Corals May Get Help Adapting to Warmer Waters

The task of mapping reef areas that are both most resistant and most vulnerable has taken on urgency among scientists. Palumbi and his colleagues are preparing to publish their map of both current and future locations of heat-tolerant algae worldwide, and Wildlife Conservation Society senior zoologist Tim McClanahan has mapped the vulnerability of Indian Ocean reefs to climate change. McClanahan discovered that many of the marine protected areas cover reefs that could disappear under warmer conditions, prompting him to push for additional protection in areas where the reefs are hardier.

Just last week, moreover, a group of researchers led by Benjamin S. Halpern at the National Center for Ecological Analysis and Synthesis in Santa Barbara, Calif., published a synthesis of 17 global data sets that concluded that nearly half of all coral reefs are experiencing "medium high to very high impact" from human pressures, including temperature increases, pollution and overfishing.

In the meantime, Baker -- who first broached the idea that corals might switch algae partners on their own in a 2001 article in the journal Nature -- is hoping to reverse the trend. He keeps 12,000 coral tissue samples from 20 countries in his lab at Miami's Rosenstiel School of Marine and Atmospheric Science, freezing them at 176 degrees below zero, and has spent several years culturing them and studying their properties. In the scientific literature the thermally resistant species of zooxanthellae Baker first identified goes under the name "clade D"; in conversation he calls these algae "sort of the weeds that do well when others don't."

Two weeks ago the Pew Institute for Ocean Science awarded him a three-year, $150,000 grant to help identify the specific genetic and physiological factors that allow some corals to cope with warming better than others.

Initially, Baker and his team of about 10 researchers will do their work in the lab, artificially bleaching corals and then adding cultured algae to the water to see if other zooxanthellae varieties can help the corals adapt to the temperature shift. Corals do not expire immediately after expelling their zooxanthellae, but if they do not find another algae partner quickly enough, they will die.

In another set of experiments, the scientists plan to inject thermally resistant algae into the polyps that allow corals to reproduce. If these two trials succeed, they will try injecting these zooxanthellae into the oldest and largest coral colonies that produce the most larvae.

Ellen Pikitch, executive director of the Pew Institute for Ocean Science, said her group chose Baker's project because it offers the promise of preserving some of the world's most valuable corals.

"Reefs are under siege from many threats, but climate change is among the most serious risks to their survival," Pikitch said. "Dr. Baker's work gives us hope that the oldest corals might be saved."

Several experts, including Palumbi and Baker, caution that the experiment could fail. The process of exchanging algae partners is an evolutionary adaptation that has taken place over thousands of years, they say, and it remains unclear whether human engineering can accelerate that process.

"Yes, it might be doomed to failure," Baker said, adding that he has no choice but to try. Otherwise, he said, "We, as scientists, are sort of rearranging deck chairs on the Titanic."