Eutrophication is water pollution caused by excess nutrients. For example, water in the Great Lakes was originally cool and clear. In other words, few biological materials (such as algae) lived there. As substances like phosphate detergents and inorganic fertilizers ran off the adjacent land, more algae grew.
oligotrophic – least productive; little algae
mesotrophic – moderately productive
eutrophic – most productive; lots of algae
Looking for some great water science experiments? In this lab, kids add liquid plant fertilizer to pond water.
Posts on this website follow a teaching journey and are written in story form.
Mr Grow Plans a Eutrophication Lab
Our favorite fifth grade teacher tapped his finger on his chin. Then he tapped his pencil on the table. What kind of experiment would help his students learn about water pollution?
Suddenly, he picked up his phone and placed a call to a chemist friend. “Cindy? Can you help me with an experiment for my students? I remember that Lake Erie was polluted by laundry detergent. However, I can’t remember exactly how or why.”
“Ah,” his 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 Mr. Grow. “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 Water Pollution
A few weeks later, Mr. Grow was ready to rock and roll.
“Good morning,” he said to his class. “Today we’ll conduct a little science research on water pollution.” He 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 his students opened their Chromebooks, they set to work. In no time, they were learning about eutrophication.
Students Experiment with Eutrophication
After the students filed in the next day, Mr. Grow began. “Today we’ll begin an experiment, and you’ll use the scientific method.”
A buzz of excitement filled the air. Mr. Grow’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.
Mr. Grow continued with a container of plant fertilizer and an eyedropper for person 3. Then he asked person 4 to get a graduated cylinder.
“Now follow the directions on your lab sheet,” the teacher said. Without missing a beat, the students got busy. Soon, everyone had prepared their jars.
Effects of Eutrophication Under a Microscope
Next, Mr. Grow asked students to collect more materials: a microscope, a slide, and a slipcover. He 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.”
Mr. Grow circulated around the room, helping students with their microscopes.
“I don’t see anything!” one child cried.
“Try moving the slide around,” Mr. Grow 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.”
Observations
Over the next few weeks, Mr. Grow’s class observed their jars. After one week, they noticed that the water with fertilizer was becoming cloudy. “Wow, increasing turbidity,” Mr. Grow 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 student shouted. “This water sure is polluted!”
That famous teacher smile spread across Mr. Grow’s face. Bingo.
Enjoy Teaching
Labs like this allowed Mr. Grow to hit multiple science concepts. This experiment, for example, focused heavily on scientific practices. However, kids also learned about algae. Furthermore, they learned how communities use science ideas to protect the environment. He planned to build on this concept with his next science activity on wastewater management.
