Ocean acidification facts for kids

Ocean acidification means the ocean's pH is dropping. This makes the water more acidic.

Ocean acidification is when the Earth's ocean becomes more acidic. This happens because its pH level goes down. Since the 1750s, the average pH of the ocean surface has dropped from about 8.25 to 8.14. This small change means the ocean waters are becoming more acidic.

Why the Ocean is Changing

The main reason for ocean acidification is the carbon dioxide emissions from human activities. Our oceans absorb a lot of CO₂ from the air. When CO₂ dissolves in seawater, it forms carbonic acid (H₂CO₃).

This carbonic acid then breaks down. It creates bicarbonate ions (HCO−
3) and hydrogen ions (H⁺). These extra hydrogen ions (H⁺) make the ocean water more acidic, which lowers its pH.

This picture shows how ocean acidification happens.

As the ocean's pH drops, the amount of carbonate ions also decreases. Carbonate ions are super important. They are the main building blocks for the shells and skeletons of many sea creatures. This includes animals like mollusks, oysters, and corals.

Other things can also affect how much CO₂ the ocean absorbs. These include ocean currents, how close the area is to big rivers, and how much sea ice there is. Air pollution from burning fossil fuels and farming can also play a role.

What are the Dangers?

When the ocean's pH drops, it can harm or even kill many marine animals. It can also destroy marine ecosystems. These ecosystems are vital because they provide food and jobs for many people. For example, about 1 billion people depend on coral reefs for fishing, tourism, and coastal protection.

If ocean acidification continues, it could threaten the food chains in the ocean. This would affect the food supply for people around the world.

The United Nations has a plan called Sustainable Development Goal 14. It focuses on "Life below Water." One of its goals is to "minimize and address the impacts of ocean acidification."

How Can We Stop It?

Right now, seawater is not acidic. But if humans keep releasing greenhouse gases into the air, ocean life will be in serious danger. The best way to fix this problem is to reduce how much carbon dioxide we put into the atmosphere. This can help reverse the damage.

Ocean acidification has happened before in Earth's history. Those past events caused major problems for ocean life. They also had long-lasting effects on the climate.

Images for kids

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  Estimated change in seawater pH caused by human impact on CO₂ levels between the 1700s and the 1990s.

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  NOAA shows evidence of "acidified" water rising onto the Continental Shelf.

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  The CO₂ cycle between the atmosphere and the ocean.

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  This map shows changes in aragonite saturation in ocean surface waters. Aragonite is used by marine animals to build shells.

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  A detailed diagram of the carbon cycle within the ocean.

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  What causes hypoxia and ocean acidification in upwelling shelf systems.

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  A demonstrator calling for action against ocean acidification.

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  Ocean acidification: average seawater pH.

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  "Present day" (1990s) sea surface pH.

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  Present day alkalinity.

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  "Present day" (1990s) sea surface human-made CO₂.

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  Vertical inventory of "present day" (1990s) human-made CO₂.

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  Change in surface CO2−
  3 ion from the 1700s to the 1990s.

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  Present day DIC.

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  Pre-Industrial DIC.

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  A NOAA (AOML) CO₂ sensor used for ocean acidification studies near coral reefs.

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  A NOAA (PMEL) buoy used for measuring CO₂ and studying ocean acidification.

See also

In Spanish: Acidificación del océano para niños