Rationale:

• There is a diversity of insects that live in and around water.
• Stream bottom material influences the type of organisms in a stream.
• Substrate is a function of stream stability reflecting the conditions of a stream channel, riparian corridor, flood plain, and watershed.
• Benthic invertebrates living in running water show preference to various bottom types.
• Benthic invertebrates not only need specific chemical water quality parameters, but they need substrate habitat providing adequate living space.
• Habitat is important in animal survival.

Student relevance:

• Substrate habitat is one component that helps determine benthic diversity.

Learning Objectives:

Upon completion, students will be able to . . .

• Determine the average size substrate material in a cross-section of a riffle or other part of a stream.
• Identify that some species prefer a particular substrate.
• Use a random number table.

Students Need to Know:

• Insects live around bodies of water.
• Insects and other animals live in water and are dependent on a wide variety of variables, including substrate composition.

Teachers Need to Know:

• Most benthic invertebrates living in water show preference to various bottom types.
• Some species prefer a particular substrate; thus, as the stream bottom changes from place to place so does the benthic invertebrate fauna.
• The more diversity in stone size within a stream provides more variety of space available for colonization by benthic invertebrates.
• Sandy bottoms often have the fewest kinds of benthic invertebrates.
• Silt reduces the fauna among stones because it fills in interstitial spaces.
  • Interstitial spaces are the gaps between different sized stones where macroinvertebrates colonize.
• The benthic invertebrate in clean, stony riffles are greater in species diversity than those in silty riffles and pools.
• Often the upstream end of a riffle has a more diverse and abundant benthic fauna because organic matter used as food reaches this area first.
• This system should be used to compare streams whose geographical, geological, and watershed characteristics are similar.
• Muddy or sand bottom streams in northern Missouri are difficult to measure using this system.

Resources:

The following materials are available from the Missouri Department of Conservation, P.O. Box 180, Jefferson City, MO 65102-0180, (573)751-4115.

Aquatic Field and Classroom Activities
Life within the Water

A Monitor’s Guide to Aquatic Macroinvertebrates - Available form the Izaak Walton League of America (IWLA), 707 Conservation Lane, Gaithersburg, MD 20878, 1-800-284-4952. ($5 each with 10% discount for ordering 10 or more)

Materials Needed for Lesson:

Transparency of Stream Cross Section of Riffle (provided)
Random Number Chart (provided)
Tape measure that will stretch across a stream (one per team)
Bow caliper—measures external diameter, obtain at an office supply store (one per team)
Two clipboards (optional)
Graph paper
Pencils

Procedure:

• Prior to field trip, show transparency of Stream Cross Section and discuss where aquatic life live.
• Divide students into at least two teams.
• Have each team select a stretch of river channel where the water is less than knee deep.
• Stretch a measuring tape across the selected sites.
• Remove 100 rock samples from the stream bed in a riffle. Remove one rock from the stream for each random number on the chart where that number is found on the tape measure.
• Have each team align their rocks from smallest to largest based upon the axis as it would be found in the stream.
• Measure and record all stones using a bow caliper. Have students take turns.
• Measure to the nearest centimeter along the horizontal or longest axis.
  Graph in groupings of five centimeters along the X axis (Dependent Variable) and number of stones along the Y axis.(Independent Variable)
• The graph is interpreted as the greater number of points along the Y axis, the greater the interstitial spaces, the greater the potential for habitat diversity.

Evaluation Strategies:

• Check measurements done by students and observe students’ sampling techniques.
• Have students write a paragraph explaining which site has greater substrate diversity and why.

Extension Activities:

• Detailed water quality monitoring.
• Attend Stream Team Volunteer Water Quality Monitoring Workshops

Scoring Guide:

Substrate Habitat

Student Name: ________________________________________

Rubric Made Using: RubiStar (http://rubistar.4teachers.org)

*Random numbers based on a 25-foot tape measure being used.

Stream Cross Section of Riffle