Concentrations of seven heavy metals (Cu, Zn, Pb, Cd, Ni, Co and Fe) were measured in the seawater, sediments, common scleractinian reef-building corals and soft corals (Octocorallia : Alcyonacea) at seven reef sites in the Northern Red Sea: I (Hurghada), II (Ras Za'farana), III (El-Ain Al-Sukhna), IV (El-Tur), V (Sha'b Rashdan), VI (Sharm El-Sheikh) and VII (Dahab). Levels of heavy metals were considerably elevated in seawater, sediments and corals collected from reef sites exposed to increased environmental contamination, as a result of diversiWed natural and anthropogenic inputs. Soft corals of genera Lithophyton, Sarcophyton and Sinularia showed higher concentrations of Zn, Pb, Cd and Ni than hard coral genera Acropora and Stylophora. Soft coral Sarcophyton trocheliophorum collected from El Ain Al-Suhkna (Gulf of Suez) had greater concentration of Cu, followed by hard corals Acropora pharaonis and Acropora hemprichi. The elevated levels of Zn, Cd and Ni were reported in the dry tissue of soft coral Sinularia spp. On the other hand, the soft coral Lithophyton arboreum displayed the highest concentration of Pb at Sha'b Rashdan (Gulf of Suez) and elevated concentration of Zn at Sharm El-Sheikh. Sediments showed signiWcantly higher concentration of Fe than corals. The higher levels of Fe in hard corals than soft corals reXected the incorporation of Fe into the aragonite and the chelation with the organic matrix of the skeleton. The greater abundance of soft corals in metal-contaminated reef sites and the elevated levels of metals in their tissue suggesting that the soft corals could develop a tolerance mechanism to relatively high concentrations of metals. Although the eVects of heavy metals on reef corals were not isolated from the possible eVects of other stresses, the percentage cover of dead corals were signiWcantly higher as the concentrations of heavy metals increased.

Chemical investigation of an ethyl acetate soluble fraction of Sinularia polydactyla (Ehrenberg) led to the isolation of three known terpenoides, two of them sterols, 24-methylcholestane-3β,5α,6β,25-tetrol 25-monoacetate (1), 24-methylcholestane-5-en-3β,25-diol (2), in addition to a cembranoid diterpene, durumolide C (3), for the first time. The cytotoxicity and antimicrobial activities of the ethyl acetate extract and the isolated compounds 1-3 were evaluated in vitro. Durumolide C (3) showed selective cytotoxicity against HepG2 (IC50 1.0 μg/mL), whereas 24-methylcholestane-3β,5α,6β,25-tetrol 25-monoacetate (1) showed IC50 of 6.1 and 8.2 μg/mL against Hep2 and HCT human cancer cell lines, respectively.

No abstract

F ifteen water quality parameters and nine coral community variables were assessed in eight reef sites along the Red Sea coast of Egypt. Coral reef environments are suffering of stress from increased anthropogenic activities, particularly in the vicinity of heavily populated and touristic areas such as Hurghada, Ain Al-Sukhna and Sharm El-Sheikh. Increased terrestrial runoff of sediments, nutrients, organic matter and other pollutants are the main causes of water quality deterioration in the investigated reef sites. The results showed that bioerosion of corals by sea urchins, and enhanced abundance of macroalgae and consequent competitive overgrowth of corals were the major reasons of coral damage observed in the area of study. Population density of sea urchins exhibited significant and positive correlations with the majority of eutrophication parameters. Salinity was significantly and negatively correlated with live hard coral cover. Exceeding levels of DIN and TSM above the threshold concentrations for eutrophication were reported to be indirectly and adversely affecting coral reefs through stimulating the growth of macroalgae, enhancing sea urchin density and reducing water transparency. The results support the predictions of bottom-up hypothesis that confirm the critical role of eutrophication in structure of coral reef community.

No abstract