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.
Highlights
Natural and anthropogenic stressors can cause phase shifts from coral-dominated to algal-dominated states
Understanding the factors that influence transitions between reef states and the ability of coral reefs to recover from disturbance is essential to inform management and conservation efforts across these valuable ecosystems
We used the recent mass mortality of coral associated with a hypoxic event on the Caribbean coast of Panama, in which >90% of coral died on some reefs, to test the generality of coral-algal phase shifts following a major disturbance. This region is subject to pervasive anthropogenic stressors that are representative of much of the Caribbean and other human-dominated coral reef ecosystems
Summary
Natural and anthropogenic stressors can cause phase shifts from coral-dominated to algal-dominated states. We show that top-down control can pre-empt phase shifts on degraded coral reefs where diminutive members of the herbivore assemblage reach sufficient levels of biomass and grazing pressure to prevent algal dominance following coral mortality.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
