siderea , the moosehorn coral Acro- 

 pora palmata , the staghorn coral 

 A. cervicornis , the soft corals 

 Gorqonia ventalina and Plexaura 

 flexuosa , the hydrozoan Millipora 

 complanata , various encrusting and 

 branching coralline algae, the green 

 algae Halimeda opuntia , and the 

 brittle stars Ophiothrix orstedii 

 and Opliocnida sp. 



The most seaward portion of the 

 outer reef habitat exhibits a verti- 

 cal gradient of corals with increas- 

 ing depth. The scleractinians and 

 alcyonarians reach a maximum level 

 of numbers and diversity in the 

 upper portions of this zone (8 to 

 10 m or 26 to 33 ft). Many of the 

 larger reef builders also flourish 

 in this area, including the star 

 corals Montastrea annularis and M. 

 cavernosa , the brain corals Diploria 

 strigosa and Colpophyllia natans , 

 the porous coral Porites astreoides , 

 the starlet coral Siderastrea side- 

 rea , the moosehorn coral Acropora 

 palmata , the staghorn coral A. 

 cervicornis , and the sclerosponge 

 Ceratoporella sp. Other organisms 

 include the alcyonarians Briarcum 

 asbestinum and Plexaura flexuosa , 

 coralline algae Halimeda opuntia , 

 the stinging coral Millipora alci- 

 cornis , the coral and sponge dwel- 

 ling brittle stars Ophiothrix sp. 

 and Ophiactis quinqueradia , and the 

 lettuce coral Aqaricia aqericites 

 (Ginsburg and James 1974, Enos 1977, 

 Kissling 1977, Jaap 1982). The pre- 

 vious lists represent only a frac- 

 tion of the outer reef assemblage. 

 Kissling (1977) has identified, from 

 9 outer reefs off the lower Keys, 

 over 350 macrobenthic species in- 

 cluding benthic macroalgae, marine 

 grasses, sponges, anemones, sclerac- 

 tinian, hydrozoan and alcyonarian 

 corals, flatworms, nemertine worms, 

 sipunculids, bryozonans, oligochaete 

 and polycheate annelids, gastropods, 

 scaphopods, pelecypods, cephalopods. 



crustaceans, pycnogonids, tunicates, 

 asteroids, ophiuroids, echinoids 

 (e.g., Diadema antillarum ), holothu- 

 rians, and crinoids. This includes 

 42 species of stony corals, 41 spe- 

 cies of soft coral and 21 species of 

 brittlestars. They estimate that 



more than 300 species of fish inha- 

 bit these reefs, which would be less 

 than the 517 species and 440 species 

 observed in Alligator Reef off Key 

 Largo (Starck 1968) and the Dry 

 Tortugas reefs (Longley and Hilde- 

 brand 1941), respectively. 



Forereef Mud/Sand Habitat 



At depths exceeding 18 to 25 m 

 (59 to 82 ft) along the fore reef 

 slope of the outer reef, blankets 

 of calcareous muddly sands occur. 

 Usually too deep for seagrasses 

 (possibly the more shade tolerant 

 Halodule sp. could survive) (Zieman, 

 1982), the predominant flora include 

 the green algae Acetabularia sp., 

 Halimeda opuntia , H. tuna , and U do- 

 tea sp., and various encrusting and 

 branching coralline algae. The 



fauna is characterized by pelagic 

 foraminifera (e.g., Globiqerina 



sp.), a few scleractinians (rose 

 coral Manicina areolata and lettuce 

 coral Agarica fraqilis ), several 

 echinoids including sea urchins 

 ( Oiadema antillarum , Ecuidaris 



tribuloides , and Astropyqa maqnifi- 

 ca ) and sand dollars ( Clypeaster 

 subdepressus ) , and gastropods (e.g. , 

 Calliostoma sp. ) (Ginsburg and James 

 1974, Enos 1977). 



Shoal Fringe Habitat 



A majority of the inner shelf 

 margin shoals have a slightly eleva- 

 ted fringe environment that supports 

 a unique organic community charac- 

 terized by calcareous red algae and 

 numerous finger corals. This habi- 

 tat occurs in shallow waters of the 

 nearshore environment and experi- 

 ences wide temperature and salinity 

 variations. The substrate is a fine 



196 



