Kathryn P. Sutherland, associate professor of biology at Rollins College, and her research collaborators, Associate Professor of Environmental Health Science Erin K. Lipp and Professor of Ecology James W. Porter of the University of Georgia, have known since 2002 that the bacterium that killed coral was the same species as found in humans. "When we identified Serratia marcescens as the cause of white pox, we could only speculate that human waste was the source of the pathogen because the bacterium is also found in the waste of other animals," Sutherland said.
In order to determine a source for the pathogen, the research team collected and analyzed human samples from the wastewater treatment facility in Key West and samples from several other animals, such as Key deer and seagulls. While Serratia marcescens was found in these other animals, genetic analyses showed that only the strain from human sewage matched the strain found in white pox diseased corals on the reef. The final piece of the investigative puzzle was to show that this unique strain was pathogenic to corals.
With funding from Florida's Mote Marine Laboratory "Protect Our Reefs" grant program, Sutherland, Lipp and Porter conducted challenge experiments by inoculating fragments of coral with the strain found in both humans and corals to see if it would cause disease. The experiments were carried out in a laboratory in closed seawater tanks to eliminate any risk of infection to wild populations of corals.
"The strain caused disease in elkhorn coral in five days, so we now have definitive evidence that humans are a source of the pathogen that causes this devastating disease of corals," Sutherland said.
"These bacteria do not come from the ocean, they come from us," said Porter. Water-related activities in the Florida Keys generate more than $3 billion a year for Florida and the local economy. "We are killing the goose that lays the golden egg, and we've got the smoking gun to prove it," Porter said.
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