The Florida Keys National Marine Sanctuary protects an area of over 3600 square miles (2800 square nautical miles) of submerged lands and waters surrounding the Florida Keys. It includes parts of Florida Bay, the southwest continental shelf, the corals of the Florida Reef Tract that parallel the seaward edge of the Florida Keys, the Keys themselves, and the Straits of Florida. Sanctuary waters range from an average depth of four feet in Florida Bay to 2000 feet. Depth of the reef tract averages about 50 feet. The submerged lands of the sanctuary are part of a plateau of marine sediments that includes all of Florida and its adjacent continental shelves. The outer edge of the reef tract is subject to open tidal exchange of warm, clear waters of the Florida Straits that are low in nutrients and conducive to reef development.
The Keys are a partial barrier between the warm-temperate waters of the Gulf of Mexico and the tropical to subtropical waters of the Atlantic Ocean to their south. A corresponding distinction in marine flora and fauna between the two regimes is a result. The biota on the Atlantic side of the Florida Keys National Marine Sanctuary is predominantly Caribbean in character, while the marine biota on the northern side are characteristic of warm-temperate areas. However, water exchange between the two regions through channels between islands allows for a mixing of biota in nearshore areas.
The dominant biological features of the major biogeographic components of the sanctuary are:
Florida Bay. Seagrass beds dominated by turtle grass and lesser amounts of manatee grass, shoal grass, and widgeon grass are the major biological features of this region. Mangrove islands are other important elements.
Southwest Continental Shelf (Gulf of Mexico region). Communities in this region include mangrove islands and mangrove-fringed shorelines, seagrass beds similar to those in Florida Bay, and hardbottom and softbottom habitats. The seagrass beds support numerous species of shrimp and crabs, and the region's seagrass community is an important spawning area for various commercially and recreationally important species of fish including snapper, spotted seatrout, red drum, barracuda, and various sharks. Hardbottom habitat supports stony and soft corals, sponges, molluscs, crustaceans, echinoderms, and several hundred species of fish.
Nearshore Habitats and Tidal Channels (The Keys). These are transitional areas of species mixing between the Gulf and the Atlantic. Major biological communities present here are mangroves, intertidal shorelines, seagrass beds, hardbottoms, and soft substrates.
Atlantic Ocean. The variety of habitat types is greater here than in other sanctuary regions, and the area's tropical habitats support a significantly greater diversity of organisms. Major habitats include mangrove fringe; nearshore hardbottom; inshore patch reef; mid-channel reef; mid-channel seagrass and softbottom; and various reef tract habitats including offshore patch reef, seagrass, back reef/reef flat, bank reef/transitional reef, intermediate reef, deep reef, outlier reef, and sand and softbottom. Corals are the principal builders of the reef community and are the main source of biological complexity.
The photo gallery contains images which portray only a small portion of the living and physical resources of the sanctuary. In addition, it portrays some of the major uses of the sanctuary. For a more detailed description of the marvels of the Florida Keys National Marine Sanctuary visit the Florida Keys description on the Marine Sanctuaries section of this site