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9 Modeling Energy Flow in Ecosystems

yo u h av e b e e n i n v e s t i g at i n g h ow obtaining energy is essential
for all organisms, whether that energy is derived from sunlight, chemicals
in the ocean, or glucose in the bodies of other organisms. Studying how
this energy flows within an ecosystem is another way for scientists to
understand how that ecosystem is structured. Similar to using models to
study food webs, scientists often use models to study energy flow in
ecosystems. This helps them make predictions about how a disruption to
any one component might affect the rest of the ecosystem. In this activity,
you will evaluate different representations of energy flow in an ecosystem.
You will then use evidence from your evaluation to support a claim about
which system model best represents how energy flows among the biotic
components of an ecosystem.

FIGURE 9.1: A seal eats salmon, which contains substances that can be broken
down into the glucose it needs to release energy through cellular respiration.

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ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

Guiding Question

How do scientists model the flow of energy among the biotic
components of an ecosystem?

Procedure

1. Based on what you know so far, which of the models in Figure 9.2 do
you think is best for representing the flow of energy among the biotic
components in an ecosystem? Record your choice and your reasoning
in your science notebook.

A. phytoplankton B.

orcas orcas
salmon
salmon herring D. herring
phytoplankton
C. orcas
salmon orcas
herring salmon
phytoplankton herring

phytoplankton

FIGURE 9.2: Four possible models of energy flow in an ecosystem

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Figure: Eco3e SB 9_2
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MODELING ENERGY FLOW IN ECOSYSTEMS ACTIVITY 9

2. With your group of four students, discuss which model you chose and
why. Be prepared to share your ideas with the class.

3. Read the following passage about a relevant scientific finding.

Scientific Finding 1

To better understand how energy flows in an ecosystem, ecologists
organize the species in the ecosystem by how they obtain the energy they
need for life functions. Scientists classify the species into trophic levels,
positions in a food web that are determined by the number of energy
transfers from primary producers to that level.

Trophic level 4 Tertiary consumers obtain energy by feeding on the
Trophic level 3 primary and secondary consumers.
Trophic level 2 Secondary consumers obtain energy by feeding on
Trophic level 1 the primary consumers.
Primary consumers obtain energy by feeding on the
primary producers.
Primary producers obtain energy by conducting
photosynthesis or chemosynthesis to convert matter
into glucose.

4. In 1957, ecologist Howard T. Odum gar

published his results from a detailed cat sh
investigation of a freshwater aquatic
ecosystem located in Silver Springs, insect snail
Florida. Review the food web from
this ecosystem in Figure 9.3. Work plant
with your partner to categorize the FIGURE 9.3: A Silver Springs, Florida, food web
organisms in this web into trophic
levels, using what you learned from
Scientific Finding 1. Write your
answers in your science notebook.
5. How is energy transferred from one
trophic level to the next in the Silver
Springs, Florida, food web? Discuss
your ideas with your partner, and
write your answer in your science
notebook.
6. Read the following passage about
another relevant scientific finding.

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ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

Scientific Finding 2
• Energy is transferred when it moves from one place to another.

Energy is transformed when it changes from one type of energy to
another.

• Energy can be transferred or transformed, but it cannot be lost,

destroyed, or gained.

• During cellular respiration, the cells of plants and animals

transform energy.
– Some of the energy is used by organisms to conduct life functions,

such as moving or excreting waste products.
– Some of the energy is used to build tissues that are stored in the

body of the organism (including fat, muscle, and cellulose).
– The remainder of the energy is transformed into thermal energy,

which is transferred from the organism’s body to the surrounding
abiotic environment.

• Plants cannot reuse or recycle the thermal energy from cellular

respiration that is transferred from organisms to their surrounding
abiotic environment. They can only use light energy during
photosynthesis.

• Animals in higher trophic levels cannot reuse or recycle the thermal

energy from cellular respiration that is transferred from the
organism’s body to their surrounding abiotic environment.

• Gross productivity is the total amount of energy captured by a

trophic level. Net productivity is the amount of energy that is
available to the next trophic level.
7. Review your choice of model from Procedure Step 1. Discuss the
following questions with your partner:
a. Was your initial choice supported by Scientific Findings 1 and 2?
Why or why not?
b. Do you need to revise your initial choice based on these scientific
findings? If so, revise your answer and explanation from Procedure
Step 1.
c. What additional information would help you be more confident in
your choice?
8. Read the following passage about another relevant scientific finding.

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MODELING ENERGY FLOW IN ECOSYSTEMS ACTIVITY 9

Scientific Finding 3

Odum’s paper was revolutionary to the field of ecology, as it was the first
detailed data collection and analysis of a natural ecosystem. Odum used
his results to construct an explanation of how energy flows among the
biotic components in this ecosystem. Figure 9.4 presents Odum’s data for
net production (in units of energy per meter squared per year) in each
trophic level.

Energy (kcal/m2/yr)

Silver Springs, Florida

21

383

3,368

20,810 FIGURE 9.4: Energy flow in the
Silver Springs, Florida, ecosystem

Tertiary consumer Secondary consumer
Primary consumer Primary producer

9. With your partner, discuss any patterns you see in this diagram. Why
do you think these patterns exist? Explain your ideas in your science
notLeabboAoidks.SEPUP SGI Ecology 3e

10. TheMFipgyeurirraecd:ePEnrcotoaR3geeegSoB9f.05e9/n1_1e0r4gy transferred from organisms in one trophic
level to a higher trophic level in an ecosystem is called ecological
efficiency. To understand the ecological efficiency of this ecosystem,
complete the following calculations:

a. What percentage of energy is transferred upward from trophic
level 1 to trophic level 2?

Hint: Divide the kcal/m2/yr number for trophic level 2 by the
kcal/m2/yr number for trophic level 1 and then multiply by 100.

b. What percentage of energy is transferred upward from trophic
level 2 to trophic level 3?
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Maps1 Maps2 Maps3 Maps4 Maps5

Hint: Divide the kcal/m2/yr number for trophic level 3 by the
kcal/m /yr number for trophic level 2 and then multiply by 100.2
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c. What percentage of energy is transferred upward from trophic
level 3 to trophic level 4?
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Hint: Divide the kcal/m2/yr number for trophic level 4 by the
kcal/m2/yr number for Trophic Level 3 and then multiply by 100.

11. Read the following passage about another relevant scientific finding.

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ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

Scientific Finding 4

In nature, ecological efficiency between trophic levels can range from
about 5% to 20%, as you observed in your earlier calculations. Many
abiotic factors can influence the net production for producers in terrestrial
and aquatic ecosystems, such as temperature, moisture, and the availability
of nutrients. Net production for consumers is also influenced by a variety
of abiotic and biotic factors.
Ecosystem ecologists agree that, in general, it is acceptable to use 10% to
estimate ecological efficiency between trophic levels in an ecosystem. This
means that when energy is transferred upward in a food web or food chain,
approximately 10% of the chemical energy stored at the lower level will
transfer to the higher level. This estimate assumes that 10% of the chemical
energy transferred upward to an organism at the higher trophic level will
be stored within the body of the organism, while the remaining 90% of the
energy will be transformed into thermal energy as the organism conducts
cellular respiration.
12. Use evidence from all four scientific findings and your own reasoning

to answer this question: Why can’t ecological efficiency in an
ecosystem be 100%? Record your explanation in your science
notebook.
13. Revisit the choice of model you made in Procedure Steps 1 and 7.
Discuss with your partner the following questions:
a. Are your previous ideas about the models supported by Scientific

Findings 3 and 4? Why or why not?
b. Do you need to revise or add to your ideas about the best model to

represent energy flow among the biotic components of an
ecosystem, based on Scientific Findings 3 and 4?
Work with your partner to reevaluate your choice and to choose a
model that you both agree best represents the flow of energy among
the biotic components in an ecosystem. Revise your answer and
explanation from Procedure Steps 1 and 7 accordingly.
14. With your group, come to a consensus about which model in
Procedure Step 1 best represents the flow of energy among the biotic
components in an ecosystem. Use evidence from each of the four
scientific findings, and support your group’s ideas with reasoning. Be
ready to share your ideas with the class.

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MODELING ENERGY FLOW IN ECOSYSTEMS ACTIVITY 9

Build Understanding

1. Use the model you selected as the best representation of the flow of
energy among the biotic components in an ecosystem to answer the
following questions:
a. What does this model show well?
b. What is missing from this model?
c. How would you improve this model? Explain your ideas by creating
a new model that shows the revisions you would make to the model
you selected in Step 14. Be sure that this new model shows the
transfer of energy in an ecosystem, using the 10% estimate for
ecological efficiency.

2. Develop an argument for why the model you chose is the best
representation of how energy flows among the biotic components of
an ecosystem. Be sure to address why the other models are not the best
representation.

3. The majority of natural ecosystems studied by ecologists have four or
five trophic levels. Why do you think that is? Explain your ideas.

4. Issue connection: Use the data presented about the Southern Resident
orcas and the Chinook salmon in Puget Sound in Figure 9.5 to answer
these questions:
a. What patterns do you notice in the graph?
b. What do these patterns tell you about the relationship between
these organisms?
c. How could changes in the availability of salmon affect the
Southern Resident orca population? Based on what you learned
in this activity, create a model that shows the flow of energy
among the biotic components of the Southern Resident orcas’
food web. Use the model to explain how disruptions related to
increases or decreases in the abundance of salmon could have an
effect on the Southern Resident orcas.

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ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

FIGURE 9.5: Chinook salmon population trends (red line) and Southern Resident orca deaths (blue bars)

8,000,000 0
Number of Chinook
J, K, and L Pod Deaths7,000,000–4

6,000,000 –8

5,000,000

4,000,000

3,000,000

2,000,000

1,000,000

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1976 1980 1985 1990 1995 2000 2005 2010 2015 2020

Year

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The Southern Resident orca population continues to be monitored and
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Chinook Salmon Abundance and Southern Resident Orca Deaths

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10 Crossing Ecosystem Boundaries

yo u ’ v e i n v e s t i g at e d h o w t h e c h i n o o k salmon are an

important part of ocean ecosystems, particularly the ecosystem of the
Southern Resident orcas. The salmon play a key role in the cycling of
matter and the flow of energy in this ecosystem. They also play an
important part in another ecosystem. Chinook salmon have an interesting
feature: They are anadromous. This means that they begin their lives in
freshwater river habitats, then migrate to the open ocean for most of their
lives. As adults, they return to the rivers they were born in to reproduce
and, eventually, die. Figure 10.1 shows the life cycle of the Chinook salmon.

Chinook salmon die in the Salmon eggs are fertilized in
freshwater river. a freshwater river during the
Chinook salmon reproduce. fall. The following spring, the
Chinook salmon migrate
tiny sh, called fry, hatch.
back to the freshwater river
they were born in Chinook salmon fry stay in
to reproduce. the freshwater river for
Chinook salmon arrive at the about 5 months. Their
ocean, where they will survival depends on the
spend up to 8 years.
quality of the river habitat.

The Chinook salmon migrate FIGURE 10.1: Life cycle
toward the sea and smolting of Chinook salmon

begins. The process of
smolting involves the sh
going through physical
changes in order to survive

in salt water.

TmhuLFiiaslgtbiuaApnreildae: sdEecSrcoEoo3PmseUyoPSsuBtSesG1m0lIi_Esf0ecao1ctloydgcilyfef3emereenatnpsotihnatts the salmon cross the boundaries of
in their lives. What does this mean
forMtyhrieadroPrleo tRheegy9.p5l/a1y1 in the cycling of matter and the flow of energy in
these ecosystems?

Guiding Question

What happens to the flow of energy when an organism
crosses ecosystem boundaries?

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ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

Materials

FOR EACH GROUP OF FOUR STUDENTS

2 pieces of chart paper
set of markers
sticky notes in four colors

FOR EACH STUDENT

completed Student Sheet 6.1 “Orca Ecosystem Model,” from Activity 6

Procedure

Part A: Chinook Salmon Life Cycle

1. Read the following information about Chinook salmon. As you read,
use the Read, Think, and Take Note strategy:

• Stop at least three times during the reading to mark on a sticky note

your thoughts and questions. Use the guidelines below to start your
thinking.

Read, Think, and Take Note: Guidelines

As you read, use a sticky note from time to time to:

• Explain a thought or reaction to something you read
• Note something in the reading that is confusing or unfamiliar
• L ist a word from the reading that you do not know
• Describe a connection to something you’ve learned or read

previously

• Make a statement about the reading
• Pose a question about the reading
• Draw a diagram or picture of an idea or connection

• After writing a thought or question on a sticky note, place it next to

the word, phrase, sentence, diagram, drawing, or paragraph in the
reading that prompted your note.

• After reading, discuss with your partner the thoughts and questions

you had while reading.

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CROSSING ECOSYSTEM BOUNDARIES ACTIVITY 10

Chinook Salmon Life Cycle

Chinook salmon begin their lives in a river. salmon carcass that the bear leaves behind.
When they are old enough, they leave the river Similar to the bear, these organisms use the
and swim to the open ocean. After several years matter obtained from eating the salmon to
at sea, adult Chinook salmon leave the ocean release energy and maintain their bodies.
and go back to a river—usually the same river—
to reproduce. Their journey involves swimming The salmon that survive to reproduce in the
hundreds of miles against the river current to river die of natural causes shortly after
their spawning (breeding) grounds, where they reproducing. Decomposers, such as bacteria
will reproduce. They do not eat as they swim and fungi, break down what remains of the
upriver; they rely on the stored matter and salmon carcass along the river or in the
energy in their bodies to complete their journey. FIGURE 10.2: A bear feeding on salmon
Along the way, the salmon may be eaten by a FIGURE 10.3: Salmon spawning in a stream
predator, such as a bear, or they may survive
until they arrive, where they will lay (females)
or fertilize (males) eggs.

During the time of the salmon spawn, bears
will eat up to 40 salmon per day. As the salmon
return to the river, the bears can catch them
easily by wading in the river and fishing them
out as they swim by. Bears also eat other food,
such as small mammals and berries, but they
have to expend a lot more energy to find and
catch these food sources. They also have to eat
more of these food resources (as compared to
the salmon) to obtain the matter and energy
they need for survival.

The brown bear doesn’t eat the entire salmon;
instead, it eats the fattiest parts of the fish, such
as the brain, and leaves the remainder of the
uneaten salmon carcass along the river or in the
forest. In the summer and fall, bears need to
gain three to six pounds of fat per day to
prepare for their upcoming winter hibernation,
so the fatty salmon are an important part of the
bears’ diet during this time. The bear’s body
uses some of the matter it obtains from eating
the salmon to release energy and maintain its
body, but mostly the matter and energy it
obtains from the fish will be stored for the long
winter season ahead.

Other organisms, such as birds and small
mammals, eat the remaining parts of the

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ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

nearby forest. The decomposers nitrogen available to producers in
use the matter from the salmon the forest soil increases the growth
to release energy and maintain rate of the plants. Larger producers
their bodies. can conduct more photosynthesis
and cellular respiration, making
Nitrogen from the salmon these forests more productive. In
carcass cannot be used directly by one study, a chemical analysis of
consumers and decomposers. trees near streams with salmon
Instead, it is released as waste into spawning determined that up to
the environment. The nitrogen is 24% of the nitrogen in these trees
then integrated into the forest soil comes from the bodies of the
and taken up by producers salmon. The growth rate for these
through their root structures. Plant trees was about three times faster
cells use nitrogen to build amino than trees near streams without
acids and cell structures, such as salmon spawning.
chlorophyll. An increase in the

FIGURE 10.4: Dead salmon decaying in the stream

2. Discuss the following questions in your group. Record your ideas in
your science notebook, citing specific evidence from the text, and be
prepared to share them with the class.

Hint: Be sure to think about decomposition.
a. What effect do the returning Chinook salmon have on how matter
cycles in the river ecosystem?
b. What effect do the returning Chinook salmon have on how energy
flows in the river ecosystem?

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CROSSING ECOSYSTEM BOUNDARIES ACTIVITY 10

Part B: Modeling Ecosystem Boundary Crossing

3. Work with your group to create a model of the feeding relationships in
the salmon ecosystem.
a. Discuss how you could modify the boundaries of the model you
developed on Student Sheet 6.1, “Orca Ecosystem Model,” to
include the role that Chinook salmon play in the river ecosystem.
Work together to create a new model, using what you learned from
the Chinook salmon case study.
b. Discuss how you could create a model of the energy flow
between trophic levels in the river ecosystem with the Chinook
salmon. Create an energy model for the river ecosystem on a
new piece of chart paper, using what you learned in the Chinook
salmon case study.

4. Join another group and present your models to each other. Discuss the
similarities and differences between your models with the other group
members. Return to your group and revise your model, based on your
discussion.

5. Read about four ecosystem disruptions, and discuss the following
questions with your group. Record your responses in your science
notebook.
a. What impact could each disruption have on how matter cycles in
the river ecosystem? Explain.
b. What impact could each disruption have on how energy flows in
the river ecosystem? Explain.

Disruption 1 river. The salmon population that returns to
swim upstream is smaller than usual.
A conservation group worked with local
organizations to complete a habitat Disruption 3
restoration project on the river and the
estuary—a body of water where fresh water The salmon fishing industry harvests 20%
from rivers and streams mixes with salt water more salmon biomass one year than they have
from the ocean. This project widened the in the past. This results in less salmon biomass
opening between the river and the ocean, being deposited in the stream after spawning.
allowing the salmon to enter and leave the
river more easily. The salmon population that Disruption 4
returns to swim upstream is larger than usual.
Thousands of Atlantic salmon escape from a
Disruption 2 fish farm pen off the coast of Washington and
invaded the ecosystem. These Atlantic salmon
A toxic spill in the ocean where the salmon live outcompete Chinook salmon, leading to
kills many salmon before they can return to the smaller and fewer Chinook returning to spawn.

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ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

6. With your group, make additions to your model with sticky notes,
using a different color for each disruption. Prepare to share your ideas
with the class.

Build Understanding

1. Energy cannot be created or destroyed—it only moves between
systems. Explain how the Chinook salmon is an example of this
concept, using evidence from this activity.

2. What effect does increased nitrogen in the soil have on how matter
cycles and energy flows in the river ecosystem? Explain your ideas.

3. One year in Alaska, the salmon did not return to their river to spawn.
The bears had to rely on consuming organisms available within the
boundary of the river ecosystem, including plants and small mammals.
Small mammals in this ecosystem also eat plants. What impact do you
think this event had on the bear population in this ecosystem?
Develop a food web and an energy model for this scenario, similar to
those you created in Procedure Steps 3 and 4. Be sure to include
quantities or proportions of energy in your model. Use the
information from these models to explain your claim.

4. Consider the two system models you used in this activity.
a. What are the strengths of each model?
b. What are the limitations of each model?

5. Issue connection: As you’ve investigated the Southern Resident orca
food web, you’ve learned about the vital role the Chinook salmon play in
the survival of the orcas. Many Chinook salmon populations in the
Pacific Northwest are identified as threatened or endangered species,
which means that the fishery in this area needs to be carefully managed.
One aspect of managing the fishery is ensuring that the Chinook salmon
population is large and stable enough to meet the energy needs of the
Southern Resident orcas. What other aspects of fisheries management
must be considered for the Chinook? Include evidence from this activity
in your explanation.

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CROSSING ECOSYSTEM BOUNDARIES ACTIVITY 10

6. At the beginning of this learning sequence, you observed patterns in the
graph of the Southern Resident orca population, as seen in Figure 10.5.

a. If you were a scientist monitoring the orcas and their ecosystem,
what data would you want to collect? Explain your ideas.

b. If you wanted to build a simulation for this ecosystem similar to
what the scientists used to study the song sparrows in Activity 3:
Factors Affecting Population Size, how would you do it? Explain
the biotic, abiotic, and intrinsic factors that would be part of your
simulation.

c. What additional questions do you have about the Southern
Resident orcas and their ecosystem?

Population count (number of whales)FIGURE 10.5: Southern Resident orca population, J, K, and L pod census as of July 1 JKL Population (CWR)
each year (Center for Whale Research) L Population (CWR)
J Population (CWR)
110 K Population (CWR)
100

90
80
70
60
50
40
30
20
10

0
1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 2025
Year

KEY SCIENTIFIC TERMS

energy
matter
system model
trophic level
LabAids SEPUP SGI Ecology 3e
Figure: Eco3e SB 06_02
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Source: Center for Whale Research Orcas Survey July 1, 2018 + 2018/2019 Population updates
CWR is the Center for Whale Research

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11 Ecosystems and the Carbon Cycle

Investigative PhenomenonCarbon dioxide level (parts per million)

In the last learning sequence, you explored the cycling of matter within and
between ecosystems. In this sequence, you will look at one type of
matter—carbon—on a much larger scale: the entire earth. This requires you
to expand your thinking beyond ecosystem boundaries to include other
Earth systems. Look at Figure 11.1, a graph of carbon dioxide levels found in
the atmosphere from 800,000 years ago until 100 years ago. What do you
notice? What questions do you have about this data?

460
440
420
400
380
360
340
320
300
280
260
240
220
200
180
160

800k 700k 600k 500k 400k 300k 200k 100k

Years before today

FIGURE 11.1: This graph shows carbon dioxide levels in Earth’s atmosphere from 800,000 years ago
to 100 years ago.

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LabAids SEPUP SGI Ecology 3e

➔ ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY➔

You have also learned how carbon cycles within an ecosystem through
the cellular processes of photosynthesis and cellular respiration. This
cycle is relatively fast. If we followed a carbon atom through an
ecosystem, it could complete this cycle in as fast as a few minutes or as
slow as several hundred years. A carbon atom (C) in a glucose molecule
(C6H12O6) in an organism’s body combines with oxygen during cellular
respiration to produce a carbon-containing waste product—carbon
dioxide (CO2). This molecule is released into the atmosphere, where it
can be taken up by a producer. When this happens, the carbon atom in
the carbon dioxide molecule reacts with water during photosynthesis to
form glucose. No new carbon atoms are created or destroyed; rather, they
are rearranged during chemical reactions to become part of new
molecules. The cycle looks like this:

CO2 + H2O + energy = C6H12O6 + O2


C6H12O6 + O2 = CO2 + H2O + energy

FIGURE 11.2: Photosynthesis and cellular respiration are one part of Earth’s
carbon cycle.

In this activity, you will learn about how carbon cycles into and out of the
atmosphere on two scales: at the ecosystem level and at the global level. The
carbon cycle is a global cycle in which carbon is exchanged throughout
Earth’s systems by various processes. In order to understand the carbon
cycle on a global level, and the role that ecosystems play in it, we need to
expand the boundary of the system to include the entirety of Earth’s
systems. In this learning sequence, you will develop and use a model that
shows how carbon is cycled globally as a result of interactions between the
atmosphere and Earth’s biosphere, hydrosphere, and lithosphere. You will
use this model to explain the role of ecosystems in the global carbon cycle.

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ECOSYSTEMS AND THE CARBON CYCLE ACTIVITY 11

Guiding Question

What role do ecosystems play in the global carbon cycle?

Materials

FOR EACH PAIR OF STUDENTS

set of Carbon Cycle Interactions cards

FOR EACH STUDENT

Student Sheet 11.1, “Carbon Cycle Model”

Procedure

1. Earth is a complex system made up of interacting subsystems. Energy
flows and matter cycles within and among these subsystems. With
your partner, review the definitions of Earth’s four subsystems in the
following text box.

Earth’s Subsystems

Atmosphere: The set of layers of gases surrounding Earth.
Biosphere: All of Earth’s ecosystems combined.
Hydrosphere: Earth’s oceans, rivers, lakes, groundwater, and water
frozen in glaciers.
Lithosphere: The part of the earth consisting of the crust and outer
mantle, including rocks, minerals, and abiotic parts of soils.

2. With your partner, rank these four subsystems according to which you
think contains the most carbon and which contains the least. Record
your ranking and the reasoning for it in your science notebook. Be
prepared to share your ideas with the class.

3. Your teacher will display for the class the actual amount of carbon
stored in each subsystem. Record this information on Student Sheet
11.1, “Carbon Cycle Model.” Discuss with your partner how your
predicted ranking compares to the actual ranking. Be prepared to
share your ideas with the class.

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ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

4. Use Student Sheet 11.1 to develop a system model that shows how
carbon cycles into and out of the atmosphere as a result of interactions
between Earth’s subsystems. Begin by discussing the following
questions with your partner:

• What cellular processes cycle carbon within the biosphere?
• Where does the carbon that cycles during these cellular processes

come from?

• Where does the carbon that cycles during these cellular processes go?

5. Based on your discussion, add arrows and labels to your model to
represent the cellular processes that cycle carbon between Earth’s
subsystems and the atmosphere.
a. Use the direction of the arrow to indicate if the cellular process
results in carbon added to or removed from the atmosphere.
b. Label each arrow to indicate the cellular process it represents.

6. With your partner, brainstorm other ways that interactions between
any of Earth’s subsystems could result in the cycling of carbon into and
out of the atmosphere. Record your ideas in your science notebook,
and be prepared to share them with the class.

7. Obtain a set of Carbon Cycle Interactions cards. The cards describe the
major ways that Earth’s subsystems interact and move carbon
throughout Earth’s systems. With your partner, review the information
on the cards.

8. Select the cards that relate to the cellular processes you added to your
carbon cycle model in Step 5. For each card, identify if carbon is being
added to or removed from the atmosphere:
a. Draw arrows to show how carbon is moving between Earth’s
subsystems for each of these interactions.
b. Indicate how much carbon is moving in each interaction.

9. Repeat Step 8 for the remaining cards.
10. Compare your carbon cycle model with the model created by the other

pair in your group. Discuss the similarities and differences between
your models. Make any revisions to your model that you think might
be needed, based on your group’s discussion.
11. In your group, use your carbon cycle models to help you answer the
following questions:

• What processes add carbon to the atmosphere?
• What processes remove carbon from the atmosphere?

A-78

ECOSYSTEMS AND THE CARBON CYCLE ACTIVITY 11

• How does the amount of carbon added to the atmosphere during

Earth’s subsystem interactions compare to the amount of carbon
removed from the atmosphere during these interactions?
Take notes about your group’s responses to these questions in your
science notebook, and be prepared to share your ideas with the class.
12. Work with your partner to use your model and your responses from
Step 11 to construct an explanation for how carbon is cycled into and
out of the atmosphere as a result of Earth’s subsystem interactions.
Write your explanation in your science notebook.

Build Understanding

1. Referring to your carbon cycle model, compare and contrast the sphere
or spheres that store the most carbon with the sphere or spheres that
have the most flux (that is, the most carbon flowing in or flowing out).

2. How did using a system model help you understand the global carbon
cycle and the role of cellular respiration and photosynthesis in that
cycle?

3. Develop an explanation for the pattern of atmospheric carbon dioxide
in the graph in the introduction. Your explanation should include:
a. the cycling of carbon dioxide
b. the upper limit of 300 parts per million (ppm) and the lower limit
of 180 ppm

4. Earth formed approximately 4.6 billion years ago, but photosynthetic
organisms didn’t begin to appear until 3.4 billion years ago. What do
you think atmospheric carbon dioxide levels were like before
photosynthetic organisms evolved?

Hint: Think about the processes in your carbon cycle model that would
have been occurring before photosynthetic organisms evolved.

KEY SCIENTIFIC TERMS

atmosphere
biosphere
carbon cycle
hydrosphere
lithosphere

A-79



12 Rebalancing the Equation?

f i g u r e 12.1 s h ows t h e g r a p h you saw in Activity 11: Ecosystems
and the Carbon Cycle, but it now includes data for approximately the last
100 years. What do you notice about the data compared to the original
graph? What questions do you have about these differences?

Carbon dioxide level (parts per million) 460
440
420 0
400
380
360
340
320
300
280
260
240
220
200
180
160

800k 700k 600k 500k 400k 300k 200k 100k

Years before today

FIGURE 12.1: This graph shows carbon dioxide levels in Earth’s atmosphere from 800,000
years ago to today.

LabAids SEPUP SGI Ecology 3e
Figure: Eco3e SB 12_1b
MyriadPro Reg 9.5/11

A-81

Source: Luthi, D., et al.. 2008; Etheridge, D.M., et al. 2010; Vostok ice core data/J.R. Petit et al.; NOAA Mauna Loa CO2 record.

ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

Guiding Question

To what extent can ecosystems help to address increased
atmospheric carbon dioxide levels?

Materials

FOR EACH STUDENT

completed Student Sheet 11.1, “Carbon Cycle Model,” from Activity 11
red pen or colored pencil

Procedure

Part A: Modeling Human Activity and the Carbon Cycle

1. Read the following information about the carbon added to the atmosphere
as a result of human activity. With your partner, revise your carbon cycle
model from Activity 11 based on this additional information. Use a red
pen or colored pencil to add this information to your model to distinguish
the interactions that are due to human activity.

Carbon is added to the atmosphere when humans burn fossil
fuels (including petroleum, natural gas, and coal) found in
sedimentary rocks. This human activity started during the
Industrial Revolution, from the late 1700s to the early 1800s, and
has increased steadily as the human population has increased.
Currently, about 10 gigatons of carbon per year are added to the
atmosphere as a result of this interaction.
Carbon is added to the atmosphere when humans cause
deforestation and/or use land for agriculture. While these practices
have occurred for thousands of years, they increased significantly
starting at the beginning of the 20th century and continue today.
Currently, 2–4 gigatons of carbon per year are added to the
atmosphere as a result of this interaction.

2. With your partner, compare the amount of carbon added to the
atmosphere to the amount of carbon removed in your revised model.
What do you notice? Share your ideas with your partner.

A-82

REBALANCING THE EQUATION ACTIVITY 12

3. With the other pair in your group, discuss your ideas about the pattern
in atmospheric CO2 levels in the last 100 years, using your revised
models as evidence to support your explanations.

4. Use your revised model to revise your explanation for how carbon is
cycled into and out of the atmosphere from Activity 11 to include
processes that are the result of human activity. Write your explanation
in your science notebook.

Part B: Evaluating Ecosystems as Solutions

5. With your group, brainstorm how you might use ecosystems to reduce
atmospheric CO2 levels. Be sure to refer to your model for ideas, and
think about the various ecosystems you have investigated thus far.
Record your ideas in your science notebook, and be prepared to share
them with the class.

6. Follow your teacher’s instructions for sharing your ideas with the class.
Use the information from the class discussion to add to or revise your
ideas in your science notebook. Be sure to consider these questions:

• Do these design solutions seem effective and practical?
• What are some of the potential strengths and limitations of using

ecosystems to store carbon?

• What are some other possible solutions for reducing atmospheric

carbon dioxide?

• Given the amount and rate of increase of carbon dioxide in the last

100 years, do you think that ecosystem solutions are enough to
address the problem?
Hint: Look at the amounts of carbon flux in your model related to the
different processes.

Build Understanding

1. Use your revised carbon cycle model and the data from the graph in
the introduction to explain the patterns of fluctuation in atmospheric
CO2 levels from 800,000 years ago to the present day.

2. Reflection: What are some actions you can take as an individual to
help “rebalance the equation” and reduce your footprint in regard to
atmospheric carbon dioxide levels? What local, state, national, and/or
international policies and practices could help reduce atmospheric
carbon dioxide levels?

A-83

ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

Extension 1

In 2020, the increasing spread of the respiratory virus COVID-19 resulted
in shelter-in-place orders across the globe. People were required to stay at
home and only allowed to travel for the most essential reasons. What do
you predict happened to atmospheric carbon dioxide levels during that
time? Record your prediction. Visit the SEPUP SGI Third Edition page of
the SEPUP website at www.sepuplhs.org/high/sgi-third-edition for links
to data and information that you can compare to your prediction.

Extension 2: Engineering Connection

Increasingly, scientists are turning to climate engineering to try to
reverse the increasing carbon dioxide levels and their effects on Earth’s
systems. Also referred to as geoengineering, this field of science and
engineering focuses on using technology to find solutions to these
problems. Visit the SEPUP SGI Third Edition page of the SEPUP website
at www.sepuplhs.org/high/sgi-third-edition to learn more about this
growing field.

KEY SCIENTIFIC TERMS

atmosphere
biosphere
carbon cycle
hydrosphere
lithosphere

A-84

13 Ecosystems at the Tipping Point

Investigative Phenomenon

The World Conservation Union has created map? Do you see any patterns? What are
a system to identify healthy vs. unhealthy some things that can cause an ecosystem
ecosystems. The map in Figure 13.1 shows to become threatened? What would cause
some of the ecosystems they have an ecosystem to collapse entirely?
evaluated. What do you notice on this

EN CR VU CO
EN ENEN
EN
EN

CR EN CR
LC
LC

KEY: EN EN
EN VU
LC = Least Concern CRCR VUCLRCCREN CR
NT = Near Threatened
VU = Vulnerable LC
EN = Endangered
CR = Critically Endangered
CO = Collapsed

FIGURE 13.1: Map of ecosystem evaluation results

A-85

LabAids SEPUP IAPS Eco3e
Figure: Eco3e 13_1

ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

As you have learned throughout this unit, ecosystems are constantly
changing—sometimes gradually in ways that are hardly noticeable, and
sometimes rapidly and dramatically. You have also discovered that some
disruptions are “natural,” and others are caused by human activity. In this
activity, you will explore two ecosystems that have experienced major
disruptions, due to a combination of natural and anthropogenic (human-
caused) disruptions. You will consider what factors make an ecosystem
either resistant to these disruptions, resilient following a disruption, or
permanently changed. An ecosystem that is resistant is one that is stable
and can withstand a disturbance without experiencing much change. An
ecosystem that is resilient is one that returns to its original, stable state
after a disturbance.

Guiding Question

How do different factors influence how ecosystems respond
to disruptions?

Materials

FOR EACH STUDENT

Student Sheet 13.1, “Ecosystem Disruption Comparison”
Student Sheet 13.2, “Aral: The Lost Sea”

Procedure

Part A: Comparing Disruptions

1. In your group, have each pair choose one of the following ecosystems
to read about. With your partner, read about your chosen ecosystem,
and take notes on Student Sheet 13.1, “Ecosystem Disruption
Comparison.”

A-86

ECOSYSTEMS AT THE TIPPING POINT ACTIVITY 13

The Yellowstone Fires of 1988

The ecosystems of Yellowstone National Park FIGURE 13.2: Wapatis (elk) were traditionally
have been shaped by fire for over 14,000 hunted by Indigenous communities in the area
years. The number and size of the fires that that is now Yellowstone.
burn every year depend on factors such as caused by lightning strikes, but several were
rainfall, density of vegetation, and how long it anthropogenic. Clearly this was a major
has been since an area last burned. Many of disruption to the Yellowstone ecosystem.
the plant species in Yellowstone have evolved
to co-exist with fires. The lodgepole pine, In 2020, 32 years later, the Yellowstone
which makes up nearly 80% of Yellowstone’s ecosystem was rated by the World Heritage
forests, has thin bark and burns easily in fires, Outlook program as “Good, with Some
but the cones from this tree only open for the Concerns.” After the 1988 fires, Yellowstone
seeds inside to disperse under the heat of a started showing signs of recovery within
fire. Indigenous cultures practiced the use of months, and several decades later much of
what are now called controlled burns for the ecosystem is thriving. Fire can be a
millennia in the area that is now Yellowstone, disruptive, and destructive, force. However,
often to promote the growth of plants for fire can also stimulate growth. Soil receives
particular species that relied on them as food, nutrients from burned plant materials. When
such as wapitis (elk). forests burn, more light reaches the ground,
stimulating different types of plants to grow.
Yellowstone was established in 1872. For Occasional fire can prevent the buildup of
the first 100 years of the park’s existence, the woody debris, meaning that when fire does
management policy was to suppress any fires happen, it is less intense and less destructive.
that started, whether they were natural, such The fire management plan in Yellowstone
as from lightning strikes, or anthropogenic. now allows for more fires to burn, and there
This eventually led to a buildup of old trees is evidence that as more time passes this is
and brush, and in the summer of 1988 benefiting the ecosystem, as it did before the
Yellowstone had the largest series of fires in park was established.
the park’s history—close to 800,000 acres
burned that summer. Most of the fires were
FIGURE 13.3: Many areas that burned in the
1988 Yellowstone fires started to show signs of
recovery within months.

A-87

ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

The Collapse of the Aral Sea

The Aral Sea, an inland Kazakhstan L. Balkhash
saltwater lake in central Asia,
was once the fourth largest lake Aral
in the world. For thousands of Sea
years, nearby communities
relied on fish from the Aral Sea Caspian Uzbekistan Kyrgyzstan
Sea

as a food source. In the early Turkmenistan Tajikistan
1900s, commercial fisheries
provided local income. By the China

late 1950s, fisheries in the Aral Iran Afghanistan
Sea produced more than 48,000
tons of fish, about 13% of the Indus

Soviet Union’s total fish stocks. FIGURE 13.3: The Aral Sea is fed by two major rivers
The water in the lake comes from two major that flow through the neighboring countries of
rivers. Throughout history, those rivers have Kazakhstan and Uzbekistan.

been used to support nearby agriculture.
AcKenphrBfsluihfraooevarfIoravewftceznrojncehratoeertostgkebcudehoeothtetneotdnihlesthnodot1enpmtetagi9horndendiw6oacexgi,tanv0vatahlUmdeesilyated,nerrdkzmttteryltbeiihamgwdtewepkuehskdialeeanvaSahit,stsettaeioaeditnrttrilvvraihstsavftneiifrherhboieo,osontareonrahumtdUutn1aeogphtndg9adwhrte5r6,iohsoTnoi5ca0ijecuugneonstukttcnr.hudwblmtkhitan,efuomoiMFLtiw3tgscrtiarttpgmaheyeaahibonuernenetAoeriaesrrarityanejisrrdwdooy,:tiPsefbtarvEihrsanecuSoereorE.t.sR3PeeUgPSBaBtscgytt(m9Sohhttomee.yG1ho5aTleeaorl3/pIetonraoeg1ll_hE.paauyfpad1r0cAeetkeamnsoa4oeredep1stylfdoo1t,h9itcottag9nuh7yehhony8nace0cemecd0rnot3swhenAsepsoibeaa,aaytlfrcnyscettswaesoeiogtt2vladeersame0eSlmly,sdfty1elsafm.ldoia.t0densewiEsehridsimssrtacsdcstomotwcphitheollahvaoaceeanlsaetrcgndfsietdiaiicieesashhdraisthpsoanalseetildulsrynhudftye.nuhgs,tdiaThdennetnhhhaagdt4wadteihesdokairsfsltmagefe.toldrie3Bnn)rtpyiemooteyfar
dramatic change that results in a severe
reduction of the carrying capacity for many,
if not all, of its native organisms. Depending
on the nature of the change, this collapse can
be permanent. In the case of the Aral Sea,
some of the native fish can still be found in
the small bodies of water that remain, but
many of the mammals, birds, and other
species that rely on the lake ecosystem have
disappeared. Reversing the water diversion
project would be an extremely complex
process and would mean the loss of
agriculture and income. Even if it were
FIGURE 13.4: On the left is an aerial photograph of possible, many scientists doubt that the
the lake prior to the water diversion project; on the ecosystem could recover.
right is the lake in its present state.

A-88

ECOSYSTEMS AT THE TIPPING POINT ACTIVITY 13

2. Share what you learned about your ecosystem with the other pair in
your group. As you listen to the other pair, complete Student Sheet
13.1 for the ecosystem you did not read about.

3. As a group, discuss what happened in each ecosystem as you consider
the following questions:

• How were the disruptions to the ecosystems different?
• What evidence do you have that each ecosystem is resilient?

Part B: Watching the Video

4. Read Part A of Student Sheet 13.2, “Aral: The Lost Sea,” so that you are
prepared to answer the questions as you watch the video on the Aral Sea.

5. With your class, watch the story of the Aral Sea. Complete Student
Sheet 13.2, Part A, while you watch the video.

6. Compare your responses with those of your group and come to an
agreement on all the answers. Be prepared to share your responses
with the class.

Part C: Talking It Over

7. In your group, discuss the claims about the Aral Sea in Part B of Student
Sheet 13.2. Try to find evidence to both support and rebut each claim. Be
prepared to discuss your group’s responses with the class.

Build Understanding

1. Choose a claim from Student Sheet 13.2, Part B, decide whether you
support or rebut it, and write an argument expressing your opinion,
using reasoning based on evidence from both “The Collapse of the
Aral Sea” reading and the video.

2. Issue connection: The government of the Soviet Union diverted the
two rivers that flowed into the Aral Sea in order to support cotton
agriculture, but this also caused the commercial fisheries to shut down.
What effects did this have in this region on the three pillars of
sustainability: environmental, economic, and social?

3. Reflection: The Aral Sea is the only ecosystem considered collapsed by
the World Conservation Union. What are some factors that you think
might lead to the collapse of other ecosystems? Use what you have
learned about natural and anthropogenic disruptions as you identify
these factors.

A-89

ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

KEY SCIENTIFIC TERMS

anthropogenic
disruption
resilient
resistant
stable

A-90

14 The Great Lakes Ecosystem

p r i o r to 1900, c h o l e r a a n d typhoid outbreaks commonly

affected residents of Chicago, a city on the western shore of Lake Michigan.
Lake Michigan was the source of drinking water for city residents. Sewers
emptied into the Chicago River, which flowed into the lake. The untreated
sewage sometimes carried water-borne diseases. City planners realized that
they needed to address this problem. Their solution was to undertake a
massive engineering project that reversed the flow of the Chicago River so
that it no longer drained into the lake. This project has been called one of
the top 10 engineering marvels in the world. But this feat, along with others
like the construction of the Erie Canal and the Saint Lawrence Seaway,
caused major changes to the Great Lakes ecosystem.

FIGURE 14.1: The Great Lakes Basin eventually drains to the Atlantic Ocean through the Saint Lawrence Seaway.
A-91

ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

In this activity, you will predict how the potential introduction of two
fish—bighead and silver carp—into the Great Lakes may affect this
ecosystem, which has already undergone major disruptions. These carp
were brought to the United States by fish farmers along the Mississippi
River to clean their aquaculture ponds of excess algae. However, flooding
in the 1990s allowed these fish to escape the ponds and wash directly into
the Mississippi River. Both species are fast-growing big eaters that
outcompete native fish for food in the Mississippi.

a b
FIGURE 14.2: Many ecologists are concerned that the introduction of the bighead (a) and
silver (b) carp to the Great Lakes could seriously endanger the health of this ecosystem.

Guiding Question

Is the health of the Great Lakes ecosystem at risk?

Materials

FOR EACH PAIR OF STUDENTS

set of Lake Michigan Invasive Species cards

FOR EACH STUDENT

Student Sheet 14.1, “Original Lake Michigan Food Web”
Student Sheet 14.2, “Great Lakes Ecosystem Research”

A-92

THE GREAT LAKES ECOSYSTEM ACTIVITY 14

Procedure

1. With your group, examine the information on Student Sheet 14.1,
“Original Lake Michigan Food Web.” Discuss how you think changes
by engineering projects, such as the building of the Erie Canal and
Saint Lawrence Seaway and the project that changed the course of the
Chicago River, might affect this food web. Record your ideas in your
science notebook.

2. Obtain a set of Lake Michigan Invasive Species cards, and examine the
information with your partner.

3. Create a data table similar to the one below in your science notebook.
Include a row for each invasive species in the cards.

INVASIVE SPECIES YEAR INTRODUCED EFFECT ON FOOD WEB

4. Arrange the cards in chronological order, based on the year that the
invasive species was introduced. Beginning with the first card, use the
information about the invasive species to determine what effect it is
likely to have on the food web. Record this information in your data
table, and add the invasive species to the food web on the Student
Sheet. Be sure to include arrows indicating how the invasive species
connects to other organisms in the food web.

5. Discuss your thoughts on the current health of the Lake Michigan
ecosystem with your class.

6. Some scientists are concerned about the possibility that two more
invasive species, the bighead and silver carp, might be introduced to
Lake Michigan and the other Great Lakes. Follow your teacher’s
instructions for gathering information from Internet sources about
this possibility. You will use the information you find to evaluate the
following claim:

If bighead and silver carp were to invade the Great Lakes, the
ecosystem would be in danger of collapse.
Use Student Sheet 14.2, “Great Lakes Ecosystem Research,” to record
the information you find. Be prepared to share your evaluation of the
claim with the rest of the class.

A-93

ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

Build Understanding

1. Develop an argument to support or rebut this claim: If bighead and
silver carp were to invade the Great Lakes, the ecosystem would be in
danger of collapse. Use evidence that you gathered during this activity
to support your reasoning.

2. Should scientists and engineers restore the flow of the Chicago River
so that it flows into Lake Michigan like it originally did? Support your
answer with evidence and reasoning. Be sure to identify any trade-offs
associated with your decision.

3. Issue connection: Several species of fish in the Lake Michigan
ecosystem are fished commercially and recreationally, including the
burbot, bloater, and lake trout. How might the sustainability of these
fisheries have been affected by the past introduction of invasive
species? How might it be affected by the introduction of bighead and
silver carp?

Extension 1: Engineering Connection

Scientists and engineers are working together in a number of ways to
try to prevent and repair disruptions to the Great Lakes ecosystem.
Visit the SEPUP SGI Third Edition website at www.sepuplhs.org/high
/sgi-third-edition to learn more about how engineering and
technology are being used to support the health of this ecosystem.

Extension 2

Continue to research the issue of the possible invasion of bighead and
silver carp in the Great Lakes ecosystem. Use Student Sheet 14.5,
“Evaluating Websites,” to guide you in examining the resources you find.
You can also visit the SEPUP SGI Third Edition page of the SEPUP website
at www.sepuplhs.org/high/sgi-third-edition to watch a video on how to
evaluate websites.

KEY SCIENTIFIC TERMS

disruption
resilient
resistant
stable

A-94

15 Is Aquaculture a Solution?

s o m e f i s h e r i e s fac e t h r e ats b e c au s e their entire ecosystem is
threatened. The Aral Sea fishery collapsed because the entire ecosystem
collapsed, and the fishery cannot be restored. In the Great Lakes, the
sustainability of the fisheries is potentially threatened by invasive species
disrupting the food web. Other fisheries, such as the salmon fishery along
the West Coast of the United States and the cod fishery in the Atlantic,
may need to close for a period of time due to shrinking populations
caused by overfishing.
Whatever the cause for the decline of a fishery, solutions to restoring those
fisheries are not always easy or straightforward. Many people suggest that
one solution to the growing demand for seafood in the face of declining
fisheries is aquaculture—the farming of fish and other aquatic species for
human consumption. Many species of fish can be farmed, such as tilapia.
Native to Africa, tilapia grow and reproduce well in captivity and are
raised in enclosed inland ponds where their wastewater is treated. Tilapia
farms in the United States are often viewed as sustainable and very
successful. With more and more wild fish populations declining,
aquaculture is becoming an increasingly important food source.
However, not all fish species can be farmed. Some fish need specific
habitats that cannot be recreated in captivity, while others do not breed
in captivity. In addition, some species, such as salmon, that can be
farmed can cause major impacts on the local ecosystems. In this activity,
you will explore a model of aquaculture and consider both its potential
for providing more food for people and the consequences of aquaculture
for wild populations of fish.

Guiding Question

How can the sustainability challenges connected to
aquaculture be addressed?

A-95

ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

Materials

FOR EACH GROUP OF FOUR STUDENTS

number cube

FOR EACH STUDENT

Student Sheet 15.1, “Comparing Wild and Farmed Salmon Populations”
4 colored pencils (red, orange, yellow, green)
sheet of graph paper

Procedure

Part A: Aquaculture Systems

1. Read the following text about aquaculture systems, and mentally note
the key points in the reading.

Aquaculture Systems

Aquaculture can be located on land, in water is treated and recirculated to prevent
oceans, or in bays, depending on the species contamination of the environment. This is
raised. The most familiar aquaculture systems costly and requires electricity.
consist of inland ponds that hold a particular
freshwater or saltwater species, such as trout, Raceways are another type of aquaculture
tilapia, shrimp, or catfish. Some of these system. They divert water from a river or other
ponds are enclosed systems in which the source and guide it through long channels that
house the fish being raised. The water is then

FIGURE 15.1: Open-net aquaculture setup
A-96 3299 SEPUP SGI Ecology SB

Figure: EcoSB 15.01
Agenda MedCond 9/9.5

IS AQUACULTURE A SOLUTION? ACTIVITY 15

treated before it rejoins the original source.
In the United States, raceways are used to
raise rainbow trout, striped bass, and other
species. There is concern among ecologists
that these farmed fish might escape and
either interbreed with the wild fish or
compete with them for food.
In this activity, you will examine the
aquaculture system of open-net pens—large
net pens suspended in coastal waters or
lakes that are frequently used for tuna and
salmon farming. The water from the pens
exchanges freely with the water in the
surrounding habitat. This causes pollution
and can spread disease from the farmed fish
to the wild populations. There is also the
chance that the farmed fish will escape, as FIGURE 15.2: Net pens are used to farm salmon.

with the raceway systems. You will explore
some of the benefits and trade-offs involved in
a widespread debate over farmed salmon.

FIGURE 15.3: Most wild salmon hatch
from their eggs in fresh water and
migrate down rivers or waterways to the
N ocean. Mature salmon migrate back to

the same freshwater location to
reproduce. The simplified map on the left
shows net pens located along wild
salmon migration routes. Below, a wild
salmon swims upstream during the fall.

KEY land Atlantic Ocean
water
open-net pen
aquaculture site
wild salmon
migration routes

3299 SEPUP SGI Ecology SB A-97
Figure: Eco SB 15.02

ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

2. Work with your partner to write a short summary of the reading,
following your teacher’s instructions.

3. Compare your pair’s summary with the summary written by the other
pair in your group, and discuss the similarities and differences.

4. With your group, compile a list of challenges connected to aquaculture.
Categorize the challenges based on the three pillars of sustainability:
economic, social, and environmental. Include any challenges you have
learned or know about that were not included in this reading.

Part B: Modeling

The Model

Your group will use a model to simulate events for two salmon
populations, one wild and one farmed. The salmon farm is an
open-net system set up in the coastal waters off the East Coast of
the United States, similar to the one shown in the map of net
pens and migration routes in the reading. The wild salmon’s
migration route brings them into close contact with the salmon
farms. You will explore how different events that happen in the
fish pens affect both the farmed salmon population and the wild
salmon population.
5. Begin your simulation by rolling the number cube to determine what
event happens to the first generation of salmon. Record the number
you roll in Column B of Student Sheet 15.1, “Comparing Wild and
Farmed Salmon Populations.”
6. Use the number cube key in Table 15.1 to determine what the number
you rolled means. Enter the effect of that event in Column D for the
wild population and Column G for the farmed population. Be sure to
note whether the population increases (+) or decreases (–).

A-98

IS AQUACULTURE A SOLUTION? ACTIVITY 15

TABLE 15.1: Number Cube Key

NUMBER EVENT ENVIRONMENTAL WILD POPULATION FARMED
ROLLED Farmed salmon I M PAC T EFFECT POPULATION
escape Escapees interbreed Loss of 500 EFFECT
1 and compete for salmon due to No change in
resources with the lack of resources population size
2 Disease at salmon wild population and reduced
farm fitness because of Loss of 250 salmon
Disease spreads to interbreeding from disease
3 Antibiotics given to the wild population Loss of 1,500 salmon Disease decreases;
farmed salmon to Kills “good” bacteria from disease population increases
prevent disease that the ecosystem Ecosystem by 250 salmon
needs to function disrupted; causes Fewer salmon per
4 Decrease in density Milder loss of 750 salmon pen; loss of 350
of salmon in pens environmental Improved habitat salmon
impact causes increase of Decrease in water
5 If farm has more Wastewater in local 500 salmon quality causes loss of
than 1,400 salmon, ecosystem causes Reduction of 500 salmon
waste accumulates habitat and food loss available resources New pen houses
under pens causes loss of 1,000 more salmon;
Takes up the space salmon increase by 350
6 If farm has more of wild salmon’s Decrease of salmon
than 1,400 salmon, habitat resources causes loss
new pen is built of 500 salmon

7. Add to or subtract from both salmon populations as directed. Record
the new population size of the wild salmon in the row immediately
below in Column C. Record the new population size for the farmed
salmon in the row immediately below in Column F.

Note: If you roll a 5 or 6 and your population is not 1,400 or greater,
keep rolling until you get a 1, 2, 3, or 4.

8. Repeat Steps 5 through 7 until you have gone through 20 generations
of salmon. If either population reaches 0 during the simulation, stop
and move on to Step 9.

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ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

9. Use the guidelines in Table 15.2 to determine the status of your wild
salmon population in Column E. Use colored pencils to shade in the
boxes with the color corresponding to the status for each generation.

TABLE 15.2: Wild Salmon Population

NUMBER ≤ 5,000 5,001–7,000 7,001–9,000 9,001–12,000
OF FISH red orange yellow green
POPULATION critically marginally stable at carrying
STATUS overfished overfished capacity

10. Use the guidelines in Table 15.3 to determine the status of your farmed
salmon population in Column H. Use colored pencils to shade in the
boxes with the color corresponding to the status for each generation.

TABLE 15.3: Farmed Salmon Population

NUMBER ≤ 800 801–1,100 1,101–1,300 > 1,300 green
OF FISH red orange yellow substantial
PROFIT negative no profit moderate profit
LEVEL profit (loss) (break even) profit

11. Construct a line graph that shows the population curves for the wild
and farmed salmon populations. Use color-coding or labels along the
y-axis to show the status of the populations at different sizes. For
example, the y-axis from 0 to 5,000 for the wild salmon population
should be labeled as critically overfished and/or color-coded in red.

12. With your group, discuss what happened with the wild and farmed
salmon populations in your model. Be sure to consider the social,
environmental, and economic impacts. Be prepared to share your
results with the class.

Build Understanding

1. Based on the line graph you constructed in Procedure Step 11 and your
group discussion in Step 12, explain the relationship between the
population growth in the farmed and wild salmon populations.

2. How is the model in this activity similar to and different from real-life
aquaculture?

3. In the previous activity, you read about an unintended consequence of
aquaculture: the silver and bighead carp that were brought in to clean
out fish aquaculture ponds, then escaped when the ponds flooded. What
are some possible unintended consequences of open-pen aquaculture?

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IS AQUACULTURE A SOLUTION? ACTIVITY 15

4. Recall what you learned in the third learning sequence about salmon
and their importance to both the orca ecosystem and the stream
ecosystems where the salmon spawn. What impact might aquaculture
have on those ecosystems?

5. Issue connection: When engineers and scientists work to design a
solution to a problem, such as a sustainable fish farm, they aim to
design the best solution. Part of this process is identifying the criteria
and constraints they need to work with. Criteria are the desired goals
and features of the solution. Constraints are things that limit the
solution to the problem. If you were to build and operate an open-net
pen salmon farm, what are some criteria and constraints you might set
to make the farm as sustainable as possible? Explain your choices, being
sure to consider the economic, environmental, and social aspects.

KEY SCIENTIFIC TERMS

aquaculture
criteria
constraints

Extension: Engineering Connection

Aquaponics is a combination of aquaculture and hydroponics (the soil-less
growing of plants for food). In an aquaponics system, microbes convert
ammonia in fish waste into usable forms of nitrogen taken up by edible
plants. Research the basics of aquaponics. In what kinds of environments
might it be a good option for raising fish (and growing plants)? What criteria
and constraints did you use to come up with this decision? Then put your
research in motion by building and maintaining an aquaponics system in
your classroom. Visit the SEPUP SGI Third Edition page of the SEPUP
website at www.sepuplhs.org/high/sgi-third-edition to learn more.

A-101



16 Sustainable Fisheries Case Studies

you are a fisheries biologist who has been asked to provide input on
an upcoming decision: whether to reopen the tuna fishery in the Avril Gulf
(a fictitious fishery modeled after a combination of fisheries in the United
States). The tuna near the Avril Gulf spend most of their lives off the coast or
in the open ocean. The Avril Gulf tuna fishery was closed to fishing in 2010
after years of declining fish catches. The ecosystem reached such a state of
depletion that federal and state officials decided to ban all commercial and
sport fishing of this species.

Recall from the unit opener that as the demand for seafood increases, more
and more fisheries are being overfished, and the percentage of fisheries that
are sustainable is decreasing as shown in Figure 16.1, which you saw in the
unit opener. In this activity you will read about four different sustainable
fisheries-management approaches that were adopted when communities
faced a fisheries crisis. What can be learned from these examples? How can
these learnings be applied to situations like the Avril Gulf tuna fishery?

100 Over shed
90
Percentage 80 Fully shed
70
60 Under shed
50
40 1979 1984 1994 1999 2004 2009 2013
30
20
10

0
1974

FIGURE 16.1: Sustainability of fisheries over time

LabAids SEPUP SGI Ecology 3e
Figure: Eco3e SB 01_1
MyriadPro Reg 9.5/11

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ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

Guiding Question

What can you learn from past and current examples about
making fisheries more sustainable?

Materials

FOR EACH STUDENT

Student Sheet 16.1, “The Avril Gulf Tuna Fishery”
Student Sheet 16.2, “Case Study Analysis”
3–5 sticky notes

Procedure

1. Due to the decline in the Avril Gulf tuna fishery, the governments of
the areas near the Avril Gulf want to implement new management
strategies for the fishery. They have commissioned background studies
on four strategies successfully implemented in other locations:

• Creating a marine reserve
• Opening aquaculture farms
• Implementing new fishing regulations
• Temporarily closing some fishing areas

You will read the case study for one strategy, along with others in your
class who will read the same study. You’ll then return to your group
and share your findings.

2. With your reading group, read about your assigned strategy. As you
read, use the Read, Think, and Take Note strategy:

• Stop at least three times during the reading to mark on a sticky note

your thoughts and questions. Use the following guidelines to start
your thinking.

A-104

SUSTAINABLE FISHERIES CASE STUDIES ACTIVITY 16

Read, Think, and Take Note: Guidelines

As you read, use a sticky note from time to time to:

• Explain a thought or reaction to something you read
• Note something in the reading that is confusing or unfamiliar
• L ist a word from the reading that you do not know
• Describe a connection to something you’ve learned or read

previously

• Make a statement about the reading
• Pose a question about the reading
• Draw a diagram or picture of an idea or connection

• After writing a thought or question on a sticky note, place it next to

the word, phrase, sentence, diagram, drawing, or paragraph in the
reading that prompted your note.

• After reading, discuss with your reading group the thoughts and

questions you had while reading.
3. With your reading group, use Student Sheet 16.2, “Case Study

Analysis,” to take notes on the following for the management strategy
you read about:

• The challenge the fishery was facing
• The plan the fishery used to address the challenge
• The impact the strategy had on the ecosystem’s food web
• The trade-offs associated with the strategy
• How the strategy affected the community economically,

environmentally, and socially
4. With your reading group, decide how the fisheries-management

approach in your case study might affect the sustainability of the Avril
Gulf tuna population and the community near the Avril Gulf. Record
your predicted outcomes in your science notebook.
5. Return to your regular group and share your findings for the fisheries-
management study you read about.

A-105

ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

CASE STUDY 1

Creation of the Goat Island Marine Reserve

Goat Island Marine Reserve

g oat i s l a n d i s a tiny 0.1 km2 island north Leigh Marine
of the town of Leigh, which is on the eastern Laboratory
coast of New Zealand (see Figure 16.2).
Okakari Goat Island
DY The 5-km2 marine ecosystem in the waters Point beach

surrounding the island once supported large
populations of snapper fish and spiny lobsters.
This allowed thriving fishing communities to Cape
develop in nearby shoreline towns. With its Marine Education Center Rodney

clear water and abundant, diverse fish species, Auckland FIGURE 16.2: Map of
the ocean around Goat Island also was popular the Goat Island
for recreational scuba diving. Unfortunately, Marine Reserve
the snappers and lobsters were fished at such a
high rate that their populations crashed in the
late 1960s. Without any predators, the sea
urchin population soon grew out of control.
Christchurch

They devastated the kelp forests, which NEW ZEALAND
eventually became barren and rocky
underwater flats, known as urchin barrens.

Establishment of the Marine Reserve with governmental limits on human activity—in
In 1975, the local communities convinced the
New Zealand government to establish the first LFNIiasgbleuaAwnreiddZ: s,EeacSasoEla3PshneUodPSwBSinnG16Itih_En0ceto3whloeagtmeyra3spes.uNrroosupnodritnogrGoat
marine reserve—a protected area in the ocean McoymriamdPerrocRiaelgfi9s.h5i/n1g1 is allowed in these protected
waters, and no plants or animals can
be trapped, fished, or removed from
Hector’s New Zealand the reserve. When the marine reserve
dolphin fur seal

was established, fishing ceased and
few boats roamed the Goat Island
spiny rock snapper blue maomao waters, allowing scientists the
lobster ( sh) opportunity to study the ecosystems

and changing populations of the c0 m42 y92 k0 c100 m0 y20 k70 c25 m0 y15 k90
c7 m0 y0 k9

kina paua Maps1 Maps2 reMsapes3rve. InMaps4 1977,Maps5 a marine education
(sea urchin) (abalone) center opened to provide educational

zooplankton tours and to guide diving expeditionsc60 m30 y100 k0 c50 m20 y75 k0 c15 m90 y90 k0 c90 m55 y40 k0
c0 m30 y70 k0 c0 m43 y94 k0 c15 m10 y0 k85 c95 m50 y30 ko c15 m90 y90 k0

c39 m7 y12 k0

seaweed in the waters of the reserve.

c15 m10 y0 k85 c80 m0 y0 k55 c12 m7 y0 k0 c0 m0 y0 k6 c25 m0 y15 k90

FIGURE 16.3: Goat Island food web phytoplankton

LabAids SEPUP SGI Ecology 3e
Figure: Eco3e SB 16_03
MyriadAP-r1o06Reg 9.5/11

SUSTAINABLE FISHERIES CASE STUDIES ACTIVITY 16

The Marine Reserve Benefits Average number per 500 m2visitors who snorkel in the waters. Increased
the Waters of Goat Island tourism means more jobs and greater awareness
of the importance of protecting marine
The growth of the fish and lobster populations populations. But environmental protection
in the Goat Island Marine Reserve was slow but agencies question how the increased use of the
steady. Within several years, fish and lobster land might affect the long-term sustainability of
populations grew at such a rate and density the Goat Island Marine Reserve and the
within the reserve that some spilled over into ecosystems it was built to protect. There are also
non-reserve waters. This “spillover effect” was a factors that cannot be controlled within the
welcome surprise for sport and commercial marine reserve, such as those due to climate
fishers who fished the waters beyond the change. Monitoring of species within the
boundaries of the marine reserve. reserve continues, and while many indicators
are steady or showing positive trends, some are
The vegetation on the marine floor gradually declining—such as the rock lobster population,
changed as well. Algae grew back in many of the as shown in Figure 16.4.
rocky flats. The ecosystem became lush with
mixed algae, including kelp—key producers in 50
the marine ecosystem. As the algae returned, so 40
did other organisms that depended on the algae 30
for food and shelter. Between 1977 and 2006, 20
areas of bare rock declined from 56% to 4% of
the reserve, and seaweed-dominated habitat
rose from 38% to 77% of the reserve.
TABLE 16.1: Habitat Type In the Goat Island Marine
Reserve

HABITAT TYPE % AREA, % AREA, 10
Mixed algae 1977 2006
Large kelp   5  17 0 2000 2005 2010 2015
forests  28  60 1995 Year
Urchin barrens
 31   1 Inside Outside

Moving Forward FIGURE 16.4: Number of rock lobster inside and
outside Cape Rodney-Okakari Point Marine Reserve
While the marine reserve has provided valuable
shelter to the endangered populations of fish LabAids SEPUP SGI Ecology 3e
and invertebrates of the Goat Island waters, Figure: Eco3e SB 16_04
questions remain about its long-term benefits.
Since the creation of the Goat Island Marine ScientMisytrsiacdoPnrotiRneuge9t.o5/c1l1osely monitor the
Discovery Centre, more roads and public Goat Island Marine Reserve. They hope to
facilities have been built near the mainland continue to learn more from this long-
beach to accommodate the growing number of established marine reserve that will help inform
conservation efforts in other areas of New
Zealand and the world.

Number of rock lobster inside and outside
Cape Rodney-Okakari Point Marine Reserve

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ECOLOGY SCIENCE & GLOBAL ISSUES: BIOLOGY

CASE STUDY 2

Open-Ocean Aquaculture in Hawaii

s i n c e 1927, f i s h farmers have been Australian farms use dried food, which causes
less pollution but still contains a high
growing yellowtail, a tasty fish and very popular percentage of wild-caught fish. Recently, some
sushi item. Much of the yellowtail that is sold Australian yellowtail farms have started moving
worldwide comes from yellowtail farms, which to a land-based model, where fish are raised in
are mainly in Japan, Australia, Mexico, and large tanks and the water can be treated before
Hawaii. The oldest farms are in Japan, and they being released into the environment, which is
provide a majority of the yellowtail to the considered to be a more sustainable method of
world’s markets. farming yellowtail.

Over the past several decades, concerns over Kona, Hawaii: Farming Differently
the sustainability of yellowtail farms have
emerged. One of the biggest problems is that In 2005, as the consequences of the farming of
many of the older yellowtail farms use nets kept yellowtail became more worrisome, an
in shallow coastal areas, where the waste from aquaculture farm in Kona, Hawaii, was built,
the fish and leftover fish food pollutes the with the goal of being the world’s first
surrounding ecosystems. In Japan, this has sustainable yellowtail fish farm. Open-ocean
caused rapid growth of the algae population, pens were anchored in ocean waters less than 1
sometime called algal blooms. Also, the km off the coast of the island of Hawaii, where
yellowtail at the Japanese farms are fed wild- deep water and fast currents could move clean
caught sardines, which has caused a decline in water through the pens and help prevent
the local sardine population. Another problem pollution of the surrounding habitats.
with the Japanese farms is that they catch wild
juvenile yellowtail and then raise them at the The fish farmers chose to raise a species of
farms, which means that the farms are depleting yellowtail native to Hawaii, kahala (Seriola
the wild population of yellowtail. rivoliana), to minimize the risk of escaped

FIGURE 16.5: World production of yellowtail

Japan Hawaii

Baja,
Mexico

Spencer Gulf, A-108
Australia
Major locations of
yellowtail aquaculture