ANDROS, Bahamas, Aug. 25 — Brisk winds have been blowing in from the direction of the reef these past few days, reminding us that Tropical Storm Debby, formerly Hurricane Debby, was bearing down on Forfar Field Station.

But Poseidon spared us this time. Debby — just a few days ago a Category 1 hurricane headed straight for the beach in front of the station — sputtered and veered south. The boards that were nailed over the windows have been removed so the tropical sun can stream in again; the boats remain in the water; and the scientists continue to arrive.

I got a taste of the storm Wednesday, when our sea expeditions took us twice to the reef crest about a mile offshore, the highest point on the 140-mile-long reef. It's usual for breaking waves 2 and 3 feet high to make white slashes over the elkhorn coral that thrives in the pulsing water just near the surface, some of it sticking right up into the air. Those tame breakers greeted us in the morning as project coordinator Dan Brumbaugh and his assistant Josh Drew did some preliminary work in the 16-square-mile survey zone.

But as we headed out for our afternoon dive, it became clear once we passed the protection of the cays just offshore that the waves had grown. Five-foot swells made our 19-foot motor boat feel puny, tossing us around as we struggled to shrug on heavy scuba tanks. Dave Burdick, Forfar's staff dive master, looked nervous as he maneuvered the boat into anchor position.

Big storms can devastate a reef, especially the waves generated by hurricane-force wind.

"The pounds of force from those waves is unimaginable," Dan says.

On the crest, hurricane waves catch the hand-shaped elkhorn coral and snap it off at its thick, wrist-like stem. "The stems are incredibly strong, but not strong enough to survive those waves," says Dan. We saw one old elkhorn that had been flipped on its head during a long-ago storm so that its stem — about 18 inches across — stuck out of the water.

On the fore reef or shelf, where we dove yesterday, the hard and soft corals, sea fans, sponges and all of their companions live at 20 feet or deeper, where the water is calmer. Here, the hard corals are smoother, rounder, not hand-shaped like the elkhorn coral. But that doesn't mean they're safe.

Powerful storm waves also stir up the bottom, sending sand and sediment flying through the water to coat the coral.

Corals are comprised of interconnected units called polyps. Each polyp has tentacles, "fingers," that at night extend as far as six inches into the dark waters to catch any minute plankton the current carries by. These tentacles can also sweep an entire coral of sediment in 30 seconds. The elkhorn coral of the reef crest lacks such a cleaning system, which is why it likes the sediment-free water.

But if the sediment coats the coral too thickly, it clogs the polyps and prevents them from putting out their tentacles. Within the polyps live single-celled zooanthellae, plant-like organisms that provide the coral with a large part of its nourishment. These plants, like all others, depend on photosynthesis to survive. If a coating of sediment blocks the light, the zooanthellae will die, and the coral will starve.

Overall, sediment stirred up by storm waves can block light, starving other reef plants of sun. Given the symbiotic relationship of reef plants and the creatures that feed on them, days or weeks without sunlight can severely damage the entire reef system. But just as wildfires that periodically denude the forest bring later abundance of flora, violent storms that destroy reefs usually bring about rich renewal in the following decades.

This time, we got off lightly. But this unprecedented study of the Andros Barrier Reef and its creatures is only kicking off, and it is the height of hurricane season in the Bahamas.

Before I came to Andros, I asked Dan and project co-leader Paula Mikkelson why we were coming here at a time when storms can line up like baseballs to batter the area.

"July and August are the best times for underwater study because the water's so calm," Paula explained. "Unless there's a hurricane, of course."

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