Ocean acidification is the decrease in the pH of the Earth's oceans,
caused by the uptake of carbon dioxide from the atmosphere. The main cause
of ocean acidification is the burning of fossil fuels.
The uptake of anthropogenic carbon occurs through the injection of carbon
dioxide and causes a shift in the distribution of carbon species (i.e.,
the balance between carbon dioxide, carbonate and bicarbonate). The
availability of carbonate is particularly important because it controls
the maximum amount of carbon dioxide that the ocean is able to absorb.
Marine organisms use carbonate to produce their shells.