title: Habitat constraints and self-thinning shape Mediterranean red coral deep population structure: implications for conservation practice.
abstract: The Mediterranean red coral, Corallium rubrum, is one of the most precious corals worldwide. Below 50 m depth, C. rubrum populations are generally characterised by large and sparse colonies, whereas shallow populations (above 50 m depth) show high densities of small colonies. We show here instead that populations dwelling between 80 and 170 m depth exhibited a continuous range of population density (from 2 to 75 colonies per 0.25 m(2)), with less than 1% of variance explained by water depth. An inverse relationship between maximum population density and mean colony height was found, suggesting that self-thinning processes may shape population structure. Moreover, demographically young populations composed of small and dense colonies dominated along rocky vertical walls, whereas mature populations characterised by large and sparsely distributed colonies were found only in horizontal beds not covered by sediment. We hypothesise that, in the long term, shallow protected populations should resemble to present deep populations, with sparsely distributed large colonies. Since the density of red coral colonies can decay as a result of self-thinning mechanisms, we advise that future protection strategies should be based also on a measure of red coral spatial coverage instead of population density.
authors.affiliation: Department of Architecture, Design and Urban planning, University of Sassari, Alghero, Italy.|Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Cau
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire d'Ecogéochimie des Environnements Benthiques (LECOB), Observatoire Océanologique, F-66650, Banyuls sur Mer, France.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Bramanti
authors.affiliation: Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy.
authors.forename: Rita
authors.initials: R
authors.lastname: Cannas
authors.affiliation: Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy.
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Follesa
authors.affiliation: Department III 'Tutela degli Habitat e della Biodiversità Marina', CRA 15 - ISPRA, Roma, Italy.
authors.forename: Michela
authors.initials: M
authors.lastname: Angiolillo
authors.affiliation: Department III 'Tutela degli Habitat e della Biodiversità Marina', CRA 15 - ISPRA, Roma, Italy.
authors.forename: Simonepietro
authors.initials: S
authors.lastname: Canese
authors.affiliation: Dipartimento per lo Studio del Territorio e delle sue Risorse, Università degli Studi di Genova, Genova, Italy.
authors.forename: Marzia
authors.initials: M
authors.lastname: Bo
authors.affiliation: Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy.
authors.forename: Danila
authors.initials: D
authors.lastname: Cuccu
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire d'Ecogéochimie des Environnements Benthiques (LECOB), Observatoire Océanologique, F-66650, Banyuls sur Mer, France.
authors.forename: Katell
authors.initials: K
authors.lastname: Guizien
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000254:growth & development*; D003247:Conservation of Natural Resources; D003710:Demography; D017753:Ecosystem; D008522:Mediterranean Sea; D011156:Population Density