Alaska Sea Grant

Teacher Resources

Master Materials List

An Aquatic Eco-Mystery: The Case of the Missing Sea Otters

Student Handouts

Items for Group Display

Material Items

Facility/Equipment Requirements

Investigation 1

Sea Otter Story Part 1

Readings 1, 2, 3, and 4

Food Chain Cards Image

Science notebooks

Map of Aleutians

Sea Otter Data Graphs

Large Diagram of Beach Image

Food Chain Diagram Image

Butcher paper

Tagboard and felt-tip pens (if clue cards are used)

Art materials for making murals, if time permits

Internet access

LCD projector OR

Student computers and overhead projector

Investigation 2

Sea Otter Story Part 2.

Sampling the “e’s” Organism Data Sheet Image

Quadrat Data Sheet Image

Data Table Image

Newspaper(s) with 1 page per student

Quadrats (small), empty color slide frames OR similar cardboard squares, 1 per student

Calculators (optional)



Quadrats (large) made from meter sticks, hula hoops, or PVC pipes (optional)

For alternate activity if playground space not available:

Large photos or posters showing animal populations on beach or elsewhere, 1 per student group

LCD or overhead projector

Internet access

Playground or other outdoor area divided into two sections

Investigation 3

Sea Otter Story Part 3


Pictures of Kelp Forest (photo 1, photo 2)

Graph of Otter Populations Image

Pictures of Urchin Barrens  (photo 1, photo 2)

Food Chain Diagrams Image (diagram 1, diagram 2)

1 “Ziploc” bag per student

Masking tape

Sashes or signs: green, blue, red (1 per student)


LCD or overhead projector

Large indoor or outdoor playing area

Investigation 4

Field Etiquette Handout


Bag or box

Grab bag items: boot, hat, piece of litter, shell, rock, toy shovel, plastic toy crab or substitute

How to Make a Quadrat

Quadrat Data Sheet


Measuring tape

Hand lenses

Aquatic field site—beach, riverbank, or pond

Culminating Activities for the Aquatic Eco-Mystery Unit

Statewide Data Sharing

Share the investigation of your local ecosystem with students statewide via the Alaska Seas and Watersheds Website Forum. Take a picture of something important at your field site and post it, along with a description. Be sure to include the time and date that it was taken and the weather that day.

You can also share the data and conclusions from your ecosystem investigation at the site, and post questions that your class has generated.

Investigate the Web site to see the ecosystem discoveries that students have made in other parts of the state. How are their ecosystems different from yours?

A School-Wide Celebration of our Aquatic Ecosystem

Present your learning to other students in the school and to the community by organizing a school-wide celebration. Include a scientific poster session that teaches people about the sea otter’s ecosystem and about your local ecosystem. Make a mural, make costumes, have an art show, put on a dramatic production, have a feast, sing songs about the aquatic environment. Use your imagination to help your whole school learn and celebrate.

Making a Quadrat

A quadrat is a frame used by marine biologists to perform counts of the density of organisms or the percentage of cover in a standard area. You may use quadrats made with 4 meter sticks for an area of one square meter, or you may use quadrats that are smaller. Hula hoops also work as quadrats if you have access to those. A scientist always knows the area of his or her quadrat, since it is used for sampling and making estimates of what will be found in a bigger area.

To make a ¼ square meter quadrat, use pvc tubing and elbow joints. Cut tubing so that the inside dimensions of your square measure 25 cm x 25 cm. You will need one quadrat for each group of sampling students.

Field Etiquette Activity

This activity will help students to learn and review proper field etiquette. Students will be properly prepared for both the field trip experience and the ways in which their presence and activities in the field could impact the habitat they are trying to study.

You Will Need:

What to Do:


Prepare students for their field trip by discussing possible impacts their presence at the beach might have and ways in which they can help to minimize the impact and prepare themselves for a successful trip.


Have students come up, one at a time, and pull an item out of the grab bag. Ask the student to try to think of a way that their item symbolizes a field etiquette "rule" that should be followed or action they should take at the field site.

Once all of the items have been pulled from the bag, distribute the Field Etiquette Handout and discuss any other items that are useful to your group

Field Etiquette Grab Bag Contents


Walk single file over areas of attached plants and animals. Walk, don’t run and watch your step!


Dress warmly!

Snail Shell:

If you find an animal tightly attached, leave it attached! Don't collect shells and other “stuff" because they can be a home to other animals.


Don't litter, in fact—let's pick up trash!

Plastic Toy Crab:

Hold animals close to the ground—they may be slippery, slimy, or quick. Use small tubs and buckets if possible to view animals. Cup hands and keep them moist with a little bit of water if you are holding animals.

Toy Shovel:

Fill in holes! Small animals left underneath a big pile of mud and sand can be killed and someone could fall in the hole and get hurt.

Rock: (covered with barnacles on one side if relevant)

Return rocks to original position. Turn rocks over gently. Don't turn over really large rocks or you might crush the animals that live below!

Teacher Background for Investigation 3


Type of Data or Observation
(Intertidal Zone)

Rat Islands

Near Islands

Sea Otter Presence/Absence

Abundant (10-30/km2 of habitat)

Scarce or absent

Kelp Presence/Absence

Complete mat of kelp

Kelp sparse or absent

Average Intensity of Grazing

<1% of kelp plots grazed

50-75% of kelp plots grazed

Average Urchin Density (per m2.)



Urchin Size (Length in Inches)

<12 mm

Maximum of 21 mm

(Adapted from Estes and Palmisano. 1974.)


1. The differences between the two benthic (bottom) communities on the Near and Rat islands are probably related to the presence or absence of sea otters.

2. The otters control the sea urchin populations, and the absence of grazing pressure allows the kelp beds to flourish.

3. Reducing the population of sea otters makes it possible for sea urchin populations to increase, and this leads to a significant reduction in the size of kelp beds and associated animals.


James Estes and his colleagues did repeat the study in 1986-87 (when otters had reached the Near Islands and were thought to be at maximum density), and during the 1997-2000 period. In the ten-year period between 1987 and 1997, they found that sea urchin size and density increased to produce 8 times the amount of biomass, while kelp density decreased to one-twelfth. The percentage of kelp grazed increased from 1.1% per day in 1991 to 47.5% in 1997—all indicative of an “urchin barrens” in the absence of a high density of otters.

The data they collected at Amchitka in 1997 were similar to those for Adak (high urchin numbers, small urchin size, sparse kelp beds, high grazing rates on kelp).

Sample Data Table:

1990s Observations

Type of Data or Observation
(Intertidal Zone)

Rat Islands

Near Islands

Sea Otters



(Teacher fills in)


(Teacher fills in)



(Student Prediction)

"little" or "not much"

(Student Prediction)

"little" or "not much"


(Student Prediction)

"lots" or "many"

(Student Prediction)

"lots" or "many"


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