The Chesapeake Bay is filled with a variety of plants and animals and each one has an important role to fill. The interaction between all of these organisms is called an ecosystem. When an organism exists naturally in a given ecosystem, it is considered a native species. Organisms that flourish in the Bay might not do very well in another habitat, such as the desert; however, some organisms thrive in places where they are not native, causing serious disruption to the rest of that ecosystem.

In this activity, students will explore the ways that native species interact in a healthy Chesapeake Bay. They will then learn about some of the ways that exotic or invasive species can threaten the balance of the ecosystem. Students will discover how the various elements of the Bay ecosystem are interconnected and investigate some of the issues associated with invasive species.

Geography, science, economics, language arts

Standard 8: "The characteristics and spatial distribution of ecosystems on Earth's surface"
Standard 12: "The processes, patterns, and functions of human settlement"
Standard 14: "How human actions modify the physical environment"

One to two hours

• Computer with Internet access
• Poster paper
• Writing and drawing materials
• "Ecosystem cards" (large index cards with the names of Chesapeake Bay organisms written on one side; see below for list of organisms)

Students will

• learn about the elements of the Chesapeake Bay ecosystem;
• study the native species and invasive species currently living in the Chesapeake Bay, and how they interact; and
• discuss ways to solve the problem of invasive species in the Chesapeake Bay and in other ecosystems.

Thousands of plant and animal species live in the Chesapeake Bay region. Explain to students that some of these species are not native to the region and disrupt the Bay's delicately balanced ecosystem.

Ask students how they think these exotic species got into the Bay in the first place. Explain that exotic species are transported to the Bay's watershed in a number of ways: by air, over land, and in water. Some have been introduced in the ballast water that large ships carry for stabilization. When the ballast is pumped from the ship and it begins to mingle with the Bay's waters after a voyage, marine plants and animals from the ship's originating ecosystem are released. Unwanted "travelers" such as these can also be transferred to the Bay via airplanes, cars, and trucks.

Not all exotic species are introduced to the ecosystem by accident. Some species, like the honeybee, are considered valuable resources. Other species reproduce too quickly and have caused large economic and ecological problems; they are called exotic invasive species.

Some of the more familiar exotic species in the Bay watershed include the tall shoreline plant Phragmites australis (common reed), the grass carp, resident Canada geese, and mute swans, which cause problems in the Bay region by destroying wetlands and other habitats that sustain native species of resident and migratory birds.

The task of removing exotic species can be extremely costly, running into the millions of dollars at times. Although regulatory controls currently exist to prevent further introduction of exotics, public education is the best possible method for controlling accidental and intentional introduction.

Divide the class into groups of five students each. Hand out ecosystem cards to each group (see groups below for a list of organisms to put on your cards). Each group will receive five cards, and each card will have the name of an organism on it that can be found in the Chesapeake Bay. One student in each group will be assigned a species to represent; at least one should be an underwater grass. Some other possibilities include water, fish, algae, oxygen, people, sediment, clams, ducks, weather (hurricanes or drought), and crabs.

[Note: If your students are knowledgeable about the Bay's ecosystem, you may ask them to come up with their own roles, rather than using the ones on the cards.]

Ecosystem cards:

Group 1: oyster, widgeon grass, plankton, American wigeon duck, crab
Group 2: eelgrass, crab, seahorse, cownose ray, soft-shelled clam
Group 3: periwinkle, saltmarsh cordgrass, diamond-back terrapin, rockfish, sago pond weed
Group 4: oyster, sea nettle, anchovy, comb jelly, red head grass
Group 5: blue gill, elodea, scud, mosquito fish, mosquito
Group 6: osprey, rockfish, humans, crab, wild celery
Group 7: spottail shiner, yellow perch, wild celery, canvasback duck, humans

Have the students in the groups work together to determine and explain how all of the organisms in each group are interconnected. In order to accomplish this, each student in the group should answer the following questions on the back of each organism card.

• What does the organism eat, or how does it get its nourishment?
• What eats that particular organism?
• What sort of habitat does the organism need to survive?
• What other special needs does it have?

The following Web sites will help them in their research:

National Geographic News: Chesapeake Bay Watermen Question Limits on Crab Harvests
Bay Grasses
Chesapeake Bay Foundation
Chesapeake Bay Program: Animals and Plants (click on "Exotic Species" on the left)
University of Maryland: Alien Ocean

Have each group use their poster paper to create a web connecting the four or five organisms they chose. Students should draw lines connecting organisms to each other. Have students write a brief description of what the connection is on each line.

Each group will create a five to seven minute presentation or dramatic performance that demonstrates how all of the elements in their group are interconnected.

As a class, create a single large web showing how all the species students researched in their groups are connected to each other.

Ask each student to comment about what might happen to each of the other organisms in the web if the organism he or she studied disappeared.

Pose the following question to students: If you could create a real or fictional device/solution to get rid of an invasive species but cause no harm to native species, how would it operate? Have the students write a short essay describing their ideas. Share students' ideas with the rest of the class and have a classroom discussion covering these ideas.

• Have the students represent an invasive species during gym class by playing "Blob Tag" where one person is "it" (an invasive species). When they catch someone that person joins hands and now the two people are "it." Every person that gets tagged becomes part of the "blob/invasive species." After the game is over, conduct a reflection in which students can consider the ways in which invasive species mirror "the Blob" in their interactions with the local environment.
  
  
• Invasive exotic species in the Chesapeake Bay have become a complex problem. Some people think that we should leave them alone. Others think that exotic species should be destroyed because they change native ecosystems and affect the careers of people who rely on this environment, such as watermen and the fishing industry. This would cost billions of dollars and take many years. What do students think should be done about this issue? Have students explain their answers in an essay and then present their thoughts to the class.

This lesson is adapted from Bay Grasses in Classes Curriculum (Chesapeake Bay Foundation).

Bay Grasses
Chesapeake Bay Program
National Geographic News: Chesapeake Bay Watermen Question Limits on Crab Harvests
National Geographic: Geography Action! 2003Habitats
University of Maryland: Alien Ocean