its power by using additional energies has a competitive advantage
over other systems. Energy may be used to meet all contingencies.
Given a finite available energy source, a system is further
limited in its power level by the energy required for each transform
ation. This observed energy for transformation is described by the
second law of thermodynamics as a necessary decrease of available
work energy in most energy-transforming processes. In other words,
much energy is converted to a lower quality state when a transforma
tion to another type occurs. This phenomenon has been quantified in
various branches of science and was summarized by Odum and Pinkerton
(1955). Their review of physical and biological systems concluded
that maximum power level is possible only at 1ower-than-maximum
efficiency for competing systems and may be at 50% transformation
efficiency for a single storing process. The necessary loss to
unusable heat limits the total number of tranformations possible for
any energy entering a system and results in a predictable spectrum of
energy transformers in all adapted systems (Odum 1979).
All systems are but subsystems within larger competing systems
and thus are exposed to control by the next system's deterministic
behavior. Therefore, biological systems such as mature forests or
ancient lakes may be greatly simplified by volcanic eruptions or
human toxic wastes, resulting in a decreased local power level but an
increased power at the next larger scale. Circumstantial evidence is
available to show that many systems are on a successional and evolu
tionary course towards the maximum power level within the boundaries
of their exogenous controls.
Table A.7. (Continued).
Total dry matter export
Nitrogen uptake by macrophytes
Nitrogen diffusion between open
water and periphyton
Nitrogen uptake by algae
Gross production by algae
Gross production by macrophytes
Light absorption by algae
Light absorption by macrophytes
Light absorption by detritus and
Algal Cd uptake
trations of Cd reported are probably maximum average values based on
the measured weight loss of the Cd-metal strips.
At the very low Cd levels used in this study, net primary pro
duction was consistently stimulated compared to control microcosms
(Fig. 4.10 and Table 4.6). On days 10 and 14, stimulation was mea
sured in all treated microcosms. Smoothing of the curves in Fig.
4.10 indicates that the optimal Cd value for maximum productivity may
be near 0.03 ppb with a stimulation of about 0.8 g 02*m2*hr1 possibl
A slight toxic effect of the Cd was measured near the beginning of
the experiment on day 7 at the highest nominal concentration of 0.038
Stream Model Simulations
An aggregated model of a stream ecosystem was developed for
experimentation with toxin and consumer manipulations. Figure 4.11
illustrates the overall model with the inflow and outflow of water
carrying nutrients (where N represents nitrogen) and the toxin, Cd
(C), which interact with a complicated biological system. The bio
logical system tested is typical of streams in low-slope areas with
moderate to slow current velocities. Primary producers include
macrophytes (rooted plants, Q3) and their associated periphytic
algae (C^)* In this model, consumers are lumped into one unit
(Q4). All unassimalated and dead material are cycled through the
detrital-microbial storage (Q5), which in many stream systems is
intimately associated with the periphytic algae.
The energy embodied in Cd storages by three different systems
was evaluated. Calculations suggest that the world geologic cycle is
producing economically recoverable Cd at a slow pace, only 53 kg*yr"l.
The energy transformation ratio of this Cd is 2.5 x 1016 Solar
Equivalent Calories (S.E. Cal)*g Cd-1, or 6.4 x 1017 S.E.
CalCal"!. The industrial concentration of Cd adds an addi
tional 4.6 x 107 S.E. Calg Cd"l in the synthesis of the pure
metal. A calculation of the biological concentration in experimental
stream systems indicated that 1.3 x 109 S.E. Cal*g Cd-1 are
required for biological concentration to 0.8 ppm on a live-weight
Information collected during research on Cd effects in experi
mental streams was summarized and used to calibrate an energy and
material model of the Cd streams. Several mechanisms of Cd toxicity
were examined, and the model includes a stimulation of system compon
ents at low Cd levels. Simulation results allowed a detailed corre
lation of the relationship between embodied energy in Cd and the Cd
effect in equal units. This correlation was found to be first posi
tive, then negative, and eventually approached zero at higher Cd con
Consumer control was studied at Silver Springs, Florida. Total
system metabolism was measured and compared to published data.
Although major alterations in some top consumers have occurred (cat
fish and mullet largely replaced by gizzard shad), system primary
productivity was little altered after about 24 yr.
In addition, consumer control was studied at Silver Springs in
replicable, flow-through microcosms. System productivity was
B.4 Diurnal oxygen change curves from October 20, 1976,
for six experimental streams receiving Cd inputs 175
B.5 Diurnal oxygen change curves from November 24, 1976,
for six experimental streams receiving Cd inputs 176
B.6 Diurnal oxygen change curves from February 9, 1976,
for six experimental streams receiving Cd inputs 177
B.7 Diurnal oxygen change curves from March 16-17, 1976,
for six experimental streams receiving Cd inputs 178
B.8 Diurnal oxygen change curves from April 29, 1976,
for six experimental streams previously receiving
Cd inputs 179
B.9 Diurnal oxygen change curves from May 31-June 1, 1976,
for six experimental streams previously receiving
Cd inputs 180
B.10 Diurnal oxygen change curves from July 6, 1976, for
six experimental streams previously receiving Cd
C.l Diurnal oxygen data and analysis for Silver Springs
on August 31, 1978 183
C.2 Diurnal oxygen data and analysis for Silver Springs
on October 5, 1978 184
C.3 Diurnal oxygen data and analysis for Silver Springs
on December 13, 1978 185
C.4 Diurnal oxygen data and analysis for Silver Springs
on March 7, 1979 186
C.5 Diurnal oxygen data and analysis for Silver Springs
on April 15, 1979 187
C.6 Diurnal oxygen data and analysis for Silver Springs
on May 16, 1979 188
C.7 Diurnal oxygen data and analysis for Silver Springs
on June 19, 1979 189
C.8 Diurnal oxygen data and analysis for Silver Springs
on July 17, 1979 190
C.9 Diurnal oxygen data and analysis for Silver Springs
on August 15, 1979 191
Figure B.10. Diurnal oxygen change curves from July 6,
1976, for six experimental streams previously
receiving Cd inputs.
Footnotes to Fig. 4.24.
a. Total solar insolation integrated over a 1-yr period: from Odum
(1957) 1.7 x 103 Calm"2yr"l 4 365 d = 4658 Cal*nr2*d-1 (these are
b. Assimilation of free energy by nitrogen uptake: from Odum (1957)
NO3 change from boil to 1200-m station during the day was 0.445
to 0.384 mg N-.N03*L~1
Gibb's Free Energy Change: AG = nRT ln(0.384/0.445)
AG = -0.0062 Cal-g IT1
with average flow = (2 x 106 m3*d_1)(0.445 g N*m'3)/(76,000 m2)
= 11.71 g N*m2,d"l
multiply by the free energy change to get 0.073 Calnr^d-1
From Wang et al. (1980) use transformation ratio for dissolved
solids in stream flow (1.17 x 106 S.E. Cal*Cal"l) to get:
84,944 S.E. Cal-m-2-d-1
c. Assimilation of potential energy in water flow: from Odum (1957)
0.144 m*kml fall, using potential energy equation for
E = pVgh = (103 kg*m~3)(9.8 m*s"2)(144 m*km-*-)(1.2 km)
(2 x 10^ m3*dl) = 3.39 x 10^ kg*m2*s2,d"l
= 3.39 x 10^6 ergs*dl
using area = 76,000 m2 and 2.389 x 10-*1 Cal'erg-^, energy =
10.7 Cal nr2*d~1
From Wang et al. (1980) use tranformation ratio for potential
energy in rain (4000 S.E. CalCal"1) to get:
42,800 S.E. Cal-m-2-d-1
d. Export of organic matter with energy content: from Odum (1957)
2500 Calnr2,yr"l 4 365 dyr-^- to get:
6.85 Cal'm-2*d-1 -
Embodied energy of this flow is equal to the entire energy income
of the stream production system = 1.32 x 103 S.E. Calm"2,dl.
Figure 4.20. Model simulation results for system-level parameters at
two Cd input levels: 5 ppb (solid lines) and 10 ppb
(dashed line). Refer to Fig. 4.4 for actual measured
Figure 4.24. Aggregated energy model for the upper 1200-m section
of the Silver River with energy flows modified from
Odum (1957). Upper model gives actual heat equiva
lent energies and lower model gives calculated embod
ied energies in Solar Equivalent Calories. Letters
refer to footnotes on following page.
Figure B.2. Diurnal oxygen change curves
from July 28, 1976, for six
experimental streams receiving
CELL Cd (ppm)
UPTAKE BY MICROORGANISMS
Figure 3.26. Uptake of Gd by five microorganisms in static culture
(from Doyle et al. 1975).
Table A.6. (Continued).
585 IF SU>=DT THEN GOTO 587
586 GOTO 542
587 IF Q2<0 THEN (32=8. 01
588 IF Q3<0 THEN 03=0. 01
589 IF Q4<0 THEN Q4=0. 01
590 IF Q5<0 THEN Q5=0. 01
597 IF T<138 OR T>503 THEN GOTO 610
620 IF I=J GOTO 640
630 GOTO 320
652 IF T>138 THEN C1=ZZ
653 IF T>503 THEN Cl=. 023
655 IF T>475 THEN K9=Z1
660 IF T>ND GOTO 990
698 PLOT 29,18
700 PLOT S
720 PLOT 29,18
740 PLOT 2, TG, 75+J0/150, 255
750 PLOT 29, 22
755 PLOT 2, TG, 02, 255
760 PLOT 29, 17
765 PLOT 2, TG, 03, 255
770 PLOT 29,20
775 PLOT 2, TG, 05/2, 255
782 PLOT 29,18
800 GOTO 310
990 PRINT fll, fl2, R3
999 PLOT 29,18
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In order to generalize on Cd uptake ability, a short review is
made of curves of Cd uptake as a function of Cd concentration for
various groups of organisms. A simple computer model is presented
that generates similar results.
Through passive and active concentrating mechanisms, biological
systems can have a large impact on cycling of minerals in nature.
When absorbed or adsorbed by a motile organism, elements may be
transported and relocated in a system. Through uptake and death, an
animal or plant may store toxicants for varying time spans, effec
tively removing them from biological circulation. If inputs of a
metal such as Cd are low, biological uptake may greatly lower effec
tive toxin concentration. Mechanisms of storage are systems of
detoxification. However, when systems receive chronic elevated
inputs, detoxifying systems may be overloaded.
Different species have variable abilities to remove Cd. Through
system selection, species with high resistence to Cd and detoxifying
mechanisms may be selected at elevated Cd concentrations.
Unfortunately, few of the reported experiments were conducted in
flow-through systems with continuous Cd renewal. In this review it
is assumed that the researchers monitored Cd concentration at the end
of each experiment and would have reported any major depletion.
Microbes. Research reported by Doyle et al. (1975) for various
microbial species shows the variability of uptake by different
species (Fig. 3.26). However, the shape of the uptake curve is
generally hyperbolic if high enough concentrations are examined. The
one fungal species, Aspergillus niger, did not demonstrate this
The eight microcosms were held parallel to one another and to
the river's current by two racks. The racks were loosely anchored to
the stream bottom by ropes and concrete blocks and held 1 m off the
bottom by floats. Thus, the microcosm tubes were maintained 2 m
below the water surface. Because these systems were submerged, they
required no corrections for oxygen diffusion and were safe from van
Metabolism of the enclosed microcosms was measured by upstream-
downstream DO changes. For DO measurement, water was pumped from the
microcosms through garden hoses using a 12-volt impeller pump. One
hose led to the upstream rack and was used to measure the DO of water
before it entered the tubes. A hose was also attached to the down
stream end of each microcosm for measurement of the final DO of water
after it passed through the tubes. The nine resulting hoses were
attached to nine gate valves from which a manifold directed the water
to one hose connected to the inlet side of the pump (see Fig. 2.3).
Water from the outlet side of the pump was passed through another
hose to fill and overflow a small container housing a standard DO and
temperature probe. Since the hose and pump system from the microcosm
to the probe was air tight, no atmospheric oxygen could contaminate
the water before the measurement.
Upstream DO was measured alternately with two downstream mea
surements. After the upstream value was recorded, the upstream valve
was closed and the next valve was opened. Three minutes of contin
uous flow was allowed for equilibration of the DO probe reading, and
Table A.6. (Continued).
166 FP=. 1
168 FQ=. 005
170 FR=. 2
172 FS=. 003
174 FX=. 002
204 K2=. 126
216 K8=. 004
213 K9=. 001
224 KC=. 001
228 KE=. 001
220 KF=. 002
232 KG=1. 5E-4
242 KL=. 82
244 KM=. 02
243 KO=. 02
250 KP=. 008
260 KU=1. 5E-6
266 KX=. 008
263 KY=. 008
272 L2=. 005
274 L2=. 005
278 L4=. 004
280 L5=. 0002
282 L6=. 004
289 LP=. 008
290 L8=. 136
291 LB=. 25
Figure B.l. Diurnal oxygen change curves from June 30,
1976, for six experimental streams receiv
ing Cd inputs.
however, the percentage of production exported increased with
increasing Cd treatment from approximately 19% in the controls to 29%
in the 10 ppb Cd streams (Figs. 4.4c and 4.5). Nutrient regeneration
by microbial communities was significantly reduced by Cd treatment as
indicated by weight loss in leaf litter packs.
In summary, Cd input at concentrations of 5 and 10 ppb demon
strated inhibitory effects in every trophic level examined, and yet
was not completely inhibitory to any biological parameter.
Cadmium uptake by the stream periphyton communities was rapid
with steady state levels reached within 50 days. Steady state levels
were 3, 36, and 58 yg Cd*g dry weight-1 for control, 5, and 10
ppb Cd treatments. When Cd inputs were turned off, periphyton Cd
levels dropped to control levels within 50 days.
Macrophyte uptake of Cd in the treated channels was much slower
than for the periphyton, with steady state concentration attained
after 5 mo of continuous input. Root Cd concentrations were 3-4X as
high as leaf concentration in the two macrophytes examined. Whole
plant averages were approximately 2, 75, and 150 yg Cd*g dry
weight-1 for control, 5, and 10 ppb Cd treatments.
Mosquito fish residing in the stream channels demonstrated the
slowest Cd uptake observed, with saturation apparently not reached
after 6 mo of uptake. Cadmium concentrations at that time were
approximately 2, 24, and 40 yg Cd*g dry weight-1 for control,
5, and 10 ppb Cd treatments.
Biological food chains represent concentrations of energy, with
each level requiring energy diverted from the machinery of primary
production. This diverted energy must be compensated for by energies
fed back from storages to capture greater free energy for the system.
Thus, a control hypothesis follows directly from the maximum power
theory. In adapted systems, components must have controlling actions
that are proportional to their energy of transformation.
Since poisons may be powerful controllers of ecosystems, knowl
edge of stimulative roles of poisons may be used to enhance produc
tivity and manage systems. More control may be achieved by using
toxins to control consumer organisms that, in turn, have controlling
roles. If a toxin occurs at low concentration, biological energies
may be used to concentrate it to a stimulatory level; or, if the
natural concentration of a toxin is high, biological energy may be
used to detoxify the substance by reducing its effective concentra
tion in the environment.
Embodied Energy and the Control Hypothesis
In the previous section it was stated that the degraded energy
resulting as a by-product of any energy transformation may be consid
ered as "low quality" in that it is no longer capable of performing
work in the system. On the other hand, we may consider the remainder
of the transformed energy as being of higher quality than both the
original input energy to the transformation process and the dispersed
low-quality energy that was a necessary by-product of the transforma
tion. As a logical convention, we can assume that the total energy
Metabolism of Silver Springs, Florida, estimated from oxygen
changes between the boil and a point 1200 m downstream (76,000
Uptake of Cd by Chlorella pyrenoidosa at two pH values in
static culture (from Hart and Cook 1975).
Figure 3.21. Effect of Cd on brook trout in flow-through
systems (from Benoit et al. 1976).
I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is
fully adequate, in scope and quality, as a dissertation for the degree
of Doctor of Philosophy.
/ / -- /
, -L <-,j_
John P. Giesy, Savannah
River Ecology Laboratory ,Jt
This dissertation was submitted to the Graduate Faculty of the College
of Engineering and to the Graduate Council, and was accepted as
partial fulfillment of the requirements for the degree of Doctor of
Dean, Graduate School
Figure B.9. Diurnal oxygen change curves from May
31June 1, 1976, for six experimental
streams previously receiving Cd inputs.
CADMIUM EFFECT RATIO(SÂ£Â£al-g Cd~x I06)
Figure 4.22. Predicted correlation between Cd transformation ratio and Cd effect ratio for gross
productivity, community respiration, and stream export. Values are calculated from
1-yr averages of simulation data from Cd-streams models.
summarized the model results for the case when both mechanisms are
operating together. A subsidy-stress (Odum et al. 1979) curve was
found typical of those discussed in the literature review but with
the possibility of more than one stimulatory region.
Thus, this model suggests that either of the proposed mechanisms
of stimulation or a combination of both of them may be responsible
for the observed results. Cropping of primary producers to optimum
growth stages can increase production at lowered standing stocks.
Also, nutrient regeneration can be responsible for greater productiv
ity at lowered producer populations. The generality of stimulation
of primary production by consumers at optimum densities may thus be
the result of several control mechanisms in nature.
As a natural part of organic evolution, biological systems
have developed toxic substances to control energy flows and theoret
ically to maximize power. Thus, plants have allelopathic chemicals
and insects have venom. These substances represent a concentration
of energies and have a high embodied energy.
Human technological systems may be similar in this respect.
Toxins are collected from nature or synthesized in laboratories for
the purpose of controlling environmental energy flows. These
substances also represent large energy flows and have high embodied
On the other hand, toxicity is a drag on the energy flow in a
system if it is not a part of material cycles and regenerative pro-
and Gratiola virginiana, which had naturally colonized the channels
during previous studies, were transplanted into the systems. Con
sumer organisms consisting of clams, crayfish, and two species of
fish (mosquito fish and bluegill) were added to the systems after
some plant growth had occurred.
Cadmium inputs into four of the six channels began on March 18,
1976. Cadmium (as CdCl2) was metered into the turbulent region of
the head pools with a 4-channel peristaltic tubing pump. The Cd
levels established were 5 yg*L~l in two channels and 10
yg*Ll in another two, with the remaining two channels serving
as controls. Cadmium inputs were discontinued on March 18, 1977, a
full year after they began, and data were collected for 5 mo after
Periphyton biomass, pigment levels, species composition (algal
only), and algal volume were determined monthly on vertical glass
microscope slides oriented parallel to the current flow in the chan
nels. The same parameters were also measured bimonthly on clean
glass slides that were allowed to colonize for 30 days, as well as
from the channel walls on four occasions, and twice as complete cores
through the water column, macrophytes, benthic mat, and sand sub
strate. Samples were also analyzed for total Cd content from all of
On two occasions after Cd inputs were terminated, population
densities of naturally colonizing macrophytes were high enough that
plant biomass sampling by quadrat analysis was feasible. Ten
(James Lowry, personal communication), these two dominants have
virtually disappeared from the Silver River wildlife. These changes
are closely correlated in time to the construction of the Rodman Dam
and Reservoir on the Oklawaha River approximately 50 km downstream
from Silver Springs. Observations during the 2 yr of this study
indicated small, scattered groups of mullet and very few catfish in
the study area. Fish counts on five dates are reported in Table 4.2.
Examination of these data indicates an important new component in the
fish populations since Odum's study, i.e., the presence of the "blue
shad," more commonly known as gizzard shad, Dorosoma cepedianum, all
of which were large fish (>30 cm). A mixture of sunfish of several
species, Lepomis spp., and largemouth bass, Micropterus salmoides,
were the other dominant consumer fish at the time of this study.
Average live weight of these fish during a 1-yr period over the
entire area was estimated as 11.5 gm-^. About half of this
mass was made up of herbivorous species, and half was carnivorous
The apple snail, Pomacea paludosa, and Goniobasis floridense
were the only abundant snails in the area sampled. The four samples
collected had a mean live snail biomass of 104 g*m-^ with a 61%
coefficient of variation (CV). Biomass of Â£. floridense was measured
as 42 gm'^ with CV equal to 75%.
of one type necessary to make another type is embodied in the energy
of the second type.
If we divide the energy of one type necessary to produce another
by the energy of the second type, we have the ratio of "energy trans
formation." This dimensionless parameter (efficiency) has been
called the "energy quality factor" or the "energy transformation
ratio" (TR) by Odum (1978) and may be assumed to have some theoret
ically minimum value in competing systems. When transformation
ratios for various processes are related to energy of one type (e.g.,
S.E. Cal or Coal Equivalent Calories [C.E. Cal]), we have a parameter
to compare quality of all types of energy or matter.
In order to evaluate the primary energy necessary to produce an
energy flow after several transformations, we must recognize that the
energy necessary to produce the intermediaries is necessary to the
production of the final product. Thus, if a food-chain system were
relying on a single input source, the embodied energy for all energy
flows and storages would be evaluated in terms of the single incoming
If a production process has more than one major energy input,
then the embodied energies of all inputs must be summed to evaluate
the energy quality of the resulting products. In most systems, some
of the auxiliary energies of the process are fed back from the
products and therefore must not be added to avoid double counting.
Examples of energy transformation ratio calculations are included
below, or, for a more detailed discussion of this concept, see Odum
The Cd-stream study lasted 2 yr with five persons actively
sampling various components of the biota for toxicity effects and
measurement of Cd concentration. The final report for the project
(Giesy et al. 1979) summarized the major findings but did not include
a summary model of how the overall system was reacting to Cd dosing.
Data that are necessary to calibrate a simulation model of the
streams are integrated in this section.
Unfortunately, only a small part of the data was collected in
convenient form for a system model; therefore, it has been necessary
to extrapolate from artificial samplers to the whole stream community
and to prepare new graphs on a m^ basis. All of the data presented
here are averaged over the entire stream area of 55.8 m^, but, in
fact, the communities observed were quite variable depending on their
location in the streams. Thus, rapid colonization of most algae and
macrophyte species was at the upstream end of the channels while
other species were always most luxuriant at the downstream end. Data
from all samplers showed position effects; however, a zonation model
of the channels was not attempted.
Figure 3.8. Summary model of tadpole-periphyton interactions discussed
by Dickman (1968). The development of tadpoles from frog
eggs acts as a logic switch on periphyton biomass regenera
Table A.7. (Continued).
Algal consumption by consumers
Macrophyte consumption by
Particulate Cd loss from macro
phytes to consumers
Detrital-microbial Cd decay
Macrophytic loss to detritus
Particulate Cd loss from macro
phytes to detritus
Cd toxicity to algae
Cd toxicity to macrophytes
Particulate Cd loss from detritus-
microbes to consumers
Nitrogen remineralization from
Total assimilation by consumers
Consumer loss to detritus
Particulate Cd loss from consumers
Straskraba, M. 1979. Natural control mechanisms in models of
aquatic ecosystems. Ecol. Monogr. 6:30521.
Thorp, J. H., J. P. Giesy, and S. A. Wineriter. 1979. Effects of
chronic cadmium exposure on crayfish survival, growth, and
tolerance to elevated temperatures. Arch. Environ. Contam.
Turner, M. A. 1973. Effect of cadmium treatment on cadmium and zinc
uptake by selected vegetable species. J. Environ. Qual.
United States Geological Survey. 1978. Water resources data for
Florida, vol. 1. Report FL-77-1.
Vlasov, K. A. 1966. Geochemistry of rare elements, Vol. 1; Cadmium.
Israel Program for Scientific Translations, Jerusalem.
Volterra, V. 1926. Variations and fluctuations of the number of
individuals in animal species living together. Pages 409-48 in
R. N. Chapman (ed.), Animal ecology. McGraw-Hill Book Co.,
Inc., New York.
Wallace, A., E. M. Romney, G. V. Alexander, S. M. Sonfi, and P. M.
Patel. 1977. Some interactions in plants among cadmium, other
heavy metals, and chelating agents. Agron. J. 69:18-20.
Wang, F. C., H. T. Odum, and P. C. Kangas. 1980. Energy analysis
for environmental impact assessment. J. Water Res. Plan.
Manage. Division ASCE 106:451-66.
Wedepohl, K. H. 1970. Handbook of geochemistry, Vol. 2; Cadmium.
Springer-Verlag, New York.
Williams, D. R., and J. P. Giesy. 1978. Relative importance of food
and water sources to cadmium uptake by Gambusia affinis
(Poeci1iidae). Environ. Res. 16:326-32.
Woodwell, G. M. 1967. Radiation and the patterns of nature.
(KCAL m-2* d"')
Figure 5.2. Response of total community gross produc
tivity to total incident radiation at the
Silver River. Data are compared between
the study reported here and the study
reported by Odum (1957). Correction fac
tors for tree shading are included as des
cribed by Odum (1957); however, total
incident radiation is used rather than his
visible light reaching plant level. Oxy
gen metabolism data converted on the basis
of 4.22 Calg 02_1.
Robert Lee Kniqht was born on September 16, 1948 in Bethesda,
Maryland. Life in a U.S. Navy family took Bob at a young age to
Egypt, Florida, Maryland, and North Carolina. Upon retiring from the
Navy, Dr. Kenneth Knight took his family to Ames, Iowa, where Bob
attended high school and 2 yr of study at Iowa State University as a
physics major. In 1968, Bob transferred to the University of North
Carolina at Chapel Hill into the Department of Zoology, where he
received the Bachelor of Arts degree in zoology in 1970.
After one quarter of study at the University of Florida, Bob
returned to the University of North Carolina where he worked for 1 yr
on the Provisional Algal Assay Procedure and went on to earn a
Masters in Public Health decree in 1973 with research on phytoplank
ton entrainment in a coal-fired power plant.
In the fall of 1973, Bob beqan 4 yr of work at HWCTR artificial
streams facility, operated by the Savannah River Ecology Laboratory
under the Institute of Ecology of the University of Georgia. Bob
helped to design and complete two research projects, studying mercury
and cadmium, while at Aiken, South Carolina.
In the fall of 1977, Bob returned to graduate study at the Uni
versity of Florida under the supervision of Dr. H. T. Odum, where he
is now a graduate student. Work assistantships at the University of
Florida have included 1 yr on the Crystal River Power Plant project
spring and by the end of that summer the macrophyte populations
had increased greatly, resulting in a substantial change of habitat
in the channels.
An initial sensitivity of some groups such as protozoans, ostra-
cods, cladocerans, and copepods to Cd input was demonstrated in
microinvertebrate studies. Cadmium severely reduced copepods, ostra-
cods, and testate amoebas; however, overall populations of microin
vertebrates were increased because of stimulation of protozoans and
Macroinvertebrate data indicated variable population responses
in the different Cd treatments. At some sampling times, chironomid
larvae were more abundant in the Cd streams than in controls; but,
during most of the study, total macroinvertebrate biomass was reduced
in the treated channels (Fig. 4.3).
Initially, 200 mosquito fish, Gambusia affinis, were released
into each channel. Recovery of dead fish indicated increased mortal
ity in the 10 ppb Cd treatment (55%) compared to the 5 ppb Cd treat
ment (23%) and controls (21%) within 3 mo of the beginning of Cd
inputs. No further attempt was made to quantify the fish populations
during this study.
Overall community metabolism was significantly lower in
Cd-treated streams throughout the period of Cd input, and showed
quick recovery soon after Cd input was stopped (Figs. 4.4a, b, and
4.5). The complete diurnal oxygen change curves from the Cd streams
are given in Figs. B.1-6.10. All streams were autotrophic (P/R > 1),
although the treated streams were less so. Cadmium treatment signif
icantly lowered community export of organic matter during this study;
DISSOLVED OXYGEN (mg-L-1)
1000 1200 1600
TIME OF DAY (H)
1000 1200 1600
TIME OF DAY (H)
Diurnal oxygen data and analysis for Silver Springs on
June 19, 1979.
measured in these microcosms along a gradient of increasing consumer
densities. Typical subsidy-stress curves were found for herbivorous
consumers (snails), carnivorous consumers (mosquito fish), and a
toxin (Cd). Maximum primary productivity was measured at consumer
densities similar to the actual measured densities in the adapted
The results of these studies with a single toxin and a few con
sumer organisms are predicted to be general to controllers in other
systems. Tables of embodied energy values for controllers and their
resulting energy effect may be useful to environmental engineers in
the wise management of ecosystems.
Figure 4.18. Stream model simulation results for system-level parame
ters at background Cd concentration, 0.023 ppb. Refer to
Fig. 4.4 for comparison to actual data.
Intercolor desk top microcomputer. Integration was by means of sim
ple difference equations with variable time steps.
The model evolved considerably during the 12-mo period of simu
lations as mechanisms were seen to be inconsistent with actual data
or as other mechanisms that were necessary to generate the observed
results became clear.
Calculations of embodied energy are made according to the con
ventions set forth by Odum (1978). A model is prepared showing the
major energy flows responsible for generating the flow of interest in
order to calculate the energy embodied in a particular energy flow or
storage. If these flows can be estimated in terms of energy of one
quality such as Solar Equivalent Calories (S.E. Cal), and double
counting of sources is eliminated, then these energies may be added
to calculate an estimate of embodied energy in the products. Precise
values of energy quality of many energy types and flows are not yet
known, so all calculations are assumed to be preliminary until some
future time. The embodied energy of a storage is taken as the inte
grated input energy flow over the time of growth to a steady state
level. The by-products of a production or concentration process are
assumed to have the same energy embodied in their energy flows.
Energy Effect >, .
The energy effect of a toxin or controller is measured as an
amplification (either positive or negative) of an energy flow or
Figure 2.3. Schematic diagram of flow-through microcosms. The microcosms consist of plastic
tubing located 1 m above the river's bottom and 2 m below the water's surface.
Screens over both ends allow manipulation of consumer density. Hoses to a boat on the
river's surface allow measurement of chemical changes such as dissolved oxygen over
the length of the tubes (6 m).
Table A.l. Computer model for Intercolor computer used to simulate minimodel
illustrated in Fig. 3.13.
5 PLOT 12
10 PLOT 29, 13
20 PLOT 2, 253, 0, 0,
242, 0, 191, 159, 191, 159, 0, 0, 0, 255
130 K3=. 001
140 K4=5. 55E-7
150 K5=. 05
160 K7=. 005
170 K8=. 005
180 K6=. 05
220 Ll=. 01
600 P=P+DT*< FR-FB-FC)
620 N=N+DT*C JN+FF-FI-FH)
630 IF P<0 THEN P=0
640 IF D<0 THEN D=0
650 IF N<0 THEN N=0
710 IF I=J GOTO 300
720 GOTO 400
805 IF T=ND GOTO 1000
810 PLOT 29, 13
PLOT 2, T, P, 255
PLOT 2, T, D/10, 255
PLOT 29, 20
PLOT 2, T, N/10, 255
PLOT 29, 13
PRINT C, FR, P, D, N
IF C-100 GOTO 2000
Mo controlled experiments of Cd's effect on aquatic macrophytes
at a series of different concentrations were found; however, a large
number of experiments have been reported from crop species of terres
trial plants. In hydroponic culture, Turner (1973) found the yield
of garden vegetables (radishes, lettuce, beets, tomatoes, carrots,
and swiss chard) to be lowered by 100 ppb Cd; yet tomatoes, lettuce,
and radishes were all stimulated at 10 ppb Cd. Hydroponic culture of
bush beans (Wallace et al. 1977) and beans, beets, turnips, and corn
(Page et al. 1972) also showed yield reduction at 100 ppb Cd in solu
tion, but no lower experimental levels were tested.
Vascular plants, when grown in soil, show sensitivity only at
much higher Cd concentrations. John and van Laerhoven (1976) found
growth reduction of nine lettuce varieties at 1 ppm Cd and slight
stimulation at 0.5 ppm. Wallace et al. (1977) found yield reductions
of 607-807 at Cd concentrations of 200 ppm in soil. Bingham et al.
(1976) found slight reduction in growth of several pasture species at
soil Cd concentration of 5 ppm.
Animals. Many species of aquatic animals have been tested for
sensitivity to Cd exposure. The most useful experiments to this
report are those where some functional property such as metabolism,
net growth, or reproductive capacity is determined for a series of Cd
concentrations from just above background to severely toxic. LC-50
(the lethal concentration for 507= of the test organisms in a stated
time period) values or survivorship curves may also be useful if they
are determined for several Cd concentrations over the life span of
the test organisms.
The concept of embodied energy may quantify system control and
provides generality and predictabiliy of a control hypothesis. In a
control situation a low-energy agent controls a larger energy flow or
storage. The theory of embodied energy predicts that the amplifica
tion effect of a system controller is related to a storage of
embodied energy in that controller. The two components of a control
process, i.e., the control effect and the control energy required,
can be quantified in the same units to determine their relationship
in surviving systems. If a general pattern of correlation emerges,
then a powerful tool of prediction may be available from knowledge of
either the required energy or energy effect of a control process.
Embodied Energy of Consumers
The quantification of "embodied energy" in consumers may date to
Lindeman (1942) when he calculated ratios of energy transfer in an
aquatic ecosystem. His energy ratios give a preliminary idea of the
energy of one type required to form energy of anather type. However,
Lindeman neglected auxiliary energies in his calculations and had no
clear scheme of energy quality relationships.
The energy quality conventions set forth by Odum (1978) allow
more accurate quantification of the energy requirement of consumers
in biological systems. Figure 3.2 presents a simple food-chain model
that summarizes the energy flows necessary for TR calculations.
As an introduction to energy quality factors calculated in this
report for consumers, some other published values are listed. Work
ing in the estuarine ecosystem at Crystal River, Florida, McKeller
(1975) estimated that the TR of herbivore metabolism was about 5X as
2.1 Map of Silver Springs study area showing location
of tourist attraction, main spring boil, and
1200-m station 13
2.2 Summary of oxygen diffusion measurements made at
Silver River during the present study 15
2.3 Schematic diagram of flow-through microcosms 17
3.1 Model of autocatalysis 28
3.2 Generalized trophic level model used to evaluate
embodied energy in consumers 33
3.3 Model of geological production process for Cd-rich
sulfide ores 36
3.4 Model of Zn and Cd production by the electrolytic
process with actual energy and dollar flows
3.5 Aggregated model of Zn and Cd production with flows
evaluated in terms of Solar Equivalent Calories 41
3.6 Evaluation of Cd embodied energy in biological systems....44
3.7 Aggregated model of stream production and biological
Cd concentration used to evaluate embodied energy
of Cd 45
3.8 Summary model of tadpole-periphyton interactions 49
3.9 Summary model of grazing effect of Notropis minnows
in experiment microcosms 51
3.10 Summary model of in situ sediment microcosms 53
3.11 Summary model of crayfish-plant interactions in Lake
3.12 Summary model of plankton interactions 56
Abstract of Dissertation Presented to the Graduate Council of
the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy
ENERGY BASIS OF CONTROL IN AQUATIC ECOSYSTEMS
Robert L. Knight
Chairman: Howard T. Odum
Major Department: Environmental Engineering Sciences
In surviving systems that have evolved designs for maximizing
power, ability to amplify and control may be in proportion to embod
ied energy. The evaluation of control effect and energy required in
equivalent embodied energy units allows the direct correlation of
these two properties of a generalized controller. This "control
hypothesis" was examined using biological consumers and a toxic metal
as examples of ecosystem controllers.
The heavy metal cadmium (Cd) was used to analyze the control
hypothesis for a toxin. A literature review indicated a stimulatory
(Arndt-Schulz) effect of Cd at low concentrations in many laboratory
studies. Most data sets were found to be described by a general
subsidy-stress curve. The bioconcentration of Cd as a mechanism in
natural systems for controlling free Cd concentration and its toxic
effect are discussed.
COMPONENT BIOMASS ( g dry wt. m~2) Jp(Kcdl-
Figure 4.17. Stream model simulation results for background Cd
concentration, 0.023 ppb. Refer to Figs. 4.1-4.3
and text for comparison to measured values.
GROSS PRODUCTION, gOm2 d"'
Figure 5.1. Comparison of gross primary production during the
study reported in this disseration with the data
measured by Odum (1957) at Silver Springs, Florida,
for the entire aquatic community to a point 1200-m
downstream from the main spring boil.
OXYGEN RATE OF CHANGE (ppm Zh'1)
Figure B.3. Diurnal oxygen change curves from September
23, 1976, for six experimental streams
receiving Cd inputs.
Table A.3. Computer model for Intercolor computer used to simulate
minimodel illustrated in Fig. 3.24.
10 PLOT 29,13
20 PLOT 12
55 TX=. 1
90 Kl=5. 52E-5
110 K2. 011
214 IF JR<0.THEN JR=0
220 P=K!1* JR+TX+EXP <-K4*TX > *Q
240 JX=K2*JR*TX*EXP < -K4*TX ) +Q
260 IF Q<0 THEN Q=0
280 IF I=J GOTO 200
290 GOTO 220
210 IF T=ND GOTO 850
211 S=S+. 2
212 IF S<1 GOTO 210
215 PLOT 3
216 PRINT T, Q, P, R, JX
220 PLOT 29,18
220 PLOT 29,22
240 PLOT 2, T, Q/15, 255
250 PLOT 29,18
800 GOTO 208
850 PLOT 29,18
860 PLOT 2, TX*10, Q/10, 255
864 PRINT TX, Q, P, R, JX
870 TX=TX+. 5
330 IF TXM0 GOTO 999
890 GOTO 60
999 PLOT 29,18
A.4 Computer model for Intercolor computer used to simulate
minimodel illustrated in Fig. 3.25 156
A.5 Computer model for Intercolor computer used to simulate
minimodel illustrated in Fig. 3.30 157
A.6 Computer model for Intercolor computer used to simulate
A.7 List of parameters with descriptions and equations
for Cd-streams model 163
A.8 List of initial conditions and transfer coefficients
used in simulation of Cd-streams model 170
general methods of regulation in ecosystems or even if such general
principles exist. However, as reviewed in Section 3, a consensus of
opinion on the controlling role of consumers is growing.
An indication from this study is that feedback control action
emanates from the top of the hierarchy down' through the levels in
complex systems, with most control actions linking adjacent levels
rather than distant ones in most adapted systems. This hypothesis
contradicts others that implement resource limitation (starvation,
territory, etc.) as the only basic control on most populations. The
hypothesis presented in this paper predicts that control action con
tinues on up the hierarchical scale so that top consumers of one sys
tem are actually being controlled by more concentrated energies of
the next larger system. Thus, catastrophies such as violent weather,
floods, earthquakes, or epidemics regulate populations of animals
with long generation times (Alexander 1978).
In addition, limits to growth and energy flow are set by larger
systems through the regulation of the amount of free energy available
to smaller subsystems. Thus, the maximum levels of productivity at
any spot on the earth are ultimately limited by a combination of
environmental factors such as sunlight (solar system), rainfall
(weather system), land form and nutrients (geological system), and
human perturbations (human system). These are called "feed-forward"
controls by Straskraba (1979) as opposed to the "feedback" controls
discussed in the previous paragraphs. It is this feed-forward con
trol of populations that has dominated thought in population biology.
Some feedback controls such as predation have long been recognized
and now many others are being qualitatively described.
Table 4.2. Results of five fish counts over the entire spring area (76,000 m2). Fish were counted
if they were readily visible (>10 cm) by a diver at the water's surface. Fish weights (kg)
are calculated from measured weights of average-sized fish collected by the author and
members of Florida
on January 22
Blue Shad (Dorosoma
Striped Mullet (Mugi1
Spotted Gar (Lepisosteus
Bowfin (Amia calva)
Chain Pickerel (Esox niger)
Black Crappie (Pomoxis
FISH BIOMASS (g-m"2)
Figure B.6. Diurnal oxygen change curves from February
9, 1976, for six experimental streams
receiving Cd inputs.
NET PRODUCTIVITY (g 02 rn2 hr'')
1 1 1
i 1 1 r
1 1 L_
1 1 1 L
LIGHT (/j E- rrf2- s-1 )
Figure 4.6. Response of net productivity measured as oxygen changes
in three control microcosms on April 21, 1980. Light was
measured as photosynthetically available radiation with
an underwater photometer at the same depth as the micro
Table 4.5. Summary of Silver Springs microcosm experiment started on April 7, 1980.
Fish were released in microcosms on April 7 and harvested and reweighed on
April 30, 1980.
Net Production, g 02'rn"2
Consumer Effect3 (g 02-m"2-d"b)
4/14b 4/16b 4/21b
aConsumer effect calculated as algebraic change between given microcosm net production
and average control net production divided by time of measurement.
b4/141.43 hr, 3.32 E-m"2 173.5 Cal-m"2: 4/165.33 hr, 17.98 E-m"2, 939.8 Cal-m"2;
4/215.97 hr, 15.98 E-m"2, 835.3 Cal-m"2.
Fish Experiment 22
Cadmium Experiment 22
Stream Model 23
Energy Relationships 24
Embodied Energy 24
Energy Effect 24
SECTION 3-BACKGROUND, CONCEPTS, AND MINIMODELS 26
Maximum Power Theory 26
Embodied Energy and the Control Hypothesis 30
Embodied Energy of Consumers 32
Embodied Energy of Cd 34
Earth production of Cd 35
TR for Cd 38
Industrial concentration 38
Biological concentration 43
Consumer Control 46
Literature Review 46
Consumer Control Model 55
Toxicity Control 59
Arndt-Schulz Law 60
Review of Cd Toxicity and Proposed Models 62
Cadmium Concentration 79
the DO value was recorded at 10-s intervals for 1 min. The six
resulting DO values were averaged to give a 1-min integrated reading
for each microcosm. At the end of these readings this valve was
closed and the next valve was opened. After a 3-min wait, DO was
again recorded for 1 min, the valve was closed, and the upstream
valve was reopened. The upstream (ambient) DO readings were much
less variable and therefore one reading was taken after 2 min of
equilibration. Using this technique one average measurement from
each of the eight microcosms could be made in a 40-min period with
upstream values interspersed between each pair of measurements.
Photosynthetically active radiation was measured concurrently
with each daylight DO reading using a submersible sensor at the depth
of the microcosms. Values were automatically integrated over a 100-s
interval for each reading. Solar radiation measured as moles of pho
tons (Einsteins) was converted to total energy by applying the con
version factor of 52.27 CalEinsteinl calculated for sun and
sky radiation from McCree (1972).
Upstream-downstream DO measurements were made for two 8-hr per
iods on each sampling date. Oxygen rate-of-change curves were inte
grated for each microcosm to calculate system metabolism. Daylight
DO increases measure net production, and nighttime decreases measure
system respiration. Graphical areas in ppnrhr were converted to
metabolism estimates by multiplying by the average thickness of the
microcosm tubes (7.05 cm) and dividing by the flow time of a water
mass through the tubes. This method gave the average metabolism in g
02,m"2 during the measurement period.
2.1 Average analysis of major water quality parameters
in Cd streams input water after treatment with
hydrated lime 5
2.2 Major components of water chemistry at Silver Springs,
FI orida 11
3.1 Actual and embodied energy flows in the industrial
purification of Zn and Cd from Zn ore 39
4.1 Metabolism of Silver Springs, Florida 100
4.2 Results of five fish counts over the entire spring area..102
4.3 Summary of Silver Springs microcosm experiment started
on December 5, 1979 108
4.4 Summary of Silver Springs microcosm experiment started
on February 20, 1980 109
4.5 Summary of Silver Springs microcosm experiment started
on April 7, 1980 112
4.6 Summary of Silver Springs microcosm experiment started
on July 29, 1980 115
4.7 Energy transformation ratios for major storages and
flows in Cd-streams model 132
4.8 Summary of actual energy flows and transformation ratios
for Silver Springs 140
A.l Computer model for Intercolor computer used to simulate
minimodel illustrated in Fig. 3.13 153
A.2 Computer model for Intercolor computer used to simulate
minimodel illustrated in Fig. 3.23 154
A.3 Computer model for Intercolor computer used to simulate
minimodel illustrated in Fig. 3.24 155
vi i i
MACROINVERTEBRATE BIOMASS (gdwnrf2)
Figure 4.3. Biomass of macroinvertebrates during the Cd-stream study.
Data are extrapolated from plate samples for control, 5
ppb Cd, and 10 ppb Cd.
TIME OF DAY (H)
1000 1200 1600
TIME OF DAY (H)
Rn = I0.9
Diurnal oxygen data and analysis for Silver Springs on
October 5, 1978.
Exported organic material and associated Cd were quantified from
October 1976 to August 1977. All effluent water from each channel
was passed through a 4-in. plastic pipe that contained a motor-
driven, stainless-steel mixer blade. Material collected on the end
screens was washed into the sampling system daily. Mixed effluent
was subsampled from each channel at a rate of 4 L*d"l with a
peristaltic pump. These subsamples were filtered onto prefired,
Gelman A-E glass-fiber filters, dried, weighed, ashed at 450C, and
reweighed to obtain ash-free dry weight of exported material. From
the length of sampling, the volume of water exported, and the volume
of the collected subsample, channel export was calculated as
g*nT2 channel bottonrd-*.
For Cd analysis, dried biological samples were wet-ashed in
30-ml porcelain crucibles with 2 ml of concentrated nitric acid at
80C for 1-3 hr or until all solid material had dissolved and NO2
evolution ceased. The samples were cooled, 2 ml of 30% hydrogen per
oxide added, and reheated until gas evolution ceased. Samples were
cooled to room temperature, diluted volumetrically using deionized
water, and stored in acid-washed polyethylene bottles.
Total Cd was determined using flameless atomic absorption spec
trophotometry. For 10 ]il samples, sensitivity was approximately 0.2
ug CdL'l in solution. All determinations were corrected for
reagent blanks and compared to commercially prepared certified stan-
Table 3.1. Actual and embodied energy flows in the industrial purification of Zn and Cd from Zn
ore resulting in 1 kg of pure Cd as illustrated in Figs. 3.4-3.5.
8206 kg Zn ore3
5.1 x 1015 S.E. Cal/kgb
4.19 x 1019 S.E. Cal
5.31 x 106 Elec. Calc
8000 S.E. Cal/Elec. Cald
4.25 x 1010 S.E. Cal
37 x 106 S.E. Cal/$f
3.53 x 109 S.E. Cal
2597 Elec. Cal9
8000 S.E. Cal/Elec. Cal
2.08 x 107 S.E. Cal
37 x 106 S.E. Cal/$
2.54 x 108 S.E. Cal
1.62 x 1017 S.E. Cal/kg
4.19 x 1019 S.E. Cal
4.19 x 1019 S.E. Cal/kg
4.19 x 1019 S.E. Cal
aFrom Petrick et al. (1979), 492 kg Zn concentrate with 60% Zn; 90% recovery from ore with 4%
dFrom this report, page 38.
cBattelle Columbus Laboratories (BCL) (1975) total energy costs in Zn production converted to
dFrom Odum and Odum (1980).
eFrom BCL (1975), $36.34 materials and reagents; from Cammarota (1978), $36.34 labor and $22.80
capital assuming 20-yr life for plant,
fodum et al. (1980).
9petrick et al. (1979).
^79% efficiency of recovery from ore (Cammarota and Lucas 1977).
DIURNAL OXYGEN CURVES FROM SILVER SPRINGS, FLORIDA
(Fig. 4.9 and Table 4.5). Maximum stimulation of productivity (+0.9
g 02m2*hr_1) was found at a fish density of 3.2 g*m"2
while curve smoothing indicates that the optimal density was about 6
gvn"2. Of equal significance was the observation that these
predaceous fish lowered net productivity of the microcosms at high
fish densities. Thus, a fish biomass between 15 and 31 g*m-2
lowered productivity by -0.8 g 02*nr2hrl compared to control
microcosms without fish (Table 4.5).
Some mosquito fish mortality was observed although this was
caused by the initial shock of seining and introduction to the micro
cosms. Microcosm 8 became unattached shortly after the fish were
added, and most of them escaped so the data from this microcosm were
not included in the summaries. Average weights of the fish at the
beginning and end of the experiment indicated no consistent gain or
loss of weight by surviving fish during the length of the study.
As was expected only a small amount of Cd dissolved from the
thin metal strips put into the microcosms. However, such a small
quantity of Cd dissolved that assuming an average dissolution rate
over the time of exposure in the river, the maximum estimated
increase in dissolved water Cd was less than twice the background
concentration of 0.02 ppb Cd in the river (Henry Kania, personal com
munication). Careful analysis of water samples using flameless
atomic absorption could detect no significant difference between con
trol and treated water Cd concentrations. Therefore, water concen-
Table 4.7. Energy transformation ratios for major storages and flows in Cd-streams model. Energy
values are derived from dry weight (d.w.) values using the factor 4 Cal = 1 g d.w.
Total energy input to streams taken as 33,606 S.E. Cal*nf2*d"l and growth times of
storages taken from model simulation data. All data used are from control stream
simulation (0.023 ppb Cd).
Flow or Storage
4.55 g d.w.m2*d"l
3.57 g d.w.m-2*d"l
1.44 g d.w.m-2*d-l
30.0 g d.w.*m-2
146.4 g d.w.*m-2
3.85 g d.w.itT^
4.36 x 105
0.92 g d.w.nT^
1.83 x 106
aCharge-up time to steady state biomass was estimated as 40 days.
bCharge-up time to steady state biomass was estimated as 200 days.
Figure 4.9. Effect of a range of fish densities on normalized net produc
tion in flow-through microcosms at Silver Springs, Florida, on
3 days in April 1980. Star (*) indicates that value is more
than two standard errors from control mean.
UPTAKE BY AQUATIC INVERTEBRATES
Cd CONCENTRATION (ppm)
Figure 3.29. Uptake of Cd by two aquatic invertebrates in
batch cultures (from Spehar et al. 1978).
4.15 Detail of the Cd-stream model showing the aggregated
consumer interactions 121
4.16 Detail of Cd-stream model showing configuration of
detrital-microbial segment of periphyton 123
4.17 Stream model simulation results for background Cd
concentration, 0.023 ppb 124
4.18 Stream model simulation results for system-level
parameters at background Cd concentration, 0.023 ppb..126
4.19 Model simulation results for biological storages
at two Cd input levels: 5 ppb and 10 ppb 127
4.20 Model simulation results for system-level parameters
at two Cd input levels: 5 ppb and 10 ppb 128
4.21 Average gross productivity, respiration, and export
values during 1 yr of continuous Cd input predicted
by Cd-stream models for Cd concentrations up to
50 ppb 129
4.22 Predicted correlation between Cd transformation
ratio and Cd effect ratio for gross productivity,
community respiration, and stream export 134
4.23 Predicted correlation between Cd transformation ratios
and Cd effect ratio for algae, macrophytes,
consumers, and detritus-microbes 136
4.24 Aggregated energy model for the upper 1200-m section
of the Silver River 138
5.1 Comparison of gross primary production during the study
reported in this dissertation with the data measured
by Odum (1957) at Silver Springs, Florida, for the
entire aquatic community to a point 1200-m downstream
from the main spring boil 145
5.2 Response of total community gross productivity to total
incident radiation at the Silver River 146
B.l Diurnal oxygen change curves from June 30, 1976,
for six experimental streams receiving Cd inputs 172
B.2 Diurnal oxygen change curves from July 28, 1976,
for six experimental streams receiving Cd inputs 173
B.3 Diurnal oxygen change curves from September 23, 1976,
for six experimental streams receiving Cd inputs 174
xi i i
duction of 1.0 x 106 S.E. Cal*g Cd"l. These optimal correla
tion values were found at a water concentration of 0.06 ppb Cd, which
is within the range of natural water concentrations of Cd (Hammons et
al. 1978). Figure 4.22 also predicts that Cd would have little mar
ginal effect above a concentration of 100 ppb in the stream systems
Figure 4.23 summarizes the model data for the algae, macro
phytes, consumers, and detritus-microbes. A much greater Cd effect
is seen in this figure than in the previous one (compare the
Cd-effect ratio values). This effect was lowest for the algae and
greatest for the consumers. Macrophytes responded with greater
growth to all concentrations of Cd that were simulated, which was
contrary to the observed results from the Cd-streams study. Data for
consumers showed a much greater negative than positive correlation,
while the algae and detrital-microbial correlation curves were sym
metrical in their positive and negative segments.
The results presented in Figs. 4.22 and 4.23 are model predic
tions and therefore only as accurate as the model is an accurate
description of the real Cd streams. A second qualifier of this
simulation data (and the actual data, too) is that the streams
were still in a successional state during the period of Cd inputs.
Actual stream systems that are capable of steady state growth
populations may have much tighter correlations between the energy
quality of Cd (its energy cost to the system) and the energy effect
of Cd (its ability to control the system). If these correlations are
found to be consistent in other systems and with other controllers,
embodied energy of a controller may be calculated from its effect and
Embodied Energy-Controller Effect Relation
As discussed earlier in this dissertation, a consistent rela
tionship is expected between the controlling effect of a consumer or
toxin and its embodied energy. The nature of this correlation may
now be hypothesized. Given the generalized control curve in Fig.
3.31a, major changes are expected in the correlation between these
parameters for any given system, tending to give zero control effect
at very low and very high controller concentrations (Fig. 3.31b). A
positive correlation is expected at low concentration and a negative
effect at higher controller concentrations. The areas where there is
no correlation between embodied energy of the controller and its con
trol effect may correspond to concentrations of the controller that
the real systems have not been exposed to long enough for adaptations
to occur. It is hypothesized that the segment of the curve showing a
positive correlation corresponds to controller densities naturally
occurring in the environment.
observations of this effect for heavy metals with no known biological
role such as mercury (Rzewuska and Wernikowska-Ukleja 1974) and Cd
(Doyle et al. 1975).
In their summary of the Arndt-Schulz effect for bacteria,
Lamanna and Mallette (1953) continue: "While the universal occur
rence of stimulation by poisons suggests the possibility for the
existence of a single basic mechanism, the very diversity of chemical
compounds and biological processes involved presents enormous diffi
culties to the imagination in conceiving of such a mechanism" (p.
599). They present several plausible mechanisms for this effect in
biology, but based on more recent developments in theoretical ecology
there is another important possibility: perhaps the mechanisms of the
response vary, but the cause of these adaptations is consistent
namely, the criterion of maximum power. Thus, all organisms have
evolved under selection pressure to maximize their life processes and
have been continually exposed to minute concentrations of toxic
metals, free radicals, and ionizing radiation. Given evolutionary
time, mechanisms that utilize these "poisons" in stimulatory ways
would be selected. In experimental toxicity studies, these low stim
ulatory levels are often below the range of the lowest concentration
studied and when stimulation is measured, the data are often ignored.
Stimulatory effects are evidences of organization for maximum power.
Adaptive systems can gain by using substances with large effects.
Just as there is a range of concentration effects by a chemical,
there is also a range of reactions by different organisms to a single
concentration. Due to the tremendous diversity of adaptation, some
species may thrive at extreme chemical concentrations and flourish
Table 2.1. Average analysis of major water quality parameters in Cd
streams input water after treatment with hydrated lime.
Total dissolved solids
9.14 mg*L'l as CaC3
11.1 mg*L~l as CaC03
2.5 x 10"4
Nitrogen (NO2" + NO3--N)
Figure 3.6. Evaluation of Cd embodied energy in biological systems.
a. Model of Cd and energy inputs to concentration process;
b. Idealized uptake curve for Cd in biomass with uptake
time used to evaluate embodied energy. B is biomass; M is
a Michaelis-Menton accumulation process.
Mattson, W. J., and N. D. Addy. 1975. Phytophagous insects as regu
lators of forest primary production. Science 190:515-22.
McCree, K. J. 1972. Test of current definitions of photosynthet-
ically active radiation against leaf photosynthesis data.
Agrie. Meteorol. 10:443-53.
McKellar, H. N. 1975. Metabolism and models of estuarine bay eco
systems affected by a coastal power plant. Ph.D. dissertation,
University of Florida, Gainesville. 270 pp.
McKellar, H., and R. Hobro. 1976. Phytoplankton-zooplankton rela
tionships in 100 liter plastic bags. Contrib. Asko Lab, Univer
sity of Stockholm, Sweden, No. 13. 83 p.
Northcote, T. G., and D. W. Wilke. 1963. Underwater census of
stream fish populations. Trans. Am. Fish Soc. 92:14651.
Odum, E. P., J. T. Finn, and E. H. Franz. 1979. Perturbation theory
and the subsidy-stress gradient. BioScience 29:349-52.
Odum, H. T. 1956. Primary production in flowing waters. Limnol.
Odum, H. T. 1957. Trophic structure and productivity of Silver
Springs, Florida. Ecol. Monogr. 27:55-112.
Odum, H. T. 1968. Work circuits and system stress. Pages 81138 j_n
Y. Young (ed.), Primary production and mineral cycling in
natural ecosystems. University of Maine Press, Orono.
Odum, H. T. 1971. Environment, power, and society. Wiley-inter-
science, New York. 331 pp.
Odum, H. T. 1975. Combining energy laws and corollaries of the max
imum power prinicple with visual systems mathematics. Pages
239-63 in S. A. Levin (ed.), Ecosystem analysis and prediction.
Proceedings of a SIAM-SIMS Conference held at Alta, Utah, July
Odum, H. T. 1978. Energy analysis, energy quality, and environment.
Pages 55-78 jn_ M. W. Gilliland (ed.), Energy analysis: A new
public policy tool. Westview Press, Boulder, Colo.
Odum, H. T. 1979. Energy quality control of ecosystem design.
Pages 22135 J_n R. F. Dame (ed.), Marsh-estuarine systems simu
lation. University of South Carolina Press, Columbia.
Odum, H. T., and E. C. Odum. 1980. Energy basis of New Zealand and
the use of embodied energy for evaluating benefits of inter
national trade. Pages 106-67 _i_n Proceedings of Energy Modeling
Symposium, Ministry of Energy and Victoria University of
Wellington, Tech. Publ. No. 7, Wellington, N.Z. November 1979.
Figure 3.13. Consumer control model including both density-dependent
inhibition of producers and nutrient regeneration effects
of consumers. Simulation results of this model are
presented in Fig. 3.14, and the BASIC program used for
these simulations is given in Table A.l.
theory. Useful power is a measure of the energy flows and transfor
mations that result in structures or processes feeding back to help
maintain themselves and the system that supports them. Thus, useful
power differs from dissipation of energy that is not part of a self-
maintaining system. The conceptual idea of maximum power is illus
trated by an autocatalytic unit (Fig. 3.1). In this simple model, a
nonlinear interaction acts to accelerate energy flow to the maximum
sustainable level. The generality of autocatalysis is some measure
of support for the theory that systems are selected for maximum
Observation indicates that there is more to the maximization of
power of natural systems than just rapid growth, depletion, and loss
of a storage. The surviving systems have mechanisms to sustain the
cycling of materials to facilitate the overall energy being processed
by the system (system power). Tuned complexity is a criterion for
maximum power in competing systems, and the diversity of natural sys
tems is further circumstantial evidence in support of this theory.
The power of a system may be limited by the quantity of usable
energy sources and by the constraints of energy transformation.
These limits to the growth of power of a system are not reached
immediately, but are approached in time after succession and evolu
Few environmental systems have just one energy source; most have
several types of energy inputs. If untapped energy sources exist,
some of the existing energy flow is routed to help use new sources
through exchange or pumping. The system that effectively increases
pulled out of the river, and all snails were removed, counted, and
The second snail experiment began on February 20, 1980. Snails
were put into the microcosms 6 days later, and measurements of net
production were made 13, 15, 20, 23, and 26 days after the beginning
of the experiment. The microcosms were removed, and the snails were
counted and weighed on April 2, 1980.
One experiment was made using mosquito fish, Gambusia affinis,
as the regulated organism. Clean microcosms were placed in the river
on April 7, 1980. Three tubes served as controls and the other five
received from 11 to 80 fish each. The fish were weighed and placed
in the microcosms on April 7. Measurements of net production were
made 7,9, and 14 days after the experiment began. The microcosms
were pulled out on April 30, and all remaining fish were counted and
The last microcosm experiment began on July 29, 1980. Three
microcosms served as controls and the other five received nylon-mesh
bags containing from 8 to 132 g of pure Cd metal cut into narrow
strips. The screens were removed from both ends of the microcosms
for this study. Net production was measured 7, 10, and 14 days after
the experiment began. On August 8, water samples from each microcosm
were collected in acid-washed 100-ml polyethylene bottles and
preserved with 2 ml of concentrated nitric acid for Cd analysis. The
Respiration was measured as nighttime decrease in DO in the
microcosms and was found to be low in all of the experiments (<10% of
net production); therefore, respiration was not used in comparing the
various treatments, and net production may approximately equal gross
production. To normalize data from different sampling dates with
different solar inputs, net production data were divided by the
measured solar energy giving values in g 02Cal"1.
Flow rates were measured through the microcosms by visually
timing rhodamine dye released at the upstream end. These flows were
measured at the beginning of each study and in a few cases while a
study was in progress.
Two experiments were made to test the effect of the locally
abundant snail, Goniobasis floridense, on primary production. This
species is an important component of spring runs throughout north-
central Florida and feeds on periphytic algae. Snails were collected
from the submerged macrophytes in slow-current areas of the river
near the experimental site. Three microcosms served as controls, and
the other five received from 20 to 325 snails each. Snails were
live-weighed using a triple-beam balance.
On December 5, 1979, a clean set of microcosms was placed in the
river. Nylon screen was placed over both ends of all microcosms to
insure that no snails escaped during the experiment. Snails were
introduced into the tubes 5 days later on December 10. Measurements
of net production were made 8, 11, and 16 days after the clean tubes
were placed in the river. On January 10, 1980, the microcosms were
Figure 2.1. flap of Silver Springs study area
showing location of tourist attrac
tion, main spring boil, and 1200-m
Section 4, 1.68 x 10 S.E. Cal*m_2 of stream was calculated
to attain equilibrium Cd concentrations in the biological compon
For the control channels this energy input resulted in 1256 yg
Cd*m~2 stored in the biological community. Hot including the
energy embodied in the Cd by the next larger system, 1.3 x 109 S.E.
Calg Cdl was calculated to be required to develop a concen
tration of 0.8 ppm on a live-weight basis.
For the Cd-treated streams the energy embodied in the Cd inputs
by the human controllers of the next larger system may be added.
This embodied energy was taken as the industrial cost of the Cd (4.6
x 10l S.E. Cal kg Cd-1) rather than the much greater world
system cost. At 136,800 L*dl flow rate, 55.8 m^ surface
area, and 50 days charge-up time, we calculate inputs of 0.615 g
Cd*m-2 for the 5 ppb treatment, and 1.23 g Cd*m"2 for the
10 ppb treatment, resulting in storages of 0.003 g Cd*m"2 and
0.020 g Cd*m_2, respectively. Adding the input energies and
dividing by the Cd storages gives 2.26 x 109 S.E. Cal*g Cd-1
at a biological concentration of 7.5 ppm, and 2.92 x 109 S.E.
Cal*g Cdl at 11.6 ppm.
The controlling influence of consumers in natural ecosystems has
received much attention recently through a series of review papers by
The values in Table 4.8 may now be used to calculate the energy
required to maintain a consumer and its energy effect on the plant
production system in units of equal energy quality.
For the two snail experiments no significant positive effect on
primary production was measured; however, net production was not
lowered at low snail densities so that some mechanism was
compensating for their metabolic energy requirement. Using a dry
weight:wet weight ratio of 0.2, average respiration as 0.6 mg
2*g dry weightl*hrl (from Odum 1957), and a conversion factor of
4 Cal*g O2"!; snail respiratory metabolism at a density of 33 g wet
weightm"^ was calculated as 0.38 Cal*m"2*d"!. Referring to
Table 4.8 shows a TR of 25,285 S.E. CalCal-1 for herbivore
respiration, and multiplication gives the energy required for
maintenance of the snails as 9646 S.E. Cal*m"2*d"l.
The energy effect of these snails apparently compensated for
their maintenance cost as calculated above since no consistent
significant decrease in productivity was measured at these natural
snail densities. Thus the snails were "paying their way" at low
densities in the microcosms while at higher snail densities
productivity was significantly lowered. These high population level
would be selected against due to depletion of food resources and
starvation of snails.
Average stimulation found for mosquito fish was 0.49 g
02*m2*hr"! at the optimal density of approximately 3.2 g
live weight tT^ in the microcosm experiment. Using the same
conversion factors listed previously and the respiration rate of 1.1
mg O2*g dry weighf!*hrl given by Odum (1957) for small fish, 0.068
CONTROLLER EMBODIED ENERGY
Figure 3.31. Toxicity curve (a) and cor
responding energy effect-
energy quality correlation
curve (b). Region 1 repre
sents a positive amplifier
action and region 2 indi
cates a negative action.
Spehar et al. (1978) found that 27.5 ppb Cd severely reduced the
survivorship of a freshwater snail, Physa integra, at 28 days, while
concentrations of 3 and 8.3 ppb increased survivorship. Working with
another freshwater snail, Biomphalaria glabrata, Ravera et al. (1974)
observed severe Cd toxicity at 100 ppb.
Respiration in tubificid worms was found to be enhanced by 10
ppb Cd by Brkovic-Popovic and Popovic (1977) and decreased with
respect to controls at 60 ppb (see Fig. 3.19). The percent survival
of a mayfly, Ephemerel1 a sp., was considerably reduced at the lowest
concentration tested (3 ppb Cd) by Spehar et al. (1978).
The effect of Cd on egg production and percent survival at 30
days on fathead minnows, Pimephales promelas, was reported by
Pickering and Gast (1972). As may be seen in Fig. 3.20, both parame
ters were reduced compared to controls at 30 ppb, but egg production
was greatly stimulated at 15 ppb Cd. Benoit et al. (1976) found
embryo viability in brook trout to be inhibited at less than 1 ppb Cd
(Fig. 3.21). Survivorship in two other fish species, bluegill sun-
fish and largemouth bass, was lowered at 8 ppb in laboratory tests
reported by Cearley and Coleman (1974).
Summarizing the review of Cd toxicity, animals have sensitivity
similar to that of plant and algal species. Concentrations of Cd as
low as 30 ppb are toxic to many aquatic animals, and some sensitive
organisms or life-history stages are sensitive to less than 10 ppb.
Cadmium at low levels may enhance functional parameters in aquatic
animal species, but toxicity is highly dependent on hydrogen ion,
ligand concentrations, salinity, and temperature. All curves of tox
icity were similar to one of the three graph forms in Fig. 3.22.
DISSOLVED OXYGEN (mg-L"1)
TIME OF DAY (H)
1000 1200 1600 2000 2400
TIME OF DAY (H)
Diurnal oxygen data and analysis for Silver Springs on
August 15, 1979.
Figure 4.10. Response of microcosm normalized net production to a range of
Cd concentrations in input water. Cadmium concentrations are
calculated from weight loss of solid Cd metal strips during
the experiment and water flow rates through the microcosms.
Star (*) indicates that value is more than two standard errors
from control mean.
OXYGEN RATE OF CHANGE (ppnv2h")
Figure B.5. Diurnal oxygen change curves from
November 24, 1976, for six experimental
streams receiving Cd inputs.
TIME OF DAY (H)
1000 1200 1600
TIME OF DAY (H)
RN = 10.4
Diurnal oxygen data and analysis for Silver Springs on
December 13, 1978.
Silver Springs Consumer Microcosms
Microcosms for measurement of consumer control of productivity
were completely submerged, flow-through units (Fig. 2.3). Each
microcosm consisted of two PVC fittings joined by replaceable 0.4-mm
thick, 9-cm diameter clear polyethylene tubing. The upstream fitting
consisted of a PVC reducer (15-7.6 cm) connected to a short piece of
7.6-cm inside diameter PVC pipe. This reducer acted as a funnel to
increase internal pressure and flow rate in the microcosm. The down
stream fitting consisted of two sections of 7.6-cm PVC pipe connected
by a PVC union with a standard garden hose connector inserted in the
side. The polyethylene microcosm tube was attached at each end to
the short pieces of PVC pipe with hose clamps. The additional piece
of pipe at the downstream end assured that the water pumped from the
microcosms through the hose fitting would not entrain water from out
side the microcosm. The adequacy of this extender was verified by
releasing rhodamine dye into the end and observing that, with the
pump on, there was no movement upstream towards the sampling port.
The replaceable portion of the microcosms consisted of contin
uous 9-cm diameter polyethylene tubing. Initial studies determined
an optimal microcosm length of 6 m for subsequent studies. At
greater lengths, upstream-downstream DO changes were increased, but
the flow rate was insufficient to sustain internal pressure in the
tubes and they were partly collapsed at the downstream end. New 6-m
lengths of polyethylene tubing were used for each study.
DIURNAL OXYGEN CURVES FROM CD STREAMS
snail Goniobasis floridense (Figs. 4.7-4.8 and Tables 4.34.4);
however, this apparent stimulation was not statistically significant
due to high variability in the control microcosms. The characteris
tic subsidy-stress curve was observed on several of the measurement
days with apparent stimulation of +0.22 g 02*m2*hr_1 at
a snail density of 44 gvn-2 in the first experiment and +1.87 g
02*m2,hr"l at a density of 22 g*nT2 in the second
snail experiment. Higher snail densities caused reduction in micro
cosm net production compared to controls. In the first experiment,
the highest snail density of 270 g*m2 lowered net production
by -2.38 g 02'm"2*hr~^. In the second experiment the
highest snail density lowered net production by -3.18 g 02*nT2*h"l.
These high-density microcosms had thinner peri phytic algal growth on
the walls and were visibly different from the controls.
Most snails were recovered when the microcosms were harvested.
In the first experiment 41% of the snails originally put into the
high-density microcosm were lost or had died by the time they were
recounted. In the low-density microcosms the snails not only
survived the experiment but actually gained weight. It appears
therefore that some of the increased net production caused by the
snails was transferred to their trophic level as net growth. Snails
in overcrowded microcosms may have eventually reached a stimulatory
population level through food limitation and starvation.
Carnivore ControlMosquito Fish
Significant enhancement of net primary productivity was observed
in the microcosms receiving a gradient of mosquito fish populations
Q4 = !-9Q4(Q2+Q3+Q5)-KsQ4-LBQ42-LpQ4Cz-KpQ42
C4 = LlQ4(C2+C3+C5)+KjQ42/3(-^+^)-KqCd-LdCd(LbQ42+LpQ4Cz)-LiCd(KsQ4)
Figure 4.15. Detail of the Cd-stream model showing the aggregated con
sumer interactions. Cadmium is taken up through both
surface adsorption and feeding.
Figure 3.30. Model of Cd adsorption in periphyton.
Growth of biomass (B) is dependent on
sunlight (S) and nutrients (N). Cadmium
is adsorbed by surface area (A) result
ing in Cd-saturated surface area (AC),
a. Model; b. Simulation showing effect
of increasing surface area/Cd ratio;
c. Simulation showing effect of
increased cell radius. BASIC program
used for simulations is given in Table
surface to volume ratio in disrupted algal colonies; algal nutrient
uptake while in the cladoceran's gut; reduction in algal competition;
and released nutrients in the water available for algal growth.
These mechanisms are modeled in Fig. 3.12.
Consumer Control Model
The proposed mechanisms explaining consumer stimulation of pri
mary productivity basically fit into two categories: 1. the stimu
latory effect of cropping of senescent growth stages to optimal,
low-density, maximum growth-rate stages; and 2. the regeneration and
delivery of available nutrients for plant growth. In order to deter
mine if both of these mechanisms can in fact generate stimulation of
productivity and under what conditions they might do so, a simple
model of consumer feedback was simulated. Figure 3.13 presents the
model showing the two mechanisms discussed above. Consumers are
modeled as an exogenous input to the system with a single function of
moving biomass from the producer to the detritus pool. Nutrients may
be in short supply or may be added to the system from an external
source. The RASIC computer program used to simulate this simple
model is presented in Table A.l.
Three cases were tested as shown in Fig. 3.14. Constant nutri
ents with inhibitory growing effects are shown in Fig. 3.14a at two
nutrient concentrations. A unimodal stimulation curve was observed
to result from this mechanism. In Fig. 3.14b the result of no
crowding effect (k3=0) is seen at three different nutrient input
rates. Again a stimulation curve by consumers was observed but under
some conditions this curve was found to be bimodal. Figure 3.14c
BACKGROUND, CONCEPTS, AND MINIMODELS
The controlling action of consumers and toxic substances may
seem to be as variable a subject as the number of existing chemicals
and organisms. In order to identify general principles of control,
some principles that are general to all real systems are reviewed.
Included is a concept of "embodied energy" that evaluates energies of
differing qualities. Literature on consumer control and Cd toxicity
is reviewed with simple models demonstrating points of generality to
Maximum Power Theory
The designs of systems and their ways of processing toxins are
related to energy. Lotka (1922) proposed a principle of thermodynam
ics for open systems stating that selection in the struggle for exis
tence is based on maximum energy use (power). Later, Odum and Pink
erton (1955) and Odum (1968, 1971, 1979) suggested ways control
actions generate more power and thus tend to persist in real, com
Power has been defined as the rate of useful energy transforma
tion. The concept of useful power is important in the maximum power
research. As the literature review in Section 3 had previously pre
dicted, Cd, a toxic metal, was found to give apparent stimulation of
primary productivity at low concentration in the microcosms just as
the consumers had done before it. Whether the full subsidy-stress
curve illustrated in Fig. 3.31a would have been found at higher con
centrations of Cd in Silver Springs was not determined in this study;
however, the calculations of energy effect and energy cost of the Cd
show a striking ability of a toxin to amplify energy flow in propor
tion to the energy expended in its concentration.
A review of the literature concerning environmental toxicity of
Cd and numerous observations from the Cd-streams study reported here
indicates that Cd has its greatest effect on the consumer organisms
rather than on the more quickly selected microbes and plants. Thus,
Cd probably regulates consumers, which in turn regulate the levels
below them in their adjustment for maximum production. It is hypoth
esized then that Cd actually regulated the herbivorous consumers in
the microcosms (chironomids and others) to an optimal level of plant
grazing just as the mosquito fish apparently had done in the earlier
experiment. Thus, the analogy of a toxin to a consumer in an envi
ronmental hierarchy seems justified.
Ecosystem Manipulation and Control
Hairston et al. (1960) state that "the method of regulation of
populations must be known before we can understand nature and predict
its behavior" (p. 421). In spite of the time span since those words
were published, the science of ecology still is unable to agree on
Energy Quality-Energy Effect Correlation
The Cd-streams model was simulated at a series of Cd concentra
tions from background (0.023 ppb) to 100 ppb Cd. Yearly averages of
gross productivity, respiration, export, algae, macrophytes, consum
ers, and detritus-microbes were calculated for an analysis of the
effect of Cd on components of varying energy quality. The effect of
Cd on a given energy flow or storage was converted from actual energy
to embodied energy using the values in Table 4.7. This effect could
be both positive and negative at different Cd levels.
The embodied energy of Cd was calculated using the industrial
cost (4.6 x 10? S.E. Cal-g Cd~l) and the free-energy equation
(3.1) to give the free-energy difference between the stock solution
of 1000 ppm and the ambient water concentration of 0.023 ppb. This
free-energy change is calculated as -0.0912 Cal*g Cd-1; combin
ing it with the energy quality of pure Cd of 4.6 x 10? S.E. Cal *g
Cd-1, 5.04 x 10s S.E. CalCal-1 is calculated. It is now
possible to calculate back to get the embodied energy of Cd at some
hiqher concentration. For example, at 10 ppb the free-energy change
from 0.023 ppb is 0.0315 Cal*g Cd-1, and multiplying this value
by 5.04 x 10^ S.E. Cal*Cal"l will give the TR of Cd at 10 ppb
as 1.6 x in? S.E. Cal-g Cd"1.
Figure 4.22 presents the model data for gross productivity, res
piration, and export. All three of these parameters showed a posi
tive and a negative correlation with Cd energy quality. The positive
part of each curve was nearly a one-to-one correlation between energy
quality and energy effect. Thus, a Cd transformation ratio of 2.5 x
106 S.E. Cal-g Cd-1 resulted in a stimulation of gross pro-
Figure B.7. Diurnal oxygen change curves from March
1617, 1976, for six experimental streams
receiving Cd inputs.
COMPONENT BIOMASS (g dry wt. m'2) J0 (Kcal-
Figure 4.19. Model simulation results for biological storages at two
Cd input levels: 5 ppb (solid line) and 10 ppb (dashed
ENERGY BASIS OF CONTROL IN AQUATIC ECOSYSTEMS
ROBERT L. KNIGHT
A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF THE
UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
UNIVERSITY OF FLORIDA
sedimentary ores (Lucas 1979), this is equal to 200 ppm Cd. Solar
energy or solar-produced hydrologic energy (Flow B) was used as the
major input to this concentration process, although traditional view
regards residual deep heat (Flow A) as a separate input to ore pro
As mentioned above, the earth's average crustal concentration of
Zn and Cd was taken as zero-embodied energy because these elements
cannot be used in work processes at such low densities. Therefore,
Flow C in Fig. 3.3 is equal to zero.
Flow B is the rate of energy absorption from the sun by the
entire earth system, and was taken as 13.4 x 10^0 Cal*yr"l
Flow D is the production rate of Zn and Cd ore in the world sys
tem. Of interest is the production of recoverable ore that may be
mined and has enough purity to warrant extraction. Estimates for the
world resources of Zn and Cd are 1.8 x 109 tonnes (t) and 9 x 108
t, respectively (Bureau of Mines 1980). Since this ore is largely
contained in sedimentary-derived deposits (Lucas 1979) and an
approximate turnover time is known for the world sedimentary cycle
(1.7 x 108 yr; from Judson 1968), the formation rate of new ores
can be calculated if a steady state of production is assumed:
Production rate of recoverable Zn in ore =
(1.8 x 109 t Zn)/(1.7 x 108 yr) = 10.6 t Zn-yr"1
Production rate of recoverable Cd in ore =
(9 x 106 t Cd)/(1.7 x 108 yr) = 53 kg Cd-yr"1.
energy input was integrated from a recording solar pyranometer on the
days when diurnals were run.
Upstream and downstream curves of DO were each shifted by one-
half of the flow time between stations (1.6 hr), and an hourly rate-
of-change curve was constructed by multiplying the oxygen changes by
the average depth of 1.8 m (Odum 1957). Two corrections were applied
to this curve to account for other oxygen sources and sinks. First,
the accrual of oxygen from side boils with higher DO was corrected by
subtracting 0.61 mg D0*L-1 from all downstream measurements
(Odum 1957). Second, corrections for oxygen diffusion are necessary
because of the consistently undersaturated DO values in the river and
they were made using Eq. 2.1 and the average percent-saturation
values calculated from the measured DO and temperature values.
Odum's (1957) value for k was applied to new data in order to compare
results with his. He used a value of 1.82 g O2*m"^*hr-1
at 100% saturation deficit, which he derived from a combination of
In this study, an independent measurement of k was also ob
tained. The diffusion rate of oxygen was measured in several loca
tions of the study area using McKellar's (1975) modification of the
floating-dome technique. A large range of diffusion coefficients was
measured (0.11 to 5.15 g 02'm"2*hr"l at 100% saturation
deficit) (Fig. 2.2a). These values were closely correlated to the
measured current velocity (Fig. 2.2b), and an average value of 1.72 g
02*m2.hrl was determined for the entire 76,000 m^ of
river area studied. This measured value is not appreciably different
from the above value estimated by Odum.
Computer model for Intercolor computer used to simulate
minimodel illustrated in Fig. 3.30.
30 C0=. 0001
160 Kl=3. 33E-3
170 K2=3. 0E-5
180 K4=3. 33E-5
190 K5=. 05
200 K6=. 03
210 K7=. 005
220 K8=. 005
230 K9=. 03
240 Kfl=. 07
250 KB=. 01
260 KC=. 01
430 FD= < F7-F8 > + < FB-FC >
470 K5=. 08
490 B=B+DT*< F2-F5-F6 >
500 C1=C1+DT*< F9-FR-FF >
510 R=R+DT* < FC-F7-FE+F3')
550 IF B<0 THEN B=0
560 IF CK0 THEN C1=0
570 IF R<0 THEN R=0
580 IF RS<0 THEN RS=0
590 IF RT<0 THEN RT=0
610 IF I=J GOTO 630
620 GOTO 310
640 IF T=ND GOTO 660
650 GOTO 300
660 PLOT 29,18
670 PLOT 2, 00*100, C/10, 255
680 PLOT 29,18
690 PLOT 11
700 PRINT 00,0
710 00=00+. 005
720 IF 00=1 GOTO 999
730 GOTO 40
999 PLOT 29,18
Figure 3.20. Effect of Cd on egg production and survival of fat
head minnows in flow-through culture (from Picker
ing and Gast 1972). Two solid lines refer to sep
arate experiments using similar Cd concentrations on
different fish populations.
Figure 3.3. Model of geological production process for Cd-rich sulfide
ores. Flow B is assumed to be more important than Flow A,
and Flow C is assumed to have zero embodied energy as
discussed in the text. Calculations indicate that Flow D,
the rate of production of recoverable, Cd-rich ore may
contain only 53 kg Cd-yrl for the entire earth.
Table 4.6. Summary of Silver Springs microcosm experiment started on July 29, 1980.
Pure Cd metal strips were placed in microcosms on July 29 and removed and
reweighed on August 19, 1980.
Net Production, g 02m-2
Toxin Effect3 (g 02*nT2*d-l)
8/5b 8/8b 8/1lb
Toxin effect calculated as algebraic change between given microcosm net production
and average control net
b8/53.17 hr, 11.19 E*m"
roduction divided by time of measurement.
8/114.17 hr, 12.37 Emii"*, 646.6 Cal-m
584.9 Cal-rrT2^ 8/a4.87 hr, 13.87 E*nT2, 725 Cal'm-2;
I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is
fully adequate, in scope and quality, as a dissertation for the degree
of Doctor of Philosophy.
Howard T. Odum, Chairman
Graduate Research Professor
of Environmental Engineering
I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is
fully adequate, in scope and quality, as a dissertation for the degree
of Doctor of Philosophy.
Patrick L. Brezonik
Professor of Environmental
I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is
fully adequate, in scope and quality, as a dissertation for the degree
of Doctor of Philosophy.
Thomas L. Crisman
Assistant Professor of
I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is
fully adequate, in scope and quality, as a dissertation for the degree
of Doctor of Philosophy.
in the world system. Using the input flows alone and the percent
recovery of each metal, the transformation ratios are calculated
TRpure Zn = 1*6 x 1017 S.E. Cal kg pure Zn~l
TRpure ^d = 4.2 x 10^ s.E. Cal kg pure Cd_l.
Although the industrial embodied energy inputs in the Cd puri
fication process are much smaller than the environmental energies,
they represent the minimum amplification ability that the Cd must
have in the human system. Thus, metals such as these may be used
very inefficiently compared to their actual embodied energy because
of the cheapness of their extraction from world storages. If the
embodied energy in pure Cd is evaluated only from the industrial
energy inputs, 4.6 x 1010 S.E. Cal kg pure Cd"l is calcula
ted, a much smaller quantity of embodied energy.
For comparison to other quality factors, the TR may be calcula
ted as a dimensionless ratio by evaluation of the free energy differ
ence between Cd at background concentration and its concentration in
Zn ore. To make this calculation, it must be assumed that Cd atoms
present in the various solid phases are analagous to atoms in a true
solution. This assumption allows use of the Gibb's free energy
AG = nRT In (3.1)
where AG is the change in Gibb's free energy; n is the number of
moles of reactants; R is the universal gas constant (1.99 x 103
great as gross primary production (GPP), the TR of primary carnivore
metabolism was 25X GPP, and the TR of top carnivore metabolism was
100X GPP. If we take the TR of GPP to be about 1000 S.E. Cal*Cal-1,
then the TR for herbivores is 5000 S.E. CalCal-1; the primary
carnivore value is 25,000 S.E. Cal*Cal; and the top
carnivore TR is 100,000 S.E. CalCal"1.
Working in salt-marsh creeks in the Crystal River area, Kemp
(1977) reported ranges of TR for the various trophic levels depending
on their place in the grazing or the detritus food chains. He
reported herbivores as between 280 and 3000 S.E. CalCal;
primary carnivores between 840 and 10,440 S.E. Cal Cal1; and
higher carnivores between 2880 and 126,400 S.E. Cal Cal~1.
These values are for the storage of biomass rather than the rate of
Working with data from a freshwater pond in Florida, Brown
(1980) reported TR for the respiration of the various trophic levels.
For zooplankton and benthic invertebrate consumers, he found a TR of
1200 S.E. CalCal-1; for primary and secondary fish consumers
he reported 34,000 S.E. Cal'Cal-1; and for higher level consum
ers he reported values between 170,000 and 1.8 x 10? S.E. Cal*Call
Embodied Energy of Cd
The atoms of an element such as Cd have been in a continuous
turnover for as long as the solar system has been in existence and
longer, with the dispersion of atoms followed by concentration and
dispersion again. Potential energy is required for concentration of
prevent major alterations in the aquatic community. The biological
communities are the same as those described by Odum (1957) with the
exception of the change in dominant fish from mullet to shad as dis
cussed in the results section of this dissertation.
Figure 2.1 is a map of the river area described in this report.
System productivity measurements were made for the entire upper sec
tion of the river to a point where the river narrows and enters a
more shaded run 1200 m downstream from the main boil, covering an
area approximately 76,000 m2 (Odum 1957).
Microcosm experiments were conducted under water in the center
of the river just above the 1200-m station. This point was chosen
because it lies downriver from those areas frequented by glass-bottom
boats and yet was close enough to their route that vandalism was min
imized. The Silver River is also wide enough at this point to pro
vide continuous sunlight with only minimal shading by trees during
the morning hours. The river bottom is wide and level, and the con
tinuous covering of Sagittaria in this area indicates consistent cur
rent and nutrient input characteristics.
Measurements of community metabolism were made using the
upstream-downstream DO change method of Odum (1956, 1957). DO,
temperature, and conductivity were measured with submersible probes
at 2-hr intervals for a 24-hr period at the main boil and at 1200 m
downstream on August 31, October 5, December 13, 1978, and on
March 7, April 15, May 16, June 19, and August 15, 1979. Total solar
Table A.7. (Continued).
Model Parameter Description
Macrophytic Cd uptake
Consumer Cd uptake
Detrital-microbial Cd uptake
Algal Cd decay
Macrophytic Cd decay
Consumer Cd decay
Cd release in microbial
Algal loss to detritus
Particulate Cd loss from alg
Particulate Cd loss from a1g
C2 = KhQ22/3(^y|'z^ "KLCB-KWCB ( kxQ2^4 ) "KVCB (kuQ22jR+l4Q2CZ ) "LFCB (KpQ'2)
Figure 4.13. Detail of Cd-stream model showing interactions of the al
gal component of the periphyton. Points of interest
include stimulatory effect of Cd on primary production
(Ls) and photorespiration.
NORMALIZED NET PRODUCTION (mg 02 S.E.Caf
Figure 4.8. Effect of a range of snail densities on normalized
net production in flow-through microcosms at Silver
Springs, Florida, on 5 days in February and March
1980. Star (*) indicates that value is more than
two standard errors from control mean.
No Cd was found to be associated with the sand sediments in the
streams or with the plastic liner material. Therefore, all Cd losses
from the stream water must be due to biological uptake. Measurements
of Cd concentration in unfiltered water samples indicated an average
lowering of effective concentration by 0.2 ppb in the 5-ppb treatment
and 0.35 ppb in the 10-ppb channels.
Silver Springs continues to be an extremely productive natural
ecosystem (Table 4.1). Spring and summer values for GPP on clear
days were near 30 g 02,m2.dl. The low value measured
was on July 17, 1979, when low light during a long afternoon thunder
storm reduced productivity to 13 g 02*nr2*d-1. Calcula
tion of the P/R ratio indicated a balanced trophic status for the
river with an average P/R ratio of 1.1 throughout the year. Observa
tion of the quantity of particulate export from the river each day
indicates that the actual P/R ratio may be higher. The exported
organic matter was not quantified during this study. The complete
diurnal oxygen change curves from Silver Springs, Florida, are given
in Figs. C. 1C.9.
In their comprehensive studies, Odum (1957) and Caldwell et al.
(1955) reported the striped mullet, Mugil cephalus, and several
species of catfish, letalurus spp., among the dominant consumers at
Silver Springs. Since that time and most probably in the last 10 yr
Summary of Silver Springs microcosm experiment started on February 20,
1980. Snails were released in microcosms on February 26 and harvested and
reweighed on April 2, 1980.
Net Production, g 02-nr2
Consumer Effect3 (g 02-nr2-d"l)
aConsumer effect calculated as algebraic change between given microcosm net production and average control net
production divided by time of measurement.
b3/40.75 hr 1.94 E-nT2, 101.4 Cal-nT2: 3/62.12 hr, 6.89 E-nT2, 360.1 Cal-nT2; 3/115.37 hr, 14.40 E-nT2,
752.7 Cal-nT2; 3/140.02 hr, 0.07 E-nT2, 3.7 Cal-nT2; 3/172.60 hr, 4.65 E-nT2, 243.1 Cal-nT2.
Table A.7. (Continued).
Particulate Cd loss from algae
Particulate Cd loss from macro
phytes to export
Particulate Cd loss from detritus-
microbes to export
Particulate Cd loss from consumers
Total particulate Cd flow in export
Loss of unassimilated food by
consumers to detritus
Assimilation of particulate Cd
Loss of unassimilated particulate
Cd from consumers to detritus
Cd toxicity to consumers
Cd stimulation of algal
Cd stimulation of macrophytes
LL Q4 *(C2+C3+C5)
ALGAE (gdw m 2)
Figure 4.1. Live algal biomass during the 22-mo Cd-stream study.
Values are stream averages extrapolated from glass slide
and wall data for control, 5 ppb Cd, and 10 ppb Cd.
Chew (1974), Mattson and Addy (1975), Owen and Wiegert (1976), Batzli
(1978), and Kitchell et al. (1979). These authors outline basic
mechanisms of consumer populations in the regulation and enhancement
of system energy flow such as nutrient regeneration and cropping of
density-dependent primary producers. Efford (1972) and Chew (1974)
suggest the need for experiments designed to quantify consumer
effects by regulating consumers over realistic density ranges. The
consensus of the literature is that consumers are indeed important in
energy flow but for what reason and to what degree are still
The wealth of data concerning consumer effects in terrestrial
ecosystems is overwhelming as indicated in the reviews mentioned
above. Grazing of terrestrial systems by herbivorous mammals and
insects has consistently been found to stimulate the net productivity
of those systems. The principles of control discussed in this dis
sertation are possibly general to all systems; however, the following
literature review of consumer control is limited to only aquatic eco
Some of the earliest recognition of consumer control includes
the prey-predator interaction models of Lotka (1925) and Volterra
(1926). In these models, predation is seen as an important negative
feedback control on population size and growth rate. The major limi
tation of the basic prey-predator model is that it does not include
the overall system that is ultimately supporting the populations in
question; therefore, results of the model are unrealistic in many
environments with changing driving functions. Predation and grazing
are, however, a part of all real systems studied.
because of reduced competition from other organisms. Species with
short generation times may quickly recover from a chronic toxin level
through intensive selection pressure. By the same manner, ecosystems
may adapt to continuous toxin inputs through redesigning food webs to
contain resistent organisms. A look at some specific reactions to
varying Cd concentrations will allow the formulation of some general
Review of Cd Toxicity and Proposed Models
Data from the literature are examined for the effect of Cd con
centrations on growth in order to determine a general organism
response to this toxin. Parameters of the storages examined were net
yield, cell density, and chlorophyll content; and, the parameters of
energy flow examined were growth rate, oxygen evolution for algae,
and oxygen uptake by animals.
Microbes. Hammons et al. (1978) reviewed the literature on Cd
toxicity to microorganisms and determined that, in general, levels
above 0.2 ppm were necessary to show a toxic effect on bacteria.
Doyle et al. (1975) published data for several bacteria and one yeast
in which toxicity effects were generally observed above 10-20 ppm
(Fig. 3.15). A whole range of toxic responses is seen in this
figure, several of which show some stimulation at the lower Cd con
centrations studied (Escherichia coli, Streptococcus faecal is, and
Lactobaci11 us acidophi1 us).
Plants. In most aquatic systems there are generally two dis
tinct groups of primary producersthe attached algae, or periphyton,
and the macrophytes, or vascular plants. Due to their difference in
Gardiner, J. 1974. The chemistry of cadmium in natural water, II.
The adsorption of cadmium on river muds and naturally occurring
solids. Water Res. 8:15764.
Giesy, J. P. 1978. Cadmium inhibition of leaf decomposition in an
aquatic microcosm. Chemosphere 6:46775.
Giesy, J. P., G. J. Leversee, and D. R. Williams. 1977. Effects of
naturally occurring aquatic organic fractions on cadmium toxic
ity to Simocephalus serrulatus (Daphnidae) and Gambusia affinis
(Poeciliidae). Water Res. 11:1013-20.
Giesy, J. P., H. J. Kania, J. W. Bowling, R. L. Knight, S. Mashburn,
and S. Clarkin. 1979. Fate and biological effects of cadmium
introduced into channel microcosms. EPA-600/3-79-039. 156 pp.
Gliwicz, Z. M. 1975. Effect of zooplankton grazing on photosyn
thetic activity and composition of phytoplankton. Verh.
Internat. Verein. Limnol. 19:1490-97.
Gloyna, E. F., and J. D. Ledbetter. 1969. Principles of radiolog
ical health. Marcel Dekker, Inc., New York. 473 pp.
Hairston, N. G., F. E. Smith, and L. B. Slobodkin. 1960. Community
structure, population control, and competition. Am. Nat.
Hammons, A. S., J. E. Huff, H. M. Braunstein, J. S. Drury, C. R.
Shriner, E. B. Lewis, B. L. Whitfield, and L. E. Towill. 1978.
Reviews of the environmental effects of pollutants: IV Cad
mium. 0RNL/EIS-106. EPA-600/1-78-026. 251 pp.
Hargrave, B. T. 1970. The effect of a deposit-feeding amphipod on
the metabolism of benthic microflora. Limnol. Oceanogr.
Hargrave, B. T. 1975. The central role of invertebrate faeces in
sediment decomposition. Pages 30121 _i_n J. M. Anderson and A.
MacFadyer (eds.), The role of terrestrial and aquatic organisms
in decomposition processes. The 17th Symposium of the British
Ecological Society, April 15-18, 1975. Blackwell Sci. Publ.,
Hart, B. A., and P. W. Cook. 1975. The effect of cadmium on fresh
water phytoplankton. Water Resour. Res. Center Completion
Report. University of Vermont, Burlington.
Hiatt, V., and J. E. Huff. 1975. The environmental impact of cad
mium: An overview. Int. J. Environ. Stud. 7:27785.
John, M. K., and C. J. van Laerhoven. 1976. Differential effects of
cadmium on lettuce varieties. Environ. Pollut. 10:16372.
DISSOLVED OXYGEN (rng-L'1)
1000 1200 1600
TIME OF DAY (H)
1000 1200 1600
TIME OF DAY (H)
Figure C.8. Diurnal oxygen data and analysis for Silver Springs on
July 17, 1979.
Figure 2.2. Summary of oxygen diffusion measurements made at Silver
River during the present study, a. Oxygen reaeration
curves for plastic dome flushed with N2 with diffusion
coefficient indicated in brackets in g 02-m-2-hr-l at
100% saturation deficit; b. Linear regression of
diffusion coefficient with current for measurements in
Silver Springs Consumer Microcosms
Clean microcosms placed in the Silver River underwent a rapid
and consistent succession. Colonization by a diverse periphyton
assemblage proceeded from the upstream to the downstream end of each
tube. Small consumers such as chironomid and trichopteran larvae
were abundant in screened tubes, and small fish such as darters were
observed inside unscreened tubes.
Within 3 wk, growth of filamentous algae and fungi had nearly
filled the tubes, lowering the current rate from 9 cm*s_1
initially to about 2 cm*s"l. By this time periphytic growth on
the outside of the tubes had begun to lower light levels reaching the
inside, and net growth slowed down.
During optimal growth periods, the diverse microcosm communities
demonstrated rapid response of net production to light intensity.
Upstream-downstream oxygen change decreased within a few minutes when
clouds obscurred the sun and increased as quickly when greater sun
light was again available. Net productivity was directly related to
light intensity with greatest efficiency at low-light intensity and
reduced efficiency at higher light levels (Fig. 4.6). The curve of
production response to light input showed only slight indication of
leveling, even at the highest light intensity values recorded.
Net primary production was slightly enhanced with respect to
controls in microcosms receiving low densities of the herbivorous
Table A.6. Computer model for Intercolor computer used to simulate
minimodel illustrated in Fig. 4.11-4.16.
10 PLOT 29,18
20 PLOT 12
20 PLOT 2, 253, 0, 0, 242, 0, 191, 159, 191, 159, 0, 0, 0, 255
108 Nl=. 02
109 ZZ=. 023
110 Cl=. 023
111 C=4. 6
112 Q2=. 1
116 Q4=. 1
118 Q5=. 1
122 N3=. 02
132 Cfl=. 023
141 CZ=. 023
152 FI =2. 73
158 FL=3. 4
160 FM=. 2
162 JZ=27. 94
164 F0=22. 39
lost from this storage by the same mechanisms modeled in the producer
units, and Cd toxicity acts directly as a drain on consumer biomass.
The last section of this stream model is diagramed in Fig. 4.16.
The storage of detritus and associated microbes (bacteria and fungi)
is indicated as Q5, receiving inputs from all of the biological
components in the model. Cadmium is taken up and lost as in the
other components but exerts its toxic action as a reduction of nutri
ent regeneration and metabolism of the microbes. As shown in Figs.
4.13 and 4.14, the storage Q5 intercepts a portion of the incoming
sunlight and therefore reduces remaining sunlight (Jp) available
A complete list of the model storages, pathways, and parameters
is given in Tables A.7 and A.8 along with a copy of the BASIC
computer program (Table A.6) used for the simulations reported in
As a baseline for calibration of the stream model, data from the
control channels of the Cd streams project were used. This control
model was simulated for the period when data are available, i.e.,
November 1975 to August 1977. Initial conditions in this model were
roughly those in the experimental streams: clean and uncolonized
except for the plants and consumers that were added. Model parame
ters were adjusted and pathways were added to the model until simula
tions were comparable to the actual data measured.
Figure 4.17 illustrates a control stream simulation of incoming
sunlight, algal biomass, macrophyte biomass, consumer biomass, and
detrital-microbial biomass using the parameters listed in Table A.7.
3.31 Toxicity curve (a) and corresponding energy effects
energy quality correlation curve (b) 89
4.1 Live algal biomass during the 22-mo Cd-stream study 92
4.2 Detrital and microbial biomass during the 22-mo Cd-
stream study 93
4.3 Biomass of macroinvertebrates during the Cd-stream
4.4 Summary of system-level data during the Cd-stream
study for control, 5 ppb Cd, and 10 ppb Cd treatments..96
4.5 Summary graph of system-level parameters measured
in artificial streams receiving continuous Cd
4.6 Response of net productivity measured as oxygen changes
in three control microcosms on April 21, 1980 104
4.7 Effect of a range of snail densities on normalized net
production in flow-through microcosms at Silver
Springs, Florida, on 3 days in December 1979 106
4.8 Effect of a range of snail densities on normalized net
production in flow-through microcosms at Silver
Springs, Florida, on 5 days in February and March
4.9 Effect of a range of fish densities on normalized net
production in flow-through microcosms at Silver
Springs, Florida, on 3 days in April 1980 Ill
4.10 Response of microcosm normalized net production to a
range of Cd concentrations in input water 114
4.11 Overall system model of Cd streams 116
4.12 Detail of nitrogen and Cd flows and storages in the
thick periphyton layer of the Cd streams 118
4.13 Detail of Cd-stream model showing interactions of the
algal component of the periphyton 119
4.14 Detail of the Cd-stream model showing interaction of
macro phytic plant community 120
Table A.6. (Continued).
446 IF JR<0 THEN JR=0
450 JS=LS*CZ#F3/< LU+CZ )
500 Q2=Q2+DT* < F8+JS-FD-FX-FP-FU-J4 )
531 IF Q2<0 THEN Q2=0. 01
532 IF Q3<0 THEN 0.3=0. 01
533 IF Q4<0 THEN 04=0. 01
534 IF Q5<0 THEN 05=0. 01
543 FH=KH+flZ* <. 02~. 667)
545 FI=KI*PZ*<03~ 667)
547 FJ=KJ*Z*<04~. 667)
549 FK=KK*Z*< OS''. 667)
560 JZ=KN* < CZ-C)
570 C2=C2+NT *< < FH-FL-FW-FV-JF)/56)
577 IF C5<0 THEN C5=0. 31
578 IF N<0 THEN N=0
580 IF C<0 THEN C=0
581 IF C2<0 THEN C2=0. 01
582 IF C3<0 THEN C3=0. 01
583 IF C4<3 THEN C4=3. 01
Figure 3.10. Summary model of in situ sediment microcosms discussed by
Hargrave (1970) with amphipod-detritus interactions that
may result in stimulated productivity.
Castenholz (1961) indicated recognition of grazer feedback con
trol when he examined the effects that snails and limpets had on
attached diatom communities. His data with controlled grazer popula
tions indicated an inverse correlation between grazer and algae, but
he also found that highest algal growth rates were correlated with
low standing crop. Therefore a grazer may stimulate net productivity
by keeping its food cropped to some non-zero optimal level.
Dickman (1968) studied the relationship between a massive peri
phyton disappearance and the concurrent hatching of tadpoles in a
northern lake. A simple diagram of the proposed mechanism is illus
trated in Fig. 3.8. He found that the tadpoles behaved like a digi
tal switch mechanism in cropping periphyton standing crop and releas
ing bound nutrients to an available form. He did not extend his
experiments to examine a possible correlation between periphyton pro
ductivity and tadpole density.
After studying grazing effects on primary production and species
composition of the phytoplankton, Gliwicz (1975) hypothesized that
the increased nutrient availability resulting from grazed algal popu
lations drives a faster total productivity by a smaller population.
Cooper (1973) varied the biomass of an herbivorus minnow,
Notropis spilopterus, in experimental microcosms and found an
increase in primary production at low consumer densities and a
decrease in productivity with greater densities of minnows. He
interpreted the decreased production with high grazing as an
indication of factors other than nutrient regeneration being respon
sible for the observed data. He felt as Castenholz had earlier, that
productivity is enhanced by a lowered standing crop of producers. An
STREAM METABOLISM AND EXPORT (g dry wt. m-2 d-')
Figure 4.21. Average gross productivity, respiration, and export
values during 1 yr of continuous Cd input predicted
by Cd-stream models for Cd concentrations up to 50
ppb. Measured data from Cd streams are indicated
by dashed lines for comparison.
DETRITUS AND MICROBES (gdwm2)
Figure 4.2. Detrital and microbial biomass during the 22-mo
Cd-stream study. Values are extrapolated from glass
slides, wall, and core samples for control, 5 ppb Cd,
O.Zb-m^ sections of sediment and associated plants were removed
from each channel, and plant biomass per unit area by species was
Quantitative samples for macroinvertebrates and microinverte
brates were taken on a routine basis from plate samplers and polyure
thane sponges. Most organisms were identified as to species, and
biomass and Cd concentrations were measured when practical.
Measurements of total community primary production and respir
ation were made over 24-hr periods by measuring upstream-downstream
change in oxygen by a method adapted from Odum (1956). Water samples
were removed from the streams by siphon at 2-hr intervals and dis
solved oxygen (DO) content was determined using a YSI model 54 DO
meter calibrated using the azide modification of the Winkler method
(American Public Health Association 1975).
In the spring of 1977 a semiautomatic method of collecting oxy
gen diurnal data was put into service. This system utilized 12 sole
noid valves (one at'the head and one at the tail of each channel),
two YSI oxygen probes and meters, two timer boxes, and a chart
recorder with another timer attached. At each end all six gravity-
fed lines passed through solenoid valves into a single common line
feeding the water over the end of the probe. DO was monitored for 10
min each hour. Signals from the corresponding meters were fed into a
timer that switched input to the recorder at 5-min intervals. In
this manner, 5-min recordings of DO concentrations at each location
Figure 3.5. Aggregated model of Zn and Cd production with flows eval
uated in terms of Solar Equivalent Calories.
any substance, and the total energy degraded to heat in the coupled
process of Cd concentration is the "embodied energy."
The embodied energy of Cd may be calculated at various concen
trations and in different systems to evaluate its role as a toxin or
stimulator of metabolism. Calculated values of embodied energy may
be based on global averages or specific production cases. Recause of
the statistical uncertainties in data and also because specific cases
may not have been evolving long enough to develop the adaptations for
maximum power, the numbers resulting may be subject to considerable
variability and revision. Of most importance in this work are com
parisons of energy required for Cd concentration in different systems
and the relationship of energy required to the feedback effect.
Earth production of Cd. The concentration of Cd in the solar
system is roughly 3 ppb (calculated from elemental abundances given
by Abell ) as compared to an average value of 110 ppb in the
earth's crust (Vlasov 1966). Thus the crustal Cd has embodied energy
from the earth's formation process. Since this energy is the result
of concentration in the next larger system (i.e., the solar system),
the crustal Cd embodied energy is assumed to be equal to zero in
order to set a baseline for the calculation of energy embodied by the
earth's production process of Cd ore.
Figure 3.3 illustrates the energies used to estimate the Cd con
centration in the earth process. Cadmium ores are very rare in
nature so the much more abundant Cd-bearing zinc (Zn) ores are con
sidered. Although Cd concentrations as high as 8000 ppm are found in
some Zn ores (Wedepohl 1970), the world average for minable ores
is 4% Zn (Cammarota 1978), and with an average Zn:Cd ratio of 200 in
Table A.8. List of initial conditions and transfer coefficients used in
simulation of Cd-streams model illustrated in Figs.
4 mg Nm"2
0.023 yg Cd-L'1
4.6 yg Cd*m"2
0.023 yg CdL-1
0.023-100.0 yg Cd
1.0 yg Cd*g|
1.0 yg Cd gl
1.0 yg Cd-gJ
0.1 yg Cd*m"2
1.0 yg Cd-g"1
5.0 yg Cd*m"2
0.1 yg Cd*m"2
0.1 yg Cd*m-2
0.02 mg N*L"2
2736 mg N'd"1
0.02 mg NL"2
3146 yg Cd-d"1
0.02 mg N.L-1
200 yg CdL-1
1.5 x 10-6 m4,d-1*'
1 mg N*m2*g"2
1 mg N*m2*g"2
0.004 L*m2*Cal2'mg N"2
0.001 L*m2*Cal-2*mg N"2
0.004 L-d"2-yg Cd"
1 x 10"^ m4,g"2,Cal"2
0.0002 L-d_1-yg Cd
1.5 x 10"4 m2-d"2;g"2
1 mg N*m2-g"2
2 x 104 yg Cd*m|/2.c|-l.g-2/3
4 x 102 yg Cd*m.d~1-g2/3
0.008 L-d"2-yg Cd"
1 x 102 yg Cd-m4/2-d"2-g"2/2
2 x 102 yg Cd-m4/2-d"2-g"2/2
1 x 10"4 L-yg Cd"1
1 x 104 L-d"2
0.2 yg Cd-L"2
Figure 3.11. Summary model of crayfish-plant interactions in Lake Tahoe
discussed by Flint and Goldman (1975). Nutrient regenera
tion was considered to be an important stimulant to
increased primary productivity by natural crayfish densi
Figure 3.14. Simulation results for consumer control model shown in
Fig. 3.13. a. Model results for constant nutrient (N)
concentration at two different levels; b. Model results for
three nutrient input rates (J^) with no crowding effects in
producer population; c. Model results when both mechanisms
were combined. All results are data after 50-day simulation
a stonefly. Once again we see the general hyperbolic relationship
between Cd in solution and Cd concentrated by the organisms. A con
centration factor for Cd >30,000X was seen at low solution concentra
tion for the caddisfly and 2300X for the stonefly.
Models. A model of Cd uptake and concentration by organisms
must generate asymptotic charge-up curves and a hyperbolic relation
ship between steady state concentration in the organism and in its
growth medium. Models used previously for adsorption of metals by
solids include the Fruendlich isotherm (Gardiner 1974) and the
Langmuir isotherm (Castellan 1964). These models of Cd uptake by
adsorption include a cycling-receptor of surface area for collection
of Cd. The model diagramed in Fig. 3.30a showing Cd accumulation as
regulated by biomass includes the adsorption loop. The BASIC compu
ter program used for simulations of this uptake model is listed in
Figure 3.30b presents results of a simulation of this model in
which the parameter KZ was varied from 10 to 300 cm^-yg Cd-1.
Where fewer Cd adsorption sites are present, a lower total Cd concen
tration is possible. Smaller sizes have a greater surface area per
biomass and may collect more but store it for shorter times. Figure
3.30c illustrates the effect of increasing the average radius from
0.1 mm to 1.0 mm in this model. Thus, there are two mechanisms
available to reduce the effective concentration of a toxin in solu
tion: increasing number of surface binding sites and developing
Table A.7. List of parameters with descriptions and equations for Cd-streams model illustrated in Figs.
Dissolved nitrogen in periphyton
Dissolved Cd in periphyton layer
Bound Cd in algae
Bound Cd in macrophytes
Bound Cd in consumers
Bound Cd in detritus-microbes
Dissolved nitrogen concentration
Dissolved Cd concentration in
Dissolved nitrogen concentration
in periphyton layer
Dissolved Cd concentration in
Figure 4.11. Overall system model of Cd streams. Sunlight interacts with dissolved chem
icals to maintain complicated biological systems and Cd cycling. Each unit
has stimulative and toxic action of Cd (see details in Figs. 4.12-4.16).
BASIC program used for simulations is given in Tables A.6-A.8.
Populations of large fish (>10 cm long) were estimated by visual
survey on October 20, 1978, and on April 11, May 16, July 17, and
October 22, 1979. The author wore a face mask and snorkel and was
towed in a criss-cross fashion down the spring run while holding the
bow of a boat. All fish seen were counted, and the numbers in gen
eral groups or specific species were reported to an assistant in the
boat. A survey of the 76,000-m^ area took about 1 hr to complete.
Northcote and Wilke (1963) reported good agreement between visual
fish counts and rotenone poisoning techniques for larger fish in
cl ear-water environments. At Silver Springs it may be assumed that
the visual counts are an underestimate with greatest accuracy for the
larger free-ranging fish such as shad, bass, mullet, and bluegill
sunfish; and less accurate for the secretive or smaller species such
as spotted gar or small sunfish.
Snail Population Estimates
Snail populations were estimated in a low currentvelocity cove
near the 1200-m station for comparison to microcosm data. A stiff-
handled net with a 0.0671-m2 opening was used to sweep the Sagit-
taria beds in this cove, which are the habitats of the snails stud
ied. Several passes were made and the captured snails were sorted
and weighed for live weight. These values are reported on a m^
basis by multiplying the volume of water and plants sampled by the
average depth of the sample area.
CELL DENSITY AT 7 DAYS (cells field-1)
Effect of Cd on net growth of the green alga
Chiamydomonas reinhardii in batch culture
(from Kneip et al. 1974).
3.13 Consumer control model including both density-dependent
inhibition of producers and nutrient regeneration
effects of consumers 57
3.14 Simulation results for consumer control model 58
3.15 Effect of Cd on net growth of six microorganisms in
batch culture 63
3.16 Effect of Cd on oxygen evolution by the blue-green
alga Anacystis nidulans in batch culture 65
3.17 Effect of Cd on cell numbers of the green alga
Scenedesmus quadricauda in batch culture 66
3.18 Effect of Cd on net growth of the green alga
Chlamydomonas reinhardii in batch culture 67
3.19 Effect of Cd on respiration of tubificid worms in
static culture 70
3.20 Effect of Cd on egg production and survival of
fathead minnows in flow-through culture 71
3.21 Effect of Cd on brook trout in flow-through systems 72
3.22 General curves relating toxin concentration to toxin
3.23 Model of toxicity as a drain on biomass 76
3.24 Model of toxin effect on an organism including a stim
ulatory function and an exponential toxic function 77
3.25 Model of toxicity effect on recycle showing stimula
tion of production (P) because of storage (Q) decay
and nutrient (N) recycle 78
3.26 Uptake of Cd by five microorganisms in static culture 80
3.27 Uptake of Cd by Chi ore! la pyrenoidosa at two pH values
in static culture 82
3.28 Uptake of Cd by the submerged macrophyte Najas
guadalupensis in flow-through systems 83
3.29 Uptake of Cd by two aquatic invertebrates in batch
3.30 Model of Cd adsorption in periphyton 87
storage expressed in embodied energy units. For example, a decrease
in primary productivity of -10 CalnT^d-1 by a Cd flow of
1 ug*m"2*d-1 would be equivalent to an energy effect of
-10,000 S.E. Calyg Cd-1 at the specified Cd concentration if
we assume a quality factor for primary productivity of 1000 S.E.
Cal*Cal~l. The energy effect of a controlling substance may be
a function of its concentration, and therefore the concentration must
be specified for comparisons. As with embodied energy calculations,
energy effect calculations are in a learning stage and subject to
interpretation of Cooper's system is illustrated in Fig. 3.9. Since
Cooper did not precisely define the mechanism by which productivity
might be enhanced at low algal density, two possible models are
Hargrave (1970) found the same relationship between grazer den
sity and primary productivity as Cooper when he controlled amphipod
numbers in his in situ sediment microcosms. Maximum primary produc
tion was observed at densities of amphipods naturally found in the
lake. He felt that grazing increased productivity by cycling nutri
ents and providing substrate for increased algal and bacterial
growth. In addition, Fenchel and Harrison (1975) measured stimula
tion of decomposition by bacteria in grazing experiments with proto
zoans. Hargrave (1975) generalized these stimulatory effects to all
deposit-feeding invertebrates that create additional space for
microbial growth. These mechanisms are summarized in Fig. 3.10.
Flint and Goldman (1975) found a stimulation of primary produc
tion in periphyton that were exposed to varying crayfish densities in
Lake Tahoe. Besides obtaining verification of the theory of
increased nutrient availability, they indicated that crayfish may
speed nutrient cycling by seeding and conditioning excreted algal
material for better bacterial growth. They also found that crayfish
remove macrophytes that compete with attached algae for nutrients.
Figure 3.11 shows a summary model of the crayfish-periphyton inter
actions discussed by these authors.
Porter (1975) studied the effect of grazing by Daphnia on pri
mary production of phytoplankton. She speculated that after viable
gut passage, primary production might be stimulated by: increased
Model of autocatalysis. The feedback inter
action between a storage (S) and an energy
source (E) develops rapid growth as long as
source can supply increased flow. Feedbacks
include those to maximize its own system
directly (F]_) and those to maximize the
larger system (F2).
Thus, Flow D in Fig. 3.3 is 265 t of recoverable Zn ore*yr_1
for the whole world, or 10.6 t Zn and 53 kg Cd in ore produced each
year. At a world mining rate of about 5.4 x 106 t Zn and 17 x
103 t Cd in 1978, the depletable nature of these resources is
TR for Cd. The TR for Zn and Cd in ore on a weight basis may
now be calculated if the production of ore is assumed to be a
by-product of the whole earth sedimentary system driven by solar
TPzn ore = (13.4 x 10^0 $.E. Cal*yrl)/(265 t Zn ore*yr"l)
= 5.1 x 1018 S.E. Cal*t Zn ore"l
TRZn in ore = (13.4 x 10^0 S.E. Cal-yr"1)/(10,600 kg Zn-yr"1)
= 12.6 x 10l6 s.E. Calkg Zn-3 in ore
TRcd in ore = (13.4 x 10^0 s.E. Cal*yr-l)/(53 kg Cd-yr'1)
= 2.5 x 10^9 s.E. Cal kg Cdl in ore.
Industrial concentration. Cd metal is produced commercially
from by-products of Zn production; therefore, in order to evaluate
the embodied energy for Zn and the resulting flue dust with Cd
content, it is necessary to evaluate the Cd case. Figure 3.4
presents a simplified model of this process showing the evaluated
actual energy and material flows. Table 3.1 lists the flows and
their equivalent values in embodied energy of solar equivalent
kilocalories. Figure 3.5 presents an aggregated model of this
purification process with embodied energy flows of one type. These
calculations indicate that the human costs of extracting and purify
ing these metals greatly underevaluate their overall embodied energy
Cal K"l*mo']"l; T is the absolute temperature in K; and
C]_ and C2 are the concentrations of Cd in the lithosphere before
and after concentration. When C]_ = 110 ppb and C2 = 200,000 then
AG is calculated as 0.0389 Ca1 *g Cd-1 at a temperature of 20C.
When this value is divided into the TR of Cd in ore of 2.5 x lO1^
S.E. Calkg Cd-1, a new TR of 6.4 x 101? S.E. Cal'Cal-1 is obtained.
This value may be compared to other published ratios such as
6 x 10^ S.E. CalCal-! for mined phosphorus (Odum and Odum
1980) or 1.4 x 10^ S.E. Cal Ca11 for goods and services in
the United States economy (Odum et al. 1980).
Biological concentration. As discussed earlier in this section
most biological components have the ability to concentrate Cd to ele
vated levels over water concentrations. This concentration repre
sents an embodiment of solar energy into upgraded Cd storage. Sev
eral calculations of biological Cd processing are made in this sec-
Figure 3.6a illustrates the inputs evaluated in these calcula
tions. Primary energy inputs are the embodied energy in the dis
solved Cd and solar energy being processed by the biological system.
Cadmium uptake is generalized in Fig. 3.6b as a simple charge-up
model. The inputs of solar, water potential, structural, and Cd
embodied energies are integrated over the time indicated on the
Data for the entire biological communities of the Cd streams of
Giesy et al. (1979) were used for analysis (Fig. 3.7). Using the
figure of 50 days for saturation of the periphyton Cd levels and
embodied energy flows for solar, water, and structure reported in
Table 4.8. Summary of actual energy flows and transformation ratios
for Silver Springs based on data from Odum (1957) and
evaluation of total energy income in Fig. 4.24. The
embodied energy of each flow in Silver Springs is equal
toJL.32 x 105 S.E. Cal'irf^'d"1 and the transformation
ratios are calculated by dividing this total energy by
the actual energy of each flow in heat Calories.
Top carnivore respiration
3.67 x 106
Figure 4.14. Detail of the Cd-stream model showing interaction of
macrophytic plant community. As with the algae, a stim
ulatory effect of Cd is included (Lt).
I would also like to thank the wonderful group of students and
friends who found the time and energy to leave their work and studies
for the rigors of fieldwork at Silver Springs.
The staff of the Center for Wetlands helped make this disserta
tion and earlier project reports a reality through fine editing,
typing, and drafting skills.
My final thanks go the my wife, Gail, and my father, Dr. Kenneth
L. Knight, both of whom have served as levels of excellence to which
i i i
were recorded for each hour during day and night. Probes were cali
brated several times during each 24-hr period
The hourly rate of change of DO was calculated for a given water
mass using the flow time of 2 hr between stations. These values were
corrected for diffusion by calculating percent saturation and using
the following equation:
D = kS (2.1)
where D = diffusion rate (g 02-m_2-hrl)
k = diffusion coefficient (g 02-m2-hr'l at 100% saturation
S = saturation deficit, calculated as S = (100 % satura-
A positive diffusion value indicates oxygen diffusion into the water
and therefore changes in DO are corrected by subtracting D. Values
of k between 0.04 and 0.8 g 02*m2.hr"l were measured in
the streams using the floating-dome method of Copeland and Duffer
(1964) modified by McKellar (1975). Values of k between 0.1 and 1.0
were used in the productivity calculations depending on weather con
ditions, with the highest value used for windy and rainy days. In no
case did the diffusion correction alter metabolism values by more
than 10% of their uncorrected values.
Corrected rate-of-change data were plotted, and areas were inte-
grated by counting squares. Nighttime respiration values were aver
aged, and 24-hr respiration (R24) was assumed to be equal to the
average nighttime hourly rate times 24 hr. Gross photosynthesis
(Pg) was the area above this average R line, and net photosynthesis
(Pnet) equals Pq-R24- P/R ratios were calculated as Pq/R24-
Judson, S. 1968. Erosion of the land or what's happening to our
continents? Am. Sci. 56:35674.
Kania, H. J., and R. F. Beyers. 1974. NTA and mercury in artificial
stream systems. EPA-660/3-73-025. 25 pp.
Kania, H. J., R. L. Knight, and R. J. Beyers. 1976. Fate and bio
logical effects of mercury introduced into artificial streams.
EPA-600/3-76-060. 128 pp.
Katagiri, K. J. 1975. The effects of cadmium on Anacystis nidulans.
Master's thesis, University of Vermont, Burlington.
Kemp, W. M. 1977. Energy analysis and ecological evaluation of a
coastal power plant. Ph.D. dissertation, University of Florida.
Kerfoot, W. B., and S. A. Jacobs. 1976. Cadmium accrual in combined
wastewater treatment^-aquacultural system. Environ. Sci.
Kitchell, J. R., R. V. O'Neill, D. Webb, G. W. Gallepp, S. M.
Bartel 1, J. F. Koonce, and B. S. Ausmus. 1979. Consumer regu
lation of nutrient cycling. BioScience 29:28-34.
Klass, E., D. W. Rowe, and E. J. Massaro 1974. The effect of cad
mium on population growth of the green algae Scenedesmus
quadricauda. Bull. Environ. Contam. Toxicol. 12:442457
Knauer, G. A., and J. H. Martin. 1973. Seasonal variations of cad
mium, copper, manganese, lead, and zinc in water and phytoplank
ton in Monterey Bay, California. Limnol. Oceanogr. 18:597604.
Kneip, T. J., K. Buehler, and H. L. Hirshfield. 1974. Cadmium in an
aquatic ecosystem: Distribution and effects. Interim Progess
Report, N.Y. Med. Center Inst. Environ. Med. 85 pp.
Kumada, H., S. Kimura, M. Yokote and Y. Matida. 1973. Acute and
chronic toxicity, uptake, and retension of cadmium in freshwater
organisms. Bull. Freshwater Fish Res. Lab. Tokyo 22:15765.
Lamanna, C., and M. F. Mallette. 1953. Basic bacteriology.
Williams & Wilkins Co., Baltimore. 677 pp.
Lindeman, R. L. 1942. The trophic-dynamic aspect of ecology.
Lotka, A. J. 1922. Contributions to the energetics of evolution.
Proc. Natl. Acad. Sci. 8:14751.
Lotka, A. J. 1925. Elements of physical biology. Williams &
Wilkins Co., Baltimore. 460 pp.
Lucas, J. M. 1979. Cadmium. Mineral commodity profiles. U.S. Bur.
Mines. 13 pp.
Q = K1JNQ(1-K2Q)-(K3+K4)Q
Q = K1JNQe'K2Q-(K3+K4)Q
Figure C.l. Diurnal oxygen data and analysis for Silver Springs on
August 31, 1978.
cesses. If the system's goal is maximum power, the ideal use for a
controlling substance is to enhance the capture and use of energy
sources. Consequently, toxins that decrease a system's power must be
detoxified by surviving systems or be adapted to through species sel
ection and evolution. If possible, powerful controlling agents may
be incorporated into productive processes within an organism as part
of enzyme systems or respiratory and photosynthetic pathways. Thus,
copper and zinc are recognized essential nutrients for many plants at
low concentrations, but are toxic at higher levels. It is proposed
that this subsidy-stress gradient (see Odum et al. 1979) is the gen
eral case for any substance that has been a part of natural systems
for evolutionary time, and quantification of this effect is possible
through embodied energy calculations.
In the fields of medicine and bacteriology there has long been a
recognition of stimulation by a variety of normally toxic substances
at low levels. This phenomenon has been named the "Arndt-Schulz Law"
after two German physicians working on the effects of drugs in the
late 19th century. Lamanna and Mallette (1953) discuss this effect
in their treatise on bacteriology. "Growth rates, crop yields, and
specific metabolic activities of all bacterial species studied have
been found to be stimulated by low concentrations of a diversity of
inorganic and organic poisons" (p. 598). This phenomenon has been
recognized in the effects of ionizing radiation on plants (Gloyna and
Ledbetter 1969) and on whole forest communites (Woodwell 1967; Odum
and Pigeon 1970). Of particular interest to this report are the
Silver Springs System Comparison
In his landmark paper on energy flow in aquatic ecosystems,
Odum (1957) warned of one danger in working in an apparent steady
state system: "Most terrible and healthy for the poor ecologist is
the realization that anyone can check his field work at any later
time" (p. 58). Comparisons of GPP can be made directly between the
study reported here and Odum's study 25 yr ago because of the overlap
of methods and correction factors applied. Figure 5.1 illustrates
this comparison with an uncanny similarity of values. These include
a low summer value resulting from afternoon thunderstorms that are
typical of the area and time of year. Winter values during the more
recent study were substantially higher than those reported by Odum.
This may be the result of exceptionally clear days being encountered
in this study or by an actual increase in productivity.
Figure 5.2 compares total solar energy reaching the river's
surface with resulting primary productivity. Odum's original figure
used estimated visible energy reaching plant level and meteorological
tables for insolation modified semiquantitatively for cloud cover.
The apparent higher production efficiencies measured during this
study may be the result of more accurate light measurements used.
for Florida Power studying the canal ecosystems and 2 yr on an EPA
grant studying the controlling role of toxins.
In April, 1980, Bob married Gail Irene Stringer with whom he now
shares Seven Springs Farm near LaCrosse, Florida.
vice versa. Widely different studies of toxicity effect can be com
pared using embodied energy values. Studies of several seemingly
unique toxins may be comparable if their embodied energy content is
known. The idea of toxin effect being a direct function of embodied
energy may allow a needed synthesis of information in dealing with
the modern world's increasing toxic wastes. The recognition of the
stimulatory role of naturally occurring chemicals in biological sys
tems greatly broadens our theoretical understanding of the world's
processes and allows a more finely tuned control of our life-support
Data from the Silver Springs microcosm experiments are directly
amenable to the comparison of the embodied energy required and the
energy effect of controllers in an adapted system. Comparison data
from Odum (1957) were used for the same system because of similar
ities found in production now compared with the earlier period (see
Section 5 for further discussion of this comparison).
The system model presented by Odum (1957) was used to calculate
TR for the energy flows of concern to this comparison. Table 4.8 and
Fig. 4.24 present the aggregated model with evaluated energy flows
and the TR calculated from these flows. Figure 4.24 summarizes the
major energy inputs to Silver Springs as sunlight plus the potential
energy in water flow with associated free energy of dissolved nutri
ents. Table 4.8 indicates that the TR for gross productivity and
community respiration were the lowest energy flows evaluated while
top carnivore respiration was the highest.
S.E. Cal'iir^'d"!. As calculated in the previous paragraph this Cd
resulted in a stimulation of productivity equal to 54,472 S.E.
Cal*m~2.d~l. Once again these calculations of energy invested in a
system component and its energy effect indicate similar energy values
in the region of optimal controller density.
Silver Springs System Comparison 144
Consumer Control 147
Cadmium as a Consumer 148
Ecosystem Manipulation and Control 149
A-COMPUTER PROGRAMS 153
BDIURNAL OXYGEN CURVES FROM CD STREAMS 172
C-DIURNAL OXYGEN CURVES FROM SILVER SPRINGS, FLORIDA 183
LITERATURE CITED 192
BIOGRAPHICAL SKETCH 199
q. ? 3
Figure 4.4. Summary of system-level data during the
Cd-stream study for control, 5 ppb Cd,
and 10 ppb Cd treatments, a. Gross pro
duction; b. Community respiration; c.
Figure 3.16. Effect of Cd on oxygen evolution by the blue-
green alga Anacystis nidulans in batch cul
ture (from Katagiri 1975).
' RESPIRATION FOR TUBIFICID WORMS
i i i i i
Cd CONCENTRATION (ppm)
Figure 3.19. Effect of Cd on respiration of tubificid
worms in static culture (from Brkovic-
Popovic and Popovic 1977).
Figure 3.23 illustrates a model of the overall effect of a toxi
cant on storages as a product of storage and toxicant. A BASIC com
puter program of this model is given in Table A.2. The curves gener
ated by this simple model are typical of the results seen for many
studies in the literature (see Figs. 3.153.21).
Figure 3.24 summarizes the effect of the toxicant in a more
mechanistic manner. In this model, Cd is represented both as a
required nutrient for organic synthesis and as an inhibitor on meta
bolic feedback processes such as enzyme reactions. The computer pro
gram for this model is given in Table A.3. Figure 3.24b presents
representative output for this model at two toxicities for several
toxin concentrations. These curves show a stimulatory region for the
metal as well as the stress region more generally considered.
In Fig. 3.25a toxic action is combined with nutrient recycle.
The computer program is given in Table A.4. A wide ranqe of toxici
ties and nutrient uptake rates were examined and stimulation of
production was found at some combinations even though biomass was
simultaneously reduced (Fig. 3.25b). The optimum effect was the
result of an increase in available nutrients and would not be found
in systems with nutrient excess.
In summary, we conclude that observed Cd toxicity data may be
generated from simple models of toxin interaction for organisms or
trophic levels. Models of toxicity must include more than just nega
tive interactions such as those in Fig. 3.23 to be inclusive of the
Arndt-Schulz phenomenon; however, for producers, stimulation is pos
sible indirectly through nutrient recycling (Fig. 3.25).
Figure B.4. Diurnal oxygen change curves
from October 20, 1976, for six
experimental streams receiving
Figure 3.7. Aggregated model of stream production and biological Cd
concentration used to evaluate embodied energy of Cd. For
the artificial streams of Giesy et al. (1979); Flow A =
4360 S.E. Cal-m-2-d-1; Flow B = 1346 S.E. Cal-m_2-d_1;
Flow C = 27,900 S.E. Cal nT^-d-!; Flow D varied from zero
for the controls to 1,130,000 S.E. Cal-m^-d-1 in the 10 ppb
Cd treatment streams.
DISSOLVED OXYGEN (mg-L'1)
TIME OF DAY (H)
1000 1200 1600
TIME OF DAY (H)
TIME OF DAY (H)
Diurnal oxygen data and analysis for Silver Springs on May 16,
size, microscopic algae may have generation times of a few days while
aquatic macrophytes generally have one generation per year. Although
laboratory studies show similar sensitivities for these two groups,
species replacement and redesign by plant communities are much faster
in the algae.
Most laboratory studies of algal toxicity have been made with
the "laboratory weed" algae, which are easy to culture in artificial
conditions. Sensitivity of these species to a chemical may not be
typical of all algae just as their ease of culture is not typical of
all algae. Nevertheless, the replicability of laboratory studies is
useful in a comparison over a large range of concentrations of Cd.
Figure 3.16 shows the effect of Cd up to 1 ppm on oxygen evolu
tion in a blue-green algae, Anacystis nidulans, reported by Katagiri
(1975). A concentration of 100 ppb was found to be inhibitory while
50 ppb gave a slight stimulation over controls. A small amount of
photosynthesis was reported at 1 ppm Cd.
In a study of Cd effect on growth of Scenedesmus quadricauda
(Fig. 3.17), Klass et al. (1974) reported reduced cell densities at
6.1 ppb with some cell growth still observed at 610 ppb. Once again
a small stimulation of maximum cell numbers was reported at a concen
tration of 0.6 ppb Cd.
Studying another green alga, Chiam.ydomonas reinhardii, Kneip et
al. (1974) reported reduced growth at a Cd concentration of 10 ppb
(Fig. 3.18) and almost total inhibition at 1 ppm Cd. Once again at
the lowest levels tested, 0.01 ppb, a slight stimulation of net
growth was observed.
Table 4.3. Summary of Silver Springs microcosm experiment started on December 5, 1979.
Snails were released in microcosms on December 10 and harvested and
reweighed on January 10, 1980.
Net Production, g 0;?*nr2
Consumer Effect3 (g 02*nT2*d-l)
Consumer effect calculated as algebraic change between given microcosm net production
and average control net production divided by time of measurement.
bl2/135.33 hr, 5.08 E-nT2, 265 Cal-irT2; 12/160.67 hr, 0.14 E*m"2, 7.3 Cal*m"2;
12/211.58 hr, 2.63 E-m"2, 137.5 Cal-nr2.
dards. Standard addition curves had the same slope as curves con
structed from standards in distilled water, indicating that the sel
ected charring and atomization time and temperature regime removed
most matrix interferences.
Concurrent studies of Cd toxicity were run using the stream
water with crayfish (Thorp et al. 1979), mosquito fish (Giesy et al.
1977; Williams and Giesy 1978), and leaf decomposition (Giesy 1978).
Silver Springs Metabolism and Consumer Populations
Silver Springs is a natural environmental feature located in
north-central Florida in Marion County, east of Ocala. Two billion
liters of water flow each day from one major boil and numerous smal
ler boils forming the Silver River, which flows with only minor dilu
tion for 11 km to its confluence with the Oklawaha River (U.S. Geo
logical Survey 1978). Typical water chemistry of this spring water
(Table 2.2) remains unchanged since measurements were taken in 1907
(Rosenau et al. 1977). The data indicate water of moderate hardness,
low DO, low organic carbon, and moderate levels of the primary plant
nutrients (nitrogen and phosphorus).
Although Silver Springs was recently donated to the University
of Florida, it is leased by the American Broadcasting Corporation and
operated as a tourist attraction, offering guided tours in battery-
powered, glass-bottom boats. Restrictions on swimming and fishing
Figure 3.12. Summary model of plankton interactions as discussed by
Porter (1975). Optimal phytoplankton density and nutrient
regeneration mechanisms are combined in a comprehensive
view of zooplankton stimulation of primary productivity.
Literature Review and Minimodels
A literature review of experimental and theoretical studies
was made in order to generalize control processes in ecological sys
tems. In particular, experimental work dealing with the effects of
consumer and Cd manipulations on system-level parameters, such as
primary production, was included. The mechanistic processes that may
lead to system control were identified by these authors and summar
ized in a series of minimodels using the energy circuit language of
Odum (1975). Similarities between these models were easily seen and
incorporated into the more complex control model of a stream ecosys
tem presented in Section 4.
Six experimental streams were operated as microcosms receiving
two different Cd treatments. Detailed descriptions of the methods
used in the Cd-streams study were presented by Giesy et al. (1979).
The author of this dissertation was a participant in the Cd-streams
study, with responsibility for measuring periphyton dynamics, system
metabolism, and export.
Table A.7. (Continued).
Cd diffusion between open water
Total gross production
Figure 3.23. Model of toxicity as a drain on biomass.
a. Model; b. Representative output for three
values of K3. BASIC program used for simula
tions is given in Table A.2.
NORMALIZED NET PRODUCTION (mg 0? S.E.Cal
SNAIL WEIGHT (g)
Figure 4.7. Effect of a range of snail densities on normalized net
production in flow-through microcosms at Silver
Springs, Florida, on 3 days in December 1979. star
(*) indicates that value is more than two standard
errors from control mean.
magnitude of the numbers reported, the qualitative results remain the
The average yearly solar energy used in the model was 4360 S.E.
Cal m"2d''l. The total structure of the streams including
plastic, sand, and concrete blocks cost approximately 6 x 10~3 $m-2*d-1.
This expenditure probably represents the minimum possible energy cost
of this structure. Using the 1972 energy-to-dol1ar ratio .of Odum et
al. (1980), this expenditure is equivalent to 2.79 x 104 S.E.
Cal*m"2*d! for the channel area. The other major energy
input is the water flow in the streams. This flow may be approxi
mated by the free-energy change for the essential nutrient, nitrogen.
Using the concentration change measured in the control channels (10.4
ppb3.6 ppb N) and the equation (3.1) for Gibb's free energy, a
decrease in free energy along the reach of the streams of 0.045
Cal *g N"1 is calculated, which is equivalent to 1.15 x 10"3
Cal*m"2*d-1. Using the quality factor for chemical
potential of dissolved solids in stream flow of 1.17 x 10 S.E.
Cal*Ca11 given by Wang et al. (1980), an energy contribution
from stream flow of 1346 S.E. Calm^*d~^ was calculated.
The total energy contribution to the streams is the sum of the
three factors listed above in equivalent energy quality units and is
equal to 33,606 S.E. CalnT^d"1. Energy transformation
ratios have been calculated using yearly averages from the stream
model and the total energy input given above. A conversion factor of
4 Cal*g dry weight"! was used to convert the biomass units to
energy units. These values are listed in Table 4.7.
Table A.7. (Continued).
Model Parameter Description
in inflow water
Dissolved Cd concentration in
Cd concentration in
Cd concentration in
Cd concentration in
Cd concentration in
Solar energy flux
Remaining solar flux (albedo)
Sine function, 365 days;
maximum value = 7080 Cal-m-2-d-l
minimum value = 4360
Figure 3.4. Model of Zn and Cd production by the electrolytic process
with actual energy and dollar flows evaluated. Cadmium pro
duction is entirely a by-product recovery of Zn purifica
tion. See Table 3.1.
DISSOLVED OXYGEN (mg-L"')
TIME OF DAY (H)
1000 1200 1600
TIME OF DAY (H)
Pnet= 3 8
Rn = 14.1
Diurnal oxygen data and analysis for Silver Springs on
April 15, 1979.
A significant replacement of the absent catfish and mullet
species was observed with the density of blue shad similar to pre
vious recorded levels of mullet. Unfortunately the actual effect of
this species replacement on system productivity increases cannot be
deduced from this 1-yr comparison study. Results from the microcosm
studies must be extrapolated to the larger system, or additional
studies of the entire river must be continued.
There are several speculations over the reason for the disap
pearance of the popular catfish and mullet of Silver Springs. Their
disappearance is closely correlated in time with the construction of
the Rodman Dam on the Oklawaha River approximately 50 km downstream
from the springs. One hypothesis suggests a competitive food
resource in the newly formed Lake Oklawaha (Sam McKinney, personal
communication). Another hypothesis concerns the difficulty encount
ered by the catadromous mullet in navigating the infrequently used
locks circumventing the dam. In either case, a large-scale experi
ment of consumer replacement may occur if the Rodman Dam is removed
as part of the cleanup of the ill-fated Cross-Florida Barge Canal.
Data supporting the consumer-control hypothesis have appeared
in the literature long before the study reported here. Besides evi
dence from terrestrial systems as sumnarized by Chew (1974) and
Mattson and Addy (1975), studies of aquatic systems have also shown
stimulatory roles of consumers. Hargrave (1970) varied amphipod den
sity in his in situ microcosms and measured maximum primary produc
tion at natural consumer density. Cooper (1973) found similar
Figure 3.28. Uptake of Cd by the submerged macrophyte Najas guadal upens'is in flow-through systems (from
Cearley and Coleman 1973).
Figure 3.17. Effect of Cd on cell numbers of the green alga Scenedesmus
quadricauda in batch culture (from Klass et al. 1974).
The biological effects of Cd input to the artificial streams
were affected by season, successional state, and taxonomic affinity.
Prior to the addition of Cd the streams were all quite similar in
composition of periphyton, populations of invertebrates, and plant
growth. After Cd inputs of 5 or 10 pg*Ll began, the streams
demonstrated significant changes in response to the low Cd levels
tested (Giesy et al. 1979).
Algal populations in the treated channels were never as high as
those in control channels (Fig. 4.1). Significant treatment as well
as seasonal effects on algal pigment ratios were observed throughout
the Cd input, and, on a macroscopic basis, the different treatments
were visibly different in color. At least two algal species common
in the control channels were never found in the treated channels
during Cd input while other species formed luxuriant filamentous
blooms in the Cd streams.
The nonalgal portion of the periphyton was considered collec
tively as detritus and microbes. The biomass of this community was
significantly lower in the treated channels than in controls within 2
mo of initial Cd input, but within 6 mo significant differences in
this assemblage between treatments had disappeared (Fig. 4.2). At
all times during the study, the detrital biomass was about 5X as
great as the algal component individually.
At the end of 1 yr of continuous Cd dosing, macrophyte popula
tions were greatly reduced with respect to control populations. In
March 1977, average dry matter densities were: control, 39; 5 ppb Cd,
5; and 10 ppb Cd, 6 gvrT^. Cadmium input was suspended in the
Odum, H. T., and R. F. Pigeon (eds.). 1970. A tropical rain forest.
U.S. Atomic Energy Commission, NTIS, TID-24270(PRNC-138),
Odum, H. T., and R. C. Pinkerton. 1955. Time's speed regulator: The
optimum efficiency for maximum power output in physical and
biological systems. Am. Sci. 43:33143.
Odum, H. T., M. J. Lavine, F. C. Wang, M. A. Miller, J. F. Alexander,
and T. Butler. 1980. A manual for using energy analysis for
power plant siting. Final Report to the Nuclear Regulatory
Commission, Center for Wetlands, University of Florida,
Owen, D. F., and R. G. Wiegert. 1976. Do consumers maximize plant
fitness? Oikos 27:488-92.
Page, A. L., F. T. Bingham, and C. Nelson. 1972. Cadmium absorption
and growth of various plant species as influenced by solution
cadmium concentration. J. Environ. Qual. 1:288-91.
Petrick, A., H. J. Bennett, K. E. Starch, and R. C. Weisner. 1979.
The economics of by-product metals Pt. 2. U.S. Bur. Mines
Info. Cir. 8570. 10-14 pp.
Pickering, Q. H., and M. H. Gast. 1972. Acute and chronic toxicity
of cadmium to the fathead minnow (Pimephales promelas). J.
Fish. Res. Board Can. 29:1099-106.
Porter, K. G. 1975. Viable gut passage of gelatinous green algae
ingested by Daphnia. Verh. Internat. Verein. Limnol.
Ravera, 0., R. Gommes, and H. Muntau. 1974. Cadmium distribution in
aquatic environment and its effects on aquatic organisms. Pages
31730 j_n European colloquim problems of the contamination of
man and his environment by mercury and cadmium. Commission of
European Communities Conference, Luxenbourg, 35 July 1973.
Rosenau, J. C., G. L. Gaulkner, C. W. Hendry, and R. W. Hall. 1977.
Springs of Florida. Florida Geological Survey Bull No. 31
(revised). 461 pp.
Rzewuska, E., and A. Wernikowska-Ukleja. 1974. Research on the
influence of heavy metals on the development of Scenedesmus
quadricauda (Turp.) Breb. Pt. 1. Mercury. Pol. Arch. Hydro-
Sellars, W. D. 1965. Physical climatology. University of Chicago
Press, Chicago. 272 pp.
Spehar, F. L., E. N. Leonard, and D. L. DeFoe. 1978. Chronic
effects of cadmium and zinc mixtures on flagfish (Jordanel1 a
floridae). Trans. Am. Fish. Soc. 107:35460.
effect and was able to concentrate Cd from solution by a factor of
2000X. Of the microbial organisms tested, Bacillus cereus had the
greatest concentration factor with a value of 3870X at 10 ppm Cd in
Plants. A great number of Cd uptake studies have been made for
plants and algae. Two representative curves are shown in Figs.
3.27 and 3.28. The uptake of Cd was studied by Hart and Cook (1975)
for Chiorella p.yrenoidosa at a series of Cd concentrations (Fig.
3.27). Hyperbolic uptake was observed with the highest concentration
factor reported as 4500X. Other workers have found Cd concentration
by algae of 2000X for Anacystis nidulans (Katagiri 1975); 4000X-6700X
for marine diatoms (Kerfoot and Jacobs 1976); 80,000X for mixed algae
(Kumada et al. 1973); and 10,000X for marine phytoplankton (Knauer
and Martin 1973). Although these concentration factors are dependent
on water chemistry as well as reaction time (see Fig. 3.27), they
represent significant immobilization of Cd in biological systems.
Figure 3.28 presents an uptake curve for the aquatic macrophyte
Najas guadalupensis reported by Cearley and Coleman (1973), which is
representative of Cd uptake by plants at increasing metal concentra
tions. At a Cd concentration of 100 ppb in solution, a concentration
factor of 40,000X was measured. Giesy et al. (1979) reported Cd con
centrations >40,000X for roots of Juncus diffusissimus and 10,000X
for leaves in stream microcosms.
Animals. As with microbes and plants, Cd uptake by animals is a
hyperbolic function of Cd in solution. Figure 3.29 illustrates
steady state Cd levels reported by Spehar et al. (1978) for larval
stages of Hydropsyche betteni, a caddisfly, and Pteronarcys dorsata,
LIST OF TABLES viii
LIST OF FIGURES x
SECTION 1-INTRODUCTION 1
SECTION 2METHODS 3
Literature Review and Minimodels 3
Cadmium Streams 3
Site Description 4
Community Structure 6
System Responses 7
Cadmium Analysis 9
Other Studies 10
Silver Springs Metabolism and Consumer Populations 10
Study Site 10
Community Metabolism 12
Fish Counts 16
Snail Population Estimates .-.16
Silver Springs Consumer Microcosms 18
Experimental Design 18
Production Measurements 19
Snail Experiments 21
Figure 3.25. Model of toxicity effect on recycle showing stimula
tion of production (P) because of storage (Q) decay
and nutrient (N) recycle, a. Model; b. Representa
tive output. BASIC program used for simulations is
given in Table A.4.
. ..an .rnfflTV HP PI HR1DA
3 1 262 0867 6 729 9
Calvn^'d-1 was calculated as the energy requirement of these fish.
Using a TR of 151,724 S.E. CalCal-1 from Table 4.8 for primary
carnivores, the energy requirement of the fish was calculated as
10,317 S.E. Calm2,d1.
The stimulatory effect of mosquito fish on primary production of
0.49 g 02*m"2-hr"1 was multiplied by 12 hr*d_1 of productive time
and a conversion factor of 4 Cal*g 02-1 to give 23.52 Cal m_2*d''l.
Referring to Table 4.8 the TR of 2316 S.E. Cal*Calfor gross
productivity was used (recalling that the DO changes in the
microcosms more closely represented gross rather than net
productivity). These numbers were multiplied to give 54,472 S.E.
Cal*m2*d_1 as the feedback effect of mosquito fish. This stimulation
is about 5X greater than the calculated energy requirement of the
fish to the system. Within the variability and assumptions of these
calculations this difference may or may not be significant; however,
the numbers clearly indicate that the fish can return services to the
system in proportion to what they use.
The third controller tested in the microcosms was the toxic
metal Cd. An optimal concentration for maximum productivity was
approximately 0.031 yg Cd'L"1 resulting in an average stimula
tion of productivity equal to 0.49 g 02,m"2*hr1 (this is equal to the
stimulation by the optimal fish density). Applying the average flow
rates through the microcosms (457 cm3*s_1) and microcosm surface area
(0.539 m2), a Cd flow rate of 2.27 x 10"3 g cd*m"2*d_1 was calculated.
Using the TR for Cd calculated in Section 3 of 4.6 x 107 S.E.
Calg pure Cd-1, the energy cost for the Cd controller was 104,420
Table A.4. Computer model for Intercolor computer used to simulate
minimodel illustrated in Fig. 3.25.
10 PLOT 29,13
20 PLOT 12
25 PLOT 2, 253, 0, 0, 242, 0,191, 159, 191,159, 0, 0, 0, 255
55 TX=. 01
93 K5=. 1
95 K6=4. 9E-6
97 K7=. 05
880 IF TX>10 GOTO 999
890 GOTO 70
999 PLOT 29, 13
260 IF Q<0 THEN Q=0
262 IF N<0 THEN N=0
280 IF I=J GOTO 300
290 GOTO 220
310 IF T=ND GOTO 850
311 S=S+. 2
312 IF S<1 GOTO 210
314 PLOT 8
315 PRINT T, Q, N, P, R
320 PLOT 29, 18
330 PLOT 29,22
340 PLOT 2, T, Q, 255
350 PLOT 29, IS
300 GOTO 208
850 PLOT 29, 13
360 PLOT 2, TX+10, P+10, 255
364 PRINT TX, Q, N, P, R
870 TX=TX+. 5
BIOMASS OR METABOLISM UNITS
Q = P-R
P = K, JRQTK4T
Figure 3.24. Model of toxin effect on an organism including a
stimulatory function and an exponential toxic func
tion. a. Model; b. Representative output for two
toxicity levels. BASIC program used for simulations
is given in Table A.3.
The results of the Cd-streams study and the Silver Springs
microcosm study indicate the practicability of quantifying feedback
control action in aquatic systems. Energy values in equivalent units
can be used to summarize control cost and control effect for a whole
spectrum of controllers from herbivores to toxic chemicals. With
more research, tables of these control factors can be made along with
data over a range of controller densities such as is shown in Figs.
4.22 and 4.23 for Cd. All controllers could be cataloged in terms of
their energy cost and control effect. A book that summarized these
values would be a handbook for environmental engineersthose people
who actually engineer environmental systems to optimize a chosen
function. The human may maximize his control action by manipulating
a toxin or top consumer in an environmental system, resulting in a
chain reaction of control to obtain a desired end result.
The study of the mechanisms controlling environmental systems
is essential for understanding ecosystems and for managing them
rationally. The discovery of general principles of control spanning
many different types of systems may improve symbiotic relationships
between human civilization and the environment. The purpose of this
research is to develop a quantitative means to evaluate, compare, and
utilize controllers in environmental management and to illustrate the
approach with examples from aquatic ecosystems. In particular, con
sumer control at Silver Springs, Florida, was quantified and compared
to toxin control by the heavy metal cadmium (Cd) in stream micro
A "controller" is a chemical substance or biological component
that has the ability to divert, enhance, or stop energy flows that
are greater than its own energy content. Predators may regulate prey
populations while chemical substances may control the predators.
Small quantities of a controller may have strong feedback effects in
A theory proposed by Odum (1979) and the author is that control
action or "amplification" effect may be a function of the energy
"embodied" in the controller. Embodied energy is defined as the
total energy flow of a system necessary to form the controller
Cd strips were removed from the microcosms on August 19, air-dried,
and reweighed at the laboratory.
An energy and matter flow model of the artificial streams was
constructed first as a diagram using the energy circuit language of
Odum (1971, 1975). The model is of intermediate complexity, combin
ing storages of nutrients, algae, macrophytes, consumers, and detri
tus and their uptake of and response to Cd at different concentra
tions. Further details of the model are described in the results
The major biomass storages and their Cd content were monitored
throughout the 2-yr study and have been used directly to calibrate
the model when possible. However, few of the data were for average
levels throughout the microcosms, but rather were for concentrations
on replicable substrates. Thus, to calibrate the model to whole-
system averages, assumptions and extrapolations from a few measure
ments were made to other data.
Also, few of the rates were actually measured during the project
other than Cd uptake and release, system production and respiration,
and export; therefore, a considerable amount of parameterization was
done by simulating the model and comparing results to the actual mea
sured storages over time. Specific rates from the literature were
used when available.
Computer simulations were made in FORTRAN computer language
during the early stages and finished using BASIC language with an
Because of the thickness of the periphyton (>5 cm), and the
intensity of the metabolic activity within this community, N and C
represent the nitrogen and Cd concentrations within this layer and
are replenished from the stream flow of these elements by simple dif
fusion (Fig. 4.12). Nitrogen replenishment within the community is
entirely from microbial decomposition of detritus in this model.
Figure 4.13 is a diagram of the details of the algal community.
Remaining sunlight (Jr) interacts with nitrogen and algal biomass
to contribute to gross photosynthesis. A direct enhancement of pri
mary production by Cd was also included as a limiting-factor rela
tionship because the literature data indicated such an effect (Arndt-
Schulz Law). Cadmium is also absorbed from solution in a cycling-
receptor module with the surface area as the limiting substrate.
Cadmium is lost from the algae by depuration and particulate loss to
export, consumers, and detritus.
Cadmium toxicity to the algal component is modeled as a direct
interactive drain by water Cd concentration on algal biomass. Sun
light also acts on algal biomass through photorespiration, which may
have been important in the shallow Cd streams.
Macrophyte interactions are summarized in Fig. 4.14. All flows
are analogous to the algal flows described for Fig. 4.13 except that
no photorespiration mechanism was included in the respiration path
Figure 4.15 illustrates the aggregated consumer community in
this model stream ecosystem. Consumer biomass (Q4) feeds on algae,
macrophytes, and detritus-microbes, with some of the material assimi
lated and some lost directly to detritus. Cadmium is absorbed and
Table 2.2. Major components of water chemistry at Silver Springs,
Florida, as reported by United States Geological Survey
Alkalinity (as CaCOg)
Hardness (as CaCOg)
Dissolved sol ids
Total organic carbon
Fiqure 3.9. Summary model of qrazinq effect of Notropis minnows in
experiment microcosms discussed by Cooper (1973). a.
Overall model; b. Proposed density dependent growth
Cd IN SOLUTION (ppb)
Figure B.8. Diurnal oxygen change curves from April 29,
1976, for six experimental streams previously
receiving Cd inputs.
The artificial streams used to study Cd fate and effects are
located in Aiken County, South Carolina, on the Savannah River Plant,
which is operated by the United States Department of Energy. The
streams were built with funds provided by the Environmental Protec
tion Agency to study the fate of pollutants in natural water systems.
Previous work at this site has included studies of the fate of NTA
and mercury in stream ecosystems (Kania and Beyers 1974; Kania et al.
The six channels used for the Cd study measured 92 m long, 0.61
m wide, and 0.31 m deep, with head and tail pools 1.5 m long, 3 m
wide, and 0.9 m deep. The pools and channels were lined with
0.05-cm thick black polyvinyl chloride (PVC) film. Washed quartz
sand was distributed in the channels to a uniform depth of 5 cm, and
a 10-cm layer of natural streambed sediment was distributed in the
Water for the channels was taken from a deep well and mixed with
a hydrated lime slurry before being added to the systems. Major par
ameters of input water quality are listed in Table 2.1 and indicate
the soft, low organic carbon nature of the stream water. Flows were
maintained continuously at 95 L-min"1 and resulted in a water
depth of 20 cm in the channels. The mean water retention time and
current were 2 hr and 1.3 cm*s-1, respectively.
Water flow began on November 1, 1975, and the systems were
seeded from the control channels of a previous study (Kania et al.
1976) to rapidly establish biological communities known to be well
adapted to channel conditions. Two macrophytes, Juncus diffusissimus
Q5 L2Q32+KuQ22Jr+LbQ42+l4Q2CZ+l5Q3CZ+lpQ4CZ_kgQ52 (1~lECZ)_krQ5
(kX-L9 )Q2Q4+(kY-L9)Q3Q4+( l6l9 )Q5Q4l6Q5Q4
C5 = l3cc(l2Q32+L5Q3Cz)+kVCb(KuQ22jR+^Q2Cz)+kkQ52/2 (]q+c^)+1-DcD(LBQ42+1-pQ4cz)
-l1cE_lHcE (krQ5 ) l7cE (I-6Q5Q4) ~kTcE (kgQ52C 1-LeCz^ )
' v '
Figure 4.16. Detail of Cd-stream model showing configuration of detrital-
microbial segment of periphyton. Cadmium toxicity is expressed as
a negative interaction with nutrient regeneration.
These curves may be compared to the actual data illustrated in Figs.
4.1-4.3. Simulation results for overall stream production, respira
tion, and export are presented in Fig. 4.18. This figure may be com
pared with the actual data summarized in Fig. 4.4.
After the control model simulation was considered satisfactory,
simulations of other Cd concentrations began. Parameters were
adjusted to give realistic toxic responses for the biological com
ponents actually measured in the stream study.
Results of simulations of the effect of 5 and 10 ppb Cd intro
duced into stream microcosms are given in Figs. 4.19-4.21. Figure
4.19 illustrates the effect of 5 and 10 ppb Cd on biomass of the
major storages in the stream model.
Cadmium concentrations in all of the biotic components were
monitored in the stream model simulations. Yearly averages for bound
Cd at a water concentration of 5 ppb were between 26 and 38 ppm. At
a water Cd concentration of 10 ppb, Cd levels in biota were predicted
between 54 and 78 ppm. These uptake values are in good agreement
with the actual values measured in the Cd streams.
Figure 4.20 illustrates the effect of 5 and 10 ppb Cd on the
gross production, community respiration, and export of the Cd streams
model. While the toxic effects of Cd in the model on individual com
ponents were not identical to the actual measurements, the integra
tive parameters shown in Fig. 4.20 compare favorably with the model
simulations and the actual data (see Fig. 4.4).
through convergence of webs or concentrating factors. In systems
selected for maximum energy flow, controllers may be used to manipu
late productive processes through positive amplification. The theory
suggests that controllers will have an energy consumption from the
system that is proportional to their value as a stimulant to produc
tivity and that natural selective processes will eliminate items that
use more energy than they stimulate. In an immature system, two
values of a controller, i.e., the embodied energy and the amplifier
effect, might be widely different, but in an adapted system they must
balance or a more productive arrangement will be selected. Thus, an
adapted system requires consumers and may be able to use toxins.
In this study the controlling action of Cd is quantified using
an energy-mass model calibrated from stream microcosms. In addition,
the controlling role of Cd is summarized from other published
studies, and a general toxicity function is presented. The subject
of control by consumer organisms was studied during a 2-yr period at
Silver Springs. In addition to a whole-system experiment made pos
sible by alterations in the river ecosystem and a previous system
study by Odum (1957), controlled experiments of consumer manipula
tions were made in submerged microcosms in the river channel. The
generality of control in ecosystems is demonstrated through simple
computer models and a single microcosm experiment with Cd as the
Cd CONCENTRATION (ppb)
Figure 4.5. Summary graph of system-level parameters measured
in artificial streams receiving continuous Cd in
puts. Points represent 1-yr averages for two
replicate streams at each treatment (gdw is grams
Figure 3.2. Generalized trophic level model used to evaluate embodied
energy in consumers. Total outside energies are added in
embodied energy units and divided by actual energies of
consumers to get energy transformation ratios.
Table A.2. Computer model for Intercolor computer used to simulate
minimodel illustrated in Fig. 3.23.
10 PLOT 29, IS
20 PLOT 12
S0 TX=. 1
90 Kl=. 001
110 K2=. 05
260 IF Q<0 THEN 0=0
280 IF I=J GOTO 200
290 GOTO 220
210 IF T=ND GOTO 850
215 GOTO 210
220 PLOT 29,18
220 PLOT 29,22
240 PLOT 2, T, Q/15, 255
250 PLOT 29, 18
260 PLOT 2, T, P, 255
270 PLOT 29,17
280 PLOT 2, T, JX, 255
800 GOTO 210
850 PLOT 29, 18
860 PLOT 2, TX*10, Q/10, 255
864 PRINT TX, 0, P, R, JX
870 TX=TX+. 5
880 IF TX>10 GOTO 999
890 GOTO 200
999 PLOT 29,18
My greatest appreciation goes to Dr. H. T. Odum for 11 yr of
stimulating interaction in the principles of systems ecology and, in
particular, for the past 3 yr of graduate study at the University of
Florida. I would also like to thank the other members of my commit
tee: Dr. P. L. Brezonik, Dr. J. P. Giesy, Dr. F. Nordlie, and Dr. T.
Crisman, who all gave me valuable guidance through class lectures,
field excursions, and work supervision.
The cadmium streams study was made possible through an inter
agency agreement (IAG-D6-0369-1) between the Environmental Protection
Agency (EPA) and the Department of Energy, with Dr. Harvey Holmes as
project officer. In addition to the fine staff who worked on this
project, my special thanks go to Dr. Henry Kania, the spiritual
leader of the streams project and myself for many years.
Thanks also go to Dr. Larry Burns, who served as project officer
on EPA Grant No. R-806080, "Energy Model and Analysis of a Cadmium
Stream with a Study Correlating Embodied Energy and Toxicity Effect,"
under which a portion of this research was completed.
I would also like to thank Mr. Tom Cavanaugh, Mr. Jim Lowry, and
many other employees of the American Broadcasting Corporation for the
use of facilities at Silver Springs as well as information concerning
the history of the biological communities.
Embodied EnergyController Effect Relation 88
SECTION 4-RESULTS 90
Cadmium Streams 90
Biological Effects 91
Silver Springs 99
System Metabolism 99
Fish Populations 99
Snail Populations 101
Silver Springs Consumer Microcosms 103
Successional Development 103
Herbivore ControlSnails 103
Carnivore ControlMosquito Fish 105
Toxin ControlCd 110
Stream Model Simulations 113
General Model 113
Control Simulation 122
Toxin Effect 125
Model Experimentation 130
Embodied Energy and Control 130
Quality Factors 130
Energy Qua! ityEnergy Effect Correlation 133
Silver Springs 137
Figure 3.22a represents an accelerating effect of Cd concentration on
growth reduction presumably resulting from a drain on the structure
remaining. Figure 3.22b illustrates a decreasing effect with concen
tration indicating a saturation of the toxic action at elevated con
centrations. Figure 3.22c may be the most general in that the other
two are special cases. This is the typical Arndt-Schulz effect curve
described for all poisons by Lamanna and Mallette (1953). Whether
these low-level, stimulatory effects are real or statistical arti
facts cannot be proven in this review; however, the consistency of
this stimulatory effect warrants its inclusion in the Cd-toxicity
models that follow.
Models. If general models of Cd effect are recognized, data
from diverse experiments may be organized in terms of model param
eters and more precise comparisons can be made. Although only
species-effect data have been reviewed for Cd toxicity, the models
presented are descriptive of trophic levels, also. In Section 4,
these trophic-level models are combined in an ecosystem model cali
brated with data from the Cd streams study of Giesy et al. (1979).
Numerous mechanisms of Cd toxicity have been suggested for par
ticular organisms and groups of species. As reviewed by Hammons et
al. (1978), most of these mechanisms result from inactivation of
enzymes by binding Cd with sulfhydryl groups of proteins interfering
with photosynthetic and respiratory pathways of energy transforma
tion. Although no known requirement for Cd exists in living systems
(Hiatt and Huff 1975), the stimulatory responses measured at low Cd
concentrations must result from some beneficial mechanisms. Three
models of Cd action are presented to generalize these experimental
C = KlCb+KmCc+KoCd+KtCeKgQ52(1-LeCz)+L1Ce-Kn(Cz-C/\)
- (KkQ52/3+KjQ42/3+kiQ32/3+KhQ22/3) (iq+^
Figure 4.12. Detail of nitrogen and Cd flows and storages in the
thick periphyton layer of the Cd streams. Exchanges are
indicated as simple diffusion with open-water concentra
tions and release by biological organisms.
results for grazing by an herbivorous minnow. Flint and Goldman
(1975) report stimulation of productivity by crayfish grazers at den
sities comparable to natural populations. McKellar and Hobro (1976)
observed the stimulation of primary production by zooplankton grazing
in large plastic enclosures in the Baltic Sea.
In this study at Silver Springs stimulation of primary produc
tion with an aquatic herbivore was found. At snail densities between
22 and 44 g'rrT^, optimal productivity was measured. These den
sities compare favorably to the density of 42 g*m"^ measured in
one portion of the natural river ecosystem.
Perhaps of greater interest is the discovery that predaceous
consumers such as mosquito fish could not only enhance productivity
but could also lower it compared to controls (Fig. 4.9). This obser
vation may be explained in terms of high fish predation lowering her
bivores to suboptimal levels, resulting in lowered productivity.
Thus mosquito fish may also have an optimal density for maximum sys
Thus, the consumer-control hypothesis may span all trophic
levels; while energy flows up from the lower levels, control may flow
down from the upper levels. Each controller must be regulated by the
next controller up the hierarchy scale. Energy from the ecosystem
will not reach those consumers that do not optimize the density of
their prey because of reduced system productivity, and thus selection
by the maximum power criterion may apply at all levels.
Cadmium as a Consumer
The final experiment using the Silver Springs microcosms
served as a symbolic link between two different related parts of this
CADMIUM EFFECT RATIO (S.E. Cal.-g CcT1 xIO9)
Figure 4.23. Predicted correlation between Cd transformation ratios and Cd effect ratio
for algae, macrophytes, consumers, and detritus-microbes. Values are calcu
lated from 1-yr averages of simulation data from Cd-streams model.
RATE OR STORAGE
TOXIN CONCENTRATION TOXIN CONCENTRATION
Figure 3.22. General curves relating toxin concentration to toxin
effect, a. Accelerating effect; b. Exponential effect;
c. General curve with optimum concentration.
NET GROWTH (relative scale)
Figure 3.15. Effect of Cd on net growth of six microorganisms in batch culture
(from Doyle et al. 1975).
The calibrated Cd-streams model allows experimentation with
exogenous controls other than those actually tested in South Caro
lina. For example, the stream model allows a prediction of the
effects of other Cd concentrations on stream energy flow. Figure
4.21 illustrates the effect of a series of Cd concentrations on gross
production, respiration, and export predicted by model simulations.
As designed in Figs. 4.11-4.16, this stream model predicts enhance
ment of stream metabolism at a Cd concentration of 0.5 ppb over a
1-yr period of continuous input.
Embodied Energy and Control
The calibrated Cd-streams model also facilitates calculation of
quality factors for analysis of the amplifier effect by toxins on
system energy flow.
The entire energy income of the Cd streams must be known in
order to calculate ratios of energy transformation (quality factors).
If we consider the situation in natural streams, we can appreciate
the effect of energy concentration in the maintenance of a stream.
Not only is energy received directly from the sun, but energy is also
concentrated from indirect sources such as runoff from the watershed,
which creates the stream flow and structure. In the Cd streams this
flow and structure were added to the incoming sunlight from human
energies and fossil fuel work. These additional energies can only be
estimated, and although errors in their calculation may affect the
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DISSOLVED OXYGEN (mg-L-1)
1000 1200 1600
TIME OF DAY (H)
1000 1200 1600
TIME OF DAY (H)
Figure C.4. Diurnal oxygen data and analysis for Silver Springs on
March 7, 1979.
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