RENEE MONTAGNE, HOST:
For the first time, biologists have caught a rare type of coral in the act of reproducing. The scientists were then able to breed the coral in a lab. As NPR's Christopher Joyce reports, it's part of an effort to stem the decline of coral around the world.
CHRISTOPHER JOYCE, BYLINE: Coral reefs are actually colonies of tiny organisms encased in hard skeletons. Often the whole colony reproduces at once in a spectacular event called broadcast spawning. Males eject clouds of sperm into the water, then females do the same with eggs. They cross their fingers - or whatever the coral equivalent of that is - and hope for the best. Scientists have observed this before, but not with pillar coral, a rare type in the west Atlantic and Caribbean that forms columns or pillars. Kristen Marhaver says that's because their timing was off.
KRISTEN MARHAVER: For years, scientists were underwater about 30 minutes after the pillar coral spawned.
JOYCE: They were late because they were focusing on another type of coral - elkhorn. It turns out elkhorn coral spawns just after the pillar coral does. Divers were always getting suited up for the elkhorn spawning and missed what the pillar coral was doing underneath their boats. Three years ago, Marhaver and colleagues with a group called Caribbean Research and Management of Biodiversity figured that out. Eventually they nailed down the pillar coral's mating moment.
MARHAVER: Three days after the August full moon, 100 minutes after sunset.
JOYCE: So the next time they spawned, near the island of Curacao, Marhaver was in the water waiting and saw what looked like a cloud rising from the reef.
MARHAVER: They're very flamboyant. It's quite obvious what they're up to.
JOYCE: The divers frantically collected sperm and eggs - the gametes as they're called.
MARHAVER: You're running around underwater with flashlights and tarps and doing hand signals and collecting tubes, and it's beautiful to see. We screamed through our scuba regulators and snapped millions of photos and breathe our air tanks down really fast.
JOYCE: Back at the lab, the team fertilized the eggs with the sperm and bred the coral there, a first for pillar coral. Marhaver describes all this in a journal called BMC Ecology. She says the goal is to return these juvenile corals to the ocean and get them to thrive. Pillar coral isn't doing very well on its own and scientists and don't know exactly why.
MARHAVER: Bringing them together in the lab is a little bit of a way of spiking the sauce, ensuring that the gametes meet. And then we can put them back underwater and say, OK, now do your thing.
JOYCE: Corals have been doing their thing for ages, but Kim Ritchie, a marine biologist at the Mote Marine Laboratory in Florida, says they don't like surprises.
KIM RITCHIE: They're incredibly sensitive to both temperature changes and storm damage.
JOYCE: These surprises include warmer water from climate change as well as more acidic water. The acidity increases as the ocean absorbs the extra carbon dioxide that's in the air now from fossil fuels. Ritchie's part of a team of scientists that's written a plan to help coral in U.S. waters survive these changes. Many now are not. They're dying. She says besides breeding coral, scientists are trying to identify strains that are resilient and then put them back in the ocean.
RITCHIE: Take eggs and sperm from any coral and then rear them under certain conditions in the laboratory that are already challenging conditions and see which ones make it.
JOYCE: The ones that do make it would theoretically have a better chance of surviving back in the sea. Like those broadcast spawners she studies, Ritchie is hopeful.
RITCHIE: Nature finds a way, and I don't believe these corals are going to be gone. I believe they're shifting and they will adapt.
JOYCE: With a little help from their friends. Christopher Joyce, NPR News.
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