RHODOLITH FORMATION INDUCED BY REEF EROSION IN THE RED-SEA, EGYPT

Along the northwestern margin of Safaga Island (Northern Bay of Safaga , Red Sea, Egypt) a small fringing reef (several hundred meters long, up to 2m high) and small patch reefs are developed due to the local cu rrent regime which is favorable for coral growth. Corals and reef rock are encrusted by coralline algae, predominantly by branched Lithophyl lum kotschyanum. Owing to destructional processes dominated by sea urc hin activities, fragmentation of (1) corals, (2) reef rock, and (3) co ralline algae takes place resulting in the formation of almost monospe cific, branched Lithophyllum kotschyanum rhodoliths. Rhodolith formati on takes place in various reef environments: (1) in depressions on the reef flat where ellipsoidal rhodoliths develop, with interlocking and fusing branches leading to a coralline algal framework; (2) in discha rge channels where smaller elongated rhodoliths occur; (3) in leeward positions between reef flat and seagrass meadows, where a dense belt o f spheroidal to ellipsoidal rhodoliths is formed; scattered rhodoliths occur in adjacent seagrass beds. The formation and preservation of rh odoliths requires a complex interplay of destruction, growth, transpor tation, movement, and stabilization.