Dry Tortugas National Park

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Location on Continental Shelf
Mid-Shelf Bank
Area of Coverage
308.21km2
Width
11.27km
Length
27.36km

From: NOAA, 2002; Wallace, 2003

Dry Tortugas is located 110 km west of Key West, Florida in the eastern Gulf of Mexico. It is elliptical, atoll-like, coral reef formation, approximately 27 km long and 12 km wide with shallow water depths ranging from 12-20 m in channels between reefs. The Dry Tortugas was discovered by the Spanish explorer Ponce de Leon in 1513 and named in Spanish, “Tortugas” for its resemblance to sea turtles, and “Dry” for its lack of freshwater. Designated as a National Park in 1992, the area comprises a cluster of seven islands, composed of coral reefs and sand. The area is known for its famous bird and marine life, and its legends of pirates and sunken gold. Ft. Jefferson, the largest of the 19th century American coastal forts is a central feature.

Community Structure

Reef deposits are mainly Holocene reef and living reef deposits. These are as much as 15 m thick on top of the bedrock, but thinner areas flank the reefs. These reefs consist of the same corals as contained in the bedrock that they overlie. Dominant species belong to the genera Diploria, Montastraea, and Siderastrea. Elkhorn is quite rare. On most of the carbonate sands that occupy the seafloor at Dry Tortugas live communities of soft corals, algae, sea grass and various invertebrates.

Geological Characterization
The atoll-like reef is not of volcanic origin. Primary bedrocks underlying the Dry Tortugas are both Pleistocene in age and these underline much of southeastern Florida. Key Largo Limestone and the Miami Limestone are the most common. Several of the islands are actually made of large piles of unconsolidated Holocene sands, carbonate sands and debris from corals and algae.
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