title: Biodiversity loss and turnover in alternative states in the Mediterranean Sea: a case study on meiofauna.
abstract: In the Mediterranean Sea hard-bottom macroalgal meadows may switch to alternative and less-productive barrens grounds, as a result of sea urchins overgrazing. Meiofauna (and especially nematodes) represent key components of benthic ecosystems, are highly-diversified, sensitive to environmental change and anthropogenic impacts, but, so-far, have been neglected in studies on regime shifts. We report here that sedimentary organic matter contents, meiofaunal taxa richness and community composition, nematode α- and β-biodiversity vary significantly between alternative macroalgal and barren states. The observed differences are consistent in six areas spread across the Mediterranean Sea, irrespective of barren extent. Our results suggest also that the low biodiversity levels in barren states are the result of habitat loss/fragmentation, which is associated also with a lower availability of trophic resources. Furthermore, differences in meiofaunal and nematode abundance, biomass and diversity between macroalgal meadow and barren states persist when the latter is not fully formed, or consists of patches interspersed in macroalgal meadows. Since barren grounds are expanding rapidly along the Mediterranean Sea and meiofauna are a key trophic component in marine ecosystems, we suggest that the extension and persistence of barrens at the expenses of macroalgal meadows could also affect resilience of higher trophic level.
authors.affiliation: Dipartimento di Scienze della Vita e dell'Ambiente, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Bianchelli
authors.affiliation: Dipartimento di Scienze della Vita e dell'Ambiente, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy.
authors.forename: Emanuela
authors.initials: E
authors.lastname: Buschi
authors.affiliation: Dipartimento di Scienze della Vita e dell'Ambiente, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy.|Stazione Zoologica Anton Dohrn, Villa Comunale 1, Napoli, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Danovaro
authors.affiliation: Dipartimento di Scienze della Vita e dell'Ambiente, Università degli Studi di Cagliari, Via Tommaso Fiorelli 1, 09126 Cagliari, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Pusceddu
mesh_terms: D000818:Animals; D044822:Biodiversity; D020387:Food Chain; D008522:Mediterranean Sea; D058086:Microalgae / Q000502:physiology*; D009348:Nematoda / Q000502:physiology*