Ask: what is an invasive species? If students are unfamiliar with the term invasive species, consider doing the Explore section from “Introduction to Invasive Species” lesson. If students are familiar with the term, ask them to name some common invasive species in our region, and to discuss the benefits and drawbacks of these species living in our region. Examples include purple loosestrife, common reed, water chestnut, Norway maple, emerald Ash borer, rusty crayfish, European starling.
Jigsaw activity: Each station should have the fact sheets, laminated photos and physical examples (if available), a copy of the marsh field guide and a copy of the Tidal Zone Diagram.
1) Graminoid vegetation: cattail and common reed
2) Broadleaf station: spatterdock and yellow flag
3) Submerged plants: water celery and water chestnut station.
Assign students to an expert station. When students go to their expert station, they should read the fact sheet as a group, decide on important facts, benefits, concerns, and fill in the Plants Data table. Make sure that students figure out if the plants are native or non-native and if they are invasive. This information can be noted in the general information section of the table. When students have completed the data table then the experts should split up into groups of three, with one representative from each expert group. All students should share their information, filling in their data tables.
Explain: The types and amounts of plants that are found in different parts of a wetland determine how that wetland section functions.
Submerged: Water celery is a submerged plant that oxygenates water, is a food source, and provides spawning habitat. Water chestnuts are a submerged plant that provide habitat for certain species of juvenile fish and invertebrates, but is invasive and has several concerns that may not make it a good plant for marsh. The leaflets of water chestnuts grow on the surface of the water and do not allow sunlight to penetrate the water and also hinders the photosynthesis of other submerged plants. The lack of photosynthesis creates a reduction in the amount of oxygen in the water which can stress fish populations.
Broadleaf: Spatterdock is a broad-leaf plant that provides a rich food source, valuable habitat, shade, cover, protection from predators as well as helps to stabilize shorelines, reduces erosion and slows down floodwaters. Yellow flag is an iris that, while beautiful, is invasive. It can cause skin irritation and tends to form monotypic stands in wetland areas. It spreads both by underground rhizomes and by seed, and can survive several months without water. However, it is also known to be beneficial as it can remove heavy metals from sewage.
Graminoid: Tall grasses such as common reed and cattails also have benefits and concerns. Both cattail and common reed stabilize shorelines, help reduce erosion, remove nitrogen, and provide habitat. Common reed is invasive and is not a habitat preferred by birds, however it is very good at removing excess nitrogen from the water. Students need to know that there is more nitrogen stored in common reed than in cattails which allows for the assumption that common reed is better at removing nitrogen from the water than cattails. Excess nitrogen in water can cause algae populations to increase which is harmful for many aquatic species. Common reed is non-native and invasive, however would be a beneficial plant if the wetland was in proximity to areas with excess nitrogen runoff such as agricultural areas where farming is prevalent.
Show the youtube video: “Ecosystems: Working with farmers to decrease Nitrogen pollution” . This video reinforces how wetland plants help reduce the effects of nitrogen run-off.
Evaluate: Tell students that they are being challenged to design a marsh based on specific needs. They can work either in groups or individually, depending on how you want to assess them, and you may want to have students present their work to the class as a poster or brochure (see example). There are four missions (see Mission Cards). All students should hand in answers to the evaluation questions, which focus on whether students understand the different types of benefits provided by different wetland plants.