title: High CO2 enhances the competitive strength of seaweeds over corals.
abstract: Space competition between corals and seaweeds is an important ecological process underlying coral-reef dynamics. Processes promoting seaweed growth and survival, such as herbivore overfishing and eutrophication, can lead to local reef degradation. Here, we present the case that increasing concentrations of atmospheric CO(2) may be an additional process driving a shift from corals to seaweeds on reefs. Coral (Acropora intermedia) mortality in contact with a common coral-reef seaweed (Lobophora papenfussii) increased two- to threefold between background CO(2) (400 ppm) and highest level projected for late 21st century (1140 ppm). The strong interaction between CO(2) and seaweeds on coral mortality was most likely attributable to a chemical competitive mechanism, as control corals with algal mimics showed no mortality. Our results suggest that coral (Acropora) reefs may become increasingly susceptible to seaweed proliferation under ocean acidification, and processes regulating algal abundance (e.g. herbivory) will play an increasingly important role in maintaining coral abundance.
authors.affiliation: Griffith School of Environment, Australian Rivers Institute and ARC Centre of Excellence for Coral Reef Studies, Nathan Campus, Griffith University, 170 Kessels Road, Brisbane, Nathan, Qld 4111, Australia. g.diaz-pulido@griffith.edu.au
authors.forename: Guillermo
authors.initials: G
authors.lastname: Diaz-Pulido
authors.forename: Marine
authors.initials: M
authors.lastname: Gouezo
authors.forename: Bronte
authors.initials: B
authors.lastname: Tilbrook
authors.forename: Sophie
authors.initials: S
authors.lastname: Dove
authors.forename: Kenneth R N
authors.initials: KR
authors.lastname: Anthony
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000254:growth & development*; D002245:Carbon Dioxide / Q000737:chemistry*; D057894:Coral Reefs; D006863:Hydrogen-Ion Concentration; D000459:Phaeophyceae / Q000254:growth & development*; D011793:Queensland; D012624:Seaweed / Q000254:growth & development
chemical_list: D002245:Carbon Dioxide