Benthic community associated with coral reefs in the coastal area of Gulf of Aqaba, Red Scs, Egypt

Abstract

Benthic community associated with coral reefs was investigated at four sites along the coastline of Gulf of Aqaba, Red Sea Egypt. The four sites (Taba, Nuweiba, Dahab and Shann El-Sheikh) are important popular spots for recreational activities and the reefs of these sites are of fringing type. Drupella cornus and Trochus maculatus were the most important gastropods associated with coral reefs. Taba and Sharm El-Sheikh showed high occurrence of worm shells (Gastropoda) Dendropdma maximum (up to 30 individuals / colony). Concerning the abundance of bivalves (Mollusca), Taba showed greater abundance of Spondylus varium and Pteria penguin ^ whereas Sharm El-Sheikh had the greatest abundance of Tridacna maxima (up to 40 individuals/lOm). The studied sites exhibited high density of Echinoderms, particularly the sea urchins Diadema setosvm, Tripneitstes gratilla and Heterocentrotus mammillatus. The study revealed selective associations between mollusc species and coral growth forms. The bivalve Pteriapenguin was found to be attached with plate-like coral Mellipora platyphylla and the branching coral Millepora dichotoma. The vennetid gastropod Dendropoma maximum was also found to be inserted into the Melliporid coral colonies. Aggregates of Drupella cornus were observed attached with branching corals, especially Acropora spp. and Stylophora spp. In contrast to the Drupella cornus, the corallivore gastropod CoralUphila neritoidea and the bivalve Tridacna maxima were predominantly preying on the massive corals of Poriies spp. The distribution of coral growth forms was compared. In general, massive, branched and plate-like colonies were the dominant growth forms of corals in the area of study. Massive colonies were dominant in the reef flat area, reef margin and the deep parts of the outer reef slope. Branching coral colonies were flourishing on the fringing reef flat, the barrier reef flat and the outer reef slope until 10m depth (upper layers of outer reef slope), their importance declined with depth. All plate-like coral colonies in the area of study belong to Hydrocorals (Milleporidae); Millepora platyphyla. They are abundant in the reef edge and upper zone of outer reef slope (the reef zone exposed to high wave action). The considerable abundance of macroalgae in the coral communities of the sampling sites were probably resulting from increased levels of nutrients caused by enhanced terrestrial runoff of sewage and sediments concomitant with increased human pressure in the area and coastal