Excess nutrient loads human activities lead to algal bloom, the world wide problem, by increasing production of algae. When those algae occur in dense blooms, they can cause fish and invertebrate killed because dissolved oxygen is consumed when the bloom decomposes and it also degrade the recreation amenity of the beaches. The growth of macroalgae is controlled, in large part, by nutrients as well as salinity, light and temperature. N and P are the two most common nutrients that limit macroalgal growth.(Kamer and Schiff.,2002)For the majority of algal species, ammonium is the most easily assimilated type of Dissolved Inorganic Nitrogen(DIN), although some species may prefer nitrate, nitrite or and organic form such as urea. (Jones.,1993) Oppotunistic macroalgae can uptake, assimilate and store a large amount of nutrients, resulting in low nutrients concentration in the water column, even in the area of high loading (Valiela et al.,1992;Peckol et al., 1994) thus, they are allowed to grow at maximal rates for several days without nutrients supplies. Ulva spp.,also known as sea lettuce, are a common fast-growing macroalgae of the littoral zone and are generally known as one of the species forming “green tides” . Ulva spp. Are usually the first colonizers on open substrata, and their cosmopolitan presence is attribute to their tolerance of a wide range of environment. (Littler and Littler, 1980) Moreover, Ulva sp. Are particular good bioindicators of eutrophication, even better than simply testing water itself. Their levels of nutrients in the tissue results from the long-term integration and accumulation from the surrounding water while water-column analysis would only detect the instantaneous nutrients concentration in the time of sampling However it has recently been shown the analyses of pigment content of macroalgae can provide an accurate representation of the nutrient status in the water body .(Jones 1994)