rockbottom habitat (Enos 1977, 

 Multer 1977, Jaap 1982). 



Calcareous Mud/ Grass Habitat 



In general, calcareous mud 

 bottoms are found in the inner shelf 

 margin associated with areas of 

 restricted circulation, from Florida 

 Bay seaward to the lee side of the 

 shelf edge sand shoals, e.g., White 

 Bank. Water depth is usually less 

 than 8 m (26 ft) and the mud sub- 

 strate is typically covered by one 

 of the most rich and diverse species 

 communities in the Keys marine envi- 

 ronment, the seagrasses (Zieman 

 1982). The seagrass community, 

 typically composed of turtle grass 

 ( Thalassia testudinum ), manatee 

 grass ( Syrinqodium filiforme ), and 

 the shoal grass Halodule wrightii , 

 stabilizes the fine calcareous mud 

 which is necessary for its exis- 

 tence. This fine mud is the product 

 of many of the community inhabi- 

 tants, but most significantly of a 

 few green algal species including 

 Halimeda opuntia , H. incrassata , 

 Penicillus pyriformis , and P. capi - 

 tatus , (Turmel and Swanson 1976, 

 Enos 1977). Other commonly found 

 flora include the green algae 

 Caulerpa paspaloides , Udotea sp., 

 Rhipocephalis oblonqus , and Aurain- 

 villea nigricans ; the red algae 

 Jania sp. and Amphiroa sp.; the 

 encrusting coralline algae Melobesia 

 membranacea and Fosliella farinosa ; 

 and the brown algae Padina sp. (Enos 

 1977, Zieman 1982). 



The fauna, following the pat- 

 tern set by the flora, includes many 

 sediment producing forms, most sig- 

 nificant of which are: foram mili- 

 olid ( Quinqueloculina lamarkiana ) 

 and peneroplid ( Archais anqulatus ); 

 the gastropods Modulus modulus , 

 Tequla fasciata , Astrea americana , 

 A. lonqispina , Cerithium eburneum , 

 and C. literatum ; the bivalves 

 Codakia orbicularis, C. orbiculata. 



and Chione cancellata ; and the 

 tunneling shrimp Calianassa sp. 

 (Enos 1977). Numerous species of 

 foraminifera are present, including 

 several species of the genus Quin- 

 queloculina and Triloculina . This 

 habitat contains the greatest var- 

 iety of erect, most siliceous, spon- 

 ges on the reef tract, and Sponqia 

 sp. Alcyonarians (soft corals) are 

 rare, and the scleractinians (stony 

 corals) are generally limited to a 

 few smaller species including the 

 rose coral Manicina areolata , the 

 tube coral Cladacora arbuscula and 

 the finger corals Porites divaricata 

 and P. furcata . Numerous species of 

 small invertebrates are found among 

 the sponges, corals, and bases of 

 the grassblades, including turbella- 

 rian flatworms, errant polychaetes, 

 crabs, and brittlestars. Several 



species of gastropod snails feed on 

 the epiphytic flora of the grass 

 blade including Tequla fasciata . 

 Modulus modulus , and two species of 

 Astraea listed above (Zischke 1973, 

 Enos 1977, Zieman 1982). 



Common infaunal species in the 

 seagrass beds include tube dwelling 

 annelids Onuphis magn a, Arenicola 

 cristata , and Spirorbis sp.; several 

 burrowing bivalves including the pen 

 shells Atrina riqida and A. seminu- 

 da , the cross-barred venus ( Chione 

 cancellata ), and several species of 

 the genera Area , Anadara , Barbatia , 

 and Tellina sp. ; and numerous inter- 

 stitial species (e.g., Caecum ) . 

 These infaunal bivalves are fed upon 

 by the gastropods Fasciolaria tulipa 

 and Pleuroploca qiqantea (which also 

 preys on the herbivorous queen 

 conch, Strombus gisas ), and by the 

 starfishes Oreaster reticulata and 

 Echinaster sentus . Other common 

 echinoderms include the herbivorus 

 sea urchin Eucidaris tribuloides , 

 Lytechinus varieqatus , and juveniles 

 of the long-spined urchin Diadema 

 antillarum , and the deposit feeding 



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