Courtesy of Andrew Baker, Wildlife Conservation Society
Rutgers University scientists have identified a physiological mechanism behind the bleaching that has affected coral reefs worldwide over the past three decades. Bleaching follows a rise in sea temperature, and it involves the ejection by coral polyps of symbiotic, photosynthetic algae from their tissues. Led by Paul Falkowski, professor of biological oceanography, the study finds that the melting of the fatty acid-based thylakoid membrane of the algal chloroplasts triggers this event.
"As you raise the temperature, the membrane starts to fall apart," says Falkowski. "They spew out reactive oxygen species right into the animal cells, [which] view this as an attack and expel the algae." Andrew Baker, a marine biologist with the Wildlife Conservation Society, says that superoxide radical production and damage to photosystem II have long been associated with coral bleaching. This paper, he says, "succeeds in unifying all that into a convenient theory."
Falkowski suggests that differences in thylakoid fatty-acid saturation and, therefore, temperature sensitivity between symbiont taxa might be used to predict bleaching vulnerability. He also raises the possibility of genetically engineering symbiont lipid composition to prevent bleaching events should sea temperatures continue to rise.
- Stuart Blackman