Why is this reef thriving in acidic water?

Though coral reefs cover less than 1 percent of the ocean, they are ecosystems that are home to at least one-fourth of all marine life. Researchers want to know why coral reefs in the Pacific Ocean are so healthy despite very high acidification levels. (Credit: Hannah Barkley/Woods Hole Oceanographic Institution)

A large reef in the far western Pacific Ocean seems to be defying all odds and thriving in high levels of acidification, says a team of international researchers.

The team examined eight coral reefs in the Palauan archipelago and found high levels of acidification within the lagoons and inlets of the Palau Rock Islands. But despite the high levels, the Rock Island coral reefs appear to be extremely healthy.

“Ocean acidification is happening in every ocean everywhere on Earth.”

“Based on lab experiments and other studies, this is the opposite of what we expected,” says Hannah Barkley of the Woods Hole Oceanographic Institution.

“Ocean acidification is happening in every ocean everywhere on Earth,” says Kathryn Shamberger of Texas A&M University. “We do know that adding carbon dioxide to the atmosphere from burning fossil fuels and deforestation contribute to higher acidification levels.

“It is very important for us to understand how coral reefs around the world will respond to continuing ocean acidification and places like Palau with natural acidification provide valuable clues.”

‘Looks like Swiss cheese’

The researchers found that acidification levels in the Palau Rock Islands are as high now as the open ocean is projected to be by the end of this century. They detail their findings in the current issue of Science Advances.

“The reefs appear healthy, but they have high levels of bioerosion, which occurs when organisms like mollusks and worms bore into the reef and break it down,” says Shamberger.


“We see coral skeletons that are eaten up and have holes on top and the sides. The coral almost looks like Swiss cheese because of the volume that has been removed,” says Barkley.

“But the reefs appear to be thriving despite acidification and bioerosion, and we want to understand why,” says Shamberger.

The team says that the acidification process in Palau is a natural one, due to a combination of biological activity and the slow flushing of water through the Rock Island lagoons that allows acidification levels to build up over time.

The National Science Foundation, the Dalio Foundation Inc., the Tiffany & Co. Foundation, the Nature Conservancy, and the WHOI Access to the Sea Fund helped support the project.

Source: Texas A&M University