At precisely 9:47 one night last week, corals shaped like Greek columns began spawning in shallow water off North Key Largo in a place known as Pillar Coral Forest.

The cloud of milky sperm was in clear view under a nearly full moon. Six minutes later, the girl pillar corals did their part for reproduction of the threatened species, releasing little white eggs that looked stringy when clumped together.

The three state research scientists who witnessed the event while scuba diving last Saturday night would have cheered had they not had regulators in their mouths.

“We were so excited to see the girls,” said Kate Lunz, research scientist with the Florida Fish and Wildlife Conservation Commission. “We were kind of wondering if there were any girls here. But they all sort of mixed together with multiple coral colonies going off — sometimes twice.”

It was the first documented case of male and female pillar corals spawning together in Florida waters, according to the FWC.

That’s good news for the state-listed threatened species — extremely rare along the Florida reef tract, which runs from Palm Beach County to the Dry Tortugas that are 70 miles west of Key West.

“Colonies that are healthy enough to invest energy to produce eggs and sperm have the potential to reproduce,” Lunz said. “Sometimes corals are stressed and cannot sexually reproduce at all.”

The hope is that the eggs and sperm fuse in the water column and become larvae, and eventually settle as new corals.

All corals can break off a piece and re-cement themselves to the hard bottom of the ocean floor through a process known as fragmentation, but sexual reproduction offers more diversity in the population.

“Genetic diversity is good,” Lunz said. “Some genotypes are more susceptible to diseases than others.”

The slow-growing pillar coral was never abundant in Florida waters. But its numbers greatly diminished during the 1950s and ’60s, when the whitish pillars were a popular target of the curio trade.

While the collection of coral has been banned, all corals continue to face threats from disease, sedimentation and other factors.

The spawning news thrilled Bill Goodwin, resource manager for the Florida Keys National Marine Sanctuary, where it occurred.

“I was doing cartwheels,” he said. “It is one of the most beautiful sites we have in the Upper Keys.”

In 1992, Goodwin and Harold Hudson (known as the Reef Doctor) rescued 22 pillar coral colonies that were in peril of perishing after breaking off and falling into sand during Hurricane Andrew.

Had the corals fallen onto hard bottom, they might have had a chance for fragmentation, but not on the sand. Goodwin and Hudson set the fragments upright and stabilized them onto hard bottom.

The area became known as Pillar Coral Forest, one of the largest clumps of the species known in the Keys. Some are four to five feet tall, which means they are 40 to 50 years old. One colony in the center is especially large, probably the parent colony.

In the Dry Tortugas, “some of the pillar corals are huge, as tall as three meters,” Lunz said.

Unlike most corals, pillar polyps come out during the day and give a fluffy appearance. “One of my friends calls it the Muppet coral,” Lunz said.

The good news of the pillar coral spawning was tempered a bit by the lack of spawning sightings the past weekend among other types of coral.

Ken Nedimyer, founder of the nonprofit Coral Restoration Foundation in Key Largo, said his team of volunteers was disappointed they did not see any spawning of endangered elkhorn or staghorn coral offshore.

However, when the group returned home after the first night of watching for spawning at about 10:30, he discovered that coral previously collected from his pioneering nursery and put in a lab tank was doing the wild thing at 11:10 p.m.

So the next night, the group stayed out in the water until 11:30 p.m. Nothing. Once again, he discovered spawning coral back in the tank, this time at 12:30 a.m.

Lunz and Nedimyer say they plan to return to their sites during August’s second full moon to watch for more spawning.

“Maybe they are spawning really late at night on the reef and we’re just not seeing it,” Nedimyer said. “It’s odd, but this is not an exact science.”