In the Krusadi area a luxuriant growth of sea weeds such as Sargassum, Caulerpa, Turbinnria, Spatoglo- ssum, Gracilaria, Ulva, Enteromorpha, Chaetomorpha and Polysi- phonia. The abundant sponges of this reef are Spirastrella incorstans and Callyspongia fibrosa. The other inhabitants of this reef are following —hydroid coelenterates like Syncoryne, Sertularia, Euden- drium, Pennaria, Tubuluria. Thyroscypus, Flumularia ; alcyonarians like Clavularia, Alcyonium, Lobophytum, Sclerophytum, Telesto, zooantharians like Zoanilius, Gemmaria ; polychaete annelids like Nereis, Polynoe, Eunice, Lepidonotus, Iphione, Eurythoe, Hesione ; sipunculid species like DendroStomum, Aspidosiphon and Phascolo- soma; molluscs like Doris, Dendradoris, Acanthochiton, Ischinochiton, Haliotis, Emarginula, Trochus, Turbo, Nerita, Natica, Cypraea, and echinoderms like Holothuria atra, H. scabra, H.
edulis and starfish Proteaster lincki. Beautifully pigmented fishes like Holocentrus, Lutianus sp., Pomacanthoides, Chaetodontopsis, Chaetodon, Linophora, Thallasoma and Zanclus and the eels Gymnothorax undulatus and punctatus are commonly frequent in the coral reefs. These inhabitants of coral reef community, when exposed to lowtides are subjected to predation by large number of birds like the crested tern Sterna bergii, golden plover Pluvialis dominica fulva, etc. According to Clapham, Jr. (1973) the great productivity of reefs is obviously caused by something more than the abundance of light and oxygen. He considers nutrient cycles which run very quickly and efficiently between the components of reef ecosystem to be main cause of great productivity of reef ecosystems.
In fact, no organic matter is incorporated permanently into the sedimentary system portion of reef. The conditions of rapid nutrient cycling allow a mechanism by which the natural scarcity of nutrients in the ocean can be effectively circumvented. It may also allow a gradual increase in nutrient availability by incorporating the nutrients of the non-reef organisms that wash into the reef, while still continuing to prevent the reef’s own nutrients from being lost to the deeper seas.