"Coral reefs are like the rain forests of the oceans -- the consequences will be catastrophic if coral reefs are lost in great numbers," said Backman, who invented the optical technique used by the team. "Corals are also optical machines. By identifying how much light the skeletons of individual coral species reflect, we have learned which species are more resilient under stress."
Algae provide nutrients to the corals and receive shelter and light for photosynthesis in return. When stressed, the corals can lose their algae. The corals often die of starvation shortly afterward, exposing their white skeletons.
The team used LEBS to measure light transport and light amplification inside the skeletons of 96 different coral species. How fast the light amplification increases with the loss of algae depends on the light transport at the microscale. This was impossible to measure until Backman's low-coherence enhanced backscattering (LEBS) technique became available, which is one of the reasons why this phenomenon has never been studied before.
The specimens were from long-held collections of corals from the Field Museum, including dozens retained from the original Chicago Columbian Exposition and World's Fair of 1893, and the Smithsonian Institution.
The researchers created a family tree of corals that showed bleaching is associated with the physics of light scattering across the entire evolutionary history of corals. Living reef corals are thought to have originated about 220 million years ago, and corals living today are descendants of various branches of these older lineages.
"We found that bleaching and light scattering are associated across the history of reef corals," Westneat said. "T
|Contact: Megan Fellman|