One Rational Strategy for Restoration of Coral Reefs: Application of Molecular Biological Tools to Select Sites for Rehabilitation by Asexual Recruits

Abstract

Experiments for reef rehabilitation were performed at two selected sites near Hurghada (Red Sea, Egypt) the reef close to the Marine Biological Station (with a high sedimentation rate from landfilling) and El-Fanadir Reef (a clear water site). Since only little is known about the influence of the physical environmental conditions, novel molecular biological approaches have been introduced to assess the metabolic status of corals. In order to avoid possible interference with symbionts the molecular studies have been performed with the octocoral Dendronephthya klunzingeri; this species does not contain zooxanthellae. The metabolic enzymes fructose-1,6-bisphosphatase and the succinat-dehydrogenase served as markers for the assessment of the health status of the corals. The cDNAs for both enzymes were isolated and their levels of expression were found to be correlated with the degree of environmental stress. High expression was found at the El-Fanadir Reef, while only low levels were measured at the Marine Biological Station, which is characterized 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 fixation of coral nubbins in plastic meshes with narrow openings. The asexual recruits remained either unfixed or had been glued to the mesh with epoxy resin. A total of 236 coral fragments were transplanted at the Marine Biological Station Reef and 108 fragments at El-Fanadir Reef. The referred technique was successful and the survival rates were higher for samples fixed with epoxy resin than for those without epoxy resin. The survival and growth rates 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, the mortality rates at the leeward side of El-Fanadir Reef were still lower compared to the Marine Biological Station. The coral species Pocillopora damicornis grew well in the clearer water and hard rocky substrate but it did not grow at all in turbid water and sandy substrate; however, the species Acropora humilis grew well in both environments but with higher rates in the clearer water. After one year of transplantation, the massive coral Favia stelligera recorded the highest survival rate of all coral species at the Marine Biological Station Reef; but among branching corals, A. humilis had the highest value and P. damicornis the lowest. Contrary to this result, P. damicornis recorded the highest value at El-Fanadir Reef. It is concluded that asexual recruits of corals, taken from a site ( D. klunzingeri from El-Fanadir) physiologically favourable for them, are suitable for a coral restoration strategy.