SEAS
Student Experiments At Sea
Activity 1: Please Pass the Energy
Food Webs in the Upper Ocean and Hydrothermal Vent Communities
Overview
Students study the trophic ecology of two ocean communities. Students
are given cards of a typical ocean community of plants and animals. They
assemble a food web by selecting a food item and an animal that eats it. They
continue showing the food relationships between organisms until they have
used all organism cards. Students add arrows to show the flow of energy from
one organism to the next. It is important to include the sun in the diagram as
it provides energy to plants, and without it, plants could not survive. Student
groups share their food webs with the class and notice similarities and differences; there is no single correct answer. Next, students are challenged to create a food web for hydrothermal vent organisms. They use cards to examine
the relationships and build a food web. Students are challenged to understand
how the organisms survive without plants and sunlight at the base of their
food web. Students also learn that far less is currently known about this
ecosystem than other ecosystems, partly because it has only recently been discovered, and also because it's a challenging environment to visit and study.
Development of Lesson (Steps):
1. Tell the students they will be creating food webs for two different ocean
communities today. First ask if anyone can explain what a food web is.
Students typically talk about food chains and food webs in elementary science units. Their response will let you know how familiar they are with the
idea and how much time you need to spend emphasizing or reinforcing different concepts.
2. Hand out the cards showing the organisms from the surface of the ocean.
Explain to the students that you want them to arrange the organisms in order of
who eats whom. For example, large fish eat smaller fish. What do the smaller
fish eat? Large fish may also eat zooplankton. The cards list some of the organisms eaten by each animal. Students can use the scissors and tape to cut out the
pictures and assemble them on a separate sheet of paper. Encourage them to
draw pictures of other ocean animals they know to include in their food web.
3. Once the webs are finished, have a few of the groups share their food webs
with the class. Look for similarities and differences. Ask the students why
animals have to eat. The primary response should be to get energy. Then ask
how plants get energy. The response should be from the sun.
4. Have the students draw arrows to show the direction that energy flows in
the food web. They should start with the sun and draw an arrow from the sun
to each plant. Then draw arrows from each plant to each primary consumer,
from each primary consumer to each secondary consumer, etc. Remind students that plants are called primary producers because they produce their own
food (sugars) from sunlight, carbon dioxide and water in a process called photo-
Essential Concept /
Focus Question:
What is a food web?
How is energy transferred to
different organisms in the
HTV communities?
Learning Objectives
Students will be able to:
• draw a food web of a
typical ocean surface
community and of a
HTV community;
• show the flow of energy
through a food web.
National Standards:
• Unifying concepts and processes:
• Systems, order and organization
• Life Science
• Populations and ecosystems
• Diversity and adaptations
of organisms
Time Frame: 1 period
Materials:
• Copies for each student:
• “Ocean Surface
Organisms”
• Copies for each group
• “Vent Environment
Organisms”
• 11” x 14” white paper or
large piece of butcher
paper (optional)
• Tape (1 roll/table group)
• scissors (1 pair/student)
Cruise 4 - Activity 1 - Page 1
SEAS
Student Experiments At Sea
Activity 1 (cont.)
Resources
Extreme 2002
For excellent pictures and
background information
on vent organisms, visit
the Extreme 2002 website
and select Creature
Features.
http://www.ocean.udel.edu/
extreme2002/
Dive and Discover
The Infomod “Vent Biology”
has a good overview of
vent animals with excellent photographs. Go to
Expedition 4-7: Deeper
Discovery: Infomod Vent
Biology: click on “click
here to meet these amazing animals.” Click on
the words on the painting
to view information on the
animals. Excellent photos in each description can
be enlarged.
http://www.divediscover.whoi.
edu/
Cruise 4 - Activity 1 - Page 2
synthesis. Point out the pyramidal nature of the food web—the primary producers are the most numerous organisms and the top carnivores are the least numerous. Would this information help them predict the roles of various HTV organisms? How?
5. Now tell the students that their challenge is to assemble a food web for the
hydrothermal vent community they have been studying. They can do this in
their lab books or on a larger piece of white paper. Tell them they must include
arrows showing the flow of energy and try to label the different organisms as
primary producers or consumers. They can discuss their food webs in their lab
groups but each student should draw their own web.
Note: This part is more challenging as there are still many unknowns in this
environment. It is difficult to observe organisms eating when we are only able
to visit vent sites so infrequently. There are studies in progress looking at stomach or gut content analysis (to see who eats what) but even these are inconclusive as yet and need to be verified with direct observation and more analyses.
Understanding that we don't have a complete understanding of the vent ecosystem
food web is actually one of the points of this activity.
6. After they have finished their food webs, have a discussion in small groups or
with the class. Ask them to compare the two food webs. What are the similarities and differences? To help them with this, they can construct a T-chart
where they list similarities and differences. Then have them write answers to
the discussion questions below in their lab books.
Discussion Questions:
1. Describe 2 of the most important differences and similarities between the
ocean surface community food web and the ocean bottom hydrothermal
vent community food web.
2. What is the ultimate source of energy in the ocean surface community? ( Sun)
3. What do you think is the ultimate source of energy in the hydrothermal vent
community? (Chemical energy from the oxidation of vent fluids)
4. How could we learn more about the interrelationships of the hydrothermal
vent community? Be specific. You can design an experiment to answer this
question.
5. Are HTV communities entirely independent of surface photosynthetic production? (No, they need oxygen produced from surface photosynthesis.)
6. How would you go about figuring out HTV food webs for real? (gut analysis,
remote observation (e.g., with cameras), stable isotope analysis)
7. What additional questions do you have about the hydrothermal vent systems?
Cruise 4 - Activity 1- Surface Food web
ALGAE
Producer
Eaten by: Fish, sea urchins
HERBIVOROUS FISH
Eats: Algae, phytoplankton
Eaten by: Larger fish, sharks,
skates, squid, octopus, seal
ORCA WHALE
Eats: Large fish, seals, occasionally humpback whales
Top predator
CARNIVOROUS FISH
Eats: Smaller fish, squid, crabs
and zooplankton
Eaten by: Larger fish, sharks,
orcas, seals and squid
CLAM
Eats: Phytoplankton and zooplankton
Eaten by: Sea-stars, skates,
octopus and crabs
HUMPBACK WHALE
Eats: Zooplankton, small fish
Eaten by: Orcas and sharks
JELLY FISH
Eats: Small fish and zooplankton
Eaten by: Fish, octopus, and sea
turtles
PHYTOPLANKTON
Producer
Eaten by: Herbivorous fish,
clams, sea turtles, zooplankton
SEAL
Eats: Fish, squid, crabs and zooplankton
Eaten by: Orcas and sharks
Cruise 4 - Activity 1- Surface Food web
STAR FISH
Eats: Phytoplankton, zooplankton, algae and clams
Eaten by: Larger star fish
SKATE
Eats: Clams and small fish
Eaten by: Sharks
SUN
SEA TURTLE
Eats: Algae, phytoplankton,
crabs and jellyfish
Eaten by: Sharks and large fish
SHARK
Eats: Sea turtles, fish, humpback whales and seals
Top predator
SQUID
Eats: Zooplankton and small
fish
Eaten by: Seals and fish
ZOOPLANKTON
Eats: Algae, phytoplankton
Eaten by: Nearly all carnivores
OCTOPUS
Eats: Fish, crabs and clams
Eaten by: Larger fish and
sharks
CRABS
Eats: anything, clams
Eaten by: Sea turtle,
octopus, seals, fish
Cruise 4 - Activity 1- Hydrothermal Vent Food Web
ALVINELLA WORM
Eats: deposit feeds (processes
sediments through gut), mostly
on bacterial mats
Eaten by: unknown
BRACHYURAN CRABS
Eats: feeds on everything from
bacteria to tubeworms
Eaten by: unknown
FREE-LIVING BACTERIA
Eats: produces own food
Eaten by: just about everything
including limpets, snails, crabs,
squat lobster, serpulid worms
LIMPETS
Eats: grazes on bacteria, detritus,
and possibly larvae
Eaten by: unknown (but possibly crabs)
AMPHIPODS (small, shrimp-like
OCTOPUS
Eats: bivalves
Eaten by: unknown (considered
a non-resident)
organisms - "insects of the sea"):
Eats: scavenger/predator on
small things in water, but
specifics unknown
Eaten by: vent fish (zoarcid)
CLAMS
Eats: gets sugars produced by
symbiotic bacteria in gills
Eaten by: octopus and possibly others
MUSSELS
Eats: filter feeds on microbes in
water AND gets sugars from
symbiotic bacteria in gills
Eaten by: octopus and possibly
others
SQUAT LOBSTER
Eats: limpets, polychaetes (different worms), bacteria and dead
animals
Eaten by: unknown
Cruise 4 - Activity 1- Hydrothermal Vent Food Web
SERPULID WORM
Eats: filter feeds on microbes
in water
Eaten by: unknown
HYDROTHERMAL
VENT
TUBEWORMS
Eats: gets sugars produced by
symbiotic bacteria in trophosome
Eaten by: unknown but crabs
may be a “non-lethal predator”
ZORACID FISH
Eats: amphipods and limpets,
Eaten by: unknown