Flash interactive
Produced by the American Museum of Natural History, September 2005.
San Salvador is one of several islands biologists from the Bahamas Biocomplexity Project investigated. The scientists charted the benthic, or seafloor, habitats surrounding the island using on-site surveys and high-resolution satellite imagery. Variations in color and shading on the satellite image helped distinguish different habitat types, which were then mapped and color-coded. By analyzing just a few islands this way, scientists can understand the overall organization of underwater habitats across The Bahamas.
This interactive displays a high-resolution IKONOS satellite image of the northern tip of San Salvador Island in The Bahamas and the surrounding ocean. Twelve different habitats of the seafloor are color-coded on the satellite map. Their plant and animal life and other features are described. The interactive enables you to turn the color coding for each habitat on or off, so that you can see the extent of individual habitats, or see several habitats at once to see how they relate geographically to one another.
Dark green: Dense Seagrass
Dense, tall meadows of mostly Thalassia seagrass, an underwater plant. Seagrass, which is found along shallow seafloors wherever sediment is deep enough for it to root, provides food and shelter to many species. How lush a seagrass bed is depends on the substrate and the temperature, clarity, and wave activity of the water.
Light green: Medium Density Seagrass
Seagrass of medium density and height.
Medium green: Sparse Seagrass
A sparse scattering of seagrass.
Yellow: Sand and Sparse Algae
This habitat includes both sand with different varieties of alga emerging from it and clean sand with no algae.
Orange: Sand with Silt
Silt, which is finer than sand, is often present in San Salvador's near-shore areas. Seagrass and algae are also found in this shallow-water habitat.
Tan: Sargassum on Hardbottom
Hardbottom is a carbonate rock seafloor thinly covered with sediment. Sargassum, a branching brown algae, anchor to the rock and can grow more than a meter high. Other algae often occur between the sargassum.
Blue: Dense Gorgonians and Algae
Gorgonians are soft corals, which secrete flexible substrates. They include sea fans, sea feather plumes, sea whips, and sea rods which anchor to a hardbottom seafloor that is dotted with algae.
Turquoise: Uncolonized Pavement
This sloping, rocky limestone floor with very few corals and algae is found between areas of shallow forereef.
Orange: Forereef
This habitat is located seaward from the main elkhorn-dominated reef crest. Spurs of coral are separated by grooves of sand or hardbottom. This rich habitat supports stony and soft corals, algae, and some fish.
Purple: Elkhorn Coral Reef
Elkhorn coral's large, sturdy, antlerlike branches create high vertical relief, forming the main reef crest that follows the shoreline. Other stony corals, soft corals, and algae live here also. This habitat is found between one and five meters deep.
Navy Blue: Patch Reef
These multispecies coral reef formations dot near-shore lagoons and are surrounded by seagrass beds. They are commonly ringed by a halo of sand grazed clean of algae by herbivorous fish and invertebrates.
Brown: Dead Coral and Microdictyon
Colonies of coral polyps secrete calcium carbonate substrates that build up over time. In some areas, the polyps have died, leaving barren stony substrates. The meshlike alga Microdictyon covers these structures seasonally.