title: Asymmetric competition prevents the outbreak of an opportunistic species after coral reef degradation.
abstract: Disturbance releases space and allows the growth of opportunistic species, excluded by the old stands, with a potential to alter community dynamics. In coral reefs, abundances of fast-growing, and disturbance-tolerant sponges are expected to increase and dominate as space becomes available following acute coral mortality events. Yet, an increase in abundance of these opportunistic species has been reported in only a few studies, suggesting certain mechanisms may be acting to regulate sponge populations. To gain insights into mechanisms of population control, we simulated the dynamics of the common reef-excavating sponge Cliona tenuis in the Caribbean using an individual-based model. An orthogonal hypothesis testing approach was used, where four candidate mechanisms-algal competition, stock-recruitment limitation, whole and partial mortality-were incorporated sequentially into the model and the results were tested against independent field observations taken over a decade in Belize, Central America. We found that releasing space after coral mortality can promote C. tenuis outbreaks, but such outbreaks can be curtailed by macroalgal competition. The asymmetrical competitive superiority of macroalgae, given by their capacity to pre-empt space and outcompete with the sponge in a size-dependant fashion, supports their capacity to steal the opportunity from other opportunists. While multiple system stages can be expected in coral reefs following intense perturbation macroalgae may prevent the growth of other space-occupiers, such as bioeroding sponges, under low grazing pressure.
authors.affiliation: School of Biological Sciences and Australian Research Council Centre of Excellence for Coral Reef Studies, University of Queensland, St. Lucia, QLD, 4072, Australia. m.gonzalezrivero@uq.edu.au.|College of Life and Environmental Sciences, University of Exeter, Exeter, EX44PS, UK. m.gonzalezrivero@uq.edu.au.|Global Change Institute, University of Queensland, St Lucia, QLD, 4072, Australia. m.gonzalezrivero@uq.edu.au.
authors.forename: Manuel
authors.identifier: http://orcid.org/0000-0003-0252-584X
authors.initials: M
authors.lastname: González-Rivero
authors.affiliation: School of Biological Sciences and Australian Research Council Centre of Excellence for Coral Reef Studies, University of Queensland, St. Lucia, QLD, 4072, Australia.
authors.forename: Yves-Marie
authors.initials: YM
authors.lastname: Bozec
authors.affiliation: School of Biological Sciences and Australian Research Council Centre of Excellence for Coral Reef Studies, University of Queensland, St. Lucia, QLD, 4072, Australia.|College of Life and Environmental Sciences, University of Exeter, Exeter, EX44PS, UK.|Smithsonian Marine Station, Smithsonian Institution, Fort Pierce, FL, USA.
authors.forename: Iliana
authors.initials: I
authors.lastname: Chollett
authors.affiliation: School of Biological Sciences and Australian Research Council Centre of Excellence for Coral Reef Studies, University of Queensland, St. Lucia, QLD, 4072, Australia.|Coastal and Marine Ecosystems Group, School of Biological Sciences and Australian Centre for Field Robotics, University of Sydney, Sydney, NWS, Australia.
authors.forename: Renata
authors.initials: R
authors.lastname: Ferrari
authors.affiliation: Oceans Institute, University of Western Australia, 39 Fairway, Crawley, WA, 6009, Australia.
authors.forename: Christine H L
authors.initials: CH
authors.lastname: Schönberg
authors.affiliation: School of Biological Sciences and Australian Research Council Centre of Excellence for Coral Reef Studies, University of Queensland, St. Lucia, QLD, 4072, Australia.|College of Life and Environmental Sciences, University of Exeter, Exeter, EX44PS, UK.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Mumby
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000254:growth & development / Q000502:physiology*; D001531:Belize; D017691:Caribbean Region; D057894:Coral Reefs; D008954:Models, Biological; D011157:Population Dynamics; D011161:Porifera / Q000254:growth & development / Q000502:physiology*; D012624:Seaweed / Q000254:growth & development
keywords: Disturbance; Marine ecosystems; Population regulation; Porifera; Transient ecosystems