ocean chemistry

To survive in the ocean, soft-bodied organisms must possess one of five traits: big teeth, toxic flesh, invisibility, quickness or a hard shell. Most marine organisms that employ the latter, called calcifiers, build their hard shells from the mineral calcium carbonate. However, increasing atmospheric carbon dioxide levels are making the oceans more acidic — which, in turn, is reducing the concentration of carbonate ions dissolved in seawater that organisms use to build their protective shells and skeletons.

The ocean’s surface waters contain many more microorganisms than fish — and so for years, the carbonate-shelled microorganisms were thought to be the main contributor to the carbonate chemistry in deep ocean waters. Now, new research suggests that the tiny pellets that most bony fish produce in their guts can affect the chemistry of the oceans.