pH (acidity and alkalinity)
Seawater averages about 8.1 on a scale from 1 – 14 (1 is acidic, 14 is basic and 7 is neutral).
Seawater is a buffered system meaning it is controlled in a range.
If it gets too acidic it dissolves CaCO3, if its too basic it precipitates CaCO3
Seawater becomes slightly more acidic near the CCD (carbonate compensation depth). Animals with carbonate shells and tests need slightly basic (alkaline) water in order to precipitate and maintain their shells. This is a potentially HUGE problems for the oceans with the increasing accumulation of CO2 in the atmosphere and oceans.