Spatial and temporal variation of motile macro-invertebrate assemblages associated with Posidonia oceanica meadows

Abstract

         The present study assesses the spatial and temporal distribution of motile invertebrates in Posidonia oceanica meadows located off the coast of Tuscany, in the northwestern Mediterranean Sea. A hierarchical sampling design was used to evaluate changes in composition and abundance of assemblages in relation to depth and to different periods over one year. A total of 136 taxa were determined, among them 34 Mollusca, 94 Arthropoda, 5 Annelida and 1 Echinodermata. Results of both multivariate and univariate analyses showed that the macro-invertebrate assemblage structure varied along a depth gradient but this pattern was not consistent in the two study periods. Results suggest that temporal and spatial differences in the structure of P. oceanica meadows are key drivers in determining the structure of associated macro-invertebrate assemblages, as values of richness and abundance decreased with a decrease in leaf length and shoot density.