Coral killer: It’s sewage.

Science reveals the cause of the shoreline-threatening epidemic of coral decline. It’s simple – the reefs are sick to death of our crap:

Nine years ago, a research team led by coral reef ecologists Kathryn Sutherland, now of Rollins College in Winter Park, Florida, and James Porter of the University of Georgia, Athens, linked white pox to a bacterium called Serratia marcescens, which is found in the intestines of humans and a handful of other animals. In humans, Serratia can cause respiratory and urinary tract infections. But although Sutherland and her team strongly suspected human waste—stemming from septic tanks that leak sewage into the Florida Keys’s porous bedrock—was the culprit, they had no proof that the disease didn’t start with Key deer, cats, seagulls, or any of the Caribbean’s other Serratia-harboring wildlife. “There was considerable skepticism—it was too easy to blame other things,” Porter says.

The duo and colleagues spent years collecting Serratia samples from healthy and diseased corals, from humans via a wastewater treatment facility in Key West, and from other animals. To obtain each sample’s genetic fingerprint, they added an enzyme that breaks up the bacterium’s genome wherever a specific gene sequence is found.

Because every strain’s genome differs slightly, each one yields a unique pattern of breaks. Comparing the patterns among all their samples, the team found only two that matched each other exactly: the Serratia strain found in white pox-afflicted coral and the one drawn from human waste.

It’s not all bad news – now we know that new wastewater treatment plants can prevent outbreaks, too. We can clean up our act.