“No one expected” sounds like they didn’t talk to any coral reef biologists.
It’s been known for a long time that marine invertebrate shells are mostly made of calcium carbonate which dissolves into the water, acting as a pH buffer. Since coral skeletons are also made of calcium carbonate, corals need calcium carbonate rich water to grow.
Ocean acidification is one of the big downstream negative effects of climate change. CO2 in the air dissolves in water and becomes carbonic acid, lowering ocean pH. As the pH drops, coral reefs begin to bleach and die off. By adding large amounts of calcium carbonate rich material to the ocean, ocean acidification can be counteracted and coral reefs protected.


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