Floristic composition and zonation of seaweeds on Zabargad Reef (Red Sea, Egypt)

Document Type : Original Article

Author

Botany Dept., Fac. of Science, Suez Canal University

Abstract

Composition, dominance, distribution and zonation of seaweeds were investigated, using line-transect technique,
in three sites of varied water activity on Zabargad reef during November 1994. Fifty-four taxa included 16 green,
13 brown and 25 red macroalgae were identified, adding four new records for the Red Sea. The flora appears
rich and diverse, composed of filamentous, turf-forming, fleshy sac, foliose, erect shoot, and coralline forms. It
showed a geographic distribution pattern similar to that of the Indo-Pacific.
The seaweed vegetation appears heterogeneous, having a dissimilar construction at each side of the
reef. It showed a conspicuous zonation, revealing six zones related in general to reef topography, water
movement and in a lesser extent to grazing and nutrient enrichment. The intertidal zone had a marked reduced
flora due to exposure to air during low tide, and mobility of coral sand. Reef flat was the richest in species
composition and dominance, as it lies in a shallow, well-illuminated, and less fluctuated subtidal region. Peculiar
was the presence of high species dominance in strong surf on the windward reef crest. The reason for this is that
the crest is extensively eroded, rich in crevices and fissures within which the algae hideaway from wave action.
Moreover, strong rhizoids, dwarfing of thalli, crustose morphologies, growing in adherent to substrata were
some modifications allowing algae to persist in strong surf.

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