Creating Coral: Keys Team Aims To Save One Species At Risk By Mixing Eggs And Sperm In Buckets

Aug 28, 2017

A few days after the August full moon, a team of divers enters the water off the Lower Keys.

They're looking to make babies. Specifically, baby pillar corals.

Corals only spawn once a year, in a timed event that scientists are still studying to figure out. In the Keys, a new project takes advantage of that spawning to collect pillar coral gametes — eggs and sperm. The gametes are mixed together in buckets, then raised in the lab.

Pillar coral populations along the Florida reef have crashed in the last five years.
Credit Karen Neely

Marine biologist Karen Neely has been studying pillar corals for the last five years. In that time, the range and the number of pillar corals along the Keys has crashed.

Pillar corals are more vulnerable than other species of hard corals, like staghorn and elkhorn. Most corals release bundles of eggs and sperm together, but pillar corals have a gender. Which means each colony releases only eggs or sperm.

"They have to get lucky and find not just another individual out in the water column, but it has to be of the opposite gender," Neely said. "We just don't think there's any natural fertilization going on in the wild. We call this species reproductively extinct, at least on the Florida reef tract."

That means "there's a very real possibility of it going regionally extinct -- without help," Neely said.

That help comes from teams of divers she organizes from Florida Keys Community College, Mote Marine Lab, the Florida Fish and Wildlife Conservation Commission, the Florida Keys National Marine Sanctuary and the Florida Aquarium.

Marine biologist Karen Neely shows the team how to use a 'coral condom' — a plastic bag clipped to a plastic ring — in a pre-dive briefing at Mote Marine Laboratory on Summerland Key.
Credit Nancy Klingener / WLRN

Neely deploys them to pillar coral sites around Looe Key Reef off the Lower Keys. That area has some of the healthiest coral left in the region.

After sunset, divers are stationed underwater at the coral heads, which were already located by GPS and marked with buoys earlier in the day. Each team has a flashlight and what is called a "coral condom." It's a big plastic bag attached with clips to a hard plastic ring.

Neely says one of her students came up with the method last year.

"We've tried lots of different things to try to catch these gametes, everything from syringes to slurp guns," she said.

As the corals release their eggs or sperm, the divers wave the genetic material into the bags. At around 10 p.m., they return to the boat and the team starts mixing the eggs and sperm together, right there.

"There's evidence with other coral species that the faster you can get those gametes together to fertilize the greater success you're going to have with fertilization," Neely said.

Pillar coral larvae are monitored in the lab as they swim around for a few days, preparing to settle on the bottom.
Credit Karen Neely

Samuel Richardson, a recent FKCC graduate, was along for the dive. He is now interning with the Coral Reef Foundation in Key Largo.

"I grew up around the ocean. Always on a boat my entire life. Always had fish tanks and had coral in them, fish, everything," he said. "Coming down here for school in 2012, I really was able to get into that love and get my hands on some coral and especially restoration."

Most coral restoration work involves the fragmenting and growing of corals in the lab, then replanting on the reef.

But the pillar coral project is even more basic, starting with the fertilization and growing the corals one polyp at a time.

Last year was the first successful collection and fertilization. The larvae swim around in the water for a few days, then settle onto the bottom. In the wild, that would be the sea floor. In the Mote Marine Laboratory on Summerland Key, they land on specially prepared settlement plates with algae to make it look like an attractive new home.

Last year was the first time pillar corals were successfully fertilized in the lab. One year later, this is one of the five surviving polyps, at Mote Marine Lab's International Center for Coral Reef Research and Restoration on Summerland Key.
Credit Dan Mele /

"We had really great fertilization rates and we ended up with about 100 settlers," Neely said. Of those, five survived the year.

"They're still smaller single polyps, about the size of a pencil eraser," Neely said. "But they represent the future of this species."