fniforme ). The algae, which represent a much smaller biomass than that of 

 the grasses, consist primarily of species of the genera Halimeda , Udotea , 

 and Penicillus . 



Due north of the Looe Key Reef Flat are numerous Patch Reefs scattered 

 throughout the seagrass community. Most of these reefs have little profile 

 and generally project up less than 2 m from the shallow bottom. 



The algal flora is quite sparse on the Patch Reefs themselves. The 

 coralline red algae Goniolithon sp . and Amphiroa rigida are most abundant.* 

 Scattered clumps of the attached brown alga ( Sargassum polyceratium ) , the 

 red alga ( Laurencia intricata ), and the green alga ( Bryopsis pennata ) were 

 observed. This scarcity of algae is a result of grazing pressure by herbi- 

 vorous fish and invertebrates. 



Among the faunal components in all Patch Reefs, octocorals are by far 

 dominant. They not only grow dense enough to give certain Patch Reefs the 

 appearance of the heavily vegetated landscape, but also attain unusual sizes. 

 Among giant sea feathers and sea whips, the largest specimens, close to 2 m in 

 height, are mainly Plexaurella nutans and Pseudoplexaura flagellosa . Compared 

 with prominent main reef structures, the abundance of stony corals is quite 

 low, while sponges are comparatively well represented. Both stony corals 

 and sponges grow here to small or medium size and comprise about an equal 

 share of the Patch Reefs' biomass. The most important species of stony 

 corals in this zone are the hydrocoral (firecoral) ( Millepora complanata ) , the 

 scleractinians ( Colpophyllia natans ), ( Diploria labyrinthiformis ) , ( D. strigosa ), 

 ( D. clivosa ), ( Siderastrea siderea ), and especially the staghorn coral ( Acropora 

 cervicornis ) that occurs here with greater frequency than in any other part of the 

 Looe Key Reef. Elkhorn coral ( Acropora palmata ) is not found in the Patch 

 Reef association. The pillar coral ( Dendrogyra cylindrus ), is found on 

 several patch reefs. Four colonies of this rare species were located on one 

 patch. One colony was especially impressive with six large pillars rising 1 m 

 from the base, along with several smaller spires adjacent to it. 



Frequently observed inhabitants of the patch reefs include: the anemones 

 ( Bartholomea annulata ), ( Condylactis gigantea ), and the mat-forming zoanthids 

 ( Palythoa mammillosum ) and ( Zoanthus sociatus ); serpulid and sabellid worms, 

 a variety of small crustaceans, especially the arrow crab ( Stenorhynchus 

 seticornis) . In the sandy and grassy areas adjacent to the Patch Reefs, the 

 echinoids Plagiobrissus grandis , Clypeaster rosaceus , and Diadema antillarum 

 are common. The latter are most abundant at the interface between the reef and 

 the surrounding halo. Summarizing all these data, the sand-sea-grass-reef 

 community of the Patch Reef zone appears to be a lagoon-type reef environment, 

 sheltered from violent wave action by the Looe Key Reef Flat, but subject to a 

 considerable sediment load suspended in the water column during rough weather. 



Numerous consumers utilize patch reefs as habitat and feed directly on 

 seagrasses, their epiphytes and associated macro-algae (Ogden and Zieman, 1977). 



''See Appendix B for complete list. 



51 



