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Ocean acidification facts for kids

Kids Encyclopedia Facts
Ocean acidification means that the average ocean pH value is dropping over time.

Ocean acidification is the reduction in the pH value of the Earth’s ocean. Between 1751 and 2021, the average pH value of the ocean surface has decreased from approximately 8.25 to 8.14. That means that the waters of the ocean have become more acidic.


The main cause of ocean acidification is carbon dioxide emissions from human activities. The oceans absorb CO2 from the atmosphere. This leads to the formation of carbonic acid (H2CO3). It dissolves, breaking into a bicarbonate ion (HCO
) and a hydrogen ion (H+). The free hydrogen ions (H+) decrease the pH of the ocean, therefore increasing acidity.

Ocean Acidification Infographic
Ocean acidification infographic

As pH decreases, the concentration of carbonate ions is also decreasing. Carbonate ions are the main building block for shells and skeletons of many Marine organisms, like mollusks, oysters and corals.

Other factors that affect the atmosphere-ocean CO2 exchange and impact local ocean acidification, are: ocean currents, proximity to large continental rivers, sea ice coverage, and atmospheric exchange with nitrogen and sulfur from fossil fuel burning and agriculture.

Potential risks

Decreased ocean pH can kill many marine organisms and destroy marine ecosystems that provide food, livelihoods, and other ecosystem services for a large portion of humanity. Some 1 billion people are wholly or partially dependent on the fishing, tourism, and coastal management services provided by coral reefs. Ongoing acidification of the oceans may therefore threaten future food chains linked with the oceans.

The United Nations Sustainable Development Goal 14 ("Life below Water") has a target to "minimize and address the impacts of ocean acidification".

How to stop ocean acidification

Seawater is not acidic yet. However, if humans continue to emit greenhouse gases into the atmosphere, ocean life will be in severe danger. The only solution is to reduce carbon dioxide emissions. This can reverse the situation.

Ocean acidification has occurred previously in Earth's history. The resulting ecological collapse in the oceans had long-lasting effects on the climate.

Images for kids

See also

Kids robot.svg In Spanish: Acidificación del océano para niños

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