“Fire coral will be the last remaining living coral on earth.”
I remember writing those words once, in a bluster of prophetic arrogance. That’s not exactly the most positive Earth Day message to consider as I dive this week on a shallow reef in the French West Indies at Île Fourchue, Saint Barthélemy.
First of all, fire coral is not even a true coral. Instead, it is more closely related to hydra, a very small predatory animal similar to jellyfish and other stinging anemones. But, for the sake of consistency, I will still refer to it as fire coral.
Fire coral can be either blade-like or encrusting. It is colored a mustard-yellow to dark orange, often with white edges. It has strong stinging cells that on contact cause intense pain lasting from two days to two weeks. Relapses of inflammation, itching, and welts are common. Fire coral releases venom through tiny hairs called cilia. It is their only defense mechanism against predators, including thoughtless human beings. Do not touch it, or any coral.
Because fire coral has the unusual ability to grow in two different forms, some marine biologists believe it has a survival edge over other Caribbean corals. It can grow like a bush with a stem and branches sprouting upward, or in sheets that appear as a flat coating across rocks and other surfaces.
“Fire corals have been around for millions of years and what they are doing is pretty darn successful,” says California State University marine biologist Peter Edmunds. For the past 30 years, he has been traveling to the Caribbean to document the life history of fire coral on inshore reefs.
“They are now poised to be… the inheritors of the reef, while other corals, particularly stony corals, die back,” he said. ”When it’s not stormy, they can produce branches and exploit the light and plankton in the water. When it’s storming and everybody gets beaten up, it loses its branches but it still has its sheets, which it can use to spread out and claim more territory.”
Researchers believe this adaptation may help save Caribbean reefs, which have been plagued by hurricanes, global warming, disease, and an overabundance of algae. Because fire corals are thriving as other corals die off, they are creating structures for fish and other organisms. Fire corals “are going to be very important habitat providers because they are able to survive under these stresses,” says Colleen Bove, a marine ecologist at Boston University.
But fire coral is not bulletproof. Some species have brittle skeletons that can easily be broken during storms, by anchors, or by careless divers and collectors who are taking fish for the aquarium trade. I watched blueheaded wrasse spawn over fire coral. Rock beauties, butterfly fish, yellow tangs, and the aggressive beau gregory retreat into branches of fire coral when threatened. In Brazil, fire coral colonies are extensively damaged by divers harvesting yellowtail damselfish. The fire coral is deliberately smashed and the fish hiding among the branches are captured in plastic bags.
Reproduction in fire corals is more complex than in other reef-building corals. The polyps reproduce asexually, producing the jellyfish-like medusae. These contain the reproductive organs that release eggs and sperm into the water. Fertilized eggs develop into free-swimming larvae that will eventually settle on the substrate and form new colonies.
Most divers wouldn’t mind seeing less fire coral on the reef, but I like to think of fire coral as a tactile warning to tread more carefully underwater. When the alternative may be a reef of dead rock, the sting of fire coral is a potent reminder that there is still life on that reef. And, it is one of the few ways the habitat has of fighting back.
As always, sailing is not just about the wind and the sea; the places, the flora, fauna, and people encountered along the way are equally important.
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