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Solutions to Nitrate Fluctuation

Algae’s involvement in the nitrogen and carbon cycle can cause fish kills, but it could potentially be a solution in preventing it.

Lake Orient, Adair, Iowa

Possible Guiding, Compelling and/or Anchoring Questions

  • What is causing the nutrient levels to go up and down nearly every year?
  • Are these new nutrients coming in every year? Or are the same ones staying?
  • Could we use the algae and other aquatic plants being grown every year?

Classroom Suggestions

  • Go over the eutrophication phenomena before this nitrate fluctuation one OR teach them in parallel. As the eutrophication phenomena gives reason to find potential solutions to the hypoxia problem. 
  • Algae, like other aquatic plants, provide oxygen for fish (carbon cycle), take in nutrients from the water (nitrogen cycle) and provide food for fish (carbon cycle again). 
  • In this case, the aquatic plants are causing the decrease in the nitrogen. As the days get longer and the water gets warmer the ideal growing conditions for aquatic plants arises. Here, the plants (primarily algae) are growing until the nutrients are gone. As soon as more nutrients are introduced, more plants grow. When these plants die, some nutrients go into the atmosphere, while the rest of the nutrients return back into the water. In addition, runoff is contributing to the nutrient load every year as well.
  • An important part of the nitrogen cycle to keep in mind is bacteria. And this type of bacteria works slower in the cold.
  • This website that has all of Iowa’s water quality data. I realize it may seem overwhelming, so I provided a short video on how to use this site to find nitrogen data.
  • After students are familiar with the nitrogen fluctuations. Ask them if they think we could harvest the algae and do something good with it. We farm everything else, why not algae? Below I provided some articles on some potential ways algae could be used. But feel free to have students research on their own. 
  • Many commercial algae farmers need to add nutrients to their water. Iowa already has those nutrients. Sometimes too much of those nutrients. Algae is helping us by lowering the nutrient levels of our waters. If only we could take the algae during the summer and use it for another purpose. It isn’t the algae that causes fish kills, it is the algae decomposing in the water that does it. Could it be harvested before it decomposes?
    • Realize Iowa’s water wouldn’t be a monoculture of algae like those commercial systems either.

Related Resources

Iowa Core Alignment

Disciplinary Core Idea
LS2: Ecosystems: Interactions, Energy, and Dynamics

Credit Info

Submitted by Nathan Van Zante

Graph taken from the Iowa DNR AQuIA database. 


Have you used this resource in your classroom? Do you have ideas for improvement? Share your ideas, experiences and feedback about this phenomena.

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