Raw sewage discharged into the ocean kills coral reefs at an alarming rate, a new U.S. Virgin Islands study says.
Coral reefs are far more likely to develop disease and die when exposed to bacteria and nutrients in raw sewage than coral in unpolluted areas, according to a study published last month in the Puerto Rico-based Caribbean Journal of Science.
“It appears to be a major factor contributing to coral disease,” biologist Longin T. Kaczmarsky said Tuesday. He co-authored the study with scientists from Long Island University in New York and the University of Puerto Rico.
The study compared the health of coral reefs to wastewater release around St. Croix, the largest island in the U.S. Caribbean territory of 110,000 residents.
Coral reefs, home to millions of species of organisms, are vital to ocean life. “It’s the rain forest of the sea,” he said.
In the St. Croix town of Frederiksted, where untreated sewage was regularly released during the study that started in 2001, nearly 30 percent of coral was infected with two main coral diseases _ black-band and white plague, which can kill a foot-long (0.3-meter) coral colony in a week.
Three miles (5 kilometres) north in Butler Bay, where no sewage was released, only three or four percent was infected, the study said.
Only about 10 percent of sewage in the Caribbean and Central America is treated before being discharged into the sea, according to the scientists.
The U.S. Virgin Islands has tried for more than 20 years to comply with federal orders to improve its sewage systems, paying more than $2.7 million (euro7.9 million) in court fines.
Government officials say the wastewater systems are improving, but they couldn’t be reached immediately for comment on the study.
Coral disease isn’t caused by sewage alone, but by human activity in general, said Jack Sobel, a scientist with the Ocean Conservancy, a Washington-based ecology activist group.
Reefs in Haiti and Jamaica have been devastated by fishing, which kills the small algae-eating fish that keep coral healthy, and by soil runoff, which blocks coral’s access to sunlight, contributing to disease and death, he said.
Coral reefs in the Bahamas and some of the small islands outlying Belize and Colombia are relatively healthy, because they are sparsely inhabited, he said.
Hurricanes and volcanic eruptions also kill coral, Sobel said.
Source: Washington Post