NC0000272_Sediment Toxicity Data Watershed Stressor Study_20070125

Division of Water Quality
-Aquatic Toxicology Unit-
January 25, 2007
To: Jennifer Everett,Modeling/TMDL Unit
Through: Cindy A. Moore,Aquatic Toxicology Unit Supervisor
From: Sandy Mort, Aquatic Toxicology Unit
Subject: Pigeon River, Haywood Co., sediment toxicity data
for the watershed stressor study
ATU completed sediment toxicity studies on three surficial sediment composite samples
submitted for the Pigeon River watershed stressor study, as requested by the DWQ
Modeling/TMDL Unit. Samples were collected on August 14, 2006 and identified as:
Pigeon River at NC 215
Pigeon River at SR 1642
East Fork Pigeon River US 276 near Cruso, reference site
ATU performed toxicity assays on each sediment composite utilizing bacteria metabolic
inhibition,measured as bioluminescence, and benthic ostracod Cladoceran growth and
survival measurement endpoints. Detailed descriptions of each assay are included in the
Appendix.. ATU also performed ecological screening value analysis on metal and organic
analytical data. Discussion of toxicity study findings and methods follow.
Low-level toxicity effects were observed for the NC 215 and SR 1642 sediments. Bacteria
inhibition at potentially significant levels was observed for the NC 215 and SR 1642
sediments. Statistically significant levels of growth inhibition were also observed for these
two sediments in the benthic Cladoceran assay, but effect levels were below the 20.0%
criteria used to identify likely ecologically significant levels of inhibition. No significant
toxicity was observed in the reference site sediment.
Negative effects detected in aquatic toxicity assays have been directly related to observed
impacts in the aquatic environment. Effects observed in study sediment can be expected to
represent responses anticipated in situ to organisms of the same ecosystem functional level
and similar sensitivity. Identification of potential toxicity is limited by the test systems
employed and their sensitivity to toxicants that may exist at sampled sites. Toxicity to other
organisms or measurement endpoints cannot be ruled out.
Environmental Sciences Section page 1 Aquatic Toxicology Unit

Table 1 is a summary of sediment toxicity results and pertinent assay data for the three study
samples. Figure 1 provides a representation of relative toxicity levels for each endpoint
grouped by site,with increasing toxicity represented as decreased "% sample response".
Combined relative toxicity levels for each sediment are illustrated in Figure 2, with
cumulative toxicity for all endpoints increasing as the horizontal length decreases. Endpoint
measurements in Figures 1 and 2 were normalized to an equivalent scale to aid with data
comparison.
Bacteria inhibition assay data for sediments NC 215 and SR 1642 indicate IC50 values (IC50'
=sample concentration resulting in a 50% inhibition of the measurement endpoint)>16 times
lower than reference site values. This indicates substantially greater toxicity to bacteria in
NC 215 and SR 1642 sediments compared to reference site sediment. Only the metal buffer
system IC50 value for NC 215 met sediment toxicity classification criteria for toxicity at
levels of concern, using the most conservative criteria(criteria=IC50<1.0%, sample IC50=
1.03 % sample). (The bacteria assay metal buffer system enhances the detection of toxicity
due to metals.) ATU utilizes sediment toxicity classifications developed by other monitoring
groups in the assessment of sediment toxicity levels of concern. These criteria are listed in
Table 2. Sediment fines were visually estimated as<20% for the study samples. None of the
sediments caused significant mortality effects to the'benthic Cladocera test organism.
Based on the estimated low percent fines and observed low TOC values,these sediments
likely have limited organic carbon based sorption capacity for chemical contaminants. This
could result in increased mobility and bioavailability of metal or organic contaminants that
find their way into the sediments or pore water.
Metal and organic analytical data provided limited information regarding the cause of the
observed sediment toxicity. Ecological screening value analysis revealed similar potential
toxicity due to metals for NC 215 and SR 1642 sediments, although no metals were
quantified at concentrations exceeding selected screening values (Table 3). No organic
compounds were identified in NC 215 and SR 1642 sediments, although estimated
concentrations were provided for several "tentatively identified compounds". No metal or
organic analyses were performed on the reference site sediment (US 276 near Cruso),
limiting identification of possible causative toxicants.
cc: Alan Clark, DWQ
Darlene Kucken,DWQ
Roger Edwards, ARO
Harold Quidley, ESS
Environmental Sciences Section page 2 Aquatic Toxicology Unit

Table 1.Pigeon River sediment toxicity study,Haywood Co.,watershed stressor study.Surficial sediment
composite toxicity data summary.Sediments collected August 14,2006.
E Fit Pigeon R US276 ar
sample 10: FigeonR@NC215 Pigeon R@SR 1642 Cruso-Reference Site
test,criteria
Percent Solids 80.5 80.8 81.1
TOO,mg/kg 950 1,300 1.400
Bacteria toxicity.CheckLipht(as%sample in diluent)
IC20,Metal Buffer,drywl.normalized <0.756 <0.759 293
IC50,Metal Buffer,drywt normalized 1.03 �0.759 17.3
IC20,Metal Buller,OC-normalized m.000718 -O.000987 0.00410
IC50,Metal Buffer,CC-non alized 0.000982 <10.000987 0.0243
%effect@ 80.0%suspension 96.8 98.3 55.2
hortnesis,Wetal Buffer
FIT,days-metal buffer 8 9 9
IC20,Organic Buffer,drywt.normalized <0.756 <0.759 7.39
IC50,Organic Buffer,dryA.normalized <0.756 <0.759 152
IC20,Organic Buffer,OC-nomallzed m.000718 �0.000987 0.0104
IC50,Organic Buffer,OC-norrelized m.000718 m.000987 0.0214
[e-mail] 99.8 99.9 69.0
h omesis.Organic Buffer
HT,days-organic buffer 8 9 9
ostracodroxlOt 0stmicad 6-day Chronic Assay
gro.Mh result(pass/fail) Pass Pass Pass
mean%gnxfh increment ratio 81.5 832 95.7
statistically significant effect @>10.0&<20.0%effect yes yes
control growth,%of TAC 192.0 190.2 190.4
survival result(passtfail) Pass Pass Pass
statistically significant effect @210.0&<20.0%effect
%survival sampleloontrols 105 100 100
%survival,sample 91.7 100 96.7
%survival,controls# 96.7 100 96.7
Ffr,days 9 9 9
tMI
1. Percent total solids by USEPA method.dry @ 103-105 degrees G performed by DWO Chemistry tab.
2. IC20,IC50 =inhibition concentration,effect level. Sample concentration resulting in a 20%or 50%,inhibiton of measured
endpoint relative to negative control resporse.
3. Fbrn is(biosfirrulation)indurated when sample response is positive and exceeds control response by>20.0%
ATU considers tltis level of stimulation potentially ecologically significant for specified test organisms.
4. W=holdnglme
5. Mean%growth increment ratio = (mean gr nth increment sarrplehrean growth inclement controls)x 100
6. Statistically significant effect>10.0&Q0.0%effect for highest sarple oonoenfra8on tested
7. TAC=test acceptance criteria,>100%
8. %survival samplelcontrds(Ostrawdrmd<it)=%inhibition of sample survival relative to contra survival
Environmental Sciences Section page 3 Aquatic Toxicology Unit

Table 2. Sediment toxicity classification criteria.
Criteria source <20%tines 220% tines
Environment Canada,EPS Toxic: IC50<1000 mg/L Toxic: IC50<1000 mg/L
I/RM/42—April 2002
Toxic: if IC50>_I000 mg/L-
Environment Canada,EPS IC50>50%lower than reference
1/RM/42—April 2002t sediment IC50,and IC50s for
test and reference sediment are
significantly different
Ringwood,AH,DeLorenzo,ME, Toxic: EC50<0.5% Toxic: EC50<0.2%
Less conservative criteria.
iteriaa..Ross,PE,Holland, 199 (<5,000 mg/L DW) (<2,000 mg/L DW)
Ringwood,AH,DeLorenzo,ME, o °
Ross,PE,Holland,F. 1997 2 Toxic: EC50<1.0/o Toxic: EC50<0.5/o
More conservative criteria. (<10,000 mg/L DW) (<5,000 mg/L DW)
Notes:
mg/L units=mg sediment/L diluent
All criteria data normalized to sample dry weight("DW",at 103 to 105°C)
"fines"=sediment particles:50.063 mm in size,fines=silts+clays
"silt"=particles<0.063 and>_0.004 mm
"clay"=particles<0.004 mm
The test sediment and corresponding reference sediment%imes should differ by<30%.
References:
Environment Canada,EPS 1/RM/42—April 2002. Biological Test Method.-Reference Method for Determining the
Toxicity of Sediment Using Luminescent Bacteria in a Solid-Phase Test
'Ringwood,All,DeLorenzo,ME,Ross,PE,Holland,F. Interpretation of the Microtox Solid-Phase Toxicity Tests: The
Effects of Sediment Composition. Environmental Toxicology and Chemistry,vol. 16,no.6,pp 1135-1140, 1997
Table 3.Pigeon River sediment toxicity study,Haywood Co.,watershed stressor study.Ecological screening
value analysis of surficial sediment composite anal ical data.
�^** QorEanfu Individual analyte
Site TXQmelals OC corrected HQ>1
Pigeon River at NC 215 3.78 No compounds detected' None
Pigeon River at SR 1642 4.08 No compounds detected' None
East Fork Pigeon River
US 276 near Cmso, Not analyzed Not analyzed Not applicable
reference site
Notes:
ES V=ecological screening value
Environmental Sciences Section page 4 Aquatic Toxicology Unit

Figure 1.Pigeon River sediment toxicity study,Haywood Co.,watershed stressor study. Toxicity bioassay 50%effect levels and ostracod 6-day chronic growth
and survival inhibition values. Bacteria data normalized to sediment organic carbon(OC)concentration. Sample toxicity increases as %sample response level
decreases.All endpoints adjusted to an equivalent scale.
100
so
60
I'Ii l II I
70
' I
c 60
p ` III r'i it+ R
50
E
Ji
y
30 ' III gill'
20 I I i'III I�I�'rH N'
10
III ,'III �II'
0 rr+ts III k l 4u'
Pigeon R @ NC 215 Pigeon R @ SR 1642 E Fk Pigeon R US 276 nr Cruso-Reference Site
■Bacteria toxicity, metal buffer OC normalized IC50 toxicity factor O Bacteria toxicity, organic buffer OC normalized IC50 toxicity factor
El Ostracod chronic, %growth increment O Ostracod chronic, % relative survival
Environmental Sciences Section page 5 Aquatic Toxicology Unit

Figure 2.Pigeon River sediment toxicity study,Haywood Co.,watershed stressor study. Combined multi-trophic level toxicity measurements. Combined
toxicity increases as the numerical value decreases.Data represented as summed normalized endpoint responses.
�� I i II Dili i�I ii i i,PI iI II �I l�,i
�50
•n a iul
c '¢�e
ee i I
5P
�4
�6c
J ,
::•:.•.:.:::.•
Q Q° l
i
,
coil, 'i"iII , ul III 'Ill li',I I ,i ,
Gry,6
Q`Om
0 50 100 150 200 250 300 350 400
combined multi-trophic level toxicity
■Bacteria toxicity, metal buffer OC normalized IC50 toxicity factor 0 Bacteria toxicity, organic buffer OC normalized IC50 toxicity factor
0 Ostracod chronic, %growth increment 0 Ostracod chronic, % relative survival
Environmental Sciences Section page 6 Aquatic Toxicology Unit

-Appendix—
TMDL Watershed Stressor Study, Sediment Toxicity Methods
A panel of toxicity assays employing multiple organisms and endpoints was conducted on
sediments collected from each sampling location to assess potential toxicity to aquatic
organisms. Application of toxicity tests in water quality assessments is beneficial as
chemical and physical tests alone are not sufficient to assess potential negative effects on
aquatic biota. Toxicity tests allow the determination of effects of chemical interactions and
the influence of sample matrix characteristics on bioavailability. Toxicity testing combined
with matrix-specific analytical data, habitat suitability evaluations and aquatic population
studies,provide a powerful tool for ecosystem health assessment.
Aquatic toxicity testing utilizes biological systems (aquatic organisms or cellular componer
of aquatic organisms) to identify ecologically relevant adverse (toxic) effects caused by
chemical agents (toxicants) in the water or sediment sample of concern. Negative effects
detected in aquatic toxicity assays have been directly related to observed impacts in the
aquatic environment. Assays are performed with organisms of a particular sensitive life-
stage that are known to be healthy and free of disease or other detrimental effects. Each ass
-includes parallel"controls"consisting of organisms subjected to the same assay conditions
organisms exposed to the sample of concern ("test sample"), except they are exposed to a
non-toxic "control'water or sediment. Control organism response characteristics are used .
the baseline for evaluation of responses of organisms exposed to test samples. Specific
responses are monitored for a particular test and may include death; growth as weight, lengl
or cell number; production of young; cellular responses such as bioluminescence,
photosynthesis, or DNA-repair activity; or, generalized physiological responses such as
feeding rate. Individual test conditions are tightly controlled (temperature, exposure period
lighting, feeding, number and age of organisms) so that the only variable between organism
in a particular test is the exposure medium (controls or test sample). Test validity is based
control responses meeting pre-established performance criteria and ability to maintain
specified test operational parameters throughout the exposure period. Tests may involve
exposure of organisms to different concentrations of test sample (multi-concentration tests).
or to a single test sample concentration (percent inhibition test). Multi-concentration tests

uncertainty in toxicity assessments relying on single organisms. Sensitivity to classes of
potential toxicants may vary by the test organism, the life-stage of the organism, species-
specific metabolic characteristics, ecosystem functional characteristics, and location-specifi
media characteristics. Due to physiological and ecological niche differences species of
aquatic organisms are not equally exposed or susceptible to specific classes of toxicants. 13:
using a variety of organism types and endpoints, the ability to detect unique sensitivity
patterns to specific classes of toxicants is enhanced, enabling detection of inhibitory effects
that may not be observed with a single assessment endpoint. Additionally, using organisms
of various functional levels provides an indication of potential cumulative inhibitory effects
across aquatic food chain or nutrient cycling components. Yet, the use of multiple organis
and endpoints does not rule out the potential for detrimental aquatic impacts to go
undetected.
Sediment toxicity is a critical component of comprehensive watershed toxicity assessments.
Water quality criteria(WQC) were developed to protect water column organisms and were
not intended to protect benthic organisms. Sediments serve as a sink for accumulation of
both inorganic and organic chemicals with bulk chemical concentrations not highly correlat
with bioavailability and toxicity. Surficial sediments are complex systems where toxicant
bioavailability and fate is controlled by sediment physicochemical characteristics and varyil
microbial micro-environment horizons. Partitioning of compounds between water and
sediment compartments, and between sediment phases, is a complex relationship dependent
upon multiple factors including solubility,pH, redox, grain size, cation-exchange capacity,
sediment organic carbon and microbial-mediated acid volatile sulfide(AVS) concentrations
Sediments provide a potential exposure source to benthic organisms, organisms in
association with the sediment-water interface, and to water column organisms through
trophic—level transfer. Organisms can be exposed through direct sediment or interstitial
water(pore water) contact or by ingestion of sediment particulates. Contaminants complex
to particulates or colloidal organic carbon have limited bioavailability,but may become
bioavailable under particular circumstances, such as direct contact or selective ingestion of
particulates and species-specific gut desorption characteristics. For metals and non-ionic
organic contaminants, the free-dissolved concentration in sediment interstitial water(the
"free-dissolved"phase, not associated with colloidal dissolved organic carbon) is the
dominant bioavailable fraction and generally correlates to toxicity effects. In anaerobic
sediments, AVS-metal complex formation kinetics are the primary factors controlling
cationic metal bioavailability, with organic carbon serving as an additional binding phase. ]
aerobic sediments, free sulfides are not microbially generated and organic carbon and iron
and manganese oxides serves as the primary factors controlling interstitial water metal
concentrations [2,3]. Although it is recognized that the sample collection and handling
' nrnracc oltnre rmm�lav carlimant mirrn_anvirnnmanhe nnA nn4nntially tnvinont hinmroilohilit

Ecological Screening Values Analysis
ATU performed ecological screening value analysis on Pigeon River sediment composite
samples submitted for toxicity bioassay studies. The screening value(SV) analysis and
hazard quotient (HQ) calculations utilized only organic compounds that were reported with
quantified or estimated analyte concentrations. Organic analytes reported as not-detected
(ND) above the method detection limit WL) or at the practical quantitation limit(PQL)
were not included in the assessment to better provide an indication of the impact of
quantified analytes. A limited number of metal and organic compounds were detected in th
sediments. ATU used SVs from The Risk Assessment Information System web page
(httu://rais.oml.govn and established use precedence based on a preference for conservative
toxicity levels and values compiled by various USEPA Regions.
Calculated HQs are listed in Table 3. Organic HQs were corrected for sample organic carbi
(OC) concentrations. Individual analytes with HQs >_1.0 are also listed. HQs>1.0 indicate
potential for toxicity. Toxicity is impacted by a number of site and analyte characteristics
that may reduce ultimate toxicity(pH, OC, complexation with biotic and abiotic particulate
or colloids, etc.). HQs are summed(EHQ) to provide an indication of the total potential
toxicity due to metals or organics. Ultimate toxicity may be related to compounds that werc
not analyzed.

Sediment Toxicity Bioassay Descriptions
CheckLight ToxScreen-II Bacterial Inhibition Assay
The CheckLight system is a bacterial toxicity assay utilizing a highly sensitive variant of tht
marine bioluminescent bacterium Photobacterium leiognathi (strain SB). Under suitable
metabolic conditions Photobacterium emit high levels of bioluminescence, produced when
the protein luciferin comes in contact with oxygen. Chemical,physical and biological
toxicants that affect cell respiration, electron transport systems, ATP generation, or the rate
protein or lipid synthesis,will alter the level of luminescence. Agents tho
impact microbial cell integrity including membrane function also affect
luminescence [1,2]. The assay system exposes the bacteria to various
" concentrations of test sample in a medium adjusted to provide a suitable
matrix for the bacterium's growth. Substances present in the test sample
that are toxic to the bacteria result in changes to the amount of luminescence generated by t
bacteria. These changes are quantified instrumentally. The changes in luminescence of
bacteria exposed to the test sample concentrations are compared to luminescence produced
bacteria in non-toxic control media, prepared simultaneously with the test sample.
Bacteria are supplied in a lyophilized form (freeze-dried) and reconstituted at the time of th•
assay, with kit-supplied hydration and storage buffers. The system utilizes two assay buffet
one which favors the detection of heavy metals (Pro-Metal Buffer), and the other which
favors the detection of organic toxicants (Pro-Organic Buffer). Samples submitted to ATU
are tested with both buffer systems. A minimum of five sample dilutions is prepared in eac
buffer system. Negative controls are prepared at the time of sample preparations and consk
of buffer solutions. Reconstituted bacteria are added to control solutions and sample
dilutions and incubated at 26.0± 3.0°C for 60.0 minutes. Luminescence data is measured
with the Microtox 500 Analyzer, and data gathered and reduced with the Microtox Omni
software system [3,4]. Organic and metal reference toxicant tests are run each month of
sample analysis to validate system performance. Sediment and soil sample matrices are
prepared as a 37.5% suspension in dcionized water (DIW) and stirred for 30.0 minutes.
Aliquots of the suspension are serially diluted in each of the two buffer systems. Test
bacteria are added to the sample suspensionibuffer mixtures prior to incubation. Filtrates o:
the sedimentibufferlbacterium solutions are prepared for luminescence determination.
Sample data is reported as sample mass per volume of buffer resulting in a 20% (IC20) of
50% (IC50) inhibition of luminescence compared to control solutions. Sediment data is
reported relative to dry weight solids or organic carbon concentrations.

optimization of assay conditions, the CheckLight system reportedly provides 1 to 2 orders c
magnitude enhancement in sensitivity to a broad range of toxicants with differing modes of
action, as compared to other bacterial toxicity assays utilizing luminescent species [1,2].
The CheckLight ToxScreen-II system has completed verification in USEPA's
Environmental Technology Verification Program (ETV) program. The purpose of the ETV
program is to convey objective, third party data to the environmental marketplace regarding
the performance of new environmental technologies. The ETV program develops testing
protocols and verifies the performance of innovative technologies that have the potential to
improve protection of human health and the environment. ETV was created to accelerate
the entrance of new environmental technologies into the domestic and international
marketplace [5].
The CheckLight bacteria assay represents effects expected in decomposer components of th
aquatic ecosystem. Bacteria are uni-cellular prokaryotic organisms that utilize absorptive
modes of nutrition. Bacteria play a critical role in aquatic ecosystems as heterotrophic
decomposers, along with fungi, drawing nourishment from dead plant and animal matter.
decomposers, bacteria break down complex energy-rich organic material into simpler organ
molecules, carbon dioxide, inorganic nutrients and water, releasing some of this material to
be used by consumers. P. leiognathi are widely distributed marine bioluminescent gram-
negative motile heterotrophic rods of the Eubacteria group, generally found in warm, shallc
tropical waters. P. leiognathi serve as surrogate bacterium decomposers for the freshwater
ecosystem, providing a convenient, sensitive effect monitoring system.
Heterocyprisincongruens Chronic Ostracod Crustacean Assay
ATU utilizes the MicroBioTests Inc. OstracodToxKit FTM assay for 6-day direct contact
whole-sediment testing. This test system utilizes the benthic ostracod crustacean
Heterocypris incongruens.hatched from cysts prior to test initiation. Whole-sediment tests
provide for assessment of toxicity effects due to direct contact of the to
organism with contaminants associated with sediment particles,
interstitial water, and overlying water, as well as ingestion of
- = contaminated detritus, or adsorbed to algae supplied as a food source
during the test. Organism survivability and growth as length are
monitored at the end of the 6-day exposure period,with test sediment response compared tc
organism response in kit-supplied non-toxic control sediment. Six replicates are prepared c
both control and test sediments, with 10 ostracods added to each replicate. Average percem
,..1.:1.:}:,,.. ,.F....'..:....1.:1:4......A ........41. :.. 41.n}o„} . A:...o..4 ...e .............oA 4,. .....,4.,.1 ..vA:...n..l

continents. The trophic position of ostracods is that of herbivore and detbvore, feeding
primarily at the sediment-water interface, consuming algae, both fresh and decaying
particulate organic matter, diatoms, and plants. Some species are known to feed on living
animals. Typical behavior includes intimate contact with sediment particles and interstitial
spaces in organic-rich, aerobic sediment environments. Ostracods are consumed by higher
animals including bottom-dwelling fish, other invertebrates, insects and birds [7].
References
1. CheckLight ToxScreen-H bacterial toxicity assay system.2004. CheckLight Ltd., Qiryat-Tivo'i
36000,Israel.
2. Ulitzur S,Lahav T,Ulitzur N. 2002.A novel and sensitive test for rapid determination of water
toxicity. Env Tox J.
3. Microtox®Toxicity System. Strategic Diagnostics Inc.,Newark,DE.
4. Microtox Omni" Software for Windows 95/98/NT. 2003. Strategic Diagnostics Inc.,Newark
DE.
5. U.S.EPA Environmental Technology Verification Program(ETV). 1995.
littn://A"vNv.epa.Gov/etv/index.htrnl
6. OstracodToxKit FTM. 2005. Chronic direct contact toxicity test for freshwater sediments.
MicroBioTests Inc.,Nazareth Belgium. vivyw.microbiotests.be
7. Thorp, JH, Covich, AP. 2001. Ecology and Classification of North American Freshwa
Invertebrates, second edition.Academic Press, Orlando FL,USA.