Disease from sewage 'is devastating coral'

A disease that is devastating coral reefs around the Florida Keys in the Caribbean has been traced back to a bacterium living in the human gut, indicating that sewage is now contributing to the destruction beneath the sea.

A disease that is devastating coral reefs around the Florida Keys in the Caribbean has been traced back to a bacterium living in the human gut, indicating that sewage is now contributing to the destruction beneath the sea.

The disease, white pox, was first identified in 1996 off Key West and has since been observed on reefs throughout the Caribbean. It attacks elkhorn coral, a fast-growing and important shallow-water variety on which many animals and plants rely.

Scientists had been puzzled about the origin of the pathogen causing the problem, until they used gene sequencing to identify the bacterium responsible.

Now research by a team led by Professor James Porter at the Institute of Ecology at the University of Georgia has discovered that the culprit is Serratia marcescens, often found in the human gut, though it is also known as the cause of chest and urinary infections.

The problem is worst in the Florida Keys because human waste is treated in septic tanks, rather than in systems which would wipe out all bacteria. Reefs in Jamaica, Belize, St Croix and the Bahamas have also been affected.

Professor Porter said: "Elkhorn used to be the commonest coral in the Caribbean, but now it has been proposed for inclusion on the endangered species list. It is the giant redwood of the coral forest."

The new threat adds to the dangers posed to coral reefs by the rising temperature of the Earth's oceans caused by global warming, which could kill off species by causing "bleaching".

Coral reefs are estimated to contain one-quarter of the undersea world's diverse species while covering less than 0.2 per cent of the ocean floor.

Research in 2000 suggested that without urgent action, 40 per cent of the world's coral reefs will be lost by 2010 due to climate-related bleaching, pollution and disease. But preventing white pox will be difficult. The study has not drawn a direct link between the disease and untreated sewage, and S. marcescens is very common in nature.

Dr John Bythell, from the Department of Marine Sciences and Coastal Management at Newcastle University, said he thought it was the first time that a bacterium found in humans had been implicated in coral disease. But he said the bacterium might simply be acting opportunistically to attack coral already weakened by other stresses.