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Sensitive Shells

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Earth and Environmental Sciences

Discover the impacts of ocean acidification by observing the effect of acidity on shellfish.

Explore the impact of ocean acidification on marine organisms by completing an activity where you dip seashells (or other calcium carbonate-based substances) in vinegar. This activity also teaches about acid-base reactions.

What You Need

  • Water
  • Vinegar
  • 2 thin seashells (or egg shells)
  • 2 dishes for sand
  • 2 beakers or glasses for water and vinegar
  • pH strips
  • Pipette or eye dropper
  • Optional: print out pictures of pteropods, coral, etc.

Guide:

What To Do

48 hours before the event: Immerse a thin shell in a container of vinegar and another shell in a container of water to display to youth after the following activity:

  1. Pour water into a glass and vinegar into a different glass. Have youth test the pH of both liquids with pH strips.
  2. Put sand in two separate dishes.
  3. Add about 10 drops of water to the first dish. Observe what happens.
  4. Add about 10 drops of vinegar to the second dish. Observe what happens.

Discovery

The sand has a large concentration of calcium carbonate (CaCO3) in it. The same compound composes corals and many marine shells. Calcium carbonate is a basic compound. When water is added to the sand, you will not see a reaction take place because water is a neutral substance. However, when you add vinegar to the sand, you will see bubbles and the sand dissolving which forms holes. This is because vinegar is an acidic substance, so when it reacts with calcium carbonate, the calcium in the ocean as seawater becomes more acidic. The acidic seawater reacts with organisms' carbonate structures to dissolve them. This is why the shell in the acidic vinegar is starting to dissolve.

Ocean acidification refers to the increase in acidity (thus the decrease in pH) in the oceans. Over the past 150 years, the surface waters of the ocean have become 30% more acidic. This is because the oceans absorb carbon dioxide (CO2), a greenhouse gas, from our atmosphere and this has increased sharply over the last century due to human activities. CO2 emitted from activities such as burning fossil fuels to generate electricity or clearing forests for agriculture contributes to both global warming and ocean acidification. Increased acidity can have negative impacts on a variety of marine ecosystems.

Scientists are researching different ways to remove CO2 from our oceans to decrease its acidity. However, we can help reduce ocean acidification by reducing our own carbon footprint. Start a conversation about ways we can reduce our greenhouse gas emissions individually or as a community.

What's Happening?

The sand has a large concentration of calcium carbonate (CaCO3) in it. The same compound composes corals and many marine shells. Calcium carbonate is a basic compound. When water is added to the sand, you will not see a reaction take place because water is a neutral substance. However, when you add vinegar to the sand, you will see bubbles and the sand dissolving which forms holes. This is because vinegar is an acidic substance, so when it reacts with calcium carbonate, the calcium in the ocean as seawater becomes more acidic. The acidic seawater reacts with organisms' carbonate structures to dissolve them. This is why the shell in the acidic vinegar is starting to dissolve.

Why Does It Matter?

Ocean acidification refers to the increase in acidity (thus the decrease in pH) in the oceans. Over the past 150 years, the surface waters of the ocean have become 30% more acidic. This is because the oceans absorb carbon dioxide (CO2), a greenhouse gas, from our atmosphere and this has increased sharply over the last century due to human activities. CO2 emitted from activities such as burning fossil fuels to generate electricity or clearing forests for agriculture contributes to both global warming and ocean acidification. Increased acidity can have negative impacts on a variety of marine ecosystems.

Investigate Further

Scientists are researching different ways to remove CO2 from our oceans to decrease its acidity. However, we can help reduce ocean acidification by reducing our own carbon footprint. Start a conversation about ways we can reduce our greenhouse gas emissions individually or as a community.