One rational strategy for restoration of coral reefs: Application of molecular biological tools to select sites for rehabilitation by asexual recruits

Experiments for reef rehabilitation were performed at two selected sites ne ar Hurghada (Red Sea, Egypt) the reef close to the Marine Biological Statio n (with a high sedimentation rate from landfilling) and El-Fanadir Reef (a clear mater site). Since only little is known about the influence of the ph ysical environmental conditions, novel molecular biological approaches have been introduced to assess the metabolic status of corals. In order to avoi d possible interference with symbionts the molecular studies have been perf ormed with the octocoral Dendronephthya klunzingeri; this species does not contain zooxanthellae. The metabolic enzymes fructose-1,6-bisphosphatase an d the succinat-dehydrogenase served as markers for the assessment of the he alth status of the corals. The cDNAs for both enzymes were isolated and the ir levels of expression were found to be correlated with the degree of envi ronmental stress. High expression was found at the El-Fanadir Reef, while o nly low levels were measured at the Marine Biological Station, which is cha racterized by high sedimentation rates. From this it is concluded that the health state of D. klunzingeri from El-Fanadir is superior to the one from the Marine Biological Station. Six reef-building corals have therefore been selected from El-Fanadir for the transplantation studies. We applied fixat ion of coral nubbins in plastic meshes with narrow openings. The asexual re cruits remained either unfixed or had been glued to the mesh with epoxy res in. A total of 236 coral fragments were transplanted at the Marine Biologic al Station Reef and 108 fragments at El-Fanadir Reef. The referred techniqu e was successful and the survival rates were higher for samples fixed with epoxy resin than for those without epoxy resin. The survival and growth rat es of the coral transplants were found to be higher at the windward side of El-Fanadir Reef than on the leeward side of the same reef. Furthermore, th e mortality rates at the leeward side of El-Fanadir Reef were still lower c ompared to the Marine Biological Station. The coral species Pocillopora dam icornis grew well in the clearer water and hard rocky substrate but it did not grow at all in turbid mater and sandy substrate; however, the species A cropora humilis grew web in both environments but with higher rates in the clearer water. After one year of transplantation, the massive coral Favia s telligera recorded the highest survival rate of all coral species at the Ma rine Biological Station Reef; but among branching corals, A. humilis had th e highest value and P. damicornis the lowest. Contrary to this result, P. d amicornis recorded the highest value at El-Fanadir Reef. It is concluded th at asexual recruits of corals, taken from a site (D. klunzingeri from El-Fa nadir) physiologically favourable for them, are suitable for a coral restor ation strategy. (C) 2000 Elsevier Science Ltd. All rights reserved.