Name: dayanara Date:

Student Exploration: Coral Reefs 2 – Biotic Factors

Directions: Follow the instructions to go through the simulation. Respond to the questions and
prompts in the orange boxes.

[Note to teachers and students: This lesson was designed as a follow-up to the Coral Reefs 1 – Abiotic Factors
lesson. We recommend doing that activity before trying this one.]

Vocabulary: biotic factor, black band disease, invasive species, white band disease

Prior Knowledge Questions (Do these BEFORE using the Gizmo.)

In 1992, Hurricane Andrew left a wake of destruction through Florida. One victim of the
storm was a reptile-breeding facility. Over 900 Burmese pythons were set free, and today
thousands of pythons live in Florida. These pythons are an invasive species, or a harmful
species not native to the region.

1. What impacts do you think the Burmese pythons might have on local ecosystems?

they can be a danger to the birds

2. In general, why might ecologists be concerned when new invasive species arrive in an ecosystem?

they can cause harm to the old animals and endanger them

Gizmo Warm-up
Like terrestrial environments, coral reefs can be damaged by invasive
species. Reefs are also impacted by disease-causing bacteria, humans, and
other biotic factors, or living parts of the ecosystem. In the Coral Reefs 2 –
Biotic Factors lesson, you will explore how these factors affect coral reefs.

1. On the CONDITIONS tab, select Fishing. Set Net fishing to 50%. Click Advance year 10 times. What
changes do you notice on the Coral reef tab?

Alot of the fish are gone

2. On the DATA tab, select every organism. What happens to the reef populations?

the fish population goes down

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 Get the Gizmo ready:
Activity A:
● Click Return to original settings and Restart.
Fishing regulation
● On the CONDITIONS tab, check that Fishing is selected.

Introduction: Fishing is a major part of many Caribbean economies. The yellowtail snapper and Nassau
grouper are important food fishes. However, a lack of adequate regulation has led to overfishing in many areas
and consequent damage to reefs. The goals of this activity are to observe the effects of overfishing and
determine how much fishing the reef can withstand.

Question: What are the effects of fishing on the reef ecosystem?

1. Describe: On the CORAL REEF tab, click on the stoplight parrotfish, queen angelfish, yellowtail snapper,
and Nassau grouper. Describe what each of these fishes eat.

Stoplight parrotfish: algae Yellowtail snapper: worms, crabs, shrimp, and little
fish

Queen angelfish: sponges Nassau grouper: parrot fish angel fish,

2. Predict: Set Grouper to 70%. How do you think this level of fishing will affect the populations of the other
fish in the simulated reef? Explain your reasoning.

The groupers prey will slowly die from over hunting

3. Experiment: Select the DATA tab, and check that every species is selected. Click Advance year 10 times.
Which fish populations increased, and which fish populations decreased?

decreased : Groupers, Queen angel fish, parrot fish, snapper

increased: sponge

4. Explain: Why do you think the snapper population changed the way it did?

The grouper fish ate all the snapper populations

5. Predict: Click Return to original settings and Restart. Set Snapper to 70%. How do you think this will
affect the other fish populations? Explain your reasoning.

The snappers will decrease and their prey will increase

6. Experiment: Click Advance year 10 times. What changes occur?

The snapper population greatly decreased and the other live increased

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7. Explain: Explain the results of the last experiment. Why did the grouper, parrotfish, and angelfish
populations rise? Why did the sea urchins decline? How did this affect algae?

They had more prey to eat, so they were healthier and reproduced moreThe algae and the smaller
fish decreased because the larger fish the more they eat.

8. Explore: Click Return to original conditions and Restart. Experiment with different levels of Net fishing.
Net fishing kills all fish approximately equally. It also can damage delicate corals. For each experiment, run
the simulation for approximately 40 years to see the long-term effects on the reef. Summarize the results of
each experiment in the table below.

Net fishing level Results

The queen angel fish increase the mos
20%

Sponges, Queen angel, and sea urchins increase the mos

40%

sponges, urchins, and groupers increase Queen angel decreases

60%

Sponges and Algae increases

80%

9. Draw conclusions: What level of net fishing can the model reef sustain? Explain.

That the more net fishing then the more no fish survive

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 Get the Gizmo ready:
Activity B:
● Click Return to original settings and Restart.
Disease ● On the CONDITIONS tab, select Disease.
● On the DATA tab, select every organism.

Introduction: Corals are susceptible to many diseases, including black band disease and white band
disease. Other reef animals are also affected by disease. For example, in 1983 a mysterious plague wiped out
most of the long-spined sea urchins throughout the Caribbean.

Question: How are reefs impacted by disease?

1. Observe: Select the CORAL REEF tab. Set the Black band infection rate to 100%. Click Advance year
several times. Which coral appears to be affected, and what do you see?

2. Predict: How do you think the reef will change when black band disease is present?

3. Observe: Click Advance year until you reach year 20. What changes do you see?

4. Analyze: Look at the coral populations in the DATA tab. Why do you think the population of staghorn corals
increased?

5. Observe: Select the CORAL REEF tab. Click Return to original settings and Restart. Set the White
band infection rate to 100%. Click Advance year two times. What do you see?

6. Observe: Click Advance year to year 20. What changes do you see? Confirm your observations by
viewing the DATA tab.

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7. Set up the Gizmo: Click Return to original settings and Restart. Coral diseases often crop up in reefs
that are already stressed by high temperatures, high nutrient levels, or low pH. To model these conditions,
select Ocean conditions. Set the Ocean temperature to 29 °C and Ocean pH to 7.7. Then, select Land
use and set Agriculture to 50%. Finally, select Disease and set the Black band infection rate and White
band infection rate to 100%. Select the SUMMARY tab. What is the current coral stress level?

8. Predict: How do you think stressed corals will respond to disease?

9. Experiment: Click Advance year to year 20. How does the impact of disease in a stressed reef compare to
the impact of disease in a healthy reef? (To make a direct comparison, run an experiment with the original
settings and black and white band infection rates of 100%)

10. Predict: On the CONDITIONS tab, click Return to original settings and Restart. To model the die-off of
long-spined sea urchins in 1983, set the Sea urchin infection rate to 90%. How do you think this will affect
the reef?

11. Experiment: Click Advance year to year 20. What changes occurred?

12. Infer: Parrotfish rely on corals for protection and shelter. Look at the parrotfish population over time. Why
did the parrotfish population increase at first and then later decline?

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 Get the Gizmo ready:
Activity C:
● Click Return to original settings and Restart.
Invasive species
● On the CONDITIONS tab, click Invasive species.

Introduction: A native of the Pacific Ocean, the red lionfish were first observed in the Atlantic Ocean in 1985.
Red lionfish are voracious predators and are well protected by their toxic spines. Today they have spread
throughout the Caribbean.

Question: How do invasive species affect reefs?

1. Predict: Select the Red lionfish checkbox. How do you think lionfish will affect the reef?

2. Observe: Select the SUMMARY tab. How many fish species are present on the reef?

3. Experiment: Click Advance year to year 20. What changes occur to the reef?

4. Observe: Look at the SUMMARY tab. How many fish species are present now?

5. Predict: How do you think the reef will react to a lionfish invasion if there are no sea urchins?

6. Experiment: Click Restart. On the CONDITIONS tab, select Disease. Set the Sea urchin infection rate to
100%. Click Advance year to year 20.

A. How did the lack of sea urchins change the effect

of lionfish on the reef?

B. Explain these results.

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7. Predict: Click Return to original settings and Restart. On the CONDITIONS tab, select Invasive species
and select the Crown-of-thorns starfish checkbox. The crown-of-thorns starfish is a native of the Pacific
Ocean that has not invaded the Caribbean Sea—yet.

A. What does the crown-of-thorns starfish eat?

B. How do you think the crown-of-thorns starfish

would affect Caribbean reefs?

8. Experiment: Click Advance year to year 10. What happens?

9. Extend your thinking: Click Return to original settings and Restart. Many Caribbean reefs face multiple
environmental and biological threats. You can use the Coral Reefs Gizmo to design your own experiment to
see how a combination of factors affects the reef. You can also design an experiment to see how quickly a
reef recovers from a disturbance.

In the space below, describe your question, experimental design, experimental results, and conclusions.
Continue on additional pages if necessary.

Question and hypothesis:

Experimental design:

e Results:

Conclusions:

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