Seasonal Changes in Cystoseira Myrica and Phosphorus Input at Two Sites of the Red Sea Egyptian Coast

Elevated phosphate concentrations at Safaga and Quseir, Red Sea, Egyptian coast, wererelated to some ecological and nutritional aspects of the macro-alga Cystoseira myrica during1985. The results obtained were compared with those recorded for a non-polluted control site atGhardaqa. Chemical analysis of surface seawater samples revealed that the concentrations of dissolvedphosphate 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 yield(491 g m-2) and number of individuals (127 m-2) of C. myrica were recorded in the spring at theGhardaqa site. Quseir C. myrica samples contained significantly higher protein-N, total-N andtotal-P values but lower carbohydrate values than the Safaga and Ghardaqa samples (LSD at 1%level). Tissue N:P molar ratios for C. myrica, Laurencia papillosa and Ulva lactuca collected fromGhardaqa ranged from 68-98, compared to 30-59 for the same species collected at thephosphorus polluted sites at Safaga and Quseir. The carbon levels and the C:N ratios of C. myricaexhibited no significant variations in the three studied sites. However, the C:P ratios of Ghardaqaplants were significantly higher than those of Safaga and Quseir.