Clams to Data to Questions

What did we find? That was the question that Sumner Memorial High School Students began to answer as they analyzed the samples that they helped collect from John Small Cove in late October, 2017. This post is a little bit about clams and a lot more about supporting productive inquiry in the classroom. It revisits work students did three years ago, but that work, both in the classroom and on the clam flats, is still relevant today.

What the Experiment Was About

The class session began with a review by Department of Marine Resources (DMR) biologist Heidi Leighton about how the experiment was laid out on the clam flat in John Small Cove. Most of the students had been to the cove and had helped in collecting samples and so knew something about what the site looked like, where it was easy to walk and where it was really muddy and knew how the site was sheltered to the south as the shoreline curved out to the west. Now Heidi was providing them with information about why the boxes had been laid out on the mud as they were, why some were netted, and about other aspects of the study design.

Maine DMR biologist Heidi Leighton describes the study design and the thinking behind it.

The primary question explored in the study was whether placing inexpensive, open topped boxes (the kinds of boxes that a nursery might use to hold seedlings) on the clam flats would improve settlement and recruitment of first year clams The different rectangles that Heidi drew on the board represented the different experimental plots; each plot corresponded to a different treatment condition: settlement boxes or not, protective netting or not, higher on the tidal gradient or lower.

The study drew upon what we know about how clams reproduce and settle into new area. (Here is a quick summary). The idea was that the boxes would disturb the water flow as the tide and waves came in, creating eddies and slowing the water down so that the juvenile clams would settle out of the water and into the boxes. This conjecture grew out of the experience of clam diggers, who have noted that there are often more clams around rocks and other obstructions on the clam flats. A second conjecture had to do with predation: small green crabs eat small clams. (Here is more information about crabs and predation.) So, in some of the experimental plots, 12-foot square nets were stretched over the boxes. Since the clams are only about a fifth of a millimeter across when they begin to settle, the idea was that the mesh would allow the juvenile clams to settle into the boxes while keeping crabs out.

Heidi and Susan Walsh, the lead teacher in Sumner’s Pathways program, engaged the students in a conversation about where the students thought they would find the largest number of juvenile clams, asking the students to explain the reasoning behind their thinking. The students’ answers varied: some thought the nets would help, others thought they might get in the way. Some thought the boxes would increase settlement, others thought that the obstruction that they created would interfere with settlement. As the students offered their thinking, we wrote their ideas on the whiteboard along with notes about the reasoning behind the expectations. We noted that the expectations differed but we did not dig more deeply into those differences as this point. We would wait until we had some data.

Turning Samples Into Data

The students had been out in the field the previous week helping Heidi and shellfish warden Mike Pinkham collect the samples. Since then, Heidi had washed and sieved the samples to separate the clams out from the mud. She had placed each sample from a settlement box or a core sample into a separate plastic bag. The picture up at the start of this post shows the students working in pairs, one doing the measuring with digital calipers that measure down to hundredths of a millimeter, the other recording the size of each tiny clam. The picture below shows that this was exacting work. The clam in this picture was actually one of the larger ones, measuring 4.9 mm. Notice that there are others on the paper towel that are much smaller.

Measuring a juvenile clam with digital calipers.

There were many hundreds of clams to measure, so this work went on for about two and a half hours. The only complaint we heard was that students’ hands were getting tired from all the fine, exacting work of placing clams in calipers in the correct orientation. Otherwise, the students were fully engaged in turning the samples they had helped collect into data they could use.

As someone who has worked with and observed high school students for years, the students’ interest in sticking with this task was a little surprising. It is less surprising now, after working with students in the Sumner Pathways program for a few more years. The Pathways program accommodates the needs of students who need to work or who, in other ways, have obligations and circumstances that would interfere with engagement in the typical structures of high school programs. Many of them work to support themselves or to support their families. My perception is that paying attention to detail and working until a job is done is something that they already know about and do.

It also mattered that all but a few of these students had been at John Small cove in late October, helping pull nets, collect samples, and clean equipment. Heidi’s whiteboard drawing of the arrangement of the experimental plots was not an abstraction for these students; they were able to visualize what Heidi was describing. They had observed the holes in the mud after the nets had been pulled, holes caused by clam siphons reaching up to the surface.

Initial Results, and More Questions

Below is a picture of the final counts for the boxes and core samples, posted on the whiteboard. These are just counts and do not reflect all the measurements that the students did; the students will have to key the measurements into a spreadsheet before we can do anything with them. But just looking at the counts was interesting and a little surprising.

Counts of the number of juvenile clams found in the boxes and core samples. These counts became the basis for an extended discussion.

What was NOT surprising, but reassuring, was that we did see evidence of clam settlement into the boxes. But what WAS a little surprising was that the boxes that were not covered by nets had higher numbers of juvenile clams than the boxes that were protected from green crabs. Why?

Heidi, Mike, and the students thought and talked about that question. One idea that emerged was that maybe the nets interfered with settlement in some way. Maybe some of the veliger larvae bounced off the netting rather than settling through a hole. Would we perhaps find that the seed clams in the netted boxes are a bit smaller than the boxes? That would not allow us to be completely sure that the netting was interfering with settlement, since the clams had months to grow since settling into the boxes, which means we really do not know how big they were when they settled in. But it might suggest that it would be worthwhile to dig up a couple of boxes in July, while settlement was still underway, to explore the question further.

Heidi and the students also wondered why most of the core samples, which were taken between boxes in the plots with boxes, contained so few clams. If the boxes were affecting water flow, why wouldn’t clams settle between the boxes and well as within the boxes? They also talked about Plot 1-1, where, unlike everywhere else, the core samples had a lot of clams. Why could that be? While we were out on the mudflat, one student noticed that there was a freshwater stream that ran across the area at about that point, as illustrated in red on the drawing of the plots with counts of clams. Clams can tolerate substantial changes in salinity, so if there was food or something else useful to clams coming in with the stream water, might that be a factor? One way of exploring what is going on would be to do a population survey of the area around the area of the streamflow next spring. Another would be to collect and analyze samples of the stream water.

Supporting Productive Science Learning

From an educational standpoint, one of the things that can be tricky about exploratory investigations such as this one is that they sometimes raise more questions than they answer. This can be surprising and even frustrating for students. The kind of science that is normally presented in schools, together with popular portrayals of science and scientists, can give students the expectation that successful science produces clear answers and, conversely, that not getting clear answers means that the science is a failure.

Helping students get past the idea that science is about getting closure and unambiguous answers is important, not only to keep them from getting discouraged about their project, but also because they should understand that science is tentative, sometimes moves forward slowly, sometimes jumps ahead, and sometimes even turns back to revisit questions. Even if they choose not to pursue a career that involves scientific work, it is essential that they learn that “not being sure” is not the same as “not knowing anything.” How do we help students see that asking new questions is important, productive work and that much of the value of an early stage study such as this one is that it helps us ask better questions? Here are a few ideas:

  • Most important: Bring the students into the discussion. Get them thinking about how the data that they have collected suggest other things that we need to know. When they don’t have ideas about new questions that emerge from their data (and they often will not), resist the impulse to suggest questions or next steps. Give them time to ponder, perhaps setting the conversation aside until the next time the class meets.
  • If necessary, get them started by asking them what they think is going on — by asking them to offer an explanation for the findings. Then ask them … and their student colleagues … “How could we find support for that explanation?” When they respond, do not evaluate their answers. Either just write their explanations and ideas about finding suppor down and ask other students whether they have anything to add.
  • Work to get the students asking each other, “How could we test that? How could we find out?” This should not be a question that is reserved for adults to ask. Make a game of it. Help them learn to ask this question in ways that are productive.
  • Distinguish between “Why do you think that?” and “How could we find support for that explanation?” For our purposes here, the second question will usually be the better one.
  • Just as we expect the students to think about ways to test their ideas and explanations, resist our own impulses as adults to say “I know what is going on” — what we really have are conjectures that need to be tested. We need to recognize that too.
  • Keep a shared record of conjectures and possible explanations, and of ideas for testing them. The students should all have access to this shared record.
  • There will be too many conjectures and explanations to test. Are there ways we can test several at once? Can we agree on the ones that seem most important to test first? These are issues for the students to sort through.
  • Be clear that the adults who are doing this work as part of their jobs — people like Heidi and Mike — may have questions that they NEED to explore in subsequent work, but that these are not necessarily the only important questions. Make sure that there is also budget support and time to explore ideas and questions that emerge from the students’ thinking and conversations.

It is through this process of following the data where it leads, coming up with new questions and conjectures and devising ways to explore them, that we can begin to introduce students to what science is really about. But this is a different way to teach science, one that requires different approaches to instruction. What do you think of these ideas? Do you see problems with them? Do you have suggestions about how to improve them? We would be interested in your comments.

A Postscript

This post draws upon work and reporting that CSI-Maine did in 2017. Here are a few additional thoughts that emerge as we revisit and reflect on this report now, after three more years of work with Sumner Pathways students, Heidi, Mike, and and the Gouldsboro shellfish committee.

Students Had More to Offer, Beyond Community Service

The work that the students did assisting Heidi in 2017 was the first time that we had students involved in working with data. Before that, they had helped pull nets off of clam flats and do other things where they helped with physical labor. This project also gave them an opportunity to think and reason.

Heidi is a professional biologist who has been doing field work for a long time. Listening to her later that week as she presented the early results from the work with the students to the Gouldsboro shellfish committee, it was clear that work and the data were useful to her. The success in recruiting clams that she saw in this experiment, even though it was uneven across the plots, had her thinking about other kinds of structures to induce settlement. The shellfish committee was (and, in 2020, continues to be) interested in finding ways to increase clam recruitment and to capture clam seed that can be used to restore flats. They were interested in what Heidi had to say. They were also pleased to know that the students were involved in the work and especially pleased to learn that it was helping students meet standards required for graduation.

In subsequent work with the shellfish committee students undertook studies that provided the committee with information that was even more directly connected to decisions that the committee needed to make. The path toward doing those studies began here.

We Now Know Much More About Recruitment and Predation

Over the past three years, work by the Downeast Institute and others, including students involved in CSI-Maine, has enabled us to develop a better understanding of clam recruitment and clam predation by green crabs. We now understand that the presence of just one or two green crabs in the settlement boxes in the 2017 study described above could easily account for the absence of clams in some of those boxes. Because the boxes had been filled with mud from the John Small site, it is entirely possible that crabs could have been introduced to the boxes from the outset. That might explain why some boxes had no clams, even though they had been covered by nets.

For more information, see work that the Downeast institute has done to collect information about clam growth and predation and to monitor soft-shell clam recruitment.

Now More than Ever: Put Students at the Center of the Inquiry

The list of suggestions about supporting productive science learning that we provide above came from a report that we wrote in 2017 after working with Heidi and the Sumner Pathways students. Our work since then has made us even more certain about the importance of keeping students at the center of the conversations and thinking. In work since then, students have taken on increasing responsibility for figuring out how to do the analysis and the reporting to the shellfish committee.

Helping the students figure out how to do this work, rather than just telling them what to do and how to do it, means allocating the time required for learning. That can sometimes be challenging because the shellfish committee or someone else might need the data and analysis to help in making a decision. The time frames and objectives of the world outside of school and the world within school are sometimes different. Keeping them “aligned enough” is part of the challenge of connecting schools and the communities that they serve.

For a look at some of our recent work in putting students at the center of the inquiry process — work that is related to a different community project — see the recent post about our work with Sumner Pathways students as they look at drinking water quality.

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