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Water: Middle School

Exercise V. Macroinverte-whats?

Part 2: The Saga Continues

This discussion is from materials developed by the Izaak Walton League of America's Save Our Streams program.

Before You Get Started

Be sure you read the background information on "Why Study the Stream-Bottom Macroinvertebrates?". Exit EPA Disclaimer



Macroinvertebrates are an Indicator Species

In other words, the presence or absence of certain kinds of macroinvertebrates can signal the presence of pollution in water.

Background Information

In this exercise you will use a key to identify macroinvertebrate species in hypothetical water samples. You will use the numbers and types of organisms in six stream samples to determine water quality.

Materials Needed

  • 6 copies of the Sample Record and Assessment Sheet
  • 1 copy of each of the 6 sample streams


  1. Begin with sample stream 1.
  2. teamx5-2

  3. Use the identification key at the Macroinvertebrate Key Exit EPA Disclaimer Web site to identify the macroinvertebrate organisms represented in each stream sample. (Directions on how to use the key are provided at the Key Directions Exit EPA Disclaimer Web site.)
  4. Record your findings on the Sample Record and Assessment sheet.
  5. Use the Macroinvertebrate Count section in the second half of the form to calculate the water quality index value and determine an overall water quality rating for each stream sample.
  6. Repeat steps 1 through 4 for each sample stream, each time using a new Sample Record and Assessment sheet.
  7. When you have completed all your sample assessments, check your results against the answers at the Practice Samples. Exit EPA Disclaimer Web site.


Middle Schools  |  Join a Stream Team!  |  Exercises: I  |  II  |  III  |  IV  |  V  | 

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