ATHENS, Ga. -- A disease apparently new to science is attacking coral reefs near Key West, Fla., and scientists still don't know what is causing the disease -- or how to stop it. If it spreads, it could threaten the coral reefs of the Florida Keys and potentially damage the marine ecosystem of the area.
The disease, first described this week by a marine biologist from the University of Georgia, has been tentatively named "White Pox," and is already causing extensive damage to reefs some five to 10 miles south of Key West.
"This disease has killed a great deal of coral on some reefs," said Dr. James Porter, who has studied corals off the Florida Coast for many years. "In some areas, it has killed between 50 and 80 percent of the elkhorn coral, which is the dominant coral in the area. In disease terms, this is a `hot zone.'"
Porter collected samples of the diseased coral in late October and sent them to the U.S. Environmental Protection Agency, which confirmed the diseased nature of the tissue; however, no one is yet sure if it is caused by a bacterium, a fungus or a virus. The disease was first noticed by Craig Quirolo from a marine conservation organization in Key West called Reef Relief. G.P. Schmahl, manager for the Lower Keys office of the Florida Keys National Marine Sanctuary, also was involved in the discovery of the disease.
White Pox appears as blotches all over the coral from the base to the tip, and in its advanced stages, the living tissue of the coral becomes flimsy, streams off and falls away from the coral skeleton -- which itself can be damaged. The disease has no known counterparts on coral reefs, though Porter said it was closest to White Band disease, with which it shares more differences than similiarities. White Band decimated coral reefs in St. Croix in the early 1990s.
Like White Band, the new disease prefers to attack a coral called Acropora, specifically Acropora palmata, and both diseases can result in partial or whole-colony mortality. In addition, colonies appear white, as infected coral tissue dies over the underlying skeleton. Still, these similiarities are no more than superficial, said Porter, and considerable differences between White Pox and White Band have been seen. That is why Porter describes White Pox as "new to science." The main difference of the new disease is the indefiniteness of the dying or "necrotic" area.
"Overall, a diseased Acropora field has a distinctly `beaten-up' appearance," said Porter, "as if a toxic substance had been splattered on to an otherwise healthy stand. The size of the discolored areas range from a few centimeters in diameter to large patches some 20 centimeters in diameter. Diseased portions of the colonies are neither bands nor circles but instead irregular blotches distributed across the colony as well as on the blade tip."
Initially, the destruction of coral by White Pox looks somewhat like an attack by the coral-eating snail, Coralliophyla, which is a natural predator on elkhorn coral. The problem, according to Porter, is that there are no snails in the vicinity of these diseased coral patches. Also, close examination reveals that the actual tissue manifestation of White Pox is quite different from snail predation. Snails strip the tissue off coral in neat rows and circles. White Pox causes the tissue to melt off the skeleton in "great gobs."
White Pox has already killed extensive areas of the coral on Eastern Dry Rocks and Rock Key Reef off Key West, and Porter believes that if the disease spreads rapidly it has the potential to decimate shallow-water reefs of A. palmata. Porter, who has used photographic monitoring stations throughout the keys for more than two decades, said it is astounding that so many new diseases (including White Pox) have shown up in so short a period of time in such a small section of the Florida Keys.
"Examination of one infected field of coral on Rock Key reveals that 100 percent of the colonies within a 30-meter diameter are infected with White Pox," said Porter.
The good news so far is that no other EPA-maintained coral monitoring sites throughout the Keys studied by Porter last summer show signs of White Pox.
The next step in the process of understanding White Pox will be taken by Dr. Deborah Santavy of the U.S. Environmental Protection Agency in Gulf Breeze, Fla., who is studying five samples of infected corals that Porter sent her at the end of October. Santavy will use a technique known as transitional electron microscopy to determine if the disease originates from a fungus, bacterium or virus.
Water activities in and around Florida's coral reefs bring in an estimated $1.5 billion a year, so the stakes are high, Porter said.
"Corals are the canaries of the coral reef," he said, referring to the use many years ago of canaries to detect the presence of dangerous gases in coal mines. "But they are a lot more important than canaries. They provide the primary structure of the reefs that are home to fishes and myriads of invertebrates that colonize the reef. If the corals die, reefs as we know them will die, too."
(Editors/writers: Other sources that might be helpful in reporting this story include Craig Quirolo, Reef Relief, 305/294-3100; Dr. Deborah Santavy, U.S. Environmental Protection Agency, 904/934-9358; G.P. Schmahl, Florida Keys National Marine Sanctuary, 305/292-5065; and Laurie McLaughlin, also of FKNMS, 305/292-0311. Color slides are available by calling Rick O'Quinn at the University of Georgia Office of Public Information at 706/542-8085.)