ACID

http://www.clf.org/blog/?p=23

The concentration of atmospheric carbon dioxide has skyrocketed from 280 parts per million (ppm) in the mid 18th century to 385 ppm at the beginning of the 21st century. As a result of a simple chemical reaction, the ocean has absorbed approximately one third of the carbon emissions that were released into the atmosphere. While scientists believe this has shielded the upper atmosphere from the full effects of our carbon dioxide emissions, they are also cautioning that the chemistry of the ocean has and will continue to change, having long-term, serious consequences for marine life.