Macroalgal forest vs sea urchin barren: Patterns of macro-zoobenthic diversity in a large-scale Mediterranean study

The study aimed at contributing to the knowledge of alternative stable states by evaluating the differences ofmobile and sessile macro-zoobenthic assemblages between sea urchin barrens and macroalgal forests in coastalMediterranean systems considering a large spatial scale. Six sites (100 s km apart) were selected: Croatia,Montenegro, Sicily (Italy), Sardinia (Italy), Tuscany (Italy), and Balearic Islands (Spain). A total of 531 taxa, 404mobile and 127 sessile macro-invertebrates were recorded. Overall, 496 and 201 taxa were found in macroalgalforests and in barrens, respectively. The results of this large-scale descriptive study have met the expectation oflower macrofauna complexity and diversity in barrens rather than in macroalgal forests, and have allowedestimating the differences in levels of diversity and the consistency of variability across Mediterranean sites.Some peculiar patterns in barrens, related to both abundance of specific taxa and to high values of beta diversity,have been evidenced.