Acute, Chronic, Sublethal Effects to Individuals

Question 1

Single Species Testing Benfits

Answer 1

Control and isolation of variables
* Sensitivity (overestimate toxicity?)
* Provide insight into effects seen at
higher levels of organization
* Simplicity allows rapid incorporation
of new chemicals into testing

Question 2

Microcosms

Answer 2

Microcosm: laboratory systems intended to Microcosm: laboratory systems intended to
physically simulate an ecosystem or major physically simulate an ecosystem or major
subsystem of an ecosystem while permitting subsystem of an ecosystem while permitting
control of conditions and replication of control of conditions and replication of
treatments
** Microcosm: small studies, usually in the lab

Question 3

Mesocosm:

Answer 3

Mesocosm: large, containing many species,
usually outdoorsusually outdoors
** ‘‘Cosms used to study changes at population, Cosms used to study changes at population,
community, ecosystem levels and contain at least community, ecosystem levels and contain at least
2 trophic levels (primary producers, grazers)

Question 4

Cosms benefits

Answer 4

Validate single species lab studies or
mathematical models
* Predict potential fate and effects of
chemicals
–Degradation of compound Degradation of compound
–Bioaccumulation/Biomagnification Bioaccumulation/Biomagnification
–Detect disturbances among populations Detect disturbances among populations
and/or communities and/or communities
* Cheaper than field studies Cheaper than field studies

Question 5

Field Evaluations Advantages

Answer 5

• Site-specific testing
• Realistic
• Account for functional redundancies

Question 6

Field Evaluations Disadvantages

Answer 6

Not predictive (not applicable to other sites)
* Not replicative
* Studies are often long-term
* Temporal and spatial variability

Question 7

Single Species 4 main beniftis

Answer 7

Uncertainty
Reproducibility
Interpretability
Sensitivity

Question 8

Field Test 4 main benefits

Answer 8

Complexity
Cost
Realism

Question 9

Acute exposures time

Answer 9

Exposures 48-96 hours

Question 10

Acute exposures advantages

Answer 10

Rapid building of comparative databases (species and chemical)
* Manipulate water quality to evaluate interactions with toxicity
* Rapid screening of new chemicals, formulations, mixtures, etc…

Question 11

Acute exposures disadvantages

Answer 11

Some acute exposures can take long periods to manifest effects
* Miss sub-lethal effects that may occur

Question 12

Chronic exposures time

Answer 12

10 percent duration of the lifespan of the test organism.

Question 13

Chronic test advantages

Answer 13

More ecologically relevant
* Examine sub-lethal endpoints (growth, reproduction)
* Shows effects at lower doses

Question 14

Chronic test disadvantages

Answer 14

Expensive to run
High maintenance

Question 15

Life cycle study

Answer 15

determines lethality, growth, reproduction, development, or other important qualities at all life stages.

Question 16

Critical life stage test

Answer 16

Focuses on a particular life stage such as neonates. Often, the most critical stage is assumed to be an early life stage.

Question 17

Early life stage (ELS) tests

Answer 17

Often done under the assumption that the most critical stage is often the earliest stages. Embryo to larval stage.

Question 18

Weakest Link Incongruity

Answer 18

Early life stage testing is applied to the
premise that the population will remain viable
if the weakest link in an individual life stage is
protected
– False paradigm
– Early life stage not always the most crucial relative
to the population
– r/K spectrum of reproduction strategies

Question 19

Static toxicity tests

Answer 19

Individuals are placed in a series of exposure concentrations. Exposure water not changed during the test.

Question 20

Static-renewal test

Answer 20

Test solutions are completely or partially replaced periodically

Question 21

Flow-through test

Answer 21

Continuous flow or intermittent flow of toxicant solutions

Question 22

Static Advantages

Answer 22

cheap, easy, minimal waste

Question 23

Static Disadvantages

Answer 23

loss of chemical, poor
water quality/BOD, metabolic products

Question 24

Static-Renewal

Answer 24

Test solutions completely
or partially renewed periodically (typically or partially renewed periodically (typically
every 48 hours)

Question 25

Flow-Through

Answer 25

test solution flows
into and out of test chambers on a
once-through basis

Question 26

Flow-Through Advantages

Answer 26

maintain chemical
concentration, better water quality

Question 27

Flow-Through Disadvantages

Answer 27

expensive, high
maintenance, large volume of waste, maintenance, large volume of waste,
require more space

Question 28

Model Test Species Fresh Water Invertebrates

Answer 28

Daphnia magna
Daphnia pulex
Ceriodaphnia dubia

Question 29

Model Test Species Fresh Water Fish

Answer 29

• Rainbow trout
  *Bluegill
  *Fathead minnow

Question 30

Model Test Marine Invertebrates

Answer 30

Mysid shrimp
Urchin
Sand dollar

Question 31

Model Test Marine Fish

Answer 31

Silverside
Top smelt
Sheepshead minnow

Question 32

Acute Endpoints

Answer 32

Survival
Analyses: LCx

Question 33

Chronic Endpoints

Answer 33

Survival, growth, reproduction
Other endpoints: histology, behavior, etc..
Analyses: NOEC, LOEC, MATC, LCx, ECx

Question 34

Where to start a test

Answer 34

Concentrations
-from Literature
-EPA databases
- Ecotox EPA database
-IRS EPA database
-Hazardous substance database (NIH)
-Pilot Study

Question 35

Dose-Response Models

Answer 35

Standard test method
* Serial dilution of test concentrations (50% dilutions)
* Replicate containers for each treatment
* At least one control treatment
* Individuals randomly placed into the containers
* Mortality tallied in each tank/cage at a set time
* Data used to calculate a measure of lethality
– proportion dying (#dead/#exposed)
– relate to exposure concentration

Question 36

Median lethal dose (LD50) or LC50

Answer 36

The LD50 is the dose resulting in death of 50% of
exposed individuals by a predetermined time, e.g.,
96 h.

Question 37

INCIPIENCY OR THRESHOLD

Answer 37

Lowest concentration (or dose) at which an increase in
toxicant concentration (or dose) begins to produce an
increase in the measured effect or effect metric.

Question 38

Incipient median lethal concentration
(incipient LC50)

Answer 38

Concentration below which 50% of exposed individuals
will live indefinitely relative to the lethal effects of the
toxicant.