What Is Eutrophication? | Water Pollution Activity for Kids

Eutrophication is water pollution caused by excess nutrients. For example, water in the Great Lakes is cool and clear. In other words, few biological materials (such as algae) lived there. As substances like phosphate detergents and inorganic fertilizers run off the adjacent land, more algae grew.

oligotrophic – least productive; little algae

mesotrophic – moderately productive

eutrophic – most productive; lots of algae

In this water science experiment, kids add liquid plant fertilizer to pond water.

Ms. Sneed Plans a Eutrophication Lab

Our favorite fourth grade teacher tapped her finger on her chin. Then she tapped her pencil on the table. What kind of experiment would help her students learn about water pollution?

Suddenly, she picked up a her phone and placed a call to a chemist friend. “Cindy? Can you help me with set up an experiment for my students? I remember how Lake Erie was polluted by laundry detergent. However, I can’t remember exactly how or why.”

“Ah,” her friend replied, “you’re talking about eutrophication. Phosphates in the detergent caused algae blooms. Therefore, that nutrient was removed from detergent in that region. But it also happens as a result of fertilizers. For example, when people fertilize their lawns or farmers fertilize their fields, it runs off into adjacent lakes.”

“Hmm,” said Ms.Sneed. “What do you think about kids experimenting with fertilizer and water.”

“Sure. You’ll need to collect some water from a pond or lake and get some liquid plant fertilizer. Then, to ensure a fair test, kids should measure the same amount of water into each jar. First, establish a control jar. Don’t put any fertilizer in it. Second, add maybe five, ten, and fifteen drops of fertilizer into three additional jars.”

Students Research Nutrient Pollution

A few weeks later, Ms. Sneed was ready to rock and roll.

“Good morning,” she said to her class. “Today we’ll conduct a little science research.” She moved around the room, distributing a handout. “I’ve shared a video and four webpages from the EPA. As you peruse them, complete this worksheet.”

After her students opened their Chromebooks, they set to work. In no time, they were learning about eutrophication.

Students use a simple note-taking sheet to explore causes and effects of nutrient water pollution. They list sources and solutions, as well as effects. Finally, they write two things they can do to reduce eutrophication from nutrients.

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Students Experiment with Eutrophication

After her students filed in the next day, Ms. Sneed began. “Today we’ll begin an experiment, and you’ll use the scientific method.”

A buzz of excitement filled the air. Ms. Sneed’s students loved labs.

“Since you’ll be working in your science groups, I’ve placed all the materials on the side table. First, I’d like person 1 to pick up four jars.” One member of each group walked to the table and grabbed the jars.

“Second, person 2 will take a beaker of pond water.” Again, one student from each group gathered materials.

Ms. Sneed continued with a container of plant fertilizer and an eyedropper for person 3. Then she asked person 4 to get a graduated cylinder.

“Now follow the directions on your lab sheet,” the teacher said. Without missing a beat, her students got busy. Soon, everyone had prepared their jars.

This lab sheet asks kids to experiment with eutrophication. They begin with this question: How does fertilizer affect algae growth in lake water. Then they hypothesize and use a prescribed set of materials and procedures to conduct the experiment.
Effects of Eutrophication Under a Microscope

Next, Ms. Sneed asked students to collect more materials: a microscope, a slide, and a slipcover. She distributed a page with some circles. “Observe a drop from each jar. Draw what you see. Then use the link for algae identification that I sent to you.”

Ms. Sneed circulated around the room, helping students with their microscopes.

“I don’t see anything!” one child cried.

“Try moving the slide around,” Ms. Sneed said. In the end, however, they realized that there was little to see.

“Hmm, not much algae. This water is relatively oligotrophic. In other words, it doesn’t have much algae living in it.”

Every week, students observe samples of water under a microscope. They draw and label algae found in each sample. Then, at the end of the lab, they answer questions about their observations and draw conclusions.

Over the next few weeks, Ms.Sneed’s class observed their jars. After one week, they noticed that the water with fertilizer was becoming cloudy.  “Wow, increasing turbidity,” Ms. Sneed remarked. By the end of the second week, the jars with ten and fifteen drops had turned decidedly green.

Each week, the students also looked at the samples under the microscope. More and more algae appeared in the jars with extra nutrients.

“Yuck!” one boy shouted. “This water sure is polluted!”

That famous teacher smile spread across Ms. Sneed’s face. Bingo.

This image shows changes in four jars of pond water over three weeks. After one week, water in all jars is relatively clear. By the second week, slight turbidity can be detected in jars that have fertilizer in them. At the end of the third week, evidence of algae is clear. The jar with no fertilizer is still clear. The jar with five drops is milky. The jar with ten drops is light green. The jar with fifteen drops is darker green.

Enjoy Teaching

Over the course of her career, Ms. Sneed realized that there were 6 steps to enjoy teaching. In order to survive, she had to organize, plan, and simplify. Then, to thrive, Ms. Sneed needed to learn, engage, and finally – dive in! Follow the Fabulous Teaching Adventures of Ms. Sneed and learn how you can enjoy teaching too.

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