THE MONTICELLO EXPERIMENT - A CASE STUDY
by: W.E. Cooper and R.J. Stout
Introduction:
The use of animal toxicity tests to determine the water quality
characteristics of permitted discharges generates an array of assumptions that
need direct experimental verification. Issues involving the transfer of
laboratory results to field situations, the sensitivity of test organisms
compared to the natural residents, the ecological impacts of single-species
versus multi-species responses and, finally, the independence of repeated
insults versus additivity with increasing sensitivity are all critical research
subjects. The E.P.A. (Environmental Protection Agency) outdoor experimental
stream facility located at Monticello, Minnesota, and directed through the
E.P.A. laboratory in Duluth, Minnesota represented a unique opportunity to test
all of the above simultaneously.. This paper reports on the effects of p-
cresol application on the benthic macroinvertebrate fauna.
The experimental facility contains eight channels 500 in in length
constructed with earthen bottoms. The channels consist of alternating 30 m
long pools and riffles. Four channels were altered to create two isolated
recycling stream ecosystems, each containing 1.5 million liters. The streams
are physically, chemically and biologically typical of warm-water, grassland,
third to firth order streams• The 1000 x 3 m channels were driven by
recirculation pumps that propelled the stream water up to 11,000 1/m.
Velociti es could be run up to 12.2 cm/sec in the pools and up to 25 cm/sec in
the riffles.
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2
These two stream ecosystems were large enough and, owing to their history,
were biologically diverse enough to be considered good analogs of natural
streams. The only components of the biological community that were added were
young-of-the-year sraallmouth bass, largemouth bass, walleyed pike and fathead
minnows. Fish were added to test ecological hypotheses concerning competitive
displacements and to provide a vertebrate component to the spec^yte array for
toxicity testing (Anderson, 1983}.
Methods;
With the alteration of the channels to generate a recycling system, an
application regime of the toxicant, p-cresol, could be generated that would
hold a fixed exposure level for any given period of time. An onsite dedicated
computer system monitored stream flows and was coupled with inputed p-cresol
concentrations in the water so that it executed control over the toxicant
injections to maintain approximate steady-state conditions. This system
represents, therefore, a flowingL static test apparatus for acute toxicity
testing (Cooper and Stout, 1982).
Several adjunct facilities were.built to implement the laboratory anayses
and testing. The computer facility was designed and operated by
Dr. Robert Boling from Michigan State University. The organic chemistry
laboratory was designed and operated by Dr. Robert Huggett from the Virginia
Institute of Marine Sciences. The microcosm and bacteriological laboratory was
designed and operated by Dr Hap Pritchard from the E.P.A. Gulf Breeze
Laboratory. The ecological experiments and field work were designed and
implemented by Drs. Bill Cooper and Jean Stout from Michigan State University.
The laboratory acute toxicity tests were performed by Dr. Don Mount at the
E .P.A. Duluth Laboratory. Experiments of this type require the involvement of
a truly interdisciplinary team and are rarely done. For this reason,
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3
similar case studies will accumulate very slowly in the literature.
Details as to operating procedures and results of the microcosm,
experiments are being published elsewhere (Coleman et al., 1982; Pritchard et
al., 1981; Anderson, 1983; Cooper and Stout, 1982; Stout and Cooper, 1983;
Stout and Kilham, 1982). The effects of p-cresol on the benthic macro-
invertebrates is the subject of this paper.
The field sampling was performed weekly, utilizing artificial substrate
samplers for the riffles and a macrophyte sampler for the pools (Crowder and
Cooper, 1982). Samples were washed through a 60 micron mesh Tyler seive and
preserved in formalin, after which, the organisms were sorted, measured and
identified to taxa. Means and variances were calculated by lo a wn and by
date for population parameters (density, biomass, size dsitribution) and for
community indices (number of species, diversity, evenness) calculated as the
information measure of diversity and evenness (Pielou, 1969). The single
species parameters were used to validate the laboratory-to-fieId transfer of
the dose-response curves. The community indices are descriptive parameters
which reflected the multi-species response to the toxicant¦
Two other parameters reflect functional processes. Dis^ol ed oxygen was
measured continuously because it provides a measure of total community
metabolism. Decomposition rates of leaves attached as packs to bricks were
used to reflect organic carbon metabolism. Comparisons of population versus
community responses were used to test for the presence of multispecies
interactions. This is an essential issue in determining whether or not the
extra effort and monies involved in multispecies testing is worth the
commitment.
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4
The experimental
following pattern:
Duration
24 hr Continuous
48 hr Continuous
96 hr Continuous
48 hr Pulsed
involved four maj
Channel
B
A
B
A
p-cresol applications in the
Date
7/18/80 - 7/19/80
8/9/80 - 8/11/80
6/29/81 - 7/3/81
7/19/81 - 7/24/81
Each pair of channels followed its own seasonal pattern-of population and
community dynamics (Figs. 1 and 2). Within channel variation (Table I)
represents raicrohabitat differences as there was no consistent trend from the
headend (origin of pumping system) to tailend (turnaround area of channels)
within the recycling system. The undosed channel for each experimental period
was used as the e"erence channel. The species composition and life history
patterns of the macroinvertebrates were similar for both channels. Assuming
the community response would be correlated with the p-cresol addition, the
companion channel, which at the time 'was not receiving p-cresol, was used to
verify that no major shift, such as insect emergences or macrophyte dieoff8,
was occurring.
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5
TABLE I BENTHIC POOL SAMPLES, CHANNEL B, June 20, 1981
INTERPQQL VARIANCE (N = 2)
Location Total Total tfean Number Evenness Diversity
Numbers Biomass Bioroass of Spp.
Headend
c4P2
1688
615.8
0.36
11
0.33
1.16
C4P6
1074
153.S
0.14
15
0.25
0.99
c3p6
1744
117.4
0.07
15 •
0.45
1.77
c3p6
1091
128.8
0.12
12
0.47
1.70
C.3P4
1162
128.5
0.11 ¦
12
0.41
1.47
c3p4
779
133.3
0.17
. 17
0.42
1.71
C3P2
1475
280.9
0.19
15
0.26
1.03
C3P2
19^3
502. 5
0.25
'l3
0.39
1.44
Taxlend
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6
P-cresol was added at a rate that would maintain ambient water
concentrations of 8 ppra. This level was chosen as the best *11 ite from
existing literature for a moderate toxic effect. The laboratory toxicity tests
(Table II) confirms this estimate. The fish species showed a distinct "all or
none" response pattern with no mortality at 10 ppm, The damselfly, Ischnura
vertlcalis, showed no mortality response. The araphipod, Hyalella azetea,
»
showed a more gradual dose pattern with mortality evident at 5 ppm at 96 hrs
exposure time. Paphnia magna experienced mortality at all concentrations and
exposure ci t Since the field experiments involved an exposure
concentrations of 8 ppm for dilations of 24, 48 and 96 hrs, the amphipods should
have experi(%ced a moderate mortality, and the fish and damself lies should have
shown only behavioral effects.
The technology required to generate and maintain a dynamic system of this
size at 8 ppm for periods up to 96 hrs required a massive effort. These
developments have been, previously reported by Bo ling, 1981; and Coleman, et
al., 1982. Figure 3 from Cooper and Stout, 1982, presents the p-cresol
concentrations during the 96 hr dose experiments at the head and tail end of
the recycling system.
An illustration of the complex dynamics that occur within a field system
Is provided by Figure 4 from Cooper and Stout, 1982. This figure presents the
amount of p-cresol that was required to maintain the ambient concentrations
illustrated in Figure 3. The diurnal oscillations reflect the changing rates
of p-cresol degradation by bacteria in response to the diurnal cycle of
dissolved oxygen. The four-day trend of increasing p-cresol additions
reflected the adaptation of the bacterial community to the unique carbon
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TABLE IT
Dose-Response Data on P-Cresol" Wich Selected Fish
"and Invertebrates from Monticello, Minn,
. Mount and Norberg
E.P.A. Lab. at DuluCh
Initial
TIME
Organism
(number)
Concentration
24-hour t
48-hour%
72-hour %
;8-hour %
of P-Cresoi »
Survival
Survival
Survival
Survival
40 mg/1
60, 30
20, 0
0, 0
()» 0
20 mg/1
60, 90
30, 40
0, 10
¦), 0
10 mg/1
100,100
100,100
100,100
100,100
5 mg/1
100,100
100,100
. 100,100
100,100
2,5 mg/1,
100,100
100,100
100,100
100,100
Control
100,100
100,100
100,100
100,100
32 mg/1
0 *
_
-
_
16 mg/1
100
100
100
100
8 mg/1
100
*100
100
100
b tng/1
100
100
100
100 *
2 mg/1
100
100
100
100
Control
100
100
100
100
40 mg/1
0
-
-
-
20 mg/1
"o ,
-
-
-
10 mg/1
100
100
80
80
5 mg/1
100
100
100
100
2.5 mg/1
100
100
100
100
Control
100
-
-
-
20 mg/1
0
-
-
-
10 mg/1
100
100
100
100
5 mg/1
100
100
100
100
2,5 mg/1
100
100
100
100
1.25mg/l
100
100
100
100
Control
100
100
100
100
Fathead
minnow
(10/run)
2 replicates
LargemouCh
bass
(5/run)
I replicate
Smallmouch
bass
(5/run)
1 replicate
Largemouth
bass
Test if2
(5/run)
1 replicate
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8
TABLE II» continued
Organism
(number)
Initial
Concentration
of F-Cresol
TIME
24-hour2
48-hourX
72~hour%
96-hourX
Survival
Survival
Survival
Survival
-
100
-
* 100
100
-
100 .
-
80
-
70
50,37.5
0, 0
0, 0
0, 0
87.5,50
25 , 25
12.5,12.5
12.5,12.5
87.5,100
37 .*5,50
37.5,37.5
12.5,25
100,100
75, 87.5
50, 50
37,5,50
100,100
87.5,87.5
87.5,50
75, 37.5
100,100
100,100
100,100
100,100
0 , 0
0 , 0
•
0 , 0
o » o
0 » 0
0 , 0
60 » 80
60 , 40
80 , 80 *
o
o
N>
O
Damsel fly
(10/run)
1 replicate
Amphipod
Hyalelia
azteca
(8/run)
2 replicates
Waterflea
Daohnia
cagna
(5/run)
2 replicates
40 rag/1
20 mg/1
10 xg/1
5 mg/1
2.5 mg/1
Control
80 mg/1
40 mg/l
20 mg/1
10 mg/1
5 mg/1
Control
40 mg/1,
20 mg/1
10 mg/1
5 mg/1
2.5 rag/1
Control
100,100 100,100
1. Flow per minute in chambers ranged from 21 Co 60 ml/min.
2. Initial D.O. values ranged from 5,5 Co 7.9 pp©
3. Final D.O, values ranged from 5,5 Co 8,4 ppm
4. pH ranged from 7,2 to 7 , 5
5. Alkalinity3 40; hardness=46
6. Temperature was 24 to 2S°c,
7. Measured concentration of p-cresol was done for each run. Those data
are not presented here, but are part of the Mount and Norberg report
to us and are available on request.
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9
source. The control systems had to be on-line, dynamic, and with a short time
lag in order to compensate for those transient behaviors.
Results;
Population Parameters:
The 24 hr dose produced no ^measurable effect on the populations (Figs. I
and 2), The densities of individuals paralleled the total dry weight bioraass;
neither parameters indicated a reduction in populations in either the riffle or
pool habitats as a result of p-cresol exposure.
The 48 hr dose resulted in varied behavioral effects on. fish and on some
invertebrates (Cooper and Stout, 1382). The responses ranged from death with
walleyed pike, inhibition of feeding with largemouth base, no observable
Impacts on fathead minnows to observable mortality with amphipods and mayflies.
The causal relationships are more complex than, simply acute toxicity to target
organisms. The p-cresol inhibited the photosynthetic activity of the
filamentous algae. This, coupled with increasing respiration due to toxicant
stress, generated a serious reduction in dissolved oxygen (Stout and Kilham,
1982), Levels of around 1 ppo were observed at 5:00 a.m. the morning at the
end of the 48 hr dose.
The unexpected impact on photosynthetic activity generated a confounding
effect of low dissolved oxygen stress on the acute toxicity testing of
p-cresol. The data Indicate a predominance of the low dissolved oxygen in that
the less sensitive species to p-cresol also showed behavioral stress and
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limited mortality rates- It is quite likely- that the stress of p-cresol
increased the sensitivity to low dissolved oxygen. Either way, the effect on
the total biomass of benthic invertebrates was only moderate and the recovery
was rapid (Figure 1).
The 96 hr dose produced a dramatic effect on both the population and
community parameters. The total^density of benthic invertebrates sharply
declined in the pool habitat during the dose period (Figure 5). This time
response was not as evident in the riffle habitat (Figure 6). The ambient
concentrations of p-cresol were the same in both habitats. The most likely
variant was the dissolved oxygen in specific raicrohabitats (Figure 7). The
pools, with their macrophyte populations, have less mixing and a longer water
turnover time than the riffle habitat. It is very likely that the dissolved
oxygen reduction at night was much greater at the bottom of the pools and
within the macrophyte beds than in the riffles. The dissolved oxygen probes
were located in the pool habitats at a depth of approximately two feet. There
are no microdistrlb lonal data available for dissovled oxygen, but the
patterns are very suggestive that dissolved oxygen stress was most pronounced
in the pools.
The total biomass of benthic invertebrates showed a similar trend of a
much higher impact of p-cresol on the pool habitat as compared to the riffle
habitat (Figs. 8 and 9). The amphipod, Hyalella azteca, was the most abundant
macroinvertebrate In the benthos and macrophyte habitats (Table III). This
organism also showed a high sensitivity to p-cresol (Table I). The reduction
in biomass of Hyalella is obvious in Figure 10. The percentage surviving the
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11
Mean Densities of Macroinvertebrates In
i
TABLE III BENTHIC SAMPLES, CHANNEL B, 1981
RIFFLE HABITAT*
Date
Chironomids
Physa
Hyalella
Leeches
Planaria
Isopods
8/20
26, 80
58, 7
1522,
1396
13,
16
5» 1
36 , 2
6/28
OS
CO
56, '8
989,
- 744
2,
10
43, 5
23, 1
7/1
31, 61
38, 19
834,
1143
44,
15
12, 2
30, 11
7/3
37, 19
84, 37
537,
198
28,
79
34, 4
96, 31
7/6
18, 20
118, 25
512,
786
22,
38
59, 0
22, 17
7/16
151,260
74, 7
' "442,
247
10,
7
21, 2
18, 3
7/21
62, 92
85, 28
. 350,
542
4,
12
34, 8
16, 6
7/26
35,165
59, 40
¦626,
400
12,
16
34, 6
58, 1
7/30
17,372
36, 62
682,
340
22,
31
110, 8
64, 7
The pair of numbers is the mean density (-N- = 2) per sample for a ciffle at the
head end and the tail end of Channel B. Dose Period: 6/29 - 7/3
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96 hr acute dose of 8 ppra is estimated from the laboratory data (Table I) to be
approximately 50%. The survivorship rate observed in the field test was less
than 10%. Further, the reduction in biomass, excluding Hyalella, ranged from
16 to 30% (Figure 11)= Since many of these species are less sensitive to
p-cresol, the indication is that low dissolved oxygen contributed appreciably
to the reduction in benthic populations.
In an attempt to uncouple the low dissolved oxygen (secondary effect) from
the acute toxicity of p-cresol (primary effect), we injected a pulsed dose
whose integrated exposure (concentration x duration) approximated the same
exposure as the continuous 48 hr experiment (Figure 12). A general reduction
in total densities of macroinvertebrates was observed following the pulsed dose
in both pools (Fig. 13) and riffles (Fig. 14). These reductions were more
gradual than those observed in the pools during the 96 hr continuous
application (Fig. 5). The dissolved oxygen was also reduced by the pulsed
application but the recovery rate was more rapid than experienced during the 96
hr continous dose (Fig. 15).
The total biomass of both riffles (Fig. 16) and pools (Fig. 17) showed
similar temporal trends. Again, the reduction in total biomass is not as
striking as that observed in the pools during the 96 hr continuous dose
(Fig. 8), Furthermore, there is no indication that the reductions in either
biomass or density during this period are normal seasonal fluctuations
(Fig. 1, 2 and 5).
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The two macroinvertebrates that were tested in the laboratory were
H. asetca and I_. vertically. The araphipod had an estinaced survivorship of 80X
after 48 hrs exposure at 8 ppra and the daraselfly had 100% survivorship. These
two species were the most abundant amphipod and daraselfly in the field samples.
Table IV presents the average density of Coenigrionidae in the pools and the
one riffle that contained a significant population. The densities
raonotonically increased with the largest populations being present after
mid-July. There was no indication of a reduction in daraselfly densities
associated with the pulsed injection of p-cresol.
The mean biomass of amphipods is presented in Table V. There was a
reduction in amphipod biomass following the pulsed dose. The observed
reduction depends upon which data one used for the baseline. The 16 July date
was just prior to the initiation of the pulsed'dose on 19 July. The July 26
date was the first date after the accumulated 8 ppra, 48 hr integrated exposure,
dose (Figure 12). If these two points are used, the percent survivorship was
66% for the pools and 77% for the riffles. If the July 30 date is utilized as
endpoint, the estimated percentage survivorship is 31.6% for pools and 56.4%
for riffles. These survivorship estimated still in.. Lude the effects of both
p-cresol toxicity and some low dissolved oxygen stress. The laboratory
estimate was 80% survivorship (Table 1). The field data appear to validate the
laboratory estimates of survivorship when the acute toxicity of p-cresol was
partially uncoupled from the secondary effect of low dissolved oxygen.
The comparison of the coupled and uncoupled effects can be further
illustrated by comparing the reduction in amphipod biomass on 3 July in
Channel B which received the 96 hr continuous dose with the period 19 July
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TABLE' IV. COENAGRIONIDAE, MEAN DENSITIES (1981) (M=2)
{Pulsed Dose, Channel A)
Pools, A __ Riffle, A Pools, B _
Tallend Headend Tailend Tailend Headend
6/20
0.5
0.0
1.0
1.0
6/28
9,5
2.5
0.0
2.0
4.0
7/1
10.0
8,5
0.5
1.0
1.0
7/3
4.5
0,5
2.5
1.0
1.5
7/6
2.5
7.0
6,5
0.0
1,5
7/16
48.0
25.5
7.0
15.0
8.5
7/21
23.5
45.0
9,5"
7.5
13,0
7/26
16.0
46.0
3.5
12.0
1.5
7/30
18.0
10.5
2.5 "
15.5
17.5
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15
TABLE T/.- AMPHIPODS, MEAN' BIOMASS (1981)
N=4
Date Channel A Channel B
Pools Riffles Pools Riffles
6/20
271,6
120.3
98.6
161.8
6/28
164.2
144. S
*
123.4
79.9
7/1
228.7
130.3
164.8
93.3
7/3
147.0
113.2
10,8
21.6
7/6
126,0
129.8
18,2
41.2
7/16
249.1
131.4 _
53.2
30.7
7/21
230.7
200.6
131.8
45.3
7/26
164.4
101.0 •
59.8
54.1
7/30
78,8
74.1
92.2
36.7
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16
through 25 July in Channel A (Table 111). The esitraated survivorship during
Che 96 hr dose was 8.6% In pools and 2.7,0% In riffles. The uncoupled effect of
p-cresol on amphipods is also clearly illustrated in Table VI. The percentage
composition of the macroinvertebrate biomass attributed to amphipods dropped
sharply during the 96 hr dose and recovered within two weeks. No such shift in
percenage composition appeared.with the pulsed dose.
Community Parameters:
The community analyses are now presented as a comparison with the results
of the population analyses. The community'structure is measured as < enness
and diversity indices. The community function is measured as total dissolved
oxygen (already presented) and leaf pack degradation. To be comparable to the
single specis analyses, the results should show no effect of the 24 hr and
48 hr doses in 1980. A strong effect of the 96 hr dose and a moderate effect
of the pulsed dose should be seen in the 1982 data.
Table VII gives the mean evenness and diversity values for both habitats
and channels for 1980. Cha i el A rec.eived the 48 hr dose from 9 August through
11 August. Channel B received the 24 hr dose from 19 July to 20 July. The
pool habitat consistantly had a higher evenness and diversity throughout the
summer. There are no discontinuities in either parameter associated with
either temporal patterns or injection of p-cresol. This is consistant with the
single species analyses.
Table VIII gives the mean evenness and diversity values for 1981, with
Channel B receiving the 96 hr dose from 29 June to 3 July and Channel A
receiving the pulsed dose from 19 July to 23 July. The 96 hr dose resulted
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17
(
TABLE VI.
AMPHIPODS,
mm PERCENT B10MASS (1981) *
N=4
Date
Channel
A
Channel
B
Pool
Riffle
Pool
Riffle
6/20
83.2
55.1
37.6
49.6
6/28
46,1
66.4
16.5
46.7
7/1
42.9
42,4
17.3
33.7
7/3
20.2
39,6
4,6
7.9
7/6
17.0
29.5
9.6
17.8
7/16
37.9 '
37,0
8.8
25.0
7/21
19.5
28.0
15.9
23.5
7/26
21.6
33.0
12.6
28.3
7/30
28.4
60.5
24.1
20.3
*
The 98 hr continuous dose : Channel B, 6/29 - 7/3
The pulsed dose : Channel A, 7/19 - 7/24
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18
TABLE VII. COMMUNITY PARAMETERS '(EVENNESS, DIVERSITY), 1980
. Mean Community Evenness (N=4)
Channel A Channel B
Date
Evenness
POOLS
Date
Evenness
RIFFLES
Date
Evenness
POOLS *
Date
Evenness
RIFFLES
6/23
0,54
6/24
0.43
• 6/23
0.47
6/24
0.40
7/14
0.57
7/10
0,28
7/9
0.49
7/17
0.45
7/20
0.39
7/17
0.24
7/14
0.52
7/20
0.46
7/21
0.44
7/20
0.38
7/20
0.52
7/21
0.46
7/23
0.49
7/21
0.24
7/21
0.57
7/23
0.43
8/4
0.47
7/23
0.21
7/23
0.58
7/31
0.32
8/11
0,58
7/31
0.24
8/4
0.52
8/11
0.27
8/12
0.50
8/11
0.23 *
8/12
0.56
8/12
0.34 '
8/14
0.47
8/12
0.21
8/14
0.41
8/14
0,44
8/31
0.24
8/14
0.17
8/31
0.41
8/25
0.36
8/25
0.28
9/7
0.38
Mean Community Diversity (N=4)
Channel A Channel B
Date Diversity* Date Diversity . Date Diversity Date Diversity
POOLS
RIFFLES
POOLS
RIFFLES
6/23
2.14
6/24
1.53
6/23
1.68
6/24
1.36
7/14
2.14
7/10
0.32
7/9
1.89
7/17
1,74
7/20
1.45 ,
7/17
0,82
7/14
1,99
7/20
1.77
7/21
1.51
7/20
1.25
7/20
1.94
7/21
1.84
7/23
1.67
7/21
0.82
7/21
2.14
7/23
1.76
8/4
1,72
7/23
. 0.77
7/23
2.24
7/31
. 1.23
8/11
2.03
7/31
0,78
8/4'
' 1.86
8/11
1.09
8/12
1.81
8/11
0.82
8/12
2.02
8/12
1.36
8/14
1.67
8/12
0,77
8/14
1.49
8/14
1,74
8/31
0.85
8/14
0.60
8/31
1.47
8/25
1.36
8/25
0.96
•
.
9/7
1.26
-------
19
*
TABLE VIII. COMMUNITY
PARAMETERS
(EVENNESS,
DIVERSITY),
1981
Mean. Community Evenness (N-4)
C h
a n n e 1
A
C h a n n
e 1
B
Date
Evenness
Date
Evenness
Date
Evenness
Date
Evenness
POOLS
RIFFLES
POOLS
RIFFLES
6/20
0.24
6/20
0.28
6/20
0.30
6/20
0.19
6/28
0.34
6/28
0.30
• 6/28
0.38
6/28
0.26
7/1
0.27 .
7/1
0.24
7/1
0,-30
7/1
0.26
7/3
0.38
7/3
0.24
7/3
0.57
7/3
0.52
7/6
0.38
7/6
0.26
7/6
0.59
7/6
0.32
7/16
0.28
7/16
0.25
7/16
0.49
7/16
0.46
7/21
0.35
7/21
0.25
7/21
0.38
7/21
0.44
7/26
0.42
7/26
0,27
7/26
0.47
7/26
0.42
7/30
0.44
7/30
0.31
7/30
0.47
7/30
0.48
Mean Community Diversity (N-4)
Channel A Channel B
Date
Diversity
Date
Diversity
Date
Diversity
Date
Divers! 1
POOLS
RIFFLES
POOLS
RIFFLES
6/20
0.82
6/20
0.86 .
6/20
1.15
6/20
0.67
6/28
1.22
6/28
0.84
6/28
1.44
6/28
0.97
7/1
0.94
7/1
0.79
7/1
1.18
7/1
0.94
7/3
1.27
7/3
0.80
773
2.15
7/3
1.96
7/6
1.34
7/6
0.84
7/6
2.04
7/6
1.10
7/16
1.08
7/16
0.94
7/16
1.94
7/16
1.74
7/21
1.34
7/21
0.88
7/21
1.50
7/21
1.68
7/26
1.56
7/26
0.94
7/26
1.86
.7/26
1.54
7/30
1.60
7/30
1.04
7/30
1.92
7/30
1.81
-------
20
in a sharp increase in both community parameters. Neither of these recovered
to their original values during the study.
The pulsed dose failed to generate a comparable response. There is a
slight increase in evenness and diversity in the pools where the effects are
expected to be a result of both acute toxicity of p-cresol and,low dissolved
oxygen. The community parameters again gave bascially the same results as the
single species parameters. These results are understandable since the most
abundant macroinvertebrate (Hyalella azteca) is also very sensitive to p-cresol
and low dissolved oxygen. The disproportionate reduction of the dominant
(Table VI) will affect both these parameters in the same fashion.
The remaining community parameter measures an aggregate process of leaf
degradation. This experiment has been reported by Stout and Cooper (1983).
Figure 18 presents the results measured as percent of dry weight biomass of
poplar leaves for both the 96 hr and pulsed doses of p-cresol- There is a
significant reduction in the degradation rate only during the period of the
96 hr dose. The processing function recovered rapidly. There is no
significant reduction during the pulsed dose. These results are consistant
with both the single species impacts and the community structure results.
Conclusions:
The Monticello experiment was designed to test several hypotheses. These
are listed below accompanied with the conclusions that have resulted from the
analysis of the ecological responses.
Hypothesis I: The transfer of laboratory acute toxicity tests to a field
situation is possible without serious distortion.
-------
21
Conclusion I: The acute toxicity tests with fathead minnows, largemouth
bass, smallmouth bass, daroselflies and araphipods produced estimated
survivorship rates of exposure to p-cresol that were consistent with the
results of the field experiments.
Hypothesis 1.1; The results of single-species analyses will give similar
results as will multispecies (community level) responses to exposure of
p-cresol.
Conclusion II; The community parameters, both structural (evenness and
diversity) and functional (community metabolism and leaf pack
degradation), indicated the same type of ecological impacts on macro-
invertebrates as did the single species analyses.
Hypothesis III: Pulsed exposures with short time intervals between events
will produce the same ecological responses as a continuous exposure with
the same integral of "exposure concentration x duration."
Conclusion III; The pulsed exposure produced slightly more, impacts than
continuous 48 hr exposure with a comparable "ppm x days" integral.
In addition to these anticipated impacts, some real ecological lessons
resulted that were not previously anticipated. The major impact was not the
primary impact of p-cresol on the macroinvertebrate community or on selected
fish species. Rather, the major impacts were mediated through a primary effect
of p-cresol on photosynthetic and respiration processes of aquatic plants. The
secondary effects of low dissolved oxygen in addition to the acute toxicity of
p-cresol generated striking impacts on both population and community
parameters. Eventhough these impacts were rather severe, he populations and
communities recovered over a period of several weeks.
The Monticello experience was a unique team effort that will be difficult
-------
22
to repeat with any frequency- On the other hand, the results of direct field
validation of more simple test, systems are essential to the regulatory process-
The Monticello facility is uniquely suited to this type of field toxicity
testing. The scale, diversity and recycling characteristics of these stream
ecosystems are essential for ecological validation experiments.
-------
23
REFERENCES
Anderson, 0. 1983. The foraging behavior of largemouth bass in structured
environments. Ph.D. Dissertation, submitted to Michigan State University
Department of Zoology. East Lansing, MI.
Boling, R. 1981. A technique for computer controlled toxicant injection.
Environmental Contamination, and Toxicology, Vol. 27;
Coleman, R.A., R.D. Estrom, M.A. Unger, R.J. Huggett. i982 A rapid field
technique for monitoring p-cresol in streams. J. of Analytical Chemistry,
54(14): 2631-2632.
Cooper, W.E, and R.J. Stout. 1982. Assessment of transport and fate of toxic
materials in an experimental stream ecosystem. In: Modeling the Fate of
Chemicals in the Aquatic Environment. Dickson, Maki an Cairns, eds.
Ann Arbor Science.
Crowder, L. and W.E. Cooper. 1982. Habitat structural complexity and the
interaction between Bluegills and their prey. Ecology 63(6), 1802-1813.
Pielou, E.C. 1969. An Introduction to Mathematical Ecology. John Wiley and
Sons, New York.
Pritchard, P., J. Boyer, P. VanVeld and W. Cooper. 1981. Fate and effects of
p-cresol in outdoor stream channels: reproducibility in microcosms. SETAC
meetings presentation. (in preparation).
Stout, R.J. and W.E, Cooper. 1983. Effect of a toxicant on leaf decomposition
and invertebrate colonization in experimental outdoor streams. Can. Jour.
Fisheries and Aquatic Sciences. Vol. 40(10), 1647-1657,
Stout, R.J. and S. Kilham. 1983. Effects of p-cresol on Photosynthic and
Respiration Rate > of a Filamentous Green Alga (Spirogyra). Bull.
Environm. Contam. Toxicol. 30(1-5).
-------
24'
LEGENDS FIGURES
Figure 1. Total mg dry weight biomass of macroinvertebrates from pools (™) and
riffles ( ) in Channel A for 1980. The vertical bars represent
the range of duplicate samples. Riffle samplers included .050 m^»
Pool samplers included .0
-------
25
Figure 9. Mg dry weight biomass of macroInvertebrates in two riffle habitats
in Channel B, 1981, The riffle samples included .050 .
Vertical bars represent the range of duplicate samples.
Figure 10. Mg dry weight biomass of amphipods in two pool habitats in
Channel 8, 1981. The pool samples Included .042 m^. Vertical
bars repreent the range of duplicate samples.
Figure 11. Mg dry weight biomass of macroinvertebrates minus the amphipods in
*
two pool habitats in Channel B, 1981. The pool samples included
.042 Vertical bars represent the range of duplicate samples-
Figure 12. Ambient concentrations of p-cresol at the head (-*-) and tail (—)
end of Channel A, 1981, during the pulsed dose.
Figure 13. Numerical densities of macroinvertebrates in two pool habitats in
Channel A, 1981. The pool samples included .042 . ' ^rtical
bars represent the range of duplicate samples.
Figure 14. Numerical densities of macroinvertebrates in two riffle habitats in
Channel A, 1981. The riffle samples included .050 m^. Vertical
bars represent the range of duplicate samples.
Figure 15. Ambient dissolved oxygen in the experimental (-) and control (-•-•-)
channels during the pulsed dose.
Figure 16. Mg dry weight biomass of macroinvertebrates in two riffle habitats
in Channel A, 1981. The riffle samples included .050
Vertical bars represent the range of duplicate samples.
Figure 17. Mg dry weight biomass of macroinvertebrates in two pool habitats in
Channel A, 1981. The pool samples included .042 m^. Vertical
bars represent the range of duplicate samples.
Figure 18. Percent of original dry weight biomass of poplar leaves (Populus
deltodies) remaining during the 96 hr and pulsed dose experiments
in 1981.
-------
-------
-------
3 . AMBIENT CONCENTRATIONS OF P-CRESOL (ppm)
PHRED GR PHRED YE
Noon Midnight Noon Midnight Noon Midnight Noon Midnight Noon
rr
'i *+
iw
-------
INJCT B
AMOUNT OF P-CRESOL ADDED
Midnight Noon Midnight Noon
\j - tJ' *j'"' )
] ci -f
Cml/min)
7/1
" Midnight
7/2
Midnight
7/3
8:58 AM
-------
3200
2800
JD
£ 2000
=3
!Z
—. 1600
H 1200
400 -
7/6
I \ I »
7/l6 7/21 7/26 7/30
-------
3200 -
2800
CD
JD
05
2400
2000
1600
o
I— 1200
800
400
6/20
DOSE
i r
6/28 771 7/3 7/6
7/l 6 7'21 7/26 7/30
-------
":i L'-'Alii . .J • - I
DISSOLVED OXYGEN (ppm)
.DO ¦ BE
iu
Jr..!
D:c'«;r.n
n''A
6/30 7/1 . 7/2
Midnight Midnight Midnight
7/3 7/4 7/5
Midnight • Midnight Midnight
7/6
Midnight
-------
1200
1000
O) 800
400
200
DOSE
, ; |___ | | |
6/20 6/287/l 7/3 ^6
1
1 1 1 " I
Z/16 7/21 ^26 7/30
-------
-------
-------
1500
1300
1100
100
6/28 7/1 7/3 7/6
7/21 7/26 7/30
-------
W
AMBIENT P-CRESOL CONCENTRAT I )Nb (ppm)
Ui
/w
1
.PHRED GR
a.
CL
.PHRED YE
A
7/1 g
Noon
7/13
Midnight
7/20
Noon
7/20
Midnight
7/21
Noon
7/21
Midnight
7/22
Noon
7/22
Midnight
7/23
Noon
7/23
Midnight
i \1 -1 ~ r'^fi " p.-:- :r~ p y,^ /. ' > [• n r
-------
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m 5000
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4000
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3000
2000
1000
6/20
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6/28 7/l
DOSSED
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-------
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3600
3200
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2 2400
03
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1600
1200
800
JDOSE^D
~T 1 I I ~~
J/Q 7/16 7/21 7/26
-------
1600
1400
1200
1000
O) 800
600
400
200
6/20
6/28 Z/1
S I I i
7/16 ^21 7/26 ^30
-------
3400
2600
2200
1800
1400
600
200
e/28 7/1
DOSED
.lllllljl "nil"*
7/21 V26
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