This step-by-step guide will lead you through the Stressor Identification (SI) process, analyses, and characterization activities. The most important tools to bring to the SI process are experience in multiple disciplines (especially ecology); careful, deliberate critical thinking; and a strong desire to find the cause of biological impairment.
Figure 1 is a clickable diagram of the process: click on any step shown in the figure to go to that section of the guide. In Step 1, investigators define the biological impairment that has
prompted the investigation and the scope of the investigation. In Step 2, investigators list
candidate causes. In Steps 3, 4, and 5, evidence is brought in and analyzed as needed until
sufficient confidence in the causal characterization is reached. Three methods for causal
characterization are described: elimination (Step 3), diagnosis (Step 4), and strength of evidence
(Step 5). The Handbook for Characterizing Causes[PDF Format, 23 pp, 1817 KB, About PDF] provides a printer-friendly summary of these three steps.
In Step 6, the probable cause is identified with its associated levels of confidence. In
straightforward cases, the process may be completed in linear fashion, or only one method may
be used. In more complex cases, all three methods may be used, or additional data or analyses
may be required. Step 7 describes options for iterating the process.
Figure 2 provides an overview of the SI process within the context of water quality management and data collection. SI can play an important role in many different water management programs. The SI process is initiated by the observation of a biological impairment (shown in the yellow box, and described in Step 1). Decisionmaker and stakeholder involvement is shown along the left-hand side; their involvement is particularly important in defining the scope of the investigation and listing candidate causes.
At any point in the process of identifying stressors, the need for additional data may be identified; the acquisition of this data is shown in the box on the right-hand side of the diagram. The accurate characterization of the probable cause allows managers to identify appropriate management action to restore or protect biological condition, shown in the lower boxes. Approaches for identifying and implementing effective management actions are outside of the scope of CADDIS. Once stressors are identified and management actions to control them are in place, the effectiveness of the SI process (as demonstrated by improved conditions) can be monitored using appropriate monitoring tools and designs.
