DISTRIBUTION, ABUNDANCE, AND SPECIES COMPOSITION OF SEAGRASSES AT SEVERAL SITES IN OMAN

Distribution, abundance, and biomass data for seagrass communities at several locations on the coast of Oman are presented. The main study s ite was on the western side of Masirah Island on the Arabian Sea coast of Oman. This area is an important feeding ground for the green turtl e, Chelonia mydas L., and it is affected by upwelling of low temperatu re waters during the summer monsoon. The depth distributions of Halodu le uninervis (Forssk.) Aschers, and Halophila ovalis (R. Brown) Hook, f., the two most abundant seagrasses at this site, overlapped but were inversely related. Halodule dominated the intertidal zone and Halophi la was more predominant in the deep subtidal, although total biomass o f the two seagrasses were similar in this depth zone. At all depths, b iomass of Halophila was about equally distributed between leaves and r oots and rhizomes. Leaf biomass of Halodule was only 7-20% of the tota l biomass and the highest below-ground biomass occurred in the interti dal zone. Biomass of these species here and at other sites and of Thal assodendron ciliatum (Forssk.) den Hartog at this site was generally l ower than comparative data in the Gulf and the Red Sea. Small patches of Syringodium isoetifolium (Aschers.) Dandy were also observed in Umm ar Rasas Bight making a total of four species recorded to occur in Om an. The reduced growth of seagrasses at Masirah Island seems to be due to stresses associated with the summer monsoon and grazing pressure, Survival of these populations is discussed in terms of seasonal growth and flowering.