Fragile Coral Gardens Threatened

WHILE visitors throng the rails of cruise ships and charter boats to savor the tranquil splendor to the US Virgin Islands, just beneath their feet there may be scenes of silent carnage. Daily, the anchors of these thousands of vessels plummet down in the midst of coral gardens that have taken centuries to form, and on sea-grass beds that provide critical pasture for marine life. Anchors can devastate fragile formations as they move to follow the pendulum swings of the boat shifting in the wind. ``It has been only during the last five years that anyone has gained any concept of what's been happening to the reefs and sea-grass beds here,'' says Caroline Rogers, who directs the Virgin Islands National Park's biological research program.

The sea bottoms that cover nearly half the park's 13,000 acres vary. Some bays offer sandy bottoms, some rock, others a mixture of sand and mud, and still others the precious coral.

In the past few years, Dr. Rogers and her staff have mapped the bottoms of each bay in the park to identify where the coral reefs are. Now the park is taking steps to control these anchorages, installing marker buoys designating ``swimming only'' and ``no boats allowed.''

Those steps came too late to avert one major episode last fall, however. While still under way, a 3,200-ton cruise ship lowered its anchor in Francis Bay and gouged a 400-foot-long furrow through a coral reef. Park divers inspected and photographed the damage, and the issue may yet end in litigation. The ultimate solution, Rogers says, will be a comprehensive mooring plan in which moorings would be fixed in sandy bottoms in the park's most favored bays. Arriving ships and boats, then, would be required to tie up to the mooring buoy instead of dropping anchor.

Coral damage can and does result from heavy groundswells, from careless swimmers and snorkelers, and from boats that ground on reefs. The park keeps on record all reports and evidence of such incidents. It also maintains a number of reef test sites and has marked more than 100 coral deposits in key areas to monitor damage and loss, and to try to identify the causes. The underwater mapping encompasses park waters to a depth of about 60 feet.

The coral gardens are one of the most appealing resources of these islands, a lure to thousands of visitors. But they have a critical role that transcends aesthetics.

Biologists say coral reefs provide food and cover for a wide variety of fish and other marine life, including lobster, and reduce shoreline erosion - especially important in this region of internationally renowned white sand beaches.