(By investigating aquatic ecology using Vital Signs hand held computers with Leaf Packs) students will learn about decomposition and aquatic invertebrates and gain an appreciation for the link between lake or streamside forests and the waters' invertebrate inhabitants. In general, students will gain experience in answering a question by conducting an ecological field experiment.

Important Note: This activity is ideally an in-depth field experiment. While it can potentially be condensed to several class periods, it is more appropriate as a longer-term science project.

• 5-8:
  2. Analyze how the finite resources in an ecosystem limit the types and populations of organisms within it.

• 5-8:
  3. Verify and evaluate scientific investigations and use the results in a purposeful way.
  2. conduct scientific investigations: Make observations, collect and analyze data, and do experiments.
• 9-12:
  2. Verify, evaluate, and use results in a purposeful way.

• 5-8:
  6. Support reasoning by using a variety of evidence.

• 5-8:
  4. Describe an individual's biological and other impacts on an environmental system.
  6. Give examples of actions which may have expected or unexpected consequences that may be positive, negative, or both.
  7. Explain the connections between industry, natural resources, population, and economic development.

[This activity is rich with just about all higher order skills here, as it requires real analysis, synthesis, and evaluation skills! So, this list is really just partial.]

• Analyzing
• Applying
• Presenting
• Associating
• Concluding
• Inferring
• Assessing
• Criticizing
• Comparing
• Judging
• Weighing

The class must be able to use the Vital Signs equipment including protocols for data collection. (left this in from other activity - appropriate here also?)

• Linguistic/Verbal
• Naturalistic
• Interpersonal
• Visual/spatial

• Vital Signs hand-held computer w/temperature probe, PalmPix camera and invertebrate ID key
• (Analog alternative: mercury-free thermometers; invertebrate indentification field guide; pencil, paper/data sheets, and clipboard.)
• [printed and laminated illustrated macroinvertebrate sorting sheet - PDF]
• 6 mesh bags (onion bags or clam bags with small holes)
• 6 Scales
• Waterproof marker
• Nylon twine
• Scissors
• 6 Plastic labels and 6 plastic ties (tags)
• 6 Buckets (to place leaf packs before identifying/sorting contents)
• 12 white ice cube trays (for sorting and counting invertebrates)
• 1 strainer with very small holes
• hand lenses/magnifying glasses, if possible
• 6 large white trays, if possible (for spreading out debris for a closer look to find inverts.)
• sorting tools (e.g., small fish tank nets, plastic spoons, small paint brushes, plastic eyedroppers/pipettes...)
• Rubber boots / water sandals (for teacher and at least 1 member of each of 6 teams.)
• Bug data sheet

The science of ecology is the study of the relationships among plants and animals and their environments. Lakes and streams are aquatic environments but they are not isolated from the plants, animals and land just beyond the water's edge. Forests growing alongside lakes and streams affect them in many ways. Roots of the trees hold onto soil. Leaves from the trees often drift down into the water and slowly decay. These leaves can serve as both food and habitat for aquatic animals and can even change the chemistry of the water. Tiny spineless animals (invertebrates) often eat, live, hide and lay eggs in among these castaway leaves.

Clumps of leaves often collect naturally in streams. Ecologists studying streams and lakes often place packs of leaves in streams and then collect them later. In this way, they can answer many different questions such as how fast the leaves decay and what types of invertebrates live in the fallen leaves. They can even compare what happens when they place packs of leaves in different streams or with different leaf types. In this activity, the class will conduct its own leaf pack experiment and use the Vital Signs hand held computer to identify invertebrates and record data and observations.

Resources:

• Technical aquatic invertebrate key
• The "Buglopedia". (Although this is "from away," it is general and includes pictures, pollution tolerance ratings, and tips for catching and sorting bugs.)
• The Stroud Water Research Center's Leaf Pack Network

(Note: Presented here is a sample experiment with basic step-by-step instructions; these could be modified to custom design leaf pack experiments for many different questions. See extensions.)

Preparation

Assemble materials. With or without students, collect leaves from 2 common deciduous leaf types and 2 common evergreen leaf types near your stream. Spread leaves out to dry.

Question:

Do a stream's spineless critters prefer deciduous or evergreen leaves for food and shelter?

Class 1: Introduction/Preparation

(Note: in class 1, ideally students will weigh and assemble leaf packs. Alternatively, the teacher may have prepared them in advance to save time.)

1. To introduce this topic, consider having students look at their Vital Signs PalmPix photos of the stream or lake that your class monitors. List out what they see in the photo. (Water, ground, trees, etc...) What kinds of plants grow along the edge of the stream/lake? (If they have done the "Know Your Place" activity, this could provide a starting point as well.)
2. Lead the class to a discussion of the trees and forests that grow alongside lakes and streams. Do they have a role in the underwater ecology? How? (For review, define the term ecology.) Consider brainstorming a list of ways that lake or streamside trees are connected to the underwater ecosystem.
3. After discussing natural clumps of leaves in the water provide food and shelter for living things, explain that the class is going to do create their own packs of leaves. They will use them in an experiment to answer an ecological question -whether their stream's invertebrates prefer evergreen leaves or deciduous leaves for food and shelter. (If necessary, define/review the terms evergreen versus deciduous.) Form a hypothesis: ask the students to imagine they are slow moving, small snails or insects. Which kind of leaf would they like to snack on or hide in, and why?
4. Have students record predictions of what they will find after leaving the leaf packs in the water for 3-4 weeks. What will happen to the leaves? Which will decompose the most: evergreen needles or deciduous leaves? Which will have more small invertebrates hiding inside?
5. Prepare a total of 6 leaf packs. Divide students into 6 groups - groups 1 to 6. They will keep their group number throughout this activity. Give each group a scale, 1 short and 1 long length of twine, a mesh bag, plastic labels and ties, and a waterproof marker.
6. Each bag will contain 30 grams total made of 2 leaf types. Have students place 15 grams each of the 2 leaf types (2 deciduous for 3 teams, 2 evergreen for 3 teams.)
7. Have students securely tie the bags shut with the short length of twine, attach the plastic tie and tag, and label the tag with the bag number for their group (1-6), a letter D or E for deciduous or evergreen, and the school name and date.
8. Have students tie the long length of twine to the bag on one end. Collect leaf packs for the next class.

In advance of Class 2 and 3, talk with the students about safety for both the class and the bugs. To attach and retrieve the packs, students may need to wade into water more than in typical Vital Signs activities. Watch for slippery conditions and beware of fast-flowing water. Consider bringing a chaperone or second teacher. Always handle bugs gently and keep them wet. Work in the shade to prevent the insects overheating. Return bugs to the stream/lake at the end of Class 3.

Class 2: Deploy Leaf Packs

Give each student group their leaf pack and explain that you will travel to the site to place these in the stream. The group will need to look for a secure site to attach the leaf packs (a large rock or root for example.) If your site does not have large rocks, you can take cinder blocks or something similar for the experiment. (Be sure to remove these afterwards.) Travel to stream site with vital signs tools and prepared leaf packs.

1. Have students divide into their six groups.
2. Have each group wet their leaf pack and photograph the wet pack using the PalmPix tool.
3. Explain that the different leaf packs should be placed at similar depths and currents. One option is to have two groups place evergreen and deciduous packs at the same rock.
4. While 1 or 2 students from the group are attaching the pack to a rock or root, the other students can use the Vital signs tools to record observations, take a temperature reading, and document the leaf pack location. Have students use the sketchy tool and GPS tool to record the coordinates and draw a map of the leaf pack location. Have students photograph the leaf pack's location with the PalmPix tool.

Class 3: Sorting Bugs

After 3-4 weeks, return to the site to retrieve the leaf packs. If possible, schedule this trip so that it runs for approximately 3 hours to allow time to carefully sort and count insects. Consider enlisting a second teacher or a chaperone for assistance.

1. Divide students into original groups. Remind students to treat bugs gently and keep them wet and cool.
   ---Each team should:
2. Use their PalmPix photos, Sketchy maps, and notes to locate their leaf pack.
3. Spread out and locate a shady, level spot near the water's edge and lay out their trays and sorting tools. Place small amounts of stream/lake water on the white trays and in the ice cube trays.
4. Collect several inches of water in the bucket and take the bucket with them to retrieve the pack.
5. Cut the twine while the pack is submerged, then quickly lift up the pack and transfer it to the bucket. (Some invertebrates will quickly try to escape.)
6. Record observations about the leaf pack. Photograph the pack with the PalmPix camera.
7. Carefully open and empty the pack. Check the mesh bags for attached inverts, and use a small magnifying glass to find small bugs. Look closely, gently shaking the bucket; some bugs can be difficult to spot. (If there is an excessive amount of mud making the sorting difficult, carefully rinse the bucket contents in a strainer.)
8. Begin netting and transferring bugs to the white trays, where it will be easier to spread them out, spot them, and separate them. As the buglopedia website points out, the tray should look white with dark blotches-not the reverse. Remove the leaves one at a time, checking that there are no bug hitchhikers on board.
9. Gently pick bugs out with pipettes, plastic spoons and paint brushes. Separate them into groups in ice cube trays or petri dishes (containing small amounts stream/lake water), with similar bugs grouped in each dish.
10. Some students in the group can record observations, use the PalmPix tool to photograph the sorting process and the bugs themselves, and draw the insects using the Sketchy program.
11. Once bugs are separated out, use the bug key to identify the catch. Count the number of each type and record the counts in the bug data sheet.
12. After recording the counts, gently return the bugs to the water as close to the habitat where you found them as possible. Rinse the buckets and trays in the lake/stream to ensure that all critters are returned.
13. Clean up, being sure to collect all spoons, trays, nets, twine, cinderblocks, etc.

Class 4 - Analysis and Discussion

1. Have the groups assemble their data, leaf "before-and-after" photographs, "Sketchy" drawings, and observations.
2. Depending on time, students could create simple bar graphs of their results. (For an in-depth experience, students could assemble their results as science posters).
3. Combine the data from the 6 groups to determine the results for the entire class. (Older students can average the numbers for the 3 packs for deciduous or evergreen, while younger students can simply total the numbers.)
4. As a class, answer the following questions:
5. (Again, older students can average for the three replicate leaf packs, while younger ones can total the results for the three packs per leaf type.)
   • Evergreen leaf packs:
     1. How many bugs were found in total? (abundance)
     2. How many different KINDS of bugs were found? (diversity)
   • Deciduous leaf packs:
     1. How many bugs were found in total? (abundance)
     2. How many different KINDS of bugs were found? (diversity)
   • Which leaf packs decomposed the most?
6. Discuss these results and draw conclusions about the deciduous versus evergreen question. Which type of pack appeared to be a better "leafy living room" for bugs? Which had more invertebrates hiding inside? Why might this be true? Look at the students' original predictions: were the results what the students expected?

1. Bug Bioindicators

   Use aquatic insects to calculate a measure of the health of your Vital Signs ecosystem. Some aquatic insects are sensitive to pollution, while others are very tolerant of poor water quality. The bugs you find give you a clue about your stream or lake's water quality. Collect your data from the deciduous leafpack. Based on the invertebrate key (also see buglopedia website), assign a value of 1 for insects that are very tolerant, 2 for tolerant, 3 for sensitive, and 4 for very sensitive. In the classroom after the field activity, have students calculate a stream health index based on the bugs they found. This is basically a weighted average of the different tolerances of the insects found. Have students multiply the index number times the count number for each insect type. Add these values together, and divide the sum by the total number of insects found. This number (ranging from 1 to 4) is the stream health index for your site. Low numbers are evidence of a polluted stream; high numbers are evidence of a healthy stream. Consider comparing 2 sites or sharing your results with those of another school.

2. Invertebrate Classifying/Sorting Race (Optional pre-activity extension)

   This is best carried out as an introductory activity - after introducing the experiment but before carrying out leaf pack experiments. In preparation, print and copy sheets of common aquatic invertebrates:

   Cut the sheets into small squares with invertebrate pictures. Mix the squares and place an equal amount of them into mesh bags that will be used for the experiment. Tie the top of the bags. Label petri dishes as dragonfly nymph, mayfly nymph, fly larva, snail, etc, such that each team has 1 dish for each common invertebrate on the sheet. In class, divide students into small teams. Explain that they will have a race to see which team is the fastest at correctly classifying and sorting the invertebrates. Give each team a copy of the laminated ID sheets or the hand held with the invertebrate key, the labeled dishes, and the bag with paper "insects." Each team will then race to indentify and physically sort the photographs of common aquatic invertebrates into the finger bowls or petri dishes. This activity will preview the leaf pack activity and give the students practice at identifying and sorting common invertebrates. When the first team finishes, have the students "freeze" and quickly check the teams sorting to verify that it has been done correctly. If they have correctly sorted, have the class discuss how they could tell the different invertebrates apart. If they have not accurately or carefully sorted the invertebrates, tell all the teams to keep going - the race is still on. The team that finished can try to correct their sorting.

3. Creative Connections

   Research the connections between the streamside forest and aquatic ecosystems. Have the class draw a mural, or student groups draw and present posters, representing these connections. Or, have the students write and volunteer to read first-person creative writing stories about the adventures of a leaf falling towards a stream and what happens to it once it lands in the water. (These follow-up extensions would engage visual, linguistic, and interpersonal intelligences.)

4. School Partners

   With the help of the Vital Signs program manager, identify another participating Vital Signs classroom at a school in another region of Maine. Communicate with that school about a local stream near your school and one near their school. Share data, photos and observations they have already collected with the Vital Signs tools. Based on your communications, have students discuss the differences between the two streams and then predict what will happen if packs of leaves are placed in the two streams. Which stream will have more small invertebrate animals? In which stream will the leaves decompose the most? Which is more polluted (see bug bioindicators)? Have the students place leaf packs with equal weights of the same 3 deciduous leaves in the two streams. The two schools should coordinate to place the same kind and size of packs on the same day for the same length of time. Compare results and discuss.

5. Custom-designed experiments (older grades)

   After discussing and/or researching the background information and reviewing experimental design and control/experimental variables, have the class or student groups pose an ecological question and design their own leaf pack experiments to answer that specific question. Building on the same basic procedure described above, students can measure different variables such as macroinvertebrate abundance and diversity and/or leaf decomposition (e.g., original dry weight minus dry weight after stream placement). Students could study the difference between locations (e.g., road side versus isolated), stream health (see bug bioindicators), the effects of temporal variables (season, exposure time), the effects of physical factors (pH, temperature, depth, bottom type, light exposure, turbidity, water movement) or leaf composition. They could also measure leaf pack decomposition or invertebrate composition over time by monitoring the packs in a time series. The students should analyze/graph their data and present their results and conclusions in poster and/or presentation format.

6. Qualitative Leaf Pack Exploration (younger grades)

   In this simple, qualitative adaptation of Leaf Pack experiments, students will learn to appreciate the connection between trees along a stream or lake and the small animals that live in a stream. They will gain experience with making and testing simple predictions. Discuss the relationship between trees and aquatic environments. Why do many trees grow well near lakes and streams? (There is water under the soil near streams and lakes.) How do trees affect these places and the animals that live in the water? (They hold onto the soil, and provide food and habitat.) Consider having the students investigate these connections at the site, looking for natural clumps of leaves, submerged roots, etc. Tell the students that the class is going to place packs of leaves in a stream/lake and return several weeks later to find them. Ask the students to predict what they will find when they collect the packs. What will happen to the leaves in the water? What might they find hiding in the leaves? Prepare simple leaf packs, without worrying about the weight, leaf type, etc. After placing them in the stream, return several weeks later to retrieve them. Remind students of their predictions. Quickly and carefully empty the contents of the leaf packs into buckets. Using their Vital Signs tools, students can observe, draw and photograph the leaves and the small snails and bugs inside. Discuss what they found and whether it surprised them. Did they know what would happen to the packs of leaves? Possibly wrap up with students creating a mural or posters representing the connection between streamside trees and stream ecology.