Raw sewage discharged into the waters around the U.S. Virgin Islands is killing coral reefs at an alarming rate, researchers have documented in a recent study and book.
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 the study published in the Puerto Rico-based Caribbean Journal of Science.
"It appears to be a major factor contributing to coral disease," said biologist Longin Kaczmarsky. 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. 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," Kaczmarsky said.
30 percent infection rate
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 coral colony in a week.
Three miles 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.
U.S. Virgin Islands officials say the wastewater systems are improving, but the local government has paid nearly $3 million in court fines as it has struggled for more than 20 years to comply with federal orders to improve its sewage systems.
Other stress on coral
In a separate book released this year, the Ocean Conservancy, a Washington-based group, documented the stresses on coral throughout the U.S. Virgin Islands.
"Humans have an impact on corals in a number of ways," says spokesman Tom McCann. "Overfishing, pollution, and habitat destruction all unbalance the natural marine ecosystem. If we are going to be better stewards of our oceans we need to address these preventable forms of damage."
Jack Sobel, a scientist with the group, adds that reefs in Haiti and Jamaica, for example, have been devastated by fishing that 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.
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.
Marine reserves touted
"The problems we see in the marine environment around the U.S. Virgin Islands are similar to the ones we see around the country," Sobel added. "These are the same issues found by the U.S. Commission on Ocean Policy when they presented their national study to President Bush and Congress last year."
Sobel also cited efforts to create networks of protected marine areas, saying they "can return coral reefs to a more healthy state.
"The East End Marine Park on St. Croix," he said, "provides a tremendous local opportunity to begin turning the tide on coral reef health in the U.S. Virgin Islands."
The Ocean Conservancy's book is online at .