To make inferences about the quality of freshwater using macroinvertebrate data collected from local water systems. To explain the factors that contribute to the presence or absence of a species.
In this lesson, students will collect macroinvertebrates from a river or stream site then sort and identify them. By noting which types are most abundant and which of the sensitive species are missing, we can learn a lot about present and past conditions of a stream.
*Click here for information on purchasing equipment or supplies or creating your own equipment. Contact USU Water Quality Extension (email@example.com or 435-797-2580) for information on borrowing equipment.
NOTE: If you have already done the activity Who Lives in the Water? you can review the classroom activity with the students, then skip to step 6 of the field activity.
1. Ask the students to identify the types of plants and animals that live in streams (or other aquatic systems such as wetlands or ponds). Tell them this activity will focus on the diversity of macroinvertebrates found in streams. (Make sure they know the definition of a macroinvertebrate.)
2. Explain to the students they will collect a macroinvertebrate sample in a stream, identify the different types of organisms in their sample, and calculate a water quality index, which is a numeric way of rating the health of a stream. An index like this allows them to compare different sites in an objective way.
3. Ask the students to think about what might affect the diversity of plants and animals they would find in this aquatic ecosystem (e.g., pollutants entering the water, changes in habitat, natural or human caused changes in temperature, flow, substrate, food abundance or quality, predators in the system).
4. Review common macroinvertebrates found in your area with the students. Have the students hypothesize what kinds of macroinvertebrates they expect to find. Be sure they are familiar with the macroinvertebrate keys they will be using in the field. Printable keys and online keys are available through USU Water Quality Extension.
5. Review sampling instructions with your students before they go into the field. Click link below for step by step photos.
Prepare for Field Activity:
Proper preparation, before entering the field, is important to class safety. Follow the links below for tips for thorough preparation.
1. Set up stations for sampling macroinvertebrates. These areas should be easily accessible and, if possible, have a range of substrate, such as small pebble, larger cobble, or woody debris.
--Each Station Should Include:
- Macroinvertebrate sampling instructions
- Kick net
- Plastic pan
- Macroinvertebrate keys
- Transfer pipettes
- Magnifying glasses
- Petri dishes
2. Divide the students into groups. Group size should be six students or less to make sure that everyone gets to participate. Provide each group with clipboards, pencils,and macroinvertebrate sorting worksheet. Each group will sample at a different station.
3. Demonstrate to the group how to sample for macroinvertebrates, then have the students collect samples. Have the students follow the instructions on the macroinvertebrate sampling instructions.
4. If time allows, give students an opportunity to observe the various types of macroinvertebrates
in their sample.
5. The students must sort and count the types of organisms found in a subsample (~100 organisms). They will record this
information on the macroinvertebrate sorting worksheet. Complete instructions on taking a subsample and sorting organisms are provided on the macroinvertebrate sampling instructions.
NOTE: The subsampling, sorting and counting can be done in the field or back in the classroom with preserved samples.
6. Calculate the water quality index for each sample using the Water Quality Index worksheet. Have the students follow the instructions on the water quality index instructions. NOTE: This step can be done in the classroom.
7. Have the students hypothesize the driving factors behind their water quality index. If they have a low water quality index (an absence of some species of macroinvertebrates), what is causing the populations to disappear?
Students can further their understanding of macroinvertebrates as an indicator of water quality by looking at their data in various ways or participating in a variety of research projects. Some helpful ways to assist students in a better understanding are:
1. Use your data to create graphs and comparisons.
- Compare the diversity of macroinvertebrates and water quality index at:
- each station sampled
- at the same station on multiple days
- at a river site and a pond site
- at a upstream location and a downstream location (e.g.above an urban area and below an urban area)
2. Discuss what the results mean.
- Research factors that would contribute to a decline in the diversity of macroinvertebrates.
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