Gases

Dissolved gases in seawater help make life possible. In this topic, you learned about the three main gases in seawater: carbon dioxide, oxygen and nitrogen.

The abundance of oxygen in surface waters occurs as a by-product of photosynthesis and through diffusion from the atmosphere. Carbon dioxide plays an important role in seawater as carbonic acid, which breaks down into hydrogen ions and bicarbonate ions. Hydrogen ions control the acidity of the seawater. Finally, although most life forms in the ocean require nitrogen, they must rely on other organisms to "fix" atmospheric nitrogen gas into a usable form.