title: The emergent role of small-bodied herbivores in pre-empting phase shifts on degraded coral reefs.
abstract: Natural and anthropogenic stressors can cause phase shifts from coral-dominated to algal-dominated states. In the Caribbean, over-fishing of large herbivorous fish and disease among the long-spined urchin, Diadema, have facilitated algal growth on degraded reefs. We found that diminutive species of urchin and parrotfish, which escaped die-offs and fishing pressure, can achieve abundances comparable to total herbivore biomass on healthier, protected reefs, and exert sufficient grazing function to pre-empt macroalgal dominance following mass coral mortality. Grazing was highest on the most degraded reefs, and was driven by small herbivores that made up >93% of the average herbivore biomass (per m2). We suggest that previously marginal species can achieve a degree of functional redundancy, and that their compensatory herbivory may play an important role in ecosystem resilience. Management strategies should consider the potential role of these additional herbivore functional groups in safeguarding natural controls of algal growth in times of increased uncertainty for the world's reefs.
authors.affiliation: Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancon, Republic of Panama.|Marine Science Center, Northeastern University, 430 Nahant Road, Nahant, Massachusetts 01908 USA.|Centre for Biodiversity and Conservation Science, School of Biological Sciences, University of Queensland, St. Lucia, QLD 4072, Australia.
authors.forename: Caitlin D
authors.initials: CD
authors.lastname: Kuempel
authors.affiliation: Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancon, Republic of Panama.
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Altieri
mesh_terms: D000818:Animals; D018533:Biomass; D057894:Coral Reefs; D005399:Fishes / Q000502:physiology; D060434:Herbivory; D012617:Sea Urchins / Q000502:physiology; D012624:Seaweed / Q000254:growth & development*