Trout Are Made of Trees: How Are Leaves Important to Streams?

Transcription

1 Trout Are Made of Trees: How Are Leaves Important to Streams? Subject/ target grade: Middle School (8 th grade) Earth Science Duration: Four 50 minute periods Setting: Classroom, computer lab, and local site with easy stream access Materials and Equipment Needed: Per class Fact sheets / books Macroinvertebrate Identification Resources Per small group 3 pairs rubber boots 3 Leaf Pack bags Strong, nylon twine 6 Garbage twist ties 3 gallon Ziploc bags 3 Cinder blocks or large bricks 1D frame nets 3 White sorting trays Sorting equipment: Forceps, spoons, eyedroppers, magnify glasses 3 ice cube trays 200g of dry leaves 1 Bucket 1 pair of scissors Per student Student Background Reading Leaf Pack Experimental Design Sheet Leaf Pack Field Data Sheet Leaf Pack Macroinvertebrate Datasheet Leaf Pack Presentation Rubric Lesson Overview: Students will design and conduct a scientific investigation involving the use of artificial stream packs to collect macroinvertebrates. Students will manipulate their leaf packs to test one of the following variables: leaf type, amount of leaves, size of leaf pack, shape of leaf pack, location of leaf pack within the stream, or other variables as needed. Students will design the experiment, deploy their leaf packs in the stream for 2 weeks, and then collect the leaf packs. Once collected, students will count and identify any macroinvertebrates. In addition, students will determine the mass of leaves used by the macroinvertebrates in the stream. Lesson Core The Guiding Question: How are leaves important to streams? Safety precautions: Students will wear appropriate footwear when wading in the stream. Students must take care in deep streams or in streams with rapidly running water. Advanced Preparation: MS Powerpoint presentation describing and defining the important concepts (see included presentation) A student packet including the following: Background Reading Leaf Pack Experimental Design Sheet 1

2 Leaf Pack Field Data Sheet Leaf Pack Macroinvertebrate Datasheet Leaf Pack Presentation Rubric Learning Objectives: Design and carry out a scientific investigation. Collect stream macroinvertebrates using artificial leaf packs. Correctly identify common groups of macroinvertebrates. Identify the important influences that contribute to stream health. Effectively communicate scientific research in a slide presentation. Michigan Content Expectations: E1.1A. Generate new questions that can be investigated in the laboratory or field. E1.1H. Design and conduct a systematic scientific investigation that tests a hypothesis. Draw conclusions from data presented in charts and tables. Background Information for Teachers: This experiment may take anywhere from 3 6 weeks to complete. Review the background reading for students below. In addition, review the attached PowerPoint presentation to prepare for the lesson. Important Terms: organic matter decomposers detritus detritivores decomposers nitrogen nitrogen fixing bacteria leaf pack oxygenated water ecosystem fungi macroinvertebrate CPOM FPOM shredders collectors grazers scrapers algae predators Engage: How do stream organisms get the food that they need? Building on prior knowledge: What are key ingredients for a successful scientific study? What do we need to consider when designing an experiment? Why are invertebrates important to streams? Why is it important to monitor stream health? Pre teaching: Students will have experience in designing an experiment through the completion of Watershed Connections Lesson 1: What is Scientific Inquiry?. Students should be familiar with macroinvertebrates and water quality through completing Watershed Connections Lesson 4: How is Water Quality Affected by Land Use? as well as Watershed Connections Lesson 5: Bugs, Brook Trout, and Water Quality?. See Student Reading below. Assign students to read the Student Reading and define all the bold words. 2

3 Watershed Connections Lesson 6 Trout Are Made of Trees: How Are Leaves Important to Streams? Background Information for Students Throughout late summer and fall, leaves fall from trees and shrubbery found by the sides of creeks. Many of these leaves will end up floating down the creek while others will sink to the bottom. Once dead organic matter (once living material) sinks into the water, it starts to be attacked by bacteria and aquatic fungi, known as decomposers and detritivores. These leaves can start to become slimy from this attack. These microorganisms break down the organic matter into its primary components, such as nitrogen rich ammonia by nitrogen fixing bacteria. Other microorganisms transform these primary components into compounds that plants and algae can use to grow, such as nitrites or nitrates. The leaves flowing in the current get caught between rocks and logs and gradually build up into clumps. The leaves have a new name now detritus. Actually, any organic matter that is dead and being decomposed is called detritus, even animal matter. The detritus, now stuck between rocks and covered with microorganisms, becomes the dream house of some everyday macroinvertebrates. The detritus can also be habitat for some aquatic organisms, providing a safe place to stay, keep away from predators, or keep out of the stream flow. The clump of leaves also provides a welcome break from the stream current, allowing the macroinvertebrates to rest in comfort. The leaves allow a small flow of water through them however, giving the macroinvertebrates their needed supply of oxygenated water. This is important because the large populations of bacteria produce large amounts of carbon dioxide that displaces the oxygen. Detritus is important to the stream ecosystem because it provides a food source directly or indirectly for a multitude of organisms (Figure 1). Not all creatures eat the leaves directly because they are low on nutritional value and can be difficult to digest. The fungi and bacteria that decompose the leaves provide their own byproducts with nutritional value to supplement what the leaves lack. The detritus and microorganism supply is processed by different groups of macroinvertebrates in a series of steps. 3

4 Figure 1. Cycle of the life of a leaf in a stream ecosystem. The first step is to break down the large leaf matter, called CPOM (coarse particulate organic matter), into fine particulate organic matter, or FPOM. This is accomplished by shredders, a group of macroinvertebrates with specially adapted anatomy, such as pinchers, to tear apart and eat the fibrous leaves. Examples of shredders are cranefly larvae, casebuilding caddisfly larva, stonefly nymphs, scuds, and sowbugs. As they feed on the CPOM, the FPOM produced floats downstream and eventually into the devices of collectors. Collectors filter the water in the stream for FPOM by using hairy gills or legs, or in other cases by spinning a web. Examples of collectors are mussels, brush legged mayfly larvae, net spinning caddisfly larvae, midges, and blackfly larvae. As mentioned before, the bacteria feeding on the leaves convert some compounds into ammonia, and others convert the ammonia into nitrites and nitrates that plants and algae use to grow. Another group of macroinvertebrates, called grazers or scrapers, feed on algae that grow on nearby rocks and other hard surfaces. The grazers crawl along the creek bottom scraping rocks for any algae. These organisms typically have a flat, oval body to protect them against the current. Examples of scrapers include snails, flathead mayfly larvae, waterpenny beetle larvae, and stone case building caddisfly larvae. All the mentioned macroinvertebrates above are in turn food sources for the 4th class of macroinvertebrates, predators, which include dobsonfly and fishfly larvae, crayfish, beetles, water bugs, dragonfly nymphs, and some stoneflies. These invertebrate predators are a food source for vertebrate predators such as fish, birds, reptiles, and amphibians. 1

5 Explore: Day 1 Discuss possible variables for the student s experiments. What variables could affect the amount or type of macroinvertebrates collected in your stream packs? Write the possible answers on the board. [These may include amount of leaves, type of leaves, habitat (both in stream and surrounding), substrate, canopy cover, etc.] Divide students into pairs or groups of 3. Have students complete the Experimental Design worksheet to formalize their experiment. Be sure the students check their experimental design with their instructor(s) prior to preparing their leaf packs. Once all group have finished, have students share their design with the class for peer review. Assign students to bring in a small bag of leaves to class the next day. Pass out a gallon Ziploc bag for each student to fill up and bring in the following day. If students are looking at specific types of leaves as per their experimental design (e.g., yellow leaves or oak leaves), have those students choose only those types of leaves. Day 2 Have students prepare their leaf packs according to their experimental design. Demonstrate how to put together a leaf pack for the class. Preparing your leaf pack bag: To be consistent in experimentation, have the students place the same amount of leaves in each leaf pack bag. For instance, they can use a scale to weigh 30g of dry leaves for each mesh bag. You may want to have students record this information on the enclosed Leaf Pack Field Data Sheet Tie leaf pack bag shut using strong twine or garbage twist ties. Insert a length of strong twine through the mesh of the bag so that the bag can be secured to something in the stream. That object can either be natural like a large rock, a fallen log, tree roots along the end of the stream OR you can tie the bag to a brick, cinder block, or something else to anchor it. Day 3 Have students go to the chosen stream. Place the packs in the stream according to the student s experimental design. Be sure each student has a copy of the Leaf Pack Field Data sheet to fill out when placing the packs in the stream. Placing leaf packs in the stream: Find a position in the stream where a leaf clump would naturally form, such as between two stationary objects or in front of a large rock or log. Place the leaf pack in the stream on the upstream side of the object so that as much surface area of the bag possible is facing the current. Attach the leaf pack bag to the object (large rock, log, brick or cinder block etc.) using the strong twine. Make sure that all of the leaves are submerged and that the leaf pack is securely tied to the weight so it does not become loose and float away. You or the students may want to 2

6 make a map for each location in the stream where the leaf packs were placed on the enclosed data sheet. You may also tie some flagging tape to some vegetation along the stream bank directly across from or beside the leaf pack location. However, if other people visit your stream, the flags may be incidentally torn down. Have the students fill out the remainder of the enclosed data sheet. Leave the leaf packs in the stream for about 2 3 weeks. Without disturbing the leaf packs, you may want to check them every few days or after storms to make sure they remain submerged. Note: Leaf packs can be lost during floods and should be removed early if floods are predicted. After 2 3 weeks (1 day): Collecting the leaf packs from the stream: Collect a few inches of stream water in the bottom of a gallon size ziploc bag or other type of plastic bag. Gently hold onto the submerged leaf pack and cut the twine that is securing it to the object. Pick up the leaf pack bag quickly and gently. Some of the insects are very quick to escape so do your best to minimize moving the leaf pack around. If you have D frame nets (included in module), place them downstream of the leaf pack bags before cutting the twine and removing it from the stream. The net will catch bugs that escape. Place the leaf pack bag into the ziploc bag with the stream water and then seal. Collect additional stream water in a bucket or other container. This will be used during freshwater macroinvertebrate sorting. If not sorting through the leaf pack bags right away, place the ziploc bags into a refrigerator or ice filled cooler. Most aquatic insects can be refrigerated or iced in coolers overnight. Do not leave the bugs in the ziploc bags for more than 24 hours or they will die. If you need to keep them longer before sorting, consider placing the contents of each leaf pack bag into a separate container of water, which is kept cool and ideally aerated. Have the students identify the insects using resources included in the unit. View them closer using magnifying glasses or microscopes. Explain and Elaborate: Have students prepare a written scientific report explaining their research results. In addition, have them give a short 3 minute talk to the class about their results. Supplement their explanations with the following questions. Identify the types of macroinvertebrates residing in a stream s leaf packs Correctly conducted sampling procedures Correctly completed data sheet List the food sources for the different classes of macroinvertebrates 3

7 Evaluate: Students will be graded on both their participation and Powerpoint presentation using the following rubric for a total of 150 points. Lesson Closure: What did you learn about stream ecosystems through this experiment? How could you have improved upon your experimental design? How do inputs from trees help the ecosystem? Are trees next to streams good for fish? make it Artificial Leaf Pack Activity ( LineActivities/AquaticMacros/Artifi calleafpackactivity.pdf): a source for lesson plans using leaf packs and macroinvertebrate identification games. Stroud Water Research Canter ( ): great source of information explaining the premise behind the use of leaf packs. Lesson Extension Additional Resources: Michigan Environmental Education Curriculum, Water Quality module, Stream Monitoring. m Aquatic Entomology is amazingly beautiful. The illustrations alone 4

8 Watershed Connections Lesson 6 Trout Are Made of Trees: How Are Leaves Important to Streams? Leaf Pack Experimental Design Worksheet 1. What is the variable you are manipulating? 2. What is your research question? 3. Your formal hypothesis: If, then we expect. 4. Describe your experimental design in as much detail as possible. 5. What data will you collect? 6. How will you analyze your data to answer your research question? 7. How will you represent your data in your results section? Evaluated by Approved? 2

9 Watershed Connections Lesson 6 Trout Are Made of Trees: How Are Leaves Important to Streams? Leaf Pack Field Data Sheet Lab Group Members: I. Project title: (in the form of a question) II. Hypothesis: III. Describe each of your leaf packs: Control or experimental? Mass of leaves (g) Treatment? Color(s)? Leaf Pack 1 Leaf Pack 2 Leaf Pack 3 IV. Location of sampling site (i.e., 60m upstream from bridge): 1

10 V. Stream Observations (i.e.,flow rate, appearance, size): VI. Description of vegetation along the stream at your sampling site: VII. Sketch your sample location. Note where each of your leaf packs is located in the stream. Note any natural or artificial features near the stream that can be used to locate your leaf packs. 2

11 Watershed Connections Lesson 6 Trout Are Made of Trees: How Are Leaves Important to Streams? Macroinvertebrate Data Sheet Species Treatment Treatment Treatment Total Total Begin Leaf Pack Mass (g) End Leaf Pack Mass (g) 3

12 Watershed Connections Lesson 6 Trout Are Made of Trees: How Are Leaves Important to Streams? Leaf Pack Lab Report Your lab report should include the following: Title: Name. Descriptive title of your experiment. Introduction: Background information on the role of leaves in streams. A diagram of the life of a leaf in a stream ecosystem. Explanation of your diagram in paragraph form. Reference to your diagram in the text. i.e., When a leaf falls into a stream, it is first broken down by detritivores (Figure 1). The objective(s) or purpose of your research. Clear statement of your hypothesis using an if/then statement. Methods: Detailed step by step methods in paragraph form describing how you completed your experiment. Results: Explanation of your results in paragraph form. Describe the differences in the data you collected (e.g., highest and lowest value, trends). One data table containing the data from your leaf packs with a descriptive caption. Your data should be set up like the following: Table 1. Number, species, and PTI score for macroinvertebrates we collected in our three leaf pack treatments. Species Treatment 1 Treatment 2 Treatment 3 Total PTI group 4

13 One graph demonstrating an important aspect of your data. Reference both the table and graph in your text. Example: We observed the highest number of macroinvertebrates in our leaf pack placed in the run of the stream (Table 1). Using this data, we compared the number of craneflies, or pollution sensitive macroinvertebrates, across our three treatments (Figure 1). Discussion: Interpret your data and the conclusions you can draw from it. Explain whether your data supports or does not support your hypothesis. Conclusions: Briefly summarize the experiment and your conclusions. Provide one suggestion for how to improve the experiment or what you would do differently if you repeat the experiment. Notes: Your report must be typed using MS Word and free of grammar mistakes. All information must be in your own words. Any plagiarism in the report earns a score of zero. 5

14 Watershed Connections Lesson 6 Trout Are Made of Trees: How Are Leaves Important to Streams? Leaf Pack Lab Report Rubric Grading Standard: None (0 points) the student has not met any of the requirements for this criterion. Fair (1 4 points) the student has only minimally met the requirements for this criterion and it is incomplete or incorrect. Good (3 8 points) the student has met most of the requirements or it contains minor mistakes. Excellent (5 or 10 pts) the student has met all of the requirements; it is complete and correct. The report is free of grammar and spelling mistakes The report contains a title, student name, and the five sections of a scientific report. The Introduction contains sufficient background information. A correctly labeled flowchart is included and referenced in the text. The hypothesis and justification for the experiment is clearly explained in the Introduction The Methods are clearly explained and logically organized. Results are easy to interpret and summarize data collected. A table of data is included with proper format and labels with a reference in the text. A figure describing an important aspect of the data is included with proper labeling and referenced in the text The Discussion contains interpretation of the results and contains a properly labeled figure. A statement of acceptance or rejection of the hypothesis is explained in the Discussion. The Conclusion section contains a summary of the experiment and suggestions for improvement. The student worked efficiently to preparing the report. Student was mature and respectful when working together to complete the experiment Student contributed equally to the group project. The report is free from plagiarism. Total of 100 points 6

15 Watershed Connections Lesson 6 Trout Are Made of Trees: How Are Leaves Important to Streams? Leaf Pack Presentation Instructions and Rubric 10 slide minimum: Slide 1: Title and group member names. Slides 2 3: Introduction to material with an explanation of flowchart and your hypothesis. Slide 4: Description of the methods you used. Slides 5 6: Description of your results including your data table and graph. Slides 7 8: Interpretation of your results from your Discussion section. Slide 9: Summary of your conclusions section and ways you can improve. Slide 10: Acknowledgments and end credits. A title slide is included with group names and a descriptive title of your project. The two Introduction slides contain sufficient background information. The Introduction slides contain a flowchart what is well explained by the presenter. The Methods are explained step by step. The Results section contains sufficient detail with one table and one graph. The Discussion slides interpret your results. The presentation describes conclusions that can be drawn from your data. Each member contributed equally to the design and delivery of the presentation. Presenters maintained eye contact, explained slides well, and kept the audience engaged. The presentation is creative in its use of color, photos, and font. Total of 50 points 7