Turns out that, before they die from overheating, corals glow brightly—a fluorescent signal that could help scientists sense the health of a reef.
Warming water causes the algae that live in (and provide food for) corals to abandon ship, leaving the corals with no food source—a process called coral bleaching. These algae (zooxanthellae) usually mask the corals’ natural fluorescent glow. But when they’re driven out, the corals true colors shine bright: a swan song before their inevitable death.
"Like a supernova before a star’s final collapse, the corals send out a steady stream of intense glow just before their inevitable demise," wrote Rachel Nuwer at Smithsonian.com.