SEASONAL-CHANGES IN CYSTOSEIRA-MYRICA AND PHOSPHORUS INPUT AT 2 SITESOF THE RED-SEA EGYPTIAN COAST

Elevated phosphate concentrations at Safaga and Quseir, Red Sea, Egypt ian coast, were related to some ecological and nutritional aspects of the macro-alga Cystoseira myrica during 1985. The results obtained wer e compared with those recorded for a non-polluted control site at Ghar daqa. Chemical analysis of surface seawater samples revealed that the concentrations of dissolved phosphate at Safaga and Quseir were 3 and 20 times as much as that at Ghardaqa, respectively. The standing crop of C. myrica showed two peaks in spring and autumn. Maximum biomass yi eld (491 g m(-2)) and number of individuals (127 m(-2)) of C. myrica w ere recorded in the spring at the Ghardaqa site. Quseir C. myrica samp les contained significantly higher protein-N, total-N and total-P valu es but lower carbohydrate values than the Safaga and Ghardaqa samples (LSD at 1% level). Tissue N:P molar ratios for C. myrica, Laurencia pa pillosa and Ulva lactuca collected from Ghardaqa ranged from 68-98, co mpared to 30-59 for the same species collected at the phosphorus pollu ted sites at Safaga and Quseir. The carbon levels and the C:N ratios o f C. myrica exhibited no significant variations in the three studied s ites. However, the C:P ratios of Ghardaqa plants were significantly hi gher than those of Safaga and Quseir.