Caribbean Fire Corals Survive Global Warming, Diseases, Hurricanes

The Caribbean's fire corals have a unique survival mechanism that can endure even if the rest of the reef is destroyed due to hurricanes, diseases, and global warming.

Fire corals can be a scuba diver's worst nightmare. An unintentional bump against a fire coral can be excruciatingly painful. However, they might also contribute to the preservation of Caribbean reefs, which are under threat from hurricanes, disease, global warming, and an excess of algae.

According to a long-term study, fire corals (Millepora) are flourishing there even as other corals are dying off. This could help preserve some of the 3D environment that makes reefs such excellent homes for fish and other organisms.

Colleen Bove, a marine ecologist at Boston University, says that Because they can withstand these stresses, fire corals are going to be crucial habitat providers. Bove was not a part of the project.

Peter Edmunds started conducting annual surveys of the marine life off St. John, one of the U.S. Virgin Islands, thirty years ago. A 20-meter transect along a reef under the ocean was marked out by a marine biologist from California State University, Northridge. He has taken pictures of the vegetation that grew there every summer, including a 40-meter expanded transect.

Edmunds has tracked how algae and different corals have fared through warming sea temperatures, hurricanes, and other environmental stresses by looking at the abundance of each organism in these "photo quadrats."

Caroline Dubé, a marine biologist at Laval University who studies plasticity in Pacific fire coral, says that Edmunds has accomplished something truly amazing. Since coral reefs are experiencing so many disturbances, more needs to be done in this area.

Fire corals

Despite looking like typical stony corals, fire corals are closely related to jellyfish, which accounts for their painful sting. They can develop into "trees," sprouting upward with a stem and branches, or into sheets, expanding as a flat coating across rocks and other surfaces. Jeremy Jackson, an ocean biologist with the American Museum of Natural History and the Smithsonian Tropical Research Institute, first suggested more than 40 years ago that fire corals would have an advantage as the Caribbean reefs were subjected to hurricanes and global warming. Now, Edmunds believes Jackson was correct.

Overall, Edmunds' long-term data shows that numerous species of macroalgae, which are multicellular algae, have taken over Caribbean reefs. However, Edmunds reports today in the Proceedings of the Royal Society B that fire corals quickly invade and encrust surfaces if hurricanes or other factors decimate the macroalgae. To survive in confined spaces and provide an upright structure that other organisms can eat, live in, or use in other ways, fire coral sprouts into its branching tree form when the reef becomes overpopulated.

The corals occasionally lose their green algal partners and die as a result of abnormally warm water, allowing macroalgae to repopulate the area. The branches of the tree form are also lost during hurricanes. However, Edmunds discovered that the fire coral quickly resurfaces in one way or another. As a result, the abundance of this coral has been able to maintain itself and possibly even grow slightly.

According to Edmunds, the fire corals' stony coral friends don't do a great job of producing sheets and trees. Fire corals are therefore prepared to take over the shallow reefs in a world with frequent storms and fierce competition for space on the bottom.

Jackson expresses satisfaction in the fact that Edmunds' extraordinary tenacity allowed him to observe the ups and downs of fire coral dynamics. Sadly, Edmunds' data also indicate that other corals are becoming progressively more scarce. As a result of coral bleaching and marine heat waves, millepora might take their place.

Bad News for Reefs

Nikolaos Schizas, a marine scientist at the University of Puerto Rico, Mayagüez, cautions that because fire corals rarely form reefs that are meters high and wide, they might not be able to save reefs. Schizas emphasized the need to be reasonable about the scope of that potential.

Terry Hughes, a marine scientist from the Australian Research Council Centre of Excellence for Coral Reef Studies, pointed out that although the fire corals were repeatedly destroyed by hurricanes and other disturbances, according to Edmunds' data, the fire corals will fare better than most other corals.