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CADDIS Volume 1: Stressor Identification

Summary Tables of Types of Evidence

Types of Evidence that Use Data from the Case

Type of Evidence The Concept
Spatial/Temporal Co-occurrence The biological effect must be observed where and when the cause is observed, and must not be observed where and when the cause is absent.
Evidence of Exposure or Biological Mechanism Measurements of the biota show that relevant exposure to the cause has occurred, or that other biological mechanisms linking the cause to the effect have occurred.
Causal Pathway Steps in the pathways linking sources to the cause can serve as supplementary or surrogate indicators that the cause and the biological effect are likely to have co-occurred.
Stressor-Response Relationships from the Field As exposure to the cause increases, intensity or frequency of the biological effect increases; as exposure to the cause decreases, intensity or frequency of the biological effect decreases.
Manipulation of Exposure Field experiments or management actions that increase or decrease exposure to a cause must increase or decrease the biological effect.
Laboratory Tests of Site Media Controlled exposure in laboratory tests to causes (usually toxic substances) present in site media should induce biological effects consistent with the effects observed in the field.
Temporal Sequence The cause must precede the biological effect.
Verified Predictions Knowledge of a cause's mode of action permits prediction and subsequent confirmation of previously unobserved effects.
Symptoms Biological measurements (often at lower levels of biological organization than the effect) can be characteristic of one or a few specific causes.

Types of Evidence that Use Data from Elsewhere

Type of Evidence The Concept
Stressor-Response Relationships from Other Field Studies At the impaired sites, the cause must be at levels sufficient to cause similar biological effects in other field studies.
Stressor-Response Relationships from Laboratory Studies Within the case, the cause must be at levels associated with related biological effects in laboratory studies.
Stressor-Response Relationships from Ecological Simulation Models Within the case, the cause must be at levels associated with effects in mathematical models simulating ecological processes.
Mechanistically Plausible Cause The relationship between the cause and biological effect must be consistent with known principles of biology, chemistry and physics, as well as properties of the affected organisms and the receiving environment.
Manipulation of Exposure at Other Sites At similarly impacted locations outside the case sites, field experiments or management actions that increase or decrease exposure to a cause must increase or decrease the biological effect.
Analogous Stressors Agents similar to the causal agent at the impaired site should lead to similar effects at other sites.

Evaluating Multiple Types of Evidence

Type of Evidence The Concept
Consistency of Evidence Confidence in the argument for or against a candidate cause is increased when many types of evidence consistently support or weaken it.
Explanation of the Evidence Confidence in the argument for a candidate cause is increased when a post hoc mechanistic, conceptual, or mathematical model reasonably explains any inconsistent evidence.

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