Look Closely for Water Quality Activity by Alison Smith, SRP

Lesson adapted with permission from Arizona Project WET (more info at

What bugs are in the river? When water comes out of your sink, you hope it doesn’t have bugs in it! But water in a stream SHOULD have some bugs in it. A healthy river system is a source for all kinds of life, including bugs.

Macroinvertebrates Macroinvertebrates are… Macro = large (things that can be seen with the naked eye) Invertebrate = animals without a spine

What can macroinvertebrates tell us? Macroinvertebrates are valuable indicators of the health of an aquatic environment because of three things: They don’t move over large distances in their environment like fish do, for example; therefore, they can’t easily migrate away from environmental stressors. Each type of macroinvertebrate is tolerant or intolerant of different conditions of the water. So depending on the types of macroinvertebrates in a water sample, we can determine what can and can’t live there, which then can give us a sense of what the quality of the water is like.

Examples of Environmental Stressors Water pollution A large amount of sediment coming in to a system Warming due to low flows Low dissolved oxygen Algal blooms

What? If something happens to the water (say an algae bloom), the macroinvertebrates that are intolerant of that “stressor” will die. When we collect the water sample, we will find NONE of that type of bug. Therefore we know that there may be something wrong with the water.

Let’s simulate it Tolerant (can live in even lower quality water) bugs will be represented by this symbol = Intolerant (can live only in high quality water) bugs will be represented by this symbol =

Good Water Quality If a lot of intolerant bugs can live in a stream, it must be a pretty high quality stream (there also may be bugs that are tolerant of any water quality). The higher the number of intolerant bugs present in your sample, the better the water quality. Count the number of weak and strong bugs in our stream sample.

Poor Water Quality If the stream sample is dominated by tolerant bugs and has no intolerant bugs, it probably has a lower water quality (the intolerant bugs are NOT protected so they die and the tolerant bugs live) – the fewer intolerant bugs present in your sample, the lower the water quality. Count the number of intolerant and tolerant bugs in this stream sample.

Your turn Go out to a local pond, stream or lake and do your own bioassessment. This picture was taken at Verde River in Camp Verde

Collect your sample. Use the net to sample along the stream or pond bottom.

Collect your sample

Look closely for bugs.

Use the ice cube tray to sort the different types. Use magnifiers and three way viewers to begin to identify different types.

Record your Data What kinds of bugs are in your sample? (Use the dichotomous key to identify them.) Count the number of bugs you have that are the same type. Record your data on the students worksheet.

Use a dichotomous key to identify your macroinvertebrates. Link for Dichotomous Key: Pond Key: River Key:

Analyze your data (back in the classroom) Mayflies (Ephemeroptera), stoneflies (Plecoptera), and Caddisflies (Trichoptera) are very intolerant bugs (weak). Put a red square on your data sheet to represent each of those that you found. Mayfly larvaStonefly larva Caddisfly larva

Analyze your data Leeches (Hirudinea), Tubifex worms (Tubifex sp.), and Pouch Snails (Gastropoda) are very tolerant bugs. Put a green star on your data sheet to represent each of those that you found. LeechTubifex wormPouch snail

Analyze your data Dragonflies and Damselflies prefer better quality water but can survive in lower quality water than the intolerant species. The presence of these organisms would mean that the water is of moderate quality.

Making a conclusion Look at your data and draw a conclusion about the quality of the body of water that you are analyzing. Remember: if you’ve found a lot of intolerant bugs, then you must have a great stream.

Conclusion Looking closely at our environment, even at the smallest creatures, can help us learn about our world. For additional research: Travel to your city’s water treatment facility and research the water quality in your area.

Thank You Alison Smith, Sr. Community Outreach Representative- Education at SRP (Salt River Project) Arizona Project WET