الفهرس 
Coordinates of study sites in the Red Sea.Only 14 pages are availabe for public view
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Abstract
During January-December 2013,surface seawater temperature (22-31 °C) and salinity (40.4-44‰) were measured at four selected sites in Wadi El Gemal National Park.Percentage cover and abundance of seaweeds were estimated using quadrate method. The most abundant species of seaweeds belonging to the Phaeophyceae (Turbinaria ornata, Cystosiera myrica, and Padina pavonica) were chosen to evaluate their antibacterial activity. The extracts of seaweed were prepared by soaking the algal powder in three solvents (acetone, isopropyl and ethyl alcohol).The antimicrobial activity of the brown algaeextracts were examined against the human pathogenic bacteria (Pseudomonas aeruginosa, Staphylococcus aureusand Escherichia coli)using disc diffusion method.
The number of recorded species of seaweeds at Wadi El-Gemal was 38 species. Rhodophyta was the richest group, represented by 22 species (56% of the total recorded seaweeds) belong to 17 genera, Chlorophyta included 9 species (23%) belong to 6 genera and Ochrophyta (Phaeophyceae) contained 7 species (21%) belong to 7 genera. Phaeophyceae was the most dominant in terms of vegetative cover. Variation in the number of species between sites was not significant. This is because the environmental conditions are almost identical between sites. However, there was a clear monthly variation in the presence of species, recording the highest rates in the months with the lowest temperatures (November-February).
Accordingly, the most abundant species of Phaeophyceae (Turbinaria ornata, Cystoseira myrica and Padina pavonica) have been chosen to carry out studies of the vital activities of their extracts. Three types of organic solvents have been used (acetone, isopropyl and ethyl alcohols) to extract the active substances from these seaweeds. The study proved that the vital activities of seaweeds extracts as bacterial antigens depend on the species of seaweeds, type solvent and the microbial properties. where three types of different bacteria were used (Pseudomonasaeruginosa, Staphylococcus aureus and Escherichia coli). The different effects of solvents could be related to the solubility difference of active constituents of each alga. Moreover, the ability of seaweed to produce natural compounds varies in quantity and quality, depending on the type of seaweeds, efficacy and method of secondary metabolism for them. It is worth noting that the sensitivity of microbes to natural products of algae varies depending on the type of bacteria as well.