaminated food chains in coal ash settling basins and
reported that only selenium was of concern to biota. Other investigations reaching similar
conclusions were reported by Sorensen (1988), Lemly (1985), Saiki and Lowe (1987), Nakamoto
and Hassler (1992), Gillespie and Baumann (1986), Bryson et al. (1984), MW (1999), and
Hamilton et al. (2001a, 2001b).
A workshop on selenium aquatic toxicity and bioaccumulation concluded that the tissue-
based national criterion might be the best approach for a criterion because tissue residues
accounted for selenium’s biogeochemical pathways by integrating the route, duration, and
magnitude of exposure, chemical form, metabolic transformations, and modifying biotic and
abiotic factors (USEPA 1998a). A recent paper gave the rationale for a tissue-based criterion for
selenium in fish (Hamilton 2002). That paper proposed a national criterion of 4 µg/g in whole
body based on the review of several laboratory and field studies. This value was the same as the
whole-body toxicity threshold for fish proposed earlier by Lemly (1993, 1996b) and similar to
the threshold of 4.5 µg/g proposed by Maier and Knight (1994). Other papers have proposed

40
selenium toxicity thresholds of 6 µg/g for coldwater anadromous fish and 9 µg/g for warm water
fish (DeForest et al. 1999, Brix et al. 2000). The approach, information, and conclusions
presented in DeForest et al. (1999) and Brix et al. (2000) have been reviewed and problems in
their interpretation and conclusions have been discussed in Hamilton (2003). DeForest et al.
(1999) and Brix et al. (2000) used selective data to propose high toxicity thresholds for selenium
in whole-body and diet of fish, cited older selenium literature containing errors, excluded data
from publications based on minor justifications, and overlooked key studies from the extensive
selenium literature.
Based on a whole-body toxicity threshold of 4-5 µg/g, the geometric mean selenium
concentrations in fish from upper and lower Slug Creek, Trail Creek, and lower Blackfoot River
would probably have some effects on early life stages of sensitive species. Fish in Angus Creek
and Dry Valley Creek contained selenium concentrations above the 4-4.5 µg/g threshold value,
thus suggesting possible effects in sensitive fish species in these streams. Elevated whole-body
residues of selenium in fish from East Mill Creek suggested sensitive and moderately sensitive
fish are probably being adversely affected by selenium exposure (e.g., reduced recruitment).

Comparison to other Idaho fish data

Rich and Associates (1999) reported concentrations of inorganic elements in cutthroat
trout, rainbow trout (Oncorhynchus mykiss), brook trout, sculpin species, dace species, and
redside shiner collected from Dry Valley Creek immediately upstream of the Blackfoot River,
and Dry Valley Creek directly below Maybe Creek. In general, their concentrations were higher
than in the present study for cadmium, chromium, copper, vanadium, and zinc, but lower for
selenium. They concluded that selenium and other elements (cadmium, copper, lead, vanadium,
and zinc) were probably causing stress in fish populations in Dry Valley Creek. In the present
study selenium was the only element elevated in fish from Dry Valley Creek.
MW (1999) reported salmonid fillets collected in 1998 contained selenium
concentrations of 6 µg/g wet weight (maximum 7.9 µg/g) from East Mill Creek, whereas fish
from two reference sites (Blackfoot River above Wooley Range Ridge Creek and South Fork
Sage Creek) contained 1.2-1.3 µg/g. Converting these values to a dry weight basis (dry weight =
wet weight × 4; assuming 75% moisture) results in 24 µg/g in fish fillets from East Mill Creek
and 4.8-5.2 µg/g in fish fillets from the reference sites.
Selenium concentrations in fillets reported by MW (1999) may underestimate the
concentrations in whole-body fish, which is the dominant matrix of selenium residues in fish
reported in the literature. Muscle contains less selenium than whole-body due to the relatively
high amounts of selenium found in spleen, liver, kidney, heart, and other tissues, especially
mature ovaries (Adams 1976, Sato et al. 1980, Lemly 1982, Hilton et al. 1982, Hilton and
Hodson 1983, Kleinow and Brooks 1986, Hermanutz et al. 1992). Consequently, the actual
whole-body selenium concentrations in trout would be about 40 µg/g in fish from East Mill
Creek and 8-8.7 µg/g in fish from the Blackfoot River and South Fork Sage Creek based on a
conversion factor of 1.667 × muscle concentration = whole body concentration (Lemly and
Smith 1987). Other conversion factors reported in the literature were 2.355 based on data from
Adams (1976) for rainbow trout, and 1.745 from Lemly (1982) for bluegill and largemouth bass,
both of which would have increased the converted values for trout in MW (1999). The
converted selenium concentration in MW (1999; 40 µg/g) is similar to the selenium
concentrations in whole-body trout in East Mill Creek in the present study (27-52 µg/g) and the
previous study (24-43 µg/g; Hamilton et al. 2002).

41
 Selenium concentrations in whole-body salmonids collected in September 1999 from
Blackfoot Reservoir and the mainstem and tributaries of the Blackfoot River were elevated in 21
of 50 samples (4.2 to 9.7 µg/g) and high in 7 samples (12 to 31 µg/g) (converted to dry weight
using the appropriate percent moisture from MW 2001a, and whole-body using a factor of 1.667,
Lemly and Smith 1987). For salmonids collected in May 2000 from various locations in the
Blackfoot River, selenium concentrations in whole-body were elevated in 13 of 27 samples (5.2
to 9.2 µg/g) and high in 12 samples (10 to 48 µg/g) (converted to dry weight using the
appropriate percent moisture from MW 2001b, and whole-body using a factor of 1.667, Lemly
and Smith 1987). These selenium residues in salmonids were substantially above background
concentrations in fish from laboratory and field investigations, which are typically 1-2 µg/g
(Maier and Knight 1994; Hamilton et al. 2000). More importantly, the selenium residues were
above those reported to cause adverse effects in early life stages of fish, including salmonids (4-5
µg/g; Hamilton et al. 2000). In particular, selenium residues of 5.2 µg/g in rainbow trout were
associated with reduced survival (Hunn et al. 1987), and 3.8-4.9 µg/g in chinook salmon
(Oncorhynchus tshawytscha) were associated with reduced survival and growth (Hamilton et al.
1986, Hamilton and Wiedmeyer 1990). Older life stages typically are more tolerant of
contaminant stresses than are early life stages (Rand and Petrocelli 1985), thus effects in adults
such as mortality and growth may not be as readily apparent as effects in early life stages.
However, effects on adults could occur through reduced reproductive success.
Based on the above discussion, selenium contamination of the Blackfoot River and its
tributaries is most likely adversely affecting aquatic resources, especially early life stages of fish.
Thurow et al. (1981) reported that 13 fish species used the Blackfoot River and its tributaries,
and that the indigenous cutthroat trout was the dominant species. They noted that cutthroat trout
used several tributaries, as well as the main stem river and the Blackfoot Reservoir during their
life cycle. Thurow et al. (1981) noted the potential for mining activities to cause negative effects
on trout and others species, primarily from erosion, sedimentation, and nutrient loading from
phosphorous, but did not specifically mention impacts from inorganic elements.
MW (2000) reported that eggs from cutthroat trout in 1999 contained selenium
concentrations of 4.4 and 6.7 µg/g dry weight in two ripe females from the Blackfoot River, 4.0
µg/g in two partially spawned females from the Blackfoot River, and 1.4 µg/g in females from
the reference site Henry’s Lake. These data demonstrated that trout were accumulating selenium
and depositing it in their eggs. However, the selenium concentrations in eggs were less than the
toxic effects threshold of 10 µg/g proposed by Lemly (1993, 1996b). The low number of egg
samples in MW (2000) precludes further speculation on the extent of selenium contamination of
fish eggs.
Selenium concentrations in forage fish reported by MW (2001a, 2001b) were similar to
those in the present study and the previous study (Hamilton et al. 2002). Forage fish samples
collected in September 1999 from various sites in Blackfoot River watershed contained selenium
concentrations ≥4 µg/g (MW 2001a), which was above the generally accepted toxic threshold of
4 µg/g (Lemly 1993, 1996b, Maier and Knight 1994, Hamilton 2002). Nine of 13 samples
contained elevated selenium concentrations in fish (5.2 to 8.3 µg/g, after conversion to dry
weight using the percent moisture given for each sample), and two samples contained high
selenium concentrations of 10 and 12.9 µg/g (MW 2001a). For forage fish collected from
various sites in the Blackfoot River watershed in May 2000, 13 of 36 samples contained
selenium concentrations of 5.0 to 9.4 µg/g, and 13 samples contained concentrations of 10 to 37
µg/g (MW 2001b).

42
 The large number of samples with substantial selenium concentrations above the
proposed toxic whole-body threshold of 4 µg/g suggested that fish populations have accumulated
elevated selenium concentrations similar to aquatic plants and aquatic invertebrates. Thus,
forage fish and salmonids probably pose a hazard from dietary selenium toxicity to predatory
fish and fish-eating wildlife.

Other considerations
One concern may be the presence of elevated selenium residues in fish without readily
apparent biological effects. However, data in the current study and studies by others (Rich and
Associates 1999, MW 1999, 2000, 2001a, 2001b) were results from contaminant surveys and not
biological effects studies. No biological or behavioral effects such as survival, growth,
reproduction, diversity, population structure, community structure, predator/prey relationships,
or other biological effects were measured. Secondly, residues measured in fish were for adults
or subadults. This life stage is generally less sensitive to the effects of environmental
contaminants than are early life stages (Rand and Petrocelli 1985). The third consideration was
the movement of fish in the Blackfoot River watershed or in any open river system. Adverse
effects on a demographically-open fish population in a section of the river with contaminant
impacts would be difficult to detect and must be confirmed with detailed biological studies
because of immigration of individuals from the portion of the population in non-affected river
reaches or tributary streams. The review by Skorupa (1998) addresses this concern succinctly
and stated, “It is common for instream studies to report the counterintuitive combination of
abnormally elevated levels of selenium in fish tissue associated with what is viewed as a
normally abundant and diverse fish fauna.” Papers that seem to have reached this unproven
conclusion include Canton and Van Derveer (1997), Van Derveer and Canton (1997), and
Kennedy et al. (2000). These papers tended to conclude that the toxic thresholds for selenium
derived from laboratory studies or field studies in closed basins, i.e., demographically closed
populations, do not apply to stream studies. Effects of selenium on species or populations of fish
in the lake and reservoir studies were substantiated with appropriate biological tests, whereas
stream or river investigations typically have not incorporated appropriate biological tests
(Hamilton and Palace 2001).
Monitoring of fish populations in rivers is an insensitive measure of contaminant effects
unless substantial effort is made to assess the health of the fish community. This assertion was
addressed by the USEPA in their guidelines for deriving water quality criteria. Stephan et al.
(1985) stated that, “The insensitivity of most monitoring programs [for number of taxa or
individuals] greatly limits their usefulness for studying the validity of [water quality] criteria
because unacceptable changes can occur and not be detected. Therefore, although limited field
studies can sometimes demonstrate that criteria are under protective, only high quality field
studies can reliably demonstrate that criteria are not under protective [i.e., overprotective].”
Claim of no biological effects in stream or river studies cannot often be confirmed
without appropriate biological effects tests. Statements of no biological effects in streams or
rivers without appropriate testing fall into the null fallacy trap: (1) There is no evidence for
adverse effects, versus (2) There is evidence for no adverse effects (J. Skorupa, USFWS,
personal communication). The null fallacy occurs when statement 1 (a null finding) is given
equal weight as statement 2 (a positive finding). What often is overlooked is that a null finding
usually implies a lack of positive evidence in both directions -- for effects or for absence of
effects. The null fallacy is just one of several errors in logic found in scientific dialogues (Sagan

43
1996).
MW (2001b) acknowledged that higher than expected selenium concentrations in forage
fish from a reference site on Spring Creek above influences of East Mill Creek were probably
due to the mobility of fish. Forage fish in upper Spring Creek contained selenium concentrations
of 10, 12, and 22 µg/g. However, in spite of high selenium residues in whole-body forage fish
collected in May 2000, MW (2001b) stated that, “There is no evidence of forage fish in the
Blackfoot Reservoir being impacted by either selenium or cadmium at either time of year.”
Likewise, MW (2001a) reported elevated selenium concentrations in forage fish collected in
September 1999, yet stated that, “Evaluation of forage fish data show no evidence that this
medium is impacted in the reservoir.” Because no biological effects were assessed in fish
collections in September 1999 or May 2000, their statements were unsupported.

Hazard assessment
Lemly (1995) presented a protocol for aquatic hazard assessment of selenium, which was
formulated primarily in terms of the potential for food-chain bioaccumulation and reproductive
impairment in fish and aquatic birds. The protocol incorporated five ecosystem components
including water, sediment, benthic invertebrates, fish eggs, and bird eggs. Each component was
given a numeric score based on the degree of hazard: 1, no identifiable hazard (no toxic threat is
identified and selenium concentrations are not elevated in any ecosystem component); 2,
minimal hazard (no toxic threat identified but concentrations of selenium are slightly elevated in
one or more ecosystem components [water, sediment, benthic invertebrates, fish eggs, bird eggs]
compared to uncontaminated reference sites); 3, low hazard (a periodic or ephemeral toxic threat
that could marginally affect the reproductive success of some sensitive species, but most species
will be unaffected); 4, moderate hazard (a persistent toxic threat of sufficient magnitude to
substantially impair but not eliminate reproductive success; some species will be severely
affected whereas others will be relatively unaffected); 5, high hazard (an imminent, persistent
toxic threat sufficient to cause complete reproductive failure in most species of fish and aquatic
birds). The final hazard characterization was determined by adding the individual scores and
comparing the total to the following evaluation criteria: 5, no hazard; 6-8, minimal hazard; 9-11,
low hazard; 12-15, moderate hazard; 16-25, high hazard.
Lemly (1996a) modified his protocol for use with four ecosystem components due to the
difficulty in collecting residue information for all five components in an assessment, and
adjusted the final ecosystem-level hazard assessment to the following four-component evaluation
criteria: 4, no hazard; 5-7, minimal hazard; 8-10, low hazard; 11-14, moderate hazard; 15-20,
high hazard. Table 16 gives the hazard term and corresponding selenium concentration range for
each

44
Table 16. Aquatic ecosystem components and selenium concentrations posing various hazards based on Lemly (1996a).

Hazard
None Minimal Low Moderate High
Ecosystem Lemly1 Modified Lemly1 Modified Lemly1 Modified Lemly1 Modified Lemly1 Modified
component Conc. score score Conc. score score Conc. score score Conc. score score Conc. score score

Water <1 1 1 1-2 2 2 2-3 3 3 3-5 4 4 >5 5 5

(µg/L)

Sediment <1 1 1 1-2 2 2 2-3 3 3 3-4 4 4 >4 5 5

(µg/g)

Benthic <2 1 2 2-3 2 4 3-4 3 6 4-5 4 8 >5 5 10

invertebrate
(µg/g)

Fish eggs <3 1 3 3-5 2 6 5-10 3 9 10-20 4 12 >20 5 15

(µg/g)

Sum 4 7 8 14 12 21 16 28 20 35

Final hazard (Lemly1) 4 5-7 8-10 11-14 15-20

Final hazard (Modified) 7 8-13 14-20 21-27 28-35

1
Lemly 1996a.

45
of the four ecosystem components in the four-component model (Lemly 1996a).
These protocols have been used to assess the selenium hazard to aquatic ecosystems at
Ouray NWR, UT (Lemly 1995, 1996a), the Animas, LaPlata, and Mancos rivers in the San Juan
River basin (Lemly 1997), three Wildlife Management Areas in Nevada (Lemly 1996a), and
three sites near Grand Junction, CO (Hamilton et al. 2001a, 2001b). Stephens et al. (1997) and
Engberg et al. (1998) has reported hazard classification schemes that were similar to Lemly
(1995, 1996a).
The selenium hazard protocols give equal weight to each component (Lemly 1995,
1996a). However, there may be the need to give more weight to the biological components:
benthic invertebrates, fish eggs, and bird eggs (written communication, H. Ohlendorf, 1996).
Ohlendorf suggested a multiplication factor of two for the score for benthic invertebrate
information and a factor of three for the score for fish eggs and bird eggs. Similar concerns have
been raised by a USGS scientist (written communication, M. Sylvester, Menlo Park, CA, 2002),
and a USFWS Environmental Contaminant Specialist (written communication, B. Osmundson,
Grand Junction, CO, 2001). The weighting of the three biological components seems justified
based on the repeated expression of their importance in the selenium literature (reviews by
Lemly 1985, 1993, Maier and Knight 1994, Presser et al. 1994, Hamilton and Lemly 1999,
Hamilton 2002, 2003).
Incorporating these factors into the protocol using the offset summation approach results
in modified final hazard characterizations for the four-component protocol of 7, no hazard; 8-13,
minimal hazard; 14-20, low hazard; 21-27, moderate hazard, and 28-35, high hazard (Table 16).
The offset summation is explained as follows: for the low hazard column, Lemly (1996a) gives
a score of 3 for each of the four components being evaluated (water, sediment, benthic
invertebrate, and fish eggs), which results in a summed score of 12 (Table 16). However, if in an
environmental situation all measured selenium concentrations of the four components fell into
the “low” column, the additive effect of the combined low exposures would most likely result in
a “moderate” final hazard to biota. Thus, Lemly (1996a) set the final hazard range for a “low”
final hazard at 8-10, instead of closer to the summed total of 12. This offsetting of the final
hazard total seems biologically reasonable and is referred to here as the offset summation
approach. Similar offsets for other final hazards are given in Table 16. For the five-component
protocol, the modified final hazard characterization would be 10, no hazard; 11-19, minimal
hazard; 20-28, low hazard; 29-38, moderate hazard, and 39-50, high hazard. This modified
hazard assessment was used in a previous investigation in the Blackfoot River watershed
(Hamilton et al. 2002).
In the present study, fish eggs were not collected. In the hazard assessment, we
converted the geometric mean whole-body concentrations of selenium in fish to fish eggs
concentrations using the conversion factor based on Lemly (1995, 1996a), who reported: whole-
body × 3.3 = fish egg. The hazard assessment for the nine sites is given in Table 17.
The site with low selenium concentrations in most aquatic ecosystem components had a
low overall hazard rating was Sheep Creek. Using the original Lemly (1996a) approach, this site
would have received a moderate final hazard in spite of the low score for benthic invertebrates
and fish eggs (converted from whole-body residues). This final hazard rating is the only one that
was changed by the use of the multiplication factors for benthic invertebrates or whole-body
residues.
Selenium concentrations were high in water at upper Slug Creek, lower Slug Creek, and

46
Table 17. Hazard assessment of selenium at nine sites in the Blackfoot River watershed using
modified scores.

Evaluation by
Site1 and ecosystem Selenium component Total for the site
component concentration2 Hazard Score Score Hazard

ACM
Water 6 High 5
Sediment 1.0 Minimal 2 32 High
Benthic invertebrate 6.7 High 10
Fish eggs3 24 High 15
UEMC
Water 24 High 5
Sediment 32 High 5 35 High
Benthic invertebrate 27 High 10
Fish eggs 89 High 15
LEMC
Water 24 High 5
Sediment 39 High 5 35 High
Benthic invertebrate 75 High 10
Fish eggs 173 High 15
TC
Water 5 High 5
Sediment 1.2 Minimal 2 21 Moderate
Benthic invertebrate <0.5 None 2
Fish eggs 18 Moderate 12
USC
Water 7 High 5
Sediment 1.8 Minimal 2 21 Moderate
Benthic invertebrate 0.5 None 2
Fish eggs 15 Moderate 12
LSC
Water 6 High 5
Sediment 1.7 Minimal 2 21 Moderate
Benthic invertebrate <0.5 None 2
Fish eggs 13 Moderate 12
ShpC
Water 8 High 5
Sediment 1.5 Minimal 2 18 Low
Benthic invertebrate 1.9 None 2
Fish eggs 9 Low 9

47
Table 17. Continued.

Evaluation by
1
Site and ecosystem Selenium component Total for the site
component concentration2 Hazard Score Score Hazard

DVC
Water 8 High 5
Sediment 3.0 Low 3 33 High
Benthic invertebrate 13 High 10
Fish eggs 28 High 15
LBR
Water <5 None 1
Sediment 1.8 Minimal 2 25 Moderate
Benthic invertebrate 7.7 High 10
Fish eggs 16 Moderate 12
1
ACM: Angus Creek, UEMC: upper East Mill Creek, LEMC: lower East Mill Creek, TC: Trail
Creek, USC: upper Slug Creek, LSC: lower Slug Creek, DVC: Dry Valley Creek, ShpC: Sheep
Creek, LBR: lower Blackfoot River.
2
Selenium concentrations in µg/L for water, µg/g for sediment, benthic invertebrates, and fish
eggs.
3
Fish eggs: fish egg values converted from whole-body residues using: whole-body × 3.3 = fish
egg (Lemly 1995, 1996a).

48
Trail Creek, but low in sediments and benthic invertebrates, and moderate in whole body
residues converted to fish egg concentrations, thus resulting in moderate overall hazard ratings.
Selenium concentrations in water and sediment were in the none or minimal categories at the
lower Blackfoot River, but high in benthic invertebrates and moderate in whole-body residues,
thus this site received a moderate final hazard. Upper and lower East Mill Creek, Dry Valley
Creek, and Angus Creek consistently contained elevated selenium concentrations in sediment,
invertebrates, or whole-body residues (which were converted to fish eggs), thus resulting in high
overall hazard rating. These hazard ratings were similar to those derived in the June 2000
investigation of the same nine sites (Hamilton et al. 2002).
Based on the final hazard score the streams can be listed from highest environmental
selenium hazard to lowest as follows: LEMC, UEMC, DVC, ACM, LBR, USC, LSC, TC,
ShpC. This ranking is nearly identical to the results of the Freidman test using the ranked
selenium concentrations: LEMCa, UEMCa, DVCab, LBRbc, ACMc, USCc, ShpCc, LSCc, TCc.
Only slight differences in the position of lower Blackfoot River and Sheep Creek sites occurred
when comparing the two approaches. Thus, the selenium hazard protocol seems to be a useful
tool in assessing the differences among sites due to the comparable outcome of a statistical
approach such as the Freidman test.
Reports by MW (1999, 2000, 2001a, 2001b) do not present hazard assessments.
However, the data evaluations of the various aquatic ecosystem components for water, sediment,
submerged macrophytes, benthic invertebrates, forage fish and salmonid fillets, tend to suggest
no impacts from selenium and other elements, with the exception of creeks influenced directly
by phosphate mining.
A preliminary assessment of selenium hazard in the Caribou National Forest was
conducted using selenium residue data in water and fish collected from 1997-1998 (Lemly
1999). Lemly (1999) concluded that there was a high potential for toxic impacts occurring in fish
and wildlife associated with the Blackfoot River, its tributaries, and Blackfoot Reservoir. The
results of the present study and the previous study (Hamilton et al. 2002) add substantially more
support to the premise that selenium concentrations in several aquatic ecosystem components
were sufficiently elevated to cause adverse effects to aquatic resources and terrestrial species that
utilize these resources in the Blackfoot River watershed.

Acknowledgement: The authors thank the following personnel for assistance in this study: Bill
Janowski, Jeff Jones, and Larry Michelson, U.S. Forest Service; Brad Vandekamp, Don Cole,
Mark Hardy, Jim Herring, Phil Moyle, and Theresa Presser, U.S. Geological Survey; and Peter
Oberlindacher, U.S. Bureau of Land Management. The authors thank Tina Bridges, Susan
Burch, Laverne Cleveland, and Carmen Thomas for reviewing the report, Theresa Presser for an
early draft of Figure 1, and Karen Faerber for preparing numerous drafts of the report.

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Appendix 1. Wet weight (g) of aquatic plant (white-water buttercup Ranunculus longirostris)
from nine sites in the Blackfoot River watershed submitted for either selenium
analysis (Se) or inorganic element analysis (ICP).

Analysis

57
 Site1 Se ICP

ACM 15.73 16.24

UEMC 17.96 18.34
LEMC2 6.72 6.56
TC3 6.12 7.25
USC 4.75 5.00
LSC 6.32 5.60
ShpC 5.60 5.40
DVC3 7.30 7.35
LBR 7.59 7.18
1
ACM: Angus Creek, UEMC: upper East Mill Creek,
LEMC: lower East Mill Creek, TC: Trail Creek, USC:
upper Slug Creek, LSC: lower Slug Creek, DVC: Dry
Valley Creek, ShpC: Sheep Creek, LBR: lower
Blackfoot River.
2
Filamentous green algae.
3
Watermilfoil (Myriophyllum).

58
Appendix 2. Wet weight (g) of aquatic invertebrates from nine sites in the Blackfoot River watershed submitted for either selenium analysis (Se) or
inorganic element analysis (ICP).

Aquatic invertebrate type

Chemical Composite Beetle Tendipedidae
Site1 analysis weight Gammaridae Caddisfly Mayfly Damselfly larvae Stonefly Diptera Dragonfly midge

ACM Se 3.94 - 0.36 0.46 0.29 0.22 1.32 0.11 1.18 -

ICP 3.29 - 0.42 0.44 0.28 0.22 1.12 0.13 0.90 -

UEMC Se 3.34 - 0.22 3.08 - 0.04 - - - -

ICP 4.17 - 0.14 4.01 - 0.02 - - - -

LEMC Se 6.85 - 4.47 1.48 - - - - - 0.90

ICP 7.68 - 5.08 1.80 - - - - - 0.80

TC Se 7.52 0.84 1.31 - 4.09 - - - 1.28 -

ICP 8.41 0.69 1.66 - 4.59 - - - 1.47 -

USC Se 4.45 3.98 0.26 0.21 - - - - - -

ICP 4.79 4.26 0.27 0.26 - - - - - -

LSC Se 12.55 9.11 - 0.33 3.11 - - - - -

ICP 13.14 10.21 - 0.25 2.68 - - - - -

ShpC Se 9.59 - 4.99 0.05 - - 4.55 - - -

ICP 9.36 - 4.85 0.03 - - 4.48 - - -

DVC Se 15.74 4.50 8.93 1.88 - 0.43 - - - -

ICP 15.24 5.01 7.94 1.80 - 0.49 - - - -

LBR Se 6.28 - 1.08 - - - 5.20 - - -

ICP 8.11 - 1.11 - - - 7.00 - - -
1
ACM: Angus Creek, UEMC: upper East Mill Creek, LEMC: lower East Mill Creek, TC: Trail Creek, USC: upper Slug Creek, LSC: lower Slug
Creek, DVC: Dry Valley Creek, ShpC: Sheep Creek, LBR: lower Blackfoot River.

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Appendix 3. Total length (mm), weight (g), and use (selenium analysis [Se], inorganic element
analysis [ICP], or archive [A]) of fish from nine sites in the Blackfoot River
watershed.

Site1 Species Total length Weight Use

ACM Cutthroat trout 69 2.74 ICP

67 2.44 ICP
90 6.39 Se

Mottled sculpin 70 3.77 ICP

64 2.83 ICP
91 8.25 Se

Speckled dace 74 4.18 Se

68 2.98 Se
72 3.96 ICP
40 0.65 ICP
69 3.45 A

Redside shiner 73 3.90 Se

73 4.44 Se
67 3.25 ICP
81 5.19 ICP

UEMC Cutthroat trout 149 29.52 Se

145 30.18 ICP

LEMC Cutthroat trout 64 1.82 ICP

60 1.72 ICP
71 2.87 Se

TC Mottled sculpin 86 8.46 Se

66 3.80 Se
93 10.63 ICP

Longnose dace 88 6.58 Se

68 3.20 Se
110 14.82 ICP

Speckled dace 68 3.34 Se

70 3.58 Se
69 2.79 Se
60 2.47 ICP
55 1.89 ICP
71 3.74 ICP
62 2.74 A
71 3.42 A

60
Appendix 3. Continued.

Site1 Species Total length Weight Use

TC Redside shiner 95 8.94 Se

90 7.11 Se
99 10.34 ICP

USC Brook trout 147 30.29 Se

130 19.03 Se
144 27.74 ICP
137 21.57 ICP

Mottled sculpin 86 8.18 Se

75 4.86 Se
85 7.99 ICP
84 6.94 ICP

Speckled dace 72 3.90 Se

57 1.96 Se
67 3.29 ICP
65 2.71 ICP
71 3.65 A

LSC Mottled sculpin 95 9.62 Se

83 6.89 ICP

Speckled dace 66 3.31 Se

66 3.35 Se
72 4.05 Se
54 1.66 Se
81 6.13 ICP
64 3.04 ICP
45 0.89 ICP
48 1.18 ICP
90 8.46 A
75 4.97 A
73 4.17 A
69 3.56 A
57 1.56 A
50 1.34 A
48 1.08 A
48 1.24 A

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Appendix 3. Continued.

Site1 Species Total length Weight Use

LSC Redside shiner 62 1.96 Se

57 1.60 Se
53 1.34 Se
52 1.24 Se
60 1.89 ICP
62 2.22 ICP
56 1.50 ICP
56 1.51 ICP
89 7.41 A
52 1.31 A
53 1.33 A
34 0.35 A

ShpC Cutthroat trout 146 29.35 ICP

123 17.71 Se

Mottled sculpin 64 2.79 ICP

59 2.09 ICP
100 13.10 Se

DVC Cutthroat trout 151 32.15 Se

107 11.21 Se
168 39.44 ICP

Brook trout 117 16.96 Se

63 2.30 Se
113 13.68 ICP
84 5.29 ICP
255 160.46 A

Mottled sculpin 84 8.37 Se

85 7.98 Se
108 17.66 ICP
85 7.98 ICP

Speckled dace 52 1.25 Se

48 1.05 Se
62 2.25 ICP

LBR Mottled sculpin 83 6.64 Se

58 2.03 Se
103 16.01 ICP

62
Appendix 3. Continued.

Site1 Species Total length Weight Use

LBR Longnose dace 54 1.40 Se

39 0.55 Se
51 1.28 ICP
47 0.95 ICP

Speckled dace 73 4.00 Se

68 3.35 Se
61 2.21 Se
72 3.86 ICP
69 3.08 ICP

Redside shiner 57 1.57 Se

46 0.89 Se
45 0.82 Se
64 2.27 ICP
45 0.67 ICP
38 0.47 ICP
1
ACM: Angus Creek, UEMC: upper East Mill Creek, LEMC: lower East Mill Creek, TC:
Trail Creek, USC: upper Slug Creek, LSC: lower Slug Creek, DVC: Dry Valley Creek, ShpC:
Sheep Creek, LBR: lower Blackfoot River.

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