Students often spend a LONG time on this lesson.
The calculations made at the end of the lesson can be tough for students to understand. It is best when done as a 2-hour lesson or combined with another aquatic activity.
DESCRIPTION: Students will use a variety of tools and their own observations to conduct a water quality assessment. Using their observations, they will form a HYPOTHESIS about the health of the pond and creeks at The Outdoor School. Using the data they collect on BENTHIC (bottom dwelling) aquatic invertebrates, they will then discover if their initial hypothesis was true.
OBJECTIVES: Students will be able to:
- Use low impact collection techniques and equipment to collect macro invertebrates
- Record their observations to produce accurate field notes
- Use field guides to identify various types of macro invertebrates found in water ecosystems.
- Perform a macro invertebrate survey to determine the overall water quality of a water ecosystem using a BIOTIC INDEX.
AREA OF ACTIVITY: Lower end of the pond, creek below spillway and dam.
MATERIALS PROVIDED: 5 gallon collecting bucket, observation trays, ice cube trays, field microscopes, bug boxes, field guides, ID charts, Biotic Index charts, pond nets, Pencils/papers/copies of worksheets
PROCEDURES: INTRODUCTION (20 minutes including travel time)
While looking at the pond, have students share their opinions on the health of the pond and creek. Use the OBSERVATIONS worksheet to guide their questioning, filling out one form as a group.
PLEASE IMPRESS UPON THE STUDENTS THE IMPORTANCE OF LOW IMPACT COLLECTING TECHNIQUES!
The following guidelines should be followed at all times:
- Stay out of the creeks with your shoes – COLLECT FROM THE BANK
- Turn over rocks slowly and gently and always replace them
- Stay off eroding areas
- Try to stay on rocks/gravel – not squashing plants or in the mud
- Replace all plant material/water to the pond or creek – do not pour it on the grass
- Look carefully for critters – they are very well camouflaged and usually stick to plants and rocks.
CENTERED ACTIVITY (40-45 minutes)
Divide the group into smaller work groups of 3 or 4 students. Give the students guidelines on proper collecting techniques and have them set up a collecting station at least 20 feet from the water’s edge.
After about 30 minutes, combine all students’ information until you have reached 100 critters. Use their breakdown of species to fill out the Biotic Index Chart (Critter Counter). If you have not collected 100 critters, collect 50 and compare to half the Biotic Index number result.
Biotic Index Procedure:
- Working with their group, students should take an approximate 500ml sample of the water (including debris) and place it in the collecting tray.
- Students should then carefully sift through the debris to see if they have any macroinvertebrates (critters).
- Any macroinvertebrates should be separated into either bug boxes or the ice cube tray for closer identification.
- Using the identification charts, students should count and identify their macroinvertebrates.
Encourage students not to hunt for only the large animals such as fish or tadpoles or the sample will be biased. Identify and count the numbers of each type of organism listed on the Biotic Index Chart. (Critter Counter)
- Multiply the number of each type by its biotic value.
- Add up all the numbers and divide by 10. This gives the Biotic Index Value. Check the Biotic Value chart at the bottom of the page to determine the quality of your water sample.
SOME TERMS STUDENTS WILL NEED TO KNOW:
Riparian – the area adjacent to the water – the banks
Sediment – the gravel/ soil/ plant materials that lie on the stream or pond bottom
Macroinvertebrate – critters without backbones (such as bugs and worms) that are visible to the naked eye
Class I Pollution intolerant: These organisms are highly sensitive to pollution. They are not found where pollution is present.
Class II Somewhat pollution tolerant: These organisms will be found in clean and slightly polluted waterways.
Class III Pollution tolerant: These organisms will be found in polluted, as well as clean aquatic ecosystems. These do not prefer polluted waters; they are just able to survive there! The presence of these critters does not signal pollution (students often get confused with this concept).
CONCLUSION (15 minutes)
Have the students compare their first thoughts about water quality with their findings. Do they agree? Why or why not? Did the season affect the results? What other factors may change the results other than pollution?
Students should understand that they COLLECTED DATA and used their own data to form a CONCLUSION to their hypothesis.
RETURN ALL WATER, PLANTS AND CRITTERS TO THE CREEK.
