species diversity and biomass, 

 with several species of polychaete 

 worms representing the dominant 

 organisms. 



Sheltered Rocky Shores and 

 Seawalls 



The sheltered rocky shores are 

 the result of canals dug through 

 limestone bedrock. The vertical 



faces are often pitted or irregular, 

 reflecting the varied strata of the 

 Miami Oolite and Key Largo Limestone 

 formations. The other man-made 

 structure for this habitat is the 

 seawall. Both dominate shorelines 

 along the interior and sheltered 

 areas in populated regions, and both 

 extend below low-water levels. Wave 

 and current energies here are low. 



Rooted terrestrial vegetation 

 is negligible, as are the seagras- 

 ses, with the exception of in the 

 shallow canals. Getter et al. 



(1981) observed seven species of 

 attached flora and one species of 

 black lichen which was prevalent in 

 the supratidal zone. The red algae 

 Bostrychia tenella and several other 

 red and green algal forms populate 

 the mid and lower intertidal zones. 



The infauna generally is absent 

 and the epifauna exhibits low diver- 

 sity and high density, as observed 

 in the exposed, vertical rocky shore 

 and seawall habitat. Barnacles 



Balanus sp. and Chthamalus sp., and 

 snails Nerite sp. and Littorina sp. 

 are generally present. 



Sheltered Tidal Flats 



Removed from even moderate waves 

 and/or tidal currents, this habitat 

 is found associated with interior 

 island lagoons. The sediment, a 

 carbonate mud, is much less consoli- 

 dated than its counterpart the ex- 

 posed tidal flat habitat. However, 

 like its counterpart, this habitat 

 is uncommon in the Florida Keys. 



The flora and fauna are repre- 

 sented by few species. The rooted 

 vegetation is confined to the tidal 

 flat fringe generally consisting of 

 red and black mangroves, saltwort 

 ( Batis maritima ), and key grass 

 ( Monanthocloe littoralis ) . T he 



attached marine vegetation, distri- 

 buted throughout the tidal flat, is 

 composed primarily of micro green 

 and blue-green algae, shoal grass 

 ( Halodule wrightii ), and turtle 

 grass ( Thalassia testudinum ). The 

 only infaunal species reported by 

 Getter et al. (1981) was a nereid 

 polychaete worm, Notomastus sp. 

 The epifauna is represented by 

 large populations of the gastropod 

 Batillaria minima . 



9.23 MARINE HABITATS 



The habitat descriptions of 

 the Florida Key's marine systems 

 follow, in a seaward progression, 

 the profile habitats illustrated in 

 Figure 57. 



Rocky or Dead-reef Bottom 

 Habitats 



This habitat occurs in two gen- 

 eral belts: (1) from the Florida 

 Keys shoreline out as far as 8 km (2 

 mi), to water depths less than 5 m 

 (16 ft); and (2) near the shelf 

 break where the Pleistocene rock is 

 again exposed, forming elongated 

 areas of dead and partly eroded 

 coral reef ranging in depth from sea 

 level to greater than 30 m (33 yd) 

 (Enos 1977). 



The nearshore rock bottom habi- 

 tat may be divided into several sub- 

 environments. Several of these are 

 discussed in the Shoreline Habitat 

 Section, 9.22. For this discussion, 

 two subenvironments are identified: 



(1) nearshore high velocity or tidal 

 channel hardbottom communities; and 



(2) the nearshore restricted circu- 

 lation hardbottom community. 



188 



