Light-producing properties of corals send up warning flares that the organisms are in trouble, according to a study released Tuesday by researchers with Scripps Institution of Oceanography and U.C. Berkeley.
The study, published in the journal Scientific Reports, explains how changes in coral fluorescence can alert marine researchers and ocean managers that a reef is dangerously stressed. That tip could help them avert coral bleaching, the loss of symbiotic algae that are critical for coral survival.
“It could be used like a canary in the coalmine, as a very early indication of coral stress,” said study author Melissa Roth, post-doctoral fellow at UCB and Lawrence Berkeley National Laboratory.
The study grew out of work by Dimitri Deheyn, a marine biologist with Scripps. His lab studies bioluminescence – the process by which living organisms produce light through chemical reactions. He wondered if changes in fluorescence – in which organisms absorb and then re-emit blue light – could also predict biological stress.
“If you recall the movie E.T., when E.T. was sick and trying to communicate with the light on his finger to his own species, he was unable to communicate because the light was dim,” Deheyn said. “We decided to look at whether fluorescence does the same thing.”
They found that fluorescence in branching corals dropped when the organisms endured excessive heat or cold. Those conditions can trigger bleaching and eventual reef collapse.
“Once you have those corals bleached, they are already under severe conditions of stress, and the likelihood that they come back is limited,” Deheyn said.
Fluorescence begins to fade before bleaching advances, giving researchers a brief lead time to protect sections of a reef with tarps, or to address other problems – such as pollution or dumping – that might also weaken the coral.
Corals have declined worldwide because of pollution, over-fishing, climate change and ocean acidification, the study stated, noting the high stakes for their preservation.
“Coral reefs are not only one of the most diverse and productive ecosystems in the world, but also provide economic goods and ecosystem services valued at almost 400 billion a year,” it stated.