Abstract.--The lower San Gabriel River is an urban watershed
located on the border of Los Angeles and Orange Counties. It has a
diversity of potential pollutant sources including five water
reclamation plants (WRPs) that discharge treated wastewaters and more
than 100 storm drains that discharge largely untreated urban runoff to
the river. The goal of this study was to assess the magnitude of
toxicity to Ceriodaphnia dubia throughout the lower San Gabriel River
watershed during wet and dry weather, identify the responsible
toxicants, and compare the magnitude of toxicity over time to evaluate
the effectiveness of previous watershed management actions. Wet weather
runoff was sampled from sites located at the end of the four main
reaches of the lower San Gabriel River; Walnut Creek, San Jose Creek,
Coyote Creek, and San Gabriel River mainstem. None of the samples
collected over two wet seasons exhibited acute or chronic toxicity. Dry
weather samples were tested from 16 locations distributed throughout the
lower watershed for up to 18 months. None of the dry weather samples
from Walnut Creek, San Jose Creek, or the San Gabriel River mainstem
exhibited acute or chronic toxicity. Acute and chronic toxicity was
intermittently measured in the Coyote Creek tributary. Toxicity
identification evaluations suggested nonpolar organic constituents,
likely diazinon and perhaps surfactants, as possible toxicants. Toxicity
observed in this study was significantly reduced compared to a similar
study of the watershed 12 years previously, especially in the San
Gabriel River mainstem. Much of the reduction in toxicity was associated
with upgrades in WRP treatment. Little to no change in toxicity was
observed in Coyote Creek upstream of the WRP discharge where little to
no control of dry weather urban runoff had occurred.
**********
Urban watersheds receive a multitude of potential pollutants that
can affect aquatic life (Bay et al. 1996, Ackerman et al. 2005,
Tiefenthaler and Stein 2005). The San Gabriel River, located on the
border between Los Angeles and Orange Counties in southern California,
is an ideal example of the ways in which aquatic life may be impacted by
potential pollutants. Sources of potential pollutants include: 1)
treated sanitary wastewaters from five Water Reclamation Plants (WRPs);
2) untreated urban runoff from approximately 350 (km.sup.2) of developed
land discharged into the river via a municipal separate storm sewer
system; and 3) once-through cooling waters from two power generating
stations that is mixed with low volume industrial and sanitary wastes
then discharged into the watershed's estuary.
To complicate the fate and transport of anthropogenic pollutants
and their resultant effects on aquatic life, the hydrology of many urban
watersheds is often highly modified. For example, three major dams were
constructed in the upper undeveloped reaches of the San Gabriel River
watershed in order to capture, retain, and utilize wet season runoff for
potable water use during the dry season. While this provides much needed
water for the citizens of Los Angeles, the upper watershed is now
hydrologically disconnected from the urbanized lower watershed. The
result is that runoff from natural areas are unavailable for mixing and
dispersion of anthropogenic discharges downstream. Even greater
hydromodification exists in the urbanized lower San Gabriel River
watershed. Many miles of the river in this portion of the watershed are
lined with concrete in an effort to reduce flooding and property damage,
but this modification also results in the maximum exposure of pollutants
to aquatic life through the loss of natural stream and treatment
processes. Where unlined channels exist in the lower watershed,
temporary dams are inflated to enhance groundwater recharge.
In response to pollutant inputs and hydrologic modification, many
urban watersheds have been the focus of water quality regulatory
efforts. Urban Los Angeles once again provides a good example. More than
180 waterbodies in the Los Angeles region have been placed on the United
States Environmental Protection Agency's (EPA's) list of
impaired waters. This list, also referred to as the 303(d) list
(referring to section 303 d of the Clean Water Act), identifies
locations impacted by specific pollutants that can result in toxicity to
aquatic life and other impacts. Virtually all of the urbanized portions
of the San Gabriel River are one the 303(d) list for pollutants such as
nutrients (and related impacts), certain trace metals, and aquatic
toxicity. The effect of the 303(d) list is the mandate for future
regulation (termed a total maximum daily load or TMDL), which will
require the mitigation of these pollutant inputs.
In the San Gabriel River watershed, managers have been implementing
mitigation to negate the effects of these pollutant inputs. Over the
past 10 years, WRPs in the San Gabriel River watershed have installed
additional treatment processes, costing over $40 million, that have
dramatically improved the water quality of their discharges for
nutrients and trace metals. Controlling pollutant impacts due to urban
runoff has been more difficult. Up to $10 million has been spent on
structural best management practices (BMPs) in the San Gabriel River,
yet few (if any) trends in concentrations of toxic constituents
monitored have been observed (LACDPW 2005). Unlike WRPs, urban runoff
discharges are diffuse and, as a result, perhaps more difficult to treat
and/or control.
The objective of this study was to evaluate the impact of
pollutants on aquatic life in the highly urbanized lower watershed of
the San Gabriel River. Impact to aquatic life was assessed through the
use of toxicity testing. Four specific goals were identified: 1) assess
the magnitude of toxicity at selected locations throughout the San
Gabriel River watershed; 2) determine whether or not this magnitude
changes seasonally; 3) if toxicity exists, identify the responsible
toxicants; and 4) compare the magnitude of toxicity in this study to
studies conducted historically in the San Gabriel River watershed to
evaluate the effectiveness of watershed management actions.
Material and Methods
Toxicity in the San Gabriel River watershed was evaluated by
separating the study into wet weather and dry weather components (Figure
1; Table 1). The wet weather component consisted of four sampling sites
located at the downstream end of major reaches that receive urban
runoff. Twenty-liter flow weighted composites samples were collected
during three storm events on December 29, 2004 (5.3 cm precipitation),
April 22, 2005 (2.2 cm precipitation), and January 1, 2006 (3.7 cm
precipitation). The dry weather component consisted of sampling a total
of 10 sites that included the same four sites sampled during wet
weather, plus an additional six sites strategically located in the
immediate vicinity of WRP discharges or urban runoff inputs. Dry weather
samples were collected at least three days after rain events.
Twenty-liter samples were collected from each site during dry weather on
a monthly basis from March 2005 to February 2006. Within seven months of
this study's initiation, an additional six sites were added for dry
weather sampling, all in a single tributary (North Coyote Creek), as a
result of observed toxicity. All sites from the Coyote Creek
subwatershed, including the additional sites in North Coyote Creek, were
sampled until August 2006.
[FIGURE 1 OMITTED]
All samples were tested for toxicity using Ceriodaphnia dubia
examining both acute (lethality) and chronic (reproductive success)
endpoints. Testing was initiated within 36 hours of sample collection
using undiluted sample and a negative control following standard US EPA
protocols (US EPA 1993a; Table 2). Test organisms were obtained from
in-house brood cultures and test duration/exposure lasted until 60% of
the surviving females in the control had released three broods
(typically between six and seven days). Test solutions were renewed
daily.
Toxicity was defined as a 25%, or greater, organism response in the
sample exposure relative to control organism response (i.e., <75%
survival or reproduction in the 100% sample exposure). In addition,
hypothesis testing was conducted following EPA guidelines (US EPA
1993a). Hypothesis testing consisted of the nonparametric Fisher's
Exact Test for the survival endpoint and an analysis of variance (ANOVA)
followed by a multiple comparison procedure for the reproduction
endpoint. The parametric Dunnet's Test was used to identify
statistically significant differences from the control for reproduction
data that were normally distributed with homogeneous variances. The
nonparametric Steel's Many-One Test was employed when the data
failed normal distribution or equality of variance assumptions.
If a sample was toxic, a toxicity identification evaluation (TIE)
was initiated (US EPA 1991, 1993b). TIE testing used the remaining
sample, stored at 4[degrees]C, within seven days of baseline test
conclusion. For those samples in which only the reproductive endpoint
elicited a toxic response, only 100% and control concentrations were
evaluated in the TIE. In these cases, the TIE consisted of a full
seven-day chronic test with each sample manipulation consisting of 10
replicates, with daily renewals. For those samples where the survival
endpoint elicited a toxic response, three dilutions (25%, 50%, 100%) and
a control were evaluated using four replicates containing five test
organisms each. In the case of a TIE in response to survival, the
exposure duration was 96 hours, with renewal after 48 hours.
The TIE manipulations focused on both characterization and
identification phases (EPA 1991, 1993b). These manipulations included:
1) pH adjustment; 2) aeration; 3) Ethylenedinitrilo-Tetraacetic Acid
(EDTA); 4) Sodium thiosulfate (STS); 5) filtration; 6) piperonyl
butoxide (PBO); 7) anion exchange column; 8) solid phase extraction
(SPE); 9) SPE elution; and 10) no manipulation. By conducting each of
these manipulations, the results, alone or in combination, can help to
identify the responsible toxicant(s) (Table 3).
All quality assurance/quality control criteria were met for this
study. These criteria included all of the test acceptability criteria
(Table 2). In addition, positive control samples using reference
toxicants (copper chloride) confirmed the relative sensitivity and
stability of test organisms during the course of the study.
Results
None of the storms sampled during this study were acutely or
chronically toxic to Ceriodaphnia. At all four sites, during all three
storms, survival and reproduction were greater than 75% relative to
controls.
Eighteen of 196 (9%) total dry weather samples exhibited chronic
toxicity during this study (Table 4). Twelve of 196 (6%) total dry
weather samples exhibited acute toxicity during this study. All of the
dry weather samples that exhibited acute toxicity also exhibited chronic
toxicity. In only one case was statistically significant toxicity
observed when the response was less than 25% relative to controls
(Station 15, Jan 2006). This resulted from low control variability. Only
once was toxicity greater than 25% relative to controls and not
statistically significant (Station 15, Mar 2006). This resulted from
large sample variability.
All observed toxicity during this study was from Coyote Creek
(Table 4). No toxicity was observed in Walnut Creek, San Jose Creek, or
San Gabriel River Reaches 1 or 3. Widespread toxicity in Coyote Creek
was observed in April 2005. As a result, an additional six stations
upstream were added between July and October 2005. Widespread toxicity
was observed again in August 2005. Widespread toxicity was not observed
again for the remaining 12 months (September 2005 to August 2006).
In the two events for which widespread toxicity was observed in
Coyote Creek (April and August 2005), the toxicity appeared to originate
in the upper portions of the tributary (Figure 2). In April 2005, 100%
reproductive impairment was observed at the site sampled furthest
upstream (site 10) and reproductive success remained minimal moving
downstream. Ceriodaphnia survival was also severely impacted at the
furthest upstream station, then survival slowly increased downstream of
the WRP discharge (Sites 7 and 6) indicating a potential dilution effect
from the WRP effluent. The WRP in this reach was discharging 13 mgd of
effluent to Coyote Creek upstream of Site 6 during this sampling event.
In August 2005, severe reproductive impairment was again observed at the
site sampled furthest upstream (site 14) and reproductive success
remained minimal moving downstream. The WRP in this reach was not
discharging effluent to Coyote Creek during this sampling event.
Ceriodaphnia survival was more sporadic moving downstream during August
2005. Seventy eight percent survival was measured at site 14 and
decreased to 0% survival for downstream Sites 13 and 12. Survival
increased to 100% at site 11, but fell back to 0% survival for the
remaining seven miles of Coyote Creek. The sudden increase in survival
at Site 11 remains unexplained.
[FIGURE 2 OMITTED]
[FIGURE 3 OMITTED]
Seven TIEs were initiated during the study on dry weather samples
exhibiting a 25% or greater effect (Table 5). Toxicity was no longer
present for three of the samples (sites 9 and 10 March 2005, site 15
March 2006); consequently, no toxicant was identified.
Organophosphorus pesticides, most likely diazinon, were identified
as the causative agent in one sample (site 10 April 2005). This result
was based on the exclusive removal of toxicity using SPE and the
addition of PBO, which removes non-polar organic toxicants and inhibits
toxicity due to diazinon, respectively (Figure 3). The SPE was
sequentially eluted and these fractions were subsequently tested.
Toxicity was recovered in the 80% methanol elution of the SPE column, a
fraction associated with many organophosphorus pesticides including
diazinon (Figure 4). Finally, 1,700 [micro]g/L diazinon was quantified
in the sample using Enzyme-Linked Immuno-Sorbant Assay (ELISA)
techniques.
[FIGURE 4 OMITTED]
A non-polar organic toxicant(s), possibly a surfactant(s), was
identified as the causative agent in the remaining three samples (site
10 April, June, and August 2005). This result was based on the removal
of toxicity using SPE. Toxicity was recovered in the 75% methanol
elution, a fraction commonly associated with organophosphorus pesticides
with surfactant toxicity recovery also documented (Norberg-King et al.
2005). An anion exchange column was used on two samples, with complete
removal of toxicity observed in one sample (June 2005) and partial
removal in the other (August 2005). This may be indicative of anionic
surfactants, but might also suggest the presence of some trace metals.
Elution of the anion column would help to confirm anionic surfactant
toxicity, but attempts to recover toxicity from the anion column were
not successful. However, other treatments to identify trace metals did
not reduce toxicity (i.e., EDTA), which helps to rule-out metals as a
major source of toxicity. Aeration partially removed toxicity in the
April 2005 sample. Some surfactants can be removed or partially removed
through aeration. Finally, PBO did not reduce toxicity, and levels of
diazinon in these three samples were low (< 100 [micro]g/L).
Discussion
Toxicity was not widespread in the San Gabriel River watershed over
the 18 months examined during this study. No toxicity was observed at
any site during any of the storm events sampled. Similarly, no toxicity
was observed in four of the five major reaches in the lower watershed
during dry weather. In Coyote Creek where toxicity was observed, the
toxicity was intermittent and occurred only during six of the 18
sampling periods. This was despite an adaptive monitoring strategy, in
which the number of sites sampled in Coyote Creek was doubled and the
sampling period was extended by six months.
[FIGURE 5 OMITTED]
The lack of toxicity observed in this study was in direct contrast
to historical studies in this watershed. While 9% of the samples were
toxic in 2005/06, 55% of the samples collected for a similar study in
1992/93 were toxic (Bailey et al. 1995). Moreover, toxicity was observed
in only a single reach (Coyote Creek) in 2005/06, while Bailey et al.
(1995) identified toxicity in all five major reaches in the lower San
Gabriel River watershed.
The difference in toxicity from tests conducted 14 years ago is
likely due to changes in water quality. Bailey et al. (1995) concluded
that toxicity in the San Gabriel River watershed was likely due to
non-polar organics and possibly ammonia. This is not unexpected as there
are multiple WRPs discharging to the San Gabriel River; these treated
effluent discharges comprise roughly 80% of flow during the dry season,
contributing as much as 99% of the total ammonia input (Ackerman et al.,
2005). In 1992/93, ammonia levels averaged over 10 mg/L. In 2003,
however, the WRPs fully implemented nitrification and denitrification
treatment (NDN) processes, which subsequently reduced discharged ammonia
levels more than 80% to an average of less than 2 mg/L (Figure 5). Thus,
a reduction in toxicity for reaches in the San Gabriel River watershed
dominated by WRP effluents can be easily explained.
The lack of toxicity observed in the current study is consistent
with other toxicity data collected in recent years. In 2005, a
probability-based watershed survey was conducted in the entire San
Gabriel River watershed, and 7% of the stream-miles were considered
toxic to Ceriodaphnia (Stein and Bernstein, in prep). Even this
toxicity, however, was eliminated after a TIE and subsequent follow-up
investigations helped identify and eliminate the illicit discharge
responsible.
A second example of reduced toxicity in recent years was observed
in routine toxicity monitoring required in the vicinity of the WRPs as a
part of their National Pollutant Discharge Elimination System (NPDES)
permit requirements. Between June 2003 and June 2006, only 14% of the
269 total samples from 14 different sites exhibited toxicity (i.e.,
greater than 25% response relative to controls). For this period,
toxicity was largely constrained to Coyote Creek (6% of total number of
samples) and the uppermost portions of San Jose Creek (6% of total
number of samples). Coyote Creek is the same tributary in which the
current study round intermittent toxicity. The uppermost section of San
Jose Creek was not monitored during the current study.
In contrast to the main stem of the San Gabriel River, much less
effort has been spent on identifying and remediating sources of toxic
pollutants in the Coyote Creek subwatershed. As a result, the toxicity
in Coyote Creek has remained. The frequency of toxicity in Coyote Creek
has remained similar between 1992/93 and 2004/05; roughly 12% to 22% of
the samples were considered toxic. Pesticides available for application
by homeowners continue to be one toxicant of concern. Diazinon was
identified in 2004/05 (this study), as well as in the 1992/93 study
(Bailey et al. 1995). The toxicity observed in urban runoff-dominated
reaches during this study was intermittent, which is consistent with
contributions by homeowner pesticide use (Schiff and Tiefenthaler 2003),
illegal/ illicit discharges, and observations in other dry weather
runoff toxicity studies (Greenstein et al. 2004).
Acknowledgements
Toxicity testing was conducted by the Los Angeles County Sanitation
Districts (Jay P. Bottomley and the staff of the San Jose Creek Water
Quality Laboratory) and Nautilus Environmental, Inc. (Chris Stransky,
Howard Bailey and staff). Wet weather sampling was conducted by Mactec
Engineering, Inc. (Jay Shrake and staff). Dry weather sampling was
conducted by the Los Angeles County Sanitation Districts (Misty Rogalski
and Jeaneal Davis) and the Southern California Coastal Water Research
Project (Dario Diehl, David Tsukada, Dawn Petschauer and Diana Young).
Information management was provided by Southern California Coastal Water
Research Project (Jeff Brown and Larry Cooper). This project was
partially supported by the Los Angeles Regional Water Quality Control
Board.
Accepted for publication 30 January 2007.
References
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quality in the San Gabriel River watershed. Bull So Cal Acad of Sci,
104:125-145.
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Hinton. 1995. Site specific study for effluent dominated streams (San
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California Regional Water Quality Control Board, Los Angeles Region.
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Bay, S.M., D.J. Greenstein, S-L. Eau, M.K. Stenstrom, and C.G.
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Watershed. Bull So Cal Acad of Sci, 95:33-45.
Brown, J. and S. Bay. 2003. Organophosphorus pesticides in the
Malibu Creek watershed. Technical Report 403. Southern California
Coastal Water Research Project. Westminster, CA.
Greenstein, Darrin J., L. Tiefenthaler, and S. Bay. 2004. Toxicity
of parking lot runoff after application of simulated rainfall. Env
Contam and Tox, 47:199-206.
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water impact report. Los Angeles County Department of Public Works,
Alhambra, CA.
Norberg-King, T.J., L.W. Ausley, D.T. Burton, W.L. Goodfellow, J.L.
Millet, and W.T. Waller. 2005. Toxicity reduction and toxicity
identification evaluations for effluents, ambient waters, and other
aqueous media. Society of Environmental Toxicology and Chemistry (SETAC)
Press, Pensacola, FL.
Schiff, K. and L. Tiefenthaler. 2003. Contributions of
organophosphorus pesticides from residential land uses during dry and
wet weather. Technical Report 406. Southern California Coastal Water
Research Project. Westminster, CA.
Stein, Eric D. and L.L. Tiefenthaler. 2005. Dry-weather metals and
bacteria loading in an arid, urban watershed: Ballona Creek, California.
Water, Air, and Soil Pollution, 164:367-382.
US EPA. 1991. Methods for aquatic toxicity identification
evaluation: Phase I toxicity characterization procedures, Second
Edition. EPA 600/6-91/003. US Environmental Protection Agency,
Environmental Research Laboratory, Duluth, MN.
US EPA. 1993a. Methods for measuring acute toxicity of effluents
and receiving waters to freshwater and marine organisms, Fourth Edition.
EPA 600/4-90/027. US Environmental Protection Agency, Environmental
Research Laboratory, Duluth, MN. US EPA. 1993b. Methods for aquatic
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600/R-92/080. US Environmental Protection Agency, Environmental Research
Laboratory, Duluth, MN.
Kenneth Schiff, (1)* Beth Bax, (2) Phil Markle, (2) Terry Fleming,
(3) and Jennifer Newman (4)
* corresponding author: 3535 Harbor Blvd, Costa Mesa, CA 92626,
kens@sccwrp.org (714)-755-3202 V (714) 755-3299 F
(1) Southern California Coastal Water Research Project,
Westminster, CA
(2) Los Angeles County Sanitation Districts, Whittier, CA
(3) US Environmental Protection Agency, San Francisco, CA
(4) Los Angeles Regional Water Quality Control Board, Los Angeles,
CA
Table 1. Station location information (NAD83 datum).
Site # Water Body Location
1 Walnut Creek Walnut Creek At Merced Ave
2 Walnut Creek At Baldwin Park Blvd
3 San Jose Creek San Jose Creek at access gate from
Reach 1 SJCWRP/JAO - Upstream of SJCWRP,
approximately 100 yards downstream of
Workman Mill Rd
4 San Gabriel River San Gabriel River at Peck Rd -
Reach 3 Downstream of confluence of SGR with
SJC
5 San Gabriel River San Gabriel River at Spring St -
Downstream of LCWRP outfall 001
6 Coyote Creek Coyote Creek at pedestrian foot bridge
south of LBWRP - Downstream of LBWRP
outfall 001 and upstream of estuary
7 Coyote Creek Coyote Creek at Cerritos Ave - Upstream
of LBWRP outfall; downstream of entrance
of Carbon Creek into Coyote Creek
8 Coyote Creek Coyote Creek at Centralia Ave -
Downstream of confluence with Fullerton
Creek and an industrial drain
9 Coyote Creek Coyote Creek at Artesia Blvd-Downstream
of Brea Creek/Coyote Creek confluence
10 Coyote Creek North fork of Coyote Creek at Alondra
(North Fork) Blvd-Downstream of La Mirada Creek
11 Coyote Creek Coyote Creek North Fork at La Mirada
(North Fork) Creek/Coyote Creek confluence
12 Coyote Creek Coyote Creek North Fork- 1.0 mile
(North Fork) upstream of Alondra
13 Coyote Creek Coyote Creek North Fork - 2.0 miles
(North Fork) upstream of Alondra
14 Coyote Creek Coyote Creek North Fork - 2.5 miles
(North Fork) upstream of Alondra
15 La Mirada La Mirada Creek before entering Coyote
Creek Creek North Fork
16 Milan Creek Milan Creek before entering Coyote Creek
North Fork
Site # Water Body Latitude Longitude
1 Walnut Creek N34[degrees]03'53.1"
W117[degrees]57'09.6"
2 Walnut Creek N34[degrees]03'47.7"
W117[degrees]58'54.5"
3 San Jose Creek N34[degrees]02'06.7"
Reach 1 W118[degrees]01'14.9"
4 San Gabriel River N34[degrees]02'02.9"
Reach 3 W118[degrees]02'20.2"
5 San Gabriel River N33[degrees]48'38.9"
Reach 1 W118[degrees]05'26.8"
6 Coyote Creek N33[degrees]47'41.9"
W118[degrees]05'22.0"
7 Coyote Creek N33[degrees]48'36.9"
W118[degrees]04'33.3"
8 Coyote Creek N33[degrees]50'19.3"
W118[degrees]03'37.9"
9 Coyote Creek N33[degrees]52'23.7"
W118[degrees]01'08.0"
10 Coyote Creek N33[degrees]53'15.4"
(North Fork) W118[degrees]01'58.9"
11 Coyote Creek N 33[degrees]53.731'
(North Fork) W 118[degrees]02.155'
12 Coyote Creek N 33[degrees]54.133'
(North Fork) W 118[degrees]02.488'
13 Coyote Creek N 33[degrees]54.862'
(North Fork) W 118[degrees]02.346'
14 Coyote Creek N 33[degrees]55.411'
(North Fork) W 118[degrees]02.138'
15 La Mirada N 33[degrees]53.503'
Creek W 118[degrees]01.846'
16 Milan Creek N 33[degrees]54.369'
W 118[degrees]02.422'
Table 2. Test conditions and requirements.
Test Organism: Ceriodaphnia dubia
Organism Source: In-house Cultures
Organism Age at Initiation: <24 hours old and released within an
eight hour period
Test Duration: Until 60% or ore of the surviving
females have three broods
Concentrations Tested: 0% and 100%
Solution Renewal: Daily
Feeding: 0.1 ml YCT and 0.1 Selenastrum algal
suspension daily
Test Chamber: 50 ml Disposable
Solution Volume: 15 ml
Control Water: Either diluted mineral water (8 parts
deionized water: 2 parts Perrier
water) or Reconstituted deionized water
(hard)
Number of Replicates: 10
Organisms per Replicate: 1 assigned by blocking by known
parentage
Photoperiod: 16 hours light (50-100 ft-c), 8 hours
dark
Test Temperature: 25 [+ or -] 1[degrees]C.
Endpoints Measured: Survival and Reproduction
Test Acceptability Criteria: 80% or greater survival with an average
of 15 or more young per surviving
female in the control organisms. 60%
of surviving females in the controls
must produce three broods within 8
days.
Table 3. Toxicity Identification Evaluation (TIE) sample manipulations
and their respective interpretations.
TIE Sample Manipulation Expected response
pH Adjustment (pH 7 and 8.5) Alters toxicity in pH sensitive
compounds (i.e., ammonia and some
trace metals)
Aeration Reduces toxicity attributable to
volatile, sublatable, and/or easily
oxidizable compounds
Ethylenedinitrilo-Tetraacetic Chelates trace metals, particularly
Acid (EDTA) Addition divalent, cationic metals
Sodium thiosulfate (STS) Reduces toxicants attributable to
Addition oxidants (i.e., chlorine) and some
trace metals
Filtration Removes toxicity related to and/or
associated with particulates
Solid Phase Extraction (SPE) Removes toxicity associated with
with [C.sub.18] non-polar organics (i.e., pesticides,
surfactants)
Sequential Solvent Extraction SPE extraction can be used to confirm
of with [C.sub.18] Column toxicity due to nonpolar organic
compounds. Sequential extraction using
solvents of gradually decreasing
polarity can separate these compounds
into fractions providing further
toxicant resolution and isolation for
chemical analysis
Piperonyl Butoxide (PBO) Removes toxicity caused by
metabolically activated pesticides
(i.e., organophosphorous pesticides).
Increases toxicity attributable to
pyrethroid pesticides
Anion Exchange Removes toxicity associated with
anionic compounds, including some
trace metals and surfactants
No Manipulation For comparing the relative
effectiveness of other manipulations
and quantifies the persistence of
toxicity in the stored sample
Table 4. Summary of dry weather Ceriodaphnia dubia toxicity from
San Gabriel River from March 2005 through August 2006.
Mar. Apr. May Jun.
Location 2005 2005 2005 2005
Walnut Creek
1 -- -- -- --
2 -- -- -- --
San Jose Creek Reach 1
3 -- -- -- --
San Gabriel River Reach 3
4 -- -- -- --
San Gabriel River Reach 1
5 -- -- -- --
Coyote Creek
6 -- [S.sup.1] -- --
7 -- [L.sup.1][S.sup.1] -- --
8 -- [L.sup.1][S.sup.1] -- [S.sup.1]
9 [S.sup.1] -- -- --
10 [S.sup.1] [L.sup.1][S.sup.1] -- [L.sup.1][S.sup.1]
11 # # # #
12 # # # #
13 # # # #
14 # # # #
15 # # # #
16 # # # #
Jul. Aug. Sept. Oct.
Location 2005 2005 2005 2005
Walnut Creek
1 -- -- -- --
2 -- -- -- --
San Jose Creek Reach 1
3 -- -- -- --
San Gabriel River Reach 3
4 -- -- -- --
San Gabriel River Reach 1
5 -- -- -- --
Coyote Creek
6 -- [L.sup.1][S.sup.1] -- --
7 -- [L.sup.1][S.sup.1] -- --
8 -- [L.sup.1][S.sup.1] -- --
9 -- -- [L.sup.1][S.sup.1] --
10 -- [L.sup.1][S.sup.1] -- --
11 -- [S.sup.1] -- --
12 -- [L.sup.1][S.sup.1] -- --
13 -- [L.sup.1][S.sup.1] -- --
14 -- [L.sup.1][S.sup.1] -- --
15 # # # --
16 # # # --
Nov. Dec. Jan. Feb. Mar. Apr. May
Location 2005 2005 2006 2006 2006 2006 2006
Walnut Creek
1 -- -- -- -- -- # #
2 -- -- -- -- -- # #
San Jose Creek Reach 1
3 -- -- -- -- # # #
San Gabriel River Reach 3
4 -- -- -- -- # # #
San Gabriel River Reach 1
5 -- -- -- -- # # #
Coyote Creek
6 -- -- -- -- # # #
7 -- -- -- -- # # #
8 -- -- -- -- # # #
9 -- -- -- -- -- -- --
10 -- -- -- -- -- -- --
11 -- -- -- -- -- -- --
12 -- -- -- -- -- -- --
13 -- -- -- -- -- -- --
14 -- -- -- -- -- -- --
15 -- -- [--.sup.1] -- S -- --
16 -- -- -- -- -- -- --
Jun. Jul. Aug.
Location 2006 2006 2006
Walnut Creek
1 # # #
2 # # #
San Jose Creek Reach 1
3 # # #
San Gabriel River Reach 3
4 # # #
San Gabriel River Reach 1
5 # # #
Coyote Creek
6 # # #
7 # # #
8 # # #
9 -- -- --
10 -- -- --
11 -- -- --
12 -- -- --
13 -- -- --
14 -- -- --
15 -- -- --
16 -- -- --
Shaded areas = samples not collected, "--" represents not toxic with
effects less than 25% relative to control, L = Lethal, effect with
toxicity less than 75% relative to control, S = Sub-lethal effect;
reproduction less than 75% relative to control, "[sup.1]" = statically
significant from control.
Note: Samples not collected indicated with #.
Table 5. Summary of dry weather TIE results.
Site # Sample Date No Manipulation STS(a) EDTA(b) pH 7.0
9 Mar 2005
10 Mar 2005
10 Apr 2005 0% 0% 0% 0%
10 Jun 2005 0% 0% 0% 0%
10 Aug 2005 0% 0% 0% 0%
9 Sep 2005 0% 0% 0% 0%
15 Mar 2006
Site # Sample Date pH 8.5 PBO(c) Aeration Filtration
9 Mar 2005 Sample No longer Toxic
10 Mar 2005 Sample No longer Toxic
10 Apr 2005 0% 0%(d) 35% 0%
10 Jun 2005 0% 0% 10% 10%
10 Aug 2005 0% 0% 0% 0%
9 Sep 2005 0% 100%(g) 0% 0%
15 Mar 2006 Sample No longer Toxic
Site # Sample Date Centrifuge SPE Anion
9 Mar 2005
10 Mar 2005
10 Apr 2005 NT 87.5%(e) NT
10 Jun 2005 30% 100%(e) 100%
10 Aug 2005 NT 100%(e) 0%(f)
9 Sep 2005 NT 100%(e) 0%
15 Mar 2006
(a)-Sodium thiosulfate addition, two treatments of 10 and 25 ppm
(b)-Ethylenedinitrilo-tetraacetic acid addition, two treatments of 25
and 50 ppm
(c)-Piperonyl butoxide addition, two treatments of 50 and 100 ppb
(d)-5% survival observed in the 50 ppb treatment with 0% survival in
the 100 ppb treatment
(e)-Toxicity recovered in only the 75% methanol elution
(f)-Survival observed in lower concentrations of the sample indicating
partial toxicity removal
(g)-80% survival observed in 50 ppb treatment and 100% survival in 100
ppb treatment