NAME:___________________________
Biodiversity in a Desktop Estuary:
Estuaries, also called salt marshes, lagoons, or wetlands, are shallow, partially enclosed coastal bodies of
water where fresh water and salt water meet and mix. Most estuaries occur where rivers empty into the ocean.
Because river water is full of organic (dead plant and animal) matter, estuaries are rich in nutrients, and tiny
water plants and animals, called plankton, are plentiful. Not surprisingly, estuaries are highly productive
communities. Although they represent only 2-3 percent of the total ocean area, estuaries alone are responsible
for 75-90 percent of shellfish caught each year. Abundant fish life, in turn, attracts hundreds of species of birds.
Estuaries contain a diverse array of plant and animal life.
The makeup of all estuaries is not the same because some areas of an estuary may contain more fresh
water than others, while other areas may contain more salt water. The pattern of salinity is crucial to the
diversity of organisms that live in an estuary. In this activity, you will examine an estuary, subject it to
environmental change, and determine how biodiversity is affected.
Procedure:
1. Study the table to familiarize yourself with the organisms, their salinity (salt), and food requirements.
2. Using Figure 1 (on a separate sheet) cut out each row of the table to make 12 strips of paper. Set aside the
blank strips and place the others on a flat surface face up.
3. Read the following scenarios and decide how you think each situation would alter the water conditions in the
estuary. Then, determine what effects the changes would have on each organism. Be sure to carefully examine
the food sources for each of the organisms. From your desktop estuary, remover the paper strips that represent
the species that you think would decline or disappear in each scenario. Explain your reasoning. When you
consider new scenarios, assume that you are beginning with the same original estuary.
Scenario 1: After a severe drought, the river that feeds your estuary almost completely dries up and ocean
water invades the river channel. The estuary is now primarily filled with salt water. Explain what changes will
take place in your estuary. Include your reasoning for the changes.
Scenario 2: After an unusually cold winter, a large amount of sea water freezes into icebergs. Because of the
freezing, the sea level drops and the estuary is now primarily fed by the river. Explain what changes will take
place in your estuary. Include your reasoning for the changes.
4. Use the blank strips of paper to add the following animals to your estuary: Fish C lives in fresh water and eats
any plankton; Crab C eats any plankton and lives in salt water. Repeat Step 3 for Scenario 1. Record below
what happened to your desktop estuary.
5. Now add your new strips (Fish C and Crab C) to the population and repeat Step 3 for Scenario 2. Record
below what happened to your desktop estuary
6. Did the increased biodiversity (increased type of animals) make the estuary more or less stable? Use data to
support your answer.
7. Why do food webs illustrate the relationships in an ecosystem better than a food chain?
Figure 1