FACULTY NOTES

   *** On the Question - Figure 4A shows changes in turtle grasses over 10 years in the Florida Bay. Imagine yourself snorkeling over these seagrass beds. What do you think they looked like in 1994 compared to 1984? How do you think the scientists got these data - what did they actually do?

      Visualizing a data set helps student understand the findings concretely - it can make a abstract finding more real, especially for more visual learners. Asking the students to think about the methods also achieves this and it also helps students realize that many people, even they, could do this part of the project. In this case, 15 cm diameter cores were collected by divers off a boat; the sediment cores were taken back to the lab and grass stem density and dry weight measured.

      Figure 4B (Tomasko et al. 1996) shows a nice relationship between watershed N loading and Thalassia biomass in Sarasota Bay on the west coast of Florida. Five nutrient sources were included in the watershed loading calculation: stormwater, groundwater, point sources (sewage and industrial outfalls), septic tanks, and rain. Various beds were studied and their watershed inputs calculated individually.

      Figure 4C is from temperate eelgrass (Zostera marina) beds in Waquoit Bay on Cape Cod, MA. These data show a linear relationship between biomass of algal epiphytes (algae growing on the seagrass leaves) and nutrient loading. Data like these give support to the idea that nutrient loading to seagrass beds results in high biomass of epiphytic macroalgae, which in turn shade the seagrass. High phytoplankton biomass in the water column also results in shading. In both cases, the seagrasses die as a result of light limitation. For each data set give students the methods in writing either in a handout or an overhead.


   *** On the Question - The *s on the figure indicate locations where the difference between the 2 years is significant. What do scientists mean when they say a difference is “significant”? What do the vertical little lines at the top of the histograms indicate?

      Four randon cores were taken at each site. The figure legend does not say whether the “error bars” are standard deviation or standard error; what you want your students to think about in a general way is the importance of replication and the meaning of statistical significance.


   *** On the Question - Make sure you understand the data in Figures 4B and 4C. Figure 4B is from Sarasota Bay Thalssia beds off the west coast of Florida and 4C from eelgrass (another type of seagrass) beds off Cape Cod. If you were asked to propose why seagrasses were declining in Florida Bay based on the findings from Sarasota and Cape Cod, what would you say? Is it valid to use information from one site and apply it to another? How would you assess the validity of doing that in this case - what types of information would you like to know?

      This question helps students better understand the process of science - that scientists must use information from all sorts of sources and judge the usefulness of these findings for their particular situation. Good responses include: how did the scientists working in Sarasota Bay measure watershed input? How did they know what it was? Where is the N coming from there and are these the same types of sources in Florida Bay? Are the seagrass data good (e.g. valid methods)? There is a lot of variation in blade biomass for the same input; this might be a problem. How did the scientists working off Cape Cod measure nutrient load? How did they measure epiphyte biomass? Are these methods good? Can we use data about eelgrass and apply it to turtle grass? Can we use data from Cape Cod and use it for Florida? What you are looking for in their responses, either written or oral, are not answers to these questions but various ways that they might be able to address them.

      This exercise will take a good amount of class time. You could also assign it as a group homework assignment if your students have enough experience with data interpretation to do this on their own.


Student Assessment: Essay.

      Loss of submerged aquatic vegetation (SAV) is a severe problem in estuaries receiving high nutrient loads from agriculture and other sources. Explain the link between nutrient loading and loss of SAV.



EVALUATING AN ISSUE: How do you know whether it is working?

      On-going (also called formative) evaluation of the approaches your are using is critical to the success of student-active teaching. Why try out new ideas if you don't know whether or not they are working? This is a brief overview of formative evaluation. For more information, go to the Formative Evaluation essay in the Teaching Section.

Course Goals:

      Formative evaluation only works if you have clearly described your course goals - because the purpose of the evaluation is to assess whether a particular technique is helping students reach these goals. For instance, most of us have "learn important ecological concepts and information" as a course goal. If I reviewed the nitrogen cycle in a class, for evaluation I might ask students to sketch out a nitrogen cycle for a particular habitat or system. Each student could work alone in class. Alternatively, I might ask students to work in groups of 3 and give each group a different situation (e.g. a pond receiving nitrate from septic systems, an organic agricultural field, an agricultural field receiving synthetic fertilizer). The students could draw their flows on a large sheet of paper (or an overhead transparency) and present this to the rest of the class.

The Minute Paper:

      Minute papers are very useful evaluative tools. If done well they give you good feedback quickly. Minute papers are done at the end of a class. The students are asked to respond anonymously to a short question that you ask. They take a minute or so to write their response in a 3x5 card or a piece of paper. You collect these and learn from common themes. In the next class it is important that you refer to one or two of these points so that students recognize that their input matters to you. The UW - FLAG site (www.wcer.wisc.edu/nise/cl1/flag/) gives a good deal of information about using minute papers including their limitations, how to phrase your question, step-by-step instructions, modifications, and the theory and research behind their use.