ECOTOXICOLOGY: A Comprehensive Treatment - Chapter 2 pptx

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Part II
Organismal Ecotoxicology
Conventionalities are as bad as impurities.
Uncommon Learning (H.D. Thoreau 1851)
Organismal ecotoxicology explores toxicant effects to individuals and, where possible, links them to
effects to populations and communities. Such exploration has been at the center of ecotoxicology and
its predecessors (aquatic, wildlife, and environmental toxicology) since their inceptions. Because of
our proclivity toward study of toxicant effects to the soma—the body of the individual organism—
much in this section should be comfortably familiar to the professional ecotoxicologist or advanced
student. What might not be as familiar will be the focus on fundamental principles and linkage of
these effects to those at higher levels of biological organization.
The preoccupation of ecotoxicologists with the soma emerges from the historical foundations of
our new science. It is obvious during even a cursory examination of the most popular ecotoxicology
textbooks (e.g., Cockerham and Shane 1994, Connell et al. 1999, Landis and Yu 1995, Newman
1998, Walker et al. 2001) that many basic concepts and techniques blended into ecotoxicology
come from mammalian toxicology, a field with a justifiable emphasis on the individual. Still other
concepts and techniques come from classic autecology. Used with balance and insight, this offers
several advantages to the field. Ecotoxicologists can draw deeply from the mechanistic knowledge
base of classic toxicology, a field focused on individuals. This knowledge is directly useful for
charismatic, endangered, or threatened species that are protected by prohibiting the taking of even a
single individual. It also provides a firm base at one level of biological organization from which to
extend scientific insight upward to the next.
The mechanistic andtechnological richness of classic toxicology and autecology comes at a price.
The paradigms around which phenomena are explored by ecotoxicologists are often those associ-
ated with the soma. Exploration of other important ecotoxicological phenomena are unintentionally
addressed with less intensity or quietly dismissed as secondary. The rich technology associated with
organismal toxicology naturally draws practitioners to these tools. The result is a rapid enrichment
of the field: an enrichment that also maintains the present imbalance. Resolution of this incongru-
ity requires application of concepts and technology in a way that does not foster any unintentional
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12 Ecotoxicology: A Comprehensive Treatment
neglect of higher levels of organization and with the intent of producing predictive insight about
phenomena at higher levels of organization. That is the intent of this section.
REFERENCES
Cockerham, L.G., and Shane, B.S., Basic Environmental Toxicology, CRC Press, Boca Raton, FL, 1994.
Connell, D., Lam, P., Richardson, B., and Wu, R., Introduction to Ecotoxicology, Blackwell Science Ltd.,
Oxford, UK, 1999.
Landis, W.G., and Yu, M H., Introduction to Environmental Toxicology, CRC Press, Boca Raton, FL, 1995.
Newman, M.C., Fundamentals of Ecotoxicology, CRC Press/Lewis, Boca Raton, FL, 1998.
Thorean, H.D., Uncommon Learning, Bickman, M. (ed.), Houghton, Mifflin, Co., Boston, 1851.
Walker, C.H., Hopkin, S.P., Sibly, R.M., and Peakall, D.B., Principles of Ecotoxicology, Taylor & Francis,
New York, 2001.
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2
The Organismal
Ecotoxicology Context
2.1 OVERVIEW
The science of ecotoxicology has grown rapidly in 30 years and has brought together a vast body of
facts around several explanatory systems. Explanatory systems were borrowed in necessary haste
from mammalian toxicology and ecology. The immediacy of our environmental problems required
this haste. Required now is coherence among the clusters of explanatory hypotheses that are rapidly
coalescing at each level of biological organization. Together, these paradigms form the foundation
for ecotoxicological theory.
1
If these paradigms are not made mutually supportive, the foundation
of ecotoxicology will not be adequate to support further knowledge accumulation and organization.
The field will break into semi-isolated scientific disciplines.
Conceptual consilience is not an intellectual nicety: it is vital to the health of any science. Without

consistency among theories and facts, there is no way for the ecotoxicologist to choose from among
many the explanation providing the best foundation for predicting pollutant effects.
The requirement of consistency will be appreciated if one realizes that a self-contradictory system is
uninformative. It is so because any conclusion we please can be derived from it. Thus no statement is
singled out, either as incompatible or as derivative since all are derivable. A consistent system, on the
other hand, divides the set of all possible statements into two: those which it contradicts and those with
which it is compatible . This is why consistency is the most general requirement for a [scientific]
system if it is to be of any use at all.
(Popper 1959)
As articulated by Popper, sciences lacking self-consistency are not viable. Ecotoxicological
explanations need to be consistent among all levels of organization or the science of ecotoxicology
will eventually fail to be useful. Beyond this, efforts spent finding consistency have another desirable
effect relative to scientific logic. It can identify common causes for phenomena described at different
levels of biological organization. The identification of a common cause allows the overall number
of theories to be reduced. Why have two distinct theories to explain the same thing? The parsimony
resulting from theory reduction—that is, intertheoretical reduction (Rosenberg 2000)—enhances
any science and is particularly warranted in ecological sciences (Loehle 1988).
A final reason exists for the emphasis on integrating explanatory systems from different levels
of biological organization. Not doing so allows the current condition to remain in which an ecotox-
icologist trying to describe and solve a particular environmental problem may present and defend
findings based on contradictory explanations. This diminishes the legal defensibility of arguments
1
Definitions of Rosenberg (2000) are being used in this discussion. A set of explanatory principles or paradigms comprise
the established scientific theory of a discipline, for example, evolutionary theory contains many explanatory principles such
as genetic drift or natural selection. The paradigms have withstood rigorous testing and currently provide the best causal
explanation of natural phenomena, for example, evolution theory explains genetic change in a population exposed to a
toxicant.
13
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14 Ecotoxicology: A Comprehensive Treatment
calling for costly remediation. It also increases the risk of pathological science, science practiced
with an excess loss of objectivity (Langmuir 1989, Rousseau 1992).
It is a fault which can be observed in most disputes, that, truth being mid-way between the two opinions
that are held, each side departs the further from it the greater his passion for contradiction.
(Descartes, translated by Sutcliffe 1968)
Integration, combined with differentiation, is a major theme here because it fosters the identifica-
tion of causal mechanisms that are consistent among levels of organization, is logically necessary in
any healthy science, fosters resolution of environmental issues, and decreases the tendency toward
pathological science.
2.2 ORGANISMAL ECOTOXICOLOGY DEFINED
2.2.1 W
HAT IS ORGANISMAL ECOTOXICOLOGY?
Every species of plant is a law unto itself, the distribution of which in space depends upon its individual
peculiarities of migration and environmental requirements. It grows in the company with any other
species of similar environmental requirements, irrespective of their normal associational affiliations.
(Gleason 1926)
The scope of ecotoxicology is so necessarily encompassing that an ecotoxicologist can study
fate or effect of toxicants from the molecular to the biospheric scales. This book attempts to
discuss this wide range of topics. The focus of attention in this particular section is organismal
ecotoxicology, the science of contaminants in the biosphere and their direct effects on individual
organisms.
The prominence of the organismal context is so long-standing and familiar to ecologists that it
has its own name, autecology. Autecology is the study of the individual organism or species, and its
relationships to its physical, chemical, and biological environment. The quote above from Gleason’s
classic paper articulates the autecological framework.
The boundaries of autecology are often vague. Since its origins, autecology has been described
as either distinct from (e.g., Emmel 1973) or synonymous with (e.g., Reid 1961) population ecology.
In reality, it overlaps with population ecology but tends to characteristically emphasize species
requirements, physiological tolerances, means of adaptation, and life history traits, and how these

influence success or failure in certain environs. It emphasizes the soma and how it manages to
survive. For example, a wildlife manager concerned with a specific game bird species might take an
autecological vantage to managing that particular species. Another example of an autecological topic
might be how the physiological tolerances of an estuarine crab relative to salinity and temperature
influence its spatial distribution within an estuary. Astudy by Costlow et al. (1960) is a classic one of
this sort (Box 2.1) in which tests of the physiological limits of individuals were used to suggest that
salinity confines the spatial distribution of an estuarine crab. The emphasis is plainly on qualities of
individuals, not complex interactions among species or even the interactions among individuals in
populations of this crab species.
2
Several fundamental laws of ecology emerge from this context. Liebig’s law of the minimum
(Liebig 1840), first formulated to explain how nutrients limit plant standing crop, states that the factor
in the shortest supply of all required factors will limit the number or amount of individuals that a
2
In contrast to autecology, the subdiscipline of ecology focused on the integrated interactions of groups of individuals
within an environment is called synecology. Conventional topics of synecology are discussed principally in the last sections
of this book. The population ecotoxicology section is the boundary between autecology and synecology, and covers a blend
of autecology with some synecology.
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The Organismal Ecotoxicology Context 15
Box 2.1 Autecology of a Crab: Physiological Tolerances Determine Adult
Distribution
Costlow et al. (1960) reared larvae of the estuarine crab, Sesarma cinereum, at different combin-
ations of salinity and temperature, hoping to gather enough information to explain the observed
distribution of adult crabs in estuaries. The assumption was simple: the physiological tolerances
of the larval stages, as reflected in survival rates, will determine the most likely part of the estu-
ary in which the larvae will survive to become adults.
Salinity stronglyinfluenced survival anddevelopment timefor alllarval stages. Forexample,
the first zoea withstood higher salinities much better than lower salinities (Figure 2.1). Eggs

hatched at all tested salinity and temperature combinations. However, close to 100% mortality
occurred at low (<12.5‰) and high (>31.1‰) salinities for most larval stages. This suggested
that those larvae of any stage that were brought into intermediate salinity (and temperature)
conditions would have the highest chances of survival. Those hatching and staying in the low-
est or highest salinity waters would have the poorest survival probability. The optimum salinity
and temperature for each larval stage were the following:
Optimal Optimal
Larval Stage Salinity (‰) Temperature (
◦
C)
Zoeal Stage 1 27.9 23.5
Zoeal Stage 2 12.4 25.0
Zoeal Stage 3 24.1 26.0
Zoeal Stage 4 No maximum or
minimum
Megalops No maximum or
minimum
Zoeal Stage 1
Megalops
Zoeal Stage 4
Zoeal Stage 3
20
35
30
5
25
Salinity (parts per thousand)
15
10
15

20
25
30 35
40
Temperature (°C)
The shaded area is that
in which mortality is
approximately 25% or less
Zoeal Stage 2
FIGURE 2.1 Salinity and temperature tolerances
of Sesarma cinereum larvae. The 25% mortality
contours were arbitrarily chosen to show the differ-
ences in tolerances among stages. (Modified from
Figures 8–12 of Costlow et al. 1960 and larval
drawings rendered from Figures 1–5 in Costlow and
Bookhout 1960.)
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16 Ecotoxicology: A Comprehensive Treatment
In contrast to the first and third zoea, the second zoea had high tolerances of salinity
and temperature. The first and second zoea had best survival at 21–31
◦
C and 23–28‰. The
last zoeal stage showed an increase in temperature tolerance (to 35
◦
C) and a salinity tolerance
down to 3‰. The megalops, the stage reached just before settling to the bottom, showed wide
tolerances. The authors concluded that completion of this crab’s life cycle to the adult depended
primarily on the fourth zoea and that “the survival and molting to the megalops can only occur
in estuarine waters.” Any earlier stage larvae that were transported by water movements outside

of the estuarine conditions had very low probabilities of producing megalops. Survival was less
dependent on temperature or salinity once the megalops stage was reached. So, the tolerances
of the larval stages determined the estuarine region in which the life cycle of this crab will
be successfully completed. The weak links in the life cycle were the earlier larval stages.
If the fourth zoeal larvae emerged under the appropriate salinity–temperature conditions, the
relatively tolerant megalops would be produced, resulting in adults in that particular part of
the estuary.
particular habitat can sustain. As an example, phosphorus might limit the standing crop of a nuisance
blue-green algalspecies ina freshwaterlake and, based on Liebig’slaw, lakemanagers mightfocus on
controlling phosphorus input to the lake. Shelford’s law of tolerances (the tolerance of individuals of
a species over one or more environmental gradients determines the species’geographical distribution
or abundance) (Shelford 1911, 1913) is another such law that is neatly illustrated by the Costlow
et al. (1960) study.
The ecological niche concept was formulated originally with emphasis on individual tolerances
and requirements, and only later was enlarged to include biotic factors. In fact, the niche concept
theorizes that the organism occupies a realized niche in the presence of other species that is only a
portion of itsfundamental niche asdefined by its organismal tolerancesand requirements.As a classic
example, the realized niche of the intertidal barnacle, Chthamalus stellatus, is strongly influenced
by desiccation at one extreme and interspecific competition for space with Balanus balanoides at
the other (Connell 1961).
In ecotoxicology, an autecological study might be conducted of the effects of a pollutant on
individuals of a protected or threatened species. An autecological approach might also be used if
synecological aspects of a species’ niche occupation were thought to be unimportant or secondary.
Such an approach isalso taken reluctantly if there was an absence of sound synecologicalinformation
available relative to contamination.
Much of ecotoxicology is done within an autecological context and is justified by the indisputable
success of classic autecology (Calow and Sibly 1990). As successful as this approach might be
for many situations, the autecological approach is often applied in ecotoxicology for situations in
which a moment of introspection might reveal that crucial synecological factors are unjustifiably
ignored.

3
Reflecting the stage of ecology almost half a century ago, Costlow et al. (1960) described how the
physicochemical tolerances of a crab species contributed to its distribution in the coastal systems.
Twenty-five years later, when the understanding of contaminant effects became more and more
essential, they approached the ecotoxicological consequences of drilling fluid discharge in the same
way, implying whether populations would remain viable based on acute assays on the notionally
most sensitive stages of a species’ life cycle (Box 2.2). This approach drew on a well-established
autecological approach and, in this case, produced a reasonable conclusion. They also adopted,
with minimal adaptation, a technological paradigm from mammaliam toxicology—the LC50/LD50
3
Staying with a coastal marine theme, see Harger (1972) for further discussion of the importance of species interactions
in determining intertidal species distributions.
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The Organismal Ecotoxicology Context 17
Box 2.2 Crab Autecotoxicology: Do Chromium Tolerances of Larvae Determine
Adult Fate?
Twenty-four years after the study described in Box 2.1, these researchers (Bookhout et al. 1984)
again described crab larval survival relative to environmental conditions. In keeping with the
emerging concern about anthropogenic chemicals, they focused on a pollutant this time.
4
The
intent was very similarto that of their first paper—to determine the tolerancesof the larval stages
to an environmental quality and, in doing so, to predict the likelihood of life cycle completion
in the presence of a specified intensity of that quality.
They studied chromium used in drilling fluids to thin mud as it becomes dense. Added as
ferrochrome or chrome lignosulfonate, chromium was discharged during and after the drilling.
At the time of this study, there was little information on whether its use was harmful to mar-
ine species. To explore the potential hazard, Bookhout et al. (1984) exposed decapod larva to
different concentrations of hexavalent chromium (as Na

2
CrO
4
). Results for mud crab, Rhithro-
panopeus harrisii, larvae are described here. Figure 2.2 summarizes the cumulative mortality
experienced at different larval stages exposed to 0–58 µg/L of sodium chromate. Sodium chro-
mate concentrations from 7 to 29 µg/L were considered to be sublethal concentrations because
10% or more of exposed larvae reached the first crab stage. The lethal range was above 29 µg/L.
The LC50 for the complete hatch → zoea → first crab life stages was 13.7 µg/L.
5
After integrating this information with knowledge about drilling fluid distributions around
points of discharge, the authors concluded that “it is probable that Cr in drilling fluids, whether
Cr
3+
or Cr
6+
, is notlikely to reducethe populationof crab larvae and otherplanktonic organisms
in the area around oil wells except possibly in the immediate vicinity of the discharge pipes.”
Implied from these acute lethality tests on individual larvae was that the persistence of the mud
crabs population was not jeopardized, except in the immediate vicinity of a discharge. This
reasoning was adapted from that used to define the fundamental niche, that is, application of the
law of tolerances to predict the habitat that a species could occupy. However, other aspects of
the niche concept, such as interspecies competition, predation, and disease, were ignored. This
expedient neglect seems understandable in this particular application but is not always justified.
58 µg/L
46
µ
g/L
41
µ

g/
L
29
µ
g/
L
15
µ
g/
L
7
µ
g/
L
100
0
25
75
Mud crab larval stage
1
2
Zoea
3
4
Megalops
Cumulative mortality (%)
50

1
µ

g/
L
0
µ
g/
L
FIGURE 2.2 Cumulative mortality of mud crab
larvae resulting from hexavalent chromium
exposure. (Modified from Figure 4 in Bookhout
et al. 1984.)
4
The research described in Box 2.1 was published 2 years prior to Rachel Carson’s watershed book, Silent Spring (Carson
1962). As evidenced by the shift in Costlow et al.’s research, Carson’s book mandated that our research efforts become more
focused on ecotoxicological questions.
5
Note that this last metric, the LC50, was borrowed from the mammalian toxicology literature to measure toxic effects
here but was absent in the temperature–salinity study described in Box 2.1.
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18 Ecotoxicology: A Comprehensive Treatment
approach. The approach taken by these authors and many others dominates ecotoxicology to this day.
(See Chapter 9 for details.) It is sufficient in many cases or useful in others for quickly identifying
gross problems associated with contamination. Despite its utility in such cases, this autecotoxicolo-
gical approach is insufficient in many others and a synecotoxicological context is needed. The key
to successful prediction of ecotoxicological consequences is being able to accurately discriminate
between situations requiring autecological or synecological vantages, and being able to integrate
information from both vantages into reliable predictions of exposure consequences.
2.3 THE VALUE OF ORGANISMAL ECOTOXICOLOGY
VANTAGE
If the modes of action of toxicants are better understood, we could more accurately predict their effects

as pollutants; much knowledge already exists in medical sciences, and could be transferred.
(Sprague 1971)
Although this discussion may appear hostile to single species toxicity testing efforts, it is not intended
to be. Single species tests are exceedingly useful and are presently the major and only reliable means
of estimating probable damage from anthropogenic stress. Furthermore, a substantial majority, perhaps
everyone in this meeting is certainly aware of the need for community and system level toxicity testing.
How then does one account for the difference between awareness and performance?
(Cairns 1984)
Just as autecology is an essential component of ecology, organismal ecotoxicology—
autecotoxicology, if you will—is an essential component of ecotoxicology. Unfortunately, as
exemplified in the quote by Cairns above, organismal ecotoxicology tends to overshadow equally
crucial investigative vantages. In the remainder of this chapter, the many appropriate and essential
applications of organismal ecotoxicology will be highlighted.
2.3.1 TRACTABILITY AND DISCRETENESS
Organismal effects are generally the most discrete and tractable of ecotoxicological effects. Few
ecotoxicologists would disagree with this statement. After agreeing, a good number of ecotoxico-
logists would immediately identify this truism as a sad statement about the field, or point out that
this condition may simply be a matter of the historical amounts of effort and thought that have gone
into autecotoxicology and synecotoxicology. Here, the follow-up to this statement will simply be
to demonstrate the important advantages of drawing on our comprehensive knowledge of organis-
mal effects. The ease with which organismal effects or exposure can be assessed will be described
first. Next, the relatively effective extrapolation among individuals will be detailed. Organismal
information also contributes to our abilities to do reasoned extrapolations of effect to populations
and communities, and to predict toxicant transfer within communities.
2.3.2 INFERRING EFFECTS TO OR EXPOSURE OF ORGANISMS WITH
SUBORGANISMAL METRICS
Sprague, as quoted above, stated correctly that knowledge of suborganismal modes of action greatly
improves predictions of toxicant effects to individuals. A current example is endocrine system mod-
ulation by xenobiotics. Our newfound understanding of this mode of action for diverse classes of
xenobiotics, such as 17β-estradiol from oral contraceptives, 4-nonylphenols, and polychlorinated

biphenyls (PCB), improves prediction of similar effects of new chemicals or from new sources of
existing xenobiotics (Brown et al. 2001, Hale and La Guardia 2002, Schultz 2003). Knowledge of the
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The Organismal Ecotoxicology Context 19
suborganismal mode of action also provides a means by which diverse phenomena can be linked by a
common thread. As an example, Bard (2000) opined that multixenobiotic resistance in aquatic organ-
isms can be explored in the context of the multidrug resistance phenomena. The important insight
is that aquatic toxicologists could greatly advance their understanding of multixenobiotic resistance
in exposed populations by exploring the extensive literature on the role of P-glycoprotein overex-
pression in determining antitumor drug resistance of cancer cells. Transmembrane P-glycoproteins
tend to inhibit the transport of xenobiotics into cells, reducing the concentration of xenobiotics at
intracellular sites of action. The same is true whether the xenobiotic is a cancer drug or a contamin-
ant. Environmental xenobiotic resistance and anticancer drug resistance share a common theme of
adaptation by P-glycoprotein overexpression.
Suborganismal qualities also provide evidence of contaminant exposure or effects. As a sur-
prising example, mesopelagic fish sampled at 300–1500-m depth in the open Atlantic Ocean show
evidence of exposure to aryl hydrocarbon receptor antagonists, e.g., polynuclear aromatic hydro-
carbons (PAHs) and coplanar-halogenated aromatic hydrocarbons (Stegemen et al. 2001). Elevated
cytochrome P450 1A also suggests exposure at considerable distance from coastal sources of aryl
hydrocarbon receptor antagonists.
2.3.3 EXTRAPOLATING AMONG INDIVIDUALS:SPECIES,SIZE,SEX,
AND
OTHER KEY QUALITIES
Often predictions require extrapolation from data in hand to some less well-defined situation.
6
Suter (1998) describes two typical examples: extrapolation from LC50 values of Salmoniformes
to those for Perciformes, and prediction of carbamate pesticide LD50 based on a test species weight.
Ellersieck et al. (2003) provide a computational means for extrapolation of toxicant effects among
species. Although challenging and error prone, interpolation among individuals within a species

is perhaps the most credible of ecotoxicological interpolations. As an example, Newman (1995)
describes interpolation among mosquitofish sexes, genotypes, and sizes relative to survival during
acute mercury exposure.
2.3.4 I
NFERRING POPULATION EFFECTS FROM
ORGANISMAL EFFECTS
Sound inference about population effects is possible based on effects on individuals as has already
been discussed in our treatment of autecology. The population ecotoxicology section of this book
also explores many instances of such reasoning. These instances can be rendered as the following
general statements:
Population Genetics. (1) Genotypic and phenotypic qualities of individuals sampled from a
study population can be used to document population consequences of toxicant exposure. (2) Tox-
icants can influence the germ line of a population and, in so doing, influence the phenotypes present
in the population. (3) Differences in individual genotypes’ fitnesses in critical life stages can be used
to suggest key selection components acted on by toxicants.
Population Demographics. (1) Vital rates derived by sampling individuals from populations
can be used to document current or to project future conditions of a population. These vital rates
include rates of mortality, growth, natality, and migration. (2) Toxicants that lower an individual’s
fitness can influence the demographics of an exposed population.
Metapopulation Biology. (1) Differences in vital rates of individuals occupying habitat patches
that differ in their capacity to maintain the species can produce differences in metapopulation
6
See Suter (1998) for a general discussion of ecotoxicological extrapolation.
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20 Ecotoxicology: A Comprehensive Treatment
dynamics and persistence. (2) Spatial distributions of individuals relative to the distribution of
toxicant in habitat patches will influence metapopulation dynamics and vitality.
Epidemiology. (1) Disease prevalence, incidence, and distribution in a population can be
defined by measuring disease state in sampled individuals. (2) Causal knowledge derived from the

suborganismal or organismal levels reinforce epidemiological inferences.
Life History. (1) In the presence of phenotypic plasticity, an organism will experience a shift
in its life history traits if stressed. Ideally, such a trade-off in life history traits will optimize the
individual’s Darwinian fitness under the environmental conditions it finds itself. (2) Toxicants can
change the life history traits of individuals in predictable ways and, in so doing, also influence
the population demographics of exposed populations. (3) Phenotypic expression by individuals can
involve reaction norms or polyphenisms.
It is also true that the abundance of individual-based data tempts intelligent and well-intended
ecotoxicologists to make flawed inferences about population consequences from individual-based
effects data. As an important example, Newman and Unger (2003) identify the weakest link incon-
gruity: the inappropriate prediction of the most sensitive quality relative to population persistence
based on the most sensitive life stage of an individual. Often, toxicity testing is done for all life
stages of a species and the most sensitive life stage is identified as that stage with the lowest NOEC
or LC50. The incorrect extension of such an approach is to falsely infer from this that the most
sensitive life stage relative to individual fitness (i.e., survival, growth, or reproduction) is also the
most crucial or sensitive relative to population persistence or vitality. Although there are cases in
which this approach is adequate, it would be inconsistent with the foundation concepts of popula-
tion ecology (Hopkin 1993) to assume that it is always adequate. It is demonstrably false in some
cases (e.g., Kammenga et al. 1996, Petersen and Petersen 1988). Another important example is
the assumption that individual-derived effect metrics are accurate, albeit conservative, predictors of
concentrations that will adversely affect important population qualities. Forbes and Calow (2003)
found that this was sometimes the case, but in general, individual-based metrics of adverse effect
were not reliable predictors of concentrations adversely impacting populations. More information
was needed to accurately infer population effects.
2.3.5 INFERRING COMMUNITY EFFECTS FROM
ORGANISMAL EFFECTS
If done cautiously, potentially useful inferences about community consequences can be made from
the effects of contaminants on individuals. These are detailed in the community ecotoxicology
section. A quick review of that section reveals that many community metrics are generated with
counts of individuals for the community of interest. Presence of individuals of key or indicator

species is also crucial to many of the community-oriented methods. Species-specific sensitivity
of individuals to toxicants can be used to develop biotic indices for implying toxicant effect to
communities. Colonization or succession theory draws on individual life history qualities for its
causal foundation. The autecologically oriented laws of Liebig and Shelford are used to describe
the transition in community types along environmental gradients. Rapoport’s rule relating species
richness and latitude (or elevation) is also based on individual species’ tolerances.
Ambiguously useful applications of individual-based metrics to predictions of community-level
consequences are also present in ecotoxicology.Acurrent example is the emerging species sensitivity
distribution method. The LC50 (or NOEC) values are collected for all relevant species and used to
produce a curve that describes the distribution of toxicant sensitivities of the tested species. The
curve is used to compute the LC50 or NOEC concentration associated with only the lowest 5%
(or 10%) of species. Only the most sensitive 5% of test species would have an LC50 (or NOEC)
at or below that concentration. This HC
p
is then used to imply a concentration below which all
but a small percentage of species in a community will be protected from the adverse effects of the
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The Organismal Ecotoxicology Context 21
toxicant. Phenomena that would bring such an implication into question are discussed in detail in the
population and community ecotoxicology sections. The interested reader is encouraged to browse
these sections before applying the species sensitivity distribution method.
2.3.6 INFERRING POTENTIAL FOR TROPHIC TRANSFER FROM
BIOACCUMULATION
Bioaccumulation is the accumulation of a contaminant in (and occasionally also on) an individual
organism. Models and associated concepts applied to toxicant bioaccumulation in individuals estab-
lish the foundation on which many community trophic transfer models are built (e.g., Mason
et al. 1994, Simon and Boudou 2001). An explicit example of such a model is provided by
Laskowski (1991). Consequently, knowledgeof contaminantuptake, transformation, and elimination
by individuals is useful in predicting transfer of contaminants within food webs.

2.4 SUMMARY
• The organismal focus in mammalian toxicology and early ecology (i.e., autecology)
contributed to an organismal bias in the new science of ecotoxicology.
• Although resulting in an imbalance in ecotoxicological research, the organismal bias does
have positive consequences. These include (1) transfer of new technologies rapidly into
ecotoxicology, (2) providing mechanisms for effects seen at higher levels of organization,
(3) providing sensitive indicators of exposure or effect, and (4) providing a highly discrete
and tractable approach to any ecotoxicological questions.
• Careful interpretation of organismal data enhances our ability to predict consequences at
the population and, sometimes, community levels of organization.
• Careful application of bioaccumulation data enhancesour ability topredict trophic transfer
of toxicants in food webs.
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