V. Millepora -Sponge Zone: A zone where crusts 

 of the hydrozoan coral Millepora share the 

 tops of siltstone and claystone outcrops 

 with sponges and other epifauna. 



VI. Antipatharian Zone: A zone where limited 

 crusts of coralline algae and several 

 species of corals exist within a zone marked 

 by sizeable populations of antipatharians. 

 Banks supporting Algal-Sponge Zones 

 generally possess a zone comparable to an 

 Antipatharian Zone as a transition between 

 the Algal-Sponge Zone and deeper, 

 turbid-water, lower bank zones. 



VII. Nepheloid Zone: A zone located at the bases 

 of all banks wherein high turbidity, 

 sedimentation, resuspension of sediments, 

 and resedimentation dominate. Rocks and 

 drowned reefs here are generally covered 

 with veneers of fine sediment. Epifauna are 

 depauperate and variable; deep-water 



octocorals and solitary stony corals are 

 often conspicuous. This zone occurs in some 

 form on lower flanks of all banks below the 

 depths indicated for Zone VI, above. 



Of the above zones, I- IV are considered to be characterized by major 

 reef-building capabilities (Category A), Zone V by minor reef-building 

 capability (Category B) , Zone VI by some (but negligible) reef-building 

 capability (Category C) and Zone VII by no reef-building capability 

 (Category D) . 



Each of the seven characteristic zones were ranked on a scale of 1 

 to 8, based upon considerations of its reef-building attributes, 

 biological diversity, aesthetics, rarity and areal extent. This was 

 done to provide an index of their environmental priority. These indices 

 were then used to assign a priority rating to each of the outer shelf 

 banks by s ummi ng the respective indices for each zone represented on the 

 bank in question. On this basis, the East and West Flower Garden Banks 

 had the highest priority rating (Index value was 36, Figure 20) as Zones 

 I-IV are all represented along with Zones VI and VII. With the 

 exception of Sackett Bank near the Mississippi River Delta and 

 characterized by Zones VI and VII only, the banks along the shelf edge 

 had higher ratings (values ranged from "11 to 17) than banks located 

 more shoreward (values ranged from 6 to 8, Figure 20). The shelf edge 

 banks other than the Flower Gardens were characterized by the presence 

 of Zones III and/or IV in conjunction with Zones VI and VII. The more 



43 



