Global warming's 'evil twin': acid oceans

Coral reef
An aerial view of Vlassof Cay in the Great Barrier Reef off Australia: Coral is threatened by increasing carbon levels in the oceans.
Mark Kolbe/Getty Images

Ocean scientists have been warning for years that the increase of carbon dioxide emissions is causing profound changes in not only the atmosphere but the earth's oceans as well.

"Evidence gathered by scientists around the world over the last few years suggests that ocean acidification could represent an equal — or perhaps even greater threat — to the biology of our planet than global warming," wrote Prof. Ove Hoegh-Guldberg of the University of Queensland in a report quoted by Science Daily in 2010.

The National Oceanic and Atmospheric Administration warns that "by the end of this century the surface waters of the ocean could be nearly 150 percent more acidic, resulting in a pH that the oceans haven't experienced for more than 20 million years."

Ocean acidification presents a serious threat to the ocean's ecosystems, notably to coral and shellfish. Woods Hole Oceanographic Institute explains that "Acidification can affect many marine organisms, but especially those that build their shells and skeletons from calcium carbonate, such as corals, oysters, clams, mussels, snails, and phytoplankton and zooplankton, the tiny plants and animals that form the base of the marine food web."

How healthy are the world's oceans? What's being done to conserve them, and is it enough?