Dangerous chemistry

The same stuff that causes global warming in the atmosphere—carbon dioxide gas—is making the oceans more acidic. The oceans absorb about half of all the CO2 produced by human activity, so the more CO2 we release, the more gets mixed in with the water. Some of that CO2 combines with water molecules to form carbonic acid. The extra carbonic acid might be unnoticeable to humans, but even slight changes in acidity levels, or pH, can affect other organisms tremendously, especially if they have shells.

Organisms from coral to clams obtain the chemicals they need to grow shells from seawater. But as the acidity of the oceans changes, these chemicals are becoming less available.
Organisms from coral to clams obtain the chemicals they need to grow shells from seawater. But as the acidity of the oceans changes, these chemicals are becoming less available.
Courtesy zeandroid