pH is a measure of the relative acidity of the water. Hawai‘i's aquatic species have evolved to thrive within a narrow range of pH (~6.5-8.5). When the pH is outside of this range, native species have trouble competing with hardier, introduced species. Changes in pH can also activate toxic chemicals in the water and hinder reproduction in certain organisms.
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Water Quality
pH :
pH is a measure of how acidic a substance is. Acidity is caused by hydrogen ions in a liquid, with more hydrogen ions making the liquid more acidic. However, the concentration of hydrogen ions can range from just a few ions per litre to many billions of ions per litre of liquid, so the pH scale has been designed to make the numbers a bit more manageable. pH numbers range from 1 to 14, with 1 being very acidic, and 14 being very "alkaline", with neutral solutions (such as distilled water) having a pH of 7 (ref).