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WHAT’S SO SPECIAL ABOUT AN ESTUARY?

In the previous lesson, you learned that the Chesapeake Bay is the largest estuary in the United States. You learned that it began to form about 15,000 years ago due to melting glaciers that flooded the Susquehanna River Valley, but what makes the Chesapeake Bay so important? The answer to this question centers on your understanding of estuaries. In this investigation, you will explore the Chesapeake Bayestuaries in order to determine their value as natural resources.

Objective: Students will analyze characteristics of the Chesapeake Bay estuary in order to determine its value as a natural resource.

Activity 1: Bay Cuisine

  1. Brainstorm and record with a partner some foods that you eat that come from the Chesapeake Bay.
  1. View the video clip and record the names of at least 5 organisms that live in the Chesapeake Bay in the space below.

Organisms that Live in the Chesapeake Bay

  1. Predict why there is such great diversity of organisms living in the Chesapeake Bay.

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Activity 2: It’s All About the Salt

Have you ever tasted the seawater at the beach in Ocean City, MD? If you have, you already know that the water tastes salty. One of the reasons for all of the diversity of organisms in the Chesapeake Bay is the property of salinity.

  1. Complete the vocabulary exercise by indicating your level of understanding of the words in the chart below.

Use the following symbols:

+ means I know the meaning of the word and can provide examples

- means I have heard the word and know something about its meaning

0 means I have no understanding or knowledge of the word

Chart 1: It’s All About the Salt

Level of Understanding / Vocabulary / What I Know About the Word
Estuary
Salinity
Freshwater
Saltwater
brackish
  1. Read the passage, “It’s All About the Salt” on the student resource sheet in order to determine the importance of estuaries as natural resources.
  1. Reread and highlight the definitions of the words from Chart 1, “It’s All About the Salt.”
  1. Complete the key questions that follow.

8. Describe the main difference between saltwater and freshwater. Use evidence from the reading to support your response.

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  1. Which statement best describes the salinity of the Chesapeake Bay estuary?

A. The salinity is the same throughout the Bay.

B. Most of the Bay consists of brackish water.

C. The salinity is the greatest in the upper Bay area.

D. There is no salinity in the Chesapeake Bay.

  1. Refer to the prediction you made in Activity 1. Modify your prediction based on the information from the reading.
  1. Complete the chart by determining how each of the organisms make use of the Chesapeake Bay.

Name of Organism / How they use the Chesapeake Bay?
American Shad
Menhaden
Waterfowl

Class Discussion

Make an organizer to illustrate all of the resources that the Chesapeake Bay provides.

Analysis

Captain John Smith, the first explorer to set foot on the Chesapeake Bay area once wrote this statement in his journal to describe the beauty and value of the Chesapeake Bay.

“Heaven and earth never agreed better to frame a place for man’s habitation…”

  1. Evaluate Captain John Smith’s remarks about the value of the Chesapeake Bay as a natural resource. Support your response with evidence from the investigation.

IT’S ALL ABOUT THE SALT

Saltwater vs. Freshwater

Salt is the main ingredient that makes an estuary special. In order to understand the importance of salt, we need to distinguish between types of water. Water from the ocean is considered saltwater because it has a high concentration of salts dissolved in it. If you have ever been to the beach, you probably already know that ocean water tastes salty! On the other hand, water from rivers and streams is generally freshwater, meaning that is has very little to no salt dissolved in it.

What is an Estuary?

In areas where freshwater and saltwater mix, the salinity or concentration of dissolved salts will vary. This mix of fresh and salt water is called brackish water. Because the Chesapeake Bay is partly enclosed by land, freshwater and saltwater meet and mix there. By definition, this meeting and mixing of saltwater and freshwater in a semi-enclosed body of water is an estuary. In the case of the Chesapeake Bay estuary, the saltwater comes from the Atlantic Ocean and the freshwater source comes from the rivers and tributaries that empty into the body of the Bay. Most of the water in the Bay is brackish, but the amount of salt varies from place to place. See Figure 1.

Lots of Habitats

Because of the wide range of salinities, the Chesapeake Bay waters provide perfectly suitable habitats for a variety of freshwater and saltwater species. Those plant and animal species with the greatest tolerance for salinity changes can be found well into the main body of the Bay. No matter what the habitat-a beach, a marsh, or a mud flat- salinity determines, to a large extent, the kinds of plant and animal species that live there.


The Bay as a Nursery

Due to the variation in salinity, estuaries serve as nurseries for many young animals that will eventually live in the ocean. Fish like shad, herring, and striped bass migrate from the ocean through the estuary and into the rivers to spawn (lay eggs) each year. The eggs develop into larval fish which move down into the estuary to feed and grow before journeying to live in the open sea.

A Good Place to Call Home

Other kinds of animals migrate to the estuary from the ocean for the good supply of food. An abundance of fish called menhaden come for the phytoplankton or tiny algae in the water. In turn, bluefish come to feed on the menhaden. Many waterfowl spend winters in estuaries and fly north in the spring to nest. About half of the fish and other sea animals we eat depend on an estuary during some part of their lives.