Student’s Choice.

Merissa_and_BenMy faithful readers know me as That Guy Who Visits Wetlands and Blogs About Them. So true! But now let me tell you a bit about my day job. I teach Biology and Environmental Studies (plus “other duties as assigned”) at Central College in Pella, Iowa USA.

Last week, I took my BIO 345-Limnology class to Fox Forest Wildlife Area and nearby Diamond Lake in Poweshiek County (just west of the city of Montezuma). “But Paul,” you say. “What is this ‘Limnology?’ And what does this have to do with wetlands?”  Limnology is “the study of inland waters,” in other words all aquatic (or semi-aquatic) ecosystems located on the continents. We study lakes, rivers, and wetlands. So—everything in the 99wetlands blog is just one part of Limnology. Got it?




The Limnology class sampled one of the wetlands at Fox Forest. I say “one of,” because this narrow valley contains a small stream interrupted by a series of three small dams, each forming a wetland! We parked on the south edge of the property, hiked a short distance in and visited the last of this chain of wetlands…and got busy collecting water and the organisms within. We don’t retain any vertebrates we catch, although we saw both larvae (tadpoles) and adults of Green frogs. But mostly we caught various insects and mollusks. Back in the lab, under the microscope, we could see features such as miniature (proto-) wings on the backs of the dragonfly nymphs or wire-like extensions of the tip of the abdomen in Damselfly nymphs. We could observe the modifications of their mouths, such as a hinged jaw with a sharp hook on the tip, that swings out to snare prey. We could compare snails with spiral vs planospiral shells (that’s the term in our lab manual for a ram’s-horn type shell. There, you just learned something.). We made drawings and observed behavior. But we didn’t just collect a bunch of facts and figures—in fact, that’s only a small part of science.


Last week, I blogged about a wetland as a place to encounter nature. Now, let’s think about the famous scientific method as a way of understanding nature. Essentially, we organize observations and measurements into coherent stories about How Nature Works. Our explanations are always provisional, subject to testing and refinement (It’s a method, not an endpoint). I asked my Limnology students to use the scientific method: what are observations, questions, and explanations (hypotheses) about this ecosystem? I’m calling this blog entry Student’s Choice because I’ll share these and comment a bit.

  1. Why are the nutrient levels so low? We measured nitrate-N as 0.2 mg/L and phosphate-P as 0.03 which are much lower than we typically find in Iowa waters. Well, with the cautionary note that any particular sample at a specific time and place is just a snapshot…I’ll suggest that these low nutrient levels are exactly why wetlands are famous for “cleaning the water,” which really implies that the ecosystem has chemical processes in soil sediments and in plant and microbial growth “transforming” the nutrients from freely-available, dissolved in water to other, unavailable forms. No chemical magic trick, just hard work on the part of the ecosystem.
  2. But aren’t these organisms indicators of water pollution? The citizen water-monitoring programs will often include charts with bioindicator organisms: pollution-intolerant (suggesting good water quality) to pollution-tolerant (i.e., poor water quality). Generally those classifications are coming from a stream, not wetland, perspective. There’s a bit of a bias against low-oxygen habitats (such as is typical in wetlands). Applying indicator ratings developed for one habitat to an entirely different (i.e., wetland) habitat is…problematic.
  3. Does management for waterfowl affect the balance of the rest of the aquatic ecosystem (suitability for other biota)? The specific aims of the County Conservation Board staff will determine how much emphasis is placed on waterfowl; available resources (i.e., time and money) will play a big part. But generally, “waterfowl management” is usually habitat management: using the water-control structure to flood desired depth, timing, and duration. “Drawing down” the water allows seeds in exposed mud to germinate; kills unwanted species like carp, and facilitates certain maintenance work. Raising water levels provides a resting stopover spot for waterfowl, spawning sites for amphibians and insects, and manipulates growth of many plants. Certainly, managing for waterfowl can be compatible with typical ecological functions.
  4. Vestiges of the stream, remaining in the wetland. This idea is based on the standing dead trees (snags) meandering in a path along a slightly deeper area within the wetland. These were once living trees growing along the stream in this little valley. After the small dams were constructed and these wetland-reservoirs flooded, the trees died. Are the snags important habitat (for whom)? Do animals use the snags differently from nearby living trees or various artificial nest structures (boxes, platforms) provided? Do abandoned meanders (oxbows) serve different ecological functions than the last (active) channel, since wetland construction? I admit—there are plenty of interesting questions and hypotheses we could generate, and I’m certain we couldn’t address them all. But I love the conversation we had.

During our semester, the students and I will have a continuing conversation and experience together, visiting ecosystems and practicing the scientific method. We’ll learn a lot, no doubt, but really it’s about something bigger than our class and this semester. It’s about growing as naturalists and as scientists; it’s about experiencing beauty and wonder; it’s about making a contribution to society (whether it wants to hear from us, or not). As an educator, it’s truly a privilege for me to be part of this. And I’m proud to share it with you, dear reader. I hope you’ll come along on my journey and join in the conversation. Thanks for visiting my class today.

Author: Paul Weihe

Associate Professor of Biology at Central College, traditional author (Textbook of Limnology, Cole & Weihe, 5th ed.; Waveland Press), and now...blogger!

One thought on “Student’s Choice.”

  1. Paul
    Would your class like to visit our constructed wetland in NE Mahaska Co
    If interested in learning more call me at 319-331-0597.


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