pH of ocean surface water is normally 7.5.to 8.5 pH.
Over the years however, acidification tendency is to decrease 0.1 to 0.2 pH units/century. Acidification is a consequence of carbon dioxide (CO₂) absorption in seawaters and oceans. Carbon dioxide reacts with seawater to produce carbonic acid (H₂CO₃).
pH modifications affect marine life growth, reproduction, and communication. Hydrogen ions have a tendency to bond with carbonate to form bicarbonate. The greater attraction to carbonate over calcium can adversely affect skeleton building and can limit coral growth.