Acute, Chronic, Sublethal Effects to Individuals Flashcards
Single Species Testing Benfits
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
Microcosms
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
Mesocosm:
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)
Cosms benefits
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
Field Evaluations Advantages
- Site-specific testing
- Realistic
- Account for functional redundancies
Field Evaluations Disadvantages
Not predictive (not applicable to other sites)
* Not replicative
* Studies are often long-term
* Temporal and spatial variability
Single Species 4 main beniftis
Uncertainty
Reproducibility
Interpretability
Sensitivity
Field Test 4 main benefits
Complexity
Cost
Realism
Acute exposures time
Exposures 48-96 hours
Acute exposures advantages
Rapid building of comparative databases (species and chemical)
* Manipulate water quality to evaluate interactions with toxicity
* Rapid screening of new chemicals, formulations, mixtures, etc…
Acute exposures disadvantages
Some acute exposures can take long periods to manifest effects
* Miss sub-lethal effects that may occur
Chronic exposures time
10 percent duration of the lifespan of the test organism.
Chronic test advantages
More ecologically relevant
* Examine sub-lethal endpoints (growth, reproduction)
* Shows effects at lower doses
Chronic test disadvantages
Expensive to run
High maintenance
Life cycle study
determines lethality, growth, reproduction, development, or other important qualities at all life stages.
Critical life stage test
Focuses on a particular life stage such as neonates. Often, the most critical stage is assumed to be an early life stage.
Early life stage (ELS) tests
Often done under the assumption that the most critical stage is often the earliest stages. Embryo to larval stage.
Weakest Link Incongruity
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
Static toxicity tests
Individuals are placed in a series of exposure concentrations. Exposure water not changed during the test.
Static-renewal test
Test solutions are completely or partially replaced periodically
Flow-through test
Continuous flow or intermittent flow of toxicant solutions
Static Advantages
cheap, easy, minimal waste
Static Disadvantages
loss of chemical, poor
water quality/BOD, metabolic products
Static-Renewal
Test solutions completely
or partially renewed periodically (typically or partially renewed periodically (typically
every 48 hours)
