Using Benthic Marcoinvertebrates Captured by Rock Baskets to Determine Biodiversity in a River.
Summary
In this investigation of macroinvertebrates, students will build rock baskets and place them in various parts of a river. After time, the rock baskets will be collected and contents examined for macroinvertebrate samples. Students will group insects according to their pollution tolerance and use the PTI to determine the biodiversity of various stretches of the river. Finally, Google Earth can be used examine land use along the river and create hypotheses regarding the changing biodiversity of macroinvertebrates in the river.
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Learning Goals
The objectives of this investigation include that the students will:
1) Observe and classify benthic macroinvertebrates.
2) Calculate the PTI for various areas of a river system.
3) Create hypotheses connecting land use and the quality of water in a river system.
Inquiry skills developed by this investigation include:
1) observation
2) analyzing
3) organization of data/ideas
Concepts discovered by this investigation are:
1) Different areas of a river contain different habitats.
2) Macroinvertebrates can be used to indicate water quality.
3) Human actions have various impacts on ecosystems.
Vocabulary words students will discover through this investigation are:
1) benthic macroinvertebrate
2) riparian
3) riffle, run, pool
4) biodiversity
5) indicator species
1) Observe and classify benthic macroinvertebrates.
2) Calculate the PTI for various areas of a river system.
3) Create hypotheses connecting land use and the quality of water in a river system.
Inquiry skills developed by this investigation include:
1) observation
2) analyzing
3) organization of data/ideas
Concepts discovered by this investigation are:
1) Different areas of a river contain different habitats.
2) Macroinvertebrates can be used to indicate water quality.
3) Human actions have various impacts on ecosystems.
Vocabulary words students will discover through this investigation are:
1) benthic macroinvertebrate
2) riparian
3) riffle, run, pool
4) biodiversity
5) indicator species
Context for Use
This activity is designed to be used for a High School Ecology class, but alterations could be made so that it could be used for a variety of ages of students. The teacher will need access to an aquatic ecosystem for at least 6 weeks, so the activity should be used in the early fall or spring in Minnesota. It will take about 3 total class days to complete. The subject of macroinvertebrates is most closely tied to aquatics, but this activity could be used with any life science class to get students interested in observing and classifying their natural world.
Description and Teaching Materials
For this investigation, the students will need:
- Chicken wire, cheesecloth, strong rubber bands, and rope or twine to make rock baskets.
- Dried leaves and rock for filling the baskets.
- Ice cube trays – one for each student group.
- Plastic spoons, forceps, petri dishes.
- Stereoscopes and hand lenses.
- Benthic macroinvertebrate identification guides. (The Minnesota DNR has guides available.)
- Worksheet for calculating Pollution Tolerance Index (PTI) – attached below.
- Access to Google Earth or similar application.
PRIOR TO CLASS: The instructor should create one-foot square pieces of chicken wire, one for each student or pair of students, depending on class size. Collect dried leaves and small rock (ex. river rock) for students to use. The leaf samples should be from trees native to the collection area.
Student Activities
A. Building the Basket
1. Students roll up their chicken wire into a tube and wire the ends together so that it maintains its shape.
2. They should cut 2 small squares of cheesecloth to cover the ends, and then rubber band a square of cheesecloth on one end.
3. Students add a couple handfuls of dried leaves and rock into the open end of the rock basket.
4. Cover the remaining open end with the second piece of cheesecloth and rubber band.
5. Cut a three-foot piece of rope or twine and tie it onto the rock basket.
B. Placing the Baskets
1. Discuss areas of the river to place the baskets and determine student access to the river shoreline.
2. Send the baskets home with the students to place in a designated area of the river's edge.
3. Students place the rock basket at the river's edge (submerged in the water), and use the rope to stake or tie the rope on the shore.
C. Analyzing the Data
1. After at least 6 weeks, have students collect the baskets and bring them into school in a bucket.
2. Give each student group one ice cube tray – they should fill each container with water. This will be used for sorting macroinvertebrates.
3. Students open one end of their rock basket and dump all materials into their bucket.
4. Using the spoons and forceps, students pick through the basket materials for macroinvertebrates. Any that they find should go into one of the compartments in the ice cube tray. They do NOT need to identify the macros at this point, but they should put similar macros in the same compartment of the ice cube tray. In other words, each species gets its own compartment.
5. Once the students have sorted through all of their materials, they should begin work on identification of each type of macro in their ice cube tray. They can place one sample of a macro on a petri dish, examine it under the stereoscope, and use the identification guide to determine the type of macro.
6. Have the students draw, identify, and count each different type of macro that they found.
7. Students use the worksheet provided below for determining the pollution tolerance index (PTI) for each river site.
8. As an extension, have the students map out the PTI's for each site on the river. Use Google Earth, or a similar application, to study land use at those sites and relate it to the PTI's. Teacher guide and student worksheet for calculating PTI. (Microsoft Word 2007 (.docx) 1.9MB Aug2 09)
- Chicken wire, cheesecloth, strong rubber bands, and rope or twine to make rock baskets.
- Dried leaves and rock for filling the baskets.
- Ice cube trays – one for each student group.
- Plastic spoons, forceps, petri dishes.
- Stereoscopes and hand lenses.
- Benthic macroinvertebrate identification guides. (The Minnesota DNR has guides available.)
- Worksheet for calculating Pollution Tolerance Index (PTI) – attached below.
- Access to Google Earth or similar application.
PRIOR TO CLASS: The instructor should create one-foot square pieces of chicken wire, one for each student or pair of students, depending on class size. Collect dried leaves and small rock (ex. river rock) for students to use. The leaf samples should be from trees native to the collection area.
Student Activities
A. Building the Basket
1. Students roll up their chicken wire into a tube and wire the ends together so that it maintains its shape.
2. They should cut 2 small squares of cheesecloth to cover the ends, and then rubber band a square of cheesecloth on one end.
3. Students add a couple handfuls of dried leaves and rock into the open end of the rock basket.
4. Cover the remaining open end with the second piece of cheesecloth and rubber band.
5. Cut a three-foot piece of rope or twine and tie it onto the rock basket.
B. Placing the Baskets
1. Discuss areas of the river to place the baskets and determine student access to the river shoreline.
2. Send the baskets home with the students to place in a designated area of the river's edge.
3. Students place the rock basket at the river's edge (submerged in the water), and use the rope to stake or tie the rope on the shore.
C. Analyzing the Data
1. After at least 6 weeks, have students collect the baskets and bring them into school in a bucket.
2. Give each student group one ice cube tray – they should fill each container with water. This will be used for sorting macroinvertebrates.
3. Students open one end of their rock basket and dump all materials into their bucket.
4. Using the spoons and forceps, students pick through the basket materials for macroinvertebrates. Any that they find should go into one of the compartments in the ice cube tray. They do NOT need to identify the macros at this point, but they should put similar macros in the same compartment of the ice cube tray. In other words, each species gets its own compartment.
5. Once the students have sorted through all of their materials, they should begin work on identification of each type of macro in their ice cube tray. They can place one sample of a macro on a petri dish, examine it under the stereoscope, and use the identification guide to determine the type of macro.
6. Have the students draw, identify, and count each different type of macro that they found.
7. Students use the worksheet provided below for determining the pollution tolerance index (PTI) for each river site.
8. As an extension, have the students map out the PTI's for each site on the river. Use Google Earth, or a similar application, to study land use at those sites and relate it to the PTI's. Teacher guide and student worksheet for calculating PTI. (Microsoft Word 2007 (.docx) 1.9MB Aug2 09)
Teaching Notes and Tips
In the past, I went with students down to the river and we attempted to collect macros in one day. We do not have very good riffles in our area of the river, so our samples were very limited. I am hoping that the rock baskets will increase the quality and quantity of our samples. They also give us the opportunity to compare different areas of the river.
If you are concerned about the rock baskets being disturbed while out in the river, you could have your students make up ID tags to attach to the baskets that identify them as a school investigation. For younger students, you may want to send a letter home to describe the project and ensure that an adult will accompany the child to place the basket by requiring a signed permission.
Drawing the macros carefully and correctly is an important part of the observations and identification in this lesson, so make sure to discuss your expectations of this activity with your students ahead of time. Be specific about how big and detailed you want the drawings to be.
If you are concerned about the rock baskets being disturbed while out in the river, you could have your students make up ID tags to attach to the baskets that identify them as a school investigation. For younger students, you may want to send a letter home to describe the project and ensure that an adult will accompany the child to place the basket by requiring a signed permission.
Drawing the macros carefully and correctly is an important part of the observations and identification in this lesson, so make sure to discuss your expectations of this activity with your students ahead of time. Be specific about how big and detailed you want the drawings to be.
Assessment
Student drawings and calculations of PTI's are graded for accuracy. Students are also assigned a short paper to write relating land use along the river to the PTI's.
Standards
(2009 Standards) 9.4.4.1.2 - Describe the risks and benefits of changing a natural ecosystem as a result of human activity.