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It’s a Group Thing

Activity Summary

Students learn about the properties and functions of oyster reefs by 

building and testing models of reefs. They also learn about the 

importance of reefs to oysters.

Learning Objectives

Student will be able to:

• Explain the function of healthy Eastern oyster reefs.

• Explain why being part of a healthy reef helps Eastern oysters 

obtain food, defend themselves and cope with changes.

Essential Questions

1. What role do Eastern oyster reefs play in the Chesapeake Bay?

2. How and why is a reef structure beneficial to the Eastern oyster?

Background Information

Oysters are bivalves that live in eastern coastal waters from the Gulf 

of St. Lawrence to the Gulf of Mexico. Large aggregations of oysters

K-12 Oysters in the Chesapeake Bay

Grade Level: 

Grade 3

Teaching Time: 

3 -5 minute sessions

Materials:

• Oyster shells (at least 

one per student) or 

photos of oysters

• Chart paper

• Plastic tubs (6-8)

• Water

• Legos

• Straws

• Sculpey or other 

plasticine clay

• Student science 

journals
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can sometimes cover extensive areas of bottom in estuarine areas and may exist above the 

substrate attached to various objects such as stones, pilings, shipwrecks, and even discarded 

bottles. These dense groups of living oysters and shells are variously referred to as oyster 

bottoms, oyster beds, oyster bars, oyster banks, or oyster reefs. Because these terms 

sometimes are used interchangeably and are not well defined, it is important to note that not 

all species of oysters form dense clusters that we normally refer to as "oyster reefs". To help 

differentiate, we define oyster reefs here as large colonial aggregations of living oysters and 

oyster shells that can have submerged as well as intertidal portions, and provide habitat for a 

community of other species (e.g., tunicates, fish, crabs, worms, mussels, bryozoans, and 

barnacles). The best examples of oyster reefs are found along the Atlantic and Gulf coasts, 

where oyster reefs are formed by one species - Eastern oyster (Crassostrea virginica). As the 

older oysters die, they form the foundation for the reef and live oysters form a living layer atop 

and around the structure of older, nonliving shells. 

Besides being excellent and tasty sources of food, oysters and oyster reefs serve vital roles in 

estuarine ecosystems. For example, oysters filter the water and reduce turbidity by extracting 

phytoplankton and organic and inorganic particles from the water column. Good water clarity, 

in turn, promotes the growth of submerged aquatic vegetation (SAV), which provides habitat 

for juvenile crabs, fish, and other organisms. In addition, the reefs may provide some protection 

from waves and currents. Oyster reefs form a complex ecosystem on and within their structure

and provide large surface areas for attachment by other organisms such as barnacles, tunicates, 

mussels, sea anemones, and tube worms. Many of these organisms, like oysters, are filter 

feeders and contribute to the overall filtration capacity of the reef. They also serve as food for 

other reef inhabitants, such as crabs and fish. Small crustaceans called amphipods are abundant 

on most oyster reefs and are favorite prey items for some fish. In addition to providing habitat 

for prey items, oyster reef crevices and empty shells provide habitat and protection for a 

variety of animals. Some fish (e.g., gobies, blennies, skillet fish, and oyster toadfish) deposit 

their eggs inside the empty oyster valves, where they are less likely to be eaten by predators. 

Other fish normally found on East and Gulf Coast oyster reefs include spot, pinfish, lizardfish, 

sea trout or weakfishes, red drum, American eel, and black drum (an important oyster 

predator), which forage on the diverse invertebrate assemblage (Brietburg, 1995). 

Oyster reefs in the United States are not only unique ecosystems that support multitudes of 

other organisms, but they are a valuable food source and constitute important commercial 

fisheries. The loss of oyster reefs in the United States during the past 200 years has not only 

significantly decreased the amount of food harvested from them, but has also removed habitat 

for other estuarine animals and plants, decreased water quality, and reduced income and jobs 

for workers in the oyster industry. Once the nation's crown jewel of oyster production, oyster 

harvests in Chesapeake Bay have reached an all-time low, and the once massive reefs have 

been reduced to 1 percent or less of their former mass. Similar scenarios have occurred in other 
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locations as well, due to disease, water pollution, overharvesting, cumulative loss of clutch 

base, and mining of shell resources.

Key Words

Bivalve - An aquatic mollusk that has a compressed body enclosed within a hinged shell.

Density – The amount of something in an area.

Disease - A condition that impairs the proper function of the body or of one of its parts.

Ecosystem - All the living organisms that occur together in a particular area.

Filter - To separate or remove matter.

Habitat - Place where an organism or a community of organisms lives; includes all living and 

nonliving factors or conditions of the surrounding environment.

Harvest – Process of gathering as in a crop.

Hatchery – Place where oyster larvae and young oysters are grown.

Larvae – Early form of an animal that is unlike its parent; Changes to look like/act like parent.

Mollusk - Invertebrate that has a soft unsegmented body and lives in aquatic habitats and often 

has a shell.

Oyster - Bivalve mollusk with rough irregular shell sometimes eaten as a delicacy and may be 

farmed for food or pearls.

Oystermen – Women and men who harvest oysters to sell to restaurants or to eat themselves

Phytoplankton – Free swimming algae.

Pollution – Contamination of air, water or soil with harmful substances.

Reef – Strip of oysters rising close to the surface of the water.

Restore – Bring back into existence.

Seed – Plant or lay down young oysters so they will grow.
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Spat – Name for oyster larvae after the attach to a surface.

Substrate – Base on which an organism lives.

Water current - Part of a fluid body (as air or water) moving continuously in a certain direction.

Activity Procedure

Day 1

Engagement 

Separate students into small groups and have them investigate oyster shells for a few minutes. 

Suggest they try to build with the shells. Or, give each small group several photos of oyster 

reefs to review. Have them record their observations and what they already know about 

oysters in their science journals. Discuss their entries.

Exploration

1. Pose the following problem to the students:

There are many fewer oysters in the Chesapeake Bay than there were in the past. Since 

the Bay needs oysters to help keep it clean, scientists are conducting research to decide 

how to replenish the oyster population in the Bay. Scientists know oyster larvae attach 

best to other oyster shells, but they are not sure how to lay the shells in the water to help 

the oyster and the Bay ecosystem recover.

2. Divide the students into small groups and give each group Legos (to serve as oysters), 

straws, Sculpey or other plasticine clay, and a tub filled with several inches of water.

3. Have a student in each group place several individual Lego blocks on plasticine clay pads 

and submerge them (Lego/clay oyster reef sculpture) at one end of the tub. The blocks 

should sink and be covered by at least an inch of water. More clay can be added to the 

pads on which the Legos rest if needed.

4. Ask a student(s) in the group to place other Legos in the water at the opposite end from 

the reef sculptures, and using the straw, blow or nudge the free-floating blocks once or 

twice toward the submerged block. The floating Legos need to touch the blocks, but the 

students cannot guide the floating blocks clay to the reef sculpture with the straws. 

Have students try several times with several different size blocks. Record the data on 

the Student Response Sheet 1.

Explanation

1. Ask the students if the floating blocks touched the oyster reef sculpture. Why or why 

not? Discuss the data they recorded. Have them record their thoughts in their science 

journal and discuss with the class.
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2. Ask the students to modify their Lego structure until they can blow or nudge the clay to 

have it touch the blocks. Discuss the modifications and observe the different shapes 

created.

3. Emphasize that taller and wider reefs catch more food. There is more surface area to

block water, which carries the phytoplankton, and divert it to the oysters.

Day 2

Engagement

Watch the first five minutes of the video, “Restoring Oyster Reefs in Chesapeake Bay: Sea Grant 

Documentary.” (https://www.youtube.com/watch?v=v4pKoDPdmzM) This section shows 

examples of healthy oyster reefs and the current state of oysters in the Bay.

Exploration

1. Have a student attach three blocks together to simulate a tiny group of oysters and 

submerge them in the tub. Plasticine clay can be used again to weigh down the blocks

so they stay close to or on the bottom. 

2. Another student should create wave action in the tub, from both sides of the tub with a 

straw or their hands. They can start gently and gradually increase the action. Have 

students record their observations in their journals.

3. Have the groups remove the clay, add a few more Legos to the original structure, and 

repeat the wave action. Students can keep track of the number of Legos used in their 

reef on Student Response Sheet 2.

4. Each group should continue making additions to their Lego reefs and repeat testing until 

the reefs move very little or not at all in the wave action. 

Explanation

1. Discuss the activity and data with the students. Compare the number of blocks (oysters) 

needed to make the reef stable and withstand the wave action with the original three 

Lego structure.

2. If the students used different size blocks, discuss how the differing sizes affect the 

stability of the structure and ask how that could apply to oyster reefs.

3. Emphasize that larger, more complex reefs resist changes to their environment better 

(strong wave action, removal or addition of additional shells).
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Day 3

Engagement

Watch minute 9:15 through minute 14:45 of “Restoring Oyster Reefs in Chesapeake Bay: Sea 

Grant Documentary.” This section shows the results of “lightly seeding” (spreading shells in the 

water) and “densely seeding” (clumping shells in piles close together) oyster reefs for 

restoration. Note: You will need to explain what “seeded” and “density” mean prior to the 

video. Discuss the services healthy oyster reefs provide for the Bay besides filtering the water 

(nursery ground for young aquatic animals and source of food for larger animals).

Exploration

1. In groups, students should build new large reefs that will sit on the bottom of their tubs. 

These reefs should have a single color core made up of five to ten blocks with blocks of 

other colors around it. Make sure the solid color core can be seen through the outer 

layer. This design simulates an oyster reef where the outer shells will help protect the 

inner oysters.

2. The students repeat the Day 1 Exploration activity with their reefs trying to touch the 

solid color core of the reef with the floating block.

3. Ask them to record in their journals the number of times they tried and the number of 

actual core touched.

4. Have them repeat the activity placing multiple floating blocks in the water and recording 

the number of “hits” on the core of the reef on the Student Response Sheet 3.

Explanation

Discuss the activity and data emphasizing how oysters (blocks) with other oysters around them 

are less likely to be affected by predation (hits with the clay). Using different size blocks

simulates predators at various levels of the water column. Refer back to the video section 

showing the predators and prey in a healthy oyster reef.

Revisit the original problem posed to the students:

There are many fewer oysters in the Chesapeake Bay than there were in the past. Since the Bay 

needs oysters to help keep it clean, scientists are conducting research to decide how to replenish 

the oyster population in the Bay. Scientists know oyster larvae attach best to other oyster shells, 

but they are not sure how to lay the shells in the water to best help the oyster and the Bay 

ecosystem recover.

As students to return to their groups and decide the best way to lay the shells based on their 

tests. Discuss their ideas as a whole class.
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Extension

1. Give each pair or small group of students a card with one of the scenarios below. Have 

them discuss how living in a group (reef) with many generations of oysters helps or 

hinders the oysters in the situation and then share their conclusions.

a. A boat passes dragging the propeller on the reef

b. A bad storm arrives and waves pound the reef. 

c. A bad storm brings waves and sediment is dropped on the reef.

d. Fisherman harvest oysters.

e. One of the oysters catches a very contagious disease.

f. A group of flat worms settle in the reef eating small oysters. (natural oyster 

predator)

g. A very hungry blue crab visits the reef. (natural oyster predator)

2. Invite a speaker(s) who works with oysters and/or oyster restoration into your 

classroom. Ask them to describe what they do, how it affects the oysters in the 

Chesapeake Bay, and describe the career path they took. Have the students prepare 

questions about oysters, oyster reefs, and restoration ahead of time.

Evaluation

Formative: 

1. Class discussions and participation

2. Model building

3. Journal entries

Summative: 

Students can complete one or both of the following:

1. Have students draw the most effective oyster reef they built and prepare a written 

response to the following questions:

a. What are the functions of healthy Eastern oyster reefs?

b. Why does being part of a healthy reef help Eastern oysters obtain food, defend 

themselves from predators and cope with changes?

2. Revisit the problem posed to students at the beginning of the lesson. Have students 

write a letter to a scientist to convince them to place oysters or oyster shells in large 

groups around the Bay. A sample rubric for the letter is below.
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Education Standards

Three Dimensional Learning

Disciplinary Core 

Idea(s)

3-LS2.D: Social Interactions and Group 

Behavior

Being part of a group helps animals 

obtain food, defend themselves, and 

cope with changes. Groups may serve 

different functions and vary 

dramatically in size. (3-LS2-1)

How Standard is Addressed

Students learn how large 

reefs with oyster shells close 

together help oysters obtain 

food, defend themselves, and 

cope with changes by building 

and testing reef models.

Science/Engineering 

Practice

Engaging in Argument from Evidence

Engaging in argument from evidence in 

3–5 builds on K–2 experiences and 

progresses to critiquing the scientific 

explanations or solutions proposed by 

peers by citing relevant evidence about 

the natural and designed world(s).

• Construct an argument with 

evidence, data, and/or a model. 

(3-LS2-1)

Students construct oyster 

reef models and then use 

what they learned by testing 

them in various conditions to 

the ways large, healthy oyster 

reefs help and protect oysters 

so they can grow and help the 

Bay ecosystem.

Cross – Cutting 

Concepts

Cause and Effect

Cause and effect relationships are 

routinely identified and used to explain 

change. (3-LS2-1)

Students modify their reefs, 

retest them, and identify how 

the design changes affect the 

outcomes of the tests.

Common Core Standards

Ties to Common 

Core

W3.1

1. Write opinion pieces on topics or 

texts, supporting a point of view with 

reasons. a. Introduce the topic or text 

they are writing about, state an opinion, 

and create an organizational structure 

that lists reasons. b. Provide reasons 

that support the opinion. c. Use linking 

words and phrases (e.g., because, 

therefore, since, for example) to 

connect opinion and reasons. d. Provide 

a concluding statement or section 

Students write a letter to a 

scientist to convince them 

that large reefs with many 

shells benefit oysters and the 

Chesapeake Bay.
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Maryland Environmental Literacy Standards

Ties to MD 

Environmental 

Literacy Standards

Standard 3 Flow of Matter and Energy

C. Interaction of Physical Systems and 

the Biosphere

Indicator 1. Analyze and explain the 

movement of matter and energy 

through earth’s systems and the 

influence of this movement on the 

distribution of life.

Students develop and test 

models of oyster reefs and

analyze models of oyster 

reefs to the ways individuals 

and groups of organisms 

interact with each other and 

their environment.

Additional Resources

Web Resources

Protecting Our Water Resources: Student Activities for the Classroom Water and educational 

activities for Kindergarten through Ninth Grade 

http://www.stormwater.ucf.edu/toolkit/vol3/Contents/pdfs/Student%20Activities/student_act

ivities.pdf

Olly the Oyster: Visit this website for coloring pages, puzzles, word searches, crafts, and more. 

http://www.ollytheoyster.com

Sammy’s Corner: An Oyster Recycling Program: The site contains teacher resources including a 

poster, curriculum guides, and additional oyster activities. 

http://oysterrecycling.org/sammys-corner/

YouTube Videos:

• Oyster Filtration: A one minute time-lapsed video of oyster filtration in action. 

https://www.youtube.com/watch?v=saAy7GfLq4w

• OYSTERFILTER: A one minute and 20 second time-lapsed video of six oysters filtering a 

gallon of water. https://www.youtube.com/watch?v=LOp3V_QpAyA

• Restoring Oyster Reefs in Chesapeake Bay: Sea Grant Documentary

https://www.youtube.com/watch?v=v4pKoDPdmzM

TeacherTube Videos:

• Oyster Filtering: Excerpt from The Chesapeake Bay Foundation's documentary

"Common Ground.” (42 seconds)

• http://www.teachertube.com/viewVideo.php?video_id=211324
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• Oyster Rap: An oyster restoration scientist raps about Eastern oysters in the Chesapeake 

Bay

• http://www.teachertube.com/viewVideo.php?video_id=93158

Book Resources

Allen, Elaine Ann. Olly the Oyster Cleans the Bay. Tidewater Publishers, May 1, 2008. ISBN-10: 

0870336037. 

Tate, Suzanne. Pearlie Oyster: A Tale of an Amazing Oyster. Nags Head Art, Inc., June 1, 1989. 

ISBN 10: 0961634472. 
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Student Information

The Eastern Oyster in the Chesapeake Bay

Two halves of a single Eastern Oyster.

What are Eastern oysters, Crassostrea virginica?

Eastern oysters are bivalve mollusks. That means they have two shells. 

You will see one shell on the left side and one shell on the right side 

when you open an Eastern oyster. 

Where do Eastern oysters live?

Eastern oysters live on the East Coast of North America from Canada to 

Venezuela.

Very young oysters float in water currents looking for a place to stick to 

and grow into adults. As they float, they grow a foot. They use the foot 

to find a hard surface to attach to. Then they make a cement-like glue 

to stick the foot to the hard surface. They cannot attach to mud and 

sand or to a place with too much sunlight. They need to be in flowing 

water where their food (phytoplankton) is. Other oyster shells are the 

best place for oyster larvae to attach. Once attached, the larvae are 
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called spat. Over time, the spat grow and make shells, and other oyster 

larvae attaches to them. As more and more oysters attach to older 

oysters, oyster reefs grow. 

Oyster spat attached to oyster shell (left), restored oyster beds. Photo: NOAA

What do Eastern oysters look like?

Adult Eastern oysters have a grey and white bumpy shell. They are 

shaped like giant kidney beans with one skinny end. They can grow to 

eight inches long. There were once oysters as big as dinner plates!

Those oysters had grown for many years because Native Americans 

could only harvest small numbers of oysters.

Why are Eastern oysters important to the Chesapeake Bay?

For thousands of years, people have eaten Eastern oysters, and Native 

Americans used oyster shells for jewelry and money in the past. 

Starting about 400 years ago, people also made money by harvesting 

and selling oysters.

Eastern oysters filter the water in the Bay. Oysters suck in water and 

filter out phytoplankton for food. They also filter sediment and 

pollution out of the water. Then they spit clean and clear water back 
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into the Chesapeake Bay. Without oysters, the water in the Bay would 

become cloudy and polluted; not a good place for other animals to live.

Oyster reefs also provide habitat to other animals such as small crabs 

and fish. The young animals live in the oyster reefs for protection from 

predators and for food.

What happened to the Eastern oysters?

For hundreds of years, Eastern oysters were known as the best tasting 

oysters in the United States. Oystermen harvested oysters faster than 

the oysters could reproduce. Oysters live close together in reefs, and 

their young like to stick to other oyster shells to grow. There were not 

enough oysters to reproduce or provide shells for oyster larvae to 

attach to, so fewer oyster reefs were made. People also used oyster 

habitat as places for building docks and houses.

Also, in the 1940s and 1950s, scientists found two diseases in Eastern 

oysters called MSX and Dermo. Both of these kill oysters and make it 

harder for more reefs to grow in the Chesapeake Bay.

What are people doing to help the 

Eastern oyster?

People are doing many things to help the 

Eastern oyster. Scientists are learning 

more and more about oysters and their 

habitat, and water currents in the 

Chesapeake Bay. They use this information to find the right places to

place piles of empty oyster shells to give oyster larvae sticking places. 

The new reefs are often built on old oyster shells from restaurants.
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People are also growing oysters from boat docks in bags that look like 

mesh socks and give the oysters to oyster restoration groups to put 

onto reefs when the young oysters are large enough. Businesses are 

growing oysters on floating rafts. They sell the oysters for food and use 

the shells to help new oysters grow.

What can you do to help the Eastern oyster?

Learning about the Eastern oyster is the first step toward helping more 

oysters grow in the Chesapeake Bay. You can share the story of the 

Eastern oyster and its importance to the Chesapeake Bay and to 

Maryland with others. You can also collect oyster shells from 

restaurants and take them to groups around the Chesapeake Bay who 

are working to restore oyster beds. If you live on the Bay, you can grow 

oysters from your dock in oyster socks and then take the sock to a 

group that will plant them on an oyster bed. And if you are boating in 

the Chesapeake, watch for oyster beds. Putting down your anchor on a 

bed can hurt the living oysters and destroy the bed. Anything you do to 

bring oysters back to the Chesapeake Bay benefits all Marylanders and 

Virginians.

Tiny oysters at a hatchery.
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Sample rubric for scoring student letters

Below Average Average Above Average Excellent

Conclusion from 

Activity Analysis 

(Yes or no, 

oysters benefit 

from living in 

reefs/groups.)

No conclusion Only writes a 

conclusion 

statement.

Writes and 

overview and a 

conclusion.

Clearly writes a 

brief overview of 

the activities 

AND states the 

conclusion they 

drew in response 

the problem.1

Main Concepts 

(Reefs help 

oysters get food, 

protects them 

from predators, 

and helps them 

adapt to 

changes.)

Does not cite any 

of the main 

concepts.

Includes one 

main concept.

Includes two 

main concepts.

Include all three 

main concepts to 

make argument 

for the 

conclusion.2

Concept 

Elaboration 

(Living in reef 

helps protect 

oysters from 

predators 

because...)

No elaboration 

or description.

Elaborates on 

one main 

concept or gives 

a general 

description.

Elaborates on 

two main 

concepts.

Elaborates on all 

three main 

concepts.3

Examples:

1 In my class we did three activities to help us understand if oysters are better living by 

themselves or living in reefs. My conclusion is that oysters should live in reefs to survive.

2-3Living in reefs helps oysters get food because living in a wide and tall group blocks more food 

and keeps it from floating past the oyster. In class, we built Lego reefs and the larger reefs 

blocked more Cheerios. Oysters are also protected from changes when they live in reefs 

because reefs are less likely to move. The larger the Lego reefs we built the less likely they 

were to move in the waves and be destroyed. A reef also helps oysters survive predators. The 

more oysters there are in a reef the less likely they are to be completely eaten.

* This rubric addresses the science concepts. You may wish to include other items for 

evaluation.
Name

Data Sheet 1

Color a square each time the free floating blocks 

hits the block structure.

It’s a Group Thing—Student Response Sheet 1

Block Number Color 1st Hit 2nd Hit 3rd Hit 4th Hit 5th Hit 6th Hit
Name

Data Sheet 2

Do your blocks move when waves hit them? Check yes or no.

It’s a Group Thing—Student Response Sheet 2

How many blocks are in your 

structure?

Yes No

3

How many blocks did you have to add to your structure for it to be stable in the water? 

Why?
Name

Data Sheet 3

Did your floating block hit the inside blocks? Check yes or no.

It’s a Group Thing—Student Response Sheet 3

Try Yes No

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Was it easy to hit the inside (protected) blocks? Why or why not?