MACROPHYTOBENTHOS OF ROCKY INTERTIDAL SEM I-EXPOSED PLATFORMS OF THE SAFI-ESSAOUIRA REGION (WESTERN MOROCCO)

In 1990, a study of the phytobenthos of the rocky intertidal platforms in the Safi-Essaouira region (Sidi Boulbra, Western Morocco) was carr ied out at three sites. The intertidal zonation was analysed along per manent transects, and a qualitative and quantitative study of two char acteristic units of the eulittoral vegetation - the vegetation belt of Fucus spiralis and the communities of Florideophyceae - was made. One hundred and twenty-nine macroalgal taxa and three phases were listed: 19 Ulvophyceae, 19 Fucophyceae, 1 Bangiophyceae and 93 Florideophycea e. The intertidal communities of the area are typical of semi-exposed and unpolluted platforms of Western Morocco, in the eulittoral zone, m ost of the typical Fucales that occur along the NE Atlantic coasts are absent, with the result that Florideophyceae are dominant. The compos ition and distribution of the communities are influenced by the short morphology (extensive platform, gentle slope and roughness degree), th e substrate (sandstone), the occurrence of sediment and by high exposu re to wave action. The vegetation belt of Fucus spiralis of Sidi Boulb ra ranks floristically amongst the richest described in the NE Atlanti c, and is characterized by the presence of southern species. The commu nities of Florideophyceae exhibit a mixture of exposed-shore, sheltere d-shore and sand-tolerant species, resembling those described from SW Portugal. The dominant species change according to the season and envi ronmental conditions. Over low-roughness platforms, an Osmundea, Gigar tina (site 1) and a Leptosiphonia (site 3) community may be observed i n winter-spring, and a Caulacanthus, Ceramium, Gelidium community in s ummer-autumn, Over extensive high-roughness platforms (site 2), this s cheme is somewhat obscured by the development of varied Fucophyceae (D ictyotales, Sphacelariales). Moreover, any extensive destruction of eu littoral communities usually induces a green algal bloom (Ulvales). Am ongst the common algae from Sidi Boulbra, several Gelidiales and Gigar tinales are potentially commercial taxa.