Summary
Dissolved CO2 forms carbonic acid, lowering seawater pH and making it harder for shell builders to form calcium carbonate.
In depth
Surface pH fell from about 8.2 to 8.1, a 30 percent rise in H+. Lower carbonate ion availability makes calcification harder for corals, pteropods and oysters. Effects on fish behaviour were reported.
Chemistry: CO2 + H2O gives carbonic acid, which releases H+ and lowers carbonate. Aragonite saturation falls in cold waters first. Effects on larval stages are strong.
Example: pteropods show shell dissolution in Southern Ocean.
The ocean absorbs about 25 to 30 percent of human CO2 emissions. CO2 reacts with water to form carbonic acid, which releases hydrogen ions, lowering pH and reducing carbonate ion concentration. Surface pH has fallen from about 8.2 to 8.1, a 30 percent increase in acidity, since the industrial revolution.
Shell- and skeleton-building organisms such as corals, oysters, pteropods and some plankton need carbonate to make calcium carbonate; lower saturation makes this harder and shells can dissolve. It can also affect fish behaviour and sensory function.
Example: oyster hatcheries in the US Pacific Northwest lost larvae to corrosive water.
Common mistake: the ocean is still slightly basic; it is becoming less alkaline.
Frequently asked questions
What is Ocean Acidification?
Dissolved CO2 forms carbonic acid, lowering seawater pH and making it harder for shell builders to form calcium carbonate.
Which area of biology covers Ocean Acidification, and how advanced is it?
Ocean Acidification is one of the 54 topics in Marine & Environmental Biology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Oceans, Global Warming, Coral Reefs.
Can you give an example of Ocean Acidification?
Oyster hatcheries in the US Pacific Northwest were hit by acidified water.
What should I learn before Ocean Acidification?
Work through the Beginner topics in Marine & Environmental Biology first, such as Oceans, Ocean Zones, Plankton, then return to Ocean Acidification. Intermediate topics assume the Beginner vocabulary.
What topics are related to Ocean Acidification?
The closest topics to Ocean Acidification are Oceans, Global Warming, Coral Reefs, Acid Rain. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Ocean Acidification?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Ocean Acidification. To practise the whole of Marine & Environmental Biology, use the Marine & Environmental Biology quiz.
How is Ocean Acidification different from Oceans?
Ocean Acidification: Dissolved CO2 forms carbonic acid, lowering seawater pH and making it harder for shell builders to form calcium carbonate. Oceans: Salt water covering about 71 percent of Earth, home to most of the planet's living space. Read both side by side and note what each one explains.
What is a common mistake about Ocean Acidification?
The ocean is still slightly basic; it is becoming less alkaline.
How should I study Ocean Acidification step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Oceans and explain the difference aloud. Finally, take the Marine & Environmental Biology quiz and come back to this page for any question you miss.