Purpose of Activity

Using simple laboratory gear, students can simulate the stratification properties of a freshwater lake and the impact of salt on the relationship between temperature and density. Because some students have little or no intuition for different thermal stratification regimes, this activity is designed to focus on this fundamental behavior of freshwater lakes. The experiment exposes students to basic data collection, analysis, and visualization techniques using an inexpensive, commercially available data logger and sensors. It can be used as motivation for a discussion of sampling techniques, such as sampling density and sampling rate, and how choosing among them can influence the reliability of an experiment’s results. 

Austin, J.A., E.B. Voytek, J. Halbur, and M.A. Macuiane. 2011. Hands-on oceanography: Lake in a bottle—A laboratory demonstration of the unusual stability properties of freshwater. Oceanography 24(4):136–142, https://doi.org/10.5670/oceanog.2011.107.

Chen, C.-T.A., and F.J. Millero. 1986. Precise thermodynamic properties for natural waters covering only the limnological range. Limnology and Oceanography 31:657–662, https://doi.org/10.4319/lo.1986.31.3.0657.
1. Halfman, J.D. 1993. Water column characteristics from modern CTD data, Lake Malawi, Africa. Journal of Great Lakes Research 19:512–520, https://doi.org/10.1016/S0380-1330(93)71237-X.
2. Lewis, W.M.J. 1983. A revised classification of lakes based on mixing. Canadian Journal of Fisheries and Aquatic Science 40:1,779–1,787.
3. Peeters, F., D. Finger, M. Hofer, M. Brennwald, D.M. Livingstone, and R. Kipfer. 2003. Deep-water renewal in Lake Issyk-Kul driven by differential cooling. Limnology and Oceanography 48:1,419–1,431, https://doi.org/10.4319/lo.2003.48.4.1419.
4. Vollmer, M.K., H.A. Bootsma, R.E. Hecky, G. Patterson, J.D. Halfman, J.M. Edmond, D.H. Eccles, and R.F. Weiss. 2005. Deep-water warming trend in Lake Malawi, East Africa. Limnology And Oceanography 50:727–732, https://doi.org/10.4319/lo.2005.50.2.0727.
5. Wetzel, R.G. 2001. Limnology, Third Edition: Lake and River Ecosystems. Academic Press, 1,006 pp.

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