35th Anniversary logo for Friends of Casco Bay



pH is a measure of how acidic the seawater is. As more carbon dioxide is absorbed by the ocean from the burning of fossil fuels and the decomposition of marine plants, the pH of the water drops, becoming more acidic. Ocean acidification threatens the ability of marine life such as clams, mussels, and oysters, to grow healthy shells. Pure fresh water has a pH of 7; typically, seawater pH is between 7.5 and 8.4.