Modeling Feedbacks in Ocean Acidification & Coral Bleaching

Part 1: Engage (Anchoring Phenomenon)

The colorful coral reefs in La Parguera, Puerto Rico, are vibrant ecosystems teeming with life. However, local scientists and divers have observed that parts of the reef are turning completely white, a phenomenon known as “coral bleaching.” This isn’t just an aesthetic issue; bleached corals are starving and vulnerable to disease. Over the last few decades, global industrialization has increased the amount of carbon dioxide (CO₂) released into the atmosphere.

Think about it: How could human activities occurring thousands of miles away, such as driving cars or burning coal, affect a coral reef underwater in Puerto Rico?

Record your initial thoughts and questions below: ___ _____ _______

Part 2: Explore (Simulation Investigation)

In this investigation, you will use a computational simulation to model the relationship between global carbon emissions and the health of the coral reef ecosystem in La Parguera. The simulation connects changes in the atmosphere to changes in the ocean (hydrosphere) and the coral reef (biosphere).

Estimated Time:

45 minutes

Materials:

• Computer or tablet with internet access
• Ocean Acidification & Coral Bleaching Simulator
• Calculator (optional)

Directions:

1. Open the Ocean Acidification & Coral Bleaching Simulation.
2. Locate the Global Carbon Emission Rate slider. This controls how many Gigatons of Carbon (GtC) are released per year globally.
3. Keep the emission rate at the default value of 10.0 GtC/yr. Click Play.
4. Observe the simulation for at least 100 simulated years (watch the x-axis on the charts).
5. Pause the simulation. Record the final values from the charts in the data table below for the 10.0 GtC/yr rate.
6. Click Reset. Change the emission rate to a higher value (e.g., 20.0 GtC/yr) and run the simulation for another 100 years. Record the data.
7. Click Reset again. Change the emission rate to a lower value (e.g., 5.0 GtC/yr or lower) and run the simulation for 100 years. Record the data.

Data Collection Table: Ecosystem State After 100 Years

Note: You may choose different emission rates to test, as long as you test one higher and one lower than the default.

Part 3: Explain (Sensemaking)

Using the data you collected from the simulation, answer the following questions to explain the relationships between these Earth systems:

1. Organizing Data: What patterns do you notice in the data? As the Global Emission Rate increases, what happens to Atmospheric CO₂, Water Temperature, and Ocean pH? ___ _______

2. Identifying Relationships (Atmosphere to Hydrosphere): Based on the data, describe the relationship between atmospheric CO₂ levels and ocean water temperature. Why does an increase in atmospheric greenhouse gases like CO₂ cause the ocean temperature to change? ___ _______

3. Identifying Relationships (Hydrosphere to Biosphere): Coral bleaching is an indicator of stress in the coral. Look at the relationship between water temperature, ocean pH, and the percentage of coral bleaching. How do these physical and chemical changes in the hydrosphere affect the biosphere? ___ _______

4. Identifying Feedbacks: The simulation models a positive feedback loop related to climate change. As greenhouse gases rise, global temperatures increase. This warms the oceans. Warmer oceans absorb less CO₂ than cooler oceans, leaving more CO₂ in the atmosphere to cause further warming. Is this an example of a positive (destabilizing) or negative (stabilizing) feedback? Explain using data from your model. ___ _______

Part 4: Elaborate/Evaluate (Argumentation & Modeling)

Your Task (Deliverable): Using your data as evidence, write a scientific argument forecasting the future impacts of continued high global carbon emissions on the coral reefs of La Parguera.

Your argument must include:

• A Claim: Make a clear forecast about the future of the coral reefs if emission rates remain high (e.g., > 15 GtC/yr).
• Evidence: Use specific numbers from your simulation data table (CO₂ ppm, Temperature °C, pH, Bleaching %) to support your claim.
• Reasoning: Explain the mechanism for the feedbacks between Earth’s systems (how changes in the atmosphere [emissions] cause changes in the hydrosphere [temperature, pH], which then cause changes in the biosphere [coral]). Explain whether these changes are currently reversible based on your simulation runs.

Extension Option:

In the simulation, try to find the “tipping point” for the coral reef. Is there a specific emission rate where the reef completely dies (100% bleaching) within 50 years? Run multiple trials to find the threshold and describe the limitations or uncertainties of your prediction.

Teacher Notes

NGSS Alignment

This task is designed to assess student understanding of the following Next Generation Science Standards (NGSS):

• HS-ESS2-2: Analyze geoscience data to make the claim that one change to Earth’s surface can create feedbacks that cause changes to other Earth systems.
• HS-ESS3-5: Analyze geoscience data and the results from global climate models to make an evidence-based forecast of the current rate of global or regional climate change and associated future impacts to Earth systems.

Dimensions

• Science and Engineering Practices (SEPs): Analyzing and Interpreting Data. Students analyze data from the computational simulation to make valid scientific claims about the relationships between variables and to make an evidence-based forecast.
• Disciplinary Core Ideas (DCIs):
  • ESS2.A: Earth Materials and Systems (Earth’s systems cause feedback effects).
  • ESS2.D: Weather and Climate (Redistribution of energy among atmosphere and ocean).
  • ESS3.D: Global Climate Change (Magnitudes of human impacts and human abilities to model them).
• Crosscutting Concepts (CCCs): Stability and Change. Students quantify rates of change and identify feedbacks (positive or negative) that destabilize the coral reef system.

Evidence Statements Addressed

HS-ESS2-2

• 1. Organizing data (a, b): Students organize data from the simulation representing measurements in the atmosphere (CO₂), hydrosphere (temp, pH), and biosphere (bleaching).
• 2. Identifying relationships (a.i, a.ii, b): Students describe the relationships between changes in the atmosphere (emissions) and changes in the ocean and biosphere, including human activity effects and positive climate feedbacks.
• 3. Interpreting data (a): Students use data to describe the mechanism for the feedback between the atmosphere and hydrosphere, identifying it as a positive (destabilizing) feedback.

HS-ESS3-5

• 1. Organizing data (a): Students organize data from the global climate model over time relating to physical/chemical parameters of the atmosphere and hydrosphere.
• 2. Identifying relationships (a.i, a.ii): Students analyze data to identify changes over time and relationships between quantities.
• 3. Interpreting data (b): Students use their analysis to predict the future effect of climate change (emissions) on ocean pH and coral bleaching in the Elaborate/Evaluate section.