Evaluating macroinvertebrates

Stress Tolerance 

Stress tolerance is the organism’s ability to withstand a certain amount of anthropogenic influences.  The index range for each category is based upon a (0-10) scale.  For example, invertebrates with a low tolerance need adequate dissolved oxygen and chemical and physical stability, while those with a high tolerance can survive for a period of time when dissolved oxygen levels are less than adequate or other disturbances may be present.  Note: There are some types that are un-determined (U) or un-known.

Description of the major categories

: Occur with little or no disturbance to moderately disturbed conditions. Moderate: Occur from moderately to highly disturbed conditions but can also occur in less disturbed conditions. An overabundance (dominance) of moderate organisms is often a good indication of disturbance. High: Occur most often under disturbed conditions with only one or two groups may dominate the entire community. They are also found in good conditions, but usually in low numbers. 

Additional Resources