What is pH and Why is It Important? pH is a scale that measures how acidic or basic the water is and ranges from 0 to 14. A pH of 7 is neutral, while values below 7 are acidic and values above 7 are basic. Each whole pH value (for example 7 to 8) represents a tenfold change in acidity or basicity. Typical open ocean pH is 8.2 to 8.1, whereas coastal and estuarine pH is lower, typically around 7.9.
Organisms can not survive when pH is too low or too high. When pH gets too low, or acidic, for organisms, biological functions such as reproduction, shell or skeleton formation, and growth can decrease or stop altogether.