In the present study we describe, throughout a single year, subtidal macroalgal assemblages present on a shallow platform and on a deep cliff, using species and functional groups as descriptors. The study site is located south of Leghorn in the north-western Mediterranean Sea. Univariate and multivariate analyses were performed to detect spatial and temporal variations.A total of 101 macroalgal species were found: 17 Chlorophyta, 13 Phaeophyta and 71 Rhodophyta. The shallow platform assemblage was more structured than that on the cliff, in fact the number of species was higher and a well developed stratified structure, consisting of turf, encrusting and erect vegetation layers was present. On the platform, functional groups showed qualitative and quantitative seasonal variations, while the cliff assemblage exhibited a dominance of crustose species throughout the year. The species richness found in the present study is lower than that observed in other Mediterranean macroalgal assemblages. This condition may be linked both to the spread of Womersleyella setacea turf, that may exclude other macroalgae by overgrow and pre-emption, and to the stress caused by sediment deposition and burial, that may damage macroalgal growth and recruitment. The multidimensional scaling analysis, performed both on the samples-species matrix and on the samples-functional groups matrix, showed a similar pattern, even if the use of species-level approach permitted a more accurate description of the assemblages.
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