Nutrient Cycling: Limnology

Chapter Overview

In the second module, we look at more complex systems. We study nutrient flows in lakes where the concentration of chemicals dissolved in water is important. Residence times are longer and the role of energy more apparent. We don't assume that students have any background in limnology. We teach them the basic ideas by focusing on the role of energy in stratifying and mixing water. We want them to understand how the flow of energy from the sun generates seasonal patters in thermal stratification, which is also a function of the way in which the density of water changes with temperature. The lab that we have developed for this section of the course (again a rather

"place-specific" lab) asks students to predict and then measure the distribution of dissolved oxygen in a frozen lake. In class, we ask them to think about the fact that mixing water against a density gradient requires energy and what effect this will have on the concentration of dissolved oxygen and minerals.

Some of the students in our course had taken introductory chemistry, Chemical Reactivity in Environmental Systems, with one of us (Austin). In that class, students learned how to measure many of the basic elements of aquatic chemistry.

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