Ecosystems

Marine Ecosystems  |  Terrestrial Ecosystems

San Salvador Island is comprised of numerous ecosystems, many of which are fragile and subject to degradation from development and excessive disturbance. Descriptions here are brief and introductory, but detailed discussion, including geological and climate details, can be found in other references.

Deep ocean – Deep waters in excess of 2,000 m completely surround San Salvador, beginning at the wall drop-offs. These harbor a rich diversity of deep sea and surface-dwelling organisms and support a thriving fishery. Phytoplankton (microscopic plants) and zooplankton (microscopic animals, usually larvae of larger animals) form the basis of the pelagic (deep sea) food chain. A vast throng of zooplankton resides in deeper water by day but moves upward to the surface at night. Large invertebrates (e.g., jellyfish, squid) and small fish feast on the zooplankton, and these in turn become prey for larger fish, sea turtles, seabirds, and marine mammals. Sargassum weed (an algal plant) floats on the surface, sometimes forming extensive mats and supporting a unique community of invertebrates and fishes.

Coral reefs – San Salvador’s spectacular reefs provide important habitat for a rich diversity of algae, invertebrates, and vertebrates. A brief snorkeling or SCUBA experience would convince anyone that coral reefs boast extraordinary beauty, with vibrant colors and remarkable diversity. The corals (tiny colonial invertebrates) and coralline algae (plants) combine to build impressive reefs of several types, including fringing (barrier) reefs that surround much of the island and patch reefs in isolated areas of shallow water. The more conspicuous corals include Elkhorn, Stag Horn, various Star, Brain corals, and an assortment of soft corals. The corals, in turn, provide shelter for many other invertebrates, including sponges, worms, shrimp, crabs, urchins, and starfish.

The fish assemblage includes numerous species of sharks, rays, triggerfish, groupers, squirrelfish, jacks, grunts, snappers, and damselfish. This ecosystem, and the biodiversity it supports, is highly vulnerable to severe storms and human impacts from commercial fishing and recreational activities.

Seagrass meadows – Seagrass communities occur in shallow waters and serve diverse ecological roles. They stabilize marine sediments and provide habitat for a variety of other organisms, including worms, mollusks, urchins, sea cucumbers, seastars, and fishes. A number of plants comprise these communities, including Thalassia, Syringodium, and Halodule.

Mangroves – Mangroves of up to four species occur along protected portions of the coast (Pigeon Creek and French Bay) and fringe the many hypersaline lakes. The root systems of red mangroves can be extensive, supporting a diverse community of invertebrates, fishes, and heron rookeries. Some evidence suggests that many of San Salvador’s mangroves are stressed, with stunted growth, small and rigid leaves, vertical leaf orientation, thinned canopy, and a high incidence of albino seedlings.

Rocky intertidal zone – A cursory examination of this fascinating community reveals marked zonation, with different species occupying distinct zones at varying distances from the low tide mark. <more material to be added>

Coastal communities – Several plant communities occupy the immediate coastline, including the rocky shore and the sea strand/sea oats communities. Plants of the rocky shore are generally low-growing forms (under 1 m height) and include Sea Ox-eye (  ), Bay Lavender (Mallotonia gnaphalodes), Black Torch (Erithalis diffusa), Ink Berry (Scaevola plumieri), Horse Bush (Gundlachia corymbosa). Plants characteristic of the sea strand/sea oats community include Railroad Vine (Ipomeas escaper), Sea Grape (Coccoloba unifier), and Sea Oats (Neola aciculate). These plants are important for stabilizing dunes, which provide an important buffer against hurricane damage.

Australian Pine (Casuarina equisitafolium), an invasive exotic species, has become very dominant in these and other communities, crowding out the native vegetation. Although Bahamians and tourists alike appreciate the shade provided by this ecologically-disruptive tree, Casuarina eradication should be considered a high priority.

Some of the more conspicuous animals within these communities include <more material to be added>.

Nearshore communities – Being further from the immediate coast, these communities are better protected from salt spray. Also known as “coastal coppice,” the dominant plants here include Silverthatch Palm (Coccothrinax), Poisonwood, and numerous thicket-forming trees and shrubs. <more material to be added>

Inshore communities – Several ecosystems occur here, including mangrove swamps, freshwater forests, the whiteland community, and the blackland community. <more material to be added>

Cave communities – A number of caves occur in the karst (limestone) rock that forms the porous surface of much of the island. A fascinating community exists within these caves, including numerous invertebrates (with one species of isopod occurring nowhere else in the world) and several species of bats that roost and raise their young here. You can learn more about these creatures by clicking on the corresponding buttons for invertebrates and mammals. <more material to be added>

Gerace, D. T., G. K. Ostrander, and G. W. Smith. 1998. San Salvdor, Bahamas. In UNESCO (Editors), CARICOMP – Caribbean Coral Reef, Seagrass, and Mangrove Sites. Coastal region and small island papers 3, UNESCO, Paris.     PDF (145 kb)

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