Cnidarians, sponges, echinoderms and molluscs all contribute to reef 

 building in that they can remove dissolved material from the water and deposit 

 it as hard mineral compounds. Calcium carbonate (CaCOo), the building material 

 of reefs, comprises much of this material. Stony corals and molluscs contri- 

 bute with their hard skeletal remains; gorgonians and certain sponges, by 

 secretions of microscopic rods of CaC03 released with the death of the animals; 

 echinoderms, through skeletal remains composed of carbonate plates. 



The Looe Key Reef System 



All major taxa of coral reef-dwelling organisms are represented at Looe 

 Key. A report, based on a resource inventory conducted by Antonious et al , 

 in 1978, indicates the existence of several hundred species of marine 

 organisms, co-existing in the intricate functional web of the reef ecosystem. 



The inventory divides the Looe Key Reef area, from an ecological /topo- 

 graphical point of view, into five zones: (1) a Patch Reef area between 

 Hawk Channel and the Looe Key reef flat, (2) the Reef Flat, triangular in 

 shape, with the Looe Key marker in the southeast corner, (3) the Fore Reef, 

 facing Florida Straits to the south, consisting of a spur and groove system, 

 and the reef crest (4) a Deep Reef area with a drop-off, southwest of the 

 Fore Reef and (5) a Deep Ridge, separated from the Deep Reef by an estimated 

 1 km of sand bottom (Figure 2). The proposed sanctuary boundary was selected 

 to insure inclusion of portions of all five zones. 



Patch Reef 



A flat and relatively shallow area of about 8 m in depth stretches from 

 Hawk Channel south to the Looe Key Flat. The area is dominated by a mixed 

 association of seagrasses, such as turtle grass and manatee grass, and green 

 algae and octocorals. 



Continued survival of the seagrass beds is critical for maintenance of 

 the habitat utilized by numerous fishes and the spiny lobster. Utilization 

 of the patch reefs for shelter from predators allows both juveniles and 

 adults to exploit an enormous and nearby source of energy, the biomass of 

 seagrass association. 



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. 



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

 far the most dominant. They not only grow densely enough to give certain 

 Patch Reefs the appearance of a heavily vegetated landscape, but also attain 

 unusual sizes. Octocoral species diversity is greater in the Patch Reefs than 

 on the more spectacular Fore Reef. Among giant sea feathers and sea whips, 

 the largest specimens are close to 2 m in height. 



