14
Sampling Macroinvertebrates Using Two Different Capture Methods
This is a laboratory intended to teach sampling techniques for aquatic macroinvertebrates to upper level undergraduate students. Students also learn how to collect data on basic water chemistry. The intention of the exercise is to provide students with the basic sampling skills they would need to address their own questions about the diversity and abundance of macroinvertebrates. The lab requires two weeks in the field (one for sampler placement, and a second for sample collection), and one to two weeks in the lab for invertebrate identification to the family level. After learning the basic techniques, student groups were charged with developing a research question and designing and implementing experiments to answer it. They were given two additional lab periods in which to do so. Part of an additional lab or class period is devoted to a formal presentation of their research proposals. At the end of the semester, each student group produced a paper and a PowerPoint presentation that they then presented to the class. This lab was used in a 400-level Ecology class, which is the capstone course for seniors. It is therefore meant to incorporate research skills that would be expected of a graduate with a B.S. degree in biology, namely, the ability to develop research questions and hypotheses, design and implement research protocols, and analyze, interpret, and present research results both in writing and orally. This lab can be downloaded and adapted as needed. For specific questions or comments please contact Judy Guinan, Assistant Professor of Biology, Radford University, Box 6931, Radford VA 2414. Email: . Phone: 540-831-5222.
Instructor Notes
Background
This laboratory was developed as part of an NSF-funded Course, Curriculum, and Laboratory Improvement (CCLI) grant which incorporates the study of a storm water wetland into the curricula in four different disciplines: biology, chemistry, geology, and geography. All of the data collected by students in the courses in the project are included in the project database which is made available on a publicly-accessible webpage. However the concept for this laboratory module can be adapted for use in any freshwater aquatic ecosystem.
Overview
As designed, the module takes 6.5 – 7.5 weeks of a course with a 3-hour lab period (Figure 1). Up to four weeks are spent in the field. During the first week, students place the sampling devices. Two to three weeks later, they return to the field to collect their data. An additional 1 to 2 weeks is spent learning how to use keys to identify (to family) and tally abundances for the species in their samples. Each group of 4 students is then charged with the task of developing a research question about macroinvertebrates living in the wetland, and designing and implementing a study to answer the question. After it is developed, each group must consult with the instructor to have the plan approved, and with a statistician to review their plan for data analysis. (This is something the instructor can do, but we take advantage of a statistics consulting course that is offered by our Math and Statistics Department to provide upper level statistics major to act as consultants. This provides a peer teaching/learning experience for the students in the two departments). After the research plan is approved, we devote either a class period or part of a lab period for formal presentations of the research proposals. Each group presents their plan, and the other students critique it. This exercise is graded for thoroughness of the plan, and the feasibility and creativity of the question. We have typically given them two additional laboratory periods to work on their projects. No formal labs are held during those weeks, however the instructor is available for consultation during that period. Students were also expected to devote significant time outside of class for the completion of this project, including data collection, library research, data analysis and the development of their papers and presentations.
We typically divide our class of 24 students into 6 groups of 4 students. Each activity (including report writing and presentations) is done in groups.
Week 1(early semester) / Week 2
(2 – 3 weeks later) / Week 3 – 4
(at least by mid-semester) / Week 5 (only 1/2 lab period) / Week 6 – 7 / Last Day of Lab
Set out samplers / Collect inverts and water chemistry data / Identification of families (may take 1 or 2 lab periods / Presentation of research proposals / Free periods to work on research projects / Presentation of research to class
Fig 1. Sample schedule of activities for semester long projects.
Schedule of activities
Week 1
During the first week of lab, we familiarize the students with the wetland structure and purpose, as well as train them in the use of the various instruments they will be using to collect their basic water chemistry data (e.g., temperature, pH, salinity, conductivity) in the field. One problem we ran into in the implementation of this laboratory was in the proper use of the instrumentation. We did the training on this in the field, but given the size of the wetland area over which the student groups were dispersed, it was very difficult to monitor the results that the students were recording. One way to avoid this problem in the future is to have each group practice using each meter in the lab using water collected ahead of time until the instructor is satisfied that the students are sufficiently familiar with the use of the meters and can achieve consistently accurate results before departing for the field.
Once in the field, the students place two types of sampling devices in each site to be sampled. We used a Hester-Dendy sampler, secured to the site by rope and stakes, as well as a sediment sampler, buried to a depth of 2.5 cm. Sediment samplers can be made by building a wooden frame and stretching and stapling plastic screening around one side of the opening. The site of each sampler is marked with a wire staking flag so that it can be easily located for collection. Distance and direction from markers within the wetalnd are also recorded so that the precise location of each sample can be pinpointed for comparisons to samples in future semesters. Students can also practice using their instruments in the field to assure that all members of the group understand their use. We found a great deal of variation between the groups in the amount of care they took to assure the accuracy of their readings in the field. In the future, we could require them to record their practice measurements at each site when the samplers are put into place and direct them to alert the instructor for help if the readings fall outside a pre-determined range. The worksheets could then be turned in for grading.
Week 2
After the samplers have been in place for at least 2 – 3 weeks (3 weeks is preferred), we go into the field to collect macroinvertebrates. Each group is charged with collecting invertebrates from 4 different sites (8 samplers in total), as well as collecting water chemistry and depth information at each site. This was quite easy to accomplish in a three hour lab. Specimens taken from the samplers were placed in vials with 70% ethanol and taken back to the lab for later identification.
Weeks 3 and 4
This activity will take from 1 to 2 weeks and can take place at any time after the samples are collected. Each group was responsible for identifying the invertebrates collected in their samples, using keys and dissecting microscopes. We placed a variety of keys on each bench along some field guides and students were given instruction on the proper use of keys. We had two instructors present during these lab periods to assist the six student groups with their identification and were able to complete the identification in a single week. With a single instructor to assist the students, an additional week may be required. Each time a group felt that they had identified a novel family in their samples, an instructor confirmed the identification, and the students recorded it on the board. Specimens were keyed to the family level, although in a few cases genus or species level identification was possible. In case of the annelids, some specimens could not be identified past the phylum level.
The largest difficulty with this activity to trying to assure that the student identifications are correct, and that the correct number of species for each family is counted and recorded. Students should be reminded several times to have the instructor verify the identity of each novel organism type in their sample. They should also be encouraged to compare members of families between samples so that the number of species within families can be correctly tallied. If the identity of each novel organism is confirmed by the instructor, this can also serve as a check for species tallies. An even better way to assure that the tallies are correct would be to have the students sort their specimens by family as they proceed. Once all of the specimens have been identified to family, a class-wide inventory can then established and checked.
We kept the sorted, identified specimens as a reference collection at the end of the semester. Doing this provides an additional resource for future students to use to aid in identification. New families/species can be added to the collection as they are discovered.
At the end of the class period, the instructor developed a template for data entry using Excel, which was uploaded to the course webpage (Figure 2). Each group downloaded the template, filled in their data, and emailed it back to the instructor. The compiled file was then uploaded to the class webpage for dissemination.
date collected / group ID / sampler type (HD or SS) / sitenbr / water depth (cm) / temperature (C) / water depth (cm) / pH / conductivity (μS) / salt
(ppt) / nbr Heptageniidae (Ephemeroptera) / etc.
Fig 2. Sample template for invertebrate data. Each row represents one sample. Additional columns were added to the right for each family identified by the class. Template distributed to the class for data entry included all families identified in all samples.
Additional Activities
After the invertebrate identification was complete, the students met with within their groups to identify a research question, and design their studies. They were permitted to use the class data, as well data collected on their own for their projects. Since at Radford the wetland project spans several courses, students were also permitted to collaborate with students from other classes and disciplines (e.g., one group also used data on copper and zinc uptake by plants and soil being collected by students in the Pollution Biology course that semester) or use data from the wetland database as well, but designing a research project without these additional resources should not present a problem.
Some groups needed help developing a feasible project, and therefore, they should be encouraged to start their planning immediately and meet with the instructor as soon as possible before the deadline for the project proposal. Some of the projects selected by students were the effects of water depth, H, salinity, conductivity, etc. on species diversity and abundance, a comparison of alpha and beta diversity between sampler types (sediment vs. Hester-Dendy), and use of the Hilsenhoff Biotic index to examine the pollution tolerance of invertebrates from the input to the output areas of the wetland. Other ideas could include change in species richness, diversity, and/or abundance over time, effects of substrate (e.g., algal type, cover) on species composition, etc. If hydrology and/or additional chemical data are available, students could also make use of these data in the development of their questions. Once the students developed their proposal, including plans for statistical analyses, and sought approval from their instructor, the proposals were presented for review by the entire class. Students then implemented their research plan, collecting the additional data required to complete their study.
At the end of the semester, each group submitted a research paper on their project, and made a research presentation to the class. Students are also encouraged to submit their work for presentation at the multidisciplinary annual wetland symposium held each spring on campus.
Student Handout
Overview
Most field labs done by undergraduate students consist collecting some data in the field so that students can become familiar with sampling techniques, taxonomic identification, data analysis, etc. While those are all important skills to develop, the projects themselves are artificial, in that they usually serve no purpose beyond training. At Radford, we are fortunate to have an opportunity for our students to learn the necessary skills to enhance their education, while at the same time, contributing to a long-term database which will enable us to monitor a project intended to improve the quality of our environment.
The Radford University Stormwater Wetland is located adjacent to the New River, and was intended to drain storm water runoff from several parking lots. Runoff from parking lots can contain pollutants from automobiles (e.g., petrochemicals, antifreeze, etc.), and from asphalt, as well as chemicals used for deicing, and fertilizer runoff from nearby lawns. If allowed to runoff into the New River unimpeded, these chemicals could adversely affect the river’s ecosystem. By diverting the flow into a stormwater wetland instead, the pollutants can be sequestered and broken down by the action of plants and microbes.
Besides helping to protect the quality of the New River, this project has other benefits. For one, we can use it as a training laboratory for our undergraduates, so that they get experience with sampling techniques and instrumentation commonly used in environmental fields. Secondly, the data that the students collect can be used to monitor the effectiveness of the wetland in sequestering and removing pollutants. That information will be reported to the university administration and to the Department of Conservation and Recreation, so that any needed improvements in the design and implementation of these types of projects can identified. Finally, since the wetland is a completely artificial environment, and only recently constructed, it provides us with a unique opportunity to study succession in a novel aquatic system. As each semester students collect and add their data to the database, it will be possible to track the development of aquatic animal and plant communities over the long term, something that rarely happens in field projects conducted by undergraduates. In addition, since students from various biology classes, as well as from Chemistry, Geology, and Geography are also collecting data from the wetland, this project offers the chance to incorporate data about various aspects of the system from multiple disciplines to the study of this artificial ecosystem as it develops.