How Do You Measure the Acidity (pH) of the Ocean?

Description: In a chemistry lab, you determine how acidic or basic something is by using the pH scale. The scale ranges from 0 to 14 with 7 considered neutral, as is the case with plain water. Anything below a pH of 7 is an acid, and anything above 7 is a base, or alkaline. What makes a solution more acidic is the presence of positively charged hydrogen ions (H+), and conversely the presence of negatively charged hydroxide ions (OH-) makes it more basic. But these measurements don’t just apply to liquid solutions in beakers and flasks in a lab. The biggest water source on Earth, the ocean, has a pH too — and its pH is extremely important to our planet’s ecosystem. The average pH of the surface water in the ocean is 8.1. Ocean water is more basic than drinking water because the presence of other weak acids and their associated bases known as buffers causes the ocean to resist changes in pH. Different instruments, ranging from hand-held devices to large sensors mounted on ships, measure the acidity of ocean water, by either measuring the amount of positively charged hydrogen ions in the liquid or detecting the color of a pH-sensitive indicator dye added to the solution.