Preparing for Possible Coral Extinctions, Columbus Dispatch, 10/03/06
By Mike Lafferty
Source: Columbus Dispatch
It’s pitch black off the southwestern coast of Puerto Rico as Mike Brittsan drifts in the warm current 20 feet below the waves.
The only light comes from a flashlight he has trained on a patch of coral.
For two nights, the Acropora palmate has done absolutely nothing, defying Brittsan and the other biologists who have gathered, waiting for this odd animal to reproduce.
Then, with no warning, the elkhorn coral comes alive and releases enormous bundles of sperm and eggs.
"The coral, they’re all going off," said Brittsan, an aquatic biologist at the Columbus Zoo and Aquarium.
"I’ve seen a lot of things in my career, but this was the coolest."
Brittsan assembled the U.S. portion of an international scientific team focused on saving this species, which has suffered 90 percent losses in the Caribbean.
This release gives them hope.
"It’s pretty amazing to see this," said Mark Schick, a biologist with the Shedd Aquarium in Chicago.
"It’s perfectly clear, then a few pink globes start to appear. Then in 10 minutes, it’s like a snowstorm underwater."
The divers don’t have enough arms, nets or time to collect a fraction of the milky cloud floating above the reef.
Brittsan pushes his capture net through the water and kicks his legs to keep from drifting.
"We looked like people trying to catch butterflies," he said.
The nets are about 16 inches wide at the mouth and 2 feet long. Each has a small bottle attached at the closed end to collect the sperm and eggs.
Later, on the beach, the contents of the bottles are mixed to ensure genetic diversity when sperm and eggs finally unite.
Over several nights, the biologists gather enough material to produce more than 1 million elkhorn larvae.
The hope is that the tiny embryonic coral they capture can be grown to maturity in zoos and research centers and eventually returned to the sea.
In some coral species, egg and sperm unite before being released in the water. Elkhorn coral, however, broadcast huge amounts of sperm and eggs to overcome predators that gather to feast at spawning time.
After egg and sperm unite in the water, the embryo immediately begins dividing. Some groups of cells sink to the reef; others travel on ocean currents for miles.
They are choosy about where they settle. "If they like the spot, they’ll turn into a polyp and start to form coral. If they don’t like it, they can reversemetamorphose and turn back into a larva and look for a better spot," Brittsan said.
Perhaps one in 10,000 survive.
Brittsan and scientists at other zoos and aquariums must learn to mimic the ideal coral environment to coax their elkhorn to grow. About 15 aquariums and research organizations are paying for the effort.
There has been success with collecting coral pieces and growing them in the lab (a process called cloning), but sexual reproduction is trickier. At the Columbus Zoo, Brittsan has been growing the coral Pocillipora damicornis from larvae for 14 years. He said he will use this experience to raise the elkhorn larvae.
"Water movement is very important to a species like this. They live where waves are crashing. Light is very important," Brittsan said. "If you don’t have a water-filtration system, these little things will defecate themselves to death."
The rescue effort is a sign of the crisis facing coral, said Gerald Bakus, a researcher at the University of Southern California.
"I’ve watched things get worse for 35 years," he said.
More than 60 percent of the world’s coral is threatened by human activity, especially soil erosion from deforestation that pollutes water.
At the elkhorn coral reef where Brittsan and the other researchers worked, sediment from streams a few miles from the ocean limited visibility to about 20 feet.
Elkhorn grows long, treelike arms that makes it prone to vandalism from scuba divers and damage from pleasure-boat propellers.
Storms that rake the shallow reefs also take a toll, although the coral has evolved with this natural process. Pieces that are swept away often settle in new spots and establish reefs.
It’s an efficient way to spread when conditions are right. Elkhorn, staghorn and other relatives have used storms to spread across the Caribbean for 2 million years. This is the same as cloning in the lab.
The trade-off for this success is genetic diversity.
"When environmental changes occur, you’ve lost that diversity, so a species does not have so many chances of having (genetically different) individuals that can adapt to new conditions," said Dennis Hubbard, a marine geologist and Caribbean coral expert at Oberlin College, southwest of Cleveland.
On top of all the other problems, global warming is boosting ocean temperatures and has been blamed for eliminating or degrading a quarter of the world’s coral, scientists say.
A 1-degree or 2-degree increase in water temperature affects a balance that shallow-water coral have with microscopic algae called dinoflagellates.
The algae live in coral cells, absorbing carbon and other nutrients from their hosts and, in turn, make sugars that the coral use for food. Bakus said that coral grows 10 times faster when this symbiotic relationship occurs.
Increased water temperatures cause the algae to flee, leaving the coral to have to capture tiny bits of food that happen to float by for sustenance.
Before time runs out, Smithsonian Institution biologist Mary Hagedorn wants to freeze sperm from all warmwater coral species.
"We’re not really sure what’s going to happen," said Hagedorn, one of the scientists on the Caribbean elkhorn hunt.
"I want to make sure we have a choice about the future."
Sixty percent of the world’s coral might be gone by 2020, Hubbard said.
Hagedorn said if scientists can slow down the effects of global warming, she wants to be able to provide the genetic material to reseed the coral.
Schick is not optimistic: "This animal is going to be gone in the next 10 to 15 years."