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What is ocean acidification? Plain-English meaning
Ocean acidification is the ongoing process by which the ocean becomes less alkaline (its pH decreases) as it absorbs carbon dioxide from the atmosphere, changing the chemistry of seawater.
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Definition
Ocean acidification is the ongoing process by which the ocean becomes less alkaline (its pH decreases) as it absorbs carbon dioxide from the atmosphere, changing the chemistry of seawater.
Also seen as: acidification of the ocean, decreasing ocean pH
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- Last updated
- September 7, 2026
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- Science & Nature
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Plain-English explanation
The ocean naturally absorbs carbon dioxide from the air. When carbon dioxide dissolves in seawater, it forms a weak acid, which lowers the water's pH, making it less basic (or more acidic). This change in chemistry can affect marine life, especially organisms that build shells or skeletons from calcium carbonate. Ocean acidification is different from global warming, though both are driven by the same carbon dioxide emissions. It is a gradual but measurable shift in the fundamental chemistry of the ocean.
Why it matters
You should understand ocean acidification because it affects the health of the oceans, which drive weather and climate and support billions of people who rely on seafood. It can harm shellfish, corals, and other marine animals, which may disrupt food webs and coastal economies. Even if you live far from the coast, the ocean's ability to absorb carbon dioxide influences the pace of climate change.
Concrete example
Imagine a coral reef. Corals build hard skeletons from calcium carbonate. As the ocean absorbs more carbon dioxide, the water becomes slightly more acidic, making it harder for corals to build and maintain their skeletons. Over time, reefs can become weaker and more vulnerable to erosion and storm damage, affecting the fish and other life that depend on them.
Often confused with
People sometimes confuse ocean acidification with ocean warming or climate change. They are related because both are caused by increased carbon dioxide in the atmosphere, but they are different processes. Ocean warming is the increase in ocean temperature, while ocean acidification is a change in seawater chemistry (lower pH). They can both harm marine life but through different mechanisms.
Short definition: Ocean acidification is the ongoing process by which the ocean becomes less alkaline (its pH decreases) as it absorbs carbon dioxide from the atmosphere, changing the chemistry of seawater.
Plain-English explanation
The ocean naturally absorbs carbon dioxide from the air. When carbon dioxide dissolves in seawater, it forms a weak acid, which lowers the water's pH, making it less basic (or more acidic). This change in chemistry can affect marine life, especially organisms that build shells or skeletons from calcium carbonate. Ocean acidification is different from global warming, though both are driven by the same carbon dioxide emissions. It is a gradual but measurable shift in the fundamental chemistry of the ocean.
Why it matters
You should understand ocean acidification because it affects the health of the oceans, which drive weather and climate and support billions of people who rely on seafood. It can harm shellfish, corals, and other marine animals, which may disrupt food webs and coastal economies. Even if you live far from the coast, the ocean's ability to absorb carbon dioxide influences the pace of climate change.
Concrete example
Imagine a coral reef. Corals build hard skeletons from calcium carbonate. As the ocean absorbs more carbon dioxide, the water becomes slightly more acidic, making it harder for corals to build and maintain their skeletons. Over time, reefs can become weaker and more vulnerable to erosion and storm damage, affecting the fish and other life that depend on them.
Common confusion
People sometimes confuse ocean acidification with ocean warming or climate change. They are related because both are caused by increased carbon dioxide in the atmosphere, but they are different processes. Ocean warming is the increase in ocean temperature, while ocean acidification is a change in seawater chemistry (lower pH). They can both harm marine life but through different mechanisms.
Related terms
carbon dioxide, pH, calcium carbonate, marine ecosystems, climate change
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More context
Ocean acidification rates are faster today than at any time in the last 300 million years, according to geological studies. It affects not only marine life but also human economies, particularly shellfish aquaculture and coral reef tourism. Some marine organisms may adapt over generations, but the current pace of change is too rapid for many species to evolve quickly enough.
Sources and further reading
- Earth's MoonThe Moon is Earth's natural satellite in the solar system, and its gravity drives ocean tides.
- Earth ScienceEarth science covers weather, oceans, earthquakes, and climate, and satellites observe Earth from orbit.
- Ocean FactsOceans cover most of Earth, drive weather and climate, and are studied with ships, buoys, and satellites.
- NOAA Ocean and Weather ResourcesNOAA explains oceans, ocean currents, tides, climate, weather forecasts, clouds, rain, snow, and wind patterns.