Inquiry in Limnology Lessons

Evan Variano and Karen Taylor

Inquiry can be implemented in various ways, ranging from simple classroom discussions to long-term research projects. We developed a project in which high school students were introduced to the nature and process of scientific discovery through a two-week guided inquiry unit on limnology—the study of fresh water, which includes lakes, rivers, and ponds.

The focal point of the project was a research trip on the Cayuga Lake Floating Classroom (see “Details on the Cayuga Lake lesson”), a teaching vessel equipped to measure the physical, chemical, and biological indicators of lake health for our 11th- and 12th-grade scientists. The field trip was a two-hour experiment performed after all the classroom material—related techniques and concepts—had been covered. After the field trip, we focused on data analysis and interpretation, as well as concept review.

Details on the Cayuga Lake lesson.

Students use a Van Dorn bottle to find the location of the thermocline by taking water samples at different depths in Cayuga Lake. Photos by Evan Variano As suggested in NSTA’s Cornell Scientific Inquiry Series (Carlsen et al. 2004), we taught students techniques first and used these to motivate students to ask questions about Cayuga Lake, their local lake in upstate New York. Techniques and concepts covered included water chemistry testing with water Students measure the Secchi depth turbidity) from the deck of the Floating Class- room. This skill was chosen by students as an important measurement to make while in the field. testing kits, nutrient cycles, thermal stratification and temperature profiling, plankton taxonomy, and aquatic food web structure. Research questions were brainstormed in discussions with the entire class; the most interesting and tractable was chosen: “Where is the most life in the lake?” This question grew from a “big picture” discussion of why scientists even bother studying lakes. Each student made an individual hypothesis about whether the richest habitats would be located in water that was near shore, offshore deep, offshore shallow, or offshore on the thermocline (the region that separates warmer surface water from cold deep water and where temperature decreases rapidly with depth.) Working in small teams, students created data tables and experimental plans. The best elements from each team’s efforts were shared, and a master plan was constructed for the entire class to use. The experiments were performed by small teams while onboard the floating classroom and included water chemistry measurement (dissolved oxygen, pH, and nitrate concentration), plankton tows, Secchi depth, and temperature profiles to find the thermocline. The class discussed the findings, after which each student analyzed appropriate data to test his or her own hypothesis.

Preliminary learning

Inquiry-based learning was not restricted to the field trip. We developed and tested the following five techniques to include “inquiry moments” in classroom sessions leading up to the trip, but these techniques can be used in any science class and do not need to be part of a larger inquiry-style research project. These simple techniques take little time and can be used even by busy teachers in classes with overpacked curricula. Even if you do not plan to conduct research projects with your students, the inquiry skills will (1) help students become better citizen scientists; (2) prepare students for research projects in other classes; and (3) develop their higher-order thinking skills, which can help students with all aspects of learning.

Questioning—“Leading by example”
Because scientific inquiry is about asking questions (NRC 2000), we created an atmosphere in which questions were encouraged and accepted. To achieve this, we used team teaching to model questioning: We interrupted each other with questions to clarify the material, connect it to other topics, and demonstrate basic curiosity in a scientific framework.

An example of the type of question we asked was, “Excuse me, but when you say that in late fall the warm upper layer of water suddenly gets mixed with the cold bottom layer for the first time in months, isn’t that disastrous for life in the lake?” The hope is that by seeing teachers ask questions, students (1) understand that nobody knows all the answers, (2) learn that this is okay, and (3) see how questions can become motivation for learning the material at hand. If a team-teaching situation is not available, you can model questioning by inviting a guest lecturer for one day, post questions to an online “ask-the-experts” bulletin board in front of the class, or simply create an atmosphere in which questioning is an expected part of classroom discussions.

Hypotheses—“Practice, practice, practice”
Once comfortable asking questions, students must learn to make hypotheses to try to answer these questions. However, a lot of fear is attached to doing this: both the fear of the unfamiliar (students often are not asked to do this) and the fear of being wrong (making a hypothesis that is not supported). To help students overcome this fear, students practiced making many types of hypotheses in many contexts.

Students made some hypotheses that they tested, as well as others that we explicitly said would be left untested, which allowed students to think creatively without the fear of being wrong. Sometimes we asked students to justify their prediction by sharing their reasoning, other times we did not. Some hypotheses were open-ended (“What do you think has the biggest effect on plant life in the lake?”), while others were more guided (“If pH is dropping to the very low value of 5, yet we see an increase in catfish populations, why do you think this is happening?”). We also asked students to hypothesize about concepts that go beyond facts, exploring the nature of science as well as the social context in which scientific research is performed (“Why do you think scientists repeat measurements?” and “If we told everyone that banning motorboats from the lake would increase fish populations, how do you think they would react?”).

Experimental design—“Strawman science”
Students can have difficulty designing an experiment to test their hypotheses. Because it is easier to identify flaws in an experiment than to design a flawless one, we introduced “strawman science.” A strawman is a proposal that people put forth solely to learn through knocking it down. We gave students an example of a flawed experimental design and asked them to point out the faults (Figure 1).

We found this technique extremely powerful. First, it helped alleviate the typical complaint, “I don’t know how to design an experiment.” Second, a very common flaw in students’ previous experimental designs had been the lack of repeated measurements. Once students had pointed out this flaw in another person’s hypothetical work, they tended not to repeat it themselves.

Analyzing data—“Inquiry iterates”
When there is no clear-cut answer to a question, the ambiguity can encourage students to ask more questions and excite their desire to investigate further. For example, while analyzing our field trip data, we found a single pH measurement that contradicted the interpretation suggested by our other data. One student remarked, “If we could only go back again and measure pH more times and in more places, we could find out what that value means.” Thus, the final step of an experiment, the analysis, feeds back into the other parts of the process—asking questions, making hypotheses, and designing new experiments.

Although ambiguity and inconclusive results in an experiment can be frustrating to students, their attitude changes when they learn that real scientific research is much more likely to lead to more questions than to definitive answers. Our goal was to prepare students to take advantage of the mystery, rather than be discouraged by it. This could likely be encouraged by presenting examples from cutting-edge science in which there is conflicting information and interpretations, or by starting a class with a quick yet inconclusive experiment that encourages questioning and ideas for potential follow-up experiments. The iterative nature of scientific research can be harnessed in many ways. For example, students could follow up on their new questions and ideas, repeating the experiment or designing new ones. Alternatively, you can use their follow-up ideas to review and consolidate their learning without having them take time to conduct further experiments on this topic.

Ownership of concepts—“Demystifying jargon”
Throughout our lesson we encouraged students to rename scientific terms. We explained the reasoning behind the original term, translating from Greek or Latin when necessary, and then asked students to suggest or create a better word. This helped students to really think about the details of a concept or fact and its role in the bigger picture. For example, while renaming the major groups of zooplankton, one student called rotifers “little slimy things.” When he saw that copepods also looked little and slimy, he was forced to be more descriptive in his naming scheme, paying closer attention to specific identifying features of the different groups.

Results—“To each according to their strengths”

Throughout the limnology project, we emphasized three aspects of science:

• scientific facts of limnology (including topics from fluid mechanics, water chemistry, and plankton biology);
• the process of scientific research (asking questions based on observations, making hypotheses, and designing and analyzing experiments to test these); and
• the social context in which scientific research is performed (answering the question “why do scientists care about this stuff?”).

We found that there was little correlation between students’ understanding of these three aspects. A typical student would show mastery of one aspect and yet misunderstand another. In fact, no student showed mastery of all three, yet almost all students showed good understanding of at least one aspect. Our interpretation of this is that students were able to focus on the aspects they were most interested in, and did so at the expense of the others.

Given that few of our students were dedicated to science (many choose this class to fulfill a science requirement and avoid chemistry or physics), we consider this a success. There was a part of science that each of them could excel at, as long as we offered a “complete” view of science including science facts, experimental design and analysis, and the “big picture.”

Making scientific discoveries

Inquiry can be part of any science curriculum, with or without a large research project. Through either a longterm project or short inquiry moments, the goal is to enable students to ask scientific questions, think of appropriate ways to address their questions, and learn to critically analyze evidence to reach appropriate conclusions. Through working both collectively and individually to design, conduct, and interpret experiments, students learned in various ways about scientific facts and the ways in which scientific discoveries are made.

Evan Variano (ev42@cornell.edu) is a PhD student at Cornell University, DeFrees Hydraulics Laboratory, School of Civil and Environmental Engineering, Ithaca, NY 14853 and Karen Taylor (ktaylor1@dryden.k12.ny.us) is a science teacher at Dryden High School, PO Box 88, Dryden NY 13053.

Acknowledgments

This work was conducted with the help of Cornell Science Inquiry Partnerships (CSIP), an NSF GK–12 program. This material is based in part on work supported by the National Science Foundation (NSF) under GK12 award No. 0231913. Any opinions, findings, and conclusions or recommendations are those of the author(s) and do not necessarily reflect the views of the NSF.

References

Carlsen, W.S., N.M. Trautmann, M.E. Krasny, and C.M. Cunningham. 2004. Watershed dynamics, student edition and teachers manual. Arlington, VA: NSTA Press.
Kalff, J. 2002. Limnology. Upper Saddle River, NJ: Prentice Hall.
Mitchell, M., and W. Stapp. 2000. Field manual for water quality monitoring: An environmental education program for schools. 12th Ed. Dubuque, IA: Kendall/Hunt Publishing.
National Research Council (NRC). 2000. Inquiry and the national science education standards. Washington, DC: National Academy Press.

Additional resources

Cornell Science Inquiry Partnerships
http://csip.cornell.edu
Environmental Inquiry at Cornell
http://ei.cornell.edu
Cayuga Lake Floating Classroom
www.cayugawatershed.org/floatingclassroom/
Ask-a-Scientist Websites
www.madsci.org
www.newton.dep.anl.gov
Local Government Resources in Water Quality
www.usgs.gov
Lamotte Water Chemistry Kits
www.lamotte.com/pages/edu/index.html
Hach Water Test Kits
www.hach.com/populartestkits

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