Elevated C02 Enlarges Inner Ears Of Fish

June 26, 2009

Release from: United Press International

SAN DIEGO - The inner-ear bones of fish grow larger as a result of higher carbon dioxide levels in the ocean, University of California researchers say.

The finding, published July 26 in the journal Science, found the fish themselves did not grow larger, only the inner-bone, called the otolith.

Researchers at the Scripps Institution for Oceanography at the University of California, San Diego, say their study marks the first known case of higher carbon dioxide levels affecting the fundamental structure of fish. Otoliths, the researchers say, play a vital role because they help fish stay upright and navigate, both essential to their survival.

The study compared white sea bass in water with normal and high levels of carbon dioxide.

The results surprised researchers, who said they had thought, if anything, the higher carbon dioxide levels would have reduced the size of the otolith.

It's too early to predict the implications, the researchers say.

"But fish have evolved to have their bodies the way they are," David Checkley, the study's lead author, said in a release.

"The assumption is that anything that departs significantly from normality is an abnormality, and abnormalities at least have the potential for having deleterious effects."

In May, U.S. marine scientists said they have discovered that rising levels of atmospheric carbon dioxide threaten shellfish populations in many ecosystems.