Abstract
Algae play a very important role as feed and shelter for fish, crustacean and gastropods. Thus, this study was carried out to know dynamics of epiphytic microalgae and their host macroalgae of Florideophyceae at Jeddah coast, the Red Sea. The water temperature, salinity, pH and dissolved oxygen varied from 21.6 to 32.30 degrees C, 36.40 to 39.70 ppt, 8.04 to 8.60, and 3.00 to 8.90 mg/L, respectively. A total of 10 seaweeds species of Florideophyceae was found, and among them Gracilaria corticata was found throughout the year. Gracilaria tikvahiae and Digenea simplex occurred from spring to autumn, and Acanthophora muscoides occurred from winter to summer. A total of 108 taxa of epiphytes were identified; 95 belong to Bacillariophyceae, 9 Cyanophyceae, 2 Dinophyceae, 1 Chlorophyceae and 1 Raphidophyceae. The epiphytes on A. muscoides varied from 9.50 to 66.10x10(5) cells/100 g of A. muscoides, and the highest cell abundance was in spring. Epiphytic cell abundance on Amphiroa sp., fluctuated from 5.38 to 40.78x10(5) cells/100 g of Amphiroa sp. Similarly, for Digenea simplex, epiphytes varied from 27.56 to 51.69x10(5) cells/100 g of D. simplex. Epiphytic cell abundance on Gracilaria corticata varied from 7.28 to 74.21x10(5) cells/100 g of G. corticata, and the lowest and highest cell abundance were in winter and summer, respectively. Among the microalgae, the contribution of Bacillariophyceae was highest (87.96%), followed by Cyanophyceae (8.33%) and Dinophyceae (1.85%). A total of 32 species contributed above 10% in epiphytic microalgae, and Licmophora sp., Navicula sp., Leptocylindrus sp., Nitzschia sp., Tabellaria sp., and Thalassionema sp., were the dominant species.