903R94026
CBP/TRS 130/94
The Effect of Salinity on the Acute Toxicity
of Total Dissolved and Free Cadmium to the
Copepod Eurytemora affinis and the
Larval Fish Cyprinodon variegatus
,
;^:;'ul Street
TD
225
.C54
C125
1994
Chesapeake Bay Program
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The Effect of Salinity on the Acute Toxicity of Total
Dissolved and Free Cadmium to the Copepod
Eurytemora affinis and the
Larval Fish Cyprinodon variegatus
October 1994
U S. F.u:..cnmital Pcalecfeon ftgency
iu.,,,ofl ill iiUOiiJiaUea Resource
Cwlar (1PM52)
841 Chestnut Street
MDE
Printed by the U.S. Environmental Protection Agency for the Chesapeake Bay Program
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October 1994
Report
The Effect of Salinity on the Acute Toxicity
%
of Total Dissolved and Free Cadmium to the
Copepod Eurytemora affinis and the
Larval Fish Cyprinodon variegatus
Lenwood W. Hall, Jr.
Michael C. Ziegenfuss
Ronald D. Anderson
University of Maryland
Maryland Agricultural Experiment Station
Wye Research and Education Center
P.O. Box 169
Queenstown, Maryland 21658
and
Brent L. Lewis
University of Delaware
College of Marine Studies
Lewes, Delaware 19958
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ABSTRACT
The objective of this study was to determine the influence of
a range of salinities (5, 15 and 25 ppt) on the acute toxicity of
total dissolved and free cadmium to sheepshead minnow, Cyprinodon
variegatus larvae and the copepod, Eurytemora affinis nauplii.
s
Data were analyzed to determine if the acute toxicity (96 h LC50s)
-*.
was different among salinities for the test species. Total
dissolved cadmium was measured in selected test conditions and the
proportion of total cadmium as Cd+2 (free ion or toxic form) was
determined at each salinity. Ninety six hour LC50 values for C.
variegatus were 180.3, 312.4 and 495.5 Mg/L total cadmium at 5, 15
and 25 ppt, respectively. A significant increase in LC50 values
with salinity was likely related to a decrease in the free ion as
salinity increased. Ninety-six hour LC50 values for E. affinis
were 51.6, 213.2 and 82.9 liqfL total cadmium at 5, 15 and 25 ppt,
respectively. A comparison of LC50 values for the copepod between
salinities showed a significant difference between 5 and 15 ppt and
between 15 and 25 ppt. There was no difference in LC50 values
between 5 and 25 ppt. The physiological characteristics of E.
affinis were likely responsible for the higher tolerance at the
middle salinity. Cadmium speciation in the various test salinities
was dominated by association with inorganic binding ligands;
organic complexation was negligible. The speciation at all
salinities was dominated by CdCl* and CdCl2°. The free ion
accounted for 20, 8 and 4.5 % of the total cadmium at 5, 15 and 25
ppt, respectively. As current water quality criteria do not
-------
distinguish among individual cadmium species these data have
important implications for estuaries such as Chesapeake Bay because
the presence of the toxic form of cadmium will increase as salinity
decreases.
11
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TABLE OF CONTENTS
Page
ABSTRACT ' . . i
INTRODUCTION 1
METHODS 5
Test Organisms 5
Test Procedures 5
Cadmium Analysis 8
General Procedures 8
Total Dissolved Cadmium Analysis 9
Organic Complexation 10
Cadmium Speciation Calculations 13
Statistical Analysis 15
RESULTS 16
Water Quality and Cadmium Chemistry 16
Toxicity Data 22
DISCUSSION 28
ACKNOWLDEGEMENTS 33
REFERENCES 34
APPENDIX A - Raw data from the Eurytemora and Cyprinodon
96 h toxicity tests at three salinities
. iii
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INTRODUCTION
One commitment of the 1988 Chesapeake Bay Basinwide Toxics
Reduction Strategy was to give contaminants on the Toxics of
Concern List priority in the development of water quality criteria
(U.S. EPA, 1991a). Presently the United States Environmental
Protection Agency develops water quality criteria for both
freshwater and marine systems. Estuarine organisms are supposed to
be protected under the marine criteria. There are ,however,
compelling biological and chemical factors that may prevent
estuarine biota from being protected under marine criteria and
these factors justify the need for specific estuarine criteria.
Estuarine organisms, because of their inherent physiological
differences from freshwater and marine organisms, may differ
substantially in sensitivity to some toxic substances. For example,
recent toxicity studies with an estuarine zooplankter and fish
showed that salinity ranging from 5 to 25 ppt significantly
influenced the toxicity of atrazine (Hall et al., in press). . The
unique water chemistry of estuarine environments may also be
responsible for differences in bioavailability of some toxic
substances, thus affecting their toxicities.
Four metals listed on the Toxics of Concern list for
Chesapeake Bay were potential candidates for assessing the effects
of salinity on their toxicity (cadmium, chromium, copper and lead).
We eliminated chromium and copper because of potential problems
with the speciation chemistry. Lead was eliminated due to
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solubility problems at various salinities and possible differential
precipitation rates at various salinities. Cadmium was, therefore,
selected for this study due to less projected problems with
speciation chemistry. The toxicity data base for cadmium with
Chesapeake Bay species was also more extensive when compared with
the other metals considered for this project (Hall et al.,, 1994).
The environmental impact of cadmium in aquatic systems is
determined by its total concentration, by. partitioning between
dissolved and particulate phases, and by its "chemical speciation"
(i.e. by the physicochemical forms in which the element is found).
The toxicity and/or bioavailability of a trace metal to aquatic
organisms has in most instances been found to correlate with the
activity of the free metal ion rather than with the total metal
concentration (e.g. Brand et al., 1983, 1986; Sunda et al., 1987,
1990) . The concentration of the free ion may be much lower than
the total metal concentration due to complexation by various
inorganic and organic ligands in solution. The association of
metals with natural complexing ligands may therefore serve to
buffer the system with respect to the toxicity of a given metal.
The inorganic speciation of cadmium in natural waters is a
function of pH, temperature, the ionic strength of the solution,
and the relative concentrations of potential binding ligands. In
seawater, the inorganic speciation of cadmium is predicted to be
dominated by association with the chloride ion, while in freshwater
total cadmium will be dominated by the free hydrated ion (Cd2*) at
pH 6 and partitioned between the free ion and carbonate complexes
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at higher pH (Turner et al., 1981; Byrne et al., 1988). Byrne et
al. (1988) estimated that 97.2% of dissolved inorganic Cd in
seawater exists as chloride complexes, predominantly CdCl* and
CdCl2°. In an estuarine environment, where freshwater and seawater
mix and chemical reactions can occur, the change in cadmium
speciation from the free ion and carbonate species to predominately
chloride complexes occurs at low salinities (< 5 ppt). Chloride
complexes will therefore dominate the cadmium speciation over most
of the estuary.
In contrast to its we 11-characterized inorganic speciation,
the speciation of dissolved cadmium with respect to natural organic
ligands is poorly known. In the central North Pacific, cadmium
appears to be 60-70% complexed by strong, relatively Cd-specific,
organic ligands. The latter are present, however, at very low
concentrations (approx. 0.1 nM) (Bruland, 1992). Similar behavior
has been observed for cadmium in coastal waters of the northwest
Atlantic, with complexing ligand concentrations on the order of 0.3
nM (Lewis and Luther, unpublished data).
The study described in this report was conducted to determine
the influence of salinity on the toxicity of total dissolved and
free cadmium to estuarine species. Specific objectives were to
determine the acute toxicity (96 h LCSOs) of cadmium to two
Chesapeake Bay resident species, the sheepshead minnow, Cyprinodon
variegatus larvae and copepod Eurytemora affinis nauplii, at
salinities of 5, 15 and 25 ppt. These data were analyzed to
determine if acute toxicity (96 h LC50 values) was different among
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salinities for each species. Total dissolved cadmium was measured
in selected test conditions. The solution speciation of cadmium
with respect to free hydrated ions and inorganic complexes in the
sample solution was also determined using MINEQL+, an interactive
PC version of the original MINEQL equilibrium modeling program
(Schecher and McAvoy, 1991). MINEQL+ utilizes equilibrium
constants to solve mass balance expressions, using a modified
Newton-Raphson iterative procedure.
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METHODS
Test Organisms
Eurytemora affinis cultures were maintained at 8, 15, 'and 22
ppt salinity and 23-25 C in our laboratory. Copepods were reared
in autoclaved estuarine water (14 ppt) obtained from the Choptank
River at Horn Point Center for Environmental and Estuarine Studies
(GEES). Salinity was adjusted with H-W Marinemix or deionized
water. Copepods were fed a diet consisting of equal volumes of two
phytoplankton species, Thalassiosira fluviatilis and Isochrysis
galbana, each maintained in log-phase growth. The phytoplankton
were also cultured in autoclaved estuarine water supplemented with
F/2 media (Guillard, 1975).
Cyprinodon variegatus larvae were obtained from Aquatic
Biosystems, Inc. (Fort Collins, CO). Larvae were <24-h old and
shipped at three salinities (8, 15, and 24 ppt). Larvae were
placed in aquaria containing salinity adjusted (5, 15, and 25 ppt)
Choptank River water and fed Artemia nauplii for overnight
acclimation.
Test Procedures
Cadmium chloride (lot number 50H-0879) used in these
experiments was obtained from Sigma Chemical Company (St. Louis,
MO) . Autoclaved estuarine water from the Choptank River (10 ppt)
was used as control water and diluent for all toxicity tests.
Salinity adjustments to the desired test salinities (5, 15, and 25
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ppt) were made with HW Marinemix or deionized water. Acute toxicity
tests (96 h) with Eurytemora and sheepshead larvae were conducted
as static non-renewal. All tests were conducted in a biological
incubator to maintain a constant temperature of 25 C and a
photoperiod of 16-h light:8-h dark. Standard water quality
parameters (temperature, dissolved oxygen, pH, and salinity) were
recorded initially and at the end of the exposure period for each
test condition. Selected test conditions were sampled initially
and at 96 h for total cadmium analysis and speciation.
The Eurytemora experiment at 5 ppt salinity was conducted at
the following nominal cadmium concentrations: 0, 32, 56, 100, and
180 jig/L. The test at 15 ppt salinity was conducted at the
following nominal concentrations: 0, 32, 56, 100, 180, 320, and
560 M9/L cadmium. Nominal concentrations of cadmium in the 25 ppt
salinity test were: 0, 56, 100, 180, 320, and 560 ngfL. Each test
concentration was prepared by diluting a stock solution (100 ug
cadmium/L) of cadmium chloride with salinity adjusted Choptank
River water. The salinity adjusted diluent for all conditions was
prepared by diluting the estuarine water to 5 ppt with deionized
water and adding synthetic seasalt to the desired salinity. Stock
solutions were prepared 1-2 days prior to testing by dissolving
40.77 mg of anhydrous cadmium chloride in 250 mL of deionized
water.
Toxicity tests were initiated with copepodids (48 to 72-h
old). Copepodids were obtained by isolating adult gravid copepods
in polycarbonate jars containing salinity adjusted estuarine water
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for '24-h and collecting the recently hatched neonates. Neonates
were held for 48-h prior to starting each test. Three replicate
150 mL glass beakers containing 100 mL of test solution were used
for each condition. A test chamber was suspended within each
beaker to contain the organisms. Chambers were constructed from
3.8 cm diameter rigid polycarbonate tubing cut to a length of 5.0
cm to provide a 40 mL volume when suspended in the beaker. The
bottom of the chamber was covered with 53 urn mesh Nitex screen.
Copepodids were counted by drawing small aliquots of copepods and
water into a wide-bore glass pipet and examining under a dissecting
microscope (15x magnification). The initial number of copepods
(10-15) and the corresponding test chamber were recorded.
Eurytemora were fed daily with 1.0 mL of a two-species
phytoplankton mixture (50/50; v/v). Algal densities within the
test chamber were generally 1-2 x 104 Isochrysis cells/mL and 2-3
x 103 Thalassiosira cells/ml. Algal cell counts were conducted
with a Spencer improved Neubauer corpuscle counting chamber.
Survival was evaluated in each condition after a 96 h exposure.
Copepods were counted by first lowering the volume of solution in
the test chamber, then removing the remaining copepods and water in
small aliguots with a pipet. Each aliquot within the pipet was
examined with the aid of a dissecting microscope for the presence
of live copepods.
Cyprinodon acute toxicity tests (96 h) were conducted
following U.S. EPA protocol (U.S. EPA., 1991b). For the test
conducted at 5 ppt salinity, larvae were exposed to the following
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nominal cadmium concentrations: 0, 56, 100, 180, 320, 560, and
1000 /ig/L. The 15 ppt salinity test was conducted with the
following nominal concentrations: 0, 100, 180, 320, 560, 1000, and
1800 /xg/L. The 25 ppt salinity test was conducted with the
following nominal concentrations: 0, 180, 320, 560, 1000, 1800,
and 3200 Mg/L- Each concentration was prepared by diluting a stock
solution of cadmium (1000 Mg/L) with the appropriate volume of
salinity adjusted diluent. Tests were initiated with 48-h old
larvae following a 24-h acclimation period. The maximum salinity
change was » 5ppt. Three replicate 600 mL glass beakers containing
400 mL of test solution were used for each condition. Each
replicate received ten larvae by transferring them from the
acclimation water to a test beaker with a fire-polished, wide-bore
glass pipet. Larvae were fed at :48 h with 100 uL of concentrated
Artemia nauplii. At that time, dead larvae were counted and
removed from each beaker. Larval survival was evaluated in each
condition after 96 hours of exposure.
Cadmium Analysis
General Procedures
Total dissolved cadmium and cadmium speciation measurements
were conducted by the College of Marine Studies, University of
Delaware (Lewes, DE). Samples for total dissolved cadmium and
speciation analyses were filtered (0.4 um polycarbonate membrane)
and collected in precleaned polyethylene containers. Total
dissolved cadmium samples were preserved with Seastar ultrapure
8
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nitric acid (Seastar Chemicals, Inc., Seattle, WA) . Samples
collected in polyethylene bottles for speciation measurements were
immediately frozen and shipped to the University of Delaware on dry
ice by Federal Express courier service. The following test
conditions were sampled initially and at 96h for total dissolved
cadmium and speciation measurements: Eurytemora test at 5 ppt (32,
100, 180, and 560 Mg/L) / Eurytemora test at 15 ppt (32, 100, and
560 M9/L) ; Zurytemora test at 25 ppt (56, 180, and 560 pq/L) ;
Cyprinodon test at 5 ppt (56, 180, and 1000 M9/L) ; Cyprinodon test
at 15 ppt (100, 320, and 1800 jxg/L) ; Cyprinodon test at 25 ppt
(180, 560, and 3200
Total Dissolved Cadmiu^ Analyses
Total dissolved cadmium concentrations were measured by
Inductively Coupled Plasma - Atomic Emission Spectroscopy (ICP-
AES) . Concentrations were determined by comparison of sample
emission values with a linear calibration curve. Working standards
were prepared by serial dilution of a 1000 ppm commercial ICP
cadmium standard (Inorganic Ventures, Inc., Toms River NJ) .
Standards were prepared in an organic-free (ultraviolet-irradiated)
natural seawater matrix, diluted to the appropriate salinity (5, 15
or 25 ppt) and acidified to 0.1 N with high purity quartz-distilled
nitric acid. Thus the matrix of the standards was equivalent to
that of the samples, correcting for any signal suppression due to
seasalts in the samples. Analytical sensitivity was 1.46±0.1
emission units/jig/L-Cd, with a detection limit of approximately 3
-------
Mg/L.
Organic Complexation
Voltammetric measurements of cadmium were conducted using an
EG&G Princeton Applied Research (PAR) Model 384B-4 polarographic
analyzer with a PAR Model 303A mercury drop electrode. Analyses
were performed in the square wave anodic stripping voltammetry
(SWASV) mode with a hanging mercury drop electrode (HMDE) . Cadmium
was reduced and deposited in the mercury drop for one minute at a
deposition potential of -1.0 V. Instrumental parameters for
reoxidation and stripping of the cadmium from the mercury drop
were: scan rate - 200 mV sec'1, pulse amplitude = 20 mV, pulse
frequency - 100 Hz, scan range - -1.0 to -0.4 V.
The form of the metal deposited at a mercury electrode is
dependent upon both the thermodynamic stability and the kinetic
lability of the complexes, as well as the thickness of the
diffusion layer at the electrode surface and the diffusion rate of
a complex through this layer. For a metal-ligand complex, the
dissociation of the complex, and subsequent reduction of the metal
to form the mercury amalgam can be represented as:
*d
MLpn+ <==> M"+ + p L
*i
M"+ + n e' > M°(Hg)
where M and L are the metal and complexing ligand respectively, and
k is the rate of reaction for the dissociation (kd) or the
formation of (kf) of the metal-ligand complex ML.
10
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For a given deposition potential a stripping voltammetric
method will detect only the free ionic form of the metal plus those
complex species which dissociate to the free ion within the
timespan required for diffusion of the complex into and out of the
electrode diffusion layer. This is illustrated schematically in
Figure l. Such complexes can be defined as electrochemically
active or "labile" in the context of detection by stripping
voltammetry. All other complexes (e.g. strong organic complexes)
will be electrochemically inert, or "non-labile", passing through
the electrode diffusion layer without dissociation and hence
yielding no measurable current.
Assuming that there are no electroactive organic cadmium
complexes in solution, the measured current will be directly
proportional to the concentration of Cd', where [Cd'] is the total
concentration of dissolved inorganic cadmium species present (i.e.
free hydrated Cd2* plus inorganic complexes) (Bruland, 1992). Cd'
is related to the concentration of the free ion, [Cd2+], by an
inorganic side reaction coefficient, such that [Cd'] = [Cd2*]acd.
(Ringbom and Still, 1972).
In the absence of electrochemically inert cadmium complexes,
titration of the samples with cadmium should yield Cd'
concentrations equivalent to the total dissolved cadmium
concentration measured by ICP-AES. For the purposes of this study,
the extent of cadmium complexation by natural organics in the
source water should be negligible. Even if we assume an initial
binding ligand concentration in the diluted source water of 10 nM
11
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Hg Electrode
* + ne'-> M°(Hg)
+ pL
Diffusion
Layer
Bulk
Solution
Figure 1. Dissociation and reduction of a metal complex at a
mercury electrode (after Florence, 1986). (M and L are
the metal and complexing ligand respectively, and fc is
the rate of reaction for the dissociation (kj or the
formation (k{) of the netal-ligand complex ML.
12
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(an'order of magnitude above reported values for seawater), this
represents less than 4% of the total cadmium in the lowest
concentration sample (32 ppb). The organic complexation of cadmium
will be unimportant assuming that the test organisms did not
produce prodigious amounts of complexing material over the course
of the experiment.
Cadmium Speciation Calculations
The solution speciation of cadmium with respect to free
hydrated ions and inorganic complexes in the sample solutions was
estimated using MINEQI/ (Schecher and McAvoy, 1991), an interactive
PC version of the original MINEQL equilibrium modeling program.
MINEQL (Westall et al., 1976), and its predecessor REDEQL (Morel
and Morgan, 1972), utilizes equilibrium constants to solve mass
balance expressions, using a modified Newton-Raphson iterative
procedure.
The input for MINEQL* consists of the total solution
concentrations of all components to be modeled and an extensive
data base of equilibrium constants for the formation of solution
species and solid phases consisting of combinations of the basic
components. For the purposes of this study, the components
consisted of the cadmium ion, the major and minor seawater cations
and anions, and H* (Table 1).
The concentrations of the seawater ions were calculated based
upon the sample salinity and the relative proportions of each ion
in natural seawater. Based on information supplied by the
13
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Table 1. Dissolved solution components for MINEQL equilibrium
modeling program.
Anions
Na* Cl"
K* Br~
Ca2* F-
Mg2* C032~
Sr2+ S042'
Cd2*
14
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manufacturer, the major ion composition of the "MarineMix" used to
amend sample salinities to 15 and 25 ppt is equivalent to that of
natural seawater. Therefore, no correction was necessary for the
use of commercial salts rather than natural seawater. The hydrogen
ion concentration (pH) was considered as a fixed parameter, set to
t
the pH measured in each sample. In the absence of total inorganic
-*.
carbon or alkalinity measurements, the samples were assumed to be
in equilibrium with the atmosphere with respect to the carbonate
system (pC02 = 10'3 5 atm). It was further assumed that no
precipitation of the mineral phase otavite (CdC03) occurred over
the course of the 96 h experiments. Total cadmium concentrations
were within 8% and 16% of the nominal concentrations added for
Cyprinodon and Eurytemora tests, respectively, indicating no
significant removal of cadmium due to precipitation reactions.
Statistical Analysis
The 96h LC50 values with 95% confidence limits were generated
from the mortality data using the Trimmed Spearman-Karber method
(Hamilton, et al., 1978). The LC50 values from adjacent salinities
were compared by standard error of means (USEPA, 1985a) to
determine significant effect (p<0.05).
15
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RESULTS
Water Quality and Cadmium Chemistry
Water quality conditions measured every other day during the
six 96 h toxicity tests are presented in Table 2. All conditions
appeared adequate for survival of test species. Nominal and
measured concentrations of total cadmium on day 0 and 4 during the
acute tests are shown in Table 3 and Figure 2. Measured
concentrations were very similar to the nominal concentrations in
all tests as the relative standard deviation ranged from 0.42 to
6.89 %. In most instances, the relative standard deviation was
less than 3%. All three saline controls contained no detectable
cadmium at a detection limit of 3 M9/L-
Four samples were selected for voltammetric analysis (Table
4) . The resulting titration curve in Figure 3 was linear in each
instance thus suggesting no significant organic complexation (r2 >
0.997). The presence of strong, electrochemically inert complexes
would result in a significant deviation from linearity at low
cadmium concentrations (Bruland, 1992). The electroactive cadmium
concentrations agreed within 2.5 to 5 % with the total cadmium
values determined by ICP-AES, indicating that the speciation of
cadmium in the test solutions is dominated by the free ion and
inorganic complexes (Table 4). Voltammetric analysis therefore
yeilded no additional information beyond the total dissolved
cadmium concentrations, rendering it unnecessary to perform ASV
measurements with every sample. Note that the voltammetric
analyses also serves as an independent check upon the accuracy of
16
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Table s . Total cadmium concentrations as determined by ICP-AES.
Nominal cadmium values represent the original cadmium
concentrations added to the samples at the beginning
of each experiment. (Analytical precision is reported
as the standard deviation and the coefficient of variation
(C.V.) based upon replicate analyses (n-5) of the same sampli
Nominal Measured
Organism Time Salinity
Cyprinodon
Cyprinodon
Cyprinodon
Cyprinodon
Cyprinodon
Cyprinodon
Cyprinodon
Cyprinodon
Cyprinodon
Cyprinodon
Cyprinodon
Cyprinodon
Cyprinodon
Cyprinodon
Cyprinodon
Cyprinodon
Cyprinodon
Cyprinodon
Eurytemora
Eurytemora
Eurytemora
Eurytemora
Eurytemora
Eurytemora
Eurytemora
Eurytemora
Eurytemora
Eurytemora
Eurytemora
Eurytemora
Eurytemora
Eurytemora
Eurytemora
Eurytemora
Eurytemora
Eurytemora
DO
DO
DO
D4
D4
D4
DO
DO
DO
D4
D4
D4
DO
DO
DO
D4
D4
D4
DO
DO
DO
D4
D4
D4
DO
DO
DO
D4
D4
D4
DO
DO
DO
D4
D4
D4
5
5
5
5
5
5
15
15
14
15
15
16
25
25
25
26
26
26
5
5
5
6
6
6
14
14
14
14
15
14
24
24
24
26
27
26
[Cd]
56
180
1000
56
180
1000
100
320
1800
100
320
1800
180
560
3200
180
560
3200
32
100
560
32
100
180
32
100
560
32
100
560
56
180
560
56
180
560
[Cd]
52.98
166.10
963.01
55.88
177.09
994.23
97.53
312.99
1736.46
99.81
318.12
1893.76
175.01
559.11
3274.89
183.77
561.38
3252.98
27.01
93.17
550.10
28.16
92.27
168.86
30.21
100.19
535.90
28.16
88.29
501.66
50.51
176.37
523.50
49.44
160.28
518.72
Std.
Dev.
1.12
2.04
24.78
0.74
1.88
18 . 69
2.66
6.89
19.47
3.25
6.15
8.64
1.84
15.81
125.69
6.02
2.36
101.08
0.87
0.97
15.67
1.94
1.11
3.65
1.10
1.47
7.96
1.30
1.98
17.70
0.52
5.. 90
4.95
2.80
1.99
13.29
C.V.
2.12
1.23
2.57
1.33
1.06
1.88
2.73
2.20
1.12
3.25
1.93
0.46
1.05
2.83
3.84
3.28
0.42
3.11
3.23
1.04
2.85
6.89
1.21
2.16
3.64
1.47
1.49
4.61
2.24
3.53
1.03
3.34
0.94
5.66
1.24
2.56
18
-------
3500
0 500 1000 1500 2000 2500 3000 3500
600
(b) Eurytemora
i i
0 100 200 300 400 500 600
Nominal Cadmium Concentration (//.g/L)
Figure 2. Total cadmium as determined by ICP-AES versus the
nominal cadmium concentrations added to samples at the
beginning of the experiments. The solid lines represent
the expected 1:1 lines for perfect agreement between the
data sets. 19
-------
Table 4. Voltammetric analysis of selected samples. [Cd']
represents the sum of all electroactive cadmium species.
[Cd] is the value from ICP-AES analysis.
Organism
Time
ICP-AES
Salinity
[Cd]
[Cd']
Cyprinodon
Cyprinodon
Eurytemora
Eurytemora
D4
D4
D4
D4
15
26
6
14
99.81 95.10
183.77 179.81
28.16 27.49
28.16 28.92
20
-------
<
c
c
£
3
o
jse
o
«
0.
20.59 X + 56.48
2345
Cadmium added (/xg/L)
Figure 3. Titration curve for the voltaametric analysis of
Eurvtemora. 5 ppt salinity, 32 M9/L Cd, t-4. The solid
and dotted lines represent the linear regression and
95% confidence intervals, respectively, through the
data.
21
-------
the ICP-AES results for total dissolved cadmium.
The inorganic cadmium speciation as predicted by MINEQL+ is
present in Table 5 and 6. The predicted concentrations for each
dissolved species in terms of concentration is presented in Table
5 while Table 6 lists the species as a percentage of the total
cadmium in solution. Seven species were identified as significant
(>1%) : the free hydrated ion (Cd2*); carbonate and sulfate complexes
(CdCO3 and CdS04) and the four chloride complexes (CdCl*, CdCl2°,
CdCl3~, and CdOHCL0. The speciation was dominated at all salinities
by CdCl* and CdCl2°. The free ion accounted for 20, 8 and 4.5% of
the total dissolved cadmium at 5, 15 and 25 ppt, respectively.
Small variations between tests were due to small differences in
sample pH and salinity.
Toxicity Data
Ninety-six hour LC50 values for E. affinis and C. variegatus
are presented in Table 7 (See Appendix A for raw data) . The copepod
values were 51.6, 213.2 and 82.9 M9/L total cadmium at 5, 15 and 25
ppt, respectively. Acute toxicity values for Cyprinodon were
180.3, 312.4 and 495.5 nq/L total cadmium at 5, 15 and 25 ppt,
respectively. A comparison of LC50 values for E. affinis between
various salinities showed a significant difference between 5 and 15
ppt and between 15 and 25 ppt (Table 8). There was no significant
difference in LC50 values between 5 and 25 ppt. A comparison
between the various LC50 values for Cyprinodon showed a significant
increase with salinity (Table 8). The LC50 at 5 ppt was
22
-------
Table 5 . Thermodynamic equilibrium model results as a function of species
concentration. Equilibrium modeling was done using the MINBQL+
interactive personal computer program.
Org. Time
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
DO
DO
DO
D4
D4
D4
DO
DO
DO
D4
D4
D4
DO
DO
DO
D4
D4
D4
DO
DO
DO
D4
D4
D4
DO
DO
DO
D4
D4
D4
DO
DO
DO
D4
D4
D4
Sal
5
5
5
5
5
5
15
15
14
15
15
16
25
25
25
26
26
26
5
5
5
6
6
6
14
14
14
14
15
14
24
24
24
26
27
26
pH
7.63
7.62
7.56
7.5
7.46
7.57
8.03
8.06
8.06
7.75
7.73
7.87
8.21
8.21
8.22
7.93
7.91
8.01
7.62
7.60
7.63
8.09
8.11
8.1
8.09
8.13
8.13
8.32
8.38
8.37
8.18
8.16
8.23
8.24
8.15
8.45
Total
[Cd]
52.98
166.10
963.01
55.88
177.09
994.23
97.53
312.99
1736.46
99.81
318.12
1893.76
175.01
559.11
3274.89
183.77
561.38
3252.98
27.01
93.17
550.10
28.16
92.27
168.86
30.21
100.19
535.90
28.16
88.29
501.66
50.51
176.37
523.50
49.44
160.28
518.72
Predicted Cone, of
Cd(2+) CdOHCl
10.33
32.48
188.83
10.99
35.07
194.45
7.81
24.84
146.12
8.27
26.41
146.12
7.74
24.62
143.87
8.26
25.40
145.00
5.26
18.21
107.23
4.42
14.27
26.30
2.54
8.31
44.51
2.09
5.91
35.74
2.37
8.37
24.05
2.06
6.62
19.78
0.57
1.74
8.85
0.45
1.30
9.34
2.26
7.72
43.39
1.26
3.83
30.46
5.02
15.96
95.65
2.83
8.28
59.80
0.28
0.94
5.90
0.79
2.69
4.82
0.81
2.90
15.51
1.16
4.00
22.59
1.38
4.64
15.85
1.48
3.93
23.27
CdCl +
32.26
101.38
590.10
34.28
109.37
608.08
51.14
162.98
916.06
54.06
173.10
996.99
74.97
239.41
1393.76
80.48
247.28
1416.24
16.41
56.87
334.95
15.62
50.58
92.84
15.85
52.04
278.75
13.49
40.35
232.67
22.14
77.78
225.92
20.57
67.33
200.07
Dissolved Complexes (ug/L)
CdC13 -
0.35
1.08
6.31
0.37
1.17
6.51
4.11
13.04
64.74
4.34
13.83
90.03
15.85
50.36
294.49
18.10
55.30
318.09
0.18
0.61
3.57
0.23
0.76
1.39
1.12
3.69
19.67
0.97
3.32
16.75
4.30
15.06
44.29
4.69
16.30
45.75
CdC12.
6.87
21.58
125.89
7.31
23.27
129.26
27.31
87.00
460.84
28.89
92.06
560.88
62.83
200.07
1168.96
69.01
211.31
1213.92
3.50
12.14
71.26
3.87
12.59
23.04
8.00
26.19
140.50
6.89
22.03
119.14
17.87
62.61
183.21
17.98
60.13
175.34
CdCO3
0.66
1.98
8.74
0.39
1.02
9.44
2.63
9.62
57.32
0.77
2.24
23.27
5.63
17.98
109.59
1.63
4.55
41.36
0.32
1.01
6.85
2.28
8.09
14.16
1.15
4.50
24.05
2.75
10.21
59.57
1.51
4.83
19.33
1.71
3.60
43.50
CdS
1.
5.
29.
1.
5.
30.
1.
5.
31.
1,
5,
31.
2.
7,
43
2
6
38
0
2
16
0
2
4
0
1
9
0
1
9
0
2
7
0
1
6
23
-------
Table 6. Thermodynamic equilibrium model results as a percentage of the
total cadmium concentration. Equilibrium modeling was done using
the MINEQL+ interactive personal computer program.
Org. Time
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Cyp.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
Eur.
DO
DO
DO
D4
D4
D4
DO
DO
DO
D4
D4
D4
DO
DO
DO
D4
D4
D4
DO
DO
DO
D4
D4
D4
DO
DO
DO
D4
D4
D4
DO
DO
DO
D4
D4
D4
Sal
5
5
5
5
5
5
15
15
14
15
15
16
25
25
25
26
26
26
5
5
5
6
6
6
14
14
14
14
15
14
24
24
24
26
27
26
PH
7.63
7.62
7.56
7.5
7.46
7.57
8.03
8.06
8.06
7.75
7.73
7.87
8.21
8.21
8.22
7.93
7.91
8.01
7.62
7.60
7.63
8.09
8.11
8.1
8.09
8.13
8.13
8.32
8.38
8.37
8.18
8.16
8.23
8.24
8.15
8.45
Total
[Cd]
Predicted Cadmium Speciation
As A Percentage of Total [Cd]
(Mg/L) c<*(2+) CdOHCl CdCl + CdC13 -
52.98
166.10
963.01
55.88
177.09
994.23
97.53
312.99
1736.46
99.81
318.12
1893.76
175.01
559.11
3274.89
183.77
561.38
3252.98
27.01
93.17
550.10
28.16
92.27
168.86
30.21
100.19
535.90
28.16
88.29
501.66
50.51
176.37
523.50
49.44
160.28
518.72
19.5
19.5
19.6
19.7
19.7
19.6
8.0
7.9
8.5
8.3
8.3
7.7
4.4
4.4
4.4
4.5
4.5
4.5
19.5
19.6
19.5
15.7
15.5
15.6
8.4
8.3
8.3
7.4
6.7
7.1
.7
.7
.6
.2
.1
3.8
1.1
1.0
0
0
0
0
2.3
2.5
2.5
1.3
1.2
1.6
2.9
2.9
2.9
1.5
1.5
1.8
1.0
1.0
1.1
2.8
2.9
2.9
2.7
2.9
2.9
4.1
4.5
4.5
2.7
2.6
3.0
3.0
2.4
4.5
60.9
60.9
61.2
61.5
61.6
61.2
52.4
52.1
52.9
54.2
54.3
52.8
42.8
42.8
42.6
43.9
44.0
43.6
60.9
61.0
60.9
55.3
54.8
55.0
52.5
52.0
52.0
47.9
45.8
46.5
43.8
44.1
43.2
41.7
41.9
38.6
0
0
0
0
0
0
.2
.2
.7
.3
.4
.8
9.0
9.0
9.0
9.8
9.9
9.8
0
0
0
0
0
0
3.7
3.7
3.7
3.4
3.8
3.4
8.5
8.5
8.4
9.5
10.2
8.8
CdC12
13.0
13.0
13.0
13.1
13.1
13.0
28.0
27.8
26.6
28.9
28.9
29.7
35.9
35.9
35.8
37.7
37.7
.37.4
13.0
13.0
13.0
13.7
13.6
13.7
26.5
26.2
26.2
24.5
25.0
23.9
35.4
35.5
35.0
36.3
37.4
33.8
CdC03
1.2
1.2
0
0
0
0
2.7
3.1
3.3
0.0
0.0
1.2
3.2
3.2
3.3
0
0
1.3
1.2
1.1
1.2
8.1
8.8
8.4
3.8
4.5
4.5
9.8
11.6
11.9
3.0
2.7
3.7
3.5
2.2
8.4
CdS(
3,
3,
3,
3,
3,
3,
1,
1.
1.
1,
1,
1,
1,
1,
1,
1
1
1
3
3.
3
2,
2
2
1
1
1,
1
1
1
1
1
1,
1,
1.
1,
* 0 - less than 1Z
24
-------
Tabje 7. Ninety-six h LC50 values (M9/L) (with 95% confidence
limits) and mean control survival for E. affinis and C.
variegatus tested at three salinities.
Species Test Mean 96-H LC50
Salinity Control (95% C.L.)
(ppt) Survival
% (S.E.)
E. affinis 5 91.7 :(8.3) 51.6 (36.2-73.5)
15 97.0 (3.0) 213.2 (182-249.7)
25 80.0 (5.8) 82.9 (51.1-134.3)
C. variegatus 5 100 180.3 (151.5-214.5)
15 93.3 (3.3) 312.4 (275.1-354.7)
25 100 . 495.5 (420.9-583.2)
25
-------
Table 8. A comparison of LC50 values between adjacent salinities
using the standard Error of Means Method.
Species
Salinity
(PPt)
Z Value
H Value
Significant
(P<-05)
S. affinls 5-15
15-25
5-25
C. variegatus 5-15
15-25
5-25
4.1348
2.5729
1.6071
1.7222
1.6129
2.7778
1.4736
1.6614
1.8192
1.2166
1.2112
1.2384
*
*
*
*
*
26
-------
significantly lower than 15 ppt and the value at 15 ppt was
significantly lower than 25 ppt. The value at 5 ppt was also
significantly lower than at 25 ppt.
I
27
-------
DISCUSSION
Voltamroetric analysis of selected samples were in excellent
agreement with the ICP-AES measurements. Standard addition curves
were linear, indicating no significant organic complexation. The
"cadmium complexing capacity" of the experimental sample matrix was
therefore negligible. Furthermore, there was no significant
production of cadmium binding ligands by the test organisms over
the course of the experiments. The data presented above were
important for these experiments because it was demonstrated that
cadmium speciation was dominated by association with inorganic
binding ligands.
In freshwater at pH of 6, Turner et al. (1981) predicted that
the inorganic cadmium would be approximately 96% free with
carbonate complexes becoming important at higher pH. In seawater
at 35 ppt and a pH of 8.2, the chloride complexes were predicted to
account for approximately 97% of the inorganic species with the
free ion responsible for less than 3% of the total (Turner et al.,
1981; Bryne et al., 1988). Assuming that only chemical factors are
important and the organic ligands are negligible, the cadmium
toxicity due to Cd*2 would be expected to decrease significantly
over the course of an entire estuary (i.e., Chesapeake Bay) where
salinity may range from 1 to greater than 26 ppt. At natural total
cadmium concentrations, binding of cadmium by strong complexing
ligands may reduce toxicity even further.
The inorganic complexation of cadmium in the sample solutions
was estimated by the use of the MINEQL+ thermodynamic equilibrium
28
-------
model. Model results indicated that the cadmium speciation was
largely dominated by complexation with the chloride ion, with small
contributions by the free ion and carbonate and sulfate species.
The free ion decreased from 20% of the total dissolved cadmium at
5 ppt to less than 5% of the of the total at 25 ppt salinity.
Similar data have been reported by other investigators as more free
cadmium was present at low salinities varing in logarithmic fashion
from about 23% of total as free cadmium at 5 ppt to only about 4%
at 32 ppt (Sunda et al., 1978; Engle and Fowler, 1979). Our data
would suggest a four fold decrease in toxicity from 5 to 25 ppt
assuming that the free ion is bioactive form of the element and
physiological factors of the test species are negligible. The
toxicity data with Cyprinodon generally support this prediction as
there is approximately a three fold decrease in toxicity from 5 to
25 ppt. The Eurytemora data however do not support this prediction
as the 96 h LC50 values at both 5 and 25 ppt were similar. This
species was most resistant to cadmium at the middle salinity (15
ppt) . The physiological characteristics of Eurytemora may have
been responsible for higher tolerance at the middle salinity.
Sprague (1985) has suggested that euryhaline species are most
resistent to toxic conditions at isosmotic salinities due to
minimization of osmotic stress. Other investigators have also
reported there is decreased osmotic stress in various aquatic
species as salinity increases toward the isosmotic point, with a
decreased inward flow of water, which presumably would be
accompanied by reduced intake of toxic ions (Herbert and Wakefield,
29
-------
1964; Herbert and Shurben, 1965).
The 96 h LC50 values for E. affinis reported from the three
cadmium toxicity tests at the various salinities ranged from 51.6
to 213.2 M9/L total cadmium. Sullivan et al. (1983) reported a
similar 96 h LC50 of 147.7 ng/L total cadmium for E. af finis at 10
ppt. Another investigator reported a substantially higher 96 h
LC50 of 1,080 M9/L total cadmium for Eurytemora (Gentile, 1982).
Acute toxicity values ranging from 90 to 337 /ig/L total cadmium at
30 ppt for a similar copepod species, Acartia tonsa were also
similar to our Eurytemora data (Gentile, 1982; Sosnowski and
Gentile, 1978). The lowest LC50 value (51.6 M9/L) reported for E.
af finis in our experiments was only slightly higher than the U.S.
EPA acute marine water quality criterion of 43 pg/L (U.S. EPA,
1987). The range of acute cadmium values reported for saltwater
invertebrate species in the U.S. EPA cadmium water quality criteria
document was 41.29 to 135,000 M9/L total cadmium (U.S. EPA, 1985b).
These data suggest that Eurytemora is very sensitive to cadmium
when compared with other estuarine aquatic biota.
The 96 h LC50 values for Cyprinodon larvae ranged from 180.3
to 495.5 M9/L total cadmium at the three test salinities. Cardin
(1982) reported acute toxicity values of 577 to 602 Mg/L for the
larval stages of the Atlantic silverside and the winter flounder,
respectively at 20 ppt. These values are similar to the acute
LCSOs we reported for Cyprinodon. Other investigators have reported
higher acute values for other larval estuarine fish. Middaugh and
Dean (1977) reported 48 h LC50s of 9,000 and 32,000 /ig/L for 7 and
30
-------
14 .day larval mummichogs, respectively at 20 ppt. These
investigators also reported 48 h LC50s of 3,800, and 2,200 nqfL for
1 and 14 day old Atlantic silverside larvae at 20 ppt.
In a recent review synthesizing the influence of salinity on
the toxicity of various classes of chemicals, it was reported from
33 cadmium toxicity studies that cadmium toxicity generally
increased with decreasing salinity (Hall and Anderson, 1994). The
Cyprinodon data from the experiments follow this trend as 96 h LC50
values were significantly lower at lower salinities thus suggesting
that cadmium bioavailablity (chemical factors) were the predominant
mechanism for toxicity. The Eurytemora data do not follow this
trend due to the physiological factors previously discussed. One
important aspect of this study was the calculation of the free
cadmium along with the total cadmium concentration in the
experiments. The free cadmium ion (Cd*2) is generally considered
to be the toxic form of cadmium to aquatic biota in the water
column and it is virtually inversely proportional to salinity
(Sunda et al., 1978; Engle and Fowler, 1979). A calculation of 96
h LC50s for free cadmium for Eurytemora based on using 20, 8 and
4.5% of the total cadmium at 5, 15 and 25 ppt, respectively, showed
that free cadmium was still less toxic at the middle salinity
(Figure 4) . The calculated free cadmium LC50 values for Cyprinodon
were similar at both 15 and 25 ppt but were somewhat higher at 5
ppt (Figure 4).
31
-------
CO
«
H
§
i
is
«^
* «
14
O
CD
Q>
O
10
s
I
H
Pk
(0
0
'o
0)
a
to
'c
(C
O)
0)
jj: ro
to >
LU (J
LO
CM
IT)
CO
o
in
O
CO
O
CM
32
-------
ACKNOWLEDGEMENTS
We are grateful to the U.S. Environmental Protection Agency
Chesapeake Bay Program and the Maryland Department of the
Environment for funding this research. Special consideration is
extended to Mr. Richard Batiuk, Ms. Deirdre Murphy and Mrs. Mary Jo
Garreis for comments on the study design. Mary Hancock is
acknowledged for typing.
33
-------
REFERENCES
Brand, L.E., Sunda, W.G., and Guillard, R.R.L. 1983. Limitation
of marine phytoplankton reproductive rates by zinc, manganese
and iron. Linnol. Oceanogr., 28:1182-1198.
Brand, L.E.., Sunda, W.G., and Guillard, R.R.L. 1986. Reduction
of marine phytoplankton reproduction rates by copper and
cadmium. J. Exp. Mar. Biol. Ecol., 96:225-250.
Bruland, K.W. 1992. Complexation of cadmium by natural organic
ligands in the central North Pacific. Limnol. Oceanogr.,
37:1008-1017.
Byrne, R.H., Kump, L.R., and Cantrell, K.J. 1988. The influence
of temperature and pH on trace metal speciation in seawater.
Mar. Chem., 25:163-181.
Cardin, J.A. 1982. Memorandum to J.H. Gentile. United States
Enivronmental Protection Agency, Narragansett, RI.
Engel, D.W., and Fowler, B.A. 1979. Copper and cadmium induced
changes in the metabolism and structure of molluscan gill
tissue. In Marine Pollution: Functional Responses, Vernberg,
W.B., Thurberg, F.P., Calabrese, A., and Vernberg, F.J.
(eds.). Academic Press, New York, NY, pp. 239-256.
Florence, T.M. 1986. Electrochemical approaches to trace element
speciation in waters - a review. Analyst, 111:489-505.
Gentile, S.H. 1982. Memorandum to John H. Gentile. United States
Environmental Protection Agency, Narragansett, RI.
Guillard, R.R.L. 1975. Culture of phytoplankton for feeding
34
-------
marine invertebrates. In Culture of Marine Invertebrate
Animals, Smith, W.L., and Chanley, M.H. (eds.). Pleum
Publishing, New York, pp. 29-60.
Hall, L.W. Jr., and Anderson, R.D. 1994. The influence of
salinity on the toxicity of various classes of chemicals to
aquatic biota. Report. Maryland Department of Environment,
Baltimore, MD.
Hall, L.W. Jr., Ziegenfuss, M.C., Anderson, R.D., Spittler, T.D.,
and Leichtveis, H.C. in press. Influence of salinity on
atrazine toxicity to a Chesapeake Bay Copepod (.Eurytejnora
affinis) and fish (Cyprinodon variegatus; . Estuaries.
Hamilton, M.A., Russo, R.C., and Thurston, R.V. 1978. Trimmed
Spearman-Karber method for estimating median lethal
concentrations in toxicity bioassays. Environ. Sci. Technol.,
11:714-719.
Herbert, D.W.M., and Shurben, D.S. 1965. The susceptibility of
salmonid fish to poisons under estuarine conditions - II
ammonium chloride. Jnt. J. Air Wat. Poll., 9:89-91.
Herbert, D.W.M., and Wakeford, A.C. 1964. The susceptibility of
salmonid fish to poisons under estuarine conditions - I zinc
sulphate. Int. J. Air Wat. Poll., 8:251-256.
Middaugh, D.D., and Dean, J.M. 1977. Comparison sensitivity of
eggs, larvae and adults of the estuarine teleosts, Fundulus
heteroc.Zitus and Menidia menidia to cadmium. Bull. Environ.
Contain. Toxicol., 17:645-652. .
Morel, F., and Morgan, J.J. 1972. A numerical method for
35
-------
computing equilibria in aqueous chemical systems. Environ.
Sci. Tech., 6:58-67.
Ringbom, A., and Still, E. 1972. The calculation and use of alpha
coefficients. Anal. Chim. Acta., 59:143-146.
Schecher, W.D., and McAvoy, D.C. 1991. MINEQL*: A Chemical
Equilibrium Program for Personal Computers, User's Manual,
Version 2.22. Environmetal Research Software, Hallowell, ME.
Sosnovski, S., and Gentile, J.H. 1978. Toxicological comparison
of natural and cultural populations of Acartia tonsa to
cadmium, copper and mercury. J. Fish. Res. Board Can.,
35:1366-1369.
Sprague, J.B. 1985. Factors that modify toxicity. In
Fundamentals of Aquatic Toxicology, Rand, G.M., and
Petrocelli, S.R. (eds.). Hemisphere Publishing Co.,
Washington, DC, pp. 124-163.
Sullivan, B.K., Buskey, E., Miller, O.C., and Ritacco, P.J. 1983.
Effects of copper and cadmium on growth, swimming and predator
avoidance in £uryte;nora affinis (Copepoda). Mar. Biol.,
77:299-306.
Sunda, W.G., Engel, D.W., and Thuotte, R.M. 1978. Effect of
chemical speciation on toxicity of cadmium to grass shrimp,
Palaemonetes pugio: Importance of free cadmium ion. Environ.
Sci. Technol., 12:409-413.
Sunda, W.G., Tester, P.A., and Huntsman, S.A. 1987* Effects of
cupric and zinc ion activities on the survival and
reproduction of marine copepods. Mar. Biol., 94:203-210.
36
-------
Sunda, W.G., Tester, P.A., and Huntsman, S.A. 1990. Toxicity of
trace metals to Acartia tonsa in the Elizabeth River and
southern Chesapeake Bay. Estuar. Coast. Shelf Sci., 30:207-
221.
Turner, D.R., Whitfield, M., and Dickson, A.G. 1981. The
equilibrium speciation of dissolved components in freshwater
and seawater at 25°C and 1 atm pressure. Geochim. Cosmochim.
Acta., 45:855-881.
U.S. EPA (United States Environmental Protection Agency). 1985.
Ambient water quality criteria for cadmium - 1984. U.S. EPA,
Office of Water Regulations and Standards, Criteria and
Standards Division, Washington, DC.
U.S. EPA (United States Environmental Protection Agency). 1985b.
Methods for measuring the acute toxicity of effluents to
freshwater and marine organisms. 3rd ed. EPA 600/4-85-013.
Environmental Monitoring and Support Laboratory, U.S. EPA
Cincinnati, OH.
U.S. EPA (United States Environmental Protection Agency). 1987.
Water quality criteria summary. U.S. EPA Office of Water
Regulations and Standards, Criteria and Standards Division,
Washington, DC.
U.S. EPA (United State Environmental Protection Agency). 199la.
Chesapeake Bay toxics of concern list information sheets.
Report. U.S. EPA Chesapeake Bay Program, Annapolis, MD.
U.S. EPA (United States Environmental Protection Agency). 1991b.
Methods for measuring the acute toxicity of effluents and
37
-------
receiving waters to freshwater and marine organisms, 4th ed.
Weber, C.I. (ed.). EPA/600/4-90/027. U.S.; EPA, Cincinnati,
OH, pp. 66-67.
Westall, J.C., Zachary, J.L., and Morel, F.M.M. 1976. MINEQL, A
Computer Program for the Calculation of Chemcial Equilibrium
Composition of Aqueous Systems. Technical Note 18, Department
of Civil Engineering, Massachusetts Institute of
Technolnology., Cambridge, MA. :
38
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APPENDIX A
Raw data from the Eurytemora and Cyprinodon
96 h toxicity tests at three salinities
-------
-------
96 h Eurytemora Tests
# Alive/Total per Rep x % Survival
Salinity Cd cone (mg/L) A B c
5 ppt 0
.032
.056
.100
.180
15 ppt 0
.032
.056
.100
.180
.320
.560
25 ppt 0
.056
.100
.180
.320
.560
8/8
2/8
3/8
4/7
0/7
10/10
8/10
8/11
10/11
9/10
1/11
0/11
9/10
7/10
0/10
5/10
1/11
0/12
8/8
6/8
4/8
0/7
0/7
10/10
12/12
11/13
10/10
8/11
1/10
0/10
7/10
6/10
3/10
5/12
0/11
0/10
6/8
6/8
5/9
1/8
0/7
10/11
9/10
9/10
il/12
8/10
0/11
0/12
8/10
6/10
8/11
4/10
0/11
0/10
91.7
66.7
47.7
23.2
0
97
90
83
94
81
6
0
80
63.3
35.5
43.8
3
0
A-l
-------
96 h Cyprinodon Tests
Salinity
5 ppt
15 ppt
25 ppt
Cd cone (mg/L)
0
.056
.10
.18
.32
.56
1.00
0
.10
.18
.32
.56
1.00
1.80
0
.18
.32
.56
1.00
1.80
3.20
# Dead/ 10
A
0
1
1
8
9
10
10
1
0
2
4
10
10
10
0
1
2
6
9
10
10
per Rep
B
0
0
1
4
8
10
9
0
0
1
8
10
10
10
0
0
3
5
9
10
10
X %
C
0
2
1
7
5
9
10
1
0
0
2
9
10
10
0
0 .
3
5
9
10
10
Mortality
0
10
10
63
73.3
96.7
96.7
6.7
0
10
46.7
96.7
100
100
0
3.3
26.7
53.3
90
100
100
A-2
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