Featured Lesson

Lesson 3:2 - Function of aquatic plants

by Michelle Kelly, Aquatic Education Specialist

November 2008

We've all heard it before when out fishing with kids, the cry “Help! My line’s stuck in the weeds!” Weeds? Are all aquatic plants “weeds”? Of course not!!Chapter 3 of the MinnAqua Leader’s Guide - Fishing: Get in the Habitat! focuses on water stewardship. Water quality not only determines where fish live, how they behave, and their survival, it is also important for human health and our quality of life. Chapter 3 houses seven of our 39 lessons. This edition’s highlighted lesson is the second lesson in Chapter 3, Lesson 3:2 – Function of Aquatic Plants.

After completing Lesson 3:2 with your students, the next time you take them fishing, instead of hearing “Help! I caught a weed!” you just might hear a student say “Look! I reeled in an aquatic plant! I think I found a great place to catch fish!”

Lesson summary

Students conduct experiments to explore the value of aquatic vegetation to lakes and streams. In Part 1, students learn that aquatic vegetation provides food and shelter for fish and other wildlife. They will also learn about the types of aquatic vegetation living in the littoral zone. In Part 2 students learn how algae blooms can occur in nutrient-rich conditions. In Part 3, students learn that aquatic plants absorb nutrients and some polluting chemicals.

Tips and tricks

cross section of a pond littoral zone

With three parts to this lesson it is important to read through the entire lesson before planning the time you will need for the entire lesson.

Part 1

  • Students create some type of littoral zone mural or model. We’d love to see a photo of your students’ work! You can e-mail photos to us at [email protected].

Part 2

  • You may want to first experiment with the amount of fertilizer you will be using to stimulate algal growth before having students do this part of the activity. Depending on the size of your containers, the type of fertilizer used, and temperature and light conditions in your room, results may vary, and you may want to decrease the amount of fertilizer that is suggested in the lesson.

Discussion notes

The vast majority of plant species growing in Minnesota’s lakes, rivers streams and wetlands are considered beneficial and only rarely become a problem. Most healthy ecosystems have natural restraints that limit the abundance of native plants preventing them from becoming weeds. The major weed species having a negative effect on Minnesota’s waterways are non-natives like Eurasian water milfoil and curly leaf pondweed. But even a native species like algae can be a problem in some cases when excessive nutrients from runoff cause dense algal blooms. In the absence of natural enemies, or when the local ecosystem is disrupted or out of balance, ‘weeds’ grow uncontrolled and rapidly invade new areas forming dense stands. The primary difference between aquatic plants and aquatic weeds is where they occur and their abundance. For more information on aquatic plants and shoreline habitats go to https://www.mndnr.gov/shorelandmgmt/index.html

Alternative wrap-up

After finishing all three sections:

  • Ask students to review the benefits of aquatic plants. List the benefits of aquatic plants on the white board or smart board. Then ask the students to define “aquatic plant”.
  • Then ask students to define the word “weed”. Discuss how a weed is a plant growing where it is not wanted. By this definition, any aquatic plant has the potential to be a weed if it hinders navigation, water movement in irrigation and flood control canals, swimming, recreational boating or fishing, or if its abundant growth adversely effects fish populations and other wildlife.
  • Ask students how they might feel the next time they go fishing, cast and reel in their line with a plant on the hook instead of a fish. Would they move to an area with no plants or continue fishing near the plants? Would they change whether they categorized the plant as a beneficial aquatic plant, or a weed?

MinnAqua lesson connections

Lesson 3:2 – Function of Aquatic Plants can be combined with a number of related lessons to enrich student’s learning experience.

To introduce you students to aquatic habitats and get your students “in the habitat” use Lesson 1:1 – Design a Habitat or Lesson 1:4 - Water Habitat Site Study.

Lesson 1:1 - Design a Habitat   (17 pages | 1.3 MB)

Lesson 1:4 - Water Habitat Site Study   (43 pages | 8.3 MB)

You can follow Lesson 3:2 with Lesson 3:3 – Wonderful Watersheds to investigate the value of aquatic plant buffers on a watershed scale, or with Lesson 4:3 – Aquatic Plant Power which focuses on shoreland vegetation and it’s impact on fish habitat, and on aquatic plant management.

Lesson 3:3 - Wonderful Watersheds   (25 pages | 3.2 MB)

Lesson 4:3 - Aquatic Plant Power   (24 pages | 3.8 MB)

Lesson 4:5 – Town Meeting is a nice follow-up lesson that enlists students’ citizenship skills, critical thinking and decision making skills in resolving a community’s shoreland development issue.

Lesson 4:5 - Town Meeting   (17 pages | 1.6 MB)


Suggested online student resources

Have your students access these online resources to engage in these concepts further.


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