title: Effects of ocean acidification on the potency of macroalgal allelopathy to a common coral.
abstract: Many coral reefs have phase shifted from coral to macroalgal dominance. Ocean acidification (OA) due to elevated CO2is hypothesised to advantage macroalgae over corals, contributing to these shifts, but the mechanisms affecting coral-macroalgal interactions under OA are unknown. Here, we show that (i) three common macroalgae are more damaging to a common coral when they compete under CO2concentrations predicted to occur in 2050 and 2100 than under present-day conditions, (ii) that two macroalgae damage corals via allelopathy, and (iii) that one macroalga is allelopathic under conditions of elevated CO2, but not at ambient levels. Lipid-soluble, surface extracts from the macroalga Canistrocarpus (=Dictyota) cervicornis were significantly more damaging to the coral Acropora intermedia growing in the field if these extracts were from thalli grown under elevated vs ambient concentrations of CO2. Extracts from the macroalgae Chlorodesmis fastigiata and Amansia glomerata were not more potent when grown under elevated CO2. Our results demonstrate increasing OA advantages seaweeds over corals, that algal allelopathy can mediate coral-algal interactions, and that OA may enhance the allelopathy of some macroalgae. Other mechanisms also affect coral-macroalgal interactions under OA, and OA further suppresses the resilience of coral reefs suffering blooms of macroalgae.
authors.affiliation: Griffith School of Environment &Australian Rivers Institute - Coast &Estuaries, Nathan Campus, Griffith University, 170 Kessels Road, Brisbane, Nathan, Queensland 4111, Australia.
authors.forename: Carlos
authors.initials: C
authors.lastname: Del Monaco
authors.affiliation: School of Biology, and Aquatic Chemical Ecology Center, 950 Atlantic Dr., Georgia Institute of Technology, Atlanta, Georgia, 30332, USA.
authors.forename: Mark E
authors.initials: ME
authors.lastname: Hay
authors.affiliation: Griffith School of Environment &Australian Rivers Institute - Coast &Estuaries, Nathan Campus, Griffith University, 170 Kessels Road, Brisbane, Nathan, Queensland 4111, Australia.
authors.forename: Patrick
authors.initials: P
authors.lastname: Gartrell
authors.affiliation: Marine Spatial Ecology Lab, School of Biological Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia.|Australian Research Council Centre of Excellence for Coral Reef Studies, St Lucia, Australia.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Mumby
authors.affiliation: Griffith School of Environment &Australian Rivers Institute - Coast &Estuaries, Nathan Campus, Griffith University, 170 Kessels Road, Brisbane, Nathan, Queensland 4111, Australia.|Australian Research Council Centre of Excellence for Coral Reef Studies, Townsville, Australia.
authors.forename: Guillermo
authors.initials: G
authors.lastname: Diaz-Pulido
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000187:drug effects / Q000254:growth & development*; D002245:Carbon Dioxide / Q000737:chemistry; D057894:Coral Reefs; D017753:Ecosystem; D006863:Hydrogen-Ion Concentration; D010675:Pheromones / Q000378:metabolism* / Q000633:toxicity; D011157:Population Dynamics; D012624:Seaweed / Q000254:growth & development / Q000378:metabolism*
chemical_list: D010675:Pheromones; D002245:Carbon Dioxide