Pollution Tolerance Index
Apr 16th, 2014 by Kristin Lewis
Macroinvertebrates have different levels of tolerance for low water quality.
Certain taxa or groups of organisms are known to be more or less tolerant of polluted conditions of a stream. The presence or absence of these organisms can be used to evaluate the level of pollution or human disturbance of a stream. The analysis breaks stream invertebrates into 4 groups, and the presence or absence of these organisms is can be used to calculation a “Pollution Tolerance Index” for a stream.
Click on each link below to read more about specific members of each group:
- Group 1 invertebrates – Intolerant of pollution (i.e. you would not likely find these organisms in a low quality habitat)
- Group 2 Invertebrates – Moderately intolerant
- Group 3 Invertebrates – Fairly tolerant
- Group 4 Invertebrates Very tolerant (i.e. could survive in streams even with high levels of pollution and low quality habitat)
Concept Check Question:
Which of the following statements about the pollution tolerance ratings is TRUE?
A. All invertebrates have the same ability to survive in polluted conditions.
B. Stoneflies and mayflies are examples of organisms that would be found in a high quality stream.
C. Midges, black fly larvae and planaria are all organisms that could only survive in a high quality stream.
D. Sowbugs and scuds are insects that you might find in a very polluted stream.