the elkhorn coral ( Acropora palmata ) component which is usually characteristic 

 of reef crests. Moreover, this shal low Mil lepora zone does not form a proper 

 barrier but is transected by many valley's! Several of these are extensions 

 of the seaward grooves, others are transverse channels, running perpendicular 

 to the grooves, thus breaking up the Mil lepora zone into huge, block-like 

 segments. Sections of the walls and bottoms of these channels are lined 

 with the urchin Diadema antillarum . 



Seaward, some portions of the Mil lepora zone drop abruptly to the rubble- 

 filled ends of the grooves. The sections in between gradually develop into 

 spurs, the tops of which are not deeper than about 2 m, for the first 20 to 

 30 m seaward. These platform-like "backs" of the leeward spurs, and their 

 almost vertical walls, are two distinctly different biotopes. On top, large 

 areas are covered by soft mats of colonial zoanthids Palythoa mammillosum 

 and Zoanthus pulchellus . Mil lepora complanata is the dominant stony coral 

 here although single colonies or clusters of elkhorn coral, ( Acorpora palmata ), 

 are irregularly interspersed. The only substantial concentration of Acropora 

 palmata is immediately seaward of the Mil lepora complex, exactly where one 

 would expect the highest part of the reef crest to be developed. Close 

 inspection of the reef's framework, on the spur's vertical walls, indicates 

 that the main construction element of the spurs has apparently been Acropora 

 palmata , which today does not seem to be that dominant. Discussions of 

 origin and zonation of spur and groove systems are given by Shinn (1963), 

 and Geister (1977). 



Following the spurs seaward, in depth increasing from 3 to 8 m, (= depth 

 of spur's top), one finds a zone which may well be the most important, certainly 

 the most spectacular part of the Looe Key reef. Some of the spurs show a 

 profile here of up to 7 m high, caused mainly by the vigorous construction 

 activity of the "mountainous" star coral ( Montastraea annularis ). This species 

 builds buttresses of 2 to 3 m in diameter and 4 to 5 m from bottom to top: 

 the vertical walls of these form most of the spurs' steep sides. On top of 

 the spurs, ( Montastraea annual aris ) is still represented in boulders of 1.5 

 to 2 m in diameter, accompanied by similar sized specimens which are primarily 

 brain corals such as Diploria strigosa and Colpophyll ia natans . Due to the 

 massive nature of the reef-builders in this subzone, there are few holes in 

 the reef framework, consequently allowing little insight into the history of 

 construction. 



The last segment of the spurs is a rather flat extension of the proceeding 

 high profile. The spurs' elevation over the sand bottom here is not more 

 than about 1 m, formed mainly by Montastraea cavernosa , which occurs in 

 cone-shaped colonies 30-40 cm in height. Similarly sized specimens of Sideras - 

 trea siderea , Montastraea annularis , Colpophyllia natans , Diploria strigosa , 

 U. labyrinthiformis , and Meandrina meandrites also occur here, but are much 

 less frequent. 



Among other invertebrates, bivalve molluscs are relatively common in 

 recesses on the surfaces of the spurs, but are almost invariably encrusted 

 and very difficult to distinguish from the background. Gastropods are 

 ubiquitously distributed in this zone. Brittle stars are both numerous and 

 diverse in the Fore Reef; they appear most abundant in recesses and grooves 



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