Physicochemical analysis of water at Suez Canal, Suez Gulf and Red Sea coast of Egypt all over the year indicate that there is a seasonal and local variation of the eutrophic status of water especially total phosphorous, ammonia, nitrite and nitrate. Furthermore, Ulva lactuca has a local and temporal variation in its covering percentage and its biochemical content indicates that protein, soluble carbohydrate, insoluble carbohydrate and lipid contents increased during winter at all stations. Also, minerals (K, Na, Ca, and P) and heavy metals (Fe, Co, Mn, Cd, Cu, and Zn) were measured. Maximum antimicrobial activities of U. lactuca were observed with chloroform extract as compared with the other solvents. The extract of U. lactuca was, in general, more efficient as antibacterial than as antifungal. On the other hand, the effect of the extract against Pseudomonas aeruginosae was effective more than other bacteria Klebsiella pneumoniae, Escherichia coli, Micrococcus roseus, Bacillus cereus, Enterobacter cloacae and Staphylococcus aureus. Moreover, antifungal activity against Fusarium oxysporium- pisi, F. solani, Alternaria alternta, Botrytis fabae, Aspergillus niger, A. flavus, and Rhizocotonia solani was studied. However, Faied area seemed to be the most site producing antimicrobial activity. The antibiotic activities of U. lactuca were more observed at all sites during winter and autumn than summer and spring.
Key words: Ulva lactuca, Bioactivity, Red Sea