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 undetermined (U) or unknown.

Index Scale
 

Stress Tolerance Categories

  • Low - 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.

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