Spatial and temporal variability of Mediterranean macroalgal coralligenous assemblages in relation to habitat and substratum inclination

Abstract

In the present work, coralligenous phytobenthic communities of the north-western Mediterranean Sea were studied in three deep sublittoral habitats: islands, continental coasts and offshore banks. Species and morphological groups were utilised as descriptors. A combination of univariate and multivariate analysis was used to describe variability in coralligenous macroalgal assemblages of vertical rocky cliffs between habitats and at different spatial scales within each habitat. In addition, temporal dynamics in the structure of macroalgal assemblages on horizontal and vertical surfaces were studied for one location. A total of 99 macroalgal species was identified, among them 12 Fucophyceae, 10 Chlorophyta, and 77 Rhodophyta. Results showed no major differences between assemblages of the rocky habitats studied. Spatial variability within each habitat appeared higher at the smallest scale investigated for all variables considered. In the coralligenous assemblages of the bank, patterns related to the inclination of substratum were not significant, except for filamentous species and turf layer. In contrast, the assemblages showed significant seasonal differences mostly related to the disappearance of many turf-species and the decrease in cover of most erect algae, principally foliose and corticatedterete forms, in the cold season.