Stream Quality

Flip Rocks! / Benthic Organisms

Overview
Introduce benthic organisms (creatures that live on the bottom of streams) as indicators of water quality. By monitoring benthic organisms we get an excellent picture of life in the stream over time. We get a general sense of water quality, which can be further explored by chemical testing.

Objectives
Introduce typical organisms for local stream conditions. For instance, in a typical urban, Pennsylvania, spring-fed stream one can find planarians, gammerus or scud, snails, and isopods. The presence of benthic organisms can indicate: diversity as a sign of a healthy environment, some organisms are known to exist in comparatively clean waters (such as gammerus), whereas others are more tolerant to pollution (such as planarians).

Estimated Duration
1 to 1.5 hours

Lesson Plan

Class setting
Students work in small groups.

Script of class interactions
Have the students collect around the stream. Explain the safety issues and the need to be careful when working around streams with potentially suspicious water quality. Explain the need to wash well after working in the stream. Explain that no food, candy or gum should be consumed while working with the stream, or until after they have cleaned their hands.

Hand out the sampling pans and distribute materials to the students. Have them gather around the stream and pay attention as you demonstrate a safe and sensitive manner of disturbing the benthic organisms home. Remember if you pick a rock put it back where you found it. Return all living creatures to the stream carefully, after you study.

Display and Teaching Materials
Use the accompanying field book
See drawings of benthic organisms
Review supplemental background information on classifying creatures.

Activity: Flip Rocks!
Demonstrate how to find benthic organisms. The easiest method with the least equipment is to simply choose some likely rocks in shallow but moving water. Pick up a stone and look at the underside, "wigglers" of all sorts are likely to be found and can be carefully nudged, picked and pushed into the collecting cups or directly into the sampling pan.
Observe the benthic organisms closely using a magnifying lens. Look for body structure:
Does it have legs? How many legs does it have?
How does it move?
Does it have a head?
What color is it?
Observe the environmental context for these benthic organisms:
Are they in a shady or sunny area?
Is the bottom gravel or sand?
Is the water shallow or deep?
Is the water moving really fast or sort of slow?
Are their trees or grass along the stream banks?
Are there any manmade objects nearby? (text by 5th grade student)
Observe the different kinds of benthic organisms.
How many different kinds have you found?
Are they wigglers, crawlers, backstrokers or blobs?
Are you seeing a lot of one kind and a few of another?
Draw the benthic organisms, make detailed drawings, noting all of the above.   Dickson Intermediate School Drawings by 5th grade students