Diving at the Flower Garden Banks National Marine Sanctuary, Texas

Divers at the Flower Garden reefs in the northwestern Gulf of Mexico encounter Atlantic mantas often enough to identify the regulars by their distinctive body blotches, which are as unique as fingerprints. Manta rays are the signature animals of the Flower Garden Banks National Marine Sanctuary, twin reefs 100 miles off the Texas coast. It's amazing that these two tiny coral outposts ever managed to find a foothold hundreds of miles from the nearest reefs in Florida and Mexico. But thanks to Gulf Stream eddies, the conditions here are downright Caribbean. Warm Gulf currents ferry coral larvae to the twin undersea salt domes, which were pushed to within 60 feet of the surface during the late Jurassic period, about 180 million years ago.

The West Flower Garden reef, a footprint-shaped formation no more than 100 acres in size, caps a bank five miles long and three miles wide. The East Flower Garden flaunts a reef cover almost three times the size of its western counterpart. Unlike a typical Atlantic reef with soft and hard coral species, the Flower Gardens are covered entirely in stony corals, mostly brain and star varieties. With depths from 60 to 100 feet, dive sites appear as expansive coral meadows filled with boulder-size coral heads scattered at random. Many of the enormous coral heads have undersides smeared with encrusting sponges in strawberry red, mustard yellow, and sulphur orange.

Some of the smaller coral heads have been sculpted into toadstool shapes by a process known as bioerosion, which includes the effects of animals grazing on the coral or digging holes in the formation. Small caverns riddle many of the formations, making the perfect habitat for reef fish like spotfin butterflyfish, yellowfin grouper, sharpnose puffers, and queen angelfish.

Only a few patches of sand interrupt the thick blanket of coral. In the narrow sandy alleys between the coral heads, tiny yellowhead jawfish stand vertically at attention above their burrows. Yellow goatfish probe the bottom with catfishlike whiskers called barbels. Schools of blue chromis, which can be quite pugnacious for four-inch-long fish, hover over the coral heads, while schools of two-foot-long, silvery horse-eye jacks rush through the reef. Near the dive boat, barracudas assemble below the safety lines.

More than Mantas

Besides the Atlantic mantas — year-round regulars — two different mobula ray species frequent the Flower Gardens in the spring and summer. And there are more than rays in the megafauna departments. Every summer, divers encounter at least a half-dozen whale sharks. In the late 1990s, sport divers saw these massive filter-feeders on more than 25 occasions during a three-month period. Whale sharks often mosey along, feeding near the surface. Sometimes they hang out in a tail-down position waiting for something tasty to swim overhead — when it does, the shark sucks it in, plankton, small fish, and all. Easy to identify, whale sharks can be up to 60 feet long, with a distinctive polka-dot design.

Every winter, schooling sharks and spotted eagle rays migrate to the Flower Garden reefs. The most fascinating members of the pelagic parade, scalloped hammerhead sharks, congregate here in schools of up to 50 individuals, from December to early April. The eagle rays' unusually long tails and white-ring patterns make them easy to identify. Unlike the leisurely mantas, eagle rays fly through the reef, seldom slowing down. And unlike other rays, spotted eagle rays sometimes join formations of hammerheads. In the fall, winter, and spring, silky sharks congregate en masse at the gas platform known as HI389A, a mile southeast of the East Flower Garden reef. From just below the surface to depths of about 30 feet, groups of these silvery, smooth-skinned sharks circle the metal structure, totally disregarding the thrilled divers.

Continued In: Diving at the Flower Garden Banks National Marine Sanctuary, Texas - Part 2

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