in the grasses at night. These bare 

 areas, particularly with a mud sub- 

 strate, tend to create a very turbid 

 environment. There are two basic 

 recognizable patch reef formations: 

 (1) the dome patch reef; and (2) the 

 linear coalesed patch reefs or em- 

 bryonic bank reef (Marszalek et al. 

 1977, Japp 1982). The location of 

 patch reefs in the Florida Keys Reef 

 Tract is very nicely illustrated by 

 Enos (1977) and in a continuing 

 series of large maps by Marszalek 

 (1977, 1982). 



The dome-shaped patch reef is 

 typically circular or elliptical in 

 shape with a very clear barren halo 

 around it. This form of patch reef 

 usually occurs in clusters, in 

 depths ranging from 2 to 9 m (7 to 

 30 ft) . Patch reef size varies from 

 a few meters across to more than 700 

 m (2,297 ft) and only rarely exceeds 

 5 m (16 ft) in height. Distribution 

 of these reefs is primarily seaward 

 of the upper Keys (northern Key 

 Largo and Elliott Keys), the lower 

 Keys (Sugarloaf Key to Key West), 

 and the distal islands. The commu- 

 nity consists primarily of seler- 

 actinian and alcyonarian corals, 

 mostly erect sponges, numerous ane- 

 mones, sea urchins, other inverte- 

 brates, and red and green algae 

 (Enos 1977, Marszalek et al. 1977). 

 The community assemblage varies 

 greatly depending principally on the 

 reefs age and environmental setting 

 (Jaap 1982). Jones (1977) identi- 

 fied several life stages exhibited 

 by changing patch reef species com- 

 position. The pioneer stage is 

 similar to the community assemblages 

 described for hardground, mud, and 

 sand substrate habitats. The scler- 

 actinian corals Porites porites and 

 Manicina areolata , and the star 

 coral Favia fragum are often associ- 

 ated with the patch reef beginnings. 

 The second phase of growth includes 

 the introduction of the principal 



reef builders, the starlet coral 

 Siderastrea siderea , the brain 

 corals Diploria labrinthiformis and 

 D. strigosa , the common star coral 

 Montastrea annularis , Colpophyllia 

 natans , and the finger coral Porites 

 astreoides . As the structure grows 

 upward and outward, boring and rasp- 

 ing fauna enter the scene creating 

 coral sediment which fills inter- 

 coral spaces, and excavates the 

 interior structure of the above 

 mentioned reef builders. The hol- 

 lowing out of the internal structure 

 creates a labrinth of passages, 

 caves, and crevices which in turn 

 provides a new habitat suitable for 

 a multitude of shelter seeking or- 

 ganisms. The patch reef matures as 

 the coral reaches the maximum upward 

 extension (sea level). During this 

 period alcyonarians prosper between 

 the corals while the hydrozoan fire 

 coral ( Millepora alcicornis ) invades 

 old or dead alcyonarians. Eventual- 

 ly, areas with extensive internal 

 excavation may collapse, or cata- 

 strophic events may convert portions 

 or entire patch reefs into rubble 

 mounds or hardbottom flats (Jaap 

 1982). 



The coral assemblage of the 

 dome-shaped patch reefs is similar 

 to the linear patch reefs and outer 

 bank reefs except for the absence of 

 the moose-horn or elk horn coral, 

 Acropora palmata , a principal reef 

 builder. In the dome patch reefs 

 this coral is replaced by Montastrea 

 annularis which may form single 

 colonies exceeding 5 m (16 ft) in 

 height. 



The other form of patch reef 

 was identified by Marszalek et al. 

 (1977) as the linear-type patch 

 reefs, and by Jaap (1982) as a 

 embryonic bank reef composed of 

 coalesed patch reefs. In either 



case, this form is typically found 

 seaward of the dome shaped patch 



194 



