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An estuary begins where fresh river water flows into coastal bays and inlets that drain out into the ocean. An estuary can be a bay, delta, lagoon or swamp that lies between the land and the sea. Most estuaries are shallow, and water depth varies daily based on ocean tides, seasonal rain, and river flow. Different minerals and sediments in the salt water make the water have a different color than fresh water. When fresh water meets salty sea water, both liquids combine turning into a brackish, or green brown mixture. There is one example of fresh water estuaries. The bays along the Great Lakes are examples of fresh water estuaries where river water flows into bays and harbors. However, most estuaries are found along the coast where river water meets salt water from the ocean.

Different Estuaries

Estuaries are classified by how they are formed on land and the changing water flow. Estuaries can form very slow, or more quickly. When glaciers melt, they can leave open valleys that slowly fill with ocean water and flowing rivers. Sudden earthquakes and volcanic eruptions create cracks in the earth that can quickly fill with this water mixture.

Estuaries Change

Seasons bring change with warm spring floods, hot dry summer days, cool fall rains and cold winter ice. Weather patterns change daily. The sun warms the cool morning air and slow moving water. Air and water temperatures rise. As the sun sets, the cool ocean breeze flows in. Air and water temperatures drop. Animals, insects and plants have to adapt to live in these changing conditions. Different sounds can be heard from changing weather--thunder, waves, the wind and storms. When the tide is low, there is a tangy salty smell. When the tide is high, the air smells fresher. Ask students to use all their senses when visiting an estuary.

Estuaries Protect

Estuaries are the nurseries of the sea. Estuaries shelter land and marine mammals, reptiles, amphibians, insects and plants. Millions of shorebirds migrate north each spring to warm nesting grounds. Estuaries provide shelter from ocean wind and waves, storms and river currents. Rich nutrients and sediment in the water come from the mixing of fresh river water and salty ocean water. When animals, plants and insects die they break down and provide organic matter and nutrients back into the estuary.

Super Sponges

Estuaries and surrounding wetlands act like giant sponges absorbing excess water from floods and storms. Factories can spill chemicals. Rain washes fertilizers and pesticides from farmlands and yards. Automobiles, buses and trucks leak gas and oil onto streets, which flow down into storm sewers. These pollutants flow into rivers and streams from the surrounding land, or watershed. Estuaries filter these pollutants from rivers and streams before they travel into the ocean. Yet people have to be careful to take care of estuaries, and reduce the pollution.

Initiating Activities--All Levels

Show students pictures and videos of estuaries.

National Oceanic and Atmospheric Administration (NOAA) pictures and videos:

Estuaries in the U.S.:

Estuary Diagram: /habitats/ estuaries.htm

Encourage students to view different estuary videos. Ask if they have visited an estuary at home, or on vacation.

Estuary Live TV:

US EPA Estuary Videos:

Initiating Questions Levels Pre-A--A

1. Have you been to an estuary?

2. What is a river?

3. When it rains, where does the water go?

Follow-up Questions Levels Pre-A--A

4. Have you gone fishing in a bay?

5. What does an estuary look like?

6. What happens when a river gets near the ocean?

Level Pre-A

Picture Activity

Tell your students that many plants, animals, and insects live in and are sheltered by an estuary.


Students trace and say words, and then match the words to the pictures. (bay, ocean, river).

Weekly Lab

Students will create an estuary that demonstrates the connection between the land, a river and the ocean. Ask students to draw blue rivers for fresh water, and green oceans for salt water.


Answers: 3 birds; 4 crabs; 5 turtles


Students will tell a story about what lives in an estuary.


Students will color the animals. If your students color the plant, remind them that the plant is not an animal. Discuss ways to tell the difference between a plant and an animal.

Bringing It Home

Students will combine two different words to form compound words (dragonfly, jellyfish, blackbird).

Level A


Students trace the new words and match the words to the pictures (river, ocean, estuary).

Bonus Answer: An estuary lies between a river and the ocean.

Weekly Lab

(Please see Level Pre-A.)


Answers: 1) 3 blue crabs + 2 green crabs = 5 crabs; 2) 4 seagulls + 3 blackbirds = 7 birds; 3) 4 minnows + 2 salmon = 6 fish

Writing in Science

Answers: 1) bay; 2) estuary, river, ocean; 3) Animals


Answers: horseshoe crab, jellyfish, and bluebird

Bringing It Home

Students will color the estuary picture and circle the fish. There are 4 fish. Ask students if they can identify the other animals shown in the picture.

Initiating Questions Level B

1. Have you visited an estuary before?

2. Where does the water come from in an estuary?

3. What animals or plants live in an estuary?

Follow-up Questions Level B

4. What is an estuary?

5. Why do you think estuaries are important?

6. What would happen if rivers did not flow into estuaries?

Level B


Answers: 1) estuary; 2) crab; 3) blue heron; 4) river; 5) ducks

Weekly Lab

(Please see Level Pre-A.) Students will add to this lab by drawing living creatures and plants in an estuary.


Answers: 1) 3 blue crabs + 2 green crabs + 1 red rock crab = 6 crabs; 2) 4 seagulls + 3 blackbirds + 2 blue herons = 9 birds; 3) 4 minnows + 2 salmon + 5 red cod = 11 fish; 5) 6 crabs - 5 crabs = 1 crab left over

Writing in Science

Answers: 1) An estuary is place where a river and the sea come together. 2) Students will look at the front picture and/or their WEEKLY LAB products to identify animals living in the estuary. This activity is linked to the WEEKLY LAB.


Students will color in the estuary picture, and draw lines to match the animal and insect names (blue crab, blue heron, deer, dragonfly, raccoon, and seagull).

Bringing it Home

Answer: Students should circle a deer, blue heron, raccoon, clams, and fish.

Bonus Answer: (Answers will vary.)

Initiating Questions Level C

1. Where do we find estuaries?

2. How are estuaries protected?

3. Do you think estuaries can be big and small?

Follow-up Questions Level C

4. Name different animals and birds that live in an estuary.

5. Why do you think estuaries are important?

6. Look at a map. Name some different estuaries near your home.

Level C


Level C--VOCABULARY--Word Search Solution:

Weekly Lab

Students will mix fresh blue water and salty green water to make brackish estuary water. Results may vary, but estuary water has a green-brown, or pea soup color.


Answers: 1) 18 pelicans; 2) 19 blue herons; 3) egrets and seagulls; 4) 2 seagulls; 5) 10 pelicans

Writing in Science

Answers: 1) When fresh water mixes with salt water, it turns brackish due to mixing of the different water types and nutrients in both water sources. 2) Estuaries provide protection from ocean waves, storms, and heavy winds. Estuaries provide sources of food and shelter for many different living creatures and plants. 3) Estuaries are generally located on the coast between a river and the ocean. This activity is linked to the WEEKLY LAB.


(Please see Level B--WEEKLY LAB.) This activity can be done in small groups.

Bringing It Home

Answers: 1) dragonfly; 2) seagull; 3) deer; 4) spider; 5) fish; 6) blue heron; 7) racoon; 8) horseshoe crab; 9) turtle; 10) clams; 11) snail 12) crab or blue crab

Bonus Answer: (Answers will vary.)

Initiating Questions Levels D-E

1. Can you name some animals and plants that live in estuaries?

2. Where do we find estuaries?

3. How would a flood affect an estuary?

Follow-up Questions Levels D-E

4. Why do you think estuaries are called the nursery of the sea?

5. Look at a map and identify estuaries in your area.

6. Do you think estuaries are important for commercial fishing? Why?

Level D


Answers: 1) Estuaries; 2) bayou, lagoon; 3) water, brackish; 4) nutrients; 5) waves, currents; 6) Geology, land

Weekly Lab

By combining warm fresh water with cold salt water, students will see how fresh warm river water and salty cold sea water mix in an estuary. Cold sea water settles to the bottom. When the sea water warms up, it rises from the bottom to mix with the warmer fresh water.


Answers: 1) 3:23 AM, 11.9 feet; 2) 7 hours 9 minutes; 3) 12:06 PM, 4:59 AM; 4) 12[degrees] Fahrenheit

Writing in Science

Answers: 1) Cold salt water is heavier and settled to the container bottom. 2) The blue salt water started to rise and became diluted with fresh water. 3) Cold ocean water flows to the bottom of an estuary, but when water temperature rises, the ocean water warms up and mixes with fresh river water. This activity is linked to the WEEKLY LAB.


(Please see Level B--WEEKLY LAB.)

Bringing It Home

Answers: 1) 35 pelicans; 2) 75 seagulls; 3) blue herons, pelicans, egrets, seagulls; 4) 2 seagulls;

5) 13 pelicans

Level E


(Please see Level E--Crossword Puzzle Solution on the following page--page 4.)

Weekly Lab

(Please see Level D.) Adding black coffee, black ink and dirt imitates the release of oil, gas, spilled chemicals, and sediment from storm water runoff and construction that can pollute estuaries. Students can also add twigs and crumbled leaves.


Answers: 1) 4:10 AM, 11.8 feet; 2) Monday 10:33 AM, 6.7 feet; Thursday 12:53 PM, 2.0 feet; 3) 12:06 PM, 4:59 AM; 4) 65.25, rounded to 65[degrees] Fahrenheit; 5) At low tide, the water level is decreasing as water flushes out to the sea.

Writing in Science

Answers: 1) As the cold salty water warmed up, it started to mix and become diluted with the fresh water. 2) Shallow water becomes warmer by absorbing the heat from sunlight and the air temperature. 3) Animals need to learn to adapt and survive in an estuary. Every day, the water level and temperature changes. This activity is linked to the WEEKLY LAB.


(Please see Level E--CHALLENGE Solution, top right.)

Bringing It Home

Answers: 1) 35 pelicans; 2) 75 seagulls; 3) blue herons, pelicans, egrets, seagulls; 4) 89 birds; 5) 18 pelicans.

Bonus Answer: If the estuary became polluted with chemicals or pesticides, they would have a hard time finding clean food, water and shelter. The pollution may make them sick.

Level E--CHALLENGE--Solution

Weekly Resources

Helpful Sources for Planning Your Science Weekly Classroom Activities

Recommended Resources--Books

* Martin, Fred. Investigating Coasts (Explore Geography). North Mankato, Minnesota: Heinemann Library, 2006.

* Walker, Sally. Life in an Estuary (Ecosystems in Action). Minneapolis, Minnesota: Lerner Publishing Group, 2003.

Internet Resources

Exploring Estuaries-

National Oceanic and Atmospheric Administration (NOAA) Ocean Service-- /tutorial_ estuaries/

NOAA Estuary Site--

NOAA Estuary Games-

Alignment with A Framework for K-12 Science Education (developed by the National Research Council [NRC] July, 2011)

Dimension 1

1: Asking questions and defining problems

2: Developing and using models

3: Obtaining, evaluating and communicating information

4: System models and dimensions

Dimension 2

1: Patterns

2: Cause and effect

7: Stabillity and change

Dimension 3

LS2: Ecosystem Interactions, Energy and Dynamics


Estuaries are in trouble. People build homes, factories and shopping centers near estuaries. These cover the land and cause pollution.


Medical scientists use horseshoe crab blood to make sure drugs, vaccines and medical equipment are bacteria free.


Weather changes estuaries. Spring rains and floods push logs, plants and trees into estuaries.


Many Native American tribes lived near estuaries. Estuaries provided fish and shells, reeds for housing, and trees for canoes.


Many estuaries are shallow. When water flows out, estuaries become warm from the sun. When water flows back in, the water Cools down.


Ocean waves pull in sea minerals, nutrients, marine animals and plants. Ocean waves flush out dead branches and plants.

DID YOU KNOW?? Waves and wind change estuaries. Waves are created by wind blowing across the water.


Horseshoe crabs tire in estuaries. They can live 20-22 years.


Female horseshoe crabs can lay 4,000 eggs in each clutch.


The horseshoe crab has special blue blood.

Level A


New Words






A river (riv-er) flows to a bay.

A bay is an estuary (es-tu-ar-y).

An estuary flows into the ocean (o-cean).

An estuary is between (be-tween) a river and the ocean.


Write the word next to the picture.

WORD BANK: river ocean estuary

Weekly Lab

Can you make an estuary?

You need: white paper, green paper, ruler, scissors, crayons, glue stick estuary book,

Step 1: Fold the white paper in half. Open up.

Step 2: Make an estuary, Cut out a circle from the green paper 9 cm (3 1/2 in) wide.

Step 3: Glue the green circle in the paper center.

Step 4: Draw a blue river above the green circle.

Step 5: Draw green ocean waves below the green circle.

Step 6: Draw crabs. Draw a turtle. Draw birds.

Who lives in an estuary?


How many animals live in the estuary?

3 blue crabs + 2 green crabs = [] total crabs

[] seagulls + [] blackbirds = [] total birds

[] minnows + [] salmon = [] total fish

Writing in Science

Finish the sentences. Use your new words.







An estuary is a _______________.

An __________________ lies between a ______________ and

the _______________ live there.


What lives in the estuary? Make new words.

horse + shoe + crab = horseshoe


jelly + fish = ____________

blue + bird = _____________

Bringing It Home

Adult Supervision Recommended

See the estuary. Color the animals. Circle the fish.

Write a sentence about estuaries. Use a separate sheet of paper.

"Do you like science or art better?"

"I like both. Besides, artists actually use science for their work.

"Our next issue will teach us all about the connections between science and art!"
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Publication:Science Weekly
Geographic Code:1USA
Date:Dec 5, 2012
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