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Can Nutrients in Water Cause Harm?

Author(s): Nancy P. Moreno, PhD, Barbara Z. Tharp, MS, and Judith Dresden, MS.

Session 2

Have students observe the three containers and record their observations. Ask, Do you notice any differences among the bottles? Why do you think this is so? Let the students use hand lenses to observe the containers.

Explain that students will be observing what happens when fertilizer is added to an aquatic ecosystem. Most students will remember the word “fertilizer” from the story, Mystery of the Muddled Marsh, but make sure they understand that fertilizer has positive uses, and that it can be very important for food production.

Show the fertilizer and fish food to the class. Help students to understand that each substance will add nutrients to the water in the bottles.

Have a student add three drops of liquid fertilizer to the bottle labeled “C” and a large pinch of fish food to the bottle labeled “N.” Then have students predict what they think will happen in each bottle over the course of the next week. The bottles should be kept in a bright window or under bright fluorescent lights. As mentioned earlier, low-light conditions often cause hay infusions to develop mold and/or foul-smelling bacteria within 2–3 days.


Funded by the following grant(s)

National Institute of Environmental Health Sciences, NIH

National Institute of Environmental Health Sciences, NIH


The Environment as a Context for Opportunities in Schools
Grant Number: 5R25ES010698


Houston Endowment Inc.

Houston Endowment Inc.

Foundations for the Future: Capitalizing on Technology to Promote Equity, Access and Quality in Elementary Science Education