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FLORIDA'S DEEP REEFS - AN OVERVIEW
Deep-sea coral ecosystems (DSCEs) are common off the southeastern U.S. within the Exclusive Economic Zone (EEZ).
These include a variety of high-relief, hard-bottom habitats at numerous sites from the Blake Plateau off North
Carolina, southward through the Straits of Florida, and in the eastern Gulf of Mexico. However, only a few have
been mapped or have had their benthic and fish resources characterized.
Deep-water reefs are sometimes defined
as coral banks, coral mounds, bioherms, or lithoherms. In general, deep-water banks occur below the effects of
waves and the corals lack symbiotic algae (zooxanthellae). A bioherm is a deep-water coral bank that over centuries
has formed a mound of unconsolidated sediment and coral debris and is capped with thickets of coral, such as Oculina
or Lophelia, whereas lithoherms are high-relief, lithified carbonate mounds, rather than unconsolidated sediment
mounds, and also may be covered with thickets of live coral. The dominant corals on deep-water reefs in this region
are the azooxanthellate, colonial scleractinian hard corals, Oculina varicosa, Lophelia pertusa, Enallopsammia profunda,
Madrepora oculata, and Solenosmilia variabilis. These reefs provide hard-bottom substrate and habitat for sessile
macrofauna including scleractinian corals, gorgonians, black corals, and sponges, which in turn provide habitat and
living space for a biologically rich and diverse community of associated fishes, crustaceans, mollusks, echinoderms,
and other fauna.
The Miami Terrace is a 65-km long carbonate platform that lies between Boca Raton and South Miami at depths of
200-600 m in the northern Straits of Florida. It consists of high-relief, Tertiary-age limestone rock ridges and
scarps that provide extensive hard-bottom habitat for a variety of fish and invertebrates. Previous investigations
include geological studies and trawl-based faunal surveys in the 1970s. Deep-water coral mounds are present at the
base of the Miami Terrace escarpment (~670 m) within the axis of the Straits of Florida, but little is known of their
distribution, abundance or associated fauna.
In 2004 and 2005, JSL submersible dives and echosounder transects were conducted by HBOI scientists from the Division
of Biomedical Marine Research (DBMR) at several sites along the eastern edge of the Miami Terrace. These revealed that
the outer terrace rim consisted of a ridge system with steep, phosphoritic limestone escarpments and relief >90 m.
The ridges provide habitat for a rich, deep-water reef ecosystem of corals, sea fans, sponges, and fish. Both habitat
and faunal zonation varied considerably among the sites. In general, the lower slopes below the ridges and the flat
pavement on top of the terrace were relatively barren and had low biodiversity compared to the ridge tops and upper
escarpments.
Dominant sessile fauna consisted of colonial corals (Lophelia pertusa), stylasterine corals (Stylasteridae),
gorgonian sea fans (Gorgonacea), bamboo coral (Isididae), black coral (Antipatharia), and diverse sponge populations
(Hexactinellida and Demospongiae). Motile invertebrates included the echinoderms, mollusks, and decapod crustaceans.
In total, 19 fish taxa were identified, including conger eel, red dory, blackbelly rosefish, codling, dogfish, schools
of jacks, and wreckfish.
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