THE SPATIAL VARIABILITY OF MACROALGAL COMMUNITIES AND THEIR FUNCTIONAL GROUPINGS ON THE FRINGING REEFS OF GHARDAQAH, EGYPT

Abstract

Spatial variation in cover and biomass of macroalgae was investigated during February 3-5, 2008 on three locations representing the north, mid and south reefs of Ghardaqah. Data were collected from inner, middle, outer and fore zones using 1 m2 quadrate. Four functional groups were distinguished: upright leathery, upright fleshy, turf and crustose coralline algae. Cover and biomass were higher at both middle and outer reefs than inner and fore reefs. Species composition and abundance and the relative contribution of each group to the overall cover and biomass considerably varied in relation to the reef health. Abundant and conspicuous upright leathery assemblage of Cystoseira with Sargassum, Turbinaria and Hormophysa dominated the northern reefs and benefited from increases in substrate availability due to large areas of dead corals. Living corals did not exceed 5% of this reef and dominated by crustose corallines. Mid region had low macroalgal coverage of upright, crustose and turf algae (all not exceed 30%), and could be an example of the healthy reef. Southern reef had low abundance of leathery, crustose and turf assemblages, but had high upright fleshy algae and could be considered as an intermediate stage of reef degradation. As a group, fleshy upright macroalgae such as Caulerpa, Halimeda, Amphiroa, Gelidium, Padina and Dictyota are likely to benefit from many of the environmental changes brought about by tourism. Enteromorpha intestinalis was rare (cover 3%±0-2) on reef flat, but extensively colonized the bottom and sides of yachts, their mooring ropes and drifted in very large amount on the beaches.