Coral Disease Hot Spot in Florida Keys

Science  20 Dec 1996:
Vol. 274, Issue 5295, pp. 2017
DOI: 10.1126/science.274.5295.2017a

A host of new diseases has been killing coral off the Florida Keys, and so far, biologists are mystified as to the causes.

The latest is “white pox,” recently described by University of Georgia marine ecologist James Porter. It attacks branching corals called Acropora, mainly elkhorn and staghorn corals, making them blotchy and, ultimately, killing them.

The afflicted coral tends to be concentrated in one “hot zone” less than 3 km long starting 10 km south of Key West, says Craig Quirolo of a Key West group called Reef Relief. Other mystery scourges that have appeared in the area in the last few years are “white band” (which also affects branching coral), “yellow blotch” (which attacks boulder corals), and “white plague” (which can consume coral at the rate of a centimeter a day). There's also “black band,” which was recently traced to cyanobacteria, or blue-green algae.

The newly identified pox first shows up as stunted growth: In one patch of reef, coral grew only 2% rather than the expected 30% one year, says Porter. A year later, most of the coral in the area had died.

Porter has sent samples to the Environmental Protection Agency (EPA) as part of the agency's reef-monitoring program. “There obviously is something very serious going on,” says microbial ecologist Deborah Santavy of EPA's Gulf Breeze lab, who is analyzing samples of diseased corals. It's not clear yet, she says, whether the diseases are caused by living organisms—bacteria, viruses, or fungi—or environmental stresses that make reefs more susceptible to passing pathogens.

Quirolo suspects that nitrogen and phosphates from soil runoff and nutrients from sewage have a big role in the new afflictions. “The Keys have over 20,000 illegal septic tanks,” he says. All this runoff has helped turn the fabled “gin-clear” waters off the Keys closer to absinthe green.

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