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Draft Report
Selection and
Ranking of
Endpoints for
Ecological Risk
Assessment
5®
Til
Submitted To:
Exposure Assessment Group
Office of Research and Development
U.S. Environmental Protection Agency
Submitted By:
Technical Resources, Inc.
3202 Monroe St., Rockville, MD 20852
Work performed under contract #68-02-4199

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Oil!
Ecological Risk Assessment
SELECTION AND RANKING OF ENDPOINTS FOR ECOLOGICAL
RISK ASSESSMENT
by
Abe Mittelman, Project Manager
Joanne Settel
Technical Resources, Inc.
3202 Monroe Street, Suite 200
Rockville, Maryland 20852
Contract No. 68-0224199
September 30, 1988
Project Officer
John Segna
Exposure Assessment Group
Office of Research and Development
U.S. Environmental Protection Agency
Washington, D.C. 20460

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SELECTION AND RANKING OF
ENDPOINTS FOR ECOLOGICAL RISK ASSESSMENT

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TABLE OF CONTENTS
PAGE
I. Selection of Endpoints
Introduction	1
Endpoint selection chart	3
Endpoint selection guidelines	7
Part I-Endpoints of concern	7
Part II-Organisms of concern	18
II. Endpoint Ranking
Introduction	22
Endpoint ranking tables	25

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SELECTION OF ENDPOINTS
LIST OF TABLES
PAGE
Tables
1.	Factors Affecting Chemical Degradation and Transformation	8
2.	Habitat - Zones	12
3.	Factors Causing Increased Vulnerability of Ecosystem Processes	16
4.	Behavior Causing Contact with Polluted Zones of the Habitat	18
5.	Factors Leading to High Levels of Exposure in Organisms	19
6.	Secondarily Exposed Organisms	20
7.	Potentially Vulnerable Organisms	21

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ENDPOINT RANKING
LIST OF TABLES
PAGE
Tables
A-I	Endpoint Ranking Summary	25
A-II	Endpoint Ranking Including Practicality	26
A-III	Ecosystem/Population Endpoint Ranking	27
A-IV	Ecosystem/Population Endpoint Ranking with Practicality	28
A-V	Species Endpoint Ranking	29
A-VI	Species Endpoint Ranking Including Practicality	30
A-VII	Ecosystem/Population Endpoint Information	31
Content Summary
A-VIII	Information Content - Ecosystem/Population-Level Endpoints	32
A-IX	Species-Level Information Content Summary	35
A-X	Information Content - Species-Level Endpoints	36
A-XI	Ecosystem/Population-Level Predictive of Stress - Summary	38
A-XII	Ecosystem Stress - Ecosystem/Population-Level Endpoints	39
A-XIII	Species-Level Predictive of Species Stress - Summary	42
A-XIV	Species Stress - Species-Level Endpoints	43
A-XV	Ecosystem/Population-Level Long-Term Effects - Summary	45
A-XVI	Predictive of Long-Term Effects - Ecosystem/Population -	46
Level Endpoints
A-XVII	Species-Level Predictive of Long-Term Effects	49
A-XVIII	Predictive of Long-Term Effects Species-Level Endpoints	50
A-XIX	Ecosystem/Population-Level Low Pollutant Levels Summary	52

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ENDPOINT RANKING
LIST OF TABLES (cont.)
PAGE
A-XX Sensitivity to Pollutant Levels - Ecosystem/Population -	53
Level Endpoints
A-XXI Species-Level Ranking Low Pollutant Level Summary	55
A-XXII Sensitivity to Pollutant Levels - Species-Level Endpoints	56
A-XXIII Population/Ecosystem-Level Practicality - Summary	58
A-XXIV Practicality - Ecosystem/Population-Level Endpoints	59
A-XXV Species-Level Ranking Practicality - Summary	61
A-XXVI Practicality - Species-Level Endpoints	62

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I. SELECTION OF ENDPOINTS
A critical step in the performance of an ecological risk assessment is
the endpoint selection process. Ideally, the process should focus on
ecosystem-level, community-level, and species-level endpoints, using a wide
variety of endpoints from all three levels and incorporating a broad
spectrum of individual species. Limitations in resources and time, however,
naturally restrict the endpoints and species to be selected to a small
representative sample. It may then be necessary to further narrow selected
endpoints based on practical considerations. Cost and resource limitations
could be dealt with by using a tiered testing approach. When species-level
tests provide the most practical measures available, they may serve as a
first level of testing, indicating the potential for ecosystem effects. If
ecosystem-level effects are indicated, these would then be tested through
microcosm and mesocosm tests. Finally, if necessary, field tests could be
initiated.
Irrespective of the test scheme being used, it is necessary to
prioritize the endpoints to be measured. It thus becomes critical for an
investigator to be able to identify those endpoints that would be most
sensitive to the effects of a pollutant on a system and most predictive of
ecosystem stress.
The selection of appropriate endpoints Is not a trivial matter. It is
not possible to produce a simple delineation of ideal endpoints for a
general type of ecosystem or a general category of pollutants. Appropriate
endpoints can only be selected with a knowledge of effects of a particular
pollutant, the nature of pollutant loading, and the critical features of the
impacted ecosystem. The choice of endpoints measuring ecosystem function,
for example, can be based on factors such as pollutant loading, pollutant
levels, and mechanisms of toxicity. The choice of endpoints measuring
ecosystem structure or community-level effects can be determined with
knowledge of the kinds of species impacted and the nature of community
interactions. The choice of species-level endpoints would be based on
factors such as pollutant persistence, pollutant levels, pollutant
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bioaccumulation, and mechanisms of toxicity. Finally, the choice of species
and parts of the environment to examine can be made based on knowledge of
pollutant loading, species exposure, and species susceptibility.
Although it is not currently possible to produce specific
recommendations for endpoints to be selected, it is possible to provide
general guidelines for selection. The discussion that follows presents
these guidelines as a series of questions, which are then followed by a
collection of endpoint ranking tables. The questions are designed to
provide focus on the categories of endpoints and the kinds of species that
would be most appropriate to monitor in each particular situation. Each of
these questions is described in terms of the kinds of variables that need to
be considered in a given ecosystem. The questions are then summarized in an
Endpoint Selection Chart.
The Endpoint Selection Guidelines section is organized into two parts.
The first group of questions is directed towards selection of appropriate
ecosystem-level, community-level, and species-level endpoints. The second
group of questions is directed towards selection of appropriate groups of
organisms to monitor. The ordering of the group of questions is not
absolute. It is often appropriate to select endpoints to be measured
following selection of organisms of concern.
The endpoint ranking tables are designed to be used in conjunction with
the endpoint selection guidelines. They provide an ordering of selected
endpoints based on their predictive strengths, information content, and
overall sensitivity. The rankings have been determined subjectively, to
some extent, using available data, and are thus meant only as a form of
guidance, not as absolute measures. It is the responsibility of the
assessor to consider site-specific factors in ranking endpoints.
Within the context of the guidelines described, an investigator must
exercise a considerable amount of judgment in choosing measurements
appropriate to his or her unique situation. At the current time, the
state-of-the-science does not include enough of a research base to provide
any more specific guidance. Eventually, an expanded ecotoxicological
research base should make It possible to create endpoint selection
guidelines which eliminate more of the subjectivity in the selection process.
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ENDPOINT SELECTION CHART
PART I - ENDPOINTS OF CONCERN
1. Is the pollutant degraded or transformed into other toxic compounds in
this system?
Yes
No
Determine the basic physical and
chemical properties of the pollutant
and its toxic products.
Avoid selection of ecosystem
or species-level endpoints
that would be masked by high
levels of toxicity.
2. Has the pollutant been present in the system over a long period of time?
Yes, the pollutant has been persistent
or chronically released into the system
over a long period of time.
No, the pollutant has been
recently introduced or will
be eliminated from the
system in a relatively
short period of time.
Select ecosystem, community, and species-
level endpoints that are sensitive
to long-term or short-term effects.
Select endpoints that are
sensitive to short-term
effects but have long-term
predictive value.
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ENDPOINT SELECTION CHART (cont.)
Has the system been exposed to small amounts of the pollutant or
pollutants with low levels of toxicity?
Yes	No
Select ecosystem, community, and species-
level endpoints sensitive to low levels
of toxicity.
Is the distribution of the pollutant focused in specific zones of the
habitat
Yes, the chemical is concentrated In
specific zones of the habitat (i.e.,
pond sediments, tree canopy, soil, etc.),
No, the chemical seems to be
ubiquitous in the habitat.
Focus studies primarily on polluted
zones of the habitat.
Focus studies on a variety of
representative zones or use
other factors to choose
ecosystem zones.
Are certain processes particularly vulnerable to damage in this system?
Yes
Focus on sensitive ecosystem
processes.
No
Use other factors to choose
ecosystem processes to
measure.
Are the mechanisms of toxicity known for the pollutant?
Yes, the mechanisms of toxicity are	No
known (suppression of cell growth,
Inhibition of enzymes, etc.).
Use this knowledge to predict or
corroborate expected toxic
effects of the chemical (see step 7).

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ENDPOINT SELECTION CHART (cont.)
7. Are the generalized toxic effects of the pollutant known?
Yes, the toxic effects have been
identified (neurotoxicity, inhibition
of photosynthesis, inhibition of
nitrification, etc.).
No
Focus on ecosystem and species-
level endpoints associated with
identified effects.
Use other factors to select
ecosystem and species-level
endpoints.
8. Is the pollutant known to bioaccumulate?
Yes, the chemicals bioaccumulate (in
leaves, liver, bone, lipids, etc.).
No, the chemical is rapidly
degraded or eliminated from
exposed organisms.
Focus on endpoints associated with
bioaccumulation.
PART II - ORGANISMS OF CONCERN
9. Can organisms be identified which come into contact with polluted zones of
the habitat?
Yes, the organisms which nest, feed,	No
or otherwise pass through the polluted
zones can be identified.
Focus on species and community level	Use other factors to select
endpoints for guilds of organisms	organisms to be monitored,
associated with these parts of the
habitat.
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ENDPOINT SELECTION CHART (cont.)
10. Can highly exposed organisms be identified in the ecosystem?
Yes, some organisms have experienced	No
large amounts of exposure due to
migration patterns, feeding behavior,
biomagnification, etc.
Focus on highly exposed species.	Use other factors to select
organisms to be monitored.
11.	Can organisms which are particularly vulnerable to the effects of this
pollutant be identified?
Yes, this pollutant affects photo-	No
synthesis, insect development,
olfactory perception etc, and thus
selectively impacts upon certain
groups of organisms.
Focus on vulnerable organisms.	Use other factors to select
organisms to be monitored.
12.	Can secondarily impacted organisms be identified?
Yes, certain organisms may be secondarily No
impacted through effects on their
predators, prey, competitors, etc.
Focus on community-level endpoints	Focus on more general measures
involving impacted organisms.	of ecosystem structure.
13. Can impacted organisms which are particularly vulnerable to stress be
identified?
Yes, organisms which are particularly	No
vulnerable to stress due to re-
productive cycles, population
levels, disease etc. can be identified.
Focus on vulnerable impacted	Use other factors to select
organisms.	organisms to be monitored.
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ENDPOINT SELECTION CHART (cont.)
14. Can indicator, keystone, or dominant species be identified?
Yes	No
Include studies of these ecologically	Use other factors to select
significant species.	organisms to be monitored.
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ENDPOINT SELECTION GUIDELINES
PART I - ENDPOINTS OF CONCERN
1. Is the pollutant degraded or transformed into other toxic compounds in
this system?
Any evaluation of the toxic effects of a pollutant on an ecosystem must
include an assessment of pollutant transformation and degradation. These
processes can potentially convert pollutants into compounds of equal or
greater toxicity. The fungicide thiram, for example, may, be environmentally
transformed or metabolized to yield carcinogenic nitrosamines (Ayanaba et
al., 1973). Thus, ecosystem-level effects of derived toxic products must be
characterized and evaluated along with the original pollutant.
The tendency for a pollutant to be degraded or transformed is related to
its physical, chemical, and biological properties and the character of the
receiving environment. Some properties of concern include molecular weight,
water solubility, and partitioning behavior. Knowledge of these properties
can be used to determine the susceptibility of a chemical to processes such
as oxidation, microbial degradation, hydrolysis, and photolysis (Mitchell
and Roberts, 1984) (see Table 1 for a detailed listing of properties and
processes). Degradative and transformation processes will only proceed
under appropriate environmental conditions. Factors such as the pH,
temperature, and nature of the microbial populations, (See Table 1) can all
effect the amount of degradation or transformation that will take place.
The rate of organophosphorus and carbamate insecticide hydrolysis, for
example, will depend heavily on the pH and temperature of the environment.
In soil, the breakdown of these insecticides is further influenced by
mineral components, organic matter, and moisture level of the soil (Murphy,
1986). It is thus necessary to characterize both the pollutant and the
affected environment in order to properly evaluate the tendency for the
pollutant to decompose or transform.
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TABLE 1
FACTORS AFFECTING CHEMICAL DEGRADATION AND TRANSFORMATION
Chemical Properties
Chemical Stability
Lipid Solubility
Molecular Weight
Partitioning Behavior:
Organic Carbon Soil Sorption Coefficient (Kd)
Soil Sorption Constant (Koc)
Water-Air Ratio (Kw)
n-Octanol-Water Coefficient (Kow)
Bioconcentration Factor (BCF)
pKa
Vapor Pressure
Water Solubility
Major Degradation and Transformation Processes
Hydrolysis
Microbial Processes:
Conjugation
Dehalogenation
Dimerization
Hydrolysis
Methylation
Oligomerization
Oxidation
Polymerization
Oxidation
Photolysis
Reduction
(Menzer and Nelson, 1986; NCR, 1981)
Environmental Conditions
Microbial Ecology:
Redox Potential
Nutrient Availability
Microbial Interactions
Microbial Growth
Moisture Content of Soil
Nature of Microbial Population
PH
Presence of Clay Surfaces
Presence of Metal Ions and
Metal Oxides
Presence of Organic Compounds
and Organic Surfaces
Presence of Other Interactive
Chemicals
Sorption to Environmental
Surfaces
Temperature
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2. Has the pollutant been present in the system over a long period of time?
If a pollutant has been present in a system for a long period of time,
due either to its persistence or its chronic introduction into the system,
toxic effects may be evident in measures of long-term change (see Tables
A-XV and A-XVI). In this situation, ecosystem-level endpoints such as
species richness and long-term changes in productivity, community-level
endpoints such as shifts in trophic structure, and species-level endpoints
such as growth, reproduction, and genetic changes, will provide highly
informative endpoints.
Although certain measures are clearly associated with long-term stress,
any endpoint can undergo changes following long-term exposure. In
instances, however, when systems or species acclimate to pollutant stress,
certain measures will be particularly uninformative. For example, endpoints
such as diversity, productivity, or biomass often remain unchanged in
systems where replacement species have caused major shifts in similarity or
trophic structure. Thus lack of change in these measures can only be
interpreted in conjunction with assessment of changes that have occurred in
others. Choices of appropriate combinations of endpoints at the ecosystem,
community, and species level, should be made to ensure that long-term
effects are properly accounted for.
When a system's exposure to a toxicant is acute and the chemical is not
persistant, short-term measures of changes in behavior, physiology,
diversity, or productivity can serve as useful descriptions of the status of
the system. Even with acute exposures, however, short-term measures may not
be sufficient to evaluate ecosystem stress. In some instances short-term
changes will create long-term changes in the system. For example,
short-term reproductive changes in a highly vulnerable species may result in
elimination of that species from the system which, in turn, could have far
reaching effects on predators and prey. In addition, certain toxicants can
produce long-term changes in a system or organism after only brief
exposure. Thus organisms which have been briefly exposed to certain
carcinogens may develop cancer a number of years later. Similarly, a brief
exposure to a genotoxic chemical can induce permanent changes in the gene
pool of an exposed population.
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It thus seems clear that whenever long-term effects can be predicted for
a system, long-term and short-term measures will need to be used in a risk,
assessment. If, however, it can be determined that an acute exposure will
produce only acute effects, then short-term measures will provide an
adequate evaluation of the ecosystem.
3. Has the system been exposed to small amounts of the pollutant or to a
pollutant with low levels of toxicity?
When small amounts of a pollutant or pollutants with low levels of
toxicity enter a system, the effects produced may be subtle and difficult to
measure. Certain ecosystem and species-level endpoints such as nutrient
cycling, behavior changes, and biochemical changes, moreover, are often
highly sensitive to low levels of pollutants (See Tables A-XVII - A-XX).
These endpoints will show measureable effects before any changes can be
detected in other components of the system. An Increased leaching of
nutrients from the soil can be detected, for example, at low levels of
exposure, before its cumulative effects cause a reduction in primary
productivity.
When moderate or large amounts of a toxic pollutant enter a system, on
the other hand, any of a large number of endpoints will serve as sensitive
measures of pollutant stress. At high levels of exposure, however, species
mortalities will sometimes mask effects in species-level endpoints such as
behavior, reproduction, growth, or genetic shifts. Thus, ecosystem effects
at high pollutant levels are sometimes assessed most effectively by focusing
primarily on community-level and ecosystem-level endpoints, along with
mortality.
A large variety of endpoints can be monitored if a pollutant is
dispersed along a gradient. In this situation, endpoints sensitive to low
levels of exposure and endpoints sensitive to high levels of exposure can be
combined to provide a description of the dose-response effects for the
pollutant.
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4. Is the distribution of the pollutant focused in specific zones of the
habitat?
Habitats are comprised of vertical and horizontal zones (see Table 2),
which differ in both their biotic and abiotic components. The distribution
of a pollutant across these zones is clearly an important factor in
determining both the kinds of organisms and the kinds of processes that will
be affected. A pollutant that is absorbed into soil, for example, will tend
to affect soil microorganisms, soil invertebrates and decomposition, while a
pollutant that is sequestered in the leaves of trees, might manifest its
toxic effects as a reduction in primary productivity and damage to
tree-dwelling organisms. Endpoint selection must thus take pollutant
distribution into account.
The ultimate distribution of a pollutant is determined by a wide variety
of factors. Initial deposition of the chemical will be determined by the
geology, topography, and weather patterns of the ecosystem, as well as the
mechanism of pollutant exposure. In a densely foliated forest, a pollutant
which is dispersed atmospherically will be deposited primarily on the canopy
foliage. In an area that is sparsely foliated, on the other hand, much of
the pollutant will be deposited on the forest floor.
Following initial deposition, the pollutant may be secondarily deposited
in different parts of the habitat. The pattern of a secondary deposition
depends on both the nature of the chemical and the nature of the ecosystem.
A chemical deposited on vegetation may be adsorbed, absorbed, or
translocated by the plants; washed off the foliage onto nonvegetative
surface; or volatilized back into the atmosphere. Likewise, a chemical
deposited in water may be absorbed by biota, adsorbed onto abiotic surfaces,
degraded, transported, or volatilized.
Both primary and secondary deposition sites are likely to be the most
highly Impacted parts of the ecosystem. Endpoints selected should thus be
primarily those that would reflect toxic effects in these parts of the
habitat.
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TABLE 2
HABITAT - ZONES
FOREST
Canopy - Upper level of leafy branches of trees.
Understory - Lower level, shrubs, young trees, etc.
Topsoil - Decomposing litter nutrient-rich humus, and nutrient-poor mineral
layer.
Subsoil - Accumulated silicates, clays, iron, aluminum, and organic matter.
Parent material - Unconsolidated weathered rock.
GRASSLAND
Vegetation - Grasses and herbs.
Topsoil - Organic matter mixed with mineral soil.
Subsoil - Calcified soil.
Parent material - Dry subsoil.
DESERT
Vegetation - Scattered xerophytes
Topsoil - Thin band, low organic matter, high nutrient content prevelent in
valley floors.
Desert pavement - Stony poorly developed soil, prevalent on slopes.
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TABLE 2 (CONT.)
PONDS AND LAKES
Littoral zone - Shallow marginal region with rooted vegetation.
Euphotic zone - Open water extending to the depth of light penetration.
Aphotic or Profoundal zone - Area beneath zones of photosynthesis.
Sediment - Detrital bottom layer with active decomposer communities.
STREAMS
Upper waters:
Rapids - Regions with flow rates above 50 cm/sec.
Pools - Regions with flow rates below 50 cm/sec.
Stream beds:
Rocky surfaces - Firm, rocky bed beneath rapids. Soft stream bed - sandy
or silty bed beneath pools.
WETLANDS
Estuarine Wetlands - Coastal wetlands associated with estuaries or brackish
tidal waters.
Regularly flooded zone.
Irregularly flood zone.
Palustrine Wetlands - Interior wetlands generally freshwater, may be
emergent, scrub-shrub or forested.
Permanently flooded.
Semipermanently flooded.
Seasonally flooded.
Temporarily flooded.
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TABLE 2 (CONT.)
ESTUARIES
Open water - salinity gradients in large estuaries.
Mouth - Area of relatively high salinity large species numbers.
Region of Critical Salinity - Salinity range of 5%-8% low species numbers.
Region of fresh water - Species richness increases.
(Owen, 1980; McNaughton and Wolf, 1973; Levinton, 1982; Tiner, 1984)
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5. Are certain processes particularly vulnerable to damage in this system?
It is often possible to identify ecosystem processes within a particular
system which, if damaged, would seriously affect the system (see Table 3).
These processes can serve as important indicators of pollutant effects and
thus help the investigator focus on useful ecosystem-level endpoints to
measure, and specific species to monitor.
The importance of specific processes in ecosystem stability is evidenced
in a mature forest system. During the late stages of succession, nutrient
cycling becomes well developed and a forest becomes highly nutrient
conservative. Late successional plants are correspondingly poorly adapted
to conditions of nutrient flux. Thus, in this system, measures of nutrient
leaching provide highly sensitive indicators of ecosystem stress (Sheehan,
1986).
When limiting factors such as sunlight, oxygen, or specific nutrients
can be identified, these also provide an important focus for determining
endpoints to monitor. For example, if phosphorus is the limiting element in
an aquatic system, phosphorus cycling would serve as a critical endpoint to
be measured. Similarly, in the summer, the profundal zone of a eutrophic
lake is subject to depleted oxygen levels. Most organisms living in this
region of the lake are particularly vulnerable to pollutants which further
reduce oxygen levels. Thus, mortality in the profundal zone would provide a
particularly sensitive endpoint for monitoring the effects of organic wastes
with a high biological oxygen demand (Owen, 1975).
6. Are the mechanisms of toxicity known for the pollutant?
When the biochemical mechanisms of toxicity are known for a pollutant or
a closely related compound, this information will clearly narrow the
endpoint selection process. Information on mechanisms is a critical factor
in predicting generalized toxic effects which are themselves measureable
endpoints. Such information is particularly useful in helping to select
species-level endpoints and measures of ecosystem function. For example,
chemicals that inhibit acetylcholinesterase are best assessed by selecting
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TABLE 3
FACTORS CAUSING INCREASED VULNERABILITY OF ECOSYSTEM PROCESSES
Productivity;
o Producers are highly vulnerable to effects of pollutant
o Producers are not readily renewable
o Producers cannot readily be replaced by other producers
Nutrient Cycling
o Specific endpoints are limited for system productivity
o System is poorly adapted to conditions of nutrient flux
Decomposition
o Decomposer organisms are highly vulnerable to effects of pollutant
o System is strongly dependent on decomposition for limiting nutrients
Metabolism
o Oxygen levels become limiting in certain parts of the habitat
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informative, physiological endpoints such as neurological, respiratory, and
cardiovascular effects (Klaasen et al., 1986). Optimally, the physiological
endpoints selected should be those that can be shown to be related to
organism growth, survivorship, and reproductive capacity. Similarly, when a
heavy metal such as copper is known to cause membrane damage resulting in an
increased loss of dissolved organic carbon, it becomes logical to assess
pollutant effects on nutrient availability (Sheehan, 1984).
7.	Are the generalized toxic effects of the pollutant known?
The generalized toxic effects of a pollutant are, as previously
mentioned, measureable endpoints. Pollutants that are known to cause
effects such as reduction in photosynthesis, inhibition of nitrification, or
neurotoxicity, provide obvious ecosystem and species-level endpoints to
measure on the ecosystem or species level. When this kind of information is
available, it provides a critical component of the endpoint selection
process.
8.	Is the pollutant known to bioaccumulate?
The tendency of some pollutants to bioaccumulate or concentrate in
certain kinds of organisms and tissues is important in determining toxic
effects. Bioaccumulation influences both the kinds of organisms which will
be highly exposed, and the ways in which the exposure will be manifested.
The extent and nature of an organism's exposure is affected by its tendency
to bioaccumulate the chemical, and the kinds of tissues in which the
chemical is stored.
Bioaccumulation occurs as a result of the binding and nondegradative
properties of a chemical. Certain compounds are highly lipophilic or have a
strong tendency to bind to specific kinds of protein. Typical tissues in
which chemicals are stored include plasma, fat, kidney, liver, and bone. If
the site of storage is different from the site of toxicity, the process of
storage may prevent the release of large amounts of toxicant to a vulnerable
site. On the other hand, any factor that would promote sudden release of
the chemical from storage could lead to severe toxic effects. Thus,
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toxicants such as DDT, chlordane, and polychlorinated biphenyls which
concentrate in body fat, could be released in large amounts during periods
of reproduction, migration, or starvation. Endpoint selection for
lipophilic chemicals should therefore focus on processes that would enhance
the release of the toxicants from fat depots.
In situations where a toxicant is stored at its known site of action,
the process of bioaccumulation is likely to produce proximal toxic effects.
With these kinds of toxicants, endpoints can be selected to reflect the
toxic effects. In the case of fluoride, for example, which accumulates in
bone, an appropriate endpoint would be skeletal morphology. Thus knowledge
of a chemical's tendency to bioaccumulate should be Integrated with a
knowledge of the chemical's toxic effects, in determining ecological
endpoints (Klaassen et al., 1986).
PART II - ORGANISMS OF CONCERN
9. Can organisms be identified which come into contact with polluted zones
of the habitat?
Once primary and secondary deposition sites have been identified for a
pollutant, it becomes possible to identify organisms which come into contact
with these parts of the ecosystem. Guilds or groups of organisms which
nest, feed, or reproduce In polluted zones of the habitat, and organisms
which pass through for other purposes may be characterized (See Table 4).
It thus becomes possible, with knowledge of species' life histories, to
identify the groups of organisms which are most likely to be exposed to the
pollutant.
TABLE 4
BEHAVIOR CAUSING CONTACT WITH POLLUTED ZONES OF THE HABITAT
Breeding
Burrowing
Denning
Drifting
Feeding
Migrating
Nesting
Passing through
Resting
Roosting
Sunning
Hibernating
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10. Can highly exposed organisms be identified?
Organisms that come into contact with polluted areas may be exposed to
particularly. large amounts of pollutants as a result of a variety of
behavioral and life history factors. For example, organisms which filter
feed in polluted sediment, or retain large amounts of the pollutant in their
bodies, may be subject to high levels of exposure.
Organisms which do not come into direct contact with polluted areas of
the ecosystem may also be indirectly exposed to large amounts of pollutant
through the process of biomagnification up the food chain. These highly
exposed organisms are clearly important candidates for endpoint measurements.
TABLE 5
FACTORS LEADING TO HIGH LEVELS OF EXPOSURE IN ORGANISMS
o	Biomagnification
o	Organisms retain pollutant
o	Organisms bioconcentrate pollutant
o	Organisms feed on exposed materials
o	Organisms readily absorb pollutant
11. Can Organisms Which Are Particularly Vulnerable to the Effects of this
Pollutant be Identified?
The toxic effects of some pollutants are only manifested in certain
selected types of organisms. Various categories of pesticides, for example,
may produce toxic effects on specific target organisms, and little or no
effects in non-target species. Thus, an herbicide which is highly toxic to
weeds, may not be toxic to other autotrophs or heterotrophs. Similarly, an
insecticide may have minimal direct impact on species of plants or higher
vertebrates.
It thus may be possible to narrow the selection of species to be
monitored based on knowledge of the toxic mechanisms of a particular
pollutant. An identification of primarily impacted organisms can then
facilitate the identification of secondarily impacted organisms (see
Question 12).
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12. Can secondarily impacted organisms be identified?
Fluctuations in populations of exposed organisms may have a secondary
impact on other members of the community. Secondary impact will be
particularly significant in communities where species interactions are
strong (Levin et al., 1984). It is manifested through interactions such as
predation, competition, and symbiosis. Elimination of exposed prey species
for a highly specialized predator could be devastating to the predator
population. On the other hand, elimination of an exposed organism could
allow a large increase in the density of a competitor population.
Secondarily impacted organisms may thus become severely stressed or
increasingly dominant as a result of shifts in populations of exposed
species.
Organisms which may be secondarily impacted can be identified within
both exposed and unexposed communities based on knowledge of the community
structure. This knowledge can help direct the selection of population-level
endpoints.
TABLE 6
SECONDARILY EXPOSED ORGANISMS
o	Competitors with exposed species
o	Competitors with prey of exposed species
o	Herbivores feeding on exposed plants
o	Organisms that obtain shelter in or on exposed plants
o	Predators on exposed species
o	Symbiotes of exposed species
13. Can organisms which are particularly vulnerable to stress be identified?
When large numbers of impacted organisms have been identified, it
becomes useful to be able to focus on those species which are most likely to
manifest effects of exposure. In the population of exposed and secondarily
impacted species some may be identifiable as being particularly vulnerable
at the time of exposure. Examples of vulnerable species which can be
identified include those with large numbers of larval or newly emergent
individuals, k-selected species with a relatively long reproductive lag
time, and previously stressed species which already have low population
densities (see Table 7).
20

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In addition to organisms which exhibit system-specific vulnerability,
accounting must be taken of endangered species which possess a global
vulnerability. Although an endangered population may not be highly
sensitive to a particular pollutant in a particular system, exposure effects
that produce even a small impact on the endangered population could have
broad-ranging implications for the species as a whole. It thus becomes
important to include an evaluation of any endangered species as a component
of a risk assessment.
TABLE 7
POTENTIALLY VULNERABLE ORGANISMS
o	Endangered species
o	Larva or newly emergent individuals
o	Overwintering organisms*
o	Populations with very low densities
o	Populations at the carrying capacity of the environment
o	Species with a relatively long reproductive lag time
*These species would be more vulnerable due to lack of avoidance behavior
and slowed metabolic detoxification and elimination of chemicals. They may,
however, be less vulnerable, due to slowed transformation of chemicals to
more toxic substances.
14. Can indicator, dominant, or keystone species be identified?
When indicator, dominant, or keystone species can be identified in an
ecosystem, they often provide sensitive indicators of ecosystem stress.
Indicator species are designated as organisms whose absence from an
environment suggests a lack of suitable environmental conditions. Although
only limited work has been done in this area, when indicator organisms can
be identified in a particular system, they provide an obvious focus for
endpoint investigations. Lichens, for example, have been found to be
effective monitors of SO^ stress in a number of different studies
(Sheehan, 1986). Other species may ultimately be identified to serve as
standard indicators for certain kinds of pollutants or habitats.
21

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II. ENDPOINT RANKING
Endpoint rankings provide a means of comparing endpoints based on their
overall predictive value. They can thus serve as a useful tool to aid in
choosing from among previously selected, situationally appropriate endpoints.
The tables that follow present a sample endpoint ranking scheme. Within
this scheme, endpoints have been evaluated for their information content,
sensitivity to low pollutant levels, predictive values for assessing ecosystem
stress and long-term effects, and practicality. The rankings obtained are
summarized in Tables I-VI. These are followed by detail tables which describe
the basis for each ranking.
None of the rankings provided here are meant to be absolute. The
endpoints listed include general categories of measurement. Within these
categories individual measures may prove to be more or less sensitive. In
addition, ranking decisions are, to some extent subjective, and are often
based on a fairly limited database. These rankings should therefore serve as
a model, which should be modified as necessary in accordance with the needs of
the investigator.
Description of Ranking Factors
Five factors were chosen as components of ranking. These factors include:
o Information Content - The extent to which the endpoint describes the
status of the whole ecosystem
o Predictive of Ecosystem Stress - The value of the endpoint in
predicting damage to the ecosystem
o Predictive of Species Stress - The value of the endpoint In predicting
damage to the species
o Predictive of Long-Term Effects - The value of the endpoint In
predicting long-term damage to the species or the system
o Sensitive to Low Pollutant Levels - Tendency of endpoint to change in
response to small amounts of exposure
o Practicality - A combination of cost and ease of measurement.
22

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Using these factors as criteria, endpoints were than rated on a 3-point
scale, with a score of 3 being given to the most predictive, practical, or
informative endpoints. A final rank order was determined by adding up the
endpoint scores for all the factors except practicality. A second rank order
was also determined with practicality included. The final ranking tables
provide a rough order of prioritization for selected ecosystem, population,
and species-level endpoints. It is recognized that other ranking systems are
possible. However, the approach selected here provides a useful basis for
decision-making and for data collection.
23

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ENDPOINT RANKING TABLES
TABLE A-I
ENDPOINT RANKING SUMMARY*
ECOSYSTEM POPULATION LEVEL
Nutrient Cycles	12
Decomposition	11
Similarity	11
Trophic Structure	11
Keystone Species	10
Primary Production	10
Species Richness	9.5
Metabolism	9
Predator-Prey	9
Indicator Species	8
Competition	8
Biological Indices	6.5
Biomass	6.5
Behavior	9
Diversity	6.5
Abundance	5.5
SPECIES LEVEL
Growth
Reproduction
Developmental
Acute Mortality
Carcinogenic
Physiology
Genetics/
(hereditable)
Year-class
distribution
Morphology
Behavior
Biochemical
12
12
11
11
10
10
10
10
9
9
8
* Excluding practicality, but including factors described on pgs. 27-31.
24

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TABLE A-II
ENDPOINT RANKING INCLUDING
PRACTICALITY*
ECOSYSTEM/POPULATION LEVEL	SPECIES LEVEL
Nutrient Cycles
14
Growth
14
Decomposition
13
Reproduction
14
Primary Production
12.5
Acute Mortality
14
Similarity
12.5
Developmental Changes
13
Keystone Species
12
Carcinogenic
12
Trophic Structure
12
Physiological
12
Species Richness
11.5
Morphology
12
Metabolism
10.5
Year-Class Distribution
12
Indicator Species
10
Biochemical
11
Predator-Prey
10
Genetics/(hereditable)
11
Biomass
9.5
Behavior
10.5
Abundance
8.5


Biologic Indices
8.5


Diversity
8.5


Competition
8


* See discussion of factors on pgs. 27-31.
25

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TABLE A-III
ECOSYSTEM/POPULATION
ENDPOINT RANKING
ECOSYSTEM/
POPULATION-
LEVEL ENDPOINTS
INFORMA-
TION
CONTENT
PREDICTIVE
OF ECOSYSTEM
STRESS
PREDICTIVE
OF LONG-TERM
EFFECTS
SENSITIVE
TO LOW
POLLUTANT
LEVELS
TOTAL
SCORE
Abundance
1
1.5
1
2
5.5
Biological Indexes
1.5
2
1
2
6.5
Biomass
1
1.5
2
2
6.5
Competition
2
2
2
2
8
Decomposition
3
3
3
2
11
Diversity
1.5
2
2
1
6.5
Indicator Species
2
2
2
2
8
Keystone Species
3
2
3
2
10
Metabolism
2
3
1
3
9
Nutrient Cycles
3
3
3
3
12
Predator-Prey
2
2
2
3
9
Primary Production
3
3
2
2
10
Species Richness
2
2.5
2
3
9.5
Similarity
3
3
2
3
11
Trophic Structure
3
3
3
2
11
Key: 1 - Minimally informative/predictive/sensitive
2	- Informative/predictive/sensitive
3	- Highly informative/predictive/sensitive
26

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TABLE A-IV
ECOSYSTEM/POPULATION ENDPOINT
RANKING WITH PRACTICALITY
SENSITIVE
ECOSYSTEM/	INFORMA- PREDICTIVE PREDICTIVE TO LOW
POPULATION-	TION	OF ECOSYSTEM OF LONG-TERM POLLUTANT PRACTI- TOTAL
LEVEL ENDPOINTS	CONTENT STRESS	EFFECTS	LEVELS CALITY SCORE
Abundance
1
1.5
1
2
3
8.5
Biological Indexes
1.5
2
1
2
2
8.5
Biomass
1
1.5
2
2
3
9.5
Competition
2
2
1
2
1
8
Decomposition
3
3
3
2
2
13
Diversity
1.5
2
2
1
2
8.5
Indicator Species
2
2
2
2
2
10
Keystone Species
3
2
3
2
2
12
Metabolism
2
3
1
3
1.5
10.5
Nutrient Cycles
3
3
3
3
2
14
Predator-Prey
2
2
1
3
2
10
Primary Production
3
3
2
2
2.5
12.5
Species Richness
2
2.5
2
3
2
11.5
Similarity
3
3
2
3
1.5
12.5
Trophic Structure
3
3
3
2
1
12
Key: 1 - Minimally informative/predictive/sensitive
2	- Informative/predictive/sensitive
3	- Highly informative/predictive/sensitive
27

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SPECIES-LEVEL
ENDPOINTS
INFORMA-
TION
CONTENT
TABLE A-V
SPECIES ENDPOINT RANKING
PREDICTIVE
OF SPECIES
STRESS
PREDICTIVE OF
LONG-TERM
EFFECTS
SENSITIVE TO
LOW POLLUTANT TOTAL
LEVELS	SCORE
Acute Mortality
3
3
3
2
11
Behavior
2
2
2
3
9
Biochemical
3
1
1
3
8
Carcinogenic
2
3
3
2
10
Developmental
3
2
3
3
11
Genetics/
(hereditable)
2
3
3
2
10
Growth
3
3
3
3
12
Morphology
2
2
3
2
9
Physiology
3
2
2
3
10
Reproduction
3
3
3
3
12
Year-Class
Distribution
2
2
3
3
10
Key: 1 - Minimally informative/predictive/sensitive
2	- Informative/predictive/sensitive
3	- Highly informative/predictive/sensitive
28

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TABLE A-VI
SPECIES ENDPOINT RANKING
INCLUDING PRACTICALITY
SPECIES-LEVEL	INFORMA- PREDICTIVE
ENDPOINTS	TION	OF SPECIES
CONTENT	STRESS
Acute Mortality	3	3
Behavior	2	2
Biochemical	3	1
Carcinogenic	2	3
Developmental	3	2
Genetics/
(hereditable)	2	3
Growth	3	3
Morphology	2	2
Physiology	3	2
Reproduction	3	3
Year-Class
Distribution	2	2
PREDICTIVE	SENSITIVE TO PRACTIC- TO:
OF LONG-TERM	LOW POLLUTANT ABILITY SC(
EFFECTS	LEVELS
3	2	3
2	3	1.5
13	3
3	2	2
3	3	2
3	2	1
3	3	2
3	2	3
2	3	2
3	3	2
3	3	2
Key: 1 - Minimally informatlve/predlctive/sensltive
2	- Informative/predictive/sensitive
3	- Highly Informative/predictive/sensitive
29

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TABLE A-VII
ECOSYSTEM/POPULATION ENDPOINT
INFORMATION CONTENT SUMMARY
INFORMATION CONTENT
DECOMPOSITION
KEYSTONE SPECIES
NUTRIENT CYCLES
SIMILARITY
TROPHIC STRUCTURE
Competition
Indicator Species
Metabolism
Predator-Prey
Species-Richness
Abundance
Biologic Indices
Biomass
Diversity
30

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TABLE A-VIII
INFORMATION CONTENT - ECQSYSTEM/POPULATION-LEVEL ENDPOINTS
ECOSYSTEM/
POPULATION-
LEVEL END-
POINTS	INFORMATIVE	COMMENTS
ABUNDANCE	1	The absolute numbers of living
organisms in an ecosystem. An aspect
of ecosystem structure. Not very
informative. Best when used with other
measures.
BIOLOGIC INDEXES	1.5*	Numerical rating of species and species
assemblages. Integrates measures of
species abundance and pollution
tolerance. Information value not
clear. Many indexes require subjective
determinations of organism tolerance.
In addition scores do not distinguish
different combinations of evaluated
factors.
BIOMASS	1	The total weight of organisms in an
ecosystem. Not very informative. A
gross measure of ecosystem structure.
Best when used with other measures.
COMPETITION	2*	Exclusion of one species in favor of a
competitor. Provides information on
community structure. Potentially
informative but difficult to measure.
DECOMPOSITION	3	Measures of litter decomposition and
decomposer organisms. Serves as a
major link between nutrient
availability and primary production.
Informative about potential shifts in
other aspects of ecosystem function.
DIVERSITY	1.5	Combines measures of species richness
and equitability. Measured using a
variety of indices. There is no clear
theoretical basis for application of
these indices. Most indices are,
further, Insensitive to changes in
community structure.
Provides minimal information
Informative
Highly informative
Not well studied with toxic chemicals
Highly informative in selected situations
31
Key: 1	-
2	-
3	-
*	_
++	-

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INFORMATION CONTENT (coat.)
ECOSYSTEM/
POPULATION-
LEVEL END-
POINTS
INFORMATIVE
COMMENTS
INDICATOR SPECIES
The presence of one or more species
serves as an indication of acceptable
environmental conditions. Can be
informative when used with knowledge of
the system.
KEYSTONE SPECIES
3++
Key predators whose elimination can
lead to major changes in the
ecosystem. Can be very informative
when used with knowledge of the system.
METABOLISM
P/R
The photosynthesis/respiration ratio
provides an integrative measure of
ecosystem metabolism. Particularly
predictive in a mature successional
system.
NUTRIENT CYCLES
Measures of nutrient concentrations in
soil and living organisms, and levels
of nutrient leaching in soil.
Informative about functional status of
ecosystem. Sensitive to low levels of
pollutant stress. Thus, provides early
warning of pollutant damage.
PREDATOR-PREY
Predator-prey measures include changes
in prey escape, antipredator behavior,
and shifts in predator and prey
populations. Provides information
concerning effects on species and
community structure. May be
informative about system if species are
keystone, indicator, or dominant.
Key: 1 - Provides minimal information
2	- Informative
3	- Highly informative
* - Not well studied with toxic chemicals
-H- - Highly informative in selected situations
32

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INFORMATION CONTENT (cont.)
ECOSYSTEM/
POPULATION
LEVEL END-
POINTS
INFORMATIVE
COMMENTS
PRIMARY PRODUCTION 3	Measures of gross or net autotroph
productivity through monitoring of
O2, CO2, chlorophyll, or biomass.
Determines the amount of living tissue
that an ecosystem can support. Thus,
provides critical information about
status of system.
SPECIES RICHNESS	2	The number of species per unit area or
per fixed number of individuals.
Provides limited information on
community structure. Suggestive of
whole system stress. Best when used
with other measures.
SIMILARITY	3	A comparative measure of species
presence or proportional abundance over
time and space. Provides important
information concerning changes in
community structure.
TROPHIC STRUCTURE	3	Changes in the composition of different
trophic levels can be made using
measures such as biomass, richness,
productivity etc. Such measures made
at several levels are highly
informative about community structure.
Key: 1 - Provides minimal information
2	- Informative
3	- Highly informative
* - Not well studied with toxic chemicals
++ - Highly informative in selected situations
33

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TABLE A-IX
SPECIES-LEVEL
INFORMATION CONTENT SUMMARY
INFORMATION CONTENT
ACUTE MORTALITY
BIOCHEMICAL CHANGES
DEVELOPMENTAL CHANGES
GROWTH
PHYSIOLOGICAL EFFECTS
REPRODUCTIVE EFFECTS
Behavioral Changes
Carcinogenic Effects
Genetic Changes
Morphological Effects
Year-Class Distribution
34

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TABLE A-X
INFORMATION CONTENT - SPECIES-LEVEL ENDPOINTS
SPECIES-LEVEL
ENDPOINTS
INFORMATIVE
COMMENTS
ACUTE MORTALITY
3
Direct counts of dead organisms. This
is a gross measure. Laboratory tests
can provide information concerning
dose-response levels. Not informative
about mechanisms of toxicity. May be
informative about effects on system
particularly if indicator or keystone
species is monitored. The relationship
between acute mortality and success is
well established.
BEHAVIORAL CHANGES
2
Avoidance, locomotion, feeding, escape
etc. Information gained depends on the
behavior monitored. Can provide
information on the mechanism of
toxicity. Not highly informative about
the extent of ecosystem stress.
BIOCHEMICAL
CHANGES
3
Changes in levels of enzymes and
hormones, or chromosomal damage. Very
informative about the mechanism of
toxicity. Minimal predictive value
about species or ecosystem stress.
CARCINOGENIC
EFFECTS
2
Counts of tumor incidence and
precarcinogenic tissue changes. The
lack of data on normal tumor incidence
and the complex etiology of different
forms of cancer makes data difficult to
interpret.
DEVELOPMENTAL
CHANGES
3
Fertilization of egg through maturity.
Informative about effects on species
and mechanism of toxicity.
GENETIC CHANGES
(HEREDITABLE)
2
Permanent change in the genotype of the
species. This represents a long-term
adaptive change in the species. Very
informative about species effects.
Key: 1 - Provides minimal information
2	- Informative
3	- Highly informative
35

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INFORMATION CONTENT (cont.)
SPECIES-LEVEL
ENDPOINTS
INFORMATIVE
COMMENTS
GROWTH
Integrated index of physiological
status. Net result of consumption,
excretion, and respiration.
Informative concerning effects of
pollutant on species.
MORPHOLOGICAL
EFFECTS
Cell and tissue changes and gross
deformities. May be informative
concerning species stress and the
mechanism of toxicity.
PHYSIOLOGICAL
EFFECTS
Feeding activity, metabolism,
osmotic-ionic balance and
photosynthetic activity. Highly
informative about species stress. Also
informative concerning mechanisms of
toxicity.
REPRODUCTIVE
EFFECTS
Courtship, mating, fertilization,
and reproductive success. Highly
informative about species stress. Also
informative concerning mechanisms of
toxicity.
YEAR-CLASS
DISTRIBUTION
The distribution of the different life
stages of a particular species.
Provides information about stress to
overall species effects. A particular
life stage, but it is difficult to
extrapolate.
Key: 1 - Provides minimal information
2	- Informative
3	- Highly informative
36

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TABLE A-XI
ECOSYSTEM/POPULATION-LEVEL
PREDICTIVE OF STRESS - SUMMARY
PREDICTIVE OF ECOSYSTEM POPULATION-LEVEL STRESS
DECOMPOSITION
METABOLISM
NUTRIENT CYCLES
PRIMARY PRODUCTION
SIMILARITY
TROPHIC STRUCTURE
Biologic Indices
Competition
Diversity
Indicator Species
Keystone Species
Predator-Prey
Species Richness
Abundance
Biomass
37

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TABLE A-XII
ECOSYSTEM STRESS - ECOSYSTEM/POPULATION-LEVEL ENDPOINTS
ECOSYSTEM/
POPULATION
LEVEL END-
POINTS
PREDICTIVE
ECOSYSTEM
STRESS	COMMENTS
ABUNDANCE	1.5	Changes in abundance are suggestive of
ecosystem stress, but do not provide
enough information to be used alone as
indicators.
BIOLOGIC INDEXES	2*	Designed primarily as a method of
evaluating effects of municipal sewage
or organic wastes on aquatic systems.
Can be predictive, but usefulness with
toxic chemicals not well tested.
BIOMASS	1.5	Changes in biomass are suggestive of
ecosystem stress but do not provide
enough information to be used alone as
indicators. Autotroph biomass is also
used as a measure of primary
productivity. Can be useful when
measured as a change in biomass.
COMPETITION	2	May not be highly predictive between
the laboratory and the field. Could be
predictive if measured in the field.
DECOMPOSITION	3	As an important functional process in
an ecosystem, damage to process of
decomposition can have effects on both
nutrient availability and primary
productivity. Thus it is highly
predictive of stress on whole systems.
DIVERSITY	2	Good indicator of gross environmental
deterioration. Useful at high levels
of pollutant stress. Not effective
with all pollutants and often a poor
measure at low pollutant levels.
Key: 1 - Minimally predictive
2	- Predictive
3	- Highly predictive
* - Not well tested
++ - Can be highly predictive in appropriate systems
38

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ECOSYSTEM
STRESS (cont.)
ECOSYSTEM/
POPULATION
LEVEL END-
POINTS
PREDICTIVE
ECOSYSTEM
STRESS
COMMENTS
INDICATOR SPECIES
2
Can be very useful when appropriate
species can be identified and their
life histories are well understood.
Choice of indicator species is based,
however, on a subjective determination
of species tolerance.
KEYSTONE SPECIES
2++
When keystone species can be identified
damage to the species will be highly
predictive of ecosystem stress.
METABOLISM
P/R
3
1
Can serve as a sensitive indicator of
ecosystem stress. However, this
measure can be deceptive in situations
where a toxic chemical reduces both
primary production and respiration.
NUTRIENT CYCLES
3
Highly sensitive to low levels of
pollutant stress. Because impacts of
nutrient shifts are ultimately
manifested in changes in productivity,
this endpoint serves as an important
measure of ecosystem stress.
PREDATOR-PREY
2
May have predictive power between
laboratory and field. Could be
predictive if measured in the field.
Key: 1 - Minimally predictive
2	- Predictive
3	- Highly predictive
* - Not well tested
++ - Can be highly predictive in appropriate systems
39

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ECOSYSTEM STRESS (cont.)
ECOSYSTEM/
POPULATION	PREDICTIVE
LEVEL END-	ECOSYSTEM
POINTS	STRESS	COMMENTS
PRIMARY PRODUCTION 3	Changes in productivity are indicative
of changes in the energy base of the
system. Short-term changes, however,
may not be predictive in situations
where replacement species can take over
productive functions. Highly
predictive long-term measure.
SPECIES RICHNESS	2.5	Generally a good predicator of
ecosystem stress with richness
decreasing in the presence of
pollutants.
SIMILARITY	3	When comparative or gradient
information is available, similarity
indices provide a highly sensitive
measure of ecosystem stress. Studies
show sensitivity at low levels of
pollutant input.
TROPHIC STRUCTURE	3	This involves multiple measures of
selected endpoints at different trophic
levels. Shifts in trophic dominance
can have serious implications for the
state of the ecosystem.
SPECIES-LEVEL
ENDPOINTS
GENERAL	2	May be predictive if effects are
monitored for indicator, keystone, or
dominant species. Serious effects on
critical species are indicative of
serious effects on the system.
Key: 1 - Minimally predictive
2	- Predictive
3	- Highly predictive
40

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TABLE A-XIII
SPECIES-LEVEL
PREDICTIVE OF SPECIES STRESS - SUMMARY
RANKING	PREDICTIVE OF SPECIES STRESS
High - 3 - ACUTE MORTALITY
CARCINOGENIC EFFECTS
GENETIC CHANGES
GROWTH
REPRODUCTIVE CHANGES
Medium - 2 - Behavioral Effects
Developmental Changes
Morphological Effects
Physiological Effects
Year-Class Distribution
Low - 1 - Biochemical Changes
41

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TABLE A-XIV
SPECIES STRESS - SPECIES-LEVEL ENDPOINTS
SPECIES-LEVEL
ENDPOINTS
PREDICTIVE
SPECIES STRESS
COMMENTS
ACUTE MORTALITY
Clearly predictive of stress to an
individual species. Lab tests,
however, do not always predict field
mortality.
BEHAVIORAL
EFFECTS
Behavior may be predictive of species
stress, particularly changes in
feeding, parental, or reproductive
behaviors. Behavioral changes may be
temporary, however, returning to normal
over time.
BIOCHEMICAL	1
CHANGES
Biochemical changes are difficult to
extrapolate to the long-term well being
of effected organisms.
CARCINOGENIC CHANGES 3
Clearly detrimental to effected
organisms and thus predictive of stress
to a species.
DEVELOPMENTAL	2
CHANGES
Effect of pollutant at any stage of
development can reduce the probability
of the individual successfully
completing its life cycle. Thus, this
endpoint is predictive of species
success.
GENETIC CHANGES
(HEREDITABLE)
Represents long-term pollutant effects
of species. Highly predictive of
species effects.
GROWTH
Integrated index of physiological
status of species. Good predicator of
species stress.
MORPHOLOGICAL	2
EFFECTS
May suggest damage to species, but the
fact that the animal survives suggests
that changes may not be detrimental.
Suggestive if damage effects other
measures as well.
Key: 1 - Minimally predictive
2	- Predictive
3	- Highly predictive
42

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SPECIES STRESS (cont.)
SPECIES-LEVEL
ENDPOINTS
PREDICTIVE
SPECIES STRESS
COMMENTS
PHYSIOLOGICAL
EFFECTS
These changes can be seriously damaging
to the species. In some instances
these changes are only short-lived,
thus they are most predictive with
long-term monitoring.
REPRODUCTIVE
CHANGES
A critical function essential to
continuation of the species. This
provides the ultimate test of the
effects of sublethal concentrations of
pollutants on a species.
YEAR-CLASS
DISTRIBUTION
Particular life stages are sometimes
more sensitive to toxicant stresses
than others. This can have important
consequences on the species, which are
difficult to predict.
Key: 1 - Minimally predictive
2	- Predictive
3	- Highly predictive
43

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TABLE A-XV
ECOSYSTEM/POPULATION-LEVEL
LONG-TERM EFFECTS - SUMMARY
RANKING
High - 3
PREDICTIVE OF
LONG-TERM EFFECTS
DECOMPOSITION
KEYSTONE SPECIES
NUTRIENT CYCLES
TROPHIC STRUCTURE
Medium -2 - Biomass
Competition
Diversity
Indicator Species
Predator-Prey
Primary Production
Species Richness
Similarity
Low - 1 -
Abundance
Biologic Indices
Metabolism
44

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TABLE A-XVI
PREDICTIVE OF LONG-TERM EFFECTS - ECOSYSTEM/POPULATION-LEVEL ENDPOINTS
ECOSYSTEM/	PREDICTIVE
POPULATION	OF LONG-
LEVEL END-	TERM
POINTS	EFFECTS	COMMENTS
ABUNDANCE	1	Altered abundance may return to normal
over time due to replacement species or
species acclimation. Thus short-term
changes in abundance do not predict
long-term changes.
BIOLOGIC INDEXES	1*	May be predictive but this has not been
well tested with toxic substances.
BIOMASS	2	Altered biomass may return to normal
over time due to replacement species or
species acclimation. Thus, short-term
changes in biomass may not predict
long-term changes. Short-term changes
in autotroph biomass can lead to loss
of energy base and have long term
effects on higher trophic levels.
COMPETITION	2*	Affects species composition.
Structural changes likely to be long
lasting. Long-term effects on system
may be difficult to predict based on
short-term competitive interactions.
DECOMPOSITION	3	Changes in decomposer organism
populations predictive of long-term
changes in decomposition, primary
productivity, and nutrient cycling.
DIVERSITY	2++	Can be predictive in situations where
pollutant levels are high. May be
predictive in other situations but more
work needs to be done to show this. In
stressed communities under relatively
constant pollution pressure, diversity
tends to be high. Thus this endpoint
would not be predictive under these
conditions.
Key: 1 - Minimally predictive
2	- Predictive
3	- Highly predictive
* - Not well tested
++ - Can be highly predictive in appropriate systems
45

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PREDICTIVE OF LONG-TERM EFFECTS (cont.)
ECOSYSTEM/
POPULATION
LEVEL END-
POINTS
PREDICTIVE
OF LONG-
TERM
EFFECTS
COMMENTS
INDICATOR SPECIES
2++
If indicator species can be identified
it would be suggestive of serious
long-term changes in the system.
KEYSTONE SPECIES
3-H-
If keystone species is identified,
effects on this species will, by
definition, have long-term effects on
the other species in the system.
METABOLISM
P/R
Metabolism may vary over the long-term
time. Predictability depends on the
system.
NUTRIENT CYCLES
Changes in nutrient levels can result
in long-term effects on productivity
and thus on the energy base for the
system.
PREDATOR-PREY
Affects species composition.
Structural changes likely to be long
lasting. Long-term effects on system
may be difficult to predict based on
short-term shifts in predator-prey
interactions.
PRIMARY PRODUCTION
2++
Short-term changes be reversed by
replacement species in some systems,
SPECIES RICHNESS
Can be predictive in systems stressed
with high levels of pollutants.
Effects in other systems not certain.
Key: 1 - Minimally predictive
2	- Predictive
3	- Highly predictive
* - Not well tested
++ - Can be highly predictive in appropriate systems
46

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PREDICTIVE OF LONG-TERM EFFECTS (cont.)
ECOSYSTEM/
POPULATION
LEVEL END-
POINTS
PREDICTIVE
OF LONG-
TERM
EFFECTS
COMMENTS
SIMILARITY
Likely to be predictive in systems
stressed with high levels of
pollutants, effects on other systems
not certain.
TROPHIC STRUCTURE
Shifts in trophic structure reflect
long-term effects on all components of
the ecosystem.
SPECIES LEVEL
ENDPOINTS
GENERAL
May be predictive if effects are
monitored for indicator, keystone, or
dominant species. Serious effects on
critical species will produce long-term
effects on entire system.
Key: 1 - Minimally predictive
2	- Predictive
3	- Highly predictive
* - Not well tested
++ - Can be highly predictive in appropriate systems
47

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TABLE A-XVII
SPECIES-LEVEL
PREDICTIVE OF LONG-TERM EFFECTS
RANKING	INFORMATION CONTENT
High - 3 - ACUTE MORTALITY
CARCINOGENIC EFFECTS
DEVELOPMENTAL CHANGES
GENETICS/HEREDITABLE
GROWTH
MORPHOLOGICAL EFFECTS
REPRODUCTIVE EFFECTS
YEAR-CLASS DISTRIBUTION
Medium - 2 - Behavioral Changes
Physiological Effects
Low - 1 - Biochemical Changes
48

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TABLE A-XVIII
PREDICTIVE OF LONG-TERM EFFECTS SPECIES-LEVEL ENDPOINTS
SPECIES-
LEVEL
ENDPOINTS
PREDICTIVE
OF LONG-
TERM
EFFECTS
COMMENTS
ACUTE MORTALITY
3
Predictive of damage to species as a
result of loss of individuals.
BEHAVIOR
3
Predictive of damage to species as a
result of loss of individuals.
BIOCHEMICAL CHANGES
2
Biochemical changes are generally
sensitive to short term pollutant
stress. Evidence is limited on
long-term predictiveness of biochemical
changes.
CARCINOGENIC EFFECTS
3
Predictive of weakened Individuals and
thus damage to the species.
DEVELOPMENTAL
3
Predictive of long-term damage to the
species.
GENETICS/
HEREDITABLE
3
These changes generally occur over long
periods of time. Even rapid turn-over
insect populations take 2-3 years to
develop resistance. Thus, this is a
long-term measure.
GROWTH
3
This is a long-term measure that is
predictive of long-term stresses to the
species.
MORPHOLOGICAL
EFFECTS
3
Depending on the severity of
morphological changes, may be
predictive of weakened organisms and
thus, species damage.
49

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PREDICTIVE OF LONG-TERM EFFECTS SPECIES LEVEL ENDPOINTS (CONT.)
SPECIES-
LEVEL
ENDPOINTS
PREDICTIVE
OF LONG-
TERM
EFFECTS
COMMENTS
PHYSIOLOGICAL
EFFECTS
Depends on the physiological changes
being measured. Short-term changes in
respiration may vanish if species
acclimates. Changes in osmoregulatory
function or photosynthetic rates may,
on the other hand, be predictive of
long-term species damage.
REPRODUCTIVE
EFFECTS
Diminished reproductive capacity will
diminish the survival potential of the
species.
YEAR-CLASS
DISTRIBUTION
An integrative measure of long-term
changes in a species. Predictive of
species damage.
50

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TABLE A-XIX
ECOSYSTEM/POPULATION-LEVEL
LOW POLLUTANT LEVELS SUMMARY
SENSITIVE TO LOW POLLUTANT LEVELS
METABOLISM
NUTRIENT CYCLES
PREDATOR-PREY
SPECIES RICHNESS
SIMILARITY
Abundance
Biologic Indices
Biomass
Competition
Decomposition
Indicator Species
Keystone Species
Primary Production
Trophic Structure
Diversity
51

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TABLE A-XX
SENSITIVITY TO POLLUTANT LEVELS - ECOSYSTEM/POPULATION-LEVEL ENDPOINTS
ECOSYSTEM/
POPULATION	SENSITIVE TO
LEVEL END-	LOW LEVELS OF
POINTS	POLLUTANTS	COMMENTS
ABUNDANCE
2
Dependent on the nature of the
pollutant and the system.
BIOLOGIC INDEXES
2
Known to be sensitive for organic
wastes. Not well tested with toxicants
BIOMASS
2
Dependent on the nature of the
pollutant and the system.
COMPETITION
2*
Potentially sensitive with highly
sensitive species.
DECOMPOSITION
2
Studies indicate that decomposition
will be disrupted, at least at moderate
to high pollutant levels.
DIVERSITY
1
Tends to be insensitive at low to
moderate levels of pollution.
INDICATOR SPECIES
2
Depends on species level endpoint used.
KEYSTONE SPECIES
2
Depends on species-level endpoint used.
METABOLISM
3*
Studies indicate sensitivity.
NUTRIENT CYCLES
3
Studies show that these are highly
sensitive to low levels of pollutants.
PREDATOR PREY
3
Studies suggest that this endpoint can
be sensitive to low levels of
pollutants.
Key: 1 - Minimal sensitivity
2	- Sensitive
3	- Highly sensitive
* - Not well studied
52

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SENSITIVITY TO POLLUTANT LEVELS (CONT.)
ECOSYSTEM/
POPULATION
LEVEL END-
POINTS
SENSITIVE TO
LOW LEVELS OF
POLLUTANTS
COMMENTS
PRIMARY PRODUCTION 2
May be slow to manifest effects from
low-levels of pollutants.
SPECIES RICHNESS
Sensitive at different pollutant
levels. Useful for measuring gradient
effects. But sensitivity may vary with
system.
SIMILARITY
3
Studies show sensitivity at low
pollutant levels.
TROPHIC STRUCTURE
2
Depends on endpoints measured within
trophic levels.
Key: 1 - Minimal sensitivity
2	- Sensitive
3	- Highly sensitive
53

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TABLE A-XXI
SPECIES-LEVEL RANKING
LOW POLLUTANT LEVEL SUMMARY
RANKING	SENSITIVE TO LOW POLLUTANT LEVELS
High - 3 - BEHAVIORAL CHANGES
BIOCHEMICAL CHANGES
DEVELOPMENTAL CHANGES
GROWTH
PHYSIOLOGICAL EFFECTS
REPRODUCTIVE EFFECTS
YEAR-CLASS DISTRIBUTION
Medium - 2 - Acute Mortality
Carcinogenic Effects
Genetic Changes
Morphological Effects
Low - 1
54

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TABLE A-XXII
SENSITIVITY TO POLLUTANT
LEVELS - SPECIES-LEVEL ENDPOINTS
SPECIES-LEVEL
ENDPOINTS
SENSITIVE TO
LOW LEVELS OF
POLLUTANTS
COMMENTS
ACUTE MORTALITY
2+
Dependent on toxicity of pollutant and
sensitivity of the species monitored.
BEHAVIORAL
CHANGES
3
Behavioral responses are often
sensitive to low levels of pollutants.
CARCINOGENIC
CHANGES
Dependent on Che carcinogenicity of the
pollutant and sensitivity of the
species monitored.
DEVELOPMENTAL	3
CHANGES
Early life stages have been shown to be
sensitive to low levels of pollutants.
Changes in response to low levels of
pollutants have also been noted in
eggshells.
GENETIC CHANGES
(HEREDITABLE)
Long-term measure. More research needed
to determine effects of low pollutant
levels.
MORPHOLOGICAL
EFFECTS
2*
Evidence not sufficient concerning low
level pollutant effects on
morphological endpoints.
Key: 1 - Minimal sensitivity
2	- Sensitive
3	- Highly sensitive
* - Not well studied
+Mortality will mask other species level effects at high levels of pollutant
stress.
55

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SENSITIVITY TO POLLUTANT LEVELS (CONT.)
SPECIES
LEVEL END-
POINTS
SENSITIVE TO
LOW LEVELS OF
POLLUTANTS
COMMENTS
PHYSIOLOGICAL
EFFECTS
Studies indicate that certain
physiological endpoints such as
respiration demonstrate a graded
response over a range of pollutant
exposures.
REPRODUCTIVE
EFFECTS
Certain measures of reproduction can be
highly sensitive to low pollutant
levels. For example, certain metals
are toxic to gamates of aquatic species
which exhibit external fertilization.
YEAR-CLASS
DISTRIBUTION
Early life stages have been shown to be
sensitive to low levels of pollutants.
Key: 1 - Minimal sensitivity
2	- Sensitive
3	- Highly sensitive
56

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TABLE A-XXIII
POPULATION/ECOSYSTEM-LEVEL
PRACTICALITY - SUMMARY
RANKING
High - 3
PRACTICALITY
ABUNDANCE
BIOMASS
Medium - 2 - Biologic Indices
Decomposition
Diversity
Indicator Species
Keystone Species
Nutrient Cycles
Predator-Prey
Primary Production
Species Richness
Low - 1 -
Competition
Metabolism
Trophic Structure
57

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TABLE A-XXIV
PRACTICALITY - ECOSYSTEM/POPULATION LEVEL ENDPOINTS
ECOSYSTEM/
POPULATION
LEVEL END-
POINTS
EASY/
INEXPENSIVE
COMMENTS
ABUNDANCE
3
Relatively simple measure. Does not
require species identification.
BIOLOGIC INDEXES
2
Requires comparative judgment on groups
of Important species.
BIOMASS
3
Relatively simple measure. Does not
require species identification.
DECOMPOSITION
2
Depends on endpoint measured. At least
some measures such as litter
decomposition are relatively easy to
perform.
DIVERSITY
1
Requires identification of both species
and species distribution.
COMPETITION
1*
Difficult to measure.
INDICATOR SPECIES
2
Relatively simple to focus on the
effects on a single species or groups
of species as representative of the
whole.
KEYSTONE SPECIES
2
Relatively simple focus on the effects
on a single species.
METABOLISM
1.5
Depends on system. Easier to measure
in an aquatic than a terrestrial system
NUTRIENT CYCLES
2
Depends on which aspects of nutrient
cycle is being examined.
Key: 1 - Difficult/expensive
2	- Moderate
3	- Easy/inexpensive
* - Not well studied

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PRACTICALITY (cont.)
ECOSYSTEM/
POPULATION
LEVEL END-
POINTS
EASY/
INEXPENSIVE
COMMENTS
PREDATOR-PREY
Moderately easy to perform in the lab
with organisms such as fish. More
difficult to perform in the field.
PRIMARY PRODUCTION 2.5
Depends on how and where measures are
made. Biomass is fairly easy to
measure in a terrestrial system; C^-^
and O2 techniques can be more
difficult.
SPECIES RICHNESS
Requires identification of species.
SIMILARITY
1.5
A comparative measure. Requires
collection and analysis of data from
multiple sites and identification of
species.
TROPHIC STRUCTURE
Requires identification of species and
examination of feeding habits of
organisms at different trophic levels.
Key: 1 - Difficult/expensive
2	- Moderate
3	- Easy/inexpensive
* - Not well studied
59

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TABLE A-XXV
SPECIES-LEVEL RANKING
PRACTICALITY - SUMMARY
PRACTICALITY
ACUTE MORTALITY
BIOCHEMICAL CHANGES
MORPHOLOGICAL EFFECTS
Carcinogenic Changes
Developmental Changes
Growth
Physiological Effects
Reproductive Effects
Year-Class Distribution
Behavioral Effects
Genetic Changes
60

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TABLE A-XXVI

PRACTICALITY
- SPECIES-LEVEL ENDPOINTS
SPECIES-LEVEL
ENDPOINTS
EASY/
INEXPENSIVE
COMMENTS
ACUTE MORTALITY
3
Direct counts of dead organisms. This
is relatively easy to measure.
BEHAVIORAL
EFFECTS
1.5
Difficult to assess quantitatively due
to variability over time and subject.
BIOCHEMICAL
3
Can be quantified in the lab with
relative ease.
CARCINOGENIC CHANGES 2
Relatively easy to monitor in the lab
or in populations where large numbers
of deaths have occurred.
DEVELOPMENTAL
CHANGES
2
Developmental changes can be relatively
easy to monitor in the lab. May be
evidenced as mortality at early life
stages in the field.
GENETIC CHANGES
(HEREDITABLE)
1
Requires monitoring of changes in
population over relatively long periods
of time.
GROWTH
2
Requires monitoring of changes over
time.
MORPHOLOGICAL
EFFECTS
3
Highly visible. Serves as ready
evidence of adverse impact.
PHYSIOLOGICAL
EFFECTS
2
Moderately easy to monitor. Includes
measures such as feeding,
photosynthesis, and metabolism.
REPRODUCTIVE
EFFECTS
2
Depends on the measure. Behavioral
changes may be difficult to monitor.
Hatch success is simpler to measure.
Key: 1 - Difficult/expensive
2	- Moderate
3	- Easy/inexpensive
61

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PRACTICALITY (CONT.)
SPECIES-LEVEL	EASY/
ENDPOINTS	INEXPENSIVE	COMMENTS
YEAR-CLASS
DISTRIBUTION
Requires identification and monitoring
of different age classes. This can
vary in difficulty depending on the
species and the spatial and temporal
distribution of age class.
Key: 1 - Difficult/expensive
2	- Moderate
3	- Easy/inexpensive
62

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