Oysters and other marine creatures could find forming their shells difficult in the future if ocean acidification continues.

According to Wei-Jun Cai, a professor of marine sciences in the University of Georgia Franklin College of Arts and Sciences, increased acidification in coastal waters could affect the ability of shellfish to form and keep their shells.

Water acidification occurs when the amount of oxygen in the water decreases and the dissolved carbon dioxide reacts with water, forming acid.

Cai said fertilizer runoff that goes into coastal waters, as well as excess carbon dioxide released by burning fossil fuels absorbed from the air at the ocean’s surface, contribute significantly to the ocean’s acidity.

As the ocean becomes more acidic, sea creatures that form carbonate shells or skeletons, such as oysters and corals, will find it harder to produce and maintain them.

Cai and his co-workers warned that if the acidity of coastal waters continues to increase, shellfish won’t be able to form shells by the end of the century.

“Many of our fisheries resources, especially shellfish, are concentrated in areas where rivers discharge onto the coast, like the northern Gulf and the East China Sea, and thus are at risk,” said James T. Hollibaugh, UGA Distinguished Research Professor of marine sciences.

Hollibaugh, who collaborated with Cai on the project, added that there are likely ramifications for fish and animals further up the food chain that depend on the shellfish.

Though the researchers focused mainly on the Gulf of Mexico coastal waters, they found similar results in the largest river in Asia, the Changjaing (Yangtze) River, making them conclude that their findings can be extended globally.

In order to reduce water acidification, Cai and his colleagues recommend farmers to better manage their fertilizer use and for societies to limit their fossil use.

In the future, the researchers will explore seasonal patterns of acidification and its influence on the coastal ecosystem.