The photograph above shows two branches of elkhorn coral growing in the water near Key West, Florida. The brown and bumpy parts of the coral branches are alive and healthy. The white spot on the left branch is infected with the bacteria. Click on image for full size ( 191 KB) Courtesy of University of Georgia

New research has found that bacteria are responsible for killing 85% of the corals in reefs near the Florida Keys. The bacteria is a fecal coliform bacteria called Serratia marcescens and it is commonly found in the intestines of humans as well as other animals. That means that when you flush the toilet, you have flushed some Serratia marcescens down the drain with the rest. These bacteria doesn’t hurt people; it lives within our intestines without bothering us. Coral, however, can be killed by it.

The bacteria affect only one species of coral, elkhorn coral. A few years ago in the Florida Keys, elkhorn coral was the most common species, but now it is difficult to find living elkhorn coral, and it has been recommended for the endangered species list.

Scientists have been observing the deteriorating health of the corals near Florida for many years, calling the white spots that develop on elkhorn corals white pox disease. They saw that once the disease first appeared on the corals of a reef, it would spread to the entire reef within a year. They could see how the disease was affecting the corals, but they didn’t know what caused it until Kathryn Patterson, a scientist on the research team, found the bacteria in the bodies of diseased corals.

Researchers still don’t know exactly how the bacteria get into the corals, but they suspect that sewage pollution is the cause. If water flushed down toilets in southern Florida does not receive proper treatment before it winds up in the ocean, it may contain bacteria that kill corals. “We must maintain the highest possible water quality standards in the Florida Keys,” said James Porter, head of the research team.

Reef corals, like elkhorn coral, build large stony skeletons on the shallow ocean floor in warm tropical places. They provide shelter and food for many other reef creatures. “These coral reefs are so beautiful and so important,” said James Porter, “We must do out best to protect them.”