Black corals, rarely found in the Florida Keys, thrive in the strong currents that circle the walls of coral pinnacles. Plantlike in appearance, their yellow to red outer layer disguises a hard black skeleton. Jewelers consider the skeleton a semiprecious material, and collectors have wiped out these creatures in many areas. Also seldom seen, the ancient and graceful creatures known as crinoids, or feather stars, lurk in narrow crevices or inside sponges, rewarding the observant diver. Many species of sponges, corals, algae and other animals and plants account for the riot of color on Tortugas reefs.
Pelagic species cruise the deep waters, lured by the warm, swift current of the Gulf Stream.
Research suggests that some tuna species may use the Tortugas as a spawning ground, and about 40 species of sharks pass through the region. The Tortugas region owes its very name to the sea turtles once found here in abundance, but decimated by commercial fishing in the late 1800s and early 1900s. Green, loggerhead, Kemp's Ridley, hawksbill and leatherback turtles still travel these waters, protected now from capture. The islands of Dry Tortugas National Park host the largest remaining loggerhead and green turtle rookeries in the Florida Keys. Seabirds depend on the clear water of these foraging grounds to sight the small, fast-moving fish upon which they prey.