Activities

Activity 3
Experiment: How Does Climate Change Affect Seashells?

Teacher-led Classroom Activity
Science, Scientific Process, Language Arts

 

One consequence of climate change is that seawater becomes more acidic, affecting marine life in negative ways.

Note: You might want to prepare yourself for this activity by reading an excellent overview of the causes and consequences of ocean acidification from the National Oceanic and Atmospheric Administration (NOAA) here.

Objective:

Students conduct an experiment to discover how increased acidity of ocean water affects sea creatures that live inside shells.

Students will need:

• Effect of Acidic Ocean Water on Seashells data sheet, 1 per group or student
• Water; at least 4-1/4 cups, but amount will depend on size of containers and number of experiments
• Table salt; at least 3-1/2 teaspoons, but amount will depend on size of containers and number of experiments
• Measuring spoon
• Measuring cup
• Spoon(s) for stirring
• Seashells, at least 2 per student group
• Glass containers, 1 for each shell tested
• White vinegar; amount will vary depending size of shells and containers and number of experiments
• Water
• Masking tape, sticky notes, or other labels
• Markers

Suggested time:

20 minutes for discussion and setting up the experiment; two 10-minute periods for later observations and recording; 20 minutes for follow-up discussion

What to do:

1. Review with students the article “What’s Causing Climate Change?” on page 2 of their Audubon Adventures student magazine. Explain that carbon dioxide, the greenhouse gas that is one of the main causes of climate change, dissolves in ocean water. The effect of increased dissolved carbon dioxide in seawater caused by climate change is to raise the acidity of ocean water. This is happening in all oceans as well as bays and other coastal bodies of water.
2. Explain to students that they will be conducting an experiment to demonstrate the effect of increased ocean acidity on the shells of marine creatures. In the experiment, saltwater made from table salt and tap water will represent typical ocean water that does not have increased acidity caused by dissolved carbon dioxide. Vinegar, which is an acid, will be used to represent increased acidity in ocean water.
3. Combine the salt and tap water to create the “seawater” for the experiment using these equivalents: 3-1/2 teaspoons of salt to 4-1/4 cups of water. You might want to demonstrate with one batch and let students do the measuring and mixing as more is needed.
4. Divide students into groups of two or three. Distribute data sheets (one per student) and review it to make sure students understand what to do. Then distribute seashells (two for group), making sure that each group has two shells that are the same kind and similar in size and shape. Give each group two glass containers (one for each seashell per group), tape or sticky notes for labels, and markers.
5. Have students place one shell in each glass container and label one container “vinegar” and the other “saltwater.”
6. Next pour vinegar into the “vinegar” container, enough to cover the shell, and the saltwater into the “saltwater” container, enough to cover the shell.
7. Ask students to observe the containers for a few minutes. Are there any changes? They might notice bubbles forming around the shell in the vinegar, evidence that a chemical reaction is already happening. Have them record their observations on their data sheets.
8. Place all of the containers in a place where they will not be disturbed. After four hours, let students check the shells and record their observations on their data sheets. Then leave the containers overnight and have students check them again the next day. At this point they can remove the shells from the containers and test them for strength. Are there differences between the shells that were in vinegar and those that were in saltwater? Again, they should record their observations on the data sheets.
9. Bring the class together to review and discuss results of the experiment. Ask each group to report their findings. In most cases they should have observed that the shells in vinegar became weaker or more brittle.
10. Follow up with a discussion of the implications of this effect on seashells in terms of the ocean food web. Why might weaker shells be a problem? You can choose to summarize the consequences or continue the study by having students do further research. Many marine animals depend on shelled creatures for food, including seabirds and shorebirds as well as some fish. If the number of shelled creatures decreases because of their weakened shells, animals, including birds, that depend on them for food will also suffer.

Photos: Patricia Monteiro; Toyota TogetherGreen. Illustration: IngImage.com.