sea cucumbers Holothuria floridana 

 and Actinopyqa aqassizi . Two com- 

 monly occurring snails without 

 external shells are the nudibranch 

 Tridachia crispata (seasonal) and 

 the large spotted "sea hare" Aplysia 

 dactylomela . The resident crusta- 

 ceans include the large blue crab 

 Callinectes ornatus and many smaller 

 forms like the shrimp Palaemon 

 tenuicornis , Latrentis fucorum , 

 Penaeus brasiliensis , and Tozeuma 

 carolinensis , and the mantis shrimp 

 Pseudosquila ciliata . 



The seagrass meadows provide 

 nursery grounds for the early stages 

 in the life histories of several 

 organisms including the pink shrimp 

 Penaeus duorarum , the cephalopod 

 Octopus briarcus , the spiny lobster 

 Panulirus arqus , and numerous fish 

 species, such as sea trout, jacks, 

 pompano, barracudas, mullet, cow- 

 fish, and snappers (Zischke 1973, 

 Zieman 1982). 



Calcareous Mud/ Bare Bottom 

 Habitat 



Progressing seaward from the 

 nearshore hardground and seagrass/ 

 mud substrate meadows, the depth 

 increases to a maximum of 7 to 17 m 

 (23 to 56 ft) in Hawk Channel. In 

 these deeper waters ( > 8 to 10 m or 

 26 to 33 ft), particularly where 

 turbidity is high, are large regions 

 of bare mud lacking any grass cover, 

 presumably due to the excess silta- 

 tion and the subsequent lack of sun- 

 light penetration. Both biological 

 (e.g., fish, benthonic organisms, 

 and burrowers), and physical forces 

 (wind drien currents) probably put 

 enough sediment into suspension to 

 create the continuous high turbidi- 

 ty. Circulation in this environment 

 is somewhat restricted, except 

 during late fall and winter when 

 strong prevailing winds from the 

 north/northeast and northeast blow 

 parallel to Hawk Channel, causing 



resuspension rather than movement of 

 the sediments out of the channel. 



Compared to the shallower 

 grass-covered mud bottom, the spe- 

 cies density and diversity is great- 

 ly reduced. The vegetation is pri- 

 marily restricted to several calcium 

 carbonate producing green algae 

 including Penicillus sp., Halimeda 

 tridans , Udotea cf . , U. cyathifor - 

 mis , and Rhipocephalus sp. The 

 faunal community consists of several 

 foraminifera, principally the pene- 

 rolids Peneroplis sp., and miliolids 

 Quinqueloculina sp.; generally no 

 alcyonarians (soft corals); few, if 

 any sponges; the scleractinian rose 

 coral Manicina areolata ; the scapho- 

 pod Dentalium sp.; the gastropods 

 Cerithium sp., Olivella sp., and 

 Vermicularia knorri ; the burrowing 

 pelecypods Chione cancellata and 

 Codakia sp. ; annelids and arthropods 

 such as the tunneling shrimp, Cali- 

 nassa sp.; and the echinoid sea 

 biscuit Clypeaster rosaceus (Enos 

 1977). 



Calcareous Sand/ Grass Habitat 



Between Hawk Channel and the outer 

 reef on the back-reef platform, 

 large areas are blanketed with cal- 

 careous sands. Two varieties of 

 habitat exist within this environ- 

 ment: (1) the first is characterized 

 by loose, often fairly well-sorted, 

 clean, rippled sand with a paucity 

 of obvious life; (2) the second is 

 characterized by grass-held sands 

 having a comparatively rich variety 

 of living fauna and flora. The 



distribution of the grass-held sand 

 habitat does not appear to be parti- 

 cularly systematic, except that, in 

 general, where wave action is most 

 vigorous, grass is absent. Unlike 

 the landward mud substrate habitats, 

 the deeper less wave-agitated areas 

 on this sany back reef platform 

 exhibit low turbidities because few 

 fines are available in the sediment. 



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