- 1 350µ mesh D-frame dip net
- Small fish nets
- 1 pair rubber gloves (shoulder length)
- Shallow plastic white trays
- Ice cube trays
- Plastic boxes with magnifier tops (“bug boxes”)
- Hand Lenses
- Pipette droppers
- Plastic spoons
- Macroinvertebrate Identification Guide, laminated
- Aqua-Scope Underwater Viewer
- Field Microscope
- Discovery Scope
NGSS Performance Expectation
Students who demonstrate understanding can:
3-LS4-3. Construct an argument with evidence that in a particular habitat some organisms can survive well, some survive less well, and some cannot survive at all.
- the types of macroinvertebrates in a stream are an indicator of water quality and habitat quality for salmon.
- salmon cannot survive well in streams with poor water quality.
- collect macroinvertebrates from a stream and identify them to species group.
- interpret a chart to infer water quality based on the types of macroinvertebrates observed.
- Select a spot along the stream where:
a. Access to the stream and wading in it is easy and safe for students.
b. There’s a diversity of habitats for collecting: pools and riffles, undercut banks, in-stream vegetation,
cobbles and larger rocks that can be moved in front of the kick net.
- Organize the collecting and sorting equipment and guides to species identification.
- Prepare a science notebook to include a Science Notebook Page for Macroinvertebrates as Indicators and a Macroinvertebrates Indicator Datasheet.
Make copies of the Science Notebook Page to include in a science notebook or use as a data sheet.
- You may choose to collect a sample in advance of the student’s arrival to make sure students will have success collecting macroinvertebrates and to maximize their investigation time.
Tell, or remind, the students the question they are trying to answer: Could salmon survive well here? Then ask them how the insects in the stream might be important to salmon and at what stage of their lives. (Remind them that insects that are big enough to see with their naked eye are called “macro,” and because they have no spine, or vertebrae, they’re called “macroinvertebrates. These are the right size for salmon fry and juveniles to eat; adults don’t eat anything after they enter their spawning streams.)
Explain that they will be gathering evidence about not only whether there is some food for young salmon in the stream by sampling the macroinvertebrates that are part of the salmon food web. Certain species of macroinvertebrates that young salmon and other predators eat can only live where the water is not polluted and there’s plenty of dissolved oxygen. They are considered Indicator Species of “good” or “neutral” water quality required by salmon. Other macroinvertebrates are quite tolerant of pollution and require less oxygen. If students find those species in the stream, it means that the water quality is poor, likely too poor for salmon to find food and survive. Check to see if they understand the concept of an indicator. (One analogy would be a dipstick used to check the level of the oil in a car. The oil level won’t tell you about how every part of the car is doing, but cars don’t run well when they’re low on oil. A stream ecosystem doesn’t run well when it’s low on oxygen and certain types of macroinvertebrates that are the food for a diversity of predators.)
- Call their attention to the table on their data sheet or in their science notebook.
- List the types of indicator species you would expect to see in a stream where water quality is good: stonefly, dobsonfly and mayfly nymphs, caddisfly larvae, and water pennies. Point to the picture of each species.
- Do the same for the indicator species of neutral or poor water quality.
- Reinforce the ways to identify the three main types of macroinvertebrates they will be looking for as indicators of good water quality - mayflies, stoneflies and caddisflies.
- Mayfly – swim up and down like a dolphin, triangular in shape, have 2-3 tails
- Stonefly – swim side-to-side, are long and thin, always have 2 tails
- Caddisfly – crawl, have tube-shaped bodies, usually live in a case
- Students attempt to collect macroinvertebrates from several habitat types.
- They will use D-Nets and rubber gloves.
- Point out different habitat types to sample: rocks, undercut/vegetated banks, snags, aquatic vegetation
- Even if you collected a sample in advance of the student’s arrival, briefly demonstrate the use of the D-net so they learn how to use it.
- Demonstrate how to use a pipette to pick up critters and drop them into a small bead of water in a petri dish.
NOTE: Emphasize to students that the insects are LIVING THINGS and that they need to be gentle in handling and moving them!
- Have the students put some creek water in the sorting and ice cube trays to prepare.
- Empty the contents of the net into 4-5 sorting trays.
- Collect softball-sized rocks from the creek bottom and put a few in each of the trays for the students to explore. (These often have critters clinging directly on them.)
- Distribute forceps, pipettes, and Petri dishes to the students and tell the students: THEY ARE RESPONSIBLE FOR RETURNING THEM AT THE END OF THE SESSION
- Have them look through the sample to look for different types of organisms and sort them into the ice cube trays. Guide them in using pipettes and forceps to help separate macroinvertebrates from creek debris and in the use of the Macroinvertebrate Identification Key to making identifications. Be sure that each student has classified all three main species.
- As students identify their species, they will make sketches on their data sheet or in their science notebook and write down the names in one of the categories: good quality, neutral quality, or poor quality, using the table to decide which category they should be placed in.
Indicators of Good Water Quality (Sensitive or Intolerant To Pollution)
Organisms easily killed, impaired or driven off by bad water quality include:
- Mayfly nymphs
- Caddisfly larvae
- Stonefly nymphs
- Dobson fly larvae
- Water pennies
- Riffle beetles
Indicators of neutral water quality (Somewhat Tolerant To Pollution)
Organisms with the ability to live under varying conditions. You may find them in good or poor quality water:
- Dragonfly larvae
- Damselfly larvae and nymphs
Indicators of poor water quality (Tolerant to Pollution):
Organisms capable of withstanding poor water quality.
- Midge fly larvae
- Blackfly larvae
- Aquatic worms
- Mosquito larvae
Macroinvertebrates that can survive at a lower dissolved oxygen level because they can come to the surface to get oxygen through a breathing or "snorkel" tube or carry a bubble of air with them around their bodies or under their wings. Several species of macroinvertebrates are indicative of water systems with lower dissolved oxygen levels and include aquatic worms and leeches. Lower dissolved oxygen levels are often associated with polluted waters while higher levels indicate good quality water.
After the students have completed their observations and notes, have them return all the equipment and then RETURN THE INSECTS TO THE CREEK.
Ask students to share their results in terms of whether they found species that fit into each of the three categories for water quality. Remind them that salmon need a water quality index of good or neutral to survive well.
Draw their students’ attention to the question on page 13 of their Science Notebook:
Based on your results, could salmon survive well in our stream? Yes or No & Why?
If you have time, have a discussion about how they would answer the question. Ask students to explain their answers by providing evidence to answer the “Why?” If there isn’t enough time for this discussion during the field trip, tell them to write their answers when they’re back in their classroom.
This field trip activity was developed for the Anchorage School District Watershed Education Program. The field trip program supplements a 4th grade STEM Kit on the theme of Interdependence and a focus on Anchorage watersheds and salmon.
Macroinvertebrates are relatively easy to collect and observe. They are important indicators of water quality for salmon and stream food web that supports salmon because certain species are indicators of intolerant to organic pollution (sewage and other waste materials that require oxygen to decompose) and to other types of pollution that are also toxic to salmon.
Common macroinvertebrate species can be separated into three categories as indicators of water quality as good, neutral, or poor. Salmon can survive well where the water quality is good or neutral but not where the water quality is poor.
Prior Student Knowledge: Salmon and insect life cycles, food chains and webs
Possible Learner Misconceptions and Instructional Clarifications:
Learner Misconception: Students can tell if a stream is “clean” through observations of litter or debris in a stream.
Instructional Clarification: Pollution is defined as something introduced into the stream that doesn’t occur naturally. Even natural substances, however, such as heat or organic wastes that use up available oxygen during decomposition, can change the conditions for life in the stream. Many types of litter and debris are not toxic to salmon or other life in the stream, but substances that dissolve into the water, like pesticides that wash off lawns, can be very toxic. Sampling macroinvertebrates in the streams provides a way to determine how “clean” the water is in terms of pollutants that affect the survival of salmon and the food web they depend on in a way that visual observations of whether or not a stream “looks clean” can’t.
Learner Misconception: If students find only small numbers and a few species of macroinvertebrates that indicate good or neutral water quality, this is evidence the stream is likely polluted or poor quality.
Instructional Clarification: Using macroinvertebrate diversity and tolerances to pollution an indicator of stream health is highly dependent on the timing and location of sampling because macroinvertebrate populations fluctuate seasonally and each species has different habitat preferences in the stream. The presence of any tolerant and sensitive species an indicator they can survive under the current water quality conditions in the stream. Low abundance of food, however, could affect salmon survival or growth rates.
Components of Next Generation Science Standards Addressed
Engaging in Argument from Evidence Construct an argument with evidence. (3-LS4-3)
For any particular environment, some kinds of organisms survive well, some survive less well, and some cannot survive at all. (3-LS4-3)
Cause and Effect
Cause and effect relationships are routinely identified and can be used to explain change.