Abstract
Coral reefs are among Earth’s best-studied ecosystems, yet the degree to which large predators influence the ecology of coral reefs remains an open and contentious question. Recent studies indicate the consumptive effects of large reef predators are too diffuse to elicit trophic cascades. Here, we provide evidence that such predators can produce non-consumptive (fear) effects that flow through herbivores to shape the distribution of seaweed on a coral reef. This trophic cascade emerged because reef topography, tidal oscillations, and shark hunting behaviour interact to create predictable “hot spots” of fear on the reef where herbivores withhold feeding and seaweeds gain a spatial refuge. Thus, in risky habitats, sharks can exert strong ecological impacts even though they are trophic generalists that rarely feed. These findings contextualize the debate over whether predators influence coral reef structure and function and move us to ask not if, but under what specific conditions, they generate trophic cascades.
Highlights
Large predators generate powerful trophic cascades within many of Earth’s ecosystems[1,2]
If fear hot spots exist in some reef habitats, such as the shallow backreef, it would suggest that sharks and other large predators can play important ecological roles in these ecosystems, but that their ecological impacts are highly context-dependent
Past studies of trophic cascades in these ecosystems have largely focused on the consumptive effects of predators and have generally done so using coarse community assemblage data
Summary
Large predators generate powerful trophic cascades within many of Earth’s ecosystems[1,2]. Recent studies indicate that some coral reef herbivores reduce their feeding when in close proximity to reef predators or stationary predator decoys, but it is unclear if this fear causes only a temporary redistribution of herbivore feeding or an overall reduction in herbivory[23,24,25] Some of these studies have focused on small site-attached herbivores[26] rather than the large roving species that drive herbivory on coral reefs. As such, it remains unclear when or where large mobile predators may create fear effects that cascade to affect seaweed community structure and function. We conducted observations and experiments in a shallow marine reserve in Fiji to explore whether large predators (>50 cm total length) create a trophic cascade through this very mechanism
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.
