MIAMI A human fecal bacterium kills coral, new research shows, and U.S. scientists say this is a warning to Florida and the Caribbean to protect prized reefs from sewage or face a threat to a key pillar of their tourism.
In an article published on Wednesday in the PLoS ONE scientific journal, U.S. researchers said they had identified a bacterium from human fecal waste as a killer of common Caribbean elkhorn coral, whose spiky, layered, ochre-colored growths populate reefs off Florida and across the Caribbean.
The bacterium, Serratia marcescens, causes a coral disease known as "white pox," producing leprosy-like lesions that eat away at, and kill, the coral, said the report by the scientists from Georgia and Florida universities.
"This strain that kills coral comes only from human beings," James W. Porter of the University of Georgia's Odum School of Ecology, one of the report's authors, told Reuters.
Porter said the white pox disease caused by human waste, known scientifically as acroporid serratiosis (APS), had contributed heavily to an 88 percent decline of elkhorn coral in the Florida Keys over the last 15 years. Hurricanes and high temperature bleaching were other killers of coral.
"Elkhorn coral are the Giant Redwoods (trees) of the reef ... That would be as if we lost 88 percent of the Giant Redwoods from Sequoia National Park" in California, he said.
Most of the human-origin wastewater affecting the seas in the Florida Keys and wider Caribbean was untreated and was seeping into the ocean after being disposed of in in-ground receptacles such as septic tanks, the research article said.
Coral reefs are among the most critically endangered habitats on earth and the Florida Keys and Caribbean islands rely on the attraction of their fabulous natural reefs to draw divers, snorkelers and fishermen. Such visitors are a major element of the job-creating tourism industries there.
"People ... want to see a healthy reef, intact corals, and all the organisms associated with it, the fishes and invertebrates," said Kathryn Patterson Sutherland of the Department of Biology of Rollins College in Florida, another of the authors of the report.
Porter said the research findings highlighted the urgent need for human wastewater to receive proper chemical treatment to remove the coral-killing Serratia marcescens bacterium from effluent. This could be a costly challenge in poorer Caribbean states where infrastructure is often badly underdeveloped.
"The lesson is unless we protect the environment, we're killing the goose that lays the golden egg and our discovery shows that we've got the smoking gun to prove it," he said.
'TRIPLE JUMP' MICROBE
Porter said Key West, the city on Florida's southernmost point, had used $70 million of taxpayers' money to install an upgraded advanced wastewater treatment plant and sewage system several years ago, and the research showed this money had been well spent.
The plant was eliminating the harmful coral-killing bacterium from effluent. Porter and Sutherland said installing a similar advanced system in the rest of the Florida Keys would cost nearly $1 billion, but would be a good investment.
The University of Georgia scientist said the white pox infection of elkhorn coral caused by the Serratia marcescens bacterium was the first time that a human pathogen or disease had been shown to kill a marine invertebrate such as coral.
"It's also a very, very rare example of a microbe making a triple jump: from vertebrate to invertebrate, from terrestrial to marine, and from the anaerobic conditions of our stomach to the full oxygenated conditions on a reef," Porter said.
Sutherland said human sewage was another threat to the world's fragile corals, which were already under heavy stress from worsening ocean conditions like deteriorating water quality and rising temperatures caused by global warming.
"Corals are the canary in the coal mine when we talk about climate change, because they live at their upper lethal limits for temperature," she said.
The article can be found at: www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0023468
(Editing by Mohammad Zargham)