Academic journal article The Science Teacher

The Green Room

Academic journal article The Science Teacher

The Green Room

Article excerpt

Too Much of a Good Thing

Eutrophication is a decline in water quality due to increasing concentrations of inorganic nutrients. It's a natural process for an aging lake, but agricultural runoff and sewage can greatly accelerate it. Learn more on the National Oceanic and Atmospheric Administration (NOAA) website (see "On the web") and in a Nature Education Knowledge article (Chislock et al. 2013).

As excess nutrients cause algae and phytoplankton to proliferate, the eutrophic (meaning "well-nourished") lake turns green-brown (see photo). When the algae die, aerobic decomposers gobble up dissolved oxygen while breaking down the decaying plants. Low oxygen levels can kill fish.

You might introduce eutrophication in class while teaching the major biogeochemical cycles (Beckrich 2014). This topic also deserves mention if you teach aquatic ecology, water pollution, agriculture, runoff, or plant productivity.

Classroom activities

Students seeing collected pond water turn green after adding nitrogen and phosphorous is an "a-ha" moment. The American Museum of Natural History has several eutrophication lesson plans to get you started. Or use a lesson plan by the Centers for Ocean Sciences Education Excellence (COSEE) Mid-Atlantic, which also offers a useful animation, as does the Monterey Institute for Technology and Education.

Students can design and conduct environmental inquiry eutrophication experiments based on background information and prompts from Cornell University. They gain understanding of the dynamics of eutrophic systems by culturing nutrient-enriched pond water samples in the classroom and monitoring turbidity, pH, dissolved gases, and other parameters. An even simpler eutrophication experiment is available from the Cary Institute of Ecosystem Studies. Students spike water with algae and differing amounts of fertilizer, then count algae under a microscope every few days. …

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