Ocean Acidification
Introduced| English | Meaning |
|---|---|
| ocean acidification/ˈəʊʃn əˌsɪdɪfɪˈkeɪʃn/ | A sustained decrease in ocean pH, driven mainly by uptake of atmospheric carbon dioxide; the water need not become acidic overall. |
| carbonic acid/kɑːˈbɒnɪk ˈæsɪd/ | The weak acid formed when carbon dioxide reacts with water, in equilibrium with hydrogen and hydrogencarbonate ions. |
| carbonate/ˈkɑːbəneɪt/ | A salt containing the carbonate ion, CO₃ with a two-minus charge. |
| pH/piː eɪtʃ/ | pH |
The other CO2 problem
- We know extra CO2 warms the air.
- But the ocean absorbs a lot of that CO2 too.
- Dissolved in seawater, CO2 turns the ocean more acidic.
- This is ocean acidification 海洋酸化.
How the acid forms
- CO2 from the air dissolves into the surface water.
- There it combines with water to form carbonic acid 碳酸.
- This is a weak acid, but there is a lot of it.
- More CO2 in the air means more acid in the sea.
Dissolved CO₂ produces H⁺, leaving less carbonate 碳酸盐 for shells
Ocean acidification is caused by the ocean absorbing extra…
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The ocean absorbs extra carbon dioxide, which reacts with water to form acid.
The pH drops
- Acid lowers the water's pH 酸碱度.
- The ocean is still slightly basic, but less than before.
- Even a small pH drop is a big chemical change.
- The surface ocean is now measurably more acidic than a century ago.
How CO2 acidifies the ocean
Follow carbon dioxide into the sea, where it forms acid and dissolves shells.
When CO2 dissolves in seawater, it forms…
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CO2 plus water makes carbonic acid, so more CO2 means a lower (more acidic) ocean pH.
Acidic water makes it hard for animals to build shells out of calcium ____.
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Shells and coral are made of calcium carbonate, which dissolves more easily in acidic water.
Shells and coral struggle
- Many sea animals build shells from calcium carbonate.
- Acidic water makes carbonate harder to get, and dissolves shells.
- Corals, clams, and tiny plankton are all at risk.
- Since plankton feed the ocean, the whole food web is threatened.
Ocean acidification threatens shellfish, corals, and the tiny plankton at the base of food webs.
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Anything that builds a calcium carbonate shell is at risk — including plankton that feed the whole ocean.
Select all true statements about ocean acidification.
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Absorbed CO2 lowers pH and harms shelled life. It makes the ocean more acidic, not more basic.
Ocean acidification is often called "the other CO2 problem" — a separate crisis from warming, caused by the same gas. The ocean does us a favour by absorbing CO2 (slowing warming), but pays for it by turning acidic. And it hits the base of the food web hardest: the tiny shelled plankton that everything else eats. Two problems, one cause — cutting CO2 solves both.
A clam in a changing sea:
- Extra carbon dioxide dissolves into the water and forms carbonic acid, lowering the pH.
- The clam tries to build its shell from calcium carbonate, but the acidic water keeps dissolving it faster than it can grow.
- Across the reef, corals weaken and plankton shells thin — and every fish that eats them feels it too.
Ocean acidification happens when the sea absorbs extra carbon dioxide, which forms carbonic acid and lowers the ocean's pH. The more acidic water makes it hard for corals, shellfish, and plankton to build shells from calcium carbonate. Because plankton are the base of the food web, it threatens ocean life broadly. It shares one cause with warming: CO2.