of the bottom sediments in the reefs of the West Atlantic (Goreau, 

 Goreau, 1973). Another important source of material for the formation 

 of coral sand is the skeletons of dead corals, sea stars, sea urchins, 

 the shells of benthic mollusks, as well as the shells of ostracods, 

 foraminifera and pteropods, ground up by the surf. 



2.2 Types of Coral Reefs, their Zonal ity. Growth and 

 Population with Flora and Fauna 



Large reef structures can be subdivided into coastal, barrier and 

 atoll-type reefs. There are transitional forms between these basic 

 types as well. The development of any given type of reef depends on the 

 nature and tectonic mobility of the bottom on which it develops, as well 

 as the intensity of the arrival of terrigenous material from the land. 

 An important factor influencing the formation of the outlines of reef 

 structures is the fact that a most active growth of the corals creating 

 the skeletal basis of the reef occurs on the outer side of the reef, the 

 side directed toward the ocean. It is here that the optimal conditions 

 are created for the growth of coral (Yonge, 1953). On the inside of the 

 reef, the conditions are much worse for the growth of coral ; they 

 frequently die here. This factor leads to the formation of circular 

 atoll reefs where the growth of the corals is not limited by a 

 shorel ine. 



Coastal, or fringing, reefs are usually formed on rocky plateaus of 

 small islands, with no significant terrigenous runoff, not subject to 

 constant tectonic downwarding. One characteristic feature of this type 

 of reef is that there is no lagoon. The reef plateau (reef flat) is 

 directly adjacent to the shoreline. An example of this type of reef is 

 the reef associated with the island of Titia (Fiji) (Fig. 1). 



Barrier reefs are also formed on shallow coastline plateaus. They 

 differ from surrounding reefs in that there is a lagoon between the reef 

 flat and the shoreline. The lagoon is formed as a result of the death 

 of corals and cessation of their subsequent growth near the shore. The 

 growth of corals near the shore is depressed by the terrigenous runoff 

 and the decrease of the water in circulation. An example of a barrier 

 reef is the reef associated with the island of Tuvuta (Fiji) (Fig. 2). 

 The structures of barrier reefs achieve gigantic dimensions. The 

 largest of these is the Great Barrier Reef along the east coast of 

 Australia. It is an entire system of reefs extending about 2000 km in 

 length, with a total area of some 250,000 km . In contrast to most 

 other reefs, where the main mass of the lime material is created by 

 calcareous algae, the Great Barrier Reef was constructed by corals, the 

 algae being of secondary significance. The thickness of the reef 

 limestone, according to drilling information, is 300-700 m (Ladd, 

 1969). The second largest barrier reef, over 700 km in length, is 

 located off the north and northeast coasts of the island of New 

 Caledonia. The third is considered to be the barrier reef off the north 

 coast of the Fiji Islands. Its length reaches 400 km. The barrier off 

 the coast of Arabia in the Red Sea is also worthy of mention in any 

 discussion of large barrier reefs. 



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