Teacher preparation:

Overarching learning goal: Students recognise the role of the oceans in the carbon cycle. They begin to understand the risks to the oceans from the climate change and the greenhouse effect and learn what is meant by the term 'ocean acidification'. Students understand that the acidification of our oceans is one of the most significant environmental challenges we will have to face, and that it won't just be marine species and ecosystems that are impacted; humans will also be affected by ocean acidification.

Teacher content information: Climate change is predicted to have a range of effects on our environment, some barely noticeable, others devastating. One of those predicted devastating effects is the impact on our oceans.

Carbon dioxide in the atmosphere and the oceans are exchanged at the surface layer between these two environments. When the concentration in the atmosphere increases, the ocean takes in much of it, sequestering the CO₂ from the atmosphere. In this way, the oceans are moderating the amount of greenhouse gases in the atmosphere. Without the oceans, atmospheric CO₂ levels would be even higher.

Unfortunately, this process may cause long-term damage to life in the oceans. As CO₂ is transferred into the ocean it lowers the pH and creates a more acidic environment. This already sounds pretty nasty, but when you think what it means for all those marine species whose bodies have calciferous part (molluscs, plankton, sea stars, corals and other shell inhabiting creatures), you can begin to understand why rising acidity in our oceans is being recognised as one of the most significant environmental problems we will have to face.

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Cut Worksheet 2 into strips along the dotted lines before starting this activity.

Student and classroom organisation:

Step 1.

Begin this activity by refreshing student understanding of the carbon cycle. Draw a carbon cycle on the board and explain the cycle.

Step 2.

Give each student (or group) a copy of Worksheet 1 (download here or on Student Worksheet). Ask them to brainstorm the different carbon sources and sinks that exist in our world. They should indicate the carbon sources with a plus sign (+), and indicate the carbon sinks with a minus sign (-). Students should also include a short description explaining why they have elected each point as a carbon sink or source. Ask students to use a coloured pen to make the notes on their carbon cycle worksheets.

Step 3.

Ask students to look at their carbon cycles and spend a short time discussing the following points as a class:

Why is the amount of carbon in the carbon cycle rising? (because of human behaviour)
How will this rising carbon in the atmosphere affect life on land? (impacts of climate change)
How will this affect life in the oceans? Ask students to consider what kinds of chemical reactions might take place when carbon is absorbed by the oceans.

Step 4.

Give each student or group one or more of the statements written on Worksheet 2 (download here) so that all the statements are handed out. These statements relate to both the carbon cycle and to ocean acidification. Students should move around the class, sharing their information about the carbon cycle with other students. As they go, students should make adjustments to their carbon cycle - including notes about ocean acidification - with a different coloured pen from the one they used initially and add notes to explain their changes.

Step 5.

Once complete, ask students to watch the short clip from 'The Acid Test’ (also available on the Student Worksheet).

ACID TEST: 3 Minute Science of Ocean Acidification https://vimeo.com/8990924

Step 6.

Once again students should make amendments to their carbon cycle, using a different coloured pen this time. Give the students a few minutes to make any changes they wish to add to their carbon cycle diagrams (they are not to re-draw them as the point of this exercise is to evaluate what they learned after each reading). Remind them to indicate with plus sign or a minus sign all the sinks and sources.

Step 7.

Ask students to work in groups to create a diagram or infographic (e.g. Piktochart) called "The new carbon cycle - more carbon, big problems". This should be a more comprehensive version of the carbon cycle that incorporates that facts about ocean acidification and its impacts.

Step 8.

Display the new diagrams around the class for discussion. Consider the following questions:

What happens when CO2 is in excess in the atmosphere?
How does CO2 relate to the greenhouse effect?
What would CO2 levels in the atmosphere be like if the oceans covered a smaller area of the planet? Why?
Make a list of organisms that will be directly affected by more acidic ocean waters.
Make a list of the organisms that will be indirectly affected by oceans with a lower pH. What might be the consequences for marine ecosystems?

Assessment/Reflection

Ask students to work through the reflection questions on the Student Worksheet.

Extension/Homework activities

1. Ask students to investigate either a marine species or a marine ecosystem in more detail, researching what the likely impacts of ocean acidification are likely to be on that species or ecosystem. Ask students to prepare a report or a poster to share their research.

2. Ask students to undertake some research into how rising ocean acidity might affect Australia: what are the social, economic and environmental impacts likely to be?

Useful resource

Image courtesy of the Commonwealth of Australia and the Climate Commission.

Earth Hour - Ocean Acidification

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