title: The role of competition in the phase shift to dominance of the zoanthid Palythoa cf. variabilis on coral reefs.
abstract: Phase shift phenomena are becoming increasingly common. However, they are also opportunities to better understand how communities are structured. In Southwest Atlantic coral reefs, a shift to the zoanthid Palythoa cf. variabilis dominance has been described. To test if competition drove this process, we carried out a manipulative experiment with three coral species. To estimate the natural frequency of encounters we assess the relationship between the proportion of encounters and this zoanthids coverage. The contact causes necrosis in 78% of coral colonies (6.47 ± SD 7.92 cm(2)) in 118 days. We found a logarithmic relationship between the proportion of these encounters and the cover of P. cf. variabilis, where 5.5% coverage of this zoanthid is enough to put 50% of coral colonies in contact, increasing their partial mortality. We demonstrate that zoanthid coverage increase followed by coral mortality increase will reduce coral cover and that competition drives the phase shift process.
authors: Programa de Pós Graduação em Ecologia, Universidade do Estado do Rio de Janeiro, Rua São Francisco Xavier 524, ZIP 20559-900, Rio de Janeiro, RJ, Brazil; Laboratório de Manejo, Ecologia e Conservação Marinha, Instituto Oceanográfico, Universidade de São Paulo, Praça do Oceanográfico, 191, Cidade Universitária, ZIP 05508-120, São Paulo, SP, Brazil; Laboratório Recifes de Corais e Mudanças Globais, Instituto de Geociências, Universidade Federal da Bahia, Rua Barão de Geremoabo, s/n Ondina, ZIP 40170-115, Salvador, BA, Brazil; Laboratório de Ecologia Marinha Bêntica, Departamento de Ecologia, Instituto de Biologia Roberto Alcântara Gomes, Universidade do Estado do Rio de Janeiro - UERJ, PHLC Sala 220, Rua São Francisco Xavier 524, ZIP 20559-900, Rio de Janeiro, RJ, Brazil. Electronic address: igorcruz@gmail.com.
authors: Igor Cristino Silva
authors: IC
authors: Cruz
authors: Laboratório Recifes de Corais e Mudanças Globais, Instituto de Geociências, Universidade Federal da Bahia, Rua Barão de Geremoabo, s/n Ondina, ZIP 40170-115, Salvador, BA, Brazil.
authors: Verena Henschen
authors: VH
authors: Meira
authors: Laboratório Recifes de Corais e Mudanças Globais, Instituto de Geociências, Universidade Federal da Bahia, Rua Barão de Geremoabo, s/n Ondina, ZIP 40170-115, Salvador, BA, Brazil.
authors: Ruy Kenji Papa
authors: RK
authors: de Kikuchi
authors: Laboratório de Ecologia Marinha Bêntica, Departamento de Ecologia, Instituto de Biologia Roberto Alcântara Gomes, Universidade do Estado do Rio de Janeiro - UERJ, PHLC Sala 220, Rua São Francisco Xavier 524, ZIP 20559-900, Rio de Janeiro, RJ, Brazil.
authors: Joel Christopher
authors: JC
authors: Creed
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D037421:Anthozoa / Q000502:physiology*; D001267:Atlantic Ocean; D044822:Biodiversity; D001938:Brazil; D057894:Coral Reefs; D011157:Population Dynamics
keywords: Assembly rules; Brazilian coral reefs; Community ecology; Community structure; Montastraea cavernosa; Mussismilia hispida; Phase regime; Siderastrea stellata; Todos os santos bay