Summary
In this lesson, students investigate the phenomenon of differences in water clarity among four Oklahoma lakes. Students investigate how local environmental conditions and the survival strategies and growth of phytoplankton (algae) affect water clarity. Students then design and conduct experiments that investigate the relationship between water clarity variables and phytoplankton growth. They use this information to analyze patterns in phytoplankton community composition and to create models of the cause-and-effect relationships among local conditions, genetic factors, and phytoplankton growth. To conclude the lesson, students compare their data analyses with findings summarized in official water clarity reports. Students then use their models to develop summative explanations for the relationship between phytoplankton growth and water clarity in a single lake.
Essential Question(s)
How do genetic and environmental factors influence the growth of phytoplankton? How does phytoplankton growth affect water clarity?
Snapshot
Engage
Students examine photographs of lake water at macro and micro scales, then create an initial model to explain how phytoplankton growth affects water clarity.
Explore
In groups, students plan and carry out investigations that test how phytoplankton growth is affected by different water clarity variables. They also sort phytoplankton species into groups according to physical and functional characteristics.
Explain
Student groups develop claims about phytoplankton growth based on data obtained during their investigations. Students then work together as a class to create a Concept Card Map that links their claims and evidence to the lake water clarity phenomenon. Students refine their models to reflect the cause-and-effect relationships among water clarity variables, phytoplankton survival strategies, and water clarity.
Extend
Students use a Venn Diagram to compare their previous data analysis with data from official water quality reports, then evaluate and revise their models.
Evaluate
Students use their final models to explain the relationship between phytoplankton growth and the water clarity of a lake of their choice.
Materials
Lesson Slides (attached)
Facilitation Guide document (attached; for teacher use)
Four Lakes Phytoplankton Communities handout (attached; one per group; print in color, one-sided)
Phytoplankton Cards handout (attached; one per group; print in color, one-sided)
Four Lakes Data Reports handout (attached; one set per group; print two-sided)
DIY Secchi Disk Instructions handout (attached; optional)
Procedure Example document (attached; one per teacher; optional)
Student Notebook (Print) handout (attached; optional; one per student; print two-sided)
Student Notebook (Digital) (attached; optional)
Chart paper (three per class period)
Water bottles
Pond water or fast-growing algae culture
Nutrient variables
Secchi disks (buy or create using attached instructions)
Water resistant paint (black and white)
Hot glue gun
Metric ruler
Permanent marker
Metal washers (small enough to fit in the water bottles)
Plastic straw
Poster board (optional, one per group)
Markers (optional, one per group)
Fluorescent lights
Preparation
Guiding Attachments
See the attached Facilitation Guide document for additional lesson guidance, possible student responses, recommendations for facilitating discussions, and formative assessment opportunities throughout the lesson.
Prior to beginning the lesson, choose whether you would like students to use a student notebook. If so, decide whether you would prefer them to work on paper or digitally. The attached Student Notebook (Print) handout and Student Notebook (Digital) resource include space for students to record their reflections, data, and class discussion notes for all activities in the Engage through Extend sections of the lesson.
Lesson Prep
Prepare two chart papers for each class period. Label one chart paper “I Notice” and the other chart paper “I Wonder.”
Investigation Setup
Use slide 19 to record your specific instructions for students to complete the following activity. For this investigation, you must collect pond water with algae in it or order a fast-growing algae culture ahead of time. If you choose to use pond water, remove large grazers, like Daphnia by pouring the water through a fine mesh of window screen, ideally around the size of of 200 µm. Expect the experiment to last around 5–10 days.
The performance expectation for this lesson is about constructing explanations from evidence, so it is up to your discretion how much focus to put on experimental design. However, you may want to have all groups use a consistent setup (e.g., 500mL of pond water in a plastic model) to facilitate reliable comparisons among variables and groups. A consistent setup also allows the class to use a single set of controls rather than a different control for each group of students. See the attached Procedure Example document for an example of detailed investigation instructions.
Expert Panel Instructions
Use slide 26 to provide class-specific instructions on grouping students, analyzing and graphic data, and making claims.
Concept Mapping Instructions
Use slide 27 to provide class-specific instructions for creating the Concept Card Map.
Engage
Introduce the lesson using the attached Lesson Slides. Display slides 3–4 and share the essential questions and lesson objectives.
Display slide 5 and engage students in the phenomenon—variation in lake water clarity and what affects it—by introducing them to images of water from four Oklahoma lakes. Have students make observations and ask questions about the image using the I Notice, I Wonder instructional strategy in their science notebooks. Have students share their thoughts with the class. As students share, record their ideas on the prepared chart paper. Repeat this process with slides 6–9.
Distribute one copy of the attached Four Lakes Phytoplankton Communities handout to each student. Display slides 10–13 and show students the phytoplankton communities found in each lake, as seen under a microscope. Have students look for patterns in the communities and share out their observations and questions. Add their responses to the I Notice, I Wonder chart papers.
Display slide 14 and define phytoplankton, also called algae. Display slide 15 and define water clarity.
Display slide 16 and guide students in a discussion about what might cause the amount of phytoplankton to increase in the water. Ask them to list things that help plants grow and record their responses on either a new sheet of chart paper or on the slide. Students might mention light, water, carbon dioxide, and nutrients.
Ask students to consider the question, “What factors explain how phytoplankton affect water clarity?” Further break down the question into two questions, “What factors cause phytoplankton to grow?” and “How do those factors indirectly affect water clarity?”
Display slide 17. Ask students to use the the ideas they’ve observed and discussed so far to draw a model that explains the phenomenon. Have students draw their models in their Student Notebooks.
Explore 1
Display slide 18 and ask students to review the factors they believe affect phytoplankton growth. Ask them how they can test one of their factors to see if their idea is correct.
Organize students into pairs or small groups. Inform students that they should choose a single variable that may affect phytoplankton growth and use that variable to carry out an investigation.
Communicate to students that some groups must test increased nitrogen, some must test increased phosphorus, and some must test an addition of fertilizer that contains both nitrogen and phosphorous. If students are interested in testing light levels, pH, temperature, etc., consider adding these factors to the investigation.
Have students record phytoplankton abundance data daily. The most efficient method for this is using a modified Secchi disk. Secchi disks can be purchased online or you can make your own using the attached DIY Secchi Disk Instructions document. For reference, the YouTube video The Dirty Labcoat: The Secchi Stick demonstrates how to use a Secchi stick. Unhide slide 20 if students need further direction on how to use a Secchi stick.
Display slide 21 and distribute one set of the attached Phytoplankton Cards to each investigation group. Have students compare the cards with the microscopic view of the four lakes’ phytoplankton communities to identify the number of each type of phytoplankton found in each lake.
Display slide 22 and have students use the genetic factors listed in the table on each card to sort the phytoplankton into groups. Have students record the factor they used to sort the cards and have them list their groups of phytoplankton in their science notebooks. Next, have students choose a different factor, sort the phytoplankton again, and record their factor and groups. Repeat the process, having students sort the phytoplankton according to at least three factors.
Explain 1
Display slide 23. Have students compare their sorted lists of phytoplankton with the groups of phytoplankton in each lake community. Have them take note of any patterns or relationships they notice.
Lead a whole class discussion about students’ sorted groups of phytoplankton. Have students describe the ecological significance of the genetic factors listed on each card. For example, students may respond that functional groups that are able to use more than once resource have more nutrients available than functional groups that cannot use more than one.
Ask students what they can conclude about the phytoplankton in each of the four lakes. If relevant, take the opportunity to guide students to take notes and make connections between the activity and other ecological concepts they have previously learned. Next, ask students in what kind of environment they would find each functional group of phytoplankton. Guide the discussion to focus specifically on nutrient conditions (high, low, and both).
Display slide 24. Ask students to revise their initial models based on the collected evidence and their conclusions about the data. If students did not previously include genetic factors, encourage them to add them at this point.
Explore 2
Display slide 25. Organize students into experiment focus groups, or “factor expert panels,” by combining groups that tested the same variable in their investigations. Have these new focus groups compile and compare data from their experiments. Have groups treat their individual experiments as replicates and use them to calculate averages that summarize their collective data.
Display slide 26 and explain the investigation to the class. Tell groups that they must develop a claim about their results (e.g., “[Our experimental factor] results in [some result]”) using the collective data. Note that water clarity is most likely to be influenced by nutrient resource levels. Have groups prepare for a whole class discussion by creating a graph that displays their results summary and includes their claim in a caption.
Have expert panels discuss their phytoplankton classifications to identify patterns among phenotypes (e.g., nitrogen fixers tend to be toxic) and make comparisons between the phytoplankton community data for each lake. Students should develop a few claims based on the patterns they observe during the group comparisons.
Explain 2
Inform the class that they must work together to create a Concept Card Map. Explain that their map must synthesize what they have learned about the relationships among water clarity, environmental factors, and phytoplankton growth.
Display slide 27 and introduce your class-specific instructions for creating the concept card map. Ask all groups to share out their claims and evidence from their experiment results and add these and their graphs to the concept map. Next, have students share their claims about phytoplankton functional groups and communities.
As students share their ideas about the relationships among phytoplankton characteristics, environmental variables, and the phenomenon, have them use evidence to add new concepts to the map and identify relationships among existing concepts. Once all groups have shared, allow them time to identify any other relationships or concepts they think should be added to the map.
After the concept map is complete, display slide 28. Have students use the compiled information and relationships from the map to revise their models again.
As students work, ensure that their revisions explain the cause-and-effect relationships that influence phytoplankton growth and water clarity. Remind students that their models should show how changes to the different variables in the investigations affect water clarity, either directly or indirectly.
Display slide 29. Ask students to make a prediction about the nutrient conditions for each of the four lakes. If students investigated other factors (e.g., light), encourage them to use these as part of their predictions as well.
Extend
Distribute one copy of the attached Four Lakes Data Reports handout to each student. Use these water quality reports to model how to interpret the information.
Inform students that they must use a Venn Diagram to compare and contrast their predictions about nutrient conditions with the “Parameters” data in the reports. Have students draw a Venn Diagram or have them use the diagram provided in their Student Notebook handouts. Have them evaluate their models by comparing the factors in their models with the scientific data in the reports.
Initiate a class discussion about students’ Venn Diagrams and evaluations of their models. Consider discussing the purpose and limitations of models based on student responses. Encourage students to use their evaluations and information from the discussion to further revise their models.
Evaluate
Display slide 30. Have each student choose one of the four lakes, other than Tecumseh Lake, and use their model to explain their chosen lake’s water clarity. Emphasize that students must reference evidence that supports their model.
Have students deliver their explanations as a written paragraph, storyboard, stop-motion animation, or video. Have them present their explanations or curate them for other students to view using a tech tool like Padlet, your school LMS, or an activity like a Gallery Walk. After viewing their peers’ explanations, students should evaluate their classmates’ presentations.
Resources
Algae Research Supply. (n.d.). Brainy Briny’s: Estimating algae biomass. https://algaeresearchsupply.com/products/brainy-brinys-estimating-algae-biomass
Algae Research and Supply. (2016, June 15). The dirty labcoat: The Secchi stick [Video]. YouTube. https://www.youtube.com/watch?v=du1PA0pzdnQ
Andersen, T. (1997). Pelagic nutrient cycles: Herbivores as sources and sinks. Springer Berlin. https://doi.org/10.1007/978-3-662-03418-7
Bdcarl. (2012, April 13). Anabaena circinalis. Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Anabaena_circinalis.jpg
Buyukates, Y. & Roelke, D. L.. (2005). Influence of pulsed inflows and nutrient loading on zooplankton and phytoplankton community structure and biomass in microcosm experiments using estuarine assemblages. Hydrobiologia. 10.1007/s10750-005-5195-x
Canter-Lund, H. (2016). Stephanodiscus. Freshwater Biological Association.
Corvallis Environmental Research Laboratory & Environmental Monitoring and Support Laboratory. (1978). A compendium of lake and reservoir data collected by the national eutrophication survey in the central United States. U.S. Environmental Protection Agency National Eutrophication Survey. https://nepis.epa.gov/Exe/ZyPDF.cgi/91023FC6.PDF?Dockey=91023FC6.PDF
CSIRO. (2000, January 1). Microalgal cultures.
Fritzmann2002. (2017). Closterium under a light microscope. Wikimedia Commons. https://en.wikipedia.org/wiki/File:Closterium_under_a_light_microscope.jpg
Janse van Vuuren, Sanet. (2006). Easy identification of the most common freshwater algae: A guide for the Identification of microscopic algae in South African freshwaters. North-West University & Department of Water Affairs.
K20 Center. (n.d.). Concept card mapping. Strategies. https://learn.k20center.ou.edu/strategy/123
K20 Center. (n.d.). Data match. Strategies. https://learn.k20center.ou.edu/strategy/1280
K20 Center. (n.d.). Gallery walk. Strategies. https://learn.k20center.ou.edu/strategy/118
K20 Center. (n.d.). I notice, I wonder. Strategies. https://learn.k20center.ou.edu/strategy/180
K20 Center. (n.d.). Mentimeter. Tech Tools. https://learn.k20center.ou.edu/tech-tool/645
K20 Center. (n.d.). Padlet. Tech Tools. https://learn.k20center.ou.edu/tech-tool/1077
K20 Center. (n.d.). Venn diagram. Strategies. https://learn.k20center.ou.edu/strategy/2918
Lortou, U., & Gkelis, S. (2019). Polyphasic taxonomy of green algae strains isolated from Mediterranean freshwaters. Journal of Biological Research-Thessaloniki, 26, 11. https://doi.org/10.1186/s40709-019-0105-y
Miller-DeBoer, C. (2016). Tecumseh Lake [Photograph].
Miller-DeBoer, C. (2016). Shawnee Twin Lake #1 [Photograph].
Miller-DeBoer, C. (2016). Lake Stanley Draper [Photograph].
Miller-DeBoer, C. (2016). Lake Thunderbird [Photograph].
Miller-DeBoer, C., & Shaffery, H. (2016). Lake Thunderbird 40x [Image].
Miller-DeBoer, C., & Shaffery, H. (2016). Lake Stanley Draper 40x [Image].
Miller-DeBoer, C., & Shaffery, H. (2016). Shawnee Twin Lake #1 40x [Image].
Miller-DeBoer, C., & Shaffery, H. (2016). Tecumseh Lake 40x [Image].
National Aeronautics and Space Administration. (n.d.). Phytoplankton exploration. https://pace.oceansciences.org/phytopia.htm
Oklahoma Water Resources Board. (n.d.). https://oklahoma.gov/owrb.html
Peters, K. (2009). Melosira varians. Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Melosira_varians.jpeg
Sandgren, C. (1992). Growth and reproductive strategies of freshwater phytoplankton. Cambridge University Press.
Specious Reasons. (2010, June 22). Serious bacterial bloom. Flickr. https://www.flickr.com/photos/28594931@N03/4726267363/
STEM Teaching Tools. (n.d.). Talk resource tools: Card sets.
