MnSTEP Teaching Activity Collection > MnSTEP Activities > Healthy Waters

Healthy Waters

Summary

Animals are often more finely-tuned than humans to changes in an environment. At one time, coal miners used canaries to detect the presence of dangerous gases because these birds are sensitive to shifts in air quality. Similarly, aquatic macroinvertebrates have different tolerances to water pollution. The health of a stream can be judged by the macroinvertebrate species that are present and may indicate shifts in an environment before such changes are easily recognizable to humans.

Both macroinvertebrate species that are sensitive to and those tolerant of pollution can live in a stream with good water quality. With increased pollution however, fewer sensitive species will be found. If the stream's water quality is very poor, only those macroinvertebrates tolerant of pollution will survive. EPT is an abbreviation for Ephemeroptera, Plecoptera, and Trichoptera (mayflies, stoneflies, and caddisflies), insect groups that are largely intolerant of pollution. If many EPTs are present, the water quality is probably good. Macroinvertebrates capable of surviving in very polluted water include aquatic worms, leeches, and midge larvae.

The Hilsenhoff Biotic Index, or HBI, measures the health of a stream by assigning tolerance values to macroinvertebrates which range from 0 for organisms that are very sensitive to organic wastes to 10 for organisms that are very tolerant of organic wastes. The biotic index of a stream site is found by collecting a sample of benthic macroinvertebrates, then multiplying the number of individuals within each separate species by the tolerance value of the species. The resulting products are then added together and this sum is divided by the total number of organisms in the sample.

*taken from "Windows into wonderland-mystery into the missing bugs" lesson from Yellowstone National Park

Learning Goals

- Interpret how biological indicators are used to gauge the health of a stream.
- Calculate the Biotic Index of each site.
- Analyze the "water quality" of their sample with 100% accuracy.
- Comparatively determine the sample site that indicates high pollution.

Concepts: By the end of this lesson, students should understand how we can use macroinvertebrates to determine the quality of water in a river/stream.

By the end of this lesson, students should be able to determine how a community can increase or decrease the water quality of its local steams/rivers through its practices (runoff, fertilizers, pollution, etc)

Vocab: Biotic indicators, Biotic Index, macroinvertebrate, pollution tolerance, benthic, Ephemeroptera, Plecoptera, and Trichoptera

Context for Use

7th Grade Life Science Class - Lab (60 minutes) and Lecture (20-30 minutes)

Estimated time - (2) 45 minute class periods

Equipment - (if using lab from website)
Large bag of M&Ms
Bag of macaroni noodles
Box of Cheerios
Bag of beans
Small plastic bags
Paper
Pencils

Equipment - (if using modified lesson)
10 ice cube trays
Tweezers
stereoscopes
Transparencies (cut out each species of macroinvertebrates)
Ziploc baggies (to put "samples" in from each stream)
Pencil
Paper

I am using this activity in the very beginning of the year to introduce my insect collection. I want to do more ecology in my class and have it as a recurring theme throughout the year. I believe this lesson can be adapted to high school (actually going out and collecting the macroinvertebrates and then calculating). Could also be used in an elementary setting.

Subject: Geoscience, Environmental Science:Water Quality and Quantity
Resource Type: Activities:Field Activity:Field laboratories
Special Interest: Field-Based Teaching and Learning
Theme: Teach the Earth:Enhancing your Teaching:Teaching in the Field, Teach the Earth:Teaching Environments:K12, Teach the Earth:Teaching Topics:Water, Teach the Earth:Course Topics:Environmental Science

Description and Teaching Materials

The lesson will be introduced as a question...why do we need to study biology? Why do we need to know about insects? What is life and what are the needs for life (water)?

We will discuss these questions and make a concept map on the board from these questions/answers. We will then talk about water and ecology in a lecture/ Q & A format. The lab will be explained after the lecture and students will start the investigation. The closure for the activity will be to post all the results on an overhead and then discuss why each stream is different and what the difference means to us.

Equipment - (if using lab from website)
Large bag of M&Ms
Bag of macaroni noodles
Box of Cheerios
Bag of beans
Small plastic bags
Paper
Pencils

Equipment - (if using modified lesson)
10 ice cube trays
Tweezers
stereoscopes
Transparencies (cut out each species of macroinvertebrates)
Guide to macroinvertebrates
Ziploc baggies (to put "samples" in from each stream)
Pencil
Paper

Reference website: Windows Into Wonderland - Mystery of the Missing Bugs
Biotic index lesson plan (modified) (Microsoft Word 33kB Aug24 07) Data Table Macroinvertebrates (modified) (Microsoft Word 65kB Aug24 07) Data table macroinvertebrates (yellowstone version) (Acrobat (PDF) 19kB Aug24 07) Rubric (yellowstone version) (Acrobat (PDF) 41kB Aug24 07)

Teaching Notes and Tips

Students might have a hard time understanding why certain species are more or less tolerant of pollution than others. Semi-tolerant and tolerant vocabulary words might also be a little confusing. Other than that, I would make sure that all the bags have the same # of species and also make sure that they all have a different combination of tolerant and intolerant pollution species (I would record the answer to the Biotic index for the 10 sites in a separate document for teacher's use only)

Assessment

Assessment of the information will be done formally and informally. Informally, the teacher needs to be active during the lab and asking questions to all the students while they are processing the information ("What type of macroinvertebrate is that?" "Do you think it's tolerant of pollution?" Why would one macro be tolerant and the other intolerant?"
Formal assessment for this lab would be done with the data table worksheet and the questions included on it. Also, if doing the Yellowstone version, you can use the supplied rubric.