Patterns of spatial variability of mobile macro-invertebrate assemblages within a Posidonia oceanica meadow.

The study evaluated patterns of spatial variability of mobile macro-invertebrate assemblages associated withPosidonia oceanicaleaves within a meadow at three different depths and three different coastal wave-exposures. A total of 171 taxa was found, among them two Nemertea, 65 Mollusca, 91 Arthropoda, eight Annelida and five Echinodermata. The total number of taxa per sample was higher in intermediate and deep stands than in shallow ones, while no significant differences among coastal wave-exposures were observed. Multivariate analyses detected significant differences in the structure of assemblages in relation to depth and coastal wave-exposure. Mollusca were more abundant in shallow stands, while Crustacea and Echinodermata increased in intermediate and deep stands. Moreover, patterns of spatial variability changed with depth: shallow and intermediate assemblages showed high small-scale (tens of metres apart) variability, while deep assemblages showed high variability at intermediate scale (hundreds of metres apart). [ABSTRACT FROM AUTHOR]